GB2555121A - Pipe coupling - Google Patents

Abstract

A pipe coupling for connecting the ends of two tubular conduits 9,10 comprises: an annular gasket arrangement 14 for straddling and for forming a seal against two such conduit ends; a casing arrangement for surrounding the gasket arrangement, wherein said casing arrangement comprises a pair of mutually cooperating casing elements 83,84 having a tapered outer profile; and a fixing sleeve 12 slideably mountable around the casing arrangement, wherein an inner profile of the sleeve is tapered to correspond to the tapered outer profile of the casing arrangement, such that the fixing sleeve 12 may only be fitted to the casing arrangement in one direction and whereby fixing means 23 are provided to secure the fixing sleeve to the casing arrangement. The fixing means may be a pressure plate 23 and screws 11. In another embodiment (figure 12) the fixing means may be screw clips 300,310,320.

Description

(54) Title of the Invention: Pipe coupling

Abstract Title: Pipe Coupling using tapered sleeve (57) A pipe coupling for connecting the ends of two tubular conduits 9,10 comprises: an annular gasket arrangement 14 for straddling and for forming a seal against two such conduit ends; a casing arrangement for surrounding the gasket arrangement, wherein said casing arrangement comprises a pair of mutually cooperating casing elements 83,84 having a tapered outer profile; and a fixing sleeve 12 slideably mountable around the casing arrangement, wherein an inner profile of the sleeve is tapered to correspond to the tapered outer profile of the casing arrangement, such that the fixing sleeve 12 may only be fitted to the casing arrangement in one direction and whereby fixing means 23 are provided to secure the fixing sleeve to the casing arrangement. The fixing means may be a pressure plate 23 and screws 11. In another embodiment (figure 12) the fixing means may be screw clips 300,310,320.

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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 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, aluminum and plastic.

For smaller diameter pipes, push fit couplings can be used, for example as described in GB2, 378, 992. However, for pipe diameters above around 5cms, 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 meter long lengths of steel pipe, and with a 1 meter 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 (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 external surface. An example of a Victaulic type pipe joint is shown in Figure 1. 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 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 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 Figure 1, 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, labeled “pressure’ in Figure 1. This force acts to pull the casing halves apart, and so high fluid pressure within the pipe joint of Figure 1 is transferred to the bolts (114) holding the casing halves (108, 110) together. Such Victaulic type pipe joints are typically rated to fluid pressures of 150psi and have been known to fail around 200 psi, typically by failure of the bolts (114).

In addition, pipes connected by a Victaulic type pipe joint, of the type shown in Figure 1, may be able to rotate with respect to each other and with respect to the casing (108, 11), which may cause problems of movement of pipe valves, etc. to inaccessible locations. Victaulic 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 with prior art pipe coupling systems, whether mentioned herein or not.

According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

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:

Figure 1 shows a prior art Victaulic-type pipe coupling arrangement;

Figure 2a and 2b show cross-sectional views through parts of casing arrangements, each forming part of a pipe coupling according to an embodiment of the present invention;

Figures 3a and 3b show cross-sectional views through parts of casing arrangements, each forming part of a pipe coupling according to an embodiment of the present invention;

Figure 4 shows a perspective view of a fully assembled coupling according to an embodiment of the invention;

Figure 5 shows an exploded perspective view of the coupling assembly of Figure 3a;

Figures 6a and 6b show cross-sectional views through parts of casing arrangements, each forming part of a pipe coupling according to an embodiment of the present invention;

Figure 7 shows an exploded perspective view of the coupling assembly of Figure 6b;

Figure 8 shows an exploded perspective view of the coupling assembly of Figure 6a;

Figure 9 shows an exploded perspective view of an alternative embodiment of the present invention;

Figure 10 shows an alternative embodiment including interlocks;

Figure 11 shows an alternative embodiment of the fixing sleeve; and

Figures 12a-c show a further embodiment of the invention.

Figures 2a and 2b show cross-sectional views of two pipe couplings according to an embodiment of the present invention. In each case, the pipes 9, 10 being joined have grooved portions 96 near their end. In Figure 2a, an gasket 14, comprising a pair of O rings 13 is provided and in Figure 2b, a gasket 20 is provided which has a substantially C-shaped cross section and which encompasses the ends of pipes 9, 10. The gasket 20 is of the type typically used in prior art Victaulic-type pipe couplings.

The gasket is formed from resilient sealing material and may, for example, be molded of natural or synthetic rubber. Other material 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.

In both these embodiments, a pair of casing elements 83, 84 and 17, 18 are provided which are shaped with an internal profile to surround the respective gasket 14, 20 and to have a tapered outer profile having a smaller diameter at a first end and a larger diameter at a second end.

The casing halves 84 and 83 are made of a rigid material and each are shaped generally as a half- annulus with a C-shaped longitudinal cross-section. Two end portions 84 and 83 of the casing halves extend radially inwardly of a half-cylinder shaped main body 84 and 83 of the casing halves.

Once in position as shown, the two casing elements 83, 84 and 17, 18 entirely enclose the gasket and surround the ends of the pipes. An inner portion 95 of each casing element protrudes into groove 96 and tends to secure the casing elements in position.

To securely clamp the casing elements in position, a fixing sleeve 12 is provided which has in internal profile arranged to match substantially the external profile formed by the two casing elements. The fixing sleeve is substantially frusto-conical in profile and it’s wider end is arranged to pass over the first end of the pair of casing elements and is then driven towards the second end, such that the external surface of the pair of casing elements abuts the internal surface of the fixing sleeve. This is shown by the bold arrows at the top of Figures 2a and 2b.

The fixing sleeve is formed from a rigid material. It may be formed from a suitable plastics material or a metallic material, such as steel, depending on the scale and requirements.

In the embodiment shown, the change in radius from the first end to the second end of each casing element is linear. In alternative embodiments, the change in radius from first to second ends may change in a non-linear manner.

Once secured in position, one or more fixing bolts 11 are driven into complementary threaded recesses in the casing elements, such that the head of the bolt 11 prevents the fixing sleeve from sliding off.

In certain situations, especially with high-pressure pipelines, it is necessary to adapt the couplings shown in Figures 2a and 2b to include a pressure plate. This is shown in Figures 3a and 3b. The couplings shown in Figures 3a and 3b correspond exactly to those shown in Figures 2a and 2b, with the addition, in each case, of a pressure plate 23, which is in the form of an annular plate which is affixed to the narrower end of the pair of casing elements and through which the at least one bolt 11 passes, as described previously.

This can be seen clearly in Figure 5 which shows an exploded perspective view of the embodiment shown in Figure 3a. The two pipes 9, 10 are surrounded by gasket 14, which is then enclosed with the pair of casing elements 83, 84. The fixing sleeve 23 is slid into position and then pressure plate 23 is positioned and firmly bolted into position. The pressure plate 23 acts to distribute the pressure experienced at the pipe joint more evenly and helps to preserve joint integrity.

Figure 4 shows a fully assembled view of the pipe coupling of Figure 3a. It clearly shows the pressure plate 23 in position and how this prevents the fixing sleeve from sliding off. It cannot move leftwards, in the orientation shown in Figure 4 due to the tapering of the sleeve, and it cannot move rightwards, because of the pressure plate 23 and bolts 11.

Figures 6a and 6b show alternative embodiments of the present invention. These are similar to the embodiments shown in Figures 3a and 3b except these couplings are for use with plain ended (i.e. non-grooved) pipes 9a, 10a.

Figure 6a uses the same gasket 14 and O rings 13 as shown in Figures 2a and 3a, and Figure 6b uses the C-shaped gasket 20 of Figures 2b and 3b.

The casing elements 83a, 84a and 17a, 18a differ from those used in previous embodiments in that they include inwardly-facing gripping teeth 49. These are intended to ‘bite’ into the surface of the pipe and may be formed from ridges on a surface of the casing element, or may be relatively sharpened metallic or ceramic inserts, as required, depending on the materials used for the casing elements and the pipes.

Figures 7 and 8 show exploded perspective views of the embodiments shown in Figures 6b and 6a respectively.

Figure 9 shows an embodiment of the present invention which utilizes an alternative form of gasket 20a. The gasket 20a is identical with gasket 20, shown in Figure 7, except it is provided with a pair of outwardly extending tabs 97. Only one is shown in Figure 9 and the other extends from the opposite side to that shown.

The tabs 97 are integrally formed with the gasket 20a and are arranged to be trapped by the casing elements 17a and 18a. Once the fixing sleeve 12 is put into position, the tabs 97 are compressed and held firmly in place. The tabs serve to more securely anchor the gasket 20a in position at the junction between the pipes 9, 10. This is to prevent the gasket being forcibly ripped from position when flow of fluid in the pipeline begins. It is known for the sudden increase in flow to create a partial vacuum which can displace the gasket. By providing fixings which secure it firmly in the coupling, this can be prevented or at least mitigated.

The gasket 20a can also be used in prior art coupling of the type shown in Figure 1, whereby the tabs 97 can be provided with apertures to cooperate with flanges and fixings 112, 114.

Figure 10 shows an interlock mechanism that ensures that the casing elements 91 and 94 are properly engaged. The facing surfaces of casing elements 91 and 94 are provided with stepped portions which interlock as shown and ensure that the two casing elements are properly aligned before the coupling is fully assembled.

Figure 11 shows a feature of an alternative embodiment. Instead of a separate fixing sleeve 12 and pressure plate 23, a unitary part 200 is provided, which may be formed from a plastics material or metallic material as require.

It comprises a pressure plate part 220 and a tapered part 230 which operate exactly as set out previously, with the advantage that only a single part is required, saving on inventory costs and easing assembly.

The pressure plate part 220 is provided with a plurality of apertures to receive fixing bolts which couple with the casing elements as before.

Figures 12a-c show a further embodiment of the present invention. In this embodiment, a fixing sleeve 330 is provided which is frusto-conical in shape, as per the fixing sleeve 12 described earlier. The sleeve 330 differs in that it is provided with a plurality of slots or notches 340 arranged around the circumference of the wider end of the tapered structure. The notches 340 are arranged to each receive a fixing device comprising a substantially U-shaped member 320 which is fixed to a threaded nut 310, preferably by welding. In use, one leg of the member 320 is inserted into the notch 340 as shown in Figure 12b. A bolt 300 is then screwed into nut 310 as shown. The U-shaped member 320 is preferably formed from a metallic material, such as steel.

As the bolt 300 is tightened, the end of the bolt 300 passes through nut 310 and the adjacent leg of member 320 to contact the casing elements directly. This forcibly pulls the frusto-conical sleeve 330 more tightly over the casing elements and ensures a tight fit of the coupling. The sleeve 330 can then not slip free in either direction.

In a further advantageous development, once properly assembled, there are no protrusions from the completed coupling, as can be seen from Figure 4. 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.

Embodiments of the present invention find utility in a range of different pipe environments, ranging from small-bore pipes used in domestic situations 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 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 invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract or drawing), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims (10)

1. A pipe coupling for connecting the ends of two tubular conduits comprising:

an annular gasket arrangement for straddling and for forming a seal against two such conduit ends;

a casing arrangement for surrounding the gasket arrangement, wherein said casing arrangement comprises a pair of mutually cooperating casing elements having a tapered outer profile; and a fixing sleeve slideably mountable around the casing arrangement, wherein an inner profile of the casing arrangement is tapered to correspond to the tapered outer profile of the casing arrangement, such that the fixing sleeve may only be fitted to the casing arrangement in one direction and whereby fixing means are provided to secure the fixing sleeve to the casing arrangement.

2. The pipe coupling of claim 1 wherein the casing arrangement comprises a pair of radially inwardly extending projection arrangements, each projection arrangement for engaging an annular groove formed in each such conduit end.

3. The pipe coupling of claim 1 wherein the casing arrangement comprises inwardly-facing gripping teeth arranged to bite into the surface of each such conduit end.

4. The pipe coupling of any preceding claim wherein the fixing sleeve has a frusto-conical inner profile.

5. The pipe coupling of any preceding claim wherein the fixing means comprise a plurality of bolts or screws arranged to fasten into the casing arrangement and hold the fixing sleeve in position.

6. The pipe coupling of claim 5 further comprising a pressure plate arranged to abut the casing arrangement at its thinner end and to be held in place by the fixing means.

7. The pipe coupling of claim 6 wherein the fixing sleeve and pressure plate are integrally formed.

8. The pipe coupling of any one of claims 1 to 4 wherein the fixing sleeve is provided with a plurality of apertures adjacent its wider end, wherein the apertures, in use, receive fastening means arranged to prevent the fixing sleeve from sliding off the

5 casing arrangement.

9. The pipe coupling of claim 8 wherein the fastening means comprise a substantially U-shaped member fastened to a nut for coupling to a bolt.

10

10. The pipe coupling of any preceding claim wherein the annular gasket arrangement comprises a pair of radially extending tabs arranged, in use to be secured between the casing elements.

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Application No: GB1617675.2 Examiner: Mr Philip Osman