Single or multiple stage blower and nested volute(s) and or impeller(s) thereof

1. An impeller comprising a plurality of vanes at least partially sandwiched between first and second substantially planar shrouds that extend in substantially parallel planes, said first shroud having an outer diameter larger than an outer diameter of said second shroud, each vane having a length along opposite edges of the vane extending substantially radially outwardly in a lengthwise direction, a width less than said length and defined by a distance between said opposite edges, and a radially outer transverse tip edge connecting said opposite edges; and wherein the width of each vane reduces continuously in the lengthwise direction from an outer edge of said second shroud to the radially-outer transverse tip edge of the vane.

2. The impeller according to claim 1 , wherein the first shroud is formed with a center opening and the outer diameter of the second shroud is less than a diameter of the center opening in the first shroud.

3. The impeller according to claim 1 , wherein said first shroud is a top shroud and said second shroud is a bottom shroud.

4. The impeller according to claim 1 , wherein the first and second shrouds are disk-like.

5. The impeller according to claim 1 , wherein the plurality of vanes include a prime number of vanes.

6. The impeller according to claim 1 , wherein each of the plurality of vanes includes a substantially straight or planar configuration.

7. The impeller according to claim 1 , wherein each of said opposite edges includes a substantially straight or planar configuration.

8. The impeller according to claim 1 , wherein the first shroud is a top shroud and the second shroud is a bottom shroud, and said opposite edges include a top edge at least partially engaged with the top shroud and a bottom edge at least partially engaged with the bottom shroud, and wherein the bottom edge extends upwardly at an angle from the outer edge to the radially-outer transverse tip edge.

9. The impeller according to claim 1 , wherein the radially-outer transverse tip edge includes a lower end spaced upwardly from the plane of the second shroud.

10. The impeller according to claim 1 , wherein the width tapers between 1-3 mm.

11. The impeller according to claim 10 , wherein the width tapers between 1.5-2 mm.

12. The impeller according to claim 1 , wherein the radially-outer transverse tip edge comprises a stepped and/or notched or chamfered tip edge.

13. The impeller according to claim 12 , wherein the radially-outer transverse tip edge includes a straight chamfer.

14. The impeller according to claim 12 , wherein the radially-outer transverse tip edge includes a convex chamfer.

15. The impeller according to claim 12 , wherein the outer transverse tip edge includes a concave notch.

16. A positive airway pressure device for delivering pressurized therapy gas, comprising:

a blower to pressurize gas in the range of about 4-30 cm H 2 O;

each said blower including a motor having the shaft and the impeller according to claim 1 .

17. The positive airway pressure device of claim 16 , wherein said shaft has two ends and at least one said impeller provided to each said end.

18. The positive airway pressure device according to claim 16 , wherein the motor includes a motor body having an end bell, and a base plate insert is provided to the end bell to sit under the impeller.

19. The positive airway pressure device of claim 18 , wherein the base plate insert is tapered.

20. The positive airway pressure device according to claim 18 , wherein the base plate insert is clipped or snap-locked to the end bell.

21. The impeller according to claim 1 wherein the second shroud overlaps an inner portion of said plurality of vanes and the first shroud overlaps an outer portion of said plurality of vanes.

22. The impeller according to claim 21 , wherein the first shroud extends to the radially-outer transverse tip edges of said plurality of vanes.

23. The impeller according to claim 1 , wherein the impeller is molded in one piece.

24. The impeller according to claim 23 , wherein the impeller is formed from a plastic material.

25. The impeller according to claim 23 , wherein the impeller is formed of a polycarbonate or polypropylene material.