FIELD OF THE INVENTION

The 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

Nasal Continuous Positive Airway Pressure (CPAP) treatment of Obstructive Sleep Apnea (OSA) was invented by Sullivan. See U.S. Pat. No. 4,944,310. 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

Blowers 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.

Generally, 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.

With reference toFIGS. 1 and 2, three directions are defined, i.e., radial R, tangential T and axial A. Prior art centrifugal blower10includes an outlet20, an inlet30, an electric motor40, an impeller50and a shaft60. Arrows70indicate the general direction of airflow. Air enters the blower at the inlet30and 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 outlet20.

In 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.

The 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

Another form of known blower design is described in ResMed's International Patent Application PCT/AU99/00444, published as WO 99/64747, the contents of which are hereby expressly incorporated by reference. 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

Respironics International Patent Application PCT US98/19635, published as WO 99/13932, 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.

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

Respironics REMstar

Another 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

U.S. Pat. No. 6,910,483 (Daly et al) 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. The contents of this patent are hereby expressly incorporated by reference. In this device, air exits the blower in a generally tangential direction.

PCT Application Nos. PCT/AU2006/001617, filed Oct. 27, 2006, and PCT/AU2006/001616, filed Oct. 27, 2006, describe multiple stage blowers. The contents of both of these PCT applications are hereby incorporated by reference.

As 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.

SUMMARY OF THE INVENTION

A 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.

In 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.

In 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.

In 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.

An 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.

An 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.

In one form, the blower has one stage. In 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.

In 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.

Another 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.

Another aspect of the invention 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.

Another 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.

Other 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.

