WO2013048238A1

WO2013048238A1 - Dynamic blower module

Info

Publication number: WO2013048238A1
Application number: PCT/NL2012/050667
Authority: WO
Inventors: Geert Van Dijk; Eugène Herben
Original assignee: Macawi International B.V.
Priority date: 2011-09-26
Filing date: 2012-09-20
Publication date: 2013-04-04
Also published as: NL2007470C2

Abstract

A blower module (28) for a ventilator (50) is disclosed. The blower module (28) comprises an impeller (3) mounted within a stator housing (11) on a rotatable shaft (7), the rotatable shaft (7) defining an axis of rotation (12) of the impeller (3). The housing (11) has a central gas inlet (13) substantially coaxial to the axis of rotation (12), and a substantially annular compression chamber (14) coaxial to the axis of rotation (12), wherein the compression chamber (14) has an annular gas inlet (16) and a gas outlet (17). The impeller (3) is arranged for directing a gas mixture from the central gas inlet (13) of the housing (11) into the annular gas inlet (16) of the compression chamber (14). The annular compression chamber (14) is bounded by a circular outer wall (19). At least part of the circular outer wall (19) is uninterrupted by the gas outlet (17).

Description

Dynamic blower module

FIELD OF THE INVENTION

The invention relates to a blower module, in particular a centrifugal turbine. The invention further relates to a pressure and/or flow generator. The invention further relates to a medical ventilator. The invention further relates to a method of providing a pressure and/or flow. BACKGROUND OF THE INVENTION

Medical ventilators are designed to deliver pressure and flow towards a patient. Principally, such a device may be configured to deliver flow at a controlled pressure level, or up to a maximum set pressure level.

Known medical ventilators typically provide the ability to change the set pressure level, and increase or decrease the flow level accordingly.

Known medical ventilators typically include a blower unit comprising a brushless direct current (BLDC) electric motor that drives a radial fan, or impeller. The motor speed can be adapted to obtain a desired flow or pressure level at the output side of the blower unit. The pressure generated by a radial blower is mainly related to the centrifugal effect of the rotating gas or gas mixture.

US 6,960,854 B2 discloses a centrifugal turbine for breathing-aid devices. The turbine comprises a turbine rotor, a turbine stator, an electric motor member for driving the rotor in rotation relative to the stator. The turbine stator comprises a stator body defining a generally toric compression chamber. The compression chamber is open to the outside by means of a substantially cylindrical tangential duct whose longitudinal axis is horizontal, towards the mask of the user. The turbine rotor includes a plurality of blades integral with a shaft mounted coaxially rotating in the body of the turbine stator.

However, it is desirable to improve the responsiveness and/or efficiency of blower units. Moreover, it is desirable to provide a more compact design.

SUMMARY OF THE INVENTION

It would be desirable to provide an improved centrifugal turbine blower module. To address this need, a blower module is provided that comprises an impeller mounted within a stator housing on a rotatable shaft, the rotatable shaft defining an axis of rotation of the impeller,

the housing having a central gas inlet substantially coaxial to the axis of rotation, and a substantially annular compression chamber coaxial to the axis of rotation, wherein the compression chamber has an annular gas inlet and a gas outlet; wherein the impeller is arranged for directing a gas mixture from the central gas inlet of the housing into the annular gas inlet of the compression chamber;

wherein the annular compression chamber is bounded by a circular outer wall.

Because the outer wall is circular, the gas flow experiences less discontinuities, which improves the flow pattern inside the compression chamber with respect to the tangential velocity. The efficiency to generate pressure may be improved this way, by reducing losses. For example, in the centrifugal turbine of US 6,960,854 B2, the compression chamber is not circular near the cylindrical tangential duct, which causes the gas mixture to be directed into the cylindrical tangential duct towards the outlet, thereby reducing the pressure built up in the compression chamber through impulse losses and friction.

Other benefit of the circular outer wall is that the perimeter of the blower module may be minimized relative to the size of the impeller. This makes it possible to design a compact housing. Additionally the circular shape makes it easy to interface the blower module with an appropriate housing that conducts the gas towards the inlet of the blower and conducts the gas towards the outlet of a ventilator. Separation between the gas inlet and outlet can be achieved, for example, with a simple annular shaped gasket around the circumference of the blower module.

At least part of the compression chamber may be bounded by a surface that is substantially helicoidal with parabolic cross-sections towards the outlet. The compression chamber and its outlet may be arranged helicoidally parabolic to create an outlet diffusor with sufficient opening surface for the maximum outlet flow while the annular shape of the blower can be maintained.

At least part of the circular outer wall may be shaped in such a way that the circular shape is uninterrupted by the gas outlet. This further improves the flow and pressure properties of the blower module, because the flow is less disturbed by the shape of the gas outlet. The annular compression chamber may comprise an annular gas passage enabling at least part of the gas mixture to make a repeated circular motion within the annular compression chamber, by-passing the gas outlet. This way, at least part of the gas mixture in the annular compression chamber persists in the annular compression chamber and moves beyond the outlet, thus building up a pressure more efficiently. The circular motion of the gas mixture may define a circular trajectory through the annular compression chamber.

The annular gas passage may comprise an orifice to allow said at least part of the gas mixture to by-pass the gas outlet. This arrangement causes at least part of the gas mixture to enter the orifice instead of leaving the compression chamber via the outlet. For example, the gas outlet and the orifice may be arranged adjacent to each other.

The blower module may comprise a guiding element for guiding at least part of the gas mixture into the orifice. The guiding element increases the amount of the gas mixture that enters the orifice to continue the circular movement through the annular compression chamber. That guiding element may, for example, comprise a spoiler. Such a spoiler may be formed by an edge separating the gas outlet from the orifice.

The outlet may be disposed radially in between an inner wall and the outer wall. Consequently, the outlet does not protrude outside a cylinder generated by the circular shape of the outer wall. This further improves the aerodynamic properties of the blower module.

A distance from the inner wall to the outer wall in a radial direction may be substantially the same for all radial directions. This further improves the aerodynamic properties.

A size of the annular compression chamber in axial direction may increase in a tangential direction. That is, the size of the annular compression chamber measured in axial direction may be different for different tangential positions. When measuring the distance from a point to the outlet, along the direction of the flow, then the size may be smaller for a larger distance, and the size may be larger for a smaller distance to the outlet measured along the path that the gas would follow. This way, a natural widening of the annular compression chamber towards the gas outlet is realized, while it is still possible to maintain the circular shape of the circumference of the blower module, defined by the outer wall. The annular compression chamber may comprise a diffuser.

The diffuser may comprise a substantially helicoidal surface, wherein the helicoidal surface is arranged coaxial to the axis of rotation. The helicoidal surface may help to obtain the increase of the size of the annular compression chamber in axial direction along the tangential direction.

An intersection of the substantially helicoidal surface with a plane comprising the axis of rotation may be shaped substantially parabolic. Such a parabolic shape, is a good compromise, relative to a circular shape for conducting the helicoidal flow to the outlet.

A curve defined by tops of the parabolic intersections of at least part of the inner surface of a wall of the diffuser with different planes comprising the axis of rotation may form part of a helix.

The housing may be referred to hereinafter as the primary housing.

The blower module may further comprise a secondary housing that forms at least part of a secondary compression chamber coaxial to the axis of rotation, wherein the gas outlet diffuses the gas mixture into the secondary compression chamber. This way, it is not necessary to attach any tubing directly to the gas outlet.

The gas inlet and the secondary compression chamber may be disposed on opposite sides of the primary housing. This construction makes it easy to separate a low-pressure portion, around the inlet, from a high-pressure portion, formed by the secondary compression chamber on the other side of the primary housing.

The blower module may comprise an elastic ring extending around a

circumference of the primary housing, wherein the primary housing is arranged for being clamped inside the secondary housing and wherein the primary housing with the elastic ring provides a gas-tight closure of the secondary compression chamber. This is an advantageous construction. It may allow a more compact design. For example, the elastic ring comprises an elastic material with an inner surface and an outer surface opposite the inner surface, wherein the inner surface touches and grips the primary housing and the outer surface touches and grips the secondary housing.

The circumference of the primary housing may be circular. This allows a more compact design.

Another aspect of the invention provides a pressure generator comprising a blower module set forth. Another aspect of the invention provides a medical ventilator comprising a blower module set forth.

Another aspect of the invention provides a method of providing a pressure and/or flow by controlling a rotation of the impeller of a blower module set forth.

The person skilled in the art will understand that the features described above may be combined in any way deemed useful.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, aspects of the invention will be elucidated by means of examples, with reference to the drawings. The drawings are diagrammatic and may not be drawn to scale.

Fig. 1 A shows a bottom view or outlet view of a blower module.

Fig. IB, 1C, and ID show side views of the blower module.

Fig. 2A shows the top view or inlet view of the blower module, in perspective.

Fig. 2B shows the bottom view or outlet view of the blower module, in perspective.

Fig. 3 shows a cross sectional view of the blower module.

Fig. 4 shows an exploded view of the blower module.

Fig. 5 shows a worked open perspective view of a ventilator comprising the blower module.

Fig. 6 shows another worked open perspective view of the ventilator comprising the blower module.

Fig. 7 shows a sectional perspective view of another ventilator comprising a blower module.

DETAILED DESCRIPTION OF EMB ODFMENT S

Medical devices are arranged for delivering pressure and flow towards a connected patient. For example, a device may deliver flow at a controlled pressure level or up to a maximum set pressure level.

Modern ventilators are typically capable of fast transition of pressure levels with corresponding fast increasing or decreasing flow levels. Because pressure levels are maintained for a longer period than flow levels, and peak patient flow levels are only approximately 100 liters per minute, it may be advantageous to provide an efficient pressure source with moderate flow capabilities.

A ventilator may comprise a BLDC motor driven blower unit with a radial fan, defined as turbine, which can rapidly change motor speed to adapt to the momentarily set flow or pressure level. The pressure generated by a radial blower is mainly caused by the centrifugal effect of the rotating gas(mixture).

The ability to rapidly adapt the motor speed may be achieved by a lightweight rotor with a compact impeller. Lightweight may be obtained by using high strength plastic material that can be injection molded into an impeller with minimal thicknesses.

Reducing the diameter of the impeller dramatically increases responsiveness of the blower unit. Reducing the radius has also effect on the expected outlet pressure of the blower unit. Because the tangential velocity (V=co*r) is proportional to r, the resulting pressure will be proportional to r². Therefore reducing the radius reduces the pressure output. To achieve approximately the same tangential velocity, and

consequently also output pressure, the (motor) speed has to increase proportional to 1/r.

The centrifugal effect is the primary effect regarding pressure build up. This pressure build up is created by the centripetal acceleration of the gas mixture. This means that the gas mixture also has kinetic energy. In a system without losses this kinetic energy can be transferred partly into additional (static) pressure (according to Bernouilli's law). This is what typically happens in a diffuser in which the velocity of the gas flow is reduced. Partly the kinetic energy remains present in the gas flow leaving the blower-unit. This kinetic energy may cause losses, which result in temperature increase of the blower and patient-gas and vibration and noise. The losses are caused by basic friction of the gas moving tangentially and radially inside the blower housing and impulse losses and leakage flows inside the impeller or inside the housing.

Friction may generate additional pressure as well as the reduction of the velocity of the gas flow. But this pressure contribution is at the cost of high power consumption and it also leads in the case of medical blowers to unwanted pressure characteristics.

Other important considerations may include simplicity of the design and manufacturability relative to the performance. And the awareness that the blower unit is designed to be part of an as small as possible assembly, also to reduce noise and vibration. The blower unit may further provide appropriate interfacing to the ventilator. For example, mixing of oxygen and air may take place inside the blower unit.

The design of the impeller may be adapted to have a solid base with a plurality of blades protruding therefrom. The blades may be bent backwards in respect of the direction of rotation. The outer diameter may be designed taking into account the desired maximum motor speed and outlet pressure range.

The impeller may have a conical shape because this may cause less impulse losses at the entry of the impeller and the gas flow may be ejected into the primary blower housing under an inclination angle which may better fit the geometry of the primary blower housing.

Traditionally, the housing of a radial blower has a tangential outlet with a long gradually widening diffuser. This construction reduces flow-resistance and maintains pressure at higher flows because it transfers kinetic energy into pressure. However this construction is less efficient to generate pressure at low outlet flows because of the discontinuities in the circumference of the impeller. It is also space consuming and interfacing to other components may be complicated if noise and vibration measures are needed.

The primary blower housing disclosed herein may be better adapted to an enveloping housing, or secondary housing, of the blower-module. The housing may be made circular, making it compact and easy to attach into a secondary housing. The patient gas outlet diffuser may be integrated into the lower part of the primary housing. To make the lower part circular, and to provide a minimal outlet surface area for the diffuser, the diffuser may have a parabolic shape with a steadily increasing distance between the vertex and the focus of the parabola. The inclination angle of the impeller may help to direct the flow towards the lower part of the primary blower.

The secondary housing may comprise a casing in which the primary blower unit may be flexibly mounted to reduce structural noise. Because the primary blower unit is circular, circular silicon grommets can be used.

The secondary housing may comprise an inlet cover with integrated labyrinth structure and appropriate damping foam for noise cancelling. This cover may interface with an inlet filter housing or device housing. The inlet cover may be inserted into the secondary housing until the blower grommet is firmly clamped. The inlet cover can be fixed inside the secondary housing by adding for example screws. The secondary housing may enclose a volume that is used for mixing oxygen and air. Therefore interfacing to an oxygen dosage unit has to be provided. Interfaces for sensors or sensor elements may be integrated into the secondary housing as well as an interface for a pressure regulating unit.

Figs. 1 through 4 show different views of a blower module. Fig. 5 shows a ventilator that comprises the blower module. The drawings are diagrammatic and may not be drawn to scale. Moreover, what is shown in the drawings only presents an exemplary embodiment of the invented concepts. It will be apparent to the skilled person that modifications of this embodiment are within the spirit and scope of the invention as defined by the appended claims and their equivalents. Throughout the drawings, similar items have been marked with the same reference numerals.

Typically, as can be seen for example in the exploded view of Fig. 4, the blower module may comprise a motor 5 that is arranged for driving a rotatable shaft 7. An impeller 3 may be attached to the rotatable shaft 7 driven by the motor 5. The motor 5 may be an electric motor, for example a brushless direct current (BLDC) electric motor. However, other kinds of motor may also be used. The blower module may further comprise a housing. In the exploded view of Fig. 4, the blower housing comprises two housing parts 1 and 4. During the assembly stage these two housing parts 1 and 4 are joined together, for example using screws and the holes 9 and 10, to form a housing 11 (see e.g. Fig. 2A and 2B). The rotatable shaft 7 extends through a hole 8 in housing part 4 and is fixed to the impeller 3. The impeller is located inside the housing, in between the two housing parts 1 and 4. A ring 2, such as a grommet, for example a flexible grommet, or a flexible ring, may be arranged around the

circumference of the two housing parts 1 and 4. For example, the grommet or ring 2 may be clamped in between the two housing parts 1 and 4. For example, a groove may be foreseen in the housing parts 1 and 4 that engages with an edge of the grommet or ring 2. Other ways of arranging the grommet or ring may also be used. Another ring 6, for example a flexible ring, may be arranged around the motor 5. The ring 6 may assist in affixing the blower module inside a ventilator. When the ring 6 and/or the grommet or ring 2 is made of a flexible material, this helps to reduce vibrations and/or noise produced by the ventilator. Generally, the housing 11 is a stator, whereas the rotatable shaft 7 and the impeller 3 are rotors. The rotation of the shaft 7 and the impeller 3 defines an axis of rotation 12 (as indicated in Fig. 1 A and 1C). The housing has a gas inlet 13, which may be referred to hereinafter as central gas inlet. This central gas inlet may comprise an opening in the housing 11, in particular the housing part 1. As shown in the drawing, the opening may be a circular opening. The central gas inlet may be arranged coaxial to the axis of rotation 12. The housing 11 further defines a compression chamber 14 (as indicated in Fig. 3). The compression chamber 14 may also be referred to as primary compression chamber 14. The compression chamber 14 is substantially annular and arranged around the impeller 3, substantially coaxial to the axis of rotation 12. The compression chamber 14 has an annular gas inlet 16 generally around the impeller 3. The impeller 3 is disposed generally in a gas passage 15 defined by the housing 11 and extending from the central gas inlet 13 to the annular gas inlet 16. The impeller 3 is arranged for driving a gas mixture from the central gas inlet 13 through the gas passage 15 and through the annular gas inlet 16 into the annular compression chamber 14. The compression chamber has a gas outlet 17. The impeller 3 causes a circular motion of the gas mixture inside the compression chamber 14, generally in the direction of the arrow 25 in Fig. 1A.

The annular compression chamber 14 has an inner wall 18 and an outer wall 19. These walls at least partly define the interior space of the annular compression chamber 14. The inner wall 18 is the wall of the compression chamber 14 on the side of the annular gas inlet 16. The outer wall 19 may be described as the wall of the compression chamber 14 facing the annular gas inlet 16. Another way to describe the outer wall 19 is the wall defining the maximum diameter of the compression chamber 14. The outer wall 19 may be a circular wall. A large part of this circular wall 19 is visible in Fig. 1 A. Fig. 3 shows the outer wall 19 near the gas outlet 17. It can be seen at numeral 19a how a part of the circular outer wall 19 continues beyond the gas outlet 17.

The outer wall 19 of the annular compression chamber 14 is also circular at the gas outlet 17. That is, the gas outlet 17 does not extend beyond the circular shape defined by the outer wall 19. Moreover, at least part of the circular outer wall 19 is uninterrupted by the gas outlet. This part is marked with reference numeral 19a in Fig. 3.

As shown in Fig. 1 A, the annular compression chamber 14 has a first portion 21 before the gas outlet 17 and a second portion 22 after the gas outlet, as viewed in the direction of the flow. The annular compression chamber 14 comprises a gas passage 20, as shown in Fig. 3, that fluidly connects the first portion with the second portion, bypassing the gas outlet 17. This gas passage enables at least part of the gas mixture circulating in the annular compression chamber 14 to make a repeated circular motion through the annular compression chamber 14, by-passing the gas outlet 17.

The gas passage 20 may comprise an orifice 23 to allow the at least part of the gas mixture to by-pass the gas outlet. This orifice may be oriented generally orthogonal to the direction of the gas flow.

The blower module may comprise a guiding element 24 for guiding at least part of the gas mixture into the orifice. The aim of this guiding element is to cause a better recirculation of the gas flow inside the compression chamber, in particular when there is a low to moderate amount of flow leaving the compression chamber 14 through the gas outlet 17. This guiding element may have the form of a spoiler, as shown in the Figures.

The gas outlet 17 is arranged in between the inner wall 18 and the outer wall 19. This way the circular circumference of the compression chamber is maintained. The outlet may be arranged radially, i.e. it may be arranged perpendicular to the tangential direction of the gas flow, allowing the gas to easily flow out of the compression chamber 14. Other arrangements are also possible, however. For example, the outlet may be oriented oblique with respect to the direction of the gas flow.

A distance from the inner wall 18 to the outer wall 19 in a radial direction is substantially the same for all radial directions. Herein, radial direction means perpendicular to the axis of rotation 12. However, this distance may also be increasing along the flow direction 25. The size of the annular compression chamber measured in an axial direction increases in a tangential direction.

It is noted that the annular compression chamber 14 may have the functionality of a diffuser.

The compression chamber 14, or the diffuser, comprises a substantially helicoidal surface, wherein the helicoidal surface is arranged coaxial to the axis of rotation. In particular, the portion of the wall 18,19 of the compression chamber 14 that is defined by the portion 4 of the housing 11 has a generally helicoidal shape. The intersection of the substantially helicoidal surface with a plane comprising the axis of rotation 12 is substantially parabolic. However, other arrangements are also possible. The parabolic intersection has a top 27. The "tops" of the parabolic intersections with different planes comprising the axis of rotation define a curve. This curve has a shape of a helix. However, other configurations may also be made by the person skilled in the art.

Fig. 5 shows a perspective view of a ventilator 50 comprising the blower module 28 of Figs. 1-4. The housing 11 of the blower module 28 acts as a primary blower housing. The ventilator 50 further comprises a secondary housing 51. The secondary housing 51 may comprise, as shown in the drawing, a plurality of joined portions 52 and 53. These portions 52 and 53 define an inner space 54. In Fig. 5, portion 53 is drawn only in part, so that part of the inner space 54 becomes visible.

Fig. 6 shows another perspective view of the ventilator 50. Portion 53 has been omitted in Fig. 6 to make more of the inner space 54 visible in the drawing.

The primary blower housing is disposed inside the inner space 54. On the diffuser side of the primary blower housing 28, the wall of the secondary housing 51 and the wall portion 4 of the primary blower housing 28 define a secondary

compression chamber 55. This secondary compression chamber 55 may be at least in part coaxial to the axis of rotation 12. The gas outlet 17 diffuses the gas mixture into the secondary compression chamber 55.

Other configurations of the primary blower housing 28 are also possible. For example, another embodiment of a secondary housing could be constructed that is arranged for being attached to the primary blower housing 28, with an opening covering at least the gas outlet 17, such that the gas outlet 17 diffuses the gas mixture into a secondary compression chamber defined by the secondary blower housing.

As shown in Figs. 5 and 6, the construction may be made such that the gas inlet 13 and the secondary compression chamber 55 are disposed on opposite sides of the primary housing 11 of the blower module 28. As shown, the blower module 28 may comprise a ring 2, for example an elastic ring, that is positioned around a circumference of the primary housing 11. The primary housing 11, the elastic ring 2, and the secondary housing 51 may be shaped such that the primary housing 11 is or can be clamped inside the secondary housing 51, with the elastic ring 2 in between the primary blower housing 11 and the secondary housing 51. This way, the elastic ring 2 provides a gas-tight closure that prevents leakage of gases by closing any space in between the primary housing 28 and the secondary housing 51. In the embodiment shown, the circumference of the primary housing 11 and the elastic ring are circular. This allows a compact design, because the primary compression chamber is annular. Moreover, another ring 6 has been provided around the motor 5. This ring 6 may also be a flexible ring. The motor may be clamped within the secondary housing 51 with the ring 6 in between. Either or both of the elastic rings 2 and 6 comprises an elastic material with an inner surface and an outer surface opposite the inner surface, wherein the inner surface touches the blower module and the outer surface touches the secondary housing. This configuration does not allow the blower module 28 to move much within the secondary blower housing 51. Consequently, less energy may be wasted and/or the construction may be made more rigid. The inner surface of either or both of the elastic rings 2 and 6 may be shaped to grip the primary housing and the outer surface may be shaped to touch and grip the secondary housing. This may be arranged by providing a protruding edge in the elastic ring that fits into a corresponding groove in the blower module or secondary housing, respectively. Other ways providing sufficient fixation of the blower module within the secondary blower housing by means of an elastic ring will be apparent to the person skilled in the art. It is also possible to omit either or both of the flexible rings 2 and 6, wherein the primary blower housing 28 and/or the motor 5 are clamped directly within the secondary blower housing 51.

The secondary compression chamber 55 may have a gas outlet 56, as shown in Fig. 5. The gas outlet shown in Fig. 5 protrudes from the secondary blower housing 51 and the secondary compression chamber 55 in a direction parallel to the axis of rotation of the impeller 3. However, this is not a limitation. The gas outlet 56 of the secondary compression chamber may also protrude in a direction away from the axis of rotation, or may not protrude at all from the secondary compression chamber. The construction of the blower may be such, that it is not necessary to provide a gas outlet that protrudes tangentially from the secondary compression chamber with respect to the axis of rotation of the impeller. In the examples shown in Figs. 5 to 8, the gas outlet 17 of the primary compression chamber does not protrude tangentially from the primary compression chamber. Moreover, in the examples shown in Figs. 5 to 8, the gas outlet 56 of the secondary compression chamber 55 does not protrude in tangential direction from the secondary compression chamber. However, this is not a limitation. This way, the blower may be relatively compact. Fig. 7 shows a section view of another embodiment of a ventilator 70. In this embodiment, the primary blower housing 11 is attached to the secondary blower housing 73 with a flexible grommet 71. Also, the motor 5 is attached to the secondary blower housing 51 with another flexible grommet 72. Because the blower module is not clamped inside the secondary housing but is suspended on the flexible grommets 71 and 72, the blower module 28 is arranged movably within the secondary blower housing 73. The ventilator 70 also has a means 74 for mixing an additive fluid, such as oxygen, to the incoming gas mixture. Also shown is a unit 75 for providing power supply, control means and the like. Similar means 74 and unit 75 may also be built into the embodiment shown in Figs. 5 and 6.

The ventilator 50 may be, for example, a medical ventilator. The ventilator 50 may also be used as a pressure generator. The skilled person is capable of adding the features to the shown ventilator that may be used in or with a medical ventilator, such as a pressure and/or flow sensor, tubing, mouth piece, user interface elements, power source, oxygen supply, and means for mixing the gas mixture with additional oxygen, if needed.

In use, a control unit 75 may send signals to the motor 5 to control the rotation and rotation speed of the impeller 3 mounted on the rotatable motor shaft 7. A gas mixture, such as ambient air or a gas mixture from e.g. a gas tank (not shown), enters the ventilator 50 or 70 through an inlet 57 of the secondary blower housing 51 and the inlet 13 of the primary blower housing 11, where the gas mixture comes in contact with the impeller blades 29 that direct the gas mixture towards and through the annular inlet 16 of the annular primary compression chamber 14 by means of a centrifugal force. Inside the annular compression chamber 14, the gas mixture circulates; part of the gas mixture passes the gas outlet 17 of the primary compression chamber and is guided by a guiding element 24, such as a spoiler, through an orifice 23 into a gas passage 20 that is a continuation of the annular compression chamber 14. This way part of the gas mixture makes a circular motion of more than 360 degrees inside the annular compression chamber 14. Another part of the gas mixture leaves the annular compression chamber 14 through gas outlet 17 and enters the secondary compression chamber 55. Here an additive gas or additive gas mixture may be added as needed using a means 74. However this may also be done at another stage of the gas flow. Finally, the gas mixture (with optional additive) leaves the secondary compression chamber through a gas outlet 56 of the secondary compression chamber 55. For example, tubing may be connected to the gas outlet 56. To this end, the gas outlet 56 may have the form of an appropriate connector.

The examples and embodiments described herein serve to illustrate rather than limit the invention. The person skilled in the art will be able to design alternative embodiments without departing from the scope of the claims. Reference signs placed in parentheses in the claims shall not be interpreted to limit the scope of the claims. Items described as separate entities in the claims or the description may be implemented as a single item combining the features of the items described.

Claims

CLAIMS:

1. A blower module, comprising

an impeller (3) mounted within a stator housing (11) on a rotatable shaft (7), the rotatable shaft (7) defining an axis of rotation of the impeller (3),

the housing (11) having a central gas inlet (13) substantially coaxial to the axis of rotation (12), and a substantially annular compression chamber (14) coaxial to the axis of rotation (12), wherein the compression chamber (14) has an annular gas inlet (16) and a gas outlet (17), wherein a height of the annular compression chamber in an axial direction (12) increases in a tangential direction (25) towards the outlet (17);

wherein the impeller (3) is arranged for directing a gas mixture from the central gas inlet (13) of the housing into the annular gas inlet (16) of the compression chamber (14);

wherein the annular compression chamber (14) has an inner wall (18) and is bounded by a circular outer wall, wherein the outlet (17) is arranged radially in between the inner wall (18) and the circular outer wall (19).

2. The blower module according to claim 1, wherein the gas outlet (17) does not extend beyond the circular shape defined by the outer wall (19).

3. The blower module according to claim 1, wherein at least part of the circular outer wall (19a) is uninterrupted by the gas outlet (17).

4. The blower module according to claim 1, wherein the annular compression chamber (14) comprises a gas passage (20) enabling at least part of the gas mixture to make a repeated circular motion within the annular compression chamber (14), by-passing the gas outlet (17).

5. The blower module according to claim 4, wherein the gas passage (20)

comprises an orifice (23) to allow at least part of the gas mixture to by-pass the gas outlet (17).

6. The blower module according to claim 5, further comprising a guiding element (24) for guiding at least part of the gas mixture into the orifice (23).

7. The blower module according to claim 1, wherein a distance from the inner wall (18) to the outer wall (19) in a radial direction is substantially the same for all radial directions.

8. The blower module according to claim 1, wherein the annular compression chamber (14) comprises a diffuser.

9. The blower module according to claim 8, wherein the diffuser comprises a

substantially helicoidal surface (4), wherein the helicoidal surface is arranged coaxial to the axis of rotation (12).

10. The blower module according to claim 9, wherein an intersection of the

substantially helicoidal surface (4) with a plane comprising the axis of rotation (12) is substantially parabolic.

11. The blower module according to claim 8 or 10, wherein a curve defined by tops (27) of the intersections of at least part of an inside surface of a wall (18, 19) of the diffuser with different planes comprising the axis of rotation (12) forms part of a helix.

12. The blower module according to claim 1, the housing (11) being referred to hereinafter as the primary housing (11), and further comprising a secondary housing (51) that forms at least part of a secondary compression chamber (55), wherein the gas outlet (17) is arranged for diffusing the gas mixture into the secondary compression chamber (55).

13. The blower module according to claim 12, wherein the gas inlet (13) and the secondary compression chamber (55) are disposed on opposite sides of the primary housing (11).

14. The blower module according to claim 13, comprising an elastic ring (2) extending around a circumference of the primary housing (11), wherein the primary housing (11) is arranged for being clamped inside the secondary housing (51) and wherein the elastic ring (2) prevents leakage of gases from the secondary compression chamber (55).

15. The blower module according to claim 12, wherein the secondary compression chamber (55) comprises a gas outlet (56) that does not protrude tangentially from the secondary compression chamber with respect to the axis of rotation (12).

16. The blower module according to claim 12, wherein the secondary compression chamber (55) comprises a gas outlet (56) that protrudes substantially in perpendicular or parallel direction from the secondary compression chamber with respect to the axis of rotation (12).

17. The blower module according to claim 1 or 14, wherein a circumference of the primary housing (11) is circular.

18. A pressure generator comprising the blower module according to any one of the preceding claims.

19. A medical ventilator comprising the blower module according to any one of claims 1 to 16.

20. A method of providing a pressure and/or flow by controlling a rotation of the impeller (3) of a blower module according to any one of claims 1 to 19.