GB2337147A

GB2337147A - Electrified security fence

Info

Publication number: GB2337147A
Application number: GB9910466A
Authority: GB
Inventors: Thomas Arthur Wadkin
Original assignee: RUTLAND ELECTRIC FENCING COMPA
Current assignee: RUTLAND ELECTRIC FENCING COMPA
Priority date: 1998-05-09
Filing date: 1999-05-07
Publication date: 1999-11-10
Anticipated expiration: 2019-05-07
Also published as: GB9809901D0; GB9910466D0; GB2337147B

Abstract

The fence comprises a fence wire (1) connected to power supply means (4) adapted to apply to the fence wire (1) a low voltage or a pulsed high voltage. Switching means (7) selectively apply either the low voltage or the high voltage to the fence wire (1), and monitoring means (8,9) detect the voltage drop across the fence wire (1). Alarm means are actuated in the event that the voltage drop falls outside a permitted range.

Description

RUTI.95O.GB 1 Title - Impro-yements relating tQ encin -security f -g

2337147 The invention relates to improvements in security fencing, in particular to electrified security fencing.

Security of commercial and residential properties is a matter of intense and increasing concern. Theft of materials from stockyards, factories and other commercial premises is increasingly frequent and such premises must be adequately secured at all times, but especially when not in use, eg at night.

It is known to employ electrified security fencing around commercial premises to protect them against theft. Such fencing is normally energised with pulses of high voltage which are sufficient to give a considerable shock to anyone who grasps the fencing or attempts to tamper with it. Whilst such an arrangement does not generally endanger the life of an attempted intruder, it does nonetheless represent a potential danger and for health and safety reasons therefore the high voltage must normally be switched off during normal business hours. This means that during the day the premises are unprotected and vulnerable. Areas of the premises may not be easily monitored and intruders may cut through the fence with impunity, even during business hours, and make off with goods. In addition, it may be possible for a would-be intruder to cut through the wires of the fence when it is switched off. The damage may then be discovered only at the close of business, by which time it may be too late to repair it, with the result that the premises are left unprotected and vulnerable overnight.

There has now been devised an improvement to electrified security fencing which overcomes or substantially mitigates the above-mentioned or other disadvantages.

According to the invention, there is provided an electrified security fence comprising a fence wire connected to power supply means adapted to apply to the fence wire a low voltage or a pulsed high voltage, switching means adapted to selectively apply either the low voltage RUTL95O.GB 2 or the high voltage to the fence wire, and monitoring means to detect the voltage drop across the fence wire and to actuate alarm means in the event that the voltage dropfalls outside a permitted range.

The security fence according to the invention is advantageous primarily in that the low voltage may safely be applied during, for example, business hours. The low voltage serves to provide an immediate indication of any damage to, or tampering with, the fence wire, thereby alerting security personnel to the damage or attempted intrusion. The high voltage may be applied outside of business hours in the conventional fashion. Because the low voltage and the high voltage are applied to the same fence wire (albeit normally at different times) it is impossible for the fence wire to be surreptitiously damaged in such a way that the high voltage becomes ineffective.

By the term "high voltage" is meant a voltage in the kilovolt range, most typically a voltage in the range of about SkV to 15kV, eg around 9kV. The high voltage is applied in pulses, most typically of a duration of the order of 1 0Ogs, using a high voltage energiser of generally conventional form. Such energisers are known for the application of such pulsed high voltage to security fencing, as well as to agricultural fencing and the like.

By "low voltage" is meant a voltage generally of less than 10OV, more preferably less than 50V and most preferably less than 20V. Typically, the low voltage applied to the fence wire is of the order of 15V. The low voltage is most preferably full wave rectified with a 20 frequency of 100 cycles/s.

Preferably, separate monitoring means are provided for the high voltage and the low voltage, the appropriate monitoring means being automatically selected when the switching means is used to select either the low voltage or the high voltage. The monitoring means may be of generally conventional construction. Most preferably, the monitoring means for the high voltage is capacitance coupled, whereas that for the low voltage is optically coupled.

0 Where appropriate, the security fence may be divided into a plurality of zones, each zone RUTL95MB 3 comprising a single fence wire and the high or low voltage being applied to the wires in each zone either simultaneously or sequentially.

The monitoring means are preferably connected or interfaced to one or more alarm devices. Such devices may, for instance, be visual or audible alarm indicators, security cameras or an autodialler.

Most preferably, the security fence comprises not only the fence wire to which the live high or low voltage is applied, but also one or more earth wires. Most preferably, the earth wires and the live wire are arranged horizontally, in alternating configuration. The earth wires are preferably bonded to metalwork, eg metal fence posts, while the live wire forms a single 10 series circuit.

The invention will now be described in greater detail, by way of illustration only, with reference to the accompanying drawing which is a schematic and simplified diagram of an electrified security fence according to the invention.

is Referring to the diagram, an electrified security fence according to the invention comprises an electrically conducting Eve fence wire 1 which is arranged in a single series loop on a line of fence posts 2. The drawing shows three such posts 2 and also shows the wire 1 following a path which defines six horizontal courses of wire extending between the posts 2. In practice, more than three posts 2 may be used, and a considerably higher number of horizontal courses of wire 1. Alternating with the successive courses of wire 1 are earth wires 3 which are earthed by bonding to available metalwork, eg to the posts 2 in the event that the posts 2 are of metal construction. The separation of successive courses of live wire 1 and earth wire 3 will generally be small enough to represent an effective barrier to a wouldbe intruder, a separation of 10cm or so being typical.

The live wire 1 is connected to a power supply unit 4 which incorporates both a low voltage 25 module 5 and a high voltage module 6. A switching unit 7 is interposed between the power supply unit 4 and the wire 1.

RUTL9SO.GB 4 A low voltage monitor 8 is optically coupled to the low voltage module 5, and a high voltage monitor 9 is capacitatively coupled to the high voltage module 6. A control unit 10 is operably linked to the power supply unit 4 and switching unit 7, as well as to the monitors 8,9 as well as to one or more alarm units (not shown).

In use, during normal business hours the wire 1 is connected via the switching unit 7 to the low voltage module 5 which applies a full wave rectified oscillating voltage of approximately 15V across the ends of the wire 1. The voltage is monitored by the low voltage monitor 8. In the event that the measured voltage falls outside a predetermined range, as would be the case if for example the live wire 1 were to be cut or connected to one of the earth wires, the control unit 10 triggers an alarm. This may be an audible alarm, eg a buzzer, a visual alarm, eg a lamp, or any other form of alarm device.

At close of normal business, the system is switched to high voltage operation by connection of the high voltage module 6 to the wire 1 via the switching unit 7. The switching operation may be accomplished by entry of a code into a keypad forming part of the control unit 10.

is In this mode of operation, the high voltage module 6 supplies pulses of approximately 9W with a duration of about 10Ogs at intervals of approximately Is to the wire 1. Again, the voltage is monitored, this time by the high voltage monitor 9 and if the measured voltage falls outside a predetermined range one or more alarm devices is actuated by the control unit 10.

In the example illustrated, there is only a single live wire 1. In practice, a number of such wires 1 may be used to form a corresponding number of zones, the wires 1 in each zone forming a corresponding number of series loops and the high or low voltage being applied to each zone either simultaneously or sequentially. A corresponding number of inputs to the high and low voltage monitors enable the status of the wire in each zone to be monitored, and hence for the location of any damage or fault to be determined.

RUTL95O.GB

Claims

1. An electrified security fence comprising a fence wire connected to power supply means adapted to apply to the fence wire a low voltage or a pulsed high voltage, switching means adapted to selectively apply either the low voltage or the high voltage to the fence wire, and monitoring means to detect the voltage drop across the fence wire and to actuate alarm means in the event that the voltage drop falls outside a permitted range.

2. A security fence as claimed in Claim 1, wherein the high voltage is a voltage in the range of about 5W to 15kV.

3. A security fence as claimed in Claim 1 or Claim 2, wherein the high voltage is 10 applied in pulses.

4. A security fence as claimed in Claim 3, wherein the pulses have a duration of the order of 1 0Ogs.

5. A security fence as claimed in any preceding claim, wherein the low voltage is less than 20V.

is

6. A security fence as claimed in any preceding claim, wherein the low voltage is full wave rectified with a frequency of 100 cycles/s.

7. A security fence as claimed in any preceding claim, wherein separate monitoring means are provided for the high voltage and the low voltage, the appropriate monitoring means being automatically selected when the switching means is used to select either the low voltage or the high voltage.

0

8. A security fence as claimed in Claim 7, wherein the monitoring means for the high voltage is capacitance coupled, whereas that for the low voltage is optically coupled.

0 RUTL950.0B 6

9. A security fence as claimed in any preceding claim, wherein the fence is divided into a plurality of zones, each zone comprising a single fence wire and the high 9r low voltage being applied to the wires in each zone either simultaneously or sequentially.

10. A security fence as claimed in any preceding claim, wherein the monitoring means 5 are connected or interfaced to one or more alarm devices.

A security fence as claimed in any preceding claim, wherein the fence comprises not only the fence wire to which the live high or low voltage is applied, but also one or more earth wires.

12. A security fence as claimed in Claim 11, wherein the earth wires and the live wire are 10 arranged horizontally, in alternating configuration.

13.

An electrified security fence substantially as hereinbefore described and as illustrated in the accompanying drawing.