Abstract: A device for welding thermoplastic tubes to a welding method, and to a welding knife. The device is provided for welding thermoplastic tubes, wherein the tubes are placed into tube holders and squeezed with the aid of tube clamps. A welding knife is moved between the first and the second tube holder and severs the tubes in the process. Cut ends and residual ends are thereby produced. The cut ends are aligned with one another by a relative movement of one tube holder with respect to the other tube holder and, by a horizontal movement of the two tube holders, are welded simultaneously to form continuous tubes.

Abstract: An apparatus for welding together thermoplastic hoses comprising two clamping units which in part can be rotated and displaced relative to each other. The two clamping units each have two clamping jaws which comprise through-passages between the clamping jaws in which the hoses can be inserted continuously parallel to each other and squeezed transversely to each other. The apparatus further comprises a heatable blade for severing the hoses and melting the cut edges thereof between the clamping units. An intermediate piece is disposed between the clamping jaws of the clamping units, thereby separating the clamped hoses from each other, and at least one of the two clamping units has inner and outer clamping jaws, wherein the inner clamping jaws are held by the outer clamping jaws and can be adjusted together. In a closed position, the inner clamping jaws and the intermediate piece can be rotated with each other.