| 摘要 |
A heat control system used in apparatus for packaging articles in a tray by applying a film of thermoplastic material over the articles in the tray. The apparatus includes a plurality of electrically operated heating units successively moving along a prescribed path and adapted to captivate each tray and the film over the articles in the tray between adjacent heating units as the heating units move along a prescribed portion of the prescribed path to press the film against opposite sides of the tray and heat the film to a temperature to cause the film to bond to the tray. The heat control system includes temperature control means for controlling the temperature of each of the heating units, detection means for detecting when each of the heating units is in position to press the film against the tray, and timing means connecting the temperature control means and the detection means so that the timing means is activated while the detection means detects that the heating unit is in position to press the film against the tray to cause the temperature control means to lower the temperature of the heating unit from a prescribed higher welding temperature sufficient to bond the film to the tray to a prescribed lower holding temperature to prevent deterioration of the film after a prescribed period of time and to cause the temperature control means to raise the temperature of the heating unit back to the prescribed higher welding temperature after the heating unit releases the film. The method of operating the apparatus is also disclosed. |
