Cyclonic vacuum cleaner ribbed cyclone shroud

A dirt collection assembly for a vacuum cleaner, the dirt collection assembly comprising:

• a cyclone chamber having a generally cylindrical sidewall, an air inlet and an air outlet, the cyclone chamber being adapted to direct an airflow into a cyclonic pattern to remove a first amount of debris from the airflow;
• a filter shroud located within the cyclone chamber and separating the air inlet from the air outlet, the filter shroud comprising an air-pervious filter surface adapted to allow the airflow to pass from the air inlet to the air outlet and remove a second portion of debris from the airflow;
• one or more protrusions associated with the filter surface, the one or more protrusions being configured and dimensioned to direct at least a portion of the airflow passing generally parallel to the filter surface away from the filter surface before passing through the filter surface;
• and
• a dirt collection chamber adapted to receive the first amount of debris and the second amount of debris;
• wherein the filter surface is generally cylindrical or frustoconical, and the one or more protrusions comprise a plurality of ribs extending in a generally helical pattern around the filter surface, the ribs being oriented generally perpendicular to the portion of the airflow passing generally parallel to the filter surface.

A method for removing debris from an airflow, the method comprising:

• introducing an airflow through an inlet into a cyclone chamber;
• causing the airflow to spiral downward through the cyclone chamber, thus forming an outer cyclone column located adjacent an outer wall of the cyclone chamber;
• causing the airflow to move radially inward towards a center axis of the cyclone chamber;
• causing the airflow to spiral upward through the cyclone chamber, thus forming an inner cyclone column located radially inward of the outer cyclone column;
• passing at least a first portion of the airflow forming the inner cyclone column across a filter surface;
• and
• passing the first portion of the airflow over a series of obstructions extending from the filter surface before passing the first portion of the airflow through the filter surface;
• wherein the first portion of the airflow is traveling in a first helical direction with respect to the center axis, and the series of obstructions comprises a plurality of ribs extending in a second helical direction with respect to the center axis, and the first helical direction and the second helical direction have a crossing angle of at least about 15 degrees.