The stick hydraulic system is composed of constant power series pump, three position four-way directional valve, three position six way directional valve, stick cylinder, proportional pilot valve, etc. When the three position six way directional valve is in the left position, the oil cylinder extends outward and the stick descends to excavate the earth. At the same time, the three position four-way directional valve is in the right position, and the flow valve supplies oil to the stick cylinder, and the oil in the stick cylinder has a rod cavity is directly supplied to the rodless cavity through the check valve inside the valve, so as to avoid the phenomenon of insufficient oil supply in the rodless cavity of the stick cylinder caused by the overspeed sliding of the stick due to gravity; When the three position six way directional valve and the three position four-way directional valve are in the middle position, the stick cylinder stops and the excavator stick stops at any position; When the three position six way directional valve is located on the right side, the stick cylinder retracts and the stick rises. The auxiliary bucket completes the dumping action.
Bucket hydraulic system analysis the bucket hydraulic system is shown in Figure 2-7. The bucket hydraulic system is composed of constant power series pump, three position six way directional valve, bucket cylinder, proportional pilot valve, etc. The bucket oil cylinder is equipped with an overload oil replenishment valve, which can effectively protect the overload of the bucket oil cylinder. 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. When the change-over valve is in the left position, the oil cylinder retracts and the bucket unloads earth; When the three position six way directional valve is in the middle position, the oil cylinder stops to stop the excavator bucket at any position: when the directional valve is on the right side, the oil cylinder extends and the bucket excavates the earth. When the bucket excavates the earth, the oil return throttling is adopted to avoid the bucket impact phenomenon caused by the rapid start of the bucket oil cylinder and protect the bucket device
