Tamper-Resistant Fastener With Shear Cap and Rotating Cover
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Solution Overview
Problem
Existing tamper-resistant fasteners lack effective mechanisms to prevent unauthorized access and removal, as they can be easily rotated or removed once installed, compromising the security of protected assets.
Innovation Solution
A tamper-resistant fastener design featuring a slot with an enlarged region and a cap member that can only be inserted transversely, with a rotational drive feature that secures the fastener in a counterbored opening, making removal difficult by shearing at a predetermined force, and allowing the cap member to rotate for protective coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional fastener is used, then installation is simple and quick, but the fastener can be easily rotated or removed once installed, compromising security
Solution Approach 1:
The fastener is divided into two separate components: a threaded fastener with a slot and a cap member. This segmentation allows the fastener to provide both secure installation and tamper-resistance functions that would be difficult to achieve in a single conventional fastener design.
Solution Approach 2:
The cap member is inserted into the slot of the fastener head, creating a nested structure where one component fits within another. This nesting mechanism enables the cap member to rotate within the slot, providing tamper-resistance while maintaining a compact overall structure.
2Reliability
If a tamper-resistant mechanism is added to prevent unauthorized removal, then security is improved, but the device complexity increases
Solution Approach 1:
The slot in the fastener head has an asymmetric enlarged region that receives the enlarged second shank portion of the cap member. This asymmetric design allows the cap member to be inserted only in a specific orientation and prevents easy removal, providing security while maintaining a relatively simple overall structure.
Solution Approach 2:
The cap member is designed to rotate dynamically within the slot after insertion. This dynamic movement allows the fastener to transition from an installed state to a secured state, providing tamper-resistance through rotation rather than requiring a complex locking mechanism.
3Ease of operation
If the cap member can rotate freely, then protective coverage is improved, but unauthorized removal becomes easier
Solution Approach 1:
The foot of the cap member is positioned to abut the slot before rotation occurs. This preliminary positioning creates a mechanical constraint that prevents the cap member from being removed while still allowing it to rotate for protective coverage. The foot acts as a stop that must be overcome for removal.
Solution Approach 2:
The slot has a localized enlarged region that specifically receives the enlarged second shank portion of the cap member. This local variation in the slot geometry provides rotational freedom in one area while maintaining constraints in other areas to prevent removal.
Data Source
AI summary
A tamper-resistant threaded fastener including a circular head having a slot formed in the head transverse to the longitudinal axis, the slot having an enlarged region intermediate an apex and a base of the slot. A cap member includes a head having a drive feature formed therein, the head extending to a first shank portion, extending to an enlarged second shank portion, extending to a foot. The cap member is insertable in the slot only from a direction transverse to the longitudinal axis. During rotational installation of the fastener and cap member in a threaded counterbored opening for securing a barrier for protecting an asset, the foot shears inside the slot at a predetermined rotational drive force, the cap member being rotatable in the opening and protectively covering the fastener head.