Cam Profile Angle Optimization for Instantaneous Display Jumps
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Solution Overview
Problem
Conventional drive devices for display elements in timepieces, such as calendar mechanisms, face challenges in achieving precise and reliable instantaneous changes in date or hour displays due to variability in speed and friction coefficients, leading to inconsistent timing and potential jumps at inappropriate moments.
Innovation Solution
A drive device with a cam, lever, and spring system where the angle between specific axes is optimized to minimize friction and maximize torque variation, featuring a roller for reduced friction and a cam peak design that enhances control over the transition zone, ensuring repeatable and precise jumps without distinction between normal and correction modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the cam speed varies between normal operating mode and correction mode, then the display can be adjusted during time setting, but the instantaneous change timing becomes inconsistent and may occur at incorrect moments
Solution Approach 1:
The invention changes the geometric parameter of the cam profile, specifically optimizing the angle alpha (between the normal to the cam profile at the peak and the direction of cam rotation) to be between 40-60 degrees. This parameter optimization ensures that the torque variation remains effective across different cam speeds, making the instantaneous change timing consistent whether the cam is driven by the going train at normal speed or by the quick-setting mechanism at variable speeds.
2Adaptability or versatility
If friction coefficients between drive elements vary, then the drive device can accommodate different operating conditions, but the time of instantaneous display change becomes unpredictable
Solution Approach 1:
The invention optimizes the cam profile geometry parameter (angle alpha between 40-60 degrees) to maximize torque variation during the instantaneous change. This optimized geometry creates a more pronounced torque peak that overcomes friction variations more reliably, ensuring consistent timing of the display jump even when friction coefficients vary between elements like the lever-cam contact, roller-cam contact, and gear meshing.
3Ease of manufacture
If the cam peak is manufactured as a rounded surface rather than a sharp point, then manufacturing is easier, but the trigger location for display jump becomes less precise
Solution Approach 1:
The invention specifies that the angle alpha (between the normal to the cam profile at the peak and the rotation direction) should be between 40-60 degrees. This optimized angle parameter ensures that even with a rounded cam peak surface from manufacturing, the torque variation remains sufficiently sharp and pronounced to trigger the instantaneous display change at a well-defined moment, thus maintaining precision despite the rounded geometry.
Solution Approach 2:
The invention replaces reliance on a sharp geometric point (which would give precise trigger location) with an optimized rounded surface geometry characterized by a specific angle alpha. This substitution maintains functional precision through optimized mechanical parameters rather than relying on sharp edges, accommodating manufacturing realities while preserving performance.
4Duration of action of stationary object
If the lever is returned into contact with the cam using a spring, then the drive device can reset for the next instantaneous change, but friction losses occur during lever movement
Solution Approach 1:
The optimized cam profile geometry (angle alpha = 40-60 degrees) maximizes the torque variation during the instantaneous change, creating a stronger driving torque that can overcome friction losses more effectively. This ensures that the spring-powered lever reset mechanism maintains reliable operation for repeated instantaneous changes despite energy losses to friction during lever movement and contact.
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 optimized drive device achieves unequivocal and repeatable instantaneous changes in date or hour displays, minimizing sensitivity to friction variations and ensuring accurate timing, even when the timepiece is not indicating exact midnight or whole hours, thereby improving reliability and precision.
Implementation Method 1
a spring (5) which is designed to return the lever (4) into contact with the cam (3)
Implementation Method 2
The lever (4) comprises a roller (4a) which is mounted on the lever (4) so as to pivot about a third axis (A4a)
Data Source
AI summary
A drive device for a display element for displaying a quantity associated with time or derived from time,includes a cam that is pivoted about a first axis and designed to drive the movement of the display element, the cam having a peak,a lever that is pivoted about a second axis, anda spring that is designed to return the lever into contact with the cam, wherein an angle (α) is formed, in a plane perpendicular to the first and second axes, between(i) a straight line passing through(a) the contact point between the peak, in particular the point is farthest from the first axis, and the lever, and(b) the first axis, and(ii) a straight line passing through the first axis (A3) and the second axis, the angle (α) is less than or equal to 70°.