Patent ID: 7347252

Claim:
An improved centrifugal impeller for use in low profile heat sinks and the like having a multiplicity of small upright spaced apart heat dissipating elements in an array defining a multiplicity of small airflow passageways there between with a cavity located centrally there within, the impeller being adapted to be disposed adjacent to and about the array of heat dissipating elements and to be driven by an electric motor disposed in the central cavity, and the impeller being open radially inwardly for radial communication with the air flow passageways between the heat dissipating elements at least partially open radially outwardly for the discharge of spent air, the impeller also having a radially extending backplate which is exposed upwardly and which defines an inlet opening for the axial downward flow of cooling air, and a plurality of 20 to 26 rearwardly curved air moving blades forming a part of the impeller and serving to effect a right angle turn in air flow direction and to withdraw air radially outwardly through the passageways between the heat dissipating elements and direct the same radially outwardly, wherein the ratio of the radial dimension W measured between the leading and trailing edges of the blades to the overall radius R of the impeller falls in the 0.31 to 0.37, wherein the impeller blades each have an inlet angle in the range of 32 degrees to 36 degrees measured between a line tangent to a circle intersecting the inner blade edges and a line tangent to the blade centerline at its leading edge and a discharge angle in the range of 36 degrees to 40 degrees measured between a line tangent to the blade the impeller periphery and a line tangent to the blade centerline at its trailing edge.