Abstract:
A portable vacuum cleaner having a fan which draws air inwards through inlet duct and inlet to coarse filter element. Larger dirt particles are trapped within coarse filter element, and the filtered air passes through fine filter element and into fan, where it is expelled through outlet duct and outlet aperture. A cleaning member mounted on the coarse filter element that engages the fine filter element so that upon remove of the coarse filter element, the cleaning member slides along the fine filter element removing particles thereon.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to Patent Application No. GB 08 070 97.1 filed Apr. 18, 2008. The entire contents of that application are expressly incorporated herein by reference thereto. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to vacuum cleaners, and particularly, but not exclusively, to portable vacuum cleaners. 
       BACKGROUND OF THE INVENITON 
       [0003]    Portable vacuum cleaners are known in which a fan mounted in the housing of the vacuum cleaner causes suction of air into an intake in the housing and expulsion of air from an exhaust in the housing. Air drawn through the vacuum cleaner in this way is passed through a dual filter arrangement consisting of a convex coarse filter element comprising a screen of durable plastics material having a large number of small apertures and defining a recess which contains a fine filter element in the form of a fine filter medium such as fibrous paper which is crimped or undulated to maximise its effective surface area in relation to its volume. Large particles of dirt travelling in the stream of air from the inlet towards the outlet are trapped on the outer surface of the coarse filter element, and finer dirt particles which pass through the coarse filter element are trapped on the fine filter element. 
         [0004]    Prior art vacuum cleaners of this type suffer from the drawback that although provision is made for emptying larger dirt particles from the first, coarse filter element, the fine filter element must normally operate until it becomes filled with dirt and dust, and must then be replaced. There is generally no provision for emptying the fine filter element of dirt and dust until it becomes necessary to replace that filter element. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present disclosure describes a vacuum cleaner comprising at least one inlet for allowing entry of air, at least one outlet for allowing exit of air, suction means for generating a difference in air pressure between the inlet and the outlet, a first filter means for at least partially removing particles larger than a first particle size from air flowing from said inlet to said outlet, and a second filter means for at least partially removing particles larger than a second particle size, smaller than said first particle size, from air flowing from said first filter means to said outlet. 
         [0006]    The first filter means comprises at least one removable first filter element having at least one cleaning member mounted thereto and adapted to engage said second filter means, such that removal of the first filter element, which has a cleaning member mounted thereto, causes the cleaning member to remove particles trapped on said second filter means. 
         [0007]    By providing at least one cleaning member mounted to the first filter element such that the cleaning member engages the second filter means, this provides the advantage that removal of a removable first filter element having (e.g. for emptying of dirt therefrom) automatically removes some of the dirt from the second filter means at the same time. This in turn provides the advantage of prolonging the useful lifetime of the second filter means. 
         [0008]    In one embodiment, the cleaning member comprises a brush. Additionally, the first filter element defines a respective recess therein for collecting particles, and said second filter means is arranged outwardly of the first filter element. 
         [0009]    By providing a first filter element defining a respective recess therein for collecting particles, this provides the advantage that by collecting particles on the inside of said first filter element, the surface area of the first filter element can be increased, together with the volume of the corresponding particle collection recess, and no reduction of the particle storage space available within the vacuum cleaner results, which would be the case with prior art arrangements in which dirt is collected on the outside of a convex filter element. Also, by collecting particles in the interior of a recess defined by the first filter element, this provides the advantage of enabling dirt collected in the recess to be more effectively confined and therefore more tidily removed from the vacuum cleaner. 
         [0010]    The first filter element may have a concave inner surface. This provides the advantage of reducing the instances of incoming particles becoming stuck to the first filter element. 
         [0011]    The first filter element may comprise a screen having apertures therein. The filter element may comprise a mesh. 
         [0012]    The vacuum cleaner is adapted to be opened to allow emptying of particles from said first filter means. 
         [0013]    In another embodiment, the first filter element is elongate and adapted to receive air adjacent a first end thereof and having a component of motion from said first end towards a second end thereof. 
         [0014]    This provides the advantage of causing air to have a component of motion axially along the first filter element, as a result of which that filter element tends to fill up with dirt from one end. Since the filter element may become blocked in those regions where it fills with particles, the tendency of an incoming air stream to disturb particles already collected in the interior of a said first filter element is thereby reduced. In addition, this at the same time provides the advantage giving an indication when a said first filter element needs to be emptied, since the first filter element will no longer be effective. 
         [0015]    The second filter means may comprise a second filter element, wherein the second filter element is undulated. This provides the advantage of increasing the effective surface area of the second filter means for a given volume of filter element. The cleaning member may engage the undulations in said second filter member. 
         [0016]    In another embodiment, the first filter element is elongate, and the vacuum cleaner in use directs air in a helical path over a surface of said elongate first filter element. 
         [0017]    This provides the advantage of directing incoming air onto as large a proportion of the surface area of the filter element as possible, and not just over that part of the surface area facing towards the direction of the incoming air. This in turn provides the advantage of maximising the efficiency of the first filter means. 
         [0018]    The vacuum cleaner may further comprise an inlet duct for introducing air to the first filter element having a component of movement transverse to the longitudinal axis of said first filter element. 
         [0019]    The vacuum cleaner may further comprise outlet duct means at least partially surrounding said first and second filter means, for directing air from said second filter means to said outlet. 
         [0020]    This provides the advantage of enabling the cross-sectional area of the airstream passing out of the outlet or outlets to be made larger than that of the airstream received from the inlet or inlets, as a result of which the velocity of air passing out of the outlets can be minimised. This is particularly advantageous in the case of suffers from asthma or other allergies, since the amount of dust blown towards a user of the vacuum cleaner by exhausted air is minimised. Furthermore, by providing outlet duct means which at least partially surrounds said first and second filter means, this provides the advantage of enabling the vacuum cleaner to still be made of compact construction. 
     
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
         [0021]    Preferred embodiments of the invention will now be described, by way of example only and not in any limitative sense, with reference to the accompanying drawings, in which: 
           [0022]      FIG. 1  is a schematic perspective view of a portable vacuum cleaner of a first embodiment of the present invention in a closed condition thereof; 
           [0023]      FIG. 2  is a view along the line B-B of the portable vacuum cleaner of  FIG. 1  in an open condition thereof; 
           [0024]      FIG. 3  is a cross-sectional end view of portable vacuum cleaner of a second embodiment of the present invention; and 
           [0025]      FIG. 4  is a view along the line A-A in  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Referring to  FIG. 1 , a portable vacuum cleaner  1  comprises a housing  2  of durable plastics material and consisting of a main part  3  to which a rear part  4  is pivotally attached by means of a hinge  5 . 
         [0027]    A diffuser  6  is mounted within the main part  3  of housing  2  and has a fan  7  mounted at the end thereof remote from the rear part  4  of housing  2 . The fan  7  is powered by an electric motor  8  to displace air radially outwards through apertures  9 . 
         [0028]    The main part  3  of housing  2  has an intake  10  at a front end thereof for receiving air into an inlet duct  11  which directs air through 180° into inlet  12  of a removable first, coarse filter element  13  in the form of a generally cylindrical cup, closed at one end thereof, and provided with suitably sized holes  14 . The cup is made of any suitable material which will be well known to persons skilled in the art, such as durable plastics or metal, and is designed to trap larger particles of dirt in its interior. 
         [0029]    A brush  20  is mounted to the closed end of coarse filter element  13 . The brush  20  has bristles extending outwardly of the longitudinal axis of the coarse filter element  13 . 
         [0030]    The coarse filter element  13  is surrounded by a generally cylindrical second, fine filter element  15  of fibrous paper or textile material, which is pleated to maximise the effective surface area of the filter element  15  in relation to its volume. The bristles of brush  20  fit within the pleats of fine filter element  15 . The fine filter element  15  is sealed at the end thereof remote from fan  7  to the coarse filter element  13 , and is surrounded by a chamber  16  which is sealed to an input of the fan  7 . This ensures that air passing through the fine filter element  15  enters the fan  7 . 
         [0031]    The apertures  9  of fan  7  direct air radially outwards and then along an annular outlet duct  17 , formed by the space between the inner wall of diffuser  6  and outer wall of chamber  16 , to a series of exhaust outlets  18  in the rear part  4  of housing  2 . 
         [0032]    The operation of the vacuum cleaner  1  shown in  FIG. 1  will now be described. 
         [0033]    When the fan  7  is actuated by means of motor  8 , air is displaced outwards through apertures  9  along outlet duct  17  and exhausted through outlet apertures  18 . As a result, air is drawn into the fan  7  through intake  10 , along inlet duct  11 , and into inlet  12  of coarse filter element  13 , where large particles contained in the air are trapped by holes  14 . 
         [0034]    Air passing out of coarse filter element  13  is then drawn through fine filter element  15 , where smaller particles are removed, and is then drawn into fan  7  and expelled from apertures  9  and along outlet duct  17 . As can be seen from  FIG. 1 , because the air stream through coarse filter element  13  has a significant axial component, the coarse filter element  13  fills up from its end remote from the rear part  4  of housing  2 , i.e. it fills up from its downstream end. This means that dirt collected in the interior of coarse filter element  13  is not disturbed of otherwise displaced by incoming air. 
         [0035]    By constructing an annular exhaust aperture  18  that surrounds the chamber  16 , the outlet duct  17  can be made to have relatively large surface area, as a result of which the velocity of air discharged though outlet  18  is minimised. This minimises the disturbance of dirt and dust in the vicinity of the outlet  18 , which is of particular advantage in the case of users of the vacuum cleaner suffering from an allergy to dust. 
         [0036]    Referring now to  FIG. 2 , which shows a view along the line B-B in  FIG. 1 , when the rear part  4  of housing  2  is pivoted relative to the main part  3  about hinge  5 , the coarse filter element  13  containing larger dirt particles can be removed from the housing  2  to enable the filter element  13  to be emptied. At the same time, as the coarse filter element  13  is withdrawn from the main part  3  of housing  2 , the bristles of the brush  20  are moved axially along the pleats of fine filter element  15 . This causes dust and/or dirt to be displaced from the fine filter element. 
         [0037]    Referring to  FIGS. 3 and 4 , which shows a second embodiment of the invention and in which parts common to the embodiment of  FIGS. 1 and 2  are denoted by like reference numerals but increased by 100, an inlet duct  111  is connected to an intake (not shown) provided at a distal end thereof with a suitable cleaning accessory such as a brush. The inlet duct  111  is removably mounted to inlet  112  of coarse filter element  113  by means of a bayonet-type fitting  130 . 
         [0038]    As can be seen from  FIG. 3 , inlet  112  is of generally cylindrical internal profile and longitudinal axis  131  of the inlet duct  111  is slightly displaced from the axial plane  132  of inlet  112 , as a result of which circular motion in the direction of arrow C is imparted to air entering inlet  112  from inlet duct  111 . 
         [0039]    The coarse filter element  113  is blocked by an un-perforated end cap  133  at the end thereof remote from inlet  112 , and a brush  120  is mounted to the end cap  133 . The coarse filter element  113  is surrounded by a cylindrical fine filter element  115  of pleated fibrous paper such that the bristles of brush  120  fit within the pleats of fine filter element  115 . The fine filter element  115  is also sealed by means of an un-perforated end cap  134  adjacent end cap  133 , and is sealed at fitting  135  within chamber  116 . As a result, any air passing through coarse filter element  113  is directed through the sides thereof into fine filter element  115 . 
         [0040]    A fan  107  having blades  136  is arranged at the end of chamber  116  remote from fitting  135  and expels air radially outwards into annular outlet duct  117  which surrounds chamber  116 . The air is then exhausted from annular exhaust aperture  118 . 
         [0041]    In operation, actuation of fan  107  causes expulsion of air along annular outlet duct  117 , as a result of which air is drawn axially inwards through inlet duct  111 , inlet  112  and into the interior of coarse filter element  113  in the direction of arrow D shown in  FIG. 4 . As a result of the combination of axial motion (arrow D in  FIG. 4 ) and circular motion (arrow C in  FIG. 3 ), air undergoes a spiral motion along filter element  113 , as a result of which incoming air travels over the entire side internal surface of coarse filter element  113 . This maximises the effective use of filter element  113 . Also, because the internal surface of filter element  113  is concave, dirt particles are less likely to become trapped in the holes of filter element  113 . As was the case with the embodiment of  FIGS. 1 and 2 , dirt particles trapped by coarse filter element  113  tend to congregate at the closed distal end of filter element  113 , as a result of which dirt is not disturbed by incoming air. 
         [0042]    After passing through filter element  113 , the filtered air passes through fine filter element  115  and through chamber  116  to fan  107 . Where it is expelled into outlet duct  117  and then discharged through exhaust aperture  118 . 
         [0043]    In order to empty dirt from the coarse filter element  113 , the inlet  112  is removed from the housing of the vacuum cleaner, and the coarse filter element  113  is removed from the housing. As the coarse filter element  113  is withdrawn from the housing, the bristles of brush  120  move axially along the individual pleats of fine filter element  115  and thereby displace dust and/or dirt trapped on the fine filter element  115 . 
         [0044]    It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.