Title:  Powder inhaler

United States Patent:  6,347,629

Assignee:  Innovata Biomed Limited (Hertfordshire, GB)

Filed:  June 18, 1999

A dry powder inhaler comprises a body 1 defining a storage chamber for a powder and further defining an inhalation passage 2 through which air is drawn via a mouthpiece 3. A flow duct passing through the mouthpiece includes a circulatory section 25 in which the flow duct is in the form of one or more passageways. The flow duct further includes a cyclone chamber 35 between the circulatory section and the outlet of the mouthpiece.

SUMMARY OF THE INVENTION

The present invention provides a dry powder inhaler comprising a body defining a storage chamber for a powder and further defining an inhalation passage through which air is drawn via a mouthpiece, the mouthpiece having an inlet and an outlet and defining a flow duct for the flow of an air/powder mixture therethrough, the flow duct extending between said inlet and said outlet and including a circulatory section (for effecting centrifugal separation of heavier and lighter particles) in which the flow duct is in the form of one or more passageways, said one or more passageways being circulatory about an axis extending between said inlet and said outlet, and the flow duct further including a cyclone chamber (for restraining heavier particles from reaching said outlet) between said circulatory section and said outlet.

The circulatory section of the flow duct serves primarily for effecting separation of heavier particles from lighter particles but also serves to convert the linear flow of the air/powder mixture entering the mouthpiece into a circulating flow in a smooth manner, with relatively little loss of kinetic energy, so that the air/powder mixture enters the cyclone chamber at relatively high speed.

Centrifugal forces act on the particles of the powder as the air/powder mixture circulates about the axis of the mouthpiece through the passageway(s) of the circulatory section. These forces set up a size distribution of particles across the passageway(s), the heavier particles being at the outside of the passageways, away from the axis of the mouthpiece, and the lighter particles at the inside of the passageway(s), towards the axis of the mouthpiece. Therefore, the powder enters the cyclone chamber with the lighter particles so positioned as to be preferentially drawn towards the centre of the chamber, from which air is being removed due to suction applied to the outlet of the mouthpiece by the patient. The heavier particles, on the other hand, remain in orbit in the chamber until the patient ceases to apply suction force.

In effect, the flow duct divides into two paths after the circulatory section. One path, followed by the lighter particles, leads to the outlet of the mouthpiece and to the patient, and the other path, followed by the heavier particles, leads to the radially outer region of the cyclone chamber. This maximises the proportion of lighter particles delivered to the patient, while minimising the proportion of heavier particles inhaled.

Earlier proposals to make use of cyclone chambers in powder inhalers have been for the purpose of effecting de-agglomeration, or for separating from one another the heavier and lighter particles of a powder in an air/powder mixture in which the particles have not previously been subjected to any separation and are still substantially uniformly distributed. In this invention the primary function of the cyclone chamber is not to effect de-agglomeration and/or separation but to retain in orbit the heavier particles which have previously been separated from the lighter particles by the circulatory section, thereby retaining them in the mouthpiece, to be discarded after the inhaler has been used. Some de-agglomeration of particles and some separation of particles may take place in the cyclone chamber but this is incidental and not essential. Accordingly, the term "cyclone chamber" is used herein to mean any chamber within which an air/powder mixture can be caused to circulate with an angular velocity generating centrifugal forces sufficient to maintain heavier particles of a powder mixture in orbit about an axis through the chamber.

The circulatory section of the flow duct may have any conformation adapted to effect circulatory flow of the air/powder mixture about the axis of the mouthpiece in such manner that the heavier and lighter particles of the powder are separated from one another by centrifugal forces.

The circulatory section is preferably a helical section in which the flow duct is in the form of one or more passageways of substantially helical conformation, preferably arranged as a helix or as helices about the aforementioned axis. Preferably the diameter of the or each helix increases in the direction from the inlet towards the outlet. The terms "helix" and "helical" are used to include both spiral and helical conformations, flat or extended, and with constant or variable diameters, and to include less than one turn and one or more turns.

Preferably, the cross-sectional area of each of the passageways in the circulatory section decreases in a direction from the inlet towards the outlet.

Preferably, the flow duct includes a section, located between the inlet and the helical section which is arranged so that the air/powder mixture flowing through the mouthpiece makes an abrupt change of direction. Accordingly the air/powder mixture encounters, in this section, a surface against which it impacts. This action causes agglomerated particles to break up.

Preferably the helical section of the flow duct terminates short of the outlet and the flow passage between said helical section and the outlet includes a section of cross-sectional area substantially less than the pitch circular diameter of the or each passage within the helical section. More preferably, said outlet section is located along the longitudinal axis of the helical section.

Preferably, the cyclone chamber extends, transversely of, for example at right angle to, the axis between the inlet and the outlet, the centre of the chamber preferably being on that axis.

Preferably, the flow duct is such that air passing from the helical section to the centrally located outlet section creates a Venturi effect producing a negative pressure in the outer chamber which serves to retain particles which have deposited in the chamber.

The present invention also provides a mouthpiece for a dry powder inhaler, the mouthpiece being for attachment to the body of the inhaler, and having an inlet and an outlet and defining a flow duct for the flow of an air/powder mixture therethrough, the flow duct extending between said inlet and said outlet and including a circulatory section in which the flow duct is in the form of one or more passageways, said one or more passageways being circulatory about an axis extending between said inlet and said outlet, and the flow duct further including a cyclone chamber between said circulatory section and said outlet.

Claim 1 of 6 Claims

What is claimed is:

1. A dry powder inhaler comprising a body defining a storage chamber for a powder and further defining an inhalation passage through which air is drawn via a mouthpiece, the mouthpiece having an inlet and an outlet and defining a flow duct for the flow of an air/powder mixture therethrough, the flow duct extending between said inlet and said outlet and including a circulatory section in which the flow duct is in the form of one or more passageways, said one or more passageways being circulatory about an axis extending between said inlet and said outlet, and the flow duct further including a cyclone chamber between said circulatory section and said outlet, said circulatory section serving to convert the linear flow of the air/powder mixture entering the mouthpiece into a circulatory flow that causes the powder particles of the air/powder mixture to separate by size, and said cyclone chamber serving to trap the largest powder particles.

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