Abstract:
A cyclonic surface cleaning apparatus incorporates a series of sequential physical filtration members to progressively remove smaller particulate matter whereby the physical filtration members collectively have a longer in use time prior to being clogged, thereby permitting a longer operating time prior to the cleaning or replacement of the physical filtration members.

Description:
FIELD 
       [0001]    This application relates to surface cleaning apparatus, such as vacuum cleaners. 
       BACKGROUND 
       [0002]    Various types of vacuum cleaners are known in the art. Currently, many of the vacuum cleaners, which are sold for residential applications, utilize at least one cyclone as part of the air filtration mechanism. More recently, to obtain higher levels of filtration, cyclonic vacuum cleaners have been designed which utilize two cyclonic stages. An example is shown in Conrad (U.S. Pat. No. 6,782,585). As shown therein, a vacuum cleaner has a first cyclonic cleaning stage comprising a single first stage cyclone and a second cyclonic cleaning stage that is downstream from the first cyclonic cleaning stage and comprises a plurality of cyclones in parallel. 
         [0003]    The plurality of second stage cyclones typically remove particulate matter finer than the particulate matter that is removed in the first cyclonic cleaning stage. Accordingly, the coarsest particulate matter that is entrained in an air stream is removed in the first cyclonic cleaning stage and finer particulate matter is removed in the downstream cyclonic cleaning stage. However, the air exiting the second cyclonic cleaning stage may still contain sufficient particulate matter to damage a suction motor positioned downstream from the second cyclonic cleaning stage. Accordingly, as disclosed in Conrad, a screen or filter may be positioned downstream from the second cyclonic cleaning stage and upstream from the suction motor. Further, a HEPA filter may be positioned downstream from the suction motor. 
       SUMMARY 
       [0004]    In accordance with this invention, a surface cleaning apparatus uses a plurality of filtration members having varying filtration ability. In accordance with this embodiment, a surface cleaning apparatus utilizes a foam filter positioned downstream from a cyclone, a felt filter positioned downstream from the foam filter and a HEPA filter positioned downstream from the felt filter. Preferably, a screen is provided for the air outlet of a cyclone chamber. The suction motor of the surface cleaning apparatus is preferably provided downstream from the HEPA filter, but may be upstream of the HEPA filter. 
         [0005]    An advantage of this design is that filtration materials having finer pore sizes are positioned downstream from a series of coarse filtration elements thereby extending the lifetime of the finer filter elements. 
         [0006]    In accordance with this invention, there is provided a surface cleaning apparatus comprising:
       (a) a dirty air inlet, a clean air outlet downstream, a fluid flow passage extending from the dirty air inlet to the clean air outlet;   (b) a suction motor provided in the fluid flow passage;   (c) a filtration apparatus downstream from the dirty air inlet and comprising a cyclone having a cyclone outlet;   (d) a foam filter downstream from the cyclone outlet;   (e) a felt filter downstream from the foam filter; and,   (f) a HEPA filter downstream from the felt filter.       
 
         [0013]    In one embodiment, the surface cleaning apparatus further comprises a screen downstream from the cyclone outlet and upstream from the foam filter. Preferably, the screen comprises an open wire mesh. 
         [0014]    The screen may have a surface area that is 2 times, preferably at least about 5 times, more preferably at least about 10 times and, most preferably at least about 20 times, e.g. 20-50 times, the cross sectional area of the cyclone air outlet. It will be appreciated that the screen may be flat or may be curved, e.g., bowl shaped. The use of such a large screen enhances the time during which the vacuum surface cleaning apparatus may be used without having to clean or replace the screen. Further, by positioning the screen exterior to the cyclone chamber, a large screen may be provided without reducing the size of the cyclone chamber 
         [0015]    In any embodiment, the cyclone outlet may comprise a vortex finder, the vortex finder may have an upstream end in the cyclone and the upstream end may be unobstructed. 
         [0016]    In any embodiment, the cyclone outlet may have a shroud. Preferably, the shroud comprises an apertured end of the cyclone outlet. 
         [0017]    In any embodiment, the suction motor may be positioned downstream from the HEPA filter. Alternately, the suction motor may be positioned upstream from the HEPA filter. 
         [0018]    In any embodiment, the screen may be mounted in a housing having an outer wall that is transparent. Preferably, the outer wall is openable, e.g. a pivotally mounted door. Alternately, it may be removably mounted, such as by a screw thread or a bayonet mount, a snap fit or the like. Alternately, it may be slidably mounted or rotationally mounted. 
         [0019]    In any embodiment, the foam filter, the felt filter and the HEPA filter may be individually or selectively removably mounted in the surface cleaning apparatus and, preferably removable as a unit. 
         [0020]    In any embodiment, each layer of physical filtration media may be selected to remove a particular size range of particles that is larger than that of the next downstream, layer of filtration material. 
         [0021]    In any embodiment, the cyclone may have a separation efficiency for IEC dirt of 98% of particles that are from 3 to 5 microns and at least 96.5% of particles that are from 1-2 microns. 
         [0022]    In any embodiment, the foam may have a separation efficiency of 70-85% of particles that are 1-2 microns and 30-50% of particles that are 0.3-0.9 microns. 
         [0023]    In any embodiment, the felt may have a separation efficiency of 70-85% of particles that are 0.5-0.9 microns and 30-50% of particles that are 0.3 microns. 
         [0024]    It will be appreciated by those skilled in the art that any of the embodiments may be used individually or in a single surface cleaning apparatus, as exemplified in a preferred embodiment described herein, or in any particular sub-combination. Accordingly, any two or more embodiments may be used in a single surface cleaning apparatus. In addition, any of the optional features described herein may be used in combination with any alternate embodiment or sub-combination or combination of alternate embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    These and other advantages of the instant invention will be more fully and completely understood in conjunction with the following description of the preferred embodiments of the invention in which: 
           [0026]      FIG. 1  is a side elevational view of a preferred embodiment of a vacuum cleaner in accordance with this design wherein the outer casing surrounding the cyclone and forming an outer wall of a dirt collection chamber is optionally transparent; 
           [0027]      FIG. 2  is a perspective view from the front and the right side of the vacuum cleaner of  FIG. 1 ; 
           [0028]      FIG. 3  is a cross-section along the line  3 - 3  in  FIG. 2 ; 
           [0029]      FIG. 4  is a schematic drawing of the vacuum cleaner of  FIG. 1  showing the airflow passage therethrough; 
           [0030]      FIG. 5  is a perspective view from the bottom of the vacuum cleaner of  FIG. 1  wherein the bottom of the first and second housings is open; 
           [0031]      FIG. 6  is a perspective view of the bottom of the vacuum cleaner of  FIG. 1  wherein the first and second housings are closed but an access door is open; and, 
           [0032]      FIG. 7  is a longitudinal section through an alternate embodiment of a vacuum cleaner in accordance with this invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    As shown in  FIGS. 1-6 , a surface cleaning apparatus comprises a vacuum cleaner  10  having a filtration apparatus having at least one cyclone. The filtration apparatus may be of any design or configuration. As exemplified, surface cleaning apparatus  10  has a first housing  12  and a second housing  14 . First housing  12  comprises at least one cyclone  16  and a dirt collection chamber  18  and second housing  14  houses the filtration members and the suction motor. Dirty air entrained in dirty air inlet  38  travels through the filtration apparatus, through suction motor  26  and exits the surface cleaning apparatus via clean air outlet  60 . As shown in  FIG. 7 , a surface cleaning apparatus  10  has a first cyclonic cleaning stage comprising a single cyclone  150  having a dirt collection chamber  152  and a second cyclonic cleaning stage comprising a plurality of second stage cyclones  154  in parallel. 
         [0034]    It will be appreciated that, surface cleaning apparatus may be a vacuum cleaner, a carpet extractor, a bare floor cleaner or the like. As exemplified, the surface cleaning apparatus is hand held. However the surface cleaning apparatus may be configured as an upright vacuum cleaner, a stick vacuum cleaner, a canister vacuum cleaner, a back pack or shoulder strap vacuum cleaner or other configuration known in the art. The surface cleaning apparatus may have a single cyclonic cleaning stage, which may be of any construction known in the art, or a plurality of cyclonic cleaning stages, each of which may be of any construction known in the art, e.g. they may comprise a single cyclone or a plurality of cyclones in parallel. 
         [0035]    In accordance with this invention, a series of filtration members are positioned in series downstream from the cyclone chamber of cyclone  16 , or alternately downstream from the outlet of the last cyclonic cleaning stage. The filtration members comprise a foam filter  20 , a felt filter  22  downstream from foam filter  20  and a HEPA filter  24  downstream from felt filter  22 . Preferably, all of these filters are positioned upstream from suction motor  26 . Alternately, one or more of these filters may be positioned downstream from suction motor  26 . In particular HEPA filter  24  may be downstream from suction motor  26  (see for example  FIG. 7 ). Accordingly, a plurality of filtration members, each of which have a finer filtration capacity (e.g. smaller pores) than the previous filter, are provided in series in the downstream direction. 
         [0036]    For example, the foam filter may be an open cell foam made from materials currently used to manufacture foam filters for vacuum cleaners and may be selected to have pore sizes from 0.25-5 microns and may have a mean pore size of 2 microns. Accordingly, the foam will filter particles larger than 5 microns and some of the particles that are between 0.25-5 microns. The felt filter may be woven or non-woven and may be made from plastic, preferably rayon, nylon, polypropylene or a combination thereof. The felt may be selected to have pore sizes from 0.1-2.5 microns and may have a mean pore size of 1 micron. Accordingly, the felt will filter particles larger than 2.5 microns and some of the particles that are between 0.1-2.5 microns. HEPA filtration is typically defined as removal of 99.97% of particles larger than 0.3 microns. 
         [0037]    In a preferred embodiment, cyclone  16 , or the cyclonic cleaning stages combined (e.g. cyclone  16  in  FIG. 1  or cyclones  150  and  152  in  FIG. 7 ), may achieve a separation efficiency for IEC dirt as specified as IEC 60312, which is representative of household dirt, of 98% of particles that are from 3 to 5 microns and at least 96.5% of particles that are from 1-2 microns. By removing a high percentage of particles in this size range, the foam will not prematurely clog. Similarly, the foam preferably has a separation efficiency of 70-85% of particles that are 1-2 microns and 30-50% of particles that are 0.3-0.9 microns. By removing a high percentage of particles in this size range, the felt will not prematurely clog. Similarly, the felt preferably has separation efficiency of 70-85% of particles that are 0.5-0.9 microns and 30-50% of particles that are 0.3 microns. By removing a high percentage of particles in this size range, the HEPA will not prematurely clog. 
         [0038]    It will be appreciated that each of the foam and the felt may have varying pore sizes as long as each filters a significant amount of particles that would prematurely clog the next sequential filter media. Accordingly, the filtration specification of each layer of filtration media is selected to be complimentary to the next sequential layer of filtration media and may essentially remove particles that are larger than those that are within the size range targeted for the next sequential filtration media. In other words, each layer of filtration material is selected to remove a particular size range of particles. Accordingly, each upstream layer is selected to remove a particular size range of particles that is larger then that of the next downstream layer of filtration material. 
         [0039]    In a preferred embodiment, foam filter  20 , felt filter  22  and HEPA filter  24  are removably mounted as a unit (e.g., they may be mounted in a filter housing or directly secured to each other). For example, when second housing  14  is opened, e.g., by opening bottom  66 , foam filter  20 , felt filter  22  and HEPA filter  24  may be removed together. Alternately, they may be separately removable. In either embodiment, it is preferred that they are separable when removed so that individual filters may be cleaned and/or replaced. Alternately, the foam filter  20 , felt filter  22  and HEPA filter  24  may be an assembly that is replaceable as a unit, e.g., a new filter housing containing all three filters may be inserted. 
         [0040]    It will be appreciated that each of the foam filter  20 , felt filter  22  and HEPA filter  24  may comprise a single filter or a plurality of filters. For example, foam filter  20  may comprise a series of layers of foam. 
         [0041]    Preferably, a screen  78  is provided upstream from foam filter  20  and preferably downstream from the cyclone chamber of cyclone  16 , or alternately downstream from the outlet of the last cyclonic cleaning stage. For example, it may be adjacent outlet  52  of outlet or vortex finder  36 , e.g., connected thereto, or positioned in the air flow path, e.g., filtration chamber  80 , such that air flow is caused to pass therethrough. It will be appreciated that screen  78  may be provided immediately upstream of foam filter  20 , e.g., it may be provided below foam filter  20  in second housing  14 . 
         [0042]    Optionally, a shroud (e.g. a perforated or apertured plastic cover) may be provided surrounding or overlying inlet  50  of outlet  36 . 
         [0043]    In the exemplified embodiment, cyclone  16  has a dirt outlet  28  and an optional impingement surface  30  spaced from dirt outlet  28  in dirt collection chamber  18 . As shown in  FIG. 3 , impingement surface  30  is preferably spaced a distance D from outlet  28  wherein distance D is from 8 to 30 millimeters and, preferably from 12 to 25 millimeters. It will be appreciated that impingement member  30  may be mounted to lid  32  of dirt collection chamber  18 . Alternately, impingement member  30  may be mounted to a sidewall of dirt collection chamber  18  and/or cyclone  16 . 
         [0044]    As exemplified in  FIG. 3 , cyclone  16  is an inverted cyclone. Accordingly, cyclone  16  has a lower air inlet  34  and a lower air outlet  36 . Air inlet  34  is positioned downstream from dirty air inlet  38  of surface cleaning nozzle  40 . Surface cleaning nozzle  40  may be any surface cleaning nozzle known in the art. Air inlet  34  of cyclone  16  may be in airflow communication with surface cleaning nozzle  40  in any manner known in the art. The exact structure of surface cleaning nozzle  40  and the communication passage between surface cleaning nozzle  40  and air inlet  34  will vary depending on if the surface cleaning apparatus is an upright vacuum cleaner, canister vacuum cleaner or, as exemplified, a portable hand held vacuum cleaner. 
         [0045]    In operation, air will enter cyclone  16  through inlet  34  and travel upwardly, as exemplified in  FIG. 4 . The air will then travel downwardly to exit cyclone  16  via outlet  36 . As shown in  FIG. 4  by the hatched arrows, dirt will exit upwardly through outlet  28  and deposit on dirt collection chamber floor  42 . In addition, some of the heavier particulate matter may not be entrained in the air stream and may be deposited on cyclone floor  44 . 
         [0046]    In an alternate embodiment, it will be appreciated that cyclone  16  need not be inverted. Cyclone  16  may be any cyclone with a dirt outlet provided wherein, preferably, impingement member or members are positioned spaced from the dirt outlet. The cyclone may accordingly be an upright cyclone or a cyclone having a single direction of travel of the air. 
         [0047]    As exemplified, cyclone  16  is a frustoconical cyclone having cylindrical portion  46  and frustoconical portion  48 . Alternately, or in addition to the orientation of cyclone  16 , it will be appreciated that cyclone  16  may be cylindrical, entirely frustoconical or any other shape known in the art. 
         [0048]    As exemplified in  FIG. 3 , cyclone outlet  36  of cyclone  16  comprises a vortex finder that extends inwardly into the cyclone chamber defined by cyclone  16 . Outlet  36  preferably comprises a generally cylindrical passage, i.e. vortex finder, having an inlet  50  and an outlet  52 . It will be appreciated that, in an alternate embodiment any outlet known in the art for cyclones may be utilized. 
         [0049]    In some embodiments, inlet  50  may be covered by a screen, shroud or filter as in known in the art. However, it is preferred that vortex finder  36  is unobstructed, i.e., no screen, shroud or filter is provided on inlet  50 . Accordingly, as exemplified in  FIG. 3 , vortex finder  36  is not surrounded by a screen, shroud or filter and no physical separation member is positioned in the cyclone chamber of cyclone  16 . Accordingly, no filtration or screen member interior of cyclone  16  requires cleaning. Elongate material such as hair or fibre can become adhered to a shroud, requiring the shroud to be manually cleaned. If the shroud is inside the cyclone chamber, then the chamber should be openable sufficiently to permit a user to insert their hand to clean the shroud, or to remove the shroud for cleaning. Accordingly, it will be appreciated that bottom  44  need not be openable to permit a screen or a shroud or filter associated with inlet end  50  of outlet  36  to be cleaned. Preferably, a screen is positioned downstream from cyclone  16  and upstream from the pre-motor filters. For example, a screen  78  is preferably provided. 
         [0050]    As exemplified in  FIGS. 1-6 , vacuum cleaner  10  comprises a hand held vacuum cleaner. Accordingly, vacuum cleaner  10  may be provided with handle  54 , which is affixed to lid  32  and lid  58  of second housing  14 . Handle  54  may alternately be affixed to any other portion or portions of vacuum cleaner  10  as is known in the art. Optionally, as exemplified, on/off switch  56  may be provided on handle  54 . On/off switch  56  may alternately be provided on any other portion of vacuum cleaner  10 . 
         [0051]    As exemplified in  FIG. 3 , suction motor  26  is positioned in second housing  14 , preferably with a suction fan provided below the electric motor. Clean air outlet  60  is provided downstream from suction motor  26 . An optional post-motor filter may be provided downstream from suction motor  26 , such as in post-motor filter housing  62 , which may be accessible via post motor filter housing door  64 , which could be pivotably mounted to second housing  14 . 
         [0052]    As exemplified, dirt collection chamber  18  surrounds cyclone  16 . Accordingly, cyclone  16  may be positioned in dirt collection chamber  18  and, preferably, generally centrally therein. Accordingly, vacuum cleaner  10  is preferably configured such that the dirt collected on floor  44  of cyclone  16  is emptied at the same time as dirt collected on floor  42  of dirt collection chamber  18 . Accordingly, floor  42  and floor  44  are both movable and connected to each other whereby both floor  42  and  44  are concurrently movable such that dirt collection chamber  18  and cyclone  16  are concurrently emptied. 
         [0053]    As exemplified in  FIG. 5 , floors  42  and  44  may comprise a pivoting bottom  66  of first housing  12  and, alternately, of the filtration apparatus (e.g. housings  12  and  14  of this embodiment). Accordingly, as seen in  FIG. 5 , when floors  42  and  44  are opened, both cyclone  16  and dirt collection chamber  18  may be emptied by holding vacuum cleaner  10  in the upright position (as shown in  FIG. 1 ). Accordingly, the dirt will fall out of collection chamber  16  and cyclone  16  and will fall downwardly off of floors  42  and  44 . 
         [0054]    As shown in  FIG. 5 , housings  12  and  14  have a pivoting bottom  66 , which is secured to each of housings  12  and  14  by a pivot  68 . In the closed position exemplified in  FIGS. 1 and 4 , pivoting bottom  66  is secured in position by latch  70 . Latch  70  has a button  72  which, when pressed, causes arm  74  to move outwardly thereby disengaging a flange provided on the bottom end of arm  74  from flange  76  provided on pivoting bottom  66 . A gasket or other sealing member may be provided at the interface of housings  12  and  14  and pivoting bottom  66  to provide an air tight or fluid tight seal. It will be appreciated that bottom  66  may be moveable in any other direction by any other means known in the art and may optionally be removable from housings  12 ,  14 . Further, bottom  66  may be moveably secured in position by any other means known in the art and need not be connected to surface cleaning apparatus  10  for relative motion thereto. 
         [0055]    As exemplified in  FIG. 5 , outlet  36  is provided as part of floor  42 , and is preferably integrally molded therewith. In an alternate embodiment, it will be appreciated that outlet  36  need not be removable from cyclone  16  with floor  42 . 
         [0056]    In an alternate embodiment, it will be appreciated that only floors  42  and  44  may be pivotably mounted to housing  12 . In such an embodiment, foam filter  20  may remain sealed when cyclone  16  and dirt collection chamber  18  are emptied. In such a case, the housing that contains foam filter  20  may be separately opened. In an alternate embodiment, a side-by-side design as exemplified in  FIG. 1  need not be utilized. In such a case, floor  42  and floor  44  may comprise the entire floor of the filtration assembly. 
         [0057]    If bottom  66  opens both housings  12  and  14 , then it will be appreciated that dirt positioned on the upstream surface of filter  20  will be emptied when bottom  66  is opened. 
         [0058]    Preferably a screen is provided adjacent outlet  36  and, preferably, in sealing engagement with outlet  52 . Screen  78  may be mounted in a housing (filtration chamber  80 ), having an outer wall all or a portion of which is preferably transparent and positioned downstream from vortex finder  36 . Referring to  FIG. 3 , screen  78  is positioned spaced from and in sealing engagement with rear surface  84  of floor  44  and overlies outlet  52 . Accordingly, air that exits outlet  36  travels through screen  78 . The air then travels through filtration chamber  80  and travels laterally to outlet  86 , which is in air flow communication with headspace  88  below filter  20 . 
         [0059]    Preferably, screen  78  may be an open mesh screen, e.g., a wire mesh screen or, alternately, a plastic mesh screen. 
         [0060]    An access door  82  may be provided to permit access to screen  78  such that screen  78  may be cleaned. Access door  82  may be any door that is movably mounted in overlying relationship to filtration chamber  80 . As exemplified in  FIG. 6 , access door  82  comprises the lower half of filtration chamber  80  and is pivotally mounted by pivot  90  to pivoting bottom  66 , and is secured in position by a latch  120 . Latch  120 , for example, may have a button  122  which, when pressed, causes arm  124  to move outwardly thereby disengaging a flange on the bottom end of arm  124  from flange  92  provided on the front end of access door  82 . A sealing gasket or other sealing member known in the art may be utilized to provide an air tight or fluid tight seal for filtration chamber  80 . Any other securing member known in the art may be used. Further door  82  may be removable and need not be connected to surface cleaning apparatus  10  for relative motion thereto. 
         [0061]    Preferably, screen  78  is mounted and, more preferably, movably mounted and, most preferably, removably mounted to access door  82 . As shown in  FIG. 6 , screen  78  is pivotally mounted to the inner surface of access door  82 . Accordingly, when a user desires to clean screen  78 , it may be pivoted in the direction shown by arrow A in  FIG. 6  to an open or cleaning position. It will be noticed that access door  82  may be opened independently of pivoting bottom  66 . In an alternate embodiment, it will be appreciated that a pivoting bottom  66  need not be provided. 
         [0062]    Preferably, at least a portion of and, more preferably, all of access door  82 , which as exemplified is the outer wall of filtration chamber  80 , is transparent. Accordingly, a user may lift the vacuum cleaner, invert the vacuum cleaner or tilt the vacuum cleaner on its side to view screen  78  and determine whether screen  78  requires cleaning or, alternately, replacement. 
         [0063]    The use in a vacuum cleaner of a foam filter, a felt filter and a HEPA filter in series, preferably with a screen upstream of the foam filter, may be used alone or in combination with one or more of the spacing of an impingement surface, an access door to permit cleaning or replacement of the screen, the screen being positioned downstream of a cyclone outlet and mounted in a housing which is transparent, a configuration to allow a cyclone chamber and a surrounding dirt collection chamber to be emptied concurrently, a bottom door that opens to expose the foam filter and permit the filters to be removed such that one or more of them may be cleaned or replaced, or any particular combination or sub-combination thereof. 
         [0064]    It will also be appreciated that any of the aforementioned embodiments may be used singly or in any particular combination or sub-combination of the remaining features listed above. 
         [0065]    Although the invention has been described in conjunction with specific embodiments thereof, if is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention.