The hydraulic system of Kobelco excavator boom consists of constant power series pump, two three position six way reversing valve, boom oil cylinder, retaining valve, confluence valve, proportional pilot valve and so on. When the three position six way directional valve 6 is in the left position, the boom oil cylinder is extended, the boom is lifted and the earthwork is transferred. At the same time, the three position six way directional valve 7 is in the right position, and the flow valve supplies oil to the boom oil cylinder, so as to speed up the extension speed of the boom oil cylinder, and then speed up the lifting speed of the boom; When the three position six way directional valve 6 and the three position six way directional valve 7 are in the middle position, the boom oil cylinder stops moving, so that the excavator boom stops at any position. Due to the installation of the retaining valve, it has a good anti leakage function, which can ensure that the boom is in a certain position for a long time without sinking; When the three position six way directional valve 6 is in the right position and the three position six way directional valve 7 is in the middle position, the boom oil cylinder retracts, and the oil return throttling method is adopted inside the valve, which can effectively prevent the overspeed sliding phenomenon caused by the boom gravity and assist the bucket to complete the earth excavation action.
The boom cylinder is equipped with an overload oil replenishment valve, which can effectively protect the boom cylinder from overload. At the same time, when a negative pressure is formed in a cavity, it can replenish oil under the pressure of the back pressure valve. Installing a one-way throttle valve at the oil port of the boom cylinder circuit for oil return speed regulation can also effectively prevent the occurrence of overspeed and sliding caused by the boom gravity and cause accidents.
