Ratcheting Hold-Down Assembly for Vibration-Resistant Avionics Trays
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Solution Overview
Problem
Conventional hold-down assemblies for securing portable electronic units in avionics equipment mounting trays fail to maintain a robust connection due to vibrations experienced during aircraft operation, leading to disengagement from the mating wire harness.
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 device complexity is reduced, but the reliability of the connection deteriorates due to vibration-induced loosening
Solution Approach 1:
The hold-down assembly employs a dynamic locking mechanism where the actuator knob can be rotated to adjust the locking force applied by the locking collar. The spring-loaded ball bearing and detent holes provide dynamic adaptation to vibration forces, automatically maintaining engagement during aircraft operation while allowing manual adjustment when needed.
Solution Approach 2:
The actuator knob contains nested components including the ratchet plate with detent holes and the spring-loaded ball bearing mechanism within its body. The locking collar slides along the shaft and engages with the portable electronic unit, creating a nested structure where smaller components are housed within larger ones, optimizing space while maintaining functionality.
2Object-affected harmful factors
If a simple hold-down assembly is used, then the ease of manufacture is improved, but the ability to resist vibration forces deteriorates
Solution Approach 1:
The spring-loaded ball bearing mechanism converts the harmful vibration forces into beneficial engagement forces. When vibration occurs, the spring compresses and the ball bearing remains seated in the detent holes, actually strengthening the locking engagement. The design transforms vibration-induced loosening into vibration-resistant locking through the elastic deformation of the spring and the geometric constraint of the detent holes.
Solution Approach 2:
The hold-down assembly is segmented into distinct functional components: the hinge block for mounting, the shaft for pivoting motion, the locking collar for engagement, and the actuator knob with integrated ratchet mechanism. This segmentation allows each component to be manufactured separately using standard machining processes, then assembled together, balancing manufacturing ease with vibration resistance.
3Force
If a robust locking mechanism is implemented, then the force applied to maintain engagement is improved, but the ease of operation deteriorates due to manual adjustment requirements
Solution Approach 1:
The spring-loaded ball bearing and detent hole mechanism provides self-service by automatically maintaining locking engagement during vibration without requiring continuous manual intervention. The spring force automatically adjusts to counteract vibration-induced loosening, and the detent holes provide automatic positioning as the actuator knob rotates, reducing the operational effort required while maintaining strong locking force.
Solution Approach 2:
The actuator knob allows periodic manual adjustment of the locking force when needed, while the spring mechanism provides continuous automatic adjustment during operation. The periodic manual rotation of the knob engages different detent holes to set the desired locking force, after which the system operates autonomously, combining periodic user input with continuous automatic maintenance of engagement.
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 robust connection by applying a significant locking force that resists aircraft vibrations, maintaining the portable electronic unit's engagement with the avionics equipment, even under severe flight conditions.
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 shaft includes external threads and is coupled to pivot with the hinge block. The actuator knob is threadably engaged with 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.