Watch Barrel Bung Diameter Reduction for Power Reserve
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Solution Overview
Problem
Existing mechanical watch barrels face challenges in reducing the bung diameter to increase power reserve while maintaining structural integrity and material fatigue strength, as conventional designs often require minimum material sections that are difficult to reduce without compromising reliability.
Innovation Solution
The barrel assembly features a bung with a maximum radius less than ten times the spring thickness, where the spring is fixed to the bung by friction, welding, or brazing, forming a one-piece subassembly, and includes extraction means for axial plug removal, allowing for reduced dimensions without compromising structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the bung diameter is reduced to increase power reserve, then the space available for the spring increases, but the structural integrity and material fatigue strength deteriorate
Solution Approach 1:
The patent applies parameter changes by reducing the bung diameter to a specific range (5-10 times the spring thickness) and optimizing the ratio between bung radius and spring thickness. This allows minimizing the bung diameter to maximize spring space while maintaining sufficient structural strength through precisely controlled dimensional parameters.
Solution Approach 2:
The invention segments the barrel assembly into distinct functional components: a reduced-diameter bung for spring mounting, a drum for energy storage, and a shaft for power transmission. This segmentation allows each component to be optimized independently - the bung can be minimized for space efficiency while the drum and shaft maintain necessary structural integrity.
2Duration of action of moving object
If the bung diameter is reduced to increase spring space, then the power reserve improves, but the reliability deteriorates due to insufficient material sections
Solution Approach 1:
The patent establishes specific parameter ranges to balance space efficiency and reliability: the bung diameter is set to 5-10 times the spring thickness, and the ratio of bung radius to spring thickness is maintained within 5-10. These parameter changes ensure sufficient material sections for reliability while maximizing spring space.
Solution Approach 2:
The invention uses partial action by providing extraction means that are present but not always actively used. The extraction means (such as a square drive or groove) are included in the design to enable removal if needed, but the normal operation relies on the friction fit, thus achieving reliable operation with minimal additional material.
3Duration of action of moving object
If the bung diameter is reduced to increase spring space, then the power reserve improves, but the ease of manufacture deteriorates due to difficult dimensional reduction
Solution Approach 1:
The patent simplifies manufacturing by establishing standardized parameter relationships: the bung diameter is defined as 5-10 times the spring thickness, creating a scalable design that can be manufactured using standard processes. The extraction means are designed with simple geometries (squares, grooves) that are easy to machine into the reduced-diameter bung.
Solution Approach 2:
The invention segments the assembly to allow independent manufacturing of components. The bung can be manufactured separately with its extraction features, then assembled to the drum and shaft. This segmentation enables each component to be optimized for its specific manufacturing requirements rather than requiring the entire assembly to meet all constraints simultaneously.
4Duration of action of moving object
If the bung diameter is reduced to increase spring space, then the power reserve improves, but the device complexity increases due to additional extraction means
Solution Approach 1:
The invention applies partial action by including extraction means that are designed to be simple and minimal. The extraction features (such as a square drive or single groove) are provided but not over-engineered - they are just sufficient to enable removal when needed, adding minimal complexity to the already simplified reduced-diameter design.
Solution Approach 2:
The patent manages complexity through parameter optimization - the extraction means are designed with dimensions proportional to the reduced bung size, maintaining the 5-10 times ratio. This ensures that even the extraction features remain compact and simple, adding minimal complexity while enabling the power reserve improvement.
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 design enhances the power reserve by optimizing the spring's space within the barrel while ensuring sufficient material strength and ease of assembly, addressing the limitations of conventional designs.
Implementation Method 1
said spring is fixed to said bung by friction
Implementation Method 2
said spring is welded or brazed to said bung
Implementation Method 3
said spring is welded or brazed to said bung
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A barrel assembly (1) comprising a spring (2) mounted between a coaxial drum (3) and plug (4) with a shaft (18) about a pivot axis (D). Said shaft (18) extends between a first end (186) having an end shoulder (185) and a second end (187) having a bearing surface (184) pressed into a bore (411) of said plug (4) along said axis (D). The said plug (4) has a first external shafted part (43) on which slides a bore (35) of the said drum (3), and the said shaft (18) has, between the said end shoulder (85) and the said bearing (84), a ratchet holder (81) having a bearing for the driving of a ratchet (12), which ratchet holder (81) limits, directly or indirectly, the play of the said drum (3) with respect to a bearing face (43A) of the said plug (4) at the edge of the receiving surface (5) of a spring (2).