Abstract: An electro-hydraulic control for a hydrostatic transmission including a variable displacement hydraulic pump and fluid operable servos to vary the displacement of the pump. The electro-hydraulic control is in series between the charge pump and the standard manual controller and determines the maximum pressure of the charge fluid ported to the standard controller. The electro-hydraulic control includes a spool biased toward a first position to port fluid from the charge pump to the standard controller, and biased toward a second position to relieve to tank the pressure of fluid ported to the manual controller. The biasing toward the second direction is accomplished, in part, by pressure in a fluid chamber exerting a biasing force on the spool, the fluid chamber being in communication with drain through a variable orifice which is variable in response to a pressure command signal.

Abstract: A system for controlling the operation of a reversible hydrostatic transmission including an engine-driven pump, particularly for a self-propelled utility vehicle such as a forklift truck, comprises a switchover member coupled with a setting lever of the hydrostatic pump which is biased by a pair of counteracting springs into a normal centered position. A shift lever, upon being moved from "neutral" to "forward" or "reverse", causes a displacement of the switchover member into a corresponding off-normal position by a fluidic or electromagnetic directive force generally proportional to engine speed.

Abstract: A hydrostatic transmission is disclosed which includes a pump assembly in which a main pump, a charge pump, and an auxiliary pump are commonly housed and are drivingly connected to a single shaft assembly. An external fluid connection is provided through which fluid is directed from the auxiliary pump to a power take off, and valving is provided to short circuit the auxiliary pump when power is not demanded. Means of controlling the rate of operation of the valve are also provided to prevent excessive pressure rise rates at the outlet of the auxiliary pump upon actuation of the valving.

Abstract: A hydraulic system and control valve assembly therefor characterized in that it provides a two wheel pressure compensated hydraulic drive for mobile equipment in forward or rearward direction at any speed up to maximum as determined by the operation of the control valve assembly. Said control valve assembly is further characterized in that it incorporates an override for the pressure compensating means to achieve steering control by decreasing the rate of flow of fluid to either wheel motor or to achieve braking action in conjunction with a counterbalance valve in the motor return circuit by decreasing the rate of flow of fluid to both wheel motors.

Abstract: A hydraulic pump apparatus including an outer housing having internal walls which are spherically configured, a hydraulically actuable variable position control ring which cooperates with the spherical housing walls to define the geometry of a hydraulic working cavity, and a rotor assembly having vanes which divide the working cavity into a plurality of working chambers and which follow the position of the control ring to vary the volume of the working chambers so as to move fluid into and out of inlet and outlet ports, respectively. The vanes are supported by a plurality of concentric rings which are attached in gimbal fashion to a rotor hub and pin assembly.

Abstract: A mixed loop hydrostatic transmission circuit for use principally with orbit, gear, vane and other non-piston type motors, which generate contaminants making them less suitable for applications using conventional closed loop hydrostatic transmission circuits. The mixed loop hydrostatic transmission drive retains the precise load control and high efficiency of a closed loop system, while introducing the benefits of contamination control of open loop hydrostatic transmission circuits. While maintaining the speed of the motor proportional to the output flow of the pump, both in positive and regenerative modes of operation, the flow of fluid is diverted from the motor to an injector type inlet booster connected to the reservoir, which supplies the full flow of fluid, required by the pump.

Abstract: A hydrostatic transmission for accelerating, driving and braking a high inertia load, such as the swing mechanism of a power shovel or crane, includes an engine-driven swashplate-type variable displacement constant speed reversible main hydraulic pump coupled in a closed loop circuit to a swashplate-type fixed displacement variable speed reversible hydraulic motor. A pair of control lever operated pilot pressure modulated pump displacement control valves selectively direct control fluid from an engine-driven fixed displacement constant speed charge pump to the stroking pistons of the servo control cylinders on the main pump to thereby control motor direction and speed. The charge pump also supplies replenishing fluid to the main pump/motor circuit through replenishing check valves.

Abstract: An auxiliary hydrostatic drive system for a vehicle includes a pump, a reservoir, fluid motors connected to the normally non-driven steerable wheels of the vehicle, reciprocating piston-type wheel drive motors connected to the normally nondriven steerable wheels, fluid lines interconnecting the pump and reservoir with the inlet and outlet ports of the wheel motors, and a motor control valve movable to either side of a neutral fluid blocking position to forward and reverse drive positions. An additional valve interconnects the motor ports with the drive chambers of the motors whenever the motor control valve is in the neutral position so that during periods when the motors are not connected to the pump and are driven mechanically, they function as pumps to pressurize their drive chambers and hold their pistons off the drive cams.

Abstract: A normally closed solenoid valve operates conjunctively with a two position pilot valve to limit the amount of engine braking through the drive train of a vehicle by reducing the drive relief valve setting in the disengaged side of a hydrostatic transmission. A second normally closed solenoid valve operates a second two position pilot valve to modulate the rate that the forward drive relief valve in the engaged side of the transmission hydrostatic drive loop permits drive pressure to build up as the vehicle is started in motion. An electrical switch on the transmission control rod initiates activation of the normally closed solenoid valves when the vehicle operator selects a direction of travel.

Abstract: The hydrostatic transmission includes a main pump having a plurality of reciprocating pistons projecting into and biased towards a drive chamber and has both its inlet and its drive chamber connected to a substantially constant pressure charge circuit. Displacement of the pump is controlled by controlling the fluid flowing from the charge circuit to the inlet. The pump outlet is connected to the drive chamber through a combined safety and inching valve which normally blocks fluid flow therebetween but which is responsive to excess pressure at the pump outlet to open and increase the pressure in the drive chamber. The valve is also manually operable through a pedal on the vehicle which can be used to destroke the pump in emergency situations or to provide inching control.

Abstract: A first pump and a second pump have respective mechanical inputs and are operative when the mechanical inputs are driven at constant speed for pumping fluid at an adjustable volumetric flow rate and at a constant non-adjustable volumetric flow rate, respectively, the maximum volumetric flow rate of the first pump being at least as great as that of the second pump. Connecting conduits connect the first pump in hydraulic circuit with an hydraulic consumer. An adjusting mechanism is provided for adjusting the volumetric flow rate of the first pump. A control arrangement is provided for bringing the second pump into and out of hydraulic circuit with the consumer in dependence upon the operation of the adjusting mechanism.

Abstract: A control valve for a variable displacement pump or motor. The valve includes a pair of solenoids which are independently actuatable to port relatively high pressure fluid to their respective servo motor. A shuttle valve actuated by the high pressure fluid is used to simultaneously port the fluid from the other servo motor to a low pressure fluid source. A manual valving system is also provided having a pair of balls each biased into engagement with a seat to seal a passage to one of the servo motors. Movement of either ball off of its seat allows high pressure to flow to the respective servo motor. The high pressure fluid actuates the shuttle valve to port fluid from the other servo motor to the low pressure fluid source.

Abstract: A mixed loop hydrostatic transmission circuit for use principally with orbit, gear, vane and other non-piston type motors, which generate contaminants making them less suitable for applications using conventional closed loop hydrostatic transmission circuits. The mixed loop hydrostatic transmission drive retains the precise load control and high efficiency of a closed loop system, while introducing the benefits of contamination control of open loop hydrostatic transmission circuits. While maintaining the speed of the motor proportional to the output flow of the pump, both in positive and regenerative modes of operation, the full flow of fluid is diverted from the motor to the reservoir, while the full flow of fluid, required by the pump, is supplied directly from the system reservoir.

Abstract: A hydrostatic unit of the type contemplated by the present invention includes one or more pump and motor combinations interconnected by means of a conventional closed loop. Controls for the hydrostatic unit include a speed control and vent valve assembly together with a venturi manifold which function together to normally establish a selected pressure differential in a pair of supply conduits for determining instant operating conditions for the transmission. In order to automatically regulate displacement of each pump unit in response to engine or prime mover speed as determined by load conditions, an underspeed actuator valve unit includes a piston which is hydraulically responsive to the differential pressure in order to adjust the effective moment arm for a lever which controls displacement of the pump unit.

Abstract: A hydrostatic unit of the type contemplated by the present invention includes one or more pump and motor combinations interconnected by means of a conventional closed loop. Controls for the hydrostatic unit include a speed control and vent valve assembly as well as a venturi manifold which functions to normally establish a selected pressure differential in a pair of supply conduits. In order to automatically regulate displacement of each pump unit in response to both engine or prime mover speed and instant load conditions, an underspeed actuator valve unit is hydraulically responsive to the differential pressure in the two conduits and also to changes in output pressure developed by the pump unit.

Abstract: A stepless, preferably hydrostatic, transmission is provided for an internal-combustion engine and the system is controlled by an operating member. A mechanism connects the members to the transmission and the engine so that both the engine and the transmission controls respond to this member. Means is provided for affecting the linkage in response to the torque on the transmission shaft, preferably in dependence upon the pressure in a transmission-fluid line.