PATENT DOCUMENT

Publication Number: US-9449769-B2
Application Number: US-201314066197-A
Country: US
Kind Code: B2

Title: Low travel dome and systems for using the same

Abstract:
A low travel switch and systems for using the same. A low travel switch may include a key cap and an elastomeric dome configured to provide a predefined tactile feedback over a predefined travel distance of the key cap when the key cap is depressed by a user.

Claims:
We claim: 
     
       1. An elastomeric dome for use with a key, the elastomeric dome comprising:
 a lower portion; 
 an upper portion; and 
 a wall that spans from the lower portion to the upper portion, each of the wall, the lower portion, and the upper portion comprising:
 a physical property comprising one of a thickness or a diameter, and the elastomeric dome being tuned to provide predefined tactile feedback over a predetermined travel amount of the key based on a predefined ratio between one of the physical properties and another one of the physical properties. 
 
 
     
     
       2. The elastomeric dome of  claim 1 , wherein the physical property of the wall is a wall thickness. 
     
     
       3. The elastomeric dome of  claim 2 , wherein the physical property of the lower portion is an outer diameter. 
     
     
       4. The elastomeric dome of  claim 3 , wherein the physical property of the upper portion is an upper diameter. 
     
     
       5. The elastomeric dome of  claim 1 , wherein the wall forms an angle with respect to the lower portion. 
     
     
       6. The elastomeric dome of  claim 1 , wherein the elastomeric dome is tuned to provide the predefined tactile feedback over the predetermined travel amount based on a predefined ratio between the angle and another one of the physical properties. 
     
     
       7. The elastomeric dome of  claim 1 , wherein the predefined tactile feedback is determined from a predefined force-displacement curve characteristic. 
     
     
       8. An elastomeric dome for use with a key in a keyboard, the elastomeric dome comprising:
 a footprint; 
 a roof portion having a predetermined diameter; and 
 a wall of a predetermined thickness that connects the roof portion to the footprint wherein;
 a ratio between the predetermined thickness and the predetermined diameter is less than 0.10; and 
 the elastomeric dome is operative to enable a keystroke of the key to undergo an abrupt force change when the keystroke is 1.25 millimeters or less. 
 
 
     
     
       9. The elastomeric dome of  claim 8 , wherein a hollow cavity exist within an internal surface of the wall. 
     
     
       10. The elastomeric dome of  claim 8  further comprising:
 a nub disposed opposite the roof portion. 
 
     
     
       11. The elastomeric dome of  claim 8 , wherein the predetermined thickness is in a range from 0.19 millimeters to 0.24 millimeters. 
     
     
       12. The elastomeric dome of  claim 8 , wherein the predetermined diameter is in a range from 3.16 millimeters to 3.19 millimeters. 
     
     
       13. The elastomeric dome of  claim 8 , wherein the footprint comprises an outer diameter that is greater than the predetermined diameter. 
     
     
       14. The elastomeric dome of  claim 13 , wherein the outer diameter is in a range from 5.6 millimeters to 6 millimeters. 
     
     
       15. The elastomeric dome of  claim 8 , wherein:
 the footprint is operative to reside over a planar surface; and 
 the wall is disposed at a predetermined angle from the planar surface. 
 
     
     
       16. The elastomeric dome of  claim 15 , wherein the predetermined angle is one of 50 degrees and 51 degrees. 
     
     
       17. The elastomeric dome of  claim 16 , wherein the elastomeric dome comprises material having a predefined durometer. 
     
     
       18. The elastomeric dome of  claim 8 , wherein the abrupt force change provides a predefined tactile feedback to a user when the user depresses the key. 
     
     
       19. The elastomeric dome of  claim 8 , wherein the abrupt force change is based on a peak force and a draw force associated with the elastomeric dome. 
     
     
       20. A switch assembly comprising:
 a key cap; and 
 a hemispherical structure residing beneath the key cap and comprising:
 an upper portion; 
 a lower portion having an outer diameter; and 
 a domed surface extending from the upper portion to the lower portion, the domed surface having a predefined thickness; wherein: 
 a ratio between the predetermined thickness and the outer diameter is less than or equal to 0.04; and 
 the hemispherical structure is operative control movement of the key cap according to a predetermined force-displacement curve characteristic when the movement is less than a predetermined amount. 
 
 
     
     
       21. The switch assembly of  claim 20 , wherein the predetermined amount is one of less than and equal to 1.25 millimeters. 
     
     
       22. The switch assembly of  claim 20 , wherein the domed surface comprises a predefined height from the lower portion to the upper portion. 
     
     
       23. The switch assembly of  claim 22 , wherein a ratio between the predetermined thickness and the predefined height is one of less than and equal to 0.12. 
     
     
       24. The switch assembly of  claim 20 , wherein the predefined force-displacement curve characteristic comprises a variation in a force required to move the upper portion over a range of predefined distances. 
     
     
       25. The switch assembly of  claim 20 , wherein the predefined force-displacement curve characteristic comprises a variation in a force required to move the key cap over a range of predefined distances. 
     
     
       26. The switch assembly of  claim 20 , wherein the hemispherical structure comprises material having a predefined durometer. 
     
     
       27. An apparatus for use with a key of a keyboard, the apparatus comprising:
 an inner dome at least partially defining a top surface of the apparatus; and 
 an outer dome at least surrounding the inner dome; wherein: 
 the inner dome defines a first opening that faces a first direction opposite the top surface; and 
 the outer dome defines a second opening that faces a direction opposite the first direction. 
 
     
     
       28. The apparatus of  claim 27 , wherein the inner dome and the outer dome share a common footprint. 
     
     
       29. The apparatus of  claim 28 , wherein the inner dome comprises a roof portion and an inner hemispherical surface that extends from the roof portion to the footprint. 
     
     
       30. The apparatus of  claim 29 , wherein a diameter of the roof portion is less than a diameter of the footprint. 
     
     
       31. The apparatus of  claim 28 , wherein the outer dome comprises an upper rim portion and an outer hemispherical surface that extends from the upper rim portion to the footprint. 
     
     
       32. The apparatus of  claim 31 , wherein a diameter of the upper rim portion is greater than a diameter of the footprint. 
     
     
       33. The apparatus of  claim 27 , wherein the first direction is opposite a direction of a keystroke of the key. 
     
     
       34. The apparatus of  claim 27 , wherein a thickness of the inner dome is the same as the thickness of the outer dome. 
     
     
       35. The apparatus of  claim 27 , wherein a combination of the inner dome and the outer dome is operative to provide predefined tactile feedback in response to a keystroke of the key. 
     
     
       36. The apparatus of  claim 27 , wherein a combination of the inner dome and the outer dome is operative to operate according to a predefined force-displacement curve characteristic.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Patent Application No. 61/720,372, filed Oct. 30, 2012 and titled “Low Travel Dome and Systems for Using the Same,” the disclosure of which is hereby incorporated herein in its entirety. 
    
    
     TECHNICAL FIELD 
     This can relate to a low travel dome and systems for using the same. 
     BACKGROUND 
     Many electronic devices (e.g., desktop computers, laptop computers, mobile devices, and the like) include a keyboard as one of its input devices. There are several types of keyboards that are typically included in electronic devices. Each of these types is mainly differentiated by the switch technology employed. One of the most common keyboard types is the dome-switch keyboard. In an elastomeric dome-switch keyboard, for example, each key of the keyboard resides over a corresponding elastomeric (e.g., rubber) dome that may be a discrete component or part of an elastomeric pad. The elastomeric dome resides over a membrane that is sectioned into regions that each corresponds to a respective key and elastomeric dome. When a user depresses a particular key, the key moves downward from an initial position and displaces its corresponding elastomeric dome. As a result, the elastomeric dome buckles or collapses, which provides tactile feedback to the user. Moreover, when the elastomeric dome buckles, the elastomeric dome presses onto a corresponding region of the membrane and causes opposite facing electrical pads of that region to contact one another. This contact is detected by a processing unit (e.g., a chip), which generates a code corresponding to the key that is depressed. The key can move downward until it reaches a maximum displacement from its initial position. The total displacement from the initial position to the maximum displacement is referred to as the travel of the key. 
     It is often desirable to make devices, such as electronic devices and keyboards, lighter and smaller. For devices that include a dome-switch keyboard, one of the ways to achieve this is to decrease the amount of travel of the keys of the keyboard. However, a decrease in the travel of a key can affect the level of tactile feedback that the key provides to a user. 
     SUMMARY 
     A low travel dome and systems for using the same are provided. 
     In some embodiments, an elastomeric dome for use with a key is provided that includes a lower portion, an upper portion, and a wall that spans from the lower portion to the upper portion. Each of the wall, the lower portion, and the upper portion includes a physical property. The elastomeric dome is tuned to provide predefined tactile feedback over a predetermined travel amount of the key based on a predefined ratio between one of the physical properties and another one of the physical properties. 
     In some embodiments, an elastomeric dome for use with a key in a keyboard is provided. The elastomeric dome includes a footprint, a roof portion having a predetermined diameter, and a wall of a predetermined thickness that connects the roof portion to the footprint. A ratio between the predetermined thickness and the predetermined diameter is less than 10%. The elastomeric dome is operative to enable a keystroke of the key to undergo an abrupt force change when the keystroke is 1.25 millimeters or less. 
     In some embodiments a switch assembly is provided that includes a key cap, a hemispherical structure residing beneath the key cap and including an upper portion, a lower portion, and a domed surface extending from the upper portion to the lower portion. The domed surface has a predefined thickness, and the lower portion has an outer diameter. A ratio between the predetermined thickness and the outer diameter is one of less than and equal to 4%. The hemispherical structure is operative control movement of the key cap according to a predetermined force-displacement curve characteristic when the movement is less than a predetermined amount. 
     In some embodiments, an apparatus for use with a key of a keyboard is provided. The apparatus includes an inner dome at least partially surrounded by an outer dome. The inner dome has a first opening that faces a first direction, and the outer dome has a second opening that faces a direction opposite the first direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects and advantages of the invention will become more apparent upon consideration of the following detailed description, taken in conjunction with accompanying drawings, in which like reference characters refer to like parts throughout, and in which: 
         FIG. 1  is a cross-sectional view of a switch assembly that includes a low travel elastomeric dome, a key cap, a support structure, and a membrane, in accordance with at least one embodiment. 
         FIG. 2  is a cross-sectional view of the elastomeric dome of  FIG. 1 , in accordance with at least one embodiment. 
         FIG. 3  is a cross-sectional view of a switch assembly including the elastomeric dome of  FIG. 2  and the key cap of  FIG. 1 , in accordance with at least one embodiment. 
         FIG. 4  is a perspective view of the elastomeric dome of  FIG. 2 , in accordance with at least one embodiment. 
         FIG. 5  is a perspective view of a three-layer membrane of a PCB that may interact with the elastomeric dome of  FIG. 2 , in accordance with at least one embodiment. 
         FIG. 6  shows a predefined force-displacement curve according to which the key cap of  FIG. 3  and the elastomeric dome of  FIG. 2  may operate, in accordance with at least one embodiment. 
         FIG. 7  is a cross-sectional view of another elastomeric dome, in accordance with at least one embodiment. 
         FIG. 8  is a cross-sectional view of yet another elastomeric dome, in accordance with at least one embodiment. 
         FIG. 9  is a cross-sectional view of an elastomeric dome including air pockets therethrough, in accordance with at least one embodiment. 
         FIG. 10  is a perspective view of a double-wall dome, in accordance with at least one embodiment. 
         FIG. 11  is a cross-sectional view of the double-wall dome of  FIG. 10 , taken from a plane that extends in a Z-direction from the center of the doublewall dome, in accordance with at least one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A low travel dome and systems for using the same are described with reference to  FIGS. 1-10 . 
       FIG. 1  is a cross-sectional view of a switch assembly that includes a low travel elastomeric dome  100 , a key cap  200 , a support structure  300 , and a membrane  500 . Elastomeric dome  100  may be composed of any suitable type of material (e.g., plastic, rubber, metal, silicone, etc.), and may have a predefined durometer value. When a force is applied to elastomeric dome  100 , its elasticity may cause it to return to its original shape when the force is subsequently released. In some embodiments, elastomeric dome  100  may be one of a plurality of domes that may be a part of a dome pad or sheet (not shown). For example, elastomeric dome  100  may protrude from such a dome sheet in the positive Y-direction. This dome sheet may reside beneath a set of key caps (e.g., key cap  200 ) of a keyboard (not shown) such that each dome of the dome pad may reside beneath a particular key cap of the keyboard. In other embodiments, elastomeric dome  100  may be manufactured from and cut out from such a dome sheet as a discrete component. 
     As shown in  FIG. 1 , for example, elastomeric dome  100  may reside beneath key cap  200 . Key cap  200  may be supported by support structure  300 . Support structure  300  may be composed of any suitable material (e.g., plastic, metal, composite, etc.), and may provide mechanical stability to key cap  200 . Support structure  300  may, for example, be a scissor mechanism or a butterfly mechanism that may contract and expand during depression and release of key cap  200 , respectively. In some embodiments, rather than being a standalone scissor or butterfly mechanism, support structure  300  may be a part of an underside of key cap  200  that may press onto various portions of elastomeric dome  100 . Regardless of the physical nature of support structure  300 , key cap  200  may press onto elastomeric dome  100  to effect a switching operation or event via membrane  500  (described in more detail below with respect to  FIGS. 5-8 ). Although not shown in  FIG. 1 , key cap  200  may also include a lower end portion that may be configured to contact an uppermost portion of elastomeric dome  100  during depression of key cap  200 . 
       FIG. 1  may show key cap  200 , elastomeric dome  100 , support structure  300 , and membrane  500  in an under-pressed state (e.g., where each component may be in its respective natural position, prior to key cap  200  being depressed). Although  FIG. 1  does not show key cap  200 , elastomeric dome  100 , support structure  300 , and membrane  500  in a partially depressed or a fully depressed state, it should be appreciated that these components may occupy any of these states. 
     In addition to facilitating a switching event when a key cap is depressed, a dome of a dome-switch may also serve other purposes. As an example, the dome may cause the key cap to return to its natural state or position after the key cap is released from depression. As another example, the dome may provide tactical feedback to a user when the user depresses the key cap. The physical attributes (e.g., elasticity, size, shape, etc.) of the dome may determine the level of tactical feedback it provides. In particular, the physical attributes may define a relationship between the amount of force required to move the key cap (e.g., when the key cap rests over the dome) over a range of distances. This relationship may be expressed by a force-displacement curve, and the dome may operate according to this curve. 
     The amount of force required to move the key cap may vary depending on how far the key cap has moved from its natural position, and a user may experience the tactile feedback as a result of this variance. For example, the force required to move an uppermost portion of the dome from its natural or initial position to a first distance (e.g., right up to the point before the dome collapses or buckles) may be a force F 1 . 
     The force required to continue to move the uppermost portion past this first distance may be less than force F 1 . This is because the dome may buckle or collapse when the uppermost portion moves past the first distance, which may lessen the force required to continue to move the uppermost portion. 
     The force required to move the uppermost portion to a point when the dome is just completely buckled or collapsed may be a force F 2 . The force required to continue to move the uppermost portion until the key cap reaches its farthest or most depressed point may then increase. A user may thus experience a certain tactile feedback due to the force-displacement characteristics of the dome. 
     It should be appreciated that the tactile feedback can be quantified when the force-displacement characteristics of a dome are known. More particularly, the tactile feedback is a function of the click ratio (F 1 −F 2 )/F 1 , where F 1  is the force required to move the uppermost portion of the dome from its natural position to a distance right before the dome begins to buckle or collapse and F 2  is the force required to move the uppermost portion from its natural position to a distance when the dome is just completely buckled or collapsed. 
     Because a dome&#39;s tactile feedback is tied to the force-displacement characteristics of the dome, it should also be appreciated that force-displacement characteristics of a dome can be determined when an optimal or suitable tactile feedback is predefined. For example, a dome may provide optimal tactile feedback when a click ratio is about 50%. This click ratio may be used to determine force-displacement characteristics (e.g., force F 1  and force F 2 ) required to provide the optimal tactile feedback. Accordingly, because the physical attributes of the dome correspond to the force-displacement characteristics, the dome may be specifically constructed in order to meet these characteristics. 
     As described above, it is often desirable to make electronic devices and keyboards smaller. To accomplish this, some components of a device may need to be made smaller. Moreover, certain movable components of the device may also have less space to move, which may make it difficult for them to perform their intended functions. For example, the travel of the key caps of a keyboard will have to be smaller. However, a smaller travel requires a smaller or restricted range of movement of a corresponding dome, which may interfere with the dome&#39;s ability to operate according to its intended force-displacement characteristics and to provide suitable tactile feedback to a user. 
     Since the physical attributes of the dome are associated with the dome&#39;s tactile feedback, they may be adjusted, modified, or manipulated, or otherwise tuned to compensate for the smaller travel, while also providing the predefined optimal tactile feedback. 
     Certain physical attributes of a dome may be adjusted, modified, manipulated, or otherwise tuned to compensate for a specified travel, while also providing predefined tactile feedback. That is, certain physical attributes of a dome may be tuned such that the dome operates according to predetermined force-displacement curve characteristics. In some embodiments, the height, thickness, diameter, and various other dimensions of the dome may be tuned. In some embodiments, the dome may be tuned by determining ratios between certain dimensions (e.g., height, thickness, diameter, angle, etc.) of the dome that may allow the dome to operate according to the predetermined force-displacement curve characteristics. 
       FIG. 2  is a cross-sectional view of elastomeric dome  100 . Elastomeric dome  100  is axis-symmetric, therefore the right and left halves of dome  100  are mirror images of each other. Dome has footprint  130  defined by foot portion  131 . Foot portion  131  is coupled to roof portion  106  by wall  102 , which has thickness  103 . Wall  102  is a contiguous surface that may, for example, be hemispherically-shaped or domed-shaped, and may form a hollow cavity within. 
     Roof portion  106  may include a nub or contact surface  107 , a top surface  109 , and a recess  111  nestled within roof portion  106 . A key cap (e.g., key cap  200  of  FIG. 1 ) may reside over top surface  109  and recess  111 . When an external force is applied (e.g., via key cap  200 ) to any one of top surface  109  and recess  111 , roof portion  106  may move in the negative Y-direction, and may cause wall  102  and  104  (and thus, the contiguous wall) to change shape and buckle. When roof portion moves a sufficient distance in the negative Y-direction, contact surface  107  may contact a portion of a membrane of a keyboard (e.g., described below with respect to  FIG. 5 ) to trigger a switch event. 
       FIG. 3  is a cross-sectional view of a switch assembly including elastomeric dome  100  and key cap  200 .  FIG. 3  may be similar to  FIG. 1 , but does not show support structure  300 . In some embodiments, support structure  300  may not be necessary, and a switching assembly can include key cap  200 , elastomeric dome  100 , and membrane  500  (discussed below in more detail in connection  FIG. 5 ). Key cap  200  may include a cap surface  202  and an underside  204 . Underside  204  may reside over top surface  109  of roof portion  106 . When an external force A is applied (e.g., by a user) onto cap surface  204  in the negative Y-direction, the force may cause roof portion  106  to move in the negative Y-direction. Although not shown in  FIG. 3 , in some embodiments, key cap  200  may also include one or more protruding portions that may protrude from underside  204  in the negative Y-direction, and that may press onto any suitable portion elastomeric dome  100 . 
       FIG. 4  is a perspective view of elastomeric dome  100  of  FIG. 2 . As shown in  FIG. 4 , wall  102  extends from top surface  109  to top surface  133  of footprint  130 . As shown here, wall  102  exhibits a conically-shaped wall. 
       FIG. 5  is a perspective view of a three-layer membrane  500  of a printed circuit board (“PCB”) that may interact with elastomeric dome  100 . As described above with respect to  FIG. 2 , elastomeric dome  100  may be a component of a keyboard (not shown). In some embodiments, the keyboard may include a PCB and membrane that may provide key switching (e.g., when key cap  200  is depressed in the negative Y-direction via an external force A). As shown in  FIG. 5 , membrane  500  may reside beneath elastomeric dome  100 . Membrane  500  may include a top layer  502 , a bottom layer  506 , and a spacer layer  504  that may reside between top layer  502  and bottom layer  506 . In some embodiments, top layer  502  and bottom layer  506  may each have a thickness in the Y-direction of about 0.075 micrometers, and spacer layer  504  may have a thickness of about 0.05 micrometers. Each one of top layer  502 , spacer layer  504 , and bottom layer  506  may be composed of any suitable material (e.g., plastic, such as polyethylene terephthalate (“PET”) polymer sheets, etc.). For example, each one of top layer  502 , spacer layer  504 , and bottom layer  506  may be composed of PET polymer sheets that may each have a thickness in the range of about 0.025 millimeters to about 0.1 millimeters. 
     Top layer  502  may couple to or include a corresponding conductive pad  508 , and bottom layer  506  may couple to or include a corresponding conductive pad  510 . Conductive pad  508  may include conductive traces (not shown) on an underside of top layer  502 , and conductive pad  510  may include conductive traces (not shown) on an upper side of bottom layer  506 . Conductive pads  508  and  510  and the conductive traces may be composed of any suitable material (e.g., metal, such as silver or copper, etc.). 
     As shown in  FIG. 5 , spacer layer  504  may include voids  514  that may allow top layer  502  to contact bottom layer  506  when, for example, elastomeric dome  100  buckles and roof portion  106  moves in the negative Y-direction (e.g., due to external force A on key cap  200 ). In particular, voids  514  may allow conductive pad  508  physical access to conductive pad  510  such that their corresponding conductive traces may make contact with one another. This contact may then be detected by a processing unit (e.g., a chip of the electronic device or keyboard), which may generate a code corresponding to key cap  200 . 
     Although  FIG. 5  shows a specific layered membrane that may be used to trigger a switch event, it should be appreciated that other mechanisms may also be used to trigger the switch event. For example, in some embodiments, nub  107  of elastomeric dome  100  may be conductive or may include a conductive material. In these embodiments, a separate conductive material may also reside beneath nub  107 . When a keystroke occurs (e.g., when external force A is applied to key cap  200 ), the nub  107  (or the conductive material of nub  107 ) may contact the separate conductive material, which may trigger the switch event. 
     Operating characteristics of a dome-switch key can be defined using a force-displacement curve.  FIG. 6  shows a predefined force-displacement curve  600  according to which the combination of key cap  200  and elastomeric dome  100  may operate. The F-axis may represent the force (in grams) that is applied to key cap  200 , and the D-axis may represent the displacement of key cap  200  in response to the applied force. 
     The force required to depress key cap  200  from its natural position  220  (e.g., the position of key cap  200  prior to any force being applied thereto, as shown in  FIG. 2 ) to a maximum displacement position  250  (e.g., as shown in  FIG. 2 ) may vary. As shown in  FIG. 6 , for example, the force required to displace key cap  200  may gradually increase as key cap  200  displaces in the negative Y-direction from natural position  220  (e.g., 0 millimeters) to a position  230  (e.g., VIa millimeters). This gradual increase in required force is at least partially due to the resistance of elastomeric dome  100  to change shape (e.g., the resistance of roof portion  106  to displace in the negative Y-direction). The force required to displace key cap  200  to position  230  may be referred to as the operating or peak force. 
     When key cap  200  displaces to position  230  (e.g., VIa millimeters), elastomeric dome  100  may no longer be able to resist the pressure, and wall  102  may begin to buckle. The force that is subsequently required to displace key cap  200  from position  230  (e.g., VIa millimeters) to a position  240  (e.g., VIb millimeters) may gradually decrease. 
     When key cap  200  displaces to position  240  (e.g., VIb millimeters), contact surface  107  of elastomeric  100  may contact membrane  500  to cause or trigger a switch event or operation. In some embodiments, contact surface  107  may contact membrane  500  slightly prior to or slightly after key cap  200  displaces to position  240 . When contact surface  107  contacts membrane  500 , membrane  500  may provide a counter force in the positive Y-direction, which may increase the force required to continue to displace key cap  200  beyond position  240 . The force required to displace key cap  200  to position  240  may be referred to as the draw or return force. 
     When key cap  200  displaces to position  240 , elastomeric dome  100  may also be complete in its buckling. In some embodiments, roof portion  106  may continue to displace in the negative Y-direction, but the wall of elastomeric dome  100  may be substantially buckled. The force that is subsequently required to displace key cap  200  from position  240  (e.g., VIb millimeters) to position  250  (e.g., VIc millimeters) may gradually increase. Position  250  may be the maximum displacement position of key cap  200  (e.g., a bottom-out position). When the force (e.g., external force A) is removed from key cap  200 , elastomeric dome  100  may then unbuckle and return to its natural position, and key cap may also return to natural position  220 . 
     In some embodiments, one or more portions that may protrude from underside  204  of key cap  200  may contact top surface  133  of lower portion  130 . The size or height of these protruding portions may be defined to determine the maximum displacement position  250  or travel of key cap  200  in the negative Y-direction. For example, the travel of key cap  200  may be defined to be about 0.75 millimeter, 1.0 millimeter, or 1.25 millimeters. 
     To provide a predefined tactile feedback to the user pressing key cap  200 , force VIr (required to displace key cap from natural position  220  to position  230 ) and force VIq (required to displace key cap  200  from position  230  to position  240 ) of elastomeric dome  100  may have a predefined relationship. In particular, the level of tactile feedback may be a function of the ratio (e.g., click ratio) of VIr to VIq. The click ratio may be calculated as: [(VIr−VIq)/VIr]×100. In some embodiments, for example, the predefined level of tactile feedback may be provided when the click ratio is set to 50%. For example, a click ratio that is lower than 50% may provide insufficient tactile feedback to a user (e.g., elastomeric dome  100  may be too soft or mushy). In contrast, a click ratio that is higher than 50% may provide too much tactile feedback, making it difficult for the user to depress key cap  200  (e.g., elastomeric dome  100  may be too stiff or hard). 
     It should be appreciated that a variety of factors may affect the ability of elastomeric dome  100  to operate according to force-displacement curve  600 . For example, any one of the physical characteristics (e.g., size, shape, material composition characteristics (e.g., hardness, elasticity, etc.), and the like) of elastomeric dome  100  may be defined such that elastomeric dome  100  may operate according to force-displacement curve  600 . 
     Moreover, in making an electronic device smaller or thinner (and thus decreasing the travel of the keys of the keyboard), physical dimensions of an elastomeric dome may be further defined based on spacing requirements. 
     For example, in some embodiments, the travel of key cap  200  may be defined to be at most 1.25 millimeters. In these embodiments, for example, lower portion  130  of elastomeric dome  100  may have a thickness that is less than a predefined thickness. As another example, height h 1  of elastomeric dome  100  may be less than a predefined height. For example, height h 1  may be less than or equal to 2.10 millimeters. In this example, contact distance c 1  between contact surface  107  of roof portion  106  and a plane that is parallel to bottom surface  134  of elastomeric dome  100  may also be less than a predefined contact distance. For example, contact distance c 1  may be less than or equal to 0.82 millimeters. It should be appreciated that the smaller the height of elastomeric dome  100 , the less roof portion  106  may displace prior to contacting membrane  500 . As yet another example, diameter d 1  (e.g., the outer diameter of the footprint) of elastomeric dome  100  may be less than a predefined diameter. For example, outer diameter d 1  may be less than or equal to 6.00 millimeters. 
     The aforementioned lower portion thickness, dome height, roof portion and membrane contact distance, and outer diameter may, for example, allow the elastomeric dome  100  to conform to strict spacing requirements within an electronic device or keyboard housing, and meet a predefined travel (e.g., 1.25 millimeters) of key cap  200 . In some embodiments, these defined parameters may also allow elastomeric dome  100  to operate according to predetermined force-displacement curve  600  (and thus, provide a specified tactile feedback). In some embodiments, other features of elastomeric dome  100  may also be specifically defined. In particular, an angle between wall  102  and a plane that is parallel to bottom surface  134  of elastomeric dome  100  may be less than a predefined angle. For example, angle θ 1  between wall portion  102  and the plane that is parallel to bottom surface  134  may be less than or equal to a predefined angle (e.g., 50 degrees). 
     Additionally, thickness  103  wall  102  of elastomeric dome  100  may be less than a predefined thickness. For example, thickness  103  may be about equal to one another, and may be less than or equal to 0.24 millimeters. In this manner, elastomeric dome  100  may begin to buckle when key cap  200  displaces a predefined distance (e.g., VIa millimeters), and may also provide a predetermined click ratio (e.g., 50%). 
     Moreover, the hardness of the material of elastomeric dome  100  may be greater than a predefined hardness such that thinner a wall may not buckle as easily (e.g., such that the wall of elastomeric dome  100  does not buckle prior to key cap  200  reaching position  230 ). In this manner, elastomeric dome  100  may operate according to force-displacement curve  600 . 
     In some embodiments, a width or diameter of roof portion  106  may be greater than a predetermined diameter. For example, diameter r 1  of roof portion  106  may be greater than or equal to 3.17 millimeters. A wider roof portion may, for example, compensate for a weakened structural integrity of elastomeric dome  100  due to thinner wall portions. 
     In some embodiments, elastomeric dome  100  may be configured such that a ratio between thickness  103  (or thickness  105 ) and diameter r 1  is less than or equal to a predetermined value (e.g., 10%). For example, the ratio between a thickness  103  of 0.24 millimeters and a diameter r 1  of 3.17 millimeters may be calculated as: (0.24/3.17)×100=7.57%. In some embodiments, elastomeric dome  100  may be configured such that a ratio between thickness  103  and outer diameter d 1  may be less than or equal to a predetermined value (e.g., 4%). For example, the ratio between a thickness  103  of 0.24 millimeters and an outer diameter d 1  of 6 millimeters may be calculated as: (0.24/6)×100=4%. In some embodiments, elastomeric dome  100  may be configured such that a ratio between thickness  103  and height h 1  may be less than or equal to a predetermined value (e.g., 12%). For example, the ratio between a thickness  103  of 0.24 millimeters and a height h 1  of 2.10 millimeters may be calculated as: (0.24/2.10)×100=11.4%. For example, the ratio between a thickness  103  of 0.24 millimeters and a height h 1  of 2.10 millimeters may be calculated as: (0.24/2.10)×100=11.4%. Elastomeric dome  100  may be configured to have any of these ratios so as to operate according to force-displacement curve  600 . 
     Thus, various physical characteristics of elastomeric dome  100  can be defined based on spacing requirements of an electronic device or keyboard housing, the travel of key cap  200  of a keyboard, and predefined force-displacement curve  600  to provide a low travel switch. 
       FIG. 7  is a cross-sectional view of an elastomeric dome  700 . Elastomeric dome  700  is axis-symmetric, therefore the right and left halves of dome  700  are mirror images of each other. Dome  700  has footprint  730  defined by foot portion  731 . Foot portion  731  is coupled to roof portion  706  by wall  702 , which has thickness  703 . 
     Roof portion  706  may include a contact surface  707 , a top surface  709 , and a recess  711  on to surface  709 . A key cap (e.g., key cap  200 ) may reside over top surface  709  and recess  711 . When an external force is applied (e.g., from the key cap  200 ) to any one of top surface  709  and recess  711 , roof portion  706  may move in the negative Y-direction, and may cause wall  702  to change shape and buckle. As a result, contact surface  707  may contact a portion of a membrane of a keyboard (e.g., membrane  500 ) when roof portion  706  moves a sufficient distance in the negative Y-direction. 
     Similar to elastomeric dome  100 , elastomeric dome  700  may be configured based on spacing requirements, as well as to provide a predefined travel (e.g., of keys of a keyboard). In some embodiments, elastomeric dome  700  may be configured to provide a predefined travel of at most 1.00 millimeters. In these embodiments, for example, height h 2  of elastomeric dome  700  may be less than a predefined height. For example, height h 2  may be less than or equal to 1.90 millimeters. In this example, contact distance c 2  between the contact surface  707  of roof portion  706  and a plane that is parallel to bottom surface  734  of elastomeric dome  700  may also be less than a predefined contact distance. For example, contact distance c 2  may be less than or equal to 0.63 millimeters. It should be appreciated that the smaller the height of elastomeric dome  700 , the less roof portion  706  may displace prior to contacting a membrane (e.g., membrane  500 ). As yet another example, diameter d 2  of elastomeric dome  700  (e.g., the outer diameter of the footprint) may be less than a predefined diameter. For example, outer diameter d 2  may be less than or equal to 6.00 millimeters. 
     Similar to elastomeric dome  100 , the aforementioned dome height, roof portion and membrane contact distance, and dome diameter may, for example, allow elastomeric dome  700  to conform to strict spacing requirements within an electronic device or keyboard housing, and may meet a predefined travel (e.g., 1.00 millimeters) of the keys of the keyboard. In some embodiments, these defined parameters may also allow the elastomeric dome to operate according to a predetermined force-displacement curve (and thus, provide a specified tactile feedback). In some embodiments, other features of elastomeric dome  700  may also be specifically defined. In particular, an angle between a wall portion (or contiguous wall) of elastomeric dome  700  and the plane that is parallel to bottom surface  734  of elastomeric dome  700  may be less than a predefined angle. For example, angle θ 2  between wall  702  and the plane that is parallel to bottom surface  734  may be less than or equal to a predefined angle (e.g., 51 degrees). 
     Additionally, thickness  703  of wall  702  may be less than a predefined thickness. For example, thickness  703  may be about equal to one another, and may be less than or equal to 0.21 millimeters. In this manner, elastomeric dome  700  may begin to buckle when the roof portion  706  displaces a predefined distance, and may also provide a predetermined click ratio (e.g., 50%). 
     Moreover, the hardness of the material of elastomeric dome  700  (e.g., silicone) may be greater than a predefined hardness such that a thinner wall does not buckle as easily (e.g., such that wall  702  of elastomeric dome  700  does not buckle prior to key cap  200  reaching a position that may be similar to position  230 ). 
     In some embodiments, a width or diameter of the roof portion of elastomeric dome may  700  be greater than a predetermined diameter. For example, diameter r 2  of roof portion  706  may be greater than or equal to 3.19 millimeters. A wider roof portion may, for example, compensate for a weakened structural integrity of elastomeric dome  700  due to thinner wall portions. 
     In some embodiments, elastomeric dome  700  may be configured such that a ratio between thickness  703  and diameter r 2  is less than or equal to a predetermined value (e.g., 10%). For example, the ratio between a thickness  703  of 0.21 millimeters and a diameter r 2  of 3.19 millimeters may be calculated as: (0.21/3.19)×100=6.58%. In some embodiments, elastomeric dome  700  may be configured such that a ratio between thickness  703  and outer diameter d 2  may be less than or equal to a predetermined value (e.g., 4%). For example, the ratio between a thickness  703  of 0.21 millimeters and an outer diameter d 2  of 6 millimeters may be calculated as: (0.21/6)×100 3.5%. In some embodiments, elastomeric dome  700  may be configured such that a ratio between thickness  703  and height h 2  may be less than or equal to a predetermined value (e.g., 12%). For example, the ratio between a thickness  703  of 0.21 millimeters and a height h 2  of 1.9 millimeters may be calculated as: (0.21/1.9)×100 11.05%. Elastomeric dome  700  may be configured to have any of these ratios in order that elastomeric dome  700  may operate according to a force-displacement curve that may be similar to force-displacement curve  600 . 
     Thus, various physical characteristics of elastomeric dome  700  can be defined based on spacing requirements of an electronic device or keyboard housing, the travel of the keys of the keyboard, and a predefined force-displacement curve. 
       FIG. 8  is a cross-sectional view of elastomeric dome  800 . Elastomeric dome  800  is axis-symmetric, therefore the right and left halves of dome  800  are mirror images of each other. Dome has footprint  830  defined by foot portion  831 . Foot portion  831  is coupled to roof portion  806  by wall  802 , which has thickness  803 . 
     Roof portion  806  may include a contact surface  807 , a top surface  809 , and a recess  811  on to surface  809 . A key cap (e.g., key cap  200 ) may reside over top surface  809  and recess  811 . When an external force is applied (e.g., from the key cap  200 ) to any one of top surface  809  and recess  811 , roof portion  806  may move in the negative Y-direction, and may cause wall portions  802  and  804  (and thus, a contiguous wall) to change shape and buckle. As a result, contact surface  807  may contact a portion of a membrane of a keyboard (e.g., membrane  500 ) when roof portion  806  moves a sufficient distance in the negative Y-direction. 
     Similar to elastomeric dome  100 , elastomeric dome  800  may be configured based on spacing requirements, as well as to provide a predefined travel (e.g., of keys of a keyboard). In some embodiments, elastomeric dome  800  may be configured to provide a predefined travel of at most 0.75 millimeters. In these embodiments, for example, height h3 of elastomeric dome  800  may be less than a predefined height. For example, height h 3  may be less than or equal to 1.70 millimeters. In this example, contact distance c 3  between the contact surface  807  of roof portion  806  and a plane that is parallel to bottom surface  834  of elastomeric dome  800  may also be less than a predefined contact distance. For example, contact distance c 3  may be less than or equal to 0.55 millimeters. It should be appreciated that the smaller the height of elastomeric dome  800 , the less roof portion  806  may displace prior to contacting a membrane (e.g., membrane  500 ). As yet another example, diameter d 3  of elastomeric dome  800  (e.g., the outer diameter of the footprint) may be less than a predefined diameter. For example, outer diameter d 3  may be less than or equal to 5.60 millimeters. 
     Similar to elastomeric dome  100 , the aforementioned dome height, roof portion and membrane contact distance, and dome diameter may, for example, allow elastomeric dome  800  to conform to strict spacing requirements within an electronic device or keyboard housing, and may meet a predefined travel (e.g., 1.00 millimeters) of the keys of the keyboard. In some embodiments, these defined parameters may also allow the elastomeric dome to operate according to a predetermined force-displacement curve (and thus, provide a specified tactile feedback). In some embodiments, other features of elastomeric dome  800  may also be specifically defined. In particular, an angle between a wall portion (and thus, a contiguous wall) of elastomeric dome  800  and the plane that is parallel to bottom surface  834  of elastomeric dome  800  may be less than a predefined angle. For example, angle θ 3  between wall  802  and the plane that is parallel to bottom surface  834  may be less than or equal to a predefined angle (e.g., 51 degrees). 
     Additionally, thickness  803  may be less than a predefined thickness. For example, thicknesses  803  may be about equal to one another, and may be less than or equal to 0.19 millimeters. In this manner, elastomeric dome  800  may begin to buckle when the roof portion  806  displaces a predefined distance, and may also provide a predetermined click ratio (e.g., 50%). 
     Moreover, the hardness of the material of elastomeric dome  800  (e.g., silicone) may be greater than a predefined hardness such that a thinner wall may not buckle as easily (e.g., such that wall  802  does not buckle prior to key cap  200  reaching a position that may be similar to position  230 ). 
     In some embodiments, a width or diameter of the roof portion of elastomeric dome may  800  be greater than a predetermined diameter. For example, diameter r 3  of roof portion  806  may be greater than or equal to 3.16 millimeters. A wider roof portion may, for example, compensate for a weakened structural integrity of elastomeric dome  800  due to thinner wall portions. 
     In some embodiments, elastomeric dome  800  may be configured such that a ratio between thickness  803  and diameter r 3  is less than or equal to a predetermined value (e.g., 10%). For example, the ratio between a thickness  803  of 0.19 millimeters and a diameter r 3  of 3.16 millimeters may be calculated as: (0.19/3.16)×100=6.01%. In some embodiments, elastomeric dome  800  may be configured such that a ratio between thickness  803  and outer diameter d 3  may be less than or equal to a predetermined value (e.g., 4%). For example, the ratio between a thickness  803  of 0.19 millimeters and an outer diameter d 3  of 5.6 millimeters may be calculated as: (0.19/5.6)×100 3.39%. In some embodiments, elastomeric dome  800  may be configured such that a ratio between thickness  803  and height h 3  may be less than or equal to a predetermined value (e.g., 12%). For example, the ratio between a thickness  803  of 0.19 millimeters and a height h 3  of 1.7 millimeters may be calculated as: (0.19/1.7)×100=11.2%. Elastomeric dome  800  may be configured to have any of these ratios in order that elastomeric dome  800  may operate according to a force-displacement curve that may be similar to force-displacement curve  600 . 
     Thus, various physical characteristics of elastomeric dome  800  can be defined based on spacing requirements of an electronic device or keyboard housing, the travel of the keys of the keyboard, and a predefined force-displacement curve. 
       FIG. 9  is a cross-sectional view of elastomeric dome  900  including a wall  902  having air pockets  952  and  954  incorporated therein. As shown in  FIG. 9 , elastomeric dome  900  may be similar to each one of elastomeric domes  100 ,  700 , and  800 , and include similar components such as wall  902 , roof portion  906 , and foot  931 , which forms footprint  930   
     Air pockets  952  and  954  may have any suitable size and shape. In some embodiments, the size and shape of air pockets  952  and  954  may be defined based on a predefined key cap travel amount, and such that elastomeric dome  900  may operate according to a force-displacement curve that may be similar to force-displacement curve  600 . In some embodiments, wall  902  may include any number of air pockets, even though only two are shown. In these embodiments, the size and shape of each one of these air pockets may be defined such that elastomeric dome  900  may operate according to a force-displacement curve that may be similar to force-displacement curve  600 . 
     In making devices smaller (and thus decreasing the travel amount of keys), a thickness of a wall of a dome may also need to be made smaller. However, as described above, a thickness of a wall of a dome may be associated with the dome&#39;s ability to provide sufficient tactile feedback to a user upon depression of a corresponding key. For example, a thinner wall may buckle more easily, but may provide less tactile feedback, making it difficult for the dome to operate according to a predefined force-displacement curve. Thus, in some embodiments, a dome having multiple thin walls may be provided. The dome may be operative to buckle easily (e.g., according to a predefined force-displacement curve) over a predefined travel, while also providing sufficient tactile feedback to a user. 
       FIG. 10  is a perspective view of a double-wall dome  1000 .  FIG. 11  is a cross-sectional view of doublewall dome  1000 , taken from a plane that extends in the Z-direction from the center of double-wall dome  100 . Dome  1000  may be composed of any suitable material (e.g., similar to elastomeric dome  100 ), and may resemble a smaller dome in an up-right orientation disposed within or at least partially surrounded by a larger dome in an upside down orientation. In particular, dome  1000  may include a lower portion or footprint  1030 , and upper rim portion  1040 , and an outer hemi-spherical surface  1050  that may extend from lower portion  1030  to upper rim portion  1040 . In addition, dome  1000  may include a roof portion  1010  and an inner hemi-spherical surface  1020  that may extend from lower portion  1030  to roof portion  1010 . Roof portion  1010  may include a hole  1014  that may lead to a cavity or opening  1060  therein that may span from an inner side of lower portion  1030  to roof portion  1010 , and that may face the −Z-direction. Dome  1000  may also include a cavity or opening  1052  that may span from lower portion  1030  to upper rim portion  1040 , and that may face the positive Z-direction. 
     It can be appreciated that, if dome  1000  did not include inner-hemispherical surface  1020  and roof portion  1010 , then dome  1000  would be an upside down dome including upper rim portion  1040 , lower portion  1030 , and outer-hemispherical surface  1050 . Similarly, if dome  1000  did not include outer-hemispherical surface  1050  and upper rim portion  1040 , then dome  1000  would be an upright dome including lower portion  1030 , inner-hemispherical surface  1020 , and roof portion  1010  (e.g., similar to elastomeric dome  100 ). 
     As described above, multiple thin walls may allow a dome to buckle easily (e.g., according to a predefined force-displacement curve) over a predefined travel, while also providing sufficient tactile feedback to a user. Thus, each one of inner and outer hemispherical surfaces  1020  and  1050  may have a predefined thickness. In some embodiments, inner and outer hemispherical surfaces  1020  and  1050  may have substantially the same thickness. In other embodiments, inner and outer hemi-spherical surfaces  1020  and  1050  may have different thicknesses. 
     As shown in  FIG. 10 , lower portion  1030  may have a diameter of d 4 , upper rim portion  1040  may have an outer diameter of d 5  and an inner diameter of d 6 . Roof portion may have a diameter of d 7  that may be smaller than any one of diameters d 4 , d 5 , and d6. Moreover, dome  1000  may have a predefined height h 4  that may accommodate a shorter predefined travel amount. Similar to elastomeric domes  100 ,  700 , and  800 , any one of diameters d 4 -d 7  and height h 4  may also be tuned or predefined such that dome  1000  may operate according to a predefined force-displacement curve over a predefined travel, while also providing sufficient tactile feedback to a user. 
     In some embodiments, top surface  1012  of roof portion  1010  may be level or on the same plane as top surface  1042  of upper rim portion  1040 . In these embodiments, one or more of top surfaces  1012  and  1042  may interface with a portion of a key cap (e.g., key cap  200 ) to receive a force in the −Z-direction (e.g., when key cap  200  is depressed by a user). Each one of inner and outer hemi-spherical surfaces  1020  and  1050  (e.g., tending to buckle more easily due to its smaller thickness) may receive the force from the key cap, and, in combination, may buckle according to a predefined force-displacement curve, while providing sufficient tactile feedback to a user. In other embodiments, top surface  1012  may be higher in the positive Z-direction than top surface  1042 . In yet other embodiments, top surface  1042  may be higher in the positive Z-direction than top surface  1012 . 
     While there have been described a low travel dome and systems for using the same, it is to be understood that many changes may be made therein without departing from the spirit and scope of the invention. Insubstantial changes from the claimed subject matter as viewed by a person with ordinary skill in the art, now known or later devised, are expressly contemplated as being equivalently within the scope of the claims. Therefore, obvious substitutions now or later known to one with ordinary skill in the art are defined to be within the scope of the defined elements. It is also to be understood that various directional and orientational terms such as “up” and “down,” “front” and “back,” “top” and “bottom,” “left” and “right,” “length” and “width,” and the like are used herein only for convenience, and that no fixed or absolute directional or orientational limitations are intended by the use of these words. For example, the devices of this invention can have any desired orientation. If reoriented, different directional or orientational terms may need to be used in their description, but that will not alter their fundamental nature as within the scope and spirit of this invention. Moreover, an electronic device constructed in accordance with the principles of the invention may be of any suitable three-dimensional shape, including, but not limited to, a sphere, cone, octahedron, or combination thereof. 
     Therefore, those skilled in the art will appreciate that the invention can be practiced by other than the described embodiments, which are presented for purposes of illustration rather than of limitation.

Metadata:
Filing Date: 20131029
Publication Date: 20160920
Grant Date: 20160920
Priority Date: 20121030
Inventors: LEONG CRAIG C.
NIU JAMES J.
BROCK JOHN M.
HENDREN KEITH J.
WILSON, JR. THOMAS W.
Assignee: APPLE INC
CPC Classifications: [{"code": "H01H13/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H2215/006", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2215/02", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/85", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H13/85", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H2215/006", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2215/02", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50545987