1 A pipe coupling having a collet and seal ring where the seal ring is removably attached to the collet FIELD OF THE INVENTION This invention relates to a pipe coupling including a collet and a seal ring, 5 and in particular to a collet and seal ring with means for attachment to each other for use in the pipe coupling assembly for pipes typically made from plastic. BACKGROUND OF THE INVENTION Couplings and transition fittings of the type having a gripping member are well known, see for example Applicant's U.S. Pat. No.5,593,186. In general these 10 couplings include a nut, body, gripping member or collet having a plurality of inwardly directed barbed projections, as well as a sub-assembly of a compression sleeve and resilient seal ring that is typically permanently attached to the inner end of the compression sleeve. The nut and the gripping member (also referred to as the gripping ring or collet) include abutting tapered surfaces. A pipe end is freely 15 insertable through the sub-assembly and into a socket in the body of the coupling. As the nut is tightened it exerts both a radial and longitudinal force on the grip ring that in turn longitudinally exerts a force on the sleeve and seal ring. The seal ring encounters an abutment in a socket in the body, and further tightening of the nut then further radially compresses the gripping member so that its inwardly directed 20 barbed projections engage the outer surface of a pipe to which the coupling is attached. There may also be provided abutment surfaces within the body of the coupling and the nut that abut inner and outer surfaces of a flange outstanding from the outer end of the compression sleeve. One skilled in the art will appreciate that as the nut is tightened, the tapered 25 surface of the nut acts upon the tapered surface of the gripping member causing it to be both compressed and urged into the body. As the gripping member engages the pipe it is also drawn into the assembly. In some instances the compression sleeve is not required and the gripping member or collet acts directly on the seal ring. Thus a pipe coupling assembly may 30 consist of a body in which a seal ring and a collet is inserted and a nut threadedly 2 engaged with the body and holding the collet in place. Each of the components of the assembly can come in a variety of interchangeable styles which can be combined to produce a large number of assemblies. The ability to interchange components has obvious advantages for inventory 5 levels in retail and workshop environments but also has a disadvantage. When a person takes a collet from a first assembly for use in a second assembly they may inadvertently leave the corresponding seal ring behind in the first assembly. This would lead to assemblies with no seal rings and also to assemblies with two seal rings. Also, when making an assembly kit from scratch, the seal ring could easily 10 be omitted. Having an assembly with no or an incorrect number of seal rings is a problem. Using an assembly with no seal ring would lead to leaks. Using an assembly with two seal rings could lead to a coupling prone to failure under pressure. When noticed, an extra seal ring is easily remedied, but for the case of 15 having no seal ring it may be a great inconvenience at best and at worst the coupling may not be used if a seal ring has to be obtained from a third party. The object of this invention is to provide a pipe coupling and a collet and seal ring that alleviates the above problems, or at least provides the public with a useful alternative. 20 SUMMARY OF THE INVENTION Therefore in one form of the invention there is proposed a pipe coupling wherein a pipe is insertable into the coupling, comprising: a hollow body having external threads and an inner surface; a nut having internal threads co-operable with said body external threads at a 25 first end and an outwardly converging inner abutment surface; a deformable gripping member having an internal bore adapted to receive said pipe therethrough, said member having an outer abutment surface at an outer end co-operable with said nut inner abutment surface, the gripping member having an internal surface with projections extending radially inwardly therefrom; and 30 a seal ring secured to the gripping member.
3 In preference the seal ring is secured to an inner end of the gripping member. In preference the smallest internal diameters of the gripping member, hollow body and the nut are all only slightly greater than an external diameter of the pipe to which the coupling is securable, such that an end of such pipe is freely insertable 5 through said nut, gripping member, seal ring into said hollow body, and tightening of said nut over said external threads causes axial movement of said gripping member, sealing engagement of said seal ring with said body and such pipe, and radially inward deformation of said gripping member such that said projections clamp such pipe. 10 In preference the gripping member is a split ring. In preference the gripping member includes a cylindrical skirt having a groove, the seal ring being correspondingly shaped to engage the groove so as to be secured to the gripping member. In preference the skirt steps down from a first surface to a second smaller 15 diameter surface and includes a circumferential lip extending radially outwardly from the end of the second surface to define the groove, the diameter of the lip being smaller then the diameter of the skirt first surface. In preference the seal ring is correspondingly shaped to engage the groove and the lip. 20 In preference the seal ring includes a groove and a lip, the seal ring groove being of a width to engage the gripping member lip, the seal ring lip being of a size to engage the gripping member groove. In a further form of the invention there is proposed a gripping member for use with a pipe coupling the gripping member having a resilient seal ring secured to 25 the gripping member. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various implementations of the invention and, 4 together with the description, serve to explain the advantages and principles of the invention. In the drawings: Figure 1 is a cross-sectional view of a pipe coupling embodying a gripping member and seal ring according to a preferred 5 embodiment of the invention; Figure 2 is a cross-sectional view of the gripping member and seal ring; Figure 3 is a close-up partial cross sectional view of the gripping member engaging the seal ring; 10 Figure 4 is a side view of the gripping member and seal ring; Figure 5 is an exploded perspective view of the pipe coupling embodying the present invention; and Figure 6 is an exploded side view of the pipe coupling assembly. LIST OF COMPONENTS 15 10 pipe coupling 12 body 14 external (male) threads 16 nut 18 internal (female) threads 20 20 hooked projection 22 inner abutment surface 24 shoulder 26 cavity 28 gripping member or collet 25 30 bore 32 internal surface 5 34 barbs 35 pipe 36 outer abutment surface 37 seal ring 5 38 inner shoulder 40 collet skirt 42 collet lip 44 collet groove 46 seal ring lip 10 48 seal ring groove 50 seal ring body DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The following detailed description of the invention refers to the accompanying drawings. Wherever possible, the same reference numbers will be 15 used throughout the drawings and the following description to refer to the same and like parts. Dimensions of certain parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration. Referring to the drawings now in greater detail there is provided a pipe coupling 10 including a body 12 having external or male threads 14, the threads 20 adapted for use by a nut 16 having internal or female threads 18 to engage male threads 14 in the body 12. The Figures illustrate one nut 16 engaging body 12 on one end. It is to be understood that the present invention may equally well be used on a pipe coupling having symmetrical ends, thus nuts on either end, as well as pipe couplings where 25 one of the ends is adapted for connection to a different type of pipe and may accommodate a different fitting. The nut 16 includes a hooked projection 20 having an inner abutment surface 22 that is generally outwardly diverging. It is to be understood that other 6 configurations of a nut may be provided such as those nuts that instead of having a hooked projection may instead simply be extended and have the inner abutment surface in the extension of the nut. For that the reader is referred to the above mentioned US patent. 5 The body 12 includes a shoulder 24 defining a cavity 26 within which is generally located gripping member or collet 28 including a bore 30 defined by inner surface 32. Located on the inner surface 32 are projections or barbs 34 that may extend rearwardly. The gripping member 28 includes an outer abutment surface 36 generally correspondingly shaped to the inner abutment surface 22 of the nut 16 so 10 that as the nut 16 is screwed onto the body 12, the nut abutment surface 22 engages the gripping member outer abutment surface 36 causing the gripping member 28 to move both axially into the body 12 and be compressed radially causing the barbs 34 to bite into and engage the pipe 35. To complete the seal a seal ring 37 is provided that is located between the 15 end of the gripping member 28 and inner shoulder 38 in the body 12 so that as the nut is tightened the gripping member compresses the seal ring 37 providing a seal. To ensure that as the gripping member is removed from the body that the seal ring does not remain behind the seal ring 37 is secured to the gripping member 28 essentially by an arrangement of the end of the gripping member and the front of 20 the seal ring adapted to mate by being correspondingly shaped. In this particular embodiment that is achieved by the gripping member providing a groove that is engaged by a lip in the seal ring. However, although not discussed further it is to be understood that other configurations may be equally well used. Thus the gripping member or collet 28 includes a skirt 40 with a lip 42 at its 25 end defining a groove 44. The seal ring 37 is correspondingly shaped to engage the collet and includes a lip 46, groove 48 and body 50, the body providing a seal within the pipe body 12 when compressed by the collet 28. The collet skirt 40 steps down to a smaller diameter so that the collet lip 42 is of a smaller diameter than the larger diameter of the skirt. This ensures that when the seal ring is secured to the collet the 30 combined outer surface is generally level.
7 The collet is a split type collet to allow for it to be easily removed from a tool. The split may be keyed, so as to provide a locking mechanism to prevent axial movement between the split ends. It is not however intended to limit the invention to a particular type of collet. 5 The reader will now appreciate the invention which assists in ensuring that if a gripping member is removed from the body of a pipe coupling the seal ring is not left behind. Whilst the O-ring may be removed, the engaging arrangement ensures that this must be a conscious action by the user. Further advantages and improvements may very well be made to the present 10 invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all 15 equivalent devices and apparatus. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in this field. In the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" 20 is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.