Timepiece Thread Geometry for Fragile Material Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional threaded assembly methods for timepieces using fragile materials like ceramics, glass, or sapphire are prone to cracking or breaking due to tensile stresses, especially under tightening torque and overpressure, limiting their application in watchmaking where sealing and robustness are critical.
Innovation Solution
A threaded timepiece design with a first thread having a reduced contact zone and a higher thread angle compared to standard threads, along with a larger thread root radius, to distribute tensile stresses more effectively and prevent damage, allowing for the use of fragile materials without modifying existing assembly tools or designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If standard threaded assembly methods are used with fragile materials like ceramics, then the materials can be assembled and disassembled, but the threads are prone to cracking or breaking due to tensile stresses from tightening torque and overpressure
Solution Approach 1:
The patent modifies the thread geometry parameters including the thread profile shape, pitch, and root radius to reduce stress concentration. The thread profile is specifically designed with optimized angles and curvature to distribute tensile stresses more uniformly across the thread engagement, preventing crack initiation and propagation in fragile materials like ceramics while maintaining assembly and disassembly functionality
Solution Approach 2:
The thread engagement is segmented into multiple zones with different geometric characteristics along the engagement length. The thread geometry varies along the axial direction, with different sections having optimized parameters for stress distribution, sealing, and mechanical engagement, allowing the fragile material to withstand tightening torque and overpressure while remaining assembleable
2Reliability
If higher tightening torque is applied to ensure assembly security, then the sealing and robustness are improved, but the tensile stresses exceed the resistance of ceramic threads leading to irreversible deformations, cracks, or breakage
Solution Approach 1:
The thread geometry parameters are specifically optimized to allow higher tightening torque application. The modified profile includes increased root radius and adjusted flank angles that distribute the tensile stresses generated by higher torque across a larger area, preventing stress concentration that would lead to ceramic failure while maintaining assembly security and sealing capability
Solution Approach 2:
The thread design incorporates geometric features that act as stress distributors before the full tightening torque is applied. The optimized profile and root geometry cushion the impact of high torque by progressively engaging the thread elements, preventing sudden stress peaks that would cause ceramic thread failure while ensuring secure assembly
3Adaptability or versatility
If standard thread profiles with maximum contact area are used, then the thread contact area is maximized for standard compatibility, but the tensile and shear stresses concentrate on the thread resulting in cracking or breaking
Solution Approach 1:
Different sections of the thread engagement have locally optimized geometric properties. The thread profile varies along the engagement length with specific sections having different flank angles, root radii, and contact area distributions. This local optimization allows certain zones to handle tensile stresses while other zones manage shear stresses, preventing cracking and breaking while maintaining overall compatibility with standard threaded interfaces
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a watch component comprising a first shaft and a first thread intended to cooperate with a second thread provided on a second watch component. The first thread is configured such that a contact area between the first thread and the second thread extends over less than 50% of the thread height of the second thread, or is configured such that the contact area between the first thread and the second thread extends over less than 0.3 times the thread pitch.