The four limit plates positioned on top of the rocker arm in the concrete pumps manufactured by Zoomlion Heavy Industry and Sany Heavy Industry serve specific functions in controlling the range of motion and ensuring the proper operation of the rocker arm.

Upper Limit Plate: The upper limit plate acts as a stopper to define the maximum upward movement of the rocker arm. It prevents the rocker arm from extending beyond the desired limit, ensuring that it does not collide with other components or structures. The upper limit plate helps maintain the safe operation and structural integrity of the concrete pump.

Lower Limit Plate: The lower limit plate serves as a stopper to determine the minimum downward movement of the rocker arm. It restricts the rocker arm from retracting excessively, preventing interference with other components and ensuring proper alignment and synchronization during the pumping process.

Left Limit Plate: The left limit plate functions as a boundary to constrain the lateral movement of the rocker arm towards the left side. It prevents the rocker arm from shifting too far to the left, maintaining its proper positioning and avoiding interference with adjacent components or structures.

Right Limit Plate: The right limit plate serves a similar purpose as the left limit plate but for the right side. It restricts the lateral movement of the rocker arm towards the right, ensuring it remains within the intended range and avoiding any potential collision or misalignment with neighboring parts.

By incorporating these four limit plates, the concrete pump manufacturers establish precise boundaries for the rocker arm's movement in multiple directions. This helps to maintain the stability, safety, and proper functioning of the rocker arm and the overall concrete pumping system. The limit plates prevent unintended movements, protect against component damage, and contribute to the accurate and efficient operation of the equipment.