Balance Spring Torque Measurement Using Obelisk Arbor
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Solution Overview
Problem
The existing methods for measuring the torque of balance springs, particularly those made of silicon, face issues such as chipping due to mechanical stress, wear and contamination of tools, and alignment difficulties, leading to inaccurate measurements.
Innovation Solution
A method using an obelisk-shaped mock arbor with a static holding principle, allowing the balance spring to be centered and measured without intense local forces, minimizing stress and ensuring precise angular and vertical positioning through its own weight, eliminating the need for clamping and reducing friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cylindrical arbor with clamping is used to hold the balance spring collet, then the balance spring can be held in position during measurement, but mechanical stress causes chipping and microfractures in the brittle silicon material
Solution Approach 1:
The patent replaces the mechanical clamping system with a magnetic field-based holding system. The cylindrical arbor incorporates a magnet that magnetically retains the collet during measurement, eliminating the need for mechanical clamping forces that cause stress and chipping in brittle silicon balance springs.
Solution Approach 2:
The patent changes the holding mechanism from mechanical force to magnetic force. By using a magnet in the cylindrical arbor, the collet is held through magnetic attraction rather than mechanical clamping, significantly reducing the stress applied to the silicon material and preventing chipping while maintaining reliable positioning.
2Productivity
If a cylindrical arbor is used for repeated insertions and removals, then the balance spring can be measured multiple times, but friction causes wear and contamination of the arbor
Solution Approach 1:
The patent replaces mechanical friction-based holding with a magnetic field-based holding system. The magnet in the cylindrical arbor retains the collet without mechanical friction during insertion and removal, eliminating wear and contamination of the arbor while enabling repeated measurements.
Solution Approach 2:
The patent extracts the harmful friction element from the system by using magnetic fields instead of mechanical contact for holding. The magnet provides retention forces without the sliding friction that occurs in mechanical clamping systems, preventing arbor wear and contamination during repeated operations.
3Measurement precision
If a cylindrical arbor requires precise alignment during insertion, then measurement accuracy can be maintained, but misalignment causes impact and shock on the collet
Solution Approach 1:
The patent replaces mechanical alignment and clamping with a magnetic field-based holding system. The magnet in the cylindrical arbor attracts the collet without requiring precise mechanical alignment during insertion, eliminating impact and shock while maintaining measurement accuracy through magnetic retention.
Solution Approach 2:
The patent provides beforehand cushioning by using the magnetic field to gently guide and retain the collet during insertion. The magnetic attraction acts as a cushioning force that prevents impact and shock, allowing for more tolerant alignment during insertion while maintaining measurement precision.
4Manufacturing precision
If a cylindrical arbor with clamping force is used to ensure angular and vertical positioning, then the balance spring can be held securely, but the clamping force generates stress that depends on manufacturing tolerances
Solution Approach 1:
The patent replaces mechanical clamping with a magnetic field-based holding system. The magnet in the cylindrical arbor provides retention forces that secure angular and vertical positioning of the collet without generating the high stress associated with mechanical clamping, reducing sensitivity to manufacturing tolerances.
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
This approach prevents chipping, reduces tool wear, ensures accurate torque measurements, and enhances the reliability of the process by maintaining the balance spring's integrity and alignment, thereby improving the precision and reproducibility of the measurement.
Implementation Method 1
maintaining the angular and vertical position in the field of gravity of the collet of a balance spring
Data Source
AI summary
A method for measuring the torque of a balance spring, made, in particular, of micromachinable material. A gripper places the collet on an insertion guide on the vertex of a mock obelisk-shaped arbor for a first centring of the collet, this balance spring is allowed to slide under its own weight along the guide surmounting a frustoconical shank that completes the self-centring of the collet on the tool axis, and for holding this balance spring without stress on the shank, the mock arbor including a drive device cooperating with the inner contour of the collet for the relative driving in rotation thereof without slipping, a holding tool holds the outer coil of the balance spring, to measure the torque of the balance spring by rotating the main tool and/or the holding tool about the axis, without stressing the balance spring.