US 3343535 A
Description (OCR text may contain errors)
Sept. 26, 1967 J. P. LYTLE ET AL BREATHING MASK SEAL Filed May 24, 1965 w T N E V m JOHN P. LYTLE 0A V/D G. HANNAN BY CHARL E5 C. P0852715 m wwm wuaw ATTORNEYS.
United States Patent 3,343,535 BREATHING MASK SEAL John P. Lytle, Whitehall, and David G. Hannan and Charles C. Roberts, Pittsburgh, Pa., assiguors t0 Mine Safety Appliances Company, Pittsburgh, Pa.,
a corporation of Pennsylvania Filed May 24, 1965, Ser. N 457,957 Claims. (Cl. 128141) This invention relates to seals around the edges of breathing masks, both full and half masks.
The inside of a breathing mask generally is provided near its edge with an inwardly extending continuous flexible lip that engages the face in order to form a seal against the entrance of contaminated air. There are two types of leakage that tend to occur at the seal. The first is the bulk flow of outside gas into the mask because of the lower pressure in the mask during inhalation. The second type of leakage is by diffusion of the contaminant into the mask because of the lower partial pressure of the contaminant inside the mask, regardless of the total pressure in the mask. Leakage will occur to some extent past any seal, since a perfect seal between a flexible lip and the face cannot be achieved.
It is among the objects of this invention to provide a breathing mask that has a seal which prevents contaminants that start to enter the mask by leakage from reaching the breathing area in the mask.
In accordance with this invention a breathing mask has a face-piece for covering at least the nose and mouth. The face-piece is provided with the usual inhalation valve. The inside of the face-piece is provided around its marginal portion with an inwardly opening channel that has spaced flexible side walls for sealing engagement against the face. The channel is provided with an air inlet from the inside of the face-piece and with an outlet some distance from the inlet for connecting the channel with the atmosphere. The outlet is provided with an exhalation valve. With this construction, air exhaled inside the facepiece will flow through the channel inlet into and through the channel and then out through the exhalation valve. This flow of air through the channel during every exhalation cycle purges the channel of any contaminants that may have leaked into it past its outer side wall during the preceding inhalating cycle. Consequently, the contaminant is forced out of the mask before it can be inhaled.
The invention is illustrated in the accompanying drawing, in which FIG. 1 is a side view of our breathing mask, with parts broken away;
FIG. 2 is a vertical section taken on the line 11-11 of FIG. 1;
FIG. 3 is a front view of a modification; and
'FIG. 4 is an enlarged fragmentary section taken on the line IVIV of FIG. 3.
Referring to the FIGS. 1 and 2 of the drawings, a mask is shown which has a full face-piece 1 for covering the eyes as well as the nose and month. However, this inven tion is equally applicable to half masks or oral-nasal masks that protect only the nose and mouth. The edge of the face-piece is provided with the usual tabs 2, to which head straps 3 are fastened for holding the mask in place. The face-piece also is provided with a conventional inhalation valve 4 in any suitable location, which can be connected by a flexible hose 5 with an air purifying canister or oxygen supply. Like known masks, there is a flexible sealing lip 6 extending around the inside of the face-piece near its edge for engaging the head around the entire face to form a seal.
Regardless of how good a seal is formed by the sealing lip just mentioned, there will be at least some leakage past it into the mask. To prevent such inward leakage from being breathed by the wearer of the mask, it is the purpose of this invention to construct the mask in such manner that the leakage will be purged from it before the contaminants can be breathed. Accordingly, the inside of the mask is provided with a second or inner sealing lip 7 that is spaced a short distance from the outer lip 6. This inner lip also seals against the face along a line that is substantially parallel to the edge of the outer lip. The two sealing lips form between them a channel 8 that opens inwardly toward the face. Anything leaking inwardly past the outer lip or wall of the channel will enter the channel and will have to leak on past its inner lip or wall before it can be breathed. To get rid of this undesirable and harmful leakage before it can pass the inner wall of the channel, the air exhaled by the wearer of the mask is used for sweeping the contaminant out of the channel during each exhalation.
In order to purge the mask of contaminants, the channel is provided with an inlet and an outlet. The inlet or inlets may be simply holes 10 in the inner wall of the channel, and the outlet 11 can be formed in the face-piece between the channel walls. A conventional exhalation valve 12 is connected with the channel outlet. This may be the only exhalation valve for the mask, but if desired an auxiliary valve (not shown) may be provided at the lowest point of the mask to permit the escape of moistures that may collect inside the mask. The exhalation valve for the channel is most suitably located at the highest point of the channel, while the channel inlets may be located below the chin in order to space them as far as possible from the outlet.
It will be seen that every time the wearer of the mask exhales, the exhaled air will have to flow into and through the channel -8 and then out through the exhalation valve. This air, which will flow up both sides of the mask to the outlet, will carry up and out with it any contaminants that have leaked into the channel past its outer wall during the preceding inhalation. Therefore, the contaminants will not have a chance to build up in the channel and leak past its inner wall into the mask where they would 'be inhaled.
With the construction just described, in which the channel inlet always is open, there will be a slight reduction of pressure inside the channel every time the wearer inhales. This reduction in pressure not only can be essentially avoided, but the channel can be maintained under a slight pressure by providing the inlet to the channel with a check valve that allows exhaled air to flow into the channel during exhalation but not back out of it during inhalation. A mask 15 with such construction is shown in FIGS. 3 and 4. The check valve 16 will close during inhalation so that the pressure in the channel 17 will not be reduced. This continuous pressure inside the channel also helps prevent leakage into the channel from outside the mask. As shown, the wall of the channel may project from the body of the face-piece and form a ridge. A single check valve below the chin may be used, but because of space requirements it may be more desirable to move the check valve around to the side of the chin. In that case, a like check valve 18 should be added at the opposite side of the chin so that exhaled air will be sure to flow up through both sides of the channel. The short length of channel connecting the two check valves beneath the chin will be purged to some extent when the rest of the channel is purged. The check valves may be mounted in the sides of the face-piece above the channel and be connected with it by short conduits 19 molded onto the face-piece. The exhalation valve 20 for the channel again is located at the top of the face-piece.
According to the provisions of the patent statutes, we have explained the principle of our invention and have 3 illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims,
the invention may be practiced otherwise than-as spesealing engagement. against the face, the channel beingprovided with an air inlet from the inside of the facepiece, the face-piece having an outlet therein at a point remote from said inlet and connecting the channel with the atmosphere, and an exhalation valve for said outlet, whereby air exhaled in the face-piece 'will flow through said inlet into the channel and through the channel to said exhalation valve.
2. A breathing mask according to claim 1, in which said channel inlet and exhalation valve are spaced apart by long lengths of the channel.
3. A breathing mask according to claim 1, in which said channel inlet its near the bottom of the face-piece and said exhalation valve is near the top of the facepiece.
4. A breaking mask according to claim 1, including a check valve opening into said channel at said inlet.
5. A breathing mask comprising a face-piece for covering at least the nose and month, an inhalation valve connected with the face-piece, the inside of the face-piece being provided around its marginal portion with an inwardly opening channel having spaced flexible side walls for sealing engagement against the face, the lower part of the channel being provided with a pair of laterally spaced inlets from the inside of the face-piece, a check valve opening into the channel at each of said inlets, the top of the face-piece having an outlet therein connecting the channel with the atmosphere, and an exhalation valve for said outlet, whereby air exhaled in the face-piece will flow through said inlets into the channel and through the channel to said exhalation valve.
References Cited UNITED STATES PATENTS 577,956 2/ 1897 Henderson 128-146.4 1,288,647 '12/1918 Miller 128-145 2,560,665 7/ 1951 Stark 49-498 X 2,939,458 7/ 1960 Lundquist 128146 3,167,070 1/1965 'Silverman 128146.4 X
FOREIGN PATENTS 428,338 5/ 1935 Great Britain.
RICHARD A. GAUDET, Primary Examiner.
W. E. KAMM, Assistant Examiner.