Elastic Ring Assembly Device for Watch Bracelet Screw Retention

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Solution Overview

Problem

Existing assembly devices for watch bracelets are prone to untimely unscrewing due to repeated movements and shocks, requiring complex assembly and potentially difficult disassembly, with significant clamping force needed to prevent unscrewing.

Innovation Solution

An assembly device featuring a screw with a pivoting guide pin and an elastic ring that deforms axially during screwing, providing radial clamping force to secure the screw in place, minimizing the risk of unscrewing while simplifying assembly and disassembly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a tubular barrel with annular constriction is used to clamp the screw, then the risk of untimely unscrewing is reduced, but the assembly time increases and disassembly becomes difficult

Engineering Contradiction:
Improveresistance to untimely unscrewingVSAvoidassembly time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent changes the physical state of the elastic ring from a static clamping structure to a dynamically deformable one. During assembly, the elastic ring is compressed axially between the screw head and the link surface, which transforms this compression into radial expansion that exerts clamping force on the screw. This parameter transformation allows the same component to provide strong retention during wear while enabling easy disassembly when force is applied.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The elastic ring transitions from a rigid clamping structure to a dynamic system that can deform during assembly and disassembly. The ring's elastic properties allow it to be compressed during assembly operations and then maintain a constant radial clamping force on the screw during normal wear, while still permitting controlled disassembly when needed.

Inventive Principle:
Principle #15Dynamics

2Reliability

If significant clamping force is exerted by the barrel constriction on the screw, then the risk of untimely unscrewing is reduced, but the assembly and disassembly operations become difficult

Engineering Contradiction:
Improvescrew retentionVSAvoidease of assembly and disassembly
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The elastic ring utilizes elastic deformation to transform axial compression force into radial clamping force. When compressed between the screw head and the link surface during assembly, the ring expands radially to grip the screw with significant force. During disassembly, applying axial force in the opposite direction releases this clamping, allowing easy removal. This parameter transformation enables both strong retention and ease of operation.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The elastic ring automatically adjusts its clamping force based on the assembly state. During normal wear, the ring maintains constant radial pressure on the screw to prevent unscrewing. During disassembly, when axial force is applied to compress the ring further, the ring's deformation naturally releases its radial grip on the screw, allowing the operator to remove it easily without requiring excessive force.

Inventive Principle:
Principle #25Self-service

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 solution effectively secures the assembly device against untimely unscrewing during wear or shocks, reducing assembly time and making disassembly straightforward, while minimizing wear and stress on the elastic ring.

Implementation Method 1

an elastic ring (6) arranged around the body (41) of the screw (4), having two elastic tabs (65) extending in a longitudinal direction, parallel to the axis of the assembly device (3)

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

a screwing step during which the screw (4) is screwed into a first part (M1a), driving in axial translation the pivoting guide pin (5) of the assembly device (3)

Methodology Applied
Scientific EffectMechanical force transmission: Mechanical Force

Data Source

PatentEP2939560B1Device and method for pivotably connecting at least two parts, corresponding set of two assembled parts
Publication Date: 2018.07.11 ROLEX SA
  • EP2939560B1 patent drawingFigure 1~2
  • EP2939560B1 patent drawingFigure 3~4
  • EP2939560B1 patent drawingFigure 5~6

AI summary

Assembly device (3) for pivotally attaching at least two parts (M1, M2), comprising a screw (4) intended to be screwed into a first part (M1) and carrying a pivoting guide axis (5) of a second part (M2), characterized in that the assembly device (3) comprises at least one elastic ring (6) capable of cooperating with an obstacle-forming element of one of the two parts (M1, M2), in order to block the untimely axial displacement of the assembly device (3).