The figure shows the integral multi-way valve used in the loader. Besides the main valve body, it also includes two main spools and several auxiliary elements, which control the working circuit of the boom lifting hydraulic cylinder and the bucket hydraulic cylinder.It can be seen from the diagram that the multi-way valve is of series type, i.e. the working circuit of boom lifting cylinder and bucket cylinder form a series circuit. The oil inlet cavity of boom connection and the neutral position return channel of bucket connection are connected. Therefore, the boom and bucket can not perform complex actions and the thrust of each hydraulic cylinder is larger.
When the bucket coupler is in the left position, the high-pressure oil enters the rod chamber of the bucket cylinder through the valve opening, the bucket cylinder retracts, the bucket rotates downwards and discharges quickly. During the process of rapid discharging, the bucket cylinder retracts quickly. In order to prevent the pressure of the rod chamber from decreasing due to the rapid withdrawal of the bucket cylinder, the rod chamber is refueled by the overload filling valve; when the bucket coupler is in the right position, the high-pressure oil enters the bucket cylinder through the valveNo rod cavity, bucket cylinder extended, bucket up.
Similarly, when the boom linkage is in the left position, the high pressure oil enters the rod chamber of the boom cylinder through the valve opening, and the boom cylinder drops rapidly. In order to prevent the pressure of the starting arm cylinder from decreasing due to the rapid drop of the boom cylinder, the rod chamber is refueled by the check valve. When the boom linkage is in the right position, the high pressure oil enters the rod chamber of the bucket cylinder through the one-way valve and multi-way valve opening, and the boom lifts.In order to prevent the boom cylinder from falling due to leakage and gravity, the check valve can lock and hold pressure.According to the operation requirements of loader, the hydraulic transmission system needs to complete the following work cycles: bucket swing up (shovel excavation) boom lifting locking (transporting) bucket swing down (unloading) boom lowering.