Rotatable Rolls for Perforating Web Materials
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Solution Overview
Problem
Conventional methods for perforating web materials, such as paper towels and toilet tissue, face issues with reliability, manufacturing costs, flexibility, and perforation quality due to vibrations between moving blades and stationary anvils, leading to inferior product quality, increased waste, and lengthy changeover times.
Innovation Solution
The use of rotatable male and female rolls with pockets allows for precise control of perforation patterns, enabling overstraining of the web without contact, allowing for flexible production of linear and nonlinear perforations that complement embossed or printed patterns, and enabling quick changes between perforation formats.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a moving blade and stationary anvil are used for perforating, then the perforation function is achieved, but vibrations occur at high speeds causing inferior perforation quality and web breaks
Solution Approach 1:
The patent inverts the conventional perforation approach by using two rotating rolls instead of a moving blade and stationary anvil. Both rolls rotate in the same direction at the same speed, eliminating relative motion and vibrations between opposing surfaces. The perforating elements on one roll engage with corresponding pockets on the other roll to create perforations without the harmful vibrations that occur in traditional high-speed blade-anvil systems.
2Reliability
If a moving blade is used for perforating, then perforation is achieved, but the blade becomes dull or broken requiring shutdown and replacement
Solution Approach 1:
The patent uses a copying mechanism where perforating elements on the male roll engage with corresponding pockets on the female roll. The pockets are precisely shaped to receive and guide the perforating elements, ensuring consistent perforation geometry. This copying approach eliminates blade wear and breakage issues, as the rigid pockets maintain their shape indefinitely unlike flexible blades that become dull or break.
3Adaptability or versatility
If conventional perforation equipment is used, then basic perforation is achieved, but changeover between perforation patterns requires several hours of shutdown
Solution Approach 1:
The patent implements dynamic adjustability where the spacing between perforating elements on the male roll and corresponding pockets on the female roll can be easily modified. This allows quick changeover between different perforation patterns (linear, nonlinear, cross-direction, machine-direction) by adjusting the relative positioning of the rolls or replacing modular element sets, eliminating the need for lengthy shutdown periods required by conventional fixed-pattern equipment.
4Ease of operation
If perforations are made to facilitate sheet separation, then easy tearing is achieved, but the web strength is reduced making it vulnerable during handling
Solution Approach 1:
The patent applies local quality by creating perforations with specific geometric characteristics at precise locations. The perforating elements and pockets are designed to create controlled weaknesses only at the perforation sites while leaving the bulk web material intact and strong. This allows sheets to separate easily at the perforation lines during consumer use while the web maintains sufficient strength to withstand winding, handling, and storage operations.
Data Source
AI summary
Methods are disclosed which include forming selected perforation designs and patterns. The perforation designs and patterns can be formed in linear or nonlinear fashion, can extend in the cross direction or the machine direction and can be formed to complement or match an embossed or printed design on the web. The perforation designs and patterns can be formed utilizing various mechanical perforating techniques.