GB2351133A

GB2351133A - Coupling member for creating a seal between a socket and a pipe end

Info

Publication number: GB2351133A
Application number: GB0010860A
Authority: GB
Inventors: Eric Bridgstock; David Michael Anthon Kenworthy
Original assignee: BRIDGSTOCK KENWORTHY Ltd
Current assignee: BRIDGSTOCK KENWORTHY Ltd
Priority date: 1999-05-07
Filing date: 2000-05-08
Publication date: 2000-12-20
Also published as: DE10032623A1; GB0010860D0; GB9910442D0

Abstract

A coupling member 5 comprises a coupling ring wound helically with a conducting wire 9, the ring having a cross-section to fit a gap between a socket on one end of a pipe 3, and another pipe end 2 inserted into the socket. Electrical supply to the helical winding may cause it to heat the coupling member to melt and expand into the gaps between the pipe and socket to either side of the coupling member. At the same time melting of the outer surface of the pipe and the inner surface of the socket may occur to create a seal at the joint. The coupling member may be of tapered or rectangular (see fig7) cross-section, and may be used to enable the creation of a branch connection (see figs 10 and 11) or to enable the fitting of an accessory to a hole in the pipe. An external clamping system 8 may be provided, to urge the pipe end into the socket and hold it there until the joint has been created.

Description

2351133 COUPLING MEMBERS This invention relates to coupling members

particularly but not necessarily exclusively for use in jointing large diameter plastics pipes and connecting pipe fittings and branches (normally in excess of 400mm diameter).

There is a growing employment of plastics pipes in large diameters for applications which have previously been supplied by rigid metallic or concrete pipes. Considerable attention has been given to the problem of jointing large plastic pipes and connecting fittings and branches and it is generally accepted that a welded (fusion) joint is superior to a conventional rubber ring joint. Thermoplastic pipes, fittings and branches have been successfully jointed by means of electro-fusion couplers in sizes up to 400mm diameter but larger sizes have proved not to be as easy particularly because of the difficulty of maintaining sufficient dimensional control in the pipe and fitting during manufacture.

A first object of the present invention is to provide an improved coupling member and a method of application which is more tolerant to variations in pipe and coupling dimensions and poor alignment on site.

According to the present invention, a coupling member comprises a coupling ring wound helically with a conducting wire, and the ring having a cross-section to fit a gap between a socket on one pipe end and a plain end of another pipe end inserted into the socket. The cross-section may be tapered and the coupling ring can be used in conjunction with a matching socket incorporated into one end of a pipe or pipe fitting during manufacture, or in conjunction with a hole in a pipe wall to receive a fitting or branch.

The coupling ring may be positioned over the plain end of the pipe to be joined. During installation the plain end is entered into the inwardly tapered socket end of the adjoining pipe.

When the pipe is fully engaged into the socket, the coupling ring is drawn into the triangular annular space created between the pipe and socket. The triangular section of the coupling ring engages fully into the triangular annular space thus providing a wedge action capable of exerting pressure radially outwards and inwards. This radial pressure ensures good contact between the heating wires contained in the wedge and the surfaces to be joined.

As an alternative to the above, the socket may have a plain bore to provide a parallel sided annulus between the socket and the plain end of the pipe. The tapered coupling ring fitted to the pipe end generates an expansion chamber with the inner wall of the socket to take up expansion of the coupling ring during its heating and melting. Equally possible is the employment of a coupling ring with a rectangular cross-section, for use with sockets of tapered cross-section, where again an expansion chamber is created between the coupling ring and the inner wall of the tapered socket, or with a socket with a plain bore, where the tolerances provided on the diameters of the coupling ring, the pipe end and the socket are such that manufacturing inaccuracies are allowed for and the heating and melting of the coupling ring ensures complete contact with the pipe end and the socket, to ensure a good leak free joint.

It will be understood that references above to the connection of a pipe end to a socket, can apply equally to a pipe end connection in a hole through the wall of another pipe, such as to create a branch connection.

Engagement of the coupling ring into the socket may be assisted by means of pairs of external clamps, one of which is secured behind the socket end of the pipe and the second loosely attached to the spigot end of the adjoining pipe behind the coupling ring. The clamps are connected to each other by pulling means such as hydraulically activated cylinders or mechanical devices, so that operation of the pulling means causes the loose clamp to contact the end of the coupling ring and urge it into the annular space provided by the pipe spigot and pipe socket. The pulling means may be maintained during the application of electrical current to the coupling ring so that melted plastic is forced into all void spaces at the interface. Because of the relative movement of the various members in relation to each other there is no requirement to scrape the surfaces (unlike other electro-fusion joints) as the shearing action breaks the surface.

A further advantage of the electrically helically wound coupling ring is the possibility of easily providing a plurality of unconnected heating helices such that the power requirement of each helix falls within the maximum power capabilities of standard portable generators.

A further feature of the invention is that the coupling ring wound helically with electrical conductors can be easily formed from extruded section subsequently wound with wires and displaced into a hoop. This has the advantage of the production of a simple cross section of undefined length which can be cut to any desired length to suit the periphery of the particular size of pipe which is required to be jointed.

Relatively inexpensive winding equipment can be devised to wind the conductor onto the tapered section.

A second feature of the coupling ring is that after production by extrusion a series of grooves at the extremities of the ends can be cut into the section to provide engagement keys for the wire to enable the wire to be positively displaced along the length of the section.

An alternative to the method of assembly already described is to produce the helically wound element as defined above and to mould this into the socket end of a pipe. The engaging spigot end of the pipe may be tapered and by pushing with external means the spigot would engage with the internal element to conform with each other to produce an effective homogeneous joint.

As mentioned above, in addition to its application to a pipe and socket connection, the connecting ring can equally be employed at the connection between a pipe fitting or branch and a main pipe. With a receiving hole cut in the wall of the main pipe, and with the ring having a tapered inner surface the spigot of a fifting or the end of a plain branch pipe can be pushed into the ring, the tapered section ensuring a compression of the ring between the hole wall and the spigot or pipe end and hence full contact to facilitate the creation of an effective sealing joint therebetween. To allow the ring to be fitted to the hole, the outer surface of the ring can be recessed to receive the edge of the hole, and a loose collar may be provided also to fit in the recessed outer surface of the ring to assist in holding it in place during insertion of the spigot on a fitting or the end of a branch pipe.

The ring may be similarly fashioned with, eg, grooves to receive a wire winding, as has been discussed above, and the ring can be formed with an integral collar to provide for the grooves and assist in holding the ring in the hole in the wall of the pipe.

Several embodiments of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a schematic sectional side view of one embodiment of a coupling member in accordance with the invention; Figure 2 is an enlarged view of part W of Figure 1; Figure 3 is a perspective view of a part of the coupling member of Figure 1; Figure 4 corresponds to Figure 1 but shows a tapered coupling member and a plain socket; Figure 5 is an enlarged view of part 'B' of Figure 3; Figure 6 corresponds to Figure 1 but shows a rectangular cross-sectioned coupling member and a tapered socket; Figure 7 is an enlarged view of part 'C' of Figure 5; Figure 8 corresponds to Figure 1 but shows a rectangular cross-sectioned coupling member and a plain socket; Figure 9 is an enlarged view of part'D' of Figure 7; Figure 10 is a schematic sectional side view of a coupling member for a fitting or a branch pipe., Figure 11 shows a variant of Figure 9; and Figures 12 and 13 are enlarged sections of alternative forms of ring for the coupling member of Figure 9.

In Figures 1 and 2 a pipe"l has a plain end 2 inserted into a socket 3 of a second pipe 4. Around the plain end 2 of the pipe 1 is a coupling member 5, and the coupling member 5 has an outer inclined face 6 to co-operate with a correspondingly inclined inner face 7 to the socket 3. At the junction between the pipe end 2 and socket 3, an encircling clamping arrangement 8 is provided, to urge the pipe end 2 into the socket 3 and to hold the pipe end 2 in its 5 juxtaposition with the socket 3 until the joint has been created.

The coupling member 5 is provided with a helical winding 9 of heating wire such that with the joint assembled as is indicated in Figures 1 and 2, electrical supply to the helical winding causes it to heat and the coupling member 5 to melt and expand into the gaps between the pipe end 2 and socket 3 to either side of the coupling member 5. At the same time there is a melting of the outer surface of the pipe end 2 and the inner surface of the socket 3 whereby to create a most effective seal at the joint created by the coupling member.

In Figures 4 and 5, a similar arrangement is illustrated, but here the socket 3 has a plain bore 10, the tapered outer surface of the coupling member 5 creating an expansion chamber between it and the plain bore 10 to receive molten material as the coupling member melts on being heated. Again, there is a substantially simultaneous melting of the outer surface of the pipe end 2 and the inner surface of the socket 3 whereby to provide an effective seal between the pipe end and the socket.

Figures 6 and 7 show the alternative of having a coupling member 5 of rectangular section for use in conjunction with the plain end 2 of the pipe 1 and a socket 3 with a tapered bore 11. Here again an expansion chamber is provided to receive the material of the coupling member as it melts, and again there is a melting of the outer surface of the pipe end and the inner surface of the socket to create a seal between the pipe end and the socket.

In Figures 8 and 9 the arrangement is the provision of a coupling member 5 of rectangular section to locate between the pipe end 2 of the pipe 1 and the socket 3 of the second pipe 4, the bore of the socket being plain. Because of the tolerances that can be allowed in the coupling member, all distortions and ovalities that may be present at the pipe end -6 2 and in the socket 3 can be accommodated, and here again the melting of the coupling ring, the surface of the pipe end and the inner surface of the socket creates an effective seal.

The coupling member whether of rectangular or of tapered cross-section can relatively easily be created by extrusion of long lengths, subsequently cut to a length to suit the diameter of a particular pipe end and socket, and the ends of the cut length being brought together to form a hoop. To assist in the correct positioning of a helix of heating wire on the coupling ring, it may be cut with appropriate grooves around its periphery and into which the winding of wire can engage.

As is indicated in Figures 10 to 13, essentially similar principles can be applied to the connection of a pipe end in a hole formed in a second pipe, to enable the creation of a branch connection or to enable the fitting of an accessory to a hole in the second pipe. In Figure 10 a coupling ring 12 is illustrated having a tapered internal surface 13 to be contacted by the end of a pipe 14, and having an outer surface recessed at 15 to engage the wall of the hole 16 through a pipe 17. In Figure 11 and essentially similar coupling member 18 is provided, but which has an outer recess 19 to receive not only the wall of the hole of the pipe 17 but also a locking ring 20.

As is indicated in Figures 12 and 13 the connecting members 12 and 18 are each provided with grooves 21 in equal spaced relationship around the coupling member to receive and correctly space a helical winding of a heating wire.

As is described in relation to Figures 1 to 9, the situation in Figures 10 and 11 is substantially the same in that a heating of the coupling member 12, 18 causes it to melt at least at its periphery, to cause a melting of the surface of the hole 16 and that of the locking ring 20 when provided, to create an effective seal of the pipe 14 in the hole 16 of the pipe 17.

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Claims

1. A coupling member comprises a coupling ring wound helically with a conducting wire, and the ring having a cross-section to fit a gap between a socket on one pipe end and a plain end of another pipe end inserted into the socket.

2. A coupling member as in Claim 1, wherein the cross-section of the ring is tapered and the coupling ring used in conjunction with a matching socket incorporated into one end of a pipe or pipe fitting during manufacture, or in conjunction with a hole in a pipe wall to receive a fitting or branch.

3. A coupling member as in Claim 1, wherein the socket has a plain bore to provide a parallel sided annulus between the socket and the plain end of the pipe.

4. A coupling member as in Claim 1, wherein the coupling ring has a rectangular cross section, to locate in an inwardly tapered socket.

5. A coupling member as in Claim 1, wherein the coupling ring has a rectangular cross section to locate in a socket with a plain bore.

6. A coupling member as in Claim 1, comprising a coupling ring as in any of Claims 1 to 5, applied to a pipe end and inserted in a hole in a second pipe, to enable the production of a seal at a branch connection to a pipe or a seal at the connection of a fitting to a pipe.

7. A coupling member as in Claims 1 to 5, wherein external clamp means are provided to urge a pipe end into a socket, and hold the pipe end and socket against movement during heating of the coupling ring.

8. A coupling member as in Claim 7, wherein pairs of external clamps are provided, one of which is secured behind the socket end of the pipe and the second loosely attached to the spigot end of the adjoining pipe behind the coupling ring, the clamps being connected to each other by pulling means to cause the loose clamp to contact the end of the coupling ring and urge it into the annular space provided by the pipe spigot and pipe socket.

9. A coupling member as in any of Claim 1 to 8, wherein the coupling ring has recesses -8 in its outer surface to locate and space the helix of heating wire.

10. A coupling member as in any of Claim 1 to 9, wherein the coupling ring is formed as an extrusion and cut to lengths to suit the diameters of pipe ends an which the coupling ring is to be located, the cut length being pulled into a loop.

11. A coupling member as in any of Claims 1 to 10, wherein a number of unconnected helices, of heating wire are used on one coupling ring.

12. A coupling member as in Claim 6, wherein the coupling ring has a tapered inner surface for engagement by pipe end, and a recess in its outer surface to engage the wail of the hole through the second pipe.

13. A coupling member as in Claim 12, wherein the said recess is of a size to fit the wall of the hole through the second pipe and receive a clamping ring.

14. A coupling member substantially as hereinbefore described with reference to any one or more of Figures 1 to 12 of the accompanying drawings.