Magnetic Shaft Centering in Clockwork Bearings With Recentered Flux
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Solution Overview
Problem
Existing magnetic centring devices for clockwork movements face high rejection rates due to off-centre magnetic fields, making it challenging to produce reliable and precise clockwork mechanisms with small dimensions.
Innovation Solution
A magnetic device with a central part made of ferromagnetic material positioned between the magnet and the shaft pivot, within a non-magnetic washer, to centre the magnetic field flux, increasing the magnetic restoring force and radial gradient, thereby ensuring proper centring of the shaft on a predetermined axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a magnet is used in a magnetic bearing to hold the shaft on a predetermined axis, then substantial holding forces are generated with limited friction, but the magnetic field can be off-centre by an excessive amount leading to high rejection rates
Solution Approach 1:
A ferromagnetic central part is introduced as an intermediary element between the magnet and the shaft pivot. This central part acts as a flux concentrator that redirects and centres the magnetic field lines, ensuring they pass through the centre of the shaft pivot rather than being offset. The intermediary component thus mediates between the magnet's field generation and the required centred holding force, resolving the contradiction between generating substantial force and achieving precise magnetic field centring.
2Manufacturing precision
If the magnetic field is recentred using a central part made of ferromagnetic material, then the magnetic field flux is properly centred reducing rejection rates, but the device complexity increases
Solution Approach 1:
The ferromagnetic central part is merged with the existing magnetic bearing structure, specifically positioned within the magnet assembly rather than being a separate external component. This integration approach combines the flux-concentrating function with the existing bearing structure, reducing the number of discrete parts and simplifying assembly while still achieving proper magnetic field centring and reducing rejection rates.
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 magnetic field is recentred by a factor of 2 to 3, significantly reducing the number of rejected parts and simplifying the production process, while ensuring accurate centring and increased magnetic force for precise clockwork operation.
Implementation Method 1
the first central part being positioned centrally in a first washer or bush made of non-magnetic material in such a way as to centre the magnetic field flux generated by the first magnet through the first central part
Implementation Method 2
at least one first magnetic bearing including a first magnet, which is intended to exert an attractive force on a first end pivot, made of ferromagnetic material, of the shaft
Data Source
AI summary
A magnetic device for centring a shaft on a predetermined axis in a clockwork movement includes at least one first magnetic bearing provided with a magnet to exert an attractive force on a first ferromagnetic end pivot of the shaft. The first magnetic bearing includes a central part made of soft ferromagnetic material mounted between the magnet and the first end pivot of the shaft. The central part is positioned centrally in a washer made of non-magnetic material so as to centre the magnetic field flux generated by the permanent magnet through the central part in order to magnetically attract the first end pivot of the shaft on the predetermined axis. The diameter of the central part can be identical to, or 0 to 20% less than, or 0 to 20% greater than, the diameter of the first end pivot.