Composite Watch Hand with Textured Pipe for Weight Reduction
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Solution Overview
Problem
Current techniques for fabricating timepiece display hands result in high-density hands with high moment of inertia and unbalanced forces, leading to floating or slipping during shocks, and are limited in producing desired forms and shapes due to mechanical stresses and material constraints.
Innovation Solution
A display hand comprising a composite material body and a metallic pipe with a textured connection surface, allowing for reduced weight and varied forms, fabricated using injection molding and micro-machining techniques such as laser cutting or CNC milling, enabling attachment to a drive arbor and decoration with patterns or coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional materials (brass, steel, gold) are used for display hands, then structural strength is maintained, but weight increases leading to high moment of inertia and unbalanced forces
Solution Approach 1:
The patent applies composite materials consisting of a polymer matrix reinforced with aromatic polyamide fibers (such as Kevlar®). This composite provides both the necessary structural strength and significantly reduced weight compared to traditional metallic materials like brass, steel, or gold, thereby resolving the contradiction between strength and weight in display hand construction.
2Productivity
If machining or stamping techniques are used, then hands can be produced, but high mechanical stresses result requiring additional adjusting operations
Solution Approach 1:
The patent employs preliminary action by pre-forming the display hand shape through injection molding of the composite material before final assembly. This preliminary shaping eliminates the need for subsequent high-stress machining or stamping operations and their associated adjusting steps, thereby reducing fabrication complexity while maintaining production efficiency.
3Productivity
If traditional fabrication techniques are used, then hands can be produced, but desired forms and shapes cannot be fully achieved
Solution Approach 1:
The patent utilizes parameter changes by varying the injection molding parameters (temperature, pressure, injection rate) and composite material properties to achieve different hand forms, shapes, and surface characteristics. This flexibility allows the same fabrication process to produce diverse hand designs, significantly improving form versatility compared to traditional machining or stamping methods.
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 reduces the moment of inertia and unbalanced forces, allowing for lightweight, versatile, and aesthetically customizable display hands with reduced mechanical stresses, capable of accommodating various sizes and forms without compromising weight or structural integrity.
Implementation Method 1
a pipe (20), comprising, over all or part of the outer periphery, a surface (24) for connection to the hand body to ensure the adhesion of the composite material to the pipe
Implementation Method 2
the connecting surface is textured
Data Source
AI summary
A display hand intended to equip a timepiece, including a body and a pipe, providing an arbor hole arranged for fitting the display hand onto a drive arbor. The body is made of a composite material, the pipe includes, over all or part of the outer periphery, a surface for connection to the hand body to ensure the adhesion of the composite material to the pipe.