Non-Magnetic Watch Pivot Axis with NiP Shock-Resistant Coating

Solution Overview

Problem

Existing watch pivot materials, such as martensitic carbon steels, are magnetic and prone to corrosion, affecting watch performance and chronometry, while non-magnetic alternatives like austenitic steels lack sufficient hardness and shock resistance.

Innovation Solution

A non-magnetic pivot axis is created by using a first non-magnetic metallic material, preferably austenitic stainless steel, with an external surface coated with a layer of Ni or NiP, preferably chemical NiP, to enhance shock resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If martensitic carbon steel is used for pivot shafts, then mechanical properties and shock resistance are improved, but magnetic sensitivity and corrosion resistance worsen

Engineering Contradiction:

Improveshock resistanceVSAvoidmagnetic sensitivity

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The pivot shaft is divided into two distinct parts with different material properties: the core is made of martensitic carbon steel for high shock resistance, while the external surface is covered with a non-magnetic coating layer. This segmentation allows each part to fulfill its specific function independently, resolving the contradiction between mechanical strength and magnetic sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining martensitic carbon steel substrate with a non-magnetic coating material (such as austenitic stainless steel or nickel alloy). This composite approach integrates the advantages of both materials: the steel core provides exceptional shock resistance and hardness, while the non-magnetic coating eliminates magnetic interference with the balance spring.

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If austenitic stainless steel is used for pivot shafts, then magnetic sensitivity is reduced, but hardness and shock resistance worsen

Engineering Contradiction:

Improvemagnetic sensitivityVSAvoidshock resistance

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The pivot shaft is divided into two distinct parts with different material properties: the core is made of martensitic carbon steel for high shock resistance, while the external surface is covered with a non-magnetic coating layer. This segmentation allows each part to fulfill its specific function independently, resolving the contradiction between mechanical strength and magnetic sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining martensitic carbon steel substrate with a non-magnetic coating material (such as austenitic stainless steel or nickel alloy). This composite approach integrates the advantages of both materials: the steel core provides exceptional shock resistance and hardness, while the non-magnetic coating eliminates magnetic interference with the balance spring.

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If cobalt or nickel alloy is used for pivot pins, then magnetic sensitivity is reduced, but ease of manufacture and cost worsen

Engineering Contradiction:

Improvemagnetic sensitivityVSAvoidmachinability

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The pivot shaft is divided into two distinct parts with different material properties: the core is made of martensitic carbon steel for high shock resistance, while the external surface is covered with a non-magnetic coating layer. This segmentation allows each part to fulfill its specific function independently, resolving the contradiction between mechanical strength and magnetic sensitivity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite structure combining martensitic carbon steel substrate with a non-magnetic coating material (such as austenitic stainless steel or nickel alloy). This composite approach integrates the advantages of both materials: the steel core provides exceptional shock resistance and hardness, while the non-magnetic coating eliminates magnetic interference with the balance spring.

Inventive Principle:

Principle #40Composite materials

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 pivot axis achieves low magnetic sensitivity and excellent shock resistance, preventing damage and maintaining chronometric accuracy.

Implementation Method 1

at least the external surface of said pivot is covered with a layer of a second material chosen from the group consisting of Ni, NiP and preferably chemical NiP in order to improve the shock resistance of said pivot

Methodology Applied

Scientific EffectHardening:

Data Source

PatentEP3273306B1Part for clock movement

Publication Date: 2025.08.27 NIVAROX FAR SA

Figure 1~2
Figure 3~4

AI summary

The invention relates to a pivot axis for a watch movement comprising at least one pivot (3) made of a first non-magnetic metallic material (4) at at least one end to limit its sensitivity to magnetic fields. At least the external surface of said pivot (3) is coated with a layer (5) of a second material selected from the group including Ni and NiP, and preferably chemical NiP. The invention relates to the field of watch movements.