Method and apparatus for zig-zag folding

Claim 1

In a method for zig-zag folding a web wherein a web is fed between a pair of rotating folding members, each member having at least one tucker and one gripper, said gripper having an anvil and a gripper element, all of said tucker, gripper anvil and gripper element being shaped to define a tip on each, said members being disposed relative to each other to position the tucker of one member in web tucking engagement with the gripper of the other member to cooperate in folding said web, the steps of perforating an elongated web along a plurality of longitudinally spaced apart transversely extending lines, advancing said web at a given speed between said members, moving the tucker of one member between an anvil and gripper element on the other member to fold the web substantially along a perforation line while maintaining each of said gripper anvil tip and gripper element tip a constant distance from the tip of said tucker during entry of said tucker into said gripper, repeating the above step of folding at succeeding perforation lines to form a zig-zag folded stack, said gripper anvil tip rotating at a speed equal to the web given speed, visually ascertaining the presence of lean in said stack, and angularly shifting the tucker of one member relative to the anvil and gripper element of the other to eliminate said lean.