Abstract: High frequency reactors for interconnecting a high frequency electrical power source and a load which reactors include a pair of plates having opposite surfaces with a length and width and a thickness between the surfaces which is small relative to the length and width of the surfaces. The plates are disposed with opposing closely spaced surfaces insulated from each other, and each of the plates has longitudinally aligned first and second portions with one portion of one of the plates electrically insulated from another portion of the plates and conductively interconnected by a variable reactance with another portion of the plates.

Abstract: High frequency electrical heating apparatus in which metal parts are heated as they are advanced,either for annealing or forge welding purposes,and in which the electrical heating current is supplied by solid state D.C. to A.C. inverter through a load matching and frequency control circuit which maintains the desired load current and current frequency with changes in the load impedance caused by the metal parts as they are advanced.

Abstract: An electrical assembly (10) comprising a first electrical device (12) comprised of a non-linear resistant, temperature responsive element (14) and first and second electrodes (16,18), the device (12) being connectable to a first power supply (20) such that a first electrical current (i.sub.1) travels through the resistive element (14) from the first electrode (16) to the second electrode (18). A second electrical circuit (24) is in electrical contact with the electrical device (12) such that the second circuit (24) may introduce a secondary electrical current (i.sub.2) into a localized portion of the non-linear resistant element (14), the second current (i.sub.2), when applied to the non-linear resistant element (14), causes the element (14) to change from a first resistant state to a second resistant state.

Abstract: A method and apparatus in which edge portions of metal parts, the edge portions being disposed with opposed surfaces, are heated by high frequency electrical currents as the edge portions are advanced and brought together at a weld point. The electrical currents are induced in the edge portions in advance of the weld point by two induction coils, one at one side of the metal parts and the other at the other side of the metal parts, disposed and energized from a high frequency electrical source so that the electrical currents at the opposed surfaces flow in opposite directions at any given time and the currents induced by one coil add to the currents induced by the other coil.

Abstract: A method of severing a metal piece into parts in which electrical contacts engage the piece at the end of the severing line and high frequency electrical current is fed to the contacts for the length of time required to at least significantly reduce the tensile strength of the metal along the line, the current being fed to at least one of the contacts through a proximity conductor overlying the line. After such heating of the metal, the portions of the piece can merely be pulled apart. If shaping of the edge faces is desired, they can be pressed together while heated and malleable and after separation or can be pressed against an anvil while heated and malleable. Before separation, the portions on opposite sides of the line can be pushed toward each other or be moved transversely to each other. If the metal along the line is heated to "burning" temperature, the portions can be separated by burning out the heated metal with an oxygen containing gas.

Abstract: Method and apparatus for depositing metal on, and bonding it to, a metal part or parts, either to provide hard facing metal on the metal part or to produce a cast weld between the parts. In the method, the metal to be deposited is melted before depositing it by an induction coil supplied with high frequency electrical current. The metal part or parts are advanced toward a point where such metal is deposited, and in advance of such point, the surface of the metal part, or for welding, the surfaces of the metal parts to be joined, are heated to melting temperature by high frequency electrical current. The high frequency current is supplied to such surface or surfaces by the same induction coil, by a separate induction coil or by contacts engaging the metal part or parts.

Abstract: Method and apparatus for butt welding the edge faces of metal skelp which has been heated to a temperature of at least 1000.degree. F. but below the welding temperature of the metal of the skelp. The skelp is continuously advanced through a furnace in which the skelp is heated to such temperature and then, to forming rolls where the skelp is formed into a substantially complete tube with closely spaced skelp edge faces, to a spacing roll for maintaining the edge faces in closely-spaced relation and to pressure rolls where the edge faces are pressed together. Intermediate the spacing roll and the pressure rolls, the edge faces are heated to welding temperature with an induction coil fed with electrical current having a frequency of at least 10 Khz. The induction coil does not encircle the skelp in its tubular forms and instead, has legs adjacent the edge faces and at opposite sides of the gap between the edge faces.

Abstract: Methods and apparatus for manufacturing tapered, hollow metal poles which can be used for manufacturing poles of various lengths, tapers and cross-sectional dimensions with the same apparatus. A substantially complete, tapered tube is formed from a plate or sheet of metal having lips at its longitudinal side edges which extend transversely to the major surface of the plate or sheet. The tube is guided at its lip portions to a weld point where pressure is applied to force the lips together by a grooved roller which applies pressure to the oppositely facing surfaces of the lips in directions transverse to such surfaces. The lips are spaced in advance of the weld point, and high frequency, electric heating current is supplied to the tube at opposite sides of the gap between the lips to heat the tube at the lips to welding temperature as it is advanced to the weld point.

Abstract: A method of manufacturing a solar panel element comprising a metal sheet or sheets secured to fluid-tight tubing substantially continuously along its length by metal which has been heated and cooled, e.g. weld metal, in which the tubing and the metal sheet or sheets are held in contact while they are heated to welding temperature, either forge welding or melting temperature. In the preferred methods, the heating is accomplished by high frequency, electric currents using a proximity conductor. Also, in the preferred methods, the tubing is formed with longitudinal lips as the heating is carried out, and the lips are secured together by welding them together simultaneously with the welding of the sheet or sheets to the tubing.

Abstract: A method of removing ripples from the metal sheet portion of a heat exchanger panel element which is manufactured by joining a metal tube to a metal sheet by means of heated and cooled weld metal, and the product of the method. In the method, the sheet is corrugated, after the tube is joined thereto, without stretching the metal of the sheet by more than 2% so that the sheet length with corrugations is substantially equal to the length of the tube joined thereto.

Abstract: Heat exchanger elements, particularly for solar panels, comprising metal tubing secured to a metal strip which is wider than the tubing and relatively thin by a weld which is metal of at least one of the tubing and the strip which has melted and cooled, the welding conditions being selected so that molten metal is expelled from between the tubing and the strip at the ends of short intervals and the strength of the weld varies longitudinally of the tubing. High frequency electric welding is used under conditions which cause the expulsion of the molten metal.

Abstract: Methods and apparatus for the welding and heat treating of metal parts in which an electric arc extends between a pair of adjacent metal parts or between an electrode and one or more metal parts with the arc traversing the metal part or parts a plurality of times during the heating cycle. For finite length metal parts, i.e. when the surface or surfaces to be heated do not provide closed paths to be followed by the arc, the arc is initiated, caused to follow the surface, extinguished and then reinitiated, or is caused to traverse the surfaces in alternately opposite directions after initiation. With finite length metal parts, run-off tabs are provided at the ends of the surfaces to prevent overheating at such ends. A magnetic field causes the arc to traverse the surfaces and may be modified in strength or distribution to vary traverse rate.

Abstract: Apparatus for supporting and feeding high frequency electric current to a pair of contacts for engaging a work piece or pieces and supplying current thereto in which a co-axial line has relatively movable inner and outer conductors with a pair of contacts respectively mounted at one end of each conductor, electric current being supplied to the conductors adjacent the other ends of the conductors. In one embodiment, the conductors are rotatable and the contacts are mounted on radially extending arms secured to the ends of the conductors. In other embodiments, one conductor is rotatable and the other conductor is axially movable, one contact being mounted on a radially extending arm secured to the rotatable conductor and the other contact being secured to the end of the axially movable conductor. Also, flexible lead and conductive bearing current feed systems and contact mounting arms which are readily convertible into an induction coil support.

Abstract: A method and apparatus for modifying the surface properties of a metal part in which electric current having a frequency of at least 3000 Hz is supplied to a narrow area on the part by means of contacts, one at each end of the area, and a proximity conductor or is induced therein by an induction coil until the metal in the area reaches a temperature at least equal to its melting temperature. A material which will alloy with the metal of the part is added to the molten metal so that when the molten metal is cooled an area of an alloy of the metal and the added material is produced. The added material may be in the form of a gas, powder, salt, wire, rod, bar, foil, etc. and may be applied to the area before, during, or after the melting of the metal of the area. The spacing between the proximity conductor or the induction coil and the work is no greater than three times the width of the proximity conductor or the coil conductor.

Abstract: Methods and apparatus for the welding and heat treating of metal parts in which an electric arc extends between a pair of adjacent metal parts or between an electrode and one or more metal parts with the arc traversing the metal part or parts a plurality of times during the heating cycle. For finite length metal parts, i.e. when the surface or surfaces to be heated do not provide closed paths to be followed by the arc, the arc is initiated, caused to follow the surface, extinguished and then reinitiated, or is caused to traverse the surfaces in alternately opposite directions after initiation. With finite length metal parts, run-off tabs are provided at the ends of the surfaces to prevent overheating at such ends. A magnetic field causes the arc to traverse the surfaces and may be modified in strength or distribution to vary traverse rate.

Abstract: Method and apparatus for modifying the surface properties of a metal part made of a metal which changes its properties with heating to a transformation temperature and subsequent cooling in which method electric current having a frequency of at least 3000 Hz is supplied to a pair of contacts respectively at the opposite ends of the surface area to be modified through a proximity conductor or conductors which are spaced from the surface area by not more than two times the width of the conductor. The duration, frequency and magnitude of the current and the width of the proximity conductor or conductors are chosen so that the metal of such area heats at least to the transformation temperature before the adjacent metal reaches a temperature which would prevent self-quenching of the area metal, by means of conduction of heat from the area metal to the adjacent metal, when the current is discontinued. Apparatus for producing lines of hardening on valve seats is disclosed.

Abstract: Methods of heating and welding together portions of a metal part or parts in which the portions are positioned in facing, generally parallel and spaced apart relation and an induction coil overlies the part or parts and is positioned so as to induce oppositely flowing currents in the part or parts which flow in two closed paths, one each side of the portions to be heated. The portions may be stationary or be advanced during heating, and after the portions reach welding temperature, they are pressed together to form a weld therebetween.

Abstract: A method and apparatus for embedding in a surface area of a metal part a plurality of particles of a material having a melting point higher than, and mechanical properties different from, the metal of the part. The metal part is contacted with a pair of contacts, one at each end of the area, and electric current having a frequency of at least 3000 Hz is supplied to the contacts through a proximity conductor or conductors which overlies or overlie the area and which are spaced from the area by not more than five times the conductor width. The current is maintained until the metal of the area reaches a temperature at least equal to the melting temperature thereof and the particles are inserted into the molten metal which is then cooled. If the temperature of the molten metal exceeds the melting temperature of the particles, the molten metal is cooled before the particles completely melt.

Abstract: Method for manufacturing heat exchange panels each comprising a plurality of sub-panels of finite length, each sub-panel comprising a metal tube welded to a metal sheet except at the end portions thereof which are secured to headers in fluid-tight relation thereto, in which method tubing and metal sheet having a length several times the length of the sub-panel are continuously advanced and welded together by high frequency electric current which is interrupted periodically so that a unit several times the length of a sub-panel and having tubing welded to the sheet by a weld which is continuous except at portions of the tubing spaced apart longitudinally by a distance substantially equal to the length of a sub-panel. The unit is cut at the unwelded portions to provide several sub-panels which are assembled to form the heat exchange panels. The metal sheet may be bent during manufacture of the unit to provide sub-panels having stiffening ribs or having projections for interlocking adjacent sub-panels.

Abstract: Methods for manufacturing heat exchange panels each comprising metal tubes of finite length welded to a metal sheet except at the end portions of the tubes which are secured to headers in fluid-tight relation thereto, in which methods the metal sheet, having end edges and side edges, is formed into a hollow cylinder with the end edges adjacent each other and metal tubing is welded to the cylinder in a spiral path. Welding is interrupted adjacent the end edges and the tubing is cut above the end edges to provide tubes welded to the cylinder except at end portions of the tubes. The end portions of the tubes, after the cylinder-tube combination is formed to the desired shape, e.g., flat, are secured to the headers. If tubes parallel to the side edges of the sheet are desired, the hollow cylinder is formed with adjacent portions of the side edges in axially offset relation prior to welding the tubing to the cylinder.