Theft of motor cars and other vehicles is a growing problem. Thefts are usually performed by short-circuiting of the ignition system.

It is a purpose of the present invention to describe a procedure for protection against theft of vehicles, which ensures that in practice it is impossible to steal them.

This is achieved by the procedure described in the characterising part of claim 1.

The invention also relates to a barring device for the implementation of the procedure according to the invention.

Such a barring device is described in claim 2.

Claim 3 relates to another kind of barring device according to the invention, and claim 4 relates to a third kind of barring device according to the invention.

The invention is described in detail below with reference to the drawing in which fig. 1 is a schematic illustration of a brake circuit, which consists of a main cylinder and a brake cylinder, which is in its unloaded position and in which a barring device according to the invention is coupled between the main cylinder and the brake cylinder. fig. 2 is an illustration corresponding to the one shown in fig. 1, in which the brake cylinder in its braking position. fig. 3 is an illustration corresponding to the one shown in fig. 1, in which the brake cylinder is in its braking position, and in which is coupled another embodiment of a barring device according to the invention,

fig. 4 is an illustration corresponding to the one shown in fig. 3 in which is coupled a third kind of barring device according to the invention, fig. 5 is a perspective view of a braking system for a road wheel with a barring device according to the invention embodied as a valve box, fig. 6 is a section through a barring device according to the invention which is embodied as a valve box, fig. 7 is a perspective view of a servo system for a car, fig. 8 is a perspective view of a hydraulic braking system for a car, fig. 9 is a schematic view of pneumatic/hydraulic braking system for a car, fig. 10 is a schematic view of a pneumatic braking system for a lorry, and fig. 11 is a schematic view of a pneumatic braking system for a trailer.

As shown in fig. 1 a braking circuit consists in principle of a main cylinder 1, which is activated by a brake pedal 2. Hereby a brake fluid is forced into a brake cylinder 3 on the upper side of a piston 4, which is then forced downwards against the spring pressure from a spring 5 to the position shown in fig. 2. The piston 4 is connected to a piston rod 6, and the brake cylinder 3 and the piston rod 6 are, as shown in fig. 8, coupled each to its own brake arm 7,8 with a brake block 9, which can come to rest against the inside of brake drum 10 in a so-called drum brake. The brake can also be embodied as a disk brake.

The brake described here is a hydraulic brake. There are other types of brake, such as hydraulic brakes with vacuum enhancement, and pneumatic brakes in which the brake cylinder is embodied as a brake diaphragm, but in principle they all function in the way that they cause a braking effect, when a brake medium is admitted to the brake cylinder/diaphragm. When the pressure on the brake pedal 2 is released the spring 5 will force the piston upward, and the brake is released.

According to one embodiment of the invention there is between a main cylinder 1 and a brake cylinder 3 installed a barring device 11 with an electronic control

box 12 with a relay, which is coupled to the vehicle's power supply and which can be activated by a signal from a control box 13, which can be keyed with a code.

The barring device 11 can, as shown in figs. 1 and 2, consist of a solenoid valve 14 and a parallel-coupled non-return valve 15, which permits a flow of brake fluid from the main cylinder 1 in the direction towards the brake cylinder 3, but not in the opposite direction. When a vehicle is left and the solenoid valve is closed a subsequent activation of the brake pedal 2 will cause a flow of brake fluid through the non-return valve 15 with the result that the brake is activated and can be released only when the code is keyed on the control box 13.

As shown in fig. 3 the barring device 11 can also consist of a solenoid valve 14. Before the vehicle is left, the brake pedal 2 is pressed and the solenoid valve 14 is closed, whereby the brake on one or more road wheels is activated and can be released only when the code is keyed on the control box 13.

As shown in fig. 4 the barring device 11 can also be embodied as a solenoid 16, which is mounted on a brake cylinder 3 on the spring side of the piston 4.

The solenoid is embodied with an electronic control box 12 with a relay, which is coupled to the vehicle's power supply and can be activated by a signal from a control box 13, which can be keyed with a code. When the solenoid is live with power the brake is activated. When the power to the solenoid is cut by means of a remote control from a control box 13, then the brake is released.

Fig. 7 shows a servo steering system for a car. If a barring device 11 is installed in a pipe for hydraulic fluid to or from a hydraulic pump 16 the steering system can be barred and theft thereby prevented.

Fig. 8 shows a hydraulic brake system for a car. If a barring device 11 is built in as shown, the brakes on both rear wheels can be barred.

Fig. 9 shows a pneumatic-hydraulic braking system for a car. The compressed air is supplied from a compressor 17 via compressed-air receiver 18 to brake valves 19, which exerts an influence on the pressure to compressed-air cylinders 20, which in turn has an influence on the pressure in each individual brake cylinder 21. If a barring device 11 is built in between a brake valve 19, which is activated by a foot pedal 2, and a compressed-air cylinder 20, the belonging brake can be barred.

Figs. 10 and 11 show a pneumatic braking system for a lorry and a trailer, respectively. The braking system on the trailer is coupled to the braking system on the lorry through a hose connection 17. Compressed air is sent into the trailer's braking system through a change-over valve 22 to a compressed-air receiver 23. If, as shown in fig. 9, a barring device 11 is inserted between a brake valve 19 and a brake diaphragm 24 and, as shown in fig. 10, a barring device is inserted between the compressed-air receiver 23 and the brake diaphragms 24, the brakes on the lorry as well as those on the trailer are barred.

The shown and described barring device serves only to illustrate the invention.

Within the scope of the invention it is possible to imagine various modifications.

For example, the barring device might be activated by a key or over a satellite.