Dakin compressors are divided into two types: the reciprocating type and Hermetic type, the reciprocating compressor is mainly composed of house, crankshaft, connecting rod, piston valve plate assembly, shaft seal complete, oil pump, capacity regulator, oil filter, suction and exhaust shut-off valve and set of gasket etc. compression is performed by reciprocating movements of the piston in the cylinder, the valve controls gas in and out of the cylinder.