GB2424049A

GB2424049A - A brake mechanism for a rail vehicle

Info

Publication number: GB2424049A
Application number: GB0504907A
Authority: GB
Inventors: Derek Vincent Conrad Chatto
Original assignee: AEA Technology PLC
Current assignee: Ricardo AEA Ltd
Priority date: 2005-03-09
Filing date: 2005-03-09
Publication date: 2006-09-13
Also published as: GB0504907D0

Abstract

A braking mechanism suitable for use on a rail vehicle 24 (eg. train, bogie) having wheels 21, the braking mechanism including at least one brake pad 30 and means for urging the brake pad 30 against a side surface of the wheel 21. Two brake pads 30 could be urged against the side faces two wheels 21 belonging to a wheel set 20. The pads 30 preferably engage the inside surface near the rim of the wheels 21, so as to maximize the torque of the friction force. The urging means may comprise a lead screw 40, having two oppositely threaded portions 37, 38 serving to move the brake pads apart, operable by a handle 42. The brake pad may be supported on a lever arm 32 pivotally supported by the vehicle. The braking mechanism is intended to serve only as parking brakes for the rail vehicle, the service brakes being completely separate.

Description

- 2424049 Parking Brake The present invention relates to a parking brake

for a railway vehicle, and to a railway vehicle incorporating such a parking brake.

A common design of parking brake, particularly for freight wagons, includes a brake block that is mechanically pushed against the wheel tread. However, if the suspension of the vehicle or bogie is such that a change of the load on the vehicle causes relative movement between the brake block and the wheel, for example as a result of a small change in the wheelbase, then the holding force of the brake can be affected. A change of load will occur during loading or unloading of a vehicle.

According to the present invention there is provided a brake mechanism for use on a rail vehicle having wheels, the brake mechanism including at least one brakepad, and a mechanism for urging the brakepad against a side surface of the wheel.

Preferably the mechanism incorporates two brakepads, which are urged against side surfaces of the two wheels of a wheel set, one brakepad against each wheel.

Preferably the brakepads are urged against the inside surfaces of the two wheels. Preferably the surfaces against which they are urged are near the rim of the wheel, as this maximises the torque of the friction force. Preferably such a brake mechanism is provided to enable at least half the axles of a vehicle to be braked.

It will be appreciated that such a brake mechanism will be independent of the rail vehicle's service brake, and is indeed intended only for use as a parking brake.

It can therefore be a comparatively simple mechanism. The function and operation of the parking brake is unaffected by suspension movements. Preferably an interlock is S provided to the train control, so that the train cannot start moving without first releasing this parking brake.

A wide range of different mechanisms would be suitable for moving the brakepads. For example the mechanism may incorporate levers, springs and/or latches.

A preferred mechanism incorporates a lead screw which can be turned by a handle, the lead screw being arranged to move both the pads. This mechanism can provide the operator with a considerable mechanical advantage, so that the pads can be urged against the wheels with considerable force. Other suitable mechanisms for urging the pads against the wheels include hydraulic systems and cable operated systems.

The invention accordingly also provides a railway vehicle provided with such a parking brake.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which: Figure 1 shows a plan view of a bogie of a railway vehicle (shown only in part) incorporating a parking brake of the invention; Figure 2 shows a partial view on the line A-A of figure 1; Figure 3 shows a sectional view in a horizontal plane of a bogie of a railway vehicle incorporating an alternative parking brake of the invention; and Figure 4 shows a view on the line B-B of figure 3.

A railway vehicle such as a freight wagon typically consists of a body supported by bogies, one near each end of the body, each bogie having two wheelsets. Each wheelset consists of two wheels fixed to an axle, the axle locating in bearings that are connected to the bogie by a primary suspension; and the vehicle body is connected to the bogie by a secondary suspension.

Referring now to figure 1, this shows a plan view of one such wheelset 20, comprising two wheels 21 fixed to an axle 22. Part of a bogie 24 is shown in section. A parking brake mechanism 28 includes brakepads 30 supported by A-frames 32 which are pivotally connected to the bogie 24 by hinges 34, such that each brakepad 30 is just inside the rim of one of the wheels 21 of the wheelset 20. Each A-frame 32 extends in a generally horizontal direction between the bogie 24 and the wheelset 20; and each A- frame 32 incorporates a threaded block 35, 36 which engages a respective threaded portion 37, 38 of a shaft 40. This shaft 40 can be operated by handwheels 42, one at each end of the shaft 40. The shape of the A-frame 32 and of the brakepad 30 are shown more clearly in figure 2, in which the wheel 21 is shown by a broken line.

In operation, rotation of one or other of the handwheels 42 rotates the shaft 40 and so causes the brakepads 30 to move into contact with the rims of the wheels 21; while rotation in the opposite direction moves the brakepads 30 free of the rims. It will be appreciated that since the parking brake mechanism 28 is supported only by the hinges 34, the force exerted by each brakepad 30 will be the same.

The parking brake 28 is shown only by way of example, and may be modified in various ways while remaining within the scope of the present invention. For example the A-frames 32 might be moved apart by a hydraulic cylinder (not shown) or by a cable mechanism, in place of the threaded shaft 40. The A-frames 32 act as levers, and could have a different shape, for example a simple rectangular frame pivoted at one end and carrying the brakepad 30 at the other end. In yet a further modification, such levers might be pivotally connected to the bogie 24 at an intermediate position along their lengths, the mechanism incorporating means (such as a threaded shaft 40 or a hydraulic cylinder) to move the ends of the levers remote from the brakepads 30 towards or away from each other.

It will be appreciated that for security it is desirable to apply brakepads to at least half the axles of a vehicle. For example a parking brake mechanism 28 as described above might be provided on each bogie of a two-bogie vehicle. Alternatively both the wheelsets of a bogie might be provided with a parking brake mechanism.

Such a mechanism 28 could also be provided on a vehicle without bogies, in this case the hinges 34 being supported by the vehicle body.

Referring now to figure 3, a bogie includes two spaced-apart wheelsets 20. A service brake mechanism includes two brake beams 50 each carrying a brake block 52 at each end such that the brake blocks 52 are adjacent to the tread of the wheels 21; the supports for the brake beams 50 are not shown. An additional part of the service brake mechanism (not shown) pushes the two brake beams 50 apart, so that all four brake blocks 52 are pushed against the treads of the wheels 21, when the service brake mechanism is actuated to slow the train down. These features are conventional A parking brake mechanism 54 incorporates brakepads 56 adjacent to the inside of the rim of each wheel 21, and each supported by a pair of parallel lever arms 58 or 59 that extend in a generally horizontal direction.

Midway between the two wheelsets 20 the left-hand lever arms 58 and 59 are linked by a pivot pin 60, and similarly the right-hand lever arms 58 and 59 are linked by a pivot pin 60. Each lever arm 58 or 59 passes through a guide channel 61 or 62 attached to the end of the respective brake beam 50. The channels 61 and 62 support the weight of the lever arms 58 and 59, but provide sufficient clearance that the lever arms 58 and 59 do not restrict the movement of the brake beams 50 during operation of the service brake mechanism, and such that the lever arms 58 and 59 can pivot to bring the brakepads 56 into contact with the wheels 21. This pivoting movement of the lever arms 58 and 59 is brought about by movement of the pivot pins 60 towards each other, as indicated by the arrows 64. This may for example be achieved using a threaded shaft 40 as shown in figures 1 and 2, or using a hydraulic cylinder, or a cable mechanism.

In operation of the mechanism 54, when it is necessary to apply the parking brake, the pivot pins 60 are moved towards each other, and consequently the brakepads 56 move into contact with the rims of the wheels 21. If the parking brake is applied in this manner while the service brake mechanism is also on, this does not prevent operation of the parking brake; and if the service brake mechanism is then released the brake beams 50 move towards each other slightly (into the position shown in figure 3), and this tends to push the brakepads 56 even more firmly onto the rims.

In another alternative, the brakepads might be arranged to push against the outside of the wheels. As a rule, however, this would not be convenient, because there is usually less rim area to push against (whereas at the inside of the wheel the brakepads 30 or 56 can push against the back of the flanges)

Claims

Claims 1. A brake mechanism for use on a rail vehicle having wheels, the

brake mechanism including at least one brakepad, and a mechanism for urging the brakepad against a side surface of the wheel.
2. A brake mechanism as claimed in claim 1 which incorporates two brakepads, which are urged against side surfaces of the two wheels of a wheel set, one brakepad against each wheel.
3. A brake mechanism as claimed in claim 1 or claim 2 wherein each brakepad is urged against the inside surface of the respective wheel.
4. A brake mechanism as claimed in any one of the preceding claims wherein the surface against which each brakepad is urged is near the rim of the wheel.
5. A brake mechanism as claimed in any one of the preceding claims incorporating a lead screw which can be turned by a handle, the lead screw being arranged to move each brakepad.
6. A brake mechanism as claimed in any one of the preceding claims wherein the or each brakepad is supported by a lever arm which is pivotally supporte by the vehicle.
7. A brake mechanism as claimed in any one of claims 1 to 5 wherein the or each brakepad is supported by a lever arm which is supported by a gui such that the lever arm can both move longitudinally and turn relative to the guide.
8. A brake mechanism as claimed in claim 7 wherein each guide forms part of a service brake mechanism.
9. A brake mechanism substantially as hereinbefore described with reference to, and as shown in, figures 1 and 2, or figures 3 and 4, of the accompanying drawings.
10. A railway vehicle provided with a brake mechanism as claimed in any one of the preceding claims.

15857 MdDe P T Mansfield

Chartered Patent Agent Agent for the Applicant