Deck Screw Shank Segmentation for Dense Composite Fastening
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Solution Overview
Problem
Conventional deck screws are less effective in securing dense composite materials due to difficulties in driving fasteners into such materials, leading to issues like volcanoing or mushrooming.
Innovation Solution
A deck screw design featuring a head with a socket for torque application, an elongated shank with a left-hand thread and a tri-lobed right-hand thread, and notches on the tip thread, which allows for easier penetration and prevents material displacement, reducing resistance and the likelihood of volcanoing or mushrooming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deck screws are used to fasten dense composite material, then the fastening function is compromised, but the driving difficulty increases significantly
Solution Approach 1:
The screw shank is segmented into multiple functional zones: an upper portion with a first thread configuration (coarser pitch, larger major diameter) for initial penetration and material displacement, and a lower portion with a second thread configuration (finer pitch, smaller major diameter) for secure fastening. This segmentation allows each zone to perform its specific function optimally without compromising the other.
Solution Approach 2:
Different portions of the screw possess different local properties tailored to their specific functions. The upper shank portion has coarser threads with larger diameter for cutting and penetration, while the lower shank portion has finer threads with smaller diameter for gripping and fastening. The tip geometry is also locally optimized with a reduced diameter and specific point angle for initial penetration.
2Ease of manufacture
If conventional single-thread configuration is used, then the thread design is simple, but the ability to penetrate dense material and prevent volcanoing is insufficient
Solution Approach 1:
The threading is segmented into two distinct configurations along the shank length. The first portion has coarser threads spaced further apart to facilitate material displacement and penetration, while the second portion has finer threads for secure engagement. This segmentation provides the dual functionality needed for dense composite material fastening.
Solution Approach 2:
The thread parameters (pitch, major diameter, minor diameter) are changed along the length of the shank. The upper portion features larger pitch and larger major diameter for penetration, while the lower portion features smaller pitch and smaller major diameter for fastening. This parameter variation optimizes performance for each functional zone.
3Ease of manufacture
If uniform thread pitch is used throughout the shank, then the manufacturing process is simpler, but the performance in dense composite material is reduced
Solution Approach 1:
The shank is divided into two threaded portions with different pitch characteristics. The first portion has a coarser pitch suitable for penetration, while the second portion has a finer pitch suitable for fastening. This segmentation can be achieved through sequential threading operations or by using a threaded insert, balancing manufacturing complexity with performance requirements.
Solution Approach 2:
Each portion of the shank has locally optimized thread properties. The upper portion's coarser threads are specifically designed for cutting into dense material, while the lower portion's finer threads are designed for gripping and fastening. This local optimization enhances overall fastening performance despite increased manufacturing complexity.
4Strength
If the screw tip has full diameter, then the structural integrity is stronger, but the penetration into dense composite material is difficult
Solution Approach 1:
The screw tip is预先 reduced in diameter and shaped with a specific point angle to facilitate initial penetration into the dense composite material. This preliminary action of reducing tip diameter allows the screw to start penetration more easily before the full-diameter shank engages the material.
Solution Approach 2:
Instead of having a full-diameter tip for strength, the screw employs an inverted approach with a reduced-diameter tip for penetration. The structural integrity is maintained through the threaded portions and head design, while the tip is optimized for penetration by having a smaller diameter and specific geometry.
Data Source
AI summary
A fastener for composite material having a dense composition employs a head which has a socket and a recessed underside and a lower rim. The shank has an upper portion with an enlarged diameter and a left hand thread while the lower portion has a tri-lobed configuration and is traversed by a right hand thread. The right hand thread may have a plurality of notches which, in one embodiment, are arranged in a spiral array.