Working principle of deck crane

Deck cranes, as gravity-driven lifting equipment, are widely used in ports, docks, construction sites, and other locations. Their working principle involves the coordinated operation of several key components.

Deck cranes achieve kinetic energy conversion through a gear system and pulley system. When a heavy object is placed on the hook, gravity causes the hook to descend, driving the gear system to rotate and converting gravity into mechanical energy.

Lifting and Lowering Mechanism: The lifting and lowering functions of a deck crane primarily rely on the precise control of a hydraulic system. A hydraulic pump generates high-pressure oil, driving the lifting motor to rotate, which in turn drives the drum. The wire rope on the drum is then wound up and down, achieving the vertical movement of the hook assembly. During lifting, the flow rate of the hydraulic system is regulated through a proportional valve to control the motor speed, thus achieving high-speed operation under no-load conditions and low-speed stable operation under heavy load conditions. Simultaneously, the hydraulic system's pressure feedback mechanism monitors the load weight in real time through pressure sensors. Once the rated load is exceeded, the hydraulic system automatically unloads through an overflow valve to ensure operational safety.

Luffing Mechanism Operation: The luffing mechanism is responsible for adjusting the pitch angle of the boom to accommodate cargo lifting needs at different heights. This function is achieved through the extension and retraction of the piston rod of the luffing cylinder. The piston rod pushes the boom to rotate around its fulcrum, thereby changing the angle between the boom and the horizontal plane. During luffing, the thrust of the cylinder is balanced by the cargo's gravitational moment and the boom's own weight. Some booms are also equipped with counterweights to enhance stability. This design ensures the smoothness of the boom during pitching movements.

Slewing Mechanism Design: The slewing mechanism enables the crane to rotate on a horizontal plane to lift goods to a designated location. The slewing motor drives the slewing bearing (large gear ring) at the base of the column via gear meshing, rotating the entire superstructure. During slewing start-up and shutdown, the hydraulic system uses buffer valves to reduce shock and ensure smooth operation. Some deck cranes are also equipped with a slewing brake to lock the slewing mechanism when the goods are aligned, improving positioning accuracy.

Combined Motion and Coordinated Control: One of the significant features of the deck crane is its ability to simultaneously perform any combination of lifting, luffing, and slewing actions. This combined motion is achieved through multi-valve linkage control of the hydraulic system, ensuring coordination and consistency between the various actions. For example, when lifting goods, the deck crane can first adjust the boom above the goods using the luffing mechanism, then grab the goods using the lifting mechanism, and finally lift the goods to the target location using the slewing mechanism.