Pipe fittings

Abstract

A pipe fitting for coupling together opposed ends of two plastics pipes by fusion welding, the pipe fitting comprising an annular body having an inner cylindrical surface of plastics material surrounding a cylindrical cavity for receiving opposed ends of two plastics pipes to be coupled together, an electrically conductive coil provided in said inner cylindrical surface and surrounding the cylindrical cavity, the coil having opposed ends, a pair of terminals each connected to a respective end of the coil and provided on the body for connection to a source of controlled electrical power, and an annular reinforcing member disposed in the body and surrounding the coil, the annular reinforcing member having a grooved surface which interfaces the annular body, the grooved surface defining a plurality of axially facing surfaces.

What is claimed is:  
     
         1 . A pipe fitting for coupling together opposed ends of two plastics pipes by fusion welding, the pipe fitting comprising an annular body having an inner cylindrical surface of plastics material surrounding a cylindrical cavity for receiving opposed ends of two plastics pipes to be coupled together, an electrically conductive coil provided in said inner cylindrical surface and surrounding the cylindrical cavity, the coil having opposed ends, a pair of terminals each connected to a respective end of the coil and provided on the body for connection to a source of controlled electrical power, and an annular reinforcing member disposed in the body and surrounding the coil, the annular reinforcing member having a grooved surface which interfaces the annular body, the grooved surface defining a plurality of axially facing surfaces.  
     
     
         2 . A pipe fitting according to  claim 1  wherein the annular body is composed of injected moulded plastics and comprises an inner annular part and an outer annular part surrounding the inner annular part and the annular reinforcing member is positioned between the inner and outer annular parts.  
     
     
         3 . A pipe fitting according to  claim 1  wherein the grooved surface is provided on at least one of an outer cylindrical surface and an inner cylindrical surface of the annular reinforcing member.  
     
     
         4 . A pipe fitting according to  claim 3  wherein the grooved surface comprises a plurality of annular grooves or at least one helical groove, on the respective cylindrical surface.  
     
     
         5 . A pipe fitting according to  claim 3  wherein the or each groove is defined between a pair of opposing axially facing surfaces of the annular reinforcing member.  
     
     
         6 . A pipe fitting according to  claim 5  wherein the axially facing surfaces are defined by a groove profile selected from a square, rectangular, rounded square, or rounded rectangular groove shape.  
     
     
         7 . A pipe fitting according to  claim 1  wherein the or each groove has a depth of from 1.5 to 6 mm and a width of from 2 to 12 mm.  
     
     
         8 . A pipe fitting according to  claim 1  wherein the annular reinforcing member is further provided with a plurality of perforations extending therethrough.  
     
     
         9 . A pipe fitting according to  claim 8  wherein each perforation is circular in area.  
     
     
         10 . A pipe fitting according to  claim 9  wherein each circular perforation has a diameter substantially equal to a width of a groove.  
     
     
         11 . A pipe fitting according to  claim 8  wherein each perforation is formed as a linear slit extending in an annular direction.  
     
     
         12 . A pipe fitting according to  claim 11  wherein each slit has a width substantially equal to a width of a groove and a length of from 2 to 10 times the width of the slit.  
     
     
         13 . A pipeline including at least two polyethylene pipes having opposed ends which are coupled together by at least one pipe fitting according to  claim 1 , the inner cylindrical surface of the annular body being fusion welded to an outer cylindrical surface of each pipe end, wherein the annular body is composed of polyethylene and the annular reinforcing member has at least the same tensile strength in a hoop direction as that of the polyethylene pipes.  
     
     
         14 . A pipeline according to  claim 13  wherein the pipes are selected from multilayer pipes and reinforced pipes and the pipeline has a maximum pressure of greater than 25 bar.  
     
     
         15 . A method of producing a pipe fitting for coupling together opposed ends of two plastics pipes by fusion welding, the method comprising the steps of: 
 (a) forming an electroconductive coil around a substantially cylindrical core body;    (b) moulding a first annular body part of the pipe fitting around the coil and the core body and disposing an annular reinforcing member around the first annular body part;    (c) moulding a second annular body part of the pipe fitting around the reinforcing member and the first annular body part and the core body to form the pipe fitting; and    (d) removing the core body from the pipe fitting.    
     
     
         16 . A method according to  claim 15 , wherein steps (b) and (c) are carried out as a sequence of steps.  
     
     
         17 . A method according to  claim 15 , wherein steps (b) and (c) are carried out in a single step in which the first and second annular body parts are simultaneously moulded with the reinforcing member located therebetween.  
     
     
         18 . A method according to  claim 15  wherein the annular reinforcing member has a grooved surface which interfaces the annular body, the grooved surface defining a plurality of axially facing surfaces and during the moulding of at least one of the first and second annular body parts at least one of those parts is moulded into the grooved surface.  
     
     
         19 . A method according to  claim 18  wherein the grooved surface is provided on an inner cylindrical surface of the annular reinforcing member and the second annular body part is during moulding shrunk into the grooved surface.