Brittle Micro-Mechanical Part Shaped Aperture Assembly
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Solution Overview
Problem
Micro-mechanical parts made of brittle materials like glass, quartz, or silicon face a high risk of breaking during assembly onto a shaft or stud due to the lack of a plastic deformation region, and existing solutions such as adhesives or resilient tongues do not ensure precise centering and secure attachment.
Innovation Solution
A shaped aperture with alternating rigidifying and positioning zones, including tangentially abutting tongues and shoulders, is used to securely attach a micro-mechanical part to a shaft or stud, allowing for precise centering and gripping without risking breakage, and optionally supplemented with adhesive or weld points for additional fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a push fit is made to prevent stresses in the brittle material, then the risk of breakage is reduced, but the part may become detached or a moving element may not be driven by the shaft
Solution Approach 1:
The aperture is designed with non-uniform wall thickness, creating localized resilient zones with different mechanical properties. These zones have varying flexibility to provide both stress absorption and secure gripping, resolving the contradiction between preventing breakage and ensuring reliable attachment.
Solution Approach 2:
The aperture walls are designed to be dynamically responsive, allowing elastic deformation during assembly to absorb stresses and prevent breakage, while maintaining sufficient friction and geometric interlocking to prevent detachment during operation.
2Strength
If adhesive bonding is used to secure the part, then the risk of breakage during assembly is reduced, but additional machining steps and assembly steps are required
Solution Approach 1:
The adhesive bonding step is completely removed from the assembly process. The shaped aperture's resilient walls provide inherent mechanical interlocking and stress absorption, eliminating the need for separate adhesive application and curing operations.
Solution Approach 2:
The aperture structure itself provides the bonding function through its resilient walls that deform elastically during assembly to create secure mechanical interlocking, making the system self-sufficient without requiring external adhesive materials or additional processing steps.
3Strength
If adhesive bonding is used to secure the part, then the risk of breakage during assembly is reduced, but play may develop over time due to aging
Solution Approach 1:
The resilient walls are designed to undergo permanent elastic deformation during assembly, creating irreversible mechanical interlocking. This eliminates the aging and degradation issues associated with adhesives, ensuring long-term stability without play development.
4Strength
If resilient tongues are fitted to the aperture, then the risk of breakage is reduced, but the male part cannot be precisely centred in the aperture
Solution Approach 1:
The aperture features asymmetric elements including a flat section and strategically positioned resilient walls with varying thickness. These asymmetric features provide both resilient stress absorption and precise geometric reference surfaces for accurate centering of the shaft.
Solution Approach 2:
Specific localized zones within the aperture are designed with different wall thicknesses and mechanical properties. The thinner resilient zones provide flexibility for stress absorption, while thicker rigid zones provide precise geometric reference surfaces for accurate centering.
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 enables secure and precise assembly of micro-mechanical parts made of brittle materials onto shafts or studs without breakage risk, ensuring precise centering and stable attachment, even in applications requiring continuous or alternate rotation, while minimizing additional machining steps and play over time.
Implementation Method 1
resilient deformation zones for gripping or tightening around the shaft. The resilient deformation zones are formed of portions of plate having a recess on either side joining the aperture and the end of which penetrates said aperture. These plate portions have the shape of a tongue that abuts the shaft tangentially when the latter is driven in.
Data Source
AI summary
The part is made from a plate (1) made of a brittle material, such as glass, quartz or silicon and includes at least one aperture (2, 4, 6) for driving in a shaft (5). This aperture is characterized in that it includes alternately rigidifying and positioning zones (8) and resilient deformation zones (10). Application to securing a shaft onto the moving parts of a timepiece movement.