Hinged dry powder inhaler comprising a circulating airflow chamber

A dry powder inhaler comprising two parts connected by an integrally moulded hinge configured to hinge the two parts of the inhaler from an open position to a closed position, at least one of said parts defining at least part of a circulating airflow chamber, wherein when said parts are in said closed position, the inhaler comprises an airflow path including the circulating airflow chamber, the inhaler further comprising a dose to be inhaled which is sealed in the at least part of the circulating airflow chamber by a frangible membrane and being arranged such that the frangible membrane is broken by an action of closing the inhaler prior to use and the dose is exposed to an entraining airflow in the circulating airflow chamber upon inhalation, and

• wherein the circulating airflow chamber having air and entrained substance particles circulate further comprises an axis and being elongate along said axis, an air inlet, a closed base and a vortex finder, said chamber being shaped wherein at least a part of the chamber decreases in cross-sectional area in a direction away from the air inlet,
• wherein the air inlet is configured to direct air to circulate around the periphery of the chamber, and the vortex finder is configured such that air exits therethrough after a reversal of axial direction at the base of the chamber to set up a reverse flow cyclone in the chamber wherein air circulates in two generally concentric overlapping columns in opposite axial directions.