Method and apparatus for induction heating of an elongated workpiece

摘要

A method for uniformly heating a workpiece such as a sucker rod or the like having a uniform cross-section over a major portion of its length and an enlargement adjacent each end thereof. A multi-turn inductor is coaxially disposed around an elongated workpath with the rod being longitudinally moved along the workpath at some preselected rate of travel toward the inductor entrance end. The inductor is normally at one level of energization adapted to inductively heat the enlargement adjacent the rod leading end to some predetermined temperature as it passes through the inductor. After a first predetermined time interval triggered by the rod as it travels along the workpath, the inductor is automatically placed at another, lower level of energization for inductively heating the elongated major portion to the same predetermined temperature. The inductor then automatically returns to the normal level of energization for inductively heating the enlargement adjacent the rod trailing end to the predetermined temperature. The inductor energization levels are adjustable to accommodate different rod and feed characteristics. Also, a plurality of like inductors may be electrically interconnected to facilitate the simultaneous heating of a plurality of the rods.