RAIL GRIP BRAKING WHEEL

Abstract: A method and means for braking a vehicle relative to a stationary rail. A rolling wheel (2) attached to the vehicle and able to be lowered onto a stationary rail (1) to laterally grip the head of said rail (3). The friction between the wheel and the rail being such as to prevent slipping of the wheel on the rail while a braking force (6) is applied to the wheel to decelerate the vehicle.

Description: RAIL GRIP BRAKING WHEEL TECHNICAL FIELD The preferred invention relates to a braking system and more particularly but not exclusively to an emergency braking system for use with vehicles running on rails such as are employed in mines or other areas where there are major problems in braking. BACKGROUND ART Where railed vehicles are running on steep gradients and/or where the track or tracks may be wet or oily the use of band, block or pad brakes is most ineffective. Such conditions are typical in mining operations where water and dust (e.g. coal dust) and maybe oil or * grease is present on the track surface. A number of techniques have been developed but they have been found to be ineffective or rather expensive. One system provides for a skid type dump brake which contacts the rail surface when a car is dumped on the rail in an emergency braking operation. The braking materials developed for this type of dump brake have not proven to be up to the task even though this form of emergency braking is in common use. Another form of emergency braking system requires the use of a special rail which enable the emergency brake to grip an additional flanged extension and this is being developed during trials at the British National Coal Board's Ankwright Colliery near Chesterfield, Derbyshire (The Mining Engineer Vol. 141 No. 248 p.674). Such a system is extremely expensive in that it will require the fitment of special rails not to mention the brake actuating assembly itself. The present invention proposes a braking system which does not require the fitment of a special form of rail and which is adapted to operate in conjunction with existing rails. DISCLOSURE OF THE INVENTION The present invention consists in a braking system comprising a braked wheel adapted to provide a gripping contact laterally of the head of the rail. In one form the flanges of the braked wheel , are so inclined as to provide a pair of small contact points on opposite sides of the rail head whereby the friction between the wheel and the rail is sufficient to allow transmission of torque to the wheel and thus turn the wheel as the vehicle to which the wheel is attached advances along the rail. A braking force can then be applied to the wheel to decelerate the vehicle. Due to the friction between the rail head and the wheel, the wheel does not slip on the rail when braking force is applied to the wheel and thus the braked wheel is able to decelerate the vehicle. Advantages of the present invention will be core readily appreciated by the description in relation to the embodiment but it is contemplated that higher rail track gradients will be possible. Existing braking devices such as pad brakes which come into sliding contact with the top of a rail head have been restricted to use on approximately 1 in 3.5 gradients whereas the present invention may be suitable for gradients up to 1 in 2. The braking system of this invention is not effected by - wet or oily rails which nullify the braking effect of pad type brake. BRIEF DESCRIPTION OF DRAWINGS Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:— Fig. 1 is a sectional view through a rail showing the operation of a first embodiment in accordance with this invention; Fig. 2 is a sectional view through a rail showing the operation a second embodiment; and Fig. 3 is a side elevation of a rail supported vehicle incorporating a braking system in accordance with the first BEST MODES OF CARRYING OUT THE INVENTION Referring to the drawings Fig. 1 shows the main constructional features of a first embodiment wherein a wheel 2 contacts a rail 1 through wedge shaped wheel flanges 3. The wedge angle is nominally 1 in 10 but may be varied according to the gradient of the rails and hence the friction required between the wheel 2 and rail 1. Increased angular zones 4 are added to the outer wheel diameter for guiding the wheel 2 onto the rail 1 to effect braking. The wheel 2 rotates on an axle 5 which is securely attached to a vehicle (not shown). Braking pads 6 are used to transmit braking forces to the vehicle. Braking pad 6 may contact the wheel directly as shown in Fig. 1 or may use an independent brake disc attached to the wheel 2. During normal vehicular operation the wheel 2 is suspended above the rail by, say, 20 mm. When braking is required the wheel is lowered onto the rail and the vehicle weight is transferred from the vehicle support wheels to the rail grip braking wheel 2. A wheel or wheels 2 will normally be mounted adjacent to the vehicle support wheels (see Fig. 3). Fig. 2 shows an alternative configuration where the force between the rail 1 and the wheel 2 is generated by springs 4a acting on thrust ring 2a. The loading force on the sides of the head of rail 1 could also be applied by hydraulic or other means. Braking force is transmitted to the vehicle (not shown) through brake pads 6. The wheel rotates on and is secured to the vehicle by axle 5. During normal operation thrust ring 2a is spaced from the rail head against the bias of springs 4a. When braking is required springs 4a are released to drive thrust ring 2a into contact with the side of the rail head so gripping the rail 1. Fig. 3 shows, a rail supported vehicle 10 supported on rail 1 by vehicle support wheels 11. A rail grip braking wheel 2 in accordance with the first embodiment is mounted on the vehicle adjacent one of the support wheels 11 and a conventional pad brake 12 is mounted adjacent the other support wheel 11. The pad brake 12 and rail grip brake wheel 2 operate as emergency brakes in the form of an emergency dump brake which dumps the vehicle 10 onto pad 12 and wheel 2 upon its actuation. By adjusting the wedge angle of flanges 3 of the embodiment of Fig. 1 or the force applied by springs 3 in the Fig. 2 embodiment the friction between the wheel and the rail can be varied to accommodate a range of inclines or slippery rail surfaces. It will be apparent that maintenance of braking systems in accordance with the invention can be minimised as the braking components need not be in continuous running contact with the rail.

Claims: We claim:- 1. A braking system comprising a braked wheel adapted to provide a gripping contact laterally of the head of a rail. 2. A braking system as claimed in claim 1 wherein said braked wheel comprises a pair of flanges which grip laterally of the head of the rail and are in rolling contact with the rail. 3. A braking system as claimed in claim 2 wherein said flanges are tapered to form a wedging action between the rail head and the braked wheel. 4. A braking system as claimed in claim 2 wherein the flanges form a wedging action with lateral surfaces of the head of the rail by applying an axial load to said flanges so that they grip said lateral surfaces. 5. A braking system as claimed in any one of the preceding claims wherein said wheel is braked by brake pads applied directly or indirectly to said wheel. 6. A braking system as claimed in claim 3 wherein the taper of the flanges is varied in accordance with the gradient of the rail. 7. A braking system as claimed in claim 4 wherein the axial load is applied to said flanges by spring, hydraulic or electro-magnetic means. 8. A method of braking a vehicle comprising placing a braked wheel in contact with the head of a stationary rail, laterally gripping the head of the rail by flanges of said wheel and applying braking force to said wheel so that the wheel does not slip on said rail but remains in rolling contact with said, rail head while said braking force is applied. 9. A braking system substantially as hereinbefore described with reference to the accomapanying drawings. 10. A method of braking a vehicle substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: FRANCIS ROBERT JOHN, MELANE LESLIE JAMES, FRANCIS, ROBERT, JOHN, MELANE, LESLIE, JAMES
Applicants: FRANCIS ROBERT JOHN, MELANE LESLIE JAMES, FRANCIS, ROBERT, JOHN, MELANE, LESLIE, JAMES
Application year: 1982
Main classification: B61H7
IPC codes: B61H5, B61H7, B61H11