GB2259339A - Brake booster mounting - Google Patents

Abstract

An auxiliary booster (10) for a hydraulic actuator, in which the booster casing (21) has an integral mounting means (42) formed on the casing whereby the booster can be mounted on support (14) by a "twist - lock" action. The mounting comprises a non-circular opening in the support (14), lugs (50) on the booster casing passing through the opening in one orientation of the booster and holding the booster in place on rotation thereof. <IMAGE>

Description

A FLUID PRESSURE OPERABLE BOOSTER This invention relates to boosters, primarily for use with vehicle hydraulic systems.

A typical booster provides auxiliary power assistance for actuation of a hydraulic master cylinder and generally comprises a casing having a piston slideably mounted in the casing and sealed to the wall of the casing by a diaphragm to divide the casing into a pair of chambers. One of the chambers is connected to a source of low pressure and the other chamber is connected to a source of a higher pressure and a valve means controls the pressure differential across the piston to provide the power assistance.

In particular one side of the piston can be connected to the atmosphere and the other side of the booster to a compressed air source.

The booster can be arranged in tandem with a hydraulic master cylinder, as is well known.

For some vehicles such as trucks, light vans, it may be desirable for there to be some auxilary power assistance to aid operation of a hydraulic actuator.

In such a case the booster will be arranged between the clutch pedal input and the master cylinder by fixing to the engine compartment bulkhead.

The present invention provides a booster having an improved means of attachment to a support wall on the vehicle.

Accordingly there is provided a fluid operated booster having a casing in which a power piston is slideably located in the casing to apply an auxiliary load to an output rod, the casing having integral mounting means formed in the casing whereby the booster can be mounted into a co-operating opening in a support surface, such means provides a twist-lock action for securing the booster to said support member.

Preferably the integral mounting means, comprise an axially directed annular surface formed on the casing which in use confronts the support surface, and at least two circumferentially spaced radially projecting lugs axially spaced from the annular surface, said mounting means being insertable in the opening which has a periphery conforming to the perimeter said lugs and casing, resilient means permitting passage of the lugs through the opening, and a first abutment means on the casing which permits limited rotation of the booster in one direction after insertion of the lugs through the opening for disposing the lugs in engagement with the rear surface of the support, and a locking means on the casing that has an interference fit with the support surface to inhibit rotation in the opposite direction.

The invention will be described by way of example and with reference to the accompanying drawing in which: Fig 1 is a longitudinal cross section through a fluid operated booster according to this invention, Fig 2 is a section on the booster after insertion of the mounting means through an opening in a support wall.

Fig 3 is a section on the line 3-3 of the booster after turning the booster to lock the booster in position on the support wall The booster 10 shown in Fig 1 is a direct acting booster whose output rod 11 is connected directly to the piston 12 of a hydraulic master cylinder 13.

The booster 10 has a casing 21 formed from a front shell 22 and rear shell 23 joined at their outer peripheries 24 in a well known manner. The front wall of the front shell 22 is provided with mounting means, preferably welded-in bolts, or studs 25, hy which the hydraulic master cylinder 13 is fixed to the casing 21. The rear portion of the rear shell 23 serves to mount the booster to a fixed support surface 14 such as a vehicle engine compartment bulk head.

A piston 26 is located within the casing 21, the piston 26 having a tubular extension 28 which extends through an aperture 27 on the end in a centre spigot 39 on the end wall 29 of the rear shell 23. The tubular extension 28 is screwed into the piston 26 and defines a valve housing in which a control valve member 30 is located to operate in the conventional manner. The extension 28 is slidingly sealed through the aperture 27 hy means of a seal 31.

An elastomeric diaphragm 32 is located by an inner peripheral bead to the piston 26 and the outer peripheral bead is clamped between the shells 22 and 23 to provide a seal therebetween and to divide the casing 21 into two fluid tight chambers 33 and 34. Chamber 33 is connected to atmosphere and the chamber 34 is connected to a source of compressed air via the pipe 35 and inlet 36.

The tubular extension 28 is formed as a separate component which is secured to the booster piston 26 and forms the valve housing but could be formed integrally.

The control valve 30 is operated by a coaxial plunger 37 mounted in sliding relationship within the central bore of the valve housing 28 and piston 26. The plunger 37 is mounted on an input rod 38 by means of a ball and socket joint by which it is staked thereto. The input rod 38 is coaxial with the tubular housing 28 and is connected to the clutch actuating pedal (not shown) for operation of the booster in the conventional manner.

With reference also to Figs 2 and 3, the rear booster shell 23 is attached to the support wall 14 which is provided with a generally square opening 16. (see Fig 2 and Fig 30).

The casing shell 23 is provided with a "limit and lock" mounting means generally designated 42 for simple and rapid installation of the booster 10 through the opening 16 without the use of conventional fasteners such as nuts and bolts.

The 'twist and lock' mounting means 42 comprises an annular rearwardly axially directed annular surface 44, perhaps formed on a flange, which is cast or moulded integrally on the shell 23 and has a diameter larger than the widest dimension of the opening 16 are rounded. The rear shell 23 has four ears of lugs 50 spaced equilaterally apart and projecting radially of the casing, located a predetermined axial distance away from the annular surface 44. The lugs 53 define a square flange 51 with rounded corners and the lugs 50 are such a size adn dimension so as to fit freely with in the opening 16. The outer peripheral surface 52 of the shell 23 located between annular surface 44 and the lugs 50 has two circular arcuate surface portions 54 and 56 which have a common centre and a diameter which is just less than the distance between the sides 47 of the opening 16.The arcuate portions 54 and 56 are separated by two pairs of tangential planer surfaces 58 and 60, 62 and 64.

An imaginary line 66 interconnecting the intersections of the two pairs of planer surfaces 58,60,62,64 has a length longer than the distance between opposite sides 47 of the opening. Four pyrimidal projections 68, spaced apart are provided on the outer surface 52 at the junction between each lug and the peripheral surface. Each lug 50 has a frontwardly directed surface which is inclined to the annular surface 44 to form a sloping ramp.

A resilient gasket 72 is located against the annular surface 44 and around the peripheral surface 52.

The booster 10 is installed in the opening 16 by passing the central spigot 39 and square flange 51 through the opening 16 with the booster 10 inclined so that the lugs 50 are aligned with corners 48 in the opening. (See Fig 2).

Pressure is then applied towards the surface 14 to squeeze the gasket 72, rotation of the booster 10 in a counter clockwise direction is prevented by the plane peripheral portions 58 and 62 engaging the sides of the opening.

Clockwise rotation is permitted by the arcuate surface portion 54 and 56. Clockwise rotation also moves the sloping front surface of the lugs 50 against the support surface 14 causing the gasket to be squeezed. Clockwise rotation of about 45 degrees around the axis of the booster lock the rear shell 23 in position in the opening.

The lugs 50 have rotated to a position shown in Fig 3 and further clockwise rotation is prevented by the planer surfaces 60,64 abutting the sides of the openingl6.

The booster is loked in position by the pyramidal projections 68 which are an interference agains the counter clockwise rotation by abutting against the sides 47 of the opening 16.

When the booster is locked in position in Fig 2 to that shown in Fig 3, thepyramidal projections resist the rotation as they pass "over centre". This resistance can be overcome by manual load, and also by further squeezing of the gasket 72.

After installation of the booster 10, rotation of the booster in any direction is prevented by the high compression load in the gasket 72 and the interference of the pyramidal projections 68, and planer surfaces 60,64.

The rear shell 23 can be a die casing from a suitable metal such as zinc or aluminium, or could be a plastic moulding from a suitable material such as glass filled nylon 66.

The front shell 22 can be manufactured from a sheet metal pressing as is conventional, or again could be plastic moulding.

The hydraulic master cylinder 13 could also be fixed to the booster front shell 22 by a "twist and lock" mechanism such as that operating between the booster and the bulkhead.

Claims (7)

1. A fluid operated booster having a casing in which a power piston is slideably located in the casing to apply an auxiliary load to an output rod, the casing having integral mounting means formed in the casing whereby the booster can be mounted into a co-operating opening in a support surface, such means provides a tvJist-lock action for securing the booster to said support member.

2. A booster as claimed in Claim 1 wherein the integral mounting means comprise an axially directed annular surface formed on the casing which in use confronts the support surface, and at least two circumferentially spaced radially projecting lugs axially spaced from the annular surface, said mounting means being insertable in the opening which has a periphery conforming to the perimeter said lugs and casing, resilient means permitting passage of the lugs through the opening, and a first abutment means on the casing which permit limited rotation of the booster in one direction after insertion of the lugs through the opening for disposing the lugs in engagment with the rear surface of the support, and a locking means on the casing that has an interferance fit with the support to prevent rotation in the opposite direction.

3. A booster as claimed in Claim 1 wherein each lug has an inclined ramp surface thereon for causing further compression of the resilient means.

4. A booster as claimed in Claim 3 wherein the resilient means comprises an elastomeric gasket located against said annular surface to be squeezed against the supporting surface.

5. A booster as claimed in any one of Claims 2 to 4, wherein the mounting means further includes a second abutment means which prevents rotation of the booster in opposite directions to said one direction after insertion in the opening.

6. A booster as claimed in any one of Claims 2 to 5 wherein the locking means comprises pyramidal projections that interfere with the edges of the opening.

7. A booster as claimed in Claim 6 when dependant upon Claim 5, wherein the outer surface of the casing between said annular surface and the lugs has two arcuate surface portions thereon coaxial with the casing, the two surfaces being spaced apart by tangential planer surfaces, and the first and second abutment means are constituted by said tangential surfaces.