SPECIFICATIONPipe couplingsThis invention relates to pipe couplings of the compression fitting type in which an olive or ferrule is axially compressed between mutually opposed tapers within the mouth of a socket and within a nut screwing onto the socket, whereby the olive or ferrule is radially compressed to effect both a seal and a mechanical hold or grip on a pipe (e.g., of copper or other metal) inserted up to a shoulder in the socket. Such a pipe coupling will hereafter be referred to simply as being of the compression fitting type.
Various attempts have been made to overcome grip and leakage problems associated with using such a fitting with plastics pipe in hot water applications.
It is known to provide a rigid sleeve inside an end of a plastics pipe in order to obtain an effective grip when the olive or ferrule is compressed (which sleeve usually has an outward flange abutting the end of the plastics pipe), and an effective seal can be ensured by means of a sealing ring within the socket, but the latter requires modification of the inner wall of the socket (i.e., a groove) to house the sealing ring.
The object of the invention is to overcome the above disadvantages in a very simple manner.
According to the present invention, a pipe coupling of the compression fitting type for use with plastics pipe comprises a rigid sleeve adapted to fit within the plastics pipe and be centralised in the socket by a sealing ring making a close fit between the inner end of the sleeve and the wall of the socket adjacent the shoulder, whereby, when an end of plastics pipe is fitted over the sleeve and pushed into the socket until the end face of the pipe presses against the sealing ring, tightening of the nut on the socket compresses the olive or ferrule to effect a grip on the pipe and urge it inwards of the socket, thus causing axial compression of the sealing ring which consequently is distorted to effect sealing engagement with all four surfaces embracing it.In particular, good sealing will be effected between the end face of the pipe and the sealing ring and also between the sealing ring and the wall of the socket.
The rigid sleeve preferably has an outward flange at one end, to afford positive location of the sealing ring on the sleeve and of the latter against the shoulder. The other end of the sleeve is preferably tapered, to afford a lead-in for fitting of the sealing ring and an end of a plastics pipe. Thus the sleeve may be formed of deep drawn stainlesssteel with an outwardly curving flange at one end(which curvature may correspond closely to that ofan O-ring sealing ring) and in inwardly curving tapered portion at the other end. The sleeve maybe provided with one or more barbs, nibs or ribson its outer surface, to hold the sleeve in a pipeduring assembly and before tightening of the nuton the socket.
The sealing ring is conveniently an O-ring, and preferably has an initial inner diameter slightly less than the outside diameter of the sleeve and a diameter of the ring section slightly greater than the radial distance between the sleeve and the wall of the socket, whereby the elasticity of the ring will enable it to hold itself on the sleeve, and the compressibility of the ring can enable it to hold itself and the sleeve in the socket prior to the insertion of an end of a plastics pipe, but - in general - it is more convenient to fit the sleeve into the end of a plastics pipe before inserting the latter into the socket.
The invention also embraces a pipe joint consisting of a pipe coupling in accordance with the invention with a plastics pipe secured and sealed therein.
Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:~Figure 1 consists of part-sectional elevations of the five parts of a pipe coupling in accordance with the invention;Figure 2 is a greatly enlarged fragmentary section showing the parts of Figure 1 assembled together with an end of a plastics pipe;Figure 3 corresponds to Figure 2 but shows the assembly after tightening of the nut on the socket and forming a pipe joint in accordance with the invention; andFigures 4 to 6 are part-sectional elevations of modified forms of sleeeve for use in the invention.
In Figure 1 a pipe coupling comprises a socket A, a nut B, an olive or ferrule C, a rigid sleeve D, and a sealing ring E. The socket A may form part of any fitting, e.g., a tap, or a straight connector having a similar oppositely directed socket, or a branched connector having three such sockets, and is provided externally with flats 10 for a spanner or wrench and a screwthread 1 1 mating with the screwthread 12 of the nut B.
Mutually opposed tapers 13, 14 within the mouth of the socket and within the nut respectively cooperate with the tapered ends 1 5 of the olive or ferrule C (see Figures 2 and 3) either way round.
The inside of the socket A has a shoulder 16 for abutment by a flange 17 at one end of the sleeve D, and the sealing ring E is an O-ring having an inner diameter slightly less than the outside diameter of the sleeve D and a diameter of the ring section slightly greater than the radial distance between the sleeve and the wall 1 8 of the socket.
The other end 1 9 of the sleeve D has a slight taper affording a lead-in for fitting the sealing ring E and an end of a plastics pipe 20 (see Figures 2 and 3) to be secured and sealed in the pipe coupling to make a joint.
It will be seen in Figure 2 that the plastics pipe 20 has been pushed over the sleeve D as far as the sealing ring E will allow and into the socket A as far as the shoulder 16 will allow. The sealing ring E is slightly distorted by radial compression between the sleeve D and the wall 18 of the socket A, but it is distorted further, as shown in Figure 3, when the nut B is tightened on the socket A, to compress the olive or ferrule C axially between the tapers 13, 14, the resultant radial compression causing the olive to grip the pipe 20 and urging it inwards of the socket, to effect sealing engagement of the O-ring E with all four surfaces embracing it, namely, the sleeve D and its flange 17, and - especially - the wall 18 of the socket A and the end face 21 of the pipe 20.
Figures 4 to 6 show sleeves D provided respectively with barbs 22, nibs 23, and ribs 24 to hold the sleeve in a pipe during assembly and before tightening of the nut B on the socket A.