GB638503A - Improvements in hydraulic pressure regulating valve devices - Google Patents

Abstract

638,503. Fluid-pressure servomotor-control systems; valves. BENDIX AVIATION CORPORATION. Nov. 27, 1946, No. 35181. Convention date, Jan. 11. [Class 135] A pressure-responsive device in a hydraulic power system arranged to effect the rapid opening and closing of a pump byepass valve between predetermined upper and lower pressure limits in the system, comprises a piston 25 having large and small diameter heads 25e, 25a respectively, slidable in a stepped bore 28, 24 in a casing 1 and urged by a spring 29 towards the small end of the bore, and a spring-urged selector valve 26. The valve 26 is formed with a head 26b controlling an axial bore 25c in the piston and a coned end 26a engageable with the lower end of a stationary but adjustable ported stem 30 on which the piston slides, and which communicates with a tank 11. The piston 25 is reduced in diameter to form a space open through ports 25h to the piston interior and through a duct 32 with the underside of a piston 34, the upper side of which is connected to the tank 11. The piston 34 is operatively connected to the spring-loaded byepass valve 20. In the position shown, the byepass valve 20 is closed and the pump P is delivering liquid past a non-return check-valve 22 to a supply line 17 which may be fitted with an accumulator 13. On the pressure in the line 17 reaching a value determined by the loading of the spring 29, the piston 25 and the selector valve 26 are both urged upwardly until the end 26a of the latter engages the stem to isolate the underside of the piston 34 from the tank 11. On a further increase in pressure in the line 17, the piston 25 moves away from the valve head 26b and the pressure liquid immediately acts on the underside of the piston head 25e to snap the piston 25 away from the valve head 26b and supply pressure liquid to the underside of the piston 34 to cause the rapid opening of the valve 20. On the pressure in the line 17 now decreasing, the piston 25 first moves downwardly until it contacts the valve head 26b whence further downward movement thereof breaks the end 26a away from the stem 30 and immediately opens the underside of the head 25e and the underside of the piston 34 to the tank 11, to permit the closure of the byepass valve 20.