Patent Publication Number: US-8539638-B2

Title: Filter and vacuum cleaner having such a filter

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Patent Application No. DE 10 2010 016 788.6, filed May 5, 2010, which is hereby incorporated by reference herein in its entirety. 
     FIELD 
     The present invention relates to a filter with an indicator device which is acted upon by the air to be filtered and in which filtered material serves as an indicator. 
     BACKGROUND 
     EP 0 396 803 A1 describes a filter with an indicator device that is acted upon by air to be filtered and that displays a degree of saturation of the filter. 
     Vacuum cleaners, in particular electric vacuum cleaners designed for use in the home, nearly exclusively use multi-stage particulate filters. Typically, a pre-filter, preferably in the form of a dust bag, is provided upstream of a vacuum cleaner fan, and an exhaust filter is disposed downstream thereof to remove fine dust that has passed through the dust bag. The exhaust filter also collects, for example, the particles which are abraded from the carbon brushes or the like of the drive motor of the fan. Both filter stages are consumable items, which need to be replaced by a user of the vacuum cleaner. To this end, it is advantageous to give the user a reliable and usage-based indication of when the bag or the exhaust filter needs to be replaced as a result of an upper limit for the fill level or saturation being reached. For the dust bag, it is common to use sensors which operate based on the differential pressure principle. For the exhaust filter, it is known to use the time of use of the filter as a criterion for determining when replacement is necessary. For this purpose, a time counter may be used which is manually reset by the user after insertion of the exhaust filter and which, after a predetermined operating time has elapsed, indicates that the filter needs to be replaced. The algorithm and the controls and indicators needed for this are implemented in and form part of a vacuum cleaner control system. 
     German Patent Publication DE 102 29 796 describes a filter having a usage indicator which operates based on temperature-dependent integration. The color of the indicator changes in a temperature-dependent manner each time the vacuum cleaner is used for a prolonged period of time. German Patent Publication DE 602 057 53 T2 describes time-dependent usage indicators which need to be activated by a user by opening a liquid reservoir. A colored indicator liquid diffuses into an absorbent material which is provided in the usage indicator and which then changes color as a function of time and, therefore, is a measure for the period of use. 
       FIG. 1  shows, in a simplified schematic form, a conventional vacuum cleaner  10  having a dust chamber  12  in which may be positioned a dust bag  14 . Dust  18  is conveyed through a suction hose  16  to dust bag  14  and collected therein. Dust  18  is transported by air flow  20 , which is generated by a fan  22  (vacuum cleaner fan). Dust chamber  12  is closed by a dust chamber cover  24 . Finer fractions of dust  18 , which pass through dust bag  14 , are carried into a vacuum cleaner exhaust filter  26  by the exhaust air or vacuum air flow  20  of fan  22 . 
     Vacuum cleaner  10  includes a control processor  28 , which is in operative connection with a control and display unit  30  disposed on vacuum cleaner  10 . The signals from control and display unit  30  are used by control processor  28  to adjust the suction power of fan  22 , and thus, the amount of dust  18  that can be picked up by vacuum cleaner  10 . 
     In some designs of conventional vacuum cleaners  10 , an indication of an upcoming need to replace vacuum cleaner exhaust filter  26  is provided by control and display unit  30  based on, for example, the accumulated operating time of vacuum cleaner  10 , which is determined by control processor  28 . In a vacuum cleaner  10  having such a function, the operating time meter is reset via control and display unit  30  after replacement of vacuum cleaner exhaust filter  26 . 
     However, when the time of use is used as a criterion for determining when a filter needs to be replaced, the load actually placed on the filter is not, or not optimally, taken into account, because the linear time progression alone is not able to reproduce the actual usage behavior, which varies over time. 
     SUMMARY 
     In an embodiment, the present invention provides a filter including a filter medium, a filter inlet side, a filter outlet side and an indicator device. The indicator device is configured to be acted upon by air flow through the filter and is disposed adjacent to the filter medium and extends from the filter inlet side to the filter outlet side. The indicator device includes an air path starting from the filter inlet side, a viewing window covering the air path on the filter outlet side, and a flow-through usage indicator configured to receive filtered material and disposed in the air path and visible beneath the viewing window on the filter outlet side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An exemplary embodiment of the present invention will be described in more detail below with reference to the drawing. Corresponding objects or elements are identified by the same reference numerals in all figures. It is understood that neither this or any other exemplary embodiment should be construed as limiting the scope of the present invention. Rather, within the framework of the present disclosure, numerous revisions and modifications are possible, in particular such variants, elements and combinations, which, for example, by combining or altering individual features or elements or method steps described in connection with the general description and the, or each, particular embodiment, as well as the claims, and contained in the drawings, may be inferred by one skilled in the art with regard to achieving the objective, and lead, through combinable features, to a new subject matter or to new method steps or sequences of method steps. In the drawings: 
         FIG. 1  shows a conventional vacuum cleaner; 
         FIG. 2  shows a filter including an indicator device according to an embodiment of the present invention; 
         FIG. 3  shows another embodiment of a filter including an indicator device; 
         FIG. 4  shows another embodiment of an indicator device; 
         FIG. 5  shows yet another embodiment of an indicator device; and 
         FIG. 6  schematically shows two perspective views of a filter including an indicator device. 
     
    
    
     DETAILED DESCRIPTION 
     In an embodiment, an aspect of the present invention is to provide a filter with a device for generating a filter replacement or fill level signal that corresponds to the level of usage, or to the degree of saturation. 
     In an embodiment, the present invention provides a filter that may be used as a vacuum cleaner exhaust filter; i.e., a filter which is disposed in the exhaust air stream of the suction fan of an electric vacuum cleaner and functions, for example, as a fine particulate filter or hygiene filter and which is sometimes also referred to as “exhaust port filter” or “after-filter”. 
     An embodiment of the present invention provides a filter including at least one filter medium, a filter inlet side and a filter outlet side, the indicator device is advantageously acted upon by the air to be filtered. To achieve this, the indicator device is adjacent to at least one side of the or each filter medium and extends from the filter inlet side to the filter outlet side; the indicator device including an air path which starts at the filter inlet side and is covered by a viewing window on the filter outlet side; and a flow-through usage indicator located in the air path being visible beneath the viewing window on the filter outlet side. The usage indicator visible beneath the viewing window is used, for example, to collect the filtered material, and thus serves to indicate when the filter needs to be replaced or to monitor the fill level of the filter. 
     Accordingly, the filtered material itself is used for indicating when the filter needs to be replaced or for monitoring the fill level the filter. For this purpose, the indicator device is acted upon by the air to be filtered, so that material filtered from the air to be filtered can be collected in or on the indicator device and, as the amount of filter material increases, indicates the increasing degree of saturation of the filter. 
     The viewing window preferably bounds the air path of the indicator device on the filter outlet side, so that the air path is confined in this region and none of the air to be filtered and to act upon the indicator device can emerge in an uncontrolled manner from the filter and/or the indicator device. If the viewing window also functions as a deflector for the air flowing in the air path so that the air flow is directed through the usage indicator, the viewing window performs two functions at the same time, namely confining the air path at the filter outlet side and diverting the air flow through the usage indicator. The diversion of the air flow through the usage indicator causes the indicator device; i.e., the usage indicator forming part of the indicator device, to be acted upon by the air to be filtered. Since the usage indicator changes color according to the amount of filtered material collected, the color change occurring during deposition of such material on the usage indicator serves as a means for indicating when the filter needs to be replaced or for monitoring the fill level the filter. 
     If the air path leads from the viewing window via the flow-through usage indicator to the filter inlet side, the air to be filtered that is passed through the air path can be fed to the filter medium along with the remaining air, so that a common outlet is provided for both the air that flows through the filter medium directly and that which flows through the filter medium indirectly. 
     If, in the region of the filter inlet side, the air path terminates in a channel section oriented parallel to the filter inlet side, the end of the channel section functions as a nozzle directed toward the remainder of the filter. Because of the incident flow entering directly into the filter medium, this nozzle acts as a Venturi nozzle, as a result of which negative pressure is created at the outlet of the air path. Due to the negative pressure, the air to be filtered is drawn into the indicator device. 
     In an alternative embodiment, the air path leads via the usage indicator to the filter outlet side. In this case, preferably, an effective width of an inlet opening of the flow path at the filter inlet side is greater than an effective width of an outlet opening of the flow path, so that a sufficient amount of air which is to be filtered and which carries the medium to be filtered enters the indicator device and acts thereupon. 
     An embodiment of the invention includes a symmetric, in particular mirror-symmetric, arrangement of two air paths, which each include a viewing window and a usage indicator, or which have a common viewing window and a common usage indicator, and which may or may not have a separating layer provided therebetween. In a symmetric arrangement of two or more air paths, it is also possible to increase the effective width of an inlet opening of an air path at the filter inlet side. In addition, a symmetric, in particular mirror-symmetric, arrangement of two air paths which each include a viewing window and a usage indicator provides favorable conditions for the reading of the, or each, usage indicator because of the increased size of the viewing window. Specifically, it may be possible to read each of the usage indicators from different viewing angles. This facilitates the use of the filter and the indicator device thereof. 
     Reading of the usage indicator, and thus the use of the filter/of the indicator device, may also be facilitated if the viewing window includes a lens, in particular a lens having a suitably selected focal point to provide an enlarged representation of the usage indicator. 
     The filter discussed herein and described below may be used, in particular, in a vacuum cleaner, in particular an electric vacuum cleaner. Accordingly, in an embodiment, the present invention relates to a vacuum cleaner having a filter as described herein. The filter is particularly suited for electric vacuum cleaners because it retains small amounts of graphite, which is abraded from the carbon brushes of the fan motor. During the use of a conventional filter, this and other filtered material normally accumulates on the underside of the filter, where it changes the color thereof. However, this change in color is usually not perceived by the user, because the underside of the filter is not visible when in the installed position. In addition, the underside of the filter is usually covered by a dark, activated carbon-containing layer, so that accumulations of dirt are rather unlikely to attract the attention of the eye. In a filter having an indicator device which is disposed adjacent to one side of the filter medium and includes an air path in which is disposed a flow-through usage indicator, graphite particles enter the air path and are carried to the usage indicator therein, which takes the form of, for example, a fibrous filter mat, in particular a white panel filter, so that the usage indicator changes color over the useful life of the filter, and does so as a function of the amount of filtered material depositing therein. This change in color is visually perceivable by the user, allowing him or her to read the state of usage therefrom and to infer a need to replace the filter. 
     Overall, therefore, in an embodiment, the present invention also relates to the use of a filter, as discussed herein and described below, as a vacuum cleaner exhaust filter in the exhaust air stream of a suction fan of an electric vacuum cleaner. 
     In an embodiment, the present invention provides an indicator device in which a change in color or in a different optical property of a usage indicator provided on vacuum cleaner exhaust filter  26 , or combined with vacuum cleaner exhaust filter  26  in a different suitable manner, may be controlled by a quantity which correlates with the amount of dust picked up by vacuum cleaner  10 , and thus with the transfer of dust into exhaust filter  26 , so as to implement a filter replacement indicator or filter fill level indicator that is based on the level of usage; i.e., saturation. 
     In this regard,  FIG. 2  illustrates a filter  40  according to an embodiment of the present invention in a simplified schematic form, using the example of a vacuum cleaner exhaust filter  26  in the form of a HEPA filter. Accordingly, the partially visible filter  40  includes an indicator device  42 , which is acted upon by the air to be filtered and in which filtered material serves as an indicator. In the right portion of the figure, filter  40  including indicator device  42  is shown in an enlarged view. 
     Filter  40 , as illustrated, includes at least one filter medium, here a carbon filter  44  and a fibrous filter mat  46 . According to its geometry and installation direction, the filter has a filter inlet side  48  and a filter outlet side  50 . On filter inlet side  48 , the air which is to be filtered during operation of filter  40  is represented by a plurality of parallel arrows directed toward filter  40 . Indicator device  42  is adjacent to at least one side of filter  40 , or of the or each filter medium, and extends from filter inlet side  48  to filter outlet side  50 . The indicator device includes an air path  52 , which starts at filter inlet side  48  and is covered by a viewing window  54  on filter outlet side  50 . On filter outlet side  50 , a flow-through usage indicator  56  is located in air path  52  beneath viewing window  54  in a position visible to a user. Filtered material serves as an indicator because it is trapped by flow-through usage indicator  56 , where it remains visible, for example, due to different optical properties. If flow-through usage indicator  56  takes the form of, for example, a light-colored, in particular white, fibrous mat, fine dust, in particular particles which are abraded from the carbon brushes of the drive motor of vacuum cleaner fan  22 , stands out thereagainst with high contrast, so that the resulting change in a color of the surface of flow-through usage indicator  56  serves as a measure for a saturation of the overall filter  40 , or as an indication that filter  40  has reached a saturation limit. 
     During operation of filter  40 , as can be seen in the enlarged view on the right, which shows a portion of filter  40  including indicator device  42 , viewing window  54  functions as a deflector for the air flowing in air path  52  so as to direct it through or into usage indicator  56 . In the case of an air path  52  having the geometry shown in  FIG. 2 , the air path leads from viewing window  54  via flow-through usage indicator  56  to filter inlet side  48 . In particular, in the region of filter inlet side  48 , air path  52  terminates in a channel section oriented parallel to filter inlet side  48 , so that the end of the channel section functions as a nozzle  58  (Venturi nozzle) directed toward the remainder of the filter. During operation, the end of the channel section which is oriented parallel to filter inlet side  48  and acts as a Venturi nozzle produces a Venturi effect, creating negative pressure at the end of air path  52  so that, due to this negative pressure, the air to be filtered is drawn into air path  52 . 
     In a manner similar to  FIG. 2 ,  FIG. 3  shows a filter  40  including an indicator device  42 , in which air path  52  leads via flow-through usage indicator  56  to filter outlet side  50 . Apart from that, the components are the same as those shown in  FIG. 2 . Here, viewing window  54  and the end of air path  52  are both located at the surface of indicator device  42  that forms filter outlet side  50 . In the embodiment shown, an effective width of an inlet opening of flow path  52  at the filter inlet side is greater than an effective width of an outlet opening of flow path  52 . With regard to a practical ratio of the size of the inlet that of the outlet, the inlet size may be twice, three times, four times, etc., that of the outlet. 
       FIG. 4  shows a specific embodiment of indicator device  42  without a laterally adjacent or surrounding filter  40  ( FIG. 2 ;  FIG. 3 ). This embodiment includes a symmetric, in particular mirror-symmetric, arrangement of two air paths  52 , which each include a viewing window  54  and a flow-through usage indicator  56 . It is possible to use several viewing windows  54  and several flow-through usage indicators  56  for each of the symmetrically arranged air paths  52 , or to use one common viewing window and/or one common usage indicator. Moreover, a separating layer may be provided between the at least two symmetrically arranged air paths  52 . The dashed arrows indicate the flow path of the air to be filtered, so that in this configuration, too, indicator device  42  is acted upon by the air to be filtered. Since the air to be filtered flows through the or each usage indicator  56 , and because filtered material is trapped by the or each usage indicator, in this configuration of indicator device  42 , too, filtered material serves as an indicator for a degree of saturation of the filter  40  combined with the indicator device. 
       FIG. 5  shows an alternative embodiment for an indicator device  42 , in which air path  52  leads from filter inlet side  48  via flow-through indicator  56  to filter outlet side  50 . Thus, this configuration is similar to that shown in  FIG. 3 , but differs, for example, in the arrangement of flow-through usage indicator  56 , whose entire surface is here oriented horizontally. 
     The upper and lower portions of  FIG. 6  show, in schematic a simplified three-dimensional representation, a filter  40  having a laterally disposed indicator device  42 . However, the only parts of the combined configuration of indicator device  42  and filter  40  that are visible here are an exhaust port  60  at the end of air path  52  ( FIG. 2 ;  FIG. 3 ;  FIG. 4 ;  FIG. 5 ) and usage indicator  56 , which is located beneath a viewing window  54 . In this configuration, filter  40  including indicator device  42  is also accessible for viewing by the user. Accordingly, based on the amount of material filtered by usage indicator  56  and the resulting change in color of usage indicator  56 , the user is able to determine the degree of saturation of filter  40  and, if necessary, to replace the filter or have it replaced. 
     As an alternative, or in addition, to being visually checked by a user, usage indicator  56  may also be evaluated electronically, because its optical properties, in particular its reflective properties, change as the amount of filtered material increases. These optical properties can be evaluated using electronic sensor means operating in the manner of a reflective light barrier or the like. 
     In summary, the present invention provides a filter  40 , in particular a filter  40  which functions as a vacuum cleaner exhaust filter  26  and includes an indicator device  42  which is acted upon by the air to be filtered and in which filtered material serves as an indicator, for example in that the filtered material deposits on a fibrous mat, or the like, which allows flow therethrough and acts as a usage indicator  56 , and in that there, the filtered material represents or causes a change in color of usage indicator  56 , which can be visually perceived and thus evaluated by a user. 
     The scope of the invention is defined by the claims and back-references used in the dependent claims refer to the further development of the subject matter of the main claim by the features of the respective dependent claim. In addition, they may also include independent inventions, whose creation is independent of the subject matters of the preceding claims, and are not to be understood as renouncing attainment of an independent protection of subject matter for the features thereof. Furthermore, with regard to an interpretation of the claims in the case of a more detailed concretization of a feature in a subordinate claim, it is to be assumed that a restriction of said kind is not present in the respective preceding claims. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.