WO1993024349A2

WO1993024349A2 - Security devices, systems or the like

Info

Publication number: WO1993024349A2
Application number: PCT/GB1993/001178
Authority: WO
Inventors: Brian Lewis Fisher
Original assignee: Backstop Limited
Priority date: 1992-06-04
Filing date: 1993-06-03
Publication date: 1993-12-09
Also published as: GB9211797D0; WO1993024349A3

Abstract

The invention relates to a vehicle security system comprising a linear hydraulic actuator (3) of the piston and cylinder type connected between the vehicle chassis (4) and hand brake lever (1). The cylinder (3b) of the actuator is connected to a hydraulic circuit including a shuttle valve (9) and a non-return valve (10). When the system is unlocked, the shuttle valve is open, and hydraulic fluid is free to flow from a reservoir (8) via the shuttle valve, both into and out of the actuator cylinder (3b), allowing the piston (3a) and therefore the hand brake lever (1) to move freely in both directions for normal driver-operation of the hand brake. When the system is locked, the shuttle valve is closed, and the non-return valve (10) permits fluid flow, and therefore piston movement, in one direction only. In this condition, the hand brake lever (1) can be moved in a brake-application direction but not in a brake release direction.

Description

-1-

SBCTJ I Y DEVICEST SYSTEMS OR THE LIKE

This invention relates to security, locking or fastening devices, systems or the like.

In a first aspect, the invention relates to secu¬ rity devices or systems for impeding or preventing the unauthorised driving away of a ve.iicle. The device or system may, for example, be caparle of being fitted as an accessory to existing vehicles, or as original equipment by vehicle manufacturers.

Current security devices supplied for fitting to existing vehicles typically comprise a separate mechanical device which the driver has to attach and lock to one or more of the movable controls of the vehicle, such as the clutch pedal, steering wheel, gear lever and/or handbrake, each time the vehicle is to be immobilised. The driver must remember to fit the device when leaving the vehicle, and because of the time and trouble involved, the driver may well not fit the device if the vehicle is only to be left for a short period of time.

It is an object of this first aspect of the present invention to provide a security device or system which alleviates or effectively overcomes at least some of the disadvantages of such current devices.

From this aspect, the invention consists in a vehicle security system comprising a locking arrangement, including a locking device permanently anchored to the vehicle structure and to a driver-operable control of the vehicle, the device having an unlocked condition in which it accommodates normal movement of the control relative to the vehicle structure, and a locked condition in which it accommodates movement of the control in one direction only to or towards a position in which the normal driver-opera¬ tion of the control is impeded or prevented, and means, operable by an authorised person, to actuate the locking device to change from its locked to its unlocked condition.

The locking arrangement may include a locking device comprising a hydraulic actuator, such as a linear actuator of the piston and cylinder type, connected between the vehicle chassis or equivalent and the lower end of the hand brake lever. The actuator cylinder is connected to a hydraulic shuttle valve arrangement incorporating a non¬ return valve. The actuator and valve arrangement are located in an inaccessible position so that they cannot easily be seen or disabled by an intruder. When the shuttle valve is open, i.e. in the unlocked condition of the device, hydraulic fluid is free to flow both into and out of the actuator cylinder, allowing the piston to reciprocate freely in opposite directions, so that the handbrake lever is also free to be moved in opposite direc¬ tions by the driver, to apply or release the hand brake in the usual way.

However, when the shuttle valve is shut, i.e. in the locked condition of the device, the non-return valve permits fluid flow, and therefore piston movement, in one direction only, and the hand brake may be moved in the brake-application direction but not the brake-release direction. The hand brake may therefore be applied, or applied more firmly, in the usual way, but any attempt to move the hand brake in the release direction will be blocked by the hydraulic lock in the cylinder.

The shuttle valve may be actuated, i.e. opened and closed, by manual means, such as a coded or key-operated lock, or a remotely operated lock.

Alternatively, first means may be provided for automatically detecting when the vehicle is being, or has been, le t in a parked condition, and consequently to lock the locking device, second means being provided, operable by an authorised person, to unlock the locking device.

The present invention also consists in a vehicle security system comprising a locking arrangement including a locking device anchored to the vehicle structure, and displaceable between a locke condition in which it cooper¬ ates with a movable driver- erable control of the vehicle to lock the control relative to the vehicle structure in a position in which its normal driver-operation is impeded or prevented, and an unlocked condition in which the control is free to be operated normally; first means operable automatically to e^'etect when the vehicle is being, or has been, left in a parked condition and consequently to actu¬ ate the locking device to change rom its unlocked to its locked condition; and second me .-s operable by an autho¬ rised person to actuate the locking device to change from its locked to its unlocked condition.

Thus, when the driver leaves the vehicle parked, locking is automatically effected without the need for any further action by the driver.

The first means preferably detects when the driver is leaving or has left the vehicle, and may, for example, comprise, or be associated with, the courtesy light cir¬ cuit or switch triggered by the driver's door, and/or a load cell associated with the driver's seat. Additionally or alternatively, the first means may comprise, or be associated with, means to detect when the vehicle engine has been switched off and the vehicle has been stationary for a predetermined minimum length of time.

The second means preferably comprises a driver- actuable coded transmitter and a corresponding receiver associated with the locking device. The transmitter may be hand-held, and may be of the type used to remotely lock and unlock the doors of the vehicle, and/or arms or disarm an alarm system.

The invention also consists in a kit of parts for use in the security systems defined herein, comprising said locking arrangement, means to attach the locking device of the locking arrangement to a vehicle and to a driver-opera¬ ble control of the vehicle, and means to actuate the lock¬ ing device.

As described earlier, the device or system may incorporate a fluid actuator, such as a linear hydraulic actuator of the piston and cylinder type. The fluid circuit, for example hydraulic circuit of the actuator incorporates a non-return or one-way valve. In a first condition or state of the circuit, the non-return valve is effective to allow fluid flow in the circuit, and therefore displacement of the actuator, in one direction, but not in a reverse direction. In a second condition or state, the non-return valve is not effective to prevent fluid flow in the circuit in either direction, so that fluid flow, and therefore displacement of the actuator can take place in both directions.

According to a second aspect of the invention, a device or system of the latter type may be utilised in applications other than those referred to earlier which act on a driver-operable control of the vehicle to impede or prevent the unauthorised driving away of the vehicle.

For example, the device or system, with appropriate modifications if necessary, may be used in other locking or securing applications, both vehicular and non-vehicular. The device or system may, for example, be employed as, incorporated in or combined with, locking or closing mecha¬ nisms for doors, hatches, windows, tailgates or other clo¬ sures, etc. of land vehicles such as road or rail vehicles, trucks or trailers, water craft, aircraft, or of buildings, rooms, cabinets, or used in any other securing, locking or fastening applications . The device and system could also be associated with a trailer or other towable vehicle so as to prevent unauthorised coupling of the trailer etc. to a towing vehicle, and thus function as an anti-theft device.

In order that the invention may be more readily understood, reference will now be made to the accompanying drawings, in which:

Figure 1 illustrates, schematically, a vehicle security system according to a first embodiment of the invention;

Figure 2 illustrates, schematically, a vehicle security system according to a second embodiment of the invention;

Figure 3 is a longitudinal partial section through a security or locking device or system according to a third embodiment of the invention;

Figure 4 is a longitudinal partial section at right angles to the plane of Figure 3; and

Figure 5 is a section on the line A-A in Figure 4.

Referring to Figure 1, a conventional automobile hand brake lever 1 is pivotally mounted at 2 to the chas¬ sis, sub frame or equivalent of an automobile, for example to a box-section cross-member 4. The lower end la. of the lever is attached by a clevis pin 5 or the like to the piston 3a, of a hydraulic actuator cylinder 3, the latter being anchored by a clevis pin 6 or the like to the box- section cross-member 4. The lower end of the brake lever will also be connected to the vehicle brakes in a known manner by appropriate cables or the like, which have been omitted from the drawings for clarity, since they form no part of the present invention.

Hydraulic lines 7a_, 7b_. connect the chamber 3b_ within the cylinder 3 to a hydraulic fluid reservoir 8 located, for example, beneath the vehicle bonnet. A dou¬ ble-acting solenoid-operated spool or shuttle valve 9 is connected between the lines 7a_, 7b.. A non-return or one¬ way valve 10 is connected to the lines 7a,, 7b_ in parallel with the shuttle valve 9 so as to bypass the latter. The non-return valve 10 allows hydraulic fluid, for example conventional clutch or brake fluid, to flow from the reservoir 8 towards the actuating cylinder 3 , but not in the reverse direction.

The shuttle valve 9 is provided with a first sole¬ noid 9a. connected by wiring 11 to the interior or courtesy light circuit or switch 15 which is triggered by the driv¬ er's door. When the driver's door is initially opened and the associated courtesy light circuit is energised, the solenoid 9a. will also be energised, displacing the shuttle or spool of the valve 9 to a position in which the valve 9 is shut. When the driver's door is subsequently closed and the courtesy light circuit and solenoid 9a. are deener- gised, the valve shuttle remains in its "shut" position.

The shuttle valve 9 is also provided with a second solenoid 9b_ connected by wiring 12 to an energising circuit including a coded receiver 13. The receiver is intended to receive signals from a corresponding coded driver-actuated transmitter 14. When the receiver is triggered by the transmitter, the second solenoid 9b. is energised to displace the valve shuttle from its "shut" position to an "open" position. The shuttle remains in its "open" position until the first solenoid 9a. is energised again.

The receiver 13 and transmitter 14 may be of the type used to remotely actuate vehicle door lo ks and/or alarm systems, and may utilise radio, ultrasound or infra-red transmission, etc. The transmitter, which may be hand-held, may be specific to the security system, although it may also be the same transmitter used to remotely actu¬ ate the central lockiⁿg system of the vehicle, and/or the vehicle alarm system.

The actuator cylinder 3 and its linkage to the hand brake and chassis, as well as the hydraulic line 7b_, shut¬ tle valve 9 and non-return valve 10, will, in practice, be located within the box-section 4 of the chassis, or will be otherwise concealed and rendered inaccessible, so that the system will not be apparent to, and cannot be disabled by, an intruder.

In use, when a driver parks the vehicle, i.e. applies the hand brake and switches off the engine, and opens the driver's door to leave the vehicle, the latter action will energise the first solenoid 9a. temporarily, shutting the shuttle valve 9. Hydraulic fluid will be prevented from flowing out of the cylinder 3, and the resultant hydraulic lock will prevent the hand brake from being pivoted clockwise in the brake-release direction. If the brake is pulled further in an anticlockwise brake- applying direction, for example as is usual in order to release the normal hand brake ratchet mechanism, the non¬ return valve 10 will allow additional fluid to flow into the cylinder 3, but will prevent the fluid from flowing back out again. This avoids the formation of an air lock in or between the cylinder and shuttle valve, and ensures that the hand brake will be applied even harder. Since the hydraulic fluid, for example brake or clutch fluid, is a liquid, and is therefore incompressible, any attempt to force the hand brake in the clockwise brake-release direc¬ tion will be positively blocked by the actuator cylinder 3 which acts as a rigid strut.

The system will remain in this locked condition until the associated coded transmitter is actuated by the authorised driver or other authorised person. This tempo¬ rarily actuates the second solenoid 9b_, opening the shuttle valve, and allowing hydraulic fluid to flow from the actua¬ tor cylinder to the reservoir. The actuator piston 3a. is thus free to move in either direction, allowing the hand brake to be released and re-applied normally as required.

Appropriate mechanisms, time delay circuitry, and/or interlock circuitry, may be provided to prevent inadvertent actuation of the system by the authorised driver. For example, if the driver unlocks the system before entering the vehicle, subsequent opening and closing of the driver's door as the driver enters the vehicle should not trigger the first solenoid 9a.. Similarly, the authorised driver, when in the vehicle, should be able to open and close the driver's door, at least momentarily for example if it is not shut properly, or if the driver's seat belt, clothing, etc. is trapped in the door, without re- energising the first solenoid 9a.. The system may, for example, be prevented from operation until the vehicle engine has been switched off and the vehicle has been stationary, for a predetermined minimum period of time.

The embodiment illustrated in Figure 2 is similar to that of Figure 1 in so far as the hydraulic circuitry, etc. is concerned. In this embodiment, the shuttle or spool of the shuttle valve 9 is actuated by a driver-operated lock 16, which may be a key-operated or coded lock located adjacent the hand brake. Alternatively, the lock may remotely be operable via a transmitter-receiver system. The lock may be attached to the shuttle valve and mechani¬ cally connected to the shuttle of the valve 9, thus elimi¬ nating the solenoids 9a. and 9b and all associated electri¬ cal circuitry. Alternatively, the lock may be operable to selectively energise the solenoids 9a,, 9b.

It will be understood that various modifications may be made.

For example, the system may be used to immobilise driver-operable controls other than, or in addition to, the hand brake, for example the clutch or brake pedal. In this alternative, the actuator or equivalent may be located in the engine compartment, and the closure, for example bon¬ net, of the engine compartment may be associated with a locking device, for example similar to the actuator previ¬ ously described, linked to the system and operable to lock the engine compartment (for example the bonnet) when the system is locked, to prevent unauthorised access to the actuator associated with the driver-operable control.

The system may be applied to private vehicles such as automobiles or motor cycles, or to commercial vehicles. The sy tern may employ a pneumatic fluid such as air or other gas, instead of a liquid such as brake fluid.

The system may be

with an audible and/or visual warning or alarm device which is activated if an attempt is made to move the driver-operable control when the system is in its locked condition. For example, the warning device may be activated by a pressure sensor con¬ nected into the hydraulic circuit of the system.

Although, in the embodiments of Figures 1 and 2, the actuator 3 acts directly between the chassis and the hand brake lever, the actuator or equivalent could be linked to the driver-operable control, or could be operable to actuate a mechanical lock associated with the control. The lock may incorporate, instead of a non-return valve, a one-way clutch or the like, such as a ratchet and pawl mechanism, enabling the control, when locked, to be further displaced in one direction towards a position in which the normal operation of the control, and preferably the move¬ ment of the vehicle, is impeded or prevented.

The hydraulic actuator 3 or equivalent may also incorporate mechanical means to retain it in its locked position for extended periods of time, even if there should be a leak in the hydraulic system. Furthermore, the hy¬ draulic actuator could be replaced by a mechanical actua¬ tor.

The non-return valve 10 may be incorporated in the shuttle valve or equivalent, instead of being a separate bypass valve. The non-return valve may only be operative or open when the shuttle valve is "shut", and may be closed when the shuttle valve is open.

Although the embodiment of Figure 1 uses a remotely operated transmitter-receiver system to unlock the system, the system could be unlocked by a mechanically operable lock, such as key-operated or coded lock mounted on or in the vehicle. Alternatively, the system could be connected to the vehicle central locking system, and/or alarm system, so as to be locked and unlocked when the central locking system is locked and unlocked, and/or when an associated alarm system is armed or disarmed.

Instead of linking the system into the courtesy light system of the driver's door in order to detect when the driver is about to leave the vehicle, and the system should be locked, the system may be linked to some other means indicative of the driver leaving the vehicle. For exc. pie the first solenoid 9a. or equivalent may additional¬ ly or alternatively be connected a load cell associated with the driver's seat, which is sensitive to the driver's weight. Additionally or alternatively, the first solenoid or equivalent may be connected to means operable to detect when the engine has been switched off, and the vehicle has been stationary, for a predetermined minimum period of time.

The shuttle or spool valve could be replaced by any other suitable form of valve. The valve may be a latched solenoid valve, i.e. a valve which is actuated by a single solenoid, which will eliminate one of the solenoids em¬ ployed in the embodiment of Figure 1. In this alternative, the valve is normally open, for example biased to an open position, allowing the hand brake to be released and ap¬ plied as required. When the latching solenoid is ener¬ gised, for example by energisation of the driver's door courtesy light circuit, the solenoid closes the valve, and the solenoid, and therefore the valve, ar. latched and retained in the valve-closed position, even when the sole¬ noid is subsequently de-energised. When a signal is ap¬ plied to the latching solenoid, for example via a transmit¬ ter-triggered receiver connected to the solenoid, the solenoid is unlatched and released, and the valve returns to its open position, freeing the handbrake. Alternative¬ ly, the solenoid could retain the valve in its open posi¬ tion when latched, and displace the valve, or allow it to be biased, to its closed position, when unlatched.

An example of the latter alternat-'.ve will now be described with reference to Figures 3 to 6

In the embodiments described with reference to Figures 1 and 2, the locking device includes a hydraulic actuator 3 connected to a separate hydraulic control sys¬ tem. In the embodiment of Figures 3 to 5, the actuator and control system form part of a self-contained unit.

In particular, the locking device comprises a cylindrical housing 20 closed at its opposite ends by end caps 21 and 22. The housing and end caps are preferably formed from hardened steel or equivalent so as to prevent unauthorised access to the components within the housing.

A manifold block 23, having a cylindrical section 23a., is anchored within the housing by a locking pin 24. The manifold section 23a. has a stepped passage 25 extending axially therethrough, with the transition or step 25a. between the larger and smaller diameter passage portions 25b., 25c. being frusto-conical so as to form an annular valve seat for a valve member comprising a ball 26 located in the larger diameter passage portion 25b.. The ball is normally urged into sealing engagement with the seat 25a. by a compression spring 27 trapped between the ball and a circlip 28 within the open end of the larger diameter passage portion 25b.

The outer end of the passage portion 25b is defined by a coaxial cylindrical spigot 23b of the manifold section 23a., which serves to locate and mount one end of a cylinder 29. The other end of the cylinder is located within an annular groove 21a, in the end cap 21. A piston 30, formed for example from nylon, is slidable within the cylinder 29, and is attached by a screw 30a. to the end of a piston rod 31 which extends through an axial opening and bearing 21b in the end cap 21.

Between the cylinder 29 and housing 20 is an annular, outer chamber 32 containing an annular, axially slidable, resilient seal or piston 33, which is preferably biased towards the manifold section 23a. by a compression spring 34. On the side of the annular piston 33, adjacent the end cap 21, the outer chamber 32 communicates with an inner chamber 35 within the cylinder 79 via a port or passage 29a.. The opposite end of the outer chamber 32 communicates, via passages 33 in the manifold section 23a., with the smaller diameter passage portion 25c_ which, in turn, communicates with the larger diameter passage portion 25b. and the region of the inner chamber 35 to the left of the piston 30 when the ball 26 is unseated. The hydraulic circuit, comprising the inner end outer chambers and asso¬ ciated passages are filled with a hydraulic fluid, for example oil, bled and sealed, during assembly of the de¬ vice. The closed circuit, incorporating the outer chamber 32, thus dispenses with the need for a separate i servoir or equivalent.

The manifold section 23a,, remote from the cylinder 29, is provided with a longitudinal extension 23c. terminat¬ ing in a flange 23d., to which a solenoid 36 is secured by screws (not shown). The solenoid 36 may be a magnetically latching solenoid of the type supplied in the UK by Radio Spares, identified by No. RS 352-907. The solenoid basi¬ cally includes an outer permanent magnet and reversible energising winding 36a., within which an armature or pin 36b. is axially slidable. The armature 36b is coupled via a spring pin 37 to a stepped connecting rod or plunger 38 slidable within the smaller diameter passage portion 25c. in the manifold section 23a..

The plunger 38 is shown in full lines in its re¬ tracted position, in which its right hand or outer end is spaced from the ball 26. In this condition, the ball is resiliently urged by the spring 27 against its seat 25a. so as to act as a one-way or non-return valve, allowing the hydraulic oil to flow from the smaller diameter passage portion 25c. to the larger diameter passage portion 25b, but not in a reverse direction. In the extended position of the plunger 38, the plunger engages the ball 26, displacing it from the seat 25a., as indicated in broken lines, allow¬ ing oil to flow freely between the smaller and larger diameter passage portions 25c. and 25b in either direction.

The piston 30, stepped plunger 38, end cap opening 21b., and manifold section 23a., are provided with O-ring seals or the like to prevent leakage of oil from the sealed hydraulic circuit.

The self-contained, unitary device just described may be substituted for the actuator 3 and associated hy¬ draulic circuitry in the embodiments of Figs. 1 and 2, with the end cap 22 anchored to the chassis section 4 or equiva¬ lent, the outer end of the piston rod 31 connected to the handbrake 1, and with the energising winding 36a. of the solenoid 36 connected into the associated electrical cir¬ cuitry.

In the locked condition of the device shown in full lines, in which the non-return valve is effective, if the handbrake is applied, the piston rod 31 will be drawn from its retracted position shown in full lines, displacing the piston 30 to the right, towards end cap 21. Hydraulic fluid will be displaced and flow from the inner cylinder or chamber 35 on the right-hand side of the piston 30, through passage 29a. into the outer chamber 32, displacing annular outer piston 33 to the left. Hydraulic fluid to the left of piston 33 will be displaced and flow through passages 33 in the manifold section 23a. into the smaller passage portion 25c., and the pressure differential acting on the ball 26 will displace it from its seat, allowing the fluid to flow into the inner cylinder through the larger passage portion 25b. and left hand end of the inner chamber 35. However, any attempt to subsequently release the handbrake, i.e. return the piston rod 31 to the left, will be blocked by the closed non-return valve 25a., 26. The armature 36b and plunger 38 will be retained in their full line position shown by the permanent magnet latch of the solenoid 36 whilst winding of the latter is de-energised.

When an authorised driver actuates and unlocks the device, for example when entering the vehicle, the winding of the solenoid 36 will be energised, for example pulsed, in one direction, displacing the armature 36b_ and plunger 38 from their retracted position. The plunger 38 will displace the ball 26 from the seat 25a., rendering the non¬ return valve ineffective, allowing hydraulic fluid to f-.ow through the passage 25 in either direction, and likewise allowing the piston 30 and piston rod 31 to be freely displaceable toward and away from the manifold section 23a.. Thus, the handbrake may be released and applied in the usual way. The armature and plunger will then be retained in their right-hand extended position by the permanent magnet latch of the solenoid, when the solenoid is de- energised. An armature spring 39 serves to at least par¬ tially offset the bias force exerted by the ball spring 27 so that the latter spring will not inadvertently drive the armature and plunger back to their retracted, valve-closed position.

When the device is actuated and locked, for example when the vehicle is locked, or the driver opens the door to leave the vehicle, the solenoid winding is energised, for example pulsed, in the reverse direction, retracting the armature 36b. and plunger 38 to the left against the action of the magnetic latch, and the ball 26 is returned to its seat 25a. by the spring 27. In this condition, as previously explained, the handbrake can be displaced in a brake-applying direction but not a brake-release direction.

Since the device is a self-contained unit, con»- tained in an armoured housing, its components are concealed and inaccessible, and cannot be disabled by an intruder.

It will be appreciated that the non-return valve 25a, , 26, 27 could be rendered ineffective or effective by means other than the solenoid 35. For example, the device, if substituted for the actuator 3 of Figure 2, could be actuated by a key-operated or coded lock built into the device.

The devices and systems described herein, and in particular, self-contained units as described with refer¬ ence to Figures 3 to 5, are not limited in their applica¬ tion to the immobilisation of vehicles by acting on driver-operable controls of the vehicles. For example, it will be apparent that the unit or device, and in particular the piston rod of the actuator, could function as the sliding fastening or bolt member of a lock device. The device could therefore also be used in place of, or as part of, or in combination with, existing locking systems, both in vehicular and non-vehicular applications. For example, as applied to a road vehicle or rail vehicle door, the device could be incorporated into the door, or the door frame. The piston rod 31, with an appropriately modified outer end, would normally be biassed, for example by an additional compressor spring between the manifold section 23a. and piston 30 (and/or by the spring 34), into an ex¬ tended position. In the manner of a conventional bolt member, the piston rod would be retracted by engagement with a cam surface, catch plate, or the like as the door is closed, and would spring out into or behind the catch plate, etc. in the closed position of the door to lock the door. The door handle or equivalent operating member would be coupled to the device, for example to the piston rod, so as to retract the rod and release the door when the device is unlocked and the non-return val- e is ineffective, i.e. open. F wever, when the device is locked, i.e. the non¬ return valve is effective, the piston rod would be locked against retraction by the door handle or equivalent.

Alternatively, as applied, for example to the doors of passenger-carrying vehicles such as railway carriages, the door handle or equivalent could be operaϊ^{^} \e both to op^cn the non-return valve and retract the piston rod, thus minimising the risk of unintentional retraction of the piston rod without operating the door handle, should the lock mechanism develop a fault.

The device may incorporate an over-ride facility to enable the lock to be released in an emergency. For exam¬ ple, means such as a valve may be provided to vent the hydraulic fluid, or means may be provided to by-pass the non return valve, or to open the non-return valve, accessi¬ ble from outside the vehicle.

The device could be applied i a similar manner to lock non-vehicular as well as vehicular doors, windows, hatches or other closures, etc. of buildings, rooms, cham¬ bers, cabinets, safes, drawers, etc.

The device could be used as an anti-theft device for trailers, for example to prevent unauthorised coupling of a trailer to a towing vehicle. Commercial vehicle trailers usually incorporate a plate having a downwardly directed face which bears on an upwardly directed face of a corresponding plate of a tractor unit when the trailer and tractor unit are coupled together. The actuator device could be mounted in or above the trailer bearing plate with the piston rod 31 normally projecting through and below the bearing face of the trailer bearing plate, biassed by an internal spring as described above. With the device locked, i.e. the non-return valve effective, the projecting piston rod prevents the trailer bearing plate from cooper¬ ating with and coupling to the tractor bearing plate. When the device is unlocked, i.e. the non-return valve is inef¬ fective, the piston rod will be retracted, or will be free to retract when engaged by the tractor bearing plate during coupling of the trailer to the tractor unit.

Although the illustrated embodiments refer to the use of linear actuators, this is not essential, and non¬ linear actuators, such as rotary actuators may equally be employed, depending upon the particular application.

Claims

CIAIMS

1. A vehicle security system comprising a locking arrangement, including a locking device permanently an¬ chored to the vehicle structure and to a driver-operable control of the vehicle, "he device having an unlocked condition in which it accommodates normal movement of the control relative to the vehicle structure, and a locked condition in which it accommodates movement of the control in one direction only to or towards a position in which the normal driver-operation of the control is impeded or pre¬ vented, and means, operable by an authorised person, to actuate the locking device to change from its locked to its unlocked condition.

2. A system as claimed in claim 1, wherein the locking device comprises a fluid actuator connected between the vehicle chassis or equivalent and a lever of the driver- operable control.

3. A system as claimed in claim 2, wherein the fluid actuator is a linear actuator of the piston and cylinder type, the actuator cylinder being connected to a fluid shuttle valve arrangement incorporating a non-return valve, with the actuator and valve arrangement being located in a position which is inaccessible to an intruder, the shuttle valve being open in the unlocked condition of the locking device to permit the working fluid to flow both into and out of the actuator cylinder to allow the piston to reciprocate freely in opposite directions, so that the lever of the driver-operable control is also free to be moved in opposite directions by the driver to accommodate normal movements of the driver-operable control, the shut¬ tle valve being shut in the locked condition of the locking device whereby the non-return valve permits fluid flow, and therefore piston movement, in one direction only, and the lever can only be moved in a direction to or towards a position in which the normal driver-operation of the con¬ trol is impeded or prevented.

4. A system as claimed in claim 3, wherein the driver- operable control is the vehicle hand brake lever, the lever being movable in a brake-application direction, but not in a brake-release direction, when the shuttle valve is closed in the locked condition of the locking device.

5. A system as claimed in claim 3 or 4 , wherein the shuttle valve is actuatable by manual means, comprising a coded or key-operated lock, or a remotely operated lock.

6. A system as claimed in claim 3 or 4 , including first means operable to automatically detect when the vehicle is being, or has been, left in a parked condition, and consequently to lock the locking device, and second means operable by an authorised person, to unlock the locking device.

7. A vehicle security system comprising a locking arrangement including a locking device anchored to the vehicle structure, and displaceable between a locked condi¬ tion in which it cooperates with a movable driver-operable control of the vehicle to lock the control relative to the vehicle structure in a position in which its normal driver-operation is impeded or prevented, and an unlocked condition in which the control is free to be operated normally; first means operable automatically to detect when the vehicle is being, or has been, left in a parked condi¬ tion and consequently to actuate the locking device to change from its unlocked to its locked condition; and second means operable by an authorised person to actuate the locking device to change from its locked to its un¬ locked condition.

8. A system as claimed in claim 6 or 7, wherein the first means is operable to detect when the driver is leav¬ ing or has left the vehicle.

9. A system as claimed in claim 8, srein the first means includes, or is associated with, t a courtesy light circuit or switch triggered by the driver's door, and/or a load cell associated with the driver's seat.

10. A system as claimed in claim 8 or 9, wherein the first means includes, or is associated with, means to detect that the vehicle engine has stopped, and the vehicle has been stationary, for more than a predetermined minimum period of time.

11. A system as claimed in any of claim, j to 10, wherein the second means comprises a driver-actuable coded transmitter, and a corresponding receiver associated with the locking device.

12. A kit of parts for use in a security system as claimed in any preceding claim, comprising said locking arrangement, means to attach the locking device of the locking arrangement to a vehicle and to a driver-operable control of the vehicle, and means to actuate ^khe locking device.

13. A device or system incorporating a fluid actuator provided with a fluid circuit incorporating a non-return or one-way valve, the valve, in a first condition or state of the circuit, being effective to allow fluid flow in the circuit, and therefore displacement of the actuator, in one direction, but not in a reverse direction, the valve, in a second condition or state, not being effective to prevent fluid flow in the circuit in either direction, so that fluid flow, and therefore displacement of the actuator, can take place in both directions.

14. A device or system as claimed in claim 13, wherein the actuator is a linear actuator of the piston and cylin¬ der type, comprising an intrusion-resistant cylindrical housing, containing an inner fluid cylinder in which the piston is reciprocable, an outer annular fluid reservoir concentric with the inner cylinder, the outer reservoir and inner cylinder being in open communication at or adjacent one of their ends, and communicating at or adjacent their other ends via a coaxial one-way ball valve, means being provided, within the housing, cooperable with the valve to switch the valve between one-way and two-way operation.