Figure 4462c shows a mechanical pump, consisting of a belt-driven, eccentrically mounted mechanism, an inlet port (valve), and an outlet port (valve). The eccentric motion of the rotator creates a vacuum that sucks air into the inlet port from the EM chamber and forces the air through the outlet port to the atmosphere. The air expands significantly in volume before sealed off by the opposite vane (Figure 4462c (b)) because the rotation axis is offset from the axis of the cylinder.