Roll-molding
Discrete male touch fastener elements are molded of thermoplastic resin extending from a common, flexible base sheet, by introducing molten resin to a molding nip between two counter-rotating rolls consisting of a mold roll and a pressure roll arranged such that their rotation axes are parallel and together define a common plane containing each of the rotation axes. Solidified resin is stripped from molding cavities of the mold roll after the cavities have passed a rotating reaction roll forming a pressure nip with the mold roll. The reaction roll is spaced from the pressure roll by a distance less than an outer diameter of the mold roll, and the mold roll is simultaneously held against both the pressure roll and the reaction roll in a non-planar roll stack.
1. A method of molding discrete features of thermoplastic resin extending from a common, flexible base sheet, the method comprising
introducing molten resin to a molding nip between two counter-rotating rolls consisting of a mold roll and a pressure roll, each of the mold roll and pressure roll defining and rotatable about a respective rotation axis, the mold roll and pressure roll arranged such that their rotation axes are parallel and together define a common plane containing each of the rotation axes, the mold roll having an axle supported by a frame;
filling, with the introduced resin under pressure applied at the molding nip, molding cavities extending into the mold roll as the mold roll rotates;
solidifying resin in the filled molding cavities, and then
stripping the solidified resin from the molding cavities as the mold roll continues to rotate;
wherein the solidified resin is stripped from the molding cavities after the filled molding cavities have passed a rotating reaction roll forming a pressure nip with the mold roll, the reaction roll spaced from the pressure roll by a distance less than an outer diameter of the mold roll and rotatable about an axis spaced from the common plane; and
wherein the mold roll is simultaneously held against both the pressure roll and the reaction roll while the resin solidifies through more than 180 degrees of mold roll rotation before being stripped, such that during filling the molding cavities the frame applies a load to the axle to urge the mold roll toward both the pressure roll and the reaction roll to maintain pressure in the molding and pressure nips.
2. The method of claim 1 , further comprising introducing a pre-formed sheet material into the pressure nip with the molten resin, such that the sheet material is laminated to the resin in the pressure nip and is carried about the mold roll with the solidifying resin and stripped from the mold roll with the solidified resin.
3. The method of claim 2 , wherein the molten resin is introduced continuously to the nip and forms a longitudinally continuous layer laminated to the sheet material.
4. The method of claim 2 , wherein the molten resin is introduced in multiple parallel flows to one or more pressure nips and forms multiple layers of resin spaced apart across the sheet material.
5. The method of claim 2 , wherein the sheet material comprises a fabric.
6. The method of claim 5 , wherein the fabric comprises a non-woven fabric, the method comprising causing molten resin to encapsulate surface fibers of the non-woven fabric as the molding cavities are filled.
7. The method of claim 5 , wherein the fabric has a surface comprising hook-engageable fibers, the method further comprising forming fiber-engaging structures from resin solidified in the molding cavities.
8. The method of claim 1 , wherein the cavities are arranged in an array about a peripheral surface of the mold roll.
9. The method of claim 1 , wherein the cavities are each shaped to mold at least a stem of a fiber-engaging structure.
10. The method of claim 1 , wherein the introduced resin forms a layer disposed on a peripheral surface of the mold roll and interconnecting the filled cavities, the layer solidifying and passing through the pressure nip before being stripped from the peripheral surface.
11. The method of claim 1 , wherein the mold roll is a non-driven roll rotated by torque imposed at one or more of the pressure and molding nips.
12. The method of claim 1 , wherein the pressure and mold rolls are arranged such that the common plane is essentially horizontal, the molten resin being fed to the molding nip by gravity from an exposed extrusion nozzle.
13. The method of claim 1 , wherein the mold roll is simultaneously held against both the pressure roll and the reaction roll while the resin solidifies through between 190 and 300 degrees of mold roll rotation before being stripped.
14. The method of claim 1 , wherein the frame is a movable frame, the method comprising moving the frame with respect to the pressure and reaction rolls to pull the mold roll toward both the pressure roll and the reaction roll to generate pressure in both the molding nip and the pressure nip.
15. The method of claim 14 , wherein the mold roll is one of multiple mold rolls mounted on respective, independently movable frames, the method comprising independently moving each frame with respect to the pressure and reaction rolls to generate pressure between a respective one of the multiple mold rolls and the pressure and reaction rolls.
16. The method of claim 15 , wherein the independently movable frames extend between the reaction and pressure rolls.