GB2451628A

GB2451628A - Fluid pressure activated pipe coupling comprising folded sleeve secured by clamping rings

Info

Publication number: GB2451628A
Application number: GB0715199A
Authority: GB
Inventors: Noel Silverthorne
Original assignee: Tricorn Group PLC
Current assignee: Tricorn Group PLC
Priority date: 2007-08-03
Filing date: 2007-08-03
Publication date: 2009-02-11
Anticipated expiration: 2027-08-03
Also published as: GB0715199D0; GB2451628B

Abstract

A coupling for coupling together pipes 11,12 comprises a tubular sleeve 6 defining a socket for receiving a deformable pipe 11,12 to which the coupling is to be connected. An outer coupling body 1 extends around and defines a substantially annular chamber 10 with a main central portion (9, figure 1) of the sleeve 6. The chamber is sealed and can be pressurised by introduction of a fluid through an inlet 5 communicating with the chamber 10. The main portion of the sleeve 6 is inwardly compressible by pressurisation of the chamber 10 to grip the pipe 11,12 within the socket. At least one end (7,8, figure 1) of the sleeve 6 is folded over a corresponding end 2,3 of the outer member 1 such that it is disposed outwardly of the first portion (9, figure 1). A clamping ring (15, figure 4) clamps said end of the sleeve 6 against a generally outwardly facing surface of the outer member 1 so as to resist its outwards deformation. Increased pressure in the chamber 10 thus serves to increase the clamping force applied by the clamping ring (15, figure 4) thereby providing for a secure sealing arrangement.

Description

A COUPLING

The present invention relates to a coupling, particularly, but not exclusively, to a pipe coupling, and to a method for connecting an element such as a pipe to a coupling.

Many designs of couplings are known which seek to achieve a reliable sealed connection between the coupling and an element such as a pipe inserted into the coupling. Many known couplings rely upon mechanical compression of, for example, a deformable metal ring between a coupling socket and the outer surface of the pipe.

Other couplings are known in which pipe to coupling seals are achieved using thermosetting intermediate components. The present invention is concerned with couplings which rely upon mechanical deformation of coupling components.

Mechanical couplings are used in circumstances in which it is often difficult to rely upon those responsible for assembling the couplings to carry out all the necessary procedures in a systematic manner. For example, where pipes to be interconnccted are relatively easily deformable, for example HDPE pipes as widely used in the water and gas industries, it is necessary to push an insert into the end of a pipe to which a coupling is to be connected so as to prevent the pipe being excessively deformed radially inwards when the coupling is assembled, and with many couplings it is also necessary to position further components around the pipe which are not visible in the final assembly. External inspection of an assembled coupling does not enable the inspector to check that the insert and any other components have been properly positioned. It is also difficult to ensure that the pipe end inserted into a coupling is not contaminated with dirt to an extent which compromises coupling integrity. This is a real problem in circumstances in which mechanical couplings are used that rely upon only a limited axial interengagement between the external surface of the pipe and a radially compressed coupling element. It is also not possible by visual inspection to check that sufficient force has been applied to coupling components to achieve a reliable interconnection. For example, couplings which rely upon the application of a predetermined force by a crimping tool or relative rotation of a coupling body and a threaded compression element may appear on visual inspection to have been correctly assembled even if the required force has not been applied by the assembler.

A further problem with certain known couplings is that complex and cumbersome tools such as hydraulic presses are required for coupling assembly. This is particularly the case with large diameter couplings. Such tools cannot be readily used on-site, e.g. in trenches excavated to give access to buried pipes.

A coupling is described in our international patent application W000/39495 which comprises a deforn-iable tubular inner member defining a socket for receiving a tubular deformable element (e.g. a pipe) to which the coupling is to be connected. The inner member is disposed in an outer tubular body, which extends around and defines an annular chamber with the inner tubular member. An inlet communicates with the chamber and enables pressunsation of the chamber by introduction of a fluid such that the inner member is deformed radially inwards so as to grip the tubular deformable element within the socket. A tubular insert is supported in the tubular deformable element and limits the inward defonnation thereof. The axial ends of the inner member and the outer tubular body are sealed together by, for example, welding, soldering, brazing or similar.

It is an object of the present invention, amongst others, to provide an improved coupling of the kind referred to above.

According to the present invention there is provided a coupling comprising a tubular member defining a socket for receiving a tubular deformable element to which the coupling is to be connected, an outer member which extends around and defines a substantially annular chamber with a first portion of the tubular member that is disposed inwardly of the outer member, an inlet communicating with the chamber to enable pressurisation of the chamber by introducing fluid to the chamber through the inlet, the first portion of the tubular member being radially compressible by pressurisation of the chamber to grip an element within the socket, characterised in that a second portion of the tubular member is folded over at least one end of the Outer member such that it is disposed outwardly of the first portion, and a clamping member clamps said second portion of the tubular member against a surface of the outer member.

The arrangement is such that when the chamber is pressurised with fluid the first portion of the tubular member is inwardly deformed to grip the element within the socket and the outer member is outwardly deformed to grip the second portion of the tubular member between said surface and the clamping member.

The surface of the outer member against which the second portion of the tubular member is clamped may be an outwardly facing surface.

The socket and tubular deformable element may be generally circu]ar and therefore the inward deformation is substantially radial inward deformation.

The tubular deformable element may be a pipe.

The coupling may further comprise a tubular insert which, in use, is inserted into the end of the tubular deformable element to which the coupling is to be connected, the insert being arranged to limit the radially inwards deformation of the deforrnable element by pressurisation of the chamber to grip an element within the socket.

The clamping member resists radially outwards expansion of the outer member resulting from pressurisation of the chamber.

The clamping member may be substantially annular and may be disposed over said end of the outer member. The second portion of the tubular member may be clamped between a surface of the clamping ring and a surface of the outer member.

One or both of the surfaces may have gripping formations such as teeth, ribs, serrations or the like to resist slippage of the tubular member relative thereto. The clamping member may have a substantially axially extending portion and a substantially radially extending portion. It may also have a snap connection with the outer member. A first formation of the clamping member may be movable in a radial direction but it biased radially inwardly. In a first radial position the formation on the clamping member co-operates with a second formation on the outer member and prevents significant relative axial displacement. In a second radial position it is outwardly deflected so as to permit relative axial movement.

The second portion of the tubular member may be defined at one or both ends thereof.

The invention also provides a method for connecting an element to a coupling comprising an inwardly deformable tubular member defining a socket into which the element is inserted, wherein an outer member is disposed around a first portion of the tubular member, folding a second portion of the tubular member around an end of the outer member, clamping said second portion to a surface of the outer member such that a sealed chamber is defined between the first portion of the tubular member and the outer member, introducing pressurised fluid into the chamber, the clamping force serving to resist outwards expansion of the outer member such that the clamping force increases with increased pressure in the chamber.

Pressure can be applied up to a predetermined limit at which it is known from the design of the coupling that appropriate tube deformation has occurred.

Alternatively, pressure can be applied until fluid leaks from a seal of the chamber, in which case seal failure can be taken as confirmation that the required pressure has been applied. The pressurised fluid may be delivered by a simple fluid pumping system.

Although the coupling has particular utility in connecting tubular pipes together, it could be used to make a connection to any element which could be inserted into the socket and which is dimensioned such that it is gripped after compression of the inner member.

The tubular insert member may define a radially outwards extending projection to limit the depth of insertion of an element into the socket.

When the coupling is used with a deformable element such as a HDPE pipe, the tubular insert is inserted into the end of the pipe. The insert is preferably provided with surface formations to grip the pipe after radially inward deformation thereof, for example, circumferentially extending teeth, or circumferentially extending rectangular grooves, or openings extending radially through the insert.

The insert may have one end of which, in use, is inserted inside the end of one of two pipes to be interconnected by the coupling and the other end of which in use is inserted inside the end of the other of the two pipes. The tubular insert may be ribbed to define an expansion joint to enable axial expansion and contraction of the tubular insert. The tubular insert may be ribbed to limit the depth of insertion of the insert into the pipes.

A specific embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a sectional view of coupling components of the present invention being used to couple together two pipe ends; Figure 2 is a view similar to that of Figure 1 but afler deformation of a component of the coupling to grip securely the inserted pipe ends; Figure 3 is a detailed view of part of the coupling of figure 2; and Figure 4 is a perspective view from above of the coupling of figures 1 to 3.

Referring to Figures 1 to 4, the exemplary coupling is used to couple together the ends of two plastic pipes 11,12 and has an outer body I comprising a wall of generally cylindrical configuration with first and second ends 2, 3. The wall of the body is penetrated radially by a single inlet port 4 that is fitted with a valve 5. A single deformable tubular sleeve 6, which is slightly longer in length than the outer body 1, lines the inside of outer body 1. The protruding ends 7 and 8 of the sleeve 6 are folded (e.g. bent or otherwise deformed) radially outwardly and rearwardly over the ends 2, 3 of the coupling body where they are fixed in a sealed relationship so as to retain the sleeve 6 within the body 1. In between the two ends 7, 8, a main section 9 of the sleeve 6 lines the inner surface of the outer body 1 but is separable therefrom so as to define a variable volume sealed chamber 10 between the inner surface of the outer body 1, the outer surface of the sleeve 6 and the sealed ends 7, 8 of the sleeve 6.

The ends 7,8 of sleeve 6 are fixed to an outer surface 13 of the ends 2,3 of the outer body 1 by means of clamping rings 15 so as to form a sealed relationship. Each of the rings 15 is concentrically disposed over a respective end portion 2, 3 of the outer body 1 and comprises an annular wall with an axially extending portion 16 and a radially extending portion 17 that fits over the respective end 2 or 3 of the outer body 1. The axially extending portion 16 overhes the outer surface 13 of the end portion 2 or 3 of the outer body and the radially extending portion 17 extends inwardly adjacent to the ends 2, 3. The ends 7, 8 of the sleeve 6 are gripped between the axially extending portion 16 of the clamping ring 15 and the underlying surface 13 of the outer body 1.

A single piece steel pipe insert 20 is disposed inside the end of each pipe 11, 12. It has a central annular projection 21 that defines two shoulders 22, 23, the projection 21 being flanked on each side by a stepped outer surface comprising annular serrations 24 for engagement with the inside surfaces 25 of the pipes 11, 12.

0-ring seals 26, four of which are shown in the embodiments of figures 1 and 2, may optionally be provided in annular grooves 27 on the outer surface of the insert 20. In an alternative embodiment the insert 20 may be provided in two pieces that abut in the assembled coupling as described in our international patent application WO 00/39495.

The coupling is completed by injecting pressurised fluid through the inlet port 4 to inflate the chamber 10. As the pressure within the chamber 10 increases, the main portion 9 of the sleeve 6 is progressively deformed radially inwards on to the pipe ends 11 and 12 whose consequent inward deformation is in turn limited by the presence of the insert 20, the extent of the deformation of the sleeve 6 and the pipe ends ii and 12 being a function of the applied pressure. As the plastic material of the pipe ends is forced on to the insert 20 the inner surfaces 25 deform over the serrations 24 thus forming a fluid-tight seal and creating a robust coupling. At the same time the fluid pressure in the chamber 10 causes the outer body 1 to expand radially outwardly.

The clamping rings 15 resist the outward expansion at the ends 2, 3 thus imparting an additional clamping force on the clamped ends 7, 8 of the sleeve 6. This serves to prevent any slippage of the sleeve ends 7, 8 relative to the outer body 1 and maintains the sealing relationship there. As can be seen in figure 3, the outer surface 13 of each end 2, 3 of the outer body 1 may have teeth 28 or other suitable formations that assist in gripping the sleeve 6. As an alternative, or an addition, the inwardly facing surface of the clamping ring 15 may be provided with such serrations or formations.

The degree of deformation and hence the security of the grip of the sleeve 6 on the pipe ends 11, 12 and the grip of the clamping rings 15 on the sleeve ends 7, 8 is a function of the applied pressure.

The deformation of the inner surfaces 25 of the pipes 11,12 over the serrations 24 serves to resist an end load applied to the pipes so that the pipes can only be pulled out if the force applied is so large as to either pull the pipe over the serrations 24.

Such an arrangement accordingly provides very good pull-out resistance even when used with materials such as HDPE which in known couplings have a tendency to "creep" over a long service life.

The fluid may be injected into the chamber 10 from any suitable device, for example a hand-operated or motor driven pump. The injected fluid could be, for example, mineral oil although in some applications, for example in the water industry, it may be appropriate to use a different fluid which could not in any circumstances cause unacceptable contamination. For example it is possible to use water, vegetable oil or biodegradable rapeseed oil (or the like) as the injection fluid. The injection fluid may incorporate, for example, a dye so if it should escape from the coupling after a seal failure this will be evident during subsequent inspection. In certain applications the fluid may be grease (which may be used to prevent water ingress) or a hardenable resin. Resin is particularly suitable for use in applications where the pipes carry a high pressure as the collapsed inner sleeve benefits from some support from the outer tube due to the hardened resin.

The valve 5 in the inlet 4 is ideally a one-way valve such as a grease nipple to retain the grease or other fluid in the chamber.

The couplings as described may be manufactured from any appropriate material. For example the coupling body I could be manufactured from mild steel, the deformable sleeve 6 could be manufactured from annealed copper, and the insert from stainless steel. Whilst the above-described coupling is used to couple plastic pipes it is to be appreciated that it may be used to couple pipes made from other material.

The sequential assembly of the coupling is achieved by pushing one end of insert 20 into a pipe end 11, 12 until it abuts shoulder 22 or 23. The pre-assenibled outer body 1 and sleeve 6 of the coupling are then placed over the end of the pipe 11, 12 and insert 20. An end of a second pipe 11 or 12 is then inserted into the other end of coupling, between the insert 20 and sleeve 6 until it abuts the other shoulder 22 or 23. The ends 7, 8 of the sleeve 6 are folded over the ends 2, 3 of the outer body I as shown in the figures and the clamping rings 15 are then pushed into place so as to grip the folded ends.

The connection of the clamping rings 15 to the outer body I is conveniently achieved by a snap-fit arrangement. The axially extending portion 16 of each ring 15 is resilient such that is able to deflect radially as part of the snap-fit arrangement and terminates in a radially inward directed lip 30 with a tapered surface 31. When the clamping member 15 is fitted in place over the outer body I this lip 30 occupies a corresponding annular groove 32 defined on the outer surface of the body 1.

Immediately adjacent to the groove 32, towards each end 2, 3 of the body 1, there is a tapered surface 33 that extends radially outwards in the direction the clamping member 15 is presented to the body 1. To fit the clamping rings 15 they are presented to the body 1 such they are aligned with the ends 2, 3 and are then displaced axially over the folded ends 7, 8 of the sleeve until the tapered surfaces 31, 33 engage.

Further axial displacement in the same direction causes the tapered surfaces 31, 33 to ride over one another and the lip 30 to deflect radially outwards. Still further displacement brings the lip 30 into axial alignment with the groove 32 thereby allowing it to snap back into place in the radial direction to the position shown in figure 3.

It should be appreciated that for all embodiments of the present invention, the inner sleeve 6 that forms the seal around the pipe 12, 13 does not need to be made of copper, as described, but could be made of any suitable material (for example aluminium) that will deform as required and retain the shape into which it has been deformed.

For embodiments of the present invention to function effectively it is necessary to ensure that the pipe to which a connection is to be made can resist the radially inward forces applied when pressurised fluid is introduced into the coupling.

In the case of plastics pipes, the necessary resistance to the compressive forces applied by the coupling is provided by an insert pushed into the end of the plastics pipes. With large diameter pipes, thick walled inserts may be required to provide the necessary support for the plastics pipe during the application of pressure, and it may be undesirable to use inserts with the required wall thickness. It is possible however to avoid the use of an insert with an undesirably thick wall by providing reinforcement to a relatively thin-walled insert during coupling pressunsation, the reinforcement subsequently being removed.

One significant advantage of the arrangement described above is that it eliminates the requirement to braze, weld, solder or otherwise join the ends 7,8 of the sleeve 6 to the outer body I. The provision of a mechanical seal on a surface of the outer body I ensures that the outward expansion of the body serves to increase the sealing force and therefore improve the sealed relationship between the sleeve 6 and the outer body I of the coupling.

It will be appreciated that the coupling may be used to connect a flange to a pipe as illustrated in figures 29 and 30 of our international patent application WO 00/39495 in which case only one end of the sleeve may be sealed by a clamping ring, the other end being sealed in any convenient manner. Moreover, there may be other applications in which a clamping ring may only be required at one end of the coupling.

Numerous modifications to the above-described designs may be made without departing from the scope of the invention as defined in the appended claims. For example, the exact shape and form of the clamping ring may vary provided it creates a mechanical seal between the sleeve and the outer body. The surface of the outer body against which the sleeve is sealed does not necessarily have to be its outermost surface. It may be any suitable surface including, in particular, a generally outward facing surface that is forced outwards against the clamping ring by the pressure of fluid in the chamber.

Claims

A coupling comprising a tubular member defining a socket for receiving a tubular deformable element to which the coupling is to be connected, an outer member which extends around and defines a substantially annular chamber with a first portion of the tubular member that is disposed inwardly of the outer member, an inlet communicating with the chamber to enable pressurisation of the chamber by introducing fluid to the chamber through the inlet, the first portion of the tubular member being inwardly compressible by pressurisation of the chamber to grip an element within the socket, characterjsed in that a second portion of the tubular member is folded over at least one end of the outer member such that it is disposed outwardly of the first portion, and a clamping member for clamping said second portion of the tubular member against a surface of the outer member.
2. A coupling according to claim 1, wherein said surface of the outer member is an outwardly facing surface.
3. A coupling according to claim 2, wherein when the chamber is pressurised with fluid the first portion of the tubular member is inwardly deformed to grip the deformable element within the socket and the outer member is outwardly deformed so that the second portion of the tubular member is clamped between said outwardly facing surface and the clamping member, the clamping member resisting outwards expansion of the outer member.
4 A coupling according to claim 1, 2 or 3, wherein the clamping member is substantially annular.
5. A coupling according to any preceding claim wherein the clamping member is disposed over said end of the outer member. ll
6. A coupling according to any preceding claim, wherein the second portion of the tubular member is clamped between a clamping surface of the clamping ring and a surface of the outer member, at least one of said surfaces having one or more gripping elements to resist slip of the tubular member relative thereto
7. A coupling according to any preceding claim, Wherein' the clamping member has a substantially axially extending portion and a substantially radially extending portion.
8. A coupling according to any preceding claim, wherein the clamping member has a snap-fit connection with the outer member.
9. A coupling according to claim 8, wherein the snap-fit connection comprises a first formation on the clamping member that is movable between a first radial position in which it co-operates with a second formation on the outer member so as to prevent significant relative axial movement arid a second radial position where it is clear of said second formation so as to allow relative axial movement.
10. A coupling according to claim 9, wherein axial displacement of the clan'iping member towards the outer member first brings the first formation into engagement with the second formation which then co-operate first to deflect the first formation to said second radial position and then to allow the first formation to move to said first radial position.
11. A coupling according to any preceding claim, wherein the second portion of the tubular member is defined at one or both ends thereof.
12. A coupling according to any preceding claim, further comprising a tubular insert which, in use, is inserted into the end of the tubular deformable element to which the coupling is to be connected.
13. A coupling according to claim 12, wherein the insert is arranged to limit the inwards deformation of the deforrnable element by pressurisation of the chamber to grip an element within the socket.
14. A coupling according to claim 13, wherein the insert has one or more surface formations to grip the element after inward deformation thereof.
15. A coupling according to any one of claims 12 to 14, further comprising one or more sealing elements between the insert and the tubular deformable element.
16. A pipe coupling comprising a coupling according to any preceding claim and at least one tubular deformable element in the form of a pipe.
17. A pipe coupling according to claim 16, comprising two tubular deformable elements coupled together by said coupling.
18. A method for connecting an element to a coupling comprising an inwardly deformable tubular member defining a socket into which the element is inserted, wherein an outer member is disposed around a first portion of the tubular member, folding a second portion of the tubular member around an end of the outer member, clamping said second portion to a surface of the outer member such that a sealed chamber is defined between the first portion of the tubular member and the outer member, introducing pressurised fluid into the chamber, the clamping force serving to resist outwards expansion of the outer member such that the clamping force increases with increased pressure in the chamber.
19. A method according to claim 18, wherein said second portion is defined at an end of the deformable tubular member.
20. A method according to claim 18 or 19, wherein the second portion is clamped to an outwardly facing surface of the outer member.
21. A method according to claim 19, wherein the first portion of the deformable tubular element is defined between two second portions each of which is defined by an end.