PATENT DOCUMENT

Publication Number: US-8592699-B2
Application Number: US-86054710-A
Country: US
Kind Code: B2

Title: Single support lever keyboard mechanism

Abstract:
A keyboard mechanism for a low-travel keyboard and methods of fabrication are described. The low-travel keyboard is suitable for a thin-profile computing device, such as a laptop computer, netbook computer, desktop computer, etc. The keyboard includes a key cap that can be formed of a variety of materials in the form of a flat slab. The key cap is attached to one end of a support lever that supports it from underneath. In one embodiment, the support lever is formed of a rigid material and is pivotally coupled with a substrate on the other end. In another embodiment, the support lever is formed of a flexible material and is fixedly attached to the substrate on the other end. The portion of the support lever that is attached to the key cap is positioned over a metal dome that can be deformed to activate the switch circuitry of the membrane on printed circuit board underneath the dome.

Claims:
What is claimed is: 
     
       1. A thin profile keyboard for a computing device, comprising:
 a plurality of baseplates arranged in a plurality of rows; and 
 a plurality of keys, each of the plurality of keys associated with one of the plurality of baseplates, wherein the plurality of keys associated with a first baseplate are offset from the plurality of keys associated with a second baseplate, each key comprising:
 a key cap; 
 an actuator attached to the respective baseplate, the actuator being configured to deform to activate electrical switch circuitry; and 
 a rigid support lever having a first end attached to a bottom surface of the key cap and a second end attached to a substrate at a pivot point, wherein a portion of the support lever is positioned over the actuator and wherein when a force is applied to a top surface of the key cap, the force causes the support lever to rotate about the pivot point, causing a bottom surface of the support lever to contact and deform the actuator, wherein the rigid support lever at least partially underlies at least one of the plurality of baseplates. 
 
 
     
     
       2. The keyboard of  claim 1 , wherein the actuator is a metal dome for providing a low-travel keystroke having an abrupt force drop. 
     
     
       3. The keyboard of  claim 2 , wherein the low-travel keystroke has a travel distance that is less than about 1.85 mm. 
     
     
       4. The keyboard of  claim 2 , wherein the low-travel keystroke has a travel distance that is in a range of about 0.2 mm to about 0.5 mm. 
     
     
       5. The keyboard of  claim 1 , wherein the top surface of the key cap is substantially flat and the bottom surface of the key cap is substantially flat. 
     
     
       6. The keyboard of  claim 5 , wherein the key cap is formed of glass. 
     
     
       7. The keyboard of  claim 5 , wherein the key cap is formed of metal. 
     
     
       8. The keyboard of  claim 1 , wherein the support lever comprises an elastomeric spacer configured to contact the actuator only when the force is applied to the top surface of the key cap. 
     
     
       9. A method of assembling at least a portion of a low-travel keyboard for a computing device, comprising:
 providing a first and second baseplate; 
 providing a metal dome above the first baseplate, the metal dome configured to deform when depressed from above, wherein the metal dome is configured to activate electrical switch circuitry of the keyboard when the metal dome is deformed; 
 disposing a support lever over the metal dome, wherein the support lever is coupled with a substrate at a point on a first end of the support lever; and 
 adhering a bottom surface of a key cap to a top surface of a second end of the support lever, wherein the second end of the support lever is positioned over the metal to deform the dome when depressed from above; wherein 
 the support lever is positioned to at least partially underlie the second baseplate. 
 
     
     
       10. The method of  claim 9 , wherein the support lever is formed of a rigid material and pivotally coupled with the substrate, wherein the support lever is configured to pivot about the point when depressed from above. 
     
     
       11. The method of  claim 9 , wherein the support lever is formed of a flexible material and fixedly attached at the first end to the substrate. 
     
     
       12. The method of  claim 9 , further comprising providing a compliant component on the support lever, wherein the compliant component is positioned directly over the metal dome and configured to contact the metal dome when the support lever is depressed from above. 
     
     
       13. The method of  claim 9 , wherein a total travel distance of the keyboard is less than 1.85 mm. 
     
     
       14. The method of  claim 9 , wherein the key cap is formed of a slab of material. 
     
     
       15. The method of  claim 9 , wherein the electrical switch circuitry is in a membrane disposed below the metal dome, wherein the membrane comprises conductive traces. 
     
     
       16. The method of  claim 15 , wherein the membrane comprises a top layer, a spacer layer, and a bottom layer. 
     
     
       17. The method of  claim 16 , wherein the top layer contacts the bottom layer when the metal dome is deformed. 
     
     
       18. A thin-profile keyboard for a computing device having a plurality of key switches arranged in a plurality of rows, each key switch comprising:
 a portion of a membrane including electrical switch circuitry; 
 a metal dome disposed over the membrane and configured to deform to activate the electrical switch circuitry; 
 a single support lever having:
 a first end coupled to a first substrate; 
 a second end of the support lever disposed over the metal dome; 
 a first planar segment extending from the first end, the first planar segment at least partially underlying a second substrate; 
 a second planar segment extending from the second end; and 
 a non-planar segment connecting the first end to the second end; 
 
 wherein the support lever is configured to deform the metal dome when the support lever is depressed from above; and 
 a key cap disposed over and rigidly adhered to the second end of the support lever. 
 
     
     
       19. The keyboard of  claim 18 , wherein the support lever includes an elastomeric component positioned over the metal dome, wherein the elastomeric spacer is configured to contact and deform the metal dome when the support lever is depressed from above. 
     
     
       20. The keyboard of  claim 18 , wherein the support lever is formed of a rigid material and is pivotally coupled to the first substrate. 
     
     
       21. The keyboard of  claim 18 , wherein the support lever is formed of a flexible material and is fixedly coupled to the first substrate. 
     
     
       22. The keyboard of  claim 18 , wherein the membranes and support levers are interwoven. 
     
     
       23. The tactile low-travel keyboard of  claim 18 , wherein the key cap has a substantially flat top surface and a substantially flat bottom surface. 
     
     
       24. The keyboard of  claim 18 , wherein the metal dome comprises stainless steel. 
     
     
       25. The keyboard of  claim 18 , wherein some of the support levers are curved.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The described embodiments relate generally to peripheral devices for use with computing devices and similar information processing devices. More particularly, the present embodiments relate a thin profile, aesthetically pleasing keyboard well suited for use with computing devices, and methods of assembling such thin profile, aesthetically pleasing keyboards. 
     2. Description of the Related Art 
     The outward appearance, as well as functionality, of a computing device and its peripheral devices is important to a user of the computing device. In particular, the outward appearance of a computing device and peripheral devices, including their design and heft, is important, as the outward appearance contributes to the overall impression that the user has of the computing device. One design challenge associated with these devices, especially with portable computing devices, generally arises from a number of conflicting design goals, including the desirability of making the device attractive, smaller, lighter, and thinner while maintaining user functionality. 
     Therefore, it would be beneficial to provide a keyboard for a portable computing device that is aesthetically pleasing, yet still provides the stability for each key that users desire. It would also be beneficial to provide methods for manufacturing the keyboard having an especially aesthetic design as well as functionality for the portable computing device. 
     SUMMARY OF THE DESCRIBED EMBODIMENTS 
     This paper describes various embodiments that relate to systems, methods, and apparatus for providing a trapdoor keyboard mechanism for a low-travel footprint keyboard that allows the use of aesthetically pleasing key caps and also provides key stability for use in computing applications. 
     According to one embodiment, a thin profile keyboard for a computing device is described. The keyboard includes a plurality of keys arranged in a plurality of rows. Each row includes a plurality of keys and the keys in a first row are offset from the keys in a second row. Each key includes a key cap and an actuator attached to a base plate. The actuator is configured to deform to activate electrical switch circuitry when it is deformed. A portion of a rigid support lever is positioned over the actuator, which can be a metal dome. The support lever has one end that is attached to a bottom surface of the key cap and a second end that is attached to a substrate at a pivot point. When a force is applied to the top surface of the key cap, the force causes the support lever to rotate about the pivot point, causing a bottom surface of the support lever to contact and deform the actuator. In an embodiment, the key cap can be in the form of a flat slab. An elastomeric spacer may be provided on the support lever over the metal dome such that the elastomeric spacer deforms the metal dome when the key is depressed by a user. The use of a single support lever allows the key cap to be simply adhered to the support lever and the support lever also reduces instability when the key is depressed by a user. As the key cap can be adhered to the support lever, intricate attachment features on the underside of the key cap are unnecessary, thereby allowing the key cap to be formed of a variety of materials, including glass and metal. 
     A method of assembling at least a portion of a low-travel keyboard for a computing device is disclosed. The method can be carried out by the following operations: providing a metal dome configured to deform when depressed from above, disposing a support lever over the metal dome, and adhering a key cap to the support lever. The metal dome can activate electrical switch circuitry of the keyboard when the metal dome is deformed. The support lever is coupled with a substrate at a point on a first end of the support lever. The bottom of the key cap is adhered to a top surface of the second end of the support lever, which is positioned over the metal dome to deform the dome when depressed from above. In an embodiment, the support lever is formed of a rigid material and is pivotally coupled to the substrate such that the support lever deforms the metal dome when the support lever is depressed from above, as the support lever rotates slightly about the pivot point where it is coupled to the substrate. In another embodiment, the support lever is formed of a flexible material and fixedly coupled to the substrate on one end. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  is a side view of a typical key switch of a scissor-switch keyboard. 
         FIG. 2  is a side view of an embodiment of a key having a single support lever. 
         FIG. 3  is a detailed view of an embodiment of the pivoted attachment of the support lever to the topcase. 
         FIG. 4  is a simplified top perspective view of a key cap  210  positioned in an embodiment of the topcase. 
         FIG. 5  is a bottom plan view of an embodiment of a keyboard arrangement. 
         FIG. 6  is a detailed perspective view of the bottom of the keyboard arrangement shown in  FIG. 5 . 
         FIG. 7  is a detailed perspective view of an embodiment of a three-layer membrane of a printed circuit board. 
         FIG. 8  is a flow chart of a method of assembling an embodiment of a key switch having a single support lever. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EMBODIMENTS 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The embodiments herein relate to a thin profile peripheral input device that is both efficient and aesthetically pleasing. In particular, the thin profile peripheral input device can take the form of a keyboard that can include at least a low profile key cap assembly. The low profile key cap assembly can, in turn, be formed of a key cap connected to one end of a beam or lever, the beam or lever having another end pivotally connected to base portion. The key cap can be positioned proximate to a switch mechanism that can be engaged by the key cap impinging thereupon. In one embodiment, the beam can be rigid in nature and formed of, for example, stainless steel, aluminum, or any other suitable material. The rigid beam can be pivotally connected to the base portion at a pivot point using, for example, bushings. In this way, in order to engage the actuator, a force can be applied to the key cap causing the beam and the key cap to rotate about the pivot point resulting in the key cap moving in an arc-like manner. However, due to the relatively long distance between the pivot point and the key cap and the reduced Z stack of the key cap assembly, the angle of rotation of the key cap is small enough and any rotational wobble is substantially reduced. 
     In another embodiment, the beam can be formed of a more compliant material fixedly connected to the base. In this way, when the force is applied to the key cap, the beam can bend allowing a more compliant feel to the key cap. It should be noted that, in some cases, a compliant material layer formed of, for example, silicone rubber can be positioned between the key cap and the actuator providing a distinctive feel to the key cap. In some cases, this distinctive feel can be customized to a particular application by using various materials. For example, a harder material can provide a more firm feel whereas softer, more compliant materials, such as silicone rubber, a more compliant feel. In this way, it is contemplated that selected key cap assemblies can be fashioned to have their own associated “feel” that can depend upon a number of factors such as a position on the keyboard, function associated with key cap, and so on. 
     Furthermore, since there is no restriction on the material used to form an observable portion of the key cap, the key caps can be formed to include an upper layer formed of materials heretofore deemed unsuitable for use in keyboards. Such materials as wood, stone, polished meteorite (watch dials have been made from polished meteorite), glass, etc. can be used as opposed to standard key caps that rely on plastic material. 
     There are several types of keyboards, usually differentiated by the switch technology employed in their operation. The choice of switch technology affects the keys&#39; responses (i.e., the positive feedback that a key has been depressed) and travel (i.e., the distance needed to push the key to enter a character reliably). One of the most common keyboard types is a “dome-switch” keyboard, which works as described below. When a key is depressed, the key pushes down on a rubber dome sitting beneath the key. The rubber dome collapses, which gives tactile feedback to the user depressing the key, and causes a pair of conductive lines on the printed circuit board (PCB) below the dome to contact, thereby closing the switch. A chip in the keyboard emits a scanning signal along the pairs of lines on the PCB to all the keys. When the signal in one pair of lines changes due to the contact, the chip generates a code corresponding to the key connected to that pair of lines. This code is sent to the computer either through a keyboard cable or over a wireless connection, where it is received and decoded into the appropriate key. The computer then decides what to do based on the particular key depressed, such as display a character on the screen, or perform some other type of action. Other types of keyboards operate in a similar manner, with the main difference being how the individual key switches work. Some examples of other keyboards include capacitive keyboards, mechanical-switch keyboards, Hall-effect keyboards, membrane keyboards, roll-up keyboards, and so on. 
       FIG. 1  is a side view of a typical key switch  100  of a scissor-switch keyboard. A scissor-switch keyboard is a type of relatively low-travel dome-switch keyboard that provides the user with good tactile response. Scissor-switch keyboards typically have a shorter total key travel distance, which is about 1.5-2 mm per key stroke instead of about 3.5-4 mm for standard dome-switch key switches. Thus, scissor-switch type keyboards are usually found on laptop computers and other “thin-profile” devices. The scissor-switch keyboards are generally quiet and require relatively little force to press. 
     As shown in  FIG. 1 , the key cap  110  is attached to the base plate or PCB  120  of the keyboard via a scissor-mechanism  130 . The scissor-mechanism  130  includes two separate pieces that interlock in a “scissor”-like manner, as shown in  FIG. 1 . The scissor-mechanism  130  is typically formed of a rigid material, such as plastic or metal or composite material, as it provides mechanical stability to the key switch  100 . As illustrated in  FIG. 1 , a rubber dome  140  is provided. The rubber dome  140 , along with the scissor-mechanism  130 , supports the key cap  110 . 
     When the key cap  110  is pressed down by a user in the direction of arrow A, it depresses the rubber dome  140  underneath the key cap  110 . The rubber dome  140 , in turn, collapses, giving a tactile response to the user. The scissor-mechanism  130  also transfers the load to the center to collapse the rubber dome  140  when the key cap  110  is depressed by the user. The rubber dome also dampens the keystroke in addition to providing the tactile response. The rubber dome  140  can contact a membrane  150 , which serves as the electrical component of the switch. The collapsing rubber dome  140  closes the switch when it depresses the membrane  150  on the PCB, which also includes a base plate  120  for mechanical support. The total travel of a scissor-switch key is shorter than that of a typical rubber dome-switch key. As shown in  FIG. 1 , the key switch  100  includes a three-layer membrane  150  (on a PCB) as the electrical component of the switch. The membrane  150  can be a three-layer membrane or other type of PCB membrane, which will be described in more detail below. 
     The following description relates to a single support lever keyboard mechanism for a low-travel keyboard suitable for a small, thin-profile computing device, such as a laptop computer, netbook computer, desktop computer, etc. The use of a single support lever to support the key cap and to activate the switch circuitry not only allows for the key cap to be formed of almost any material but also provides stability to each key, as will be described in more detail below. The aesthetic appearance of a keyboard therefore depends greatly on the key caps, which form most of the visible portion of a keyboard. It will be understood that the material of the key caps will be important, not only because the key caps are highly visible but also because the material should have a desired tactile feel to a user&#39;s fingers. 
     These and other embodiments of the invention are discussed below with reference to  FIGS. 2-8 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments. 
       FIG. 2  is a side view of an embodiment of a key switch  200 . As shown in  FIG. 2 , the key cap  210  in this embodiment is different from standard key caps like the one shown in  FIG. 1 . The key cap  210  of this embodiment can be a slab of material that is flat. In other words, the key cap has a substantially flat top surface and a substantially flat bottom surface. The key cap  210  does not need to have any features on the underside for attaching any other components of the key  200 . The key cap  210  can simply be adhered to a support lever  220 . In an embodiment, the key cap  210  can be adhered to the support lever  220  with an adhesive, such as VHB™ double-sided bonding tape, available from 3M Company of St. Paul, Minn. 
     The keyboard can include a key cap  210 , such as the one shown in  FIG. 2 , positioned over and rigidly attached to a support lever  220 . According to embodiments described herein, the key cap  210  can be formed of almost any suitable material, including, but not limited to, wood, stone, polished meteorite, ceramic, metal, and glass. An outer surface of the key cap can also be coated with a non-slip material, such as rubber. The key cap  210  can have a thickness in a range of about 0.5-1 mm. In one embodiment, a glass key cap has a thickness of about 1 mm. According to another embodiment, a ceramic key cap has a thickness of about 0.5 mm. It will be appreciated that the thickness of the key cap  210  may depend on the material of the key cap  210 . In some embodiments, the top surface of the key cap  210  is surface-marked. In other embodiments, the key cap  210  can be laser-cut, two-shot molded, engraved, or formed of transparent material with printed inserts  215 . 
     A standard key, such as the one shown in  FIG. 1 , has a key cap  110  typically formed of a molded plastic material so that the underside of the key cap  110  can include intricate features for attaching the scissor mechanism  130 . As described in more detail below, the key cap  210  in the described embodiments can be in the form of a flat slab that is adhered to a support lever  220 . Thus, the key cap  210  need not be formed of a moldable plastic material to accommodate intricate attachment features for a scissor mechanism. Instead, the key cap  210  can be formed of other materials, including, but not limited to, glass, wood, stone, and polished meteorite. 
     According to one embodiment, the support lever  220  can be formed of a rigid material, such as stainless steel or ceramic. Stainless steel has a number of characteristics that make it a good choice for the support lever  220 . For example, stainless steel is rigid, durable and fairly resistant to corrosion, and it is a relatively inexpensive metal that can be easily machined and has well known metallurgical characteristics. Furthermore, stainless steel can be recycled. According to an alternative embodiment, the support lever  220  is formed of a ceramic material. 
     According to some embodiments, the support lever  220  is fixedly attached at one end to the underside of the key cap  210 . The fixed attachment provides rotational stability to the key  200  because there is essentially only one moving part when the key cap  210  is depressed by a user. In other words, the support lever  220  and the attached key cap  210  together form the single moving part. A standard key, such as the one shown in  FIG. 1 , typically has three moving parts: the key cap  110  and the two linked parts of the scissor mechanism  130 . 
     The rigid support lever  220  provides stability to the key by reducing wobble from side to side. The key  200  may rotate slightly forward when depressed, which may be ergonomically desirable. However, such slight rotation is virtually imperceptible for low-travel keys, as is described in more detail below. As shown in  FIG. 2 , a single support lever  220  supports the key cap  210 . 
     The support lever  220 , which, on one end, has its top surface attached to the underside of the key cap  210 , can also dictate the height of the key cap  210  or the distance between the key cap  210  and the base plate  270 . In the embodiment shown in  FIG. 2 , the support lever  220  has an upper portion in a plane and a lower portion in a lower plane, and the upper portion and the lower portion are connected by a portion in a plane perpendicular to the planes of the upper and lower portions. The other end of the support lever  220 , which is on the lower portion, is pivotally coupled with the topcase  260 , as described in more detail below. It will be understood that the topcase  260  is the portion of the housing or substrate surrounding the keys. In the event the key cap  210  is depressed in an off-center manner, the support lever  220  transfers the load to the center of the key. According to an embodiment, the support lever  220  is formed of steel and has a thickness of about 0.5 mm. 
     In this embodiment, the support lever  220  is formed of a rigid material and rotatably or pivotally coupled, at its other lower end, with the topcase  260  at a pivot point at a distance from the key cap  210 . In some embodiments, the distance is about one key pitch. As illustrated in  FIG. 2 , a bearing  222  is positioned at the lower end of the support lever  220 . The distance between the bearing  222  and the key cap  210  can be dictated by the pitch between the rows of keys. As the skilled artisan will appreciate, the distance, and therefore the length of the support lever  220 , can be limited by the space available and depends on the size of the device and the individual key caps  210 . In some embodiments, the distance between the bearing  222  and the key cap  210  can be in a range of about 25-30 mm. As shown in  FIG. 2 , the bearings  222  are positioned underneath the topcase  260  of the device. 
     As shown in  FIG. 2 , the end of the support lever  220  that is attached to the key cap  210  is higher than the end that is pivotally coupled with the topcase  260  at the bearing  222 . In the embodiment shown in  FIG. 2 , the bearings  222  are integrally formed with the support lever  220 . In other embodiments, the bearings  222  can be rigidly attached to the support lever  220 . The skilled artisan will understand that such a configuration of the support lever  220  and the attachment of the key cap  210  to a single support lever  220  allows the support lever  220  to rotate slightly when the key cap  210  is pushed down by a user. In an embodiment where the bearing  222  is located closer to the user than the key  200 , the support lever  220  will rotate slightly forward when the key cap is depressed. Such a forward rotation during key travel can be ergonomically desirable. For low travel keyboards, such rotation can be almost imperceptible. 
     According to some embodiments, the keys  200  are low-travel keys that have a total travel in a range of about 0.2 mm to about 1.85 mm. In other embodiments, the keys have a total travel in a range of about 0.2 mm to about 0.5 mm. 
       FIG. 3  is a detailed view of an embodiment of the pivoted coupling of the support lever  220  to the topcase  260 . In this embodiment, the support lever  220  has a pair of bearings  222  through which a dowel pin  230  threaded. According to this embodiment, the dowel pin  230  acts as the pivot axis about which the support lever  220  pivots or rotates. In an embodiment, the dowel pin  230  can be fixedly coupled to the topcase  260  using snaps that trap the dowel pin  230  in its bearing such that it can simply be pressed in during assembly. In another embodiment, the bearings can be pressed onto the ends of the dowel pin  230  and the assembly of the dowel pin  230  and two bearings can be trapped in a recess in the topcase  260 . According to some embodiments, the dowel pin  230  can have a diameter in a range of about _ mm to _ mm. In one embodiment, the dowel pin  230  has a diameter of about 0.8 mm. 
     According to another embodiment, the support lever  220  is formed of a flexible material that can be fixedly adhered to the underside of the key cap  210  on its upper end and is fixedly attached to the topcase  260  at the lower end. In this embodiment, the support lever  220  can be formed of spring steel and does not rotate about a pivot point. Instead, the flexible nature of the support lever material allows a similar motion when the key is depressed, like a linear flex-spring. 
     As shown in  FIG. 2 , the support lever  220  can include a compliant component, such as an elastomeric spacer  225 , between the key cap  210  and a metal dome  240  positioned underneath the elastomeric spacer  225 . The elastomeric spacer  225  may be formed of an extremely compliant material, such as rubber or silicone rubber. The compliant nature of the elastomeric spacer  225  can provide a desirable and distinctive feel to the user when the key is depressed. The elastomeric spacer  225  also reduces rattle of the keyboard by being in constant mild compression and also improves overall sensitivity to tolerance variation during assembly. As described in more detail below, the elastomeric spacer  225  contacts and collapses the metal dome  240  to activate the switch circuitry. The metal dome  240  therefore acts as an actuator. 
     As illustrated in  FIG. 2 , a metal dome  240  is positioned over the membrane  250  and the base plate  270 . The metal dome  240  can be formed of a material, such as stainless steel. As noted above, stainless steel is durable and fairly resistant to corrosion, and it is a relatively inexpensive metal that can be easily machined and has well known metallurgical characteristics. In some embodiments, the stainless steel metal dome can be plated with gold, silver, or nickel. 
     The skilled artisan will appreciate that it is desirable to make the keyboard (and computing device) thinner, but users still want the tactile feel to which users are accustomed. It is desirable for the keys to have some “bounce-back” or “snappy” feel. As can be appreciated by the skilled artisan, substantially flat keyboards, such as membrane keyboards, do not provide the tactile feel that is desirable for a keyboard. Similarly, simply reducing the travel of a typical rubber dome scissor-switch keyboard also reduces the tactile or “snappy” feel that a conventional dome-switch keyboard provides. 
     Metal domes can provide very low travel as well as a crisp tactile feel. Like a rubber dome, a metal dome also dampens the keystroke in addition to providing a very crisp tactile response to the user. A metal dome typically has a good tactile force drop with a relatively short travel distance, which is typically about 0.1-0.2 mm. 
     The skilled artisan will appreciate that a metal dome has a quick force drop over a short travel distance relative to an elastomeric dome. Elastomeric domes lack the quick force drop and therefore the crisp snap of metal domes. Thus, elastomeric domes do not provide the positive crisp tactile response of metal domes, especially when the amount of travel is reduced. However, although a metal dome can provide a positive crisp tactile feel, a metal dome alone cannot provide the desired tactile feel and travel distance for a keyboard suitable for typing or otherwise inputting text. The skilled artisan will appreciate that a metal dome cannot achieve travel greater than about 0.7 mm, as the metal is difficult to deform and would require a large amount of force for deformation. Even if enough force were applied to the metal dome, it would not be able to achieve a travel distance greater than about 0.7 mm unless the metal dome is quite large. A larger metal dome would cause each individual key to also be quite large, which can be undesirable and impractical, especially in portable devices. 
     According to some embodiments, the support lever  220  can be provided with an elastomeric spacer  225 , as shown in  FIG. 2 . The elastomeric spacer  225  can be positioned over a metal dome  240  such that the elastomeric spacer  225  contacts the top surface of the metal dome  240  when the key cap  210  is depressed by a user. The elastomeric spacer  225  can be formed of a compliant material, such as silicone rubber, and increases the travel distance of the key  200 . As discussed above, the metal dome  240  typically has a relatively short travel distance, but provides crisp, tactile feedback to the user, but the elastomeric spacer  225  can increase the travel distance, which can be desirable, and also provide the tactile feedback to which users have become accustomed. Thus, the combination of the elastomeric spacer  225  with the metal dome  240  allows the key to have a low-travel distance while maintaining the positive tactile feedback that is desirable for a keyboard. The elastomeric spacer  225  also allows for easier assembly of the keys  200 , as the assembly tolerance is less sensitive with the inclusion of the elastomeric spacer  225 . The elastomeric spacer  225  also provides the further benefit of reducing rattling in the keyboard. 
     As shown in  FIG. 2 , the metal dome  240  is substantially concave or hemispherical and oriented with the vertex of each of the dome being at the highest point. In other words, the metal dome opening is facing downward. As the dome  240  is concave, it is a normally-open tactile switch. The switch only closes when the dome  240  is collapsed, as will be described in more detail below. 
     In this embodiment, the elastomeric spacer  225  also provides the ability for longer travel. The metal dome  240  provides the majority of the tactile force drop and also activates the switch circuitry of the membrane  250  on the base plate  270 . The abrupt or quick force drop of the metal dome  240  provides the crisp “snappy” feel for the user. It provides the kind of force drop that the metal dome allows, and also the initial compliancy and force build-up that are absent in metal domes. 
     When a user presses down on the key cap  210 , it causes the support lever  220  to which the key cap  210  is rigidly attached to rotate slightly and move downward. As the support lever  220  moves downward, the elastomeric spacer  225  contacts and collapses the elastomeric dome  220 . As shown in  FIG. 2 , the elastomeric spacer  225  is positioned directly over the center of the top of the metal dome  240 . Thus, when the support lever  220  moves downward, the elastomeric spacer  225  then contacts and pushes down on the center of the top of the metal dome  240 , and collapses the metal dome  240 . As shown in  FIG. 2 , the elastomeric spacer  225  does not contact the metal dome  240  when the key cap  210  is not depressed. The underside of the center of the collapsing metal dome  240  contacts the top side of the top layer  252  ( FIG. 7 ) of the membrane  250 , thereby causing the contact pads  258  of the circuit traces ( FIG. 7 ) on the top layer  252  ( FIG. 7 ) and the bottom layer  256  ( FIG. 7 ) of the membrane  250  to connect and close the switch, which completes the connection to enter the character. As shown in  FIG. 2 , the membrane  250  is secured to a base plate or PCB  270 . 
     According to an embodiment, the support lever  220  has a thickness of about 0.5 mm. In other embodiments, the support lever may have a thickness that is less than 0.5 mm. In some embodiments, the elastomeric spacer can have a thickness in a range of about 0.3 to 1 mm. In other embodiments, the elastomeric spacer can have a thickness in a range of about 0.5 to 1 mm. The metal dome  240  can have a height in a range of about 0.3 mm to about 0.7 mm. According to another embodiment, the metal dome  240  has a height in a range of about 0.3 mm to about 0.5 mm. In still another embodiment, the metal dome  240  has a height in a range of about 0.5 mm to about 0.7 mm. 
     In an embodiment, the metal dome  240  has a thickness in a range of about 0.03 mm to about 0.1 mm. It will be understood that the metal dome  240  typically has a uniform thickness if it is formed from a sheet of metal. The skilled artisan will appreciate that the thicknesses of the dome  240  and elastomeric spacer  225  can be adjusted and/or varied to obtain the desired force drop. The base diameter of the dome  240  can be in the range of about 3 mm to 7 mm. 
     According to an embodiment, as shown in  FIG. 2 , the metal dome  240  can be secured, at its base in its non-concave portions, to the membrane  250  by means of adhesive, including pressure-sensitive adhesive tape. In an alternative embodiment, the metal dome  240  is not adhered to the membrane  250 , but is instead encapsulated by an additional membrane sheet that extends over the metal dome  240  and is adhered to the membrane  250 . 
       FIG. 4  is a simplified top perspective view of a key cap  210  positioned in an embodiment of the topcase  260 . For simplicity,  FIG. 4  shows only a single key cap  210  and only a portion of the topcase  260 . As illustrated, keys are positioned in the topcase  260  of this embodiment in a staggered manner. That is, the rows of keys can be slightly shifted so that keys in one row are not positioned directly below the keys in the row above. The skilled artisan will appreciate that the keys can be arranged in any manner that is desired. 
       FIG. 5  is a bottom plan view of an embodiment of a keyboard arrangement.  FIG. 6  is a detailed perspective view of the bottom of the keyboard arrangement shown in  FIG. 5 . As shown in  FIG. 5 , the base plate  270  is arranged in rows across the keyboard. The base plate  270  can be a rigid printed circuit board (PCB). As shown in the embodiments of  FIGS. 5 and 6 , the base plate  270  and the support levers  220  can be interwoven. It will be understood that the keys  200  of the keyboard can be arranged in any manner that is desired and that the components of the keys  200  can similarly be arranged in any manner such that they fit in the available space. For example, the support lever  220  for some keys can be curved, as illustrated in  FIG. 5 , to accommodate the different positions of the keys and to conform to an existing keyboard arrangement. 
       FIG. 7  is a detailed perspective view of an embodiment of the membrane  250 . According to an embodiment, the membrane  250  can have three layers, including a top layer  252 , a bottom layer  256 , and a spacer layer  254  positioned between the top layer  252  and the bottom layer  256 . The top layer  252  and the bottom layer  256  can include conductive traces and their contact pads  258  on the underside of the top layer  252  and on the top side of the bottom layer  256 , as shown in  FIG. 7 . The conductive traces and contact pads  258  can be formed of a metal, such as silver or copper. As illustrated in  FIG. 7 , the membrane sheet of the spacer layer  254  includes voids  260  to allow the top layer  252  to contact the bottom layer  256  when the metal dome  240  is collapsed. According to an embodiment, the top layer  252  and bottom layer  256  can each have a thickness of about 0.075 μm. The spacer layer  254  can have a thickness of about 0.05 μm. The membrane sheets forming the layers of the membrane  250  can be formed of a plastic material, such as polyethylene terephthalate (PET) polymer sheets. According to an embodiment, each PET polymer sheet can have a thickness in the range of about 0.025 mm to about 0.1 mm. 
     Under “normal” conditions when the key pad is not depressed by a user (as shown on the left side of  FIG. 7 ), the switch is open because the contact pads  258  of the conductive traces are not in contact. However, when the top layer  252  is pressed down by the metal dome  240  in the direction of arrow A (as shown on the right side of  FIG. 7 ), the top layer  252  makes contact with the bottom layer  256 . The contact pad  258  on the underside of the top layer  252  can then contact the contact pad  258  on the bottom layer  256 , thereby allowing the current to flow. The switch is now “closed”, and the computing device can then register a key press, and input a character or perform some other operation. It will be understood that other types of switch circuitry can be used instead of the three-layer membrane  250  described above. 
     A process for assembling the key switch  200 , such as the one shown in  FIG. 2 , will be described with reference to  FIG. 8 . A process for assembling the components of the key switch  200  will be described below with reference to steps  800 - 870 . In step  800 , a base plate  270  is provided for mechanical support for the PCB as well as the entire key switch  200 . In one embodiment, the base plate  270  is formed of stainless steel. In other embodiments, the base plate  270  can be formed of aluminum. According to an embodiment, the base plate  270  has a thickness in a range of about 0.2 mm to about 0.5 mm. 
     A process for forming the three-layer membrane  250  on the base plate  270  will be described below with reference to steps  810 - 830 . In step  810 , the bottom layer  256  of the membrane  250  can be positioned over the base plate  270 . Next, in step  820 , the spacer layer  254  can be positioned over the bottom layer  256  such that the voids  260  are in the areas of the contact pads  258 . In step  830 , the top layer  252  can be positioned over the spacer layer  254  such that the contact pads  258  on the underside of the top layer  252  are positioned directly over the contact pads  258  on top side of the bottom layer  256  so that they can contact each other when the metal dome  240  is deformed. The layers  252 ,  254 ,  256  can be laminated together with adhesive. It will be understood that steps  810 - 830  can be combined into a single step by providing a three-layer membrane  250  that is pre-assembled or pre-laminated. The membrane  250  is positioned over the base plate  270  and held in place by one or more other components of the key switch  200 , such as the scissor mechanism  230 . 
     According to this embodiment, in step  840 , the metal dome  240  can be attached to the top side of the top layer  252  of the membrane  250  such that the concave dome portion is positioned over the contact pads  258  and the void  260 . In step  850 , the support lever  220  is positioned over the metal dome such that the elastomeric spacer  225  is positioned directly over the center of the metal dome  240 . In step  860 , the support lever  220  is coupled to the topcase  260  at a point at a distance from the key switch  200 . In an embodiment, the support lever  220  may be formed of a rigid material and has bearings  222  and the support lever  220  is pivotally coupled, at one end, to the topcase  260  at the point so that the support lever  220  can rotate slightly when a downward force is applied from above. In another embodiment, the support lever  220  may be formed of a flexible material and is fixedly coupled, at one end, to the topcase  260 . In this embodiment, in step  870 , to complete the key switch  200 , the key cap  210  is positioned over and attached to the support lever  220 . According to an embodiment, the underside of the key cap  210  can be adhered to the top side of the support lever  220 . 
     The advantages of the invention are numerous. Different aspects, embodiments or implementations may yield one or more of the following advantages. One advantage of the invention is that a low-travel keyboard yet may be provided for a thin-profile computing device without compromising the tactile feel of the keyboard. 
     The many features and advantages of the described embodiments are apparent from the written description and, thus, it is intended by the appended claims to cover such features and advantages. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.

Metadata:
Filing Date: 20100820
Publication Date: 20131126
Grant Date: 20131126
Priority Date: 20100820
Inventors: KESSLER PATRICK
HAMEL BRADLEY JOSEPH
NIU JAMES J.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01H2223/014", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H3/125", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H2223/058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H3/125", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H2223/014", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T29/49105", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2223/058", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 45593199