Retrograde Timepiece Movement Cam Force Regulation
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Solution Overview
Problem
Existing timepiece movements with retrograde displays face significant frictional force variations due to the remote axis of rotation of the lever and the spring's point of support, leading to operational disturbances and precision issues, especially when driving display members over large angular sectors.
Innovation Solution
A force-regulating device is introduced between the elastic means and the lever, utilizing a second cam with a shared axis of rotation and a long spring, which applies a rotational torque directly to the lever, and an additional cam with a variable radius periphery to regulate the force transmitted to the lever, minimizing friction and maintaining precision across significant angular sectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the lever axis of rotation is positioned remotely from the feeler-spindle to enable retrograde display over large angular sectors, then the display range is improved, but the spring deformation amplitude increases significantly causing frictional force variations that disturb movement operation
Solution Approach 1:
The patent introduces a second cam as an intermediary element between the spring and the lever. This second cam is positioned close to the lever's axis of rotation and works in conjunction with a feeler-spindle on the lever to regulate the spring's action, thereby mediating the force transmission and reducing direct frictional disturbances to the lever while maintaining the retrograde display function over large angular sectors
Solution Approach 2:
The patent modifies the geometric parameters of the cam mechanism by positioning the second cam's axis of rotation close to the lever's axis and designing the cam profile with specific curvature characteristics. This parameter change allows the spring to act more centrally on the lever system, reducing the moment arm and thereby minimizing frictional force variations while preserving the extended display range
2Device complexity
If the spring support point is positioned at the feeler-spindle level to simplify construction, then the device complexity is reduced, but the spring deformation amplitude increases causing significant frictional force variations
Solution Approach 1:
The second cam serves as a mediating structure that redistributes the spring's force application points. Instead of the spring acting directly at the feeler-spindle, it now interacts with the second cam which is positioned closer to the lever axis, thereby reducing the deformation amplitude while maintaining constructional simplicity through the integration of this additional cam element
3Measurement precision
If a force-regulating device with a second cam is introduced between the spring and lever, then the operation precision is improved, but the device complexity increases
Solution Approach 1:
The second cam acts as a precision-regulating intermediary that controls the spring's force transmission to the lever. By positioning this cam close to the lever axis and designing its profile appropriately, it provides precise force regulation that improves operation precision while adding minimal complexity compared to alternative solutions
4Reliability
If the cam axis of rotation is positioned close to the lever axis to reduce spring deformation, then the frictional force variation is reduced, but the display sector coverage may be limited
Solution Approach 1:
The second cam, positioned close to the lever axis, mediates the spring's action to reduce frictional force variations. Simultaneously, the first cam (driven by the going train) and the lever's geometric configuration are designed to work together to maintain the retrograde display coverage over the required angular sector, thus resolving the contradiction between friction reduction and display coverage
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
This solution enhances the precision of the timepiece movement, maintaining accuracy even when driving display members over sectors greater than 60 degrees, particularly 270 degrees, with reduced spring tension variation impacting the going train, resulting in a smoother operation and slower return of the hour hand.
Implementation Method 1
deformable elastic means undergoing a deformation of variable amplitude. This drives the application of a corresponding force on the lever
Implementation Method 2
a force-regulating device is inserted between the elastic means and the lever... utilizing a second cam with a shared axis of rotation and a long spring
Data Source
AI summary
A movement for a timepiece having a retrograde display member displaying at least one time division, includes a going train, elements for driving the display member including a wheel unit driven by the going train and carrying a first cam sharing the same axis of rotation. The movement also includes a rocker supporting a probe held against the edge of the first cam by deformable elastic elements undergoing a deformation of variable amplitude. This results in the application of a corresponding force on the rocker in proportion to the distance between the probe and the axis of rotation of the first cam. The movement also includes drive members to connect the rocker to a retrograde display member. A force-regulating device is interposed between the elastic elements and the rocker.