Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
SEALING PIPE LINER FOR CONNECTING METAL PIPES TO PLASTIC PIPES
Document Type and Number:
WIPO Patent Application WO/2018/158585
Kind Code:
A1
Abstract:
A pipe liner (1) comprises a seal (2) which is arranged to move from a relaxed configuration, in which at least part of the seal (2) has a smaller inner diameter, to an expanded configuration having a larger inner diameter. The seal (2) transitions from the relaxed configuration to the expanded configuration as the pipe liner (1) is pushed over a spigot (18). Consequently, the pipe liner (1) can be introduced into a pipe (5) in the relaxed configuration, with a smaller internal (and external) diameter and thereby ease introduction into the pipe (5). Then, when pushed over the spigot (18), the increase in internal diameter can force the external surface of the seal (2) against the internal surface of the pipe (5), sandwiching the seal (2) in a compressed (sealing) condition between the spigot (18) and the pipe (5). This allows metal pipes (5) to be connected to plastic pipes (14) using standard connectors (7) intended for plastic pipes (14).

Inventors:
WHITELEY, Paul Nicholas (Strafford Road, WheatleyDoncaster, South Yorkshire DN2 4BW, DN2 4BW, GB)
Application Number:
GB2018/050537
Publication Date:
September 07, 2018
Filing Date:
March 02, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
PEGLER YORKSHIRE GROUP LIMITED (St. Catherine's Avenue, Doncaster, South Yorkshire DN4 8DF, DN4 8DF, GB)
International Classes:
F16L21/00; F16L21/02; F16L25/14; F16L33/22; F16L47/24
Domestic Patent References:
WO1998037351A11998-08-27
Foreign References:
GB1083451A1967-09-13
US7404581B22008-07-29
US6746055B12004-06-08
Attorney, Agent or Firm:
WILSON GUNN (MANCHESTER) (5th Floor, Blackfriars HouseThe Parsonag, Manchester Lancashire M3 2JA, M3 2JA, GB)
Download PDF:
Claims:
CLAIMS

1. A pipe liner comprising a seal wherein the seal is arranged to move from a relaxed configuration, in which at least part of the seal has a smaller inner diameter, to an expanded configuration having a larger inner diameter. 2. A pipe liner according to claim 1 wherein the seal comprises one or more sealing rings.

3. A pipe liner according to claim 2 wherein the one or more sealing rings are formed integrally in a sealing element.

4. A pipe liner according to claim 2 or 3 wherein the one or more sealing rings have a triangular cross section.

5. A pipe liner according to any preceding claim wherein the seal is elastomeric.

6. A pipe liner according to any preceding claim, for connecting metal pipes to pipe fittings intended for plastic pipes, and sized to sit between a metal pipe and a spigot in the pipe fitting. 7. A pipe liner according to claim 6 wherein the seal is arranged to transition from the relaxed configuration to the expanded configuration as the pipe liner is pushed over the spigot, whereby, the pipe liner can be introduced into the pipe in the relaxed configuration, with a smaller internal and external diameter, then, when pushed over the spigot, the increase in internal diameter can force the external surface of the seal against the internal surface of the pipe, sandwiching the seal in a compressed, sealing condition between the spigot and the pipe.

8. A pipe liner according to any preceding claim wherein the seal is provided at an end that, in use, is innermost in the pipe into which the liner is introduced.

9. A pipe liner according to any preceding claim which is substantially

cylindrical. 10. A pipe liner according to any preceding claim comprising a substantially

cylindrical support portion.

11. A pipe liner according to claim 10 when directly or indirectly dependent on claim 6 wherein the substantially cylindrical support portion is arranged to seal against a seal on the spigot of the pipe fitting. 12. A pipe liner according to claim 10 or 11 when directly or indirectly dependent on claim 6 wherein the cylindrical support portion has an inner diameter approximately equal to the inner diameter of plastic pipe for which the pipe fitting is intended and an outer diameter approximately equal to or less than the inner diameter of metal pipe of the same outer diameter as the plastic pipe, for which the pipe fitting is intended.

13. A pipe liner according to any of claims 10 to 12 wherein the cylindrical

support portion is formed of metal, or thin plastic.

14. A pipe liner according to any of claims 10 to 13 when dependent on claim 8 wherein the cylindrical support portion comprises longitudinally extending slots forming fingers at an end where the seal is provided.

15. A pipe liner according to claim 14 wherein the seal extends between the

fingers.

16. A pipe liner according to claim 15 wherein the seal forms a web between the fingers.

17. A pipe liner according to any of claims 10 to 16 wherein the seal comprises a sealing element overmoulded, adhered or otherwise retained on the cylindrical support portion.

18. A pipe liner according to claim 8 or any of claims 9 to 17 when dependent thereon, the pipe liner being provided with an annular flange extending radially outwardly at the opposite end to the seal.

19. A pipe liner according to claim 18 wherein the flange has an outer diameter equal to the outer diameter of pipe which is intended to be used in the pipe fitting.

20. A pipe liner according to claim 19 wherein the flange is curved so as to

provide a smooth, rounded face, which is less likely to damage the seals in the fitting. 21. A kit comprising a pipe liner according to any of claims 1 to 20 and a pipe fitting intended for connecting to plastic pipe, the pipe fitting comprising a spigot to support and sealingly engage with the inside of plastic pipe and a retaining mechanism intended to retain the pipe on the spigot; whereby, the pipe fitting is adapted for use with metal pipe by introducing the pipe liner between the spigot and the metal pipe.

22. A kit according to claim 21 wherein the retaining mechanism is arranged to engage the outer surface of the pipe.

23. A kit according to claim 21 or 22 wherein the spigot comprises one or more external seals arranged to seal between the spigot and plastic pipe, or the pipe liner.

24. A kit according to any of claims 21 to 23 wherein the pipe fitting is a Tee joint.

25. A kit according to any of claims 21 to 24 wherein the pipe fitting is intended for plastic pipe of a predetermined outer diameter and the pipe liner allows the pipe to be used with metal pipe of the same predetermined outer diameter.

26. A method of connecting a metal pipe of a predetermined outer diameter to a pipe fitting comprising a spigot and intended for use with plastic pipe of the same predetermined outer diameter; the method comprising introducing a pipe liner according to any of claims 1 to 20 between the metal pipe and the spigot.

27. A method according to claim 26 comprising connecting the metal pipe of a predetermined outer diameter to a pipe fitting according to any of claims 21 to 25.

28. A method according to claim 26 or claim 27 comprising introducing the pipe liner into the pipe and then introducing the lined pipe into the pipe fitting.

Description:
Sealing Pipe Liner for Connecting Metal Pipes to Plastic Pipes

Technical Field of the Invention

The present invention relates to a pipe liner intended to create a seal so as to allow metal pipes to be connected to plastic pipes using standard connectors intended for plastic pipes.

Background to the Invention

The majority of plastic plumbing fittings are only designed to work with plastic tubes/pipes, including "multilayer" pipes, which may have plastic outer and/or inner tubes, sandwiching a metal tube. Usually the seals will be on a central spigot that the pipe gets pushed over, and the retaining mechanism will be provided on the inner surface of a cylindrical surface arranged outwards of the spigot to grip the external surface of the tube. This central spigot also provides support for the soft plastic tube to prevent it collapsing and helps to re-round it after cutting.

Though the external diameter of plastic and metal tubes can be the same (e.g. 015mm) the wall section and therefore the internal diameter of the tubes varies. The following table illustrates typical wall thicknesses and internal diameters of certain conventional pipes:

O/D Wall thickness I/O

15mm PEX Tube 15.0 mm 2.0 mm 1 1.0 mm

15mm Copper Tube 15.0 mm 0.7 mm 13.6 mm

15mm Multilayer Tube 15.0 mm 2.0 mm 1 1.0 mm O/D Wall thickness I/O

22mm PEX Tube 22.0 mm 2.0 mm 18.0 mm

22mm Copper Tube 22.0 mm 0.9 mm 20.2 mm

22mm Multilayer Tube 22.0 mm 2.0 mm 18.0 mm

Therefore, as the seals on the spigots are designed to provide enough compression to seal against the inner surface of a plastic tube, if a metal tube, such as a copper pipe, is pushed in, the greater internal diameter leads to the seals not being compressed correctly or at all, and the joint leaks. As the outer diameters are the same the retaining mechanism normally works satisfactorily, assuming it is strong enough to grip the harder material such as a metal grab ring.

In certain markets (particularly the UK) a lot of plumbers use plastic fittings and pipe for plumbing systems when they are protected and out of sight (e.g. under floors/behind walls) but switch to copper tube when the pipework becomes exposed and visible to the customer (such as up to a radiator or to a tap). This is usually done by buying a special transition fitting, for example a fitting such as set out in US6746055B, with a socket suitable for plastic on one end and metal on the other, alternatively 2 fittings (one plastic and one metal) can be joined together to form a transition fitting using a thread sealant if they have matching threads to achieve the same result.

This situation requires the plumber to buy 1 or 2 extra transition fittings for each point that the pipe work becomes exposed. Consequently, both the cost and the plumber' s inventory is increased. A typical scenario showing current techniques is shown schematically in figure 7, where plastic pipe 100 is running beneath and parallel to a floor 200, into a Tee joint 300. Since the Tee joint 300 is only suitable for plastic piping, a small length of additional plastic pipe 400 has to be cut and attached to the Tee joint, extending upward to a transition joint 500 (either a specialist transition fitting, or one formed from two fittings as set out above). Copper pipe 600 then extends out of the transition fitting upwards, through the floor 200 to the radiator 700.

The present invention has been made in light of this problem.

Summary of the Invention According to a first aspect of the invention, in its broadest aspect, the invention relates to a pipe liner comprising a seal.

More particularly, the invention provides a pipe liner for connecting metal pipes to pipe fittings intended for plastic pipes (including multilayer plastic pipes), and sized to sit between a metal pipe and a spigot in the pipe fitting; the pipe liner comprising a seal for sealing between the metal pipe and the pipe fitting (and/or sealing between the metal pipe and the pipe liner).

The seal may comprise one or more sealing rings, which may be formed integrally in a sealing element.

The one or more sealing rings may have a triangular (i.e. generally triangular) cross section.

The seal may be elastomeric. The seal (and the or each sealing ring if present) may be arranged to move from a relaxed configuration, in which at least part of the seal (and optionally one or more sealing rings, if present) has a smaller inner diameter, to an expanded configuration having a larger inner diameter. The seal may be arranged to transition from the relaxed configuration to the expanded configuration may occur as the pipe liner is pushed over the spigot. Consequently, the pipe liner can be introduced into the pipe in the relaxed configuration, with a smaller internal (and external) diameter and thereby ease introduction into the pipe and reduce the chance of the seal snagging on the end of the pipe. Then, when pushed over the spigot, the increase in internal diameter can force the external surface of the seal against the internal surface of the pipe, sandwiching the seal in a compressed (sealing) condition between the spigot and the pipe.

The pipe liner may be substantially cylindrical and may comprise a substantially cylindrical support portion. The substantially cylindrical support portion may be arranged to seal against a seal on the spigot of the pipe fitting.

Those skilled in the art will appreciate that such pipe liners may be produced in various different sizes depending on the size of the metal pipe and the size of plastic pipe that the pipe fitting is intended for. The cylindrical support portion may therefore have an inner diameter approximately equal to the inner diameter of plastic pipe for which the pipe fitting is intended (so as to engage with seals intended for the inner surface of plastic pipe) and an outer diameter approximately equal to or less than the inner diameter of metal pipe of the same outer diameter as the plastic pipe, for which the pipe fitting is intended. Thus, for example, for use connecting 15mm copper pipe to a pipe liner intended for 15mm PEX pipe, the cylindrical support portion may have an inner diameter of 11mm and an external diameter of 13.6mm (thus, a wall thickness of 1.3mm). In view of the sealing function of the seal a precise match is not essential, provided the cylindrical support portion can fit into the gap between the O/D of the spigot and the I/D of the metal pipe.

The cylindrical support portion may be metal, or thin plastic.

The seal may be provided at the end that, in use, is innermost in the pipe into which the liner is introduced. The cylindrical support portion may comprise longitudinally extending slots forming fingers at the end where the seal is provided. These fingers allow contraction and expansion of that part of the cylindrical support portion.

The seal may extend between the fingers. The seal may form a web between the fingers. The seal may comprise a sealing element overmoulded, adhered or otherwise retained on the cylindrical support portion.

The pipe liner may be provided with an annular flange extending radially outwardly at the opposite end to the seal.

The flange may have an outer diameter equal to the outer diameter of pipe which is intended to be used in the pipe fitting. The flange stops the pipe liner moving too far into the pipe (or indeed the pipe fitting. It may also provide a smooth axial face. The flange may be curved. The curve of the flange may be part-toroidal. Thus, the "front" of the pipe liner, which is inserted into the pipe fitting, may have a smooth, rounded face, which is less likely to damage the seals in the fitting (e.g. an O-ring arranged on the spigot). The provision of a flange, especially a flange forming a smooth axial face, avoids interaction between the end of the metal pipe (which is often burred and sharp) and the pipe fitting (which is intended for deburred pipe, especially plastic pipe which is generally less sharp than metal in any case).

According to a second aspect of the invention, there is provided kit comprising a pipe liner according to the first aspect of the invention (optionally including any optional features and any combination of optional features) and a pipe fitting intended for connecting to plastic pipe, the pipe fitting comprising a spigot to support and sealingly engage with the inside of plastic pipe and a retaining mechanism intended to retain the pipe on the spigot; whereby, the pipe fitting is adapted for use with metal pipe by introducing the pipe liner between the spigot and the metal pipe.

The retaining mechanism may be arranged to engage the outer surface of the pipe and may comprise a grab ring.

The spigot may comprise one or more external seals (which may be one or more O-rings) arranged to seal between the spigot and plastic pipe, or the pipe liner. The pipe fitting may be a Tee joint. Alternatively, the pipe fitting may be a bend, or a straight joint. The pipe fitting may be intended for plastic pipe of a predetermined outer diameter and the pipe liner may allow the pipe to be used with metal pipe of the same (i.e. substantially the same) predetermined outer diameter.

According to a third aspect of the invention, there is provided a method of connecting a metal pipe of a predetermined outer diameter to a pipe fitting comprising a spigot and intended for use with plastic pipe of the same (i.e. substantially the same) predetermined outer diameter; the method comprising introducing a pipe liner according to the first aspect of the invention (optionally including any optional features or combination of optional features) between the metal pipe and the spigot. The pipe fitting (and the pipe liner) may be the pipe fitting (and pipe liner) of the second aspect of the invention (optionally including any optional features or combination of optional features).

The method may comprise introducing the pipe liner into the pipe and then introducing the lined pipe into the pipe fitting. Detailed Description of the Invention

In order that the invention may be more clearly understood an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

Figure 1 shows an isometric view of a pipe liner; Figure 2 shows an isometric view of a cross section through the pipe liner of figure 1; Figure 3 shows a lateral cross sectional view through a pipe fitting, two plastic pipes, the pipe liner of figure 1 and a metal pipe, prior to insertion of the pipe liner, or insertion of the lined metal pipe;

Figure 4 shows a lateral cross sectional view through a pipe fitting, two plastic pipes, the pipe liner of figure 1 and a metal pipe, after insertion of the pipe liner, and prior to insertion of the lined metal pipe;

Figure 5 shows a lateral cross sectional view through a pipe fitting, two plastic pipes, the pipe liner of figure 1 and a metal pipe, as the lined metal pipe is inserted into the pipe fitting; Figure 6 shows a lateral cross sectional view through a pipe fitting, two plastic pipes, the pipe liner of figure 1 and a metal pipe, with the lined metal pipe fully inserted into the pipe fitting, in the region of the connection between the metal pipe and the pipe fitting; and

Figure 7 shows a schematic diagram of the prior art. Referring to figures 1 and 2, a pipe liner 1 is shown, which comprises an elastomeric seal 2. The pipe liner 1 is substantially cylindrical and comprises a substantially cylindrical support portion 3 to which, the seal 2 is attached.

In this embodiment, the cylindrical support portion 3 is formed of thin (e.g. 0.5mm thick) metal, such as copper. The pipe liner of this embodiment is intended for connecting a metal pipe having an outer diameter (O/D) of 15mm to a pipe fitting intended for plastic pipe (including multilayer plastic pipe) of the same O/D. Accordingly, the inner diameter (I/D) of the cylindrical support portion 3 is 11mm, as this corresponds to the I/D of a 15mm plastic (PEX) pipe of typical thickness.

A first end 4 of the pipe liner 1 is intended to be introduced into metal pipe 5 (see figs 3-6), whereas the opposite, second, end 6 is intended to be introduced (with the metal pipe 5) into a pipe fitting 7 (see figs 3-6). The seal 2 is provided at the first end, intended to be introduced into the mouth of the metal pipe 5.

The cylindrical support portion 3 comprises longitudinally extending slots forming fingers 8 at the end where the seal 2 is provided. These fingers 8 extend approximately one third to half of the length of the cylindrical support portion 3 and are equidistantly spaced circumferentially around the pipe liner 1. The fingers 8 and the slots between them are of approximately the same width.

The fingers 8 are resilient, bendable along their length, to allow contraction and expansion of the part of the cylindrical support portion 3 where they are formed. In this embodiment, eight fingers are formed, but of course those skilled in the art will be able to conceive of other numbers of fingers, along with alternative widths relative to the slots, different lengths etc.

The seal, or sealing element, 2 is formed on the outside of the fingers 8, extending from (and overlapping with) the solid part of the cylindrical support portion where the slots are absent, and in this embodiment along the entire length of the fingers 8 to their tips. It may be overmoulded, adhered or otherwise retained on the cylindrical support portion 3. In extending along the length of the fingers 8, and right round the circumference of the cylindrical support portion, the seal forms a web 9 extending between the fingers 8.

In this embodiment, the web 9 extends along the entire length of the slots between the fingers 8, from their bases to their tips. In this embodiment, the sealing element 2, is provided with two sealing rings 10, 11 extending radially outwardly from the fingers 8. The two sealing rings 10, 11 are axially spaced along the sealing element and each have triangular cross sections, with apices radially outermost.

The longitudinally outermost sealing ring 11 (closest to the tips of the fingers 8 and the first end 4 of the pipe liner 1) is thicker than the inner sealing ring 10, but in the relaxed position, shown in figures 1 and 2, has an outer diameter approximately equal to that of the thinner inner sealing ring 10, because the sealing element 2 is sized to bias the fingers radially inwardly, such that the inner diameter of the first end 4 of the pipe liner 1 is smaller than the second end 6, when relaxed. Since the seal is elastomeric and flexible, and the fingers are resiliently flexible, the seal 2, including the webs 9 and sealing rings 10, 11 are able to be stretched so as to move from the relaxed configuration (of figures 1-5), to an expanded configuration having a larger inner diameter (shown in figure 6).

At the opposite end to the seal 2, the pipe liner 1 is provided with a flange 12. The flange 12 is annular and extends radially outwardly. The flange 12 has an outer diameter equal to the outer diameter of pipe which is intended to be used in the pipe fitting, i.e. in this case the outer diameter is 15mm, corresponding to the O/D of the plastic pipe and the O/D of the metal pipe 5 that it will be used with. The flange 12 stops the pipe liner moving too far into the pipe 5 or the pipe fitting 7.

The flange 12 is curved, such that the cross section through the pipe liner in the region of the flange 12 is j-shaped; the curve of the flange 12 being part-toroidal. Thus, the "front" second end 6 of the pipe liner 1, which is inserted into the pipe fitting 7, has a smooth, rounded face, which is less likely to damage the seals 13 in the fitting, and avoids interaction between the end of the metal pipe 5 (which is often burred and sharp) and the pipe fitting 7 (which is intended for deburred pipe, especially plastic pipe which is generally less sharp than metal in any case). Generally speaking, the pipe liners of the invention will be supplied separately from pipe and pipe fittings, but with an indication of the pipe and fitting that it is intended to be used with. For example, the pipe liner 1 of the embodiment, might be marked "15mm", indicating it is intended for use with metal pipes having an O/D of 15mm, such that they can be used with fittings intended for plastic pipes having an O/D of 15mm. Of course, more complex marking may be provided, to cover unconventional pipe or fittings e.g. fittings intended for use with particularly thick pipe which may have a smaller I/D than standard, (in which case the I/D of the pipe liner would be correspondingly small), or for use with unusually thin metal pipe etc.

However, the invention also contemplates the sale of kits including pipe fittings intended to be used with plastic pipe, together with at least one pipe liner to allow the pipe fitting to be used with metal pipe 5.

Referring to figures 3-6 a kit of parts comprising a pipe liner 1 and a pipe fitting 7 is shown (along with metal pipe 5 and plastic multilayer pipe 14). The pipe liner 1 is as described in relation to figures 1 and 2 and the pipe fitting 7 in this embodiment is a "Tee" joint. A Tee-joint is a particularly preferred fitting for the kit, as it comprises two coaxial (longitudinally spaced) sockets 15 which can receive plastic pipe 14 through which e.g. hot water for a heating system flows beneath a floor, and one perpendicular socket 16 extending orthogonally between the coaxial sockets 15. The perpendicular socket 16 can also receive plastic pipe 14, but it is intended to be used with the pipe liner 1 of the invention, so as to allow metal pipe 5 to be fitted thereto. Thus, metal pipe 5 can be used to extend through the floor and connect to a radiator.

Each socket 15, 16 comprises a spigot 18, which in this embodiment is snap- fitted into the socket 15, 16 and sealed therewith by an O-ring seal 13 between the spigot part and the main body of the pipe fitting 7. An annular gap is defined between the I/D of the socket 15, 16 and the O/D of the spigot. 18, and into this gap a grab ring 19 extends from the I/D of the socket to grab the outer surface of the pipe 5, 14 introduced thereto. On the outer diameter of each spigot 18, extending into the annular gap, a seal 13 (in the form of an O-ring) is provided, so as to seal against the inner diameter of pipe 14 introduced into the socket 15, 16.

Of course, as will be seen from the discussion below, where the pipe liner 1 is used, the seal 13 on the spigot 18 seals against the I/D of the pipe liner 1 instead. Thus, the pipe liner 1 is sized to sit between the metal pipe 5 and the spigot 18 in the pipe fitting and the cylindrical support portion 3 has an I/D corresponding to that of plastic pipe intended to be introduced into the pipe fitting 7.

The O/D of the cylindrical portion 3, on the other hand, is less than the inner diameter of metal pipe 5 of the same outer diameter as the plastic pipe 14, for which the pipe fitting 7 is intended. The seal 2 seals between the metal pipe 5 and the spigot 18, with the sealing rings 10, 11 sealing against axial leakage, and the web 9 sealing against any leakage that could otherwise occur in the region of the slots between the fingers 8. Thus, fluid passing through the pipe 5 enters the bore 20 through the spigot and vice versa.

In use, the pipe liner 1 is introduced from outside the metal pipe 5 (as shown in figure 3) into it as shown in figure 4. To achieve this, the first end 4 is pushed into the metal pipe 4 up to the point where the flange 7 at the second end abuts the end of the pipe 5. This takes place whilst the seal 2 is in the relaxed configuration, with the sealing element 2 biasing the fingers 8 inwardly, such that the O/D of the sealing element 2 is less than the I/D of the metal pipe 5, reducing the chance of the seal snagging on the end of the pipe.

The lined pipe 5 (i.e. the pipe 5 with the liner 1 inserted) is then introduced into the gap between the spigot 18 and the socket 16. The curved surface of the flange 12 enters the gap first, pushing past the grab ring 19 as shown in figure 5, such that the grab ring 19 begins to act on the outer surface of the metal pipe 5. The cylindrical support portion has the same I/D as the pipe intended to be used in the fitting, and thus fits snugly over the spigot.

As the lined pipe 5 is pushed further into the pipe fitting 7, to the final position shown in figure 6, the inner surface of the pipe liner 1 passes over the O-ring seal 13 on the spigot, which seals against leaks between the spigot 18 and the pipe liner 1. Also, as the lined pipe 5 is pushed further into the pipe fitting 7, to the final position shown in figure 6, the fingers 8 are bent outwards by the spigot 18, such that they fit round it. This in turn moves the seal 2 from the relaxed configuration (with a smaller internal and external diameter) to the expanded configuration with a larger diameter. In this movement, the two rings 10, 11 and the webs 9 are all stretched, with the rings also being compressed radially inwardly by the inner surface of the metal pipe 5, sandwiching the seal 2 in a compressed (sealing) condition between the spigot 18 and the pipe 5, so as to seal against any leakage therebetween.

Accordingly, in the final position, the pipe liner 1 seals between both the metal pipe 5 and the spigot 18, such that the metal pipe 5 can be used in the pipe fitting 7 intended for use with plastic pipe, despite having a much larger I/D. The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.