Patent Publication Number: US-2013229788-A1

Title: Illumination device for a cooking hob with a glass ceramic panel

Description:
The present invention relates to an illumination device for a cooking hob with a glass ceramic panel according to claim  1 . Further, the present invention relates to a cooking hob with a glass ceramic panel and at least one illumination device according to claim  14 . 
     The cooking zone, the switches and the displays on a glass ceramic panel of a cooking hob are typically indicated by printed symbols. It would be especially aesthetic, if the indicating symbols would vanish in the switch-off state of the cooking hob. 
     This can be realized be electrically illuminated cooking zones, switches and displays on the glass ceramic panel of the cooking hob. However, there are usually non-uniform illuminations and spots on the glass ceramic panel. 
     It is an object of the present invention to provide an illumination device, which allows uniform illuminations of the object on the glass ceramic panel. 
     The object of the present invention is achieved by the illumination device according to claim  1 . 
     According to the present invention an illumination device is provided for a cooking hob with a glass ceramic panel, wherein:
         the illumination device includes a funnel-shaped reflector with an upper open side and a lower open side,   the illumination device includes at least one light source arranged or arrangable at the lower open side,   the illumination device includes a transparent cover element arranged or arrangable at the upper open side of the reflector,   the illumination device includes at least one diffuser screen arranged or arrangable between the light source and the cover element,   the diffuser screen is made of a semitransparent material, and   the cross-section of the diffuser screen is smaller than the cross-section of the reflector enclosing said diffuser screen, so that lateral light beams from the light source to the cover element can pass the diffuser screen.       

     The main idea of the present invention is the arrangement of the components of the illumination device. In particular, the diffuser screen, which is smaller than the reflector, allows that the lateral light beams pass said diffuser screen and propagate directly from the light source to the cover element. In contrast, central light beams are scattered by the diffuser screen, so that the intensity in the central portion is reduced. This results in a uniform intensity distribution of the light on the cover element. 
     According to a preferred embodiment of the present invention a circuit board is arranged or arrangable at the lower open side of the reflector, wherein the light source is attached on said circuit board. 
     Preferably, the reflector is made of plastics. The inner side of the reflector may be coated by reflective material. 
     For example, the diffuser screen is made of polycarbonate. This 
     In particular, the cover element is made of silicone. 
     According to the preferred embodiment of the present invention the light source includes a number of light emitting diodes. 
     Further, the reflector may comprise snap-fits at its lower side for fastening the circuit board. The reflector and the snap-fits may be formed as a single-piece part, so that the fastening of the circuit board may be performed without any tools and further fastening means. 
     Additionally, the reflector may comprise means for aligning the diffuser screen in its central portion. The reflector and the means for aligning the diffuser screen may also be formed as a single-piece part. 
     Moreover, the reflector may comprise snap-fits in its interior for fastening the diffuser screen. 
     The reflector may comprise latch elements engaged or engageable with corresponding sleeve elements of the cover element in order to fasten said cover element at the reflector. 
     Further, the cover element may comprise a hollow for receiving at least one temperature sensor. 
     Preferably, the illumination device may comprise a heat conducting element providing a heat transfer from a cooking zone of the cooking hob to the temperature sensor. 
     In particular, the illumination device is provided for indicating a corresponding cooking zone of the cooking hob. 
     Further, the present invention relates to a cooking hob with a glass ceramic panel and at least one illumination device described above. 
     In particular, the cooking hob is an induction cooking hob and the illumination device is arranged in the centre of a corresponding induction coil. 
     Novel and inventive features of the present invention are set forth in the appended claims. 
    
    
     
       The present invention will be described in further detail with reference to the drawings, in which 
         FIG. 1  illustrates a sectional side view of an illumination device for a cooking hob according to a preferred embodiment of the present invention, 
         FIG. 2  illustrates a schematic sectional side view of the light propagation within the illumination device according to the preferred embodiment of the present invention, 
         FIG. 3  illustrates a sectional side view of the illumination device mounted within the cooking hob according to the preferred embodiment of the present invention, 
         FIG. 4  illustrates a perspective view of a reflector of the illumination device according to the preferred embodiment of the present invention, 
         FIG. 5  illustrates a perspective view of the inverted reflector of the illumination device according to the preferred embodiment of the present invention, 
         FIG. 6  illustrates a perspective view of the reflector of the illumination device with an inserted diffuser screen according to the preferred embodiment of the present invention, 
         FIG. 7  illustrates a perspective view of the diffuser screen according to the preferred embodiment of the present invention, 
         FIG. 8  illustrates a perspective view of the inverted reflector of the illumination device with an inserted circuit board according to the preferred embodiment of the present invention, 
         FIG. 9  illustrates a perspective view of the circuit board for the illumination device according to the preferred embodiment of the present invention, 
         FIG. 10  illustrates a perspective view of a cover element for the illumination device according to the preferred embodiment of the present invention, 
         FIG. 11  illustrates a perspective view of the reflector of the illumination device with the fitted cover element according to the preferred embodiment of the present invention, 
         FIG. 12  illustrates a perspective view of a heat conducting element for the illumination device according to the preferred embodiment of the present invention, 
         FIG. 13  illustrates a perspective view of the reflector of the illumination device with the fitted cover element and heat conducting element according to the preferred embodiment of the present invention, 
         FIG. 14  illustrates a perspective view of the illumination device with the heat conducting element and a temperature sensor according to the preferred embodiment of the present invention, 
         FIG. 15  illustrates a perspective view of the reflector with the diffuser screen and the temperature sensor according to the preferred embodiment of the present invention, and 
         FIG. 16  illustrates a perspective view of the temperature sensor with a cable according to the preferred embodiment of the present invention. 
     
    
    
       FIG. 1  illustrates a sectional side view of an illumination device for a cooking hob according to a preferred embodiment of the present invention. The illumination device is arrangable below a glass ceramics panel of the cooking hob. 
     The illumination device includes a reflector  10 , a circuit board  12 , a cover element  14  and a diffuser screen  16 . The reflector  10  is funnel-shaped and made of plastic. The plastic is opaque. Alternatively, the inner side of the reflector  10  is coated by a reflective material. The diffuser screen  16  is made of a semi-transparent material. In particular, the diffuser screen  16  is made of polycarbonate. The cover element  14  is made of a transparent material. For example, the cover element  14  is made of silicone. The circuit board  12  is arranged in the bottom of the reflector  10  and comprises one or more light sources. 
     Further, the illumination device includes a temperature sensor  18 , a cable pair  20  and an elongated heat conducting element  22 . 
       FIG. 2  illustrates a schematic sectional side view of the light propagation within the illumination device according to the preferred embodiment of the present invention. 
     A central light beam  50  extends upwards form the circuit board  12  to the diffuser screen  16 . Lateral light beams  52  extend upward to the cover element  14 . The lateral light beams  52  pass by the diffuser screen  16 , so that the lateral light beams  52  reach directly the cover element  14 . 
     The central light beam  50  is scattered by the diffuser screen  16 , so that diffuse light beams  54  extend upward from diffuser screen  16  to the cover element  14 . The diffuser screen  16  allows a uniform intensity distribution of the light on the cover element  14 . 
     If the diffuser screen  16  would be absent, then the intensity distribution of the light would have a maximum in the centre of the cover element  14 . 
       FIG. 3  illustrates a sectional side view of the illumination device mounted within the cooking hob according to the preferred embodiment of the present invention. 
     In this example, the illumination device is arranged in the centre of an induction coil  24 . Thus, the illumination device indicates the positions of the induction coil  24  and the corresponding cooking zone within the cooking hob. The induction coil  24  is arranged upon a base layer  30  of the cooking hob. 
     The heat conducting element  22  extends horizontally above the induction coil  24 , so that the effective temperature on the cooking zone occurs also at the temperature sensor  18 . 
       FIG. 4  illustrates a perspective view of the reflector  14  of the illumination device according to the preferred embodiment of the present invention. The reflector  10  is funnel-shaped and comprises inside a number of vertical fins  26 . In this example, the reflector  10  comprises four vertical fins  26 . 
     The fins  26  are provided for supporting the diffuser screen  16  in the centre of the reflector  10 , so the lateral light beams  52  can pass by said diffuser screen  16 . Two opposite fins  26  includes a snap-fit  28  in each case in order to fasten the diffuser screen  16 . 
     Two latch elements  42  are arranged at the upper border of the reflector  10 . The latch elements  42  are provided for fastening the cover element  14 . The latch elements  42  are arranged at opposite sides of the upper border of the reflector  10 . 
       FIG. 5  illustrates a perspective view of the inverted reflector  10  of the illumination device according to the preferred embodiment of the present invention. 
     At its bottom the reflector  10  comprises an inclusion  32  for receiving the circuit board  12 . Two opposite snap-fits  34  are arm ranged on the bottom side of the reflector for fastening the circuit board  12 . 
       FIG. 6  illustrates a perspective view of the reflector  10  of the illumination device with an inserted diffuser screen  16  according to the preferred embodiment of the present invention.  FIG. 6  shows the reflector  10  from the same position as in  FIG. 4 . The diffuser screen  16  is inserted between the fins  26  and fixed by the snap-fits  28 . 
       FIG. 7  illustrates a perspective view of the diffuser screen  16  according to the preferred embodiment of the present invention.  FIG. 7  clarifies that the diffuser screen  16  has the form of a circular disk. 
       FIG. 8  illustrates a perspective view of the inverted reflector  10  of the illumination device with an inserted circuit board  12  according to the preferred embodiment of the present invention.  FIG. 8  shows the reflector  10  from the same position as in  FIG. 5 . The circuit board  12  is inserted in the inclusion  32  and fixed by the both opposite snap-fits  34 . 
       FIG. 9  illustrates a perspective view of the circuit board  12  for the illumination device according to the preferred embodiment of the present invention. A number of light emitting diodes  36  are arranged on the circuit board  12 . In this example, the circuit board  12  comprises seven light emitting diodes  36  are arranged on the circuit board  12 . 
       FIG. 10  illustrates a perspective view of the cover element  14  for the illumination device according to the preferred embodiment of the present invention. The cover element  14  has substantially the same cross section as the upper side of the reflector  10 . In this example, the cover element  14  is made of silicone. 
     The cover element  14  includes two sleeve elements  44  arranged at opposite sides of said cover element  14 . The sleeve elements  44  are provided for receiving the corresponding latch elements  42  of the reflector  10 . The cover element  14  is fixed at the reflector  10  by the latch elements  42  and the sleeve elements  44 . 
     Further, the cover element  14  includes a hollow  38  in its upper side. The hollow  38  is provided for receiving a corresponding curve  40  of the heat conducting element  22 . 
       FIG. 11  illustrates a perspective view of the reflector  10  of the illumination device with the fitted cover element  14  according to the preferred embodiment of the present invention. In  FIG. 11  the cover element  14  is fixed at the reflector  10 . The sleeve elements  44  of the cover element  14  have received the corresponding latch elements  42  of the reflector  10 . 
       FIG. 12  illustrates a perspective view of the heat conducting element  22  for the illumination device according to the preferred embodiment of the present invention. The heat conducting element  22  includes a curve  40  corresponding with the hollow  30  in the cover element  14 . The curve  40  is provided for receiving the temperature sensor  18 , and the hollow  38  is provided for receiving the curve  40 . The heat conducting element  22  transfers the effective temperature on the cooking zone to the temperature sensor  18 . 
       FIG. 13  illustrates a perspective view of the reflector  10  of the illumination device with the fitted cover element  14  and heat conducting element  22  according to the preferred embodiment of the present invention. The heat conducting element  22  is arranged at the cover element  14 . The curve  40  of the heat conducting element  22  is received by the hollow  38  of the cover element  14 . 
       FIG. 14  illustrates a perspective view of the illumination device with the heat conducting element  22  and the temperature sensor  18  according to the preferred embodiment of the present invention.  FIG. 14  is similar to  FIG. 13 . Additionally, the temperature sensor  18  with the cable pair  20  is shown in  FIG. 14 . The temperature sensor  18  is arranged within the curve  40  of the heat conducting element  22  and within the hollow  38  of the cover element  14 . 
       FIG. 15  illustrates a perspective view of the reflector  10  with the diffuser screen  16  and the temperature sensor  18  according to the preferred embodiment of the present invention. In other words,  FIG. 15  shows the illumination device of  FIG. 14  without the heat conducting element  22  and the cover element  14 .  FIG. 15  clarifies that the cable pair  20  penetrates the reflector  10 . 
       FIG. 16  illustrates a perspective view of the temperature sensor  18  with the cable pair  20  according to the preferred embodiment of the present invention. In this example, the cable pair  20  comprises two Z-shaped portions beside the temperature sensor  18 . The Z-shaped portions allow a distance between the cable pair  20  and the heat conducting element  22 . 
     The illumination device of the present invention allows a simple installation of the illumination device itself and said illumination device within the cooking hob. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  reflector 
           12  circuit board 
           14  cover element 
           16  diffuser screen 
           18  temperature sensor 
           20  cable pair 
           22  heat conducting element 
           24  induction coil 
           26  fin 
           28  snap-fit 
           30  base layer 
           32  inclusion 
           34  snap-fit 
           36  light emitting diode 
           38  hollow 
           40  curve 
           42  latch element 
           44  sleeve element 
           50  central light beam 
           52  lateral light beam 
           54  diffuse light beams