Hydrostatic transmission speed and steering control system

Claim 2

Apparatus for controlling the operation of a plurality of fluid motors each of which has a piston movable in a chamber to vary the output speed of an associated hydrostatic transmission, said apparatus comprising hydraulic control means for controlling the operation of said plurality of fluid motors, said hydraulic control means including a plurality of steering valves connected in fluid communication with said fluid motors, each of said steering valves being associated with at least one of said fluid motors and being operable to connect a chamber portion on one side of the piston in an associated fluid motor in fluid communication with a chamber portion on the opposite side of the piston to effect movement of the piston in the associated fluid motor and a variation in the output speed of the associated hydrostatic transmission.

Claim 3

An apparatus as set forth in claim 1 wherein each of said steering valves includes metering means for effecting gradual operation of the associated one of said fluid motors upon operation of the associated steering valve.

Claim 4

An apparatus as set forth in claim 1 wherein said hydraulic control means further includes first conduit means for conducting fluid at a first pressure between one of said steering valves and the associated one of said fluid motors and second conduit means for conducting fluid at a second pressure between said one of first steering valves and the associated one of said fluid motors, said one of said steering valves being operable to connect said first fluid conduit means in fluid communication with said second fluid conduit means to thereby effect the connection between the portions of the chamber on opposite sides of the piston in the associated one of said fluid motors.

Claim 5

An apparatus as set forth in claim 1 wherein said hydraulic control means further includes speed control valve means for effecting contemporaneous operation of each of said plurality of fluid motors to vary the output speeds of each of the hydrostatic transmissions by substantially the same amount.

Claim 6

An apparatus as set forth in claim 4 further including fluid conduit means for conducting fluid between said speed control valve means and said steering valves and for conducting fluid between said steering valves and the chamber portions on oppposite sides of the pistons in said plurality of fluid motors.

Claim 7

Apparatus as set forth in claim 5 wherein said fluid conduit means includes a first fluid conduit extending between the chamber portion on one side of the piston of one of said fluid motors, and the associated one of said steering valves and a second fluid conduit extending between the chamber portion on the opposite side of the piston of said one of said fluid motors and the associated one of said steering valves, said steering valve associated with said one of said fluid motors being operable between a first postion blocking fluid communication between said first and second fluid conduits and a second position connecting said first and second fluid conduits in fluid communication with each other to effect a variation in the output speed of the associated hydrostatic transmission.

Claim 8

Apparatus for controlling the operation of a plurality of hydrostatic transmissions, said apparatus comprising a plurality of fluid motors each of which is operatively connected with an associated one of the hydrostatic transmissions and is operable to vary the output speed of the associated hydrostatic transmission, and hydraulic control means for controlling the operation of said plurality of fluid motors, said hydraulic control means including speed control valve means for effecting contemporaneous operation of each of said plurality of fluid motors to vary the output speeds of each of the hydrostatic transmissions by substantially the same amount, conduit means for conducting fluid between said speed control valve means and said plurality of fluid motors, and steering control valve means for varying the output speed of selected hydrostatic transmissions relative to each other, said steering control valve means including a plurality of steering valves each of which is associated with one of said fluid motors, and is connected with said conduit means between said speed control valve means and the associated one of said fluid motors, each of said steering valves being operable to effect operation of the associated one of said fluid motors to vary the output speed of at least one of the hydrostatic transmissions while maintaining the output speed of another of the hydrostatic transmissions substantially constant.

Claim 9

Apparatus for controlling the operation of a plurality of hydrostatic transmissions, said apparatus comprising a plurality of fluid motors each of which is operatively connected with an associated one of the hydrostatic transmissions and is operable to vary the output speed of the associated hydrostatic transmission, and hydraulic control means for controlling the operation of said plurality of fluid motors, said hydraulic control means including speed control valve means for effecting contemporaneous operation of each of said plurality of fluid motors to vary the output speeds of each of the hydrostatic transmissions by substantially the same amount, conduit means for conducting fluid between said speed control valve means and said plurality of fluid motors, and steering control valve means for varying the output speed of selected hydrostatic transmissions relative to each other, said steering control valve means including a plurality of steering valves each of which is associated with one of said fluid motors, and is connected with said conduit means between said speed control valve means and the associated one of said fluid motors, each of said steering valves being operable to effect operation of the associated one of said fluid motors to vary the output speed of at least one of the hydrostatic transmissions while maintaining the output speed of another of the hydrostatic transmissions substantially constant.

Claim 10

An apparatus as set forth in claim 7 wherein each of said plurality of fluid motors includes housing means for defining a chamber and a piston slidably disposed in said chamber, each of said steering valves being operable to connect a portion of the chamber on a first side of the piston in the associated one of said fluid motors in fluid communication with a portion of the chamber on a second side of the piston in the associated one of said fluid motors to effect operation of the associated one of said fluid motors.

Claim 11

An apparatus as set forth in claim 8 wherein each of said steering valves includes metering means for gradually connecting the portion of the chamber on the one side of the piston in fluid communication with the portion of the chamber on the other side of the piston upon operation of the associated one of said steering valves.

Claim 12

An apparatus as set forth in claim 7 wherein the direction of operation of the hydrostatic transmissions is reversible, each of said steering valves being selectively operable to operate the associated one of said fluid motors to reverse the direction of operation of the associated one of the hydrostatic transmissions.

Claim 13

An apparatus as set forth in claim 7 wherein said conduit means includes first and second fluid passage means for connecting said speed control valve means in fluid communication with each of said steering valves, and third and fourth fluid passage means for connecting one of said steering control valves with the associated one of said fluid motors, said speed control valve means being selectively operable to provide a first fluid pressure in said first fluid passage means and a second fluid pressure in said second fluid passage means, said one of said steering control valves being selectively operable between a first condition in which said third fluid passage means is exposed to the fluid pressure in said first fluid passage means and said fourth fluid passage means is exposed to the fluid pressure in said second fluid passage means and a second condition in which said third fluid passage means is exposed to the fluid pressure in said second fluid passage means and said fourth fluid passage means is exposed to the fluid pressure in said first fluid passage means.

Claim 14

An apparatus as set forth in claim 11 wherein said speed control valve means includes means for maintaining the fluid pressure in said first and second fluid passage means substantially constant during operation of said one of said steering control valves between the first and second conditions.

Claim 15

An apparatus as set forth in claim 12 wherein said one of said steering valves blocks fluid communication between said first and second fluid passage means and between said third and fourth fluid passage means when said one of said steering valves is in said first condition and connects all of said fluid passage means in fluid communication with each other when said one of said steering valves is in said second condition.

Claim 16

An apparatus as set forth in claim 12 wherein said one of said steering valves blocks fluid communication between said first and second fluid passage means and between said third and fourth fluid passage means when said one of said steering valves is in said first condition and when said one of said steering valves is in said second condition.

Claim 17

An apparatus as set forth in claim 14 wherein said one of said steering valves connects all of said fluid passage means in fluid communication with each other as said one of said steering valves is operated between said first and second conditions.

Claim 18

An apparatus as set forth in claim 7 wherein each of said fluid motors includes a housing defining a chamber having first and second end portions and a piston disposed in said chamber and movable toward and away from said first and second end portions of said chamber, said apparatus further including means for operatively connecting each of said pistons with an associated one of the hydrostatic transmissions in such manner that movement of one of said pistons varies the output speed of the associated one of the hydrostatic transmissions, said conduit means including first and second fluid passage means for connecting said speed control valve means in fluid communication with each of said steering valves, third fluid passage means for connecting one of said steering control valves in fluid communication with the first end portion of one of said chambers, and fourth fluid passage means for connecting said one of said steering control valves in fluid communication with said second end portion of said one of said chambers, said one of said steering control valves being selectively operable between first and second conditions, said one of said steering control valves when in said first condition connecting said third fluid passage means and said first end portion of said one of said chambers in fluid communication with said first fluid passage means and said fourth fluid passage means and said second end portion of said one of said chambers in fluid communication with said second fluid passage means, said one of said steering control valves when in said second condition connecting said third fluid passage means and said first end portion of said one of said chambers in fluid communication with said second fluid passage means and said fourth fluid passage means and said second end portion of said one of said chambers in fluid communication with said first fluid passage means to thereby effect movement of said piston in said one of chambers and a variation in the output speed of the associated hydrostatic transmission upon operation of said one of said steering valves between the first and second conditions.

Claim 19

Apparatus for controlling the operation of a hydrostatic transmission, said apparatus comprising hydraulic actuator means for varying the output speed of the hydrostatic transmission, said hydraulic actuator means including a primary fluid motor which is operatively connected with the hydrostatic transmission and is operable to vary the output speed of the hydrostatic transmission, pilot valve which is connected in fluid communication with said primary fluid motor and is operable to effect operation of said primary fluid motor, and a secondary fluid motor which is operatively connected with said pilot valve and is operable to actuate said pilot valve to thereby effect operation of said primary fluid motor to vary the output speed of the hydrostatic transmission, and hydraulic control means for controlling the operation of said hydraulic actuator means, said hydraulic control means including speed control valve means movable to any one of a plurality of positions to effect operation of said secondary fluid motor to vary the output speed of the hydrostatic transmission, conduit means for conducting fluid between said speed control valve means and said secondary fluid motor, and secondary control valve means for varying the output speed of the hydrostatic transmission while maintaining said speed control valve means in a selected operating position, said secondary control valve means including a secondary valve connected in fluid communication with said conduit means, said secondary valve being associated with said secondary fluid motor and being operable to effect operation of said secondary fluid motor to operate said pilot valve and primary fluid motor to vary the output speed of the hydrostatic transmission.

Claim 20

Apparatus for controlling the operation of a hydrostatic transmission, said apparatus comprising hydraulic actuator means for varying the output speed of the hydrostatic transmission, said hydraulic actuator means including a primary fluid motor which is operatively connected with the hydrostatic transmission and is operable to vary the output speed of the hydrostatic transmission, pilot valve which is connected in fluid communication with said primary fluid motor and is operable to effect operation of said primary fluid motor, and a secondary fluid motor which is operatively connected with said pilot valve and is operable to actuate said pilot valve to thereby effect operation of said primary fluid motor to vary the output speed of the hydrostatic transmission, and hydraulic control means for controlling the operation of said hydraulic actuator means, said hydraulic control means including speed control valve means movable to any one of a plurality of positions to effect operation of said secondary fluid motor to vary the output speed of the hydrostatic transmission, conduit means for conducting fluid between said speed control valve means and said secondary fluid motor, and secondary control valve means for varying the output speed of the hydrostatic transmission while maintaining said speed control valve means in a selected operating position, said secondary control valve means including a secondary valve connected in fluid communication with said conduit means, said secondary valve being associated with said secondary fluid motor and being operable to effect operation of said secondary fluid motor to operate said pilot valve and primary fluid motor to vary the output speed of the hydrostatic transmission.

Claim 21

Apparatus as set forth in claim 17 wherein said secondary control valve is connected with said conduit means between said speed control valve means and said secondary fluid motor.

Claim 22

An apparatus as set forth in claim 18 wherein said secondary fluid motor includes a housing defining a chamber having a first and second end portion and a piston disposed in said chamber and movable toward and away from said first and second end portions of said chamber, said conduit means including first fluid passage means for connecting said speed control valve means in fluid communication with the first end portion of said chamber, second fluid passage means for connecting said secondary control valve in fluid communication with said first end portion of said chamber, and third fluid passage means for connecting said secondary control valve in fluid communication with said second end portion of said chamber, said secondary control valve being selectively operable between first and second conditions, said secondary control valve when in said first condition connecting said second fluid passage means and said first end portion of said chamber in fluid communication with said first fluid passage means, said secondary control valve when in said second condition connecting said third fluid passage means and said second end portion of said chamber in fluid communication with said first fluid passage means to thereby effect movement of said piston in said chamber and movement of said pilot valve to effect operation of said primary fluid motor and a variation in the output speed of the hydrostatic transmission upon operation of said secondary valve between the first and second conditions.

Claim 23

Apparatus for controlling the operation of a plurality of hydrostatic transmissions, said apparatus comprising hydraulic actuator means for varying the output speeds of the plurality of hydrostatic transmissions, said hydraulic actuator means including a plurality of primary fluid motors each of which is operatively connected with an associated one of the hydrostatic transmissions and is operable to vary the output speed of the associated hydrostatic transmission, a plurality of pilot valves each of which is connected in fluid communication with an associated one of said primary fluid motors and is operable to effect operation of the associated one of said primary fluid motors, and a plurality of secondary fluid motors each of which is operatively connected with an associated one of said pilot valves and is operable to actuate the associated one of said pilot valves to thereby effect operation of the associated one of said primary fluid motors to vary the output speed of the associated one of the hydrostatic transmissions, and hydraulic control means for controlling the operation of said hydraulic actuator means, said hydraulic control means including speed control valve means for effecting contemporaneous operation of each of said plurality of secondary fluid motors to vary the output speeds of each of the hydrostatic transmissions by substantially the same amount, conduit means for conducting fluid between said speed control valve means and said plurality of secondary fluid motors, and steering control valve means for varying the output speed of selected hydrostatic transmissions relative to each Other, said steering control valve means including a plurality of steering valves each of which is associated with one of said secondary fluid motors and is connected with said conduit means between said speed control valve means and the associated one of said secondary fluid motors, each of said steering valves being operable to effect operation of the associated one of said secondary fluid motors to operate the associated pilot valve and primary fluid motor to vary the output speed of at least one of the hydrostatic transmissions while maintaining the output speed of another of the hydrostatic transmissions substantially constant.

Claim 24

Apparatus for controlling the operation of a plurality of hydrostatic transmissions, said apparatus comprising hydraulic actuator means for varying the output speeds of the plurality of hydrostatic transmissions, said hydraulic actuator means including a plurality of primary fluid motors each of which is operatively connected with an associated one of the hydrostatic transmissions and is operable to vary the output speed of the associated hydrostatic transmission, a plurality of pilot valves each of which is connected in fluid communication with an associated one of said primary fluid motors and is operable to effect operation of the associated one of said primary fluid motors, and a plurality of secondary fluid motors each of which is operatively connected with an associated one of said pilot valves and is operable to actuate the associated one of said pilot valves to thereby effect operation of the associated one of said primary fluid motors to vary the output speed of the associated one of the hydrostatic transmissions, and hydraulic control means for controlling the operation of said hydraulic actuator means, said hydraulic control means including speed control valve means for effecting contemporaneous operation of each of said plurality of secondary fluid motors to vary the output speeds of each of the hydrostatic transmissions by substantially the same amount, conduit means for conducting fluid between said speed control valve means and said plurality of secondary fluid motors, and steering control valve means for varying the output speed of selected hydrostatic transmissions relative to each Other, said steering control valve means including a plurality of steering valves each of which is associated with one of said secondary fluid motors and is connected with said conduit means between said speed control valve means and the associated one of said secondary fluid motors, each of said steering valves being operable to effect operation of the associated one of said secondary fluid motors to operate the associated pilot valve and primary fluid motor to vary the output speed of at least one of the hydrostatic transmissions while maintaining the output speed of another of the hydrostatic transmissions substantially constant.

Claim 25

An apparatus as set forth in claim 20 wherein each of said secondary fluid motors includes a housing defining a chamber having first and second end portions and a piston disposed in said chamber and movable toward and away from said first and second end portions of said chamber, said conduit means including first and second fluid passage means for connecting said speed control valve means in fluid communication with each of said steering valves, third fluid passage means for connecting one of said steering control valves in fluid communication with the first end portion of one of said chambers, and fourth fluid passage means for connecting said one of said steering control valves in fluid communication with said second end portion of said one of said chambers, said one of said steering control valves being selectively operable between first and second conditions, said one of said steering control valves when in said first condition connecting said third fluid passage means and said first end portion of said one of said chambers in fluid communication with said first fluid passage means and said fourth fluid passage means and said second end portion of one of said chambers in fluid communication with said second fluid passage means, said one of said steering control valves when in said second condition connecting said third fluid passage means and said first end portion of said one of said chambers in fluid communication with said second fluid passage means and said fourth fluid passage means and said second end portion of said one of said chambers in fluid communication with said first fluid passage means to thereby effect movement of said piston in said one of said chambers and movement of the associated one of said pilot valves to effect operation of the associated one of said primary fluid motors and a variation in the output speed of the associated hydrostatic transmission upon operation of said one of said steering valves between the first and second conditions.

Claim 26

An apparatus as set forth in claim 7 wherein said speed control valve means includes means for controlling the fluid pressure conducted through said conduit means to said plurality of fluid motors, each of said fluid motors including pressure responsive means for effecting operation of the associated one of said fluid motors to an extent which varies as a function of variations in the fluid pressure conducted to the associated one of said fluid motors through said conduit means, each of said steering valves being selectively operable to vary the fluid pressure conducted to the associated one of said fluid motors to effect operation of the associated one of the fluid motors without operating said speed control valve means.