Watch Case Back Indexing Ring for Compact Water-Resistant Assembly
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Solution Overview
Problem
Existing fastening devices for watch components face challenges in achieving angular indexing with good tightening and water-resistance, often requiring complex components and materials that degrade over time.
Innovation Solution
A compact indexing ring made of polymer material, such as hytrel®, is used to secure the back of a watch to the middle, ensuring angular indexing and water-resistance by compressing between the back and middle, with catches to prevent rotation and chamfers for easy alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If elastic closing elements are used for fastening watch components, then assembly is simplified, but the overall size becomes too large
Solution Approach 1:
The patent uses a flexible indexing ring made of elastomeric material that can be compressed between the back and middle of the watch case. This thin, flexible element provides the necessary fastening and indexing functions without requiring a bulky elastic closing element, thus resolving the contradiction between simplified assembly and compact size.
2Adaptability or versatility
If compressible material studs are used for angular indexing, then shaping flexibility is improved, but material elasticity degrades significantly during ageing
Solution Approach 1:
The patent changes the material parameter from highly compressible elastomeric studs to a flexible indexing ring made of elastomeric material that maintains stable elastic properties over time. The indexing ring is compressed between rigid surfaces (back and middle) to provide consistent angular indexing, avoiding the material degradation issues of compressible studs while maintaining case shaping flexibility.
3Reliability
If complex fastening devices are used to ensure water-resistance and angular indexing, then sealing reliability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the indexing function and fastening function into a single flexible indexing ring component. This ring is compressed between the back and middle to simultaneously provide angular indexing and secure the assembly, reducing the number of separate components while maintaining water-resistance and indexing reliability.
Solution Approach 2:
The flexible indexing ring acts as an intermediary element between the back and middle, transmitting compression forces to ensure both water-resistance through the gasket and precise angular indexing. This mediator component simplifies the overall assembly by combining multiple functions in one element.
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 provides a secure, water-resistant assembly with precise angular positioning (±1°) and minimal components, preventing accidental dismantling while maintaining manufacturing efficiency.
Implementation Method 1
A compact indexing ring made of polymer material, such as hytrel®, is used to secure the back of a watch to the middle, ensuring angular indexing and water-resistance by compressing between the back and middle
Data Source
AI summary
Provided is a device for fastening a back on a middle portion of a watch. The back includes a cover arranged to form a bearing surface with the middle portion and a body arranged to rest in the middle portion. The device includes an indexing ring disposed between the back and the middle portion, and the ring includes at least one lower catch arranged to cooperate with the back and ensure the indexing with the back and an upper catch are arranged to cooperate with the middle portion and ensure the indexing of the back and ring assembly in relation to the middle portion, and the upper catch has a height greater than that of the lower catch, or vice versa.