GB2332028A

GB2332028A - Releasable push-fit tube coupling

Info

Publication number: GB2332028A
Application number: GB9725794A
Authority: GB
Inventors: William Sydney Deason
Original assignee: IMI Norgren Ltd
Current assignee: Norgren Ltd
Priority date: 1997-12-05
Filing date: 1997-12-05
Publication date: 1999-06-09
Also published as: GB9725794D0; GB2332028A9

Abstract

The coupling of the type having a body 1 and a tube-gripping collet 3 comprising a release sleeve 6, is characterised by the provision of an elastomeric cap 11 retained by the release sleeve 6. The cap 11 has an annular end surface 14 that sealingly abuts the outermost end of the body 1, while the outermost end 15 of the cap 11 defines an aperture 16 through which a tube 5 coupled to the coupling sealingly extends. The cap 11 therefore completely seals the interior of the coupling against the ingress of foreign matter which otherwise could impair releasability of the coupling.

Description

1 2332028 Releasable 12ushfit tube coul' g This invention relates to

releasable push-fit tube couplings and more particularly to such couplings of the type having a plurality of tube gripping teeth which normally engage the tube and prevent it from being accidentally withdrawn from or blown out of the coupling, and a release sleeve which projects axially from the coupling body and which, when axially depressed, causes the teeth to release or loosen their grip on the tube whereupon it may be withdrawn from the coupling.

Such a coupling, which hereinafter is referred to as a "tube coupling of the type describeC, is well-known in the art and in one form the tube-gripping teeth are defined by an annular, so-called grab ring and the release sleeve is a separately made item. In a second form, the tube-gripping teeth and the release sleeve are made as a unitary item commonly referred to in the art as a "collet".

Such couplings have a variety of applications but we are especially, although not exclusively, concerned with their use in pneumatic installations. For example, we manufacture a range of releasable push-in couplings of the aforesaid second form for use in vehicle air brake systems. In such systems, the pneumatic pipelines and couplings are typically fitted externally on the vehicle chassis and, as such, a long-standing problem is the susceptibility of the couplings to the ingress of dirt, moisture etc during service and also of paint when the vehicles are painted, with the brake system already in place, during manufacture. Ingress of such foreign material may, in particular, cause 2 the release sleeve to become jammed thereby adversely affecting releasability of the coupling.

It is an object of the present invention to solve or at least mitigate that problem.

According to the present invention, there is provided a tube coupling of the type described, characterised in that a resilient, annular cover is retained on a tube-receiving end of the coupling, said cover being configured substantially to seal said end, in use of the coupling, against the ingress of foreign matter.

In a preferred embodiment, the resilient annular cover is retained by, and conforms closely to, the external surface of the release sleeve and has an axially innermost annular end surface that abuts the end of the coupling body from which the release sleeve projects. Thus, ingress of foreign matter between the body and the release sleeve is substantially prevented. Further, the axially outermost portion of the cover preferably defines a circular aperture through which a tube coupled to the coupling sealingly extends. Thus, ingress of foreign matter also between the release sleeve and the tube itself is substantially prevented.

The annular cover is preferably moulded in an elastomer and is preferably sufficiently resiliently pliable that the requisite axial movement of the release sleeve is possible whilst the cover is Ln situ.

A tube coupling constructed in accordance with the invention will now be described in more detail, by way of example only, with 3 reference to the accompanying drawing which is a side elevation, in section, of the coupling.

Referring to the drawing, the releasable push-in tube coupling comprises a body 1, an 0-ring seal 2 and a tube-gripping collet 3. The particular coupling shown is a "straight adaptor" the body 1 of which has at one end a male thread 4 for connection to, for example, a valve or manifold and the other end of which, in use, receives as a push-fit a tube 5. The body may be made of brass or other suitable material, including plastics materials.

More particularly, the collet 3 comprises a generally cylindrical release sleeve 6 the inner end of which supports a plurality of, for example six, integrally formed, circumferentally spaced, radially flexible arms 7 which extend axially into the body 1. The innermost ends of the arms 7 are enlarged and each carries a radially inwardly directed tube-gripping tooth 8. The collet 3 may be machined in one piece from, for example, brass although any suitable material, including plastics materials, may be used.

As can be seen, the stepped bore in the body 1 includes a tapering portion 9. In the absence of the tube 5, the collet 3 may be assembled with the body 1 simply by pushing it into the bore from outside whereupon the arms 7 flex radially inwardly in order to enable the enlarged ends to pass through the narrowest diameter portion of the bore. The arms 7 then flex back to the position shown in the drawing with the enlarged ends positioned adjacent to the tapering portion 9.

4 When it is desired to couple the tube 5 to the coupling, it is simply pushed into the coupling through the collet 3 until it reaches the tube stop 10 defined by an annular shoulder on the internal surface of the body 1. During this step, the 0-ring seal becomes slightly deformed and provides a fluid-tight seal about the external surface of the tube 5.

Also, the arms 7 flex slightly radially outwards with the teeth 8 lightly gripping the tube 5.

If now the tube 5 is accidentally pulled, or if the fluid pressure in it becomes excessive, the collet 3 tends to move slightly axially outwards and so the teeth 8 increase their grip on the tube 5 by virtue of co-action between the enlarged ends of the arms 7 and the tapering portion 9 of the bore in the body 1. Accordingly, accidental withdrawal or blow out of the tube 5 is prevented. However, if it is desired to de couple the tube 5, the release sleeve 6 is simply pushed axially inwards, whereupon the teeth 8 loosen their grip on the tube 5, and at the same time the tube 5 is withdrawn.

The features described above are all conventional and well-known in the art. In accordance with the present invention, an elastomeric cap designated generally 11 and made for example from a nitrile rubber is retained on, and in contact with, the external surface of the release sleeve 6. More particularly, the internal surface of the cap 11 is formed with an annular rib 12 which resiliently engages in an annular groove 13 formed in the external surface of the release sleeve 6. The innermost annular end surface 14 of the cap 11 sealingly abuts the outermost end of the body 1. Further, the outermost end 15 of the cap 11 defines an 1 1 aperture 16, the diameter of which is selected such that not only can the tube 5 be inserted through it but also that the end 15 defining the aperture 16 will sealingly engage the tube 5. Accordingly, the cap I I completely seals the interior of the coupling against the ingress of foreign matter such as dirt, dust, moisture and, in the context of commercial road vehicle manufacture, paint.

Because the cap 11 is made of resilient material, the release sleeve 6 is, with the cap 11 in situ, able to move axially as usual, for example during coupling and de-coupling of the tube 5 during which the innermost end portion of the cap 11 deforms radially outwards by virtue of co-action between the surface 14 and the end of the body 1. In order to facilitate such deformation of the cap 11, it can be seen that its innermost end portion is slightly flared. When, in particular, the tube 5 is inserted into the coupling, the flare tends to increase as the collet 3, and therefore the cap 11, move slightly axially inwards. In certain cases, this may result, by virtue of a cantilever action transmitted through the cap 11, in enhanced sealing of the end 15 with the external surface of the tube 5.

As will be appreciated, alternative designs are possible for the cap 11. For example, the innermost end of the cap I I could overlap, and be retained in place by, the external surface of the body 1. However, an arrangement substantially as shown in the drawing is preferred because:

a) no change is required to the existing body designs. Indeed, 6 in the arrangement shown, only the design of the collet 3 needs alteration by providing the groove 13 in the sleeve 6, although the cap 11 could be retained on the latter purely by a frictional fit; b) the maximum O.D. of the cap 11 does not extend beyond the diameter of the flats 17 formed on the body 1 and which serve to facilitate installation of the coupling body 1. Thus, the cap 11 does not restrict the use of, say, a socket spanner for installing the coupling body 1; and as the seal between the body 1 and the cap 11 is made on the end face of the body 1, the external diameter of the body may be of any size.

Finally, whilst the drawing depicts a straight adaptor, it will be appreciated that a coupling of the invention may be of any form, for example a straight, T- or elbow coupling for coupling together two or more tubes, in which case each tube receiving end would be provided with a protective cover such as a cap 11.

i 7

Claims

CLAIMS: 1. A tube coupling of the type described, characterised in that a

resilient, annular cover is retained on a tube-receiving end of the coupling, said cover being configured substantially to seal said end, in use of the coupling, against the ingress of foreign matter.
2. A tube coupling according to claim 1 wherein the resilient annular cover is retained by, and conforms closely to, the external surface of the release sleeve and has an axially innermost end portion that sealingly abuts or overlaps the end of the coupling body from which the release sleeve projects, whereby in use ingress of foreign matter between the body and the release sleeve is substantially prevented.
3. A tube coupling according to claim 2 wherein the axially outermost end portion of the cover defines a circular aperture through which a tube coupled, in use, to the coupling sealingly extends whereby ingress of foreign matter between the tube and the release sleeve is substantially prevented.
4. A tube coupling according to any one of claims I to 3 wherein the cover is made of an elastomer.
5. A tube coupling according to any one of claims I to 4 wherein the cover is sufficiently resiliently pliable that the requisite axial movement of the release sleeve is possible while the cover is in situ.
6. A tube coupling substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawing.