Mechanical Watch Movement Backlash Regulation via Pivoting Lever
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Solution Overview
Problem
Mechanical watch movements with striking mechanisms face issues due to backlash in the minute train, leading to inaccuracies in the position of the minute hand relative to the dial and the number of strokes, which is unacceptable for high-quality timepieces.
Innovation Solution
A mechanical watch movement with a striking mechanism that includes a second cannon pinion engaging with the going train and a minute wheel mounted on a pivoting lever, allowing adjustment of the angular position to regulate the backlash between the first and second cannon pinions, ensuring precise alignment of the minute hand with the dial.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a secondary cannon pinion connected to the principal cannon pinion by an intermediate wheel is provided to offset the minute hand axially, then the aesthetic or functional offset is achieved, but the backlash in the minute train increases to 3-8° causing reading errors
Solution Approach 1:
A motion work is introduced as an intermediary mechanism between the principal cannon pinion and the secondary cannon pinion. This motion work includes a cam profile that converts the rotational motion of the principal cannon pinion into a combined rotational and oscillating motion, thereby transmitting power while minimizing backlash accumulation and ensuring precise angular positioning of the minute hand.
Solution Approach 2:
The invention changes the transmission parameters by using a cam mechanism with specifically designed profile geometry. The cam profile parameters are optimized to maintain minimal backlash while achieving the required axial offset, thereby controlling the angular position accuracy within acceptable tolerances despite the intermediate transmission stages.
2Manufacturing precision
If the minute snail is fixed directly to the principal cannon pinion, then there is no offset between the minute hand position and the minutes striking mechanism, but it is not possible to achieve axial offset for aesthetic or functional reasons
Solution Approach 1:
The motion work serves as a mediator that decouples the principal cannon pinion from the secondary cannon pinion while maintaining precise angular correspondence. The cam mechanism in the motion work ensures that the angular position of the minute hand remains accurately correlated with the minutes striking mechanism, even though the minute hand is axially offset on a separate cannon pinion.
Solution Approach 2:
The timekeeping and striking functions are segmented into separate axial levels. The principal cannon pinion with its minute snail remains on the main axis for accurate striking, while the secondary cannon pinion carrying the offset minute hand operates on a separate axial level, allowing both functions to coexist without interference while maintaining their respective precision requirements.
3Shape
If a complex mechanism with multiple pinions and intermediate wheels is used to achieve axial offset, then the offset is achieved, but the device complexity and space requirements increase
Solution Approach 1:
The motion work combines multiple functions into a single integrated component. It simultaneously serves as the intermediate transmission mechanism, the cam mechanism for motion conversion, and the support structure for the secondary cannon pinion. This merging reduces the total number of separate components while achieving the axial offset and maintaining precision requirements.
Solution Approach 2:
The motion work is designed as a multi-functional element that performs several roles: it transmits power from the principal to the secondary cannon pinion, provides the cam mechanism for motion conversion, supports the offset minute hand assembly, and controls the backlash in the transmission train. This multi-functionality reduces overall device complexity despite the added axial offset capability.
Data Source
AI summary
A mechanical watch movement includes a striking mechanism with a first cannon equipped with a first cannon pinion having at least one snail intended to cooperate with a sensor device of the striking mechanism. The watch also includes a second cannon equipped with a second cannon pinion and carrying the minute hand. The first cannon pinion engages with a going train of the movement and a minute wheel. The minute wheel engages with the first cannon pinion. A motion-work pinion engages with an hour wheel coaxial with the second cannon. The minute wheel is mounted on a lever arranged to pivot about a fixed point. An angular position of the lever may be adjusted by pivoting in such a way as to permit regulation of the position of the minute wheel with respect to the first cannon pinion and to the second cannon pinion.