Compact low noise efficient blower for cpap devices

FIELD OF THE INVENTION

0001The invention relates to an efficient, low-noise, compact blower. The blower may be used in a range of devices including medical, cleaning, automotive or computer devices. The blower may also be used as an extractor or suction device. In an embodiment, the blower may be used in a non-invasive ventilation (NIVV) device such as a CPAP or ventilator device.

BACKGROUND OF THE INVENTION

Nasal CPAP treatment of OSA

0002Nasal Continuous Positive Airway Pressure (CPAP) treatment of Obstructive Sleep Apnea (OSA) was invented by Sullivan. See <patcit id="pcit0001" dnum="US4944310A"><text>U.S. Patent No. 4,944,310</text></patcit>. Apparatus for treating OSA typically comprises a blower that provides a supply of air or breathable gas to a patient interface, such as a mask, via an air delivery conduit. Since patients typically sleep while wearing the device, it is desirable to have a system which is quiet and comfortable.

Generic blower/air pump

0003Blowers are typically classified as centrifugal, axial or mixed flow. Generally, blowers comprise two main parts: a rotating part, namely an impeller and shaft; and a stationary part that defines a fluid flow path, typically a chamber such as a volute. Rotation of the impeller imparts kinetic energy to the air. The stationary part redirects the air expelled from the impeller into an enclosed outlet passage. During this redirection, resistance is encountered to flow because of the pressure generated by downstream resistance or a downstream pressure source. As the flow is slowed against this resistance, a portion of the kinetic energy is converted to potential energy in the form of pressure.

0004Generally, the faster the impeller is rotated, the higher the pressure that will be developed. A less effective blower must rotate its impeller faster to generate the same pressure as a more effective blower. Generally, running a given blower slower makes it quieter and prolongs its life. Hence, it is generally desirable to make blowers more effective at generating a supply of air at positive pressure.

0005With reference to <figref idref="f0001">Fig. 1</figref> and <figref idref="f0002">2</figref>, three directions are defined, i.e., radial R, tangential T and axial A. Prior art centrifugal blower 10 includes an outlet 20, an inlet 30, an electric motor 40, an impeller 50 and a shaft 60. Arrows 70 indicate the general direction of airflow. Air enters the blower at the inlet 30 and is accelerated by the rotating impeller. The rotation imparted by the impeller generally directs the airflow in a tangential direction T. The volute then constrains the airflow to spiral the volute. The airflow then exits the blower in a generally tangential direction T via the outlet 20.

0006In some blowers, such as axially developed volute blowers, the volute geometry directs the tangential spiraling airflow in a slight axial direction A prior to exiting the blower in a generally tangential direction T.

0007The performance of a blower is often described using fan curves, which show the flow rate of air versus outlet pressure of air. Many factors affect the fan curve including impeller diameter and the number and shape of the impeller blades. The design process is a complex balance between competing priorities such as desired pressure, flow rate, size, reliability, manufacturability and noise. While many combinations of size, shape and configuration of components may produce a flow of pressurized air, such a result may be far from optimal, or be impractical.

ResMed Axial volute design

0008Another form of known blower design is described in ResMed's International Patent Application <patcit id="pcit0002" dnum="AU9900444W" dnum-type="L"><text>PCT/AU99/00444</text></patcit>, published as <patcit id="pcit0003" dnum="WO9964747A"><text>WO 99/64747</text></patcit>, . As described in this patent application, the volute geometry develops in a generally axial direction, however air exits this blower in a generally tangential direction.

Respironics Ventilator

0009Respironics International Patent Application <patcit id="pcit0004" dnum="US9819635W" dnum-type="L"><text>PCT US98/19635</text></patcit>, published as <patcit id="pcit0005" dnum="WO9913932A"><text>WO 99/13932</text></patcit>, describes a medical ventilator which has a blower assembly that preferably includes three rotating impellers and two stationary stators. In this device, a conventional volute design is used such that air exits the blower assembly in a generally tangential direction.

0010A disadvantage of this blower design is it tends to suffer from blade pass tonal noise emission.

Respironics REMstar

0011Another known blower is found in the Respironics REMstar series of CPAP devices. In this device, air exits the blower in a generally tangential direction.

ResMed blowers

0012<patcit id="pcit0006" dnum="US6910483B"><text>U.S. Patent No. 6,910,483 (Daly et al</text></patcit>) assigned to ResMed Limited describes a double ended variable speed blower for Continuous Positive Airway Pressure (CPAP) ventilation of patients that includes two impellers in the gas flow path that cooperatively pressurize gas to desired pressure and flow characteristics. In this device, air exits the blower in a generally tangential direction.

0013PCT Application Nos. <patcit id="pcit0007" dnum="AU2006001617W" dnum-type="L"><text>PCT/AU2006/001617, filed October 27, 2006</text></patcit>, and <patcit id="pcit0008" dnum="AU2006001616W" dnum-type="L"><text>PCT/AU2006/001616, filed October 27, 2006</text></patcit>, describe multiple stage blowers.

0014As noted above, known CPAP and VPAP blowers use a more or less conventional volute design, namely one where the air leaves the volute tangentially. These designs have the disadvantage that the asymmetry of the volute leads to asymmetry of flow patterns in the volute and impeller. This problem is especially significant at flow rates away from the ideal "design" flow rates of the volute. CPAPs and VPAPs, unfortunately, are used for a substantial portion of their operational time under non-ideal flow conditions as a consequence of very high excursions in the flow demand. This means that the flow patterns within the volute, and consequently within the impeller, become highly asymmetrical, uneven, and even unstable. This in turn leads to pressure pulses and turbulence. As a consequence, acoustic blade pass tonal noise and turbulence noise are produced.

0015<patcit id="pcit0009" dnum="WO2004108198A1"><text>WO 2004/108198 A1</text></patcit> relates to a multiple stage variable speed blower for Continuous Positive Airway Pressure (CPAP) ventilation of patients which include two impellers in the gas flow path that cooperatively pressurize gas to desired pressure and flow characteristics.

0016<patcit id="pcit0010" dnum="JPH0893683A"><text>JP H 0893683 A</text></patcit> relates to a motor-driven centrifugal blower.

0017<patcit id="pcit0011" dnum="JPS53112805U"><text>JP S 53112805 U</text></patcit> discloses a two-stage blower.

SUMMARY OF THE INVENTION

0018The invention is set out in the appended set of claims.

0019A first aspect of the invention is directed to a respiratory device that quietly and effectively provides a supply of air at positive pressure. Another aspect of the invention is to provide a blower for a NIVV device for use in treatment of a range of respiratory diseases. Another aspect of the invention is to achieve a large pressure delivery for a given motor speed. Another aspect of the invention is a blower that can supply a given pressure at a relatively low motor speed and with a fast response time. Another aspect of the invention is a blower that has reduced blade pass tonal noise emission and/or turbulence noise emission.

0020In one form of the invention suitable for respiratory devices, the blower is configured to provide air pressurized in the range of 2 cm H₂O to 100 cm H₂O. In another form suitable for treatment of Sleep Disordered Breathing, the blower is configured to provide pressure in the range of 2 cm H₂O to 30 cm H₂O.

0021In one form, the blower is configured to provide air at flow rates up to 200 L/min. In one form, the blower is configured to provide air at flow rates ranging -50 L/min to +200 L/min.

0022In one form of the invention suitable for respiratory devices, the blower comprises at least one impeller having a relatively small diameter, for example in the range of 20 to 200 mm. In an embodiment, the impeller comprises two differently sized shrouds to provide a rigid impeller with relatively low inertia. The impeller may be injection molded from plastic such as polycarbonate or polypropylene.

0023An aspect of the invention is that the stationary portion of the blower defines an airflow path that is quiet and efficient. In an embodiment, the stationary portion defines an airflow path that is substantially axially symmetrical.

0024An aspect of the present invention has a stationary portion or volute design that is substantially axially symmetric on all stages. So no matter what the flow rate, the air feed pattern through the impeller blade passages, and in the volute, remains symmetrical and steady. This leads to lower strength pressure pulses and less turbulence, which in turn lead to lower levels of acoustic blade pass tone, and lower levels of turbulence noise.

0025In other forms of the invention, the blower has more than one stage. In forms of the invention where multiple stages are used along an axis, the motor may be positioned in the center and similar numbers of impellers may be positioned on either side of the motor along the axis.

0026In an embodiment, the stationary component of the blower includes a vane structure that receives airflow from an impeller and directs it in a radial direction. In an embodiment, the blower includes a shield positioned between an impeller and a vane structure to direct airflow to the stator inlet vanes in an orientation favorable to minimize losses and turbulence. In an embodiment, the airflow is directed in an axial direction between the impeller and vane structure. In an embodiment, the shield also presents a barrier between the impeller blades and the stator vane leading edges such that impeller blade pressure pulses are substantially isolated from the stator vanes.

0027Another aspect of the invention relates to a blower for supplying air at positive pressure including a stationary portion including an inlet and an outlet, a rotating portion provided to the stationary portion, and a motor adapted to drive the rotating portion. The inlet and outlet are co-axially aligned along an axis of the stationary portion such that air enters and exits the stationary portion in a generally axial direction.

0028Another aspect of the disclosure relates to a method for supplying air at positive pressure to a patient for treatment including providing air to a blower via an inlet that is axially aligned with an axis of the blower, directing the air through one or more stages of the blower, and supplying the air at positive pressure via an outlet that is axially aligned with the inlet.

0029Another aspect of the invention relates to a blower for supplying air at positive pressure including a stationary portion including an inlet and an outlet, a rotating portion provided to the stationary portion, and a motor adapted to drive the rotating portion. The stationary portion includes a shield to isolate stator vanes of the stationary portion from impeller blades of the rotating portion. The shield includes a tube portion having an interior surface and an exterior surface. The interior surface is adapted to support a bearing of the rotating portion and the exterior surface is adapted to support a stator assembly of the motor.

0030Other aspects, features, and advantages of this invention will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

0031The accompanying drawings facilitate an understanding of the various embodiments of this invention. In such drawings: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> shows a plan view of a generic prior art blower assembly;</li><li><figref idref="f0002">Fig. 2</figref> shows an elevation view of the generic prior art blower assembly shown in <figref idref="f0001">Fig. 1</figref>;</li><li><figref idref="f0003 f0004 f0005">Figs. 3a to 3g</figref> show various views of a blower ;</li><li><figref idref="f0006 f0007 f0008">Figs. 4a to 4c</figref> show various exploded views of the blower shown in <figref idref="f0003 f0004 f0005">Figs. 3a-3g</figref>;</li><li><figref idref="f0009 f0010 f0011 f0012">Figs. 5a to 5g</figref> show various views of the blower shown in <figref idref="f0003 f0004 f0005">Figs. 3a-3g</figref>;</li><li><figref idref="f0013 f0014">Figs. 6a to 6g</figref> show various views of an impeller ;</li><li><figref idref="f0015">Figs. 7a to 7d</figref> show various views of a stator component ;</li><li><figref idref="f0016">Figs. 8a to 8c</figref> show various views of a shield ;</li><li><figref idref="f0017">Fig. 9</figref> shows a two-shrouded impeller ;</li><li><figref idref="f0017">Figs. 10a to 10b</figref> show various views of an alternative stator component ;</li><li><figref idref="f0018 f0019 f0020">Figs. 11-14</figref> show various views of a blower ;</li><li><figref idref="f0021">Fig. 15</figref> is an exploded view of the blower shown in <figref idref="f0018 f0019 f0020">Figs. 11-14</figref>;</li><li><figref idref="f0022">Fig. 16</figref> is a cross-section view of the blower shown in <figref idref="f0018 f0019 f0020">Figs. 11-14</figref>;</li><li><figref idref="f0023">Fig. 17</figref> is a cross-sectional view illustrating a support system for a blower ;</li><li><figref idref="f0024">Fig. 18</figref> is a cross-sectional view of a blower ; and</li><li><figref idref="f0025">Fig. 19</figref> is a cross-sectional view of a blower according to another embodiment of the present invention.</li></ul>

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

0032Aspects of the invention will be described herein in its application to non-invasive ventilation (NIVV) treatment apparatus (e.g., positive airway pressure (PAP) devices or flow generators), such as CPAP, mechanical ventilation and assisted respiration, but it is to be understood that the features of the invention will have application to other fields of application where blowers are used, such as vacuum cleaners, cooling equipment in computers and HVAC devices such as those found in buildings and vehicles.

0033In this specification, the words "air pump" and "blower" may be used interchangeably. In this specification, the phrase "stationary part" will be taken to include "volute". The term "air" will be taken to include breathable gases, for example air with supplemental oxygen. It is also acknowledged that the blowers described herein may be designed to pump fluids other than air.

0034In this specification, the word "comprising" is to be understood in its "open" sense, that is, in the sense of "including", and thus not limited to its "closed" sense, that is the sense of "consisting only of". A corresponding meaning is to be attributed to the corresponding words "comprise", "comprised" and "comprises" where they appear.

0035While particular embodiments of this invention have been described, it will be evident to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential characteristics thereof. The present embodiments and examples are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing examples or description, and all changes which come . within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. It will further be understood that any reference herein to known prior art does not, unless the contrary indication appears, constitute an admission that such prior art is commonly known by those skilled in the art to which aspects of the invention relate.

1. General Description

0036A blower 100 according to an embodiment of the invention may be in the form of a centrifugal air pump comprising a stationary portion, a rotating portion and an electric motor.

0037In an exemplary embodiment as shown in <figref idref="f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012">Figs. 3a-5g</figref>, the stationary portion includes an external housing 170 in two parts 172, 174 and an assembly of internal flow directing components including three sets of stator components 180, 182, 184 and two shields 190, 192. The rotating portion comprises three impellers 150, 152, 154 and a shaft 160 adapted to be driven by electric motor 140. In an embodiment, the electric motor 140 may be a brushless D.C. motor. In the illustrated embodiment, the blower has three stages each with a corresponding impeller and set of stationary vanes and shields. As shown in <figref idref="f0003 f0004 f0005">Figs. 3a-3g</figref> and <figref idref="f0006">4a</figref>, the blower 100 is generally cylindrical and has an inlet 130 at one end and an outlet 120 at the other end.

0038In the illustrated embodiment, all the components of the blower are aligned along the shaft of the motor which defines an axis about which all components are generally symmetric. In an embodiment, the blower may be self similar sector-wise about its axis. This axial symmetry may apply to all stages.

0039An advantage of the blower according to an embodiment of the present invention is that it promotes symmetrical and stable flow patterns within the volute over the range of pressures and flow rates encountered during use. Thus, blade pass tone and turbulence noise emissions are reduced.

0040An advantage of the illustrated embodiment is the ease of manufacture and of assembly offered by the component geometry, particularly if injection molded, and by the stacked nature of the assembly.

2. Fluid flow path

2.1 First stage

0041The first stage of the blower will now be described. As best shown in <figref idref="f0006 f0007 f0008">Figs. 4a-4c</figref> and <figref idref="f0009 f0010 f0011 f0012">5a-5g</figref>, air enters the blower 100 at the inlet 130 and passes into the first rotating impeller 150 where it is accelerated tangentially and directed radially outward. It then passes around the sides of the motor 140 flowing in a spiral manner with a large tangential velocity component and also an axial component towards the first set of stator vanes 185 in stator component 180. In this embodiment, no shield is provided for the first stage since the shielding function is provided by the motor case. At the first set of stator vanes 185, air is directed radially inwardly towards orifice 181, and thereafter onto the second stage.

2.2 Second stage

0042In the second stage, as shown in <figref idref="f0006 f0007 f0008">Figs. 4a-4c</figref> and <figref idref="f0009 f0010 f0011 f0012">5a-5g</figref>, air is first accelerated tangentially by second rotating impeller 152 and also flows outwardly in a radial direction. Air then flows in a spiral manner with a large tangential velocity component and also an axial component passing through the gap 164 defined by the outer edge of circular disc 190 and the inner surface of the stator component 182. Air then enters the second set of stator vanes 187 formed in stator component 182 and is directed radially inwardly towards orifice 183, and thereafter onto the third stage.

2.3 Third stage

0043The fluid flow path in the third stage is similar to the fluid flow path in the second stage. As shown in <figref idref="f0006 f0007 f0008">Figs. 4a-4c</figref> and <figref idref="f0009 f0010 f0011 f0012">5a-5g</figref>, air enters the stage via orifice 183 and is accelerated tangentially and also directed outwardly in a radial direction by third rotating impeller 154. Air then flows in a spiral manner with a large tangential component and also an axial component passing through the gap 166 defined by the outer edge of circular disc 192 and the inner edge of the housing 174. The air then is directed by stator vanes 184 formed in the housing 174 towards the outlet 120.

3. Stationary portion

3.1 General

0044The stationary portion of the blower includes the two external housing parts 172, 174, the internal flow directing stator components 180, 182, 184 and two shields 190, 192 and may be made from any suitable rigid or semi-rigid material that is dimensionally stable. In an embodiment, the stator component may be made from material that provides one or more of the following characteristics: good thermal conductivity; relatively low cost; low density; acoustic dampening properties; and ease of molding to reduce post machining. The use of thermally conductive material may also assist in keeping the motor cool and warming the air. The ability to heat the air may provide an additional advantage for blowers used in NIVV devices.

0045In an embodiment, at least some of the components of the stationary portion may be made from aluminum, or an alloy thereof, e.g., aluminum die castings.In another embodiment, at least some of the components of the stationary portion may be made from magnesium, or an alloy thereof. In yet another embodiment, at least some of the components of the stationary portion may be made from a plastic material.

3.2 Inlet

0046The air inlet 130 is adapted to allow sufficient airflow into the blower to ensure desired flow requirements are met while not allowing excessive noise emission back out of the air inlet 130. Also, the dimensions of the air inlet 130 are dependent upon the desired level of flow required by the blower and the particular application of use. In a NIVV embodiment, the air inlet 130 may have a diameter between 2 mm and 100 mm, e.g., between 15 mm and 20 mm.

3.3 Stator components

0047The stator components including stator vanes are structured to promote a smooth transition in flow direction. In an embodiment, two of the stator components 180, 182 are injection molded from a plastic (e.g., see <figref idref="f0015">Figs. 7a-7d</figref>). The third stator component includes stator vanes 184 molded into the bottom casing 174. In another embodiment, the stator vanes may be made using a thermally conductive material such as metal.

3.3.1 Radial flow direction

0048In an NIVV embodiment of the invention, the stator vanes direct flow in a generally radial direction. The vanes have a height in the range of 1mm to 100 mm, e.g., 3 mm to 5 mm. This arrangement brings the flow through an approximate right angle and assists in maintaining a compact design for the blower as a whole when compared to vanes or stage-to-stage paths that include a significant axial component.

3.3.2 Shape

0049Each stage has a plurality of stator vanes to direct the airflow, e.g., between 2 and 100 stator vanes. In one embodiment, each stage has 7 stator vanes. Each vane is substantially identical and has a generally spiral shape with a radius of curvature that is smaller at its inner end than at its outer end, to decelerate the air before turning it too hard.

0050In other applications, such as ones where very high flow rates are needed. and noise is not a main consideration, the air may not be decelerated by the stator vanes.

3.3.3 Mixed axial/radial flow direction

0051In an alternative embodiment of the invention, the vanes may direct flow in a plane normal to the axis, or there may be an axial component to the directed flow such that at least one set of stator vanes direct flow in both radial and axial directions. In such an embodiment, the stator vanes on the final stage can be positioned on an incline or otherwise are not of constant height, but develop axially as well as radially, such that the air is turned more gradually to the axial direction. For example, <figref idref="f0017">Figs. 10a and 10b</figref> illustrate impeller 250 attached to motor shaft 260, a shield 290, and a stator 280 including stator vanes 285 structured to direct flow in both radial and axial directions. Thus, the vanes begin tangentially (as they do in the above embodiments), but end up directing the flow axially (rather than radially as in the above embodiments). This arrangement may improve pressure generation, though it takes up a little more space. This arrangement means that air does not pass through a right angle.

3.4 Shield isolating stator vanes

0052Another aspect of the invention relates to a shield, located between stator vanes and impeller blades (e.g., see <figref idref="f0016">Figs. 8a-8c</figref>). In an embodiment, the shield is formed of injection molded plastic although other suitable materials (such as metals) may be used. In the illustrated embodiment, the shield extends radially beyond the outer edge of the stator vanes. This means there is not a "line-of-sight" path between the stator vanes and impeller blades and consequently acts to ensure that the airflow impinging on the stator blades is of a uniform circulating nature.

0053As best shown in <figref idref="f0009">Figs. 5b</figref>, <figref idref="f0010">5d</figref>, and <figref idref="f0011">5e</figref>, shield 190, 192 directs the flow via an annular aperture 164, 166, respectively. A peripheral aperture may also be used. In one form, the shield leaves only a narrow annular gap between its outer edge and the wall of the stationary portion. The gap is sufficient to allow enough airflow to the next stage without introducing excessive pressure drop. In an embodiment for a blower for use in a NIVV device, the gap may be between 0.5 mm and 100 mm, e.g., between 1 mm and 2 mm. The shield also provides an acoustic barrier by isolating the impeller blade pressure pulses from the stator vanes.

0054In one form, the shield is a circular disc and in NIVV devices may be welded to the stator vanes.

0055In an alternative embodiment, the shield may rotate. Such a rotating shield may be integral to the impeller such that the lower shroud acts as a rotating shield between the impeller blades and stator vanes. For example, <figref idref="f0017">Fig. 9</figref> illustrates impeller 350 attached to motor shaft 360. The impeller 350 includes upper and lower shrouds 352, 354 with the lower shroud 354 acting as a rotating shroud between impeller blades 355 and stator vanes 385 of stator 380.

3.5 Outlet

0056In contrast to the known prior art centrifugal blowers which direct air exiting the blower in a generally tangential direction, a centrifugal blower in accordance with an embodiment of the present invention directs air in a generally axial direction. This axis-symmetry is effective in reducing airflow turbulence and in reducing blade pass tone, as the impeller and vanes experience symmetrical flow patterns at all device flow rates.

3.6 Housing

0057The housing comprises chamfers on the external housing to assist with fitting the separate components of housing together. This design allows for an overall smaller package.

0058A gap between the interior wall of the external housing and the external wall of motor allows air to pass down around the sides of the motor. In an embodiment, the size of the gap is sufficient to prevent significant frictional losses but not too large that the overall size of the device becomes excessive. In an embodiment for a blower used in NIVV devices, the size of the gap may be between 0.1 mm and 100 mm, e.g., approximately 4 mm.

0059The ability of the air to flow around the motor may assist in keeping the motor cool. It may also assist in heating the patient air in an NIVV device.

4. Rotating Portion

4.1 Impeller

0060In an NIVV embodiment, a blower comprises a plurality of impellers 150, 152, 154 as shown in <figref idref="f0006 f0007 f0008">Figs. 4a to 4c</figref>. In the illustrated embodiment, the impellers are identical in design, thus only impeller 150 will be described in detail. With particular reference to <figref idref="f0013 f0014">Figures 6a to 6g</figref>, impeller 150 is of one-piece molded plastic construction, although other suitable materials and manufacturing techniques could be employed. The impeller 150 comprises a plurality of continuously curved blades 200 sandwiched between a pair of disk-like shrouds 202, 204. The smaller shroud 202 incorporates the hub or bushing 206 that is adapted to receive the motor shaft 160. The shroud 202 overlaps an inner portion of the blades 200, i.e., the outer diameter (OD) of the smaller shroud is substantially smaller than the OD of the larger shroud 204. The larger shroud 204 is formed with a relatively large center opening 208 and extends to the radially outer tips of the blades. Making the OD of the smaller shroud 202 slightly smaller than the diameter of the center opening 208 in shroud 204 facilitates the molding process used to manufacture the impellers.

0061By utilizing differentially sized shrouds, the inertia of the impeller 150 is reduced while the overall rigidity of the impeller is maintained. In this regard, the impeller 150 may be constructed of a polycarbonate, polypropylene, polyamide, or other material which provides acoustic dampening properties that dampen the resonance of the impellers. Glass fiber reinforcement may be employed to increase the stiffness of any of these materials.

4.1.1 Diameter

0062In an NIVV embodiment, the impeller 150 may have a diameter in the range of 20mm to 200mm. In one embodiment, the impeller 150 may have a diameter in the range of 40mm to 50mm, for example 42 mm. An impeller with a diameter in this range may provide a good compromise between overall size of the blower, rotational inertia, and turbulence levels.

4.1.2 Number of blades

0063In an NIVV embodiment, the impeller has 4-100 primary blades 200, e.g., 11. The impeller may include secondary and tertiary blades and may be of variable blade passage cross section (not shown).

4.1.3 Blade shape

0064In an embodiment, the impeller blades 200 are continuously curved in radial direction, and may also be tapered in width in the radially outer portions. The reduced width at the tips of the blades may reduce turbulence (e.g., Reynolds number is less in blowers with 3 impellers, 2 impellers, 1 impeller (in order)). In one embodiment, the outermost transverse edges of the blades may be stepped along their respective transverse widths (not shown) to assist in reducing turbulence noise at the tips of the blades. In another embodiment, the outermost transverse edges of the blades 200 are flat. In an embodiment, the blades 200 have an outlet height in the range of 1 mm to 40 mm, e.g., 3 to 6 mm. In one form, the blades 200 have an inlet height that is the same as the outlet height, however in other forms, the inlet and outlet heights may be different.

0065The blades 200 have an inlet angle with respect to a tangent of between 0° and 90°, e.g., about 20°. The blades have an outlet angle with respect to a tangent between 70° and 110°, however other angles are possible.

4.2 Shaft

0066In an embodiment, there is a gap between the shaft 160 and the shields 190, 192. This gap is sufficient to allow the shaft to rotate within the shields but is small enough to prevent significant leak between the impellers 152, 154 and the internal flow directing components 182, 184. In a blower for a NIVV device, the gap may be less than 10 mm, e.g., less than 2 mm.

5. Axial Symmetry

0067The blower according to an embodiment of the present invention comprises axially symmetric volutes, using stator vanes. The airflow enters and exits each stage within the blower in a substantially axial direction. Consequently, the air enters the blower axially at one end, and leaves it axially at the other. The airflow path is substantially axially symmetrical throughout the blower maintaining a constant feed pattern through the impeller, and in the volute. The symmetric blower provides balance, which leads to lower levels of blade pass tone, and lower levels of turbulence noise. Shields positioned between the impeller and the stator vanes provide a barrier for the vane leading edges from the impeller blade tips, thus reducing blade pass tone.

6. Multiple Stages

0068In the illustrated embodiment, the blower includes three stages with three corresponding impellers. In this embodiment, one impeller is positioned on one side of the motor and two impellers on the other side of the motor.

0069In an alternative embodiment, the blower may include two stages, one on either side of the motor. Another further embodiment uses four stages, with two on either side of the motor. Another embodiment is a single stage design. A further embodiment comprises multiple stages only on one side of the motor.

7. Alternative Embodiments

0070The following illustrates blowers according to alternative embodiments of the present invention. In each embodiment, air enters the blower axially at one end, and leaves the blower axially at the other end.

7.1 Two-Stage Blower

0071<figref idref="f0018 f0019 f0020 f0021 f0022">Figs. 11-16</figref> illustrate a blower 400 . As illustrated, the blower 400 includes two stages with two corresponding impellers 450, 452. In this embodiment, the two impellers are positioned on the same side of the magnet 462 and the stator assembly 465 but a bearing 444 is positioned between the impellers 450, 452.

0072Such blower may be used in Snore PAP, CPAP, APAP, and/or VPAP and may be configured to provide a ventilator variant.

7.1.1 Compact Size

0073The blower 400 has a relatively tiny size to provide a more compact or miniature blower. For example, as shown in <figref idref="f0020">Fig. 14</figref>, the blower 400 may have an overall diameter d of about 50-60 mm, e.g., 53 mm, and an overall length 1 of about 40-50 mm, e.g., 44 mm. However, other suitable sizes are possible.

7.1.2 General Description

0074The stationary portion of the blower 400 includes a housing 470 with first and second housing parts 472, 474, a stator component 480 including stator vanes 485, and first and second shields 490, 492. The rotating portion of the blower 400 includes first and second impellers 450, 452 adapted to be driven by motor 440. The motor includes a magnet 462 provided to shaft 460 and a stator assembly 465 to cause spinning movement of the shaft 460. In an embodiment, the motor may include 2 poles (for compact size), be sensorless, and/or be slotless (for low noise).

0075The blower 400 is generally cylindrical and has an inlet 430 provided by the first housing part 472 at one end and an outlet 420 provided by the second housing part 474 at the other end. As best shown in <figref idref="f0019">Figs. 12</figref> and <figref idref="f0022">16</figref>, the outlet 420 has an annulus or ring shape. In an embodiment, the inlet may also have an annulus or ring shape (not shown).

0076Similar to the above embodiments, the blower 400 has axial symmetry and air enters the blower axially at one end and leaves the blower axially at the other end. Such arrangement may provide relatively low noise in use, e.g., due to axial symmetry and/or low volute turbulence.

7.1.3 Stationary Portion

0077As best shown in <figref idref="f0021">Figs. 15</figref> and <figref idref="f0022">16</figref>, the stator component 480 includes a cylindrical hub 486 that engages within a corresponding opening 491 provided to the shield 490, e.g., press-fit, to secure the shield 490 in position. In addition, the hub 486 provides a recess 488 to retain or house a bearing 444 that rotatably supports the shaft 460. As illustrated, the bearing 444 is recessed into the stator component 480 so that it is positioned along a plane of where air is fed from the impeller 450. This arrangement saves space axially because the bearing 444 is positioned out of the housing that encloses the motor component, i.e., stator assembly and magnet.

0078As best shown in <figref idref="f0021">Figs. 15</figref> and <figref idref="f0022">16</figref>, the housing part 474 includes stator vanes 487 to direct flow towards the outlet 420. In addition, the housing part 474 includes an outer annular flange 478 and a hub 475 that provides an inner annular flange 476 to support motor components. Specifically, the inner annular flange 476 retains or houses a bearing 446 that rotatably supports the shaft 460. The outer annular flange 478 retains or housings the stator assembly 465. The shield 492 engages the outer annular flange 478, e.g., press-fit, to enclose the stator assembly 465 along with the magnet 462 on the shaft 460 within the housing part 474.

0079In an embodiment, the housing part 474 may be constructed of metal so that the housing part 474 can act as a heat sink to conduct and dissipate heat generated from the stator assembly 465 in use. Also, at least a portion of the outer annular flange 478 supporting the stator assembly 465 is exposed to the flow of air, which allows cooling of the stator assembly 465 as air flows through the housing part 474 in use. However, the housing part along with other blower components may be constructed of other suitable materials, e.g., aluminum, plastic, etc.

7.1.4 Rotating Portion

0080In the illustrated embodiment, each impeller 450, 452 includes a plurality of continuously curved or straight blades 454 sandwiched between a pair of disk-like shrouds 455, 456. The lower shroud 456 incorporates the hub or bushing that is adapted to receive the shaft 460. Also, each impeller 450, 452 includes a tapered configuration wherein the blades 454 taper towards the outer edge. Further details of impellers are disclosed in PCT Application No. <patcit id="pcit0012" dnum="AU2006001617W" dnum-type="L"><text>PCT/AU2006/001617, filed October 27, 2006</text></patcit> . Such arrangement may provide relatively fast pressure response, e.g., due to relatively low inertia impellers.

7.1.5 Fluid Flow Path

0081In the first stage, air or gas enters the blower 400 at the inlet 430 and passes into the first impeller 450 where it is accelerated tangentially and directed radially outward. Air then flows in a spiral manner with a large tangential velocity component and also an axial component passing through the gap 464 defined by the outer edge of the shield 490 and the inner surface of the housing part 472. Air then enters the stator vanes 485 formed in the stator component 480 and is directed radially inwardly towards orifice 483, and thereafter onto the second stage.

0082In the second stage, air or gas passes into the second impeller 452 where it is accelerated tangentially and directed radially outward. Air then flows in a spiral manner with a large tangential velocity component and also an axial component passing through the gap 466 defined by the outer edge of the shield 492 and the inner surface of the housing part 474. Air then enters the stator vanes 487 formed in the housing part 474 and is directed towards the outlet 420.

7.1.6 Support System

0083As shown in <figref idref="f0023">Fig. 17</figref>, the blower 400 may be supported within an outer casing 415 (e.g., forming a portion of a NIVV device such as a PAP device) by a support system. The outer casing 415 includes a base 416 and a cover 418 provided to the base 416. The support system includes a side support 424, a top support 425, or a bottom support 426 or combinations thereof to support the blower 400. The support system may also be adapted to provide a seal between the inlet and the outlet sides of the blower 400.

0084The side support 424 may be in the form of an annular flexible ring adapted to support the blower in a flexible and/or vibration-isolated manner within the outer casing 425. In addition, the flexible ring 424 divides the inlet of the outer casing 425 from the outlet of the outer casing 425 to avoid the need for a connection tube that directs flow towards the outlet of the outer casing. Also, the flexible ring 424 may provide a seal between the base 416 and the cover 418 of the outer casing 415.

0085The bottom support 426 includes a biasing member 427, e.g., leaf spring, and a conducting member 428. In use, the bottom support 426 provides a flexible structure to isolate the blower 400 from the outer casing 415, e.g., vibration isolated. In an embodiment, the conducting member 428 is coupled with the stator assembly 465 to conduct current from an external source to the stator assembly 465.

7.2 Two-Stage Blower with Bearing Tube

0086<figref idref="f0024">Fig. 18</figref> illustrates a two-stage blower 500 . The two-stage blower 500 is similar to blower 400 described above. In contrast, the second housing part 574 and second shield 592 provide a different structure for supporting motor components.

0087As illustrated, the second housing part 574 includes stator vanes 587 to direct flow towards the outlet 520. In addition, the housing part 574 includes a hub 575 that provides an annular flange 576. The annular flange 576 is structured to engage a lower side of the stator assembly 565.

0088The second shield 592 includes a tube portion 595 extending therefrom (e.g., integrally formed in one piece). As illustrated, the stator assembly 565 is provided along an exterior surface of the tube portion 595 such that the stator assembly 565 is enclosed and sandwiched between the annular flange 576 of the second housing part 574 and a tapered projection 593 on the shield 592.

0089In the illustrated embodiment, the exterior surface of the stator assembly 565 is exposed to the flow of gas passing through the housing part 574, which allows cooling of the stator assembly 565 in use. Also, heat from the stator assembly may be used to heat the gas for the patient without the need for a separate heater.

0090The interior surface of the tube portion 595 retains or houses a bearing 546 that rotatably supports the shaft 560. In addition, the tube portion 595 encloses the magnet 562 on the shaft 560, which is aligned with the stator assembly 565. In an embodiment, the tube portion 595 may be "magnetically transparent", which allows the stator assembly 565 to act on the magnet 562 positioned within the tube portion 595 without significant loss of flux density and/or increased heat, if any. Further details of a magnetically transparent tube are disclosed in <patcit id="pcit0013" dnum="US85377806" dnum-type="L"><text>U.S. Provisional Application No. 60/853,778, filed October 24, 2006</text></patcit> .

0091A balance ring 598 may be optionally provided to an end portion of the shaft 560 (e.g., opposite the end portion supporting the impellers).

0092In the illustrated embodiment, the hub 575 protrudes further outwardly from the housing than the hub 475 of the blower 400 described above. This arrangement may add about 1-10 mm, e.g., 5 mm, to the height of the blower 500, e.g., with respect to the blower 400. For example, the blower 500 may have an overall diameter d of about 50-60 mm, e.g., 53 mm, and an overall length 1 of about 40-55 mm, e.g., 49 mm. However, other suitable sizes are possible.

7.3 Three-Stage Blower with Tapered Configuration

0093<figref idref="f0025">Fig. 19</figref> illustrates a three-stage blower 600 according to an embodiment of the present invention. Similar to the three-stage blower 100 described above, the blower 600 includes three stages with one impeller 650 positioned on one side of the motor 640 and two impellers 652, 654 positioned on the other side of the motor 640.

0094In the illustrated embodiment, each impeller 650, 652, 654 of the blower 600 has a tapered configuration. In addition, corresponding portions of the housing 670 and stator components 680, 682 are tapered to match the tapered configuration of the impellers 650, 652, 654.

0095In the illustrated embodiment, each impeller 650, 652, 654 includes a plurality of continuously curved or straight blades 653 sandwiched between a pair of disk-like shrouds 655, 656. The lower shroud 656 incorporates the hub or bushing that is adapted to receive the shaft 660. Also, each impeller 650, 652, 654 includes a tapered configuration wherein the blades 653 taper towards the outer edge. Further details of impellers are disclosed in PCT Application No. <patcit id="pcit0014" dnum="AU2006001617W" dnum-type="L"><text>PCT/AU2006/001617, filed October 27, 2006</text></patcit>.

0096The upper wall 673 of the housing part 672 is tapered to match the tapered configuration of impeller 650, and the lower wall 657, 659 of respective stator components 680, 682 are tapered to match the tapered configuration of impellers 652, 654.

0097Also, in the illustrated embodiment, a central portion 693 of the lower shield 692 is shaped to direct the airflow down towards the outlet 620. The central portion 693 includes a void 696 along the surface facing the impeller 654, e.g., to maintain a constant section/thickness for the shield 692 and save on material costs.

0098As illustrated, the bearings 644, 646 that support the shaft 660 are provided within the housing 642 of the motor 640. In an alternative embodiment, another bearing, i.e., a third bearing, may be added towards the end of the shaft 660 near the lower impeller 654 to add additional support. In another alternative embodiment, rather than adding a third bearing, one of the bearings 644 or 646 within the motor housing 642 may be maintained in its position and the other of the bearings 644 or 646 may be moved towards the end of the shaft 660 near the lower impeller 654 to add additional support. However, other bearing arrangements are possible.

0099In this embodiment, the blower 600 may be supported within an outer casing 615 (e.g., forming a portion of a NIVV device such as a PAP device) by a support system. The support system includes side supports 624 to support the sides of the blower 600 and a bottom support 626 to support the bottom of the blower 600.

0100The side and bottom supports 624, 626 may be flexible members, e.g., elastomer, to isolate the blower 600 from the outer casing 615, e.g., vibration isolated. As illustrated, the side supports 624 are adapted to engage respective pegs 635 provided to the blower 600. The bottom support 626 provides a conduit from the outlet 620 of the blower 600 to the outlet 617 of the outer casing 615 (e.g., which may connectable to an air delivery conduit to deliver pressurized air to a patient for therapy).

8. Other comments

0101While the invention has generally been described in terms of a centrifugal pump, it is not limited to this form, and may also take the form of a mixed flow type.

0102An aspect of the invention is that the chamber that defines the airflow path is generally axially symmetric. This does not mean that the entire airflow path of the device that uses a blower in accordance with the invention must also be axially symmetric. Variations within the scope of the present invention may include some asymmetries. These asymmetries may lie in a region where velocities are low such that losses and noise are less affected.

0103In an embodiment, the blower allows the airflow feed pattern through the impeller, and in the volute, to remain symmetrical irrespective of the flow rates. This results in lower levels of blade pass tonal noise emission, and lower levels of turbulence noise emission.

0104While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the invention. In addition, while the invention has particular application to patients who suffer from OSA, it is to be appreciated that patients who suffer from other illnesses (e.g., congestive heart failure, diabetes, morbid obesity, stroke, barriatric surgery, etc.) can derive benefit from the above teachings. Moreover, the above teachings have applicability with patients and non-patients alike in non-medical applications.