Abstract: A threading and scale removing device is disclosed which includes a heating apparatus having an inlet and an outlet. A work-piece is fed through the inlet and exits through the outlet. A plurality of rollers are operatively associated with the heating apparatus. A belt is mounted on the plurality of rollers and is adapted to rotate through the heating apparatus. As the belt rotates, it functions to thread the work-piece through the heating apparatus. Once the work-piece has been threaded through the heating apparatus, the belt functions to catch and remove metal scales that flake from the work-piece during heating. A motor is operatively connected to the plurality of rollers for driving the rollers and allowing the belt to rotate through the heating apparatus.

Abstract: A multi-furnace control system selectively delivers preselected percentages of available power to furnaces of the system, preferably designated as either a melt furnace or a hold furnace. The power supply delivers power to both furnaces. A capacitor station in parallel connection to the power supply and the furnaces is tuned to form a tank circuit therewith. Switches control the selected power delivered to the furnaces respectively and control the delivery of a first portion of the power for holding molten product in the hold furnace as the master control. A remaining portion of the power is then delivered for melting product in the melt furnace. The capacitor station acts as a reactive tank for both furnaces.

Abstract: A high frequency power inverter comprises a power supply, a thyristor for switching the energy from the power supply to a load and a neutral capacitor for storing energy cyclically to assure reverse voltage is applied to the thyristor. A clamp circuit is associated with the switch to limit the ring-up voltage on the capacitor to a preselected value. The clamp circuit is comprised of an inductor having a relatively large value for permitting a gradual leaking of the capacitor voltage during an inverting of the power supply voltage to the load so that the capacitor can ring-up to a higher value than the supply voltage. The inductor is selected so that under all conditions, the voltage on the capacitor will be safely larger than the power supply voltage plus a load voltage peak for a time long enough to assure thyristor turn off.

Abstract: Transverse flux heating assembly for inductively heating a moving strip includes opposite spaced J-shaped conductors to form an inductive heating coil. The coils define a middle spacing therebetween which is unobstructed by flux guides to permit free translation movement between the conductors in a direction parallel to the strip width. The inductors provide a fully adjustable coil width to accommodate different strip widths in the heating operation.

Abstract: A furnace refractory extraction system and method includes a selectively removable bottom portion which is attached to a refractory extraction device associated with a container for drawing the refractory lining of a coreless induction furnace into the container. A plug portion in the furnace bottom is selectively removable to provide access to a bottom wall of the refractory lining. An opening is made in the bottom wall of the lining through which an extractor shaft is inserted and then attached to the removable bottom portion of the furnace bottom. The other end of the shaft is attached to a piston and cylinder assembly associated with the container at the open end of the furnace. When the piston and cylinder assembly is powered, the lining is drawn into the container.

Abstract: An induction strip heating assembly is provided having multiple induction coils disposed in coaxial tandem and including at least two coil power sources for generation of first and second inducing currents in the coils for the induction heating of a workpiece, such as steel strip, passing therethrough. It is a feature of the invention that the assembly includes a closed loop of electrically conductive material coaxially interposed relative to the induction coils and disposed for induction therein of a circulating current opposite to a one of the inducing currents whereby a magnetic field of the circulating current in opposition to an inducing magnetic field of the inducing current causes a reduction in net magnetic field strength on a side of the loop opposite of the inducing current. Such an assembly provides suppression of intercoil magnetic coupling so that the coils may be spaced adjacent one another with less space between them than would be required if no loops were used.

Abstract: A method particularly adapted for alloying a coating on a steel strip. The invention uses an induction heating furnace to produce a galvannealed product. In particular, the operating frequency to the heating coils of the furnace is modulated to avoid a resonant vibration in the steel strip through the heating zone of the furnace. Preferably the invention comprises imposing a frequency modulation on the operating frequency of the power signal to the heating coils.

Abstract: A control circuit particularly useful for controlling the application of power to a single phase induction furnace from a normal line frequency power supply is provided. The load has a large inductance and a resistance. A switch, preferably formed from thyristors, is provided in series connection with the furnace load. A first capacitor is provided in parallel connection with the series connected switch and load. A second capacitor is provided in series connection with the series connected switch and load and the first capacitor whereby selective operation of conduction of the switch results in the smooth and continuous control of furnace power. In an alternative embodiment small inductors are placed in series with the capacitors to provide a filter preferably tuned to the fourth harmonic of the power supply.

Abstract: A method and apparatus particularly adapted for alloying a coating on a steel strip. The invention uses an induction heating furnace to produce a galvannealed product. In particular, the operating frequency to the heating coils of the furnace is modulated to avoid a resonant vibration in the steel strip through the heating zone of the furnace. Preferably the invention comprises imposing a frequency modulation on the operating frequency of the power signal to the heating coils.

Abstract: A method and apparatus for induction heating or melting furnaces of varying conductance, comprising controlled adjustment of the power factor angle in response to variations in load conductance to maintain constant power.

Abstract: There is disclosed herein a power control unti for controlling the voltage and power delivered to a single phase load, said control unit being preferably employed with loads whose impedance changes but slightly over the work cycle. The circuit utilizes a diode rectifier and a controlled rectifier connected in parallel therewith connected in series with capacitance and achieves transient-free and harmonic-free power control.

Abstract: There is disclosed herein a circuit for controlling the voltage and power delivered to a single phase induction melting or heating furnace wherein the impedance of the furnace varies. The circuit utilizes diode rectifier means and controlled rectifier means connected in series with capacitance and achieves transient-free and harmonic-free power control.