US 3130722 A
Description (OCR text may contain errors)
April 1954 c. A. DEMPSEY ETAL 3,130,722
RESPIRATORY MASK 2 Sheets-Sheet 2 Filed Sept. 8, 1959 FIG-7 f FIG-'6 giw Y iil l IN V EN TORS CHARLES A. DEMPSEYQ LOUIS PERENY April 1964 c. A. DEMPSEY ETAL 3,130,722
RESPIRATORY MASK Filed Sept. 8, 1959 Z SheetS-Sheet 1 FIG-T IN V EN TORS.
CHARLES A. DEMPSEY 8: BY LOUIS PERENY ATTORNEYS United States Patent 3,130,722 RESPIRATORY MASK Charles A. Dempsey and Louis Pereny, Dayton, Ohio, assignors to Protective Treatments, Inc., Dayton, Ohio, a corporation of Ohio Filed Sept. 8, 1959, Ser. No. 838,510 6 Claims. (Cl. 128-143) This invention relates to respiratory masks, and more particularly to a disposable sterilizable mask formed of sheet materials relatively impervious to passage of bacteria therethrough, which are adaptable for use with either negative or positive pressure difie-rential between the interior of the mask and the atmosphere, and which may include in embodiments of the invention means for inducing such a pressure differential.
While designed and intended primarily for use by surgeons and members of the operating team during surgical operations, the masks provided by the invention are suitable for any use in which an inexpensive disposable respiratory mask for the nose and mouth is required. When desired for use with a negative pressure differential, the mask of the present invention may include means for transponting fresh air through the mask by inducing subatmospher-ic pressure with-in it, arranged to carry the users exhaled breath away from the immediate openating area for release at a point removed from the operating field, so as to preserve sterility at such field. The air is admitted from the atmosphere through supply ports covered by filters which permit passage of the air while functioning to prevent bacteria from escaping outwardly through the ports.
The construction of the mask is such, however, that if the pressure differential is reversed by supplying gases under slight pressure from the outside to the inside of the mask, the invention provides an efficient, inexpensive, sterilizable and disposable mas-k suitable for use as an oxygen mask in hospitals or sick rooms, or for other appropriate uses such, for example, as a safety mask for passengers in aircraft at high altitudes in the event of failure of the cabin pressure.
In a modified form which does not include connection with means for inducing a pressure differential, the mask may be used in the conventional manner as an efficient, inexpensive, disposable anti-contagion respiratory mask.
In all three embodiments the use of relatively soft molda'ble non-woven sheet material such as sterilizable paper provides a mask substantially free from interstitial openings such as occur between the strands of woven material, and producing a high degree of sterility in use.
Respiratory masks in use today are generally of two types. The type comprised of folds or layers of woven textile materials supported in position over the users nose and mouth for filtering the users exhalations, which is that used generally during surgical operations, is recognized to have a number of disadvantages. The user must inhale through the filter in addition to exhaling through it, tending to restrain his breath and after a period of time to become uncomfortable. The exhaled breath causes moisture to build up within the mask, to the discomfort of the user, :and making the mask progressively less efficient in filtering out bacteria exhaled by the wearer, so that in surgical operations of extended duration surgeons often find it desirable to replace the mask one or more times. Such masks of woven materials even under favorable conditions have a relatively low elficiency because of the comparatively arge size of the interstitial spaces between their strands compared to the average size of bacteria, and their efliciency progressively decreases as the textile materials absorb moisture. They tend also to be ice hot and uncomfortable and, if the wearer uses glasses, to cause them .to cloud.
The other type of mask in general use is the familiar rubber or plastic mask covering a smaller or larger part of the head, or even enclosing it entirely. Examples are gas masks used extensively in mines, quarries, chemical plants and similar places where it is desirable to exclude dust or noxious fumes from the wearers lungs, or in spraying, dusting and fumigating operations. Such masks by reason of their initial cost are not disposable, and tend to develop unpleasant odor-s, to become brittle, and to develop leaks from exposure to heat during sterilizing.
In both types of masks, furthermore, there is a tendency of the pressure inside the mask to build up as a result of the users breathing, thus establishing a momentary superatmospheric pressure within the mask which tends to cause undesirable leakage around its edges.
It is accordingly an object of this invention to provide a sterilizable, disposable mask of inexpensive relatively impervious sheet materials such as paper, with its inner area adjacent the user and enclosing the nostrils and mouth having a configuration which will fit in sealing relation against the wearers face in use, and which by reason of its design will provide a relatively broad front-to-back band in contact with the wearers face around the edge of the breathing cavity within the mask for preventing undesirable leakage.
Another object is to provide such a mask in which the supply ports and exhaust vents will be properly located with respect to the users nostrils, and which also will be adaptable in a single size or limited number of sizes to a broad range of sizes and configurations of the human face.
It is a further object of the invention to provide a disposable surgical mask within which constant slightly subatmospheric pressure may be induced, so as to carry the exhaled breath of the wearer away from the immediate area of the operation and discharge it at a point remove-d therefrom and which at the same time will not interfere with comfortable breathing.
Another object of the invention is to provide such a mask which includes means for inducing the desired pressure diiferential, which means will be sufficiently small and light in-weigh-t to be supported on the wearers person.
A still further object of the invention is to provide such a mask in which positive pressure may be induced and which will be suitable for use in supplying air or oxygen to the user.
An additional object of the invention is to provide such a mask which may be formed from inexpensive sterilizab-le paper sheet materials, which is efficient and comfortable to wear, which is highly sanitary, and which may be manufiactured at sufliciently small cost to be disposable.
Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
In the drawings FIG. 1 is a perspective view showing a mask embodying the invention in use on the wearers face and including negative pressure-inducing means;
FIG. 2 is a front elevational view of the mask of FIG. 1;
FIG. 3 is a side elevational view of such mask indicating in dotted lines the position of the wearers face within it;
FIG. 4 is a front View of a blank for the body of the mask;
FIG. 5 is a front view of a blank for the central reinforcing member;
FIG. 6 is a sectional view approximately on the line 66 of FIG. 2;
FIG. 7 is a diagrammatic view on a small scale of one form of negative pressure-inducing apparatus operated by a pressure fluid motor;
FIG. 8 is a view similar to FIG. 7 showing a mask having electrically operated pressure inducing means;
FIG. 9 is a front view of another embodiment of the invention, particularly adapted for positive pressure within the mask;
FIG. 10 is a sectional view approximately on the line 1010 of FIG. 9;
FIG. 11 is a View of an alternative form of hose connection showing co-axial supply and exhaust lines partly cut away to show details of construction; and
FIG. 12 is a side View, partly in section, of a further embodiment of the invention for use as a conventional mask, without supply and exhaust line connections.
Referring to the drawings, which illustrate preferred embodiments of the invention, the device as shown in FIGS. l includes an integral body portion indicated generally by the numeral arranged symmetrically on both sides of a center fold line 11, including lower side areas or wings 12 and upper side areas 13 adapted to be received against the wearers cheeks and nose, respectively, in sealing relation therewith when the mask is fitted to the wearers face, a lower area or extension 14 adapted to be received against the fleshy portion underlying the wearers chin in sealing relation therewith, and a central area 15 shaped to lie in spaced relation with the wearers nose and mouth, providing a generally cone-shaped breathing chamber or cavity 16, as shown in FIG. 3.
The wing portions 12 extend generally from a point at approximately the lower end of the nasal bone, about midway between the bridge and tip of the nose, approximately to the jawbone, and when in position on the wearers face accordingly provide in conjunction with the lower extension 14 a band of appreciable depth in the front-to-back direction of the mask, lying in contact with the fleshy portion of the wearers face from about midway of the nose along the cheeks and under the chin in a continuous line. With this construction it has been found that when secured to the face the mask will adapt itself to the configuration of a wide variety of faces irrespective of the particular shape, and to a considerable degree the size, of the face.
Adjacent the edges of upper side areas 13 is a nose strip 17 of moldabl'e material which will hold the shape into which it is pressed, such as wire, wire mesh, strip metal or plastic, which may conveniently be secured in place by providing flaps 18 in the blank for the body portion and folding them over the nose strip, where they are secured in place by a suitable adhesive. This strip maintains its position when fitted against the sides and bridge of the nose, and by pressing the upper side areas 13 of the mask against this part of the face completes the sealing band around the entire breathing chamber 16. The central part of this nose strip is shaped to extend above the upper edge of the body portion aligned with center line 11 of the mask to provide a fastener 19. Similarly, a grommet 21 is secured in lower extension 14, also aligned along center line 11.
The fastener and grommet are adapted to be secured by suitable hooks 21 in a head harness for securing the mask to the face which is indicated generally by the numeral 22, and comprises a head strap 23 passing from fastener 19 over the top of the Wearers head and connected behind his neck with the center of an elastic neck strap 24, the ends of which are secured in grommet 26 under the wearers chin. Head strap 23 is fitted with adjusting means for providing in cooperation with the neck strap the desired tension for securing the mask to the face, and the elasticity of the neck strap permits freedom of movement of the users face and neck without binding of the strap at the neck and without destroying the sealing relation of the mask against the users face. Experiments based on anthropological measurements have shown that a neck strap of width webbing elastic 17 inches long will provide the proper tension for automatically adjusting itself by reason of its elasticity to secure the mask in sealing relation with the face on proper adjustment of the head strap, irrespective of the wearers neck size.
If the mask is intended for use with negative or positive pressure within it, the central area 15 preferably should be strengthened and supported by a reinforcing member 25 of the same shape as the central area, secured in place preferably to the outside of such central area by an adhesive applied to the entire area between the two members. This will insure against collapse of breathing chamber 16 in the event a higher than normal negative pressure should be created within the mask, and also that the mask is not torn as a result of movement by the wearer at the connection into the interior of the mask of the tube communicating with its interior.
A pair of ports 26 are provided in the mask, opening into breathing chamber 16 on opposite sides of center line 11 for admitting air from the atmosphere into the mask, with filters 27 in such ports to prevent escape of the wearers exhaled breath. These filters may be made of any suitable material, including materials such as flannel, muslin, or gauze, or of a suitable sponge rubber, or plastic material such as urethane foam, or glass fiber.
The ports should be positioned above the wearers nostrils when the mask is in use. Anthropological measurements show that if they are placed equidistant from center line 11 with their centers at the intersection of a line parallel to and spaced approximately 7 inwardly from such center line, and of a second line normal to the axis of the cone-shaped breathing chamber 16 and approximately %1 from the apex thereof, they will be about 7 above the tip of the wearers nose, and that this relationship will not vary significantly throughout large numbers of human beings and will provide a most comfortable and eificient arrangement.
Also opening into breathing chamber 16 is a nipple connection 30, as shown on an enlarged scale in FIG. 6, into an exhaust tube 31 and having an enlarged inner end 32, with collar 33 fitted over its outer end to maintain it in position. Exhaust tube 31 should be no higher than and preferably below the level of the wearers nostrils, and its cross-sectional area should be approximately half the combined cross sectional area of ports 26 to provide for passage of an adequate amount of air through the mask under small pressure differentials. Since ports 26 are covered with a suitable filter medium, they prevent the outward flow of bacteria and function in the nature of upstream check valves, by acting to impede gas flow therethrough in a direction opposed to the normal pressure differential between the interior and exterior of the mask, and thus exhalations into the mask will flow out the exhaust tube.
Tube 31 constitutes a fitting for a flexible exhaust hose line 34 for carrying the exhaled breath from the interior of the mask to be discharged at a point removed from the operating field. In appropriate cases, the outer end of this tube may be connected with any suitable source of negative pressure inducing means such as a mechanical vacuum pump, a pressure fluid operated ejector pump, or any other suitable means. As is apparent, such means may be located outside of the operating room proper, and the connection may be through a wall outlet, an overlying header or any of a variety of conventional connections, it being necessary only that the position and length of hose line 34 be such as to provide the wearer with sufiicient freedom of movement for his purposes. In practice, it is convenient for this line to be led over and behind the wearers shoulder as indicated in FIG. 1, where it may be fastened to his gown at the back.
In many instances, it will not be convenient to use a connection into a separate outside source of negative pressure by reason of the number of persons in the operating team, the necessary movements of the wearer about the operating room, or the like. The invention accordingly includes motor driven means for inducing a pressure differential between the inside and outside of the mask, which are sufficiently small and light in weight to be secured directly to the wearers body. Such means are indicated generally by the numeral 40 in FIG. 7, which shows a miniature exhaust fan indicated diagrammatically at 41 and operated by a fluid pressure motor 42 driven by the force of an inert pressure gas such as carbon dioxide supplied from the pressure cylinder 43 under control of the valve 44. This is controlled from outside container 45 for the fan, motor and cylinder, which is indicated diagrammatically by a dotted line, and which should be made to be readily opened so that as cylinder 43 becomes exhausted it may be removed and replaced with a fresh cylinder. The inlet side of exhaust fan 41 is connected into hose line 34, and the exhaust side into an exhaust line 46 which is of sufficient length that the discharge end 47 thereof will extend to or near the floor. To guard against the possibility of explosion by a spark from static electricity built up by the continuous passage of air in the tube and the wearers movements, a static discharge wire 48 may be fitted into line 46 and should be of sufficient length to remain in contact with a ground source irrespective of the wearers movements.
Container 45 is provided with fastening means 49 for securing it to the wearers gown, belt, or other convenient location. Such means may take any of a variety of forms such as the hook indicated in FIG. 1, or a tab, loop, snap connection or other means appropriate for the particular use being made of the mask.
Presently available small exhaust fans driven by miniature explosion-proof electric motors designed for safe operation in atmosphere containing flammable gases make practical the use of such electrically driven fans in an operating room, or when furnigating or using in the chemical industries, or the like. The invention accordingly provides alternatively for an electrically operated fan drive such as indicated diagrammatically in FIG. 8, in which exhaust fan 141 is contained in container 145 connected with a miniature electric motor 55 operated by a battery 56 and controlled by a switch 144. Satisfactory results have been obtained with a combined blower and motor weighing together approximately 4 ounces and which with the addition of a 9 volt battery required for operation and its container case does not exceed approximately a pound in weight.
A mask embodying a form of the invention intended and adapted for use with a positive pressure in the breathing chamber within the mask derived from an outside source of air or oxygen (not shown) is indicated in FIG. 9. 'Such source may be in fixed position, or portable on the users person, as desired. This form is generally similar to the form shown in FIGS. 1-5, and includes substantially the same body portion 114? with its lower side areas or wings 112, upper side areas 113, lower extension 114 and nose strip 117, including also the fastening portion 119 and grommet 120 both positioned on center line 111. In this form, line 134 functions as a supply rather than an exhaust line, and accordingly communicates with breathing chamber 116 at a point above the wearers nostrils rather than below them. A form of connection for line 134 is shown in FIG. 10, and includes a tube 131 with an enlarged end 132' on the inside of body portion 11% and an outer collar 133 for securing the nipple in place. This connection is shown as being readily detachable, and in it the end 60 of line 134 is flared so as readily to be press-fitted over the outer end of tube 131.
In this embodiment for use with a positive pressure differential within the mask, the area of vents 65 should be sufficient to maintain a relatively low positive internal pressure by passing all exhaust gases through the vents and avoiding momentary increases of pressure in the interior of the mask such as might cause leakage at the sealing area around the face. Such vents are accordingly shown in FIG. 9 as larger than those in the negative pressure embodiment, their size depending in part on the particular filtering medium 55 employed, which may be foam rubber, glass fiber, a flexible plastic foam material such as urethane foam, or flannel or gauze. The filter will prevent escape of undesirable bacteria in uses where it is desirable to maintain sterility, as well as wasteful escape of oxygen or other gases supplied to the interior of the mask.
In some instances of negative pressure within the mask it may be desirable also to provide a direct supply of air or oxygen to the wearer, from an outside source, rather than from the atmosphere, an arrangement for which is provided by the coaxial supply and exhaust lines shown in FIG. 11. In this embodiment, air or oxygen is supplied through the inner line '76 located coaxially within outer line 71, the tubes being of such relative sizes as to provide an ample annular passage 72 between them. The supply connection should preferably be above the level of the users nostrils, as in the embodiment of FIG. 9, to provide for downward flow of the air or oxygen for comfortable breathing. It would be possible also to provide a one-way stop valve indicated diagrammatically at 75 in the supply line '70; although it has been found that in the usual case the pressure of the incoming gas or oxygen may be maintained sufficient to prevent any escape so that all of such exhalations will pass off through the annular passage '72. This embodiment includes the reinforcing member 225 to provide support for connector 230 and the coaxial lines 75 and 7 1 and for reinforcing the body of the mask against tearing due to the weight of the connector and tubes, and to support the central portion 215 of the mask so as to insure that the breathing chamber will keep its proper shape. Inasmuch as both gas supply and gas exhaust are directly connected through the lines 70 and 71 to points spaced from the mask, in this embodiment of the invention no vents such as 26 and 65 are necessary, and they are omitted.
A further and simpler embodiment of the invention is shown in 'FIG. 12. This form is intended for use as an ordinary respiratory mask in which the user inhales and exhales directly to and from the atmosphere, as in the case of the conventional flannel or gauze mask. In this form it is desirable to provide a larger area for admission of air and exhaustion of the users exhalations than in the embodiments heretofore described. Accordingly, in this embodiment a substantial portion of the central area of the mask at the outer part of the breathing chamber is cut away to provide a single large vent fitted with a filtering medium 81 secured to the body portion 10 by a suitable adhesive for restricting passage of the users exhalations from the inside to the outside of the mask and filtering out the droplets of moisture, bacteria or other undesirable contents of the users exhalations. No central reinforcing member is necessary, and the remaining portions of the mask are the same as those in the form of FIGS. '1-5, and are indicated by the same reference numerals. For the filtering medium it has been found that a pad of foam rubber so selected and arranged as to insure that there are no direct passages from the inner to the outer surface thereof and with its surface finished on one side only may be used, although it would be possible to use several layers of flannel or gauze as in the case of the conventional gauze mask. Another, and in some instances, more desirable, filtering medium is a flexible plastic foam material such as urethane foam.
In all embodiments of the mask, it is fitted to the face by the wearer and used in essentially the same manner, i.e., whether in the negative pressure differential, positive pressure differential, or absence of pressure differential form. The wearer applies it over his nose and mouth with the lower extension 14 or 1.14 passing below the chin, and retains it loosely in place by securing fastening member 19 or 119 and grommet 2G or 121% to the hooks 21 on the head strap 23 and at the ends of the elastic neck strap 24. He then presses the nose piece 15 or 1'15 against the sides of his nose, fitting it closely to the facial contours. This initial fitting causes wing portions 12 or 112 to flatten out somewhat and adapt themselves to the contours of the wearers cheeks, and by then adjusting the length of the head strap 23 the wearer provides a slight tension in them which draws the mask into the desired position so that it bears against his face around the entire outer portion of the breathing chamber within the mask. it is held securely along the upper portion of the nose by the moldable nose piece, and since the body portion is formed of tough yet relatively soft and moldable paper, the wing portions and lower portion will press against the face from about the center of the nose on one side downward along the fleshy portion of the face, around and under the chin, and back to the other side of the nose in a l'me or band of contact which is in fact of appreciable breadth in a fronbto-back direction. Thus by properly adjusting the head strap 23, the resultant tension in the head and neck straps causes the mask to lie in sealing relation entirely around his nose and mouth from the bridge of the nose, along the sides of the nose and the cheeks, and under the chin. By reason of the breadth of this band the mask will form a secure seal entirely around the central area which lies in spaced relation with the wearers face, providing a breathing chamber within the mask which is sealed entirely around the edges.
The construction thus provides a respiratory mask which is relatively impervious to passage of bacteria therethrough, and includes embodiments for use with either a negative or positive induced pressure within it or, by omitting exhaust or supply line connections, may be used without induced pressure differential in the manner of the conventional gauze mask.
It has been found by experiment that the average amount of air inhaled and exhaled in ordinary breathing during ordinary use of a mask in accordance with the invention is about 300 to 350 cc. With each breath in a mask formed from a blank measuring approximately 6 /2 inches from edge to edge across the wings and approximately -6 inches from top to bottom, at their greatest dimensions, the average volume of air within the breathing chamber will be about 30 cc. Accordingly, a large proportion of the exhaled breath is dispelled from the breathing chamber before the next breath is taken. The breathing action of the wearer has a pumping effect within the chamber, which tends to change momentarily the pressure differential within the mask during normal breathing not exceeding an inch of water pressure and with forced strenuous breathing not exceeding a 2 inch water pressure. The constant flow of air through the mask induced by the source of pressure difierential rapidly removes the exhaled air and reduces the momentary pressure built up with each breath. Thus it provides for minimum condensation of moisture or of rebreathing of exhalations, giving the wearer the sensation of continuously breathing relatively cool, fresh air.
Inasmuch as the sheet material, such as paper, forming the body of the mask is essentially impervious to passage of inhalations or exhalations therethrough, the exhaled gases will pass only through the exhaust connection or the filter depending on whether the use is with negative or positive pressure.
The negative pressure mask design prevents outward passage of bacteria through ports 26 due to the constant inward flow of atmospheric air through the filter covered port into the breathing chamber and out the discharge connection 30. In the positive pressure mask embodiment surgical sterility is maintained by filtering the exhaiations,
and in the embodiment providing for admission to and exhaustion from the breathing chamber through the coaxial external connections the omission of other vents provides essentially a closed breathing chamber.
It has been found that non-pressure masks embodying the invention having a filter area of approximately 10 square centimeters with respect to an inside volume of approximately 30 cubic centimeters in the breathing chamber have effectively prevented the escape of any colonycausing bacteria in tests of varied lengths up to 30 minutes.
As will be apparent, the blanks for the body portion and the central reinforcing member may readily be diecut from appropriate sheet materials, such as moistureresistant kraft paper of 60-70 pounds weight for the body portion, and foodliner board for the reinforcing member. For the filtering medium satisfactory results have been obtained with A3 thick medium density latex foam rubber having a skin on one surface only. All grommets, hooks, and connections should be of rust-proof metal, or plastic capable of withstanding sterilization.
While the forms of devices herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of devices, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.
What is claimed is:
1. A respiratory breathing mask adapted to carry the exhaled breath of the user for discharge at a location remote from the user such as to preserve sterility in a surgical operating area, comprising a face mask having a body portion defining a breathing chamber adapted to cover only the nose and mouth and surrounding facial areas of the user, port means in said body portion for passage of ambient air into said breathing chamber, said port means communicating with the interior of said mask in the upper portion of said breathing chamber to avoid direct exhalation from the nose or mouth against said port means, restricting means for impeding gas flow between said breathing chamber and the exterior of said mask through said port means, a tube connected into the lower region of said chamber for carrying a flow of gas from said chamber to a location remote from the mask, and suction means operatively connected with said tube to induce a slight negative pressure in said chamber with respect to ambient air pressure suificient to withdraw normal exhalation from said chamber through said tube, said restricting means providing for sutficient inflow of ambient air to said chamber to support normal breathing. 2. A respiratory breathing mask as defined in claim 1 including means connected to said face mask and adapted to support said mask against the users face in continuous sealed relationship therewith around said breathing chamber.
3. A respiratory breathing mask as defined in claim 1 wherein said suction means is adapted to be supported on the users person, and an additional tube from said suction means is adapted to carry a fiow of gases therefrom to a remote location for disposal.
4. A respiratory breathing mask as defined in claim 3 wherein said suction means includes an exhaust fan and a connected power source adapted to be supported on the users person.
5. A disposable respiratory mask for use by surgeons and the like comprising a body formed from a relatively soft non-woven material such as paper substantially free from interstitial openings therethrough, said body including a central area shaped to lie in spaced relation with the users nose and mouth providing a breathing chamber, said body including also extensions along the sides, the bottom and the top of said central area, a nose strip of moldable material on said top extension for urging the inner surface thereof against the bridge and upper sides of the nose in sealing relation thereto, the other said extensions being flexible over a peripheral band of substantial width to adapt themselves when under slight force to the contours of the fleshy portion of the cheeks and the chin of the wearer with the inner surface of said band received against the face in sealing relation to form a continuous sealing band of appreciable width around said breathing chamber, a vent in said body for passage of ambient air to the interior of said mask, means associated with said vent for restricting the flow of air passing through said vent, a tube communicating with the interior of said mask providing a conduit for flow of air between the breathing chamber and a location remote from said mask, harness means secured to an opposite two of said extensions for maintaining a continuous seal of the inner surface of all said extensions against the face around said breathing chamber, and suction means operatively connected with said tube to induce a slight negative pressure in said chamber sufiicient to withdraw normal exhalation from said chamber through said tube.
6. A disposable respiratory mask as defined in claim 5, wherein said body of said mask is formed of thin mate rial such as paper which is incapable of maintaining a predetermined shape and which will mold to the contour of the users face, and a reinforcing member of relatively stifi material secured to the central area of said body for supporting said area against collapse, said reinforcing member forming the breathing chamber about the users nose and mouth.
References Cited in the file of this patent UNITED STATES PATENTS 916,886 Merryman Mar. 30, 1909 2,039,681 Chatfield May 5, 1936 2,070,754 Schwartz Feb. 16, 1937 2,634,724 Burns Apr. 14, 1953 FOREIGN PATENTS 393,650 Germany Sept. 2, 1924 484,638 Great Britain May 9, 1938 50,041 Netherlands Mar. 15, 1941 5,104 Great Britain 1913