Watch Crown Ring Structure for High-Quality Female Screw Cutting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing screw lock type crowns face challenges in forming female screws on hard-to-cut materials like titanium, leading to increased tool wear, higher costs, and degraded quality and durability due to the limited space for cutting and the use of roll taps.
Innovation Solution
A crown design with a separately formed ring member having female screws on its inner peripheral surface, allowing cutting without interference from the axial portion, and fixed to the crown body via press-fitting or adhesive, ensuring improved screw quality and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a cutting tool is used to form the female screw on the inner peripheral surface of the recessed portion, then the female screw can be formed with good quality, but the limited space causes the cutting tool to wear quickly when processing hard-to-cut materials like titanium
Solution Approach 1:
The crown is divided into a head portion and an axial portion that are integrally formed, creating a recessed portion with sufficient space to accommodate the cutting tool. This segmentation allows the female screw to be formed on the inner peripheral surface without interference from the axial portion, providing adequate working space for the cutting tool while maintaining good screw quality
Solution Approach 2:
The female screw is formed on the inner peripheral surface of the recessed portion, utilizing the radial dimension of the crown structure. This dimensional arrangement provides sufficient space for the cutting tool to access and process the screw formation without interference from the axial portion, solving the tool wear problem while maintaining precision
2Ease of manufacture
If a roll tap is used to form the female screw by plastic working, then the limited space issue is avoided, but the quality of the female screw is degraded leading to poor operability and durability
Solution Approach 1:
The patent replaces the plastic working method (roll tap) with a cutting method using a cutting tool. This substitution allows the female screw to be formed with high precision and good quality while providing sufficient space for the cutting tool to operate effectively, thereby improving both manufacturability and screw quality simultaneously
3Device complexity
If the axial portion is provided in the recessed portion, then the crown structure is complete, but the space for cutting the female screw becomes too small
Solution Approach 1:
The crown is segmented into a head portion and an axial portion that are integrally formed. This segmentation creates a recessed portion in the head portion that provides sufficient space for the cutting tool, while the axial portion extends from the bottom portion without interfering with the screw formation area, thus maintaining structural completeness while enabling manufacturability
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A crown includes a crown body and a ring member. The crown body includes a head portion and an axial portion which are integrally formed. The head portion has a bottomed tubular shape and includes a bottom portion and a tubular portion. The axial portion extends from the bottom portion and is disposed inside the tubular portion. The ring member includes a screw formed on an inner peripheral surface. The ring member is disposed along an inner peripheral surface of the tubular portion, and is fixed to the head portion.