Watch Arbour Rotation Testing for Full-Circumference Bending Resistance
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Solution Overview
Problem
Existing methods for testing the mechanical properties of clock shafts, particularly resistance to bending, are destructive and inadequate for systematic control in production flows, as they are not representative of the stresses a clock shaft undergoes over its entire circumference, especially for components made of materials with failure modes that cannot be revealed by punctual force applications.
Innovation Solution
A test device that dynamically tests the resistance of clock shafts by simulating the guiding conditions in a clock movement, allowing the shaft to be stressed over its entire circumference through rotation, using a mounting system with supports and a force application mechanism that replicates the stresses encountered by the shaft, including axial and radial loads, while controlling the applied force and movement to ensure accurate characterization of mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a knife-edge is used to apply radial load to the pivot, then the bending resistance can be measured, but the test is destructive and cannot be used for systematic inspection of all production parts
Solution Approach 1:
The invention creates a copy of the operational conditions by using a support that replicates the jewel's geometry and material properties. Instead of directly loading the pivot with a knife-edge, the test uses a support that mimics the actual bearing surface, allowing non-destructive testing that can be repeated on all production parts.
Solution Approach 2:
The invention replaces the destructive knife-edge mechanical system with an optical measurement system. The pivot's rotation under load is measured optically using a laser and detector, eliminating the need for destructive mechanical contact while maintaining measurement precision for production inspection.
2Measurement precision
If a knife-edge is used to apply localized force to the pivot, then the angle of deformation can be measured, but the test cannot detect failure modes that occur elsewhere on the shaft's circumference
Solution Approach 1:
The invention introduces dynamic rotation of the pivot during testing, allowing the localized load to be applied at different angular positions around the shaft's circumference. By rotating the pivot and measuring deformation at multiple positions, the test becomes representative of the entire shaft rather than just one localized point.
Solution Approach 2:
The invention adds the rotational dimension to the testing process. Instead of applying force at a single fixed point, the pivot is rotated through 360 degrees while the force is applied, transforming a one-point static test into a multi-point dynamic test that covers the entire circumference of the shaft.
3Strength
If static force is applied via knife-edge, then the breaking load can be determined, but the test does not simulate the dynamic operational stresses experienced by the shaft
Solution Approach 1:
The invention transforms the static testing method into a dynamic one by rotating the pivot during the application of force. This dynamic rotation simulates the operational conditions of the shaft in actual watch movement, where the shaft rotates while supporting radial loads from the jewels, providing a more accurate representation of real-world stress patterns.
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
Enables reliable and repeatable testing of clock shafts, including those made of fragile materials, by simulating operational stresses, thereby identifying defective components and validating shaft geometries, ensuring resistance to compression, bending, and shearing without causing plastic deformation or breakage.
Implementation Method 1
a support for simulating the guidance of the watch arbor within a watch movement, enabling the dynamic test to reproduce as closely as possible the stresses potentially experienced by the arbor
Implementation Method 2
an element for applying a mechanical force on the watch shaft at least substantially perpendicular to the axis of rotation so that this force is at least partially taken up by the support at the level of at least one pivot
Data Source
Figure 1~2
Figure 3~4B
Figure 5~6
AI summary
Test device (3) of a watch shaft (1) comprising at least one first pivot (10, 10') and an axis (A1) of rotation, the device comprising: - a fixture (2) comprising two supports (12, 12') intended to receive the watch shaft (1), of which at least one of the two supports (12) is intended to receive the at least one first pivot (10), - an element (4; 4') for applying a mechanical force to the watch shaft, positioned so that this force is at least partially taken up by the support (12) at the level of the at least one first pivot (10), characterized in that the element (4; 4') for applying a mechanical force is arranged so that the watch shaft (1) is driven in rotation by a relative movement of the element (4; 4') for applying a mechanical force and the fixture (2).