Buckled Shroud Retainer for Free-Spinning Security Fasteners
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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 the shroud or spin cap, allowing unauthorized tools to grip and remove them.
Innovation Solution
The implementation of a buckled shroud retainer mechanism, where a substantially arch-shaped axially-buckled radially-extending annular protrusion is formed by applying an axial force to the shroud or shroud-receiving body portion, creating a groove that restrains the shroud from movement in specific axial directions, ensuring it rotates relative to the fastener body before the fastener itself rotates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a free-spinning shroud is fitted over the security fastener, then theft prevention is improved by preventing rotational purchase on the fastener, but the shroud can be easily removed without proper retention mechanism
Solution Approach 1:
The buckled retainer structure is pre-formed on the fastener body before shroud installation. The axial buckle creates a protrusion that engages with the shroud's groove, establishing retention capability before any assembly issues arise. This preliminary structural preparation ensures the shroud will be properly retained once assembled.
Solution Approach 2:
The retainer structure is divided into distinct functional segments: the axial buckle portion that provides radial extension, the groove engagement feature that interfaces with the shroud, and the retention element that prevents axial movement. This segmentation allows each component to perform its specific function while working together to solve the retention problem.
2Reliability
If the shroud is tightly retained on the fastener body, then security is improved by preventing unauthorized removal, but the shroud cannot rotate freely relative to the fastener body
Solution Approach 1:
The retainer design creates a dynamic retention system where the shroud can rotate freely around the fastener body while being constrained from axial movement. The radial protrusion engages the groove to prevent removal, but allows rotational motion, creating a dynamic balance between security and operational flexibility.
Solution Approach 2:
The retention mechanism operates in the radial dimension (preventing axial movement) while allowing freedom in the rotational dimension. By using a radially-extending protrusion that engages a groove, the system constrains movement in one dimension (axial) while permitting movement in another (rotational), effectively solving the contradiction through dimensional separation.
3Reliability
If conventional retention methods like flared end portions are used, then shroud retention is achieved, but manufacturing complexity increases and retention strength is insufficient
Solution Approach 1:
The axial buckle structure is self-forming and self-retaining. The buckle portion naturally creates the radially-extending protrusion through its geometric configuration, eliminating the need for separate retention components or complex assembly steps. The structure serves its own retention function without requiring additional parts or complicated manufacturing processes.
Solution Approach 2:
The retainer uses geometric parameter optimization where the axial buckle's thickness, buckle angle, and protrusion height are specifically designed to provide adequate retention strength. By carefully controlling these parameters, the system achieves strong retention without requiring excessive material or complex structures, balancing strength and simplicity.
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 design enhances security by requiring higher forces to remove the fastener, as the shroud is securely retained and free to rotate, preventing unauthorized access and theft.
Implementation Method 1
the axial buckle of the shroud-receiving body portion buckles inwardly into the annular groove under an applied axial force to form a substantially arch-shaped axially-buckled radially-extending annular protrusion
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 having an inner surface facing an outer surface of the shroud-receiving body portion; the inner surface of the shroud comprising an annular groove and the shroud-receiving body portion comprising a substantially arch-shaped axially-buckled radially-extending annular protrusion extending outwardly transverse to the central axis and disposed in the annular groove of the shroud; and the annular protrusion and annular groove of the shroud forming a shroud-retaining element restraining the shroud from movement in at least a first axial direction along the central axis such that the shroud will rotate relative to the fastener body under an applied external torque prior to the fastener body rotating when the fastener is engaged with an external structure at a design installation torque.