Patent ID: 8109730

Claim:
A pump for pumping contaminated liquid including solid matter, comprising a pump housing ( 2 ) provided with a rotatable impeller ( 3 ) having at least one vane ( 9 ) and an impeller seat ( 4 ), the impeller seat ( 4 ) presenting at least one recess ( 13 ) in the top surface ( 11 ) thereof, a sheering/cutting action arising between a cutting edge ( 15 ) of said recess ( 13 ) and a lower edge ( 14 ) of the vane ( 9 ) as the impeller ( 3 ) rotates relative to the impeller seat ( 4 ), wherein the pump ( 1 ) also comprises means for guiding the solid matter towards said recess ( 13 ), the guiding means comprising at least one guide pin ( 18 ) and at least one projection ( 20 ), an upper surface ( 19 ) of the guide pin ( 18 ) extending from a position contiguous to the most inner part of the vane ( 9 ) of the impeller ( 3 ) towards the impeller seat ( 4 ), and the projection ( 20 ) protruding from the impeller seat ( 4 ).