Abstract:
A high-level built-in oven unit including a bottom opening in the oven unit. A removable trap-door including lifting elements to open and close the bottom opening of the oven unit. The trap door has a baking tray mounting arrangement detachably mounted thereon.

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The present invention relates to a high-level built-in oven unit and, in particular, to a high-level built-in oven with a lowerable trap-door and a baking tray mounting arrangement. 
   The wall-mounted oven known from the WO 98/04871 publication should be considered as a generic high-level built-in oven unit. The wall-mounted oven includes a cooking space or an oven chamber which is surrounded by sidewalls, a front, back and upper wall and which has an opening in its floor, whereby the back of the wall-mounted oven is to be mounted on a wall in the manner of a kitchen wall unit. The opening in the floor of the oven chamber can be closed by a lowerable trap-door. A support arrangement or a fixing piece for baking trays and other oven accessories is mounted on the upper surface of the trap-door. 
   In order to adjust the trap-door the wall-mounted oven has a lifting device with lifting elements which are connected with the trap-door. The lifting elements are shaped as linkage levers which are pivotably mounted, on the one hand, inside the oven chamber on its sidewalls and, on the other hand, on the fixing piece for baking trays, which is mounted on top of the trap-door. When the trap-door is adjusted the linkage levers may be pivoted parallel to a level of the sidewalls of the oven chamber. 
   One of the ends of the linkage levers mounted on the sidewalls of the oven chamber is non-rotatably connected with an actuating shaft. This actuating shaft protrudes from a sidewall of the oven chamber and may be driven by a drive motor located outside the oven chamber. Thus when the drive motor is activated the linkage levers may be pivotally adjusted. 
   The pivotal mounting of the linkage levers on the fixing piece requires a comparatively complicated constructional assembly of the fixing piece. This means that cleaning of the fixing piece which is exposed to contamination is costly. Further, since the fixing piece is stationarily mounted on the trap-door, it is difficult to access for cleaning. 
   The present invention includes a high-level built-in oven unit which facilitates cleaning of the fixing piece of a baking tray mounting arrangement easier. 
   BRIEF SUMMARY OF THE INVENTION 
   The fixing piece of the baking tray mounting arrangement is detachably connected with the trap-door. Therefore the fixing piece can be removed from the trap-door following a cooking operations and cleaned spatially separate from the high-level built-in oven unit in a dishwasher. 
   According to a special embodiment of the invention, the fixing piece of the baking tray mounting arrangement is arranged spatially separate from the lifting elements. In contrast to the state of the art the baking tray mounting arrangement is not an integrated part of the lifting elements. This means that the baking tray mounting arrangement can be specially adapted to suit the cleaning requirements in the high-level built-in oven unit without adversely affecting the function of the lifting elements. 
   In order to facilitate easy handling of the fixing piece by a user it is especially favourable to design the connection of the fixing piece with the trap-door in such a way that the removal of the fixing piece from the trap-door or the attachment of the fixing piece to the trap-door can be carried out by the user without using any tools. 
   A particularly simple attachment on, or removal of the fixing piece from, the trap-door can be achieved if the fixing piece is fixed by means of an easy-to-detach plug-in connection. To achieve such a plug-in connection the fixing piece includes at least one plug-in portion which may be plugged into a corresponding anchoring of the baking tray mounting arrangement fastened to the trap-door. 
   A constructionally particularly simple design of the plug-in connection includes the anchoring in the door including a cylindrical base and the plug-in connection of the fixing piece having a corresponding hollow profile. 
   In order to ensure an accurate positioning of the fixing piece on the base of the floor-side anchoring, a positioning pin is provided on the base. When the fixing piece is accurately positioned on the base, the positioning pin is received in a recess of the plug-in connection of the fixing piece. If, however, the positioning pin and the recess are not aligned with each other, the fixing piece cannot be placed onto the base. 
   In order to avoid contamination of the floor-side anchoring of the baking tray mounting arrangement, the anchoring is covered by a heat-resistance plate in such a way that only the base of the anchoring protrudes through a mounting hole in the heat-resistant plate. 
   The anchoring of the baking tray mounting arrangement is even more effectively protected against contamination if an O-ring seal is arranged between an annular flange of the cylindrical base and a circumferential area of the mounting hole of the heat-resistant plate. In this way the mounting hole in the heat-resistant plate is sealed hermetically towards the base. 
   In this context it is especially advantageous to manufacture the heat-resistant plate from a material with a small thermal expansion coefficient, preferably from a glass-ceramic material. Due to the small thermal expansion coefficient of glass-ceramics thermal deformations of the plate, which adversely affect the operability of the above mentioned seal between the base and the heat-resistant plate, are almost totally prevented during operation of the high-level built-in oven unit. 
   It is particularly favourable from both a manufacturing and an assembly point of view if the fixing piece includes two support columns identical to each other and if the support columns can be plugged with their plug-in portions onto corresponding identical anchorings. By designing the support columns as well as the anchorings in an identical way the manufacturing cost are considerably reduced and assembly is simplified. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     An embodiment of the invention will now be described with reference to the attached drawings of which: 
       FIG. 1  shows a perspective view of a wall-mounted high-level built-in oven unit with lowered trap-door; 
       FIG. 2  shows a perspective view of a wall-mounted high-level built-in oven unit with closed trap-door; 
       FIG. 3  shows an enlarged sectional view of the trap-door resting against the frame of the heated chamber along line III—III in  FIG. 1 ; 
       FIG. 4  shows a perspective view of a housing of the wall-mounted high-level built-in oven unit without trap-door; 
       FIG. 5  shows a schematic side view of the wall-mounted high-level built-in oven unit with lowered trap-door; 
       FIG. 6  shows a perspective view of the trap-door without lifting elements, whereby the glass-ceramic plate  8  has been removed from the trap-door; 
       FIG. 7  shows a sectional view of an anchoring of the baking tray mounting arrangement attached to the trap-door with one support column removed from it; 
       FIG. 8  shows a sectional view of the trap-door having a support column mounted on it into which a baking tray has been hooked; and 
       FIG. 9  shows a perspective view of a support piece attached to the baking tray. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a high-level built-in oven unit  100  with a housing  38 . The rear of the housing  38  is mounted onto a wall  35  in the manner of a wall-mounted kitchen unit. In the housing  38  a cooking space  32  is defined which may be inspected via a window  63  inserted into the front of the housing  38 .  FIG. 4  shows that the cooking space  32  is defined by a heated chamber  21  provided with a heat-insulating casing not shown, and that the heated chamber  21  has a floor opening  17 . The floor opening  17  can be closed, for example, by a trap-door  2  shown in  FIGS. 1 and 2 . In  FIG. 1  the trap-door  2  is shown in the lowered position, whereby its bottom surface is in contact with a work surface  36  of a kitchen unit. 
   In order to close the cooking space  32  the trap-door  2  must be moved into the position shown in FIG.  2 . In order to move the trap-door  2  the high-level built-in oven unit  100  includes a lifting device  3 ,  31 . The lifting device  3 ,  31  includes a drive motor  31  shown as a broken line in  FIGS. 1 ,  2  and  5 , which is arranged between the heated chamber  21  and the outside wall of the housing  38 . The drive motor  31  is arranged in the area of the rear of the housing  38  and is, as shown in  FIG. 1  or  5 , effectively connected with one of a pair of lifting elements  3  connected with the trap-door  2 . According to the schematic side view in  FIG. 5  each lifting element  3  is shaped as an L-shaped support. The vertical arm  12  of the L-shaped support  3  extends starting from the drive motor  31  on the housing  38 , through frame openings  30  of a floor frame  25  and may be inserted into or retracted from the housing  38  in a vertical direction. The horizontal arm  14  of the L-shaped support  3  engages into a support portion  40  of the trap-door  2  in order to support the trap-door  2 . A support portion  40  of this kind is formed on each narrow side of the trap-door  2  as shown in FIG.  6 .  FIG. 6  shows a perspective view of a profiled sheet  52  of the trap-door  2  as well as of a glass-ceramic plate  8  to be mounted on the profiled sheet  52 . The support portions  40  were formed by bending upper portions of the sidewalls of the profiled sheet  52  of the trap-door  2  at 90° towards each other so that the horizontal arms  14  of the L-shaped supports  3  can grip underneath the support portions  40 . 
   To adjust the trap-door  2 , the drive motor  31  of the lifting device can be operated by means of a control on a control panel of a control unit  34 , which is arranged on the front of the trap-door  2  as shown in  FIGS. 1 and 2 . 
   As can be seen from  FIG. 1  the upper surface of the trap-door  2  includes a hob or cooktop  10 . Most of the entire area of the hob  10  is occupied by heating elements  5 ,  6 ,  7 , which are indicated by chain-dotted lines in FIG.  1 . In  FIG. 1  the heating elements  5 ,  6  are two hotplate heating elements of different size arranged at a distance from each other, whereas the heating elements  7  provided between the two hotplate heating elements  5 ,  6 , is a sheet-type heating elements the side portions  9  of which almost enclose the hotplate heating elements  5 ,  6 . The heating elements  5 ,  6 ,  7  are each associated with switching elements which can be controlled from the control unit  34 , as will be described later. 
   In the embodiment shown the heating elements  5 ,  6 ,  7  are radiant heating elements which are covered by the glass-ceramic plate  8 . The glass-ceramic plate  8  shown dissembled from the trap-door  2  in  FIG. 6  has approximately the dimensions of the upper surface of the trapdoor  2 . At its rear corners the glass-ceramic plate  8  has two recesses  26  on its outer circumference rim which can partially enclose the openings of the holders  40 . Consequently the L-shaped supports  3  are connected with the trap-door  2  outside the glass-ceramic plate  8 . In addition the glass-ceramic plate  8  also has mounting holes  22  through which bases  50  described later protrude for mounting a fixing piece  19  of a baking tray arrangement  19 ,  51 . 
   According to the enlarged sectional view shown in  FIG. 3  the upper surface of the trap-door  2  lies opposite the face of the floor frame  25 . The glass-ceramic plate  8  of the trap-door  2  is surrounded on its circumference by a profiled frame  28  of a profiled sheet of the trap-door  2 . A space  41  is formed between the glass-ceramic plate  8  and the bottom surface of the profiled sheet of the trap-door  2 , in which the radiant heating elements  5 ,  6 ,  7  are arranged. For heat insulation the heating elements  5 ,  6 ,  7  are all received in a heating elements housing  24 , the circumferential rim  44  of which is connected with an underside of the glass-ceramic plate  8 . Inside the heating element housing  24  the radiant heating elements  5 ,  6 ,  7  are positioned on an insulating body  29 . In addition the space  41  houses functional components indicated by chain-dotted lines such as electronic components of the control unit  34 . These functional components are arranged in a boundary area of the trap-door  2 . 
   As shown in  FIG. 3  the hob  10  occupied by the heating elements  5 ,  6 ,  7  directly extends as far as the area of the inside wall of the heated chamber  21 . In this way a far-reaching area forming the hob  10  is achieved on the upper surface of the trap-door  2 . Due to the low thermal conductivity of the glass-ceramic plate  8  the temperature of the glass-ceramic plate  8  outside the hob  10  quickly drops in the direction marked with x when the hob  10  is in operation. Thus an excessively large heat dissipation in the glass-ceramic plate  8  in x-direction is avoided due to the low thermal conductivity of the glass-ceramic plate  8 . 
     FIG. 3  also shows that a seal  20  is arranged between the glass-ceramic plate  8  and the floor frame  25 . The seal  20  is fitted into the floor frame  25  in a manner not shown and extends frame-like around the floor opening  17 . When the trap-door  2  is closed a sealed zone  18  is thus created between the floor frame  25 , the seal  20  and the glass-ceramic plate  8 . The hob  10  is arranged inside the sealed zone  18 , whereas the already mentioned boundary area of the glass-ceramic plate  8  lies outside the sealed zone  18 . The boundary area of the sealed zone  18  situated outside the sealed zone  18  in the x-direction is therefore thermally very effectively uncoupled relative to the cooking space  32 . This thermally uncoupled boundary area of the glass-ceramic plate  8  warms up only slightly when the high-level built-in oven unit is operated with the trap-door  2  closed, so that it is possible to avoid the burning-on of food on the glass-ceramic plate  8  outside the sealed zone  18  and to protect users from high temperatures of the trap-door  2 . The boundary area of the glass-ceramic plate  8  which is critical as regards cleaning can thus be easily cleaned after a cooking operation. 
   As already mentioned above, and as shown in  FIGS. 5 ,  7  and  8  the baking tray mounting arrangement  19 ,  51  is mounted on the upper surface of the trap-door  2  and is contained within the cooking space  32 , when the trap-door  2  is closed. The baking tray mounting arrangement, according to  FIG. 8 , includes the fixing piece  19  for hooking up baking trays and an anchoring  51  next to the trap-door  2 . In the present embodiment the fixing piece  19  includes two hollow-cylindrical support columns  11 . Each of the support columns  11  has cut-outs  13  on the same respective levels formed into it, into which the baking tray  58  is hooked as shown in FIG.  8 . The support columns  11  are arranged in the rear area of the cooking space  32 , i.e. between the hob  10  and the sealed zone  18  indicated as a broken line. 
   Now the mounting of the support columns  11  in the anchoring  51  fastened in the trap-door  2  according to the invention will be discussed. Each anchoring  51 , according to  FIG. 6 , consists of a profiled sheet  52  shaped as a “U”, of which one side is attached to an inside wall of the trap-door  2 . A hollow-cylindrical bearing piece  55  is placed in between the arms  53 ,  63  of each U-profile sheet  52 . Each longitudinal end  54  of the bearing piece  55  includes a portion  57  of reduced diameter. These portions  57  are retained in opposite openings of the arms of each U-profile sheet  52  as shown in FIG.  7 .  FIG. 7  also shows that a cylindrical base  50  is mounted inside each hollow-cylindrical bearing piece  55  which can be fixed in the bearing piece  55  by means of a locking screw  59 . 
   The hollow profile  60  of each support column  11 , according to  FIG. 7 , corresponds to the shape of the cylindrical base  50  in such a way that the support columns  11  can be placed so as to fit loosely onto each of the bases  50 . The cylindrical wall  60  of each support column  11  also comprises a recess  61  which receives a positioning pin  53  formed on the base  50  when the support column  11  is accurately placed onto the base  50 . 
   In order to seal the mounting holes  22  in the glass-ceramic plate  8  receiving the bases  50 , each base  50  is formed with an annular flange  70  in its central area according to FIG.  7 . The outer diameter of the annular flange  70  is larger than the diameter of the mounting hole  22  so that the annular flange  70  of the base  50  covers the mounting hole  22 . An O-ring seal  56  is arranged between the annular flange  70  and the glass-ceramic plate  8 . When the bearing piece  55  is mounted in the base  50  the annular flange  70  can exert a certain pressure upon the glass-ceramic plate  8  via the O-ring seal  56 , which rests on the profiled sheet  52  of the anchoring  51  serving as a buttress. Thus the anchoring  51  is securely sealed relative to the glass-ceramic plate  8 . 
   On each of its narrow sides the baking tray  58  is provided with a support piece  64 , which is arranged below a horizontal rim of the baking tray  58  indicated by a chain-dotted line as shown in FIG.  9 . According to  FIG. 9  each support piece  64  has mounting projections  65 ,  66 . When the baking tray  58  is hooked into the support columns  11 , the upper mounting projections  66  of the support pieces  64  of the baking tray  58  shown in  FIG. 9  are initially inserted into the window-like cut-outs  13  and come to rest against the inside wall of the support column  11 , whilst the lower mounting projections  65  of the support pieces  64  of the baking tray  58 , come to rest against an outside wall of the support column  11 . Due to the torque exerted upon the mounting projections  65 ,  66  of the baking tray  58 , the mounting projections  65 ,  66  remain resting securely against the inside and outside wall of the support columns  11 . 
   With the help of a control provided on the control panel of the control unit  34  the high-level built-in oven unit  100  may be switched between a hotplate mode and a bottom heat mode, and these will now be discussed. 
   In the hotplate mode the hotplate heating elements  5 ,  6  can be individually operated via controls provided on the control panel of the control unit  34 , whilst the sheet-type heating element  7  is inoperative. The hotplate mode can be used with the trap-door  2  lowered as shown in FIG.  1 . But it can also be used in an energy-saving function when the cooking space  32  is closed due to the trap-door  2  having been raised. 
   In the bottom heat mode, according to the invention, not only the hotplate heating elements  5 ,  6  but also the sheet-type heating element  7  is controlled from the control unit  34 . Moreover, when using the bottom heat mode, a top-heat heating element (not illustrated) provided at the top of the heated chamber  21  may be controlled from the control unit  34 . 
   To ensure that the food browns as evenly as possible in bottom heat mode, it is critical that the hob  10  providing the bottom heat supplies an evenly distributed heat output across its surface, although the heating elements  5 ,  6 ,  7  have different nominal outputs. Therefore, according to the invention, the heating elements  5 ,  6 ,  7  are not switched by the control unit  34  to continuous operation, but the power supply to the heating elements  5 ,  6 ,  7  is clocked by switching elements (not illustrated) controlled by the control unit  34 . With this arrangement the different nominal outputs of the heating elements  5 ,  6 ,  7  are individually reduced in such a way that the heating elements  5 ,  6 ,  7  produce an evenly distributed heat output across the surface of the hob  10 . 
   This sufficiently evenly distributed heat output may be adjusted by means of a further control of the control unit  34  by the user depending upon the heat output required.