Abstract:
The present invention is a filter cartridge with integrated inhalation and exhalation valves. The exhalation valve integrated into the filter cartridge prevents unfiltered air from being inhaled. The inhalation valve(s), also integrated into the filter cartridge, effectively reduces the dead space inside the filter cartridge and thereby limits re-breathing of carbon dioxide.

Description:
FIELD OF INVENTION 
   This invention relates to a filter cartridge with integrated inhalation and exhalation valves that minimize re-breathed carbon dioxide, reduce package size and maximize reliability. 
   SUMMARY OF INVENTION 
   The present invention is a filter cartridge that reduces re-breathed carbon dioxide, minimizes package size and maximizes reliability. Accumulation of carbon dioxide in the filter cartridge is minimized by directing exhaled air out an exhalation valve and minimizing the effective dead space inside the filter cartridge. The package size is reduced by locating all inhalation and exhalation valves inside the filter cartridge thus eliminating the need to mount corresponding valves directly to a full face piece, half-mask, hood or any other type of breathing interface. Overall reliability is improved by fully enclosing all inhalation and exhalation valves, thereby protecting all valves from dust, dirt, impact or tampering. 
   The filter cartridge includes filtration media through which inhaled air is passed, a housing encasing the filtration media, a respiration port in the housing for passing filtered air and exhaled air to and from a breathing interface, an exhalation port in the housing for discharging exhaled air, an inhalation plate disposed between the filtration media and the respiration port, an inhalation check valve set in the inhalation plate, the inhalation check valve having an open state during inhalation and a closed state during exhalation, an exhalation check valve set in the exhalation port, the exhalation check valve having a closed state during inhalation and an open state during exhalation, whereby inhaled air is passed through and filtered by the filtration media, is then passed through the inhalation check valve in its open state, is blocked from the exhalation port by the exhalation valve in its closed state, and passed to the respiration port. 
   It should be noted that the filter cartridge envelopes the inhalation check valves, the filtration media and the respiratory pathway through which air passes within the filter cartridge. This feature clearly advances the art over filters that have exposed check valves subject to damage, tampering or degradation. An embodiment of the invention fully encases the check valves and filtration media with only the respiration port, exhalation port and the particulate filter housing externally exposed. By internalizing many of the mechanical components of protective respiratory devices into a single filter cartridge, reliability is increased while costs are reduced. In addition, by aggregating multiple mechanical functions common to respiratory devices into a single housing more efficient and rigorous testing may be done on future respiratory protective device designs. 
   The inventive design described and enabled herein provides improved usability for the wearer as carbon dioxide, heat and moisture are reduced. Improved usability and comfort are often directly related to the maximum amount of time a protective respiratory device is donned or engaged. Thus, by increasing the maximum amount of time the protective device is used, the overall safety of the user is enhanced. 
   Exhaled air is passed from the respiration port, blocked by the inhalation valve in its closed state, passed through the exhalation check valve in its open state and is then discharged out the exhalation port. The filter cartridge may have a plurality of inhalation check valves and a plurality of exhalation check valves. The check valves may be annular diaphragms or other construction as known in the art of check valve design. 
   A mount for fluidly coupling the filter cartridge to the breathing interface may be of various means including screw-threaded, bayonet, interference fit or the like. The filter may couple to any breathing interface including, but not limited to the following: hood, helmet, full face piece, half-mask, quarter-mask, mouthpiece and protective suit with integrated hood. 
   An advantage of the invention is that the inhalation valves prevent moisture, heat and carbon dioxide present in exhaled air from saturating and/or accumulating in the filtration media. Thus, the invention reduces the amount of moisture, heat and carbon dioxide that would otherwise be re-breathed absent the present design. 
   Another advantage of the invention is that the inhalation and exhalation check valves are protected from dust, direct impact and/or tampering. 
   Another advantage of the invention is that the overall size of the apparatus is reduced due to the integration of inhalation and exhalation valves inside the filter cartridge thus eliminating the need to mount corresponding valves directly to a full face piece, half-mask, hood or any other type of breathing interface. 
   Still another advantage of the present invention is that the collection of critical parts, namely, the exhalation valve, inhalation valve and filtration media may be collectively replaced with a single unit filter cartridge. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
       FIG. 1  is a perspective view of the rear side of the filter housing with the exhalation valve cover removed. 
       FIG. 2  is a perspective view of the rear side of the filter housing with exhalation valve cover attached. 
       FIG. 3  is a partially exploded, perspective view of the carbon retention pad which is shown over the interior of the filter housing. 
       FIG. 4  is a perspective view of the interior of the filter housing with the carbon retention pad installed. 
       FIG. 5  is a partially exploded, perspective view of the particulate filter housing in overlying relation to the filtration media, which is in turn below the interior chamber of the filter housing. 
       FIG. 6  is a side view of the filter housing secured to a respiratory protective hood. 
       FIG. 7  is a front view of the filter housing secured to a respiratory protective hood. 
       FIG. 8  is a side sectional view of the filter housing showing an inhalation air pathway and an exhalation air pathway according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Turning to  FIG. 1 , rear side  30  of filter housing  20  has single respiration port  40  and exhalation check valve  50 . Exhalation check valve  50  is a resilient elastomeric disc secured to filter housing  20  at the center axis of the disc. Exhalation ports  60  are formed by the attachment of exhalation valve cover  35 . Single respiration port  40  provides a pathway from filter housing  20  through barrier  100  ( FIGS. 6 through 8 ). In  FIG. 2 , the placement of exhalation valve cover  35  is shown. It can therefore be seen how exhaled air, the flow of which is indicated by arrows, is discharged through exhalation ports  60 . 
   In  FIG. 3 , the interior chamber of filter housing  20  is viewable. A carbon retention pad  70  is laid within filter housing  20  over inhalation plate  41  which comprises a pair of inhalation check valves  42 . It should be noted that while two inhalation check valves are illustrated, any number of inhalation check valves may be used balancing inhalation breathing resistance, structural integrity, operational simplicity and manufacturing costs. Dual inhalation check valves  42  prohibit exhaled air from entering filtration media  80  ( FIG. 5 ), thereby reducing heat, moisture, and carbon dioxide accumulation. In  FIG. 4  inhalation plate  41  is hidden. In this manner, the relation of carbon retention pad  70  to the inner volume of filter housing  20  can be seen. The interface between carbon retention pad  70  and inhalation plate  41  is planar. 
     FIG. 5  is an exploded view of the inventive filter cartridge, indicated as a whole by numerical identifier  10 . Here it can be seen how the carbon bed  80  is sandwiched between two carbon retention pads  70  to form the retained carbon bed  90 . Retained carbon bed  90  is enclosed between filter housing  20  and particulate filter housing  25 . The particulate filter housing  25  provides fluid communication between ambient air and the inner volume of the filter cartridge  10 . The invention should not be construed to be limited to any particular type of breathing filter or breathing filter application. Exhalation of moisture, carbon dioxide and heat occurs regardless of filter medium type and the re-breathing of exhaled air, particularly carbon dioxide is undesirable. 
     FIGS. 6 and 7  show filter cartridge  10  fluidly connecting through barrier  100 . The relative position of filter cartridge  10  is shown in relation to barrier  100 . It can be seen that the internalization of exhalation and inhalation valves within the cartridge itself greatly simplifies the complexity of the hood. The cartridge as provided in this invention may be deployed on a wide variety of protective devices. Thus, a single design produced in high volume provides opportunities to increase overall quality, standardized testing and reduced replacement inventory requirements compared to proprietary designs for various models of protective hoods and masks. Another advantage of the internalization of the valves within the cartridge is that the protective hood has less potential points of failure. The more openings and seals made in the hood, the more likely one of those seals may fail. By using the present invention, protective respiratory apparatus may be manufactured, assembled and deployed with a higher reliability factor while reducing overall cost. Visor  110  is illustrated to identify the ocular area of the wearer. 
     FIG. 8  illustrates the inhalation pathway whereby air passes through particulate filter housing  25 , retained carbon bed  90  and inhalation check valve  42 , in an open state, then through respiration port  40 . Exhalation check valve  50 , subject to a vacuum during inhalation, is drawn into a closed state. During exhalation, inhalation check valve  42  closes to prevent moisture, heat and carbon dioxide from entering retained carbon bed  90 . The exhalation check valve  50  opens allowing air to discharge first through plenum  120  and then through the exhalation ports  60  ( FIGS. 1–2 ). The volume of plenum  120  is limited in order to minimize total dead space inside filter cartridge  10 . Accordingly, as shown in  FIG. 8 , inhalation check valve  42  is interposed between retained carbon bed  90  and exhalation check valve  50 . Applicant&#39;s novel design disposes exhalation check valve  50  proximate to respiration port  40  relative to carbon bed  90 . 
   It will be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained and since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
   It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween. Now that the invention has been described,