Abstract:
A filter cartridge assembly including a replendam that combines a particulate filter with an irregular shaped gas sorbent bed. Best operational practice requires that the air passing through the filter be distributed uniformly over the sorbent bed. The repledam directs the air over the surface of the larger sorbent bed utilizing vane-like structures extending from the reticulated member providing for uniform distribution.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Applicant hereby claims priority based on U.S. Provisional Application No. 60/243,918 filed Oct. 27, 2000, entitled “Combination Filter/Cartridge Assembly,” which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to air-purifying filter cartridge assemblies and in particular to a combination filter/cartridge assembly containing a particulate filter media in series arrangement with a sorbent bed. 
     BACKGROUND OF THE INVENTION 
     Cartridge filtering assemblies have been described previously in the art. One such assembly U.S. Pat. No. 4,548,626 to Ackley, discloses a combination of a radially pleated filter and a sorbent bed. This invention does not disclose a support between the round filter and the sorbent bed having radially directed vanes for distributing air over the sorbent bed. Thus, the airflow through the sorbent bed may be short circuited and cause premature exhaustion of the bed. 
     U.S. Pat. No. 6,044,842 to Pereira et al., discloses a gasketless adapter for fastening two filter elements to one another. However, the geometrical structure of the arrangement of the first and second does not allow for full utilization of the filtering capability and may cause excessive pressure drop. 
     U.S. Pat. No. 4,714,486 to Silverthorn, discloses a filter canister having a canister body with top and bottom parts sealed together, a filter for particulate material sealed into the top part and a separate sorbent cartridge fitted into the bottom part of the body. The design of the prior air filter cannister does not allow for uniform air distribution throughout the plenum chamber between the first and second filters which is an undesirable attribute of the design. 
     Therefore, as can be seen from the prior art patents, there is a need for a novel filter cartridge assembly which can be used with one or more filter assemblies and thus provide for structure bed integrity and for uniform distribution of air throughout the assembly. 
     SUMMARY OF THE INVENTION 
     The present invention meets the above-described need by providing a housing that combines with a particulate filter having an irregular shaped gas sorbent bed. Proper usage of the filter cartridge requires that the air passing through the filter be distributed uniformly over the sorbent bed. Thus, the filter cartridge directs the air radially over the surface of the sorbent bed utilizing the vane-like structures radiating out from the reticulated members. A multi-functional assembly located within the filter housing has been named a replendam. The term “replendam” is an acronym for an assembly which is a retention screen, a plenum chamber, and an adhesive barrier for a particulate filter. 
     As a retention screen, it provides stability to the sorbent bed to ensure individual grains of sorbent do not move or otherwise shift in the sorbent column. Errant settling or shifting of the sorbent changes the flow characteristics of the bed and effects essential residence time of the gases that the bed must absorb. 
     As a plenum chamber, it ensures that the face velocity across the sorbent bed is uniform. 
     As an adhesive barrier, it prevents migration of glue into the plenum when the particulate filter is potted in place. Since the immobilization screen must apply pressure evenly, the adhesive barrier must be designed to allow a cushion so the filter area under it is not crushed. 
     The foregoing and additional advantages and characterizing features of the present invention will become clearly apparent upon reading of the following detailed description together with the included drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the combination filter/cartridge assembly of the present invention. 
     FIG. 2 is a side elevational view of the combination filter/cartridge assembly of FIG.  1 . 
     FIG. 3 is a partially cutaway side elevational view of the combination filter/cartridge assembly. 
     FIG. 4 is a detailed partial view of the combination filter/cartridge assembly shown in FIG.  3 . 
     FIG. 5 is a detailed partial view of the combination filter/cartridge assembly shown in FIG.  3 . 
     FIG. 6 is a perspective view of the replendam. 
     FIG. 7 is a bottom plan view of the replendam. 
     FIG. 8 is a cross-sectional view taken along line  8 — 8  of FIG.  7 . 
     FIG. 9 is a cross-sectional view taken along line  9 — 9  of FIG.  7 . 
     FIG. 10 is a detailed partial view from FIG.  9 . 
     FIG. 11 is a perspective view of the cover. 
     FIG. 12 is a top plan view of the cover. 
     FIG. 13 is a side elevation view of the cover. 
     FIG. 14 is a bottom plan view of the cover. 
     FIG. 15 is a sectional side elevational view of the cover. 
     FIG. 16 is a detailed partial sectional view of the cover. 
     FIG. 17 is a perspective view of the body. 
     FIG. 18 is a top plan view of the body. 
     FIG. 19 is a sectional side elevational view of the body. 
     FIG. 20 is a bottom plan view of the body with the reticulated wall removed for clarity. 
     FIG. 21 is a top plan view of an alternate embodiment of the present invention. 
     FIG. 22 is a side elevational view of an alternate embodiment of the replendam of the present invention. 
     FIG. 23 is an alternate embodiment of the cover of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Now, referring to FIGS. 1-23 generally and initially to FIG. 1, a combination cartridge/filter assembly  10  of the present invention is shown. The assembly  10  includes a particulate filter media  13  (FIG. 4) and a sorbent bed  16  (FIG.  4 ). The sorbent bed  16  is formed out of a sorbent media  17  that may include carbon materials comprising impregnated carbon and/or activated carbon. Other granular sorbent materials may also be suitable. Also, any materials that are air permeable and that are capable of absorbing or reacting with the gas contaminants to be removed or neutralized would also be suitable. The filter media  13  and the sorbent bed  16  are disposed in a series arrangement with a relatively small plenum chamber disposed between the filter media  13  and the sorbent bed  16  as will be described herein. The assembly  10  comprises a cover  19  that snaps onto a body  22 . The cover  19  includes a grill or reticulated wall  23  spanning an opening  24 . The filter media  13  fits inside the cover  19  and is separated from the sorbent bed  16  by a replendam  25  (FIGS.  4  and  6 - 10 ) as described below. The cover  19 , body  22 , and replendam  25  are formed out of suitable thermoplastic materials in injection molding processes or the like. Other materials having suitable properties for use as a filter cartridge and replendam may also be used. 
     In FIG. 2, the cover  19  has an air inlet  28  where ambient air is drawn into the assembly  10  for purification. The assembly  10  is suitable for use with a respiratory mask of the type disclosed in U.S. Pat. No. 6,016,804 which is assigned to the assignee of the present invention and which is incorporated herein by reference. The outlet  31  of assembly  10  attaches to the inlet of a respiratory mask. 
     Turning now to FIG. 3, the path for the flow of air is indicated by arrows  34  and  37 . The particulate filter media  13  is a round pleated filter media. Other particulate filters may also be suitable and other shapes of filters may also be suitable. The body  22  for the sorbent bed  16  is significantly larger than the filter media  13  and has an irregular six-sided shape. However, the number of sides and the shape of the sorbent bed  16  is not critical. 
     In FIG. 4, the cover  19  houses the particulate filter media  13  which as described above is typically a round pleated filter media. The pleated filter media  13  is potted in the cover  19  as will be described in detail hereinafter. The inside of the cover  19  in cooperation with the bottom surface of the media  13 , the replendam  25 , and the top of the sorbent bed  16  forms a plenum chamber  40  between the filter media  13  and the sorbent bed  16  which is located in body  22 . The replendam  25  maintains separation between the filter media  13  and the sorbent bed  16  to form plenum chamber  40 . Also, the replendam  25  applies pressure to immobilize the sorbent bed  16  when the cover  19  is snapped onto the body  22  as will be described in detail hereinafter. In part, the immobilizing pressure is applied through a plurality of plastic springs  41  which will be described in detail hereinafter. The replendam  25  engages with a retention filter media  43  disposed over the sorbent media  17 . The last layer inside the body  22  is a second retention filter media  49 , which is preferably a fines filter that may be placed in the bottom of the body  22  or attached to the bottom of the body  22  by sonic welding, glueing, or other process. 
     As shown in FIG. 4, the perimeter of the replendam  25  has a V-shaped rib  50  extending downward toward the sorbent bed. Above the V-shaped rib  50 , the replendam  25  has a V-shaped groove  53  disposed therein. A corresponding V-shaped rib  56  disposed on the cover  19  engages with the groove  53  when the cover  19  is snapped onto the body  22 . The cover  19  has a second V-shaped rib  59  that engages with a V-shaped groove  62  disposed in the upper edge of the side wall  65  of the body  22 . The cover  19  also includes a hook portion  68  (best shown in FIGS. 5 and 16) that snaps over a shoulder  71  (best shown in FIG. 19) formed in the outside top of the side wall  65  of the body  22 . 
     Turning to FIG. 5, a sealing compound  74  is applied in a bead to the area around the V-shaped rib  59  to seal the joint where the rib  59  engages with the groove  62  (FIG. 4) in the body  22 . 
     In FIGS. 6-10, the replendam  25  includes a grill or reticulated wall  80  that is round to correspond to the shape of the filter media  13 . Other shapes for different shaped filter media would also be suitable. An air dam  83  is disposed in substantially parallel and spaced apart relation above the reticulated wall  80 . The air dam  83  is also round to correspond to the shape of the filter media  13 , however, other shapes for non-round media would also be suitable. The air dam  83  acts as a adhesive barrier when the filter media  13  is potted in the cover  19  as described herein. Air dam  83  is attached to the reticulated wall  80  by a plurality of first inner legs  86  of the plurality of springs  41  (best shown in FIG.  10 ). In the embodiment shown, there are eight springs  41  that are approximately equidistant around the circumference of the reticulated wall  80 . The springs  41  are U-shaped with the first legs generally designated as  86  being attached to the air dam  83  and the second outer legs generally designated as  88  being attached to a circular inner support frame  89  (FIG.  7 ). The circular or round inner support frame  89  is disposed substantially coplanar with the reticulated wall  80 . The inner support frame  89  is circular or round for the round filter media  13 , however, it could be other shapes for non-round media. As best shown in FIG. 10, the outer frame  95  extends below the plane formed by the reticulated wall  80 , the inner frame  89 , and the support members  92  so that the outer frame  95  makes the initial contact with the retention filter media  43 . The plurality of lateral support members  92  attach the inner support frame  89  to an outer frame  95  forming a second reticulated wall  93  that conforms to the six-sided shape of the body  22 . A plurality of vane-like members generally designated as  100  extend from the center of the reticulated wall  80  and connect between the inner support frame  89  and the outer frame  95 . As shown the vane-like members  100  extend radially in substantially straight lines. For non-round filter media, the vane-like members  100  may be straight or curved depending on the filter geometry and may or may not extend radially. The vane-like members  100  extend vertically above the support members  92  between the horizontal planes defined by the reticulated wall  80  and the air dam  83 . The vane-like members  100  are connected by a pair of curved members  101 ,  102  that are concentric with the inner frame member  89 . The vanes  100  direct the air flow and also function as stiffening ribs for applications where sorbent bed immobilization is required so that energy can be transferred through the springs  41  across the replendam  25 . 
     In FIG. 10, the V-shaped rib  50  and the V-shaped groove  53  of the replendam  25  are shown with relation to one of the springs  41  located at the side of the replendam  25 . The first leg  86  of the spring  41  extends to the reticulated wall  80  and the second leg  88  extends to the inner support frame  89 . A short lateral support member  92  connects the inner support frame  89  to the outer frame  95 . As described above the outer frame  95  conforms to the six-sided shape of the sorbent bed  16 . The outer frame  95  is formed with the V-shaped rib  50  on the bottom and with the V-shaped groove  53  on the top. 
     In FIGS. 11-16, the cover  19  is shown in greater detail. The cover  19  has a complex shape with a round section  110  extending outward from a six-sided planar section  113 . The round section  110  corresponds to the shape of round filter media  13 . Other shapes for section  110  for use with non-round filters would also be suitable. The six-sided planar section  113  terminates in side walls  115  that extend substantially perpendicular to the planar section  113 . In FIG. 12, the opening  24  is covered by the grill or reticulated wall  23 . 
     The round filter media  13  (FIG. 4) is potted in the round section  110  by applying a glue  111  (best shown in FIG. 4) to the perimeter of the filter media  13  such that a r is prevented from passing around the edges of the filter media  13  between the media  13  and the inner wall of the cover  19 . As shown in FIG. 4, the air dam  83  acts as a adhesive barrier to prevent glue from entering the plenum chamber  40 . 
     In FIG. 16, the hook  68  and the first and second V-shaped ribs  56 ,  59  are shown in greater detail. Also shown is an inner wall  116  that extends downward for a short distance and surrounds the round section  110  for the round filter media  13 . As shown in FIG. 15, the wall  116  has openings generally designated as  117  defined therein that are sized to receive the springs  41  that extend toward the air dam  83  when the replendam  25  is installed in the cartridge assembly  10 . When the replendam  25  is installed in the assembly  10 , the air dam  83  fits inside the inner wall  116 , and the V-shaped groove  53  in the replendam  25  engages with the first rib  56  (best shown in FIG.  4 ). 
     FIGS. 17-20, illustrate the body  22  in greater detail. The body  22  has a set of ribs generally designated as  120  disposed on a bottom surface  123 . The ribs  120  are designed to channel the air flow toward the outlet and to assist in the immobilization of the sorbent materials  46 . The bottom surface  123  is substantially planar and is shaped in a six-sided shape. Other shapes may also be suitable. The bottom surface  123  is bordered by a plurality of side walls  65  that extend substantially perpendicular to the bottom surface  123  to form a chamber. 
     In FIG. 18, the outlet  31  has a grill or reticulated wall  140  that supports the sorbent bed  16 . Turning now to FIG. 19, the body  22  has an opening  145  that is disposed in spaced apart relation to the reticulated wall  140 . The opening  145  has a pair of truncated sides  148  that provide for inserting a quarter-turn bayonet mount adapter such as disclosed in U.S. Pat. No. 6,016,804 through the opening. The space between the opening  145  and the reticulated wall  140  provides clearance for the adapter on the respiratory mask to fit inside the cartridge assembly  10  and to turn into a locked position. 
     As shown in FIG. 19, the side walls  65  have shoulder  71  extending around the periphery of the top edge  133  of the side walls  65 . As described above, the shoulder  71  cooperates with the hook  68  on the cover to provide for a snap-fit. 
     In FIG. 20, the opening  145  is shown with the reticulated wall  140  removed such that the sides  148  are clearly shown. The opening  145  is designed with sides  148  such that the assembly  10  is capable of mounting onto a respiratory mask by means of a quarter turn bayonet adaptor of the type disclosed in U.S. Pat. No. 6,016,804. 
     In operation, the combination filter/cartridge assembly  10  performs several functions. Returning to FIG. 4, the replendam  25  serves several functions. First, the replendam  25  is sized such that the bottom surface provides an immobilization force when the cover  19  is snapped onto the body  22 . When the cover  19  is snapped onto the body  22 , the bottom of the round filter media  13  engages with the air dam  83  to provide a downward force against the sorbent bed  16 . The force is transmitted through the springs  41  to the entire bottom surface of the replendam  25  such that an immobilization force is applied throughout the bottom surface of the replendam  25  onto the top surface of the sorbent bed  16 . Also, the rib  50  disposed around the perimeter of the replendam  25  is forced downward onto the retention filter  43  when the cover  19  is snapped onto the body  22 . The rib  50  provides a knife edge engagement with the retention filter media  43  that holds the media  43  in position. 
     Accordingly, the force of the replendam  25  on the top of the sorbent bed  16  promotes sorbent pack density and stability. As known to those of ordinary skill in the art, the settling or shifting of sorbent changes the flow characteristics of the bed and effects residence time of the gases that the bed must absorb. 
     In addition to transmitting force to the bottom surface of the replendam  25  through the springs  41 , the air dam  83  also provides a adhesive barrier to prevent the glue that is used to pot the filter media  13  in the cover  19  from entering the plenum chamber  40 . 
     Returning to FIG. 7, the design of the replendam  25  also promotes uniform distribution of air over the sorbent bed  16 . The plenum  40  is designed to provide a chamber where equalization of the air flow can occur prior to entry of the air into the sorbent bed  16  such that the sorbent bed  16  surface uniformly receives air having the same or approximately the same face velocity. Uneven distribution of airflow will underutilize the sorbent bed  16  and decrease the bed life. Also, the radial vane-like structures  100  of the replendam  25  direct the air flow in the plenum chamber  40  over the entire surface of the sorbent bed  16  to promote uniform distribution of air flow across the bed. 
     The embodiment shown in FIGS. 1-20 provides a replendam  25  for use between filter media  13  and sorbent bed  16 . However, the replendam  25  of the present invention could also be disposed between two different sized filter media or a multi-stage cartridge could be constructed with more than one replendam  25  disposed in combination with filter media and/or sorbent beds. 
     Also, the springs  41  may be utilized in a single stage filtering system such that the device would not include the vanes  100  and the plenum chamber  40 . For example in an alternate embodiment shown in FIG. 21, the springs  41  could engage with an alternate cover  200  (FIG. 23) such that the springs  41  could be used to transmit a force from the cover  200  to the retention filter  43  through the outer frame  95  and the reticulated structure  201  above the so-bent bed  16 . The cover  200  has an irregular-shaped opening. As an alternative, the cover  200  could be provided with a round, smaller opening such as the opening covered by a reticulated wall shown in FIG.  11 . Accordingly, the smaller round opening would facilitate an easy negative pressure check by the user of the device who would be able to cover the opening with one hand. 
     In certain applications the force on the sorbent bed transmitted through the springs  41  to the replendam  25  may not be required. These applications may include situations where the replendam  25  is disposed between two filters or if the sorbent does not require the force on the top of the bed. 
     Also, in another alternate embodiment for forming a plenum, an alternate replendam  300  shown in FIG. 22 could be constructed without plastic springs generally designated as  41 . The replendam  300  could have the adhesive barrier air dam  83  connected to the inner support member  92  by means of a solid member  303  without spring properties. Accordingly, the springs  41  and the design of the replendam  25  may or may not be used in combination depending on the application. 
     While the invention has been described in connection with certain embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention.