GB2066917A - Compression joints - Google Patents

Abstract

A combination of parts for making a compression joint includes male and female screwthreaded members (18,16), an O-ring (34) and means which when the male and female members are tightened together are arranged to tightly embrace a tube on which the joint is being formed, this means being constituted by a deformable retaining ring (26) having a plurality of resilient elements (28) which in their free condition extend at right angles or substantially at right angles to the general plane of the ring, end portions of said elements being inturned to project radially inwards and back towards the general plane of the ring. <IMAGE>

Description

SPECIFICATION Compression joints The invention relates to compression joints of the kind for producing a leak-proof seal on a tube or tubular connecting piece, for example, a tubular connecting piece on a water tap or valve.

Various kinds of compression joints are already known. For example, in one prior proposal a combination of parts for making a compression joint has included male and female screwthreaded members, a ferrule and an O-ring seal, the female screwthreaded member having a portion with a tapered bore within which the ferrule, having a complementary external taper, can be fitted before the screwthreaded members are connected together, the arrangement being such that when the two screwthreaded members have been fitted together the male member bears against the end of the ferrule to urge it against the tapered bore within the female member so that the ferrule is inwardly compressed to tightly embrace a tube or tubular connecting piece which has been entered into a bore in the male screwthreaded member, the end of said male screwthreaded member which is to abut against the end of the ferrule having a counterbore which forms a groove for the reception of the O-ring seal, one wall of said groove being formed by a radially inner part of the end surface of the ferrule against which the end of the male screwthreaded member is to bear.

Such an arrangement has been found to work quite well, primarily because in such an arrangement the mechanical connection function is quite separate from the leak-proof seal function. (It has been found that mechanical joints which have attempted to perform the additional function of a leak-proof seal have been unreliable and difficult to seal against leakage, particularly when the tube or tubular connecting piece has been a relatively weak walled tube, that is to say when it has been a relatively thin walled metal tube or a synthetic plastics tube, due to the high crushing pressure which it has generally been necessary to apply to said tube). However, it is now desired to provide a compression joint which whilst having these same advantages of separate mechanical and leak-proof seal functions can be assembled very quickly and tightened manually without the use of tools.The invention aims to provide such a joint.

According to one aspect of the invention, there is provided a combination of parts for making a compression joint, including a body part, an end cap, an O-ring and a deformable retaining ring, the body part having a bore portion which forms a groove for the reception of the O-ring and the end cap having screwtbreaded connection with said body part, the deformable retaining ring being provided with a plurality of resilient elements which in their free condition extend at right angles or substantially at right angles to the general plane of the ring, end portion of said elements being inturned to project radially inwards and back towards the general plane of the ring, said elements extending within a frustoconical portion of the end cap, the arrangement being such that, in use of the compression joint, in one axially adjusted position of the end cap the resilient elements of the retaining ring are spaced from the surface of the tube or tubular connecting piece on which the joint has been assembled and in another axially adjusted position of the end cap the frusto-conical surface of the end cap contacts the resilient elements to deflect them radially inwards.

The deformable retaining ring may include a flat annular ring part which can abut against an abutment surface within the body part and in this case said flat annular ring part may be provided with at least one aperture at its periphery which accommodates a key piece formed within a bore portion of the body part, the arrangement being such that the retaining ring is thereby held against rotation. On the other hand, the deformable retaining ring may be a split ring of deeply dished form, a part of said ring conforming to the frusto-conical shape of the end cap and an inturned lip portion of said ring having a plurality of slots between which are provided the plurality of end portions which project inwards and back towards the general plane of the ring.

According to another aspect of the invention, there is provided an assembled compression joint made by the combination of parts referred to above.

In order that the invention may be fully understood and readily carried into effect, the same will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a longitudinal section through a compression joint embodying the invention, Figure 2 is a plan view, Figure 3 is an exploded view, Figure 4 is a longitudinal section similar to Figure 1 of a slightly different form of compression joint embodying the invention, and Figures 5 and 6 are respective sectional and plan views of a deformable retaining ring element forming part of said joint.

Referring now to the drawings, the double ended compression joint there illustrated is the same at both ends. The joint at the left hand side of the assembly will therefore be described. The joint is intended to form a leak-proof seal on a tube or tubular connecting piece such as shown in chaindotted lines in Figure 1 and includes a body part 10 with stepped bore portions 12, 14 and 16, the bore portion 16 constituting a female portion within which a male portion 18 of an end cap 20 is received.

The male portion 18 is of generally cylindrical shape but is formed interiorly with a frusto-conical surface 22. An outer portion 24 of the end cap is internally screwthreaded and engages a screwthread on the exterior of the body part.

The compression joint also includes a spring steel retaining ring 26 which is to be located in the bore portion 16 of the body part and which, as best seen in Figure 3, is constituted by an annular ring part with three equally spaced resilient elements 28 which in their free condition, as shown in Figure 1, extend substantially at right angles to the general plane of the ring, end portions of said elements being inturned to project radially inwards and back towards the general plane of the ring. The arrangement is such that in their free condition the elements 28 of the retaining ring are spaced from the surface of the tube or tubular connecting piece on which the compression joint is to be made.The periphery of the annular ring part of the retaining ring is provided with three equally spaced apertures 30 which when the ring has been located in position within the bore portion 16 of the body part accommodate respective key pieces 32 which are formed within the latter. The retaining ring is therefore held against rotation.

In the assembled joint the bore portion 14 of the body part forms a groove for the reception of an O-ring 34 the O-ring being retained in position by a flanged abutment ring 36. The tube or tubular connecting piece concerned on which the joint forms a a leak-proof seal extends through the retaining ring 26, which forms a part of what can be termed the mechanical connection, through the O-ring 34 which performs the leak-proof seal function, and through or into the bore portion 12. (In the compression joint illustrated the body part is shown to be provided with a somewhat smaller bore portion 38 so that when a tube or tubular connecting piece has been entered into the body part the bore of the tube or tubular connecting piece, as the case may be, is continuous with the reduced diameter portion 13 as shown. However, this is not essential).

On the assembly of the compression joint, when the component parts have been loosely connected together as shown in Figure 1 with the retaining ring in its free condition the end cap 20 can be turned to advance it along the screwthread on the body part, and this then causes the frusto-conical surface within the male portion 18 of the end cap to ride onto the elements 28, and deflect them radially inwards.

Consequently, the end portions of the elements 28 of the retaining ring tend to bite into the surface of the tube or tubular connecting piece concerned as the end cap is turned. (Alternatively, if, as is very likely, the joint is fully assembled and tightened before it leaves the factory, the inner ends of the elements 28 will be disposed at a pitch circle diameter somewhat smaller than the outside diameter of a tube or tubular connecting piece which is to be entered into the joint. In this case, the tube or tubular connecting piece will be able to be entered into the joint by push fitting causing the elements to be deflected outwards so that they tend to bite the surface of said tube or tubular connecting piece). This has been found to produce a strong mechanical connection.It will be seen that the joint cannot be overtightened in a way which would deform the elements 28 because on continued rotation of the end cap the latter is able to seat itself against the end of the body part.

Furthermore, since the end portions of the elements 28 are inclined at an angle as shown, that is to say inwardly towards the O-ring and abutment ring 36, any tendency for the tube or tubular connecting piece to be forcibly removed from the assembled joint will result in the end portions of the elements biting deeper into the surface with which they have been engaged. However, it has been found that with normal usage the amount by which the elements 28 bite into the surface of the tube or tubular connecting piece concerned has not been sufficient to damage the tube or the retaining ring. Consequently, it is found that the component parts of the joint and the tube itself can be re-used, and in fact it is a useful feature of the invention that a plumber can make a number of such joints before tightening them.He can alternatively tighten such a joint and then dismantle it again if he finds that the tube on which he has assembled the joint is fractionally too long.

He can re-make the joint with the O-ring seal substantially at the location previously taken by the mechanical connection without danger of a damaged pipe wall causing leakage.

The assembled joint can very quickly and easily be dismantled by the simple process of turning the end ring 20 relative to the body part 10 in the reverse direction so that the frusto-conical surface of the male member rides off the elements 28 of the retaining ring. Consequently, the end portions of the elements 28 cease to bite into the surface of the tube or tubular connecting piece concerned and this is released.

Referring now to Figures 4 to 6, in a rather different form of compression joint embodying the invention, the deformable retaining ring 26 is shown to have been formed as a split ring of deeply dished form, a part 40 of said ring conforming to the frusto-conical shape of the end cap 20 and an inturned lip portion 42 of said ring having a plurality of slots 44. The slots 44 define a plurality of end portions which project inwards and back towards the general plane of the ring, that is to say towards an end surface 48 of the part 40 which in this embodiment abuts against an end surface of the body part 10. However, it will be seen that, in use, the compression joint operates in exactly the same manner as that described with reference to Figures 1 to3.

Various other modifications may be made to the compression joint described. For example, if the compression joint is intended exclusively for fitment on a plastics tube or tubular connecting piece it is possible that the retaining ring could be made of plastics (ideaily of a somewhat harder plastics material). It is not essential for the spring steel retaining ring 26 in the compression joint illustrated in Figure 1 to be held against rotation.Consequently, the apertures 30 at the periphery of the ring and the moulded key pieces in the body part could be omitted; the reasons why they are provided in the illustrated embodiment is simply so that there is no danger of a plastics pipe being grooved or "scored" by the rotation of the retaining ring during the tightening or slackening of the joint (if in fact the joint is tightened with a pipe in position within it rather than the joint being used simply as a plug-in connector fully assembled at the factory). Furthermore, it will be seen that in the illustrated compression joint the O-ring remains in a free condition throughout, that is to say, the retaining ring in each case bears against a shoulder portion of the body part. However, if preferred, the arrangement in either case could be such that the O-ring is very slightly compressed by the end force applied to the retaining ring before the joint is fully tightened.

It will be understood that the tube or tubular connecting piece shown chain-dotted in each of Figures 1 and 4 may be simply a plain length of tube or may be a tubular spigot portion formed on some kind of fitting, for example, on a water tap or valve. It will also be understood that although in the joint illustrated by way of example in Figure 1 the body part is shown to be double ended (and may of course form the body part of two such joints whereby for example two lengths of tube may be connected together end to end) the body part could be formed integrally with some kind of fitting to which a tube or tubular connecting piece is to be connected.

Claims (6)

1. A combination of parts for making a compression joint, including a body part, an end cap, an O-ring and a deformable retaining ring, the body part having a bore portion which forms a groove for the reception of the O-ring and the end cap having screwthreaded connection with said body part, the deformable retaining ring being provided with a plurality of resilient elements which in their free condition extend at right angles or substantially at right angles to the general plane of the ring, end portions of said elements being inturned to project radially inwards and back towards the general plane of the ring, said elements extending within a frustoconical portion of the end cap, the arrangement being such that, in use of the compression joint, in one axially adjusted position of the end cap the resilient elements of the retaining ring are spaced from the surface of the tube or tubular connecting piece on which the joint has been assembled and in another axially adjusted position of the end cap the frusto-conical surface of the end cap contacts the resilient elements to deflect them radially inwards.

2. A combination of parts according to claim 1, in which the deformable retaining ring includes a flat annular ring part which can abut against an abutment surface within the body part.

3. A combination of parts according to claim 2, in which the flat annular ring part is provided with at least one aperture at its periphery which accommodates a key piece formed within a bore portion of the body part, the arrangement being such that the retaining ring is thereby held against rotation.

4. A combination of parts according to claim 1, in which the deformable retaining ring is a split ring of deeply dished form, a part of said ring conforming to the frusto-conical shape of the end cap and an inturned lip portion of said ring having a plurality of slots between which are provided the plurality of end portions which project inwards and back to wards the general plane of the ring.

5. An assembled compression joint made by the combination of parts referred to in any one of the preceding claims.

6. A combination of parts for making a compression joint, substantially as hereinbefore described, with reference to and as illustrated by Figures 1 to 3 or Figures 4 to 6 of the accompanying drawings. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~