Category 1: According to the over-current part of the first, plunger, piston; Second, the mechanical diaphragm type; Third, the hydraulic diaphragm type II: Drive a motor drive; Second, electromagnetic drive Third, the pneumatic classification of three: First, the reciprocating; Second, the rotary type; Third, the gear type; Fourth, the hydraulic diaphragm type Other classification: electric control type; controlled type; insulation type; heating type;