Self-Hoisting Crane Cable Crawler for Hook Block Lowering
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Solution Overview
Problem
The weight of cables extending from the hook block to the cable winch at ground level poses a challenge when lifting or lowering the hook block without an external load, leading to issues such as cables running backwards or inability to lower the block, especially in taller wind turbines, necessitating heavier cranes and reduced hook block weight to compensate.
Innovation Solution
A self-hoisting crane equipped with a motor-driven cable crawler featuring a traction sheave that shifts between active and passive states to provide a pulling force through friction, counteracting the weight of the cables, allowing the hook block to be lowered without external loads and preventing interference during lifting operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If ballast weights are added to the hook block to counteract cable weight, then the hook block can be lowered without external loads, but the working load limit is reduced
Solution Approach 1:
The patent replaces the mechanical ballast weight system with a motor-driven cable crawler system. The cable crawler uses a motor to actively control cable tension, substituting passive mechanical ballast with an active electromechanical system that can dynamically adjust to operational needs.
Solution Approach 2:
The cable crawler system transitions from a static ballast weight configuration to a dynamic system where the motor can adjust cable tension in real-time. The system can switch between active mode (providing pulling force) and passive mode (allowing free movement), enabling adaptive operation during different phases of crane movement and loading.
2Productivity
If the crane structure is strengthened to increase working load limit, then the crane can lift heavier loads, but the cable weight increases making it harder to lower the hook block
Solution Approach 1:
The motor-driven cable crawler replaces the need for mechanical compensation systems that would be required to handle increased cable weights from strengthened crane structures. The motorized system actively manages cable tension regardless of cable weight variations.
Solution Approach 2:
The system changes the operational parameters by introducing motorized control over cable tension. This allows the system to maintain optimal tension levels regardless of variations in cable weight due to crane structure strengthening, enabling both increased load capacity and ease of operation.
3Productivity
If the hook block weight is reduced to compensate for heavier crane components, then the cable weight challenge is exacerbated, but the working load limit is improved
Solution Approach 1:
The motor-driven cable crawler system replaces the mechanical advantage that would traditionally be achieved through optimized mass distribution (heavier hook block to counteract cable weight). The motorized system provides active tension control that makes passive mechanical compensation unnecessary.
4Ease of operation
If a cable crawler is added to provide pulling force, then the hook block can be lowered without external loads, but the device complexity increases
Solution Approach 1:
The cable crawler is designed with multi-functionality, serving both as a pulling mechanism for lowering the hook block and as a tension control system during lifting operations. The motor-driven system integrates multiple functions into a single device, reducing overall system complexity despite the added capability.
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
Enables the hook block to be lowered independently of cable weight, allowing for a lighter hook block design and increased working load limit without exceeding cable strength limits, ensuring smooth operation without manual control of the cable crawler.
Implementation Method 1
a cable crawler having at least one motor driven traction sheave adapted to transfer a pulling force to the at least one cable through friction
Data Source
AI summary
Self-hoisting crane (1) and method of mounting and operating such crane The self-hoisting crane is adapted to be hoisted from ground to a nacelle (2) or a tower (46) of a wind turbine (3) by operation of a cable winch (9) arranged at ground (10) and is adapted to be operated in its mounted position on the nacelle or on the tower by operation of the same cable winch. The cable extends from a hook block (6), out through a pedestal (4) of the crane, from the nacelle or from the tower and to the cable winch at the ground. The self-hoisting crane is provided with a cable crawler (11) having at least one motor driven traction sheave (122) adapted to, during operation of the self-hoisting crane, transfer a pulling force to the cable (8) through friction. The cable crawler is shiftable between an active state (13) in which the traction sheave may transfer a pulling force to the cable and a passive state in which the traction sheave may transfer no pulling force to the cable.