GB746441A - Relief valve - Google Patents

Abstract

746,441. Fluid-pressure servomotor-control systems. DROITCOUR, H. A., and DROITCOUR; J. M. May 3, 1954, No. 12793/54. Class 135. A relief valve comprises a main valve plug 31 controlling a conduit between an inlet port 12 and an outlet port 13 and connected to a pressure-responsive member 32 movable in response to the difference between inlet port pressure in a chamber 35 having a restricted connection 65 with the inlet port 12 and a control port 37 for venting the chamber, the port 37 being closed against the pressure within the chamber 35 by a pilot valve plug 40 mechanically connected to a control member 57 responsive to the inlet port pressure and blocking a second conduit between the inlet port and the outlet port, the control member 57 being loaded by a spring 49. In Fig. 1 the spring acts through a pivoted member 54, which engages both the plug 40 and the control member 57. The working parts of the valve are all assembled in a unit 15 removably mounted in a bore 11 of a housing 10. The unit 15 is sealed by O- section rings 16, 17, and is held against rotation by a screw 19. The pressure-responsive member is formed as a grooved piston 32 integral with the plug 31 and slides in a bore 20 open to the inlet by a port 34. The piston may have a fit which allows some leakage of the inlet fluid into the chamber 35 or a restricted passage 65 may be provided in the piston. The plug and piston unit 31, 32 is pressed by a spring 36 against a seat formed on a block 23. The block 23 rests on a screwed plug 21 and has a bore 24 which connects by channels 25, 27 with the exhaust port 13. The pilot valve plug 40 is guided by a coil of wire 42 and co-operates with a seat 39. The upper end of the plug 40 engages a recess in the member 54 which is pivoted at 55 in a slot 44. The control member 57 is formed as a piston and has an 0-section packing 62 and a projection 58 to engage a recess in the lever member 54. The loading spring 49 is adjusted by a screw 50 carrying a lock-nut 66 and engaging a slidable block 46 above the spring 49. The inlet pressure has access to the piston 57 through channels 64, 63, which with the inlet port are sealed by a ring 18. In a modification, the pistons 32, 57 are replaced by bellows and the pilot bellows operates on a yoke carrying the pilot valve.