Patent Publication Number: US-8528164-B2

Title: Cyclone chamber for a surface cleaning apparatus

Description:
FIELD 
     The disclosure relates to surface cleaning apparatuses, such as vacuum cleaners. 
     INTRODUCTION 
     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 
     The following summary is provided to introduce the reader to the more detailed discussion to follow. The summary is not intended to limit or define the claims. 
     According to one broad aspect, a cyclone bin assembly comprises a cyclone chamber and a dirt collection chamber. The cyclone air outlet is in communication with an exit duct conduit (which may be a down duct depending upon the orientation of the duct conduit) extending away from the cyclone air outlet and preferably through (e.g., linearly through) a dirt collection chamber facing the end of the cyclone chamber with the air outlet. The down duct may extend from the floor of the cyclone chamber to the floor of the dirt collection chamber. Reinforcing ribs extend between the down duct and the floor of the cyclone chamber. The ribs may help reduce vibrations in the down duct, including, for example, vibrations induced by air flowing through the down duct. Optionally, the down duct and/or the support ribs can be removable. 
     An advantage of this configuration may be that vibration of the down duct may be reduced. Reducing the vibration of the down duct may help reduce the overall amount of noise generated by the surface cleaning apparatus and/or improve the separation efficiency of the cyclone chamber and the dirt collection chamber. 
     The dirt collection chamber may extend from a dirt inlet towards a dirt collection area. For example, the dirt inlet may be in an upper portion of the dirt collection chamber and the dirt collection area may be the floor of the dirt collection chamber. The dirt collection chamber comprises a sidewall (preferably an outer sidewall) that extends longitudinally between opposing first and second ends of the dirt collection chamber. Air circulating within the dirt collection chamber may flow along the sidewall. For example, air may exit the dirt outlet of the cyclone chamber and rotate around the dirt collection chamber and travel towards the dirt collection area. The air will at some point travel in the reverse direction towards the dirt inlet and re-enter the cyclone chamber. The dirt collection chamber may be configured such that the cross sectional area of the dirt collection chamber in a plane transverse to its length changes at least once along the length of the dirt collection chamber. In some embodiments, the cross-sectional area at the first end of the dirt collection chamber is different than the cross-sectional area at the second end of the dirt collection chamber. 
     An advantage of this configuration may be that changes in the cross-sectional area may be used to enhance the separation efficiency of the cyclone chamber and associated dirt collection chamber. By varying the transverse cross sectional area of the dirt collection chamber, the flow dynamics of the air in the dirt collection chamber may be varied and the amount of dirt that is dis-entrained from the air may be decreased, or the amount of dirt that is re-entrained may be reduced. For example, if the cross sectional area of the portion of the dirt collection chamber distal to the dirt inlet (e.g., the lower portion) is less than the opposed portion (e.g. upper portion) adjacent the dirt inlet, then the air will slow down as it enters the upper portion. As the velocity decreases, the amount of dirt that may be re-entrained in the return airflow may decrease. If the cross sectional area of the portion of the dirt collection chamber distal to the dirt inlet (e.g., the lower portion) is greater than the opposed portion (e.g. upper portion) adjacent the dirt inlet, then the air will slow down as it enters the lower portion allowing more dirt to be dis-entrained. 
     The cyclone chamber and dirt collection chamber assembly may be used in any surface cleaning apparatus. The surface cleaning apparatus comprises an air flow path extending from a dirty air inlet to a clean air outlet. A suction motor is provided in the air flow path, and a cyclone bin assembly is provided in the air flow path, preferably upstream from the suction motor. The cyclone bin assembly may comprise the cyclone chamber and a dirt collection chamber. Dirty air from the dirty air inlet can circulate within the cyclone chamber and may exit the cyclone chamber to circulate within the dirt collection chamber. 
     The cyclone bin assembly may also comprise a fine particle separator, to help separate relatively fine dirt particles from the dirty air. The fine particle separator comprises a flow chamber through which the dirty air can circulate. Dirty air, carrying entrained fine dirt particles can flow from the cyclone chamber into the fine particle separator. Air exiting the fine particle separator can re-enter the cyclone chamber, and travel to the suction motor via a cyclone air outlet. 
     The fine particle separator is configured so that air circulating in the flow chamber can travel at a relatively high velocity, and may travel faster than the air circulating within the cyclone chamber. To help increase the air flow velocity the cross-sectional area of the flow chamber, in the flow direction, can be varied, and preferably is reduced. Accelerating the dirty air to a relatively higher velocity may help dis-entrain fine dirt particles. 
     The air outlet of the fine particle separator flow chamber may be configured to disrupt the flow of air exiting the flow chamber. Disrupting the flow of air, for example by introducing eddy currents and/or turbulence and/or directing the air away from the cyclone dirt outlet, may help separate fine dirt particles from the air stream. Separated dirt particles can fall into the dirt collection chamber. 
     An advantage of this configuration may be a more efficient separation of fine dirt particles from the dirty air stream. Separating fine dirt particles from the dirty air stream in the fine particle separator may help prevent the fine dirt particles from continuing downstream from the cyclone bin assembly, and, for example, fouling the suction motor and/or a pre-motor filter. 
     In accordance with this aspect, a surface cleaning apparatus may comprise an air flow path extending from a dirty air inlet to a clean air outlet and a suction motor. The surface cleaning apparatus may comprise a cyclone chamber provided in the air flow path. The cyclone chamber may comprise a cyclone chamber first end and a cyclone chamber second opposed end, a cyclone air inlet, a cyclone air outlet provided at the cyclone chamber second opposed end and a cyclone chamber wall. An air exit conduit may be exterior to the cyclone chamber and may extend from the cyclone air outlet. At least one reinforcing rib may be positioned in abutting relationship with the air exit conduit and the cyclone chamber second opposed end. 
     The reinforcing rib may be connected to the air exit conduit. 
     The reinforcing rib may be connected to the cyclone chamber second opposed end. 
     The air exit conduit may extend through a dirt collection chamber that may be positioned exterior to the cyclone chamber. 
     The air exit conduit may be removably mounted to the cyclone chamber. 
     The cyclone chamber may comprise a vortex finder and the vortex finder remains in position when the air exit conduit is removed. 
     The cyclone air inlet may be located adjacent the cyclone chamber second opposed end. 
     The cyclone chamber may comprise a cyclone dirt outlet located adjacent the cyclone chamber first end. The surface cleaning apparatus may comprise a dirt collection chamber in communication with the cyclone dirt outlet. 
     The dirt collection chamber may extend at least part way around the cyclone chamber. The dirt collection chamber may have a dirt collection chamber first end and a dirt collection chamber second opposed end that may be spaced from and may face the cyclone chamber second opposed end. The air exit conduit may extend between the cyclone chamber second opposed end and the dirt collection chamber second opposed end. 
     The surface cleaning apparatus may comprise a cyclone bin assembly that is removably mounted to the surface cleaning apparatus, the cyclone bin assembly comprising the cyclone chamber and a dirt collection chamber. 
     The air exit conduit may extend through the dirt collection chamber. 
     The cyclone air outlet may be provided in the cyclone chamber second opposed end. The dirt collection chamber may have a dirt collection chamber end that is spaced from and faces the cyclone chamber second opposed end. The air exit conduit may extend between the cyclone chamber second opposed end and the dirt collection chamber end. 
     The dirt collection chamber end may be openable. 
     The dirt collection chamber end may have an air exit port in communication with the air exit conduit and the air exit conduit remains in position when the dirt collection chamber end is opened. 
     The air exit conduit may be removably mounted to the cyclone chamber. 
     The cyclone chamber may comprise a vortex finder and the vortex finder may remain in position when the air exit conduit is removed. 
     The cyclone air inlet may be located adjacent the cyclone chamber second opposed end. 
     The cyclone chamber may comprise a cyclone dirt outlet located adjacent the cyclone chamber first end. The surface cleaning apparatus may comprise a dirt collection chamber in communication with the cyclone dirt outlet. 
    
    
     
       DRAWINGS 
       Reference is made in the detailed description to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of an embodiment of a surface cleaning apparatus; 
         FIG. 2  is perspective cross sectional view of the cyclone bin assembly of the surface cleaning apparatus of  FIG. 1 , taken along line  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a side view of the cyclone bin assembly as shown in  FIG. 2 ; 
         FIG. 4  is a perspective cross sectional view of the cyclone bin assembly as shown in  FIG. 2 , with its lid and dirt chamber floor open; 
         FIG. 5  is a perspective view of the cyclone bin assembly of from the surface cleaning apparatus of  FIG. 1 , with its lid and dirt chamber floor open; 
         FIG. 6  is a partial cut away view of the cyclone bin assembly of  FIG. 5 , with the lid and floor removed; 
         FIG. 7   a - 7   e  are alternate schematic representations of a fine particle separator; 
         FIG. 8  is a side view of an alternate embodiment of a cyclone bin assembly that is usable with a surface cleaning apparatus; 
         FIG. 9  is cross-sectional side view of the cyclone bin assembly of  FIG. 8 ; 
         FIG. 10  is a top perspective view of the cyclone bin assembly of  FIG. 8 , with the lid removed; 
         FIG. 11  is a bottom perspective view of the cyclone bin assembly of  FIG. 8 , with the dirt chamber floor removed; 
         FIG. 12   a  is a schematic side view of the cyclone bin assembly of  FIG. 2 ; 
         FIG. 12   b  is a schematic side view of the cyclone bin assembly of  FIG. 8 ; 
         FIG. 12   c  is a schematic side view of an alternate embodiment of a cyclone bin assembly usable with a surface cleaning apparatus; and 
         FIG. 12   d  is a schematic side view of an alternate embodiment of a cyclone bin assembly usable with a surface cleaning apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an embodiment of a surface cleaning apparatus  100  is shown. In the embodiment illustrated, the surface cleaning apparatus  100  is an upright surface cleaning apparatus. In alternate embodiments, the surface cleaning apparatus may be another suitable type of surface cleaning apparatus, including, for example, a hand vacuum, a canister vacuum cleaner, a stick vac, a wet-dry vacuum cleaner and a carpet extractor. 
     General Overview 
     Referring still to  FIG. 1 , the surface cleaning apparatus  100  includes a surface cleaning head  102  and an upper section  104 . The surface cleaning head  102  includes a pair of rear wheels  106  and a pair of front wheels (not shown) for rolling across a surface and a dirty air inlet  108  provided at the front end. The upper section  104  is moveably connected to the surface cleaning head  102 . The upper section  104  is moveable (e.g., pivotally mounted to the surface cleaning head  102 ) between a storage position and an in use position. An air flow passage extends from the dirty air inlet  108  to a clean air outlet  110  on the upper section  104 . 
     A handle  116  is provided on the upper section  104  for manipulating the surface cleaning apparatus. 
     Referring to  FIGS. 1 and 2 , in the example illustrated, the upper section  104  comprises an air treatment housing  112  and a suction motor housing  114 , which is preferably positioned below air treatment housing  112 . The air treatment housing  112  houses an air treatment member, which is positioned in the air flow passage downstream from the dirty air inlet  108  to remove dirt particles and other debris from the air flowing through the air flow path. In the illustrated example, the air treatment member comprises a cyclone bin assembly  118 . The suction motor housing  114  is configured to house a suction motor (not shown). The suction motor is in air flow communication with the air flow path, downstream from the cyclone bin assembly  118 . The cyclone bin assembly  118  comprises a cyclone chamber  120  and a dirt collection chamber  122 . 
     Cyclone Bin Assembly 
     As exemplified in  FIGS. 2-6 , the cyclone chamber  120  may be an inverted cyclone and may be oriented with the dirt inlet at an upper end thereof. In other configurations, it will be appreciated that cyclone chamber  120  may be in a different orientation and may be of a different configuration. 
     Cyclone chamber  120  is bounded by a sidewall  124 , a first end wall  126  and a second end wall, or floor,  128  that are configured to provide an inverted cyclone configuration. A lid  130  covers the top of the cyclone chamber  120 , and an inner surface of the lid  130  comprises the first end wall  126  of the cyclone chamber  120 . Preferably, the lid  130  is openable. Opening the lid  130  may allow a user to access the interior of the cyclone chamber  120 , for example for cleaning. In the illustrated example, the lid  130  is pivotally connected to the cyclone bin assembly  118  by a hinge  132 , and is movable between a closed configuration ( FIG. 2 ) and an open configuration ( FIGS. 4 and 5 ). The lid  130  can be held in the closed position by any means known in the art, such as a releasable latch  134 . A handle  136  may be provided on the lid  130 . The handle  136  can be used to manipulate the cyclone bin assembly  118  when it is detached from the upper section  104 . 
     A tangential air inlet  138  may be provided in the sidewall  124  of the cyclone chamber  120  and is in fluid communication with the dirty air inlet  108 . Air flowing into the cyclone chamber  120  via the air inlet  138  can circulate around the interior of the cyclone chamber  120  and dirt particles and other debris can become dis-entrained from the circulating air. 
     Dirt collection chamber  122  is in communication with cyclone chamber  120 . Air with entrained dirt exits the cyclone chamber  120  via a cyclone dirt outlet  140  and enters the dirt collection chamber via a dirt collection chamber inlet. After circulating in the dirt collection chamber  122 , air may re-enter the cyclone chamber  118  via the dirt collection chamber inlet and the cyclone dirt outlet  140 . Preferably, the dirt collection chamber inlet and the cyclone dirt outlet  140  are the same element. For example, as exemplified, the cyclone dirt outlet  140  may be a slot formed between the sidewall  124  and the first end wall  126 . The slot  140  may also function as a dirt inlet for the dirt collection chamber  122 . Debris separated from the air flow in the cyclone chamber  120  can travel from the cyclone chamber  120 , through the dirt outlet  140  to the dirt collection chamber  122 . Preferably, the slot comprises a gap formed between the end of the sidewall  124  and end wall  126  that extends part way around the cyclone chamber  118  (e.g., up to 150°, preferably 30-150°, more preferably 60-120°). 
     As exemplified, the cyclone chamber  118  may be positioned within the dirt collection chamber  122  and the dirt collection chamber  122  may comprise an annular portion surrounding part or all of the cyclone chamber  118 . Alternately, or in addition, the cyclone chamber  118  may be positioned such that a portion of the dirt collection chamber  122  is positioned opposed to and facing (e.g., below) the air exit end of the cyclone chamber  118 . The annular portion may merge into, and be contiguous with, the lower portion of the dirt collection chamber  122 . 
     The cyclone chamber  120  extends along a longitudinal cyclone axis  156  ( FIG. 3 ). In the example illustrated, the longitudinal cyclone axis  156  is aligned with the orientation of the vortex finder  144 . The cyclone chamber  120  has a generally round cross-sectional shape and defines a cyclone chamber diameter  158 . 
     In the illustrated example, a rear a portion of the dirt collection chamber sidewall  152  is integral with a rear portion of the cyclone chamber sidewall  124 , and at least a portion of the second cyclone end wall  128  is integral with a portion of a first dirt collection chamber end wall  196 . 
     Air Exit Duct 
     Air can exit the cyclone chamber  120  via an air outlet  142 . As exemplified, the dirt collection chamber  122  is positioned below the lower end wall  128  of the cyclone chamber in which air outlet  142  (e.g., vortex finder  144 ) is provided. Accordingly, the cyclone air outlet includes a vortex finder  144  extending into the cyclone chamber  120  and a passage that extends through a portion of the dirt collection chamber  122 , and preferably linearly through the dirt collection chamber, e.g. down duct  146 . Optionally, a screen  148  can be positioned over the vortex finder  144 . In some embodiments, the screen  148  and vortex finder  144  can be removable. The down duct  146  may comprise a generally cylindrical duct member extending through the interior of the dirt collection chamber  122 . 
     In use, the down duct  146  and/or end wall  128  of the cyclone chamber  118  may vibrate. The vibrations may produce an undesirable noise. Further, the vibrations may interfere with the dirt separation efficiency of the cyclone bin assembly. Accordingly as exemplified, one or more stiffening ribs  150  may extend between the down duct  146  and the second end wall  128 . Providing stiffening ribs  150  may help reduce the vibration of the down duct  146  and/or second end wall  128  when the surface cleaning apparatus  100  is in use. Alternatively, or in addition to connecting to the second end wall  128 , stiffening ribs  150  may be configured to connect to the sidewall  152  and/or floor  154  of the dirt collection chamber  122 . 
     Optionally, the down duct  146  may be detachable from the second end wall  128  of the cyclone chamber  120 . If the down duct  146  is detachable from the second end wall  128 , the stiffening ribs  150  may also be detachable from the down duct  146 , or the second end wall  128  to help facilitate removal of the down duct  146 . 
     The floor  154  of the dirt collection chamber  122  is openable. Opening the dirt collection chamber floor  154  may help facilitate emptying dirt and other debris from the dirt collection chamber  122 . In the example illustrated, the dirt collection chamber floor  154  is pivotally connected to the dirt collection chamber sidewall  152  by hinge  198 , and is pivotable between and open position ( FIGS. 3-5 ) and a closed position ( FIG. 2 ). The dirt collection floor  154  also comprises an air outlet aperture  200  that allows air from the down duct  146  to pass through the floor  154 , and into the suction motor housing  114 . Optionally, sealing gaskets  202 , or other sealing members, can be provided around the perimeter of the floor  154  and around the air outlet aperture  200 , to help seal the dirt collection chamber  122  when the floor  154  is closed. 
     Fine Particle Separator 
     Optionally, the cyclone bin assembly  118  can include a fine particle separator to help dis-entrain relatively fine dirt particles from the dirty air stream. In the example illustrated, the fine particle separator comprises an air recirculation chamber  160  surrounding the cyclone chamber  120  wherein air may rotate or swirl prior to re-entering the cyclone chamber  118 . Preferably, as exemplified, the air recirculation chamber  160  comprises a generally annular flow chamber  162 , part or all of which may be between the cyclone chamber sidewall  124  and an outer bin sidewall  164  (see for example  FIG. 6 ). It will be appreciated that the annular flow chamber may be positioned above the cyclone chamber  118  and that some or all of the annular flow chamber  162  may face the dirt outlet  140 . 
     The inner surface of the lid  130  may comprise an upper end wall  166  of the flow chamber  162 . In this configuration, a user can access the flow chamber  162  as well as the cyclone chamber  118  when the lid is opened, for example, for cleaning or inspection. Alternatively, the flow chamber  162  can have an upper end wall that is separate from the lid  130 . Air circulating within the air recirculation chamber flows in a rotational direction, generally about rotation axis  161 . 
     Referring to  FIG. 3 , in the illustrated example, the flow chamber  162  surrounds the cyclone chamber  120 . The height  170  of the flow chamber  162  can be selected so that it is approximately the same height  172  as the dirt outlet  140  of the cyclone chamber  120 . Optionally, the flow chamber height  170  may be greater than or less than the dirt outlet height  172 , and optionally can extend the entire height  174  of the cyclone chamber  120 . While illustrated in combination with a vertically oriented cyclone chamber  120 , the air recirculation chamber  160  can also be used with a cyclone chamber  120  oriented in another direction, including, for example, a horizontal cyclone chamber. 
     The fine particle separator is preferably also in communication with the dirt collection chamber  122 . Accordingly, dirt collection chamber  122  may collect particulate matter separated by both the cyclone chamber and the fine particle separator. Preferably, the end of the fine particle separator closest to the dirt collection chamber  122  (e.g., the lower end) is continuous with the dirt collection chamber  122 . 
     Referring to  FIG. 6 , when the surface cleaning apparatus is use, a portion of the dirty air circulating within the cyclone chamber  120  can exit the cyclone chamber  118  via the dirt outlet  140  and travel into the flow chamber  162 , as illustrated using arrows  176 . The air entering the flow chamber  162  can carry entrained dirt particles. The air circulates in the annular flow chamber  162  before re-entering the cyclone chamber  118 . Concurrently, particulate matter separated in the cyclone chamber  118  may be ejected through dirt outlet  140  and pass into the dirt collection chamber  122 . 
     The cross sectional area of the annular flow chamber  162  in a plane transverse to the direction of rotation may be constant. Preferably, as exemplified, the cross-sectional area of the flow chamber varies, and preferably decreases, in the downstream direction. For example, the flow area of a first upstream portion  178  of the flow chamber  162  is greater than the flow area of a second downstream portion  180  of the flow chamber  162 . In this configuration, when air flows from the first portion  178  into second portion  180 , the velocity of the air can increase. Preferably, the area can be selected so that air traveling through the second portion  180  of the flow chamber  162  is traveling at a higher velocity than the air circulating within the cyclone chamber  120 . Circulating the air at an increased velocity in the flow chamber  162  may help dis-entrain finer dirt particles then those that are dis-entrained in the cyclone chamber  118 . Air exiting the second portion  180  of the flow chamber passes through a second portion outlet  182 . Fine dirt particles dis-entrained in the air circulation chamber  160  can fall into the dirt collection chamber  122 . 
     Referring to  FIGS. 5 and 6 , in the example illustrated, the flow area of the second portion  180  remains generally constant between the second portion inlet  184  and the second portion outlet  182 . Alternatively, the second portion  180  can be configured so that the flow area of the second portion varies between the inlet and outlet  184 ,  182 . For example, the second portion  180  can be configured so that the area at the outlet  182  is smaller than the area at the inlet  184 . This configuration may further increase the velocity of the air traveling from the inlet to the outlet  184 ,  182 . Alternatively, the second portion  180  can be configured so that the area at the inlet  184  is less than the area at the outlet  182 . 
     To vary the cross-sectional area in the second portion  180 , the thickness  186  of a portion of the cyclone chamber sidewall  124  can be varied, or the thickness  188  of the outer bin sidewall  164  can be varied, or both. Alternatively, instead of modifying the wall thicknesses  186 ,  188 , a separate ramp insert can be positioned within the second portion  180  of the flow chamber. Alternately, or in addition, the height  170  of the annular flow region  162  may be varied. 
     Referring to  FIG. 7   a , in a schematic representation of the second portion  180  of the flow chamber  162 , the thickness  186  of the cyclone chamber sidewall  124  at the inlet  184  is equal to the thickness  186  of the cyclone chamber sidewall  124  at the outlet  182 . Similarly, the thickness  188  of the sidewall  164  at the inlet  184  is equal to the thickness  188  of the sidewall  164  at the outlet  182 . While not shown, the height may remain constant such that the cross sectional area remains constant. 
     In other embodiments, the wall thickness  186  at the outlet  182  may be different than the wall thickness  186  at the inlet  184 , as illustrated using schematic representations in  FIGS. 7   b - 7   e . Similarly, the wall thickness  188  may be varied.  FIGS. 7   e  and  10  illustrate embodiments in which a separate ramp member  189  is placed within the second portion  180  of the flow chamber  162 , instead of varying the wall thickness  186  of the cyclone chamber sidewall  124 . 
     Referring to  FIGS. 5 ,  6  and  10 , alternately, or in addition, a portion of the cyclone chamber sidewall  124  adjacent the second portion outlet  182  may be configured to disrupt the flow of air exiting the second portion outlet  182  and\or direct the air flow away for the dirt inlet  140 . For example, the side wall or a ramp insert  189  may be provided at the outlet  182  to that the distance between the air flow region of portion  180  at outlet  182  and outlet  140  is increased. This will require the air to make a sharper turn to return to the cyclone chamber and may assist in separating finer dirt particles. 
     Alternately, or in addition, the cyclone chamber sidewall  124  may comprise a relatively sharp corner  190 , which may help disrupt the air flow  176 . Disrupting the air flowing past the corner  190  may help dis-entrain dirt particles from the air flow  176 , and may help urge the air flow  176   a  to re-enter the cyclone chamber  12  via the dirt outlet  140 . 
     Optionally, the dirt outlet slot  140  may be configured to have a varying slot height  172  along its length. Varying the height of the dirt outlet slot  140  may alter the behaviour of the air flowing through the slot  140 , between the cyclone chamber  120  and the air recirculation chamber  160 , for example air flows  176  and  176   a.    
     Rib in the Dirt Collection Chamber 
     As exemplified in  FIGS. 2-4 , optionally, one or more ribs  194  may extend between the cyclone chamber sidewall  124  and the dirt collection chamber sidewall  152 . The rib may be used with or without the fine particle separator. The rib may extend partway across the annular spaced between the sidewalls and preferably extends across the annular space between the sidewalls. Preferably, the rib  194  is positioned adjacent the dirt outlet  140  and more preferably, is positioned on the side of the dirt outlet  140  towards end wall  154  of the dirt collection chamber  122 . Accordingly, the rib is provided in the upper annular portion of the dirt collection chamber  122  and may be below the fine particle separator if one is used. The rib  194  may accordingly impede the flow of the air flow circulating within an upper portion of the dirt collection chamber  122 , which may help separate dirt particles from the air stream and may reduce re-entrainment of separated particulate matter. 
     Variable Dirt Collection Sidewall 
     Referring to  FIG. 3 , optionally, the dirt collection chamber  122  can include a sidewall  152  having a variable cross-sectional area, and preferably the outer wall. In the illustrated example, the dirt collection chamber  122  comprises an upper portion  204  and a lower portion  206 . The upper portion  204  is positioned adjacent the cyclone chamber  120  and comprises an upper portion sidewall  208  that at least partially surrounds the cyclone chamber  120 . The upper portion  204  may also comprise some or all of the air recirculation chamber  160 . The upper portion  204  of the dirt collection chamber  122  has a generally round cross-sectional shape, and has an upper dirt chamber diameter  210 . 
     The lower portion  206  of the dirt collection chamber is positioned generally below the cyclone chamber  120 . The lower portion  206  has a lower portion sidewall  212  with a generally round cross-sectional shape, and has a lower dirt chamber diameter  214 . In the illustrated configuration, the lower dirt chamber diameter  214  is greater than the upper dirt chamber diameter  210 . In this configuration, the dirt collection chamber  122  can be described as having a stepped out configuration. A transition surface  216  may connect the upper and lower portion sidewalls  208 ,  212 . In the illustrated example, the transition surface  216  comprises an angled wall. In other examples, the transition surface can have another configuration, including, for example a horizontal or curved wall. 
     In use, a portion of the dirty air entering the cyclone chamber  120  may exit the cyclone chamber  120  via the dirt outlet, and can circulate within the dirt collection chamber  122 . Air circulating within the dirt collection chamber  122  may eventually re-enter the cyclone chamber  120 , via the dirt outlet  140 , and exit the cyclone bin assembly  118  via the air outlet  142 . 
     The cross sectional area or diameter of the dirt collection chamber may be varied using other sidewall configurations. For example, referring to  FIGS. 8-11 , another embodiment of a cyclone bin assembly  518  that can be used with a surface cleaning apparatus includes a cyclone chamber  520  and a dirt collection chamber  522 . Features of the cyclone bin assembly  518  that are analogous to features of cyclone bin assembly  118  are represented by like reference characters, indexed by 400. Dirt collection chamber  522  includes an upper portion  604  and a lower portion  606 . In this embodiment, the upper dirt collection diameter  610  is greater than the lower dirt collection diameter  614 . In this configuration, the dirt collection chamber  522  can be described as having a stepped in configuration. 
     By way of further example, referring to  FIG. 12   a , a schematic representation of the stepped out cyclone bin assembly  118  illustrates a dirt collection chamber  122  with a lower portion diameter  214  that is greater than the upper portion diameter  210 .  FIG. 12   b , is a schematic representation of the stepped in cyclone bin assembly  518 , in which the upper portion diameter  610  is greater than the lower portion diameter  614 . Other variable cross-section dirt collection chamber configurations can also be used. For example,  FIG. 12   c  is a schematic representation of another embodiment of a cyclone bin assembly  718 . The dirt collection chamber  722  in cyclone bin assembly  718  comprises an upper portion  804  having an upper portion diameter  810 , a lower portion  806  having a lower portion diameter  812  and an intermediate portion  840  having an intermediate portion diameter  842 . The upper and lower portion diameters  810 ,  814  are generally equal, and are both greater than the intermediate portion diameter  842 . In this configuration the dirt collection chamber  822  comprises two transition surfaces  816 .  FIG. 12   d , is a schematic representation of another embodiment of a cyclone bin assembly  918 . The dirt collection chamber  922  in cyclone bin assembly  918  comprises an upper portion  1004  having an upper portion diameter  1010 , a lower portion  1006  having a lower portion diameter  1014  and an intermediate portion  1040  having an intermediate portion diameter  1042 . In this example, the upper and lower portion diameters  1010 ,  1014  are generally equal, and are both less than the intermediate portion diameter  1042 . Like dirt collection chamber  718 , dirt collection chamber comprises two transition surfaces  1016   
     Changes in the cross-sectional area may be used to enhance the separation efficiency of the cyclone chamber and associated dirt collection chamber. By varying the transverse cross sectional area of the dirt collection chamber, the flow dynamics of the air in the dirt collection chamber may be varied and the amount of dirt that is dis-entrained from the air may be decreased, or the amount of dirt that is re-entrained may be reduced. For example, if the cross sectional area of the portion of the dirt collection chamber distal to the dirt inlet (e.g., the lower portion  206 ) is less than the opposed portion (e.g. the upper portion with rib  194 ) adjacent the dirt inlet, then the air will slow down as it enters the upper portion. As the velocity decreases, the amount of dirt that may be re-entrained in the return airflow may decrease. If the cross sectional area of the portion of the dirt collection chamber distal to the dirt inlet (e.g., the lower portion) is greater than the opposed portion (e.g. upper portion) adjacent the dirt inlet, then the air will slow down as it enters the lower portion allowing more dirt to be dis-entrained. 
     Dirt Collection Chamber Wall Recesses 
     Referring to  FIGS. 5 and 6 , in the illustrated example, the dirt collection chamber sidewall  152  may comprise one or more recessed columns  220 , on opposing sides of the dirt collection chamber  122 . The recessed columns  220  can provide a discontinuity on the inner surface of the outer dirt collection chamber sidewall  152 , which may create eddy currents or other disruptions in the dirty air flow circulating within the dirt collection chamber  122 , represented by arrows  176   b . Preferably, the angle  222  formed at the intersection between the dirt collection chamber sidewall  152  and the upstream or leading edge  223  of the recessed column  220  walls is sufficient to create a relatively sharp corner, which may help disrupt the air flow. Preferably, the angle  222  is between about 30 and about 90°, and more preferably is between 45 and 90°. Disrupting the circulation of the dirty air passing over the recessed columns  220  may help dis-entrain dirt particles. In other embodiments, the dirt collection chamber  122  can comprise a different number of recessed columns  220 . 
     The depth  224  of the recessed columns  220  can be selected to provide a sufficient depth such that an area with reduced or no air flow is created such that dirt particles may settle out and travel to the dirt collection floor. Collecting dirt particles within the recessed columns  220  may also help prevent re-entrainment of the dirt particles in the circulating air flow. Preferably, the depth  224 , represented using a dashed line to approximate the circumference of the uninterrupted sidewall  152 , is between about 6 and about 18 millimeters, or optionally can be greater than 18 millimeters. 
     Connecting Wall 
     Referring to  FIGS. 9 and 11 , in addition to the stiffening ribs  550  the down duct  546  includes a vertically oriented connecting wall  630  extending between the down duct  546  and the dirt collection chamber sidewall  552 . Preferably, the connecting wall  630  extends downward from the upper end wall  596 , and has a height  632  that is between about 5% and about 80% of the height  634  of the lower portion  606  of the dirt collection chamber  522 . More preferably, the connecting wall height  632  is between about 15% and 50% of the lower portion height  634 . The connecting wall  630  can impede the circulation of the dirty air flowing within the lower portion  606 . Impeding the circulation of the dirty air flow may help dis-entrain dirt particles from the dirty air flow. The dis-entrained particles can then be retained within the lower portion  606  when the circulating air re-enters the cyclone chamber  520 . The connecting wall  630  may also provide additional stiffness and vibration damping to the down duct  546 , as described above. 
     It will be appreciated that the following claims are not limited to any specific embodiment disclosed herein. Further, it will be appreciated that any one or more of the features disclosed herein may be used in any particular combination or sub-combination, including, without limitation, a dirt collection chamber with a variable diameter or cross sectional area, the fine particle separator, an annular dirt collection chamber with a rib or baffle, reinforcing ribs for a cyclone chamber floor and/or a down flow duct and a recess in the outer sidewall of the dirt collection chamber. 
     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.