Air-Cooled Induction Heater for Efficient Sealing of Containers Using Wide Range Foils

Induction cap sealing is a complex process. Through nonuniform spatial distribution of power over fine annular ring on thin foil, it not only ensures tamper proof sealing of container lip but also removes wax from the top surface of foil. The indirectly controlled sealing process does not have any feedback to execute any corrective measures. Traditionally, sealing operation is dominantly performed by induction effect and wax removal is by thermal conduction. Due to inferior heat conduction features, the sealing quality degrades if large thin foil is used. Therefore, modern cap sealing process needs to be dominantly controlled (both sealing and wax removal) by induction heating through the use of multiple heat sources over the foil surface to reduce the role of thermal conduction. In this paper, the controlled multizone heating is effectively implemented through proper coil design. The coil is fed by single-resonant inverter.