Dual-Thread Screw with Serrated Middle Segment for Fast Wood Insertion
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Solution Overview
Problem
Conventional screws experience high frictional resistance and waste chip accumulation, requiring significant operator force and time due to thread friction and incomplete chip removal during screwing into wooden articles.
Innovation Solution
A screw design featuring a tapered shank with dual threads, including a first thread with serrate cutting teeth and a second thread with spaced convolutions, along with oblique ribs and a chip-collected groove, to reduce friction and efficiently remove waste chips, allowing for smoother and faster insertion with less operator force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional screw with continuous threading is used, then the screw can be driven into the article, but high frictional resistance occurs and waste chips accumulate, requiring significant operator force and time
Solution Approach 1:
The screw thread is segmented into two distinct threads: a first thread with continuous convolutions for initial engagement and chip formation, and a second thread with spaced convolutions for reduced friction and smooth advancement. This segmentation allows each thread to perform its specific function optimally, resolving the contradiction between screwing speed and operator force requirement
Solution Approach 2:
Different regions of the screw shank are given different thread characteristics: the first thread portion has continuous convolutions suited for cutting and chip removal, while the second thread portion has spaced convolutions suited for low-friction advancement. This local differentiation enables the screw to overcome high frictional resistance without requiring excessive operator force
2Reliability
If a conventional screw with continuous threading is used, then the screw can fasten the article, but waste chips impede movement and cause the article to chap under compression
Solution Approach 1:
The second thread is designed with spaced convolutions that extract and remove waste chips from the screw path during the fastening process. This prevents chip accumulation that would otherwise impede screw movement and cause chapping of the article, while maintaining reliable holding power through the first thread's continuous engagement
3Ease of operation
If a prior art screw with intermediate thread is used, then self-tapping qualities are improved, but the thread structure is complex and may be subject to damage during insertion
Solution Approach 1:
Instead of using a complex intermediate thread structure, the invention segments the threading into two distinct threads with clear functional differentiation. The first thread provides self-tapping action with continuous convolutions, while the second thread provides smooth advancement with spaced convolutions. This segmentation achieves self-tapping quality without the complexity and vulnerability of intermediate thread structures
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 dual-thread design and chip removal features enable faster screwing with reduced resistance and waste chip accumulation, enhancing driving speed and anchoring strength while minimizing operator effort.
Implementation Method 1
A plurality of serrate cutting teeth is provided on each thread convolution of the middle thread portion of the first thread
Implementation Method 2
frictional resistance obviously exists between the screw thread of a conventional screw and an article in which the screw is contiguously driven
Data Source
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AI summary
A screw (10) includes a shank (12), a first thread (26), and a second thread (40). The shank (12) includes a screw-in portion (14), a head portion (16), and a straight rod portion (18) between the screw-in portion (14) and the head portion (16). The first thread (26) surrounds the shank (12) spirally and includes an upper thread portion (28) formed around the straight rod portion (18), a lower thread portion (30) formed around the screw-in portion (14), and a middle thread portion (32) continuously connected between the upper and lower thread portions (28, 30). A plurality of serrate cutting teeth (38) is provided on the middle thread portion (32) of the first thread (26). The second thread (40) is helically formed around the screw-in portion (14) of the shank (12) and includes a plurality of thread convolutions (41) spaced from thread convolutions of the lower thread portion (30) of the first thread (26). The screw (10) can be quickly driven into articles to be joined without degradation of binding capacity between the screw (10) and the articles.