Curved Flute-Forming Bars for Web Width Reduction
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Solution Overview
Problem
Conventional corrugating methods damage paperboard webs due to oscillatory frictional and tension forces, and are impractical for commercial applications as they require significant space and introduce lateral tension variations during web gathering for longitudinal corrugating.
Innovation Solution
A forming device with curved flute-forming bars that converge in the cross-machine direction to gather web width uniformly, minimizing lateral tension and friction, and a corrugating die that smoothly transitions flutes from intermediate to final geometry, maintaining consistent web width throughout processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional corrugating rollers with interlocking ribs are used to form flutes in the cross-machine direction, then flutes are successfully introduced into the web, but substantial oscillatory frictional and tension forces damage the paperboard web
Solution Approach 1:
The patent inverts the conventional corrugating approach by forming flutes in the machine direction rather than the cross-machine direction. Instead of using rotating corrugating rollers that drag the web through a labyrinth, the invention uses a stationary or slowly moving forming device with curved bars that guide the web through a gradually tightening corrugating labyrinth, allowing flutes to form as the web progresses forward without significant lateral movement.
Solution Approach 2:
The forming device employs curved bars that define a corrugating labyrinth with smooth, continuous curves rather than sharp angles or rigid structures. The curved geometry allows the web to follow a gentle path as flutes are formed, reducing friction and tension forces compared to conventional rigid corrugating rollers.
2Strength
If longitudinal corrugating is implemented to reduce web damage, then flutes extend along the machine direction improving strength, but web width must be consumed to accommodate the corrugations requiring significant gathering space
Solution Approach 1:
The curved bars in the forming device create a compact corrugating labyrinth that achieves the necessary web gathering in a short distance. The curved geometry allows for gradual convergence of the web edges without requiring long straight sections, enabling the entire corrugating process to occur within a compact footprint suitable for commercial applications.
Solution Approach 2:
The invention transitions the corrugating process from a lateral gathering approach to a longitudinal progression approach. Instead of gathering web width in the cross-machine direction over a long distance, the curved bars guide the web to follow a three-dimensional path that achieves the same gathering effect within the machine direction over a short distance.
3Productivity
If conventional corrugating rollers are used, then flutes are formed quickly, but the oscillatory nature of web tension through the corrugating labyrinth produces structural damage
Solution Approach 1:
By inverting the corrugating approach to form flutes in the machine direction rather than cross-machine direction, the patent eliminates the reciprocating motion of corrugating ribs that causes oscillatory tension. The web progresses continuously forward through the forming device while flutes form gradually, maintaining more uniform tension and reducing structural damage while preserving productivity.
Solution Approach 2:
The forming device enables continuous web progression through the corrugating process without the start-stop or reciprocating motion inherent in conventional corrugating rollers. The curved bars guide the web continuously forward as flutes are formed, eliminating oscillatory tension cycles and maintaining both productivity and web integrity.
Data Source
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AI summary
A forming device for gathering the width of a traveling web is disclosed. The forming device includes opposing arrays of flute-forming bars that can be interlaced to define therebetween a longitudinal flute-forming labyrinth effective to reduce the width of a web traveling therethrough by a preselected take-up ratio. The flute-forming bars are curved beginning at an entry end of the forming device such that they converge in a lateral direction as they proceed in the machine direction. In this manner, individual elements of the web traveling between the respective arrays in the machine direction follow contour lines along the curved bars or between adjacent ones of the curved bars so that no such element crosses any flute-forming bar in the cross-machine direction as the web travels and is fluted. A corrugating die for introducing a near-net shape to the intermediate-fluted web is also disclosed, as are a corrugating line incorporating these operations and methods for its operation.