GB2130669A

GB2130669A - Retention device

Info

Publication number: GB2130669A
Application number: GB08328734A
Authority: GB
Inventors: David John Parker; Redmon Mccusker; Stuart John Briggs
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-11-09
Filing date: 1983-10-27
Publication date: 1984-06-06
Also published as: GB2130669B; GB8328734D0

Abstract

A retention device (12) for retaining an actuating rod (4) for piston (2) within a hydraulic brake cylinder(1) is in the form of a generally annular body (Fig. 3) of resilient material which is split radially to form a gap (14) enabling the body to be radially compressed for insertion into an annular internal groove (13) of the cylinder (1). The annular body (12) has inwardly projecting legs (15) of which the inwardly facing surfaces form seat portions shaped to correspond with a surface (11) on a head (8) of the rod (4) whereby it is retained within the cylinder (1) by the device (12) whilst being permitted a degree of angular movement relative to the cylinder. <IMAGE>

Description

SPECIFICATION Retention device This invention relates to a retention device for retaining an elongate member within a hollow body, the device being particularly useful for retaining an operating rod within a pressure cylinder such as an hydraulic brake master cylinder. The invention also embraces an assembly of an elongate member within a hollow body incorporating such a retention device.

One cònventional means for retaining an operating rod within a pressure cylinder consists of a washer shaped to correspond with and engage an outer surface portion, typically of partspherical form, of an enlargement at or near one end of the rod and a circlip or similar divice to retain the washer in position so as to prevent withdrawal of the rod from the cylinder, whilst at the same time permitting a degree of angular movement of the rod relative to the cylinder in order to facilitate its actuation by a foot pedal for example. A typical operating rod may have an enlarged head at one end to provide a pivotal bearing for engagement with the retaining means, and a clevis or the like at the other end for connection to said foot pedal.One disadvantage of the conventional arrangement is that either the clevis or head of the rod must be removable in order to permit the washer to be placed over the rod. It is also disadvantageous in terms of economy and assembly time for the retaining means to include a plurality of parts.

An object of the present invention is to provide a retention device for retaining an elongate member within a hollow body, which enables the disadvantages referred to above to be overcome.

According to the present invention, a retention device for retaining an elongate member within a hollow body comprises a generally annular body of resilient material which is radially split to permit the passage laterally therethrough of a relatively narrow part of the elongate body and to permit radial compression of the annular body to enable it to be engaged by resilient recovery in a circumferential groove in an internal wall of said hollow body, the internal annular circumferential surface of the annular body being shaped to correspond with a surface of a relatively enlarged portion of said member in such a manner that, with the annular body engaged in said groove, and the member extending axially through the annular body with said surface in engagement with the annular body, the member is retained in the cylinder whilst being permitted a degree of angular movement by relative sliding movement of said surfaces.

In one convenient arrangement, the body has a plurality of inwardly projecting portions of which radially inner surface portions are shaped to correspond with said member surface and engageable with the latter. An advantage of this arrangement is that the circumferential portions of the body between the projections are relatively narrow in the radial direction and contribute to the flexibility of the body.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an end view of a cylinder and rod assembly incorporating one form of the retention device of the invention; Figure 2 is a view, partly in cross-section, along the line A-A of Figure 1, and Figure 3 is an elevation of an alternative form of the retention device of the invention.

The assembly illustrated in Figures 1 and 2 includes a cylinder 1, such as a master cylinder for use in a vehicle hydraulic braking system for example, the cylinder containing a reciprocal piston 2 and an associated seal 3. The piston is actuated by means of an operating rod 4, of which one end portion is housed in a recess 5 of the piston.

The rod 4 includes a shank 6 which extends between a clevis 7 at one end of the rod for connection to actuating means, such as a driveroperated pedal for example, and an enlarged head 8 disposed within the cylinder. A free end portion 9 of the head is of part-spherical or any other convenient arcuate shape for engagement with the interior of the recess 5 in a manner such as to permit some angular movement of the rod to occur relative to the piston 2 during actuation of the latter. A further portion 10 of the head 8 has a part-spherical surface 11 facing in the opposite direction to the surface 9 and of somewhat larger diameter than the latter.

The rod 4 is retained within the cylinder 1 by a retention device 12 housed within a groove 1 3 towards one end of the cylinder 1. The retention device 12 is of resilient material such as spring steel or plastics for example and, as will be seen more clearly from Figure 1, is of generally annular form but split to provide a gap 14 which enables the device to be radially inwardly compressible for assembly purposes.In its free state as shown, the external diameter of the device is slightly larger than the internal diameter of the groove 1 3. The device is provided with a plurality, in this case four, of radially inwardly projecting portions forming legs 15, the radially inner extremity of each leg being bent out of the main plane of the device and shaped to form an arcuate seat portion 16 of frusto-conical part-spherical form matching that of the rod head surface 11.

The seat portions 1 6 are arranged at equivalent radial positions so as to be simultaneously engageable with the rod head surface 11 in the manner and for the purpose to be described.

In order to assemble the cylinder 1, rod 4 and retention device 12, the gap 14 of the latter is offered to the shank portion 6 of the rod which is passed therethrough to an approximately central position within the device. The rod is then inserted into the cylinder and its free end surface 9 is engaged within the piston recess 5. The retainer is then passed along the shank 6 towards the cylinder and radially inwardly compressed to an extent such that it is of sufficiently small diameter to pass into the cylinder until opposite the groove 13, whereupon it is allowed to expand into the groove by resilient recovery.When in this position, the seat portions 1 6 of the legs 1 5 will engage the head surface portion 1 thereby to retain the rod within the cylinder and at the same time, by relative sliding movement between the seat portions and said head surface portion permit the rod a degree of angular movement which will be required to permit normal reciprocal actuation of the piston 2 from the pedal or other actuating device connected to the clevis 7. The head 10 is also able to move freely angularly within the piston recess 5 by virtue of its arcuate end surface 9.

It will be seen from Figure 1 that, with the retainer device installed in the cylinder, the width of the gap 14 is slighly less than the diameter of the rod 6. Although not essential, this is desirable in that it precludes the rod from passing through the gap, in use, into possibly damaging contact with the cylinder wall.

An alternative form of the retention device is shown in Figure 3, being basically similar to that of Figures 1 and 2, except that it is provided with only three projections or legs 1 5 upon which suitable seat portions are formed for engagement with the rod head surface 11. The device is again split to form a gap 14 so as to be radially inwardly compressible and assembly of the cylinder, rod and retention device is as described in connection with Figures 1 and 2.

It will be seen that the retention device of the invention performs both retention and seating functions, the provision of which has hitherto often necessitated the use of two separate components, such as a circlip and washer, and the device of the invention therefore permits economy of manufacture, as well as simplicity of assembly.

A further advantage over conventional arrangements is that the device, being split, may be passed over the relatively narrow shank 6 of the rod, which means that the rod may be manufactured in one piece, rather than having a removable end portion to permit passage of one or more components along the rod, as has hitherto been necessary with some conventional devices.

Claims

1. A retention device for retaining an elongate member within a hollow body comprising a generally annular body of resilient material which is radially split to permit the passage laterally therethrough of a relatively narrow part of the elongate body and to permit radial compression of the annular body to enable it to be engaged by resilient recovery in a circumferential groove in an internal wall of said hollow body, the internal annular circumferential surface of the annular body being shaped to correspond with a surface of a relatively enlarged portion of said member in such a manner that, with the annular body engaged in said groove, and the member extending axially through the annular body with said surface in engagement with the annular body, the member is retained in the cylinder whilst being permitted a degree of angular movement by relative sliding movement of said surfaces.

2. A retention device according to Claim 1 wherein the body has a plurality of inwardly projecting portions of which radially inner surface portions are shaped to correspond to said member surface and engageable with the latter.

3. A retention device according to Claim 2 wherein said inner surface portions are of partspherical form.

4. A piston and cylinder device having a piston actuating rod thereof retained within the cylinder by a retention device according to any one of the preceding claims engaged in an annular groove in the internal cylinder wall, said rod having a relatively enlarged head disposed within the cylinder, the surface portion of the enlarged head facing outwardly of the cylinder being shaped to correspond with said internal circumferential surface of the retention device, whereby the device retains the rod within the cylinder whilst permitting it a degree of angular movement by relative sliding movement of said surfaces.

5. A piston and cylinder device according to Claim 4 wherein the inwardly facing surface portion of the head is of arcuate shape and is engaged within a recess of the piston.

6. A retention device substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.

7. A piston and cylinder device substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 1 and 2 as modified by Figure 3 of the accompanying drawings.