Timepiece Thread Geometry for Ceramic and Sapphire Assembly
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Solution Overview
Problem
Fragile materials like ceramic and glass, used in timepiece components, are unsuitable for threaded assemblies due to their poor tensile strength, which leads to cracking or breaking under high tightening torque or pressure, limiting their use to applications with minimal mechanical stresses.
Innovation Solution
A threaded timepiece member with a modified threading configuration that reduces the contact zone between threads to less than 50% of the thread height and adjusts the thread angle and root radius to distribute stress more evenly, allowing for the use of ceramic or sapphire components in assemblies that previously required metal, while maintaining compatibility with standard tools and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard threaded systems are used with fragile materials like ceramic or glass, then chemical resistance and temperature resistance are improved, but tensile strength and resistance to tightening torque deteriorate, leading to cracking or breaking
Solution Approach 1:
The patent modifies the threading parameters specifically for fragile materials: reducing the thread pitch angle from the standard 60 degrees to between 30 and 45 degrees, and limiting the engaged thread length to less than 50% of the total thread height. These parameter changes reduce the tensile stresses on the threads during tightening while maintaining adequate mechanical strength and sealing capability.
2Strength
If the contact zone between threads is extended to maximize strength, then resistance to tightening torque is improved, but stress concentration increases leading to cracking in fragile materials
Solution Approach 1:
The patent applies local quality by creating a non-uniform stress distribution through the modified thread geometry. The reduced pitch angle and limited engagement length concentrate the contact zone in a specific region that optimizes stress distribution, preventing stress concentration at critical points while maintaining adequate load-bearing capacity.
3Ease of operation
If standard thread profiles are used to ensure compatibility with existing tools, then ease of operation is improved, but the risk of seizure and thread damage increases under high pressure
Solution Approach 1:
The patent modifies the thread profile parameters (reducing the pitch angle to 30-45 degrees and limiting engagement length) to create a threading system that is compatible with standard assembly tools while significantly reducing the risk of seizure and thread damage under high pressure conditions.
4Weight of moving object
If fragile material components are used to replace metal, then weight and corrosion resistance are improved, but mechanical strength under tension deteriorates
Solution Approach 1:
The patent enables the use of lightweight fragile materials like ceramic and glass by modifying the thread parameters (reduced pitch angle and limited engagement), which compensates for the lower tensile strength of these materials through optimized stress distribution.
Data Source
AI summary
The invention concerns a timepiece member including a first axis and a first threading intended to cooperate with 5 a second threading provided on a second timepiece member. The first threading is configured so that a zone of contact between the first threading and the second threading extends over less than 50% of the height of the threads of the second threading or is configured so that the zone of contact between the first 10 threading and the second threading extends over less than 0.3 times the pitch of the threading.