US3815592A

US3815592A - Closed circuit breathing apparatus

Info

Publication number: US3815592A
Application number: US00358173A
Authority: US
Inventors: C Staub
Original assignee: Mine Safety Appliances Co
Current assignee: MSA Safety Inc
Priority date: 1973-05-07
Filing date: 1973-05-07
Publication date: 1974-06-11
Anticipated expiration: 1991-06-11
Also published as: DE2421297A1; DE2421297B2

Abstract

A plurality of chambers containing oxygen-generating and carbon dioxide-removing chemical have outlets connected with the inhalation tube of a breathing apparatus facepiece, and inlets connected by individual conduits to separate outlets in normally closed valve means provided with an inlet connected with the exhalation tube of the facepiece. Timing means operate the valve means to first connect the exhalation tube with only one of said conduits and then at regular intervals thereafter to connect it additionally with each of the remaining conduits in succession until it is connected with all of them simultaneously, thereby periodically reducing the rising breathing resistance of the apparatus.

Description

United States Patent [191 Staub, Jr. June 11, 1974 CLOSED CIRCUIT BREATHING Primary Examiner-Richard A. Gaudet APPARATUS Assistant Examiner-Henry J. Recla [75] lnventor: Charles H. Staub,.lr., Pittsburgh, Attorney" Agent or FlrmBrown Murray & 7 Pa Peckham [73 Assignee: Mine Safety Appliances Company, 5 7 I ABSTRACT I Pmsburgh A plurality of chambers containing oxygen-generating [22] Filed: May 7, 1973 and carbon dioxide-removing chemical have outlets I connectedwith the inhalation tube of a breathing ap- [211 App! 358l73 paratus facepiece, and inlets connected by individual conduits to separate outlets in normally closed valve [52] US. Cl 128/142, 128/ 191 means provided with an inlet connected with the exha- [51] Int. Cl. A62b 7/00, A62b 9/00 lation tube of the facepiece. Timing means operate the [58] Field of Search 128/142, 145, 140, 142.6, valve means to first connect the exhalation tube with 128/l46.6, 191, 202, 188, 142.4, 274; only one of said conduits and then at regular intervals l37/624.l8; 23/281 thereafter to connect it additionally with each of the remaining conduits in succession until it is connected [56] References Cited with all of 'them simultaneously, thereby periodically UNITED STATES PATENTS reducing the rising breathing resistance of the appara- 3,390,676 7/1968 Warneke 12s/|42.2

9 Claims, 3 Drawing Figures CLOSED CIRCUIT BREATHING'APPARATUS tubes are provided with the usual check valves (not When workers must carry out their duties in atmospheres containing noxious gases or lacking sufficient oxygen, they need to be equipped with breathing apparatus that will supply oxygen, or supply oxygen and also remove carbon dioxide, depending upon whether the apparatus is open circuit or closed circuit. Lightweight equipment for this purpose is available where the need is for only short periods of time up to about an hour in length. When the period of use is to beef longer duration, most breathing apparatus is heavy, bulky and not approved by Govemment agencies for more than three hours service.

In an attempt to provide closed circuit breathing apparatus that can be used for a long period and not have the disadvantages that standard apparatus has, breathing apparatus such as shown in- FIG. 3 of Bovard et al. U.S. Pat. No. 3,148,034 was designedxThat apparatus has three chemical canisters arranged in parallel and two of them are provided with spring-closed outlet valves in which the spring forces are different. A person using the apparatus first breathes only through the valveless canister until the breathing resistance therein builds up, due to the reaction of the chemical bed with a the moisture in the breath, until the air pressure at the inlets of the canisters is sufficient to open the valve of the second canister. Breathing then continues through both canisters but, of course, at the higher pressure. When the breathing resistance created by the second canister becomes still greater, the spring pressure holding the valve of the third canister closed will be overcome and breathing then will also occur through that canisterbut at the increased pressure. Such apparatus can be used for a considerably longer period of time than earlier apparatus, but it has the disadvantage that the continually increasing breathing resistance requires more and. more effort until it becomes considerable.

It is among the objects of this invention to provide closed circuit breathingapparatus which can be used for a long period of time without creating objectionable breathing resistance, and which makes maximum use of its chemical.

The invention is illustrated in the accompanying drawings, in which FIG. I is a perspective view;

FIG. 2 is an enlarged exploded plan view of the valve and timer of the apparatus; and

FIG. 3 is a schematic view of a modification.

Referring to FIG. 1 of the drawings, a casing 1 shown in dotted lines is provided with straps or the like (not shown) for carrying it on the back of a person who is to enter a hazardous atmosphere. Mounted inside the casing in any suitable manner is a chemical housing 2 provided inside with a plurality of spaced parallel vertical partitions 3 separating it into a row of chambers, four being illustrated. The bottom of the housing is provided with a separate inlet opening into the bottom of each chamber. The upper ends of the partitions, however, do not reach the top of the housing, so the tops of all of the chambers open into a common space in the top of the housing. The top wall of the housing is provided with an outlet connected by a short tube 4 to a breathing bag 5 that has an outlet connected to the flexible inhalation tube 6 of a facepiece 7 or mask of conventional form. This mask is likewise provided with a flexible exhalation tube 8 that extends down into casing 1 to the inlet of a second breathing bag 9. The two shown) which compel the air flow in only one direction through the tubes.

The outlet of the second or exhalation bag is connected by a conduit 11 to the inlet of a rotary valve 12 that has four different outlets, each of which is connected by a separate conduit 13 to the inlet of a different one of the chambers. The valve is of such construction that when operated it first connects its inlet with the outlet conduit 1 1 leading to the chamber at one end of housing 2 and then at regular intervals it connects its inletadditionally with each of the remaining conduits in succession until all of them are connected with the valve inlet at the same time in order to put the valve inlet in communication with all four chambers simultaneously. A valve suitable for this purpose is shown in more detail in FIG. 2. It has a cylindrical case 15 provided at one end with an inlet, from which a short tube '16 projects for connection to conduit 11 from the exhalation bag; Theside wall of this case isprovided at the top with a row of circumferentially spaced outlet openings 17 corresponding in number to the number of is provided with an arcuate slot 19, the width of which is at least as great as the diameter of the case outlets -17,

and the length of which is great enough to fully expose all four of those outlets to the inside of the closure memberwhen the slot is opposite them. To rotate this member, a short shaft 20,projects from its inner end wall and extends into a conventional spring-operated timer 21 that is attached in any suitable manner to the adjoining end of the valve case. The timer slowlyrotates the closure member at intervals in the direction of the arrow, so that the outlets of the valve are opened gradually and in succession. v

. Each of the chambers in the housing is nearly filled with a granular bed of a chemical 23 that ,will produce oxygen and absorb carbon dioxide when the user of the apparatus exhales into the chemical. The most suitable chemical is K0 although there are other alkali metal superoxides or peroxidesthat could be used, such'as sodium superoxide. Lithium peroxide and sodium peroxide also are satisfactory.

An air purifying canister normally will allow objectionable amounts of carbon dioxide to pass through it before its oxygen generating capacity is fully expended, with the result that the canister is taken out of service while it is still capable of generating oxygen. Therefore, to increase the service life of the canister it is highly desirable to spread over the top of the chemical just described a layer 24 of lithium hydroxide or other anhydrous CO absorber of light weight and high density to prevent build up of CO in the system as a result of flow of air through partially depleted beds, thereby permitting longer use of the beds.

At the start of the work period with this apparatus a chemical bed at one end of housing 2, such as the lefthand end, is placed on stream by turning the valve to connect its left-hand outlet with its inlet. At the end of a prescribed period of time (from thirty minutes to an open its outlet to the second chemical bed and in about thirty minutes the valve outlet to this bed is fully open.

The first bed remains on stream, so the air flow is split between the two beds, with a higher flow rate through the-second bed because of the increased resistance to flow caused by the reaction of moisture and CO in the breath with the chemical in the first bed. At prescribed time intervals the third and fourth beds are brought on stream in succession until all four beds are in use at the same time, with the major flow through the fourth bed. It will be seen that the breathing resistance in the circuit when only the first bed is on stream will gradually increase to a certain point, but that as soon as the second bed is switched into the circuit the breathing resistance will drop back again to what it was originally, or possibly lower since there are now two'beds in use. The breathing resistance again will increase as the chemical in the second bed is depleted, until the third bed isbrought on stream, whereupon the breathing resistance again will be reduced as before. The same thing will happen in connection with the fourth bed, so that by the time the fourth bed has completed its service the breathing resistance in the circuit should be no greater than it'was just before the second bed was switched in. The breathing resistance therefore goes up and down within acceptable limits instead of increasing steadily from start to finish.

7 Since the. valving is positively controlled by the timer, the production of oxygen by the canisters is under better control than in the Bovard patent, where with sufficiently high exhalation pressure (such as at a heavy work load) air can flow through all of the canisters at the same time even though the first canister may still be producing oxygen at a rather high rate. Therefore, the apparatus disclosed herein provides for better and more economical utilization of the chemical in the canisters.

It is desirable to load exhalation bag 9 to the equiva lent of one-half inch of water in order to ensure continuous flow of air through the canisters. One way of loading the bag is to place a tension coil spring 25 in the bag, with its opposite ends attached to the adjoining ends of the bag so as to urge them toward each other.

in the modification shown in H0. 3 there are again an 1 inhalation breathing bag 26 and an exhalation breathing bag 27, a valve 28 and a timer 29 for operating it. The housing for the chemical beds, however, is different from the one first described. in this modification, the housing is divided into two rows of chemical beds 30, preferably upper and lower, two being shown in each row by way of example. Each bed is supported by a screen (not shown) and the two beds in each row are separated by a solid vertical partition 31. The two partitions engage the upper and lower walls of the housing but are spaced apart. The tops of the upper beds are spaced from the top of the housing, and the bottoms of the lower beds are spaced from the bottom of the housingThe two rows of chemical beds are spaced apart to form an area between them that is exposed to all four beds. This open area is connected by an outlet 32 in one end of the housing with a conduit 33 leading to the inhalation breathing bag. The top and bottom of the housing are providedwith a total of four inlets 34, each for a different chamber. These inlets are connected by conduits 35 to the four outlets of the timer-operated valve 28, the inlet of which is connected by a conduit 36 with the exhalation breathing bag. This apparatus is used and operates in the sameway as the one first described. For the best temperature conditions, the two upper chambers in the chemical housing are placed in communication with thevalve inlet before the valve opens the conduits'to the lower chambers.

According to the provisions of the patent statutes, 1 have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. Howevenl desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. Breathing apparatus comprising a facepiece, an inhalation tube and an exhalation tube connected to the facepiece, a plurality of chambers containing oxygengenerating and carbon dioxide-removing chemical and having inlets and outlets, means connecting said outlets with the inhalation tube, a separate conduit connected to each of said inlets, valve means having separate outlets connected to said conduits and having an inlet, means connecting the exhalation tube with the valve inlet, said valve means being operable to place the exhalation tube in communication with said conduits, and timing means for operating said valve means to first connect the exhalation tube with only one of said conduits and then at regular intervals thereafter to connect it additionally with each of the remaining conduits in succession until it is connected with all of them simulta-.

neously, whereby rising breathing resistance is reduced periodically. v

2. Breathing apparatus according to claim 1, including a housing containing said'chambers in a row and having a wall provided with said chamber inlets, the housing having therein an open space between another wall and said chamber outlets, and said other wall being provided with an outlet connected with said inhalation tube.

3. Breathing apparatus according to claim 1, in which said connecting means includea first breathing bag be-' tween said chamber outlets and the inhalation tube,

and a second breathing bag between the exhalation tube and said valve inlet.

4. Breathingapparatus according to claim 1, includ ing a housing. containing said chambers and having a I and spaced circumferentially thereof, a hollow cylindrical closure member rotatably mounted in said case in engagement with said surface and having an'inlet in one end registering with said case inlet, the side wall of said closure member being provided with an arcuate slot positioned to register with said case'outlets as the closure member is rotated in the case, and means operatively connecting said timing means to said closure member to rotate the latter.

6. Breathing apparatus according to claim 1, including a housing containing said chambers, there being two rows of said chambers spaced apart with said chamber outlets opening into the space between said rows, a wall of the housing being provided with an outlet connecting said space with the inhalation tube, and two other walls of the housing being provided with said chamber inlets.

7. Breathing apparatus according to claim 6, in which one row of chambers is disposed above the other row, and said valve means is adapted to connect the exhalation tube with the upper row of chambers before connecting it with the lower row of chambers.

' breathing bag connecting the exhalation tube with said valve inlet.

9. Breathing apparatus according to claim 1, includ ing beds of carbon dioxide-removing material disposed between said chemical in said chambers and said inhalation tube.

Claims

1. Breathing apparatus comprising a facepiece, an inhalation tube and an exhalation tube connected to the facepiece, a plurality of chambers containing oxygen-generating and carbon dioxide-removing chemical and having inlets and outlets, means connecting said outlets with the inhalation tube, a separate conduit connected to each of said inlets, valve means having separate outlets connected to said conduits and having an inlet, means connecting the exhalation tube with the valve inlet, said valve means being operable to place the exhalation tube in communication with said conduits, and timing means for operating said valve means to first connect the exhalation tube with only one of said conduits and then at regular intervals thereafter to connect it additionally with each of the remaining conduits in succession until it is connected with all of them simultaneously, whereby rising breathing resistance is reduced periodically.

2. Breathing apparatus according to claim 1, including a housing containing said chambers in a row and having a wall provided with said chamber inlets, the housing having therein an open space between another wall and said chamber outlets, and said other wall being provided with an outlet connected with said inhalation tube.

3. Breathing apparatus according to claim 1, in which said connecting means include a first breathing bag between said chamber outlets and the inhalation tube, and a second breathing bag between the exhalation tube and said valve inlet.

4. Breathing apparatus according to claim 1, including a housing containing said chambers and having a wall provided with said chamber inlets, the housing having therein an open space between another wall and said chamber outlets, and said connecting means including a first breathing bag connecting said housing wall outlet with the inhalation tube, and a second breathing bag connecting the exhalation tube with said valve inlet.

5. Breathing apparatus according to claim 1, in which said valve means includes a case provided with a cylindrical inner surface, the case having said valve inlet in one end and having said valve outlets in its side wall and spaced circumferentially thereof, a hollow cylindrical closure member rotatably mounted in said case in engagement with said surface and having an inlet in one end registering with said case inlet, the side wall of said closure member being provided with an arcuate slot positioned to register with said case outlets as the closure member is rotated in the case, and means operatively connecting said timing means to said closure member to rotate the latter.

8. Breathing apparatus according to claim 6, in which one row of chambers is disposed above the other row, said valve means is adapted to connect the exhalation tube with the upper row of chambers before connecting it with the lower row of chamBers, and said connecting means include a first breathing bag connecting said housing wall outlet to the inhalation tube, and a second breathing bag connecting the exhalation tube with said valve inlet.

9. Breathing apparatus according to claim 1, including beds of carbon dioxide-removing material disposed between said chemical in said chambers and said inhalation tube.