Axial flow pump

Abstract

Disclosed is an axial flow pump including a combined impeller integrally formed of an axial impeller and a centrifugal impeller, the axial impeller being composed of a first cylinder on which a first groove is formed, the centrifugal impeller being composed of a second cylinder on which a second groove is formed. The second groove is smoothly connected with the first groove and a distance between a bottom surface of the second groove and a centerline of the second cylinder gradually increases to prevent turbulent flow of liquid which may occur at the connection point between first and second grooves thereby achieving a high pump performance and a decreased external size of the pump.

1 . A pump for transporting liquid, comprising: 
 a housing having a cylindrical wall defining a liquid passage inside the housing, the housing having opposite sides;    an inlet port, formed at one side of the housing, which is fluidly communicated with the passage;    an outlet port, formed at the other side of the housing, which is fluidly communicated the passage; and    a combined impeller rotatably arranged along a center line of the cylindrical wall to forcibly generate flow of the liquid through the inlet port and discharge the liquid out of the outlet port, the combined impeller including an axial impeller and a centrifugal impeller which are located, in order, along the passage from the inlet port to the outlet port, the axial impeller being composed of a first cylinder having a first outer diameter and a first groove spirally formed on the first cylinder, and the centrifugal impeller being composed of a second cylinder having a second outer diameter larger than the first outer diameter and a second groove spirally formed on the second cylinder,    wherein the second groove is smoothly connected with the first groove through a connection point and the second groove is shaped such that a distance between a bottom surface of the second groove and a rotational center of the centrifugal impeller gradually increases from the connection point in a direction opposite to the rotational direction of the combined impeller.    
   
   
       2 . A pump according to  claim 1 , wherein the second groove has a bottom surface termination edge and includes a forcing surface, formed on the bottom surface termination edge, which projects toward the rotational direction of the combined impeller to push out the liquid along with substantially a tangential direction of the second cylinder.  
   
   
       3 . A pump according to  claim 2 , wherein the projecting area of the forcing surface is 30% or less to the entire area of the bottom surface of the second groove from the connection point to the bottom surface termination edge.  
   
   
       4 . A pump according to  claim 2 , wherein the bottom surface of the second groove is formed such that a width of the bottom surface in a direction along the center line of the cylindrical wall gradually decreases toward the bottom surface termination edge.  
   
   
       5 . A pump according to  claim 1 , wherein the second groove has a bottom surface termination edge and the bottom surface of the second groove is formed such that a width of the bottom surface in a direction along the center line of the cylindrical wall gradually decreases toward the bottom surface termination edge.  
   
   
       6 . A pump according to  claim 5 , further comprising a circular top plate having a diameter equal to or larger than the second diameter and provided on a surface having the bottom surface termination edge.  
   
   
       7 . A pump according to  claim 1 , further including a driving unit for supplying a driving current to drive the combined impeller and a stator having windings, the stator being opposite to the combined impeller through the cylindrical wall in the housing.  
   
   
       8 . A pump according to  claim 7 , wherein the combined impeller includes a plurality of magnets arranged at a distance along the rotational direction inside the combined impeller, and the combined impeller is rotated around the rotational center when the driving unit supplies a driving current to the windings of the stator.