Abstract: A sensor system for determining acceptable magnetization between a magnetic clamp and a mold patent for a quick mold change system on an injection molding machine includes secondary sensing coils magnetically coupled with a switchable magnet in the clamp effecting a voltage output in accordance with magnetic flux conditions between the magnets and the mold and providing a control signal based on changes in said flux condition for controlling activity of said workpiece in accordance therewith.

Abstract: A magnetic device includes a cylindrical outer pole having a central axis and formed of a ferromagnetic material including a circular base and a cylindrical sleeve defining an outwardly opening cylindrical cavity. A reversible magnetic unit located in said cavity includes a cylindrical core having a magnetic axis aligned with the central axis and a normal magnetic polarity in an inactive state. A cylindrical inner pole formed of a ferromagnetic material is operatively coupled to the core and inwardly radially spaced from said sleeve. An annular band between said sleeve and said inner pole formed of a permanent magnetic material has a magnetic polarity transverse to said central axis and magnetically aligned with said normal magnetic polarity of the core whereby an internal magnetic circuit is established in the inactive state through the poles, the core and the permanent magnet to the exclusion of said workpiece.