Watch Dial Fastening Using Integral Flexible Tabs

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Solution Overview

Problem

Existing methods for fastening dials in watch movements require high precision, are cumbersome, and often result in dial deformation or the need for additional assembly stations, adhesive use, and increased production costs, especially when dealing with flexible materials.

Innovation Solution

The use of flexible fastening elements integral with the dial, such as tabs, that cooperate with vertically oriented studs on the main plate to secure the dial without external deformation or additional assembly stations, and a subsequent axial locking by the timepiece crystal for permanent fixation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional feet pressing method is used to fasten dial to movement, then permanent fastening is achieved, but machining precision requirements are very high and assembly speed is considerably slowed

Engineering Contradiction:

Improvepermanent fasteningVSAvoidmachining precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The dial is divided into multiple segments with individual elastic arms, allowing each segment to be independently positioned and fastened. This segmentation enables tolerance accumulation to be distributed across multiple points rather than requiring single-point precision, thereby reducing overall machining precision requirements while maintaining secure fastening.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the physical state of the fastening elements by using elastic arms that can deform elastically during assembly. This parameter change from rigid to elastic allows the arms to absorb positioning tolerances and achieve secure fastening without requiring high machining precision, while still providing permanent attachment.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If setting ring method is used for low end watches, then assembly is simplified, but dial deformation occurs and additional adhesive station is required

Engineering Contradiction:

Improveassembly simplicityVSAvoiddial deformation

Core Design Contradiction:

Ease of manufactureVSShape

Solution Approach 1:

The invention uses thin elastic arms made of flexible material that can bend and deform elastically during assembly without causing permanent deformation to the dial. These flexible elements provide the necessary compliance to simplify assembly while maintaining dial integrity, eliminating the need for adhesive stations.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The elastic arms transition from a deformed state during assembly to a recovered state during operation, dynamically adapting to the assembly process. This dynamic behavior allows the arms to accommodate positioning tolerances and secure the dial without requiring the dial to be deformed, thus preventing permanent shape changes while simplifying assembly.

Inventive Principle:

Principle #15Dynamics

3Reliability

If adhesive dot is added to prevent dial slippage, then temporary fastening reliability is improved, but aesthetic quality deteriorates and production cost increases

Engineering Contradiction:

Improvetemporary fastening reliabilityVSAvoidaesthetic quality

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The elastic arms are designed to automatically engage with the movement's reference surfaces through their own elastic deformation, without requiring external adhesive application. This self-service mechanism provides reliable temporary fastening during assembly while maintaining aesthetic quality, as no visible adhesive dots are needed.

Inventive Principle:

Principle #25Self-service

4Reliability

If elastic return means with clips are used to press dial against main plate, then dial retention is achieved, but movement thickness is considerably increased

Engineering Contradiction:

Improvedial retentionVSAvoidmovement thickness

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The invention moves the fastening action from the vertical dimension (using clips that extend along the axis) to the horizontal dimension by using elastic arms that bend laterally to engage with reference surfaces on the movement. This dimensional change achieves secure dial retention without increasing movement thickness, as the fastening force is applied through lateral bending rather than vertical extension.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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

Facilitates easier and quicker dial mounting without deformation, eliminates the need for additional assembly stations, and reduces production costs by using integral flexible tabs and axial locking, ensuring secure and precise positioning without external tools or adhesive.

Implementation Method 1

at least one flexible fastening element integral with the dial and arranged in the plane of the dial

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS10928778B2Timepiece provided with a dial and associated fastening method

Publication Date: 2021.02.23 ETA SA MFG HORLOGERE SUISSE

AI summary

A timepiece including a case that houses a main plate of a movement surmounted by a dial, and a support including fastening studs arranged on an upper face of the main plate for mounting the dial. The dial and the support include an angular locking mechanism for locking an angular position of the dial on the support, and the dial is assembled to the main plate by at least one flexible fastening element integral with the dial and arranged in the plane of the dial.