Back-out Resistant Fastener with Thread Discontinuity
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Solution Overview
Problem
Screw-type fasteners used in applications like sheet metal roofing or siding can loosen over time due to vibrations, thermal expansion, or twisting, leading to compromised seals and potential serious issues.
Innovation Solution
A fastener design featuring a cylindrical shaft with a thread that terminates in a back-out discontinuity and integrally formed rings between the discontinuity and the head, providing a press-fit seal and resisting back-out through a combination of radial geometry and thread termination angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional screw thread terminates gradually, then the thread engages smoothly with the material, but the screw can back out under vibration and stress
Solution Approach 1:
The thread termination is designed with a back-out discontinuity that creates preliminary resistance to back-out motion. The abrupt change in thread geometry at the termination point generates a mechanical barrier that prevents the screw from backing out under vibration and stress, addressing the reliability issue before it occurs
Solution Approach 2:
The thread termination features asymmetric geometry with different profiles on the advancing side versus the retreating side. This asymmetry creates a mechanical lock that allows easy insertion but resists removal, preventing back-out while maintaining manufacturing feasibility through standard threading processes
2Reliability
If a flexible washer is used to dampen vibration, then the fastener secures better against loosening, but the device complexity increases
Solution Approach 1:
The anti-backout functionality is merged directly into the screw thread structure itself through the back-out discontinuity design. This integration eliminates the need for separate washers or locking mechanisms, maintaining fastener security while reducing overall device complexity to a single-component solution
Solution Approach 2:
The thread termination structure provides self-contained anti-backout protection through its inherent geometric discontinuity. The design serves its own locking function without requiring additional components or external mechanisms, achieving reliability through self-service rather than added complexity
3Strength
If the thread extends to the very end of the shaft, then the fastener engagement is maximized, but the screw is more prone to back-out under stress
Solution Approach 1:
The thread termination is designed with a back-out discontinuity that creates preliminary resistance to back-out motion. The abrupt change in thread geometry at the termination point generates a mechanical barrier that prevents the screw from backing out under vibration and stress, addressing the reliability issue before it occurs
Solution Approach 2:
The thread structure features localized variation in geometry at the termination point, with different characteristics at the end of the thread compared to the engaged portion. This local quality change creates the back-out discontinuity that provides anti-backout protection while maintaining strong engagement along the majority of the thread length
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
The design effectively prevents screw back-out and maintains a seal even if the fastener loosens, ensuring a secure connection and preventing leaks in sheet metal applications.
Implementation Method 1
the at least one ring forming a seal against an inner periphery of the hole by a press fit
Implementation Method 2
the back-out discontinuity is formed by an abrupt thread termination at an angle approximately perpendicular, preferably 75° to 95°, to the shaft forming a radial face
Data Source
AI summary
A fastener is provided having a cylindrical shaft with a generally constant diameter located between a head and a tapered point. The fastener has a thread integrally extending from the shaft and extending along a portion of a length thereof that terminates at an end of the shaft proximate the head with a back-out discontinuity. At least one ring integrally extends from the shaft in an area of the shaft between the back-out discontinuity and the head. The at least one ring has an outside diameter that is less than an outside diameter of the thread.