Patent Publication Number: US-8979960-B2

Title: Motor, fan and cyclonic separation apparatus arrangement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to EP Patent Application No. EP 11 184 789.3 filed Oct. 12, 2011, the contents thereof to be incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to a motor, fan and cyclonic separation apparatus arrangement. In particular, but not exclusively, the present invention relates to a motor, fan and cyclonic separation apparatus arrangement for use in vacuum cleaners. 
     BACKGROUND OF THE INVENTION 
     Vacuum cleaners are well known for collecting dust and dirt, although wet-and-dry variants which can also collect liquids are known as well. Typically, vacuum cleaners are intended for use in a domestic environment, although they also find uses in other environments, such as worksites or in the garden. Generally, they are electrically powered and therefore comprise an electric motor and a fan connected to an output shaft of the motor, an inlet for dirty air, an outlet for clean air and a collection chamber for dust, dirt and possibly also liquids. Electrical power for the motor may be provided by a source of mains electricity, in which case the vacuum cleaner will further comprise an electrical power cable, by a removable and replaceable battery pack, or by one or more in-built rechargeable cells, in which case the vacuum cleaner will further comprise some means, such as a jack plug or electrical contacts, for connecting the vacuum cleaner to a recharging unit. When the vacuum cleaner is provided with electrical power from one of these sources, the electric motor drives the fan to draw dirty air along an air flow pathway in through the dirty air inlet, via the collection chamber to the clean air outlet. The fan is often a centrifugal fan, although it can be an impeller or a propeller. 
     Interposed at some point along the air flow pathway, there is also provided some means for separating out dust and dirt (and possibly also liquids) entrained with the dirty air and depositing these in the collection chamber. This dirt separation means may comprise a bag filter, one or more filters and/or a cyclonic separation apparatus. 
     In the event that the dirt separation means comprises a bag filter, dirty air, which has entered the vacuum cleaner via the dirty air inlet, passes through the bag filter. This filters out, and collects within the bag filter, dust and dirt entrained with the dirty air. The filtered material remains in the bag filter which lines the collection chamber. The clean air then passes to the other side of bag filter and through a grille in the collection chamber under the influence of the fan. The fan draws air in and expels it out, from where the air then passes to the clean air outlet of the vacuum cleaner. 
     There is always a small risk of dust and dirt passing through the bag filter and it is undesirable that it be allowed to pass through the fan and cause damage. To reduce this potential problem, there is often a fine filter located across the grille of the collection chamber to remove any fine dust and dirt particles remaining in the air flow after passage through the bag filter. This is commonly known as a pre-fan filter. 
     Occasionally, and in addition to any pre-fan filter, there is a high efficiency filter located downstream of the fan before the air flow leaves the vacuum cleaner. This is to remove any remaining extremely fine particulate matter which will not harm the fan or motor, but which may be harmful to the household environment. The term “filtering efficiency” is intended to relate to the relative size of particulate matter removed by a filter. For example, a high efficiency filter is able to remove smaller particulate matter from air flow than a low efficiency filter. A HEPA filter is a high efficiency filter which should be able to remove extremely fine particulate matter having a diameter of 0.3 micrometers (μm) and lower. 
     The purpose of the bag filter is to filter dust and dirt entrained in dirty air flow and to collect the filtered material within the bag filter. This progressively clogs the bag filter. The volumetric flow rate of air through the vacuum cleaner is progressively reduced and its ability to pick up dust and dirt diminishes correspondingly. Hence, the bag filter needs replacement before it becomes too full and before vacuum cleaner performance becomes unacceptable. The volume of the collection chamber must be sufficiently large to merit the cost of regular bag filter replacement. 
     An upright vacuum cleaner commonly has an upright main body with a dirt separating means, a motor and fan unit, a handle at the top and a pair of support wheels at the bottom. A cleaner head with a dirty air inlet facing the floor is pivotally mounted to the main body. A cylinder vacuum cleaner commonly has a cylindrical main body with a separating dirt means, a motor and fan unit and maneuverable support wheels underneath. A flexible hose with a cleaner head communicates with the main body. Bag filters are commonly used in upright and cylinder vacuum cleaners as separation means because their main body has sufficient internal space for the large collection chamber required to accommodate the bag filter. 
     In the event that the dirt separation means comprises a filter, dirty air, which has entered the vacuum cleaner via the dirty air inlet, passes through the filter. This filters out dust and dirt entrained with the dirty air and the filtered material remains in the collection chamber on the upstream side of the filter. Sometimes the filter is supplemented by a sponge to absorb any liquids entrained in the dirty air flow. The clean air then passes to the other side of filter under the influence of the fan, and from the fan the air then passes to the clean air outlet of the vacuum cleaner. 
     Filtered material accumulates around, and progressively clogs, the filter. The volumetric flow rate of air through the vacuum cleaner is progressively reduced and its ability to pick up dust and dirt diminishes correspondingly. Hence, the collection chamber needs regular emptying and the filter needs frequent cleaning to mitigate against this effect. Sometimes, the vacuum cleaner has a filter cleaning mechanism. Alternatively, the filter needs to be removable for cleaning with a brush, or in a dish washer, for example. 
     Hand-holdable vacuum cleaners, as their name would suggest, are compact and lightweight and are intended to perform light, or quick, cleaning duties around a household. Typically, hand-holdable vacuum cleaners are battery-powered to be easily portable. 
     An example of a hand-holdable vacuum cleaner having the conventional motor, fan and filter arrangement is described in European patent publication no. EP 1 752 076 A, also in the name of the present applicant. This vacuum cleaner has dirty air inlet at one end of a dirty air duct leading to a collection chamber with a filter. The collection chamber is generally cylindrical and is arranged transverse the body of the vacuum cleaner. The dirty air duct is rotatable, with the collection chamber, in relation to the body. The dirty air duct may be adjusted to access awkward spaces while the vacuum cleaner is held comfortably by a user. 
     In the event that the dirt separation means comprises cyclonic separation apparatus, dirty air, which has entered the vacuum cleaner via the dirty air inlet, passes through the cyclonic separation apparatus having one or more cyclones. A cyclone is a hollow cylindrical chamber, conical chamber, frustro-conical chamber or combination of two or more such types of chamber. The cyclone may have a vortex finder part way, or all way, along its internal length. The vortex finder is commonly a hollow cylinder and it has a smaller external diameter than the internal diameter of the cyclone. 
     Dirty air enters via a tangentially arranged air inlet port and swirls around the cyclone in an outer vortex. Centrifugal forces move the dust and dirt outwards to strike the side of the cyclone unit and separate it from the air flow. The dust and dirt is deposited at the bottom of the cyclone and into a collection chamber below. An inner vortex of cleaned air then rises back up the cyclone. The role of a vortex finder is to gather and direct the cleaned air through an air outlet port at the top of the cyclone. As an alternative to a vortex finder, the cyclone may have an inner cylindrical air permeable wall providing the cleaned air with a path from the cyclone. From the cyclone the cleaned air passes, under the influence of the fan, to the clean air outlet of the vacuum cleaner. 
     As with a bag filter, a vacuum cleaner with a cyclonic separation apparatus may have a pre-fan filter to protect the fan and motor, especially if the air flow is used to cool the motor. Nevertheless, volumetric flow rate of air through the vacuum cleaner remains virtually constant as separated material accumulates in the collection chamber. Thus, an attraction of cyclonic separation apparatus in a vacuum cleaner is a consistent ability to pick up dust and dirt. Another attraction is that the cost of regular bag filter replacement is avoided. 
     An example of an upright vacuum cleaner having a motor, fan and cyclonic separation apparatus is described in European patent publication no. EP 0 042 723 A. This cyclonic separation apparatus is divided into a first cyclonic separating unit with a cyclone formed by an annular chamber and a second cyclonic separating unit with a generally frustro-conical cyclone. The first cyclonic separating unit is ducted in series with the second cyclonic separating unit. Air flows sequentially through the first, and then the second, cyclonic separating units. The frustro-conical cyclone has a smaller diameter than the annular chamber within which the frustro-conical cyclone is partially nested. Separated material from both cyclonic separating units collects in the cylindrical collection chamber formed at the bottom of the annular chamber. 
     The term “separation efficiency” is used in the same way as filtering efficiency and it relates to the relative ability of a cyclonic separation apparatus to remove small particulate matter. For example, a high efficiency cyclonic unit can remove smaller particulate matter from air flow than a low efficiency cyclonic separating unit. Factors that influence separation efficiency can include the size and inclination of the dirty air inlet of a cyclone, size of the clean air outlet of a cyclone, the angle of taper of any frustro-conical portion of a cyclone, and the diameter and the length of a cyclone. Small diameter cyclones commonly have a higher separation efficiency than large diameter cyclones, although other factors listed above can have an equally important influence. 
     The first cyclonic separating unit of EP 0 042 723 A has a lower separating efficiency than the second cyclonic separating unit. The first cyclonic separating unit separates larger dust and dirt from the air flow. This leaves the second cyclonic separating unit to function in its optimum conditions with comparatively clean air flow and separate out smaller dust and dirt. 
     A hand-holdable vacuum cleaner having a motor, fan and cyclonic separation apparatus is described in United Kingdom patent publication no. GB 2 440 110 A. This cyclonic separation apparatus is smaller than that of EP 0 042 723 A in order to be used in a hand-holdable vacuum. It is divided into a first cyclonic separating unit and a second cyclonic separating unit located downstream of the first cyclonic separating unit. The separating efficiency of the first cyclonic separating unit is lower than that of the second cyclonic separating unit. 
     The second cyclonic separating unit of GB 2 440 110 A comprises six cyclones arranged in a circular array protruding into an annular chamber. The space within this circular array of cyclones is used to duct air flow from the annular chamber to the air inlet ports of the cyclones. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a motor, fan and cyclonic separation apparatus arrangement which makes more efficient use of the space it occupies. This is particularly desirable in a vacuum cleaner, where the efficient use of space is of great importance and any wasted space will necessarily add to the overall size and weight of the vacuum cleaner, without giving any counteracting benefit. It is also an object of the present invention to provide a motor, fan and cyclonic separation apparatus arrangement particularly suitable for use in a compact or hand-holdable vacuum cleaner. A further object of the invention is to provide a vacuum cleaner comprising such a motor, fan and cyclonic separation apparatus arrangement. 
     Accordingly, in a first aspect, the present invention provides a motor, fan and cyclonic separation apparatus arrangement for a vacuum cleaner, the arrangement comprising: a motor coupled to a fan for generating air flow; and a cyclonic separation apparatus located in a path of the air flow generated by the fan, wherein the cyclonic separation apparatus comprises: a plurality of cyclones each with an air inlet port and an air outlet port; and a cooling air flow path, wherein the motor comprises a permanent magnet brushless motor, a switched reluctance motor or a flux switching motor, wherein the fan is coaxial with the motor and the fan has an outer diameter substantially the same as or less than the outer diameter of the motor, wherein the plurality of cyclones, the motor and the fan are arranged in a generally circular array about a central axis of the cyclonic separation apparatus, wherein the arrangement further comprises a baffle for directing air flow from the fan out of the circular array and wherein the motor is located in the cooling air flow path. 
     The present invention makes improved use of the space occupied by the motor and fan by clustering them amongst a circular array of cyclones. This is possible because the outer profile of the motor and fan is generally cylindrical, like the cyclones. The motor and fan may be located on the edge of the circular array, in the middle or somewhere in between. The smaller diameter fan takes less space and, as a result, enables a more compact cyclonic separation apparatus than has hitherto been possible. 
     Preferably, the motor and the fan are nested within the plurality of cyclones. This surrounds the motor and fan with cyclones thereby reducing the air flow path between individual cyclones and the fan. 
     Preferably, the central axis of the cyclonic separation apparatus passes through the motor and the fan. The motor and fan are located near, or at, the middle of the circular array of cyclones so that the motor and fan occupy space that may otherwise be unused. 
     Preferably, the circular array of cyclones is axially symmetric and wherein the motor and the fan are concentric with the central axis. This provides a more compact cyclonic separation apparatus as the components are arranged evenly about the central axis. 
     Preferably, the axes of the plurality of cyclones are substantially parallel to the central axis of the cyclonic separation apparatus. This provides an array of cyclones which may be more easily arranged within a cylindrical dirt container, like, for example, the cyclones of the first and second embodiments of a cyclonic separation apparatus described below. 
     Preferably, the plurality of cyclones is at least eight cyclones arranged in a generally circular array having an inner annulus and an outer annulus and wherein the inner annulus diameter is at least  30  percent of the outer annulus diameter. This may provide space for a motor with sufficient power to drive the fan and provide sufficient air flow through the cyclonic separating apparatus. 
     Preferably, each cyclone comprises: a cyclone body with a hollow generally frustro-conical portion and a longitudinal axis; a discharge nozzle arranged at a longitudinal end of the frustro-conical portion; the air inlet port arranged tangentially through a side of the cyclone body; and the air outlet port through an opposite end of the cyclone body to the discharge nozzle. The vortex of air flowing towards the discharge nozzle of each cyclone accelerates as the cyclone body&#39;s diameter decreases to separate ever smaller dirt particles and to increase separation efficiency. 
     Preferably, the axes of the plurality of cyclones are outwardly inclined with respect to the central axis of the cyclonic separation apparatus to reduce space between the motor and the generally frustro-conical portion of each respective cyclone. The inclination of the cyclones provides a gap between the cylindrical portions of the cyclones which may be used by the baffle to expel air from the fan, as may be the case with a motor and fan nested amongst the cyclones of the hand-holdable vacuum cleaner disclosed by GB 2 440 110 A. 
     Preferably, the cyclonic separation apparatus comprises: a first cyclonic separating unit comprising a hollow substantially cylindrical dirt container concentric with the central axis of the cyclonic separation apparatus and an air inlet port arranged tangentially through a side of the dirt container; and a second cyclonic separating unit comprising the plurality of cyclones, wherein the second cyclonic separating unit receives air flow downstream from the first cyclonic separating unit. A dual cyclonic separation apparatus improves cleaning of dirty air by sharing separation of different particulate matter sizes between cyclonic separating units of varying separation efficiencies. 
     Preferably, the motor, the fan and the second cyclonic separating unit are located within the dirt container. This provides a more compact arrangement with regard to its axial dimension. 
     Preferably, an outer diameter of the motor is at least 15 percent of an outer diameter of the dirt container. This may provide a suitably sized dirt container to separate and collect larger dirt particles and provide suitable space for the circular array of cyclones, motor and fan. 
     Preferably, the second cyclonic separating unit has a higher separation efficiency than the first cyclonic separating unit. Large particulate matter is separated in the dirt container initially, leaving the high efficiency cyclones to separate the more difficult small particulate matter. 
     Preferably, the cyclonic separation apparatus comprises an intermediate wall arranged within the dirt container, wherein the intermediate wall surrounds the air inlet ports of the cyclones, wherein the intermediate wall defines a chamber with an air permeable wall arranged as an air outlet from the first cyclonic separating unit and wherein the second cyclonic separating unit receives air flow downstream from the first cyclonic separating unit via the chamber. The intermediate wall shields the air inlet ports from the dirty air flow vortex within the cylindrical dirt container. The air permeable wall provides an extra dirt filtration stage and deposits filtered dirt in the dirt container. Both these features help the cyclonic separation process. 
     Preferably, the fan is an impeller. This provides a compact design of fan capable of delivering suitable volumetric airflow at high rotational speeds. 
     In a second aspect, the present invention provides a vacuum cleaner comprising the motor, fan and the cyclonic separation apparatus arrangement according to the first aspect. The vacuum cleaner may be a more compact design because it benefits from the compact design of the motor, fan and cyclonic separation apparatus arrangement of the first aspect and it need not accommodate the motor or the fan within its body housing. 
     Preferably, the cyclonic separation apparatus comprises at least one protruding lip arranged to impede movement of separated material from said longitudinal end of the dirt container. This helps to avoid re-entrainment of separated dirt into the air flow destined for the cyclones. Preferably, the dirt container comprises a generally cylindrical exterior wall and a generally circular end wall at said longitudinal end of the exterior wall, wherein the air inlet port is arranged tangentially through the exterior wall and wherein the end wall is detachably connected to the exterior wall. The detachable end wall facilitates emptying of dirt in the dirt container. Preferably, the end wall is hingedly connected to the exterior wall so that the end wall is not mislaid after opening. Preferably, the plane of the discharge nozzle is inclined with respect to the longitudinal axis of the cyclone body. This helps to avoid separated material from re-entering the discharge nozzle. Preferably, the longitudinal axis of each cyclone is in line with the, central axis of the cyclonic separation apparatus. Preferably, the longitudinal axis of each cyclone is parallel with the central axis of the cyclonic separation apparatus. Preferably, the fan is a centrifugal fan having a tangential output. Preferably, the plurality of cyclones is no more than sixteen cyclones. More preferably the plurality of cyclones is no more than fourteen cyclones. Preferably, the plurality of cyclones is no fewer than eight cyclones. More preferably the plurality of cyclones is no fewer than ten cyclones. Most preferably, the plurality of cyclones is twelve cyclones. Preferably, the ratio of the outer diameter of the dirt container to the outer diameter of each cyclone is no greater than 28:3. More preferably the ratio of the outer diameter of the dirt container to the outer diameter of each cyclone is no greater than 24:3. Preferably, the ratio of the outer diameter of the dirt container to the outer diameter of each cyclone is no less than 12:3. More preferably the ratio of the outer diameter of the dirt container to the outer diameter of each cyclone is no less than 16:3. Most preferably, the ratio of the outer diameter of the dirt container to the outer diameter of each cyclone is about 20:3. 
     Preferably, the vacuum cleaner is a battery-powered hand-holdable vacuum cleaner comprising a detachable and/or rechargeable battery. This provides a vacuum cleaner that may be readily portable and convenient to use without need to find a mains electrical supply. Preferably, the vacuum cleaner comprises a body with a handle and a dirty air duct located in the path of air flow up stream of the cyclonic separation apparatus. Alternatively, the vacuum cleaner comprises a flexible hose located in the path of the air flow upstream of the cyclonic separation apparatus. Alternatively, the vacuum cleaner comprises an elongate body with a handle at one end and a cleaner head at an opposite end, wherein the cleaner head is located in the path of the air flow upstream of the cyclonic separation apparatus. Preferably, the vacuum cleaner comprises at least one support wheel for supporting the vacuum cleaner upon a floor, wherein the at least one support wheel rotates about the central axis of the cyclonic separation apparatus. The cyclonic separation apparatus is located close to the floor so that fluid communication with the cleaner head is as shortened. This reduces energy loss by reducing the overall length of the air flow path. Preferably, the at least one support wheel defines a cylinder surrounding the dirt container. The cyclonic separation apparatus performs an additional role of axle to the support wheel which makes the vacuum cleaner more compact and reduces the number of parts. Preferably, the elongate body is telescopically extendible so that it can be extended for use and retraced for storage in a much smaller location. Alternatively, the vacuum cleaner is a blower-vac, which is an outdoor garden tool which can perform the role of blowing garden debris for collection and the role of vacuum cleaner for sucking garden debris into a container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the present invention will be better understood by reference to the following description, which is given by way of example and in association with the accompanying drawings, in which: 
         FIG. 1  shows perspective view of a first embodiment of a hand-held vacuum cleaner with a motor, fan and cyclonic separation apparatus arrangement; 
         FIG. 2  shows a longitudinal cross-section of the motor, fan and cyclonic separation apparatus arrangement of  FIG. 1 ; 
         FIG. 3  shows a perspective view of the longitudinal cross-section of  FIG. 2 ; 
         FIG. 4  shows an exploded perspective view of the motor, fan and cyclonic separation apparatus arrangement of  FIG. 1 ; 
         FIG. 5  shows an exploded perspective view of internal components of the cyclonic separation apparatus of  FIG. 1 ; 
         FIG. 6  shows a partially exploded perspective view of the motor, fan and cyclonic separation apparatus arrangement of  FIG. 1 ; 
         FIG. 7  shows a perspective view of an end cap of the cyclonic separation apparatus arrangement of  FIG. 1 ; 
         FIG. 8  shows a perspective view of a vortex finder assembly of the cyclonic separation apparatus of  FIG. 1 ; 
         FIGS. 9A to 9H  show the longitudinal cross-section of  FIG. 2  including the air flow pathways through the motor, fan, cyclonic separation apparatus and a motor cooling passage, in use; 
         FIG. 10  shows a perspective view of a second embodiment of a hand-held vacuum cleaner with a motor, fan and cyclonic separation apparatus arrangement; 
         FIG. 11  shows the perspective view of  FIG. 10  with a portion of the body removed; 
         FIG. 12  shows a longitudinal cross-section of the cyclonic separation apparatus of  FIG. 10 ; 
         FIG. 13  shows a perspective view of the cross-section of  FIG. 12 ; 
         FIG. 14  shows a longitudinal cross-section of the motor, fan and cyclonic separation apparatus arrangement of  FIG. 10 ; 
         FIG. 15  shows an exploded perspective view of the motor, fan and cyclonic separation apparatus arrangement of  FIG. 10 ; 
         FIG. 16  shows an exploded perspective view of internal components of the cyclonic separation apparatus of  FIG. 10 ; 
         FIG. 17A to 17F  shows the longitudinal cross-section of  FIG. 12  including the air flow through the cyclonic separation apparatus arrangement, in use; 
         FIGS. 18 to 22  show diagrammatical representations of various constructions of the cyclonic separation apparatus of  FIG. 10 ; 
         FIG. 23  shows a perspective view of a third embodiment of a hand-held vacuum cleaner with a motor, fan and cyclonic separation apparatus arrangement; 
         FIG. 24  shows a perspective view of the vacuum cleaner of  FIG. 23  without a dirt container wall; 
         FIG. 25  shows a perspective view of a vortex finder; 
         FIG. 26  shows a perspective view of the vacuum cleaner of  FIG. 23  with a transparent dirt container wall; 
         FIG. 27  shows a diagrammatical cross-section XXVI-XXVI of the vacuum cleaner of  FIG. 23  including air flow pathways; 
         FIG. 28  shows a diagrammatical cross-section XXVII-XXVII of the vacuum cleaner of  FIG. 23  including air flow pathways; 
         FIG. 29  shows side elevation view of a battery-powered vacuum cleaner with an extendible dirty air duct and the motor, fan and cyclonic separation apparatus arrangement of  FIGS. 2 to 9 ; 
         FIG. 30  shows a perspective view of the vacuum cleaner of  FIG. 29 ; 
         FIG. 31  shows a cross-sectional view, of a portion of the vacuum cleaner of  FIG. 29  showing a battery pack; 
         FIG. 32  shows a perspective view of the vacuum cleaner of  FIG. 29  with the dirty air duct extended; 
         FIG. 33  shows a side elevation view of a battery-powered vacuum cleaner with a flexible hose and the motor, fan and cyclonic separation apparatus arrangement of  FIGS. 2 to 9 ; 
         FIG. 34  shows a perspective view of the vacuum cleaner of  FIG. 33 ; 
         FIG. 35  shows a perspective view of a battery-powered vacuum cleaner with a telescopic body and a cleaner head with the motor, fan and cyclonic separation apparatus arrangement of  FIGS. 2 to 9 ; 
         FIG. 36  shows a close-up perspective view of the vacuum cleaner of  FIG. 35 ; 
         FIG. 37  shows a side elevation view of the vacuum cleaner of  FIG. 35  with the telescopic body retracted; 
         FIG. 38  shows a perspective view of a removable battery pack and the cyclonic separation apparatus of  FIGS. 2 to 9 ; 
         FIG. 39  shows a transverse cross-section XXXVIII-XXXVIII of the battery pack of  FIG. 38  with cylindrical rechargeable cells; 
         FIG. 40  shows a transverse cross-section XXXVIII-XXXVIII of the battery pack of  FIG. 38  with flat plate rechargeable cells; 
         FIG. 41  shows a transverse cross-section of an annular battery pack with cylindrical rechargeable cells; 
         FIGS. 42 and 43  show a transverse cross-section of an annular battery pack with flat plate rechargeable cells; and 
         FIG. 44  shows a table of test data relating to the temperature of the motor of  FIG. 2  in different operational conditions. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , there is shown first embodiment of a hand-held vacuum cleaner  2  comprising a main body  4 , a handle  6  connected to the main body, a cyclonic separation apparatus  8  mounted transverse across the main body, and a dirty air duct  10  with a dirty air inlet  12  at one end. The vacuum cleaner comprises a motor coupled to a fan for generating air flow through the vacuum cleaner and rechargeable cells (not shown) to energise the motor when electrically coupled by an on/off switch  14 . 
     Referring to  FIGS. 2 to 8 , there is shown an arrangement comprising the motor  16 , the fan  18  and the cyclonic separation apparatus  8 . The motor has a drive shaft  20  with a central axis  21 . The fan is a centrifugal fan  18  with an axial input  22  facing the motor and a tangential output  24 . The fan has a diameter of 68 mm. The fan is mounted upon the drive shaft at the top of the motor. In use, the motor drives the fan to generate air flow through the cyclonic separation apparatus, as will be described in more detail below. A small portion of the drive shaft  20  protrudes from the bottom of the motor  16 . A second fan, comprising a paddle wheel  26 , is mounted upon the drive shaft  20  at the bottom of the motor. The motor and the paddle wheel are clad in a cylindrical outer body of the motor, which is often referred to as a “motor can”. In use, the motor turns the paddle wheel to circulate and augment air flow inside the motor can and about the bottom of the motor. 
     The motor  16  and the fan  18  are housed in a motor fan housing  27  comprising a generally cylindrical body portion  28  enclosing the motor and a generally circular head portion  29  enclosing the fan. The head portion  29  has a larger diameter than the body portion  28 . The motor fan housing  27  comprises a perforated end cap  30  mounted upon the head portion on the opposite side to the body portion. The end cap  30  protects the fan. The end cap has a circular array of perforations  36  near where air flow is expelled from the fan. The head portion acts as a baffle to direct air flow from the fan and out the perforations. The body portion has an array of bottom slots  32  around the bottom of the motor and an array of top slots  34  about where the drive shaft  20  protrudes from the top of the motor. 
     The cyclonic separation apparatus  8  comprises a pre-fan filter  40 , a vortex finder assembly  50 , a generally cylindrical inner wall  60 , a cyclone seal  70 , a cyclone assembly  80 , a cylindrical perforated intermediate wall  90 , a circular bulkhead  100 , a tapered funnel  110 , a transparent generally cylindrical dirt container  120 , and a circular bowl door  130  all arranged about the central axis  21  of the motor drive shaft  20 . 
     The pre-fan filter  40  is an annular shape surrounding the top air flow slots  34  of the body portion  28  of the motor fan housing  27 . The pre-fan filter is enclosed in an annular shell  42  except where the pre-fan filter communicates with the vortex finder assembly  50  and with the top air flow slots  34  of the body portion  28 . This permits air flow from the cyclonic separating apparatus, through the pre-fan filter and on to the fan. 
     The vortex finder assembly  50  comprises planar ring  52  moulded with twelve hollow cylindrical vortex finders  54  protruding from one side of the planar ring. Holes  56  through the vortex finders penetrate the opposite side of the planar ring whereupon the pre-fan filter  40  is seated. The pre-fan filter  40  helps to muffle high frequency sounds caused by Helmholtz resonance as air flows through the vortex finder holes  56 . The vortex finders are arranged in a circular array about the central axis  21  of the motor drive shaft  20 . Each vortex finder has its own longitudinal central axis  57  arranged parallel to the central axis  21 . The vortex finders may have longitudinal internal ribs (not shown) along the vortex finder holes to further reduce high frequency noise caused by Helmholtz resonance. The longitudinal ribs also tend to straighten air flow in the vortex finder to help reduce energy losses as the air flows into the pre-fan filter  40 . 
     The inner wall  60  is a generally cylindrical shape in two portions of different diameter. The inner wall comprises an annular flange  62  at an open end of the inner wall, a hollow cylindrical cup  64  at an opposite closed end of the inner wall, a hollow cylindrical wall  66  and an annular shoulder  68 . The flange extends radially outwardly from the open end of the cylindrical wall. The cylindrical wall is located between the flange and the cylindrical cup. The cylindrical wall has a larger diameter than the cylindrical cup. The annular shoulder joins the cylindrical wall to the cylindrical cup. The shoulder is perforated with a circular array of twelve holes  69  spaced at equi-angular intervals about the central axis  21 . The annular flange  62  is connected to an annular roof wall  121  of the dirt container  120 . 
     The vortex finder assembly  50  is seated in the cylindrical wall  66  with the planar ring  52  facing the shoulder  68  and the vortex finders  54  protruding through the shoulder&#39;s holes  68 . The pre-fan filer  40  is nested within the cylindrical wall  66 . The bottom of the motor fan housing&#39;s body portion  28  is nested within the cylindrical cup  64 . 
     The cyclone seal  70  is perforated with a circular array of twelve holes  72  spaced at equi-angular intervals about the central axis  21 . The shoulder  68  of the inner wall  60  is seated upon the cyclone seal. The vortex finders  54  protrude through the seal holes  72 . 
     The cyclone assembly  80  comprises a cylindrical collar  82  and a circular array of twelve cyclones  84  surrounded by the collar. The cyclones are spaced at equi-angular intervals about the central axis  21 . Each cyclone has a hollow cylindrical top part  85  and a hollow frustro-conical bottom part  86  depending from the cylindrical top part and terminating with a discharge nozzle  87  at the bottom of the cyclone. 
     The shoulder  68  of the inner wall  60  is arranged upon the cyclone assembly  80  with the cyclone seal  70  interposed therebetween. The collar  82  has the same outer diameter as, and abuts with, the cylindrical wall  66  of the inner wall  60 . The vortex finders  54  protrude through the holes  72  in the cyclone seal and into the cylindrical top part  85  of a respective cyclone  84 . The only passage through the top of the cyclone  84  is via its vortex finder  54  which acts as an air flow outlet port to the pre-fan filter  40 . Each vortex finder is concentric with its respective cyclone. The plane of each nozzle  87  is inclined with respect to the central axis  57 . This helps to prevent dust and dirt particles from re-entry after discharge from the nozzle. 
     The cylindrical top part  85  of each cyclone  84  has an air inlet port  88  arranged tangentially through the side of the cyclone and proximal the vortex finder  54 . The twelve air inlet ports are in communication with a distribution chamber  170  below the collar  82  around the cyclones  84 , as is described in more detail below. 
     The intermediate wall  90  is arranged upon the cyclone assembly  80 . The intermediate wall  90  has the same outer diameter as, and abuts with, the cylindrical collar  82 . 
     The bulkhead  100  is arranged upon, and has approximately the same outer diameter as, the intermediate wall  90 . The bulkhead  100  is perforated by a circular array of twelve holes  102  spaced at equi-angular intervals about the central axis  21 . The discharge nozzles  87  of the cyclones  84  protrude through respective bulkhead holes  102 . The bulkhead  100  has a circumferential lip  104  inclined radially outwardly from the central axis  21  towards the bowl door  130 . The lip  104  protrudes a small way from the intermediate wall  90 . 
     The tapered funnel  110  comprises a hollow circumferential skirt  112 , a frustro-conical cone  114  depending from the skirt, and a hollow cylindrical nose  116  depending from the cone. The skirt is arranged upon, and has approximately the same outer diameter as, the bulkhead. The cone tapers radially inwardly from the bulkhead  100  towards the bowl door  130 . A perforated portion  118  of the skirt protrudes axially rearward from the cone towards the bowl door  130 . 
     The generally cylindrical dirt container  120  comprises the annular roof wall  121  and a hollow cylindrical exterior wall  122  with a frustro-conical dirt collection bowl  124  depending from the exterior wall. The dirt container has a dirty air inlet port  126  arranged tangentially through the exterior wall  122 . The dirt container  120  has a circumferential lip  128  inclined radially inwardly towards the central axis  21  and towards the bowl door  130 . The lip  128  protrudes a small way in from the transition between the exterior wall and the dirt collection bowl. The motor fan housing&#39;s head portion  29  is nested within the centre of the annular roof wall  121 . The annular roof wall is detachably connected to an outer circumferential edge  138  of the exterior wall  122 . The annular roof wall  121  may be connected to the exterior wall  122  and the inner wall  60  by snap-fit, bayonet fit, interlocking detents, interference fit or by a hinge. A resilient seal or seals made of polyethylene, rubber or a similar elastomeric material is provided around the annular roof wall to ensure airtight connection with the exterior wall. 
     The bowl door  130  is detachably connected to an outer circumferential edge  132  of the dirt collection bowl  124 . The bowl door abuts the cylindrical nose  116  thereby dividing the dirt collection bowl into two separate chambers: a generally circular chamber  134  inside the tapered funnel  110  and a generally annular chamber  162  outside the tapered funnel. The bowl door  130  may be connected to the dirt collection bowl  124  by snap-fit, bayonet fit, interlocking detents, interference fit or by a hinge. A resilient seal made of polyethylene, rubber or a similar elastomeric material is provided around bowl door  130  to ensure airtight connection with the dirt collection bowl. 
     The annular flange  62  of the inner wall  60  is in complementary mating relationship with a circular ring  123  protruding from inside the annular roof wall  121 . The nose  116  is in complementary mating relationship with a circular ring  140  protruding from inside the bowl door  130 . This ensures that components of the cyclonic separation apparatus  8  remain concentric with the central axis  21  when the bowl door is closed. 
     Between the annular roof wall  121  and the bowl door  130 , the various components of the cyclonic separation apparatus  8  (i.e. pre-fan filter  40 , vortex finder assembly  50 , inner wall  60 , cyclone seal  70 , cyclone assembly  80 , intermediate wall  90 , bulkhead  100 , tapered funnel  110 ) are arranged upon each other by detachable connection, typically a snap-fit, bayonet fit, interlocking detents, or interference fit. The permits disassembly and reassembly, without tools, of the cyclonic separation apparatus  8  in order to clean, or replace, its individual components. Resilient seals made of polyethylene, rubber or a similar elastomeric material, or other suitable seal material, are provided around connections of the annular flange  62  and pre-fan filter shell  42  with the annular roof wall  121 . The seals are to ensure airtight connection. The internal diameter of the dirt container  120  and the bowl door  130  is large enough to permit removal of the components of the cyclonic separation apparatus  8  (i.e. pre-fan filter  40 , vortex finder assembly  50 , inner wall  60 , cyclone seal  70 , cyclone assembly  80 , intermediate wall  90 , bulkhead  100 , tapered funnel  110 ) through either end of the dirt container. 
     In use, dirty air flows, under the influence of the fan  18 , in the dirty air inlet  12 , up the dirty air duct  10  and into the cyclonic separation apparatus  8  where dust and dirt entrained in the air flow is separated therefrom. The dust and dirt is collected within the cyclonic separation apparatus. The air flows out the cyclonic separation apparatus  8 , through the pre-fan filter  40 , into the motor fan housing  27  via the top slots  34 , though the fan  18  and out the perforations  36  in the end cap  30 . 
     Referring to  FIG. 9A , the cyclonic separation apparatus  8  is divided into a first cyclonic separating unit  160 , a second cyclonic separating unit  150  and a distribution chamber  170 . The first cyclonic separating unit is located in the air flow pathway upstream of the distribution chamber. The distribution chamber is located in the air flow pathway upstream of the second cyclonic separating unit. 
     The first cyclonic separating unit  160  comprises the cylindrical dirt container  120 . The second cyclonic separating unit  150  comprises the circular array of twelve cyclones  84 . The dirt container is concentric with the central axis  21  of the motor drive shaft  20 . The distribution chamber  170  is bounded by the hollow cylindrical cup  64  of the inner wall, cyclone assembly  80 , intermediate wall  90  and bulkhead  100 . The second cyclone unit  150  received air flow from the first cyclone unit  160  via the distribution chamber  170 . 
     The exterior wall  122  of the dirt container  120  has a diameter of approximately 130 mm. The cyclones  84  have a much smaller diameter than the dirt container. Helical air flow in the cyclones experiences greater centrifugal forces than in the annular chamber. Thus, the cyclones of the second cyclonic separating unit  150 , when combined, have higher separation efficiency than the dirt container of the first cyclonic separating unit  160 . 
     The air flow pathway though the cyclonic separation apparatus  8  is described in more detail with reference to  FIGS. 9B to 9E . 
     Referring to  FIG. 9B , dirty air (triple-headed arrows) flows into the first cyclonic separating unit  160  via the dirty air inlet port  126 . The tangential arrangement of the dirty air inlet port  126  causes the dirty air to flow in a helical path around the cylindrical dirt container  120 . This creates an outer vortex in the dirt container. Centrifugal forces move the comparatively large dust and dirt particles outwards to strike the side of the dirt container and separate them from the air flow. The dust separated and dirt (D) swirls towards the dirt collection bowl  124  where it is deposited. 
     Referring to  FIG. 9C , partially-cleaned air (double-headed arrows) flows back on itself to follow an inner helical path closely about the tapered funnel  110  and towards the cylindrical intermediate wall  90 . The partially-cleaned air flows through the perforated portion  118  of the tapered funnel&#39;s skirt  112  largely unimpeded. The circumferential lip  104  of the bulkhead  100  and the lip  128  of the dirt container  120  converge at a width restriction X in the first cyclonic separating unit  160 . The width restriction reduces a radial width between the dirt container and the intermediate wall by at least 15 percent The width restriction tapers towards the bowl door  130  so that air, and entrained dirt, can flow more easily towards the bowl door than in the opposite direction. Thus, the circumferential lips  104 ,  128  and perforated portion  118  of the tapered funnel&#39;s skirt  112  catch separated dirt in the bowl  124  before it can be re-entrained in the partially-cleaned air flow. The partially-cleaned air flows through perforations in the intermediate wall, which filters any remaining large dirt particles, and into the distribution chamber  170 . 
     As can be seen in  FIG. 5 , the air inlet ports  88  of the twelve cyclones are moulded into the collar  82  of the cyclone assembly  80 . The distribution chamber  170  is in communication with the air inlet ports  88  of the twelve cyclones  84 . Referring to  FIG. 9D , the partially-cleaned air flow (double-headed arrows) divides itself, in the distribution chamber, evenly between the twelve air inlet ports  88  from where it flows into the twelve cyclones  84  of the second cyclonic separating unit  150 . The air inlet ports  88  direct the partially-cleaned air flow in a helical path around the vortex finders  54 . This creates an outer vortex inside each cyclone  84 . Centrifugal forces move the dust and dirt outwards to strike the side of the cyclone and separate it from the air flow. The separated dust and dirt swirls towards the discharge nozzle  87 . The internal diameter of the frustro-conical part  86  of cyclone diminishes as the air flow approaches the nozzle. This accelerates the outer helical air flow thereby increasing centrifugal forces and separating ever smaller dust and dirt particles. The dust and dirt particles exit the nozzle to be deposited inside the part of the bowl  124  bounded by the tapered funnel  110 . 
     Referring to  FIG. 9E , cleaned air (single-headed arrows) flows back on itself to follow a narrow inner helical path through the middle of the cyclone  84 . The cleaned air flows out the internal hole  56  of the vortex finder  54 , under the influence of the fan, into the pre-fan filter  40 . The pre-fan filter  40  is to remove any fine dust and dirt particles remaining in the air flow after the cyclonic separation apparatus  8 . 
     The pre-fan filter is in communication with the motor fan housing  27 . Cleaned air flows, via the top slots  34  in the motor fan housing, to the axial input  22  of the fan  18 , out the tangential output  24  of the fan and through the perforations  36  of the end cap  30  where it is exhausted from the vacuum cleaner  2 . Dust and dirt separated by the first and second cyclonic separating units and deposited in the dirt collection bowl  124  which can be emptied by opening the bowl door  130 . 
     Returning to  FIG. 7 , there are shown three of a total of four motor cooling inlet ports  31  in the annular roof wall  121  of the dirt container  120 . One other motor cooling inlet port is obscured by the end cap  30  in  FIG. 7 . 
     Returning to  FIGS. 8 , there are shown four vortex finder seals  58 . Each vortex finder seal forms a webbed collar around three consecutive vortex finders  54 . Four equiangular spaced small gaps  59  exist between the four vortex finder seals. The vortex finder seals  58  seal the connection between the vortex finder assembly  50  and the inner wall  60  except where the gaps  59  are located. 
     Referring to  FIG. 9F , there is shown the pathway of clean motor cooling air (single-headed arrow) flow through the motor  16  and fan  18 . The four motor cooling inlet ports are in communication with a first motor cooling passage  61   a  between the shell  42  of the pre-fan filter  40  and the cylindrical wall  66  of the inner wall  60 . 
     Referring to  FIG. 9G , there is shown a longitudinal cross-section of a vortex finder  54  in the region of Detail X of  FIG. 9F . Here, the vortex finder seal  58  blocks communication between the first motor cooling passage  61   a  and a second motor cooling passage  61   b  between the motor fan housing  27  and the cylindrical cup  64  of the inner wall  60 . 
     Referring to  FIG. 9H , there is shown a longitudinal cross-section between two vortex finders  54  and two vortex finder seals  58  in the region of Detail X of  FIG. 9F . Here, the gap  59  between the vortex finder seals  58  permits communication between the first and second motor cooling passages  61   a ,  61   b.    
     Returning to  FIG. 9F , in use, clean motor cooling air flows under the influence of the fan though the four motor cooling inlet ports  31  and along the first motor cooling passage  61   a , through the gaps  59  and along the second motor cooling passage  61   b  from where it enters the motor fan housing  27  via the bottom air flow slots  32 . The motor comprises motor vents  17   a  in the bottom, and motor vents  17   b  in the top, of the motor can to ventilate the interior of the motor. The paddle wheel  26  circulates and augments motor cooling air about the bottom of the motor. Motor cooling air is drawn, under the influence of the fan, into the bottom motor vents  17   a , through the interior of the motor, and passes out of the top motor vents  17   b . The motor is cooled by the motor cooling air flow. The motor cooling air flow pathway joins the cleaned air flow pathway from the cyclonic separation apparatus  8  around the axial input  22  of the fan  18 . The motor cooling air flow is expelled from the tangential output  24  of the fan and out the perforations  36  of the end cap  30 . 
     The motor cooling inlet ports  31  are spaced at equiangular intervals about the central axis  21 . The motor cooling inlet ports are axially aligned with the gaps  59  between the vortex spaces seals  58  and with the bottom air flow slots  32  in the motor fan housing  27 . This axial alignment is to help minimise any resistance encountered by the motor cooling air flow along the motor cooling passages  61   a ,  61   b . The bottom motor vents  17   a  are also aligned with the bottom air flow slots  32  in the motor fan housing  27  to help minimise any resistance encountered by the motor cooling air flow. 
     The clean motor cooling air flow pathway is separate from the air flow pathway through the cyclonic separation apparatus  8  up to the axial input of the fan  18 . This has particular benefits in vacuum cleaning. Typically, motor speed increases as the fan encounters resistance to volumetric air flow and the pressure across the fan increases accordingly. An example of how this may occur is when the vacuum cleaner is operational and the dirty air inlet contacts carpet, hard floor, curtains or other surface to restrict air flow. Should the air flow path through the cyclonic separation apparatus  8  become blocked, or impeded, for whatever reason, the motor cooling air flow path would not necessarily be blocked, or impeded. Instead, the increased pressure across the fan  18  would increase suction through the motor cooling air flow pathway. This has the benefit of increased motor cooling when the motor is working hardest and cooling is needed most. 
     Referring to  FIG. 44 , there is shown a table of test data relating to the temperature of the motor  16 . Two thermocouples were attached to the motor can while the motor was driving the fan  18  to generate air flow. The cyclonic separation apparatus  8  was subjected to three separate tests involving different operational conditions: (a) free air flow (dirty air inlet  12  fully open); (b) maximum power output (air watts) of cyclonic separation apparatus; and (c) sealed suction (dirty air inlet  12  closed). As the skilled person will appreciate, air watt is a measurement of vacuum power calculated from volumetric flow rate (volume/time) multiplied by suction (force/area) multiplied by a correction factor depending on humidity and atmospheric pressure. The ambient temperature was measured and compared to the motor temperature after ten minutes run time. The same three tests were carried out with four motor cooling inlet ports  31  and then repeated with one of the four motor cooling inlet ports  31  closed. The test data clearly reveal the benefits of the motor cooling air flow pathway and the importance of having four motor cooling inlet ports  31 . 
     Referring to  FIGS. 10 and 11 , there is shown a second embodiment of a hand-held vacuum cleaner  202  comprising a main body  204  with a main axis  205 , a handle  206 , a cyclonic separation apparatus  208  mounted transverse to the main axis of the main body, and a dirty air duct  210  with a dirty air inlet  212  at one end. The vacuum cleaner comprises a motor  216  coupled to a fan for generating air flow through the vacuum cleaner and rechargeable cells  217  to energise the motor when electrically coupled by an on/off switch  214 . 
     Referring to  FIGS. 12 to 16 , there is shown an arrangement comprising the motor  216 , the rechargeable cells  217 , the fan  218 , a pre-fan filter  240 , a cyclonic separation apparatus outlet duct  260  and the cyclonic separation apparatus  208 . 
     The motor has a drive shaft  220  with a longitudinal central axis  221 . The fan is a centrifugal fan  218  with an axial input  222  facing away from the motor and a tangential output  224 . The fan has a diameter of 68 mm. The fan is mounted upon the drive shaft at the top of the motor. The cells  217  are arranged in a circular array about the motor  216  with the longitudinal axis of the cells parallel to the central axis  221 , as is shown most clearly in  FIGS. 11 and 14 . In use, the motor drives the fan to generate air flow through the cyclonic separation apparatus, as will be described in more detail below. 
     The main body  204  comprises a central housing  226 , a motor housing  228 , a frame  230  and an end cap  232 . The fan  218  is housed in the central housing  226 . The central housing is connected to the handle  206 . The motor  216  and the cells  217  are housed in the motor housing  228 . The motor housing is generally elongate to suit the profile of the cells. The end cap  230  is connected to an opposite end of the motor housing to the fan. The end cap has a circular array of perforations  236 . 
     The frame  230  connects the central housing  226  to the cyclonic separation apparatus  208 . One end of the frame supports a pre-fan filter  240  arranged in front of the axial input  222  of the fan  218 . The other end of the frame supports the cyclonic separation apparatus. 
     The outlet duct  260  is defined by a generally oval-shaped duct wall  262  arranged upon the frame  230  to form the outlet duct between the duct wall and frame. The outlet duct  260  provides an air flow path between the cyclonic separation apparatus  208  and the pre-fan filter  240 . The duct wall is detachable from the frame. The duct wall is transparent to permit visual inspection of the pre-fan filter. The duct wall is removed from the frame if the pre-fan filter needs cleaning or replacement. 
     The cyclonic separation apparatus  208  comprises, a vortex finder assembly  250 , a vortex finder seal  270 , a cyclone assembly  280 , a cylindrical perforated intermediate wall  290 , a circular bulkhead  300 , a tapered funnel  310 , a transparent generally cylindrical dirt container  320  with a longitudinal central axis  321 , and a circular dirt collection bowl  330  all arranged about the central axis  321  of the dirt container  320 . 
     The vortex finder assembly  250  comprises a planar generally circular base  252  with six hollow cylindrical vortex finders  254 . Each vortex finder has a central through-hole  256  and its own longitudinal central axis  257 . The vortex finders are arranged in a circular array about the central axis  321  of the dirt container  320 . Each vortex finder is parallel to the central axis  321 . The vortex finders protrude from one side of the base. A small portion of each vortex finder also protrudes from the opposite side of the base. The vortex finders may have longitudinal internal ribs (not shown) along the through-holes to help dampen high frequency sounds caused by Helmholtz resonance as air flows through the vortex finder though-holes  256 . 
     The cyclone assembly  280  comprises a generally cylindrical collar  282  and a circular array of six cyclones  284  surrounded by the collar. The cyclones are spaced at equi-angular intervals about the central axis  321  of the dirt container  320 . Each cyclone has a hollow cylindrical top part  285  and a hollow frustro-conical bottom part  286  depending from the cylindrical top part and terminating with a discharge nozzle  287  at the bottom of the cyclone. 
     The vortex finder assembly  250  is arranged upon the collar  282  of the cyclone assembly  280 . The vortex finders  254  protrude into the cylindrical top part  285  of a respective cyclone  284 . The only passage through of the top of the cyclone  284  is via its vortex finder  254  which acts as an air flow port to the outlet duct  260 . Each vortex finder is concentric with its respective cyclone. The plane of each nozzle  287  is inclined with respect to the central axis  257 . This helps to prevent dust and dirt particles from re-entry after discharge from the nozzle. 
     The cylindrical top part  285  of each cyclone  284  has an air inlet port  288  arranged tangentially through a side of the cyclone and proximal the vortex finder  254 . The six air inlet ports are in communication with a distribution chamber  370  located below the collar  282  around the cyclones  284  as described in more detail below. 
     The intermediate wall  290  is arranged upon the cyclone assembly  280 . The intermediate wall  290  has approximately the same outer diameter as, and abuts with, the cylindrical collar  282 . 
     The bulkhead  300  is arranged upon, and has approximately the same outer diameter as, the intermediate wall  290 . The bulkhead  300  is perforated by a circular array of six holes  302  spaced at equi-angular intervals about the central axis  321 . The discharge nozzles  287  of the cyclones  284  protrude through respective bulkhead holes  302 . The bulkhead  300  has a circumferential lip  304  inclined radially outwardly from the central axis  321  towards the collection bowl  330 . The lip  304  protrudes a small way from the intermediate wall  290 . 
     The tapered funnel  310  comprises a hollow circumferential skirt  312 , a frustro-conical cone  314  depending from the skirt, and a hollow cylindrical nose  316  depending from the cone. The skirt is arranged upon, and has approximately the same outer diameter as, the bulkhead  300 . The cone tapers radially inwardly from the bulkhead towards the collection bowl  330 . A perforated portion  318  of the skirt protrudes axially rearward from the cone towards the collection bowl  330 . 
     The generally cylindrical dirt container  320  comprises a hollow cylindrical exterior wall  322  with a circular shoulder  324  extending radially inwardly from the top of the exterior wall. The dirty container has a dirty air inlet port  326  arranged tangentially through the exterior wall  322 . The dirty air inlet port communicates with the dirty air duct  210 . The exterior wall  322  is rotatingly connected to the frame  230  to enable the cyclonic separation apparatus  208  to rotate about its central axis  321  in relation to the main body  204 . The dirty air duct  210  is rotatable with the cyclonic separation apparatus  208 , as is shown in  FIG. 11  where the dirty air duct is in a folded position. 
     The planar base  252  of the vortex finder assembly  250  nests within the aperture in the circular shoulder  324  of the dirt container  320 . The collar  282  of the cyclone assembly  280  abuts the circular shoulder  324 . The cyclones  284  are located within the dirt container  320 . 
     The dirt collection bowl  330  is detachably connected to an outer circumferential edge  332  of the dirt container  320 . The dirt collection bowl abuts the nose  316  thereby dividing the dirt container and dirt collection bowl into two separate chambers: a circular chamber  334  inside the tapered funnel  310  and a generally annular chamber  362  outside the tapered funnel. The dirt collection bowl  330  may be connected to the dirt container&#39;s outer circumferential edge by snap-fit, bayonet fit, interlocking detents, interference fit or by a hinge. A resilient seal  336  made of polyethylene, rubber or a similar elastomeric material is provided around the dirt collection bowl  330  to ensure airtight connection with the dirt container. 
     The dirt container  320  has an annular lip  328  inclined radially inwardly to the central axis  321  towards the collection bowl  330 . The lip  328  protrudes a small way in from the exterior wall. The lip  328  is proximal to the bowl  330 . 
     The nose  316  of the tapered funnel  310  is in complementary mating relationship with a circular ring  340  protruding from inside the dirt collection bowl  330 . This ensures that components of the cyclonic separation apparatus  208  remain concentric with the central axis  321  of the dirt container  320 . 
     In use, dirty air flows, under the influence of the fan  218 , in the dirty air inlet  212 , up the dirty air duct  210  and into the cyclonic separation apparatus  208  where dust and dirt entrained in the air flow is separated therefrom. The dust and dirt is collected within the cyclonic separation apparatus. The air flows out the cyclonic separation apparatus  208 , via the through-holes  256  of the vortex finders, along the outlet duct  260 , through the pre-fan filter  240 , through the fan  218  and over the motor  216  and batteries cells  217  via the motor housing  228  and out the perforations  236  in the end cap  230 . 
     Referring to  FIG. 17A , the cyclonic separation apparatus  208  is divided into a first cyclonic separating unit  360 , a second cyclonic separating unit  350  and the distribution chamber  370 . The first cyclonic separating unit is located in the air flow pathway upstream of the distribution chamber. The distribution chamber is located in the air flow pathway upstream of the second cyclonic separating unit. 
     The first cyclonic separating unit  360  comprises the cylindrical dirt container  310 . The second cyclonic separating unit  350  comprises the circular array of six cyclones  284 . The dirt container is concentric with the central axis  321  of the dirt container. The distribution chamber  370  is bounded by the collar  282 , cyclone assembly  280 , intermediate wall  290  and bulkhead  300 . The second cyclonic separating unit  350  receives air flow from the first cyclonic separating unit  360  via the distribution chamber  370 . 
     The exterior wall  322  of the dirt container  320  has a diameter of approximately 120 mm. The cyclones  284  have a smaller diameter than the annular chamber  362 . Helical air flow in the cyclones experiences greater centrifugal forces than in the dirt container. Thus, the cyclones of the second cyclonic separating unit  350 , when combined, have higher separation efficiency than the dirt container of the first cyclonic separating unit  360 . 
     The air flow pathway though the cyclonic separation apparatus  208  is described in more detail with reference to  FIGS. 17B to 17F . 
     Referring to  FIG. 17B , dirty air (triple-headed arrows) flows from the dirty air duct  210  and into the dirt container  320  via the dirty air inlet port  326 . The tangential arrangement of the dirty air inlet port  326  causes the dirty air to flow in a helical path around the dirt container. This creates an outer vortex in the dirt container. Centrifugal forces move the comparatively large dust and dirt (D) particles outwards to strike the side of the dust container  320  and separate them from the air flow. The separated dust and dirt swirls towards the dirt collection bowl  330  where it is deposited. 
     Referring to  FIG. 17C , partially-cleaned air (double-headed arrows) flows back on itself to follow an inner helical path closely about the tapered funnel  310  and towards the cylindrical intermediate wall  290 . The partially-cleaned air flows through the perforated portion  318  of the tapered funnel&#39;s skirt  312  largely unimpeded. The circumferential lip  304  of the bulkhead  300  and the lip  328  of the dirt container  320  converge at a width restriction Y in the first cyclonic separating unit  360 . The width restriction reduces a radial width between the dirt container and the intermediate wall by at least 15 percent. The width restriction tapers towards the bowl  330  so that air, and entrained dirt, can flow more easily towards the bowl door than in the opposite direction. Thus, the circumferential lips  304 ,  328  and perforated portion  318  of the tapered funnel&#39;s skirt  312  catch separated dirt in the bowl  324  before it can be re-entrained in the partially-cleaned air flow. The partially-cleaned air flows through perforations in the intermediate wall, which filters any remaining large dirt particles, and into the distribution chamber  370 . 
     As can be seen in  FIG. 16 , the air inlet ports  288  of the six cyclones are moulded into the collar  282  of the cyclone assembly  280 . The distribution chamber  370  is in communication with the air inlet ports  288  of the six cyclones  284 . Referring to  FIG. 17D , the partially-cleaned air flow (double-headed arrows) divides itself, in the distribution chamber, evenly between the six air inlet ports  288  from where it flows into the six cyclones  284  of the second cyclonic separating unit  350 . The air inlet ports  288  direct the partially-cleaned air flow in a helical path around the vortex finders  254 . This creates an outer vortex inside each cyclone  284 . Centrifugal forces move the dust and dirt outwards to strike the side of the cyclone and separate it from the air flow. The separated dust and dirt swirls towards the discharge nozzle  287 . The internal diameter of the frustro-conical body  286  of cyclone diminishes as the air flow approaches the nozzle. This accelerates the helical air flow thereby increasing centrifugal forces and separating ever smaller dust and dirt particles. The dust and dirt particles exit the nozzle to be deposited inside the part of the bowl  330  bounded by the tapered funnel  310 . 
     Referring to  FIG. 17E , cleaned air (single-headed arrows) flows back on itself to follow a narrow inner helical path through the middle of the cyclone  284 . The cleaned air flows out the internal through-hole  256  of the vortex finder  254 , under the influence of the fan. 
     Returning to  FIG. 17F , the cleaned air flows from the vortex finders  254  into the outlet duct  260  and to the pre-fan filter  240 . The pre-fan filter  240  is to remove any fine dust and dirt particles remaining in the air flow after the cyclonic separation apparatus  208  and before the fan  218 . The clean air flows into the axial input  222  of the fan  218  and is expelled from the tangential output  224  of the fan. Pathways in the central housing  226  direct the clean air flow from the fan over the motor  216  and cells  217 , to cool the motor and cells, before the air flows out the perforations  236  in the end cap  232 . 
     Dust and dirt separated by the first and second cyclonic separating units and deposited in the dirt collection bowl  330  which can be opened for emptying. 
     Referring to  FIG. 18 , there is shown a diagrammatical view of the various components of the cyclonic separation apparatus  208  (vortex finder assembly  250 , vortex finder seal  270 , cyclone assembly  280 , intermediate wall  290 , bulkhead  300 , tapered funnel  310 ) located within confines of the outlet duct  260 , frame  230 , dirt container  320  and dirt collection bowl  330 . 
     The vortex finder seal  270  seals the connections between the vortex finder assembly  250  and the dirt container  320  in an airtight manner. An outlet duct seal  266  seals the connection between the frame  230  and the outlet duct wall  262  in an airtight manner. The vortex finder seal  270  and the outlet duct seal  266  are made of polyethylene, rubber or a similar elastomeric material. 
     Certain components of the cyclonic separation apparatus  208  are detachably connected, typically by a snap-fit, bayonet fit, interference fit or by interlocking detents. This permits disassembly and reassembly, without tools, of the cyclonic separation apparatus in order to clean, or replace, its individual components, as is described with reference to  FIGS. 19 to 22 . 
     Referring to  FIG. 19 , there is shown a method of disassembling a first construction of the cyclonic separation apparatus  208  whereby the outlet duct wall  262  is detachable from the frame  230 . The dirt container  320  is detachable from the frame. The vortex finder assembly is detachable from the frame with, or without, the dirt container. The cyclone assembly  280 , intermediate wall  290 , bulkhead  300 , and tapered funnel  310  are also detachable, in unison, from the vortex finder assembly. The dirt collection bowl  330  has a large enough diameter to enable, when the dirt collection bowl is opened, removal of the cyclone assembly  280 , intermediate wall  290 , bulkhead  300 , and tapered funnel  310  out the dirt container  320 . 
     Referring to  FIG. 20 , there is shown a method of disassembling an alternative construction of the cyclonic separation apparatus  208  whereby the outlet duct wall  262  is detachable from the frame  230 . The dirt container  320  is detachable from the frame. The vortex finder assembly  250 , cyclone assembly  280 , intermediate wall  290 , bulkhead  300 , and tapered funnel  310  are detachable, in unison, from the frame with, or without, the dirt container. The dirt collection bowl  330  is can be opened for emptying. 
     Referring to  FIG. 21 , there is shown a method of disassembling a second alternative construction of the cyclonic separation apparatus  208  whereby the outlet duct wall  262  is detachable from the frame  230 . The dirt container  320 , vortex finder assembly  250 , cyclone assembly  280 , intermediate wall  290 , bulkhead  300 , and tapered funnel  310  are detachable, in unison, from the frame. The dirt collection bowl  330  can be opened for emptying. 
     Referring to  FIG. 22 , there is shown a method of disassembling a third alternative construction of the cyclonic separation apparatus  208  whereby the outlet duct  260  (i.e. duct wall  262  and frame  230 ) is detachable from the frame. The dirt container  320  remains with the frame. The vortex finder assembly  250 , cyclone assembly  280 , intermediate wall  290 , bulkhead  300 , and tapered funnel  310  are removable, in unison, from the frame when the dirt bowl  330  is opened. 
     Referring to  FIG. 23 , there is shown a third embodiment of hand-held vacuum cleaner  402  comprising a main body  404  with a handle  406 , a cyclonic separation apparatus  408  mounted to the main body, and a dirty air duct  410  with a dirty air inlet  412  at one end. The vacuum cleaner comprises a motor coupled to a fan for generating air flow through the vacuum cleaner and rechargeable cells to energise the motor when electrically coupled by an on/off switch  414 . 
     Referring to  FIGS. 24 to 27 , there is shown in more detail the motor  416 , the rechargeable cells  417 , the fan  418 , a pre-fan filter  440 , a cyclonic separation apparatus outlet duct  460  and the cyclonic separation apparatus  408 . 
     The motor has a drive shaft  420 . The fan  418  is mounted upon the drive shaft at the top of the motor. The fan has a diameter of approximately 68 mm. The cells  417  are arranged about the motor  416 . In use, the motor drives the fan to generate air flow through the cyclonic separation&#39; apparatus, as will be described in more detail below. 
     The main body  404  comprises a central housing  426  and a frame  430 . The motor  416 , fan  418  and cells  417  are housed in the central housing  426 . The central housing is connected to the handle  406 . The central housing has an array of perforations  436  near the bottom of the motor. The perforations  436  are for air flow expelled from the central housing. 
     The frame  430  connects the central housing  426  to the cyclonic separation apparatus  408 . One end of the frame supports a pre-fan filter  440  arranged in front of the fan&#39;s input. The other end of the frame supports the cyclonic separation apparatus. The cyclonic separation apparatus is rotatingly connected to the frame. 
     Outlet duct  460  comprises a duct wall  462  arranged upon the frame to form a passage between the duct wall and frame approximately 10 mm deep. The outlet duct  460  provides an air flow path between the cyclonic separation apparatus  408  and the pre-fan filter  440 . The duct wall is detachable from the frame. The duct wall is transparent to permit visual inspection of the pre-fan filter. A resilient seal made of polyethylene, rubber or similar elastomeric material is provided around the duct wall to ensure air tight connection with the frame. The duct wall is removed from the frame if the pre-fan filter needs cleaning or replacement. 
     The cyclonic separation apparatus  408  comprises a vortex finder assembly  450 , a cyclone assembly  480 , and an elongate generally oval-shaped dirt container  520  with a transparent door  530 . 
     The vortex finder assembly  450  has a hollow cylindrical vortex finder  452  with a tapered deflector fin  454 . The vortex finder has a central through-hole  456  with a longitudinal central axis  457 . The deflector fin protrudes radially from the outer surface of the vortex finder. In the present embodiment the tapered deflector fin is triangular although it could have another tapered profile. The triangular profile of the deflector fin  454  is a right angled triangle. 
     The cyclone assembly  480  comprises a cyclone  484  and a dirty air inlet port  488 . The cyclone has a hollow cylindrical body  485  with the dirty air inlet port and a hollow frustro-conical bottom body  486  extending from the cylindrical body and terminating with a discharge nozzle  487  at the narrower end. The air inlet port is arranged tangentially through a side of the cylindrical body. The vortex finder  454  is arranged inside the cyclone  484 . The vortex finder is concentric with the cyclone. The deflector fin  454  is arranged transverse to the path of air flow from the air inlet port. The radially extending short side of the deflector fin abuts the frame  430 . An apex  4541  of the deflector fin is proximal to the air inlet port. The hypotenuse side of the deflector fin tapers radially inwardly from the apex to the end of the vortex finder proximal to the discharge nozzle  487 . There is a small gap of Z approximately 5 mm between the apex and the cylindrical body  485  of the cyclone  484 . 
     The dirt container  520  is connected to the central housing  426  at one end and the discharge nozzle  487  of the cyclone  484  at the other end. The dirt container comprises a perimeter wall  522  following the outer perimeter of the elongate generally oval-shaped dirt container and base wall  524  with a cylindrical pocket  526  protruding from the base wall into the confines of the dirt container. The cyclone  484  is in communication with the dirt container where the nozzle  487  protrudes through the base wall  524 . The bottom of the motor  416  is seated inside the pocket  526  on the opposite side to the dirt container thereby reducing the overall width of the vacuum cleaner by about 20 to 25 mm. 
     The cyclone  484  has a curved fin  490  protruding axially from the discharge nozzle  487  into the dirt container  520 . The curved fin circumscribes an arc of about half the circumference of the nozzle facing the pocket  526 . The ends of the curved fin taper towards the nozzle. The dirt container has a flat fin  492  protruding from the base wall  524 . The flat fin extends tangentially from the top of the pocket  526  to about the middle of the dirt container. The flat fin is generally parallel to an adjacent initial flat portion  522   a  of the perimeter wall  522  uppermost on the dirt container in normal use. 
     The door  530  is detachably connected to the perimeter wall  522  of the container  520 . The door  530  may be connected to the dirt container by snap-fit, interlocking detents, a hinge  528  or by interference fit with the dirt container&#39;s exterior wall. In the example shown, the door is held firmly closed by a spring-loaded latch  529 . A resilient seal (not shown) made of polyethylene, rubber or a similar elastomeric material is provided around the door  530  to ensure connection to the dirt container  320  in an airtight manner. Dust and dirt separated by the cyclonic separation apparatus and deposited in the dirt container  520  can be emptied by opening the door  530 . The door is transparent to enable visual inspection of when the dirt container  520  is full and is in need of emptying. 
     In use, dirty air flows, under the influence of the fan  418 , in the dirty air inlet  412 , up the dirty air inlet duct  410  and into the cyclonic separation apparatus  408  where dust and dirt entrained in the air flow is separated therefrom. The dust and dirt is collected within the cyclonic separation apparatus. Air flows out the cyclonic separation apparatus  408 , via the through-hole  456  of the vortex finder, along the outlet duct  460 , through the pre-fan filter  440 , through the fan  418  and over the motor  416  and cells  417  via the central housing  426  and out the perforations  436  in the central housing. 
     Referring to  FIGS. 24 ,  27  and  28 , air flow though the cyclonic separation apparatus  408  is described in more detail. Dirty air (triple headed arrows) from the dirty air duct  410  enters the cylindrical body  485  of the cyclone  484  via the air inlet port  488 . The tangential arrangement of the air inlet port  488  and presence of the triangular deflector fin  454  protruding from the vortex finder  452  direct the dirty air to flow in a helical path around the cyclone and towards the frustro-conical body  486  and then the discharge nozzle. This creates an outer vortex in the cyclone. Centrifugal forces move the comparatively large dust and dirt particles outwards to strike the side of the cyclone and separate them from the air flow. The separated dust and dirt swirls towards the discharge nozzle  487  and into the dirt container  520 . 
     The partially-cleaned air flow (double-headed arrows) is directed by the curved fin  490  and a proximal curved portion  522   d  of the perimeter wall  522  to leave the cyclone  484  in an anti-clockwise upward direction, as viewed in  FIG. 24 . This helps maintains air flow speed. The flat fin  492  and the pocket  526  help to direct the partially cleaned air flow to follow an elongate circuit about the perimeter wall  522  of dirt container  520 , similar in shape to a two-pulley belt drive wherein the discharge nozzle  487  simulates a pulley at one end and the pocket  526  simulates a pulley at the opposite end. For example, the elongate circuit of air flow begins outbound away from the discharge nozzle in proximity to the initial flat portion  522   b  of the perimeter wall  522  and is redirected inside a distal curved portion  522   c  of the perimeter wall  522  to turn around the pocket  526  and continue inbound towards the discharge nozzle adjacent to a further flat portion  522   d  of the perimeter wall lower most on the dirt container in normal use. An axis of elongation of the elongate circuit runs approximately through the centres of the discharge nozzle and the pocket. The flat fin and the pocket prevent the bulk of the dust and dirt particles (D) from dropping out of the circulating air flow before being deposited upon the further flat portion  522   d  of the perimeter wall at the bottom of the dirt container. The perimeter wall  522  has a generally lozenge shape in cross-section parallel to the base wall  524 . The initial flat portion  522   a  and the further flat portion  522   c  of the perimeter wall taper inwardly and away from the distal curved portion  522   b  of the perimeter wall. This encourages deposit of dust and dirt around the pocket end of the dirt container where there is more space than at the opposite discharge nozzle end of the dirt container. Also, the curved fin  490  acts as an obstacle to laminar air flow inbound to the discharge nozzle. The air flow is forced to deviate around the curved fin. This disruption of laminar air flow provokes deposit of any remaining entrained dirt and dust (D) in the dirt container. As such, the shape of the perimeter wall  522 , the flat fin  492 , the pocket  526  and the curved fin  490  combine to help to separate any remaining dust and dirt from air flow path destined for the pre-fan filter  440 . This increases sustained performance of the vacuum cleaner  502 . 
     Having deviated past the curved fin  490 , clean air flow (single-headed arrows) turns back on itself and, under the influence of the fan, flows in a narrow inner helical path into the vortex finder&#39;s through-hole  456  from where it leaves the cyclonic separation apparatus  408  and enters the outlet duct  460 . 
     Referring to  FIGS. 29 to 38 , there is shown a variety of battery-powered vacuum cleaners with the motor  16 , fan  18  and cyclonic separation apparatus  8  arrangement of the first embodiment. The arrangement is, in all examples, arranged with the central axis  21  of the drive shaft  20  orientated transverse a main axis of the main body of the vacuum cleaner. In particular, there is shown a hand-holdable vacuum cleaner  602  with pivotable dirty air duct  610 ; a hand-holdable vacuum cleaner  702  connected to a cleaning nozzle  712  by a flexible hose  710  to resemble a small cylinder vacuum cleaner; and a vacuum cleaner  802  with an elongate body  806 , a support wheel  807  and a cleaner head  812  to resemble an upright vacuum cleaner, also commonly referred to as a “stick-vac”. 
     Referring to  FIGS. 29 to 32 , the hand-holdable vacuum cleaner  602  comprises a main body  604  with a main axis  605  and a handle  606 . The motor  16 , fan  18  and cyclonic separation apparatus  8  of the first embodiment are rotatingly connected to the main body  604  at the annular roof wall  121  of the dirt container  120 . The central axis  21  of the cyclonic separation apparatus is orientated at a right angle (i.e. transverse) to the main axis of the main body. The vacuum cleaner  602  comprises a battery pack  900  of rechargeable cells  917  to energise the motor  16  when electrically coupled by an on/off switch. The dirty air duct  610  is connected to the air inlet port  126 . 
     Referring in particular to  FIG. 31 , the battery pack  900  has a curvilinear cross-sectional profile with a curvilinear inner wall  902  shaped to fit around the cylindrical dirt container  120 . The battery pack  900  has a pair of electrical contacts  904  on a curvilinear outer wall  906  so that the cells may be recharged in situ. The battery pack is detachably connected to the dust container  120 . The battery pack may be detached from the duct container to enable replacement, or external recharging of the cells, if necessary. The cells have a generally cylindrical shape. Longitudinal axes of cells are arranged parallel to the central axis  21  of the motor  16 . 
     The dirty air duct  610  and the battery pack  900  are rotatable, with the cyclonic separation apparatus  8 , about the central axis  21  through an arc subtending 210 degrees from a folded position. This allows the vacuum cleaner  602  to be pointed in different directions, whilst a user is able to hold the vacuum cleaner in the same orientation. The vacuum cleaner may be used to access awkward spaces and can be held more comfortably by orientating the main axis  605  of the main body  604  to suit the user and adjusting the position of the dirty air inlet  612  to point at a surface to be cleaned, rather than orientating the main axis to best suit the surface to be cleaned and requiring the user to hold the vacuum cleaner in whichever orientation this demands. 
       FIGS. 29 and 30  show the vacuum cleaner  602  in the folded position where the dirty air duct is folded at zero degrees under the handle  606  for compact storage. The battery pack  900  is rotated to the diametrically opposite side of the dirt container  120 . The vacuum cleaner may be cradled by a battery charger  916  in the upright position shown in  FIG. 29 . This allows the vacuum cleaner to be stood in a small surface area and without excessive height because the dirty air duct is folded under the handle. Arranged like this, the vacuum cleaner is easier to grab. The vacuum cleaner&#39;s centre of gravity is lowered by the battery pack thus making the upright position more stable. Moreover, the cells  917  are electrically coupled by the electrical contacts  904  to the battery charger  916  for recharging in the upright position. 
       FIG. 32  shows the vacuum cleaner  602  in an extended position. The dirty air duct  610  is rotated through 180 degrees from the folded position and is ready for use. The dirty air duct  610  has been telescopically extended to double its length. The battery pack  900  occupies a gap  616  between the handle  606  and the dirt container  120 . The battery pack is relatively heavy and its location in the gap  616  moves the vacuum cleaner&#39;s centre of gravity closer to the handle. This improves the ergonomics of the vacuum cleaner. 
     Referring to  FIGS. 33 and 34 , the hand-holdable vacuum cleaner  702  comprises a body  704  with a handle  706 . The motor  16 , fan  18  and cyclonic separation apparatus  8  is connected to the body  704  at the annular roof wall  121  of the dirt container  120 . The vacuum cleaner  702  comprises a pack  910  of rechargeable cells. The cells are to energise the motor  16  when electrically coupled by an on/off switch. The air inlet port  126  is connected to one end of the flexible hose  710 . The cleaning nozzle  712  is connected to the other end of the flexible hose. 
     The battery pack  910  has a curvilinear inner wall  902  which is shaped to cradle the cylindrical dust container  120 . The battery pack is detachably connected to the dust container  120 . The cells may be recharged in situ. The battery pack may be detached from the dirt container to enable replacement, or external recharging of the cells, if necessary. The battery pack has a pair of feet  912  arranged to support the vacuum cleaner  702  in a stable manner when placed upon a flat surface. The cells have a generally cylindrical shape. Longitudinal axes of the cells are arranged parallel to the central axis  21  of the motor  16 . 
       FIGS. 32 and 34  show a compact configuration of the vacuum cleaner  702 . The flexible hose  710  is wrapped around the dirt container  120  and under the battery pack  910  via rebates  914  in the battery pack feet  912 . The cleaning nozzle  712  is cradled by the handle  706 . The handle is moulded in plastics material with natural resilience. The cleaning nozzle is gripped by the handle. The cleaning nozzle can be readily detached from the handle for use in vacuum cleaning. 
     Referring to  FIGS. 35 and 37 , the vacuum cleaner  802  comprises the elongate body  804 . The elongate body is telescopic. The elongate body has a handle  806  at one end and a bracket  805  at the other end. The motor  16 , fan  18  and cyclonic separation apparatus  8  of the first embodiment are rotatingly connected to the bracket  805  at the annular roof wall  121  of the dirt container  120 . The bracket arches around one side of the dirt container so that the latter may be connected transverse to the elongate body. The support wheel  807  surrounds the dirt container  120 . The support wheel is supported for rotation about the dirt container by a bearing  809 . The air inlet port  126  is connected to one end of the dirty air duct  810 . The cleaner head  812  is connected to the other end of the dirty air duct  810 . The cleaner head is pivotable in relation to the dirt container about a longitudinal axis  8100  of the dirty air duct. The dirty air duct is arranged tangentially to the dirt container. 
     The vacuum cleaner comprises a battery pack  900  of rechargeable cells  917  to energise the motor  16  when electrically coupled by an on/off switch. Referring to  FIG. 37 , the battery pack  900  has a curvilinear inner wall  902  which is shaped to embrace the support wheel  807  and part of the cylindrical dirt container  120 . The battery pack is detachably connected to the bracket  805 . The cells  917  may be recharged in situ. The battery pack may be detached from the bracket to enable replacement, or external recharging of the cells, if necessary. The cells have a generally cylindrical shape. Longitudinal axes of the cells are arranged parallel to the central axis  21  of the motor  16 . 
     Returning to  FIG. 35 , there is shown the vacuum cleaner  802 , prepared for use, with the support wheel  807  and the cleaning head  812  upon a floor and the elongate body  804  fully extended. The support wheel  807  is arranged about the midpoint of the axial length of the dirt container. The diameter of support wheel  807  is approximately the same as the axial length of the dirt container  120  so that the elongate body can be rocked from side to side by about 45 degrees each way and the vacuum cleaner  802  can be steered with ease. 
     Returning to  FIG. 37 , there is shown the vacuum cleaner with the elongate body  804  fully retracted to approximately a quarter of the elongate body&#39;s extended length. The vacuum cleaner&#39;s overall length when the elongate body is extended is at least double the vacuum cleaner&#39;s overall length when the elongate body is retracted. The vacuum cleaner  802  is prepared for storage in a kitchen cupboard when the elongate body is retracted. The elongate body may be locked in its retracted and extended positions. The skilled person will appreciate that any suitable locking system will suffice, like, for example, a spring-loaded detent interlockable with holes along the elongate body corresponding to the retracted position, the extended position and any intermediate position therebetween. 
     Referring to  FIG. 38 , there is shown in perspective the shape of the battery pack  900  and, in particular, the curvilinear inner wall  902  which is to embrace, or connect to, the outside of the dirt container  120  of the cyclonic separation apparatus  8 . 
     Referring to  FIGS. 39 and 40 , there is shown the battery pack  900  along cross-section XXXVIII-XXXVIII. Commercially available rechargeable cells may be cylindrical in shape.  FIG. 39  shows five cylindrical cells  917  stacked in a curved array to conform to the internal cavity of the curvilinear cross-section profile of the battery pack. Also commercially available are plate rechargeable cells  927  composed of flexible anode and cathode plates, or sheets, interposed by a polymer electrolyte material and separator material. The anode sheets are electrically connected to the positive cell terminal and the cathode sheets are electrically connected to the negative cell terminal, and those sheets can be connected in series or in parallel to form a battery pack. These plate cells are flexible and they can be stacked upon each other.  FIG. 40  shows three plate cells  927  stacked upon each other and curved to conform to the internal cavity of the curvilinear cross-section profile of the battery pack. 
     Referring to  FIGS. 41 to 43  there is shown an annular battery pack  920  in cross-section which is adapted to surround the dirt container  120  of the cyclonic separation apparatus  8  with a hollow cylindrical inner surface  922 . The annular battery pack has a cylindrical inner wall  922  and a cylindrical outer wall  926 . 
       FIG. 41  shows 12 cylindrical cells  917  arranged in a circular array to conform to the internal cavity of the annular cross-sectional profile of the annular battery pack  920 . 
       FIG. 42  shows three plate cells  927  stacked upon each other and curved into a hollow cylindrical shape to conform to the internal cavity of the annual cross-section of the annular battery pack  920 . 
       FIG. 43  shows five plate cells  927  wound into a hollow cylindrical shape to conform to the internal cavity of the annular cross-section of the annular battery pack  920 . 
     The curved plate cells  927  improve use of the internal cavity of the battery packs  920  by eliminating the gaps which naturally exist between the cylindrical cells  917 . This results in a more compact design of battery pack with reduced packaging and a higher energy density. 
     The curvilinear or cylindrical inner walls  902 , 922  of the curvilinear battery pack  900 , 910  and the annular battery pack  920  embrace, or attach themselves to, the dirt container  120 . This facilitates new design choices for accommodating cells in a compact manner. 
     The skilled addressee will appreciate that the rechargeable cells can be any type of energy accumulator, including rechargeable Lithium Ion, Nickel Metal Hydride or Nickel Cadmium rechargeable cells, for driving the electric motor  16 ,  216 ,  416 . 
     The skilled addressee will appreciate that the specific overall shapes and sizes of the arrangements comprising the motor  16 ,  216 ,  416  the fan  18 ,  218 ,  418  and the cyclonic separation apparatus  8 ,  208 ,  408  can be varied according to the type of vacuum cleaner in which either of the arrangements is to be used. For example, the overall length or width of each arrangement, and, in particular, the cyclonic separation apparatus, can be increased or decreased with respect to its diameter, and vice versa. 
     In particular, the hand-holdable vacuum cleaner  702  of  FIGS. 33 and 34  can be modified to comprise the motor  216 , fan  218  and cyclonic separation apparatus  208  of the embodiment by modifying the form of the battery pack  910  to suit the underside of the dirt container  320 . The flexible hose  710  would need extension to be wrapped around the dirt container  320  and the central housing  226  and motor housing  228 . 
     Further, the hand-holdable vacuum cleaner  802  of  FIGS. 35 to 38  can be modified to comprise the motor  216 , fan  218  and cyclonic separation apparatus  208  of the second embodiment by substituting the central housing  226  and motor housing  228  for the main bracket  805 . This could be done by attaching the elongate body  804  directly to the central housing  226  in place of the handle  206  and the bracket  805 . The cyclonic separation apparatus outlet duct  260  would need extension to create enough clearance for the support wheel  807  and bearing  809  to surround the dirt container  320 . 
     The motor  16 ,  216 ,  416  discussed above is a typically a brushed d.c. motor with its drive shaft  20 , 220 , 420  directly coupled to the centrifugal fan  18 ,  218 ,  418 . The motor&#39;s drive shaft has a rotational speed within a range of 25,000 and 40,000 revolutions per minute (rpm). A centrifugal fan with a rotational speed within this range has an outer diameter approximately double the outer diameter of the motor can in order to have sufficient tip speed to generate the required volumetric flow rate through the cyclonic separation apparatus. The skilled person will appreciate that the motor  16 , 216 , 416  can be a d.c. motor, an a.c. motor, or an asynchronous multi-phase motor controlled by an electronic circuit. A permanent magnet brushless motor, a switched reluctance motor, a flux switching motor, or other brushless motor type, may have a high rotational speed within a range of 80,000 to 120,000 rpm. If such a high speed motor were used then the fan diameter could be at least halved and yet still generate the required volumetric flow through the cyclonic separation apparatus because the fan&#39;s tip speed would be so much higher. This would make the fan&#39;s outer diameter the same as the motor can&#39;s outer diameter and could possibly make it less than the motor can&#39;s outer diameter if the motor operates at around the upper end of the high rotational speed range. A smaller diameter fan operating within this range of high rotational speeds would typically be an impeller although it may be an axial fan or a centrifugal fan. The outer profile of the smaller fan coupled to the drive shaft of the high rotational speed motor would have a generally cylindrical outer profile. This provides additional flexibility in the layout of the cyclonic separation apparatus. 
     In a modification of the first or second embodiment of a cyclonic separation apparatus  8 , 208  which is not shown in the drawings, the cyclones  84 , 284  can be rearranged to accommodate a high rotational speed permanent magnet brushless motor, a switched reluctance motor or a flux switching motor coupled to a fan which is coaxial with the motor and has an outer diameter substantially the same as or less than the outer diameter of the motor. The generally cylindrical outer profile of high speed motor and fan can be sunk into the cyclonic separation apparatus amongst the cyclones and clustered into a generally circular array. Air flow can be directed to the axial input of the fan and expelled from the tangential output of the fan by a baffle. The high speed motor and fan may be located on the periphery of the circular array in which case air flow from the fan may be expelled from one side of the circular array and directed out of the cyclonic separating apparatus. The high speed motor and fan may be nested near, or at, the middle of the circular array in which case air flow from the fan may be expelled from one end of the circular array and directed out of the cyclonic separating apparatus. If the high speed motor and fan were nested in a circular array of cyclones inclined with respect to a central axis, like, for example, a modified version of the cyclones disclosed by GB 2 440 110 A, then air flow from the fan may be expelled from one end of the circular array of cyclones or through gaps between the cyclones.