Plastic and nonmetallic article shaping or treating: processes – Direct application of fluid pressure differential to... – Producing multilayer work or article
Reexamination Certificate
1995-12-20
2001-10-02
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of fluid pressure differential to...
Producing multilayer work or article
C264S547000, C264S554000, C425S388000
Reexamination Certificate
active
06296803
ABSTRACT:
TECHNICAL FIELD
This invention relates to a method and apparatus for making a multi-layer blow molded container and also relates to a multi-layer blow molding preform as well as to the resultant multi-layer blow molded container that is blow molded from the multi-layer preform.
BACKGROUND ART
Prior blow molded containers have been made from multi-layer preforms so as to have the capability of using different materials that have desired properties for the particular use of the container. For example, U.S. Pat. No. 4,391,861 Nilsson discloses a multi-layer preform for use in blow molding and having inner and outer “part-preforms” that are disclosed as being made by injection molding or extrusion, and this patent also discloses the use of reprocessed plastic for one of the part-preforms.
U.S. Pat. No. 3,717,544 Valyi, U.S. Pat. No. 3,719,735 Valyi and U.S. Pat. No. 4,067,944 Valyi disclose multi-layer blow molded containers made from preforms having an inner layer provided by a liner about which an outer layer is formed by injection molding. The U.S. Pat. No. 3,717,544 Valyi patent discloses the liners as being made by a thermoforming process wherein a vacuum is applied to a female mold to deform a heated plastic sheet to the shape of the mold.
DISCLOSURE OF INVENTION
One object of the present invention is to provide an improved method for making a multi-layer blow molded container.
In carrying out the above object, the method for making a multi-layer blow molded container in accordance with the invention is performed by moving a sheet of resin having oppositely facing first and second surfaces between a pair a vacuum is drawn at a confined area at the first surface of the heated sheet of resin such that the first surface has a convex shape and the second surface has a concave shape. Thermoforming is performed to the heated sheet of resin by engagement at the concave second surface thereof with a male vacuum mold through which a vacuum is drawn to form the sheet of resin into a preform liner. Injection molding of an outer layer of resin around the preform liner provides a multi-layer preform. Blow molding of the multi-layer preform provides the multi-layer blow molded container.
In the preferred practice of the method, the vacuum is drawn at the first surface of the heated sheet of resin before the male vacuum mold engages the second surface of the heated sheet of resin. This vacuum is maintained at the first surface of the heated sheet of resin after the initial engagement of the male vacuum mold with the second surface thereof and while the male vacuum mold is thereafter moved to form the heated sheet of resin. This movement of the male vacuum mold is terminated and the vacuum drawn at the first surface of the heated sheet of resin is terminated whereupon the vacuum is then drawn through the male vacuum mold to complete the forming of the preform liner to the shape of the male vacuum mold. After the thermoforming of the heated sheet of resin by the male vacuum mold, the preform liner is trimmed from the rest of the sheet of resin prior to injection molding of the outer layer of resin to provide the multi-layer preform.
The injection molding of the outer layer of resin is performed with sufficient resin such that the outer layer by weight constitutes at least 75% of the total weight of the preform. The thermoforming may be performed on a virgin sheet of resin and the injection molding performed with post consumer recycled resin. The thermoforming may also be performed on a sheet of resin that is a barrier material. In addition, the thermoforming may be performed on a sheet of resin that includes more than one layer to provide a multi-layer liner around which the outer layer of resin is injection molded.
Another object of the present invention is to provide improved apparatus for making a preform liner for use in blow molding.
In carrying out the immediately preceding object, apparatus for making a preform liner for use in blow molding is disclosed as including a vacuum enclosure for drawing a vacuum within a confined area at a first surface of a heated sheet of resin which has a second surface that faces in the opposite direction as the first surface such that the first surface assumes a convex shape and the second surface assumes a concave shape. A male vacuum mold of the apparatus provides thermoforming of the heated sheet of resin by engagement therewith at the second surface thereof and has passages through which a vacuum is drawn to form the sheet of resin to the shape thereof to provide the preform liner.
In the preferred construction, the apparatus includes an actuator for moving the vacuum enclosure into and out of the sealed engagement with the heated sheet of resin. The preferred construction of the apparatus also includes an actuator for moving the male vacuum mold into engagement with the heated sheet of resin.
Another object of the present invention is to provide an improved multi-layer blow molding preform.
In carrying out the immediately preceding object, the multi-layer blow molding preform of the invention includes a liner that is thermoformed by applying a vacuum to one surface of a heated sheet of resin to provide a dome shape thereto and by engaging the other surface thereof with a male mold through which a vacuum is drawn to form the final shape of the liner. An injection molded outer layer of the preform extends around the liner and constitutes at least 75% by weight of the total preform weight. This outer layer has a closed end that has reduced crystallinity by virtue of the manner in which the liner is formed by the vacuum applied to the one surface of the heated sheet of resin and engagement of the other surface by the male vacuum mold.
The multi-layer blow molding preform of the invention can be manufactured with the liner as a virgin resin and the outer layer as post consumer recycled resin. The liner can be a barrier material that limits transmission of gas and other fluids and can also include more than one layer.
Another object of the present invention is to provide an improved multi-layer plastic blow molded container.
In carrying out the above object, the multi-layer plastic blow molded container of the invention includes an inner layer blow molded from a liner that is thermoformed by applying a vacuum to one surface of a heated sheet of resin to provide a dome shape thereto and by engaging the other surface thereof with a male vacuum mold through which a vacuum is drawn to form the final liner shape. An other layer of the container is blow molded from an injection molded outer layer around the liner. The container includes a body portion and an upper dispensing end located above the body portion as well as including a lower freestanding base that closes the lower extremity of the body portion. This lower freestanding base of the container has reduced crystallinity by virtue of the manner in which the liner is formed by vacuum applied to the one surface of the heated sheet of resin and the engagement of the other surface by the male vacuum mold.
The objects, features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
REFERENCES:
patent: 2365637 (1944-12-01), Helwig
patent: 3717544 (1973-02-01), Valyl
patent: 3719735 (1973-03-01), Valyi
patent: 3726953 (1973-04-01), Jones et al.
patent: 3954923 (1976-05-01), Valyi
patent: 3955697 (1976-05-01), Valyi
patent: 4034054 (1977-07-01), Sauer
patent: 4067944 (1978-01-01), Valyi
patent: 4092391 (1978-05-01), Valyi
patent: 4149645 (1979-04-01), Valyi
patent: 4224275 (1980-09-01), Sauer
patent: 4391861 (1983-07-01), Nilsson
patent: 4528219 (1985-07-01), Yamada et al.
patent: 4800129 (1989-01-01), Deak
patent: 4818465 (1989-04-01), Mente
patent: 5443766 (1995-08-01), Slat et al.
patent: 5599589 (1997-02-01), Valyi
patent: 0 672 721 A2 (1994-03-01), None
Brooks & Kushman P.C.
Eashoo Mark
Plastipak Packaging, Inc.
Silbaugh Jan H.
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