GB2110779A

GB2110779A - Retaining disc brake pads

Info

Publication number: GB2110779A
Application number: GB08135991A
Authority: GB
Inventors: Philip Norman Paginton
Original assignee: Westinghouse Brake and Signal Co Ltd
Current assignee: Siemens Mobility Ltd
Priority date: 1981-11-28
Filing date: 1981-11-28
Publication date: 1983-06-22
Also published as: GB2110779B

Abstract

In a retention arrangement for disc brake pads 6 in a disc brake caliper head the brake pad is mounted by means of a mortise and tenon 7, the dove-tailing pads being a sliding fit to facilitate easy brake pad replacement. In order to retain the brake pads in position the open end of the mortise is closed by a swinging plate 9 pivoted on the caliper head. In the closed position the leading edge of the plate abuts a fixed stop and a spring loaded plunger 16 lies transversely across the rear edge to hold it in place. The plunger may be depressed to allow the plate to be swing back for brake pad replacement. The arrangement avoids the dismounting of loose retaining parts and the plunger requires only a light spring and may be finger operated without any special tools. <IMAGE>

Description

SPECIFICATION Disc brake pad retention arrangement The invention relates to disc brake pad retention arrangements.

In disc brakes the friction material is carried on removable pads which have to be changed from time to time when the material is worn.

Therefore the pads have to be easily removable. When a disc brake is actuated the force perpendicular to the disc plane between the pad and the disc is balanced by an equal and opposite reaction force between the brake caliper and the pads. There are virtually no forces parallel to the plane of the disc so retention arrangements are not normally subjected to significant forces and can be relatively light in construction.

Disc brakes for railway vehicles are covered by an internationally agreed standard, under the auspices of the U.l.C., Union Internationale des Chemins de Fer. According to this standard disc brake pads shall have a dovetailed tenon of such dimensions on the back of the pad and the brake calipers or housings shall have corresponding dove-tailed mortises as means for mounting the brake pads.

In the case of railway vehicles at least the brake pads are relatively large and undervehicle accessibility is strictly limited. Also the underside of the vehicles is generally extremely dirty and equipment is usually covered with a layer of dirt. This makes changing brake pads more difficult and increases the risk that retention means such as removable pins and springs or the like will be lost or damaged, it also makes the use of special tools difficult and therefore undersirable.

The invention is intendend to solve these problems by providing a retention arrangement which is simple to operate, needs no special tools and which does not need dismantling to change the brake pads.

According to the invention there is provided a disc brake pad retention arrangement for a brake pad which is a sliding fit in a slot in a housing comprising a retention plate pivotally attached to the housing so that it may be swung across the sliding line of the brake pad to close the mouth of the slot and is retained there by the front edge of the plate abutting a fixed stop in the housing and a resiliently biassed plunger behind the back edge of the plate lying transversely of the plate wherein to open the mouth of the brake pad slot the plunger is depressed to allow the plate to be swung back.

Preferably the retention plate lies in a slot formed in the housing transversely of the brake pad slot so that the plate may abut a face of said transverse slot to transfer to the housing any force exerted on the plate by the brake pads. Also, the retention plate is loosely pivoted in the housing to obviate strain on the pivotal attachment under the influence of said forces exerted by the brake pads.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a detailed view of a disc brake including a side view of a retention plate, and Figure 2 shows a view along the section A-A of Fig. 1.

Referring now to Fig. 1 there is shown a detail of one end of a disc brake pad housing 1, referred to in the art as a brake head, which is pivotally mounted on brake caliper arm 2 by means of a cross shaft 3 which is journalled in the brake head 1 at 4 and in the caliper arm at 5. The detailed drawing of Fig.

1 shows only part of the brake head 1 caliper arm 2 and there is a further caliper arm of opposite hand journalled to the other end of the brake pad which is to the left of the drawing.

The disc brake pad 6, see Fig. 2, is slidably fitted into the brake head 1 by means of a dove-tailed mortise and tenon joint generally indicated at 7 in Fig. 2. The outline of the mortise slot is generally indicated in Fig. 1 by a chain-linked line 8, this slot is closed at the left-hand end of the brake head 1 and is open only at the right-hand end, which is shown in Fig. 1, and the brake pad 6 is mounted by sliding the dove-tailed tenon into the mortise slot from the end of the brake head 1 shown in Fig. 1. For reasons of lack of under vehicle accessibility the brake head is mounted such that the mortise slot 8 extends vertically with the open end downwards so that without means of positively retaining the brake pads in the brake heads they will fall out.

The retention arrangement shown in the drawings, Fig. 1 and Fig. 2, comprises a retention plate 9 pivotally attached to the brake head 1 by means of a pivot pin 10 formed by the smooth shank of a bolt 11 screwed into the housing 1 and locked by a tab washer 1 2. The retention plate 9 is received into a slot 1 3 milled into brake head 1 in a plane lying transversely of the longitudinal axis of mortise slot 8. The plate 9 is shaped to fit closely within the slot and when the front edge 14 of the plate abuts face 1 5 of the slot, thereby forming a fixed stop in the housing, it closes the open end of mortise slot 8 positively preventing withdrawal of disc brake pad 6.

To hold retention plate 9 in the closed position a plunger 1 6 resiliently biassed into the extended position shown in Fig. 1 by means of a spring 1 7 is provided adjacent the rear edge 1 8 of the plate to prevent the plate swinging back. The plunger 1 6 and spring 1 7 are mounted in an open ended cylinder 1 9 cast into the brake head 1.

The outer end of the plunger 1 6 may be chamfered or rounded as shown in Fig. 1 to avoid dragging on the underside of plate 9 which impair its swinging movement. In the extended position plunger 1 6 lies adjacent the rear face 1 8 of plate 9 thereby positively preventing any rearward swinging movement of the plate.

Preferably the plate 9 is a loose fit on the pivot pin 10 so that plate 9 is free to move slightly, for example under the weight of brake pads 6, so that its "outer" face bears against the adjacent face of the groove 1 3 formed by the underside of the overlying part 21 of brake head 1, thereby transferring any forces directly to the brake head casting.

When it is necessary to disengage the retention arrangement in order to permit replacement of brake pads 6 the plunger 1 6 is depressed and plate 9 is swung back far enough to uncover the open mouth of mortise slot 7. The brake pad 6 can be easily slid out and replaced by a similar fresh brake pad whereupon plate 9 is swung back into position which will be indicated by plunger 1 6 popping out to provide the back stop to hold the plate in the closed position. The spring 1 7 may be a relatively light spring, allowing the plunger to be fully depressed by hand without the use of any tools whatsoever, if desired. As the plate 9 is shaped so that plunger 1 6 is not uncovered when the plate is swung open the plunger 1 6 does not have to be redepressed before the plate can be swung back into the closed position.

To limit the backswing plate 9 an extension 22 is provided on the plate which contacts an abutment 23 formed on the housing when the fully open position is reached. A further extension 24 is provided at the opposite end of the plate 9 to facilitate manual movement of the plate when changing brake pads.

This brake pad retention arrangement has no loose parts which have to be dismounted and replaced when changing brake pads and requires no special tools, or indeed any tools, as the arrangement may be released and easily reset by hand.

Claims

1. A disc brake pad retention arrangement for a brake pad which is a sliding fit in a slot in a housing comprises a retention plate pivotally attached to the housing so that it may be swung across the sliding line of the brake pad to close the mouth of the slot and is retained there by the front edge of the plate abutting a fixed stop in the housing and resiliently biassed plunger behind the back edge of the plate lying transversely of the plate wherein to open the mouth of the brake pad slot the plunger is depressed to allow the plate to be swung back.

2. A disc brake pad retention arrangement as claimed in Claim 1 wherein the retention plate lies in slot formed in the housing transversely of the brake pad slot so that the plate may abut a face of said transverse slot to transfer to the housing any force exerted on the plate by the brake pads.

3. A disc brake pad retention arrangement as claimed in Claim 2 wherein the plate is loosely pivoted in the housing to obviate string on the pivotal attachment under the influence of said forces exerted by the brake pad.

4. A disc brake pad retention arrangement as claimed in any preceding claim wherein there is provided a second fixed stop to limit backswing of the plate such that the resiliently biassed plunger remains covered.

5. A disc brake pad retention arrangement as claimed in Claim 4 wherein said second stop comprises in combination an edge face of the plate which abuts a face on the housing at said backswing limit.

6. A disc brake pad retention arrangement as herein described with reference to the accompanying drawings.