Molded product and method of manufacture

Details Molded product and method of manufacture Molded product and method of manufacture

1997-09-15

2003-07-01

Thibodeau, Paul (Department: 1773)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including variation in thickness

C428S172000, C428S213000, C428S318600, C428S318800

Reexamination Certificate

active

06586074

ABSTRACT:

TECHNICAL FIELD
This invention relates generally to molded objects and methods of molding. It particularly concerns an object molded of foam material which has many of the characteristics of a solid molded object, and molding methods for achieving such characteristics.
BACKGROUND OF THE INVENTION
Toys and other objects which are fabricated from porous materials such as foamed plastics have certain advantages: they are light in weight, owing to their low density; and they are safe for children, owing to their compressibility. Such lightness, safety and compressibility makes these materials especially suitable for bouncing balls, flying toys such as gliders, and throw-toys such as darts. But these materials have not generally produced very good results when used for other types of toys and other products.
In the past it has been difficult or impossible to fabricate such materials in a form which is acceptable to the marketplace. Foam materials are usually supplied in sheet form, making it difficult to fabricate them into objects of non-uniform thickness. By comparison, injection-molded plastic objects can be made in a wide variety of shapes of non-uniform thickness. Injection molding also has been favored for the inclusion of molded-in-place inserts of various types. Historically, foam materials have not held such inserts well.
In addition, the toy marketplace favors objects with a shiny surface, preferably decorated with a variety of bright colors. Foam materials have heretofore had a dull, porous surface which is unsuitable for finishing with brightly colored paints, silk screens, tampo printing and decals. Such surfaces are also unsuitable for the molding of fine surface detail, which lends a desirable realism to toy objects. Another problem encountered with foam objects of the prior art is their vulnerability to tearing because of the softness of the surface layer.
The present invention, however, contemplates the molding of toys and other objects from foam materials, yet provides such objects with a tough, smooth, shiny surface which is similar to that which results from insert molding. As a result, the molded foam objects of this invention combine foam's advantages of lightness, safety and compressibility with a superior ability to hold molded-in-place inserts and to accept various types of surface decorations, preferably brightly colored, plus fine surface detail. The molded foam objects of the invention are also more durable, because the tough surface layer resists tearing.
BRIEF SUMMARY OF THE INVENTION
These desirable results are achieved by a method of molding a low-density object having an impermeable surface, from porous material, comprising the steps of preparing a mold having a cavity the outline of which defines the outline of the object, stamping from the porous material a blank having substantially the outline of the object, inserting the blank into the cavity with the outline of the blank substantially congruent with the outline of the cavity, heating the mold with the blank therein to form the blank permanently into a product, and then removing from the mold and freezing the product, the durations and temperatures of the heating and freezing steps being chosen such that an impermeable surface is permanently formed on the product, whereby the product has the appearance of having been formed from non-porous material.
In a most preferred form of the invention, after heating the mold is quenched in cold water, after which the molded product is removed and subjected to freezing.
The result of this molding method is a low-density product having an impermeable surface and a foam interior integral with the impermeable surface.


REFERENCES:
patent: 3654061 (1972-04-01), Berwanger
patent: 3752695 (1973-08-01), Finelli
patent: 3812225 (1974-05-01), Hosoda et al.
patent: 4576855 (1986-03-01), Okina et al.
patent: 5098782 (1992-03-01), Hovis et al.
patent: 5350544 (1994-09-01), Bambara et al.
L.J. Fonovan, “Polystyrene Foam”, Modern Plastics Encyclopedia, vol. 49/No. 10A, pp. 271 and 272, Jan. 1972.

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