A BREAKAWAY BRAKING SYSTEM

The present invention relates to a braking system, whilst especially a safety braking conversion system for use on road/rail vehicles. For a number of years rail maintenance has been carried out in many countries using road vehicles that are capable of both driving on the road and on the rail system. This is achieved by the vehicle having rail wheels added to the road vehicle. A recent example of such a vehicle is the Land Rover ® Discovery ® which have been have been used on the British Railway network. When such vehicles are used on the railway they obviously have to conform to railway safety standards including the stationary braking of the vehicle such that a runaway of such a vehicle does not occur. Furthermore, when such a vehicle needs to be used to tow another road/rail vehicle back to back this problem is compounded as these vehicles are designed for braking on roads not on the rail system.

It is an aim of the present invention to provide a brake system for use on a road vehicle which overcomes these problems .

Accordingly a first aspect of the present invention is directed to a brake system for a road/rail vehicle in which a braking device is attached to the prop shaft of the vehicle. This provides the advantage that the brake system is connected to a readily accessible part of the vehicle. This provides the further advantage that an

entirely separate brake system is added to the vehicle which is independent of the normal braking system and the handbrake of the vehicle, thus providing added safety should either of there two systems fail. Furthermore, as it is attached to the prop shaft of the vehicle it has all the mechanical braking effects that run therefrom.

Advantageously the braking means is a disk brake. In a preferred embodiment the brake actuating means is a hand brake, fitted inside the rear of the vehicle cab. A second aspect of the present invention is directed to a vehicle brake system for a road/rail vehicle wherein the brake system is equipped with one or more actuating means, at least one of which can be automatically activated. Preferably the automatic actuating means comprises a spring actuator activated on the breaking of a coupling. This provides the advantage that if a road/rail vehicle is towing another road/rail vehicle should the towing vehicle break away from the towed vehicle the spring actuator will activate the braking system upon the runaway.

In a preferred embodiment the braking system is equipped with an additional brake actuating means comprising a handbrake in the rear part of the cab of the vehicle. Preferably the brake system includes a breakable link attached to the spring actuator. This provides the advantage that upon pulling away the breakable link actuates the spring whilst ensuring that the other

vehicle is not carried away by the runaway.

In a preferred embodiment the brake system is further equipped with a retained pin which secures the spring actuator and is pulled out by the breakable link. This ensures the simple construction for the spring actuator link. In a preferred embodiment a spring actuator comprises a spring inside a metal tube which is pre-tensioned by the retaining pin. This provides the advantage of very simple construction giving a powerful release of energy acting upon the braking system enabling a high level of actuation of braking to be exerted.

An example of a braking system embodying the present invention will now be described herein below with reference to the accompanying drawings, in which: Figure 1 shows a schematic diagram of a road/rail vehicle equipped with a braking system according to the present invention;

Figure 2 shows a cross-sectional view of a automatic braking means made in according to the present invention; and

Figure 3 shows a perspective view of a retaining pin for use in the present invention and its relation to the braking system shown in Figure 2.

Figure 1 shows the rear part of a road/rail vehicle 10. A rear axle 12 of the road/rail vehicle is shown equipped with a central differential 16 to which a prop shaft 18 of the vehicle 10 runs. The prop shaft 18 is equipped with a disk brake 20. The disk brake 20 is

connected to a brake cable 22. The brake cable 22 passes through an automatic braking system 24 to a cab handbrake 26. The cab handbrake 26 is mounted inside the rear part of the vehicle and can be readily actuated by a person using the vehicle. The vehicle is equipped with a tow hook or coupling on its rear which is not shown. The tow hook can be connected to a draw bar 28. The draw bar 28 is equipped with a breakable link 30 which is attached via a snap ring to two eye rings 32 at one end of an unsheathed cable 33. The other end of the unsheathed cable is attached to a forked retaining pin 34.

Figure 2 shows a detailed cross section of the automatic breaking means described in regard to Figure 1.

As shown in the drawing the brake cable 22 is attached at one end via eyelet 42 to the disk brake 20 and at the other end via the eyelet 44 to the handbrake 26. The brake cable 22 is split into two parts, the first part 22a runs from the eyelet 42 to the automatic braking means 24 and the second part 22b which runs from the eyelet 44 to the automatic braking means 22. The automatic braking means 22 comprises a housing 40 which has a circular internal cross section and contains a high tension spring 46. The spring 46 surrounds a moveable centre member 48 and braces against a shoulder 50 on the member 48. The moveable member 48 contains two circular holes 52 and 54 at either end. The hole 52 receives brake cable 22a from the disk brake 20 and is attached thereto by a bolt 56 that goes through an eye 58 in the

end of the brake cable 22a. Similarly the brake cable 22b enters hole 54 and is attached to the moveable member 48 via a bolt 50 which passes through eyelet 62 in the end of the brake cable 22b. The other end of the spring 46 is braced against a removable end part 64 of the automatic braking housing 40. The end part 64 screws into the end of the housing 40. At the opposite end to the end part 64 the housing 40 has a collar 66 which surrounds one end of the moveable member 48. The moveable member's cross section is increased by the shoulder 50 such that it matches the internal diameter of the housing 40. The moveable member 48 is held by the forked retaining pin 34 tensioning the spring 46 which is on the other side of the shoulder 50 to the spring 46. The forked retaining pin passing through both sides of the housing 40 in slots 49.

Figure 3 shows the forked retaining pin 34. The retaining pin has a base 72 and two prongs 70. The prongs 70 internally form a U-shape. The base 72 is attached to the unsheathed cable 33. The retaining pin 34 fits in the slots 49 such that the prongs 70 are on either side and abut the shoulder 50 of the moveable member 48.

As can be seen when the handbrake 26 is operated the brake cable 22 operates as a normal cable and moves backwards and forwards however when it acts automatically the pin 34 is pulled out and the pre tension spring 46 expands and pushes the moveable member 48 along inside

the housing 40 until it is stopped by the collar 66 thus engaging the brake.

If the vehicle is not braked or the brake fails or the vehicle breaks away from a coupled vehicle the draw bar 28 detaches and the breakable link 30 pulls on the eye rings 32 resulting in the pin 34 being pulled out and the spring 48 actuated. Obviously once the vehicles are a certain distance the breakable link 30 breaks thus ensuring that the vehicle does not become a runaway as well. The system works in an analogous way if the vehicle is being towed and the tow breaks .

Once the automatic breaking means have been engaged they can be reset using an appropriate tool acting on the spring.