WO2001090627A1

WO2001090627A1 - Pipe coupling

Info

Publication number: WO2001090627A1
Application number: PCT/GB2001/002085
Authority: WO
Inventors: Matthew Readman
Original assignee: The University Of Manchester
Priority date: 2000-05-20
Filing date: 2001-05-14
Publication date: 2001-11-29
Also published as: GB0012110D0; AU2001254971A1

Abstract

A pipe coupling is described comprising a body (1) defining a socket (3) having a longitudinal axis and an inner assembly (2) located within the socket for receiving a pipe inserted into the socket in a predetermined direction so as to extend generally parallel to the axis. The inner assembly is displaceable relative to the body to permit limited angular movement between the body and a pipe received by the inner assembly, and comprises a grab ring (14) adapted to grip an inserted pipe, and means for tightening the grab ring onto a gripped pipe in response to displacement of the grab ring relative to the body with a gripped pipe in the direction opposite to the direction of pipe insertion. The pipe coupling thus allows limited angular movement of the pipe whilst resisting end loads applied to the pipe, and may thus be used in high pressure applications.

Description

PIP E COUPLING

The present invention relates to a pipe coupling, particularly to a pipe coupling allowing limited angular movement between the coupling and a pipe connected to the coupling.

Known pipe couplings that allow for angular movement of pipes to which they are connected can generally only be used at low pressures, as it is difficult to provide a coupling that will give both a reliable seal over a range of angles and an adequate resistance to end loads arising for example from the application of high pressures to the coupled pipe.

It is an object of the present invention to provide an improved pipe coupling.

According to the present invention there is provided a pipe coupling comprising a body defining a socket having a longitudinal axis and an inner assembly located within the socket for receiving a pipe inserted into the socket in a predetermined direction so as to extend generally parallel to the axis, the inner assembly being displaceable relative to the body to permit limited angular movement between the body and a pipe received by the inner assembly, wherein the inner assembly comprises a grab ring adapted to grip an inserted pipe, and means for tightening the grab ring onto a gripped pipe in response to displacement of the grab ring relative to the body with a gripped pipe in the direction opposite to the direction of pipe insertion.

The pipe coupling according to the present invention allows limited angular movement of the pipe whilst resisting end loads applied to the pipe, and may thus be used in high pressure applications.

Preferably, the grab ring comprises a C-shaped washer, and the tightening means comprise means for reducing the gap between free ends of the C-shaped washer. The tightening means preferably comprise levers engaged between the free ends of the C-shaped washer and a socket ring, the levers being arranged to pivot relative to the socket ring so as to control the width of the gap.

The free ends of the C-shaped washer preferably define projections each of which is engaged by one end of a respective lever, a second end of each lever engaging a respective edge defined by a cut-out in the socket ring.

The inner assembly preferably includes an O-ring adapted to form a seal between the body and an inserted pipe, the O-ring applying axial pressure which biases the grab ring towards the socket ring. The O-ring is preferably located between a pair of anti-extrusion rings.

The body may be a one-piece structure defining a part-spherical socket and the inner assembly may comprise a plurality of components each of which can be inserted edge-on into the socket and rotated to an orientation in which it cannot be withdrawn from the socket in the direction opposite to the direction of pipe insertion.

The grab ring is received in a groove provided in the pipe surface.

Preferably, the grab ring has a chamfered inner edge to grip the pipe. Movement of the pipe in the direction opposite to the direction of pipe insertion preferably causes the grab ring to flex such that the chamfered edge is displaced radially inwardly.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a part cross-sectional view through a pipe coupling according to the present invention;

Figure 2 is an exploded perspective view of the component parts of an inner assembly of the pipe coupling shown in Figure 1;

Figure 3 shows the coupling of Figure 1 with the internal assembly positioned outside a socket defined by the coupling body;

Figures 4 to 14 illustrate the sequence of steps involved in assembling the coupling of Figure 1 and installing a pipe in the assembled coupling;

Figures 15a to 15c show the coupling of Figure 1 coupled to a pipe at various different angles to a longitudinal axis of the coupling;

Figures 16 and 17 show the coupling of Figure 1 used with a pipe extension;

Figures 18 to 20 show an alternative embodiment of coupling having apertures so that wedges may be driven in to the coupling to release it from a pipe; and

Figures 21 to 23 are part-sectional enlargements of the wedge and coupling of Figures 18 to 20.

Referring to Figures 1 to 3 of the accompanying drawings, there is illustrated a pipe coupling comprising an outer body 1 and an inner assembly 2.

The outer body 1 has a socket 3 extending therethrough and defining a longitudinal axis indicated by a broken line. The body has a flange 4 at one end 5 thereof, the flange 4 having apertures 6 spaced around the periphery thereof and sized to receive bolts or other connectors in order to connect the coupling to another coupling or to a flange provided on machinery or the like. Adjacent to the flange 4, the outer surface of the body 1 is generally cylindrical but the outer surface of the body 1 tapers inwardly towards an opposite end 7 of the body.

The inner surface of the body 1 which defines socket 3 is part-spherical. A shoulder 8 defines one end of the part-spherical interior surface of socket 3, the shoulder 8 being interior of the flange 4. The interior surface of socket 3 flares outwardly between shoulder 8 and end 5. At the end 7 of the body 1, the inner surface of the socket 3 also flares outwardly, creating a chamfered lip 9.

The inner assembly 2 is formed of eight interconnecting parts. These are a first end socket ring 10, a first anti-extrusion ring 11, a rubber O-ring 12, a second anti-extrusion ring 13, a grab ring 14, two levers 15 and a second end socket ring 16.

First end socket ring 10 is annular having a cylindrical inner surface and a part-spherical outer surface extending between end surfaces 17 and 18. Two diametrically opposed axial projections 19 extend from end 18, each having a cross- section of a chord of a circle, and each being located between two diametrically opposed flattened areas 20 on the outer surface. Second end socket ring 16 is a similar shape to first end socket ring 10, but has a cut-out area 21 into end surface 18 adjacent one of the flattened areas 20.

First anti-extrusion ring 11 is a generally circular washer having two diametrically opposed flattened edge portions. Second anti-extrusion ring 13 is the same shape as first anti-extrusion ring 11, but is approximately half as thick.

The grab ring 14 is a C-shaped washer of approximately the same thickness as second anti-extrusion ring 13. The ends of the C-shaped grab ring 14 define a gap 22. Again, grab ring 14 has two diametrically opposed flattened edge portions. The grab ring 14 has a chamfered inner edge 23, and in its free state has a slightly smaller internal diameter than rings 11 and 13. The ends of the grab ring 14 which define the gap 22 support projections 24 that extend to one side of the grab ring 14. Each projection 24 is T-shaped such that the ends of the projections 24 are wider than central portions of the projections.

Each lever 15 is a flat member one end edge of which defines a cut-out 25. One side edge of each lever is straight, whilst the other side edge defines an arc of a circle. The cut-out portion 25 is designed to fit around the central portion of a projection 24 of grab ring 14. The other edge of the lever 15 engages an edge 26 defined by the cut-out area 21 of the second end socket 16, the ends of the T-shaped projections being received in a deeper central section of the cut-out 21.

Referring now to Figures 4 to 14 of the accompanying drawings, the assembly and use of the coupling of Figures 1 to 3 is as follows:

As shown in Figure 4, the first end socket 10 is first positioned so that it is held edge-on to body 1, and is pushed in to body 1. The flattened areas 20 allow the socket 10 to slide into the body 1. The socket 10 is then rotated from the position shown in Figure 4 to the position shown in Figure 5, that is, so that one of the flattened areas 20 abuts shoulder 8, and the other flattened area 20 projects from lip 9. The first anti-extrusion ring 11 is then inserted into body 1 and positioned next to end 18 of the first end socket 10 so that the flattened edges of the ring 11 align with the projections 19 of first end socket 10. Thus, together the socket 10 and anti-extrusion ring 11 define a circular surface facing in the direction in which the projections 19 extend.

With reference to Figure 6, the second end socket 16 is then inserted into the body 1 on the opposite side of anti-extrusion ring 11 to the first end socket 10. The second end socket 16 is then rotated, so that the projections 19 of the second end socket 16 point towards and are aligned with the projections 19 of the first end socket 10. Grab ring 14 is then inserted as shown in Figure 7 between the anti-extrusion ring 11 and second end socket 16 with its flattened edges adjacent to projections 19 of end socket 16. As shown in Figure 8, the levers 15 are then engaged between projections 24 on grab ring 14 and the second end socket 16, and the second anti-extrusion ring 13 is inserted between grab ring 14 and the first anti-extrusion ring 11, with its flattened edges aligned with projections 19. Finally, the O-ring 12 is inserted between the first and second anti-extrusion rings 11, 13, to complete the formation of inner assembly 2.

The inner assembly 2 is then rotated through 90° so that the centres of the rings 11, 12, 13, 14 and sockets 10, 16 are aligned with the longitudinal axis through the body, resulting in the assembly shown in Figure 1. A pipe 27 may then be offered up to and connected to the pipe coupling, as shown in Figures 9 to 14.

An end of pipe 27 is offered up to the coupling, and is pushed through the rings and sockets. As can be seen in Figures 9 to 11, initially the levers 15 lie flat against the cut-out 21 in the end socket 16. This is because the O-ring 12 biases the ring 13 against the grab ring 14. As a result the gap 22 between the ends of the grab ring is a minimum. As shown in Figure 12, as the pipe is pushed through the grab ring 14 and up against shoulder 8 of body 1, the pipe 27, the outside diameter of which is slightly greater than the minimum diameter of the grab ring 14, forces the grab ring 14 to expand. This causes the levers 15 which are engaged with the ends of the grab ring to pivot about the ends of the levers which engage the edge 26 of the cut-out 21 (Figure 2). The anti-extrusion ring 13 is forced away from the socket 16, compressing the O-ring 12. The O-ring 12 is also compressed between the pipe 27 and the body 1, providing a reliable seal.

If the pipe 27 is then pulled backwards as a result of the application of an end- load to the pipe, this causes levers 15 to butt up against cut-out area 21 of end socket 16, thus tightening grab ring 14. This causes the chamfered edge 23 of grab ring 14 to dig in to the surface of the pipe 27, as shown in Figure 13. A further backwards movement of pipe 27 causes further deformation of grab ring 14 as shown in Figure 14, this further deformation driving the chamfered edge of the grab ring further into the pipe. The anti-extrusion rings 11, 13 prevent the O-ring 12 from being extruded past the flattened areas 20 of the sockets 10 and 16 from its desired position.

The pipe and inner assembly may be rotated with respect to the longitudinal axis of body 1, as shown in Figures 15a - 15c. This is achieved by the co-operating part spherical surfaces of inner assembly 2 and outer body 1, with the chamfered lip 9 of body 1 allowing a wide range of pipe angles.

Figures 16 and 17 show the use of the pipe coupling as previously described with a pipe made of a material such that the grab ring 14 could not bite into the pipe surface, or made of a material that is too readily deformable to be reliably gripped by the grab ring 14. An extension 28 and a collar 29 are attached to one end of a pipe 30. Extension 28 may be formed of stainless steel and has teeth 31 provided on one end that bite into the interior surface of the pipe 30, and a groove 33 cut into its outer surface. Collar 29 has an internal chamber 34 that is expandable under pressure (using for example pressurised fluid) to force the pipe onto teeth 31. The use and components of the illustrated extension are described in PCT patent application PCT/GB99/0424.

As the pipe extension 28 is inserted into the coupling, grab ring 14 is able to flex so that the edge 23 moves into groove 33, thus gripping the pipe extension 28, and hence pipe 30. It should be appreciated that a groove 33 may be provided on the outer surface of any pipe formed of a hard material such as stainless steel, to enable the grab ring to grip the pipe.

Referring now to Figures 18 to 23, if the coupling is to be used in a situation where there is a requirement to remove it from the pipe after use, three apertures 34 may be provided in each of the second end socket 16, the grab ring 14 and the anti- extrusion ring 13 to enable wedges 35 to be driven in to the apertures and hence release the grab ring 14.

The apertures 34 are semi-circular in cross-section and extend around the inner edges of socket 16, grab ring 14 and anti-extrusion ring 13 at 90°, 180° and 270° relative to the position of the gap 22 in grab ring 14. Apertures 34 in grab ring 14 have a chamfered inner edge 36. Three wedges 35 are used, one for each aperture, each wedge 35 having a generally semi-cylindrical shape, with a reduced diameter end 37 having a chamfer 38 defining a shoulder 39, next to which a groove 40 is formed. The other end of each wedge 35 has a flange 41.

The wedges 35 are driven into the apertures 34 one at a time by means of pressure applied to flange 41 for example by means of a hammer. A wedge 35 and coupling showing rings 13, 14 and end socket 16 are shown in Figures 18 and 21. As chamfer 38 of wedge 35 meets chamfered edge 36 of grab ring 14, the grab ring 14 is caused to expand. This expansion continues until edge 36 of grab ring 36 has passed over shoulder 39, at which point grab ring 14 contracts slightly into groove 40, as shown in Figures 19 and 22. In order to allow for this expansion, the end socket 16 and/or the anti-extrusion ring 13 may be formed of a material that will deform under the pressures involved, an example of which is PNC. Alternatively, a deformation of the pipe 27 may be caused at the same time that the grab ring 14 is expanded. After all three wedges 35 have been driven into the coupling, the grab ring 14 has been expanded sufficiently to release pipe 27, which may be pulled out of the coupling, as shown in Figures 20 and 23. The wedges 35 then fall into the space left by the pipe, allowing the coupling and wedges to be re-used.

Claims

1. A pipe coupling comprising a body defining a socket having a longitudinal axis and an inner assembly located within the socket for receiving a pipe inserted into the socket in a predetermined direction so as to extend generally parallel to the axis, the inner assembly being displaceable relative to the body to permit limited angular movement between the body and a pipe received by the inner assembly, wherein the inner assembly comprises a grab ring adapted to grip an inserted pipe, and means for tightening the grab ring onto a gripped pipe in response to displacement of the grab ring relative to the body with a gripped pipe in the direction opposite to the direction of pipe insertion.

2. A pipe coupling according to claim 1, wherein the grab ring comprises a C- shaped washer, and the tightening means comprise means for reducing the gap between free ends of the C-shaped washer.

3. A pipe coupling according to claim 2, wherein the tightening means comprise levers engaged between the free ends of the C-shaped washer and a socket ring, the levers being arranged to pivot relative to the socket ring so as to control the width of the gap.

4. A pipe coupling according to claim 3, wherein the free ends of the C-shaped washer define projections each of which is engaged by one end of a respective lever, a second end of each lever engaging a respective edge defined by a cutout in the socket ring.

5. A pipe coupling according to claim 3 or 4, wherein the inner assembly includes an O-ring adapted to form a seal between the body and an inserted pipe, the O-ring applying axial pressure which biases the grab ring towards the socket ring.

6. A pipe coupling according to claim 5, wherein the O-ring is located between a pair of anti-extrusion rings.

7. A pipe coupling according to any preceding claim, wherein the body is a one- piece structure defining a part-spherical socket and the inner assembly comprises a plurality of components each of which can be inserted edge-on into the socket and rotated to an orientation in which it cannot be withdrawn from the socket in the direction opposite to the direction of pipe insertion.

8. A pipe coupling according to any preceding claim, wherein the grab ring is received in a groove provided in the pipe surface.

9. A pipe coupling according to any preceding claim, wherein the grab ring has a chamfered inner edge to grip the pipe.

10. A pipe coupling according to claim 9, wherein movement of the pipe in the direction opposite to the direction of pipe insertion causes the grab ring to flex such that the chamfered edge is displaced radially inwardly.

11. A pipe coupling according to any preceding claim, wherein at least one aperture is provided in the grab ring to enable a wedge to be driven between an inserted pipe and the grab ring, thereby to release the grip of the grab ring from the pipe and allowing the pipe to be withdrawn from the coupling.

12. A pipe coupling substantially as hereinbefore described, with reference to the accompanying drawings.