Watch Bracelet Clasp Length Adjustment Without Snagging

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Solution Overview

Problem

Existing watch clasps with fine adjustment mechanisms are prone to snagging on external objects and lack a discreet, integrated length adjustment that is independent of the clasp's closing mechanism, and they do not provide an aesthetically pleasing appearance.

Innovation Solution

A clasp design with a movable part pivotally mounted on a support, featuring a locking element that allows axial movement for independent length adjustment, integrated into the clasp's structure without protruding elements, and compatible with various clasp types.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a fine adjustment mechanism with protruding push tabs is used, then length adjustment precision is improved, but the clasp becomes prone to snagging on external objects

Engineering Contradiction:
Improvelength adjustment precisionVSAvoidsnagging on external objects
Core Design Contradiction:
Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The harmful protruding push tabs are extracted and removed from the design. Instead, the patent uses a pull tab system where the locking element is actuated by pulling inwards, eliminating the protruding elements that cause snagging while maintaining fine adjustment precision through the notched positions.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The actuation direction is inverted from pushing outward to pulling inward. The pull tab mechanism allows the user to pull the locking element towards the clasp body to unlock and adjust the length, then release to lock, achieving the same function without protruding elements.

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

2Shape

If the length adjustment device is integrated into the clasp structure, then aesthetic appearance is improved, but the adjustment mechanism becomes less accessible

Engineering Contradiction:
Improveaesthetic appearanceVSAvoidadjustment accessibility
Core Design Contradiction:
ShapeVSEase of operation

Solution Approach 1:

The adjustment mechanism is integrated along the longitudinal axis of the clasp rather than protruding laterally. The pull tab and locking element are positioned within the clasp body structure, maintaining a sleek profile while remaining accessible through the longitudinal opening for user interaction.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Device complexity

If the fine adjustment mechanism is coupled with the clasp closing mechanism, then device complexity is reduced, but the adjustment cannot be made independently of the clasp state

Engineering Contradiction:
Improvemechanism complexityVSAvoidindependent adjustment capability
Core Design Contradiction:
Device complexityVSAdaptability or versatility

Solution Approach 1:

The clasp is segmented into functionally independent parts: the closing mechanism (first and second blades with locking means) and the length adjustment device (movable part with locking element and notched positions). This allows the adjustment mechanism to operate independently regardless of whether the clasp is open or closed.

Inventive Principle:
Principle #1Segmentation

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

Enables precise and snag-free length adjustment of the bracelet, maintaining a harmonious appearance and allowing adjustment regardless of the clasp's state, enhancing user comfort and aesthetics.

Implementation Method 1

a movable part to which one of the two fixing members is attached, said movable part being pivotally mounted on said first support

Methodology Applied
Scientific EffectPivotal mounting: Hinge

Implementation Method 2

an axis of a locking element constituting the pivot axis of said movable part, characterized in that the locking element is intended to be moved axially to unlock the adjustment device and to allow adjustment of the bracelet length

Methodology Applied
Scientific EffectAxial movement locking: Cam

Data Source

PatentEP3419470B1Bracelet clasp comprising a device for adjusting the length of the bracelet
Publication Date: 2026.04.01 DEXEL SA
  • EP3419470B1 patent drawingFigure 1~2
  • EP3419470B1 patent drawingFigure 3~4
  • EP3419470B1 patent drawingFigure 5~6

AI summary

The invention relates to a band clasp, particularly a wristwatch band clasp, including a device for finely adjusting the length of the band. In one embodiment, the invention relates to a folding clasp, and the adjustment device is placed on a strip to be inserted between two vertical members of a main strip when the clasp is closed. The adjustment device comprises a locking shaft, arranged in a direction orthogonal to the longitudinal direction of the clasp and placed therein such that at least part of the shaft is placed above a top surface common to the strips of the clasp. In one embodiment, the movable portion of the adjustment device is pivotally mounted on the clasp.