Coaxial Escapement Wheel Set for Wristwatch Size Reduction
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Solution Overview
Problem
The existing tangential impulse escapement, as described in the Melly Frères design, faces challenges with size constraints and operational safety due to its large size and limited energy transmission angles, which are difficult to reconcile for use in a wristwatch and lack a sufficient safety reserve considering mechanical manufacturing tolerances.
Innovation Solution
The implementation of a coaxial escapement wheel set comprising multiple integral wheels of varying diameters, where each wheel cooperates with dedicated impulse and rest pallets, allowing for improved size reduction and enhanced safety through increased displacement angles during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single escape wheel is used in the tangential impulse escapement, then the structure is simple, but the size becomes too large for wristwatches and operational safety is insufficient
Solution Approach 1:
The single escape wheel is divided into multiple coaxial wheels (first escape wheel and second escape wheel) with different diameters. Each wheel has its own impulse pallet and rest pallet, creating multiple independent impulse transmission paths. This segmentation reduces the size of each individual wheel while maintaining the overall functional complexity through coordinated operation of multiple wheels.
Solution Approach 2:
Multiple escape wheels are merged onto a common coaxial mounting structure sharing the same axis and pivot point. The impulse pallets and rest pallets are arranged around this common axis, combining the functions of multiple wheels into a unified compact assembly that maintains simplicity while improving safety through redundancy.
2Volume of moving object
If the displacement angle of the pallet is kept small (2°), then the escapement size is reduced, but the energy transmission effectiveness decreases and safety reserve is insufficient
Solution Approach 1:
The total displacement angle is segmented across multiple wheels. Each wheel provides a portion of the total impulse, allowing each individual pallet to operate with smaller angles while the cumulative effect of multiple wheels achieves the necessary energy transmission and safety reserve.
Solution Approach 2:
Multiple escape wheels operate in sequence to provide continuous impulse transmission. As one wheel completes its impulse cycle, another wheel is positioned to provide the next impulse, ensuring continuous and reliable energy transmission to the balance wheel without interruption.
3Reliability
If multiple coaxial escape wheels are introduced, then the size is reduced and safety is improved, but the device complexity increases
Solution Approach 1:
Multiple escape wheels are merged onto a common coaxial mounting structure that shares the same axis, pivot point, and rocketer interaction mechanism. This merging approach reduces the overall footprint and maintains structural coherence while providing the safety benefits of multiple wheels through coordinated operation around a common center.
Data Source
Figure 1~3
Figure 4~7
Figure 8~11
AI summary
The escapement has a latch (1) with a rod (3) and a ring (7) acting as two arms, respectively. The ring surrounds an escapement moving body (8), and has lock pallets (9, 11) and impulse pallets (10, 12) cooperated with teeth (13-16) of the moving body to alternately block the moving body and impart a plate (6). The moving body has a set of interdependent and coaxial large and small escapement wheels (17, 18), where one wheel (17) has a diameter larger than another wheel (18). Each of the wheels cooperates with the impulse pallets. The lock pallets are cooperated with any of the wheels.