Vacuum cleaner cyclone with helical cyclone expansion region

A vacuum cleaner dirt collection assembly comprising:

• a housing;
• an air inlet connected to the housing;
• an air outlet connected to the housing;
• a cyclone chamber inside the housing and fluidly connected between the air inlet and the air outlet, the cyclone chamber comprising:
• a top wall,
• a bottom wall,
• an outer wall extending between and joining the top wall and bottom wall to form a generally enclosed space having a central axis extending from the top wall to the bottom wall, the outer wall further comprising a helical guide channel extending radially outward from an outer surface of the outer wall with respect to the axial centerline;
• an inner wall located inside the generally enclosed space, the inner wall having a generally cylindrical or frustroconical surface having one or more openings fluidly connecting the enclosed space to the air outlet;
• a separator plate located inside the generally enclosed space at a location along the central axis between the top wall and the bottom wall, the separator plate extending towards the outer wall and spaced from the outer wall by a gap.