Note: Descriptions are shown in the official language in which they were submitted.
CA 02793228 2012-10-19
PRODUCT GAS CONCENTRATOR AND METHOD ASSOCIATED THEREWITH
by
Sprinkle, Daniels, Drobnak, Felty, Hodos, Fabian, Shelnutt, and Olszewski
BACKGROUND
[0002] Various applications exist for the separation of gaseous mixtures. For
example, the separation of nitrogen from atmospheric air can provide a highly
concentrated
source of oxygen. These various applications include the provision of elevated
concentrations of oxygen for medical patients and flight personnel. Hence, it
is desirable to
provide systems that separate gaseous mixtures to provide a concentrated
product gas, such as
a breathing gas with a concentration of oxygen.
[0003] Several existing product gas or oxygen concentrators, for example, are
disclosed in U.S. Pat. Nos. 4,449,990, 5,906,672, 5,917,135, and 5,988,165
which are
commonly assigned to Invacare Corporation of Elyria, Ohio .
SUMMARY
[0004] In one aspect, an apparatus associated with providing a concentrated
product
gas is provided. In one embodiment, the apparatus includes an input device
adapted to select
a desired output setting for the concentrated product gas from a plurality of
output settings,
first and second sieve tanks arranged to separate one or more adsorbable
components from a
pressurized source gaseous mixture in alternating and opposing pressurization
and purging
1
CA 02793228 2012-10-19
cycles to form the concentrated product gas, a variable restrictor to
selectively provide an
adjustable flow between the first and second sieve tanks, and a controller in
operative
communication with the input device and variable restrictor to selectively
control the variable
restrictor based at least in part on the desired output setting such that the
flow between the
first and second sieve tanks for at least one output setting is different from
the flow between
the first and second sieve tanks for at least one other output setting in
relation to
corresponding pressurization cycles.
[0005] In another embodiment, the apparatus includes first and second sieve
tanks
arranged to separate one or more adsorbable components from a pressurized
source gaseous
mixture in alternating and opposing pressurization and purging cycles to form
the
concentrated product gas and a controller in operative communication with the
first and
second sieve tanks to selectively control the pressurization and purging
cycles over a plurality
of predetermined altitude ranges while maintaining an acceptable purity level
for the
concentrated product gas.
[0006] In still another embodiment, the apparatus includes an input device to
select a
first desired output setting for the concentrated product gas, a product gas
source to provide
the concentrated product gas for dispensing, a pressure sensor monitoring a
pressure of the
concentrated product gas, a conserver valve including an output connection
associated with a
user, a vent connection associated with a vent port, and a gas connection
associated with the
concentrated product gas, wherein the output connection is switched from the
vent
connection to the gas connection and vice versa, and a controller in operative
communication
with the input device and pressure sensor to selectively switch the conserver
valve to
selectively dispense the concentrated product gas based at least in part on
the selected output
setting and monitored pressure.
[0007] In yet another embodiment, the apparatus includes a body forming an
assembly with a sieve bed portion and a product tank portion separated by a
common wall,
the sieve bed portion adapted to separate one or more adsorbable components
from a
pressurized source gaseous mixture, the product tank portion adapted to store
a volume of
concentrated product gas.
[0008] In still yet another embodiment, the apparatus includes a frame
comprising a
plurality of structural support members forming a cage-like structure and a
compressor
suspended within the frame by a plurality of suspension members and adapted to
provide a
pressurized source gaseous mixture to first and second sieve tanks of a
product gas
concentrator.
2
CA 02793228 2012-10-19
[0009] In another embodiment, the apparatus includes a main body enclosing a
filter,
the filter adapted to filter a concentrated product gas from a product gas
source and provide
filtered product gas.
[0010] In another aspect, a method associated with providing a concentrated
product
gas is provided. In one embodiment, the method includes: a) selecting a
desired output
setting for the concentrated product gas from a plurality of output settings,
b) separating one
or more adsorbable components from a pressurized source gaseous mixture via
first and
second sieve tanks in alternating and opposing pressurization and purging
cycles to form the
concentrated product gas, and c) selectively controlling a variable restrictor
based at least in
part on the desired output setting to selectively provide flow between the
first and second
sieve tanks such that the flow between the first and second sieve tanks for at
least one output
setting is different from the flow between the first and second sieve tanks
for at least one
other output setting in relation to corresponding pressurization cycles.
[0011] In another embodiment, the method includes: a) separating one or more
adsorbable components from a pressurized source gaseous mixture via first and
second sieve
tanks in alternating and opposing pressurization and purging cycles to form
the concentrated
product gas and b) selectively controlling the pressurization and purging
cycles over a
plurality of predetermined altitude ranges while maintaining an acceptable
purity level for the
concentrated product gas.
[0012] In still another embodiment, the method includes: a) selecting a first
desired
output setting for the concentrated product gas, b) providing a product gas
source for
supplying the concentrated product gas to be dispensed, c) monitoring a
pressure of the
concentrated product gas, and d) selectively switching an output connection
associated with a
user from a vent connection associated with a vent port to a gas connection
associated with
the concentrated product gas and vice versa to selectively dispense the
concentrated product
gas based at least in part on the selected output setting and monitored
pressure.
DRAWINGS
[0013] These and other features, aspects, and advantages of the present
invention will
become better understood with regard to the accompanying drawings, following
description,
and appended claims.
[0014] Figure 1 provides a perspective view of an exemplary embodiment of a
product gas concentrator;
3
CA 02793228 2012-10-19
[0015] Figure 2 provides an exploded view of the product gas concentrator of
Figure
1;
[0016] Figures 3A-H provide various perspective, sectional, exploded views of
an
exemplary embodiment of a sieve bed and product tank assembly for an exemplary
product
gas concentrator;
[0017] Figures 3I-O provide various perspective, sectional, exploded views of
an
alternate exemplary embodiment of an end cap for the sieve bed and product
tank assembly
of Figure 3A;
[0018] Figures 4A-D provide various perspective, sectional, exploded views of
an
exemplary embodiment of a compressor assembly for an exemplary product gas
concentrator;
[0019] Figure 4E provides a top view of an alternate exemplary embodiment of a
plurality of suspension links for the compressor assembly of Figure 4A;
[0020] Figure 4F provide a perspective view of another exemplary embodiment of
a
compressor assembly for an exemplary product gas concentrator;
[0021] Figure 5A provides several block diagrams of an exemplary embodiment of
another product gas concentrator;
[0022] Figure 5B provides a timing diagram for an exemplary embodiment of a
valve
control scheme for the product gas concentrator of Figure 5A;
[0023] Figure 5C provides a block diagram showing several exemplary strategies
for
bleed flow from sieve tank 1 to sieve tank 2 in an exemplary embodiment of an
exemplary
product gas concentrator;
[0024] Figure 5D provides a block diagram showing several strategies for bleed
flow
from sieve tank 2 to sieve tank I in an exemplary embodiment of an exemplary
product gas
concentrator;
[0025] Figure SE provides top and side views of an exemplary embodiment of a
valve
assembly for the product gas concentrator of Figure 5A;
[0026] Figure 5F provides a block diagram of the valve assembly of Figure 5E;
[0027] Figures 6A and B provide perspective and sectional views of an
exemplary
embodiment of an output port for an exemplary product gas concentrator;
[0028] Figure 7 provides a flow chart of an exemplary embodiment of a process
for
determining pressure in relation to an exemplary pressure sensor in an
exemplary product gas
concentrator;
4
CA 02793228 2012-10-19
[0029] Figure 8 provides a flow chart of an exemplary embodiment of a process
for
determining a time duration for dispensing a bolus of concentrated product gas
in an
exemplary product gas concentrator;
[0030] Figure 9 provides a timing diagram for an exemplary embodiment of a
conserver valve control scheme for an exemplary product gas concentrator;
[0031] Figure 10 provides a block diagram of still another exemplary
embodiment of
a product gas concentrator; and
[0032] Figure 11 provides a flow chart of an exemplary embodiment of a process
for
dispensing a concentrated product gas to a user in conjunction with a product
gas
concentrator.
DESCRIPTION
[0033] Illustrated in Figure 1 is one embodiment of an oxygen concentrator
100.
Oxygen concentrator 100 includes a housing 102 having a front portion 104 and
a rear
portion 106. Front and rear portions 104 and 106 include a plurality of
openings for the
intake and discharge of various gases such as, for example, the intake of room
air and the
discharge of nitrogen and other gases. Oxygen concentrator 100 generally
intakes room air,
which is mostly comprised of oxygen and nitrogen, and separates the nitrogen
from the
oxygen. The oxygen is stored in a storage tank and the nitrogen is discharged
back into the
room air. For example, the oxygen gas may be discharged through port 108 a
patient through
tubing and nasal cannula.
[0034] Figure 2 is an exploded perspective of the oxygen concentrator 100 of
Figure
1. Oxygen concentrator 100 further includes a central frame 202 having a
circuit board and
other components connected thereto. These components include a battery pack
204, sieve
bed and product tank assemblies 206 and 208, cooling fan 212, and valve
assembly 214.
While these components are described as being connected to central frame 202
that need not
be the case. One or more of these components may be connected to housing
portions 104 or
106. Other components are also housed within oxygen concentrator 100
including, for
example, compressor assembly 210, sound attenuators or mufflers 216 and 218
and inlet filter
220.
[0035] SIEVE BED AND PRODUCT TANK ASSEMBLY
[0036] Referring now to Figures 3A and 3B, and more particularly to the
perspective
view Figure 3A, sieve bed and product tank assembly 206 is shown. Sieve bed
and product
tank assembly 208 is similarly configured and will not be described
separately. Assembly
CA 02793228 2012-10-19
206 includes a body having a sieve bed portion 300 and a product tank portion
302. The
distal ends of the body have first and second end caps 304 and 306. End cap
304 includes
outlet ports 308 and 310. Outlet port 308 is associated with the sieve bed
portion 300 and
outlet port 310 is associated with the product tank portion 302. End cap 306
includes input
ports 312 and 314. Input port 312 is associated with sieve bed portion 300 and
input port 314
is associated with product tank portion 302. End caps 304 and 306 are suitably
connected to
the body of assembly 206 with fasteners such as screws or bolts, although any
other suitable
attachment means may also be used.
[0037] Figure 3C and 3D illustrate section views taken along section lines 3C-
3C and
3D-3D of Figure 3A. Sieve bed portion 300 includes first and second perforated
inserts 316
and 318. A spring 320 is also provided and presses against insert 316, which
in turn presses
against the separation medium disposed between inserts 316 and 318. This
insures that the
physical separation medium is compressed between the inserts 316 and 318.
[0038] The space between perforated inserts 316 and 318 is filled with a
physical
separation medium or material. The separation material selectively adsorbs one
or more
adsorbable components of a gaseous mixtures such as, for example, a gaseous
mixture of
nitrogen and oxygen, and allows one or more nonadsorbable components of the
gaseous
mixture to pass. The physical separation material is a molecular sieve with
pores of uniform
size and essentially the same molecular dimensions. These pores selectively
adsorb
molecules in accordance with molecular shape, polarity, degree of saturation,
and the like. In
one embodiment, the physical separation medium is an aluminasilicate
composition with 4 to
angstrom pores. In this embodiment, the molecular sieve is a sodium or calcium
form of
aluminasilicate, such as type 5A zeolite. Alternately, the aluminasilicate may
have a higher
silicon to aluminum ratio, larger pores, and an affinity for polar molecules,
e.g. type 13x
zeolite. In another embodiment, a lithium-based zeolite may be used. In other
embodiments,
any suitable zeolite or other adsorbent material. The zeolites adsorb
nitrogen, carbon
monoxide, carbon dioxide, water vapor, and other significant components of
air. Gases such
as oxygen that have not been adsorbed in sieve bed portion 300 are collected
and stored in
product tank portion 302.
[0039] Figure 3E is a section view taken along line 3E-3E of Figure 3D.
Product tank
portion 302 and insert 316 of sieve bed portion 300 are illustrated. Figure 3F
is a further
section view along line 3F-3F of Figure 3D and is shown in perspective. As
illustrated in this
embodiment, sieve bed portion 300 and product tank portion 302 are formed from
a single
6
CA 02793228 2012-10-19
extruded piece of material such as, for example, aluminum. Other materials
capable of being
extruded may also be used.
[0040] Sieve bed portion 300 and product tank portion 302 share a common wall
portion and form an integrated sieve bed and product tank assembly. In
particular, the inner
spaces of sieve bed portion 300 and product tank portion 302 are at least
partially bounded by
a common wall structure. In this embodiment, the common wall structure is
shown as a
portion of an arcuate or curved wall that is shared by sieve bed portion 300
and product tank
portion 302. In other embodiments, the common wall structure need not be
arcuate or curved
and can be linear or any other shape. Furthermore, other structures capable of
being extruded
may join otherwise separate sieve bed portions and product tank portions
including, for
example, web(s), projections, or extensions.
[0041] Still further, more than one sieve bed portion 300 and one product tank
portion
302 many be formed by extrusion and connected as described herein. For
example, sieve bed
portion 300 shown in Figure 3F may share a common wall structure with multiple
product
tank portions 302, which may partially or fully circumscribe sieve bed portion
300 in the
same manner as product tank portion 302. Similarly, product tank portion 302
may share a
common wall structure with multiple sieve bed portions 300.
[0042] Referring to now to Figure 3G, an exploded perspective view of sieve
bed and
product tank assembly 206 is shown. As described earlier, assembly 206
includes end caps
304 and 306, which attach to sieve bed portion 300 and product tank portion
302. The
attachment of end caps 304 and 306 is facilitated through seal members 322 and
324. As
shown in Figure 3G, seal members 322 and 324 have a physical geometry that
matches the
cross-section of the distal ends of sieve bed portion 300 and product tank
portion 302. Seal
members 322 and 324 are configured to receive the ends of sieve bed portion
300 and product
tank portion 302. Seal members 322 and 324 are also configured to be received
within a
mating portion of end caps 304 and 305. In this manner, seal portions 322 and
324 provide a
gasketing effect facilitating attachment of end caps 304 and 306 and sealing
of the inner
spaces of sieve bed portion 302 and product tank portion 304. Each seal
portion includes
components for sealing the sieve bed portion 300 and product tank portion 302.
In other
embodiments, seal members 322 and 324 may be omitted by providing a sealing
portion
within end caps 304 and 306.
[0043) Figure 3H is a detail view of the upper portion of sieve bed and
product tank
assembly 206. Seal member 322 includes a plurality of recesses 326, 328, and
330, for
example, for receiving the ends of sieve bed portion 300 and product tank
portion 302. Each
7
CA 02793228 2012-10-19
recess is walled and includes top portions 332, 334, and 336, for example. Top
portions 332,
334, and 336 of seal member 322 are received within recesses 338, 340, and
342, for
example, of end cap 304. End cap 304 recesses 338, 340, and 342, for example,
are formed
by walls that project from end cap 304. When end cap 304 is secured to sieve
bed portion
300 and product tank portion 302 via fasteners, end cap 304 and sieve bed
portion 300 and
product tank portion 302 compress seal member 322 thereby providing a gas-
tight seal. End
cap 306 and seal member 324 are similarly configured. As described above, seal
members
322 and 324 can be omitted and recesses 338, 340 and 342 in end cap 304 can be
made to
form a gas-tight seal.
[0044] Referring to now to Figures 31-3L, and more particularly to Figure 3J,
perspective views of an alternate end cap design 350 is shown. End cap 350
differs from the
previously described end cap 304 in that it includes an integrated sound
attenuator or muffler.
Whereas the embodiment of Figure 2 includes discreet sound attenuators or
mufflers 216 and
218, the embodiment of end cap 350 integrates a sound attenuator or muffler
into its
structure.
[0045] As shown in Figure 3J, end cap 350 includes a body having a sieve
bed/product tank interface portion 352. Interface portion 352 also serves as a
base from
which muffler portion 354 extends. Also extending from interface portion 352
is a mounting
boss 356. A muffler block 358 is housed within muffler portion 354 and a
perforated exhaust
cap 360 closes muffler portion 354. Mounting boss 356 accepts a fastener that
passes
through exhaust cap 360 and muffler block 358. Alternative means for securing
these
components can also be utilized.
[0046] End cap 350 further includes an input port 362 and a fitting 364 that
may be
attached to it. End cap 350 also includes an input port 365 to the muffler
portion 354. Input
port 365 is connected to muffler portion 354 through passageway 367. In this
manner, gases
exhausted from the sieve bed are input through port 365 and passageway 367
into muffler
portion 354. The gases are then exhausted by muffler portion 354 through
perforated end cap
360.
[00471 Referring now to Figures 3M and 3N, and particularly to Figure 3N, an
exploded sectional view of end cap 350 is shown. Sieve bed/product tank
interface portion
352 is shown having walled structures similar to end cap 304 for accepting a
seal member
similar to seal member 322 (See Figure 3F and its accompanying text). Muffler
portion 354
has walls that extend from interface portion 354 so as to form a perimeter
bounding space
366. Mounting boss 356 also extends from interface portion 352 and resides in
space 366.
8
CA 02793228 2012-10-19
[0048] Muffler block 358 is porous and includes a bore or hole 368 extending
therethrough. The bore or hole 368 is sized so that mounting boss 356 can be
received
thereinto hold and retain muffler block 358. In other embodiments, muffler
block 358 can be
semi-porous having non-porous portions or can be made of any other sound-
deadening
material. Muffler block 358 is disposed proximate interface portion 352 within
space 366,
though it can sized so as to at least partly fill space 366. As gases are
exhausted, muffler
block 358 may be displaced so as to reside more proximate or against
perforated cap 360 (see
Fig. 30 showing un-displaced position).
[0049] Perforated cap 360 includes a plurality of holes for exhausting gases
introduced into muffler portion 354. Cap 360 includes a base portion having
the holes and
walls that extend therefrom so as to form a space 370. End cap 360 and its
walls are
structured to receive an end section of muffler portion 354 therein. This is
accomplished by
providing the walls of cap 360 with a shoulder portion for abutting against
the end section of
the muffler portion 354. A fastener then passes through cap 360 and interfaces
with boss 356
to hold the two components together. Other means of fastening can also be used
including
snap clips, glue, ultrasonic welding, etc. Figure 30 shows a cross-sectional
perspective of
end cap 350 illustrating the assembled structure.
[0050] COMPRESSOR ASSEMBLY
[0051] Referring to now to Figure 4A, a perspective view of compressor
assembly
210 and rear housing portion 106 is shown. Compressor assembly 210 has frame
406 within
which compressor 408 is mounted or suspended. Rear housing portion 106 has
slots 400 and
402 that interface with the compressor assembly 210. Frame 406 has tabs such
as, for
example, tab 404, which are received in slots 400 and 402 to locate and secure
the
compressor assembly 210 to the rear housing portion 106. Other means of
mounting
compressor assembly 210 to rear housing portion 106 can also be employed such
as, for
example, brackets and fasteners.
[0052] Figure 4B is an exploded perspective view of the compressor assembly
210.
Compressor assembly 210 includes compressor 408, a multi-piece interface
bracket having
members 420, 422, and 424, frame 406, and a plurality of suspension members
430.
Interface bracket member 420 includes a plurality of hook-type portions 428
that couple with
apertures 426 in interface bracket members 422 and 424. Figure 4C illustrates
the interface
bracket when members 420, 422 and 424 are coupled together. The interface
bracket is
coupled or affixed to a body of compressor 408 through appropriate fastening
means such as,
for example, screws, bolts, clips, or pins.
9
CA 02793228 2012-10-19
[0053] Still referring to Figure 4B, suspension members 430 include enlarged
end
portions that are connected together through elongated central portions.
Suspension members
430 are resilient in that they can be stretched under tension. In one
embodiment, suspension
members 430 are formed from an elastomeric material such as, for example,
rubber. In other
embodiments, suspension members 430 can be made of metal to form resilient
springs.
[0054] Frame 406 includes a plurality of structural support members generally
forming a cage-like structure having a top 414, bottom 416, and sides 412 and
418. The
corner portions of frame 406 include openings or apertures 434 that are used
in conjunction
with suspension members 430 to mount or suspend compressor 408 within frame
406 as
shown in Figure 4A.
[0055] Referring now to Figure 4D, a sectional view of compressor assembly 210
with compressor 408 removed is shown. Interface bracket member 424 is shown
and
includes hook portions 432 that interface with suspension members 430. In
particular, the
enlarged end portions of suspension members 430 are inserted within the eye of
hook
portions 432 and the recesses or openings 434 of frame 406. While Figure 4D
illustrates the
suspension or mounting of interface bracket 424 within frame 406, interface
bracket 422 is
similarly suspended or mounted within the frame 406 thereby suspending or.
mounting
compressor 408 within frame 406.
[0056] Configured as such, compressor 408 is suspended or mounted relative to
frame
406 in a manner that isolates the movement or vibration of compressor 408. The
movement
or vibration of compressor 408 is isolated through elastic suspension members
430. Elastic
suspension members 430 allow compressor 408 to move within frame 406 without
translating
that movement to frame 406. In this embodiment, a total of eight suspension
members 430
are employed at the corners of frame 406 but this need not to be the case. Any
number of
suspension members may be used at any location(s) with respect to frame 406
and
compressor 408 in a manner that suitably allows compressor 408 to move
relative to frame
406 without translating that movement to frame 406.
[0057] Referring now to Figure 4E, a second embodiment of a suspension member
is
shown in the form of suspension member 436. Suspension member 436 is similar
to
suspension members 430 in that it structurally incorporates a plurality of
suspension members
430. As shown, suspension member 436 incorporates four individual suspension
members
430. Suspension member 436 further includes connective portions 438 that
connects together
the individual suspension member portions 430 to form a unitary whole. In
other
embodiments, suspension member 436 need not be formed as a continuous
structure but may
CA 02793228 2012-10-19
also form an open structure such as, for example, by omitting one of the
connective portions
438 shown in Figure 4E. Another configuration that provides for the physical
communication of individual suspension members 430 can also be employed.
[0058] Suspension member 436 is connected to interface bracket members 422 and
424 in the same manner as described for the individual suspension members of
430. That is,
the enlarged end portions 440 of suspension members 430 are inserted into the
eye of hook
portions 432 of the interface bracket members and the enlarged end portions
442 are inserted
into the openings or recesses 434 of frame 406. It may be that in some cases
suspension
member 436 allows for easier assembly of compressor assembly 210. In the
embodiment
shown, two suspension members of 436 would be required to replace the eight
suspension
members 430 shown in Figure 4B. Figure 4F illustrates yet another embodiment
of
compressor assembly 210 having and interface bracket with circular end
portions that are
suspended within a frame by suspension members 430.
[0059] Configured as such, compressor assembly 210 reduces noise, vibration
and
vibration induced noise that may emanate from the compressor during operation.
Also,
compressor assembly is configured that compressor 408 may be mounted within
frame 408
according to a plurality of orientations, The interface bracket members 420,
422 and 424 and
frame 406 can be made of any suitable material including, for example, metal
or plastic or
combinations thereof.
[0060] VARIABLE BLEED VALVE
[0061] Another embodiment of a concentrator includes a variable bleed valve
502.
Referring now to Figure 5A, bleed valve 502 and a fixed orifice 514 are in
series and in
pneumatic communication with sieve tanks 300. In operation, a flow setting
input 504 is
selected by a user and received by a microprocessor-based controller 506.
Controller 506 has
associated therewith memory and logic for controlling the operation of, for
example, the
compressor 408, main valves MV I and MV2, exhaust valves EVI and EV2,
conserver valve
512, pressure equalization valve PE and bleed valve 502. All of these valves
are solenoid
controlled. In one embodiment, the compressor 408 is run at a variable speed
based on the
flow setting input 504. For example, low flow settings allow for the
compressor 408 to be
run at a slower speed thereby conserving energy. The compressor 408 can be run
at higher
speeds for higher flow settings. For example, the controller 506 may run the
compressor 408
at 1,100 revolutions per minute (rpm), 1,500 rpm, 2,050 rpm, 2,450 rpm, and
3,100 rpm with
respect to the lowest to highest flow setting inputs 504. Of course, other
speed values are
11
CA 02793228 2012-10-19
envisioned and any suitable speed value may be implemented. Controller 506
also receives
input from a pressure sensor 510.
[0062] The flow setting input 504 is received by controller 506. The flow
setting
input 504 may designate a flow rate that the user desires for delivery of the
product gas (e.g.,
oxygen) in a pulsed output mode. For example, a plurality of flow input
settings 504 may
include 300 cc/min (e.g., 15 cc/pulse at 20 breaths per minute (bpm)), 460
cchnin (e.g., 23
cc/pulse at 20 bpm), 620 cc/min (e.g., 31 cc/pulse at 20 bpm), 740 cc/min
(e.g., 37 cc/pulse at
20 bpm), or 840 ce/min (e,g., 42 cc/pulse at 20 bpm). Based on this setting,
controller 506
appropriately controls the compressor 408 and valves to deliver the desired
pulsed output
flow of oxygen. Of course, other flow rate values are envisioned and any
suitable flow rate
value may be implemented. Additionally, the flow setting input 504 may
designate a flow
rate that the user desires for delivery of the product gas in a continuous
output mode.
[0063] Generally, the concentrator operates using a pressure swing adsorption
(PSA)
process. The compressor 408 delivers room air, through main valves MV I and
MV2, in an
alternate fashion to sieve tanks 300. While one sieve tank 300 is being
filled, the other sieve
tank 300 is typically being purged of its contents. As described earlier, each
sieve tank 300 is
filled within a nitrogen adsorbing material so that nitrogen gas is trapped
within the sieve
tank 300 and oxygen gas is allowed to pass to the product tank 302. When a
particular sieve
tank has reached its adsorption capacity, which can be known by its output
pressure, the
adsorbed gases, such as nitrogen, must be purged before the sieve tank 300 can
be used again.
[0064] Pressure equalization valve PE allows for a more efficient generation
of
oxygen by equalizing the pressure between the output lines of a sieve tank
nearing fill
completion and a sieve tank nearing the end of its purge cycle. US Pat. Nos.
4,449,990 and
5,906,672, further describe the operation of
pressure equalization valves. The oxygen that is being output by a particular
sieve bed 300
may be stored in one or both product tanks 302. Both product tanks 302 are
utilized in the
embodiment of Figure 5A.
[0065] As mentioned above, controller 506 can detect when the sieve tank 300
being
pressurized has reached its adsorption capacity via pressure sensor 510. As
shown in Figure
5A, in one embodiment, pressure sensor 510 provides a signal indicative of
pressure at the
product tank side of a first check valve 516 that passes oxygen flow from the
pressurized
sieve tank 300 to interconnected product tanks 300 and a second check valve
516 that blocks
oxygen flow from the interconnected product tanks 300 to the other sieve tank
300 while it is
being regenerated. For example, the signal may reflect the difference between
the
12
CA 02793228 2012-10-19
pressurized oxygen gas and ambient air. In other embodiments, the pressure
sensor 510 may
be located anywhere in fluidic communication with the output of the sieve tank
300 being
pressurized. Multiple pressure sensors 510 may be implemented if directly
monitoring the
output of each sieve tank 300 is desired. Once the pressurizing sieve tank 300
has reached its
capacity, controller 506 shifts the pressurizing sieve tank 300 into a purging
or exhausting
cycle and shifts the other sieve tank 300, which is now regenerated, to a
pressurizing cycle.
This is the basic repetitive, alternating operation of the PSA process. For
example, the
controller 506 may shift or alternate cycles for sieve tanks 300 when the
pressure sensor 510
detects 9.0 pounds per square inch gauge (psig), 12.5 psig, 16.5 psig, 19.0
psig, and 23.5 psig,
with respect to the lowest to highest flow setting inputs 504. Of course,
other psig values are
envisioned and any suitable psig value may be implemented.
[0066] In one embodiment, bleed valve 502 has a variable "on delay" before
activation to an open or "on" state. The variable "on delay" is associated, in
one
embodiment, with the flow setting input 504. For example, the controller 506
may activate
the bleed valve 502 after an "on delay" of 3.3 seconds (see), 3.2 see, 3.0
sec, 2.9 see, and 2.9
sec, with respect to the lowest to highest flow setting inputs 504. Of course,
other "on delay"
values are envisioned and any suitable "on delay" value may be implemented. In
one
embodiment, bleed valve 502 is de-activated by the controller 506 after the
pressurizing sieve
bed 300 has reached its capacity in conjunction with the end of the
corresponding
pressurizing cycle (i.e., the start of the next pressurization cycle for the
other sieve tank 300).
In general, bleed valve 502 "bleeds" oxygen out of one sieve tank 300 and into
the other
sieve tank 300 at a flow rate that is restricted by orifice 514. That is,
oxygen is allowed to
flow from the sieve tank 300 being pressurized to the sieve tank 300 being
exhausted or
purged. This oxygen flow assists the exhausting or purging of the sieve tank
300 to expel its
captured nitrogen and to regenerate itself for its next pressurization cycle.
Since the
compressor 408 is variably pressurizing a sieve tank 300 based on the flow
setting input 504,
a bleed flow between the sieve tanks 300 that can be variably controlled can
assist in the
efficient purging of the exhausting sieve tank for the corresponding product
gas output flow
rate of the concentrator at a suitable purity level.
[0067] Generally, the higher the value of the flow setting input 504, the
shorter the
"on delay" time (i.e., closed time) and the longer the time that the bleed
valve 502 will be
open with more bleed flow being sent to the exhausting sieve tank 300. This is
because
higher pressurization levels may be used for the higher values for flow
setting inputs 504.
The higher pressurization levels may require more bleed flow to regenerate the
exhausting or
13
CA 02793228 2012-10-19
purging sieve tank 300. Conversely, the lower the value of the flow setting
input 504, the
longer the "on delay" time (i.e., closed time) and the shorter the time that
the bleed valve 502
will be open. This is because lower pressurization levels may be used for the
lower values
for flow setting inputs 504. The lower pressurization levels may require less
bleed flow to
regenerate the exhausting or purging sieve tank 300. Accordingly, the variable
"on delay"
logic described above allows for an increased level of system efficiency in
terms of
maximizing the utilization of the oxygen that is generated by controlling the
amount used in
the purging of an exhausting sieve tank 300. In other embodiments, other
variable logic may
be used to vary other control parameters (e.g., bleed flow duration) for the
bleed valve 502
for different flow setting inputs 504. In further embodiments, the variable
logic may use
other sensed parameters (e.g., pressure) to vary the "on delay" or other
control parameters for
for different flow setting inputs 504,
[0068] As described above, the "on delay" time period prior to activation of
the bleed
valve 502 is dependant upon the value for the flow setting input 504 which in
turn is based on
certain other operating parameters, such as product tank output pressure,
sieve tank output
pressure, compressor speed, and volumetric capacity of various components. In
one
embodiment, the specific "on delay" time period for each flow setting input
504 may be
determined empirically based on the physical specifications of the
concentrator components.
The "on delay" times for each value for the flow setting input 504 are then
stored in a look-up
table in the memory or logic of controller 506. Hence, after reading the flow
setting input
504, controller 506 looks up the bleed valve variable "on delay" time from the
look-up table
stored in its memory or logic. The corresponding "on delay" time is then used
to delay
activation of the bleed valve 502 from the start of the pressurization cycle
for the sieve tank
300 providing the bleed flow. As shown, the pressurization cycle starts after
the pressure
equalization valve PE closes (see timing diagram of Figure 5B). Upon
expiration of the "on
delay" time, which can be monitored by a timer in the memory or logic, the
bleed valve 502
is activated (i.e., opened or "on") and remains open until the start of the
next PSA cycle in
which the roles for the two sieve tanks 300 is shifted.
[0069] In other embodiments, the variable "on delay" may be based at least in
part on
a minimum "on delay" time. In another embodiment, the variable "on delay" may
be based
at least in part on one or more other parameters, such as product tank output
pressure, sieve
tank output pressure, compressor speed, and volumetric capacity of 'various
components in
any combination. In still other embodiments, the variable "on delay" may be
based at least in
part on a minimum "on delay" time in combination with one or more other
parameters. For
14
CA 02793228 2012-10-19
example, after the minimum "on delay" time, activation of the bleed valve 502
may be
triggered if the other parameter exceeds a predetermined threshold at that
time or any time
before the current pressurization cycle is complete. Of course, alternate or
opposite logic is
envisioned and any suitable logical relation between the parameter and
threshold may be
implemented. In still other embodiments, activation of the bleed valve 502 may
be triggered
if the other parameter exceeds the predetermined threshold at any time during
the
pressurization cycle without a minimum "on delay."
[0070] In any of the embodiments described herein, bleed valve 502 may also
have a
variable "maximum on time" after activation in order to limit the continuous
time it remains
open or in the "on" state. The variable "maximum on time" may be associated
with the flow
setting input 504. For example, the controller 506 may de-activate the bleed
valve 502 after a
"maximum on time" of 2.2 sec, 2.4 see, 2.6 see, 2.8 sec, and 3.0 see, with
respect to the
lowest to highest flow setting inputs 504. Of course, other "maximum on time"
values are
envisioned and any suitable "maximum on time" value may be implemented. In
this
embodiment, the bleed valve 502 would also be de-activated if the end of the
current
pressurization is reached before the "maximum on time" expires. Conversely, if
the
"maximum on time" expires before the end of the current pressurization cycle
is reached, the
bleed valve 502 could be activated again based on any combination of the "on
delay" time or
parameter triggers described above. If desired, the bleed valve 502 may also
be fixed to
provide a continuous bleed or fixed to a predetermined open time that is
independent of the
flow setting input 504. Additionally, the "on delay" time may be set to zero
for a particular
flow setting input 504 to provide a continuous bleed and the "maximum on time"
may be set
to zero for a particular flow setting input 504 to inhibit activation of the
bleed valve 502.
[0071] Figure 5B illustrates one embodiment of a timing diagram for the valves
shown in Figure 5A. As shown, after the first pressurization cycle, each
pressurization cycle
begins when the pressure equalization valve PE transitions from closed (i.e.,
off, de-
activated) to open (i.e., on, activated). For example, upon the first
activation of pressure
equalization valve PV, pressurized oxygen from the first sieve tank 300 (i.e.,
associated with
main valve MVI) flows through the pressure equalization valve PV to increase
the pressure
in the second sieve tank 300 (i.e., associated with main valve MV2). Exhaust
valve EV2 is
de-activated along with this activation of pressure equalization valve PE or
shortly thereafter
if the pressure equalization valve PE is to be used to assist in purging and
regeneration of the
second sieve tank 300. Shortly after this activation of the pressure
equalization valve PE,
main valve MV I is de-activated and main valve MV2 is activated to switch
inlet air flow
CA 02793228 2012-10-19
generated by the compressor 408 from the first sieve tank 300 to the second
sieve tank 300.
The pressure equalization valve PE is de-activated shortly after the main
valves MV I and
MV2 are switched. Typically, exhaust valve EVI is activated along with this de-
activation of
pressure equalization valve PE to permit pressure equalization between the
sieve tanks 300 to
continue. However, if desired, the exhaust valve EV 1 could be activated along
with de-
activation of main valve MV 1 or shortly thereafter and before de-activation
of pressure
equalization valve PE. This process continues in alternating fashion to
provide the PSA
process.
[0072] In particular, it can be seen that the bleed valve 502 may be generally
closed
or "off' while the pressure equalization valve PE is open or "on," though this
need not
necessarily be the case. It can also be seen that the variable "on delay" time
for the bleed
valve begins when the pressure equalization valve PE transitions from closed
or "off' to open
or "on.," though this need not be the case as well. It may be beneficial under
some
circumstances to allow overlapping of the open or "on" states of these valves.
In other
words, under certain circumstances, both the bleed valve 502 and the pressure
equalization
PE may be utilized simultaneously or in any combination to provide bleed flow
from the
pressurizing sieve tank 300 to the other sieve tank 300 for its purging and
regeneration.
[0073] Figure 5C shows an exemplary path for bleed flow from sieve tank I
through
orifice 1 and sieve tank 2 to an exhaust gas outlet when main valve MV1, bleed
valve 502,
and exhaust valve EV2 are activated (i.e., open) and main valve MV2 and
exhaust valve EV1
are de-activated (i.e., closed). Figure 5D shows an exemplary alternate path
for bleed flow
from sieve tank 2 through orifice I and sieve tank 1 to the exhaust gas outlet
when main
valve MV2, bleed valve 502, and exhaust valve EV 1 are activated and main
valve MV I and
exhaust valve EV2 are de-activated. As shown by dotted lines, in one
embodiment, the
functions of bleed valve 502 and orifice 1 may be provided in a single
component which may
be referred to as a variable restrictor. In another embodiment, orifice 2 may
provide a
continuous fixed bleed flow in parallel to bleed valve 502 and orifice 1.
Orifice 2 would
establish a minimum bleed flow which could be increased by activation of the
bleed valve
502 as described herein. In still another embodiment, a PE valve may be
activated to provide
or supplement bleed flow in combination with orifice 2 or the series
combination of bleed
valve 502 and orifice 1,
[0074] In another embodiment, the controller 506 may monitor the PSA shifting
time
(i.e., pressurization cycle time) to identify alternate modes of operation for
certain Earth
altitude ranges in which the concentrator is being operated. For example, a
low altitude mode
16
CA 02793228 2012-10-19
may be implemented for operation up to approximately 6,300 feet and a high
altitude mode
may be implemented for operation above 6,300 feet. Of course, other altitude
ranges are
envisioned and additional altitude modes may be implemented. PSA shifting time
tends to
increase at higher altitudes due to lower ambient atmospheric pressures (i.e.,
thinner air).
Certain operating parameters of the concentrator may be adjusted based on a
given altitude
range in order to improve efficiency and sustain suitable levels of product
gas volumetric
output, flow rate, and purity.
[0075] Testing has demonstrated that a fixed "on delay" for bleed valve 502
based on
flow setting input 504 may be acceptable in a low altitude mode of operation.
However, the
higher the altitude, the longer the shift time between pressurization of
alternate sieve tanks
300 because the concentrator takes longer and longer to build up to the
desired shift pressure.
In response to the longer shift times, the concentrator may shift to a higher
altitude mode
which may adjust one or more operating parameters (i.e., product tank output
pressure, sieve
tank output pressure, bleed valve control) to keep the shift time in an
optimum range. If a
fixed "on delay" for the bleed valve 502 were maintained across a wide
altitude range there
may be little or no bleed flow at the lower elevations of the altitude range.
Moreover, the
fixed "on delay" could result in too much bleed flow at higher elevations when
the shift time
has been significantly stretched out. No bleed flow and too much bleed flow
may result in
the product gas from the concentrator being outside desired purity levels for
operation at the
lower and higher elevations of a wide altitude range.
[0076] Data was collected and analyzed at various altitudes over the range of
5,300 to
11,150 feet above sea level. Nominal values for low and high altitude shift
times for each
flow setting input 504 were identified. For example, 1) at the lowest flow
setting input 504,
nominal values of 5.5 and 14 seconds for low and high altitude shift times
were identified and
threshold of 6,300 feet was associated with transitioning from low altitude
mode to high
altitude mode; 2) at the next higher flow setting input 504, nominal values of
5 and 13
seconds for low and high altitude shift times were identified and a threshold
of 6,200 feet was
associated with transitioning from low altitude mode to high altitude mode; 3)
at the middle
flow setting input 504, nominal values of 5 and 11.5 seconds for low and high
altitude shift
times were identified and a threshold of 6,200 feet was associated with
transitioning from low
altitude mode to high altitude mode; 4) at the next higher flow setting input
504, nominal
values of 5 and 10.5 seconds for low and high altitude shift times were
identified and a
threshold of 6,300 feet was associated with transitioning from low altitude
mode to high
altitude mode; and 5) at the highest flow setting input 504, nominal values of
5.5 and 11
17
CA 02793228 2012-10-19
seconds for low and high altitude shift times were identified and a threshold
of 6,000 feet was
associated with transitioning from low altitude mode to high altitude mode.
[0077] Suitable shift time thresholds may be established for transitioning
from low
altitude mode to high altitude mode (e.g., approximately 12 seconds) and for
transitioning
from high altitude mode to low altitude mode (e.g., approximately 5.5
seconds). Of course,
different shift time thresholds can be established for different flow setting
inputs 504. For
example, the shift time thresholds for transitioning from low altitude mode to
high altitude
mode could range between 10.5 and 14 seconds for different flow setting inputs
504.
Simlarly, the shift time thresholds for for transitioning from high altitude
mode to low
altitude mode could range between 5.0 and 5.5 seconds for different flow
setting inputs 504.
Typically, the thresholds will be different and the threshold for
transitioning from high
altitude mode to low altitude mode will be less than the other threshold to
establish a suitable
hysteresis. In another embodiment, transition between altitude modes can be
delayed for a
fixed time or until the shift times for a predetermined quantity of
consecutive pressurization
cycles (e.g., three consecutive cycles) indicate that the altitude mode
transition is appropriate.
[0078] The bleed valve 502 may be controlled in any manner described herein
for any
altitude mode. Notably, the bleed valve 502 may be controlled differently in
different
altitude modes. Accordingly, preferred bleed valve control techniques can be
implemented
based at least in part on altitude mode and transitions in altitude modes can
produce
corresponding transitions in bleed valve control techniques.
[0079] In one embodiment, an "on delay" time associated with activation the
bleed
valve 502 and the PSA shifting time (i.e., pressurization cycle time) may have
a generally
linear relation encompassing the range of the flow setting inputs 506. The
shift time may be
represented by the shift pressure set-point for each flow setting input 506
because the shift
time is the time it takes a given sieve tank 300 to reach a pressure related
to its full capacity.
In the embodiment being described, pressure build in the sieve tank 300 may be
assumed to
be linear. This allows a bleed valve activation pressure to be expressed as a
ratio of pressure
set-point for each flow setting input 506. The ratio may then be used to
determine a threshold
pressure value. During the pressure build up, if the pressure exceeds the
threshold pressure
value, the controller 506 activates (i.e., opens) the bleed valve 502. This
may ensure there is
at least enough bleed flow to maintain a desired level of purity while also
limiting bleed flow
to avoid unnecessary loss of oxygen. In other embodiments, the "on delay" time
may be a
non-linear function of the PSA shifting time. Similarly, the function used to
determine the
"on delay" time may be different for different flow setting inputs 506 in
other embodiments.
18
CA 02793228 2012-10-19
[0080] The table below shows exemplary pressure set-points for each flow
setting
input 506 when the concentrator is operating in a low altitude mode (LAM). In
one
embodiment, pressure set-points for high altitude mode (HAM) can be determined
from the
exemplary pressure set-points for LAM using the following equation:
HAM Pressure Set-Point = LAM Pressure Set-Point *Ratio (1),
where the Ratio may be 0.875 for all flow setting inputs 506. Of course, HAM
pressure set-
points can be established using other techniques or other suitable criteria.
For example, the
Ratio may be a different value or may be replaced by a variable function for
any particular
flow setting input 506. Additionally, where additional altitude modes are
implemented any
suitable technique or criteria may be used to establish alternate pressure set
points for each
altitude mode.
[0081] In one embodiment, the threshold values for triggering activation of
the bleed
valve 502 during HAM may be determined using the following equation:
HAM Pressure Threshold = HAM Pressure Set-Point * Ratio (2),
where the Ratio may be: i) 0.55 for the lowest flow setting input 506, ii)
0.60 for the next
higher flow setting input 506, iii) 0.65 for the middle flow setting input
506, iv) 0.70 for the
next higher flow setting input 506, and v) 0.75 for the highest flow setting
input 506. In
another embodiment, the Ratio may be 0.90 for all flow setting inputs 506. .
Of course,
HAM pressure thresholds can be established using other techniques or other
suitable criteria.
For example, the constant may be a different value or may be replaced by a
variable function
for any particular flow setting input 506. Additionally, where additional
altitude modes are
implemented any suitable technique or criteria may be used to establish
alternate pressure
thresholds for each altitude mode.
Example 1
Plow LAM Pressure HAM Pressure Ratio HAM Pressure Threshold
Setting Set-Point Set-Point for Bleed Valve Activation
(psig) (prig) (psig)
1 9.0 7.88 .55 4.33
2 12.5 10.94 .60 6.56
3 16.5 14.44 .65 9.38
4 19.0 16.63 .70 11.64
23.5 20.56 .75 15.42
19
CA 02793228 2012-10-19
Example 2
Flow LAM Pressure HAM Pressure Ratio HAM Pressure Threshold
Setting Set-Point Set-Point for Bleed Valve Activation
(psig) (psi9) (psig)
1 9.0 7.88 .90 7.09
2 12.5 10.94 .90 9.84
3 16.5 14.44 .90 12.99
4 19.0 16.63 .90 14.96
23.5 20.56 .90 18.51
[0082] In another embodiment, the controller 506 may utilize a timer function
to
monitor PSA cycle shift time. This monitored shift time measurement may be
compared
against shift time ranges stored in non-volatile memory. The controller 506
may use the
result of this comparison to determine if the concentrator should be operating
in low or high
altitude modes. In low altitude mode, for each flow setting input 504, the
concentrator may
operate from a fixed pressure value that is stored in non-volatile memory. In
high altitude
mode, the concentrator may operate from a fixed pressure value for each flow
setting input
504 that is based at least in part on the corresponding low altitude fixed
pressure value.
[0083] In yet another embodiment, in low altitude mode, for each flow setting
input
504, the concentrator may operate from a fixed "on delay" time for activation
of the bleed
valve 502 that is stored in non-volatile memory. In high altitude mode, the
concentrator may
operate from a variable bleed valve activation time that is scaled based on
the fixed pressure
value for each flow setting input 504 or the monitored PSA cycle shift time.
The bleed valve
scale factor may be calculated from the fixed pressure value or the monitored
PSA cycle shift
time.
[0084] The aforementioned functions can be performed either as software or
controller logic. "Logic," as used herein, includes but is not limited to
hardware, firmware,
software and/or combinations of each to perform a function(s) or an action(s),
and/or to cause
a function or action from another component. For example, based on a desired
application or
needs, logic may include a software controlled microprocessor, discrete logic
such as an
application specific integrated circuit (ASIC), or other programmed logic
device. Logic may
also be fully embodied as software.
[0085] "Software," as used herein, includes but is not limited to one or more
computer readable and/or executable instructions that cause a computer or
other electronic
device to perform functions, actions, and/or behave in a desire manner. The
instructions may
CA 02793228 2012-10-19
be embodied in various forms such as routines, algorithms, modules or programs
including
separate applications or code from dynamically linked libraries. Software may
also be
implemented in various forms such as a stand-alone program, a function call, a
servlet, an
applet, instructions stored in a memory, part of an operating system or
another type of
executable instructions. It will be appreciated by one of ordinary skill in
the art that the form
of software is dependent on, for example, requirements of a desired
application, the
environment it runs on, and/or the desires of a designer/programmer or the
like.
[00861 The systems and methods of the present invention can be implemented on
a
variety of platforms including, for example, networked control systems and
stand-alone
control systems. Additionally, the logic, databases or tables shown and
described herein
preferably reside in or on a computer readable medium such as, for example, a
Flash
Memory, Read-Only Memory (ROM), Random-Access Memory (RAM), programmable
read-only memory (PROM), electrically programmable read-only memory (EPROM),
electrically erasable programmable read-only memory (EEPROM), magnetic disk or
tape,
and optically readable mediums including CD-ROM and DVD-ROM. Still further,
the
processes and logic described herein can be merged into one large process flow
or divided
into many sub-process flows. The order in which the process flows herein have
been
described is not critical and can be rearranged while still accomplishing the
same results.
Indeed, the process flows described herein may be rearranged, consolidated,
and/or re-
organized in their implementation as warranted or desired.
[0087] Figures 5E and 5F further illustrate an exemplary embodiment of a valve
assembly 214 that includes bleed valve 502 and other components. In this
embodiment,
bleed valve 502, pressure equalization valve PE a conserver valve 512, fixed
orifice 514,
fixed orifice 515, and check valves 516 are mounted or affixed to a block-like
manifold body
having a plurality of inlets, outlets and inner passageways connecting the
inlets, outlets and
valves as shown. So configured, the valve assembly 214 results in a space and
weight
savings that is adaptable to a portable oxygen concentrator and other devices.
The
configuration also allows for easy service and replacement of the valve
assembly 214 should
that be necessary. In other embodiments, the concentrator may include discrete
components
or any suitable combination of components in one or more valve assemblies. In
particular,
bleed valve 502 and fixed orifice 514 may be combined in a modular assembly.
[0088] OUTPUT PORT
[0089] In one embodiment of the present invention, output port 108 includes a
suitable air filter. Though the oxygen exiting the sieve and product tanks has
already been
21
CA 02793228 2012-10-19
filtered prior to the nitrogen-oxygen separation process, additional filtering
may be of
assistance to some patients. Referring now to Figure 6A, the perspective view
of one
embodiment of output port 108 is shown. The output port 108 includes a main
body 600,
input 602, extension 604 and output 610. Input 602 is configured to meet with
pneumatic
tubing that delivers oxygen. The oxygen received through input 602 enters main
body 600.
Main body 600 includes a suitable filter therein such as, for example, a HEPA
filter or other
suitable filter, for the filtering the oxygen. Extension 604 includes a key
surface 606 and
threads 608. The surface 606 facilitates a proper orientation of the output
port 108 during our
assembly with the housing of the oxygen concentrator. Threads 608 facilitate
fastening of the
output port 108 to the housing of the oxygen concentrator via a HEX nut or
other type of
fastener. Output 610 is configured to mate with tubing that delivers the
oxygen to the patient
or a medical accessory.
[0090] Referring now to Figure 6B, a day cross-sectional view taken along a
section
lines 6B-6B of Figure 6A is shown. The filter of main body 600 is shown at
612. Filter 612
occupies a substantial portion of the inner space of main body 600 to filter
the oxygen being
received through input 602. As such, filter 612 has a shape and geometry that
complements
the shape and geometry of the inner space of main body 600. In one embodiment,
filter 612
is made of a Boro-Silicate Glass microfiber and is hydrophobic. Filter 612
also provides for
a filtration efficiency of greater than 99.99% for particle sizes 0.2
micrometers or greater.
Other filters having less than all of these properties may be used as well.
[0091] In one embodiment, the main body 600 is made from a polypropylene
material
and its inner space provides for an effective filtration area of 3.5 em2. The
main body
material can be any suitable material and the filtration area can be made
larger or smaller than
described. In one embodiment, output port 108 is preferably fabricated by
joining two
sections that interface in the region of the main body 600 to form the entire
output port 108.
In this example, two sections are shown being divided by interface axis 614
extending
through main body 600. Filter 612 is inserted into one of the sections forming
part of the
inner space of main body 600. The other section would then be joined through
bonding or
welding, thereby sealing filter 612 into the inner space of main body 600. In
other
embodiments, the two sections can be joined via mating threads or other non-
permanent
connections that would allow removal and replacement of filter 612.
[0092] PRESSURE SENSOR CALIBRATION AND CONSERVER
[0093] Figure 7 illustrates one embodiment of a process 700 for calibrating
pressure
sensor 510 within controller 506. The rectangular elements denote "processing
blocks" and
22
CA 02793228 2012-10-19
represent computer software instructions or groups of instructions. The
diamond shaped
elements denote "decision blocks" and represent computer software instructions
or groups of
instructions which affect the execution of the computer software instructions
represented by
the processing blocks. Alternatively, the processing and decision blocks
represent steps
performed by functionally equivalent circuits such as a digital signal
processor circuit or an
application-specific integrated circuit (ASIC). The flow diagram does not
depict syntax of
any particular programming language. Rather, the flow diagram illustrates the
functional
information one skilled in the art may use to fabricate circuits or to
generate computer
software to perform the processing of the system. It should be noted that many
routine
program elements, such as initialization of loops and variables and the use of
temporary
variables are not shown. Also the order flow may be changed with the same
results being
obtained.
[0094] The calibration routine, for example, may be performed by a qualified
technician using an adjustable external pressure source. Of course, other
scenarios are
possible and any procedure that suitably accomplishes the pressure sensor
calibration may be
implemented. In block 702, a signal (e.g., analog to digital count (A-D
count)) from the
pressure sensor 510 is read by the controller 506 after an external pressure
source is adjusted
to a first fixed pressure setting and pressure is applied to the pressure
sensor. For example,
the first fixed pressure setting may be a pressure associated with normal
operation of the
concentrator, such as 10 psig. For example, controller 506 includes as one of
its structures an
analog-to-digital converter that allows it to read analog signals that emanate
from sensors
such as pressure and flow sensors. The conversion of an analog sensor signal
to a digital or
binary value allows the controller to read and use the sensor signal in its
processing. In other
embodiments, the first fixed pressure setting can be any pressure setting
including ambient or
vacuum. In block 704, a value for the signal read in 702 (e.g., corresponding
A-D count) is
stored in memory.
[0095] In block 706, the signal (e.g., A-D count) from the pressure sensor 510
is read
by the controller 506 after the external pressure source is adjusted to a
second fixed pressure
setting. For example, the second fixed pressure setting may also be a pressure
associated
with normal operation of the concentrator, such as 20 psig. Similar to the
first pressure
setting, the second pressure setting can be any pressure setting. Block 708
stores a value for
the signal read in 706 (e.g., corresponding A-D count) in memory. Block 710
generates a
linear extrapolation (Y=m(X) + B) using the first and second signal values
(e.g., A-D count
readings). The linear extrapolation is then used in block 712 by controller
506 to convert
23
CA 02793228 2012-10-19
signal values (e.g., A-D counts) from the pressure sensor 510 to psig. In the
linear
extrapolation, X represents signal values (e.g., pressure sensor A-D counts or
readings) and Y
represents pressure in psig. In alternate embodiments, any pressure setting
can be used from
unit-less or un-calibrated measures of pressure to external calibrated
pressure sources.
[0096] Figure 8 illustrates one embodiment of a conserver process 800 for
determining a time duration associated with providing a bolus of gas, such as
oxygen, to a
user of the oxygen concentrator 100. "Bolus," as used herein includes, but is
not limited to, a
dose or pulse of concentrated product gas, such as oxygen, provided to the
user via a suitable
user interface, such as a nasal cannula or nasal mask. Bolus parameters
relating to flow
through pneumatic components include duration and amplitude. The duration
parameter
relates to activating and de-activating a valve to start and end the bolus.
The amplitude
parameter relates to flow capacity of the components and pressure of the
product gas.
Oxygen concentrator 100 can include, for example, a conserving device for
controlling the
flow of oxygen to the patient. For example, the conserving device may be
adjustable in
relation to one or more parameters to conserve power consumption of the oxygen
concentrator 100 while maintaining suitable purity, flow rate, and volume of
the product gas.
In one embodiment, the conserving device is formed by controller 506, flow
sensor 508,
pressure sensor 510 conserver valve 512, and fixed orifice 515 (see, Figure
5A). The
conserver process 800 represents one embodiment of logic that can reside
within controller
506. Controller 506 uses, for example, flow sensor 508 to monitor the
breathing of a user to
determine breathing characteristics (e.g., breath rate, inhalation,
exhalation, volume, flow,
etc.) of the user. Upon the start of inhalation (i.e., the end of exhalation),
controller 506 is
programmed to deliver a bolus of gas, such as oxygen, to the user. In this
regard, the size of
the bolus can be fixed or determined at least in part from the patient's
breathing
characteristics(e.g., breathing rate, duration of inhalation, volume, flow,
etc.). Once fixed or
determined, controller 506 controls the on and off state of conserver valve
512 to deliver the
proper bolus of gas to the patient. For example, a bolus can be provided
during the inhalation
portion of each breathing cycle.
[0097] In block 802, the controller 506 has detected a trigger associated with
the
patient's breathing characteristics, determined that a bolus of gas is to be
delivered to the
patient, and opened or switched the conserver valve 512 to dispense
concentrated product gas
to the patient. A loop now begins where the controller 506 reads the signal
(e.g., A-D count)
of the pressure sensor (block 802), converts the signal (e.g., A-D count) to
psig (block 804),
and sums the psig values until a pre-determined psig value is reached (block
806), For
24
CA 02793228 2012-10-19
example, the pre-determined summation of psig values may relate to a pre-
determined
volumetric measure of concentrated breathing gas to be provided by the bolus.
The pre-
determined volumetric measure of concentrated breathing gas may be based at
least in part on
the patient's breath rate and a desired output volume over a pre-determined
time duration
(e.g., 300 cc/min). For example, the physical characteristics of the fixed
orifice 515, the
monitored pressure of the product tanks 302, and the time the conserver valve
512 is
activated to provide product gas flow may be considered by the controller 506
in order to
provide the desired volume of product gas in a given bolus. The relation of
pressure over
time for product gas flow through a fixed orifice is a classic integral
calculus function.
Where the pressure is variable, the time the conserver valve 512 is activated
is adjustable in
order to provide the desired volume of product gas. Accordingly, the
controller 506 may
control the conserver valve 512 based at least in part on the monitored
pressure.
[0098] In block 804, the conversion from signal value (e.g., pressure sensor A-
D
count) to psig is accomplished using the linear extrapolation obtained from
Figure 7. In other
embodiments, alternative methods of obtaining the psig values from the signal
value (e,g., A-
D counts) can also be utilized. In block 806, the psig values are summed by
adding them
together such as, for example, by the formula P = P + PSIG. In the formula,
PSIG represents
the current psig reading and P represents the current summation of pressures.
This formula is
derived from the classic integral calculus function defining the relation of
pressure over time
for product gas flow through a fixed orifice discussed above. In an
alternative embodiment,
the signal values (e.g., A-D counts) from the pressure sensor 510 can be
summed until a pre-
determined summation value (e.g., summation A-D count) is reached. Once the
summation
of pressures equals a pre-determined pressure summation threshold, at 810, the
controller 506
closes the conserver valve 512 and waits for the next bolus trigger to occur.
For example, the
pre-determined pressure summation threshold may relate to a pre-determined
volumetric
measure of concentrated breathing gas to be provided by the bolus.
[0099] The pre-determined volumetric measure of concentrated breathing gas may
be
based at least in part on the patient's breath rate and a desired output
volume over a pre-
determined time duration (e.g., 840 cc/min). For example, the desired output
flow rate
setting (e.g., 840 cc/min) may be divided by the patient's breath rate to
allocate the
corresponding desired volume for the longer time scale to individual boluses
for each patient
breath. For an exemplary breath rate of 20 bpm, the desired volume for each
bolus may be 42
cc. Similarly, for an exemplary breath rate of 10 bpm, the desired volume for
each bolus may
be 84 cc. Normally, a bolus would be delivered with each patient breath.
However, the
CA 02793228 2012-10-19
concentrator may intentionally skip a breath under certain circumstances to
ensure that
suitable product gas purity levels and system efficiency is achieved. For
example, if the
breath rate exceeds a predetermined rate (e.g., 36 bpm), the concentrator may
not provide a
bolus with every breath and may selectively skip breaths in a manner the
achieves suitable
product gas purity levels and system efficiency.
[00100] Figure 9 illustrates one embodiment of timing operation of the
conserver valve
512 with respect to a breathing characteristic (e.g., inhalation) associated
with a user
breathing cycle (i.e., BREATH 900). An exemplary breathing cycle 901 is shown
with an
inhalation period followed by an exhalation period. Flow sensor 508 measures a
flow rate
associated with the user breathing cycle when the conserver valve 512 is
diverting user
breathing through the vent port, which is represented by FLOW 902 and an
exemplary flow
signal 903 corresponding to the exemplary breathing cycle 901. Flow signal
903, for
example, can represent analog signal levels, digital representations of analog
signal levels, or
actual flow rate units. In any event, trigger threshold 904 is established for
flow signal 903.
Trigger threshold 904 can, depending on the particular implementation, be a
zero-crossing
point, offset (positive or negative) from the zero-crossing point, an average
flow per cycle, or
off-set (positive or negative) from the average flow. In the embodiment shown
in Figure 9,
the trigger threshold 904 is shown as occurring just after the inhalation
phase has started.
This is an example of a positive offset from the zero-crossing point. In one
embodiment, the
trigger threshold can be 12 standard cubic centimeters per minute (seem).
[00101] Once the trigger threshold 904 has been reached by flow signal 903,
controller
506 opens conserver valve 512 for a time duration long enough to deliver the
required size
bolus 905 to the user. In one embodiment, the time duration that the conserver
valve 512
remains open may be determined by the logic of process 800 (Figure 8). As
described above
in reference to Figure 8, once the summation of pressures reaches the pre-
determined
summation value, conserver valve 512 is closed 906 by controller 506. The
controller 506
may ignore or otherwise avoid taking action in relation to the trigger
threshold 904 at least
until a time duration associated with breath rates is exceeded in order to
avoid triggering
another bolus 905 before the start of the next inhalation. This may be
referred to as a trigger
lock-out period 907. The trigger lock-out period 907 can be determined as a
percentage of a
breathing characteristic (e.g., breath rate, breath cycle, exhalation, or
other breathing
characteristics including flow, flow rate and pressure) for an average person,
exemplary
person, or a particular person, such as the patient. For example, if a breath
rate of 350
milliseconds (msec) is selected, the trigger lock-out period would be some
percentage of 350
26
CA 02793228 2012-10-19
insec, such as 175 msec. This trigger lock-out period 907 ensures that the
next trigger is not
falsely or prematurely initiated until the start of the patient's next
inhalation. After expiration
of the trigger lock-out period 907, the next trigger threshold is active. In
one embodiment,
after the trigger lockout period, the controller 506 may also wait for the
flow signal to fall
below the trigger threshold 904 before enabling the next activation of the
conserver valve
512. In this manner, a bolus 905 of gas (e.g., oxygen) may be delivered to the
patient each
time flow signal 903 rises through the trigger threshold 904 after the start
of an inhalation
portion of a breathing cycle. As described above, the concentrator may
intentionally skip a
breath under certain circumstances to ensure that suitable product gas purity
levels and
system efficiency is achieved.
[00102] The conserver valve 512 may also be controlled in any manner described
herein for any altitude mode. Notably, the conserver valve 512 may be
controlled differently
in different altitude modes. Accordingly, preferred conserver valve control
techniques can be
implemented based at least in part on altitude mode and transitions in
altitude modes can
produce corresponding transitions in conserver valve control techniques.
[00103] In one embodiment, in high altitude mode, the controller 506 may
automatically adjust operation of the conserver valve 512 to maintain suitable
levels of
purity, flow rate, and volume for the product gas as elevation changes. If not
adjusted, for
example, the conserver valve 512 may stay activated longer as the PSA cycle
shift time .
increases in relation to higher elevations. This may result in larger bolus
volumes than
necessary and higher product gas outputs than desired. For example, in low
altitude mode,
the concentrator may operate using a low altitude fixed time duration for
activation of the
conserver valve 512 for a given flow setting input 504. The low altitude fixed
time duration
may be different for different flow setting inputs 504. Each low altitude
fixed time duration
may be a function of PSA cycle shift time and decay in pressure of the
concentrated product
gas associated with the shifting. These low altitude fixed time durations may
be stored in
non-volatile memory.
[00104] Similarly, in high altitude mode, the concentrator may operate using a
high
altitude fixed time duration for activation of the conserver valve 512 at a
given flow setting
input 504. The high altitude fixed time duration may be different for
different flow setting
inputs 504. Each high altitude fixed time duration may be a function of the
low altitude fixed
time duration for the corresponding flow setting input 504. The functional
relationship
between the low and high altitude fixed time durations may be different for
different flow
setting inputs 504. In other words, the algorithm defining the function at a
given flow setting
27
CA 02793228 2012-10-19
input 504 may be different from the algorithm defining the function at a
different flow setting
input 504. These high altitude fixed time durations may be stored in non-
volatile memory.
In other embodiments, values for certain parameters of the functions (i.e.,
algorithms),
particularly parameters that vary for different flow setting inputs 504, may
be stored in non-
volatile memory.
[00105] With reference to Figure 10, another exemplary embodiment of a product
gas
concentrator 10 may include an input device 12, a product gas source 14, a
pressure sensor
16, a conserver valve 18, and a controller 20. The input device 12 may be used
to select a
first desired output flow rate setting for the concentrated product gas. The
product gas source
14 may provide the concentrated product gas for dispensing. The pressure
sensor 16 may
monitor a pressure of the concentrated product gas. The conserver valve 18 may
include an
output connection, a vent connection, and a gas connection. The output
connection may be
associated with a user 22. The vent connection may be associated with a vent
port 24. The
gas connection may be associated with the concentrated product gas. The output
connection
may be switched from the vent connection to the gas connection and vice versa.
The
controller is in operative communication with the input device 12 and pressure
sensor 16 and
may selectively switch the conserver valve 18 to selectively dispense the
concentrated
product gas based at least in part on the selected output flow rate setting
and monitored
pressure. For example, the pressure sensor 16 may monitor pressure between the
conserver
valve 18 and the product gas source 14, In another embodiment, the pressure
sensor 16 may
monitor pressure in another suitable location.
[00106] In one embodiment, the controller 20 may store a first pressure value
based at
least in part on the corresponding monitored pressure. The controller 20 may
also store a
second pressure value based at least in part on the corresponding monitored
pressure after the
input device 12 is used to select a second desired output flow rate setting.
In this
embodiment, the controller 20 may determine an intermediate pressure value
between the
first and second pressure values based at least in part on a linear relation
between the first and
second pressure values and the monitored pressure.
[00107] In another embodiment, the product gas concentrator 10 may also
include a
flow sensor 26. The flow sensor 26 may monitor a flow indicative of a
breathing cycle for
the user 22. The controller 20 may be in operative communication with the flow
sensor 26.
For example, the flow sensor 26 may monitor flow between the conserver valve
18 and the
vent port 24. In the embodiment being described, the controller 20 may
determine a
breathing characteristic of the user 22 based at least in part on the
monitored flow. The
28
CA 02793228 2012-10-19
controller 20 may selectively switch the conserver valve 18 based at least in
part on the
determined breathing characteristic. In another embodiment, the flow sensor 26
may monitor
a flow indicative of a breathing cycle for the user 22 in another suitable
location.
[00108] In the embodiment being described, the controller 20 may determine a
start
time for dispensing a bolus of concentrated product gas to the user 22 via the
conserver valve
18 based at least in part on a relation between the determined breathing
characteristic and a
trigger threshold indicative of inhalation. The controller 20 may determine a
pressure
summation threshold based at least in part on the selected output flow rate
setting. In the
embodiment being described, the controller 20 may also determine the start
time for
dispensing the bolus of concentrated product gas based at least in part on
expiration of a lock-
out time associated with a previous bolus. The controller 20 may determine a
time duration
for. dispensing the bolus of concentrated product gas based at least in part
on a relation
between the monitored pressure and the pressure summation threshold.
[00109] With reference to Figure 11, an exemplary embodiment of a process 50
for
providing a concentrated product gas may begin at 52, where a first desired
output flow rate
setting for the concentrated product gas may be selected. Next, a product gas
source for
dispensing the concentrated product gas may be provided (54). At 56, a
pressure of the
concentrated product gas may be monitored. Next, an output connection
associated with a
user may be selectively switched from a vent connection associated with a vent
port to a gas
connection associated with the concentrated product gas and vice versa to
selectively
dispense the concentrated product gas based at least in part on the selected
output flow rate
setting and monitored pressure (58).
[00110] In one embodiment, the process 50 may also include storing a first
pressure
value based at least in part on the monitored pressure, selecting a second
desired output flow
rate setting for the concentrated product gas, storing a second pressure value
based at least in
part on the monitored pressure, and determining an intermediate pressure value
between the
first and second pressure values based at least in part on a linear relation
between the first and
second pressure values.
[00111] In still another embodiment, the process 50 may also include
monitoring a
flow indicative of a breathing cycle for the user and determining a breathing
characteristic of
the user based at least in part on the monitored flow. In this embodiment, the
selective
switching in 58 may be based at least in part on the monitored breathing
characteristic. In the
embodiment being described, the process 50 may further include determining a
start time for
dispensing a bolus of concentrated product gas to the user via the output
connection based at
29
CA 02793228 2012-10-19
least in part on a relation between the monitored breathing characteristic and
a trigger
threshold indicative of inhalation. The process 50 may also include
determining the start
time for dispensing the bolus of concentrated product gas based at least in
part on expiration
of a lock-out time associated with a previous bolus. Additionally, in this
embodiment, the
process 50 may also include determining a pressure summation threshold based
at least in
part on the selected output flow rate setting and determining a time duration
for dispensing
the bolus of concentrated product gas based at least in part on a relation
between the
monitored pressure and the pressure summation threshold.
[00112] While the present invention has been illustrated by the description of
embodiments thereof, and while the embodiments have been described in
considerable detail,
additionally advantages and modifications will readily appear
to those skilled in the art. For example, components that are described as
being connected,
affixed, or joined, can be connected, affixed. or joined directly or
indirectly such as through
one or more intermediary components. Furthermore, sizes and geometries of
various
components can be changed from the various embodiments and examples shown and
described herein. Therefore, the invention, in its broader aspects, is not
limited to the specific
details, the representative apparatus, and illustrative examples shown and
described.
