CONTROL LOOP AND UNLOADING MULTIPATH REVERSING VALVE FOR MULTI SUPPORT LEGS OF CRANE

摘要

A control loop for multi support legs of a crane is disclosed. The crane includes a first to fourth legs at the side portion and a fifth leg at the front portion. The control loop includes a three-position six-way valve (4) and a first to fifth reversing valves (9). Wherein, the three-position six-way valve comprises a first inlet port and a second inlet port both connected to a pressured oil source, an oil returning port connected to an oil tank, a first working oil port connected to the loading control system, a second working oil port connected to the support leg rod cavities of each of the first to fifth support legs and a third working oil port connected to the support leg non-rod cavities of each of the first to fifth legs by the first to fifth reversing valves. The control loop further includes a normal closed two-position two-way hydraulic control valve (7) so that the non-rod cavity of the fifth support leg is communicated with the oil tank when the other support legs are retracted, thus realizing that the step-down multipath valve reliably controls the retraction of the fifth leg and ensuring the fifth leg is retracted firstly. An unloading multipath reversing valve is also disclosed.