The present invention relates to digitizing tablets, and the like, and, more particularly, to a digitzer tablet structure comprising, a glass substrate having top and bottom surfaces; a plurality of parallel, spaced conductive ink first conductors disposed on the top surface of the substrate, the first conductors terminating in conductive ink pads adjacent a side edge of the substrate; a plurality of parallel, spaced conductive ink second conductors disposed on the bottom surface of the substrate perpendicular to the first conductors, the second conductors terminating in conductive ink pads adjacent another side edge of the substrate; a flexible connector strip containing a plurality of flexible conductors terminating in conductive pad ends disposed with the pad ends over respective ones of the conductive ink pads; and, electrically conductive adhesive means disposed between respective ones of the conductive pad ends and the conductive pad end's associated conductive ink pad--wherein, the preferred electrically conductive adhesive means comprises an adhesive tape which is conductive from one outer adhesive surface thereof therethrough to a second outer adhesive surface thereof but which is not conductive longitudinally therealong.
In a digitizing tablet system, a cursor is moved over the surface of a digitizing tablet. The position of the cursor is sensed to develop positional signals that are then input to a computer to accomplish the digitizing purposes of the system. Typically, the tablet contains a grid of horizontal and vertical conductors. In smaller tablets, the conductors can be formed in the manner depicted in FIGS. 1-4. As shown in FIGS. 1 and 2, the tablet contains a substrate 10 of an insulative material having a plurality of parallel, spaced vertical conductors 12 on one side and a plurality of parallel, spaced horizontal conductors 14 on the other side. The conductors 12,14 in combination form a grid 16 as depicted in FIG. 3. The manner in which the conductors 12,14 are carried by and separated by the insulative substrate 10 is depicted in FIG. 4.
In very large digitizing tablet systems, the conductors 12',14' are usually discrete wires that are stretched across the area to be occupied by the tablet and then hand soldered to connectors at the edges in a very labor intensive manufacturing process as depicted in FIGS. 5-8. The wire conductors 12',14' are stretched between pins at the edges of a form 18 and then the form 18 is filled with a resin material 20. After curing and cutting the ends of the conductors 12',14' loose a solid resin grid structure 22 with the conductors 12',14' sealed therein and with their ends as depicted in FIG. 7 is produced. As depicted in the partial cross section drawing of FIG. 8, the top of the grid structure 22 has a plastic surface 24 bonded thereto. Further resin material is employed to bond the grid structure 22 to a honeycomb material 26 (to supply overall rigidity) and to bond the honeycomb material 26 to a backing plate 27. As can be appreciated, the resultant structure is very heavy because of the large quantities of resin contained therein. This is in addition to the high cost of manufacture caused by the above-described labor intensive construction and assembly process.
Recently, the assignee of this application filed co-pending patent application Ser. No. 093,483, filed 09/04/87, entitled DIGITIZING TABLET by Lynn H. Rockwell which is directed to initial work with a digitizing tablet employing conductive ink on a glass substrate referred to as ink-on-glass technology. The teachings of that application are depicted in simplified form in FIGS. 9 and 10. The vertical conductors 12" and horizontal conductors 14" are deposited on the bottom surface of a glass substrate 28 employing a conductive ink in a silkscreening process with an insulative ink 30 between the two layers. Optionally, an layer of the insulative ink 30 can be deposited over the outer (i.e., bottom) conductors (12" or 14") as well to prevent inadvertent shorting thereof. The top surface of the glass substrate 28 (over which a stylus is moved in use) has the same adhesive plastic 24 as described above bonded thereto. As depicted in FIG. 10, the conductors 12",14" are connected to conductive ink traces 32 which terminate in conductive ink pads 34 in a common location. The traces 32 and pads 34 are formed by silkscreening at the same time as the conductors 12",14" to which they are connected. A connector socket 36 is shown to be connected to the pads 34 employing various techniques, including solder or a conductive adhesive which is cured after being disposed between the pads 34 and contacts contained within the socket 36. A plug 38 having a ribbon cable 40 attached thereto is then connected to the socket 36 to connect the conductors 12",14" to the remaining digitizing circuitry. That application contains no further teaching relative to the overall structure of a large digitizer tablet employing the ink-on-glass grid formed by the above-described process. Further, as those skilled in the art will appreciate, the more silkscreening steps that are involved in a manufacturing process and the more complex the pattern formed, the higher the cost and the greater the chance for misformed or broken conductors, or the like. Moreover, with a close-spaced pattern of the traces 32, there is the potential for cross-talk causing improper data readings and other irregularities that can affect the accuracy of the resultant digitizing tablet over its working area.
Wherefore, it is an object of the present invention to provide a structure and method of manufacture for a digitizer tablet employing ink-on-glass components along with the interconnection of their conductors, as necessary, in a manner which is quick and inexpensive to manufacture as well as being compatible with the special nature of the components.
It is another object of the present invention to provide a structure and method of manufacture for a digitizer tablet employing ink-on-glass components and flexible, directly connected interconnecting conductors which is lightweight and reliable.
It is a further object of the present invention to provide a structure and method of manufacture for a digitizer tablet employing ink-on-glass technology which is an improvement over the teachings of patent application Ser. No. 093,483, filed 09/04/87.
Other objects and benefits of the present invention will become apparent from the description which follows hereinafter when taken in conjunction with the drawing figures which accompanying it.