Patent ID: 8043148

Claim:
A damper system comprising an airflow passage and a rotating portion: the rotating portion rotatably disposed within the airflow passage about a longitudinal axis, the rotating portion comprising a distal end defined as the end of the rotating portion that is downstream of a plane formed by the longitudinal axis and a transverse cross section of the airflow passage; the airflow passage comprising the space between a wall proximate the downstream end of the rotating portion in a closed and a second wall; the wall comprising: a rib extending from the wall toward the rotating portion longitudinal axis; a rib protrusion disposed on a downstream portion of the rib and spaced from the wall, the rib protrusion contacting the rotating portion downstream end when the damper system is in the closed position; and a protruding convex curved wall portion directly adjacent and downstream of the rib that does not contact the rotating portion downstream end when the damper system is in the closed position, wherein the flow rate of the air flowing along the protruding convex curved wall portion is increased, and the pressure rise in the region around the protruding convex curved wall portion is reduced.