Control system for hydrostatic drive tractors

Claim 2

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotatIon of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios, the improvement comprising: control means operatively associated with the transmission sensor means, the valve means, and the switch means to effect reversible automatic shifting of the valve means from high torque to low torque connections when high torque has been selected with the switch means, and the transmission sensor means senses an intermediate transmission ratio, and to effect reversible automatic shifting of the valve means to the off connection when the transmission sensor means senses a high transmission ratio.

Claim 3

The invention as claimed in claim 1 wherein the control means includes means to effect shifting of the valve means into the high torque connection when low torque has been selected with the switch means and the transmission sensor means senses a reverse transmission ratio.

Claim 4

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting the torque valve means connections between high and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, and the torque valve means to effect reversible automatic shifting of the torque valve means from high to low torque connections when high torque has been selected with the torque switch means and the transmission sensor means senses an intermediate transmission ratio; and forward and reverse direction control means operatively associated with the transmission sensor means and the direction valve means to effect reversible automatic shifting of the direction valve means to the off connection when the transmission sensor means senses a high transmission ratio.

Claim 5

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting the torque valve means connections between high and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, and the torque valve means to effect reversible automatic shifting of the torque valve means from high to low torque connections when high torque has been selected with the torque switch means and the transmission sensor means senses an intermediate transmission ratio; and forward and reverse direction control means operatively associated with the transmission sensor means and the direction valve means to effect reversible automatic shifting of the direction valve means to the off connection when the transmission sensor means senses a high transmission ratio.

Claim 6

The invention as claimed in claim 3 wherein the torque control means includes means to effect shifting of the torque valve means into the high torque connection when low torque has been selected with the switch means and the transmission sensor means senses a reverse transmission ratio.

Claim 7

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward higH, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward conection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level, and to effect reversible automatic shifting of the valve means to the off connection when either high or low torque has been selected with the switch means and either one or both the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 8

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward higH, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward conection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level, and to effect reversible automatic shifting of the valve means to the off connection when either high or low torque has been selected with the switch means and either one or both the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 9

The invention defined in claim 5 wherein the pressure signal means includes time delay means delaying operation of the control means so that short interval reversible high-low-off torque cycling of the valve means is prevented.

Claim 10

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels, a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting the torque valve means connections between high and low torque; transmission sensor means operatively aSsociated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means and the torque valve means to effect reversible automatic shifting of the torque valve means from the high and the low torque connections when high torque has been selected with the torque switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure means senses a pressure of the pressurized fluid below a predetermined high pressure level; and forward and reverse direction control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the direction valve means to effect reversible automatic shifting of the direction valve means to the off connection when high or low torque has been selected with the torque switch means and either one or both of the transmission control sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 11

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels, a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting the torque valve means connections between high and low torque; transmission sensor means operatively aSsociated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means and the torque valve means to effect reversible automatic shifting of the torque valve means from the high and the low torque connections when high torque has been selected with the torque switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure means senses a pressure of the pressurized fluid below a predetermined high pressure level; and forward and reverse direction control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the direction valve means to effect reversible automatic shifting of the direction valve means to the off connection when high or low torque has been selected with the torque switch means and either one or both of the transmission control sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 12

The invention defined in claim 7 wherein the pressure signal means includes time delay means delaying operation of the torque control means and the forward and the reverse direction control means so that short interval high-to-off and forward-to-off and reverse-to-off cycling of the direction valve means are prevented.

Claim 13

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratio; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to effect reversible automatic shifting of the valve means from the the high to the low torque connections when high torque has been selected with the switch means and either the transmission sensor means senses a forward intermediate transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level or the transmission sensor means senses a forward low or a reverse transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either the transmission sensor means senses a forward high transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above the predetermined low pressure level or the transmission sensor means senses a forward or reverse transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 14

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratio; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to effect reversible automatic shifting of the valve means from the the high to the low torque connections when high torque has been selected with the switch means and either the transmission sensor means senses a forward intermediate transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level or the transmission sensor means senses a forward low or a reverse transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either the transmission sensor means senses a forward high transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above the predetermined low pressure level or the transmission sensor means senses a forward or reverse transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 15

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means and the switch means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and either the transmission sensor means senses a forward intermediate transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level or the transmission sensor means senses a forward low transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either the transmission sensor means senses a forward high transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined low pressure level or the transmission sensor means senses a forward transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined low pressure level or the transmission sensor means senses a reverse transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level.

Claim 16

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means and the switch means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and either the transmission sensor means senses a forward intermediate transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level or the transmission sensor means senses a forward low transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either the transmission sensor means senses a forward high transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined low pressure level or the transmission sensor means senses a forward transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined low pressure level or the transmission sensor means senses a reverse transmission ratio while the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level.

Claim 17

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by an engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motor to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the valve means and the switch means to effect shifting of the valve means to the high or the low torque connections when high or low torque, respectively, has been selected with the switch means and the transmission sensor means senses a forward low or a reverse transmission ratio, to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and the transmission sensor means senses an intermediate transmission ratio, and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and the transmission sensor means senses a high transmission ratio.

Claim 18

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by an engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motor to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the valve means and the switch means to effect shifting of the valve means to the high or the low torque connections when high or low torque, respectively, has been selected with the switch means and the transmission sensor means senses a forward low or a reverse transmission ratio, to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and the transmission sensor means senses an intermediate transmission ratio, and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and the transmission sensor means senses a high transmission ratio.

Claim 19

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motor to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means and the switch means to effect shifting of the valve means to the high or the low torque connectioNs when high or low torque, respectively, has been selected with the switch means and the transmission sensor means senses a forward low or reverse transmission ratio and the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level, to effect reversible automatic shifting of the valve means from the high torque to the low torque connections when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure sensor means senses a pressure of the pressurized fluid below a predetermined high pressure level, and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either one or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 20

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motor to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means and the switch means to effect shifting of the valve means to the high or the low torque connectioNs when high or low torque, respectively, has been selected with the switch means and the transmission sensor means senses a forward low or reverse transmission ratio and the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level, to effect reversible automatic shifting of the valve means from the high torque to the low torque connections when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure sensor means senses a pressure of the pressurized fluid below a predetermined high pressure level, and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either one or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 21

A hydrostatic driven control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means and the switch means to effect shifting of the valve means to the high or the low torque connections when high or low torque, respectively, has been selected with the switch means and the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level, to effect reversible automatic shifting of the valve means from the high torque to the low torque connections when high torque has been selected with the switch means and either one or both of the transmission sensor means senses a forward intermediate transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level or the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level and the transmission sensor means senses a forward low or reverse transmission ratio, and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch and either the transmission sensor means senses a forward high transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermiNed high pressure level or the pressure signal means senses a pressure of the pressurized fluid below the predetermined low pressure level while the transmission sensor means senses a forward or a reverse transmission ratio.

Claim 22

A hydrostatic driven control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; and transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means and the switch means to effect shifting of the valve means to the high or the low torque connections when high or low torque, respectively, has been selected with the switch means and the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level, to effect reversible automatic shifting of the valve means from the high torque to the low torque connections when high torque has been selected with the switch means and either one or both of the transmission sensor means senses a forward intermediate transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermined high pressure level or the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level and the transmission sensor means senses a forward low or reverse transmission ratio, and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch and either the transmission sensor means senses a forward high transmission ratio while the pressure signal means senses a pressure of the pressurized fluid above a predetermiNed high pressure level or the pressure signal means senses a pressure of the pressurized fluid below the predetermined low pressure level while the transmission sensor means senses a forward or a reverse transmission ratio.

Claim 23

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connection between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to shift the valve means between its forward and reverse connections in accordance with forward and reverse ratios, respectively, of the transmission when either high or low torque has been selected with the switch means, to effect reversible automatic shifting of the valve means from the high to the low torque connection when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level, to effect reversible automatic shifting of the valve means to off when high or low torque has been selected with the switch means and either or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level, to effect reversible automatic shifting of the valve means from the low to the high torque connection when low torque has been selected with the switch means and the pressure signal means senses a pressure of the pressurized fluid above the predetermined low pressure level while the transmission sensor means senses a reverse transmission ratio.

Claim 24

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connection between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to shift the valve means between its forward and reverse connections in accordance with forward and reverse ratios, respectively, of the transmission when either high or low torque has been selected with the switch means, to effect reversible automatic shifting of the valve means from the high to the low torque connection when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level, to effect reversible automatic shifting of the valve means to off when high or low torque has been selected with the switch means and either or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level, to effect reversible automatic shifting of the valve means from the low to the high torque connection when low torque has been selected with the switch means and the pressure signal means senses a pressure of the pressurized fluid above the predetermined low pressure level while the transmission sensor means senses a reverse transmission ratio.

Claim 25

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in thE hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors; and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque, transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to shift the valve means between its forward and reverse connections in accordance with forward and reverse ratios, respectively, of the transmission when high or low torque has been selected with the switch means, to effect reversible automatic shifting of the valve means from the high to the low torque connection when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either one or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below the predetermined low pressure level while the transmission sensor means senses a forward transmission ratio, and to effect reversible automatic shifting of the valve means from the low to the high torque connection when low torque has been selected with the switch means and the pressure signal means senses a pressure of the pressurized fluid above the predetermined low pressure level while the transmission sensor means senses a reverse transmission ratio.

Claim 26

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts connected to the additional wheels; a hydraulic system interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in thE hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors; and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque, transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to shift the valve means between its forward and reverse connections in accordance with forward and reverse ratios, respectively, of the transmission when high or low torque has been selected with the switch means, to effect reversible automatic shifting of the valve means from the high to the low torque connection when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means and either one or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below the predetermined low pressure level while the transmission sensor means senses a forward transmission ratio, and to effect reversible automatic shifting of the valve means from the low to the high torque connection when low torque has been selected with the switch means and the pressure signal means senses a pressure of the pressurized fluid above the predetermined low pressure level while the transmission sensor means senses a reverse transmission ratio.

Claim 27

The invention defined in claim 15 wherein the pressure signal means includes time delay means delaying operation of the control means so that short interval reversible high-low-off torque cycling of the valve means is prevented.

Claim 28

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump to the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein It connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting between the off position of the direction valve means, and the high torque and low torque positions of the torque valve means; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the torque valve means to effect reversible automatic shifting of the torque valve means from the high to the low torque connections when high torque has been selected with the torque switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, and to effect reversible automatic shifting of the torque valve means from the low to the high torque connection when low torque has been selected with the switch means and the transmission sensor means senses a reverse transmission ratio; and direction control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, the torque valve means and the direction valve means to shift the direction valve means between its forward and reverse positions in accordance with forward and reverse ratios, respectively, of the transmission when either high or low torque positions of the torque valve means have been selected with the switch means, to effect reversible automatic shifting of the direction valve means to the off position when the high or low torque connection of the torque valve means has been selected by the torque switch means and either one or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 29

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump to the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein It connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting between the off position of the direction valve means, and the high torque and low torque positions of the torque valve means; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the torque valve means to effect reversible automatic shifting of the torque valve means from the high to the low torque connections when high torque has been selected with the torque switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, and to effect reversible automatic shifting of the torque valve means from the low to the high torque connection when low torque has been selected with the switch means and the transmission sensor means senses a reverse transmission ratio; and direction control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, the torque valve means and the direction valve means to shift the direction valve means between its forward and reverse positions in accordance with forward and reverse ratios, respectively, of the transmission when either high or low torque positions of the torque valve means have been selected with the switch means, to effect reversible automatic shifting of the direction valve means to the off position when the high or low torque connection of the torque valve means has been selected by the torque switch means and either one or both of the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 30

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connection between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to Shift the valve means between its forward and reverse connections in accordance with forward and reverse ratios, respectively, of the transmission when either high or low torque has been selected with the switch means, to effect reversible automatic shifting of the valve means from the high to the low torque connection when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, to effect reversible automatic shifting of the valve means to the off connection when either the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level while the transmission sensor means senses a reverse transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level while the transmission sensor means senses a forward transmission ratio and to effect reversible automatic shifting of the valve means to the high torque connection in response to low torque selection of the switch means and the transmission sensor means sensing of a reverse transmission ratio.

Claim 31

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system interconnecting the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connection between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the transmission sensor means, the pressure signal means, the valve means, and the switch means to Shift the valve means between its forward and reverse connections in accordance with forward and reverse ratios, respectively, of the transmission when either high or low torque has been selected with the switch means, to effect reversible automatic shifting of the valve means from the high to the low torque connection when high torque has been selected with the switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, to effect reversible automatic shifting of the valve means to the off connection when either the transmission sensor means senses a high transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level while the transmission sensor means senses a reverse transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level while the transmission sensor means senses a forward transmission ratio and to effect reversible automatic shifting of the valve means to the high torque connection in response to low torque selection of the switch means and the transmission sensor means sensing of a reverse transmission ratio.

Claim 32

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting between the off position of the direction valve means, and the high torque and low torque positions of the torque valve means; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the torque valve means to effect reversible automatic shifting of the torque valve means from the high to the low torque connections when high torque has been selected with the torque switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, and to effect reversible automatic shifting of the torque valve means from the low torque to the high torque connection when low torque has been selected with tHe torque switch means and the transmission sensor means senses a reverse transmission ratio; forward and reverse direction control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the direction valve means to shift the direction valve means between its forward and reverse positions in accordance with forward and reverse ratios, respectively, of the transmission when-ever either high or low torque positions of the torque valve means have been selected with the switch means, to effect reversible automatic shifting of the direction valve means to the off position when either the transmission sensor means senses a high transmission ratio or the pressure signal means senses pressure of the pressurized fluid below a predetermined low pressure level while the transmission sensor means senses a forward transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level while the transmission sensor means senses a reverse transmission ratio.

Claim 33

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels and having associated transmission controls adapted to change the transmission between forward high, intermediate, and low ratios and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting between the off position of the direction valve means, and the high torque and low torque positions of the torque valve means; transmission sensor means operatively associated with the transmission for sensing the forward high, intermediate, and low transmission ratios and the reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: torque control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the torque valve means to effect reversible automatic shifting of the torque valve means from the high to the low torque connections when high torque has been selected with the torque switch means and either one or both of the transmission sensor means senses an intermediate transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level while the transmission sensor means senses a forward transmission ratio, and to effect reversible automatic shifting of the torque valve means from the low torque to the high torque connection when low torque has been selected with tHe torque switch means and the transmission sensor means senses a reverse transmission ratio; forward and reverse direction control means operatively associated with the transmission sensor means, the torque switch means, the pressure signal means, and the direction valve means to shift the direction valve means between its forward and reverse positions in accordance with forward and reverse ratios, respectively, of the transmission when-ever either high or low torque positions of the torque valve means have been selected with the switch means, to effect reversible automatic shifting of the direction valve means to the off position when either the transmission sensor means senses a high transmission ratio or the pressure signal means senses pressure of the pressurized fluid below a predetermined low pressure level while the transmission sensor means senses a forward transmission ratio or the pressure signal means senses a pressure of the pressurized fluid below the predetermined high pressure level while the transmission sensor means senses a reverse transmission ratio.

Claim 34

The invention claimed in claim 19 wherein the pressure signal means includes time delay means delaying operation of the torque control means and the forward and reverse direction control means so that short interval high-to-low torque cycling of the torque valve means and forward-to-off and reverse-to-off cycling of the direction valve means are prevented.

Claim 35

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, and a low torque connection wherein it connects the motors with the pump in series relationship with each other; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the valve means, the switch means, and the pressure signal means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and the pressure signal means senses pressure of the pressurized fluid below a predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 36

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, and a low torque connection wherein it connects the motors with the pump in series relationship with each other; switch means for selecting the valve means connections between off, high torque, and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the valve means, the switch means, and the pressure signal means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means and the pressure signal means senses pressure of the pressurized fluid below a predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 37

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels in forward and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motoRs with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward and reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the valve means, the switch means, the transmission sensor means, and the pressure signal means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means, the transmission sensor means senses a forward or reverse transmission ratio, and the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means, the transmission sensor means senses a forward or reverse transmission ratio and the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 38

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels in forward and reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motoRs with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward and reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the valve means, the switch means, the transmission sensor means, and the pressure signal means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means, the transmission sensor means senses a forward or reverse transmission ratio, and the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high or low torque has been selected with the switch means, the transmission sensor means senses a forward or reverse transmission ratio and the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 39

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels in forward or reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward and reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the valve means, the switch means, the transmission sensor means, and the pressure signal means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means, the transmission sensor means senses a forward transmission ratio, and the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high torque or low torque has been selected with the switch means and either the transmission sensor senses a forward transmission ratio and the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level or the transmission sensor senses a reverse transmission ratio and the pressure signal means senses a pressure of the Pressurized fluid below the predetermined high pressure level.

Claim 40

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels in forward or reverse ratios; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; valve means in the hydraulic system shiftable between an off connection wherein it disconnects the motors from the pump, a high torque connection wherein it connects the motors with the pump in parallel relationship with each other, a low torque connection wherein it connects the motors with the pump in series relationship with each other, a forward connection wherein it connects the motors with the pump for forward rotation of the motors, and a reverse connection wherein it connects the motors with the pump for reverse rotation of the motors; switch means for selecting the valve means connections between off, high torque, and low torque; transmission sensor means operatively associated with the transmission for sensing the forward and reverse transmission ratios; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising: control means operatively associated with the valve means, the switch means, the transmission sensor means, and the pressure signal means to effect reversible automatic shifting of the valve means from the high to the low torque connections when high torque has been selected with the switch means, the transmission sensor means senses a forward transmission ratio, and the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level and to effect reversible automatic shifting of the valve means to the off connection when high torque or low torque has been selected with the switch means and either the transmission sensor senses a forward transmission ratio and the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level or the transmission sensor senses a reverse transmission ratio and the pressure signal means senses a pressure of the Pressurized fluid below the predetermined high pressure level.

Claim 41

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting the torque valve means connections between high torque and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising; torque control means operatively associated with the torque switch means, the torque valve means, and the pressure signal means to effect reversible automatic shifting of the torque valve means from the high to the low torque connections when high torque has been selected with the torque switch means and the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level; and direction control means operatively associated with the direction valve means and the pressure signal means to effect reversible automatic shifting of the direction valve means to the off position when the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 42

A hydrostatic drive control system in a vehicle having an engine; a pair of main drive wheels; a variable ratio transmission adapted to drivingly connect the engine to the drive wheels; an axle structure having additional wheels journaled at opposite ends thereof; a hydraulic pump driven by the engine to provide pressurized fluid; a pair of hydraulic wheel motors mounted at opposite ends of the axle structure and including output shafts operatively connected to the additional wheels; a hydraulic system operatively interconnecting the pump and the motors to supply pressurized fluid from the pump to the motors; torque valve means in the hydraulic system shiftable between a high torque position wherein it connects the motors with the pump in parallel relationship with each other and a low torque position wherein it connects the motors with the pump in series relationship with each other; direction valve means in the hydraulic system shiftable between an off position wherein it disconnects the motors from the pump, a forward position wherein it connects the motors with the pump for forward rotation of the motors, and a reverse position wherein it connects the motors with the pump for reverse rotation of the motors; torque switch means for selecting the torque valve means connections between high torque and low torque; pressure signal means operatively associated with the hydraulic system for sensing fluid pressure; the improvement comprising; torque control means operatively associated with the torque switch means, the torque valve means, and the pressure signal means to effect reversible automatic shifting of the torque valve means from the high to the low torque connections when high torque has been selected with the torque switch means and the pressure signal means senses a pressure of the pressurized fluid below a predetermined high pressure level; and direction control means operatively associated with the direction valve means and the pressure signal means to effect reversible automatic shifting of the direction valve means to the off position when the pressure signal means senses a pressure of the pressurized fluid below a predetermined low pressure level.

Claim 43

The invention defined in claim 24 wherein the pressure signal means includes time delay means delaying operation of the torque control means and the forward and the reverse direction control means so that short interval high-to-low torque cycling of the torque valve means and forward-to-off and reverse-to-off cycling of the direction valve means are prevented.