GB2261992A

GB2261992A - An anti-theft device for a motor vehicle

Info

Publication number: GB2261992A
Application number: GB9125431A
Authority: GB
Inventors: Keith Nunnerley Aitchison; Graeme John Lewis
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-11-29
Filing date: 1991-11-29
Publication date: 1993-06-02
Also published as: GB9125431D0; GB9213202D0

Abstract

An anti-theft device for a motor vehicle comprises a flexible cable (12) disposable between an ignition key operated steering column lock and a rotary electrical ignition switch (16) for transmitting rotational movement of the ignition key to the rotary switch (16) during normal operation and enabling the switch (16) to be disposed at an inaccessible location remote from the steering column lock. One end of the cable (12) is normally coupled to the rotary switch (16) by way of a spring biased piston (50) having a projecting member (52) drivingly engaging a recess (54) on the switch (16). Should the connection of the cable (12) with the steering column lock be broken, eg by tampering, the spring (48) biasing the piston (50) acts to separate the projecting member (52) from the switch and thereby break the rotary coupling between the cable and switch. A spring loaded detent (68) prevents reengagement of the piston (50) with the switch (16). <IMAGE>

Description

DESCRIPTION AN ANTI-THEFT DEVICE FOR A MOTOR VEHICLE The present invention relates to an anti-theft device for a motor vehicle.

As shown in Fig.3 of the accompanying drawings, in a conventional key ignition system of a motor vehicle having a steering column lock, a key slot 11 located to one side of the steering wheel (not shown) is connected by a rod 13 housed in a steering wheel mount 14 to an electrical switch mounted in a housing 16 on the other side of the steering wheel, in close proximity to the steering wheel mount 14. The switchend of the rod 13 is formed with a pin portion 17 which is adapted to engage a recess of a rotatable switching member in the switch 16, the rotation of the switching member via the key and rod resulting in the formation of connections with the ignition and starter circuits, in turn.Rotary movement of the key initially disengages the steering lock, the lock usually comprising a transverse bar carried by the rod which is removably engageable with a recess in the steering column by rotation of the key. Further motion of the key in its rotary path respectively connects the ignition and then the starter circuits in the switch, after which the key springs back to reconnect the ignition circuitry. When the ignition is switched off and the key is removed from the key slot, the steering column is automatically locked in position.

Once illegal access to the interior of a car has been gained by a potential thief, it is only necessary for the steering wheel to be twisted violently in order to break the above mentioned rod and free the steering column and thereby restore the possibility of rotary motion of the steering wheel. In order then to start the vehicle, the typical practice is for the switch housing 16 to be removed from the steering mount 14 to expose the aforementioned recess in the switch 16. A screwdriver or other suitable implement is then inserted into the recess of the switch to enable the switching member to be rotated, whereby to make the respective connections between the battery and the ignition and starter circuits and thereby enable the vehicle to be driven away.

It is an object of the present invention to provide an anti-theft device for a motor vehicle which will protect against unauthorised operation of the aforementioned switch.

In accordance with the present invention there is provided an anti-theft device for a motor vehicle fitted with ignition-key-operated steering column lock and a rotary electrical switch for controlling the energisation of the vehicle ignition and starter by way of the ignition key, the anti-theft device comprising a flexible cable adapted to be disposed between the steering column lock and the electrical switch for transmitting rotational movement of the key to the rotary switch during normal operation and enabling the switch to be disposed at an inaccessible location remote from the steering column lock, and means by which, in the event of disconnection of the cable from the steering column lock, for example as a result of tampering, the cable is arranged to be disengaged automatically from the switch and to be prevented from re-engagement.

In a preferred embodiment, the cable is rotatably housed within a flexible sheath, the sheath being adapted to be connected at one end to the steering column lock and being connected at the other end to a housing which is adapted to receive said electrical switch.

The housing contains a spring means which is arranged so that the cable is resiliently mounted between the steering column lock and the electrical switch.

Preferably, one end of the cable is normally coupled to the rotary switch by way of a piston member which is received slidably within a through-bore in said housing and is drivingly coupled to said one end of the cable, the spring means comprising a helical spring disposed so as to bias the piston away from the switch.

By virtue of the engagement of the opposite end of the cable with the steering column lock mechanism, the spring is normally compressed sufficiently for a projecting member coupled to the piston to drivingly engage a recess on the switch for rotatably coupling the cable to the switch, but, should the connection of the cable with the steering column lock be broken, the spring acts to separate said projecting member from the switch and thereby break the rotary coupling between the cable and switch.

Preferably, the housing contains a spring loaded detent which normally has no effect on the rotary coupling between the cable and the switch bolt which, upon the spring being able to displace the piston sufficient to break said rotary coupling, engages a recess in the piston to prevent the piston from being returned and thereby permanently to prevent the rotary coupling from being re-established in the absence of access to the housing.

A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig.1 is a perspective partial view of an antitheft device for a motor vehicle, in accordance with the present invention; Fig.2 is a cross-section through a switch and a housing of the anti-theft device in Fig.1, and Fig.3 is an exploded perspective view of a typical steering wheel mount and switch arrangement as conventionally mounted in a motor vehicle.

Referring to Fig.1 of the accompanying drawings, the illustrated anti-theft device 10 in accordance with the present invention is adapted to be fitted between a conventional steering column mount 14, housing a conventional steering column lock, and a conventional ignition/starter switch 16 so that the switch 16 can be mounted at an inaccessible position remote from the steering column mount 14, preferably to the rear of the dashboard at a concealed location where it cannot be reached without wholesale disassembly of the dashboard.

The device 10 comprises an elongate flexible cable 12 disposed rotatably within an outer flexible sheath 20, made for example, of a strong plastics material. The cable 12 is preferably made of braided metal for strength. At one end, the outer sheath 20 is connected to a first cylindrical housing 22 which is adapted to be fitted to the socket 17 of the steering column mount 14 in place of the usual connection with the switch 16. When so mounted, a socket (not shown) formed on the associated end of the cable 12 is adapted to be connected to the pin portion 17 at the switch end of the rod 13 whereby rotation of the rod 13 by the key 19 results in corresponding rotation of the cable 12 within the sheath 20.

At its other end, the outer sheath 20 is connected via an annular, internally threaded coupling member 22 to a second housing 18 which is adapted to receive in a recess 42 at its one end the conventional electrical switch 16 for controlling the ignition and starter circuits 8. As shown in Fig.2, the switch 16 (which does not form part of the present device 10 as such) is arranged to be held securely within the housing recess 42 by means of a grub screw 40. When so located, the conventional recess 54 of the switching member within the switch 16 receives a pin portion 52 formed at one end of a piston member 50 which is itself received slidably within a longitudinal bore 44 in the housing 18. The piston member 50 has a main cylindrical body portion 51 which is received with a sliding fit within the housing bore 44 and is formed adjacent its left-hand end (as viewed in Fig.2) with a peripheral recess 62. The piston member 50 also has a stem portion 46 which is of smaller diameter than the main body portion 51 and which carries the pin portion 52 at its free end.

Disposed around the stem portion 46 and acting between the shoulder 52, formed between the stem portion 46 and main body portion 51, and the adjacent end surface 56 of the switch 16 is a helical coil spring 48. The spring 48 thus biasses the piston to the right, as viewed in Fig.2.

As shown in Fig.2, the right-hand end 54 of the main body portion 51 of the piston 50 has a central slot 58 which receives a flattened end portion 24 formed on the end of the flexible cable 12 which projects from the sheath 20 into the housing 16. By virtue of the connection between the cable and the piston slot 58, rotation of the cable 12 is transferred to the piston 50 and thence, via the connection between the pin portion 52 of the piston and the recess 54, to the switching member of the switch 16.

In the normal operational condition of the device 10, the dimensions of the components are such that the spring is in a compressed state so that the piston 50 and cable 12 are urged to the right as viewed in Fig.2. However, the piston and cable cannot move any further to the right because of the connection of the cable to the steering column mount at its other end.

As shown in Fig.2, there is mounted within a radical bore 64 in the housing 16, by means of a grub screw 66, a spring loaded detent 68 which, in the normal operation condition, simply rests on the periphery of the main body portion of the piston and has no operational effect. However, in the event that the coupling between the cable 12 and the steering column mount 14 is broken, the spring 48 is able to displace the cable 12 within the sheath 20 to the right as viewed in Fig.2 by corresponding axial displacement of the piston 50 in the housing 18. Such displacement of the piston eventually brings the peripheral recess 62 into radical alignment with the spring loaded detent 68 which is therefore then able to move radially inwardly into this recess and thereby prevent further axial movement of the piston in either direction.In this position, the pin end 62 of the piston 50 is arranged to be clear of the slot 54 in the switching member so that rotation of the cable and piston no longer rotates the switching member. Thus, once the detent has engaged the piston recess 62, the cable cannot be moved back to the left to re-engage the pin portion 52 with the switching member recess without disassembling the switch 16 from the housing 18 and re-setting the whole assembly. What is particularly important is that the re-engagement of the pin portion 52 with the switching member cannot be achieved by any action at the steering column end of the device, i.e.

the end which would be accessible to anyone attempting to tamper with the device.

It will also be appreciated that if the cable and sheath should be cut at any point, the same effect will occur and non-returnable disengagement of the pin 52 and switching member will take place.

Thus, the device 10 provides a means which enables the switch 16 to be located at a remote and inaccessible position and which will automatically render the switch 16, and hence the ignition and start circuits, inoperable in the event of tampering.

In the illustrated embodiment, the rotational axes of the switch 16 and the rod 13 are parallel coincident. However, in other embodiments, it may be desirable for these axes to be at some angle to one another. In this event the cable can be coupled to the rod 13 in the steering column mount 14 by way of a suitable gear arrangement (not shown) whereby the angle between the latter axes can be pre-selected.

Claims

1. An anti-theft device for a motor vehicle fitted with ignition-key-operated steering column lock and a rotary electrical switch for controlling the energisation of the vehicle ignition and starter by way of the ignition key, the anti-theft device comprising a flexible cable adapted to be disposed between the steering column lock and the electrical switch for transmitting rotational movement of the key to the rotary switch during normal operation and enabling the switch to be disposed at an inaccessible location remote from the steering column lock, and means by which, in the event of disconnection of the cable from the steering column lock, for example as a result of tampering, the cable is arranged to be disengaged automatically from the switch and to be prevented from re-engagement.

2. An anti-theft device as claimed in claim 1, wherein the cable is rotatably housed within a flexible sheath, the sheath being adapted to be connected at one end to the steering column lock and being connected at the other end to a housing which is adapted to receive said electrical switch.

3. An anti-theft device as claimed in claim 2, wherein the housing contains a spring means which is arranged so that the cable is resiliently mounted between the steering column lock and the electrical switch.

4. An anti-theft device as claimed in claim 3, wherein one end of the cable is normally coupled to the rotary switch by way of a piston member which is received slidably within a through-bore in said housing and is drivingly coupled to said one end of the cable, the spring means comprising a helical spring disposed so as to bias the piston away from the switch.

5. An anti-theft device as claimed in claim 4, wherein by virtue of the engagement of the opposite end of the cable with the steering column lock mechanism, the spring is normally compressed sufficiently for a projecting member coupled to the piston to drivingly engage a recess on the switch for rotatably coupling the cable to the switch, but, should the connection of the cable with the steering column lock be broken, the spring acts to separate said projecting member from the switch and thereby break the rotary coupling between the cable and switch.

6. An anti-theft device as claimed in claim 5, wherein the housing contains a spring loaded detent which normally has no effect on the rotary coupling between the cable and the switch bolt which, upon the spring being able to displace the piston sufficient to break said rotary coupling, engages a recess in the piston to prevent the piston from being returned and thereby permanently to prevent the rotary coupling from being re-established in the absence of access to the housing.

7. An anti-theft device as claimed in any of claims 2 to 6, wherein the housing contains a recess for receiving the electrical switch and a locking means for retaining the switch rigidly within that recess.

8. An anti-theft device substantially as hereinbefore described with reference to and as illustrated in Figs.1 and 2 of the accompanying drawings.