Buckles – buttons – clasps – etc. – Including readily dissociable fastener having numerous,... – Combined with diverse fastener
Reexamination Certificate
2001-02-27
2002-11-26
Sandy, Robert J. (Department: 3677)
Buckles, buttons, clasps, etc.
Including readily dissociable fastener having numerous,...
Combined with diverse fastener
C024S452000
Reexamination Certificate
active
06484371
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to mechanical fasteners, and more particularly to mechanical fasteners having improved physical properties.
BACKGROUND OF THE INVENTION
Various types of mechanical fasteners are known to the art. Among these are the hook-and-loop type fasteners described in U.S. Pat. No. 4,775,310 (Fischer) and U.S. Pat. No. 4,872,243 (Fischer). Strip-like fasteners of this type, which comprise a large number of closely spaced hook-like projections that releasably engage loops of a companion fastener strip, are currently sold under brand names such as GET-A-GRIP®, Velcro®, and Aplix®.
While these early fasteners had some admirable properties, they also suffered from a number of infirmities. For example, early hook-and-loop type fasteners exhibited notch sensitivity, that is, a pronounced tendency to tear in one or more directions when the base film was notched or nicked by even slight tearing, or by sewing or otherwise securing the fastener to some other product. Typically, the tear would propagate between the rows of hooks.
To reduce notch sensitivity, so-called rip-stops have been integrally molded with the base of some fasteners. Rip-stops are features, typically in the form of humps or bumps, that reduce notch sensitivity by providing localized thickening of the base of the fastener. Rip-stops typically extend between, and are integrally molded with, the hooks in adjacent rows as well as the base. However, while rip-stops may be advantageous in certain applications, they add to the flex modulus, weight and bulk of the overall construction, and also inherently require additional molding provisions and the use of additional materials.
Other methods of reducing notch sensitivity have also been investigated. Thus, U.S. Pat. No. 6,035,498 (Buzzell et al.) discloses the lateral orientation of fastener preforms having discrete fastener elements integral with a base web. The preforms are laterally stretched between 2 and 10 times the width of the original preforms. These products are said to have lateral rip resistance due to the molecular orientation of the film. Moreover, the stretching is said to be capable of reducing the thickness of the base web significantly, depending on the stretch ratio. Thus, the reference notes that, while conventional fasteners have been formed with web thicknesses (between the hooks) of greater than 0.005 inches (0.127 mm), and typically 0.008 inches (0.203 mm) or more, some of the fasteners disclosed in the reference have base film thicknesses of 0.001 to 0.002 inches (0.025 to 0.051 mm). The reference also advocates the use of thermoplastic resins having a flex modulus of at least 150,000 pounds per square inch (1.03 GN/m
2
) in the constructions described therein, noting that the use of such resins provides higher fastener performance.
However, the approach suggested by Buzzell et al. also has its disadvantages. Because the fasteners disclosed in this reference are stretched laterally, they have significant notch sensitivity in this direction. This is so even if the base film is first oriented longitudinally, followed by lateral stretching. Notch sensitivity in the lateral direction is a substantial detriment in bundling applications, because the propagation of tears in the lateral direction are a common cause of fastener failure in such applications. This is especially true if the items being bundled have sharp edges.
Another problem with earlier hook-and-loop type fasteners was their tendency to cause skin irritation. This problem, which was particularly an issue when these early devices were employed in personal care products such as diapers, sanitary napkins and hospital gowns, was an artifact of the method used to manufacture them. In particular, the methodology commonly used to make hook-and-loop type fasteners often caused the bases of these fasteners to terminate in a stiff, sharp edge. Also, the hook components of these fasteners frequently had an abrasive feel when placed against the skin.
U.S. Pat. No. 5,692,271 (Provost et al.) represents one approach to providing hook and loop type fasteners with a reduced tendency to cause skin irritation. The fasteners disclosed therein have edge margins that are feathered to reduce their thickness and stiffness, which is said to result in a softer, less irritating fastener tape. The product is also provided with rip-stops that are integrally molded with the base and which are offset relative to the hook elements so as to reduce the widthwise stiffness of the product.
U.S. Pat. No. 4,894,060 (Nestegard) represents another approach at reducing the skin irritation associated with the use of mechanical fasteners. This reference discloses a disposable diaper with an improved hook fastener portion (best shown in
FIG. 2
) whose hooks terminate in a rounded edging. Such a hook, termed a low Profile Extruded Hook (PEH), was designed to have peel and shear values highest in the cross direction as opposed to the machine direction. The individual hooks are formed by notching a ridged preform and then stretching the web in the longitudinal direction.
Profile Extruded Hooks provide excellent holding power on diapers and are resistant to the wearer accidentally (or purposefully) peeling the holding tabs and thus removing the diaper. In addition, the strength of PEH in the lateral direction has been sufficient for diaper tab applications. The reference notes that, as a result of the geometry of these hooks, the hook portions do not have an abrasive feel when they come into contact with the skin. The reference also notes that the hook members are more easily and firmly engaged with many types of loop fastener portions than the hook members on known commercially available hook fastener portions, in large part because they are very small compared to them.
Various methods have also been developed for the production of hook and loop type fasteners, in addition to the methods disclosed in the above noted U.S. Pat. No. 4,775,310 (Fischer) and U.S. Pat. No. 4,872,243 (Fischer). Thus, for example, U.S. Pat. No. 5,260,015 (Kennedy et al.) and U.S. Pat. No. 5,518,795 (Kennedy et al.) describe a method for forming extruded hook fastener strips on a roll equipped with hook-forming cavities in its surface. The strips are formed by extruding a plastic material into the interface between the forming roll and a loop web carried by a backing roll. The loop web is thus firmly bonded to the hook backing on the surface opposite from the hooks.
In spite of the above noted efforts at improving mechanical fasteners and the methods for making them, however, currently existing fasteners still suffer from a number of infirmities. One such infirmity is the stiffness or flex modulus of the overall article and, in particular, of the backing material. Another infirmity is thickness. In particular, most conventional fasteners have relatively stiff (high flex modulus), thick backing materials. For example, as noted above, Buzzell et al. advocates the use in the backing materials of high modulus resins, which would be expected to assume even higher moduli subsequent to the film orientation procedures described therein. This is undesirable for a number of reasons.
First of all, it is difficult to wind a fastener with a high flex modulus backing into a tight radius, as would be required in the bundling of small items (e.g., groups of optical fibers). Even if the fastener is successfully wound into a small radius, the increased bulk usually inherent in higher modulus backings causes the fastener to contribute significantly to the overall diameter of the bundled goods. This is undesirable in many bundling applications such as the bundling of optical fibers, because the bundled item must often be stored in splice enclosures and in other areas where space is at a premium.
Moreover, a high flex modulus contributes to flagging, i.e., the tendency of the fastener to decouple from itself at the terminal end of the mating surfaces. Flagging is especially problematic in the formation of small bundles having small radii
Ausen Ronald W.
Larson Curtis L.
Mills Michael W.
Mody Kirit C.
Romanko Walter R.
Fonseca Darla P.
Rodriguez Ruth C.
Sandy Robert J.
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