Method and apparatus for making plastic tubes

Claim 1

Apparatus for manufacturing a thermoplastic tube of substantially uniform thickness and having an end closed pinhole free and with substantially the thickness of the remainder of the tube comprising: a heated die having one end portion shaped to form a hollow cylinder with a shaped closed end; means for heating said die; a heat conductive metallic collar surrounding the hollow cylinder end portion of said die and acting as a heat sink to dissipate heat therefrom; means for supporting an open ended thermoplastic tube of substantially uniform thickness in spaced relationship from said heated die; a mandrel having an end portion shaped to form a hollow cylinder with a closed end complementary to the shape of said heated die and insertable into said tube through one end thereof; means for advancing said mandrel into said tube a predetermined distance so that an end portion of the tube projects beyond the shaped end of the mandrel; means for holding said tube on said mandrel; first means for relatively moving said tube and mandrel with respect to said heated die so that the tube extends into the heated die and has its projecting end shaped and closed pinhole free by interaction between the heated die and the shaped end of said mandrel, said heated die and shaped end of said mandrel pressing against the outside and inside respectively of said tube to form the same closed pinhole free in a single forming step to the thickness of substantially that of the thickness of the remainder of said tube and the inner and outer shapes of said heated die and mandrel, said metallic collar dissipating heat from said cylinder to prevent excessive heating of the side walls of the tube during shaping and closing of the projecting end; and second means for relatively moving said tube and mandrel with respect to said heated die to thereby withdraw the tube from said die.