Plastic and nonmetallic article shaping or treating: processes – Forming continuous or indefinite length work – Of varying cross-sectional area or with intermittent...
Reexamination Certificate
1999-02-25
2002-08-13
Eashoo, Mark (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Forming continuous or indefinite length work
Of varying cross-sectional area or with intermittent...
C264S172190, C264S173100, C264S177190, C264S210100, C264S210500, C264S213000, C264S214000, C264S313000, C264S318000, C264S334000
Reexamination Certificate
active
06432339
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the continuous molding of fastener products, such as those having a multiplicity of miniature fastening elements extending from a common sheet-form base.
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 “crooks”, such as the hook 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 (the full disclosure of which is hereby incorporated herein by reference as if fully set forth). 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 (or rings) 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. Molten resin is introduced to the rotating mold roll and forced into the cavities to form the fastener elements while a layer of the resin on the circumference of the roll forms the integral strip-form base. The mold roll is cooled (e.g., by circulating a liquid coolant through the barrel) to sufficiently solidify the fastener elements to enable them to be stripped from their cavities before making a complete revolution about the mold roll. Thus, in prior implementations of the Fischer process the production speeds obtainable for a given diameter mold roll have been limited by the required “residence time” of the cooling fastener elements in their cavities to enable successful withdrawal. Over-chilling the mold roll to reduce the required residence time can impede proper filling of the cavities by solidifying the resin as it is forced into the cavities.
Another implementation of the general Fischer process, also using stacked mold plates in the form of a multi-plate mold roll apparatus for continuously molding fastener products is described by Murasaki et al. in U.S. Pat. No. 5,441,687.
Multi-plate mold rolls are more prone to bending deflection caused by molding pressures than solid rolls of similar diameter. Such bending deflection can result in undesirable base thickness variation across the width of the fastener product at higher molding pressures.
In U.S. Pat. No. 3,594,863 George Erb discloses a different method and apparatus for molding hook-type fastener elements without employing a mold roll. Erb forms his hooks in cavities partially defined by grooves cut into a moving belt, by injecting molten nylon against the belt (i.e., from the “hook side” of the resulting product), thereby forming narrow ribbons, each ribbon having only two rows of hooks, one row extending from each of its longitudinal edges. To form a useful sheet of fastener product having an entire two-dimensional array of hooks (i.e., of many rows of hooks), Erb laminates many individual ribbons to a preformed base sheet.
SUMMARY OF THE INVENTION
We have realized that touch fastener products, with either hook-type or mushroom-type fastener elements integrally molded with a solid base and arranged in wide arrays, can be formed in a continuous process by molding the fastener elements and base together on a moving belt defining an entire array of cavities.
According to a first aspect of the invention, a method is provided for continuously forming a fastener product having an array of fastener elements extending from a continuous, sheet-form base. The method includes the steps of:
(1) providing a mold belt defining a two-dimensional array of cavities extending from an outer surface of the belt;
(2) training the mold belt in a loop about first and second rolls;
(3) introducing molten plastic resin to the outer surface of the mold belt;
(4) forcing the plastic resin into the cavities of the belt under pressure in a gap to fill the cavities while forming the sheet-form base of the product on the outer surface of the belt;
(5) solidifying the resin as the resin is carried on the belt; and then
(6) stripping the solidified resin from the mold belt, the mold belt continuing along its loop and returning to the gap.
In some embodiments, the cavities of the belt are shaped to mold hook-type fastener elements having distal ends extending toward the sheet-form base. In some other embodiments, the cavities of the belt are shaped to mold mushroom-type fastener elements having heads overhanging the sheet-form base in multiple directions.
Preferably, the cavities of the belt are sized to mold fastener elements of less than about 0.050 inch in total height, as measured from the product base (more preferably, less than about 0.020 inch in total height).
In some embodiments, the mold belt includes a belt-form substrate and plating material deposited upon one side of the substrate in a predetermined pattern to form the fastener element-shaped cavities.
In some cases, the cavities of the mold belt extend only partially through the mold belt.
In some arrangements, the plastic resin is forced into the cavities under pressure at a nip defined between the first roll (which may be driven) and a pressure roll.
In some embodiments, the method also includes cooling the mold belt away from the gap.
In some embodiments, the cavities of the mold belt extend completely through the mold belt.
For some applications, the method also includes timing the mold belt to the first roll such that the cavities of the mold belt align with dimples in the surface of the first roll. The step of forcing plastic resin into the cavities includes filling the dimples of the first roll through the aligned cavities to form fastener element heads while forming corresponding fastener element stems in the aligned belt cavities.
In some other embodiments, the method includes timing the mold belt to the first roll such that the cavities of the mold belt align with protrusions extending from the surface of the first roll. The protrusions extend into the aligned cavities as the resin is forced into the cavities, to form fastener elements with heads defining top recesses formed by the protrusions.
In some configurations, the step of stripping the solidified resin from the mold belt includes passing the belt about the second roll, the second roll having projections arranged to push the resin from the belt cavities. The second roll is timed to the mold belt to align the projections with the belt cavities.
In some cases, the gap is defined adjacent the first roll, such as between the first roll and a pressurized extruder.
In some embodiments, the method includes introducing a backing material to the resin in the gap, whereby the backing material is laminated to one side of the sheet-form base of the product.
In some cases, the method includes cooling the resin as it is carried on the belt.
The mold belt comprises metal in some instances, the cavities forming holes extending through the belt.
In some arrangements, the belt includes solidified resin molded to define the cavities.
In some embodiments, the belt has a series of rigid mold plates, each mold plate having an exposed edge defining a row of the cavities. The mold plates are spaced apart and held together by flexible resin in the form of a continuous belt.
According to a second aspect of the invention, a method is provided for continuously forming a fastener product having an array of fastener elements extending from a continuous, sheet-form base. The method includes the steps of:
(1) providing a mold belt defining an array of cavities extending from an outer surface thereof;
(2) training the mold belt about first and second rolls;
(3) forcing molten plastic resin into
Babineau James W.
Clune William
Jens Stephen C.
Provost George A.
Eashoo Mark
Velcro Industries B.V.
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