Hydraulic Crane Link System for Extended Moment Arm
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Solution Overview
Problem
Z-type hydraulic cranes lack sufficient lifting capacity and stability at normal working positions due to the short moment arm of the force exerted by hydraulic cylinders at the crane boom joint, restricting their operational efficiency and angular range.
Innovation Solution
A link system comprising parallel pairs of link elements and a cross bar element is integrated to mechanically guide the force application, extending the moment arm and stabilizing the crane boom joint, allowing for increased lifting capacity and maintaining the angular range during both working and parking positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a direct connection between hydraulic cylinder and crane boom is used, then the structure is simple, but the lifting capacity at normal working positions is insufficient due to short moment arm
Solution Approach 1:
A link system comprising link elements and a cross bar element is introduced as an intermediary between the second hydraulic cylinder and the second crane boom. This link system extends the moment arm of the hydraulic cylinder force at normal working positions, thereby increasing lifting capacity without requiring direct connection of the cylinder to the boom
2Strength
If the moment arm of hydraulic cylinder is extended to increase lifting capacity, then lifting capacity improves, but the angular range of motion is restricted
Solution Approach 1:
The link system is designed with pivotable link elements that can dynamically adjust their configuration. During normal working positions, the link elements extend the moment arm for maximum lifting capacity. During folding operations to parking positions, the link elements can retract or reconfigure to accommodate the required angular range of motion, thus resolving the contradiction between extended moment arm and angular range
3Strength
If link system is added to extend moment arm, then lifting capacity increases, but device complexity increases
Solution Approach 1:
The link system is segmented into multiple independent link elements (first and second link elements) and a cross bar element, each pivotably connected to others. This segmentation allows each element to be relatively simple in structure while collectively achieving the moment arm extension function. The modular segmented design reduces overall system complexity compared to a single complex linkage
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 link system enhances the lifting capacity of the crane boom joint at normal working positions and facilitates easier movement to parking positions by adjusting the force application point and maintaining the cross bar element's position, thereby improving operational efficiency and stability.
Implementation Method 1
a second hydraulic cylinder arranged on a first side of the first crane boom for lifting and lowering the second crane boom in relation to the first crane boom
Implementation Method 2
the link elements of the link system are configured to mechanically guide the cross bar element in an arcuate path about said crane boom joint
Data Source
Figure 1~2
Figure 3~4
Figure 5~7
AI summary
A hydraulic crane comprising: - a hydraulic cylinder (10) for pivoting an outer boom (8) in relation to an inner boom (6); and - a link system comprising a first pair of link elements (13a, 14a) and a second pair of link elements arranged in parallel with each other on opposite sides of said booms at the joint (9) between them, wherein said hydraulic cylinder at its outer end is articulately connected to the first pair of link elements. The first and second pairs of link elements are connected to each other by a cross bar element (15), wherein the link elements are configured to mechanically guide the cross bar element in an arcuate path about said joint so as to make it assume a position below the joint when the crane is in a working position and a position above the joint when the crane is in a Z-shaped parking position.