Molecular sieve abstract
A molecular sieve for an oxygen concentrator free of internal filtering
elements and suitable for personal use to provide substantially
pure oxygen for a medical patient to breathe, having a container
formed of metal with an inlet thereto and an outlet and seamed with
welded seams so as to be leak-proof to moisture and able to withstand
passage of hot re-activating gas, an oxygen concentrating molecular
sieve material contained within the container and having a longitudinal
extent concentric with the longitudinal axis of the container, filter
screens and springs contained within the container extending the
full diametrical extent of the container and positioned on opposite
sides of the sieve material, coaxial with the longitudinal axis
of the container, the sieve material being a material re-activatable
by passage therethrough of a hot gas and being sandwiched between
the filter screens and springs and maintained in alignment with
the longitudinal axis of the container.
Molecular sieve claims
I claim:
1. For an oxygen concentrator free of internal filtering elements
and suitable for personal use to provide substantially pure oxygen
for a medical patient to breathe, a molecular sieve, comprising:
a container formed of metal and including an inlet thereto and
an outlet therefrom and seamed with all seams therebetween welded
so as to be leak-proof to moisture and so that the molecular sieve
is able to withstand passage of hot re-activating gas therethrough,
said container having a longitudinal axis;
an oxygen concentrating molecular sieve material contained within
said container, said sieve material having a longitudinal extent
concentric with the longitudinal axis of said container; and
a filter screen and spring combination positioned on opposite sides
of said sieve material, coaxial with the longitudinal axis of said
container for preventing the sieve material from moving around in
said container to ensure an even gas flow, said sieve material and
said filter screen and spring combination being coextensive with
each other and with said sieve material and extending orthogonally
to the longitudinal axis of said container, said filter screen being
uniformly continuous and free of any interruption and extending
the full internal diametrical extent of said container to prevent
a dislocation or a moving around of said sieve material;
said sieve material being a material re-activatable by passage
therethrough of a hot gas and being sandwiched between said filter
screen and spring combination and maintained in alignment therewith
and with said longitudinal axis of said container by said filter
screen and spring combination.
2. The sieve as claimed in claim 1 wherein said container has
an outer configuration in the form of a longitudinal tube and is
provided with an end cap at each end thereof, said end caps having
sides extending towards each other, and welding means for seam welding
the sides of said end caps to the outer surface of said tube.
3. The sieve as claimed in claim 2 including retainers connected
with said springs for assisting in holding said sieve material in
place and to prevent shifting of said sieve material.
4. The sieve as claimed in claim 1 wherein said container includes
ends caps, and including means welding said springs to said end
caps for preventing said springs from shifting internally of said
container.
5. The sieve as claimed in claim 4 wherein said welding means
includes welds connecting said springs to an inner portion of said
end caps.
6. The sieve as claimed in claim 1 wherein both said filter screen
and said spring are each uniformly continuous in their transverse
extent within said container and each are adjacent to the inner
wall of said container.
7. The sieve as claimed in claim 1 wherein said sieve material
and said filter screen are juxtaposed in face-to-face relationship
to each other and each are uniformly continuous in a transverse
direction orthogonal to said longitudinal axis.
8. The sieve as claimed in claim 1 wherein said container includes
heat-resistive metal components together with said screen and spring
combination coacting with end caps welded to a body portion of said
container for holding said sieve material in place and oriented
in a direction coaxial with said longitudinal axis and positioned
at opposite ends of said sieve material, and said screen and spring
combination being connected by welds to said caps for preventing
shifting of said screen and spring combination relative to said
sieve material in response to pressure on said container.
9. For an oxygen concentrator free of internal filtering elements
and suitable for personal use to provide substantially pure oxygen
for a medical patient to breathe, a molecular sieve, comprising:
a container formed of metal and including an inlet thereto and
an outlet therefrom and seamed with all seams therebetween welded
so as to be leak-proof to moisture and so that the molecular sieve
including said seams are able to withstand passage of a hot re-activating
gas therethrough having a temperature of up to 800.degree. F., said
container having a longitudinal axis;
an oxygen concentrating molecular sieve material contained within
said container, said sieve material having a longitudinal extent
concentric with the longidinal axis of said container;
a filter screen and spring combination positioned on opposite sides
of said sieve material, coaxial with the longitudinal axis of said
container, said sieve material and said filter screen and spring
combination being coextensive with each other and with said sieve
material and extending orthogonally to the longitudinal axis of
said container free of interruption, uniformly continuous and extending
the full inner diametrical extent of said container and in contact
with the inner wall of said container to prevent a dislocation or
a movement around of said sieve material;
said sieve material being a material re-activatable by passage
therethrough of a hot gas and being sandwiched between said filter
screen and spring combination and maintained in alignment therewith
and with said longitudinal axis of said container by said filter
screen and spring combination; and
means welding the screen of said filter screen and spring combination
to said container for retarding movement of said sieve material
past said filter screen and spring combination.
10. The sieve as claimed in claim 9 wherein said container includes
heat-resistive metal components together with said screen and spring
combination coacting with end caps welded to an outer body portion
of said container for holding said sieve material in place and oriented
in a direction coaxial with said longitudinal axis and positioned
at opposite ends of said sieve material, and said springs being
connected by welds to said caps.
11. The sieve as claimed in claim 10 wherein said inlet and said
outlet each include a port fitting fitted to the sides of said end
caps and seam welded thereto, said port fittings including rediussed
tubes free of sharp bends, and said port fittings being proximate
to said screen and spring combination.
12. The sieve as claimed in claim 9 wherein said container includes
a tubular member having its opposite open ends closed by end caps,
and said welding means includes welds connecting said springs to
an inner portion of said end caps.
13. The sieve as claimed in claim 12 wherein said end caps include
sides extending over said outer tubular member and said sides extend
over the ends of said container in their assembled condition a distance
which is between 2 to 4 cm.
14. The sieve as claimed in claim 9 wherein said sieve material
and said filter screen are juxtaposed in face-to-face relationship
to each other and each are uniformly continuous in a transverse
direction orthogonal to said longitudinal axis.
15. The sieve as claimed in claim 9 including an end cap at each
end of said container having aides extending towards each other
and including welded seams between said end caps and said tube.
Molecular sieve description
BACKGROUND OF THE INVENTION
This invention relates to molecular sieves for use in oxygen concentrators
and a novel container for use therewith.
More particularly, the invention is concerned with a container
having a tubular body and provided with end caps which are seam
welded to the tubular body to prevent leakage as well as to assist
in the maintenance of the position of the sieve material in the
container. The ports of entry and outlet to and from the container
are also seam welded to prevent leakage. The oxygen concentrators
are primarily intended for home use, so that long life is of extreme
importance, as well as to have the ability to be free-standing.
The molecular sieve is intended for an oxygen concentrator which
is primarily intended for supplying pure oxygen to a patient to
breathe and for recharging in the field.
A molecular sieve is a filter comprising a material which has a
high affinity for one or more particular gases and therefore can
remove such gases by adsorption, thus concentrating the remaining
gas or gases.
It is important to prevent the sieve material from moving around
in the container in order to ensure an even gas flow. Therefore,
alignment of the sieve material is an important requirement, and
avoidance of a by-pass around the sieve material is important.
Molecular sieves are used in two main fields. One of these is for
large scale, heavy duty preparation of fluids, requiring expensive
apparatus and often producing extremely high purities, perhaps of
the order of 99.9999% pure. Examples are the preparation of purified
atmosphere for use in the manufacture of semi-conductor devices
or for spacecraft research. The other main field is for personal
use, as for oxygen concentrators, wherein ordinary air is passed
through a molecular sieve to adsorb the nitrogen and leave perhaps
95% pure oxygen for a medical patient to breathe. The sieves in
this field tend to be much cheaper and smaller.
DESCRIPTION OF THE PRIOR ART
Oxygen concentrators are popularly used to provide sufficiently
high purities of oxygen for medical patients without the need of
high pressure tanks or liquid oxygen. These machines produce their
oxygen by using air compression and valving to pass room air through
a molecular sieve comprising a container which holds the sieve material
as a sandy type of substance.
This material is one chosen for its ability to attract and absorb
nitrogen molecules while letting oxygen molecules pass through the
sieve material. This concentrates the oxygen to perhaps 95%, whereas,
in room air, it is present only to the extent of about 21%. However,
one major problem with molecular sieves for oxygen concentrators
is that they readily absorb water molecules and, when this occurs,
the molecular sieve will no longer perform the primary function
of absorbing nitrogen nor concentrating oxygen. Difficulty arises
because the molecular sieve will absorb moisture from the room air
via any leak in the oxygen concentrator. Therefore, sealing is an
important feature, and poor sealing creates problems.
In the past, molecular sieves for this purpose have been contained
in glued PVC, in gasket-sealed metal containers and in gasket-sealed
plastics. Gaskets are known to leak as well as age and lose their
pliability. Port fittings (for the ingress and egress of the air
being processed) have been taped and screwed into these containers.
Such connections also, in time, lose their sealability, and extraneous
leakage results. Unfortunately, almost all of these containers tend
to leak because of the number of leakage areas related to connections
and provide a means for room air to gain access to the sieve material,
thus destroying its ability to concentrate oxygen.
Once water vapor has intruded into the sieve material, the sieve
must be disposed of and replaced, or the sieve material must be
removed and exposed to high temperatures of the order of 500.degree.
F. (260.degree. C.) and vacuum in order to remove the water vapor.
Attempts have been made to remove the water vapor in situ by a cycle
of high vacuum steps, but these have required expensive additions
to the oxygen concentrators.
A "molecular sieve material" is normally a zeolite, which
is formed of hydrated aluminosilicates and group II elements having
a crystalline framework.
Wall thickness of containers used heretofore have been about one
quarter of an inch or about 6.35 millimeters.
The inventor is aware of prior art, such as Hauser, U.S. Pat. No.
3490205 from the prosecution of the parent application, and this
patent discloses a High Pressure Gas Filter System of large and
heavy magnitude and intended for industrial use. There is no teaching
or appreciation of spring-loading the sieve material to prevent
its moving around or dislocation. The lack of any structure to prevent
the sieve material from moving around does not ensure an even gas
flow, and the gas can escape from the material. The fittings are
of the conventional type and not welded so that there is no certainty
that leak problems due to temperature expansion are eliminated.
There is no disclosure of using filters and screens extending the
full diameter of the vessel so that there is no internal filtering
element.
The inventor is also aware of U.S. Pat. No. 3024867 to Milton
which discloses the use of zeolite as a molecular sieve material,
and the use of two molecular sieve beds so that one bed is in an
adsorption stroke and the other bed is in the desorption stroke.
While Milton is concerned with reactivation of the sieve material,
there is no concept of leakproofing to moisture and being free of
gasket material.
Gannon, U.S. Pat. No. 2593132 discloses a container in which
only one end is welded and the other end is screwed onto the container
so that desiccant material contained therein can be removed, baked
out to remove the adsorbent moisture, and then replaced into the
container.
The inventor is also aware of Hradek, U.S. Pat. No. 4496396
which discloses a fluid separator apparatus employing a container
having an adsorption material positioned between two plates, and
in one embodiment the adsorbent material is placed into a container
of varying diameter. The conical container is provided to compensate
for any decrease in flow of fluid mixture resulting from adsorption
of the element by the material. The containers are schematically
shown without a clear description of their detailed structure and
specific arrangement of parts, and there is no suggestion or teaching
of welding seams between end caps and the tubular body and the port
fittings.
Dechene, U.S. Pat. No. 4552571 discloses end caps and ports
of entry and egress associated with the end caps, but there is no
teaching of welding the end caps or the ports as well as the arrangements
of the inner sieve material and springs.
SUMMARY OF THE INVENTION
An object of the present invention is to ameliorate the situation
and overcome the problems with the prior art resulting from leakage
through the seams.
The present inventor, after much research, realized that the most
efficient method of reactivation is in situ and, although never
before successfully applied in the field of oxygen concentrators,
is a method of heating; for this purpose, he finally resolved on
a method of passing hot gas through a molecular sieve and designing
a sieve container that would stand up to the temperature and pressure
requirements of this process.
According to the invention, a molecular sieve is provided for use
in an oxygen concentrator. The molecular sieve comprises an oxygen
concentrating molecular sieve material and a container for the same,
wherein the material can be reactivated by passage therethrough
of a hot reactivating gas. An important feature is that the container
is fabricated of metal and is seamed with all seams welded so as
to be leakproof to moisture while being free of gasket material,
so that the sieve is capable of withstanding the passage of the
hot reactivating gas therethrough. The welded seams which seal all
the interconnected parts, end caps to tubular body and ports to
the end caps prevent the ingress of atmospheric water vapor into
the container so that the container is completely airtight (other
than by way of the port fittings for ingress and egress of gas being
treated). This avoids any need to use gaskets or O-rings which are
easily tractable and can shrink or burn, to use plastics which can
melt, as well as any other material which might cause misalignment
of end caps or loosened port fittings.
Another object of the invention is to provide small, inexpensive,
rugged, reusable molecular sieves (zeolite) for oxygen concentrators
that preferably enable the associated operating apparatus of the
molecular concentrator to be simple, rugged, easy, inexpensive and
quick to operate.
To this end, the molecular sieve material is chosen so that the
reactivating temperature of the hot gas does not have to exceed
260.degree. C. or 500.degree. F., and the material preferably comprises
aluminum oxide. The material is held in place by heat-resistive
metal components, and the components comprise filter screens, retainers
and springs.
An important feature of the invention is that the sieve can be
reactivated by reheating without the necessity of having to remove
the end caps and thereby disturb the sealing. The seam welding of
the end caps to the tube is sufficient to maintain the end caps
and tube as an unitary structure which can be subjected to high
pressures when the sieve is reactivated, so that such reactivation
can take place in the field. Clearly, the elimination of gaskets
which results from the seam welding is a distinct advantage of the
sieve according to the invention over heretofore known sieves.
This invention, therefore, proposes seam welding to eliminate leak
problems due to temperature expansion while, at the same time, dispensing
with the use of gaskets or sealants, as well as facilitating recharging
in the field.
Further, to this end, the container can be made entirely of aluminum,
with a substantial wall thickness, usefully in the range from 1
to 5 mm, preferably about 2 mm but desirably within a range of 1.5
to 2.1 mm (0.60 to 0.80 inches), and this has been found to be cost
efficient and result in a lighter unit than a similar unit fabricated
from steel. This is to be compared with the prior art which requires
a wall thickness of about 6.35 millimeters or about one quarter
of an inch.
A preferred configuration of the container is in the form of a
tube with end caps and port fittings fitted to the caps, all welded
together along seams therebetween. The seams and fittings are welded
to provide a leakproof vessel to withstand the temperatures of 500.degree.
F. or 260.degree. C. regeneration gases which can be passed through
the port fittings without damage to the air-tightness of the joints.
With the present invention, the end caps are welded to the central
tubular body while the internal springs are held under a spring
tension of forty (40#) pounds and the springs and end caps are welded
together to the tubular member at the same time.
Further, retainers are provided which are also connected with the
springs so as to assist in holding the sieve material in place and
prevent shifting.
To avoid stress on the welded joints at the ends of the sieve container,
the caps extend towards each other so that the seams between these
and the tube are a substantial distance from the ends of the container.
The distance can usefully be in the range 2 to 4 cm, preferably
2.5 cm or one (1) inch. The lower direction of 2 cm or about 182
" is chosen so that the ports are welded to the end caps and
thereby avoid a further welding to the tubular body so as to avoid
excess seaming on the tubular body.
The sieve can be designed so that one end of the container has
a flat or otherwise non-projecting configuration so as to be able
to serve as a base on which the sieve can stand. If the port fittings
are fitted to the sides of the container (conveniently to the caps)
and do not project beyond the ends of the container, they can have
the maximum length consistent with the space available for it and
can then contain the maximum amount of sieve material.
Better flow is able to be provided if the port fittings comprise
radiussed tubes free of sharp bends. Flow is also improved by having
the filter element arranged to allow at least 50% through-flow area.
The seams are preferably heat-welded, but they can be pressure-welded,
e.g., by making a suitably large temperature differential fit, as
by heating up the outer part and cooling down the inner part until
there is a differential between them of 500.degree. C. or 932.degree.
F., placing them together and then allowing them to come to the
same temperature.
It should be noted that the welding of each end cap to the center
tube is an important feature of the invention so as to avoid leakage
under heat and the use of gaskets is avoided. With the welding of
the various parts together, the sieve can take care of both high
temperature and high pressure requirements. Welding the end caps
with the springs together prevents the springs from shifting. Additionally,
further assistance to prevent shifting of the sieve material is
also accomplished by having the retainers connected with the springs.
A molecular sieve is like a sponge and, if the sponge shifts, the
sieve material will also shift and the air/oxygen gas goes around
the sieve material. It is critical that the sieve material be held
solid so that the nitrogen will not go around the sieve material.
Movement of the sieve material enables the oxygen molecules to come
back and not go through the sieve material.
With the present combination, the sieve material together with
the intermediation of the springs positioned between the sieve material
and the end caps welded thereto provides an extremely efficient
manner of holding the sieve material in its appropriate position.
Also, when it is desired to reactivate the sieve material, the absorbent
mixture can be removed without having to disassemble the entire
structural container. The springs at opposite ends also hold the
sieve material in place and prevent shifting during the reverse
procedure to reactivate the sieve material.
As a result of the combination of the opposed springs and the sieve
material sandwiched therebetween all contained within an hermetically
sealed container (except for access and egress through the ports),
there is no access to the sieve material; the opposed springs maintain
the sieve material appropriately aligned therewith so that molecules
do not get loaded between the sieve material and the interior walls
of the container or go around the sieve material as it moves away
from the interior wall.
There is an internal membrane of aluminum which is the molecular
sieve, and the internal membrane along the edges of the wall is
melted and adheres to the wall. The center portion is not welded,
and this is the reason that the springs are necessary to hold the
membrane under compression. The center portion of the membrane actually
moves but, because of the welding, the edges will stay put but,
since the metal moves to the edges, the sealed ends will stay in
a better position.
Thick filter material is preferred, because the sieve then retains
dust so that no external filter is necessary. In addition, with
the springs extending across the full width of the tube diameter,
the sieve material is held solidly and prevented from moving so
that the material achieves its maximum absorption.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of one embodiment of a molecular sieve
according to the invention;
FIG. 2 is a side elevational view of the FIG. 1 embodiment;
FIG. 3 is a view corresponding to FIG. 2 of an alternative embodiment;
FIG. 4 is a fragmentary perspective view corresponding to FIG.
1 of a modification of the FIG. 1 embodiment;
FIG. 5 is a view like FIG. 4 of a modification of the FIG. 3 embodiment;
FIG. 6 is a vertical section through the FIG. 2 embodiment;
FIG. 7 is an enlarged fragmentary view of part of FIG. 6;
FIG. 8 is a partial schematic view of an end cap of the molecular
sieve of FIGS. 1-7 prior to assembly;
FIG. 9 is a partial schematic view of a tubular body portion forming
part of the container for the molecular sieve of FIGS. 1-7 and
together with the ends caps of FIG. 8 forms the container; and
FIG. 10 is a schematic diagram of an oxygen concentrator comprising
a molecular sieve according to any of the previous embodiments.
DETAILED DESCRIPTION OF THE INVENTION
Reference is now made to the accompanying drawings, which show
the presently preferred mode for carrying out the invention.
FIGS. 1 to 9 show different embodiments of a molecular sieve for
use in the oxygen concentrator shown in FIG. 10. The oxygen concentrator
10 in FIG. 10 includes two identical molecular sieves 12 and 14
One of which, 12 will be described first.
Referring more particularly to FIG. 6 sieve 12 comprises oxygen
concentrating molecular sieve material 16 which is a zeolite and
is able to be reactivated by passage through it of a hot gas 18
at some temperature up to 260.degree. C. or 500.degree. F. The sieve
12 comprises a container 20 formed as a tube entirely of metal;
the preferred metal is aluminum or an aluminum alloy that can be
welded to itself and withstand temperatures well above 260.degree.
C. For example, the alloy can be welded at a temperature of about
425.degree. C. (797.degree. -800.degree. F.) and can withstand temperatures
almost up to 425.degree. C. before being adversely affected. Molecular
sieve material 16 together with springs 44 retainers 42 filter
screens 36 38 and 40 all extend across the full diameter of tube
22 and remain in place extended across the full diameter of tube
22 thereby providing excellent flow. Each side of the material
is provided with the filter screens and springs 44 for holding the
material 16 solid to ensure even gas flow to thereby prevent the
gas from escaping from the material.
To make a suitably rigid and durable container that can be readily
welded, the thickness of material of which the container wall is
made is 1 to 2 mm.
Container 20 which is in the form of the tube 22 is provided with
end caps 24 and 26 and port fittings 28 and 30 which are fitted
to and welded to the ends caps 24 and 26. End caps 24 and 26 are
welded to tube 22 at weldments 32 and ports 28 and 30 are welded
to the end caps 24 and 26 at weldments 34 so as to provide a complete
welding together along seams formed by the weldments 32 and 34.
The caps 24 and 26 extend towards each other so that the seams 32
between these caps 24 and 26 and the tube 22 are a substantial distance
from the end of the container 20. This distance, in the FIG. 7 embodiment,
is about 2.5 cm or one (1) inch. The distance is selected and preferred
for two reasons. One is to provide an area on the outer circumference
of the end caps to weld the port fittings 28 and 30. The other reason
is to have less stress placed onto the end caps due to the pressure
of springs 44.
The exact arrangement of the port fittings such as 28 30 can be
varied according to the configuration of the molecular concentrator
10 and different arrangements are shown in FIGS. 1 to 5 as required.
It is thus also possible to interchange the upper port fitting of
one embodiment with that of another embodiment, e.g., the FIG. 5
upper port fitting can be associated with the FIG. 1 lower port
fitting. As seen in the embodiment of FIGS. 1 and 2 the lower end
of the container has a flat (or it could be concave or otherwise
non-projecting) configuration so as to be able to serve as a base
on which the sieve can stand. Both ends can have this configuration
so that, as seen in FIGS. 1 and 2 the port fittings 28 30 are
fitted to the sides of the container 20 and do not project beyond
the ends of the container, with the advantages mentioned above.
As seen clearly in FIG. 6 the port fittings 28 30 comprise radiussed
tubes without sharp bends.
Within the container 20 the material 16 is held in place by heat-resistive
metal components, which components comprise filter screens 36 38
40 (of which 36 and 38 are woven wire screens and 40 is a spun aluminum
wire screen), retainers 42 of perforated metal with 50% open area
and springs 44. Molecular sieve material 16 together with springs
44 retainers 42 filter screens 36 38 and 40 all extend across
the full diameter of tube 22 thereby providing excellent flow.
Each side of the material is provided with the filter screens and
springs 44 for holding the material 16 solid to ensure even gas
flow to thereby prevent the gas from escaping from the material.
The springs 44 are preferably welded to the inner surfaces 25 and
29 of end caps 24 and 26 respectively, at welds 31 and 33 (see
FIGS. 6 and 8) to avoid and assist in preventing the springs 44
from shifting after assembly and welding the end caps 24 and 26
to tube 22. To further assist in preventing the retainers 42 from
shifting, metal ties 43 are used to tie retainers 42 to springs
44 as best seen in FIG. 8.
Referring now more particularly to FIGS. 8 and 9 which show one
end cap 24 and tube 22 with sieve material 16 in place. The sieve
material is held in place in tube 22 prior to assembly with woven
wire screens 36 and 38 in place and the spun aluminum wire screen
sandwiched therebetween and bowed outwardly along the longitudinal
axis 47 of tube 22. Prior to placement of end caps 24 and 26 onto
tube 22 the filter screens 36 38 and 40 are bowed outwardly. Placement
of the end caps 24 and 26 onto tube 22 created pressure onto filter
screens 36 38 and 40 and they are moved into a substantially horizontal
or orthogonal position to longitudinal axis 47 and compress the
sieve material 16 therebetween. During the welding of the end caps
24 and 26 to the outside of tube 22 the retainer 42 tied to the
spring 44 is welded to the inside of the end caps 24 and 26 to hold
the retainers 42 in an orthogonal position to the longitudinal axis
47 of the container and, at the same time, hold the sieve material
in place between the retainers 42 and the filter screens 36 38
and 40.
The end caps 24 and 26 can be pushed tightly onto tube 22 so that,
with the alignment of springs 44 the molecular sieve material is
prevented from shifting.
After assembling the tube 22 with end caps 24 and 26 thereon, the
retainers 42 have the bowed position removed as a result of the
pressure of the springs 44 onto the retainers 42 and the holding
of retainers 42 under spring pressure after assembly.
The screen mesh or filter screens comprising woven wire screens
36 38 with the spun aluminum wire screen 40 positioned therebetween
and forms a sandwich construction and, after assembling, the screen
mesh is horizontally directed, or transversely to the longitudinal
axis or center of tube 22 so that the cooperation of the retainers
42 springs 44 and screen mesh maintains the molecular sieve material
16 in place and it cannot be moved out of or escape from axial alignment
with the geometrical center of tube 22. The end caps 24 and 26 which
are welded in place onto tube 22 further assist in maintaining such
axial alignment.
The sieve material 16 and the filter screens 36 38 and 40 and
the springs 44 extend across the full diametrical extent of the
interior of the container 20 and are substantially orthogonal to
the longitudinal center axis of the container 20.
Referring to FIG. 10 in use, air is drawn from the atmosphere
by pump 46 passes three ways to a heater 48 and two valves 50
52 whose action will be explained below. From valves 50 52 air
passes to molecular sieves 12 14 and through these sieves to valves
54 56 having exit ports 58 60 and out to atmosphere through the
exit ports and to alternative exit ports connected to a common input
to detector 62 and thence to patient 64. The valves 50 52 54
56 are of a cylindrical type with an L-shaped passage that can be
rotated to interconnect one pair of ports or another pair of ports.
In the positions shown, these valves ensure that fresh air is pumped
through valve 60 and sieve 12 that concentrates it to relatively
pure oxygen and through valve 54 and detector 62 to patient 64.
At the same time, air is pumped from the atmosphere through heater
48 and valve 52 to the other molecular sieve 14 and thence through
valve 56 to exit at port 60 back to atmosphere. When this air is
heated by heater 48 it reactivates the material in sieve 14 and
carries the nitrogen and moisture therefrom through port 60 to atmosphere.
When detector 62 determines that the concentration of oxygen through
sieve 12 is becoming insufficient, it signals control system 66
to operate all four of the valves, which are ganged together, to
rotate 90.degree. clockwise as seen in FIG. 8. This pumps air through
sieve 14 to the patient 64 and air from heater 48 through sieve
12 and exit port 58 to atmosphere. Control system 66 also controls
the period that heater 48 is switched on, which may be 30 seconds
every five minutes. There may be isolation valves at the outlet
port of heater 48 and at outlet ports 58 60 to ensure that, once
the relevant sieve 12 14 is reactivated, it does not start to collect
nitrogen and moisture before it is put back into use. Further, a
moisture provider 68 may be inserted between detector 62 and patient
64.
While there has been disclosed what is considered to be the preferred
embodiments of the invention, various changes and modifications
may be made therein without departing from the scope of the invention. |