Molding of fastening hooks and other devices
View Patent ↗Methods of forming mold cavities suitable for hook and loop fastening are disclosed, along with effective hook construction and hook and loop fastener products that have an ultrathin cross-section. Photochemical techniques are employed to form plates that define hook-form mold cavities, and, alternatively, chemical etching is employed following preforming of the cavities and machining. Hooks having three-dimensional tapers with enhanced loop engaging characteristics are disclosed. By utilization of special surface finishes and tolerances, hook fasteners, having ultrathin cross-sections are realized, that pave the way for practical use of touch fasteners in a wide range of new areas.
1. A method of forming a multiplicity of elements with stems integrally molded with and extending from a common strip-form base, the method comprising
providing a molding apparatus including
a series of circular mold plates held together face to face to form a rotating cylindrical mold roll defining, at outer edges of the plates, rows of mold cavities extending into the mold roll for molding the elements, and
an opposed forming member having a surface defining, together with the edges of the plates, a mold gap for forming the strip-form base integral with the molded stems when moldable resin is applied to the gap under conditions that cause the resin to fill the mold cavities, wherein
the mold cavities extend into the mold roll to a depth of less than about 0.025 inch; and
the gap has a nominal thickness of less than about 0.003 inch, for forming a correspondingly thin fastener tape;
supplying a continuous flow of resin to the gap under conditions causing the resin to fill the molding cavities;
cooling the resin on the rotating mold roll; and then
stripping the cooled resin from the mold roll.
2. The method of claim 1 wherein the resin has a melt flow index greater than 5.
3. The method of claim 2 wherein the resin has a melt flow index greater than 10.
4. The method of claim 3 wherein the resin has a melt flow index greater than 20.
5. The method of claim 1 wherein the molding cavities are shaped to form fastener elements.
6. The method of claim 5 wherein the molding cavities are hook-shaped.
7. The method of claim 1 wherein the resin has a tensile yield strength of about 5,000 to 5,300 pounds per square inch.
8. The method of claim 1 wherein the resin has an elongation of at least 10 percent.