Abstract:
A calculator keyboard includes a face plate and a plurality of keys supported in a predetermined location with respect to the face plate. In the face plate there are provided narrow recesses in alignment with respective keys. Each recess has a width dimension sufficient for providing access to the associated key by a fingernail of the user.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a keyboard for electronic calculators, particularly miniature calculators incorporated, for example, in wristwatches. Such a miniature calculator is manufactured, for example, by SEIKO (Japan) under the designation &#34;FH-001 Digital Calculator&#34; or by EMEX AG (Switzerland). 
     The progressive reduction in the size of electronic calculators has made it increasingly difficult to operate the keyboards with the bare finger of the user. Thus, a point has already been reached where a secure actuation of the selected keys of miniature calculators are possible only with an auxiliary instrument such as a pencil tip or a tool of similar configuration. A disadvantage of this arrangement resides in the inconvenience involved with the necessity of using an additional tool which may not be always immediately available. A further disadvantage is considered to reside in the risks of damaging the calculator by hard tools or by soiling it, for example, by graphite particles that could break off a pencil. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved keyboard, particularly for miniaturized electronic calculators, which can be operated by the user without resorting to an auxiliary tool. 
     More particularly, it is an object of the invention to provide an improved keyboard, particularly for a miniaturized electronic calculator in which the individual keys may be operated by a fingernail of the user. 
     These objects and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the keyboard comprises a fixed support face engageable by the user&#39;s finger tip and keys arranged in recesses in the support face. For operation, the user may place a finger tip on the support face adjacent to the key to be actuated and by pivoting his finger about the support face as a fulcrum, may cause his fingernail to penetrate into the recess and thus depress the desired key. 
     It is an advantage of the invention that keys of reduced surface may be actuated by the user in an error-free manner without an additional tool, thus eliminating the above-discussed disadvantages. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic top plan view, on an enlarged scale, of a calculator incorporating a preferred embodiment of the invention. 
     FIG. 2 is a schematic sectional view taken along line II--II of FIG. 1, showing one component in the actuated state. 
     FIG. 3 is a schematic top plan view, on an enlarged scale, of another preferred embodiment of the invention. 
     FIG. 4 is a schematic top plan view of still another preferred embodiment of the invention. 
     FIG. 5 is an enlarged fragmentary schematic top plan view of a further preferred embodiment of the invention. 
     FIG. 6 is a sectional view taken along line VI--VI of FIG. 5, showing one component in the actuated state. 
     FIG. 7 is an enlarged fragmentary schematic top plan view of still another preferred embodiment of the invention. 
     FIG. 8 is a sectional view taken along line VIII--VIII in FIG. 7, showing one component in the actuated state. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to FIG. 1, there is shown, in a schematic illustration, the top face of an electronic calculator, such as a miniaturized calculator incorporated in a wristwatch. The top face is divided into a display portion which may indicate separately the time and the calculations performed and a keyboard situated in the area below the display. 
     The keyboard comprises a rigid plate 1 which, at the same time, may constitute the entire top face of the watch-calculator assembly. The keyboard further comprises a plurality of keys 2 to be individually actuated. Conventionally, the plate 1 carries identifications for each key. Such identifications are shown in FIG. 1 only for the digit keys 0 to 9. The structure of the keys 2, particularly their contact-making arrangement is conventional and is therefore not described in more detail. 
     Also referring now to FIG. 2, according to the invention, the keys 2 are arranged for being actuated by the user&#39;s fingernail. For this purpose with each key 2 there is associated a slot 3 aligned with the respective key 2. As shown in FIG. 2, each key may have an upper stem portion which normally (that is, in the non-actuated state) projects from below into its respective slot, but does not protrude beyond the upper face (support surface) 1a of the plate 1. It is feasible, however, to so arrange the keys that even in the normal (non-actuated) state they do not extend into their respective slot. Each slot 3 has a length dimension and a width dimension measured transversely to and being smaller than the length dimension. The area defined by the length and width dimensions of each slot 3 as well as the thickness of the plate 1 are such that the fingernail of the user can easily penetrate thereinto and depress the key 2, as shown for the extreme right-hand key 2 in FIG. 2. On the other hand, however, the finger tip of the user positioned over a slot should gain no access to the key associated with that slot, as may be observed for the key 2 which is second from the right in FIG. 2. 
     Thus, for depressing, for example, the right-hand key 2 as shown in FIG. 2, the user places his finger tip on the support face 1a which is adjacent that key and which forms part of the plate 1, and then rocks his finger slightly, fulcrumating it about the support face 1a, so that his fingernail penetrates into the slot 3 and depresses the key 2. As it may be further observed in FIGS. 1 and 2, each key has an outline that extends over substantially the entire width dimension of the slot with which it is associated, so that the user&#39;s fingernail is effectively prevented from slipping off the key and into the slot as depression of the key is effected. 
     Turning now to FIG. 3, the embodiment shown therein differs from the previously discussed embodiment only in that continuous slots 4 are provided, each extending over a plurality of keys 2. Advantages of this embodiment reside in a simpler manufacture as well as a better adaptation to various fingernail dimensions and configurations. 
     Turning now to FIG. 4, the embodiment shown therein differs from the FIG. 3 embodiment only in that the continuous slots are diagonally extending, criss-crossing slots 5. The keys 2 are situated at the intersection of two slots 5. 
     According to the embodiment illustrated in FIGS. 5 and 6, the face plate of the calculator is so designed that it has separate elevated parts 6 associated with each key 2. Each elevated part 6 slopes upwardly towards the associated key 2 and is adapted to serve as a rigid support face for the finger tip of the user. Each elevated part 6 is complemented by a ridge 7 situated at the other side of the associated key 2 at a small distance from the part 6 to form therewith a recess 8, into which the user&#39;s fingernail may penetrate for depressing the key 2 aligned with the recess, as shown in FIG. 6. The ridges 7 protect the keys 2 from lateral exposure in their non-actuated state and they also serve for guiding the user&#39;s fingernail. 
     Turning now to the embodiment illustrated in FIGS. 7 and 8, the horizontal rows of the keys 2 are separated by inclined support surfaces 9. From row to row, each support surface 9 slopes upwardly towards the consecutive row of keys 2 as particularly well seen in FIG. 8. It is noted that in the FIG. 8 illustration, each key 2 represents a key belonging to a different row. The adjoining support surfaces 9 are spaced from one another such that between them a recess 10 is defined through which the user&#39;s fingernail may project and depress the selected key as his finger tip rests on the support surface 9 rising towards the keys 2 on the associated key row. The mode of actuation is illustrated in FIG. 8 for a key 2 which belongs to a key row second from the right. 
     While in all of the above-described embodiments the contacting member is identified as a key 2, it is to be understood that in most embodiments the individual keys 2 may be readily replaced by a locally deformable, conventional, continuous contact foil. 
     While in all the embodiments the recesses or slots are linear, it is to be understood that they may be of curving course for more closely following the general curvature of the nail as seen in end view. 
     It is to be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.