Abstract: A method for forming cooling coils of successive layers of rectangular configuration, in which the front end of an elongated tube is threaded between rolls of a straightening apparatus and clamped onto the periphery of a rectangular table, whereafter the table is rotated about a central axis while the incoming tube shifted in direction of this axis, and while the tube upstream of the table is held in taught condition by the straightening apparatus so that the tube is wound into a coil of rectangular configuraton about the table. After a coil of predetermined length has thus been wound, the table is stopped, the tube cut between the straightening apparatus and the table and the cut rear end of the tube is also clamped to the table.

Abstract: A rotatable shaft has a roller electrode mounted on it for rotation therewith. A transformer and a rectifier are structurally integrated to form a unit which is also mounted on the shaft for rotation with it, and serve to convert high-voltage low-amperage net current into low-voltage high-amperage DC current. Slip rings are mounted on the shaft to transmit electrical current to the unit for supply to the roller electrode.