GB662067A - Improvements in or relating to fluid pressure operated electric switches - Google Patents

Abstract

662,067. Fluid actuation of switches. CONSOLIDATED VULTEE AIRCRAFT CORPORATION. March 4, 1949. [March 5, 1948] No. 5973/49. Class 38 (v). A fluid-pressure actuated switch comprises a chamber 57 containing a micro-switch 75 the operating button 76 of which is operable by a trigger 64 mounted on an extension 61 of a piston rod 32. The piston 31 is slidable in a lined cylinder 18 against the action of a weak spring 42 and a strong spring 43 which normally hold the piston against a stop 28. The lefthand face of the piston is exposed to pressure through bores 48, 51 in stop 28 and a hole (not shown) in the cylinder 18. The structure is mounted on the nose casing of an aircraft engine, Fig. 4 (not shown), which, as it is run up, increases the pressure and moves the piston to the right so as to compress spring 42' Further increase in pressure causes compression of spring 43 also and the trigger is moved past the button 76 of the switch, which is not actuated, however, since the trigger pivots counter-clockwise against the action of a spring 65 when it engages the button 76 and then snaps back to its normal position with a stop 71 engaging the extension 61. The piston stays in this position until the engine torque drops, whereupon the spring 43 moves the piston sharply to the left, but exhausts itself at the moment when the trigger engages the button 76 to actuate switch 75. The continued slow movement of the piston due to spring 42 keeps the trigger and button in contact for a prolonged time thus ensuring that the switch 75 is really actuated. The springs 42, 43 surround a sleeve 33, the end 34 of which acts as a piston stop, having a flange 35 pressed against a washer 36 covering one end of a stuffing box 38. The washer has a number of small holes so that any fluid that leaks past the piston may escape to atmosphere through a second hole (not shown) in the cylinder.