Improvements in or relating to valve assemblies particularly for pumps

摘要

605,862. Relief valves. THOMPSON PRODUCTS, Inc. March 31, 1944, No. 6017. Convention date, March 26, 1943. [Class 135] A combined relief and byepass valve assembly for pumps especially fuel pumps for aircraft, comprises an open-ended sleeve 50 formed intermediate its ends with a wall 50c having an external valve face 50d and an internal valve seat 50e for the byepass valve 55. In Fig. 2, the assembly is shown in a positive displacement type of pump having an eccentric rotor 20 with slidable vanes 21 operating in a sleeve 19 arranged between inlet and discharge chambers 17, 18 in a pump casing 11. The valve assembly is arranged in a casing 12 between the pump casing 11 and a spring casing 13, the three casings being secured together by bolts 14. A diaphragm 16 of synthetic rubber or fabric impregnated with synthetic rubber is clamped between the casings 12 and 13. The chambers 17, 18 connect respectively with passages 29, 31 which in turn open through respective ports 30, 32 into counter-bores 24, 26 in the valve casing 12. A seat 25 for relief valve face 50d is formed between the bores 24, 26. The valve sleeve 50 is guided at its upper end by a flange 50a working in the bore 24 and at its lower end by cylindrical faces 50g on legs 50f working in a further bore 27. Ports 51 are formed in the sleeve 50 below the flange 50a to permit access of fluid to the interior of the sleeve 50. The byepass valve 55 like the relief valve 50 may be made of metal or of plastic material and has on its upper face a resilient washer 58 of fabric impregnated with synthetic rubber held in place by a dished metal spring washer 59 itself retained by a cotter-pin 60 passing through a boss 55b on the byepass valve. The byepass valve is loaded by a light spring 57 abutting a shoulder 28a on the valve casing. The relief valve 50 is loaded by a coil spring 41 having an upper retainer 39 adjustable on a screw 36 and a lower retainer 42. The latter has a boss 42a pressing into a complementary depression 43a in a washer 43 and thence through the diaphragm 16 into a similar depression in an inverted cup member 53 resting on shoulders 50h on the relief valve. The spring retainer 39 is prevented from rotating by a key 40. The screw 36 has a flange 36b which after adjustment of the screw is clamped against the underside of the casing 13 by a nut 38 threaded on a wider part 36c of the spindle. The upper side of the diaphragm 16 is subject to the pressure of the ambient air or to the pressure in the engine intake manifold through an aperture in a boss 13b. A washer 33 determines the effective area of the diaphragm.