WO2006017398A2 - Method and apparatus for attenuating compressor noise - Google Patents
Method and apparatus for attenuating compressor noise Download PDFInfo
- Publication number
- WO2006017398A2 WO2006017398A2 PCT/US2005/027057 US2005027057W WO2006017398A2 WO 2006017398 A2 WO2006017398 A2 WO 2006017398A2 US 2005027057 W US2005027057 W US 2005027057W WO 2006017398 A2 WO2006017398 A2 WO 2006017398A2
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- Prior art keywords
- flow path
- gas flow
- compressor
- inlet
- chambers
- Prior art date
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0057—Pumps therefor
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0057—Pumps therefor
- A61M16/0063—Compressors
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/06—Silencing
- F04C29/061—Silencers using overlapping frequencies, e.g. Helmholtz resonators
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/06—Silencing
- F04C29/065—Noise dampening volumes, e.g. muffler chambers
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0057—Pumps therefor
- A61M16/0066—Blowers or centrifugal pumps
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M16/00—Devices for influencing the respiratory system of patients by gas treatment, e.g. mouth-to-mouth respiration; Tracheal tubes
- A61M16/0057—Pumps therefor
- A61M16/0066—Blowers or centrifugal pumps
- A61M16/0069—Blowers or centrifugal pumps the speed thereof being controlled by respiratory parameters, e.g. by inhalation
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
- A61M2205/00—General characteristics of the apparatus
- A61M2205/42—Reducing noise
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
- F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
- F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
- F04C18/126—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type
Definitions
- the present invention relates to compressors, and more particularly to a method and apparatus for reducing the noise generated by compressors, including Roots-type blowers used in portable mechanical ventilators.
- Roots-type blowers have potential application in a wide variety of environments. They are relatively efficient, and can produce a wide range of delivery pressures and volumes. However, they produce a high level of noise. The high noise level produced by Roots blowers has limited their use in environments where such high noise levels are unacceptable. One such environment is providing breathing assistance to patients by means of a mechanical ventilator.
- a purpose of a mechanical ventilator is to reproduce the body's normal breathing mechanism. Most mechanical ventilators create positive intrapulmonary pressure to assist breathing. Positive intrapulmonary pressure is created by delivering gas into the patient's lungs so that positive pressure is created within the alveoli (i.e. the final branches of the respiratory tree that act as the primary gas exchange units of the lung).
- a mechanical ventilator is essentially a device that generates a controlled flow of gas (e.g. air or oxygen) into a patient's airways during an inhalation phase, and allows gas to flow out of the lings during an exhalation phase.
- Mechanical ventilators use various methods to facilitate precise delivery of gas to the patient. Some ventilators use an external source of pressurized gas. Other ventilators use gas compressors to generate an internal source of pressurized gas.
- Constant speed compressors are usually continuously operating, rotary-based machines that generate a fairly constant rate of gas flow for ultimate delivery to the patient.
- These constant speed systems generally use a downstream flow valve to control flow of the gas to the patient, with a bypass or relief mechanism to divert excess flow that is at any time not needed by the patient (e.g. during exhalation).
- Variable speed compressors operate by rapidly accelerating from a rest state to the rotational speed needed to produce the flow rate necessary during the beginning of the inhalation phase, and then decelerating to a rest or nearly rest state at the end of the inhalation phase to allow the patient to exhale.
- variable speed compressor systems Two types are typically employed in the mechanical ventilator art: piston-based systems and rotary-based systems.
- An example of a prior art variable speed compressor system for use in a mechanical ventilator is described in U.S. Patent No. 5,868,133 to DeVries et al. This system uses drag compressors to provide the desired inspiratory gas flow to the patient.
- Rotary compressor systems deliver the required gas flow during inhalation by accelerating the compressor rotor(s) to the desired speed at the beginning of each inspiratory phase and decelerating the compressor rotor(s) to rest or nearly rest speed at the end of each inspiratory phase.
- the rotary compressor is stopped, or rotated at a nominal base rotational speed, prior to commencement of each inspiratory ventilation phase.
- the rotary compressor is accelerated to a greater rotational speed for delivering the desired inspiratory gas flow to the patient.
- the rotational speed of the compressor is decelerated to the base speed, or is stopped, until commencement of the next inspiratory ventilation phase.
- Prior art systems typically use a programmable controller to control the timing and rotational speed of the compressor. Great strides have been realized in reducing the size of mechanical ventilators.
- Ventilators are now available that are portable, and allow users a limited degree of autonomous mobility. Further reducing the size and power requirements of mechanical ventilators hold the potential of giving patients even greater freedom of movement, enhancing their quality of life.
- Roots blower can potentially contribute to the reduction in size and power consumption of mechanical ventilators.
- Roots blowers use a pair of interacting rotors. Each rotor has two or more lobes. The rotors are rotated inside a housing having an inlet and an outlet. The rotors rotate with the lobes of one rotor moving into and out of the spaces between the lobes of the other. Gas is moved through the blower in chambers formed by adjacent lobes of a rotor and the adjacent rotor housing wall. These chambers will be referred to herein as "gas transport chambers.”
- Noise is generated by roots blowers in a number of ways.
- One type of noise is caused by pulsing flow.
- the gas transport chambers between the lobes of each rotor are sequentially exposed to the outlet.
- a lobe of the mating rotor rotates into the chamber, displacing the gas in chamber to the outlet, causing a flow/pressure pulse.
- a second type of noise is generated by a phenomenon known as "flow back."
- flow back As each rotor rotates, it inducts gas at low pressure at the inlet. This gas is generally trapped in the gas transport chambers as the rotor moves towards the outlet. When this pocket of gas initially reaches the outlet, it is exposed to higher pressure gas at the outlet. At that time, the higher pressure gas at the outlet rushes backwardly into the gas transport chamber that contains the lower pressure gas that is being delivered from the inlet.
- Roots blower configured with noise reducing flow-back channels is described in co-pending U.S. Patent Application Serial No. 10/985,528. Although such flow-back channels are effective in reducing the level of noise, the resultant noise level may still not be sufficiently low for some mechanical ventilator applications. Accordingly, additional methods and apparatus for reducing Roots blower noise are desired.
- the invention comprises a method and apparatus for reducing the noise generated by compressors, including Roots-type blowers.
- the invention has particular use for reducing noise generated by compressors used in mechanical ventilators, though the advantages thereof may be realized in many different applications, including in attenuating noise generated by devices other than compressors and Roots-type blowers and in other applications than mechanical ventilators in which noise attenuation is desires.
- One embodiment of the invention comprises a noise-attenuating gas flow path for a compressor contained in a portable ventilator housing.
- the gas flow path comprises an inlet flow path from an inlet of the ventilator housing to an inlet of the compressor, and/or an outlet gas flow path from an outlet of the compressor to an outlet of the ventilator housing.
- Each gas flow path includes a plurality of interconnected chambers.
- the inlet flow path comprises at least two chambers interconnected by means of a flow tube. The dimensions of the chambers and the flow tubes are selected so that an impedance mismatch is created between the chambers and the flow tubes.
- this impedance mismatch is created by sizing adjacent chambers so that they have a cross-sectional flow area substantially larger than the cross-sectional area of the flow tube that interconnects the two chambers. This impedance mismatch reduces the amount of noise transmitted from one chamber to the next.
- the chambers and flow- tubes may e configured in a folded flow path that allows the flow path to fit into a housing of limited space, such as a portable ventilator housing.
- the flow path comprises one or more perforated tubes.
- one or more perforated tubes are located in one or more of the chambers comprising the gas inlet and/or outlet flow paths.
- the perforated tube is configured to provide a large impedance mismatch without excessively impeding gas flow.
- the perforated tube has at least one exterior tube extending from the tube wall through which gas exits. The cross-sectional area of the at least one exterior tube is substantially reduced compared to the effective flow area of both the inlet chamber of the perforated tube and the chamber in which the perforated tube is located. In this matter, impedance mismatches are created between the inlet chamber and the exterior tubes and between the exterior tubes and the chamber in which the perforated tube is located, which are useful in attenuating noise.
- the perforated tube includes a plurality of exterior tubes. In this configuration, an impedance mismatch is created relative to each exterior tube, but the total cross-sectional flow area through the perforated tube via the multiple exterior tubes remains relatively large.
- One embodiment of the invention comprises a noise attenuating mounting system for a compressor.
- the mounting system comprises flexible mounts that cooperate to dampen vibrations generated by the compressor.
- a plurality of mounts are positioned between a housing of the compressor and a supporting structure, such as the walls of a compartment of a mechanical ventilator in which the compressor is disposed.
- the mounts comprise a connecting member that is connected to the compressor housing and a damping member that is positioned between the connecting member and the supporting structure.
- Each mount is configured so that the natural frequency of the blower and its associated mounts, when assembled, is below the frequency of the forces that are to be damped.
- the blower is generally configured to operate at relatively high speeds, from about 6000 rpm to about 20,000 rpm, and the mounts are configured such that the compressor/mount assembly has a natural frequency below the range of about 10 Hz.
- the mounts are constructed of silicon rubber having a hardness of about 70 shore.
- FIGURE 1 is a perspective view of a mechanical ventilator comprising one embodiment of the invention
- FIGURE 2 is a perspective view of a housing for a Roots-type blower comprising a plurality of flexible mount of an embodiment of the invention
- FIGURE 3 is a perspective view of one of the flexible mounts illustrated in
- FIGURE 4 is a cross-sectional view of the flexible mount illustrated in Figure 3 taken along line 4-4 therein;
- FIGURE 5 is a cross-sectional view of the mechanical ventilator illustrated in Figure 1 showing the inter-relationship of the flexible mounts with the Roots blower housing and a compartment of a mechanical ventilator;
- FIGURE 6 is a perspective view of a perforated tube in accordance with one embodiment of the invention.
- FIGURE 7 is a cross-sectional view of the perforated tube illustrated in Figure 6 taken along line 7-7 therein;
- FIGURE 8 is a cross-sectional view of the perforated tube illustrated in Figure 7 taken along line 8-8 therein.
- the invention comprises a method and apparatus for attenuating or reducing noise generated by compressors, including Roots-type blowers.
- compressors including Roots-type blowers.
- the invention comprises a method and apparatus for reducing or attenuating generated noise.
- the invention has particular application to reducing or attenuating noise generated by compressors used in noise-sensitive environments, such as, for example, a Roots-type blower used in a portable mechanical ventilator.
- One embodiment of the invention comprises a specially configured gas inlet path from an inlet of a housing in which the compressor is disposed to an inlet of the compressor, and/or a specially configured gas outlet path from an outlet of the compressor to an outlet of the housing in which the compressor is disposed.
- the path(s) include one or more chambers and connecting tubes configured to reduce the noise generated by the compressor.
- the invention comprises one or more noise attenuating perforated tubes.
- the perforated tubes may be disposed along the inlet and/or outlet paths to reduce the noise generated by the compressor.
- the invention comprises a compressor mounting system comprising one or more shock absorbing or damping elements.
- the various embodiments of the noise-reducing method and apparatus of the invention may be used together or apart from one another to reduce the noise generated by a compressor. It will also be appreciated that the invention may have application in other environments, including compressors used in noise sensitive environments other than in mechanical ventilators.
- the method and apparatus of the invention are "external” in the sense that they are located outside of the compressor or other device that is the source of the noise to be attenuated. This contrasts to "internal” noise attenuating techniques, such as the Roots-type blower configuration described in co-ending U.S. Patent Application Serial No. 10/985,528 filed November 10, 2004, incorporated by reference herein.
- FIG. 1 illustrates the portion of a portable mechanical ventilator 20 containing a compressor 24 and inlet and outlet flow paths of an embodiment of the invention.
- Ventilator 20 comprises one environment in which the noise reducing method and apparatus of the invention may be used.
- the mechanical ventilator 20 illustrated in Figure 1 comprises a housing 22 containing or supporting a plurality of components.
- Figure 1 is a rear view of the housing illustrating the ventilator 20 with a rear cover portion of the housing 22 removed to expose various components located within the housing 22.
- mechanical ventilators 20 generally include a great number of components. Various of those components do not comprise portions of the present invention, and as such are not described in detail herein.
- the ventilator 20 includes a plurality of gas flow control equipment, including circuitry, input buttons and the like.
- the ventilator 20 includes a Roots-type blower 24.
- the Roots-type blower 24 is of the type described and illustrated in co-pending U.S. Application Serial No. 10/985,528 filed November 10, 2004, which is incorporated in its entirety herein.
- the blower 24, including its associated drive motor is mounted within a housing 26 (shown in Figure 2).
- the housing 26 may have a wide variety of configurations. Referring to Figure 2, in one embodiment, the housing 26 is generally rectangular in shape, having first and second opposing ends 28,30, a first and a second opposing side 32,34, and a top 36 and a bottom 38. The housing 26 may have a great number of other shapes and configurations.
- the blower 24 has an outlet 33 and an inlet (not visible in Figure 2).
- the outlet 33 is located at the first side 32 and the outlet is located at the second side 34 of the housing 26 of the blower 24.
- the blower 24 is mounted in the ventilator housing
- blower 24 is mounted in a blower chamber or compartment 40. Details of the compartment 40 are provided below.
- the gas flow path comprises an inlet gas flow path from an inlet of a housing in which a compressor is disposed to an inlet of the compressor, and/or an outlet gas flow path from the outlet of the compressor to an outlet of the housing.
- the compressor is part of a mechanical ventilator, and the housing is the mechanical ventilator housing.
- the compressor is a Roots-type blower.
- a gas flow path is provided from an inlet port 200 of the ventilator housing 22 to an inlet of the blower 24.
- a second gas flow path is provided from an outlet of the blower to an outlet of the ventilator housing.
- an inlet and/or outlet gas flow path includes one or more chambers interconnected by one or more flow tubes configured to create impedance mismatches at each tube/chamber interface that reduce the noise generated by the blower.
- the terms "chamber” and "flow tube” refer to any passage configured so as to allow the flow of gas there through.
- Figure 1 illustrates one embodiment of such a flow path.
- a first point of the flow path comprises an inlet port 200 in a ventilator housing 22.
- the port 200 may include a filtration element 202, as is known to those of ordinary skill in the art.
- Inlet port 200 provides a flow path to a first chamber 202.
- the fist chamber 202 is defined by one or more walls 204.
- the walls 204 may comprise a portion of the ventilator housing 22, such as by being integrally molded.
- the first chamber 202 is generally enclosed when the blower 24 is in use.
- a cover in one embodiment forms a portion of the housing 22 and forms a top portion of the chamber 202 during use.
- gas enters first chamber 202 through port 200 and exits through an outlet port 206 leading from the chamber.
- the configuration of the first chamber 202 including its shape and size, may vary.
- the configuration of the first chamber 202 may in one embodiment be determined so that the first chamber 202 is effective in attenuating noise at one or more frequencies.
- the outlet port 206 from the first chamber 202 comprises an inlet to a flow tube 212.
- An outlet port 208 of flow tube 212 forms an inlet to a second chamber 210.
- the gas flow area of the passage defined by the flow tube 212, or at least of outlet port 206 and/or inlet port 208 thereof, is substantially smaller than the respective gas flow areas of first and second chambers 202,210. In this manner, an impedance mismatch is created. This impendence mismatch attenuates the sound generated by the Roots-type blower 24 that is transmitted along the inlet gas flow path to the Roots-type blower 24.
- flow tube 212 comprises a generally circular wall defining a central passage.
- the passage has a first end corresponding to the outlet port 206 and a second end corresponding to the inlet port 208.
- the flow tube 212 is mounted to the ventilator housing 22 and, more particularly, in or to a dividing wall 204a dividing the first chamber 202 and second chamber 210.
- the tube 212 has a pair of flanges 214a,b.
- the flanges 214a,b are annular and spaced from one another to define a slot 216 there between.
- the slot 216 is of sufficient width to fit into a semi ⁇ circular opening formed in the dividing wall 204a that divides the first and second chambers 202,210.
- a portion of the dividing wall 204a is connected to or formed as part of the cover, and part is connected to or formed as part of the housing 22.
- the flow tube 212 extends through a semi-circular opening in the dividing wall 204a.
- a portion of an opening through which the flow tube 212 extends is formed in the portion of the dividing wall associated with the cover, and the remaining portion of the opening is defined by the portion of the dividing wall associated with the main portion of the housing 22.
- the flow tube 212 when the cover is removed, the flow tube 212 is accessible and may be removed from the housing 22, such as by lifting it out of engagement with the portion of the dividing wall 204a associated with the housing 22. As illustrated in Figure 1, one or more tabs 218 may extend from the flow tube
- the tabs 218 in one embodiment help ensure correct placement of flow tube 212 during assembly.
- the tabs 218 comprise generally planar elements that are integrally formed with the flow tube 212, and more particularly, are formed as extensions of flanges 214a,b.
- the flow tube 212 may be constructed from a variety of materials and in a variety of ways. In one embodiment, the flow tube 212 is constructed of flexible urethane material.
- gas flows to the second chamber 210 from the first chamber 202 via the flow tube 212.
- the second chamber 210 has an outlet port 220 which leads to an inlet port 222 of a third chamber 224.
- the second and third chambers 210,224 are in one embodiment linked by a connecting flow tube 228, similar in form to flow tube
- the flow tube 228 spans a dividing wall 229 between the second and third chambers 210,224.
- the cross-Osectional flow area of flow tube 228, like that of flow tube 212, is chosen such that an impedance mismatch is created between chamber 210 and flow tube 228 and between flow tube 228 and chamber 224. These impedance mismatches further reduce the noise generated by Roots-type blower 24.
- the third chamber 224 has an outlet port 230 that leads to a fourth chamber 232.
- the outlet port 230 of the third chamber 224 leads to a perforated tube 234 disposed within a fourth chamber 232. Details of the perforated tube 234 are described in more detail below.
- a second perforated tube (not visible in Figure 1) is disposed in the fourth chamber 232 underneath perforated tube 234. This second perforated tube is in communication with the fourth chamber 232 and the inlet to the
- Roots-type blower 24 As described above, the Roots-type blower 24 is located in a compartment 40 defined by one or more walls. In one embodiment, the fourth chamber 232 and the compartment 40 are separated at least in part by a dividing wall 236. An opening (no shown) is provided in the dividing wall 236, allowing the second perforated tube to mate with the inlet to the Roots-type blower 24 such that gas may flow from the fourth chamber 232 through the second perforated tube to the inlet of the Roots-type blower.
- an inlet flow path is defined from a point outside of the ventilator housing 22 through the first, second, third and fourth chambers 202,210,224,232, flow tubes 212 and 228, perforated tube 234 and the second perforated tube to the inlet of the Roots-type blower 24. Gas flows through this path from outside ventilator housing 22 to the Roots-type blower 24.
- the size of one or more of the chambers 202,210,224,232 and flow tubes 212 and 228 are in one embodiment selected so that multiple impedance mismatches are created along the inlet flow path to the Roots-type blower 24.
- these impedance mismatches are created by sizing the chambers so that their respective cross-sectional gas flow areas are substantially larger than the corresponding cross-sectional flow areas of the flow tubes interconnecting the chambers.
- the ventilator housing 22 it is desirable to make the ventilator housing 22 generally as small as possible so as to reduce the total size or dimensions of the ventilator 20.
- various of the components of the ventilator occupy space in the housing 22, such as the control circuitry, the Roots-type blower and the like. This leaves only a finite mount of . space within the housing 22 for the noise attenuating flow path of the invention.
- the size and shape of the chambers, and their configuration is to some extent limited by the size and shape of the ventilator housing
- the size of the chambers is selected to attenuate noise of specific frequencies.
- the size and shape of the second chamber 210 may be selected so that the impedance mismatch between chamber 210 and flow tube 228 substantially eliminates noise generated by the Roots-type blower at one or more first frequencies.
- the size and shape of the third chamber 224 may be selected so that the impedance mismatch between chamber 224 and perforated tube 234 substantially eliminates noise generated by the Roots-type blower at one or more second frequencies different from the first frequency(ies).
- a plurality of chambers and connecting flow tubes are selected to reduce the noise generated by a Roots-type blower at a plurality of frequencies.
- chambers and connecting flow tubes there may be a greater or lesser number of chambers and connecting flow tubes.
- the number, size, shape of chambers and flow tubes and the configuration of the resulting flow path may depend upon the available space for the chambers within the ventilator housing 22. For example, a finite space may remain to define the inlet flow path once the housing size is fixed and the other components are associated with the housing. It may be found that as few as one or as many as four or more chambers may be arranged in this space to meet the desired goals.
- the use of multiple chambers and flow tubes allows the creation of a flow path that does not have to be linear, but that can be "folded," as in the embodiment of Figure 1 , to fit within the limited size and shape of space available in a housing or other enclosure, such as the portable ventilator housing of figure 1.
- the flow path is "folded" in the sense that it is configured to provide at least one change in direction of the gas flow along the flow path.
- the gas flow path is configured to provide a plurality of changes in direction of approximately 90 degrees.
- Certain portions of the flow path of figure 1 providing a change in direction of greater than 90 degrees including portions that provide a change in direction of approximately 180 degrees (for example the portion of the flow path that comprises flow tube 228 and chamber 224) and approximately 270 degrees (for example the portion of the flow path that comprises chamber 210, flow path 228, and chamber 222).
- the shape of the chambers may be generally rectangular, or may have irregular shapes, such as, for example, the "dogleg" shape of chambers 210 and 224 in the embodiment of Figure 1.
- a flow path is defined from an outlet of the Roots-type blower 24 to a second point.
- this second point comprises an outlet of the ventilator housing 22.
- an outlet of the Roots-type blower 24 leads to a fifth chamber 240.
- an opening is provided in a wall forming the compartment 40 in which the Roots-type blower 24 is located. The opening is in one embodiment aligned with the outlet of the Roots-type blower 24.
- expelled gas is directed from the outlet of Roots blower 24 through a pair of perforated tubes (perforated tube 242 and a fourth perforated tube, not visible in Figure 1, that is disposed in fifth chamber 240 underneath perforated tube 242) arranged in a similar manner to the two perforated tubes disposed inside fourth chamber 232.
- the expelled gas flows from the outlet of the blower through the fourth perforated tube (not shown) into the fifth chamber 204.
- the ventilator outlet includes a nipple or connector to which a delivery tube (not shown) may be connected.
- the delivery tube is in one embodiment used to deliver gas to a user of the ventilator 20.
- the outlet flow path leads from the Roots-type blower 24 via the fourth perforated tube (not visible) to the fifth chamber 240, and from there via perforated tube 242 to the ventilator outlet.
- the outlet flow path may not include a chamber at all, but simply a passage to the outlet.
- the outlet flow path might include a plurality of noise attenuating chambers and flow tubes, in a fashion similar to the inlet path described above.
- an elongate delivery tube that is connected to the outlet of the ventilator 20 to deliver gas to the patient.
- an externally connected tube less noise attenuation need be created along the outlet flow path from the outlet of the Roots-type blower 24 to the outlet of the housing 22 than along the inlet flow path from the inlet port 20 of housing 22 to the inlet of the Roots blower 24, because additional noise attenuation is provided externally by the delivery tube.
- the configuration of the outlet flow path is in one embodiment is particularly configured to stay within the space which is available for the housing 22, while attenuating the particular frequency(ies) of noise desired to be attenuated.
- the outlet flow path may be linear, or may be "folded" in the same manner as the inlet flow path.
- the size and shape of the ventilator housing overall may be dictated by a number of factors.
- the configuration of the inlet and outlet flow paths may then be determined, given the set amount of space that remains.
- iterations of flow path configurations may be performed to determine the best noise-attenuating configuration overall for the particular operational parameters of the blower or compressor.
- life-size models of each chamber and flow tube are connected in a linear fashion to construct a flow path prototype.
- the prototype flow path is connected to the Roots-type blower or other compressor and tested at the desired operating ranges of the compressor. Changes in number, sizes, and configurations of the chambers and flow types may be iteratively made to determine the combination that produces the most satisfactory noise attenuation.
- the ventilator 20 illustrated in Figure 1 has both a particularly configured noise-attenuating inlet flow path and outlet flow path, the ventilator 20 may be provided with only one or the other flow paths. It will also be appreciated that gas flow paths having the characteristics described above may be used in other environments, including with other types of blowers or compressors and in environments other than mechanical ventilators.
- One or more embodiments of the invention comprise a noise-attenuating perforated tube.
- the perforated tube provides a gas flow path, while at the same time attenuating noise that is transmitted through the flowing gas.
- the perforated tube may be utilized in conjunction with a gas flow path to or from a
- the perforated tube 300 comprises a body 302 defining at least one port 304 and a plurality of exterior tubes
- port 304 may act as either an inlet or an outlet port, and exterior tubes 306 may form flow passages out of or into perforated tube 300.
- the port 304 in one embodiment comprises a circular port defined by a generally circular wall portion of the body 302.
- the port 304 leads to an interior chamber 308 defined by the body 302.
- the plurality of exterior tubes 306 are also in communication with the interior chamber
- a flow path is defined from the port 304 via the interior chamber 308 to an through the plurality of exterior tubes 306 or from the exterior tubes 306 via the interior chamber 308 through port 304, depending on the direction of gas flow.
- the port 304 is connected to a right-angle tube 260 that defines a pathway from a first chamber through a dividing wall, in similar fashion to the tubes 212 and 228 described above. As illustrated in Figure 1, this allows the port 304 to be in communication with one chamber, while the main portion of the body of the perforated tube, including the at least one exterior tube, is positioned inside another chamber.
- the body 302 includes a plurality of exterior tubes 306 each of which has a cross-sectional flow area that is substantially smaller than the diameter of body 302. In this manner, an impedance mismatch is created between the cross-sectional flow area of internal chamber 308 and each exterior tube 306 that is useful in attenuating noise.
- the perforated tube 300 includes a plurality of exterior tubes 306 that collectively provide a sufficient total flow area so that any impediment to gas flow is reduced. In this configuration, an impedance mismatch is created relative to each exterior tube 306, but the total flow rate of gas through the perforated tube 300 via the multiple exterior tubes 306 remains substantially unimpeded.
- each exterior tube 306 comprises a flow path of reduced diameter (compared to the diameter of internal chamber 308) having a length.
- each exterior tube flow path has a first end 310 at the interior chamber 308, and a second end 312 that extends beyond the external dimension of body 302.
- This length provides additional noise attenuation benefits.
- each exterior tube 306 is defined by a cylindrical projection that extends outwardly from the body 302.
- the amount of space within the chamber in which the perforated tube 300 is located that is not occupied by the perforated tube is greater than if the length of the exterior tube flow path were provided solely by a wall thickness of body 302 (which would require a wall thickness equal to the exterior tube length).
- the exterior tube flow path could have a length defined by a passage through a thick wall comprising the body of the perforated tube. Compared to the embodiment illustrated in Figure 1, this would result in the body occupying a substantially greater amount of space. In a case such as that illustrated where the size of the chamber in which the perforated tube is located is limited, such a configuration would substantially reduce the unoccupied volume of the chamber in which the .
- One embodiment of the invention comprises a method of fabricating the perforated tube 300.
- the perforated tube is molded from a two- piece mold. When the perforated tube leaves the mod, the body is generally cylindrical in exterior shape with a wall thickness equal to the length of the flow paths of exterior tubes 306. Thereafter, material comprising the body is removed except in the areas of the exterior tubes 306, thus forming the cylindrical projections shown in
- the perforated tube 300 of the invention may be constructed in a variety of other manners and may be constructed from a variety of other materials.
- the perforated tube could be constructed using a multi-piece mold that directly forms the perforated tube into the shape and configuration illustrated in
- the perforated tube 300 could have a rectangular cross-section instead of the circular cross-section shown in Figures 6-8.
- the perforated tube 300 is constructed from a durable and resilient material, such as an ABS thermoplastic.
- the perforated tube 300 is configured to be located in a chamber or compartment.
- the perforated tube is located in a chamber along a flow path to or from a Roots-type blower or other compressor.
- the size of the chamber may be selected so that the chamber housing the perforated tube creates an impedance mismatch with the exterior tubes of the perforated tube and with the next and/or preceding element in the gas flow path.
- a multiple perforated tubes may be disposed in the same chamber, forming a gas flow path through the first perforated tube into the chamber, and then through the second perforated tube out of the chamber.
- the configuration of the perforated tube and/or the chamber in which it is disposed may be selected so that the impedance mismatch results in an attenuation of noise at one or more frequencies or frequency ranges.
- the size and number of the exterior tubes 306, including their location may be selected relative to the desired gas flow rate, chamber size and the amount of noise attenuation desired and the frequencies of noise that are to be attenuated. For example, changing the cross-sectional area and/or length of the exterior tubes 306 will typically result changes in noise attenuation characteristics of the perforated tube.
- each of the various noise attenuating components along the flow paths to an from the Roots-type blower 24 may be selected so that the components (in cooperation with adjacent components) attenuate noise at one or more frequencies or frequency ranges, and collectively the nose is attenuated over a variety of frequencies or frequency ranges.
- the configuration of the noise attenuating components illustrated in Figure 1 are as shown in Table 1 :
- One or more embodiments of the invention comprise a noise reducing component mounting system.
- One embodiment comprises a method and apparatus for mounting a compressor such as Roots-type blower 24 so as to isolate the compressor assembly (including its housing and electric motor), from the housing or frame to which the compressor assembly is mounted.
- a compressor such as Roots-type blower 24
- one or more damping elements are located between the housing 26 of the blower 24 and the ventilator hosing 22 or other support structure in which the blower is located.
- the damping elements comprise resilient mounts 100.
- each resilient mount 100 comprises a supporting member and a damping member.
- Each resilient mount 100 is configured so that the natural frequency of the blower assembly, when mounted to the ventilator housing 22 by means of resilient mounts 100, is below the frequency of the forces which are intended to be damped.
- the resilient mounts 100 are configured to damp forces generated by blower 24 during its operation.
- each resilient mount 100 comprises a support member 102 and a damping member 104.
- the damping member 104 comprises a resilient, bellows-shaped element.
- the damping member 104 has a first end 106 and an opposing second end 108.
- the first end 106 comprises a first support portion 110 of the damping member 104
- the second end 108 comprises a second support portion 112 of the damping member 104.
- the first support portion 110 comprises a generally solid, cylindrical portion of damping member 104.
- the first support portion 110 is configured to engage the support member 102, described in more detail below.
- the second support portion 112 comprises an annular member defining a central opening 114.
- central opening 114 is tapered such that the diameter of the opening increases moving in the direction of second end 108 of the damping member 104.
- a flexible or resilient bellows-shaped portion 116 is located between the first and second support portions 110,112 of the damping member 104. As illustrated, this portion 116 comprises a generally annular member defined by a foldable wall 118.
- the foldable wall 118 extends between first support portion 110 and second support portion 112 of the damping member 104.
- the foldable wall 118 defines a plurality of bellows or accordion-shaped elements that allow the foldable wall 118 to expand and contract in the axial direction between the first and second support portions 110,112.
- the foldable wall 118 defines an internal space 120 that is in communication with the opening 114 of the damping member 104.
- the support member 102 is configured to attach the damping member 104 to the blower housing 26.
- the support member 102 is a Phillips head, flathead screw.
- damping member 104 is constructed of silicon rubber having a hardness of about 70 shore.
- the support member 102 and damping member 104 may each be molded as separate elements, and then assembled together to form the resilient mount 100.
- the resilient mount 100 may have a plurality of sizes/configurations and damping characteristics.
- the size/configuration of the resilient mount 100 is selected to provide a particular degree of damping, when considering the mass of the compressor assembly and the forces generated by the compressor, and the total number of resilient mounts
- each resilient mount 100 is about 0.3 in. tall and has a diameter of about 0.25 in.
- the size, shape and materials of the resilient mounts 100 are selected so that the compressor assembly when mounted on resilient mounts 100 has a natural frequency less than the frequency of the forces generated by the compressor that are to be damped.
- a plurality of resilient mounts 100 are positioned between the top 36 of the blower housing 26 and the ventilator housing 22, and between the bottom 38 of the blower housing 26 and the ventilator housing 22.
- resilient mounts 100 are position between the blower housing 26 and the bottom of the compartment 40, as defined by the ventilator housing 22, and a top of the compartment 40 as defined by a cover portion (not shown) of the housing 22.
- a resilient mount 100 is located at each of the four corners of the blower housing 26 at its top 36, and at each of its four corners at its bottom 38. In one embodiment, the resilient mounts 100 are connected to the blower housing 26.
- recesses or openings 130 are provided in the housing 26 for accepting the base 122 of the resilient mounts 100.
- the compartment 40 is partially defined by one or more wall elements.
- the wall elements are located in close proximity to the ends 28,30, sides 32, 34 and top and bottom 36,38 of the blower housing 26.
- openings are provided in the walls of the compartment 40 in alignment with the inlet and outlet, respectively, of the blower 24.
- the proximal location of the compartment 40 walls to the inlet and outlet of the blower 24 allows gas to flow through those walls into and out of the blower 24.
- blower housing 36 is on the order of about .04 to .06 inches.
- the walls that define a top and bottom of the compartment 40 are in one embodiment spaced from the blower housing 26 a sufficient distance to accommodate the resilient mounts 100. In one embodiment, this distance is about 0.04 to 0.10 in.
- the walls that define the top and bottom of the compartment 40 are configured to positively engage the mounts 100.
- projections 132 extend from the walls and engage the tapered openings 114 of the resilient mounts 100.
- the projections 132 are conical in shape, having a sloping outer surface that matches that of the tapered opening 114 of the second support portion 112 of the damping member 104. In this configuration, the damping member 104 is configured to engage the projection 132, securing the resilient mount 100 in position.
- resilient mounts 100 may be used, and their location may vary.
- resilient mounts 100 may be located at the ends and/or sides of the compressor housing 26 in addition to or instead of at the top and bottom of the blower housing 24.
- the various embodiments of the invention have particular advantages. While embodiments of the invention may be used in a variety of environments for reducing or attenuating noise, they have particular applicability to an environment where space is limited, such as in a portable ventilator housing.
Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2007524871A JP4773443B2 (en) | 2004-08-04 | 2005-07-29 | Method and apparatus for attenuating compressor noise |
EP05777464.8A EP1773455B1 (en) | 2004-08-04 | 2005-07-29 | Method and apparatus for attenuating compressor noise |
BRPI0514146A BRPI0514146B1 (en) | 2004-08-04 | 2005-07-29 | noise attenuation system for a compressor |
AU2005271658A AU2005271658B9 (en) | 2004-08-04 | 2005-07-29 | Method and apparatus for attenuating compressor noise |
CA2574018A CA2574018C (en) | 2004-08-04 | 2005-07-29 | Method and apparatus for attenuating compressor noise |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
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US10/912,747 | 2004-08-04 | ||
US10/912,747 US7188621B2 (en) | 2003-08-04 | 2004-08-04 | Portable ventilator system |
US11/088,316 | 2005-03-23 | ||
US11/088,316 US7527053B2 (en) | 2003-08-04 | 2005-03-23 | Method and apparatus for attenuating compressor noise |
Publications (2)
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WO2006017398A2 true WO2006017398A2 (en) | 2006-02-16 |
WO2006017398A3 WO2006017398A3 (en) | 2007-11-01 |
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PCT/US2005/027057 WO2006017398A2 (en) | 2004-08-04 | 2005-07-29 | Method and apparatus for attenuating compressor noise |
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US (1) | US7527053B2 (en) |
EP (2) | EP1773455B1 (en) |
JP (2) | JP4773443B2 (en) |
AU (1) | AU2005271658B9 (en) |
BR (1) | BRPI0514146B1 (en) |
CA (2) | CA2765227A1 (en) |
WO (1) | WO2006017398A2 (en) |
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- 2005-07-29 AU AU2005271658A patent/AU2005271658B9/en not_active Ceased
- 2005-07-29 EP EP05777464.8A patent/EP1773455B1/en not_active Not-in-force
- 2005-07-29 EP EP16192373.5A patent/EP3153762A1/en not_active Withdrawn
- 2005-07-29 CA CA2765227A patent/CA2765227A1/en not_active Abandoned
- 2005-07-29 JP JP2007524871A patent/JP4773443B2/en not_active Expired - Fee Related
- 2005-07-29 CA CA2574018A patent/CA2574018C/en not_active Expired - Fee Related
- 2005-07-29 BR BRPI0514146A patent/BRPI0514146B1/en not_active IP Right Cessation
- 2005-07-29 WO PCT/US2005/027057 patent/WO2006017398A2/en active Application Filing
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JP2014524268A (en) * | 2011-08-05 | 2014-09-22 | レスメド・モーター・テクノロジーズ・インコーポレーテッド | Blower |
US10124135B2 (en) | 2011-08-05 | 2018-11-13 | Resmed Motor Technologies Inc. | Blower |
US11191913B2 (en) | 2011-08-05 | 2021-12-07 | Resmed Motor Technologies Inc. | Blower |
Also Published As
Publication number | Publication date |
---|---|
AU2005271658B2 (en) | 2011-04-28 |
US7527053B2 (en) | 2009-05-05 |
WO2006017398A3 (en) | 2007-11-01 |
EP1773455A2 (en) | 2007-04-18 |
CA2574018C (en) | 2014-05-06 |
AU2005271658B9 (en) | 2011-06-30 |
CA2765227A1 (en) | 2006-02-16 |
EP1773455A4 (en) | 2008-12-17 |
BRPI0514146B1 (en) | 2016-12-27 |
JP4773443B2 (en) | 2011-09-14 |
EP1773455B1 (en) | 2016-11-02 |
EP3153762A1 (en) | 2017-04-12 |
JP2011214576A (en) | 2011-10-27 |
AU2005271658A1 (en) | 2006-02-16 |
BRPI0514146A (en) | 2008-05-27 |
US20050166921A1 (en) | 2005-08-04 |
JP2008509331A (en) | 2008-03-27 |
CA2574018A1 (en) | 2006-02-16 |
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