Sequential Screw Drive Interface for Misalignment-Resistant Torque
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Solution Overview
Problem
Conventional fasteners fail when torqueing tools are not aligned with the central axis, leading to failure modes such as camming out of alignment due to the application of torque via a single drive feature.
Innovation Solution
A driver system and fastener configuration that applies torque sequentially between a center drive feature and outboard drive features, engaging the outboard drive only after an initial torque is applied, allowing for distributed torque application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque is applied via a single drive feature, then the fastener can be driven, but the fastener fails when torqueing tools are not aligned with the central axis due to camming out of alignment
Solution Approach 1:
The drive interface is segmented into multiple drive features (first drive feature and second drive feature) distributed around the fastener head. This segmentation allows the torque application to be distributed across multiple contact points, eliminating the camming out problem that occurs with single-point drive features when misalignment occurs.
2Force
If high torque is applied to a small dimension fastener, then the fastener can achieve required clamping force, but the screw head experiences high stress and requires increased thickness
Solution Approach 1:
The torque application is segmented into multiple drive features that distribute the mechanical stress across different regions of the screw head. This prevents stress concentration at a single point, allowing high torque to be applied without requiring increased screw head thickness.
Solution Approach 2:
The drive features are arranged in a distributed pattern around the fastener head, transitioning from a single-point (0D) or line (1D) contact to a distributed areal (2D) contact pattern. This dimensional distribution of contact points reduces stress concentration and allows high torque application on compact fastener geometries.
Data Source
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AI summary
A sequential torque application retention system includes a driver mechanism having a shaft; a center drive coupled to a tip end; an outboard drive coupled to the tip end; a screw including a screw head with a central receiver, the central receiver corresponding to the center drive, the central receiver configured to receive the center drive; a pair of outboard receivers formed in the screw head corresponding to the outboard drive, the pair of outboard receivers configured to receive the outboard drive; wherein the center drive is engaged with the screw head at the central receiver responsive to an initial torque and the outboard drive is engaged with the screw head at the pair of outboard receivers responsive to a subsequent torque; and wherein the outboard receivers are positioned so that they do not engage with the outboard drive responsive to the initial torque.