Abstract:
An oxygen concentrator for supplying supplemental oxygen to a patient. The oxygen concentrator is adapted to supply supplemental oxygen directly to the patient and/or to a cylinder filler which is controlled to automatically fill a portable oxygen cylinder for use by an ambulatory patient. The cylinder filler is controlled to check the initial gas pressure in the cylinder prior to filling. If the initial cylinder pressure is below a preset minimum pressure, the cylinder filler will not fill the cylinder so that an empty cylinder which may be contaminated cannot be filled.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     Oxygen concentrators have been available for many years as a source of oxygen enriched air for patients requiring supplemental oxygen. The oxygen concentrator includes a filter element which passes oxygen while blocking the flow of nitrogen. This will typically result in a gas which is up to about 95% pure oxygen, with at maximum separation efficiency the remainder of the gas being primarily argon. An oxygen concentrator is not designed for portable applications because of its size, weight and power requirements. Typically, an ambulatory patient requiring supplemental oxygen will carry a relatively small container containing either compressed gaseous oxygen or liquefied oxygen. In the past, the portable compressed gaseous oxygen cylinders were filled from a larger container of compressed oxygen. The system may include a flow controller which delivers oxygen pulses only during inspiration to conserve oxygen and thus prolong the ambulatory time for the patient. Recently, oxygen concentrators have sometimes been provided with a compressor suitable for compressing the oxygen enriched air sufficiently for filling a portable oxygen cylinder. Another recent development is apparatus which cools and liquefies the oxygen enriched air from an oxygen concentrator for filling portable liquid oxygen containers. 
     When oxygen is to be breathed by a patient, it is critical that the oxygen not be contaminated. If a portable oxygen cylinder is completely empty prior to filling, there is a risk that the cylinder valve may have been left open and that the interior of the cylinder has become contaminated. For patient safety, it is necessary that an empty oxygen cylinder be cleaned and flushed with oxygen prior to filling to remove any possible contaminants that may have entered the cylinder. To avoid this problem, the Compressed Gas Association has recommended that gaseous oxygen cylinders not be emptied below 25 psig. The Association recommends that the tank pressure be manually checked prior to filling. 
     U.S. Pat. No. 4,856,284 to Mattiola et al. discloses a system for automatically filling a liquid gas cylinder. Prior to filling the cylinder, the cylinder is evacuated. As gas is evacuated from the cylinder, it is automatically analyzed for contamination to prevent filling a contaminated cylinder. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is directed to an oxygen concentrator which is capably of supplying oxygen enriched air of from about 85% to about 95% oxygen concentration to a patient and/or to a compressor or a cooler for filling a portable gaseous or liquid oxygen cylinder for use by an ambulatory patient. The oxygen concentrator includes a programmed cycle for automatically filling the oxygen cylinder to a programmed maximum pressure. The cylinder pressure is constantly monitored during the fill cycle. According to the invention, the initial cylinder pressure is compared with a programmed minimum acceptable pressure, such as 100 psig. If the cylinder pressure falls below the programmed minimum acceptable pressure, the oxygen concentrator is prevented from filling the cylinder. Consequently, an empty cylinder which may be contaminated cannot be filled. The patient must take the empty cylinder to a dealer who is qualified to check for contaminants prior to filling the cylinder. 
     Accordingly, it is an object of the invention to provide a cylinder filling oxygen concentrator which cannot automatically fill an empty oxygen cylinder which may be contaminated. 
     Other objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of an oxygen concentrator and compressor connected for automatically filling an oxygen cylinder with oxygen enriched air according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, apparatus  10  is shown according to the invention for filling a portable oxygen cylinder  11  with oxygen enriched air from an oxygen concentrator  12 . The oxygen concentrator  12  may be of a conventional design which includes one or more molecular sieve beds (not shown) which pass oxygen and argon and block the passage of nitrogen. Each molecular sieve bed is cycled between a filter cycle wherein nitrogen is separated from air and a purge cycle wherein the beds are back flushed to purge nitrogen. When two molecular sieve beds are provided, the beds are operated alternately in filter and purge cycles. The oxygen enriched air from the concentrator  12  will be up to about 95% oxygen and about 5% argon. Frequently, the oxygen enriched air output from the concentrator  12  passes through. an oxygen sensor  13  which determines the percentage of oxygen in the output from the concentrator  12 . The oxygen sensor  13  may be a component of the oxygen concentrator  12 , or it may be a separate element through which the oxygen enriched air output from the concentrator  12  flows. If the sensed oxygen level falls below a preset minimum acceptable level, such as 85% oxygen, the oxygen concentrator  12  may be shut off and/or an alarm may be sounded to alert the patient that service is required. Alternately, the output from the concentrator  12  can be diverted from use by a patient and/or from filling the oxygen cylinder  11  when the concentration is below a minimum acceptable level, such as when the concentrator  12  is first started. 
     From the optional oxygen sensor  13 , the oxygen enriched air is connected to flow through a pressure sensor  14  and a bacteria filter  15  to the inlet of a compressor  16 . The high pressure output from the compressor  16  is applied through a pressure sensor  17  to a hose  18  connected for filling the oxygen cylinder  11 . The hose  18  is connected to the cylinder  11  with a suitable fitting (not shown) which engages a cylinder fitting  11 ′. From the optional oxygen sensor  13 , the oxygen enriched air also may flow through a flow regulator  19  and a bacteria filter  20  to a hose  21  for delivery to a patient, for example, through a nasal cannula (not shown). 
     According to the invention, the apparatus  10  includes a controller  22  for automatically filling the oxygen cylinder  11 . Depending on the output capacity of the oxygen concentrator  12 , the oxygen cylinder  11  may be filled either simultaneously while supplemental oxygen is supplied to the patient, or while the patient receives supplemental oxygen from another source. Preferably, the oxygen concentrator  12  has a sufficient capacity to simultaneously supply the patient&#39;s needs and to permit filling the oxygen cylinder  11 . For example, an oxygen concentrator  12  having an oxygen enriched air output flow capacity of between 5 and 6 lpm (liters per minute) can deliver a flow of between ½ lpm and 3 lpm of oxygen enriched air to the patient, depending on the prescribed needs of the patient, and simultaneously deliver a flow of between 1 and 2 lpm to the compressor  16  for filling the oxygen cylinder  11 . 
     According to the invention, a controller  22  controls the compressor  16  for filling the oxygen cylinder  11 . The controller  22  has data inputs which receive data from the optional oxygen sensor  13 , the pressure sensor  14  and the pressure sensor  17  and an output which controls the compressor  16 . When an oxygen cylinder  11  is connected to the hose  18  and the valve on the cylinder  11  is opened, the pressure sensor  17  detects any residual gas pressure in the oxygen cylinder  11 . If the measured gas pressure within the cylinder  11  falls below a predetermined safe minimum pressure above the ambient atmospheric pressure, the controller  22  is programmed to prevent the compressor  16  from operating to fill the oxygen cylinder  11 . Preferably, the minimum acceptable pressure in the oxygen cylinder  11  is about 100 psig. However, it may be set to a lower level such as about 25 psig. By requiring at least a minimum cylinder pressure before filling the cylinder, the risk of filling an empty cylinder which possibly has been subject to contamination infiltration is eliminated. 
     The apparatus  10  also is designed to prevent filling the oxygen cylinder  11  with gas having less than a predetermined minimum oxygen concentration. A normally functioning oxygen concentrator  12  will produce an output gas having an oxygen concentration of between about 85% and about 95% . If the output falls below about 85% oxygen, the concentrator  12  requires servicing. Also, after an oxygen concentrator is first turned on there is a delay before its output reaches at least 85% oxygen. If the oxygen sensor  13  is an integral component of the oxygen concentrator  12 , the output from the oxygen concentrator  12  may be vented to atmosphere until it reaches the required minimum concentration level. If during operation of the concentrator  12  the output gas oxygen concentration falls from an acceptable level to an unacceptable level, such as below 85% , the oxygen sensor  13  may be connected to sound an alarm. The oxygen sensor  13  may provide data to the programmed controller  22  for use in controlling the compressor  16 . For example, after starting the oxygen concentrator  12 , the compressor  16  may be prevented from operating to begin filling the oxygen cylinder  11  until the oxygen sensor  13  detects at least 85% oxygen concentration in the concentrator output gas. If the apparatus  10  does not include an oxygen sensor  13 , the controller  22  may use data from the pressure sensor  14  for timing the beginning of filling the oxygen cylinder  11 . For example, if commercially available oxygen concentrators take a maximum of 15 minutes to warm up before they product an output gas with at least 85% oxygen concentration, the controller  22  may measure an elapse time of 15 minutes from when the low pressure output from the concentrator  12  is applied to the pressure sensor  14  before starting the compressor  16  for filling the oxygen cylinder  11 . 
     It will be appreciated that various modifications and changes may be made to the above described preferred embodiment of a cylinder filling oxygen concentrator without departing from the scope of the following claims. For example, the apparatus  10  was illustrated and described as having a compressor  16  for filling an oxygen cylinder  11  with gaseous oxygen. It will be appreciated that the compressor  16  may be replaced with cooling apparatus which liquefies the oxygen enriched air for filling the cylinder  11  with liquefied oxygen enriched gas.