A folding arm type lifting crane, commonly known as a knuckle boom crane or a loader crane, is a type of hydraulic crane that features a segmented boom designed to fold and unfold like a human finger or knuckle.
This design allows the crane to be compacted into a small space when not in use, making it ideal for mounting on trucks and commercial vehicles.
Structure and Operation
The key feature of the folding arm crane is its articulated structure, which is more complex than a standard telescopic boom:
- Main Boom (Inner Boom): The primary structural section connected to the slewing base.
- Outer Boom (Folding/Knuckle Boom): This section is attached to the main boom via a knuckle joint. This joint allows the outer boom to fold back toward the main section, providing the crane with its characteristic compact storage capability.
- Telescopic Extensions: Both the main and outer booms often have hydraulic extensions to increase reach.
- Hydraulic System: The crane is powered entirely by hydraulic cylinders that control the lifting, slewing (rotation), and the folding/unfolding action of the knuckle joints
Key Advantages
The crane folds into a small package when not in use, typically resting neatly behind the truck cab or flatbed, freeing up cargo space.
The articulated segments allow the operator to reach over or around obstacles (like fences or low roofs) and reach deep into confined spaces (like doorways or below ground level), which a straight boom cannot do.
The ability to articulate the boom allows for extremely precise positioning of the load, making it excellent for delicate placement tasks or material delivery.
They are generally lighter than equivalent telescopic cranes, which is advantageous for road travel, as it leaves more capacity for payload on the truck.
Knuckle boom cranes are widely used in construction, waste management, and utility work for tasks like loading and unloading building materials, placing small structural elements, and servicing underground equipment.
Post time: Oct-27-2025