Abstract: A hydro-pneumatic system has an air powered motor driving a hydraulic pump with a pressure limiting valve that turns off air flow to the air motor when a hydraulic pressure output by the pump at a sense port of the valve reaches a certain limit. A valve element of the valve has spring, hydraulic and pneumatic sections, with an unbalanced area of the hydraulic section in a sealed pressure chamber of a cartridge that is part of the valve housing. The pneumatic section extends out one end of the cartridge to fill a bore between the air inlet and outlet ports when the pneumatic section is extended, and allow air to pass when it is retracted.

Abstract: A hydro-pneumatic system has an air powered motor driving a hydraulic pump with a pressure limiting valve that turns off air flow to the air motor when a hydraulic pressure output by the pump at a sense port of the valve reaches a certain limit. A valve element of the valve has spring, hydraulic and pneumatic sections, with an unbalanced area of the hydraulic section in a sealed pressure chamber of a cartridge that is part of the valve housing. The pneumatic section extends out one end of the cartridge to fill a bore between the air inlet and outlet ports when the pneumatic section is extended, and allow air to pass when it is retracted.

Abstract: A hydro-pneumatic system has an air powered motor driving a hydraulic pump with a pressure limiting valve that turns off air flow to the air motor when a hydraulic pressure output by the pump at a sense port of the valve reaches a certain limit. A valve element of the valve has spring, hydraulic and pneumatic sections, with an unbalanced area of the hydraulic section in a sealed pressure chamber of a cartridge that is part of the valve housing. The pneumatic section extends out one end of the cartridge to fill a bore between the air inlet and outlet ports when the pneumatic section is extended, and allow air to pass when it is retracted.

Abstract: A rotary air motor driven hydraulic pump has separate pressure and return actuators and first and second stage eccentric driven pistons 180 degrees out of phase and driven by the motor through a gear reduction unit. The pressure and return actuators are on/off/proportional valves and the pump has two pressure relief valves with one adjustable from outside of the pump for a user to set a pressure limit of the pump. Above a certain output pressure limit, a bypass valve shunts flow in excess of that needed to precharge the second stage compression chamber from the first stage piston to an elastic reservoir from which the hydraulic fluid pumped by the pump is drawn. To make the pump stall at a certain output pressure, a pressure limiting valve can be used that cuts off the air supply to the pump at the desired output pressure.

Abstract: A rotary air motor driven hydraulic pump has separate pressure and return actuators and first and second stage eccentric driven pistons 180 degrees out of phase and driven by the motor through a gear reduction unit. The pressure and return actuators are on/off/proportional valves and the pump has two pressure relief valves with one adjustable from outside of the pump for a user to set a pressure limit of the pump. Above a certain output pressure limit, a bypass valve shunts flow in excess of that needed to precharge the second stage compression chamber from the first stage piston to an elastic reservoir from which the hydraulic fluid pumped by the pump is drawn. To make the pump stall at a certain output pressure, a pressure limiting valve can be used that cuts off the air supply to the pump at the desired output pressure.