# US 2013/0155819 A1 · Timepiece movement with low magnetic sensitivity

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- Number: US 2013/0155819 A1
- Document ID: US20130155819A1
- Status: Published application
- Kind: A1
- Application number: 13/720,167
- Filed: 2012-12-19
- Published: 2013-06-20
- Earliest claimed: 2011-12-19
- Assignees: Nivarox-FAR S.A.
- Inventors: Christian CHARBON; Thierry Hessler; Jean-Pierre Mignot
- Web page: https://patentgrep.com/patent/US20130155819A1

## CPC

- G04C 5/005: {Magnetic or electromagnetic means}
- G04B 17/26: for the effect of variations of the impulses
- G04B 43/007: {Antimagnetic alloys (antimagnetic alloys with temperature compensation G04B17/227; apparatus for antimagnetising G04D9/00; alloys in general C22C)}
- G04C: ELECTROMECHANICAL CLOCKS OR WATCHES
- G04B: MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS (spring- or weight-driven mechanisms in general F03G; electromechanical clocks or watches G04C; electromechanical clocks with attached or built-in means operating any device at pre-selected times or after predetermined time intervals G04C23/00; clocks or watches with stop devices G04F7/08)

## Abstract

The invention relates to a timepiece movement (1) comprising a sprung (7) balance (5) resonator (3) mounted between a bar (2) and a bottom plate (4) wherein the balance (7) is formed from a ferromagnetic material. According to the invention, the timepiece movement includes a magnetic polarising device (15) for said balance spring for maintaining a predefined state of polarisation in the balance spring (7) and including permanent magnetising means which forms a magnetic field in the plane of the balance spring so as to totally or almost totally magnetically saturate the balance spring (7) in the absence of an external magnetic field. The invention concerns the field of timepieces.

## Claims

### Claim 1

A timepiece movement comprising a sprung balance resonator mounted between a bar and a bottom plate and wherein the balance spring is formed from a ferromagnetic material, wherein it includes a magnetic polarising device for said balance spring for maintaining a predefined state of polarisation in the balance spring and comprising a permanent magnetising means which forms a magnetic field in the plane of the balance spring in order to totally or almost totally magnetically saturate the balance spring in the absence of an external magnetic field.

### Claim 2 (depends on 1)

The timepiece movement according to claim 1, wherein the field lines of the permanent magnetising means are aligned with the axis of the balance spring wire.

### Claim 3 (depends on 1)

The timepiece movement according to claim 1, wherein the permanent magnetising means includes at least one permanent magnet.

### Claim 4 (depends on 1)

The timepiece movement according to claim 1, wherein the permanent magnetising means includes at least one permanently powered electro-magnet.

### Claim 5 (depends on 1)

The timepiece movement according to claim 1, wherein the permanent magnetising means generates a field equal to at least three times the coercive field of the balance spring material.

### Claim 6 (depends on 1)

The timepiece movement according to claim 1, wherein the permanent magnetising means generates a field equal to at least 1 mT.

### Claim 7 (depends on 1)

The timepiece movement according to claim 1, wherein the magnetic polarising device is secured to a fixed part of the timepiece movement.

### Claim 8 (depends on 7)

The timepiece movement according to claim 7, wherein the magnetic polarising device is secured to the bar, to a balance spring stud or to the bottom plate of the timepiece movement.

### Claim 9 (depends on 1)

The timepiece movement according to claim 1, wherein the magnetic polarising device is secured to a moving part of the timepiece movement.

### Claim 10 (depends on 9)

The timepiece movement according to claim 9, wherein said magnetic polarising device is secured to the balance or to the balance spring.

### Claim 11 (depends on 1)

A timepiece wherein it includes a timepiece movement according to claim 1.