Watch Barrel Spring Neck Geometry for Small-Radius Durability
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Solution Overview
Problem
Barrel springs with small barrel bung radii experience significant plastic deformation and premature breakage due to marked curvature differences between the armed and manufactured states, especially at the neck region, leading to reduced efficiency and reliability.
Innovation Solution
The neck of substantially zero curvature preceding the calendered part is lengthened to between 1.5 and 10 times the outer radius of the calendered part, reducing plastic deformation and enhancing the spring's robustness during the first winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the barrel radius is reduced to allow greater number of turns, then the number of turns increases, but the spring experiences significant curvature variations that cause plastic deformation and premature breakage
Solution Approach 1:
The patent applies preliminary action by pre-forming the spring with a longer neck of zero curvature before the calendered portion. This pre-configured geometry prepares the spring to better withstand the curvature variations during winding, reducing plastic deformation and preventing premature breakage while enabling greater number of turns.
Solution Approach 2:
The patent changes the geometric parameters of the spring, specifically increasing the neck length to between 1.5 and 10 times the outer radius of the calendered portion. This parameter modification allows the spring to maintain structural integrity under the stress of small barrel radius applications, resolving the contradiction between achieving more turns and maintaining reliability.
2Reliability
If the neck length is increased to reduce plastic deformation, then the spring durability improves, but the spring geometry becomes more complex
Solution Approach 1:
The patent modifies a single geometric parameter (neck length) within a specific range (1.5 to 10 times the outer radius) to achieve improved durability. This controlled parameter change maintains relative geometric simplicity while effectively resolving the plastic deformation issue, avoiding excessive complexity.
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
This optimized geometry ensures greater than 80% efficiency in both winding and unwinding operations, reducing the risk of premature rupture and improving the spring's durability, particularly for applications with a k factor less than 10.
Implementation Method 1
barrel springs are preformed by a calendering process to ensure a stress exceeding the elastic limit along the entire length of the spring
Implementation Method 2
barrel springs are preformed by a calendering process to ensure a stress exceeding the elastic limit along the entire length of the spring when it is formed into a drum
Data Source
Figure 1~2
AI summary
The invention relates to a watch barrel spring (1) comprising, in the manufactured state, a shell (2) and a portion (3) formed of coils with an outer coil having a radius R, the shell (2) and the portion (3) formed of coils being connected by a neck (4) having substantially zero curvature, the watch barrel spring (1) being characterized in that the neck (4) has a length Lc between 1.5 and 10, preferably between 2 and 8, times the radius R. The barrel spring (1) having this specific geometry makes it possible in use to reduce the risk of premature breakage for typically an application with a k factor less than 10.