Patent Application
20060042923
The invention relates to a tactile keyboard assembly providing at least one key and constructed on a plurality of thin layers stacked one upon the other, with one layer thereof composed of a dome support layer having for each key an elastically deformable dome positioned underneath the respective key.
Often, a standard keyboard assembly is based on a multi-layered structure with an elastically deformable dome-shaped member placed there between and underneath a respective key button. An actuator part of the key button is placed on the outer surface of the dome at the vertex thereof from which the dome opens up to an annular rim placed on a lower layer providing electrical contact terminals. By applying an external pressure onto the key button and hence onto the top surface of the dome, the dome is deformed such that the inner surface thereof is contacting the electrical contact terminals provided under the dome.
A section through a key of such a standard keyboard assembly is schematically depicted in appended
However, one of the main problems involved with a such or similar construction of providing a tactile multi-layered keyboard assembly concerns the overall thickness involved therewith, in particular in case the tactile keyboard is intended for use in small electronic devices, such as mobile phones or other handheld electronic devices. Hence the industries, for example the mobile phone industries, struggle to reduce the thickness of such keyboards by keeping or even improving the tactility.
A main object of the invention is therefore to provide with regard to the above discussed state of the art a new and improved structure of a tactile multi-layered foil keyboard assembly enabling an effective reduction of the thickness.
The inventive solution of this object is surprisingly achieved by a subject matter having the features according to one of the appended independent claims.
Advantageous and/or preferred embodiments or refinements are the subject matter of the respective dependent claims.
Accordingly, the invention proposes to provide a tactile keyboard or keypad assembly for an electronic device in that the assembly is constructed on a plurality of thin layers, in particular of foil-based layers, stacked one upon the other providing the basic structure for at least one tactile key, with one layer of the plurality of layers composed of a dome layer having an elastically deformable dome for each key, wherein the dome is positioned underneath the respective user area for key actuating or operating with its annular rim aligned thereto and with its vertex oriented to the opposite direction thereby forming or defining convex surfaces with regard to the key actuating user area.
Hence, due to the reverse orientation of the dome, with regard to the state of the art, the dome rim itself is defining an key area which is sufficient for ensuring a precise key operation by a user for applying an external force resulting in an definable flexural deformation of the dome without the additional need of a separate key button, as compared to the state of the art. Hence, the overall thickness of a keyboard assembly can be reduced in a considerable manner by simultaneously keeping the tactile operating feedback of such an inventive keyboard assembly as a user is customized to.
It is a further object of the invention to easily provide for a user a good identification functionality of the keys and/or key-operating areas. This is achieved by providing an upper layer covering and protecting the lower foil layers by a graphic foil layer forming the user visible surface of the inventive keyboard assembly by graphically defining, in particular by means of pictograms, the respective key areas which have to be applied with pressure in case of a respective user key selection. Since additional key buttons are not comprised by the inventive assembly and hence, the surface of the inventive assembly in substantial is planar, the graphical foil layer does not have to be thermoformed.
For providing an electrical connectivity functionality in response to a key operation, a flex foil comprising an electrical circuit is placed upon the dome rims of the dome layer, such that respective conductor connection terminals of the electrical circuit are preferably positioned within the areas defined by the annular dome rims underneath the flex foil. Thus, by the compression of a dome in response to an external pressure applied to the associated key area the inside surface of the dome presses onto the terminals and causes an electrical connection for closing the conductor of the electrical circuit which is assigned to the key.
For further improving a safe conduction functionality without the need of applying an undue external pressure, the at least one dome preferably is made of conductive material for closing the conductor, i.e. by directly contacting the respective conductor connection terminals with the inner surface of the dome. The dome itself may be integrally formed with the dome layer. However, at least in case the dome is made of conductive material the dome is attached to a dome support foil made of plastic by any suitable means, such as by an adhesive for example.
It is still a further object to increase the tactile key operating feedback and to further improve the safe conduction functionality. This is preferably achieved by an actuator layer positioned underneath the dome layer comprising an actuator plunger or pin directly underneath the vertex at the backside or the outside of each deformable dome for defining a kind of counteracting stop being supportive of a precise and tactile compression of the dome in response to an external pressure applied to the key area by a user.
The actuator plunger or pin are preferably moulded or printed on an actuator support foil made of a plastic material for providing withstand force and rigidity or being part of a plastic case for an electronic device on which the keyboard is placed.
To further activate the tactility of the key areas it is proposed to add an UV ink layer screenprinted on top of the graphic layer at the precise position of the key areas for supportingly simulating a key button.
Moreover, for providing a good readability or recognisability of the keyboard and in particular of the respective keys or key areas a light emitting layer, such as an electro-luminescent layer may be additionally embedded between the graphic layer and the flex foil layer with the light emitting side oriented to the graphic layer. An electrical power supply for stimulating the light emitting means embedded within such light emitting layer may be easily provided by the circuit of the flex foil directly adjacent the light emitting layer.
Accordingly, a very preferred embodiment of the inventive keyboard or keypad assembly constructed on a plurality of foil-based layers stacked one upon the other includes a lower actuator foil layer, stacked thereon a metal dome foil layer, stacked thereon a flex foil layer, stacked thereon an electro-luminescent foil layer and stacked thereon a graphic foil layer.
An electronic device having such an inventive tactile keyboard assembly thus can be provided with an overall decreased thickness and hence, such an electronic device is preferably a handheld electronic device such as a mobile phone, a MDA (Mobile Digital Assistant), a PDA (Personal Digital Assistant) or a WDA (Wireless Digital Assistant).
The above and other features and advantages will be more apparently by the following description of a preferred embodiment of the invention and with reference to the accompanied drawings.
As shown in
Generically and according to the preferred embodiments, each of the foils is based on a thin film of plastic material. In addition, in particular the foils 110, 120 and 140 may have a pre-given amount of clearance holes 118, 128 or 148 for an easy and adaptable assembly of the foils with the mechanical and electrical components depending on a respective certain intended keyboard design.
Furthermore, the electro-luminescent foil 140 includes a plurality of light emitting lamp means 145 for emitting light through the graphic layer 150, as indicated in
Moreover, the graphic foil 150 is provided with pictograms 155 visually representing respective keys for a user. Each of the plurality of flexural deformable metal domes 125 embedded within the dome support plastic foil 120 and hence electrically isolated to each other is aligned with respective one of the actuator pins or plungers 115 supported by the actuator foil 110 and arranged such, that at least one dome 125 and one pin 115 each positioned precise underneath a pictogram 155 representing a key.
Thus, as can be seen from
The metal dome 125 is positioned such within a clearance hole 128, that the vertex 126 of the dome 125 is oriented to the opposite direction of the user visible keyboard surface and it opens up towards the keyboard surface to an annular dome rim 127 on which the flex foil 130 is arranged. Thus, the annular dome rim 127 itself is defining an key area which is sufficient for ensuring a precise key operation by a user by applying an external force without the additional need of a separate key button.
As a result, the overall thickness of the inventive keyboard assembly can be reduced mostly because there is no molded key or separate key button necessary. With regard to a thickness of about 2.50 mm of a standard construction as depicted in
Due to the isolation cover 132 of the flex foil 130, the metal dome 125 and the electrical circuit 131 are electrical isolated. Within the mouth area defined by the dome rim 127 the flex foil 130 is provided with conductive terminals 135 of the printed circuit 131. Applying an external pressure P on top of the key area causes a flexural deformation of the dome 125 such that the inner surface of the metal dome 125 comes into contact with the conductive terminals 135 thereby enabling the electrical connection and providing the user with a tactile key operating feedback.
As an alternative, conductive terminals of the flex foil may be formed and arranged such, that in response to an external pressure the inner dome surface of the deformed dome causes that both conductive terminals are getting in contact to each other. Correspondingly, for such an alternative, the dome 125 does not have to be of metal material and hence, using a non conductive dome an electrical isolation between the dome and the flex foil electrical circuit is not obligatory and the dome may be formed as an integral part of the dome layer, in particular of a correspondingly formed dome support foil.
It can be further seen from
However as an alternative and as depicted in
The actuator plunger or pin 115 and the actuator support layer 110 may be produced in one or more pieces. For example, the actuator plunger or pin 115 can be moulded, injected or printed on an actuator support foil made of a plastic material providing sufficient withstand force and rigidity as described above. It is noted however, that the actuator support layer also may be provided by a plastic case, as depicted in
Moreover, as depicted in
