GB2137295A

GB2137295A - Master cylinder

Info

Publication number: GB2137295A
Application number: GB08407578A
Authority: GB
Inventors: Stuart John Briggs; David John Parker; Peter Schluter
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1983-03-31
Filing date: 1984-03-23
Publication date: 1984-10-03
Also published as: GB2137295B; GB8407578D0

Abstract

A fabricated master cylinder includes a pressure cylinder (1) and a separately made reservoir (13) mounted thereon by way of a mounting device (19) (21) on the cylinder and a mounting formation (23) on the reservoir. The mounting device (19) and reservoir (13) provide restraint surfaces for engagement by legs (28) of a locking device (29) slidable in grooves (27) and which, when so engaged, maintains the cylinder and reservoir in co-operative relationship, in an alternative bayonet coupling arrangement, Fig. 7 the restraint surfaces are on respective parts of the mounting device and formation which, themselves act as locking means. <IMAGE>

Description

SPECIFICATION Master cylinder This invention relates to a master cylinder for vehicle braking systems and more particularly to a master cylinder of the fabricated type which includes a pressure cylinder and a separately made reservoir mounted thereon, the interiors of the pressure cylinder and reservoir being in communication by way of transverse ports through the peripheral cylinder wall.

It has been proposed to retain the reservoir on the pressure cylinder by means, for example, of a variety of clamping or clipping devices co-operating with the two components, sometimes in conjunction with a further connection formed by an inter-engaging spigot and recess respectively on the two components. These arrangements can be unsatisfactory in that the assembly of the reservoir and cylinder can lack sufficient rigidity which can lead to problems of sealing between the two components. They can also lead to a significant increase in the height of the assembly as compared with some conventional types of master cylinder.

An object of the invention is to provide a master cylinder of the fabricated type in which the aforesaid disadvantages are minimised or avoided.

According to the present invention, a master cylinder comprises a pressure cylinder, a reservoir mounted thereon, a mounting device on the cylinder providing at least one retaining surface, a formation on the reservoir such as to engage with the mounting device and having at least one retaining surface which, when the device and formation are so engaged, is opposed to said mounting device retaining surface, and locking means operable to retain the reservoir and cylinder in operative working relationship by way of said opposed retaining surfaces.

Conveniently, said reservoir formation or said mounting device forms a recess complementary with and for the reception of the other of said formation and device, the recess containing a resilient sealing ring and the arrangement being such that engagement of said formation or device in the recess compresses the sealing ring between opposed surfaces to form a fluid-tight seal.

The locking means may be a separate component capable of engaging said opposed surfaces to effect the aforesaid retention of the reservoir and cylinder.

Alternatively, the locking means may be constituted by respective parts of said mounting device and reservoir formation, each of which is provided with one of said opposed surfaces which are brought into locking cooperation by relative movement between the reservoir and cylinder.

Typically, said relative movement includes a first linear movement to bring said surfaces into adjacent relationship, and a second rotary movement to bring them into locking engagement.

Preferably, said mounting device incorporates one or more ports permitting communication between the reservoir and pressure cylinder.

The invention will now be described, by way of example, with reference to the accompanying drawings: Figure 1 is a fragmentary longitudinal crosssection of one form of the master cylinder of the invention; Figure 2 is a longitudinal cross-section of part of the master cylinder of Figure 1; Figure 3 is an end view of the part illustrated in Figure 2; Figure 4 is a fragmentary perspective view illustrating part of the master cylinder of Figure 1; Figure 5 is a longitudinal cross-section of another embodiment of the master cylinder of the invention; Figure 6 is an end view, partly in crosssection, of the master cylinder of Figure 5, and Figure 7 is a view along the line 7-7 of Figure 6.

Figure 1 of the drawings illustrates part of a tandem master cylinder for use in a dual circuit braking system and comprising a pressure cylinder 1 shown as a thin walled tube of uniform wall thickness having an axial blind bore 2, the open end of which is closed by a closure member 3. The internal components of the pressure cylinder are conventional and have not been shown in detail. However, the rearmost one 4 of a pair of pistons within the bore 2 is illustrated, this piston having a rearwardly extending sleeve 5 through which would extend, in use, an actuating rod (not shown) connected in conventional manner to an actuating member (not shown) of a booster of which a body shell portion is indicated at 6.The shell 6 is shaped to form a retaining flange 7 which lies behind a shoulder 8 of the closure member 3 to retain the closure member in position against a mounting flange 9, between which and the shoulder 8 is trapped a sealing 0-ring 10. A boss 3A at the outermost end of the member 3 forms a bearing of axial extent sufficient to provide adequate support for the sleeve 5 of the piston 4. The closure member 3 is positively retained axially on the cylinder 1 by means of projections 11 on the inner wall of the closure member engaging in an annular groove 1 2 in the outer wall of the cylinder 1. This arrangement is illustrated more clearly in Figures 2 and 3, from which the projections 11 are seen to be three in number and symmetrically distributed around the inner wall of the closure member 3.

A reservoir 1 3 is mounted on the upper side of the cylinder 1 and communicates respectively with the internal chambers of the cylinder through ports 14 and 1 5 formed transversely through the cylinder wall. The reservoir communicates with the port 1 5 by way of an axial passage 1 6 formed in an axial extension 17 of the closure member which is engaged within a lateral opening 1 8 in the wall of the reservoir. The reservoir 1 3 is mounted on the cylinder 1 by way of a mounting device 1 9 which is described in more detail hereafter with reference to Figures 1 and 4.The mounting device 1 9 is in the form of a generally rectangular dish-like member, of which the base 20 is mounted on the upper side of the cylinder 1 and welded thereto. The base 20 has an opening 21 therethrough which is aligned with the port 14 in the cylinder 1 to permit communication between the mounted reservoir and the bore 2 of the cylinder 1. The device 1 9 has an outwardly extending flange 22 around the whole of its periphery for the purpose to be described. The reservoir 1 3 is provided with a mounting formation 23 which includes a central rectangular recess 24, around the periphery of which is formed a groove 25 which contains a seal 26.The formation also includes, respectively along opposed sides thereof, a pair of grooves 27 which receive the legs 28 of a generally U-shaped locking device 29 which can be seen more clearly from Figure 4.

It will be seen from Figure 4 that the peripherial extent of the flange 22 of the mounting device 1 9 is such that the flange fits closely within the recess 24 of the mounting formation of the reservoir. In order to mount the reservoir on the cylinder, the mounting formation of the reservoir is offered to the mounting device 1 9 so that the recess 24 of the formation is in register with the mounting device. The reservoir can then be lowered into position to bring the peripheral flange 22 of the mounting device within the recess 24. At this point, the sealing ring 26 protrudes slightly out of the groove 25 and a force is now applied to the reservoir to compress the seal.This action results in sufficient clearance being provided between the undersurface of the flange 22 and the facing surface of the groove 27 to permit the locking device 29 to be slid transversely between these facing surfaces to a position in which it abuts against the mounting device 1 9. The reservoir is thereby securely locked to the cylinder and the sealing ring 26 is maintained in a lightly compressed state which ensures a fluid-tight seal around the mounting device.

Fluid is able to flow from the interior of the reservoir via an opening 23A, whence it may pass through the port 14 into the pressure cylinder.

In the embodiment of Figures 5 to 7, the general arrangement of the cylinder 1 and reservoir 1 3 is similar to that described above and the internal cylinder components are again conventional. The mounting device 19 in this embodiment has a base 30 having a pair of opposed outwardly directed flanges 31, each having an outermost edge 32 of part-circular form. The remaining edges of the flanges form part of a pair of opposed flat sides 33 of the base. The base has an upstanding hollow cylindrical boss 34 which is closely fitted within a corresponding bore 35 of the reservoir. A seal 26 housed in a recess 25 is compressed radially outwardly by insertion of the boss within the bore 35 and forms a fluid-tight seal between the reservoir and boss.Figure 6 shows, respectively at the right and left hand sides of the centre line thereof, two possible alternative arrangements for housing the seal. At the right hand side of the centre line, recess 25 is open in a downward direction and the seal 26 is retained therein by the upper surface of the adjacent flange 31. At the left hand side of the centre line, the recess 25 is shown as a groove within which the seal 26 is fully contained when the components are in their assembled condition, as shown.

As will be seen more clearly from Figures 6 and 7, the reservoir is formed with a pair of opposed slots 37 which are bounded at the lowermost extremity of the reservoir formation 23 by radially inwardly directed arms 38, each of which has a radially innermost edge 38A which is arcuate about the centre of the boss 34 and spaced from the outer surface of the boss. The inner surfaces 37A of the slots 37 are similarly arcuate about the same centre and the dimensions of the slots 37 and flanges 31 are chosen so that a small clearance is provided between the edges 32 of the flanges and the surfaces 37A of the slots 37.

The radially inward extent of the arms 38 is such that they overlap the flanges 31 of the formation 1 9 so as to retain the reservoir in position on the cylinder. In order to assemble the reservoir and cylinder, the boss 34 is offered to the bore 35 with the flanges 31 angularly displaced through about 90 relative to the position illustrated in Figure 7. This enables the boss 34 to be fully inserted in the bore 35, without interference between the flanges 31 and arms 38, the flanges 31 thereby being brought into positions of alignment with the slots 37. By subsequent relative rotation between the reservoir and cylinder, the flanges 31 may be moved into the slots to the positions illustrated in Figure 7, so that the reservoir is effectively locked in position on the cylinder. Unwanted further relative rotation between these components, once assembled, is prevented by inserting the extension 1 7 into the corresponding bore in the reservoir, as explained in connection with the previous embodiment, so that the exten sion 1 7 now performs the dual function of providing a fluid path between the respective interiors of the cylinder 1 and reservoir 1 3 and of preventing the aforesaid unwanted relative rotation. It will be understood that the numbers of arms 38 and flanges 31 may be varied in any convenient manner and, in ar rangements where the extension 1 7 is not provided, or additional security against relative rotation of the components is required, alternative or additional locking means may be employed.

It will be understood that, in the Figure 1 embodiment, for which no relative rotation between the reservoir and cylinder is required, two or more mounting devices may be provided, spaced along the cylinder, in place of the single device illustrated, and an appropri ate number of mounting formations on the reservoir would then be required. In a further alternative arrangement applicable to all em bodiments, the or each mounting device may be employed solely for mounting purposes without providing any communication between the reservoir and cylinder ports. Separate porting arrangements between the reservoir and cylinder would then be provided. The invention may be applied to both single and tandem master cylinders irrespective of the nature of their internal components which may take a variety of forms.

Claims

1. A master cylinder comprising a pressure cylinder, a reservoir mounted thereon, a mounting device on the cylinder providing at least one retaining surface, a formation on the reservoir such as to engage with the mounting device and having at least one retaining surface which, when the device and formation are so engaged, is opposed to said mounting device retaining surface, and locking means operable to retain the reservoir and cylinder in operative working relationship by way of said opposed retaining surfaces.

2. A master cylinder according to Claim 1 wherein said reservoir formation or said mounting device forms a recess complementary with and for the reception of the other of said formation and device, the recess containing a resilient sealing ring and the arrangement being such that engagement of said formation or device in the recess compresses...

the sealing ring between opposed surfaces to form a fluid-tight seal.

3. A master cylinder according to Claim 1 or Claim 2 wherein the locking means is a separate component capable of engaging said opposed surfaces to effect said retention of the reservoir and cylinder.

4. A master cylinder according to Claim 3 wherein the locking means has a pair of spaced parallel legs which engage in respective opposed grooves in the internal wall of the reservoir formation, the mounting device having a pair of opposed lateral flanges which lie adjacent said grooves whereby each leg may engage a pair of said opposed surfaces to effect said retention of the reservoir and cylin der.

5. A master cylinder according to Claim 1 wherein the locking means is constituted by respective parts of said mounting device and reservoir formation, each of which is provided with one of said opposed surfaces which are brought into locking co-operation by relative movement between the reservoir and cylinder.

6. A master cylinder according to Claim 5 wherein said relative movement includes a first linear movement to bring said surfaces into adjacent relationship, and a second rotary movement to bring them into locking engage ment.

7. A master cylinder according to Claim 6 wherein said parts comprise outwardly di rected opposed flanges on the mounting de vice and corresponding grooves in said reser voir formation, the grooves being angularly spaced such that the flanges may be placed between the grooves and, by relative rotation between the reservoir and cylinder, moved into positions within the grooves such that the cylinder and reservoir are retained by said surfaces in said working relationship.

8. A master cylinder according to any one of Claims 5 to 7 wherein restraint means are provided to prevent relative movement between the reservoir and cylinder such as would move said surfaces away from locking engagement.

9. A master cylinder according to Claim 7 wherein said restraint means is a fluid connec tor pipe extending between part of the pres sure cylinder and the reservoir in a direction laterally of the latter and engaging within a laterally extending bore of the reservoir.

10. A master cylinder according to any one of Claims 5 to 9 wherein said mounting device includes a cylindrical boss engagable with a corresponding bore in said reservoir formation, a sealing ring being provided between said boss and formation and arranged so as to be radially compressed during engagement of the boss within the bore so as to provide a fluid-tight seal.

11. A master cylinder according to any one of the preceding claims wherein said mount ing device incorporates one or more ports permitting communication between the reservoir and pressure cylinder.

1 2. A master cylinder, substantially as here inbefore described with reference to Figures 1 to 4 or Figures 5 to 7 of the accompanying drawings.