GB2369663A - Pipe coupling with sleeve deformable by pressurizing fluid - Google Patents

Abstract

A pipe coupling 2 comprises a sleeve portion 6 for receiving a pipe, which has a deformable radially inner wall 14 and a deformable radially outer wall 12 the radially inner and radially outer walls being sealed together at axially spaced apart locations so as to form an annular chamber therebetween. A support clamp (222, Fig 3a) surrounds the outer wall for restricting expansion of the outer wall in use; the outer wall having an opening 18 through which a pressurising fluid can be introduced into the annular chamber so as to deform the inner wall radially inwardly and into sealing and gripping engagement with the pipes, where the deformable radially outer wall is formed from a metal.

Description

A PIPE COUPLING

This invention relates to a pipe coupling and in particular to a mechanical pipe coupling for connecting plastics pipes.

Background of the Invention WO-A-00/39495 discloses a pipe coupling in which the coupling body comprises radially inner and radially outer sleeve portions sealed together so as to form an annular chamber therebetween, an opening or port being provided in the outer sleeve so that fluid can be pumped into the chamber. In use, a pipe is inserted into the inner sleeve portion and the annular chamber is subjected to hydraulic pressure thereby deforming the inner sleeve into sealing engagement against the pipe. In one embodiment, the radially outer sleeve portion is formed such that it is substantially non-deformable under the pressure conditions encountered in use, but in another embodiment, the outer sleeve portion is formed from rubber and the inner sleeve portion is formed from copper, a clamp surrounding the outer sleeve so that when the annular chamber between the inner and outer sleeves is pressurised, expansion of the rubber outer sleeve is prevented and the inner sleeve is deformed into engagement with the pipe.

Summary of the Invention The present invention relates primarily, but not exclusively, to improvements in the pipe coupling disclosed in WO-A-00/39495.

In a first aspect, the invention provides a pipe coupling comprising a sleeve portion for receiving a pipe, the sleeve portion comprising a deformable radially inner wall and a deformable radially outer wall, the radially inner and radially outer walls being sealed together at axially spaced apart locations so as to form an annular chamber therebetween ; and a support clamp surrounding the outer wall for restricting expansion of the outer wall in use ; the outer wall having an opening

through which a pressurising fluid can be introduced into the annular chamber so as to deform the inner wall radially inwardly and into sealing and gripping engagement with the pipe; characterised in that the deformable radially outer wall is formed from a metal.

The pipe coupling of this aspect of the invention differs from the pipe couplings disclosed in WO-A-00/39495 in that the deformable outer wall of the sleeve portion is formed from a metal. In WO-A-00/39495, the outer wall is either substantially non-deformable so that no outer support clamp is required, or it is formed of a resiliently deformable material (rubber) and a support clamp is provided to prevent radial expansion of the rubber sleeve. The outer wall of the sleeve portion of the present invention is typically formed from a thin-walled metal tubing, for example mild steel tubing having a thickness in the range 0.05 mm to 5 mm, preferably 0.25 mm to 2 mm, more preferably 0.5 mm to 1 mm. The primary advantage of the thin metal wall over the rubber sleeve of WO-A-00/39495 is that the potential problem of the rubber tubing extruding out through any gaps within the clamp and/or between the clamp and the sleeve is thereby eliminated. Other advantages are discussed below.

The couplings of the invention are primarily although not exclusively intended for use with plastics pipes such as pipes made from polyolefins (e. g. polyethylene) or PVC, or thin-walled metal pipes such as pipes formed from stainless steel. In the context of the present invention, the term"thin-walled"when used in relation to metal pipes (as distinct from the sleeves of the couplings) preferably refers to pipes having a wall thickness of less than about 5 mm, typically less than about 4 mm, more typically less than about 3 mm, for example less than about 2 mm, more particularly less than about I mm, e. g. less than about 0.5 mm.

In order to prevent a plastics pipe from collapsing when subjected to radial compression, it is usual to provide a supporting spigot that is inserted into the end of the plastics pipe and stiffens the pipe wall against radial compressive forces.

However, one of the problems with such an arrangement is that it is possible for

the operative in the field when installing the pipe to forget or otherwise omit to include the support spigot with the result that the integrity of the joint may be compromised. A further object of the invention is to provide a means of obviating this problem.

Accordingly, in another aspect, the invention provides a pipe coupling comprising a spigot portion and a sleeve portion joined together so as to define radially therebetween an annular space for receiving an end of a pipe, the sleeve portion comprising a radially outer wall and a radially inner wall, the radially inner and radially outer walls being sealed together at axially spaced apart locations so as to form an annular chamber therebetween; the radially outer wall having an opening through which a pressurising fluid can be introduced into the annular chamber so as to deform the radially inner wall radially inwardly and into sealing and gripping engagement with the pipe.

The spigot portion and sleeve portion can be formed separately and then the spigot portion attached to the sleeve portion or part of the sleeve portion by, for example, welding, or the sleeve portion and spigot portion can be joined together by virtue of having been integrally formed. Thus the term"joined together"as used herein means that the spigot portion and sleeve portion are physically connected in some way and are not merely placed in contact with one another.

The spigot portion and sleeve portion together form an annular space for receiving an end of the pipe, and in particular a plastics pipe or a thin-walled metal pipe. The spigot portion fits within the bore of the plastics pipe and serves to support the pipe against radially compressive forces generated by deformation of the radially inner wall when the annular chamber between the radially inner and radially outer walls of the sleeve is pressurised.

The spigot portion can have ribs or other protrusions for enhancing grip on the pipe. The protrusions can, for example, take the form of annular serrations on the radially outer surface of the spigot portion.

In the case of a plastics pipe, the grip exerted by the deformed radially inner wall and the spigot on the pipe will usually be sufficient to provide a substantially fluid-tight seal, particularly when the spigot is ribbed or serrated such that the serrations or ribs become embedded in the plastics pipe wall. However, in the case of a thin-walled metal pipe, such as a stainless steel pipe, an additional means of providing a seal between coupling and pipe may be required, for example a sealing ring or gasket.

An advantage of the joined spigot portion/sleeve portion arrangement of this aspect of the invention is that it prevents the operative in the field from inadvertently losing the spigot or omitting to insert a supporting spigot into the end of the plastics pipe before tightening the pipe coupling down onto the pipe.

The pipe couplings of the invention can have a sleeve portion as hereinbefore defined at one end, or more than one end. For example, a pipe coupling intended for coupling together a pair of pipes (e. g. plastics pipes or a thinwalled metal pipe) may have a sleeve portion (and spigot portion where appropriate) at both ends thereof. In such an arrangement, the sleeve portions at the two ends may be the two ends of a single integral sleeve. Similarly, the spigot portions, when present, can be present at both ends and can be defined by the two ends of an integrally formed spigot member. In couplings (such as tees, Yconnectors or other branch connectors such as saddle connectors) having more than two outlets, any or each of the outlets may be formed with a sleeve (and optionally spigot) arrangement as hereinbefore defined.

The term pipe coupling as used herein refers to a fitting that can be attached to a pipe. The fitting can be a connector for connecting two or more pipes, or it can be any other type of fitting to which a pipe can be attached. For example, the coupling can constitute part of a valve such as a gate valve, butterfly valve or ball valve assembly, or an outlet from a vessel. The term pipe as used herein includes not only pipes per se but also any other pipe-like elements such as bends, tees,

adaptors, and spigot formations on valves, vessels or other fittings.

The pipe couplings of the invention can have a sleeve (and where appropriate a spigot) formation as hereinbefore defined on one end thereof and a coupling arrangement of a different type on another end thereof. For example, at one end, the pipe coupling may have a sleeve arrangement as hereinbefore defined and at the other end the coupling may be adapted for connection to a flanged element such as a flanged pipe or a valve, or a threaded connection, or connection via a fusion joint such as a butt joint or an electro fusion socket joint, or may have a spigot formation for insertion into a compression joint or adaptor.

In a further aspect, the invention provides a pipe joint comprising a pipe coupled to a pipe coupling as hereinbefore defined.

Brief Description of the Drawings Embodiments of the invention will now be described in more detail by reference to the accompanying drawings.

Figure 1 is a longitudinal sectional elevation through a pipe coupling according to one embodiment of the invention.

Figure 2 is a longitudinal sectional elevation through a pipe coupling according to a second embodiment of the invention.

Figures 3a to 3f and 4a to 4f are respectively longitudinal sectional views and cross sectional views showing the sequence of actions involved in the operation of a pipe coupling according to a third embodiment of the invention.

Detailed Description of the Preferred Embodiments Referring now to the figures, Figure 1 illustrates a pipe coupling 2

comprising an inner spigot portion 4 and an outer sleeve portion 6. The spigot portion 4 and sleeve 6 are joined together by means of an annular web 8 and together define an annular space into which the ends of a pair of pipes 10 can be inserted. In this embodiment, the pipes are formed from a plastics material such as a polyolefin or polyvinylchloride, but can alternatively be thin-walled metal pipes, for example thin walled stainless steel pipes. Where a thin-walled metal pipe is used, it may be necessary to provide an annular sealing member or gasket (not shown) to enhance the seal between the coupling and the pipe.

Either side of the annular web 8, the sleeve portion 6 has a radially outer wall 12 and a radially inner wall 14 welded together at end locations 6a and 6b, an annular chamber 16 being formed between the inner and outer walls. The outer wall 12 of the sleeve has a greater wall thickness than the inner wall with the consequence that the inner wall is more readily deformable than the outer wall.

For example, the outer wall may be formed from mild steel or stainless steel having a thickness of 3 mm or more, whereas the inner wall can be formed from mild steel or copper or another readily deformable metal having a wall thickness of 1.5 mm.

The outer wall of the sleeve has openings 18 that are connectable with a supply of pressurised hydraulic fluid in the manner described in WO-A-00/39495.

In the embodiment shown in the drawings, openings 18 are provided either side of the web 18 since the web, if un-perforated, will act as a barrier between the two annular chambers 16. However, a single opening may be provided instead, the arrangement of the inner and outer walls of the sleeve and/or the construction of the web being such that flow paths are provided between the two annular chambers. For example, the web 8 can be provided with one or more openings around its circumference to allow the passage of pressurising fluid. Alternatively, or additionally, the web 8 may be joined only to the radially inner wall 14 so that the annular chamber extends continuously for most of the length of the coupling and contains no internal formations that might obstruct or hinder fluid flow. In a further alternative, a manifold arrangement could be provided on the outer surface of the sleeve so as to connect the two openings 18 and allow fluid to be pumped

into the openings 18 in a single operation.

In use, pipes 10 are inserted into the annular space between the spigot portion and the sleeve portion, the annular web 8 acting as an abutment to limit the insertion of the pipes into the sleeve portion. Once the pipes are in place, the openings 18 are connected to a supply of pressurised hydraulic fluid in the manner described in WO-A-00/39495 so that the annular chamber 16 is pressurised.

Pressurising the annular chamber 16 results in the relatively thin and deformable inner wall 14 being deformed radially inwardly against the pipe 10 thereby causing the end of the pipe to be gripped tightly between the wall 14 and the annular serrations on the spigot portion 4.

Figure 2 illustrates a coupling for connecting a plastic pipe to a flangeended pipe. The coupling comprises a spigot portion 104 and sleeve portion 106 joined by flange 108. Flange 108 has apertures for receiving flange bolts (not shown) to allow the pipe coupling to be coupled to the flange of a flange-ended pipe or another pipe fitting such as an adaptor, valve, bend or another pipe coupling.

The spigot portion 104 is formed integrally with the flange (e. g. by casting), but could equally be formed separately and then joined to the flange, for example by welding. The sleeve portion 106 in this embodiment is formed separately and then joined to the flange 108 by welds 109 but could instead conceivably be formed integrally by, for example, a casting process. As with the embodiment of Figure 1, the sleeve portion comprises a radially outer wall 112 and a radially inner wall 114 welded together, in this case at either end thereof. The radially inner wall 114 is formed from a thinner, or more malleable metal than the outer wall 112 so that, as with the coupling of Figure 1, the radially inner wall is deformable when the annular chamber 116 is subjected to hydraulic fluid pressure such that it is

urged into gripping contact with the pipe 110.

Figures 3a to 3fand 4a to 4illustrate a further embodiment of the

invention in which a spigot portion and a sleeve portion 206 comprising radially inner and outer walls are joined together in a manner similar to that shown in Figure 1, except that in this embodiment, the radially outer wall of the sleeve portion is formed from a relatively thin layer of metal such as mild steel and is deformable. If the spigot and sleeve arrangement were pressurised in the manner described for the coupling of Figure 1, the outer wall of the sleeve portion would deform in preference to, or as well as, the inner wall of the sleeve portion and consequently the radially inwardly directed compressive forces exerted by the inner wall would be insufficient to form a durable secure joint with the plastics pipe. Therefore, a clamp 222 is provided for surrounding the outer wall to prevent radially outwards deformation of the outer wall. The clamp 222 comprises a pair of half collars 224,226 that can be clamped about the sleeve portion 206 by means of a lever arm arrangement 228. The upper half collar 224 has an opening 230 for connection to a supply of compressed fluid. Opening 230 is configured to mate with a nipple or nozzle 232 on the outer wall of the sleeve portion 206. Once the clamp has been put in place and the opening and nipple 230/232 have been connected to a supply of compressed fluid (not shown), the annular chamber between the radially inner and outer walls of the sleeve portion is pressurised in the manner described in respect of Figures 1 and 2 so that the inner wall is deformed into gripping contact with the pipe. Once the sleeve has been deformed to the required extent, i. e. a predetermined pressure limit has been reached, the clamp is removed.

The arrangement shown in Figures 3a to 3f and 4a to 4f has a number of advantages with regard to the coupling shown in WO-A-00/39495. Most importantly, since the outer wall is formed from a metal material rather than rubber, there is no tendency for the outer wall to extrude past the clamp in the manner that would occur with a rubber outer wall. This means that the clamp does not need to be made to fine tolerances since it does not matter if there are gaps between the inner surface of the clamp and the outer wall of the sleeve portion or gaps in the inner surface of the clamp.

A further advantage of the arrangement shown in Figures 3a to 3f and 4a to 4f over the coupling shown in WO-A-00/39495 is that the use of the metal outer wall of the sleeve portion provides for a longer lasting and more durable joint.

With the removal of the clamp from the coupling shown in WO-A-00/39495, the rubber outer sleeve wall is exposed to the surrounding environmental conditions and may eventually perish and deteriorate thereby exposing the surface of the inner sleeve portion. With the arrangement of the present invention, a thin layer of metal is more durable than the rubber outer sleeve of WO-A-00/39495 and hence provides a longer lasting protection to the radially inner wall. As will be appreciated, the metal outer sleeve can be provided with a coating or other surface treatment to prevent or slow down corrosion, or can be formed from a material such as stainless steel.

Still further advantages are that the shelf life of the coupling of the invention is greater than it would be if a rubber outer wall were employed for the sleeve portion and the metal outer wall is more robust in handling In addition to the advantages with regard to the couplings disclosed in WO A-00/39495, the couplings of the invention are advantageous with respect to many known type of coupling in that the weight of the coupling is considerably reduced.

This is particularly true in the case of the coupling shown in Figures 3a to 3f and 4a to 4f where a thin metal outer wall is used for the sleeve portion. The reduced weight of the coupling can be a particular advantage when installing pipes and couplings off the ground.

The foregoing specific description and accompanying drawings are intended for the purpose of illustration only and are not intended to limit the invention in any way. It will readily be apparent that numerous modifications and alterations may be made to the pipe couplings shown in the accompanying drawings without departing from the principles underlying the invention and all such modifications and alterations are intended to be embraced by this application.

Claims (12)

1. A pipe coupling comprising a sleeve portion for receiving a pipe, the sleeve portion comprising a deformable radially inner wall and a deformable radially outer wall, the radially inner and radially outer walls being sealed together at axially spaced apart locations so as to form an annular chamber therebetween; and a support clamp surrounding the outer wall for restricting expansion of the outer wall in use; the outer wall having an opening through which a pressurising fluid can be introduced into the annular chamber so as to deform the inner wall radially inwardly and into sealing and gripping engagement with the pipe ; characterised in that the deformable radially outer wall is formed from a metal.

2. A pipe coupling according to claim 1 wherein the outer wall of the sleeve portion has a wall thickness in the range 0.05 mm to 5 mm, preferably 0.25 mm to 2 mm, more preferably 0.5 mm to 1 mm.

3. A pipe coupling comprising a spigot portion and a sleeve portion joined together so as to define radially therebetween an annular space for receiving an end of a pipe, the sleeve portion comprising a radially outer wall and a radially inner wall, the radially inner and radially outer walls being sealed together at axially spaced apart locations so as to form an annular chamber therebetween; the radially outer wall having an opening through which a pressurising fluid can be introduced into the annular chamber so as to deform the radially inner wall radially inwardly and into sealing and gripping engagement with the pipe.

4. A pipe coupling according to claim 3 wherein the spigot portion and sleeve portion are integrally formed.

5. A pipe coupling according to claim 3 wherein the spigot portion is formed separately from the sleeve portion and is then joined thereto, for example by means of welding.

6. A pipe coupling according to any one of claims 3 to 5 wherein the spigot portion has ribs or other protrusions for enhancing grip on the pipe.

7. A pipe coupling according to claim 6 wherein the protrusions take the form of annular serrations on the radially outer surface of the spigot portion.

8. A pipe coupling according to any one of the preceding claims having a sleeve portion on one end only.

9. A pipe coupling according to any one of claims I to 7 having a sleeve portion at more than one end.

10. A pipe coupling according to claim 9 for coupling together a pair of pipes.

11. A pipe joint comprising a pipe formed from a plastics material, the pipe being coupled to a pipe coupling as defined in any one of the preceding claims.

12. A pipe joint substantially as described herein with reference to the drawings.