Patent ID: 7708932

Claim:
A chilled air pressure box for thermoforming a plastic sheet, the chilled air pressure box comprising: a wall defining a box having an interior surface and an opposite exterior surface, the interior surface defining an interior space within the box, the box defining an inlet opening extending through the interior surface and the exterior surface; the wall further defining a box perimeter for interfacing with a vacuum mold; an inlet valve that is a door valve disposed within the interior space, adjacent and aligned with the inlet opening such that when the inlet valve is closed the inlet opening is substantially sealed, and when the inlet valve is opened the inlet opening is not sealed; a compressed air source, capable of pressurizing the interior space with compressed air, interfaced with the box; a chilled air source communicating with the inlet opening; and an inlet seal disposed between the inlet valve and the interior surface, wherein when the interior space is pressurized, pressure from compressed air forces the door valve against the inlet seal.