Watch Control Rod Assembly with Automatic Length Adjustment
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Solution Overview
Problem
Current watchmaking technologies face challenges in precisely positioning and adjusting the control rod connecting the control crown to the watch movement, leading to tedious and time-consuming assembly processes due to mechanical play and limited precision in existing solutions.
Innovation Solution
A control device featuring a control rod with a movable and rotatable first part and a second part integral with the movement, interconnected by a coupling/uncoupling mechanism with a polygonal and conical end, and a piston slidably mounted in a broached sleeve within the control crown, allowing automatic length adjustment and reducing mechanical backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crown stem passes through a crown tube mounted to the watch case by welding, then the assembly is structurally stable, but the positional tolerance exceeds the precision necessary for perfect interaction between the crown stem and the movement
Solution Approach 1:
The patent introduces a crown stem adjustment mechanism as an intermediary element between the crown tube and the movement. This adjustment mechanism includes a crown stem holder that can be positioned at different depths, allowing precise adjustment of the crown stem length to compensate for positional deviations in the welded crown tube, thereby resolving the contradiction between structural stability and positioning precision.
2Manufacturing precision
If the crown stem length is adjusted manually during assembly, then the positional precision can be improved, but the assembly process becomes tedious and time-consuming
Solution Approach 1:
The patent implements a pre-adjusted crown stem holder that can be set to different lengths before assembly. This allows the crown stem length to be predetermined and pre-positioned, eliminating the need for time-consuming manual adjustments during the final assembly process while maintaining high positioning precision.
Solution Approach 2:
The crown stem holder is designed with dynamic adjustment capability, allowing it to be positioned at different depths during assembly and then locked in place. This dynamic feature enables quick adjustment without tedious manual operations, reducing assembly time while achieving precise positioning.
3Ease of operation
If a positioning spring is used to allow crown protrusion when unscrewed, then the crown manipulation is facilitated, but mechanical play appears in rotation at the coupling of the two stem parts
Solution Approach 1:
The patent divides the crown stem into two separate parts: a crown stem holder and a crown stem. The crown stem holder is securely attached to the movement, eliminating mechanical play, while the crown stem can protrude when unscrewed for easy manipulation. This segmentation resolves the contradiction by isolating the rotational stability function in the holder from the manipulation function in the stem.
4Adaptability or versatility
If a friction connection is used between the crown and the control rod, then the control rod can slide relative to the crown for length adjustment, but the position precision and stability over time are limited
Solution Approach 1:
The patent introduces a crown stem holder as an intermediary mechanism between the crown and the control rod. This holder provides a precise mechanical connection with defined positioning features, replacing the imprecise friction connection while maintaining the ability to adjust the control rod length through the holder's depth adjustment capability.
Data Source
Figure 1
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Figure 3~4
AI summary
The device has a control rod (2) kinematically linking a control ring (1) in a movement, and a crown tube (3) mounted on a middle part through which the control rod extends. An adjusting unit includes a housing (6) formed in the control ring, which is engaged in an axial portion of the crown tube. An end portion of the control rod is slidably mounted in the crown tube, and a spring (11) is placed in the housing between an end portion and a support located in the housing so as to axially constrain the control rod in the direction of the movement.