Abstract: A multiple pressure direct acting relief valve is disclosed. The multiple pressure relief valve comprises an actuating cylinder, a relief valve and an adjustment screw interconnecting the actuating cylinder and the relief valve. The relief valve includes a low pressure spring which biases a poppet valve arrangement permitting the poppet valve arrangement to be actuatable at a first pre-determined pressure. The actuating cylinder includes a piston that is biased by a high pressure spring causing an additional compressive force to be applied to the poppet valve arrangement through an actuating rod received through the adjustment screw. When pressure is applied to the piston within the actuating cylinder, an additional compressive force is applied by the high pressure spring and the actuator rod to the poppet valve arrangement causing the poppet valve arrangement to be actuatable at a second pre-determined pressure.

Abstract: A multiple pressure direct acting relief valve is disclosed. The multiple pressure relief valve comprises an actuating cylinder, a relief valve and an adjustment screw interconnecting the actuating cylinder and the relief valve. The relief valve includes a low pressure spring which biases a poppet valve arrangement permitting the poppet valve arrangement to be actuatable at a first pre-determined pressure. The actuating cylinder includes a piston that is biased by a high pressure spring causing an additional compressive force to be applied to the poppet valve arrangement through an actuating rod received through the adjustment screw. When pressure is applied to the piston within the actuating cylinder, an additional compressive force is applied by the high pressure spring and the actuator rod to the poppet valve arrangement causing the poppet valve arrangement to be actuatable at a second pre-determined pressure.

Abstract: A gear pump having a bypass valve within its port end cover is disclosed. The bypass valve is spring biased to open, pressure to close, rather than being pressure compensated, preventing hydraulic fluid from being "bled off" during the entire work cycle. A butterfly type structure is utilized for the dry valve which is attached to the inlet of the gear pump thus eliminating the need for a cumbersome device for actuating same.

Abstract: A thrust plate for a gear pump or motor which permits the use of high pressure fluid from the outlet side thereof to lubricate the trunnions and bushings therein. The thrust plates include two small bores which pass therethrough the which are in fluidic communication with the inlet side of the pump via the surface of the thrust plate that confronts the gears within the pump. The foregoing bores are also in fluidic communication with the bushings by means of associated slots in the opposite side of the thrust plate. The opposite ends of the bushings are in fluidic communication with fluid at atmospheric pressure. By minimizing the size of the foregoing bores and by allowing the passage of fluid through same to the inlet side of the pump via the gear tooth confronting surface of the thrust plate, pressure gradients are created across the trunnions and their associated bushings.

Abstract: Method and apparatus are disclosed for counterbalancing the high pressure forces normally generated in the high pressure fluid region of a rotary pump or motor and exerted against the rotating structure of the pump or motor. By this method and apparatus a portion of the fluid in the high pressure region of the pump housing is transported to a region of the housing interior adjacent to, but out of communication with the low pressure fluid region. This transported high pressure fluid is directed against the rotating structure in the direction of the high pressure fluid region. Consequently, the rotating structure of the pump or motor is less subject to distortion or displacement due to forces generated by fluid in the housing's high pressure fluid region.