Abstract:
A cleaning appliance such as a vacuum cleaner includes a main body housing a motor and fan unit for generating a fluid flow. The main body also houses a removable pre-motor filter located upstream of the motor and fan and a removable post-motor filter located downstream of the motor and fan. It is beneficial to permit the user to be able to monitor the condition of both the pre-motor filter and the post-motor filter, and to remove and replace them as required, and so access to both filters may be provided. It is more important that the user checks the pre-motor filter as it gets dirtier than the post-motor filter. Therefore, the post-motor filter is not accessible or removable from the main body until the pre-motor filter is removed from the main body, by removing its housing.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of United Kingdom Application No. 0821763.0 filed Nov. 28, 2008, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a cleaning appliance, such as a vacuum cleaner. 
     BACKGROUND OF THE INVENTION 
     Vacuum cleaners are designed to separate dirt and dust from an airflow. In a typical vacuum cleaner an airflow generator (for example, a motor and fan unit) generates an airflow which draws dirt- and dust-laden air into the vacuum cleaner through a dirty air inlet. The airflow then passes through a form of separating apparatus to remove dirt and dust from the airflow. Some vacuum cleaners make use of a porous bag through which the dirty air is sucked so that the dirt and dust is retained in the bag while cleaned air is exhausted to the atmosphere. In other vacuum cleaners, cyclonic separators are used to separate dirt and dust from the airflow. 
     Irrespective of the type of separating apparatus used, there is a risk of a small amount of dirt and dust passing through the separating apparatus and being carried to the airflow generator. It is undesirable for dirt and dust particles to pass through the fan of an airflow generator because the fan may become damaged or may operate less efficiently. In order to reduce this problem, some vacuum cleaners include a fine filter in an airflow path between the separating apparatus and the airflow generator. This filter is commonly known as a pre-motor filter and is used to extract fine dirt and dust particles remaining in the airflow after it has passed through the separating apparatus. 
     During normal operation of a vacuum cleaner, fine dirt and dust may be deposited on the pre-motor filter and, after a period of time, it could become blocked. Blockages reduce the efficiency at which a vacuum cleaner operates. Therefore, the pre-motor filter will occasionally need to be replaced or cleaned in order to maintain the performance of the vacuum cleaner. In order to allow cleaning or replacement of the pre-motor filter, it is common for such filters to be removable from a vacuum cleaner. 
     It is also known to provide a filter downstream of the airflow generator. This is known as a post-motor filter, and is typically employed to filter carbon dust which may be generated by brushes on the motor, as well as allergens and any microscopic particles of dirt and dust remaining in the airflow. After a period of use, the post-motor filter may need to be cleaned or replaced. Typically, the post-motor filter will need such attention much less frequently than does the pre-motor filter. 
     It is beneficial to permit the user to be able to monitor the condition of both the pre-motor filter and the post-motor filter, and to remove and replace them as required. To this end, access to both of the filters may be provided. However, it is more important that the user checks the pre-motor filter as it gets dirtier than the post-motor filter. By providing access to both filters, there is a risk that the user will check only the post-motor filter and neglect the pre-motor filter. This could lead to detrimental performance of the cleaner, and possibly even damage to the motor and fan. 
     SUMMARY OF THE INVENTION 
     The invention provides a cleaning appliance comprising a main body housing a motor and fan for generating a fluid flow, a removable pre-motor filter located upstream of the motor and fan and a removable post-motor filter located downstream of the motor and fan, wherein the post-motor filter is not accessible or removable from the main body until the pre-motor filter is removed from the main body. 
     By preventing release of, or access to, the post-motor filter until the pre-motor filter is removed, the user is directed to check the pre-motor filter first every time. Thus, the condition of the filter that is more likely to be dirty is monitored by the user, before the user goes on to check the other filter. 
     Preferably, the pre-motor filter is located in its own housing, removable from the main body and the post-motor filter is not accessible or removable from the main body until the pre-motor filter housing is removed. The pre-motor filter housing may be releasable from the main body by a manually-operable catch. 
     Advantageously, the post-motor filter is located in its own housing on the main body having an openable door. The door may be connected to the post-motor filter housing by a hinge arranged to permit the door to pivot about its rotational axis and to move axially along the rotational axis. A catch may be provided to hold the door closed. 
     Preferably, a portion of the pre-motor filter housing, such as its catch, may be arranged to obscure or make inaccessible the catch for the door of the post-motor filter housing. 
     Separating apparatus for separating dirt and dust from the airflow may be provided and releasably held on the main body. The post-motor filter may not be accessible or removable until the separating apparatus is removed from the main body. However, the pre-motor filter may be removed and replaced regardless of whether the separating apparatus is held on the main body or removed from it. 
     At least one of the filters, and preferably both of them, may be washable. The filter may comprise one or more layers of filter media delimited by a deformable rim. 
     The term “cleaning appliance” is intended to have a broad meaning, and includes a wide range of machines having a main body, a fluid flow generator and a head for travelling over a surface to clean or treat the surface in some manner. It includes, inter alia, machines which only apply suction to the surface so as to draw material from the surface, such as vacuum cleaners (dry, wet and wet/dry), as well as pressure washing machines and shampooing machines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front view of a cleaning appliance constructed according to the invention, in the form of an upright vacuum cleaner; 
         FIG. 2  is a side view of the cleaner of  FIG. 1  showing the separating apparatus being removed; 
         FIG. 3   a  is a front perspective view of part of the cleaner of  FIG. 1  showing the pre-motor filter housing being removed; 
         FIG. 3   b  is a perspective view of the pre-motor filter housing of  FIG. 3   a , showing the pre-motor filter being removed; 
         FIG. 4  is a front perspective view of part of the cleaner of  FIG. 1  with the pre-motor filter housing removed; 
         FIG. 5  is a front perspective view of part of the cleaner of  FIG. 1  showing the door of the post-motor filter housing in an open position; 
         FIG. 6  is a perspective view of parts of the hinge of the door of  FIG. 5 ; 
         FIG. 7  is a side perspective view of part of the cleaner of  FIG. 1  showing the door of the post-motor filter housing in an open position; and 
         FIG. 8  is a front perspective view of part of the cleaner of  FIG. 1  showing the pre-motor filter housing being removed with the separating apparatus in place. 
     
    
    
     Like reference numerals refer to like parts throughout the specification. 
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to  FIG. 1 , a surface-treating appliance in the form of an upright vacuum cleaner is shown and indicated generally by the reference numeral  1 . The vacuum cleaner  1  comprises a main body  2  which includes a motor and fan unit  3  and a pair  4  of wheels. A cleaner head  5  is pivotably mounted on the lower end of the main body  2  and a dirty air inlet  6  is provided in the underside of the cleaner head  5  facing the floor surface. The main body  2  further includes a spine  7  which extends vertically upward and merges into a handle  8 . The handle  8  can be manipulated by a user to manoeuvre the vacuum cleaner  1  across a floor surface. The main body  2  further includes outlet ports  9  for exhausting air from the vacuum cleaner  1 . 
     Separating apparatus  10  is releasably held on the main body  2 . The separating apparatus  10  comprises a separator  11  and a collecting chamber  12 . The separating apparatus  10  is supported on the main body  2  above the outlet ports  9  and lies adjacent the spine  7 . The interior of the separating apparatus  10  is in communication with the dirty air inlet  6  through ducting  13  adjacent the spine  7 . The separating apparatus  10  can be removed from the main body  2  for emptying and for maintenance. 
     In use, the motor and fan unit  3  draws dirty air into the vacuum cleaner  1  via the dirty air inlet  6 . The dirty air is carried to the separating apparatus  10  via the ducting  13  adjacent the spine  7 . The separating apparatus  10  includes an upstream cyclone  14  in the collecting chamber  12 . An air inlet  15  is formed in the cylindrical side wall  16  of the collecting chamber  12 . When the separating apparatus  10  is held on the main body  2  of the vacuum cleaner  10 , the air inlet  15  is in communication with the dirty air inlet  6  and forms a communication path between the ducting  13  adjacent the spine  7  and the interior of the upstream cyclone  14 . The air inlet  15  is arranged tangentially to the upstream cyclone  14  so that the incoming air is encouraged to follow a helical path around the interior of the upstream cyclone. 
     A shroud  17  is located inwardly of the cylindrical side wall  16  of the upstream cyclone  14 . The shroud  17  comprises a cylindrical wall having a plurality of through-holes. The shroud  17  provides a communication path between the upstream cyclone  14  and a downstream cyclone assembly. 
     The downstream cyclone assembly comprises a plurality of downstream cyclones  18  arranged in parallel. In this embodiment, seven downstream cyclones  18  are provided. Each of the downstream cyclones  18  has a diameter smaller than that of the upstream cyclone  14 . Therefore, the downstream cyclones  18  are able to separate smaller particles of dirt and dust from the partially-cleaned airflow than the upstream cyclone  14 . Separated dirt and dust exits the downstream cyclones  18  and passes into the collecting chamber  12 . 
     Cleaned air then flows back up through the downstream cyclones  18  and enters a duct  19 . The cleaned air then passes from the duct  19  to a pre-motor filter  20 . The pre-motor filter  20  serves to trap any fine dust or microscopic particles which have not been separated by the two cyclonic separation stages  14 ,  18 . The downstream side of the pre-motor filter  20  communicates with the fan and motor unit  3 . This unit  3  accommodates a fan impeller which is driven by a motor to generate the suction airflow. The outlet of the fan and motor unit  3  communicates with a post-motor filter  21 . The post-motor filter  21  serves to trap any remaining particles in the airflow, as well as carbon particles from the motor. Air then exits the post-motor filter  21  and is exhausted from the vacuum cleaner  1  through the outlet ports  9 . 
     A handle  22  is located over the separating apparatus  10  and is arranged to allow a user to carry the vacuum cleaner  1 . When the separating apparatus  10  is released from the main body  2 , as is shown in  FIG. 2 , the handle  22  may also be used to carry the separating apparatus alone. With reference to  FIG. 2 , a user-operable button  23  is located on the separating apparatus  10  at the upper end portion of the handle  22 . By depressing the button  23 , the user releases a catch holding the separating apparatus  10  to the main body  2 . The user can then place the separating apparatus  10  over a suitable dirt and dust receptacle such as a dustbin for emptying of dirt and dust that has been collected in the collecting chamber  12 . 
     Through use over a period of time, one or both of the pre-motor filter  20  and the post-motor filer  21  may become clogged with dust or dirt. Continued use would lead to a restriction in the airflow through the filters  20 ,  21 , thereby causing a reduction in the efficiency of the vacuum cleaner  1 . In order to alleviate this, any filter that becomes clogged must be replaced or washed. Usually, the pre-motor filter  20  will need to be replaced or washed more frequently than the post-motor filter  21 ; this is simply because the post-motor filter is downstream of the pre-motor filter and therefore receives an airflow that is less dirty. It is important that the user is directed to remove, and check the condition of, the pre-motor filter  20  first. 
     With reference to  FIGS. 3 to 5 , the pre-motor filter  20  sits inside in a pre-motor filter housing  24  located alongside the motor and fan unit  3 . The pre-motor filter housing  24  is attached to the main body  2  of the vacuum cleaner  1  by a first catch  25 . The catch  25  comprises two user-operable buttons  26   a ,  26   b  located on opposing front and back portions of the pre-motor filter housing  24 . The user simply releases the catch  25  by placing a thumb and forefinger on respective buttons  26   a ,  26   b  and squeezing the buttons towards one another. Thus, the catch  25  for the pre-motor filter housing  24  is intuitive to use. The catch  25  is manufactured so as to be conspicuous to the user; it may be made, for example, of a different colour to the components surrounding it, or it may have some visual indicia to draw the user&#39;s attention to it. It may also incorporate depressions in the buttons  26   a ,  26   b  to indicate to the user the position of the user&#39;s digits required to operate the catch  25 . 
     When the pre-motor filter housing  24  has been released from the main body  2  of the vacuum cleaner  1 , the pre-motor filter  20  may be removed from the housing for replacement by a new filter, or for cleaning, as shown in  FIG. 3   b . A tab  27  may be provided on the surface of the filter  20  to aid the user in removing it. Conveniently, the pre-motor filter  20  may be manufactured such that it is washable by the user. In this way, the user can maintain the vacuum cleaner  1  without having to purchase replacement parts or requiring the services of an engineer. The pre-motor filter  20  comprises a plurality of filter portions  20   a  of the same size and circular cross section. The filter portions  20   a  are delimited by, and held adjacent one another by a deformable rim  20   b  formed around the edges of the filter portions. The deformable, pliable nature of the rim  20   b  means that the pre-motor filter  20  is flexible and capable of being squeezed by a user. The pliability of the rim  20   b  and the filter portions  20   a  facilitates an effective washing action, including the action of wringing out the filter to dry. 
     When the pre-motor filter  20  has been washed and dried, or when the user has acquired a new filter, the filter can simply be replaced in the pre-motor filter housing  24 . A lip  20   c  on the deformable rim  20   b  assists the user in replacing the pre-motor filter  20  in the correction orientation in the pre-motor filter housing  24 . The housing  24  can then be slotted back into its location near the motor and fan unit  3 . The catch  25  is biased so as to re-engage automatically when the housing  24  is replaced on the main body  2  of the vacuum cleaner  1 . 
     When the pre-motor filter housing  24  is removed from the main body  2  of the vacuum cleaner  1 , a second catch  28  on the main body becomes visible and accessible, as shown in  FIG. 4 . This catch  28  is located underneath, and to the side of, the separating apparatus  10 . When the separating apparatus  10  also is removed, the second catch  28  may be released by a user. This second catch  28  permits a door  29  to be opened. The door  29  is circular and lies in a generally vertical plane on the main body  2 . When the separating apparatus  10  is attached to the main body  2 , the door  29  lies within its footprint such that the door is hidden from the user. The door  29  is the opening of a second housing  30 , which housing accommodates the post-motor filter  21 . The door  29  incorporates the outlet ports  9  of the vacuum cleaner. 
     The second catch  28  comprises a flange  31  extending from the door  29  of the housing  30 . The flange  31  is bent downwardly so as to engage with a lip  32  on the post-motor filter housing  30 . The flange  31  is biased inwardly so as to retain the door  29  in a closed position against the post-motor filter housing  30 . In order to release the catch  28 , the user needs to pull on the flange  31  so that it flexes outwardly, away from the lip  32 . The door  29  can then be opened. 
     The door  29  is attached to the main body  2  of the vacuum cleaner  1  by a hinge  33 , which is shown in more detail in  FIG. 6 . The door  29  has been omitted from this drawing for clarity. The hinge  33  comprises an elongate pin  34 , which is mounted in a generally horizontal plane on the main body  2 ; and a sleeve  35 , which is formed on a side of the door  29 . The sleeve  35  of the hinge  33  and the flange  31  are formed on opposite sides of the door  29 . The sleeve  35  fits over the pin  34  and swivels around it, thereby allowing the door  29  to be swung open and closed. 
     The hinge  33  is provided with a cam  36 . In this embodiment, the cam  36  comprises a lug  37  on the end portion of the pin  34  nearest the spine  7  of the main body  2 . A co-operating tapered portion  38  is formed in the sleeve  35  of the hinge  33 . The cam  36  is arranged so that, as the door  29  is swung from the closed to the open position, the tapered portion  38  of the sleeve  35  bears against the lug  37 , thus constraining the sleeve to move linearly as it is further rotated. The cam  36  urges the sleeve  35  of the hinge  33 , and hence the door  29 , away from the spine  7  of the main body  2 . The door  29  moves by a combination of rotational and translational motion: the door pivots about the rotational axis  39  of the hinge and also moves along this axis. Hence, when manufacturing the vacuum cleaner  1  there is no need to provide sufficient clearance for the door  29  to open fully, as it automatically moves away from the main body  2  and any obstructions associated with it. This can be seen in the perspective view of  FIG. 7 . 
     Conventionally, the post-motor filter housing  30  and its door  29  has had to be located further forward on the main body  2  so that, when the door opens, it is clear of the spine  7  that extends upwardly from the main body  2 , and any other components on the main body. This arrangement of the hinge  33  permits the post-motor filter housing  30  to be located close to the spine  7 , allowing for a more compact cleaner  1  to be made. 
     When the post-motor filter housing  30  has been opened, as shown in  FIG. 5 , the post-motor filter  21  can be removed for replacement by a new filter, or for cleaning. Conveniently, the post-motor filter  21  may be manufactured such that it is washable by the user, in much the same way as the pre-motor filter  20 . When the post-motor filter  21  has been washed and dried, or when the user has acquired a new filter, the filter can simply be replaced in the post-motor filter housing  30 . The door  29  can then be swung back on its hinge  33  to the closed position. As it swings, the door  29  can also move linearly along the axis  39 , back towards the spine  7  of the main body  2  by virtue of the arrangement of the cam  36 . This permits the door  29  to assume its original position. The user then simply presses on the door  29  so that the lip  32  of the post-motor housing  30  bears against the flange  31  on the door  29 . The force of the lip  32  against the flange  31  causes it to flex outwardly so that the door  29  can be pushed fully closed. The flange  31  is biased so as to re-engage automatically with the lip  32  and thereby hold the door  29  in its closed position. 
     The filter housings  24 ,  30  and respective catches  25 ,  28  are arranged so that the catch  28  of the post-motor filter housing  30  is not accessible, let alone releasable, while the pre-motor filter housing  24  is in place on the main body  2 . Thus, the first catch  25  must be released, and the pre-motor filter housing  24  removed, before the second catch  28  may be operated by the user. However, when replacing the filters  20 ,  21 , the catches  25 ,  28  may be re-engaged in either order. For example, the user may decide to replace the post-motor filter  21  and then close the door  29 ; followed by replacement of the post-motor filter housing  24 . It is just as simple for the user firstly to replace the pre-motor housing  24 , re-insert the post-motor filter  21  in its housing  30 , and then close the door  29 . The position of the pre-motor housing  24  and the first catch  25  with respect to the post-motor filter housing  30  gives sufficient clearance for the door  29  to be closed; the flange  31  does not impinge on the pre-motor filter housing  24  during closing of the door. When the door  29  has been closed, it resumes its position behind the catch  25  of the pre-motor filter housing  24 , and so cannot be released again until the pre-motor filter housing has been removed from the main body  2 . 
     The first catch  25  may be released, and the pre-motor filter housing  24  removed, while the separating apparatus  10  is attached to the main body  2  of the vacuum cleaner  1 , as shown in  FIG. 8 . However, the separating apparatus  10  needs to be removed before the post-motor filter door  29  is openable, as the separating apparatus is mounted on the main body  2  directly over the door. This prevents the user from accessing the post-motor filter  21  more frequently than the user empties the separating apparatus  10 . 
     The invention is not limited to the detailed description given above. Variations will be apparent to the person skilled in the art. For example, alternative arrangements of the cam  36  may be employed. The hinge  33  may incorporate a screw thread arranged so that, as the door  29  turns, it also moves along the axis  39  away from the spine  7  of the main body  2 . Alternatively, a rack and pinion arrangement may be provided. 
     The hinge  33  need not incorporate a cam  36 . The pin  34  is longer than the sleeve  35 , and extends beyond the sleeve, away from the spine  7  when the door is in the closed position. Thus, if a hinge without a cam is employed, the user can elect to slide the door  29  axially along the rotational axis  39  in order that the door may open clear of any obstructions. 
     The hinge has been described with reference to opening the post-motor filter housing  30 . However, similar hinge arrangements may be employed to provide access for other components. For example, the pre-motor filter housing  24  may be connected to the main body  2  by such a hinge arrangement. A cover permitting access to the motor and fan may also be hingedly connected in this way. Such an arrangement gives the user access to components that may need attention without adding to the overall size of the cleaner. 
     The first catch  25  for the pre-motor filter housing  24  and the second catch  28  for the post-motor filter housing  30  have been described as separately and independently manually operable. However, the second catch  28  may be automatically released in dependence on removal of the pre-motor filter housing  24 . This may be effected by, for example, a protrusion on the pre-motor filter housing  24  arranged so that, as the housing is lifted, the protrusion bears against the flange  31 , flexing it away from the lip  32  on the post-motor housing  30 . In this manner, the second catch  28  and hence the door  29  are automatically released. Alternatively, the second catch may be mechanically linked to the pre-motor filter housing  24 . As a further alternative, an electromechanical arrangement may be employed wherein the second catch  28  is held in a locked position until such time as the pre-motor filter housing  24  is removed. A Hall sensor arrangement is suitable for this purpose. 
     The separating apparatus need not be a cyclonic separator. Other forms of separating apparatus could be used, for example, a porous bag or filter. Additionally, the separating apparatus need not be located in the collecting chamber. A separate collecting chamber may be provided. 
     The cleaning appliance need not be an upright vacuum cleaner. The invention is applicable to other types of vacuum cleaner, for example, cylinder machines, stick-vacuums or hand-held cleaners. Further, the present invention is applicable to other types of cleaning appliances, for example, a wet and dry machine or a carpet shampooer.