Marine propellers

Abstract

Some embodiments relate to a propeller having a hub and a plurality of radially extending blades, wherein a radial extreme of each of the blades is integral with an end plate defining a ring segment coaxial with the propeller hub, each ring segment having a concave inner surface and conforming generally to a frustoconical ring, the radial cross section of which is angled at between 0° and 15° to an axis of rotation of the propeller.

1 . A propeller having a hub and a plurality of radially extending blades, wherein a radial extreme of each of the blades is integral with an end plate defining a ring segment coaxial with the propeller hub, each ring segment having a concave inner surface and conforming generally to a frustoconical ring, the radial cross section of which is angled at between 0° and 15° to an axis of rotation of the propeller. 
     
     
         2 . The propeller of  claim 1 , wherein the ring segments form part of a continuous shroud or ring. 
     
     
         3 . The propeller of  claim 1 , wherein the ring segments comprise end plates or wing tips on each blade tip which are not connected with the end plate or wing tip of a next adjacent blade. 
     
     
         4 . The propeller of  claim 3 , wherein the end plate extends outwards from the blade forwardly. 
     
     
         5 . The propeller of  claim 3 , wherein the end plate extends outwards from the blade rearwardly. 
     
     
         6 . The propeller of  claim 3 , wherein the end plate extends outwards from the blade both forwardly and rearwardly. 
     
     
         7 . The propeller of  claim 1 , wherein the leading edge of the ring segments is at a greater radius than the trailing edge, thereby defining a cant angle of the ring segments. 
     
     
         8 . The propeller of  claim 1 , wherein the ring section is asymmetric such that a camber of the ring section is outwardly defined by the concave internal surface. 
     
     
         9 . The propeller of  claim 1 , wherein the angle of the ring segments varies between one blade tip and another. 
     
     
         10 . The propeller of  claim 9 , wherein a section angle adjacent to a leading edge of a blade is between 1° and 15°. 
     
     
         11 . The propeller of  claim 9 , wherein a section angle adjacent to a leading edge of a blade is between 2° and 10° 
     
     
         12 . The propeller of  claim 9 , wherein a section angle adjacent to a leading edge of a blade is between 4° and 6°. 
     
     
         13 . The propeller of  claim 1 , wherein the pitch of each blade increases with increasing radius. 
     
     
         14 . The propeller of  claim 1 , wherein the blades increase in chord length towards the blade tips, such that a larger proportion of blade area is carried at a larger radius. 
     
     
         15 . The propeller of  claim 1 , wherein the ring camber ratio is between 1/40 and 3/40.