NZ200666A - Tamper sensitive alarm bell - Google Patents

Description

7 r)0666 Priority ,q g£ Ca«.-ie^ Spec»o«ton Filed: ■ Q-0% 6 l"2> c^c: k-*""" 28FEB 1985....

^Kiwean i*st« I 'JV?. * * * MD' N-.Z. No.

NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION "ALARM BELL ASSEMBLY" JEX fATe^TOF^5. t9 MAY 1982 £ RECEIVED We, AUTOMATED SECURITY HOLDINGS LIMITED, a British Company, of 25/26 Hampstead High Street, London N.W.3, UNITED KINGDOM, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- — 1 - (followed by 1A) % ? f\ o o o o -1A- ALARM BELL ASSEMBLY The present invention relates to alarm bell assemblies and particularly to a tamper-proof intruder alarm mounted in use on buildings, usually on an outside wall.

Conventional alarms have a steel cover, the thickness of which 5 must be at least 18 gauge or a polycarbonate cover the thickness of which must be at least 3mm. in order to comply with British Standards. Underneath the cover there is a base plate, also of 18 gauge steel or 3 mm polycarbonate on which are mounted a gong, bell operating parts including an armature and armature drive means, and a power source, usually including batteries and wires to a central alarm control circuit.

Enterprising prospective burglars and intruders can easily disable such alarms for example by cutting through the cover and removing the batteries or cutting the wires to the control 15 circuit or both. The alarm is rendered inoperative and, hence, / ineffective. Such are alarms, are therefore,not very satisfactory.

An alarm which obviates these disadvantages is required in order to foil attempting burglars and intruders.

According to the invention, we propose an alarm bell assembly comprising a gong and bell operating parts on a anting, the operating parts being concealed and protected securing means is tampered with. the gong which is secured to the mounting by means Qff <£xfornprising a detector by which the bell is actuable when 2 006 6 6 In a preferred embodiment, the alarm includes a plastics external cover, a steel base and a frame on the base, the cover being secured to tHe~frame_by a screw and" the gong being secured to the frame by a second screw, the cover screw located coaxially within the gong screw. The detector is comprised by a micro-switch, located within an aperture defined by a raised portion of the frame and is operable on any of the following: removal of the cover screw or the gong screw or the alarm assembly, or movement thereof.

The power source comprises a standby rechargable battery, a relay and battery charging circuit on a printed circuit board to an external central alarm control circuit such that the battery is kept fully charged and supplies the alarm drive means if the control circuit connections are severed.

Thus, the alarm bell assembly cannot be tampered with without the micro-switch being triggered and the aLarm sounding so disturbing anyone meddling wit h; theassemb1y.

Furthermore, a plastics cover may be used because the gong affords the bell operating means mechanical protection and this reduces the manufacturing cost of the alarm bell assembly and also results in an attractive, weather-proof assembly.

A preferred embodiment of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:- Fig. 1 is a cross-section taken from one side through the centre of an alarm bell assembly, including a gong and a cover; Fig. 2 is a front elevation of the alarm bell assembly, with—the--cover and gong removed; and Fig. 3 is a circuit diagram showing the printed circuit board and connections therefrom to an alarm system control circuit, a battery, a bell and a micro-switch.

An alarm bell assembly 13 for use as an intruder alarm has a 200666 steel base plate 1 and frame 2 mounted on the base plate, both of which may be fixed to a building by means of screws 3. The assembly has a plastics, outer cover 4, shown in Fig. 1, which completely extends over the top and sides of the gong 5.

The gong 5 entirely surrounds the bell operating means seated on the base frame 2, which comprise an armature and armature drive mechanism 6 including an electric motor, a printed circuit board 7 and a rechargeable battery 8.

A central raised portion 9 of the base frame defines an aperture which houses a micro-switch 10. This micro-switch serves to detect tampering and may be triggered when a screw 11, securing the outer cover 4 to the base is turned or when a second screw 12 is turned or when an attempt is made to move the cover or gong. The screw 11 is located coaxially within the screw 12 which secures the gong to the base.

The printed circuit board 7, as shown in Fig. 3, includes a relay A from an external alarm system control circuit. The battery 8 is kept fully charged via the relay A.

If the micro-switch is triggered via the cover ^ or the gong 5, / then return voltage is lost to the control circuit and a relay contact A2 is open; the bell is then supplied by the circuit via relay A and, simultaneously, police are alerted by the external circuit. control box.

If the control circuit supply is prevented, for example, by the assembly being pulled off the wall, by an intruder for example, and the wires being severed, then the battery supplies the bell.

Thus, the alarm bell is sounded if a prospective burglar or intruder attempts to dismantle the assembly as a result of the gong and the cover 200666 The assembly will, therefore, sound the alarm on being meddled with and so serve to disturb burglars and intruders and prevent the alarm being disabled.

Claims (8)

WHAT WE CLAIM IS:

1. An alarm bell assembly comprising a gong and bell operating parts on a mounting, the operating parts being concealed and protected by the gong which is secured to the mounting by means comprising a detector by which the bell is actuable when securing means is tampered with.

2. An assembly according to claim 1 wherein the gong is secured by screwed means movement of which triggers the detector.

3. An assembly according to claim 1 or claim 2 wherein jche assembly includes a cover which is also secured by screwed means movement of which triggers the detector. A.

An assembly according to claim 3 wherein the gong is secured by a first screw and the cover is secured by a screw co-axially within the first screw.

5. An assembly according to any one of claims 1 to 4 wherein the mounting comprises a frame having a central boss within which the detector is located.

6, An assembly according to any one of claims 1 to 5 wherein the detector comprises a micro-switch. ,

7. An assembly according to any one of the preceding claims wherein the bell operating parts comprise an alarm drive -6- 2 0 06 66 means and a rechargeable battery, and are connected to or adapted for connection to an external control circuit such that the battery is kept fully charged and supplies the alarm drive means if the control circuit connection is severed.

8. An alarm bell assembly constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings. AUTOMATED SECURITY HOLDINGS LIMITED By Their Attorneys HENRY HUGHES LIMITED