Coaxial Rescue Hoist Drive Train for Lower Bearing Radial Loads
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Solution Overview
Problem
Existing rescue hoist systems for aircraft require complex and costly gear reduction mechanisms with multiple parallel shafts, leading to high radial forces and increased complexity in installation and maintenance.
Innovation Solution
A compact drive train design with coaxially arranged stages and planetary gears supported within a housing, allowing for a single-unit installation and reducing the number of components, which simplifies installation and maintenance while minimizing radial forces on bearings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If parallel shafts are used for gear reduction, then the desired rotational speed of the cable drum is achieved, but large radial combined forces are induced requiring robust bearings and supporting components
Solution Approach 1:
The patent merges multiple parallel shafts into a single coaxial shaft arrangement. The first, second, and third stages are all disposed on a single shaft that is coaxial with the cable drum axis, eliminating the need for multiple parallel shafts and their associated radial force combinations.
Solution Approach 2:
The patent transitions from a parallel shaft arrangement (one dimension of force combination) to a coaxial shaft arrangement (rotating in the same dimension). This dimensional reorganization allows radial forces to be applied sequentially rather than combined, reducing the total radial load on bearings.
2Power
If multiple parallel shafts and gear sets are used, then the desired gear reduction is achieved, but each shaft and gear set must be individually installed and aligned increasing installation complexity
Solution Approach 1:
The patent combines multiple gear stages onto a single shaft, creating a more integrated drive train assembly. The first stage planetary gears, second stage planetary gears, and third stage planetary gears are all mounted on the same coaxial shaft, reducing the number of separate components that need individual installation and alignment.
Solution Approach 2:
The single shaft serves multiple functions by supporting all three stages of planetary gears. This multi-functional shaft design eliminates the need for separate shafts for each gear stage, simplifying both installation and maintenance procedures.
3Strength
If robust bearings and supporting components are used to handle large radial forces, then the structural integrity is maintained, but the weight and material usage of the hoist system increases
Solution Approach 1:
The coaxial shaft arrangement preliminarily reduces radial force combinations before the loads reach the bearings. By organizing gear stages coaxially, the design prevents the accumulation of large radial forces, allowing for lighter bearing selections while maintaining structural integrity.
Solution Approach 2:
The patent changes the fundamental geometric parameter of the shaft arrangement from parallel to coaxial. This parameter change fundamentally alters the force distribution characteristics, reducing radial loads and enabling the use of lighter bearing components while maintaining the required structural strength.
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 reduces the complexity and cost of installation, minimizes downtime, and allows for easier replacement of the drive train, while also reducing the material and weight of the hoist system by canceling out radial forces on bearings.
Implementation Method 1
The first stage, the second stage, and the third stage are disposed coaxially on a drive train axis. The housing directly supports a plurality of third stage planetary gears of the third stage, the plurality of third stage planetary gears is disposed in slots extending through the housing.
Data Source
Figure 1
Figure 1B
Figure 2A
AI summary
A drive train (22) for a rescue hoist includes a first stage (60), a second stage (62), and a third stage (64). The first stage receives an input from a motor and the third stage provides rotational power to a cable drum. The first stage, second stage, and third stage are disposed coaxially within a common housing. The first stage provides a first speed reduction, the second stage provides a second speed reduction, and the third stage provides a third speed reduction between the motor and the cable drum. The common housing includes a mounting flange for mounting the drive train to the rescue hoist.