COUPLING FOR PIPE

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

Fluid transport systems are known for conveying materials, such as liquids and gasses, with common examples including water and fuels such as gas and oil. The systems may vary from domestic plumbing systems installed in a building to convey water to oil and gas pipelines for conveying fuel over thousands of miles. The tubular conduits used in fluid transport systems may be made of many different materials, including steel, iron, copper, aluminium and plastic.

For smaller diameter pipes, a push fit couplings can be used, for example as described in GB2,378,993. However, for pipe diameters above around 5cms, the force required to push the end of a pipe into such a. push fit couplings 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, construction of a gas conveying pipeline, made from 40 metre long lengths

of steel pipe and with a 1 metre diameter, conventionally uses 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 such pipelines expensive and time consuming to construct. Where plastic pipes are used, heat-fused joints may be used, in which the ends of 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.

In certain pipe couplings, a pipe end has to be pushed past a ring seal of the coupling during insertion of the pipe into the coupling. This can require a considerable force, especially for larger diameter pipes and in some cases can damage the seal. Providing the required force adds to the complexity and expense of making pipelines.

A first aspect of the present invention aims to overcome at least some of the problems set out above and comprises a coupling having at least one coupling end for connection to a tubular conduit, wherein each coupling end comprises: a housing defining a tubular wall of a receiving recess for receiving an end of such a tubular conduit and a hollow expandable seal arrangement moveable from an unexpanded position in which such a

tubular conduit can be pushed past the seal to an expanded position in which the seal arrangement generates a seal between the coupling end and such a tubular conduit on the introduction of a fluid into the seal. The invention is characterized in that the hollow expandable seal arrangement, when in the expanded position, is adapted to form a set seal between the coupling end and said tubular conduit in the expanded position. Accordingly, the problem of requiring excessive force to push the tubular conduit past the seal is overcome. The seal may comprise a ring shaped balloon having a skin of an expandable material, such as rubber. Also, the seal may comprise an inlet nozzle via which fluid is introduced into the seal.

When the hollow expandable seal is in the expanded position, a set seal or irreversible lock is formed between the coupling end and the tubular conduit. By set seal or irreversible lock, it is meant the hollow expandable seal arrangement, once in the expanded position, forms a seal or lock with the tubular conduit that cannot be broken by removal of the fluid from the seal arrangement. This may, for instance, be achieved by use of a setting fluid, such that the fluid cannot leak out of the expanded seal arrangement because it has turned into a solid form. The set seal or irreversible lock may also be achieved by use of a second toroidal seal adapted to adhere to the tubular conduit when pushed against it by the hollow expandable seal arrangement in the expanded position. Subsequent deflation of the expandable seal to the unexpanded position leaves the second toroidal seal in place, adhered to the tubular conduit, and holding the tubular

conduit in the coupling end. In order to remove the tubular conduit, the set seal must be broken, and the coupling will not be reusable without replacement of the hollow expandable seal arrangement.

The formation of an set seal by the coupling of the invention is advantageous as it means that the seal between coupling end and tubular conduit is permanent or irreversible, and so cannot be lost merely because of accidental leakage of any fluid, as used to achieve the expanded position, over time.

The housing may comprise an annular recess for housing the expandable seal. In the unexpanded position of the seal, the expandable seal may fit completely within with annular recess, so as to enable a tubular conduit to be pushed past it into the coupling. A hole may formed in the housing between the annular recess and an external surface of the housing through which the nozzle of the seal extends. This provides access to the nozzle of the expandable seal from the outside of the coupling, so facilitating the introduction of fluid into the expandable seal from the outside of the coupling.

The hollow expandable seal arrangement is suitably made of a material such as rubber, but any suitable expandable material may be employed, provided that it is capable of expansion and compression such that it can form a good seal.

The fluid may be a suitable gas or a liquid. The fluid may be a settable fluid, which may permanently set to hold the seal in its expanded position. For instance, the fluid may be a liquid that is at a higher-than ambient temperature such that it is molten when used to fill the hollow expandable seal arrangement to put it in the expanded position, but which solidifies upon cooling to ambient temperature to form a solid, thus maintaining the hollow expandable seal in the expanded position, forming a set seal.

As another example, the fluid may be a mixture of two or more components which is initially in a fluid state following mixing of the components, but which solidifies over time, for instance as a result of chemical reaction between the components, e.g. by polymerisation or cross-linking. The mixed fluid is used to expand the seal whilst still in a fluid state, but then sets in the expandable seal to hold the seal in the expanded position The expandable seal, in its expanded position, may form a frictional engagement between the coupling end and such a tubular conduit. In this case, no additional fixing may be required between the tubular conduit to the coupling.

In a preferred arrangement of the first aspect of the invention, the coupling comprises a second toroidal seal positioned between the hollow expandable seal arrangement and said tubular conduit, the second toriodal seal having an outer face adapted to contact the hollow expandable seal

arrangement and an inner face comprising a first adhesive adapted to adhere the inner face to said tubular conduit.

The set seal may then be achieved by use of the second toroidal seal which will adhere to the tubular conduit when pushed against it by the hollow expandable seal in its expanded position. Subsequent deflation of the expandable seal to the unexpanded position leaves the second toroidal seal in place, adhered to the tubular conduit, and holding the tubular conduit in the coupling end. In order to remove the tubular conduit, the set seal must be broken, and the coupling will not be reusable without replacement of the hollow expandable seal arrangement and the second toroidal seal.

Suitably, the outer face of the second toroidal seal may comprise a second adhesive adapted to adhere the outer face to the hollow expandable seal. This is useful because when the hollow expandable seal arrangement is in the unexpanded position, the adhesion between the hollow seal arrangement and the second toroidal seal holds the second toroidal seal away from the tubular conduit, such that the tubular conduit can be pushed into the coupling end without fouling against the second toroidal seal.

Suitably, the second toroidal seal is of a compressible compound, such as a foamed polymer. The second toroidal seal may comprise such a foamed polymer, such as a foamed acrylic polymer.

The first and/or second adhesives may be selected to be suitable for adhesion to the respective surfaces. For the sake of simplicity, the first and second adhesives may be the same material. For instance, the second toroidal seal may be of a foamed polymer impregnated with an adhesive, such that compression of the seal leads to extrusion of the adhesive onto the inner and outer surfaces of the toroidal seal.

It may be advantageous if the second adhesive is a weaker adhesive than the fist adhesive. Then, should leakage of fluid lead to deflation of the expandable seal arrangement, there is reduced risk that the deflation will lead to the second toroidal seal being pulled away from its locked arrangement with the tubular conduit.

A suitable material for use in the second toroidal seal is, for instance, double sided adhesive tape available from 3M, such as 4941 P or 4956P acrylic foam. The inner surface of the second toroidal seal may be covered by a protective tape covering the adhesive surface prior to use of the coupling. This tape is removed before the tubular conduit is inserted into the coupling end.

In order to form a good, locking seal around the tubular conduit, the second seal is toroidal in shape. Although preferably in the form of a continuous toroid, for ease of assembly of the coupling, the second toroidal seal may

be formed from a straight piece of seal with its two opposite ends bent around into contact to form a substantially toroidal shape. The compression of the second seal will lead to any gap where the ends meet being closed in order to prevent leakage around the locked seal, provided that sufficient care is taken to mate the opposite end together.

The material of the second toroidal seal is suitably selected to be capable of forming a good seal against the material of the tubular conduit to be used with the coupling.

In addition or alternatively, the housing may comprise at least one through hole extending from an external surface of the housing through to the tubular wall of the receiving recess and may additionally comprise at least one fixing element, the or each fixing element extending through a corresponding one of the through holes in the housing for engaging such a tubular conduit. In this case, the expandable seal may be located at a position between the fixing element(s) and an open end of the receiving recess. A second seal may be provided between the housing and the, or each, fixing element. The fixing element may engage such a tubular conduit by extending at least partly through a corresponding hole formed in such a tubular conduit.

The tubular wall of the coupling may include an abutment for an end of such a tubular conduit. The abutment may be an annular shoulder

extending from the tubular wall into the receiving recess. The tubular wall may have the shape of a right cylinder.

The coupling may comprise two coupling ends and a conduit between the coupling ends. Alternatively, the coupling may comprise a single coupling end comprising a pipe termination.

The present invention also provides a method of fixing a tubular conduit in a coupling of the type described above, comprising the steps of: fitting an end of such a tubular conduit within the receiving recess of the coupling; and pumping a fluid into the expandable seal so as to move the expandable seal to its expanded position.

Where the fluid is introduced into the expandable seal via a nozzle of the expandable seal, the method may comprise the additional step of closing off the nozzle. Where the fluid is a settable fluid, the method may comprise the additional step of facilitating setting of the fluid.

The invention will now be described by way of example only and with reference to the accompanying schematic drawings, wherein:

Figure 1A shows a partial longitudinal cross-section through one end of a coupling according to a first embodiment of the present invention with an end of a pipe length connected to the coupling and the seal unexpanded;

Figure 1 B shows a partial longitudinal cross-section as for Figure 1 A but with the seal expanded;

Figure 2A shows a partial longitudinal cross-section through one end of a coupling according to a second embodiment of the present invention with an end of a pipe length connected to the coupling and the seal unexpanded; Figure 2B shows a partial longitudinal cross-section as for Figure 2A but with the seal expanded;

Figure 3A shows a partial longitudinal cross-section through a pipe termination coupling according to a third embodiment of the present invention, with a sealing arrangement similar to that shown in Figures 2A and 2B with an end of a pipe length connected to the coupling and the seal unexpanded;

Figure 3B shows a partial longitudinal cross-section as for to Figure 3A but with the seal expanded;

Figure 4A shows a partial longitudinal cross-section through a pipe termination coupling according to a fourth embodiment of the present invention with an end of a pipe length connected to the coupling and the seal unexpanded;

Figure 4B shows a partial longitudinal cross-section as for Figure 3A but with the seal expanded; and

Figure 5 shows a plan view of a coupling according to the first embodiment the present invention.

Figure 5 shows a double ended coupling (1) according to the present invention, comprising two coupling ends (2) of the type shown in Figures 1A to 1B. A length of tubular conduit or pipe (4) is connected to each end of the coupling (1). A central portion (3) of the coupling (1) may comprise a simple conduit connecting the ends of the pipes (4) or may comprise a valve or a connection to another section of pipe.

The coupling ends (2), one of which is shown in cross-section in Figures 1A and 1B has an end of a length of tubular conduit or pipe (4) connected to it. The coupling end comprises a housing (2) defining a tubular wall (14) of a receiving recess for receiving an end of the pipe (4). The coupling end (2) is tubular and in Figures 1A and 1 B is shown as a cylinder with a circular cross-section at its inwardly and outwardly facing surfaces. An annular abutment (6) extends radially inwardly from the inwardly facing surface or tubular wall (14) of the coupling end, at a set distance (D-O from an open end (8) of the coupling end (2). An annular recess (10) extends radially outwardly of the inwardly facing surface (14) of the coupling end (2) for housing an expandable seal (12) at a set distance (D ₂ ) less than distance (Di) from the open end (8) of the receiving recess of the coupling end.

A through hole (30) extends from the inwardly facing face of the annular recess (10) to the outwardly facing face (16) of the coupling end (2). The expandable seal (12), shown unexpanded in Figure 1A comprises an expandable skin (32) which takes the shape of a hollow ring, at least when expanded, and which has an inlet tube (34) which extends outwardly of a part of the outer surface of the skin. Before the pipe (4) is connected to the coupling end (2), the expandable seal (12) is positioned in the annular recess (10), as is shown in Figure 1A, with the inlet tube (34) extending through the through hole (30) from the recess (10) so that the inlet tube extends at least as far as the outer surface (16) of the coupling end (2).

The skin (32) of the expandable seal (12) is made of a suitable resilient material, for example of rubber, although many alternative materials will be apparent to a person skilled in the art.

The expandable seal (12) can be expanded into its expanded position, shown in Figure 1 B by injecting or pumping a fluid (36) into the seal (12) via the inlet tube (34). In the expanded position of the seal (12), the skin (32) of the seal takes the shape of the annular recess (10) and the inwardly facing surface of the seal (12) bears against the pipe (2) so as to provide a seal therebetween. The fluid (36) injected or pumped into the seal is a liquid which is pumped or injected into the seal (12) until the seal takes up the expanded position of Figure 1B. Then the end of the nozzle (34) remote from the skin (32) is closed off so as to maintain the seal in its

expanded position. The liquid (36) is made up of a composition which sets permanently after the ring (12) is in its expanded position.

A plurality of through holes (18) are formed through the housing of the coupling end (2) from the external (16) surface through to the tubular wall (14) of the coupling end. The bore of each through hole (18) is substantially concentric with a line (20) extending substantially radially from the longitudinal axis (21) of the coupling end. In the example shown in Figures 1A to 1B and 5, six such through holes (18) are formed in the coupling end, each at a distance (D ₃ ) from the open end (8) of the coupling end (2). Distance (D ₃ ) is greater than distance (D ₂ ) and is less than distance (D-i). Each through hole has an outer threaded portion (18a) adjacent the outwardly facing surface (16) of the coupling end (2), a central portion (18b) which is unthreaded and which houses an annular seal (22) and an inner portion (18c) adjacent the inwardly facing surface (14) of the coupling end having a smaller diameter bore than the outer and central portions (18a, 18b). Thus, a step is created between the central portion (18b) and the inner portion (18c) against which the seal (22) is seated. A fixing element (24) is fixed within each through hole (18) and passes through each hole to engage the wall of the pipe (4) fitted within the coupling end (2), as is described below. The outer portion (18a) may also comprises a frusto-conical opening to the outwardly facing face (16) of the coupling end (2) for seating a head (26) of the fixing element (24).

The fixing element (24) comprises a head (26) with a slot (28) formed in the top of the head suitable for engagement with a screwing tool, such as a screwing tool suitable for fitment in and driving by a power tool, such as a drilling and/or driving power tool. Accordingly, the slot (28) can be suitably shaped (see Figure 4 ) to provide good engagement with the type of screwing tools known in the art. Adjacent the head (26) of the fixing element, is an outer portion (24a) of the fixing element which is externally threaded so as to threadingly engage the internally threaded outer portion (18a) of the through holes (18) of the coupling end (2). The fixing element (24) also comprises an inner portion (24b) of reduced diameter as compared to the outer portion (24a), sized to engage the radially inner edge of the seal (22) and to smoothly fit within the inner portion (18c) of the through hole (18). The inner portion (24b) of fixing element (24), when fitted within the through hole (18) extends radially inwardly of the inwardly facing surface (14) of the coupling end (2).

To fix a pipe (4) within a coupling end (2), first the fixing elements (24) are removed from the coupling end (2) and the pipe (4) is slideably mounted within the coupling end, until the end of the pipe abuts the annular abutment (6). With the expandable seal (12) in its unexpanded position (Figure 1A) no additional force is required to push the pipe past the seal (12). Then with the pipe in place, a hole (30) of a suitable bore to fit the inner portion (24b) of the fixing element (24) is drilled through the wall of the pipe (4) by passing a drill bit of a drilling tool through one of the holes

(18) in the coupling end (2). In this way, the hole (30) in the pipe (4) is aligned with a corresponding one of the holes (18) in the coupling end (2). Then one of the fixing elements (24) is fitted within the through hole (18) so that the fixing element passes through the through hole (18) and their inner portion (24b) passes into the corresponding drilled hole (30) of the pipe (4). The pipe (4) is thus connected to the coupling end (2) and secured there against rotation. This drilling and fitting of the fixing element procedure is then repeated for each of the fixing elements (24) and corresponding through holes (18), until all of inner portions (24b) of the fixing elements (24) engage corresponding holes (30) drilled within the pipe (4) (as shown in Figure 1).

Pipelines tend to vibrate, and such vibration could cause the fixing elements (24) to come loose. To avoid this, a connector (33) can be fitted between the head (26) of the fixing element and the outwardly facing surface (14) of the coupling end (2) so as to hold the fixing element (24) against rotation.

After the fixings (24) are secured, the end of the nozzle (34) remote from the skin (32) of the expandable seal (12) is connected to a fluid injection device or pump. Then, a suitable liquid (36) is pumped or injected via the nozzle (34) so as to expand the skin (32) of the expandable seal (12) until the skin (32) takes up the shape of the recess (10) and bears sealingly against the pipe (4). Thereafter, the end of the nozzle (34) is closed off.

The liquid (36) is a settable liquid which is left to set and optionally the nozzle (34) is closed off.

Figures 2A and 2B show a coupling end (102) similar to that shown in Figures 1A and 1B, with like part identified by like numerals, but with the fixing elements (24) and associated fixing holes (18) removed.

The expandable seal (12) of Figures 2A and 2B is as described above in relation to Figures 1A and 1 B. However, when the seal (12) is expanded, as shown in Figure 2B, the frictional engagement between the seal (12) and the pipe (4) is sufficient to hold the pipe (4) within the coupling end (2).

To fix a pipe (4) within the coupling end (2) of Figures 2A and 2B, the pipe (4) is slideably mounted within the coupling end, until the end of the pipe abuts the annular abutment (6). With the expandable seal (12) in its unexpanded position (Figure 1A) no force is required to push the pipe past the seal (12). Then, the end of the nozzle (34) remote from the skin (32) of the expandable seal (12) is connected to a fluid injection device or pump. Then, a suitable fluid (36) is pumped or injected via the nozzle (34) so as to expand the skin (32) of the expandable seal (12) until the skin (32) takes up the shape of the recess (10) and bears sealingly against the pipe (4). Thereafter, the end of the nozzle (34) is closed off. The fluid (36), which is a settable fluid, is allowed to set and optionally the nozzle (34) is closed off.

Figures 3A and 3B show an embodiment of the present invention similar to that of Figures 2A and 2B, with like parts indicated by like numerals, except that the coupling end (2) is formed as a pipe termination for closing off an end of the pipe (4).

Turning now to the fourth embodiment in figures 4A and 4B, the coupling end (2), shown in cross-section in Figures 4A and 4B has an end of a length of tubular conduit or pipe (4) connected to it. The coupling end comprises a housing (2) defining a tubular wall (14) of a receiving recess for receiving an end of the pipe (4). The coupling end (2) is tubular and in Figures 4A and 4B is shown as a cylinder with a circular cross-section at its inwardly and outwardly facing surfaces. An end wall closes one end of the coupling. An annular recess (10) extends radially outwardly of the inwardly facing surface (14) of the coupling end (2) for housing an expandable seal (12).

A through hole (30) extends from the inwardly facing face of the annular recess (10) to the outwardly facing face (16) of the coupling end (2). The expandable seal (12), shown unexpanded in Figure 1A comprises an expandable skin (32) which takes the shape of a hollow ring, at least when expanded, and which has an inlet tube (34) which extends outwardly of a part of the outer surface of the skin. Before the pipe (4) is connected to the coupling end (2), the expandable seal (12) is positioned in the annular recess (10), as is shown in Figure 1A, with the inlet tube (34) extending

through the through hole (30) from the recess (10) so that the inlet tube extends at least as far as the outer surface (16) of the coupling end (2).

The skin (32) of the expandable seal (12) is made of a suitable resilient material, for example of rubber, although many alternative materials will be apparent to a person skilled in the art.

A second toroidal seal (40) is located in the annular recess (10) between the expandable seal (12) and the pipe (4). The outer face of the toroidal seal (40) is adhered to the skin (32) of expandable seal (12). The inner face of the toroidal seal (4) is also coated in adhesive. A covering paper (not shown) to prevent fouling of the adhesive during storage and transport is removed from the adhesive of the inner surface of the toroidal seal (40) prior to insertion of the pipe (4).

The expandable seal (12) can be expanded into its expanded position, shown in Figure 4B by injecting or pumping a fluid (36) into the seal (12) via the inlet tube (34). In the expanded position of the seal (12), the skin (32) of the seal takes the shape of the annular recess (10) and the inwardly facing surface of the seal (12) bears against the outer surface of the toroidal seal (40) pushing the inner surface of the toroidal seal (40) into sealed contact with the pipe (4) so as to provide a seal therebetween. The adhesive layer on the inner surface of the toroidal seal (40) provides a set seal between the toroidal seal (40) and the pipe (4). The fluid (36) injected

or pumped into the seal might be a gas or a liquid which is pumped or injected into the seal (12) until the seal takes up the expanded position of Figure 1 B. Then the end of the nozzle (34) remote from the skin (32) may be closed off so as to maintain the seal in its expanded position. However, even if the fluid leaks out, the adhesive bond between the toroidal seal (40) and the pipe (4) maintains a set seal between the pipe (4) and the coupling end (2).

To fix a pipe (4) within a coupling end (2), the pipe (4) is slideably mounted within the coupling end, until the end of the pipe abuts the annular abutment (6). With the expandable seal (12) in its unexpanded position (Figure 4A) no fouling results as the pipe is pushed past the seal (12).

The coupling (1) according to the present invention with a coupling end (2) as is described herein, is simple and easy to fit to a pipe (4), without requiring a skilled workforce of welders and only a simple drilling tool and without requiring extensive force to fit the pipe within the coupling end. The coupling (1) is relatively cheap to make and is much cheaper to install, especially where the pipes (4) are part of a pipeline of large diameter, for example for transporting gas or oil. The coupling (1) is safe to fit, as it does not require welding. In the Figure 1 embodiment, cold drilling, cooled by running water, can be used to drill the holes (30) in the pipe (4), so as to prevent the generation of sparks. In the embodiments of Figure 2 and 3, no such drilling is required. The expandable seal (12) provides a good seal

between the coupling end (2) and a pipe (4) fitted within it and so is not susceptible to leaks. Also, the fitting of the coupling end (2) to the pipe (4) does not obstruct the flow of fluid within the pipe (4).