The eccentric rotor mounted in the pump body has three blades, which divide the Pernock vacuum pump into three compartments, and the volume of each compartment changes periodically with the rotation of the rotor.
When the rotor rotates, the intake portion of the pumping chamber expands in volume, drawing gas in through the intake port, which passes through an air filter element and an open anti-oil return valve into the chamber pump. When the rotor rotates further, the vane separates the pump chamber part from the suction port. The volume of this part of the pump chamber is reduced and the gas is compressed. The gas is discharged from the pump chamber through an exhaust valve at slightly above atmospheric pressure.