U.S. patent number 3,776,422 [Application Number 05/301,461] was granted by the patent office on 1973-12-04 for compressed gas breathing apparatus.
This patent grant is currently assigned to Mine Safety Appliances Company. Invention is credited to Layton A. Wise.
United States Patent |
3,776,422 |
Wise |
December 4, 1973 |
COMPRESSED GAS BREATHING APPARATUS
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.
Inventors: |
Wise; Layton A. (Washington,
PA) |
Assignee: |
Mine Safety Appliances Company
(Pittsburgh, PA)
|
Family
ID: |
23163471 |
Appl.
No.: |
05/301,461 |
Filed: |
October 25, 1972 |
Current U.S.
Class: |
222/3;
222/39 |
Current CPC
Class: |
A61M
16/0051 (20130101) |
Current International
Class: |
A61M
16/00 (20060101); B67d 005/32 () |
Field of
Search: |
;222/39,57,3 ;128/203
;137/557 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tollberg; Stanley H.
Claims
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, 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.
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.
Description
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 bell 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 down through 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 valve's 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 off 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.
* * * * *