In this type of drum pump, a multi-spiral metallic eccentric screw (rotor) rotates in a stator made of an elastic or rigid plastic material.

Due to their geometry, two pumping chambers closed on the suction and pressure side are formed, which open and close alternately in a continuous sequence. On account of this displacement principle, the mechanical effect on the pumped medium is extremely low, even sensitive liquids are pumped gently in this way.