Buckle Guide Bar and Slant Lock Mechanism

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Solution Overview

Problem

Existing buckles with side-release mechanisms are prone to unintentional release due to the complexity of the release operation and the difficulty in forming undercuts in injection molding, which complicates the manufacturing process and stability of the buckle components.

Innovation Solution

A buckle design featuring slant surfaces on the lock members that allow for easy engagement and release by elastic deformation, combined with a guide bar mechanism for stable insertion and a simplified injection molding die with a slide core and displacement mechanism for forming undercuts, enabling smooth operation and reliable manufacturing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If slant surfaces are provided on lock members to prevent unintentional release, then reliability of engagement is improved, but device complexity increases due to additional molding requirements

Engineering Contradiction:

Improveengagement reliabilityVSAvoidmolding die complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The molding die is segmented into a fixed die and a movable die, with the movable die capable of moving between a first position (for normal molding) and a second position (for forming undercuts). This segmentation allows the die to switch between different functional states, enabling the formation of slant surfaces without requiring a completely complex dedicated molding structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The movable die is designed to be dynamically repositionable between two positions during the molding process. By moving the movable die to the second position, the molding cavity forms an undercut that creates slant surfaces on the lock members. This dynamic repositioning allows the same die to serve multiple functions, reducing overall device complexity while maintaining reliability.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a complex release operation is required to prevent unintentional release, then engagement reliability is improved, but ease of operation deteriorates

Engineering Contradiction:

Improveengagement reliabilityVSAvoidrelease operation ease

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

Instead of requiring a complex multi-step release operation, the invention inverts the approach by designing the lock members with slant surfaces that passively prevent unintentional release through their geometric configuration. The slant surfaces create a mechanical interference that physically blocks release unless a deliberate insertion action is taken, thereby improving reliability without complicating the release operation.

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If undercuts are formed in injection molding to create slant surfaces, then engagement reliability is improved, but manufacturing complexity increases

Engineering Contradiction:

Improveengagement reliabilityVSAvoidmolding process simplicity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The molding die incorporates a movable component that can dynamically change the shape of the molding cavity. By moving the movable die to a second position, an undercut is temporarily formed in the cavity to create slant surfaces on the lock members. After molding, the movable die returns to the first position, allowing easy ejection of the molded article. This dynamic approach enables complex geometry formation without permanent die complexity.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The movable die is positioned in advance to form the undercut in the molding cavity before injection occurs. This preliminary positioning ensures that the slant surfaces are correctly formed on the lock members during the molding process, eliminating the need for post-processing or additional manufacturing steps, thereby simplifying the overall manufacturing process.

Inventive Principle:

Principle #10Preliminary action

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 buckle achieves strong engagement with easy release and stable posture during use, while the injection molding method simplifies the formation of undercuts, enhancing manufacturing efficiency and reducing the risk of buckle misalignment.

Implementation Method 1

The lock arm is made of a flexible material and provided with an step-like engaging part

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Implementation Method 2

a slide core provided in the cavity in an advanceable and retractable manner; and a displacement mechanism for displacing the slide core in a depth direction of the undercut

Methodology Applied

Scientific EffectMechanical displacement: Displacement

Data Source

PatentUS7725994B2Buckle, injection molding die and injection molding method

Publication Date: 2010.06.01 YKK CORP

AI summary

A plug (20) has a guide bar (24) to be inserter in a socket (30). The guide bar (24) has a to-be-held section (241) at a tip end thereof, a dent (244) at a middle portion thereof, and a sub to-be-held section (242) at a base end thereof. When making an engagement, the plug (20) is slanted relative to the socket (30), so that the guide bar (24) contacts contact points (P1), P2). When the plug has been inserted into a depth end of the socket, the to-be-held section (241) and the sub to-be-held section (242) are held by a holding section (342) and a sub holding section (343) of the socket (30), thereby stabilizing engagement posture.