Plastic and nonmetallic article shaping or treating: processes – With step of making mold or mold shaping – per se
Reexamination Certificate
1999-03-25
2001-05-01
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of making mold or mold shaping, per se
C264S297100, C264S297800, C219S069170
Reexamination Certificate
active
06224807
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods of molding fasteners, e.g., the hook component of a hook and loop fastener, and methods of making molds to perform such molding.
Molded hook and loop fasteners include an array of fastener elements integrally molded with and extending from a base. The fastener elements are formed in small mold cavities in a molding device. The mold cavities typically include undercuts for molding loop-engaging shapes such as hooks or mushroom heads.
Often the mold cavities in which the elements are formed have no moving parts, the fastener elements being pulled from the mold cavities by resiliently distorting the molded fastener elements. A running strip of fastener elements is generally molded on a rotating mold roll, e.g., as described in U.S. Pat. No. 4,794,028, the disclosure of which is incorporated by reference herein. For discrete items, cyclable injection molding techniques are employed. In either case, the mold comprises a stack of thin plates which, when in correct registration, define a plurality of mold cavities. Each of the thin plates includes a portion of the mold cavity, taken along an axial cross-section through the cavity, so that when the plates are properly aligned these portions align to define a complete mold cavity.
SUMMARY OF THE INVENTION
The present invention features methods of molding fasteners and of forming a molding cavity for manufacturing a fastener element. The mold cavities used in the methods of the invention are formed in a single, integral mold body, without the use of stacked plates. In preferred embodiments, an electrode is used, e.g., in an Electrodischarge Machining (EDM) process, to machine the desired mold cavity shape into the mold body. This technique allows mold cavities for fastener elements to be easily manufactured, and facilitates the manufacture of mold cavities having complex shapes, e.g., for helical fastener elements. Moreover, when using a mold according to the invention it is not necessary to align a stack of plates, nor to keep the stack in correct registration during the molding process.
In one aspect, the invention features a method of making a mold cavity for forming a fastener element having a predetermined shape including an undercut portion. The method includes (a) providing a mold body having a surface; (b) providing a shaped electrode, the shape of the electrode being selected to enable the predetermined shape of the mold cavity to be described by motions of the electrode; (c) moving the shaped electrode into the surface of the mold body to form an initial opening in the mold body; (d) moving the shaped electrode within the initial opening in a set of motions referenced to multiple axes to enlarge the initial opening and form the predetermined shape of the mold cavity; and (e) removing the shaped electrode from the mold body.
Preferred embodiments include one or more of the following features. The step of moving the shaped electrode includes moving the electrode into the surface in a direction substantially perpendicular to the surface. The step of moving the shaped electrode within the initial opening in a set of motions includes moving the shaped electrode substantially parallel to the surface. The step of moving the shaped electrode within the initial opening includes rotating the shaped electrode. The step of removing the shaped electrode includes returning the shaped electrode through the set of motions. The step of moving the shaped electrode within the initial opening in a set of motions includes the set of motions of: (a) moving the shaped electrode in a first direction substantially parallel to the surface from a first position in the initial chamber to a second position in the mold body; and, (b) moving the shaped electrode in a second direction substantially parallel to the surface from the second position past the first position to a third position in the mold body. The method further includes the step of providing a shaped electrode wherein the shaped electrode has an elongated shaft and a curved tip. The shaped electrode has a length at least as deep as the cavity to be formed. The shaped electrode has at least one transverse dimension that is smaller than the corresponding dimension of the cavity to be formed.
In another aspect, the invention features a method for molding a fastener element having a predetermined shape, including: (a) providing a mold body having a surface; (b) providing a shaped electrode having a length at least as deep as the cavity to be formed and having at least one transverse dimension smaller than the corresponding dimension of the cavity to be formed, the shape of the electrode selected to enable the predetermined shape of the cavity to be described by motions of the electrode; (c) moving the shaped electrode into the surface of the mold body to form an initial chamber in the mold body; (d) moving the shaped electrode within the initial chamber in a set of motions to form the a stem portion and a head portion corresponding to the predetermined shape of the fastener element and to enlarge the initial chamber to form the cavity; (e) returning the shaped electrode to remove the shaped electrode from the mold body; (f) delivering moldable resin to the cavity such that moldable resin is forced into the cavity; (g) solidifying the resin in the cavity to form a fastener element; and (h) removing the fastener element from the cavity.
Preferred embodiments include one or more of the following features. The predetermined shape includes a stem and a head, the head being shaped for engagement with a loop of a hook and loop fastener.
Other features and advantages of the invention will be apparent from the following description of a presently preferred embodiment, and from the claims.
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Fish & Richardson P.C.
McDowell Suzanne E.
Vargot Mathieu D.
Velcro Industries B.V.
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