Patent GB-778292-A (GB)
Title: Improvements in or relating to emergency lighting systems for aircraft
Inventor: HORGAN WILLIAM FRANCIS
IPC: B64D47/02
Filed: 1951-04-17
Abstract: 778,292. Inertia switches. VENNER, Ltd., [formerly VENNER TIME SWITCHES, Ltd.]. April 16, 1952 [April 17, 1951], No. 8976/51. Class 38(5) [Also in Group XI]. An emergency lighting device for aircraft, e.g. for the purpose of providing illumination automatically after a crash or forced landing, comprises a source of current, e.g. a low voltage accumulator, and a lamp bulb. in a circuit including a pair of contacts which are normally electrically unconnected and are arranged to be connected by a displaceable means which is urged in the contact-connecting direction but normally restrained by inertia means which is supported in an equilibrium position by a resilient suspension so that a part of it engages with and prevents movement of the displaceable means, the resilient suspension being such that subjection of the inertia means to a shock having a component exceeding a predetermined magnitude in a number of different directions normal to a neutral axis will cause it to move from its equilibrium position and allow the displaceable means to move to its contact making position, there being also manually operable means whereby the contact-connecting means may be actuated without the inertia means having first been displaced. In the example the inertia means comprises two metal cylinders 25a, 25b connected together by a short axial spindle 26, and supported by four radially disposed helical tension springs 27 each anchored at one end to the spindle 26 and at the other end to either the back plate 3 or parallel face plate 16 of a mounting frame that has an apertured partition 17 below the lower cylinder 25b. The aperture 18 in the partition is normally obturated by a boss 28 on the bottom surface of the metal cylinder 25b, thereby preventing the upward movement of a rod 19, the top end of which is pressed upwardly through the aperture and against the boss 28 by means of a helical compression spring 24 around the rod 19. The spring 24 is located between the lower end of a spool member 23 of insulating material secured on the rod 19 at a position below the partition 17, and an'adjustable, externally threaded, bush 20 within which the bottom end of the rod 19 is slidably received. The top and bottom flanges 23a, 23b of the spool 23 are provided with conductive outer surfaces, each of which is normally spaced from a pair of contact blades 11a, 13a or 11, 13, which are mounted on the top and bottom edges of an insulating block 12 and project forwardly therefrom, the contact blades 11 and 11a being permanently connected together electrically by fixed conductors not shown, and the pair 13 and 13a being similarly connected. The blade 11 is connected by a 'lead 10 to one contact of a lamp bulb. 8 mounted in a socket 7. whilst the other bulb contact is connected to one battery terminal 4 by a resilient contact strip 5. the other battery terminal 4 and contact strip 5 being connected to the contact blade 13 by a lead 14. When a sudden force or shock causes the inertia mass 25a, 25b to move to such an extent that the boss 28 is moved clear of the aperture 18 in the partition 17, the rod 19 moves upwardly and the conductive surface on the upper flange of the spool 23 completes the lamp circuit between the contact blades 11a, 13a. The device may be reset by pulling a slidable shaft 29 outwardly by means of a manually operable knob 39, thereby tilting a bell-crank 31. 32, the latter arm of which is located between the flanges of the spool 23, which is thereby retracted. A hair-pin shaped spring 34 which is engageable with slots 35 and 36 spaced axially on the spindle 29 assists in positioning the spindle in its outermost or innermost positions. The lamp and battery may be tested by pulling the knob 39 outwardly, thereby lowering the rod 19 so that the conductive surface on the lower flange 23b of the spool connects the two contact blades 11 and 13 in the bulb circuit. The two pairs of contact blades 11, 13 and 11a, 13a maybe replaced by a single pair of blades spaced apart in a direction parallel to the axis of the rod 19 and disposed between the flanges of the spool 23, so that axial movement of the rod in either direction will cause the inner face of a flange to bear upon one contact and press it against the other.