Apparatus for thermoforming plastic materials

Abstract

An apparatus for thermoforming articles out of a sheet plastic material includes a female mold having one or more cavities and a male mold including one or more plug assists in one to one correspondence with the female mold cavities. Each cavity of the female mold communicates with a first passageway. A vacuum source communicates with each first passageway, and includes a vacuum switch. Each plug assist is provided with one or more inlets extending through the plug assist and one or more second passageways, the second passageways and inlets each communicating with the respective cavities when the mold is in a closed position. A first air source communicates with the inlet and includes a first heating means and a switch to selectively apply heated air through the inlet into the cavity under pressure. A second air source communicates with each second passageway and includes a second heating means and second switch may be opened and closed to selectively applying air through the second passageways into a cavity when the mold is in the closed position. A third air source communicates with the inlet and includes a switch to selectively supply air through the inlet into the cavity at a third pressure and temperature. Pressure of the first air source is suitably adjusted to create a cushion between the plug assist and the production sheet to prevent contact as the mold is closing.