Abstract:
The invention relates to a fan-and-filter unit to be mounted in the wall of a switch cabinet or housing, and includes a fan unit inserted in a fan housing, a filter mat arrangement mounted upstream of the fan unit and a fan cover immobilizing the filter mat. An embodiment advantageous for operation of the fan-and-filter unit may be provided where the fan-and-filter unit has a filter mat monitoring unit which is designed to detect the service life and/or a degree of soiling of the filter mat arrangement and which includes an insert integrated into the fan housing or the fan cover and having an illuminated display visible from the exterior of the fan cover facing away from the fan unit and being designed to display at least exceeding of a predetermined or predeterminable service life and/or a predetermined or predeterminable degree of soiling.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a fan-and-filter unit to be mounted in the wall of a switch cabinet or housing, comprising a fan unit inserted in a fan housing, a filter mat arrangement mounted upstream of the fan unit and a fan cover immobilizing the filter mat. 
     A fan-and-filter unit of this type to be mounted in an opening of a wall of a switch cabinet or a housing is described in DE 198 60 433 B4. The fan-and-filter unit comprises a fan housing in which a fan unit with electromotor and fan wheel for suction of air from the exterior into the interior of the cabinet or for expelling air from the interior of the cabinet is arranged and which is covered towards the outer side by a louvre grid having horizontal lamellae and air outlet openings therebetween. A filter mat is inserted between fan cover and fan unit which in turn is retained at the fan cover by means of a supporting grid. The filter mat retains dirt particles present in the flow path and may become clogged more or less quickly, according to the field of use of the switch cabinet or housing, respectively, and depending on its construction, so that fan efficiency and filtering effect of the fan-and-filter unit may be restricted considerably over time. Thus, it is important to replace the filter mat every once in a while. This is easily forgotten by a user. 
     Another fan-and-filter unit of this type is shown in DE 93 06 032 U1, wherein also a cross-section of a filter housing may be recognized, which possesses an approximately funnel-shaped construction, so that even in a relatively small fan unit a relatively large air inlet or air outlet opening, respectively, results, which is located in the region of the wall of the switch cabinet or housing and is covered by the filter mat. 
     Another fan-and-filter unit is shown in DE 10 2004 013 318 B4, that fan-and-filter unit, however, being installed within a larger housing having air inlet and air outlet openings, and a specific flow channel is formed to avoid condensation problems. A filter housing and a fan housing are arranged vertically neighboured with respect to the vertical cabinet wall within the larger housing unit to form a vertical air duct. 
     A switch cabinet air-conditioning device is shown in DE 197 14 838 C2 comprising, inter alia, an air-conditioning unit in form of a fan as well as a filter mat monitoring means which is part of a superordinate switchgear cabinet monitoring and controlling device in which error data and diagnostic data including switched-on periods may be stored and which may be connected to a personal computer serving as an operating means via an interface. A filter mat monitoring unit of this type is relatively complex and mainly suitable for service staff. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object to provide a fan-and-filter unit of the type mentioned in the introductory which offers simplified maintenance also for the user. 
     This object is solved by the features of claim  1 . Hereby it is provided that the fan-and-filter unit has a filter mat monitoring unit which is designed to detect the service life and/or a degree of soiling of the filter mat arrangement and which comprises an insert integrated into the fan housing or the fan cover and having an illuminated display visible from the exterior of the fan cover facing away from the fan unit, and designed to display exceeding of a predetermined or predeterminable service life and/or a predetermined or predeterminable degree of soiling. 
     By this configuration, the fan-and-filter unit itself is provided with a filter mat monitoring unit which may be easily controlled by a user or operating staff and which, due to its compact construction, is installed almost not influencing anything and offers a well-recognizable display of state to the user and to operating personnel. 
     For functioning of the filter mat monitoring unit, it is advantageously provided that the filter mat monitoring unit comprises a timer unit for determining the service life of the filter mat arrangement and/or a soiling sensor means having at least one sensor element for determining the degree of soiling of the filter mat arrangement as well as a monitoring electronic to analyze signals output by the timer means and/or the soiling sensor means and to produce at least one drive signal for the illuminated display. For a combination of timer means and soiling sensor means, an increased reliability of the filter mat diagnostics may be achieved, and the illuminated display may be driven either based on a signal output by the soiling sensor means or the timer means or on the basis of a signal based on a previous calculation of the signals output by the soiling sensor means and the timer means. In this way, the illuminated display may be driven with a control signal for replacement of the filter mat and produce a corresponding warning indication after expiration of a maintenance period and/or when exceeding a predetermined degree of soiling. 
     An embodiment advantageously adjusted or adjustable to different applications of a switch cabinet or a housing consists in that input means are provided so that different set values for operating conditions of the switch cabinet or housing or directly service lifes or degrees of soiling for exchanging the filter mat arrangement may be input. When inputting said values for operating conditions of the switch cabinet or housing, the filter mat monitoring unit determines in a monitoring electronics an appropriate operation period or a threshold for a degree of soiling, wherein e.g. in a dust or humidity loaded environment a shorter operation period until filter exchange is predefined. 
     If it is provided that the illuminated display includes a light emitting diode arrangement to emit light of at least two different colours, an indication of a forthcoming filter exchange may be given to the user or service staff, respectively, already before expiration of a maintenance interval or before reaching an inadmissible degree of soiling. For example, a three-step colour display is advantageous, with green indicating a proper filter mat condition, yellow indicating a forthcoming filter mat exchange and red indicating a required filter mat exchange, wherein a particularly urgent filter mat condition may additionally be signalled by a flashing display. 
     By the feature that the timer means comprises an operating timekeeper for fan operation, the maintenance interval may be adjusted to the actual operating time of the fan unit (aggregated switch-on states of the fan motor), or the operating time of the fan may be considered for weighting (reduction or extension) the maintenance interval. Also here a compensation with the signal of the soiling sensor means or a parallel analysis thereof for producing the drive signal for the illuminated display is possible. 
     Those features contribute to a compact simple construction so that all components of the filter mat monitoring unit except at least one sensor element and/or an external electric power supply are received by the insert. 
     An advantageous embodiment consist in particular in that all components of the filter mat monitoring unit including their electric power supply are received by the insert. If the insert is integrated into the fan cover, it can be completely removed from the fan housing, when exchanging filter mats, in an easy way. Energy consumption which is as low as possible is supported in combination with the light emitting diode arrangement as an illuminated display, wherein a small unit for electric power supply is sufficient. 
     Another advantageous embodiment consists in that the timer means and/or the soiling sensor means comprises a detector means for detecting the operating time and/or the operating conditions of the fan unit which is coupled to the fan unit through a wired or wireless connection for signal detection and which supplies detection signals to the timer means, the operating time and/or the operating state of the fan unit since the last filter exchange being determined on the basis of those detection signals. On the basis of the signals from the detector means, operating time or operating states (e.g. high load or low load), respectively, of the fan unit may be included when producing the drive signal for the illuminated display, e.g. to include the determined operating times of the fan and/or e.g. to draw conclusions with respect to the degree of soiling from load variations of the fan motor for increasing filter mat soiling. 
     Advantageous configuration variants consist in that the soiling sensor means includes a flow sensor, a pressure sensor, a temperature sensor, an optical sensor, an electric field sensor, a magnetic field sensor or an electric conductivity sensor or a combination of at least two such sensors, wherein the sensors comprise one or more sensor elements. An optical sensor may be embodied e.g. with light emitter and light receiver as a sensor measuring reflected light or as a transmission sensor, an electric field sensor as a capacitive sensor, an electric conductivity sensor or resistivity sensor, respectively, as a current or voltage measuring sensor having e.g. two spaced electrodes in contact with the filter mat, in particular when conductive ingredients are contained in the filter mat, such as, e.g., in an arrangement for electromagnetic shielding, or resistance variations result in a humid environment. 
     An embodiment advantageous for construction consists in that the insert comprises at least one receiving chamber for an electric power supply unit, for the timer means, for the monitoring electronics and/or for at least one sensor element. 
     Further advantageous provisions consist in that the insert is attached to the fan cover from inside or outside, in particular detachably snapped in or screwed thereto or adhered thereto. 
     Advantage for construction further result by forming a recess adapted to the insert in the fan cover. 
     For function and operation further those provisions are advantageous that the recess is arranged in the region of a grid structure with air outlet openings of the fan cover. For example, the insert may advantageously be combined with a manufacturer&#39;s logo formed as an insert and may simultaneously be used as an outer surface of a cover side of the insert for applying the logo. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in detail below with the aid of exemplary embodiments with reference to the drawings. 
         FIG. 1  shows a perspective illustration of an exploded fan-and-filter unit, 
         FIG. 2  shows a rear view of a fan-and-filter unit, 
         FIG. 3  shows a section of the fan-and-filter unit in the region of a fan cover from a rear side thereof, 
         FIG. 4  shows different views of an insert of the fan-and-filter unit, 
         FIG. 5  shows a fan unit of the fan-and-filter unit with two different flow directions of sucked and exhausted air, and 
         FIG. 6  shows a schematic illustration of a filter mat monitoring unit and a fan motor connected to a fan control. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a fan-and-filter unit  1  in a perspective illustration consisting of a fan housing  10  having a fan unit  50  with fan motor  51  installed therein (cp.  FIG. 2 ), a filter mat arrangement  20  and a fan cover  30  and further comprising a filter mat monitoring unit  40 . 
     Fan housing  10  possess, on its front side facing to fan cover  30 , a large, for example rectangular or square, opening which is surrounded by a continuous rectangular or square, respectively, frame and tapers rearwardly like a funnel with wall sections adjoining the frame and thus comprises a frustoconical shape, wherein a parallel rear side facing away from the front side is closed by a wall section. A round opening is provided in the rear side wall section of filter housing  10  which is surrounded by a cylindrical section protruding rearwards which accommodates the fan motor and a fan wheel driven thereby. Fan unit  50  is provided with a protective grid on its front side and advantageously also on its rear side. 
     Presently, filter mat arrangement  20  is comprised of two filter mats, namely a standard filter mat (A) and a fine filter mat (B) and covers completely the front opening of fan housing  10 . Alternatively, filter mat arrangement  20  may comprise only one or more than two filter mats. Further, embodiments of the filter mat arrangement  20  with more or less porous mat structure, membrane-like mat structure, e.g. for shielding humidity in damp rooms and/or with electromagnetic shielding effect may be used which may be inserted as additional filter mats and wherein a filter mat may possess one or more of these characteristics. For example, electrically conducting components, such as conductive particles or conductive threads may be introduced into the filter mat, so that a corresponding electrical conductance or resistance, respectively, is associated therewith. Filter mat arrangement  20  may also be embodied more or less porous or permeable to air, respectively, thereby having a corresponding flow resistance for air flow which, however, should be as low as possible combined with filter characteristics as good as possible. Filter mat arrangement  20  is attached to the front opening of the frame surrounding fan housing  10 , e.g. with the aid of fan cover  30 , wherein it is previously fixed to the rear side of fan cover  30  by means of a holding device, e.g. in form of a grill-like holding grid at fan cover  30 . 
     Fan cover  30  is formed as a louvre grill having horizontal lamellae with downwardly sloping top side and air passage gaps (which are not visible in  FIG. 1 ) arranged therebehind or therebetween, wherein the lamellae form, with respect to the front side in cross-section, a sawtooth-shaped structure. Fan cover  30  is placed onto the front frame of fan housing  10  with its centre approximately in an imaginary extension of the rotor axis of fan unit  50  and is fixed, in particular snapped on, wherein, in a lower corner region, e.g. a biased lock finger, releasable by means of a tool, engages in an attached station of fan cover  30  into a mating locking receptacle of fan housing  10  in region of the front frame. Further, filter mat monitoring unit  40  with an illuminated display visible from the exterior is received within fan cover  30 , for example in an upper corner region. 
       FIG. 2  shows fan-and-filter unit  1  with fan unit  50  and fan motor  51  inserted into fan housing  10  from the rear side, while also in a transparent illustration of the rear side fan housing wall (assumed, not really present) filter mat arrangement  20  as well as filter mat monitoring unit  40  are visible. 
       FIG. 3  shows a section of fan cover  30  from a rear side thereof. In the region of the upper (or alternatively lower) edge of fan cover  30  in which lamellae and gap-shaped passing openings for air are present, a recess  31  is formed to the rear side of fan cover  30  which comprises two wall-like boundaries  32  parallel and perpendicularly to the lamellae vertically to the plane of the fan cover  30  and rounded, at its upper rim, by a horizontal edge of fan cover  30  and at its lower rim by a horizontal lamella wall. Guiding grooves  33 ,  33 ′ are formed within the boundaries  32 , approximately in its middle region, which extend recess  31  outwardly vertical to the plane of the fan cover  30 . As a whole, recess  31  forms a rectangular-like cavity which is merely rounded a little bit at its upper edge region and receives an insert  41  of filter mat monitoring unit  40 , wherein lateral guiding posts  43  of insert  41  engage into guiding grooves  33 ,  33 ′, as clarified in  FIG. 4 . 
       FIG. 4  shows an exemplary embodiment for insert  41  in a perspective illustration (bottom part) and (top part from the left to the right hand side) in a view from the right hand side, in a top view to a top side  47 , in a cross-sectional illustration from the left hand side and from the bottom. Insert  41  is symmetrical with respect to a vertical center longitudinal plane except an arrangement of illuminated displays  45  or receiving openings thereof, respectively. From a top side  47  which faces in an installed state of insert  41  to the front side of filter-and-fan unit  1  laterally moulded wall sections and resilient snap-lock fingers  42  with locking tabs  421  extend perpendicularly rearwards. Guiding posts  43  which protrude outwardly are formed to the wall sections. Cover side  47  is bounded by fitting sections  44  (somewhat rounded in the example) which are transverse with respect to the two wall sections, wherein snap-lock fingers  42  are moulded to a section adjoining cover side  47  which is offset rearwardly and which is, with its free edge away from the fitting section  44 , oriented to the front side, i.e. forms an angle of less than 90° with respect to the plane of the cover side  47 . Three receiving openings for illuminated display  45  which are neighboring in transverse direction are formed in cover side  47  or the wall of insert  41 , to include e.g. three light emitting diodes for differently coloured light (preferably red, yellow, green). Alternatively, e.g. only one receiving opening for an illuminated display, in particular light emitting diode, may be provided which may emit merely light of one colour or light of several colours for signalling depending on the control thereof. Further, a receptacle  46  for receiving components of filter mat monitoring unit  40 , such as e.g. one or more sensor elements, an electrical energy supply and/or electronic circuit components is arranged in the insert  41 , as in particular shown in the illustration on the upper right hand side. Receptacle  46  is open on its rear side facing away from cover side  47  and is bounded by cover side  47  or the walls thereof on its front side, by side wall sections laterally and by transverse wall sections between side wall sections and thus forms a rectangular cavity open to the rear side. 
     As shown in  FIG. 5 , fan units  50  may be driven by a corresponding control of fan motor  51  alternatively for sucking or exhausting air. If now the fan-and-filter unit is installed in the wall of a switchgear cabinet or housing, air for cooling may be sucked through the louvre grill of fan cover  30  into the switchgear cabinet or hot air may be exhausted therefrom. For installing the fan-and-filter unit, a cut-out is made in the wall of the switchgear cabinet or housing, respectively, adapted to the frame around the opening of fan housing  10 , so that the frame abuts to the wall like a flange with a continuous rim section, as shown in references DE 198 60 433 B4 and DE 93 06 032 U1 mentioned in the introductory, incorporated by reference. For exchanging filter mats, fan-and-filter unit  1  remains installed at the switchgear cabinet or housing, respectively, with its fan housing  10  and fan unit  50  accommodated therein, and only fan cover  30  is removed. Since filter mat monitoring unit  40  with insert  41  and relevant components is mounted within the fan cover, a separate mounting at the switchgear cabinet or housing thereof with illuminated display  45  is unnecessary, wherein mounting of the illuminated display  45  within fan cover  30 , in particular within insert  41 , is well recognizable for the user or the service staff from the outside of the switchgear cabinet or housing, in particular when a filter mat exchange is signalled by illuminated display  45 . 
     For exchanging filter mat arrangement  20 , it is regularly sufficient to remove fan cover  30  with a small distance from the frame of fan housing  10 , e.g. to drop it down. To this end, flexible connection wires of filter mat monitoring unit  40  may remain connected to the fan-and-filter unit  50  or a control unit thereof, respectively, or even to further control means of the switchgear cabinet or housing, wherein the length of the connecting wires must be chosen adequately. Alternatively, connecting means which are easy to detach may be present for connecting wires of the filter mat monitoring unit  40 , or filter mat monitoring unit  40  may even, without any connecting wires to fan unit  50  or switchgear cabinet or housing, respectively, completely be integrated into the fan cover  30  wirelessly. To this end, monitoring components  48 , sensor elements  481 , an electrical energy supply and/or a monitoring electronics  482  with corresponding electronic circuit components, as shown in  FIG. 6 , are partly or completely accommodated by insert  41 . 
     Filter mat monitoring unit  40  comprises e.g. a timer means for determining the service life of filter mat arrangement  20  and/or a soiling sensor means comprising at least one sensor element  481  and monitoring electronics  482  in which signals output by the timer means and/or the soiling sensor means can be processed and analyzed by means of a processing means and at least one drive signal for the illuminated display  45  can be produced. If the illuminated display is embodied e.g. as light emitting diode display, it will consume very little electrical energy, so that even the electrical energy supply may be miniaturized and accommodated in very confined spaces. As sensors, e.g. flow sensors, pressure sensors, temperature sensors, optical sensors based on reflection or based on transmission, electrical field sensors, such as capacitive sensors, magnetic field sensors, electrical conductivity sensors or resistance sensors, respectively, or a combination of at least two of those sensors, may be considered, wherein the sensors in turn may comprise one or more sensor elements, such as the optical sensor a light emitting and a light receiving element or the conductivity sensor two spaced apart electrodes to be contacted with the filter mat arrangement. Such sensors may also be used for the timer means for forming a detection unit by which the operation condition of fan unit  50  is detected to measure an operating time of fan unit  50  and to aggregate operating periods, so that the service life or the service state of fan unit  50  may be detected even without a wired connection to a fan controller  60 . Alternatively, a wired connection of filter mat monitoring unit  40  to fan controller  60 , e.g. for tapping a current signal or a voltage for determining the operation of fan unit  50  may be provided. 
     By means of said sensors, not only the operation time of fan unit  50  may be measured, but, in a more sophisticated embodiment of the monitoring electronics  482 , also the operation condition of the fan unit, e.g. whether it is often driven in a high load operation or mostly with low power. Such information retrieved from monitoring electronics  482  may then additionally be considered in the monitoring electronics  482  for evaluating the state of filter mat arrangement  20  and be used for signalling a filter mat exchange via illuminated display  45 . 
     In a simplest case, a fixed maintenance interval may be predefined by means of the timer means, and illuminated display  45  may be driven for signalling the filter mat exchange when the time interval expires. Alternatively or additionally, the degree of soiling of filter mat arrangement  20  may be detected by means of the soiling sensor means and, when a predetermined degree of soiling (threshold) is exceeded, a signal for filter mat exchange is output via illuminated display  45 . Additionally, the signals from the timer means and from the soiling sensor means may be analyzed in combination. An advantageous embodiment of filter mat monitoring unit  40  consists in that a service person may set different set values for operating conditions of the switchgear cabinet or housing, for example in an environment with high air pollution and humidity or low air pollution or low humidity. Thereby, input means and associated monitoring electronics  482  of filter mat monitoring unit  40  may be configured such that an operation period or a degree of soiling for filter mat exchange may also be directly predefined. 
     If filter mat monitoring unit  40  is equipped with a programmable integrated circuit, such as a microcontroller, different monitoring scenarios may be programmed and predefined in this way to control the illuminated display dependent thereon.