Timepiece Bearing Pivot Centring via Curvature Radius
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Solution Overview
Problem
Conventional shock absorber bearings in timepiece movements face issues with friction variability affecting the angle of rotation and centring problems, leading to reduced precision and risk of arbor jamming.
Innovation Solution
A bearing design featuring a housing with an endstone having a cavity with a second cone shape and a pivot with a first cone shape, where the second radius of curvature is smaller than the first, ensuring proper centring and consistent friction across positions, preventing jamming and maintaining precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a domed olive hole jewel is used in the bearing, then the pivot is protected from impact, but friction increases when the staff is perpendicular to gravity, reducing rotation angle and precision
Solution Approach 1:
The invention changes the geometric parameters of the cavity by rounding the apex with a specific radius of curvature (5-50 μm) and configuring the conical surface with a solid angle of 60-120°. These parameter modifications optimize the friction characteristics across different gravitational positions while maintaining pivot protection, resolving the contradiction between reliability and precision.
2Manufacturing precision
If a cup-bearing type endstone with cone-shaped cavity is used, then friction difference is controlled, but proper centring of the arbor cannot be obtained, risking arbor jamming
Solution Approach 1:
The invention applies local quality by creating a rounded apex at the cavity bottom with a specific radius of curvature (5-50 μm). This localized geometric modification provides the necessary centring function while maintaining the overall conical cavity structure that controls friction, thus resolving the contradiction between friction control and arbor centring.
3Manufacturing precision
If the solid angle of the pivot cone is smaller than the cavity cone, then friction is reduced in perpendicular position, but the arbor cannot be properly centred between cup-bearings
Solution Approach 1:
The invention optimizes the geometric parameters by configuring the cavity with a solid angle of 60-120° and rounding the apex with a radius of curvature of 5-50 μm. These parameter changes enable proper arbor centring while maintaining reduced friction characteristics, resolving the contradiction between friction reduction and reliable centring.
Data Source
AI summary
A bearing for an arbor or staff of a rotary wheel set of a timepiece movement, the bearing including a bearing block provided with a housing and an endstone arranged inside the housing, the endstone having a main body provided with a cavity configured to receive a pivot of the arbor of the rotary wheel set, the pivot having the shape of a first cone having a first solid angle, the apex of the first cone being rounded with a predefined first radius of curvature in a range from 0.2 μm to 50 μm, the cavity having a second cone shape with a second solid angle, greater than the first solid angle, so that the pivot can rotate in the cavity, the apex of the second cone being rounded and having a predefined second radius of curvature. The second radius of curvature is smaller than the first radius of curvature.