Escape Lever Locking Surface Curvature for Constant Draw Angle
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Solution Overview
Problem
Timepieces with escapement mechanisms experience energy loss and reduced resistance to external shocks due to a decreasing torque ratio of the escape lever to the escape wheel during the unlocking period, leading to insufficient draw power and increased energy loss.
Innovation Solution
The escape lever features a pallet fork with a locking surface that maintains a constant draw angle during the unlocking period, ensuring consistent moment application through a curved entrance-pallet side locking surface and exit-pallet side locking surface, formed from a material containing silicon, which enhances precision and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the locking surface is shaped so that the draw angle decreases during the unlocking period, then energy loss is suppressed by reducing the torque ratio, but resistance to external shock is reduced and sufficient draw power cannot be achieved at the end of the unlocking period
Solution Approach 1:
The locking surface is designed with a specific curved shape so that the draw angle formed by a normal to the contact point with the locking corner and a line through the contact point and the axis of the pallet staff remains constant during the unlocking period. This curvature compensates for the changing position of the escape wheel, maintaining consistent torque transmission and draw power throughout the unlocking cycle, thereby ensuring reliable operation even under external shocks.
2Reliability
If the minimum required moment is assured at the end of the unlocking period, then resistance to external shock is improved, but energy loss is increased due to greater moment at the beginning of the unlocking period
Solution Approach 1:
The curved locking surface geometry is specifically designed to maintain a constant draw angle throughout the unlocking period. This ensures that the moment applied to the pallet lever remains consistent, providing sufficient draw power at the end of the unlocking period to resist external shocks, while avoiding excessive moment at the beginning that would cause energy loss.
Data Source
AI summary
An escape lever suppresses energy loss and provides strong resistance to external shocks. An escape lever has a pallet fork; a pallet formed in unison with the pallet fork for engaging the escape wheel; and a pallet staff that is a pivot of the pallet fork and passes through the pallet fork. The pallet has a locking surface that the locking corner of the escape wheel contacts in the unlocking period when the escape wheel is released by the pallet and freed to move. The locking surface is shaped so that the draw angle formed by a normal to the contact point with the locking corner of the escape wheel, and a line through the contact point and the axis of the pallet staff, remains constant during the unlocking period.