How does a rotary vane vacuum pump work?

How does a rotary vane vacuum pump work?
Pressure increase by volume reduction is the principle behind rotary vane operation. This design offers excellent service for pressure, vacuum or a combination of both. In a cylindrical casing a rotor is positioned eccentrically so that it is on the top almost touching the cylinder. Rotor blades or vanes as they are called, are positioned inside rotor slots.Ex When the rotor starts turning, due to centrifugal force the blades are thrown out and slide against the internal surface of the cylinder.
In this way a cell is formed between two blades with a volume that changes constantly during rotation. Air enters from the inlet port into a cell until the rear blade reaches the far end of the
inlet port. At this point the cell has achieved its maximum air volume.
As the cell then moves away from the port its volume becomes smaller and smaller, the air is thus compressed and the pressure rises. Some models are fitted with outlet valves next to the outlet port which stop the backflow of discharged air when the maximum pressure has been reached.