Department of highland, the product imported from the U.S. Sauer-series hydraulic gear manufacturing, 20-series variable displacement piston pump with the swashplate institutions, to change the flow for closed loop hydrostatic transmission system. The pump is a variable displacement pump with a charge pump, motor quantitative motors with integrated valve block. Variable control mode to manual control, the output of oil flow, direction and power. Hydraulic pump output flow rate and spindle speed and the displacement is proportional to the displacement of the variable depends on the inclination of the swash plate, and in the zero to the maximum between the regulation and control .Pump output flow is changed by changing the swash plate corner of the positive and negative (then both sides), but must go through the swashplate in transition. This series of pumps, hydraulic gear motor components wide speed range, reliable, simple operation, transportation tankers supporting the production, has been widely used in concrete.