Vertical Door Fan Shutter

Abstract

A fan shutter having one end attachable to an exhaust fan and the opposite inlet end having a pair of vertical doors that are biased to close when the fan is off and to open by the force of vacuum when the fan is on. The use of vertical doors prevents the accumulation of dust and dirt on the doors. The vertical doors pivot horizontally in a housing that may have any desired shape, including a tubular shape with a bell mouth. The tubular bell mouth shutter design further provides improved air flow characteristics and decreased stress on the exhaust fan, compared to conventional fan shutters.

1 . A fan shutter, comprising:
 a) a housing having one end attachable to a fan;   b) said housing having an opposite end with one or more doors attached pivotably and centrally to said opposite end of said housing; and   c) said one or more doors biased to close said opposite end of said housing.   
   
   
       2 . The fan shutter of  claim 1  wherein said one or more doors are attached to a center post by hinges at said opposite end of said housing. 
   
   
       3 . The fan shutter of  claim 1  wherein said one or more doors are biased to close by gravity by said opposite end of said housing being tilted from vertical. 
   
   
       4 . The fan shutter of  claim 1  wherein said one or more doors are biased to close by gravity by said housing being tilted downward while said opposite end of said housing remains vertical. 
   
   
       5 . The fan shutter of  claim 1  wherein said one or more doors are biased to close by the use of one or more counterweights. 
   
   
       6 . The fan shutter of  claim 1  wherein said one or more doors have hinges and are biased to close by the use of springs in said hinges. 
   
   
       7 . The fan shutter of  claim 1  wherein said housing is tubular. 
   
   
       8 . The fan shutter of  claim 7  wherein said opposite end of said housing has a bell mouth. 
   
   
       9 . The fan shutter of  claim 8  wherein said housing and said fan form a single unit. 
   
   
       10 . The fan shutter of  claim 1  wherein said opposite end of said housing has a bell mouth. 
   
   
       11 . The fan shutter of  claim 1  wherein said housing and said fan form a single unit. 
   
   
       12 . A fan shutter, comprising:
 a) a housing having one end attachable to a fan and an opposite end having one or more doors attached pivotably to a centerpost; and   b) said one or more doors being vertically oriented, biased to close said opposite end of said housing when said fan is not operating, and opening said opposite end of said housing when said fan is operating.   
   
   
       13 . The fan shutter of  claim 12  wherein said one or more doors are attached to said center post by hinges. 
   
   
       14 . The fan shutter of  claim 13  wherein said one or more doors are biased to close by gravity by said opposite end of said housing being tilted from vertical. 
   
   
       15 . The fan shutter of  claim 13  wherein said one or more doors are biased to close by gravity by said housing being tilted downward while said opposite end of said housing remains vertical. 
   
   
       16 . The fan shutter of  claim 13  wherein said one or more doors are biased to close by the use of one or more counterweights. 
   
   
       17 . The fan shutter of  claim 12  wherein said one or more doors have hinges and are biased to close by the use of springs in said hinges. 
   
   
       18 . A fan shutter, comprising:
 a) a tubular housing having one end attachable to a fan and an opposite end having a bellmouth and one or more doors attached pivotably and centrally to said opposite end; and   b) said one or more doors being vertically oriented, biased to close said opposite end of said housing when said fan is not operating, and opening said opposite end of said housing when said fan is operating.   
   
   
       19 . The fan shutter of  claim 18  wherein said one or more doors are biased to close by gravity by said opposite end of said housing being tilted from vertical. 
   
   
       20 . The fan shutter of  claim 18  wherein said one or more doors are biased to close by gravity by said housing being tilted downward while said opposite end of said housing remains vertical. 
   
   
       21 . The fan shutter of  claim 18  wherein said one or more doors are biased to close by the use of one or more counterweights. 
   
   
       22 . The fan shutter of  claim 18  wherein said one or more doors have hinges and are biased to close by the use of springs in said hinges. 
   
   
       23 . The fan shutter of  claim 18  wherein said housing and said fan form a single unit.