Abstract: A hydraulic pump arrangement and control circuit for supplying fluid at high volume and high pressure to a work circuit. The system utilizes a fixed displacement pump, a variable displacement pump with a compensator, and a relief valve at a pressure setting higher than the variable displacement pump's compensator setting.

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 fluid control system for master-slave power steering combinations includes master and slave steering units, a pump, a low pressure discharge line from the master unit, a low pressure transfer space in the slave unit and a low pressure return line to the pump. The transfer space receives heated, low pressure exhaust fluid through the discharge line from the exhaust chamber or space of the master unit. The fluid return line is connected to the transfer space of the slave unit to feed the intake side of the pump. Build-up of pressure in the slave unit is prevented. Secondly, the fluid circulated through the transfer space of the slave unit transfers heat generated in the pump and the master unit. The temperature gradient between the master and slave unit is thereby minimized to effect cooling or heating in the system, as needed. Further, build-up or accumulation of air bubbles in the slave unit is alleviated.

Abstract: An improved hydraulic drive system for a doubleacting hydraulic cylinder which drives or rocks the walking beam of an oil well pump. A closed circuit hydrostatic drive system is used to operate the double-acting hydraulic power cylinder unit and includes a variable displacement reversing swashplate pump driven at a predetermined constant speed by a prime mover such as an electric motor. Suitable automatic control means are provided for synchronizing the reversing movement of the swashplate with the rocking movement of the walking beam.

Abstract: A pressurized fluid supply apparatus comprises a closed circuit including a variable delivery pump, an open circuit including a pump, a fluid reservoir and a fluid cooler, and an engine for driving said pumps having an output shaft coupled to the drive shaft of said pumps, a flow-limiter being provided in the delivery conduit of said pump of said open circuit and including a restriction whose configuration is independent of the pressure of fluid in said delivery conduit upstream of said flow-limiter.

Abstract: An improved closed loop pneumatic system for driving a piston in a cylinder which employs a low pressure tank for receiving exhaust gases, a booster compressor transferring the gases to a high pressure tank which drives the piston on the up stroke. The constant interconnecting of a low pressure tank through a piston pressure equalizing the line improves the efficiency of the actuator. The larger, deep-well system utilizes an improved means for recovering and recirculating lubricating oil within the closed loop. Two species of the invention are described in this application. One primarily designed for deep wells and one designed primarily for shallow wells.