US 5,620,715 A · Thermoforming machine with controlled cooling station

Abstract

A four-station rotary thermoformer has a rotary carriage which transports a sheet of thermoplastic material clamped on a subframe through a load/unload station; a heating station; a forming station where the sheet is molded; and a cooling station removed from the mold where the part is cooled on the subframe. The molded sheet is cooled in a cavity which has a lower portion mounted on a lift which travels vertically to engage against an upper portion and enclose the sheet for cooling. A multiplicity of air vents discharge cooling air into the cavity. Cooling air leaves the cavity through recirculation duct. The supply of air within the cooling cavity results in a uniform current of air against the article's surface, thus providing uniform cooling. A programmable controller controls the supply of cooling air and receives input from an infrared sensor which detects the temperature of the thermoformed article and also receives information from a sensor of the cooling air temperature. The programmable controller is programmed to provide a cooling cycle consisting of a three-parts. In the first part, the air is recirculated using the heat capacity of the recirculating air in the air supply system to start cooling at a low rate. During the second part, the flow of cooling air temperature is lowered until a pre-determined maximum cooling rate is reached and held for a selected time. During the third part, the cooling air is again recirculated.

Claims31

Dependent claims

A machine for thermoforming a thick gauge thermoplastic sheet against a rigid mold, the machine comprising:

a) a frame;
b) a carriage mounted for movement on the frame;
c) at least one subframe connected to the carriage, wherein the subframe is engageable with a sheet;
d) a heating station mounted to the frame, wherein the subframe is movable through the heating station for heating of the sheet;
e) a forming station mounted to the frame, wherein the forming station has a thermoforming mold positioned to engage a heated sheet on the subframe which has traversed the heating station, and the mold being operable to mold the heated sheet to a desired shape;
and
f) a controlled cooling station mounted to the frame, the controlled cooling station including an upper portion, a lower portion, the upper and lower portions being relatively movable between a closed position wherein the upper and lower portions define a cavity which is adapted to surround the molded sheet to receive the molded sheet on the subframe after the forming station, and an opened position, a multiplicity of first ducts for introducing cooling air into the cavity to cool the molded sheet held in the subframe, each of the first ducts extending from one of the upper and lower portions to direct cooling air uniformly around the formed thermoplastic sheet, and at least one second duct extending from one of the upper and lower portions for removing heated air from the cavity, wherein the second duct is in fluid communication with the first ducts so recirculation of the cooling air can be effected.

4 more elements

A rotary thermoforming apparatus for molding at least one thick gauge sheet of thermoplastic material, the apparatus comprising:

a) a frame;
b) a carriage mounted to the frame for rotary motion;
c) at least one subframe mounted to the carriage which releasably engages a sheet;
d) heaters mounted on the frame and positioned to heat the sheet when the carriage is rotated to bring the subframe into proximity thereto;
e) a thermoforming mold mounted on the frame and spaced from the heaters, wherein the heated sheet is rotatable on the carriage away from the heaters to be formed by the mold into a desired shape;
and
f) a cooling cavity mounted on the frame and spaced from the thermoforming mold, the cooling cavity having at least one duct mounted therein to discharge cooling air onto a molded sheet engaged by the subframe which has been displaced from the thermoforming mold by the carriage, and at least one duct opening into the cavity for removing heated cooling air.

4 more elements

A rotary thermoforming apparatus for molding at least one thick gauge sheet of thermoplastic material, the apparatus comprising:

a) a frame;
b) a carriage mounted to the frame for rotary motion;
c) at least one subframe mounted to the carriage which releasably engages a sheet;
d) heaters positioned on the frame to heat the sheet when the carriage is rotated to bring the subframe into proximity thereto;
e) a thermoforming mold on the frame and spaced from the heaters, wherein the heated sheet is rotatable on the carriage away from the heaters to be formed by the mold into a desired shape;
and
f) a controlled cooling station mounted to the frame, wherein the controlled cooling station has a cavity which is adapted to surround the molded sheet to receive the molded sheet on the subframe, at least one first duct in fluid communication with the cavity for introducing cooling air into the cavity to cool the molded sheet held in the subframe, and at least one second duct in fluid communication with the cavity for removing heated air from the cavity and wherein the second duct is in fluid communication with the first duct;
g) a fan disposed in the first duct for moving cooling air to the cavity;
h) an air intake in fluid communication with the first duct for intaking ambient air for cooling;
i) a valve disposed between the first duct and the second duct, the valve controlling the mixture of the ambient air and heated air from the second duct, the mixture of the ambient air and heated air being supplied as the cooling air to the cavity.

7 more elements

Dependencies are inferred from the claim text.

Thermoforming machine with controlled cooling station

Life of this patent

Thermoforming machine with controlled cooling station

Life of this patent

Abstract

Claims31