GB2062321A

GB2062321A - Fence Structure

Info

Publication number: GB2062321A
Application number: GB7935624A
Authority: GB
Original assignee: FENSECURE Ltd
Current assignee: FENSECURE Ltd
Priority date: 1979-10-13
Filing date: 1979-10-13
Publication date: 1981-05-20

Abstract

A security fence is provided with upright pales 8 and a length 18 of optic fibre or other non-electric medium carrying line is connected to the pales in a manner such that removal of the pales will cause breakage of the length of optic fibre. A supply applies pulsed light to one end of the optic fibre, and a detector is provided at the other end to detect the flow of pulsed light from the optic fibre. On detection of any alteration in the flow of pulsed light from the optic fibre, an alarm may be activated. In a modification the optic fibre is replaced by a hollow tube through which fluid is passed, e.g. air or water. <IMAGE>

Description

SPECIFICATION Improvements Relating to Fence Structures This invention is concerned with improvements relating to fence structures, particularly security fence structures.

Difficulty is encountered in the provision of a security fence structure, which is one which cannot be disrupted without causing an alarm to be activated. One method of providing a security fence structure is to utilise an electric cable, across which an electric potential is established, and in the event of breakage of the cable (as may occur if any attempt is made to interrupt the integrity of the fence structure) an alarm is sounded. This provision however may easily be overcome, by the use of a conductive bridge which may be secured in conductive contact with the cable at remote points, prior to cutting of the cable.

Another method involves the use of photo cells, and transmission of a beam of light along the length of the fence structure, an alarm being activated in the event, that the beam of light is interrupted. This provision may similarly be circumvented relatively easily, and is additionally difficult to install without the incurrence of prohibitive expense on extensive fence structures, particularly those which do not follow straight lines.

According to this invention there is provided a fence structure having secured to successive sections thereof an elengate carrier member, supply means being provided at one end of the carrier member to cause a flow of a medium (not being electricity) into the carrier member, and detector means at the other end of the carrier member to detect flow of the medium from the carrier member, signalling means being provided which is operative in response to the detector means sensing a reduction in the flow of the medium from the carrier member, the carrier member being secured to the sections of the fence structure in a manner such as to render removal of one or more of said sections without breakage of the carrier member difficult.

Thus, should an intruder attempt to remove one of the fence sections, and break the carrier member, the reduction or loss in flow of the medium through the carrier member will cause the signalling means to operate, conveniently to activate an alarm.

The carrier member may be afforded by a hollow conduit, and the medium may be a fluid such as air or water.

Preferably however the medium is light, and the carrier member is in the form of an optic fibre, that is one along which it is possible to pass light.

In this manner the carrier member (fibre) may be made very sensitive and extremely likely to be broken should an attempt be made to interfere with the fence structure, and a considerable degree of security may be obtained.

Preferably, the fibre is no greater than 0.5 millimetre in diameter, and is preferably contained in a thin sheath of rubber or plastics material. In this manner, the carrier member may be protected against accidental breakage, whilst reducing the tendency for it to break when the fence structure is interfered with, only minimally.

Preferably the medium (light) is pulsed at or around a known frequency; in this manner the possibility of the carrier member being effectively by-passed, and subsequently deliberately broken, may be minimised.

Where the fence structure is extensive, advantageously adjacent regions thereof are each provided with a carrier member. An initial carrier member will be connected to a source of pulsed light, and extends to a decoder device, conveniently battery operated, which defines the extent of the first region, and commencement of the second region. The decoder device may be operative to provide a second source of pulsed light, preferably modulated by the pulsed light entering the decoder device from the first carrier member, the second source of pulsed light being applied to one end of a second optic fibre. This in turn may be connected to a second decoder device, and so on, around the fence structure to the detector means.In this manner, a certain frequency of pulsations received by the detector means will indicate an uninterrupted transmission of light through the several carrier members around the fence structure, and the frequency of pulsations received by the detector means should one of the carrier members be broken, may indicate the particular region of the fence structure involved.

In such construction, the decoder devices may be considered as functioning as detector means, being effective to transmit a signal to render the signalling means operative, when the optic fibre transmitting light to it is interrupted.

Preferably, the fence structure comprises a frame and upright pales secured closely together to the frame. In such a construction, preferably the carrier member is secured to the upright pales in a manner such that removal of the pales from the frame will fracture the carrier member.

Alternatively, the optic fibre may be incorporated in the fence structure (for example randomiy).

Since the attenuation of light along a length of optic fibre is relatively small, a considerable length of optic fibre may be incorporated in, for example, a link mesh fence, ensuring that it is practically impossible to cut an opening of any significant size in the fence structure without cutting through the optic fibre.

This invention also provides a method of providing a security fence structure, in which a length of an optic fibre is secured to members of the fence structure, or is incorporated in the fence structure, in a manner such that the fibre is likely to be broken in any attempt to interfere with the integrity of the fence structure and wherein a beam of light is directed into and transmitted along the fibre from one end, and is detected leaving the optic fibre at the other end, an alteration of or interruption in said detection being utilised to operate an alarm signal.

There will now be given a detailed description, to be read with reference to the accompanying drawings of a preferred embodiment of this invention, which has been selected to illustrate the invention by way of example.

In the accompanying drawings: Figure 1 is a front elevation of a fence structure in conjunction with which the invention will be described; Figure 2 is a horizontal sectional view of part of said fence strcture, taken on the lines Il-Il of Figure 1; Figure 3 is a side elevation of the fence structure, showing a frame member thereof and a pale; and Figure 4 is a mounting bracket used in the application of the invention to the fence structure shown in Figure 1.

The fence structure shown in Figure 1 comprises a frame, constituted by two generally horizontallyextending frame members 6,6 which are Lshaped in cross-section to afford some degree of rigidity. Secured to the frame members, extending generally vertically, and in closely proximate relationship, are a plurality of pales 8. The pales 8 are secured to the frame members by bolts 10, the head 12 of which is received in a countersunk aperture of the pale, to render removal of the pale by attacking the bolt 10 difficult. Within the ground confined by the fence structure (on the right-hand side, shown in Figure 3) the bolt is secured by a crimped nut 14.

In an attempt therefore to remove any of the pales 8 from the frame members 6, the crimped nut is likely to give way in preference to the head 12.

In accordance with this invention, each of the bolts 10 carries a mounting bracket 16, shown in Figure 4. The bracket 1 6 is L-shaped, and is positioned on the bolt 10 with an arm 1 7 thereof extending through an aperture 7 of the frame member. The end portion of the arm 17 is provided with a hollow cylindrical portion 18, which is located on the inside (right-hand side Figure 3) of the frame member 6.

The size of the aperture 7 is such as to allow free passage therethrough of the cylindrical portion 18.

When the pales 8 have been secured to the frame member 6, with a mounting bracket positioned on the upper and lower bolts 10 of each pale, a length 20 of optic fibre, of 0.5 millimetre diameter, and encased in a thin plastics sheath, is passed through the cylindrical portions 18 of both the upper and lower mounting brackets.

The optic fibre 20 provides a carrier member for a beam of light, which is directed into the optic fibre at one end thereof by supply means. The beam of light passes along the length of the fibre 20, and its emergence at the other end is detected by detector means (not shown).

In the event that an interloper wishes to gain access to the area bounded by the fence which is the preferred embodiment of this invention, by disruption of the integrity of the fence, an attempt to remove one of the pales 8 will cause the nut 1 8 to become disengaged from the bolt 10, and the end portion 1 8 of the mounting bracket to be drawn through the aperture 7. This places the fibre 20 under shear, and causes the fibre to be broken. Consequently the light can no longer flow along the fibre 20 from one end to the other, and the detector means detects a reduction in the flow of light from the fibre, causing signalling means to operate an alarm.

If desired, two optic fibres may be utilised, one for the upper of the frame members 6 and one for the lower of the frame members 6. However, if desired, a single length may be utilised, extending first along the length of the upper run, looping downwardly and returning along the length of the lower run.

In the preferred embodiment of this invention, light is directed into the optic fibre as a series of discrete pulses, having a frequency of 3000 pulses per second. The detector means is sensitive to the puisation rate of the light emitted from the end of the fibre optic, and will operate the alarm should either the pulsation rate change, or the intensity fall below a predetermined level.

This ensures that it is practically impossible for the optic fibre to be deliberately disrupted, and the flow of light towards the detector means replaced by an artificially contrived transmission.

Claims

1. A fence structure having secured to successive sections thereof an elongate carrier member, supply means being provided at one end of the carrier member to cause a flow of a medium (not being electricity) into the carrier member, and detector means at the other end of the carrier member to detect flow of the medium from the carrier member, signalling means being provided which is operative in response to the detector means sensing an alteration in the flow of the medium from the carrier member, the carrier member being secured to the sections, of the fence structure in a manner such as to render removal of one or more of said sections without breakage of the carrier member difficult.

2. A fence structure according to Claim 1 wherein the carrier member is afforded by a hollow conduit, and the medium is a fluid.

3. A fence structure according to Claim 1 wherein the carrier member is in the form of an elongate member along which light may be transmitted.

4. A fence structure according to Claim 3 wherein the elongate member is in the form of a fibre having a diameter no greater than 0.5 millimetre.

5. A fence structure according to any one of Claims 1 and 4 wherein the elongate member is contained in a sheath of rubber of plastics material.

6. A fence structure according to any one of Claims 3 to 5 wherein the medium is pulsed at or around a known frequency.

7. A fence structure according to any of Claims 3 to 6 wherein the fence structure comprises two sections, each section being provided with a carrier member.

8. A fence structure according to Claim 7 wherein the first carrier member extends from the supply means, and extends to a device adapted to serve as a supply means for the second section.

9. A fence structure according to Claim 8 wherein the device operates to provide a second source of pulsed light, modulated by the pulsed light entering the device from the first carrier member.

1 0. A fence structure according to any one of the preceding claims comprising a frame and upright pales secured closely together to the frame, the carrier member being secured to the pales in a manner such that removal of the pales from the frame will fracture the carrier member.

11. A fence structure according to any one of Claims 1 to 9 wherein the carrier member is incorporated in the fence structure.

1 2. A method of providing a security fence structure, in which a length of an optic fibre is secured to parts of the fence structure, or is incorporated in the fence structure, in a manner such that the fibre is likely to be broken in any attempt to interfere with the integrity of the fence structure, and wherein a beam of light is directed into and transmitted along the fibre from one end, and is detected leaving the optic fibre at the other end, an alteration of or interruption in said detection being utilised to operate an alarm signal.

13. A method according to Claim 12 wherein the light is pulsed at or around a specific of frequency.

14. A method according to one of Claims 12 and 1 3 wherein a length of optic fibre is secured to each of adjacent sections of the fence structure, the first length being connected to the supply means and the last length being connected to the detector means, a device being interposed between adjacent sections which is operative, in response to light being transmitted thereto by one of the lengths, to transmit light into the other of the lengths.

15. A method according to Claim 14 wherein the device is operative to transmit light into the other of the lengths in a form which is modulated by the light transmitted to the device by the first said length.

1 6. A fence structure constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.

1 7. A method of providing a security fence structure, when carried out substantially as hereinbefore described with reference to the accompanying drawings.

1 8. Any novel feature or combination of novel features herein before described and/or illustrated in the accompanying drawings.