Shallow draft propeller nozzle

Abstract

A nozzle for a ship propeller having an axis of rotation comprises an annular shroud having a diameter and is adapted to surround the propeller. The shroud extends along the axis of the ship propeller and has inner and outer surfaces forming a foil. The outer surface of the shroud has a truncating surface extending along at least one of a top or bottom thereof.

What is claimed is: 
     
         1 . A nozzle for a ship propeller having an axis of rotation, the nozzle comprising an annular shroud having a diameter and being adapted to surround said propeller, said shroud extending along said axis of the ship propeller and having inner and outer surfaces forming a foil, wherein said outer surface of said shroud has a truncating surface extending along at least one of a top or bottom thereof. 
     
     
         2 . The nozzle of  claim 1  wherein said truncating surface is located on a bottom of said shroud. 
     
     
         3 . The nozzle of  claim 1  wherein said truncating surface is located a top of said shroud. 
     
     
         4 . The nozzle of  claim 1  wherein said truncating surface is substantially planar. 
     
     
         5 . The nozzle of  claim 1  wherein said truncating surface is substantially horizontal. 
     
     
         6 . The nozzle of  claim 1  wherein said truncating surface is convex having a radius of curvature of at least 10 times said diameter of said shroud. 
     
     
         7 . The nozzle of  claim 1  wherein said truncating surface is concave having a radius of curvature of at least 10 times said diameter of said shroud. 
     
     
         8 . The nozzle of  claim 1  wherein said truncating surface has a rounded edge with said outer surface of said shroud. 
     
     
         9 . An apparatus for propelling a ship comprising a screw propeller having an axis of rotation and the nozzle of  claim 1  surrounding said screw propeller. 
     
     
         10 . The apparatus of  claim 9  wherein said screw propeller is rotated by a shaft. 
     
     
         11 . The apparatus of  claim 10  wherein said shaft extends from a hull of said ship. 
     
     
         12 . The apparatus of  claim 10  wherein said shaft extends from a pod suspended below said ship. 
     
     
         13 . The apparatus of  claim 12  wherein said pod is rotatable about an axis. 
     
     
         14 . The apparatus of  claim 12  wherein said shroud is supported by said pod. 
     
     
         15 . The apparatus of  claim 9  wherein said shroud is supported by said hull.