Safety Apparatus For Oxygen Supply System

Abstract

There is disclosed a safety device for use in a pulsed oxygen system for preventing a rapid build-up of partial oxygen pressure causing oxygen toxicity in the event a normally closed (or open) solenoid control oxygen supply valve fails and remains or sticks open. Following the regulator and shutoff valve on the oxygen circuit from a high pressure oxygen supply is a restricted passageway means which may be either an orifice or a capillary tube. Intermediate the restricted passageway means and the control valve is an accumulator means so that in the event the control valve fails and sticks open, the oxygen is admitted to the gas system at a metered rate. However, this rate is sufficient to supply the gas circuit with adequate oxygen when the valve is pulsed open.

Parent Case Text

This application is a continuation-in-part of application Ser. No. 6,387, filed Jan. 28, 1970.

Description

This invention in general relates to underwater breathing apparatus, and in particular, to an oxygen safety apparatus for use in closed circuit or semi-closed circuit self-contained underwater breathing systems.

In self-contained underwater breathing apparatus, the diver is provided with a mouthpiece or breathing mask and a breathing circuit connected to the mouthpiece having check valves for controlling the directional flow of exhale and inhale gases. Such breathing circuits usually include a carbon dioxide removal chemical (as for example, Baralyme), and sensors for sensing the partial oxygen pressure of the gases in the breathing system to produce a control signal for operating an oxygen control valve which is pulsed open to admit oxygen from an oxygen supply to the breathing circuit. Such system may further include devices which are responsive to the depths of the diver in water to admit more or less of a diluent gas which may be helium or heliox (a mixture of helium and oxygen). The present invention provides a safety apparatus against oxygen valve failure by including a restricted passageway means leading to an accumulator means in advance of oxygen valve.

The above and other features and advantages of the invention will become more apparent when considered in connection with the following specifications taken in conjunction with the attached drawing therein:

FIG. 1 is a diagrammatic illustration of a closed circuit breathing system incorporating the invention and is FIG. 1 of the above-mentioned application Ser. No. 6,387 modified to incorporate the present invention.

FIGS. 2 and 3 are drawings of the restricted passageway means of the present invention.

The accompanying drawing diagrammatically discloses the pertinent portions of a self-contained underwater breathing apparatus in which a mouthpiece 10 having conventional exhale and inhale check valves (not shown) leading to exhale pipe 11 and inhale pipe 12, respectively, is connected to inhale port 13 and exhale port 14 on combined carbon dioxide removal and breathing diaphragm assembly unit 16. (In the drawing, for simplicity of illustration, inhale port 13 is shown as being below exhale port 14 and connected directly to the pressure equalization chamber.) Combined carbon dioxide removal and breathing diaphragm unit, 16 in the simplified arrangement shown in the drawing, includes a central annular frame member 17 having an inwardly projecting annular divider 18 supporting an annular or donut-shaped carbon dioxide removal cannister or cartridge 19, through which exhaled gases from exhale pipe 11 are caused to flow. Cover member 15 is sealingly clamped to the upper edge of annular frame 17 by clamp element 15c. Water absorbing sponge material 22 is located on the divider plate 18 to remove moisture from the exhaled gases. Exhaled gases are caused to flow upwardly (in the diagram shown in the drawing) through cartridge 19, baffle means (not shown) causing an essentially uniform distribution of such gases on the lower surfaces of cartridge 19. The exhaled gases passing through the chemicals in cartridge 19 have carbon dioxide removed therefrom in a conventional manner and on leaving the cartridge 19 pass into a mixing chamber 24 which includes the hole 26 formed by the inner annular walls of cartridge 19. Oxygen sensing means 27 are located in the circular space or hole 26 in the cartridge and sense the partial oxygen pressure of gases passing through carbon dioxide removal cartridge 19. Such oxygen sensors may be of the type disclosed in Rutkowski et al. application Ser. No. 831,152, filed June 6, 1969.

Signals produced by oxygen sensors 27 are processed in a solenoid control circuit 28 which produces signals for operating a normally closed solenoid valve 29 to supply oxygen from an oxygen bottle 30, via shut-off valve 30v, pressure reducer 30r, restricted passageway means P1, accumulator means A and line 31 to the mixing chamber 24. Restricted passageway means P1 may be either an orifice of restricted diameter or a capillary tube, positioned somewhere between pressure reducer 30r and oxygen control valve 29. Although restricted passageway means P.sub.1 is illustrated at both the entrance and exit sides of the accumulator, ordinarily the orifice or capillary tube constituting the restricted passageway means would be present at only either the entrance side or only the exit side. Of course if desired there could be a restricted passageway means at both the entrance and exit sides as illustrated. It could also be present at the exit mouth either pressure reducer 30r or accumulator A or at the entrance mouth to accumulator A. Illustratively, FIG. 2 shows an orifice O.sub.1 of restricted diameter which may serve as the restricted passageway means of the invention.

Instead of an orifice, a capillary tube of restricted diameter may be used as the restricted passageway means. Such a capillary tube is shown in FIG. 3 at C.sub.1 and would form at least part of the connecting line between pressure reducer 30r and oxygen control valve 29. If a capillary tube is used it can have a greater diameter than would an orifice for an equivalent pressure drop because the length of the capillary tube as well as the restricted diameter is responsible for causing a pressure drop. The capillary tube because of its greater diameter would be less likely to become clogged with a foreign particle than would the orifice and hence might be more desirable in certain applications. Capillary flow areas in the order twice that of the orifice are possible with capillaries of convenient lengths. Note also that if desired any combination of orifices and capillary tubes may be used to achieve the required pressure drop.

Accumulator means A may be any vessel which is large enough to accommodate the predetermined slug of oxygen which is to be supplied to the breathing gas circuit when the oxygen control valve is pulsed open. Meter 30m indicates the pressure of gas in bottle 30, and meter 28m indicates the partial oxygen pressure of gas in the breathing circuit. A safety device in the form of an oxygen bypass valve 32 is provided to permit manual bypassing of the automatic control of oxygen supply in the event of a malfunction in the oxygen control circuitry. Bypass valve 32 is connected in series with restricted passageway means P.sub.2 to limit the flow rate of oxygen through the bypass valve 32 should valve 32 stick open. Restricted passageway means P.sub.2, as in the case of restricted passageway means P.sub.1 may be either an orifice or a capillary tube. A suitable orifice O.sub.2 is shown at FIG. 2 and a suitable capillary tube is shown at C.sub.2 in FIG. 3.

A flexible diaphragm-vent valve assembly 60 is secured along its perimetrical edges to the lower portion of frame member 17 so as to provide a variable volume chamber 59; mounted in chamber 59 is a valve 61 which is controlled by inward movement of diaphragm 60 on descents by the diver, whereby external water pressure applied to the outer surface of diaphragm assembly 60 forces the diaphragm assembly inwardly on inhalation to actuate valve 61 to permit the addition of a diluent gas from a diluent supply bottle 63. 63v is a shut-off valve which may be operated if an uncontrolled amount of diluent gas blows into the breathing circuit as 63r is a pressure regulator or reducer used to regulate the pressure of the diluent gas. As in the case of the oxygen supply, in the event of malfunction of the valve 61, a diluent bypass valve 64 is provided to permit the diver to manually control the amount of diluent gas added to the breathing gas circuit. As shown in FIG. 1, the carbon dioxide removal cartridge 19 has a smaller overall diameter than does frame element 17. Moreover, it will be noted that expelled or exhaled gases from the diver essentially substantially surround cartridge 19 so as to maintain the temperature essentially constant so that temperature variations do not affect chemical activity in cartridge 19. It will also be noted that the upper cover member 15 which is sealingly secured to frame member 17 has on the interior surface thereof a layer of water absorbing sponge or sponge-like material 40 which, likewise, removes moisture or water which condenses on housing member 15.

With further reference to FIG. 1, it will be noted that the lower cover or housing 41 opposite the flexible diaphragm 60 is a perforated cover member to permit ambient water pressure to be exerted upon diaphragm 60. Perforated lower cover member 41 is clamped to annular frame 17 by clamp 58c and protects diaphragm 60. It will also be noted that diaphragm 60 carries a relief valve assembly 70, the construction of which is described in more detail hereinafter. However, a projection 92 on relief valve assembly 70 is adapted to engage an internal surface portion on cover member 41 so that on ascending, excess pressure within chamber 59 is vented to the exterior of the chamber and the water.

In the closed breathing system described above, oxygen sensors 27 are sampled by oxygen control circuit 28 at a predetermined time interval which in the preferred embodiment of the invention is every 5 seconds. If the oxygen level is above a predetermined minimum value when the sensors are sampled, the solenoid control circuit 28 does not transmit a signal to open oxygen supply valve 29. On the other hand, if the oxygen level is below the predetermined minimum value when the sensors are sampled, solenoid control circuit 28 transmits a signal which opens oxygen supply valve 29 for a short predetermined interval to admit a predetermined slug of oxygen to the breathing gas unit. In the preferred embodiment of the invention valve 29 is opened just long enough to admit 0.5 liters of oxygen to the breathing circuit. In this way, by admitting either no oxygen or a predetermined slug of oxygen at a predetermined time interval, the oxygen present in the breathing gas circuit is kept constant to a close tolerance.

If oxygen control valve 29 gets stuck closed, manual bypass 32 may be operated to provide oxygen to the breathing gas circuit. It is when oxygen control valve 29 get stuck open that the improvement of the present invention is useful. The present invention ensures that oxygen flows at a limited rate through valve 29 if it is struck open. Thus the diver has time before the oxygen concentration becomes too great to shut valve 30v off and rise to the surface.

The invention employs restricted passageway means P.sub.1 in combination with accumulator means "A" to accomplish the above objective. Restricted passageway means P.sub.1, which can be either an orifice or a capillary tube as described tube as described above, limits the flow of oxygen to or from accumulator A so that accumulator A fills up with approximately the predetermined slug of oxygen required to be added to the breathing gas circuit at the predetermined time interval. Thus in the preferred embodiment, restricted passageway means P.sub.1 would fill accumulator A with approximately 0.5 liters of oxygen gas every 5 seconds. Thus at the sampling interval just enough oxygen is present to supply the predetermined amount to the breathing gas circuit but if the control valve gets stuck open only a limited additional amount of oxygen will flow into the breathing gas circuit because of the limiting effect of the restricted passageway means and the accumulator means. The safety feature thus provided is inexpensive, requires no moving parts and can be easily incorporated into existing equipment with little modification or change.

It will be appreciated that the regulator 30r may be eliminated so that the high pressure (about 2,000 psi) from the oxygen bottle 30 is dropped by the restricted passageway means directly, Moreover, the invention is applicable to closed and semiclosed systems and, may even be applied to open systems if desired. Hence, while there has been disclosed a preferred embodiment of the invention it will be appreciated that the invention is subject to many obvious modifications.

Claims

What is claimed is:

1. In a breathing gas system having a supply of gaseous oxygen connected to a carbon dioxide removal and breathing unit by means of a conduit system including an oxygen control valve operable to admit oxygen from said supply to said carbon dioxide removal and breathing unit, the improvement comprising, an accumulator connected in said conduit system between said oxygen supply and said oxygen control valve for accumulating a measured volume of oxygen, said oxygen control valve being normally closed and periodically pulsed open to admit said measured volume of oxygen from said accumulator into said breathing gas system, a pressure regulator connected in said conduit between said accumulator and said oxygen supply, and restricted passageway means forming a portion of said conduit system between said oxygen supply and said accumulator and limiting the rate of flow of said gaseous oxygen from said supply thereof into said accumulator whereby when said oxygen control valve is pulsed open, essentially only the measured volume of oxygen in said accumulator is admitted into said breathing unit, and whereby in the event that said oxygen control valve fails to close only a limited amount of gaseous oxygen determined by the dimensions of said restricted passageway means will be metered into said unit.

2. The system of claim 1 wherein said oxygen control valve is pulsed open at particular times to admit a predetermined slug of oxygen to the breathing gas circuit and wherein said restricted passageway means is dimensioned so that at least said predetermined slug of oxygen is present in said accumulator means at said particular times.

3. The system of claim 2 wherein said restricted passageway means is an orifice.

4. The system of claim 2 wherein said restricted passageway means is a capillary tube.

5. The system of claim 2 further including oxygen bypass valve means connected in parallel with said restricted passageway means, said accumulator, and said oxygen control valve, for bypassing said oxygen control valve in the event that it fails closed.

6. The system of claim 5 further including second restricted passageway means connected in series with said oxygen bypass valve for limiting the flow of oxygen through said bypass valve in the event that said bypass valve fails open.