Watch Strap Clasp Lever Mechanism for Rapid Length Adjustment

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Solution Overview

Problem

Existing watch strap clasps with fine adjustment mechanisms are not user-friendly for rapid and precise length adjustments, often leading to accidental loss of settings.

Innovation Solution

A clasp design featuring a connecting link with a lever and hooks that slides between engaged and disengaged positions, utilizing a torsion spring for secure locking and easy adjustment, with lateral guide surfaces and a U-shaped cover for precise positioning, and a stopper mechanism to prevent accidental extraction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If elastic uncoupling means are used to disengage the toothed element from the groove, then the position of the end link can be easily modified, but the handling does not allow simple, rapid and precise adjustment

Engineering Contradiction:
Improveease of adjustmentVSAvoidadjustment speed
Core Design Contradiction:
Ease of operationVSProductivity

Solution Approach 1:

The patent employs a dynamic lever mechanism that pivots between a first position (for engagement) and a second position (for disengagement). This dynamic transformation allows the connecting link to rapidly switch between locked and adjustable states, significantly improving adjustment speed while maintaining ease of operation through simple lever actuation.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The adjusting mechanism is divided into distinct functional segments: the lever with hooks, the bars mounted in the cover, and the connecting link. This segmentation allows each component to perform its specific function efficiently - the lever for rapid state switching, the bars for precise positioning, and the link for movement - thereby achieving both simplicity and speed in adjustment.

Inventive Principle:
Principle #1Segmentation

2Reliability

If the toothed element engages with the groove to immobilize the terminal link, then the position is secured, but the adjustment mechanism becomes complex and prone to accidental movement

Engineering Contradiction:
Improveposition stabilityVSAvoidmechanism complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the essential locking function from the complex toothed element-groove engagement and implements it through a simpler lever-and-hook mechanism. The hooks on the lever engage with the bars to provide secure positioning without requiring complex interlocking teeth, thereby reducing mechanism complexity while maintaining position stability.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The lever is designed with specific local features - hooks at specific positions - that engage with corresponding bars only when the lever is in the first position. This localized engagement provides reliable locking exactly where needed while keeping the rest of the mechanism simple and free from unnecessary complexity.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If the connecting link slides between engaged and disengaged positions for length adjustment, then fine adjustment is achieved, but the risk of losing the setting inadvertently increases

Engineering Contradiction:
Improvelength adjustment precisionVSAvoidsetting retention
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The lever mechanism is designed so that the hooks are preliminarily positioned to engage with the bars when the lever is in the first position. This preliminary positioning ensures that as soon as the connecting link reaches a desired position, the lever automatically engages to lock it, preventing accidental loss of the setting while maintaining precise adjustment capability.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The mechanism provides mechanical feedback through the lever's tendency to return to the first position under spring action or gravity. This feedback ensures that any inadvertent movement of the connecting link is counteracted, and the lever automatically re-engages with the bars to maintain the intended setting, thereby improving reliability without compromising adjustment precision.

Inventive Principle:
Principle #23Feedback

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 secure, simple, and rapid adjustment of watch strap length without risk of losing the setting, providing enhanced user convenience and precision.

Implementation Method 1

the lever is held in the first position by means of a spring housed in the connecting link

Methodology Applied
Scientific EffectTorsion spring: Torsion Spring

Data Source

PatentEP3769640B1Watch strap clasp
Publication Date: 2022.03.30 OMEGA SA
  • EP3769640B1 patent drawingFigure 1
  • EP3769640B1 patent drawingFigure 2~4
  • EP3769640B1 patent drawingFigure 5~6

AI summary

A watch strap clasp comprising a cover connected on one side to a first strap strand and on the other side to a second strap strand, connecting means being interposed between the second strap strand and the clasp cover, these connecting means comprising a connecting link sliding along a longitudinal direction of the clasp between a first position and a second position. According to the invention, the clasp comprises at least a first and a second bar mounted in the cover, and the connecting link comprises a lever equipped with a hook that can move from a first position in which the hook engages with a first bar fixed to the clasp cover, to a second position in which the hook is released from its engagement with the first bar and said link is free to slide so as to engage said second bar with a hook.