Method and device for forming a socket on a plastic tube

Claim 1

Apparatus for forming a socket with an annular external bead on a length of tubular pipe of thermoplastic material, said apparatus comprising a mandril constituted by two spaced parts which are movable axially relative to one another, said mandril having an outer surface which is shaped to form a socket on the pipe when the mandril is inserted into the pipe to deform the same, a mold positioned around said pipe in opposition to said parts of the mandril, said mold including two pairs of axially spaced jaws each associated with a respective part of said mandril and including two jaw members radially movable towards the pipe, said pairs of jaws also being movable axially relative to one another, means connected to at least one of said pairs of jaws for moving said two pairs of jaws radially inwards to clamp the pipe against said parts of the mandril at axially spaced locations, means connected to one of said mandrel parts for axially moving one pair of said jaws and associated mandril part with respect to the other pair of said jaws and mandril part to cause said pairs jaws to abut against one another and move the parts of the pipe, at the locations where they are clamped by the jaws and mandril parts, towards one another to upset the pipe between said locations, said jaws being provided with grooves defining an annular cavity when the jaws abut one another, said annular cavity defining the shape of the bead for the pipe when the jaws are clamped against the pipe and have been axially moved into contact with one another, and means between said mandrel parts for applying internal pressure against said pipe in the region between said locations to urge the upset portion of the pipe outwardly into conformance with said annular cavity in the jaws.