Asymmetric Security Fastener Recess for Single-Position Torque Engagement
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Solution Overview
Problem
Existing security fasteners can be easily removed using widely available tools, compromising security and ease of manufacture.
Innovation Solution
A security fastener design with 1-fold rotational symmetry and mirror symmetry, featuring recesses that require engagement on opposing sides and perpendicular engagement surfaces, making it difficult for standard tools to apply sufficient torque without a corresponding driver.
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 widely available security bits, but this compromises security; however, if a more complex recess design is used to prevent removal, then manufacturing complexity increases
Solution Approach 1:
The recess design employs asymmetric geometry where the recess is open at the periphery of the head and defined by engagement surfaces that are not symmetric about the longitudinal centre axis. This asymmetric configuration ensures that only a specially designed driver with matching asymmetric geometry can engage the recess, preventing removal by standard security bits while maintaining manufacturing simplicity through single-sided definition of engagement surfaces
Solution Approach 2:
The recess is segmented into distinct engagement surfaces including a first engagement surface and a second engagement surface that are differently oriented and shaped. This segmentation allows each surface to serve a specific function in preventing unauthorized removal while enabling the recess to be manufactured using standard milling techniques without requiring complex multi-step processes
2Reliability
If recesses are closed or enclosed, then dirt particles may be trapped inside interfering with engagement, but if recesses are open, then standard tools may more easily engage and compromise security
Solution Approach 1:
The recess is designed with localized opening at the periphery of the head rather than being fully enclosed or fully open. This local quality differentiation allows the recess to remain mostly enclosed for protecting internal surfaces from dirt accumulation, while the peripheral opening provides a controlled pathway that only the specially designed driver can utilize for engagement, thus maintaining both engagement reliability and security
3Force
If engagement surfaces are sloped or curved, then torque application may be improved, but manufacturing complexity and cost increase
Solution Approach 1:
Instead of using sloped or curved engagement surfaces that would require complex manufacturing processes, the invention inverts the approach by using substantially flat engagement surfaces that are defined by simple cylindrical milling operations. The security is achieved not through surface geometry complexity but through the asymmetric configuration and peripheral opening of the recess, thereby maintaining manufacturing simplicity while still enabling effective torque application through proper surface orientation
Data Source
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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.