Pivotable Cable Sheave for Crane Load Tilting Detection
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Solution Overview
Problem
Existing methods for controlling load movements in cranes are inadequate in quickly detecting and responding to tilting movements, leading to potential damage and reduced transfer capacity due to slow response times and potential cable breakage.
Innovation Solution
The method involves mounting cable sheaves on the hoisting frame to pivot about a horizontal axis, with sensors detecting pivoting movements to generate warning signals or automatic responses, allowing for quicker stopping of the hoisting or lowering movement and preventing cable damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fixed cable sheaves are used in quayside cranes, then the structure is simple and stable, but the cable may be damaged or break when the load tilts and comes into contact with the sheave at a great angle
Solution Approach 1:
The cable sheaves are made pivotable about a horizontal axis perpendicular to their rotation axis, allowing them to dynamically adjust their position in response to load tilting. This dynamic adaptation prevents the cable from contacting the sheave at dangerous angles, eliminating the damage risk while maintaining structural simplicity.
2Device complexity
If load monitoring is performed only by measuring hoisting load, then the control system is simple, but the crane continues hoisting until maximum load is reached, resulting in long braking distance and potential damage at high speeds
Solution Approach 1:
The pivotable sheave system provides preliminary warning of dangerous tilting conditions before maximum load is reached. By detecting tilting through sheave position changes, the system enables early intervention and braking, significantly reducing the braking distance and preventing damage even at high speeds.
Solution Approach 2:
The sheave position serves as a real-time feedback parameter that continuously monitors load stability. When the sheave pivots beyond a safe angle, this feedback triggers immediate braking action, creating a closed-loop control system that responds dynamically to tilting conditions.
3Reliability
If snag cylinders are incorporated in the hoisting cables to limit maximum force, then the load on the crane is limited, but the response time is very slow and testing is dangerous, making correct functioning theoretical rather than proven
Solution Approach 1:
The mechanical snag cylinder system is replaced with a pivotable sheave mechanism coupled with position detection. This substitution provides both load limiting and rapid response capabilities through mechanical geometry and real-time position monitoring, eliminating the slow response and testing dangers of snag cylinders.
4Measurement precision
If levelling instruments are used to measure the inclination of the load, then tilting can be detected, but the response is slow and not suitable for generating timely signals to prevent tilting
Solution Approach 1:
The cable sheave serves as an intermediary element that translates load tilting into a measurable position change. This intermediary approach provides both accurate tilting detection and rapid response, as the sheave position changes immediately with load tilting and can be monitored continuously without the delays inherent in traditional levelling instruments.
Data Source
AI summary
A method for controlling a hoisting or lowering movement of a load, which is suspended from a hoisting mechanism of a crane by means of at least two hoisting cables trained round cable sheaves on the load, by monitoring the position of the load and braking and/or stopping the hoisting mechanism upon detection of an undesirable position, wherein the cable sheaves are each connected to the load for pivoting about a horizontal axis, and the position of the load is monitored by detecting a pivoting movement of at least one of the cable sheaves.