Centrifugal fan and impeller thereof

Abstract

A centrifugal fan includes a fan frame ( 20 ) and a fan impeller ( 10 ) received in the fan frame. The fan impeller includes a hub ( 12 ) and a plurality of fan blades ( 14 ) extending radially from an outer periphery of the hub. Each of the fan blades has a leeward lateral surface ( 144 a ) and an opposite windward lateral surface ( 144 b ) as the fan impeller rotates. At least one of the fan blades has a rib ( 146 ) protruding longitudinally and outwardly from the leeward lateral surface of the fan blade. The rib is located adjacent to an outmost free end of the fan blade and adapted for blocking an airflow generated by the fan impeller to flow back towards the fan blades of the fan impeller.

1 . A fan impeller comprising:
 a hub; and   a plurality of fan blades extending radially and outwardly from an outer periphery of the hub, each of the fan blades having a leeward lateral surface and an opposite windward lateral surface, at least one of the fan blades having a rib protruding longitudinally and outwardly from the leeward lateral surface of the fan blade, the rib being located adjacent to an outmost free end of the fan blade and adapted for blocking an airflow generated by the fan impeller to flow back towards the fan blades of the fan impeller.   
   
   
       2 . The fan impeller as described in  claim 1 , further comprising a blade ring having an annular connecting wall covered on top surfaces of the fan blades and a vertical sidewall connected with the connecting wall. 
   
   
       3 . The fan impeller as described in  claim 2 , wherein the sidewall extends upwardly from an inner periphery of the connecting wall. 
   
   
       4 . The fan impeller as described in  claim 2 , wherein the sidewall extends downwardly from an outer periphery of the connecting wall and the blade ring further includes a flange extending radially and outwardly from a bottom of the sidewall. 
   
   
       5 . The fan impeller as described in  claim 4 , wherein the outer periphery of the connecting wall is substantially aligned with an outmost longitudinal edge of each of the fan blades and the sidewall surrounds a top edge portion of the outmost longitudinal edge of each of the fan blades. 
   
   
       6 . The fan impeller as described in  claim 1 , wherein the rib is formed at each of the fan blades, an angle formed between the rib and the outmost free end of the fan blade being varied in a range of about 65 degrees to about 90 degrees. 
   
   
       7 . The fan impeller as described in  claim 1 , wherein each of the fan blades comprises a first blade portion connected with the hub and a second blade portion bent slantwise and smoothly from a distal end of the first blade portion, the rib located at the second blade portion of the fan blade. 
   
   
       8 . A centrifugal fan comprising:
 a fan frame comprising a bottom base, an opposite top cover and a side wall interconnecting the base with the cover; and   a fan impeller rotatably received in the fan frame, the fan impeller comprising a hub and a plurality of fan blades extending radially and outwardly from an outer periphery of the hub, each of the fan blades having a leeward lateral surface and an opposite windward lateral surface, at least one of the fan blades having a rib protruding longitudinally and outwardly from the leeward lateral surface of the fan blade, the rib being located adjacent to an outmost free end of the fan blade and adapted for blocking airflow rebounded by the side wall of the fan frame to flow back towards the fan blades of the fan impeller.   
   
   
       9 . The centrifugal fan as described in  claim 8 , wherein the fan impeller further comprises a blade ring having an annular connecting wall covered on top surfaces of the fan blades and a vertical sidewall connected with the connecting wall. 
   
   
       10 . The centrifugal fan as described in  claim 9 , wherein the connecting wall of the blade ring is located just under the top cover of the fan frame, and the sidewall extends upwardly from an inner periphery of the connecting wall to be flush with a top surface of the top cover. 
   
   
       11 . The centrifugal fan as described in  claim 9 , wherein the sidewall of the blade ring extends downwardly from an outer periphery of the connecting wall and the blade ring further includes a flange extending radially and outwardly from a bottom of the sidewall. 
   
   
       12 . The centrifugal fan as described in  claim 11 , wherein the outer periphery of the connecting wall is substantially aligned with an outmost longitudinal edge of each of the fan blades and the sidewall of the blade ring surrounds a top edge portion of the outmost longitudinal edge of each of the fan blades. 
   
   
       13 . The centrifugal fan as described in  claim 11 , wherein the connecting wall of the blade ring is coplanar with the top cover of the fan frame, and the flange of the blade ring extends into the fan frame and is located just under the top cover of the fan frame. 
   
   
       14 . The centrifugal fan as described in  claim 8 , wherein the rib is formed at each of the fan blades, an angle formed between the rib and the outmost free end of the fan blade being varied in a range of about 65 degrees to about 90 degrees. 
   
   
       15 . The centrifugal fan as described in  claim 8 , wherein each of the fan blades comprises a first blade portion connected with the hub and a second blade portion bent slantwise and smoothly from a distal end of the first blade portion, the rib located at the second blade portion of the fan blade.