The operating device of the bulldozer is mainly composed of a dozer, a boom and a control mechanism. Its main function is to move materials and level the ground. The bulldozer blade control system can be divided into power winch control and hydraulic control according to different types. Most bulldozers are now hydraulically operated. The hydraulic control mechanism is composed of oil tank, hydraulic pump, pressure regulating valve, distribution valve, hydraulic cylinder, oil pipeline lever system, etc. The operation of the hydraulic bulldozer is to raise and lower the dozer by the pressure generated by the pumping oil of the hydraulic oil pump. The joystick has four operating positions: up, fixed, down and free. So what are their characteristics?

　　1: Ascending position. The distribution valve connects the ascending oil circuit to the hydraulic pump, and the top of the oil cylinder to the oil tank. At this time, the pressure oil output by the oil pump fills the lower part of the oil cylinder through the ascending oil circuit, forcing the piston to drive the piston rod upward, and the oil in the upper part of the oil cylinder Drain back to the oil tank through the oil return pipe to raise the dozer.

　　2; fixed position. The distribution valve closes the oil circuit at the upper and lower parts of the oil cylinder and connects the oil return circuit. The oil from the oil pump flows into the oil tank through the oil return circuit. The oil pressure in the upper and lower parts of the cylinder is balanced, and the piston rod cannot move. The dozer is now fixed.

　　3: Descending position. The distribution valve connects the oil pump and the oil passage of the upper part of the oil cylinder and the oil passage of the lower part of the oil cylinder and the oil tank at the same time. The pressure generated in the upper part of the oil cylinder forces the piston to move the piston rod down, and the oil in the lower part of the oil cylinder is drained back to the oil tank through the oil return pipe. At this time, the dozer is forced to descend under the action of oil pressure.

　　4: Free position. The distribution valve connects the oil circuit of the oil pump and the oil tank, as well as the oil circuit of the upper and lower parts of the oil cylinder at the same time, and can move at will due to the action of external force. This position can be used as a bulldozer to use backwards to level the ground.