GB2445796A

GB2445796A - Jointing Of Thermoplastic Spirally Wound Hollow Section Pipes

Info

Publication number: GB2445796A
Application number: GB0701005A
Authority: GB
Inventors: Eric Bridgstock
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-19
Filing date: 2007-01-19
Publication date: 2008-07-23
Also published as: GB0701005D0

Abstract

A method of modifying an end face region of a spirally wound hollow section thermoplastic pipe (fig. 1), the method comprises: welding an attachment (fig.2d) to the end face region of the pipe, the attachment is formed from an extruded channel cross-section 2a formed into a circle 2b with the closed region of said channel being welded to the end face region of said pipe, thus forming a female coupling for receiving a jointing sleeve fig.5. The jointing sleeve is formed from an extruded rectangular box section formed into a circle matching the circumference of the pipe to which it is to be attached. The sleeve having electrically conductive resistance wire wound spirally around it. Preferably clamps (fig. 6) are used to hold the pipe joint together during the electric welding process.

Description

JOINTING OF THERMOPLASTIC SPIRALLY WOUND HOLLOW SECTION PIPES

DESCRIPTION 2445796

Hollow section spirally wound thermoplastic pipes [rig 1 a,b,c] are well established and widely used.

They provide a means of using the excellent properties of polyethylene pipe without the necessity of producing a solid wall which would be uneconomic and unnecessarily heavy especially for large diameters. The only disadvantage of these hollow section pipes is the difficulty of joining them, especially by the favoured heat fusion methods. When cut at right angles to their axis these pipes present an uneven area at their ends which is not suitable for fusion.

To overcome this problem the present invention proposes the following methods and inventions:-The spirally wound thermoplastic pipes are fitted with modified ends [fig 2d], designed to accommodate an electrically heated thermoplastic jointing sleeve [fig 3d] which can be manufactured by the same method used to produce the extruded hollow sections of the pipe itself.

The modification of the pipe ends in ideally carried out during the manufacturing process. An open-ended rectangular section extrusion [fig 2a] is manufactured, similar to the closed section extrusion used to form the spirally wound pipe. The extrusion is then cut to length and the long side wound around a cylindrical former to create a circular shape [fig 2b] of similar dimensions to the pipe itself. It is then welded at the ends [fig 2c] to form a closed ring. These rings are then welded to the ends of each length of pipe [fig 2d] with the open ends at the leading edge.

The internal dimension of the socket formed by the modification of the pipe end is such that a jointing sleeve [fig 3d] will fit closely inside it, the electrical heating wires making contact with the socket as in fig 4.

The jointing sleeve [fig 3d] is formed from an extruded closed rectangular section [fig 3a] which is subsequently cut to length and formed into a circle [fig 3b], for example around a metal cylinder, and then welded at its ends [fig 3d to form a closed ring. Electrically conductive resistance wire, preferably coated with polyethylene, is wound spirally around the rectangular section and terminated on the outside surface midway between the ends of the section [fig 3d]. The wire may be wound as shown in fig 5 in order to reduce the resistance of the coil and hence the fusion time.

It may also be lacquered to reduce the consequences of wire to wire contact. The jointing sleeve [fig 3d] may be grooved in order to retain the electrical wire or the wire may be welded to the sleeve at intervals around its circumference.

Jointing of these modified pipes is achieved by inserting the jointing sleeve into adjacent pipes and sliding each pipe fully over the ring so that the jointing sleeve is completely covered [fig 4], leaving the wire ends exposed for connection to a suitable electrical power source. The passage of current through the wires softens the polyethylene surfaces and causes them to fuse.

Internal and external mechanical clamps [fig 6] may be used to provide radial forces capable of holding the abutting surfaces in contact during the heating and cooling process.

The heating ring is particularly advantageous because it provides the means of fusing the pipes and also facilitates a positive method of aligning the two pipes to be jointed without reducing the strength of the joint area.

Claims

JOINTING OF THERMOPLASTIC SPIRALLY WOUND HOLLOW SECTION PIPES

(i) A method of modifying the ends of spirally wound hollow section thermoplastic pipes [fig 1) by the welded attachment of an open sided rectangular thermoplastic extrusion formed into a circular shape and closed at the ends by welding [fig 2]. The modification has the effect of providing a regular socketted termination at the end of each spirally wound pipe [fig 2d].

(ii) A welding sleeve fabricated from a rectangular section thermoplastic extrusion [fig 3d] wound spirally with electrical resistance wire where the sleeve engages with sockets at the pipe ends [fig 4).

(iii) A welding sleeve as described in (ii) whose length is such that when entered into the sockets provided at the pipe ends provides significant self alignment of the adjoining pipes.

(iv) A welding sleeve as described in (ii) that when entered into the sockets described in (i) and electrically heated, facilitates the thermal fusion of adjoining pipes.

(v) A welding sleeve as described in (ii) (iii) (iv) that may be secured during thermal fusion and during cooling by clamps capable of applying radial forces to the joint interfaces [fig 6].