COMPUTER KEYBOARD WITH CANTILEVER SWITCH DESIGN AND IMPROVED PCB/SWITCH MEMBRANE INTERFACE

Abstract: A computer keyboard has multiple rows of cantilevered keys which are flexibly attached to common mounting strips. The rows of cantilevered keys are arranged to partially overlap adjacent rows such that the keys in one row actuate switch contacts aligned beneath mounting strips in the adjacent row. An interface between the switch contact membrane and a printed circuit board, and employing a portion of the dome sheet as supporting legs for the keyboard, are also described.

Description: DESCRIPTION Computer Keyboard With Cantilever Switch Design And Improved PCB/Switch Membrane Interface Technical Field This invention relates to computer keyboards, and more particularly to computer keyboards with cantilevered keys. Background Art As the computer keyboard industry matures, there is an increasing drive among keyboard manufacturers to produce lower cost keyboards. Traditionally, manufacturers have produced a keyboard 10 such as that shown in Fig. 1. One such prior art computer keyboard is disclosed in U.S. Patent No. 4,560,844 granted to Takamura on December 24, 1985. Keyboard 10 includes multiple keys 12 mounted in a housing 14, which includes a rigid metal backing plate 16, a rigid metal or plastic mounting plate 18, and a rigid plastic enclosure 20. Keyboard 10 also has a switch membrane 22 and a dome sheet 24 positioned between backing plate 16 and mounting plate 18. Mounting plate 18 has multiple key supports 26 into which key stems 30 of keys 12 are slidably mounted so that keys 12 can be moved from rest positions to activated positions. Switch membrane 22 comprises multiple switch contacts positioned beneath respective keys 12. The switch contacts are actuated upon depression of these keys. Dome sheet 24 comprises multiple resilient domes 28 which project upward to bias keys 12 to their rest position. Domes 28 collapse when keys 12 are depressed and rebound to their original form when keys 12 are released by the user to provide the "spring-like" feel of the computer keys. When the keys are depressed, switch membrane 22 conveys an electric signal from the actuated switch contact to an electrical circuit, such as a microprocessor, which is also provided on keyboard 10, but not shown in this figure. One of the drawbacks of the prior art keyboard shown in Fig. 1 concerns the bearing interface between monoblock key support 26 and key stem 30 of keys 12. At this interface, key stem 30 slides within key support 26, creating surface friction therebetween. As keyboards age, the surface friction increases and keys 12 begin to move less freely. As a result, keyboard users must press harder to depress the computer keys. The necessity of an increased pushing force contributes to user fatigue and other repetitive stress conditions. As the bearing interface further degrades, computer keys often "stick" in the depressed position or return very slowly to the rest position. In such situations, the friction between the key stem 30 and key support 26 is equal to, or greater than, the spring-like force provided by domes 28. Keyboard manufacturers often lubricate the bearing interface between the key stem and support in an effort to lessen the problems caused by surface friction. Unfortunately, adding such lubricant requires additional assembly time and the use of special lubricants. This contributes to the overall cost of the computer keyboard. Another drawback of the prior art keyboard shown in Fig. 1 is that individual keys must be separately and independently mounted in their corresponding key supports. Conventional keyboards typically consist of 101 keys. Individually assembling each key requires a significant amount of time and expense. This invention provides a computer keyboard which eliminates the conventional key stem/support interface and thereby removes the problems associated therewith. Brief Description of the Drawings One or more preferred embodiments is described with reference to the following accompanying drawings. Fig. 1 is a cross-sectional view of a prior art computer keyboard having keys movably mounted within a conventional monoblock structure. Fig. 2 is a diagrammatic top plan view of a computer keyboard according to this invention with a partial sectional view through the upper right hand portion of the computer keyboard enclosure. Fig. 3 is a diagrammatic cross-sectional view taken along line 3-3 in Fig. 2. Figs. 4A and 4B are an exploded cross-sectional view of the Fig. 3 keyboard. Fig. 5 is a diagrammatic, exploded top plan view of "numeric" keys positioned in an adder pad portion of the keyboard. Fig. 6 is an enlarged sectional view of a flexible hinge used to attach cantilevered keys to mounting strips. Fig. 7 is an enlarged cross-sectional view of a front section of a key in its rest position. Fig. 8 is an enlarged cross-sectional view of the front section of the key in its depressed, activated position. Fig. 9 is a diagrammatic top plan view of a cantilevered key according to one embodiment of this invention. Fig. 10 is a diagrammatic side view of the Fig. 9 key illustrated in its depressed, activated position. Fig. 11 is a cross-sectional view of a switch membrane PCB interface according to this invention. Fig. 12 is an diagrammatic, exploded, perspective view of the switch membrane/PCB interface of Fig. 11. Disclosure of Invention and Best Modes for Carrying Out the Invention Fig. 2 diagrammatically shows a computer keyboard 50 constructed in accordance to this invention. Keyboard 50 comprises a rigid, plastic housing or enclosure 52 and multiple keys 54 arranged within housing 52 in a selected configuration. Keys 54 include an "escape" key 56 and "function" keys 58 arranged across the top of the keyboard, "QWERTY" keys 60 which define the standard typewriter arrangement, and "numeric" keys 62 of the adder pad 63 at the right of the keyboard. Most of the computer keys in keyboard 50 are "single-wide" keys such as "escape" key 56 and "function" keys 58. Some keys are "multi-wide" keys such as "spacebar" key 64, "alt" keys 66, "control" keys 68, "shift" keys 70, "cap lock" key 72, "tab" key 74, "enter" key 76, and "insert" key 78. The "single-wide" keys have narrow key caps with a width less than that of the key caps of "multi- wide" keys. The key layout of keyboard 50 is provided for illustration purposes. Most computer keyboards constructed today have more keys than are shown in keyboard 50. For example, computer keyboards typically have 101 keys which include, in addition to those identified above, "cursor" keys and "edit" keys interposed between the "QWERTY" keys 54 and the "numeric" keys 62. This invention is not limited to the illustrated keyboard, but may be incorporated into a keyboard having any number of keys (including both "single-wide" and "multi- wide" keys) and arranged in any selected configuration. The upper right-hand portion of computer keyboard 50 is illustrated with a portion of enclosure 52 cut away to illustrate the underlying circuitry and interface construction. Computer keyboard 50 includes a mother board or printed circuit board (PCB) 80 having multiple integrated circuits 82 and other electronic components mounted thereon. Typically, the integrated circuits consist of one or more microprocessors. Other electronic components mounted on PCB 80 include resisters, capacitors, diodes, and frequency reference. Indicator lamps (not shown) for identifying certain operational modes (such as "num lock", "caps lock", and "scroll lock") may also be mounted on PCB 80. PCB 80 is designed to fit within the upper right hand corner of computer keyboard 50 above adder pad 63 and to the right of the "function" keys 58. The positioning of PCB 80 is facilitated by a new PCB/membrane interface constructed according to this invention which is described below in more detail. According to an aspect of this invention, individual rows of keys 54 in keyboard 50 are integrally formed with a common base unit or mounting strip. As shown in Fig. 2, the right most function keys (referenced with numeral 84) are integrally constructed with mounting strip 86. Individual keys 84 are mounted to strip 86 by elongated members 88 such that keys 84 are cantilevered about mounting strip 86. This integral construction is illustrated more clearly in Fig. 5, and is discussed below in greater detail. Figs. 3 and 4A-4B diagrammatically illustrate a cross sectional view of computer keyboard 50 taken through the adder pad 63 (along line 3-3 in Fig. 2). Computer keyboard 50 includes a top enclosure portion 120 and a lower enclosure portion 122 and multiple cantilevered keys 114-118. Top and bottom enclosure portions 120 and 122 are preferably formed of rigid plastic and molded in a suitable aesthetic appearance to provide an encasing for cantilevered keys 114-118. Bottom enclosure portion 122 includes an inclined support member or plate 124 having an upper surface 126. Support plate 124 has multiple clips 128-133 (Fig. 4B) projecting upward from upper surface 126. These clips are explained below in more detail. Keyboard 50 has a switch membrane 134 disposed on top of upper surface 126 of bottom enclosure portion 122. Switch membrane 134 comprises an upper layer 136 and a lower layer 138 which are preferably formed of a flexible, insulative material such as Mylar. Switch membrane 134 includes multiple spacers 140 formed on upper and lower layers 136 and 138. Preferably, spacers 140 are made of non-conductive silk screen material deposited onto the layers in a selected pattern. Switch membrane 134 has multiple switch contacts 142a/142b-146a/146b arranged for actuation by respective keys 114-118. Upper contacts 142a -146a on upper layer 136 are aligned with, but spaced from, respective lower contacts 142b-146b on lower layer 138. Spacers 140 maintain an appropriate air gap separation between the switch contacts such that signals are not conducted through this air gap. The separation can be overcome, however, upon depression of associated keys 114-118. Switch membrane 134 includes multiple conductive traces formed thereon (not shown) which conduct electric signals from associated contact switches to terminals or pads located at peripheral edges 148. Preferably, switch contacts 142a/142b-146a/146b and the conductive traces are formed of silver. Alternatively, the switch contacts can be formed of carbon-based materials. Although switch membrane 134 is disclosed as two separate layers, it may comprise a single layer folded onto itself to form the upper and lower layers 136 and 138. Alternatively, the switch membrane may comprise a single layer with pairs of spaced switch contacts formed on an upper surface. The contacts are then actuated by conductive shunts molded or attached to a portion of the collapsible domes. Such switch constructions are shown, for example, in U.S. Patent No. 4,677,268 to Nemeth et al. granted June 30, 1987, U.S. Patent No. 4,760,217 to Suzuki et al. granted July 26, 1988, and U.S. Patent No. 4,814,561 to Kawasaki granted March 21, 1989. As yet another alternative, the switch membrane may comprise two layers of switch contacts separated by a third insulative layer having openings formed at the switch contact locations. This alternative embodiment eliminates the use of spacers 140. Computer keyboard 50 further includes a dome sheet 150 disposed on top of switch membrane 134. Dome sheet 150 is formed of a resilient insulative material, such as rubber or an elastomeric material, and has multiple resilient and collapsible domes 152-156. Domes 152-156 are appropriately spaced on dome sheet 150 to align with corresponding switch contacts 142a/142b-146a/146b. Individual domes comprise a cylindrical section 158 and a frustoconical section 160 which suspends cylindrical section 158 above dome sheet 150. Frustoconical section 160 is designed to collapse upon application of a downward force to cylindrical section 158. However, due to the resiliency of the dome sheet material, the domes "spring back" to their non-collapsed state once the downward force is removed. Each of the domes also includes an actuator knob 162 which protrudes downward from a bottom surface of the cylindrical section 158 in direct alignment with respective switch contacts of the switch membrane 134. Dome sheet 150 also includes a raised portion 164 positioned at one peripheral end thereof. When assembled, the raised portion extends through an opening 166 formed in bottom enclosure portion 122. The raised portion 164 operates as a pad or platform peg to support the front end of computer keyboard 50. This construction eliminates the use of separate rubber pegs which are typically mounted to the exterior of the enclosure after the keyboard has been assembled. This aspect of the invention reduces material costs and assembly time. Computer keyboard 50 comprises multiple mounting strips 170-174 to which respective cantilevered keys 114-118 are flexibly attached. An additional strip 169 is positioned adjacent to mounting strip 170, but no key is attached to this strip. Strips 169-174 are positioned on top of dome sheet 150 and secured to support plate 124 via respective clips 128-133. Preferably, dome sheet 150 and switch membrane 134 have aligned apertures (not shown) formed therein through which respective clips 128-133 extend to clamp onto corresponding mounting strips 170-174. In an alternative embodiment, clips 128-133 may be formed as part of mounting strips 169-174 which extend downwardly through the aligned apertures in dome sheet 150 and switch membrane 134 to clip into support plate 124. Either embodiment constitutes a clip means for securing the mounting strips to the support plate. Additionally, apart from clips 128-133, other known fastening members, such as screws, snaps, ultrasonic welding, heat staking and glued extensions, may be employed as an effective clip means. Mounting strips 169-173 include respective apertures 176-180 formed therein to receive corresponding domes 152-156. Mounting strip 174 does not have any such openings because there is no corresponding dome. Cantilevered keys 114-118 comprise respective key caps 182-186 and elongated members 188-192. Elongated members 188-192 have one end flexibly attached to corresponding mounting strips 170-174 and the other end coupled to associated key caps 182-186. Key caps 182-186 are supported by elongated members 188-192 in a cantilevered fashion. Elongated members 188-192 are preferably attached to corresponding mounting strips 170-174 by serpentine-shaped hinges 194-198. Fig. 6 shows an enlarged view of a representative, serpentine-shaped hinge 194 which couples elongated member 188 of first cantilevered switch 182 to mounting strip 170. Hinge 194 is preferably "S"-shaped having a first bend 300 connected to mounting- ■ strip 170 and a second bend 302 connected to elongated member 188. The "S"^haped hinge helps reduce wear and fatigue of the hinge (which is preferably plastic) used to support the cantilevered keys. First bend 300 has a cross-sectional thickness T j which is less than a cross- sectional thickness T 2 of second bend 302. The thicknesses are selectable during design to identify a desired cantilevered point about which the cantilevered keys rotate. According to these thickness profiles, the cantilevered point occurs in first bend 300. While the "S"-shaped hinge is preferable, a single-bend or other multi-bend hinges can be employed according to this invention. Returning to Figs. 3 and 4A-4B, lower layer 138 of switch membrane 134 extends slightly beyond upper layer 136. PCB 80 is aligned adjacent to the end of upper layer 136 and on top of the end of lower layer 138. This arrangement provides the switch membrane/PCB interface 218 which is another aspect of this invention. This interface is described in more detail with reference to Figs. 11 and 12. Fig. 5 illustrates an exploded view of a portion of the adder pad 63 having rows of cantilevered keys. With reference to Figs. 3-5 and for purposes of continuing discussion, cantilevered keys 114, 115, and 116 will be referred to respectively as "first", "second", and "third" cantilevered keys which are aligned in respective "first" row 90, "second" row 92, and "third" row 94. Mounting strips 170, 171, and 172 will be referred to respectively as "first", "second", and "third" mounting strips. Each of the first cantilevered keys 114 in the first row 90 are operatively attached to first mounting strip 170. Similarly, each of the second and third cantilevered keys 115, 116 in respective second and third rows 92, 94 are operatively attached to a common corresponding second and third mounting strip 171, 172. First row 90 of first cantilevered keys 114 and first mounting strip 170 are preferably formed of a single, integral unit of plastic (Fig. 5). Similarly, the second and third rows of cantilevered keys are each formed of a single, integral unit of plastic. Alternatively, the key caps can be molded in a separate process and then mounted to the elongated member. Such a process is desirable where the key cap is to be shaded a different color than the other keys of the keyboard. For example, adder pad "enter key" 110 may be colored gray in a separate process and then attached to elongated member 111. Alternatively, keytops can be molded in a multiple-color process wherein two or more colors are molded simultaneously. In such a process, each cantilevered key is gated individually, allowing different colored material (such as plastic) to be directed to desired keys. This results in different colored keys attached to the same integral keystrip. The different colored plastics blend within the mounting strip, which is hidden beneath the enclosure and thus, not visible to the keyboard user. This alternative process is efficient and cost effective. Domes 152-156 of dome sheet 150 and switch contacts 142a/142b-146a/146b in switch membrane 134 are arranged in horizontal rows running longitudinally across the keyboard and are associated with the rows of corresponding cantilevered keys 114-118. The domes extend upwardly through corresponding rows of apertures in mounting strips 169-173. The rows of switch contacts are aligned beneath corresponding rows of domes and mounting strip apertures. Multi-wide "0/INS" key 78 (Fig. 5) has two elongated members 102 and 104 which connect its wider key cap to mounting strip 170. An aligned dome and switch contact are positioned beneath both elongated members 102 and 104. The switch contacts are preferably connected in parallel such that actuation of either contact (for example, by depressing only the right or left hand side of a multi-wide key) will effectuate the desired key stroke operation. This construction therefore does not employ leveling wires or the like to ensure the key is horizontally level during depression. Other multi-wide keys, such as the "spacebar" key, "control" key, "cap lock" key, etc., also employ multiple elongated members with corresponding domes and switches. According to this invention, cantilevered keys 114-118 are configured in an overlapping arrangement. The second row 92 of second cantilevered keys 115 are positioned adjacent to, and partially overlapping, the first row 90 of first cantilevered keys 114. Likewise, the third row 94 of third cantilevered keys 116 are adjacent to, and partially overlapping, the second row 92 of second cantilevered keys 115. In this configuration, elongated members 190 of third cantilevered key 116 extends above second mounting strip 171 and rests on top of dome 154. Key cap 184 of third cantilevered key 116 extends above a portion of elongated member 189 of second cantilevered key 115. As the third cantilevered key 116 is depressed to its activated position, dome 154 buckles or collapses so that actuating knob 162 forces upper switch contact 144a into actuating engagement with lower switch contact 144b. Second cantilevered key 115 extends above first mounting strip 170 and the elongated portion of first cantilevered key 114 to rest on dome 153. Second cantilevered key 115 depresses dome 153 to actuate switch contacts 143a/143b. Likewise, first cantilevered key 114 engages and buckles dome 152 to actuate switch contacts 142a/142b. According to another aspect of this invention, cantilevered keys 114-118 have one or more hooks 200-204 integrally formed with, and projecting downward from, corresponding key caps 182-186. Complementary and corresponding loops 206-209 are formed on associated mounting strips 169-172 adjacent to dome apertures 176-179 (Fig. 5). The hooks are slidably interconnected with corresponding loops. Second apertures (as represented with numeral 210 in Fig. 5) are provided beneath the loops and adjacent to the dome apertures. The purpose of these second apertures is discussed below. The loop and hook arrangement is shown more clearly in the enlarged, sectional views of third cantilevered key 116 shown in Figs. 7 and 8. In Fig. 7, third cantilevered key 116 is in its rest position. Hook 202 abuts against loop 207 to limit the upward travel of third cantilevered key 116. Upon application of a downward force F (Fig. 8), hook 202 slides downward within loop 207 and through opening or aperture 210 formed in first mounting strip 170. Hook 202 "bottoms out" against rubber or elastomer dome sheet 150. This results in a very quiet keystroke. The present invention significantly reduces noise problems encountered by prior art keyboards which experience a plastic-against-plastic collision caused by plastic key bodies striking against plastic enclosures or mounting plates. When the downward force F is removed, the cantilevered key returns upwardly towards its rest position under the influence of the resilient "spring-like" dome. Hook 202 once again abuts corresponding loop 207 to limit upward travel of the cantilevered keys. The hook and loop arrangement effectively prevents the cantilevered keys from "jumping" beyond the rest position under the spring induced force of the dome once the applied force F is removed. With reference to Fig. 3, top enclosure portion 120 includes a lip 211 which operates as the "loop" for hook 200 to limit upward travel of first cantilevered key 182. In this manner, no additional mounting strip is employed. Mounting strip 169 provides loop 206 for hook 201 of second cantilevered key 115. Although the present invention has been described as employing a hook and loop arrangement, other upstop means for establishing upward travel stop position of the cantilevered keys are possible. Preferably, the upstop means comprises complementary first and second interlocking components wherein one of the interlocking components is provided on a mounting strip and the other interlocking component is provided on the cantilevered key. One possible alternative is a cylindrical rod, with a ball formed on one end, projecting downward from a key cap and being slidably mounted within an interlocking ring¬ like component. The ball abuts against the ring-like component to limit upward travel of the key. Other mechanical arrangements are also possible. To summarize the overlapping cantilevered structure of this invention, one row of cantilevered keys depresses domes and actuates switches in rows which are arranged beneath the mounting strip of the adjacent row of cantilevered keys. The upstop means for this one row of cantilevered keys is provided in part on the mounting strip of the next adjacent row of cantilevered keys (i.e., two rows over). For example, third cantilevered key 116 depresses dome 154 and actuates switch contacts 144a/144b which are aligned beneath second mounting strip 171. The upstop mechanism for the third row of cantilevered keys 116 is provided on the first mounting strip 170 of the first cantilevered keys which are two rows over. This structure is advantageous in that it provides significant cantilevered action about the mounting strip due to the lengthy moment arm provided by the elongated members, and yet the keys are still closely packaged and arranged to provide a standard keyboard configuration to which the user is well familiar. Figs. 9 and 10 illustrate an alternative embodiment for a cantilevered key construction according to this invention. Cantilevered key 400 comprises an elongated member 402 having rigid beams 404 which support the cantilevered key 400 and a central, flexible, spring-like member 406. Flexible member 406 is a "U"-shaped cutout portion of elongated member 402 (Fig. 9). As shown in Fig. 10, flexible member 406 is positioned above and engages resilient dome 408. Upon application of a downward force F, cantilevered key 400 is moved to an intermediate position which causes dome 408 to buckle or collapse. As cantilevered key 400 is depressed beyond the intermediate position, flexible member 406 bends upward slightly to allow key cap 410 and rigid beams 404 to continue their downward movement. Flexible member 406 thereby provides an overtravel means for allowing depression of cantilevered key 400 after the collapse of dome 408. Figs. 11 and 12 diagrammatically illustrate a switch membrane/PCB interface constructed according to this invention. Support plate 124 of bottom enclosure portion 122 has a rectangular shaped channel 220 formed therein. An interconnect block or support member 222, preferably formed of resilient material such as rubber or foam, is positioned within channel 220 and is slightly raised above upper surface 126 of support plate 124. Support plate 124 includes multiple deflectable fasteners 224-227 which project upward from upper surface 126 and are aligned along channel 220. The fasteners are described below in more detail. Upper and lower layers 136 and 138 of switch membrane 134 are positioned on top of upper surface 126 and extend to the left (relative to the figure) of an interface region defined by support member 222. Lower layer 138 has slots 230 and 231 provided therein and upper layer 136 has slots 234 and 235 formed therein to receive respective fasteners 226 and 227. As an alternative to slots, openings sized to receive corresponding fasteners 226 and 227 may be provided in upper and lower layers 136 and 138. Switch membrane 134 has multiple conductive traces (as represented by conductive traces 238 on lower layer 138) deposited and patterned thereon. These traces convey electric signals from the switch contacts positioned beneath the cantilevered keys to interface pads (as represented by pads 240 on lower layer 138) at peripheral end 239. Similar traces and interface pads are deposited and patterned on the bottom surface (not shown) of upper layer 136. Lower layer 138 also includes shunting traces 242 which have first ends 244 that electrically engage pads provided on upper layer 136 and second ends which define interface pads 246. The upper layer 136 pattern engagement to lower layer 138 pattern provides the circuit connection for the upper layer 136. PCB 80 is positioned on top of upper surface 126 of support plate 124 and extends to the right (relative to the figure) of the interface region defined by support member 222. PCB 80 has slots 248 and 250 formed therein to receive corresponding fasteners 224 and 225. Peripheral end 252 of PCB 80 extends on top of peripheral end 239 such that conductive interface pads provided on PCB 80 (not shown) align with interface pads 240, 246 of switch membrane 134. PCB 80 is positioned adjacent to upper layer 136 of switch membrane 134, but does not overlap this layer. In alternative embodiments wherein a single layer switch membrane is employed, PCB 80 would simply overlap the single layer switch membrane. Alternatively, the orientation of PCB to membrane can be such that the membrane upper layer lays on top of the PCB, using a portion of the dome sheet in place of support member 222. In this instance, the upper membrane layer would contain the shunting traces (242) and the upper layer extends slightly beyond lower layer. Switch membrane/PCB interface 218 also includes an interconnect member 256 which is positioned above PCB 80 and switch membrane 134. Interconnect member 256 is stair-shaped to account for the relative heights of PCB 80 relative to switch membrane 134 which have been exaggerated in Figs. 11 and 12 for illustration purpose. Member 256 has structural ribbing 258 which enhances longitudinal strength of the interconnect member. Fasteners 224-227 fit over the outside ribs 258 of the interconnect member 256. When assembled, interconnect member 256 snaps into fasteners 224-227 to hold PCB 80 against switch membrane lower layer 138, and to hold upper layer 136 and lower layer 138 together. Fasteners 224-227 hold interconnect member 256 and PCB 80 to lower layer 138 against resilient support member 222 (which compresses slightly) to facilitate electric contact between the interface pads provided on PCB 80 and lower layer 138. The fasteners also hold upper layer 136 and lower layer 138 together to facilitate electrical connection between membrane layers. PCB 80 is thereby electrically coupled to receive electric signals from the switch contacts provided on upper and lower layers 136 and 138. Signals from lower layer 138 are interfaced to PCB 80 through pads 240. Signals from upper layer 136 are interfaced to PCB 80 through pads provided thereon and shunting traces 242 and pads 246 provided on lower layer 138. Support member 222, interconnect member 256, and fasteners 224 constitute interfacing means for connecting PCB 80 to switch membrane 134. As an additional embodiment, interconnect member 256 has multiple force concentrator knobs 254 formed thereon which apply a concentrated pressure to selected locations on PCB 80 and switch membrane 134 within the interface region defined by support member 222. The cantilevered keyboard according to this invention is advantageous over prior art keyboards because it eliminates the problems associated with the plastic- against-plastic bearing interface of conventional key structures with individual keys vertically moving within a key support. Another advantage of this invention is that entire rows of cantilevered keys are molded as an integral unit along mounting strips. During assembly, an entire row of keys may be placed on the keyboard by securing a single mounting strip to the support plate. This is more efficient than individually assembling 101 key bodies within their respect key supports. This invention also has an advantage of providing a switch membrane/PCB interface which conserves packaging space. The new interface and the positioning of a small PCB board in the upper right hand corner of the keyboard beneath the indicator lights enables the construction of a relatively narrow keyboard.

Claims: CLAIMS 1. A computer keyboard comprising: a support plate; Ck a first mounting strip secured to the support plate; a first cantilevered key having at least one elongated member with one end flexibly attached to the first mounting strip and the other end coupled to a key cap; a second mounting strip secured to the support plate; a second cantilevered key having at least one elongated member with one end flexibly attached to the second mounting strip and the other end coupled to a key cap; and the second cantilevered key being arranged to overlap the first mounting strip and a portion of the first cantilevered key. 2. A computer keyboard according to claim 1 wherein: the elongated member of the second cantilevered key extends above the first mounting strip; and the key cap of the second cantilevered key extends above a portion of the elongated member of the first cantilevered key. 3. A computer keyboard according to claim 1 wherein: the first mounting strip and the first cantilevered key are formed as a single, integral unit; and the second mounting strip and the second cantilevered key are formed as a single, integral unit. 4. A computer keyboard according to claim 1 wherein: the elongated members of the first and second cantilevered keys are attached to respective first and second mounting strips by serpentine-shaped hinges. 5. A computer keyboard according to claim 1 wherein: the elongated members of the first and second cantilevered keys are attached to respective first and second mounting strips by "S"-shaped hinges, individual "S"-shaped hinges having a first bend connected to the mounting strips and a second bend connected to the elongated member, the first bend having a cross-sectional thickness which is less than a cross-sectional thickness of the second bend. 6. A computer keyboard comprising: a support plate; a first mounting strip secured to the support plate, the first mounting strip having apertures formed therein; a first row of first cantilevered keys, individual first cantilevered keys having at least one elongated member with one end flexibly attached to the first mounting strip and the other end coupled to a key cap, the individual first cantilevered keys being movable from a rest position to a depressed activated position; a second mounting strip secured to the support plate; a second row of second cantilevered keys adjacent to, and partially overlapping, the first row of first cantilevered keys, individual second cantilevered keys having at least one elongated member with one end flexibly attached to the second mounting strip and the other end coupled to a key cap, the individual second cantilevered keys being movable from a rest position to a depressed activated position; a switch membrane positioned intermediate of the mounting strips and the support plate, the switch membrane having a row of switch contacts aligned beneath corresponding apertures of the first mounting strip; a dome sheet positioned intermediate of the mounting strips and the support plate, the dome sheet having a row of resilient domes extending upward through corresponding apertures of the first mounting strip; and the elongated members of the second cantilevered keys extending above corresponding domes that extend through the apertures in the first mounting strip and corresponding switch contacts, the second cantilevered keys actuating the corresponding switch contacts when the second cantilevered keys are depressed to their activated positions. 7. A computer keyboard according to claim 6 wherein: individual domes comprise means for actuating the corresponding switch contacts upon depression of corresponding second cantilevered keys. 8. A computer keyboard according to claim 6 wherein: the first mounting strip and the first row of cantilevered keys are formed of as a single, integral unit; and the second mounting strip and the second row of cantilevered keys are formed of as a single, integral unit. 9. A computer keyboard according to claim 6 wherein: the first mounting strip and the first row of cantilevered keys are formed as a single, integral unit; the second mounting strip and the second row of cantilevered keys are formed as a single, integral unit; and the cantilevered keys of the first and second rows are molded from one of at least two different colored materials to define different colored keys. 10. A computer keyboard according to claim 6 wherein: the elongated members of the first and second cantilevered keys are attached to respective first and second mounting strips by serpentine-shaped hinges. 11. A computer keyboard according to claim 6 wherein: the elongated members of the first and second cantilevered keys are attached to respective first and second mounting strips by "S"-shaped hinges, individual "S"-shaped hinges having a first bend connected to the mounting strips and a second bend connected to the elongated member, the first bend having a cross-sectional thickness which is less than a cross-sectional thickness of the second bend. 12. A computer keyboard according to claim 6 wherein: the individual first and second cantilevered keys are movable through an intermediate position between the rest position and the activated position; the domes are adapted to buckle as the second cantilevered keys are depressed to the intermediate position; and individual elongated members of the second cantilevered keys comprise overtravel means for allowing the second cantilevered keys to continue downward movement as they are depressed beyond the intermediate position. 13. A computer keyboard according to claim 6 wherein at least one of the rows of the first and second cantilevered keys includes "single-wide" keys and "multi-wide" keys, the "single-wide" keys having narrow key caps of a first width and the "multi-wide" keys having wide key caps of a second width greater than the first width, the "multi-wide" keys having multiple elongated members connecting the wide key caps with the respective first and second mounting strips, each of the multiple elongated members being positioned above associated domes and switch contacts. 14. A computer keyboard according to claim 6 wherein: the dome sheet and the switch membrane have aligned apertures formed therein; the keyboard further comprising: clip means for securing the first and second mounting strips to the support plate, the clip means including a plurality of fastening members which extend through the aligned apertures provided in the dome sheet and switch membrane and connect the mounting strips to the support plate. 15. A computer keyboard according to claim 6 further comprising: an enclosure with a top portion and a bottom portion for encasing the cantilevered keys, the dome sheet, and the switch membrane, the enclosure having an opening formed in the bottom portion; the dome sheet having a peripheral portion which extends through the opening in the bottom portion of the enclosure to support the computer keyboard. 16. A computer keyboard comprising: a support plate; a first mounting strip secured to the support plate, the first mounting strip having apertures formed therein; a first row of first cantilevered keys, individual first cantilevered keys having at least one elongated member with one end flexibly attached to the first mounting strip and the other end coupled to a key cap, the individual first cantilevered keys being movable from a rest position to a depressed activated position; a second mounting strip secured to the support plate, the second mounting strip having apertures formed therein; a second row of second cantilevered keys adjacent to, and partially overlapping, the first row of first cantilevered keys, individual second cantilevered keys having at least one elongated member with one end flexibly attached to the second mounting strip and the other end coupled to a key cap, the individual second cantilevered keys being movable from a rest position to a depressed activated position; a third mounting strip secured to the support plate, the third mounting strip having apertures formed therein; a third row of third cantilevered keys adjacent to, and partially overlapping, the second row of second cantilevered keys, individual third cantilevered keys having at least one elongated member with one end flexibly attached to the third mounting strip and the other end coupled to a key cap, the individual third cantilevered keys being movable from a rest position to a depressed activated position; a switch membrane positioned intermediate of the mounting strips and the support plate, the switch membrane having multiple rows of switch contacts aligned beneath corresponding apertures of respective first, second, and third mounting strips; a dome sheet positioned intermediate of the mounting strips and the support plate, the dome sheet having multiple rows of resilient domes extending upward through corresponding apertures of respective first, second, and third mounting strips; the elongated members of the third cantilevered keys extending above corresponding domes that extend through the second mounting strips and corresponding switch contacts, the third cantilevered keys actuating the corresponding switch contacts when the third cantilevered keys are depressed to their activated positions; and upstop means for establishing an upward travel stop position of the third cantilevered keys, the upstop means comprising complementary first and second interlocking components, the first interlocking components being provided on the first mounting strip and the second interlocking components being provided on individual third cantilevered keys. 17. A computer keyboard according to claim 16 wherein: individual domes comprise means for actuating the corresponding switch contacts upon depression of corresponding third cantilevered keys. 18. A computer keyboard according to claim 16 wherein: the first mounting strip and the first row of cantilevered keys are formed of a single, integral unit of plastic; the second mounting strip and the second row of cantilevered keys are formed as a single, integral unit; and the third mounting strip and the third row of cantilevered keys are formed as a single, integral unit. 19. A computer keyboard according to claim 16 wherein: the first mounting strip and the first row of cantilevered keys are formed as a single, integral unit; the second mounting strip and the second row of cantilevered keys are formed as a single, integral unit; the third mounting strip and the third row of cantilevered keys are formed as a single, integral unit; and the cantilevered keys of the first, second, and third rows are molded from one of at least two different colored materials to define different colored keys. 20. A computer keyboard according to claim 16 wherein: the elongated members of the first, second, and third cantilevered keys are attached to respective first, second, and third mounting strips by serpentine-shaped hinges. 21. A computer keyboard according to claim 16 wherein: the elongated members of the first, second, and third cantilevered keys are attached to respective first, second, and third mounting strips by "S"-shaped hinges, individual "S"-shaped hinges having a first bend connected to the mounting strips and a second bend connected to the elongated member, the first bend having a cross-sectional thickness which is less than a cross-sectional thickness of the second bend. 22. A computer keyboard according to claim 16 wherein: the individual first, second, and third cantilevered keys are movable through an intermediate position between the rest position and the activated position; the domes are adapted to buckle as the third cantilevered keys are depressed to the intermediate position; and individual elongated members of the third cantilevered keys comprise overtravel means for allowing the third cantilevered keys to continue downward movement as they are depressed beyond the intermediate position. 23. A computer keyboard according to claim 16 wherein at least one of the rows of the first, second, and third cantilevered keys includes "single-wide" keys and "multi-wide" keys, the "single-wide" keys having narrow key caps of a first width and the "multi-wide keys" having wide key caps of a second width greater than the first width, the "multi-wide" keys having multiple elongated members connecting the wide key caps with the respective first, second, and third mounting strips, each of the multiple elongated members being positioned above associated domes and switch contacts. 24. A computer keyboard according to claim 16 wherein: the first interlocking components of the upstop means comprise loops formed on the first mounting strip adjacent to the apertures; the second interlocking components of the upstop means comprise hooks projecting downward from the key caps of the third cantilevered keys, the hooks being slidably interconnected within corresponding loops to allow downward travel of the third cantilevered keys as they are depressed, the hooks abutting the corresponding loops to limit upward travel of the third cantilevered keys when they are in their rest position. 25. A computer keyboard according to claim 24 wherein: the dome sheet is positioned beneath the first, second, and third mounting strips; the first mounting strip has second apertures aligned beneath corresponding loops; the hooks passing through corresponding second apertures to contact the dome sheet when the individual third cantilevered keys are depressed. 26. A computer keyboard according to claim 16 wherein: the dome sheet and the switch membrane have aligned apertures formed therein; the keyboard further comprising: clip means for securing the first, second, and third mounting strips to the support plate, the clip means including a plurality of fastening members which extend through the aligned apertures provided in the dome sheet and switch membrane and connect the support plate to the mounting strips. 27. A computer keyboard according to claim 16 further comprising: an enclosure with a top portion and a bottom portion for encasing the cantilevered keys, the dome sheet, and the switch membrane, the enclosure having an opening formed in the bottom portion; the dome sheet having a peripheral portion which extends through the opening in the bottom portion of the enclosure to support the computer keyboard. 28. A computer keyboard comprising: a support plate; a first mounting strip secured to the support plate; a first row of first cantilevered keys, individual first cantilevered keys having an elongated member with one end flexibly attached to the first mounting strip and the other end coupled to a key cap; a second mounting strip secured to the support plate; a second row of second cantilevered keys adjacent to, and partially overlapping, the first row of the first cantilevered keys, individual second cantilevered keys having an elongated member with one end flexibly attached to the second mounting strip and the other end coupled to a key cap; the second row of cantilevered keys being arranged to overlap the first mounting strip and a portion of the first row of cantilevered keys; a swkh membrane positioned intermediate of the mounting strips and the support plate, the switch membrane having (1) switch contacts positioned for actuation by corresponding first and second cantilevered keys, (2) conductive first interface pads, and (3) conductive traces for conveying electric signals from the switch contacts to the first interface pads; a printed circuit board positioned to overlap the switch membrane, the printed circuit board having conductive second interface pads for corresponding first interface pads on the switch membrane; interfacing means for connecting the printed circuit board with the switch membrane, the interfacing means comprising: a support member; an interconnect member positioned above the printed circuit board and switch membrane; and fastening means for exerting a downward pressure on the interconnect member to force the printed circuit board together with the switch membrane and against the support member to facilitate electrical contact between the first and second interface pads. 29. A computer keyboard according to claim 28 wherein the interconnect member has a plurality of force concentrator knobs which apply a concentrated pressure to selected locations on the switch membrane within the interface region. 30. A computer keyboard according to claim 28 wherein the support member is formed of resilient material which is compressible under the downward pressure exerted by the fastening means against the interconnect member. 31. A computer keyboard comprising: a support plate; a plurality of keys operatively mounted to the support plate; a switch membrane positioned intermediate of the keys and the support plate, the switch membrane having (1) switch contacts positioned for actuation by corresponding keys, (2) conductive first interface pads, and (3) conductive traces for conveying electric signals from the switch contacts to the first interface pads; a printed circuit board positioned to overlap the switch membrane, the printed circuit board having conductive second interface pads for corresponding first interface pads; interfacing means for connecting the printed circuit board with the switch membrane, the interfacing means comprising: a support member; an interconnect member positioned above the printed circuit board and switch membrane; and fastening means for exerting a downward pressure on the interconnect member to force the printed circuit board together with the switch membrane and against the support member to facilitate electrical contact between the first and second interface pads. 32. A computer keyboard according to claim 31 wherein the interconnect member has a plurality of force concentrator knobs which apply a concentrated pressure to selected locations on the switch membrane within the interface region. 33. A computer keyboard according to claim 31 wherein the support member is formed of resilient material which is compressible under the downward pressure exerted by the fastening means against the interconnect member.

Inventors: BENEFIELD JOSEPH A, CLARK THEODORE D, DAMITIO STEPHEN S, ENGLISH GEORGE P, BENEFIELD, JOSEPH, A., CLARK, THEODORE, D., DAMITIO, STEPHEN, S., ENGLISH, GEORGE, P.
Applicants: KEY TRONIC CORP, KEY TRONIC CORPORATION
Application year: 1992
Main classification: H01H13
IPC codes: G06F3, H01H13