Plastic article or earthenware shaping or treating: apparatus – Preform reshaping or resizing means: or vulcanizing means... – Including both heating and cooling means
Reexamination Certificate
1998-11-24
2001-05-22
Pyon, Harold (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Preform reshaping or resizing means: or vulcanizing means...
Including both heating and cooling means
C425S388000, C425S398000, C425S409000
Reexamination Certificate
active
06234781
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods of forming blister pack packaging.
Articles to be displayed for retail sale are frequently packaged in “blister pack” packaging. A blister pack includes a flat backing sheet, generally of cardboard or plastic, and a plastic “bubble” or “blister”, generally of transparent plastic, the backing sheet and blister being joined to form a sealed cavity in which the article rests.
The blister portion of the packaging may be formed by thermoforming a region of a planar plastic material to a desired shape, e.g., by placing the plastic material between a pair of male and female dies that are temperature controlled at a temperature sufficient to soften the plastic and pressing the male and female dies together to form an indentation or “blister” in the plastic.
This process for forming the blister portion is generally effective, but tends to create distortion of the plastic which can be undesirable. In particular, because of this distortion, it is often difficult or impossible to use a plastic material having a decorative graphic pre-printed on it, as the graphic will also be distorted. As a result, any desired graphics are typically applied in a separate processing step, e.g., by applying a decal and/or label to the thermoformed plastic.
SUMMARY OF THE INVENTION
In one aspect, the invention features an improved method of forming blister pack packaging. Advantageously, the method of the invention allows a blister pack to be thermoformed using preprinted plastic material without undesirable deformation of the plastic material and thus the printing on the plastic. The method of the invention may also allow decals or labels to be applied to a printed or non-printed plastic material prior to thermoforming, without risk of damage to the decal or label during the thermoforming process. The method of the invention also provides excellent control over the wall thickness of the thermoformed blister.
The method of the invention includes providing a substantially planar thermoplastic material and placing the thermoplastic material between a pair of opposed male and female thermoforming dies, while cooling a portion of at least one of the dies. The cooled portion of the die is positioned to contact the area of the thermoplastic material in which it is desired to avoid distortion. By “cooling”, it is meant that the temperature of the die is reduced relative to its normal operating temperature; because the normal operating temperature of the die may be significantly higher than room temperature, due to friction, “cooling” is meant to include reducing the temperature of the die to a temperature higher than room temperature but lower than the temperature that the die would be at were it not cooled.
Preferred embodiments include one or more of the following features. A portion of the male die is cooled and the female die is temperature controlled to maintain the female die at a sufficient temperature to allow the plastic material used to be thermoformed. The male die includes (a) a metal head that has a bore for the passage of water to cool the metal head, and (b) insulating sidewalls on each side of the metal head. The thermoplastic material is preheated prior to being placed between the dies. The female die is a vacuum forming die.
In another aspect, the invention features a thermoforming system for forming blister pack packaging, including opposed male and female dies, one of which includes a cooled portion. Preferably a portion of the male die is cooled, as described above.
Other features and advantages of the invention will be apparent from the description of preferred embodiments thereof, taken together with the drawings, and from the claims.
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Hicks Robert L.
Konop Gary L.
Luebbert Lawrence H.
Fish & Richardson P.C.
Gillette Canada Inc.
Nguyen Thukhanh T.
Pyon Harold
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