Differential Gear Mechanism for Concentric Civil and True Time Hands
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Solution Overview
Problem
Existing running equation of time mechanisms in timepieces are bulky and asymmetrical, requiring additional gear trains to achieve concentricity of civil and true time minute hands, which complicates construction and increases the risk of failure.
Innovation Solution
A compact differential gear device with integrated reduction and multiplication functions, utilizing a reduction satellite wheel and pinion to drive civil time hour and true time minute hands, and a multiplier satellite wheel and pinion to drive true time minute hands, centered on the movement's center, reducing the mechanism's size and improving symmetry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If additional gear trains are used to achieve concentricity of civil and true time minute hands, then the hands are properly positioned concentrically, but the mechanism becomes bulky and complex
Solution Approach 1:
The patent merges the functions of multiple gear trains into a single integrated differential mechanism. The differential device combines the reduction function (from civil time minute to hour) and multiplication function (from civil time hour to true time minute) in one compact unit, eliminating the need for separate additional gear trains while maintaining concentric hand positioning.
Solution Approach 2:
The differential mechanism performs multiple functions simultaneously: it reduces the civil time minute hand's rotation to drive the civil time hour hand, multiplies the civil time hour hand's rotation to drive the true time minute hand, and ensures both hands rotate concentrically. This multi-functionality eliminates the need for separate dedicated gear trains for each function.
2Measurement precision
If additional gear trains are used to achieve concentricity of hands, then proper time indication is achieved, but the risk of failure increases
Solution Approach 1:
By combining multiple gear train functions into a single differential mechanism, the patent reduces the total number of moving parts and potential failure points. The integrated design maintains precise time indication through carefully designed gear ratios while improving reliability by eliminating the need for multiple separate gear trains that could fail independently.
3Volume of moving object
If a compact differential gear device is used, then the mechanism size is reduced and symmetry is improved, but additional space for other components is created
Solution Approach 1:
The patent achieves compactness by merging the reduction and multiplication functions into a single differential gear device. This integration eliminates the space required for separate gear trains and allows all components to be arranged symmetrically around the central axis, improving both size and aesthetic appearance while maintaining full functionality.
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 solution results in a more compact, reliable, and symmetrical running equation of time mechanism, allowing easier integration into watch movements and providing additional space for other components while ensuring precise time differentiation.
Implementation Method 1
a differential gear device (64) which has as respective inputs a mobile (66) of a finishing train driving a civil time minute hand (48) and an equation of time lever (68) which cooperates with an equation of time cam (54)
Implementation Method 2
a reduction satellite wheel and pinion (74) via which the civil time minute hand (48) drives a civil time hour hand (46)
Implementation Method 3
an equation of time cam (54) whose profile is determined by the difference between mean solar time or civil time and true solar time
Data Source
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AI summary
The invention relates to a running equation of time mechanism comprising a switch whose role is to indicate civil time by means of an hour hand (46) and a minute hand (48), and a true time minute hand (50), concentric with the civil time minute hand (48), and which indicates the true time minute, the running equation of time mechanism (44) also comprising an equation of time cam (54) having a profile which is determined by the difference, for each day of the year, between mean solar time or civil time, and solar time or true time, this equation of time cam (54) being driven in rotation at a rate of one revolution per year by a calendar mechanism, the daily position of the true time minute hand (50) being determined by the position of the equation of time cam (54),the running equation of time mechanism (44) also comprising a differential gear device (64) having a first input consisting of a bearing (72) integral with a civil time minute barrel (70) onto which a civil time minute hand (48) is mounted, and having a second input consisting of the equation of time cam (54), the differential gear device (64) comprising a reducing satellite gear (74) via which the civil time minute barrel (70) drives a civil time hour barrel (84) onto which the civil time hour hand (46) is mounted, and a multiplying satellite gear (90) via which the civil time hour barrel (84) drives a true time minute barrel (102) onto which the true time minute hand (50) is mounted.