Stretchable Fastener Stringer with Bulging Ratio
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Solution Overview
Problem
Existing slide fasteners tend to experience chain breaking when the element rows are subjected to a pushing force, especially in stretchable clothing applications, due to the expansion of the pitch between fastener elements, leading to disengagement of coupling heads and instability in the coupled state.
Innovation Solution
A stretchable fastener stringer configuration is introduced, where the bulging ratio of the coupling head to the leg portion is set between 1.80 and 2.33, and the coupling ratio is set between 1.23 and 1.50, with a stretchable core thread inserted between the upper and lower leg portions of the fastener element, ensuring stable engagement of coupling heads even under pushing force, preventing chain breaking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the element attaching portion is configured to be non-stretchable to prevent chain breaking, then the reliability of the fastener is improved, but the adaptability to stretchable clothes is worsened
Solution Approach 1:
The fastener tape is designed with different stretchability characteristics in different regions: the tape main portion has high stretchability (10% or more) to adapt to stretchable clothes, while the element attaching portion has limited stretchability (less than 10%) to prevent chain breaking. This local differentiation of mechanical properties resolves the contradiction between reliability and adaptability.
2Adaptability or versatility
If the element attaching portion is configured to be stretchable to improve adaptability to stretchable clothes, then the adaptability is improved, but the reliability is worsened due to chain breaking
Solution Approach 1:
The invention changes the stretchability parameter of the element attaching portion by controlling the weaving structure and yarn selection to achieve less than 10% stretchability, while the tape main portion maintains 10% or more stretchability. This parameter differentiation prevents chain breaking while maintaining adaptability to stretchable clothes.
3Adaptability or versatility
If the pitch between fastener elements is increased to allow stretching, then the adaptability is improved, but the stability of coupled state is worsened leading to disengagement
Solution Approach 1:
The invention designs the coupling head dimensions beforehand to provide a sufficient engagement buffer. The coupling head length is set to be 0.8mm or more, and the leg portion length is controlled to ensure that even when the pitch expands during stretching, the coupling heads remain engaged. This pre-designed dimensional buffer prevents disengagement while allowing stretching.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed configuration effectively maintains the coupled state of element rows by allowing the fastener chain to stretch and return to its original dimension, preventing chain breaking and ensuring smooth operation of the slide fastener, while avoiding overlapping of coupling heads and maintaining operability.
Implementation Method 1
adding appropriate stretchability to the tape main portion of the fastener tape in the tape longitudinal direction by utilizing elastic yarns
Implementation Method 2
The core thread is configured so that an elastic yarn is covered with a cover layer which is formed of a polyester bulky processed yarn (non-elastic yarn)
Implementation Method 3
The core thread is configured so that an elastic yarn is covered with a cover layer which is formed of a polyester bulky processed yarn (non-elastic yarn)
Data Source
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Figure 5
AI summary
The present invention provides a stretchable fastener stringer for a slide fastener in which an element row is attached to a stretchable fastener tape, the slide fastener being capable of preventing occurrence of chain breaking even when coupled element rows receive pushing force and capable of stably maintaining a coupled state of the element rows. The stretchable fastener stringer according to the present invention includes a fastener tape (2) having a tape main portion (2a) and an element attaching portion (2b) and a continuous fastener element (3) which is attached to the element attaching portion (2b). The fastener tape (2) has stretchability due to an elastic yarn (8) being combined by weaving or knitting and the fastener element (3) includes a coupling head (3a), upper and lower leg portions (3b, 3c) which are extended from the coupling head (3a) and a connecting portion (3d) which connects the upper and lower leg portions (3b, 3c) therebetween of adjacent fastener elements (3). In this fastener stringer (1), a value of a bulging ratio (= mountain length H / leg portion length d) which is the ratio between a dimension of the coupling head (3a) in the tape longitudinal direction (= mountain length H) and a dimension of the upper and lower leg portions (3b, 3c) in the tape longitudinal direction (= leg portion length d) is set to be larger than 1.80 and not larger than 2.33.