Patent Publication Number: US-2011067990-A1

Title: Webbed keyboard assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims priority to commonly owned and co-pending U.S. patent application Ser. No. 11/129,252, filed May 13, 2005, and entitled “WEBBED KEYBOARD ASSEMBLY,” which is incorporated by reference herein in its entirety and for all purposes. 
    
    
     BACKGROUND 
     Keyboards, along with computer pointing devices such as computer mice or trackballs, have long been employed as human-to-computer interface devices. A typical keyboard typically includes a plurality of sub-systems designed to convert keystrokes into electronic signals. In a typical laptop computer, for example, a typical keyboard module may include a plurality of key caps, a biasing arrangement for supporting the key caps in their rest position and during keystroke travel, some form of electrical contact circuitry, and other structures for stiffening the keyboard module as well as for fastening the keyboard module to the laptop computer framework. 
     To facilitate discussion,  FIG. 1  shows a portion of an example keyboard arrangement  100  including a keyboard module  102  attached to a keyboard base plate  104  of the laptop computer. The keyboard base plate  104  represents the mechanical structure of the laptop to which keyboard module  102  is attached. Keyboard module  102  includes a plurality of key caps, of which key cap  110  is representative. Key cap  110  is held in its elevated, rest position (relative to keyboard base plate  104 ) by a biasing arrangement that includes scissor linkages  112   a  and  112   b . As can be seen in  FIG. 1 , one end of each scissor linkage couples with key cap  110 , with the other end coupled with a keyboard mechanism plate  114 . As such, linkages  112   a  and  112   b  also perform the function of keeping key cap  110  from being detached from the rest of keyboard module  102 . 
     When key cap  110  is depressed, respective slots in the key cap and the keyboard mechanism plate allow scissor linkages  112   a  and  112   b  to simulate folding and unfolding actions, thereby enabling key cap  110  to move upward and downward in the Z direction without excessive wobbling. As key cap  110  travels downward, key cap  110  collapses a rubber or resilient dome (conventional and not shown). The collapsing action of the dome creates a characteristic tactile feel and/or force profile. 
     The downward movement of key cap  110  also causes key cap  110  to make contact with an electrical membrane (not shown), thereby completing the electrical connection that generates and sends a unique electrical signal representing the fact that key cap  110  has been depressed. As key cap  110  is released, the action of the aforementioned dome as well as of the scissor linkages pushes key cap  110  upward to its at-rest position. The details of prior art keyboard module  102  are conventional and will not be discussed in details herein for brevity&#39;s sake. 
     Keyboard module  102  is coupled to keyboard base plate  104  by a plurality of fasteners  120 . Keyboard base plate  104  stiffens keyboard module  102  by lending its rigidity to keyboard module  102 . This stiffening function is particularly important for a backlit keyboard module, which typically has a large percentage of the mechanism plate  114  removed to allow light to reach the key caps. 
     A certain keystroke travel distance by key cap  110  is required. With the right amount of keystroke travel, the keyboard user is provided with the appropriate tactile experience when the keys are depressed. For example, some keyboard designs call for a key cap travel distance of about 2.5 millimeters (mm) To accommodate this key cap travel distance, the total thickness in the Z direction of keyboard assembly, including keyboard module  102  and keyboard base plate  104 , is typically about 6 mm Factoring in the heads of fasteners  120 , it is not unusual to require a vertical dimension of roughly 6.6 mm in the laptop to accommodate a keyboard assembly. 
     As devices such as laptop computers become smaller, thinner and more sophisticated, there is less room to incorporate a keyboard assembly into the electronic device. Accordingly, there exists a need for an improved keyboard assembly that is thinner, smaller, and/or incorporates innovative features not found in current keyboards. The present patent application is directed toward such an improved keyboard assembly. 
     SUMMARY 
     The invention relates, in an embodiment, to a keyboard assembly configured for converting keystroke activation into electrical signals. The keyboard assembly includes a plurality of key caps, each of the plurality of key caps being configured to transition between a rest position and a depressed position. The keyboard assembly also includes a web-like structure having a plurality of interconnected ribs defining a plurality of apertures. The plurality of key caps are disposed such that the plurality of key caps move within the plurality of apertures and traverse a plane formed by an upper surface of the web-like structure when the plurality of key caps transition between the rest position and the depressed position. 
     In another embodiment, the invention relates to a keyboard assembly that includes a plurality of key caps. The plurality of key caps being configured to transition between a rest position and a depressed position. The keyboard assembly includes a mechanism plate disposed below the plurality of key caps. The plurality of key caps are coupled with the mechanism plate via movable means. The keyboard assembly further includes structural support means disposed in interstitial spaces among the plurality of key caps. The structural support means is coupled to the mechanism plate. 
     In yet another embodiment, the invention relates to a keyboard assembly coupled to an electronic device, the keyboard assembly being configured for converting keystroke activation into electrical signals. The keyboard assembly includes a plurality of key caps having at least a first key cap. The keyboard assembly also includes a mechanism plate disposed below the plurality of key caps. The keyboard assembly further includes a web-like structure having a plurality of interconnected ribs defining a plurality of apertures. The web-like structure is coupled to the mechanism plate. The plurality of key caps are disposed within the plurality of apertures. 
     These and other features and advantages of the invention will be discussed in more detail in the following detailed description of the invention and in conjunction with the following figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is illustrated by way of example, and not by way of limitation, in the figures accompanying the drawings, and in which like reference numerals refer to similar elements, and in which: 
         FIG. 1  is a prior art figure showing a portion of an example keyboard arrangement, including a keyboard module attached to a keyboard base plate of the laptop computer. 
         FIG. 2A  shows, in accordance with an embodiment of the invention, a cutaway side view of the improved keyboard assembly. 
         FIG. 2B  shows, in accordance with an embodiment of the invention, a cutaway top view of the improved keyboard assembly. 
         FIGS. 3A-3F  show, in various embodiments of the invention, the relative positions of the key cap and the ribs. 
         FIG. 4  is a prior art figure showing the relative positions of adjacent key caps. 
         FIG. 5  illustrates, in accordance with an embodiment of the invention, the relative positions of adjacent key caps and ribs. 
         FIG. 6  illustrates, in accordance with an embodiment, the taper flange feature of the key caps and the ribs. 
         FIGS. 7A and 7B  show embodiments wherein only partial flanges are provided. 
         FIG. 8  illustrates, in accordance with an embodiment, the “top hat” feature of the key caps and the ribs. 
     
    
    
     DETAILED DESCRIPTION 
     The invention will now be described in detail with reference to a few preferred embodiments, as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art, that the invention may be practiced without some or all of these specific details. In other instances, well-known process steps and/or features have not been described in detail in order to not unnecessarily obscure the invention. The features and advantages of the invention may be better understood with reference to the drawings and discussions that follow. 
     In an embodiment, the Z-stack dimension (i.e., the total thickness of the keyboard assembly) is advantageously reduced by employing a web-like structure whose interconnected ribs fit in the interstitial spaces between adjacent key caps in order to stiffen the keyboard assembly. Instead of relying on the thickness of the keyboard base plate (e.g., keyboard base plate  104  of  FIG. 1 ) or ultra-stiff (and typically expensive) keyboard base plate material to provide the stiffness reinforcement function, embodiments of the invention provide the additional stiffening structure in the form of interconnected ribs of a web-like structure. The interconnected ribs are disposed in between adjacent key caps in such as way that they do not materially contribute to an increase in the Z-stack thickness and in fact contribute to a reduction in the Z-stack thickness. 
     In another embodiment, the key caps and the web-like structure are formed with innovative shapes to improve the keyboard&#39;s resistance to damage from liquid spillage. In another embodiment, the relative positioning of the key caps and/or the web-like structure serve to improve the keyboard&#39;s resistance to tampering. 
     The features and advantages of the present invention may be better understood with reference to the figures and discussions that follow.  FIG. 2A  shows, in accordance with an embodiment of the invention, a cut-away side view of a keyboard assembly  202 . Keyboard assembly  202  typically includes a plurality of keycaps (such as the alphanumeric key caps typically found in a QWERTY keyboard or the numeric key caps found in a numeric keypad, for example). A representative key cap  204  is shown. Keyboard assembly  202  is typically employed in an electronic device, such as a computer. Because of the advantageous reduction in the thickness of the keyboard assemblies of embodiments of the present invention, keyboard assembly  202  and other keyboard embodiments discussed herein are also well suited for use in modem portable electronic devices, such as laptop computers, palmtop computers, or cell phones. 
     A mechanism plate  206  is disposed under the key caps. Mechanism plate  206  includes stamped or molded slot housings  208   a  and  208   b  for coupling with scissor linkages  210   a  and  210   b . Scissor linkages  210   a  and  210   b  also couple with slots disposed on the underside of key cap  204  to support key cap  204  in its rest position as well as to facilitate movement in the +/− Z direction as key cap  204  is depressed and subsequently released by a human operator. There may exist other conventional structures such as the aforementioned rubber dome and electrical contacts. These conventional structures and variations thereof have been omitted from  FIG. 2A  to improve clarity. 
     A plurality of ribs  214 R is shown in  FIG. 2A . These ribs are interconnected to form a web-like structure  214 A and are disposed in the interstitial spaces between adjacent key caps of the keyboard. One should understand from the reference number scheme that ribs  214 R are rib-like parts of the web-like structure  214 A; they are one and the same structure in an embodiment. As the term is employed herein, the web-like structure denote the structure that is formed by interconnected ribs.  FIG. 2B  shows, in accordance with an embodiment of the invention, a cut-away top view of a keyboard assembly  202 . The interconnected ribs  214 R define apertures  252  within which the key caps  254  may be disposed. The ribs are disposed such that they do not interfere with the up-and-down movement of the key caps within the apertures of the web-like structure. 
     In another embodiment shown in  FIG. 2A , key cap assembly  260  can include key cap assembly support pad  206   a  that can independently provide support for key cap  204  and linkages  210   a  and  210   b . As illustrated in  FIG. 2B , key cap support pad  206   a  can be completely supported on all sides by ribs  214 R as part of web-like structure  214 A. In this way, web-like structure  214 A can be used to secure key cap assembly support pad  206   a  to other key cap assembly support pads without using mechanism plate  206 . For example, an embodiment of keyboard assembly  202  can be formed by attaching a plurality of key cap assemblies to web-like structure  214 A by connecting the key cap assembly support pads associated with each of the plurality of key cap assemblies to ribs  214 R. In this way, web-like structure  214 A in combination with the key cap assembly support pads can provide support for keyboard assembly  202  without using mechanism plate  206 . 
     In an embodiment, the web-like structure is formed of a plastic material and is coupled to mechanism plate  206  via a plurality of fasteners. In an embodiment, the web-like structure has integrally formed deformable posts  220 A and  220 B, which are configured to be inserted into holes formed in mechanism plate  206 . After insertion, the ends of deformable posts are deformed (as may be seen with the left deformable post  220 A of  FIG. 2A ) to secure the web-like structure to mechanism plate  206 . For example, plastic deformable posts may be deformed using heat or ultrasonic energy or a similarly suitable method. In an embodiment, the ribs and the deformable posts are formed together as a single molded plastic part or stamped part. Alternatively or additionally, the web-like structure may be coupled to the mechanism plate using for example, swaging, riveting, or an appropriate adhesive. In an embodiment, the fasteners that fasten the web-like structure to the mechanism plate (e.g., the deformable posts) are distributed throughout the keyboard assembly (i.e., in addition to or instead of being distributed along the edge of the key cap area). By distributing the fasteners throughout the key cap area, a more rigid keyboard assembly is achieved. 
     Each individual key cap  204  may be dimensioned in the X-Y plane (i.e., the plane that is parallel to the top of the key caps) as appropriate. In an embodiment, key cap  204  may have a slightly reduced X-Y dimension to accommodate the addition of ribs  214 R of the web-like structure. Key cap  204  and ribs  214 R may be shaped in order to improve resistance to tampering and/or to contamination due to liquid spillage or the inadvertent introduction of dirt. This aspect will be discussed later herein. 
     By dispersing the web-like structure  214 A in the interstitial spaces between adjacent key caps and by coupling the web-like structure  214 A to mechanism plate  206  using a plurality of fasteners distributed throughout the key cap area, embodiments of the invention effectively increase the stiffness of the combined mechanism plate/web-like structure such that, in some cases, the stiffening function provided by the prior art keyboard base plate (such as keyboard base plate  104  of  FIG. 1 ) is no longer necessary. In other cases, the keyboard base plate may be made thinner or may be formed from a less expensive material. Furthermore, web-like structure  214 A is disposed in a vertical location in the Z-stack in such a manner that the presence of web-like structure  214 A does not materially contribute to the increase in thickness of the Z-stack. This is because the web-like structure is disposed in the vertical space that is already allotted in the Z-stack to accommodate the up-and-down movement of key cap  204 . By locating the ribs of the web-like structure in this vertical location (denote by reference number  232  in  FIG. 2A ), satisfactory keyboard assembly stiffness can be achieved with a reduced Z-stack thickness and/or without increasing the Z-stack thickness. 
     Further reduction in the Z-stack thickness can be realized by forming or stamping counter-sunk features  222  in mechanism plate  206 . These counter-sunk features  222  contain the holes employed for fastening mechanism plate  206  to web-like structure  214 A. The counter-sunk features allow the fasteners&#39; heads (which may be the deformed portions of the aforementioned deformable posts) to be counter-sunk with respect to the lower surface of mechanism plate  206 , thereby effectively reducing the protruding distance that the fasteners&#39; heads would have protruded below the lower surface of mechanism plate  206 . Such counter-sinking may be seen in  FIG. 2A  wherein the deformed head of deformable post  220 A on the left side of the figure is counter-sunk with respect to the lower surface of mechanism plate  206 . In this manner, no vertical space needs to be allotted for the height of the fasteners&#39; heads, further reducing the Z-thickness of the resultant keyboard assembly. 
     In an embodiment, the web-like structure has interconnected ribs that define a plurality of apertures, with the key caps being disposed within the plurality of apertures such that when key caps transition between the rest position and the depressed position, a horizontal plane (seen in the perspective of  FIG. 2A ) that slices through the body of a key cap traverses a horizontal plane formed by the upper surface of the web-like structure. This is in contrast to the prior art, such as that shown in  FIG. 1  wherein the key caps always remain above the keyboard mechanism plate and a plane that slices through the body of the key cap does not, in the prior art, traverses any other structure or the horizontal plane formed by the upper surface of the web-like structure (since there prior art does not even provide such a web-like structure). 
     Note that it is not necessary for the ribs to be present in between each pair of adjacent key caps of the keyboard. It is possible that sufficient stiffness and strength can be realized without having to provide ribs surrounding every key cap of the keyboard. It is also not necessary that the ribs completely surround each key cap or every key cap. As long as there is rib material present in the interstitial spaces among some key caps of the keyboard and in the vertical location that is allotted for key cap movement (but not in the horizontal location that interferes with key cap movement), some degree of stiffening is achieved without adding to the dimension of the Z-stack and/or with reduced Z-stack thickness. 
     Since the stiffness of a structure is approximately proportional to the cube of the effective thickness of the structure, thicker ribs (i.e., thick in the Z direction) tend to provide greater stiffness than thinner ribs (assuming the same modulus). Thick ribs are particularly suitable for keyboards that feature full-travel for the key caps. Furthermore, the presence of the ribs throughout the keyboard assembly renders it possible to provide a large number of fastening devices (such as the aforementioned posts) to more rigidly couple the web-like structure to the mechanism plate. In an embodiment, the post-to-post distance between adjacent posts may be 20 mm or less. 
     In an embodiment, the keyboard assembly is coupled to the rest of the device (e.g., laptop computer, keyboard housing, etc.) via the web-like structure. For example, in an embodiment, the web-like structure may be part of the device or fastened in advance to the device and the rest of the keyboard assembly (including the mechanism plate) may be mated with the web-like structure (and thereby coupled with the rest of the device) by fitting the rest of the keyboard assembly upward so that that the key caps are inserted upward into the apertures formed by interconnected ribs. After fitting, the mechanism plate may be fastened with the web-like structure (by, for example, deforming the heads of the aforementioned deformable posts. In another embodiment, the keyboard assembly is coupled to the rest of the device via the mechanism plate instead of via the web-like structure. In another embodiment, both the mechanism plate and the web-like structure is fastened with structures of the device. 
     From the mechanism plate plane, the distance to the upper surface of the ribs may vary relative to the distance to the lower surface of the key cap and the upper surface of the key cap. Furthermore, since a key cap may occupy two positions (i.e., at rest and depressed), there are multiple combinations possible. The particular combination chosen may reflect a particular tradeoff in the Z-stack thickness and ergonomics. In an embodiment, the bottom  254  of the key cap is substantially co-planar with the top surface  252  of the ribs in the at-rest position. This is seen in  FIG. 3B . When the key cap is depressed, the top surface  250  of the key cap is substantially co-planar with the top surface  252  of the ribs (as seen in  FIG. 3E ). 
       FIGS. 3A-3C  show various possible positions of the key cap relative to the ribs when the key cap is at rest. In the embodiment of  FIG. 3A , a small gap  306  may be provided between the top surface  304  of the ribs and the bottom surface  302  of the key cap when the key cap is in the at-rest position. By reducing the height or vertical thickness of the ribs, the embodiment of  FIG. 3A  may provide a slight reduction in the Z-stack thickness relative to the embodiment of  FIG. 2A  and/or provide more key travel distance. In the alternative embodiment of  FIG. 3B , the top surface  304  of the ribs and the bottom surface  302  of the key cap may be substantially co-planar when the key cap is in the at-rest position. In the alternative embodiment of  FIG. 3C , the top surface  304  of the ribs is higher than the bottom surface  302  of the key cap when the key cap is in the at-rest position. The embodiment of  FIG. 3C  offers improved reliability since there is no gap between the bottom of the key cap and the top surface of the ribs. To some users, the embodiment of  FIG. 3C  appears aesthetically pleasing. 
       FIGS. 3D-3F  show various possible positions of the key cap relative to the ribs when the key cap is depressed. In the embodiment of  FIG. 3D , the top surface  352  of the rib is higher than the top surface  352  of the key cap when the key cap is depressed. Relative to the embodiments of  FIG. 3E and 3F , the embodiment of  FIG. 3D  offers reduced Z-stack thickness for a given key travel distance. In the embodiment of  FIG. 3E , the top surface  352  of the rib is higher than the top surface  352  of the key cap. In the embodiment of  FIG. 3E , the top surface  352  of the rib is substantially co-planar with the top surface  352  of the key cap when the key cap is depressed. In the embodiment of  FIG. 3F , the top surface  352  of the rib is higher than the top surface  352  of the key cap when the key cap is depressed. To some users, the embodiment of  FIG. 3F  offers a pleasing tactile experience since the user&#39;s finger does not touch the surrounding ribs when the key cap is depressed. Note that  FIG. 2 , and  FIGS. 3A-3F  show only some example combinations; other combinations are possible. In all these embodiments, stiffness is provided by the interconnected ribs of the web-like structure that are disposed above and connected to the mechanism plate. 
     Some users, such as small children or adults with small hands and/or long fingernails, may find that their fingers occasionally slide off the depressed key and may become caught in the area  408  between the depressed key  402  and the adjacent key  404  of  FIG. 4 . A caught finger may dislodge an adjacent key cap when the finger is pulled upward, which leads to a high defect rate in the field. Embodiments of the invention include features to address the above-discussed problems with the prior art. 
     In the embodiment of  FIG. 5 , the presence of a static rib structure  502  in between adjacent key caps  504  and  506  renders it more difficult for a finger to slide off a depressed key  506  and to become trapped under an adjacent key cap  504 . This feature tends to reduce the incidence of dislodged key caps in the field, and renders the keyboard more comfortable to operate for young children and adults with small hands and/or long fingernails. 
     In the prior art, the top side of a key cap is tapered to prevent an adjacent key cap from being inadvertently depressed when the user&#39;s finger is pressing on a given key cap. Since the user&#39;s fingers do not contact the center of each key cap every time, tapering the key cap&#39;s top side is an effective way of reducing the incidence of inadvertent keystroke activation when adjacent key caps are located next to one another without any structure interposed in between. With reference to  FIG. 4 , there are shown two adjacent keys  402  and  404 , with the tapering slope of key  402  being denoted with reference number  406 . 
     Tapering the top side of the key cap, however, introduces other issues. For one, the tapered slope channels foreign materials (such as dirt or water) to the electrically sensitive and difficult-to-clean underside area of the key caps where they tend to remain trapped. With the presence of the ribs in between adjacent keys, embodiments of the invention render it possible to shape the key caps and/or the ribs to enable the keyboard to have a greater resistance to dirt and liquid spillage and/or resistance to tampering by mischievous users. Thus, the benefit provided by this embodiment includes not only reduced thickness but also anti-tampering and/or spill resistance. As such, embodiments of the invention are beneficial not only where a reduced keyboard assembly thickness is desired but also where a ruggedized keyboard is desired. 
     With reference to  FIG. 6 , key cap  602  has a taper flange  604  at its base (which may exist as an alternative to or as an addition to the tapering of the top side of the key cap). Rib  606  also has a taper flange  608  that is configured to mate with flange  604  when the key cap is in the at-rest position. 
     The mating of flanges  604  and  608  effective closes the gap between a key cap and its adjacent ribs, thereby preventing dirt, liquid, and/or other contaminants from falling into the region between the key cap and the adjacent ribs. Furthermore, the shape of the respective flanges effectively “traps” key cap  602  under the flanges of the adjacent ribs, thereby preventing a mischievous user from being able to tamper with and/or remove key cap  602  by pulling or prying key cap  602  upward. 
     The mating of the taper flanges also provides a “self-centering” action for the key cap as the key cap is released from its depressed position. This self-centering feature advantageously imparts a more precise look-and-feel to the keyboard. Furthermore, the self-centering feature, alone or in combination with the ability to hold the key cap captive under the flanges of the adjacent ribs, provides an opportunity to substantially simplify the biasing arrangement that is employed to return the key to the at-rest position. For example, a simple spring or a resilient structure may be employed to return the key cap to its at rest position without having to employ the more complicated and fragile scissor linkages. 
     In some embodiments, flange  604  does not have to encircle all the way around, or surround, the base of key cap  602 .  FIG. 7A  shows an embodiment wherein only partial taper flanges  702  are provided. The embodiment of  FIG. 7A  is not as resistant to, for example, liquid spillage as the embodiment of  FIG. 6 ; however the anti-tampering benefit remains. 
       FIG. 8  shows an alternate embodiment wherein the flange is not tapered (as was done in  FIG. 6 ). In this “top hat” embodiment, the flanges of the base of the key cap and of the adjacent ribs form a lip-and-shoulder mating configuration. Resistance to contaminants and to tampering are offered by the embodiment of  FIG. 8  while the key caps are at rest. As an alternative, the flanges of the base of the key cap and/or of the adjacent ribs may be partial flanges instead of full flanges.  FIG. 7B  shows an embodiment wherein only partial “top hat” flanges are provided. In such an embodiment, the resistance to tampering is maintained. 
     While the invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents which fall within the scope of this invention. For example, features from various embodiments discussed herein may be combined in any suitable combination as desired. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutations, and equivalents as fall within the true spirit and scope of the invention.