Multiple piece high security fastener
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Solution Overview
Problem
Current high security fasteners, such as locking wheel nuts and wheel bolts, can be vulnerable to theft due to the lack of effective rotational retention mechanisms for their shrouds or spin caps, allowing unauthorized tools to gain purchase and remove the fasteners.
Innovation Solution
The design incorporates an intermediate sleeve with a lower coefficient of friction than the fastener body and shroud, allowing the shroud to rotate freely relative to the fastener body under torque, while the sleeve is restrained from axial movement, ensuring the shroud remains securely positioned and reduces friction between the fastener body and shroud.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shroud is fitted over the fastener body to prevent theft, then security is improved, but the shroud may rotate with the fastener under torque reducing effectiveness
Solution Approach 1:
The fastener system is divided into separate functional components: the fastener body and the shroud are distinct elements that can rotate independently. This segmentation allows the shroud to spin freely under torque while the fastener body remains securely retained, resolving the contradiction between security and rotational stability.
Solution Approach 2:
A retainer mechanism acts as an intermediary between the shroud and fastener body, selectively allowing rotation while preventing axial movement. The retainer mediates the interaction between these components, permitting the shroud to rotate for security purposes while maintaining positional stability during operation.
2Reliability
If the shroud is retained on the fastener body, then security is improved, but friction and wear between components increase
Solution Approach 1:
The retainer mechanism serves as an intermediary that minimizes direct contact and friction between the shroud and fastener body. By providing a controlled retention interface, it reduces wear and energy loss while maintaining the security function of the shroud.
Solution Approach 2:
The system changes the friction parameter by allowing relative rotation between the shroud and fastener body through the retainer mechanism. This parameter change reduces static friction and wear that would occur with rigid retention, while maintaining sufficient retention for security purposes.
3Reliability
If the shroud is freely rotating for security, then theft prevention is improved, but axial retention may be compromised
Solution Approach 1:
The retainer mechanism provides dynamic retention that adapts to operational requirements: it allows rotation in the horizontal plane for theft prevention while maintaining axial position stability. This dynamic behavior resolves the contradiction between free rotation for security and axial retention for stability.
Solution Approach 2:
The retainer acts as an intermediary that selectively constrains movement: it permits rotation for security purposes while preventing axial displacement. This selective mediation resolves the contradiction between rotational freedom and axial stability.
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
This configuration enhances security by preventing unauthorized removal of the fastener, as the shroud spins freely when attempted to be gripped, and reduces friction and wear between components, improving the fastener's operational reliability.
Implementation Method 1
The outer surface of the intermediate sleeve may have a coefficient of friction less than the outer surface of the shroud-receiving body portion. The inner surface of the intermediate sleeve may have a coefficient of friction less than the outer surface of the shroud-receiving body portion. The outer surface of the intermediate sleeve may have coefficient of friction less than the inner surface of the shroud.
Data Source
AI summary
An improved fastener comprising a fastener body having a tool-engaging portion, a threaded fastening portion and a shroud-receiving body portion, a shroud concentrically mounted on the shroud-receiving body portion, and an intermediate sleeve disposed concentrically between the shroud-receiving body portion and the shroud, the shroud being supported in rotatable relationship with said shroud-receiving body portion such that said shroud will rotate relative to said fastener body under an applied external torque prior to said fastener body rotating when said fastener is engaged with an external structure at a design installation torque.