Patent Abstract:
A cooking device including a cooking area, a door for closing the cooking area and a lighting system for lighting the cooking area. The lighting system includes a light source and at least one reflector arranged in the internal space of the door, which reflects light from the light source into the cooking area. In order to reduce mechanical strain applied to the light source, it is arranged outside the door and emits light towards the reflector inside the door to be reflected into the cooking area.

Full Description:
CROSS REFERENCE 
   This application is a continuation, under 35 U.S.C. § 120, of copending international application No. PCT/EP2004/004328, filed Apr. 23, 2004, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German patent application No. 103 18 859.2, filed Apr. 25, 2003; the prior applications are herewith incorporated by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to a cooking device with a cooking area and a cooking device door for closing off the cooking area and a lighting device for lighting the cooking area, which has at least one reflector, arranged in a door interior of the cooking device door and reflects light from a light source of the lighting device into the cooking area. 
   2. Description of Related Art 
   DE-A-38 08 716 discloses a device for lighting the interiors of domestic appliances. The lighting device is built into a baking oven door and has bulged reflectors, which are designed stretching out longitudinally and have a parabolic cross-section and are arranged at the level of the viewing window. A number of lighting elements is preferably assigned to the reflectors. Dazzle-free and thoroughly uniform internal lighting of the oven muffle or respectively of the cooking area in all feed levels is achieved without any of the muffle walls having to be engaged. 
   DE-A-36 43 354 discloses another lighting device for a baking oven closable by a baking oven door. Lamps and assigned inclined reflector surfaces  21  are arranged in a door interior of the baking oven door. This ensures optimal lighting of the baking space, whereby the lamps are not visible from the outside. 
   BRIEF SUMMARY OF THE INVENTION 
   The object of the invention is to provide a cooking device, in which permanently reliable operation of the lighting device is ensured. 
   In accordance with the invention a light source of the lighting device is provided outside the cooking device door and in optical connection with a reflector arranged in the door interior. Since the light source is provided outside the cooking device door, the light source is not stressed mechanically by shaking coming from when the cooking device door is opened and closed. This guarantees adequate reliable operation of the light source of the lighting device. 
   It is particularly advantageous if the light source is arranged outside a sealed area provided between the cooking device door and a muffle flange enclosing the cooking area opening. Contamination of the light source by liquid from cooking goods is prevented by its being arranged outside the sealed area. Heat stress on the light source is also reduced. 
   It can be advantageous if the light source of the lighting device is mounted in the muffle flange. This creates a favourable installation site, since the light source is easily accessible and can be exchanged trouble-free when the cooking device door is open. 
   It is particularly preferred if the light source is arranged under a muffle floor, which creates spatial separation of the light source from the electronic components of the cooking device arranged above the cooked goods device muffle. The electronic components are thus protected from the waste heat of the light source. As well, there is no additional warming of the door handle of the cooking device door due to waste heat from the light source. 
   Conventional light sources for illuminating the cooking area of the cooking device muffle have a rating between 40 and 100 W. The light source is accordingly warmed during operation. It is advantageous to avoid overheating of the light source for the sake of increasing the service life of the light source. It is therefore particularly favourable to arrange the light source right beside a door hinge provided in the cooking device, i.e. up to a distance of 5 to 6 cm away. Door hinges are usually solid sheet metal parts with correspondingly high heat storage capacity. Heat deflection from the light source to the door hinge is accordingly advantageous. To enable heat transfer via heat radiation is it preferred to arrange both the light source and the door hinge in a hollow chamber. The hollow chamber is preferably ballasted against a heat-insulating mantle, which usually encloses the cooking area. 
   In the case of a light source arranged under the muffle floor it is also beneficial to arrange a heat-protective element between the light source and the bottom-heating heater unit. 
   Heat deflection of the waste heat from the light source can also be prevented by the light source being arranged in an air-conducting duct. 
   An air current guided through the air-conducting duct enables advantageous cooling of the light source. In this case, while the cooking device is running in the air-conducting duct a forced air current and/or air convection flow can be set. 
   With the inventive cooking device the light source is arranged outside the cooking device door, while the assigned reflector is arranged inside the cooking device door. In this case it is favourable for high lighting output if light losses are minimised during transfer of the light from the light source to the cooking device door. This can be achieved if an optical window, through which the light of the light source radiates, is provided in the cooking device door. 
   Light losses can occur in particular in a cavity between the light source and the cooking device door. Here it is preferred if a light channel element is arranged in the cavity, by which the light of the light source is transferred to the cooking device door. 
   The light channel element can be preferably arranged detachably with the cooking device door or at a slight distance away. When the cooking device door is open the light channel element is arranged separately from the door, whereby the inside of the door can be cleaned without problem. In a further embodiment the optical window can be designed in the cooking device door in a depression, into which the light source or the light guiding element extends. 

   
     DESCRIPTION OF BRIEF THE SEVERAL VIEWS OF THE DRAWING(S) 
     An exemplary embodiment of the invention is explained hereinafter with reference to the appended figures. In the figures: 
       FIG. 1  is a perspective view of a cooking device with the cooking device door open; 
       FIG. 2  is a side sectional view of a section of the cooking device; 
       FIG. 3  is a perspective view of the cooking device door with a door inner pane partly broken away; 
       FIGS. 4   a  to  4   c  show a reflector arranged in the cooking device door viewed from above and from the side and in a perspective view; and 
       FIG. 5  shows a front view of the cooking device without the cooking device door and in a partial section. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a cooking device including a rectangular baking chamber  3 . The baking chamber  3  has a front baking-chamber opening  5 . Horizontal slide-in ribs  7  are constructed on both side walls of the baking chamber  3  These are used to slide in and support baking sheets in horizontal cooking chamber levels (not illustrated). The front baking chamber opening  5  can be closed by means of a front cooking-device door  9 . This is pivotally hinged in the lower area of the cooking device by means of lateral door hinges  11 . The baking-chamber opening  5  is bordered by a front baking-chamber flange  13 . Affixed to the baking-chamber flange  13  is a ring seal  15 , which extends around the baking-chamber opening  5  on the circumferential side. 
     FIG. 2  shows the cooking device with the cooking-device door  9  closed. In this case, the cooking device door  9  abuts against the ring seal  15  with its inner side facing the cooking chamber  1 . The front baking-chamber flange  13  is located at a distance of around 7 mm from the cooking device door  9  by means of an intermediate space  16 . Attached to an underside of a bottom of the baking chamber  3  of the cooking device is a heating element housing  17 , as shown in  FIG. 2 , which holds an underheat heating element  18 . The heating-element housing  17  extends as far as close to the front baking-chamber flange  13 . Likewise arranged underneath the bottom of the baking chamber is a baking oven lamp  21 . Its housing  22  is held in the front baking-chamber flange  13 . The light from the lamp  21  is reflected into the cooking chamber  1  via the cooking-device door  9 . 
   The structure of the cooking device door  9  can be seen from  FIGS. 2 and 3 . Consequently, the cooking-device door  9  has a rectangular doorframe  25  made of a deep-drawn sheet metal, which runs around the circumference. A door handle  27  is affixed on an upper frame strip of the door frame  25 . The cooking device door further has a door inner pane  29  facing the cooking chamber  1  and a front door outer pane  31  which are spaced apart from one another. For cleaning reasons the door inner pane  29  is held detachably on the door frame  25  by means of snap-in connections which are not shown. The front outer pane  31  on the other hand is fixedly connected to the door frame  25 . The two panes  31  and  29  are made of a transparent glass ceramic material and have opaque printing  33 . These each surround transparent rectangular viewing areas or viewing windows  34  of the door panes  29 ,  31 . The door frame  25  together with the door panes  29 ,  31  spaced apart from one another delimits a door interior space  37  which is adequately sealed against moisture from the outside. In the lower corner areas of the door frame  25  it is possible to see movable hinge portions  26  of the door hinges  11  which are fixed inside the door frame  25 . The movable hinge portions  26  can be suspended in corresponding fixed hinge portions of the door hinge  11  on the housing side. 
   Located inside the door interior space  37  are two elongated reflectors  39  as shown in  FIG. 3 . These are arranged so that they are hidden from view behind the printing  33  of the door outer pane  31  and extend along the sides of the viewing window  34 . The reflectors  39  are made of a solid plastic injection moulding which is resistant to thermal stresses and is stable in shape. One of the reflectors  39  is shown in  FIGS. 4   a  to  4   c . Accordingly, the reflector  39  is constructed as having an almost U-shaped cross-sectional profile so that it extends in a groove shape in one longitudinal direction. The reflector  39  has a flat groove bottom  40 , which is surrounded by raised longitudinal side walls  41 . The groove bottom  40  and the longitudinal side walls  41  delimit a light-guiding compartment  49 . 
   Located inside the light-guiding compartment  49  are the transverse reflector surfaces  42 ,  43 ,  44 , which run transversely to the groove bottom  40  and the longitudinal side walls  41 . In this case, the outer transverse reflector surfaces  43 ,  44  close the opposing narrow sides of the reflector  39 . As is shown in  FIG. 4   c , the upper free edges  45  of the outer transverse reflector surfaces  43 ,  44  and the longitudinal side walls  41  run flush at the same distance from the groove bottom  40 . The flush profile of the upper edges  45  is interrupted by a gradation into which a cover described subsequently can be inserted. 
   Both the groove bottom  40 , the longitudinal side walls  41  and the transverse reflector surface  44  are constructed as flat. On the other hand, the transverse reflector surfaces  42 ,  43  are constructed as spherically arched. Formed on the outside on the longitudinal side walls of the reflector  39  are mounting hooks  46  which are suspended to hold the reflector  39  in corresponding sections of the door frame  35  which are not shown. Formed on the outside on the opposing longitudinal side wall  41  are retaining attachments  47  which can be used to optionally retain a further central door pane which is not shown. Edge transitions  48  between the transverse reflector surfaces  42 ,  43 ,  44  and the longitudinal side walls  41  and the groove bottom  40  are constructed as rounded. 
   It can be seen from  FIG. 3  that the two reflectors  39  are arranged mirror-symmetrically with respect to one another on the sides of the rectangular viewing window  34 . In this case, the reflectors  39  abut with their upper free edges  45  against the door inner pane  29  or are only slightly at a distance therefrom. Thus, the reflector  39  together with the door inner pane  29  delimits a light-guiding compartment  49 , which is substantially closed on the interior side of the door. Alternatively, an additional sealing element can be provided to seal light gaps between the free upper edge  45  of the reflector  39  and the door inner pane  29 . Escape of light from the light-guiding compartment  49  into the door interior space  37  is thus extensively reduced. 
   Provided in the printing  33  of the door inner pane  29  are additional transparent areas  51 , which project from the sides of the rectangular viewing window  34 . The transparent areas  51  extend in the upper area of the viewing window and are aligned with the light-guiding compartment  46  of the reflectors  39 . Light reflected by the reflector  39  can be reflected into the cooking chamber  1  through the transparent areas  51  of the door inner pane  29 . Further, circular optical windows  53  are formed in the lower area of the door inner pane  29 , which are likewise transparent areas in the printing  33 . The optical windows  53  are aligned with the transverse reflector surfaces  44  of the reflectors  39 . Thus, all focused light from the lamp  21  passes through the corresponding window  53  onto the opposing transverse reflector surface  44 . The transverse reflector surface  44  is positioned obliquely with respect to the groove bottom  40  so that the incident light is guided into the light-guiding compartment  49  as indicated in  FIG. 2 . 
   Consequently, a beam path of the light between the transverse reflector surfaces  42 ,  43 ,  44  runs substantially parallel to the longitudinal side walls  41  and to the groove bottom  40 . In this case, some of the light is incident on the middle transverse reflector surface  42  and is reflected therefrom into the cooking chamber  1  as a light cone K. The middle transverse reflector surface  42  is located in the light-guiding compartment  49  below the upper edge  45  of the reflector  39 . As a result, a light penetration gap  54  is obtained between the middle transverse reflector surface  42  and the door inner pane  29 , as shown in  FIG. 2 . Some of the light is passed on through this gap to the transverse reflector surface  43  positioned thereafter. This reflects the lights into the cooking chamber  1  as a further light cone K. In this case, the transverse reflector surfaces  42 ,  43  are aligned such that their light cones K irradiate the cooking chamber  1  obliquely downwards. Thus, only the upper side of baking sheets arranged in the cooking chamber  1  is advantageously illuminated. 
   The reflectors  39  are fully reflection-coated on the inside. A small fraction of the light guided into the light-guiding compartment  49  of the reflector  39  is thus reflected into the cooking chamber  1  as diffuse scattered light D at the reflection-coated longitudinal side walls  40  and the groove bottom  41  (see  FIG. 2 ). The longitudinal side walls  40  and the groove bottom  41  serve as additional longitudinal reflector surfaces in addition to the transverse reflector surfaces. The diffuse scattered light D is reflected into the cooking chamber  1  at arbitrary angles. As a result of the combination of the focussed light cones K with the diffuse scattered light D, the following is achieved: on the one hand, food on the baking sheets in the cooking chambers is visually emphasised by the light cones K. On the other hand, however, edge zones in the cooking chamber  1  are also adequately illuminated by the diffuse scattered light D. As a result of the rounded transitions  48  between the first and second reflector surfaces the low light intensity of the diffuse scattered light D goes over continuously into the high light intensity of the light cones K. Such a continuous transition of the light intensity is further improved if the transverse reflector surfaces  42 ,  43  are roughened. As a result, a small portion of the light reflected into the cooking chamber by the second transverse reflector surfaces  42 ,  43  is reflected as diffuse scattered light. 
   According to  FIG. 3 , the open upper side of the reflectors  39  is covered by a cover  56 , which is reflection-coated on the inside, in the area between the middle transverse reflector surface  42  and the lower transverse reflector surface  44 . An opaque light channel  59  is thereby formed in the reflector  39 . This ensures that the light from the lower transverse reflector surface  44  is guided with almost no losses of light to the middle transverse reflector surface  42 . For aesthetic reasons the cover  56  is arranged out of sight behind the printing  33  of the door inner pane  29 . The cover  56  is arranged in a gradation made in the upper free edge  45  and ends flush with the upper free edge  45  of the reflector  39 . 
   The lamp  21  is arranged in the lamp housing  22  as shown in  FIG. 2 . The lamp housing  22  is constructed as hollow-cylindrical and is aligned so that it slopes upwards at an angle of about 10° in order to increase the distance from the underheat heating element  18 . The lamp housing  22  is held by its open front end in the front baking-chamber flange  13 . The end of the housing held in the baking-chamber flange  13  is surrounded by a frame-like light channel element  58 . The light channel element  58  is positioned on the baking-chamber flange  13  at the front. It thus projects into the intermediate space  16  between the baking chamber flange  13  and the door inner pane  29 . 
   When the cooking device door  9  is closed, a face of the frame-like light channel element  58  projecting into the intermediate space  16  abuts against the door inner pane  29  or is only a short distance therefrom. In  FIG. 2  this distance is about 1 to 2 mm. The light channel element  58  thus forms a light channel sufficiently closed with respect to the intermediate space  16  through which the light from the lamp  21  can be transmitted into the cooking-device door  9 . Disadvantageous light effects in the bottom area of the cooking device can thereby be largely avoided. At the same time, the light is transmitted from the lamp  21  on the side of the cooking device to the transverse reflector surface  44  on the door side almost without losses. 
   In order to reduce heat dissipation from the cooking chamber  1 , the cooking chamber  1  together with the heating element housing  17  is surrounded by a heat-insulating jacket  61 . The heat-insulating jacket  61  almost completely fills a housing area provided outside the baking chamber  3  of the cooking device. 
   As can be seen from  FIG. 5 , a separating plate  63  is provided in the housing compartment in the area of the lamp  21 . The separating plate  63  forms a hollow chamber  65  separated from the heat-insulating jacket  61  in which the lamp  21  is located. The separating plate  63  serves as an additional heat protection between the lamp  21  and the underheat heating element  18 . Also provided in the hollow chamber  65  is a fixed hinge portion  68  of the door hinge  11 . The hinge portion  68  is usually made of a solid deep-drawn metal sheet and has a correspondingly high heat storage capacity. In this case, the lamp  21  is also located only at a small distance over about 5 cm from the fixed hinge portion  68  of the door hinge  11 . Waste heat produced by operation of the lamp  21  can thus be diverted to the fixed hinge portion  68  by means of thermal radiation indicated by the arrows in  FIG. 5 . The operating temperature of the lamp  21  is thereby reduced and its lifetime correspondingly increased. 
   In order to further reduce the operating temperature of the lamp  21 , the hollow chamber  65  can form a part of an air-guiding channel  67 . The air-guiding channel  67  has air entry slits  69  on the side of the housing bottom through which air can enter into the channel  67 . The air-guiding channel  67  extends vertically upwards outside the baking chamber  3  of the cooking device as far as a blower chamber  73  provided above the baking chamber  3  of the cooking device. Provided in the blower chamber  73  is a known cool air blower arrangement  71  which sucks air from the blower chamber  73  in the direction of the arrows in order to cool electronic components of the cooking device. According to the invention ambient air is initially sucked into the hollow chamber  65  at the bottom. In this case, the air, which has been sucked in flows around the lamp  21  in the direction of the arrow and is guided into the blower chamber  73  via the air-guiding channel  67 .

Technology Classification (CPC): 5