WO1989001885A1

WO1989001885A1 - Theft prevention device

Info

Publication number: WO1989001885A1
Application number: PCT/AU1988/000341
Authority: WO
Inventors: Joseph Robin Orbell
Original assignee: Baldwin Holdings Pty Ltd
Priority date: 1987-09-04
Filing date: 1988-09-05
Publication date: 1989-03-09
Also published as: JPH03501237A

Abstract

A theft prevention device especially intended for use in apparatus which utilise hydraulic fluid to actuate a device such as a motor vehicle with hydraulic brake system. The device comprises a member (26) arranged to be moved between a first inoperative position and a second operative position under control of a key operated lock (16). The member (26) contains at least one groove (28) with a cam profile so that in the first position a one way valve (38, 40) is rendered non-operational and in the second portion the one way valve (38, 40) prevents reverse flow of fluid in an outlet conduit (32).

Description

TITLE THEFT PREVENTION DEVICE DESCRITPION The present invention relates to a theft prevention device. FIELD OF THE INVENTION

In particular, the present invention relates to a theft prevention device which is useful in apparatuses which utilise hydraulic fluid to actuate a device such as a motor vehicle with an hydraulic brake system. SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention there is provided a theft prevention device characterised by a body having an axially rotatable member mounted therein, a fluid inlet means for the body, and a fluid outlet means for the body, wherein the rotatable member provides a groove for communication between the fluid inlet means and the fluid outlet means, and one way valve means is mounted in the body in association with the rotatable member such that when the rotatable member is in a first position fluid can flow reversibly through the theft prevention device but when the rotatable member is in a second position fluid can only flow from the fluid inlet towards the fluid outlet but not in the reverse direction. In accordance with a further aspect of the present invention there is provided a theft prevention device characterised by a body having a moveable member arranged to be moved between first and second portions, a fluid inlet means for the body and a fluid outlet means for the body, wherein the moveable member provides a groove for communication between the fluid inlet means and the fluid outlet means, and a way valve means is mounted in the body in association with the groove, the groove having a profile of varying height relative to the moveable member so that in the first position of the moveable member the one way valve is rendered non-operational and in the second position of the moveable member the one way valve is rendered operational so as to prevent reverse flow of fluid in the fluid outlet means. BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a sectional, side view of a theft prevention device in accordance with the present invention;

Figure 2 is a first side elevation of a rotatable member of the device of Figure 1;

Figure 3 is an end elevation of the rotatable member of

Figure 2; Figure 4 is a second side elevation of the rotatable member of Figure 2 rotated through 90°;

Figure 5 is a schematic view to an enlarged scale of a one way valve of the device of Figure 1; .

Figure 6 is a view of a closure member of the valve of Figure 5; and

Figure 7 is a view similar to Figure 1 showing a further embodiment of the present invention.

DESCRIPTION OF THE INVENTION

In Figure 1 there is shown a theft prevention device 10 in accordance with the present invention which is particularly designed to be installed between a master cylinder and a pressure balance unit in a dual-circuit hydraulic braking system of a motor vehicle. However, it is to be understood that the present invention can be applied to other types of hydraulic braking systems of motor vehicles and, in more general terms, can be applied to many types of hydraulically operated devices such as rudders of boats, earth moving equipment or hydraulic clutches, as a theft prevention device.

The device 10 comprises an outer hollow body 12 which is open at one end and closed at the opposite end. The hollow outer body 12 contains a cylindrical recess. A rotatable member 14 is inserted in the cylindrical recess of the outer hollow body 12. The rotatable member 14 is mounted in such manner as to be axially rotatable in the hollow body 12. Further, at the open end of the cylindrical recess the rotatable member 14 is provided with a lock 16. The lock 16 is mounted in a sleeve 18 within the cylindrical recess adjacent the open end of the hollow body 12.

A pair of opposed threaded holes 20 from respective sides of the device 10 extend through the thickness of the outer body 12 and the sleeve 18. Each hole 20 contains a grub screw 22 which engages with a circumferential groove in the lock 16 so as to retain the lock 16 securely in place. The lock 16 is arranged to be actuated by a key 24 having a specific combination which is compatible with the lock 16. The lock 16 is fixed to and arranged to rotate with a generally cylindrical member 26 which forms part of the rotatable member 14. The cylindrical member 26 is arranged for operation with a dual circuit braking system and therefore has a pair of spaced circumferential grooves 28. However, the benefits of the present invention can be obtained with a single groove 28 where the braking system has only a single circuit.

Each groove 28 has a base which is shaped so as to have a cam profile. This can best be seen in Figures 2 to 4. Further, there is a respective hydraulic fluid inlet conduit 30 leading from a master cylinder (not shown) to each groove 28 but only one of the conduits 30 can be seen in Figure 1. Also, as can be seen in Figure 3 the cam profile of the grooves 28 are arranged to be 90° out of phase with one another.

Still further, each groove 28 has a respective hydraulic fluid outlet conduit 32 leading therefrom to a brake means although only one conduit 32 can be seen in Figure 1. The cylindrical member 26 is closely engaged within the cylindrical recess and is retained in place by the sleeve 18. Further, the circuit associated with each groove 28 is sealed from the other circuit and the exterior by means of "0" ring seals 34 mounted in respective channels 16. The outer body contains a pair of apertures 38 disposed at 90° to one another^•facing respective grooves 28. Each apertures 38 contains a respective valve plunger 40 which can be seen in more detail in Figures 5 and 6. Each valve plunger 40 comprises a head 42 and a shank 44 having a free end remote from the head 42. The shank 44 extends into the aperture 38 whilst the head 42 is provided with an "0" ring seal 46 on its underside. Each valve plunger 40 is spring urged by a coil spring 48 such that the free end of the shank 44 engages with the respective groove 28. The coil spring 48 is in engagement with a braking plug 49 mounted in the body 12 as can be seen in Figure 5.

The cylindrical member 26 is also provided with a tapered slot 50. The slot 50 is arranged to engage with a push rod 52 which is engaged with a microswitch 54. The microswitch 54 is arranged to be connected in series with a vehicle starter motor solenoid circuit so that it is not possible to start the engine with the theft prevention device 10 of the present invention in its locked position.

This arrangement is a safety measure so as to prevent inadvertent starting of the vehicle by a legitimate driver when the theft prevention device is in its locked position. The device 10 is shown in Figure 1 with the key 24 in the locked position. The key 24 can be rotated through 90° to rotate the. rotatable member 14 and thus the lock 16 and the cylindrical member 26 to the unlocked position. In the locked position the lower portions of the cam profiles of the grooves 28 are in engagement with the shanks 44 of the valve plungers 38. In this position the heads 42 being spring loaded are urged into sealing engagement with the body 12 around the apertures 38 by virtue of the seals 46. In this position, when a brake pedal of the vehicle containing the device 10 is depressed hydraulic fluid is fed along the conduits 30 into the grooves 28 where the valve plungers 40 are lifted by the pressure of the fluid such that the fluid flows into the conduits 32 leading to the brake means of the vehicle. However, if the brake pedal is then released back pressure from the wheel cylinders closes the plungers 40 and urges them firmly into sealing engagement with the body 12 around the apertures 38. Thus, release of the brake pedal fails to release the brakes and the vehicle is rendered undriveable.

If a legitimate driver wishes to drive the vehicle he simply uses the key 24 to rotate the lock 16 and the member 28 through 90° so that the high parts of the cam profiles of the grooves 28 are in engagement with the shanks 44. In this way, the heads 42 are lifted away from the apertures 38 and the hydraulic fluid can flow freely in. both directions and the starter solenoid circuit is closed. Thus, the brakes can be operated in normal manner. Further, the brakes are preferably able to be applied when the lock 16 and the member 26 are at any intermediate position between the locked and unlocked positions described above.

In Figure 7 like reference numerals denote like parts to those shown in Figures 1 to 6. The apparatus shown in Figure 7 is particularly envisaged for use with dual circuit diagonal brakes. As shown, the one way valves 38, 40 and their associate braking plugs are located at the shown angular portion in the body 12. Also, the outer seals 34 are i the form of cups rather than O rings .

Modifications and variations such as would be apparent to. a skilled addressee are deemed within the scope of the present invention. For example, the valve plunger 38 may contain an internal channel as shown in the drawings, which may relieve pressure when the valve is lifted by the arm.

Claims

1. A theft prevention device characterised by a body having an axially rotatable member mounted therein, a fluid inlet means for the body, and a fluid outlet means for the body, wherein the rotatable member provides a groove for communication between the fluid inlet means and the fluid outlet means, and one way valve means is mounted in the body in association with the rotatable member such that when the rotatable member is in a first position fluid can flow reversibly through the theft prevention device but when the rotatable member is in a second position fluid can only flow from the fluid inlet towards the fluid outlet but not in the reverse direction.

2. A theft prevention device according to claim 1, characterised in that the axially rotatable member comprises an axially rotatable cylindrical member operatively connected to a lock arranged to be actuated so as to rotate the cylindrical member.

3. A theft prevention device according to claim 2, characterised in that the cylindrical member contains at least one.circumferential grooves formed with a cam profile, the cam profile of the groove being arranged to cause operation of the one way valve means.depending on the position of the cylindrical member.

4. A theft prevention device according to claim 3, characterised in that the cylindrical member contains two or more of the circumferential grooves and each groove is associated with a respective one way valve.

5. A theft prevention device according to claim 3 or 4, characterised in that the or each groove is provided with a respective fluid inlet conduit and a respective fluid outlet conduit and the one way valve is located on the fluid outlet conduit.

6. A theft prevention device according to claim 5, characterised in that, where there is more than one groove, t he fluid circuit of each groove is sealed off from the fluid circuit of each other groove.

7. A theft prevention device according to any one of the claims 4 to 6, characterised in that the or each one way valve means comprises a plunger which is spring urged into engagement with a base of a respective groove such that where the cam profile is low, the plunger sealingly engages with the body to prevent reverse flow of fluid in the fluid outlet and where the cam profile is height, the plunger is raised so that fluid can flow reversibly .in the fluid outlet.

8. A theft prevention device according to any one of the preceding claims, characterised in that it is arranged to be installed between a master cylinder and an hydraulic brake means of a motor vehicle.

9. A theft prevention device characterised by a body having a moveable member arranged to be moved between first and second portions, a fluid inlet means for the body and a fluid outlet means for the body, wherein the moveable member provides a groove for communication between the fluid inlet means and the fluid outlet means, and a way valve means is mounted in the body in association with the groove, the groove having a profile of varying height relative to the moveable member so that in the first position of the moveable member the one way valve is rendered non-operational and in the second position of the moveable member the one way valve is rendered operational so as to prevent reverse flow of fluid in the fluid outlet means.