Hoist Cable Sensor Differential Drive Mechanism
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Solution Overview
Problem
Rescue hoists used in aviation require accurate deployment length monitoring of cables, but existing solutions like multi-turn transducers lose positional data when power is lost, and single-turn transducers necessitate complex gear reductions, making them bulky and heavy.
Innovation Solution
A cable deployment sensing system utilizing a differential drive mechanism with a stationary and rotatable ring gear, a cluster assembly, and a single-turn transducer that maintains positional data even without power, ensuring accurate cable length tracking through a compact and lightweight design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-turn transducers are used to sense cable drum rotations, then the number of rotations can be directly sensed, but positional reading is not maintained if power is lost
Solution Approach 1:
The patent replaces the electrical multi-turn transducer with a mechanical differential drive system consisting of a stationary ring gear, rotatable ring gear, and cluster assembly with two gears. This mechanical system inherently maintains positional information through its physical configuration without requiring power, while still providing accurate rotation sensing capability.
2Reliability
If single-turn transducers are used to maintain positional data during power loss, then data integrity is preserved, but complex planocentric drives or bulky multi-stage gear reduction are required
Solution Approach 1:
The patent segments the gear system into distinct functional components: a stationary ring gear for structural support, a rotatable ring gear for motion transmission, and a cluster assembly containing two separate gears. This segmentation allows each component to perform its specific function efficiently, achieving the required gear ratio without complex multi-stage reductions.
Solution Approach 2:
The patent implements a nested gear configuration where the cluster assembly with two gears is positioned within the annular space between the stationary and rotatable ring gears. This nested arrangement allows compact packaging of multiple gear stages, reducing overall device complexity and size while maintaining the required gear reduction ratio.
3Reliability
If single-turn transducers are used with complex gear reduction, then positional data is maintained, but the hoist becomes bulky and heavy
Solution Approach 1:
The patent uses a nested gear arrangement where compact gear stages are positioned within the annular space between ring gears, significantly reducing the overall volume and weight of the sensing system compared to linear multi-stage gear reductions.
Solution Approach 2:
The differential drive mechanism serves multiple functions simultaneously: it provides the required gear reduction ratio, maintains positional information without power, and enables accurate rotation sensing. This multi-functionality eliminates the need for separate heavy-duty gear reduction mechanisms, reducing overall system weight.
Data Source
Figure 1
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Figure 2B
AI summary
A hoist includes a cable deployment sensor to sense the length of a cable that is deployed from a cable drum (26) of the hoist. The cable deployment sensor includes a stationary ring (44) and a rotatable ring (46) disposed coaxially on the cable drum axis. A cluster assembly (48) is mounted to rotate about the cable drum axis simultaneously with the cable drum (26). The cluster assembly (48) includes a cluster gear (52) with a first gear (54) engaging the stationary ring (44) and a second gear (56) engaging the rotatable ring (46). The second gear (54) drives the rotatable ring (44) about the cable drum axis, and the rotatable ring (46) drives rotation of an input gear (60) for a sensor assembly (40).