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The present inven-tion relates yenerally to the field of self-contained breathing apparatus, and more par~
ticularly to closed-type, oxygen breathing apparatus.
Various types of apparatus are known for enabling a user to live and function in hostile atmospheres contain-ing poisonous materials or containing insufficient oxyg~n to sustain life. One familiar example of such apparatus i9 the pumPed air sYstem used by suited, underwater di~ers.
Currentl.y more common are portable, Aqua-lung or SCUBA (Self Contained Underwater Breathinq Apparatus) gear used by free divers and in similar form, by fire fighters in many hazardous situations. Typically, scusA-type apparatus employ a relatively large compressed air tank, a mouthpiece or face mask being connected to the -tank through a flow regu-lator - usually of a demand type. With such apparatus, users inhale from the tan~ and exhale into the ambient atmosphere.
Currently, there exist requirements in the United States by MSHA (~ine Safety and Health Administration), that portable lightweight, self-contained emerc~ency breathing apparatus, having at least one hour capacity, be provided for all underground users in this country. SCUB~-type breath-ing apparatus, which may be considered "open" systems because users exhale into the ambient, are generally unsatisfactory for such an application because of the relatively large size and weight of the apparatus necessary to provide a one hour breathing capacity. Con~equently, alternative, more compact and light weight, breathing apparatus are preferred for appli-cations requiring relatively long breathing capacity.
Some types of portable oxygen breathing apparatus are constructed to provide breathable oxygen generated as a chemical reaction product~ ~hereby ordinarily eliminating the need for pressurized oxygen tanks. However, because oE
the type o~ chemical reactants used, such apparatus tend to be considered potentially unsafe~ To applicant's knowledge, no oxygen-generating breathing apparatus for one hour duration have been approved for emergency use by NIOSH (National Insti~
tute for Occupational Safety and Health~ and MSHA (Mine Safety 10 and ~lealth Administration~.
Portable oxygen breathing apparatus are more typi-cally constructed to use gaseous oxygen from one or more pressure tanks. In some systems a user breathes from the tank and exhales into the atmosphere; however, this is waste-ful of the oxygen. Preferably, closed systems are used in which oxygen from a tank is mixed with a user's exhaled breath i before breathing. Scrubbers or chemical absorbers are pro-vided to reduce ~he concentration of exhaled carbon dioxide to an acceptable level. Ordinarily in such closed-type systems 20 pre-breathing mixing of pure oxygen and scrubbed, exhaled breath is accomplished in a flexible bag.
However~ heretofore available closed oxygen tank breathing apparatus have, for various reasons, not been entire-ly satisfactory; hence, substantial improvements are required to provide the safe, reliable emergency breathing apparatus required for life endangering situations. For example, some heretofore available closed oxygen apparatus have had rela-tively exposed, and hence relatively easily damaged, mixing bags. Also, ~any known apparatus are constructed so that a 30 user inhales, as well as exhales, through the carbon dioxide :' scrubber, thereby permi~ting excessive amounts of unabsorbed carbon dioxide to be inhaled.
Some available types have relied, to obtain one hour breathing capacity, upon low oxygen flow rates~ thereby requiring complicated and expensive demand regulators. Other types have been constructd as "throw away" apparatus and are relatively expensive, since they are non-replaceable aEter use. In addi~ion, these "throw away" apparatus cannot be periodically serviced or recharged as may be necessary to lO maintain required high levels of reliability.
For these and other reasons, applicant has invented a greatly improved, closed~type, oxygen breathing apparatus in which, for example, the hreathing bag is protected against damage and in whlch danger of rebreathing exhaled carbon dioxide is substantially eliminated.
According to the present invention, a self-contained, closed-type breathing apparatus comprises a flexible breathing bag, a pressure container adapted for containing a breathable gas under pressure, and a scru~ber for absorbing carbon dioxide 20 from a user's breath that passes therethrough. Means are included for mounting the pressure container and scrubber within the breathing bag. Actuable flow control means are connected to the pressure container for regulating 10w of gas from the container into the breathing bag and means are connected to the scrubber for enabling a user to exhale into the breathing bag therethrough and to inhale directly from the breathing bag. 5ealing means are provided Eor sealing the breathing bag against the outside atmosphere to thereby enable a user to exhale into, and inhale from, the mixing bag without exhaling into, or inhaling from, th~ ambient atmosphere More particularly, the means connected to the scrubber includes first and second check valves~ the first check valve causing a user to exhale into the brea~hing bag through the scrubber and the second check valve causing the user to inhale directly from the mixing bag withou~ inhaling through the scrubber.
The pressure container is par~icularly adapted for 1~ containing gaseous oxygen and the flow control means is con-figured for regulating pressure and flow of oxygen from the pressure container into the breathing bag, preferably at a ~ate of approximately three liters per minute~ Carbon dioxide is absorbed in the scrubber by a commercially available chem-ical sold under the name "5Oda Sorb" by Dewey and Almey di-vision of W~ R. Grace. The chemical is basically sodium hydroxide and calcium oxideO
To enable a breathing time of at least about one hour, the pressuxe container is configured to contain enough 20 oxygen at a pressure of abou~ 2000 psi to supply 200 liters of oxygen to the breathing bag at a pressure o~ about 2 inches water column, the breathing bag being configured to contain approximately 5 liters of breathable gas. The scrubber is configured to contain at least about two pounds of suitable chemical, such as Soda Sorb. For such configuration the apparatus has an approximate weight of about eight pounds.
A protective cover is provided for enclosing the mixing bag to prevent damage thereto, and means are provided for enabling a user to conveniently carry the apparatus.
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Preferably, the flow con~rol means is confiyured for enabling recharging of the pressure container with oxygen (or other breathable gas) and the scrubber is constructed to be replaceable after use.
~ ecause of mount;ng the oxygen pressure container and scrubber inside the breathing bag~ the slze of the appa--ratus can be smaller and more compact than heretofore availa-ble emergency breathing apparatus of comparable capacity, thereby being particularly advantageous in such places as 10 mines where space is ordinarily restricted. The check valve arrangement in the breathing portion requires that all a user's exhaled breath pass through the sfrubber for carbsn dioxide absorption; whereas, the user inhales direc-tly from the breathing bagr bypassing the scrubber, so that reinhaling carbon dioxide, still incompletely absorbed in the scrubber, is prevented.
Construction of the apparatus with the pressure container and scrubber disposed inside the breathing bag, as well as enclosing the brea~hing bag by the external protective 20 cover, prevents damage to the bag~ such as puncturing by sharp objects of the type commonly found, for example, in mines.
Applicant' 5 apparatus is also adapted, because of its comparative light we;ght and long breathiny capacity, for many applications other than mine safety.
In addition to increasing breathing time capacity, by recycling portions of a user's breath, the essentially closed nature of the apparatus makes it useful for appli-cations in which exhaling into the surrounding atmosphere is 30 undesirable. 6 Since the pressure container is rechargeable through the 10w control means and the scrubber is replaceable~ the apparatus can easily be made reusable after use and may be periodically serviced to assure readiness for emergency use As a result, the apparatus is very cost effective.
A better understanding of the presen~ invention may be had from a consideration of the following detailed description, taken in conjunction with the accompanying drawings in which:
Figure 1 is a partially cut away perspective drawing showing general features of a portable, self-contained closed-type, pressurized oxygen breathing apparatus according to ; the present invention;
Figure 2 is a parkial c.ross-sectional view, taken generally along line 2-2 of Figure 1, showing internal con figuration of the breathing apparatus of Figure 1, and in particular an exhaling and inhaling check valve configuration;
Figure 3 is a cross~sectional view, taken along line 3-3 of Figure 2, showing features of oxygen flow control 20 portions of the breathing apparatus;
Figure 4 is a cross-sectional view, taken along line 4-4 of Figure 2, showing internal construction of the oxygen flow control portion;
Figure 5 is a cross-sectional view, taken along line 5-5 of Figure 3, also showing additional internal con-struction of the oxygen flow control portion; and Figure 6 .is a cross-sectional view, taken along line ~-6 of Figure 2, showing const r uc tion of scrubbing, i.e., carbon dioxide absorbing, means of the breathing appa-30ratus.
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As shown generally .in Figure 1, a portable, self-contained, closed type pressurized oxygen breathing apparatus 10, according to the present invention, comprises a gaseous oxygen pressllre container, -tank or cylinder 12, to an open end of which is connected an oxygen flow control system 1 Included in the apparatus 10 are a carbon dioxide absorber or scrubber 16, to which are connected a breathing assembly 18 which includes check valve structure 24, associated with the scrubber assembly for controlling the flow path of a 10 user's exhaled and inhaled breath, a flexible breathing tube ~6 connected to the check valve structure, and a user breathing end portion 28, which mayl for example, comprise a generally conventional face mask adapted for covering a user's eyes, nose and moutb, or more prefererably, a mouthpiece and nose clip of known design.
Further comprising the breathing apparatus 10 is a generally rectangular, flexible breathing bag 34. Rigid, generally rectangular, mount.ing structure 36 is provided for mounting the oxygen cylinder 12, flow control system 14, the 20 scrubber 16 and the check valve structure 24 i.n f.ixed relative relationshipl with the oxygen cylinder and the scrubber dis-posed in side-by-side spaced apart relationship entirely within the bag. The mounting structure 36, which is a plate-like affair, also forms an upper closure for the breathing bag 34.
Surrounding the breathing bag 34, to provide pro-; tection therefor, is a rigid external canister or cover 38, o~ suitable non-frangible material, such as ABS plastic, releasably at~ached to the periphery of the mounting structure 3~.6.by a plurality of conventional, spring-type, clamps 40.
A suitable ~eal, described below, is provided at the upper peripheral edge of the breathing bag 34, between the mounting structure 3~ and cannister 38 when the cannister is attached, thereby isolating interior regions of the breathing bag from the surrounding ambient atmosphere.
Wearing or carrying of the breathing apparatus 10, is enabled by a shoulder strap or harness 42, pre~erably attached to upper sides of the apparatus in regions of the mounting structure 36.
As shown, the breathing apparatus 10 is completely self-contained, with the oxygen tank 12 and scrubber 16 mounted entirely within the breathing bag 34, the bag being in turn, protectively disposed within the cannister 38. In a manner more particularly described below, oxygen from the tank 12 is mixed or combined in the breathing bag 34 with a user's scrubbed and filtered exhaled breath. Thus, the apparatus ` 10 is a closed breathing system in which the user breathes into and from the breathing bag.
; As an illustrative example of size of the apparatus 20 10, to provide a one hour breathing capacity, overall apparatus dimensions are only approximately 16-3/4" high by 11-3/8"
wide by 6-1/2~' deep, with a total weight of only approximately 8 lbs.
More particularly shown in Figures 2 and 3, the oxygen cylinder or tank 12 preferably comprises a conventional compressed-oxygen bottle having, for example, to meet a one hour breathing requirement, a capacity of approximately 247 liters, but at least about 200 liters, at breathiny pressure.
For such capacity, the tank 12 may therefore be a standard 30 medical size, about 11" in height and 4-1/4" in diameter~
The conten~s are pressurized to abou~ 2000 psig and the oxygen is released at a flow rate of approximately three liters per minute, into the breathing bag 34 through the control system 14.
As shown in Figures 4 and 5, the flow control sy,stem 14 comprises a housing 50 having a depending oxygen-bottle-connecting portion 52 formed with an internally threaded bottle connec~ing aperture 54. Threaded in~o the aperture 54 is a male adapter or connecting fitting 56 (see also Figure 10 2) onto lower regions of which the oxygen -tank 12 is threaded~
From the aperture 54, a small diameter oxygen ~low bore or aperture 58 is formed upwardly (in the vertical orientation shown in the Figures) through the housing 50 into communi-cation with a deep cylindrical recess 60. ~xtending ~hrough a side region of the housing 50 to ~he flow aperture 58 is an aperture 62 in which a pressure gauge 64 is threaded to indicate the pressure i.n the bore 58.
Formed through ~he housing 50, at right angles to the gauge-communicating aperture 62, is a pressure-relieE
20 bore or aperture 66 (Figure 5) which also extends to the bore 58. Threaded .into an outer end of the pressure relief bore 66 is a conventional burst or rup~ure diaphragm assembly 68 constructed to rupture at an oxygen tank pressure less than that which would cause system damage. For e~ample, for a 2015 psi opera~ing pressure in the tank 12, the diaphragm assembly 68 is preferably selected to have a burst pressure rating of approximately 3000 ps.i.
Oxygen flow through the ~low bore 58 is alterna-tively blocked or enabled by a manually actuated pull valve 30 70, a threaded bushing or outer sleeve portion 72 of which ~3(~
is threaded into the recess ~0~ Slidably mounted through an axial bore 74 of the bushing 72 is an elongated stem 76~ An upper end of the stem 76 is retained in a recessed region 78 of a pull cap 80, by a snapriny 82 so -that a sharp axial pull on the pull cap, upwardly in the direction of ~rrow "A", pulls the stem outwardly away from the :Elow bore 5~.
As this occurs, a pin-type orifice seal 90, which during non-use seals the upper end of the flow bore 58 and prevents oxygen 10w, is pulled out of sealing relationship with the 10 ~low bore, thereby permitting flow o~ oxygen from the tank 12 through such aperture and subsequently into the breathing - bag 34~ as described below. A coil spring 92 radialy disposed between the bushing 72 and lower regions of the stem 74 ordi-narily forces the stem downwardly with sufficient force to cause the orifice seal 90 to completely seal the flow aperture 58 until the pull cap 80 is actuated to initiate oxygen flow.
Because of small area size oE the orifice seal 90 against which tank oxygen pressure acts, the spring 90 is sufficiently strong to cause sealing of the flow aperture 58 during non-20 use. When, however, the pull cap 80 is pulled upwardly raising the stem 74, oxygen pressure acts upon a larger area, lower surface 92 of the stem 74 to keep the stem in a lifted con-dition permitting oxygen flow.
Also comprising the flow control assembly 14 are a flow regulator piston assembly 94 and end cap assembly 96, both of which are ins~alled in a deep, cylindrical recess 98 ~ formed into the housing 50 from a side region opposite the : gauge-communicating aperture 6~ (Figure 4). The end cap assembly 96, which is retained in the recess 98, and the 30 axial length of the piston assembly 94, are selected and ~;' 11 arranged to permit lim.ited axial movement of the piston a5-sembly after the cap as~embly 96 is installed.
Included in the flow regulator piston assembly 94 is a piston guide 100 and a piston 102, which are urged axially apart by inner and outer coil springs 108 and 110, respective-ly .
For~ed almost entirely through the piston 102, from an outer end and along the axis thereof, is a small diameter b~re 112. An inner end of the bore 112 communicates 10 with a small di~le~er, transverse aperture or bore 114, formed through a small dia~eter piston inner end region 116. An outer end of ~he bore 112 communicates with an axially shor~, disc-shaped pressure chamber 118 defined between the piston 102 and the end cap assembly 96.
A small diameter flow metering orifice 126 is formed axially through the piston guide 100. When the piston 102 is pushed as far as possible into the housing by oxygen pressure in the chamber 118, as described below, the metering orifice 126 is sealed oEf by a metering pin end or inner region 116 20 of the piston 102. However, the springs 108 and 110 normally urge the piston 102 outwardly towards the cap assembly 96, leaving the metering oriEice 126 open in the absence of any oxygen flow through the flow control system 14.
Flow rate from the tank 12 into the breathing bag 34 is determined by adjustable metering pin or valve 128 threadably installed in an aperture 130 formed axially through the cap assembly 96~ An inner flow metering end of the pin 128 controls oxygen flow through a metering ori.fice portion 132 of the aperture 130.
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A side bore 134 formed radially through the cap assembly 96 communica~es from the aperture 130 adjacent the orifice portion 132 to an aperture 136 formed through the housing 50, such aperture communicating with an a]igned aper-ture (not shown~ formed through the mounting structure 36, which is flush against the housing 50, as shown in Figure 2, to communicate with the bay 34. Similarly, a pressure balanc-ing aperture 140, formed through the housing 50 enables pressure communication between a chamber 142 (defined between ~he 10 piston guide 100 and piston 102) and the breathing bag 341 through an aligned aperture (not shown) formed ~hrough the mounting structure 14~
Communicating between the piston guide metering orifice 126 and the flow bore 58, when the pull cap 80 is pulled up to start oxygen flow from the tank 12, is an L
~haped housing bore or aperture 146.
Conventional "O" ring sealing means comprising individual "O" ring seals (not individually identified~ in-stalled between moving parts of the flow control system 14 20 prevent oxygen leakage from the housing 50 and between differ-ent regions thereof.
Pressure filling of the oxygen tank 12, through the flow control system 14, is enabled by a generally conven-tional check-type fill valve 154 threadably installed in a housing apeture 156 which communicates with the flow bore 58. Except when filling the tank 12, a pressure cap 158 closes and protects the fill valve 154. Retaining means 160, ~or example, a flexible cable or cord~ attached between the cap 158 and othee portions of the housing 50 or the moun~ing 0 means 14 prevents loss of the cap.
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As mentioned, under non use conditions and until the pull cap 80 is pulled upwardly in the direction of arrow "A"~ the spring 92 forces the s~em 76 into sealing relation-ship with the flow aperture 58. When ~he cap 80 is pulled upwardly with a force of about 1~ pounds, oxygen from the tank 12 is permitted to flow through the aperture 58. There-after, tank pressure on the s-tem 76 keeps the stem from re-sealing the aperture 58 unless the pull cap is returned to its initial closed position or -the tank pressure is reduced : la to less than about 100 psi.g.
With the aperture 58 held open in this manner, oxygen flows from the tank 1~ through such aperture and through the L-shaped opening 146 now in communicati.on therewith to the piston guide metering orifice 126~ Oxygen thence flows through the metering or.iEice 126, around the inner, metering pin end, of the piston 1.02, through ~he apertures or bores 114 and 112 into the pressure chamber 118 between the pi.ston and the end cap assembly 96.
From the chamber 118, oxygen flows through the 20 orifice portion 132 anc3 the apertures 130, 134~ and 136 into the mixing bag 34.
According to pressure in the breathing bag 34, as directed through the aperture 140 to the chamber 142 between the piston 102 and piston guide 100, rela~ive to pressure in the pressure chamber 118, the piston is axially moved in a manner metering or controlling oxygen flow through the meter-ing orifice 126. In this regard, pressure in the chamber 142 acts on a lesser area of the piston 102 than does the pressure in the chamber 118, a sensitive balancing being 30 provided to regulate flow o~ oxygen into the bag 34 at an 33~
average predetermined ra-te of about three liters per minute in the preferred embodiment, as determined by adjustment oE
the manually adjustable metering pin 128 in the end cap as-sembly 96, while maintaining a desirable pressure .in the bag of approximately .054 psiy (1-1/2l' of water~ in the preferred embodiment.
Returning to Figure 2, the check valve structure 24, which is mounted on the mounting structure 36, includes a depending portion 168, which extends through the moun-ting 10 structure into the mixing bag 34. An internally threaded aperture 170 in the por~ion 168 releasably receives an upper threaded neck portion 172 of the scrubber 16.
A first, flapper-type check valve 174 is disposed in a fîrst chamber 176 formed in a check valve housing as-sembly 178. The chamber 176 communicates in a lower region with the aperture 17Q and in an upper region with a second : large, generally disc-shaped chamber 180. The first check valve 174 controls flow through an aperture 175 between the chambers 176 and 180.
The second chamber 180 communicates between an end connector 182 of the breathing tube 26 and an aperture 184 formed through the mounting structure 36 into the inside of the breathing bag 34t but outside of the scrubber 16. A
second check valve 185 is installed at the aperture 184 to control direction of air flow therethrough.
In operation, when a user exhales into and through the breathing tube 26, the second check valve 186 is forced closed to seal off the aperture 184 leading from the tube directly into the breathing bag 34. Simultaneously, the 30 first check valve 174 is forced open, causing the user's ~13~
exhaled breath to ~low, ln the direc~lon of ~rrow 'IB", through the apertures 175 and 170 and into inter:ior regions of the scrubber 16~
Conversely, as the user inhales through the breath-ing tube 26, the Eirst check valve 174 closes, preventing inhaling back through the scrubber 16. Simultaneously, the second check valve 186 opens, enabling the user to inhale directly rom the breathing bag 34, through the aperture 184 (direction of Arrow l'C'I), thus, a user's exhaled breath is 10 forced through the scrubber 16 for absorption of car~on di-oxide therefrom; whereas, the inhaled breath bypasses the scrubber, breathable air being drawn directly from the bag 34.
This feature has an important advantage of assuring that no carbon dioxide from the user's exhaled breath is re-inhaled, at least so long as chemical absorbing agents in the scrubber mean~ remain active. In contrast, iE the user were to inhale back through the scrubber 16, unabsorbed carbon dioxide temporarily entrapped in the absorbing agents, before 20 complete absorption, would be drawn back out of the scrubber for rebreathiny. This would ordinaril.y increase the conkent of carbon dioxide in the inhaled air substantially above the allowable 0.2 percent permitted by governing regulations.
Installed through the housing assembly 17B, in communication with the second chamber 180, is a pressure relief valve 192 set at slightly above the desired breathing bag pressure of .054 psig. Thus, the user is protected against : over-pressure in the breathing bag 34 from the source 12, which in operation supplies oxygen at a rate sufficient to 30 allow the user to engage in the necessary activityt which 1~
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may be greater than ~he actual consumption of oxygen at any given time and the bag is~ as well, protected against pressure damage.
Comprising, as shown in Figure 6, the scrubber 16, is a slotted or perforated, tubular axial member 194, which extends the entire height (axial length) of the scrubber and which i5 closed r at a lower end, by a plug 196. An upper end of the member 19~ comprises the above-mentioned upper end or neck portion 172 of the scrubber 16~
Disposed around the member 194, along the axial ; length thereof, is an inner screen 198 which is spaced radi-ally outwardly from major portions of the member by narrow annular bosses or flanges 200 formed around the member. Spaced radially outwardly from ~he inner screen 198 is an outer screen 202, which has wrapped therearound a dust filter 204.
Packed between the two screens 198 and 202 is a granular chemical agent 206. Maintaining the screens 198 and 202, the filter 204, and agent 206, in position and closing the scrubber 16~ i5 an annular upper closing cap or disc 208 20 and an annular lower closing cap or disc 210.
Configuration of the scrubber 16 is thus such that : a user's exhaled breath travels down the inside of the member 194 and generally radially outwardly therethrough (Arrows "B")p passing also, in order, through the inner screen 198, ~he agent 206, the outer screen 202 and the filter 204 into the breathing bag 34.
Purpose of the screens 198 and 202, which may, as ~: an illustration, be formed of number 20 mesh, type 304 stain-less steel wire, is to contain the chemical agent 206~ The 30 filter 204, which may, for example, be Eormed of 3/16" thick felt, traps any exhaled dust particles within the scrubber means. Structural parts of the scrubber 16 may be macle from ABS plastic.
In operation, exhaled carbon dioxide passing through the chemical agent 206 reacts with the sodium hydroxide to form sodium carbonate, being thereby absorbed. Exhaled air passiny through the scrubber 16 thus comprises mostly nitrogen, with some traces of oxygen and carbon dioxide As the carbon dioxide reacts with the sodium hydroxide 7 the sodium hydroxide 10 iS de-activated.~l Initially, the calcium oxide absorhs moisture from the user's exhaled breath, thereby preven~ing moisture pick up by the sodium hydroxideO In the process, the calcium oxide is converted to calcium hydroxide which subsequently functions as a carbon dioxide absorber until all the calcium hydroxide is converted into calcium carbonate.
It has been determined that for a one hour breathing capacity, the chemical agent 206 should comprise about two pounds of Soda-Sorb, residing in a scrubber having an outer 20 diameter of about 4'~ and an axial length of about 8-1/2" in the preferred embodiment.
Consistent with the above mentioned size of the scrubber 16 and the oxygen tank 12 for a one hour breathing capacity, the breathing bag 34 is preferably formed having a total volume, when c]osed at the top by the mounting structure 36, of abou~ lQ liters, thereby providing an actual breathing air volume of about 5 to 5.5 liters. Preferably, the breathing bag 34 is formed of thin aluminum coated Mylar preferably .001 inch in thickness.
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Sealing of upper edge regions at the breathing bag 34 between the mountiny structure 36 and the external pro-tective cover 38 is by a circumEeren~ial neoprene seal 212.
A5 a result of the shown and described configuration, the self-contained breathing apparatus 10, even when having a one hour breathing capacity, is compact and light in weight as is important in many~ if not mos~, emergerlcy situations requiring use of the apparatusO Operation of the apparatus 13 is sa~e in that inhaled levels of carbon dioxide are assured 10 to be at low levels due to bypassing of the scrubber 16 during inhaling. The breathing bag 34 is relatively pro~ected against damage by being completely enclosed by the cover 38 and the mounting structure 36.
And since the oxygen cylinder 12 is easily recharged through the flow control system 14 and the scrubber 16 is replaceable aEter use, the apparatus 10 is reusable and is serviceable during prolonged periods of non-use, thereby assuring safe, reliable operation and causing the apparatus to be cost effective~
Although there has been described above a specific arrangement oE a closed type, portable breathing apparatus using pressurized oxygen in accordance with the invention for purposes of illustrating the manner in which the invention may be used to advantage, it will be apprecia-ted that the invention i5 not limited thereto. Accordingly, modifications, variations or equivalent arrangements may be made therein by those skilled in the art without departing from the scope of i the invention defined in the appended claims.
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