Variable Wall Thickness Drinking Straw Extrusion
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Solution Overview
Problem
Existing methods for producing hollow tubes, such as drinking straws, often result in wave-form or unstable products, lacking the desired quality and smoothness.
Innovation Solution
A device comprising two format devices arranged one behind the other, where the first device forms a hollow tube and the second device wraps a second material strip around it, creating a double-layered tube with a longitudinal seam, ensuring stability and smoothness through precise alignment and adhesive application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a tube of uniform wall thickness is produced by conventional extrusion, then the manufacturing process is simple, but the tube cannot be used for drinking because it makes a unpleasant noise when sipped through
Solution Approach 1:
The patent applies local quality by varying the wall thickness along the length of the tube. The extrusion die includes a mandrel with varying cross-sectional area that creates a tube with thinner wall at the drinking end and thicker wall at the closed end. This local variation in thickness eliminates the unpleasant noise when sipping while maintaining manufacturing simplicity through the extrusion process.
2Ease of operation
If the tube wall is made thinner to reduce noise, then drinking comfort improves, but the tube becomes more prone to breaking
Solution Approach 1:
The patent resolves this contradiction by making the wall thickness non-uniform. The drinking end has thinner wall (0.5-2.0 mm) for comfortable sipping without noise, while the closed end has thicker wall (2.0-5.0 mm) for structural strength and break resistance. This local quality variation allows each region to be optimized for its specific function.
Solution Approach 2:
The patent employs asymmetry by creating a tube with asymmetric wall thickness distribution along its length. The closed end has significantly thicker wall than the drinking end, breaking the symmetry of uniform thickness. This asymmetric design simultaneously achieves comfortable drinking experience and adequate structural strength.
3Ease of operation
If a conical tube is extruded, then the tube can be used for drinking without noise, but the extrusion process becomes more complex
Solution Approach 1:
The patent achieves drinking comfort without excessive die complexity by using a mandrel with a conical or frusto-conical cross-section that varies smoothly along the extrusion direction. This gradual variation in mandrel cross-sectional area creates the desired wall thickness profile while maintaining a relatively simple extrusion die structure that can be manufactured and operated efficiently.
Data Source
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AI summary
The invention relates to a device for producing hollow tubes (10), in particular drinking straws, comprising a first formatting device (11) which is designed to convey a first material strip (21) in a longitudinally axial direction and shape said strip into a first hollow tube (23) during the conveying process, wherein a second formatting device (12) is provided which is arranged behind the first formatting device (11) in the conveyor direction (20) and is designed to wind a second material strip (22) around the first material strip (21) while the second material strip (22) is being conveyed in a longitudinally axial direction such that a double-layer hollow tube (10) is formed which has the first hollow tube (23) on the inside and the second material strip (22) on the outside.