Dual-Thread Self-Tapping Screw for Thin-Plate Locking
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Solution Overview
Problem
Conventional self-tapping screws often idle when used on thin plates due to uniform thread crest angles and insufficient thread root diameters, leading to insecure locking and potential separation under external forces, posing safety risks.
Innovation Solution
A self-tapping screw design featuring a first thread segment with a drill tail and a second thread segment having a larger crest angle and increasing thread root diameter, allowing for tight locking without idling by expanding the screw hole and increasing contact area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform thread crest angle is used on screw rod, then manufacturing is simple, but screw hole expands and causes idling on thin plates
Solution Approach 1:
The screw rod is divided into two distinct thread segments: a first thread segment with initial crest angle α and a second thread segment with increased crest angle (1.15-1.2 times α). This segmentation allows each segment to perform different functions - the first segment creates the screw hole while the second segment provides secure locking without causing plate expansion or idling.
Solution Approach 2:
Different thread configurations are applied to different locations of the screw rod. The first thread segment has a standard crest angle suitable for hole formation, while the second thread segment has an increased crest angle specifically for reliable locking. This local differentiation optimizes both hole creation and locking functions without compromising manufacturing feasibility.
2Ease of operation
If thread pitch is larger than plate thickness, then screw can be installed, but screw cannot be properly screwed and combined with plate
Solution Approach 1:
The thread configuration transitions dynamically from the first segment to the second segment as the screw is installed. The second thread segment's increased crest angle and proportionally increased thread root diameter enable proper engagement even when plate thickness is less than the thread pitch, allowing the screw to achieve reliable locking without requiring the plate to be thicker than the pitch.
3Device complexity
If single thread configuration is used, then structure is simple, but screw idles and cannot maintain fixed position
Solution Approach 1:
The screw rod is divided into two distinct thread segments: a first thread segment with initial crest angle α and a second thread segment with increased crest angle (1.15-1.2 times α). This segmentation allows each segment to perform different functions - the first segment creates the screw hole while the second segment provides secure locking without causing plate expansion or idling.
Solution Approach 2:
Different thread configurations are applied to different locations of the screw rod. The first thread segment has a standard crest angle suitable for hole formation, while the second thread segment has an increased crest angle specifically for reliable locking. This local differentiation optimizes both hole creation and locking functions without compromising manufacturing feasibility.
Data Source
AI summary
A self-tapping screw includes a head portion, a lower side thereof configured with a screw rod, a front end thereof configured with a drill tail, a first thread segment formed on a front end of the screw rod above the drill tail, a second thread segment with at least two threads formed on a rear end of the screw rod immediately below the head portion, a crest angle of any one of the threads of the second screw segment being 1.15 to 1.2 times of a crest angle of any thread of the first thread segment, and a thread root diameter of the second thread segment increasing proportionally with the crest angle of the second thread segment. Whereby, the present invention provides a self-tapping screw capable of tight locking without idling.