Patent Application
20090214393
The present disclosure relates generally to method(s) of generating an oxygen-enriched gas for a user.
Oxygen generating systems are often used to produce an oxygen-enriched gas for a user. Oxygen generating systems typically include a gas fractionalization system configured to separate oxygen from other components (e.g., nitrogen) in a feed gas to produce the oxygen-enriched gas. The gas fractionalization system, for example, may include one or more sieve beds having a nitrogen-adsorption material disposed therein and configured to adsorb at least nitrogen from the feed gas.
Many oxygen generating systems employ pulsed oxygen delivery, where a pulse of the oxygen-enriched gas generated by the sieve bed(s) is delivered to the user during fixed time intervals based on an inhalation detection of the user. These systems also generally use fixed valve timing based on a predetermined flow setting for delivery of each pulse.
A method of generating an oxygen-enriched gas for a user via an oxygen generating system is disclosed herein. The oxygen generating system includes at least one sieve bed having a nitrogen-adsorption material disposed therein, the nitrogen-adsorption material being configured to adsorb nitrogen from a feed gas introduced thereto, thereby generating the oxygen-enriched gas therefrom. The at least one sieve bed has an internal gas pressure within a volume defined by the at least one sieve bed. The method includes measuring the internal sieve bed pressure, measuring an ambient atmospheric parameter, and detecting inhalation of the user. The method further includes selectively controlling, substantially in real time, delivery of the oxygen-enriched gas to the user based on at least one of the internal sieve bed gas pressure measurement, the ambient atmospheric parameter measurement, the inhalation detection, or combinations thereof.
Features and advantages of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though perhaps not identical components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear.
Embodiment(s) of the method as disclosed herein advantageously employ real time methods of controlling valve timing to produce pulses of oxygen-enriched gas for a user. These pulses have a non-fixed duration and may be generated based on a demand from the user such as, e.g., an inhalation detection, a pressure measurement, and/or an ambient atmospheric parameter.
Example(s) of the method disclosed herein further advantageously provide the user with a pulse of the oxygen-enriched gas having a desirably high oxygen content. Further, the example(s) of the method substantially prevent a pulse of the oxygen-enriched gas from being delivered when the oxygen purity may be low and additionally optimizes the timing of the valves in the system to allow for the fastest possible breathing rate of the user.
One non-limiting example of an oxygen generating system suitable for use with embodiment(s) of the method(s) and device(s) disclosed herein is depicted in
It is to be understood that the nitrogen-adsorption process employed by the oxygen generating system may be a pressure swing adsorption (PSA) process or a vacuum pressure swing adsorption (VPSA) process, and such processes operate in repeating adsorption/desorption cycles. In an embodiment of the present disclosure, each cycle includes at least a fill state, a user delivery state, and a counterfill state. In another embodiment of the present disclosure, each cycle further includes a vent state, a vacuum state, a purge state, a rest state, or combinations thereof.
The oxygen generating system 10 includes an inlet 13 configured to receive a feed gas. In a non-limiting example, the feed gas is air taken from the ambient atmosphere, which includes at least nitrogen, oxygen, and water vapor.
The oxygen generating device includes at least one sieve bed. In the example shown in
The first 16 and second 18 supply conduits are generally operatively connected to respective 20 and second 22 supply valves (or inlet valves). In a non-limiting example, the first 20 and second 22 supply valves are two-way valves. As provided above, the nitrogen-adsorption process employed by the oxygen generating device 10 operates via cycles, where one of the first 12 or second 14 sieve beds vents to atmosphere nitrogen-enriched (waste) gas, while the other of the first 12 or second 14 sieve beds delivers oxygen-enriched gas to the user. During the next cycle, the functions of the respective sieve beds 12, 14 switch. Switching is accomplished by opening the respective feed gas supply valve 20, 22 while the other of the feed gas supply valves 20, 22 is closed. More specifically, when one of the first 12 or second 14 sieve beds is receiving the feed gas, the respective one of the first 20 or second 22 supply valves is in an open position. In this case, the feed gas is prevented from flowing to the other of the first 12 or second 14 sieve beds. In an embodiment, the opening and/or closing of the first 20 and second 22 supply valves may be controlled with respect to timing of opening and/or closing and/or with respect to the sequence in with the first 20 and second 22 supply valves are opened and/or closed.
In an embodiment, the feed gas is compressed via, e.g., a compressor 24 prior to entering the first 16 or second 18 supply conduits. In a non-limiting example, the compressor is a scroll compressor. The compressor 24 includes a suction port 52 configured to draw in a stream of the feed gas from the inlet 13. In a non-limiting example, the suction port 52 is further operatively and selectively connected to the first 12 and second 14 sieve beds. In this configuration, the suction port 52 is configured to draw vacuum on the first 12 or second 14 sieve bed at pre-selected times during the adsorption/desorption cycle.
After receiving the compressed feed gas, the first 12 and second 14 sieve beds are each configured to separate at least most of the oxygen from the feed gas to produce the oxygen-enriched gas. In an embodiment, the first 12 and second 14 are each sieve beds 12, 14 including the nitrogen-adsorption material (e.g., zeolite, other similar suitable materials, and/or the like) configured to adsorb at least nitrogen from the feed gas.
In a non-limiting example, the oxygen-enriched gas generated via either the PSA or VPSA processes includes a gas product having an oxygen content ranging from about 70 vol % to about 95 vol % of the total gas product. In another non-limiting example, the oxygen-enriched gas has an oxygen content of at least 87 vol % of the total gas product.
A user conduit 28 having a user outlet 30 is in alternate selective fluid communication with the first and second sieve beds 12, 14. The user conduit 28 may be formed from any suitable material, e.g., at least partially from flexible plastic tubing. In an embodiment, the user conduit 28 is configured substantially in a “Y” shape. As such, the user conduit 28 may have a first conduit portion 28′ and a second conduit portion 28″, which are in communication with the first sieve bed 12 and the second sieve bed 14, respectively, and merge together before reaching the user outlet 30. The user outlet 30 may be an opening in the user conduit 28 configured to output the substantially oxygen-enriched gas for user use. The user outlet 30 may additionally be configured with a nasal cannula, a respiratory mask, or any other suitable device, as desired.
In an embodiment, as shown in
The first conduit portion 28′ and the second conduit portion 28″ may be configured with a first user delivery valve 32 and a second user delivery valve 34, respectively. In an embodiment, the first 32 and the second 34 user delivery valves are configured as two-way valves. It is contemplated that when the oxygen-enriched gas is delivered from one of the first and second sieve beds 12, 14, to the user conduit 28, the respective one of the first 32 or second 34 user valves is open. Further, when the respective one of the first 32 or second 34 user valves is open, the respective one of the first 20 or second 22 feed gas supply valves is closed.
The nitrogen-adsorption process selectively adsorbs at least nitrogen from the feed gas. Generally, the compressed feed gas is introduced into one of the first 12 or the second 14 sieve beds, thereby pressurizing the respective first 12 or second 14 sieve bed. Nitrogen and possibly other components present in the feed gas are adsorbed by the nitrogen-adsorption material disposed in the respective first 12 or second 14 sieve bed during an appropriate PSA/VPSA cycle. After: a predetermined amount of time; reaching a predetermined target pressure; detection of an inhalation; and/or another suitable trigger, the pressure of the respective first 12 or second 14 sieve bed is released. At this point, the nitrogen-enriched gas (including any other adsorbed components) is also released from the respective first 12 or second 14 sieve bed and is vented out of the system 10 through a main vent conduit 58. As shown in
In an embodiment, the oxygen delivery system 10 may be configured to trigger an output of a predetermined volume of the oxygen-enriched gas from the sieve bed 12 upon detection of an inhalation by the user. Detection of an inhalation may be accomplished via, e.g., a breath detection device, schematically shown as reference numeral 46 in
As used herein, a “masked” time or the like language may be defined as follows. Following a dynamically adjusted user oxygen delivery phase from the first 12 or second 14 sieve bed, breath detection may be “masked” for a predetermined masking time, for example, during the dynamically adjusted oxygen delivery phase and during a predetermined amount of time following the delivery phase. It is understood that such predetermined masking time may be configured to prevent the triggering of another dynamically adjusted user oxygen delivery phase before sufficient substantially oxygen-enriched gas is available from the other of the second 14 or first 12 sieve bed. As used herein, sufficient substantially oxygen-enriched gas may be a pulse having a desired oxygen content. In an embodiment, the predetermined masking time may be short in duration. As a non-limiting example, the predetermined masking time may be about 500 milliseconds in length. In an alternate embodiment, this masking time may also be dynamically adjusted, e.g., based on the average breath rate. Further, in order to accommodate a maximum breathing rate of 30 Breaths Per Minute (BPM), a maximum mask time of 2 seconds may be used, if desired.
The first 12 and second 14 sieve beds are also configured to transmit at least a portion of the remaining oxygen-enriched gas (i.e., the oxygen-enriched gas not delivered to the user during or after the masked time to the user outlet 30), if any, to the other of the first 12 or second 14 sieve bed. This also occurs after each respective dynamically adjusted oxygen delivery phase. The portion of the remaining oxygen-enriched gas may be transmitted via a counterfill flow conduit 48. The transmission of the remaining portion of the oxygen-enriched gas from one of the first 12 or second 14 sieve beds to the other first 12 or second 14 sieve beds may be referred to as “counterfilling.”
As shown in
The compressor 24, the first 20 and second 22 supply valves, the first 32 and second 34 user delivery valves, and the first 40 and second 42 vent valves are controlled by a controller 54. The sieve bed pressure sensors 37, 39, and the sieve bed temperature sensor 44 measure internal system parameters, and the ambient pressure sensor 45 and the ambient temperature pressure sensor 47 measure ambient atmospheric parameters, all of which are inputs to the controller 54. In a non-limiting example, the controller 54 is a microprocessor including a memory. As will be described in more detail below, the controller 54 receives, e.g., sieve bed pressures, and other similar variables, and uses these variables to execute one or more algorithms for controlling various components and/or processes used in the system 10.
In an embodiment, the oxygen generating system 10 may further include a vacuum valve 56 operatively connected to the main vent conduit 58 and in operative and selective fluid communication with the suction port 52 of the compressor 24 via the inlet line 13. The vacuum valve 56 assists the suction port 52 in drawing at least the feed gas from the sieve beds 12, 14 during a vacuum state of the adsorption/desorption cycle, as will be described in more detail below.
In some instances, the oxygen generating system 10 may further include a check valve 61 operatively disposed on the main vent conduit 58. The check valve 61 is configured to prevent air from the atmosphere being pulled into the system 10 via the main vent conduit 58 when the vacuum valve 56 is open and a vacuum is applied to the sieve beds 12, 14.
The oxygen generating system 10 may also include a breather valve 60 operatively connected to the inlet 13. The breather valve 60 generally assists in allowing the feed gas, taken from the ambient atmosphere, to be directed to the suction port 52 of the compressor 24.
A method of generating an oxygen-enriched gas for a user via the oxygen generating system 10 includes: measuring the internal sieve bed gas pressure; measuring an ambient atmospheric pressure; detecting inhalation of the user; and selectively controlling, substantially in real time, delivery of the oxygen-enriched gas to the user based on at least one of the internal sieve bed gas pressure measurement, the ambient atmospheric parameter measurement, the inhalation detection, or combinations thereof.
With reference now to
During the fill state A, the method includes opening the supply valve 20 of the first sieve bed 12 to supply the feed gas to the first sieve bed 12, and opening the vent valve 42 of the second sieve bed 14 to vent or purge at least a portion of the nitrogen (i.e., the nitrogen-enriched gas) from the second sieve bed 14.
Also during the fill state A, the first sieve bed 12 is pressurized to a target pressure (PT) as the first sieve bed 12 is supplied with the feed gas. The target pressure (PT) is generally determined for each adsorption/desorption cycle. In a non-limiting example, the target pressure (PT) is based on at least a flow setting of the oxygen generating device 10, the ambient temperature, and the ambient pressure. Details of an example of a suitable method of determining the target pressure (PT) may be found in U.S. Provisional application Ser. No. ______, filed concurrently herewith (Docket No. DP-317406), which is commonly owned by the Assignee of the present disclosure, and is incorporated herein by reference in its entirety.
It is to be understood that, to achieve the desired oxygen purity, the pressure of the first sieve bed 12 is substantially equal to the pressure of the second sieve bed 14. It is to be understood that this pressure equilibrium between the first 12 and the second 14 sieve beds is achieved at substantially the same pressure as the target pressure (PT). Without being bound to any theory, it is believed that having the pressure equilibrium between the sieve beds 12, 14 and the target pressure (PT) substantially the same allows for desirable operation of the compressor 24, sufficient production of the oxygen-enriched gas, and sufficient removal of the nitrogen-enriched gas from the system 10. In an embodiment, the pressure equilibrium between the first 12 and the second 14 sieve beds is achieved by controlling the speed (e.g., controlling a pulse width modulation (PWM) setting) of the compressor 24. Changes to the PWM setting for each fill state (e.g., the fill states A and D) are based on a pressure difference between the target pressure PT of the first sieve bed 12 and a peak pressure of the first sieve bed 12 determined from the previous fill state A.
It is to be understood that the PWM setting of the compressor 24 may also be controlled based on an inhalation detection of the user. If, for example, an inhalation is not detected by 1) the time the target pressure PT of the sieve bed 12 is reached, and/or 2) a predetermined time limit, the fill state A may be temporarily stopped until the next inhalation detection. While the fill state A is stopped, the internal pressure of the sieve bed 12 is substantially maintained. Also, while the fill state A is stopped, the compressor 24 may also be stopped or at least the motor driving the compressor 24 may be throttled down to a lower power. In this case, all of the valves, except the breather valve 60, (i.e., the supply valves 20, 22, the user delivery valves 32, 34, the vent valves 40, 43, and the counterfill valve 50) are closed.
After the fill state A is substantially complete and after an inhalation detection of the user, the user delivery state B begins. It is to be understood that the inhalation detection may be masked for a small interval of time (as described above) to prevent activation of the use delivery state B before enough oxygen-enriched gas is available for the user from the sieve bed 14.
During the user delivery state B, the user delivery valve 32 for the first sieve bed 12 opens and the oxygen-enriched gas generated by the sieve bed 12 flows to the user delivery conduit 28. Also, the supply valve 22 for the second sieve bed 14 opens so that the feed gas may be supplied to the sieve bed 14.
The duration of the user delivery state B is determined for each adsorption/desorption cycle of the nitrogen-adsorption process. In a non-limiting example, the duration of the user delivery state B is based on at least one of a calibration value of the supply valve 20, a calibration value of the supply valve 22, a calibration value of the user delivery valve 32, a calibration value of the user delivery valve 34, a calibration value of the vent valve 40, a calibration value of the vent valve 42, a flow setting for the feed gas, a pressure of the sieve bed 12, the ambient temperature, the ambient pressure, a breathing rate of the user, or combinations thereof. Details of an example of a suitable method for how the duration of the user delivery state B is determined may be found in U.S. Provisional application Ser. No. ______, filed concurrently herewith (Docket No. DP-317407), which is commonly owned by the Assignee of the present disclosure, and is incorporated herein by reference in its entirety.
The counterfill state C begins after the user delivery state B. In the counterfill state C, the method includes opening the counterfill valve 50, closing the supply valve 20 and the user delivery valve 32 for the first sieve bed 12, and closing the supply valve 22 and the user delivery valve 34 for the second sieve bed 14. In a non-limiting example, the counterfill state C occurs until the pressure between the first 12 and the second 14 sieve beds is substantially equal.
In another embodiment, the method further includes selectively applying vacuum to the first sieve bed 12 during delivery of the oxygen-enriched gas to the user. In a non-limiting example, the vacuum is selectively applied to the first sieve bed 12 via the suction port 52 of the compressor 24, the details of which will be described if further detail below.
With reference now to
The vacuum state generally occurs for a time period based on the target pressure PT of the first sieve bed 12 determined after each inhalation detection. In a non-limiting example, the vacuum state occurs for a time period spanning between pressurization and depressurization of the sieve bed 12 (i.e., the time between the fill state D and the user delivery state E). The time of the vacuum state may be determined as a function of sieve pressure.
In yet another embodiment, the adsorption/desorption cycle further includes a purge state (i.e., the purge state H). During the purge state, a portion of the pressurized oxygen-enriched gas produced in the sieve bed 14 is delivered to the other sieve bed 12 to substantially clean the sieve bed 12 for another adsorption/desorption cycle. The purge state H begins after the vacuum state G and substantially simultaneously with the counterfill state C. During the purge state H, the method includes closing the vacuum valve 56, opening the counterfill valve 50 and vent valve 42, and purging the first sieve bed 12. In a non-limiting example, the purge state H occurs for a time period based on a calibration value of the vent valve 40, a purge volume calibration value, the internal pressure of the sieve bed 12 at the start of the purge state H, the ambient pressure, and the ambient temperature. The length of the time of the purge state may be determined in a manner similar to that disclosed for determining the patient time to generate a gas bolus as provided in U.S. Provisional Ser. No. ______(Docket No. DP-317407), as referenced above. In a non-limiting example, the time for a purge state may range from about 50 ms to about 300 ms.
As used herein, “venting” releases a pressurized sieve bed 12 to atmosphere. In embodiment(s) of the present disclosure, vacuum may then or simultaneously be applied to that same sieve bed 12 to pull the pressure of the sieve bed 12 down further (e.g., substantially at or below atmospheric levels). During the vent (and vacuum, if used) state, waste (e.g. nitrogen-enriched) gas is expelled from the sieve bed 12. As used herein, “purging” takes a predetermined amount of pressurized oxygen-enriched gas from the other sieve bed 14 and blows it through the vented (and vacuumed) sieve bed 12 to aid in preparing sieve bed 12 for new production of oxygen-enriched gas.
In instances where the target pressure PT of the sieve bed 12 is reached before an inhalation is detected, the adsorption/desorption cycle may enter a rest state (not shown). During the rest state, the user delivery valves 32, 34, the supply valves 20, 22, the counterfill valve 50, and the vacuum valve 56 are closed, and the breather valve 60 is opened.
Once the counterfill state C is complete (i.e., the counterfill state for the sieve bed 12), the fill state D for the sieve bed 14 begins. The adsorption/desorption cycle continues for at least the fill state D, the user delivery state E, and the counterfill state F of the second sieve bed 14. In some embodiments, the cycle further includes a vacuum state 1, a vent state J, a purge state H, and possibly the rest state. It is to be understood that the method described above repeats itself for each complete adsorption/desorption cycle. For example, the cycle ends when the counterfill state F is complete for the sieve bed 14, and then a new cycle begins starting with the fill state A for the sieve bed 12.
It is to be understood that, in the embodiments of the method provided above, the feed gas is taken from the ambient atmosphere and, in some instances, the feed gas includes water. If water is present in the feed gas when the feed gas is introduced to the sieve beds 12, 14, the water may degrade or possibly deactivate the nitrogen-adsorption material disposed in the sieve beds 12, 14. This degradation and/or deactivation may, in some instances, deleteriously affect the nitrogen-adsorption process and produce an oxygen-enriched gas potentially having a lower oxygen content than desired.
It is further to be understood that embodiments of the method may be applied to both stationary and portable oxygen generating systems. Particularly for portable applications, it is advantageous to reduce the weight of the system, as well as its size (in terms of volume), as compared to other stationary oxygen generating systems. In a non-limiting example, the size of the oxygen generating system 10 ranges from about 100 in3 to about 1500 in3, and the weight of the system 10 ranges from about 1 lb to about 20 lbs.
One way of removing the water adsorbed by the nitrogen-adsorbing material (e.g., zeolite) is to apply a vacuum to the sieve beds 12, 14, such as the vacuum states G and I in some of the embodiments described above. Rather than using a vacuum pump in the system 10, the size and weight of the oxygen generating system 10 may be further reduced by using the suction port 52 of the compressor 24 to apply the vacuum to the sieve beds 12, 14. The application of the vacuum to the sieve beds 12, 14 generally occurs during the vacuum state G and I and substantially simultaneously with, or after the venting state of the methods described above. The venting states for sieve beds 12, 14 occur at the same time that the other sieve bed 14, 12 is filling (i.e., the venting state for sieve bed 12 will be the same as state D, and the venting state for sieve bed 14 will be the same as state A). It is to be understood that if the vacuum is applied to the sieve beds 12, 14 during another state, it may be possible to overload the compressor 24 and potentially damage it. Overloading the compressor 24 may also cause substantially higher power consumptions of the system 10 as a whole, thereby wasting power. To reduce overloading the compressor 24, the vacuum is applied during the time between, e.g., when the sieve beds 12, 14 are pressurized and depressurized in the adsorption/desorption cycle, as provided above.
With reference again to
It is to be understood that the terms “connect/connected” and “engage/engaged” are broadly defined herein to encompass a variety of divergent connection and engagement arrangements and assembly techniques. These arrangements and techniques include, but are not limited to (1) the direct connection or engagement between one component and another component with no intervening components therebetween; and (2) the connection or engagement of one component and another component with one or more components therebetween, provided that the one component being “connected to” or “engaged to” the other component is somehow operatively connected to the other component (notwithstanding the presence of one or more additional components therebetween).
While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified and/or other embodiments may be possible. Therefore, the foregoing description is to be considered exemplary rather than limiting.
