GB2472904A

GB2472904A - System for detecting an attempt to gain unauthorized access through a side curtain of a trailer

Info

Publication number: GB2472904A
Application number: GB1013454A
Authority: GB
Inventors: James Anthony Robert Hird
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-08-20
Filing date: 2010-08-11
Publication date: 2011-02-23
Also published as: GB201013454D0; GB0914561D0

Abstract

A security system for a curtain 3 of a vehicle trailer (1,fig.1) comprises a detector strip 8 having an elongate flexible panel (9, Fig.2) containing a conductive wire (10, Fig.2) tracing an indirect path from end to end of the panel (9, Fig.2). The strip 8 is applied to an inner face of the curtain 3, extending generally horizontally near a foot of the curtain 3, where an intruder would be likely to cut through the curtain 3 to gain entry to the trailer 1. The conductive wire (10,Fig.2) is connected to an alarm arrangement and power supply, usually in the vehicle cab, by way of a contact unit (18, 31,Fig.7) mounted to a suspension unit 4 of the curtain 3, and a corresponding contact unit (17,Fig.7) mounted either alongside the cant rail (5,Fig.6) along which the suspension units 4 run, or at an end of the cant rail (5, Fig.6) where contact would be made when the curtain 3 is closed. When an intruder cuts through the curtain 3, the detector strip 8 and conductive wire (10, Fig.2) will also be cut, breaking the conductive path and activating the alarm.

Description

SECURITY SYSTEM

The present invention relates to a system to detect an attempt to gain unauthorised access through a barrier. More particularly, but not exclusively, it relates to apparatus to detect unauthorised penetration through a side curtain of a vehicle, trailer or the like.

Lorries, and in particular heavy goods vehicle trailers, are often constructed with a load-carrying compartment having flexible curtains extending along each side, as an alternative to rigid walls. A rear of the compartment may also be enclosed by such a curtain. The curtains are typically made from flexible plasticised PVC sheet. These curtains are suspended from a rail by a series of slideable suspension units, allowing the curtain to be drawn aside to permit easy access to an entire interior of the load-carrying compartment. Thus, such a vehicle or trailer may more easily be loaded or unloaded, compared to vehicles or trailers requiring access through doors, which are usually set at the rear of an elongate load-carrying compartment.

The curtains are secured in place when closed, for example being lashed down along a lower edge to tie-downs or the like. However, the curtains must be sufficiently thin and flexible to be drawn aside easily, and so as not to occupy much space once drawn aside. As a result, it may be possible for thieves to cut through the curtains to gain access to a load within the compartment, using simple equipment, such as conventional retractable-blade knives. It may also be possible for stowaways to enter the load-carrying compartment by similar means.

Curtains incorporating reinforcing materials are available. For example, a layer of Keviar� fabric may be incorporated in the curtain, but this has proved to be prohibitively expensive.

Curtains are known comprising two layers of PVC sandwiching a layer of chicken wire or other wire mesh, but these are again significantly more expensive that conventional curtains, and sufficiently strong wire mesh may not be sufficiently flexible. In both cases, the curtain would be expensive to repair, and repair would probably be necessary even if the curtain successfully resisted penetrating attack.

It is possible to fit security systems to lorries and trailers, typically employing passive infra-red sensors or the like to monitor unexpected presences within the load-carrying compartment. However, these systems are still expensive, while the cost margins on most haulage work tend to be low. Therefore, a more affordable approach to detecting unauthorised access through a curtain of this type would be of great benefit.

It is believed that a system applicable to such vehicle curtains would probably also be useful in respect of other barriers that could be susceptible to unauthorised breach or penetration.

It is hence an object of the present invention to provide a security system adapted to detect penetration through a lorry curtain or a similar barrier, and to provide a rapid alert in the event of penetration being detected.

According to a first aspect of the present invention, there is provided an intrusion detection device comprising an elongate zone of material having electrical conductor means extending therethrough from adjacent a first end thereof to adjacent a second end thereof remote from the first, said conductor means being provided with electrical contact means connectable to an alarm system, and the elongate zone being so mountable to barrier means that breach of the barrier means causes breakage of the conductor means, so as to present passage of electrical current therethrough.

Preferably, the intrusion detection device is adapted to be mounted to an internal face of the barrier means.

Advantageously, said device is configurable to extend substantially across the barrier means from adjacent a first margin thereof to adjacent a second margin remote from the first.

The intrusion detection device may comprise a plurality of separately formed device elements so connectable as to provide a device of desired dimensions.

Said device elements may be connectable in series.

Said device elements may comprise components of the elongate zone.

Preferably, said elongate zone of material is substantially flexible in use.

Advantageously, said elongate zone of material is substantially laminar.

Said elongate zone of material may comprise a lamina of flexible plastics material, optionally provided with textile reinforcement.

Preferably, said electrical conductor means comprises at least one electrical wire means.

In a preferred embodiment, the intrusion detection device is adapted to be mounted to barrier means comprising a substantially flexible barrier element supported by a plurality of movable support elements, said support elements being movable along elongate track means to facilitate opening and/or closing of the barrier means.

The contact means of the device may then comprise a first contact element mounted or mountable to one said movable support element and a second contact element mounted or mountable to the track means.

Said first contact means is preferably mounted or mountable to a movable support element located adjacent an end of the flexible barrier element.

The device may then comprise a respective first contact means located adjacent each remote end of the flexible barrier element.

The second contact element may comprise busbar means so extending adjacent the track means that it may be contacted continuously by said first contact means as the respective movable support means is moved along the track means.

The busbar means may optionally only extend adjacent a terminal portion of the track means.

Alternatively, the second contact element may be so located or locatable adjacent an end of the track means as to be contactable by respective first contact means of the respective movable support means when the movable support means is at or near an end of its travel along the track means.

Preferably, the intrusion detection device is adapted to be mounted to curtain means extending along a side or end of load-carrying compartment means of a trailer, lorry or other vehicle.

According to a second aspect of the present invention, there is provided an alarm system comprising an intrusion detection device as described in the first aspect above, and control unit means cormectable to the intrusion detection device by means of the contact means thereof and adapted to generate an alarm signal in response to cessation of passage of electrical current through the detection device.

According to a third aspect of the present invention, there is provided a method for detecting a breach of barrier means, comprising the steps of providing an intrusion detection device as described in the first aspect above, mounting said device to said barrier means, causing an electrical current to pass through said device, monitoring passage of said current and generating an alarm indication on cessation of passage of the current.

Embodiments of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure 1A is a schematic side elevation of a load-carrying curtain-sided vehicle trailer of known form; Figure lB is a schematic side elevation of the trailer shown in Figure IA with its curtain drawn; Figure 2 is a scrap schematic elevation of a security strip embodying the present invention; Figure 3 is a cross-sectional view of the security strip shown in Figure 2, taken along the line Ill-Ill; Figure 4 is a schematic elevation of an interior face of a curtain fitted with the security strip shown in Figure 2; Figure 5 is a schematic perspective view of a roller support unit from the curtain shown in Figure 4; Figure 6 is a lateral schematic cross-section of the roller support unit shown in Figure 5, mounted to a cant rail and having a first electrical contact arrangement embodying the present invention fitted thereto; Figure 7 is a scrap schematic perspective view of a portion of the roller support unit shown in Figure 5, incorporated into a second electrical contact arrangement embodying the present invention; Figure 8 is a side elevation of a slide contact unit of a third electrical contact arrangement embodying the present invention; Figure 9 is a scrap perspective view of part of a roller hook unit of the slide contact unit shown in Figure 8; Figure 10 is an end elevation of the roller hook unit shown in Figures 8 and 9; Figure ills an end elevation of an end stop unit of the slide contact unit shown in Figure 8; and Figure 12 is a schematic perspective view of a roller shutter/door provided with a security strip embodying the present invention.

Referring now to the Figures, and to Figures IA and I B in particular, a curtain-sided trailer unit 1 of conventional form is shown. This comprises a chassis connectable to a tractor unit to form an articulated lorry of conventional form. The present invention is equally applicable to non-articulated lorries having curtain-sided load-carrying compartments and to trailers and lorries having curtains at the rear as well as to the sides of the load-carrying compartment, but it is most straightforward to set out in terms of a trailer unit as shown.

The trailer unit I comprises a load-bearing floor 2 and a superstructure comprising a rigid roof and front and rear ends, but with each side enclosable solely with a flexible curtain 3, typically comprising flexible PVC sheet or PVC-coated textile. The curtain 3 is suspended by a plurality of suspension units 4 from a cant rail 5 extending along an edge of the roof.

The suspension units 4 (shown in more detail below) are freely slideable along the horizontal cant rail 5, between a disposition (Figure 1 A) in which the curtain 3 closes off the respective side of the trailer 1, and a disposition (Figure 1 B) in which the curtain 3 is drawn back, providing easy access to cargo 6 stacked on the floor 2 of the trailer 1. This allows rapid access to the cargo 6, compared to a trailer having rigid side walls that must be loaded and unloaded through doors at its rear end.

The curtain 3 is fastenable to the floor 2 with a series of straps, lashings 7 or the like located adjacent its lower margin. Various locking arrangements are available to prevent unauthorised unfastening of these straps, lashings 7, etc, by persons wishing to enter the trailer 1, either to steal the cargo 6 or to stow away therein.

However, the curtain 3 must be sufficiently thin and flexible that it can be drawn back as far as possible to provide maximum access to the interior of the trailer I (the curtain 3 in Figure lB would probably in practice be drawn back further than is shown). The typical curtain 3 is as a result too easy to cut, using conventional retractable-blade knives or the like, for example. As mentioned above, reinforcing the curtain 3 is expensive and reduces its flexibility. Alarm systems for the interior of a trailer I are known, generally being comparable to domestic and commercial building alarm systems, for example using passive infra-red detectors. However, these are still too expensive for many hauliers.

The security system of the present invention is based around an elongate detector strip 8, shown in schematic form in Figures 2 and 3. The detector strip 8 comprises an elongate panel 9, typically of flexible PVC. A thin conductive wire 10 extends from end to end of one face of the panel 9. Typically conventional 0.22mm wire may be used. The wire 10 may follow a relatively indirect path, for example as shown, or a relatively direct path along the panel 9. ln other variants, more than one wire 10 may extend along the panel 9, connected in parallel (though not necessarily extending parallelly). The wire 10 is held in place on the panel 9 by a thin lamina Ii of PVC sheet, which is mounted to the panel 9 so as to sandwich the wire 10 between lamina Ii and panel 9. The panel 9 is relatively thicker than the lamina ii, preferably being slightly padded. This prevents the path of the wire 10 being visible from the panel 9 side of the detector strip 8, as well as importing sufficient strength to the strip 8 as a whole. The strip 9 may be considered as forming an elongate pocket to hold the wire 10 -.9..

Although for simplicity the strip 8 is shown as a single body, it is more convenient for it to comprise a plurality of shorter component strips, connectable end to end, both physically and electrically. This allows a detector strip 8 having a desired overall length to be assembled from a set of standard components. It is believed that individual component strips of about twelve inches (about 300mm) in length should give sufficient variation in strip length to fit any practical size of curtain 3.

The use of the detector strip 8 is shown in Figure 4 Preferably, the strip 8 is applied to an internal face of the curtain 3, extending roughly horizontally adjacent its lower edge. Ideally, the strip S is mounted with a suitable adhesive. The laniina 11 face of the strip 8 may be applied to the curtain 3, so that the padded panel 9 faces away from the curtain 3, concealing the path of the wire 10. AlternativelY, if the curtain 3 is sufficiently thin that the wire 10 would be visible from outside the curtain 3, the padded panel 9 face of the strip 8 may be applied to the curtain 3, so as to lie between the curtain 3 and the wire 10.

Electrical contacts (omitted from Figure 4 for simplicity) are provided at each end of the detector strip 8, and allow a small electrical current to be passed along the wire 10. The strip 8 is located so that any attempt to cut through the curtain 3 from outside will almost certainly cut through the strip 8 mounted to its internal face. The wire 10 will thus be severed, and the current will cease to flow. This is used as the detection means for an alarm arrangemeflt described in more detail below.

One problem with deploying a current-.beariflg detector strip S across a movable curtain 3 is that an electrical connection must be established from the movable curtain 3 to a remainder of the trailer I and thence to a power supply and to an alarm arrangement. Three alternative -10 -approaches are found to be of particular use. Each utilises the suspension units 4 for the curtain, one of which is shown in schematic form in Figure 5.

The suspension unit 4 in essence comprises a pair of wheels 12 mounted on either side of an upper (in use) portion of a body 13 of the suspension unit 4. A lower portion 14 of the body 13 of the suspension unit 4 is connected to an upper margin of the curtain 3 (which is omitted from the Figure for simplicity). As shown in Figure 6, the wheels 12 of the suspension unit 4 travel within the cant rail 5, which is profiled to provide a smooth travelling surface for the wheels 12, while retaining them (and hence the suspension unit 4 as a whole) securely engaged within the cant rail 5 (which may also be known as the roller bar).

In the first approach, a brass busbar 15 is mounted below the cant rail 5, extending substantially horizontally, beside the suspension units 4 and within the trailer 1. A contact unit 16 is mounted to the lower portion 14 of the suspension unit 4, in alignment with the busbar 15. The contact unit 16 comprises a spring-loaded plate (preferably of copper) which remains in contact with the busbar 15 as the suspension unit 4 travels along the cant rail 5. A wire 10 extending from the contact unit 16 along the inside of the curtain 3 (not shown) leads to an end of the detector strip 8. The busbar 15 is connected to a source of electrical current and an alarm arrangement. If a busbar 15 extending along the entire cant rail 5 is used, the detector strip 8 is thus permanently electrically connected. However, it will usually be sufficient for the busbar 15 to extend along a relatively short terminal portion of the cant rail 5, contactable by the contact unit 16 when the curtain 3 is almost or fully closed.

Figure 7 shows the second approach, in which the detector strip 8 is only electrically connected when the curtain 3 is fully closed. In this approach, an elongate spring-loaded contact probe 17 is mounted to or adjacent an end portion 5E of the cant rail 5. When a suspension unit 4 approaches an end of its travel along the cant rail 5, the contact probe 17 passes below or between the wheels 12 and meets a contact patch 18 located on an edge of the upper portion of the main body 13 of the suspension unit 4. The contact patch 18 is connected via a wire 10 to the detector strip 8, as above. (NB: complex microswitch arrangements could be used, but are likely to be jammed by grit and grime in such an application; a simple spring-loaded plunger, as shown, is likely to be more robust and more reliable, not to mention cheaper).

This second approach is believed to be slightly more complex and expensive than the first, but better concealed and harder to defeat. Since the alarm arrangement would only be required to be operable when the curtain 3 is closed, it is not important that the electrical contact is only made when the suspension unit 4 is at or near the end of its travel along the cant rail 5.

A third approach is illustrated in Figures 8 to 11. This approach is similar to the second, since it employs a contact mounted to an end-portion 5E of the cant rail 5, similar to that shown in Figure 7, although it is not essential that the contact 17 on the cant rail 5 be spring loaded, for reasons that will become clear below. The third approach has the advantage that it is not necessary to replace suspension units 4 with units specially modified for the purpose.

The third approach uses a slide contact unit 31, shown in full in Figure 8. This comprises a roller hook unit 32, and an ends stop unit 33 mounted thereto at a distal end of an elongate boom 34. -12-

The roller hook unit 32 comprises a solid body 35 having two flat-section hook members 36 extending from its first end, defining a slot 37 between them, as shown more clearly in Figures 9 and 10. Each hook member 36 defines a round-headed recess 38. The roller hook unit 32 may be attached to an existing suspension unit 4 at an end of the curtain 3 by hooking the hook members 36 over an axle 39 of the suspension unit 4, to either side of the body 13, which extends within the slot 37. The axle 39 is thus received in the respective recess 38 of each hook member. A respective face 40 of the solid body 35 of the roller hook unit 32 is recessed at an angle, so that the suspension unit 4 may swing freely about its axle 39.

A pair of wing strips 41 extend laterally from a lower, in use, edge of the solid body 35 and optionally (as shown) from an adjacent portion of each hook member 36. A height, in use, of the roller hook unit 32 is selected to fit a particular cant rail 5, or alternatively the height of a standard roller hook unit 32 may be trimmed to fit before the wing strips 41 are mounted thereto. In either case, the wing strips 41 contact an underside of the cant rail 5, when the roller hook unit 32 is in an operative disposition.

The elongate boom 34 passes through a shaft 42, extending horizontally (in use) through the solid body 35 of the roller hook unit 32, and extends outwardly through the slot 37 between the hook members 36, above the axle 39. A spring 43 is mounted around the boom 34 adjacent the solid body 35, the function of which is described below.

The end stop unit 33, shown in Figures 8 and 11, comprises a main body 44 provided with top and bottom plates 45, 46 which each extend laterally to either side of the main body 44.

An electrical contact plate 48 is mounted to a face of the main body 44 remote from the roller hook unit 32, with a connecting wire 47 running from the electrical contact plate 48 through a -13 -passage 49 extending through the main body 44. The connecting wire 47 runs to the detector strip 8.

The height of the end stop unit 33 and the widths of the top and bottom plates 45, 46 are selected such that the end stop unit 33 fits closely within the cant rail 5, while being able to slide freely along its interior.

To fit the slide contact unit 31 to the cant rail 4, the end stop unit 33 is inserted within the cant rail 5, and the roller hook unit 32 is separately hooked over an axle 39 of a suspension unit 4, as described above. They are then connected by the elongate boom 34. Once assembled, the wings 41 contact an underside of the cant rail 5, the top and bottom plates 45, 46 contact the interior walls of the cant rail 5, and the boom 34 extends substantially horizontally between the roller hook unit 32 and the end stop unit 33.

In use, the curtain 3 is closed by dragging it towards the end cant rail 5E. Each suspension unit 4 will swing round, being pulled in the direction shown by arrow 50, and will roll on its wheels 12 along the cant rail 5. The roller hook unit 32, being hooked over the axle 39 of the suspension unit 4, also travels along the cant rail 5, with the boom 34 tipped with the end stop unit 33 extending before it.

When the suspension unit 4 and associated slide contact unit 31 approach the end cant rail SE, the electrical contact plate 48 will meet a corresponding contact 17 on the end cant rail SE, thus connecting the detector strip 8 to the alarm arrangement on the vehicle. As the suspension unit 4 travels further towards the end cant rail SE, the roller hook unit 32 will move closer to the end stop unit 33, an end of the boom 34 remote from the end stop unit 33 projecting from the solid body 35 of the roller hook unit 32, and the spring 43 becoming compressed. This spring loaded action ensures a firm, reliable contact by the electrical contact plate 48, even should the suspension unit 4 and roller hook unit 32 move slightly to and fro along the cant rail 5. (Thus, it is not essential also to spring-load the contact 17 on the end cant rail 5E).

When the curtain 3 is opened, the spring 43 first returns the slide contact unit 31 to the configuration shown in Figure 8, and then contact is lost between the electrical contact plate 48 and the corresponding contact 17 on the end cant rail SE, deactivating the detector strip 8.

Whether the approach of Figure 6, Figure 7 or Figure 8 is used the detector strip 8 is connected thereby to a negative feed only electric charge (a positive feed might fuse the wire and melt the curtain). An electronic control unit (ECU) for the alarm arrangement is set up to monitor passage of current through the detector strip 8. If the curtain 3 and strip 8 are cut, the wire 10 is broken, the current fails and the ECU registers an alarm condition. To allow for brief interruptions, the ECU may be set up so that if no current is detected for three consecutive set periods (e.g. of ninety minutes each), an alarm is raised. This alarm could take the form of an audible and/or visible alarm on the tractor or trailer unit 1, or it could (preferably) take the form of a wireless signal sent to a central monitoring computer or control room, or directly to a pager, mobile telephone handset or dedicated receiver unit, which may be carried by a driver responsible for the trailer unit 1.

A similar alarm arrangement may be used to protect a doorway, for example a doorway 19 fitted with a roller shutter, as shown in Figure 12. In a typical roller shutter, the articulated slats 20 making up the shutter are mounted horizontally, extending between a pair of vertical -15 -rails or tracks 21. A detector strip 8 may be fastened to an interior face of a slat 20, so that breaking through the roller shutter would break the wire 10 within the strip 8. The wire 10 may be electrically connected to a power supply and an alarm ECU by electrical contact arrangements similar to those shown in either Figure 6 or Figure 7, preferably leading from each remote end of the detector strip 8 to a respective busbar 15 or probe 17 associated with the respective track 21.

The alarm system described provide an effective means of alerting a driver or security personnel that a trailer side curtain 3 or other barrier has been-breached, without requiring expensive equipment or elaborate installation arrangements.

Claims

CLAIMSAn intrusion detection device comprising an elongate zone of material having electrical conductor means extending therethrough from adjacent a first end of the zone to adjacent a second end of the zone remote from the first, said conductor means being provided with electrical contact means connectable to an alarm system, and the elongate zone being so mountable to barrier means that breach of the barrier means causes breakage of the conductor means and of an electrically conductive path therethrough.
2. An intrusion detection device as claimed in claim 1, adapted to be mounted to an internal face of the barrier means
3. An intrusion detection device as claimed in either claim I or claim 2, configurable to extend substantially across the barrier means from adjacent a first margin of the barrier means to adjacent a second margin remote from the first.
4. An intrusion detection device as claimed in any one of the preceding claims, comprising a plurality of separately formed device elements so electrically connectable as to provide a device of desired dimensions.
5. An intrusion detection device as claimed in claim 4, wherein said device elements are also physically connectable.-17 -
6. An intrusion detection device as claimed in either claim 4 or claim 5, wherein said device elements are connectable in series.
7. An intrusion detection device as claimed in either claims 4 to 6, wherein said device elements comprise components of the elongate zone.
8. An intrusion detection device as claimed in any one of the preceding claims, wherein said elongate zone of material is substantially flexible in use.
9. An intrusion detection device as claimed in any one of the preceding claims, wherein said elongate zone of material is substantially laminar.
10. An intrusion detection device as claimed in any one of the preceding claims, wherein said elongate zone of material comprises a lamina of flexible plastics material, optionally provided with textile reinforcement.
11. An intrusion detection device as claimed in any one of the preceding claims, provided with padding means adapted to conceal the conductor means
12. An intrusion detection device as claimed in any one of the preceding claims, adapted to be mounted to barrier means comprising a substantially flexible barrier element supported by a plurality of movable support elements, said support elements being movable along elongate track means to facilitate opening and/or closing of the barrier means. -18-13. An intrusion detection device as claimed in claim 12, wherein the or one of the electrical contact means of the device comprises a first contact element mounted or mountable to one said movable support element and a second co-operable contact element mounted or mountable to the track means.14. An intrusion detection device as claimed in claim 13, wherein said first contact element mounted or mountable to a movable support element located adjacent an end of the flexible barrier element.15. An intrusion detection device as claimed in claim 14, wherein the device comprises a respective first contact element located adjacent each remote end of the flexible barrier element.16. An intrusion detection device as claimed in any one of claims 13 to 15, wherein the second contact element of the electrical contact means comprises busbar means so extending adjacent the track means or a portion thereof that the busbar means is contactable continuously by said first contact element as the respective movable support means is moved along the track means or said portion thereof.17. An intrusion detection device as claimed in claim 16, wherein the busbar means extends adjacent only a terminal portion of the track means.18. An intrusion detection device as claimed in any one of claims 13 to 15, wherein the second contact element is so located or locatable adjacent an end of the track means as to be contactable by a respective first contact element on the respective movable support means when the movable support means is at or near an end of its travel along the track means.19. An intrusion detection device as claimed in any one of the preceding claims, adapted to be mounted to curtain means extending along a side or end of load-carrying compartment means of a trailer, lorry or other vehicle.20. An alarm system comprising an intrusion detection device as claimed in any one of the preceding claims, and control unit means connectable to the intrusion detection device by means of electrical contact means thereof, the control unit means being adapted to generate an alarm signal in response to loss of the conductive path through the detection device.21. A method for detecting a breach of barrier means, comprising the steps of providing an intrusion detection device claimed in any one of claims I to 19, mounting said device to said barrier means. applying an electrical potential across said device and generating an alarm indication on loss of the conductive path through the device.22. A barrier means provided with an intrusion detection device as claimed in any one of claims 1 to 19 mounted operatively thereto.23. A barrier means as claimed in claim 22, having said intrusion detection device mounted to an internal face thereof.24. A barrier means as claimed in either claim 22 or claim 23, wherein said intrusion detection device extends substantially across the barrier means from adjacent a first margin thereof to adjacent a second margin remote from the first.25. A barrier means as claimed in any one of claims 22 to 24, comprising a substantially flexible barrier element supported by a plurality of movable support elements, said support elements being movable along elongate track means to facilitate opening and! or closing of the barrier means.26. A barrier means as claimed in claim 25, wherein the or one of the electrical contact means of the device comprises a first contact element mounted to one said movable support element and a second, co-operable contact element mounted to the track means.27. A barrier means as claimed in claim 26, wherein the second contact element comprises busbar means so extending adjacent the track means or a portion thereof that the busbar means is contactable continuously by the first contact element as the respective movable support means is moved along the track means or said portion thereof.28. A barrier means as claimed in claim 26, wherein the second contact element is so located adjacent an end of the track means as to be contactable by first contact means on a respective movable support means when the movable support means is at or near an end of its travel along the track means.29. A barrier means as claimed in any one of claims 22 to 28, comprising curtain means extending along a side or end of a load-carrying compartment of a trailer, lorry or other vehicle.30. An intrusion detection device substantially as described herein with reference to the Figures of the accompanying drawings.