Unchokable centrifugal pump

A centrifugal pump comprising:

• a pump housing surrounding an axis and formed with a pump chamber having a side wall defining an inlet opening centered on said axis;
• an end plate ..received in a side wall of said housing;
• a driving shaft axially aligned with said inlet opening;
• a single-blade rotor having an inner end Juxtaposed with said end plate and a central suction mouth remote from the driving shaft in alignment with the inlet opening of the pump chamber;
• and
• an annular collar surrounding said inlet opening and so projecting into the inside of the rotor that an inner end of a rotor blade of said rotor forms a narrow gap with an outer surface of the collar, said outer surface being provided with a coaxial toothed rim having teeth directed substantially radially and disposed adjacent said end plate and spaced from said inner end of the rotor at a small distance, a width of the toothed rim (b) being substantially equal to a width (B) of the end face of the inner end of the rotor blade.