Folding Clasp with Rigid Hinges and Elastic Locking

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Solution Overview

Problem

Existing folding clasps for watch bracelets often suffer from fatigue and accidental opening due to flexible components, and they either increase in thickness or protrude against the skin, causing discomfort.

Innovation Solution

A folding clasp design featuring rigid parts with a mechanical connection, elastic means to hold spars together or apart, and a locking/unlocking mechanism using male and female hooking members, allowing for easy assembly and operation without increasing thickness, with optional pusher systems for unlocking.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If flexible beams are used to allow buckles to be snapped into place, then the clasp can be easily closed, but repeated opening/closing maneuvers lead to fatigue and accidental opening

Engineering Contradiction:
Improveease of closing claspVSAvoidrisk of accidental opening
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The clasp is divided into separate rigid components (base, buckles, beams) that connect through mechanical joints rather than relying on flexible deformation. The hinge connections allow movement while maintaining rigidity of individual parts, eliminating fatigue from repeated bending.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Instead of using flexible beams to achieve closure, the invention uses rigid beams with hinge connections that allow controlled movement. The flexibility is achieved through the joint mechanism rather than the beam material itself, inverting the traditional approach.

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

2Reliability

If pushers are arranged below the longerons and buckles to prevent accidental opening, then reliability improves, but the thickness of the clasp increases and causes discomfort against the skin

Engineering Contradiction:
Improveprevention of accidental openingVSAvoidthickness of clasp
Core Design Contradiction:
ReliabilityVSLength of stationary object

Solution Approach 1:

The pushers are repositioned from a vertical arrangement (below the buckles) to a horizontal arrangement (at the ends of the beams). This dimensional change allows the locking mechanism to function effectively while maintaining a slim profile that does not protrude against the wrist.

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

Solution Approach 2:

The hinge connections act as intermediaries that provide both the locking function and the movement capability. The pushers work through the hinge mechanism to engage and disengage the buckles, eliminating the need for separate protruding locking components.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Reliability

If locking/unlocking devices with pushers are arranged near the free ends of each loop, then accidental opening is prevented, but the thickness on the outside and the screeds remain fully visible

Engineering Contradiction:
Improveprevention of accidental openingVSAvoidaesthetic appearance
Core Design Contradiction:
ReliabilityVSShape

Solution Approach 1:

The locking/unlocking function is merged with the structural beams themselves. The pushers are integrated into the beam ends rather than being separate visible components, combining aesthetic and functional elements into a unified design.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The pusher mechanism is nested within the beam structure rather than protruding outward. The locking components are contained within the overall clasp profile, creating a sleek appearance while maintaining full functionality.

Inventive Principle:
Principle #7Nested doll (Nesting)

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 clasp provides robust, easy-to-use functionality with reduced risk of accidental opening and maintains a slim profile, ensuring secure closure and comfortable wear.

Implementation Method 1

These two spars slide on the connecting means while being held close together or apart from each other by elastic means to keep the latching members locked, said latching means being able to be unlocked by exerting pressure on the spars compressing the elastic means.

Methodology Applied
Scientific EffectElasticity: Elasticity

Data Source

PatentEP1925227B1Unfolding clasp for bracelets
Publication Date: 2009.01.21 DEXEL SA
  • EP1925227B1 patent drawingFigure 1~2A
  • EP1925227B1 patent drawingFigure 3~7
  • EP1925227B1 patent drawingFigure 8~9

AI summary

The clasp has an articulation axle (17) between side-rails (5) of a rigid base, and a rigid crosspiece (11) to connect rigid arms (9) of rigid buckles (7). A locking/unlocking mechanism co-operates with male and female hooking elements (20, 21) e.g. projection element and recess. The side-rails are formed by two independent rigid pieces, and slide on the axle while being maintained closer or spaced from each other by elastic units (25) for maintaining the locked hooking units. The hooking units are unlocked by exerting a pressure on the side-rails to compress the elastic units.