Plastic and nonmetallic article shaping or treating: processes – Forming articles by uniting randomly associated particles – Utilizing diverse solid particles
Reexamination Certificate
2000-01-25
2001-04-24
Davis, Robert (Department: 1722)
Plastic and nonmetallic article shaping or treating: processes
Forming articles by uniting randomly associated particles
Utilizing diverse solid particles
C425S080100, C425S082100, C425S407000
Reexamination Certificate
active
06221292
ABSTRACT:
TECHNICAL FIELD
This invention relates to an apparatus and method for molding polymeric fibers into products, such as pads or cushions for furniture, car seats, mattresses, and the like, and more particularly to the process conditions and equipment necessary to make products from polymeric fibers at a cost, quality, and performance level acceptable for commercial production.
BACKGROUND ART
The use of certain polymeric fibers, as opposed to primarily polyurethane foam, to make filled articles such as pads or cushions has been shown to result in improved performance characteristics. Compared with foam products, fiber-filled products may be more durable, have lighter weight, have greater permeability, be less costly, and be more readily recyclable.
A further improvement in the quality of fiber-filled articles was described in U.S. Pat. No. 4,940,502, wherein clusters of fibers, sometimes termed fiberballs, were used to create fiber-filled products. Fiberballs have a three dimensional structure which provides resilience upon deformation. From experiments reported in U.S. Pat. No. 5,169,580, fiberball cushions showed firmer support and higher resistance to repetitive compressions than batt cushions, even when the fiberball cushions were of a lower density. When molded, the forces which bond the fiberballs to each other are generally much weaker than the forces which resist compression of the individual fiberballs. This structure allows for resilience while also providing adequate local stiffness.
Although several patents, for example U.S. Pat. Nos. 5,169,580; 5,454,992; and 5,492,662, disclose processes and machinery for molding fiber-filled products, little attempt has been made to relate particular aspects of the molding method and apparatus to the performance and utility of the articles produced.
SUMMARY OF THE INVENTION
In order to be molded, fiber clusters must contain at least some thermoplastic fibers, defined as fibers capable of being repeatedly softened by heating, and hardened by cooling through a characteristic temperature range. Fiber clusters are often made from a mixture of high melting point matrix fibers and low melting point, thermoplastic binder fibers. The clusters are fused into a desired shape by placing the clusters in a mold formed with holes in its surfaces, then passing a heating fluid such as air through the mold. By using a heating fluid temperature which is above the binder fiber melting point, but below the matrix fiber melting point, substantially only the binder fibers soften during heating and the matrix fibers remain firm. The resulting product is cooled with a fluid which is cooler than the binder fiber melting point, thereby bonding the binder fibers such that the mixture retains the shape of the mold.
It is an object of the present invention to relate molding process conditions and machinery design to the performance of the fiber-filled products created therefrom.
Accordingly, an apparatus and method are provided for molding clusters of fibers, including at least some thermoplastic fibers, into products at a cost, quality, and performance level acceptable for commercial production. The clusters, which are typically shipped in a compressed state, are dedensified and then placed into an empty mold. The mold has apertures to facilitate the transfer of thermal energy into the mold. A conveyor is used to transport the mold through a plurality of process locations on an indexed, continuous, or semi-continuous basis. Included are one or more heating locations wherein the mold is heated, providing an influx of thermal energy sufficient to fuse the thermoplastic fibers to form a heated product. One or more cooling locations follow the heating location, wherein the mold and the heated product are cooled to produce a cooled product. The cooled product is then ejected from the mold.
In a preferred embodiment, parameters such as the heating fluid temperature, direction of heating fluid application, cooling fluid temperature, mold thickness, and mold aperture size have been selected which provide improved performance characteristics of the molded product.
The specific features and advantages of the present invention are more readily understood from a review of the attached drawings and the accompanying specification and claims.
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Brooks & Kushman P.C.
Davis Robert
Oakwood Padded Products, Inc.
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