Abstract: A low friction proportional unloading valve mechanism for pressurized fluid circuits incorporating a valve housing forming primary and bypass fluid circuits. A normally closed unloading valve normally prevents the flow of incoming fluid to the bypass fluid circuit and is opened by a pressure responsive valve actuator. The valve actuator forms a pressure responsive wall and may take the form of spaced diaphragms or a deformable flexible hose that induces opening force to the unloading valve in direct proportion to the pressure in the primary fluid circuit. Upon opening of the unloading valve, a check valve in the primary fluid circuit prevents back flow and thus maintains valve controlling pressure on the movable wall structure of the valve actuator.

Abstract: A reciprocating pump mechanism having a pump body forming a fluid inlet chamber and opposed pump cavities in communication with the fluid inlet chamber. The pump employs a piston having opposed pumping extremities adapted for pumping entry into the respective pumping cavities and is of a length such that with one pumping extremity positioned to its full extent within a pumping cavity the opposite pumping extremity there of is disposed in fluid inletting relation with the opposite pumping cavity. The piston may also include opposed drive shafts at least one of which extends from the pump body. One of the piston shafts may be adapted to be driven by any suitable reciprocating prime mover while the opposite piston shaft is adapted for connection to a similar exposed piston drive shaft of a similar double-acting piston pump to thereby provide for connection of the pumps in tandem driven relation by a single prime mover.

Abstract: Method and apparatus for recovering leaked fluid or directing fluid flow or propagation through utilization of negative pressure pulses occurring in a pressurized fluid system. The invention has particular application in double acting hydraulic fluid motors where leakage of hydraulic fluid past the output shaft seal may be efficiently collected and redirected into the pressurized hydraulic fluid system through utilization of negative pressure pulses that are developed periodically by fluid direction changes during operation of the hydraulic fluid motor.

Abstract: A fluid energized double acting motor is provided for use as the drive for reciprocating mechanisms such as paint pumps for airless spray painting. A piston within the pump housing is moved by pressurized fluid controlled by an automatic reversing valve including spaced check valves. The check valves are selectively seated and unseated by a spring biased piston and fluid pressure controlled valve actuator assembly. The reversing valve system includes anti-stalling features and is of single, low cost, field repairable nature. The motor system also includes features to prevent chattering oscillation due to abrupt changes in motor load.

Abstract: A pump control module is provided which may form an integral part of a variable volume pump or which may take the form of a pump attachment and which is operative to continually vary the volumetric output in inverse proportion to the operating pressure at the pump discharge so as to utilize a high percentage of the available horsepower at maximum output over a portion of the operating range of the pump.