Abstract:
An illuminated keyboard has at least one key carried by a support structure and operable to close an electrical contact on being depressed from above, the at least one key having a translucent top surface, a hollow space under the translucent top surface, and an opening into the hollow space other than through the top surface, and an electroluminescent illuminator comprising a region of electroluminescent material enabled to be inserted into the hollow space through the opening.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present invention claims priority to a U.S. provisional patent application Ser. No. 60/852,203 filed on Oct. 17, 2006, disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention is in the field of computer input devices and pertains particularly to illumination of individual keys of a computer input device such as a keyboard or keypad. 
   2. Discussion of the State of the Art 
   Advances in illumination technology have led to a variety of types of backlighting techniques for consumer electronics. One application for illumination technology is illuminating keyboards so that the keys are discernable under low-light or no light conditions. 
   Typically, for more advanced products an electro-luminescent (EL) sheet is used as a low power source of illumination. An EL sheet or panel, sometimes referred to as a lamp, is a flexible translucent polymer sheet containing electrical leads and conductive surface areas treated with coatings of phosphorous or other chemicals that illuminate when exposed to an electrical charge from a power source. 
   The inventor is aware of a method and apparatus taught by Andrew J. Katrinecz U.S. Pat. No. 6,199,996 entitled “Low Power, Low Cost Illuminated Keyboards and Keypads” hereinafter termed Andrew et al. Andrew et al illustrates manufacturing processes for non-illuminated data-entry devices and mice to the manufacture of illuminated data-entry devices. The method calls for luminescent sheets of one or more colors integrated into a typical manufacturing process for keyboards whereby the sheet is incorporated underlying optically translucent device components to provide illumination of the components visual to a user of the device. The optically translucent components may be doped with phosphors or tinted to provide components that emit light of different colors. The intensity of illumination of the luminescent sheet may be controlled by the user and may vary in response to the background light of the environment. 
   Although illumination may be adequately produced from the source EL sheet of Andrew, the mechanics of the keyboard and more importantly the keys render the illumination effect produced undesirable in that shadows attributed to overlying keyboard components hinder a user&#39;s ability to well discern the correct key characters printed on the key faces above the illumination panel. 
   The general problem is that the illumination panel is setting to far below the face of the keys and therefore, parallax happens where one cannot see the characters well enough because of shadowing from the underlying mechanics of the keys set above the illumination or EL panel. 
   Therefore what is clearly needed is a system and method for illuminating the keyboard or keypad in a way that eliminates any parallax or shadowing from key components or other elements of the keyboard architecture. 
   SUMMARY OF THE INVENTION 
   In a preferred embodiment of the present invention an illuminated keyboard is provided, comprising at least one key carried by a support structure and operable to close an electrical contact on being depressed from above, the at least one key having a translucent top surface, a hollow space under the translucent top surface, and an opening into the hollow space other than through the top surface, and an electroluminescent illuminator comprising a region of electroluminescent material enabled to be inserted into the hollow space through the opening. 
   In one embodiment the keyboard comprises a plurality of keys having translucent top surfaces and open at a bottom extremity providing the opening, the keys arranged in a fixed pattern and guided in operation, and overlying a panel having electroluminescent regions arranged to underlie each of the plurality of keys. 
   Also in an embodiment the electroluminescent regions are individual extensions from the panel enabled to be inserted through openings in individual keys into the hollow space of each. The support structure may be a keypad of one of a computer keyboard, a keypad on a cellular telephone or a keypad on a personal digital assistant. 
   In some embodiments the fixed pattern comprises separate rows of keys, and a plurality of separate electroluminescent panels, powered by a common connection, one provided for each row of keys. 
   In another aspect of the invention a method is provided for illuminating a keyboard, comprising the steps of (a) supporting at least one key from a support structure, the key operable to close an electrical contact on being depressed from above, the at least one key having a translucent top surface, a hollow space under the translucent top surface, and an opening into the hollow space other than through the top surface; and (b) inserting a region of electroluminescent material from an electroluminescent illuminator panel into the hollow space through the opening. 
   In some embodiments in step (a) a plurality of keys are arranged in a fixed pattern and supported to be illuminated, and in step (b) a panel having electroluminescent regions underlies each of the plurality of keys. In some embodiments the electroluminescent regions are individual extensions from the panel enabled to be inserted through openings in individual keys into the hollow space of each. Also in some embodiments the support structure is a keypad of one of a computer keyboard, a keypad on a cellular telephone or a keypad on a personal digital assistant. In still another embodiment the fixed pattern comprises separate rows of keys, and comprises also a plurality of separate electroluminescent panels, powered by a common connection, one provided for each row of keys. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is a perspective view of a translucent key of a keyboard or keypad adaptable for electroluminescence according to an embodiment of the present invention. 
       FIG. 2  is an elevation view of a row of electroluminescent keys with an electroluminescent panel strip threaded there through. 
       FIG. 3  is an elevation view of a row of electroluminescent keys with electroluminescent tabs of an electroluminescent panel inserted therein. 
       FIG. 4  is an elevation view of a row of electroluminescent keys with an electroluminescent strip disposed in between key segments. 
       FIG. 5  is an elevation view of a row of electroluminescent keys of single body having tabs of an electroluminescent panel inserted therein. 
       FIG. 6  is a process flow chart illustrating steps for illumination a key of a keyboard or keypad. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a perspective view of translucent key  100  adaptable for a keyboard or keypad adaptable for electroluminescence according to an embodiment of the present invention. Key  100  includes a key top portion  101  and a key bottom portion  102 . Top portion  101  may be manufactured of a translucent or slightly opaque polymer that is rigid or semi-rigid in finished composition. Key top portion  101  has a top surface  103  on which one or more key characters and or symbols are printed, preferably in a dark color such that adequate contrast under key illumination is presented to a user. 
   Top portion  101  has a hollowed interior and four side walls and is generally symmetric and trapezoidal in geometric shape from an elevation perspective in this embodiment. From an overhead perspective, the key top portion is substantially rectangular. Other shapes may be presented without departing from the spirit and scope of the invention. In this embodiment, the key illustrated is the number 6 key of a traditional input keyboard for a laptop or desktop computer. Other like keys aggregated and making up the total keyboard or keypad keys of an electronic device will have the appropriate printings indicating which key is which in a key array. 
   It is only required that the top surface  103  of key  100  be translucent, however, the entire key may be fabricated of translucent materials such as a clear or slightly opaque polymer material. Key top portion  101  and key bottom portion  102  are vertically aligned in this embodiment and are separable from one another. Bottom portion  102  need not be of the same geometric shape as top portion  101 , for example, an inverted trapezoid. The bottom portion may be rectangular in elevation profile while the top portion may remain trapezoidal in elevation profile. In this case both portions have the same dimensions and are diametrically opposed in alignment with one another. This consideration is simply a matter of design preference. 
   Key bottom portion  102  may or may not include a hollowed interior. In one embodiment bottom portion  102  may be a solid key-base. Like top portion  101 , bottom portion  102  may be fabricated of a translucent polymer; however any solid color polymer material may be used. For example, bottom portion  102  may include a solid top plate  104  translucent or not. Bottom portion  102  does not require a hollowed interior, though one may be provided. In the case of a hollowed interior in the bottom portion  102  of key  100 , at least one opening may be provided through a one or opposing walls of the bottom portion such that the interior thereof is accessible from opposing sides of the key body. In this embodiment it is not specifically required because top portion  101  has a hollowed interior and it is accessible via a space between the two key portions when the key is not being depressed. 
   Key portions  101  and  102  are held in alignment by two or more (in this case 4) plunger posts  105 . Posts  105  extend up through the bottom portion  102  of key  100  through openings ordered in a symmetrical pattern and adapted for the purpose. Bottom portion  102  is not affixed in any way to posts  105  and posts  105  may slide freely through the openings provided. The top ends of posts  105  extend to and are affixed to or seated against the underside of the top surface wall  103  of top portion  101  such that when one presses down on surface  103 , the key may be depressed downward until it abuts with the bottom portion  102 . When one releases the downward force, the top portion returns to the original position. Plunger posts  105  provide a spring tensioned modality to top portion  101  of key  100 . Springs or other mechanisms not shown may be provided and housed between the key portions or between the plunger post bottom ends and circuit board hardware. The act of pressing key  100  results in registry of the key&#39;s input on the host computing device as is the case with traditional keys. 
   In one embodiment of the invention, surface  104  may support an electroluminescent panel (EL) strip or tab arranged such that the side of illumination of the strip or tab faces upward underneath translucent surface  103  thereby providing illumination to key  100  above the plane of any shadow-inducing hardware. In one case, an EL strip may be supported directly on surface  104  in congruence with a row of keys arrayed on a keyboard or keypad. In another case one EL panel may have EL tabs provided therein and strategically placed to intersect with the appropriate keys of a keyboard or keypad being adapted for illumination such that the tab ends may be inserted into individual ones of the keys with the illumination side of the tab facing toward surface  103 . 
     FIG. 2  is an elevation view of a row  200  of electroluminescent keys with an electroluminescent panel strip threaded therethrough. Key row  200  includes a key  201 , a key  202 , and a key  203  for illustrative purpose. Keys  200 - 203  are analogous in construction and materials to key  100  described further above. They are given separate element numbers based only on designation by what may be printed on the key surfaces in a portion of a particular row of keys such as might be found on a keyboard or keypad. For example, key  200  may be the A key followed by the S key followed by the D key on a typical keyboard row. 
   In this example the keys are illuminated by an EL strip  204  having an electric lead  205  that may be soldered or otherwise connected to the appropriate power leads on a circuit board. In this example, EL strip  204  is threaded through keys  201 ,  202 , and  203  in approximately a sine wave pattern to allow for slack in key depression. The luminescent side of EL strip  204  faces upward, thereby illuminating each of keys  201 ,  202 , and  203  in the row. There may be 6 or more strips fashioned for a keyboard having 6 rows of keys to be illuminated, for example. The strips  204  may be provided in a single EL sheet having one electrical connection to the circuit board for power such that each of the strips illuminates when power id provided to lead  205 . Alternatively, completely separate EL strips may be provided and chained together electrically at one junction point with the circuit board of the device. 
     FIG. 3  is an elevation view of a row  300  of electroluminescent keys with electroluminescent tabs of an electroluminescent panel inserted therein. Row  300  includes keys  301 ,  302 , and  303 . Keys  301 - 303  are analogous in construction and materials to key  100  described further above except that the bottom portions of the keys have an opening (not illustrated) provided beneath, giving access to a hollowed interior inherent to the bottom portion of each key. 
   In this embodiment, an EL sheet or panel  306  is provided having an electrical lead  305  adapted to receive power from a host device. EL sheet  306  is disposed beneath the bottoms of keys  301 - 303 . Portions of EL panel  306  are formed into tabs  307  that may be disposed upward from the plane of the panel and the ends of which may be inserted into associative keys. The tabs  307  are formed strategically for each key in each row to be illuminated so that there is an EL tab for each key in an array. 
   In this embodiment, the illumination side of the EL panel faces downward but due to the position of each inserted tab  307  turns upward with insertion and faces the top surface of the keys. In one embodiment only the tab surfaces of the panel are treated with florescent chemical so that illumination is centered within each key. One panel may be provided with as many strategically placed tabs as might be required to facilitate a particular key array. 
     FIG. 4  is an elevation view of a row  400  of electroluminescent keys with an electroluminescent strip disposed in between key segments. Row  400  includes keys  301 - 303  as described with respect to  FIG. 3  above. In this example, however, an EL sheet  401  is disposed linearly in sheet form on a plane in between the top and bottom portions of keys  301 - 303 . EL panel  401  has a lead  402  adapted to receive power for charging the sheet for illumination. In this case, the EL sheet has openings provided therethrough in a strategic pattern to accommodate the plunger posts of each key in a key array. EL sheet  401  has no strips or tabs and the illumination side of the strip faces upward thereby illuminating the keys when charged. 
   In this embodiment, a single sheet may be fabricated in the shape and key pattern of an entire keyboard or keypad and is installed over the key bottom portions of the keys over the plunger posts, the openings in the sheet aligning with the plunger posts. The top portions of keys  301 - 303  may then be installed or seated to the upper post ends such as by press fit or gluing. 
     FIG. 5  is an elevation view of a row  500  of electroluminescent keys of single body construction having tabs of an electroluminescent panel inserted therein. Row  500  includes keys  501 - 503 . Keys  501 - 503  are in this embodiment, single bodied keys meaning that they do not have top or bottom key portions. 
   Such keys may be formed or molded of a single translucent polymer material that may be rigid or semi-rigid depending on the key depression architecture planned. For example, key plungers may be affixed to the bottom of a rigid or semi-rigid key so that the key is depressed and moves in whole to register a keystroke. Keys  501 - 503  have hollow interiors to enable insertion of the EL tabs. 
   This embodiment is like that of the embodiment of  FIG. 3  accept that the keys are single bodied with an opening provided for inserting EL tabs. The illumination side of the tabs faces upward when inserted as illustrated. The keys are hollow and the tab curls up and around in the same way as it does with the segmented keys. 
   It will be apparent to one with skill in the art that other embodiments may be conceived with respect to varying key architecture and EL panel configuration without departing from the spirit and scope of the present invention. For example, instead of placing the tab insert openings on a side wall, they may be provided on the underside wall of each key. Moreover, an EL strip embodiment may also be implemented with single bodied keys having openings on both key sides to thread the strip through the key. 
     FIG. 6  is a process flow chart illustrating steps  600  for illuminating a key of a keyboard or keypad. At step  601 , an EL panel or sheet is positioned in place during key mounting of the keys of a keyboard or keypad. According to design variation, the EL sheet may be a single sheet sporting tabs or strips, or it may be a single sheet disposed between top and bottom key portions. In one case, separate strips may be provided for each row of keys. 
   In this case, the process assumes the presence of tabs or strips in the EL panel or sheet. At step  602  it is determined if tab insertion will be implemented. At step  602  if tabs are present then at step  603 , the tabs are inserted free end first into the individual associated keys. If at step  602 , no tabs are present then it is assumed that strips are present for each key row. In this case, at step  604 , the strips are threaded through the keys linearly down each row. 
   In either case, at step  605  the electrical lead is provided and connected for enabling power to charge the EL sheet. At step  606 , the EL sheet is charged illuminating the strip or tab surfaces thereby illuminating the keys of the keyboard or keypad. 
   In one embodiment, the process uses a single EL sheet with no strips or tabs. In this case, steps  602 ,  603 , and  604  are not required and are replaced by a step for placing the EL sheet into position over plunger posts of the keys with the tops off. Then a step is provided for seating the key tops to the plunger post tops to finish the installation. The process in this case then resumes with step  606 . The process ends at step  607 . 
   It will be apparent to one with skill in the art that the keyboard or keypad illumination system of the invention may be provided using some or all of the mentioned features and components without departing from the spirit and scope of the present invention. It will also be apparent to the skilled artisan that the embodiments described above are specific examples of a single broader invention which may have greater scope than any of the singular descriptions taught. There may be many alterations made in the descriptions without departing from the spirit and scope of the present invention.