HYDRO-PNEUMATIC SYSTEM WITH PRESSURE LIMITING VALVE

摘要

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.

主权项

1. A method of operating a hydraulic system, the hydraulic system including a hydraulic pump in communication with a source of hydraulic fluid and operable to draw fluid from the source of hydraulic fluid and deliver the fluid under a supply pressure, an air motor in communication with and powered by a source of compressed air and operable to drive the hydraulic pump, and a pressure limiting valve including a valve housing having an air inlet port in communication with the source of compressed air, an air outlet port and a hydraulic fluid sense port, and a valve element movably supported in the housing and having a hydraulic section in fluid communication with the hydraulic fluid sense port and a pneumatic section in fluid communication with the air inlet port and the air outlet port, the method comprising:
applying a pressure from the hydraulic pump to the hydraulic fluid sense port; when the pressure is below a pressure limit, positioning the valve element in an open position to provide fluid communication between the air inlet port and the air outlet port; and when the pressure is at the pressure limit, moving the valve element toward a closed position to close fluid communication between the air inlet port and the air outlet port.