GB2072292A

GB2072292A - Compression joints

Info

Publication number: GB2072292A
Application number: GB8107873A
Authority: GB
Original assignee: Paragon Plastics Ltd
Current assignee: Paragon Plastics Ltd
Priority date: 1980-03-17
Filing date: 1981-03-12
Publication date: 1981-09-30
Also published as: GB2072292B

Abstract

A combination of parts for making a compression joint, includes a body part (10) and an end cap (20) the body part having stepped bore portions, that is to say an inner bore (12) portion for receiving an end portion of a tube or tubular connecting piece and an outer bore portion (14) for receiving means (16) for providing a mechanical connection and an O-ring (18) for providing a leak-proof seal on the tube or tubular connecting piece. So that a leak-proof joint can be formed by a simple push action of a tube into the fitting, the means (16) for providing the mechanical connection are constituted by a deformable ferrule (22) and by an abutment ring (24) the latter being slidably located in the outer bore portion (14) of the body part (10) and having a tapered bore portion within which is partly received the deformable ferrule (22), the ferrule having a similar external taper and also having an internal surface tapered in the opposite sense to the taper of its external surface and forming a sharp edge for biting into the surface of the tube in response to a pull tending to extract the tube from the ferrule (22). So that a leak-proof seal can be formed on the outside of the means (16) for providing a mechanical connection, the O-ring (18) will preferably be located between the abutment ring (24) and an end cap (20). <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 the 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 leakproof 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, and which provides a pipe joint by a simple "push" action of the pipe into the fitting.

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 stepped bore portions, that is to say an inner bore portion for receiving an end portion of a tube or tubular connecting piece and an outer bore portion for receiving means for providing a mechanical connection and an O-ring for providing a leakproof seal on said tube or tubular connecting piece, the means for providing the mechanical connection being constituted by a deformable ferrule and an abutment ring, the latter being slidably located in said outer bore portion of the body part and having a tapered bore portion within which is partly received the deformable ferrule, said ferrule having a similar external taper and also having an internal 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 lightly engage the surface of the tube or tubular connecting piece concerned, the arrangement being such that when the joint has been assembled on the tube or tubular connecting piece an axial pull tending to displace the ferrule within the abutment ring 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 an assembled joint, the O-ring will preferably be located between the abutment ring and the end cap in which case the axial pull tending to displace the ferrule within the abutment ring will urge the latter into engagement with the O-ring thus applying some slight compression to the O-ring and producing a more effective leak--proof seal. If the combination of parts is intended for the forming of a compression joint on a metal tube or tubular connecting piece the ferrule will also be made of metal and will be a slotted ferrule to allow its deformation. If the combination of parts is for forming a compression joint on a plastics tube or tubular connecting piece the ferrule may also be made of plastics and may or may not be a slotted ferrule.The body part and end cap may be connected together by means of a plug-in connection constituted by 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, and in this case the connection may be 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:~ Fig. 1 is a part sectional side view through an assembled double ended compression joint embodying the invention, Fig. 2 is an exploded view, and Figs. 3 and 4 are respective part-sectional and side views illustrating a possible modification which will presently be referred to.

Referring now to Figs. 1 and 2 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 and 14. In use, the bore portion 12 receives an end portion of a tube or tubular connecting piece (shown chain-dotted in Fig. 1) whilst the bore portion 14 contains means generally indicated 16 which provide a mechanical connection function and a resilient O-ring 18 which encircles the tube or tubular connecting piece concerned to provide a leakproof seal. An annular end cap 20 surrounds the tube or tubular connecting piece and closes the end of the bore portion 14, the end cap having an internally screwthreaded skirt portion which engages a screwthreaded portion of the body part and abuts against a shoulder formed on said body part.A part of the external surface of the skirt portion of the end cap is shown to be serrated so that it can be tightened or slackened by hand.

The means generally indicated 16 which provide the mechanical connection function on the tube or tubular connecting piece are constituted by a deformable ferrule 22 and an abutment ring 24, the latter having a cylindrical external surface and being slidably located in the bore portion 14 of the body part. The abutment ring has a tapered bore portion within which is partly received the deformable ferrule, said ferrule having a similar external taper. The deformable ferrule is provided, in addition to its external taper, with 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 the tube or tubular connecting piece on which the joint is assembled only at its wider end as shown.

On assembly of the compression joint, when the component parts have been loosely connected together as shown in Fig. 1 with the ferrule abutting or almost abutting against the shoulder between the bore portions 12 and 14 of the body part, a very slight axial pull on the tube or tubular connecting piece, against the body part and the end ring, brings the abutment ring 24 into abutment with the O-ring and then tends to cause the ferrule to slide down the internal tapered surface of the abutment ring 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 te 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.

The assembled joint can very quickly and easily be dismantled by the simple process of unscrewing the end cap and withdrawing the tube or tubular connecting piece from within the body part together with the O-ring 18, abutment ring 24 and deformable ferrule 22. As the abutment ring is withdrawn away from the ferrule, the latter is able to expand and can then be released from the tube or tubular connecting piece concerned.

Various modifications may be made without departing from the scope of the invention. For example, in Figs. 3 and 4 there is illustrated a compression joint generally similar to that described above in the sense that it includes the same means 16 which provide the mechanical connection function and a resilient O-ring 18 which encircles the tube or tubular connecting piece concerned to provide a leak-proof seal.

However, in this case, instead of having screwthreaded connection with the body part the end cap 20 has a pair of oppositely disposed slots 26 which when the joint has been assembled are engaged by a pair of oppositely disposed.and radially extending elements 28 which are formed near the end of the body part. As best seen in Fig. 4, the slots 26 are elongate slots and each slot extends at a shallow angle to a transverse plane normal to the longitudinal axis of the joint.

Each slot has at its opposite ends respective shallow depressions 30 in a side wall nearest the free end of the skirt portion of the cap and these are provided so that the cap is retained in an adjusted position relative to the body part by the seating of the respective element 28 in one or other of the depressions.The resulting cam action as the end cap is rotated relative to the body part through the distance defined by the length of the slots causes the end cap to be displaced axially of the body part. (Although the operative parts of the slots extend completely through the wall thickness of the skirt portion of the end cap they each have an entry portion at one end which, as shown in dotted lines in Fig. 4, do not extend completely through the wall thickness but enable the end cap and body part to be initially connected together.) The arrangement is such that when the end cap is rotated relative to the body part to displace it axially the O-ring is initially compressed and the abutment ring is displaced so that it contracts the deformable ferrule 22 onto the tube or tubular connecting piece. However, as in the case of the first described embodiment the arrangement is such that an axial pull tending to displace the ferrule within the abutment ring has the effect of causing the corner of the ferrule to bite into the surface of the tube or tubular connecting piece concerned and to produce a strong mechanical connection.

Various other modifications may be made to the compression joints described. For example, in each case the ferrule has been said to be made of metal (and thus to have been made as a slotted ferrule) because the particular joint 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.

In each of the illustrated embodiments the deformable ferrule is shown to be of solid form; it may for example have been machined from metal bar. However, it is possible for the ferrule to be made as a pressing from relatively thin metal plate. In this case the inner and outer tapered surfaces of the ferrule would be defined by surfaces of the pressed metal plate. The ferrule would be a slotted ferrule as in the case of the metal ferrules illustrated in the drawings. In addition, the inturned metal plate could be slotted at intervals around its circumference to define a plurality of inclined tab portions for biting into the surface of a tube or tubular connecting piece concerned.

It will of course be understood that one or the other of the tubes or tubular connecting pieces shown chain-dotted in Fig. 1 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 each of the joints 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.

It has been stated earlier that a compression joint embodying the invention can very quickly and easily be assembled or dismantled. However, the design of the joint is such that the component parts can be fully assembled at the factory and a joint can be made by a plumber by the simple process of entering the copper or plastics tubes into the fully assembled and tightened preassembly of parts.

Claims

1. A combination of parts for making a compression joint, including a body part and an end cap, the body part having stepped bore portions, that is to say an inner bore portion for receiving an end portion of a tube or tubular connecting piece and an outer bore portion for receiving means for providing a mechanical connection and an O-ring for providing a leak proof seal on said tube or tubular connecting piece, the means for providing the mechanical connection being constituted by a deformable ferrule and an abutment ring, the latter being slidably located in said outer bore portion of the body part and having a tapered bore portion within which is partly received the deformable ferrule, said ferrule having a similar external taper and also having an internal tapered surface, this being tapered in the opposite sense to the taper of its external surface and forming a sharp edge or annular surface of limited axial extent at the thicker end of the ferrule which on initial assembly of the joint is adapted to lightly engage the surface of the tube or tubular connecting piece concerned, the arrangement being such that when the joint has been assembled on the tube or tubular connecting piece an axial pull tending to displace the ferrule within the abutment ring 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.

2. A combination of parts according to claim 1, in which the arrangement is such that the O-ring can be located between the abutment ring and the end cap so that the axial pull tending to displace the ferrule within the abutment ring will urge the latter into engagement with the O-ring thus applying some slight compression to the O-ring and producing a more effective leak-proof seal.

3. A combination of parts according to either one of the preceding claims, 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.

4. A combination of parts according to either one of claims 1 and 2, for forming a compression joint on a plastics tube or tubular connecting piece, in which the ferrule is made of plastics.

5. 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 constituted by 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.

6. A combination of parts according to any one of claims 1 to 4, 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 any one of the preceding claims.

8. A combination of parts for making a compression joint, substantially as hereinbefore described with reference to and as illustrated by the 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.