Abstract: Cold cage for a crucible with melting by high frequency electromagnetic induction comprising in per se known manner a series of hollow segments traversed by the cooling water and surrounded by a high or medium frequency induction coil and in which the products to be melted are confined, wherein at least part of the walls of each cage segment is constituted by at least two layers of adjacent materials, whereof the one which resists corrosion is in contact with the products to be melted and whereof the other is a good electricity conductor and wherein the relative thicknesses of these layers as well as the supply frequency of the induction coil are chosen in such a way that the eddy currents induced in the cage mainly develop in a good electricity conducting layer.

Abstract: The novel inductor is used in a glass fiber manufacturing equipment comprising a centrifuge heated by a main gas heating device and a complementary induction heating device. The efficiency of the inductor is increased by a magnetic flow guiding element disposed between the inductor and the main heating device. The invention is particularly adapted to be used in the manufacture of glass wool.

Abstract: A device is provided for melting by direct induction substances which are dielectric when cold and whose temperatures of inductibility and melting are close to each other, such as glasses or vitreous enamels. This melting is carried out inside a receptacle whose sidewall comprises a multi-turn inductor made from metal tubing whose inward-looking faces are exposed and which combines the functions of heating the charge by induction and cooling the periphery thereof. Such a receptacle which is at the same time a heating inductor and a cooling surface is applicable more especially to industrial electric furnaces for the production of molten glass or enamel by direct induction.

Abstract: A direct induction furnace or device for melting a charge held in a cold sheath or shroud with electromagnetic confinement of the conducting portions of the charge. The cold shroud comprises a cylindrical sidewall, which is composed of a plurality of juxtaposed segments in the shape of a hairpin inductor, each formed by two parallel tubular conductors, which are insulated from each other along their entire interface with the exception of a transverse section which electrically and hydraulically connects one end of one of the sections to the adjacent end of the other section.

Abstract: Method of butt-welding metal parts by induction, in particular parts of irregular cross-section such as rails, consisting in pressing the parts against one another with an initial pressure for the entire period of heating, in heating them by induction by means of an inductor which encloses the parts parallel to their contours about the plane of their interface, firstly for a first period at a lower frequency and then, for a second period following the first, at a frequency two to four times higher than the first frequency, and, at the end of the second period, in applying the parts against one another at a forging pressure which is from two to more than six times higher than the initial pressure. The quality of the welded joint is greatly improved and the dimensions of the bulge or upset are limited by restricting the depth of the penetration of the induced current to both sides of the interface by means of two short-circuited turns disposed symmetrically relatively to the inductor to either side thereof.

Abstract: A brazing press for securing exterior claddings to bottoms of metallic receptacles, which includes a support structure and a reciprocable mandrel for exerting pressure against the former. The support structure holds a massive inductor block having a flat bottom and containing an inductor coil for respectively pressing and heating the flat portions of the workpieces, and an encompassing sleeve which is associated with an auxiliary inductor and exerts pressure on the peripheral curved portions of the cladding. Either the sleeve with its auxuliary inductor of the inductor block can be supported by said structure through resilient means which are calibrated, whereby auxiliary pressure is exerted on the peripheral curved portions independently from the one exerted on the flat central portion, when said mandrel is pushed against the inductor block.