What is a Four-Link Portal Crane?
A Four-Link Portal Crane is a high-performance, mobile, full-revolving crane designed for heavy-duty material handling in demanding environments such as ports, dockyards, metallurgy, and construction. Its defining feature is the use of a four-bar linkage mechanism in its boom system, which provides exceptional stability and precision during operation.
This crane is engineered to meet rigorous international standards, including GB, ISO, FEM, and JIS, ensuring it is strong, safe, and reliable. It is a versatile piece of equipment capable of handling various cargo types—from general goods and bulk materials to containers—with high efficiency. Its ability to perform hoisting, luffing, 360° rotation, and travel on rails makes it a cornerstone of modern industrial logistics.
Product Structure and Working Principle
The core of the crane's functionality lies in its innovative structural design and coordinated mechanisms.
The Four-Link Mechanism: This is the heart of the crane. It consists of a main boom, a large tie-rod, and a boom tip, forming a rigid linkage system. In advanced "Dual Four-Link" models, a smaller secondary four-link system is added to the boom head. This secondary system includes a front and rear compensator with sheaves, which keeps the hoist ropes in a rectangular formation above the load. This design ensures the load moves in a nearly horizontal path during luffing (boom raising/lowering), minimizing height variation and swing.
Main Components:
Portal Frame: The lower supporting structure that allows the crane to travel on rails. It has a cylindrical upper section and a sealed box lower section, providing immense strength. It can be mounted on cylinders or four outriggers.
Slewing Platform: A welded box-girder structure that houses the machinery and supports the rotating upper works. It is connected to the portal frame via a large double-row roller slewing bearing.
Hoisting Mechanism: Typically uses two double-drum units. The drums can work in unison for hook operations or independently for grab opening and closing.
Luffing Mechanism: Employs a rack and pinion drive for smooth and controlled movement of the boom.
Travel System: Comprises four bogies connected via hinges and balance beams to distribute weight evenly. It features triple-unit drives and electric wheel clamps for braking.
Power and Control:
Power Supply: The crane is powered by a 10kV/50Hz electrical supply from a ground junction box, fed through a cable reel and slip ring assembly.
Control System: A full PLC-based control system with real-time monitoring is used. All major motions—hoisting, luffing, slewing, and travel—are driven by AC variable frequency motors, allowing for smooth acceleration, deceleration, and precise speed control.
Product Advantages and Key Features
The Four-Link Portal Crane offers a multitude of advantages over conventional crane designs:
Superior Stability and Precision: The four-link mechanism is the key to its performance. It dramatically reduces load sway and tilt during operation, enabling highly accurate load placement, which is critical for container handling and delicate cargo.
High Efficiency and Performance:
Long Reach: A long boom covers large work areas, ideal for servicing big ships.
Two-Speed Hoisting: Provides steady speed with heavy loads and high speed with light loads, optimizing cycle times.
Smooth Operation: Variable frequency control ensures jerk-free starts and stops, protecting both the cargo and the crane.
Enhanced Safety and Reliability:
Complies with strict safety standards (GB6067-85, GB3811-2008).
Equipped with multiple safety devices: overload limiter, moment limiter, anemometer, limit switches, and anti-derailment systems.
Advanced braking systems and rail clamps provide two-level protection.
Durability and Easy Maintenance:
Constructed from high-strength steel to withstand heavy-duty cycles.
Modular components simplify part replacement and repairs.
Corrosion-resistant materials ensure a long service life in harsh marine environments.
Operator Comfort and Control:
A spacious, air-conditioned cabin offers excellent visibility and a low-noise environment, reducing operator fatigue.
Ergonomic controls and an adjustable seat improve handling precision and comfort.
Energy Efficiency: The efficient design and electric drives result in low power consumption, reducing operational costs.
The "Green" Evolution (Dual Four-Link Model): This advanced version solves traditional problems by:
Enabling the use of stable electric container spreaders, eliminating container tilt.
Allowing a switch to tipping grabs for dust-free, enclosed bulk handling, achieving zero pollution.
Integrating with automatic truck loading systems for a fully automated, eco-friendly solution.
What are the Application Scenarios?
The Four-Link Portal Crane is a versatile solution for a wide range of industries:
Ports & Terminals: Its primary application is for loading and unloading ships, handling containers, bulk cargo (like coal, ore, and grain), and general cargo with high efficiency.
Dockyards & Shipbuilding: Used for moving heavy machinery, steel plates, and large ship components during the construction and repair of vessels.
Metallurgy & Mining: Essential for transporting raw materials such as iron ore, steel coils, and other ingots within mills and storage yards.
Construction & Infrastructure: Capable of lifting and placing large pre-fabricated structures, beams, and other heavy building materials.
Logistics & Warehousing: Handles large-span gantry operations in major logistics hubs and storage facilities.
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Henan Yuntian, as a contemporary manufacturing leader, has consistently focused on cutting-edge technology and development in the lifting equipment industry. We invite you to get in touch for professional services including customized crane selection, accurate pricing, and technical design drawings tailored to your needs.
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