Hairspring with Variable Pitch and Counterweights for Isochronism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing hairsprings fail to accurately control the center of mass displacement during contraction and expansion, leading to significant variations in watch rate due to rough approximations in geometric conditions, resulting in disappointing rate variations.
Innovation Solution
A hairspring design featuring a first and second spiral spring with continuously variable pitch, symmetrical curves, and counterweights to minimize center of mass displacement, with specific moment equations and counterweight placement to compensate for unbalance and anisochronism, made from silicon with silicon dioxide coating for temperature and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If Phillips' criteria are used to determine the theoretical curvature of a terminal curve, then the manufacturing process is simplified, but the center of mass displacement control becomes insufficient and rate variations increase
Solution Approach 1:
The patent transitions from using Phillips' approximate criteria to implementing precise moment equations of order n (where n ≥ 0) that define the spiral curvature. This parameter change in the mathematical model enables exact control of the center of mass displacement while maintaining manufacturing feasibility through systematic curve design.
Solution Approach 2:
The patent applies counterweights in advance during the hairspring design phase to compensate for the mass of the attachment before the hairspring is assembled. This preliminary balancing action ensures that the center of mass displacement is minimized from the outset, preventing rate variations rather than correcting them later.
2Device complexity
If a single spiral spring is used, then the device complexity is reduced, but the isochronism performance deteriorates due to significant center of mass displacement
Solution Approach 1:
The patent divides the hairspring into two separate spiral springs (first and second spiral springs) with distinct curves extending in different planes. Each spiral spring has its own curve optimized to meet moment equations, and they are connected by a fastener. This segmentation allows independent optimization of each spiral to minimize overall center of mass displacement while maintaining manageable device complexity.
3Reliability
If counterweights are added to compensate for imbalance, then the anisochronism slope can be personalized, but the device complexity increases
Solution Approach 1:
The patent adds counterweights at specific local positions on the spiral springs - two counterweights located next to the attachment and two other counterweights located on the opposite side of the attachment. This localized placement of counterweights provides precise anisochronism compensation without requiring a complete redesign of the entire spiral structure, thus limiting the increase in device complexity.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The spring (1) has hairsprings (3, 5) comprising curves extending in planes, where each curve has continuously variable pitch. The curves are symmetrical relative to a straight line (A) parallel to the planes, and pass through a median projection plane (P) of an attachment element (4). Each curve is arranged such that specific relation is zero to reduce displacements of center of mass during contraction and expansion. Each hairspring has H-shaped counterweights (8, 8', 9, 9') to compensate for unbalance formed by a mass of the element and personalize anisochronism slope of the balance spring. The specific relation includes a moment of the balance spring of order n, length of the balance spring and curvilinear abscissa along the balance spring to the power of n and parameterization of the balance spring by the abscissa. The balance spring is formed from silicon and includes a part coated with silicon dioxide.