Abstract:
A portable oxygen supply for home use may include an electrolyzer for generating oxygen from water in response to electric power input, and a fuel cell electrically connected with the electrolyzer for providing electric power to the electrolyzer. A method of providing oxygen for home use may include the steps of generating electricity in a fuel cell; providing electricity from the fuel cell to an oxygen source to operate the oxygen source to produce oxygen; and directing the oxygen from the oxygen source to a patient device.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of the filing date of U.S. Provisional Application No. 60/481,805, filed Dec. 17, 2003, the entire disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a breathing aid for a person. In particular, the invention relates to an oxygen supply system, which is preferably small and light enough to be portable, as would be desirable for use by a patient, for example, for home use.  
       SUMMARY OF THE INVENTION  
       [0003]     According to one embodiment, a portable oxygen supply for home use is provided. The supply includes, for example, an electrolyzer for generating oxygen from water in response to electric power input, and a fuel cell connected with the electrolyzer for providing electric power to the electrolyzer and water. According to another embodiment, a method of providing oxygen for home use is presented. The method includes, for example, the steps of: generating electricity in a fuel cell; providing electricity from the fuel cell to an oxygen source to operate the oxygen source to produce oxygen; and directing the oxygen from the oxygen source to a patient device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]      FIG. 1  is a schematic illustration of an oxygen supply system in accordance with one embodiment of the invention;  
         [0005]      FIG. 2  is a schematic illustration of an oxygen supply that forms part of the oxygen supply system of  FIG. 1 ;  
         [0006]      FIG. 3  is a schematic illustration of one embodiment of an oxygen generator that can be used in the oxygen supply system of  FIG. 1 ;  
         [0007]      FIG. 4  is a schematic illustration of a direct methanol fuel cell that can be used as the power source of  FIG. 2 ;  
         [0008]      FIG. 5  is a schematic illustration of the operation of a methanol fuel cell system that is one embodiment of the invention; and  
         [0009]      FIG. 6  is a schematic illustration of a hydrogen fuel cell system that is another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0010]     One embodiment of the present invention relates to a breathing aid for a person; for example, an oxygen supply system for home use that is preferably small and light enough to be portable. The invention is applicable to oxygen supply systems of various different types and constructions. As representative of one embodiment of the invention,  FIG. 1  illustrates schematically an oxygen supply system  10 . The system  10  includes an oxygen supply  12  that is also an embodiment of the invention. In one embodiment, the system  10  may be of the type shown in U.S. Pat. No. 5,988,165, the entire disclosure of which is hereby incorporated by reference.  
         [0011]     The oxygen supply  12  is operable to provide oxygen-enriched gas for use in the system  10 . The oxygen-enriched gas in the illustrated embodiment is fed to a product tank  14 . In other embodiments, the product tank  14  can be omitted. A 5-psi regulator  16  emits oxygen-enriched gas from the product tank  14  into a flow line  18  and feeds the same to a flow meter  20  which subsequently emits the oxygen-enriched gas to the patient at a predetermined flow rate of from 0.1 to 6 liters per minute. Optionally, the flow meter  20  can be closed so that all the oxygen-enriched gas is directed to a compressor  21 .  
         [0012]     Gas not directed to the patient is carried via line  22  to two-way valve  24 . A very small portion of the gas in the flow line  20  is directed through a line  26  and a restrictor  28  into an oxygen sensor  30  which detects whether or not the concentration of the oxygen is of a predetermined value, for example, at least 50 percent.  
         [0013]     When the oxygen sensor  30  detects a concentration at or above the predetermined level, the two-way valve  24  is kept open to permit the oxygen-enriched gas to flow through the valve  24  and a line  32  into a buffer tank  34  wherein the pressure is essentially the same as the pressure in the product tank  14 . However, should the oxygen sensor  30  not detect a suitable oxygen concentration, two-way valve  24  is closed so that the oxygen concentrator  12  can build up a sufficient oxygen concentration. This arrangement prioritizes the flow of oxygen-enriched gas so that the patient is assured of receiving a gas having a minimum oxygen concentration therein. In other embodiments, prioritization may be omitted.  
         [0014]     The buffer tank  34  can have a regulator  36  thereon generally set at approximately 12 psi to admit the oxygen-enriched gas to the compressor  21  when needed. The output of the compressor  21  is used to fill a cylinder or portable tank  38  for ambulatory use by the patient. Alternatively, the pressure regulator  36  can be set at anywhere from about 13 to about 21 psi. A restrictor  39  controls the flow rate of gas from the buffer tank  34  to the compressor  21 . Should the operation of the compressor  21  cause the pressure in the buffer tank  34  to drop below a predetermined value, a pressure sensor (not shown) automatically cuts off the flow of gas at a pressure above the pressure of the gas being fed to the patient. This prioritization assures that the patient receives priority with regard to oxygen-enriched gas.  
         [0015]     In accordance with one embodiment, the oxygen supply  12  is preferably configured and constructed so as to be small, light weight, and self-contained—that is, portable and/or transportable. The oxygen supply  12  is shown schematically in  FIG. 2  as including an oxygen source  40  and a power source  42 . Various different types of oxygen sources  40  may be used.  
         [0016]     The oxygen source  40 , shown schematically in  FIG. 2 , is preferably, although not necessarily, an electrolyzer, that is, a device that generates oxygen by splitting water through the application of electricity. At least two different types of electrolyzers are possible. One type of electrolyzer does not generate hydrogen, while the other type does produce hydrogen as a by-product. Other types of oxygen sources are described below.  
         [0017]     In one embodiment, the oxygen source  40  includes a proton exchange medium between the electrodes. Feed water is electrolyzed at the anode to produce oxygen, hydrogen ions and electrons. The hydrogen ions are then combined with oxygen in the ambient air to produce water. The oxygen source  40  thus converts water and air into oxygen, air and water.  
         [0018]     In another embodiment, the oxygen source  40  is of the known type of electrolyzer that produces hydrogen gas in addition to one or more other by-products.  
         [0019]     The oxygen from the oxygen source  40  can be collected, treated, pressurized, etc., in any one of numerous known manners. One example is shown in  FIG. 3 , which illustrates schematically one embodiment of operation of an oxygen concentrator  50  that uses an electrochemical stack or electrolysis cell  52 , as one example of an oxygen source  40 , to electrolyze water to produce oxygen, without producing hydrogen.  
         [0020]     In this embodiment, concentrator  50  includes a water/oxygen separator  54 , a water/air separator  56 , an air source  58 , and a power supply  60 . Optionally, the oxygen concentrating system  50  may include one or more condensers  62  and one or more ion-exchange beds  64 .  
         [0021]     The oxygen from the stack  52  can be separated into a patient-grade oxygen-rich stream (oxygen, or oxygen-enriched gas)  66 . This can be accomplished by delivering the oxygen product stream  68  from the electrolysis cell  52  to the oxygen-water separator  54 . The water collects at the bottom of the oxygen-water separator reservoir  54 , while the oxygen collects in the top portion of the reservoir until it can be bled off for patient use. One advantage of this arrangement is that the oxygen-rich stream  66  that is provided to the patient is saturated with water vapor. If the oxygen stream  100  is too dry, the nasal membrane of the patient might be irritated and possibly damaged. In other embodiments, humidification can be omitted.  
         [0022]     The air product stream  70  from the electrolysis cell  52  can be separated in the water-air separator  56  to form a spent air stream  72  and a water stream  74 . The spent air  72  can be vented to atmosphere, while the water stream  74  can be fed into the oxygen-water separator  20  and then recycled through the system as feed to the electrolysis cell.  
         [0023]     A concentrator of this type, or of another type as used in the oxygen supply  12 , may include a number of warning and detection systems. For example, an oxygen concentration sensor can be placed in the system to determine whether sufficient oxygen purity is being produced. A warning system, either visual or audio, can be used when the oxygen concentration falls below a predetermined value. The oxygen concentration sensor can also be used to trigger a system shut-down if the oxygen concentration falls below a predetermined value for a determined time period.  
         [0024]     Impurities in the feed water to the electrolysis cell  40  or  52  may impair the functionality of the cell. Deionized or distilled water can be used in order to produce effective functionality of the electrolysis cell  50 . Optionally, an ion exchange bed  64 , or other filtration means, can be used in the system to filter out impurities in the feed water. The filtration mechanism can be used solely as a precautionary means, in that it will effectively remove trace amounts of impurities in the deionized feed water and allow for some use of non-deionized water in the system. Alternatively, the filtration mechanism can be larger, or replaceable, thereby allowing use of tap water on a regular basis.  
         [0025]     Water level detection systems can also be used to ensure sufficient amounts of water are available to the system  50 , most notably in the water/oxygen separator  54 . For example, water can collect in the water/air separator  56  until a predetermined amount of water is collected. Once the predetermined amount of water is collected, a drain valve  78  can be opened to allow the water to be delivered to the water/oxygen separator  54 , and subsequently as recycled water feed  80  to the electrolysis cell  52 . A warning system can be used when the water level in the system falls below a predetermined critical operational level. The warning system can be one or two stages. In a one stage system, a warning signal will be triggered when the water level in the system falls below the predetermined level. This warning signal can be visual or audio. The two stage system can include a similar warning signal at a first predetermined level and then commence a system shut-down at a second predetermined level. In other embodiments, the system shut-down can occur after a predetermined time period following the actuation of the warning signal.  
         [0026]     As noted above, different types of oxygen sources  40  can be provided. In place of the electrolysis cell and concentrator, the system could include a pressure swing concentrator, for example, that provides oxygen (or oxygen-enriched gas) from ambient air without electrolyzing water.  
         [0027]     The oxygen supply  12  also includes a source of electric power  42  for the oxygen source  40 . The power source  42  can be any conventional means of providing power, such as, for example, a battery, a generator, or an electrical connection to a power line in a house.  
         [0028]     In one embodiment, power source  42  is a fuel cell that generates electricity used to power the oxygen source  40 . Different types of fuel cells  42  can be used. One type of fuel cell  42  is a direct methanol fuel cell. Another type of fuel cell  42  is a hydrogen fuel cell.  
         [0029]      FIG. 4  illustrates schematically the operation of one embodiment of a direct methanol fuel cell  82 . The fuel cell  82  includes an anode  84  and a cathode  86 . The fuel cell  82  is powered solely by methanol. A fuel cell  82  of this type can be sized to generate any level of desired power output, for example, 400 watts, enough to run an oxygen source  40  with the desired output.  
         [0030]     A mixture of water and methanol is fed into the fuel cell  82  on the anode side  84 . The molecules are electrolyzed to produce carbon dioxide and hydrogen ions. The hydrogen ions traverse the cell and are combined with air on the cathode side  86  to produce water. The carbon dioxide, and any non-electrolyzed water and methanol, are the products on the anode side  84  of the cell, and form a methanol/water product stream  88 .  
         [0031]      FIG. 5  illustrates one embodiment of a system  100  that combines a methanol fuel cell  82  and an electrolysis cell  52 . An air supply  102  feeds air to both the fuel cell  82  and the electrolysis cell  52 . Water from water supply  104  feeds the electrolysis cell  52  and combines with methanol from methanol supply  106  to feed the fuel cell  82 . The fuel cell  82  supplies power to the electrolysis cell  52 .  
         [0032]     The products from the electrolysis cell  52  are an oxygen/water stream  110  and an air/water stream  112 . The oxygen/water stream  110  is separated into an oxygen stream  114  and a water stream  116 . The oxygen stream  114  can be fed to a patient or stored for subsequent use. Water stream  116  can be recycled to water supply  104 .  
         [0033]     The air/water stream  112  is separated into an air stream  118  and a water stream  120 . The air stream  118  can be vented to atmosphere, while the water stream  120  can combine with water stream  116  for recycling to the water supply  104 .  
         [0034]     The fuel cell  82  produces a methanol/water/carbon dioxide stream  88  and an air/water/carbon dioxide stream  124 . The methanol/water/carbon dioxide stream  88  can be fed into a separator  126 , wherein any excess air or carbon dioxide is vented in stream  128 , while the methanol and water are returned to the methanol/water feed stream  130  via stream  132 . The air/water/carbon dioxide stream  124  is separated into air stream  134  and water stream  136 . The air stream  134  can be vented to atmosphere, while the water stream  136  is recycled to the water supply  104 .  
         [0035]     The combination of the methanol fuel cell  82  and the oxygen concentrator electrolysis cell  52  can provide for an efficient and portable system that can generate patient-grade oxygen for prolonged periods of time. The patient grade oxygen supply can be used in the home or it can be used for individual use when in transit. The air water separator for the fuel cell and the oxygen concentrator can be combined, thereby making the system more compact. In addition, only one water level need be maintained. The water product of the fuel cell can also be used as a portion of the feed to the oxygen concentrating electrolysis cell, thereby requiring less water to be added to the system on a regular basis.  
         [0036]     One embodiment of a hydrogen fuel cell is shown schematically at  140  in  FIG. 6 . A hydrogen fuel cell  140  uses hydrogen as an input fuel and also has an air input. If the oxygen source  142  is an electrolyzer as in the embodiment of  FIG. 7 , it produces hydrogen  144  as a by-product. This excess hydrogen  144  can be recycled into the hydrogen fuel cell  140 . This avoids venting hydrogen to the atmosphere. The electrolyzer  142  may require external power, as shown in  FIG. 7 , in addition to the power provided by the fuel cell.  
         [0037]     In addition, for any type of fuel cell that produces water  146  as a by-product, this water can be recycled into the electrolyzer to meet its demand for water.  
         [0038]     While the present invention is disclosed through various embodiments, descriptions, and illustrations, further embodiments and modifications based on this disclosure are also possible. For example, fuel cell technology based on other sources and types of input fuels can also be used. Electrolyzers of different physical construction and material composition can also be employed. Therefore, the invention in its broader aspects is not limited to the specific embodiments, illustrations, and descriptions presented herein.