Abstract:
A stackable, portable air filtration unit utilizing a molded plastic central housing, injection-molded plastic inlet and outlet covers and accommodating a high-efficiency particulate air (“HEPA”) filter or other high efficiency particulate filter, a secondary filter and a pre-filter. The unit is versatile and flexible in that different motorized impellers can be used alternatively, depending on the desired specifications.

Description:
FIELD OF THE INVENTION 
     This invention relates to air filtration to remove hazardous and/or non-hazardous particulate, biological, and gas phase contaminants, and in some instances to create and maintain negative or positive atmospheric pressure within physically enclosed areas. 
     BACKGROUND 
     Devices that pass air and other fluids through one or more fitters are well known and have long been used. Such devices are also well known for use during abatement of aerosolized contaminants in buildings, where the air in a particular area may contain airborne materials that need to be removed from the air before they either settle onto surfaces or can escape in air exhausted from that area and potentially breathed by facility occupants outside the area or for other reasons. 
     The design of such filtration units or “portable air scrubbers” is challenging because there are a large number of demanding requirements and desired features, some of which compete with each other. For instance, it is desirable that such air scrubbers be compact, lightweight, stackable, easily transported, powered, operated, maintained, cleaned and stored. It is desirable that they be durable and able to function in numerous different environments, as well as economical to purchase and operate. It is desirable for such scrubbers to utilize multiple, economical filters and to be highly effective. 
     SUMMARY 
     The terms “invention,” “the invention,” “this invention” and “the present invention” used in this patent are intended to refer broadly to all of the subject matter of this patent and the patent claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the patent claims below. Embodiments of the invention covered by this patent are defined by the claims below, not this summary. This summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further described in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to appropriate portions of the entire specification of this patent, any or all drawings and each claim. 
     The portable air filtration unit of this invention utilizes a double walled molded housing with inlet and outlet doors or covers, a pre-filter, a secondary filter and a high-efficiency final filter, typically a “HEPA” High Efficiency Particulate Air filter, a motorized impeller to draw or drive air through the filters, and appropriate controls. It is compact, lightweight, durable, economical to operate, versatile and flexible in that different motorized impellers can be used alternatively, depending on the desired specifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described in detail below with reference to the following drawing figures: 
         FIG. 1  is a perspective view of the front, top and right side of the portable air filtration unit of this invention. 
         FIG. 2  is an exploded perspective view of the left side of the unit depicted in  FIG. 1 . 
         FIG. 3  is a perspective view of the inlet side of the unit depicted in  FIG. 1  with the inlet door open. 
         FIG. 4  is a perspective view of the unit depicted in  FIG. 1  with the inlet door open and the secondary filter removed. 
         FIG. 5  is another perspective view of the unit depicted in  FIG. 1  with the inlet door open and without any filters. 
         FIG. 6  is a perspective view of the outlet side or end of the unit depicted in  FIG. 1  without the outlet cover. 
         FIGS. 7 and 8  are inside and outside views, respectively, of the outlet cover of the unit depicted in  FIG. 1  together with the components that attach to it. 
     
    
    
     DETAILED DESCRIPTION 
     The subject matter of embodiments of the present invention is described here with specificity to meet statutory requirements, but this description is not necessarily intended to limit the scope of the claims. The claimed subject matter may be embodied in other ways, may include different elements or steps, and may be used in conjunction with other existing or future technologies. This description should not be interpreted as implying any particular order or arrangement among or between various steps or elements except when the order of individual steps or arrangement of elements is explicitly described. 
       FIG. 1  depicts one embodiment of the portable air filtration unit  10  of this invention having a housing  12  to which a carrying handle  14  is attached, together with a sloping control panel  16  and an air exhaust  18 . Handle  14  may be foldable to provide a low profile when the handle is not in use, it may be ergonomically designed to promote comfort in use, and it may be positioned on housing so that the unit  10  is balanced and does not tilt when lifted by the handle  14 . 
     These major components and their relationships may be easily seen in  FIG. 2 , which is an exploded perspective view in which the housing is centrally positioned. To the left of the housing  12  are a venturi ring  20 , high-efficiency filter  22 , high-efficiency filter securing brackets  24 , secondary filter  26 , pre-filter  28  and inlet door  30 . 
     To the right of the housing  12  in  FIG. 2  may be seen a motorized impeller  32 , motor mount  34 , outlet cover  36 , control panel box  38  and control panel assembly  40 , which includes control panel  16 . 
     When these components are assembled, inlet door  30  permits entry of unfiltered air through inlet  42 , which is drawn in and through the pre-filter  28 , secondary filter  26  and high-efficiency filter  22  by motorized impeller  32 . When closed, inlet door  30  also secures filters  28  and  26  in their appropriate places and seals against housing  12  with latch and keeper, one side  44  of which are attached to housing  12  and the other sides  46  of which are attached to inlet door  30 . A pair of hinges on the opposite side affix door  30  to housing  12 . This sealing engagement between inlet door  30  and housing  12  insures that air drawn into housing  12  must pass through the three filters  22 ,  26  and  28 . This sealing engagement may be particularly well appreciated by reference to  FIG. 3 , which shows the door  30  open with pre-filter  28  seated in a like-shaped cavity on the inner side  50  of inlet door  30 . This customized cavity prevents any significant air flow to bypass pre-filter  28  as can happen with some air filtration units. Pre-filter  28  is surrounded by a raised boss  48 , contoured to match the filter side recess in housing  12 , which is generally rectangular and has two tabs  52  extending up and two tabs  53  extending down from the rectangular portion  54  of raised boss  48 . Housing  12  has a generally rectangular recess  56  with upward facing  58  and downward facing  60  tab-receiving recesses. 
     Secondary filter  26  seats in the generally rectangular recess  56  and, with inlet door  30  open, filter  26  can be removed by reaching into one or more of recesses  58  or  60  to engage one of the upper or lower edges of filter  26 . When closed, the raised boss  48  and tabs  52 ,  52  of inlet door  30  seat in rectangular recess  56  and recesses  58  and  60  providing an air seal around the periphery of door  30 . Air sealing between inlet door  30  and housing  12  (and between housing  12  and outlet cover  36 ) may be facilitated by use of a continuous gasket (such as a closed cell foam or other gaskets) stead in a customized perimeter groove that follows the contour of raised boss  48 . Among other places, such a gasket may be positioned at the intersection  31  of boss  48  and the inner side of inlet door  30  (see  FIG. 3 ). Other types of gaskets and other gasket locations may also be used. 
     A recess  62  in inlet door  30  defined by rectangular portion  54  of the inward facing inlet door  30  boss is sized to receive a snugly-fitting pre-filter  28 , which typically may be batting material of entangled natural or synthetic fibers approximately 1″ thick. 
     Secondary filter  26  may typically be a pleated filter of synthetic media blend fibers within a rigid or semi-rigid paper board frame (known as a beverage board frame). 
     As may be appreciated from  FIGS. 4 and 5 , opposed pairs of the recesses  58  and  60  in housing  12  receive the two ends of high-efficiency filter securing brackets  24 . The depicted brackets  24  may be sections of square or rectangular cross-section tubing, channel, such as C-shaped, L-shaped or other cross-section channel, or a wide variety of other elongated structures including metal strap, rod or bar stock. The recesses  58  and  60  extend into housing  12  so that brackets  24  fully seated in pairs of recesses  58  and  60  hold high-efficiency filter  22  in its intended position in the housing  12  and may be secured, among other ways, by screws, pins, bolts or other fasteners that pass through bracket  24  ends and into housing  12  or into suitable fittings attached to housing  12  such as threaded metal inserts. Brackets  24  also separate secondary filter  26  from high-efficiency filter  22  a distance equal to the thickness of brackets  24 . 
     The tuck-in place fit of pre-filter  28  in the inlet door cavity allows for easy access to the interior of housing  12  by opening inlet door  20 , and the easy replacement of high-efficiency filter  22  simply by removing the secondary filter  26  and bracket bars  24 . As such, it is easy to replace any or all of the three stages of filtration consisting of pre-filter  28 , secondary filter  26  and high-efficiency filter  22 . 
     As is visible in  FIG. 5 , the filter-receiving cavity  64  in housing  12  is bounded, in part, by a flat, smooth baffle wall  66  designed as a high-efficiency sealing surface that faces high-efficiency filter  22  (when in place) and is framed by rectangular frame  68 . Additional recessed wall  66 A beyond surface  66  is structurally sized to create a transitional airflow plenum. This cavity also allows for plumbing a port for differential pressure sensing. This surface also contains multiple seating surfaces to accommodate different sized venturi plates. Both baffle wall  66 , recess  66 A, and frame  68  are integrally formed as part of housing  12  when housing  12  is molded of plastic material as depicted in the figures. 
     A round opening  70  is centered in wall  66 , and the venturi ring  20  is attached to the periphery of that opening to channel and increase the velocity of air drawn through opening  74 . The venturi ring  20  depicted in the figures is of relatively small diameter, but a larger-diameter venturi ring can also be used, if desired, typically with a higher capacity motorized impeller. 
     As is visible in  FIGS. 2 and 6 , housing  12  defines an impeller cavity  72  on the opposite side of wall  66  from the filter-receiving cavity  64 . The motorized impeller  32  is positioned within impeller cavity  72 , together with the control panel box  38 , both of which are attached to outlet cover  36 , which is secured to housing  12  with screws, bolts, pins or other fasteners that pass through cover  36  and into housing  12  or that otherwise attach cover  36  to housing  12 . Among many other alternatives, cover  36  would be attached to housing  12  with latches or buckles, including turn buckles, or with hinges and a latch or latches. 
     Inside and outside views of outlet cover  36  are provided by  FIGS. 7 and 8 , respectively. A collar or boss  74  on the inside of outlet cover  36  is sized and shaped to fit snugly inside the outward-facing rim  76  of housing  12 . This provides a continuous full perimeter engagement air seal and mechanical engagement between cover  36  and housing  12  that helps support cover  36  and the relatively heavy motorized impeller  32  mounted on cover  36 . Air sealing between housing  12  and outlet cover  36  may be facilitated by use of a gasket (such as a closed cell foam gasket) at the intersection  73  of boss  74  and the inner side  75  of outlet cover  36 . So positioned gasket material will seal against corner  77  at the rim  76  of housing  12  (see  FIG. 6 ). 
     As illustrated in  FIG. 7 , a 3-point mounting bracket  34  has two legs  78  that are attached to separated points  80  and  82  near the top of outlet cover  36  and to the same point  84  near the bottom of outlet cover designed to maximize airflow restriction and designed for mounting more than one size impeller while still allowing adjustment of mounting distance off throat of the venturi. The legs are attached by passing bolts, screws or pins through the legs and into the outlet cover  36  or into threaded or other fasteners attached to outlet cover  36 . Other fasteners or fastening methods also can be used. A centrally located mounting plate  86  attaches to each of the legs  78 , and the motorized impeller  32  attaches to plate  86 . Legs  78  may, but need not, be formed separately from each other, and mounting plate  86  likewise may, but need not, be formed separately from legs  78 . Legs  78  and plate  86  may be cast or sheet metal, plastic, reinforced plastic, composite or other appropriate material. Motorized impeller  36  is secured to mounting plate  86 , which plate may be configured so that different sizes of motorized impeller  32  may be attached to it and used with the air cleaner of this invention. Additionally, other mounting components may be used with larger or smaller or differently configured motorized impellers. 
     As is easily seen in  FIG. 8 , a control panel  16  is attached to the upper portion of cover  36  in a sloping orientation making it easy to see and readily accessible. Panel  16  is mounted between two ribs  37  that protrude from outlet cover  36  above the panel  16  and protect the panel and relatively delicate components on it from inadvertent, damaging contact that might otherwise occur during transportation or use of the unit  10 , particularly in building remediation or construction environments of the sort in which air filtration units are used. The panel  16  can carry various components, including switches and other controls, indicator lamps, outlets, power cords and any other appropriate devices. Portions of such devices on the inside of panel  16  are housed within and isolated from cavity  72  by a box  38  that may be a rectilinear box as depicted in the drawings or any other appropriate shape of metal, plastic or other appropriate material. 
     The lower portion of cover  36  is penetrated by a large round opening  88  providing the air exhaust  18 . Attached to the cover  36  around the opening  88  protruding outside the cover  36  is a short cylindrical tube  90  through which filtered air is exhausted. A grill  92  positioned within tube  90  blocks access to the inside of the unit  10 , and, in particular, blocks access to the motorized impeller  32 . 
     As is apparent in the figures, the openings in each of the inlet door or cover  30  and the outlet cover  36  are in the same parallel direction front to back with each other and with the opening in baffle wall  66 , and with the motorized impeller, facilitating the efficient passage of air through the unit  10 . 
     While numerous manufacturing techniques and materials can be used for the components of the air filtration unit of this invention, there are advantages associated with rotational molding of the housing  12  in medium density polyethylene (MDPE) resin. A double walled rotational molded design results in a housing that is sturdy, light weight, dimensionally consistent, resilient and durable, to which components can be attached, and which can be penetrated by fasteners, without unduly damaging the integrity of the housing or permitting undesired air flow. The interior of such a unit  10  and housing  12  has a generally continuous, smooth surface that facilitates decontamination of the unit  10  after use. Housing  12  may be structurally reinforced and walls may be stiffened by incorporation of structures that provide that function. For instance, housing  12  may include top ribs  13  and side ribs  15 . Ribs like top ribs  13  may be received in corresponding recesses  17  ( FIG. 3 ) on the bottom of housing  12  of a unit  10  stacked on top of another like unit, which helps to keep the units stacked in a rough environment like a construction or abatement site and during transport to and from the site. The top horns of cover  36  and exhaust collar  90  may be wrapped with the unit  10  power cord (not shown) for storage of the cord. 
     The internal air flow has a rotational bias and a non-direct path and one or more deflectors may be used to even out the air flow direction and exit velocity around the exhaust grill face. This may also help correct vortex occurrences in the air flow pattern. 
     The inlet door  30  and outlet cover  36  may likewise be manufactured of numerous alternative materials and using several different techniques. Injection molding the door  30  and cover  36  components in acrylonitrile butadiene styrene (ABS), polypropylene or MDPE afford doors and covers in the configurations shown in the figures that fit and seat against the housing  12  well to provide needed closure for operation of the unit  10  and easy access to the inside of unit  10  for replacement of filters, decontamination after use and any other reasons. 
     Feet  94  on the bottom of housing  12  made of rubber or another appropriate resilient material reduce transmission of vibration from the unit  10  to the floor or other surface on which the feet rest and help protect against damage to those surfaces. Feet  94  are located in positions, and the top of housing  12  is configured, so that units  10  can be stacked for transportation, storage or use. 
     Different arrangements of the components depicted in the drawings or described above, as well as components and steps not shown or described are possible. Similarly, some features and subcombinations are useful and may be employed without reference to other features and subcombinations. Embodiments of the invention have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, the present invention is not limited to the embodiments described above or depicted in the drawings, and various embodiments and modifications can be made without departing from the scope of the claims below.