Tilted Balance Wheel Axes for Gravity Compensation
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Solution Overview
Problem
Mechanical watch movements face precision issues due to the effects of gravity, particularly the Grossmann effect, which causes variations in oscillation amplitude and rate when the watch is oriented vertically, and existing solutions like Breguet hairsprings or dual balances with differential gears only partially address these issues.
Innovation Solution
The watch movement features two pairs of balance wheels with axes inclined at 45° to each other, forming a cross configuration, which maintains constant oscillation amplitude across different positions and compensates for gravity effects, along with differential gears to average the steps of the balances, ensuring orthogonality between the axes to cover all directions and reduce rate deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flat balance spring is used, then the structure is simple and easy to manufacture, but the center of gravity is not on the balance wheel axis causing imbalance in vertical position and rate variation
Solution Approach 1:
The balance spring is designed with an asymmetric configuration where the outer curve extends beyond the plane of the spring. This asymmetric shape positions the center of gravity of the balance spring on the balance wheel axis, eliminating the Grossmann effect and rate variation in vertical positions while maintaining manufacturing feasibility
Solution Approach 2:
The balance spring's outer curve extends in a third dimension beyond the plane of the spring, creating a three-dimensional structure. This dimensional change allows the center of gravity to be positioned on the balance wheel axis without complicating the manufacturing process
2Measurement precision
If the balance spring attachment point is adjusted to compensate for gravity in a predetermined position, then timekeeping accuracy is improved in that position, but the problem persists in other vertical positions
Solution Approach 1:
The asymmetric balance spring design with extended outer curve provides a universal solution that maintains the center of gravity on the balance wheel axis regardless of the watch's position. This eliminates rate variation in all vertical positions, not just a predetermined one, making the timekeeping accurate across all orientations
3Measurement precision
If a Breguet balance spring is used to keep the center of gravity on the balance wheel axis, then the Grossmann effect is eliminated, but the design is difficult to implement and does not solve rate difference between horizontal and vertical positions
Solution Approach 1:
The invention applies a localized modification to the balance spring structure - extending only the outer curve beyond the plane of the spring. This local quality change positions the center of gravity on the balance wheel axis without requiring complete redesign of the entire balance spring, simplifying implementation while eliminating the Grossmann effect
4Measurement precision
If two balance wheels with differential gear are used to average rates, then rate deviation due to gravity is reduced partially, but the solution is complex and does not fully address rate difference between positions
Solution Approach 1:
The invention extracts and eliminates the root cause of rate variation - the off-center balance spring center of gravity - by redesigning the balance spring geometry. This removes the source of the problem rather than adding complex averaging mechanisms, simplifying the overall design while fully addressing rate differences across positions
5Measurement precision
If tourbillon mechanism is implemented to average rates in different vertical positions, then timekeeping accuracy is improved, but the mechanism is complex and expensive and does not address rate difference between horizontal and vertical positions
Solution Approach 1:
The invention converts the potentially harmful effect of gravity on the balance spring by strategically positioning the center of gravity on the balance wheel axis through the extended outer curve design. This transforms gravity from a source of error into a neutral force, eliminating rate variation without requiring complex tourbillon mechanisms
Data Source
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AI summary
The invention relates to a clock movement which includes a driving means (2a, 2b), at least one pair, and preferably two pairs, of control members (5a-5d) each including a balance (9a-9d), and a connecting means (1, 3a, 3b, 4a-4d) connecting the driving means to the control members. The axes (12a, 12c; 12b, 12d) of the balances of a same pair are substantially orthogonal to one another, in order to reduce operating variations due to gravity.