Patent Publication Number: US-11040225-B2

Title: Back-up crew breathing gas system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 62/156,563, filed on May 4, 2015, the disclosure of which is incorporated herein by reference. 
    
    
     FIELD OF THE DISCLOSURE 
     The invention relates to breathing gas systems for aircraft, and more particularly to back-up sources of breathing gas. 
     BACKGROUND OF THE DISCLOSURE 
     Pressurized aircraft are provided with emergency oxygen systems (breathing gas systems) for use in the situation where cabin pressurization fails at an altitude which is above a safe level. Oxygen masks are disposed throughout the cabin of an aircraft and are pneumatically connected with oxygen source(s). 
     An emergency oxygen system is also provided in the cockpit for use by the flight crew. Masks are disposed in the cockpit for use by the crew, and are in pneumatic communication with at least one oxygen source. Typically, an emergency crew oxygen system is maintained at an operating pressure through the system to the masks by way of tubes connecting the masks to the oxygen source. When actuated, the emergency system quickly provides oxygen to the masks for use by the crew, while the crew works to bring the aircraft to a safe altitude for breathing without the need for supplemental oxygen. However, in the event of a failure in the crew emergency oxygen system, the crew may be without the use of supplemental oxygen during a critical time. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     In an embodiment, a system for providing a secondary source of breathing gas to a mask is disclosed. The system includes secondary reservoir having a breathing gas at a supply pressure. A secondary line pneumatically connects the secondary reservoir to a primary line. An actuator is configured to permit the flow of breathing gas from the secondary reservoir through the secondary line upon actuation. A pressure switch is configured to sense a gas pressure in the primary line. The pressure switch actuates the actuator upon a loss of pressure in the primary line. A primary line check valve is configured to prevent a flow of gas from the secondary line to a source side of the primary line. 
     In another aspect, a method for providing a secondary source of breathing gas to a mask is disclosed. The method includes detecting gas pressure lower than a pre-determined threshold in a primary line using a pressure switch, the primary line being in pneumatic communication with a breathing mask. An actuator is actuated to permit a flow of secondary gas to the breathing mask by way of a secondary line. The actuator may be actuated by an electrical signal sent to the actuator. A pressure of the secondary gas is reduced to an operating pressure. The gas may be prevented from flowing from the secondary line to a source side of the primary line. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a diagram of a system according to an embodiment of the present disclosure in pneumatic communication with a primary line; 
         FIG. 2  is a diagram of a system according to another embodiment of the present disclosure in pneumatic communication with a primary line; and 
         FIG. 3  is a chart showing a method according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The present disclosure may be embodied as a system  10  for providing a secondary source of breathing gas to a mask  99  (see, for example,  FIG. 1 ). The system  10  has a secondary reservoir  12  which contains a breathing gas. For example, the secondary reservoir  12  may contain oxygen. The secondary reservoir  12  stores the gas at a supply pressure. For example, the secondary reservoir  12  may store the breathing gas at a pressure higher than 500 psig, for example, 3,000 psig. The secondary reservoir  12  may store a quantity of gas sufficient for use by the crew in a particular application. The volume of gas held be the secondary reservoir  12  may be related to the pressure at which the gas is stored. For example, at 3,000 psig, the secondary reservoir  12  may hold 300 L of breathing gas. Such a volume and pressure may be sufficient as a secondary (back-up) source of breathing gas, for example, to two crew members, such as a captain and a first officer. The secondary reservoir  12  may include an indicator  13  to indicate the contents of the secondary reservoir  12 , for example, indicating the pressure of the reservoir. 
     A secondary line  20  pneumatically connects the secondary reservoir  12  to a primary line  30 . In some embodiments of the present disclosure, the primary line  30  does not make up a portion of the system  10 , but is a part of the primary crew oxygen system of an aircraft. As described above, the primary line  30  is typically maintained at an operating pressure, which is higher than an ambient pressure. As such, the pressure of the primary line  30  is typically higher than the pressure in the secondary line  20 . A check valve  26  is provided in the secondary line  20  in order to prevent a flow of gas from the primary line  30  into the secondary line  20 . 
     An actuator  14  is disposed in the secondary line  20  and is configured to allow a flow of gas from the secondary reservoir  12  through the secondary line  20 . Upon actuation, the actuator  14  permits a flow of breathing gas from the secondary reservoir  12  to the secondary line  20 . In some embodiments, such as the embodiment depicted in  FIG. 1 , the actuator  14  is disposed such that the secondary line  20  receives no gas from the secondary reservoir  12  until the actuator  14  is actuated. A pressure switch  32  is disposed in the primary line  30  and is configured to detect a pressure of the primary line  30 . The pressure switch  32  actuates the actuator  14  when a loss of pressure is sensed in the primary line  30 . 
     The pressure switch  32  may actuate the actuator  14  in any manner. For example, in the embodiment depicted in  FIG. 2 , the pressure switch  132  is in electrical communication with the actuator  114  and may provide an electrical signal to the actuator  114 . Such electrical communication may be via wire  133 , wireless, or other techniques that will be apparent in light of the present disclosure. In the example depicted in  FIG. 1 , a mechanical linkage  33  may connect the pressure switch and the actuator. Other actuation techniques are known and applicable in the present disclosure. In some embodiments, the pressure switch  32  is not a part of the system  10  and is instead a component present in the primary crew oxygen system. In other embodiments, the primary switch  32  is added to the primary crew oxygen system when such a primary system is retrofit with an embodiment of the presently disclosed secondary system. As such, the primary switch  32  may be considered to make up a part of the system  10 . 
     A pressure reducer  18  may be disposed in the secondary line  20  and configured to reduce a pressure of the breathing gas from the supply pressure (a pressure at which the gas is stored in the secondary reservoir  12 ) to an operating pressure (a pressure at which the gas is presented to the crew mask(s)). The operating pressure may be, for example, 70 psig. In some embodiments, the pressure reducer  18  is configured to reduce a pressure of the breathing gas from the supply pressure to a line pressure (an intermediate pressure for use in the secondary line  20 ). As such, the system  10  may further comprise an inline regulator  24  for reducing the gas pressure from the line pressure to an operating pressure suitable for use by the masks. 
     A primary line check valve  34  is disposed in the primary line  30  to prevent a flow of gas from the secondary line  20  into a source side the primary line  30 . Considering the point (the “connection point”) at which the secondary line  20  is connected to the primary line  30 , the source side of the primary line  30  is from the connection point back to the source of primary breathing gas—i.e., upstream. Accordingly, the mask side of the primary line  30  is from the connection point to the crew mask—i.e., downstream. As such, check valve  34  is intended to prevent the loss of breathing gas from the secondary system  10  due to the same failure which caused the loss of the primary breathing gas. One having skill in the art will note that it may be advantageous to minimize the length of the mask side so as to minimize the chance that a primary system failure will also cause a failure of the secondary system. It should be noted that providing gas to a breathing mask includes providing gas to a mask stowage box, providing gas to a plurality of breathing masks, or other configurations which will be apparent to one having skill in the art in light of the present disclosure. 
     In operation, as described above, the primary line  30  is pressurized to an operating pressure and, in the case of deployment of the crew mask(s), the primary crew oxygen system provides breathing gas to the mask(s). If there is a loss of pressure in the primary line  30 , whether such loss of pressure occurs during the use of the mask(s) by the crew or before, the pressure switch  32  will actuate the actuator  14  of the secondary system  10  and breathing gas will flow from the secondary reservoir  12  through the secondary line  20  and through the mask side of the primary line  30  thereby supplying the mask(s) with breathing gas. 
     Embodiments of the present disclosure may include components which are combined, though such components need not necessarily be combined. For example, the pressure reducer  18  and the inline regulator  24  may be combined into a single component. 
     In some embodiments of the present disclosure such as that depicted in  FIG. 2 , the secondary reservoir is a pressure vessel  112 . The pressure vessel  112  may contain a metal-organic framework (MOF) adsorbent  113 . Such an MOF adsorbent  113  is configured to selectively adsorb and desorb breathing gas (e.g., oxygen) in the operational environment of an aircraft at altitude. The MOF adsorbent  113  is configured to store breathing gas more efficiently. 
     For example, when compared to a pressure vessel without an MOF, the MOF adsorbent  113  may enable more advantageous volume to pressure ratios. For example, a greater amount of gas may be stored at the same pressure and volume, or the same amount of gas may be stored at a lower pressure or volume, etc. In a particular example, the breathing gas is oxygen and the pressure vessel contains an MOF configured to adsorb oxygen. 
     Another aspect of the present disclosure is embodied as a method  200  for providing a secondary source of breathing gas to a mask. See  FIG. 3 . The method  200  includes detecting  203  a gas pressure lower than a pre-determined threshold in a primary line using a pressure switch. The primary line is in pneumatic communication with a breathing mask. An actuator is actuated  206  to permit a flow of secondary gas to the breathing mask by way of a secondary line and a mask side of the primary line. For example, as described above, if a low pressure is detected  203  by the pressure switch, the actuator is actuated  206 . In an exemplary embodiment, the actuator may be actuated by an electrical signal sent  209  to the actuator. A pressure of the secondary gas is reduced  212  to an operating pressure. The gas may be prevented  215  from flowing from the secondary line to a source side of the primary line. For example, a valve, such as a check valve, may prevent gas from flowing to the source side of the primary line (i.e., directing gas flow to a mask side of the primary line). 
     Although the present disclosure has been described with respect to one or more particular embodiments, it will be understood that other embodiments of the present disclosure may be made without departing from the spirit and scope of the present disclosure. Hence, the present disclosure is deemed limited only by the appended claims and the reasonable interpretation thereof