Captive Fastener Push-Out Pin for Counterbored Panel Retention
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Solution Overview
Problem
Captive screws face challenges in securing panels from the opposite side, especially when limited access is available, and existing solutions do not effectively prevent the screw from falling out or counter-rotating, particularly when used with counterbores and subpanels.
Innovation Solution
A captive fastener with an elongate slot and a retractable, spring-activated push-out pin, which allows the fastener to pass through panels and subpanels while maintaining its position, utilizing a cantilevered hold-out clip and frustoconical push-out pin to secure the assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional captive screw is used to secure panels from the opposite side, then the fastener can remain in place when loosening, but the screw cannot effectively prevent falling out or counter-rotating when used with counterbores and subpanels
Solution Approach 1:
The push-out pin is designed to be dynamically changeable between extended and retracted positions. When the fastener needs to pass through panels with counterbores and subpanels, the pin retracts to allow passage. Once positioned, the pin extends to engage with the panel and prevent the fastener from falling out or counter-rotating, thus adapting to different operational requirements.
Solution Approach 2:
The fastener is divided into functional segments: the push-out pin that can extend and retract, the hold-out clip that can engage and disengage, and the threaded shank. This segmentation allows each component to perform its specific function independently, enabling the fastener to work effectively with counterbores and subpanels while maintaining security.
2Reliability
If the push out pin is extended to prevent the fastener from falling out, then security is improved, but the fastener cannot pass through panels requiring clearance
Solution Approach 1:
The push-out pin's position is dynamically controlled based on operational needs. During installation, the pin retracts to allow the fastener to pass through panels. Once the fastener is positioned, the pin extends automatically or manually to engage with the panel and provide retention, thus resolving the contradiction between passage and security.
Solution Approach 2:
The push-out pin is retracted in advance before the fastener encounters panels requiring clearance. This preliminary retraction action ensures smooth passage through panels with counterbores and subpanels. After passage, the pin extends to provide the necessary retention, thus preparing the system in advance for different operational phases.
3Reliability
If the hold-out clip is engaged to prevent counter-rotation, then fastening security is improved, but the assembly becomes difficult to disassemble
Solution Approach 1:
The hold-out clip is designed to be dynamically engageable and disengageable. During normal operation, the clip engages with the panel to prevent counter-rotation. For disassembly, the clip can be disengaged by applying force to the fastener head or using a tool, thus providing both security during operation and ease of repair when needed.
Solution Approach 2:
The hold-out clip acts as an intermediary between the fastener and the panel. It provides the counter-rotation prevention function while allowing controlled disengagement. The clip's design includes features that enable it to maintain engagement during operation but allow deliberate disengagement for repair or removal, thus mediating between security and ease of repair requirements.
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 solution ensures secure fastening by preventing the fastener from falling out or counter-rotating, allowing for effective use with counterbores and subpanels, and enabling easy assembly and disassembly by retracting the push-out pin and hold-out clip.
Implementation Method 1
The shank further comprises a cavity near the end of the shaft that houses a retractable, spring-activated push out pin. The push out pin is biased by the spring to extend out of the shank perpendicular to the surface
Data Source
AI summary
A captive fastener is disclosed having a longitudinal slot along the shank for receiving a hold-out clip, and a chamber that houses a retractable push out pin. The push out pin is spring actuated to extend out of the shank and can be retracted into the cavity against the bias of the spring to pass through a primary panel and subpanel. The push out pin is shaped to bear against a counterbore and secure the fastener within a panel while other components are affixed to the fastener.