Axial fan with tip fences

Abstract

An axial flow fan includes a generally hollow casing defining an inlet end and an outlet end of the axial flow fan. A diameter of the casing increases from the inlet end to the outlet end. An impeller is rotatably mounted within the casing. The impeller includes a hub and a plurality of fan blades extending from a root located at the hub to a blade tip. A diameter of the blade tip of each of the plurality of fan blades increases from the inlet end to the outlet end. A tip fence is located at the blade tip of at least one of the plurality of fan blades and a length of the tip fence measured perpendicular to the fan blades is greater than a thickness of the at least one of the plurality of fan blades.

What is claimed is: 
     
         1 . An axial flow fan comprising:
 a generally hollow casing defining an inlet end and an outlet end of the axial flow fan, wherein a diameter of the casing increases from the inlet end to the outlet end;   an impeller rotatably mounted within the casing, the impeller including:
 a hub; 
 a plurality of fan blades extending from a root at the hub to a blade tip, wherein a diameter of the blade tip of each of the plurality of fan blades increases from the inlet end to the outlet end; and 
 a tip fence located at the blade tip of at least one of the plurality of fan blades, wherein a length of the tip fence measured perpendicular to the fan blades is greater than a thickness of the at least one of the plurality of fan blades. 
   
     
     
         2 . The axial flow fan of  claim 1 , wherein an axial clearance, measured parallel to the diameter of the casing, is defined between the tip fence of each of the plurality of fan blades and an adjacent surface of the casing and the axial clearance remains constant between the inlet end and the outlet end of the axial flow fan with a tolerance of +/−1 mm. 
     
     
         3 . The axial flow fan of  claim 1 , wherein an outer diameter of the hub increases from the inlet end to the outlet end. 
     
     
         4 . The axial flow fan of  claim 3 , wherein the increase in the diameter of the hub from the inlet end to the outlet end is generally equal to the increase in the diameter of the casing from the inlet end to the outlet end. 
     
     
         5 . The axial flow fan of  claim 1 , wherein the hub has a radially stepped configuration extending in the circumferential direction. 
     
     
         6 . The axial flow fan of  claim 1 , wherein a ratio of the axial length of the tip fence to the thickness of the at least one of the plurality of fan blades is between 2 and 10. 
     
     
         7 . The axial flow fan of  claim 1 , wherein the tip fence has a generally constant thickness. 
     
     
         8 . The axial flow fan of  claim 1 , wherein a thickness of the tip fence varies. 
     
     
         9 . The axial flow fan of  claim 1 , wherein each of the plurality of fan blades includes a first surface and a second, opposite surface, and the tip fence extends beyond both the first surface and the second surface of the at least one of the plurality of fan blades. 
     
     
         10 . The axial flow fan of  claim 1 , wherein each of the plurality of fan blades has a leading edge and a trailing edge, and the tip fence extends beyond at least one of the leading edge and the trailing edge of the at least one of the plurality of fan blades. 
     
     
         11 . The axial flow fan of  claim 1 , wherein the tip fence is integrally formed with the at least one of the plurality of fan blades. 
     
     
         12 . The axial flow fan of  claim 1 , wherein the casing has a bellmouth contour. 
     
     
         13 . The axial flow fan of  claim 1 , wherein the casing further comprising:
 a stationary hub oriented in alignment with the hub; and   a plurality of structural members extending radially outward from the stationary hub to couple the casing to the stationary hub.   
     
     
         14 . The axial flow fan of  claim 13 , wherein at least one of the stationary hub and the plurality of structural members has one or more openings to allow an airflow to pass there through. 
     
     
         15 . The axial flow fan of  claim 1 , wherein the axial flow fan is mounted in a refrigerated display cabinet. 
     
     
         16 . The axial flow fan of  claim 1 , wherein the hub and the plurality of fan blades are formed separately. 
     
     
         17 . The axial flow fan of  claim 1 , wherein the hub and the plurality of fan blades are integrally formed. 
     
     
         18 . A refrigerated merchandiser comprising:
 a cabinet defining a product display area and having a compartment separate from the product display area;   an air circulation circuit fluidly coupling the compartment and the product display area; and   an air circulating fan for moving a flow of air axially through the air circulation circuit, the air circulating fan including:
 a generally hollow casing, wherein a diameter of the casing increases along an axial length of the air circulating fan; 
 a fan rotor rotatably mounted within the casing and having a hub and a plurality of fan blades mounted at a root to the hub and extending to a blade tip, wherein a diameter of the blade tip of each of the plurality of fan blades increases along an axial length of the air circulating fan; and 
 a tip fence located at a tip of at least one of the plurality of fan blades, wherein an axial length of the tip fence is greater than a thickness of the at least one of the plurality of fan blades. 
   
     
     
         19 . The refrigerated merchandiser of  claim 18 , wherein a ratio of the axial length of the tip fence to the thickness of the at least one of the plurality of fan blades is between 2 and 10. 
     
     
         20 . The refrigerated merchandiser of  claim 18 , wherein a clearance is defined between a blade tip of the plurality of fan blades and a surface of the casing and the clearance remains constant between the inlet end and the outlet end of the axial flow fan. 
     
     
         21 . The refrigerated merchandiser of  claim 18 , wherein a diameter of the hub increases over an axial length of the air circulating fan, and the increase in the diameter of the hub over the axial length of the air circulating fan is generally equal to the increase in the diameter of the casing over the axial length of the air circulating fan. 
     
     
         22 . The refrigerated merchandiser of  claim 20 , wherein an opening is defined between the casing and the hub, and a width of the opening remains generally constant over the axial length of the axial flow fan.