Segmented Screw Tip Geometry for Lower Torque in Hardwood
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Solution Overview
Problem
Conventional screws experience increased screw-in torque and failure when screwing into hard materials due to insufficient holding force, particularly in hardwood, making manual turning difficult.
Innovation Solution
The screw tip is designed with a first tapering tip section and a second cylindrical tip section, where the screw thread is continuous across both sections, and the cylindrical section is positioned in front of the polygonal section's front edge surface, displacing and shortening the conically tapering section. This configuration includes a pitch of 40% to 70% of the nominal diameter and a tip length of 1.0 to 2.0 times the pitch, with a diameter of 40% to 60% of the core diameter, and an inner angle of 20° to 40°, accommodating deformation forces and preventing tip flexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional screw tip with a single conical tapering section is used, then the screw structure is simple, but the holding force is insufficient when screwing into hard materials
Solution Approach 1:
The screw tip is divided into three distinct sections: a first conical tapering section (4a) for initial penetration, a second cylindrical tip section (4c) for stable engagement, and a polygonal section (4b) for torque transmission. This segmentation allows each section to perform its specific function optimally, with the cylindrical section providing the necessary holding force in hard materials while the other sections handle penetration and torque respectively.
2Ease of operation
If the conical tapering section is long, then the screw can penetrate hard materials, but the screw-in torque increases excessively
Solution Approach 1:
By segmenting the tip into a short conical section (4a) and a cylindrical section (4c), the patent reduces the length of the conical section that generates high friction and torque, while the cylindrical section provides penetration capability with lower resistance. This segmentation optimizes the balance between penetration ability and torque requirements.
Solution Approach 2:
Different sections of the tip are given different geometries optimized for their specific functions: the conical section (4a) with its self-centering geometry for initial penetration, the cylindrical section (4c) with its uniform diameter for stable engagement with reduced friction, and the polygonal section (4b) for torque transmission. This local optimization reduces overall screw-in torque while maintaining penetration capability.
3Strength
If the screw tip is short, then the screw-in torque is reduced, but the holding force in hard materials is insufficient
Solution Approach 1:
The cylindrical tip section (4c) is designed with a specific diameter (40%-60% of core diameter) and length (1.0-2.0 times the pitch) that optimizes holding force while minimizing torque. This localized geometric optimization allows the tip to achieve sufficient holding power in hard materials without requiring excessive length that would increase screw-in torque.
4Reliability
If the screw tip flexes during screwing, then ease of operation improves, but reliability of the screw connection decreases
Solution Approach 1:
The segmented tip structure with its three distinct sections (conical 4a, cylindrical 4c, polygonal 4b) provides structural rigidity while maintaining the ability to accommodate deformation forces. The cylindrical section (4c) acts as a stiffening element that prevents excessive flexing and tip failure, ensuring reliable connection while still allowing controlled deformation during the screwing process.
Data Source
AI summary
The present invention relates to a screw element (1) comprising a threaded shaft (2), a screw tip (4) formed on one shaft end and a screw head (5), formed on an opposite shaft end and with force application means (7), and comprising a screw thread (12) extending on the threaded shaft (2) and on the screw tip (4), wherein the screw tip (4) has a front tip section (4a) tapering toward the screw element end, when viewed in the screwing-in direction (Z), and a section (4b) formed on the threaded shaft with a polygonal cross section, when viewed in cross section, whose enveloping circle diameter (dh) is greater than a core diameter (dk) of the screw tip (4), and the polygonal cross section has a corner point (15) lying on the enveloping circle of the section (4b), and a front edge surface (9), radially oriented with respect to a longitudinal center axis (X-X), ends in said corner point in the sense of an increased diameter. The screw tip (4) has a first tapering tip section (4a) with a circular cross section and a second, cylindrical tip section (4c) with a circular cross section formed between the first tip section (4a) and the polygonal section (4b), wherein the screw thread (12) is continuously formed without interruption across the first and second tip sections (4a, 4c) of the screw tip (4).