Patent ID: 7591633

Claim:
An air handling blower comprising: a blower housing including at least one air inlet having a dimension defining an airflow area of said at least one inlet, an air outlet, an airflow space extending between said at least one inlet and said outlet and a cutoff edge in said housing substantially preventing recirculation of air in said space; and either a first impeller or a second impeller disposed for rotation about a common axis within said housing in said space, each of the first and second impellers having a plurality of blades having an inner edge and an outer edge where the inner edge is closer to the common axis than the outer edge, wherein said first impeller has an inside diameter defined as the diametral distance between its inner edges which is not less than said dimension of said at least one inlet and said second impeller has an outside diameter which is not less than said dimension of said at least one inlet; wherein the cutoff edge comprises a first end having a first radial dimension relative to the common axis, a second end having a second radial dimension relative to the common axis, and a midsection having a third radial dimension relative to the common axis and wherein the third radial dimension is greater than the first or second radial dimensions; and wherein the cutoff edge arcs symmetrically from the first and second ends to the midsection.