The invention belongs to the technical field of spraying machinery, and particularly relates to an external soil spraying
machine and a special two-stage energy-saving high-lift underflow pump for the external soil spraying
machine. The underflow pump comprises a transmission shaft, a pump body, a bearing chamber and a
coupling, wherein the pump body comprises a one-stage pump body, a two-stage pump body and a two-stage
feed pump body; a one-stage
impeller is fixedly mounted at the right end of the transmission shaft in a sleeving manner; an
elbow is communicated between the one-stage pump body and the two-stage
feed pump body; a guard plate is arranged between the two-stage
feed pump body and the two-stage pump body; a locating sleeve is mounted on the transmission shaft between the two-stage feed pump body and the two-stage pump body in a sleeving manner; a two-stage
impeller is mounted on the locating sleeve in a sleeving manner, and mounted between a radial
flange at one end of the locating sleeve and the guard plate; a feed channel is formed between the guard plate and the locating sleeve; the one-stage
impeller and the two-stage impeller are mounted back to back; the bending direction of a
helical blade of the one-stage impeller is counterclockwise; the bending direction of a
helical blade of the two-stage impeller is
clockwise; a horizontal feed port is formed in the right end face of the one-stage pump body; and a
discharge port is formed vertically in a tangential direction of the pump body on the front side of the two-stage pump body. The underflow pump is higher in lift, and is suitable for conveying viscous
slurry; the structure of the spraying
machine is simplified; the manufacturing cost and
engineering use cost of the spraying machine are lowered; breakdown maintenance points of the spraying machine are decreased; and the
power loss of equipment is reduced.