Cam Timepiece Mechanism With Variable Pitch for Accurate Reading
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Solution Overview
Problem
Existing cam-driven clock mechanisms suffer from positioning errors due to manufacturing tolerances and operating clearances, leading to inaccuracies in reading time information, and existing solutions like the 'surprise' mechanism are bulky and require additional parts.
Innovation Solution
A cam-driven chronograph mechanism using a kinematic chain with non-circular moving parts with conjugate profiles, ensuring the angular pitch is greater during transitions between cam profile jumps than during steps, thereby preventing reading errors and maintaining compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional cam mechanism with a feeler is used to read time information, then the mechanism is simple in structure, but positioning errors occur due to manufacturing tolerances and operating clearances leading to reading inaccuracies
Solution Approach 1:
The patent applies asymmetry by using non-circular moving parts with conjugate profiles instead of conventional circular components. The asymmetric geometry of the non-circular parts creates a mechanical advantage that amplifies the cam's rotational position, making the feeler's reading position more precise and less sensitive to manufacturing tolerances and operating clearances.
Solution Approach 2:
The patent implements dynamics by using non-circular moving parts that create variable transmission ratios during rotation. This dynamic mechanism ensures that at specific positions (when cam steps are opposite the feeler), the angular pitch is maximized, providing optimal reading accuracy while maintaining simplicity in other positions.
2Reliability
If a 'surprise' mechanism is added to prevent reading errors on snail cams, then reading reliability is improved, but the mechanism becomes bulky and occupies vertical space
Solution Approach 1:
The patent extracts the error-prevention function from the bulky 'surprise' mechanism and integrates it into the fundamental kinematic chain through non-circular moving parts. This eliminates the need for the separate surprise device while maintaining reading reliability, thereby reducing vertical space occupation.
Solution Approach 2:
The patent merges the error-prevention function with the cam driving mechanism itself. The non-circular moving parts with conjugate profiles simultaneously perform the functions of driving the cam and ensuring accurate reading positions, consolidating multiple functions into a single integrated system that is both reliable and compact.
3Measurement precision
If the angular pitch of the cam is uniform during rotation, then the mechanism is simple to manufacture, but reading errors occur during transitions between cam profile jumps
Solution Approach 1:
The patent uses asymmetric non-circular profiles in the moving parts to create variable angular pitch during cam rotation. This asymmetric geometry is manufactured as an integrated component with conjugate profiles, maintaining manufacturing simplicity while achieving precise reading positions through the variable pitch mechanism.
Solution Approach 2:
The patent changes the angular pitch parameter dynamically during cam rotation by using non-circular moving parts. The angular pitch varies throughout the rotation cycle, being maximized when cam steps are opposite the feeler for accurate reading, and adjusted in other positions to maintain smooth operation and manufacturing feasibility.
Data Source
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AI summary
A clockwork mechanism comprising a kinematic chain including a first moving part (2, 2') fixed for rotation about a first axis of rotation (20, 20') and a second moving part (3, 3') fixed for rotation about a second axis of rotation (30, 30'), the first moving part (2, 2') being meshed with the second moving part (3, 3') at a point of contact (4), the first moving part (2, 2') being configured to be driven directly or indirectly by a driving element and to directly drive the second moving part (3, 3'), a cam (1) for measuring and/or storing time information, the cam (1) comprising a variable diameter profile with at least one step (11) and at least one jump (12), the cam (1) being driven directly or indirectly by the second moving part (3, 3'), and a probe for reading the time information by pressing against the profile of the cam (1), characterized in that the first mobile (2, 2') and the second mobile (3,3') are non-circular moving parts with conjugate profiles, and in that the kinematic chain is configured such that the ratio (R1/R2) between a first distance (R1) measured between the first axis of rotation (20, 20') and the point of contact (4) and a second distance (R2) measured between the second axis of rotation (30, 30') and the point of contact (4) is greater when at least one step (12) is opposite the feeler than when a part of at least one rung (11) is opposite the feeler. A timepiece comprising a watch movement and such a timekeeping mechanism.