Abstract: An induction heating device which raises the temperature of a metal to be heated for one of melting or hot machining while providing considerably energy saving, increasing yield and observing current safety standards. The device (10) uses a cavity (11) to receive the metal to be heated and at least two magnetic yokes (13) arranged around a periphery of cavity (11), each yoke supporting an independent induction coil (14). The induction coils are mounted and wound in the same direction such that a north pole, of each coil, is located on one side of the cavity and a south pole is located on an opposite side of the cavity. The inductive coils are arranged so as to generate active non null magnetic field zones and inactive zones of null magnetic fields distributed about the periphery of the cavity. An inactive zone of null magnetic fields is located between each adjacent active non null magnetic field zone.

Abstract: A continuous tubular box body production method, particularly for cardboard boxes, using a number of stacked longitudinal strips. After sizing the continuously moving straps (2, 3, 4), they are applied lengthwise against a stationary guide (8) ending in a mandrel (10) with a circumference defining the cross-sectional shape of the tubular body (1, 17), whereby each strip has a side flap on either side of the guide which is then folded down around the circumference of the mandrel (1) as the strips move therealong. The method is characterized in that the side flaps (2a, 1b; 3a, 3b; 4a, 4b) are at least partially asymmetrically folded down so that one of the flaps on each strip is folded down before the other, whereby various longitudinal joint configurations and arrangements may be achieved, wherein the joints are arranged above one another or offset in alternate directions.