Patent Publication Number: US-2007108181-A1

Title: Domestic appliance with a linearly movable component

Description:
The invention relates to a domestic appliance with a linearly movable component.  
      A domestic appliance of this type is disclosed in DE 39 24 586 C2 and EP 0 465 800 B1 in each case; the disclosures of both of these documents are to be included in the current disclosure in their entirety.  
      DE 39 24 586 C2 relates to a domestic appliance in the form of a washing machine with a linearly movable component in the form of a detergent dispenser which can be moved by a electromagnetic drive means which can be operated by an electrical switching means. The switching means is, in particular, a key which can be operated by a user. The drive means is, in particular, an electromagnet with a movable armature or an electric motor which may be designed as a linear motor. Force may be transmitted within a correspondingly provided conventional electric motor by means of a pivoting lever or a toothed rack. EP 0 465 800 B 1 discloses a washing machine with a detergent dispenser which can be driven by an electric motor, in which force is transmitted by means of an actuating rod which can be wound at least over part of its length and in particular is toothed.  
      A domestic appliance which is designed as a domestic tumble dryer is disclosed in EP 1 050 619 B1, DE 44 03 183 C2 and DE 199 24 297 A1 in each case. The domestic appliance according to each of these documents contains a flat filter which serves to capture lint which is detached and carried along by a heated air stream during drying of the laundry which is agitated in a rotating drum. The lint which is captured on the filter have to be removed at regular intervals so that the flow resistance of the filter to the air stream remains sufficiently low and drying of the laundry is not adversely affected. To this end, a linearly movable scraper is provided in each case, which scraper is periodically operated in order to scrape off the captured lint from the filter. According to EP 1 050 619 B1, the filter is designed as part of an endless belt and, in a manner driven by a motor, can be moved past the stationary scraper over its entire effective length. The lint which is thus scraped off from the filter is collected in a reservoir.  
      According to DE 44 03 183 C2, the filter is designed as a stationary surface and a movable scraper brushes over it in order to scrape off lint which has been captured; the scraper is connected to a closing mechanism of the door of the tumble dryer by means of a corresponding transmission, so that the scraper is passed over the filter each time the door is opened. According to DE 199 24 297 A1, a domestic tumble dryer is provided with a self-cleaning lint filter, a corresponding sensor system and a correspondingly designed control device, in order to identify an impermissibly high flow resistance at the lint filter during a drying process and to remedy this by initiating self-cleaning of the lint filter. The disclosures of the three documents cited here are to be included in the current disclosure in their entirety.  
      Each of the domestic appliances described in one of the abovementioned documents is distinguished by a drive for a functionally relevant, linearly movable component and therefore meets the requirements of a user who is interested in a certain degree of convenience when operating the domestic appliance. However, each of the described drives is disadvantageous both in terms of the mechanics employed and also in terms of the costs involved.  
      Accordingly, the invention which will be described below is based on the object of providing a domestic appliance of the type mentioned in the introduction which manages with a drive which is simpler and more cost-effective than any of the known domestic appliances.  
      In order to achieve this object, the invention specifies a domestic appliance with a linearly movable component, wherein, according to the invention, the component can be moved by means of a drive band.  
      A drive band is a preferably convex strip which is produced from a highly flexible metal, in particular a suitable steel, and can transmit a shearing force in addition to a tensile force and is conventionally used as a tape measure which can be rolled up. Said drive band can be bent relatively easily and reversibly in a plane perpendicular to its transverse direction, with any convex shape which may be present disappearing at a bending point. The stability of the tape under shearing stress is largely maintained at a bending point.  
      The invention is based on the knowledge that the use of a drive band permits the guide elements for a drive of a linearly movable component to be substantially simplified, with the provided elasticity creating a high degree of design freedom for guidance and storage of the drive band. The remaining limited buckling resistance contributes to the inherent reliability of the drive since the drive band can buckle and relieve the load on the motor if the movable component were to get stuck at an unforeseen obstruction on its route.  
      The drive band preferably has a convex shape, as a result of which it is deformed to form a shallow channel. A drive band of this type can be deformed relatively easily in a reversible manner in a plane perpendicular to its transverse direction, in particular bent about a relatively small radius (with the convex shape disappearing at a bending point), but is difficult to deform perpendicular to this plane. A convex drive band accordingly has a particularly high inherent stability and can therefore be guided with a particularly low degree of outlay and its stability under shearing stress is particularly high; a drive which operates with this drive band is therefore distinguished by a particularly high innate functional reliability or inherent reliability since the drive band can buckle and relieve the load on the motor in the drive if the movable component were to get stuck at an unforeseen obstruction on its route.  
      The drive band likewise preferably has a perforation in which a pinion which can be driven by a motor engages.  
      The drive band in the domestic appliance is particularly preferably also bent. This means that the drive band can be used under conditions where space is limited.  
      According to another preferred refinement, the drive band is produced from steel and more advantageously has a coating comprising a slip agent, in particular PTFE plastic. This facilitates movement of the drive band in the domestic appliance and ensures reliable operation over a long period of time.  
      According to one preferred refinement, the domestic appliance is designed as an apparatus for drying laundry by means of an air stream and has a drum for holding the laundry and a duct system for conducting the air stream, with the duct system having a section which is arranged at the outflow end of the drum and in which the air stream is conducted in a downward direction and in which a filter for capturing lint from the air stream is arranged and the filter has an associated scraper for scraping off lint which have been captured, and with the scraper being the component which can be moved by the drive band.  
      The filter is preferably a channel which is arranged approximately horizontally and is curved in the downward direction, and the scraper is a foil which can be resiliently supported on the filter and is bent in accordance with the channel. The filter, which in an apparatus from the prior art has to cover a comparatively large surface area corresponding approximately to an entire opening in the drum, is redesigned to form a comparatively compact component in the form of a channel which can be arranged, in particular, below a charge opening for the drum in the end plate of a tumble dryer which is otherwise of customary design. The end plate firstly provides a support structure for a front face of the apparatus and a front support for the drum, and secondly supports a door for closing the drum. The shape selected for the filter provides a considerably enlarged surface compared to a flat filter and thus provides relatively little flow resistance to the air stream flowing through it. In this case, the shape of the cross section of the channel is of little importance, with a cross section which is predominantly flat and, in particular, corresponds more or less to a curve of a conical section proving expedient and appropriate. The curved shape provides the filter with stability and means said filter can be easily and reliably cleaned at regular intervals by means of a correspondingly designed scraper. Accordingly, the section of the duct system with the filter is preferably extended by an end plate, with the filter also being arranged in the end plate.  
      In addition, the scraper is in a rest position at a first end of the channel and a chute for holding lint which have been-scraped off is provided at a second end of the channel.  
      In addition, the filter is preferably supported on a grid-like filter support. As a result, spring forces which the foil exerts on the filter are absorbed and the load on the filter is reduced. 
    
    
      Exemplary embodiments of the invention are explained below with reference to the drawing, in which, in detail,  
       FIG. 1  shows a perforated drive band which can be driven by a pinion;  
       FIG. 2  shows a schematic cross section through a tumble dryer; and  
       FIG. 3  shows a partial view of an end plate of a tumble dryer, provided with a filter and a scraper as well as a reservoir for holding lint which have been scraped off. 
    
    
      Corresponding parts of the tumble dryer are each provided with the same reference symbols in all of the figures of the drawing.  
       FIG. 1  shows a detailed view of a drive band  12  for driving a linearly movable component  8 ,  9  (not illustrated in  FIG. 1 , cf. subsequent figures) of a domestic appliance. The straight sections of the drive band  12  are convex, that is to say are provided with a certain curvature, with the curvature disappearing in a reversible manner when the drive band  12  is bent; the bent section of the drive band  12  therefore does not have a convex shape. The drive band  12  is provided with perforations  31  of which only some are shown and in which the pinion  29 , of which only one tooth is shown, engages, as indicated by an arrow. The drive band  12  and the pinion  29  are illustrated at a distance from one another in  FIG. 1  solely for the sake of clarity. The drive band  12  is bent over a section which corresponds approximately to a right angle and is guided around the pinion  29 . On account of its inherent dimensional stability, said drive band can be guided largely without a special guide device outside a bending point, and this means it can be used particularly advantageously in the domestic appliance, specifically a tumble dryer, which is described below.  
      According to  FIG. 2 , the apparatus for drying laundry  1  by means of an air stream comprises a drum  2  for holding the laundry  1 , it being possible for the drum  2  to rotate about an axis  20  in order to agitate the laundry  1  in the air stream. The air stream is conducted away from the drum  2  and back to it again in a duct system  3 ,  4 ,  5 . The duct system  3 ,  4 ,  5  comprises a falling section  3  which partly passes through an end plate  10  for charging the drum  2 , a horizontal section  4  below the drum  2  and a rising section  5  through which the air stream is passed to the drum  2  again. The falling section  3  contains a filter  6  which is arranged in the end plate  10  and from which the lint  7  which are extracted from the air stream of the laundry  1  are captured. Means (which are not illustrated in  FIG. 2 ) can be used to scrape off lint  7  which have been captured from the filter  6  in order to ensure as low as possible a flow resistance of the filter  6 . The horizontal section  4  which follows the falling section  3  contains a heat exchanger  21  in which the air stream is cooled in order to remove entrained water vapor by condensation. Condensed water is separated from the air stream using means which are known per se (not illustrated in  FIG. 2 ), and disposed of. The rising section  5  which follows the horizontal section  4  contains a blower  22 , which drives the air stream through the drum  2  and the duct system  3 ,  4 ,  5 , and a heating device  23  which is used to heat up the air stream before it enters the drum  2  again. All or part of the heat exchanger  21  and the heating device  23  may optionally be part of a recuperative heat-transport system, in particular a heat pump. The end plate  10  firstly forms a support structure for a front face of the apparatus and a front support for the drum  2 , and secondly supports a door  30  for closing the drum  2 .  
       FIG. 3  shows how the filter  6 , which is supported on a filter support  19 , is embedded in the end plate  10  of the tumble dryer. In this case, the end plate  10  is seen from the drum  2 . The air stream which may have left the drum  2  enters the end plate  10  along arrows  26  and thus reaches the filter  6  (not illustrated for the sake of clarity) on the filter support  19 . At this point, the air stream is freed from entrained lint. The captured lint are removed by the scraper  8 ,  9  by said scraper being moved from a first end  14  of the filter to a second end  15  by means of a motor  11  and a transmission which is formed by said convex drive band  12 . The motor  11  drives the pinion  29 , which in  FIG. 3  is largely covered by a cover  28 , by means of a gear mechanism (not illustrated). The lint which are thus scraped off are passed to the chute  16  and the reservoir  25 ,  27 . As illustrated in  FIG. 1 , the drive band  12  is perforated and is driven by the motor  11  by means of the pinion  29  which is partially covered by a cover  28 . The drive band  12  has the advantage of inherent stability, which means a special guide means is not necessary, and is also stable when the foil  8  becomes stuck; the drive band  12  can prevent a corresponding excessive loading by bending outward. The drive band  12  is connected to the carriage  9  (see  FIG. 1 ) in particular in such a way that a lug or screw connection (not illustrated) which is provided on the drive band  12  engages in a corresponding recess  24  in the carriage  9 .  
     LIST OF REFERENCE SUMBOLS  
     
         
           1 . Laundry  
           2 . Drum  
           3 . Duct system, falling section  
           4 . Duct system, horizontal section  
           5 . Duct system, rising section  
           6 . Filter  
           7 . Lint  
           8 . Scraper, foil  
           9 . Scraper, carriage  
           10 . End plate  
           11 . Motor  
           12 . Transmission  
           14 . First end  
           15 . Second end  
           16 . Chute  
           19 . Filter support  
           20 . Axis of the drum  
           21 . Heatexchanger  
           22 . Blower  
           23 . Heating device  
           24 . Recess in the carriage  
           25 . Reservoir, first part  
           26 . Air stream in the door  
           27 . Reservoir, second part  
           28 . Cover  
           29 . Pinion  
           30 . Door  
           31 . Perforation