Asymmetric Security Fastener Head for Single-Angle Driver Engagement
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Solution Overview
Problem
Existing security fasteners can be removed using widely available tools, compromising their security against unauthorized access.
Innovation Solution
A security fastener design featuring a head with 1-fold rotational symmetry and a maximum of 1 mirror plane, requiring a specialized driver to engage the fastener on opposing sides, thereby restricting removal to authorized personnel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard security bit recesses are used in existing security fasteners, then the fasteners can be removed using available security bits, but this compromises security against unauthorized access
Solution Approach 1:
The patent applies asymmetry by designing a security fastener head with a single asymmetric recess that lacks rotational symmetry. This asymmetric geometry ensures that only a specifically designed driver with a matching asymmetric projection can engage the recess, preventing removal by unauthorized persons using standard or commonly available security bits. The asymmetric design creates a one-to-one correspondence between the fastener and its authorized driver.
Solution Approach 2:
The patent segments the engagement interface into specific geometric features: a recess with particular angular boundaries and a complementary projection. This segmentation of the mating surfaces ensures precise alignment and engagement, where only the correctly segmented driver projection can fit into the recess at the required orientation, blocking unauthorized tools from effective engagement.
2Reliability
If the recesses are closed at the periphery of the head, then engagement is secure, but dirt particles can be trapped inside the recesses interfering with engagement
Solution Approach 1:
The patent extracts the harmful effect of dirt trapping by designing the recess to be open at the periphery of the head. This extraction allows contaminants to be excluded from the recess cavity, preventing dirt particle accumulation that would interfere with driver-fastener engagement. The open peripheral design maintains engagement security through the asymmetric geometry while eliminating the closed-cavity trapping problem.
3Power
If the head is engaged at the centre, then torque application is efficient, but standard tools can easily engage the head using opposing surfaces
Solution Approach 1:
The patent applies asymmetry by positioning the single recess asymmetrically on the head face, away from the center. This asymmetric positioning prevents standard tools with opposing gripping surfaces from effectively engaging the head, as there are no symmetric opposing features to grip. The asymmetric recess requires a specifically shaped driver that can engage the unique geometry, thereby maintaining security while still allowing efficient torque application through the specialized driver.
Data Source
AI summary
A security fastener for use with a corresponding driver, the fastener comprising: a shank defining a longitudinal centre axis; and a head having a face for mating with a corresponding security bit of the driver, the face including at least one recess for receiving a corresponding projection of the bit, wherein the head has: 1-fold rotational symmetry about the longitudinal centre axis of the shank; and a maximum of 1 mirror plane containing the longitudinal centre axis, such that mating of the corresponding projection of the driver with any of the at least one recesses is achievable only when the driver is in a single angular position with respect to the head, wherein the face comprises a first surface and the at least one recess is defined within the first surface, further wherein the longitudinal centre axis intersects the first surface.