GB2183755A - Friction braking apparatus for a railway vehicle - Google Patents

Abstract

A railway vehicle chassis member includes friction braking apparatus for braking a flanged wheel (1) on the chassis member. The friction braking apparatus comprises a driven element (4) having a single annular plane rubbing surface, the driven element being secured to, or integral with, the wheel (1) so as to rotate coaxially with it with the rubbing surface exposed on one side of the wheel (1), and friction means (5) mounted on the chassis member and having a brake pad (6) which can be controllably pressed against the rubbing surface of the driven element (4) to effect braking. Application of the brake pad can be by hydraulic or pneumatic pressure, in which case the piston is returned by spring 10, or by spring pressure with the piston being returned by hydraulic or pneumatic pressure. <IMAGE>

Description

SPECIFICATION Friction braking apparatus The present invention relates to friction braking apparatus for the wheels of a railway vehicle and especially a mine railway vehicle.

Conventional wheel-engaging brakes on rail vehicles have brake shoes which are brought into contact with the running surface of the flanged wheels and pressed against them to exert a frictional force for slowing down the vehicle. Such brakes have a number of disadvantages. For example, the brake shoe material has to contend with contamination by grit or grease picked up by the wheel from the rail and is subjected to higher rates of wear because of that contamination and also because of the roughness of the running surface produced by the grit being embedded into it by the rail. This difficulty may be aggravated for a mine railway vehicle where the environment is more likely to include broken rocks.Another problem which can arise is that the wheel may skid on the rail and have a flat portion worn on the running surface, and because the running surface is no longer round it causes the braking to be irregular and increases the likelihood of skidding and further uneven wear of the running surface.

It is an object of the present invention to provide an improved brake for a railway vehicle and especially a mine railway vehicle.

According to the present invention there is provided friction braking apparatus for a flanged wheel of a railway vehicle on a chassis member of the vehicle and comprising a driven element having a single annular plane rubbing surface and which is secured to the wheel so as to rotate coaxially with it with the rubbing surface exposed on one side of the wheel and friction means mounted on the chassis member and having a friction surface which can be controllably pressed against the rubbing surface of the driven element to effect braking.

The chassis member may be the frame of a bogie which can turn relative to the body of the vehicle.

The friction means may include a single hydraulically or pneumatically operated cylinder with a movable piston to which is attached a brake pad having the friction surface. The cylinder may include spring means for returning the piston and withdrawing the brake pad from the rubbing surface when the pressure in the cylinder is reduced after a higher pressure has been used to apply the brake. Alternatively, spring means may be used to urge the brake pad towards the rubbing surface and the cylinder pressure arranged to oppose the spring force and withdraw the brake pad from the rubbing surface.

Where a single cylinder is used it may be mounted above the axle so that the bending force due to the unbalanced pressure on the wheel is opposite to the upward bending force resulting from the force of the rail on the wheel supporting the vehicle.

The driven element may be an annular disc which extends from the hub to the rim of the wheel and may be formed integrally with the wheel.

Typically, the wheel is mounted on a suspension member which is resiliently pivoted on or otherwise joined to the main part of the chassis by springs, for example, and the friction means is attached to the suspension member. Although the wheel may be carried on a cantilevered stub axle it is preferable for the suspension member to be forked with the axle extending between the limbs of the fork so as better to be able to withstand the bending effect of the offset force of the friction means. Alternatively, the braking pressure on the wheel may be balanced by providing two or more pressure operated cylinders angularly distributed around the wheel axle.

In order that the invention may be fully understood and readily carried into effect it will now be described with reference to an embodiment shown in the single figure of the accompanying drawing.

Referring to the drawing, the reference 1 indicates a flanged wheel shown in cross-section which is mounted on an axle 3 extending between limbs 2A and 2B of a forked suspension member. The method of attachment of the suspension member 2A,2B on the chassis of the vehicle is not shown in the drawing but may consist of a pivot with some kind of springing to provide a resilient suspension for the vehicle; the pivot may be attached directly to the chassis or be on a bogie. In another arrangement the wheel may be mounted on a bogie with other wheels, possibly with pairs of wheels on respective through axles, and the bogie may be mounted on the vehicle with springs. The braking apparatus consists of a driven element 4 shown as an annular plate attached to the wheel 1 and a friction means 5 mounted on the limb 2B of the suspension member.The friction means comprises a pneumatic cylinder 7 having an inlet 8 for compressed air which forms the actuating medium for the friction means. Inside the cylinder 7 a piston 9 is driven to the left by the pressure of the compressed air and compresses a spring 10, also moving piston rod 11 to the left to press a brake pad 6 against the outer surface of the annular disc 4. In this way the air pressure is used to effect the braking of the railway vehicle. When the air pressure is released from inside the cylinder 7 the force of the spring 10 moves the piston 9 to the right and withdraws the brake pad from the annular disc 4, thereby releasing the brake.

Since the normal force exerted by the brake pad 6 on the annular disc 4 is offset from the axle 3, it produces a bending moment on that axle which is transmitted to it by the two taper roller bearings on which the wheel 1 runs. The provision of the suspension member in the form of a fork having two limbs, 2A and 2B, provides support for the axle 3 against this bending moment.

Although this invention has been described with reference to a specific embodiment many modifications can be made without departure from the invention. If the friction means 5 is located above the axle 3 which is constructed as a cantilevered stub axle, the bending force on the stub axle due to the normal force of the brake pad on the annular disc will be opposite to the bending force exerted on the stub axle by the upward pressure of a rail 12 on the running surface of the wheel 1 due to the weight of the vehicle and with this form of construction it may not be necessary for the suspension member to be forked. The driven element need not be in the form of a plate provided that it has a plane annular rubbing surface facing the outside of the wheel.

The driven element may be constructed integrally with the wheel and not a separately formed component attached to it. The cylinder 7 may be actuated hydraulically rather than pneumatically. In the embodiment described above a pneumatic braking system (not shown) is provided on the vehicle and may include a compression pump, a reservoir for compressed air and suitable control valves. If the cylinder 7 is actuated hydraulically then a suitable hydraulic pressure braking system would be provided.

In another modification, the spring 10 is arranged to press the brake pad 6 towards the rubbing surface of the driven element 4 and the hydraulic or pneumatic pressure may be applied to the piston 9 so as to press the piston, piston rod and the brake pad away from the rubbing surface; such an arrangement would have the advantage that in the event of failure of the braking system the brakes would be applied automatically as the pressure in the cylinder 7 fell.

The brake pad 6 could be of any conventional material obtainable from specialist manufacturers but should preferably be chosen to give good service under the working conditions likely to be encountered.

Claims (18)

1. A railway vehicle chassis member including friction braking apparatus for braking a flanged wheel on the chassis member, the friction braking apparatus comprising: a driven element having a single annular plane rubbing surface, the driven element being secured to the wheel so as to rotate coaxially with it with the rubbing surface exposed on one side of the wheel, and friction means mounted on the chassis member and having a friction surface which can be controllably pressed against the rubbing surface of the driven element to effect braking.

2. A chassis member as claimed in claim 1, wherein the chassis member is the frame of a bogie which can, in use, turn relative to the body of the vehicle.

3. A chassis member as claimed in claim 1 or claim 2, wherein the friction means includes a single hydraulically-operated cylinder with a movable piston, and a brake pad having the friction surface, the brake pad being attached to the movable piston.

4. A chassis member as claimed in claim 1 or claim 2, wherein the friction means includes a single pneumatically-operated cylinder with a movable piston, and a brake pad having the friction surface, the brake pad being attached to the movable piston.

5. A chassis member as claimed in claim 3 or claim 4, wherein the cylinder includes spring means arranged to return the piston and withdraw the brake pad from the rubbing surface on reduction of the pressure in the cylinder after a higher pressure has been used to apply the brake.

6. A chassis member as claimed in claim 3 or claim 4, wherein spring means are provided to urge the brake pad towards the rubbing surface and the cylinder pressure is arranged to oppose the spring force and withdraw the brake pad from the rubbing surface.

7. A chassis member as claimed in any one of claims 3 to 6, wherein the single cylinder is mounted above the axle of the wheel so that, in use, the bending force resulting from the unbalanced force on the wheel from the friction means is opposite to the upward bending force resulting from the force of the rail on the wheel as it supports the vehicle.

8. A chassis member as claimed in any preceding claim, wherein the driven element is an annular disc which extends from the hub to the rim of the wheel.

9. A chassis member as claimed in any preceding claim, wherein the driven element is formed integrally with the wheel.

10. A chassis member as claimed in any preceding claim, wherein the wheel is mounted on a suspension member which is joined to the main part of the chassis by springs, and the friction means is attached to the suspension member.

11. A chassis member as claimed in any one of claims 1 to 9, wherein the wheel is mounted on a suspension member which is resiliently pivoted on the main part of the chassis, and the friction means is attached to the suspension member.

12. A chassis member as claimed in claim 10 or claim 11, wherein the wheel is mounted on a cantilevered stub axle.

13. A chassis member as claimed in claim 10 or claim 11, wherein the suspension member is forked and the stub axle extends between the limbs of the fork.

14. A chassis member as claimed in claim 1 or claim 2, wherein the friction means includes two or more hydraulically-operated cylinders each with a respective movable piston and a respective brake pad attached to the associated piston, and the two or more cylinders are angularly distributed around the wheel axle to balance the forces on the wheel during braking.

15. A chassis member as claimed in claim 1 or claim 2, wherein the friction means includes two or more pneumatically-operated cylinders each with a respective movable piston and a respective brake pad attached to the associated piston, and the two or more cylinders are angularly distributed around the wheel axle to balance the forces on the wheel during braking.

16. A railway vehicle chassis member substantially as herein described with reference to, and as illustrated by, the single figure of the accompanying drawing.

17. A railway vehicle having a chassis member as claimed in any preceding claim.

18. A railway vehicle as claimed in claim 17, wherein the vehicle is a mine railway vehicle.