Apparatus for forming plastic articles

A device for forming plastic articles comprising:

• a pair of opposed platens adapted to compress a heated sheet of thermoplastic material therebetween, said pair of opposed platens having corresponding apertures through the centers thereof to expose the center of said heated sheet of thermoplastic material, the compression between said opposed platens generally allowing for controlled planar movement of the thermoplastic material radially inwardly towards the center thereof;
• an extension member passable through the apertures through the pair of opposed platens to draw the heated sheet of thermoplastic material inwardly between the platens toward the center of the sheet and extend the material transversely through one of the apertures into an elongated conical shaped piece;
• means for monitoring the movement of the thermoplastic material radially inwardly toward the center of said sheet;
• means for controlling the compression of the heated sheet of thermoplastic material by the pair of opposed platens responsive to said monitoring means to control slippage of said sheet of thermoplastic material relative to said pair of opposed platens;
• means for clamping the thermoplastic material between the platens to prevent continued radially inward movement thereof responsive to movement of the material a preselected distance toward the center;
• an involute female mold adapted to receive the elongated conical shaped piece of thermoplastic material therein;
• and
• means for pressurizing the interior of the elongated conical shaped piece of thermoplastic material to expand and press the thermoplastic material against the interior surface of the involute female mold.