Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-10-14
2002-11-19
Eashoo, Mark (Department: 1732)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S309900, C264S167000, C264S313000
Reexamination Certificate
active
06482286
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improved equipment and methods for making continuous fastener products and the like, and to products produced by the equipment and methods.
Fastener products, such as hook components of hook-and-loop fasteners, are manufactured by a continuous molding method employing a cylindrical mold roll which has fastener-shaped cavities formed in its periphery. Often the mold roll is formed of an axially compressed stack of ring-form mold plates. In operation, molten polymer from an extruder is introduced into a pressure zone in which the molten polymer is forced under high pressure into the fastener cavities of the cooled mold roll, to form fastener elements (e.g. hooks) integrally molded with a base layer. In some cases the pressure zone is a nip formed by a mold roll and an adjacent pressure roll. In other configurations the pressure zone is formed between a conforming stationary pressure head and a mold roll. Typically, the smaller the fastener elements (or the like), the faster the optimal production speed. The more viscous the resin, or the lower the temperature of the cooled roll, the higher must be the pressure achieved in the pressure zone in order to make a satisfactory product. Typically, mold rolls of about 10 inch diameter and 12 inches in axial length have been employed.
SUMMARY OF THE INVENTION
We have realized that many advantages can be obtained by employing longer mold rolls and correspondingly wide pressure zones to form wide products, while providing means to accommodate effects of the distribution of pressure along the length of the mold roll. By this means, products molded with wide widths can have uniform product thickness and other properties previously found only in narrower materials.
We also have realized that many advantages can be obtained by raising the pressure in the pressure zone, with a conventional roll or a longer roll, to form products having finer features while providing means to accommodate effects of the distribution of pressure along the length of the mold roll.
We have realized that, because of the construction of the molding region of the mold roll as a stacked series of rings or plates about a central shaft, the mold roll has limited bending resistance. As a result, if the molding region of the mold roll is made long to produce a wide product, or if the pressure of the resin is increased, the tendency of the mold roll to bend away from the pressure zone under the extreme molding pressure can cause small separations between adjacent mold plates and undesirable base layer thickness variation across the width of the product (i.e. gap variation along the length of the molding region). Also, we realize that nonuniform geometry of the pressure zone can produce detrimental nonuniformity in the pressure distribution across the pressure zone, which can lead to incomplete filling of some of the mold cavities.
According to one aspect of the invention, improvements are made in an apparatus for continuously molding fastener elements integral with a base web from a flowable resin. The apparatus comprises a cylindrical mold roll rotatable about an axis and defining small fastener element-shaped mold cavities in the surface thereof, and pressure-applying means to apply elevated operating pressure to force the resin into the cavities at a pressure zone. The pressure-applying means and mold roll define a mold gap therebetween for forming the base web. The provided improvements include means to maintain the mold gap at a desired thickness profile across the length of the molding region under operating pressure that would otherwise tend to produce gap variations.
The provided improvements are particularly useful if the molding region of the mold roll is lengthened to about 12 inches or more or if the operating pressure is raised to higher levels, such that the mold roll is subject to loads in the range of about 1000 to 1600 pounds per lineal inch along the mold roll.
In a preferred configuration, the mold roll comprises an axially arranged stack of a large multiplicity of disks, at least many of which have mold cavities at their peripheral surfaces.
In certain advantageous embodiments, the means to maintain the mold gap comprises a moving support member on the side of the mold roll generally opposite the pressure-applying means. The support member is disposed to engage the peripheral surface of the mold roll with sufficient force to resist radial deflection of the mold roll. Preferably a support member controller is provided to vary the amount of engagement between the mold roll and the support member in response to operating conditions.
In certain embodiments, the apparatus includes a sensor to provide operating condition information to a support member controller. In some cases the sensor is constructed to detect the presence of molded resin on the peripheral surface of the mold roll and the controller is constructed to disengage the support member from the peripheral surface of the mold roll when resin is not present. In certain arrangements, the sensor is constructed to respond to a condition of the apparatus that is related to the pressure in the pressure zone.
In some preferred embodiments of the invention the depth of the mold cavities from the surface is between about 0.004 and 0.035 inches, preferably between about 0.005 and 0.020 inches, and more preferably between about 0.006 and 0.012 inches.
Broadly, the invention relates to completed fastener elements and to components or preforms that form a part of, or are modified to form, a completed fastener. The term “fastener element” as used herein is intended to include all of these forms.
In some embodiments, however, the mold cavities preferably define the shape of functional fastener elements. In some preferred arrangements the mold cavities at least partially define the shape of loop or fiber-engaging hook elements, each element having a pedestal or stem portion and at least one head portion that projects to a side of the pedestal or stem portion. In other arrangements, the fastener elements are of mushroom shape or of stem-shaped preforms that are subsequently processed to form mushrooms or other elements having flat or rounded heads.
In some particularly useful embodiments, the support member that engages the mold roll has a peripheral surface that is resiliently deformable to conform, in the vicinity of its engagement with the mold roll, generally to the peripheral surface of the mold roll. In some of these instances, the portion of the support member that directly contacts the surface of the mold roll is of a resilient substance, preferably an elastomeric material.
In some preferred embodiments the support member comprises a generally cylindrical roll arranged to rotate about an axis of rotation, while in some other embodiments the support member comprises a belt supported to engage the mold roll with substantial pressure.
In some embodiments the means to maintain the mold gap comprises adjustable structure to elastically deform the shape of the pressure-applying means, to conform to axial deflection of the mold roll. In some cases, the pressure-applying means comprises a pressure roll, the mold gap comprises a nip between the mold roll and pressure roll, and the means to elastically deform the shape is constructed to bend the axis of the pressure roll to maintain the mold gap. In some other cases, the pressure-applying means comprises a nozzle assembly for introducing the resin to the pressure zone under pressure, the mold gap comprises a gap between this nozzle assembly and the mold roll, and the means to elastically deform the shape is constructed to bend the nozzle assembly along the length of the mold gap to maintain the mold gap.
In some preferred embodiments the pressure-applying means comprises a pressure roll rotatable about an axis and positioned to form a nip with the mold roll to provide the mold gap. The means to maintain the mold gap includes a controller to vary the angle between the axes of the pressure and mold rolls to introduc
Formato Richard M.
Harvey Andrew C.
Jens Stephen C.
Kingsford Howard A.
Neumann J. Scott
Eashoo Mark
Fish & Richardson P.C.
Velcro Industries B.V.
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