Extraction Fan Assembly Including a Damper that Closes Firmly when the Fan is Not Running and Reduces the Pressure Drop when the Fan is Running at Full Speed

Abstract

An extraction fan has a housing mounted in a wall with an outlet duct extending through the wall to an outlet opening outside the wall. A damper flap is mounted on the fan suspended by a hinge at an upper edge so as to extend in a closed position across the opening and is movable to an open position under forward air flow from the fan, and tightly closes against a resilient deformable seal when the fan is shut off. A spring biasing cam applies inwards force to the damper flap to bias the damper flap into the closed position, and an outwards force also to bias the damper flap into the fully open position. The mounting plate includes a hood having a top wall extending over the top of the damper flap and a down-turned front flange extending parallel to the damper flap to a bottom edge.

1 . A damper flap assembly for mounting on a fan construction having a fan housing and a fan mounted in the housing;
 the damper flap assembly comprising:   a mounting plate having an opening through which the air passes and a flange surrounding the opening;   a pivotally mounted damper flap arranged to extend in a closed position across the opening when the fan is not running, with an outer peripheral portion of the damper flap engaging the flange around the opening;   the damper flap having a front surface facing forwardly away from the fan and a rear surface facing toward the fan;   the damper flap being movable from the closed position between a partially open position to a fully open position under forward air flow from the fan by pivoting on the hinge away from the flange;   the damper flap being suspended by a hinge member adjacent an upper edge of the damper flap and pivotal about a hinge axis of the hinge member;   the hinge member including a transverse support at the hinge axis and at least one support arm extending from the transverse support adjacent the upper edge in a direction forwardly of the damper flap to a position in front of the damper flap, said at least one support arm being connected by a connection member to the damper flap at a position below a top edge of the damper flap.   
     
     
         2 . The damper flap assembly according to  claim 1  wherein said connection member is arranged at a position adjacent or below a transverse center line of the damper flap. 
     
     
         3 . The damper flap assembly according to  claim 1  said at least one arm is connected to the damper flap only at said connection member allowing top and bottom edges of the damper flap to flex relative to said connection member. 
     
     
         4 . The damper flap assembly according to  claim 1  wherein said at least one support arm includes a depending portion extending along the front face of the flap member and spaced therefrom. 
     
     
         5 . The damper flap assembly according to  claim 1  wherein there is provided at least one bracket fastened to the front face of the flap member and said depending portion of said at least one support arm is engaged with the bracket. 
     
     
         6 . The damper flap assembly according to  claim 1  wherein the depending portion comprises a rod and the rod is engaged through a hole of the bracket. 
     
     
         7 . The damper flap assembly according to  claim 1  wherein the transverse support is located at a position in a vertical plane rearward of the rear face of the flap member. 
     
     
         8 . The damper flap assembly according to  claim 1  wherein the transverse support is located at a height above the top edge of the flap member. 
     
     
         9 . The damper flap assembly according to  claim 1  wherein the flap member is moved to the closed position solely by gravity. 
     
     
         10 . The damper flap assembly according to  claim 1  wherein there is provided a spring biasing arrangement applying biasing forces to said at least one arm in directions both toward the open position and toward the closed position. 
     
     
         11 . The damper flap assembly according to  claim 1  wherein the spring biasing arrangement includes two springs which are independently adjustable. 
     
     
         12 . The damper flap assembly according to  claim 11  wherein the two springs are arranged to provide different forces to the damper flap such that independent adjustment provides different changes in the biasing forces. 
     
     
         13 . The damper flap assembly according to  claim 11  wherein one of the two springs is arranged on one side of the hinge member and the other on the other side of the hinge member. 
     
     
         14 . The damper flap assembly according to  claim 1  wherein said at least one arm comprises two arms spaced transversely so that each is located on a respective side of a vertical centerline of the flap member. 
     
     
         15 . The damper flap assembly according to  claim 14  wherein the two arms are mounted on two separate components of the transverse support such that the arms can pivot independently. 
     
     
         16 . A damper flap assembly for mounting on a fan construction having a fan housing and a fan mounted in the housing;
 the damper flap assembly comprising:   a mounting plate having an opening through which the air passes and a flange surrounding the opening;   a pivotally mounted damper flap arranged to extend in a closed position across the opening when the fan is not running, with an outer peripheral portion of the damper flap engaging the flange around the opening;   the damper flap having a front surface facing forwardly away from the fan and a rear surface facing toward the fan;   the damper flap being movable from the closed position between a partially open position to a fully open position under forward air flow from the fan by pivoting on the hinge away from the flange;   the damper flap being suspended by a hinge member adjacent an upper edge of the damper flap and pivotal about a hinge axis of the hinge member;   the hinge member including a transverse support at the hinge axis and two depending arms spaced transversely so that each is located on a respective side of a vertical centerline of the flap member.   
     
     
         17 . The damper flap assembly according to  claim 16  wherein each of said arms is connected to the damper flap by a connection member arranged at a position adjacent or below a transverse center line of the damper flap. 
     
     
         18 . The damper flap assembly according to  claim 16  wherein said depending arms each extend along the front face of the flap member and spaced therefrom. 
     
     
         19 . The damper flap assembly according to  claim 16  wherein the transverse support is located at a position in a vertical plane rearward of the rear face of the flap member. 
     
     
         20 . The damper flap assembly according to  claim 16  wherein the two arms are mounted on two separate components of the transverse support such that the arms can pivot independently. 
     
     
         21 . The damper flap assembly according to  claim 16  wherein the flap member is moved to the closed position solely by gravity. 
     
     
         22 . A damper flap assembly for mounting on a fan construction having a fan housing and a fan mounted in the housing;
 the damper flap assembly comprising:   a mounting plate having an opening through which the air passes and a flange surrounding the opening;   a pivotally mounted damper flap arranged to extend in a closed position across the opening when the fan is not running, with an outer peripheral portion of the damper flap engaging the flange around the opening;   the damper flap having a front surface facing forwardly away from the fan and a rear surface facing toward the fan;   the damper flap being movable from the closed position between a partially open position to a fully open position under forward air flow from the fan by pivoting on the hinge away from the flange;   the damper flap being suspended by a hinge member adjacent an upper edge of the damper flap and pivotal about a hinge axis of the hinge member and at least one support arm;   wherein there is provided a spring biasing arrangement applying biasing forces to said at least one arm in directions both toward the open position and toward the closed position;   and wherein the spring biasing arrangement includes two springs which are independently adjustable.   
     
     
         23 . The damper flap assembly according to  claim 22  wherein the two springs area arranged to provide different forces to the damper flap such that independent adjustment provides different changes in the biasing forces. 
     
     
         24 . The damper flap assembly according to  claim 22  wherein one of the two springs is arranged on one side of the hinge member and the other on the other side of the hinge member. 
     
     
         25 . A damper flap assembly for mounting on a fan construction having a fan housing and a fan mounted in the housing;
 the damper flap assembly comprising:   a mounting plate having an opening through which the air passes and a flange surrounding the opening;   a pivotally mounted damper flap arranged to extend in a closed position across the opening when the fan is not running, with an outer peripheral portion of the damper flap engaging the flange around the opening;   the damper flap having a front surface facing forwardly away from the fan and a rear surface facing toward the fan;   the damper flap being movable from the closed position between a partially open position to a fully open position under forward air flow from the fan by pivoting on the hinge away from the flange;   the damper flap being suspended by a hinge member adjacent an upper edge of the damper flap and pivotal about a hinge axis of the hinge member and at least one support arm;   wherein there is provided a spring biasing arrangement applying biasing forces to said at least one arm in directions both toward the open position and toward the closed position;   said at least one arm being connected to a shaft pivotal about its longitudinal axis;   wherein the spring biasing arrangement includes a first lever connected to the shaft and a spring acting on the lever to pivot the shaft;   wherein there is provided a second lever and meshing gears connecting the first and second levers for common movement in opposite directions as the shaft pivots;   and wherein in the spring is connected between the two levers and passes an over-center position as the levers rotate so as to bias the first lever in a first direction on one side of the over-center position and in a second direction on the other side of the over-center position.