Sliding Toothed Bracelet Clasp for Fine Length Adjustment

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Solution Overview

Problem

Existing bracelet clasps fail to provide fine adjustment of length without losing the set length when opened, and require manual re-setting each time the clasp is closed, failing to accommodate varying wrist sizes due to seasonal or daily changes.

Innovation Solution

A clasp with a sliding end piece and lever mechanism, featuring asymmetrical teeth for secure locking and unlocking, allowing precise length adjustment without losing the set length, and enabling easy handling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a folding clasp with hook and trigger is used, then the clasp can be locked securely, but the bracelet length cannot be adjusted without losing the set length when opened

Engineering Contradiction:
Improvebracelet length adjustmentVSAvoidretention of set length
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The cap is divided into a fixed portion and a movable end piece that can slide relative to each other. The movable end piece carries the hook, allowing it to engage with different positions on the trigger to adjust bracelet length. This segmentation enables length adjustment while maintaining secure locking at each position.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The end piece is designed to be movable within the cap, transitioning between fixed positions for length adjustment and a locked position for securing the bracelet. This dynamic structure allows the clasp to adapt between adjustment mode and secure locking mode, preventing inadvertent length changes during wear.

Inventive Principle:
Principle #15Dynamics

2Measurement precision

If the bracelet length is adjusted by adding or removing links, then the structure is simple, but the adjustment precision is insufficient for varying wrist circumferences

Engineering Contradiction:
Improvelength adjustment precisionVSAvoidadjustment mechanism complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

Instead of adjusting length by adding or removing discrete links along the bracelet, the invention moves the hook engagement point along the longitudinal dimension of the cap. The movable end piece slides to different positions, each corresponding to a specific engagement point on the trigger, enabling fine length adjustment without changing the bracelet link structure.

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

3Adaptability or versatility

If the hook engages with a fixed hole in the cap, then the locking is simple, but the bracelet length cannot be adjusted

Engineering Contradiction:
Improvebracelet length adjustmentVSAvoidlocking mechanism complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The movable end piece acts as an intermediary between the hook and the cap body. It carries the hook and can slide to different positions within the cap, allowing the hook to engage with different positions on the trigger. This intermediary component enables length adjustment without requiring multiple holes in the cap or complex locking mechanisms.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 rapid adjustment of bracelet length without losing the set length, ensuring comfort and convenience by preventing inadvertent adjustments during use.

Implementation Method 1

the cap comprises a cavity arranged to receive a spring, the spring cooperating with the sliding end piece

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

the toothed sector has a plurality of teeth, each tooth defining an indexed position of the sliding end piece; the toothed element of the lever has a shape complementary to the asymmetrical shape of the teeth

Methodology Applied
Scientific EffectMechanical interlocking: Mechanical Fastener

Data Source

PatentEP4606253A1Adjustable bracelet clasp
Publication Date: 2025.08.27 CO DES MONTRES LONGINES FRANCILLON SA
  • EP4606253A1 patent drawingFigure 1a~1b
  • EP4606253A1 patent drawingFigure 2~4
  • EP4606253A1 patent drawing

AI summary

The invention relates to a clasp (1) for a bracelet with a folding clasp (20), the clasp comprising: - a cap (2) to which are fixed at least a first blade and a second blade articulated together and to which a first bracelet strand is fixed; - first locking means for holding the blades in the closed position on the cap; - actuating means comprising a first and a second pusher (4, 5); - means for adjusting the length of the bracelet to which a second bracelet strand is fixed. According to the invention, the length adjustment means comprise a sliding end piece (10) in the cap (2), the sliding end piece (10) having a toothed sector (15) arranged to cooperate with second locking means controlled by a pusher (4, 5).