Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Including application of internal fluid pressure to hollow...
Reexamination Certificate
1999-05-06
2001-01-09
Davis, Robert (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Including application of internal fluid pressure to hollow...
C264S334000, C425S537000, C425S540000, C425S444000
Reexamination Certificate
active
06171542
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the manufacture of blown plastic containers. More particularly, this invention relates to the manufacture of blown plastic containers by a molding machine of the wheel type in which each container is molded in a cavity defined by an opposed pair of separable radially aligned mold halves with a multiplicity of such pairs of mold halves being mounted in a circumferential array by a rotary member that is rotated in a vertical plane about a horizontal axis.
BACKGROUND OF THE INVENTION
Blown plastic containers that are manufactured on a wheel type molding machine are usually separated from the mold sets in which they are formed when each mold set is at the 12:00 o'clock position on the mold machine. At this location, when the radially aligned mold halves are vertically aligned, the lower mold half is separated from the upper mold half to allow the molded container to be separated from the mold set.
However, it is desired that the container remain with the upper mold half until a subsequent position of the mold set carrying wheel, and notwithstanding the force of gravity that would otherwise cause the container to fall from the upper mold half.
Heretofore, this problem has been addressed by including a fixed retention element as part of the upper mold half, the retention element having an undercut near an inner end thereof that engages a portion of the molded article in an interference fit. Unfortunately, the molded article must then be stripped from the mold half that has the retention element, and the quality of the ejection of the container from such mold half during such stripping is inconsistent and often requires remachining of the undercut in the retention element to achieve acceptable ejection of the molded article.
BRIEF DESCRIPTION OF THE INVENTION
According to the present invention, there is provided an apparatus for, and a method of, molding a thermoplastic container or other article in which the article is positively ejected from a half of a set of opposed mold halves in which the article was formed after the mold halves separate to permit the article to be removed and in which such ejection does not require stripping of the article from any element of the molding equipment. According to this invention, the article is positively retained by one of the mold halves, specifically, by the upper mold half of a set of radially aligned mold halves when the sets are at or near the 12:00 o'clock position of the travel in a circular path in a vertical plane where the lower mold half is separated from the upper mold half by a camming action. The retention of the article in the mold half in which it is to be retained is by way of a translatable pin that extends through such mold half to engage a portion of the article being molded, preferably a portion in the flash or other excess material that will be trimmed from the article in a subsequent operation after removal of the article from the molding machine.
The translatable pin is provided with an undercut near an end that engages the article being formed in an interference fit with such article to positively retain the article within the mold half that carries such pin, and the translatable pin is resiliently urged to a position in which it will remain in such an interference fit. However, when the translatable pin is translated to a position in which it extends further into the mold cavity in which the article is being molded, for example, by a camming action that acts on an opposed end of the translatable pin, the translatable pin will deflect the article being molded from the axis it occupied during molding, and this will eliminate the interference fit between the article and the undercut of the translatable pin and result in positive disengagement or ejection of the article from the mold half in which it had been retained, without stripping and at a desired location in the path of travel of the article.
By virtue of the translatability of the translatable pin, a more positive interference fit can be provided between the molded article and the translatable pin than was the case in prior art arrangements where the article was retained by an interference fit with an undercut in a fixed element of the mold half in which it was to be retained, because translation of the translatable pin ultimately will eliminate the interference between the translatable pin and the article, whereas an interference fit will always exist between the article and an undercut in a fixed element of the mold half, and in such an arrangement it was necessary to limit the degree of the interference fit to minimize difficulties encountered in stripping the article from the mold half.
Accordingly, it is an object of the present invention to provide an improved method of, and apparatus for, the manufacture of blown plastic containers and other articles. More particularly, it is an object of the present invention to provide an improved method and apparatus of the foregoing character for the manufacture of blown plastic containers and other articles by a process, and an apparatus, in which each container is molded in a radially aligned set of mold halves that rotate in a vertical plane about a horizontal axis. Even more particularly, it is an object of the present invention to provide an improved method and apparatus of the foregoing character in which the molded article is positively retained in a half of such set of mold halves after separation of the mold halves and is subsequently ejected from such mold half without stripping.
For a further understanding of the present invention and the objects thereof, attention is directed to the drawing and the following brief description thereof, to the detailed description of the preferred embodiment and to the appended claims.
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patent: 3025561 (1962-03-01), Ruekberg et al.
patent: 3570058 (1971-03-01), Heinig et al.
patent: 3642417 (1972-02-01), Von Holdt
patent: 3797985 (1974-03-01), Garver
patent: 5454708 (1995-10-01), Boenig et al.
patent: 5736170 (1998-04-01), Stoner
patent: 55-126428 (1980-09-01), None
patent: 9-254202 (1997-09-01), None
Davis Robert
Owens-Brockway Plastic Products Inc.
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