GB2213878A

GB2213878A - Shaft seals

Info

Publication number: GB2213878A
Application number: GB8729964A
Authority: GB
Inventors: Ronald Geoffrey Mccoy
Original assignee: AUTOSPIN
Current assignee: AUTOSPIN
Priority date: 1988-01-19
Filing date: 1988-01-19
Publication date: 1989-08-23
Anticipated expiration: 2008-01-19
Also published as: GB2213878B; GB8729964D0

Abstract

An annular seal is provided in which a coil spring 18 supporting a sealing element 12 is retained in its working position by a number of hooking elements 20 which extend between coils of the spring and are secured to a body part of the seal, e.g. inner metal shell 16 assembled in an outer metal shell 10. The hooking elements are preferably of thinner gauge wire than the spring. A clip comprising two hooking elements may be formed from a single piece of wire such that the hooking elements project from a base formation by means of which the clip is secured to the body part of the seal. <IMAGE>

Description

SHAFT SEALS This invention is concerned with improvements in or relating to annular seals for sealing around machine shafts and rolls and similar cylindrical elements, the seal being arranged to be accommodated and secured in some form of h using around the shaft.

In a conventional oil seal construction, a coil spring is arranged to support a flexible and resilient sealing element (e.g. of rubber) of the seal, the coil spring extending in a closed loop around the seal to bear laterally against the sealing element.

Particularly with larger seals, such as may be used in association with the rolls of paper and other rolling mills, buffeting of the seal in operation can cause the supporting spring to become dislodged from its required operating position.

As a guard against that problem it is known to introduce a spring retainer which is secured to a casing of the seal and is hooked over the coil spring, at intervals along its continuous length, to hold the spring in position. One way in which it is known to effect this is to utilise a thin stainless steel strip of a sharply zig-zag form, the peaks of the strip along one side edge being secured to the casing and the peaks along the other side edge being folded over the spring to hook on to the spring. However, two difficulties in particular can arise with that known kind of spring retainer. First, the portions of the flat strip folded over the spring, to form the spaced retaining hooks, come between the spring and the sealing element. These cause slight distortions of the sealing element which can impair the performance of the seal.Secondly, the coil spring is generally not free to move at all relative to the retaining hooks. The consequence of that is that the retaining hooks are subjected to loadings in operation which should more properly be absorbed by the coil spring alone, and this can lead to fractures of the retaining hooks.

It is an object of the present invention to provide an annular seal comprising a spring supporting a flexible sealing element and comprising spring-retaining means of a generally improved kind.

The invention provides in one of its aspects an annular seal comprising a coil spring arranged to support a flexible sealing element t of the seal and spring-retaining means arranged to retain the spring in a required working position within the seal, coils of the spring being spaced apart and the retaining means comprising a plurality of hooking elements each extending between adjacent spaced coils of the spring and being hooked over to the outside of the spring.

The hooking elements can most conveniently be formed of wire, for example of stainless steel, most preferably of thinner gauge than the material of the spring.

Two hooking elements may be formed from a single piece of wire, or other thin material, in a single retaining clip, the two elements projecting from a base formation by means of which the clip is secured to a body part of the seal. In a most preferred construction, the base formation is arranged to comprise gripping elements which can grip between them a flange of the body part.

There now follows a detailed description, to be read with reference to the accompanying drawings, of a seal which illustrates the invention by way of example.

In the accompanying drawings: Figure 1 is a view in cross-section through a seal; and Figure 2 is a view in perspective illustrating the mounting of a retaining clip, comprising two hooking elements, on a flange of a body part of the seal.

An annular seal, as shown in Figure 1, comprises an outer metal shell 10, a sealing element 12 of rubber, a protective strip 14 of PTFE plastics material, and an inner metal shell 16 assembled together; as seen in the drawing, the sealing element 12 is so retained trapped between, on the one side, a wall of the inner shell 16 and the protective strip 14, and on the other side a wall of the outer shell 10. The inner and outer shells 16 and 10 form effectively rigid body parts of the seal.

The seal comprises also a conventional coil spring 18 extending in a closed loop around the seal to bear laterally against the rubber sealing element 12 to support the element in use of the seal. The coils of the spring are spaced apart.

The seal comprises also spring-retaining means 20 comprising a plurality of retaining clips (see also Figure 2) which are uniformly spaced around the seal to prevent the spring becoming dislodged from its normai working position.

Each retaining clip is formed from a single piece of wire of somewhat thinner gauge than the material of the spring 18. Each clip comprises two hooking elements 22 and 24 which project from a base formation 26 by means of which the clip is secured to the inner shell 16 of the seal. The base formation, as seen in Figure 2, comprises a first loop 28 and a loop back 30 at the bottom of each hooking element and a straight run 32 which extends between them. This arrangement enables a flange portion 34 of the inner shell 16 to be gripped between the first loops 28 and the connecting portion comprising the straight run 32 which forms a large second loop.

The clip is so secured to the inner shell.

Each hooking element extends up between adjacent spaced coils of the spring and is hooked over to the outside of the spring. The hooking element so does not come between the spring and the sealing element and the spring remains free to move a distance radially inwardly, under loads transmitted through the sealing element in use, without loading the hooking elements.

Claims

1. An annular seal comprising a coil spring arranged to support a flexible sealing element of the seal and spring-retaining means arranged to retain the spring in a required working position within the seal, coils of the spring being spaced apart and the retaining means comprising a plurality of hooking elements each extending between adjacent spaced coils of the spring and being hooked over to the outside of the spring.

2. An annular seal according to claim 1 wherein the hooking elements are formed of wire.

3. An annular seal according to claim 2 wherein the wire is of thinner gauge than the material of the spring.

4. An annular seal according to claim 2 or claim 3 wherein two hooking elements are formed from a single piece of wire in a single retaining clip.

5. An annular seal according to claim 4 wherein the two hooking elements project from a base formation by means of which the clip is secured to a body part of the seal.

6. An annular seal according to claim 5 wherein the base formation is arranged to comprise gripping elements between which a flange of the body part is gripped.

7. An annular seal substantially as hereinbefore described with reference to the accompanying drawings.