US2552595A - Oxygen demand breathing system, including means for automatic altitude regulation - Google Patents

Description

H. SEELER May 15, 1951 OXYGEN DEMAND BREATHING SYSTEM, INCLUDING MEANS FOR AUTOMATIC ALTITUDE REGULATION Filed Sept. 21, 19 -18 INVENTOR. #E/VEJ j E1 .45?

UNITED STATES PATENT OFFICE OXYGEN DEMAND BREATHING SYSTEM, IN

CLUDING MEANS FOR AUTOMATIC ALTI- TUDE REGULATION Henry Seeler, Heidelberg, Germany Application September 21, 1948, Serial No. 50,343 3012111115. (01. 128-142) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes without payment to me of any royalty thereon.

The present invention relates to an oxygen demand breathing system including means for automatic altitude regulation.

The primary object of the invention is to provide an automatic regulating apparatus, including a face mask equipped with automatic inlet and outlet valves, for supplying air and oxygen to a person at varying altitudes and including means to increase the degree of oxygen dilution as the altitude increases.

A further object of the invention is to provide a breathing apparatus including a face mask having pressure responsive inhalation and ex halation valves and having connected to the mask an automatic oxygen regulator which is in turn connected to a source of oxygen under pressure for supplying oxygen supplement to the mask upon response of the oxygen regulator.

A further object of the invention is to provide a system of oxygen regulation especially for aircraft personnel in which means are provided to make full use of the outside air as a source of oxygen and in which further means are provided to automatically supplement the air supply with pure oxygen as the altitude increases and the need for more oxygen increases.

Another object of the invention is to provide an oxygen demand system for aircraft personnel wherein the system includes one or more face masks each having an automatic air inlet valve and an automatic outlet valve and wherein an oxygen regulator connected to each face mask acts to supply pure oxygen to aircraft personnel as the demand therefor arises, as for instance with increase in altitude.

Another object of the invention is to provide an oxygen demand regulator wherein a control diaphragm subject to atmospheric pressure on one side is subject to breathing pressure on the other side and wherein the control diaphragm acts on a control valve to supply oxygen to the subject when he inhales and to cut off such oxygen when he exhales. A related object of the invention is to include in the regulator means responsive to the decreased pressures at high altitudes to increase the flow of oxygen to the subject in direct proportion to the increase in altitude.

Another object of the invention is to provide an improved system of oxygen regulation in which the supply of oxygen to the subject is proportional to the current demand for the oxygen and in which the proportioning of air and oxygen is accomplished automatically.

Another object of the invention is to generally improve the reliability and efliciency of oxygen regulators for use with aircraft personnel equipped with face masks or their equivalent.

The above and other objects of the invention will become apparent upon reading the following detailed description in conjunction with the drawing, in which:

The single figure of drawing shows in vertical cross section a face mask in place on a mans face and shows in adjacent relation the oxygen regulator or diluter as used with the mask.

As commonly known a person can not survive at high altitudes unless the air he is breathing is enriched by the addition of oxygen. While there is no certain altitude at which the oxygen supply should be augmented, in general it may be stated that additional oxygen should be used above 12,000 feet reckoned from sea level and must be used above 15,000 feet if consciousness is to be maintained. While it is possible to substitute oxygen for air at higher altitudes, it is preferable to dilute the rarefied air with pure oxygen so that the proportion of oxygen in the gaseous mixture is increased as the altitude increases. Thus the present system utilizes an automatic oxygen regulator which may also be called a diluter. This part of the system is con nected to the face mask by two thin tubes.

Mask construction I For a description of the breathing apparatus reference is made to the drawing. The subject I is shown wearing a mask 2 which covers the nose and mouth and which may be held in place by straps secured behind the subjects head. At the lower side of the mask there is a pressure relief valve or outlet valve 3 which includes a housing 4 enclosing a disk valve 5 and coil spring 6. The disk valve 5 normally seats on an annu side the mask wall there is a valve seat I l against which the marginal edges of the flapper element may engage. Thus the valve 8 is normally closed but when the gas pressure inside the mask is negative or slightly below atmospheric, as it is On the forward a during the inhalation phase of the breathing cycle, the small difference between outside and inside pressures causes the fiapper element 9 to leave the valve seat II and thus allow atmospheric air to enter the mask. In the drawing the inlet or inhalation valve 8 is shown in the open position and the outlet or exhalation valve 3 is in the closed position. Thus at the instant depicted the subject I is inhaling and is drawing air from the free atmosphere into the mask. Extending away from the mask are two thin flexible tubes I2 and I3 having open end portions terminating inside the mask. These tubes, known as the oxygen tube and the control tube respectively, extend some distance to the automatic regulator or diluter I4.

Instead of the flapper-type of inlet valve made of rubber or other flexible material it may be preferred in some instances to use other forms of sensitive valve devices, such as the disk-andspring type of valve like the outlet valve 3. Since the gas pressures inside the mask are preferab'li kept rather low, the outlet and inlet valves are made to respond to very small pressure diiferentials accordingly, and must be carefully cali-.

brated and tested ,for accuracy of response. In the present system an example of the critical pressures for the valves may be stated as twenty millimeters of water for the outlet valve and five millimeters ofwater for the inlet valve. In some cases these values may be changed considerably but it must be understood that the pressure as stated for the outlet valve refers to a pressure inside the mask above atmospheric, while the pressure as stated for the inlet valve refers to a pressure inside the mask below atmospheric. Thus as the altitude is increased and the supply of oxygen to the mask is increased by the oxygen regulator, the air inlet valve 8 will respond less readily upon inhalation. The efiect of the poorer response of the inlet valve will be made clear as the description of the present system proceeds.

Regulator construction The regulator or diluter unit I4 of the present oxygen demand system includes a two-part housing comprising an upper housing part I5 and a lower housing part It. Clamped between these parts is a very thin diaphragm II, which may be made of a rubberized textile fabric. While the dimensions are not critical it is noted that a very satisfactory element may be produced having a thickness of about 0.015 of an inch and a diameter of about one and one-half inch. The diaphragm I1 separates the regulator housing into two parts, the upper or aneroid chamber and the lower or control chamber. In the lower part of the control chamber there is another diaphragm I8 providing therebelow a pressure chamber adapted at certain times to receive oxygen at appreciable pressures. The outer marginal edges of the diaphragm I8 are secured to the housing part I6 and the inner edges of the diaphragm are secured to the regulator member I9. This second diaphragm is thicker and less sensitive than the diaphragm Ii, preferably being around 0.080 of an inch thick and also being made of a rubberized textile fabric.

Considering now the aneroid chamber it is seen that the upper housing part is provided with a boss threaded internally to adjustably receive a threaded stud 2i having ananeroid bellows 22 secured thereon within the aneroid chamber. The upper end of the stud carries .a lock nut 23 to hold the stud and attached bellows in fixed position after adjustment. The aneroid chamber is open to the atmosphere by way of small apertures 24. The aneroid bellows, which contains a compression spring, is sealed up in a vacuum. Therefore at sea level the aneroid will be compressed by the pressure of the atmosphere acting thereon, but as the altitude increases and this pressure is decreased the bellows will gradually expand thus exerting pressure on the coil spring 25 and also on the diaphragm I'I. Cemented or otherwise secured to the underside of the diaphragm I I is a pressure plate 26 adapted to bear on the free end-of a lever 21, the lever being piv- .oted or fulcrumed on an abutment 28 secured to the housing part It. A second lever 29 contactsthe first lever 21 between its end points and is .fulcrumed on an abutment 30 secured to the housing part IS. The inner end of the second lever receives the stem of a control valve or pilot valve 3i having a cone-shaped poppet element at .its lower end. This poppet element, which may have a ball-like shape if desired, is operative to normally close the valve passage 32 .by action of a coil spring 33 surrounding the valve stem. However when the subject inhales there willbe a reduction in pressure in the mask 2, in the control tube I3 and in the control chamber below diaphragm I1 and the diaphragm will therefore bulge downwardly thus acting on levers .21 and 29 to raise the valve member 3i and open the passage 32. Around the .stem of valve member 3] and also encircling an inwardly extending portion of the member I3 there is a rubber sealing band 34 to more effectively close off the interior of member I9. Forming part of the member I9 is a valve element I9 extending down into an oxygen chamber 35. .A coil spring 35 surrounds the element I9 and acts to holdthis element as well as the member I9 in a lower or cut-off position. A rubber sealing band located just inside the spring 36 acts in the same way as the previously described band 34 to more eifectively seal the oxygen chamber 35 from the pressure chamber under diaphragm I8. The lower wall of chamber 35 is provided with an elevated valve seat 31 against which the valve element I9 closes to prevent escape of oxygen into the chamber;- Through the center of valve seat 31 there extendsan oxygen inlet passage 38, which opens into a tubular projection 39 adapted to be connected to a source of pure oxygen under pressure. This cup-like projection 39 is provided as a receptacle for a ceramic gas filter which acts to prevent dust and other foreign matter from reaching the delicate regulator and from reaching the face mask. It is further noted that the pressure chamber below the diaphragm I8 is open to the atmosphere by way of a narrow pinhole opening 40, While the interior of the valve member 19 is open to the pressure chamber by way of a passage 4|.

The oxygen regulator for use in the present oxygen demand system or in other similar systems is more specifically disclosed and claimed in my copending application Serial No. 54,188 filed October 12, 1948, and entitled Pressure Responsive Regulator or Relay for Use in Oxygen Demand Breathing Systems.

Operation The present oxygen supply or regulator system is characterized by its response to the demand for oxygen as evidenced by a reduced pressure in the control chamber of the regulator or diluter.

This reduced pressure is present also in the mask and therefore the demand may effect a brief opening of the inlet valve 8 as well as effecting an influx of oxygen from the regulator. Under average conditions, that is at moderately. high altitudes, the oxygen is thus used to dilute the air supply but of course its ultimate effect is to increase the proportion of oxygen in the mixture being breathed by the subject I.

It will be assumed that the subject I is inhaling in the drawing illustration and is receiving air through the flapper valve 8. Also his inhalation has induced a low enough pressure in the regulator control chamber to cause the opening of the passage 32, by reason of a slight elevation of the control valve member 3I. This in turn lets oxygen into the member I9 and also into the pressure chamber below diaphragm I8 causing the member I9 to be elevated and thereby permittingoxygen to flow into the chamber 35 by way of the oxygen inlet passage 38 and also into the face mask 2 by way of the supply tube I2. The operating conditions described may correspond to the action obtained at a moderate altitude of about 12,000 feet above sea level. At this time the proportions of air and pure oxygen inside the mask during inhalation will probably be in the neighborhood of one to one by volume. Now when the subject exhales the pres sure inside the mask will rise abruptly, thus closing the air inlet valve 8 and simultaneously causing the outlet or exhaust valve 3 to open so that the used up air and respiration products may be expelled into the outside atmosphere. Also the increase of pressure in the mask will be transmitted along the control tube l3 to increase the pressure in the control chamber of the regulator, thus raising the diaphragm I1 and lowering the valve member 3| by action of the coil spring 33. This action in turn closes the passage 32 and cuts off the flow of oxygen to the chamber below the diaphragm I8, allowing the gas'pressure therein to become equal to atmospheric by reason of the escape passage 40. Now bythe action of the coil spring 36 the valve member I9 will be forced down into a position closing oil the oxygen passage 38. By this automatic cut-off action the limited supply of pure oxygen in a charged container is conserved and is drawn upon only during the inhalation phases of the breathing cycles. Furthermore the exhalation effort of the subject I will be kept at a minimum, since the flow of oxygen to the mask is cut off as soon as exhalation commences.

Considering now the action of the oxgyen demand system at a considerable altitude, for example about 22,000 feet above sea level, it is first noted that the aneroid bellows 22 will be slightly elongated compared to its length as shown in the drawing because of reduced atmospheric pressure. Now the coil spring 25 will be compressed to a greater degree than before and the resultant increased force exerted on the control diaphragm I1 and on the lever system 21, 29 actuated thereby will act to hold the control valve 3| slightly open even though the subject I is not inhaling nor exhaling at the moment. With the valve 3I open the pressure build-up in the pressure chamher under diaphragm I8 will act to hold the oxygen supply valve I9 off the valve seat 31 and thus allow oxygen to flow through the chamber 35 and tube I2 into the mask 2. Now when the subject inhales, the reduced pressure in the control chamber will cause the diaphragm I! to move downwardly still farther under the force of spring 25 and atmospheric pressure acting on top of the diaphragm. The response of the levers 21 and 29 and valve 3I will cause a more definite elevation of the oxygen supply valve I9 and a consequent plentiful supply of oxygen to the mask through the tube I2. The valve I9 may have a throttling action when it is raised only slightly ofi the valve seat 31, so that upon further elevation of the Valve there Will be a maximum flow of oxygen. Although the oxygen pressure chamber is open to the atmosphere the passage 40 is of pinhole proportions, and is provided only for the purpose of allowing the pressure under the diaphragm I8 to return to atmospheric after closing of the valve 3 I. At the higher altitude under consideration presently the air inlet valve 8 will open during inhalation but only for a short time compared to the total time for the inhalation phase, since there is a slightly increased pressure inside the mask due to the more pronounced opening of the oxygen supply valve I9. There will be some air admitted through the inlet valve 8 at each inhalation but there will be a greater proportion of oxygen and a smaller proportion of air under the circumstances set out. For example there may be percent pure oxygen and :20 per cent air inside the mask during inhalation. Thus it is seen that as the altitude is increased and the inlet valve 8 opens less, the extent of oxygen dilution of the air being breathed will be increased proportionately. As explained previously the valves 3! and I9 will close upon exhalation because of pressure developed inside the mask 2 and within the control chamber connected to the mask by the tube I3.

Operation of the regulator at extreme altitudes, for example at 35,000 feet above sea level, differs from that explained above mostly in the further elongation of the aneroid bellows 22 and the further compression of the coil spring 25. Under these conditions of reduced atmospheric pressure the force of the spring 25 is the main influence in opening the control valve 3I. The lack of atmospheric pressure on the upper side of the control diaphragm I! will mean that during inhalation the diaphragm will not have any marked tendency to bulge downwardly, as it would at lower altitudes where the atmospheric pressure is greater. The main influence in keeping the valves 3| and I0 open under these conditions will be the bellows Z2 and the spring 25 and it should be noted that this will be a constant force at a constant altitude. This actuating force now being at a maximum, the assisting forces or the counter forces will not have much effect unless they are too increased in magnitude. However, since these forces developed during the breathing cycle will not increase noticeably at higher altitudes the bellows is the main factor at the extreme altitude. It will be seen that the valves 3i and It will now be held open at all times except during exhalation, and as a result the pressure inside the mask will tend to build very slightly from the influx of pure oxygen from the regulator Hi. The subject may now inhale with less effort and the inhalation phases will not cause the air inlet valve 8 to unseat at all. Thus he will now be breathing pure oxygen at all times. As he exhales there will be an increase in gas pressure inside the mask and the outlet or exhaust valve 3 will open to release most of the expelled respiration products. The pressure increase will be transmitted to the control chamber of the regulator by means of the control tube I3 and the diaphragm I! will bulge upwardly. The resulting action will cause the control valve 3| to seat for a brief time and thus cause seating of the oxygen supply valve I9 at least momentarily. Thus as the demand is removed the oxygen supply is cut off and the oxygen consequently conserved for the inhalation phases of breathing. By the use of the automatic inlet and outlet valves built into the mask and also the oxygen regulator connected thereto, the present demand system operates to not only proportion the supply of pure oxygen to meet the demand but also operates to make use of the outside air as a source of oxygen. This combined action of the air valves in the mask structure and the oxygen demand regulator is the most important aspect of the present invention, but of course the automatic altitude regulation or compensation whereby the oxygen supply is increased with increase in altitude is also an important feature. Another noteworthy feature is the maintenance of positive mask pressures at higher altitudes, so that any possible leakage around the edges of the mask will merely let gases out of the mask rather than permit the thin air to seep into the mask.

In passing it is noted that there are varying pressures on the opposite sides of the diaphragm l8 but they are of such difierences in magnitude that variations in pressure on the upper side of this diaphragm during the breathing cycle may be ignored entirely. The only important consideration as far as the operation of the diaphragm I8 is concerned is the rise and fall of the oxygen pressure under the diaphragm as the control valve 3| is opened and closed. While the oxygen pressure in the supply chamber 35 may often be quite considerable, the throttling effect of the oxygen supply tube l2 and the valve passage 38 always ensures that no such pressure will develop inside the mask. It must be remembered too that the mask and the subject together provide a large volume for the gas to fill and the oxygen supplied thereto must pass through a very small tube and must traversesome distance therethrough also. As the oxygen supply is used up the supply pressure is rapidly reduced, for example the initial pressure at the neck of the oxygen bottle may be as high as 400 pounds per square inch and it will continue to fulfill its function in the present system until the pressure has fallen below about pounds per square inch.

It might be noted further that the control tube l3 also exerts a throttling effect on the pressures developed within the control chamber of the regulator l4 but in any case the control pressure will always be in direct proportion to the pressure inside the face mask 2. Although the system as illustrated and described includes a face mask covering both the nose and mouth, it is understood that various types of masks or appliances'may be used to connect the subjects with the source of oxygen and with the outside atmosphere. The term face mask as used herein may accordingly be considered to apply to a mask as shown or to any reasonably similar equivalent thereof. It is clear also that a plurality of masks and regulators may be connected to a single source of pure oxygen but it is preferred to include a separate container of oxygen for each subject. While the regulator has been described and illustrated as though it were always maintained in a vertical position it should be understood that operation will be very satisfactory in other positions thereof.

a negative pressure inside said mask to open for admission of air into said mask, an exhalation valve carried on said mask and responsive to a positive pressure inside said mask to open for expulsion of products of respiration from said mask, conduit means to conduct oxygen from a charged container to said mask, an oxygen regulator including a housing and connected in said conduit means to regulate the amount of oxygen reaching said mask from said container, an oxygen valve in said regulator housing to allow oxygen to pass from said container to said face mask by way of said conduit means, spring means in said regulator housing to bias said oxygen valve toward closed position, a pressure sensing tube connected between said mask and said regulator housing, a flexible diaphragm in said regulator subject to atmospheric pressure on one side and to the pressure of said pressure sensing tube on the other side, means in said regulator housing including an aneroid bellows and a compression spring for exerting additional pressure on said one side of said diaphragm proportional to altitude above sea level, means in said regulator housing responsive to displacement of said diaphragm as the pressure on the other side thereof is reduced to a minimum to open said oxygen valve, and said spring means providing force to close said oxygen valve as said diaphragm is displaced by increase of the pressure on the other side thereof above said minimum.

2. In an oxygen demand breathing system for use at varying altitudes, a face mask, an air inlet valve carried on said mask and responsive to a negative pressure inside said mask to open for admission of air into said mask, an exhalation valve carried on said mask and responsive to a positive pressure inside said mask to open for expulsion of products of respiration from said mask into the atmosphere, conduit means to conduct oxygen from a charged container to said mask, an oxygen regulator including a housing and connected in said conduit means to regulate the flow of oxygen from said container to said mask, an oxygen valve in said regulator housing to allow oxygen to pass from said container to said mask by way of said conduit means, spring means in said regulator housing to bias said oxygen valve toward closed position, a pressure sensing tube connected between said mask and said regulator housing, a flexible diaphragm in said regulator subject to atmospheric pressure on one side and to the pressure of said pressure sensing tube on the other side, means in said regulator housing for exerting additional pressure on said one side of said diaphragm proportionalto altitude above sea level, means in said regulator housing responsive to displacement of said dia phragm as the pressure on the other side thereof is reduced to a minimum to open said oxygen valve, and said spring means providing force to close said oxygen valve as said diaphragm is displaced by increase of the pressure on the other side thereof above said minimum.

3. In an oxygen demand breathing system for use at varying altitudes, a face mask, an air inlet valve carried on said mask and responsive to a negative pressure inside said mask to open for admission of air into said mask, an exhalation valve carried on said mask and responsive to a positive pressure inside said mask to open for expulsion of products of respiration from said mask into the atmosphere, conduit means to conduct oxygen from a charged container to said mask, an oxygen regulator including a housing and connected in said conduit means to regulate the flow of oxygen from said container to said mask, an oxygen valve in said regulator housing to allow oxygen to pass from said container to said mask by way of said conduit means, spring means in said regulator housing to bias said oxygen valve toward closed position, a pressure sensing tube connected between said mask and said regulator, a flexible diaphragm in said regulator housing subject to atmospheric pressure on one side and to the pressure of said pressure sensing tube on the other side, an aneroid bellows in said regulator having one end adjustably mounted on a regulator housing wall which is open to the atmos- 10 phere, a compression spring between the other end of said bellows and said one side of said diaphragm, means in said regulator housing responsive to displacement of said diaphragm as the pressure on the other side thereof is reduced to a minimum to open said oxygen valve, and said spring means providing force to close said oxygen valve as said diaphragm is displaced by increase of the pressure on the other side thereof above said minimum.

HENRY SEELER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,926,069 Sutton Sept. 12, 1933 2,384,669 Fields Sept. 11, 194:5

FOREIGN PATENTS Number Country Date 865,609 France Mar. 3, 1941

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