Variable-Width Screw Recess for Faster Timepiece Plate Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing self-tapping screws used in watchmaking require a long time to assemble and secure the horological movement support with a motor plate due to gradual tapping and are prone to dislodgment, necessitating manual handling and multiple turns.
Innovation Solution
A self-tapping screw design with a body and recess having a variable width, allowing the screw to be fully inserted and guided before screwing, enabling faster assembly and secure holding through a matching shape that allows the entire threading to engage simultaneously, reducing the number of turns required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a self-tapping screw with a smooth first section is used to guide the screw into the recess, then the screw positioning is improved, but the assembly time increases because the first section is short and does not provide sufficient guidance
Solution Approach 1:
The recess is pre-formed with a specific shape that includes a wider upper portion and a narrower lower portion, preparing the structure in advance to guide and secure the screw body during insertion, eliminating the need for a separate long guiding section
Solution Approach 2:
The invention changes the geometric parameters of the recess by giving it a variable cross-section (wider at the top, narrower at the bottom) that matches the screw body dimensions, allowing the recess to perform both guidance and securing functions simultaneously
2Ease of operation
If the first section of the screw is made longer to improve guidance, then the screw positioning is improved, but the element thickness increases and takes up too much space
Solution Approach 1:
Instead of extending the screw length in the axial direction (first dimension), the invention modifies the cross-sectional dimensions of the recess (second and third dimensions) to create a variable width profile that provides guidance without increasing overall element thickness
Solution Approach 2:
The recess cross-sectional parameters are changed along its depth, creating a gradient from wider (at the opening) to narrower (at the bottom), which provides effective guidance within a compact thickness
3Reliability
If a self-tapping screw is used to tap the recess gradually, then the screw can be formed in the recess, but the assembly time increases due to multiple screw turns required
Solution Approach 1:
The recess is pre-formed with the final required shape and dimensions before screw insertion, eliminating the need for gradual tapping during assembly. The recess is prepared in advance to receive the screw directly in its operational position
Solution Approach 2:
The invention skips the gradual tapping process by directly inserting the screw into the pre-formed recess, rushing through the assembly process in a single action rather than requiring multiple incremental turns
Data Source
AI summary
An assembly including horological movement support, a motor plate of a timepiece and a fastener fastening the support to the plate. The fastener includes a self-tapping screw having a body that passes through a hole in the support. A recess in the plate or support is tapped when the screw is screwed into the recess. The shape of the recess has a variable width, which is wider at the opening extending to a smaller diameter at the bottom of the recess, the shape corresponding to that of the body of the screw.