Patent ID: 7857610

Claim:
A thermoforming apparatus for shaping a sheet of thermoplastic material having a generally constant first thickness, comprising: at least one heater arranged to heat at least a portion of the sheet to a temperature suitable for thermoforming the sheet by stretching and shaping; and a thermoforming station with tooling forming a supportive region on one side of the sheet and forming a sleeve and a plunger on an opposite side of the sheet, at least one of the plunger and the supportive region defining a cavity, the station further including a mechanism configured to move one of the sleeve and the supporting region together to capture a volume of heated thermoplastic material of the sheet and then to move the plunger toward the supportive region to pressurize the captured material sufficiently to fluidize and force the captured material to flow into the cavity and take on a completely filled shape of the cavity while the captured material is still heated from the at least one heater, thus leaving a thinned area where the captured material was taken from, the plunger being movable between a retracted position, an intermediate extended position first contacting the sheet, and a fully extended position in the sleeve, and further the plunger having a transverse cross section continuously slidably engaging the sleeve during extension of the plunger so that fluidized captured material cannot flow between the sleeve and the plunger when the plunger is moved from the intermediate extended position to the fully extended position.