Hole and Thread-Forming Screw with Segmented Shank
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Solution Overview
Problem
Existing screw designs for sheet metal elements either fail to efficiently remove material during the hole-forming and thread-forming process, leading to difficulties in screwing and unscrewing, or they are not designed to handle varying sheet metal thicknesses securely.
Innovation Solution
A screw design featuring a cylindrical base that tapers into a cone with a concave reduction area, where the thread configuration changes to optimize material displacement and hole formation, allowing for easy penetration and secure fastening, with adjustable thread pitches and angles to accommodate different materials and thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the screw design uses a conventional cylindrical shank with uniform thread, then the thread formation is simple, but the material removal efficiency is poor and the screwing process encounters resistance
Solution Approach 1:
The screw shank is segmented into three distinct zones: a cylindrical base area for thread formation, a conical hole-forming area with decreasing diameter, and a transition area with increasing diameter. Each zone performs a specific function in the material removal and thread formation process, improving overall productivity while maintaining manageable structural complexity through functional segmentation.
Solution Approach 2:
Different sections of the screw shank are given different geometric qualities: the cylindrical base area provides uniform thread formation, the conical area with decreasing diameter enables efficient material ejection, and the transition area with increasing diameter facilitates smooth material displacement. This local differentiation of geometric properties optimizes material removal efficiency at each stage of the screwing process.
2Reliability
If the screw design focuses on material ejection capability, then thread formation improves, but the screw cannot securely accommodate varying sheet metal thicknesses
Solution Approach 1:
The screw design incorporates dynamic geometric transitions rather than static uniform dimensions. The conical area with decreasing diameter transitions into a transition area with increasing diameter, creating a dynamic profile that adapts to different material thicknesses. This dynamic geometry allows the screw to maintain reliable thread formation while accommodating varying sheet metal thicknesses securely.
Solution Approach 2:
The screw shank diameter parameter changes continuously along its length: starting with a cylindrical base diameter, transitioning through a conical reduction to a smaller diameter, then increasing again through a transition area. This parameter variation enables the screw to form reliable threads in the base area while the varying diameter profile adapts to different material thicknesses, enhancing versatility without compromising thread formation quality.
3Ease of operation
If the screw design uses a conical area with decreasing diameter, then material ejection is facilitated, but the transition to the cylindrical base area becomes problematic
Solution Approach 1:
The transition from the conical hole-forming area to the cylindrical base area is segmented into a distinct transition area with its own geometric characteristics (increasing diameter). This segmentation separates the material ejection function (conical area) from the thread formation function (cylindrical base area), with the transition area serving as an intermediate zone that smoothly connects the two, reducing operational problems while maintaining design clarity.
Solution Approach 2:
The transition area employs curved geometric transitions rather than sharp angles or abrupt changes. The diameter increases gradually from the conical area to the cylindrical base area, creating a smooth curved profile that facilitates seamless material transition and reduces stress concentrations. This curved transition simplifies the operational complexity while maintaining the beneficial material ejection capabilities of the conical section.
Data Source
Figure 1a~4
Figure 5~9
AI summary
The hole- and thread-forming screw has a screw head (1) and a screw shaft (3). A rejuvenating hole forming area (4) is connected to the area of the screw shaft with a cylindrical base. The hole forming area has a section with concave transverse locking and multiple thread pitches. The area of the screw shaft with cylindrical base is twice as long as the thickness of the sheet metal elements.