NZ561752A - Spigot and socket screw thread pipe end joint with sealing ring at base of spigot - Google Patents

Abstract

A pipe joint includes a socket 2 formed at the first end of a first pipe section 3 and a spigot 5 formed on a second end of a second pipe section, and a sealing ring. The socket includes a threaded portion 9 with a rebate 10, 11 adjacent the mouth of the socket to receive and provide a sealing surface against the sealing ring. The spigot includes a thread 13 matching the thread of the socket to enable engagement with the socket thread, and a sealing ring groove 14 after the last thread at the base of the spigot to locate the sealing ring.

Description

19/09/2007 22:40 B4449&5949 EVT LAW PAGE *10054692916* 5617 5 2 Our Ref: IPN106 Patents Form No. 5 PATENTS ACT 1953 COMPLETE SPECIFICATION A PIPE JOINT We, iplex Pipelines New Zealand Limited, a New Zealand company of 67 Maiden Street, Palmerston North do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: t ti'itafe&xuai property Office of N.Z. f 19 SEP 2007 i RECEIVED i 19/09/2007 22:40 6444965949 EVT LAW PAGE 07/19 TECHNICAL FIELD The invention relates to a pipe joint. In particular the invention relates to a pipe joint which allows lengths of pipe to be releasably joined together to form a pipeline.

BACKGROUND ART Trenchiess pipe laying technology is increasing becoming the installation method of choice - at least in circumstances where it is an available option. This is particularly so in non-pressure sewer and stormwater applications, and in the underground installation of cable duct. The key advantage being the avoidance of disruption to above ground activities and facilities- Polyethylene is a preferred pipe material for trenchiess Installation and is typically supplied in coils (pipes up to 140mm diameter) or in welded strings for larger pipe sizes. Whilst coiled polyethylene pipe takes up little space, welded pipe strings in larger diameters take up a lot of space and can cause significant disruption to traffic and pedestrian access.

As an alternative, solvent cement joined PVC pipe is used primarily for cable duct in the DN100 and DN150mm sizes. This jointing method is not commonly used in sewer and stormwater pipes as many Councils have concerns about joint integrity and leak resistance.

Recognised problems with polyethylene and solvent cement joint PVC pipe include that polyethylene pipe strings require sufficient space for laying out which can cause traffic and pedestrian disruption, polyethylene pipe is prone to stretching during installation, solvent cement joint PVC pipe requires either pipe stringing or waiting on the solvent cement to cure before installation, wet conditions are not conducive to solvent cement or 2 19/09/2007 22:40 6444965949 EVT LAW PAGE 08/19 fusion welding, and disassembly of joined polyethylene and solvent cement joint PVC pipe requires cutting the pipe.

It is an object of the present invention to provide a pipe joint system which overcomes at least some of the abovementioned problems, or which provides the public with a useful choice.

SUMMARY OF THE INVENTION in a first broad aspect the invention provides a pipe joint including a socket formed on a first end of a first pipe section, and a spigot formed on a second end of a second pipe section, and a sealing ring, the socket including a threaded portion with a rebate adjacent the mouth of the socket to receive and provide a sealing surface against the sealing ring, the spigot including a thread matching the thread of the socket to, in use, enable engagement with the socket thread, the spigot further including a sealing ring groove after the last thread at the base of the spigot to locate the sealing ring.

Preferably the sealing ring groove has the same wall angle as the thread but is significantly wider than the thread form.

Preferably the socket includes a chamfer at its front to aid assembly and prevent sealing ring dislocation.

Preferably the thread of the socket and spigot is a multi-start thread to assist in getting the engagement of the spigot and socket started.

Preferably the thread angle is greater than standard to assist in initiating engagement. 3 19/09/2007 22:40 6444965949 EVT LAW PAGE 09/19 Preferably the joint includes a thread locking device to resist Inadvertent undoing of the threaded joint, wherein the spigot and the socket include a groove, and the socket includes an aperture through which a locking rod can be feed to locate in the groove in the spigot and corresponding groove in the socket, thereby locking the joint.

Preferably each pipe section is at least one metre long, preferably one to eight metres long.

Preferably the portion of the socket adjacent its mouth is unthreaded and of sufficient length to align the pipe sections to be joined before the threads engage.

Preferably the transition from the diameter of the socket to the diameter of the remainder of the length of the pipe section occurs over sufficient distance to ensure a substantially smooth transition and avoid creating rapid diameter variations.

Preferably the sealing ring is formed from natural rubber. Alternatively the sealing ring is a polymer seal.

Preferably the pipe joint is suitable for use in water supply networks, BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a spigot and socket for a pipe joint according to a preferred embodiment of the invention; 4 19/09/2007 22:40 6444965949 EVT LAW PASE 10/19 Figure 2 is a cross-sectional view of a sealing ring for use in the joint of figure 1; Figure 3 is a perspective view of a pipe joint according to the preferred embodiment; and Figures 4a to 4d are a series of schematic side elevations of a pipeline according to the preferred embodiment being installed using a trenchiess installation method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figures, a pipeline 100 comprising two or more sections of pipe are joined by the pipe joint of the invention.

Each joint 1 includes a socket 2 formed on a first end 3 of a first pipe section 4, and a spigot 5 formed on a second end 6 of a second pipe section 7.

A sealing ring 8 is included to provide joint @eal integrity.

The socket 2 is formed in end 3 of the pipe section 4 in the normal fashion, however, the socket 2 differs from a normal solvent cement socket in that the walls are parallel and of a smaller diameter to allow for the machining of a right hand trapezoidal thread 9 inside the socket 2 using a purpose built thread cutting machine.

A rebate 10 is machined at the mouth of the socket 2 to provide a sealing surface 11 against which the sealing ring 8 can seal. A chamfer 12 is machined onto the front of the socket 2 to aid assembly and prevent seal ring 8 dislocation. The rebate 10 also assists in assembly of the joint, as it allows the ends 3/6 of the pipe sections 4/7 to be aligned prior to engagement. 19/09/2007 22:48 6444965949 EVT LAW PAGE 11/19 A matching right hand trapezoidal thread 13 is machined on the spigot 5. A seal ring groove 14 is machined after the last thread at the base of the spigot 5, ie at the point it blends with the main length of the pipe. The seal ring groove 14 has the same wall angle as the thread 13 but is significantly wider than the thread form.

Optionally the thread form on the socket 2 and spigot 5 can be multi-start, which assists in assembly, as it facilitates engagement of the spigot and socket thread forms. A further optional feature is that the thread angle can be greater than a standard thread form to also assist in initiating engagement.

One important advantage of the present invention over the prior art is that the joint can be easily disassembled - simply by unscrewing the joint -unlike a polyethylene pipe string joint or a solvent cement jointed PVC pipeline, which must be cut. However, to resist inadvertent undoing of the threaded joint the joint can further include a thread locking device (not shown).

In one embodiment of the joint locking device the spigot 5 and the socket 2 can further include a groove which, when the socket 2 and spigotS are fully engaged, align. The socket 2 further includes an aperture through which a locking rod can be feed to locate in the groove in the spigot 5 and corresponding groove in the socket 2, thereby locking the joint.

As shown in Figure 1, the transition from the diameter of the socket 2 to the diameter of the remainder of the length of the pipe section 4 occurs over sufficient distance to ensure a substantially smooth transition and avoid creating rapid diameter variations which could provide resistance during trenchiess installation. 6 19/09/2007 22:40 6444965949 EVT LAW PAGE 12/19 The pipe sections 4, 7 may be formed from any suitable material, however, the invention is particularly suited to use with PVC piping. MPVC (modified polyvinyl chloride) or UPVC (unplasticised polyvinyl chloride) can be used, for example manufactured to AS/NZS1260. Pipe diameters of from DN 100mm to DN475mm and more are able to be joined in the manner of the invention.

The sealing ring 8 is preferably manufactured from natural rubber conforming to the requirements of AS 1646, although polymer sealing ring is also contemplated for use in certain applications.

Preferably each pipe section is at least one metre long, preferably one to eight metres long. The selected length of the sections will depend on the pipe diameter, the installation methodology, and handling and space constrains.

Pipelines using joints according to the invention can be used in non-pressure sewer and stormwater applications, and water supply applications, where installation by trenchiess technology methods is required. A further application exists where installations run through unstable ground and pipe with end load resistant joints will be of benefit.

Performance achieved out of DN160mm uPVC pipelines joined using the method of the present invention include being able to cope with straight line pulling force of up to 3,500 kg, and straight line pushing force of 3,000 kg, with a minimum radius of curvature of 60 metres.

Referring specifically to Figures 4a to 4d, pipe sections joined using the joint of the present invention have particular application in pipeline installation by directional drilling (HDD) where 6m or longer lengths can be used. Alternatively pipe sections of 1m more or less can used for installation by thrust boring or pipe jacking. 7 19/09/2007 22:40 S444965949 EVT Lm PA6E 13/19 As shown in the figures, an HDD machine 200 is set up to tunnel under a structure or the like creating a bore 201 of suitable diameter. Once drilling is completed (Figure 4b) the first pipe section 101 is attached to the end of the drill rod 202 and is drawn back through the bore 201. As each section 101 is pulled into the bore 201 another section 101 is added. Optimally the length of each pipe section 101 is the same as or a multiple of each drill rod so that as each section 101 is added at one end a drill rod section can be removed (Figure 4c). Once the pipeline 100 has been completed the installation is completed in the usual way (Figure 4d).

Assembly of the sections.101 involves fitting the sealing ring 8 to the pipe spigot 5, then applying a spray on silicon lubricant to the sealing ring 8. A recommended lubricant for the seal ring is GENSIL 601 Food Grade Silicon spray.

The silicon lubricant is also applied to the seal ring rebate 10 in the mouth of the socket 2.

The spigot 5 is then inserted into the matching socket 2 and the pipe section 101 being attached is rotated in a clockwise direction whilst the section to which it is being joined is held still. Preferably clockwise rotation ends positively after approximately 5 complete rotations, at which point the end of the thread form is encountered.

Advantages of the present invention include enabling installations to operate with a small operating footprint - short pipe lengths can be used and no pipe stringing is required. Fast assembly time is possible, and pipelines can be assembled in wet conditions.

Further pipelines according to the present invention are suitable for installation by either pushing or pulling. Eg pulling behind the drill head 8 19/09/2007 22:40 6444955949 EVT LAW PAGE 14/19 (HDD) or by pushing behind the drill head (auger boring, micro-tunnelling, pipe jacking).

Furthermore, the Applicant's pipe joint may be substantially manufactured using standard PVC pipe components and standard PVC pipe seals, so that manufacture is cheap and easy. The simplicity of the components used provides a robust joint with low cost and long life, which is easy to install.

Wherein the aforegoing reference has been made to integers or components having known equivalents, then such equivalents are herein incorporated as if individually set forth. Accordingly, it will be appreciated that changes may be made to the above described embodiments of the invention without departing from the principles taught herein.

Additional advantages of the present invention will become apparent for those skilled in the art after considering the principles in particular form as discussed and illustrated. Thus, it will be understood that the invention is not limited to the particular embodiments described or illustrated, but is intended to cover all alterations or modifications which are within the scope of the appended claims. 9

Claims (12)

19/09/2007 22:40 5444965949 EVT LAW PAGE 15/19 What We Claim is;

1. A pipe joint including a socket formed on a first end of a first pipe section, and a spigot formed on a second end of a second pipe section, and a sealing ring, the socket including a threaded portion with a rebate adjacent the mouth of the socket to receive and provide a sealing surface against the sealing ring, the spigot including a thread matching the thread of the socket to, in use, enable engagement with the socket thread, the spigot further including a sealing ring groove after the last thread at the base of the spigot to locate the sealing ring.

2. A joint according to claim 1 wherein the sealing ring groove has the same wall angle as the thread but is significantly wider than the thread form.

3. A joint according to claim 1 wherein the socket includes a chamfer at its front to aid assembly and prevent sealing ring dislocation.

4. A joint according to claim 1 wherein the thread of the socket and spigot is a multi-start thread to assist in getting the engagement of the spigot and socket started.

5. A joint according to claim 1 wherein the thread angle is greater than standard to assist in initiating engagement.

6. A joint according to claim 1 wherein the joint includes a thread locking device to resist inadvertent undoing of the threaded joint, wherein the spigot and the socket include a groove, and the socket includes an aperture through which a locking rod can be feed to locate in the groove in the spigot and corresponding groove in the socket, thereby locking the joint. 10 19/09/2007 22:40 6444965949 EVT LAW PAGE 56 1 7 52

7. A joint according top claim 1 wherein each pipe section is at least one metre long, preferably one to eight metres long.

8. A joint according to claim 1 wherein the portion of the socket adjacent its mouth is unthreaded and of sufficient length to align the pipe sections to be joined before the threads engage.

9. A joint according to claim 1 wherein the transition from the diameter of the socket to the diameter of the remainder of the length of the pipe section occurs over sufficient distance to ensure a substantially smooth transition and avoid creating rapid diameter variations.

10. A joint according top claim 1 wherein the sealing ring is formed from natural rubber.

11. A joint according to claim 1 wherein the sealing ring is a polymer seal.

12. A joint according to claim 1 substantially as herein described or exemplified with reference to the accompanying drawings. Iplex Pipelines New Zealand Limited By their Attorneys Ellis | verboeket j Terry pen a:'rirefWv£* i Office of N.Z. j 13 SEP 2007 j RECEIVED i