Screw alveolar gas enters through the intake port. When the star wheel and screw spline engagement, star tooth surface of the body and the screw alveolar space formed by a closed, forming a compression chamber, completed the process of breathing.
With the rotation of the screw, decreasing the volume of the compression chamber, the gas is compressed, the compression process is completed when the leading edge of the compression chamber communicated with the exhaust port.
Compression chamber front and exhaust vents turn after the start until after completion of the compression chamber through the exhaust port, complete the discharge process. Since the two star wheels arranged symmetrically on both sides of the screw, when the screw rotation, each of its two cogging completed intake – compression – exhaust cycle, therefore, the screw 6 cogging can be done 12 times above cycle.