Screw Element Tip Design for Hardwood Penetration
Solution Overview
Problem
Existing screw elements often cause splitting when screwing into hardwood and require high axial forces for initial penetration, due to their polygonal cross-section displacement effect.
Innovation Solution
A screw element design featuring a tapered front tip with a radially oriented cutting edge and a continuously running thread, where the conical portion has a smaller diameter than the polygonal portion, allowing for easy penetration and reduced splitting by utilizing the cutting edge and torque moment for material displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a polygonal cross-section screw tip is used to achieve self-tapping effect, then good engagement and penetration with low axial compression is achieved, but splitting occurs when screwing into hardwood
Solution Approach 1:
The screw tip is segmented into two distinct portions: a front conical portion (4a) with smaller diameter for initial penetration, and a polygonal tip portion (4b) with larger enveloping circle diameter for self-tapping. This segmentation allows each portion to perform its specific function optimally without causing splitting.
Solution Approach 2:
Different regions of the screw tip are given different geometric properties: the front conical portion has a smaller diameter and conical shape for easy penetration, while the polygonal tip portion has a larger enveloping circle diameter matching the threaded shank core for proper engagement. This local differentiation resolves the contradiction between penetration ease and splitting prevention.
2Strength
If a polygonal cross-section screw tip is used for self-tapping, then good engagement is achieved, but comparatively high axial force is necessary during initial screwing-in
Solution Approach 1:
The screw tip is divided into a front conical portion for initial penetration with reduced axial force, and a polygonal tip portion for subsequent self-tapping and engagement. This segmentation separates the penetration function from the engagement function, reducing the peak axial force required.
Solution Approach 2:
The front conical portion performs preliminary penetration into the material before the polygonal tip portion engages in self-tapping. This preliminary action creates a path that reduces the axial force needed for the main engagement process.
3Manufacturing precision
If the polygonal core cross section has an enveloping circle diameter equal to the cylindrical shank core diameter, then chip formation is avoided, but the screw hole may constrict again due to material resilience
Solution Approach 1:
The polygonal tip portion is given a larger enveloping circle diameter than the threaded shank core diameter, creating an oversized hole that compensates for material resilience and prevents constriction, while the front conical portion controls chip formation during initial penetration.
Solution Approach 2:
The solution addresses the hole constriction problem by changing the dimensional relationship between the tip and shank cores. The tip portion has a larger diameter in the radial dimension to prevent constriction, while the continuous thread provides dimensional control for chip formation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design enables easy penetration with reduced axial forces and minimizes splitting effects, allowing the screw to engage materials efficiently without significant resistance.
Implementation Method 1
the radially oriented end face edge, which acts as a cutting edge and/or milling edge
Implementation Method 2
the continuously running thread, on the other hand, grips immediately upon penetration by the front conical region
Implementation Method 3
a radial displacement effect being achieved by a torque moment which rises and ebbs during rotation
Implementation Method 4
the design of the front conically running portion with a maximum diameter which is smaller than the enveloping circle diameter of the polygonal portion adjacent thereto, easy penetration into the respective material is enabled
Implementation Method 5
The potentially resilient material is radially displaced or removed by the formed core edges, respectively
Data Source
AI summary
A screw element (1), having a threaded shank (2) and a screw tip (4), on one shank end, and a screw head (5) on the opposite end with force-application means (7), and a screw thread (12) on the threaded shank (2) and the screw tip (4). The screw tip (4), has a front first tip portion (4a), which tapers towards the end of the screw element, and a second adjacent tip portion (4b), having, a polygonal cross section, with an enveloping circle diameter (dh) larger than a core diameter (dk) of the first tip portion (4a). On the transition between the first and the second tip portions 4a,4b) at least one end edge face is radially oriented in the diameter enlargement and terminates in a vertex (15) of the polygonal cross section, which lies on the enveloping circle of the second tip portion (4b).