Segmented Wood Screw Geometry for Lower Driving Torque
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Solution Overview
Problem
Existing wood screws face issues with poor engagement between the screw thread and the workpiece due to a larger drilling unit diameter, leading to reduced connection strength and increased driving torque, especially in denser materials, making it difficult to drive the screw smoothly and firmly into the workpiece.
Innovation Solution
A wood screw design featuring a main shank portion and a tapered portion with locking threads, where the drilling units on the tapered portion have a smaller outside diameter than the locking thread, allowing the tapered portion to initially loosen workpiece material, reducing resistance and enabling smoother insertion, while the locking threads form a matching internal thread depth for enhanced rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the drilling unit outside diameter is made larger than the core diameter of the thread, then the driving torque is reduced, but the engagement between the screw thread and the workpiece becomes poor and connection strength is reduced
Solution Approach 1:
The shank is segmented into two distinct portions: a first shank portion with a first diameter and a second shank portion with a second diameter smaller than the first. This segmentation allows different functional zones - the first portion provides strong engagement while the second portion reduces cutting resistance during insertion.
Solution Approach 2:
Different portions of the shank are given different diameters to optimize local functions. The first shank portion has a larger diameter for strong thread engagement, while the second shank portion has a smaller diameter for easier material removal and reduced driving torque, particularly in the critical entry zone.
2Device complexity
If the drilling units are formed on a cylindrical shank with the same diameter, then the structure is simple, but the resistance during threading increases as the shank sectional area increases and the workpiece material becomes denser
Solution Approach 1:
The shank diameter varies dynamically along its length rather than remaining constant. The transition from the larger first diameter to the smaller second diameter creates a progressive geometry that adapts to the different requirements of thread formation versus initial material removal, reducing resistance throughout the insertion process.
3Ease of manufacture
If the drilling units destroy workpiece material adjacent to the shank surface, then a hole is generated around the periphery, but the compressed workpiece material creates higher density and increases resistance to screw insertion
Solution Approach 1:
The second shank portion with its smaller diameter performs preliminary action by removing material ahead of the main threading zone. This creates a pre-formed pathway with reduced density and lower resistance, preparing the workpiece material for subsequent thread engagement without causing excessive compression and densification.
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 allows for easier and smoother screwing into the workpiece with reduced torque requirements and enhances the connection strength by forming a matching internal thread depth, resulting in a more rigid fastening of the wood screw to the workpiece.
Implementation Method 1
the drilling units first destroy workpiece material on the outer part of the main shank portion in the relative position while the tapered portion being screwed into the workpiece
Implementation Method 2
an internal thread segment whose thread depth matches that of the locking thread of the main shank portion is formed in the workpiece by the drilling units so that the wood screw and the workpiece are fastened and connected more rigidly
Data Source
AI summary
A wood screw that includes a head and a shank is revealed. The shank is formed by a main shank portion and a tapered portion whose diameter is smaller than that of the main shank portion, both provided with a locking thread. A plurality of drilling units, whose outside diameter of the drilling unit is smaller than that of the locking thread, is disposed on the tapered portion. The drilling units first destroy workpiece material corresponding to the main shank portion so that the workpiece material becomes loose and the resistance of the locking thread of the main shank portion is reduced. Thereby the wood screw is screwed into the workpiece more smoothly. Moreover, an internal thread segment whose thread depth matches that of the locking thread of the main shank portion is formed so that the wood screw and the workpiece are fastened more firmly.