GB2106184A

GB2106184A - Brake chamber

Info

Publication number: GB2106184A
Application number: GB08224710A
Authority: GB
Inventors: Robert Baines; George Kenneth Farmery
Original assignee: Clayton Dewandre Co Ltd
Current assignee: Wabco Automotive UK Ltd
Priority date: 1981-09-11
Filing date: 1982-08-27
Publication date: 1983-04-07

Abstract

A brake chamber for vehicle braking systems, is adapted for mounting on the pressure plate side 110 by means of a central boss 134 or stud having a through bore 132 serving as an inlet for fluid under pressure, to the pressure side of the diaphragm 118. Because the non- pressure plate 112 serves no structural purpose it may be formed from plastics material or lighter gauge metal then conventional non-pressure plates. Also the need for special mounting studs is avoided. <IMAGE>

Description

SPECIFICATION Improved brake chamber This invention relates to brake chambers for vehicle braking systems.

Convention brake chambers comprise two dished steel plate pressings having peripheral flanges held together by a clamping ring with the peripheral edge of a diaphragm clamped therebetween so dividing the chamber into a pressure side and a non-pressure side. The plate or pressing on the pressure side of the diaphragm (hereinafter referred to as the "pressure plate") normally has welded thereto a central boss providing an inlet for fluid under pressure. The other plate (hereinafter referred to as the "nonpressure plate") has welded thereon studs by means of which the chamber can be mounted.

Through an opening at the centre of the nonpressure plate passes the push rod having at one end, a backing or support disc contacting a central region of the diaphragm and connected at the other end, usually via a yoke, to the brake mechanism. The push rod is biased toward the pressure plate by a spring acting between the nonpressure plate and the backing or support disc.

One conventional brake chamber of the kind described is shown in Figure 1 referred to below.

In accordance with the present invention we propose a brake chamber which in contrast to conventional brake chambers, is adapted for mounting on the pressure plate side. More particularly, we propose a brake chamber for vehicle braking systems, comprising two dished plate members held together at the periphery thereof with the peripheral edge of a diaphragm clamped therebetween so dividing the chamber into a pressure side and a non-pressure side, wherein the brake chamber is adapted for mounting on the pressure plate side, the mounting being in the form of a boss or stud secured to or integral with the pressure plate member and having therethrough a bore serving as an inlet port for fluid under pressure, to the pressure side of the chamber.

This arrangement has the advantage that the non-pressure plate serves no structural purpose and as such may be formed from plastics material or lighter gauge metal than conventional nonpressure plates. Also, the need for special mounting studs welded to the brake chamber is avoided. For the reasons, manufacture assembly and installation is facilitated and made cheaper than conventional brake chambers.

Instead of using a clamping ring, the nonpressure plate may be adapted to clip over the periphery of the pressure plate. The non-pressure plate may have, for example, a peripheral flange formed with an internal step or shoulder behind which the periphery of the pressure plate abuts, when the two plates are fitted together.

Embodiments of this invention will now be described by way of example with reference to the accompanying drawings of which: Figure 1 is an end elevation of a conventional brake chamber shown partly in cross-section; Figure 2 is a cross-sectional elevation of a brake chamber according to the present invention; Figure 3 is a front-elevation of the chamber shown in Figure 1; Figures 4 and 5 show, in cross-section, details of modified embodiments of brake chambers according to the present invention.

The conventional brake chamber shown in Figure 1, has a pressure plate 10 and a nonpressure plate 1 2 both of which comprise steel pressings and have a rim or flange 14, 1 6. Two studs 1 7 are welded to the non-pressure plate 1 2 enabling the brake chamber to be mounted on a support bracket (not shown).

A diaphragm 18 is retained around its periphery between the flanges 14 and 1 6 which are secured together by a clamping ring 20, so dividing the chamber into a pressure side 22 and a nonpressure side 24. On the non-pressure side of the diaphragm is a backing plate or support disc 26 mounted on the end of a push rod 28 linked at the other external end (not shown) to the brake mechanism. The push rod 28 is urged into contact with the diaphragm 18 by a spring 30 acting between the disc 26 and the non-pressure plate 1 2. During operation, fluid under pressure is admitted to the brake chamber as the pressure side of the diaphragm through an inlet port 32 in a central boss 34 on the pressure plate, to displace the diaphragm 18 and hence also the push rod, in opposition to the return spring 30.

Unlike the conventional brake chamber described above, the brake chamber shown in Figures 2 and 3 is adapted for mounting on a support bracket 100 by a single fixing. This is in the form of a central boss 1 34 on the pressure plate 110, which boss has an external thread 1 50 enabling the chamber to be secured to the support bracket 100 as shown, by a nut 1 52 and optional locking-nut 1 54. The boss 1 34 also has a bore 132 serving as an inlet port to the chamber on the pressure side 122 of the diaphragm 118.

The non-pressure plate 11 2 is moulded of plastics material and has a peripheral recessed flange 11 6 receiving a moulded rim 113 of the diaphragm 11 8 and with an internal step or abutment 11 5. Around the edge of the flange 116 are equally angularly spaced axial slits 117 affording sufficient resilience to enable the flange to snap over the peripheral edge of the pressure plate 110 such that the pressure plate 110 engages behind the abutments 11 5 securing the plates 110 and 112 together and retaining the diaphragm 118 in position. No clamping ring is required in this embodiment but such an arrangement may be used if desired.Alternatively, as illustrated in Figure 4, the clamping ring may be a rolled-over steel pressing 11 9. When a clamping ring 11 9 is used the recessed flange 11 6 is of a simpler construction and merely abuts the periphery of the pressure plate 110. The push rod 128 is urged into contact with the diaphragm 118 by a conical spring 1 30 acting between the disc 126 and the non-pressure plate 112 and seated at one end in a recess 1 31 in the non-pressure plate 112 and a locating ring 133 around the push rod.

In an alternative embodiment illustrated in Figure 5, both the non-pressure plate 1 12 and the pressure plate 110 are made of plastics material, the boss 1 34 being moulded integrally with the pressure plate 110 which has a somewhat heavier section than the non-pressure plate 112.

Additional strength is provided by inserting a punched metal backing plate 1 56 between the pressure plate 110 and the support bracket 100.

Figure 5 shows a chamfer or lead-in 1 53 at the periphery of the pressure plate 110, thus facilitating assembly of the two plates 110 and 112. Such a chamfer or lead-in 1 53 avoids the need for axial slits 11 7 in the flange in the embodiments of Figures 4 and 5.

Claims

1. A brake chamber for vehicle braking systems, comprising two dished plate members held together at the periphery thereof with the peripheral edge of a diaphragm clamped therebetween so dividing the chamber into a pressure side and a non-pressure side, wherein the brake chamber is adapted for mounting on the pressure plate side, the mounting being in the form of a boss or stud secured to or integral with the pressure plate member and having therethrough a bore serving as an inlet port for fluid under pressure, to the pressure side of the chamber.

2. A brake chamber according to claim 1 wherein the non-pressure plate is adapted to clip over the periphery of the pressure plate.

3. A brake chamber according to claim 2 wherein the non-pressure plate has a peripheral flange formed with an internal step or shoulder behind which the periphery of the pressure plate abuts when the two plates are fitted together.

4. A brake chamber according to any one of the preceding claims wherein the non-pressure plate and optionally also the pressure plate is moulded from plastics material.

5. A brake chamber according to claim 4 wherein the boss or stud is moulded integrally with the pressure plate.

6. A brake chamber constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figures 2 to 5 of the accompanying drawings.