Patent Publication Number: US-2019178527-A1

Title: Filter cleaning device for an air conditioner and air conditioner having such filter cleaning device

Description:
TECHNICAL FIELD 
     The present invention relates to filter cleaning devices for air conditioners, particularly so-called duct-type air conditioners and to air-conditioners having such filter cleaning devices. 
     BACKGROUND 
     Air conditioners are common in different buildings, particularly in commercial premises such as offices and hotels. In those premises often air conditioners of the so-called duct-type are employed. 
     Duct-type air conditioners are understood as air conditioners of which the indoor unit is connected to an air ducting hidden behind a false ceiling or a false wall. In many cases, also the indoor unit is completely or partly hidden behind the false ceiling or the false wall. An air conditioner according to one or more embodiments is shown in  FIG. 1 . 
     Such duct-type air conditioners  1  generally comprise air ducting  6 ,  7  located behind a false ceiling U or a false wall. One air ducting  6  leads to an exit grating  8  or exit terminal in a space to be conditioned such as an office, a corridor, a meeting room or a hotel room. Another air ducting  7  leads to an inlet grating  9  or inlet terminal which may either be located within the space to be conditioned or outside that space. The air ducting  7  may alternatively be connected to a ducting network supplying air centrally to a plurality of indoor units. 
     The air conditioner  1  has an indoor unit comprising a casing having an inlet  2  to which the air ducting  7  is connected and an outlet  3  to which the air ducting  6  is connected. A heat exchanger  4  is located within the casing downstream of the inlet  2  and downstream of one or more fans  5 . Yet, the heat exchanger  4  may also be located upstream of the fan/-s  5 . A filter  12  having opposite filter surfaces  13 ,  14  is disposed upstream of the heat exchanger  4  and in many cases located at or near the inlet  2 . 
     An air flow is generated by the fan/-s  5  during operation of the air conditioner  1 . Air flows from the inlet grating  9  via the air ducting  7  to the inlet  2 , passes the filter  12  and subsequently the heat exchanger  4  for heating or cooling the air before being introduced into the space to be conditioned via the outlet  3 , the air ducting  6  and the exit grating  8 . 
     The filter  12  has the purpose of removing particulate matter such as dust and fibers from the air flow to avoid the parts of the air conditioner, particularly the heat exchanger  4 , from being soiled and clogged. 
     Yet, the filter  12  requires regular cleaning to avoid clogging of the filter. Such clogging of the filter may result in an increased resistance to the air flow which requires a higher load on the fan/-s. Hence, clogging of the filter can reduce the efficiency of the air conditioner. 
     Yet, cleaning of the filter very often requires opening the false ceiling or the false wall and specialized maintenance engineers or cleaning personnel to remove and clean the filter. This is perceived negative. For this reason, systems have been suggested to simplify removal of the filter. Such systems are for example disclosed in KR 10 2003 0083185 A or KR 10 2004 0080810 A. 
     However, also these systems require cleaning personal to frequently access the spaces to be conditioned, which may disturb the people using the space. To address this problem, filter cleaning devices have been suggested which are able to automatically clean the filter. One system uses a suction force for cleaning the filter, wherein a suction device is communicated with a suction nozzle moving along the filter surface, whereby the particulate matter adhering to the filter surface is removed by the suction force applied via the suction nozzle. Two examples of those devices are disclosed in WO 2007/040276 A1 and WO 2016/009351 A1. However, these devices are, on the one hand, perceived to be relatively complicated and hence expensive and, on the other hand, perceived to either not sufficiently remove the particulate matter or to require a relatively high suction force which may lead to damaging of the filter. 
     To address these deficiencies, filter cleaning devices have been proposed using a mechanical cleaning member, such as a brush. The particulate matter removed from the filter by the brush is collected and retained in a dust box. One type of those filter cleaning devices moves the filter along a fixed mechanical cleaning member for removing the particulate matter. Those devices however require a specific configuration of the filter, such as having a continuous belt shape or a large space into which the filter is moved before being returned to its original position. EP 2 119 979 A1 discloses an example of such device. This device particularly employs a rotatable brush. In order to remove particulate matter adhering to the bristles of the brush after being removed from the filter, EP 2 119 979 A1 suggests a comb shaped member engaged with the brush and particularly its bristles scrapping off the adhering particulate matter for transfer to a dust box. 
     Alternative types of such filter cleaning devices disclose to slide the mechanical cleaning member along the filter surface with the dust box however being fixed relative to the casing. One such filter cleaning device is disclosed in JP H06-32926 U. Yet, also in this device the brush, being pressed against and slid along the filter, may damage the filter and/or push particulate matter into and even through the filter rather than removing the particulate matter from the filter. 
     To address these problems, the inventors considered the use of a brush rotated by a motor in opposite directions. Yet, it turned out that cleaning or removing of particulate matter adhering to the brush or its bristles by one comb shaped member is not sufficient when the brush rotates in opposite directions. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] KR 10 2003 0083185 A 
         [PTL 2] KR 10 2004 0080810 A 
         [PTL 3] WO 2007/040276 A1 
         [PTL 4] WO 2016/009351 A1 
         [PTL 5] EP 2 119 979 A1 
         [PTL 6] JP H06-32926 U 
       
    
     SUMMARY 
     In view of the aforesaid, one or more embodiments of the invention provide a filter cleaning device and an air conditioner comprising such a filter cleaning device which can overcome or at least reduce the above drawback of the prior art. 
     In particular, one or more embodiments provide a filter cleaning device having a brush rotated by a motor in opposite directions and a corresponding air conditioner which are capable of improving the removal of particulate matter adhering to the brush. 
     According to one or more embodiments, a filter cleaning device having the features described below and an air conditioner having such filter cleaning device described below are suggested. The filter cleaning device for an air conditioner ( 1 ), particularly a duct-type air conditioner, the filter cleaning device comprises: a filter ( 12 ) to be passed through by an air flow and having a filter surface ( 13 ); a brush ( 17 ) contactable with the filter surface ( 13 ) for removing particulate matter from the filter surface, wherein the brush has a cylindrical shape; and a motor ( 46 ) configured to rotate the brush in opposite directions; a first comb shaped member ( 48 ) engaged with the brush; and a second comb shaped member ( 49 ) engaged with the brush, wherein the first and second comb shaped members each have a length direction parallel to the axis of rotation of the brush and a width direction, wherein the first comb shaped member and the second comb shaped member are inclined away from each other in a cross-sectional view perpendicular to an axis of rotation ( 19 ) of the brush. The air conditioner, particularly a duct-type air conditioner, has aforementioned filter cleaning device ( 10 ). 
     In accordance with one or more embodiments, the filter cleaning device for an air conditioner, particularly a duct-type air conditioner, comprises a filter to be passed through by an air flow and having a filter surface. The filter surface defines a width and a length of the filter. In particular, the filter may have two filter surfaces on opposite sides of the filter in the direction of the air flow. The filter can be flat and/or longitudinal. The filter can in principle be of any kind as long as it is configured to remove particulate matter, particularly dust and fibers, from the air flow flowing through the filter, and to be used in combination with an air conditioner. In one or more embodiments, the filter can comprise a frame holding a mesh made of for example plastic material or metallic material. Further, the filter cleaning device comprises a brush as a cleaning member contactable with the filter surface for removing particulate matter from the filter surface, wherein the brush has a cylindrical shape (is substantially cylindrical). The brush is rotatably mounted so as to be continuously rotatable about a cylinder axis (the cylinder axis of the cylinder) in one or more embodiments. In this context “continuously rotatable” is to be understood in that the brush can be rotated clockwise and/or counterclockwise without any abutment or limitation of the rotation angle. Moreover, the filter cleaning device comprises a motor configured to rotate the brush in opposite directions. The motor may be an electric motor, particularly a stepping motor. For removing the particulate matter from the brush, the filter cleaning device comprises a first comb shaped member engaged with the brush and a second comb shaped member engaged with the brush. The comb shaped members are to be understood as members having a plurality of teeth extending from a body. Adjacent teeth are separated by a recess. As such, the comb shaped members may be configured as disclosed in EP 2 119 979 A1 the content of which is incorporated herein by reference. The first and second comb shaped members may be formed integral and being connected by a common comb body. The first and second comb shaped members each have a length direction parallel to the axis of rotation of the brush and a width direction. The width direction is perpendicular to the length direction and parallel to the axis of rotation of the brush. According to one or more embodiments, the first comb shaped member and the second comb shaped member are inclined away from each other in a cross-sectional view perpendicular to the axis of rotation of the brush. In this context, the first and second comb shaped members are angled so that their width directions intersect outside the diameter of the brush. To put it differently, the projection of the width direction of the first comb shaped member and the projection of the width direction of the second comb shaped member intersect outside the diameter of the brush. The first comb shaped member and the second comb shaped member may be disposed symmetrically in a cross-sectional view perpendicular to the axis of rotation of the brush with respect to a line perpendicularly intersecting with the axis of rotation of the brush. In this context, the projection of the width direction of the first comb shaped member and the projection of the width direction of the second comb shaped member intersect on said line. 
     According to one or more embodiments, a filter cleaning device is provided which enables sufficient cleaning of the brush to remove particulate matter adhering to the brush even when the brush rotates in opposite directions. In particular, the first comb shaped member is configured to remove particulate matter from the brush when the brush is rotating in a first direction and the second comb shaped member is configured to remove particulate matter from the brush when the brush is rotating in a second direction opposite to the first direction. Thus, the cleaning efficiency of the filter cleaning device can be enhanced. 
     According to one or more embodiments, the first comb shaped member is angled with its width direction with respect to a first tangent on a circle having a common center axis with the axis of rotation of the brush at a positive angle and the second comb shaped member is angled with its width direction with respect to a second tangent on the circle and being perpendicular to the first tangent at a negative angle. 
     According to one or more embodiments, the first and second comb shaped members are angled with respect to the axis of rotation of the brush in order to provide for an appropriate removal of particulate matter therefrom independent of the rotational direction of the brush. 
     In one or more embodiments, the absolute value of the positive angle and the negative angle is the same. Accordingly, the first comb shaped member and the second comb shaped member are disposed symmetrically in a cross-sectional view perpendicular to the axis of rotation of the brush with respect to a line perpendicularly intersecting with the axis of rotation of the brush. 
     Hence, it is possible to remove particulate matter from the brush with the same efficiency independent of the rotational direction of the brush. 
     According to one or more embodiments, the first comb shaped member is inclined away from the axis of rotation in a direction towards the first rotating direction and the second comb shaped member is inclined away from the axis of rotation in a direction towards the second rotating direction. 
     Consequently, it can be realized that the brush and particularly the bristles reliably enter the recesses between the teeth of the comb shaped members and any particulate matter adhering to the brush or its bristles is scrapped away by the comb shaped members. 
     According to one or more embodiments, a first rotatable separation roller extending parallel to the axis of rotation of the brush is disposed upstream of the first comb shaped member in the first rotating direction and a second rotatable separation roller extending parallel to the axis of rotation of the brush is disposed upstream of the second comb shaped member in the second rotating direction. 
     It may happen that particulate matter removed from the brush by the comb shaped members again adheres to the brush and/or the surfaces of the comb shaped members after being loosened by the comb shaped members. One or more embodiments suggest the separation rollers in order to transfer the loosened particulate matter from the brush and the comb shaped members. In particular, the separation rollers create an air flow moving the particulate matter away from the brush and the comb shaped members and/or centrifuge any particulate matter adhering to the separation rollers away from the separation rollers. Accordingly, the particulate matter can reliably be transferred to the dust box. 
     In one or more embodiments, the first separation roller is configured to rotate in a direction opposite to the first rotating direction and the second separation roller is configured to rotate in a direction opposite to the second rotating direction. 
     Accordingly it can be reliably achieved that the particulate matter is moved away from the brush and the comb shaped members to be transferred to the dust box. 
     Further, the first and second separation roller are driven by the motor also rotating the brush in one or more embodiments. 
     The use of a common motor has the advantage that less expensive parts are required and less wiring is necessary. 
     According to one or more embodiments, the brush is reciprocally and translationally movable along the filter surface. Particularly, the brush may span the filter surface in a direction of the width of the filter and/or is movable along the length of the filter. The brush may be disposed on one of the opposite sides of the filter so as to engage with one of the filter surfaces during cleaning operation. 
     In one or more embodiments, the cleaning member, that is the brush, has a cylindrical shape and is rotatably mounted and movable along the filter. Hence, removing the particulate matter from the filter can be effected more efficiently because the brush can be moved along the filter more quickly and the particulate matter is brushed away from the filter surface due to the rotational movement of the brush. In addition, because of the rotational movement of the brush, the mechanical forces applied to the filter surface are reduced as compared to a brush slid along the filter surface. Therefore, the risk of damaging the filter can be reduced. During cleaning operation, the brush moves along the length of the filter in opposite directions, wherein the direction of rotation of the brush is changed when changing the direction along the length of the filter (direction of movement). Accordingly, removing particulate matter from the filter can be achieved most effectively. 
     The motor of one or more embodiments is configured to respectively rotate the brush in the direction of movement of the brush along the filter surface. “In the direction of movement” is to be understood in this context in that the brush is rotated against the rotation direction which would be imparted to the brush when moving the brush along the filter surface with the brush in contact with the filter surface by friction. To put it differently, the brush is rotated so that the upstream side of the brush is rotated against the filter surface whereas the downstream side rotates away from the filter surface. For example, the brush rotates clockwise if it is moved to the right and the brush rotates counterclockwise if it is moved to the left. 
     According to one or more embodiments, particulate matter is scrapped or brushed away from the filter surface rather than being brushed and pressed into the filter surface. Thus, removing of particular matter from the filter surface is very efficient. 
     The filter cleaning device may further comprise a dust box for receiving particulate matter removed from the filter by the brush and removed from the brush by the first and second comb shaped members and optionally the third and fourth comb shaped members described below. The dust box may be movable together with the brush along the length of the filter. Further, the dust box may be arranged below the brush in a direction of gravity, whereby the particulate matter removed from the filter by the brush falls into the dust box by gravity. In one or more embodiments, the dust box may be arranged at an axial end of the brush. 
     According to one or more embodiments, particulate matter removed from the filter by the brush and removed from the brush by the comb shaped members can easily be collected in the dust box. In one or more embodiments, the particulate matter falls into the dust box automatically by gravity when being removed and loosened from the brush. 
     To obtain a reliable cleaning of the filter and removing particulate matter therefrom, the brush of one or more embodiments has a body and a plurality of bristles radially extending from the body. In addition, because of the use of bristles, optional reinforcing ribs of the filter may be accommodated by a larger bending of the bristles. Even further, the use of bristles in combination with the comb shaped members provides for a very effective loosening of any particulate matter adhering to the brush in that the separate bristles path through the recesses between teeth of the comb shaped members so that the particulate matter is scrapped away from the bristles. 
     Depending on the circumstances, it may happen that dust accumulates at the brush and the first and second comb shaped members whereby dust lumps are created. Those dust lumps that tend to be long and stick to the first and second comb shaped members or get caught in the dust box. Accordingly, it is difficult to remove the dust effectively from the filter cleaning device. A third comb shaped member and a fourth comb shaped member, each engaged with the brush, are suggested in order to cope with this problem. The third and fourth comb shaped members have a different function than the first and second comb shaped members. In particular, the first and second comb shaped members described above are configured to gather the dust from the brush, that is scratch the dust from the bristles of the brush. In contrast, the third and fourth comb shaped members form an obstacle to the bristles of the brush, wherein the bristles are bent upon rotation of the brush when engaging with the third and fourth comb shaped members. Once the bristles have passed by the third and fourth comb shaped members, the bristles spring back to their original position, whereby the dust adhering to the bristles is scattered (thrown away) into the dust box. Consequently, the accumulation of dust at the bristles is prevented and small particles are transferred into the dust box. Hence, only a relatively small amount of dust remains at the bristles and will be scratched off by the first and second comb shaped members, however without or at least with a reduced risk that dust lumps are formed. Only one of the third and fourth comb shaped members is active depending on the rotational direction of the brush in one or more embodiments. To put it differently, the third comb shaped member is only active in a first direction of rotation and the force of the comb shaped member is only active in a second direction of rotation of the brush. Further and as with the first and second comb shaped members, also the third and fourth comb shaped members may each have a length direction parallel to the axis of rotation of the brush and a width direction. 
     According to one or more embodiments, the third comb shaped member is directed toward the first comb shaped member and the fourth comb shaped member is directed toward the second comb shaped member. As a result, the arrangement of the first and second comb shaped members and the third and fourth comb shaped members is the opposite, whereby effective scattering of the dust into the dust box may be achieved by the third and fourth comb shaped members and scratching of the remaining dust is still obtained by means of the first and second comb shaped members. Also in this configuration, it may be that the projections of the width directions of the third and fourth comb shaped members intersect. As in the above embodiments, the projections of the width directions of the third and fourth comb shaped members may intersect outside the diameter of the brush. According to one or more embodiments, the projections of the width directions of the third and fourth comb shaped members intersect on the same side as the projections of the width directions of the first and second comb shaped members relative to the center axis (axis of rotation) of the brush. The third comb shaped member and the fourth comb shaped member may be disposed symmetrically in a cross-sectional view perpendicular to the axis of rotation of the brush with respect to a line perpendicularly intersecting with the axis of rotation of the brush. In this context, the projection of the width direction of the third comb shaped member and the projection of the width direction of the fourth comb shaped member intersect on said line. According to one or more embodiments, the point of intersection of the projections of the width directions of the third and fourth comb shaped members is the same as that of the projections of the width directions of the first and second comb shaped members. 
     According to one or more embodiments, the third comb shaped member is inclined toward the axis of rotation of the brush in a direction of the first rotating direction and the fourth comb shaped member is inclined toward the axis of rotation in a direction of the brush toward the second rotating direction. 
     Besides the above filter cleaning device, also an air conditioner, particularly a duct-type air conditioner, having such filter cleaning device is suggested. Even though a duct-type air conditioner is used, the present filter cleaning device may also be applied to other air conditioners in which a filter requires regular cleaning. 
     Further features and advantages are described in the following description of embodiments, which make reference to the accompanying drawings. The drawings show in: 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a schematic view of a duct-type air conditioner according to one or more embodiments; 
         FIG. 2  shows a perspective view of a filter cleaning device according to one or more embodiments of the present invention; 
         FIG. 3  shows a front view of the filter cleaning device as shown in  FIG. 2 ; 
         FIG. 4  shows a side view of the filter cleaning device as shown in  FIG. 2 ; 
         FIG. 5  shows a partial side view of the filter cleaning device shown in  FIG. 2  with the front plate and other parts being removed and with the brush in a parking position; 
         FIG. 6  shows a cross-section along the line B-B in  FIG. 5 ; 
         FIG. 7  shows a partial side view of the filter cleaning device shown in  FIG. 2  with a front plate and other parts being removed and during filter cleaning operation; 
         FIG. 8  shows a cross-section along the line C-C in  FIG. 7 ; 
         FIG. 9  shows the detail D of  FIG. 8 ; 
         FIG. 10  shows a partial isometric front view of the filter cleaning device shown in  FIG. 2  with the front plate being removed; 
         FIG. 11  shows a partial front view of the filter cleaning device shown in  FIG. 2  with the brush and its supports as well as the casing being removed; 
         FIG. 12  shows a cross-section along the line D-D in  FIG. 11 ; 
         FIG. 13  shows a partial isometric top view of the filter cleaning device shown in  FIG. 2  with some parts removed; 
         FIG. 14  shows a partial isometric view of the filter cleaning device shown in  FIG. 2  with some parts removed; 
         FIG. 15  shows a partial isometric top view of the filter cleaning device shown in  FIG. 2  with some parts removed; 
         FIG. 16A  shows a side view of the brush according to one or more embodiments,  FIG. 16B  shows a front view of the brush to be engaged with the filter surface according to one or more embodiments, and  FIG. 16C  shows a cross-section along the line A-A in  FIG. 16A ; 
         FIG. 17  shows a schematic cross-sectional view of the cleaning member unit perpendicular to the axis of rotation of the brush showing an alternative configuration of the combs. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIGS. 2 to 4  generally show a filter cleaning device  10  according to one or more embodiments. The filter cleaning device comprises a casing  11 . The casing  11  has a casing inlet  60  and a casing outlet  61 . In operation of the air conditioner, air flows through the casing  11  from the casing inlet  60  to the casing outlet  61  passing the filter  12 . 
     The filter cleaning device  10  may be mounted to existing air conditioners such as the one depicted in  FIG. 1 , wherein the existing filter  12  is first removed from the existing indoor unit and a filter cleaning device  10  is attached to the inlet  2  of the existing casing at a flange  62 . Alternatively, the filter cleaning device  10  as described herein may already be integrated into the casing of an indoor unit of an air conditioner at the time of production of the air conditioner. 
     A control box  66  is attached to one side of the casing  11  and configured to control the cleaning operation of the filter  12  described later. 
     The filter  12  contained in the filter cleaning device  10  is longitudinal and flat having a length L and a width W. In one or more embodiments, the length L is larger than the width W, whereby the filter  12  is longitudinal. Further, the lengths L and the width W are both much larger than the thickness/height, whereby the filter  12  is flat. 
     Further, the filter  12  comprises a frame  63  of plastic material, which is molded about a mesh  64  made of plastic material, metal or other suitable material. One longitudinal reinforcing rib  15  and a plurality of transverse reinforcing ribs  65  are provided in order to stabilize the mesh  64  over the length and widths of the filter  12 . The filter has a first filter surface  13  facing the inlet  60  and a second filter surface  14  facing the outlet  61 . The first and second filter surfaces  13 ,  14  can be best seen in  FIG. 6 . 
     The filter cleaning device  10  further comprises a cleaning unit  67  configured to clean the filter  12  and particularly its mesh  64 . The cleaning unit  67  comprises cleaning member unit  67   a  and a counter surface unit  67   b.    
     The cleaning member unit  67   a  has a mechanical cleaning member  16  in the form of a brush  17 . The brush  17  consists of a body  20  from which a plurality of separate bristles  21  extend in a radial direction. As can be best seen from the cross-sectional view in  FIG. 9  and the perspective in  FIG. 14 , the brush  17  has a cylindrical shape and is rotatable about an axis of rotation  19 , which corresponds to the center axis of the cylinder. The axis of rotation  19  is parallel to the filter surface  13  in one or more embodiments. Furthermore, the axis of rotation  19  of the brush  17  is disposed in a distance to the filter surface  13  which is smaller than the diameter of the brush to ensure contact of the brush  17  with the filter surface  13 . Yet, the distance is larger than the diameter of the body  20  to prevent any damaging of the filter by the brush  17  according to one or more embodiments. 
     Considering  FIG. 14 , the brush  17  is basically supported at both its axial ends  18  by supports  43   a ,  43   b  forming a support unit. The supports  43  rotatably support or retain the brush  17 . 
     The lower support  43   b  is embodied as a dust box  28 . In particular, the lower support  43   b  has a bottom  100  and sidewalls  101  surrounding the bottom, whereby the dust box  28  is formed (see  FIG. 14 ). 
     The upper support  43   a  and the lower support  43   b  of the support unit are respectively provided with two wheels  45   a, b . The wheels  45   a  of the upper support  43   a  are rotatably fixed to the upper support  43   a  or an upper portion of a wall of a housing  30  connecting the supports  43   a ,  43   b , respectively. The housing  30  connects to the side walls  100  of the dust box  28  and provides for a shielding effect as described in more detail below. The wheels  45   a  are rotatable about an axis of rotation  69 . 
     The wheels  45   b  of the lower support  43   b  are rotatably and pivotably fixed to the lower support  43   b  or a lower portion of the wall  88  of the housing  30 . In particular, the wheels  45   b  are rotatably fixed to a pivot arm  71  about an axis of rotation  69  and the pivot arm  71  is pivotably fixed to the lower support  43   b  or a lower portion of the wall  88  of the housing  30  about a pivot  70 . Furthermore, a spring (as an example of the second elastic member)  47  is fixed at one of its opposite ends to the pivot arm  41  of one wheel  45   b  and the other one of its opposite ends to the pivot arm of the other wheel  45   b . Accordingly, the wheels  45   b  are urged towards each other about the pivots  70 . 
     The wheels  45   a  at the top are engaged with a longitudinal top guide rail  44   a  (guide) extending in a length direction of the filter  12  along the filter cleaning device  10 . The same applies for the wheels  45   b  at the bottom, which are engaged with a longitudinal bottom guide rail  44   b  (guide) extending substantially in parallel to the top guide rail  44   a.    
     Accordingly, the support unit is movably guided between the guide rails  44   a ,  44   b  and hence movable along the length of the filter  12  or its filter surface  13 , respectively. 
     The filter  12  and consequently also the guide rails  44   a ,  44   b  can be relatively long. As a consequence, bending of the guide rails  44   a ,  44   b  may occur with the result that the distance D (see  FIG. 12  with respect to the counter surface unit  67   b ) parallel to the filter surface  13  and between opposite guide rails  44   a ,  44   b  at the top and bottom is not constant over the lengths of the guide rails  44   a ,  44   b . As described earlier, the wheels  45   b  of the lower support  43   b  are urged towards each other by the spring  47  about the pivots  70 . Accordingly, the wheels  45   b  are urged towards a position in which their distance D to the wheels  45   a  at the upper support  43   a  is the largest. Thus, if the distance D between the opposite guide rails  44   a ,  44   b  becomes larger, the wheels  45   b  pivot counterclockwise (left wheel  45   b  in  FIG. 10 ) and clockwise (right wheel  45   b  in  FIG. 10 ) about the pivot  70  by the force of the spring  47 . Thereby, the wheels  45   b  at the lower support  43   b  remain securely engaged with the lower guide rail  44   b  as do the wheels  45   a  at the upper support  43   a . Similar, if the distance D between opposite guide rails  44   a ,  44   b  becomes smaller, the wheels  45   b  pivot in the opposite direction, thereby automatically compensating for the change in distance D. Accordingly, support unit may reliably be moved along the guide rails  44   a ,  44   b  without becoming loose or stuck. 
     As previously mentioned, the brush  17  is rotatably supported in the support unit. As a result, the support unit serves to move the brush  17  along the filter surface  13 . For movement of the support unit along the filter  12 , the support unit is driven. 
     According to one or more embodiments, a rack  72  (see  FIG. 13 ) is provided extending along the filter  12  in parallel to the guide rails  44   a ,  44   b . Furthermore, the support unit comprises a motor  46  (see  FIG. 14 ) which may be a stepping motor. The motor  46  is attached to the upper support  43   a , thus avoiding any possible contact with condensate accumulating at the bottom of the filter cleaning device. Further, the motor  46  is with its axis connected to a first gear  73  rotatably attached to the upper support  43   a . The first gear  73  meshes with a second gear  74  again meshing with a third gear  75 . Also the second and third gear  74  and  75  are rotatably attached to the upper support  43   a . The third gear  75  meshes with the rack  72 . 
     Accordingly, the motor  46  rotates the first gear  73 , whereby the second gear  74  and the third gear  75  are rotated. Thus, the rotational force is transmitted via the gears  73  to  75  to the rack  72 . The rack  72  converts the rotational force into a translational force, whereby the support unit and, hence, the brush  17  rotatably supported therein, are moved along the rack  72  and thereby along the filter  12 . 
       FIG. 13  additionally shows a fourth gear  76  again meshing with the rack  72 . A centrally arranged fifth gear  77  meshes with the fourth gear  76  to transfer the rotation to a sixth gear  78 . The axis of rotation  19  of the brush  17  is fixed to the axis of rotation of the sixth gear  78 . Accordingly, upon operation of the motor  46  and movement of the support unit along the rack  72 , the movement of the support unit along the rack  72  results in rotation of the fourth gear  76  meshing with the rack  72 . As a consequence, the translational movement of the support unit along the rack  72  is converted into a rotational movement. This rotation is transferred via the centrally arranged fifth gear  77  to the sixth gear  78  thereby rotating the brush  17 . In this context, if the support unit moves in  FIG. 13  to the right, the fourth gear  76  is rotated clockwise whereby the centrally arranged fifth gear  77  is rotated counterclockwise and the sixth gear  78  again rotates clockwise. If the support unit moves in figure to the left, the fourth gear  76  is rotated counterclockwise whereby the centrally arranged fifth gear  77  is rotated clockwise and the sixth gear  78  again rotates counterclockwise. Thus, the brush  17  is rotated in opposite directions and depending on the direction of movement of the support unit. In particular, the brush  17  is always rotated in the direction of movement. In other words, the upstream side of the brush  17  is always rotated against the filter surface  13  whereas the downstream side of the brush  17  is always rotated away from the filter surface  13 . 
     As will be apparent from the above description, only one motor  46  is used to move the support unit and hence the brush  17  along the filter  12  and hence its filter surface  13 , and to rotate the brush  17 . 
     Due to the movability of the cleaning member unit  67   a  and hence the brush  17  in a longitudinal direction of the filter  12  as explained above, the cleaning member unit  67   a  may be moved to a parking position shown in  FIGS. 5 and 6  during non-cleaning operation of the cleaning unit. In one or more embodiments, the cleaning unit does not overlap with the filter surfaces  13 ,  14  of the filter  12  in this parking position as seen in a plan view such as in the cross section of  FIG. 6  or in a front view as shown in  FIG. 5 . Thus it can be prevented that any portion of the filter  12  is blocked by the cleaning unit during non-cleaning operation, that is during air conditioning operation. Thus, the cleaning unit does not represent any obstruction to the air flow flowing through the filter  12  and the whole filter surface  13 ,  14  may be used. 
     When the brush  17  and particularly its bristles  21  brush along the filter surface  13  and remove the particulate matter therefrom, particulate matter may adhere to the bristles  21 . In order to remove the particulate matter from the bristles and, hence, the brush  17 , the cleaning unit further comprises a first comb shaped member  48  and a second comb shaped member  49  which are respectively engaged with the brush  17  and particularly the bristles  21  (see  FIGS. 16A-16C ). The comb shaped members  48  and  49  extend parallel to the axis of rotation  19  of the brush  17  along the whole or at least a substantial part of the axial lengths of the brush  17 . Thus, the comb shaped members  48  and  49  have a length along the axial direction and a width perpendicular thereto (seen in the cross-sectional view in  FIG. 16C ). The comb shaped members  48  and  49  further have in their width direction a free edge  99  respectively engaged with the bristles  21  of the brush  17 . The opposite edge of the comb shaped members  48  and  49  is respectively connected or integrally formed with a comb body  97 . As shown in  FIG. 15 , the comb body  97  is fixed to the housing  30  or more particularly the back wall  88  of thereof. 
     The comb shaped members  48  and  49  are respectively formed along the length direction with a plurality of teeth  102  separated by recesses. In other words, the comb shaped members are configured of a plurality of merlons and crenels. The teeth  102  extend in the width direction from the comb body  97 . The cross-sectional line A-A extends through one of the teeth  102 . The two comb shaped members  48  and  49  are respectively angled or inclined with their width direction in opposite directions, that is away from each other. To put it differently, the comb shaped members  48  and  49  are inclined in different directions with respect to an axis of symmetry  103 . In particular, the teeth  102  are angled or inclined as described above. As may be best seen from the cross-section in  FIG. 16C ), the comb shaped members  48  and  49  are respectively arranged symmetrically to the line of symmetry  103 . As shown, the comb shaped members  48  and  49  are angled by a positive angle α +  and a negative angle α − , respectively. In particular, drawing a circle  52  being the outer diameter of the bristles  21  or at least co-axial with the outer diameter of the bristles  21  and drawing a first and second tangent  50 ,  51  to the circle which are perpendicular to each other, the first comb shaped member  48  is angled clockwise at a negative angle α −  and the second comb shaped member  48  is angled counterclockwise at a positive angle α +  with their width direction. The absolute value of the angles α is however the same to provide for a symmetric arrangement. In this context, the width direction is drawn as a centerline in the cross-section in  FIG. 16C ) at that position of the comb shaped members having the largest thickness perpendicular to the width direction WD and the length direction LD. Accordingly, if the brush  17  is rotated clockwise in  FIG. 16C ), the comb shaped member  48  is inclined towards the direction of rotation of the brush  17 . If the brush  17  is rotated counterclockwise, the comb shaped member  49  is inclined towards the direction of rotation of the brush  17 . Accordingly, it can be effectively achieved that the bristles  21  of the brush  17  and to the recesses between the teeth  102  so that any particulate matter can be scrapped of the bristles  21 . 
     As previously mentioned, the dust may adhere to the comb shaped members  48  and  49  promoting the formation of dust lumps which stick to the comb shaped members  48  and  49  and/or are difficult to be removed from the dust box  28 . According to one or more embodiments as shown in  FIG. 17 , two additional comb-shaped members  104 ,  105  (third and fourth the comb shaped members) are provided. In one or more embodiments, the comb shaped members  104  and  105  are provided in the proximity of the opening  31  from which the brush  17  projects. The comb shaped members  104  and  105  also engage with the bristles  21  of the brush  17 . The comb shaped members  104  and  105  extend parallel to the axis of rotation  19  of the brush  17  along the whole or at least a substantial part of the axial lengths of the brush  17 . Thus, the comb shaped members  104  and  105  have a length along the axial direction and a width perpendicular thereto (seen in the cross-sectional view in  FIG. 17 ). The comb shaped members  104  and  105  further have in their width direction a free edge  106  respectively engaged with the bristles  21  of the brush  17 . The opposite edge of the comb shaped members  48  and  49  is respectively connected or integrally formed with the housing  30  forming the dust box  28 . 
     The comb shaped members  104  and  105  are respectively formed along the length direction with a plurality of teeth separated by recesses. In other words, the comb shaped members are configured of a plurality of merlons and crenels. Alternatively, the comb shaped members  104  and  105  may have a plate-shaped with a straight edge engaging with the bristles  21 . The comb shaped members  104  and  105  are respectively angled or inclined with their width direction in opposite directions towards each other. To put it differently, the comb shaped members  104  and  105  are inclined in different directions with respect to an axis of symmetry  103 . As is the best shown in  FIG. 17 , the projections of the width directions of the comb shaped members  104  and  105  intersect at the point of intersection  108  on the line of symmetry  103 . Also the projections  107  of the width directions of the comb shaped members  48  and  49  intersect in the same point of intersection  108  on the line of symmetry  103 . 
     Moreover and as shown in  FIG. 17 , the free edges  99  of the comb shaped members  48  and  49  and the free edges  106  of the comb shaped members  104  and  105  face each other. To put it differently, the comb shaped members  48  and  49  and the comb shaped members  104  and  105  are directed towards each other, respectively. 
     As described above, the brush  17  may rotate in opposite directions and depending on the movement of the support unit. Thus, if the brush rotates clockwise, the first comb shaped member  48  serves for removing or loosening the particulate matter from the bristles  21 , whereas if the brush rotates counterclockwise, the second comb shaped member  49  provides for this effect. Thus, a very effective cleaning of the bristles  21  may be affected no matter in which direction the brush  17  rotates. 
     Further and in one or more embodiments of  FIG. 17 , when the brush  17  is rotated clockwise in  FIG. 17 , the bristles  21  engage with the third comb shaped member  104 . As a result, the bristles  21  are temporarily retained by the third comb shaped member  104  and thereby bent because of the further rotation of the brush  17  and particularly its body  19 . After the bristles  21 , temporarily retained by the third comb shaped member  104 , have passed by the third comb shaped member  104 , the bristles  21  spring back to the original, e.g. radial position. Thereby, any dust adhering to the bristles from the filter  12  is thrown from the bristles  21  and scattered into the dust box  28  as relatively small dust particles. 
     The remaining amount of dust still adhering to the bristles downstream of the third comb shaped member  104  in the rotating direction is scratched of the bristles  21  by the first comb shaped members  48  as described above. Yet, because of the reduced amount of dust adhering to the bristles  21  at this stage, the formation of dust lumps is reduced, whereby the clogging of the comb shaped members  48  and long dust lumps which are difficult to be removed from the dust box  28  can be prevented. 
     If the brush  17  is rotated counterclockwise in  FIG. 17 , the fourth comb shaped member  105  is active and functions in the same manner as the third comb shaped member  104  as described above. Also and as described earlier, the second comb shaped member  49  is active and takes over the function of the first comb shaped member  48 . 
     Furthermore, a first and second separation roller  53  and  54  are provided wherein the first separation  53  is associated to the first comb shaped member  48  and the second separation roller  54  is associated to the second comb shaped member  49 . Both separation rollers  53 ,  54  extend parallel to the axis of rotation  19  of the brush  17 . The separation rollers  53 ,  54  are respectively provided in order to remove the particulate matter loosened by the comb shaped members  48 ,  49  from the bristles  21  away from the brush  17  so that the particulate matter falls into or towards the bottom  100  of the dust box  28  by gravity. For this purpose, the separation rollers  53 ,  55  are rotated in the same direction as the brush  17 . In particular, the separation rollers  53 ,  55  is there a centrifuge particulate matter coming into contact with the separation rollers away from the brush  17  and the comb shaped members  48 ,  49  or at least create an air flow blowing the loosened particulate matter away. In this context, the separation rollers  53  and  54  are located on an outer side of the comb shaped members  48 ,  49  with respect to the axis of rotation  19  of the brush  17 , respectively. 
     According to one or more embodiments, two seventh gears  79  (see  FIG. 13 ) are provided meshing with the centrally arranged fifth gear  77 . These seventh gears  79  are respectively attached to the axes of rotation of the first and second separation rollers  53  and  54  at their axial ends. As the sixth gear  78  also the seventh gears  79  will be rotated automatically by movement of the support unit along the rack  72  and rotation of the fourth gear  76 . The axial ends of the separation rollers  53  and  54  opposite to the seventh gears  79  are rotatably accommodated in the collars  98  at the bottom of the support unit (lower support  43   b ) as shown in  FIG. 14 . In the above embodiments, when the support unit moves to the right, both seventh gears  79  are rotated counterclockwise, whereas both seventh gears  79  are rotated clockwise when the support unit moves to the left. Accordingly also in this case, the motor  46  is used to rotate the first and second separation rollers  53 ,  54  in the same direction as the brush  17 . 
     The support unit further comprises the housing  30  and a partition  68 . The housing  30  together with the partition  68  forms a chamber accommodating the brush  17 . That chamber is communicated with the dust box  28  in which particulate matter brushed off the filter  12  or its filter surface is retained before being removed by a vacuum source as explained later. The housing  30  together with the partition  68  further defines an opening  31  through which a portion of the brush  17  extends (see  FIG. 9 ). Thereby it is ensured that the brush protrudes from the housing  30  and is capable of contacting and brushing the filter surface  13 . Further, the housing  30  prevents particulate matter removed from the filter by the brush from being distributed throughout the filter cleaning device. Moreover, the housing  30  shields the dust box  28  and prevents particulate matter already collected in the dust box from being sucked from the dust box during the air conditioning operation. In addition, the relatively small opening  31  enables to reduce exchange of air at the dust box  28 , when removing the particulate matter from the dust box using a vacuum source. Thus, building up a relatively high under pressure is simplified. 
     Moreover, a suction section  32  as shown in  FIGS. 6, 8 and 9  is provided for removing the dust accumulated in the dust box  28  from the dust box. The suction section  32  comprises an outlet  37 . The outlet  37 , which may be a circular opening, has a center axis  38 . The outlet  37  is communicated with the dust box  28  via a cleaning path  80  having a cleaning opening  81  (see  FIG. 14 ) opening into the dust box  28 . 
     The suction section  32  further comprises a suction opening  33  fixed to the casing  11  of the filter cleaning device. In one or more embodiments, a fitting extends from the casing  11  and forms the suction opening  33  at the inside of the casing  11 , The fitting further has an exhaust opening  82  at the outside of the casing  11 . The suction opening  33  and the exhaust opening  82  may be both circular. The center axis of at least the suction opening  33  is congruent with the center axis  38  of the outlet  37 . 
     In one or more embodiments, a suction socket  42  (see  FIG. 2 ) may be communicated to the suction opening  33  via a hose  83  connected to the exhaust opening  82  at one end and to the suction socket  42  at the other end. The suction socket  42  may be configured to receive a fitting and/or a hose of a common vacuum cleaner and may be accessible in the false ceiling U or a false wall without the necessity to remove a part of the ceiling or a wall. Further, it may as well be conceivable to dispose the suction socket  42  outside the room to be conditioned via the air conditioner. Thus, cleaning personal is enabled to remove dust from the dust box  28  without having to enter the room to be conditioned such as the hotel room or a meeting room. 
     Once the cleaning operation is finished, the cleaning unit moves towards the left in  FIG. 8  until it reaches the parking position mentioned above. In this parking position the outlet  37  is communicated with the suction opening  33 , whereby the dust box  28  is communicated via the cleaning opening  81 , the cleaning path  80 , the outlet  37  to the suction opening  33  and, hence, to the exhaust opening  82 . 
     A sealing member  34  is provided at an area  35  surrounding the outlet  37  and/or an area  36  surrounding the suction opening  33 . Upon movement of the cleaning unit to the parking position, the sealing  34  is sandwiched and pressed between the area  35  and the area  36  and the outlet  37  is communicated with the suction opening  33 . In order to be sufficiently pressed, the stepping motor  46  is controlled by the control box  66 . Upon a feedback of a positioning sensor (such as a limit switch) that the cleaning unit has reached the parking position the control is configured to move the cleaning unit towards the left (in the direction of the parking position) at least one additional distance (one or more steps of the stepping motor). Accordingly a relatively tight and reliable seal can be achieved. 
     Additionally or alternatively to the sealing  34 , a shroud  84  may be provided surrounding the outlet  37  or the suction opening  33 . Upon reaching the parking position, the shroud  84  enters into the suction opening  33  and engages with an inner circumferential surface of the suction opening  33 , thereby achieving a sealing effect. However, to achieve a reliable and sufficient sealing, relatively small tolerances regarding the inner diameter of the suction opening  33  and the outer diameter of the shroud  84  are required. For this reason, the above-described sealing  34  is used. In one or more embodiments, the shroud  84  may, hence, dispense the sealing function and merely provide for centering the outlet  37  relative to the suction opening  33 . For this purpose, the shroud  84  may have a tapering  85  towards the suction opening  33 , whereby upon engagement of the shroud  84  in the suction opening  33  a self-centering effect is obtained. 
     Moreover, a lid  39  is fixed to the casing  11  as best shown in  FIGS. 7 and 8 . More particular, the lid  39  in one or more embodiments is rotatably fixed to the casing  11  about the rotation axis  85 . In one or more embodiments, the lid  39  is comprised of a covering  86  forming a cavity  41  and an actuating arm  40 . The covering  86  and the cavity  41  are located on one side relative to the axis  85  and the actuating arm  40  is located on the other side relative to the axis  85 . The lid  39  is urged about the axis  85  counterclockwise by a leg spring  87  (third elastic member). In particular and with reference to the following description of its function, the lid  39  is urged towards an opening position. 
     When the cleaning unit is moved towards the parking position (e.g. from the position in  FIG. 8  towards the left), the left end of the housing  30  or any other part of the cleaning unit comes in contact (engages) with the actuating arm  40 . Accordingly, the cleaning unit pushes the actuating arm  40  in a clockwise direction about the axis  85 . Thereby the covering  86  is rotated toward the housing  30  against the force of the leg spring  87 . In the parking position, shown in  FIGS. 5 and 6 , the covering  86  closes the opening  31  of the housing  30  and the cavity  41  accommodates that portion of the brush  17  protruding from the opening  31 . Lid  39  is, thus, capable of preventing any particulate matter accumulated in the dust box  28  from leaving the dust box  28  and the housing  30  during air conditioning operation. 
     In this parking position also the outlet  37  and the suction opening  33  are communicated. Thus, upon plugging a fitting of a vacuum cleaner into the suction socket  42  and applying a suction force, particulate matter accommodated in the dust box  28  is sucked from the dust box  28 . Further and due to the pressure reduction within the dust box  28 , the covering  86  is sucked against the edge of the opening  31  of the housing. In one or more embodiments, it may, hence, well be to dispense the actuating arm  40  and to merely close the lid  39  by the suction force applied by the vacuum cleaner in the parking position. In one or more embodiments, however the opening  31  will only be closed during cleaning of the dust box  28  and the effect of preventing particulate matter from being drawn from the dust box  28  during the air conditioning operation is dispensed. Yet, closing of the opening  31  by the lid  39  also provides for a more effective cleaning of the dust box  28  as compared to a non-sealed opening. In particular, a higher under pressure may be built up within the dust box  28  leading to a more effective or more complete cleaning of the dust box  28  by the vacuum cleaner. 
     The cleaning unit further comprises the counter surface unit  67   b . The counter surface unit  67   b  comprises a counter surface (see  FIGS. 11 and 12 ). In one or more embodiments, the counter surface  22  is formed by the outer surface  25  of a cylinder  26 . The cylinder  26  is rotatably supported in a supporting unit formed by an upper support  43   c  and a lower support  43   d  connected by a back wall  88 . The support unit is configured very similar to that of the cleaning member unit  67   a  and comprises two upper wheels  45   c  and to lower wheels  45   d  wherein the wheels  45   c ,  45   d  and their connection are embodied in the same manner as described with respect to the cleaning member unit  67   a  and as shown in  FIG. 10 . Accordingly and in order to avoid repetition these elements are not described in more detail at this stage. Similar, motor  46  is also provided in the support unit ( FIG. 11 ). The motor  46  is with its axis connected to eighth gear  94  meshing with a ninth gear  95  again meshing with a tenth gear  96  meshing with the rack  72 . Thus, the support unit of the counter surface unit  67   b  is moved along the rack  72  upon operation of the motor  46  in the same manner as the support unit of the cleaning member unit  67   a  and further description is omitted. 
     The cylinder  26  comprises a cylinder axis  27  which is at the same time the axis of rotation of the cylinder  26 . The cylinder  26  has at its center in the axial direction an annular groove  24 . As can be best seen from  FIGS. 11 and 12  the annular groove  24  accommodates the longitudinal reinforcing rib  15  of the filter  12 . Thereby it can be ensured that the outer surface  25  of the cylinder reliably pushes the mesh  64  of the filter  12  against the bristles  21  of the brush  17  and closes the mesh  64  at the filter surface  14  in order to prevent particulate matter from being pressed through the mesh  64 . Certainly, a plurality of such annular grooves  24  can be provided if a plurality of longitudinal reinforcing ribs  15  is provided. 
     In one or more embodiments, the cylinder  26  is hollow. For ease of production, the cylinder  26  can be produced from half shells  89 . The half shells  89  are each half circular in cross section and, thus, a half cylindrical. The half shells may be at one end be connected by a living or integral hinge. In addition, the axis of rotation  27  may be integrally formed with one of the half shells  89 . For this purpose, two coaxial protrusions may extend from the axial end of the half shells in an axial direction. Thus, the cylinder  26  may be injection molded from plastic material. To form the cylinder  26 , the half shells  89  are rotated about the living hinge and fixed together by latches  90  at one of the half shells  89  and corresponding hooks  91  at the other one of the half shells  89 . Certainly also other methods for fixing the half shells may be used. Also the half shells may be formed separately and then be fixed together without the use of a living hinge. 
     Furthermore, the filter  12  may along its length not to be completely flat but bend in a direction towards the counter surface unit  67   b  and/or the cleaning member unit  67   a  or even wavy. Accordingly, it could happen that either the brush  17  comes out of contact with the filter surface  13  reducing cleaning efficiency or that the brush  17  is pushed into the filter surface  13  to heavily with the risk of damaging the filter. To cope with this problem, the cylinder  26  and hence the counter surface  21 , formed by the outer surface  25  of the cylinder  26 , is urged towards the filter surface  14 . 
     In one or more embodiments, the axis of rotation  27  of the cylinder  26  is guided in a long hole  92  (also see  FIG. 15 ). The longitudinal direction of the long hole  92  extends in a direction perpendicular to the filter surface  14 . Accordingly, the cylinder  26  may move in a direction perpendicular to the filter surface  14 . A leg spring  23  (as an example of a first elastic member) is provided in order to urge the cylinder  26  in a direction towards the filter surface  14 . More particularly, the axis of rotation  27  of the cylinder  26  is rotatably fixed to a carriage  93 . The carriage  93  is translationally movable in the long hole. Accordingly and even though the counter surface  22  formed by the outer surface  25  of the cylinder  26  is rigid in a radial direction, the movability of the cylinder  26  in a direction perpendicular to the filter surface  14  accommodates changes in the distance of the filter surface  14  to the outer surface due to unevenness of the filter  12  along its length. Accordingly the filter is always reliably pressed against the rotating brush  17  or more particularly its bristles  21  at a relatively constant force so that a high cleaning efficiency may be achieved without the risk of damaging the filter. 
     In one or more embodiments, the cleaning member unit  67   a  and the counter surface unit  67   b  are respectively formed independent and separate from each other. More particularly, the support units are formed separately. Accordingly, the filter cleaning device  10  may have a relatively low width (or height) being substantially dependent on the width of the filter  12 . However in one or more embodiments, the support units may also be connected above and/or below the frame  63  of the filter  12 . This would provide for the advantage that only one motor  46  would be required for both units  67   a ,  67   b.    
     In the following, the function of the above-described filter cleaning device will be explained. 
     In the non-cleaning operation and during air conditioning operation, the cleaning unit including the brush  17  and the counter surface  22  is positioned in the parking position shown in  FIGS. 2 to 6 . 
     First, the control considers whether cleaning operation is required. In this context, different parameters and can trigger that cleaning operation is required. In one or more embodiments, the cleaning operation is performed in a predetermined time interval. Alternatively, a sensor may be provided capable of measuring a degree of particulate matter on the filter such as a sensor capable of measuring a flow resistance of air flowing through the filter. The output of this sensor may be used by the control to trigger the cleaning operation. Certainly, also other para meters may be used for this purpose. 
     Once cleaning operation is started, the control in the control box  66  cooperates with the control of the air conditioner to temporarily stop the air conditioning operation. Subsequently, the motors  46  are activated. Accordingly, the cleaning member unit  67   a  and the counter surface unit are moved from the left to the right along the filter surfaces  13 ,  14  respectively, wherein the rotational force of the motors  46  is transferred via the gears  73  to  75  to the rack  72  and the gears  94  to  96  to the rack  72 . At the same time the brush  17  is rotated, wherein the translational movement of the support unit of the cleaning member unit  67   a  along the rack  72  is converted and transmitted via the gears  76 ,  77  and  78  to the axis of rotation  19  of the brush  17 , thereby rotating the brush  17  clockwise. Accordingly the bristles  21  brush particular matter from the filter surface  14  away from the filter surface  14  whereby the particulate matter is transferred by the brush  17  through the opening  31  into the housing  30  and subsequently falls into the dust box  28  by gravity. 
     In the housing  30 , the particulate matter is scrapped away from the bristles  21  by the first comb shaped member  48 . The first separation roller  53  being rotated by the gear  79  in a counterclockwise direction ensures that the particulate matter scrapped away from the bristles  21  by the first comb shaped member  48  is moved away from the bristles  21 . The thus separated particulate matter will then fall into the dust box  28  or particularly towards its bottom  100  by gravity and will be collected at the bottom  100  of the dust box  28  (lower support  43   b ). 
     The counter surface  22  formed by the outer surface  25  of the cylinder  26  is moved together with the brush  17  along the filter  12  being in contact with the opposite filter surface  14 . In particular, a line connecting the axis of rotation  27  and the axis of rotation  19  is perpendicular to the filter surfaces  13 ,  14 . Accordingly, the counter surface  22  supports the filter  12  at the side of the filter surface  14  so as to keep the mesh  64  in contact with the bristles  21  of the brush  17 . During the movement of the brush  17  and the counter surface  21  along the filter  12 , the counter surface  22  may compensate for any deviations of the filter  12  from an evenly flat shape in that it may move perpendicular to the filter surfaces  13 ,  14  within the long hole  92 . Further, as the counter surface  22  is urged towards the filter surfaces  13 ,  14  by the leg spring  23 , the bristles  21  are engaged with the filter surface  13  at a relatively constant pressure/force along the length of the filter. Accordingly, an efficient and reliable cleaning can be performed without the risk of damaging the filter. 
     Further, it is to mention that the counter surface  22  particularly the cylinder  26  is not actively driven or rotated, but rotates because of its frictional contact with the filter surface  14 . When the cleaning unit moves to the right, the cylinder  26  hence rotates in the same direction as the brush  17 , that is clockwise. Due to the rotation of the counter surface and its curved shape, the contact area and the friction between the contact area and the filter surface  14  is relatively low so that any damaging of the filter  12  by the counter surface  22  can reliably be prevented. 
     Once the cleaning unit has reached the end of the filter  12  opposite to the parking position, the rotation direction of the motors  46  is switched. This can for example be triggered by the cleaning unit moving against a limit switch, thereby switching the motors  46 . Yet, also other control mechanisms are conceivable. Switching the rotational direction of the motors  46  changes the rotational direction of all gears  33  to and  94  to  96 . Accordingly, the brush  17  is rotated counterclockwise as are the separation rollers  53  and  54 . During the movement to the left, the cylinder  26  is again rotated by frictional engagement with the filter surface  14 , however, now counterclockwise. During movement in this direction, the second comb shaped member  49  and the second separation roller  54  are active for scrapping the particulate matter from the bristles  21  and move the scrapped of particulate matter away from the bristles  21  for being collected in the dust box  28 . 
     The above process may be repeated as required until the cleaning operation is finished. If a command has been provided by the control in the control box  66  that the cleaning operation can be terminated, the cleaning unit is again moved to the parking position. During this movement and as previously indicated, the housing  30  of the cleaning unit engages with/comes into contact with the actuating arm  40  thereby pivoting the lid  39  around the axis  85  in a clockwise direction, whereby the covering  86  closes the opening  31  in the housing  30 . If the cleaning unit has reached the parking position which may be indicated to the control by the use of a sensor or a limit switch, the motors  46  are activated to perform at least one more step towards the parking position in order to press the sealing  34  and securely communicate the outlet  37  and the suction opening  33 . Subsequently, the cleaning operation is finished. 
     The cleaning personal in the premises in which the filter cleaning devices are mounted may in a regular interval then plug a fitting of the vacuum cleaner into the suction socket  42  and thereby apply a sucking force to the suction opening  33 , whereby particulate matter accumulated at the bottom  100  of the dust box  28  is sucked from the dust box  28  via the cleaning opening  81 , the cleaning path  80 , the outlet  37 , the suction opening  33 , the exhaust opening  82 , the hose  83  and the suction socket  42  into the vacuum cleaner. According to one or more embodiments, it may be conceivable to connect the control in the control box  66  to a network within the premises and to output a signal that the cleaning operation has been performed to the network so as to indicate to the cleaning personal that the dust box  28  is to be emptied. It is also possible to provide a visual indicator such as a light at the suction section  42 , which could indicate to the cleaning personal that emptying the dust box  28  is required (for example a red light for cleaning and a green light for non-cleaning requirement). Instead of using a predetermined interval as requirement for removing the particulate matter from the dust box  28  or triggering the necessity to empty the dust box  28  by the termination of the cleaning operation, sensors outputting information on the amount of particulate matter accumulated in the dust box  28  can be used. This information can be outputted to the network or used to control the visual indicator. In one or more embodiments, the suction section  42  is disposed outside the space to be conditioned, whereby the cleaning personal does not need to enter this space for emptying the dust box  28 . 
     As will be apparent from the above description, the filter cleaning device described above provides for a very efficient system. 
     Although the disclosure has been described with respect to only a limited number of embodiments, those skill in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present invention. Accordingly, the scope of the invention should be limited only by the attached claims. 
     REFERENCE SIGNS LIST 
     
         
           1 : Air conditioner 
           2 : Inlet 
           3 : Outlet 
           4 : Heat exchanger 
           5 : Fan 
           6 ,  7 : Air ducting 
           8 : Exit grating 
           9 : Inlet grating 
           10 : Filter cleaning device 
           11 : Casing 
           12 : Filter 
           13 ,  14  Filter surface 
         W: Width of the filter 
         L: Length of the filter 
           15 : Longitudinal reinforcing rib 
           16 : Cleaning member 
           17 : Brush 
           18 : Axial end of the brush 
           19 : Axis of rotation (cylinder axis) 
           20 : Body 
           21 : Bristles 
           22 : Counter surface 
           23 : First elastic member 
           24 : Annular groove 
           25 : Outer surface 
           26 : Cylinder 
           27 : Axis 
           28 : Dust box 
           29 : Direction of movement 
           30 : Housing 
           31 : Opening 
           32 : Suction section 
           33 : Suction opening 
           34 : Sealing 
           35 : Area surrounding the outlet 
           36 : Area surrounding the suction opening of the casing 
           37 : Outlet 
           38 : Center axis 
           39 : Lid 
           40 : Actuating arm 
           41 : Cavity 
           42 : Suction socket 
           43   a - d : Support 
           44   a - d : Guide 
           45   a - d : Wheel 
           46 : Motor 
           47 : Second elastic member 
           48 : First comb shaped member 
           49 : Second comb shaped member 
         LD: Length direction 
         WD: Width direction 
           50 : First tangent 
           51 : Second tangent 
           52 : Circle 
         α + : Positive angle 
         α − : Negative angle 
           53 : First separation roller 
           54 : Second separation roller 
           60 : Casing inlet 
           61 : Casing outlet 
           62 : Flange 
           63 : Frame 
           64 : Mesh 
           65 : Transverse reinforcing rib 
           66 : Control box 
           67   a - b : Cleaning unit 
           68 : Partition 
           69 : Axis of rotation 
           70 : Pivot 
           71 : Pivot arm 
           72 : Rack 
           73 : first gear 
           74 : second gear 
           75 : third gear 
           76 : fourth gear 
           77 : fifth gear 
           78 : sixth gear 
           79 : seventh gear 
           80 : Cleaning path 
           81 : Cleaning opening 
           82 : Exhaust opening 
           83 : Hose 
           84 : Shroud 
           85 : Rotation axis 
           86 : Covering 
           87 : third elastic member 
           88 : Back wall 
           89 : Half shells 
           90 : Latch 
           91 : Hook 
           92 : Long hole 
           93 : Carriage 
           94 : eighth gear 
           95 : ninth gear 
           96 : tenth gear 
           97 : Comb body 
           98 : Collar 
           99 : Free edge 
           100 : Bottom 
           101 : Side walls 
           102 : Teeth 
           103 : Axis of symmetry 
           104 : Third comb shaped member 
           105 : Fourth comb shaped member 
           106 : Free edge 
           107 : Projection of width direction 
           108 : Point of intersection