Therefore, hydrostatic transmission belongs to "F03 hydraulic machinery or hydraulic engine; Wind, elastic or gravity engines; Engines that generate mechanical power or reverse thrust not included in other categories "or" F04B liquid variable displacement machinery "; Pump (engine fuel injection pump F02M；; Rotating piston or oscillating piston liquid is mechanically or pumped into F04C；; Non-variable displacement pump F04D；; The pump F04F directly contacts or utilizes the inertia of the pumped fluid through other fluids; Crankshaft, crosshead, connecting rod into f16c; ; Flywheel into f16f; ; Universal transmission device for mutual conversion between rotary motion and reciprocating motion into F16h; ; Universal piston, piston rod and working cylinder shall be f16j; ; Ion is pumped into H 01J 4112; Electric pump H02K 44/02) "