Watch Hand Assembly Using Crosslinked Polymer Intermediary
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Solution Overview
Problem
Existing methods for assembling small watch components, such as needles and axes, face challenges in maintaining consistent hunting force due to machining tolerances, leading to high scrap rates and increased production costs, especially when using delicate components like time hands.
Innovation Solution
A method involving the deposition of a monomer or polymer in a liquid or pasty state onto the axis or hole of watch components, which is then crosslinked to determine the driving force, allowing assembly at room temperature and reducing the risk of damaging components, while enabling precise control over the hunting force without requiring part retouching or matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If machining tolerances of ±3 microns are used for pins and needles, then manufacturing cost is reduced and production speed is increased, but hunting force varies from 72 to 120 newtons which is outside the required range of 30-60 newtons
Solution Approach 1:
A polymer layer is introduced as an intermediary between the needle and the pin, absorbing dimensional variations through its viscoelastic properties. This intermediate layer decouples the rigid mechanical connection, allowing standard tolerance parts to achieve consistent hunting force within the 30-60N range.
Solution Approach 2:
The polymer layer's viscoelastic parameters (viscosity, elasticity) are carefully selected to compensate for dimensional variations. By changing the material parameters rather than the geometric parameters, the system maintains consistent hunting force despite variations in needle and pin dimensions.
2Manufacturing precision
If needle barrels are squared or tightened to reduce tolerance range, then hunting force consistency is improved, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of changing the geometric parameters (squared barrels, tighter tolerances), the solution changes the material parameters by introducing a polymer layer with specific viscoelastic properties that inherently compensates for dimensional variations.
Solution Approach 2:
The assembly becomes a composite system combining rigid metal components (needle, pin) with a viscoelastic polymer layer, leveraging the complementary properties of each material to achieve consistent hunting force without complex machining.
3Manufacturing precision
If prior pairing of axes and needles is performed, then hunting force consistency is improved, but production cost increases by approximately 30%
Solution Approach 1:
The polymer layer serves as a universal intermediary that can be applied to standard parts without individual pairing or matching, eliminating the need for costly selective assembly while maintaining consistent hunting force across all components.
Solution Approach 2:
By changing from a geometry-based matching system to a material-based compensation system, the invention allows standard parts with standard tolerances to be assembled without pairing, significantly reducing production costs while maintaining hunting force consistency.
4Manufacturing precision
If PVD or CVD deposition processes are used to deposit layers between parts, then hunting force consistency is improved, but equipment complexity and manufacturing cost increase
Solution Approach 1:
The invention replaces complex physical vapor deposition (PVD) or chemical vapor deposition (CVD) equipment with a simpler polymer coating application system, using the polymer's inherent viscoelastic properties to achieve the same functional result of absorbing dimensional variations.
Solution Approach 2:
Instead of using elaborate deposition processes to create rigid or semi-rigid layers, the invention uses polymer coating processes to create a viscoelastic layer that dynamically compensates for dimensional variations, achieving similar precision with simpler equipment.
5Manufacturing precision
If polymer layers are deposited by CVD or injection molding, then driving tolerances are increased, but temperatures of 100-200°C or above 200°C can damage delicate time hands
Solution Approach 1:
The invention changes the processing temperature parameter from high (100-200°C for CVD, >200°C for injection molding) to room temperature or below, using polymer coating methods that cure at low temperatures to preserve delicate time hand components while still achieving adequate driving tolerance.
Solution Approach 2:
The polymer layer acts as a sacrificial or consumable element that absorbs dimensional variations and can be reapplied if needed, providing a cost-effective and component-safe alternative to high-temperature processes that risk damaging valuable time hand parts.
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
This method allows for consistent hunting force within a desired range, reduces scrap rates, and is suitable for delicate components, as it determines the driving force based on the crosslinked polymer characteristics rather than the materials' properties, facilitating automated and precise assembly.
Implementation Method 1
a monomer or polymer in the liquid or pasty state is deposited on all or part of either the axis of the first component or the wall of the hole of the second watch component, that is to say the monomer or polymer is solubilized in a solvent
Implementation Method 2
the monomer or polymer is dried or crosslinked in the liquid or pasty state for its solidification
Implementation Method 3
the monomer or polymer is dried or crosslinked in the liquid or pasty state for its solidification in order to obtain a crosslinked polymer
Data Source
Figure 1~4
AI summary
The invention relates to a method of assembling by pressing a first watch component, axle or pivot, into a hole in a second watch component, hand or moving part or vice versa, comprising the following steps: - a monomer or polymer in liquid or paste form is deposited on all or part of either the axle of the first component or the wall of the hole in the second watch component; - the monomer or polymer in liquid or paste form is dried or crosslinked to solidify it in order to obtain a crosslinked polymer; and - the first component is pressed into the hole in the second watch component, or the second watch component onto the first watch component, the pressing force being determined by the characteristics of the crosslinked polymer and not by the materials of the watch components.