GB2118653A

GB2118653A - Vehicle immobilisation device

Info

Publication number: GB2118653A
Application number: GB08307605A
Authority: GB
Inventors: Mark Alexander Canini
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-03-19
Filing date: 1983-03-18
Publication date: 1983-11-02
Also published as: GB8307605D0

Abstract

A device for immobilising a vehicle comprises a valve mounted in a valve casing (6) having an inlet port (7) adapted to be connected to the master cylinder (1) and an outlet port (8) adapted to be connected to the brake cylinders (3) of a vehicle braking circuit by fluid lines (2). The valve casing (6) also contains means for moving the valve between an operative position in which it prevents the flow of hydraulic fluid between the brake master cylinder (1) and the wheel brake cylinders (3) and an inoperative position in which it permits normal operation of the brakes. A logic circuit module (5) is mounted on the valve casing (6) and an electronic combination lock (4) is connected to the logic circuit module (5). The arrangement is such that, once the valve has been moved to the operative position, the brakes of the vehicle can be locked on and can only be released by depressing pre- selected keys on the electronic lock (4) in a pre-programmed sequence which is effective to activate the valve moving means for allowing the valve to be moved to a position in which it is inoperative. <IMAGE>

Description

SPECIFICATION Vehicle immobilisation device This invention relates to improvements in devices for immobilising vehicles for the purpose of preventing theft of the same.

According to the invention, there is provided a device for immobilising a vehicle comprising a valve adapted to be fitted in the hydraulic braking circuit of a vehicle and means for moving the valve between an operative position in which it prevents the flow of hydraulic fluid between the brake master cylinder and the wheel brake cylinders of the vehicle and an inoperative position in which it permits normal operation of the brakes of said vehicle, said valve moving means only being operable upon actuation by key means.

Preferably, the arrangement is such that when the valve is in its operative position and the brake pedal is depressed to apply the brakes of the vehicle, the valve is effective to allow the brakes to be applied and then ensures that the brakes remain applied, said valve being maintained in this position until the valve moving means are actuated by the key means to move the valve to its inoperative position when the brakes may be released.

The device according to the invention thus ensures that a vehicle fitted with the device cannot be driven away unless the valve moving means are first actuated by the key means because all of the brakes of the vehicle are applied.

The key means preferably take the form of a combination for a combination lock whereby the valve moving means can be locked until released by the correct combination. The combination lock may take the form of an electronic key pad having a plurality of keys and connected to an electronic logic circuit whereby the logic circuit only receives an impulse from the key pad when a predetermined number of the keys are operated in a predetermined sequence. The keys preferably take the form of touch-sensitive contact or sensor switches and ten keys are desirably provided. The logic circuit is arranged to operate the valve moving means when the keys are operated in the correct pre-programmed sequence. This sequence can be varied for each logic circuit so that the combination for each device according to the invention is unique and is known only to the owner.

The valve is desirably incorporated in a valve casing to which fluid lines in a vehicle braking circuit are connected and the valve moving means and logic circuit are desirably also incorporated in the valve casing or mounted thereon, e.g. by bonding, whereby the device cannot be interfered with and the valve can only be operated by the correct pre-programmed sequence of keys on the key pad.

The valve moving means may comprise an electric motor arranged to move a shaft which in turn is operatively connected to a valve member of the valve. The drive shaft of the motor may be fitted with a worm engageable with a gear wheel which is arranged to drive said shaft. The drive to the shaft from the gear wheel may be achieved by providing the wheel with a screw-threaded bore with which a screw-thread on the shaft is engaged. In this case, means are provided for preventing rotation of the shaft whereby rotation of the gear wheel will cause the shaft to be moved axially.

Alternatively, the gear wheel may be arranged to drive a cam shaft carrying a cam which is engaged by the said shaft for moving the valve member.

As a further alternative, the valve moving means may comprise a solenoid arranged to act on an armature in the form of-a shaft which in turn is arranged to operate a valve member of the valve.

A spring, for example a coil spring, may be provided between the shaft and the valve member.

The invention will now be further described, by way of example, with reference to the drawings, in which: Fig. 1 is a diagrammatic representation of one embodiment of a device according to the invention fitted in a vehicle hydraulic braking circuit; Fig. 2 is a section through one embodiment of a valve casing forming part of a device according to the invention taken on the line Il-Il in Fig. 3; Fig. 3 is a section through the valve casing shown in Fig. 2 but taken on the section line Ill-Ill in Fig. 4; Fig. 4 is a section taken on the line IV-lV in Fig. 2 but showing the valve casing fitted with a valve and valve operating mechanism; Fig. 5 is a part-sectional elevation of parts of the valve operating mechanism shown in Fig. 4;; Fig. 6 is a plan view of a second embodiment of a valve casing forming part of a device according to the invention; Fig. 7 is a section taken along the line VIl-VIl in Fig. 6 with parts of the valve operating mechanism omitted to show the bores in the casing; Fig. 8 is a section taken along the line Vill-Vill in Fig. 7; and Fig. 9 is a part-cutaway perspective view of the valve casing shown in Figs. 6 to 8.

In the drawings, like parts are denoted by like reference numerals.

Reference will first be made to Fig. 1 of the drawings in which a device according to the invention is fitted in the brake fluid line 2 between the master cylinder 1 and the brake cylinders 3 of a vehicle braking circuit. The device includes an electronic key pad or board 4 which is electrically connected to a logic circuit module 5 mounted on a valve casing 6. The valve casing 6 is provided with inlet and outlet ports 7 and 8 to which the fluid line 2 is connected.

Turning now to Figs. 2 and 3 of the drawings, the ports 7 and 8 lead to a bore 9 in the casing 6 at the inner end of which bore a valve seat 11 is provided. The outer end of the bore 9 opens out into a larger bore 1 2. A further bore 1 3 is provided in the casing 6 the axis of which extends at right angles to the axis of the bores 9 and 12 and a smaller bore 14 leads co-axially from the inner end of the bore 1 3. The bores 12 and 14 are so located in the casing 6 that their walls intersect as shown in Fig. 3. The valve and valve operating mechanism have been omitted from Figs. 2 and 3 of the drawings in order that the bores in the valve casing 6 may be seen more clearly.

As shown in Fig. 4, mounted in the bore 9 is a valve member 1 5 provided with an O-ring 1 6 to prevent hydraulic brake fluid from seeping past the valve member. One end of the valve member is adapted to seat on the valve seat 11 and the other end of the valve member is engaged by one end of a coil spring 17. The other end of the spring 1 7 bears against a screw-threaded shaft 1 8 which is also mounted in the bore 9 but which extends into the bore 12. A gear wheel 21 having a screwthreaded bore 22 which is engaged with the screw-thread on the shaft 1 8 is located in the bore 12 at the inner end thereof and a sleeve or slug 23 of plastics material is inserted in the bore 12 and secured therein to prevent axial movement of the gear wheel 21 with respect to the shaft 18.

Washers or shims 20 preferably of nylon material are provided on the shaft 1 8 on either side of the gear wheel 21.

As shown more particularly in Fig. 5, the sleeve or slug 23 is provided with a bore 24 having a rib or projection 25 which constitutes a key and the shaft 18 is insertable into the bore 24 and is provided with a keyway 1 9 adapted to receive the key 25. The shaft 1 8 is therefore prevented by the key from rotating and is capable of only axial movement. Electric sensors 26 and 27 are also provided in the bore 24 and lead through the material of the sleeve or slug 23 to outside contacts 28 and 29 provided at the end of said sleeve or slug. The sleeve or slug can be retained in the bore 12 by means of a circlip or like device 31 which is engageable in a groove 32 provided in the wall of the bore 12. The sensors 26 and 27 may take any suitable form but micro-switches are preferred.

The gear wheel 21 is arranged to be engaged by a worm 33 which is located in the bore 1 4 and is mounted on the drive shaft of an electric motor 34 mounted in the bore 1 3. The motor is retained in the bore 1 3 by means of a circlip or like device 35 which is engageable in a groove 36 provided in the wall of the bore 13.

Having assembled the components of the valve mechanism in the valve casing 6 in the manner shown in Fig. 4, the logic circuit module 5 is mounted on the valve casing 6 and contact is made to the contacts 28 and 29 as well as to the electric motor 34. The logic circuit module 5 and valve casing 6 are bonded together, for example by means of an epoxy resin, to leave no electrical connections exposed other than the leads to the keyboard 4. If desired, the whole of the logic circuit module 5 and valve casing 6 may be encapsulated in an epoxy resin or like material leaving only the inlet port 7 and the outlet port 8 exposed.

The keyboard contains an "arm" button which, when depressed, arms the device. Thus, when it is desired to immobilise a vehicle fitted with a device according to the invention, the "arm" button on the keyboard is depressed which is effective to transmit a signal to the logic circuit 5 which in turn is effective to activate the electric motor 34 to drive the worm 33. Rotation of the worm 33 causes the inter-engaging gear wheel 21 to rotate and thus the shaft 18, which is prevented from rotation by the key 25, is caused to move in an axial direction towards the right as viewed in Fig.

4. The end of the shaft 1 8 thus bears on the spring 1 7 which in turn acts on the valve member 1 5 to force it against the valve seat 11. This is the position indicated in Fig. 4 of the drawings. During this axial movement of the shaft 1 8, its unthreaded end provided with the keyway 1 9 is in contact with the sensor 26. However, when the shaft 1 8 is moved out of contact with the sensor, a signal is sent to the logic circuit 5 to stop the motor 34. Rotation of the worm 33 and gear wheel 21 is thus stopped and hence the axial movement of the shaft 18 is stopped.If the brake pedal of the vehicle fitted with the device is now depressed, the pressure of brake fluid from the master cylinder 1 at the inlet port 7 will be sufficient to force the valve member 1 5 off the valve seat 11 to permit the brake fluid to flow out of the valve casing 6 from the output port 8 and flow to the brake cylinders 3. However, once the pressure in the ports 7 and 8 has been equalized, the force of the spring 1 7 will then be sufficient to force the valve member 1 5 against the valve seat 11 to close the valve. The force tending to close the valve will then be greater than the force applied from the master cylinder to open the valve by the force of the spring 1 7 so that the valve will remain closed and the brakes of the vehicle will remain applied.It is thus impossible to drive the vehicle until the valve is opened and the device thus prevents theft of the vehicle.

The logic circuit 5 holds a preset combination in its memory and only when this number is keyed in will it disarm the valve to permit the vehicle to be driven away. Thus the valve can only be disarmed by punching the keys on the keyboard 4 in the correct sequence for the combination held in the memory of the logic circuit. This sequence will normally be known only to the owner of the vehicle.

Once the correct combination of keys on the keyboard 4 is depressed or touched in the correct sequence, the logic circuit 5 is effective to activate the electric motor 34 to drive the worm 33 in the reverse direction. This causes the gear wheel 21 to be driven in the reverse direction which causes the shaft 1 8 to be moved axially towards the left as viewed in Fig. 4 of the drawings. This axial movement of the shaft 1 8 continues until the end of the shaft makes contact with the sensor 27 which is effective to stop the motor 34. The force of the spring 1 7 on the valve member 1 5 is now largely removed so that if the brake pedal of the vehicle is now depressed, the valve member 1 5 will be forced by the pressure of hydraulic brake fluid from the master cylinder 1 off the valve seat 11 to open the valve.The brake pedal can then be released which will allow the brakes to come off since the valve is open and the pressure prevailing in the brake system will still be greater than the force of the spring 1 7 now acting on the valve member 1 5 so that the valve will remain in the open position allowing normal operation of the vehicle brakes. The vehicle can therefore now be driven away.

In the embodiment shown in Figs. 6 to 9 of the drawings, the screw-threaded shaft 1 8 is replaced by a plain shaft in the form of a cam follower 41 which is reciprocally mounted in the bore 9. Seals in the form of O-rings 42 are provided to prevent hydraulic fluid from seeping past the cam follower 41. The larger bore 12 is omitted in this embodiment and, instead, the bore 9 intersects a bore 43 the axis of which is perpendicular to the axis of the bore 9. A cam shaft 44 is mounted for rotation in the bore 43 and carries a cam 45 and a worm wheel 46. The surface of the cam 45 is arranged to be engaged by one end of the cam follower 41, the other end of said cam follower being acted on by the spring 1 7 to urge the cam follower against the cam.The worm wheel 46 is engaged by a worm 47 provided on one end of a shaft 48 which is located in a bore 51 in the casing 6. The axis of the bore 51 is perpendicular to the axes of the bores 9 and 43. The other end of the shaft 48 carries a gear wheel 49 which is arranged to be driven by an electric motor 34 via a worm 33 in like manner to the previous embodiment. The shaft 48, gear wheel 49 and worm 47 have been omitted in Figs. 7 and 8 in order to show that the bore 51 leads from a larger bore 52 which houses the gear wheel 49 and which is closed by a bung 53 (Fig. 9).

Further, in the embodiment shown in Figs. 6 to 9, the sleeve or slug 23 and the sensors 26 and 27 are dispensed with and, instead, the cam shaft 44 projects from the casing 6 and is provided with a lobe or the like (not shown) which is arranged to co-operate with one or more micro-switches (not shown) which are incorporated in the logic circuit module 5. Once the components of the valve mechanism have been assembled in the valve casing 6 in the manner shown in Fig. 9, the logic circuit module 5 is mounted on the valve casing 6 with the projecting end of the cam shaft 44 extending into the module 5. The module 5 and casing 6 are then bonded together as before by epoxy resin, for example, to leave no electrical connections exposed other than the leads to the keyboard 4.

This embodiment can be rendered operative by depressing the "arm" button on the keyboard 4 as before which is effective to activate the electric motor 34 to drive the worm 33. Rotation of the worm 33 causes the inter-engaging gear wheel 49 to rotate which in turn rotates the shaft 48 and worm 47. The worm 47 thus causes the worm wheel 46 to rotate and hence the cam shaft 44 and cam 45 are rotated. The cam 45 causes the cam follower 41 to move axially to the right as viewed in Fig. 7 and thus increases the compression of the spring 1 7 which increases the spring force on the valve member 1 5 forcing said valve member against the valve seat 11. When the cam shaft 44 has been rotated by.a certain predetermined amount, a sensor or micro-switch in the logic circuit 5 is actuated by the lobe on the end of the cam shaft to stop the motor 34.The device is now armed and operates in exactly the same manner as that above described with reference to Figs. 2 to 5 of the drawings.

When this device is to be rendered inoperative, the correct combination of keys on the key pad 4 should be depressed or touched in the correct sequence in order to cause the logic circuit 5 to activate the electric motor 34. The motor can in this case drive the worm 33 in the same direction as before in order to drive the cam shaft 44 in the same direction. The cam 45 is so mounted on the cam shaft that further rotation of said shaft will permit the cam follower 41 to be moved axially to the left as viewed in Fig. 7, under the action of the spring 1 7, to follow the surface of the cam 45. As a result, the force of the spring 1 7 on the valve member 1 5 is reduced so that the valve can open and the braking system of the vehicle can be operated normally as in the previously-described embodiment.Again, the motor 34 is stopped after the cam shaft 44 has been rotated by a certain predetermined amount, by actuation of a sensor or micro-switch in the logic circuit 5 by the lobe on the end of said cam shaft.

Preferably, the arrangement is such that the cam shaft 44 is rotated through 1 80C each time the motor 34 is activated. The cam 45 can then be arranged so that the cam follower 41 is moved to the right in Fig. 7 by a maximum amount when the device is to be rendered operative and is moved to the left by the same maximum amount when the device is to be rendered inoperative. The reduction gearing achieved by the worms 33 and 47 and gear wheels 48 and 46 ensures that only limited rotation of the cam shaft 44 takes place when the motor 34 is running.

This arrangement has an advantage over the previous embodiment in that, since the motor always rotates in the same direction, the need for a complicated reversing arrangement in the logic circuit module 5 is avoided.

Various safeguards may be built into the electronic circuit to prevent unauthorised use and/or theft of a vehicle fitted with the device according to the invention and to prevent unintentional arming of the device when the vehicle is being driven. For example, the logic circuit may be so programmed that if, say, three incorrect combinations are touched on the key pad, the system is locked and cannot be operated for a period of, say, one hour. This would ensure that the device cannot be disarmed by a person who does not know the correct combination. In order to prevent unintentional arming of the device when the vehicle is being driven the logic circuit is preferably provided with a sensory pickup connected to the generator/ignition lamp so that the logic circuit is activated only when the ignition is switched on and the engine is not running.

Since the logic circuit module 5 is bonded to the valve casing 6, there is no exposed wiring which could be used to disarm the device. If the valve casing is damaged by a potential thief, leaks from the hydraulic brake system will arise thereby rendering the brakes useless. The inlet and outlet ports 7 and 8 should desirably be provided with fittings for connecting the brake fluid line 2 which are incompatible with existing fittings on braking systems so that removal of the valve casing from the hydraulic brake system is not possible without the use of special tools and requires new parts and a lot of time.

The device according to the invention is however easy to fit and the electronic circuit is tamper proof and extremely reliable in operation.

It should be noted that the invention is not restricted to the above described embodiment but modifications and variations may be made without departing from the scope of the invention. For example, the key pad is not restricted to have ten keys but any number of keys may be provided.

Claims

1. A device for immobilising a vehicle comprising a valve adapted to be fitted in the hydraulic braking circuit of a vehicle and means for moving the valve between an operative position in which it prevents the flow of hydraulic fluid between the brake master cylinder and the wheel brake cylinders of the vehicle and an inoperative position in which it permits normal operation of the brakes of said vehicle, said valve means only being operable upon actuation by key means.

2. A device according to claim 1 , wherein the valve is arranged, when in the operative position, to allow the flow of hydraulic fluid in one direction to allow the vehicle brakes to be applied and being effective to prevent the flow of hydraulic fluid in the opposite direction in order to prevent the brakes from being released.

3. A device according to claim 1 or claim 2, wherein the key means take the form of a combination lock whereby the valve moving means can be locked until released by the correct combination.

4. A device according to claim 3, wherein the combination lock takes the form of an electronic key pad having a plurality of keys connected to an electronic logic circuit module which is arranged to activate the valve moving means to move the valve to the inoperative position only when selected keys are operated in a correct-preprogrammed sequence.

5. A device according to claim 4, wherein the keys take the form of touch-sensitive contact or sensor switches.

6. A device according to claim 4 or claim 5, wherein ten keys are provided on the key pad.

7. A device according to any one of claims 4 to 6, wherein the valve is incorporated in a valve casing having inlet and outlet ports adapted to be connected to fluid lines in a vehicle braking circuit and wherein the valve moving means and logic circuit module are incorporated in the casing or mounted thereon.

8. A device according to claim 7, wherein the valve moving means are incorporated in the valve casing and the logic circuit module is bonded to said casing.

9. A device according to claim 8, wherein the valve casing and logic circuit module are encapsulated in an epoxy resin or like material to leave only the inlet and outlet ports and leads to the key pad exposed.

10. A device according to any one of claims 7 to 9, wherein the valve moving means comprise an electric motor arranged to move a shaft which in turn is operatively connected to a valve member of the valve.

11. A device according to claim 10, wherein the motor has a drive shaft fitted with a worm which is engageable with a gear wheel arranged to move said shaft.

12. A device according to claim 11, wherein the gear wheel is provided with a screw-threaded bore and wherein the shaft is provided with a screw-thread engageable with the said screwthreaded bore, means being provided to prevent rotation of the shaft whereby rotation of the gear wheel will cause the shaft to move axially.

13. A device according to claim 12, wherein the shaft rotation preventing means comprise a key located in a bore in the casing in which said shaft is axially movable, said shaft being provided with a keyway which is engageable with the key.

14. A device according to any one of claims 10 to 13, wherein the shaft is arranged to actuate sensors in each of its end positions to stop the motor.

1 5. A device according to claim 14, wherein the sensors take the form of micro-switches connected to the logic circuit module.

16. A device according to claim 11, wherein the gear wheel is arranged to drive a cam shaft carrying a cam which is engaged by the said shaft for moving the valve member.

1 7. A device according to claim 16, wherein the gear wheel is arranged to drive the cam shaft via a further shaft on which the gear wheel is mounted, a second worm mounted on said further shaft and a second gear wheel mounted on the cam shaft, the second worm being engaged with the second gear wheel.

1 8. A device according to claim 1 6 or claim 17, wherein the cam shaft carries a lobe which is arranged to actuate sensors or contact switches to stop the motor when the cam shaft has been rotated by a predetermined amount.

1 9. A device according to any one of claims 7 to 9, wherein the valve moving means comprise a solenoid arranged to act on an armature in the form of a shaft which is arranged to operate a valve member of the valve.

20. A device according to any one of claims 10 to 19, wherein the shaft is arranged to act on the valve member via a coil spring.

21. A device according to claim 20, wherein the valve member is mounted in a bore in the valve casing and is urged by the spring against a valve seat provided at the inlet port leading into the casing.

22. A device according to claim 21, wherein the outlet port leads from the bore in which said valve member is located.

23. A device for immobilising a vehicle substantially as described herein with reference to the drawings.