Dispersing unit

A dispersing unit for a powder inhaler comprises a mouthpiece with an annular channel for the delivery of a stream of particles. The annular channel has an axial inlet, and an axial outlet adjoined by an annular deflection chamber in which the axially incoming stream of particles is deflected to a predominantly radial direction of flow. The deflection chamber is adjoined in the axial direction by a rotation chamber with a circular peripheral wall and an axial outlet.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 371 U.S. National Stage of International Application No. PCT/EP2007/000129, filed Jan. 9, 2007. This application claims the benefit of German Patent Application No. 10 2006 007 495.5, filed Feb. 17, 2006, the disclosures of which application are expressly incorporated herein by reference.

The present invention relates to a dispersing unit for a powder inhaler. Dispersing units of this type are generally known and serve to generate a dispersal of an aerosol, wherein the aerosol comprises a mixture of active agent and a carrier substance, e.g. lactose. The carrier substance mainly serves to control the physical properties of the formulation such as its flowability. In this process, the fine active agent primarily adheres to the surface of the coarse carrier substance. The adhesive forces present between carrier particles and active agent particles or between active agent particle agglomerates must be overcome during inhalation to generate a high proportion of respirable active agent particles. The energy required for this can be introduced in a dispersing unit.

In known dispersing units, impaction forces or turbulences or a combination of the two are used for the dispersion. It is also known to generate dispersion with the help of impact walls and additional supply air passages.

It is the object of the invention to provide a dispersing unit which is extremely compact in construction, is simple in construction and with which a fine particle fraction can be generated which is as high as possible without suction force loss.

This object is satisfied by the features of claim1and in particular by a dispersing unit having a mouthpiece in which a ring passage is provided for the supply of a particle flow. In this connection, the ring passage has an axial inlet and an axial outlet to supply the particle flow comprising a mixture of active agent and carrier substance. In accordance with the invention, a ring-shaped deflection chamber adjoins the axial outlet of the ring channel and the axially entering particle flow is deflected in a predominantly radial flow direction in it. At the same time, an acceleration of the particle flow can be achieved in this deflection chamber so that the particle flow circulates in circular form in a rotation chamber which adjoins the deflection chamber in the axial direction and has a circular peripheral wall and an axial outlet.

The particle flow supplied through the ring passage can therefore be brought into a ring-shape circulation track after exiting the deflection chamber solely by suction at the mouthpiece, with light particles, for example purely active agent particles having a particle size of less than 5 μm, being able to exit the axial outlet of the rotation chamber at an early stage due to their lower centrifugal force. On the other hand, coarser particles, for example carrier particles charged with active agent, are held longer in the rotation chamber due to their mass of inertia in which they circulate a multiple of times and impact the peripheral wall of the rotation chamber in the process, whereby the fine active agent particles additionally separate from the coarser carrier particles. All fine particles follow the airflow through the axial outlet of the rotation chamber at a slowed-down speed and are available for inhalation as a non-ballistic aerosol.

In accordance with the invention, the deflection chamber and the rotation chamber are not used for the separation of coarse particles, but a distribution between coarse and fine particles differing in the average dwell time is utilized. Coarser particles can thus also exist the rotation chamber up to the end of the inhalation procedure so that no real powder residues remain which could degrade the functionality of the inhaler or the uniformity of the dose discharge on the application of further doses.

The ring passage in accordance with the invention has an axially oriented inlet and outlet. Generally, however, the particle flow introduced into the ring passage can nevertheless also have tangential flow components.

Advantageous embodiments of the invention are described in the description, in the drawing and in the dependent claims.

In accordance with a first advantageous embodiment, guide vanes oriented obliquely to the axial direction can be arranged in the deflection chamber. The particle flow entering axially via an annular space can be deflected into a tangential flow in a simple manner using such guide vanes, with simultaneously an acceleration of the particle flow in the deflection chamber being able to be effected by the design of the deflection vanes.

It is advantageous for the guide vanes to be curved to achieve the desired deflection and acceleration effects. It can be advantageous in this process for the curvature of the guide vanes to reduce in the axial direction. The guide vane can hereby be designed in the manner of a turbine vane in order to achieve the best possible deflection and acceleration. It can also be advantageous in this connection for the guide vanes to have the profile of a wing with a curved skeleton line in section. It can also be advantageous in this connection for the guide vanes to have a rounded front edge in the region of the inlet of the deflection chamber and a rear edge with less pronounced rounding in the region of the outlet of the deflection chamber. Tests which have been made show that very good results can be achieved by such a section design.

In accordance with a further advantageous embodiment, the axial outlet of the rotation chamber is arranged centrally. Light particles can hereby exit the rotation chamber through the outlet at an early stage, whereas heavy particles circulate along the peripheral wall of the rotation chamber.

In accordance with a further advantageous embodiment, a discharge passage, which expands, adjoins the axial outlet of the rotation chamber. The expansion can be concave, whereby it is achieved that the aerosol particles exiting the outlet of the rotation chamber with relatively high speed components transversely to the direction of inhalation are slowed down in the region of the discharge passage, with the movement of the aerosol being predominantly oriented in the longitudinal direction in the outlet passage. At the same time, a slow aerosol discharge is achieved by the cross-section increase of the discharge passage so that the patient inhales a non-ballistic aerosol. The aerosol deposition in oropharyngeal region of the patient is reduced using such a mouthpiece geometry by influencing the exit direction and the exit speed. Although the aerosol exits the rotation chamber into the outlet at relatively high radial speeds, the aerosol exit speed at the end of the discharge passage is relatively low.

It can furthermore be advantageous for the discharge passage to have a circular cylindrical region in an end section at the exit side since an axial bundling of the discharge particle flow can thereby be effected. A convex design is also conceivable instead of a concave design.

The deposition of light particles from the rotation chamber can additionally be improved in that the discharge passage is sharp-edged and in particular adjoins the rotation chamber with an edge having an acute angle in cross-section.

It has also proved to be advantageous to form the transition from the circular peripheral wall to the axial outlet in the rotation chamber with a part curvature since this effects improved aerodynamics, on the one hand, and a reduced deposition of particles, on the other hand.

In the dispersing unit in accordance with the invention, no air inlet openings are provided for the supply of external air between the axial outlet of the ring passage and the outlet of the rotation chamber. It is hereby precluded that an additional suction power has to be applied to maintain the functionality of the dispersing unit, which does not benefit either the mobilization of the powder from the dispersing device nor the actual dispersing power. The deflection of the particle flow and the directed outlet into the pharynx are realized solely via geometrical implementations in accordance with the invention.

The present invention will be described in the following purely by way of example with reference to an advantageous embodiment and to the enclosed drawing.

FIG. 1shows a dispersing unit for a powder inhaler (not shown) having a mouthpiece10at whose lower side a ring passage12is provided for the supply of a particle flow. The particle flow is generally produced by suction at the mouthpiece, for example in that a predetermined dose of active agent and carrier substance is made available in the inhaler and is then sucked into the ring passage12by suction at the mouthpiece.

The ring passage12is circumferential in the peripheral direction and has an axial inlet14and an axial outlet16, with both the inlet14and the outlet16extending over the total periphery of the ring passage12.

Adjoining the axial outlet16of the ring passage12, a likewise ring-shaped deflection chamber18is provided which has approximately the same radial extent as the ring passage12and in which the axially entering particle flow is deflected into a predominantly radial direction of flow. The substantially radially directed particle flow at the outlet of the deflection chamber18is in this process guided into a rotation chamber20which has a circular peripheral wall22and an axial outlet24.

AsFIG. 1shows, the outer diameters of the ring passage12, of the deflection chamber18and of the rotation chamber20are of substantially the same size. The inner diameter of the ring passage12and the inner diameter of the deflection chamber18also correspond to one another. The inner diameter of the axial outlet24of the rotation chamber20is lower than the inner diameter of the deflection chamber18.

To deflect the axially entering particle flow in the deflection chamber18into a predominantly radial flow direction and to accelerate it at the same time, a plurality of guide vanes26are provided in the deflection chamber18, distributed over its periphery, and are oriented obliquely to the axial direction. Each of the guide vanes26extends over the total cross-section of the deflection chamber18, with each guide vane being curved and the curvature reducing in the axial direction, i.e. being more pronounced at the inlet of the deflection chamber18than at the outlet. In section (longitudinal section), the guide vanes26have the section of a wing having a curved skeleton line. In accordance with an advantageous embodiment, the guide vanes have a rounded front edge in the region of the inlet of the deflection chamber18and a rear edge of less pronounced rounding in the region of the outlet of the deflection chamber18so that the section of the guide vanes26is similar to an airplane wing.

AsFIG. 1further shows, the peripheral wall22of the rotation chamber20is of circular cylindrical form and directly adjoins the outlet of the deflection chamber18, with the axial extent of the deflection chamber18and of the rotation chamber20being approximately of equal size. At its outlet side end, the rotation chamber20has an end wall28which forms a transition between the peripheral wall22and the centrally arranged axial outlet24. In this process, the transition from the circular peripheral wall22to the end wall28is curved in the region of the corner.

A discharge passage30whose peripheral wall32expands concavely adjoins the axial outlet24of the rotation chamber20. The transition between the end wall28of the rotation chamber20and the peripheral wall32of the discharge passage30is, however, sharp-edged and is made with an acute angle in the embodiment shown. Furthermore, the discharge passage30has a circular cylindrical region33in its outlet side end section which extends up to the end of the discharge passage30and which effects an axial bundling of the discharged particle flow.

AsFIG. 1further shows, no air inlet openings for the supply of external air are provided between the inlet14of the ring passage12and the discharge passage30.

In the use of the described dispersing unit, the patient sucks at the mouthpiece10, whereby a particle flow is guided through the mouthpiece in the direction of the arrows shown (axial direction), said particle flow having been previously made available in a desired dose by a powder inhaler (not shown). The sucked-in particle flow is first introduced into the ring passage12through the inlet14and exits the ring passage12into the ring-shaped deflection chamber18through the ring-shaped axial outlet16. In the deflection chamber18, the particle flow is accelerated by the guide vanes26, on the one hand, and deflected into a predominantly radial flow direction, on the other hand, so that the particle flow enters into the rotation chamber20, which adjoins the deflection chamber18in the axial direction, approximately tangentially at the outlet of the deflection chamber18. The particle flow rotates in the rotation chamber20, with heavy particles circulating longer in the region of the circular peripheral wall22and lighter particles following the air flow and moving faster in the direction of the discharge passage30.

The heavier particles circulating in the rotation chamber20initially discharge increasingly smaller (active agent) particles during their circulation due to contact with the peripheral wall22until these particles circulating in the rotation chamber20likewise follow the air flow and are then also discharged.

The described dispersing unit is made of plastic in accordance with an advantageous embodiment. It can be advantageous in this connection to make the guide vanes26in one piece with an insert27, for example as an injection molded part, with the insert27with the guide vanes26molded thereon being able to be inserted into the interior of the mouthpiece10.