The present invention relates to anti-theft devices for motor vehicles.

BACKGROUND OF THE INVENTION

Disclosed in U.S. Patent 3,871,475 is a mechanism to prevent the theft of motor vehicles. The security system includes a manually operable valve for controlling application of fluid under pressure to the braking assemblies to manually set the vehicle brakes. The valve is arranged with a mechanical key-operated lock for controlling and locking the valve in a selected position. When the brake is in the "locked" position, it allows the brakes to be set and the vehicle in situ to prevent the unauthorised movement thereof. The brake assemblies are also secured and locked to prevent the manual operation thereof by means of a conventional lock out tool. This particular mechanism requires the inclusion in the braking system of additional valving which is relatively expensive both in respect of the cost of parts and the cost of installation.

In U.S. Specification 3,669,219 there is described an automobile safety device to prevent the theft of the automotive vehicle. There is firstly provided a brake mechanism which is de-activated by the ignition switch of the vehicle and maintains the brake mechanism engaged when the ignition is off. This particular device requires a vacuum operated diaphram for which there extends a plunger to engage the master cylinder. This device does not meet its object of being inexpensive and simple to install .

An anti-theft device which act directly on the parking brake of a vehicle is described in U.S. Patent 3,552,518. A catch engages the parking brake to retain the parking brake in the on position. A key operated vacuum switch releases the catch so that the parking brake may be released. This particular device is not effective since the catch is vulnerable and may easily be released.

U.S. Patent 3,470,974 describes an anti-theft device for a motor vehicle, which operates to set the brakes in response to movement of the vehicle when the device is operative. This device is generally complex requiring gears and solenoids and accordingly is costly and would be prone to failure.

In U.S. Patent 1,972,300 there is shown an electrically operated device which retains the brake pedal in the depressed position. More

particularly, the device includes a solenoid which moves a catch between an inoperative position allowing normal use of the brakes, and a position engaging a brake shaft to prevent its movement from a position applying the vehicle brakes. This device, although relatively simple, is easily rendered inoperative by gaining access to the wiring of the device. Also, the device is prone to failure since the catch may not always be retained in the retracted position allowing normal operation of the brake.

U.S. Patent 4,076,095 discloses an arrangement which physically prevents movement of the brake and/or clutch pedal of a vehicle, by securing them to a pair of posts fixed to the vehicle floor. This particular device is difficult to use since the user must bend and uncouple the device from the pedals.

A vehicle anti-theft device is also shown in U.S. Patent 4,196,930, which device is installed in the brake line of the vehicle. More particularly, a valve is actuated after the brake pedal is depressed, to retain the pressure in the slave cylinders of the brake system. This device is relatively expensive to manufacture and requires an interruption in the normal brake hydraulic system of the vehicle.

U.S. Patent 4,258,819 describes a device which ensures the brakes of a vehicle are applied when the engine is turned off. This particular system is rendered inoperative if the ignition switch is tampered with. Accordingly, it does not act as an effective anti-theft device.

U.S. Patent 4,432,432 describes a device which extends between the vehicle steering wheel and the brake pedal to prevent movement of the brake pedal. More particularly, the device is an adapted car jack which is activated to push the pedal to the depressed position to thereby engage the brakes. This particular device is relatively complex and is difficult to use.

A still further anti-theft device is disclosed in U.S. Patent 4,471,852. This particular device includes an electrically operated ratchet and pawl mechanism to retain the brake pedal in the depressed position. This device is relatively complex and expensive to manufacture. Still further, it is prone to tampering since the electric wiring is accessible.

A device to disable various functions of the braking system of the vehicle is shown in U.S. Patent 4,777,377. The device is solenoid operated

and accordingly suffers the disadvantages of the previously discussed devices in that the electric wiring is prone to tampering.

A hydraulic lock-up anti-theft system for a vehicle brake mechanism is described in U.S. Patent 4,546,846. This device interposes a valve in the braking system, which valve retains the pressure in the slave cylinder. The valve is operated by a cable. This particular device is relatively complex due to the construction of the valve and requires the hydraulic system to be interrupted.

The above discussed anti-theft devices either Interrupt the hydraulic system of the vehicle or rely on electric components to activate the anti-theft aspect of the device.

Shown in Australian Patent Specification 78390/87 is a lock mechanism in the door of a vehicle. The lock mechanism includes an air operated plunger which moves attach member into engagement with a striker plate. There is no consideration in this specification given to adapting this device to opt as an anti-theft mechanism associated with the brakes of a vehicle.

OBJECT OF THE INVENTION

It is the object of the present invention to overcome or substantially ameliorate the above disadvantages.

BRIEF DESCRIPTION OF THE INVENTION

There is disclosed herein an anti-theft device for an automotive vehicle having a fluid operated braking system, said assembly including: a brake pedal operatively associated with said braking system to activate the system by being moved from a raised position to a depressed position; a hollow body to be fixed relative to said pedal so as to be adjacent the pedal when in said depressed position, said body providing a cylindrical chamber into which the air under pressure is delivered; a movable wall closing said chamber and movable relative to said body upon the application of air under pressure to said chamber; a pin projecting from said wall a movable therewith from a retracted position to an extended position, with said king pin being located to be clear of the path of movement of the pedal when said pin is in said retracted position, while engaging said pedal to prevent movement thereof when in said extended position, to prevent movement of said pedal to its raised position.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figure 1 is a schematic diagram of an anti-theft device for a motor vehicle; and

Figure 2 is a schematic diagram of a further anti-theft device to that shown in Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In Figure 1 there 1s schematically depicted an anti-theft device 10 for a motor vehicle. The motor vehicle includes a brake pedal 12, including a pivotted lever 11 terminating with a foot pad 13. The lever 11 pivots about the axis 14. The pedal 12 is depressed in order to cause braking of the vehicle.

The device 10 includes an air operated cylinder 15 including a piston rod 16 movable between an extended position and a retracted position. Two conduits 17 and 18 deliver air under pressure to different sides of a piston in order to cause movement of the pin 16 attached thereto. The conduits 17 and 18 extend to a key operated valve assembly 19, which receives air under pressure from a reservoir 21 via a conduit 20.

As described above, the pin 16 is movable between an extended position and a retracted position. In the extended position, the pin 16 passes through a slot 22 in the lever 16 and engages a support 23 to retain the pedal 12 in a depressed braking position. In the retracted position of the pin 16, the pedal 12 is free for pivotting movement.

When the brake pedal 12 is retained in its depressed position, the brakes of the vehicle are applied and therefore theft of the vehicle is inhibited.

In Figure 2 of the accompanying drawings there is schematically depicted an anti-theft device 30 for a motor vehicle. The motor vehicle has a brake pedal 31 including a pivotted lever 32 which pivots about an axis 33. The lever 32 terminates at its end with a foot pad 34.

The device 30 includes an interacting piston 35 and cylinder 36, with a pin 37 extending from the piston 35.

A pair of conduits 38 and 39 deliver air under pressure to either

side of the piston 35 in order to cause movement of the pin 37 between a retracted position and an extended position.

The conduits 38 and 39 extend to a key operated valve 40 which receives air under pressure from a conduit 41. The conduit 41 extends to a reservoir of air under pressure, such as the spare tyre of the vehicle.

The pins 37 in the extended position extends across the lever 32 in order to retain the brake pedal 31 in a depressed braking position. In the extended position of the pin 37, the pin 37 is engaged in a support member 42.

In this retracted position, the pin 37 permits movement of the pedal 31.