Patent Publication Number: US-2007113846-A1

Title: Facepiece for a respirator for high performance fixed-wing aircraft crew protection

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims priority from U.S. Provisional Patent Application Ser. No. 60/694,449 which was filed on Jun. 27, 2005. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This application is directed to the field of equipment used by pilots in high-performance fixed-wing aircraft, and, more particularly, to a facepiece used by such pilots in connection with a respirator.  
      2. Description of the Related Art  
      Providing breathable air to pilots of high performance aircraft is a difficult problem. First, the air must contain the proper concentration of oxygen to enable the pilot to function. As the pilot flies the aircraft at higher and higher altitudes, the pilot cannot simply rely on ambient air as the source of breathable air, because the oxygen partial pressure decreases at altitude. Second, many fighter/attack aircraft now have as part of their G-protection features positive pressure breathing for G, or PBG with which the pressure of the breathing gas supplied to the pilot may be substantially above ambient pressure. Thus, it is necessary to provide pilots with a reliable supply of breathable air in which both oxygen concentration and pressure are controlled. For standard (no chemical/biological threat) operations, this is normally accomplished by a regulator supplying a suitable airflow to a mask worn by the pilot. Such masks usually cover only the mouth and nose of the pilot. Breathing gas is provided to the pilot through an inlet valve and waste gas is exhausted through an outlet valve.  
      The fit of such masks is very important, because they must seal well against the face to avoid leakage during pressure breathing operations. Excessive leakage can waste breathing oxygen (in limited supply in many aircraft), may reduce the required in-mask pressure, and may cause vision impairment if leakage is directly into the eyes.  
      There are also particular problems and difficulties in implementing a chemical/biological respirator for use in fighter aircraft with pressure breathing capability for high-G and/or altitude protection. While the respirator must completely enclose the head and face to protect the wearer&#39;s eyes and lungs from external chemical or biological agents, it must have a transparent visor portion in front of the eyes, and an oronasal mask (“mask”) portion covering the mouth and nose which performs the same function as the mask in standard operations with respect to delivering suitable breathing gas to the pilot. In addition, it is highly desirable, though not necessary, to have that portion of the respirator that covers the eyes, nose, and mouth (“facepiece”) be removable. This “removability” feature is for in-flight physiological emergencies (vomiting, for example) and also allows interchangeability of multiple mask sizes with the over-head hood portion, which is also commonly available in multiple sizes. Thus, for example, four sizes of masks can be used with three sizes of hoods without having to stock all different sizes of mask/hood combinations (twelve size combinations in this example). Also, damage to one part of the system (for example, a scratched visor) would not require scrapping the entire respirator but would only require replacing the damaged component.  
      One method of implementing this removable mask, or facepiece, concept that has proved itself in practice is to attach the mask internally to a more-or-less rigid frame (“faceframe”) covering the entire face, with that portion of the frame anterior to the eyes being a transparent visor. The faceframe has a periphery that is shaped to match the contours of a hood frame so that it may be attached to the hood frame in such a manner that a seal is provided to prevent the entry of contaminated air. The frames are then held together by a latch mechanism, and the seal is provided by means of an elastomeric gasket at the frame to frame interface. Normally, the faceshield frame is attached to a helmet by traditional mask-to-helmet attachments or can be used without a helmet by means of around-head straps to hold the faceshield to the face. Alternatively, a complete faceshield frame/mask/visor assembly can be directly attached to the cowl; in this case, of course, the faceshield is not removable from the cowl assembly without destroying the respirator.  
      A prior art respirator as described above with the removable facepiece feature has been designed for helicopter pilots by ILC Corp. Another, without the removable facepiece feature, is the AR5 respirator produced by Camlock, a UK manufacturer, and used by the U.S. Navy, as well as Canadian and U.K. aircrews. Both of these respirators, however, suffer from significant drawbacks for use in high performance aircraft.  
      There are two fundamental problems inherent in using such respirators in fighter aircraft. First, to provide physiological protection against G-force and high altitude, the pressure of the breathing gas inside the mask may be increased dramatically (more than 1.4 psi in extreme cases) above ambient pressure. These protective systems are known as Pressure Breathing for G (PBG) and Pressure Breathing for Altitude (PBA). For either PBG or PBA to be effective, the mask must maintain an excellent seal against the face. This demands that the mask be positioned against the face in the optimum sealing location and orientation on each wearer and held at that location and orientation throughout a flight mission and at maximum PBG or PBA pressures. Second, the visor must be located as close to the eyes as the pilot&#39;s brow and zygomatic arches allow. This is necessary both to maximize the wearer&#39;s visual field and to minimize interference with proper operation of external (normally helmet-mounted) optical devices.  
      Because optimum fit location and orientation on a wearer depends strongly on upper nose and jaw configurations, both with infinite variability, the mask&#39;s position and orientation (with respect to eye location and Frankfort horizontal plane, for example) varies over a wide range from user to user. Also, the orientation and location of the mask with respect to the location and orientation of the faceframe will vary widely from individual to individual, since the faceframe is positioned against different facial features as opposed to the facial features in contact with the mask.  
      Consequently, if the mask is rigidly mounted inside the faceframe, neither is likely to fit properly. Conversely, if the mask is soft-mounted inside the faceframe so that it might seek an independent fit, the high internal pressures inherent in PBG and PBA will cause the mask to move away from the face, compromising the mask-to-face seal. This may result in loss of mask pressure, visor fogging during exhalation, and/or direct impingement of leaking gas into the eyes.  
      To rigidly alter the mask location and orientation within the faceframe during initial fitting to a particular pilot would require elaborate externally-accessible positioning mechanisms, adding significant weight, volume, complexity, and the increased possibility of leaks to the respirator.  
      There is thus a need in the art for a facepiece for a simplified high-altitude respirator that provides for improved seal and performance.  
     SUMMARY OF THE INVENTION  
      Briefly stated, the invention is directed to a facepiece for use as part of a respirator and for attachment to a hood, the facepiece comprising: a faceframe for mounting the facepiece to a hoodframe or directly to the hood; a visor attached to the faceframe; a mask; means for removably affixing the mask to the faceframe; the mask including: means for receiving a supply of gas for breathing by a user of the facepiece; means for permitting the exhausting of the user&#39;s breath; means for removably affixing the faceframe to the hoodframe; and an interface between the faceframe and the mask; whereby the mask and the faceframe may be individually fitted to the user, after which the mask and faceframe may be fixed to each other against relative movement by mechanical means.  
      The various features of novelty that characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In the drawings, in which like numerals designate like elements:  
       FIG. 1  is a perspective view of a facepiece in accordance with the invention, shown in breakaway from a hood with which it is used; and  
       FIG. 2  is a cross-section of the facepiece of  FIG. 1 , shown in place on a user while in use.  
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS  
      A facepiece in accordance with the invention is shown in the Figures, generally at  10 . As shown in  FIG. 1 , facepiece  10  includes a mask  12  which protrudes through a faceframe  14  and is, during flight, connected directly to a helmet (not shown) worn by a pilot  16  ( FIG. 2 ) through a mechanism  18 , similar or identical to mask-helmet attachments with non-respirator flight hardware. Mask  12  is connected to faceframe  14  by means of a thin flexible elastomeric interface  20 . Interface  20  is made of any of a number of suitable chemical/biological barrier materials, for example, bromo-butyl. Its flexibility allows required translational and rotational positioning variation between mask  12  and faceframe  14  to achieve required fits on most or all users.  
      It is preferred that mask  12  and faceframe  14  be individually fitted to provide for the best customized fit therebetween. As part of this process, different sizes and shapes of masks and faceframes may be combined to form the best possible individualized overall fit for facepiece with the face of pilot  16 . After the individual elements are chosen, they are fitted individually on pilot  16  to create the tightest seal, and then a mechanism  22  rigidly connects mask  12  and faceframe  14  to prevent any further relative movement therebetween. Mechanism  22  may be any one of a variety of common mechanical designs allowing for free movement between mask  12  and faceframe  14  during fitting, and thereafter maintaining or “locking” the two in the desired positional relationship. Suitable mechanisms may include a slotted tab on the faceframe that interfaces with a threaded boss on the mask via an adjustment screw.  
      Faceframe  14  contains a transparent visor  24 . Visor  24  may be rigidly attached to faceframe  14  or, if it offers any advantages in a particular implementation (for example, the ability to selectively move the visor forward to allow for user-worn vision-corrective spectacles), interface  20  may include an extension  26  ( FIG. 1 ) that extends completely around visor  24 , connecting visor  24  to faceframe  14  in a flexible manner.  
      Visor  24  is supplied with demist air from a clean filtered source. This demist air may be supplied by means of a hose  28  attached to faceframe  14 , or it may be supplied from inside the hood, flowing forward and downward, depending on the particular application. Faceframe  14  is connected to a hoodframe  30  of a hood  32  by a latch  34 ; in a non-removable implementation, faceframe  14  is affixed directly to hood  32 .  
      The combination of mask  12 , faceframe  14 , mechanism  18 , interface  20 , mechanism  22 , visor  24 , demist air hose  28  (if present), latch  34  (if present) and hose  36  for conducting breathing air to the user comprise the facepiece portion of a respirator. The facepiece may also include such features as a lung-powered or emergency demist system, demist air flow restrictors, check valves and connectors as may be required in particular applications.  
      The remaining portion of the respirator, namely hood  32 , consists necessarily of rigid hoodframe  30  and a cowl  38  in a removable facepiece implementation; otherwise, hood  32  and cowl  38  are a single piece. Cowl  38  may or may not contain a neckdam, a head-fitting liner, size adjustments, communications, head ventilation/clean air entry, a valve to vent supplied air to ambient, or any number of other conventional features that a particular application may require.  
      When faceframe  14  is attached to hoodframe  30 , a leakproof seal is formed between the two frames by means of an elastomeric gasket  40 , the specific configuration of which is purely conventional. The two frames are held together in a positive manner until manually released by latch  34 , which may be of any known type. Both the faceframe/hoodframe/gasket sealing and the latch configurations are amenable to many workable solutions within the capabilities of those skilled in the mechanical engineering art.  
      Facepiece  10  and hood  32  together form a complete respirator. Facepiece  10  provides for an improved fit and performance of the respirator of which it is a part. The improved performance results, in part, by a seal  42  between mask  12  and user  16 , which is permitted by the individualized custom fit of separate mask  12  and faceframe  14  to adjust overall the fit of the respirator to the individualized physiognomy of the pilot to an extent not previously possible. Mask  12  can be attached directly to the pilot&#39;s helmet (as in a standard non-respirator mask) for greatly increased positional stability during pressure breathing as compared to one held in place only by the hood  32  with or without a strap around the pilot&#39;s head.  
      Although facepiece  10  has the ability to mechanically clamp faceframe  14  to hoodframe  40  after mask  12  has been properly fit to the individual user, this feature is not necessary for in-aircraft pressure breathing. Its purpose is to maintain a reasonable mask position on the face during emergency ground operations, during which the user will often want to remove the helmet since the helmet is cumbersome when not needed. Under this condition, with mask  12  no longer supported by helmet attachments, hoodframe  40 , cowl  38 , and (if present) a strap around the head provide sufficient support and maintain sufficient seal to prevent exhalation into and fogging of visor  24 .  
      Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.