Patent ID: 8231337

Claim:
A pump for pumping contaminated liquid including large pieces of solid matter, comprising a pump housing provided with a rotatable impeller ( 1 ) suspended in a drive shaft ( 3 ) and having at least one vane ( 5 ), and an impeller seat ( 2 ) having a top surface ( 9 ), the rotatable impeller ( 1 ) and the impeller seat ( 2 ) being axially separated from each other a distance of at least 0.1 mm when the impeller ( 1 ) is seated adjacent the impeller seat ( 2 ), at least one part of the impeller ( 1 ) and the impeller seat ( 2 ), during operation of the pump, being movable in the axial direction in relation to each other, wherein the impeller seat ( 2 ) presents at least one groove ( 10 ) in the top surface ( 9 ) thereof, and wherein the groove ( 10 ) extends from a centrally located open channel ( 8 ) in the impeller seat ( 2 ) towards the periphery thereof.