Wear-Induced Load Brake Locking for Rescue Hoist Drums
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Solution Overview
Problem
Rescue hoists face challenges in maintaining effective load control and braking mechanisms, particularly due to wear-induced issues that can lead to unintended cable reeling, especially under heavy loads or prolonged use, where existing load brakes may fail to securely lock the cable drum.
Innovation Solution
An automatic load brake mechanism with a wear-induced locking system, featuring a first and second shaft with angled radially outer and inner surfaces, coupled with friction discs and a sprag clutch, which engages upon thinning of the friction discs to ensure secure locking and prevent unintended reeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction discs are used in the load brake mechanism, then braking effectiveness is improved, but wear of friction surfaces occurs over time leading to reduced reliability
Solution Approach 1:
The wear indicator feature is provided in advance on the friction discs to predict when wear will reach critical levels. This allows proactive maintenance scheduling before actual failure occurs, ensuring braking effectiveness is maintained throughout the friction disc's service life.
Solution Approach 2:
The wear indicator provides visual feedback on the remaining thickness of friction discs. When the indicator becomes visible or changes appearance, it signals that wear has reached a predetermined threshold, prompting replacement before reliability degrades.
2Duration of action of stationary object
If the load brake is designed to accommodate wear, then duration of action is improved, but structural complexity increases due to additional locking mechanisms
Solution Approach 1:
The wear compensation feature is integrated into the existing shaft and friction disc assembly without adding separate locking mechanisms. The tapered surface and wear indicator are incorporated directly into the friction disc structure, merging wear accommodation into the existing design.
Solution Approach 2:
The load brake mechanism automatically compensates for wear through its inherent tapered geometry. As friction discs wear down, the tapered surface automatically adjusts the engagement position, providing self-compensation without requiring external adjustment mechanisms or complex locking systems.
3Reliability
If the radially outer and inner surfaces are angled, then automatic locking upon wear is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The tapered surfaces are designed with specific angle parameters that facilitate automatic locking. By optimizing the taper angle within reasonable tolerances, the design achieves reliable automatic engagement upon wear while maintaining manufacturability. The wear indicator also provides a visual parameter change that signals when locking should occur.
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 mechanism effectively locks the cable drum, preventing unintended reeling even after wear-induced thinning of friction surfaces, thereby ensuring reliable load control and safety during operations.
Implementation Method 1
a radially outer surface configured to engage a radially inner surface, the radially outer surface oriented at a first angle with respect to a longitudinal axis extending through the load brake, the radially inner surface oriented at a second angle with respect to the longitudinal axis
Data Source
AI summary
An automatic load brake having a wear-induced locking mechanism for a hoist is disclosed. In various embodiments, the load brake includes a first shaft defining an annular hollow portion and a radially outer surface; a second shaft defining an engagement portion and a radially inner surface, the radially inner surface configured to engage the radially outer surface; a first reaction plate coupled to the first shaft; a second reaction plate coupled to the second shaft; and a plurality of friction discs, with at least one of the plurality of friction discs coupled to a cup and disposed between the first reaction plate and the second reaction plate, the annular hollow portion of the first shaft being configured to lock to the engagement portion of the second shaft upon thinning of the plurality of friction discs.