GB820282A - Improvements in vibration actuated electric inertia switches - Google Patents

Abstract

820,282. Burglar and like alarms. CLARKE, M. July 29, 1957 [May 26, 1956], No. 16351/56. Class 118 (1). [Also in Group XXXVII] A vibration-actuated inertia switch assembly (see Group XXXVII) comprises a switch 12, which may be a mercury switch or a snapaction micro-switch, maintained open by a ball 6 balanced on the end of a switch-actuating arm 8, and is provided with setting means having a delay device 15 such that when the apparatus is mounted on a door the door may be closed before the resetting means has restored the ball to its balanced condition. A battery, or other source of electrical supply, 33, is connected in circuit with a main switch 24, micro-switch 12, indicator lamp 23, terminal block 26, wires 27, and alarm bell 25, as shown in Fig. 4. Depression of the end 21 of cranked pin 19 (Fig. 1) compresses spring 18 while the end 20 depresses the actuating arm 8 to open micro-switch 12 and allow the ball 6 to run to a hole in the centre of a dished platform 4 inside container 2. As the spring 18 reasserts itself against time delay device 15 the arm 8 is allowed slowly to rise until the ball 6 seats on a cup 10 on the end of arm 8 and stops further upward movement of the arm. The cranked pin 19 continues to rise till the end 20 is clear of arm 8. If the device is now subjected to vibration the ball 6 falls off the cup 10 and allows the arm 8 to rise fully, enabling micro-switch 12 to operate, thereby ringing alarm bell 25, or other visual or aural signalling device. Instead of lamp 23 remaining lit all the time switch 24 is closed, a contact may be arranged to flash a check lamp, the crank 19 touching it momentarily as it clears the arm 8. Instead of closing a circuit the microswitch 12 may open a circuit, closing a relay operating the warning system. Specifications 419,917 and 538,209, [both in Group XXXVII], are referred to.