Patent Publication Number: US-9844308-B2

Title: Surface cleaning apparatus

Description:
FIELD 
     The disclosure relates to surface cleaning apparatuses, such as vacuum cleaners. 
     INTRODUCTION 
     The following is not an admission that anything discussed below is part of the prior art or part of the common general knowledge of a person skilled in the art. 
     Various constructions for surface cleaning apparatuses, such as vacuum cleaners, are known. Currently, many surface cleaning apparatuses are constructed using at least one cyclonic cleaning stage. Air is drawn into the vacuum cleaners through a dirty air inlet and conveyed to a cyclone inlet. The rotation of the air in the cyclone results in some of the particulate matter in the airflow stream being disentrained from the airflow stream. This material is then collected in a dirt bin collection chamber, which may be at the bottom of the cyclone or in a direct collection chamber exterior to the cyclone chamber (see for example WO2009/026709 and U.S. Pat. No. 5,078,761). One or more additional cyclonic cleaning stages and/or filters may be positioned downstream from the cyclone. 
     SUMMARY 
     This summary is intended to introduce the reader to the more detailed description that follows and not to limit or define any claimed or as yet unclaimed invention. One or more inventions may reside in any combination or sub-combination of the elements or process steps disclosed in any part of this document including its claims and figures. 
     It will be appreciated by a person skilled in the art that a surface cleaning apparatus may embody any one or more of the features contained herein and that the features may be used in any particular combination or sub-combination. 
     In accordance with one broad aspect of the teachings described herein, a surface treatment apparatus may include an air flow path extending from a dirty air inlet to a clean air outlet and a main body movable in a longitudinal direction of travel and having a front end and a rear end spaced behind the front end in the direction of travel. A suction motor may be provided in the air flow path. A cyclone bin assembly may be provided in the air flow path and may be removably mountable to the main body. A pre-motor filter chamber may be provided in the main body. The pre-motor filter chamber may have a rear wall, a sidewall extending from the rear wall and an openable front wall opposite the rear wall and sealingly enclosing the pre-motor filter chamber. When the cyclone bin assembly is mounted on the main body the pre-motor filter chamber may be disposed longitudinally between the cyclone bin assembly and the suction motor and the cyclone bin assembly may be positioned in front of at least a portion of the openable front wall of the pre-motor filter chamber. The front wall may be accessible when the cyclone bin assembly is removed from the main body. 
     When the cyclone bin assembly is mounted on the main body the cyclone bin assembly may cover the entire front wall. 
     At least a portion of the front wall may be transparent. 
     A filter may be positioned in the pre-motor filter chamber and an upstream surface of the filter may face and may be spaced apart from the front wall. 
     The pre-motor filter chamber may include a chamber air inlet in communication with the cyclone bin assembly and disposed on the sidewall. 
     The chamber air inlet may include an elongate slit in the sidewall. The filter may have a width in a transverse direction that is generally orthogonal the longitudinal direction and the slit may have a width in the transverse direction that is between about 30% and about 100% of the width of the filter. 
     The pre-motor filter chamber may include a chamber air outlet disposed on the rear wall and in communication with the suction motor. 
     The suction motor may extend along a motor axis, and the motor axis may intersect both the front wall and the rear wall. 
     Optionally, when the cyclone bin assembly is mounted on the main body the motor axis intersects the cyclone bin assembly. 
     The front wall may include an inner surface and at least one rib projecting from the inner surface. When the front wall is sealingly enclosing the pre-motor filter chamber the at least one rib may bear against a filter positioned in the pre-motor filter chamber. 
     A bleed valve may have a valve air inlet and a valve air outlet provided in the rear wall and in air flow communication with the pre-motor filter chamber. 
     The cyclone chamber may have an axial cross-section area and a filter cross-sectional area in an air flow direction may be is equal to or greater than the cyclone chamber cross-sectional area. 
     The front wall may include a handle portion. 
     The front wall may sealingly connect to the sidewall via a friction fit and is detachable from the sidewall in the absence of releasing a retaining fastener. 
     The cyclone bin assembly may include a lower end wall comprising a bin assembly air outlet, an opposing upper end wall and an exterior bin sidewall extending therebetween, and wherein when the cyclone bin assembly is mounted on the main body the front wall abuts a first portion of the bin sidewall. 
     The cyclone bin assembly may include a bin air inlet disposed in a second portion of the bin sidewall. The second portion of the bin sidewall may be longitudinally opposite the first portion of the bin sidewall. 
     The main body may include a chassis comprising at least two wheels and a cleaning unit detachably mounted to the chassis. The cleaning unit may include the suction motor, the pre-motor filter chamber and the cyclone bin assembly and may be operable to clean a surface while detached from the chassis. 
     In accordance with another broad aspect of the teachings described herein, a surface treatment apparatus may include an air flow path extending from a dirty air inlet to a clean air outlet. A main body may be movable in a longitudinal direction of travel and may include a front end and a rear end spaced behind the front end in the direction of travel, and a suction motor provided in the air flow path. A cyclone bin assembly may be provided in the air flow path and may include a lower end wall which has a bin assembly air outlet. The cyclone bin assembly may be removably mountable to the main body. A pre-motor filter chamber may be provided in the main body. The pre-motor filter chamber may have a rear wall, a sidewall extending from the rear wall and an openable front wall opposite the rear wall and sealingly enclosing a pre-motor filter in the pre-motor filter chamber. The main body may have a platform on which the cyclone bin assembly is positioned when mounted to the main body. The platform may have a main body air inlet connected in airflow communication with the bin assembly air outlet when the cyclone bin assembly is mounted to the main body. The main body may have an airflow path from the main body air inlet to the suction motor. The air flow path may direct air travelling therethrough rearwardly and upwardly so as to reach and pass through the pre-motor filter. 
     The pre-motor filter chamber may include a chamber air inlet disposed in a lower portion of the pre-motor filter chamber sidewall and positioned below a plane containing the cyclone chamber air outlet. 
     The pre-motor filter chamber may include a chamber air inlet disposed in a lower portion of the pre-motor filter chamber sidewall and air travelling through the chamber air inlet may travel generally upwardly in a direction that is generally parallel to a plane containing the pre-motor filter chamber front wall and is generally orthogonal to a rotation axis of the suction motor. 
    
    
     
       DRAWINGS 
       The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the teaching of the present specification and are not intended to limit the scope of what is taught in any way. 
       In the drawings: 
         FIG. 1  is a perspective view of an example of a surface cleaning apparatus; 
         FIG. 2  is a perspective view of a portion of the surface cleaning apparatus of  FIG. 1 ; 
         FIG. 3  is a partially exploded perspective view of a portion of the surface cleaning apparatus of  FIG. 1 ; 
         FIG. 4  is a perspective view of an example of a cyclone bin assembly; 
         FIG. 5  is a partially exploded perspective view of a portion of the surface cleaning apparatus of  FIG. 1 ; 
         FIG. 6  is a section view of a portion of the surface cleaning apparatus taken along line  6 - 6  in  FIG. 5 ; 
         FIG. 7  is a section view of the cyclone bin assembly of  FIG. 4 , taken along line  7 - 7 ; and 
         FIG. 8  is a bottom perspective view of the cyclone bin assembly of  FIG. 4  with a bottom door open. 
     
    
    
     DETAILED DESCRIPTION 
     Various apparatuses or processes will be described below to provide an example of an embodiment of each claimed invention. No embodiment described below limits any claimed invention and any claimed invention may cover processes or apparatuses that differ from those described below. The claimed inventions are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below. It is possible that an apparatus or process described below is not an embodiment of any claimed invention. Any invention disclosed in an apparatus or process described below that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such invention by its disclosure in this document. 
     Referring to  FIG. 1 , an example of a surface cleaning apparatus  100  is shown. In the example shown, the surface cleaning apparatus  100  is a canister-type vacuum cleaner. In alternate embodiments, the surface cleaning apparatus may be another suitable type of surface cleaning apparatus, such as an upright-style vacuum cleaner, and hand vacuum cleaner, a stick vac, a wet-dry type vacuum cleaner, a carpet extractor or the like. 
     In the illustrated example, the surface cleaning apparatus  100  includes a chassis portion  102  and a surface cleaning head  104 . A surface cleaning unit  106  is mounted on the chassis portion  102 . The surface cleaning apparatus  100  also has at least one dirty air inlet  108 , at least one clean air outlet  110 , and an air flow path or passage extending therebetween. In the illustrated example, the air flow path includes a flexible air flow conduit member in the form of a hose  112  and a rigid up flow conduit  114 . 
     At least one suction motor  116  ( FIG. 6 ) and at least one air treatment member are positioned in the air flow path to separate dirt and other debris from the airflow. Preferably, the chassis portion  102  and/or surface cleaning unit  106  include the suction motor, to draw dirty air in through the dirty air inlet, and the air treatment member to remove dirt or debris from the dirty air flow. The air treatment member may be any suitable air treatment member, including, for example, one or more cyclones, filters, and bags. Preferably at least one air treatment member is provided upstream from the suction motor. In the illustrated example the air treatment member is provided in the form of a cyclone bin assembly  118 . 
     In the embodiment shown, the surface cleaning head  104  includes the dirty air inlet in the form of a slot or opening  120  formed in a generally downward facing surface of the surface cleaning head  104 . From the dirty air inlet, the air flow path extends through the surface cleaning head  104 , and through the up flow conduit  114 . In the illustrated example, the surface cleaning unit  106  includes a hose coupling member  122  that has an upstream end  124  ( FIGS. 2 and 6 ) that is connected to the hose  112 , and a downstream end  126  ( FIG. 6 ) that is connected to the air treatment member (the cyclone bin assembly in the illustrated example). 
     Referring also to  FIG. 6 , from the air treatment member  118 , air flows through an internal air flow conduit  128  in the surface cleaning unit  106  to the clean air outlet  110  provided in the rear of the surface cleaning unit  106 . 
     Referring to  FIG. 1 , a handle  130  is provided toward the top of the up flow conduit  114  to allow a user to manipulate the surface cleaning head  104 . In the illustrated example, the up flow conduit  114  extends along an upper axis  132  and is moveably mounted to the surface cleaning head  104 . In the illustrated example, the up flow conduit  114  is pivotally mounted to the surface cleaning head  104  via a pivot joint  134 . The pivot joint may be any suitable pivot joint. Alternatively, or in addition to being pivotally coupled to the surface cleaning head, the up flow conduit  114  can also be rotatably mounted to the surface cleaning head  104 . It will be appreciated that the surface cleaning head  104  and conduit  114  may be of any suitable design and the air flow path to the surface cleaning unit  106  may be of any design/configuration. 
     Referring to  FIGS. 3 and 6 , in the illustrated example, the surface cleaning unit  106  has a main body  136  that includes the suction motor  116 , in a motor housing  138 , and the air treatment member in the form of a cyclone bin assembly  118  is mounted on the main body  136 . Referring to  FIG. 1 , the cyclone bin assembly includes a cyclone chamber  140  and a dirt collection chamber  142 . 
     The following is a description of a cyclone construction that may be used by itself in any surface cleaning apparatus or in any combination or sub-combination with any other feature or features disclosed herein. 
     Referring to  FIG. 7 , in the illustrated embodiment the cyclone chamber  140  extends along a cyclone axis  144  and includes a first end wall  146 , a second end wall  148  axially spaced apart from the first end wall  146  and a generally cylindrical sidewall  150  extending between the first and second end walls  146  and  148 . The cyclone chamber  140  has an interior  152  and a cyclone chamber cross-sectional area that is measured in a plane that is generally orthogonal to the cyclone axis  144 . Optionally, some or all of the cyclone walls can coincide with portions of walls surrounding the dirt collection chamber  142  and/or may form portions of the outer surface of surface cleaning unit  106 . Alternatively, in some examples some or all of the cyclone walls can be distinct from other portions of the surface cleaning unit. 
     In the illustrated embodiment, the cyclone chamber  140  includes a cyclone air inlet  152  in fluid communication with a cyclone air outlet  154 . The cyclone chamber also includes at least one dirt outlet  156 , through which dirt and debris that is separated from the air flow can exit the cyclone chamber  140 . While it is preferred that most or all of the dirt exit the cyclone chamber via the dirt outlet, some dirt may settle on the bottom end wall  148  of the cyclone chamber  140  and/or may be carried with the air exiting the cyclone chamber via the air outlet  154 . 
     Preferably the cyclone air inlet  152  is located toward one end of the cyclone chamber (the lower end in the example illustrated) and may be positioned adjacent the corresponding cyclone chamber end wall  148 . Alternatively, the cyclone air inlet may be provided at another location within the cyclone chamber. 
     Referring also to  FIG. 3 , in the illustrated embodiment the air inlet  152  includes an upstream or inlet end  158 , which may be coupled to the hose coupling member  122 , and a downstream end  160  ( FIG. 6 ) that is spaced apart from the upstream end  158 . In the illustrated configuration, the cyclone bin assembly  118  can be removed from the surface cleaning unit  106  ( FIGS. 3 and 5 ), for example, for cleaning or emptying, while the hose  112  remains connected to the hose coupling member  122  and with the surface cleaning unit  106 . This may allow a user to remove the cyclone bin assembly  118  without having to detach or decouple the hose  112 . 
     Referring to  FIG. 7 , air can exit the cyclone chamber via the air outlet  154 . Optionally, the cyclone air outlet  154  may be positioned in one of the cyclone chamber end walls, and in the example illustrated is positioned in the end wall  148 , at the same end of the cyclone chamber  140  as the air inlet  152 . In this configuration, air can enter and exit at the bottom of the cyclone chamber  140 . 
     In the illustrated example, the cyclone air outlet  148  includes a conduit in the form of a vortex finder  162  that extends into the interior  152  of the cyclone chamber  140 . In the example illustrated, the cyclone axis  144  is aligned with the orientation of the vortex finder  162 . And the air outlet is generally circular in cross-sectional shape. 
     In the illustrated example, a screen  164  is attached to the upstream end of the vortex finder  162  to help prevent fluff, lint and other debris from exiting via the air outlet  154 . Referring to  FIG. 6 , in the illustrated example the screen  164  is generally cylindrical, but may be of any suitable shape, including for example frusto-conical, in other embodiments. Optionally, the screen  164  can be removable from the vortex finder  162 . 
     When combined with any other embodiment, the cyclone bin assembly may be of any particular design and may use any number of cyclone chambers and dirt collection chambers. The following is a description of exemplified features of a cyclone bin assembly any of which may be used either individually or in any combination or sub-combination with any other feature disclosed herein. 
     Optionally, the cyclone chamber  140  may be in communication with the dirt collection chamber  142  by any suitable means, and in the example illustrated includes a dirt outlet  156 . Preferably, as exemplified, the dirt collection chamber  142  is exterior to cyclone chamber  140 , and preferably has a sidewall  166  that partially laterally surrounds the cyclone chamber  140 . At least partially nesting the cyclone chamber  140  within the dirt collection chamber  142  may help reduce the overall size of the cyclone bin assembly  118 . Referring to  FIG. 8 , in the illustrated embodiment the cyclone chamber sidewall  150  is coincident with the dirt collection chamber sidewall  166  for approximately half its circumference. It will be appreciated that the dirt collection chamber  142  may fully surround the cyclone chamber  140 . 
     In the illustrated example, the cyclone dirt outlet  156  is provided in the form of a slot  168  bounded by the cyclone sidewall  150  and the upper cyclone end wall  146 , and is located toward the upper end of the cyclone chamber  140 . 
     Optionally, the slot  168  may extend around the entire perimeter of the cyclone chamber (forming a generally continuous annular gap) or may extend around only a portion of the cyclone chamber perimeter, as illustrated. 
     To help facilitate emptying the dirt collection chamber, one of or both of the end walls  170  and  172  of the dirt collection chamber may be openable. Similarly, one or both of the cyclone chamber end walls  146  and  148  may be openable to allow a user to empty debris from the cyclone chamber  140 . In the illustrated example, the upper dirt chamber end wall  170  is integral with the upper cyclone end wall  146  and the lower dirt collection chamber end wall  172  is integral with, and openable with, the lower cyclone chamber end wall  148  and both form part of the openable bottom door  174 . The door  174  is moveable between a closed position ( FIG. 4 ) and an open position ( FIG. 8 ). When the door  174  is open, both the cyclone chamber  140  and the dirt collection chamber  142  can be emptied concurrently. 
     Optionally, the cyclone bin assembly  118  can be detachable from the main body  136 . Providing a detachable cyclone bin assembly  118  may allow a user to carry the cyclone bin assembly  118  to a garbage can for emptying, without needing to carry or move the rest of the surface cleaning apparatus. Preferably, as exemplified in  FIG. 5 , the cyclone bin assembly  118  is removable as a closed module, which may help prevent dirt and debris from spilling out of the cyclone bin assembly  118  during transport. 
     Preferably, the cyclone bin assembly  118  can be separated from the motor housing while the surface cleaning unit  106  is mounted on the chassis portion  102  and also when the surface cleaning unit  106  is separated from the chassis portion  102  ( FIG. 3 ). Accordingly, the cyclone bin assembly  118  is preferably positioned on an upper portion of the surface cleaning unit  106  and in the example illustrated is mounted on a platform portion  176  of the main body  136  ( FIG. 5 ) provided forwardly of the suction motor  116 . 
     The cyclone bin assembly  118  is preferably configured so that seating the cyclone bin assembly  118  on the platform portion  176  will position the cyclone bin assembly  118  within the air flow path between the dirty air inlet  108  and the clean air outlet  110 . 
     In the illustrated example, mounting the cyclone bin assembly  118  on the platform establishes a connection between the hose coupling  122  and the cyclone air inlet  152 , and between the cyclone air outlet  148  and an air inlet  178  the main body  136 . 
     Referring to  FIG. 7 , in the illustrated example the vortex finder  162  is provided in the form of a conduit that is integrally formed with the cyclone chamber and has an upper portion  180  that has a first diameter  182  and a wider, lower portion  184  with a larger, second diameter  186 . A generally laterally extending shoulder surface  188  extends between the upper and lower portions  180  and  184 . 
     Referring also to  FIGS. 6 and 5 , the lower portion  184  of the vortex finder  162  is sized to accommodate a mounting post  190  that is provided on the main body  136 . In the illustrated example, the mounting post  190  is a hollow air flow conduit that extends upwardly from a platform portion  176  of the main body  136 . In this configuration the mounting post  190  provides the main body air inlet  178  and forms part of the air flow path. Inserting the mounting post  190  into the lower portion  184  of the vortex finder  162  can help align and orient the cyclone bin assembly  118  when it is placed on the main body  136  and can also establish air flow communication between the cyclone chamber air outlet  148 , the main body air inlet  178 . 
     Referring to  FIG. 6 , in the illustrated example the mounting post  190  includes an upstream end  192  that is configured to nest within the lower portion  184  of the vortex finder  162 , and a downstream end  194  that is in communication with the internal air flow conduit  128 . 
     Optionally, the surface cleaning unit may include one or more filters positioned in the air flow path between the cyclone chamber and the suction motor. The filters may be configured to filter out fine dust and debris that remains entrain with the air leaving the cyclone chamber. The filters may be contained in a filter chamber that is provided in the surface cleaning unit. Preferably, the filter chamber can be accessed by a user, which may help facilitate inspection and/or replacement of the filters positioned within the filter chamber. Optionally, more than one filter member may be contained within a single filter chamber. 
     The following is a description of a pre-motor filter housing that may be used by itself in any surface cleaning apparatus or in any combination or sub-combination with any other feature or features disclosed herein. 
     Referring to  FIG. 5 , in the illustrated embodiment, the main body  136  of the surface cleaning unit  106  includes a pre-motor filter chamber  196  that is positioned in the air flow path between the cyclone chamber  140  and the suction motor  116  (see also  FIG. 6 ). The pre-motor filter chamber  196  includes a rear wall  198 , a sidewall  200  extending from the rear wall  198  and front wall  202  opposite the rear wall  198  which together cooperate to surround a chamber interior. Referring to  FIG. 5 , in the illustrated embodiment, removing the cyclone bin assembly  118  reveals the front wall  202  of the pre-motor filter chamber  196 . 
     Preferably, one or more filters can be provided in the pre-motor filter chamber  196  to filter the air exiting the cyclone bin assembly  118  before it reaches the motor  116 . Referring to  FIG. 6 , in the illustrated example, the pre-motor filters include a foam filter  204  and a downstream felt layer  206  positioned within the pre-motor filter chamber  196 . Preferably, the filters  204  and  206  and are removable to allow a user to clean and/or replace them when they are dirty. 
     Preferably, one or more of the walls of the pre-motor filter chamber  196  are openable, removable or otherwise reconfigurable to allow a user to access the interior of the pre-motor filter chamber. In the illustrated example, the front wall  202  is removable and can be moved from a closed position, in which it seals enclosing the pre-motor filter chamber ( FIG. 5 ) and an open position in which a user can access the interior of the pre-motor filter chamber ( FIG. 3 ). 
     The front wall  202  can be attached to the sidewall  200  using any suitable mechanism, such as latches, pins and other fasteners. In the illustrated example, the front wall  202  connects to the sidewall  200  via a friction fit. In this configuration, the front wall  202  can be removed and re-connected to the sidewall  200  without having to release a latch or other type of retaining fastener. This may help facilitate one-handed removal of the front wall  202 . 
     Optionally, a gasket  208  can be provided around the perimeter of the front wall  202 . The gasket  208  may help seal the pre-motor filter chamber  196  and/or may help facilitate the friction fit between the front wall  202  and the sidewall  200 . 
     Referring to  FIGS. 2 and 6 , in the illustrated example, when the cyclone bin assembly  118  is mounted on the main body  136  the pre-motor filter chamber  196  is disposed longitudinally between the cyclone bin assembly  118  and the suction motor  116  and the cyclone bin assembly  118  is positioned in front of at least a portion of the openable front wall  202  of the pre-motor filter chamber  196 . In this configuration the pre-motor filter chamber  196  is substantially blocked/covered when the cyclone bin assembly  118  is mounted on the main body  136 , and in the example illustrated the front wall  202  abuts a portion of the sidewall  150  of the cyclone bin assembly  118 . Also, in this configuration the pre-motor filter chamber  196  overlies one end of the suction motor  116  such that a suction motor axis  210  (about which the rotor rotates) intersects the pre-motor filter chamber  196 , and specifically, in the illustrated example intersects the front wall  202 , the rear wall  198  and both of the filters  204  and  206  disposed within the pre-motor filter chamber  196 . The motor axis  210  will also intersect the cyclone bin assembly  118  when it is mounted to the main body  136  and covers the front wall  202 . 
     In the illustrated example, the front wall  202  is smaller than the cyclone bin assembly  118 , and is completely covered when the cyclone bin assembly  118  is mounted on the main body  136 . This may help protect the pre-motor filter chamber  196  and may obscure it from view when the surface cleaning apparatus  100  is in normal use. This may also help prevent a user from accessing the pre-motor filter chamber  196  while the surface cleaning apparatus is in use, and/or may help limit accidental or unwanted opening of the pre-motor filter chamber  196 . In this configuration, the front wall  202  is exposed and is accessible only when the cyclone bin assembly  118  is removed from the main body  136 . 
     Referring to  FIGS. 3 and 6 , the pre-motor filter chamber includes a chamber air inlet  212  for supplying air to the pre-motor filter chamber  196  upstream of the filters  204  and  206 , and a chamber air outlet  214  downstream from the filters  204  and  206  for withdrawing air from the pre-motor filter chamber  196 . 
     In the illustrated example, the foam filter  204  has an upstream side  216  ( FIG. 6 ) and an opposite downstream side  218  (referenced to the direction of air flow through the filter). In the illustrated example, the upstream side  218  of the foam filter faces outward (i.e. away from the main body  136  and generally toward the cyclone bin assembly  118 ) and is visible when the front wall  202  is removed. In this configuration, a user may be able to visually inspect the upstream side  216  of the foam filter  204  without having to remove the foam filter  204  from the pre-motor filter chamber  196 . 
     When the front wall  202  is attached to the sidewall  200  to enclose the pre-motor filter chamber  196  an open headspace  220  or header is provided between the front wall  202  and the upstream side  216  of the foam filter  204  and functions as an upstream air plenum. Providing the upstream plenum  220  allows incoming air to flow across the upstream side  216  of the filter  204 . To help maintain the desired spacing between the upstream side  216  of the filter  204  and the front wall  202  ribs  222  are provided on the inner surface of the front wall  202  ( FIG. 3 ). The ribs  222  extend from the front wall and will bear against the upstream side  216  of the foam filter  204  to help maintain the desired spacing between the front wall  202  and the foam filter  204 . The ribs  222  are spaced apart from each other to allow air to flow between them, within the upstream plenum  220 , and across the upstream face  216  of the foam filter  204 . 
     A similar open headspace  224  or header is provided downstream of the filters  204  and  206  between the felt filter  206  and the rear wall  198  and provides a downstream air plenum. Providing a downstream plenum allows air exiting the filters  204  and  206  to flow laterally across the downstream side of filter  206  and toward the pre-motor filter chamber air outlet  214 . In use, air exits the cyclone chamber  140  via the air outlet  154  and flows into upstream plenum  220 , through filters  204  and  206  into downstream plenum  224  and into the air outlet  214  of the pre-motor filter chamber  196 . 
     In the illustrated example, the rear wall  198  also includes a plurality of supporting ribs  222  ( FIG. 3 ) that project from the rear wall  198  into the chamber interior. The ribs  222  are configured to contact the downstream side of the filters (in this example felt filter  206 ) in the pre-motor filter chamber  196  and to hold it apart from the rear wall  198 , thereby help to maintaining the downstream plenum. The ribs  222  are spaced apart from each other to allow air to flow between them, within the plenum, and toward the suction motor air outlet. Optionally, some or all of the support ribs  222  in the pre-motor filter chamber  196  (on either the front or rear walls  202  and  198 , or both) may be configured to help guide or direct the air flowing through the plenums. 
     Optionally, the one or more of the walls of the pre-motor filter chamber can be at least partially transparent so that a user can visually inspect the condition of the filters to determine if they require cleaning or replacement without having to remove the cyclone bin assembly. In the illustrated example, the removable front wall  202  is transparent. This allows a user to visually inspect substantially the entire upstream face  216  of the foam filter  204  without having to open the front wall  202 . This may also facilitate visual inspection of the foam filter  204  each time the cyclone bin assembly  118  is removed or re-attached because the front wall  202  is positioned behind the cyclone bin assembly  118 . This may help facilitate more frequent visual inspection of the foam filter  204  than would be achieved if the front wall  202  were opaque or if the pre-motor filter chamber  196  was located at a different location on the main body  136 . 
     Referring to  FIG. 5 , in the illustrated example the front wall  202  includes a handle portion in the form of a recess  226  that is graspable by a user. Providing a handle portion  226  may help facilitate removal and/or handling of the front wall  202 . In the illustrated example, the handle portion  226  is covered by the cyclone bin assembly  118  when it is mounted on the main body  136 . 
     Preferably, the air inlet  212  of the pre-motor filter chamber  196  is positioned such that it is in communication with the upstream plenum  220 , and the pre-motor filter chamber air outlet  214  is in communication with the downstream plenum  224 . Referring to  FIG. 3 , in the illustrated embodiment, the air outlet  214  is provided in the rear wall  198  and is in communication with the suction motor inlet  228  ( FIG. 6 ). The pre-motor filter chamber air inlet  212  is in communication with the upstream plenum and is provided in the form of a generally elongate inlet slot in the chamber sidewall  200 . In the illustrated example, the inlet slot  212  is provided in a lower portion of the sidewall  200  and is in communication with cyclone air outlet  154  via the internal conduit  128 . In this configuration, air exiting the cyclone chamber  140  flows generally downwardly through the vortex finder  162  and the main body air inlet  178 , generally rearwardly through the internal conduit  128  and then generally upwardly through the inlet slot  212  and into the upstream plenum  220 . The air can then flow generally rearwardly through the filters  204  and  206  and into the suction motor  116 . In this configuration, air travelling through the inlet slot  212  travels generally upwardly in a direction that is generally parallel to a plane containing the pre-motor filter chamber front wall  202  and is generally orthogonal to the motor axis  210 . In the illustrated embodiment, the inlet slot  212  is disposed below a plane  230  that contains the bottom wall  148  of the cyclone chamber  140  and the cyclone air outlet  154 . 
     Referring the  FIG. 3 , the inlet slot has a slot width  232  and a slot length  234 . Optionally, the slot length  234  can be selected such that it is at between about 30% and about 100% of the width  236  of the filters (i.e. the foam filter width  236 ) contained in the pre-motor filter chamber  196 . In the illustrated example, the slot width is about 1 cm and the slot length is about 15 cm, which as illustrated, is about 94% of the 16 cm width  236  of the foam filter. Providing a slit with a length  234  that is relatively long may help distribute the incoming air flow across the width  236  of the upstream face  216  of the foam filter  204 . 
     The inlet slot  212  may have any suitable configuration and may include generally sharp corners (i.e. is generally rectangular), or alternatively may have rounded corners (i.e. is generally oval-like). The inlet slot  212  also has an inlet flow area (measured in a plane that is generally orthogonal to the direction of air flow through the inlet slot). Similarly, the air outlet  214  has an outlet flow area (measured in a plane that is generally orthogonal to the direction of air flow through the outlet slot). Optionally, the inlet flow area and on the outlet flow area may be between about 5% and about 30% of the area of the upstream face  216  of the foam filter  204 . Optionally, the inlet flow area may be about 30-130% of the outlet flow area. 
     In the illustrated example, the area of the upstream face  216  of the foam filter  204  is relatively large. Providing a relatively large filter surface area may help reduce back pressure in the air flow path and/or may help facilitate air flow through the foam filter  204 . In the illustrated example, the area of the upstream face of the foam filter is between about 300 cm 2  and 400 cm 2  and is greater than the cyclone chamber cross sectional area. 
     In one aspect of the teachings described herein, which may be used in combination with any one or more other aspects, the surface cleaning unit may be operable in a variety different functional configurations or operating modes. The versatility of operating in different operating modes may be achieved by permitting the surface cleaning unit to be detachable from the chassis portion. Alternatively, or in addition, further versatility may be achieved by permitting portions of the vacuum cleaner to be detachable from each other at a plurality of locations in the chassis portion, and re-connectable to each other in a variety of combinations and configurations. 
     In the example illustrated, mounting the surface cleaning unit  106  on the chassis portion  102  allows the chassis portion  102  to carry the weight of the surface cleaning unit  106  and to, e.g., rollingly support the weight using rear wheels  238  and front wheel  240 . With the surface cleaning unit  106  attached, the vacuum cleaner  100  may be operated like a traditional canister-style vacuum cleaner. 
     Alternatively, in some cleaning situations the user may preferably detach the surface cleaning unit  106  ( FIG. 3 ) from the chassis portion  102  and choose to carry the surface cleaning unit  106  (e.g. by hand or by a strap) separately from the chassis portion, while still using the up flow conduit  114  to drivingly maneuver the surface cleaning head  104 . When the surface cleaning unit  106  is detached, a user may more easily maneuver the surface cleaning head  104  and the cleaning unit  106  round obstacles, like furniture and stairs. 
     To enable the vacuum suction generated by the surface cleaning unit  106  to reach the surface cleaning head  104  when the surface cleaning unit  106  is detached from the chassis  102 , the airflow connection between the surface cleaning head  104  and the cleaning unit  106  is maintained by the flexible hose  112 . The hose  112  is preferably attached to the surface cleaning unit  106  and not the chassis  102  so as to allow a user to detach the surface cleaning unit  106  and maintain a flow connection between the portable surface cleaning unit  106  and the surface cleaning head  104  without having to reconfigure or reconnect any portions of the airflow conduit. 
     What has been described above has been intended to be illustrative of the invention and non-limiting and it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the invention as defined in the claims appended hereto. The scope of the claims should not be limited by the preferred embodiments and examples, but should be given the broadest interpretation consistent with the description as a whole.