Methods of making fastener products
View Patent ↗A method of forming a fastener is provided, including (a) forming, from a thermoformable material, a preform product having a sheet-form base and an array of preform stems integrally molded with and extending from the base to corresponding terminal ends; (b) heating the terminal ends of the stems to a predetermined softening temperature, while maintaining the sheet-form base and a lower portion of each stem at a temperature lower than the softening temperature; and (c) contacting the terminal ends with a contact surface that is at a predetermined forming temperature, lower than the softening temperature, to deform the terminal ends to form heads therefrom that overhang the sheet-form base. Fasteners and other methods of forming them are also provided.
1. A method of forming a loop-engaging touch fastener product, the method comprising:
providing a preform product formed of thermoformable material and having a sheet-form base and an array of preform stems integrally molded with and extending from the sheet-form base, each of the stems including a first portion joined to the base and a second portion extending from the first portion to a terminal end, an intersection of the first and second portions defining a discrete reduction in transverse cross-sectional area of the stem, measured parallel to the sheet-form base, from the first portion to the second portion, an exposed top surface of the first portion defining a shoulder; and
deforming at least some of the second portions toward the shoulder to form engaging heads configured to releasably engage a mating loop product.
2. The method of claim 1 , wherein the discrete reduction in transverse cross-sectional area occurs at a distance from a top surface of the sheet-form base of at least halfway to the terminal end of the stem.
3. The method of claim 1 , wherein a cross-sectional area taken parallel to the sheet-form base near the terminal end of the second portion is less than 50% of any cross-sectional area of the first portion, also taken parallel to the sheet-form base.
4. The method of claim 3 , wherein the cross-sectional area taken near the terminal end of the second portion is less than 25% of any cross-sectional area of the first portion.
5. The method of claim 1 , wherein each second portion projects above each first portion without overhanging the sheet-form base.
6. The method of claim 1 , wherein each first portion is substantially rectangular in shape in transverse cross-section.
7. The method of claim 1 , wherein each second portion is substantially rectangular in shape in transverse cross-section.
8. The method of claim 1 , wherein each second portion is substantially circular in shape in transverse cross-section.
9. The method of claim 1 , wherein each first portion is substantially cruciform in shape in transverse cross-section.
10. The method of claim 1 , wherein each second portion defines a pyramid shape, the intersection of the first and second portions defining a base of the pyramid.
11. The method of claim 1 , wherein each of the first and second portions have differently shaped transverse cross-sections.
12. The method of claim 1 , wherein each first portion is cruciform in shape in transverse cross-section and each second portion is rectangular in shape in transverse cross-section.
13. The method of claim 1 , wherein the deforming step includes heating the terminal ends of the second portions with a non-contact heat source.
14. The method of claim 1 , wherein the deforming step includes heating the terminal ends of the second portions with a non-contact heat source, and then contacting the terminal ends with a contact surface.
15. The method of claim 14 , wherein the contact surface is maintained at a temperature less than room temperature.
16. The method of claim 13 , wherein the non-contact heat source is positioned about 0.1 mm to about 30 mm from the terminal ends of the second portions.
17. The method of claim 13 , wherein the non-contact heat source is a flame heater.
18. The method of claim 13 , wherein the non-contact heat source is a radiant heat source.
19. The method of claim 1 , wherein the deforming step includes heating the terminal end of the second portions by contacting the terminal ends with an ultrasonic horn.
20. The method of claim 1 , wherein each head has an overhang aspect ratio, defined as an overall length of a chord extending fully across the head, in top view in a machine direction, directly above a nominal lateral-most extent of the stem, divided by a maximum lateral extent of the head in a cross-machine direction beyond the stem, of less than 4.0.
21. The method of claim 20 , wherein the overhang aspect ratio is less than 2.5.
22. The method of claim 21 , wherein the overhang aspect ratio is less than 2.0.
23. The method of claim 20 , wherein each head has a vertical head thickness, measured perpendicular to the sheet-form base from the top surface of the head to a lower surface of the head, of not more than about 0.015 inch.