Threaded Sleeve Flank Angle and Pitch for Wood Connection
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Solution Overview
Problem
Existing threaded sleeves cause material deformation and cracking in work pieces, particularly wood, due to high tensile stress and thermal heating during screwing, leading to a weak connection and potential breakage.
Innovation Solution
A metal threaded sleeve with a thread profile featuring a small flank angle (25°-35°), large pitch (0.1-0.4 times the outer diameter), and moderate thread depth (0.02-0.2 times the outer diameter), which cuts rather than compresses the material, reducing torque and thermal stress, and maintaining tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional thread profile with larger flank angle is used, then the tensile strength of the connection is improved, but the work piece material is deformed and cracked during screwing-in
Solution Approach 1:
The patent changes the geometric parameters of the thread profile, specifically reducing the flank angle to 25°-35° and setting the pitch to 0.1-0.4 times the outer diameter. This parameter optimization allows the thread to cut through the material with less displacement and compression, reducing harmful deformation while maintaining adequate tensile strength through the optimized geometry
Solution Approach 2:
The invention replaces the conventional mechanical displacement and compression mechanism with a cutting mechanism. The optimized thread profile acts more like a cutting tool, shearing the material along its path rather than pushing it aside, which significantly reduces material deformation and cracking while creating a clean thread form
2Object-affected harmful factors
If a thread profile that cuts the material is used, then material damage is reduced, but the torque required for screwing-in must be controlled
Solution Approach 1:
The patent optimizes the thread geometry parameters including flank angle (25°-35°), pitch (0.1-0.4 times outer diameter), and thread depth (0.02-0.2 times outer diameter). This balanced parameter selection creates a cutting action that reduces material damage while keeping the required screwing torque within acceptable limits through efficient material removal
3Object-affected harmful factors
If a great pitch of thread is used, then fewer wood fibres are damaged, but the tensile strength may decrease
Solution Approach 1:
The patent identifies and implements an optimal pitch range of 0.1-0.4 times the outer diameter of the threaded sleeve. This optimized pitch provides sufficient spacing between thread turns to minimize wood fibre damage and cracking, while maintaining enough thread engagement length to ensure adequate tensile strength of the connection
4Strength
If the thread depth is increased to improve tensile strength, then the connection strength is improved, but the material damage increases
Solution Approach 1:
The patent optimizes the thread depth parameter to be 0.02-0.2 times the outer diameter of the threaded sleeve. This optimized depth provides sufficient thread engagement to ensure adequate tensile strength while limiting the radial intrusion into the material, thereby reducing material damage and cracking around the thread region
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 solution ensures a strong and durable connection with reduced material damage and thermal heating, enhancing the tensile strength and stability of the threaded sleeve-work piece interface.
Implementation Method 1
The thread of the threaded sleeve does not displace, compress or compact the material of the work piece but cuts it
Implementation Method 2
the material may heat up during the screw-in process and break off when the stress gets too high
Data Source
AI summary
A threaded metal sleeve includes a core and a thread provided on the outside of the core, with the thread profile having a flank angle within the range from 25° to 35°. The pitch (h) of the thread is 0.1-fold to 0.4-fold of the outer diameter of the threaded sleeve, and the thread depth of the thread is 0.02-fold to 0.2-fold of the outer diameter of the threaded sleeve.