Vehicle with stepless drive and auxiliary braking force

Claim 2

A vehicle system comprising at least one vehicle having a plurality of traction wheels; respective hydraulic motors operatively connected with said wheels for driving same; an engine-driven pump for displacing a hydraulic fluid; a hydraulic supply conduit connecting said pump with said motors and a return conduit connecting said motors with said pump, said pump being of the variable displacement type; control means for regulating the displacement of said pump to vary the transmission ratio between pump-driving engine and said wheels, said pump and said motors forming a transmission operable in a vehicle driving and in a vehicle-retarding mode; at least one fluid operated friction wheel brake; a pressure sensor connected to one of said ducts and responsive to the operation of said transmission in a braking mode for applying fluid pressure to said friction brake in accordance with the degree of vehicle retardation by said transmission; and means for operating said friction brake independently of said sensor.

Claim 3

The system defined in claim 1 wherein said sensor is responsive to a pressure drop in said supply duct below a predetermined level.

Claim 4

The system defined in claim 1 wherein said sensor is connected to said return duct and is responsive to an increase in pressure therein above a predetermined level to operate said frIction brake.

Claim 5

A vehicle system comprising a towing vehicle having an engine; a wheel means provided with a traction-wheel drive; a stepless transmission on said towing vehicle connecting said engine with said drive for powering and retarding same in a driving mode and a braking mode of operation, respectively; a towed vehicle provided with an auxiliary vehicle brake operable to supplement the retarding action of said transmission upon said wheel means; driver-operated control means on said towing vehicle for said transmission; actuating means operatively coupled with said transmission for operating said auxiliary brake upon operation of said transmission in said braking mode, said transmission comprising at least one variable-displacement hydraulic pump connected to said engine, a hydraulic motor connected to said drive-wheel arrangement and conduit means connecting said pump and said motor in a closed fluid circuit, said control means being operatively connected to said pump for varying the displacement thereof, said actuating means including a pressure-responsive device connected to said conduit means and effective upon a change in pressure therein signifying said braking mode, said conduit means including a supply line connecting the output of said pump with the input of said motor and a return line connecting the input of said pump with the output of said motor, said device comprising a fluid-operated cylinder connected to one of said lines, said pump being constructed and arranged to reverse the flow direction through said lines and interchange the functions thereof; and a switchover valve connected between said cylinder and functionally identifal lines regardinless of the direction of displacement of said fluid through said lines as determined by said control means.

Claim 6

A vehicle system comprising a towing vehicle having an engine; a wheel means provided with a traction-wheel drive; a stepless transmission on said towing vehicle connecting said engine with said drive for powering and retarding same in a driving mode and a braking mode of operation, respectively; a towed vehicle provided with an auxiliary vehicle brake operable to supplement the retarding action of said transmission upon said wheel means; driver-operated control means on said towing vehicle for said transmission; actuating means operatively coupled with said transmission for operating said auxiliary brake upon operation of said transmission in said braking mode, said transmission comprising at least one variable-displacement hydraulic pump connected to said engine, a hydraulic motor connected to said drive-wheel arrangement and conduit means connecting said pump and said motor in a closed fluid circuit, said control means being operatively connected to said pump for varying the displacement thereof, said actuating means including a pressure-responsive device connected to said conduit means and effective upon a change in pressure therein signifying said braking mode, said conduit means including a supply line connecting the output of said pump with the input of said motor and a return line connecting the input of said pump with the output of said motor, said device comprising a fluid-operated cylinder connected to one of said lines, said pump being constructed and arranged to reverse the flow direction through said lines and interchange the functions thereof; and a switchover valve connected between said cylinder and functionally identifal lines regardinless of the direction of displacement of said fluid through said lines as determined by said control means.

Claim 7

The system defined in claim 4 wherein said cylinder is connected to said supply line and said actuating means is responsive to a pressure drop in said supply line below a predetermined level.

Claim 8

The system defined in claim 4 wherein said cylinder is connected to said return line and said actuating means is responsive to an increase in pressure in said return line above a predetermined level to operate said auxiliary brake.

Claim 9

The system defined in claim 4 wherein said one of said lines is said return line and said actuating means constructed and arranged to apply a braking force to said auxiliary brake in a predetermined relationship with the pressure in said return line.

Claim 10

The system defined in claim 4, further comprising a linkage mechanically connecting said switchover valve with said control means.

Claim 11

The system defined in claim 4, further comprising means in said conduit means and connected to said switchover valve for automatically operating same in accordance with the direction of displacement of fluid through said conduit means.

Claim 12

The system defined in claim 4, further comprising means connected to said control means for mechanically operating said actuating means in a neutral position of said pump.

Claim 13

The system defined in claim 4, further comprising a source of ancillary fluid pressure connectable to said actuating means by said switchover valve for operating said cylinder.

Claim 14

The system defined in claim 4 wherein said actuating means comprisies a valve housing defining a first compartment communicating with the atmosphere, a second compartment adjacent said first compartment and communicating with said brake, a third compartment communicating with said second compartment, and a valve member connected to said cylinder and displaceable in response thereto, said valve member being provided with a pair of heads respectively blocking communication between said first and second compartments and between said second and third compartments in alternate positions while permitting such communication in other position; said switchover valve having a valve body provided with three positions including a first working position connecting said cyLinder with one of said lines, an intermediate position, and a second working position connecting said cylinder with the other of said lines, said cylinder being connected with neither of said lines in said intermediate position.

Claim 15

The system defined in claim 12 wherein said control means includes two driver-controlled levers respectively displaceable for forward and reverse operation, and a bellcrank lever connecting said driver-controlled levers with said pump for displacement thereof in opposite directions, further comprising a compressed-air source connected with said third compartment.