GB2135001A - Disc brakes for rail vehicles - Google Patents

Abstract

The vehicle has driven axles (6,7) and the brake has a rotatable disc (25) fast with a shaft (22) driven by a traction motor (20) by which axle (6) is driven through transmission means (23,24) and brake shoes (29) for engagement with opposite faces of the disc (25) are carried from the housing (21) of the traction motor (20). The motor (20) is particularly described as an electric motor with the disc (25) being mounted directly on the armature shaft of the motor, or mounted on an extension of the shaft. As shown, the shoes (29) are carried by levers (27,28) pivotally connected to a mounting bracket (30) on extension (14) of housing (21). The actuator incorporates a wedge displaceable longitudinally by pneumatic pressure or by a spring, and acts between tappets (33,34). Figures 3,4 illustrate alternatives for transmitting drag on shoes (29) when brake is applied and for mounting of levers (27,28). <IMAGE>

Description

SPECIFICATION Disc brakes for rail vehicles This invention relates to disc brakes for rail vehicles ofthe kind in which pairs of spaced rail engaging wheels are rotatable with driven axles with which they are fast, and the driven axles are jou rnalled at opposite ends for rotation in bearings carried by side frames, the driven axles being arranged for relative articulation to allow free movement ofthe vehicle through curves in the railway track, and the disc brake comprising a rotatable disc associated with one ofthe axles, and friction members for engagement with opposite faces ofthe disc in order to brake the disc and the axle with which the disc is associated.

In the case of rail vehicles of the kind setforth having driven axles difficulty is experienced in mounting the brake in such a mannerthatthe performance ofthe brake is not affected by the articulation of the relative parts.

According to one aspect of our invention in a disc brake for a rail vehicle of the kind setforth the disc is fast with a shaft driven by a traction motor by which the axle is driven through transmission means.

Convenientlythe disc is mounted directly on the armature shaft of the motor. However, in a modification, the disc is mounted on an extension of the armature shaft. In such a modification, the extension may be coupled to the armature shaft by means of a flexible drive.

Mounting the disc on a shaft driven bythetraction motor ensuresthatthe disk will be driven at a faster speed than that at which it would be driven if mounted on the axle itself. A lighter brake for a given duty can therefore be provided since the relatively faster speed ofthe disc enables the required torque to be generated atthewheelfora reduced brake-applying force atthe disc and the disc heat dissipation is improved.

The ratio of a gear drive between the traction motor and the axle results in relatively low braking forces being generated at the discfor both service and parking braking.

According to another aspect of our invention in a disc brake for a rail vehicle of the kind setforth the friction members are carried from a housing of a traction motor by which the axle is driven through transmission means.

When the brake comprises a pair of caliper leavers which carrythefriction members, the levers are pivotally mounted with respecttothe housing from which an actuatorforthe levers is also carried.

Conveniently the levers and the actuator are mounted in a bracket, and the bracket itself is mounted on a rigid extension from the housing.

In a construction in which the disc is fast with a shaft driven from the traction motor, arranging for the brake itself to be carried from the housing of the motor eliminates relative movement between the disc and the brake, and the performance of the brake is not affected by relative articulation ofthe driven axles.

When the brake is installed in a bogie of the steerable type with the bearings in which the axles are journalled being resiliently carried by the side frames, the ability ofthe bogie to steerwill be substantially unaffected when the motor mounted brake is applied.

The installation of the brake is therefore facilitated since the mounting and the disc are carried by components which are restrained against relative bodily movement.

Thus any convenient brake actuator can be used to operatethe brake, suitably by separating the outer ends of the pair of caliper levers which carry the friction members attheir inner ends. This is because no compensation has to be made for relative bodily movement between the mounting for the friction members and the disc.

One embodiement of our invention is illustrated in the accompanying drawings in which: Figure 1 is a plan of a schematic layout of a twin-axle driven bogie incorporating disc brake installations; Figure 2 is a practical version, on an enlarged scale, of a portion ofthe layoutof Figure 1; Figure3isa side view of the portion ofthe bogie shown in Figure 2; and Figure 4 is an end view of one ofthe brakes showing a modification.

Thetwin-axle drivable bogie for a rail vehicle illustrated in Figures 1 to 3 of the drawings comprises side frames 1,2 which are interconnected by a transverse bolster 3 and resilient suspension assemblies, suitably in the form of springs 4 and 5, are provided between opposite ends ofthe bolster 3 and the side frame 1,2. Axles 6 and 7 are journalled for rotation at opposite ends in axle boxes 8,9 containing bearings, and the axles boxes, in turn, are carried from the side frames 1, 2through resilient suspension assemblies 10,11 ,for example coil-springs or rubber blocks.

A pair of wheels 12, 13 inboard of each frame are fast with each axle 6,7.

Each axle 6,7 is driven by an electric motor 20 of which the housing 21 is carried by the respective axle 6,7. The armature shaft 22 of each electric motor carries at opposite ends a pinion 23 in meshing engagementwith a gearwheel 24 fast with the adjacent axle 6,7, and a brake disc 25 ofthe ventilated type.

Each disc 25 is adapted to be braked by a disc brake 26 ofthe calipertype. Each brake 26 comprises a pair of caliper levers 27,28 which are pivotally connected at intermediate points in their lengths to a mounting braket30 on an extension 14 ofthe housing 21. Attheir inner ends the levers 27,28 carry a pair of brake shoes 29 carrying friction linings for engagement with braking surfaces defined by opposite faces ofthe disc 25 and attheir outer ends the levers 27,28 are adapted to be separated by means of an actuator 31 ofthe double-acting type.

The actuator 31 comprises a housing 32 which is rigidly carried from the bracket 30 and of which the axis is normal to the axis of rotation of the disc 25. The actuator incorporates a wedge which is guided in the housing 32 for movement in a longitudinal direction and acts between adjacent ends of a pair oftappets 33, 34. The tappets 33,34 are guided in aligned transverse bores in the housing 32 and act at their outer ends between the outer ends ofthe levers 27,28. The effective length of each tappet 33,34 is adjustable, either manually or automatically, to maintain, at a substantial value, the braking clearances between the shoes 29 and the disc 25.

A return spring 40, suitably a tension spring, acts between the levers 27 and 28 adjacent to their outer ends in order to urge the tappets 33,34 inwardly to maintain the desired braking clearances in the "brakerelease" position of the brakes.

The wedge, in a known manner, is displaced longitudinally to apply the brake pneumatically for service braking by means of pneumatic pressure applied to a piston working in a cylinder 42 and, for parking or emergency braking, when the pneumatic pressure is not operative, the wedge is held in an advanced, brake-applying, position by means of a compression spring which acts on the wedge through the piston.

When the brakes are applied, either pneumatically or by the release of stored energy in the spring,the drag on the shoes 29 is transmitted to the extensions 14through drag links 45 (Figure 4) which suspend from the bracket 30.

In a modification, shown in Figure 3, the drag-links 45 are omitted and the drag on the shoes 29 is taken by spaced surfaces 46 on the bracket 30 and with which the edges ofthe caliper levers 27 and 28 are engaged.

In the brake described above, a small amount of articulation is provided between the shoes 29 and the caliper levers 27 and 28to permitthefriction linings to be aligned with the disc 25. This feature forms the subject of our G.B. Patent No.1 543313. However, the friction linings will wear in a taper, so that the brake may be fitted with new linings of tapered outline which wearto a parallel sided worn outline.

lnthe modified construction of Figure 4 the levers 27 and 28 act on the shoes 29 th rough fully articulated connections, and similar connections are provided between the links 45 and the shoes. This enables the shoes to align themselves as necessary with the disc.

Friction linings which are parallel sided can befitted and will follow a parallel wear path.

In the construction described above the housing 31 can be orientated to any convenient angular position to facilitate installation provided the line of action of the tappets 33 and 34 remains substantially normal to the outer ends ofthe levers 27,28.

Claims (8)

1. A disc brake for a rail vehicle ofthe kind setforth in which the disc is fast with a shaft driven by a traction motor by which the axle is driven through transmission means.

2. A disc brake as claimed in claim 1, in which the disc is mounted directly on the armature shaft of the motor.

3. A disc brake as claimed in claim 1, in which the disc is mounted on an extension ofthe armature shaft of the motor.

4. A disc brake as claimed in claim 3, in which the extension is coupled to the armature shaft by means of a flexible drive.

5. A disc brake as claimed in any preceding claim in which the friction members are carried from a housing of the traction motor.

6. A disc brake as claimed in claim 5, in which the friction members are carried by a pair of caliper levers, and the levers are pivotally mounted with respectto the housing from which an actuatorforthe levers is also carried.

7. A disc brake as claimed in claim 6, in which the levers and the actuator are mounted in a bracket, and the bracket itself is mounted on a rigid extension from the housing.

8. A disc brake substantially as described herein with reference to and as illustrated in Figures 1,3 and 4 of the accompanying drawings.