GB2314472A

GB2314472A - Preventing unauthorised use of electrical equipment

Info

Publication number: GB2314472A
Application number: GB9612850A
Authority: GB
Inventors: Martin Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-06-19
Filing date: 1996-06-19
Publication date: 1997-12-24
Also published as: GB9612850D0

Abstract

Unauthorised operation of an electrical system, for example a vehicle such as a caravan or trailer, is prevented by connecting a switch between a system fuse and earth. When the switch is closed, any attempt to use the system will cause the fuse to blow. A warning device may be included to indicate that the protective arrangement is switched on.

Description

POSITIVE EARTH LOCK.

This invention relates to a locking device for electrical systems.

There is a need for a simple device which prevents unauthorised use of electrical systems and renders the system inoperative if challenged. By deliberately introducing a method of overloading the fuse protection within a secured circuit, total lock out from that circuit can be achieved.

An electrical switch (rotary, swipe or micro chip type) which can be operated by a key, Personal Identification Number (PIN) or sophisticated recognition device is slaved into the electrical system downstream from the power supply fuse or the equipment fuse that requires protection.

(Preferably in a covert position for some applications.) Any number of different circuits can be connected to individually isolated terminals within the switch. (The switch size is appropriate to the systems that requires protection.) The switching action puts all the connected circuits to earth and renders them inoperative if used. This is achieved by overloading the normal protection fuses within the equipment. As the fuses are specifically designed to protect the systems, no further damage to the equipment should be sustained. However, additional safety features include a safety fuse of an appropriate rating fitted within the switch to accommodate exceptional overload conditions and where applicable a warning device operates in the protected area to indicate that the positive lock is in operation.

EXAMPLE OF APPLICATION.

A caravan or car trailer fitted with the proposed new lock in operation. An unauthorisd user, attempting to tow away either caravan or trailer, would cause his own car system fuses to fail as each system was used. The lights, indicators, and brake lights plus any other linked circuits would all fail on first use after connection.

The introduction of a double earth associated with a standard towing connection would also cause other electrical problems on the illegal towing vehicle, for example a flat battery.

If the proposed new lock was fitted to a car, theft by so called, "hot wiring" would be impossible as the ignition system would remain constantly earthed via the positive loclu The car fuses would blow if the system became live. In order to steal the car the positive lock switch would have to be located and dismantled to release the ignition system for use.

The amount and variety of electrical systems for which this type of effective locking applies is beyond listing. The principle of locking for all applications is, live is passed to earth to ensure deniaL The innovative step claimed is in the simplicity of the electrical locking through deliberate equipment fuse overload during unauthorised use.

An automotive application wiring diagram is included for descriptive purposes. The principle, theory and practice of making this type of switch uses simple components and a basic electrical knowledge. No further explanation is thought to be necessary under the guide lines provided.

A prototype for use as described in the example above has been made and successfully tested.

Claims

1 The positive lock imposes denial from use of connected systems by switching (via key protection) normal live circuits to ground earth downstream of the equipment fuse. Illegal use renders power source fuses and/or equipment fuses unserviceable to a maintenance required condition.

2 The positive lock claimed in Claim 1 continues to protect the system until it is unlocked or removed from the wiring circuit.

3 The positive lock claimed in Claim 1 and Claim 2 can be designed applicable to all voltages and all current ratings required using the appropriate switch. The principle of the innovative step always remains the same, a locking device which passes LIVE TO EARTH after the fuse to ensure denial of access.

4 For automotive applications the lock is intrinsically safe for 'Do It Yourself' fitment. Making a wrong connection only connects an earth to an earth on all cars fitted with a negative earth.