Hollow fan blade rib geometry

Abstract

A fan blade has a main body extending between a leading edge and a trailing edge. Channels are formed into the main body from at least one open side. A plurality of ribs extend across the main body intermediate the channels. The fan blade has a dovetail and an airfoil extending radially outwardly from the dovetail. The ribs have a thickness defined as measured generally from the leading edge toward the trailing edge. A thickness of at least one of the ribs is generally thicker adjacent radially inner ends and becomes thinner moving in a radially outward direction.

What is claimed is: 
     
         1 . A fan blade comprising:
 a main body extending between a leading edge and a trailing edge, and having channels formed into said main body from at least one open side with a plurality of ribs extending across the main body intermediate the channels, the fan blade having a dovetail, and an airfoil extending radially outwardly from said dovetail; and   said ribs having a thickness defined as measured generally from said leading edge toward said trailing edge, with a thickness of at least one said ribs being formed to be generally thicker adjacent a radially inner end, and becoming thinner moving in a radially outward direction.   
     
     
         2 . The fan blade as set forth in  claim 1 , wherein a ratio of a thickness of said at least one rib selected near the radially inner end compared to a thickness selected near a radially outer end is between 1.1 and 8. 
     
     
         3 . The fan blade as set forth in  claim 1 , wherein a cross-section through at least one said rib from the open side, and toward the closed side is trapezoidal. 
     
     
         4 . The fan blade as set forth in  claim 3 , wherein an end of said trapezoidal rib spaced toward said open side is smaller than an end at said closed side. 
     
     
         5 . The fan blade as set forth in  claim 1 , wherein a cross-section taken through at least one rib moving from the open side and, toward said closed side is rectangular. 
     
     
         6 . A fan blade as set forth in  claim 1 , wherein a cross-section through at least one rib from the open side edge toward the closed side has generally curved sides, and is smaller at said open side than it is at said inner side. 
     
     
         7 . The fan blade as set forth in  claim 1 , wherein an outer skin closes off the channels at the at least one open side. 
     
     
         8 . The fan blade as set forth in  claim 7 , wherein said outer skin and said main body are both formed of aluminum or aluminum alloy. 
     
     
         9 . The fan blade as set forth in  claim 7 , wherein said outer skin and said main body are both formed of titanium or a titanium alloy. 
     
     
         10 . The fan blade as set forth in  claim 7 , wherein said channels extend from said open side to a closed side within said main body.