Abstract: Multiple workpieces are inductively heated by passing them through one or more induction heating coils. Passage of a section of each workpiece through a coil may oscillate in the forward and reverse directions, independent of the movement of the other workpieces, one or more times, to selectively heat each workpiece while operating the power supplies for each of the induction heating coils at constant current, voltage and/or power to maximize the efficiency of the electrical circuit and minimize the requirements for power supply control circuitry.

Abstract: This invention relates to a method and apparatus for the induction heat treatment of conducting workpieces. More particularly, this invention relates to an apparatus and method for heat treating irregularly shaped workpieces lacking rotational symmetry about a central axis. The heat treatment applied by the apparatus or method of the present invention effects the surface of the workpiece substantially uniformly at all points around the perimeter of a workpiece lacking rotational symmetry, and accomplishing such substantially uniform heat treatment without requiring excessive current flow, without requiring interruptions of large current flow.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.

Abstract: Air filtering apparatus includes a filter cell having ionizing and collecting structure, a high voltage power supply and control unit for supplying a high voltage to the filter cell, a separate low voltage power supply unit for supplying operating power to the high voltage power supply unit and a separate probe unit for monitoring the flow of air within a duct in which the filter cell is installed. The high voltage power supply and control unit includes an output transistor in series with a primary winding of a step-up transformer and controlled by an oscillator circuit which is operative to control and limit the output voltage and current and also the current through the output transistor. The probe unit includes a pair of thermistors and a bridge circuit and operates to provide a signal which is independent of variables other than air flow velocity. A modified apparatus is also disclosed, arranged for portable use and arranged for energization from a standard power line with no separate low voltage supply.