Plastic article or earthenware shaping or treating: apparatus – Means feeding fluent stock from plural sources to common...
Reexamination Certificate
2000-09-28
2003-09-16
Davis, Robert (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means feeding fluent stock from plural sources to common...
C425S185000, C425S186000, C425S19200R, C425S588000, C425SDIG002, C425S81700C
Reexamination Certificate
active
06619943
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an in-mold foam molding apparatus and method suitable for molding into a unitary molding molded portions comprising bead starting materials having different properties, and to in-mold foam molded articles.
2. Description of the Related Art
An in-mold foam molding apparatus for fabricating moldings from bead starting materials consisting of thermoplastic synthetic resin is taught, for example, in U.S. Pat. No. 5,164,257, which discloses an in-mold foam molding technique wherein the mold is provided with moveable partitioning members that are retractable from the mold cavity via actuators such as air cylinders, the mold cavity being partitioned into a plurality of partitioned mold chambers by means of these moveable partitioning members, with filling devices for supplying bead starting materials to the individual partitioned mold chambers being connected therewith individually, whereby with the mold cavity partitioned by the moveable partitioning members, adjacent partitioned mold chambers can be filled with bead starting materials having, for example, different degrees of expansion, and once so filled the moveable partitioning members can be retracted and steam supplied to the interior of the mold cavity in order to heat and weld the bead starting materials into a molded article.
In molded articles molded by means of this in-mold foam molding technique, by varying the bead starting materials used for different regions of a molded article it is possible to fabricate a molded article having, for example, different mechanical properties in different regions thereof. This has the advantage of being able to improve functionality and quality in molded articles, which are used as cores for car bumpers and cushioning materials for packaging of household electronics, furniture, and the like.
In the in-mold foam molding apparatus disclosed in the cited U.S. publication, it is necessary to provide actuators for retracting the partitioning members, and thus a larger number of partitioned mold chambers will require a correspondingly complicated drive system for the partitioning members, resulting in the problem of higher fabrication costs for the in-mold foam molding apparatus.
Further, if filling compression in adjacent partitioned mold chambers is not controlled in such a way as prevent pressure differentials from forming, there is a risk of a partitioning member deforming due to the pressure differential. Another problem is that the flow of air used for filling is obstructed by the partitioning members, depressing ease with which the mold may be filled with the bead starting materials.
In this in-mold foam molding apparatus, since passage orifices are formed in the mold so that the partitioning members may be retracted through these passage orifices, there is the additional problem that flash forms on the surface of the molded article around these passage orifices for the following two reasons.
(1) Reason 1
In order to prevent the bead starting materials from infiltrating, the wall of the passage orifice and the partitioning member will ideally be designed with as narrow a gap as possible therebetween, but this arrangement creates the problem of deformation or breakage of a partitioning member or inability to retract a partitioning member due to contact with the inside wall of a passage orifice resulting from expansion or contraction of the mold. Specifically, the mold expands when the bead starting materials are steam heated and contracts during cooling with cooling water. Where passage orifices like those described earlier are provided, mold strength is lower in the portions bordering the passage orifices, so strain in the mold becomes concentrated at the passage orifices, and is compensated for by expansion and contraction of the width of the apertures of the passage orifices. Where the passage orifices are of “L” or “C” configuration, lower mold strength in a specific direction will result in shape deformation of passage orifices. Expansion/contraction or deformation of passage orifices may result in deformation or breakage of a partitioning member through contact with the inside wall of a passage orifice. Where the mold is split into a plurality of molding sections by the passage orifices with the plurality of molding sections being fixed by means of screws or the like to an attachment plate, it will be a simple matter to form passage orifices in the mold, but expansion or contraction of the mold will result in shifting of the locations at which the mold segments are attached to the attachment plate, so that there will be significant deviation in the width of the passage orifice apertures. This phenomenon becomes more pronounced with larger mold dimensions or longer passage orifices, and represents a significant problem for in-mold foam molding apparatuses equipped with partitioning members. For such reasons, the partitioning member and the wall of the passage orifice are designed with a large gap therebetween, notwithstanding the fact that it is recognized that flash will form on the surface of the molded article around the passage orifices.
(2) Reason 2
Partitioning member distal edge shape is designed to conform to the shape of the inside surface of the mold, but as shape is not always the same as that of the inside surface of a mold provided with passage orifices, it may occur that when a partitioning member is retracted after filling the mold with bead starting materials, the partitioning member recesses partway into its passage orifice so that th e interior of the passage orifice communicates with the mold cavity. Since the width of the passage orifice apertures is designed to be smaller than the diameter of the bead starting materials in order to prevent bead starting materials from infiltrating into passage orifices, merely retracting the partitioning members will not result i n bead starting materials infiltrating into passage orifices, but when the bead starting materials are heated and welded by delivering steam to the mold cavity, softening and expansion of the bead starting materials may result in partial infiltration into passage orifices, producing long, thin flash projecting out at locations on the molded article corresponding to the locations of passage orifices.
Flash is not a particular problem for molded articles of which only rough dimensional accuracy on the surface is required, but represents a product defect for molded articles subject to strict requirements. For example, in car bumpers, it is common practice to affix an in-mold foam molded core to the front face of front beam of the car, and to then arrange a synthetic resin cover member so as to cover the core. With car bumpers of this type, flash must be removed from the core after molding in order to prevent problems such as inability to secure the core to the proper location on the mounting face of the front beam or inability to secure the cover member at the proper location on the vehicle body due to the presence of a gap between core and front beam or core and cover member.
Japanese Unexamined Patent Application H10-193375 discloses a molding apparatus for molding foam molded articles that have molded sections consisting of bead starting materials of different properties and that can be used as shock absorbent materials, the apparatus provided with fixed partitioning members situated at the boundaries of adjacent partitioned mold chambers, with these partitioning members defining spaces wherein the bead starting materials are fused. This molding apparatus is designed such that slits are formed in the molded article by the partitioning members, whereby the molded article can be split at the slits into smaller pieces by hand, thereby facilitating disposal or recycling of the molded article after use. However, the design of the molding apparatus disclosed in this publication is provided with these partitioning members situated along certain portions of the boundaries between adjacent partitioned mold chambers, in order
Kobayashi Yoshiyuki
Sameshima Masahiko
Yamaguchi Kenji
Armstrong Westerman & Hattori, LLP
Davis Robert
Del Sole Joseph S
Kaneka Corporation
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