Patent ID: 8052374

Claim:
A cut-off construction for a transverse fan assembly that includes a fan mounted generally cross-wise within an air plenum that has opposite sides, an air inlet, an air outlet, and an output throat from the downstream side of the fan towards the air outlet, with a baffle construction for separating the air inlet and the air outlet, and wherein the fan has a plurality n of spaced elongated fan blades of arcuate cross-section, between inner ends and outer tips thereof, disposed generally radially from one another about the axis of the fan and extending generally along the expanse of the fan, comprising a body construction extending across the air plenum generally along and adjacent to the outer periphery of the fan on the downstream side of the fan along the expanse of the fan and projecting laterally outwardly from the fan, from a forward position in the output throat near the outer periphery of the fan on its downstream side, to join the baffle construction and, with the baffle construction, to form an upper wall along the output throat, said body construction including first and second body portions positioned laterally to one another along the top of the output throat of the air plenum, each having a generally planar inner surface on one side thereof facing the output throat, said first body portion extending across the air plenum along said forward position near the outer periphery of the fan on its downstream side and projecting laterally therefrom with said inner surface thereof extending generally along a first line, defined to be the blade tip tangent line T 1 , tangent to the outer tip of a fan blade at a given point in the rotation of the fan as such fan blade rotates past said forward position, at a cut-off inclination angle α defined by said blade tip tangent line T 1 and a second line, defined to be the fan periphery tangent line T 2 , generally tangent to the outer periphery of the fan generally at or near such outer tip of the fan blade along blade tip tangent line T 1 , said generally planar inner surface of said first body portion extending, from said forward position, generally along said blade tip tangent line T 1 to intersect said generally planar inner surface of said second body portion at a juncture therebetween and to define a juncture angle β thereat, said generally planar inner surface of said second body portion projecting laterally from said juncture towards the air outlet, along a projection K extending generally through the output throat towards the air outlet, to meet and join the baffle construction, whereby the upper wall for the output throat formed by the baffle construction and said cut-off construction has a concavity formed therein and therealong near the outer periphery of the fan that effects a shift of the steering vortex of the fan in such a way as to permit the fan to operate with increased air flow volume at lower rotational fan speed.