GB1602744A

GB1602744A - Composite strand

Info

Publication number: GB1602744A
Application number: GB3354180A
Authority: GB
Original assignee: FIBUN BV
Current assignee: FIBUN BV
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-11-18

Description

(54) COMPOSITE STRAND (71) We, FJBUN B.V., a corporation existing under the laws of the Netherlands, of P.O. Box 70492, 1007, KL Amsterdam, Holland, 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 is concerned with a composite strand, eg. for use in a security system.

It is commonly known to construct boundary fences using cables or wires running between adjacent posts. Such fences can, for example, be used to contain animals within a field or prevent unauthorised entry into an area delimited by the fence. However, there are many such cases where it would be extremely desirable or even essential to be provided with some means of warning when any attempt, even unsuccessful, has ben made to cross the boundary.

In this specification, the terms 'strip' and 'strand' will be used. In the present context, 'strip' means a long narrow band of small thickness. 'Strand' on the other hand has a broader meaning so as to include also other cross-sectional shapes.

According therefore to the present invention there is provided a composite strand comprising a carrier strand having barbs or serrations, and a fibre-optic waveguide carried by said carrier strand.

Herein, the term 'optical radiation' includes infra-red and ultra-violet radiation as well as visible radiation.

Preferably, the carrier strand has a longitudinal groove therein in which the fibre-optic wave guide is disposed, and an adhesive strand is applied to the carrier strand so as to overlie the longitudinal groove and cover the fibreoptic waveguide. The fibre-optic waveguide may be held within the groove by a bonding agent, the adhesive strand overlying the bonding agent.

The barbs or serrations may be formed at intervals along each longitudinal edge of the carrier strand.

The carrier strand may be coated with corrosion resistant material which covers the fibre-optic wave guide.

The carrier strand may be made of steel.

Thus it may be made of a galvanised strand painted with plastics-based paint.

The wave guide may be enclosed in a plastics sheathing.

The composite strand may be bendable.

The invention also comprises a security system comprising at least one composite strand as set forth above.

Preferably, the security system comprises optical radiation means positioned to direct optical radiation along said wave guide from one end, and detector means positioned to detect radiation leaving said wave guide from the other end and arranged to change its state in response to a change in detected radiation outside a predetermined range.

If the composite strand or strands are mounted to extend between posts positioned along a boundary, then except for negligible disturbances such as produced by wind, any disturbances, for example as might be caused by an animal pressing up against the fibreoptic wave guide or an unauthorised person endeavouring to cut through the wave guide, will cause the detector means to produce the required change in its aforementioned state and this can be used to operate a warning device such as an alarm.

Conveniently, the fibre-optic wave guide comprises merely a single fibre optic filament.

As a deterrent against interfering with the security system, the carrier strand is formed with the above-mentioned barbs or serrations along its edges. A further strand can be provided which is disposed adjacent to the said composite strand or strands, the further strand being of identical appearance externally to the composite strand or strands but not including any fibre optic wave guide. In a further development, an additional composite strand is buried adjacent the first-mentioned composite strand, there being an additional optical radiation means positioned to direct optical radiation along the wave guide of said additional composite strand from one end, and additional detector means positioned to detect radiation leaving the last-mentioned wave guide from the other end and arranged to change its state in response to a change in detected radiation outside a predetermined range.

In order that the system can be used for boundaries occupying long distances, the or each optical radiation means is preferably a laser generator. For added security, the or each generator may be set for pulsed operation in accordance with a predetermined code and the associated detector means may be set to change its state in the absence, in use; of detecting that code.

The invention also comprises a method of making a composite strand comprising positioning a fibre-optic waveguide within a longitudinal groove formed in a carrier strand, the carrier strand having barbs or serrations, and securing an adhesive strand to the carrier strand so as to overlie the longitudinal groove.

The fibre-optic waveguide may be held within the groove by a bonding agent.

Preferably, the method comprises the step of winding the fibreoptic waveguide, carrier strand and adhesive strand onto a reel, the adhesive strand being arranged to cover the bonding agent and so prevent successive turns on the reel from becoming bonded together by the bonding agent.

The invention additionally comprises a fence or wall disposed to extend along a given boundary, the fence or wall comprising a number of strands running along the boundary, at least one of the strands being of said composite strand.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a plan view of a composite elongate strip incorporating a single fibre-optic filament, Figure 2 is a part-sectional view on an enlarged scale taken along the line Il-Il of Figure 1, Figure 3 is a side elevational view showing the two ends of a fence and a security system, and Figure 4 illustrates one preferred way of using a barbed strip in a security fence.

Referring to Figures 1 and 2, a strip 1 of bendable material for use in a security system comprises a carrier strip 2, which can be made of steel but which may be a galvanised strip painted with a protective plastics-based paint, formed with a longitudinal groove 3 running along the centre of one (8) of its two principal faces. Located in this groove is a single fibreoptic filament 4, of ordinary commerical quality, with a sheathing 5 of plastics material which assists in protecting the filament. The sheathed fibre-optic filament is held in the groove by means of a suitable bonding agent 6, which may be a two-part flexible resin, and a strip of adhesive tape 7 is applied to the principal face 8 of the strip 1 so as to cover the filament and bonding agent in the groove 3 and also the adjacent surface areas of the principal face 8.

The strip 1 is formed with integral barbs or serrations 9 at spaced intervals along its two longitudinal edges.

In accordance with a preferred method of manufacturing the barbed strip 1, the following manufacturing steps are carried out: 1. Edge portions of a length of carrier strip having straight longitudinal edges are punched away from both edges so as to provide the barbs or serrations 9.

2. The central groove 3 is formed in the steel strip 2 for example by passing the strip between a pair of male and female rollers. The steps 1 and 2 can be reversed, if desired.

3. Initiator chemical is smeared into the groove 3 and simultaneously resin, such as epoxy resin, is applied to the fibre-optic filament which is held ready to be introduced into the groove 3 so as to enrobe it. As an alternative to such two-part bonding agents, a single-part bonding agent may be used, in which case this bonding agent is applied to the groove and/or the fibre-optic filament.

4. Introductions of the filament into the groove can now be effected. The bonding agent then becomes cured to secure the filament in position.

The manufacturing steps can be effected in a continuous manufacturing process in which the strip is unwound from a reel and passed successively through a punching station, a rolling station to form the longitudinal groove (the order of these two stations can be reversed), and a fibre-optic filament introducing station, and is then rewound at a re-reeling station. The one or two-part bonding agent is applied at a suitable place or places. To prevent successive turns on the take-up reel from becoming bonded together by the cured bonding agent, it is necessary to take an appropriate step, i.e.

to apply the adhesive tape 7 to the principal face 8 so as to cover the bonding agent in the groove and overlie the adjacent surface areas of the principal face 8. This enable the finished strip to be wound onto a reel even before the bonding agent has become fully cured. Alternatively, the bonding agent can be cured at a stoving station between the fibreoptic filament introducing station and re-reeling station.

Referring to Figure 3, two composite strips 1 of the construction just described are disposed to extend along a boundary, of a field for example, the strips being supported by upright posts at regular intervals, of which the two end posts 10 are shown in Figure 3. A light source 11 is positioned to direct light into one end of the fibre-optic filament at one end of the lower strip 1 and a detector 12 is positioned adjacent the other end of the strip 1 so that its sensitive part receives the light leaving the end of the fibre-optic filament. The detector 12 is connected to a warning device 13 such as an audible or visual alarm. The upper strip 1 is likewise provided with a light source, detector and warning device, although these, for convenience, are not shown in Figure 3. The following description is confined to the lower strip.

In use, the detector 12 has a first, normal state in which no warning signal is sent to the warning device 13. The detector 12 is so arranged that for negligible disturbances of the strip, such as caused by the effects of wind, the detector remains in this state. However, the detector is set to respond to changes in the intensity of the light leaving the fibre optic filament which fall outside a predetermined range, so that in the event of a significant disturbance to the strip 1, for example if it is pushed sideways or compressed in any way or cut, the change in the detected light intensity will fall outside the predetermined range and the detector 12 will respond accordingly to operate the warning device 13.

It is to be noted that the fibre-optic filament 4 is preferably of ordinary commerical quality since not only is it considerably cheaper than a high quality filament but also there is inherently a larger variation in transmitted light intensity for any given variation in position of the filament and thus commercial quality filaments are especially suited to the described security system.

It is to be noted that the barbed strip shown in Figure 1 is advantageous in that, being in strip-form, it can be easily and safety stored wound on a drum while occupying less bulk as compared with a drum on which is wound an identical length of barbed wire.

As an alternative to a zinc coating, the coating may comprise plastics material such as nylon although it should be noted that the plastics material coating will reduce the sharpness of the barbs.

It is possible to direct a pulsed light beam into one end of the fibre-optic filament with a view to enabling larger light intensities to be transmitted for a given transmitting power, thus enabling longer boundaries to be monitored by the optical detector and associated warning device. For greater security, the pulses may be coded and the detector arranged to operate the warning device if the pre-selected code is not detected.

In a preferred security system using more than one strip running along the boundary in question, at least one of the strips connecting adjacent posts incorporates a fibre optic filament with its associated optical source and detector/warning system but at least one further strip is a 'dummy' strip of identical external appearance to the fibre-optic strip but not incorporating any fibre-optic filament.

Such an arrangement is shown in Figure 4 to which reference is now directed. In this arrangement, a single fibre-optic strip and a single 'dummy' strip are used, these strips being respectively denoted by reference 1 and 1'. The fence posts are denoted by reference numeral 10. The advantage of such an arrangement is that since the cost of the 'dummy' strip is obviously considerably less than that of the fibre-optic strip, the cost of installing the fence is correspondingly reduced. On the other hand, a similar measure of security is provided because an intruder, even if aware that a fibreoptic filament security system is being used, would not risk disturbing either strip in case that strip is the one containing the fibre-optic filament.In a modification, the 'dummy' strip and/or the or each strip having a fibre-optic filament contains an electrical conductor such as a copper wire through which a current is passed for use in detecting if the wire is cut by an intruder. The cost of the fence would still be significantly less than if both strips were fibre-optic strips. Where more than one 'dummy' strip is used, one or more may include an electric conductor whilst the remaining 'dummy' strip(s) contain(s) no such conductor(s). Alternatively, or in addition, one or more of the strips (fibre-optic and/or 'dummy') can include an embedded insulated, electrically conductive wire which serves to supply power to ancillary equipment (e.g.

optical booster receiver/transmitter units for the fibre-optic system) at intervals along the boundary covered by the fence.

If the boundary occupies a large distance, for example several miles, it is advantageous if the light source takes the form of a laser generator. Moreover, it is to be noted that instead of a single filament, a plurality of filaments or even a fibre-optic bundle can be used, incorporated in the strip.

A further security measure would be to bury one or more strips, each including a fibre-optic filament, beneath the fence so that any attempt to burrow-in under the fence could likewise be detected optically in the manner described above.

Fibre-optic filaments used as described with an energy source and detector can be included in a wall structure or mounted in a conduit disposed along the boundary in question. Any attempt to cross the wall by partially dismantling or destroying it, giving rise to any filament being disturbed or broken, or any attempt to cut through the conduit, will enable the attempted intrusion to be detected.

Reference is directed to our cop enduing application No. 40412/77 (Serial No. 1602743) which describes and claims a security system incorporating a fibre-optic waveguide means.

WHAT WE CLAIM IS: 1. A composite strand comprising a carrier strand having barbs or serrations, and a fibreoptic waveguide carried by said carrier strand.

2. A composite strand as claimed in claim

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. sensitive part receives the light leaving the end of the fibre-optic filament. The detector 12 is connected to a warning device 13 such as an audible or visual alarm. The upper strip 1 is likewise provided with a light source, detector and warning device, although these, for convenience, are not shown in Figure 3. The following description is confined to the lower strip. In use, the detector 12 has a first, normal state in which no warning signal is sent to the warning device 13. The detector 12 is so arranged that for negligible disturbances of the strip, such as caused by the effects of wind, the detector remains in this state. However, the detector is set to respond to changes in the intensity of the light leaving the fibre optic filament which fall outside a predetermined range, so that in the event of a significant disturbance to the strip 1, for example if it is pushed sideways or compressed in any way or cut, the change in the detected light intensity will fall outside the predetermined range and the detector 12 will respond accordingly to operate the warning device 13. It is to be noted that the fibre-optic filament 4 is preferably of ordinary commerical quality since not only is it considerably cheaper than a high quality filament but also there is inherently a larger variation in transmitted light intensity for any given variation in position of the filament and thus commercial quality filaments are especially suited to the described security system. It is to be noted that the barbed strip shown in Figure 1 is advantageous in that, being in strip-form, it can be easily and safety stored wound on a drum while occupying less bulk as compared with a drum on which is wound an identical length of barbed wire. As an alternative to a zinc coating, the coating may comprise plastics material such as nylon although it should be noted that the plastics material coating will reduce the sharpness of the barbs. It is possible to direct a pulsed light beam into one end of the fibre-optic filament with a view to enabling larger light intensities to be transmitted for a given transmitting power, thus enabling longer boundaries to be monitored by the optical detector and associated warning device. For greater security, the pulses may be coded and the detector arranged to operate the warning device if the pre-selected code is not detected. In a preferred security system using more than one strip running along the boundary in question, at least one of the strips connecting adjacent posts incorporates a fibre optic filament with its associated optical source and detector/warning system but at least one further strip is a 'dummy' strip of identical external appearance to the fibre-optic strip but not incorporating any fibre-optic filament. Such an arrangement is shown in Figure 4 to which reference is now directed. In this arrangement, a single fibre-optic strip and a single 'dummy' strip are used, these strips being respectively denoted by reference 1 and 1'. The fence posts are denoted by reference numeral 10. The advantage of such an arrangement is that since the cost of the 'dummy' strip is obviously considerably less than that of the fibre-optic strip, the cost of installing the fence is correspondingly reduced. On the other hand, a similar measure of security is provided because an intruder, even if aware that a fibreoptic filament security system is being used, would not risk disturbing either strip in case that strip is the one containing the fibre-optic filament.In a modification, the 'dummy' strip and/or the or each strip having a fibre-optic filament contains an electrical conductor such as a copper wire through which a current is passed for use in detecting if the wire is cut by an intruder. The cost of the fence would still be significantly less than if both strips were fibre-optic strips. Where more than one 'dummy' strip is used, one or more may include an electric conductor whilst the remaining 'dummy' strip(s) contain(s) no such conductor(s). Alternatively, or in addition, one or more of the strips (fibre-optic and/or 'dummy') can include an embedded insulated, electrically conductive wire which serves to supply power to ancillary equipment (e.g. optical booster receiver/transmitter units for the fibre-optic system) at intervals along the boundary covered by the fence. If the boundary occupies a large distance, for example several miles, it is advantageous if the light source takes the form of a laser generator. Moreover, it is to be noted that instead of a single filament, a plurality of filaments or even a fibre-optic bundle can be used, incorporated in the strip. A further security measure would be to bury one or more strips, each including a fibre-optic filament, beneath the fence so that any attempt to burrow-in under the fence could likewise be detected optically in the manner described above. Fibre-optic filaments used as described with an energy source and detector can be included in a wall structure or mounted in a conduit disposed along the boundary in question. Any attempt to cross the wall by partially dismantling or destroying it, giving rise to any filament being disturbed or broken, or any attempt to cut through the conduit, will enable the attempted intrusion to be detected. Reference is directed to our cop enduing application No. 40412/77 (Serial No. 1602743) which describes and claims a security system incorporating a fibre-optic waveguide means. WHAT WE CLAIM IS:

1. A composite strand comprising a carrier strand having barbs or serrations, and a fibreoptic waveguide carried by said carrier strand.

2. A composite strand as claimed in claim

1 in which the barbs or serrations are formed at intervals along each longitudinal edge of the carrier strand.

3. A composite strand as claimed in claim 1 or 2 in which the carrier strand has a longitudinal groove therein in which the fibreoptic waveguide is disposed, and an adhesive strand is applied to the carrier strand so as to overlie the longitudinal groove and cover the fibre-optic waveguide.

4. A composite strand as claimed in claim 3 in which the fibre optic waveguide is held within the groove by a bonding agent, the adhesive strand overlying the bonding agent.

5. A composite strand according to any preceding claim wherein the carrier strand is coated with corrosion resistant material which covers the fibre-optic waveguide.

6. A composite strand according to any preceding claim wherein the carrier strand is made of steel.

7. A composite strand according to any preceding claim wherein the carrier strand is made of a galvanised strand painted with plastics-based paint.

8. A composite strand according to any preceding claim wherein the waveguide is enclosed in a plastics sheathing.

9. A composite strand as claimed in any preceding claim in which the composite.

strand is bendable.

10. A composite strand as claimed in claim 1 and substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

11. A method of making a composite strand comprising positioning a fibre-optic waveguide within a longitudinal groove formed in a carrier strand, the carrier strand having barbs or serrations, and securing an adhesive strand to the carrier strand so as to overlie the longitudinal groove.

12. A method as claimed in claim 11 in which the fibre-optic waveguide is held within the groove by a bonding agent.

13. A method as claimed 12 comprising the step of winding the fibre-optic waveguide, carrier strand and adhesive strand onto a reel, the adhesive strand being arranged to cover the bonding agent and so prevent successive turns on the reel from becoming bonded together by the bonding agent.

14. A method according to any of claims 11 to 13 wherein the barbs or serrations are formed at intervals along longitudinal edges of the carrier strand by a stamping process.

15. A method of making composite strand as claimed in claim 11 and substantially as hereinbefore described with reference to the accompanying drawings.

16. A security system comprising at least one composite strand as claimed in any of claims 1 to 10.

17. A security system as claimed in claim 16 in which there are optical radiation means positioned to direct optical radiation along said waveguide from one end, and detector means positioned to detect radiation leaving said waveguide from the other end and arranged to change its state in response to a change in detected radiation outside a predetermined range.

18. A security system according to claim 17, wherein a warning device is provided arranged to be actuated by a change in state of the detector means.

19. A security system according to claim 17 or 18 wherein there is a further strand which is disposed adjacent to the or each said composite strand and which is of identical appearance externally to the or each said composite strand but whice does not include any fibre-optic waveguide means.

20. A security system according to any of claims 17 to 19 wherein an additional composite strand as claimed in any of claims 1 to 10 is buried adjacent the first-mentioned composite strand, there being an additional optical radiation means positioned to direct optical radiation along the waveguide of said additional composite strand from one end, and additional detector means positioned to detect radiation leaving the last-mentioned waveguide means from the other end and arranged to change its state in response to a change in detected radiation outside a predetermined range.

21. A security system as claimed in claims 17 to 20 wherein the or each optical radiation means is a laser generator.

22. A fence or wall disposed to extend along a given boundary, the fence or wall comprising a number of strands running along the boundary, at least one of the strands being a said composite strand as claimed in any of claims 1 to 10.