Rehumidification filter for ventilation mask

A compact, light-weight, disposable, and quick-fit rehumidification filter device adapted to fit flight-masks which deliver pressurized respiratory fluids to a human. The preferred embodiment is made up of a container, a continuous strip of micropore filter paper helically rolled so as to entirely fill the space defined by the cross section of the container, optional directionally louvered screens affixed to the container, and a securing mechanism which detachably secures the filter device to the flight-mask. The securing mechanism is adapted to mate with a retaining ring projection common to most flight-masks by use of a matingly threaded ring or by a structure which flexibly and resiliently clips onto the outer circumferential surface of the retaining ring projection. The filter paper acts as a humidification counter-exchange apparatus by first extracting moisture from exhaled breath, then subsequently returning moisture to dehumidified respiratory fluids being inhaled. The filter paper has a wicking effect that helps evenly distribute the moisture. A second embodiment of the invention is made up of filter paper generally molded to the contours of the face-mask and made from filter paper combining suitable rigidity and respiratory fluid flow properties. The filter surface may be exposed to contact with the face to maximize the absorption of transpired skin moisture. The filter paper may be used in a multilayered structure to achieve sufficient rigidity or a plasticized layer may be adhered to the external surface of the paper.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a rehumidification filter for masks used 
for ventilation of dehumidified fluids. 
2. Description of the Prior Art 
Modifying the air that a human breathes has been a concern since the 
recognition that the human condition can be affected by modifying such 
air. Therefore, respiratory devices used to modify the air breathed under 
various circumstances, involving for example high-altitude flight and 
medical conditions, are abundant in the prior art. 
Nevertheless, the devices heretofore proposed have not met with commercial 
success for a variety of reasons, including for example, extreme 
bulkiness, heavy weight, many moving parts, expensive non-disposable 
filters and tortuous passageways which cause extra expenditure of energy 
on the part of the human during both inhalation and exhalation. 
For example, U.S. Pat. No. 3,099,987 issued Aug. 6, 1963 to Bartlett, Jr 
describes a respiratory apparatus intended primarily for use in military 
high-altitude applications, i.e. a flight-mask which sealing covers the 
mouth and nose of a user having a source of pressurized respirant which 
entry into the mask is controlled by valve structures. The apparatus 
includes a filter device containing a granular moisture transfer means, 
usually silica gel, whose container is wholly incorporated into the 
pathway of the inspired and expired fluids. The container is adapted at 
one end to be inserted into the mask, and on the other end detachably 
secured onto the valve structures. The container is further described to 
require screens secured to each end of the container for suitably 
confining the moisture exchange material therein. A valve foundation plate 
serves as the main connection structure between the mask and container 
structure and the valve structures. This plate has two large holes which 
serve to channel the expired and inspired fluids through their respective 
valves. This structure fails to provide a simple and inexpensive means of 
providing humidified respirant to the user. 
U.S. Pat. No. 3,102,537 issued Mar. 7, 1963 to Bartlett, Jr also describes 
a flight-mask which is a combination valveless mask and a box-like 
structure containing valve and rehumidifying devices. Moisture transfer 
membranes, such as paper toweling having suitable capillary pores running 
throughout the thickness of the membranes, are interposed within the 
inspiratory and expiratory channels of the box-like structure. Again, this 
structure fails to provide a simple and inexpensive means of providing 
humidified respirant to the user. 
U.S. Pat. No. 4,941,467 issued Jul. 17, 1990 to Takata describes a 
relatively simple humidification face-mask, similar in appearance to a 
surgical mask, intended for use in dry air environments such as airliner 
passengers must endure. The mask combines an inner mask member and an 
outer mask member between which a moisturizing pad is held. The 
moisturizing pad is adapted to carry a volume of water to humidify the 
air. A similar application is suggested in U.S. Pat. No. 4,705,033 issued 
Nov. 10, 1987 to Halfpenny, which describes a conical humidification 
face-mask containing a open-celled foam member also adapted to hold water 
across which inhaled air passes. However, the filtering structures are 
integral to the mask. 
U.S. Pat. No. 2,468,383 issued Apr. 26, 1949 to Tiffany describes a nasal 
and sinus protector and warmer which is designed in appearance to resemble 
eyeglass frames wherein the nasal mask connects with tubing running 
contiguously with the brow of the face and which tubing terminates behind 
each ear. The terminus of the tubing contains an undefined filter. U.S. 
Pat. No. 5,386,825 issued Feb. 7, 1995 to Bates describes a respiratory 
breathing filter which is removably contained in an orally inserted 
apparatus through which the user breathes. Each of these filters are 
uniquely adapted for use with its device. 
Several patents describe the use of metal netting, mesh or wire-gauze type 
structures for the purpose of heat and moisture exchange which operate on 
the principal of a counter-flow exchange in cold air conditions, whereby a 
loose or open structure of the metal mesh allows an almost entirely free 
passage of air yet recovers some heat and condensing humidity. U.S. Pat. 
No. 603,021 issued Apr. 26, 1898 to Dight describes a thermal inspirator 
which prevents the escape or ingress of air except through a tube which 
connects a heat storing chamber inclosed in the space under a hat and open 
to the air in such space with a nasal mask, through which the air is 
expelled and drawn in. The heat storing chamber is filled with a roll of 
metal wire-gauze. U.S. Pat. No. 3,326,214 issued Jun. 20, 1967 to McCoy 
describes a breath warming device using metal corrugated structures as 
heat exchange elements within a chamber. U.S. Pat. No. 4,136,691 issued 
Jan. 30, 1979 to Ebeling et al. describes a canister combined with a 
face-mask containing a heat exchanger made up of a continuous strip of 
wire netting wound helically to form a cylindrical netting roll. However, 
none of these devices teach the use of a disposable filter with a mask or 
describe a structure wherein air flow is substantially unrestricted while 
humidifying the air. 
Therefore, despite the abundant variations of structure of devices which 
modify respiratory fluids, none of the above inventions and patents, taken 
either singly or in combination, is seen to describe the instant invention 
as claimed. 
SUMMARY OF THE INVENTION 
The present invention relates to a rehumidification filter for masks used 
for ventilation of dehumidified fluids. 
The preferred embodiment of the present invention is a compact, 
light-weight, disposable, and easily attachable and removable 
rehumidification filter device adapted to fit masks which deliver 
pressurized respiratory fluids to a human. The preferred embodiment of the 
filter device is shown adapted to a pilot's flight-mask, the filter being 
made up of a generally cylindrical container comprising a first and second 
end, a continuous strip of micro-pore filter paper helically rolled so as 
to entirely fill the space defined by the cross section of the container, 
a directionally louvered screen affixed to the first and second ends, and 
a securing mechanism which detachably secures the filter device to a 
standard and commonly used flight-mask. 
The aforementioned advantages of easy removability and attachment arise 
from the device's structural adaptation to a common component of many 
flight-masks. Commonly used flight-masks include a generally 
pyramido-conically shaped face-mask which sealingly seats over the nasal 
and oral facial areas of the pilot. The face-mask creates an internal 
space into which pressurized respiratory fluid is admitted by a complex 
valve apparatus of the flight-mask. The valve apparatus, located 
externally to the face-mask, is in communication with the internal space 
of the face-mask. 
However, a common feature found within the internal space of the mask is a 
removable, threaded, annular retaining ring, which helps secure the 
face-mask to the valve apparatus and which when removed allows access to 
the valve apparatus from within the mask. This retaining ring usually 
circumscribes certain channel openings of entry and exit for the 
respiratory fluid, behind which openings the appropriate valve structures 
are found. The retaining ring is seated on a matingly threaded and annular 
projection permanently affixed to the valve apparatus. 
Each aspect of structure of the present invention is designed to be as 
simple as possible while maintaining the purpose of the function and using 
materials throughout the device whereby the aforementioned advantages of 
quick-fit, disposability, compactness and light-weight are facilitated. 
First, the securing mechanism may be adapted to mate with the retaining 
ring projection by use of a matingly threaded ring fixedly attached to the 
filter container or by a structure which flexibly and resiliently clips 
onto the outer circumferential surface of the retaining ring projection. 
Many plastics are currently available which may be used to meet these 
requirements. 
Next, the core of the filter device contains a continuous strip of 
two-layer corrugated micro-pore filter paper, helically rolled. The 
primary function of the filter paper is to act as a humidification 
counter-exchange apparatus by first extracting moisture from exhaled 
breath, then subsequently returning moisture to dehumidified respiratory 
fluids being inhaled. The helical configuration provides a plurality of 
channels created by the corrugation of the paper, which serve to provide 
sufficient surface area for a counter-exchange of moisture as well as a 
direct, open and unimpeded channel to the valve openings. The roll is 
inserted into the container so that its cross-sectional area covers both 
the expiratory and inspiratory valve openings while maintaining a direct 
line of unrestricted respiratory fluid flow through the channels to the 
valve openings. 
Finally, fixed directional louvers help circulate, direct and mix 
respiratory fluids over the entire cross section of the roll, whereby no 
one area of the roll becomes saturated with or depleted of moisture. The 
louvered screens may be affixed to the first and second ends at right 
angles to one another as a means of distributing respiratory fluid flow 
and may be manufactured from the same material as the securing mechanism. 
Moreover, the filter paper has a wicking effect that helps distribute the 
moisture. Although the screens may be helpful, the presence of screens is 
not required to retain the roll in place within the container. Hence 
resistance to air flow may be further eliminated by the removal of the 
screens. 
A second embodiment of the invention takes further advantage of the wicking 
properties of the filter paper. The second embodiment is a generally 
conical filter molded to the contours of the face-mask and made from 
filter paper combining suitable rigidity and respiratory fluid flow 
properties. Beginning as a reference point at the retaining ring 
projection, the conical filter is secured to the mask by an annular 
securing mechanism, similar to that found on the first embodiment, which 
clips onto the retaining ring projection. The filter paper then extends 
generally along the contour lines of the mask towards the face to a 
predetermined point within the internal space of the mask. This point may 
be chosen to allow the paper to come into contact with the face to 
maximize the absorption of transpired skin moisture. 
The filter paper alone may be used in a multilayered structure to achieve 
sufficient rigidity. In addition or alternatively, a plasticized coating 
or layer may be adhered to the external surface of the paper so as to 
serve in function as the container described in the first embodiment. 
To allow unimpeded respiratory fluid flow, the inner surface of the filter 
paper may contain enlarged pores for entry of the expired respiratory 
fluid into channels created by the corrugated paper. The channels run 
longitudinally and parallel with the contour lines of the face-mask away 
from the face toward exit apertures in the external surface of the filter 
device, the exit apertures being located within the circumference of the 
annular securing mechanism. The number and positioning of the enlarged 
pores are sufficient so as not to impede free flow of respiratory fluids 
along the corrugated channels. 
Accordingly, it is a principal object of the invention to provide a device 
which humidifies a dehumidified respiratory fluid to be inhaled by a human 
through a face-mask by extracting moisture from exhaled respiratory fluid. 
It is another object of the invention to provide a device which is adapted 
to quickly and easily attach to and be removed from commonly used masks. 
It is a further object of the invention to provide a device that can 
rehumidify respiratory fluid which structure is simple and inexpensive to 
manufacture. 
Still another object of the invention is to provide a device which is 
capable of being molded to a face-mask and absorb transpired skin moisture 
as a source of moisture for rebreathing. 
These and other objects of the present invention will become readily 
apparent upon further review of the following specification and drawings.

Similar reference characters denote corresponding features consistently 
throughout the attached drawings. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention relates to a rehumidification filter for masks used 
for ventilation of dehumidified fluids. 
Referring to FIG. 1, the rehumidification filter 10 is illustrated in use 
when attached to a pilot's flight-mask 12. An internal space 14 formed by 
a seal between a face-mask 16 and a user U is shown whereinto respiratory 
fluid passes during breathing. An external area 20, relative to the 
internal space 14, is shown in which valve component and other supply 
apparatus necessary to the operation of the flight-mask are housed. An 
annular projection 22 extends from the external area 20 by which a 
securing mechanism 24 secures the rehumidification filter 10 to the 
face-mask 16. A container 26, affixed to the securing mechanism 24, forms 
a cavity which houses a filter material 30. 
Referring now to FIG. 2, peering into the internal space 14 of the 
flight-mask 12, the front of the rehumidification filter 10 can be seen. 
The filter is covered by a louvered screen 32 which assists circulation of 
air flow over the entirety of the filter material 30 housed within, as 
shown in FIG. 3. The container 26 is shown to have a cylindrical wall 31. 
Container 26 is enclosed at the proximate end solely by a screen 32. 
Disposed at the distal end of container 26 is an annular ridge 33. Annular 
ridge 33 extends inwardly from wall 31 and terminates at an edge 35 
defining an opening into container 26. Securing mechanism 24 extends 
outwardly from edge 35. In both FIGS. 3 and 5, a louvered screen 32 is 
shown affixed to each the distal and the proximate end of the container 26 
at right angles to one another as a means of circulating respiratory fluid 
flow over the filter material 30. 
Referring now to FIG. 4, The filter material 30 within the container wall 
is a continuous strip of micro-pore filter paper. The paper is made of two 
layers, a first planar layer 36 and a second corrugated layer 38. The 
filter material 30 has been helically rolled to form a roll, which when 
viewed on end, creates a plurality of channels 34, formed to travel 
uninterrupted from a first end, proximate to the user, to a second end, 
distant to the user. Referring back to FIG. 2, the roll of filter material 
30 is shown fixed and inserted within the container cavity with the 
proximate end nearest the viewer. At the distant end, expiratory and 
inspiratory valve openings (not shown) are found in the wall of the 
face-mask 16 which allow the transfer of respiratory fluid between the 
internal space 14 and the external area 20. This structure allows 
respiratory fluid flow to be directed through the channels 34 for 
counter-exchange of moisture with the filter material and yet maintain a 
direct, open and unimpeded respiratory fluid flow to the valve openings 
for exchange of expired respiratory fluid. Moreover, the filter material 
30 may be retained in place within the container 26 by the use of an 
adhesive between the outermost layer of the helical roll and the 
cylindrical container wall 34, eliminating the need for a screen 32. 
Hence, resistance to air flow may be further reduced. 
Referring now to FIGS. 3 and 5, the rehumidification filter 10 is shown in 
two embodiments wherein the securing mechanism 24 varies. In FIG. 3 the 
securing mechanism 24 is adapted to mate with a threaded annular 
projection (22 as shown in FIG. 1), having a matingly threaded cylindrical 
wall 40 fixedly attached to the filter container 26. In FIG. 5, a second 
embodiment of the securing mechanism 24 is shown made up of a plurality of 
tabs 42 which flexibly and resiliently clip onto the outer circumferential 
surface of the threaded annular projection 22. Each tab 42 has a tooth 44 
for engagement of a thread on the annular projection. 
Referring now to FIG. 6, the filter material 30 is shaped generally 
conically and molded to the contours of the face-mask 16. The conical 
filter 46 is secured to the mask by a tabbed securing mechanism 24 as 
shown in FIG. 5. The filter material 30 then extends generally along the 
contour lines of the mask towards the face of the user U to a 
predetermined point within the internal space 14 of the face-mask. This 
point may be chosen to allow the paper to come into contact with the face 
to maximize the absorption of transpired skin moisture. 
To achieve sufficient rigidity to avoid collapse of the shape of the 
conical filter 46, a plasticized coating or layer 48 may be adhered to the 
external surface of the filter material 30. In the alternative, multiple 
layers of the filter material 30 may be used to achieve sufficient 
rigidity of the conical filter 46 without the need of a plastic coating. 
In either alternative, in order to avoid impedance of respiratory fluid 
flow, the inner surface of the filter material 30 contains a plurality of 
enlarged pores 50 for entry of the expired respiratory fluid into the 
channels 34 created by the corrugation of the micro-pore filter paper. As 
can be best appreciated from FIG. 7, the channels 34 run longitudinally 
and parallel with the contour lines of the face-mask, starting from the 
pores 50. The channel then runs distally toward exit apertures 52 in the 
external surface of the first planar layer 36, the exit apertures 52 being 
located within the circumference of the annular securing mechanism 24. The 
pores are of sufficient number and positioning so as not to impede free 
flow of respiratory fluids along the corrugated channels yet provide 
adequate surface area over which moisture can be counter-exchanged. 
It is to be understood that the present invention is not limited to the 
embodiments described above, but encompasses any and all embodiments 
within the scope of the following claims.