Centrifugal Pump

Abstract

A centrifugal pump includes a housing and an impeller housed in the housing. The impeller has a main plate, a plurality of first blades, and a plurality of second blades. The first blades and the second blades extend radially along the main plate and have the same radial length. Each of the second blades has a low blade part and a high blade part extending radially from a radially outer end of the low blade part. When comparing the first blades and the second blades with each other at an equal distance from a rotational axis of the impeller, a height of the low blade part measured from the main plate is less than a height of each first blade measured from the main plate, and a height of the high blade part measured from the main plate is the same as that the height of each first blade.

What is claimed is: 
     
         1 . A centrifugal pump, comprising:
 a housing defining a discharge passage and a suction passage therein; and   an impeller configured to rotate about a rotational axis in a rotational direction, wherein the impeller is disposed in the housing and is coaxially aligned with the suction passage, wherein:   the impeller comprises:
 a main plate having a circular shape and a top surface facing the suction passage; 
 a plurality of first blades extending radially along the top surface of the main plate, and 
 a plurality of second blades extending radially along the top surface of the main plate, 
   a radial length of each of the first blades is equal to a radial length of each of the second blades,   each of the second blades has a low blade part and a high blade part extending radially outward from a radially outer end of the low blade part,   a height of the low blade part measured from the main plate is less than a height of each of the first blades measured from the main plate when comparing the first blades and the second blades with each other at an equal distance from the rotational axis, and   a height of the high blade part measured from the main plate is the same as the height of each of the first blades measured from the main plate when comparing the first blades and the second blades with each other at an equal distance from the rotational axis.   
     
     
         2 . The centrifugal pump of  claim 1 , wherein the height of the low blade part measured from the main plate continuously increases moving radially outward along the low blade part. 
     
     
         3 . The centrifugal pump of  claim 1 , wherein the height of each second blade measured from the main plate increases at a boundary between the low blade part and the high blade part thereof in a stepped manner. 
     
     
         4 . The centrifugal pump of  claim 1 , wherein:
 the main plate has a projection part protruding in an axial direction along the rotational axis and a flat part extending radially outward from a radially outer periphery of the projection part,   the flat part is oriented perpendicular to the rotational axis,   an axial length of the projection part increases moving radially inward along the projection part, and   the low blade part is formed on the projection part and does not extend along the flat part.   
     
     
         5 . The centrifugal pump of  claim 4 , wherein:
 each of the first blades includes a thin blade part and a thick blade part,   the thick blade part extends radially outward from a radially outer end of the thin blade part,   a thickness of the thin blade part relative to the rotational direction is less than a thickness of each of the second blades relative to the rotational direction when comparing the first blades and the second blades with each other at an equal distance from the rotational axis, and   a thickness of the thick blade part relative to the rotational direction is the same as of the thickness of each of the second blades when comparing the first blades and the second blades with each other at an equal distance from the rotational axis.   
     
     
         6 . The centrifugal pump of  claim 5 , wherein the thin blade part is formed on the projection part and does not extend along the flat part. 
     
     
         7 . The centrifugal pump of  claim 4 , wherein:
 each of the second blades includes a thin blade part and a thick blade part,   the thick blade part extends radially outward from a radially outer end of the thin blade part,   a thickness of the thin blade part relative to the rotational direction is less than a thickness of each of the first blades relative to the rotational direction when comparing the first blades and the second blades with each other at an equal distance from the rotational axis, and   a thickness of the thick blade part relative to the rotational direction is the same as the thickness of each of the first blades when comparing the first blades and the second blades with each other at an equal distance from the rotational axis.   
     
     
         8 . The centrifugal pump of  claim 7 , wherein the thin blade part is formed on the projection part and does not extend along the flat part. 
     
     
         9 . The centrifugal pump of  claim 1 , wherein the plurality of first blades and the plurality of second blades are arranged in a regular manner relative to the rotational direction. 
     
     
         10 . The centrifugal pump of  claim 9 , wherein the plurality of first blades and the plurality of second blades are alternately arranged in the rotational direction.