Crane Jib Sail Unit for Weathervaning Torque
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Solution Overview
Problem
Tower cranes with luffing jibs are often taken out of service at low wind speeds due to safety requirements, leading to increased operational costs and safety risks, especially in emergency situations, as active wind-safe-position-control methods are laborious and may fail, and reduced out-of-service radii can result in insufficient torque for weathervaning.
Innovation Solution
A jib device with a variably adjustable sail unit that increases windage, ensuring weathervaning even at reduced out-of-service radii, featuring retractable wind sails that can expand or contract to optimize surface area based on operational needs, and an automated control system for adjusting the sail unit's surface area in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the jib device operates at a reduced out-of-service radius to minimize collision risk, then the collision risk is reduced, but the torque available for weathervaning becomes insufficient
Solution Approach 1:
The sail unit's surface area is made dynamically adjustable through a retractable mechanism. During normal operation, the sail is retracted to minimize wind resistance. When weathervaning is required, the sail extends to maximum surface area to capture sufficient wind torque, enabling the jib to rotate into the wind even at reduced radii where gravitational torque alone would be insufficient.
Solution Approach 2:
The sail unit acts as an intermediary element that converts wind force into rotational torque. By positioning the sail at a distance from the jib's rotation axis and adjusting its surface area, it amplifies the wind's rotational effect, providing the additional torque needed for weathervaning without requiring the jib to be at a larger radius.
2Reliability
If the crane is taken out of service at low wind speeds to ensure safety, then safety is improved, but operational productivity decreases
Solution Approach 1:
The sail unit enables the jib device to perform self-service weathervaning automatically when wind conditions require it. The sail extends to capture wind torque, causing the jib to rotate into the wind direction without operator intervention or activation of active wind-safe-position-control systems, thereby maintaining safety while avoiding unnecessary service interruptions.
Solution Approach 2:
The system changes the operational parameters by adjusting the sail unit's surface area based on wind speed conditions. At low to moderate wind speeds, the sail extends to provide sufficient torque for weathervaning, allowing continued operation. Only when wind speeds exceed the maximum operational threshold does the system take the crane out of service, thereby extending productive operation time while maintaining safety.
3Force
If the sail unit has a large surface area to ensure sufficient torque for weathervaning, then weathervaning capability is improved, but wind resistance during operation increases
Solution Approach 1:
The sail unit's surface area is dynamically adjusted based on operational mode. During normal crane operation, the sail is retracted to present minimal surface area to the wind, reducing wind resistance and drag on the jib. When weathervaning is initiated, the sail extends to maximum surface area to capture wind torque, then can be partially retracted once the jib reaches the windward position, optimizing performance throughout the operation cycle.
Solution Approach 2:
The sail unit operates in periodic cycles of extension and retraction. It extends periodically when wind conditions indicate the need for weathervaning, captures the necessary torque to rotate the jib into the wind, and then retracts to minimize ongoing wind resistance during stable operation, creating a rhythm of action that balances weathervaning capability with operational efficiency.
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 jib device ensures safe operation by maintaining a reduced out-of-service radius while providing sufficient torque for weathervaning at wind speeds as low as 40 km/h, reducing collision risks and enhancing operational safety, even in emergencies, by automatically adjusting the sail unit's surface area to match changing wind conditions.
Implementation Method 1
a torque on the rotational part of the crane provided by the wind force corresponds to the out of service radius of the jib
Implementation Method 2
This out of service condition is also called weathervane condition, i.e. wind will force the crane's upper part to turn into the wind direction
Data Source
AI summary
A jib device for a crane comprises a jib (6) and a sail unit (15), wherein a surface area of said sail unit (15) is variably adjustable.