Molecular sieve abstract
A container for a plurality of molecular sieve beds for use in
a pressure swing oxygen concentrator. An extrusion defines at least
two and preferably at least three passages extending between open
ends of the extrusion. The extrusion ends are closed by first and
second end caps secured to the extrusion. Two of the passages form
separate molecular sieve containers and a third passage may form
an accumulator for storing concentrated oxygen. In a preferred embodiment,
the first end cap has separate inlet ports for each molecular sieve
container and an outlet port for the accumulator. The second end
cap has separate outlet ports for each molecular sieve container
and an inlet port for the accumulator. Optionally, the second end
cap may include a restricted passage allowing a limited oxygen flow
between the outlet ports from the molecular sieve containers and
the second end cap may include check valves and passages which allow
pressurized oxygen to flow from each molecular sieve container outlet
port to the accumulator inlet port. The first end cap may include
a feed gas port and an exhaust gas port connected through a flow
control valve to the molecular sieve container inlet ports.
Molecular sieve claims
I claim:
1. A molecular sieve container for an oxygen concentrator comprising
an elongated extrusion having first and second open ends and at
least two cavities extending between said ends, said cavities each
having an open first end at said first extrusion end and an open
second end at said second extrusion end, a first end cap secured
to said first extrusion end to close said first ends of said cavities,
a second end cap secured to said second extrusion end to close said
second ends of said cavities, wherein at least two of said cavities
define first and second containers for separate molecular sieves,
and means in said end caps forming inlet and outlet ports for each
molecular sieve container.
2. A molecular sieve container, as set forth in claim 1 and wherein
said means in said end caps forming inlet and outlet ports for each
molecular sieve container includes means in said first end cap forming
a separate inlet port for each molecular sieve container, and means
in said second end cap forming a separate outlet port for each molecular
sieve container.
3. A molecular sieve container, as set forth in claim 2 and wherein
each end cap has a separate threaded opening connecting to each
molecular sieve, said threaded opening in said first end cap connecting
with each molecular sieve container defining the inlet port to such
container and said threaded opening in said second end cap connecting
with each molecular sieve container defines the outlet port from
such container.
4. A molecular sieve container, as set forth in claim 3 and wherein
at least three cavities extend between said extrusion ends, wherein
one of said cavities defines an accumulator container for receiving
and storing concentrated oxygen from said molecular sieve containers,
wherein said first end cap has a threaded opening connecting with
said accumulator container defining an outlet port, and wherein
said second end cap has a threaded opening connecting with said
accumulator container defining an inlet port.
5. A molecular sieve container, as set forth in claim 1 and wherein
at least three cavities extend between said extrusion ends, and
wherein one of said cavities defines an accumulator container for
receiving and storing concentrated oxygen from said molecular sieve
containers.
6. A molecular sieve container, as set forth in claim 5 and wherein
said second end cap includes means forming an inlet port to said
accumulator container, and wherein said first end cap includes means
forming an outlet port from said accumulator container.
7. A molecular sieve container, as set forth in claim 6 and wherein
said second end cap includes means connecting said outlet ports
from each of said first and second molecular sieve containers to
said inlet port to said accumulator container.
8. A molecular sieve container, as set forth in claim 7 and wherein
said connecting means from each of said molecular sieve containers
includes check valve means for preventing a flow of gas from said
accumulator container back to such molecular sieve container.
9. A molecular sieve container, as set forth in claim 8 and wherein
said second end cap further includes a restricted passage means
connecting together said outlet ports from said first and second
molecular sieve containers for permitting a limited flow of gas
from a higher pressure one of said molecular sieve containers to
a lower pressure one of said molecular sieve containers.
10. A molecular sieve container, as set forth in claim 9 and wherein
said first end cap includes said inlet ports to each molecular sieve
container, a feed gas port and an exhaust gas port, valve means
mounted to said first end cap, passage means connecting said first
and second molecular sieve bed inlet ports, said feed gas port and
said exhaust gas port to said valve means, wherein said valve means
has a first position in which said feed gas port is connected to
said first molecular sieve container inlet port and said exhaust
gas port is connected to said second molecular sieve container inlet
port, and wherein said valve means has a second position in which
said feed gas port is connected to said second molecular sieve container
inlet port and said exhaust gas port is connected to said first
molecular sieve container inlet port.
11. A molecular sieve container, as set forth in claim 10 and
wherein said extrusion has a plurality of passages extending between
said first and second extrusion ends, and further including a first
plurality of screws engaging said passages to secure said first
end cap to said extrusion and a second plurality of screws engaging
said passages to secure said second end cap to said extrusion.
12. A molecular sieve container, as set forth in claim 11 and
wherein at least some of said plurality of passages have an open
side.
13. A molecular sieve container, as set forth in claim 1 and wherein
said extrusion has a plurality of passages extending between said
first and second extrusion ends, and further including a first plurality
of screws engaging said passages to secure said first end cap to
said extrusion and a second plurality of screws engaging said passages
to secure said second end cap to said extrusion.
14. A molecular sieve container, as set forth in claim 13 and
wherein at least some of said plurality of passages have an open
side.
15. A molecular sieve container for an oxygen concentrator comprising
an elongated extrusion having first and second open ends and at
least two cavities extending between said ends, said cavities each
having an open first end at said first extrusion end and an open
second end at said second extrusion end, a first end cap closing
said first ends of said cavities, a second end cap closing said
second ends of said cavities, wherein at least two of said cavities
define first and second containers for separate molecular sieves,
means forming a separate inlet port for each molecular sieve container,
and means forming a separate outlet port for each molecular sieve
container.
16. A molecular sieve container, as set forth in claim 15 and
wherein said extrusion includes a cavity closed by said first and
second end caps defining a concentrated gas accumulator, and means
forming at least one port into said accumulator.
17. A molecular sieve container, as set forth in claim 16 and
wherein said ports are formed in at least one of said first and
second end caps.
Molecular sieve description
TECHNICAL FIELD
The invention relates to pressure swing molecular sieve oxygen
concentrators and more particularly to a container for a plurality
of molecular sieve beds for use in a pressure swing oxygen concentrator.
BACKGROUND ART
Oxygen concentrators are used, for example, as a source of high
purity oxygen for medical applications. An oxygen concentrator will
separate air into two gas streams, one of which consists primarily
of oxygen and the other of which consists primarily of nitrogen.
A pressure swing molecular sieve oxygen concentrator typically has
at least two molecular sieve beds. Each molecular sieve bed typically
consists of a closed cylindrical container partially filled with
a sieve material, such as zeolite, which will pass a flow of oxygen
molecules while blocking the flow of larger nitrogen molecules.
In operation, a compressor applies filtered pressurized air through
a flow control valve to an inlet port on one of the molecular sieve
beds and about 95% pure oxygen flows under pressure from an outlet
port on such bed. The oxygen may flow to an accumulator and then
pass through a pressure regulator, an optional flow meter and a
final filter to a patient. As oxygen flows through the sieve bed,
the separated nitrogen is retained in the sieve bed. After a short
time, one or more valves are changed to apply the pressurized air
to the inlet port of a second sieve bed and to vent the inlet port
of the first sieve bed. A small portion of the pressurized oxygen
output from the second sieve bed is delivered to the outlet port
of the first sieve bed to purge nitrogen and any other trapped gases
from the first sieve bed. The valves are periodically reversed to
alternate the sieve beds between the gas separating cycle and the
trapped gas purging cycle. The optional accumulator holds a volume
of concentrated oxygen under pressure to provide a continuous oxygen
flow when the valves are cycled.
In prior art oxygen concentrators, the molecular sieve beds are
constructed as individual components which typically each includes
a cylindrical container. The accumulator is still a third container.
A typical oxygen concentrator uses at least two molecular sieve
beds which must be connected together and connected to valves either
with tubing and fittings or with manifolds. The number of fittings
and connections for handling the pressurized air feed gas and the
pressurized oxygen outlet gas present a potential for leaks and
assembly errors. Further, both the number of parts required and
the time required for assembly can adversely affect the reliability
and the manufacturing cost of prior art oxygen concentrators.
DISCLOSURE OF INVENTION
The present invention is directed to an improved container for
a plurality of molecular sieves for use in a pressure swing oxygen
concentrator. At least two molecular sieve beds are formed as a
unit with a single extruded container. Preferably, the extrusion
has three cavities. The extrusion is cut to a desired length to
provide a desired capacity to the sieve beds and end caps are secured
to the extrusion with screws and resilient seals. Each of the cavities
is closed by the end caps. Two of the closed cavities form molecular
sieve containers which are partially filled with a conventional
molecular sieve material, such as a suitable zeolite. the third
cavity serves as an accumulator for receiving and storing the concentrated
oxygen from the molecular sieve containers.
Each end cap may have separate threaded openings connecting into
each cavity for connecting suitable fittings and hoses as in a conventional
oxygen concentrator. Or, preferably, a lower one of the end caps
may include passages with check valves connecting outlet ports from
the two sieve containers to tile accumulator and a passage having
an orifice or restriction interconnecting the outlet ports of the
two sieve containers. An upper one of the end caps may be adapted
to mount the flow control valve. The upper end cap can from a manifold
and include air passages for the valve to direct the proper air
flow to and from the sieve beds. The upper end cap also may include
two threaded ports for tile feed and exhaust gas to be hooked to
the compressor.
Accordingly, it is an object of the invention to provide an improved
low cost construction for containers for molecular sieve beds for
use with a pressure swing oxygen concentrator.
Other objects and advantages of the invention will become apparent
from the following detailed description of the invention and the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating the pneumatic circuit
of an exemplary prior an pressure swing oxygen concentrator;
FIG. 2 is a perspective view of a molecular sieve container according
to a preferred embodiment of the invention;
FIG. 3 is a fragmentary cross sectional view through the molecular
sieve container as taken along line 3--3 of FIG. 2;
FIG. 4 is a cross sectional view through the molecular sieve container
as taken along line 4--4 of FIG. 3;
FIG. 5 is an enlarged fragmentary cross sectional view through
an end of a modified extruded molecular sieve container;
FIG. 6 is a schematic diagram of a pressure swing oxygen concentrator
with the molecular sieve container of FIG. 2;
FIG. 7 is a bottom plan view of a lower end cap for an extruded
molecular sieve container according to a modified embodiment of
the invention;
FIG. 8 is a cross sectional view as taken along line 8--8 of FIG.
7;
FIG. 9 is a cross sectional view as taken along line 9--9 of FIG.
7;
FIG. 10 is a top plan view of an upper end cap for an extruded
molecular sieve contains according to a modified embodiment of the
invention; and
FIG. 11 is a side elevational view of the upper end cap of FIG.
10.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring to FIG. 1 of the drawings, a pneumatic diagram is shown
for a typical prior art pressure swing oxygen concentrator 10. The
oxygen concentrator 10 has an air inlet 11 a pressurized concentrated
oxygen outlet 12 for delivering oxygen to a patient, and an exhaust
gas outlet 13. A gas consisting primarily of nitrogen is separated
from a gas consisting primarily of oxygen in two molecular sieve
beds 14 and 15. Each molecular sieve bed is partially filled with
a suitable filter material, such as a zeolite, which will pass oxygen
molecules while blocking the flow of larger nitrogen molecules.
A compressor 16 draws ambient air through a filter 17 and delivers
pressurized air through a valve 18 alternately to the molecular
sieve beds 14 and 15. The valve 18 has two positions. In the illustrated
position, the valve 18 connects the compressor 16 to apply pressurized
air to an inlet port 19 to the molecular sieve 14 and connects an
inlet port 20 to the molecular sieve 15 to the exhaust gas outlet
13. In the second position, the valve 18 connects the compressor
16 to apply pressurized air to the inlet port 20 to the molecular
sieve 15 and connects the inlet port 19 of the molecular sieve bed
14 to the exhaust gas outlet 13.
The molecular sieve beds 14 and 15 have outlet ports 21 and 22
respectively. The outlet ports 21 and 22 are connected together
through a calibrated orifice 23 to permit a limited flow of concentrated
oxygen from the higher pressure one of the molecular sieve beds
14 and 15 to the lower pressure molecular sieve bed 15 or 14. A
two position valve 24 may be provided to selectively connect one
of the molecular sieve outlet ports 21 or 22 to a concentrated oxygen
accumulator 25. From the accumulator 25 concentrated oxygen flows
through a pressure regulator 26 a flow meter 27 a filter 28 and
a check valve 29 to the outlet 12.
In operation, the valves 18 and 24 are operated together and may
initially be positioned as illustrated with the pressurized air
from the compressor 16 applied to the inlet port 19 of the molecular
sieve bed 14 and the outlet port 21 of the molecular sieve bed 14
connected to the accumulator. The inlet port 20 to the molecular
sieve bed 15 is connected to the exhaust gas outlet 13. As pressurized
air is delivered to the molecular sieve bed 14 concentrated oxygen
flows from the outlet port 21 to the accumulator 25. A small portion
of the concentrated oxygen at the port 21 also flows through the
orifice 23 and in a reverse direction through the molecular sieve
bed 15 to the exhaust gas outlet 13 to purge nitrogen from the molecular
sieve bed 15. As concentrated oxygen is discharged from the molecular
sieve 14 nitrogen is retained in the molecular sieve bed 14. After
a short period of time, both valves 18 and 24 are simultaneously
shifted (to the left in FIG. 1). This reverses the cycle and the
molecular sieve bed 15 begins separating a flow of concentrated
oxygen and retaining the nitrogen, while nitrogen is purged from
the molecular sieve bed 14.
Referring now to FIGS. 2-4 of the drawings, a molecular sieve unit
30 is shown according to a preferred embodiment of the invention.
An extrusion 31 forms a main body portion of the unit 30. The extrusion
31 has an upper end 32 which is closed by an upper or first end
cap 33 and has a lower end 34 which is closed by a lower or second
end cap 35. The illustrated extrusion 31 is a right cylinder which
has an exterior shape in section of flat sides 36 and 37 and rounded
ends 38 and 39 as shown in FIG. 4. The extrusion 31 is hollow and
is divided by webs 40 and 41 into three cavities 42-44 which extend
the length of the extrusion. A plurality of small diameter passages
45 are formed in the extrusion 31 for receiving screws 46 to secure
the end caps 33 and 35. The passages 45 may be closed, as shown
in FIG. 4 or they may be open grooves 47 as shown in FIG. 5. In
attaching the end caps 33 and 35 resilient seals 48 are positioned
between the end cap 33 and the extrusion end 32 and between the
end cap 35 and the extrusion end 34. Preferably, the end caps 33
and 35 have lips 49 which extend around the perimeter of the seals
48 and over the ends 32 and 34 respectively, of the extrusion 31.
The lips 49 position the seals 48 and also prevent the seals 48
from extruding outwardly. Three threaded nipples 50-52 are formed
in the upper end cap 33 for communicating, respectively, with the
cavities 42-44. Similarly, three threaded nipples 53-55 are formed
in the lower end cap 35 for communicating, respectively, with the
cavities 42-44.
The closed cavity 42 forms a container 56 for a first molecular
sieve bed and the nipples 50 and 53 define inlet and outlet ports,
respectively, on opposite ends of the container 56. The closed cavity
43 forms a container 57 for a second molecular sieve bed and the
nipples 51 and 54 define inlet and outlet ports, respectively, on
opposite ends of the container 57. The closed cavity 44 forms a
container 58 which functions as an accumulator for storing concentrated
oxygen received from the molecular sieve bed containers 56 and 57.
One of the nipples 52 and 55 serves as an inlet port and the other
nipple 55 or 52 serves as an outlet port for the accumulator container
58. If desired, it will be appreciated that the nipples 52 and 55
for the accumulator container 58 both may be formed either on the
upper end cap 33 or on the lower end cap 35. Or, a single nipple
on either of the end caps 33 or 35 may serve both as an inlet port
and as an outlet port for the pressurized oxygen stored in the accumulator
container 58. For the molecular sieve containers 56 and 57 the
feed gas normally flows downwardly through a filter material during
gas separation. Consequently, the inlet ports normally will be on
the upper cover 32 and the outlet ports will normally be on the
lower cover. However, additional passages (not shown) may be easily
formed to extend the length of the extrusion 31 and that such passages
may be used to locate all of the ports on one of the end caps 33
or 35.
It should be appreciated that the extrusion 31 can be extruded
to an indefinite length, with the length being limited only by the
capacity to handle a long extrusion. In manufacturing the molecular
sieve unit 30 the extrusion 31 is cut into the length needed to
give a desired volumetric capacity to the containers 56-58. The
same extrusion 31 may be used in manufacturing molecular sieve units
30 for different capacity oxygen concentrators merely by changing
the length of the extrusion 31.
During use, the molecular sieve containers 56 and 57 are partially
filled with a commercially available molecular sieve material that
will pass a flow of oxygen while blocking a flow of nitrogen. After
extensive use, it may be necessary to replace the molecular sieve
material. The molecular sieve unit 30 is easily serviced by merely
removing the upper end cap 33 and replacing the molecular sieve
material in the cavities 42 and 43. In some prior art molecular
sieve beds, assembly screw holes could become worn or damaged sufficiently
that the sieve beds could not be serviced. This problem is eliminated
by forming the screw passages 45 the length of the extrusion 31.
The ends of the passages 45 may be threaded for receiving machine
screws or self tapping screws 46 may be used to secure the end caps
33 and 35. If the threads or the ends of the passages 45 become
worn, the extrusion 31 can continue to be used and serviced merely
by using longer screws.
FIG. 6 is a pneumatic diagram of an oxygen concentrator 60 incorporating
the molecular sieve unit 30. An ambient air inlet 61 is connected
through a first filter 62 and through an optional muffler 63 to
the inlet to a compressor 64. The compressor 64 applies pressurized
air through a second filter 65 to a two position valve 66. In the
illustrated position, the valve 66 applies the filtered pressurized
air to the inlet port 50 of the molecular sieve container 56. The
concentrated oxygen flows from the outlet port 53 of the molecular
sieve container 56 through a check valve 67 to the inlet port 55
to the accumulator 58.
While oxygen is being concentrated in the molecular sieve container
56 nitrogen is purged from the molecular sieve container 57. The
outlet port 53 also is connected through a small orifice 68 to deliver
a low flow of oxygen to the outlet port 54 of the molecular sieve
container 57 for purging nitrogen from the container 57. The inlet
port 51 of the molecular sieve container 57 is connected through
the valve 66 to an optional suction pump 69 and then through an
exhaust muffler 70 of an exhaust gas outlet 71. A single motor 72
may operate both the compressor 64 and the optional suction pump
69. The suction pump 69 functions to reduce the pressure in the
molecular sieve container 57 during the purge cycle to increase
the purge efficiency.
The concentrated oxygen at the outlet port 52 from the accumulator
58 flows through a pressure regulator 73 through a flow meter 74
through a final filter 75 and finally through a check valve 76 to
a concentrated oxygen outlet 77. The outlet 77 may be connected,
for example, through a suitable hose to a cannula for supplying
supplemental oxygen to a patient's respiratory system.
As the molecular sieve container 56 becomes saturated with nitrogen,
the oxygen flow at the outlet port 53 will decrease. Periodically,
the position of the valve 66 is changed to alternate the operation
of the molecular sieve containers 56 and 57 between gas separation
and nitrogen purge cycles. When the position of the valve 66 is
changed from the illustrated position, the filtered pressurized
feed air will be applied to the inlet port 51 to the molecular sieve
container 57. The outlet port 54 from the container 57 is connected
through a check valve 78 to the accumulator inlet port 55 and through
the orifice 68 to the outlet port of the molecular sieve container
56. The valve 66 also connects the inlet port 50 to the molecular
sieve container 56 to the suction port of the pump 69 for drawing
nitrogen and any other retained gases from the molecular sieve container
56.
FIGS. 7-9 show a modified lower end cap 80 suitable for use with
the extrusion 31 for forming a molecular sieve container. Connections
between two molecular sieves and an accumulator are formed as an
integral part of the lower end cap 80. Two passages 81 and 82 form
ports to the two molecular sieves which are separated by a plug
83 having a calibrated orifice 84 which interconnects the passages
81 and 82. A third passage 85 has ends 86 and 87 which are located
to communicate with the two molecular sieves and an extension 88
which is located to communicate with the accumulator. Resilient
duck bill check valves 89 and 90 are positioned, respectively, in
the passage ends 86 and 87. The orifice 84 functions identical to
the orifice 68 in FIG. 6 and the check valves 89 and 90 function
as the check valves 67 and 78 in FIG. 6. It will be seen that the
lower end cap 80 is a simplified unitary construction which incorporates
the passages, valves and orifice in the portion of the circuit illustrated
by the lower connections to the molecular sieve unit 30 in FIG.
6.
FIGS. 10 and 11 show a modified upper end cap 91 suitable for use
with the extrusion 31 for forming a molecular sieve container. The
upper end cap 91 includes an integral housing 92 for mounting a
two position valve 93 which may be similar to the valve 66 in the
pneumatic circuit of FIG. 6. A pressurized air inlet port 94 and
an exhaust gas outlet port 95 are formed in the housing 92. An inlet
port 96 is located to communicate with one of the molecular sieves
in the extrusion 31 an inlet port 97 is located to communicate
with the other molecular sieve and a concentrated oxygen outlet
port 98 is located to communicate with the accumulator in the extrusion
31. It will be appreciated that use of the illustrated lower end
cap 80 and upper end cap 91 with the extrusion 31 simplify the construction
of a molecular sieve container for an oxygen concentrator and can
greatly reduce the risk of assembly error for the pneumatic connections
to the molecular sieves in an oxygen concentrator.
It will be appreciated that various modifications and changes may
be made to the above described preferred embodiment of a molecular
sieve container for an oxygen concentrator without departing from
the spirit and the scope of the following claims. Although the preferred
container includes two molecular sieve beds and a concentrated oxygen
accumulator, it will be appreciated that the accumulator may be
eliminated and that two or more molecular sieve beds may be formed
as a unit. It will further be appreciated that when the extrusion
forms three or more molecular sieve beds, the molecular sieve beds
can be cycled between gas separation and gas purge cycles with known
flow controllers. |