GB2488607A

GB2488607A - Pipe coupling

Info

Publication number: GB2488607A
Application number: GB1107429.1A
Authority: GB
Inventors: Paul Anthony Davidson; Joseph Parisi
Original assignee: COUPLING SOLUTIONS LLC
Current assignee: COUPLING SOLUTIONS LLC
Priority date: 2010-11-08
Filing date: 2011-05-04
Publication date: 2012-09-05
Also published as: GB201018849D0; WO2012064725A3; WO2012064725A2; GB2485350A; GB201107429D0

Abstract

A pipe coupling for connecting ends of two tubular fluid-flow conduits, comprises a sealing element 6 for straddling and for forming a seal against two such conduit ends 2, 4, and a casing 8, 10 for surrounding the sealing element 6, which casing 8, 10 comprises a pair of radially inwardly extending groove-engagement projections 18, 20. Each projection 18, 20 can engage an annular groove 22 formed at or adjacent to each conduit end 8, 10. A fixing sleeve 12 is also provided coaxially, and preferably slidably, mountable around the casing 8, 10. An outer surface of the casing 8, 10 is tapered and an inner bore of the fixing sleeve 12 is complementarily tapered, such that the fixing sleeve 12 may only be fitted to the casing 8, 10 in one direction. The fixing sleeve 12 and casing 8, 10 further comprise fixing means 30, 32 to secure the fixing sleeve 12 in position on the casing 8, 10.

Description

PIPE COUPLING

The present invention relates to a coupling for connecting tubular conduits, in particular for connecting lengths of pipe as part of a fluid transport system.

Fluid transport systems are known for conveying materials, such as liquids and gasses.

The systems may include domestic plumbing systems installed in a building for conveying, for example, water or oil. These plumbing systems may include pipes for building heating systems, fire protection sprinkler systems and rising mains pipes and waste water pipes. The systems may also include oil and gas pipelines for conveying fuel over thousands of miles and pipe systems used in mining applications. The tubular conduits used in fluid transport of fuel may be made of different metals, including steel, iron, copper, aluminium and plastic.

For smaller diameter pipes, push fit couplings can be used, for example as described in GB237 8992. However, for pipe diameters above around Scms, the force required to push the end of a pipe into such a push fit coupling becomes too high for manual connection. In addition, pipes connected by push fit couplings are able to rotate relative to each other, which can cause valve taps to move out of an optimum position.

For larger diameter pipes, welded joints can be used. However, welded joints have the disadvantage of requiring skilled workers as well as having negative health and safety and environmental implications. For example, the construction of a gas conveying pipeline made from 40 metre long lengths of steel pipe, and with a 1 metre diameter, conventionally use welded joints. Each joint can take a skilled team a whole day to make, when taking into consideration the deployment of equipment at the joint location and inspection of the joint by X-ray equipment. Also, around 1 in 10 of such welded joints will have to be repaired after such an inspection. This makes pipelines expensive and time consuming to construct.

Where plastic pipes are used, heat fused joints may be used, in which the ends of the pipes to be connected are heated up and then fused together.

Push fit couplings, welded joints and fused joints are difficult to disconnect, for example for repair or maintenance, with such disconnection often causing damage to the pipes.

Victaulic RTM (also known as victolic) pipe joints are known in the art, in which the pipe ends to be connected are formed with an annular groove in their extemal surface.

An example of a Victaulic RTM type pipe joint is shown in Figures la and lb. An annular resilient gasket (6), with a C-shaped longitudinal cross-section is placed over the pipe ends to be joined, so that the gasket straddles the two pipes. Typically, the gasket is stretched slightly to fit over the pipe ends so as to form a seal between the gasket and the pipes. The gasket is then encased by a rigid Victaulic RTM type casing (108, 110), which engages the grooves formed in the pipe ends. Generally the casing is formed in two halves (108, 110), formed with flanges (112) and the two halves are connected together by bolts (114) passing through the flanges. The casing compresses the sealing gasket (6) to further improve the seal between the gasket and the pipe ends.

There are known problems with such Victaulic RTM pipe joints. The first is that they are not well suited to high pressure pipe systems. In particular where one of the pipe elements coupled together by the joint comprises a pipe end cap, the joint has to withstand significant forces acting to pull the pipe ends connected by the joint apart.

When fluid pressure builds up within the pipe joint of Figures la and lb, the pressure acts radially outwardly on the gasket, causing the gasket to inflate and apply a radially outwardly directed force to the casing halves (108, 110). That is, the pressure acts in the direction of the double headed arrow, labelled Lpressure in Figure 1 a. This force acts to push the casing halves apart, and so high fluid pressure within the pipe joint of Figures la and lb is transferred to the bolts (114) holding the casing halves (108, 110) together.

Such Victaulic RTM type pipe joints are typically rated to fluid pressures of l5Opsi (approximately 1MPa) and have been known to fail around 200psi (approximately 1.38 MPa), typically by failure of the bolts (114).

In addition, pipes connected by a Victaulic RTM type pipe joint, of the type shown in Figures la and lb, may be able to rotate with respect to each other and with respect to the casing (108, 110), which may cause problems of movement of pipe valves, etc. to inaccessible locations. Victaulic RTM type pipe joints can also fail if the bolts come undone due to vibration of the pipe system.

It is an aim of embodiments of the present invention to address shortcomings in with prior art pipe coupling systems, whether mentioned herein or not.

According to the present invention there is provided a pipe coupling for connecting ends of two tubular conduits, comprising: a sealing element for straddling and for forming a seal against two such conduit ends; a casing for surrounding the sealing element, which casing comprises a pair of radially inwardly extending groove-engagement projections, each projection for engaging an annular groove formed at or adjacent to each such conduit end; and a fixing sleeve coaxially mountable around the casing, wherein an outer surface of the casing is tapered and an inner bore of the fixing sleeve is complementarily tapered, such that the fixing sleeve may only be fitted to the casing in one direction and whereby the fixing sleeve and casing comprise fixing means to secure the fixing sleeve in position on the casing.

Preferable and/or optional features of the present invention are set forth in claims 2 to 22, inclusive.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figures 1 and lb show a prior art Victaulic RTM-type pipe coupling arrangement; Figure 2 shows a cross-sectional view of a pipe coupling, according to a first embodiment of the present invention; Figure 3 shows a cross-section through part of a casing arrangement forming part of the pipe coupling, shown in Figure 2; Figure 4 shows a cross-section through part of a fixing sleeve forming part of the pipe coupling; Figure 5 shows a cross-sectional view of an intermediate step in the assembly of the pipe coupling shown in Figure 2; Figure 6 shows a longitudinal cross-sectional view of a pipe coupling, in accordance with a second embodiment of the present invention; Figure 7 is a perspective view of the pipe coupling of Figure 6, when assembled; Figure 8 shows a longitudinal cross-sectional view of a pipe coupling, in accordance with a second embodiment of the present invention; and Figure 9 is a perspective view of the pipe coupling of Figure 8, when assembled.

Referring firstly to Figures 2 to 5, there is shown a first embodiment of a pipe coupling.

The pipe coupling comprises a sealing element, in this case gasket 6, for straddling and sealing against the end portions of pipes 2, 4. It further comprises a pair of casing halves 8,10 which sit around the gasket and protrude into grooves 22 formed adjacent the end of each pipe 2, 4. Surrounding the casing alTangement is a fixing sleeve 12, which holds the casing halves 8, 10 together and compresses the joint formed between the pipe.

The gasket 6 is an annular gasket with a preferably C-shaped longitudinal cross-section and may be of any kind known in the art for use in a Victaulic RTM (or victolic) pipe joint. The gasket 6 is made of resilient sealing material and may, for example, be moulded of natural or synthetic rubber. Other materials from which the gasket may be made include, ethylene propylene diene monomer (EPDM) (generally used where the transported fluid is water), a nitrile compound (generally used where the transported fluid is oil), fluoro-elastomer, neoprene, white nitrile and epichlorohydrin.

The casing halves 8, 10 are made of a rigid material, such as plastics or metal, and each are shaped generally as a half-annulus with a C-shaped longitudinal cross-section. Two groove-engagement end portions 18, 20 of the casing halves 8, 10 extend radially inwardly of a half-cylinder shaped main body 24 of the casing halves 8, 10. The end portions 18, 20 have a width and an internal diameter matching the width and the external diameter of the grooves 22 formed in the pipe ends 2, 4 so that the end portions 18, 20 fit into the grooves 22, when the casing halves 8, 10 are fitted over the gasket 6, as is shown in Figure 2. The half cylindrical inwardly facing faces of the end portions 18, 20 are formed with a set of longitudinally extending gripping teeth 26. The main body 24 of each casing half 8, 10 is formed with a central half-annular groove 28 in its inwardly facing surface dimensioned to fit over and abut the gasket 6 as is shown in Figure 2.

The end portions 18 and 20 are affanged to have different outer radii so that the outer profile of the casing half 8, 10 tapers from a larger radius at end portion 20 to a smaller radius at end portion 18. When the two casing halves 8,10 are assembled around the pipe ends 2, 4, the appearance of the casing arrangement is frusto-conical, in other words, the exterior surface 25 resembles a truncated cone.

In the embodiment shown in Figures 2 to 5, the change in radius from first end portion 18 to second end portion 20 is linear. In alternative embodiments, the change in radius from first to second end portions may be in a non-linear manner.

The fixing sleeve 12, shown in Figure 4, is integrally formed as one-piece from a rigid material, such as plastics or metal, and is dimensioned to coaxially fit slidably over the two casing halves 8, 10 when the casing halves are mounted over the gasket 6, as shown in the intermediate step illustrated in Figure 5. The fixing sleeve 12, in this embodiment, preferably has a cylindrical outer surface 12a and an inner surface 12b complementarily shaped for engagement with the exterior surface 25 of the assembled casing halves 8, 10.

In this case, therefore, the inner surface l2b is generally frusto-conical. The outer surface 12a may be non-cylindrical, and may be, for example, also frusto-conical.

In the embodiment shown in Figure 2, the fixing sleeve 12 fits over the casing halves 8, 10. As the fixing sleeve 12 is urged into position, which may require the use of a tool such as a hammer or mallet, the two casing halves 8, 10 are pushed or urged radially inwardly so as to push up against the gasket 6 and improve the sealing of the gasket 6 to the pipes 2, 4. This also has the effect of improving the engagement between the toothed end portions 18, 20 of the casing halves 8, 10 and the end portions of pipes 2, 4, as well as the groove-engagement end portions 18, 20 and the grooves 22, so as to form a secure sealed coupling between the tubular conduits.

Once the fixing sleeve 12 has been applied to the casing arrangement, noting that it can only be fitted one way, due to the tapering outer profile of the casing arrangement and corresponding tapering of the inner profile of the fixing sleeve, the point at which full engagement has been achieved will be noted by the fitter as the fixing sleeve 12 clicks into position and is retained there by means of mutually interengagable fixing means 30, 32, preferably being snap-fit.

First fixing means 30 is provided on an edge of casing halve 8 and in this embodiment takes the form of a resilient cantilevered projection having a radially-outwardly protruding hook extending therefrom. When the fixing sleeve 12 is positioned over the assembled casing halves 8, 10, it will ultimately reach a position where the hook of fixing means 30 clicks into position in a complementary annular recess 32 provided at one end of fixing sleeve 32.

In this way, once the fixing sleeve 12 has been properly fitted, it will not easily separate as the mutually co-operating fixing means 30, 32 act to hold the fixing sleeve firmly in position.

In the embodiment shown here, the fixing means 30, 32 are provided at the end of the casing arrangement having the smaller radius corresponding to end portions 18.

However, the fixing means 30, 32 could equally be provided at the opposite end. As a further alternative, the resilient projection 30 could be provided midway along the outer profile of the casing halves 8, 10, and a corresponding groove 32 could be provided at a corresponding position on the inner surface of the fixing sleeve 12.

Alternative or additional fixing means may also be considered. For example, incorporating complementary screw-threads on the inner surface of the fixing sleeve 12 and on the exterior surface of the casing halves 8, 10 may be feasible. Furthermore, the fixing means may be or include a twist-lock engagement between the fixing sleeve 12 and the casing halves 8, 10, for example.

Advantageously, if the pipe coupling required disassembly at some future time, then the fixing means 30 may be deactivated by a tool such a screwdriver or chisel, and the fixing sleeve may simply be slid away, in a reversal of the fitting process. This, of course would not be possible if the fixing means 30, 32 are provided at a midway point as described previously, although such a configuration could be used in secure environments where the pipe coupling cannot then be easily disassembled.

Referring now to Figures 6 and 7, there is shown a second embodiment of a pipe coupling. Like references refer to parts which are similar to those described previously, and therefore further detailed description is omitted. The pipe coupling comprises a sealing element 40 along with the aforementioned parts being the casing element of two halves 8, 10 for surrounding the sealing element 40 and having the two radially inwardly extending groove-engagement end portions 18, 20, the fixing sleeve 12, and fixing means 58.

In this case, the sealing element 40 includes a retainer 42 in which the gasket of the first embodiment or two spaced gaskets or 0-rings 44 are held. The retainer 42 includes a rigid retainer body 46 having a bore 48 for receiving as a close fit the pipe ends 2, 4, and which extends radially beyond the 0-rings 44, and longitudinally to overlap the 0-rings 44. Inner annular grooves 50 are formed in axially spaced relationship in the surface of the bore 48, so that at least one 0-ring 44 seats on its respective pipe between the pipe end 2, 4 and the corresponding groove 22.

is Preferably, the retainer body 46 is formed in two annular halves 46a, 46b, similarly to the casing halves 8, 10. This allows the 0-rings 44 to be initially slid onto their respective pipe ends 2, 4, and then the retainer body 46 to be located therearound seating the 0-rings in their respective annular grooves 50.

As an alternative, the retainer body 46 may be integrally formed as one-piece, and with the 0-rings 44 prelocated within their annular grooves 50, may be received onto the pipe ends 2, 4 in a sliding push-fit manner.

With the retainer body 46 bridging and straddling the pipe ends 2, 4, the casing halves 8, can be clamped around the retainer 42 by the fixing sleeve 12, whereby the groove-engagement end portions 18, 20 engage with the pipe grooves 22. The radial and axial extents of the retainer body 46 are received within a complementary retainer recess 52 formed in the inner surface 54 of the casing halves 8, 10. The retainer recess 52 is spaced axially of the groove-engagement end portions 18, 20 so as to lie therebetween, preferably in spaced relationship.

The fixing means 58 again prevents or limits unintentional disengagement of the fixing sleeve 12 from the casing halves 8, 10. The fixing means 58, although may be as described previously, in this case is a locking tab preferably integrally formed as one-piece on one or each casing half 8, 10. The locking tab 58 is formed on the larger diameter end of the respective casing half 8, 10, thereby projecting axially and radially outwardly. The locking tab may be ramped from the outer surface of the casing half 8, 10. In use, the fixing sleeve 12 slides over the locking tab at least in part, and once the point of interference is reached or wedging engagement occurs, the opposite end of the fixing sleeve 12 is struck, for example, with a hammer, mallet or other suitable striking implement, urging the fixing sleeve 12 into further wedging engagement with the casing halves 8, 10 via the locking tab 58. The fixing sleeve 12 is thus held securely in place, and can be released by using a tool to drive the sleeve back out of wedging engagement with the casing halves 8, 10.

The use of the retainer 42 allows the clamping pipe coupling to be formed from plastics, if needs be, since the load transfer across the joint is now primarily longitudinal or axial.

is Refening to Figures 8 and 9, there is shown a third embodiment of a pipe coupling.

Like references again refer to parts which are similar to those described previously, and therefore further detailed description is omitted. This embodiment of the pipe coupling comprises the sealing element 40 along with the aforementioned parts being the casing element of two halves 8, 10 for surrounding the sealing element 40 and having the two radially inwardly extending groove-engagement end portions 18, 20, the fixing sleeve 12, and the fixing means 58.

By forming the 0-rings 44 from metal, such as stainless steel, instead of plastics or rubber as in the second embodiment, allows the retainer body 46 to have a smaller radial extent in comparison with that of the second embodiment. This also allows the casing halves 8, 10 to have a smaller radial extent, thereby allowing the entire coupling to have a slimline appearance. This is particularly beneficial for applications having limited installation space.

In the second and third embodiments described above, it may be beneficial for the retainer body 46 to have a radially inwardly projecting pipe-end stop 56, as see in Figures 6 and 8. This ensures equal pipe end spacing and optimal seating of the 0-rings 44.

As also indicated above, it may be beneficial mount two 0-rings or gaskets on each pipe end 2, 4, and in this case the retainer body 46 may be modified to include four spaced apart annular grooves 50, two being either side of the pipe-end stop 56 if provided.

In a further advantageous development, once properly assembled, there are no protrusions from the completed coupling, as can be seen from Figures 2, 7 and 9. This is particularly important when the coupling is used on large-scale pipelines, such as large-diameter oil pipelines, where the entire pipeline can move significantly in use, due to expansion/contraction effects caused by temperature differences. Protrusions from prior art pipe couplings which can become entangled with the ground or other structures can be torn off or damaged. The lack of any sudden discontinuity from pipe couplings according to embodiments of the present invention substantially obviates this problem.

Furthermore, it may be advantageous to include a further seal, such as an 0-ring or gasket, between the opposing surfaces of the groove-engagement end portions 18, 20 and the grooves 22. For example, the radially inner surface of each groove-engagement end portion may include an annular groove for seating an 0-ring which would then seal on the radially inner surface of the respective groove 22, once the pipe coupling was assembled.

Embodiments of the present invention find utility in a range of different pipe environments, ranging from small-bore pipes used in domestic situation up to large diameter pipes used in the transportation of oil, gas or water. Depending on the characteristics of the pipe, the materials used to manufacture the pipe coupling will vary.

In some circumstances, the various components of the pipe coupling can be formed from a plastics material, such as glass-filled nylon. In other circumstances, the components can be formed from steel, another metal or an alloy.

The pipe coupling according to the present invention may be a coupling for connecting two lengths of pipe. Alternatively, the pipe coupling according to the present invention may be a coupling for connecting a length of pipe to a pipe joint assembly. Many types of pipe joint assemblies are known, for example pipe joint assemblies for connecting three lengths of pipe in a T-junction, pipe end caps and pipe joint assemblies incorporating valves or other elements known in the art.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The embodiments described above are provided by way of examples, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined by the appended claims.

Claims

CLAIMS1. A pipe coupling for connecting ends of two tubular conduits, comprising: a sealing element for straddling and for forming a seal against two such conduit ends; a casing for surrounding the sealing element, which casing comprises a pair of radially inwardly extending groove-engagement projections, each projection for engaging an annular groove formed at or adjacent to each such conduit end; and a fixing sleeve coaxially mountable around the casing, wherein an outer surface of the casing is tapered and an inner bore of the fixing sleeve is complementarily tapered, such that the fixing sleeve may only be fitted to the casing in one direction and whereby the fixing sleeve and casing comprise fixing means to secure the fixing sleeve in position on the casing.
2. A pipe coupling according to claim 1, wherein the casing is formed from a plurality of casing parts which co-operate together to form the casing.
3. A pipe coupling according to claim 2, wherein the casing is formed from two casing halves.
4. A pipe coupling according to any one of claims 1 to 3, wherein each groove-engagement projection comprises an annular wall of the casing.
5. A pipe coupling according to any one of claims 1 to 4, wherein the casing comprises a frusto-conical main body.
6. A pipe coupling according to anyone of claims 1 to 5, wherein the casing is formed with a central annular recess on its inwardly facing surface for receiving the sealing element.
7. A pipe coupling according to claim 6, wherein the casing includes at least one annular stepped bore portion between the central annular recess and the groove-engagement projection having at least one pipe-gripping tooth.
8. A pipe coupling as claimed in claim 7, wherein a said annular stepped bore portion is provided between each groove-engagement projection and the central annular recess.
9. A pipe coupling as claimed in any one of claims 6 to 8, wherein the sealing element is an annular gasket which is held directly by the casing.
10. A pipe coupling as claimed in any one of claims 6 to 8, wherein the sealing element includes a retainer and at least two spaced apart gaskets seatable in a bore of the retainer for forming a seal against the two conduit ends.
11. A pipe coupling as claimed in claim 10, wherein a body of the retainer and the central annular recess are complementarily shaped.
12. A pipe coupling as claimed in claim 10 or claim 11, wherein the retainer body is substantially cylindrical.
13. A pipe coupling as claimed in any one of claims 10 to 12, wherein the retainer body is formed of two annular halves.
14. A pipe coupling as claimed in any one of claims 10 to 13, wherein the retainer body, casing and fixing sleeve are plastics.
15. A pipe coupling as claimed in any one of claims 10 to 13, wherein the said two gaskets are metal.
16. A pipe coupling as claimed in any one of claims 10 to 15, wherein the retainer includes a pipe-end stop for abutting the said conduit ends.
17. A pipe coupling according to any one of claims 1 to 16, wherein the fixing sleeve has a substantially frusto-conical outer surface.
18. A pipe coupling according to any one of claims 1 to 16, wherein the fixing sleeve has a substantially cylindrical outer surface.
19. A pipe coupling as claimed in any one of claims 1 to 18, wherein the fixing sleeve is slidably mountable on the casing.
20. A pipe coupling as claimed in any one of claims 1 to 19, wherein the fixing sleeve is integrally formed as one-piece.
21. A pipe coupling as claimed in any one of claims I to 20, wherein the fixing means includes a snap-fit hook and recess.
22. A pipe coupling as claimed in any one of claims 1 to 20, wherein the fixing means is a projecting locking tab.s
23. A pipe coupling substantially as hereinbefore described with reference to Figures 1 to 5, Figures 6 and 7, or Figures 8 and 9 of the accompanying drawings.