GB2187246A - Master cylinder - Google Patents

Abstract

A method of making a fabricated master cylinder includes securing a base (5) to the outer surface of a pressure cylinder (1), forming a reservoir as a one-piece plastics moulding and securing and sealing the reservoir to the base member by upsetting a flange (7) of the base to trap a peripheral flange (9) of the reservoir. The base may alternatively provide a screw formation onto which the reservoir is screwed to secure the base and reservoir together. <IMAGE>

Description

SPECIFICATION Master cylinder This invention relates to a method of making a fabricated master cylinder for a vehicle brake or clutch system and 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. The invention also embraces a master cylinder made by the aforesaid method.

In some earlier proposals of this type, the reservoir, which is normally formed from components moulded from plastics material, is provided with spigots forming fiuid port connections, the spigots being engaged with corresponding sockets secured, as by welding, to the pressure cylinder body in alignment with said cylinder transverse ports. This arrangement is structurally complicated, requiring the provision of the aforesaid sockets and their individual welding to the cylinder. Moreover, the reservoir itself is necessarily of complicated configuration requiring the moulding thereon of the aforesaid spigots, which necessitates the formation of the reservoir in two separate moulded parts and their subsequent welding together.

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

According to the invention, a method of making a fabricated master cylinder comprises securing a base member to the outer surface of a pressure cylinder, forming a reservoir element by moulding from plastics material and securing the reservoir to the base member in fluid-tight relationship.

In one convenient form of the method, the base member and cylinder are of metal, and the base member is secured to the cylinder by welding. Typically, the reservoir element is secured to the base member by upsetting part of the member, conveniently at its periphery, over a surface of the reservoir element, such surface conveniently being provided by a peripheral flange. Alternatively, the base member may include a screw formation and the reservoir element is attached to the cylinder by screwing engagement of a corresponding thread thereon with the screw formation.

From another aspect of the invention, a fabricated master cylinder comprises a pressure cylinder, a base member secured to-the outer surface of the pressure cylinder, and a separately made reservoir element secured to the base member in fluid-tight relationship, means being provided to effect communication between the reservoir element and the interior of the cylinder.

Preferably, the base member includes an upset part conveniently at its periphery, serving to secure the reservoir element to the base member by overlying a corresponding part of the reservoir element, which may be in the form of a peripheral flange.

In one convenient practical arrangement, the reservoir element has an open side which is closed by the base member and a peripheral edge portion of the base member is turned over on to an outwardly projecting flange of the reservoir element to secure the two together. This is a particularly advantageous arrangement because the open-sided reservoir element may readily be made in one piece by a moulding operation, for example from plastics material, thereby eliminating the previous necessity of a second moulded component and a welding operation to join the reservoir components together.

In an alternative arrangement, the base member-and reservoir element may be provided with complementary screw threads which are screwed together to secure said member and element together.

The base member preferably has through holes communicating with ports through the cylinder wall in order to afford the necessary communication between the reservoir and pressure cylinder.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows one form of the master cylinder of the invention and, in part, illustrates an intermediate stage in the manufacture thereof; Figure 2 is a view similar to Figure 1 illustrating an alternative form of the master cylinder of the invention in completed state; Figure 3 is a view similar to Figures 1 and 2 illustrating a modified arrangement in the form of a tandem master cylinder; Figure 4 illustrates a further alternative form of the master cylinder of the invention in a partially assembled condition, and Figures 5 and 6 are sectional views of parts of Figure 4.The master cylinder illustrated in Figure 1 includes a pressure cylinder 1, which may conveniently be a drawn steel tube having a wall thickness of uniform diameter, and a mounting flange 2 secured against an outwardly directed peripheral flange 3 surrounding the open mouth of the tube. The closed end 1 A of the tube may be integrally formed, as shown, or formed by a suitable plugging technique. The mounting flange 2 is spaced from the flange 3 by spacer element 4 illustrated as integral with the mounting flange 2, although this may be a separate component, if desired.

The sleeve and mounting flange are secured in position by suitable conventional welding or bonding techniques. The assembly further comprises a base plate 5, conveniently in the form of a steel pressing and having, prior to assembly, welding projections arranged in a suitable configuration on its underside. The plate is initially provided with an upstanding peripheral flange 7, illustrated at the right-hand side of Figure 1 for the purpose to be described.

A separately made reservoir component 8, preferably moulded in one piece from plastics material, has one side open and surrounded by a peripheral flange 9. The upper wall of the reservoir is provided with an inlet orifice 10 which is threaded for the attachment thereto of a suitable closure member, in conventional manner.

The master cylinder of the invention is constructed from the aforesaid components by first welding the base member 7 to the outer surface of the pressure cylinder. For this purpose, the base member is placed in the required position on the cylinder and an electrical projection welding operation is carried out to cause the welding projections to fuse and thereby secure the base member to the cylinder. The resulting welded areas are illustrated at 6. One or more fiuid feed and recuperation holes 11 are then formed, by drilling or punching, through both the base plate and pressure cylinder wall so as to provide communication between the interior of the pressure cylinder and subsequently the interior of the reservoir.

The assembly is completed by placing the reservoir within the upstanding peripheral flange 7 of the base member, a seal 12, conveniently of the O-ring type, being placed between the underside of the peripheral flange 9 of the reservoir member and the opposed internal surface of the base member 5. The reservoir member is finally secured in position by overturning the flange 7, as indicated at the left-hand side of Figure 1, onto the upper surface of the flange 9 so as not only to overlie the flange in tight engagement therewith to effect securement, but also to compress the seal 11 to form a fluid-tight joint between the reservoir and base members.It will be understood that any other convenient form of seal, such as a flat rubber gasket or extruded viscous sealant could be used in place of the 0ring 11 and the flange 9 may be bonded to the base member 5 for additional security, prior to overturning of the flange 7. Moreover, the upper surface of the flange 9 may be inclined downwardly away from its outer edge, or otherwise shaped, in order to assist retention by the flange 7.

In the alternative embodiment illustrated in Figure 2, the base member 5 has a more pronounced dished shape, with only a relatively small projecting area 5A secured to the pressure cylinder. The reservoir member 8 is secured to the base member, as before, by rolling over the flange 7 of the base plate onto the flange 9 of the reservoir member, with or without prior adhesion or bonding between the two. Sealing is effected by interposition of a seal 12, as previously and the flange 9 has an upper surface shaped to form a curved bead.

Figure 3 illustrates a further alternative embodiment of the invention in the form of a tandem master cylinder, in which the reservoir member 8 is provided with an internal partition 8A with a through opening A, acting as a level aperture. Alternatively, communication between the two sides of the partition 8A for levelling purposes could be provided by channels formed in the internal surface of the top portion of the reservoir element. The base member 5 is similar to that used in the previous embodiments, except that two pairs of welding projections are provided and corresponding feed and recuperation holes 11 are formed within the areas defined by the welds 6, for co-operation with the two chambers of the tandem pressure cylinder 1, the latter being of conventional internal construction.

The assembly is produced, as before, by placing the reservoir element within the upstanding flange 7 of the base plate, interposing between the two components a flat flexible gasket 11 A which has an intermediate portion extending across it for engagement by the partition 8A in order to provide a fluidtight seal between the two compartments A, B of the reservoir element. The assembly is secured together, once again, by overturning the flanges 7 onto the peripheral flange 9 of the reservoir element, with or without prior adhesion or bonding between the two.

In the alternative embodiment illustrated in Figures 4 to 6, the base member 5' is of generally hollow cylindrical form with a closed end 13 which is secured to the cylinder 1 by projection welds 6, as before. The cylindrical wall 14 of the base member is formed with a screw thread 1 5 and the reservoir element 8', in the form of a hollow generally cylindrical bottle, is provided with a corresponding thread 16, enabling the element 8' and member 5' to be secured together by screwing action. The lower end of the bottle is open and is sealed against the end 13 of the base member by interposition of an annular gasket 17. The upper end of the bottle is threaded at 8A for the reception of a closure lid of conventional type.

The bottle is formed, adjacent its lower end, with locking projections 18 equidistantly spaced around the thread helix and each having a straight locking face 1 8A perpendicular to the bottle longitudinal axis and a peripherally extending curved face 1 8B joining the locking face to the adjacent wall of the bottle.

The lowermost part of the base member thread 15 is provided with corresponding projections 19 similar to those on the bottle. The bottle is secured to the base by screwing action (Figure 4 illustrates an intermediate position prior to final securement) and is sealed against the base 13 by trapping the sealing gasket 17. As the bottle approaches its final position the projections 18 encounter the projections 19 on the base member and are able to ride over them due to engagement of the curved surfaces 18B, 1 9B of the projections until the bottle is tightly screwed in position.

Reverse screwing is then prevented by engagement of the straight sides 18A, 19A of the projections, thereby ensuring that the bottle does not become inadvertently loosened during removal of the reservoir cap, or by vibration to which the assembly may be subjected in use. It will be understood that the numbers, shapes and general arrangement of the locking projections may be varied as desired. Alternative locking devices such as clamps may be used in place of or in addition to the projections described.

It will be seen that the invention provides a convenient method of producing a master cylinder, primarily for use in vehicle brake and clutch systems, obviating, as it does, various complications in the structure of the components and in their final assembly, as compared with conventional master cylinders.

Claims (16)

1. A method of making a fabricated master cylinder comprising securing a base member to the outer surface of a pressure cylinder, forming a reservoir element by moulding from plastics material and securing the reservoir to the base member in fluid-tight relationship.

2. A method according to Claim 1 wherein the base member and cylinder are of metal and the base member is secured to the cylinder by welding.

3. A method according to Claim 1 or Claim 2 wherein the reservoir element is secured to the base member by upsetting part of the latter over a surface of the reservoir element.

4. A method according to Claim 3 wherein said surface is provided by a peripheral flange of the reservoir element.

5. A method according to Claim 1 or Claim 2 wherein the base member includes a screw formation and the reservoir element is attached to the cylinder by screwing engagement of a corresponding thread thereon with the screw formation.

6. A method according to Claim 5 wherein the reservoir element is held securely in position on the base member by the interengagement, as the reservoir element approaches its final position, of complementary formations respectively on the base member and reservoir element, said formations being shaped and arranged so that, upon said interengagement, the projections act uni-directionally to permit movement of said element only towards its final position.

7. A method of making a fabricated master cylinder, substantially as hereinbefore described with reference to Figures 1, 2, 3 or 4 of the accompanying drawings.

8. A fabricated master cylinder made by the method of any one of Claims 1 to 7, comprising a pressure cylinder, a base member secured to the outer surface of the pressure cylinder, and a separately made reservoir element secured to the base member in fluidtight relationship, means being provided to effect communication between the reservoir element and the interior of the cylinder.

9. A master cylinder according to Claim 8 wherein the base member includes an upset part serving to secure the reservoir to the base member by overlying a corresponding part of the reservoir element.

10. A master cylinder according to Claim 9 wherein said corresponding part of the reservoir element is a peripheral flange.

11. A master cylinder according to Claim 8 or Claim 9 wherein the reservoir member has an open side which is closed by the base member and a peripheral edge portion of the base member is turned over on to an outwardly projecting flange of the reservoir element to secure the two together.

12. A master cylinder according to Claim 8.

wherein the base member and reservoir element are provided with complementary screw threads which are screwed together to secure said member and element together.

13. A master cylinder according to Claim 12 wherein the reservoir is held securely in position on the base by the interengagement of complementary formations respectively on the base member and reservoir element of complementary formations which co-operate to prevent relative movement of the base member and reservoir element in a direction such as to unscrew said threads.

14. A master cylinder according to Claim 13 wherein said formations on one of the base member and reservoir element are projections each having a generally peripherally extending curved surface having an end surface extending generally perpendicularly to the rotational screwing axis of the member and element, said end surfaces co-operating with the formations on the other of the element and member to prevent unscrewing thereof.

15. A master cylinder according to any one of Claims 8 to 12 wherein the base member has through holes communicating with ports through the cylinder wall in order to afford the necessary communication between the reservoir element and pressure cylinder.

16. A fabricated master cylinder substantially as hereinbefore described with reference to Figures 1, 2, 3 or Figures 4 to 6 of the accompanying drawings.