GB1427764A - Pressure switches - Google Patents

Abstract

1427764 Fluid pressure actuated switches HANS SASSERATH & CO KG 25 Oct 1973 [28 Oct 1972] 49609/73 Heading H1N A fluid pressure actuated switch comprises a first piston 38 which can travel as far as abutment 36 under the influence of a pressure in duct 26, a second piston 42 sealed to and sliding within a bore of piston 38, biased against the pressure by a spring 64 (acting via spindle 52) and having an abutment 46 limiting its spring biased travel within the first piston against the applied pressure and a bi-stable electric switch 72 actuated in opposite senses by movement of first piston 38 against the pressure and of second piston 42 with the pressure against the force of spring 64. Mutatis matandis the piston may be replaced by diaphragms or bellows. A high pressure in duct 26 moves both pistons 38, 42, against spring 64, Outer piston 38 stops at shoulder 36 whilst inner piston 42 continues to move, lifting spindle 52 until the lower pair of locknuts 70 moves switch lever 74. As the pressure drops, the second locknut pair 68 does not engage switch lever 74 until abutment 46 has engaged the outer piston 38 and both pistons have moved together away from abutment 36, thus providing a pressure (and time) interval between switching on and off microswitch 12. The locknuts 68, 70 are adjustable in position on spindle 68. Lever 76 extends through hole 76 in wall 12 of upper casing 18. The switch may be used to control the pump of an hydraulic system.