GB2523771A - A security system - Google Patents

Abstract

A security system 31 to detect unauthorized access to an area enclosed by flexible sheeting, for example a curtain sided trailer, comprises a sensing unit 41 and a remote alarm 71. The sensing unit 41 comprises a sensor membrane 43, a controller 45 connected to the sensor membrane 43 and a power supply 47. The controller 45, the sensor membrane 43 and the power supply 47 are mounted directly onto the flexible sheeting. The sensing unit 41 and the alarm 71 communicate wirelessly to activate the alarm 71 when a change in the electrical characteristics of the sensor membrane 43 is detected. The sensor membrane 43 may be an electrically conductive fabric material mounted on the flexible sheeting in a mesh pattern. There may be a pair of flexible sheeting position sensors 59, 61, a rear door sensor 63, a tail lift sensor and/or a roof sensor (95 fig. 5). There may be a control panel 65 mounted in the cab of a tractor unit 3. There may be a panic button to actuate the alarm 71. The power supply 47 may be charged by a flexible solar panel or a lithium polymer battery. There may be a key fob for remote activation and deactivation of the security system 31.

Description

"A Security System"

Introduction

This invention relates to a security system to detect unauthorized access to an area enclosed by flexible sheeting. Although not limited thereto, the present invention is particularly suited for use in detecting unauthorized access to the cargo storage area of curtain sided trailers or trucks and the invention will be described with reference to such an application.

Curtain sided trailers are commonly used to transport goods from one location to another. These trailers typically comprise a trailer bed having a frame mounted thereon about which curtains are secured to contain the area between the frame and the trailer bed. Often, the curtain sided trailers have a rigid door at the rear end of the trailer, a rigid panel at the front end of the trailer, and a rigid roof with flexible curtains provided on either of the elongate sides of the trailer.

There are several advantages to using curtain sided trailers for haulage. First of all, the curtain sided trailers greatly facilitate the loading and unloading of goods from the trailer as the curtain may be drawn to one side and the goods may be loaded or unloaded at any point along the trailer and from either side of the trailer. Secondly, the curtain sided trailers are relatively lightweight when compared to the alternative fixed-side trailers. This will increase the cargo carrying capacity (by weight) of the trailer and may lead to a reduction in fuel consumption.

There is however a significant disadvantage associated with curtain sided trailers, namely that the curtain sided trailers are inherently less secure than fixed sided trailers.

The flexible curtain typically comprises a PVC coated material or canvas that can be cut relatively easily with a blade. It is not uncommon for goods to be stolen from curtain sided trailers by unscrupulous individuals cutting through the curtain and removing the goods from the cargo storage area. Furthermore, it is known for stowaways or smugglers to gain access to the cargo storage area by cutting through or manoeuvring around the flexible curtain. If the haulier is caught trafficking people or contraband, the haulier may face harsh penalties including fines or imprisonment.

Various solutions have been proposed to address this problem however none have yet proven to be entirely satisfactory. One solution is to incorporate a wire, Keviar (Registered Trade Mark®) or similar fibre web in the flexible sheeting. The incorporation of wire, Kevlar® or similar fibre web into the flexible sheeting will strengthen the flexible sheeting and make it harder to penetrate. However, the use of wire will increase the weight of the flexible sheeting considerably and will hamper the flexibility and manoeuvrability of the flexible sheeting. The use of Kevlar ® or similar fibre will increase the cost of the flexible sheeting making it prohibitively expensive for most hauliers.

Other known solutions entail providing a wire conductor on the internal face of the flexible sheet. The wire is connected up to a power supply and monitoring means mounted on the trailer and a current is passed through the wire conductor. The electrical characteristics of the wire are closely monitored to determine whether the wire has been interfered with, for example by being cut. If the wire has been interfered with, an alarm is triggered, alerting the haulier. Such systems are described in GB2085952 (Davco Instrumentation & Security Company Limited), GB2472904 (Hird), U55049854 (Wolfl and W003093077 (Tiss Limited).

Although these systems overcome many of the problems associated with the wire/Kevlar ®/fibre web solutions, there are still problems with these systems. First of all, in order to operate, these systems require that the haulier plug in or unplug the system each time the curtain is opened or closed. It is not uncommon for the haulier to forget to plug the system in thereby rendering them inoperable. Secondly, because the power supply and monitoring means are mounted on the trailer they will be exposed making them susceptible to tampering. Thirdly, if the circuit is damaged, the entire system will be in a constant alarm condition until such time that the circuit is repaired. Even if only a small section of the circuit is damaged, the entire circuit will have to be de-activated until repairs can be carried out. During this time, the cargo will be unprotected. Fourth, the use of a wire mounted on the surface of the curtain has several disadvantages. For example, in many cases it will be possible to detect the location of the wire through the curtain thereby allowing the system to be circumvented with ease. Furthermore, the wire may inhibit the flexibility and manoeuvrability of the curtain. Further still, it is not uncommon for the wire to become pinched over time through frequent opening and closing of the curtain, rendering the system useless until such time as a repair can be carried out.

It is an object of the present invention to provide a security system to detect unauthorized access to an area enclosed by flexible sheeting that overcomes at least some of the problems with the known systems and that offers a useful choice to the consumer.

Statements of Invention

According to the invention there is provided a security system to detect unauthorized access to an area enclosed by flexible sheeting, the security system comprising: a sensing unit and a remote alarm unit physically unconnected from the sensing unit; the sensing unit comprising an electrically conductive sensor membrane, a controller connected to the sensor membrane and being operable to monitor the sensor membrane and detect a change in an electrical characteristic of the sensor membrane, and a power supply; the controller, the sensor membrane and the power supply being mounted directly onto the flexible sheeting; the sensing unit having a wireless communications module and the alarm unit having a wireless communications module to allow wireless communication from the sensing unit to the alarm unit to activate the alarm unit on the controller of the sensing unit detecting a change in the electrical characteristic of the sensor membrane.

By having such a system, the sensing unit, mounted in its entirety on the flexible sheeting and communicating with the alarm unit using wireless communications, will be self-sufficient and will not require a haulier or other operator to connect up the sensor membrane to the controller and the power supply. The sensor membrane will be permanently connected to both the controller and the power supply and this will obviate the possibility of the system not being engaged through the failure of the operator to connect up the power supply and/or the monitoring means. Furthermore, all of the sensing unit will be located internal the trailer or other area enclosed by flexible sheeting which will prevent third parties from accessing and tampering with the controller and/or the power supply.

In one embodiment of the invention there is provided a security system in which the electrically conductive sensor membrane comprises an electrically conductive fabric material. An electrically conductive fabric material is seen as useful as it will not become pinched over time, will be more difficult to detect than an upstanding wire, and will not inhibit the manoeuvrability of the flexible sheeting.

In one embodiment of the invention there is provided a security system in which the sensor membrane comprises a plurality of independently operable sensor circuits, each of which is separately connected to the controller. This is seen as a particularly preferred embodiment of the present invention. By having a plurality of independently operable sensor circuits forming the sensor membrane, if one of the circuits should register an alarm and/or be damaged, that circuit alone may be temporarily disconnected by the operator until such time that it is possible to repair the damaged circuit. The remaining sensor circuits can continue to operate thereby providing a degree of protection to the remaining flexible sheeting and cargo protected thereby. Furthermore, preferably, the operator will not need to positively disconnect the damaged sensor path but instead this will be done automatically. It is envisaged that once the system is disarmed and rearmed, the system will run a check to see if there is any damaged paths and will ignore any damaged paths. This check is preferably done every time the system is disarmed and rearmed. The check is also able to detect if a sensor path was repaired in the interim and if so will monitor that path once more.

In one embodiment of the invention there is provided a security system in which the sensor membrane is mounted on the flexible sheeting in a mesh pattern. By having the sensor membrane in a mesh pattern, it will not be possible to provide a hole sufficiently wide in the flexible sheet to fit goods or an individual through.

In one embodiment of the invention there is provided a security system in which there is provided a flexible sheeting position sensor operable to detect proximity of the flexible sheeting to a structure defining an opening to the area to be enclosed. This is seen as a particularly preferred embodiment of the present invention, particularly when applied to curtain sided trailers. It is known for traffickers to gain access to the cargo storage area of trailers by tampering with the fasteners and/or the curtain tensioners instead of cutting a hole in the curtain. By doing so, the traffickers create a gap sufficiently large enough to fit goods or an individual between the frame and the curtain supported on the structure, thereby allowing access to the cargo storage area. By having a position sensor operable to detect the proximity of the flexible sheeting to the structure, it is possible to detect if a gap that would allow access to the interior of the cargo storage area has been formed between the flexible sheeting barrier and the structure.

In one embodiment of the invention there is provided a security system in which the flexible sheeting position sensor is mounted directly onto the flexible sheeting. Again, by having the sensor mounted directly onto the flexible sheeting, it will not be necessary to provide plug-in connections between the sensor and the controller and the curtain will be self-sufficient.

In one embodiment of the invention there is provided a security system in which the flexible sheeting position sensor is connected to the controller.

In one embodiment of the invention there is provided a security system in which the flexible sheeting position sensor is mounted directly onto the structure defining the opening to the area to be enclosed.

In one embodiment of the invention there is provided a security system in which the flexible sheeting position sensor is connected directly to the alarm unit.

In one embodiment of the invention there is provided a security system in which the flexible sheeting is a curtain of a curtain sided trailer.

In one embodiment of the invention there is provided a security system in which there is provided a rear door sensor operable to detect whether or not the rear door of the trailer is closed. By having a rear door sensor, a more complete solution for curtain sided trailers is provided as it is possible to detect if an attempt is being made to gain unauthorized access to the trailer through the rear door. A relatively simple contact sensor could be used to good effect to determine whether or not the door has been opened.

In one embodiment of the invention there is provided a security system in which the rear door sensor is connected directly to the alarm unit. Rather than connecting the door sensor to the controller which then communicates with the alarm unit, the rear door sensor may be connected directly to the alarm unit to indicate an attempt at unauthorized access to the trailer.

In one embodiment of the invention there is provided a security system in which there is provided a tail lift sensor operable to detect use of the tail lift. Again, by having a tail lift sensor, a more complete solution for curtain sided trailers is provided as it is possible to detect if an attempt is being made to use the tail lift. A relatively simple contact sensor could be used to good effect to determine whether or not the tail lift has been operated.

Similarly, the tail lift sensor may take the form of a relay device in the control panel of the tail lift that can detect operation of the control panel and by extension the tail lift.

In one embodiment of the invention there is provided a security system in which the tail lift sensor is connected directly to the alarm unit.

In one embodiment of the invention there is provided a security system in which there is provided a roof sensor for the curtain sided trailer operable to detect unauthorized access through the roof of the curtain sided trailer. A portion of the roof may be retractable in which case it is envisaged that a simple contact sensor or position sensor could be used for this purpose. The sensor would detect if the roof had been retracted.

Alternatively, if the roof is constructed from a fabric or like material, the roof sensor may comprise a sensor membrane of similar construction to the sensor membranes used is the curtains to detect if the fabric has been tampered with.

In one embodiment of the invention there is provided a security system in which the roof sensor is connected directly to the alarm unit.

In one embodiment of the invention there is provided a security system in which there is provided a control panel in communication with at least one of the alarm unit and the controller of the sensing unit.

In one embodiment of the invention there is provided a security system in which the control panel is mounted in the cab of a tractor unit coupled to the curtain sided trailer.

Alternatively, the control panel may be mounted inside the trailer. If the control panel is mounted inside the trailer, the control panel can continue to be used in conjunction with the controller and the alarm unit.

In one embodiment of the invention there is provided a security system in which the control panel includes a driver operable panic button to actuate the alarm unit.

Alternatively, a panic button may be provided on a key fob which can be used to arm and disarm the system.

In one embodiment of the invention there is provided a security system in which there is provided a flexible solar panel and a power converter circuit connected to the power supply for recharging the power supply, the flexible solar panel and the power converter circuit being mounted on the flexible sheeting. A flexible solar panel will be useful in that it will increase the longevity of the battery power supply and reduce the maintenance requirements.

In one embodiment of the invention there is provided a security system in which the power supply comprises a lithium polymer battery.

In one embodiment of the invention there is provided a security system in which the controller comprises a micro-processor. Alternatively, the controller comprises a micro controller. Typically, a micro controller will use less power than a microprocessor and therefore would be preferred.

Detailed Description of the Invention

The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings, in which:-Figure 1 is a side view of a curtain sided trailer known in the art with the curtain sealing the cargo enclosure; Figure 2 is a side view of a curtain sided trailer known in the art with the curtain drawn to one side permitting access to the cargo; Figure 3 is a side view of a curtain sided trailer fitted with a first embodiment of security system according to the invention; Figure 4 is a side view of a curtain sided trailer fitted with a second embodiment of security system according to the invention; Figure 5 is a partial, perspective view of a curtain sided trailer fitted with a third embodiment of security system according to the invention; and Figure 6 is a plan cross-sectional view of a trailer with a fourth embodiment of the security system according to the invention.

Referring to Figures 1 and 2, there is shown a curtain sided trailer known in the art, indicated generally by the reference numeral 1, pulled by a tractor unit 3. The curtain sided trailer 1 comprises a trailer bed 5 supporting a trailer frame 7 including a front end 9, a rear end 11 having doors (not shown) and a roof 13. A flexible sheeting, in this case a curtain 15, is stretched between the trailer bed 5, the roof 13, the front end 9 and the rear end 11, as illustrated in Figure 1. The curtain 15 is supported along its upper edge by a plurality of runners 17 which in turn are slidably mounted in and suspended from a track 19 mounted on the roof 13. There are provided a plurality of straps 21 connected to the external face of the curtain 15. Each of these straps 21 is tensioned by one of a plurality of ratchets 23 which in turn are connected to the trailer bed 5.

Referring specifically to Figure 2, there is shown a view of the curtain sided trailer 1 with the curtain 15 drawn to one side, in this case towards the front end 9 of the trailer. In order to manoeuvre the curtain to the configuration shown in Figure 2 from that shown in Figure 1, the straps 21 are released from the ratchets 23 and the curtain is pulled across from the rear end 11 of the trailer ito the front end 9 of the trailer. The curtain is able to slide along the trailer 1 due to the fact that the runners 17 from which it is supported are slidably mounted in the track 19. Once in the position shown in Figure 2, goods 25 may be loaded to or unloaded from the trailer bed 5. Once the goods 25 have been loaded or unloaded as necessary, the curtain iS is replaced to the first configuration shown in Figure 1. This is done by sliding the curtain 15 on the runners 17 back along the track 19 and securing the curtain 15 in position by tensioning the straps 21 with the ratchets 23.

It will be understood that the bunched curtain 15 as illustrated in Figure 2 is exaggerated for clarity and typically the curtain will fold up in a more compact manner. Furthermore, in the example shown, the curtain 15 has been moved from the rear end 11 towards the front end 9 however it could be moved from the front end 9 towards the rear end ii if desired. In addition to the foregoing, a curtain 15 along the left side of the trailer 1 is shown however the curtain 15 could be on the other side of the trailer and indeed, often there will be a curtain 15 on both sides of the trailer 1 to allow loading and unloading from either side of the trailer 1. These are all standard features of curtain sided trailers.

Referring now to Figure 3, there is shown a diagrammatic representation of the security system according to the present invention, indicated generally by the reference numeral 31, installed in a curtain sided trailer 1. For clarity, like parts have been given the same reference numeral as before. The security system 31 comprises a sensing unit, indicated generally by the reference numeral 41 and an alarm unit, indicated generally by the reference numeral 71, remote from and physically separate from the sensing unit.

The sensing unit 41 in turn comprises an electrically conductive sensor membrane 43, a controller 45 and a power supply, in this case a rechargeable battery 47.

The electrically conductive sensor membrane 43 comprises a plurality of independently operable sensor circuits 49, 51, 53, 55, each of which is separately connected to the controller 45. Each of the independently operable sensor circuits 49, 51, 53, 55 is effectively a loop of electrically conductive fabric material, sometimes referred to as -10- "smart material'. The loops of electrically conductive fabric material extend outwardly from a point adjacent to the controller 45 at the front end 9 of the trailer 1, towards the rear end 11 of the trailer, and return back to the front end of the trailer.

The controller 45 is connected to the sensor membrane 43, in this case each of the independently operable sensor circuits 49, 51, 53, 55, and is operable to monitor the sensor membrane 43 and detect a change in an electrical characteristic of the sensor membrane 43. More specifically, the controller is operable to monitor each of the independently operable sensor circuits 49, 51, 53, 55 and detect a change in an electrical characteristic of the independently operable sensor circuits 49, 51, 53, 55. The controller 45 comprises a wireless communications module 57 for reasons that will be expanded upon below.

There is further provided a pair of flexible sheeting position sensors 59, 61 mounted on the flexible sheeting, in this case the curtain 15. The flexible sheeting position sensors 59, 61 are operable to detect proximity of the flexible sheeting 15 to the front end 9 and rear end 11 of the trailer 1 respectively. The flexible sheeting position sensors 59, 61 are mounted directly onto the curtain 15 and are in communication with the controller 45 through wired communications (not shown). A rear door sensor 63 is provided and is operable to detect whether or not the rear door (not shown) of the trailer 1 is open or closed. The rear door sensor communicates wirelessly with the controller 45.

A control panel 65 is mounted in the tractor unit 3 cab. The control panel 65 will have controls thereon (not shown) to allow one or more of security system 31 activation, security system 31 deactivation, security system 31 test, independently operable sensor circuit selection, independently operable sensor circuit isolation, security system 31 resetting, panic alarm trigger, panic alarm reset and preferably comprises a graphical user interface (GUI) and an audio output. The control panel 65 has a wireless communication module (not shown) therein for communication with the controller 45 and, if desired, the alarm unit 71.

The alarm unit 71 comprises an audible alarm component and a visual alarm component. The audible alarm component comprises a pair of sirens 73, 75 whereas the visual alarm component comprises a flashing light 77. The alarm unit further comprises a -11 -wireless communications module (not shown) for communication with the wireless communications module 57 of the controller 45.

In use, the security system 31 is activated by the operator using the control panel 65.

The control panel The controller 45 controls the delivery of a current along the independently operable sensor circuits 49, 51, 53, 55 and the controller monitors an electrical characteristic of each of the independently operable sensor circuits 49, 51, 53, 55. The electrical characteristic is typically the current flowing out of the independently operable sensor circuit 49, 51, 53, 55. If a person attempts to cut through the curtain, they will encounter one of the independently operable sensor circuits 49, 51, 53, 55 and will cause a change in the electrical characteristic of that independently operable sensor circuit 49, 51, 53, 55. The controller 45 identifies this change in electrical characteristic and wirelessly transmits an instruction to the alarm unit 71 to activate. Alarm unit 71 sounds the sirens 73, 75 and illuminates the flashing light 77, thereby alerting the haulier that their trailer is being interfered with.

Alternatively, if a person attempts gain access to the interior of the trailer 1 by loosening one or more of the straps 21 and ratchets 23 and squeezing between the curtain 15 and the frame 7 of the trailer, the flexible sheeting position sensors 59, 61 will detect the curtain moving away from the trailer frame 7 and will relay this information back to the controller. The controller 45, in response to the signal received from the flexible sheeting position sensors 59, 61 will wirelessly transmit an instruction to the alarm unit 71 to activate. The alarm unit 71 will sound the sirens 73, 75 and illuminate the flashing light 77, thereby alerting the haulier that their trailer is being interfered with. Similarly, if a person opens the rear door (not shown), the rear door sensor 63 will detect this and relay the information to the controller 45. The controller 45, in response to the signal received from the rear door sensor 63 will wirelessly transmit an instruction to the alarm unit 71 to activate. Alarm unit 71 will sound the sirens 73, 75 and illuminate the flashing light 77, thereby alerting the haulier that their trailer is being interfered with.

In each alarm condition, the haulier, once alerted, can investigate the cause of the alarm and take appropriate action if need be. Once the alarm condition has been addressed, the system can be reset thereby shutting off the alarm unit 71 and if need be, the independently operable sensor circuit(s) 49, 51, 53, 55 that experienced the alarm -12-condition can be temporarily deactivated until such time that a repair is carried out. This is done using the control panel 65 in the tractor 3 cab or may be done automatically by the system during system arming/disarming as previously described.

Referring to Figure 4, there is shown a diagrammatic representation of an alternative embodiment of security system according to the present invention, indicated generally by the reference numeral 81, installed in a curtain sided trailer 1. For clarity, like parts have been given the same reference numeral as before. The security system 81 is practically identical to the security system 31 illustrated in Figure 3 with the exception that the electrically conductive sensor membrane 43 is configured in a mesh pattern 83. The mesh pattern comprises a large number of independently operable sensor circuits. The proximity of the independently operable sensor circuits means that it will be practically impossible for an unscrupulous individual to break into the trailer without raising an alarm.

Referring to Figure 5, there is shown a partial, perspective view of a curtain sided trailer 1 fitted with a third embodiment of security system according to the invention, indicated generally by the reference numeral 91, where like parts have been given the same reference numeral as before. The security system 91 will incorporate the security system 31 as illustrated in Figure 3 or the security system 81 as illustrated in Figure 4 in conjunction with the security system 91 illustrated herein. The drawing shows a rear perspective view of the trailer 1 including rear doors 93 at the rear end 11 of the trailer 1.

The security system 91 comprises an independently operable sensor circuit 95 on the roof of the trailer 1. A controller 97 is in communication with the independently operable sensor circuit 95 and a power supply 99 provides power to the independently operable sensor circuit 95. The operation of the controller 97 and the independently operable sensor circuit 95 is similar to that described above in relation to the controllers and independently operable sensor circuits 49, 51, 53, 55 described in Figures 3 and 4. If the independently operable sensor circuit 95 is disturbed, the controller will sense the disturbance and will alert the alarm unit 71.

Referring to Figure 6, there is shown a plan, cross sectional view of a trailer having a fourth embodiment of the security system according to the invention mounted therein.

The security system comprises two pairs of flexible sheeting position sensors 59, 61, on -13-pair on each side of the curtain sided trailer, a rear door sensor 63 and two independently operable sensor circuits 49, 51, one on either side of the trailer. The alarm unit 71 is mounted inside the trailer and each of the sensors 49, 51, 59, 61, 63 communicates wirelessly with the alarm unit (as indicated by the dashed lines).

Various modifications could be made to the embodiments hereinbefore described without departing from the spirit of the invention or indeed from the scope of the appended claims. For example, in Figure 3, a number of disparate pathways, substantially rectangular and zig-zagged, are shown for the independently operable sensor circuits 49, 51, 53, 55 however this is for illustrative purposes only and other pathways could equally well be employed to good effect. Indeed, the pathways could assume a labyrinthine or quasi-random pattern if desired as this may be even more difficult to circumvent. In the embodiment shown, four separate independently operable sensor circuits 49, 51, 53, 55 are shown but more or less circuits could be provided.

Furthermore, each of the independently operable sensor circuits 49, 51, 53, 55 extend all the way down the entire length of the trailer and instead there may be one or more independently operable sensor circuits 49, 51, 53, 55 in dedicated "zones" at distinct positions along the trailer. The independently operable sensor circuits 49, 51, 53, 55 could be arranged so that the entire curtain is covered by the circuits.

In addition to the sensors described above, additional sensors could be positioned elsewhere on the curtain 15. For example, it is envisaged that flexible sheet position sensors could be placed along the lower edge of the curtain so that if the curtain is raised or moved away from the trailer 1, this will trigger an alarm condition and the alarm unit can sound the alarm and/or illuminate the light. Furthermore, if a tail lift is provided, a tail lift sensor may be provided to detect when the tail lift is operated. Tail lifts are moveable platforms mounted on the rear of the trailer or truck that may be raised and lowered between the trailer or truck bed height and ground level to assist in the loading and unloading of goods from the truck or trailer. Tail lifts are commonly used on all forms of cargo carrying vehicles and not simply curtain siders. The tail lift sensor could be by way of a simple relay in the control unit for the tail lift to detect when the tail lift is operated. By having such a relay, the relay will detect if and when an unauthorized person uses the tail lift when the system is armed. Alternatively, the tail lift sensor could -14-be provided by way of a proximity sensor arranged on the rear of the vehicle to detect the proximity of the tail lift to the trailer while the security system is armed.

In the embodiments described, the controller 45 is a micro-processor but could be a micro-controller or other like device. For example, the microcontroller embedded in the curtain sensor could be an M6B430 produced by Texas Instruments. It is further envisaged that a controller in the alarm control unit where all the sensors can be fed back to can be an ARM processor and/or an MSB43O micro controller sold by Texas Instruments. The micro controller chip itself typically will not have circuitry to regulate the power for the sensors but the chip is embedded onto a small PCB printed circuit board that has power regulation. What is important is that the controller 45 is lightweight and draws relatively little power from the power supply. Ideally, the power supply is also a lightweight device and preferably comprises a rechargeable battery such as a lithium polymer (LiPo) battery.

In the embodiments illustrated in the drawings, the alarm unit 71 is shown mounted on top of the trailer 1 for illustrative purposes and it is envisaged that the alarm unit 71 or one or more components 73, 75, 77 of the alarm unit could be located elsewhere, either on the trailer 1 or on the tractor unit 3. For example, the alarm unit could be mounted on the front panel 9 of the trailer 1 or indeed could be mounted inside the trailer.

Furthermore, in the embodiments illustrated in Figures 3 and 4, various components of the security system that are in the trailer are shown in broken outline whereas other components are shown in solid outline. It will be understood that the components in the trailer are all not normally visible as they are located inside the trailer on the internal surface of the curtain 15.

In the embodiments described, the control panel has a control for resetting the system and indeed there may be other triggers for resetting the system, for example, each time the tractor engine ignition is operated to start the tractor engine, this may result in a diagnostic test of the system causing any independently operable sensor circuits 49, 51, 53, 55 that are not operational to be deactivated temporarily until such time as they are fixed. It will be understood that the haulier will have been made aware that one or more independently operable sensor circuits 49, 51, 53, 55 are inoperable due to the fact that they have experienced an alarm condition. A number of beeps from the siren can be -15-used to notify the operator that one or more paths are damaged and aie in need of repair.

The control panel 65 may have other sensors such as, but not limited to, a gas sensor to detect one or more harmful gases in the cabin. Furthermore, the control panel and/or the controller may have a GPS tracking unit, a memory to record the route of the trailer and any activity of the security system (effectively similar to a black box found in the aviation industry) and a communication module for long range communications with a remote monitoring station.

In the embodiments described in Figures 3 and 4, each curtain 15 has its own controller and the roof sensor described in relation to Figure 5 also has its own controller 97.

Therefore, it will be understood that in certain embodiments, the alarm unit will be able to communicate with multiple controllers. Alternatively, the controllers of one or more security systems on a vehicle may all route their communications through one of the controllers 45 which has been designated as the master controller to their slave controllers. In the embodiment shown in Figure 5, the sensor membrane only extends a short way along the length of the trailer 1 however this sensor membrane could extend along more or less of the trailer 1.

In the embodiments described, the additional sensors such as the rear door sensor 63, the tail lift sensor, the roof sensor 95 and the flexible sheeting position sensors 59, 61 communicate with a controller before indirectly communicating with the alarm unit.

However, if desired, these devices and in particular the roof sensor 95, the rear door sensor 63 and the tail lift sensor may have a direct wired or wireless connection with the alarm unit 71. The flexible sheeting position sensors 59, 61, if mounted on the trailer frame 7 instead of the curtain 15 may also be connected directly to the alarm unit 71 through wired or wireless connection. If one or more sensors 59, 61, 63, 95 are in direct communication with the alarm unit 71, it is envisaged that there will be an interface to reset the alarm unit 71 and these sensors 59, 61, 63, 95 if need be. This interface could be through the control panel 65 or via the controller 45.

In the embodiments described, a control panel 65 is provided in the tractor 3 unit to operate the system however control instructions may be sent from a remote monitoring -16-station direct to the controller 45 in the trailer. Indeed, it is envisaged that it would be desirable in some circumstances to have information concerning the status of the alarm unit and the various sensors to be sent to a remote monitoring location as a matter of course. This would enable the monitoring station to track the vehicles and detect unauthorized accesses to the cargo compartment.

In this specification, the terms "comprise, comprises, comprised and comprising" and the terms "include, includes, included and including" are all deemed totally interchangeable and should be afforded the widest possible interpretation.

The invention is in no way limited to the embodiment hereinbefore described but may be varied in both construction and detail within the scope of the appended claims. -17-