What are the two measures for setting speed limits on truck cranes?
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It is well known that the processes of lifting and lowering, as well as extending and retracting the boom of a truck crane, take considerable time. When the mechanism or the load decreases, gravity causes the speed of lowering to increase. Therefore, it is necessary to use speed limiting to adjust the lowering speed of the crane evenly. First, a balance valve can be connected in series in the return oil circuit. When the machine or the load decreases rapidly, the program valve inside the balance valve can, thanks to the balancing effect of the valve spool, maintain a stable return flow rate for the hydraulic motor, thereby ensuring that the hydraulic motor continues to rotate at a constant speed. This not only serves to limit speed but also allows for locking. Secondly, speed can also be limited using a manual directional valve. When the load or the system speed decreases rapidly, the operator addresses this by reducing the degree to which the handle of the manual directional control valve is pulled, thereby decreasing the valve opening. This method not only limits speed but also achieves the effect of throttling for speed control.
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