Kinked Thread Fastener for Porous Material Anchoring
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Solution Overview
Problem
Fasteners, such as screws, tend to tear out of porous materials like soft wood due to low load-bearing capacity around the external thread, resulting in insecure connections and reduced force absorption.
Innovation Solution
A fastening element with a torque-absorbing head and a shank featuring an external thread with a diameter ratio of D/d > 2.5, a kinked thread profile, and a self-tapping design that forms a thread in the material upon screwing, providing a secure connection by compressing the material and increasing force absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional screws are used in porous materials, then the fastening process is simple, but the screw tears out due to low load-bearing capacity
Solution Approach 1:
The patent changes the geometric parameters of the thread by introducing a kink in the thread profile, creating distinct first and second thread flanks with different angles. This parameter modification allows the thread to compress material more effectively while maintaining ease of installation, resolving the contradiction between simple fastening process and reliable connection.
Solution Approach 2:
The thread profile is designed with non-uniform characteristics through the kink, creating different local properties along the thread length. The first thread flank has a different angle than the second thread flank, allowing different sections to perform different functions: one for material compression and anchoring, another for cutting and entry, thus improving reliability without complicating the overall fastening process.
2Strength
If the external thread has a large diameter ratio D/d > 2.5, then force absorption increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a particular parameter range for the diameter ratio D/d > 2.5, which optimizes force absorption while remaining manufacturable. This parameter change allows the thread to engage sufficient material volume for strong anchoring without requiring excessively tight tolerances that would make manufacturing difficult.
Solution Approach 2:
The kink in the thread profile creates localized variations in thread geometry that concentrate stress and compression forces in specific regions. This local quality enhancement allows the thread to achieve high force absorption through strategic stress distribution rather than requiring uniform high precision throughout the entire thread structure.
3Strength
If the thread profile has a kink with different angles, then material compression and anchoring improve, but thread manufacturing complexity increases
Solution Approach 1:
The kink introduces a localized geometric feature that creates different thread flank angles in specific regions of the thread profile. This local modification enables superior material compression and anchoring at the thread-root interface without requiring the entire thread structure to be complex. The rest of the thread maintains simpler geometry for ease of manufacturing.
Solution Approach 2:
The patent defines specific angle ranges for the first and second thread flanks created by the kink, optimizing the balance between material compression effectiveness and manufacturability. By specifying parameter ranges rather than exact values, the design achieves strong anchoring while allowing manufacturing flexibility, thus not significantly increasing device complexity.
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 fastening element ensures a secure and stable connection in porous materials by compressing a large volume of material, enhancing force absorption and preventing the fastener from tearing out, thereby improving the structural integrity of devices using these materials.
Implementation Method 1
the section of the shank that contains the external thread extends to the tip of the fastening element... When screwed into the material, the porous material in the vicinity of the external thread is compressed, so that the material in the vicinity of the external thread becomes more wearable and the fastening element is fastened in the material with a non-positive fit
Data Source
Figure 1~3
AI summary
Fastening element (100) for a porous material, in particular balsa wood, comprising a fastening head (1) designed to absorb torque in both directions of rotation about a main axis (10), and a shaft (2) which extends from the fastening head (1) and ends in a tip (3) at the end opposite the fastening head. The shaft (2) has an external thread (4) along at least part of its extension in the direction of the main axis (10) in order to be able to screw the fastening element (100) into the material.