Pointer Stop Position Mechanism for Gear Backlash Reduction
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Solution Overview
Problem
Existing timepiece mechanisms experience fluctuations in pointer stop positions due to gear backlash, leading to noticeable movements and potential damage from unexpected loads when correcting time or performing functions that reverse the hand movement direction.
Innovation Solution
A variation reduction mechanism that includes a return gear driven by the time display mechanism, a friction member to apply friction force to the return gear, and a return spring member that applies torque in the opposite direction to the hand movement, ensuring the teeth of gears remain pressed together within the backlash, preventing damage and reducing stop position variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a spiral spring is used to press gear teeth in the direction opposite to hand movement to reduce backlash, then the stop position variation of the pointer is reduced, but the spring may be damaged when the hand moves in the opposite direction
Solution Approach 1:
The patent inverts the direction of the spring force by using a return spring that acts in the normal hand movement direction rather than the opposite direction. This is achieved by positioning the return spring to engage with the return gear and apply force in the direction of normal hand movement, thereby eliminating the risk of spring damage during reverse operations while still maintaining gear engagement
Solution Approach 2:
The patent introduces a return gear as an intermediary component between the time display mechanism and the return spring. This return gear transfers the torque from the return spring to the gear train, allowing the spring force to be applied indirectly through the return gear engagement, thus maintaining gear teeth contact without directly loading the spring during reverse movement
2Stability of the object's composition
If friction force is applied to the return gear to maintain gear engagement, then the pointer stop position stability is improved, but the device complexity increases
Solution Approach 1:
The return spring mechanism is designed to automatically engage and disengage based on the direction of hand movement. During normal operation, the return spring maintains gear engagement through its elastic force, and during reverse operation, the mechanism self-adjusts without external intervention, eliminating the need for additional control systems or complex actuation mechanisms
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 reduces pointer stop position variations and prevents damage to the spiral spring by maintaining gear engagement in the normal hand movement direction, even when reversing, thus stabilizing timepiece operations.
Implementation Method 1
a friction member that contacts the return gear to apply a friction force to the return gear to be driven
Implementation Method 2
a return spring member that applies, to the friction member, a torque of the return gear in a direction opposite to a normal hand movement direction
Data Source
AI summary
A variation reduction mechanism of a stop position of a pointer includes a return gear that is driven in conjunction with a time display mechanism, a slip torque spring (friction member) that contacts the return gear to apply a friction force to the return gear to be driven, and a return spring (return spring member) that applies, to the slip torque spring, a torque of the return gear in a direction (dashed line arrow—R direction) opposite to a normal hand movement direction (arrow R direction).