Mobile Crane Jib Tensioning via Dynamic Spread Angle
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Solution Overview
Problem
Mobile cranes face instability and reduced load capacity due to bending loads when the crane jib is inclined at small angles, leading to potential buckling, and existing solutions require multiple load capacity charts for different configurations.
Innovation Solution
A method and system for a mobile crane that adjusts the spread angle of tensioning posts between the crane jib and its base in a triangular configuration based on the luffing angle, length, and weight of the load, using a controller and hydraulic spreading drive to dynamically modify the tensioning configuration for improved stability and load handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the crane jib is inclined at small angles to increase reach, then the horizontal reach is improved, but the bending load increases causing instability and potential buckling
Solution Approach 1:
The tensioning device is made dynamically adjustable through a hydraulic spreading drive that can continuously modify the spread angle between tensioning posts based on the current luffing angle. This dynamic adaptation allows the system to optimize stability characteristics for each operating condition, resolving the contradiction between reach and stability.
Solution Approach 2:
The system changes the geometric parameter of the tensioning device (spread angle between posts) in response to changes in the luffing angle. A controller monitors the luffing angle and commands the hydraulic spreading drive to adjust the spread angle, thereby changing the mechanical parameters of the support structure to maintain stability across different reach configurations.
2Device complexity
If the spread angle of tensioning posts is fixed to simplify the structure, then the device complexity is reduced, but the adaptability to different luffing angles and load conditions deteriorates
Solution Approach 1:
The tensioning device transitions from a static fixed-geometry structure to a dynamic adjustable structure. The hydraulic spreading drive enables continuous modification of the spread angle, allowing the system to adapt to various luffing angles and load conditions while maintaining a relatively simple overall structure.
Solution Approach 2:
A hydraulic spreading drive is employed to actuate the adjustable spread angle mechanism. This hydraulic actuation system provides smooth, controlled adjustment of the tensioning posts while keeping the mechanical structure compact and manageable, balancing complexity with adaptability.
3Reliability
If multiple load capacity charts are used for different configurations to ensure safety, then the reliability is improved, but the ease of operation deteriorates
Solution Approach 1:
The system implements automatic feedback control where sensors monitor the current luffing angle and load conditions, the controller processes this information against stored load capacity data, and the hydraulic spreading drive automatically adjusts the tensioning device to maintain safe operating parameters. This eliminates manual chart consultation and simplifies operation while ensuring reliability.
Solution Approach 2:
The crane system performs self-adjustment of the tensioning device based on its own operational parameters. The controller automatically determines the appropriate spread angle from stored load capacity information and commands the hydraulic actuator to make necessary adjustments, enabling the system to serve itself without external intervention.
Data Source
AI summary
A crane, in particular a mobile crane, includes a crane jib which can be moved about a substantially horizontal luffing axis, and a tensioning device for the crane jib. The tensioning device includes two pendants which run from the jib tip to the jib base of the crane jib and tensioning posts each tensioning a respective one of the pendants relative to the crane jib in a triangular configuration. In order to operate the crane, a luffing angle of the crane jib about the luffing axis is measured or recorded, and a spread angle between the tensioning posts while the crane jib is being used is modified depending on the luffing angle.