Silicon Balance Spring Overcoil Formation
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Solution Overview
Problem
The existing silicon balance springs in timepieces suffer from eccentric deformation during operation, causing the center of gravity to shift away from the balance wheel's center, leading to anisochronous motion, which prior solutions like Breguet overcoil and Straumann double balance springs either modify the spring's plane or increase energy consumption.
Innovation Solution
A method and structure for a unitary formed silicon balance spring with an overcoil portion, where the outer portion is incrementally moved and twisted relative to the main body portion, followed by a stress relaxation process, to achieve an overcoil configuration without additional components, using micro-fabrication techniques like DRIE and oxidation to relieve internal stresses and maintain mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plane balance spring is used, then the manufacturing is simple, but the coils deform eccentrically during operation causing the center of gravity to shift
Solution Approach 1:
The patent transitions from a two-dimensional plane balance spring to a three-dimensional overcoil configuration. The outer portion is moved out of the plane of the main body portion to form an overcoil shape, which adds a vertical dimension to the spring structure. This dimensional change allows the spring to maintain better concentricity during operation while still being manufacturable using standard micro-fabrication techniques followed by a forming step
2Manufacturing precision
If the center of gravity is shifted to the center, then the initial position is corrected, but the center of gravity moves during operation and no longer coincides with the initial center
Solution Approach 1:
By forming the outer portion into an overcoil configuration that extends out of the plane of the main body, the patent creates a three-dimensional structure where the center of gravity remains stable during operation. The overcoil geometry distributes mass in a way that maintains rotational balance, preventing the center of gravity from shifting during oscillation
3Manufacturing precision
If Breguet overcoil balance spring with assembled pieces is used, then the concentricity is improved, but the device complexity increases
Solution Approach 1:
The patent combines the main body portion and outer portion into a single unitary structure made from one piece of silicon material. The outer portion is integrally formed with the main body and then moved into the overcoil configuration, eliminating the need for separate assembled pieces while maintaining the concentricity benefits of an overcoil design
Solution Approach 2:
The patent creates a three-dimensional overcoil structure from a unitary silicon piece by moving the outer portion out of the plane. This approach achieves the concentricity of traditional overcoil springs without requiring multiple assembled components, as the complex 3D shape is formed from a single monolithic structure
4Manufacturing precision
If Straumann double balance springs are used, then the anisochronous motion is reduced, but the energy consumption increases
Solution Approach 1:
The patent uses a single balance spring instead of two paired springs, combining the functions of both springs into one unitary structure. The overcoil configuration of the outer portion provides the mechanical advantage of dual-spring systems for reducing anisochronous motion while eliminating the need for a second spring, thus reducing energy consumption
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 solution enhances the concentricity and isochronicity of the balance spring, maintaining mechanical integrity while eliminating the need for separate overcoil components, thus improving the accuracy and efficiency of the timepiece's regulation.
Implementation Method 1
moving said outer portion in a direction relative to and out of the plane of said main body portion, and in a direction towards over said main body portion
Implementation Method 2
providing a stress relaxation process to the balance spring so as to relieve internal stresses induced within the balance spring from step (ii)
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3b
AI summary
A method of producing unitary formed silicon balance spring (2) having an overcoil portion for regulation of a mechanical timepiece includes providing a silicon balance spring (2) having a main body portion (23), and an outer portion (22) for formation as an overcoil portion, wherein the outer portion (22) extends radially outward from an outermost turn of the main body portion (23) and wherein said main body portion (23) and said outer portion (22) are integrally formed from a silicon based material and are formed in a co-planar configuration. The outer portion (22) is moved in a direction relative to and out of the plane of said main body portion (23), and in a direction towards over said main body portion (23) and towards the plane of the main body portion. A stress relaxation process is provided to the balance spring so as to relieve internal stresses induced within the balance spring from the second step. After movement of said outer portion (22) into the plane of said main body portion (23), the outer portion (22) is located in an overcoil configuration relative to said main body portion.