GB2322216A

GB2322216A - Electrical appliance alarm

Info

Publication number: GB2322216A
Application number: GB9702874A
Authority: GB
Inventors: Jeffrey David Dines
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-02-12
Filing date: 1997-02-12
Publication date: 1998-08-19
Anticipated expiration: 2017-02-12
Also published as: GB9702874D0; GB2322216B

Abstract

A mains powered appliance alarm device, for example for the protection of computers, will only operate and draw current from it's own power source 7 when the appliance is unplugged from a mains electricity supply and subsequently moved, without making any direct electrical connection to the piece of equipment, or the requirement of drawing any power from the protected equipment to deactivate the devices alarm outputs. The device includes a movement sensor 5, for example a mercury switch or a vibration sensor, and an antenna 2 positioned close to the electrical power supply cord to the equipment to sense the flow of current in the cord.

Description

DINES APPLIANCE ALARM The present invention relates to an electrical appliance anti theft alarm. More particulary, but not exclusively, it relates to a device which electrically triggers a warning signal if an attempt is made to remove an appliance from it's location.

The device would be particulary useful to warn of an attempted theft of a computer or other electrical appliance found in a place of commerce, a photocopier or fax machine.

The device would also find use in the home to protect television sets or video recorders or any other valuable electrical item.

It is known to provide devices which detect by means of magnetic field, the presence of electricity conducting within an appliance cable and to produce an audible or visual indication to the user, such as a Volt Stick. It is also known to provide devices which detect movement and produce an alarm signal, a mercury switch for example, or a magnetic reed switch, or vibration sensing transducers. It is also known to provide alarms exclusively for the protection against theft of computers.

Such currently available computer alarms require an internal electrical connection to the computer, to enable the devices alarm to be electrically deactivated, either by; the use of one of the computers expansion slots, or by taking a power feed from an auxiliary disk drive supply or other source of power from within the computer. If such connections are not made, the device's battery becomes exhausted after a brief period of use, thereby becoming ineffective as an alarm.

In the case of the expansion slot type alarm, if no expansion slots are available it is not possible to fit an alarm. In the case of the units requiring power from the computer to enable operation, technical knowledge limits installation and use by non technical owners.

It is an object of the present invention to provide an alarm device suitable for'the protection of computers or any other piece of mains electrically operated equipment, which will only operate when the appliance is unplugged from a mains electricity supply and subsequently moved, without making any direct electrical connection to the piece of equipment, or the requirement of drawing any power from the protected equipment to deactivate the inventions alarm outputs.

According to the present invention, there is provided an antenna means, connected to an electrical current detecting means, an electronic switching means, a movement detecting means, an alarm signal generating means, a device disabling means and a device power source means.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a flow sheet diagram embodying the invention.

Referring now to FIGURE 1, There is shown an enclosure 1 constructed from a suitably durable material containing the invention in which there is provided an antenna 2 which may consist of a suitable length of wire or a coil of wire or a ferrite rod aerial or other suitable sensing means to detect the presence of electrical current supplied to the appliance to be protected, an electronic circuit board 3 which comprises of a signal amplification circuit, a solid state switch to activate the devices alarm output driver circuit, an alerting means 4 which may be an electronic buzzer or other suitable sound generating device, alternatively but not exclusively the alerting means may be a visual bright light or the output driver may be connected to an external signalling device. A sensor means to detect movement of the appliance 5 which may consist of a mercury switch or a vibration sensing transducer, an alarm silencing switch 6 which may be electronic or mechanical and a power source 7 to operate the device's sensing, switching and alarm generating circuits.

In use, which will be described in terms of protection of a computer console, whereby the enclosure 1 is located inside the housing of the computer, the device could also be secured to the outside of the computer with a suitable adhesive, the antennae 2 is positioned so as to be close to the electrical supply power cord to the computer. After fitting the device to the computer the power source 7 is applied to the devices circuits 3. At this stage all circuitry is switched off and no power is used from the power source 7. If the computer console is now lifted and tilted the sensor means 5 in this case a mercury switch, a closed contact is made and current is allowed to flow from the power source 7 to the devices detector circuit. If the computers power cord is plugged into a mains electricity supply, the antennae 2 detects the presence of a magnetic field around the power cord, this signal is amplified and fed to a circuit which deactivates the devices alarm driver circuits. If the computer is lifted and tilted when the computers power cord is not plugged into a mains electricity supply the antennae 2 is unable to detect any magnetic field around the power cord, the deactivation circuit is inoperative resulting in the operation of the devices alarm driver circuits which feed current to the alerting means in this case an electronic buzzer. The duration of the alarm signal may be selected by the user. The device may be permanently or temporarily switched off by operation of alarm silencing switch 6 in this case a mechanical dip switch, although any form of coding switch may be used electronic or otherwise which has a security code known only to the user. A Key operated switch may be used.

Claims

CLAIMS:

1. An alarm device for an item of equipment powered by mains electricity, the device being mounted to or within the equipment and comprising a power source, alarm means powerable thereby, first sensor means to detect movement of the equipment, second sensor means unconnected to said mains electricity but adapted to detect mains current flow, said alarm means being operable when said first sensor means detects movement and said second sensor means signals the absence of mains electricity current flow.

2. An alarm device as claimed in Claim 1, where said first and second sensor means do not draw current from the power source when the first sensor means detects non movement and said second sensor means detects the prescence of mains electricity current flow.

3. An alarm device as claimed in either Claim 1 or Claim 2, wherein an output of said second sensor means indicative of mains current flow is applied to deactivate a driver of said alarm means.

4. An alarm device as claimed in any one of the preceding claims, wherein said second sensor means comprises an antenna so located adjacent a conductor of said mains electricity current flow as to detect the presence of a magnetic field generated by current flow.

5. An alarm device as claimed in any one of the preceding claims, wherein said first sensor means comprises a mercury switch.

6. An alarm device as claimed in any one of Claims 1 to 4, wherein said first sensor means comprises a vibration sensing transducer.

7. An alarm device as claimed in any one of the preceding claims, further comprising a coded switch to activate or deactivate the device.

8. An alarm device as claimed in any one of the preceding claims wherein the alarm means comprises means to signal to a receiver remote from the device.

9. An alarm device substantially as described herein with reference to the accompanying drawings.

10. An item of electrical equipment in combination with or containing an alarm device as claimed in any one of the preceding claims.