These are self-priming positive displacement rotary pumps consisting of a rotating eccentric shaft (screw or rotor) located inside the fixed housing (stator) of the appropriate shape.
These pumps pump the material due to the rotation of the screw and, accordingly, the movement of this material along the axis of rotation of the screw inside the chamber, which is formed by screw grooves, as well as the stator surface. As the screw rotates, the space at the pump inlet increases in volume, creating a vacuum, which in turn leads to the filling of this space with the transported medium.