Respiratory apparatus
A head-mountable flow generator is configured to deliver a flow of breathable gas at a continuously positive pressure with respect to ambient air pressure to a patient interface in communication with an entrance to a patient's airways including at least an entrance of the patient's nares, while the patient is sleeping, to ameliorate sleep disordered breathing. The flow generator includes a motor, an impeller assembly and housing that encases the motor and the impeller assembly. The housing is configured to be mounted on the patient's head and comprises an inlet to receive the flow of breathable gas and a pair of opposing outlets to deliver the flow of breathable gas. In addition, the impeller assembly is configured to pressurize the flow of breathable gas received from the inlet, and the housing is configured to convey the pressurized flow of breathable gas through both outlets.
1 . A flow generator for generating a flow of pressurized breathable gas for respiratory therapy, the flow generator comprising:
a cylindrical housing;
a motor supported in the cylindrical housing, the motor having a shaft having a first end and a second end opposite the first end, the shaft being generally coincident with an axis of the motor;
a first impeller attached to the first end of the shaft;
a second impeller attached to the second end of the shaft; and
a stator configured to direct a flow of the breathable gas from the first impeller back towards the motor axis,
wherein the cylindrical housing comprises an inlet adjacent the first end of the shaft and having an inlet axis generally coincident with the motor axis, and at least one outlet between the first and second impellers that discharges the pressurized breathable gas out of the flow generator, the at least one outlet having an outlet axis generally tangential to a circumference of the cylindrical housing,
wherein the motor and the cylindrical housing form an air flow path for the breathable gas flowing from the cylindrical housing inlet to the at least one outlet, and
wherein for each of the at least one outlet, the air flow path allows the breathable gas to pass between the motor and the outlet twice before the breathable gas is discharged through the outlet, in use.
2 . The flow generator according to claim 1 , wherein the cylindrical housing comprises a first cylindrical housing segment and a second cylindrical housing segment.
3 . The flow generator according to claim 2 , wherein the cylindrical housing inlet is provided in the first cylindrical housing segment and the at least one outlet is provided in the second cylindrical housing segment.
4 . The flow generator according to claim 2 , further comprising:
a third cylindrical housing segment intermediate to the first and second cylindrical housing segments, and wherein the stator is supported by the third cylindrical housing segment and the motor is supported by the stator.
5 . The flow generator according to claim 4 , further comprising noise and/or vibration dampening material between the motor and the stator and/or between the first and second cylindrical housing segments.
6 . The flow generator according to claim 5 , wherein the noise and/or vibration dampening material comprises a gel.
7 . The flow generator according to claim 1 , wherein the first and second impellers comprise straight vanes.
8 . The flow generator according to claim 1 , wherein the first and second impellers comprise curved vanes.
9 . The flow generator according to claim 1 , wherein the first and second impellers comprise vanes with varying heights.
10 . The flow generator according to claim 9 , wherein the height of the vanes of the first impeller at a circumferential edge of the first impeller is a minimum height that does not choke the flow of breathable gas.
11 . The flow generator according to claim 1 , wherein the motor is a brushless motor or an axial gap motor, and wherein the motor is configured to deliver about 1-5 W of power.
12 . The flow generator according to claim 11 , further comprising a magnet attached to at least one of the first impeller and the second impeller.
13 . The flow generator according to claim 1 , wherein the flow generator is configured to generate a flow of about 40-60 l/min.
14 . The flow generator according to claim 1 , wherein the flow generator is configured to generate a pressure of about 2-12 cm H 2 O.
15 . The flow generator according to claim 1 , wherein the at least one outlet comprises two outlets.
16 . The flow generator according to claim 1 ,
wherein the first impeller is configured to direct the breathable gas in a radially outward direction,
wherein the second impeller is configured to direct the breathable gas in a radially outward direction and the first and second impellers are located on opposite sides of the motor;
wherein the stator is configured to direct the flow of breathable gas from the first impeller in a radially inward direction, and
wherein the at least one outlet comprises a pair of outlets that are positioned so that the motor is located between the outlets.
17 . The flow generator of claim 16 , wherein a cross-sectional area of each outlet is elliptical or oval.
18 . The flow generator of claim 16 , wherein the first and second impellers comprise vanes that decrease in size in a radially outward direction.
19 . The flow generator of claim 18 , wherein the vanes of the first and second impellers are straight, and wherein the stator comprises curved vanes.
20 . The flow generator of claim 16 , further comprising a dampening layer between the first impeller and the stator.
21 . The flow generator of claim 1 , wherein for each of the at least one outlet, the air flow path allows the breathable gas to pass between the motor and the outlet prior to entering the second impeller and after exiting the second impeller, in use.
22 . The flow generator of claim 1 , wherein for each of the at least one outlet, the air flow path allows the breathable gas to pass between the motor and the outlet in a first direction and later pass between the motor and the outlet in a second direction different from the first direction, in use.
23 . The flow generator of claim 22 , wherein the first direction is opposite the second direction.