GB587796A - Improvements in unloading valve - Google Patents

Abstract

587,796. Fluid-pressure servomotorcontrol systems. MERIT ENGINEERING, Inc. Oct. 27, 1944, No. 21000. Convention date, June 27. [Class 135] An unloading valve for a fluid-pressure system comprises a body 10, having bores 11, 25 connected at their ends, a main valve 40 in one bore normally subjected to high pressure at its opposite ends and a removable unit 26 in the other bore for controlling opening and closing of the main valve. High-pressure fluidenters through a port 20 and passes to the system by way of a check valve 100 and a port 18; the pressure of.this fluid being transmitted along a passage 27 to a chamber 62, past a pilot valve 78, which is normally held off its seat 76 by a spring 86, through passages 71, 72 to a chamber 74, and thence to a chamber 54, whore the pressure acts on the lower surface of the main valve, the area of which is greater than that presented to. high-pressure fluid at the main valve seat 36, so that the valve temains closed. When the pressure in the system rises to a predetermined value, the fluid pressure'on the pilot valve 78 overcomes the opposed pressure on a ball 85 and the pressure, due to the spring 86, and the pilot valve is closed, thus cutting off communication of the high-pressure fluid with the chamber 54. At the same time the ball 85 is raised from its seat to release the pressure in the chamber 54, through passages 66, 67 and a relief port 23. The main valve is then opened by fluid pressure acting on its end adjacent the seat 36, to permit fluid to flow from the inlet 20 direct to the relief port 23. When the pressure in the system has fallen to a lower limit, the spring 86 will reopen the pilot valve to allow fluid to enter the chamber 54 and again close the main valve.