Muffler for impeller with rearwardly curved blades

Abstract

A high speed centrifugal air impeller assembly with rearwardly curved blades has it impeller backplate directly cooperating with an adjacent housing wall portion to provide a narrow annular sound attenuating passageway from an impeller chamber to a motor and discharge chamber.

1 . A high speed centrifugal air impeller assembly with rearwardly curved blades and with sound attenuation means; said impeller comprising a housing defining air inlet and air discharge openings, an air impeller with an annular backplate carrying a circumaxially spaced series of long narrow rearwardly inclined air moving blades on one side disposed in the housing with it inlet opening in communication with the housing inlet opening, said backplate also defining discrete impeller and motor chambers in the housing, an electric motor mounted in the motor chamber on an opposite and discharge side of the backplate in driving relationship therewith, said housing having an annular portion of its inner surface adjacent said backplate and said backplate having an outer diameter slightly less than the inner diameter of said housing annular portion to define therewith a narrow annular air passageway immediately adjacent the housing inner surface and which interconnects the impeller and motor chambers and provides sound attenuation during the passage of impeller discharge air therethrough.  
   
   
       2 . A high speed centrifugal air impeller as set forth in  claim 1  wherein the ratio of the annular area between the backplate and housing to that of the annular area between the blade tips and housing falls in the range 0.10 to 0.50.  
   
   
       3 . A high speed centrifugal air impeller as set forth in  claim 1  wherein the impeller is operated at a tip speed up to approximately 550 feet per second.  
   
   
       4 . A high speed centrifugal air impeller as set forth in  claim 1  wherein the backplate extends substantially beyond the outer diameter of the blades.  
   
   
       5 . A high speed centrifugal air impeller as set forth in  claim 1  wherein the housing is formed of a pair of mating cup shaped parts, and wherein said annular portion of the inner surface of the housing resides at the junction of the two parts.  
   
   
       6 . A high speed centrifugal air impeller assembly with rearwardly curved blades and with sound attenuation means; said impeller comprising a housing defining air inlet and air discharge chambers respectively having inlet and discharge openings, an air impeller with an annular backplate carrying a circumaxially spaced series of long narrow rearwardly inclined air moving blades on one side disposed in the housing with its inlet opening in communication with the housing inlet opening, said housing also having an annular portion at its inner surface adjacent said backplate with a diameter slightly greater than that of the backplate and at least as large as that of the inlet chamber to define a narrow annular air passageway adjacent the housing inner surface interconnecting the inlet and discharge chambers and providing sound attenuation during the passage of impeller discharge air therethrough  
   
   
       7 . A high speed centrifugal air impeller as set forth in  claim 6  wherein the ratio of the annular area between the backplate and housing to that of the annular area between the blade tips and housing falls in the range 0.10 to 0.50.  
   
   
       8 . A high speed centrifugal air impeller as set forth in  claim 6  wherein the impeller is operated at a tip speed up to approximately 550 feet per second.  
   
   
       9 . A high speed centrifugal air impeller as set forth in  claim 6  wherein the backplate extends substantially beyond the outer diameter of the blades.  
   
   
       10 . A high speed centrifugal air impeller as set forth in  claim 6  wherein the housing is formed of a pair of mating cup shaped parts, and wherein said annular portion of the inner surface of the housing resides at the junction of the two parts.