GB568427A - Improvements in or relating to relay action electric switches, more particularly foruse in conjunction with fluid pressure systems - Google Patents

Abstract

568,427. Fluid-pressure servomotorcontrol systems. AUTOMOTIVE PRODUCTS CO., Ltd., and CLENCH, E. C. S. Aug. 23, 1943, No. 13735. [Classes 69 (ii) and 135] [Also in Group XXXVII] An electromagnetic switch 65, which has main contacts 66, 67, 68 controlling a motor 11 driving a pump 10 in a hydraulic system; has retaining contacts 69, 70, 71 and an operating coil 72 and is associated with a controlling device consisting of a handle 34 movable either way from a central position and two contacts 56, 57 which are successively engaged when the handle is moved, the contact 56 being in series with contacts 69, 70 and the contact 57 in ' parallel with the contacts 69, 70. The handle 34 is returned to its central position by a spring 39 and also serves to operate a valve 18 admitting pressure fluid driven by the pump 10 to one side or other of a piston 29. Movement of the handle rotates a metal disc 51 permanently connected through a contact 55 with the coil 72 and the line 62. The contact 56 is situated in a narrow gap in the disc and the contact 57 in a wider gap so that operation of the handle either way causes the disc to engage first contact 56 and then contact 57. Engagement of contact 56 produces no effect, since contact 71 is disengaged, but engagement of contact 57 completes a circuit through the coil 72 to earth. The switch 65 then closes all its contacts and the motor drives the fluid through pipe 24 or 25 to'the hydraulic device. When the handle moves back the coil 72 remains energized through retaining contacts 71 till the contact 56 is disengaged at the very end of the stroke of the handle. In a modification, the handle operates a Y-shaped member which drives one or other of two metal slides carrying projections which successively engage contact springs.