Hole-Forming Screw Tip Geometry for Reduced Wood Splitting
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Solution Overview
Problem
Wood screws tend to split during hole-making in wooden structures due to local compaction and radial forces generated by the screwing process, especially in softer woods with low bulk density.
Innovation Solution
A screw design with a tip featuring two edges and a cutting curve that plastically deforms the wood matrix, reducing the need for cutting and compressing, thereby minimizing splitting effects and insertion torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional screw tip is used to screw into wood, then the screw can be driven in, but the wood may split due to local compaction and radial forces
Solution Approach 1:
The invention changes the geometric parameters of the tip by providing a recess that forms two edges with specific orientations. The first edge is oriented to displace material in the screwing direction, while the second edge is oriented to support against the screwing direction. This parameter change in edge orientation and configuration transforms the stress distribution, reducing radial forces that cause splitting while maintaining the screw's ability to drive into the wood.
2Ease of operation
If material is cut or compressed during hole-making, then the screw can be inserted, but splitting effects increase due to elastic compression
Solution Approach 1:
The invention applies local quality by creating different functional zones on the tip surface through the recess configuration. The first edge zone is designed for material displacement with its orientation parallel to the screwing direction, while the second edge zone provides support with its orientation against the screwing direction. This local differentiation in edge function and orientation allows the tip to deform material plastically without significant elastic compression, reducing splitting effects while maintaining ease of insertion.
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 achieves reduced splitting and lower insertion torque by locally deforming the wood matrix, creating a channel for the screw body without significant elastic compression, enhancing the screw connection's integrity.
Implementation Method 1
the splitting effect can be reduced by locally plastically deforming the wood matrix and not having to be cut or compressed
Implementation Method 2
the two edges (20, 22) are directed into the parent material (45) in such a way that they generate outwardly directed displacement forces (V)
Data Source
Figure 1
Figure 2~3
Figure 4a~4d
AI summary
The invention relates to a screw (10) comprising a shaft (12) which transitions into a tip (14). The tip (14) tapers starting from the support region of the shaft (12), and the tip (14) terminates at a frontmost tip (16). At least two edges (20, 22) are formed on the tip (14) by a recess of the tip, wherein a first edge (20) is formed in the screw-in rotational direction and a second edge (22) is formed opposite the screw-in rotational direction, said edges being connected via a surface (30, 50), the cross-section of which has a contour line (K). An intersection curve (S) of the screw central plane (ME) is produced by the surface (30, 50), wherein the distance (A) between the intersection curve (S) and the screw central axis increases from the frontmost tip (16) at least until the distance corresponds to half of the core diameter. An intersection point (A1) of the intersection curve (S), said intersection point being arranged at a distance of DK/4 to the screw central axis, has a length (L), which is greater than DK/3, to the closest intersection point (A2) in the longitudinal direction of the screw at a distance of DK/2 to the screw central axis. An edge angle (alpha) which forms the tangent (T) at the first edge (20) together with the contour line (K) increases over the length (L) as the distance between the intersection curve (S) and the central axis (MA) increases.