Deformable Switch Keyboard

This invention relates to electromechanical keyboards of the type used in a wide variety of applications.

Many electromechanical keyboard designs are known which are used to provide electrical signals indicating the actuation of one of a plurality of switches. In many applications, the increasing trend is toward simplicity of design and low cost, particularly in consumer oriented electronic devices, such as video games. Thus, the evolution of electromechanical keyboard designs has progressed from switch assemblies having individual key top, electromechanical switch and return spring components, through designs employing individual dome switches fabricated from a suitable material (such as beryllium copper), to assemblies incorporating a laminated sandwich in which the switching elements comprise conductive layers separated by an insulating layer, and associated switch actuation elements, typically projections suspended above the sandwich and designed to squeeze the sandwich against a flat supporting base.

The invention comprises an improved keyboard assembly which is capable of being manufactured at extremely low cost, can be configured in a wide variety of key switch patterns and provides extremely reliable, long-life operation.

The keyboard assembly of the invention includes three essential components: a top member, a bottom member, and an intermediate multilayered deformable switch assembly. The intermediate assembly includes top and bottom insulating layers, separate electrically conductive elements positioned within the top and bottom insulating layers and normally separated from one another typically by means of an apertured insulating layer. The top member comprises a rigid but flexible sheet having individual switch site defining regions located thereon in a preselected array and serving the function of a push button. The bottom member comprises a relatively rigid substrate having first and second upwardly extending projections of unequal height. The first set of projections is of lower height and each such projection is positioned directly underneath the switch site defining regions of the top member. The second set of projections is of greater height and are positioned substantially at the midpoint between adjacent switch site defining regions of the top member.

In use, in the normal unactuated state the intermediate assembly is supported by the second set of projections in such a manner that none of the individual switches contained in the intermediate assembly are actuated (i.e. none of the first and second conductors is in actual contact). When a given switch site is depressed by an operator fingertip, the top member flexes in a downward direction and presses the underlying switch region of the intermediate assembly into mechanical contact with the underlying lower height projection from the first set. In addition, the two projections from the second set which straddle the selected switch site prevent actuation of any other switch in the intermediate assembly by virtue of the greater height of the second projections.

The top member is preferably fabricated as a one-piece panel having the predetermined array of switch sites, while the bottom member may be integrated into the housing of the associated electronic device.

For a fuller understanding of the nature and advantages of the invention, reference should be had to the ensuing detailed description taken in conjunction with the accompanying drawings.

FIG. 1 is a top plan view of an electronic apparatus incorporating the invention;

FIG. 2 is a sectional view taken along lines 2--2 of FIG. 1 illustrating the keyboard in the unactuated position;

FIG. 3 is a sectional view similar to FIG. 2 illustrating one of the switches operated; and

FIGS. 4-6 are partial sectional views illustrating alternate configurations for the top member of the invention.

Turning now to the drawings, FIG. 1 illustrates the top surface of an electronic video game having a keyboard incorporating the invention. As seen in this Fig., a plurality of switch sites S1, S2 . . . , SN are arranged in a predetermined pattern as a keyboard layout on the video game housing. As seen in FIG. 2, each switch site is formed as a concave depression in an essentially planar sheet 10. Sheet 10 is preferably formed from a suitable plastic material as a monolithic member and may be attached to the housing by any suitable means, such as a snap fit arrangement or a suitable adhesive.

Immediately underlying top sheet 10 is an intermediate switch assembly generally designated with reference numeral 12 and including a top insulative layer 13, a bottom insulative layer 14, a first electrically conductive path 15 and a second electrically conductive path 16. Conductive paths 15 and 16 are normally physically separated and, in the embodiment shown, this function is achieved by means of an intermediate insulative layer 18 having a plurality of apertures (only two of which are illustrated and designated with reference numerals 22 and 23).

Underlying the intermediate switch assembly is a bottom member generally designated with reference numeral 30 and having two groups of upwardly extending projections: a first group underlying the switch sites (projections 32, 33) and a second group of greater height than the first group and underlying the midpoint of the distance between adjacent switch sites on top member 10 (projections 34-36). Projections 32, 33 of the first group cooperate with the associated switch sites S2, S3 and the aligned portions of intermediate switch assembly 12 to enable individual switch actuation. Projections 34-36 of the second group provide mechanical support for the intermediate switch assembly 12 and also isolate the switch sites from one another to ensure individual actuation of only one switch at a time.

FIG. 3 illustrates the operation of the preferred embodiment when the S2 switch site is depressed by the fingertip of a human operator. As seen in this Fig., the region of top member 10 adjacent switch site S2 is deformed downwardly and switch site S2 compresses that portion of intermediate switch assembly 12 immediately below against underlying projection 32, so as to result in mechanical contact between the two conductive layers 15, 16. In addition, flanking projections 34, 35 mechanically isolate the actuated region surrounding switch site S2 from adjacent regions (such as S3) so that only the S2 switch site region is operated. It should be understood that, for purposes of illustration, the vertical spacing between the members 10, 12 and 30 is greatly exaggerated in FIGS. 2 and 3. In the actual embodiment of the invention, there is physical contact not only between projection 35 and the overlying portion of intermediate switch assembly 12 but also between the upper surface of switch assembly 12 and the intermediate overlying portion of top member 10. Thus, the flanking projections 34, 35 from the second group of projections act as fulcrum points to permit deflection of member 10 therebetween and to prevent deflection of member 10 outboard of the flanking projections 34, 35.

In the preferred embodiment, top member 10 is fabricated from a clear plastic material such as ABS polymer and an additional sheet 19 is provided which carries indicia for identifying the function of each switch site S1-SN. Sheet 19 may be fabricated from paper, plastic or any other thin flexible sheet material which does not interfere with the operation of the keyboard assembly.

It should be understood that, for purposes of simplicity and clarity, only two conductive paths 15, 16 have been illustrated for the intermediate switch assembly 12. In most practical applications, there are a plurality of individual conductor paths serving to identify the activated switch site. For example, the conductive paths 15, 16 may comprise individual networks of conductive ink deposited on the facing surfaces of upper and lower insulative layers 13, 14.

As will now be apparent, keyboards fabricated in accordance with the invention are extremely simple, easy to assemble and durable in operation. In addition, by employing commercially available intermediate switch assemblies 12, the operation of each individual switch can be effected in a highly reliable fashion over a large number of switch cycles.

While the above provides a full and complete disclosure of the preferred embodiment of the invention, various modifications, alternate constructions and equivalents may be employed without departing from the true spirit and scope of the invention. For example, if desired indicia layer 19 may be eliminated and the key switch functions embossed, printed or otherwise placed on top member 10. In addition, although the concave depressions S1-SN are depected as having a convex bottom contour, the bottom surface of member 10 may be planar with concave depressions formed in the top surface as shown in FIG. 4, with typical thickness dimensions of 0.070 inch for the main planar portion and 0.030 inch for the minimum thickness dimension for each concave depression. Moreover, in some applications the switch site defining regions may be convex, rather than concave, or simply flat, as shown in FIGS. 5 and 6, respectively. Therefore, the above description should not be construed as limiting the scope of the invention which is defined by the appended claims.