FIELD OF APPLICATION AND PRIOR ART  
       [0001]     The invention relates to a method for the optical marking of a touch contact switch or its actuation state by an illumination means, as well as such a touch contact switch.  
         [0002]     EP 859 467 A1 describes a capacitive touch contact switch placed under a glass ceramic hob for the operation thereof. The sensor surface of the contact switch is formed by an elastic plastic body, which is electrically conductive and which is applied to the underside of the glass ceramic hob. A central recess houses an illumination means, with which it is possible to mark the spot where the contact switch or sensor element is fitted, this forming the spot to which a finger must be applied for actuation.  
         [0003]     DE 102 51 639 A1 and DE 10 2004 038 872 describe touch contact switches, in which a sensor element or several sensor elements are directly placed on one another and are elongated. Thus, it is for example possible for a functional unit of an electrical appliance, particularly a hotplate of a hob, to set different power stages, which can in particular be increased or decreased. It is also possible to carry out setting processes, such as preset times or preset weights or the like. Thus, by means of such a slider not only are purely on/off switching processes initiated, but in particular an adjustment of a value.  
         [0004]     Such touch contact switches have different actuation states. Either they are not actuated. If an operator wishes to perform an actuation, he may place a finger on a corresponding contact surface. Either this takes place in a prescribed or correct manner, so that it is clearly recognized as the desired, correct actuation. The corresponding function is initiated by a contact switch. Or the actuation was incorrect or faulty, on the edge of a corresponding contact surface or the like. Then although the contact switch records something, it is still not prescribed or correct. This is recognized and evaluated as incorrectly actuated and the corresponding function is not initiated by the touch contact switch.  
         [0000]     Problem and Solution  
         [0005]     The problem of the invention is to provide such a method and such a touch contact switch making it possible to obviate the prior art problems and in particular improve operating security by an easy, instinctively detectable recognition of an actuation state of the touch contact switch and therefore also an electrical appliance.  
         [0006]     This problem is solved by a method having the features of claim  1  and a touch contact switch having the features of claim  14 . Advantageous and preferred developments of the invention are given in the remaining claims and are further explained hereinafter. By express reference the wording of the claims is made into part of the content of the description. Features describing the method and the contact switch are only described once hereinafter. However, quite independently of this, they apply both to the method and to the contact switch.  
         [0007]     The contact switch has a contact surface for actuation, which is elongated and which can in particular be formed by one or more individual or partial contact sensors. The actuation states “not actuated”, “incorrectly actuated” and “correctly actuated” exist for the contact switch. These can for example depend on whether a signal change is correct or expected or strong enough. The illumination means can change their activation state or be activated or deactivated independently of the actuation state of the touch contact switch. In this way not only is the point of the contact switch indicated for an operator, but also whether the contact switch can respond or is at present activated. It is also possible to activate the illumination means with an actuation of the contact switch, so that said actuation is outputted as an immediately detectable response or acknowledgement to an operator. It is possible to directly switch on the same, after having previously been switched off. Thus, the operator recognizes that the contact switch or the associated electrical appliance or a control has responded to the application of a finger or the actuation and that this is also in the prescribed form as “correctly actuated”. At the end of the actuation with “not actuated”, particularly if a finger is taken away from the contact surface again, the illumination means is switched off for corresponding information to an operator.  
         [0008]     Instead of simply switching on and off the illumination means, it is also possible to change the light intensities or a colour. It is also possible to change between continuous operation and flashing, or in the case of flashing to change the frequencies. Thus, there are always numerous different ways of informing an operator of the actuation state through the state of activation of the illumination means. In certain circumstances it is also possible to generate acoustic signals. LEDs are particularly suitable as illumination means.  
         [0009]     In a simple version it is also possible to activate and deactivate in the same way the illumination means, independently of the nature of the actuation. Thus, it is possible to only indicate the position of the contact switch.  
         [0010]     A change in the state or operating mode of the illumination means can advantageously also depend on whether the actuation is admissible or intended or whether it is correctly actuated or incorrectly actuated. Thus, an operator recognizes if the actuation process was incorrect or has to be repeated.  
         [0011]     It is also possible to subdivide the contact switch or contact sensor into different areas, i.e. partial areas or partial contact surfaces. Through such a subdivision of the contact switch, in which the partial areas directly connect onto one another, the aforementioned slider function can be implemented. A deactivation or activation of the illumination means is advantageously dependent on the position where a finger contacts the contact surface or over which partial area it is located. If different illumination means are directly associated with the partial areas, at least these can change state. The remaining illumination means can be left unchanged. It is alternatively possible to illuminate already passed or swept over partial areas in the manner of an advance bar, whereas partial areas which have not been passed or swept over are not illuminated.  
         [0012]     According to a development of the invention, the illumination means are to be located within the surface of the partial areas and to this end can be provided with corresponding recesses. The partial areas or the areas of a contact sensor forming the same can be metallic or comprise a thin metal coating. Illumination means located below the recesses can emit or illuminate upwards through said recesses. The recesses can be distributed or form a through slot.  
         [0013]     In another development of the invention the illumination means are also provided within the surface of the partial areas, but the said partial areas or the areas of the contact surface are constructed in electrically conductive and light-transmitting manner. Metal oxides, such as zinc oxide or the like can be used for such light-transmitting sensor surfaces in such a limited thickness that they are transparent or light-transmitting. It is also possible to use corresponding, electrically conductive and light-transmitting polymers.  
         [0014]     Alternatively the illumination means can be provided outside the partial areas, particularly on an outer boundary of the touch contact switch or contact surface. For this purpose they can be provided on one or two longitudinal sides, so that they can indicate at what point of the contact surface a finger is located or contact is detected. Alternatively the illumination means can frame the entire contact surface.  
         [0015]     These and further features can be gathered from the claims, description and drawings and individual features, singly or 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 sections and the subheadings in no way restrict the general validity of the statements made thereunder. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     Embodiments of the invention are diagrammatically illustrated by the drawings, wherein show:  
         [0017]      FIG. 1 A  plan view of a touch contact switch with a contact surface and a partial sensor element below the same.  
         [0018]      FIG. 2  Different possibilities of providing illumination means in a contact switch according to  FIG. 1 .  
         [0019]      FIG. 3 A  side view of the contact switch according to  FIG. 2 .  
         [0020]      FIG. 4  Different operating states of the contact switch indicated by different illumination means.  
         [0021]      FIG. 5  Different operating states of a contact switch similar to  FIG. 2 , in which the illumination means are deactivated through non-prescribed actuation. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0022]      FIG. 1  is a plan view of a touch contact switch  11 , which is provided on a surface or cover  12 , for example a housing of an electrical appliance or a glass ceramic hotplate of an electric hob. Touch contact switch  11  is represented by a boundary  14 , for example as an optical marking in the form of a rectangle printed in thin line form on the cover  12 . Contact switch  11  is in particular constructed as a so-called slider, as described hereinbefore. This means that it can be contacted with a finger  26  at one point and actuation takes place by sliding the finger  26 .  
         [0023]     Contact switch  11  has sensor elements  16  formed by partial contact surfaces  17 , which are relatively closely juxtaposed and make it possible to determine a point of the actuation by a finger  26  applied to the surface of contact switch  11 . They can be formed by small metal surfaces, as well as by miscellaneous electrically conductive materials. They can also be in the form of separate components or form a common assembly. They can also be constructed in full-surface and simultaneously light-transmitting manner.  
         [0024]      FIG. 2  shows that recesses  19  in different forms are provided in the partial contact surfaces  17 . To the far left is provided a circular recess  19   a  positioned in the centre of the corresponding partial contact surface  17 .  
         [0025]     Somewhat to the right thereof two recesses  19   b  are superimposed within a partial contact surface  17 . Yet further to the right is a slot-like recess  19   c,  which passes through the partial contact surfaces  17 . To the right and alongside the same there are relatively large recesses  19   d.  It is advantageous here if the surfaces of the recesses  19   d  are either covered with a transparent, electrically conductive coating or for example with a fine, conductive grid or the like.  
         [0026]     In the case of the partial contact surface  17  to the far right on contact switch  11 , no recesses are provided. Here the LEDs  21  are positioned above and below the partial contact surface  17  and further details will be given thereon hereinafter.  
         [0027]     In each case circular LEDs  21  are provided as illumination means in recesses  19   a  to  19   c.  In particular, they substantially entirely fill the recesses  19  or form a very flat illumination. In addition, the recesses  19   d  can contain so-called illuminating surfaces  22  or similar flat illumination elements. These can also be LED components, but which contain several LEDs in a housing or in some other way represent a relatively large-area illumination.  
         [0028]     The different representations of recesses  19  and illumination means  21 ,  22  in  FIG. 2  are of an exemplified nature and are to be provided on the entire contact switch  11  in one of the constructions shown. Thus, a unitary image is provided for an operator and the contact switch  11  can be particularly easily and safely operated, particularly with regards to its functionality and response. Particularly through LEDs or other illumination means positioned outside the contact switch  11  it is also possible to represent fault states of the actuation of contact switch  11  and this will be explained in greater detail hereinafter.  
         [0029]     In the side view of  FIG. 3  it is possible to establish how the sensor elements  16  or partial contact surfaces  17  engage on the underside of a cover  12 , for example as a glass ceramic plate. LEDs  21  or other illumination means are either provided on the edge outside or below the same. Alternatively they can project into corresponding recesses  19 . Instead of the aforementioned recesses  19 , it is also possible to give a light-transmitting construction to the partial contact surfaces, for example through light-transmitting metal oxide coatings, particularly of zinc oxide or also light-transmitting, electrically conductive polymers. In this case the illumination means can be placed below the partial contact surfaces and is particularly appropriate for recesses  19   d.    
         [0030]     Touch contact switch  11  is constructed as a capacitive contact switch. With regards to the operation reference is made to the aforementioned DE 102 51 639 A1 and DE 10 2004 038 872, whose content is hereby expressly made into part of the content of the present description.  
         [0000]     Function  
         [0031]      FIG. 4  illustrates how a finger  26  is used for operating contact switch  11 , which is also represented in simplified form by the broken line circles  26 ′ in the starting position and  26 ″ in an intermediate or end position. As soon as it is applied in the prescribed manner to contact switch  11  in the form of a correct actuation, it is possible to activate the LEDs  21  or corresponding illumination means. This can take place in such a way that an illumination occurs around contact switch  11 , virtually as a frame outside or at boundary  14 . It is in this way indicated to an operator that following the correct application of the finger  26  the touch contact switch is activated and that application has correctly taken place. The finger  26  can now be moved and in particular drawn to the right in the applied state. This is illustrated by the motion arrow. In the central position of finger  26 ″ shown, it is possible to illuminate the entire partial contact surface  17  corresponding to position  26 ″. Such a position-bound illumination can be carried out independently or alternatively to a frame-like illumination of the entire contact switch. Each of the positions  26 ″ on contact switch  11  or contact surface  12  is precisely associated with a partial contact surface  17  and correspondingly illuminates the same.  
         [0032]     Instead of an illumination of the entire partial contact surface  17  it is also possible for individual LEDs  21  to precisely indicate this position inside or outside boundary  14 . Illumination means or LEDs  21  to the left thereof can either also illuminate and in certain circumstances also more weakly or flash in order to illustrate the path covered up to then. Alternatively an indicative illumination only takes place at the point of actuation  26 ″.  
         [0033]     To the far right in  FIG. 4  is shown how the position of an actuation  26 ″ is indicated by LEDs  21  located outside boundary  14 .  
         [0034]      FIG. 5  shows different actuation states or positions of the finger  26 , which are not prescribed or are incorrect. Thus, for example starting from an initial contact position  26 ′ to the far left, essentially corresponding to that of  FIG. 4 , the finger  26  is moved to the right and at the same time outside boundary  14 . Whereas initially an illumination of the contact switch was indicated, the illumination is deactivated at the latest in the represented position of the finger  26 ″, because there a faulty actuation exists. This is illustrated in  FIG. 5  in that no illuminating or emitting LEDs  21  or other illumination means are shown.  
         [0035]     Further incorrect positions  26 ″ of a finger are shown to the far right and right bottom on contact switch  11 . Here the surface of finger  26 ″ projects by more than half over the boundary  14  towards the outside, which is recognized and evaluated as incorrect by the partial contact surfaces  17  or contact switch  11 . Through the deactivation of illumination means  21  it is indicated to an operator that he has placed the finger  26  outside the boundary  14  of contact switch  11  or that an incorrect operation exists.  
         [0036]     Alternatively such an incorrect operation can be shown by the flashing of already illuminating illumination means, which can instinctively be recognized as a fault or faulty state. There can also be a colour change, for example to red in the case of a faulty operation, so that this is also indicated in a clear manner. In addition, faulty operation can also be indicated by acoustic signal generators or the like.  
         [0037]     Within the scope of the invention it is also possible to conceive further mixed possibilities with respect to what has been described hereinbefore and whose details are not listed here.  
         [0038]     The fundamental idea of the invention is that a touch contact switch, particularly of an elongated nature and with several partial contact surfaces, has associated illumination means, in order to indicate to an operator the actuation state and advantageously also the actuation point. It is particularly advantageous if the illumination means are directly associated with individual partial contact surfaces or the movement advance for an operation of the contact switch by applying a finger and drawing the same along a contact surface can be indicated in roughly positionally correct manner. It is also possible to indicate incorrect actuations, if an incorrect actuation has taken place.
An elongate contact switch with several partial contact areas has associated illumination means for indicating the actuation mode and also the actuation point to an operator in order to increase operational safety. The illumination means are directly associated with individual partial contact areas or can indicate the progress of movements for operating the contact switch by applying a finger and pulling the same along a contact area. Moreover, malfunctions can be indicated.