Abstract: An arrangement for controlling the microwave power of magnetrons, in which a multiple of magnetrons are connected in parallel with a power unit (3) for generating a high magnetron-operating voltage, and which arrangement includes for each magnetron (1,2) a separate regulating circuit (9) which includes a current measuring circuit (10) for measuring the anode current passing through respective magnetrons, and in which arrangement the waveguides (70) to which the magnetrons are connected have earth potential. The invention is characterized in that the anode (4) of each magnetron (1, 2) is isolated electrically from the earth potential, in that the current measuring circuit (10) is connected between the anode (4) of the magnetron and the one terminal (23) of the power unit, and in that an over-voltage protector (78) is connected in parallel with the measuring circuit (10) for the purpose of limiting the voltage on the magnetron anode (4) in the event of a disruption in or failure of the measuring circuit (10).

Abstract: A method for controlling magnetrons with regard to their microwave power in those cases where a multiple of magnetrons are present. The method includes connecting two or more magnetrons in parallel with a power unit operative in generating a high voltage for operating the magnetron is connected to respective magnetrons and includes a current measuring circuit by which the anode current passing through respective magnetrons is measured on the high-voltage side of the magnetrons. The current measuring circuit is galvanically separated from a control circuit, which is arranged to control the anode current of a respective magnetron in response to a signal received from the current measuring circuit. Also an arrangement for carrying out the method.

Abstract: An arrangement for heating with the aid of microwave energy, comprising a microwave generator constructed to supply a waveguide, the waveguide having provided in one side surface thereof a dielectric plate through which microwave energy propagates. In accordance with the invention the arrangement includes at least two microwave generators (1, 2), each of which is arranged to supply a feed waveguide (3, 4). The feed waveguide (3, 4) is a power divider which is arranged to distribute the power input substantially equally to at least two applicators (7, 8; 9, 10) which extend at an angle to the feed waveguide, where each of the at least four applicators (7, 8; 9, 10) is provided on one side surface thereof with a dielectric plate (11, 12, 14) of the aforesaid kind. The applicators are positioned in relation to one another so that all dielectric plates (11, 12, 14) lie in one and the same plane.

Abstract: A method for retreading vehicle tires. A carcass is provided with a prevulcanized tread and an unvulcanized tie-gum layer between the carcass and tread. A microwave applicator is located above the tread for emitting microwaves to the tire for creating heat energy in the tire. A reflector for microwaves comprising an electrically conductive material is attached in connection to or in the tie-gum layer to achieve high quality rapid vulcanization without heating the carcass.

Abstract: A tie-gum layer for retreading vehicle tires. In carrying forth retreading of a vehicle tire, a prevulcanized carcass is provided with a prevulcanized tread and an unvulcanized tie-gum layer between the carcass and tread. A microwave applicator is located above the tread for emitting microwaves to the tires for creating heat energy in the tire. A reflector for microwaves comprising an electrically conductive material is provided in association with the tie-gum layer for providing high quality rapid vulcanization without heating the carcass.

Abstract: A method and apparatus for retreading vehicle tires. A carcass is provided with a prevulcanized tread and an unvulcanized tie-gum layer between the carcass and tread. A microwave applicator is located above the tread to emit microwaves against the tire for generating heat energy in the tire whereby the tie-gum layer is vulcanized. Vulcanization of the edges of the tie-gum layer is facilitated by local heating at or in connection with said edges by heat generation outside of the tire. The heating can be effected either by utilizing a material with a high dissipation factor for microwave energy or, alternatively, by use of electric resistance wires.

Abstract: A method of heating objects by microwave energy by supplying microwave energy from a generator to a first waveguide. A second waveguide is located, separated from the first waveguide except for at least one parallel and adjacent coupling distance at a common wall between the waveguides. A coupling of microwave energy distributed in the wave propogation direction of the waveguides takes place at the coupling distance so that microwave energy passes from one waveguide to the other one. The second waveguide is dimensioned, so that action of load (objects being heated) conducts microwave energy in the second waveguide with the same wave phase constant as the first waveguide. Objects to be heated are fed only into and out of said second waveguide. A uniform field is fed-in only into the first waveguide. A uniform field distribution and heating profile is obtained and leakage of microwave energy from the open ended second waveguide is avoided.

Abstract: A device for microwave heating, including a wave guide, in which a material is intended to be heated, and a microwave source connected to the wave guide. The wave guide includes a portion wherein its cross-sectional area decreases continuously from the end of that portion located closest to the microwave source to the other end of the portion part, and along that portion the wave guide includes a portion with a geometry, at which fed-in microwave energy no longer can propagate in the wave guide, i.e., the wave guide proceeds continuously to so-called cut off at a certain distance from the narrower end of the part.

Abstract: A method and an apparatus for accomplishing substantially uniform heating of a dielectric material, e.g., an injection molded plastic, attached to, i.e., filling and engaging the walls of a metal encased cavity using microwave energy supplied simultaneously into the cavity at two different frequencies so that two resonance modes arise within the cavity, the two frequencies being so chosen to differ slightly and so that the resonance modes which arise have no coinciding zero points within the cavity. The apparatus has microwave sources connected by waveguides or coaxial conductors into different locations in the cavity. By avoiding coincidence of zero points of the resonance mode an even uniform heating of the material in the cavity is accomplished.