GB2233804A - Flexible closure alarm system - Google Patents

Abstract

The alarm system is for protecting an area at least partially enclosed by flexible closure means 10 such as the load platform of a 'curtainsider' type vehicle and includes sensor means associated with the closure means which are responsive to at least one of the following conditions: disturbance of the closure means; or separation of the closure means from an adjacent member. The sensor means comprises a network 16 of conductors 18 included with the closure means, together with conductors (not shown) which connect an edge portion of the closure means to the adjacent member. The conductors included with the closure means are connected into one or more circuits which are connected into suitable alarm circuitry by an extendable conductor 22. The alarm is preferably operable in response to breaking a conductor upon attempting to cut or lift the closure means, but it may be responsive to vibration or the making of a circuit. <IMAGE>

Description

ALARM SYSTEM This invention relates to an alarm system which is particularly suitable for protecting goods which are at least partially enclosed by flexible sheeting and to alarm tape for use in such a system.

Commercial vehicles commonly employ flexible sheeting of, for example, canvas or P.V.C. to help protect the goods they carry. Such sheeting is commonly used, for example, in vehicles of the 'flatbed' type where it is spread directly on top of the load, without any separate supporting structure, and secured around its edges to the flat load platform. Flexible sheeting is also frequently used, with a supporting structure, in vehicles of the 'curtainsider' type or those with a 'tilt-top'. In the curtainsider-type vehicle, the sheeting forms some part of the substantially vertical sidewalls of a protective enclosure, which extends around and above the load platform.

In the tilt-top vehicle, the sheeting forms a part of these sidewalls and also the substantially horizontal top of the enclosure.

Used in ways such.as these, flexible sheeting provides a simple, cheap, lightweight and adaptable protective means which allows easy access to the goods when required. However, although the material can protect goods from the effects of weather and prevents casual inspection, it is little obstacle to a person intent on stealing or damaging them. Such a person may gain access to the goods by, for example, unfastening the edges of the sheet or cutting through the sheeting material with a knife or other sharpedged implement. Preventing unauthorized access by either route is difficult, but it is especially difficult to reinforce the sheeting material so as to resist penetration, without incurring a severe penalty in its cost, weight and flexibility.

Unauthorized access to goods which are protected by flexible sheeting is a considerable problem. The impracticality of physically preventing such access has led to the disclosure of alarm systems which warn of attempts to cut through the sheeting material itself. However, these systems only work if the flexible sheet is cut, and therefore cannot protect against intrusion by means of unfastening or otherwise deflecting the edges of the sheet, without actually cutting it.

Therefore, an object of the invention is to provide an alarm system which warns of unauthorized attempts to gain access to goods, either around the edges of a flexible protective sheet, or by cutting through the sheet.

Known alarm systems, which warn of attempts to cut through a flexible sheet, employ a network of readily frangible conductors associated with, and extending over, a substantial proportion of the area of the sheet. These conductors are embedded into or otherwise attached to the sheet, so that tearing or cutting the associated portion of sheeting material disrupts them. This activates an alarm or other signalling means, by means of suitably-arranged alarm circuitry.

These known systems employ connecting means between the alarm circuitry and the network of conductors which can compromise the inherent adaptability of the flexible protective sheet.

For instance, in a curtainsider vehicle, it may be desired to roll the sheeting upwards about a horizontal axis, or to draw the sheeting to the centre or to either side, in order to gain access to the load platform. With known systems, it is necessary to provide separable connectors in order to free all of the edges of the sheet, if such adaptability is to be allowed. Repeated operation of these connectors is inconvenient, especially if situated towards the less accessible upper edges of the sheet.

Therefore, a further object of this invention is to provide a means of connecting alarm circuitry to a network of conductors associated with a flexible protective sheet, which does not seriously compromise the ready adaptability of the sheet.

According to this invention, there is provided an alarm system for deterring unauthorized access to an area protected by a flexible closure having a broad surface and a periphery, comprising a first circuit including a network of conductive wire associated with the closure and extending over the broad surface of the closure, the conductive wire being flexible so as to behave as part of the flexible closure, means for connecting the first circuit to alarm means, and a second circuit having at least one conductor for connecting the closure, along a substantial portion of the periphery of the closure, to a further member, the connecting means for connecting the first circuit to alarm means comprising an extendable conductor whereby, on disconnection of the second circuit, the flexible closure may be moved without disconnection of the first circuit, the alarm system, in use, being operable in response to at least one of the following conditions: disturbance of the flexible closure by disturbance of a portion of the conductive wire in the first circuit; and separation of the flexible closure from the further member, by breaking a conductor in the second circuit.

This invention will now be described by way of example, with reference to the accompanying drawings in which: Figure 1 is a schematic partial side view of an aspect of an embodiment of the invention; Figures 2, 3, 4, and 5 are schematic perspective views of this embodiment being used in different ways; Figure 6 is a schematic side view of an embodiment of another aspect of the invention; Figure 7 is a schematic perspective view of a further embodiment of the aspect shown in Figure 6; Figure 8 is an enlarged plan view of a detail in Figure 7; Figure 9 is a schematic perspective view of a further embodiment of the invention; Figure 10 is a schematic perspective view of an alarm tape in accordance with a further aspect of the invention.

Referring to Figure 1 of the drawings, in an embodiment of the invention a flexible protective sheet (10) extends over substantially the whole area of the side openings defined by a support structure (12) of a curtainsider goods vehicle.

The sheet (10) is of the type conventionally used in this type of vehicle, hanging as a curtain by its upper edge from the structure (12) and being made of, for example, canvas or P.V.C. A similarly sized inner sheet (14) carries a network (16) of closely spaced, readily frangible conductors (18) extending over substantially all of its area. The conductors may be impressed into or otherwise attached to the inner sheet (14), which may be made of one or more flexible materials such as P.V.C. or polythene sheeting, or they may be sandwiched between two or more layers of such materials. The inner sheet (14) is attached, for example, by adhesive bonding or welding, to the inner surface of sheet (10) so that sheet (10) completely overlays the whole area of inner sheet (14). Therefore, making a cut of significant length anywhere on sheet (10) will also cut the inner sheet (14) and will thus break at least one conductor in the network (16). This breaking of a conductor (18) may activate an alarm in a way to be described below.

Hereinafter, because the inner sheet (14) together with its associated network of conductors (16) behaves as a part of the protective sheet (10) when they are assembled together in use, they shall be referred to together simply as "sheet 10".

Sheet 10 remains affixed, along its upper edge, to the vehicle in everyday use, as shown in Figures 2 to 5 which illustrate four ways of moving sheet 10 aside so as to gain access to the load platform. Electrical connection between the network of conductors in sheet 10 and the alarm circuitry mounted on the vehicle (not shown) is accordingly made to this upper edge at point (20), by means of an extendable conductor (22) which connects point (20) to a fixed connection point (24) on the vehicle. This conductor (22) is made extendable by, for example, forming it into the shape of a coil, in which case it may be held conveniently out of the way by suspending it from a wire threaded within the coil.The extendability of conductor (22) means that, if the sheet 10 is slideably displaced to one or other side of the opening, as shown in Figures 2 and 3, the corresponding movement of the connection point (20) relative to the fixed point (24) may be accepted without breaking the connection therebetween. Therefore, although the connection between the sheet 10 and the alarm circuitry may be made readily separable in order to allow convenient removal of the sheet 10 from the vehicle, such separation need not be performed in everyday use, where the sheet 10 remains attached to the vehicle along one edge.

The provision of a network of conductors within the sheet 10 provides a means for sensing cutting of the sheet and thereby activating an alarm. However, for full protection, the alarm system also incorporates means which warn of lifting the edges of the sheet 10 away from the vehicle structure to which it is secured, in an attempt to gain unauthorized access to the protected goods without cutting the sheet. These means take the form of a number of separable connectors (26) disposed around the lower edge and vertical side edges of the sheet 10, as shown in Figure 6, which may be of any convenient type, such as jack-type connectors or magnetic pull apart cords as sold under the name MAGNAPULL.

These connectors are connected into a circuit (28) associated with the sheet 10, which in this embodiment is entirely separate from the network (16) described above but could if desired be integrated with network (16) (it should be noted that sheet 10 incorporates both network (16) and circuit (28), and that network (16) is omitted from Figures 6 and 7 only for clarity). Pulling the edges of the sheet 10 away from the vehicle separates the connectors and thus involves breaking a circuit, which can activate an alarm.

The mounting points of the connectors (26) on the curtain and vehicle are advantageously designed so that if they are dismantled, an alarm sounds due to the breaking of a circuit.

Some manufacturers are now producing curtainsided vehicles without buckles arranged along the lower edge of the curtain, in which case, connectors (26) may suitably be located at each end of the curtain, either at the base of the curtain, at the top and at the base, or at the top, the base and at points in between.

Referring now to Figure 7, an alternative arrangement of this second aspect of the invention incorporates separable connectors (26) along the lower edge of a sheet (10) connected by a circuit (28), as before. However, the vertical edges of the sheet (10) are protected by vertical poles (30) which each locate at their respective ends into an upper slot (32) and a lower slot (34), the lower slot incorporating a microswitch which detects removal of the pole therefrom. These poles are located, as far as possible, at the extreme side ends of the side openings (36) of a goods vehicle, so as not to affect the utility of the load platform. The inner sheet (14), carrying the network (16) as previously referred to, may be conveniently fixed to a pole (30) by wrapping it around the pole to form a pocket as shown in Figure 8.This allows the pole (30) to be readily slid in and out of this pocket when the sheet (10) needs to be moved, while preventing significant movement of this edge of the sheet without moving the pole from its mounting slots (thereby activating the alarm by means of the microswitch).

The inner sheet (14) is separate from the 'outer' sheet (10) at each end so as to allow the outer sheet to be fixed to its pole (38) in the usual manner. Conveniently, the microswitches in slots (34) are connected into the circuit (28) so as to simplify the wiring required.

An alternative arrangement of this embodiment instead provides microswitched slots for the 'outer' poles (38), with the sheet (10), including inner sheet (14), being wrapped around the poles (38) thereby removing the need for 'inner' poles (30) in order to sense lifting of these edges of the sheet.

A further arrangement for preventing access around the edges of the sheet (10) is shown in Figure 9, where a number of eyelets (40) are disposed around the edges of the side openings (36) on the vehicle structure (12). These protrude through slots (42) provided in the sheet (10), when the sheet is extended across the opening (36). A flexible conductor (44) is threaded through these eyelets and connected at each end (46) into an alarm circuit, thereby securing the sheet (10) to the structure (12).

Thus the sheet can only be lifted by cutting the conductor (44) or by disconnecting its ends, which can be made to activate an alarm.

The edges of the sheet may also be secured by other means such as a zip fastener, incorporating means such as connectors which are separable in response to the opening of the zip, thereby activating an alarm.

The alarm systems described so far may be activated in response to cutting a conductor, or otherwise breaking a connection, so as to break a first electrical circuit of which the conductor or connection is a part. Such an electrical circuit includes an electricity supply such as a battery, an electromagnetic relay or solenoid, the conductor (for example, the network (16) or pull apart cords (26)) and means which electrically connect these components. The relay directly or indirectly controls a switch in a second alarm circuit, this second circuit including an alarm which is activated when the switch is closed.

Thus the relay (and its associated switch) are held open while the first circuit is complete, but if the first circuit is broken by the breaking of a conductor or a connection, the relay closes the switch in the second circuit, thereby sounding the alarm.

Means may also be provided to activate the alarm in response to a significant fluctuation in the current flowing in the first circuit or in the voltage drop across the conductor, so that a complete break in the first circuit need not be required to activate the alarm. In particularly, the changing conductive characteristics of the conductors as the sheet is flexed could be used to activate the alarm.

For the fullest possible protection, it is envisaged that the various alarm circuits used in any one application of the invention are connected into and monitored by a control box. The control box may be situated in any secure and convenient place and be connected to the alarm circuits by any convenient means, including, where necessary, a radio link or other transmitting/receiving device. Such a box could, if necessary, monitor and control several alarm systems at once, thereby guarding a number of lorries at once, for example.

Alternatively, the box can be mounted directly to the vehicle or article it protects, for instance mounted to an inner corner of the load platform adjacent the front bulkhead of a curtainsider vehicle. in this case, the box can have inputs from each side curtain to warn of attempts to cut through or otherwise disturb the shoeting, as described, together with inputs from sensors which warn of, for example, attempts to force the rear doors, cut through the steel roof or move the entire vehicle. Two sirens, one outside on the front bulkhead, another inside on the steel roof structure, frustrate attempts to put the alarm system out of action. The system could further include paging means to alert the driver or the police directly if an attempt is made to gain access.In similar fashion, provision can be made for the system to emit homing signals in the event of the vehicle being stolen, so that the vehicle can be readily located by picking up those signals on a suitable receiver.

Many further variations, both of the alarm system itself and the use to which it is put, are possible.

For example, the flexible sheet may itself include the necessary conductors of the alarm system. In one such arrangement, the network of conductors (16) may be made up of individual alarm tapes attached to the inner face of the flexible sheet. Figure 10 shows an alarm tape (48) in accordance with a further aspect of this invention, comprising a backing strip (50) of P.V.C. or other suitable flexible material, which is preferably reinforced by laminating it with, for example, strands of nylon material as shown.

Preferably, the strip (50) is about 32mm wide by about 0.30mm thick, although its dimensions can be chosen to suit any particular application.

Extending along, and attached to, the central portion of one side of the tape (48) are two insulated conductors (52) which lie substantially parallel to and separate from one another. Each conductor preferably comprises four ends of twisted copper tinsel thread wrapped around a thread of polyester or cotton, although two or more ends of other suitable materials could be employed if desired. The conductors (52) may be attached to the backing strip (50) by any suitable neans such as fusion, bonding or laminating, while there need not be two conductors but any number considered desirable.

In use, tape (48) is bonded, welded, stitched or otherwise attached to the inner face of a flexible sheet, with the conductors (52) facing the sheet and with the points of attachment extending along the backing strip (50) on either side of the conductors, such that the conductors are shrouded in a pocket between the backing strip and the flexible sheet. Suitable lengths of tape (48) can be arranged and attached to the sheet so as to build up a network of conductors as desired.

The conductors associated with the various lengths of tape can be connected together to include them within an electrical circuit.

The conductors need not be in the form of wires, but could take the form of a foil strip, a conductive coating deposited on a strip of, for example, P.V.C. or polythene, or any other material which conducts an electric current or impulse.

The alarm could alternatively be operable in response to the making of a circuit, for example, between two separate conductive membranes incorporated as layers within a flexible sheet, the connection between being made when the sheet is cut. This connection could be through a metallic knife blade which is being used to cut the sheet, or could arise from deformation of the membranes into contact with one another, as a result of the cutting action. The membranes could be made up of sheeting material coated with a conductive substance and could be separated in normal use by an inner sheet or any other suitable separating/insulating means.

It will be clear to a person skilled in the art that many combinations of the aforementioned sensing means may be used as the basis of an efficient alarm system.

Claims (7)

1. An alarm system for deterring unauthorized access to an area protected by a flexible closure having a broad surface and a periphery, comprising a first circuit including a network of conductive wire associated with the closure and extending over the broad surface of the closure, the conductive wire being flexible so as to behave as part of the flexible closure, means for connecting the first circuit to alarm means, and a second circuit having at least one conductor for connecting the closure, along a substantial portion of the periphery of the closure, to a further member, the connecting means for connecting the first circuit to alarm means comprising an extendable conductor whereby, on disconnection of the second circuit, the flexible closure may be moved without disconnection of the first circuit, the alarm system, in use, being operable in response to at least one of the following conditions: disturbance of the flexible closure by disturbance of a portion of the conductive wire in the first circuit; and separation of the flexible closure from the further member, by breaking a conductor in the second circuit.

2. An alarm system according to Claim 1, wherein the first circuit comprises a plurality of conductive wires which combe into conductive contact with each other if the flexible closure is penetrated, thereby activating an alarm.

3. An alarm system according to Claim 2, wherein the first circuit comprises a conductor incorporated into a tape which is attached to the flexible closure.

4. An alarm system according to any preceding claims, wherein the first circuit comprises conductors associated with a separate sheet which is included with the flexible closure.

5. An alarm system according to any preceding claim, wherein the flexible closure includes a sheet for protecting the load area of a vehicle, the second circuit comprising an array of separable conductors disposed about the periphery of the sheet for connecting it to the vehicle's structure.

6. An alarm system according to Claim 5, wherein one or more sides of the sheet are attached to the vehicle by means of poles which locate into attachment points on the vehicle, the attachment points having sensors for detecting removal of the pole therefrom and thereby activating an alarm when appropriate.

7. A vehicle according to Claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

7. An alarm system according to Claim 6, wherein the sensors are incorporated into the second circuit.

8. An alarm system substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows

1. A vehicle including a support structure defining an opening, the structure being adapted to support a flexible closure having a broad surface and a periphery, whereby the flexible closure may be slidably displaced to one or other side of the opening, and an alarm system for deterring unauthorized access to an area protected by the flexible closure, the alarm system comprising a first circuit including a network of conductive wire associated with the closure and extending over the broad surface of the closure, the conductive wire being flexible so as to behave as part of the flexible closure, means for connecting the first circuit to alarm means, and a second circuit having at least one conductor for connecting the closure, along a substantial portion of the periphery of the closure, to a further member of the vehicle, the connecting means for connecting the first circuit to alarm means comprising an extendable conductor whereby, on disconnection of the second circuit, the flexible closure may be slidably displaced without disconnection of the first circuit, the alarm system, in use, being operable in response to at least one of the following conditions: disturbance of the flexible closure by disturbance of a portion of the conductive wire in the first circuit; and separation of the flexible closure from the further member, by breaking a conductor in the second circuit.

2. A vehicle according to Claim 1, wherein the first circuit comprises a conductor incorporated into a tape which is attached to the flexible closure.

3. A vehicle according to any preceding claims, wherein the first circuit comprises conductors associated with a separate sheet which is included with the flexible closure.

4. A vehicle according to any preceding claim, wherein the flexible closure includes a sheet for protecting the load area of a vehicle, the second circuit comprising an array of separable conductors disposed about the periphery of the sheet for connecting it to the vehicles structure.

5. A vehicle according to Claim 4, wherein one or more sides of the sheet are attached to the vehicle by means of poles which locate into attachment points on the vehicle, the attachment points having sensors for detecting removal of the pole therefrom and thereby activating an alarm when appropriate.

6. A vehicle according to Claim 5, wherein the sensors are incorporated into the second circuit.