GB640796A - Improvements in or relating to electric switches for use on aircraft which are automatically operable in the event of crash or impact, and to aircraft crash or impact detecting systems - Google Patents

Abstract

640,796. Impact operated switches; switches held set and freed mechanically. GRAVINER MANUFACTURING CO., Ltd., and WILKINSON SWORD CO., Ltd. Aug. 27, 1948, No. 22610. [Class 38(v)] [Also in Group XXI] A switch for automatically actuating fire-extinguishing equipment in aircraft in the event of a crash, is operated by an independent release member attached to the aircraft surface skin and connected to the switch by a Bowden cable, such that when the skin is distorted the switch is operated. The switch 10 comprises a plunger 34 carrying a contact plate 41 urged by a spring 35 in the direction for bridging contacts 42, but normally retained by balls 37 cooperating with a waist in the plunger and apertures 39 in a fixed bush 32. A movable sleeve 31 which is centred relatively to connected to the switch release member by a cable 12 so that when the cable is pushed or pulled, due to distortion of the aircraft skin in a crash, a pair of recesses 50 or 51 come opposite the apertures 39 and the balls 37 release the plunger 34 which slides to bridge the contacts 42. The switch is reset by pressing a button 48 on the plunger and pushing or pulling the cable 12 to move the balls 37 back into the waist. Resetting is facilitated by a groove 61 in the sleeve 31 which is centred relatively to notches 60 in a window 59, the sleeve being located by a spring-urged ball 55 when in the set position. The switch is mounted on a support 70 in the aircraft not likely to be damaged in a crash and the other end of the cable sheath 13 is terminated in a sleeve 20 mounted in a gimbal device 21, 22 also fixed to the support 70. The cable 12 extends beyond the sheath 13 and is connected to the switch release member, comprising a ball 11 having lost motion within a socket 15, 16 secured to the aircraft skin 71 by a flanged fitting 16a. The unsheathed cable end is prevented from kinking by an involute gaiter spring 25 and is enclosed by flexible dust cover 26: In an alternative construction, not shown, the cable is held under tension by a spring and a frangible guard encloses the unsheathed ca,ble end and is interposed between the ball 11 and the sleeve 20 so that on shattering of the guard the spring moves the cable to operate the switch. The fire-extinguishing system comprises a number of such switches e, Fig. 8, together with inertia-operated switches i connected to energize a relay z and close relay contacts h which actuate fire-extinguishing cylinders f, g. Flame detector devices k illuminate lamps l in the event of fire on the aircraft engines and by pressing buttons m the pilot actuates the cylinder f immediately, the cylinder g being delayed in its action for a short time by a delay switch n. Specification 613,343 is referred to.