Asymmetrical Thread Screw Shank Design for Wood Drilling
Solution Overview
Problem
Conventional screws require excessive force for deep penetration due to increasing resistance and friction, leading to difficult screwing operations and potential screw fracturing, especially when drilling through materials like wood, which complicates the drilling process and can result in resource waste or hazardous conditions.
Innovation Solution
A screw design featuring asymmetrical threads and a V-shaped tail with specific angle configurations to enhance drilling efficiency, reduce friction, and facilitate debris removal, including a shank with a taper and stem, asymmetrical saw-type threads, and a carved V-shaped tail to accommodate and convey debris, allowing for efficient hole expansion and thread formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional symmetrical threads are used for drilling into wood or building materials, then the screw can form internal threads through fracturing and thrusting, but the resistance increases gradually with sinking insertion requiring greater force that leads to difficult screwing operation and potential screw fracturing
Solution Approach 1:
The patent applies asymmetry by designing threads with different front end angles (α = 30-40°) and rear end angles (β = 10-20°). The larger front end angle enhances cutting ability to reduce drilling resistance, while the smaller rear end angle facilitates thread formation. This asymmetrical configuration allows the screw to efficiently cut through materials and form threads with reduced overall screwing force compared to conventional symmetrical threads.
Solution Approach 2:
The patent segments the thread structure into distinct functional zones: the first asymmetrical thread for initial drilling and hole formation, the asymmetrical saw-type threads for enhanced cutting and fiber separation, and the second asymmetrical thread for final thread formation. This segmentation allows each thread type to perform its specific function optimally, improving overall drilling efficiency while controlling the force required at each stage of penetration.
2Reliability
If conventional screws are driven deeper into materials, then fastening is achieved, but friction increases due to debris and powders generated during drilling process requiring greater force
Solution Approach 1:
The patent extracts the harmful debris and powders generated during drilling by incorporating a V-shaped groove that runs along the screw shank. This groove actively removes cutting debris from the thread engagement zone, preventing debris accumulation that would otherwise increase friction. By continuously extracting debris during the screwing operation, the groove maintains lower friction levels throughout the penetration process, improving ease of operation while ensuring reliable fastening.
3Ease of operation
If automatic tools are used to facilitate drilling process, then screwing operation is simplified, but user's discerning the screw conditions becomes more difficult leading to excessive force exertion and potential screw fracturing
Solution Approach 1:
The patent incorporates feedback mechanisms through the asymmetrical thread design that provides tactile and resistance feedback to the user during screwing. The transition from the first asymmetrical thread (drilling phase) to the asymmetrical saw-type threads (cutting phase) to the second asymmetrical thread (thread formation phase) creates distinct resistance patterns that inform the user of the screw's penetration status. This feedback allows users to monitor screw conditions and adjust applied force accordingly, preventing excessive force that could cause fracturing while maintaining ease of operation.
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 screw design increases drilling and thread tapping efficiency, reduces fastening time and effort by minimizing friction and debris-related issues, thereby improving operational safety and reducing resource waste.
Implementation Method 1
asymmetrical saw-type threads...to enhance forward drilling and grinding effect while the shank is expanded a hole of a working piece such as woods outwards from the taper to the stem, and also cut fibers of the working piece
Implementation Method 2
a carved V-shaped tail between the first asymmetrical thread and the asymmetrical saw-type threads to accommodate debris and powder generated during hole drilling via the first asymmetrical thread and convey the debris and the powder towards the screw head
Implementation Method 3
a first asymmetrical thread at the taper with a first front end angle α formed between 30 and 40 degrees, and a first rear end angle β formed between 10 and 20 degrees...to enhance thread drilling effect
Data Source
AI summary
A screw has a screw head and a shank. The screw head has a square cavity, a hexagonal cavity or a hexagonal boss to be wedged by a screw driver for wrenching. The shank has a first asymmetrical thread at the taper to facilitate drilling holes, asymmetrical saw-type threads behind the first asymmetrical thread, and a second asymmetrical thread behind the asymmetrical saw-type threads. The shank further has a carved V-shaped tail between the first asymmetrical thread and the asymmetrical saw-type threads to facilitate cutting and debris dispelling. The screw thus formed can rapidly perform thread tapping and debris dispelling, and reduce friction and expand drilling holes and achieve fast fastening.