Plastic and nonmetallic article shaping or treating: processes – With step of making mold or mold shaping – per se – Utilizing surface to be reproduced as an impression pattern
Reexamination Certificate
1999-02-25
2001-07-10
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of making mold or mold shaping, per se
Utilizing surface to be reproduced as an impression pattern
C264S221000, C425S363000, C425S471000, C205S070000, C205S164000, C205S165000, C205S167000, C205S169000, C427S099300
Reexamination Certificate
active
06258311
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the forming of miniature mold cavities for molding small features integral with a base sheet, and has particular application to the production of touch fasteners and the like.
Touch fastener products have arrays of miniature fastener elements (for instance, hook-shaped or mushroom-shaped elements) extending from a common base. Typically, in order to be capable of engaging a loop fiber or another fastener element, these fastener elements have overhanging portions, such as the crook portion of a hook-shaped element or the underside of the head of a mushroom-shaped element. These crooks snag and retain loop fibers, for instance, to form a fastening, but can be challenging to mold in their fully functional form in non-opening mold cavities.
One solution for continuously molding such fastener elements for touch fasteners and other products was disclosed by Fischer in U.S. Pat. No. 4,794,028. In commercial implementations of his solution, a cylindrical, rotating mold roll is composed of a large number (e.g., thousands) of thin, disk-shaped mold plates and spacer plates which are stacked concentrically about a central barrel. Extending inwardly from the periphery of the mold plates are cavities for molding the hook elements. These mold cavities are composed of contoured mold surfaces in the mold plates in combination with flat side surfaces of adjoining spacer plates. To produce mold plates for current production machines, each contoured mold surface is typically formed by electro-discharge machining (EDM) methods.
SUMMARY OF THE INVENTION
We have realized that fastener element mold cavity surfaces can be accurately formed at reasonable cost by controllably building up mold material in patterned layers, such as by plating techniques, or by depositing a thick stratum of plating material over an array of fastener elements and then removing the fastener elements to leave shaped cavities within the plating material.
According to one aspect of the invention, a method is provided for producing a mold surface defining an array of blind cavities extending from the mold surface, for molding a corresponding array of fastener elements integrally with and extending from a fastener product base. The method includes the steps of:
(1) depositing a layer of plating material on a master having an array of fastener elements extending to a given height from a surface of the master, the layer of plating material being deposited to a thickness greater than the height of the fastener elements of the master; and then
(2) removing the master from the plating material, leaving an array of shaped cavities extending into the plating material from the mold surface, the array of cavities configured for integrally molding a corresponding array of fastener elements with a product base formed on the mold surface.
In some embodiments, the cavities are hook-shaped.
In some particularly useful embodiments, the deposited plating material forms a cylindrical mold sleeve with the blind cavities extending inward from its outer surface. At least some (or all) of the blind cavities may define crooks extending in the axial direction of the mold sleeve. The blind cavities may extend in the axial direction of the mold sleeve are arranged in rows, the crooks of cavities of alternating sets of the rows extending in opposite directions.
In some cases the blind cavities are arranged in an array extending about the entire circumference of the mold sleeve, or are arranged in rows which spiral about the circumference of the mold sleeve.
In some embodiments, the master is in the form of a flexible strip of fastener product having an array of fastener elements integrally molded with a strip-form base, the method including, before the step of depositing plating material, the step of attaching the master to an inner cylindrical surface of a plating fixture.
At least some (or all) of the fastener elements of the master may extend in the axial direction of the cylindrical surface of the plating fixture, or may be arranged in rows that spiral about the circumference of the cylindrical surface of the plating fixture.
In some embodiments, the master is in the form of multiple flexible strips of fastener product, each having an array of fastener elements integrally molded with a strip-form base, the method including, before the step of depositing plating material, the step of attaching the flexible strips of fastener product to an inner cylindrical surface of a plating fixture in an arrangement in which at least some of the fastener elements of the strips extend in the axial direction of the cylindrical surface of the plating fixture. The fastener elements of adjacent strips of fastener product may extend in opposite directions.
In some embodiments, the master is in the form of multiple injection molded inserts, each insert having an array of flexible fastener elements integrally molded with and extending from a substantially rigid arcuate base, the method including, before the step of depositing plating material, the step of arranging the inserts about an inner cylindrical surface of a plating fixture to form a continuous master ring. In some cases, the inserts are molded with complementing tapered sides.
In some embodiments, the master is in the form of a continuous molded hook ring, the array of fastener elements of the master extending radially inward from an inner surface of the hook ring. The molded hook ring can be formed by the process of:
(1) molding a cavity transfer master against a fastener product having an array of flexible fastener elements extending from the product;
(2) removing the fastener product from the molded cavity transfer master, leaving an array of shaped cavities extending into the cavity transfer master corresponding to the fastener elements of the fastener product;
(3) molding the molded hook ring in cylindrical form against the cavity transfer master, the fastener elements of the molded hook ring being formed in the shaped cavities of the cavity transfer master; and
(4) removing the molded hook ring from the cavity transfer master.
In some cases, the cavity transfer master is molded as a flexible strip, the method including the step of wrapping and retaining the cavity transfer master about a mandrel, with its cavities facing outward, before the step of molding the molded hook ring.
In some other cases, the cavity transfer master is molded as a continuous cavity ring.
The molded hook ring is removed from the cavity transfer master, in some embodiments, by melting the cavity transfer master, which may be molded of either low-temperature castable metal or non-sulphur wax.
In some embodiments, the master comprises a strip of fastener product insert-molded into a rigid support sleeve in a stretched condition with its fastener elements extending radially inward and exposed for plating.
The master is formed, in some cases, by the steps of:
(1) joining opposing ends of the strip of fastener product about an expandable mandrel to form a cylindrical strip of fastener product having fastener elements facing radially inward toward the mandrel;
(2) radially expanding the mandrel to stretch the fastener product and retain the fastener product in a cylindrical form;
(3) solidifying support material about the stretched fastener product, the support material adhering to the fastener product; and thereafter
(4) radially collapsing the expandable mandrel, the fastener product retained in its stretched, cylindrical form by the solidified support material.
The width of the solidified support material may be trimmed to the axial width of the stretched fastener product, such that the fastener product strip of the master has two exposed circumferential edges. Thereafter, multiple masters of equal diameter may be arranged concentrically to form an elongated master sleeve, the plating material being deposited simultaneously on the multiple masters to form a single, elongated mold sleeve.
In some embodiments, the method also includes, after the step of depositing plating material, the
Babineau James W.
Banker Shawn C.
Buzzell Keith G.
Dowd Clinton
Filion Scott M.
Eashoo Mark
Fish & Richardson P.C.
Silbaugh Jan H.
Velcro Industries B.V.
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