Bistable Anti-Trip Mechanism for Watch Balance Wheel
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Solution Overview
Problem
Existing anti-trip mechanisms for mechanical watches disrupt the balance wheel's oscillations and efficiency due to modified inertia and friction, and often limit the angle of rotation in only one direction.
Innovation Solution
A bistable flexible element with anti-trip stops, fixed via flexible and elastic connections, is used to limit the angular movement of the balance wheel in both directions by interfering with the pin's trajectory, mimicking the Swiss anchor's position memorization principle, with minimal disturbance to the oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pinion mounted on the balance shaft meshes with a toothed wheel to limit angular movement, then the balance wheel's angular extension is limited, but the inertia of the balance is influenced and oscillations are disrupted
Solution Approach 1:
The patent extracts the anti-trip limiting function from the balance assembly itself by using a separate locking arm that interacts with the hairspring's external turn. This separation prevents the limiting mechanism from directly influencing the balance's inertia and oscillations, while still achieving the safety function of limiting angular extension.
Solution Approach 2:
The patent introduces the hairspring's external turn as an intermediary element between the balance and the locking mechanism. The locking arm interacts with this intermediary rather than directly with the balance, thereby achieving angular limitation without disrupting the balance's natural oscillations.
2Reliability
If a locking arm fixed to the external turn of the hairspring is used to limit rotation, then the angle of rotation is limited in one direction, but the mechanism only works in one direction of rotation
Solution Approach 1:
The patent divides the anti-trip protection into two separate locking arms, each responsible for limiting rotation in one direction. This segmentation allows independent optimization of each direction's limiting mechanism and enables bidirectional protection without interfering with each other.
Solution Approach 2:
The patent employs asymmetric positioning of the two locking arms relative to the balance's neutral position, with each arm configured to engage at different angular displacements in opposite directions. This asymmetric design enables effective bidirectional limitation while adapting to the different mechanical characteristics of each rotation direction.
3Reliability
If a pivoting mobile bearing a finger circulating in a cam track is used, then the anti-trip function is achieved, but friction occurs and disturbs the regulation mechanism
Solution Approach 1:
The patent replaces the traditional pivoting mobile bearing with a flexible locking arm that utilizes the elastic properties of the hairspring's external turn. This substitution eliminates the need for physical contact and friction-based operation, thereby reducing energy losses while maintaining the anti-trip function.
Solution Approach 2:
The patent changes the operational parameter from friction-based mechanical contact to elastic deformation of the hairspring. By utilizing the elastic properties of the external turn, the mechanism achieves angular limitation without the energy losses associated with friction in pivoting joints.
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 mechanism effectively limits the balance wheel's angular travel in both directions without significant loss of performance, ensuring safety and precision while minimizing interference with the balance wheel's oscillations.
Implementation Method 1
a bistable flexible element which is arranged to be fixed, by means of flexible and elastic connection elements, to a rigid structural element
Data Source
Figure 1~5
Figure 6~13
Figure 6A~10
AI summary
The mechanism has anti-trip mechanism that is provided with bistable element (5) to carry anti-trip stop element, and is fixed to a rigid structural element of timepiece movement through elastic connecting elements. An end of anti-trip stop element is arranged according to the angular position of a balance (2) to interfere with trajectory of pin (4), and to perform function of stop element, when balance exceeds normal angular travel. The anti-trip stop element (6) is provided with arms whose ends interfere with the trajectory of pin.