GB2066913A - Compression joints - Google Patents

Abstract

A combination of parts for making a compression joint, including a body part (10), an end cap (20), a tapered ferrule (30) and an O-ring (34), the arrangement being such that upon an axial pull on the tubular member the ferrule (30) can be urged against a tapered bore portion of the end cap (20) so that the ferrule (30) is inwardly compressed to tightly embrace the tubular member. In order to keep the leak-proof seal function quite separate from the mechanical connection function, the O- ring (34) is accommodated in a counter- bore (14) and is not axially compressed when the joint is tightened. The cap (20) and body (10) may be screwed (Figure 6 not shown) or push-fitted together (see also Figure 5 not shown). In the latter case the joint may be readily disconnected by turning the cap (20) relative to the body (10) so that tapered elements (24) on the cap (20) or body (10) (Figure 5) can slide out of retaining apertures (22) in the body (10) or cap (20) (Figure 5) respectively. <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 watertap or valve.

Various kinds of compression joints are already grown. 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, 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 and an end cap, the body part having a bore portion which forms a groove for the reception of an O-ring seal and the end cap having a tapered bore portion within which is received a deformable ferrule having a similar external taper, the ferrule, in addition to its external taper, having an internally tapered surface, this being tapered in the opposite sense to the taper of its external surface and forming a sharp edge or an annular surface of limited axial extent at the thicker end of the ferrule which on initial assembly of the joint is adapted to engage a shoulder at the outer end of the bore portion whch receives the O-ring seal, the arrangement being such that when the joint has been assembled on a tube or tubular connecting piece an axial pull tending to displace the ferrule within the end cap has the effect of causing the corner of the ferrule or the annular surface of limited axial extent at the wider end of the ferrule to bite into the surface of the tube or tubular connecting piece concerned and to produce a strong mechanical connection. In a combination of parts intended for the forming of a compression joint on a metal tube or tubular connecting piece, the ferrule will be made of metal and be a slotted ferrule to allow its deformation. In a combination of parts for forming a compression joint on a plastics tube or tubular connecting piece, the ferrule may also be made of plastics.The body part and end cap may be connected together by means of a plug-in connection including a pair of oppositely disposed slots extending through the wall of the body part and a pair of oppositely disposed elements formed at the end of a male portion of the end cap which are engageable in said slots, the connection being releasable by turning the end cap relative to the body part. Alternatively, the body part and end cap may be connected together by means of a plug-in connection including a pair of oppositely disposed slots extending through the wall of a skirt portion of the end cap and a pair of oppositely disposed elements formed on the body part and which are engageable in said slots, the connection again being releasable by turning the end cap relative to the body part.On the other hand, the body part and end cap may be connected together by means of a screwthreaded connection.

According to a further 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 an assembled double ended compression joint embodying the invention, Figure 2 is a plan view, Figure3 is an exploded view, Figure 4 is a view of a component part of the joint in the direction of arrow A in Figure 3, Figure 5 is a part sectional view similar to Figure 1 and illustrates a possible modification which will be referred to, and Figure 6 is a further part-sectional view of an assembled joint which will be referred to when describing a further possible modification.

Referring nowto Figures 1 to 4 of the drawings, the double ended compression joint there illustrated is the same at each end. The joint at the left hand end will therefore be described. This includes a body part 10 with stepped bore portions 12,14and 16, the bore portion 16 constituting a female portion within whch a male portion 18 of an end ring 20 is received. A pair of oppositely disposed slots 22 extend through the wall of the body part to break into the bore portion 16 and when the joint has been assembled, as shown in Figure 1, a pair of oppositely disposed and radially extending elements 24 which are formed at the end of the male portion 18 of the end ring engage said slots to hold the two parts together, that is to oppose their disengagement when the joint is subjected to a purely axial pull.However, it will be observed in Figure 1 that to facilitate the engagement of these two parts the elements 24 are chamfered at their leading ends and the body part is provided with lead-in surfaces 26 in line with the slots 22. It will also be seen in Figure 4 that the elements 24 have inclined side surfaces 28 and the purpose of these will presently be explained.

The compression joint also includes a ferrule 30 with a tapered external surface, the ferrule being received within a similarly tapered bore portion 32 of the male portion 18 of the end ring. In addition to its external taper, the ferrule has an internally tapered surface, this being tapered in the opposite sense to the taper of its external surface. The ferrule is a slotted ferrule and is made of metal. Thus it is adapted to engage the surface of a tube or tubular connecting piece on which the joint is assembled (such a tube or connecting piece being shown in chain-dotted lines in Figure 1) only at its wider end as shown.

In the assembled joint the bore portion 14 of the body part forms a groove for the reception of an O-ring seal 34, the O-ring seal being retained in position by a washer 36. The tube or tubular connecting piece concerned on which the joint has been assembled extends through the ferrule 30, which forms a part of what can be termed the mechanical connection, through the O-ring seal which performs the leak-proof seal function, and through or into the bore portion 12.

On assembly of the compression joint, when the component parts have been loosely connected together as shown in Figure 1 with the ferrule abutting or almost abutting against the shoulder between the bore portions 14 and 16 of the body part, a very slight axial pull on the tube or tubular connecting piece, against the body part or end ring 20, tends to cause the ferrule to slide down the internal tapered surface 32 so that the corner of the ferrule at the wider end of the latter tends to bite into the surface of the tube or tubular connecting piece concerned. This very slight axial pull can be effected manually and has been found to produce a strong mechanical connection. However, it has been found that the amount of inward crushing of the ferrule onto the surface of the tube or tubular connecting piece concerned has not been sufficient to damage the tube or the ferrule.Consequently, it is found that the component parts of the joint and the tube itself can be re-used. A plumber can assemble 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. By virtue of the inclined side surfaces 28 of the elements 24 this causes said elements to ride out of the slots 22.

Consequently, the end ring can be withdrawn from the end of the body part and the ferrule is able to expand to release the tube or tubular connecting piece concerned.

Various modifications may be made to the compression joint described. For example, the ferrule has been said to be made of metal (and thus to h'ave been made as a slotted ferrule) because the particularjoint described has been intended for use with a copper pipe or copper pipe connecting piece. However, in a compression joint intended exclusively for fitment on a plastics pipe or plastics pipe connecting piece the ferrule could also be made of plastics (ideally of a somewhat harder plastics material) and in this case may not require to be made as a slotted ferrule because plastics materials can be deformed more readily than metal. In this case also, it may be found that it is advantageous to form the ferrule with an annular surface of limited axial extent instead of a sharp corner which might bite too deeply into the surface of a synthetic plastics tube or tubular connecting piece.On the other hand, the sharp corner of the metal ferrule may be formed by a combination of angles in the region of the corner to provide an ideal cutting edge for biting into the surface of a copper tube or tubular connecting piece. Furthermore, it will be understood that the washer 36 is required to retain the O-ring seal in the bore portion 14 despite the ferrule having moved slightly away from the shoulder against which it initially abuts. However, the ferrule could be provided with a projecting ring part arranged to take the place of the washer 36, that is to say to project loosely into the bore portion 14 and to remain partly within the latter when the ferrule has been displaced axially on tightening of the joint.

Referring now to Figure 5, the compression joint there illustrated is similar to that of Figures 1 to 4; it operates in exactly the same way but the plug-in connection is somewhat different. That is to say, the plug-in connection between the body part 10 and end cap 20 includes a pair of oppositely disposed slots 22 extending through the wall of a skirt portion 21 of the end cap and a pair of oppositely disposed elements 24 formed on the body part. The elements 24 are chamfered as shown at their leading ends and the mouth of the skirt portion of the end cap is slightly flaired so that a push fit connection can be effected quite easily. By virtue of the inclined side surfaces (not shown) of the elements 24 the assembled joint can very quickly and easily be dismantled by the simple process of turning the end cap relative to the body part as in the first described embqdiment.

In Figure 6 there is illustrated a further compression joint similar to that of Figures 1 to 4 but in this case the body part and end cap are connected together by means of a screwthreaded connection.

That is to say, the end cap 20 is provided with an internally screwthreaded skirt portion 21 which has screwthreaded engagement on the body part. It will be understood that in this case the end cap will be initially screwed fully onto the body part so that the free end of the skirt portion 21 abuts against the shoulder formed on the body part (and of course in this condition of the joint the ferrule will be loosely captive within the end cap). The tube or tubular connecting piece will then be entered into the joint so that it causes the ferrule 30 to expand slightly, following which an axial pull on the tube ortubular connecting piece tending to displace the ferrule along the tapered internal surface of the end cap will cause the corner of the ferrule to bite into the surface on which it bears and to produce a strong mechanical connection.

It will of course be understood that one or the other of the tubes or tubular connection pieces shown chain-dotted in the drawings 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 the body part is shown to be double ended and forming the body part of two such joints whereby two lengths of tube may be connected together end to end, the body part of the joint (that is to say one half of the body part illustrated in the drawings) may be formed integrally with some kind of fitting to which a tube or tubular connecting piece is to be connected.

Claims (9)

1. A combination of parts for making a compression joint, including a body part and an end cap, the body having a bore portion which forms a groove for the reception of an O-ring seal and the end cap having a tapered bore portion within which is received a deformable ferrule having a similar external taper, the ferrule, in addition to its external taper, having an internally tapered surface, this being tapered in the opposite sense to the taper of its external surface and forming a sharp edge or an annular surface of limited axial extent at the thicker end of the ferrule which on initial assembly of the joint is adapted to engage a shoulder at the outer end of the bore portion which receives the O-ring seal, the arrangement being such that when the joint has been assembled on a tube or tubular connecting piece an axial pull tending to displace the ferrule within the end cap has the effect of causing the corner of the ferrule or the annular surface of the limited axial extent at the wider end of the ferrule to bite into the surface of the tube or tubular connecting piece concerned and to produce a strong mecha nical connection.

2. A combination of parts according to claim 1, intended for the forming of a compression joint on a metal tube or tubular connecting piece, in which the ferrule is made of metal and is a slotted ferrule to allow its deformation.

3. A combination of parts according to claim 1, for forming a compression joint on a plastics tube or tubular connecting piece, in which the ferrule is also made of plastics.

4. A combination of parts according to any one of the preceding claims, in which the body part and end cap are connected together by means of a plug-in connection including a pair of oppositely disposed slots extending through the wall of the body part and a pair of oppositely disposed ele mentsformed at the end of a male portion of the end cap which are engageable in said slots, the connection being releasable by turning the end cap relative to the body part.

5. A combination of parts according to any one of claims 1 to 3, in which the body part and end cap are connected together by means of a plug-in connection including a pair of oppositely disposed slots extending through the wall of a skirt portion of the end cap and a pair of oppositely disposed elements formed on the body part and which are engageable in said slots, the connection being releasable by turning the end cap relative to the body part.

6. A combination of parts according to any one of claims 1 to 3, in which the body part and end cap are connected together by means of a screwthreaded connection.

7. An assembled compression joint made by the combination of parts referred to in claim 1.

8. A combination of parts for making a compression joint, substantially as hereinbefore de scribedwith reference to and as illustrated bythe accompanying drawings.

9. An assembled compression joint constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.