Multi-Start Structural Screw for Lower Installation Torque
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Solution Overview
Problem
Structural screws require excessive torque for installation, leading to increased operator effort and reduced battery life in powered screw guns, and they often lack improved performance in terms of pull-through and thread strength.
Innovation Solution
A structural screw design featuring a dual-start thread with asymmetric notching and chamfered flank transition zones, combined with a unique reaming section using rotationally leading and trailing wedge projections, reduces installation torque and enhances thread strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional screw thread design is used, then thread strength is achieved, but excessive torque is required for installation
Solution Approach 1:
The screw thread is segmented into multiple independent helical threads (dual-start or multi-start configuration). Each helical thread acts as a separate load-bearing element, distributing the clamping force across multiple threads rather than a single continuous thread. This segmentation reduces the torque required for installation while maintaining overall thread strength through the combined effect of multiple threads engaging the substrate simultaneously.
Solution Approach 2:
The thread profile incorporates asymmetric flank angles with different leading and trailing flank angles. The asymmetric geometry optimizes the distribution of installation torque between thread engagement and material displacement, reducing the peak torque required during installation while maintaining adequate thread strength through the asymmetric load distribution across the thread flanks.
2Reliability
If conventional thread design is used, then basic fastening function is achieved, but installation time is excessive
Solution Approach 1:
The screw design incorporates dynamic elements including the reaming section with wedge projections that actively cut and clear material during rotation, and the multiple-start thread configuration that provides progressive engagement. These dynamic features enable faster material displacement and thread engagement compared to conventional static thread designs, reducing installation time while maintaining reliable fastening function.
Solution Approach 2:
The reaming section with wedge projections performs preliminary material removal and hole preparation before the threaded portion engages the substrate. This preliminary action reduces the resistance encountered by the main thread during installation, enabling faster penetration and reducing overall installation time while ensuring proper thread engagement for reliable fastening.
3Reliability
If conventional screw design is used, then basic structural fastening is achieved, but energy consumption is high
Solution Approach 1:
The multi-start thread configuration segments the fastening action into multiple parallel helical paths, distributing the energy consumption across different engagement sequences. This segmentation allows for more efficient energy utilization during installation, reducing peak power requirements and total energy consumption while maintaining adequate structural fastening through the combined engagement of multiple threads.
Solution Approach 2:
The screw design incorporates parameter changes including varying thread pitch, asymmetric flank angles, and reaming section geometry that optimize the energy efficiency of installation. These parameter variations reduce friction and material resistance during penetration, lowering the energy required for installation while maintaining reliable structural fastening through optimized thread engagement characteristics.
Data Source
AI summary
A structural screw usable in multiple different substrates/materials includes a head end, a shank and a tapered end, the head end including a tool engaging part, the head end located at a first end of the shank and the tapered end located at a second end of the shank. A thread is formed along the shank, wherein the thread begins on the tapered end, extends onto the shank and terminates at a first axial location along the shank that is spaced from the head end. The thread (i) is a multiple start thread formed by at least a first helical thread and a second helical thread and/or (ii) includes a thread angle of between fifteen degrees and thirty degrees. The screw may also include a reaming section with leading and trailing wedge sections and/or an asymmetric notch pattern along at least part of the thread edge.