US2998009A - Breathing apparatus - Google Patents

Description

Aug. 29, 1961 c HOLM ET AL BREATHING APPARATUS Filed May 23, 1952 5 Sheets-Sheet l m Q 2 Q q u m o N 0 Q Q 0 Q I N V EN TORS. 6924. M #01, d Aim u Paarfl Aug. 29, 1961 c. H. HOLM ET AL 2,998,00 9

BREATHING APPARATUS Filed May 25, 1952 5 Sheets-Sheet 2 INVENTORS.

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Filed May 23, 1952 9 JNVENTORS.

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Aug. 29, 1961 c. H. HOLM ET AL BREATHING APPARATUS 5 Sheets-Sheet 4 Filed May 25, 1952 9 E fi do INVENTORS. 69/24, H. H01, :8 41110 Foarfl Aug. 29, 1961 Filed May 23, 1952 C. H. HOLM ET AL BREATHING APPARATUS 5 Sheets-Sheet 5 PEI-TERENCE. /00 y,

T OXYGEN SBMPLE FROM mac/mess T0 BEEHTH/NG NED/UM OXYGEA/ FROM SUPPLY IN V ENTORS.

United States Patnt 2,998,009 BREATHING APPARATUS Carl H. Holm, Erica, Va., and Elihu Root 111, Springfield, Vt., assiguors to Old Dominion Research and Development Corporation, a corporation of Virginia Filed May 23, 1952, Ser. No. 289,632 20 Claims. (Cl. 128-142) This invention relates to an apparatus for automatically maintaining the oxygen content of a gaseous body that is being breathed by a human being. The device is of particular utility in diving apparatus, where its use permits a diver to walk about freely, underwater, and to have his air supply maintained over long periods of time, while leaving his hands free for other purposes than adjusting the oxygen supply to his breathing mask. The invention is primarily intended for use in controlling the oxygen content of air that is being continually rebreathed, as in closed circuit devices where -a continual fresh air supply is not available. Diving apparatus and especially deep sea diving apparatus is one field in which this invention is of particular value because in that field the same air must be repeatedly breathed. The mere maintenance of a sufiicient oxygen content in the medium being breathed is not all that is required for the safety of the individuals breathing the controlled air. The prevention of an oversupply of oxygen is of equal importauoe, because so-called oxygen poisoning results if too great a quantity of oxygen is supplied to the breathing medium over any considerable period of time. Some of the devices now in use and in which oxygen alone is fed into the diving mask, presents the constant danger of too great a percentage of oxygen being supplied to the diver. Other known diving apparatus supplies air alone to the diver and while this avoids danger of oxygen poisoning it is at the expense of having to use cumbersome and weighty diving gear and of radically limiting the efliciency of the diving apparatus and the length of time that the diver can remain submerged.

The invention also contemplates the provision of a novel form of container for the mechanical instrumentalities employed and a novel type of breathing diaphragm, such container and diaphragm being incorporated in a turtle like shell, adapted to be strapped upon the back of the shoulders of a diver and having an external shape such as to facilitate the underwater movements of the wearer, when swimming or walking about on the bottom of a body of water.

The container is of so-called half tear drop formation. That is, it presents an oval face both transversely and longitudinally. This conserves oxygen because it permits the wearer to move about underwater with a minimum of elfort and adds to the speed of a swimmer.

The invention and its potentialities and advantages will be best' understood by reference to'the accompanying drawings wherein:

FIG. 1 is a plan view of the bottom plate of a diving unit, illustrating one arrangement of the instrumentalities employed in carrying out the invention;

FIG. 2 is a longitudinal sectional view upon line 2-2 of FIG. 1 with parts omitted;

FIG. 3 is a fragmentary sectional view upon line 33 of FIG. 2;

FIG. 4 is a vertical sectional view upon line 4-4 of FIG. 1 illustrating the manner of connecting the inhalation tube of a diving. unit to our apparatus;

FIG. 5 is a plan view of an electrically actuated oxygen controlling valve, hereinafter described;

FIG. 6 is a central vertical sectional view through the structure of FIG. 5;

FIG. 7 is a plan view of one form of senser which may be employed; i

Patented Aug. 29, 1961 FIG. 8 is a front elevation of the structure of FIG. 7, the wall of the casing being in section;

FIG. 9 is a transverse, vertical sectional view upon line 99 of FIG. 8;

FIG. 10 is a magnified perspective view of the needle and associated parts hereinafter described;

FIG. 11 is a diagrammatic view of the electrical in strumentalities and their connections; and

FIG. 12 is a diagrammatic view of a modified form of senser.

Broadly stated the invention resides in conducting a current of the gaseous medium that has been breathed by a human being, past a senser, such senser being re sponsive to the percentage of oxygen in such medium, in a manner to automatically prevent either an over supply or an under supply of oxygen in such gaseous medium. We believe that we are the first to automatically maintain the oxygen supply to human lungs under control of the condition, (as to oxygen content), of the medium that has been breathed by said lungs.

In carrying out the invention we provide a casing of general turtle shell form. This casing comprises a housing shell 5 and a back plate 6. A shell 9 has a flange 10 around its inner edge and casing 5 has a complemental flange 11 about its upper edge. Bolts or other fastenings l2 clamp a flexible diaphragm 13, of rubber or like waterproof material, between said flanges. The plate 6 has a stout canvas web 7 riveted upon its outer or rear side to which straps 8 and 8a are stitched, said straps being of conventional form and serving to mount the structure upon the back of a diver with the left end in FIG. 2 toward the top. There are two of the straps 8 and they pass over the shoulders of the wearer and are attached to a belt which passes around the diver. The strap 8a passes between the legs of the diver and is attached to the same belt (not shown). Outer-shell 9 is provided with a number of openings 14 therethrough so that the space between the diaphragm and shell '19 is filled with sea water at the pressure existing at the depth at which the diver is working. Diaphragm 13 constitutes the breathing diaphragm of the apparatus.

Bolts, screws or like releasable fastenings 15 bind a gasket 16a between a flange 17a of shell 5 and the back plate and render the structure fluid tight. Within the space between the diaphragm and the back or bottom plate 6 are disposed a flask 16 of compressed air and a flask 17 of compressed oxygen. These are of a conventional commercial type and have angular'valve stems 18, the turning of which releases the contents of the flasks. of the casing are carried by stems20, said stems having angular sockets 21 at their inner ends for engagement with the valve stems 18. The stems 21 have both endwise and rotative movement in packing glands 22 and when they are thrust inwardly against the tension of springs 23 their socketed inner ends may be engaged with the valve stems to operate the same. The flasks are held in place on plate 6 by conventional, easily released dogging straps 24. When these straps are released and the hand wheels" and their stems are drawn outwardly, the exhausted flasks may be released from the back plate and filled flasks may be substituted therefor. At' this time the back plate 6 is removed from casing 5 to permit access to the flasks. With the shell 9 and easing 5 assembled, the hand wheels provide means for turning on or cutting oil the air and oxygen from a point outside the casing. The oxygen flask, when in place delivers its released oxygen, first to a conventional reducing-valve 25. The oxygen at greatly reduced pressure is then delivered from the reducing valve through a pipe 26 to the casing 27 of an electrically operated valve, said pipe terminating in. a valve seat 28 shaped to receive a Operating hand wheels 19, disposed exteriorly A 3 valve proper, 2 9. This electrically operated valve is a normally open one. That is to say the reducing valve is set to deliver a constant and suificient quantity of oxygen intothegaseous content of the casing 5' and which content constitutes the air that is to be breathed bythe diver. If their, the oxygen content exceeds the desired amount the valve closes and shuts off the oxygen until the content is reduced to the desired point.

Valve 29 iscarried at the free end of a plate 30 that is pivoted upon knife edges 31. These knife edges are formed upon posts 32 which upstand from a bracket 33'. spring 34 tends to lift the free end of plate 30 to open valve 29 and permit oxygen to flow from the mouth of pipe 26. Plate 30 constitutes the armature of an electro magnet indicated at 36 and which magnet is supported upon bracket 33. Upward movement of valve 29 is limited by a stop 37. When the magnet is energized armature plate-30 is drawn to core 36' and the valve is closed, as described. The supply of current to the magnet is under the control of a senser and this senser, in turn, is responsive to the oxygen content of gases imposed thereon. To secure the controlled movement of the electric valve advantage is taken of the fact that oxygen .is a strongly paramagnetic gas. Nitrogen upon the other hand is diamagnetic with a volume susceptibility of only as great in magnitude as that of oxygen. We take advantage of these difiering characteristics of oxygen and nitrogen to operate the'electric valve through the novel senser illustrated in FIGS. 7 to 10. In carrying out "our invention we convert the movement of a rotatable or swinging body, mounted to move between the pole pieces of a fixed magnet, into an electric current; then amplify that current to a point to per- :form work and deliver it to the electric valve, as aforesaid, for the purpose of closing said valve and diminishing'the supply of oxygen whenever the oxygen content of the gases between said pole pieces is great enough to cause movement of a' given amount by said swinging body. The senser by which the aforesaid result is achieved is mounted in a box-like casing 38. A bulkhead or wall 39 in this casing has an L-shaped supporting bracket 40 secured thereto by bolts 41. A permanent magnet 42 is supported from bracket 40 by through bolts "43. Pole pieces 44 of the magnet are so disposed as to leave a space 45 between them. A plate 46 of plastic or other non-conductive material is bound by the bolts 43 between bracket 40 and the pole pieces 44 and thus is rigidly supported. This plate constitutes a support for a horizontal nylon strand or thread 47, the ends of said strand passing into and being firmly secured in openings 48 of plate 46. A slender rod or needle N, pref- 'erably hollow to reduce to a minimum its mass, in proportion-to the air which it displaces, and which may be filled with air at atmospheric pressure, is secured at or nearits center to the nylon or similar strand 47 of a strong, elastic, corrosion proof material and is so positioned that its lower portion projects into space 45, so that it may swing across said space. The outer end portion of the needle carries a flag, or pennant like, lateral projection 49, which, in the swinging movement of the needle, moves into and out of the path of an optically concentrated beam of light from an electric light bulb 50 that is mounted in alamp casing 51 and shines through lenses 52. When the flag 49 is moved out of the path 'of this beam of light the light "impinges upon a photo electric cell 53 at sight opening 53a. The resultant rela- 'tively weak electric current set up in the photo electric cell is amplified by a conventional amplification vacuum tube 54 and it is the amplified current from this tube that is delivered to the windings of magnet36, to close the valve as previously described. An advantage of having a normally open valve resides in the fact that when a normally open valve is employed'the diver is assured of a substantial supply of oxygen even though the senser fails, for any reason, to function. The supply from the normally open valve is such as to give the diver all the oxygen needed and if an excess of oxygen is delivered the senser takes over and reduces the supply to the proper rate. It does this because a sampleof the air from within the casing 5, and which is being breathed by. the diver, is delivered through a tube 55 to thespace 45, which the lower end of the needle swings to a degree dependent upon the oxygen content of the gas (divers breath) in said space. The needle, being made of glass which is diamagnetic tends to be forced out from between the pole pieces by a force in addition to that exerted on it by the paramagnetic oxygen which tends to displace it. This additional force is counterbalanced by a minute quantity of paramagnetic or ferromagnetic material, for example a suspension of rouge in lacquer, which is applied to the side of the needle away from the pole pieces at about X in FIG. 9. The combination of the diamagnetic needle material close to the pole pieces and the magnetic counter-balancing material slightly more distant from the pole pieces, serves to establish a stable zero position of the needle close to the pole pieces without depending on the stiffness of the supporting fiber. Because of this it is practical to make the fiber of a material such as nylon which isinherently much more flexible and rugged than quartz for example but which has relatively poor torque stability. The nylon fiber can easily be made sufiiciently flexible so that variations in its torque are substantially ofiset by the stiifness of the magnetic balance. The casing 27 of the electric valve is a closed one and the pipe 26 delivers oxygen into this casing as long as the valve is open. This oxygen is delivered from the valve casing to the interior of main casing 5 through a pipe 58 and this pipe may carry a whistle 59 or other signal, to notify the diver that the normal flow of oxygen is proceeding. 7 To enable the diver more readily to hear the signal, pipe 58 is, preferably, brought into metal to metal contact with back plate 6. The air flask not only provides an emergency supply of air but it provides means whereby the buoyancy of the apparatus may be quickly increased to bring the wearer quickly to the surface in an emergency. To render it possible to adjust the oxygen supply we mount the light bulb casing 51 and the photo electric cell upon a second plastic plate 60. Plate 60 is laterally adjustable toward and from plate 46 by means of screws 61 and 62. Since the needle N and its flag are carried byplate 46 it follows that the described arrangement adjusts the path of the beam of light toward or from the'needle and consequently determines the degree of throw which the needle must have to carry the flag away from plate 46 and out of the path of the light beam, it being understood that an excess of oxygen content between the pole pieces will repel the lower end of the needle and move the upper end of the needle away from plate 46, until the flag and needle move into the path of the light beam. Thereupon the electric valve is closed, as described and the supply of oxygen is interrupted.

When the light beam is not interrupted, light falling on photo cell 5-3 allows current to flow from negative terminal of battery B through the high resistance R, (see FIG. 11) thereby biasing the control grid of tube 54, negatively, so that no current flows to the winding of magnet 36. When the percentage of oxygen in the atmosphere in space 45, increases, the lower end of needle N is forcedaway from the pole pieces and flag 49 moves to intercept the light beam, thereby cutting oif the current in photo cell 53 and removing the bias from the control grid of tube 54. Current now flows to the plate of tube 54 and energizes magnet 36 closing valve 29 and shutting ofi the flow of oxygen. Valve 29 remains closed until the diver by using up the oxygen in casing 5 reduces the amount of oxygen in the atmosphere in space 45 allowing the lower end of needle N to return toward the pole pieces, thereby removing flag '49 from the path of the light beam, shutting off current in tube 54 and restoring valve 29 to its former position.

While the senser described has been found to be very efiicient, it is clear that the advantages of the general form of diving apparatus, disclosed, are not dependent upon the use of this particular senser. The structure described provides a fully enclosed unit with all of the mechanism housed and protected in a hard shell. The diaphragm arrangement presents an important improvement in diving apparatus. It provides for placement of the air space close to the divers lungs. It presents less resistance to breathing than conventional apparatus inasmuch as it requires no expansion and contraction of a bag, but merely the flexing of a pre-formed, light rubber diaphragm from a convex position to a concave position in accordance with the divers exhalation and inhalation. The hard shell provides means for fully protecting the diaphragm, the equivalent of which, in conventional apparatus is a breathing bag, fully exposed and vulnerable to puncture. It is clear that such advantages as the foregoing are inherent in the assembly described irrespective of whether the oxygen control is effected by the particular senser shown, or by some other type of senser.

Conventional diving apparatus comprises a mask to fit upon the face or over the head of the user, inhalation and exhalation breathing tubes, a bag like structure constituting a breathing element to which said tubes are connec'ted and a canister or container for soda lime or Bara lime arranged in the breathing circuit, the soda lime absorbing the carbon dioxide of the exhaled breath. In FIG. 1, 64 designates a conventional lime canister. Dogging straps 65- draw the end extensions 66 and 67 tightly down upon gaskets 68 of pipe fittings 69 (only one of which is shown, see FIG. 4). These pipe fittings project through the back plate and respectively receive the conventional inhalation and exhalation tubes of a diving apparatus. The inhalation tube is indicated at 70 in FIG. 4. Air which has been breathed enters the canister at 70a, passes through the soda lime therein, and is discharged into the hollow extension 67 and thence, on the exhalation cycle, through a stub pipe 71 into the interior of easing 5. On the inhalation cycle air from within 5 is drawn through stub pipe 71 and into inhalation tube 70. Since the space within casing 5 receives the purified air which enters canister 64 at 7011 and since the air of inhalation is drawn from this space through stub pipe 71 and inhalation tube 70, it will be understood that the circulation of breathing medium to and from the diver is that circulation induced by the action of the lungs of an individual upon whose person the whole structure is carried, there being no pump required for setting up such air flow as will subject all of the air to purification in canister 76 and will thus subject the senser to the action of that air and only that air which has passed through the lungs of the individual whose oxygen supply is being controlled. Therefore in the accompanying claims the term individualized, or the equivalent thereof, is to be construed to mean that the air analyzed and circulated is that peculiar to an individual. The tube 55 which delivers the air sample to space 45 may take its supply from any point within casing 5 but we prefer to connect it to extension 67 so that the sample delivered will closely correspond to the air that is being breathed. A switch S accessible from the exterior of the casing 5 provides means for closing the circuits shown in FIG. 11. The batteries B, B' are housed in a power pack casing P and J designates a conventional plug in jack by which the batteries are brought into electrical connection with the amplification tube, voltage regulator 50' and photo electric cell in casing 38. In FIG. 12 we have shown that other forms of sensers may be employed While retaining the basic principle of varying the oxygen of a gas being breathed, under control of the condition of the breath. In the apparatus of FIG. l2 advantage is taken of the fact that the viscosities of oxygen and nitrogen differ to such a degree that an oxygen control valve may be actuated under control of such difference in viscosity.

In FIG. 12, 76 designates a normally open oxygen supply valve which is actuated by a bladder 77 to close and cut off the oxygen supply from pipe 76a whenever the percentage of the oxygen in the breathing medium (breath) rises above a predetermined point. Thus this normally open valve, in function, closely corresponds to the electrically operated valve 29, hereinbefore described and since it is normally open an oxygen supply to the user is assured even if the senser fails. The necessary movement is imparted to valve 76 through the mechanism of FIG. 12 which comprises a power cylinder 78, a reference cylinder 79 and a sample cylinder 80. A piston 81 and piston rod 82 in the power cylinder, actuate a cross head S3 to which is connected pistons 84 and 85, located in the reference and sample cylinders, respectively. A spring 86 retracts the cross head and said cross head is thrust upwardly against the tension of said spring when oxygen under pressure (20 lbs. per square inch, for example) is admitted to the lower end of the power cylinder through supply line 87. When pistons 84 and are retracted in cylinders 79 and 80 a sample of the medium being breathed is drawn into sample cylinder 89 from sample line 88a and a reference fluid, (100% oxygen for example) is drawn into the reference cylinder 7 9 through line 89. The lines 88 and 89 present approximately like resistances to gas flow. This may be accomplished by including in said lines, similar capillaries 90 and 91. A needle valve 91a in series with capillary 91 serves to adjust the total resistance of line 89 relative to that of line 88. A flexible bladder 96 is connected to cylinder 7 9 by line 79a through the main valve 93, hereinafter described, during the suction stroke of pistons 84 and 85. A housing 10! around bladder 96 is connected to cylinder 80 by line 99. Within the limits of its motion, bladder 96 tends to equalize the pressures in cylinders 79 and 80. The resistances of lines 88 and 89 are adjusted, relative to the viscosities of the sample and the reference gases and to to the displacements of pistons 84 and 85, so that when the sample has the desired concentration of oxygen, equal suction will be maintained during the suction stroke in cylinders 79 and 80, without requiring motion of bladder 96. However if the percentage of oxygen in the sample increases above the desired amount the viscosity of the sample increases, thereby retarding the flow through line 88, anclv increasing the suction. The equalizing action of bladder 96 now causes a corresponding increase in flow through line 89. The increase in flow through line 89 relative to that through line 88 is accumulated in bladder 96. Since the suction stroke starts with bladder 96' in its completely collapsed position, the volume accumulated at the ends of the stroke will be proportional to the increase in viscosity of the sample and therefore to the increase in percentage of oxygen. The discharge therefrom is back into the breathing medium in space 2 through pipe line 920, of relief valve 92. The main valve 93 is of a conventional type which has acquired a distinct-status in the arts and many of them are to be found in the Patent Oflice classified as valves, multiple way, plug. Some of these valves are provided with detents which cause them to remain in the position to which they have been moved and to then snap quickly into a new position. In FIG. 12, 93a designates a crank arm the movement of which shifts the valve. A rod 93b connected to the crank arm passes through an opening 83a in the cross head 83. A nut or stop 93c on the rod is contacted by the cross head at the limit of downward movement of said cross head to cause the valve to snap to the closed position shown in FIG. 12. At this time a barrier a of the valve cuts off communication between 88 and 88a, a barrier b cuts off communication between supply line 87 and a pipe 97 which discharges into the breathing medium, and a barrier c is shifted to cut off communication between pipe lines like stop 93c and shifts the valve to open position.

A cycle of operation of the device will now be described. At the start the pistons are in their highest positions. Valve 93 has just been shifted by contact of the cross head with tappet 930 on rod93b which is shifted so that a, b and c are all open. Oxygen, which had previously forced the pistons upwardly, exhausts from power cylinder 78 through line 87, branch 87c, valve b, and discharge line 97, allowing spring 86 to retract the pistons. Oxygen is drawn into reference cylinder 79 through line 89, capillary 91, and needle valve 91a. At the same time a sample of air is drawn into sample cylinder 80 through line 88, capillary 90, valve section a, and line 88a. If the sample of air contains excess oxygen, some of the reference gas entering cylinder 79 through line 89, flows out through line 79a and valve section c into bladder 96 as previously described. As the pistons reach the bottom of their stroke, valve 93 shifts quickly, closing all of the component valve sections a, b and c. The closing of valve b by blocking discharge line 97 causes the oxygen flowing in through line 87 and needle valve 87a to enter power cylinder 78 and to start the upward stroke of the pistons. As the pistons move up, the oxygen in cylinder 79 passes out through line 89, capillary 91, and needle valve 91a. At the same time the air in cylinder 80 passes out through line 88, capillary 90, relief valve 92, and pipe 92c back to the breathing medium. The closing of valve a, while not absolutely essential, by blocking discharge through line 88a serves to allow relief valve 92 to main- 'tain a relatively high and uniform back pressure in cylin der 80 during the upward stroke. The back pressure in cylinder 80 is communicated through line 99 to bladder housing 100 where it collapses bladder 96. Any oxygen in bladder 96 is prevented from returning to cylinder 79 by the prior closing of valve c. Instead any oxygen in bladder 96 is forced past check valve 98 into bladder 77 where it tends to close valve 76, against the tension of a spring 76b. As the pistons reach the top of their stroke, bladder 96 has been collapsed and valve 93 shifts quickly, opening all the valve sections fa, b and c. Then a new cycle starts.

A long as the sampled air is too rich in oxygen, some gas is pumped from bladder 96 into bladder 77 with each cycle as just described until valve 76 is completely closed. However, when the sampled air is too lean in oxygen, bladder 96 remains in its collapsed position during the suction stroke so that it contains no gas to be forced into bladder 77 during the succeeding pressure stroke. Under these conditions spring 76b and plate 760 gradually collapse bladder 77, forcing its contents out through a leak valve 98a, and allowing valve 76 to open.

As will be apparent from the wide dissimilarity between the two sensers disclosed in FIGS. 7 and 12, the principle of controlling the oxygen supply to a human being under control of the condition of the breath of the user is susceptible of being carried out by apparatus'o-f widely varying forms. Therefore it is to be understood that the invention includes within its purview any apparatus falling fairly ,Within either the terms or the spirit of the appended claims.

Having described our invention, we claim:

1. Means for controlling the oxygen content of a gaseous body within a given area, comprising a source of oxygen supply, a normally open control valve for oxygen supply and means for variably actuating said control valve a 2; Individualized apparatus for maintaining the proper oxygen-content of air thatisbeing breathed by ahuman being which consists of a'source of oxygen supply, a normally open controlvalvefor the same, and meansjor variably actuating the valve to vary the oxygen supply, said means acting under control of the conditionof the exhaled breath, as to oxygen contentfof sucli'usen 3. Individualized apparatus for maintaining the proper oxygen content of air that is being breathed by a human being which consists of an inhalation conduit, a breathing chamber with which said conduits communicate, an exhalation" conduit, a source of oxygen supply, a normally open valve for controlling the oxygen supply, and a con-f trol means for actuating said valve, and means for conducting a sample of air that has been breathed to said control means, said control means beingoperable under the presence of an excess of oxygen in the exhaled to move said valve toward closed position, the breathed air being circulated toand'from saidchamber under the lung action of the individual;

4. An apparatus for maintaining the proper oxygen content of air that is being breathed and under control of the condition of such air, as to oxygen content; which consists of a control member, means for creatinga magnetic field, means for mounting said control member to move in said fieldto a degree determined by the oxygen content of the air in said field, a source of oxygen supply, a control valve for the oxygen supply, and elements for actu ating said valve under control of said control member.

5. A device for maintaining the proper oxygen content of a body of air, which consists of a movable control member, responsive to the presence of oxygen, apermanent magnet having pole pieces which establish a magnetic field between them, means for pivoting the control memiber in such relation to the field that a portion of the control member enters said field and is moved therein to a degree determined by the amount of oxygen present in the air in said field, means forconverting the movement of the control element into electrical energy, a source of oxygen supply, a normally open electrically operated valve for the control of said oxygen supply and means for operating said valve under control of the electric energy aforesaid, the norm-ally open condition of the valve assuring a normal oxygen supply and said valve being moved toward closed position by the presence of an excess of oxygenin the magnetic field.

I 6. A structure of the character described comprising a magnet and pole pieces which present amagnetic field, a control element of elongated needle-like form, a strand of material to which said control element is secured, said control element lying substantially perpendicularly with respect to said strand and said strand being placed under torsion when said control element is tipped transversely of the strand, said strand being so located with respect to the magnet that an end portion of the control element projects into themagnetic field to be moved to place the strand under torsion under the influence ofthe presence of a determined amount of paramagnetic oxygen in the air in said field, a light bulb, a photoelectric cell disposed in the path of a beam of light from said bulb and means carried by the control element to interrupt said light when the control element has been moved a determined degree.

7. A structure as recited in claim 6 in combination with an amplification element for amplifying current developed in the photoelectric cell by light from said bulb, an oxygen supply tank, and an electrically actuated valve connected to the amplification element and actuated by current therefrom, said valve, in turn, controlling passage of oxygen from said tank.

8. A structure as recited in claim 6 in combination with an amplification element for amplifying current developed in the photoelectric cell by light from said bulb, an oxygen supply tank, and an electrically actuated valve connected to the amplification element and actuated by current therefrom, said valve, in turn, controlling passage of oxygen from said tank, said valve being. a normally open one and arranged to be closed when it is electrically actuated.

9". In combination a container for the breathing gases of a human being, a source of oxygen supply, a conduit leading fromsaid source of oxygen supply to said container and comprising a normally open valve controlling the flow of oxygen into the container, means responsive to a rise in the oxygen content of the breathed gases above a determined point for closing said valve to interrupt the oxygen supply and means for conducting a sample of the exhaled gases to the last named means.

10. A device for maintaining the oxygen content of a gaseous breathing medium comprising a container for such medium, a source of oxygen supply for the gaseous medium, a valve controlling the flow of oxygen through said valve, a pair of receptacles, a first conduit leading to one of said receptacles from the source of oxygen supply, a second conduit leading to the other of said receptacles from a supply of the breathing medium and means in said conduits of like restrictive characteristics to the flow of fluid thereby, whereby the volume of oxygen gas and the gaseous breathing medium which enters said respective receptacles of the pair is determined by the respective viscosities of said oxygen and gaseous breathing medium, and means for moving said valve under control of the fluctuations between the respective volumes entering said receptacles.

ll. A senser of the character described for creating a flow of electric current under control of the variations in the oxygen content of a gaseous body which consists of a magnet having pole pieces defining a space constituting a magnetic field, means for supplying a test flow of a gaseous body into said field, an elongated body having diamagnetic properties, means for pivotally mounting said body in such relation to the magnetic field that an end portion thereof may swing toward and from said field, means for setting up a beam of light, a photoelectric cell mounted in position to be impinged and energized by said light beam and means carried by the elongated body and movable to and from positions of interruption of the light beam as the said body is moved under fluctuations of the oxygen content of the gaseous body of the test fiow.

12. A structure as recited in claim 11 in combination with means for adjusting the path of the light beam with respect to the position of the elongated body to thereby vary the extent to which the elongated body must move in interrupting the light beam.

13. A senser of the character described for creating a flow of electric current under control of the variations in the oxygen content of a gaseous body which consists of a magnet having pole pieces defining a space constituting a magnetic field, means for supplying a test flow of a gaseous body into said field, an elongated needle filled with a diamagnetic gas, a supporting vertical plate, a horizontal strand of a material capable of being put under torsion, to which said needle is secured intermediate its ends, with its lower end disposed in juxtaposition to said magnetic field, an opaque element mounted adjacent the other end of the needle and movable laterally toward and from said plate as the lower end of the needle moves toward or from the magnetic field, a second vertical plate, a light source and a photoelectric cell both mounted upon said second vertical plate, said light source being of a nature such as to set up a beam of light directed upon the photoelectric cell, said opaque element being movable with the needle to positions of interruption or non-interruption of the said beam of light and means for adjusting said plates toward or from each other to thereby vary the throw required of said opaque element in interrupting the light beam.

14. A structure as recited in claim 4 in combination with a magnetically aflfected element carried by said control member for damping the movement of saidcontrol member.

15. A structure is recited in claim 11 in combination with a magnetically affected element carried by the clon gated body upon the opposite side: of its pivot point from the light interrupting means that is carried by the dialec tric body.

16. In an apparatus for maintaining the proper oxygen content of air that is being breathed by a human being and under control of the condition of such air as to oxygen content, after at least a portion of such air has been breathed, a chamber receiving air to be breathed, a source of oxygen supply, a normally open magnetically actuated oxygen supply valve disposed in position to control a supply of oxygen from said source to said chamber, means for creating a magnetic field for the actuation of the oxygen supply valve and control means for varying the strength of the magnetic field under control of the oxygen content of a sample of air from said chamber, at least a part of which air has been breathed, to thereby actuate the normally open valve toward closed position whenever the oxygen content of the air in said space exceeds a predetermined degree.

17. In an apparatus for maintaining the proper oxygen content of air that is being breathed by a human being and under control of the condition of such air as to oxygen content after at least a portion of such air has been breathed, a chamber receiving the air to be breathed, a source of oxygen supply, a normally open oxygen supply valve disposed in position to control a supply of oxygen from said source to said chamber, a sensing means comprising elements for comparing oxygen from the source of supply and a sample of breathed air from said chamber and means for actuating the valve toward closing position when such comparison shows an excess of oxygen in the air in said chamber.

18. Apparatus for controlling the oxygen content of breathing air in a confined area, comprising a source of oxygen supply, a normally open oxygen control valve controlling the passage of oxygen from said source to said breathing air, an actuating member for the oxygen control valve and a control means for said valve actuating member, said control means being operable under the relative diiferences in viscosity of two gaseous bodies, and means for conducting said two gaseous bodies to said control means, one of said gaseous bodies consisting of a reference sample of air that has been breathed and drawn from said area and the other consisting of oxygen from said source.

119. An individualized diving apparatus comprising a casing, means for mounting the casing upon the person of a diver, said casing enclosing a breathing chamber of relatively small volume, inhalation and exhalation tubes communicating with said chamber, for setting up a circulation of breathing air under the lung action of the diver, a source of oxygen supply for said chamber, an electrically actuated control valve for the oxygen supply, a senser responsive to variations of oxygen content in the breathing chamber, an electric circuit in which variations in current flow are set up under control of said senser, and in which the electrically actuated control valve is included, said control valve being a normally open one and which valve is moved toward closing position by variation in current flow in said electric circuit induced by action of the senser under the influence of excess oxygen supply.

20. An individualized diving apparatus comprising a casing, means for mounting the casing upon the person of a diver, said casing enclosing a breathing chamber of relatively small volume, inhalation and exhalation tubes communicating with said chamber, for setting up a circulation of breathing air under the lung action of the diver, a source of oxygen supply for said chamber, an electrically actuated control valve for the oxygen supply, a senser responsive to variations of oxygen content in the breathing chamber, an electric circuit in which variations in current flow are set up under control of '11 said. snser, and in whichfthe electrically actuatedx control valve is included, said valve being a normally open oneand there being a carbon dioxide removing means located in said chamber in the path'of movement of the air inta said chamber from the exhalation tube.

References Cited in the file of this patent UNITED STATES PATENTS 1,195,793 Dunn et a1. Aug. 22, 1916 1,197,454 Deuter Sept. 5, 1916 2,160,326 Carbonara May 30, 1939 Rand Oct. 20, 1942 12 Strange June 12, 1945. Bennett Oct. 4, 1949 :Sneller Apr. 15, 1952 Crawford ;2 June 17, 1952 Medlock July 22, 1952 Stockman Aug. 26, 1952 Hollmaxm Nov. 11, 11952 Krupp Nov. 2, 1954 Luft Dec. 14, 1954 Argento Mar. 1, 1955 Richardson Dec. 25, 1955

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