Method and apparatus for reducing noise in a roots-type blower

• US 20050112013A1
• Filed: 11/10/2004
• Published: 05/26/2005
• Est. Priority Date: 08/04/2003
• Status: Abandoned Application

• Current Assignee: Pulmonetic Systems Incorporated (Cardinal Health, Inc.)
• Original Assignee: Pulmonetic Systems Incorporated (Cardinal Health, Inc.)
• Inventors: Williams, Malcolm, DeVries, Douglas F.
• Application Number:
  US10/985,528
• Publication Number:
  US 20050112013A1
• Time in Patent Office: Days
• US Class Current: 418/206.100
• CPC Class Codes: A61M 11/00 Sprayers or atomisers specially adapted for therapeutic purposes in general B05B; aerosol containers B65D83/14
• CPC Class Codes: A61M 16/0057 Pumps therefor
• CPC Class Codes: A61M 16/0063 Compressors
• CPC Class Codes: A61M 16/0066 Blowers or centrifugal pumps
• CPC Class Codes: A61M 16/0069 the speed thereof being controlled by respiratory parameters, e.g. by inhalation
• CPC Class Codes: A61M 16/021 operated by electrical means A61M16/202 – A61M16/205 take precedence
• CPC Class Codes: A61M 16/12 by mixing different gases
• CPC Class Codes: A61M 16/205 used for exhalation control
• CPC Class Codes: A61M 16/206 Capsule valves, e.g. mushroom, membrane valves
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• CPC Class Codes: A61M 2016/1025 the O2 concentration
• CPC Class Codes: A61M 2202/0208 Oxygen
• CPC Class Codes: A61M 2205/16 with back-up system in case of failure
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3365 Rotational speed
• CPC Class Codes: A61M 2205/3368 Temperature
• CPC Class Codes: A61M 2205/3553 remote, e.g. between patient's home and doctor's office
• CPC Class Codes: A61M 2205/3569 sublocal, e.g. between console and disposable
• CPC Class Codes: A61M 2205/3584 using modem, internet or bluetooth
• CPC Class Codes: A61M 2205/42 : Reducing noise
• CPC Class Codes: A61M 2205/505 : Touch-screens; Virtual keyboard or keypads; Virtual buttons; Soft keys; Mouse touches
• CPC Class Codes: A61M 2205/52 : with memories providing a history of measured variating parameters of apparatus or patient
• CPC Class Codes: A61M 2205/581 : by audible feedback
• CPC Class Codes: A61M 2205/583 : by visual feedback
• CPC Class Codes: A61M 2205/70 : with testing or calibration facilities
• CPC Class Codes: A61M 2205/8206 : battery-operated
• CPC Class Codes: A61M 2205/8237 : Charging means
• CPC Class Codes: A61M 2205/8262 : connectable to external power source, e.g. connecting to automobile battery through the cigarette lighter
• CPC Class Codes: A61M 2209/086 : Docking stations
• CPC Class Codes: A61M 2230/205 : partial oxygen pressure (P-O2)
• CPC Class Codes: A61M 2230/432 : partial CO2 pressure (P-CO2)
• CPC Class Codes: F04C 18/126 : with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type
• CPC Class Codes: F04C 29/0035 : Equalization of pressure pulses silencing F04C29/06

Abstract

A Roots-type blower comprises a housing defining a rotor chamber and an inlet and outlet to the rotor chamber. First and second rotors are mounted in the rotor chamber, each rotor defining a plurality of lobes, adjacent lobes and the housing cooperating to define gas transport chambers. The blower is configured so that a net flow rate of gas into a gas transport chamber is generally or approximately constant, whereby a change in gas pressure in the gas transport chamber is generally or approximately linear, as the gas transport chamber approaches the outlet. In one embodiment, this is accomplished by providing flow channels extending from the outlet towards the inlet, and from the inlet towards the outlet, corresponding to each rotor. The flow channels permit gas to flow from the high pressure outlet to a gas transport chamber and from the gas transport chamber to the low pressure inlet. The resulting amelioration of pressure spikes associated with flow back substantially reduces the operational noise level of the blower.

Claims

1. A noise reducing configuration for a Roots-type blower comprising:

a housing defining a rotor chamber, said rotor chamber comprising having an inlet and an outlet;

a first and a second rotor rotatably mounted in said chamber, each rotor defining a plurality of lobes, adjacent lobes of each rotor cooperating with said housing to define at one or more times gas transport chambers, said rotors configured to move gas from said inlet via said gas transport chamber to said outlet; and

at least one outlet gas flow channel extending from said outlet along an inner surface of said housing at said rotor chamber in a direction opposite a direction of rotation of said rotor, said at least one outlet gas flow channel configured to permit gas to flow from said outlet into a gas transport chamber as said lobes of said rotor rotate towards said outlet, said at least one outlet gas flow channel configured so that a pressure of said gas in said chamber as said chamber moves towards said outlet changes at an approximately linear rate.

2. The blower in accordance with claim 1 including at least one outlet gas flow channel for each of said rotors, said outlet gas flow channel having a first end and a second end, said second end located at said outlet and said first end spaced therefrom in the direction opposite said direction of rotation of said rotor.

3. The blower in accordance with claim 1 wherein each outlet gas flow channel has a cross-sectional area which increases moving in the direction of the first end to the second end thereof.

4. The blower in accordance with claim 1 wherein said outlet gas flow channel has a cross-sectional area which increases non-linearly moving in the direction of the first end of the second end thereof.

5. The blower in accordance with claim 3 wherein said increase in area is associated with at least an increase in a depth of said channel.

6. The blower in accordance with claim 1 including at least one inlet flow channel corresponding to at least one of said rotors, said at least one inlet flow channel extending from said inlet along an inner surface of said rotor chamber in an opposite direction as the direction of rotation of said rotor, said inlet flow channel configured to permit gas to flow from a chamber to said inlet.

7. The blower in accordance with claim 1 wherein said Roots-type blower comprises part of a mechanical ventilator.

8. The blower in accordance with claim 1 wherein said rate of change of pressure of said gas varies from linearity by no more than about 10%.

9. The blower in accordance with claim 1 wherein said rate of change of pressure of said gas varies from linearity no more than about 5%.

10. A noise reducing configuration for a Roots-type blower comprising:

a housing defining a rotor chamber, said rotor chamber having an inlet and an outlet;

a first and a second rotor rotatably mounted in said chamber, each rotor defining a plurality of lobes, adjacent lobes of each rotor cooperating with said housing to define at one or more times gas transport chambers, said rotors configured to move gas from said inlet via said gas transport chamber to said outlet; and

at least one outlet gas flow channel extending from said outlet along an inner surface of said housing in a direction opposite a direction of rotation of said rotor, said at least one outlet gas flow channel configured to permit gas to flow from said outlet into a gas transport chamber as said lobes of said rotor rotate towards said outlet, said at least one outlet gas flow channel configured so that a gas flow rate from said outlet into said gas transport chamber is approximately constant.

11. The blower in accordance with claim 10 including at least one outlet gas flow channel for each of said rotors, said outlet gas flow channel having a first end and a second end, said second end located at said outlet and said first end spaced therefrom in the direction opposite said direction of rotation of said rotor.

12. The blower in accordance with claim 10 wherein each outlet gas flow channel has a cross-sectional area which increases moving in the direction of the first end to the second end thereof.

13. The blower in accordance with claim 10 wherein said outlet gas flow channel has a cross-sectional area which increases non-linearly moving in the direction of the first end of the second end thereof.

14. The blower in accordance with claim 12 wherein said increase in area is associated with at least an increase in a depth of said channel.

15. The blower in accordance with claim 10 including at least one inlet flow channel corresponding to at least one of said rotors, said at least one inlet flow channel extending from said inlet along an inner surface of said rotor chamber in an opposite direction as the direction of rotation of said rotor, said inlet flow channel configured to permit gas to flow from a chamber to said inlet.

16. The blower in accordance with claim 10 wherein said Roots-type blower comprises part of a mechanical ventilator.

17. The blower in accordance with claim 10 wherein said gas flow rate changes by no more than about 10%.

18. The blower in accordance with claim 10 wherein said gas flow rate changes by no more than about 5%.

19. A noise reducing configuration for a Roots-type blower comprising:

a housing defining a rotor chamber, said rotor chamber having an inlet and an outlet;

a first and a second rotor rotatably mounted in said chamber, each rotor defining a plurality of lobes, adjacent lobes of each rotor cooperating with said housing to define at one or more times gas transport chambers, said rotors configured to move gas from said inlet via said gas transport chambers to said outlet; and

at least one outlet gas flow channel extending from said outlet along an inner surface of said housing in a direction opposite to a direction of rotation of said rotor, said at least one outlet gas flow channel configured to permit gas to flow from said outlet into a gas transport chamber as said lobes of said rotor rotate towards said outlet, said at least one outlet gas flow channel defining a flow area which increases generally non-linearly towards the direction of said outlet.

20. The blower in accordance with claim 19 wherein a width of said at least one outlet gas flow channel is generally constant and a depth of said at least one channel increases non-linearly towards the direction of said outlet.

21. The blower in accordance with claim 19 including at least one outlet gas flow channel for each of said rotors, said outlet gas flow channel having a first end and a second end, said second end located at said outlet and said first end spaced therefrom in the direction opposite said direction of rotation of said rotor.

22. The blower in accordance with claim 19 wherein said increase in area is associated with at least an increase in a depth of said channel.

23. The blower in accordance with claim 19 including at least one inlet flow channel corresponding to at least one of said rotors, said at least one inlet flow channel extending from said inlet along an inner surface of said rotor chamber in an opposite direction as the direction of rotation of said rotor, said inlet flow channel configured to permit gas to flow from a chamber to said inlet.

24. The blower in accordance with claim 19 wherein said Roots-type blower comprises part of a mechanical ventilator.

25. A noise reducing configuration for a Roots-type blower comprising:

a housing defining a rotor chamber, said rotor chamber having an inlet and an outlet;

a first and a second rotor rotatably mounted in said chamber, each rotor defining a plurality of lobes, adjacent lobes of each rotor cooperating with said housing to define at one or more times gas transport chambers, said rotors configured to move gas from said inlet via said gas transport chambers to said outlet;

at least one outlet gas flow channel corresponding to said first rotor, said at least one outlet gas flow channel extending from said outlet along an inner surface of said housing in a direction opposite a direction of rotation of said first rotor, said at least one outlet gas flow channel configured to permit gas to flow from said outlet into a gas transport chamber between two lobes of said first rotor as said lobes of said first rotor rotate towards said outlet;

at least one outlet gas flow channel corresponding to said second rotor, said at least one outlet gas flow channel extending from said outlet along an inner surface of said housing in a direction opposite a direction of rotation of second first rotor, said at least one outlet gas flow channel configured to permit gas to flow from said outlet into a gas transport chamber between two lobes of said second rotor as said lobes of said second rotor rotate towards said outlet;

at least one inlet gas flow channel corresponding to said first rotor, said at least one inlet gas flow channel extending from said inlet along an inner surface of said housing at said rotor chamber in a direction of rotation of said first rotor, said at least one inlet gas flow channel configured to permit gas to flow from said gas transport chamber between two lobes of said first rotor back to said inlet as said lobes of said first rotor rotate towards said outlet; and

at least one inlet gas flow channel corresponding to said second rotor, said at least one inlet gas flow channel extending from said inlet along an inner surface of said housing at said rotor chamber in a direction of rotation of said second rotor, said at least one inlet gas flow channel configured to permit gas to flow from said gas transport chamber between two lobes of said second rotor back to said inlet as said lobes of said second rotor rotate towards said outlet.

26. The blower in accordance with claim 25 wherein said inlet and outlet gas flow channels corresponding to said first and second rotors are configured such that a net rate of gas flow into said gas transport chambers is approximately constant.

27. The blower in accordance with claim 25 wherein said inlet and outlet gas flow channels corresponding to said first and second rotors are configured to cause an approximately linear rate of pressure change within said gas transport chambers.

28. The blower in accordance with claim 25 wherein said outlet gas flow channels corresponding to said first and second rotors have a cross-sectional area which increases generally non-linearly moving in the direction of said outlet.

29. The blower in accordance with claim 28 wherein said outlet gas flow channels corresponding to said first and second rotors have a cross-sectional area which increases continuously moving in the direction of said outlet.

30. The blower in accordance with claim 25 wherein said Roots-type blower comprises part of a mechanical ventilator.

31. The blower in accordance with claim 26 wherein said gas flow rate changes by no more than about 10%.

32. The blower in accordance with claim 26 wherein said gas flow rate changes by no more than about 5%.

33. The blower in accordance with claim 27 wherein said rate of change of pressure of said gas varies from linearity by no more than about 10%.

34. The blower in accordance with claim 26 wherein said rate of change of pressure of said gas varies from linearity changes by no more than about 5%.

35. A method for configuring a gas flow path for providing a flow of gas between a port of a Roots-type blower and a gas transport chamber formed between lobes of at least one rotor of said blower, comprising the steps of:

selecting a length for said flow path;

selecting a desired gas transport chamber function that defines desired values of a characteristic of gas in said gas transport chamber as a function of rotor position;

selecting an area function that defines a cross-sectional area of said flow path along said length of said flow path;

calculating estimated values of said characteristic of said gas in said gas transport chamber corresponding to said area function;

comparing said estimated values to said desired values;

repeating said steps of selecting an area function, calculating estimated values, and comparing said estimated values to said desired values until said estimated values are approximately equal to said desired values.

36. The method of claim 35 wherein said length of said flow path comprises a taper angle.

37. The method of claim 36 wherein said rotor position is represented by a taper time.

38. The method of claim 35 wherein said characteristic of said gas in said gas transport chamber comprises a pressure of said gas.

39. The method of claim 38 wherein said desired gas transport chamber function comprises an approximately linear rate of change in pressure of gas in said gas transport chamber.

40. The method of claim 35 wherein said characteristic of said gas in said gas transport chamber comprises a flow rate of gas into said gas transport chamber.

41. The method of claim 40 wherein said desired gas transport chamber function comprises an approximately constant rate of gas flow to said gas transport chamber.

42. The method of claim 35 wherein said area function comprises a constant component and a variable component.

43. The method of claim 42 wherein said constant component comprises a leakage area.

44. The method of claim 42 wherein said variable component comprises a polynomial.

45. The method of claim 44 where said polynomial comprises a polynomial of the form Et⁴+Ft⁷+Gt¹² where “

E,”

“

F,” and

“

G”

are constants and wherein “

t”

is a normalized taper time.

46. The method of claim 45 wherein E equals approximately 0.007 in.², F equals approximately 0.02 in.², and G equals approximately 0.007 in.².

47. The method of claim 45 wherein E equals approximately 0.001 in.², F equals zero, and G equals approximately 0.001 in.

48. The method of claim 35 wherein said port comprises an outlet port of said blower.

49. The method of claim 35 wherein said port comprises an inlet port of said blower.

50. The method of claim 35 further comprising the step of configuring a gas flow channel that corresponds to said area function.

51. The method of claim 50 wherein said gas flow channel comprises a generally constant width.

52. The method of claim 51 wherein a depth of said gas flow channel increases along its length in a generally non-linear manner.

53. The method of claim 50 wherein said gas flow channel comprises an outlet flow channel.

54. The method of claim 50 wherein said gas flow channel comprises an inlet flow channel.

55. The method of claim 35 wherein said Roots-type blower comprises part of a mechanical ventilator.

56. A method for configuring a gas flow path for providing a flow of gas between a port of a Roots-type blower and a gas transport chamber formed between lobes of at least one rotor of said blower, comprising the steps of:

selecting a length for said flow path;

selecting a desired gas transport chamber function that defines desired values of a characteristic of gas in said gas transport chamber as a function of rotor position;

selecting an initial incremental rotor position;

calculating an initial desired cross-sectional flow area corresponding to said gas transport chamber function at said initial incremental rotor position;

selecting a succeeding incremental rotor position;

calculating a succeeding desired cross-sectional flow area corresponding to said gas transport chamber function at said succeeding incremental rotor position;

repeating said steps of selecting a succeeding incremental rotor position and calculating a succeeding desired cross-sectional flow area for rotor positions traversing said length of said flow path.

57. The method of claim 56 wherein said length of said flow path comprises a taper angle.

58. The method of claim 57 wherein said rotor position is represented by a taper time.

59. The method of claim 56 wherein said characteristic of said gas in said gas transport chamber comprises a pressure of said gas.

60. The method of claim 59 wherein said desired gas transport chamber function comprises an approximately linear rate of change in pressure of gas in said gas transport chamber.

61. The method of claim 56 wherein said characteristic of said gas in said gas transport chamber comprises a flow rate of gas into said gas transport chamber.

62. The method of claim 61 wherein said desired gas transport chamber function comprises an approximately constant rate of gas flow to said gas transport chamber.

63. The method of claim 56 wherein said port comprises an outlet port of said blower.

64. The method of claim 56 wherein said port comprises an inlet port of said blower.

65. The method of claim 56 further comprising the step of configuring a gas flow channel that corresponds to said desired cross sectional flow areas.

66. The method of claim 65 wherein said gas flow channel comprises a generally constant width.

67. The method of claim 66 wherein a depth of said gas flow channel increases along its length in a generally non-linear manner.

68. The method of claim 65 wherein said gas flow channel comprises an outlet flow channel.

69. The method of claim 65 wherein said gas flow channel comprises an inlet flow channel.

70. The method of claim 56 wherein said Roots-type blower comprises part of a mechanical ventilator.