Abstract:
A flexible keyboard formed from a grid of flexible wires. Crosspoints between the wires are used to define characters to be selected via the keyboard. The characters are selected by pressing at a location, pressing two wires against one another.

Description:
The present application describes a lightweight flexible keyboard formed from a grid of wires encased in an outer sheath. 
     BACKGROUND 
     It is often desirable to make a computer as small as possible. The size of a computer, however, is often limited by the sizes of the input and output devices. 
     Computer data is often input from a keyboard. Data entry by a keyboard requires a certain minimum size that accommodates the user&#39;s hands and the conventional typing style. Laptops and other portable computers can be made with reduced-size keyboards in order to save on space. However, a typist may often feel cramped by the reduced size of the keyboard. 
     SUMMARY 
     The present system teaches a flexible keyboard formed of a grid of wires which are position encoded. The flexible keyboard can be folded or rolled when not in use. The grid includes a waterproof cover, including an overlay, including an indication of a plurality of characters, and having a pressing surface allowing pressing against a location at an intersection between two wires of the grid. A position detecting circuit, detects the position of pressing and converts that position of pressing to a character that is represented thereby. 
     In an embodiment, the keyboard is formed by a grid of wires that cross at locations. The crossing locations define allowable key press locations. An encoding circuit determines the location of pressing based on the wires that are selected. 
     The grid is wrapped in a waterproof material, with a character set printed on a top surface of the material. Application of pressure at any specific location causes a contact to be made. The position of contact is determined from the encoding circuit, and converted to a letter indicating the position. A look up table can be used to convert between the position and the letter it represents. 
     In one embodiment, the wires are coated wires with openings in the coating at crosspoint locations to allow them to make contact. In another embodiment, a resistive ladder is used to produce an output voltage that depends on the location of pressing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other aspects will now be described in detail with reference to the accompanying drawings, wherein: 
     FIG. 1 shows a conceptual diagram of the overall keyboard including the wires that form the cross point. 
     FIG. 2 shows a cross-sectional view along the line  2 — 2  in FIG. 1; 
     FIG. 3 shows a second embodiment that shows how the key press position can be detected; 
     FIGS. 4 a  and  4   b  show the device as used with a laptop computer; and 
     FIGS. 5 a  and  5   b  show compacting the keyboard in two axes to allow a full size keyboard to be used with a reduced size display. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment is shown with a keyboard  99  formed of a grid of wires  100  which are position-encoded. An associated position detecting circuit detects the position of pressing and converts that position of pressing to a character that is represented by that position. 
     The wires are arranged into a plurality of column extending wires  120 ,  122 ,  124 ,  126  and row extending wires  130 ,  132 ,  134  and  136 . A key is activated by pressing an active area at or near the intersection between any two wires. That intersection area is also imprinted with an overlay that represents a specific character. 
     Each of the row and column wires is formed of wire with a coated portion  110  and an uncoated portion  112 . A character is defined at an intersection between two uncoated portions of a row wire and a column wire. Each of the wires are electrically floating. By pressing down at the location of the character, the two wires are shorted together. This electrically connects the column wire  120 , which here is shown biased to a voltage, together with the row wire  130 , which here is shown connected to ground. After the two wires are connected together, current flows between the column wire  120  and the row wire  130 . 
     The encoders  150 ,  151  can use ammeters to sense current flow in the wires. The ammeter senses which of the wires is conducting. The wires that are conducting indicate the column and row position. A look up table  152  translates this row and column position into a letter represented by that position. 
     The two orthogonally-directed parallel sets of wires are made of flexible material so that the whole unit can be folded and/or rolled, and so that the wires can be pressed to touch one wire against another of the wires. The wires can be braided or goose-neck material, for example. 
     FIG. 1 shows a first embodiment using encoder circuits  150 ,  151  to encode which of the row and column wires are conducting voltages. The system operates by detecting the position where the two wires are shorted. An overlying character set  100  is printed on the top surface  103 . Each letter is printed over uncoated portions  112  at the intersection of the two wires. 
     FIG. 2 shows a cross section along the line  2 — 2  in FIG.  1 . This shows the functional layers that make up the device. A top layer  200  includes a printing layer, which includes a print portion  202  which preferably is formed into the shape of a character, and a planarizing portion  204  surrounding the print portion. Other alternatives include a relatively flat print portion or simply allowing a raised portion  202  where the ink is placed. 
     A overlaying plastic layer  210  encases the two wires and provides waterproofing for the keyboard. The two wires are shown below the overlying plastic casing  210 . Wire  220  represents the column wire, and in the cross section is shown as bare wire. Of course, areas on both sides of the shown cross section would actually be coated. Row wire  230  is shown with its uncoated portion  112  and its coated portion  110 . 
     Layer  240  represents a tactile feedback mechanism which makes an audible sound when pressed. The click mechanism is actuated when the user presses down against the top portion at this location, to cause tactile feedback, e.g. an audible click. A piece of spring metal can be used for this click portion. 
     Layer  250  represents the bottom plastic coating. This provides the waterproof seal. 
     The unit is made of flexible materials including flexible plastic, and flexible metal wires. This allows the keyboard to be rolled or folded for storage and transportation. 
     FIG. 3 shows an alternative sensing arrangement where a plurality of resistors  300 ,  302 ,  304 ,  306  form a resistive ladder. Each position of pressing is located between two resistive elements. The resistive element causes a unique voltage to be output at that location. The voltage output is converted by the look up table into a desired keyboard entry. 
     One embodiment is shown in FIGS. 4 a  and  4   b . FIG. 4 b  shows the keyboard in its unfolded position with the display. FIG. 4 a  shows how the keyboard can be rolled up against the display. Hence, the keyboard portion of a laptop can be significantly reduced in size during storage. In addition, the keyboard can be made to any desired size including a standard size. 
     FIGS. 5 a  and  5   b  show how a standard size keyboard can be advantageously used with a much smaller-than-standard-size display. 
     For example, a folding operation could be used to allow the keyboard to be folded twice and then rolled. The result is shown in FIGS. 5 a  and  5   b . FIG. 5 b  shows the full size keyboard  510  that is wider than the display. The keyboard can be folded along the fold lines  500 ,  502  and then rolled into position as shown in FIG. 5 b.    
     Although only a few embodiments have been described in detail above, other embodiments are contemplated by the inventor and are intended to be encompassed within the following claims. In addition, other modifications are contemplated and are also intended to be covered.