Crack-Proof Screw With Segmented Threads
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Solution Overview
Problem
Conventional screws often cause cracking when used in materials like wood due to their design, which fails to effectively manage drilling forces and chip removal.
Innovation Solution
A crack-proof screw design featuring a rod thread, expanding threads that cover less than 360 degrees, and drilling threads near a tapered tail, allowing for efficient drilling with reduced force and minimizing cracking by distributing the force effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional screw design is used, then the screw can penetrate the material, but it causes cracking in wood materials
Solution Approach 1:
The screw thread is divided into multiple segments: rod threads near the head, expanding threads in the middle section, and drilling threads near the tail. Each segment performs a specific function - the expanding threads have less than 360-degree coverage and specific angle relationships (angle B > angle A, A+B ≥ 90°) that allow gradual material displacement rather than sudden cracking
Solution Approach 2:
Different sections of the screw have different thread configurations optimized for their specific functions. The rod threads provide initial engagement, the expanding threads (with partial circumferential coverage and specific angular geometry) provide gradual expansion, and the drilling threads at the tapered tail provide cutting action. This local optimization prevents cracking by distributing stress appropriately throughout the material
2Strength
If conventional screw design is used, then the screw can fasten the material, but it requires excessive drilling force
Solution Approach 1:
The threading is segmented into three functional zones that work sequentially: drilling threads at the tapered tail create the initial hole with minimal force, expanding threads gradually widen and engage the material, and rod threads provide final fastening. This segmentation reduces peak drilling force by distributing the work across multiple stages
Solution Approach 2:
The drilling threads at the tapered tail perform preliminary hole creation before the main fastening action. This preliminary action reduces the force required by the subsequent expanding and rod threads, as they are working into a pre-formed pathway rather than cutting through solid material
3Productivity
If conventional screw design is used, then the screw can penetrate the material, but chip removal is inefficient
Solution Approach 1:
The expanding threads are configured with specific geometric properties (less than 360-degree coverage, angle B > angle A, A+B ≥ 90°) that create optimized chip channels. The angular geometry and partial circumferential coverage allow chips to be efficiently evacuated through the thread spaces without clogging, improving chip removal efficiency
Data Source
Figure 1~3
AI summary
A crack-proof screw comprises a head (1); a rod (10) having a first end extending from the head and having a rod thread (2) near the head and expanding threads (3) far away from the head; each expanding thread (3) encircled through an angle smaller than 360 degrees; the screwing direction of the expanding thread (3) being identical to or different from that of the rod thread (2); a tapered tail (11) extending from a second end of the head; the expanding threads (3) on the rod being near the tapered tail (11); the tapered tail (11) having two drilling threads (4); each drilling thread (4) can be extended to or not extended to the tip end of the tapered tail.