Dual-Thread Screw With Serrated Cutting Teeth
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Solution Overview
Problem
Conventional screws experience high frictional resistance and inefficiency when driven into wooden articles, particularly those made from mixed wood and plastic resin, due to thread friction and accumulation of waste chips, requiring significant operator force and time.
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 driving 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 due to thread contact and waste chip accumulation, requiring significant operator force and time
Solution Approach 1:
The screw thread is segmented into two distinct threads: a first thread with serrate cutting teeth for cutting and chip removal, and a second thread for anchoring. This segmentation allows each thread to perform its specific function efficiently, reducing overall friction and resistance during driving.
Solution Approach 2:
Different portions of the screw have different thread characteristics optimized for their specific functions. The first thread portion has aggressive cutting teeth for chip removal, while the second thread portion has smoother convolutions for anchoring. This local differentiation reduces friction in the cutting zone while maintaining holding power.
2Ease of operation
If a conventional screw with single continuous thread is used, then the structure is simple, but waste chips are not removed smoothly, impeding screw movement and causing article chapping
Solution Approach 1:
The dual-thread design segments the chip removal function from the anchoring function. The first thread with its serrate cutting teeth is specifically designed to cut and eject waste chips smoothly, preventing accumulation that would impede movement or cause chapping.
Solution Approach 2:
The serrate cutting teeth on the first thread convert the harmful effect of waste chip accumulation into a beneficial chip ejection mechanism. The serrated edges actively cut and propel chips outward, transforming what would be a obstruction into an efficient chip removal system.
3Productivity
If the first thread has aggressive cutting teeth for chip removal, then chip evacuation is improved, but thread strength and anchoring capability may be reduced
Solution Approach 1:
The anchoring function is segmented into a separate second thread that does not bear the cutting load. This allows the first thread to have aggressive cutting teeth optimized for chip removal while the second thread maintains full strength for anchoring, eliminating the trade-off between chip removal and holding power.
Solution Approach 2:
The two threads are merged into a single integrated screw structure, sharing the same shank and working simultaneously during driving. This combination allows both chip removal and anchoring functions to operate together without requiring separate components, achieving both high productivity and strong anchoring in one fastener.
Data Source
AI summary
A screw includes a shank, a first thread, and a second thread. The shank includes a screw-in portion, a head portion, and a straight rod portion between the screw-in portion and the head portion. The first thread surrounds the shank spirally and includes an upper thread portion formed around the straight rod portion, a lower thread portion formed around the screw-in portion, and a middle thread portion continuously connected between the upper and lower thread portions. A plurality of serrate cutting teeth is provided on the middle thread portion of the first thread. The second thread is helically formed around the screw-in portion of the shank and includes a plurality of thread convolutions spaced from thread convolutions of the lower thread portion of the first thread. The screw can be quickly driven into articles to be joined without degradation of binding capacity between the screw and the articles.