Watch Balance Spring Terminal Curve for Isochronism
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Solution Overview
Problem
Traditional watch movement regulating organs face precision and isochronism issues due to the balance spring's center of gravity displacement, leading to torque fluctuations and increased complexity with the use of shock absorbers and balance bridges.
Innovation Solution
A spiral spring with a terminal curve extending above the plane of the hairspring, featuring a first and second radius of curvature and a rectilinear connection, ensures the center of gravity coincides with the center of rotation, eliminating the need for shock absorbers and balance bridges by fixing the inner end to a movement point and the outer end to the balance wheel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the balance spring has an external tail to maintain the center of gravity on its axis, then the isochronism is improved, but the torque applied to the balance staff varies and isochronism is not perfect
Solution Approach 1:
The terminal curve is elevated above the plane of the spiral, transitioning from a two-dimensional planar curve to a three-dimensional spatial configuration. This vertical displacement allows the center of gravity to be positioned on the rotation axis while maintaining uniform torque characteristics during operation.
Solution Approach 2:
The terminal curve incorporates specific curvature radii (first and second radii of curvature) to shape the spatial configuration. This curved geometry in three dimensions enables the center of gravity to coincide with the center of rotation while ensuring concentric deployment during oscillation.
2Reliability
If shock absorbers such as Incablocs systems are used to dampen shocks, then the balance wheel protection is improved, but the cost and complexity of the regulating organ increases
Solution Approach 1:
The patent removes the separate shock absorber components (Incablocs systems) from the regulating organ. Instead, the balance spring itself is designed with a fixed axis configuration that inherently provides shock resistance, eliminating the need for additional shock-absorbing devices.
Solution Approach 2:
The balance spring serves multiple functions: it provides the regulating oscillation, maintains isochronism through its terminal curve configuration, and simultaneously absorbs shocks. The fixed axis design allows the balance spring to handle both timing and shock protection functions without requiring separate dedicated components.
3Device complexity
If a fixed axis is used to eliminate shock absorbers and balance bridge, then the device complexity is reduced, but the center of gravity of the balance spring remains far from the rotation axis causing non-concentric deployment
Solution Approach 1:
By elevating the terminal curve above the plane of the spiral into three-dimensional space, the design allows the center of gravity to be positioned on the rotation axis. This spatial configuration enables the balance spring to deploy concentrically during oscillation while maintaining a simple fixed-axis structure without requiring complex shock absorbers or balance bridges.
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 design achieves concentric deployment and improved isochronism, reducing torque variations and manufacturing complexity while maintaining the simplicity of conventional hairspring production.
Implementation Method 1
having a shape enabling the position of the center of gravity of the spiral to coincide with its center of rotation
Implementation Method 2
The outer end of the balance spring is securely attached to the mainplate or balance bridge via a stud
Data Source
Figure 1~2
Figure 3
AI summary
A balance spring (1) intended to be included in a regulating organ with a balance wheel (5) of a watch movement, comprising an inner end (2), a terminal curve (3), and an outer end (4); the inner end (2) of the balance spring (1) being fixed to a fixed point (6) of the movement; the outer end (4) of the balance spring (1) being fixed to the balance wheel (5) so that the balance spring can be driven by its outer end; the terminal curve (3) extending beyond the plane of the balance spring from its outer coil (8) and having a shape enabling the position of the center of gravity of the balance spring (1) to coincide with its center of rotation (9). The balance spring of the invention allows concentric unwinding of the balance spring when driven by the outer end and provides a regulating organ offering very good isochronism.