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

摘要

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.

主权项

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 member having an opening through which air passes and an engagement surface 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 forming a seal with the engagement surface 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 a 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 having a first portion extending from the transverse support adjacent the upper edge in a direction forwardly of the damper flap to a position in front of the front surface of the damper flap and a second portion extending from the first portion along the front face at a position spaced from the front face, said second portion of 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; wherein there is provided a spring biasing arrangement applying spring biasing forces to said at least one arm; wherein the spring biasing arrangement includes a member connected to the transverse support at the hinge axis so as to apply the spring biasing forces to said at least one arm by rotating the transverse support around the hinge axis; and wherein the spring biasing arrangement Is arranged for applying force to the damper flap so that on one side of an intermediate partially open position adjacent the closed position the spring biasing arrangement acts to bias the damper flap into the closed position and on an opposed side of the intermediate partially open position adjacent the fully open position to bias the damper flap into the fully open position.