GB2210123A

GB2210123A - Pipe fitting assembly

Info

Publication number: GB2210123A
Application number: GB8822413A
Authority: GB
Inventors: Wayne Albert Harris
Original assignee: Philmac Pty Ltd
Current assignee: Philmac Pty Ltd
Priority date: 1987-09-24
Filing date: 1988-09-23
Publication date: 1989-06-01
Anticipated expiration: 2008-09-23
Also published as: GB8822413D0; NZ226227A; GB2210123B

Abstract

A pipe fitting assembly comprises a slit-type collet (16) clamped between a body (11) and a nut (12). A sealing ring (15) is compressed between a sleeve portion (17) of the collet and a groove (30) in the body (11) and urged into sealing engagement with the plastics pipe (19). The collet (16) has barbed fingers (22) which are urged inwardly by a tapered surface (26) in the nut (12). A longitudinal gap (31) in the collet (16) may close before the sealing ring (15) has fully entered its groove (30) but the barbed fingers (22) are not urged against the pipe until after the nut (12) has been tightened sufficiently to press the sealing ring (15) into position. An improved seal is thereby obtained, even at minimum tolerance for the pipe diameter and when the pipe end is slightly out-of-round. <IMAGE>

Description

DESCRIPTION PIPE FITTING ASSEMBLY.

This invention relates to a pipe fitting assembly which employs a collet.

Pipe fitting assemblies wherein use is made of a locking ring and a deformable sealing ring are already well known. Australian Patent 520863 (38462/78) describes a pipe fitting suitable for connecting an end of a polymeric pipe comprising a hollow body having a through bore formed with an internal shoulder, a locking ring having a plurality of circumferentially spaced radially outwardly projecting fingers, a deformable sealing ring arranged to abut the internal shoulder, and a nut co-acting between the body and the fingers of the locking ring to move the locking ring into the hollow body in an axial direction and also move the fingers inwardly in a radial direction.Membranes interconnect the fingers and resisted the radial inward movement until the resistance to deformation by the sealing ring inhibited further axial movement of the locking ring into the hollow body, such that any further tightening of the nut resulted in deformation of the membranes and radially inward movement of the fingers.

Owing to difficulties encountered when pipes become oval in shape, it has become evident that fittings constructed as described in the above Australian Patent are still capable of further improvement.

Other prior art includes G.B. Patents numbered 1238816 and 596397.

Although the nominal outside diameter of a pipe may be fixed, manufacturing tolerances are quite considerable, and there is also a tendency for both the shape and dimension of a polymeric pipe to change if subjected continually to hot and cold extremes as sometimes occurs.

A slit collet is capable of accommodating a wider tolerance range than a collet of the type illustrated in said Australian Patent 520863, since deflection of the collet material in a bending mode is more easily achieved than deflection in a plastic flow mode. Slit collets previously used on pipes have always had an axially extending gap, even when the collet is clamped to the pipe. The clamping effect is associated with a reduction of circumference of the collet. As a result of this, if a prior art collet is used on oval pipe, difficulties are often encountered in that the collet tends to grip the pipe before the resilient sealing ring is fully "home" in its receiving groove. It was for this reason that the membranes were left between the fingers of the collet in the fitting described in the Australian Patent 520863.

The membranes were capable of distortion but nevertheless, in some instances, the barbs on the fingers would frequently inhibit sliding of the collet over an oval or oversize pipe.

With the object of further improving a fitting, a split-collet type pipe fitting assembly comprises an annular hollow body the inner surface of which comprises an internal shoulder, a collet having a plurality of axially projecting circumferentially spaced deformable fingers converging towards one end and a sealing ring abutment surface at its other end, the collet being circumferentially discontinuous and having a pair of faces defining an axially extending gap, a sealing ring on the pipe between the abutment surface and the internal shoulder, a thread on the outer surface of the body, and a hollow nut engaging the thread, the nut having an inner surface also converging towards said one end and complementary to the converging fingers so that, upon initial tightening of the nut, said faces abut and close the gap thereby reducing the inner circumference of the collet, and the collet also moves along the pipe urging the sealing ring into engagement with the internal shoulder, and upon further tightening of the nut, the collet fingers bend radially inwardly and grip the pipe.

The collet in the rclaxed stato has an internal diameter which is significantly larger than the diameter of the pipe when it is on maximum tolerance. The gap in the collet in this state is also at its maximum.

In this invention, even when the collet is compressed to the state where the gap is completely closed, the collet is still free to move without the barbs gripping the surface of the pipe, even if the pipe has become distorted to an oval shape.

When the collet is associated with a sealing ring at one end, the action of the initial compression still permits lateral movement of the split collet which is necessary to force the sealing ring into its correct sealing location against the internal shoulder of the body When the sealing ring is thus located, it will no longer permit lateral movement, and further compression of the split collet brought about by the tightening of the nut on the threaded member, causes the fingers to bend radially inwardly so that the barbs grip the pipe.

bRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is described hereunder in some detail with reference to and is illustrated in the accompanying drawings in which: Fig. 1 is an "exploded~ view of the four elements of the fitting when placed on the end of the length of pipe, Fig. 2 is a similar view showing initial movement of the split collet in forcing a sealing ring into its receiving groove, Fig. 3 shows the fitting fully clapped onto the pipe, Fig. 4 is a side elevational section showing the split collet in more detail and to a larger scale, and Fig. 5 is an end elevation of the collet (Fig. S also showing the plane 4-4 of Fig. 4).

DESCRIPTION OF THE PREFERRED EMBODIMENT In this embodiment, a fitting comprises four parts, there being a body 11, a nut 12 having an internal thread 13 which threadably engages an external thread 14 of the body ii, a sealing ring 15 of elastomeric material, and a split collet 16.

As shown particularly in Figs. 4 and 5, the split collet 16 comprises a sleeve portion 17 which has an inner circumference defined by a surface 18 greater than the maximum outer circumference of a pipe 19 on which it is positioned, while its outer surface 20 tapers to converge towards the body 11.

One end of the split collet 16 closest to the nut 12 comprises a plurality of fingers 22 (there being six in this embodiment) and the fingers are spaced apart by slots 23 which extend into the fitting from that end as far as an end surface of an outstanding ring 24.

By this means each of the fingers 22 is capable of being bent about the reduced thickness portion 25, when a tapered surface 26 in the back of the nut 12 bears against the tapered surfaces 27 of the fingers 22. The inner surfaces of the fingers 11 are defined by barbed ring portions 28 which can grip into the wall of a pipe as best shown in Fig. 3.

It is however important that the pipe is not gripped until such time as the sealing ring 15 (a rubber 'O' ring) enters into its receiving groove 30 (as shown in Fig. 3) because otherwise the sealing ring 15 may not fully perform its sealing function. Accordingly, the included angle of the tapered surfaces 26 and 27 is between 30 degrees and 60 degrees (15 and 30 degrees with respect to the axis) and this ensures that there is a lineal forward movement even if the gap 31, by which the collet 4 is circumferentially discontinuous, is closed and gap defining faces 32 abut. Usually lineal movement of the collet along the pipe end closure of the gap 31 will occur simultaneously, as the soaling ring offers resistance to movement along the pipe, but the gap will close before completion of the lineal movement. The lineal force is thereby firstly applied to the 'O' ring 15 even though it is forced past a reduced diameter portion 33 of the body 11 before it enters its receiving groove 29 and abuts a shoulder 30.

Further tightening of the nut completes closure of gap 31 (if not fully closed), and bends the material of the split collet so that the barbs 18 grip the surface of the pipe as shown in Fig. 3.

Upon tightening of the nut 19 the body and collet will maintain a circular shape and force an oval pipe end also back into a circular shape.

Although the invention will be seen to be particularly simple it nevertheless resolves a problem which has been encountered in the field, and constitutes a marked improvement over the collet -described in Australian Patent No.520863.

Claims

1. A split-collet type pipe fitting assembly for clamping and sealing the outer surface of a pipe, which has a diameter lying within a tolerance range, comprising an annular hollow body the inner surface of which comprises an internal shoulder, a collet having a plurality of axially projecting circumferentially spaced deformable fingers converging towards one end and a sealing ring abutment surface at its other end, the collet being circumferentially discontinuous and having a pair of faces defining an axially extending gap, a sealing ring on the pipe between the abutment surface and the internal shoulder, a thread on the outer surface of the body, and a hollow nut engaging the thread, the nut having an inner surface also converging towards said one end and complementary to the converging fingers so that, upon initial tightening of the nut, said faces abut and close the gap thereby reducing the inner circumference of the collet, and the collet also moves along the pipe urging the sealing ring into engagement with the internal shoulder, and upon further tightening of the nut, the collet fingers bend radially inwardly and grip the pipe.

2. A split-collet type pipe fitting assembly according to claim 1 wherein said inner circumference of the collet when the yap is closed exceeds the outer circumference of the pipe when its diameter is at a maximum within said tolerance range.

3. A split-collet type pipe fitting assembly according to claim 1 or claim 2 wherein the included angle of convergence of both the nut inner surface and the fingers lies between 30 degrees and 60 degrees.

4. A split-collet type pipe fitting assembly according to any preceding claim wherein the body inner surface comprises a sealing ring receiving groove, said internal shoulder being a surface of that groove.

5. A split-collet type pipe fitting assembly according to any preceding claim wherein said closure of the gap occurs before completion of said movement of the collet along the pipe.

6. A split-collet type pipe fitting assembly according to any preceding claim wherein inner surfaces of the fingers comprise barbs which grip the pipe upon said radially inward bending of the fingers.

7. A split-collet type pipe fitting assembly according to any preceding claim wherein said collet comprises a sleeve- -portion having an end comprising said sealing ring abutment surface.

8. A split-collet type pipe fitting assembly according to claim 7 wherein said collet comprises a reduced thickness portion between the fingers and the sleeve portion.

9. A slit-collet type pipe fitting assembly, constructed and adapted to be used substantially as herein described with reference to and as illustrated in the accompanying drawings.