Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Flash or sprue removal type
Reexamination Certificate
2000-01-07
2001-10-30
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
Flash or sprue removal type
C264S219000, C264S257000, C264S258000, C264S320000
Reexamination Certificate
active
06309576
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to methods for obtaining closely matched die sets in molding and forming press setups for the production molding of diaphragms and like structures with thin coated fabrics; more particularly to methods for creating a closely matched die set in a given setup on a mold machine for molding diaphragms from rubber coated fabric.
2. Background Art
Thin, coated fabrics are used for molding or forming a variety of specialty products including very small flexible diaphragms which must exhibit very consistent operating characteristics. The problem in using a traditional mold for producing these products is in the machining and set up of the male and female halves of the mold to a close enough tolerance. When they are brought together with a very thin layer of material between them, there are likely to be voids for which a significant amount of flow of the coating is required to fill. Excessive voids require excessive temperature and pressure to achieve the necessary flow, and this increases the likelyhood of inconsistant performance of the product from one setup to the next, and from one cycle to the next.
The following prior art provides useful context for better understanding the invention:
U.S. Pat. 4,889,668 discloses a fixed-volume, trapped rubber molding method encompassing a complex temperature and sensor apparatus used in conjunction with casting elastomeric material cured around the die to form a die support structure.
U.S. Pat. 5,700,496 discusses a self adjusting backplate for supporting one or both sides of the mold plates of a blow-molding machine with a cushioning material on the outer plate surface. The specially designed cushioning material allegedly absorbs the pressure and allows the molding to proceed without shims, providing equal pressure along the mold plates.
U.S. Pat. 5,093,067 shows a method for injection molding of fabric reinforced elastomer diaphragms, where a fabric is placed between a mold plates. Elastomeric material is injected into the mold through ports and allowed to cure, producing thin diaphragms without migration or distortion of the fabric.
Skilled practitioners will appreciate the short comings of the prior art as contrasted to the benefits of the instant invention, including the desirability for achieving a closing confirming die pair setup, and reducing the problem of voids and the need for flowing of coating material when using coated fabrics for forming or molding formed articles such as diaphragms.
SUMMARY OF THE INVENTION
It is a goal of the invention to provide a method for setting up a molding press with a matching die set for molding formed articles from coated fabric materials, such that opposing die surfaces are closely conforming and closely aligned when the press is closed, voids between the dies and the sheet material are minimal, and dependence on flow of the coating of the coated fabrics is minimal.
It is a further goal of the invention to provide a custom setup and forming or molding methodology for fabricating formed articles from thin coated fabric materials that permits the use of thinner coated fabric materials and larger diameter diaphragms, is less susceptible to irregularities due to voids and requires less flow within the mold during the molding process, resulting in more uniformity and fewer rejects across the production run.
There is provided within the scope of the invention a method for setting up a molding press, whereby a first component forming die, typically made of a bard material that will stand up to the rigors of many, many molding cycles, is immovably installed on a first plate of a pair of molding plates. An opposing die cavity is milled, drilled or otherwise provided on the second plate, opposite the forming die. The plate set is installed in the press in the usual fashion.
The die cavity then filled with an uncured elastomer such that when cured will be resistant to high temperature, and to such elements and compounds as may be encountered in production process. The press is then closed, bringing the elastomer into contact across the full forming surface of the first die. Suitable heat and pressure are applied, causing the elastomer to be cured into an immovable, perfectly aligned, molded in place, mating die counterpart to the hard die, unique to that specific setup.
Once the elastomer is cured or vulcanized, the mold is opened and the excess flash is trimmed off, and the press is ready for production. From this point on, the mold is used in the conventional manner for molding thin coated fabrics. The benefit of the invention is lost, of course, when the setup is disturbed or disassembled.
Other objects and advantages of the invention will be apparent to those skilled in the art, from the drawings, description and claims that follow.
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Asmus Scott J.
Diacom Corporation
Kuhns Allan R.
Moine Vernon C.
LandOfFree
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