Ratcheting Hold-Down Assembly for Vibration-Resistant Avionics Mounting
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Solution Overview
Problem
Conventional hold-down assemblies for portable electronic units in avionics equipment mounting trays fail to maintain a robust connection due to vibrations during aircraft operation, leading to disengagement from the mating wire harness and improper operation.
Innovation Solution
A hold-down assembly comprising a hinge block, shaft, locking collar, and actuator knob with a ratchet plate and spring-biased ball bearing, which applies a locking force to the portable electronic unit, resisting vibrations and ensuring secure engagement with the mating wire harness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional hold-down assembly is used to secure the portable electronic unit, then the unit can be initially engaged with the mating wire harness, but vibration during aircraft operation causes the hold-down assembly to loosen and the unit to become disengaged
Solution Approach 1:
The hold-down assembly incorporates a dynamic locking mechanism where the actuator knob rotates to advance the locking collar along the shaft, creating a progressive locking action. The ball bearing and detent hole system provides dynamic vibration resistance by allowing the locking collar to self-adjust while maintaining secure engagement, preventing loosening during aircraft operation.
Solution Approach 2:
The locking collar is designed to apply preliminary counteracting force against vibration-induced loosening. The ball bearing engages with detent holes in advance to prevent the locking collar from rotating backward, creating a preliminary anti-action that counteracts the harmful vibration forces before they can cause disengagement.
2Stability of the object's composition
If the locking collar applies sufficient force to prevent vibration-induced loosening, then engagement stability improves, but the complexity of the hold-down assembly increases
Solution Approach 1:
The hold-down assembly is segmented into distinct functional components: the shaft for pivoting motion, the locking collar for applying locking force, the actuator knob for operation, and the ball bearing-detent hole system for vibration resistance. This segmentation allows each component to perform its specific function efficiently while maintaining overall simplicity and reliability of the assembly.
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 assembly provides a reliable and secure connection by applying a significant locking force that resists vibrations, maintaining proper operation of the portable electronic unit despite aircraft vibrations, with minimal manual torque required for locking and high resistance to loosening.
Implementation Method 1
a compression spring within the knob body. The compression spring biases the ball bearing into engagement with the ratchet plate
Implementation Method 2
the ball bearing is forced against the spring bias of the compression spring as the ball bearing travels between adjacent detent holes
Implementation Method 3
The actuator knob is threadably engaged with the shaft. As the actuator knob is rotated to move along the shaft
Data Source
AI summary
A hold-down assembly for retaining a portable electronic unit within an avionics equipment mounting tray includes a shaft, a locking collar, and an actuator knob. The shaft is coupled to pivot with the mounting tray. The locking collar slides along the shaft to engage the portable electronic unit. The actuator knob includes a knob body, a ratchet plate having detent holes within the knob body, a ball bearing, and a compression spring within the knob body. As the actuator knob is rotated to move along the shaft, the knob body and the ball bearing rotate with respect to the ratchet plate, and the ball bearing is forced against a spring bias of the compression spring as the ball bearing travels between adjacent detent holes.