Self-Retaining Screw Head for One-Handed Driver Engagement
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Solution Overview
Problem
Existing fasteners lack a reliable mechanism for temporary retention and centering during installation, particularly in applications where manual dexterity is limited, such as in small bone surgery or medical procedures, leading to issues like dropped screws and unintended damage.
Innovation Solution
A self-retaining fastener system featuring a proximal end with a driving head and a shaft with an externally threaded portion, incorporating a recess and projection for friction fit or detent-type engagement with a screwdriver, allowing provisional connection and secure attachment to a work piece without manual holding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional screw-based fastener is used without a retention mechanism, then the fastener can be easily removed from the driver, but the fastener may drop or be lost during the securing operation
Solution Approach 1:
The fastener incorporates a self-retaining mechanism where the head geometry (recess and projection) automatically engages with the driver, eliminating the need for separate retention devices or complex locking mechanisms. The fastener serves itself by providing both the driving interface and the retention function through its head structure.
Solution Approach 2:
The recess and projection create a friction fit engagement that maintains a balanced force distribution between the driver and fastener during the securing operation. This equipotential engagement ensures the fastener remains securely held without creating excessive stress concentrations or requiring asymmetric force application.
2Reliability
If a retention mechanism is added to the fastener, then the fastener can be securely held during installation, but the device complexity increases
Solution Approach 1:
The retention function is merged with the driving head structure. The recess and projection that provide retention are integrated into the same component (fastener head) that provides the driving interface, eliminating the need for separate retention devices, clips, or locking mechanisms.
Solution Approach 2:
The retention mechanism is localized to specific features of the fastener head (the recess and projection geometry) rather than requiring a complex overall structure. The bulk of the fastener remains simple and straightforward, with complexity concentrated only in the localized engagement features.
3Reliability
If the fastener head is enlarged to provide better driver engagement, then the driver can securely hold the fastener, but the fastener profile increases which may not be suitable for small bone surgery
Solution Approach 1:
The driver engages with the fastener head through a nested interface where the projection fits into the recess. This nested arrangement allows secure engagement while maintaining a compact overall profile, as the engagement features are contained within the head geometry rather than requiring external extensions.
Solution Approach 2:
The retention mechanism utilizes the axial dimension (depth of recess and height of projection) rather than requiring increased radial dimensions. This allows secure engagement along the axis of the fastener while maintaining a small lateral profile suitable for small bone surgery applications.
4Ease of operation
If a friction fit engagement is used between the fastener and driver, then the fastener can be easily removed without manual assistance, but the retention force may be insufficient for secure installation
Solution Approach 1:
The friction fit engagement parameters (contact area, normal force, coefficient of friction) are optimized through the recess and projection geometry. The engagement surfaces are sized and shaped to provide sufficient frictional retention force during installation while allowing controlled slip or disengagement when removal force is applied.
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
Enables secure, one-handed operation of fasteners during installation and easy removal without manual assistance, reducing the risk of dropped screws and damage, while maintaining precise alignment and secure engagement.
Implementation Method 1
The first inner surface includes at least one projection extending proximally from the first inner surface. The projection is sized and configured to engage with a corresponding engagement feature of the driving or placement tool, provisionally connecting the fastener to the tool.
Data Source
AI summary
A provisional engagement feature for selectively connecting a fastener such as a screw to a driving tool, the fastener incorporating a head with a recess extending therein and a projection contained within the recess for engagement with a corresponding engagement feature and/or selective locking feature of the driving tool.