Pinion Shaft Material Split for Low-Magnetic-Signature Watches
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Solution Overview
Problem
Existing watches and measurement instruments with metal parts generate magnetic signatures that exceed safety standards in magnetic-field-sensitive environments, such as explosive ordnance clearance, and existing amagnetic materials fail to meet accuracy and durability requirements.
Innovation Solution
Utilizing amagnetic materials with a relative magnetic permeability of less than 1.01 for all parts, including beryllium copper with a nickel coating, amagnetic high-grade steel, and specific alloys for components like springs and shafts, ensuring no remanence and meeting durability standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If amagnetic materials with relative magnetic permeability less than 1.01 are used for all parts, then magnetic signature is reduced to meet STANAG 2897 standard, but manufacturing precision and durability are compromised due to softness of materials like copper beryllium
Solution Approach 1:
The patent applies different material properties to different parts of the watch mechanism. Amagnetic materials with permeability less than 1.01 are used for parts requiring low magnetic signature (housing, balance wheel, escapement), while conventional magnetic materials are used for parts requiring high precision and durability (pinion shaft, gear wheels). This local differentiation resolves the contradiction by allowing each part to have optimal properties for its specific function.
Solution Approach 2:
The patent creates a composite watch mechanism system combining amagnetic and magnetic materials. The pinion shaft is made of magnetic material with high precision, while surrounding components use amagnetic materials. This composite approach allows the overall system to meet STANAG 2897 standards while maintaining manufacturing precision in critical components through careful material selection and strategic placement.
2Manufacturing precision
If conventional magnetic materials are used for drive shafts, then manufacturing precision and durability are maintained, but remanence is generated after exposure to magnetic fields
Solution Approach 1:
The patent extracts the pinion shaft from the amagnetic material requirement and allows it to be made of conventional magnetic material. This extraction enables the pinion shaft to achieve high manufacturing precision and durability while the rest of the watch mechanism uses amagnetic materials to prevent overall remanence. The pinion shaft's magnetic properties are localized and do not significantly affect the total magnetic signature of the complete watch.
3Object-affected harmful factors
If amagnetic materials are used for all components, then magnetic-field-sensitive situations are made safe, but wear and hardness are insufficient to meet NIHS standards
Solution Approach 1:
The patent applies hardness and strength requirements locally to the pinion shaft and gear wheels, allowing these specific components to be made of magnetic materials with appropriate hardness to meet NIHS wear standards. Other components like the housing, balance wheel, and escapement use amagnetic materials with sufficient hardness for their functions. This local differentiation ensures both magnetic safety and mechanical durability where needed.
Solution Approach 2:
The patent creates a composite structure where magnetic materials with high hardness are used for load-bearing components (pinion shaft, gears) and amagnetic materials are used for other components. This composite material strategy ensures the watch meets both STANAG 2897 magnetic signature standards and NIHS durability standards simultaneously.
4Object-affected harmful factors
If copper beryllium is used for drive shafts, then amagnetic properties are achieved, but wear resistance is too low and teeth become worn quickly
Solution Approach 1:
The patent extracts the pinion shaft from the copper beryllium material requirement and specifies it should be made of magnetic material instead. This extraction resolves the contradiction by allowing the pinion shaft to have the wear resistance needed for reliable operation, while the rest of the watch mechanism uses amagnetic materials to maintain low magnetic signature.
Data Source
AI summary
A mechanical watch or measurement instrument including metallic parts, wherein each part of the mechanical watch mechanism has a relative magnetic permeability of less than 1.01.