GB391985A - Improvements in thief resisting shutters for the protection of shop premises and thelike - Google Patents

Abstract

391,985. Window guards. LEWIS, F. J., Exeter Works, West End Lane, Kilburn, London. Aug. 9, 1932, No. 14533. [Class 20 (iii).] Relates to protecting shutters for shop windows and the like, of the kind in which the shutter is held in its retracted position by means associated with an electromagnet and is released to fall into its operative position when the circuit of the electromagnet is interrupted as the result of the breakage of the window. According to the invention, the circuit is closed by a switch comprising two arms which become separated when the window is subjected to a heavy shock but which move together when a steady pressure or only a slight vibration is applied to the window. In the form shown, the shutter comprises a plurality of telescopic tubes each consisting of a number of sections 4-9, Fig. 1, which are carried by cross-bars 10 .. 13. In the raised or inoperative position, the sections 5 .. 9 are housed in the uppermost section 4 and are retained thus by a pivoted bell-crank lever 21 which engages with a pin 20 on the lowermost cross-bar 13. The horizontal arm of the lever 21 is pivotally connected to the armature of an electromagnet 25, arranged in a circuit which is normally closed by contacts 26, 27 on two pivoted levers 28, 29, Fig. 3. These arms are held together by two springs 32, 33, the tension in the latter being adjusted by means of a nut 34. A piece of strip metal 30 firmly held at its upper end and bearing against the window 1 at its lower end is adapted to register the shocks and vibrations received by the window and to transmit such movements to the lever 29 by means of an arm 31. With a slight shock or steady vibration, the springs 32, 33 keep the contacts 26, 27 together; under a sudden shock, the contacts are separated by the arm 31, thus breaking the circuit and releasing the lever 21 from its engagement with the cross-bar 13. The cross-bars are recessed at their ends to engage a rib on the side frames 19 of the window 1. A section 35, Fig. 6, of this rib may be pivoted to the remainder and carries a contact 37 which closes the circuit of an alarm bell 39 should a wedge be inserted between this section and the cross-bar 13. A spring-urged member may be provided on the window sill to engage with and hold the lower ends of the sections 9, and spring clips on the cross-bar 13 engage with an annular rib 15 on each member 9 when the shutter is collapsed.