Abstract:
A touch-sensitive switch is disclosed whose electrical circuit is provided on a printed board ( 28 ). The touch-sensitive switch is coupled to a touch-sensitive switching area ( 12 ) on a panel or cover ( 11 ) of an electrical appliance via a sensor element ( 44 ). The sensor element ( 44 ) consists of a flexible, electrically conducting plastic or foam material. Two parts ( 24, 25 ) of the sensor element ( 44 ) are received in a receiving element or receiving cage ( 18 ) which is produced from an electrically insulating, transparent plastic. Said receiving element or cage electrically insulates the two sensor element parts ( 24, 25 ) from each other by means of a dividing wall ( 21 ) and encases them from the exterior, thereby providing a sufficiently long air and leakage path between current-carrying elements and an opening ( 16 ) in the panel. A lighting element projects through said path and guides the light emitted by an LED ( 29 ) to a light outlet in the switching area ( 12 ) in the manner of a light guide. Alternatively, an interior casing ( 23 ) can be provided downstream of the opening ( 16 ) and sealingly surrounds the lighting element ( 15 ), across the air and leakage path, and at the same time retains the sensor element ( 44 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from PCT Application No. PCT/EP2005/003943, filed Apr. 14, 2005, which is based on German Application Number 10 2004 019 304.5, which was filed Apr. 15, 2005, of which the contents of both are hereby incorporated by reference. 
     
    
     FIELD OF APPLICATION  
       [0002]     The invention generally relates to an operating device for operating an electrical appliance having a proximity or touch switch according.  
       BACKGROUND  
       [0003]     Touch switches are known from EP 859 467 A1. In the case of such switches, the contact surface whose touching or approach is evaluated for the switching process by electronic circuitry, is determined by a sensor element located beneath a cover or surface and which is made from an electrically conductive, flexible material, e.g. a rubbery plastic or foam. This leads to a good contacting of the underside of the cover and ensures constant conditions. For signalling the switching which has taken place, a light emitting diode is used and is placed in the center of a circular ring-shaped sensor element on the printed circuit board carrying the sensor element and trans-illuminates through the transparent or translucent surface, e.g., a glass ceramic plate.  
         [0004]     The problem of the invention is to design such an operating device in such a way that it ensures maximum safety for the operator with the most varied types of covers and even under extreme environmental conditions. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     Embodiments of the invention are described in greater detail hereinafter relative to the attached diagrammatic drawings, wherein show:  
         [0006]      FIG. 1 A  diagrammatic plan view of the cover or panel of an electrical appliance.  
         [0007]      FIG. 2 A  longitudinal section through part of an operating device.  
         [0008]      FIG. 3 A  section along line III-III in  FIG. 2 .  
         [0009]      FIG. 4 A  plan view of an operating device with a touch switch.  
         [0010]      FIG. 5 A  partial cross-section through the cover and touch switch of  FIG. 4 .  
         [0011]      FIG. 6 A  plan view corresponding to  FIG. 4  with an opening positioned eccentrically to the switching area.  
         [0012]      FIG. 7 A  section through a detail of the touch switch.  
         [0013]      FIG. 8 A  view along arrow VIII in  FIG. 7 , without circuit board. 
     
    
     DETAILED DESCRIPTION  
       [0014]     In one embodiment of the present invention, e.g. in the case of a non-transparent cover, such as a laundry dryer panel made from coloured plastic, a light emitting element for signalling the switching process (e.g., as when the user turns “on” the appliance) projects in the pushbutton area direction through an opening in the cover. Even if the light emitting element is ideally fitted, small gaps can arise and e.g. water can pass through the opening between the light emitting element and the cover (e.g., the gap), creating what can be termed an “air and leakage path”. The air and leakage path between a contactable part and a live part (e.g., electrically charged), according to some regulations, must be normally be 12 mm or more. The electrically insulating envelope of the sensor or light emitting element on the periphery thereof creates said leakage path without impairing the action of the electrically conductive sensor element.  
         [0015]     In one embodiment, the sensor element is constructed in two parts. One part can rest on the corresponding circuit board contact and the other part contacts the cover. Between the two is electrical insulation, so that the part adjacent to the cover is galvanically isolated from the live part engaging on the circuit board. However, it has been found that the effectiveness and control coupling of the sensor element to the circuit of the touch switch is not impaired. The two-part nature makes it particularly easy to give the two end faces of the sensor element different sizes, so that a smaller end face takes up little space on the printed circuit board, whereas the larger end face of the part engaging on the cover ensures a comfortable size for a user to press on a switching area.  
         [0016]     User operation is facilitated if the light emitting element is integrated into the touch contact surface and projects through the sensor element and, in particular, close to the cover. Thus, the switching area on the contact face surrounds the light emitting element. In one embodiment, the light emitting element is arranged eccentrically to the switching area, because then the operator does not automatically cover the same during the switching process, and can see the light emitting element during operation.  
         [0017]     The sensor element, preferably the portion near the cover (“cover-contacting end”), can be constructed as a seal for the opening. This is particularly effective if said sensor element part has on its cover-contacting end face a closed surface, e.g., being constructed as a flexible, but still solid, rubbery plastic or as a foam with a closed-pore (waterproof) surface.  
         [0018]     All these embodiments can be implemented using a reception element, which has a preferably cup-shaped receptacle belonging to the envelope for the support-near part of the sensor element. The reception element&#39;s bottom forms the insulation and carries on the other side a roughly shell or dish-shaped receptacle for the cover-near part of the sensor element, which can be constructed in relatively flat manner similar to a disk. The receptacle can be circular cylindrical, but the shell-shaped receptacle for the cover-near part has a larger diameter than the receptacle facing the printed circuit board. This leads to an offset outer face of the reception element, so that the necessary air and leakage path can be respected, without the spacing between the support (circuit board) and cover having to be too large.  
         [0019]     The reception element can be produced as a transparent plastic injection moulding and therefore forms a light guide, where a projection projecting through the shell-shaped receptacle and which extends the casing of the cup-shaped receptacle forms a through light conducting path between a light generator placed on the circuit board, e.g. a light emitting diode (LED) and the light exit face of the light emitting element projecting through the opening.  
         [0020]     The step formed as a result of the different diameters between the two receptacles can be enlarged by a rib e.g. surrounding half the circumference of the reception element and which in addition to its effect of increasing the air and leakage path also forms a dripping projection for any moisture which may have penetrated to collect on (in the worst possible case) so that the moisture does not reach the circuit board.  
         [0021]     Thus, one embodiment of a touch switch is created, whose electric circuit is located on a printed circuit board. It is coupled by means of a sensor element to the touch switching area on an electrical appliance cover or panel. The sensor element can be made in two parts from a flexible, electrically conducting plastic or foam material. The two parts of the sensor element are received in a reception element of an electrically insulating, transparent plastic, which by means of a partition electrically insulates from one another the two sensor element parts and externally envelops the same, so that between the live parts adjacent to the circuit board and an opening in the panel with an adequate air and leakage path a light emitting element which, through a reception element also serving as a light guide, is illuminated by a LED on the circuit board.  
         [0022]     The light emitting element can alternatively be surrounded by an envelope of the sensor element and can be directly connected to the opening so as to form the air and leakage path. Preferably, the sensor element surrounds the tubular envelope and is “engaged” thereon. In the case of an opening positioned eccentrically to the switching face, the envelope can touch or support the outer circumference of the sensor element and consequently also contribute to the bearing or mounting of said sensor element.  
         [0023]     These and further features of preferred developments of the invention can be gathered from the claims, description and drawings and the individual features, both 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.  
         [0024]      FIG. 1  shows a front view of a cover  11  forming the panel of the operating part of a laundry dryer. On the same panel other input devices are defined e.g. as a start/stop button the switching area  12  of a proximity or touch switch  50  and is indicated by a marking  13 , e.g. by corresponding printing or plastic highlighting. The cover is made from an opaque, i.e., non-transparent plastic or some other non-transparent material.  
         [0025]     In the switching area it is possible to see the light exit face  14  of a light emitting element  15 , which although being located within the switching area  12 , is eccentric thereto and in the present case is upwardly displaced.  
         [0026]      FIG. 2  shows in longitudinal section the cover  11 , which at the location of the light emitting element  15  has an opening  16  in which engages the light emitting element in the form of an (in this embodiment) trapezoidal projection  17  of a reception element  18 , so that the light exit face  14  is essentially terminated in a plane with the outer face  19  of the cover  11 .  
         [0027]     Reception element  18  is made from electrically non-conductive material, usually transparent injection moulded plastic, and contains two circular cylindrical portions with different diameters and whereof one portion forms a roughly cup-shaped receptacle  20 . The bottom  21  or face of the receptacle simultaneously forms the face or bottom of an oppositely directed receptacle  22 , which has a larger diameter than receptacle  20  and is significantly flatter or shallower, and may be shell or dish-shaped. The face or bottom  21  separating the two receptacles is extended in projecting manner over half the circumference (cf.  FIG. 3 ), so that it forms a semi-cylindrical rib  31 . Projection  17  traverses the shell-shaped receptacle  22  and is located in the extension of the wall of receptacle  20 . The wall of receptacle  20  forms an envelope  23  for one part  24  of a sensor element  44 , whose other part  25  is located in receptacle  22 .  
         [0028]     These sensor element parts  24 ,  25  are made from an electrically conductive, flexible plastic, plastic foam or rubber, as described in EP 859 467 A1 and which can also be referred to as conductive rubber. Express reference and incorporation is made with regards to the disclosure and also the function of the touch switch to EP 859 467 A1.  
         [0029]     End face  26  projecting from receptacle  20  engages on a contact face  27 , which is provided on a printed circuit board forming a support  28 . In conventional manner the circuit board carries a printed circuit, which also includes the contact face  27  and contains the active and passive components, together with the conducting tracks of the touch switch, optionally also several touch switches and other control and regulating units for the electrical appliance. On said circuit board is also located a light emitting diode (LED)  29 . As shown in  FIG. 2 , the LED is positioned adjacent to the outer receptacle wall  23  forming the envelope so that light is emitted into the end face  30 . The receptacle wall is shown at this point having an outward bulge  37  in order to accommodate spacing between the diode and the sensor element.  
         [0030]     The sensor element part  24  facing the circuit board and located in receptacle  20  is in the form of a relatively elongated cylinder (e.g., having a length greater than its diameter) and projects somewhat beyond the end face, i.e., out of receptacle  20 . It can be made from a more flexible, electrically conductive material, e.g. foam.  
         [0031]     The sensor element part  25  located in receptacle  22  is in the form of a somewhat thicker circular disk (e.g., having a diameter greater than its thickness) and is made from a material which is either semi-solid, but flexible, or from a foam, which on the end face  32  engaging on cover  11  is closed, e.g. by a skin  33 , such as is e.g. the case with integral foams. Sensor element part  25  also projects somewhat over the outer wall of receptacle  22  and therefore provides a flexibility reserve. Projection  17  projects through a correspondingly shaped opening in sensor element part  25 . Projection  17  is therefore surrounded by portions of said sensor element part  25 , so that the light exit face  14  of the projection is within the switching area  12 , which is essentially determined by the sensor element part  25 .  
         [0000]     Function  
         [0032]     Reception element  18  is equipped with sensor element parts  24 ,  25  and introduced between support  28  and cover  11  in that the projection  17  is fitted into opening  16 . This leads to a positive, mechanical fixing of the sensor element unit on the cover. It is also possible for equipping purposes for the sensor element or elements to be connected to the circuit board  28  of cover  11  and/or reception element  18  by an optionally electrically conductive contact adhesive.  
         [0033]     With respect to the positioning, it is also pointed out that due to the two-part nature of the sensor element unit so as to give a smaller diameter, longer part  24  and a larger diameter, shorter part  25 , in the case of a large switching area the contact face  26 ,  27  required on the circuit board can be smaller. It is also possible to achieve the independence from the precise spacing resulting from the elasticity of the sensor elements if there is an adequate contact pressure between cover  11  and support  28 , without hindering the precise orientation of the light exit face  14  with the outer face  19  of the cover. Therefore sensor element part  25  can be made from a material with reduced elasticity, the main deformation taking place in the vicinity of the longer sensor element part  44 . Most of the elasticity reserve is also stored there and ensures a uniform, full engagement of the sensor elements on the cover, support and bottom  21 .  
         [0034]     The side-wall envelope  23  of receptacles  20 ,  22  and the step  34  formed between the same and which is made from an electrically non-conducting material, acts as an external electrical insulation of sensor element  44  and the two sensor element parts  24 ,  25 , which are galvanically isolated from one another. Correspondingly, an air and leakage path of at least  12  mm is formed between the circuit board or the face of the sensor element  44  projecting from receptacle  20  and the opening  16 , or the portion of the sensor element part  44  projecting out of receptacle  22 , without the spacing between the circuit board and cover having to be larger. The two sensor element parts  44  are at different electrical potentials. The electrical sensor part  24  contacts the circuit board, on which there can be an electronic resonant circuit, which can have live voltage, but the other electrical sensor part  25  is not electrically connected, and is in fact insulated therefrom by the divider  21 . This arrangement does not adversely impact the function of the touch switch, because with capacitive touch switches, said sensor elements are parts of a capacitor and are already electrically insulated by the cover from the operating finger of the user.  
         [0035]     The cross-section of the sensor elements, described here as being circular, can in particular have a various different designs or shapes, which can be adapted to the pushbutton shape. The same applies with regards to the light emitting element, which is shown with a trapezoidal cross-section.  
         [0036]     Therefore the reception element has a multiple functions. It is, on the one hand, used for the mechanical and electrical separation of two sensor elements, but simultaneously provides the cohesion thereof, as well as their electrical insulation and providing an air and leakage path. It also serves as a light guide for the light emitting element and as a seal for opening  16  for preventing moisture penetrating the interior. It also permits functional separation between the two sensor element parts and the use of different materials for the same to ensure the positioning of the light emitting element on or in panel  11 .  
         [0037]      FIGS. 4 and 5  show a touch switch  50  having a circular switching area  12  and which is bounded by a cover  11 .  FIG. 5  shows that the switching area  12  is shaped into the cover  11  as an optionally slightly spherical elevation thereof. It can additionally be provided with an e.g. metallic covering or coating  51 , which sets it off from the surroundings.  
         [0038]     An opening  16  is shaped into the cover in the centre of switching area  12  and continues in an inner channel  52  formed within a tubular envelope  23 , shaped internally on cover  11 , i.e., is integrally connected thereto.  
         [0039]     A light emitting element  15  is engaged in the tubular reception channel. It is made from a pellucid plastic and is constructed in pin-like manner with a smaller diameter than the reception channel  52 , so that it is surrounded by an air gap  56 . Inner ribs (not shown) centre the light emitting element  15 . The light emitting element has a head  54  similar to that of a nail, whose head face forms the light exit face  14 . Head  54  is located in a countersink of the opening and beneath it can be optionally placed a seal (not shown). The light emitting element is fixed by clamping or snapping-in using, for example, latching elements or by bonding adhesives (not shown). The envelope  23  is uninterrupted up to its lower end face  30  and is as long as the desired or necessary so as to accommodate an air and leakage paths as desired, i.e., more than 12 millimeters.  
         [0040]     The tubular sensor element  44  is engaged on the tubular envelope  23  and its upper end face  32  engages in the switching area, i.e., on the underside of cover  11 , which is lowered somewhat there in accordance with the external elevation of the switching area. The tubular envelope carries and guides the sensor element which is well retained thereon due to its elasticity. It projects over and beyond the envelope  23  and is located, as described by means of  FIG. 2 , on the annular contact face  27  of printed circuit board  28 . In the centre of said contact face is provided the light emitting diode  29 , which consequently faces the light entry face  30 ′ of the light emitting element. The latter acts as a light guide for the exit of light from the light exit face  14 .  
         [0041]     It is clear that here a particularly simple and effective possibility is created for providing a light exit face with light guide inserted in an opening of a cover, which on the one hand can be tightly inserted and provides the desired air and leakage path as necessary between the first touch contact possibility by an operator (outside of the switching area) and the electrically conductive sensor element  44 , i.e. the area close to end face  30 .  
         [0042]     FIGS.  6  to  8  show another embodiment in which the switching area  12  shaped into cover  11  is once again circular, but contains an opening  16 , which is formed within the circular surface, but on the edge thereof in the form of a circular segment. Correspondingly the light exit face  14  of the light emitting element  15  located therein is circular segmental.  
         [0043]      FIG. 7  shows that the opening  16  is formed in a recess of the somewhat elevated switching face  12  of cover  11 . Through said opening  16  projects the light guide constructed in the form of a flat or bent pin. The exit face  14  projects through the opening, but not over and beyond the switching face  12  and is instead level with the cover  11 . To said projection is connected a collar  61 , which supports a seal  45 , which is located in an inner depression  46  of the cover and seals the opening with inserted light guide. To the collar is connected a longer shaft  47  of the light guide, which carries lateral latching elements  41  in the form of sawtooth-like projections, which cooperate with corresponding cutouts forming latching elements  42  on envelope  24  or tongues  48  extending the latter in the manner of a snap hinge closure. The shaft, which is circular in this area, projects beyond the latching elements  41  and ends in end face  30 ′, which is the light entry face for the light from light emitting diode  29  above which it is positioned.  
         [0044]      FIG. 8  shows the flat, bent shape of the pellucid light emitting element  15  with lateral guidance ribs  49 . Envelope  24  is adapted to the shape of light emitting element  15 , reference being made to  FIG. 8  concerning its precise shape. It is shaped onto the cover  1   1 , but could also be tightly connected thereto and surrounds the light emitting element  15  with a relatively large air gap  53 . It is uninterrupted up to the openings forming the latching elements  42 , where the tongues  48  commence. The latter are constructed in such a way that on insertion of the light emitting element (from left to right in the drawing) they spring apart somewhat and consequently form the snap hinge closure.  
         [0045]     The flexible, electrically conducting sensor element  44  is basically shaped like a circular cylinder, but at one point is constructed with a circular segmental recess  55 , which matches the external shape of the envelope in this area. Thus, the sensor element  44  is directly connected to said envelope, which also forms part of its fastening holders. The remaining holders are formed by ribs  56  shaped onto cover  11 . Thus, the sensor element can be inserted from the left between said holders and as a result of the elasticity sinks somewhat into the surface and consequently keeps the sensor element pressed onto the underside of switching area  12 . The other end face  26  of sensor element  44  is located on contact face  27 .  
         [0046]     Here again envelope  42  shields the light emitting element  15  or inner channel  52  therein against dropping below the air and leakage path from live parts to the contactable surface. This construction simultaneously serves a function in conjunction with the holding and securing of the sensor element.