System and method for detecting key actuation in a keyboard

A system and method for detecting key actuation in a keyboard assembly, which, in one embodiment, is used as a conductor to electrically communicate with an information appliance. The rows in the keyboard assembly are electrically isolated from one another, and each row contains keys bridging a two-wire bus. Each key has a switch that is closed during key actuation, a diode to polarize the key, and a resistor to provide a resistive load when the switch is closed and the diode is biased with the current flow. Alternatively, each key has a switch that is closed during key actuation, a timer with an output that goes high after a predetermined time period, and a resistor that provides an identifying load when the switch is closed and the output of the timer is high. Other features of the invention include a linear matrix coupled to a row of keys to allow the row to be scanned by sections and individual keys, and a flexible circuit that provides the electrical pathways for the linear matrix.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to systems and methods for detecting key actuation in keyboard assemblies for information devices, and more particularly to systems and methods for detecting key actuation in keyboards for such devices.

2. Background Information

Small portable computers or “palmtops” can be conveniently carried in a purse or coat pocket. Recent advances in shrinking the size of electronic components will soon allow these devices to perform all the functions of today's desktop computers. Additionally, a whole new category of “information appliances” has begun. These include portable wireless telephone/computers which can be used to access the Internet to send and receive e-mail and to interact on the World Wide Web.

Powerful and versatile as these devices are becoming, their use is greatly limited by non-existent or inadequate keyboards. Palmtops which rely on handwriting recognition have proven to be awkward, slow and error prone. Miniature keyboards commensurate with the size of small appliances are likewise frustrating, especially if the user needs to write something consisting of a few sentences or more. Voice recognition suffers from frequent errors and creates a lack of privacy when other people are near the speaker whose voice is being recognized. Further, voice recognition may not be used in all circumstances (e.g. the process of taking notes of a lecturer's lecture in an otherwise quiet auditorium may not be possible with voice recognition input systems but it is usually possible with a keyboard).

Keyboards for desktop and high quality laptop computers allow the user to comfortably, privately, quietly, and quickly “touch-type.” They have a number of desirable features in common. Most keyboards have a standard “QWERTY” layout which requires no learning on the part of the user (once the user has become familiar with this layout). The keys, which usually number 84 for a laptop computer, have full-sized tops whose center-to-center spacing is about 19 mm for both the horizontal and vertical axes. The length of the keyboard (the distance from the left edge of the left-most key to the right edge of the right-most key) is about 11 inches. Any reduction in this spacing has proven to slow down and frustrate the touch-typist. Additionally, the keys of these keyboards have sufficient “travel,” the distance the key moves when it is pressed, and tactile feedback, an over-center buckling action, that signals the user that the key has been pressed sufficiently.

Efforts have been made to provide keyboards that contain these features, yet collapse to a reduced size. Some designs only slightly reduce the size of “notebook” computers when folded. These are much larger than palmtop computers. IBM's “ThinkPad 701C” notebook computer folds in a single operation to reduce the keyboard case length (measured from the edges of its case) from 11.5 inches to 9.7 inches. Also see U.S. Pat. No. 5,543,787 which describes a foldable keyboard. U.S. Pat. No. 5,519,569 describes a keyboard which folds in multiple steps from a length of 10–11 inches to 6.125 inches. U.S. Pat. No. 5,654,872 describes a keyboard with keys that collapse when the lid is closed to allow a thinner notebook computer.

Other designs of keyboards include those where the keyboard is hinged at the center of its length and folds about a vertical axis. U.S. Pat. No. 5,457,453 describes a keyboard that folds to greater than half its length. U.S. Pat. No. 5,574,481 describes a keyboard that folds in half and appears to have a non-standard layout of keys (the keys on the center fold axis have edges which lie in a straight line). U.S. Pat. No. 5,653,543 describes a keyboard that folds in half. U.S. Pat. No. 5,502,460 describes a keyboard with two vertical hinges that folds to greater than half its unfolded length.

U.S. Pat. Nos. 5,044,798 and 5,141,343 describe keyboards whose keys have user-selectable variable spacing. These designs have non-standard layouts (e.g., the “Enter” key is rotated ninety degrees) and no self-containing housing. Their frame is made of telescoping sections that create a good deal of friction and could easily bind.

Keyboards electrically communicate information to information appliances. Most keyboards have printed circuit boards or membranes located underneath their keys. When a key is pressed it shorts the circuits in a particular column or row. The matrix of columns and rows that make up a keyboard is continually scanned by a controller to determine which keys have been pressed. Such an arrangement is described, for example, in U.S. Pat. No. 5,070,330. The electronic configuration of most keyboards thus necessitates a matrix of conductors that limits the collapsing of the keyboard to a certain size.

SUMMARY OF THE INVENTION

The present invention provides, in one example of the invention, a system and method for detecting key actuation in a keyboard assembly. In one embodiment, the keyboard assembly is a collapsible keyboard which includes a support element and a plurality of keys. The support element can be extended to provide a structure having a first footprint and contracted to a structure having a second footprint, where the second footprint takes less surface area than the first footprint. The plurality of keys are coupled to the support element. Each of these keys includes a key top, which is designed to be pressed by a user, and a key base which is coupled to the key top. The key top and the key base rotate, in one example of the invention, on a pivot point which couples the key base to the support element when the support element is extended and contracted.

In one exemplary embodiment, the invention provides detection of key actuation for a keyboard assembly that is capable of collapsing into its own protective housing. The housing consists of two symmetrical hollow box-shaped members, opened on one side. When closed, it forms a dust-proof enclosure surrounding a keyboard mechanism. When the keyboard assembly is in its collapsed position or state, it measures about 4.0–4.7 inches vertically (depending on the inclusion and height of “function” keys), 3.25 inches horizontally, and 1.25 inches deep. In the collapsed state, the keyboard assembly can be carried in a purse or coat pocket along with a palmtop computer or other information appliance, such as a cellular phone. Its small size allows it to be conveniently stowed inside an appliance, such as a desktop telephone or television. When used with desktop computers or other information appliances, the collapsed state may be used to better utilize desk space when the computer is not in operation.

Expanding the keyboard from a collapsed state to a keyboard having conventionally spaced keys is done in a single step in one example of the invention. The user simply pulls the two halves of the protective housing apart. The housing remains attached, so it cannot be misplaced, and so the unit can be enclosed and protected in an instant. The housing may also include a cursor control device or a pointing device such as a touch-sensitive trackpad or joystick-like device such as IBM's TrackPoint (found on IBM's ThinkPad laptop computers). This cursor control device is, in one exemplary embodiment, selectively positionable on either the left or the right sides of the keyboard.

In one embodiment of the invention, key actuation detection is provided for a keyboard assembly having keys coupled to and supported by a support element which is a series of rows of multiple scissors-like, diagonally or X-shaped hinged linkages connected to the assembly housing. The linkages are selectively shaped such that any keyboard layout may be adopted, including the standard ‘QWERTY’ layout with its staggered columns and various width keys. The linkages also provide a wide ratio of contraction, yet due to their diagonal shape when expanded, provide a strong and rigid structure. The hinged linkages create very little friction and do not require lubrication, so the keyboard assembly can be repeatedly opened and closed smoothly and easily. The keys are pivotally attached to the linkages, and by means of swing arms, pivot from a near vertical position, when the keyboard assembly is collapsed, to a horizontal position, when the keyboard assembly is expanded. To provide for a more compact profile when the assembly is collapsed, the keys are compressed to a closed and nesting position.

In one exemplary embodiment of the invention, the mechanical structure of the keyboard assembly is used as a conductor to electrically communicate with an information appliance. The rows are electrically insulated from one another, and each row contains keys bridging a two-wire bus. The rows are sequentially scanned by a controller. In another embodiment, each key has its own transponder circuit which identifies the particular key. When a key is pressed and the controller scans the row the key is in, the key's transponder circuit indicates the identity of the key.

In another embodiment of the invention, the keys in each row of a keyboard assembly are arranged in two polarity groups by a diode coupled to each key. Each key in a polarity group has a different resistive load provided by a coupled resistor. Polarizing the keys allows the highest and lowest resistor values to define a reasonable range. Each key includes a key switch which is normally open and is closed when the key is pressed. When the switch is closed and the diode is biased with the current flow, the resistor will determine the resistive load of the pressed key. The keys in each row are coupled in parallel between two conductors.

In another embodiment of the invention, a keyboard assembly has rows of keys in which the keys in each row bridge two buses. Each key has a timer coupled to a switch and an electrical identifier, such as a resistor. The output of each timer goes high after a particular time period. When the switch is closed and the output of the corresponding timer is high, the electrical identifier provides an identifying load. A signal is sampled at different times to determine if the signal is changed by the identifying load. If so, a pressed key will be identified.

In yet another embodiment of the invention, a linear electrical matrix is coupled to a row of keys. The row is electrically separated into sections, each of which has its own section pathway for signals. Each key in each section is coupled to a key pathway, which is shared by corresponding keys in each section. Each row has its own set of section and key pathways, making the row appear electrically as if it were arranged in a matrix and allowing the rows to be electrically isolated from one another. In one embodiment, all sections are scanned concurrently to detect any responses from the keys. If a response signal is detected, the sections are scanned individually to identify the key that provided the response signal.

In still another embodiment of the invention, a two layer flexible circuit passes through each key assembly in a row of keys and provides the electrical pathways for a linear electrical matrix. The flexible circuit has an upper layer with a contact region disposed over the contact region of a lower layer. Conductive traces on each layer act as section and key pathways to allow signals to travel along the row of the keys. The flexible circuit is guided down between keys of a keyboard assembly, allowing the keyboard assembly to be collapsed more easily.

In one example of a method according to the invention, a row of keys is electrically separated into different sections. The different sections are then scanned sequentially to detect a key actuation signal that corresponds to a pressed key. A scan code corresponding to the key actuation signal is sent to a host computer.

Additional features and benefits of the invention will become apparent from the detailed description, figures, and claims set forth below.

DETAILED DESCRIPTION

The invention relates to detecting key actuation in a keyboard assembly. Specific details of an embodiment of the keyboard assembly are described below. Numerous specific details including keyboard layouts, specific structural arrangements and relationships, etc. are presented in order to provide a thorough understanding of the invention. It is to be appreciated that these specific details need not be specifically employed to practice the invention and that there are other details that are not presented so as not to unnecessarily obscure the description of the invention that may be substituted or included that fall within the scope of the claimed invention.

FIG. 1shows a planar top view of an embodiment of the keyboard assembly of the invention. For convention, the rows of keys are numbered I through VI, with Row I being closest to the user or the front of the keyboard assembly. Row I includes the “Ctrl” key and row VI includes the “Pause” key. The “front” side of a key is closest to a user situated closest to Row I, while the “back” side of the key is farthest from the user. A vertical distance is measured from the front of the keyboard assembly, closest to the user, to the back of the keyboard assembly, farthest from the user. A horizontal distance is measured from the left (or one side) of the keyboard assembly to the right (or other side) of the assembly.

FIG. 2shows a planar top view of keyboard assembly10ofFIG. 1in its collapsed state. For illustration purposes, inFIG. 2, the top portion of each of protective housing sides1and2is transparent so as to reveal the collapsed state of keys3.FIGS. 3–5illustrate a planar front view of an embodiment of keyboard assembly10and show the collapsible nature of keyboard assembly10.

FIGS. 1 and 3show a top and a front view, respectively, of an embodiment of keyboard assembly10in its expanded position. InFIG. 1, it can be seen that the layout of keys3of the keyboard assembly10is the same as the standard keyboard. In this embodiment, spacing between keys3is full pitch (about 19 mm) in both horizontal and vertical directions. It is to be appreciated that the invention is not limited to the keyboard layout presented and that other layouts may be substituted without departing from the scope of the invention. For example, the keyboard may be a numeric keypad or a set of keys providing preprogrammed functions. As can be seen fromFIG. 3, a row of interconnected scissors linkages4is coupled at each of both ends of the row to a housing. The row of linkages4supports a row of keys. Each key includes a key top11aand a key base11b. For each key, the key top11ais coupled to the corresponding key base11b. Typically, the coupling is by some mechanism which imparts a spring action to the key top relative to the key base such that the key top resists being pressed toward the key base when the key top is pressed during typing. Pressing the key top toward the key base usually causes an electrical connection to be changed; usually this occurs by a switch on the key base being closed when the key top is pressed far enough toward the key base, although other implementations may not require a switch.

As shown inFIG. 3, the row of scissors linkages4includes a plurality of scissors linkages which are connected in series. Three such scissors linkages4a,4b, and4care shown inFIG. 3and are connected from left to right respectively. Each scissors linkage includes two legs which are coupled together at a pivot point by a pin or rivet. Each scissors linkage is coupled to the next scissors linkage in the row by a pivot point on one leg and a pivot point on another leg. Further details regarding the scissors linkages of one embodiment of the invention are described below.

When not in use, keyboard assembly10may be kept in its collapsed position or state by a protective housing composed of sides1and2.FIGS. 2 and 5illustrate planar top and front views, respectively, of keyboard assembly10in its collapsed position with protective housing sides1and2covering collapsed keys3. To open the keyboard for operation, the user holds left and right sides1and2, respectively, and pulls linearly sides1and2apart.FIG. 4shows a front view of keyboard assembly10in a partially expanded or semi-collapsed position or state. The user continues to pull apart sides1and2until the keyboard assembly stops expanding (FIGS. 1 and 3).

The keyboard assembly stops expanding, in one embodiment, when the two end legs on each side of a row of scissors linkages are restricted from closing down upon each other. This can be seen fromFIG. 3which shows that a row of scissors linkages4is coupled on each side of the row to a pivot point within the respective housing. Specifically, the housing2on the right side of the keyboard assembly is coupled to the row of scissors linkage at pivot points24and23. This pivot point23includes an opening in a leg of the last scissors linkage on the right side of the row, and a pin or rivet which extends through the opening and which is attached to the inner wall of the housing2. Pivot point24includes an opening in the other leg of the last scissors linkage on the right side of the row and a pin or rivet which extends through the opening and which pin or rivet also rides in a channel25formed in the inner wall of the housing2. The channel25allows the pin at pivot point24to ride up and down the channel as the keyboard assembly is collapsed and extended respectively. Note fromFIG. 4how the pivot point24has moved to half-way along the channel25when the keyboard is semi-collapsed. The bottom end of the channel25defines the stopping point for the extension of the keyboard assembly. A similar arrangement exists at the last scissors linkage on the left side of this row of scissors linkages as shown inFIGS. 3,4and5. A keyboard on/off switch at the end of the channel25may be activated by a pivot point24when that pivot point reaches the end of the channel at the end of the keyboard's expansion. In this way, the end of the keyboard's expansion may be automatically sensed and power to the keyboard may be automatically supplied at this point. Each row of scissors linkages is typically coupled in a similar fashion to the inside of housings1and2.

In one embodiment, the full extension of sides1and2turns on the keyboard's power, via a limit switch, for example. In another embodiment, the full extension of sides1and2tilts the keyboard by raising the rear side. Once fully expanded, the assembly10can communicate directly with a computer or other host device via an electric or electronic link. Examples of contemplated linkages include, but are not limited to, an infrared or radio frequency link, or a cable.

When not in operation, keyboard assembly10may be placed in its collapsed position (FIGS. 2 and 5) by pushing protective housing sides1and2together until the sides cover keys3. A latch may determine the end point and the side portions may lock, for example, via a key lock switch, to provide a measure of security. To provide the most compact folded size while allowing one-step expanding and collapsing, in one embodiment, keys3are pivotally linked to each other by a row of scissors-like X-shaped linkages4.FIGS. 3–5show the collapsible and expandable nature of linkages4.

FIG. 6shows a magnified view of three keys3of keyboard assembly10coupled to a row of scissors or X-shaped units or linkages4. As shown inFIG. 6, each scissors linkage is composed of two legs pivotally joined at hub5, for example, by flanged pins or rivets30. Each scissors or X-shaped linkage is pivotally joined to a horizontally adjacent scissors linkage at lower and upper hubs6and7, respectively.

As shown inFIG. 6, three scissors linkages4a,4b, and4care interconnected in series along a row. Three keys are supported by this row. Each key3is supported by and coupled to two adjoining scissors linkages. Scissors linkage4ais comprised of legs4dand4ewhich are pivotally coupled at hub5(which is also referred to as a scissors pivot point) formed by overlapping openings in legs4dand4e. The scissors linkage4aalso includes an arm8which is rotationally coupled to hub6(which is also referred to as a coupling pivot point) at one end of arm8and is rotationally coupled to hub9on the key base11bof the left-most key ofFIG. 6. Hub6is formed by overlapping openings in arm8, leg4eand leg4f. Hub9is formed by overlapping openings in arm8and key base11b. Each of these hubs is secured by a pin in one embodiment. Leg4dof scissors linkage4ais rotationally coupled to leg4gat coupling pivot point7; coupling pivot point7is also rotationally coupled to the key base11bof this left-most key. Coupling pivot point7is formed by overlapping openings in leg4d, leg4gand key base11. Coupling pivot point7is secured by a pin in one embodiment of the invention. Leg4eof scissors linkage4ais rotationally coupled to leg4fat the coupling pivot point6. Legs4fand4gform the scissors linkage4band are also rotationally coupled together by a scissors pivot point5. Scissors linkage4bincludes an arm8which is rotationally coupled at coupling pivot point6to leg4gand to leg4hof scissors linkage4c. The arm8of scissors linkage4bis rotationally coupled to a key base11bof the middle key ofFIG. 6, and this key base is rotationally coupled to leg4fof scissors linkage4band to leg4iof scissors linkage4c. The leg4hand the leg4iform scissors linkage4cwhich is rotationally coupled to the key base11bof the right-most key ofFIG. 6. The legs4hand4iare pivotally coupled at the scissors pivot point5. The key base11bof this right-most key is coupled to an arm8which extends from a coupling pivot point with leg4iand is coupled to leg4hat a coupling pivot point on this key base11b.

FIGS. 7–9illustrate the pivoting of a row of linkages4with respect to the three keys3ofFIG. 6. Keys3rotate from a horizontal position (FIG. 6) when keyboard assembly10is fully expanded, to approximately a 45° angle when keyboard assembly10is partially collapsed (FIG. 7), to a nearly vertical position (FIGS. 8–9) when keyboard assembly10is fully collapsed.FIG. 9is a rear view of the collapsed portion of keyboard assembly10ofFIG. 8. Arms8pivotally connect linkage hubs6to hubs9of keys3. When expanded, arms8and the row of scissors linkages4provide a strong, rigid truss, and the angles assumed by arms8and the row of-scissors linkages4are such that keys are prevented from rotating even if they are pressed hard by the user.

As keyboard assembly10is collapsed (FIG. 7), hubs6and7, respectively, increase in distance from each other. This causes arm8to rotate key3via hub9from its horizontal position toward a vertical position (in this case in a counterclockwise direction). Effectively, arm8pulls down the key3in a counterclockwise direction. When keyboard assembly10is fully collapsed (FIGS. 8–9), the row of linkages4, arms8, and keys3are, respectively, substantially parallel and, in one embodiment, in contact with one another. WhileFIG. 9shows that there is some space between a key top of one key and a key base on the adjacent key, there may in certain embodiments be little or no space between a key top on one key and a key base on an adjacent key.

In the embodiment described, bottom hubs6, which pivotally join the X-linkages4and arms8at their base, are approximately horizontally equally spaced. When keyboard assembly10is fully collapsed, hubs6are in close horizontal proximity to one another. This can be seen fromFIG. 5.

In one embodiment, each row of keys3of keyboard assembly10is pivotally joined to its adjacent row to provide a strong and stable structure when keyboard assembly10is in an expanded position.FIG. 10shows a planar top view of a portion of keyboard assembly10.FIG. 10shows a portion of keys3from Row IV pivotally coupled to keys3of Row V. Three rows of scissors linkages4hold these seven keys. Flanged pins29extend through linkage hubs7on each row of scissors linkages and fasten to keys3to pivotally secure the top portion of keyboard assembly10. Each of these pins29also pivotally secure at a hub7one leg from one scissors linkage to a leg from an adjacent scissors linkage as shown inFIG. 6. Each row of scissors linkages4ofFIG. 10fastens, through these pins29, to one side of each key along a row of keys through the corresponding hub7. The other side of each key along this row is secured to an adjacent row of scissors linkages4through the mating of another set of pins29in the corresponding hubs7on this other side of each key. Flanged rods31(shown inFIG. 13) pass through bottom hubs6on each of the three rows of scissors linkages and spacing sleeves32to pivotally secure the bottom portion of keyboard assembly10. Each pivot point at the connection between an arm8and a key base11bat a hub9is secured by a flanged pin9awhich extends through the opening in the arm8and into an opening in the key base11b. As noted above, flanged pins or rivets30are used to secure each scissors pivot point5.

FIGS. 11 and 12show a planar front view of an embodiment of a key3of keyboard assembly10. InFIGS. 11 and 12, key3is composed of key base11bthat is coupled to key top11a by a conventional linkage having butterfly elements12and48. This linkage allows key3to be compressed to a very thin dimension (FIG. 12), yet have a large amount of travel (the distance between its open and closed position). When keyboard assembly10is fully collapsed, adjacent keys3exert pressure on each other causing them to be maintained in their closed position. It will be appreciated that there are numerous alternative types of linkages which may be used to link between each key top and key base.

Coupled to the base of key top11a of each key3is a spring49that has the shape of a bowl or truncated cone and is made, for example, of an elastomer or elastomer-like material. To type, a user presses on the key top and compresses the spring49as the key top is pushed toward the key base11b. When the compression of spring49exceeds a predetermined amount, spring49buckles to give tactile feedback to the user.FIG. 12shows one example of the buckling of spring49. The elastomeric nature of spring49also allows it to remain in a compressed position (when keyboard assembly10is collapsed) without fatigue.

FIGS. 11 and 12show an example of a key assembly with a flexible conductor assembly disposed on a key base. In this particular example, a flexible conductor assembly for each row of keys is weaved through key bases of the keys along the row;FIGS. 30A–30Cshow how this flexible conductor assembly allows the key assemblies to rotate between an expanded and a contracted state. A flexible conductor assembly will typically include a plurality of flexible conductors disposed on or in a flexible film. The flexible conductor assembly may include one or two or three or more layers of flexible conductors. The flexible conductor assembly bends as the keys of a row are collapsed and bends as the keys are expanded. Each row of keys has its own flexible conductor assembly which in one case is a set of 8 conductors in two layers of conductors running along each row. One layer of conductors may represent “column lines” and another layer of conductors may represent “row lines.”FIG. 46shows an example of “row lines”801–804, each of which defines a separate section of a mechanical row of keys and column lines805–808, each of which is a “column” conductor that is coupled to a particular key switch. The rows are electrically insulated from each other.FIGS. 11and12show an example of a three-layer flexible conductor assembly in which the row conductor801is disposed above (and separated from) a column conductor805when the key top11ais not pressed down against key base11b. This three-layer flexible conductor assembly includes two layers of conductive material and one layer of insulating material. When the key top11ais pressed down against key base11b, the standoff45adepresses the flexible film45band the row conductor801toward the column conductor805, which causes the column conductor805on the flexible film45cto electrically contact the row conductor801as shown inFIG. 12, thereby closing the switch at this key between these two conductors. It is assumed that in this case the electrical matrix ofFIG. 46is being used with the embodiment ofFIGS. 11 and 12. The flexible films45band45care separated from each other by an insulating layer45dwhich includes an opening allowing exposed conductive regions of row conductor801and column conductor805to make electrical contact. WhileFIGS. 11 and 12show2layers of conductors in the flexible conductor assembly, it will be appreciated that alternative embodiments may use any number of layers of conductors.FIGS. 11 and 12show that the key top11aand key base11bare formed from different structures which are joined together. It will be appreciated that, in an alternative embodiment, the key base and key top may be made from a collapsible unitary structure.

As can be seen inFIG. 1, the standard key layout of computer keyboards has columns of keys which are mostly staggered, rather than in straight columns. Additionally, some keys, for example, the “Backspace” and “Enter” keys (FIGS. 1C and 5) are considerably wider than, for example, a letter key.

In order to allow the keyboard assembly of the invention to be collapsed to a minimum length and thickness, the particular embodiment depicted in the figures utilizes various configurations of linkage shapes, arm lengths, and hub locations on the keys. Additionally, the assembly is configured so that keys rotate in different directions in different rows.FIG. 13illustrates a perspective top view of a portion of keyboard assembly10of the invention. Note that there are three different key top sizes.FIG. 13shows a portion of three rows of keys3(Rows III, IV, and V) and illustrates the support mechanism of such keys in part by ghost lines to indicate the construction of the mechanism beneath the keys. Keys3are shown in an expanded (opened) position. InFIG. 13, hubs6lie in vertical columns and are equally spaced in all rows. Keys3in Row III are pivotally supported by the configuration of a series of X-linkages4, arms8, and key hub locations shown in detail inFIGS. 14 and 15. As Row III collapses, keys3rotate in a clockwise direction. The keys in Row IV are pivotally supported by the configuration shown inFIGS. 6–9. As Row IV collapses, keys3in row IV rotate in a counter-clockwise direction. This allows, in one embodiment, a full-sized laptop keyboard (about 11 inches long excluding its frame) to fold to 3.25 inches in length, including its housing.

Row III contains the wide “Enter” key37which spans two bottom hubs6.FIGS. 14–16illustrate a planar front view of the rotation of the keys of Row III shown inFIG. 13. To allow the keyboard assembly to fold to a minimum length and thickness, linkage13b, located between Rows III and IV, pivotally supports the front side of the “I\” key in Row IV at hub14b, and has an angled extension15to pivotally support the back side of the “Pg Dn” key in Row III at hub16. Similarly, linkage17, located between Row IV and Row V, pivotally supports the back side of the “I\” key at hub18, and has an angled extension19, to pivotally support the front side of the “Home” key in Row V at hub20. Linkage13shown inFIG. 13includes a hub14awhich couples the linkage13to an adjacent leg on the scissors linkage to the right of the “Enter” key. The extension15of linkage13pivotally supports the front of the “Pg Dn” key at hub16. This is also shown inFIG. 15. The hub7ais not coupled to the “Pg Dn” key but is coupled to the adjacent scissors linkage to the right of the “Pg Dn” key.

FIGS. 14–16show the wide “Enter” key37with normal width keys on either side of the “Enter” key. No key in row3is attached at hub14awhich allows “Enter” key37to rotate unobstructed, but the “I\” key is attached to hub14b.FIG. 16illustrates that when keyboard assembly10is in its collapsed position, the vertical distance between hubs6and14is sufficient to accommodate “Enter” key37without the key extending below the bottom38of the series of linkages4.FIG. 16also illustrates that the wide keys and linkage extensions do not add to the horizontal length of the folded keyboard assembly. The other wide keys of keyboard assembly10and their associated linkages and hubs are designed similarly, such that the folded depth of the keyboard is kept to a minimum.

In addition to accommodating keys of different widths, the linkage design of the invention allows keys on one row to be horizontally displaced with respect to keys on an adjacent row (e.g. staggered key columns), thereby conforming to standard keyboard layouts, such as for example a “QWERTY” layout even though the rows are pivotally joined to each other. For example, keys3in Row IV are pivotally supported on the front side by hubs7of linkages4(FIGS. 6,10, and13). However, linkages33located between Row IV and Row V have angled extensions21. This is illustrated inFIG. 13and in a front view portion of Row V shown inFIG. 17in an expanded position andFIGS. 18–19in a collapsed position. As shown in FIGS.13and17–19, there are two hubs34and35on extensions21, which lie on a horizontal axis when the keyboard is expanded (FIGS. 13 and 17). InFIG. 13, linkage33pivotally supports the “{[” key of Row IV at hub34. The same linkage33pivotally supports the “+=” key3of Row V at adjacent hub35. In this manner, the keys in Row V are displaced horizontally with respect to the keys in Row IV. When fully collapsed, extensions21“nest” allowing the linkages to be compressed to their most compact position. This is illustrated in front and rear views byFIGS. 18 and 19, respectively.

As shown inFIG. 13, hubs34lie along the same vertical axis as hubs7which lie along the same vertical axis as rod31. The X-shaped linkages4and33, respectively, and their respective extensions have centers of intersections5which lie on a common vertical axis36for all rows, even though the keys of different rows are horizontally staggered and are of different widths. This arrangement allows all rows to expand and collapse together.

While the keys in adjacent rows are horizontally staggered, the left and right terminations of the linkages in all rows lie in approximately vertical lines. Linkages supporting the left-most keys of each row (FIGS. 1 and 3) are aligned horizontally at their bottom hubs6and their top hubs22. Similarly, linkages supporting the right-most column of keys (FIGS. 1,3, and13) are aligned horizontally at their bottom hubs6and their top hubs22. This allows a compact arrangement for a housing composed of protective housing sides1and2.

The left and right-most linkages of the embodiment of the keyboard assembly of the invention are pivotally joined to the housing side portions1and2, respectively, by bottom pivot pins23at bottom hubs6and slidably joined to the housing side portions1and2, respectively, by top pins24, which slide in slots25of housing side portions1and2, respectively (seeFIGS. 3,4, and5). Two sets of scissors or X-shaped linkages (without associated keys), located on the left- and right-most sides of keyboard assembly10, allow the unit to be expanded so that housing side portions1and2, respectively, are clear of keys3. In this manner, keyboard assembly10can be opened and closed in a one-step operation and does not need to be removed from its protective housing. In one embodiment of the invention, the surface of one of housing sides1and2may include a cursor control device such as a small trackball, a touch-sensitive trackpad, a joystick, a pressure-sensitive pointing device (e.g. IBM's TrackPoint III which is used on IBM's ThinkPad laptop computers), or other cursor control (e.g. pointing) devices. In addition, small buttons may be included on the surface of the housing; these small buttons may perform the same functions as the buttons (or button) on a mouse which is often used with a computer. In another embodiment, the cursor control device is selectively positionable on either one of housing sides1and2.

FIGS. 20–23illustrate an additional feature of one aspect of an embodiment of a keyboard assembly of the invention.FIGS. 20,22, and23show front view portions of three keys in a row of keyboard assembly10.FIG. 21shows a vertical side view portion of keyboard assembly10. Each ofFIGS. 20–23illustrate an embodiment of a tilting device that raises the rear of keyboard assembly10for a comfortable angle similar to that of desktop keyboards.FIG. 20shows tilt fingers26extended when keyboard assembly10is in its fully expanded position andFIG. 23shows tilt fingers26retracted when keyboard assembly10is closed. InFIG. 21, keyboard assembly10rests on a flat surface at the bottom tips of fingers26and the front edge of left housing1and right housing2. Thus, the rear of keyboard assembly10is elevated to provide a comfortable angle for typing as shown inFIGS. 20 and 21. Each finger26is pivotally attached to the linkages4at hub7by a pin at this hub at the back side of keyboard assembly10. Flanged pin27passes through hub6.FIG. 22shows the keyboard in a partially collapsed state. As keyboard assembly10is collapsed (FIG. 22), pin27slides in slot28, until collapse is completed (FIG. 23).

FIG. 24Ashows a portion of one embodiment of a collapsible keyboard in an expanded position. Each row of keys200a–200dhas keys that are formed by a key top coupled to a key base. Rows200aand200dhave keys formed by a key top201coupled to a key base202a. Rows200band200chave keys formed by key top201coupled to a key base202b. In one embodiment, the key tops are supported by the key bases through conventional butterfly linkages (not shown) which allow the key tops to be pressed down. An interconnected series of male struts203rotatably coupled to female struts204in an X pattern connects adjacent rows. For example, key base202ain row200ais rotatably coupled to key base202bin row200bby female strut204and a male strut in an adjacent X pattern. Actuators205to facilitate key rotation are shown rotatably coupled to male struts203, to a female strut in an adjacent X pattern, and to key bases202bin rows200band200c. Actuators205operate in a similar manner as arms8, as described with reference toFIGS. 7–9. In one embodiment, male struts203, female struts204, actuators205, and key bases202aand202bsnap together for easier assembly. Although the same key top201is shown for each key, it is appreciated that key tops of different sizes can be used. The male and female struts, actuator, and key bases are discussed in more detail below.

FIG. 24Bshows the keyboard portion ofFIG. 24Ain a collapsed position. The keys in rows200aand200chave rotated counter-clockwise, while the keys in rows200band200dhave rotated clockwise. Male struts203remain substantially parallel with one another, as do female struts204, but the space between adjacent male struts203and between adjacent female struts204is decreased to give the collapsed position a thin profile.

FIGS. 25A and 25Bshow two different views of a male strut or leg250. The male strut250may be used as the male strut ofFIGS. 24A and 24B. Main body254has protrusions252a,252band253a,253bextending orthogonally from both ends of main body254. Protrusions252aand253aare longer than protrusions252band253b, respectively. A protrusion251extends orthogonally from approximately the middle of one side of main body254. In one embodiment, protrusions251,252a,252b,253a,253bare ridged to provide the snap-together feature mentioned above. The flange or ridge at the end of these protrusions has a diameter which is slightly larger than the corresponding through hole in the female strut which is designed to engage the protrusion. Once a protrusion is snapped into its corresponding hole, the ridge retains the male and female struts. Extension stops255aand255bextend from grooves256aand256b, respectively, around protrusion251. Extension stops255aand255blimit keyboard expansion by stopping the rotation of a coupled female strut. In another embodiment, male strut250is symmetric about an axis perpendicular to the length of male strut250, where the axis passes through the center of male strut250.

FIGS. 26A and 26Bshow two different views of a female strut or leg260that, in one embodiment, is coupled to male strut250. The female strut260may be used as the female strut ofFIGS. 24A and 24B. Main body264has end through holes262and263for mating with the protrusions of male struts in neighboring male-female X linkages when an interconnected series of X linkages is formed. A middle through hole261accepts protrusion251when male strut250and female strut260are coupled together to form an X linkage. Male strut250and female strut260are thus complementary. Extension stops265aand265bextending from grooves266aand266b, respectively, around middle through hole261impinge upon extension stops255band255aof male strut250as keyboard expansion occurs. In one embodiment, female strut260is symmetric about an axis perpendicular to the length of female strut260, where the axis passes through the center of female strut260.

FIGS. 27A and 27Bshow two-different views of an actuator270. Actuator270has arms274aand274b. Arm274ahas grooves272aand272b. Arm274bhas grooves273aand273b. Grooves272aand273amate with protrusions on a key base, and grooves272band273bmate with one of protrusions252band253bon male struts250in adjacent rows, depending on the orientation of male struts250.

FIGS. 28A and 28Bshow top and bottom views, respectively, of a key base280. Flanges284aand284bextend out, above and below from opposite sides of base member281. Protrusion282aextends out from one end of flange284a, and groove283areaches partially through flange284a. Similarly, protrusion282bextends out from one end of flange284b, and groove283breaches partially through flange284b. Protrusions282aand282bmate with grooves273aand272a, respectively, of actuator270. In one embodiment, protrusions282aand282bare ridged to provide a snap-together assembly with actuator270. Grooves283aand283baccept one of protrusions252band253bof male strut250, depending on the orientation of male strut250. In one embodiment, key base280is coupled to key top201to form the keys in rows200band200c.FIGS. 11 and 12show one example of a way to couple a key top to a key base using a conventional butterfly linkage.

FIGS. 29A and 29Bshow top and bottom views, respectively, of a key base290. Key base290differs from key base280primarily in the position of the protrusion292aand protrusion292b; these different positions allow for different pivot points for the different keys and allow a collapsible keyboard to have different size keys and still collapse. Flanges294aand294bextend out, above and below from opposite sides of base member291. Protrusion292aextends out from approximately the middle of flange294a, and groove293areaches partially through flange294a. Similarly protrusion292bextends out from approximately the middle of flange294b, and groove293breaches partially through flange294b. Protrusions292aand292bmate with through holes in a female strut or in some cases a groove in an actuator. Grooves293aand293baccept one of protrusions252aand253aof male strut250, depending on the orientation of male strut250. It should be noted that either of protrusions252aand253aof male strut250is long enough to mate with both an end through hole262,263of female strut260and a groove293a,293b. In one embodiment, key base290is coupled to key top201to form the keys in rows200aand200d.

FIGS. 30A–30Cshow a side view of a portion of a row of keys in one embodiment of a collapsible keyboard as the keyboard is collapsed. A key clip302is disposed between a key top301and a key base304. Although it is not shown for purposes of clarity, in one embodiment, a butterfly linkage couples key top301to key clip302. Key clip302holds a flex circuit303(e.g. a flexible bus of conductors) flat against key base304by snapping onto key base304with flex circuit303in between. A hook305at one end of key clip302guides flex circuit303down between adjacent keys, thereby allowing the keyboard to collapse more easily to a compact, closed position. The clip302relieves stress in the portions of the flexible circuit303which bend by keeping one portion fixed (around the edge of the key base) and another portion loose (with a wide angle for bending).

FIGS. 31A and 31Bshow top and bottom views, respectively, of a key clip310. Tabs312a–312dsnap key clip310onto a key base (not shown) as key clip310is pressed against the key base. In one exemplary embodiment, a flex circuit is laid on top of the key base before the key clip is snapped into place onto the key base. Once key clip310is snapped onto the key base, a flex circuit (not shown) located between key clip310and the key base is held flat against the key base. Guide arms315aand315bare curved downward to force the flex circuit down between adjacent keys. In one embodiment, each guide arm315aand315bguides separate layers of a flex circuit. Opening313allows contact to be made with the flex circuit. Hooks316aand316bsecure a butterfly linkage (not shown) that is coupled to and supports a key top.

FIG. 32shows an example of a method of using a collapsible keyboard in accordance with the teachings of the present invention. In step401, a first housing and a second housing are secured by a user's hands. Both housings are coupled to a collapsible support that supports a number of keys. In step402, the housings are pulled apart linearly such that the keys are exposed and the keyboard is expanded. In step403, the expansion of the keyboard is sensed (e.g. by a limit switch).

FIG. 33shows another example of a method of using a collapsible keyboard in accordance with the teachings of the present invention. In step411, a first housing and a second housing are secured by a user's hands. Both housings are coupled to a collapsible support that supports a number of keys. In step412, the housings are pulled apart linearly such that the keys are exposed and the keyboard is expanded. In step413, the housings are pushed together such that substantially all of the keys are covered and the keyboard is collapsed. In step414, the housings are latched together when the keyboard is collapsed.

FIG. 34shows yet another example of a method of using a collapsible keyboard in accordance with the teachings of the present invention. In step421, a first housing and a second housing are secured, where both housings are coupled to a collapsible support that supports a number of keys. In step422, the housings are pulled apart linearly such that the keys are exposed and the keyboard is expanded. In step423, power is automatically provided to a keyboard circuit when the keyboard is expanded.

Keyboard assemblies such as keyboard assembly10, which is described above, normally require some associated electrical circuitry to detect the actuation (e.g. pressing) of the various keys and the generation of appropriate signals which indicate the identity of the actuated key. Typically, each key has an associated electrical switch which produces an electrical change of state (e.g. electrically open to electrically closed) when the associated key top is depressed.

In one embodiment of the keyboard assembly of the invention, each key base11bincludes electrical elements39,40,41, and42and resistor503and diode504as shown inFIG. 35.FIG. 35illustrates an electrical configuration of four keys of keyboard assembly10. Conductive paths (e.g. conductive strips) or electrodes39and42bend at right angles over the face of key shoulders43on each key base11band electrically contact row linkages4. On each key base11b, electrode39is coupled to one terminal of resistor503, and electrode40is coupled to the other terminal of resistor503. On each key base11b, electrode40is disposed physically near, but electrically isolated from, electrode41. Electrodes40and41are electrically coupled (e.g. “shorted”) when the key top is pressed toward the key base; typically, when the key top is pressed, an electrode coupled to the key top shorts electrodes40and41, thereby closing the switch between electrodes40and41. Electrode41on each key base11bis coupled to one terminal of diode504, and the other terminal of diode504is coupled to electrode42. Linkages4are made of a conductive material such as, for example, steel, aluminum, or plastic which is conductive or which includes an electrically conductive material. Each row of linkages4acts as a single wire electrical bus44. Each bus44is connected to a keyboard controller (not shown inFIG. 24) which could be located in one side of the keyboard assembly housing. A cursor control device (such as a trackpad) and battery could be located in this same side of the housing or the other housing side. In another embodiment, a data transfer port is electrically connected to each bus44through the keyboard controller or any other appropriate interface for communicating with a computer system. The data transfer port may be a universal serial bus (USB) port or a “Firewire” port such as a port which substantially complies with IEEE Standard 1394.

In yet another embodiment, key bases11band row spacing sleeves32(seeFIGS. 13 and 35) are made of a non-conductive material, such as, for example, plastic. Other materials (e.g. rod31) in the keyboard assembly10which may serve as an electrical path from one row of linkages4to another row of linkages4is also made from non-conductive materials so that these rows remain electrically isolated. Hence, each row is electrically isolated from its adjacent row, although they share a common framework of conductive linkages.

FIG. 36shows a schematic diagram of one example of a typical key encoder circuit500for a key. In the embodiment described herein, each key assembly, having a key top11aand a key base11b, contains a key encoder circuit consisting of a key switch502, a resistor503, a diode504, and two terminals501and505. In one embodiment, key switch502(formed by electrodes40,41and conductive face45) is normally open and is closed when key top11ais pressed downward toward key base11b. Diode504determines the polarity of the key circuit. Resistor503determines the resistive load of the particular key3when switch502is closed and diode504is biased with the current flow. Terminal501is coupled to one bus44and terminal502is coupled to another bus44.

FIG. 37illustrates a row of10keys. AlthoughFIG. 37shows 10 keys in the row, it is to be appreciated that the number of keys can be more or less than this amount. In this embodiment, each key assembly has one terminal connected to bus520(which may be a row of scissors linkages) and the other terminal connected to bus521(which may be an adjacent row of scissors linkages). Keys in the row are arranged in two polarity groups with half of the keys, e.g.,510,511,512,513, and514, in one polarity and the remaining keys,515,516,517,518, and519, in the opposite polarity. Each key in a polarity group has a different resistive load and the resistor values differ exponentially from key to key. The keys are polarized by the diodes to allow the row of keys to be divided into two sections to keep the ratio of the highest and lowest resistor values within a reasonable range, particularly when there are a large number of keys coupled between adjacent busses44.

FIG. 38shows a schematic block diagram of a partial row of keys of a keyboard assembly in accordance with the invention. Key assemblies580and590are coupled in parallel between conductive pathways or buses575and576. Key assembly580includes a switch581coupled to a transponder582, which receives power via wire583. Key assembly590includes a switch591coupled to a transponder592, which receives power via wire593. Each transponder582and592is identified by a unique address. In one embodiment, a keyboard controller sends addresses down the row of keys through bus575. For each key that is pressed, thereby closing the associated switch, the transponder coupled to that switch recognizes its address and responds through bus576. In one embodiment, transponders582and592are ASIC (Application Specific Integrated Circuit) transponders. In one example, each transponder may transmit a unique, identifiable signal which is decoded by a keyboard interface which is coupled to buses575and576.

FIG. 39shows a keyboard assembly consisting of an array of keys640, a keyboard interface600, and a microcontroller650. In this example, array of keys640is6rows of15keys. Each key in each row is connected in parallel on a two-wire bus with adjacent rows of keys sharing a common bus. For example, the top row of keys (keys640a,640b, . . .640o) are coupled in parallel on a two-wire bus formed by conductors601and602. Conductor601may be a row of scissors linkages4and conductor602may be an adjacent row of scissors linkages4. Thus, each of conductors601–607may represent one of the busses44shown inFIG. 35. This arrangement has an advantage over traditional two-dimensional key matrix arrays in that wire column buses are not required, thus decreasing the number of connections to keyboard interface600. This is particularly advantageous when the keyboard is collapsible because wires in a collapsing structure may interfere with the mechanics of collapsing, and the wires may also deteriorate over time due to repeated expanding and collapsing of the keyboard.

FIG. 40illustrates a keyboard interface600between array of keys640and microcontroller650. In this embodiment, analog multiplexers608and609are used to enable one selected row of keys, in one polarity, at one time. Row address inputs621,622, and623of multiplexer608determine which keyboard bus is connected to positive current sense signal610. Row address inputs624,625, and626of multiplexer609determine which keyboard bus is connected to ground. Resistor614and618create a voltage divider to generate a reference voltage signal619for analog-to-digital converter611and operational amplifier616. Operational amplifier616outputs a voltage that is relative to the amount of current drawn at positive sense signal610. Analog to digital converter611is used to digitize the amount of current drawn by the bus, by measuring the output voltage of operational amplifier616, and makes a resulting digital value available to microcontroller650via bus612. Signal613is provided by microcontroller650and is used to start a new analog-to-digital conversion when microcontroller650needs to measure the bus current.

In the embodiment ofFIG. 40, in operation, microcontroller650scans the keyboard assembly, one row at a time, by sequentially addressing each row of keys using row address signals621,622, and623and624,625, and626. The row addresses for multiplexers608and609differ by one, in order to connect keyboard buses in adjacent pairs (e.g.,601and602,602and603, etc.). Keyboard buses602,603,604,605, and606are each shared by two rows of keys, decreasing the number of connections to the keyboard assembly. Each row is addressed twice, once in each polarity.

FIG. 41shows an example of keyboard640with three rows of eight keys each. Keyboard array640is coupled to keyboard interface600which is coupled to microcontroller650which is coupled to host computer653or another host device (e.g. a cellular phone, information appliance, personal digital assistant, etc.). On power-up initialization, microcontroller650sets all row addresses621,622,623,624,625, and626to a low state. Microcontroller650begins scanning the first row of keys by setting row address signals621,622, and623to a binary value of one. This connects bus601to current source610and the input of analog-to-digital converter611. Next, row address signals624,625, and626are set to a binary value of two, connecting bus602to ground. At this point, if any keys531,532,533, or534are pressed, the individual key's diode will be forward biased, allowing current to flow through the key's resistor. At this same time, keys535,536,537, and538have no effect on the bus since their diodes are reverse biased. Since each of the keys,531,532,533, and534have a different resistor value, microcontroller650can determine which keys are pressed by analyzing the current flow as measured by the voltage drop across resistor614. Microcontroller650then analyzes keys535,536,537, and538by setting row address signals621,622, and623to a binary value of two and row address signals624,625, and626to a binary value of one. This reverses the polarity by connecting bus602to current source610and bus601to ground. In this state, keys531,532,533, and534have no effect and current flow through keys535,536,537, and538can be analyzed to determine which of the keys are pressed. This cycle completes scanning of the first row of keys and the remaining rows are scanned in a similar fashion. When microcontroller650finds a depressed key, it uses a table look-up method to locate the scan code for the key and sends the scan code to host computer653or other host device. This entire scanning process repeats indefinitely, causing the keyboard to be continuously scanned.

Each key in a polarity, group has a unique resistor value and, when pressed, adds a specific resistive load to the bus. Any given combination of pressed keys along a row generates a unique and identifiable resistive load, allowing the keys pressed to be identified by the microcontroller650. Therefore, the design allows accurate key identification even when multiple keys are pressed simultaneously along the same row.

FIG. 42Ashows a key encoder720of another embodiment of a key identification system. Key encoder720has a timer750with two terminals751,752. Timer750is coupled to a switch753and an electrical identifier754, which in one embodiment, is a resistor. Timer750is a circuit with an output that is low when powered up and then becomes high after a predetermined time period, thereby reaching an active state. Switch753is closed when a corresponding key (not shown) is pressed. When switch753is closed and the output of timer750is high, electrical identifier754adds an identifying load. In other words, even if switch753is closed, the identifying signal provided by electrical identifier754does not become electrically visible until the output of timer750is high.

FIG. 42Bshows a row of keys761–765, each of which has a key encoder similar to key encoder720but with different timers750a–750e. Each key761–765is coupled to buses701,702. Timers750a–750eare preset to unique time constants such that identifying loads are not added at the same time. Although five keys are shown in a row, the present invention is not limited to any particular number of keys in a row.

FIG. 43is a detailed illustration of a keyboard interface700used to couple an array of keys to a microcontroller and may be used with the key encoder shown inFIGS. 42A and 42B. Analog multiplexers708,709are used to enable one selected row of keys at a time. Row address inputs721–723of multiplexer708determine which keyboard bus701–707is connected to a current sense signal715. Row address inputs724–726of multiplexer709determine which keyboard bus is connected to ground. Resistors717,718create a voltage divider to generate a reference voltage signal719for an analog-to-digital (A/D) converter711and an operational amplifier (op-amp)716. Op-amp716outputs a voltage that is relative to the amount of current drawn at current sense signal715. AND converter711digitizes the amount of current drawn by the bus connected to current sense signal715by measuring and converting the output voltage of op-amp716. The resulting digital value is sent to the microcontroller by a bus712. The microcontroller provides an A/D sample clock signal713when the microcontroller needs to measure the bus current again.

FIG. 44shows one implementation of keyboard interface700with an array of keys740coupled through buses701–707to keyboard interface700which is coupled to a microcontroller770coupled to a host computer773. The keyboard system ofFIG. 44is shown using the key encoder720ofFIG. 42Afor each of the keys. Array of keys740has six rows741–746of fifteen keys. All keys in a row are connected in parallel on a two-wire bus, with adjacent rows sharing a common bus. For example, rows741and742share bus702. By not requiring column buses, the arrangement of buses701–707decreases the number of connections to keyboard interface700and prevents buses from crossing over one another. Microcontroller770scans array of keys740, one row at a time, by sequentially addressing rows741–746using row address signals721–726. In one embodiment, the row addresses for multiplexers708,709differ by one such that adjacent buses are paired together (buses701and702for row741, buses702and703for row742, etc.).

To scan row741, microcontroller770sets row address signals721–723to the binary equivalent of 1 and row address signals724–726to the binary equivalent of 2. This connects bus701to current sense signal715and bus702to ground. Microcontroller770then determines which key(s) is/are being pressed according to the relative timing of signals, an example of which is shown inFIG. 45using the signals for keys761–765.

Timer output signals761a–765afor keys761–765, respectively, go high sequentially at even time intervals. For example, timer output signal761agoes high at t2and timer output signal762agoes high at t4. The relative bus current710drawn by bus701is shown with only keys761,763and765pressed. A/D converter711samples relative bus current710when triggered by AND sample clock signal713at odd time intervals. Starting with the sample taken at t3, microcontroller770compares each sample with the previous sample to determine if a key has been pressed. In the example shown inFIG. 45, microcontroller770will determine that key761is pressed because a current increase occurred between the samples taken at t1and t3, and timer output signal761afor key761is the only signal that goes high at t2when its corresponding key is pressed. Microcontroller770will determine that key762is not pressed because a current increase did not occur between the samples taken at t3and t5, and timer output signal762afor key762goes high only at t4when key762is pressed. Microcontroller770checks each key in a row in a similar manner until all keys in a row have been checked. Although the timer output signals for five keys are shown inFIG. 45, the present invention is not limited to any particular number of keys.

In another embodiment of the invention, microcontroller770verifies a scan by scanning a row a second time and comparing the results with the first scan. If the rescan does not match the first scan, the row is rescanned until two consecutive scans match. Once two consecutive scans match, the determination of pressed keys proceeds as described above. If microcontroller770finds any pressed keys, it uses a table look-up method to find the scan code(s) for the key(s) and sends the scan code(s) to a host computer773via bus772. All of rows741–746are scanned similarly, row by row. The scanning process repeats indefinitely, causing the keyboard to be scanned continuously.

FIG. 46shows a linear matrix coupled to a row800of keys according to another embodiment of a key identification system in accordance with the invention. Row800is separated electrically into four sections801a–804aby the connections of the keys with section pathways801–804. Section801aconsists of keys801b–801e, which are coupled to section pathway801(which may be considered to be an electrical row in an electrical matrix). Section802aconsists of keys802b–802e, which are coupled to section pathway802(which may be considered to be another electrical row in the electrical matrix). Section803aconsists of keys803b–803e, which are coupled to section pathway803. Section804aconsists of keys804b–804e, which are coupled to section pathway804. Thus, each section has its own electrical pathway and effectively each section is an electrical matrix of key switches having at least one electrical row and several electrical columns. Each section may be regarded as an electrical section of an electrical matrix. Each key in each section is also coupled to a key pathway, which is shared by corresponding keys in each section. For example, keys801b,802b,803b,804bare coupled to key pathway805(which may be considered a column) and keys801c,802c,803c,804care coupled to key pathway806(which may be considered another column). Thus, row800of keys appears electrically as if it were arranged in a 4×4 matrix, but the matrix is confined to row800which is a mechanical row of keys (e.g. row VI ofFIG. 1), thereby allowing row800to be independent of and electrically isolated from other rows. WhileFIG. 46suggests that the keys are mechanically and physically adjacent to each other along a row, it will be appreciated that the electrical sections along a row may include, in any one electrical section, distantly spaced, non-contiguous keys along the row (or another row in the case where the row [section] lines extend to the another row). This is accomplished by wiring up the switches in each non-contiguous key to the desired row line. The linear matrix defined by section pathways801–804and key pathways805–808allows each key to be checked individually through the appropriate section and key pathways. In one embodiment, the section pathway for each section is provided by an electrode to which each key in the section is coupled, and the key pathways for each section are provided by a group of electrodes, each one of which is coupled to a key in the section. It should be noted that the sections can consist of any number of keys and are not limited to having equal numbers of keys. In an alternative embodiment, a row of keys could be separated into left and right electrical sections and each receives a wiring bus from its respective side.

In one exemplary embodiment of the invention, the section pathways and the key pathways are, at least in part, provided by flexible conductors which may be flexible wires on a flexible plastic substrate. These flexible conductors may be positioned on the key bases and under the key tops as shown inFIGS. 30A through 30C. The flexible conductors allow the keyboard to be expanded and collapsed as shown inFIGS. 30A through 30Cwithout requiring, on one row, as many conductors as is normally required for a conventional keyboard electrical matrix (e.g. for a mechanical row of 16 keys, a conventional keyboard electrical matrix requires 17 conductors [16 column wires and 1 row wire], while the keyboard electrical matrix requires only 8 conductors). Furthermore, flexible conductors electrically arranged in a matrix as inFIG. 46allow a row to be isolated electrically from other rows so that no “column” wires are required to interconnect between the rows. That is, all the wires for a row can run along the row and no wires (e.g. no column wires) need to run between rows in the collapsible portion of the keyboard assembly, thereby making mechanical expansion and contraction easier to implement. This isolation between rows requires a separate set of column conductors for each row but this extra set is balanced by the improved mechanical handling of the collapsible keyboard.

The flexible conductors may consist of one or more layers of flexible material. For example, a single-layer conductor may have circuits applied to one face of a flexible material. It may have a pattern of open contacts under each key. When a key is pressed, an electrically conductive puck attached to the key shorts the contacts, which completes a circuit.

In the preferred embodiment, a two-layer membrane is used. These membranes each have circuits of silk-screened silver applied to their opposing faces. The circuits are insulated by a coating such as lacquer except in the areas under each key, where they are separated by a raised deposit of material (for example, a pattern of non-conductive ink). When a key is pressed, the two layers meet and their contacts join to complete a circuit.

A three-layer membrane has an insulating layer of non-conductive material between two layers, which have circuits of silk-screened silver applied to their opposing faces. The insulating layer has a hole under each key, such that when a key is pressed, the two outer layers meet through the hole and their contacts join to complete a circuit.

FIG. 47is a block diagram of a keyboard array150with six rows103–108of keys, where rows103–108are configured similarly to row800of coupled to a keyboard interface100which is coupled to a microcontroller101which is coupled to a host computer102or other processing system. In one embodiment, keyboard interface100allows microcontroller101to access keyboard array150as if it were an 8×12 (key×section) matrix by logically connecting common section and key signals from rows103–108. For example, rows103–105have common key signals109a–109c, and rows103and106have common section signals111aand111b. In one embodiment, section signals111a–113aand111b–113bare each associated with four sections in a row, and key signals109a–109cand110a–110care each associated with the four keys in each of the four sections. For example, section signal111ais associated with section S1–S4, and key signal109ais associated with keys K1–K4. All key signals and section signals communicate with microcontroller101via keyboard interface100and interface signals120and130.

To begin scanning keyboard array150, microcontroller101enters a mode of operation in which it activates all sections (S1–S12) through interface signal130to keyboard interface100and detects any response through interface signal120from keyboard interface100to determine if any keys are pressed. Microcontroller101remains in this mode and repeats the process periodically until it detects a pressed key.

Once a pressed key is detected, microcontroller101enters another mode of operation in which it scans keyboard array150, one section at a time, by activating individually each section (S1–S12) through interface signal130to keyboard interface100and detecting any response through interface signal120from keyboard interface100. In an alternative embodiment, one section in each of several rows may be activated concurrently to separately determine whether, in the appropriate section of each row, a key was pressed. Thus, several sections, each in an electrically separate row, may be activated concurrently. For each section, a response signal will be supplied by one or more keys depending on which keys in that section are pressed. Typically the sections are scanned in some order, such as a sequential order. If microcontroller101detects any response signal(s), it enters yet another mode of operation in which it uses a table look-up method to find the scan code(s) for the pressed key(s) and sends the scan code(s) to host computer102. The entire scanning process repeats indefinitely, causing keyboard array150to be scanned continuously.

FIGS. 48A–48Cshow one embodiment of the key identification system shown inFIG. 46. Flexible lower layer910is disposed over a key base900such that contact region915of lower layer910rests on key base900. Flexible upper layer920is disposed over lower layer910such that contact region925of upper layer920is located directly above contact region915of lower layer910. In one embodiment, conductive traces911–914are section pathways and conductive traces921–924are key pathways, where the section and key pathways are similar to those described with reference toFIG. 46. Contact regions915and925are designed to selectively bring two conductors (one from traces921–924and one from traces911–914) into electrical contact when the key top is pressed. In one embodiment, both ends of both lower layer910and upper layer920(at the end of each row) are connectable to a cursor control device and to keyboard interface circuitry thereby allowing the cursor control device to be positioned on either side of the keyboard; this is shown inFIG. 48Eand is described further below. It should be noted thatFIGS. 48A and 48Bshow lower layer910and upper layer920individually, respectively, to depict more clearly the features of lower layer910and upper layer920.

In another embodiment of the invention, a keyboard assembly has multiple rows of keys where each row is coupled to a different conductive bus. Each row is also coupled to a different group of column electrodes, and each key in the row is coupled to one row electrode. In other words, each row has its own row conductor, and each key in each row has its own column conductor.FIG. 48Dshows an example of such a system where a mechanical row944of keys has a row conductor940and several column conductors941, and another mechanical row945of keys has an electrically separate row conductor942and several column conductors943(which may be electrically separate from column conductor941).

FIG. 49shows an example of a method for detecting key actuation in accordance with the teachings of the present invention. In step950, a row of keys is electrically separated into different sections (an example of this is shown inFIG. 46). In step951, the different sections are scanned sequentially to detect a key actuation signal that corresponds to a pressed key. In step952, a scan code corresponding to the key actuation signal is sent to a host computer.

FIG. 50shows another example of a method for detecting key actuation in accordance with the teachings of the present invention. This method is similar to the manner in which the keyboard array150ofFIG. 47is scanned. In step960, a row of keys is electrically separated into different sections (for example, as inFIG. 46). In step961, the sections are scanned concurrently to detect a key actuation signal. In step962, if a key actuation signal is detected, then step963is performed. If a key actuation signal is not detected, then the step961is repeated. In step963, the sections are scanned sequentially to further detect the key actuation signal. In step964, a scan code corresponding to the key actuation signal is sent to a host computer.

FIG. 51shows yet another example of a method for detecting key actuation in accordance with the teachings of the present invention. In step970, a row of keys is electrically isolated (for example, as inFIG. 46). In step971, timers that are coupled to each key in the row are activated. In step972, a first signal from the row of keys is sampled at a first time. Then in step973, a second signal from the row of keys is sampled at a later time. In step974, the sample of the second signal is compared with the sample of the first signal to identify any pressed keys. In step975, scan code(s) corresponding to the pressed key(s) are located. In step976, the scan code(s) is/are sent to a host computer. In another example, each key produces an identifying signal when its timer is in an active state and the key is pressed. In another example, the timers reach an active state at different times.

FIG. 52shows still another example of a method for detecting key actuation in accordance with the teachings of the present invention. In step980, a row of keys is electrically isolated. In step981, timers coupled to each key in the row are activated. In step982, a first signal from the row of keys is sampled at a first time. In step983, a second signal from the row of keys is sampled at a later time. In step984, the second signal is resampled. In step985, if the resample of the second signal substantially matches the first sample of the second signal, then step986is performed. If the resample and the first sample do not substantially match, then step984is performed again. In step986, the resample of the second signal is compared with the sample of the first signal to identify any pressed keys.

In one embodiment of the invention, the surface of one of housing sides1and2may include a cursor control device such as a small trackball, a touch-sensitive trackpad, a joystick, a pressure-sensitive pointing device (e.g. IBM's TrackPoint III which is used on IBM's ThinkPad laptop computers), or other cursor control (e.g. pointing) devices. In addition, small buttons may be included on the surface of the housing; these small buttons may perform the same functions as the buttons (or button) on a mouse which is often used with a computer. In another embodiment, the cursor control device is selectively positionable on either one of housing sides1and2.

FIG. 48Bshows one example of an embodiment of the invention in which a cursor control device, such as a track pad, is selectively positionable on either side of a keyboard, such as a collapsible keyboard assembly according to the present invention. In this way, a user of such a keyboard may position the cursor control device on either the left side or the right side of the collapsible keyboard depending on the user's preference. In another embodiment, a cursor control device can be placed between the keys. For example, a pointing stick, such as IBM's TrackPoint (found on IBM's ThinkPad laptop computers) can be placed between the G, H, & B keys. The flexible conductors associated with adjacent rows of keys can conduct the electrical signals from the pointing stick to the keyboard controller. In addition, small button switches may be included on the surface of the first row of scissors linkages; these small switches may perform the same functions as the switches (or switch) on a mouse which is often used with a computer.

In the example shown inFIG. 48E, a keyboard is assumed to communicate with a host computer or other host processing systems such as a personal digital assistant. However, the keyboard may include a complete computer system as shown inFIG. 53and also provide the capability of selectively positioning the cursor control device on either side of the keyboard. The keyboard1001shown inFIG. 48Eincludes a key assembly1004having end plates1005and1006. Two rows of keys are shown, but it will be understood that fewer or more rows of keys may exist. Each row of keys includes section lines and key lines, such as section lines1007or1009and key lines1008or1010. The keyboard1001may be implemented as a collapsible keyboard by using scissors linkages or by allowing the keyboard to fold (e.g. fold in halves or thirds at hinged joints which separate foldable sections of the keyboard). It will be understood that section lines1007are similar to section lines801–804ofFIG. 46and that key lines are similar to the key lines805–808ofFIG. 46. Each of these groups of lines includes a connector which may be mounted to the end plates and which allows the lines to couple to module1003which includes the cursor control device1115. These connectors, shown as connectors1111a,1111b,1111c, and1111dare located on either side of the assembly of the keys1004, thereby allowing the module1003to be coupled to either side of the assembly of keys. As shown inFIG. 48E, the module1003is coupled to the left side of the assembly while the module1002is coupled to the right side. This may be reversed by disconnecting module1002from the right side and disconnecting the module1003from the connectors on the left side and coupling it through module1003's connectors1111e,1111f,1111g, and1111hto the corresponding connectors1111a,1111b,1111c, and1111don the right side of the key assembly. The module1003includes a cursor control device1115which is coupled to a keyboard interface and I/O interface1116which also provides a cursor control device controller. This component1116provides conventional cursor control interface as well as I/O (input/output) interface functionality and keyboard interface functionality. For example, component1116may provide the functionality of the keyboard interface100and the microcontroller101shown inFIG. 47in addition to providing the functionality of controlling the cursor control device. In addition, component1116provides the I/O interface to a host computer through the connection1117. In an alternative embodiment, the connection may be a port located in the middle of the rear of the collapsible keyboard; this port is mechanically like another key except that space around the port may exist because there are no adjoining keys next to the port and thus, a keyboard may still collapse without impinging on the port. Component1116is coupled to the connection ports on the left side of module1003by bus1114b, and it is coupled to the connection ports on the right side of the module1003by the bus1114a. It will be appreciated that module1002may be empty or may contain electronic components which are appropriate for the device. For example, the module1002may include a small liquid crystal display or a storage device or both, and these components and module1002may be coupled through a flexible conductor bus to module1003. In one embodiment of the invention, a complete personal digital assistant may be assembled into the collapsible keyboard by using the space within the modules1003and1002. An example of such a system will now be described in conjunction withFIG. 53.

FIG. 53shows an example of a collapsible keyboard system1050with a collapsible keyboard assembly1051and a processor module1052. The processor module may be housed in the housing1or the housing2shown inFIG. 1or may be housed in both housings with flexible conductors providing signals between the two housings as necessary. Module1052includes a keyboard controller1053, memory1054, a system bus1055, a microprocessor1056, and an input/output controller1057. The module also includes two input/output ports1058and1059. The keyboard controller1053, the memory1054, the microprocessor1056, and the I/O controller1057are interconnected by the system bus1055. The keyboard controller1053may be a controller which provides the functionality of the keyboard interface100and the microcontroller101ofFIG. 47or it may be other types of keyboard interfaces and/or microcontrollers which can provide scan codes to the system bus1055for use by the microprocessor1056and/or storage into memory1054. The memory1054may be DRAM or flash memory or other types of storage devices. Furthermore it may include mass storage such as a magnetic hard disk or other types of mass storage to the extent it is possible to include such memory in a small space. The microprocessor1056may be any conventional microprocessor or microcontroller although it is preferable that it is a general purpose microprocessor which is controlled under control of computer program instructions which are stored in memory1054. Alternatively, the microprocessor1056may be a microcontroller which, on a single semiconductor substrate, includes the memory which stores the computer program which is executed by the microcontroller. The I/O controller1057may be a conventional input/output controller which can perform direct memory access to the memory1054and which also can communicate data to and from the microprocessor1056. The I/O controller1057provides input and output control for the two ports1058and1059. In one example of the present invention, the input/output port1058may be a universal serial bus (USB) port or an infrared port or a serial port (such as an RS-232 port) or a conventional parallel port. The other input/output port may be a Firewire port, which may be considered to be a port which substantially complies with the IEEE standard known as 1394. This Firewire port may provide output to a display device such as a miniature head-mounted display which can project to a viewer's eye an image of a display. Alternatively, this port1059may be coupled to a standard computer monitor rather than a miniature head-mounted display. It will be appreciated that in one embodiment, no display is included into the collapsible keyboard system1050, but rather, data for the display is separately provided through the port1059as described herein. Another example of a port may be a port which complies with the PCMCIA standard, such as the conventional PC Card or PC Card bus ports found on modern laptop computers.

In one example of the present invention, the input/output port may be a universal serial bus (USB) port or a serial port (such as an RS-232 port) or a “PS/2” port or an infrared port or a radio frequency port or a parallel port or a Firewire port, which may be considered to be a port which substantially complies with the IEEE standard known as 1394 or several ports providing a combination of these ports.

In another example of the present invention, a “docking station” may be provided to accommodate various devices such as Palm Computing's “PalmPilot.” In this example, the docking station consists of a mechanical/electrical connector which allows the PalmPilot to mount to the rear of the keyboard and communicate with the keyboard through the PalmPilot's serial interface. In this manner, the user can comfortably enter data with the keyboard while viewing the PalmPilot's display. The keyboard may also include an additional port for a wired or wireless modem. With this configuration, the keyboard and PalmPilot could be used for sending and receiving e-mail or various Internet applications. Wireless phones and other information appliances may be docked in a similar manner. Additional flexible conductors associated with the last rows of keys can conduct the electrical signals from the docked device to the keyboard controller.

An alternative embodiment of a keyboard assembly of the present invention uses alphanumeric keys which use only two different key assemblies for a collapsible keyboard. In one embodiment of the present invention, the scissors linkage structure has pivot points which are designed to reach a pitch of approximately 19 millimeters from each other when the structure is fully expanded. The key switch assemblies attach to these pivot points, and common pivot points are shared between adjacent rows on the collapsible keyboard. However, standard keyboard layouts typically require that the keys in one row be offset from keys in the next row by a fixed dimension. In one example the offset between these rows is approximately one-quarter of a key width.

It is possible to satisfy this offset between the rows while using only two key assemblies which are designated as key assembly A and key assembly B. The relative center key position difference between key A and key B is one-quarter of a key width. Therefore, if key A assemblies were placed in one row and key B assemblies were placed in an adjacent row, the two rows would be offset each other by one-quarter of a key width. Since in one design the collapsing keyboard requires some rows to fold left and others to fold right, this is taken into account when positioning the key center of key A and key B relative to the pivot point of the scissors linkage structure. The result of this is that the key A center is ⅜ of a key width from the pivot point and key B is ⅛ of a key width from a pivot point. The combination of ¼ key offset and ⅛ to ⅜ pivot offsets creates additional combinations of offsets. Further, increments of ¼ key offsets can be combined to give ½ key offsets in various folding directions.

The foregoing description provides examples of different embodiments of the invention. Other implementations will be appreciated by those skilled in the art. For example, rather than using scissors linkages, a support element for the keys may be a telescoping set of elements which slide along each other to expand and collapse. Each key may be pivotally coupled to two such elements and rotate upon expanding or collapsing. The keys in one embodiment may use thin membrane switches without butterfly linkages or springs, and thus the key top and key base may be used to cause two conductive to come into electrical contact. Further, these membrane switches may fold rather than pivot. A membrane switch may be coupled to a telescoping or scissors linkage support member at two points and may fold as a cloth seat of a director's chair folds when this chair is collapsed. A flexible conductor assembly may be disposed on a surface of the membrane switch and may fold with the membrane switch. In certain embodiments, a keyboard assembly of the invention may include certain ergonomic features, such as a split keyboard or a palmrest which may be attached and detached from the keyboard assembly.

In other embodiments of the invention, the relative functions of the rows and columns may be reversed. For example, the columns, rather than the rows, may fold/collapse to achieve a keyboard which can decrease in depth but not width. This may be implemented by providing columns of scissors linkages rather than rows of scissors linkages. In a related way, the columns of keys may be electrically isolated in a similar fashion as the rows are electrically isolated (as in, for example,FIGS. 46 and 48D), and each column may include several electrical sections of an electrical matrix which is separate and distinct from another electrical matrix formed in another column. Other modifications and implementations will be appreciated from this disclosure.