Commercial vehicles commonly use flexible sheeting, for example, a tarpaulin cover, to help protect the goods they carry. Such sheeting is commonly used in vehicles of the 'flatbed' type where the sheeting is spread directly on top of the load without any supporting structure and lashed down to permanent fixings with rope. Flexible sheeting is also used in connection with 'curtain-sider' commercial vehicles.

My United Kingdom Patents Nos. 2233804 and 2209618 show alarm systems suitable for attaching this type of sheeting to the vehicle for deterring unauthorized access to the goods covered by the sheeting. Such an alarm system can typically comprise a conductor connected around the periphery of the sheeting and which is attached to fixed mountings on the bed of the vehicle. The conductor is attached to a suitable alarm, whereby, breaking the conductor operates the alarm.

The present invention provides a tensioning device which helps to keep such a conductor tight,

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and, incorporated in an alarm system, reduces the possibility of access to the goods under the periphery of the sheeting without breaking the conductor. According to the present invention there is provided tensioning means for tensioning at least one cable or conductor, the tensioning means comprising at least one gripping member in use, for gripping a respective cable or conductor, and means for deterring unauthorized access to the gripping member.

Preferably, the means for deterring access is a container in which the or each gripping member is mounted. The container may have a lid the unauthorized removal of which activates a micro- switch which in turn triggers an alarm.

The present invent on also includes an alarm system for deterring unauthorized access to an area protected by a flexible closure having a periphery, the alarm system comprising a circuit having at least one conductor for connecting the closure along a part of the periphery to a further member or another part of the closure, tensioning means for tensioning the or each conductor and alarm means connected to the or each conductor whereby, in use, the alarm means is operable in response to the breaking of the or at least one conductor.

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Such an alarm system provides an arrangement whereby the or each conductor can be tensioned to keep the periphery of the sheeting in a tightly closed arrangement, for example, in close contact with the vehicle. This helps prevent unauthorized access being obtained to the goods by the lifting of the periphery of the sheet, and any breaking of the conductor will activate the alarm.

Preferably, the tensioning means comprises at least one gripping member which, in use, grips a respective conductor. Since the conductor is gripped by the gripping member, any attempt to loosen the conductor is likely to break the conductor, thereby activating the alarm. The tensioning means may comprise at least one pair of gripping members, each gripping member comprising a body pivotally supported at one end and having an edge section including a plurality of teeth, the edge section including a plurality of teeth, the edge sections of each pair of gripping members facing each other whereby, in use, a respective conductor can be drawn between the facing edge sections until the conductor is tight and is gripped in position by said teeth. The pair of gripping members may be a cleat through which a respective conductor is drawn and held in place.

Preferably the gripping members are mounted

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within a base of a box and a lid of the box may be attached to the base of the box whereby, in use, the lid is adapted to substantially seal the connection between the id and the base. The box provides a housing to.prevent unauthorized access to the gripping members and the box may include a micro-switch to detect removal of the lid from the base.

The or each conductor may pass through a grommet in the side of the box. The grommet preferably conforms to the diameter of the respective conductor to prevent a probe, for example, a screwdriver, being pushed through the conductor entry into the box and opening the cleat.

Preferably the or each grommet comprises a half grommet provided on a free edge of the lid and a corresponding half grommet provided on a free edge of the base whereby, in use, the half grommets function together as a single complete grommet. This arrangement facilitates the positioning and adjustment of the conductor within the box.

According to another aspect of the invention, there is provided a flexible closure for covering an area to be protected, the closure including a conductive network across the surface thereof for incorporation in an alarm system, a periphery,

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means for receiving a cable or conductor for securing the periphery to a further member or to a further part of the closure, and tensioning means on the closure, in use, for tensioning the securing cable or conductor.

In another aspect of the invention, there is provided a flexible closure for covering part of a vehicle, the closure including at least one cable for connecting a periphery of the flexible closure to the vehicle and tensioning means for tensioning the cable for deterring unauthorized access to the covered part of the vehicle.

In a further aspect of the invention, there is provided a vehicle including an alarm system in accordance with the invention.

The invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a section through a bed of a commercial vehicle showing a sheet with an alarm system in accordance with the invention;

Figure 2 is a plan view of the arrangement shown in Figure 1 ;

Figure 3 is a plan view of a section through a tensioning device in accordance with the invention;

Figure 4 is an elevation of a section on line 4-4 of the tensioning device in Figure 3;

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Figure 5 is an end view on line 5-5 of the tensioning device in Figures 3 and 4, showing the box in an open position; and,

Figure 6 is a view similar to Figure 5 showing the box in closed position.

In Figures 1 and 2, goods (10) and a vehicle (11) are positioned for transport on a bed (12) of a commercial vehicle (not shown) .

A plura ity of permanent fixings (13) are provided around the edge of the bed (12). The permanent fixing (13) has an aperture therein to allow the passage of a cable or conductor through the fixing (13) .

The goods (10) and vehicle (11) are covered by a flexible tarpaulin sheet (14) having a plurality of eyelets (15) along its periphery. A tensioning device (16) is attached adjacent one end of the sheet (14). The tensioning device (16) will be described in greater detail below. An alarm control unit (17) is mounted at the opposite end of the bed (12) to which the tensioning device (16) is attached to the sheet (14). Conductors (18) are connected between the alarm control unit (17) and the tensioning device (16) on opposite sides of the bed (12) and pass through alternate eyelets (15) and fixings (13). The alarm control unit (17) may be attacked to a suitable alarm and is operable in response to

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the breakage of either conductor (18).

Figures 3, 4, 5 and 6 show the tensioning device (16) in greater detail.

The tensioning device (16) comprises a box (20) having a lid (21) and base (22). Mounted within the base ( 22 ) of the box (20) are two pairs of cleats (23). Each pair of cleats (23) comprises two gripping members (24). Each gripping member (24) has an enlarged portion at one end where it is pivotally mounted by a shaft (25) to the base ( 22 ) and an edge section (19) including a plurality of teeth (27).

The gripping members (24) are slightly spaced apart and are symmetrically disposed about a centre line (30) of the box (20). The edge sections (19) face each other to enable a conductor (18) to be drawn therebetween and to be held firmly in position.

Half grommets (28) are provided on free edges (29) of opposing end faces of both the base (22) and lid (21) and are aligned with the centre-line (30) of the box (20). When the lid (21) is in position over the base (22), the half grommets (28) act effectively as a single grommet dimensioned to accept the conductors (18) in a close fit.

The tensioning device (16) includes a micro- switch (not shown) which activates an alarm (also

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not shown) when the lid (21) is removed from the base (22) .

In use, the sheet (14) is placed over the goods (10) and vehicle (11). The conductors (18) are attached at one end to the alarm control unit (17) and are threaded alternately through fixings (13) and eyelets (15) down respective sides of the bed (12). The lid (21) of the tensioning device (16) is removed and the conductors (18) are placed within a respective half grommet (28) and between a respective pair of cleats (24) in the base (22). The teeth (27) grip the conductor (18) and, when the conductor (18) is in tension, each gripping member pivots slightly which tends to draw the opposing edge sections (19) close together which tightens the grip of the teeth (27) on the conductor (18).

The lid (21) is then placed on the base (22) to substantially seal the connection between the lid (21) and base (22) and any unauthorized removal of the lid (21) from the base (22) will activate the micro-switch (not shown) .

Any attempt to cut either conductor (18) will activate the alarm control unit (17) which will sound the alarm.

Furthermore, the cleats (23) hold the conductors (18) in such a way that any attempt to loosen the conductors (18) is also likely to break

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the conductors (18) and therefore also activate the alarm control unit (17).

Whilst an alarm system has been described herein having two conductors, the alarm system could equally well have a single conductor, which may be attached rigidly to one end of tensioning device.

The conductors described herein may, of course, be cables or wires, including fibre optic cables and the closure suitably includes a network of conductors as disclosed in my United Kingdom Patents Nos. 2233804 and 2209618, details of which are incorporated herein by reference.

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