Abstract:
In one aspect, the present invention provides a filter cleaning mechanism comprising: a filter material ( 37 ) for filtering out dust and dirt particles from air passing therethrough; a frame ( 32, 34, 35, 38, 39 ) for supporting said filter material ( 37 ); devices ( 31, 296; 25   a,    25   b,    25   c,    25   d ) for mechanically agitating said filter material to dislodge dust and dirt particles therefrom; wherein the devices for mechanically agitating said filter material comprises elements ( 31, 296; 25   a,    25   b,    25   c,    25   d ) for deforming said frame within its elastic limit and elements ( 31, 296; 25   a,    25   b,    25   c,    25   d ) for rapidly releasing said frame from said deformation to cause said frame to relax to an undeformed state. The present invention also provides a hand-holdable vacuum cleaner comprising such a filter cleaning mechanism, as well as a method of cleaning a filter assembly ( 30 ) comprising a filter material ( 37 ) and a frame ( 32, 34, 35, 38, 39 ) for supporting said filter material ( 37 ), wherein the method comprises the steps of deforming the frame within its elastic limit and rapidly releasing the frame from said deformation, thereby causing the frame to relax to an undeformed state.

Description:
FIELD OF THE INVENTION 
   This application claims priority to European Patent Application No. 07105676.6 filed Apr. 4, 2007. The entire contents of that application are expressly incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The present invention concerns filter cleaning mechanisms suitable for use in hand-holdable vacuum cleaners. Such vacuum cleaners are well known for collecting dust and dirt, although wet-and-dry variants which can additionally collect liquids are also known. Typically, hand-holdable vacuum cleaners are intended for use in a domestic environment, although they also find uses in other environments, such as worksites. Generally, they are electrically powered and therefore comprise an electric motor, an electrical on/off switch for a user to operate said motor, a fan connected to an output shaft of said 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, for connecting the vacuum cleaner to a recharging unit. When the vacuum cleaner is provided with electrical power from one of these sources and the on/off switch is set to the “on” position, the electric motor drives the fan to draw dirty air along an airflow pathway in through the dirty air inlet, via the collection chamber to the clean air outlet. 
   BRIEF SUMMARY OF THE INVENTION 
   Interposed at some point along the airflow 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 separation means may comprise one or more filters and/or a cyclonic separation device. However, in the event that the separation means comprises a filter, there is a risk that the filter material may become blocked with dust and dirt particles which adhere thereto, thereby lowering the rate of air movement (i.e. volume of air moved per unit time) through the vacuum cleaner by obstructing the airflow during operation of the vacuum cleaner and reducing the overall cleaning efficiency of the vacuum cleaner. Accordingly, in order to ensure its continued efficient operation, it is desirable to provide the vacuum cleaner with a filter cleaning mechanism. Such filter cleaning mechanisms are known in hand-holdable vacuum cleaners and an example of one is described in European patent publication no. EP 1 523 916 A, also in the name of the present applicant. However, such a filter cleaning mechanism as described in this prior art document, although not requiring any power to operate other than that supplied manually by a user and although also convenient to use as desired, suffers from the disadvantage that it involves mechanical rubbing of the filter material in order to agitate it and dislodge dust and dirt particles therefrom. This may have the undesirable consequence of shortening the lifespan of the filter material through wear and tear. 
   It is therefore an object of the present invention to provide a filter cleaning mechanism suitable for use in a hand-holdable vacuum cleaner which does not require mechanical rubbing of the filter material in order to dislodge dust and dirt particles therefrom. A further object of the present invention is to provide an improved manually operated filter cleaning mechanism suitable for use in a hand-holdable vacuum cleaner. 
   Accordingly, in one aspect, the present invention provides a filter cleaning mechanism comprising: a filter material for filtering out dust and dirt particles from air passing therethrough; a frame for supporting said filter material; means for mechanically agitating said filter material to dislodge dust and dirt particles therefrom; wherein the means for mechanically agitating said filter material comprises means for deforming the frame within its elastic limit and means for rapidly releasing the frame from said deformation to cause said frame to relax to an undeformed state. Thus, the deformation of the frame by the means for deforming it is transmitted to the filter material which is supported by the frame and the rapid release of the frame by the means for releasing it causes the filter material to be shaken, thereby dislodging dust and dirt particles therefrom without subjecting the filter material itself to direct mechanical impact or manipulation and thereby avoiding wear and tear on the filter material. The present invention also has the advantage that it may be used with both pleated and unpleated filter materials, since there is no requirement that the filter material should be pleated, which in some prior art filter cleaning mechanisms is necessary to provide surface irregularities on the filter material, direct rubbing of which causes the filter material to vibrate for the propose of dislodging dust and dirt particles therefrom. 
   In a second aspect, the present invention also provides a hand-holdable vacuum cleaner comprising such a filter cleaning mechanism. 
   In a further aspect, the present invention provides a method of cleaning a filter assembly comprising a filter material and a frame for supporting the filter material, the method comprising the steps of deforming the frame within its elastic limit and rapidly releasing the frame from said deformation, thereby causing the frame to relax to an undeformed state. 
   The deformation of the frame may be compressional, torsional, by stretching or by bending, or any combination of these various deformations. Preferably, the frame is deformed and released a plurality of times by providing a plurality of the means for deforming and releasing the frame. This has the advantage of increasing the amount of dust and dirt dislodged from the filter material in a single cleaning operation. If two or more arrangement of means for deforming and releasing the frame in different directions are provided, this has the advantage of increasing the amount of dust and dirt dislodged from the filter material in a single cleaning operation still further. Moreover, if there are two or more arrangements of means for deforming and releasing the frame in different directions, advantageously, each of them is composed of a plurality of means for deforming and releasing the frame which are separated from each other at regular intervals which are different between the different arrangements of means for deforming and releasing the frame, with the result that the frame, and hence the filter material, is agitated at two or more different frequencies during a single filter cleaning operation. The different frequencies affect different sizes of dust and dirt particles adhering to the filter material in different amounts, thereby increasing the total amount of dust and dirt dislodged from the filter material still further. 
   Preferably, the filter cleaning mechanism further comprises means for manually actuating the means for mechanically agitating the filter material in order to dislodge dust and dirt particles therefrom. This has the advantage of not requiring any electrical, pneumatic or other additional power supply to operate the filter cleaning mechanism and allows a user to actuate it as desired. In a preferred embodiment, the means for manually actuating the means for mechanically agitating the filter material comprises a mechanism for performing a filter cleaning operation in a single, first movement and for returning the filter cleaning mechanism to its starting position in a single second movement, for example by providing a lever, the down-stroke of which performs a filter cleaning operation and the up-stroke of which returns the filter cleaning mechanism to its starting position. This makes the filter cleaning mechanism particularly simple and convenient to use. 

   
     BRIEF DESCRIPTION OF THE INVENTION 
     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  is an exploded perspective view of the major components of a hand held vacuum cleaner according to an embodiment of the present invention; 
       FIG. 2  is a perspective view of a nose cone of the hand held vacuum cleaner shown in  FIG. 1 ; 
       FIG. 3  is a perspective view of a motor housing of the held vacuum cleaner shown in  FIG. 1 ; 
       FIG. 4A  is a plan view of the exterior of a coarse filter assembly of the held vacuum cleaner shown in  FIG. 1 ; 
       FIG. 4B  is a plan view of the interior of the coarse filter assembly shown in  FIG. 4A , seen from the opposite direction to  FIG. 4A ; 
       FIG. 5A  is a plan view of the exterior of a fine filter assembly of the held vacuum cleaner shown in  FIG. 1 ; 
       FIG. 5B  is a side elevational view of the fine filter assembly shown in  FIG. 5A ; 
       FIG. 5C  is a plan view of the interior of the fine filter assembly shown in  FIG. 5A , seen from the opposite direction to  FIG. 5A ; 
       FIG. 5D  is a partial cross-sectional view of the fine filter assembly shown in  FIG. 5A  along the line D-D′ represented in  FIG. 5C ; 
       FIG. 6A  is side elevational view of one of a plurality of teeth formed on an end flange of the fine filter assembly of  FIG. 5A  viewed from the location marked by the letter “X” in  FIGS. 5C and 5D ; 
       FIG. 6B  is a rear elevational view of one of the plurality of teeth formed on the end flange of the fine filter assembly of  FIG. 5A ; 
       FIG. 6C  is a plan view of one of the plurality of teeth formed on the end flange of the fine filter assembly of  FIG. 5A ; 
       FIG. 6D  is a front elevational view of one of the plurality of teeth formed on the end flange of the fine filter assembly of  FIG. 5A ; 
       FIG. 7A  is a plan view in close-up of part of an air inlet portion of the motor housing of  FIG. 3  showing a ramp formed thereon; and 
       FIG. 7B  is a side elevational view of a part of the motor housing of  FIG. 3  showing the ramp of  FIG. 7A  in profile. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring firstly to  FIG. 1 , there is shown an exploded perspective view of the major components of a hand held vacuum cleaner according to an embodiment of the invention, comprising a nose cone  10 , a coarse filter assembly  20 , a fine filter assembly  30  and a motor housing  40 . Fine filter assembly  30  is contained entirely within coarse filter assembly  20 , which in turn attaches to motor housing  40  via holes  22  formed in an end flange  24  of coarse filter assembly  20 . Holes  22  respectively engage with corresponding lugs  42  (not visible in  FIG. 1 , but shown in  FIG. 3  and described in greater detail below in relation thereto) formed on an end face of motor housing  40 . Nose cone  10  then attaches to motor housing  40  in a releasable manner to enclose coarse filter assembly  20  and fine filter assembly  30  therein. 
   In operation of the vacuum cleaner, dirty air enters the nose cone  10  in the direction indicated by arrow A in  FIG. 1  via a dirty air inlet  11 , travels along a duct built into the roof of nose cone  10  and exits the duct into a dust collection chamber  14  of nose cone  10  via an outlet  12 . As can be seen in greater detail in  FIG. 2 , outlet  12  is located within nose cone  10  such that when the vacuum cleaner is assembled, dirty air exits outlet  12  between the end flange  24  of coarse filter assembly  20  and a deflector  26  also built integrally into outer surface  28  of coarse filter assembly  20 . End flange  24  and deflector  26  therefore tend to direct the flow of air entering dust collection chamber  14  in a circumferential direction around the main body  28  of coarse filter assembly  20  anticlockwise when viewed from the direction of arrow B in  FIG. 1 . 
   Turning now to  FIG. 3 , it may be seen how coarse filter assembly  20  and nose cone  10  attach to motor housing  40 . Lugs  42  on an end face  44  of motor housing  40  engage with holes  22  formed in the end flange  24  of coarse filter assembly  20 , as mentioned previously. Holes  22  are so shaped that they each comprise both a larger portion having a diameter greater than a respective lug  42  and a smaller portion having a diameter smaller than lugs  42  but slightly larger than a respective stalk  42   a  on the end of which stalk each lug is formed. Thus, coarse filter assembly  20  containing fine filter assembly  30  may be attached to motor housing  40  by passing respective lugs  42  through the larger portion of each hole  22  and then twisting coarse filter assembly  20  until the smaller portion of each hole  22  surrounds a respective stalk  42   a  in a friction fit and is also prevented from being pulled away from motor housing  40  by the greater diameter of lugs  42 . Coarse filter assembly  20  may be detached from motor housing  40  by twisting it in the opposite direction until each lug  42  is aligned with the larger portion of a respective hole  22  and reversing the operation of passing the lugs back again through the larger portion of the respective hole  22 . 
   Nose cone  10  in turn attaches to motor housing  40  via a lip  46  formed on the underside of motor housing  40 , which lip engages with a corresponding slot  16  formed in the lower part of nose cone  10  (see  FIG. 1 ). A rim on the upper part of nose cone  10  also similarly engages with a spring-loaded latch  47  at the top of front face  44  of motor housing  40 . Depressing a release button  48  mounted on the top of motor housing  40  allows a user to disengage nose cone  10  from motor housing  40  again, since release button  48  is mechanically connected to latch  47 , such that depressing release button  48  causes latch  47  to withdraw from the upper rim of nose cone  10 . 
   Motor housing  40  contains a fan and motor assembly for transporting air through the vacuum cleaner. As may be seen from  FIG. 3 , motor housing  40  comprises a clean air inlet  43  through which air is drawn into the motor housing by the fan during operation of the vacuum cleaner. Clean air inlet  43  is covered by a rotatable grille assembly  45  to prevent a user from gaining access to the fan and motor. Air drawn in through the inlet  43  during operation of the vacuum cleaner is then expelled from an outlet  430  located on the underside of motor housing  40 , which is visible in  FIG. 1 . The motor housing further comprises a handle  41  on which is mounted a user operable on/off switch  49  for turning the motor on and off, as well as a filter cleaning lever  52  which is movable in a slot  54 . Lever  52  is rigidly connected to rotatable grille assembly  45  within motor housing  40 , such that moving lever  52  in the direction of arrow C shown in  FIG. 3  causes grille assembly  45  to rotate in a clockwise direction and conversely, moving lever  52  in the opposite direction to arrow C causes grille assembly  45  to rotate anticlockwise. 
   The filtering and flow of dirty air through the vacuum cleaner will now be described. Looking firstly at  FIG. 4A , this shows an end-on view of the exterior of coarse filter assembly  20 . As may be seen, coarse filter assembly  20  has a frusto-conical shape, such that the area of an end face  29  of coarse filter assembly  20  is less than the area which coarse filter assembly  20  presents to clean air inlet  43  of motor housing  40 . The outer rim of end flange  24  of coarse filter assembly  20  is also provided with a peripheral moulding  23 . This is made of a resilient material such as rubber or a similar elastomer, whereby coarse filter assembly  20  forms an airtight seal with motor housing  40  when mounted thereto in the manner described above in relation to  FIG. 3 . As may also be seen, deflector  26  has an edge  26   a  which follows the contours of the interior of dust collection chamber  14 , the gap visible at the top of  FIG. 4A  between edge  26   a  and peripheral moulding  23  being occupied by the duct formed in the roof of nose cone  10 . However, as may also be seen from this drawing, deflector  26  does not completely surround the main body  28  of coarse filter assembly  20 , but only approximately one third thereof. Thus dirty air exiting the duct from outlet  12  firstly passes behind deflector  26  as seen in  FIG. 4A  and then emerges in the direction of arrow E such that it is free to continue rotating in a clockwise fashion in front of deflector  26 , thereby creating an overall helical swirl of dirty air around main body  28 , which causes heavier particles of dust and dirt entrained therein to be thrown outwardly by centrifugal force towards the inner walls of nose cone  10 . These particles then fall under gravity and gather in the bottom of dust collection chamber  14  and the partially cleaned air is sucked through a plurality of small holes  280  formed in main body  28  of coarse filter assembly  20 . 
   Turing now to  FIG. 4B , this shows an end-on view of the interior of coarse filter assembly  20 . As may be seen, the holes  22  for mounting the coarse filter assembly  20  to motor housing  40  are each surrounded by a respective moulding  23   a . These mouldings are made of a resilient material such as rubber or a similar elastomer and are therefore squeezed between flange  24  and the front face  44  of motor housing  40  when the coarse filter assembly  20  is mounted thereto, thereby preventing leakage of dirty air through holes  22  from dust collection chamber  14  into motor housing  40 . As can also be seen in  FIG. 4B , the interior of coarse filter assembly  20  is also provided with a plurality of longitudinal vanes  25   a ,  25   b ,  25   c  and  25   d  projecting inwardly therefrom. These vanes create a gap between the interior of the coarse filter assembly  20  and the fine filter assembly  30  contained therein. However, each vane has a different height, such that vane  25   a  is taller than vane  25   b , which in turn is taller than vane  25   c , which itself is taller than the smallest vane  25   d . These height differences prevent the gap between the coarse filter assembly  20  and the fine filter assembly  30  from being compartmentalised into regions separated by the vanes, but rather allow a swirl of air between the coarse filter assembly  20  and the fine filter assembly  30  in an anticlockwise direction as viewed in  FIG. 4B  (which is the same direction as the swirl around the outside of coarse filter assembly  20  described in relation to  FIG. 4A ), along a path of increasingly smaller cross-section. This tends to increase the pressure and therefore force the partially cleaned air within the coarse filter assembly  20  through the fine filter assembly  30  contained therein, which filters out the remaining smaller particles of dust and dirt entrained with the air. Any of these particles which fall under their own weight towards the bottom of the gap between the coarse filter assembly  20  and the fine filter assembly  30  are able to pass through a longitudinal slit  27  formed in the lower side of coarse filter assembly  20  and thence into dust collection chamber  14 . Slit  27  is no greater in width than the diameter of holes  280 , so as to prevent the passage of larger particles of dust and dirt in the opposite direction from dust collection chamber  14  back into the interior of coarse filter assembly  20 . 
     FIG. 5A  shows an end-on view of the exterior of fine filter assembly  30 . Like the coarse filter assembly  20 , fine filter assembly  30  has a frusto-conical shape, such that the area of an end face  39  of fine filter assembly  30  is less than the area which fine filter assembly  30  presents to clean air inlet  43  of motor housing  40 . As can also be seen from  FIG. 5A , fine filter assembly  30  comprises an end flange  34 , the width of which defines the gap between the interior of coarse filter assembly  20  and the exterior of fine filter assembly  30  and which accommodates vanes  25   a ,  25   b ,  25   c  and  25   d  therebetween. A moulding  392  projecting from end face  39  helps align the fine filter assembly  30  correctly within coarse filter assembly  20  by locating within a circular recess  291  formed on the interior of end face  29  of coarse filter assembly  20  (see  FIG. 4B ). As may best be seen in the side view of  FIG. 5B , the conical surface of fine filter assembly  30  is defined by a fine filter material  37  which acts to filter out small particles of dust and dirt from air passing therethrough. Thus, the partially cleaned air swirling around the exterior of fine filter assembly  30  passes through fine filter material  37  and thence into the clean air inlet  43  of motor housing  40 . The fine filter material  37  may be woven from polyethylene or a similar type of material and may also have a non-stick coating in order to help prevent the adherence and build-up of dust particles thereon. Fine filter material  37  is shaped and held in place by hoops  38  formed on the outer surface thereof and a plurality of longitudinal supporting ribs  35  on the inner surface thereof (see  FIG. 5C ), the ribs  35  and hoops  38  being thermally welded to fine filter material  37  during the manufacturing process. 
   As may also be seen in  FIGS. 5A and 5B , the end face  39  of fine filter assembly  30  has a first set of teeth  31  formed in a ring around the circumference thereof. These teeth  31  have a triangular or ramp-shaped profile and abut against a corresponding set of radial ribs  296  formed on the inner surface of end face  29  of the coarse filter assembly  20  (see  FIG. 4B ). As shown in  FIGS. 5C and 5D , the end flange  34  of fine filter assembly  30  also has a second set of teeth  36  formed in a ring thereon. As may best be seen in the partial cross-section of  FIG. 5D , a rim  32  formed around the periphery of flange  34  means that the second set of teeth  36  are recessed into fine filter assembly  30 . The teeth  36  each have a shape as represented in the series of drawings  FIGS. 6A ,  6 B,  6 C and  6 D, which are respectively a side elevational view of one of the teeth when viewed from a location marked by the letter “X” in  FIGS. 5C and 5D , a rear elevational view, a top plan view and a front view. 
   Both the first set of teeth  31  and the second set of teeth  36  are components of the filter cleaning mechanism, the operation of which will be described shortly. A further component of the filter cleaning mechanism is a series of serrations formed around the respective outer surfaces of each of the hoops  38  on the fine filter assembly  30 . The final components of the filter cleaning mechanism not already described are shown in  FIGS. 7A and 7B . These are a pair of ramps  56  formed on opposite sides of the circumference of the rotatable grille assembly  45 . As can be seen in  FIG. 7B , ramps  56  project outwardly from end face  44  of motor housing  40  into the annular recess created by rim  32  and flange  34  in fine filter assembly  30 . Thus, when a user moves lever  52  in the direction of arrow C shown in  FIG. 3 , thereby causing grille assembly  45  to rotate in a clockwise direction, ramps  56  also rotate clockwise and an oblique end face  56   a  of each ramp  56  engages with an oblique end face  36   a  (see  FIGS. 6A ,  6 C and  6 D) of one of the second set of teeth  36  on flange  34 . This pushes fine filter assembly  30  in a clockwise direction as well and causes the radial ribs  296  formed on the inner surface of end face  29  of the coarse filter assembly  20  to ride up the ramps of the first set of teeth  31 . This compresses the fine filter assembly  30  slightly in a longitudinal direction within its elastic limit until the ribs  296  drop completely over the other side of the ramps of the first set of teeth  31 . This allows the fine filter assembly  30  to spring suddenly back to its full, uncompressed length, thereby shaking dust particles adhering to the outside of fine filter material  37  therefrom. At the same time, vanes  25   a ,  25   b ,  25   c  and  25   d  rub against successive ones of the serrations formed around the outer surfaces of hoops  38 , increasing the shaking of the fine filter assembly  30 , but due to the different separations of successive teeth  31  on the one hand and successive serrations on the hoops  38  on the other, at different frequencies from each other, which improves the effectiveness of the filter cleaning operation in dislodging dust particles from the fine filter material  37 . These two shaking actions continue until a user reaches the bottom of a down-stroke of lever  52  and the lever reaches the end of slot  54 . 
   Next, when a use reverses the direction of lever  52  by moving it in the opposite direction to arrow C shown in  FIG. 3 , thereby causing grille assembly  45  to rotate in an anticlockwise direction, ramps  56  also rotate anticlockwise, are compressed slightly within their elastic limit in the direction indicated by arrow F in  FIG. 7B  and slide up an inclined face  36   b  (see  FIGS. 6A ,  6 B and  6 C) of a respective one of the second set of teeth  36  on flange  34 . Fine filter assembly  30 , on the other hand, is prevented from rotating anticlockwise about its longitudinal axis by abutment of the end faces of the first set of teeth  31  against the radial ribs  296  formed on the inner surface of end face  29  of the coarse filter assembly  20 . The length of ramps  56  is such that a single up-stroke of lever  52  back to the top of slot  54  causes the ramps  56  to drop completely over the other side of the teeth  36  and brings their respective end faces  56   a  back into alignment with an oblique end face  36   a  of respective ones of the second set of teeth  36  on flange  34 , thereby returning the filter cleaning mechanism to its starting position.