Abstract:
According to an embodiment of the invention, a sensor element device for a capacitive contact switch can be formed from a foam body with several portions. There are electrically conductive areas with a sensor element surface and an electrical contact face, as well as insulating areas. The sensor element surfaces engage from below on a glass ceramic plate. The areas can be interconnected in cylindrically elongated and juxtaposed manner. This leads to a type of strand material from which with the predetermined spacing it is possible to produce juxtaposed, capacitive sensor elements as parts of contact switches.

Description:
FIELD OF APPLICATION AND PRIOR ART 
   The invention relates to a sensor element device and to a method for the manufacture of a body as a sensor element for a capacitive sensor element device. 
   Such sensor element devices are known from EP 859 467 B1, where a sensor element with a body is described, which has a roughly elongated and cylindrical or barrel-shape. As is apparent from this prior, art several such bodies are required for juxtaposed sensor elements or the contact switches formed by the latter and which are located on a printed circuit board. The manufacturing method described involves such bodies being cut to length from a long rod by an automatic assembly machine. 
   PROBLEM AND SOLUTION 
   The problem of the invention is to provide a sensor element device and a method of the type described hereinbefore, in which the body as the sensor element has a novel construction and extended functionality, whilst the body manufacturing method is simplified. 
   This problem is solved by a sensor element device having the features of claim  1  and a method having the features of claim  22 . Advantageous and preferred developments of the invention form the subject matter of further claims and are described in greater detail hereinafter. By express reference the wording of the claims is made into integral part of the content of the description. 
   According to the invention, the sensor element device has a three-dimensional shape-variable and elastically compressible body and which is formed as a sensor element. It is electrically conductive and extends at least in one area from an electrical contact zone on the one hand to a sensor element surface on the other. According to the invention it has different areas. There is at least one conductive area extending between an electrical contact zone and a sensor element surface and which is electrically conductive throughout. There is also at least one insulating area, which is not electrically conductive. There is at least one insulating area between several conductive areas. Thus, advantageously conductive areas and insulating areas are juxtaposed in alternating manner. Thus, according to the invention it is possible to create a single, unitary body, which as a single, easily handleable unit forms several sensor elements and therefore several contact switches. 
   Advantageously the sensor element surface is formed by the surface of part of a conductive area. The sensor element surface can be formed by the contact face between part of a conductive area and a cover on which engages the sensor element device. Consequently there is no need for a separate surface in order to reduce manufacturing costs. This principle is known from EP 859 467 B1 to which reference is expressly made in this connection. 
   Another advantage is that numerous small bodies are replaced by a single, larger body. In addition, there can be significant simplifications to the assembly processes, because it is no longer necessary to handle and optionally insert or mount several parts and instead this only applies to a single part. 
   It is apparent, particularly in comparison with the aforementioned EP 859 467 B1, that the single sensor element body, as used up to now, is difficult to handle as a result of its in part small size. However, a larger body according to the invention is easier to handle. 
   The numerous conductive areas and the at least one insulating area can be mechanically and firmly interconnected. They are advantageously interconnected in such a way that they are so-to-speak non-detachable, i.e. do not automatically come apart and instead this only takes place under force action. In particularly preferred manner they are constructed in one piece. 
   Advantageously between the electrical contact zone and the sensor element surface, the areas are elongated and extend in this direction. Advantageously all the conductive areas pass in this extension direction, i.e. in a particularly advantageous manner are parallel to one another. 
   The insulating areas can also run in this extension direction. It is particularly advantageous if the areas are cylindrical with a round or angular cross-section. 
   The body is advantageously made from a rubbery material in order to have the elastic, compressible characteristics. This can e.g. be a foam and the electrical conductivity is obtained by means of carbon black or metal inclusions. For more precise information concerning this sensor element body, particularly with regards to the manufacture, material characteristics or composition, express reference is made to EP 859 467 B1 and U.S. Pat. No. 5,087,825, whose wording is by express reference made into part of the content of the present description. 
   The body can be part of a strand and therefore has a very considerable length. The aforementioned extension direction of the areas can be perpendicular to the longitudinal direction of the strand. This means that the strand is constructed in such a way that it has a large number of juxtaposed conductive and insulating areas. 
   In a fundamental state e.g. after manufacture, said strand can be linear. This with particular advantage relates to its longitudinal direction, so that it is a straight strand. According to an advantageous variant it can be bent in a direction at right angles to the extension direction of the areas and is in particular elastically bendable. This offers the advantage that e.g. arcuately arranged sensor elements can be formed with a single body. For this purpose the body is merely bent in the desired manner, which is easily possible as a result of the elasticity. In the case of fixing to a printed circuit board or the like or behind an operating screen or the like, the bent shape can be fixed, so that e.g. also circular arrangements are possible. 
   As an alternative to such a bendable strand, the body can already be constructed in a per se predeterminable shape, i.e. in zig-zag form or shapes which can scarcely be produced by bending. This shape can be obtained with particular advantage by the joining together of the individual areas. 
   The mutual spacings of the areas and in particular their total dimensions such as cross-section and length, are identical at least in the case of some conductive areas. Advantageously all the conductive areas are identical. This more particularly has manufacturing advantages in such a way that from a long rod material it is e.g. possible to separate the conductive areas and to join them together with the insulating areas, which are e.g. produced in the same way, to form a strand-like sensor element. 
   In addition to an elongated, strand-like construction, the areas can also form a body with a bank-like or areal construction. Thus, different areas, particularly conductive and insulating areas can alternate in both areal extensions of the body and can be joined together. Advantageously the conductive areas are separated from one another in each direction by insulating areas. The resulting body can either form a closed surface or have recesses or openings. It is consequently possible for there to be in the direct link between two mutually closest conductive areas in each case forming sensor elements either an insulating area or an insulating air gap. The body can be constructed in such a way that it can be tailor-made, e.g. using blades or a laser. Alternatively or additionally the body can be separated at a junction point between two areas. This can e.g. take place by pulling or tearing off by hand and without aids. The connection of the areas, which can e.g. be an adhesive joint, can be separated without damaging the individual areas. 
   The electrical contact zone for the conductive areas advantageously has contacts, which with particular advantage are laminar and constructed as contact banks. Advantageously the contacts have at least the mutual spacing of two conductive areas or even a larger spacing. In a particularly preferred development, between two mutually closest contacts there are several, i.e. for example three or four conductive areas. Thus, there is only direct contacting of those areas which engage with contacts. The intermediate conductive areas have no direct contact. 
   It is possible for an insulating area between conductive areas to form a dielectric in such a way that between the conductive areas are formed transverse or shunt capacitances and therefore capacitive, electrical connections. In this way there can also be an electrical connection to conductive areas not directly connected to a contact. This can make it possible to require fewer contact zones than conductive areas and therefore there are fewer sensor element surfaces. It is also possible to evaluate these sensor element surfaces by means of the aforementioned transverse capacitances. For this purpose it is necessary to correspondingly design an evaluating circuit, which is connected to the sensor element device and has the contact zones. This is possible due to the fact that the transverse capacitances are known. Thus, from a signal emanating from a contact on one of the conductive areas it is possible to establish by means of the known transverse capacitances at which point the contact took place and therefore which specific signal should be emitted. 
   A conductive area and in particular the entire body can have an insulating coating or the like on the side directed towards the electrical contact zone. This makes it possible for the electrical contact zone to have elongated and upwardly projecting contact pins. On mounting the body, these push through the insulating coating into the conductive area and thereby bring about electrical contacting. This can make it possible to mount in precisely positioned manner complete strand-like or plate-like bodies on a printed circuit board. The printed circuit board can carry contact pins, which pierce through the insulating coating at precisely predetermined points and produce a desired contacting with individual, conductive areas. Other contacts left open or soldering points on the printed circuit board do not represent an undesired contact zone and in this way prevent malfunctioning. 
   A conductive area is advantageously adjacently enveloped by one or more insulating areas and is advantageously completely surrounded by the insulating areas. 
   In the aforementioned method according to the invention for the manufacture of a sensor element body conductive areas are formed, e.g. in the aforementioned manner. They are made from electrically conductive, three-dimensional shape-variable, elastically compressible material. These conductive areas are linked by insulating areas, in the manner described hereinbefore, made from three-dimensional shape-variable, elastically compressible, insulating material. Thus, such areas can e.g. be lined up in juxtaposed manner as cylinder-like pins or the like. Joining can take place by adhesion and this mainly applies to a material-linking connection. This can e.g. be heat sealing or thermal welding. 
   Far more conductive and insulating areas can be produced in juxtaformed manner as bodies in strand form than are required for a sensor element device. Through the separation of individual bodies finishing takes place so that they are available in the requisite form. 
   The above and further features can be gathered from the claims, description and drawings and the individual features, both singly 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 sections and the subheadings in no way restrict the general validity of the statements made thereunder. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention are described in greater detail hereinafter relative to the diagrammatic drawings, wherein show: 
       FIG. 1  A basic representation of the arrangement possibilities for juxtaposed conductive and insulating areas. 
       FIGS. 2 to 4  Constructions of strand-like sensor element bodies in straight or curved form, where the electrically conductive areas are surrounded by insulating areas. 
       FIG. 5  A starting form for the production of a sensor element body in laminar form from which individual sensor element bodies can be produced by transverse and longitudinal cutting. 
       FIG. 6  A sensor element body in cross-section, where there are several conductive areas between the electrical contact zones. 
   

   DETAILED DESCRIPTION OF EMBODIMENTS 
     FIG. 1  shows a strand-like sensor element device  11  or part thereof. The sensor element device  11  comprises elongated, quadrangular, cylindrical, conductive areas  13  having at one end a sensor element surface  14 , at the top in  FIG. 1 . An electrical contact face is provided on the downwardly directed surface and with this electrical contacting can take place on a circuit or the like. In this form the conductive area  13  roughly corresponds to an elastic sensor element of the type described hereinbefore. This more particularly also applies to the function of the sensor element surface  14  and the electrical contact face  15 . 
   The sensor element device  11  has several such conductive areas  13 , which in the embodiment shown are substantially identical and parallel to one another, being connected by insulating areas  17 . In each case between two conductive areas  13  an insulating area  17  is provided. This leads to a type of stringing together of areas  13  and  17 . In particular as a result of the mechanical connection producing the sensor element device  11  as a single component, easy handling and installation is possible. 
   As stated hereinbefore, for forming such a sensor element device  11  it is possible to separately manufacture and then interconnect the areas  13  and  17 . Alternatively a type of intermediate expansion operation would be possible. Either the conductive areas  13  or the insulating areas  17  can be moulded in between the in each case areas of the other type using a two-component injection moulding process such as is known in plastics processing. 
   It is finally also possible from a single, per se homogeneous piece of starting material through working individual areas to subsequently make them either electrically conductive or electrically insulating. Possibilities would e.g. be offered by thermal or chemical working or irradiation. 
   As can be gathered from  FIG. 1  and also as a general observation, it is advantageous for the sensor element surface  14  and/or the electrical contact faces  15  to all be in one plane. This simplifies manufacture as a standardized strand material and also facilitates use. In certain circumstances it is alternatively advantageous to provide different lengths of conductive areas  13  or insulating areas  17 . 
     FIG. 2  shows a variant of a sensor element device  111 , which once again has conductive, cylindrical, elongated areas  113 . In  FIG. 2  they are provided at the top with a sensor element surface  114  and at the bottom with an electrical contact face  115 . 
   Differing from the construction according to  FIG. 1  the conductive areas  113  are surrounded by material  117 , except in the areas where the sensor element surfaces  14  and electrical contact faces  115  are located. The material  117  forms the insulating areas  117  and is located not only between two conductive areas  113 , but also on the sides thereof. This avoids undesired lateral contacting of the conductive areas  113 . In addition, as a result of the greater width of the strand-like sensor element device, there can in certain circumstances be an easier assembly or installation. Finally, in certain circumstances shields or the like can be produced in this way, e.g. as an additional coating furthest to the outside on the sides of the insulating material  117 . 
     FIG. 3  once again shows a strand-like sensor element device  211  roughly corresponding to that of  FIG. 2 . Once again there are conductive areas  213  which are laterally completely surrounded by insulating material. The latter forms the insulating areas  217 , which inter alia are located between in each case two conductive areas  213 . 
   According to  FIG. 2  the sensor element surfaces  214  and electrical contact faces  215  are left free. Simple assistance is available if this leaving free of the surfaces  214  and  215  preferably in one plane proves to be difficult from the manufacturing standpoint and when it cannot be brought about in a precise manner. This advantageously involves a sensor element device being cut flat in order to create identical, planar surfaces  214 ,  215  over which the insulating material does not project. 
     FIG. 4  shows a further construction of a sensor element device  311  in strand form and which roughly corresponds to that of  FIG. 2 . It is bent in circular manner and its ends almost abut with one another. Such a sensor element device  311  can be produced either by corresponding shaping of a straight strand material according to  FIG. 2  or the bent shape can be constructed in self-maintaining manner, which permits easier installation. 
   The conductive areas  313  and consequently also the sensor element surface  314  and electrical contact face  315  here have an elongated oval shape. However, this is unimportant and is essentially variable. As in  FIG. 2  insulating areas  317  are located between the conducting areas. 
   It is also possible to diverge from the elongated and/or cylindrical shape of the conductive areas or insulating areas shown in the drawings. For example, the surfaces  14  and  15  can be made larger than the remainder of the conductive areas in cross-section form. Alternatively the surfaces can be smaller than the cross-sections. This depends on which surfaces are desired with respect to the sensor element sensitivity or release on the one hand and which cross-sections with respect to the electrical conductivity or other electrical properties on the other. 
   It is also clear that the sensor element device  311  of  FIG. 4  could also have a closed construction in the manner of a circular ring, i.e. the front gap can be closed. This is readily apparent to the expert from  FIG. 4  and is easy to technically achieve. 
     FIG. 5  shows a sensor element device  411  constructed in the manner of a plate. Parallel to the extension surface of the device are located conductive areas  413  with sensor element surfaces  414  and electrical contact faces  415 . Much as in  FIG. 2 , there are completely surrounding insulations in the form of the insulating material  417 . 
   The plate-like sensor element device  411  according to  FIG. 5  can now be split by cutting into elongated, strand-like sensor element devices corresponding to  FIG. 2 . It is possible to cut or separate in accordance with the dot-dash lines. These dot-dash lines are perpendicular to the longitudinal extension of the conductive areas  413 . The thus obtained strand-like sensor element devices can then be cut to length in accordance with the broken lines. The embodiment of  FIG. 5  provides for a subdivision into blocks of two ( 420 ) and four ( 421 ), i.e. with in each case two or four conductive areas  413 . 
   A construction of a sensor element device  411  according to  FIG. 5  has the major advantage that it can be manufactured substantially automatically or even fully automatically using plastics processing plants. Through corresponding cutting, separating or dimensioning it is possible to produce the desired, individual sensor element devices. 
   The embodiment illustrated in  FIG. 6  shows how a sensor element device  11  like that of  FIG. 1  can be used. Besides not shown electronics and further components, a printed circuit board  30  caries contact banks  32 , which can e.g. be built up from the conducting tracks. Upwardly projecting contact pins  33  may be provided, in order to produce electrical contact between the contact banks  32  and the conducting areas. 
   The printed circuit board  30  runs in parallel and at a certain distance from an underside of a glass ceramic plate  40 . Between them is provided the sensor element device  11  in such a way that it comes to rest with the electrical contact faces  15  in part on contact banks  32 . The sensor element surfaces  14  are located on the underside of the glass ceramic plate  40 . It must be borne in mind that between the individual contact banks  32  individual conductive areas  13  and also with respect to their contact faces  15  can so-to-speak dangle in the air, so that no electrical contacting occurs here. 
   As shown in  FIG. 6  by means of the glass ceramic plate  40  as dielectric serial capacitances Cs are built up towards the top. If a finger  41  contacts the top of the glass ceramic plate  40  above a conductive area  13  or its sensor element surface  14  a per se known capacitive coupling occurs. By means of a corresponding evaluating circuit, which is not described in detail here, it can be evaluated as an operation or actuation. 
   In  FIG. 6 , in addition to the serial capacitances Cs, which are in each case formed above a conductive area  13 , there are parallel capacitances Cp, which in each case are located between two adjacent, conductive areas  13 . They are formed through the electrical characteristics of the insulating areas  17  located between the electrically conductive areas  13 . By means of said parallel capacitances Cp there is also an electrical connection of conductive areas  13 , which are not directly contacted by means of their electrical contact face  15 . It is consequently possible to reduce the number of contact banks  32  or even make this number smaller than that for the conductive areas  13 . A localization of finger application can take place through the evaluation of the known, corresponding transverse capacitances Cp, which is merely a matter of the evaluating circuit. 
   By means of such a device it is possible with an acceptable expenditure to provide several sensor element surfaces along a line corresponding e.g. to a scale or gradation. Contacting effort and expenditure can be correspondingly reduced.