Reverse-Opening Zipper Slider Structure to Reduce Pull-Up Catch

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Solution Overview

Problem

Conventional reverse opening-type slide fasteners experience significant resistance when the lower slider is pulled upward due to interference between the locking claw, insert pin, and box pin, causing a catch that burdens the user.

Innovation Solution

A separable bottom end stop is introduced, featuring a release groove on the box pin or insert pin that receives the locking claw, reducing interference by allowing the locking claw to be partially released in the width direction, thus minimizing the resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional slider structure is used, then the structure is simple, but the slider easily drops off the chain when the fastener is in the fully opened state

Engineering Contradiction:
Improveslider retentionVSAvoidslider structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

Instead of extending the slider body forward to engage the chain, the patent inverts the approach by extending the chain engagement element backward toward the slider. The tongue-like chain engagement element projects rearwardly to engage the inner and outer plates of the chain, preventing the slider from dropping off when the fastener is fully opened.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

The slider is divided into distinct functional components: the main slider body, the tongue-like chain engagement element, and the release element. This segmentation allows each component to perform its specific function independently, with the chain engagement element specifically designed to prevent slider drop-off while maintaining overall structural integrity.

Inventive Principle:
Principle #1Segmentation

2Reliability

If the slider body is extended forward to prevent dropping off, then the slider would stay on the chain, but the release operation becomes difficult

Engineering Contradiction:
Improveslider retentionVSAvoidrelease operation
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent inverts the conventional approach by having the chain engagement element extend backward rather than the slider body extending forward. This inversion maintains secure retention while allowing easy release through the independently positioned release element that acts on the tongue-like engagement element.

Inventive Principle:
Principle #13The other way round (Inversion)

Solution Approach 2:

By separating the retention function (chain engagement element) from the release function (release element), the patent enables both secure retention and easy operation. The release element can be accessed and operated independently without interfering with the chain engagement mechanism.

Inventive Principle:
Principle #1Segmentation

3Reliability

If a complex retention mechanism is added to prevent slider drop-off, then the slider stays on the chain, but the overall device complexity increases

Engineering Contradiction:
Improveslider retentionVSAvoidoverall structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent adds only the necessary tongue-like chain engagement element as a separate component within the slider, rather than redesigning the entire slider structure. This segmented approach provides the required retention function with minimal additional complexity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

By inverting the engagement mechanism to use a rearwardly projecting tongue-like element rather than a forward-extending slider body, the patent achieves reliable retention without the complexity of extended slider structures or additional retention mechanisms.

Inventive Principle:
Principle #13The other way round (Inversion)

Data Source

PatentEP4238445B1Slider for reverse opening-type slide fastener
Publication Date: 2026.04.29 YKK CORP
  • EP4238445B1 patent drawingFigure 1
  • EP4238445B1 patent drawingFigure 2
  • EP4238445B1 patent drawingFigure 3

AI summary

Provided is a slider for a reverse opening-type slide fastener, which can reduce a catch when a lower slider of the reverse opening-type slide fastener starts to be pulled upward from its lower end position. The separable bottom end stop for a reverse opening-type slide fastener according to the present invention, in which left and right element rows (12) of left and right fastener stringers (10) can be opened from an upper end and a lower end, the slide fastener (100) comprising: a lower slider (30) for opening the left and right element rows (12) from the lower end, the lower slider (30) including a locking claw (40), which is elastically biased to a protruded position protruding into an element guide path (34) of the lower slider (30); an insert pin (50) connected to a lower end of one of the left and right element rows (12); and a box pin (60) connected to a lower end of the other of the left and right element rows (12). At least one of the box pin (60) and the insert pin (50) includes a release groove (63) capable of receiving the locking claw (40) on a side surface (62) opposing to the other side surface. At least one of the box pin (60) and the insert pin (50) includes a protruded piece (66) protruding from one side surface (62) toward the other side face (51), the side surfaces (62, 51) being opposing to each other. The release groove (63) extends upward at least to a lower end of the protruded piece (66).