US3776422A

US3776422A - Compressed gas breathing apparatus

Info

Publication number: US3776422A
Application number: US00301461A
Authority: US
Inventors: L Wise
Original assignee: Mine Safety Appliances Co
Current assignee: MSA Safety Inc
Priority date: 1972-10-25
Filing date: 1972-10-25
Publication date: 1973-12-04
Anticipated expiration: 1990-12-04
Also published as: DE2344150B2; JPS4973892A; CA971854A; FR2204970A5; JPS5717541B2; DE2344150A1; GB1427400A

Abstract

A pressure reducer is connected between a source of high pressure breathing gas and the inlet of a normally closed pneumatically operated control valve, the outlet of which is connected with a pressure reducing demand valve leading to a facepiece. A tube also connects the breathing gas source with another part of the control valve for holding the latter open as long as the breathing gas pressure remains above a predetermined value, whereby the control valve connects the pressure reducer with the demand valve. A normally closed pneumatically operated alarm valve also connects the pressure reducer with the demand valve, but is formed and constructed to be snapped open by the pressure drop across it only when the demand valve is opened while the control valve is closed due to reduction in the gas pressure below said predetermined value. The pulse of gas created every time the alarm valve opens signals the user that the control valve has closed.

Description

' 14 1 Dec. 4, 1973 COMPRESSED GAS BREATHING APPARATUS [75] Inventor: Layton A. Wise, Washington, Pa.

[73] Assignee: Mine Safety Appliances Company,

- Pittsburgh, Pa.

22 Filed: Oct. 25, 1972 211 App]. No.: 301,461

57 ABSTRACT A pressure reducer is connected between a source of high pressure breathing gas and the inlet of a normally closed pneumatically operated control valve, the outlet of which is connected with a pressure reducing demand valve leading to a facepiece. A tube also connects the breathing gas source with another part of the control valve for holding the latter open as long as the breathing gas pressure remains above a predetermined [52] US. Cl. 222/3, 222/39 value, whereby the control valve connects the Prey [51] lllt. Cl B6711 5/32 Sure reducer i the demand valve. A nofinally [58] Field of Search 222/39, 57, 3; closed pneumatically operated alarm valve also l 128/203; 137/557 nects the pressure reducer with the demand valve, but is formed and constructed to be snapped open by the [56] References C'ted pressure drop across it only when the demand valve is UNITED STATES PATENTS opened while the control valve is closed due to reduc- 3,524,424 8/1970 Roland et al. 137 557 x tion in the gas Pressure below Said predetermined 3,594,745 7/1971 Nickels 137/557 value. The pulse of gas created every time the alarm 3,584,596 6/1971 Westcott et al 222/3 valve opens signals the user that the control valve has closed.

Primary Examiner-Stanley H. Tollberg Attorney-Brown, Murray et al. 10 Claims 5 Draw'ng Figures ALARM-CONTROL VALVE 7 6 /0 CUM/ RESSED P DEMAND 0 2 6/15 30 VALVE L, J FACEP/ECE ALARM VALVE PATENTEBBEC 4M5 SHEET 16? 3 WQINRGGVK PATENTEUUEB 4197s sum 3 or 3 COMPRESSED GAS BREATHING APPARATUS In compressed gas breathing apparatus it is desirable to provide an alarm to warn the user when the gas pressure falls to a given low pressure so that he will know that he is running out of breathing gas. In one system a hell or whistle is sounded as the alarm, but such an alarm consumes too much of the valuable available gas. Also, under certain conditions, the signal may not be heard. In another system, high resistance to breathing is used as an alarm, but the intensity of the alarm is directly proportional to the rate of breathing, so during shallow breathing the alarm is weak and may be unnoticed. Such a system also has only one minor abrupt change in the breathing resistance. If the user is breathing shallowly when this change takes place, it may go unnoticed. Furthermore, such a system does not automatically reset. Failure to reset the alarm manually results in no alarm later. Finally, the increased resistance to breathing reduces the flow from the regulator.

It is among the objects of this invention to provide breathing apparatus having a low pressure alarm which is automatic, which does not impede the necessary flow requirements of the apparatus, which is not affected significantly by the depth of inhalation, which cannot be overlooked, and which automatically resets itself when the gas pressure is restored.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a diagrammatic view of the system;

FIG. 2 is an enlarged longitudinal section of the alarm-control valve in its open position;

FIG. 3 is a central longitudinal section of the closed alarm valve;

FIG. 4 is a side view, partly in longitudinal section, showing the alarm valve open; and

FIG. 5 is a fragmentary cross section taken on the line V-V of FIG. 4.

Referring to FIG. 1 of the drawings, the regulator of the compressed gas breathing apparatus is shown within the dotted line rectangle. This regulator is connected with a suitable source of compressed gas, such as a tank 1 of compressed air, and with a facepiece 2 or mask for the user of the apparatus. The regulator shown includes a pressure reducing valve 3, the inlet of which is connected with the compressed gas tank by a conduit 4. Assuming that the tank contains gas under a pressure of 2,000 psi, for example, the pressure reducer preferably reduces this pressure to between 65 and 80 psi. The outlet of the pressure reducer is connected by a conduit 6 to the inlet of a normally closed pneumatically operated alarm-control valve 7, the outlet of which is connected by a conduit 8 with the inlet of a'pressure reducing demand valve 9 of any suitable well-known construction. The outlet of the demand valve is connected by a hose 10 with the facepiece 2.

It is a feature of this invention that during normal operation of the breathing apparatus the high gas pressure at tank 1 maintains the alarm-control valve open so that gas can flow through it from the tank to the facepiece every time the wearer of the facepiece inhales, and thereby opens the demand valve. One way of keeping valve 7 open is to connect the first conduit 4 to the upper end of the control valve by means of a tube 12 to supply high pressure gas to that valve. As shown in FIG. 2, pressure acts on a piston 13 slidably disposed in an axial passage 14 of the valve housing and moves the piston downwardly. The enlarged base of the piston supports the upper end of a stem 15 that extends down through a sleeve 16 rigidly mounted in the housing. The lower end of the sleeve is provided with an inlet port 17 encircled at its lower end by a valve seat 18. The stem extends downthrough this port, with its lower end slidably mounted in a bearing 19 encircled by vertical openings 20. Between this bearing and the valve seat, a closure member 22 is rigidly mounted on the stem. In its lower position that is shown, the piston compressses a coil spring 23 encircling the stem between the bottom of the sleeve and a collar 24 threaded on the stem. By screwing the collar up or down the stem, the spring pressure can be adjusted so that the closure member 22 will be raised against the valve seat whenever the gas pressure above the piston falls to a predetermined value, such as 600 psi for example. The side of the sleeve is provided with outlet ports 25 that communicate with the outlet 26 of the valve housing.

Another feature of this invention is that when the pressure of the gas in the tank falls to a predetermined point or value as mentioned above, so that the user of the apparatus should be warned that his gas supply is giving out and he should either replace it or remove himself from the area in which he needs the breathing apparatus, he is warned of this situation automatically by the apparatus. Accordingly, an alarm valve 30 is connected into the system by a conduit 31 extending from this valves inlet to the outlet of pressure reducer 3 or to conduit 6 leading from that outlet. The outlet of the alarm valve is connected by a conduit 32 either with conduit 8 connecting the control valve with the demand valve, or directly to the demand valve itself. This alarm valve normally is closed as shown in FIG. 3 and is pneumatically operated to open it. It remains closed as long as the control valve is open but when that valve closes, due to a reduction in the gas pressure that was holding it open, the pressure drop across the alarm valve is increased to the point where the alarm valve opens every time the wearer of the facepiece inhales. Also, the alarm valve is so constructed that it opens suddenly with a snap action at the beginning of each inhalation, so that the user cannot help but notice at feel the momentary increase in flow of gas into his lungs every time he inhales. These repeated surges or pulses of gas provide a positive warning to him that he is inhaling through the alarm valve. To accomplish its purpose, the alarm valve may be constructed as follows.

As shown in FIGS. 4 and 5, the housing of the alarm valve has an inlet 35 at its front end and an outlet 36 at its back or downstream end. Inside the housing the marginal area of a closure-supporting diaphragm 37 is clamped. The central portion of this diaphragm is provided' with an opening and is clamped between a clamping ring 38 and an annular metal disc 39 provided with an axial passage 40 aligned with the diaphragm opening. Screws 41 extend through the ring and diaphragm and into the disc. Behind the disc there is a sleeve 42 encircled at its front end by a radial flange 43. The marginal area of a flexible diaphragm 45 is clamped between this flange and the disc by emans of circumferentially spaced screws 46. Between these screws the edge of the disc is notched and its front is provided with radial slots 47 that extend inwardly from the notches 48 to holes 49 extending through the disc around its central passage. Diaphragm 45 is a movable valve closure that is engageable with a valve seat 50 encircling the inner end of passage 40.

The back portion of sleeve 42 extends radially inward around an axially adjustable check valve body 51 provided with a central bore 52. There is a small clearance between this body and the sleeve, along which the sleeve can move back and forth. The front end of the inner part of the sleeve forms a check valve seat 53 that normally engages the back of a flexible valve disc 54 provided with a central stem 55 plugged into bore 52. Compressed between the front flange 43 of sleeve 42 and the rear wall of the chamber in which the sleeve is located there is a coil spring 56 that urges the sleeve and metal disc 39 toward their forward positions shown in FIG. 3, in which the alarm valve is closed. At this time the gas pressure at the inlet 35 and outlet 36 of this valve is substantially the same because control valve 7 is open. The flexible diaphragm 45 is held against its seat because the gas pressure between the diaphragm and the check valve behind it is substantially the same as the pressure at the alarm valve outlet 36.

Every time the wearer of the mask inhales, the demand valve 9 is opened and the pressure at its outlet is reduced to only a few inches of water as determined by the setting of that valve. Assuming the control valve 7 has just closed, each inhalation reduces the pressure in

conduits

8 and 32 for a moment to a predetermined value, such as 30 psi, which causes a pressure drop through the alarm valve so that support diaphragm 37 and metal disc 39 immediately move rearwardly against the resistance of the coil spring. This moves check valve seat 53 back away from valve disc 54 and therefore allows the gas pressure directly behind flexible diaphragm 45 to drop, whereupon gas pressure in front of the diaphragm unseats it as shown in FIG. 4 to oepn the valve. This opening of the alarm valve when inhalation occurs is very quick. It can be termed a snap action. Opening of the valve allows gas from inlet 35 to flow through disc passage 40 and into the space between the metal disc and the flexible diaphragm and then forward through holes 49 in the disc and radially outward through slots 47 and then back around the disc into the chamber behind it, from which the gas enters the outlet 36 of the valve.

The sudden surge of gas pressure above what it was a moment before the valve opened, and the resulting momentary increase in gas flow are felt in the lungs of the inhaler, which inform him of the fact that he is breathing through the alarm valve 1 and not through its control valve. This warns him that the primary supply of gas is becoming too low in pressure. As gas continues to flow from the alarm valve to the demand valve during the same inhalation phase, the demand valve recovers to control the pressure, resulting in the pressure at the outlet of the alarm building back up toward the pressure at the inlet so the coil spring can expand and move the metal disc forward to its front position, but the flexible diaphragm 45 remains ofi its seat because the gas pressure directly behind it still is not great enough to seat it. When the user stops inhaling and starts to exhale, the pressure at the alarm valve outlet becomes substantially the same as its inlet pressure so the pressure between the check valve and the diaphragm becomes great enough to force the diaphragm forward against its seat to close the alarm valve. This cycle is repeated every time the user inhales, so he soon, if not immediately, becomes aware of the fact that he is inhaling through the alarm valve.

It will be seen that breathing gas is not wasted in operating the alarm, and that the alarm valve resets itself at the end of each inhalation. The alarm device does not impede the necessary flow requirements of the apparatus, and the strength of the alarm pulse is not affected significantly by the depth of inhalation. The control valve reopens automatically when the tank pressure is renewed to raise it above the alarm pressure.

If a pressure reducing demand valve is used that can handle the high tank pressure, the first pressure reducer 3 can be eliminated, but this would require a modified alarm-control valve through which the high tank pressure gas could flow. Or, pressure reducer 3 could be placed between the demand valve and

conduits

8 and 32.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I 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. Compressed gas breathing apparatus comprising a conduit with an inlet for connection to a source of breathing gas under high pressure, a normally closed pneumatically operated control valve with an outlet, a normally closed pneumatically operated alarm valve with an outlet, a pressure-reducing demand valve having an inlet connected with said valve outlets and having an outlet for connection to a facepiece, gasconducting means connecting the outlet of conduit with the inlets of said control and alarm valves, said control valve containing pneumatic pressure actuated means for holding it open as long as said gas pressure remains above a predetermined value to thereby connect said conduit with the demand valve, the alarm valve being formed and constructed to be opened abruptly by the pressure drop across it every time the demand valve is opened while said control valve is close due to reduction in said gas pressure below said pre-determined value, whereby to create a pulse of gas at the outlet of the demand valve that will signal the user of the apparatus that the control valve has closed.

2. Compressed gas breathing apparatus according to claim 1, in which said gas-conducting means is a pressure reducer.

3. Compressed gas breathing apparatus according to claim 2, including a tube connecting said conduit with said pressure actuated means in the control valve for applying said gas pressure thereto to hold the control valve open.

4. Compressed gas breathing apparatus according to claim 3, in which said control valve includes a valve port encircled by a seat between the inlet and outlet of that valve, a closure member, and a spring normally holding said closure member against said seat, and said pressure actuated means includes a piston operatively connected with said closure member for moving it away from said seat against the resistance of said spring, the control valve having a passage connecting said tube with said piston.

5. Compressed gas breathing apparatus according to claim 4, including means for adjusting the pressure exerted by said spring, whereby to control said predetermined value of said gas pressure.

6. Compressed gas breathing apparatus according to claim 4, including a stem extending through said valve port and rigidly connected to said piston and closure member.

7. Compressed gas breathing apparatus according to claim 4, including a stem extending through said valve port and rigidly connected to said piston and closure member, and a collar threaded on said stem, said spring being a coil spring encircling said stem and compressed between said collar and valve port.

8. Compressed gas breathing apparatus according to claim 1, in which said alarm valve includes a valve seat, a diaphragm between the seat and the valve outlet, a normally closed chamber having said diaphragm as one wall whereby a predetermined gas pressure in the chamber will hold the diaphragm against said seat to maintain the valve closed, a normally closed check valve for said chamber, and means actuated by said pressure drop for opening said check valve so that the gas pressure at the valve inlet will force the diaphragm away from its seat.

9. Compressed gas breathing apparatus according to claim 8, in which said check valve includes a closure member and movable valve seat normally engaging each other, and said check valve opening means includes means supporting said first-mentioned seat for movement toward the valve outlet when said pressure drop occurs, and means connecting said supporting means with the check valve seat for moving it away from said closure member.

10. Compressed gas breathing apparatus according to claim 9, in which said supporting means includes an annular disc provided with an axial passage encircled by said first-mentioned seat, and a diaphragm supporting said disc and provided with a central opening aligned with said passage, the alarm valve also including a spring urging said check valve seat toward said closure member. v

Claims

1. Compressed gas breathing apparatus comprising a conduit with an inlet for connection to a source of breathing gas under high pressure, a normally closed pneumatically operated control valve with an outlet, a normally closed pneumatically operated alarm valve with an outlet, a pressure-reducing demand valve having an inlet connected with said valve outlets and having an outlet for connection to a facepiece, gas-conducting means connecting the outlet of said conduit with the inlets of said valves, said control valve containing pneumatic pressure actuated means for holding it open as long as said gas pressure remains above a predetermined value to thereby connect said conduit with the demand valve, the alarm valve being formed and constructed to be opened abruptly by the pressure drop across it every time the demand valve is opened while said control valve is close due to reduction in said gas pressure below said pre-determined value, whereby to create a pulse of gas at the outlet of the demand valve that will signal the user of the apparatus that the control valve has closed.

10. Compressed gas breathing apparatus according to claim 9, in which said supporting means includes an annular disc provided with an axial passage encircled by said first-mentioned seat, and a diaphragm supporting said disc and provided with a central opening aligned with said passage, the alarm valve also including a spring urging said check valve seat toward said closure member.