Abstract:
The keyboard portion of a notebook computer has incorporated in its key switch membrane section a liquid detection electrical circuit with a series of normally open detection switch structures positioned be contacted and shorted out by liquid spilled on the keyboard. A spilled liquid short-circuiting of any of these normally open membrane switch structures during operation of the computer automatically creates a liquid spill output signal that is responsively utilized to shut down the computer before its system electronics can be contacted, short-circuited and damaged by liquid spilled on the keyboard and entering the interior of the computer therethrough.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to keyboard structures used in electronic apparatus and, in a preferred embodiment thereof, more particularly relates to a specially designed liquid spill-sensing keyboard assembly operatively incorporated in a notebook computer. 
     2. Description of Related Art 
     During use of a portable notebook computer resting atop a desk or other horizontal support surface (such as an airplane seat tray), the keyboard portion of the computer is susceptible to having a drink liquid (such as coffee, water or a soft drink) spilled on it by it by the computer user. If some measure is not taken to prevent the spilled liquid from flowing from the keyboard onto to the underlying major internal electrical components of the computer (such as the circuit boards, drives and the like) these components, commonly referred to as the “system electronics” can be shorted out by the spilled liquid and severely damaged. 
     Typically, portable computer keyboard and associated electrical system designs incorporate some means for either (1) sealing off areas of the keyboard/system to prevent the spilled liquid from reaching the underlying system electronics, (2) absorbing and containing the spilled liquid, or (3) diverting the spilled liquid from the keyboard to a safe place in the computer where it will not short out the system electronics therein. 
     For example, where a liquid sealing technique is employed the keyboard installs into an opening in the portable computer with a rubber/plastic gasket which is designed to prevent liquid spills on the top surface of the keyboard from draining therefrom into the interior of the computer. In the absorption approach the bottom or perimeter of the keyboard is equipped with an absorbing material (functioning as a “diaper”) which absorbs and retains the liquid spilled on the top side of the keyboard. When the diverting approach is used the liquid is allowed to pass through or around the keyboard, via built-in “channeling” passages, in specific areas to drain the liquid into a location isolated from the computer system electronics underlying the keyboard. 
     Ensuring a tight liquid keyboard seal in a computer production environment is difficult, and absorbing or diverting liquids spilled on the keyboard undesirably adds extra cost and space requirements for these features. In view of this it can readily be seen that a need exists for apparatus that protects the computer system electronics from short circuit damage arising from a spillage of liquid on the keyboard in a manner avoiding or at least substantially reducing the above-mentioned problems, limitations and disadvantages typically associated with conventional liquid spillage sealing, absorbing and diverting techniques applied to portable computer keyboards. 
     SUMMARY OF THE INVENTION 
     In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, an electronic apparatus, representatively a portable computer notebook computer, is provided with a specially designed liquid spill sensing keyboard which is operative to sense the presence of liquid spilled on the keyboard and responsively shut down the computer&#39;s system electronics before they can be contacted, shorted out and damaged by the spilled liquid. 
     The keyboard is carried on the top side of the base housing portion of the portable computer and is preferably provided with electrical liquid spill detection circuitry having a portion positioned and configured to be contacted and shorted out by liquid spilled on the keyboard. In response, the shorted out detection circuitry creates a liquid spill detection signal which is used to shut down the system electronics. Illustratively, the detection circuitry portion positioned to be contacted and shorted out by the spilled liquid includes a spaced plurality of electrically interconnected normally open switch structures incorporated in a multi-laver signal pad portion of the keyboard which underlies the depressible keys thereof and is interposed between the keys and the underlying system electronics in the base housing of the computer. 
     In a preferred embodiment of the keyboard, the multi-layer signal pad has a top layer, a second layer disposed beneath the top layer and having a top side facing the top layer, and a spaced series of openings extending downwardly through the top layer to portions of the second layer top side, and fluid tight seal structures laterally circumscribing the openings. The normally open switch structures are carried on the top side portions of the second layer, exposed at the bottom ends of the pad openings, and are operative to be contacted and shorted out by liquid entering the openings. 
     The detection circuitry incorporated in the multi-layer signal pad is representatively coupled to a keyboard controller, and a system controller is operatively interconnected between the keyboard controller and a power supply portion of the system electronics. When liquid spilled on the keyboard passes through openings in the support structure which carries the depressible key members it enters at least one of the top side signal pad openings and shorts out the associated normally open detection switch structure(s). The spilled liquid signal is responsively transmitted from the keyboard controller to the system controller which, in turn, transmits a shut-down signal to the power supply portion of the system electronics, thereby shutting off the computer before its system electronics can be contacted, shorted out and damaged by the spilled liquid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified, partially cut away perspective view of a representative notebook computer having incorporated therein a specially designed liquid spill-sensing keyboard embodying principles of the present invention; 
     FIG. 2 is an exploded schematic cross-sectional view through the keyboard, and the underlying system electronics, taken generally along line  2 — 2  of FIG. 1; 
     FlG.  3  is an enlarged scale simplified top plan view of a portion of a signal pad structure incorporated in the keyboard; 
     FIG. 4 is a schematic diagram of a liquid spill-sensing circuitry portion the keyboard; and 
     FIG. 5 is a block diagram schematically illustrating the interconnection of the keyboard, a keyboard controller, a system controller, and the system electronics. 
    
    
     DETAILED DESCRIPTION 
     Referring initially to FIG. 1, the present invention provides an electronic apparatus  10  which is representatively in the form of a portable notebook computer. The notebook computer  10  has incorporated therein a specially designed liquid spill-sensing keyboard  12  embodying principles of the present invention. As will be subsequently described herein, during use of the computer  10  the keyboard  12  functions, in response to a liquid spilled on it, to automatically shut down the computer  10  to prevent the spilled liquid from causing electrical short circuit damage to the computer&#39;s system electronics  14  that generally underlie the keyboard  12 . 
     Computer  10  includes a hollow rectangular base housing  16  having a top horizontal side wall  18  with a rectangular opening  20  therein; a bottom horizontal side wall  22 ; front and rear vertical side walls  24  and  26 , and left and right vertical end walls  28  and  30 . A hollow rectangular lid housing  31 , having a display screen  32  on its front or inner side, is pivotally secured along a hinge joint  34  to a top rear corner portion of the base housing  16 . Lid housing  31  may be upwardly pivoted to place the computer  10  in an open use orientation (FIG. 1) in which the top side  18  of the base housing  16  is exposed and the display screen  32  forwardly faces the user of the computer, or downwardly pivoted to place the computer  10  in a closed storage and transport orientation (not shown) in which the lid housing  31  extends across and covers the top  18  of the base housing  16 . Suitable latch means (not shown) are provided to releasably retain the lid housing  31  in its closed orientation. 
     The keyboard  12  is received in and extends across the top side opening  20  in the base housing  16  and occupies only a relatively small upper portion of the interior of the base housing. Referring now additionally to FIG. 2, the keyboard  12  basically comprises a relatively thin rectangular monoblock support structure  38  that horizontally extends across the base housing top side opening  20  and is suitably anchored to the base housing  16 ; a series of manually depressible keys  40  operatively carried by the support structure  38 ; and a rectangularly configured, multilayer signal pad structure  44  that underlies the support structure  38 . The system electronics  14  that underlie the keyboard  12  include, for example, a system motherboard  45 , drive units (not shown) and a variety of other conventional electrical components (also not shown). 
     Signal pad structure  44  (see FIG.  2 ), which except as noted below is of a generally conventional construction, is suitably supported in an underlying relationship with the monoblock support structure  38  and includes, from top to bottom, (1) a plastic dome sheet  46  having a spaced series of rubber key return domes  48  projecting upwardly from its top side, with each dome  48  underlying one of the keys  40 ; (2) a plastic top circuit sheet  50  having a spaced series of circular, electrically conductive pads  52  disposed on its bottom side, aligned with the domes  48 , and connected to surface trace circuitry  52   a  formed on the bottom side of the sheet  50 ; (3) a plastic spacer sheet  54  having a spaced series of circular openings  56  formed therein and underlying the pads  52  in registry therewith; (4) a plastic bottom circuit sheet  58  having a spaced series of circular, electrically conductive pads  60  disposed on its top side, aligned with the spacer sheet openings  56 , and connected to surface trace circuitry  60   a  formed on the top side of the sheet  58 ; and (5) a metal backing sheet  62 . Sheets  50 ,  54  and  58  are suitably sealed to one another around their peripheries to prevent entry of liquid into the spaces between adjacent sheet pairs. 
     In a conventional manner, when a given key  40  is depressed it downwardly deforms the underlying resilient return dome  48  to, in turn, drive the underlying key switch pad  52  downwardly into engagement with its facing key switch pad  60 . This operatively interconnects portions of the trace circuitry  52   a , 60   a  and responsively generates a corresponding keystroke signal, via leads L connected to the trace circuitry  52   a , 60   a  and disposed on an outwardly projecting flexible “tail” or ribbon cable portion  64  of the signal pad structure  44 , to a keyboard controller  66  (see FIG. 5) operatively connected to the cable portion  64 . As schematically illustrated in FIG. 5, keyboard controller  66  is coupled to a system controller  68  which, in turn, is coupled to a power supply portion  70  of the system electronics  14 . In a conventional manner, the generation of this keystroke signal is used to generate the associated keystroke character on the display screen  32 . 
     Referring now to FIGS. 3 and 4, in accordance with a primary aspect of the present invention, the keyboard  12  is provided with specially designed liquid spill-detection circuitry  72  which functions to sense the presence of liquid spilled on the keyboard  12  and responsively shut down the system electronics  14  before the spilled liquid can contact them and cause electrical short circuit damage thereto. 
     The liquid spill-detection circuitry  72  comprises electrical trace circuitry formed on the top side of the bottom circuit sheet portion  58  of the signal pad structure  44  and including a spaced series of normally open liquid detection switch structures  74  each having spaced apart positive and negative contact portions  74   a  and  74   b . The positive switch portions  74   a  are all connected to a surface trace lead  76  which extends along the top surface of the bottom circuit sheet  58  and through the ribbon cable portion  64 . In a similar manner, the negative switch portions  74   b  are all connected to a surface trace lead  78  which extends along the top surface of the bottom circuit sheet  58  and through the ribbon cable portion  64 . Since all of the switch structures  74  are normally open, the positive and negative leads  76 , 78  are normally electrically isolated from one another. 
     Each positive and negative switch portion set  74   a , 74   b  lies at the bottom of one of a spaced series of representatively circular liquid receiving openings  80  extending downwardly through the dome sheet  46  to the top side of the bottom circuit sheet  58 . Circumscribing each opening  80  is a liquid seal area  82  which secures facing circular areas of each adjacent pair of the signal pad structure sheets  50 , 54 , 58  to one another in a manner preventing liquid entering any of the openings  80  from flowing outwardly between any facing pair of such sheets and coming into contact with the previously described key switch trace circuits  52   a  and  60   a . Representatively, these seal areas  82  are adhesive seal areas. 
     In the event that liquid is spilled on the top side of the keyboard  12  it flows downwardly through the key openings in the monoblock support structure  38  and comes in contact with the top side of the dome sheet  46 . The spilled liquid then flows downwardly through at least one of the spaced apart liquid-receiving openings  80  and electrically shorts out the spaced apart switch portions  74   a , 74   b  at the bottom of the opening. This shorting out of the switch portions  74   a  and  74   b , in turn, electrically couples the positive and negative leads  76 , 78  and thereby causes the keyboard controller  66  (see FIG. 5) to transmit a “spilled liquid” signal  84  to the system controller  68 . Upon receipt of the signal  84 , the system controller  68  responsively transmits a system shut-down signal  86  to the power supply portion  70  of the system electronics  14 , thereby terminating electrical power supply to the system electronics  14 , thus protecting them against electrical short circuit damage in the event that the spilled liquid reaches them. 
     As can be seen from the foregoing, the spill-detecting keyboard  12  of the present invention protects the system electronics  14  from liquid-created electrical short circuit damage in a simple, reliable and inexpensive manner without the previous necessity of either (1) sealing off areas of the keyboard/system to prevent the spilled liquid from reaching the underlying system electronics, (2) absorbing and containing the spilled liquid, or (3) diverting the spilled liquid from the keyboard to a safe place in the computer where it will not short out the system electronics therein. 
     While the present invention has been representatively illustrated and described as being incorporated in a notebook computer keyboard, it will be readily appreciated that it could be alternatively associated with the data input key structures of a variety of other types of electronic apparatus including, but not limited, to calculators and other types of computer keyboards such as desktop computer keyboards. 
     The foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims.