Patent Publication Number: US-2006011065-A1

Title: Inlet nozzle for oxygen concentrator

Description:
FIELD OF THE INVENTION  
      This invention relates to oxygen concentrators and, more specifically, to an inlet nozzle for an oxygen concentrator that reduces the acoustic noise or air stream noise as well as minimizes the wear on the filter of the oxygen concentrator.  
     CROSS REFERENCE TO RELATED APPLICATIONS  
      None  
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      None  
     REFERENCE TO A MICROFICHE APPENDIX  
      None  
     BACKGROUND OF THE INVENTION  
      One of the problems with oxygen concentrators is that they generate acoustic or air stream noise as the air is drawn into the oxygen concentrators. To reduce the noise input silencers or mufflers that use padding are known in the art. An oxygen concentrator with an inlet silencer/filter is shown and described in Robert&#39;s U.S. Pat. No. 6,702,880. In general, a compressor draws ambient air through a nozzle and a filter removes unwanted particles from the air as it flow through the filter. One of the difficulties is that the particles which are moving with the air stream impinge with high velocity on the filter and can cause premature failure of the filter.  
      In addition to the mechanical noise generated by the operation of the compressor acoustical noise or air stream noise is also generated as the ambient air is drawn into the filter housing. In general, it was believed that to reduce the acoustical noise one should increase the flow resistance or pressure drop through the filter housing. Consequently, an offset nozzles in the form of an insert or a through the wall orifice have been used to increase the fluid flow resistance or pressure drop therethrough. By increasing the fluid resistance and hence the inefficiency of the system one would decrease the acoustical noise. In contrast, the present invention provides for acoustical noise reduction while at the same time improving the efficiency of the system by use of nozzle that directs and disperses the flowing air over an extended area of a filter.  
     SUMMARY OF THE INVENTION  
      An inlet nozzle for an oxygen concentrator wherein the inlet nozzle contains an at least one fluid passage that substantially maintains the flow orientation of the air as it directs and disperses the incoming air over an extended area which both reduces the wear on the filter as well as reduces the acoustical noise of the system. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows a block diagram of a prior art oxygen concentrator;  
       FIG. 2  shows an exploded view of a prior art filter housing and inlet nozzle;  
       FIG. 3  shows a sectional view of prior art inlet nozzle of  FIG. 2  showing the angled lip that funnels the inlet air along a side of an inlet passage to provide for reduced acoustical noise;  
       FIG. 4  shows a top view of the inlet nozzle of the present invention; and  
       FIG. 5  shows a cross sectional view of the inlet nozzle of the present invention.  
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       FIG. 1  shows a block diagram of an oxygen concentrator system  10  comprising a filter housing  11  for filtering ambient air, a compressor  12  for drawing ambient air and an oxygen concentrator  13  for generating breathable oxygen from the ambient ari.  
       FIG. 2  shows an exploded view of a prior art filter housing  14  containing a filter (not shown) for removing particles from the incoming air. Located above filter housing  14  is a nozzle  15  that is insertable in a top extension  14   a  of filter housing  14 .  
       FIG. 3  shows a cross sectional view of the top extension  14   a  with the inlet nozzle  15  in cross section to reveal a plate  16  that extends across the opening in the nozzle  15  to direct the incoming air over a lip  16   a  to cause the air to flow along side wall  17  and into filter housing  14 . In general, it was believed that to reduce the acoustical noise in the proximity of the compressor one should increase the flow resistance or pressure drop through the filter housing and the embodiment of  FIG. 3  increases the fluid resistance or pressure drop through the filter housing by directing the fluid along an angled throat plate toward a sidewall of the nozzle and eventually over a lip. This torturous path causes the fluid to change directiion and increases the pressure drop across the filter housing. Such increase in the inefficiency of the system was used to produce low levels of acoustical noise proximate the oxygen concentrator. In contrast, the present invention provides for acoustical noise abatement while at the same time improving the efficiency of the system by reducing the pressure drop or pressure losses through the filter housing.  
       FIG. 4  shows a top view of a filter housing  20  with the housing  18  carrying inlet nozzle  21  secured to housing  25   a  through a flange  21   a . The inlet nozzle  21  includes a set of radially spaced apart fluid passages  23  that direct ambient atmospheric air into the filter housing  20 . In the embodiment shown each of the unimpeded fluid passages  23  extends in a direction substantially parallel to each other and each of the fluid passage converges for about half its length. The inlet nozzle  21  for the oxygen concentrator comprises an at least one fluid passage  23  in the nozzle  21  for directing air through the nozzle. A base  21   a  on the nozzle  21  secures the nozzle to a filter housing  25   a  to enable air flowing through the nozzle  21  to enter the filter housing  25   a.    
       FIG. 5  shows a cross sectional view of the inlet nozzle  21  that comprises a one-piece molded inlet nozzle  21  having a plurality of spaced apart unimpeded fluid passages  23  therein. In the embodiment shown the inlet nozzle  21  includes an inlet conduit  21   a , an external fluid face  22  having a plurality of fluid passages  23  extending through cross member  21   b  with the fluid passages exiting on internal fluid face  24 . Each of the fluid passages  23  include a frusto conical converging region  23   a  and a cylindrical region of uniform cross section  23   b . With a converging region the passages cause the velocity of the air flowing through the at least one fluid passage to be increased as it flows through the at least one fluid passage. Although a converging fluid passage is shown the fluid passage need not be converging to maintain the proper flow orientation through the fluid passages.  
      In operation of the inlet nozzle  21  the compressor connected to conduit  26  draws ambient air into the inlet conduit  21   a . The arrows indicate the direction of flow of ambient air flow into the inlet nozzle as it enters the fluid passage  23 . During normal compressor operation the fluid is drawn at sufficiently high flow rate so that turbulent flow occurs in the fluid passages in the inlet nozzle. As can be seen in  FIG. 5  the direction of fluid flow through the cross member or throat plate  21   b , which is located generally normal to the sidewall  21   a , is generally maintained in the same direction even though dispersed. That is, the fluid flow through the inlet nozzle comprises a coaxial flow direction with respect to a central axis  18  of the inlet nozzle  21 .  
      In order to appreciate the difference between the offset fluid entry of the prior art shown in  FIG. 3  and the present invention reference should be made to  FIG. 5  which shows the pressure drop as a function of flow rate. The top curve  30  illustrates the increase of pressure drop through the filter housing with increase of flow rate and the lower curve  31  illustrated\s the increase of pressure drop through the filter housing with increase in flow rate. In general it was believed that the generation of the higher pressure drop (curve  30 ) through the filter housing was preferable since it produces less acoustical noise in the proximity of the oxygen concentrator. Contrary to belief that the higher pressure drop in the filter housing was preferred in order to reduce acoustical noise, the measurement of the flow rate and the acoustical noise of the prior art offset nozzle of  FIG. 3  revealed that the present invention, while having less pressure drop at the same flow rate, had actually lower acoustical noise. Tests revealed that the decibel level for the prior art inlet nozzle shown in  FIG. 3  was 63 db at two feet from the filter housing. In contrast the decibel level for the present invention as shown in  FIG. 4  and  FIG. 5  was only 56.1 db. In addition the dispensing of the fluid over an extended area of the filter reduces localized wear on the filter due to particles in the ambient air being dispersed over a wider area of the filter in the filter housing.  
      Thus the embodiment of  FIG. 5  shows an inlet nozzle  21  for an oxygen concentrator for providing reduced acoustical noise when connected to an oxygen concentrator comprising: a molded one piece polymer plastic housing  19  with a cross member or throat plate  21   b  having an external fluid face  22  thereon. Throat plate  21   b  extends from wall to wall of inlet conduit  21   a . A plurality of unimpeded fluid passages  23  located in the housing with the plurality of fluid passages  23  each having an inlet  23   a  in external fluid face  22  for drawing ambient air into conduit  21   a  and into each of the plurality of fluid passages  23 . The fluid discharges through an internal fluid face  24  on housing  19  through the plurality of unimpeded fluid passages  23  each having an outlet  23   b  in the internal fluid face  23  with a total inlet area of plurality of fluid passages  23  in the external fluid face  22  greater than a total outlet area of the plurality of fluid passages  23  in the internal fluid face  24 .  
      Thus the present invention further includes method of reducing the acoustical noise in an oxygen concentrator by directing incoming air in a first direction into an inlet nozzle  21  by maintaining a downstream pressure less than atmospheric pressure at the inlet nozzle. By maintaining sufficiently low downstream pressure one can induce a turbulent air flow condition in at least one fluid passage  23  in the inlet nozzle  20  and by dispersing an outgoing air flow from the at least one fluid passage  23  in the inlet nozzle  20  over an extended area while maintaining the outgoing air flow in the first direction one thereby reduces acoustical noise while minimize pressure losses through the filter housing thus increasing the efficiency of the system.  
      While the invention is shown with a plurality of fluid passages located in cross member it is envisioned that a single continuous fluid passage that extends diametrically across the external face or a fluid passage or fluid passages that extend across the external face of the nozzle could also be used to disperse and direct the air into the filter housing while at the same time reducing the acoustical noise.