GB2032554A

GB2032554A - Master cylinders

Info

Publication number: GB2032554A
Application number: GB7934432A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1978-10-23
Filing date: 1979-10-04
Publication date: 1980-05-08

Abstract

A master cylinder comprises a cylinder body (1), and a collar (6) located on the cylinder body. To avoid problems associated with welding or brazing of the collar to the body, the collar is located by a retaining member (9) engaging in an aperture (12) in the cylinder body, a fluid passageway (12, 14, 13) extending from within the cylinder body and through the collar. The retaining member may take the form of a screw or bolt which has a screw-threaded connection with the collar and which has a projection (11) extending into said recess or aperture. <IMAGE>

Description

SPECIFICATION Master cylinders This invention relates to master cylinders for vehicle braking systems.

Master cylinders comprise a body having a bore in which a piston is sealingly slidable to pressurise fluid in a chamber having an outlet opening for connection to one or more wheel brake cylinders and an inlet opening for connection to a reservoir.

For a braking system having a plurality of braking circuits the master cylinder has a corresponding number of pistons and chambers.

For many years the master cylinder was cast from iron and the cylinder bore and the inlet and outlet openings were machined. The housing was enlarged in the region of the inlet and outlet openings to permit formation of the openings and to permit coupling of pipework, for example by screw-threaded unions. Such master cylinders had the disadvantages that they were heavy and relatively expensive to produce, requiring skilled machining operations.

To overcome the disadvantage of weight, it has been proposed to cast the master cylinders from aluminium, but because of the problems associated with the aluminium castings, such as porosity, a high scrap rate has been experienced, with consequential high costs.

Another proposal for overcoming the disadvantages has been to form a cylinder by deep drawing to provide the bore for the piston and drilling in the cylinder the openings for the inlet and outlet Thereafter a collar is attached to the cylinder, the collar having an aperture for communication with the outlet and having a means, usually a screw thread, for connection of a brake pipe to the aperture. Also, the reservoir is connected to the cylinder with an opening communicating with the inlet opening of tha cylinder. The collar may be brazed or welded to the cylinder, with the disadvantage that the welding or brazing may cause distortion of the cylinder and thus of the internal bore. Also, the attachment operation has to be performed either by skilled labour or by a machine, and in either case is expensive.It has been proposed that the collar be of plastics material molded on to the cylinder, but such a collar is subject to "creep" and difficulties arise in sealing between the collar and the cylinder to prevent fluid leaks.

The aim of the present invention is to provide a master cylinder which is relatively cheap and easy to produce and which obviates one or more of the above-mentioned disadvantages.

In accordance with the invention, there is provided a master cylinder comprising a cylinder body, and a collar located on the cylinder body by a retaining member engaging in an aperture or recess in the cylinder body, a fluid passageway extending from within the cylinder body, and through the collar.

Preferably, the retaining member is a screw or bolt which has a screw threaded connection with the collar and which has a projection engaging in said recess or aperture.

Optionally the closure plug disclosed in our copending application number 19605/78 could be used in place of the screw threaded retaining member, engaging said recess or aperture in like manner.

The retaining member may have a passageway therein which communicates the opening in the collar with the interior of the cylinder body.

Alternatively the opening in the collar may communicate with an outlet port in the cylinder body.

Preferably, the master cylinder has two such collars, one of which also serves to locate a reservoir for hydraulic fluid.

Some forms of master cylinder in accordance with the invention and a modification thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial cross-sectional view of one form of master cylinder, Figure 2 is a sectional view taken on line Il-Il of Figure 1, Figure 3 is a sectional view of a collar of Figures 1 and 2 taken on line Ill-Ill of Figure 2, Figure 4 is an axial cross-sectional view of another form of master cylinder, Figure 5 is a cross-sectional view taken on line V-V of Figure 4, Figure 6 is a transverse cross-sectional view of a modified form of collar, and Figure 7 is a sectional view of the collar of Figure 6 taken on line VIl-VIl of Figure 6.

Referring to Figures 1 to 5, each form of master cylinder comprises a deep drawn cylinder body 1 in which are slidable two pistons 2, 3 arranged to pressurise chambers 4, 5 in the usual way. Two collars 6, 7, one associated with each chamber, are a sliding fit on the cylinder body 1 and each collar has an aperture 8 which is partially screw threaded to receive a retaining member 9 in the form of a bolt or screw.

In the master cylinder of Figures 1 to 3, each retaining member 9 has a projection 11 which engages in an aperture 1 2 formed in the cylinder body 1. A transversely extending aperture 13 opens into the interior of the collar and communicates with the interior of the body 1 through an annular passageway portion 14 and through the aperture 12. Two face seals 1 5 seal the passageway portion 14, as best seen in Figure 1, the seals 1 5 seating in recesses 1 6 formed in the collar (Figure 3). Thus, a passageway is formed by the aperture 13, portion 14 and aperture 12.

Alternatively, an aperture may be formed in the master cylinder wall adjacent the inner end of aperture 1 3 to provide a more direct fluid flow path. The aperture 1 3 has a screw thread portion 1 3A for attachment of pipework through a suitable union.

A reservoir 1 7 is mounted on and located by the collar 7 and is secured to the cylinder body 1 by any suitable means.

The form of assembly of Figures 4 and 5 is similar to that of Figures 1 to 3, and corresponding parts have been given the same reference numerals. In the assembly of Figures 4 and 5, the transverse aperture 1 3 in the collar communicates with the interior of the body 1 through a passageway portion 18 formed in the retaining member 9. In that case, seals 20 are provided to prevent the passage of fluid past the retaining member.

An annular recess 1 8A is formed between the member 9 and the collar to allow for possible misalignment of the passageway portion 18 and aperture 13. In this embodiment the passageway is provided by portion 18, recess 1 8A and aperture 13.

In Figures 6 and 7 there is shown a modified form of collar which is only part annular. The transverse aperture 1 3 opens into a shallow recess 21 formed in the inner surface of the collar.

Extending radially inwardly from the inner surface of the collar and fast therewith is a pin 22 which is engageable in an aperture 1 2 in the master cylinder body to locate and retain the collar on the body. Surrounding the recess 21 is a deeper, oval recess 23 which receives a seal, not shown. The part annular form of the collar provides sufficient resilience to enable the collar to be assembled on the cylinder body, with the pin sliding along the outer surface of the body until it engages in a recess or aperture in the body.

It will be appreciated with some modification of the configuration of the member 9, to provide for connection of a union, the passageway could extend axially through the member.

The above-described master cylinder assemblies have the-advantage that the body 1 is relatively cheap to produce, as compared to castings, and the collars can be filled thereto using unskilled labour, as compared to the skilled labour or expensive machinery required for welding or brazing collars to a body.

Claims

1. A master cylinder comprising a cylinder body, and a collar located on the cylinder body by a retaining member engaging in an aperture or recess in the cylinder body, a fluid passageway extending from within the cylinder body and through the collar.

2. A master cylinder according to claim 1, wherein the retaining member comprises a screw or bolt which has a screw-threaded connection with the collar and which has a projection extending into said recess or aperture.

3. A master cylinder according to claim 1 or 2, wherein the passageway has an opening from the exterior of the collar and a portion of the passageway extends between the exterior of the cylinder body and the interior of the collar, said portion being surrounded by one or more seals.

4. A master cylinder according to claim 3, wherein said portion of the passageway is annular.

5. A master cylinder according to any of claims 1 to 4, wherein the retaining member engages in an aperture in the cylinder body, said aperture forming part of said passageway.

6. A master cylinder according to claim 1 or 2, wherein at least a portion of the passageway extends through the retaining member.

7. A master cylinder according to claim 6, wherein said portion of the passageway communicates with an opening in the collar through the intermediary of an annular portion between the retaining member and the collar.

8. A master cylinder according to any one of claims 1 to 7, wherein the collar is annular.

9. A master cylinder according to claim 1, wherein the retaining member is a projection fast with the collar and extending from the internal surface of the collar.

10. A master cylinder according to claim 9, wherein the collar is part annular to provide a degree of resilience to permit assembly of the collar on the cylinder body.

11. A master cylinder according to any of claims 1 to 10, wherein two said collars are provided, one collar serving to locate a reservoir for hydraulic fluid.

12. A master cylinder constructed and arranged substantially as herein described with reference to Figures 1 to 3, or Figures 4 and 5, or as modified by Figures 5 and 6 of the accompanying drawings.