Compact Constant-Force Escapement Mechanism for Watch Movements
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Solution Overview
Problem
Existing constant-force escapement mechanisms for watch movements either modify the going train, are bulky, or require complex mechanisms to ensure identical impulses to the balance-spring, failing to provide a compact and efficient solution.
Innovation Solution
A compact constant-force escapement mechanism with a simplified design that integrates an auxiliary spring between the escape wheel and balance-spring axes, using a pivoted impulse anchor and control elements to maintain consistent energy transmission without altering the going train, reducing inertia and enhancing chronometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an auxiliary spring is inserted in the kinematic chain connecting the mainspring barrel to the escape wheel, then constant torque is transmitted to the balance wheel, but the mechanism becomes bulky and requires additional space
Solution Approach 1:
The patent combines the auxiliary constant-force spring mechanism with the existing impulse anchor and escape wheel assembly. The auxiliary spring is integrated into the same spatial envelope as the going train components, merging multiple functions (torque regulation and impulse transmission) into a unified structure that does not increase the overall watch movement volume.
Solution Approach 2:
The auxiliary spring is arranged in a different spatial dimension or orientation relative to the main spring, allowing it to operate within the same cylindrical space of the barrel without interfering with the going train. This dimensional reorganization enables constant-force functionality without increasing the radial or axial dimensions of the movement.
2Device complexity
If the auxiliary spring is wound every five oscillations of the balance wheel, then the mechanism is simplified, but the torque transmitted to the balance wheel is not strictly constant
Solution Approach 1:
The auxiliary spring is pre-loaded to a specific tension before engagement, ensuring that it delivers a precise and constant torque from the first oscillation. The spring is initially wound to a predetermined state during assembly, eliminating the need for periodic rewinding mechanisms and ensuring continuous constant-force delivery throughout the power reserve period.
Solution Approach 2:
The auxiliary spring maintains continuous engagement with the escape wheel throughout the entire power reserve period, providing uninterrupted constant torque. The spring is designed to deliver consistent force from full wind to complete unwind, ensuring that the balance wheel receives identical impulses on every oscillation without interruption or variation in torque delivery.
3Reliability
If the auxiliary spring actuates the escape wheel through a lever arm mechanism, then constant torque is achieved, but the mechanism becomes very complicated and expensive
Solution Approach 1:
The patent extracts the complex lever arm mechanism from the design and replaces it with a direct actuation system. The auxiliary spring is connected directly to the escape wheel through a simple arbor or arbor-like component, eliminating the need for intermediate levers, linkages, or variable-length arms. This direct connection maintains constant torque while dramatically simplifying the mechanism.
Solution Approach 2:
Instead of using a lever arm to modify the torque output, the invention inverts the approach by having the auxiliary spring directly drive the escape wheel arbor at a fixed radius. The constant torque is achieved not through variable lever arm length but through the inherent constant-force property of the auxiliary spring acting at a fixed moment arm, simplifying the transmission path.
4Reliability
If gears are added to transmit constant torque to the escape wheel, then the mechanism functions, but it cannot be integrated into the space occupied by the classic anchor-escapement
Solution Approach 1:
The auxiliary spring mechanism is merged with the existing anchor-escapement assembly, sharing the same central space. The auxiliary spring arbor is co-located with the escape wheel arbor, and the impulse transmission path is integrated into the existing anchor geometry. This merging allows constant-force functionality to be added without requiring separate gear trains or additional spatial envelopes.
Solution Approach 2:
The impulse anchor is designed to perform multiple functions: it serves as both the traditional impulse transmitter from the escape wheel to the balance wheel and as the carrier for the auxiliary spring's torque transmission. The anchor's geometry is optimized to accommodate both functions simultaneously, making the mechanism universally applicable to classic escapement designs without requiring separate dedicated components for constant-force delivery.
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 achieves consistent energy delivery to the balance-spring with reduced inertia and improved precision, maintaining identical impulses while being compact and efficient, thus enhancing the chronometry of the watch movement.
Implementation Method 1
an auxiliary constant-force spring, intended for use in a watch movement including a balance wheel and hairspring and an escape wheel connected to a mainspring barrel by a finishing gear train
Data Source
Figure 1
Figure 2
Figure 2a~3a
AI summary
The mechanism has an impulsion lever (8) pivoted on a part of a frame of a timepiece movement and co-operating with an escapement gear (1) and control elements. The control elements are fixed to an arbor of a hairspring. An outer end (11-1) of a constant force auxiliary spring (11) i.e. helical spring, is fixed on the part of the frame of the movement, while an inner end of the auxiliary spring is angularly fixed to the impulsion lever. The impulsion lever is mounted on the movement so as to be angularly and axially displaceable with respect to the frame of the movement. An independent claim is also included for a timepiece movement.