Method for perforating tissue sheets
View Patent ↗Curvilinear or other complex perforation patterns for paper products, such as paper towels and bath tissue, can be produced using a differential speed perforation nip formed between a rotating pattern roll and a moving anvil surface. The relative speed between the perforation elements on the surface of the pattern roll and the anvil surface shears the web at the perforation points.
1. A method of perforating a paper web comprising:
(a) carrying a moving paper web over a rotating pattern roll having protruding perforation elements which protrude from the surface of the pattern roll and are arranged on the surface of the pattern roll in a perforation pattern, whereby one side of the paper web is in contact with and supported by the surface of the pattern roll and wherein the angle of wrap of the paper web around the pattern roll is about 180 degrees or greater, said paper web and the surface of the rotating pattern roll moving at the same speed; and
(b) passing the paper web through nips formed between the protruding perforation elements and a moving anvil surface which is traveling at a speed that is faster than the speed of the paper web, whereby the paper web is locally sheared and perforated in the nips to create a perforation pattern in the web.
2. The method of claim 1 wherein the anvil surface is traveling from about 1 to about 20 percent faster than the speed of the paper web.
3. The method of claim 1 wherein the anvil surface is traveling from about 5 to about 20 percent faster than the speed of the paper web.
4. The method of claim 1 wherein the anvil surface is traveling from about 10 to about 20 percent faster than the speed of the paper web.
5. The method of claim 1 wherein the anvil surface is traveling from about 10 to about 15 percent faster than the speed of the paper web.
6. The method of claim 1 wherein the anvil surface is a moving belt.
7. The method of claim 1 wherein the anvil surface is a rotating anvil roll.
8. The method of claim 7 wherein the anvil roll has a hardened steel surface supported by a resilient material.
9. The method of claim 8 wherein the resilient material is rubber.
10. The method of claim 1 wherein the perforation elements are supported by resilient material.
11. The method of claim 10 wherein the resilient material is rubber.
12. The method of claim 10 wherein the resilient material is an inflatable bladder.
13. The method of claim 1 wherein the coefficient of friction between the surface of the pattern roll and the paper web is of about 0.3 or greater.
14. The method of claim 1 wherein the coefficient of friction between the surface of the pattern roll and the paper web is from about 0.3 to about 1.5.
15. The method of claim 1 wherein the angle of wrap of the paper web around the pattern roll is from about 180 to about 330 degrees.
16. The method of claim 1 wherein ink is printed onto the paper web along the perforation pattern.
17. The method of claim 1 wherein debonder is printed onto the paper web along the perforation pattern.