Gas mask for operation in contaminated areas

A gas mask is provided which includes a facepiece including a front portion of semi-rigid rubber highly resistant to chemical agents and a sealing skirting of soft rubber having a high mechanical resistance, co-vulcanized with the front portion of the facepiece. A nozzle, connected to a half mask situated inside the facepiece, is tightly fastened to the front portion of the facepiece. An inflow opening and an outflow opening are provided which are substantially coaxial and are located in the lower portion of the nozzle. The inflow opening places the interior of the facepiece into communication with the external atmosphere and the outflow opening places the interior of the half mask into communication with the external atmosphere through an inflow chamber and an outflow chamber which are separated by a partition. The inflow chamber communicates bilaterally with a space located between the half mask and the facepiece. The outflow chamber communicates with the external atmosphere, over the inflow opening, and in front of the phonic cap assembled in the upper part of the nozzle.

FIELD OF THE INVENTION 
The present invention relates to a gas mask for operation in contaminated 
areas. This type of gas mask finds a large employment in the event of 
natural calamities, industrial accidents, and/or in any situation in which 
the user's survival must be ensured even in the presence in the area of 
highly noxious substances, be they in the form of gases, aerosols or 
powders. 
BACKGROUND OF THE INVENTION 
As known, gas masks intended for the above-described use comprise 
substantially a facepiece made of impermeable material, resistant to 
chemical agents and associated with a harness which allows the mask to be 
put on the user's head so as to provide a tight seal between the edges of 
the facepiece and the user's face. 
Once the mask is put on, the user can inhale air from the outside through 
an inflow opening arranged on the facepiece and provided with a threaded 
fitting on which is assembled a filtering element intended to 
decontaminate the air being inhaled. The air subsequently exhaled by the 
user is expelled from the mask through an outflow opening, also arranged 
on the facepiece and provided with a respective single-acting valve. 
The facepiece comprises, moreover, two eye-pieces or, alternatively, a 
single transparent screen to give the user full visibility. To prevent the 
air being breathed out from causing clouding of the eye-pieces, in many 
cases, provision is made of a so-called "half mask," associated with the 
facepiece and communicating with the outside through the outflow opening 
and the single-acting valve. 
The half mask allows the air breathed out to be directly discharged outside 
without filling completely the inner portions of the facepiece, in 
particular those corresponding to the eye-pieces. Still, in order to 
prevent a possible clouding of the eye-pieces, it is foreseen that, in the 
inhalation phase, the air flow inhaled through the filter may be guided 
into the inner portions of the facepiece so as to skim the surfaces of the 
eye-pieces and to be then sucked inside the half mask through further 
check valves. 
In this way, also, the clouding of the eye-pieces due to the user's 
perspiration is significantly reduced. 
Generally, the facepiece includes also a phonic cap, functioning to 
transmit outside the user's voice to prevent an excessive muting of the 
same owing to the presence of the facepiece. 
In masks of modern design, both the inflow and the outflow openings are 
obtained in a so-called "nozzle," tightly engaged in the lower portion of 
the facepiece and housing also the phonic cap. More particularly, the 
inflow opening is provided in the upper part of the nozzle and flows 
almost directly, by means of a short connection duct, into the interior of 
the facepiece, at the base of the eye-pieces and in a median position 
between them. 
The outflow opening is instead provided in the lower part of the nozzle and 
opens directly outside the mask, below the inflow opening. The phonic cap 
is situated over the inflow opening and is directed toward a chamber 
placed behind the connection duct and communicating with the outlet of the 
outflow opening downstream of the corresponding single-acting valve. 
It has been noted that the arrangement of the above-described elements 
yields certain inconveniences regarding the practical and functional 
employment of the gas mask. At first, it can be seen that the position of 
the inflow opening involves a corresponding position of the filtering 
element which is not quite appropriate in view of a rational distribution 
of the mask portion. In fact, the filtering element, which is situated in 
the upper part of the nozzle and has a considerable weight, may provide 
high moments of inertia opposing movements of the user's head. In this 
situation, a comfortable use of the mask is compromised. Further, the 
position of the filtering element limits the user's downward field of 
view. 
It was also noted that the position of the inflow opening limits the 
possibility of building up the facepiece in such a way that the eye-pieces 
are sufficiently near the user's eyes to permit the use of binoculars, 
microscopes or optical instruments in general, when the mask is worn. 
Moreover, the direct connection between the inflow opening and the interior 
of the facepiece can cause some problems if the mask is to be used at low 
temperatures. In fact, in these circumstances, the inhaled air cannot be 
heated before skimming the user's face, giving, therefore, rise to a 
significant discomfort level for the user. 
Furthermore, the entrance of air at the base of the eye-pieces, in a median 
portion between them, does not represent an ideal condition to obtain an 
optimum distribution of the air flow inside the facepiece. This can result 
in an irregular de-clouding of the eye-pieces. It is also to be noted that 
the air skimming the surface of the eye-pieces is not heated at all, so 
that it is not in the best condition to yield an efficient de-clouding 
function. 
Another disadvantage of the prior art is that the air coming out from the 
outflow opening tends to skim the surfaces of the filtering element. At 
low temperatures and after a prolonged use of the mask, this circumstance 
can cause formation of a certain amount of ice on the filtering element, 
due to freezing of the water molecules present in the exhaled air. The 
consequent increase in the weight of the filtering element compromises 
therefore the comfort, and above all the safety, of the mask. 
The position of the phonic cap, situated behind the inflow opening, affects 
significantly a good transmission of the user's voice toward the outside. 
In fact, the user's voice is compelled to reach the outflow opening and to 
come out below the filtering element. To compensate for the poor quality 
of this transmission, it is at present necessary to provide large-sized 
phonic caps, to the detriment of the space available for the single-acting 
valve associated with the outflow opening. 
In this condition, the diameter of the single-acting valve must be 
considerably reduced, with a consequent increase in the effort required by 
the user to expel air from the mask. Alternatively, the single-acting 
outflow valve can have an elongated configuration, involving, however, 
high production costs and giving results, as to an efficient and reliable 
employment, which are anyhow worse than those obtainable by the use of 
circular valves of appropriate diameter. 
In the production of masks according to the conventional technique, some 
problems arise from the contrasting needs of providing facepieces which 
must be sufficiently stiff to prevent excessive oscillations of the unit 
formed by the nozzle and the filtering element and which must be, at the 
time, sufficiently soft and elastic to ensure a perfect sealing action 
around the user's face. 
Generally, these objectives are satisfied by making the facepiece with soft 
rubber layers having a reduced thickness along the edges to be sealed 
around the user's face and a greater thickness, to provide additional 
stiffness, in the front portions of the facepiece. These expedients, 
however, result in a significant increase in the overall mask weight and, 
therefore, may compromise its comfort, in particular in view of a 
prolonged use. 
Attempts to eliminate such disadvantages have led to the production of 
facepieces whose front portions are reinforced with fabric layers embedded 
in the rubber. However, this requires long and complicated procedures, not 
suitable for mass production. 
Also, masks were built up, whose facepieces comprise two portions stuck 
together. A first portion, which extends around the edges of the 
facepiece, functions to ensure a seal around the user's face and is 
therefore made of soft rubber, and the remaining portion of the facepiece 
is made of stiffer rubber. This solution involves problems regarding 
reliability of use, since the mask may be employed in atmospheres 
containing solvents able to attack chemically the bonding agents used to 
join the two portions forming the facepiece. 
SUMMARY OF THE INVENTION 
The primary objective of the present invention is substantially to 
eliminate the above-noted disadvantages of the conventional masks, and in 
particular, to provide a gas mask having improved characteristics of 
comfort, versatility and functionality, even for long periods of 
continuous use in unfavorable atmospheric conditions. 
The above and other purposes, which will be more clearly apparent from the 
following detailed description, are substantially achieved by means of a 
gas mask for operation in contaminated areas, wherein (1) the phonic cap 
is situated in an upper portion of the nozzle, (2) the inflow opening is 
provided in a lower portion of the nozzle and is in communication with the 
interior of the facepiece through an inflow chamber which opens 
bilaterally in a lower portion of the facepiece, and (3) the outflow 
opening is obtained in the lower portion of the nozzle substantially at 
the level of the inflow opening and is in communication with the external 
atmosphere through an outflow chamber opening into a communication 
chamber, which opens in turn over the inflow opening at the level of the 
phonic cap, with the inflow and outflow chambers being mutually separated 
by a partition extending inside the nozzle. 
The invention is directed to a gas mask comprising (1) a facepiece, (2) a 
nozzle tightly engaged in a lower portion of the facepiece, (3) a 
half-mask situated inside the facepiece, tightly engaged on the nozzle and 
provided with a terminal edge intended to provide a seal around the user's 
nose and mouth, (4) connection means to allow passage of air from the 
interior of the facepiece to the interior of the half-mask, (5) an inflow 
opening provided in the nozzle, including a fitting for assembling a 
filter and communicating with the interior of the facepiece, (6) closing 
valve means associated with the inflow opening, (7) an outflow opening 
placing the interior of the half-mask into communication with the external 
atmosphere, (8) a single-acting outflow valve associated with the outflow 
opening and (9) a phonic cap housed in the nozzle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With particular reference to FIGS. 3 and 4, reference numeral 1 refers to a 
gas mask for operation in contaminated areas in accordance with the 
present invention. 
Mask 1 comprises a facepiece 2 having a front portion 3 intended to cover 
entirely the face of a user and conventionally provided with eye-pieces 4. 
A sealing skirting 5 is fastened along a peripheral edge 3a of front 
portion 3; skirting 5 extends toward the interior of front portion 3 and 
is intended to ensure a tight seal around the user's face. 
Front portion 3 is made of semirigid rubber, having a hardness ranging 
between 50 and 70 Shore A, and highly resistant to chemical agents, be 
they in the form of gases, liquids, aerosols or powders. For instance, 
butyl rubber can be used to build up front portion 3. 
Sealing skirting 5 is instead made of a rubber of high softness and 
elasticity, having preferably a hardness ranging between 40 and 70 Shore 
A, and a high mechanical resistance to tearing. For instance, natural 
rubber can be used to build up sealing skirting 5. 
Advantageously, sealing skirting 5 is vulcanized together with the front 
portion 3 such that it is joined to the edge of front portion 3 of 
facepiece 2. 
At edge 3a, sealing skirting 5 forms a peripheral step 5a intended to 
reinforce the area of union between the two compounds and to provide an 
abutment seat for the terminal edge of a hood (not illustrated) making 
part of a garment of the kind conventionally adopted to carry out 
operations in contaminated areas. Peripheral step 5a is advantageously 
able to avoid any incidental slipping off of the hood from the user's 
head. 
Further, to prevent the hood edge from unduly covering eyepieces 4, the 
profile of front portion 3, cutoff along a vertical median plane, 
comprises a first section 3b (as shown in FIG. 4) which projects frontally 
with respect to sealing skirting 5, thus providing a wide supporting seat 
for said edge. 
Conveniently, first section 3b is followed by a second section 3c which 
extends almost vertically, terminating with a ridge 3d. Due to the 
combination of first section 3b and second section 3c, front portion 3, at 
the latter, is very close to the user's face. 
Therefore, eye-pieces 4 are situated a very short distance from the user's 
eyes, so that he may use optical instruments, such as microscopes, 
binoculars and so on, even when the mask is worn, this being facilitated 
by the absence of any protuberance external to his eyes which may 
interfere with the structure containing said optical instruments. For this 
purpose, protruding section 3c is entirely situated below the level of the 
user's pupils. 
As visible in FIG. 3, ridge 3d originates a pinching protrusion 6 which, 
when the mask is worn, is situated around the user's nose. Protrusion 6 
enables the user to stop his nostrils to effect a decompression if, during 
his work, he should be subjected to variations of atmospheric pressure. 
Facepiece 2 is, moreover, provided with a flexible hose 43 engaged through 
one side of front portion 3 and comprising a closing member 44 arranged 
externally to mask 1. Hose 43, normally arranged along the corresponding 
inner side of mask 1, is able to engage, after the opening of closing 
member 44, a tubular rigid element, not illustrated, to be oriented such 
that its free end 43a is brought to the level of the user's mouth. 
In this way, the user, still with the mask on, can drink water or 
nourishing liquids supplied by a container associated with said tubular 
rigid element. 
In a conventional manner, facepiece 2 is secured to the user's face by 
means of a harness 7 (FIG. 4), substantially composed of a cap 7a from 
whose edges are initiated braces 7b, each provided with a respective 
gripping element 8. Each gripping element 8 comprises a buckle 8a on which 
is fixed a respective brace 7b, and an orientable loop 8b comprising a 
hole 8c by which it can be removably engaged with a respective button 9 
fixed to an extension 5b of sealing skirting 5. 
Button 9 comprises a pin-shaped element 9a which passes through a 
corresponding extension 5b and is provided with an abutment base 9b 
abutting against extension 5b. A retainer 9c, shaped as a circle ring and 
secured to pin 9a by a force engagement, acts against extension 5b at the 
opposite side with respect to base 9b to fasten button 9 to sealing 
skirting 5. 
Front portion 3 of facepiece 2 includes in its lower part an opening 
through which a nozzle 11 is tightly locked by means of a strap 10. Nozzle 
11 comprises a front portion 12, facing toward the outside of mask 1, 
around which is sealed the edge of said opening. 
The lower part of front portion 12 includes an inflow opening 13 positioned 
so as to be substantially situated at the level of the user's mouth; 
opening 13 is provided with a threaded fitting 13a to allow the connection 
of a conventional filtering device 14, illustrated in the figures but not 
described in detail. 
Inflow opening 13 communicates with the interior of facepiece 2, as will be 
described in more detail below, and is provided with closing valve means 
functioning to prevent any inhalation of external air on the user's part 
during the substitution of filtering device 14. 
The closing valve means comprise a check valve 15, having a diaphragm 15a 
which can be subjected to the action of a small plate 16 fixed to the end 
of a stem 17 which is subjected to the action of a spring 18 which 
operates to bring plate 16 against diaphragm 15a. Further, a rubber ring 
19 is connected to stem 17, at the side opposite to plate 16, by means of 
spokes 19a. 
When filtering device 14 is correctly assembled, ring 19 is pushed in the 
direction of valve 15 as illustrated in FIG. 1. In this situation, plate 
16 is spaced apart from diaphragm 15a, which is able to carry out its 
action directed to open or close valve 15. 
On the other hand, when filtering device 14 is disengaged from mask 1, the 
action of spring 18 causes the detachment of ring 19 from valve 15 and 
brings plate 16 into contact with diaphragm 15a. As a result, diaphragm 
15a is continuously pressed against a corresponding sealing seat 15b, so 
as to prevent the inhalation of air inside mask 1. 
Nozzle 11 comprises, moreover, a rear portion 20, facing toward the inside 
of mask 1 and having, as shown in FIG. 2, a width smaller than that of 
front portion 12. A half mask 22 is tightly engaged, by means of a 
fastening ring 21, around rear portion 20; it is intended to exert a tight 
seal around the user's nose and mouth and flexible hose 43 passes 
therethrough. 
The lower part of rear portion 20 comprises an outflow opening 23 provided 
with a respective single-acting outflow valve 24. Outflow valve 24 is 
conventionally formed by a rubber diaphragm 24a fixed to a support 24b and 
acting to seal a projection 24c which extends around the edge of outflow 
opening 23 externally to half mask 22. As clearly shown in FIGS. 1 and 2, 
outflow opening 23 is, in a novel and advantageous manner, arranged at the 
level of inflow opening 13 and is oriented in a direction substantially 
parallel to it. 
In the illustrated embodiment, the axis of outflow opening 23 is inclined 
with respect to the axis of inflow opening 13 through an angle .alpha. 
smaller than 15.degree. and more precisely preferably equal to 10.degree.. 
Further, rear portion 20 includes a phonic cap 25 tightly engaged, through 
an O-ring 25a, in a housing 26 provided over outflow opening 23. In a 
conventional way previously known per se, phonic cap 25 substantially 
comprises two half-shells 27 having respective holes 27a distributed along 
concentric circumferences and mutually fastened together by means of a 
seam 27b extending along a peripheral edge. 
A diaphragm 28 is interposed between the two half-shells 27; during the 
formation of seam 27b, it is radially stretched so as to vibrate, without 
originating resonance phenomena, when subjected to acoustic vibrations 
comprised in the frequency range of the human voice. Phonic cap 25, 
maintained in position by a locking nut 29 screwed in housing 26, faces 
toward the inside of half mask 22 and, at the opposite side, faces towards 
a communication opening or chamber 30 which extends through the upper 
portion of nozzle 11. Communication opening 30 opens toward the outside 
over inflow opening 13, through a protection grate 31 removably connected 
to front portion 12 to prevent the penetration of foreign bodies into 
nozzle 11. 
Advantageously, between phonic cap 25 and communication opening or chamber 
30 is provided a separation wall 32 formed as a single piece in rear 
portion 20 and provided with a plurality of holes 33 distributed along 
concentric circumferences, offset with respect to the circumferences along 
which are distributed the above indicated holes 27a. This arrangement is 
provided to protect diaphragm 28 from possible luminous or thermal flashes 
and from pressure waves. 
Rear portion 20 is made integral with front portion 12 via the 
interposition of a partition 34, whose peripheral extent is substantially 
coincident with that of rear portion 20. In a preferred embodiment, front 
portion 12 and rear portion 20, as well as partition 34, are made of 
synthetic resin and are mutually tightly connected by melting the material 
along the coupling surfaces at the points of mutual contact. 
Partition 34, with respect to rear portion 20, originates an outflow 
chamber 35 which communicates with the interior of half mask 22 through 
outflow opening 23 and with the external atmosphere through communication 
opening 30. Further, at the base of nozzle 11, outflow chamber 35 extends 
into a discharge duct 36 which passes through partition 34 and front 
portion 12 and comes out from the latter below inflow opening 13. 
With respect to front portion 12, the presence of partition 34 originates 
an inflow chamber 37 which communicates with inflow opening 13 through 
inlet valve 15. Inflow chamber 37, tightly separated from outflow chamber 
35 by virtue of partition 34, is contained between an upper wall 38 and a 
lower wall 39, formed in a single piece construction with front portion 
12, extending along the whole width of the latter and provided with 
respective terminal edges 38a, 39a, tightly connected on partition 34. 
Upper wall 38 separates in a tight manner inflow chamber 37 from 
communication chamber 30, and lower wall 39 separates in a tight manner 
said inflow chamber from discharge duct 36. 
As can be seen in FIG. 2, since the width of rear portion 20 and that of 
partition 34 are smaller than the width of front portion 12, inflow 
chamber 37 opens bilaterally into the lower part of facepiece 2, in the 
space formed between the inner walls of the latter and the outer walls of 
half mask 22. 
During normal use of gas mask 1, the vacuum originated inside half mask 22 
by the user's inhalation causes the intake of air from the outside through 
filtering element 14. The air penetrating into nozzle 11 through inflow 
opening 13 strikes wall 34d of the partition in the zone opposite to that 
from which the partition is skimmed by the air exhaled by the user. 
When the mask is to be used at low temperatures, the air conveyed into 
inflow chamber 37 would be advantageously ready to receive heat from the 
wall of partition 34, heated by the exhaled air. Subsequently, the inhaled 
air is conveyed into the free space between facepiece 2 and half mask 22, 
as indicated by arrow A in FIG. 2. 
Advantageously, half mask 22 can be provided, at symmetrically opposite 
parts, with two guiding baffles 40, only one of which is shown in FIG. 4, 
which are positioned over inflow chamber 37, project toward facepiece 2 
and extend symmetrically along half mask 22. The presence of baffles 40 
prevents the air conveyed to the base of facepiece 2 from penetrating 
immediately into the upper portions of facepiece 2. 
In fact, the air outflowing bilaterally from inflow chamber 37 is guided 
along the entire lower portion of facepiece 2, to be then conveyed to the 
upper portion of the same so as to flow laterally to eye-pieces 4 and to 
move toward the center of facepiece 2 with a centripetal motion. 
In this situation, still with reference to the employment of the mask at 
low temperatures, the air would be further heated before reaching the 
upper part of the facepiece, so as to avoid any risk of freezing the 
user's face and to afford optimum characteristics necessary for a good 
de-clouding of eye-pieces 4. 
Subsequently, air is conveyed into half mask 22 through connection means 
represented by single-acting valves 41 conventionally provided on the 
latter and functioning to prevent, in the next exhalation phase, the 
exhaled air from filling the free space between half mask 22 and facepiece 
2. 
Still with reference to the inhalation phase, the vacuum originated inside 
half mask 22 actuates outflow valve 24 so as to create a perfect adherence 
of diaphragm 24a on edge 24c. In this way, the air present in outflow 
chamber 35, communicating with the external atmosphere, is prevented from 
being sucked int half mask 22. 
During the exhalation phase, the pressure produced in half mask 22 causes 
the closure of single acting valves 41 and the opening of outflow valve 24 
further to the detachment of diaphragm 24a from edge 24c. The air 
outflowing from outflow opening 23 fills outflow chamber 35 and transfers 
heat to the wall of partition 34. The condensate consequently deposited on 
partition 34 is released through discharge duct 36. 
Advantageously, partition 34 may be provided with a rib 42 extending 
vertically along a direction containing the axis of outflow valve 24 and 
having a terminal edge 42a situated near diaphragm 24a. Rib 42 reduces the 
opening of valve 24 to prevent a large part of the exhaled air from 
reaching communication opening or chamber 30 without skimming the wall of 
partition 34. 
The exhaled air, flowing along outflow chamber 35, passes also on 
separation wall 32, cleaning it from contaminating agents which may have 
deposited thereon. At last, the exhaled air is discharged outside through 
communication opening 30 and protection grate 31, as indicated by arrow B 
in FIG. 1. 
The present invention achieves its original objectives. In fact, the mask 
forming its subject matter is superior to the prior art with respect to 
functionality, practicality and comfort. 
In particular, the arrangements adopted in respect of nozzle 11, in the 
lower portion of which is situated the filtering element, have yielded a 
better distribution of the various parts of the mask and have eliminated 
the disadvantages, occurring in the conventional masks of the above type, 
of the downward limitation of the visual field of the user. 
Further, the position of the filter in the lower portion of the nozzle 
avoids the inconvenience in the prior art represented by the limitation of 
the efficiency of the phonic cap. Instead, the mask of the invention 
enhances its efficiency. In fact, in the mask according to the invention, 
sounds transmitted by the phonic cap may reach the external atmosphere 
directly through connection chamber 30. This has made possible a 
significant reduction in the size of the phonic cap, to the advantage of 
the single-acting outflow valve, which is provided with a circular 
diaphragm of comparatively large diameter. 
Further, the novel structure of the nozzle prevents the inhaled air from 
flowing directly into the highest portions of the facepiece. This enables 
a pre-heating of the inhaled air, which results in turn in an improved 
de-clouding action of the eye-pieces and in the elimination of any risk of 
freezing the operator's face. 
These results are enhanced by the particular construction of the facepiece 
and of the half mask, which appear able to induce the air to effect a long 
centripetal travel before reaching the eye-pieces. In particular, the 
structure of the outer portion of the facepiece permits the eye-pieces to 
be situated in close proximity to the user's eyes, so that he is able to 
use optical instruments with facility. 
Another important advantage of the present invention is provided by the 
structure whereby the exhaled air is discharged in the external atmosphere 
without skimming the surface of the filtering element. In this way, the 
formation of ice on the latter, in the presence of low temperatures, can 
be prevented. 
Further, the adoption of two different rubber compounds, vulcanized 
together to obtain the facepiece, gives rise to a very light and resistant 
structure of the overall mask without in any way diminishing its 
functional characteristics. Moreover, the presence of peripheral step 
portion 5a and of the supporting seat formed by first section 3b ensures 
the correct positioning of the hood of the protective garment on the mask. 
It should be noted that the above description and the accompanying drawings 
are merely illustrative of the application of the principles of the 
present invention and are not limiting. Numerous other arrangements which 
embody the principles of the invention and which fall within its spirit 
and scope may be readily devised by those skilled in the art.