Electric induction heater

Abstract

In an electric induction furnace for heating a bar-shaped workpiece, wherein the workpiece has a longitudinal axis and is conveyed through the furnace in a conveying direction orthogonal to the longitudinal axis, an induction coil comprises a continuous conductor including a plurality of substantially horizontal primary conductor members and a plurality of substantially vertical return bends. The primary conductor members and return bends are serially connected and wound about a coil axis into a spiral having a substantially rectangular shape when viewed along the coil axis, which is substantially parallel to the conveying direction. The coil encloses a heating zone and generates a varying magnetic field in the heating zone when a varying electric current is conducted in the conductor. The coil includes first and second ends and has at the second end a workpiece exit portion, which encloses an exit section of the heating zone. The return bends of the workpiece exit portion of the coil are configured to permit removal of the workpiece from the exit section of the heating zone in a removal direction coincident with the longitudinal axis of the workpiece. These return bends preferably are arcuately shaped, having a convex side facing the first end of the coil and a concave side facing the second end of the coil. The workpiece is removed from the exit section by an extendable plunger that pushes the workpiece out of the exit section in the removal direction.