Movable Crane Counterweight Layout for Load and No-Load Stability
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Solution Overview
Problem
Existing mobile lift cranes face challenges in balancing load moments without increasing total counterweight, especially when no load is on the hook, requiring ground support for extra counterweights and necessitating additional components and site preparation.
Innovation Solution
A mobile lift crane design with a movable counterweight system that adjusts position to balance boom and load moments, allowing counterweights to be positioned forward or rearward without ground support, using a rotating bed, counterweight support frame, and movement devices to optimize counterweight placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If extra counterweight attachment is added to enhance lift capacity, then lifting capacity is improved, but device complexity and ground support requirements increase
Solution Approach 1:
The counterweight is made movable along the rotating bed rather than fixed or separately supported. The counterweight unit can be positioned at different locations on the rotating bed using a movement device, allowing dynamic adjustment of the counterweight position to balance moments during operation without requiring separate ground support structures.
Solution Approach 2:
The counterweight support function is merged into the rotating bed structure itself. Instead of having a separate counterweight attachment that requires independent ground support, the counterweight is integrated onto the rotating bed which is already supported by the crane's crawlers, eliminating the need for additional ground support components.
2Power
If extra counterweight attachment is added to enhance lift capacity, then lifting capacity is improved, but ease of operation deteriorates due to ground preparation requirements
Solution Approach 1:
The counterweight support function is merged into the rotating bed structure which is already supported by the crane's crawlers. This integration eliminates the need for separate ground support structures and ground preparation activities, allowing the crane to move freely over the ground without requiring timbers or other ground preparation measures.
3Power
If counterweight is positioned rearward to balance load moment, then lifting capacity is improved, but stability deteriorates when no load is on the hook
Solution Approach 1:
The counterweight position is made dynamic rather than fixed. The counterweight unit can be moved along the rotating bed to different positions using a movement device, allowing the operator to adjust the counterweight position optimally for each specific lifting condition. When no load is present, the counterweight can be positioned to maintain stability, and when load is present, it can be repositioned to maximize lifting capacity.
Solution Approach 2:
The position parameter of the counterweight can be changed dynamically based on operational requirements. By varying the distance of the counterweight from the crane's center of rotation, the system can adapt to different loading conditions, changing the moment balance to either prevent backward tipping or maximize lifting capacity as needed.
4Stability of the object's composition
If fixed mast structure is used to support counterweight, then structural stability is improved, but ease of manufacture and site delivery deteriorate
Solution Approach 1:
The fixed mast structure is extracted from the design. Instead of using a fixed mast to support the counterweight, the patent uses the rotating bed structure itself as the support platform. This eliminates the need for separate mast components, reducing the number of parts that need to be manufactured, delivered, and assembled at the job site.
Data Source
AI summary
A lift crane includes a carbody and movable ground engaging members mounted on the carbody. A rotating bed is rotatably connected to the carbody and includes a counterweight support frame including a rack coupled directly to a lower surface of the rotating bed. A boom is pivotally mounted to the rotating bed. A counterweight unit includes a trolley, the counterweight unit being in a movable relationship with respect to the rotating bed. A counterweight unit movement device is configured to move the counterweight unit toward and away from the boom. Other embodiments include a counterweight support beam movably connected to the rotating bed, the counterweight support beam including another rack coupled to a lower surface of the counterweight support beam. A counterweight support beam movement device is connected between the counterweight support beam and the counterweight support frame.