Constant Force Device Friction Reduction in Watch Movements
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Solution Overview
Problem
Existing watch movements with a 'constant force' device experience energy loss and irregular oscillations due to friction caused by the blocking member engaging with the stop wheel, which varies with the winding state of the motor, affecting the regularity of the oscillator's amplitude.
Innovation Solution
A lever is designed to prevent the release of the gear train for a predetermined number of oscillator alternations, driven only after those alternations, reducing friction and dependency on the winding state by minimizing contact between the rocker and lever during energy storage and release phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the locking element continuously engages with the stop wheel during the first phase, then the gear train is effectively immobilized, but friction is generated that consumes energy and disrupts oscillator regularity
Solution Approach 1:
The locking element is designed to engage and disengage periodically rather than continuously. It immobilizes the gear train for N oscillations, then releases it for one oscillation to reset the periodic energy storage spring. This periodic engagement reduces cumulative friction while maintaining effective control over the gear train throughout the operating cycle.
2Stability of the object's composition
If the locking element continuously contacts the stop wheel, then the gear train remains immobilized, but the friction varies with mainspring winding state affecting oscillator amplitude
Solution Approach 1:
The locking mechanism operates in periodic cycles, immobilizing the gear train for N oscillations then releasing it for one oscillation. This periodic operation reduces the cumulative friction effect while maintaining stable immobilization during the majority of the cycle, thereby improving oscillator amplitude regularity.
Solution Approach 2:
The locking element maintains continuous control over the gear train through periodic engagement and disengagement. Rather than losing control entirely, the system continuously alternates between immobilization and reset phases, ensuring both stability during operation and regularity over time.
3Ease of operation
If the locking element engages the stop wheel for the entire first phase, then the gear train is fully controlled, but the friction disrupts energy delivery consistency
Solution Approach 1:
The locking element periodically engages the stop wheel for N oscillations to control the gear train, then disengages for one oscillation to allow friction-free resetting of the periodic energy storage spring. This periodic operation maintains ease of control while ensuring consistent energy delivery to the escapement.
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 configuration maintains low friction and enhances the constancy of the oscillator's amplitude by ensuring energy delivery from the spring is consistent, reducing the impact of winding state variations, and improving the precision and reliability of the timekeeping mechanism.
Implementation Method 1
a periodic energy storage spring arranged to act on the rocker arm
Implementation Method 2
the stop wheel bears against the locking element attached to the rocker arm, so the rocker arm's movement generates friction
Data Source
Figure 1
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Figure 3
AI summary
The watch movement (1) according to the invention comprises: a gear train (3), a driving member (2) for driving the gear train (3), an escapement (4), an oscillator (5) arranged to cooperate with the escapement (4), a rocker (6) carrying an intermediate mobile (7) which connects the escapement (4) to the gear train (3), a periodic energy storage spring (8) arranged to act on the rocker (6), and a locking member (9) for immobilizing and releasing the gear train (3), this locking member (9) being controlled by the rocker (6).The watch movement (1) operates according to a cycle comprising a first phase during which the locking member (9) immobilizes the gear train (3), allowing the periodic energy storage spring (8) to unwind and move the rocker (6) in a first direction by steps at the rate of the alternations of the oscillator (5) until the locking member (9) releases the gear train (3), and a second phase triggered by the release of the gear train (3) during which the rocker (6) is moved in the opposite direction to the first direction under the action of the gear train (3) to re-arm the periodic energy storage spring (8) and return the locking member (9) to a position where it can again immobilize the gear train (3).The locking member (9) is a lever arranged so that, during the first phase, it is prevented by the rocker (6) from releasing the gear (3) during a non-zero integer number N of alternation(s) of the oscillator (5) and is driven by the rocker (6) only after the N alternation(s) to release the gear (3).