Pipe having a socket and an apparatus for making same

Abstract

A method and an apparatus for making a pipe, and a pipe, wherein the pipe is made from a plastic feedstock pipe by expanding it against a mould. In the first step, that portion of the plastic feedstock pipe ( 4 ) which is to have a greater diameter than the rest of the pipe is partly expanded. Only after this is the entire plastic feedstock pipe ( 4 ) expanded against the mould ( 1 ).

1 - 6 . (canceled)  
   
   
       7 . An apparatus for making a pipe having a socket, the apparatus comprising a mould, means for expanding a plastic feedstock pipe against the mould and means arranged to expand the plastic feedstock pipe partly in the portion intended to have a greater diameter than the rest of the pipe, so that a pre-expansion is formed at said portion, the means for expanding the plastic feedstock pipe against the mould being arranged to expand the plastic feedstock pipe against the mould after the pre-expansion.  
   
   
       8 . An apparatus as claimed in  claim 7 , further comprising means for raising the temperature of the material of the plastic feedstock pipe during pre-expansion higher than the orientation temperature of the material.  
   
   
       9 . An apparatus as claimed in  claim 7 , wherein the means arranged to expand the plastic feedstock pipe partly in the portion intended to have a greater diameter than the rest of the pipe is a mechanical expanding device for pre-expanding the plastic feedstock pipe.  
   
   
       10 . An apparatus as claimed in  claim 9 , wherein the mechanical expanding device is arranged, after pre-expansion, to expand against the mould that portion of the plastic feedstock pipe which is intended to have a greater diameter than the rest of the pipe.  
   
   
       11 . A pipe having a socket and made from a plastic feedstock pipe by expanding it against a mould so that a portion of the pipe has a larger diameter than the rest of the pipe, wherein the plastic feedstock pipe is expanded partly in the portion intended to have a greater diameter than the rest of the pipe, and the plastic feedstock pipe is expanded against the mould after said pre-expansion.  
   
   
       12 . A pipe as claimed in  claim 11 , wherein the temperature of the material of the plastic feedstock pipe is arranged to be higher during pre-expansion than the orientation temperature of the material, the blow up ratio of the entire pipe being substantially equal.