Patent ID: 8261739

Claim:
A dry powder inhaler comprising: a main airflow path including a reverse flow cyclone chamber in which in use air and entrained substance particles circulate, said chamber comprising an axis and being elongate along said axis, an air inlet, a closed base and a vortex finder, said chamber being so shaped that at least a part of the chamber decreases in cross-sectional area in an axial direction away from the air inlet, wherein the air inlet is arranged to direct air so that it circulates about the axis around the periphery of the chamber, and the vortex finder being arranged 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 in which air circulates in two generally concentric overlapping columns in opposite axial directions; and wherein the vortex finder is arranged such that the entrained substance particles which are smaller than a predetermined size exit the chamber but the entrained substance particles which are larger than the predetermined size are retained in the chamber; the inhaler further comprising a bypass airflow path bypassing the cyclone chamber; wherein the main and bypass airflow paths communicate with a mouthpiece.