Abstract:
A vacuum cleaner comprising a cyclonic separating apparatus including a dirty air inlet, a main body connected to the cyclonic separating apparatus and a motor and fan unit for generating an airflow through the cyclonic separating apparatus from the dirty air inlet to a clean air outlet, wherein the cyclonic separating apparatus includes at least a first cyclonic cleaning stage and an elongate filter arranged fluidly downstream from the first cyclonic cleaning stage, the elongate filter being housed in a duct at least partially surrounded by the first cleaning stage, and wherein the filter comprises an inlet portion and a filter portion defining a generally tubular filter chamber, the inlet portion including one or more radially facing inlets to permit air to flow into the inlet portion in a radial direction from where the air flows from the inlet portion to the filter chamber in an axial direction.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of United Kingdom Application No. 1122162.9, filed Dec. 22, 2011, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a vacuum cleaner, particularly of the handheld type of vacuum cleaner being generally compact and lightweight. The invention also relates to a filter for such a vacuum cleaner. 
       BACKGROUND OF THE INVENTION 
       [0003]    Handheld vacuum cleaners are popular with users due to their light weight and inherent portability, as well as the lack of power cords, which makes such vacuum cleaners particularly convenient for spot cleaning tasks as well as for cleaning larger areas. The cleaning efficiency of handheld vacuum cleaners is improving and it is known to equip a handheld vacuum cleaner with a cyclonic separating apparatus to separate the dirt and dust from the incoming flow of dirt laden air. One such example is disclosed in EP2040599B, which incorporates a first cyclonic separating stage in the form of a relatively large cylindrical cyclone chamber and a second cyclonic separating stage in the form of a plurality of smaller cyclones fluidly downstream from the first cyclonic separating stage. In such an arrangement, the first cyclonic separating stage works to separate relatively large debris from the airflow, whilst the second cyclonic separating stage filters relatively fine dirt and dust from the airflow by virtue of the increased separation efficiency of the smaller cyclones. 
         [0004]    Whilst two-stage cyclonic separation is efficient at separating dirt and dust from the incoming airflow, it is still prudent to provide a filter downstream of the cyclonic separating apparatus and upstream of the motor in order to protect the motor from the ingress of fine dust which may still be entrained in the airflow. EP2040599B includes a generally planar filter member that is located in a recess adjacent an outlet duct of the cyclonic separating unit. The plane of the filter member lies generally parallel to the longitudinal axis of the cyclonic separating unit. Although this configuration permits a relatively large filter to be used, the overall size of the vacuum cleaner is increased significantly. It is with this drawback in mind that the invention has been devised. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention provides a vacuum cleaner comprising a cyclonic separating apparatus including a dirty air inlet, a main body connected to the cyclonic separating apparatus and a motor and fan unit for generating an airflow through the cyclonic separating apparatus from the dirty air inlet to a clean air outlet, wherein the cyclonic separating apparatus includes at least a first cyclonic cleaning stage and an elongate filter arranged fluidly downstream from the first cyclonic cleaning stage. The elongate filter is housed in a duct at least partially surrounded by the first cleaning stage, and comprises an inlet portion carrying a filter portion defining a filter chamber. The inlet portion includes one or more radial inlets to permit air to flow into the inlet portion in a radial direction, wherein the air flows from the inlet portion to the filter chamber in an axial direction. 
         [0006]    Preferably, the filter is a sock filter arranged in the duct and so is generally tubular and defines a filter wall having a longitudinal axis generally parallel with a longitudinal axis of the duct/separating apparatus. Commonly, elongate filters such as sock filters are arranged such that air flow enters the interior or lumen of the filter in a direction along the longitudinal axis of the filter, through the open end of the filter. Such a configuration requires a chamber adjacent the open end of the filter to define the entry zone and allow air to flow in an axial direction in to the filter. Conversely, in the invention, the filter defines one or more radial inlets so that airflow is directed into the interior of the filter in a radial direction, that is to say in a direction normal to the longitudinal axis of the filter, thereby avoiding the need for a chamber adjacent the open end of the sock filter as in conventional arrangements. This enables the housing of the filter i.e. the surrounding part of the duct and the separating apparatus to be more compact, which is beneficial in particular for handheld vacuum cleaners for which important characteristics are compactness and low weight. 
         [0007]    Various configuration of radial inlets are possible. For example, the radial inlet may be a single annular opening extending either partly or wholly about the circumference of the inlet portion. Alternatively, the inlet portion may have a plurality of inlets spaced angularly around the periphery of the inlet portion. A plurality of inlet apertures may improve the air flow through the filter and so reduces pressure drop. In the case of a plurality of inlet apertures, each aperture may be aligned with a respective air channel or ‘vortex finger’ defined by a cyclone outlet manifold of the separating apparatus. Once the airflow has entered the interior of the filter, due to the configuration of the filter the air flows radially outwards through the wall of the filter media portion. 
         [0008]    In order to improve accessibility of the filter, the inlet portion may define a filter cap that is engageable within a complementary shaped aperture defined by the separating apparatus such that the filter cap defines an outer surface of the cyclonic separating apparatus. In this way, the user is able to grip the top of the filter and remove it from the separating apparatus without removing the separating apparatus from the main body of the vacuum cleaner. The filter may therefore extend along the duct from a point above the cyclonic separating apparatus to a point below the first cyclonic cleaning stage and near to the base of the separating apparatus. 
         [0009]    The separating apparatus may include a second cyclonic cleaning stage arranged fluidly downstream of the first cyclonic cleaning stage. In such a configuration, the filter may be configured such that the first cyclonic cleaning stage, the second cyclonic cleaning stage and the filter may be concentric about a common axis. 
         [0010]    The invention is applicable to upright and cylinder type vacuum cleaner, but is particularly suited to handheld vacuum cleaners due to the packaging benefits it provides particularly in terms of size and weight of the separating apparatus. 
         [0011]    From another aspect, the invention provides a filter for a vacuum cleaner comprising a generally tubular inlet portion carrying a generally tubular filter media portion defining an interior chamber having an axis, the inlet portion including one or more radially facing inlets such that a radial air path is defined for air to flow into the inlet portion and an axial air flow path is defined for air to flow from the inlet portion to the filter chamber. 
         [0012]    In a second aspect, the invention resides in a vacuum cleaner comprising a cyclonic separating apparatus including a dirty air inlet, a main body connected to the cyclonic separating apparatus and a motor and fan unit for generating an airflow through the cyclonic separating apparatus from the dirty air inlet to a clean air outlet. The cyclonic separating apparatus includes at least a first cyclonic cleaning stage and an elongate filter arranged fluidly downstream from the first cyclonic cleaning stage, the elongate filter being housed in a duct at least partially surrounded by the first cleaning stage. The filter comprises an inlet portion and a filter portion, the inlet portion including one or more inlets to permit air to flow into the inlet portion, wherein the inlet portion includes a cover portion that is receivable in the separating apparatus such that the cover portion defines at least a part of an outer surface of the separating apparatus. 
         [0013]    Such an arrangement improves the accessibility of the filter, since a user can simply grip the top of the filter and remove it from the separating apparatus without removing the separating apparatus from the main body of the vacuum cleaner. The filter may therefore extend along the duct from a point above the cyclonic separating apparatus to a point below the first cyclonic cleaning stage and near to the base of the separating apparatus. 
         [0014]    In order to improve the sealing of the filter within the separating apparatus and prevent ambient air from bleeding into the filter duct or unfiltered air from entering the filter duct, the inlet portion may include a first sealing member above the one or more inlets and a second sealing member below the one or more inlets. The first sealing member may be provided about the periphery of the cover portion so as to seal against a complementary shaped aperture in an exhaust manifold of the separating apparatus. 
         [0015]    The vacuum cleaner may also include a second cyclonic cleaning stage located downstream of the first cyclonic cleaning stage, the second cyclonic cleaning stage comprising a plurality of cyclones arranged fluidly in parallel about an axis, and wherein the duct is in communication with an outlet passage which extends between two of the cyclones in the second cyclonic cleaning stage and defines an outlet port which is centred on an axis that is orthogonal with the axis of the second cyclonic cleaning stage. Such an arrangement provides a height reduction benefit for the separating apparatus since the outlet extends rearwardly and between a gap defined between two of the cyclones of the second cyclonic separation stage instead of air being exhausted from the top of the apparatus. 
         [0016]    It should be noted that preferred and/or optional features of the first aspect of the invention can be combined with second aspect of the invention, and vice versa. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
           [0018]      FIG. 1  is a side view of a handheld vacuum cleaner in accordance with the invention; 
           [0019]      FIG. 2  is a view from above of the vacuum cleaner of  FIG. 1 ; 
           [0020]      FIG. 3  is a vertical section through the separating apparatus along line A-A in  FIG. 2 ; 
           [0021]      FIG. 4  is an exploded perspective view of the separating apparatus of the vacuum cleaner in  FIGS. 1 and 2 ; 
           [0022]      FIG. 5  is a view looking down into the cyclones of the separating apparatus; and 
           [0023]      FIG. 6  is a perspective view of an embodiment of a vortex finder member of the separating apparatus. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Referring firstly to  FIGS. 1 and 2 , a handheld vacuum cleaner  2  has a main body  4  which houses a motor and fan unit (not shown) above a generally upright handle or grip portion  6 . The lower end  6   a  of the handle  6  supports a generally slab-like battery pack  8 . A set of exhaust vents  10  are provided on the main body  4  for exhausting air from the handheld vacuum cleaner  2 . 
         [0025]    The main body  4  supports a cyclonic separating apparatus  12  that functions to remove dirt, dust and other debris from a dirt-bearing airflow drawn into the vacuum cleaner by the motor and fan unit. The cyclonic separator  12  is attached to a forward part  4   a  of the main body  4  and an air inlet nozzle  14  extends from a forward portion of the cyclonic separator that is remote from the main body  4 . The air inlet nozzle  14  is configured so that a suitable brush tool can be removably mounted to it and includes a catch  16  for securely holding such a brush tool when the tool is engaged with the inlet. The brush tool is not material to the present invention and so is not shown here. 
         [0026]    The cyclonic separating apparatus  12  is located between the main body  4  and the air inlet nozzle  14  and so also between the handle  6  and the air inlet nozzle  14 . The separating apparatus  12  has a longitudinal axis Y which extends in a generally upright direction so that the handle  6  lies at a shallow angle to the axis Y. 
         [0027]    The handle  6  is oriented in a pistol-grip formation which is a comfortable interface for a user since it reduces stress on a user&#39;s wrist during cleaning. The separating apparatus  12  is positioned close to the handle  6  which also reduces the moment applied to the user&#39;s wrist when the handheld vacuum cleaner  2  is in use. The handle  6  carries an on/off switch in the form of a trigger  18  for turning the vacuum cleaner motor on and off. In use, the motor and fan unit draws dust laden air into the vacuum cleaner  12  via the air inlet nozzle  14 . Dirt and dust particles entrained within the air flow are separated from the air and retained in the separating apparatus  12 . The cleaned air is ejected from the rear of the separating apparatus  12  and conveyed by a short duct to the motor and fan unit located within the main body  4 , and is subsequently expelled through the air outlets  10 . 
         [0028]    The separating apparatus  12  forming part of the handheld vacuum cleaner  2  is shown in more detail in  FIG. 3  which is a cross section through the separating apparatus  12  along the line A-A in  FIG. 2 , and  FIG. 4  which shows an exploded view of the components of the separating apparatus  12 . In overview, the separating apparatus  12  comprises a first cyclonic separating unit  20  and a second cyclonic separating unit  22  located downstream from the first cyclonic separating unit  20 . In this example, the first cyclonic separating unit  20  extends about part of the second cyclonic separating unit  22 . 
         [0029]    It should be appreciated that the specific overall shape of the separating apparatus can be varied according to the type of vacuum cleaner in which the separating apparatus is to be used. For example, the overall length of the separating apparatus can be increased or decreased with respect to the diameter of the separating apparatus  12 . 
         [0030]    The separating apparatus  12  comprises an outer bin  24  defined by an outer wall being substantially cylindrical in shape and which extends about a longitudinal axis Y of the separating apparatus  12 . The outer bin  24  is preferably transparent so that components of the separating apparatus  12  are visible through it. 
         [0031]    The lower end of the outer bin  24  is closed by a bin base  26  that is pivotably attached to the outer wall  24  by means of a pivot  28  and held in a closed position by a catch  30 . Radially inward of and coaxial with the outer wall  24  is a second cylindrical wall  32  so that an annular chamber  34  is defined between the two walls. The second cylindrical wall  32  engages and is sealed against the base  26  when it is closed. The upper portion of the annular chamber  34  forms a cylindrical cyclone of the first cyclonic separating unit  20  and the lower portion of the annular chamber forms a dust collecting bin of the first cyclonic separating unit  20 . 
         [0032]    A bin inlet  36  is provided at the upper end of the chamber  34  for receiving an air flow from the air inlet nozzle  14 . Although not shown in the Figures, the bin inlet  36  is arranged tangentially to the chamber  34  so as to ensure that incoming dirty air is forced to follow a helical path around the chamber  34 . 
         [0033]    A fluid outlet is provided in the outer bin in the form of a generally cylindrical shroud  38 . More specifically, the shroud has an upper frusto-conical wall  38   a  that tapers towards a lower cylindrical wall  38   b  that depends downwardly into the chamber  34 . A skirt  38   c  depends from the lower part of the cylindrical wall and tapers outwardly in a direction towards the outer wall  24 . The lower wall  38   c  of the shroud is perforated therefore providing the only fluid outlet from the chamber  34 . 
         [0034]    A second annular chamber  40  is located behind the shroud  38  and provides a manifold from which airflow passing through the shroud  38  from the first separating unit  20  is fed to the second cyclonic separating unit  22  through a plurality of conduits or channels  74  defined by a centrally positioned cyclone support structure  42 . The second cyclonic separating unit  22  comprises a plurality of cyclones  50  arranged fluidically in parallel to receive air from the first cyclonic separating unit  20 . In this example, the cyclones  50  are substantially identical in size and shape, each comprising a cylindrical portion  50   a  and a tapering portion  50   b  depending downwardly therefrom (only one cyclone is labelled in  FIG. 3  for clarity). The cylindrical portion  50   a  comprises an air inlet  50   c  for receiving fluid from one of the channels  74 . The tapering portion  50   b  of each cyclone is frusto-conical in shape and terminates in a cone opening  52  at its bottom end through which dust is ejected, in use, into the interior of the cyclone support structure  42 . An air outlet in the form of a vortex finder  60  is provided at the upper end of each cyclone  50  to allow air to exit the cyclone. Each vortex finder  60  extends downwardly from a vortex finder member  62  as will be explained. 
         [0035]    As is shown clearly in  FIGS. 3 and 4 , the cyclones of the second cyclonic separating unit  22  are grouped into a first set of cyclones  70  and a second set of cyclones  72 . Although not essential to the invention, in this embodiment the first set of cyclones  70  contains more cyclones (ten in total) than the second set of cyclones  72  (five in total). 
         [0036]    Each set of cyclones  70 ,  72  is arranged in a ring which is centred on a longitudinal axis Y of the separating unit. The first set of cyclones  70  has a greater number so this forms a relatively large ring of cyclones into which the second set of cyclones is partially received or ‘nested’. Note that  FIG. 4  depicts the first and second set of cyclones in an exploded view for clarity, whilst  FIG. 3  shows the relative positioning of the first and second sets of cyclones when in a nested, but axially spaced, position so that the second set of cyclones can be considered to be ‘stacked’ on the first set of cyclones. 
         [0037]    Each cyclone  50  of both sets has a longitudinal axis C which is inclined downwardly and towards the longitudinal axis Y of the outer wall  52 . However, to enable a greater degree of nesting of the second set of cyclones into the first set of cyclones, the longitudinal axes C 2  of the second set of cyclones  72  are all inclined at to the longitudinal axis Y of the outer wall at a shallower angle than the longitudinal axes C 1  of the first set of cyclones  70 . 
         [0038]    Referring now to  FIG. 5 , and specifically the outer ring defined by the first set of cyclones  70 , it can be seen that the cyclones are arranged into subsets  70   a  which each comprise at least two cyclones. In this example, each subset of cyclones comprises an adjacent pair of cyclones so that the first set of cyclones  70  is divided into five subsets of cyclones  70   a,  one subset of which  70   b  are spaced apart more than the others. Within each subset, the cyclones  70   a  are arranged so that the air inlets  50   c  are located opposite to each other. The cyclone subset  70   b  located that the rear of the separating apparatus  12  are spaced apart to allow the passage of an exhaust duct  94 , as will be explained. 
         [0039]    In this example, each subset of cyclones  70   a,    70   b  is arranged to receive air from a respective one of the plurality of channels  74  defined by the cyclone support structure  42  which channel airflow from the annular chamber  40  located behind the shroud  38  to the air inlets  50   c  of respective cyclones. 
         [0040]    It will also be noted from  FIG. 5  that the cyclones  50  in the second set of cyclones  72  are arranged also in a ring-like pattern and distributed annularly such that each cyclone is positioned between an adjacent pair of cyclones in the first set of cyclones  70 . Furthermore, the respective inlets  50   c  of the second set of cyclones are oriented to face a respective one of the channels  74  that feed air also to the first set of cyclones  70 . Since the air inlets  50   c  of both the first and second sets of cyclones are fed air from a channel  74  that leads from the same annular chamber  40 , the first and second sets of cyclones can be considered to be fluidly in parallel. 
         [0041]    Turning once again to  FIGS. 3 and 4 , the vortex finders  60  are defined by a short cylindrical tube that extends downwardly into an upper region of a respective cyclone  50 . Each vortex finder  60  leads into a respective one of a plurality of radially distributed air channels or ‘vortex fingers’  80  defined by an exhaust plenum or manifold  82  located at the top of the separating apparatus  12  that serves to direct air from the outlets of the cyclones to a central aperture  84  of the manifold  82 . The aperture  84  constitutes the upper opening of a central duct  88  of the separating apparatus into which a filter member  86  is received. In this embodiment, the filter member  86  is an elongate tubular filter or ‘sock filter’ that extends down into the central duct  88  along the axis Y, and is delimited by a third cylindrical wall  90  defined by the cyclone supporting structure  42 . 
         [0042]    The third cylindrical wall  90  is located radially inwardly of the second cylindrical wall  32  and is spaced from it so as to define a third annular chamber  92 . An upper region of the cyclone support structure  42  provides a cyclone mounting arrangement  93  to which the cone openings  52  of the cyclones of the second cyclonic separating  22  are mounted so that they communicate with the interior of the support structure  42 . In this way, in use, dust separated by the cyclones  50  of the second cyclonic separating unit  22  is ejected through the cone openings  52  and collects in the third annular chamber  92 . The chamber  92  therefore forms a dust collecting bin of the second cyclonic separating unit  22  that can be emptied simultaneously with the dust collecting bin of the first cyclonic separating unit  20  when the base  26  is moved to an open position. 
         [0043]    During use of the vacuum cleaner, dust laden air enters the separating apparatus  12  via the bin inlet  36 . Due to the tangential arrangement of the bin inlet  36 , the dust laden air follows a helical path around the outer wall  24 . Larger dirt and dust particles are deposited by cyclonic action in the first annular chamber  34  and collect at the bottom of the chamber  34  in the dust collecting bin. The partially-cleaned dust laden air exits the first annular chamber  34  via the perforated shroud  38  and enters the second annular chamber  40 . The partially-cleaned air then passes into the air channels  74  of the cyclone support structure  42  and is conveyed to the air inlets  50   c  of the first and second sets of cyclones  70 ,  72 . Cyclonic separation is set up inside the two sets of cyclones  70 ,  72  in order to separate the relatively fine dust particles still entrained within the airflow. 
         [0044]    The dust particles separated from the airflow by the first and second set of cyclones  70 ,  72  are deposited in the third annular chamber  92 , also known as a fine dust collector. The further cleaned air then exits the cyclones via the vortex finders  60  and passes into the manifold  82 , from which the air enters the sock filter  86  in the central duct  88  and from there passes into the exhaust duct  94  of the cyclone separator whereby the cleaned air is able to exit the separating apparatus. 
         [0045]    As can be seen in  FIGS. 3 and 4 , the filter  86  comprises an upper mounting portion  86   a  and lower filter portion  86   b  that carries out the filtering function and so is formed from a suitable mesh, foam or fibrous filter media. The upper mounting portion  86   a  supports the filter portion  86   b  and also serves to mount the filter  86  within the duct  88  by engaging with the aperture  84  of the exhaust manifold  82 . The mounting portion  86   a  defines a circular outer rim that carries a sealing member  96 , for example in the form of an o-ring, by which means the mounting portion is received removably, but securely, within the aperture  84  of the manifold, simply by way of a press fitting. Since the mounting portion  86   a  is circular, there is no restriction on the angular orientation of the filter, which aids a user in relocating the filter. Although not shown here, it should be appreciated that the filter  86  could also be provided with a locking mechanism if it is desired to more securely hold the filter in position. For example, the filter mounting portion  86   a  could carry a twist-lock fitting formation so that the filter could be twisted in a first direction to lock it into position within the aperture  84 , and twisted in the opposite direction to unlock the filter. 
         [0046]    The mounting portion  86   a  also includes an annular upper section provided with apertures or windows  100  distributed around its circumference, the apertures  100  providing an airflow path for air to enter the interior of the filter member  86 . The sealing member  96  prevents airflow from entering into the region of the filter from outside of the separating apparatus. Beneficially, the apertures  100  are distributed angularly around the periphery of the mounting portion  86   a  and are arranged so as to be in line with a respect one of the radially distributed vortex fingers  80  of the manifold  82  which means that air can flow substantially uninterrupted from the ends of the vortex fingers  80  into a neighbouring one of the inlet apertures  100  of the filter  86 . Air therefore flows into the filter  86  in a radial direction through the apertures  100 , following which the air flows down the interior of the filter  86  and then exits through the cylindrical filter media in a radial direction. A second sealing element  97 , also in the form of an o-ring, is located in an annular groove on the exterior of the mounting portion  86   a  thus extending circumferentially about the mounting portion thereby preventing air from flowing down the side of the filter from the inlet section. 
         [0047]    After flowing out of the filter  86 , the cleaned air then travels up the outlet passage  94  and exhausts the separating apparatus  12  via an exit port  101  located at the rear of the separating unit. It should be noted that the outlet passage  94  is shaped so as have a generally inclined orientation relative to the central axis Y of the duct  88  and rises to a position so that it lies between the two rearmost cyclones on the first set of cyclones  70 . 
         [0048]    The exit port  101  of the outlet passage  94  is oriented generally horizontally and rearwardly from the separating apparatus  12  and is aligned on an axis  103  that is substantially orthogonal to the longitudinal axis Y of the separating apparatus  12 . 
         [0049]    This configuration of airflow inlet enables the housing of the filter to be more compact since the alternative of allowing air to flow into the filter  86  in an axial direction requires a chamber above the inlet end of the filter to direct air into the top of the filter. The filter of the invention therefore avoids the need for such a chamber which enables the filter housing to be reduced in height. 
         [0050]    Having described the general function of the separating apparatus  12 , the skilled reader will appreciate it includes two distinct stages of cyclonic separation. First, the first cyclonic separating unit  12  comprises a single cylindrical cyclone  20  having a relatively large diameter to cause comparatively large particles of dirt and debris to be separated from the air by virtue of the relatively small centrifugal forces. A large proportion of the larger debris will reliably be deposited in the dust collecting bin  34 . 
         [0051]    Second, the second cyclonic separating unit  22  comprises fifteen cyclones  50 , each of which has a significantly smaller diameter than the cylindrical first cyclone unit  20  and so is capable of separating finer dirt and dust particles due to the increased speed of the airflow therein. The separation efficiency of the cyclones is therefore considerably higher than that of the cylindrical first cyclone unit  20 . 
         [0052]    Reference will now be made also to  FIG. 6  which shows the vortex finder member  62  in more detail. The vortex finder member  62  is generally plate-like in form and performs two main functions. Its primary function is to provide a means by which air is channelled out of the cyclones  50  on an upwardly spinning column of air and thereafter to direct the airflow exiting the cyclones  50  to an appropriate zone on the adjacent exhaust manifold  82 . Secondly, it serves to seal to upper end of the cyclones  50  so that air cannot bleed away from the primary airflow inside the cyclones. 
         [0053]    In more detail, the vortex finder plate  62  of the invention comprises upper and lower vortex finder portions  62   a,    62   b,  each of the portions providing vortex finders  60  for respective cyclones in the first and second sets of cyclones  70 ,  72 . The first, upper, vortex finder portion  62   a  includes five planar segments  102  configured into a ring so as to define a central aperture  104  matching the central aperture  84  of the exhaust manifold  82 . Each of the upper segments  102  defines a central opening  106  (only two of which are labelled for clarity) from which the cylindrical vortex finders  60  depend. As can be seen clearly in  FIG. 3 , the vortex finders  60  associated with the second set of cyclones  72  sit within the outlet end of the cyclones and are coaxial to the cyclone axis C 2 . Accordingly, the segments  102  in the first ring are dished downwards slightly out of a horizontal plane. The outer edge of the segments  102  define a downwardly depending wall or skirt  108 , the lower end  108   a  of which defines the inner edge of the lower vortex finder portion  62   b.    
         [0054]    The lower vortex finder portion  62   b  comprises ten segments  110  in total (only three of which are labelled for clarity), corresponding to the number of cyclones in the first set of cyclones  70 . Once again, each segment  110  includes a central opening  112  from which depends a respective one of the vortex finders  60 . With reference to  FIG. 3 , it should be noted that the vortex finders  60  of the lower vortex finder portion  62   b  sit coaxially within the upper end of each respective cyclone in the first set  70  so as to be centred on the cyclone axis C 1 . Therefore, each segment  110  is angled downwardly with respect to the first ring so that the plane of the segment  110  is perpendicular to the axis C 1 . 
         [0055]    It will be appreciated from the above that each of the vortex finders for the stacked sets of cyclones is provided by a common vortex finder plate. Such an arrangement improves the sealing of the cyclone outlets since a single vortex finder plate can be assembled on both upper and lower sets of cyclones which reduces the possibility of air leaks which may occur if the vortex finders for each set of cyclones were provided by an individual vortex finder plate. 
         [0056]    In order to secure the vortex finder plate  62  to the second cyclonic separating unit  22 , lugs  111  are provided on the lower vortex finder portion  62   b.  Screw fasteners may then pass through the lugs  111  to engage with corresponding bosses  113  (shown in  FIG. 5 ) provided on the lower set of cyclones  72 . On assembly, suitable rubber gasket rings  115   a,    115   b  are positioned so as to be sandwiched between the upper face of the second cyclone separating unit  22  and the underside of the vortex finder plate  62 . Although various materials may be used for the gasket rings, for example natural fibre-based material, a flexible polymeric material is preferred. It will be noted that since the vortex finder plate  62  fastens directly to the lower set of cyclones  72 , that the gaskets  115   a, b  and the second set of cyclones  70  are clamped between them. As a result the gaskets and the vortex finder plate are secured without needing additional fasteners, which reduces the part count of the separating apparatus as a whole as well as reducing weight and manufacturing complexity. 
         [0057]    In this embodiment, each vortex finder segment in both the lower and upper portions  62   a,    62   b  is demarcated from its neighbouring segment by a line of weakness to allow a degree of relative movement between them. The lines of weakness allow the segments  102 ,  110  an element of ‘play’ so that they may find a natural position on top of the cyclones when separator is assembled. However, it should be noted that these lines of weakness are not essential to the invention and the vortex finder member could instead be made rigid with limited or no flexibility between the segments. A suitable material for the vortex finder member is any suitably rigid plastics, for example acrylonitrile butadiene styrene (ABS). 
         [0058]    The skilled will appreciated that various modifications may be made to the inventive concept without departing from the scope of the invention, as defined by the claims. 
         [0059]    For example, although the vortex finder plate has been described here as being defined by a plurality of interconnected, and integral, segments, optionally demarcated by lines of weakness, the vortex finder plate could also be formed from continuous ring elements with no differentiating features. 
         [0060]    With reference to the filter member  86 , it should be noted that in the specific embodiment described above the filter member  86  is provided with a plurality of apertures  100  distributed around its circumference to provide a radial airflow path for air to enter the interior of the filter, the apertures  100  being aligned with a respective one of the radially distributed vortex fingers  80  of the manifold  82 . However, it should be appreciated that the alignment is not essential, and the number of apertures in the filter  86  need not coincide with the number of the vortex fingers  80 . One possibility, for example, is that a single aperture could extend circumferentially about the inlet portion of the filter. It should be noted for example that airflow benefits may be attained by reducing the number of apertures, whilst increasing the aperture area. The important feature is that air is able to flow radially inward into the filter member to access the interior of the filter and then to flow axially inside the tubular structure defined by the filter media before passing through the wall of the filter media. This avoids the need for a chamber to be provided above the filter. 
         [0061]    Furthermore, although the filter portion  86   b  has been described as cylindrical, it may also be conical or frusto-conical such that the filter portion  86   b  tapers towards its lower end  86   c  which has a smaller diameter compared to its upper, or inlet, end. A tapered filter portion  86   b  may be beneficial in resisting deformation due to the comparatively reduced pressure region in the outlet duct  94  which may tend to impart a ‘curved’ shape to the filer portion  86   b  in use.