Patent Publication Number: US-2006011612-A1

Title: Control panel for an electrical appliance and method for manufacturing the control panel

Description:
BACKGROUND OF THE INVENTION  
     FIELD OF THE INVENTION  
      The invention relates to a control panel for an electrical appliance, in particular for a domestic appliance, and a method for manufacturing such a control panel.  
      With domestic appliances, in particular with “white goods” such as washing machines, tumble driers, dish washing machines etc., a manufacturer normally offers a very large range of models of an appliance type, for example of a dishwasher. The various models differ particularly here with regard to their technical functions and/or their visual configuration.  
      The appliances are operated by the user via a control panel. The control panel normally contains a plurality of individual controls such as buttons or rotary controls. A dedicated control panel is necessary for each model of an appliance type owing to the large variety of models. The control panels for different models differ for example here in the number of controls and/or the positioning of the controls. Since a dedicated control panel needs to be provided and stocked with components for each model, this leads to high model-specific costs.  
      Membrane keypads are also known as one form of control panel, in which the different buttons and mechanical components of the buttons are covered by a film. A method for embedding a pressure sensor film in a foam-type material for example is described in European patent EP 0 829 891 B1.  
      In addition, a pressure-sensitive sensor film for providing, for example, pressure-sensitive buttons or keypads, is described in European patent EP 0 576 400 B1 (corresponding to U.S. Pat. No. 5,374,449). These films are provided with individual piezoelectric elements using a type of printing technology so that a plurality of pressure-sensitive pressure zones are formed on the film.  
     SUMMARY OF THE INVENTION  
      It is accordingly an object of the invention to provide a control panel for an electrical appliance and a method for manufacturing the control panel which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, which enables a large variety of models and hence a high level of variability with regard to the configuration of an electrical appliance while keeping costs low.  
      The object is achieved according to the invention by a control panel for an electrical appliance, in particular for a domestic appliance, having an appliance-independent technical functional component that contains a sensor film forming a switch panel having a plurality of individual switch zones, each of which can be selected independently of each other. Usually only a specific selection of the switch zones is activated depending on what devices are fitted in the electrical appliance. In addition, an externally accessible keypad is provided having a plurality of individual visually identified button zones assigned to each of the activated switch zones.  
      Each of the individual visually identified button zones is here disposed directly in front of the activated switch zones. The button zones themselves are normally irrelevant to the switching function, i.e. the provision of electrical signals. They are used merely for visual identification of the position of the activated switch zones. The number of visually identified button zones therefore equals the number of activated switch zones. Usually only some of the available switch zones are activated, so that the number of activated and used switch zones is less than the total number of switch zones available on the sensor film.  
      This embodiment is based on the idea of connecting and combining a model-independent, and hence appliance-independent, technical functional component containing the sensor film with an appliance-specific, externally accessible visual functional component (keypad), wherein only the required switch zones of the sensor film are activated i.e. only a number of the switch zones are operational after final assembly. This measure results in that just one standardized sensor film is sufficient for all models, which can hence be manufactured in large numbers and hence economically.  
      The individual switch zones are preferably activated via a selection of the individual switch zones. In addition to the individual switch zones, conductor tracks are normally integrated on the sensor film for electrical selection of the switch zones. These are taken, for example via a cable loom, to an adapter or connector that constitutes an interface to an appliance controller. The particular switch zones that are needed depending on the required configuration of the given model are activated or “enabled” by a corresponding selection. The selection is performed either purely in software and/or in hardware or a combination of software and hardware. In the second case, an adapter or connector is preferably provided via which only selected conductor tracks are connected. Some of the contacts of the connector are not fitted. The configuration of the whole controller hardware is preferably also independent of the model. Only the software used or the adapters/connectors via which the selection of the sensor film is made are model specific.  
      According to a useful development, the sensor film is pressure sensitive and contains a plurality of individual pressure zones. A switch zone is therefore actuated by applying pressure. In particular, the film is formed with integrated conductor tracks and a printed piezo-layer, pressure zones being defined via the printed piezo-layer, and each individual pressure zone being formed as a piezo-element. Such a piezo sensor-film is described for example in European patent EP 0 576 400 B1 (corresponding to U.S. Pat. No. 5,374,449). The key advantage of such a film lies in the electrical functionality, i.e. the individual piezo-elements and their connection via the integrated conductor tracks, being printed on a polyester film, for example, in a simple and economic manner using printing technology. Thus such a piezo sensor-film can be manufactured almost as “piece goods”. In this case the production costs are set mainly by the size of the sensor film and less by the number of pressure zones integrated on the sensor film. In this respect, not activating a few or more of the integrated switch zones is uncritical from the cost viewpoint.  
      Instead of the pressure-sensitive embodiment of the switch zones, in an alternative embodiment these are formed as capacitive or proximity switches, for example.  
      According to a useful embodiment, the keypad is configured as a control plate having a plurality of buttons or button zones, the buttons being assigned to the individual activated switch zones. The buttons in this case are in particular pushbuttons that act on the switch zones, i.e. they exert a pressure on the zones when pushed. The control plate is the whole front panel of a household appliance, for example, or alternatively in a preferred version it is configured as an insert fitted in the front panel.  
      According to a useful embodiment the control plate is an injection molding and the sensor film is embedded in the control plate, in particular fully embedded. In injection molding, the sensor film is thus placed in a suitable mold and surrounded with the plastic material. Only the electrical connections, i.e. the cable loom provided on the sensor film, extends out of the embedding. This measure results in that a hermetic seal of the electrical component is already achieved when the control panel is manufactured, and no further precautions need to be taken at final assembly to protect against moisture or the like.  
      In order to increase the variability and reduce costs, it is provided according to a useful development that the control plate contains a plurality of technical function-button zones, wherein only a specific selection of the individual function-button zones are formed as visually identifiable button zones, i.e. as buttons, depending on what devices are fitted in the electrical appliance. Thus by this measure, in a similar way to the sensor film, an initially appliance-independent control plate is provided with an array-type configuration, for example, of the function-button zones only visual identification of those button zones that are needed and placed in front of the activated switch zones depends on the given model. In the simplest version here, the appliance-independent function control plate is formed as the injection molding in which the sensor film is integrated, because owing to the high sensitivity, in particular of the sensor film with the printed piezo-layer, no separate button elements passing through holes in the control plate are required.  
      In order to identify the position of the individual button zones and hence the activated switch zones, a printed pattern is preferably applied to the control plate or a film bonded over it on which the individual button zones are visually represented. With a sufficiently large sensor film, a different selection of the positions of the individual button zones or buttons can be made over a large area, so that the widest range of models, in particular also in terms of visual appearance, can be formed in a simple manner.  
      In addition, decoupling elements, for instance ribs, a lattice structure or the like are usefully disposed between the individual button zones, providing decoupling, in particular mechanical decoupling, between adjacent function-button zones. This measure guarantees a precisely defined actuation of the respective activated switch zones when the assigned button zone is pressed and avoids malfunctions. A precise spatial resolution of the exerted pressure is thus achieved by the decoupling elements.  
      The object is also achieved according to the invention by a method for manufacturing a control panel. The preferred embodiments and advantages cited for the control panel shall also apply analogously to the method. The method is characterized in that first an appliance-independent “technical” component is manufactured in large numbers and the configuration, i.e. the specification of which of the pressure zones are activated, is not performed until the domestic appliance is assembled. The technical component here is in particular the plastic injection molding, formed as a control plate, together with the integrated sensor film. For configuration at final assembly, first a printed pattern is applied or a film is bonded onto the control plate in order to identify visually the button zones, and second the required switch zones are actuated by the software selection and/or hardware selection.  
      Other features which are considered as characteristic for the invention are set forth in the appended claims.  
      Although the invention is illustrated and described herein as embodied in a control panel for an electrical appliance and a method for manufacturing the control panel, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.  
      The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a diagrammatic, rear view of a control plate, formed from injection molding, with an embedded sensor film, according to the invention;  
       FIG. 1B  is a diagrammatic, rear view of the sensor film embedded in the control plate as shown in  FIG. 1A  prior to the injection molding process;  
       FIGS. 2A and 2B  are diagrammatic, sectional views each showing the sensor film with a printed piezo-layer;  
       FIG. 3  is a diagrammatic, cross-sectional view through the control plate with the embedded sensor film; and  
       FIG. 4  is an illustration of the sensor film having a plurality of individual switch zones. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      In all the figures of the drawing, sub-features and integral parts that correspond to one another bear the same reference symbol in each case. Referring now to the figures of the drawing in detail and first, particularly, to  FIGS. 1A and 1B  thereof, there is shown a pressure-sensitive sensor film  2  which contains a plurality of individual pressure zones  4  each formed by an individually selectable piezo-element. The sensor film  2  is formed overall like a sensor panel having the pressure zones  4  disposed in an array. The individual pressure zones  4  are here selectable via conductor tracks  6  that are brought together in a cable loom  8 . The individual conductor tracks  6  and the individual piezo-elements for forming the individual pressure zones  4 , are printed onto a film-type base material, for example a polyester film.  
       FIGS. 2A and 2B  show a schematic cross-section through the film  2 , in one case not under load, and in one case with pressure applied,  FIG. 2B . The sensor film  2  contains a base film  10  onto which an electrode  12 , for example a carbon layer, a piezo-layer  14  made of a piezo-active material and another electrode  12  are applied in succession. The electrodes  12  are used for making electrical contact with the piezo-layer  14  via the conductor tracks  6 . The electrodes  12  are physically restricted to the area of the pressure zone  4 , i.e. they define the position of the pressure zone  4 . Within the piezo-layer  14  are areas  16 A,  16 B having negative and positive polarization respectively. When pressure is applied with a force F in the direction of the arrow shown in  FIG. 2B , the sensor film  2  is deformed which, owing to the piezoelectric effect, results in a voltage signal being generated, which is transmitted as a switching signal via the individual conductor tracks  6  to a control unit not shown here.  
      Owing to the manufacturing technique of the sensor film  2  based on printing process steps, the manufacturing costs of the sensor film  2  are substantially independent of the number of the individual pressure zones  4 . They depend solely on the overall size of the sensor film  2 .  
      In order to form a control panel, the rear side of which is shown in  FIG. 1A , the sensor film  2  in the exemplary embodiment of  FIGS. 1A and 1B  is embedded in a control plate  18  by injection molding. The control plate  18  in turn contains a multiplicity of individual function-button zones  20 , as shown in  FIG. 1A , which are disposed here in the same array-type configuration as the individual pressure zones  4 . In the exemplary embodiment of  FIG. 1A , the individual function-button zones  20  are formed by a circular region, each centrally positioned, having a reduced wall thickness and bounded laterally by ribs  22  disposed like a lattice. These form decoupling elements for explicit and precise actuation of the underlying pressure zone  4  when pressure is applied to the individual function-button zones  20 .  
      The combined component shown in  FIG. 1A  made of the sensor film  2  and the control plate  18  still has a model-independent configuration that can be used for the widest range of models of an appliance type, for example a washing machine or dishwasher or other domestic appliance of the “white goods” type or even an electronic home-entertainment device. The appliance-specific configuration with regard to the pressure zones  4  is achieved by a corresponding selection or enabling of the required pressure zones  4 , which then provide their functions as activated pressure zones  4 ′ (in  FIG. 1B , for example two pressure zones are labeled with the reference  4 ′). The selection is performed in software here, i.e. only the signals output from the pressure zones  4 ′ of interest (activated pressure zones  4 ′) via the interface to a control unit are evaluated or only the activated pressure zones  4 ′ are electrically connected.  
      With regard to the control plate  18 , the appliance-specific configuration is achieved by a visual identification of the respective function-button zones  20 , so that visually identifiable button zones  20 ′ are formed. This is achieved, for example, by applying a film or a printed pattern on the front face of the control plate  18  (for example in  FIG. 1A  two button zones labeled  20 ′ are provided).  
      The complete embedding of the sensor film  2  in the control plate  18  can be seen in  FIG. 3 . Only the cable loom  8  extends out of the embedding. The sensor film  2  as such is thereby hermetically sealed. Alternatively, the sensor film  2  is only partially embedded, i.e. the sensor film  2  is only partially enclosed by the plastic material, and a sub-section of the rear side of the sensor film  2  remains exposed for example.  
      According to  FIG. 4 , the sensor film  2  contains a plurality of pressure zones  4  disposed in an array, only some of the zones being activated via the selection. These form the activated pressure zones  4 ′ shown hatched.  
      This application claims the priority, under 35 U.S.C. § 119, of German patent application No. 10 2004 033 656.3, filed Jul. 12, 2004 and German patent application No. 10 2004 043 578.2, filed Sep. 9, 2004; the entire disclosures of the prior applications are herewith incorporated by reference.