U.S. patent number 3,747,598 [Application Number 05/034,114] was granted by the patent office on 1973-07-24 for flow conditioner.
Invention is credited to Kenneth W. Cowans.
United States Patent |
3,747,598 |
Cowans |
July 24, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
FLOW CONDITIONER
Abstract
A respiratory gas flow conditioner for providing biologically
required heat and moisture to gas flows for a respiring user has
high thermal efficiency and low resistance to respiratory flow. The
flow conditioner comprises a cylindrically shaped, hollow, high
surface area heat and moisture regenerator having a relatively
large orifice at one longitudinal end. Exhaled gases having
relatively high heat and moisture content pass into the orifice,
expand omnidirectionally, pass uniformly through the regenerative
material comprising the sides of the cylinder and give out heat and
moisture thereto; inspiratory gases at relatively low humidity and
temperature take up the moisture and heat retained by the
regenerator and pass to the respiratory organs of the user at
biologically desirable humidity and temperature levels.
Inventors: |
Cowans; Kenneth W. (Los
Angeles, CA) |
Family
ID: |
21874391 |
Appl.
No.: |
05/034,114 |
Filed: |
May 4, 1970 |
Current U.S.
Class: |
128/201.13 |
Current CPC
Class: |
B63C
11/24 (20130101); A61M 16/1045 (20130101); A62B
9/003 (20130101); A61M 2202/03 (20130101); A61M
2202/0208 (20130101); A61M 2202/0208 (20130101); A61M
2202/0007 (20130101) |
Current International
Class: |
A61M
16/10 (20060101); B63C 11/24 (20060101); B63C
11/02 (20060101); A62B 9/00 (20060101); A62b
007/06 () |
Field of
Search: |
;128/142,142.2,142.6,145.8,146-146.7,212,147,142.3,203,202
;55/387,484,516,518,529,DIG.33,DIG.35 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Dunne; G. F.
Claims
What is claimed is:
1. Apparatus for adjusting the temperature and humidity levels of
respiratory gas flows for a respiring user successively expelling
expiratory gases and inspiring inspiratory gases, said apparatus
comprising:
a housing having a fluid sealing connection adapted to be connected
to a user and defining an orifice for passage of said respiratory
gases to and from said user; and
a flow conditioner comprising at least one thermal regenerator
matrix comprised of a permeable material, said matrix defining at
least one cylinder having a central cavity and defining an orifice
at one longitudinal end thereof and including means providing a
transverse seal at the other longitudinal end thereof, said
cylinder being disposed axially and internally with respect to the
housing, said cylinder and said seal being spaced from said housing
whereby gas is allowed to flow through said matrix along the inner
walls of said housing and past said seal.
2. The invention as set forth in claim 1 wherein said at least one
matrix comprises a plurality of adjacently disposed layers of
highly heat conductive filaments configured in a peripherally
multi-fluted cylinder having a central cavity.
3. The invention as set forth in claim 2 wherein said at least one
matrix has a total volume of approximately 10-100 cc and wherein
the thickness of said plurality of layers comprises approximately
0.040 inch, and said layers comprise copper wire screen of
approximately 200 mesh, there being at least 10 layers thereof.
4. The invention as set forth in claim 3 including hygroscopic
means having an extended surface for moisture exchange with said
gas flows, said hygroscopic means comprising an activated molecular
sieve material coating upon at least one of said plurality of
layers.
5. The invention as set forth in claim 4 wherein said flow
conditioner comprises a pair of like adjacent cylinders disposed
axially with respect to the gas flows, and including an open end
adjacent said orifice and a closed interior end, such that gas
flows pass substantially radially through the layers thereof with
respect to the central axis of each cylinder, and substantially
uniformly across the entire surface area of each cylinder, and
wherein in addition said hygroscopic means is substantially
uniformly disposed on all said layers and comprises activated
charcoal powder and means adhesively binding said powder to said
layers.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to means for treating fluid flows,
particularly for conditioning and improving gas flows in life
support systems where gases flow to and from a respiring user.
2. Description of the Prior Art
Means for supporting respiration in hostile environments have
assumed increasing importance particularly because of increasing
scientific, industrial, and military activity relating to undersea,
high altitude, and contaminated environments. Undersea exploration,
for example, has recently assumed substantial scientific and
economic significance. In undersea operations, life support systems
have been developed to a substantial level of sophistication with
respect to the function of supplying oxygen for divers'
respiration. An example of such a life support system is the
traditional deep sea diver system wherein the oxygen supply is
maintained on the surface, and oxygen is pumped down to the diver
through a conduit system extending through substantial depths.
Expiratory exhaust gases are pumped through the conduit system to
the environment and expelled from the system. The more recently
developed self-contained underwater breathing apparatus (SCUBA)
utilizes an oxygen supply carried by the diver. A highly
sophisticated system recently developed and the subject of patent
application Ser. No. 623,616 (filed Mar. 13, 1967), assigned to the
assignee of the present invention, utilizes a recirculating gas
flow whose oxygen content is maintained at a desired level by
passage in contact with a liquid oxygen source at cryogenic
temperatures.
During all of this development and across a broad spectrum of
systems exemplified by the classical deep sea diver's system, the
SCUBA system, and the cryogenic system, users have generally had to
accept the fact that the life supporting gas mixture supplied to
the diver deviates substantially from biologial requirements of
heat and moisture content. Such deviation may have deleterious
effects ranging from simple inconvenience and minor efficiency loss
to substantial danger to the health and safety of the diver, who
may be losing substantial quantities of biologically vital heat and
moisture with every breath. At suboceanic depths of 300 feet, this
type of heat loss may account for 20-30 percent of total heat loss
by the diver's body.
In the conventional deep sea diving system, the incoming gas
supplied to the user is generally dry and cold partially because of
its initial condition when it is injected into the respiratory gas
flow and partly because of its passage through the long conduit
distance between the surface and the diver, during which passage
heat is lost to the undersea enironment whose temperature may range
below 50.degree. F. Heat is similarly lost from the expired gas
flows in the passage of the flows through the conduits to the
surface. SCUBA systems also encounter such problems. The SCUBA
system may inject oxygen gas at a fixed rate necessary to
compensate for oxygen consumed by the diver and maintain mass
balance by expulsion to the environment of some expiratory flow,
thus losing heat and moisture. Oxygen added to the system gas flow
is generally at the environment temperature and is of relatively
low humidity. A cryogenic system, on the other hand, requires
removal of heat and moisture from the system gas flow preliminarily
to passage of the flow through the liquid oxygen supply for
reoxygenation. Hyperefficient heat exchangers are utilized to
return the system gas flow to biological temperatures; however,
under all conditions improvement in performance can be expected
with decrease of the heat transfer load on a heat exchange element
and under some circumstances this may prove critical. In the
conventional SCUBA and deep sea diving systems heat and moisture
may be supplied to compensate for respiratory heat and moisture
requirements. Bulky and heavy apparatus may be required for such
heat and moisture conditioning, comprising for example sensors or
other regulator means as well as relatively complex injection
means. Such apparatus is not only costly and complex but is
inefficient from a system point of view since at one point heat and
moisture in the expiratory flow from the user are expelled from the
system and at another point heat and moisture are added with the
aid of cumbersome apparatus.
Similar problems, arising from the deviation of inspired life
supporting gases from biological norms for optimum performance and
safety, are experienced by those within environments having
adequate oxygen content to support life but deviating substantially
from biological standards of temperature and humidity. Such
environments are encountered, for example, in desert and Arctic
regions or by firefighters in the course of their activities.
Continuing inspiration from the atmosphere in such environments may
result in serious damage to the respiratory system and other organs
of the user through exposure to the extremes of temperature and
humidity of the environment.
A further source of inefficiency in life support systems is in
their mouthpiece that is, structures which immediately connect the
respiratory system of the user to external life support elements.
Such mouthpieces generally comprise merely passive conduits for the
passage of the life supporting as flows incoming to, and outgoing
from the user's respiratory system.
SUMMARY OF THE INVENTION
The objectives and purposes of the present invention are realized,
in a gas flow system connecting a respiring user and external
elements, by a flow conditioner comprising a regenerator matrix for
transferring usable components, such as heat and moisture, from one
fluid flow to another in regenerative fashion. Preferably such a
regenerator matrix is disposed within a mouthpiece connecting the
respiring user with external life supporting elements. The matrix
may comprise extended filamentary surfaces for removing usable
contents from one gas flow by contact through conduction,
absorption, adsorption or condensation; retaining the components;
and surrendering them to another contacting gas flow. The matrix is
disposed in exchange relation with the gas flow path and may be
heat or moisture active or active with respect to other flow
components. The matrix surfaces may be compacted together or
extended over a substantial length.
When life supporting gases are added at temperature and humidity
levels falling below biological levels heat is removed through
conduction by the matrix from expired respiratory gases flowing in
contact with the matrix. Heat is retained by the matrix and
surrendered by conduction to the cold life support gases incoming
to the user. Moisture is removed from the expired flow by
condensation, adsorption and absorption, retained, and surrendered
to the incoming dry gas mixture, in an analogous manner.
An further aspect of the invention relates to the provision of
highly efficient means for extracting, retaining, and adding heat
and moisture. Folded wire mesh layers may be arrayed to define at
least one hollow cylinder having a small orifice and presenting a
large surface for heat and moisture transfer and retention while
comprising a low impedance path for gas flow. Gas passing along or
through the mesh layers to the orifice tends to expand and contact
the mesh uniformly, promoting efficient heat distribution. In one
form of the system, the regenerator matrix volume may receive
bidirectional flows, whereas in another system opposite flows may
be directed through different parts of the matrix.
Another aspect of the invention relates to an improved diver's
mouthpiece incorporating at least one regenerator matrix to utilize
efficiently, and for a significant function, mouthpiece volume that
otherwise would serve only as a passive conduit for flows of life
supporting gases. In a specific example, an improved mouthpiece
structure includes a pair of flow conditioners, each comprising a
hollow fluted cylinder of multi-layered heat conductive mesh having
hygroscopic surface layers. The cylinders are disposed adjacent the
mouthpiece orifice within and along the gas flow conduit, and are
of short length but extremely high surface area. The interior ends
of the cylinders are closed, so that inspiratory and expiratory
gases pass relatively uniformly through the available surface area
of the conditioners between the mouthpiece and the conduit.
Separately or in conjunction with the flow conditioner system, a
bypass arrangement may be disposed to provide freer flow when high
flow rates are needed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram and schematic representation of a life
support system utilizing a flow conditioner in accordance with the
invention;
FIG. 2 is a perspective view, simplified and partially broken away,
of a flow conditioner in accordance with the invention;
FIG. 3 is a sectional view of the flow conditioner of FIG. 1 taken
along the line 2--2;
FIG. 4 is a fragmentary view of a portion of the flow conditioner
of FIG. 2;
FIG. 5 is a graphical representation of temperature vs. position
along a regenerator matrix, useful in explaining operation of flow
conditioners in accordance with the invention;
FIG. 6 is a fragmentary view of a portion of an alternative flow
conditioner in accordance with the invention; and
FIG. 7 is a simplified sectional view of yet another flow
conditioner in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates an example of a flow conditioner in accordance
with the invention, operating with a gas flow system. A utilization
system 10 is connected to an external flow path system 12 through
flow paths including an inlet-outlet conduit system 13 and a flow
conditioner 14 (described in detail below). The conditioner 14 may
generally be disposed at any system point between the utilization
system 10 and an oxygen source 24 (discussed below), but for a life
support system is preferably adjacent, or integral with the
inlet-outlet conduit system 13. The oxygen source 24 may be
included in the system as with a conventional SCUBA or in the life
support system of copending application Ser. No. 623,616.
Alternatively, the oxygen source 24 may comprise an environment
containing life supporting levels of oxygen. A gas mixture is
exhausted from the utilization system 10 (one or a group of users
in a life support system) and passes in contact with the
conditioner 14, which includes passive elements for retaining
selected constituents or properties of the gas flow, retaining the
constituents, and adding the constituents to a subsequent gas flow
incoming to the conditioner 14. In the life support context these
are shown generally as a heat active means 16 and a moisture active
means 18, although these may be advantageously combined, or other
types of flow constituents may be transferred by such means.
A pre-oxygenation system 20 may be disposed between the utilization
system 10 and the oxygen source 24. In systems in accordance with
the invention disclosed in copending application Ser. No. 623,616
cited above, the pre-oxygenation system 20 comprises a heat
exchanger 22--reducing temperature of the exhaust gas flow from the
biological range to the near cryogenic range--and a desiccant
chamber 23 for removing moisture from the flow. Thus, the demands
upon the preoxygenation system 20 are substantially lessened by the
heat and moisture transferring means 16, 18 in the flow conditioner
14. In other life support systems the pre-oxygenation means may
operate differently, as in the conventional SCUBA, or such means
may not be used, as in systems drawing oxygen from the
environment.
The flow then circulates to the oxygen source 24, which comprises
means for maintaining the respiratory gas flow at a life supporting
concentration of oxygen. In specific examples, the oxygen source
may comprise a cryogenic processor (as in the invention of the
copending application cited above wherein an oxygen liquid vapor
system 28, maintained at a desired temperature by a cryogen 30,
adds oxygen to the appropriate partial pressure), an arrangement
for adding oxygen as in the conventional SCUBA, or merely the
environment, among others. A post-oxygenation system 26 may be
disposed between the utilization system 10 and the oxygen source 24
for operating upon the oxygenated gas flow prior to entry into the
conditioner 14 (in the cryogenic system, the post-processing system
26 comprises a post-processor for warming the processed flow to
biological temperature and contains a heat exchanger 32 in thermal
relation with the heat exchanger 22 for the purpose). Total gas
pressure, including oxygen and inert gas partial pressures is
maintained by appropriate means varying with the specific system.
In partial recirculation systems the inert gas may be continuously
added with the oxygen. In complete recirculating systems, like the
cryogenic processor system, routine loss of inert gas does not
occur and adjustment of partial pressure to changed conditions is
effected by conventional valve, sensor and storage arrangements. In
non-oxygen supplying systems connected with the atmosphere, of
course, no such inert gas problems arise.
The gas flow then passes to the utilization system 10 through the
flow conditioner 14 and the inlet-outlet system 13. In the flow
conditioner 14, flow constituents such as heat and moisture removed
from the flow by the means 16, 18 and retained therein are
surrendered to the incoming gas mixture.
The path taken by the flow through the oxygen source 24 may be
viewed as the principal path. Thus, usable flow constituents such
as heat or moisture which would otherwise have been discarded from
the outgoing exhaust flow and omitted from, or subsequently readded
from external sources to the incoming oxygenated flow, are instead
extracted from the exhaust flow, retained and surrendered to the
incoming flow for reuse without passing through the principal path
including other elements of the system. In effect the flow
conditioner 14, which transfers particular flow constituents
between the respective flows, comprises a shunt flow path and
storage only for these flow constituents such as heat and moisture.
The shunt path bypasses or is parallel to the principal flow path,
and other flow constituents are not diverted. As indicated above
the principal path need not be closed.
Though flow conditioners in accordance with the invention comprise
shunt paths for particular flow constituents, such flow
conditioners comprise purely passive elements operating through
contact with system gas flow and utilizing basic physical and
chemical principles and processes without the complexities of
structural requirements imposed upon active elements, as shown
below.
FIGS. 2 to 4 illustrate in detail an example of a flow conditioner
in accordance with the invention, as used for an underwater life
support application. A flow conditioner 14 enclosed by a housing 34
is connected with external elements including an oxygen source (not
shown) and a user (not shown), through a conduit system 35, for
respiratory gas flows (the conduit system 35 may, of course, be of
any appropriate shape and is shown as T-shaped for clarity). The
conditioner 14 comprises a pair of adjacent heat and moisture
active flow conditioner regenerator matrices 36, 38. The conduit
system 35 includes a principal cross-arm conduit 40 having colinear
and communicating ends for receiving and transmitting inspiratory
and expiratory flows respectively, associated system elements not
being shown. Also included in the conduit system 35 is a base leg
conduit 42 which comprises a respiratory passage extending from the
cross-arm conduit 40 and terminating in a diver's mouthpiece 44,
including a breathing orifice 45 and comprising a fluid connection
to the respiratory system of the diver. Other arrangements
permitting inflow and outflow of gas to the respiratory system of
the user in operative relation to the flow conditioner 14 may also
be employed in accordance with the invention. The matrices 36, 38
may, for example, be disposed transversely or longitudinally within
the mouthpiece 44 in the absence of a respiratory passage 45. In
the example shown, the matrices 36, 38 are of cylindrical form, and
disposed axially within and along the base leg conduit 42 as best
seen in the perspective and sectional views of FIGS. 2 and 3
respectively. The matrices are preferably disposed axially as
shown, but may also be in other orientations with respect to the
mouthpiece or the respiratory flows, e.g., transversely. As shown
also in FIG. 4, the cylindrical matrices 36, 38 comprise
multi-layer bodies having their central axes spaced apart but
parallel to the central axis of the base leg conduit 42. The
matrices 36, 38 are alike in this example, although they may be of
different sizes and shapes for particular installations (they may,
for instance, comprise packs of stacked screens). Each is shown as
peripherally multi-fluted or corrugated longitudinally to maximize
operative surface area and minimize bulk. The matrices comprise
separate layers 39 in contacting and conforming relation to one
another to define the porous-walled, fluted cylindrical shape. In
one specific matrix 36, the layers 39 are mounted at their opposite
ends in mountings 46, 48, the mounting 46 being adjacent the
orifice 45 and fixed to the inner wall of the base leg conduit 42
and having an open central portion. The mounting 48 at the free end
of the matrix 36 comprises a transverse closure member and is
hermetically sealed to the layers 39, blocking gas flow from
entering the matrix cavity directly from the conduit 40.
Referring now specifically to FIG. 4, each mesh layer 39 of a given
matrix 36 comprises in this example a fine woven screen of highly
heat conductive material, such as copper. The filaments of the
screen are coated with a hygroscopic layer of an activated
molecular sieve material 50, such as activated charcoal. In the
particular example being discussed, approximately 10 layers 39 of
200 mesh copper screen were employed in the flow conditioner, which
was designed for operation at approximately 600-foot depth and with
a helium-oxygen mixture. A desired total surface area of the matrix
36 was provided within a 0.8 inch diameter section approximately 1
inch long. This configuration was sufficient in surface area and
total volume to permit operation with a pressure drop of
approximately 0.1 inch of water or less. The total volume of the
matrix 36 is preferably substantially smaller than the average
volume of the average breath of the diver, to avoid problems
related to mixing of inspiratory and expiratory flows, and may
preferably range between 10-100 cc.
In the specific example of operation of the flow conditioner in
conjunction with a cryogenic life support system, therefore,
inspiratory flow passes from one side of the cross-arm conduit 40
to the mouthpiece 44 through the matrices 36, 38, and expiratory
flows are directed again through the matrices 36, 38 to the other
end of the cross-arm conduit 40. These flows pass essentially
radially through the porous layers 39 of the matrices 36, 38 and
are distributed evenly over their entire surface areas. One way or
check valves (not shown) may be disposed in the conduits or
elsewhere for flow control in the system.
The regenerator matrices 36, 38 are in operative heat and moisture
relation with the respiratory gas flows. Heat is transferred
through condensation. Moisture is transferred through condensation
and evaporation accompanying the heat transfer, and through the
separate action of the molecular sieve. In underwater operation,
where extremely high pressures are involved and where the oxygen
supply for respiration is cold and dry, both heat and moisture are
rapidly extracted from the outgoing expiratory flows by the
matrices 36, 38. Moisture is absorbed by the molecular sieve
material 50, and moisture condenses upon the layers 39 through the
cooling of the gas flow. The heat and moisture are thus diverted
into a separate shunt path that does not act upon other flow
constituents of the gas, and are retained or stored by the matrix
for surrender to a subsequent incoming flow. The subsequent
inspiratory flow enters the cross-arm conduit 40, and absorbs heat
and moisture retained by the matrices 36, 38. Heat extracted by the
matrices 36, 38 is evenly distributed over the mesh layers 39
because of their high thermal conductivity and because of the
expansion of the gases to occupy the entire cavity in which the
matrices 36, 38 are contained, and thus to contact substantially
all of the mesh layers 39. Heat exchange with a surrounding gas is
therefore highly efficient, and augmented by heat transfer along
the length of the layers 39. Pressure drop is extremely small
because of the thinness of the layers 39 (for the 200 mesh screen
previously referred to, the total thickness of 10 layers was
approximately 0.040 inch).
For specificity, the invention has been discussed within the
context of life support and particularly as related to temperature
and humidity. Such particular aspects are not necessary to the
invention which may be employed generally and may be active with
respect to heat or moisture singly or in combination, or to other
properties.
Though the regenerator matrix 36 is preferably of coated wire mesh,
it may comprise other configurations allowing intimate
intermingling of the gas flow and the matrix elements such as
various arrangements of spatially separated filamentary
elements--woven or unwoven--apertures in an otherwise integral
structure, as well as intermingled, or separated, adjoining layers
of porous or permeable moisture and heat active materials or a
single moisture and heat active material. Fluid permeable materials
such as copper wool may be utilized also.
The activated molecular sieve material 50 may comprise heat treated
activated charocal or other well known comparable materials. The
sieve 38 is disposed upon the mesh 37 by conventional procedures as
by applying a charcoal-containing paint or applying finely divided
charcoal to an adhesive coated upon the mesh 37.
Where large temperature differentials exist, the adsorptive process
may be relatively unimportant. In situations, however, where such
differentials do not exist or where the temperature at the oxygen
source is higher than the body temperature of the user, the
adsorptive process may become more significant. The interaction of
the moisture content of the respiratory gas flow with the
regenerator matrix 36 is essentially analogous to that of the heat
content in accordance with well known principles of thermodynamics
and chemistry; thus, moisture is retained and surrendered by the
matrix 36 in a manner similar to that described above for heat, and
the matrix 36 serves as a regenerator for moisture as well as
heat.
It should be noted that the regenerator matrix 36 is not confined
to use in situations where the source of life supporting gas is at
a lower temperature of humidity level than required for biological
processes. The regenerator matrix 36 may be used in situations
where there is a difference in any direction of the characteristics
of the oxygen source from biologically favorable levels of
temperature and humidity. For example, where the oxygen source--as
in the desert environment--is at an elevated temperature level and
a depressed humidity level, the regenerator matrix 36 with the
molecular sieve material 50 operates as described above with
respect to the mositure content of the respiratory gas flow while
operating in a reverse manner with respect to thermal content of
the respiratory gas flow.
FIG. 6 depicts another specific example of a flow conditioner in
accordance with the invention. Alternating layers 52, 54 of
moisture active and heat active materials respectively are disposed
adjacent one another, to form a regenerator matrix 56. The layers
52 are shown to comprise separated filaments or mesh of a
hygroscopic moisture active material such as fibrous carbon or
leached silica.
The layers 54, as in the example of FIG. 4, comprise filaments or
mesh of highly heat conductive material such as copper. The
disposition and configuration of the layers 52, 54 are similar to
those of FIG. 4. The layers 52, 54 are thermally insulated from the
housing and may be removably connected thereto.
The operation of the example of FIG. 6 is similar to that of the
example of FIG. 4 except that here the respiratory gas flows pass
through twice as many separate mesh layers in each respiratory
cycle as in the previous example, and the storage effects take
place in different elements.
In a different arrangement in accordance with the invention as
shown in FIG. 7, a flow conditioner 60 may be positioned at a
remote location between a mouthpiece 62 and a processor system or
other life support means or oxygen source 64. The term "remote"
does not indicate that a substantial spacing is necessarily
required, only that the flow conditioner 60 may be disposed
somewhere along a preexisting or specially adapted inspiratory
conduit 66 and expiratory conduit 68 instead of being disposed
adjacent to or as a part of a mouthpiece apparatus. In this
arrangement, the flow conditioner 60 comprises a housing 70
containing a matrix 72 comprising a plurality of heat conductive
elements, specifically a mass of copper wool. Bypass conduits 74,
76 shunt the housing 70, each conduit including a pressure
responsive valve 78. The bypass valve 78 may be set adjustably to
respond to any desired pressure differential across it, to open so
as to permit free flow in response to a selected pressure
differential. Check valve 80 insures proper flow direction of the
regenerating flows. It should be noted that the bypass arrangement
may be employed with the mouthpiece regenerator as such.
In the operation of the system of FIG. 7, the primary function of
flow conditioning is effected within the separate inspiratory
conduit 66 and expiratory conduit 68 by the copper wool body 72.
Heat taken into the mass 72 during the expiratory cycle is readily
conducted throughout the mass within the housing 70, and given up
to the inspiratory flow. Moisture is accumulated within the copper
wool mass 72, migrating on successive exhalations into the region
of the inspiratory conduit 66. Thus, a substantially greater
storage volume is made available for both heat and moisture
retention and release, and the structure not only provides an
interchange between the incoming and outgoing flows but an
averaging or integration of the characteristics of the flows.
The invention is not to be considered to be confined in scope or
construction to the specific examples illustrated above but rather
is to be considered to embrace all variations and modifications
within the scope of the invention as set out in the following
claims.
* * * * *