Vaneless multistage pump

Claim 1

In a centrifugal, multistage pump having an input state, an outlet stage and a plurality of intermediate stages, the improvement wherein each of said intermediate stages comprises: an impeller; a divider plate serving to separate said stage from the next and formed with an inclined oval opening extending therethrough to provide undisturbed fluid flow between said stages; a center plate interposed between said divider plate and the divider plate of the preceding stage and having a front surface and a rear surface; a first recess formed in said rear surface of said center plate having a central portion shaped to mate with said impeller, a second portion extending radially outward from the exit portion of said impeller, a groove extending about the periphery of said second portion and gradually increasing in depth and width through approximately 360° and having a final curved portion formed to direct fluid flow through the oval opening in the subsequent divider plate; and a second recess formed in said front surface of said center plate having a curved portion formed to receive fluid flow from the oval opening in the preceding divider plate, a helical portion of substantially constant cross-sectional area spiralling inwardly through approximately 360°, and an axially diverting portion which continues to spiral inwardly through approximately another 360° while gradually deflecting the fluid flow axially rearward to deliver said fluid flow to the input of said impeller.