APET Foam Bag Closures for Machine Breakability
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Solution Overview
Problem
Existing bag closures made of high-impact polystyrene (HIPS) break off quickly in closing machines and are costly due to material limitations, with HIPS being difficult to improve for strength and toughness, and availability issues leading to high costs and sealing challenges.
Innovation Solution
A strip of flat bag closures made from foamed amorphous polyethylene terephthalate (APET) plastic foam, which provides the desired fracture behavior and is more cost-effective, with a closed-cell structure and improved sealability, allowing for 'tamper-proof' closures and reusability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If HIPS is used for bag closures, then the closures are easy to manufacture, but the tensile strength is insufficient and the cost is high
Solution Approach 1:
The patent changes the material parameters by transitioning from solid HIPS to foamed PET, adjusting density, tensile strength, and fracture characteristics to achieve optimal breaking behavior in closing machines while reducing cost
Solution Approach 2:
The invention uses foamed PET as a composite material structure that combines the benefits of foam (cost-effectiveness, appropriate fracture behavior) with the necessary mechanical properties for machine processing, replacing the homogeneous HIPS structure
2Reliability
If HIPS is used for bag closures, then the closures are easy to manufacture, but the sealability is poor
Solution Approach 1:
The patent changes the material composition from HIPS to foamed PET, which has superior sealability characteristics while maintaining ease of manufacture through established foam sheet production and stamping processes
3Strength
If the coupling parts are strongly connected, then the strip remains intact during feeding, but the closures cannot be broken off in the machine
Solution Approach 1:
The patent applies different mechanical properties to different parts of the closure structure: the coupling parts are designed with specific fracture characteristics that allow controlled breaking, while the body maintains integrity during feeding, achieving both secure transport and easy separation
Solution Approach 2:
The invention optimizes the fracture parameters of the coupling parts by using foamed PET material with appropriate tensile strength and elongation characteristics, enabling the coupling to remain intact during feeding but break cleanly during the closing machine operation
4Ease of operation
If the coupling parts are weakly connected, then the closures can be broken off easily, but they detach prematurely during feeding
Solution Approach 1:
The patent designs the coupling parts with specific local mechanical properties that provide sufficient strength for feeding while allowing controlled breaking, achieving both strip integrity during transport and easy separation during operation
Solution Approach 2:
The invention optimizes the mechanical parameters of the coupling parts through material selection (foamed PET) and geometric design, creating a balance between coupling strength for feeding and fracture ease for separation
Data Source
Figure 1
AI summary
The invention relates to a strip (10) of flat closures (12) coupled together, made of plastic, wherein each closure (12) comprises a body (14) with an opening (16) therein for receiving and holding the access side (18) of a flexible packaging, as well as a slot (22), delimited by leg parts (20), which extends between the perimeter of the body (14) and the opening (16), and coupling parts (32a, 32b) for coupling to an adjacent closure, wherein the plastic is a plastic foam. A strip of this kind displays good fracture behaviour in existing closing machines.