Abstract:
According to an exemplary embodiment of the invention a radiant heater ( 11 ) for a glass ceramic cooking area ( 25 ) is created. The radiant heater comprises a carrier shell ( 12 ) carrying a flat insulator ( 14 ), on which is placed a heating means ( 16 ). A thermal relay ( 18 ) projects with its tube-like sensor ( 19 ) into the central area of the radiant heater ( 11 ) and the sensor can rest on an elevation ( 23 ) of the insulator ( 14 ). By means of a holder ( 45 ) the sensor ( 19 ) can be fixed to the carrier shell ( 12 ). The holder does not project over the underside of the carrier shell ( 12 ). In one embodiment the holder with barb-like ends reaches into an opening in the carrier shell and is fixed to locking edges of the carrier shell.

Description:
FIELD OF APPLICATION AND PRIOR ART  
         [0001]    The invention relates to a radiant heater. The invention specifically relates to a radiant heater for placing beneath a cooking area, particularly a tempered glass or glass ceramic plate, having a carrier shell, which carries an insulator, on and/or in which is located a heater forming a heating zone, and with at least one elongated temperature sensor of a protective switch projecting over part of the heating zone and running between the latter and the cooking area, the sensor being retained by the insulator and fastening means reaching the carrier shell.  
           [0002]    Such radiant heaters conventionally have a temperature sensor, whose outer tube is made from an insulating material, particularly quartz or quartz glass. It is either incorporated into the expansion system of the sensor, in which it forms a tube with a low expansion coefficient, in which is located a tension bar with a higher expansion coefficient, or it is shoved onto an expansion tube. This is necessary in order to ensure the necessary air gaps or leakage distances in the space between the heating resistors and the plate through which the temperature sensor passes. It must be borne in mind that glass ceramic plates become electrically conductive at the operating temperature, so that here the necessary insulation distances must be maintained.  
           [0003]    A sensor fastening of this type is described by DE 35 36 981. As sensor fastenings are proposed spacers with respect to the glass ceramic plate and the insulator. The sensor can also be fastened in the insulator by nail clamps or the like.  
           [0004]    DE 91 13 992 describes a sensor fastening, in which the retaining clips embrace the sensor and are guided by the insulator and carrier shell and behind the passage through said shell have a locking member preventing an extraction from the carrier shell. Inter alia such a sensor fastening ensures that the sensor does not strike against the glass ceramic plate, which could lead to the breakage of the latter. This can occur both during testing and during the transportation or installation of a cooking area.  
         PROBLEM AND SOLUTION  
         [0005]    The problem of the invention is to provide a radiant heater of the aforementioned type in which a reliable sensor fastening is possible, whilst also bringing about an improvement to the fitting of both the sensor fastening and the radiant heater, together with the subsequent working of the finished radiant heater.  
           [0006]    This problem is solved by the features of claim  1  and those of claim  17 . Advantageous developments of the invention form the subject matter of the subclaims and are described hereinafter. The essence of the invention is that the fastening means are at least partly shaped from the material of the carrier shell. On fastening temperature sensors to radiant heaters using conventional fastening means generally openings or holes are e.g. punched out on the carrier shell and in them are then inserted and secured the fastening means. However, waste occurs with this process and said waste material can stick to the punching tool and make it dirty. As a result exact, clean punching is no longer possible. The punching tool must be cleaned or, if necessary, replaced, which takes up a relatively large amount of time. The punched out openings or holes are provided with projecting lugs or nozzles, which prevent an exact fixing of the fastening means. These disadvantages are obviated according to the invention in that the fastening means are essentially formed from the same material as the carrier shell. Thus, there is no waste and there are also no prejudicial openings or lugs.  
           [0007]    Sheet metal is preferably used as the carrier shell material. Sheet metal is heat resistant and has a relatively low weight. In spite of this its carrying capacity is so high that it is able to carry the insulator. It would also be possible to use other heat resistant materials, such as ceramics or the like.  
           [0008]    The fastening means preferably comprise a holder for holding the sensor and an abutment for securing the holder. Compared with the holder portion extending through the insulator, the abutment advantageously has a different configuration. Thus, it is possible for the abutment to be inclined or to be substantially transversely directed. Thus, e.g. a holding leg of the holder can be bent at right angles behind the insulator in order to prevent extraction. The holder is preferably retained by engaging the abutment with its entire or a large surface against the underside of the insulator. This reduces or eliminates the risk of the fastening being torn out of the insulator.  
           [0009]    In particularly preferred manner the abutment is shaped out of the carrier shell. The abutment can be formed from several lugs formed out of the carrier shell and to which the holder can be fixed. However, preferably the abutment is shaped in one piece from the carrier shell, e.g. by a punching process, where two mirror symmetrical notches are punched into the carrier shell and the material between the two notches can then be bent up as abutments.  
           [0010]    Preferably a locking connection is located between the holder and the abutment. It can have an insertion bevel for inserting the holder and a locking edge for locking a barb-like end of the holder. On sliding over the insertion bevel the holder, e.g. two holding legs, can be elastically bent upwards to a certain extent. On reaching the locking edge, its barb-like end can engage below the locking edge and snap in. The abutment can have all conceivable cross-sectional shapes, e.g. an inverted V-shaped cross-section or a trapezoidal cross-section. However, it preferably has a substantially cap-shaped cross-section and a central portion of the abutment is arcuately directed towards the insulator and two lug-like legs of the abutment are bent away from the insulator. The arcuately constructed central portion can be supported on the underside of the insulator without damaging the latter, as could be the case with e.g. tapering central portions. To obtain a relatively large contact surface on the underside of the insulator, the central portion is preferably made wider than the two legs.  
           [0011]    It is possible for the abutment to be formed in a bulge of the carrier shell directed towards the insulator, the carrier shell bulge projecting into an insulator bulge constructed in complimentary manner thereto. The two complimentary bulges on the carrier shell and insulator enable them to be stacked in one another.  
           [0012]    The holder can have an elongated portion or long holding legs, which extend through the insulator up to the abutment. The holder or holding legs can preferably engage over or round in an at least partial manner said sensor and in this way position it, e.g. by pressing against the insulator.  
           [0013]    The holder can be a clip with two legs and a U or O-shaped upper part for retaining the sensor. The upper part can extend or engage over the sensor and hold it in position, particularly by pressing against the insulator.  
           [0014]    In an alternative the holder can be connected in one piece with the carrier shell and in this case the carrier shell forms the abutment. The carrier shell then engages on the underside of the insulator. Starting from the insulator, the holder can extend from the carrier shell to the sensor, which can e.g. project through a recess or receptacle in the vicinity of the upper portion of the holder.  
           [0015]    One possibility for connecting the holder to a metal carrier shell is the welding or riveting of corresponding components. Preferably the holder is joined to or worked out from the carrier shell in one piece. This makes it possible to rough-work an elongated sheet metal strip separated by three notches, which form a U, from the carrier shell and bend or set up the same. The insulator can be engaged over the holder or at least one leg thereof. In particular during the fitting of the radiant heater, the holder can automatically pierce the insulator, at least partly project over the same and receive the sensor. Either the holder can pass through the insulator on engaging the latter or can project through a prefabricated slot in the insulator.  
           [0016]    The invention also covers a radiant heater according to the preamble of claim  1 , in which part of the fastening means is anchored in an abutment which is at least separate from the insulator, the abutment being located behind the underside of the insulator remote from the heater without projecting over the underside of the carrier shell remote from the insulator.  
           [0017]    This makes it possible with radiant heaters having planar carrier shells to easily and advantageously stack the same, because the underside or the carrier shell is not projected over by interfering abutments or the like. In certain circumstances it is advantageously possible to economize the costs involved in providing the carrier shell from below with a recess for receiving the abutment.  
           [0018]    Preferably the abutment is constructed separately from the carrier shell and can be anchored between the insulator and said shell.  
           [0019]    One possibility for manufacturing the abutment involves the use of a firm, insulating material, e.g. vermiculite or the like. In it can be engaged at least one leg of the fastening means. A counterabutment is advantageously shaped like a disk and in particular with a large contact surface against the underside of the insulator. Further possibilities are truncated cones or cylinders.  
           [0020]    These and further features can be gathered from the claims, description and drawings and the individual features, both individually and in the form of subcombinations, can be implemented in an embodiment of the invention and in other fields and can represent advantageous, independently protectable constructions for which protection is claimed here. The subdivision of the application into individual segments and the subheadings in no way restrict the general validity of the statements made thereunder. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]    Embodiments of the invention are described hereinafter relative to the attached drawings, wherein show:  
         [0022]    [0022]FIG. 1 A plan view of a radiant heater with a sensor fastening according to the invention.  
         [0023]    [0023]FIG. 2 A section through a radiant heater, the sensor being fastened by a clip to an abutment connected in one piece with the carrier shell.  
         [0024]    [0024]FIG. 3 A larger scale plan view of the abutment of FIG. 2.  
         [0025]    [0025]FIG. 4 A section through a variant of the radiant heater under a glass ceramic plate, the sensor being fastened by a clip to an insulating piece as the abutment.  
         [0026]    [0026]FIG. 5 A variant of the radiant heater according to FIG. 4, in which the abutment is a sheet metal part.  
         [0027]    [0027]FIG. 6 Another variant in which a sheet metal leg is bent upwards out of the carrier shell and extends through the insulator.  
         [0028]    [0028]FIG. 7 An inclined view of a radiant heater showing the erected sheet metal strip of the carrier shell. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0029]    [0029]FIG. 1 shows in plan view a radiant heater  11  in which an insulating border  13  and a flat insulator  14  are inserted in a carrier shell  12 . The insulator  14  covering the bottom of the carrier shell  12  carries a heating means  16  comprising an elongated, meandering heating band or the like. The heating means  16  is electrically connected by means of a terminal or a thermal relay  18 , which switches off the radiant heater  11  or heating means  16  in the case of an excessive temperature. For this purpose the thermal relay  18  has an elongated sensor  19  extending into the radiant heater  11  and which in known manner is made from materials having different thermal expansion coefficients and in particular one in rod-like form and the other surrounding it in tubular manner. The sensor  19  covers part of the heating zone formed by the heating means  16  and which essentially takes up the surface or area of the insulator  14 . The sensor  19  extends by a portion over the centre of the radiant heater  11  and is fastened by a clip  28  to the insulator  14  or an elevation  23  thereof. A precise fixing of the position of the sensor is also considered advantageous for the operation thereof.  
         [0030]    [0030]FIG. 2 shows in section the arrangement of the sensor  19  on the insulator  14 , together with the fastening thereof. In cross-section it is possible to see an elevation  23  in the central area of the insulator  14  and on which rests the sensor  19 . Below the elevation  23  is provided a space  24 , which is roughly frustum-shaped, in much the same way as the elevation  23 . Below the insulator  14  is located the carrier shell  12 , which carriers the insulator  14 . The bulge  37  of the carrier shell  12  projects into the space  24  on the underside of the insulator  14 . On the top of said bulge  23  an abutment  38  is shaped in one piece out of the carrier shell  12 . For producing the abutment  38 , two substantially U-shaped notches  39  are punched in the carrier shell  12  (FIG. 3). Firstly the cap-shaped central part  41  is shaped. The downwardly moving punch of a punching tool (not shown) separates or cuts out the width of the central part and, in much the same way as with a chisel, sets up during the further introduction of the central part  41 . In the next step lug-like legs  42  are cut out in the opposite direction and set up or erected. The notches  39  are mirror symmetrical to a central axis  40  through the abutment  38 . Four narrow connecting webs  51  by means of which the abutment  3 , particularly its central part  41 , is connected to the carrier shell  12  are not punched out. During the bending process the material of the carrier shell  12 , particularly the metal sheet, is stretched, so that the two notches  39  retain the same mutual spacing. The ends of the two legs  42  form locking edges  43  into which can be locked the barb-like ends  50  of the holder  45 . The central part  41  is wider than the two legs  42 . It mainly serves as a bearing surface on the underside of the insulator  14 . The cap-shaped cross-section of the abutment  38  creates an insertion bevel for inserting the two holder legs.  
         [0031]    For fastening the holder  45 , the latter is initially introduced by means of two holes, which are formed in the insulator  14 , through said insulator  14  until its terminally inwardly bent barb-like ends  50  meet the two insertion bevels of the abutment. the holder  45  is widened by the insertion bevels widening in the insertion direction until it has reached the two locking edges  43  on the ends of the two abutment legs. The two barb-like ends  50  of the holder  45  engage below the locking edges  43  and snap into the latter.  
         [0032]    [0032]FIG. 4 shows in section the structure of a variant of the radial heater  11 , where it is possible to see the glass ceramic plate  25  above the insulator  14 . In the space  24  between the insulator  14  and the carrier shell  12  is placed a frustum-shaped abutment  26 , which roughly has the dimensions of the space  24 . In the embodiment shown the abutment  26  is made from a preferably compacted insulating material, e.g. vermiculite or some other firm insulating material used in the electric heating field.  
         [0033]    Over the sensor  19  is guided a U-shaped clip  28 , whose two elongated legs  29  penetrate the insulator  14  and engage in the abutment  26 . The base portion  30  between the two legs  29  engages over the sensor  19  and presses it against the insulator  14  or the top of the elevation  23 . In this way the sensor  19  is virtually nailed against the abutment  26  by the clip  28  and is in this way fastened to the abutment or pressed against the insulator  14 . An upward movement of the sensor  19  is prevented by the clip  28 , which is not firmly retained in the insulator  14  and does not tear it or locally destroy it and instead engages with the much larger surface of the top of the abutment  26  on the underside of the elevation  23  of insulator  14 . The legs  29  of clip  28  can have a roughed surface or tip for better anchoring purposes, e.g. in the manner of small barbs or the like. In place of a two-legged clip  28 , it would also be possible to use a single bent nail or the like, e.g. an angle nail. However, the two legs reliably engage over the sensor  19  and the latter is thereby anchored with twice the retaining strength in the abutment  26 . It is possible to fasten the abutment  26  to the carrier shell  12 .  
         [0034]    [0034]FIG. 5 shows a variant of a radiant heater  11  similar to FIG. 4, but in which the abutment  32  is made from a frustum-shaped flat material, e.g. thin sheet metal. The two legs  29  of the clip  28  are securely anchored therein. Alternatively the clip  28  can be nailed into the carrier shell  12  in a direct manner without an abutment.  
         [0035]    It is admittedly adequate to construct the abutment merely in the form of a disk and not as a frustum, because the surface engaging on the underside of the elevation  23  of insulator  14  contributes to the loadability of the sensor fastening. However, the frustum-shaped construction of the abutment  32  has the advantage that when constructing the radiant heater  11  by placing on one another the individual parts the top of the abutment  32  extends to or just in front of the underside of the elevation  23 . As a result for nailing the clip  28  there is no need to additionally counterhold the abutment and it is instead supported on the carrier shell  12 .  
         [0036]    [0036]FIG. 6 again shows a variant of the sensor fastening in which from the carrier shell  12  is separated and substantially vertically upwardly bent a strip-like sheet metal portion on both longitudinal sides and one end side. This leg-like fastening strip  31  projecting upwards from the carrier shell  12  extends through the insulator  14  or elevation  23  and projects over the latter. Into a recess  35  is introduced the sensor  19  and is pressed against the top of the elevation  23  and is prevented from an upward movement. As shown, the recess  35  can run roughly parallel to the plane of the heating means  16  or preferably rises slightly to the border, so that the sensor  19  cannot of its own accord slide out of it. It is also possible to bend over the upper end  36  of the fastening strip  34  for fixing the sensor  19 . As the fastening strip  34 , corresponding to the carrier shell  12 , is made from a relatively thin metal sheet and as a result of separating or cutting therefrom has relatively sharp edges, on placing the insulator  14  on the carrier shell  12  it can penetrate the same without great effort. This is aided by a construction of the end in pointed manner.  
         [0037]    A perspective view of the radiant heater  11  similar to FIG. 6 is shown in FIG. 7. The insulator  14  is now shown in the rear part of the carrier shell  12 . It is easy to see how the fastening strip  34  is on three sides punched or cut out of the bottom of the carrier shell  12  and bent upwards. In the recess  35  located at its end and which is inclined in the aforementioned manner, is introduced the sensor  19  and consequently through the upper end  36  is prevented from sliding out and from moving upwards. The recess  35  can be constructed in such a way that in the marginal area it is at least partly located within the insulator  14 . Thus, on introducing the sensor  19  the insulator must be slightly displaced or pressed downwards with the advantage that it expands again after introduction and virtually closes the recess. Through a fastening according to FIGS. 6 and 7 the sensor  19  can be positioned engaging not only directly against the insulator  14  or its elevation  23 , but also at a random height between the top of the insulator  14  and the underside of the glass ceramic plate  25 . This is also possible by a clip with a fixed ring or the like engaging round the sensor.  
         [0038]    In place of a fastening strip  34  cut out from the carrier shell  12  and set up, it is possible to fit the same or a similar fastening element to the carrier shell, e.g. by welding.  
         [0039]    The work effort for a fastening strip, particularly the cutting out according to FIGS. 6 and 7, is relatively limited and permits, without additional components, a reliable sensor fastening. A major additional advantage can be brought about in that the sensor fastening or the fastening means form a holding down means for the insulator  14  in the radiant heater  11 , particularly against the carrier shell  12 . If the pushing through the insulator  14  by the fastening strip  34  gives rise to problems, it is possible to prefabricate a through slot in the insulator  14 . The advantage of an insulator as the abutment  26  is inter alia that it does not lead to heat conduction via clip  28  into space  24  or to the carrier shell  12 .  
         [0040]    In order to reduce any heat conduction problems between the heating zone and the carrier shell  12  or the space located below it, it is possible to provide the fastening strip  34  with transversely directed notches or the like, in order to reduce its thermal conductivity. If an electrical insulation is desired or required between the sensor  19  and carrier shell  12 , prior to the introduction of the sensor  19  into the recess  13 , an insulating tube, e.g. of ceramic material, can be placed over the sensor.