GB1599847A - Fencing element - Google Patents

Abstract

An element for an electric safety fence comprises a frame (7) which is tensioned with double electrical conductors. This type of conductor has at least one electrical characteristic sensitive to the pressure between the two insulated conductors, together forming the double conductor. The double conductors are arranged, on the one hand, in an interlaced manner (9) and, on the other hand, horizontally (10), the horizontal double conductors (10) passing through the intersection joints (11) of the interlaced conductors (9). The conductors are joined together so that any pressure or cutting is detected. This arrangement is selected to prevent the intersection joints from being moved, so that any tampering with the fence is detected electrically and cannot be concealed. <IMAGE>

Description

(54) FENCING ELEMENT (71) We, N.V. BEKAERT S.A., a Belgian body corporate, of Zwevegem, Belgium, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a fencing element for an electric security fence, which comprises a frame and at least one wire as hereafter defined incorporated in meshform in said frame.

The term "wire" as used herein refers to a combination of at least two elongate electrically conductive elements extending alongside one another and separated by an insulating layer, whereby when the elements are moved laterally relative to one another a change occurs in the resistance and/or capacitance therebetween. The insulating layer may be provided by providing one of the elements with an insulating sleeve or wrapping. Example of suitable wires are shown in co-pending Application 21672/77 (Serial No. 1585602). This wire preferably consists of a strand or a cable of several strands, wherein one of the filaments of the strand or the cable is wrapped in or provided with a thin insulating layer.These wires can be made in an easy and inexpensive manner; this is particularly true for the embodiment in the form of a strand or cable, which can be fabricated on conventional cabling machines. The wire, as for example in the form of a strand or cable, is preferably wrapped in an anticorrosive coat as. for example, of synthetic material.

Such a composite wire, for use in a fence, is such that when a pressure is applied to the wire, at least one of the electrical characteristics, preferably the contact resistance between the elements. is changed to a measurable extent. Therefore, a security fence comprises at least one wire as described hereabove, a circuit connected to both conductors for detecting a deviation from the normal value of at least one the electrical characteristics, preferably the contact resistance, and an alarm circuit controlled by said circuit. This ensures that any impact on a fence comprising such a wire or wires, whereby the contact resistance between the elements of the wire or wires is changed to a measurable extent, will be detected immediately.

Thus it is impossible to destroy such a fence unnoticed, for example by cutting.

The safety fence may particularly comprise fencing elements as described hereabove.

A disadvantage of such a fencing element comprising a frame and at least one wire of the type described hereabove and which is incorporated in mesh-form in said frame is the possibility to move or shift the enmeshed wire or wires with respect to each other. So it is possible to make in the fencing element of a safety fence unacceptably large openings that offer access to intruders without the contact resistance between the elements being changed to a measurable extent or without the alarm being put into operation.

A possible solution may be found in embedding the mesh crossings in a knot of synthetic material. However, this is a timeabsorbing and difficult operation. Moreover, it would remain possible to remove said plastic knots without putting the alarm into operation.

According to the invention, there is provided a fencing element for an electric security fence, comprising a frame, at least one wire (as hereinbefore defined) forming a mesh in the frame and at least one secondary wire (as hereinbefore defined) associated with at least some of the crossings of the mesh in such manner as to prevent substantial deformation of the mesh at the crossings, said at least one wire forming the mesh and said at least one secondary wire being electrically connected.

In one embodiment, the or each wire forming the mesh is bent or turned through an angle of at least 1800 with respect to the plane of the frame at each mesh crossing whereby two loops are formed at each crossing through which the or one of the secondary wires runs.

The secondary wires are preferably horizontal in use and are preferably maintained under tension. The invention will be further described in the following, with reference to the accompanying drawings in which: Figure 1 is a view of a wire for use in a fencing element according to the invention; Figure 2 is a first embodiment of a fencing element according to the invention; and Figure 3 is a second embodiment of a fencing element according to the invention.

Figure 1 shows a "wire" 1 for use in a fencing element according to the invention.

The wire 1 comprises a plurality of strands 2, one of the filaments 3 of a strand 2 being wrapped in or provided with a thin insulating layer 4. The whole wire or cable is surrounded by a thin anti-corrosive coating 5 of synthetic material. It is evident that the filament 3 wrapped in or provided with the insulating layer 4 forms one conductor and the other filaments together form the other condutor of the "wire" 1.

Figure 2 shows a first embodiment of a fencing element 6 according to the invention. The fencing element 6 consists of a frame of two upright or vertical sides 7 and two horizontal or longitudinal sides 8. The vertical sides 7 are hollow tubes of which the front side is removable and fixed by means of bolts and nuts to the rear side. In this frame a number of wires 9 of the above described type are enmeshed between the upright sides 7. The wires 9 may be separated lengths of wire, whereby the conductors of successive wire lengths are connected in series. The electric connections between the wires 9 are located inside the hollow tubes 7. It is also possible to tension a single wire 9 in mesh-form in the frame.

To prevent substantial deformation of the mesh at the crossings, the frame 6 is provided with a number of horizontal secondary wires 10. The wires 10 are built up in the same way as the wires 9. The two conductors of the wires 9 and the wires 10 are connected in series, the electrical connection between the wires 9 and 10 being located inside the hollow tubes 7. It is obvious that it is not necessary that the wires 10 be horizontal. The wires 10 may also run through a row of crossings which extends obliquely in the plane of the frame 6. Also, the wires 10 may follow an arbitrary pattern through a number of crossings of the netting which is tensioned in the form of a mesh.

Figure 3 shows on a larger scale parts of the two portions of a preferred embodiment of a fencing element 6 according to the invention. The embodiment according to Figure 3 is built up in substantially the same manner as the embodiment shown in Figure 2. Moreover, in the embodiment according to Figure 3, the crossings 11 of a number of rows of two interwoven wires 9 are bent or turned through an angle of 1800 with respect to the plane of the frame 6, so that at each crossing 11 two loops 12 are formed. The horizontal wires 10 extend through the loops 12. It is obvious that also in this case it is not essential for each wire 10 to run through a horizontal row of crossings. This embodiment provides a network of meshes of which the meshes can not be mutually moved and in which the wires are subjected to almost no pressures.

WHAT WE CLAIM IS: 1. A fencing element for an electric security fence, comprising a frame, at least one wire (as hereinbefore defined) forming a mesh in the frame and at least one secondary wire (as hereinbefore defined) associated with at least some of the crossings of the mesh in such manner as to prevent substantial deformation of the mesh at the crossings, said at least one wire forming the mesh and said at least one secondary wire being electrically connected.

2. A fencing element as claimed in claim 1 wherein the or each wire forming the mesh is bent or turned through an angle of at least 1800 with respect to the plane of the frame at each mesh crossing, whereby two loops are formed at each crossing through which the or one of the secondary wires runs.

3. A fencing element as claimed in claim 1 or 2, wherein said secondary wires are substantially parallel to one side of the frame.

4. A fencing element as claimed in any preceding claim, wherein said at least one secondary wire is maintained under tension.

5. A fencing element substantially as herein described with reference to Figures 2 or 3 of the accompanying drawings.

6. An electric security fence comprising at least one element as claimed in any preceding claim, a first circuit connected to the conductive elements of said wires for detecting a deviation from the normal value of at least one electrical characteristic, and an alarm circuit controlled by said first circuit.

7. A fence as claimed in claim 6, wherein said first circuit is capable of detecting a change in the contact resistance between the electrically conductive elements of the wires.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. being electrically connected. In one embodiment, the or each wire forming the mesh is bent or turned through an angle of at least 1800 with respect to the plane of the frame at each mesh crossing whereby two loops are formed at each crossing through which the or one of the secondary wires runs. The secondary wires are preferably horizontal in use and are preferably maintained under tension. The invention will be further described in the following, with reference to the accompanying drawings in which: Figure 1 is a view of a wire for use in a fencing element according to the invention; Figure 2 is a first embodiment of a fencing element according to the invention; and Figure 3 is a second embodiment of a fencing element according to the invention. Figure 1 shows a "wire" 1 for use in a fencing element according to the invention. The wire 1 comprises a plurality of strands 2, one of the filaments 3 of a strand 2 being wrapped in or provided with a thin insulating layer 4. The whole wire or cable is surrounded by a thin anti-corrosive coating 5 of synthetic material. It is evident that the filament 3 wrapped in or provided with the insulating layer 4 forms one conductor and the other filaments together form the other condutor of the "wire" 1. Figure 2 shows a first embodiment of a fencing element 6 according to the invention. The fencing element 6 consists of a frame of two upright or vertical sides 7 and two horizontal or longitudinal sides 8. The vertical sides 7 are hollow tubes of which the front side is removable and fixed by means of bolts and nuts to the rear side. In this frame a number of wires 9 of the above described type are enmeshed between the upright sides 7. The wires 9 may be separated lengths of wire, whereby the conductors of successive wire lengths are connected in series. The electric connections between the wires 9 are located inside the hollow tubes 7. It is also possible to tension a single wire 9 in mesh-form in the frame. To prevent substantial deformation of the mesh at the crossings, the frame 6 is provided with a number of horizontal secondary wires 10. The wires 10 are built up in the same way as the wires 9. The two conductors of the wires 9 and the wires 10 are connected in series, the electrical connection between the wires 9 and 10 being located inside the hollow tubes 7. It is obvious that it is not necessary that the wires 10 be horizontal. The wires 10 may also run through a row of crossings which extends obliquely in the plane of the frame 6. Also, the wires 10 may follow an arbitrary pattern through a number of crossings of the netting which is tensioned in the form of a mesh. Figure 3 shows on a larger scale parts of the two portions of a preferred embodiment of a fencing element 6 according to the invention. The embodiment according to Figure 3 is built up in substantially the same manner as the embodiment shown in Figure 2. Moreover, in the embodiment according to Figure 3, the crossings 11 of a number of rows of two interwoven wires 9 are bent or turned through an angle of 1800 with respect to the plane of the frame 6, so that at each crossing 11 two loops 12 are formed. The horizontal wires 10 extend through the loops 12. It is obvious that also in this case it is not essential for each wire 10 to run through a horizontal row of crossings. This embodiment provides a network of meshes of which the meshes can not be mutually moved and in which the wires are subjected to almost no pressures. WHAT WE CLAIM IS:

1. A fencing element for an electric security fence, comprising a frame, at least one wire (as hereinbefore defined) forming a mesh in the frame and at least one secondary wire (as hereinbefore defined) associated with at least some of the crossings of the mesh in such manner as to prevent substantial deformation of the mesh at the crossings, said at least one wire forming the mesh and said at least one secondary wire being electrically connected.

2. A fencing element as claimed in claim 1 wherein the or each wire forming the mesh is bent or turned through an angle of at least 1800 with respect to the plane of the frame at each mesh crossing, whereby two loops are formed at each crossing through which the or one of the secondary wires runs.

3. A fencing element as claimed in claim 1 or 2, wherein said secondary wires are substantially parallel to one side of the frame.

4. A fencing element as claimed in any preceding claim, wherein said at least one secondary wire is maintained under tension.

5. A fencing element substantially as herein described with reference to Figures 2 or 3 of the accompanying drawings.

6. An electric security fence comprising at least one element as claimed in any preceding claim, a first circuit connected to the conductive elements of said wires for detecting a deviation from the normal value of at least one electrical characteristic, and an alarm circuit controlled by said first circuit.

7. A fence as claimed in claim 6, wherein said first circuit is capable of detecting a change in the contact resistance between the electrically conductive elements of the wires.

8. A fence as claimed in claim 6 or 7,

wherein said first circuit is capable of detecting a change in the capacitance of the wires.