GB542568A - Improvements in or relating to fluid pressure regulating devices for fluid supply systems - Google Patents

Abstract

542,568. Relief-valves. AUTOMOTIVE PRODUCTS CO., Ltd., CLENCH, E. C. S., and CARLTON, Q. H. Dec. 6, 1940, No. 17393. [Class 135] A relief-valve device for use in connection with a constantly driven pump feeding an accummulor or other device through a non-return valve is actuated by a piston or like device acting through a lost-motion connection. The piston device is urged in the valve closing direction by a main spring and in the opposite direction by an auxiliary spring so arranged that as the piston device moves from the valve closed towards the valve open position said auxiliary spring ceases to exert force on the piston device before it moves the valve member away from its seat. In the form shown in Fig. 1 the actuating device comprises a pair of pistons 33, 39 arranged in tandem. The smaller piston 33 has a packing 35 and is subject to the pressure in the pump delivery conduit on the side of a non-return valve 22 remote from the pump 16 and has its movement limited by a flange 38 co-operating with the shoulder between the bores. The larger piston 39 has a packing 40, is subject to pump delivery pressure and has a short spindle adapted to be engaged by the piston 33. The piston 39 is extended across a casing 11 to slide in a bearing 73 and is loaded by the main spring 75 arranged between a packed adjustable abutment 79 and an abutment 76 mounted on a reduced extension of the piston. The auxiliary spring 26 is arranged between an adjustable packed abutment 27 and a sliding abutment engaging a short spindle on the piston 33. Movement of the abutment is limited by shoulder 32. Abutments 71-72 on the piston 39 co-operate with a roller 70 on a lever 60 pivoted at 61 and carrying a pin 59 moving in a slot 58 in a link 57 pivoted to the valve member at 56. The free end of the lever moves between stops 68, 69 under the action of a spring strut arranged between the end of the lever and an adjustable abutment 65. The valve member which slides in a bore 45 comprises a cylindrical part 51 adapted to control communication between passages 44, 14 leading to the pump delivery and the chamber 11 connected by a pipe 13 with a reservoir 12. The valve is normally retained in its closed posiiton by a spring-pressed ball catch 55 engaging a groove 54 in the valve member. As pressure builds up in the conduit 14 the pistons move towards the right. After the abutment 31 reaches the shoulder 32 the piston 39 continues alone until the spring strut passes its dead centre position when it snaps over to open the relief passage. This causes the pressure acting on the piston 39 to fall and it moves back under the influence of the spring 75 until the spindle engages the piston 33, subject to accummulor pressure, and moves the auxiliary spring abutment 31 from the shoulder 32. This brings the spring strut nearly to its dead centre but leaves the valve in the open position. When the accummulor pressure falls a predetermined amount the spring tumbler snaps over and closes the relief valve.