Blade structure for a radial airflow fan

Abstract

A fan includes a hub rotatable about an axis and having an open end and a closed end, and a plurality of blades extending from the hub. Each of the blades has a leading side surface, a trailing side surface, an inner lateral edge corresponding to the open end of the hub, an outer lateral edge corresponding to the closed end of the hub, and a radial outer edge having opposite inner and outer ends connected respectively to the inner and outer lateral edges, and at least one end portion extending from one of the inner and outer ends toward both the axis and one of the inner and outer lateral edges.

1 . A fan comprising: 
 a hub rotatable about an axis and having a peripheral wall, an open end and a closed end; and    a plurality of blades extending from said peripheral wall of said hub, each of said blades having a leading side surface, a trailing side surface opposite to said leading side surface, an inner lateral edge corresponding to said open end of said hub, an outer lateral edge corresponding to said closed end of said hub and opposite to said inner lateral edge, and a radial outer edge having opposite inner and outer ends connected respectively to said inner and outer lateral edges, and at least one end portion extending from one of said inner and outer ends toward both said axis and one of said inner and outer lateral edges.    
   
   
       2 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades has an inclined straight inner edge portion extending from said inner end of said radial outer edge of a corresponding one of said blades toward both said axis and said outer lateral edge of the corresponding one of said blades, and an inclined straight outer edge portion extending from said outer end of said radial outer edge of the corresponding one of said blades toward both said axis and said inner lateral edge of the corresponding one of said blades, an imaginary extension line of each of said straight inner and outer edge portions forming an acute angle with respect to said axis.  
   
   
       3 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades is concaved and curved, and is disposed nearest said axis at a middle portion thereof, an imaginary tangent line of each point of said radial outer edge of each of said blades forming an acute angle with respect to said axis.  
   
   
       4 . The fan as claimed in  claim 1 , wherein said blades include a plurality of adjacent pairs of blades, said radial outer edge of one of each adjacent pair of said blades having an axial straight inner edge portion extending from said inner end of said radial outer edge of a corresponding one of said blades toward said outer lateral edge along a direction parallel to said axis, and an inclined straight outer edge portion extending from said outer end of said radial outer edge of the corresponding one of said blades toward both said axis and said inner lateral edge of the corresponding one of said blades and having an imaginary extension line forming an acute angle with respect to said axis, and an end connected to an end of said inner edge portion, said radial outer edge of the other one of each adjacent pair of said blades having an axial straight outer edge portion extending from said outer end of said radial outer edge of a corresponding one of said blades toward said inner lateral edge along a direction parallel to said axis, and an inclined straight inner edge portion extending from said inner end of said radial outer edge of the corresponding one of said blades toward both said axis and said outer lateral edge of the corresponding one of said blades and having an imaginary extension line forming an acute angle with respect to said axis, and an end connected to an end of said outer edge portion.  
   
   
       5 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades has an axial straight outer edge portion extending from said outer end of said radial outer edge of a corresponding one of said blades toward said inner lateral edge along a direction parallel to said axis, and an inclined straight inner edge portion extending from said inner end of said radial outer edge of the corresponding one of said blades toward both said axis and said outer lateral edge of the corresponding one of said blades and having an imaginary extension line forming an acute angle with respect to said axis, and an end connected to an end of said outer edge portion.  
   
   
       6 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades has an axial straight inner edge portion extending from said inner end of said radial outer edge of a corresponding one of said blades toward said outer lateral edge along a direction parallel to said axis, and an inclined straight outer edge portion extending from said outer end of said radial outer edge of the corresponding one of said blades toward both said axis and said inner lateral edge of the corresponding one of said blades and having an imaginary extension line forming an acute angle with respect to said axis, and an end connected to an end of said inner edge portion.  
   
   
       7 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades is straight, and extends from said inner end of said radial outer edge of a corresponding one of said blades toward both said axis and said outer lateral edge of said radial outer edge of the corresponding one of said blades, an imaginary extension line of said radial outer edge of each of said blades forming an acute angle with respect to said axis.  
   
   
       8 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades is straight, and extends from said outer end of said radial outer edge of a corresponding one of said blades toward both said axis and said inner lateral edge of said radial inner edge of the corresponding one of said blades, an imaginary extension line of said radial outer edge of each of said blades forming an acute angle with respect to said axis.  
   
   
       9 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades is curved, extends from said inner end of said radial outer edge of a corresponding one of said blades toward both said axis and said outer lateral edge of the corresponding one of said blades, and is disposed nearest said axis at said outer end of said radial outer edge of the corresponding one of said blades, an imaginary tangent line of each point of said radial outer edge of each of said blades forming an acute angle with respect to said axis.  
   
   
       10 . The fan as claimed in  claim 1 , wherein said radial outer edge of each of said blades is curved, extends from said outer end of said radial outer edge of a corresponding one of said blades toward both said axis and said inner lateral edge of the corresponding one of said blades, and is disposed nearest said axis at said inner end of said radial outer edge of the corresponding one of said blades, an imaginary extension line of each point of said radial outer edge of each of said blades forming an acute angle with respect to said axis.  
   
   
       11 . The fan as claimed in  claim 1 , wherein said blades include a plurality of adjacent pairs of blades, said radial outer edge of one of each adjacent pair of said blades being curved, an imaginary tangent line of each point of said radial outer edge of each of said blades forming an acute tangential angle with respect to said axis, said radial outer edge of each adjacent pair of said blades extending from said inner end of said radial outer edge of a corresponding one of said blades toward both said axis and said outer lateral edge of the corresponding one of said blades and being disposed nearest said axis at said outer end of said radial outer edge of the corresponding one of said blades, said radial outer edge of the other one of each adjacent pair of said blades extending from said outer end of said radial outer edge of a corresponding one of said blades toward both said axis and said inner lateral edge of the corresponding one of said blades and being disposed nearest said axis at said inner end of said radial outer edge of the corresponding one of said blades.