Abstract: Method and apparatus for joining together edge surfaces of polytetrafluoroethylene material by a butt joint in which abutting surfaces of the material are placed in a chamber bounded by clamps along the abutting surfaces which press together the abutting surfaces, and heating elements in the space between the clamps to heat both sides of the material between the clamps, the boundaries of the chamber inhibiting the volume expansion of the material resulting from heating. Pressure generated in chamber may be controlled by moving a heating element. Additional pressure during cooling-down is exerted on the butt joint by moving one clamping in the direction of the butt joint. A thin foil of a fluorine-containing thermoplastic inserted between the abutting surfaces facilitates joining of the surfaces.

Abstract: Method and apparatus for joining together edge surfaces of polytetrafluoroethylene material by a butt joint in which clamps along the abutting surfaces press together the abutting surfaces, heating means spaced from and out of direct contact with a strip between the clamps heats the strip by radiation or convection, and a cooling arrangement is provided via the clamps to remove heat from the clamping zone. A thin foil of a fluorine-containing thermoplastic inserted between the abutting surfaces facilitates joining of the surfaces.

Abstract: The apparatus for welding articles of thermoplasts using additional welding material is provided with a special melting device for the welding material. The melting device comprises a guide channel for the supply and preheating of the welding material, which channel merges into a melting channel of diminishing cross section closed at one end. The melting channel is provided with lateral bores which discharge into a melting chamber of low height in communication with a collecting zone for the plasticized welding material, which collecting zone is connected with the outlet opening of the welding shoe.