Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
1999-02-02
2001-08-14
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C264S313000, C264S317000
Reexamination Certificate
active
06274072
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for producing such a plastic molded article having at least partly a hollow portion as a tube or a container, and a core used therefor, and particularly to a process for producing a plastic molded article the hollow portion of which can be molded to have a freely selected shape, and a core used therefor.
BACKGROUND OF THE INVENTION
When a plastic branch tube
1
as shown in
FIG. 7
is integrally molded by conventional injection molding, slide molds
4
which are provided to an elevation mold
3
so that they can be moved back and forth are used. That is, the hollow portion of the branch tube
1
is formed by getting the tips of the three slide molds
4
butted against each other, and the branch tube
1
shown in
FIG. 7
is produced by withdrawing the slide molds
4
after finishing injection.
However, in the conventional process in which the slide molds are used, the slide molds must be withdrawn after finishing injection. Accordingly, a branch tube
1
which, for example, has a curved hollow portion as shown in
FIG. 6
cannot be molded. Moreover, screw portions la cannot be integrally molded, and there is no other way but to form them by another step after molding.
DISCLOSURE OF THE INVENTION
The present invention has been achieved in view of the problems associated with the prior art as mentioned above. An object of the present invention is to provide a process for producing a plastic molded article the hollow portion of which can be molded to have a freely selected shape, and a core used therefor.
In order to attain the object, the process for producing a plastic molded article having at least partly a hollow portion of the present invention comprises conducting molding by using a core composed of a water-soluble molded article which has been formed to have the shape of the hollow portion.
In the process for producing a plastic molded article according to the present invention, a water-soluble molded article is used as a core during molding, and it is removed with water thereafter. That is, first, a water-soluble molded article is molded to have the shape of the hollow portion of a desired plastic molded article. The molded article is set in a mold, and a plastic material is molded by a procedure such as injection molding. When the molding is completed, the water-soluble core remaining in the hollow portion is removed by dissolving it with water.
The core composed of the water-soluble molded article of the present invention can be molded to have a freely selected shape, and can be easily removed after molding because it is soluble in water. The hollow portion having an arbitrary shape can, therefore, be molded. Moreover, screws and partial recesses and protrusions can be freely molded.
Furthermore, the water-soluble core of the present invention is not required to be heated as in the lost wax process used in the field of casting because it can be removed with water. Accordingly, there is no possibility at all that the molded article is thermally influenced at the time of removing the core. Moreover, since it is not necessary to use a core having a low melting point in contrast to the lost wax process, there is no possibility at all that the core is dissolved at the time of injecting a molten plastic material.
When molding is carried out using a water-soluble core in the process for producing a plastic molded article of the present invention, while the water-soluble core is held by a mold, a plastic material is injected into a cavity formed between the core and the mold, whereby a plastic molded article having a hollow portion is obtained. That is, a plastic molded article is produced by one molding step.
Furthermore, there may be the case where the water-soluble core cannot be held by the mold, depending on the shape or structure of the desired plastic molded article. In such a case, the following production process can be adopted.
That is, the process for producing a plastic molded article according to claim
3
comprises the step of injecting a plastic material, wherein part of the surface of the core is covered therewith, the step of injecting the plastic material, wherein the remainder or at least the remainder of the surface of the core is covered therewith, and the step of removing the core with water.
In the process for producing the plastic molded article, a plastic material is injected to cover part of the surface of the core, and as a result a molded article is formed on part of the surface of the core. The remainder of the surface of the core is held by a mold. Next, while the molded article having been molded is held by a mold, the plastic material is injected to cover the remainder of the surface of the core. The procedure may be conducted by one step or a plurality of steps. Since the core can thus be held by the mold, a desired plastic molded article can be produced.
Furthermore, the process for producing a molded article of the present invention as claimed in claim
4
comprises the step of molding an intermediate molded article which is to cover part of the surface of the core, the step of mounting the core on the intermediate molded article, the step of injecting the plastic material, wherein the remainder or at least the remainder of the surface of the core having been mounted on the intermediate molded article is covered therewith, and the step of removing the core with water In the process for producing a plastic molded article, an intermediate molded article which is to cover part of the surface of the core is molded first. The core is mounted thereon, and both are set in a mold, whereby the core is held by the mold. Finally, the plastic material is injected to cover the remainder of the surface of the core.
In the process for producing a plastic molded article of the present invention, there is no specific limitation on the material of the water-soluble molded article. One of the examples of the material comprises polyvinyl alcohol as a principal component and an added water-soluble bulk filler. Although there is no specific restriction on the water-soluble bulk filler, examples of the bulk filler include starch, sodium chloride and corn starch.
Furthermore, there is no specific limitation on the shape and structure of the molded article produced by the process for producing a plastic molded article according to the present invention, and the process can be applied to a plastic molded article so long as it has at least partly a hollow portion.
REFERENCES:
patent: 3610314 (1971-10-01), Hochgraf
patent: 4027903 (1977-06-01), Hannover
patent: 5262100 (1993-11-01), Moore et al.
patent: 5520871 (1996-05-01), Rosenberg et al.
patent: 5985197 (1999-11-01), Nelson et al.
patent: 6045745 (2000-04-01), Reno
patent: 3-45116 (1991-04-01), None
patent: 7-316379 (1995-12-01), None
patent: 9-29780 (1997-02-01), None
Arent Fox Kintner & Plotkin & Kahn, PLLC
Kuhns Allan R.
Taisei Plas Co., Ltd.
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