Spring-Loaded Captive Fastener for Tool-Free Withdrawal Locking
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Solution Overview
Problem
Existing fasteners require special tools and external components to secure themselves in place, making them costly and inconvenient to install, and lack a reliable mechanism to prevent withdrawal through apertures.
Innovation Solution
A captive fastener design featuring spring-loaded pins within a threaded shaft, where the pins retract during insertion and expand outward to secure the fastener in place, using an annular rim to prevent withdrawal and an alignment pin for positioning, eliminating the need for external tools and components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fasteners use expansion mechanisms like umbrellas or tri-pods, then the fastener can prevent withdrawal through the opening, but the device complexity increases and requires special installation tools and external components
Solution Approach 1:
The fastener is divided into distinct functional segments: a shaft portion for insertion, a head portion for retention, and multiple independent spring-loaded pins distributed within the shaft. Each pin operates independently within its own cavity, allowing the system to achieve reliable withdrawal prevention through distributed simple components rather than a single complex expansion mechanism.
Solution Approach 2:
The spring-loaded pins are nested within cavities in the shaft, with each pin contained within its own chamber. The pins are hidden within the shaft during insertion and only protrude after passing through the panel, eliminating the need for external retainer rings or complex external retention mechanisms.
2Reliability
If traditional fasteners use retainer rings and special installation tools, then the fastening can be secured, but the ease of manufacture decreases and installation becomes more difficult
Solution Approach 1:
The retention function previously requiring separate retainer rings is merged into the fastener shaft itself through integrated spring-loaded pins. The installation tool requirement is eliminated by designing the pin mechanism to automatically activate upon insertion, combining the fastening and retention functions into a single integrated component that requires no external tools or additional parts.
Solution Approach 2:
The spring-loaded pins are designed to automatically protrude from the shaft after the fastener passes through the panel, using the insertion motion itself to activate the retention mechanism. The fastener is self-installing and self-securing, requiring no external tools, retainer rings, or additional components to achieve reliable fastening.
3Reliability
If the fastener shaft expands like an umbrella or tri-pod, then the fastener can be retained in the opening, but the ease of operation decreases due to tool requirements
Solution Approach 1:
The spring-loaded pins transition from a retracted state during insertion to a protruding state after insertion, dynamically adapting their configuration based on the insertion process. The pins are compressed during passage through the panel and automatically expand to the protruding position when the compressive force is released, providing automatic retention without requiring manual tool operation.
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 fastener securely holds itself in place without external tools, provides a reliable locking mechanism to prevent withdrawal, and ensures proper alignment, offering a low-cost, efficient, and reliable fastening solution.
Implementation Method 1
Each spring loaded pin is located in a chamber of the shaft with an annular rim on at a proximal end of the pin that prevents the pin completely passing through an aperture and out the chamber. The distal end of the pin projects through the aperture and out of the shaft when the spring is not compressed. That is, the spring biases the pin outward such that a distal portion of the pin projects through the hole
Implementation Method 2
After passing through the panel, nut, or other object, the compressive force on the end of the pins will be released, causing the springs to expand the pins outwardly until the pins project out of the shaft of the fastener
Data Source
AI summary
A captive fastener comprising a head, a neck, and a threaded shaft, and one or more spring loaded pins disposed within respective cavities of the shaft along at least first and second radial directions. Each spring loaded pin is located in a chamber of the shaft with an annular rim on at a proximal end of the pin that prevents the pin completely passing through an aperture and out the chamber. The distal end of the pin projects through the aperture and out of the shaft when the spring is not compressed. That is, the spring biases the pin outward such that a distal portion of the pin projects through the hole, but the spring can collapse to allow the fastener to pass through a fitted opening sized to receive the shaft of the fastener before the pin expands outward.