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The Present Plastic Packaging Machine [2009-12-09]

The present plastic packaging machine relates to a multiple section heater for plastic skin packaging and vacuum-forming machines. In the present plastic packaging machine which employ sheet for skin packaging or vacuum forming, the object to be packaged is placed on a platform under a framed plastic sheet. The latter is heated by a hot plate which is moved in laterally from the back to heat the sheet. When the sheet is heated to softening temperature, the hot plate is retracted laterally as the sheet is lowered over the object to be packaged. To prevent conduction of heat into the plastic chamber when the hot plate is retracted, a baffle and often a sandbox are provided under the hot plate to absorb the undesired heat. Some plastic packaging machine leave the hot plate in place and shut off the heat with an on-off switch. Among the objections to the present heating methods are ''first" the uneven heating of the plastic sheet. For example, as the heated plate is being moved laterally to cover the plastic sheet, the portion first covered by the heater becomes unnecessarily overheated by the time the entire sheet is covered. Secondly, the machine requires extra floor space to allow for the retracted plate. Thirdly, the plastic packaging machine cycle is slowed down because of the waiting period required to move the entire hot plate. In the units having on-off switches, there is time wasted waiting for the hot plate to heat up for each article packaged.