Abstract: A hydromechanical drive wherein a prime mover drives an input shaft which, in turn, can drive a coaxial output shaft by way of a clutch or transmission having one or more axial piston pumps. The pressure and/or rate of fluid flow in the pump or pumps is adjustable by one or more valves or by one or more tiltable wobble plates in response to signals from one or more adjusting devices which receive signals from an electronic control circuit. The latter further receives signals from tachometer generators which monitor the RPM of the input and output shafts, from a gauge which monitors the pressure in the pump or pumps, from the valve or valves, or from the adjusting devices(s) for the tiltable wobble plate(s).

Abstract: A hydraulic pressure system comprising a hydraulic pump, a hydraulic motor, a pair of main hydraulic pressure lines connecting the pump and the motor so as to form a closed loop or circuit, a booster line for supplying a hydraulic pressure from a booster pump to the low pressure side of the closed circuit, a pilot line for taking out a pilot pressure from the high pressure side of the circuit to operate an actuator for controlling the hydraulic pump and the hydraulic motor, and a boost pressure regulator for causing the pressure in the booster line to rise only when the differential pressure between the two main hydraulic pressure lines of the closed circuit becomes lower than a predetermined level.

Abstract: A hydraulic transmission has a pump and a hydraulic motor which are in communication with each other through a fluid passage and each of which has an eccentric or inclined movable member that is moved to vary the volume of liquid discharged by the pump or motor, the pump receiving an input rotation that is developed from the motor as an output rotation of a varied rotational frequency. The hydraulic transmission further includes a first element for urging the movable member of the pump in a first direction, a second element for urging the movable member of the motor in a second direction; and an actuating mechanism which moves the movable member of the pump a distance proportional to a control input, and which, when the displacement of the pump is varied, retains the movable member of the motor to keep the displacement of the motor constant, and which, when the movable member of the pump is retained at a certain position, moves the movable member of the motor a distance proportional to the control input.

Abstract: A hydrostatic-transmission control system for fork-lift trucks and like industrial vehicles has at least one of variable-displacement hydrostatic motor driving wheels on opposite sides of the vehicle and supplied by a pump having a control element for varying its displacement under the control of an operator. The prime mover, e.g. a gasoline engine or electric motor, drives the pump. The control system comprises means whereby, for low and average output speeds of the transmission consisting of a combination of the pump and motors, the control of the transmission ratio is a function only of the operator-set position of the aforementioned element whereas, for the highest output speeds, the ratio is controlled by both the position of this element and by a further parameter, usually the output speed of the prime mover.

Abstract: An axial piston-type transmission in which a group of axially displaced pump pistons, that move in a cylinder block rotated by an input shaft, slidably engage one surface of a swash plate that rotates an output shaft. A group of axially displaced motor pistons, that move in a stationary cylinder block, slidably engage an opposite surface of the swash plate so that the plate is squeezed between the two groups of pistons. The swash plate is pivotally attached to the output shaft so that the angles between the two surfaces and the axis of rotation of the swash plate can be adjusted. The pump pistons and motor pistons are hydraulically connected in pairs. A rotary valve driven by the output shaft connects half the pump cylinders together hydraulically to form an output port and the other half together to form an input port.

Abstract: A hydrostatic transmission in which a hydraulic pump and motor are in a generally U-shaped arrangement with a fluid transfer manifold extending between the pump and the motor. The pump is driven on one side of the manifold by the drive motor of the vehicle on which the transmission is used, and a drive shaft from the motor extends through the manifold, to power the drive wheels on the other side of the manifold. A housing surrounds the pump, motor and manifold and contains hydraulic fluid for the operation of the transmission. Servo controls for the pump and motor are located on the outside of the housing, and a control cover has preloaded servo pistons which properly adjust the servo control when the cover is attached to the housing. A charge pump for the servo controls is in the manifold, and rigid tubular conduits extend between the charge pump and the control cover.

Abstract: Pump-motor hydraulic power system incorporation means to limit the power transmitted and the pressure in the transmission lines. High pressure line is connected to one end of a servo motor comprising a cylinder with a spring loaded piston therein. When the pump pressure increases above a certain amount it overcomes the spring and moves the piston and the piston rod to a blocking position, acting to limit movement of the three way control valve or to move the three way control valve back if it already exceeds the limit imposed by the power limiter's piston rod.

Abstract: A hydrostatic-transmission control system for fork-lift trucks and like industrial vehicles has at least one variable-displacement hydrostatic motor driving wheels on opposite sides of the vehicle and supplied by a pump having a control element for varying its displacement under the control of an operator. The prime mover, e.g. a gasoline engine or electric motor, drives the pump. The control system comprises means whereby, for low and average output speeds of the transmission consisting of a combination of the pump and motor, the control of the transmission ratio is a function only of the operator-set position of the aforementioned element whereas, for the highest output speeds, the ratio is controlled by both the position of this element and by a further parameter, usually the output speed of the prime mover.

Abstract: A power steering system for a wheeled agricultural tractor includes a pump circulating oil through a known steering-wheel-operated hydrostatic steering unit. A double-acting hydraulic cylinder communicates via conduits with the steering unit and is connectible to the tractor frame. A piston having a rod which projects from one end only of the cylinder is connectible to steer the tractor. A valve block interposed in the conduits causes oil displaced from the piston-rod end of the cylinder to flow to its other end when oil under pressure is supplied to said other end, and causes oil displaced from said other end to return directly to the steering unit when oil under pressure is supplied to the piston-rod end of the cylinder.

Abstract: A hydrostatic transmission is provided with a variable capacity pump and a variable capacity motor. A control is operable to operate sequentially the pump and motor. A second control is provided to operate on the pump to override the signal to the pump from the first control without altering the setting of the motor. The first control thus acts as a ratio selector and the second control as a clutch.