Crane Luffing Mode via Hoist Rope Reeving Change
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing crane systems face challenges in combining the advantages of luffing and trolley modes, particularly in terms of increased dead weight moment and reduced tip load capacity when a trolley is mounted on the jib tip, and limited hoist rope length with steep jib positions.
Innovation Solution
The method involves changing the reeving of the hoist rope to allow independent deflection from the trolley, enabling the trolley to be positioned anywhere on the jib during luffing operation, and switching between 1-strand and multi-strand operations to optimize load capacity and radius, with the trolley locked near the boom pivot point for reduced dead weight and increased hoist rope length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the trolley is mounted on the jib tip for luffing operation, then the crane can operate in luffing mode, but the dead weight moment of the jib system increases and tip load capacity is reduced
Solution Approach 1:
The invention extracts the hoist rope deflection function from the trolley and relocates it to a separate deflection pulley system on the jib. This separates the luffing function from the trolley, allowing the trolley to be positioned anywhere on the jib without being constrained to the tip, thereby reducing the dead weight moment while maintaining luffing capability
Solution Approach 2:
A deflection pulley is introduced as an intermediary element between the hoist rope and the load hook. This deflection pulley is mounted on the jib structure rather than on the trolley, serving as a mediator that enables luffing operation while keeping the trolley position flexible and reducing the moment arm of the trolley weight
2Adaptability or versatility
If the trolley is mounted on the jib tip, then luffing operation is enabled, but hoist rope length is lost which is necessary for steep jib positions
Solution Approach 1:
The hoist rope deflection point is extracted from the trolley and relocated to a fixed deflection pulley on the jib. This extraction allows the hoist rope to maintain its full length from the drum to the load hook, as the rope no longer needs to extend to the trolley position but instead deflects at the fixed pulley location, preserving rope length for steep jib positions
Solution Approach 2:
Instead of having the hoist rope attach to the moving trolley, the invention inverts the arrangement by having the rope attach to the stationary jib structure via a deflection pulley. This inversion ensures that the rope length is determined by the fixed pulley position rather than the variable trolley position, maintaining adequate rope length for all jib angles
3Adaptability or versatility
If the trolley is locked at the top of the jib for luffing mode, then the boom can climb at any gradient, but the dead weight moment increases and tip load capacity is reduced
Solution Approach 1:
The invention makes the trolley position dynamic rather than fixed at the jib tip. The trolley can be locked at any position along the jib based on operational requirements, allowing the system to adapt its dead weight moment characteristics to match the specific gradient and load requirements of each task
Solution Approach 2:
Different sections of the jib are utilized for different purposes: the upper portion can accommodate the trolley at various positions for load handling, while the deflection pulley system is positioned to optimize the luffing function. This local differentiation allows gradient adjustment without consistently incurring the maximum dead weight moment
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
This approach enhances the crane's flexibility and load capacity by reducing the dead weight moment, increasing the effective radius, and providing additional hoist rope length, especially with steep jib positions, allowing for efficient operation in both luffing and trolley modes.
Implementation Method 1
the hoist rope of the crane is guided over at least one deflection pulley on the crane boom, in particular the boom tip, in luffing operation
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
The invention relates to a method for operating a crane having a luffing crane jib and a trolley which can be displaced on the crane jib, wherein the crane can be operated, on the one hand, in a luffing mode and, on the other hand, in a trolley mode. According to the invention the switch between a luffing mode and a trolley mode takes place by virtue of the hoist-rope reeving being altered. The invention also relates to such a crane for implementing the method.