Cold-Formed Screw Shank for Hard Wood Anchoring
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Solution Overview
Problem
Screws used for screwing into hard wood often twist and break off below the screw head due to strain hardening from rolled threads, leading to the screw getting stuck and failing to provide a secure fastening.
Innovation Solution
A screw design where the unthreaded shank section is cold-formed, such as by rolling, to increase its strength, and features a thread geometry or groove profile with a specific orientation and diameter ratio that does not interfere with the screwing process, allowing it to anchor itself without a separate screw head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the unthreaded shank section is left in its original state without cold-forming, then the manufacturing process is simple, but the screw shank breaks off below the screw head when screwing into hard wood
Solution Approach 1:
The patent applies cold-forming (rolling, squeezing, or extruding) to the unthreaded shank section to change its physical parameters. This cold-forming process increases the strength of the shank section without requiring heat treatment or other complex manufacturing steps, thereby resolving the contradiction between improved strength and manufacturing simplicity.
2Reliability
If the holding section has a thread geometry with significant pitch, then it can anchor into the substrate, but it interferes with the screwing process and prevents proper fastening
Solution Approach 1:
The patent applies local quality by creating a slight profile (grooves or minor threading) only in the holding section, while keeping the screwing section with its proper thread geometry intact. This localized modification provides anchoring capability in the holding section without interfering with the screwing process, as the profile is deliberately kept minor and non-interfering.
Solution Approach 2:
The screw shank is segmented into two distinct functional sections: a screwing section with proper thread geometry for engaging the substrate, and a holding section with slight profiling for anchoring. This segmentation allows each section to perform its specific function independently without interference between the two functions.
3Reliability
If the unthreaded section is made larger in diameter, then it provides better anchoring, but it increases the overall screw size and may require pre-drilling
Solution Approach 1:
The patent uses cold-forming processes (rolling, squeezing, or extruding) to create a curved or profiled geometry in the holding section. This profiling creates anchoring grooves or slight threading that provide mechanical interlocking without requiring the holding section to be larger in diameter, thereby maintaining adaptability to different substrate thicknesses and types.
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 cold-formed unthreaded section enhances the screw's strength, preventing breakage and allowing secure fastening in hard wood without pre-drilling, as the thread-free section is designed to twist and anchor within the wood, ensuring the screw remains effective.
Implementation Method 1
the section that is not provided with a thread in the prior art is also cold-formed, for example by rolling, squeezing or the like, so that its strength increases due to the cold-forming
Implementation Method 2
The rolling of the thread onto the front shank section results in strain hardening, which leads to an improvement in the hardness of the screw
Implementation Method 3
the screw shank is subjected to torsional stress by braking the unthreaded section against the wall of the hole
Data Source
Figure 1~4
Figure 5~6
AI summary
The invention proposes a screw and a method for manufacturing the screw, in which the typically smooth part of the screw shank (5) between the screw head end (3) and the screw thread (4) is also work-hardened by cold forming. For example, a flat thread profile can be rolled to produce such a cold forming. A grooved profile is also possible. If the thread form in the holding section is more pronounced, it can also be used to be drawn into the material during the screwing process, so that this alone secures the holding section. In this case, a screw head can be omitted.