GB2031060A

GB2031060A - Security Enclosure

Info

Publication number: GB2031060A
Application number: GB7932199A
Authority: GB
Original assignee: FAWKES J
Current assignee: FAWKES J
Priority date: 1978-09-29
Filing date: 1979-09-17
Publication date: 1980-04-16
Also published as: GB2031060B

Abstract

An electrical accumulator 20 is connected to a metal cabinet 10 within which it is contained so as to produce an electrical potential difference between the cabinet and earth sufficient to impart an electric shock to any human being attempting to tamper with the cabinet. The accumulator 20 and a control unit 40 which is also contained within the cabinet are thus protected against theft. The control unit 40 is connected to the accumulator 20 and serves to power an external electrical load, such as an electric fence. An indicator lamp when energised shows that the cabinet is "live": the cabinet is, however, disconnected from the accumulator by a push button switch 24 when a door 12 thereof is opened, thus rendering the cabinet "dead". <IMAGE>

Description

SPECIFICATION Security Enclosure The invention relates to a security enclosure, particuiarly though not exclusively for containing a control unit for an electrical load, such as an electric fence. The invention may also be applied to security enclosures for the storage of valuables.

It is known to provide an electric fence to prevent animals, for instance cattle, from straying into areas of land where their presence is undesirable. Typically, such a fence is energised and controlled by a system which modifies a mains supply to give an electrical potential difference between the fence wire and the earth (from which the wire is electrically isolated), sufficient to give a noticeable but harmless electric shock to-a human or animal.

Where such fences have to be located in remote regions where a mains supply is not available, an accumulator or a battery, usually of the lead-acid type is used to supply the electrical -energy required. The battery and associated control equipment is usually mounted in a cabinet mounted on a support such as a post.

Unfortunately, the cost of lead-acid accumulators is such that these are often stolen along with the control equipment from the cabinet.

It is an object of the present invention to provide a security enclosure which is particularly suited to this purpose.

According to the present invention, there is provided a security enclosure comprising a closed casing having an electrically conductive outer surface and means within the casing arranged to produce an electrical potential difference between said outer surface and earth sufficient to impart an electric shock to a human being in direct or indirect contact with both outer surface and earth.

Switch means is preferably arranged to disconnect the outer surface of the casing from the potential difference when a closure of the casing is opened. An indicator can be provided to show, when energised, that the outer surface of the casing is connected to the potential difference. Test means can also advantageously be provided to test the operation of the potential difference producing means when the outer surface of the casing is disconnected from said potential difference.

The casing can include a closure which is lockable in a closed position by means of a locking device electrically insulated from said outer surface. The casing can be in the form of a metal cabinet or a wire cage.

In a particular example of the invention, a control unit is contained within the casing and is arranged to control the operation of an electrical load, such as an electric fence, disposed externally of the casing. Preferably, the casing includes a lockable closure and means is arranged to render the control unit inoperative when a lock of the lockable closure is locked.

Conveniently, the casing is mounted on a metal support post so as to be electrically insulated therefrom, and a conductor which is connected to the post and electrically insulated from the outer surface of the casing passes into the interior of the casing to provide an earth potential lead for said potential difference producing means.

Desirably, said means arranged to produce an electrical potential difference is an electrical accumulator, in which case an electrical generator can be provided for charging up the accumulator.

The generator can be wind-operated or can be in the form of one or more solar panels.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic front elevation view of a security enclosure according to the invention mounted on a first type of support post; Figure 2 is a schematic side view of the security enclosure shown in Figure 1; Figure 3 is a schematic view of an insulated lock forming part of the security enclosure shown in Figures 1 and 2; Figure 4 is a front elevational view of an electronic component mounting board for the security enclosure shown in Figures 1 to 3; Figure 5 is a circuit diagram of one form of electrical control unit for the security enclosure shown in Figures 1 to 3; Figure 6 is a circuit diagram of a modified form of electrical control unit; and Figure 7 is a front elevation view of a security enclosure according to the invention mounted on a second type of support post.

The security enclosure shown in Figures 1 to 5 comprises a rectangular metal cabinet 10 with a hinged metal door 12. The cabinet 10 is mounted on a metal angle-iron post 14 by means of a pair of insulators 1 6 (shown in Figure 2), a lower end of the post 14 being sunk into the ground. An upper end of the post 14 mounts a windmillpowered generator 18, electrical connections (not shown) from which are led down the post and into the cabinet 1 0.

At least one of the insulators 16 is annular and a metal conductor (not shown) passes through the insulator annulus and electrically connects the post 14 with an earth terminal inside the cabinet The earth connection cannot therefore be easily broken by tampering.

A lead-acid accumulator 20 is housed inside the cabinet 10 together with a mounting board 22 insulated from the cabinet and located near the door 12. An electrical push-button switch 24 is mounted on the board 22 so as to be depressed by an interior surface of the door 12 only when the latter is closed. A microswitch 26 is also mounted on the board 22 and is disposed so as to be actuated by a locking bar 27 of a lock 28 mounted in the door 12 and insulated therefrom.

The locking bar 27 co-operates with an abutment 27a on the cabinet to secure the door 12.

The board 22 also mounts the following electrical components, i.e. a light-emitting diode 30, double-pole single-throw switch 32, and a resistor 34. A neon indicator lamp 36 and insulated output terminal 38 are mounted on the cabinet 10, the terminal 38 being for connection to an electric fence in this particular embodiment.

Although shown mounted on a side wall of the cabinet 10, the neon indicator lamp 36 can equally well be provided on a front wall of the cabinet to facilitate its visibility. A conventional fence energising unit 40 is also mounted in the cabinet and provides a high tension supply from the accumulator.

With reference to Figure 5 the above mentioned electrical components are wired as follows. The accumulator positive terminal is connected to one contact of the microswitch 26 and also to two contacts of the switch 32 (one contact on each pole end of the "throw"). The other contact of the microswitch 26 is connected to a positive low tension input terminal 42 of the energising unit 40. The remaining two contacts of the switch 32 are connected, respectively, to the light-emitting diode 30 and the contact of the microswitch connected to the unit 40. The lightemitting diode is connected via the resistor 34 to a common earth connection 44 of the unit 40 which is itself connected to earth via the post 14 and also, via the neon indicator lamp 36, to a first contact 24a of the push button switch 24.A connection is also made from the contact 24a to the metal cabinet 10 and door 12 through a resistor 46 (shown only in Figure 5). A positive high tension output terminal 48 of the unit 40 is connected to a second contact 24b of the push button switch 24 and also the output terminal 38.

The negative terminal of the accumulator 20 is connected to the common earth connection 44.

Operation of the circuit shown in Figure 5 is as follows: The unit 40 is supplied by the accumulator 20 when the contacts of the microswitch 26 are closed. This occurs when the door is locked and the locking bar 27 closes the microswitch contacts. The unit 40 thus creates a high tension potential difference between the terminal 38 and the earth (ground). When the door is closed the contacts of the push button switch 24 are closed and the unit 40 creates a high tension potential difference between the earth (ground) and the cabinet 10 and door 12, this potential difference being attentuated by the resistor 46. The neon indicator lamp 36 is illuminated when the contacts of the push button switch 24 are closed, i.e. when the cabinet 10 and the door 1 2 are "live".The switch 32 is a test switch and by closing the contact of this switch when the door is open the accumulator circuit supplying the unit 40 can be tested with the cabinet 10 and door 12 "dead", the light-emitting diode 30 illuminating if the accumulator 20 is satisfactory and the neon indicator lamp 36 illuminating if the terminal 38 is live, i.e. if the unit 40 is operating satisfactorily.

It should be noted that the generator 1 8 and its associated wiring have been omitted from Figure 5 for clarity. The generator would be wired to the accumulator via a conventional charger and circuitry in known manner.

An operator can gain access to the cabinet without getting a shock by use of the insulated lock. Once the door is open, the cabinet and door are dead and servicing may be carried out. The circuits may be tested using switch 32 without the cabinet and door becoming live.

The resistor 46 is provided so that the potential difference between the cabinet and earth is less than that between the terminal 38 and earth since the former is for deterring human tampering whilst the latter is for animals, chiefly cattle, for which a larger potential difference is required.

Figure 6 shows a modified form of electrical circuitry in which the provision for testing the operation of the control unit is omitted. The positive and negative terminals of the accumulator 20 are now connected directly to the positive and negative low tension input terminals 42 and 44 of the fence energising unit 40 via a terminal block 50 mounted on an insulated panel 52 (shown in chain-dotted lines8. The positive high tension output terminal 48 of the unit 40 is connected commonly to the insulated output terminal 38 and to the cabinet by way of the push button switch 24. The electric fence connected to the terminal 38 is now switched on and off by means of a switch (not shown) which forms a part of the unit 40 and which is readily accessible once the cabinet door has been opened.As in the previously described arrangement, the cabinet is connected to the high tension output terminal 48 of the unit 40 by actuation of the switch 24 upon closure of the cabinet door: the resistor 46 is, however, now omitted.

The negative terminal of the accumulator 20 is also connected to earth via the terminal block 50, and is further connected to the cabinet 10 by way of the neon indicator lamp 36. The lamp 36 thus becomes energised when the cabinet is "ljve".

Figure 7 shows a security enclosure as described above mounted on a support post having a lower metal part 60 which is sunk into the ground and an upper metal part 62 which is electrically insulated from the part 60 by an insulating insert 64. The security enclosure, referenced 66, is mounted on the post so as to bridge the parts 60 and 62 and has points of securement to each of these parts. A windmill operated generator 68 is mounted atop the upper part 62 of the post, the post being retained in an upright position by means of stays each of which comprises a first wire 70 connected to a flange 72 on the upper post part 62 and a second wire 74 secured to the ground, the wires 70 and 74 being connected together by an electrically insulating member 76. The upper post part 62 and the wire 70 of each stay are thus electrically isolated from the ground.

Inan alternative embodiment (not shown), the windmill-powered generator 1 8 is replaced by one or more solar panels. Moreover, the metal cabinet 10 can be replaced by a wire cage where appropriate.

Claims

1. A securtiy enclosure comprising a closed casing having an electrically conductive outer surface and means within the casing arranged to produce an electrical potential difference between said outer surface and earth sufficient to impart an electric shock to a human being in direct or indirect contact with both said outer surface and earth.

2. A security enclosure as claimed in claim 1, wherein switch means is arranged to disconnect the outer surface of the casing from the potential difference when a closure of the casing is opened.

3. A security enclosure as claimed in claim 1 or 2, further comprising an indicator to show, when energised, that the outer surface of the casing is connected to the potential difference.

4. A security enclosure as claimed in any preceding claim, further comprising test means operable to test the operation of the potential difference producing means when the outer surface of the casing is disconnected from said potential difference.

5. A security enclosure as claimed in any preceding claim, wherein the casing includes a closure which can be locked in a closed position by means of a locking device electrically insulated from said outer surface.

6. A security closure as claimed in any preceding claim, further comprising a control unit contained within the casing and arranged to control the operation of an electrical load disposed externally of the casing.

7. A security enclosure as claimed in claim 6, wherein the casing includes a lockable closure and means is arranged to render the control unit inoperative when a lock of said lockable closure is unlocked.

8. A security enclosure as claimed in claim 6 or 7, wherein the electrical load is an electric fence.

9. A security enclosure as claimed in any preceding claim, wherein- the casing is mounted on a metal support post so as to be electrically insulated therefrom, and a conductor which is connected to the post and electrically insulated from the outer surface of the casing passes into the interior of the casing to provide an earth potential lead for said potential difference producing means.

10. A security enclosure as claimed in any preceding claim, wherein said means arranged to produce an electrical potential difference includes an electrical accumulator.

11. A security enclosure as claimed in claim 10, wherein an electrical generator is provided for charging up the electrical accumulator.

12. A security enclosure as claimed in claim 11, wherein the electrical generator is windmill operated.

13. A security enclosure as claimed in claim 9, wherein said means arranged to produce an electrical potential difference includes an electrical accumulator, and a windmill-operated generator for charging up the electrical accumulator is mounted on an upper end of the support post.

14. A security enclosure substantially as hereinbefore described with reference to Figs. 1 to 5 or Figs. 1 to 5 as modified by Fig. 6 of the accompanying drawings.