GB775756A - Improvements in or relating to fluid pressure control systems - Google Patents

Abstract

775,756. Automatic pressure control systems. MERCIER, J. April 9, 1954 [April 27, 1953], No. 11604/53.. Class 38 (4). [Also in Group XXXVII] In a system for maintaining fluid pressure within predetermined limits, a snap-action micro contact switch or switches, responsive to the fluid pressure, is associated with two external springs and switches on or off electrically-driven pumps or compressors supplying the fluid. In Fig. 1 fluid pressure acting on a diaphragm 11 moves a piston 2 in opposition to a spring 10 to operate the button 23 of a snapaction micro contact switch 12 through a rod 22 and a leaf-spring 24. The limited longitudinal movement of piston 2 in cylinder 1 prevents excessive deflection of diaphragm 11. The stiffness of spring 24 determines the switch differential. In a modification, Fig. 4, in which rod 22 operates switch button 23 through a pivoted lever 30 and a leaf-spring 24, button 23 is only operated when the end of screw 31 abuts spring 24 but not released until the end of lever 30 engages the turned over end of spring 24. In other modifications (not shown) rod 22 operates two micro contact switches in succession, one at the lower pressure limit and the other at the upper. In Fig. 6, fluid pressure acting on a diaphragm 62 moves a piston 33, having limited movement, to apply a force through a knife-edged strut 39 to a lever 38 to which an opposing force is also applied by a spring 41. Lever 38, which is pivoted at 43 and balanced against shock at 44, operates a microcontact switch 46 through a spring 50 and lever 49 at the upper pressure limit, and operates a micro contact switch 45 through a spring 56 at the lower pressure limit. In this arrangement springs 50 and 56 serve to determine the switch differentials. In Fig. 7 a diaphragm-operated piston 70, having limited movement, acts in opposition to springs 72, 73 in succession, to operate a micro contact switch button 76 through a spring 74. A large differential is obtained in this case by virtue of spring 74 and the fact that spring 73 becomes effective after spring 72.