BACKGROUND TO THE INVENTION When plumbing is being installed fittings are used to connect the pipes to one another and to other components in the plumbing system. A plumbing fitting has to make a leakproof connection to the pipe, and must prevent the pipe being withdrawn from the fitting.

A seal, often an O-ring seal, within the fitting encircles the pipe and prevents leaking between the pipe and the fitting.

A toothed metal ring within the fitting prevents the pipe being withdrawn from the fitting, the ring encircling the pipe and its teeth being in the form of an array of radially inwardly directed teeth around the hole in the ring. The pipe passes through the hole in the ring and the inner peripheries of the teeth bite into the pipe.

In one form known to Applicant the teeth are angled. This permits the pipe easily to be slid through the ring in one direction deflecting the teeth as it does so.

However, the pipe cannot then be withdrawn and the fitting must be destroyed to get the pipe out.

In another form known to Applicant the ring is crushed onto the pipe by tightening a nut after the pipe has been passed through the ring. Crushing the ring pushes the teeth into the pipe. The intention is that, when the nut is loosened, the crushing action on the ring is released thus permitting the pipe to be withdrawn and the fitting to be re-used. In practice, however, getting the pipe out is difficult and the ring is often too badly damaged to be re-used.

As the nut of the type of prior art fitting known to applicant is tightened, the ring is pushed along the pipe. Once the gripping force is sufficient the ring can no longer move with respect to the pipe, and the pipe moves with the ring.

When the plumber is creating the joint, he cuts the pipe to length and inserts the cut end into the fitting until it abuts a stop. Because pipe ends are rarely cut "square", one part only of the periphery of the pipe contacts the stop. When the ring pushes on the pipe during tightening of the nut, the pipe tends to pivot about the point where it contacts the stop. This causes misalignment of the fitting and the pipe and hence the potential for leaks past the seal.

BRIEF DESCRIPTION OF THE INVENTION According to one aspect of the present invention there is provided a pipe fitting comprising a body defining a socket for receiving the end of a pipe, the socket being encircled by a threaded flange, a camping nut which can be screwed onto said flange, said nut having an internal clamping surface, and a pipe clamp which is circular in form and has a gap in the circumference thereof, the pipe clamp having an outwardly facing clamping surface, the clamping surface of said nut bearing upon the clamping surface of the pipe clamp when said pipe clamp is within the nut and the nut is tightened onto said flange thereby to compress said pipe clamp and reduce its internal diameter so that it grips a pipe which is in the socket, said gap closing up as said pipe clamp is compressed.

Said pipe clamp preferably comprises an annular member and a metal clip of generally annular form, the annular member having a bore which is stepped to provide a smaller diameter part and a larger diameter part, the larger diameter part constituting a recess which is open on one side, the recess receiving said metal clip and said clip having a gap in the circumference thereof.

In one form the cylindrical face which forms the radially outer face of said recess has a groove therein which receives the radially outer periphery of said clip.

To achieve the requisite clamping force the diameter of the inner

periphery of said clip is less than the diameter of the inner periphery of said member whereby the clip protrudes radially inwardly from the inner periphery of said member.

For sealing purposes said socket can be stepped to provide a smaller diameter part for receiving said pipe end and a larger diameter part which is open on one side, said larger diameter part serving to receiving a sealing ring which, in use, lies between a radial surface which forms one end of said larger diameter socket part and a radial surface of said pipe clamp member.

Said clamping surfaces are preferably both frusto-conical.

According to a further aspect of the present invention there is provided a method of securing the end of a pipe to a pipe fitting which comprises placing a clamping nut and an annular pipe clamp around said pipe so that the pipe passes through the nut and the pipe clamp, the pipe clamp having a gap in the circumference thereof, screwing the nut onto the flange so that axial movement of the nut with respect to the flange causes a clamping surface of the nut to exert a radially inwardly directed force on the pipe clamp to reduce its effective internal diameter and close up said gap, and inhibiting said pipe clamp from performing any axial movement with respect to the pipe whilst its internal diameter is being reduced and the gap in its periphery is being closed up to clamp it onto the pipe.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which:- Figure 1 is an axial cross-section of a pipe fitting body; Figure 2 is a cross-sectional view of a pipe fitting in accordance with the present invention; Figure 3 is a pictorial view of an annular member of the pipe fitting of Figure 2; Figure 4 is a pictorial view of a spring clip of the pipe fitting of Figure 2; Figure 5 is a section through a modified form of the annular member of Figure 3, and Figure 6 is a section through another form of annular member.

DETAILED DESCRIPTION OF THE DRAWINGS The body 10 shown in Figure 1 is in the form of a T-piece having stepped sockets 12.1,12.2 and 12.3. The smaller diameter part 14.1,14.2,14.3 of each socket is for receiving a pipe (not shown in Figure 1). The larger diameter parts 16.1,16.2, 16.3 of the sockets receive 0-rings (not shown in Figure 1). The sockets 12.1,12.2, 12.3 are bounded by externally threaded flanges 18.1,18.2,18.3 respectively. The flanges have end faces 19.1,19.2 and 19.3 respectively.

It will be understood that, whilst a T-piece has been shown in Figure 1, the body could be for joining two c-axial pipe ends. In this event the socket 12.3 is omitted. Alternatively the fitting could be in the form of an elbow to join two pipes which are at right angles to one another, in which event one of the sockets 12.1,12.2 is 5 omitted.

Turning now to Figure 2, this shows the socket 12.1, the flange 18.1 and the parts associated therewith which serve to secure a pipe 20 to the body 10.

The end of the pipe 20 is in the smaller diameter part 14.1 of the socket 12.1 and there is an 0-ring 22 in the larger diameter part 16.1. The 0-ring 22 encircles 10 the pipe 20.

A member 24 (see also Figure 3) and a clip 26 (see also Figure 4) together forming a pipe clamp encircle the pipe 20 externally of the socket 12.1.

A clamping nut 28 having an internally threaded cylindrical portion 30 is- screwed onto the flange 18.1. The nut 28, in addition to the cylindrical portion 30, has a 15 portion 32 bounded internally by a frusto-conical surface 34 and also has a collar 36 which extends inwardly from the portion 32.

The member 24 is generally annular (see Figure 3) but has a gap 38

therein. The member 24 has an external frusto-conical surface 40 which matches the surface 34 in conical angle. The bore of the member 24 is stepped so as to provide bore sections 42.1 and 42.2 of different diameters. The diameter of the smaller section 42.1 is slightly greater than the external diameter of the pipe 20. The bore section 42.2, and the adjacent radially extending surface 42 of the member 24, define a recess for the spring clip 26. The recess is open on one side.

The face of the member 24 opposite to the face 42 is designated 43 and lies in a plane which is at right angles to the axis of the member. The face 43 abuts the end face 19.1.

The spring clip 26 is also generally annular (see Figure 4) and has a gap 44 in its periphery. The radially inner periphery of the clip 26 is, apart from where it is interrupted by the gap 44, circular in shape and devoid of any discontinuities or teeth.

The member 24 is preferably of a resiliently deformable synthetic plastics material and the clip 26 is preferably of a metal such as spring steel.

In Figure 5 there is shown a modified annular member designated 24.1.

This member differs from that illustrated in Figures 1 to 3 in that there is a circumferentially extending groove 46 in the cylindrical face which forms the radially outer face of the recess which receives the clip 26. The radially outer periphery of the

clip 26 fits in this groove. The radially inner peripheries of the member 24.1 and the clip 26 are designated 24.2 and 26.2 respectively in Figure 5. A surface of the pipe 20 is also shown in Figure 5.

In the form shown in Figures 6 the member and clip are combine into a one piece pipe clamp 48 which is of any suitable material and provides the surface 40 as well as a radially inner edge 26.3 which contacts the pipe. The pipe clamp 48 has a gap, equivalent to the gap 38, in its periphery.

To attach the pipe 20 to the body 10, the O-ring 22 is inserted into the larger diameter part 16.1 of the socket 12.1. The clip 26 is pressed into the recess provided therefor in the annular member 24. The gaps 38 and 44 can be aligned but this is not essential. The pipe clamp constituted by the assembled member 24 and clip 26 is then dropped into the clamping nut 28 through the open end opposite to the collar 36. The surfaces 34 and 40 abut.

The easiest way of assembling the fitting is to slide the clamping nut 28, member 24 and clip 26 onto the pipe 20. The end of the pipe 20 is then inserted into the flange 18.1 until it abuts the end surface of the socket part 14.1. The nut 28 is then screwed onto the flange 18.1 and tightened onto the flange 18.1. Because the face 43 of the member 24 is against the end face 19.1 by the time the surface 34 bears on the surface 40, the pipe clamp cannot move to the left (as viewed in Figure 1) upon radially

inward pressure being exerted on it by the nut 28. The only movement possible is movement of the assembled pipe clamp's components radially inwardly to close up the gaps 38,44. The face 43 of the annular member 24, because it abuts the end face 19.1 of the flange 18.1, does not exert any significant crushing forces on the 0-ring 22.

It will be noted from Figure 2, and also from Figure 5, that the inner edge of the clip 26 is radially inwardly of the inner edge of the member 24. These edges are those designated 24.2 and 26.2 in Figure 5. The radially inner edge of the metal clip 26 thus engages the pipe 20 and the member 24,24.1 acts firstly as a carrier for the clip 26 and secondly as the means through which the force required to deform the clip 26 and close up its gap 44 is transmitted. The member 24 is not intended to touch the pipe 20.