GB2209810A

GB2209810A - Master cylinder

Info

Publication number: GB2209810A
Application number: GB8821414A
Authority: GB
Inventors: Anthony George Price; Roy Campbell
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1987-09-15
Filing date: 1988-09-13
Publication date: 1989-05-24
Also published as: GB8721691D0; GB8821414D0

Abstract

A master cylinder having a pressure cylinder (1) and a reservoir (3) mounted thereon. The cylinder has a recuperation port (23) in communication with the reservoir and valve means (24) is arranged to control fluid flow between the reservoir and cylinder. The reservoir is connected to the cylinder by a connector (14) having a portion (18) surrounding the outer surface of the cylinder (1) in fluid-tight relationship, the connector providing a fluid flow passage between the reservoir (3) and recuperation port (23). The reservoir may be connected to two parallel master cylinders (Figs 2, 3, 5, 6, not shown). <IMAGE>

Description

MASTER CYLINDER.

This invention relates to a master cylinder, primarily for use in a vehicle hydraulic brake system and of the general kind having a pressure cylinder and a separately made fluid reservoir mounted thereon. The cylinder would normally have a recuperation port in communication with the reservoir and valve means arranged to control fluid flow through the port.

The invention is particularly concerned with the connection of the reservoir to the cylinder and has for an object to facilitate this in a simple and convenient manner.

According to the invention, a master cylinder comprises a pressure cylinder and a separately made fluid reservoir mounted thereon, the reservoir being connected to the cylinder by connecting means surrounding the outer surface of the cylinder in fluid-tight relationship.

In one convenient arrangement, a wall portion of the connecting means or reservoir is spaced from an end wall of the cylinder to form a flow passage between the reservoir interior and a port provided in said end wall.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a longitudinal cross-section of one form of the master cylinder of the invention forming part of a dual master cylinder assembly; Figure 2 is an end view of the assembly of Figure 1; Figure 3 is a plan view of the assembly of Figures 1 and 2; Figure 4 is a longitudinal cross-section of an alternative form of master cylinder of the invention, again embodied in a dual master cylinder assembly; Figure 5 is a plan view of the assembly of Figure 4, Figure 6 is an end view of the assembly of Figures 5 and 6.

Referring to Figures 1 to 3 of the drawings, the master cylinder of the invention is illustrated as part of a dual master cylinder assembly for use on an agricultural tractor for example, although the invention may equally be applied to a single cylinder.

The assembly includes a pair of master cylinders 1, 2 fed from a common reservoir 3 which bridges between the cylinders and connects to them by way of respective outlet connections 4 a-nd 5. Each cylinder has a downwardly extending pressure fluid outlet, one of which can be seen at 6 in Figure 1, by means of which the cylinder can be connected to a brake actuator associated with a wheel to be braked (not shown). The cylinders are provided with a common mounting flange 7 enabling the assembly to be mounted on a convenient support such as a vehicle bulkhead 8, for example.

Respective force input rods 9, 10 for the two pressure cylinders would normally be connected to driver-operated pedals (not shown) which may be latched together for simultaneous operation of the cylinders in order to effect straight line retardation of a vehicle, such as a tractor, but which may be unlatched for independent operation so that one or other cylinder may be actuated individually in order to effect a spin turn of the vehicle. The cylinders 1 and 2 are interconnected by a transfer passage formed by a pipe 11 secured to respective bosses 12, 13 welded to the outer surfaces of the respective cylinders. Each end of the transfer passage is provided with a conventional transfer valve mechanism, of which one can be seen at llA in Figure 1 and which forms no part of the present invention.

The reservoir 3 is connected to the cylinders by way of a connector element, illustrated generally at 14 and having a pair of tubular bosses 15, 16 into which the reservoir connections 4 and 5 are press-fitted, the bosses communicating with a transverse body 17 which extends between the cylinders 1 and 2 and forms, at each end thereof, a cylindrical connector 18, 19 having an internal dimension such as to enable it to be press fitted over the adjacent end portion of the cylinder in fluid-tight manner. The bosses 15, 16 are surrounded by respective clamping rings 15A, 16A and the cylindrical connectors 18, 19 have corresponding clamping rings, one of which is seen at 18A, in Figure 1. The body 17 of the connector element 14 is spaced from the adjacent end walls 20 of the cylinders 1 and 2 at 21, enabling the body 17 to act as a fluid supply passage, in the manner to be described.The connector element is inherently resilient, being made from plastics material, for example, and the body 17 is thus able to provide a degree of flexibility accommodating slight relative movement between the two cylinders when mounted for use.

The cylinders 1 and 2 are identical in construction and operation and one of them will now be described in more detail in relation to Figure 1. The cylinder is formed by a thin-walled drawn steel tube and contains a pressure piston 22 slidable therein to perform a working stroke under the action of the force input rod 10. The end wall 20 of the cylinder has a recuperation port 23 which is conveniently produced during the upsetting of an originally open cylinder end to form the cylinder end wall 20. The recuperation port 23 is controlled by a conventional centre valve assembly 24 carried by a rod 25 mounted in the piston 22, in the usual manner. The cylinder 1 is formed, at an upper region thereof, with a bleed port 28 and an associated valve which forms no part of the present invention.

The alternative embodiment illustrated in Figures 4 to 6 is again in the form of a dual master cylinder assembly including a pair of master cylinders 30, 31 of the invention, similar in construction and operation to those of Figures 1 to 3. The reservoir has a relatively narrow central part 36 extending forwardly to join a wider part 37 which spans the ends of the cylinders and is provided with a pair of integral necks 38, one of which is seen in Figure 4, into which the forward end portion of the cylinders are inserted.

The reservoir portion 36 has a pair of oppositely extending lateral projections 32, 33 towards its rear end which rest on the cylinders to afford additional support for the reservoir. They also engage closely behind transfer passage connectors 34, 35 to aid axial retention of the reservoir on the cylinders. The entire reservoir may conveniently be made in a single piece by a blow moulding or similar operation. Housed closely within each neck 38 is a grommet 39 which is a sealing fit around the external cylinder surface. A lip 44 of the grommet provides a retaining abutment for the end of the neck 38 and further axial retention is provided by inwardly curving the neck 38.

Respective inward protrusions 40 opposite each cylinder end ensure that the outer wall 41 of the reservoir remains spaced from the cylinder end walls 42 to permit flow of fluid through recuperation ports 43 in those end walls.

Although in the embodiments described, the reservoir has been mounted on the cylinder, it may alternatively be mounted remotely and the connector extended, as required, from its mounting location on the cylinder outer surface, to form a connection therewith. All embodiments of the invention may be used in multi-cylinder assemblies, as described, or as single master cylinders, depending on the intended manner of use.

Claims

CLAIMS.

1. A master cylinder comprising a pressure cylinder and a separately made fluid reservoir mounted thereon, the reservoir being connected to the cylinder by connecting means surrounding the outer surface of the cylinder in fluid-tight relationship.

2. A master cylinder according to Claim 1 wherein the connecting means forms an elbow of which one branch surrounds said cylinder outer surface and the other branch forms a connection with a reservoir port.

3. A master cylinder according to Claim 2 wherein a wall of the connector is spaced from an end wall of the cylinder to form a passage between a recuperation port of the cylinder and said reservoir port.

4. A master cylinder according to Claim 1 wherein the connecting means is generally annular and the reservoir forms an axially directed connecting portion which surrounds said cylinder outer surface in spaced relationship, the connecting means sealing between said cylinder outer surface and the opposed internal surface of said reservoir connecting portion.

5. A master cylinder according to Claim 4 wherein an internal wall of the reservoir lies in spaced relationship to an outer end wall of the cylinder to permit communication between a recuperation port formed in said end wall and the interior of the reservoir.

6. A master cylinder according to Claim 4 or Claim 5 wherein the reservoir is restrained axially of the cylinder by a portion thereof engaging a surface remote from said connecting means of a port connector of the cylinder.

7. A master cylinder according to any one of Claims 4 to 6 wherein the reservoir extends along a substantial part of the cylinder length and is supported on said cylinder outer surface.

8. A master cylinder according to any one of the preceding claims wherein said connecting means is inherently flexible.

9. A master cylinder substantially as hereinbefore described with reference to Figures 1 to 3 or Figures 4 to 6 of the accompanying drawings.

10. A master cylinder assembly comprising a pair of master cylinders according to any one of the preceding claims and a common reservoir connected to each master cylinder by way of said connecting means.