GB148602A - An improved burglar or thief alarm - Google Patents

Abstract

148,602. Cressall, F. March 31, 1919. Theft and like alarms.-In alarms of the kind in which a circuit is closed by movement of a rolling ball or a pendulum from its central position, the support for the ball or pendulum is itself mounted to allow a swinging movement independent of the movement of the pendulum &c., and of the article to which the device is attached. Means may be provided for damping such movement of the support. The device is described as particularly applicable to motor-cars, and the independent movement above referred to allows the device to adjust itself, for example, when the car is inclined by the camber of the road, without operating the pendulum or ball contact. Fig. 1 shows a contact ball a<7> normally resting in a recess or seating in a ball a<5> itself forming the upper end of a pendulum b, which tends to hang so as to keep the seating horizontal. Movement of the member b is damped by fins b<1> immersed in a viscid liquid such as glycerine. When the ball is displaced by a sudden movement, it closes circuit between the support a<4> on which it rests and an insulated contact ring b<4>. The ball is attached to a light chain b<5> secured to the inner member of a Bowden mechanism, the outer member being secured to a telescopically-mounted sleeve c<2> carrying a rubber ring c<3>. By this means the ball a' can be raised out of action or reset on its seat. Fig. 5 shows a tubular pendulum e with a heavy ring e<1> mounted to swing on a central support e<5> carried by the closure e<4> of a hollow member e<3> which is itself mounted to swing on an eye support g<2>. The member e<3> is immersed in viscid liquid in an outer casing g. Modifications are also described in which a pendulum swings about an axis only slightly inclined to the vertical and two such devices may be used normally in vertical planes at rightangles to one another. Closing of the circuit by the ball or pendulum device may sound the alarm directly, or may operate a relay which closes the alarm circuit so that the alarm continues to sound until stopped by the opening of a preferably key-operated switch. A switch may be arranged so that either direct or relay operation may be used at will, or the device put out of use. The alarm, which may be an electric horn, is preferably covered by a grating provided with spikes or otherwise given an irregular surface to make it difficult to apply a cover with a view to stopping egress of sound. The batteries, horn, relay, and contact closing device may be disposed in a locked casing.