Pump for pumping contaminated liquid including solid matter

1. A pump for pumping contaminated liquid including large pieces of solid matter, comprising

an open impeller ( 1 ), which is rotatable in a pump chamber of said pump, the impeller ( 1 ) being movable in the axial direction in relation to a seal housing cover ( 3 ) between a first position adjacent to an impeller seat ( 2 ) and a second position spaced apart from said impeller seat ( 2 ),

said pump also comprising a cavity ( 17 ) defined by the seal housing cover ( 3 ) and the impeller ( 1 ), and

at least one radial opening gap ( 20 ) connecting said cavity and said pump chamber,

wherein said opening gap ( 20 ) has a first flow area when the impeller ( 1 ), in the normal operation of the pump is in the first position, and a second flow area bigger than said first flow area when the impeller ( 1 ) is spaced apart from said first position.

2. A pump according to claim 1 , wherein the opening gap ( 20 ) is annular and defined by the seal housing cover ( 3 ) and the circumference of the impeller ( 1 ).

3. A pump according to claim 1 , wherein the cavity ( 17 ) is defined by a cup shaped recess of the seal housing cover ( 3 ) and a generally flat surface of a connection part ( 6 ) of the impeller ( 1 ), which connection part ( 6 ) is movable into said recess.

4. A pump for pumping contaminated liquid including solid matter, comprising

an open impeller ( 1 ), which is rotatable in a pump chamber of said pump, the impeller ( 1 ) being movable in the axial direction in relation to a seal housing cover ( 3 ) between a first position adjacent to an impeller seat ( 2 ) and a second position spaced apart from said impeller seat ( 2 ),

said pump also comprising a cavity ( 17 ) defined by the seal housing cover ( 3 ) and the impeller ( 1 ), and

at least one radial opening gap ( 20 ) connecting said cavity and said pump chamber,

wherein said opening gap ( 20 ) has a first flow area when the impeller ( 1 ), in the normal operation of the pump is in the first position, and a second flow area bigger than said first flow area when the impeller ( 1 ) is spaced apart from said first position;

wherein the cavity ( 17 ) is defined by a cup shaped recess of the seal housing cover ( 3 ) and a generally flat surface of a connection part ( 6 ) of the impeller ( 1 ), which connection part ( 6 ) is movable into said recess; and

wherein the connection part ( 6 ) of the impeller ( 1 ) presents a first outer diameter, an outer flange ( 22 ) protruding radially outwards at said surface of the connection part ( 6 ) presenting a second outer diameter bigger than said first outer diameter, and wherein the cup shaped recess of the seal housing cover ( 3 ) has a first inner diameter, an inner flange ( 23 ) protruding radially inwards at the orifice of said recess presenting a second inner diameter smaller than said first inner diameter as well as bigger than said second outer diameter of the connection part ( 6 ).

5. A pump according to claim 4 , wherein the outer flange ( 22 ) of the connection part ( 6 ) and the inner flange ( 23 ) of the seal housing cover ( 3 ) are in flush with each other when the impeller ( 1 ) is in the first position.

6. A pump according to claim 1 , wherein the impeller ( 1 ) is movable at least 15 mm from the impeller seat ( 2 ).

7. A pump according to claim 1 , wherein the impeller ( 1 ) is movable at least 40 mm from the impeller seat ( 2 ).

8. A pump according to claim 1 , wherein the impeller ( 1 ) is suspended in a drive shaft ( 4 ) of the pump and movable in the axial direction in relation to said drive shaft ( 4 ).

9. A pump according to claim 8 , wherein the pump comprises at least one discrete element ( 12 ) arranged at an interface between the impeller ( 1 ) and the drive shaft ( 4 ), which discrete element ( 12 ) allows axial mutual movement as well as transmits rotary motion.

10. A pump according to claim 9 , wherein the impeller ( 1 ) and the drive shaft ( 4 ) presents recesses in opposite surfaces at said interface, which recesses jointly accommodate said element ( 12 ).

11. A pump according to claim 9 , wherein the interface accommodate at least two discrete elements ( 12 ), which are equidistant separated from each other along the circumference of the drive shaft ( 4 ).

12. A pump according to claim 9 , wherein each element ( 12 ) is constituted by a bar extending in the longitudinal direction of the drive shaft ( 4 ).

13. A pump for pumping contaminated liquid including large pieces of solid matter, comprising

an impeller ( 1 ) rotatable in a pump chamber, and a fixed impeller seat ( 2 ) against which said impeller seats when said impeller ( 1 ) is at rest;

a shaft and a seal for said impeller ( 1 ), and a seal housing cover ( 3 ), the impeller ( 1 ) being movable in the axial direction in relation to the seal housing cover ( 3 ) between a first position when the impeller ( 1 ) is seated against the impeller seat ( 2 ) and a second position spaced apart from said impeller seat ( 2 ),

the impeller ( 1 ) having a connection part ( 6 ) which is axially movable with the impeller ( 1 ), a cavity ( 17 ) defined by the seal housing cover ( 3 ) within which the connection part ( 6 ) moves when the impeller ( 1 ) is in the second position, and

a radial opening gap ( 20 ) between the connection part ( 6 ) and the cavity ( 17 ), the opening gap ( 20 ) connecting said cavity ( 17 ) and the pump chamber, wherein the opening gap ( 20 ) has a first flow area when the impeller ( 1 ) is in the first position, and a second flow area bigger than the first flow area when the impeller ( 2 ) is spaced apart from the first position.