PATENT DOCUMENT

Publication Number: US-9412533-B2
Application Number: US-201414287915-A
Country: US
Kind Code: B2

Title: Low travel switch assembly

Abstract:
A low travel switch assembly and systems and methods for using the same are disclosed. The low travel dome may include a domed surface having upper and lower portions, and a set of tuning members integrated within the domed surface between the upper and lower portions. The tuning members may be operative to control a force-displacement curve characteristic of the low travel dome.

Claims:
What is claimed is: 
     
       1. A low travel dome comprising:
 a domed surface having upper and lower portions; 
 an array of tuning members integrated within the domed surface between the upper and lower portions, the array of tuning members operative to control a force-displacement curve characteristic of the low travel dome; and 
 wherein the domed surface defines the tuning members and an array of radially-distributed arms separating each of the array of tuning members. 
 
     
     
       2. The low travel dome of  claim 1 , wherein the force-displacement curve characteristic comprises a variation in a force required to displace the upper portion over a range of predefined distances. 
     
     
       3. The low travel dome of  claim 1 , wherein the domed surface is formed from metal. 
     
     
       4. The low travel dome of  claim 1 , wherein each one of the array of tuning members comprises a cutout of the domed surface. 
     
     
       5. The low travel dome of  claim 4 , wherein the cutout is one of L-shaped and wedge-shaped. 
     
     
       6. The low travel dome of  claim 1 , wherein the tuning members are further operative to provide tactile feedback to a user according to the force-displacement curve characteristic. 
     
     
       7. The low travel dome of  claim 1 , wherein the upper portion comprises an uppermost point of the domed surface. 
     
     
       8. The low travel dome of  claim 1 , wherein the lower portion comprises one of a circular, a polygonal, a square, and an elliptical shape. 
     
     
       9. The low travel dome of  claim 1 , wherein the domed surface comprises a cross-shaped portion. 
     
     
       10. The low travel dome of  claim 1 , wherein the array of radially-distributed arms each extend from the upper portion to the lower portion. 
     
     
       11. The low travel dome of  claim 1 , wherein the cross-shaped portion is operative to buckle when a predefined force is applied to the upper portion. 
     
     
       12. A method for manufacturing a low travel dome, the method comprising:
 providing a dome-shaped surface having an upper portion and a lower portion; 
 selectively removing an array of predefined portions of the dome-shaped surface between the upper portion and the lower portion, thereby defining an array of arms connecting the upper portion to the lower portion; and 
 wherein:
 a shape of each of the array of the predefined portions defines a force-displacement curve characteristic of the low travel dome; and 
 the array of arms defines a cross-shaped portion of the dome-shaped surface. 
 
 
     
     
       13. The method of  claim 12 , wherein the selectively removing comprises forming openings at the array of predefined portions, each of the openings having a predefined shape. 
     
     
       14. The method of  claim 13 , wherein the selectively removing comprises one of cutting out and stamping out the array of predefined portions. 
     
     
       15. The method of  claim 12 , 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. 
     
     
       16. A switch assembly comprising:
 a key cap; 
 a support structure residing under the key cap; 
 a domed surface disposed beneath the key cap and having an array of openings formed therein defining an array of arms connecting a central portion of the domed surface to an outer edge of the domed surface, wherein one of the array of arms is disposed transverse to another of the array of arms; and 
 an electrical membrane situated below the domed surface and operative to trigger a switch event, wherein the array of openings are operative to:
 maintain the switch assembly in position when the electrical membrane is not triggering the switch event; and 
 control the domed surface to behave according to a predefined force-displacement curve. 
 
 
     
     
       17. The switch assembly of  claim 16 , wherein the support structure is operative to provide support for the key cap. 
     
     
       18. The switch assembly of  claim 16 , wherein the support structure comprises one of a scissor mechanism and a butterfly mechanism. 
     
     
       19. The switch assembly of  claim 16 , wherein the domed surface is operative to at least partially collapse according to the predefined force-displacement curve when the key cap presses onto an upper portion of the domed surface. 
     
     
       20. The switch assembly of  claim 16 , wherein the key cap is operative to travel at most 0.5 millimeters. 
     
     
       21. The switch assembly of  claim 16 , wherein the electrical membrane comprises a top layer and a bottom layer. 
     
     
       22. The switch assembly of  claim 21 , wherein each one of the top layer and the bottom layer is coupled to a corresponding conductive gel that provides support to the key cap and the domed surface when the key cap displaces towards the electrical membrane. 
     
     
       23. The switch assembly of  claim 21 , further comprising a support layer residing beneath the bottom layer and having a through-hole aligned with an upper portion of the domed surface. 
     
     
       24. The switch assembly of  claim 16 , wherein the domed surface comprises a substantially square base. 
     
     
       25. The switch assembly of  claim 24 , wherein the substantially square base includes at least one angled edge.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a nonprovisional patent application and claims the benefit of U.S. Provisional Patent Application No. 61/827,708, filed May 27, 2013 and titled “Low Travel Switch Assembly,” the disclosure of which is hereby incorporated herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     Embodiments described herein may relate generally to a switch for an input device, and may more specifically relate to a low travel switch assembly for a keyboard or other input device. 
     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. These types are mainly differentiated by the switch technology that they employ. One of the most common keyboard types is the dome-switch keyboard. A dome-switch keyboard includes at least a key cap, a layered electrical membrane, and an elastic dome disposed between the key cap and the layered electrical membrane. When the key cap is depressed from its original position, an uppermost portion of the elastic dome moves or displaces downward (from its original position) and contacts the layered electrical membrane to cause a switching operation or event. When the key cap is subsequently released, the uppermost portion of the elastic dome returns to its original position, and forces the key cap to also move back to its original position. 
     In addition to facilitating a switching event, a typical elastic dome also provides tactile feedback to a user depressing the key cap. A typical elastic dome provides this tactile feedback by behaving in a certain manner (e.g., by changing shape, buckling, unbuckling, etc.) when it is depressed and released over a range of distances. This behavior is typically characterized by a force-displacement curve that defines the amount of force required to move the key cap (while resting over the elastic dome) a certain distance from its natural position. 
     It is often desirable to make electronic devices and keyboards smaller. To accomplish this, some components of the 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, a typical key cap is designed to move a certain maximum distance when it is depressed. The total distance from the key cap&#39;s natural (undepressed) position to its farthest (depressed) position is often referred to as the “travel” or “travel amount.” When a device is made smaller, this travel may need to be smaller. However, a smaller travel requires a smaller or restricted range of movement of a corresponding elastic dome, which may interfere with the elastic dome&#39;s ability to operate according to its intended force-displacement characteristics and to provide suitable tactile feedback to a user. 
     SUMMARY OF THE DISCLOSURE 
     A low travel switch assembly and systems and methods for using the same are provided. 
     In some embodiments, a low travel dome is provided that includes a domed surface having upper and lower portions, and a set of tuning members integrated within the domed surface between the upper and lower portions. The tuning members may be operative to control a force-displacement curve characteristic of the low travel dome. Further, the domed surface may define the tuning members and at least one region separating the tuning members. 
     In some embodiments, a method for manufacturing a low travel dome by selectively removing a set of predefined portions of the dome-shaped surface to tune the dome-shaped surface to operate according to a predefined force-displacement curve characteristic. 
     In some embodiments, a switch assembly is provided that includes a key cap, a support structure residing under the key cap, a domed surface disposed beneath the key cap and having a set of openings formed thereon, and an electrical membrane situated below the domed surface and operative to trigger a switch event. The set of openings may be operative to maintain the switch assembly in position when the electrical membrane is not triggering the switch event, and control the switch assembly to behave according to a predefined force-displacement curve. 
    
    
     
       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 mechanism that includes a low travel dome, a key cap, a support structure, and a membrane, in accordance with at least one embodiment; 
         FIG. 2  is a perspective view of the low travel dome of  FIG. 1 , in accordance with at least one embodiment; 
         FIG. 3  is a top view of the low travel dome of  FIG. 2 , in accordance with at least one embodiment; 
         FIG. 4  is a cross-sectional view of the low travel dome of  FIG. 3 , taken from line A-A of  FIG. 3 , in accordance with at least one embodiment; 
         FIG. 5  is a cross-sectional view, similar to  FIG. 4 , of the low travel dome of  FIG. 3 , the low travel dome residing between the key cap and the membrane of  FIG. 1  in a first state, in accordance with at least one embodiment; 
         FIG. 6  is a cross-sectional view, similar to  FIG. 5 , of the low travel dome, the key cap, and the membrane of  FIG. 5  in a second state, in accordance with at least one embodiment; 
         FIG. 7  is a cross-sectional view, similar to  FIG. 5 , of the low travel dome, the key cap, and the membrane of  FIG. 5  in a third state, in accordance with at least one embodiment; 
         FIG. 8  is a cross-sectional view, similar to  FIG. 5 , of the low travel dome, the key cap, and the membrane of  FIG. 5  in a fourth state, in accordance with at least one embodiment; 
         FIG. 9  shows a predefined force-displacement curve according to which the key cap and the low travel dome of  FIGS. 5-8  may operate, in accordance with at least one embodiment; 
         FIG. 10  is a top view of another low travel dome, in accordance with at least one embodiment; 
         FIG. 11  is a top down view of yet another low travel dome, in accordance with at least one embodiment; 
         FIG. 12  is a cross-sectional view, similar to  FIG. 4 , of the low travel dome of  FIG. 3  including a nub, in accordance with at least one embodiment; 
         FIG. 13  is an illustrative process of providing the low travel dome of  FIG. 2 , in accordance with at least one embodiment; and 
         FIG. 14  is a top view of yet another sample low travel dome. 
     
    
    
     DETAILED DESCRIPTION 
     A low travel switch assembly and systems and methods for using the same are described with reference to  FIGS. 1-13 . 
       FIG. 1  is a cross-sectional view of a switch mechanism that includes a low travel dome  100 , a key cap  200 , a support structure  300 , and a membrane  500 . Low travel dome  100  may be composed of any suitable type of material (e.g., metal, rubber, etc.) and may be elastic. For example, when a force is applied to low travel dome  100 , its elasticity may cause it to return to its original shape when the force is subsequently released. In some embodiments, low travel 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, low travel dome  100  may protrude from such a dome sheet in the +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. 
     As shown in  FIG. 1 , for example, low travel 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, and so on), 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 low travel dome  100 . Regardless of the physical nature of support structure  300 , key cap  200  may press onto low travel 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 low travel dome  100  during depression of key cap  200 . 
       FIG. 1  may show key cap  200 , low travel dome  100 , support structure  300 , and membrane  500  in an undepressed 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 , low travel 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, and the like) 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 ratio (e.g., click ratio) of 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 (e.g., force F 1 ) to the force required to move the uppermost portion from its natural position to a distance when the dome is just completely buckled or collapsed (e.g., force F 2 ). 
     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 the 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, manipulated, or otherwise tuned to compensate for the smaller travel, while also providing the predefined 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, and diameter of the dome may be tuned. In some embodiments, a surface of the dome may be adjusted or modified to tune the structural integrity of the surface. 
       FIG. 2  is a perspective view of low travel dome  100 .  FIG. 3  is a top view of low travel dome  100 . As shown in  FIGS. 2 and 3 , low travel dome  100  may include domed surface  102  having an upper portion  140  (e.g., that may include an uppermost portion of domed surface  102 ), a lower portion  110 , and a set of tuning members  152 ,  154 ,  156 , and  158  disposed between upper and lower portions  140  and  110 . Domed surface  102  may have a hemispherical, semispherical, or convex profile, where upper portion  140  forms the top of the profile and lower portion  110  forms the base of the profile. Lower portion  110  can take any suitable shape such as, for example, a circular, elliptical, rectilinear, or another polygonal shape. 
     The physical attributes of low travel dome  100  may be tuned in any suitable manner. In some embodiments, tuning members  152 ,  154 ,  156 , and  158  may be cutouts or openings of domed surface  102  that may be integrated or formed in domed surface  102 . That is, predefined portions (e.g., of a predefined size and shape) of domed surface  102  may be removed in order to control or tune low travel dome  100  such that it operates according to predetermined force-displacement curve characteristics. 
     Tuning members  152 ,  154 ,  156 , and  158  may be spaced from one another such that one or more portions of domed surface  102  may extend from lower portion  110  of domed surface  102  to uppermost portion  140  of domed surface  102 . For example, tuning members  152 ,  154 ,  156 , and  158  may be evenly spaced from one another such that wall or arm portions  132 ,  134 ,  136 , and  138  of domed surface  102  may form a cross-shaped (or X-shaped) portion  130  that may span from portion  110  to uppermost portion  140 . 
     As shown in  FIG. 2 , portions  172 ,  174 ,  176 , and  178  of domed surface  102  may each be partially contiguous with some parts of cross-shaped portion  130 , but may also be partially separated from other parts of cross-shaped portion  130  due to tuning members  152 ,  154 ,  156 , and  158 . 
     Although  FIGS. 2 and 3  show only four tuning members  152 ,  154 ,  156 , and  158 , in some embodiments, low travel dome  100  may include more or fewer tuning members. In some embodiments, the shape of each one of tuning members  152 ,  154 ,  156 , and  158  may be tuned such that low travel dome  100  may operate according to predetermined force-displacement curve characteristics. In particular, each one of tuning members  152 ,  154 ,  156 , and  158  may have a particular shape. As shown in  FIG. 3 , for example, when viewing low travel dome  100  from the top, each one of tuning members  152 ,  154 ,  156 , and  158  may appear to have an L-shape. In some embodiments, tuning members  152 ,  154 ,  156 , and  158  may have a pie or wedge shape. 
     Generally, it should be appreciated that the dome  100  shown in  FIGS. 2-3  defines a set of opposed beams. Each beam is defined by a pair of arm segments and is generally contiguous across a surface of the dome  100 . For example, a first beam may be defined by arm portions  134  and  138  while a second arm is defined by arm portions  132  and  136 . Thus, the beams cross one another at the top of the dome but are generally opposed to one another (e.g., extend in different directions). In the present embodiment, the beams are opposed by 90 degrees, but other embodiments may have beams that are opposed or offset by different angles. Likewise, more or fewer beams may be present or defined in various embodiments. 
     The beams may be configured to collapse or displace when a sufficient force is exerted on the dome. Thus, the beams may travel downward according to a particular force-displacement curve; modifying the size, shape, thickness and other physical characteristics may likewise modify the force-displacement curve. Thus, the beams may be tuned in a fashion to provide a downward motion at a first force and an upward motion or travel at a second force. Thus, the beams may snap downward when the force exerted on a keycap (and thus on the dome) exceeds a first threshold, and may be restored to an initial or default position when the exerted force is less than a second threshold. The first and second thresholds may be chosen such that the second threshold is less than the first threshold, thus providing hysteresis to the dome  100 . 
     It should be appreciated that the force curve for the dome  100  may be adjusted not only by adjusting certain characteristics of the beams and/or arm portions  132 ,  134 ,  136 ,  138 , but also by modifying the size and shape of the tuning members  152 ,  154 ,  156 ,  158 . For example, the tuning members may be made larger or smaller, may have different areas and/or cross-sections, and the like. Such adjustments to the tuning members  152 ,  154 ,  156 ,  158  may also modify the force-displacement curve of the dome  100 . 
     In some embodiments, each one of arm portions  132 ,  134 ,  136 , and  138  of low travel dome  100  may be tuned such that low travel dome  100  may operate according to predetermined force-displacement curve characteristics. In particular, each one of arm portions  132 ,  134 ,  136 , and  138  may be tuned to have a thickness al (e.g., as shown in  FIG. 3 ) that may be less than a predefined thickness. For example, thickness al may be less than or equal to about 0.6 millimeters in some embodiments, but may be thicker or thinner in others. 
     In some embodiments, the hardness of the material of low travel dome  100  may tuned such that low travel dome  100  may operate according to predetermined force-displacement curve characteristics. In particular, the hardness of the material of low travel dome  100  may be tuned to be greater than a predefined hardness such that cross-shaped portion  130  may not buckle as easily as if the material were softer. 
     Although  FIGS. 2 and 3  may show domed surface  102  having a cross-shaped portion  130 , it should be appreciated that domed surface  102  may have a portion that may include any suitable number of arm portions. In some embodiments, rather than having four arm portions  132 ,  134 ,  136 ,  138 , domed surface  102  may include more or fewer arm portions. In some embodiments, low travel dome  100  may be tuned such that it is operative to maintain key cap  200  and support structure  300  in their respective natural positions when key cap  200  is not undergoing a switch event (e.g., not being depressed). In these embodiments, low travel dome  100  may control key cap  200  (and support structure  300 , if it is included) to operate according to predetermined force-displacement curve characteristics. 
     Regardless of how low travel dome  100  is tuned, when an external force is applied (for example, on or through key cap  200  of  FIG. 1 ) to upper portion  140 , cross-shaped portion  130  may move in the −Y-direction, and may cause arm portions  132 ,  134 ,  136 , and  138  to change shape and buckle. As a result, an underside (e.g., directly opposite uppermost portion  140  of domed surface  102 ) may contact a portion of a membrane (e.g., membrane  500  of  FIG. 1 ) of a keyboard when cross-shaped portion  130  moves a sufficient distance in the −Y-direction. In this manner, a switching operation or event may be triggered. 
       FIG. 10  is a top view of an alternative low travel dome  1000  that may be similar to low travel dome  100 , and that may be tuned to operate according to predetermined force-displacement curve characteristics. As shown in  FIG. 10 , low travel dome  1000  may include a cross-shaped portion  1030 , and a set of tuning members  1020 ,  1040 ,  1060 , and  1080 . When viewing low travel dome  1000  from the top (e.g., as shown in  FIG. 10 ), each one of tuning members  1020 ,  1040 ,  1060 , and  1080  may appear to be pie-shaped. 
       FIG. 11  is a top view of another alternative low travel dome  1100  that may be similar to low travel dome  100 , and that may be tuned to operate according to predetermined force-displacement curve characteristics. As shown in  FIG. 11 , low travel dome  1100  may include a surface  1180 , and a set of tuning members  1150 . When viewing low travel dome  1100  from the top (e.g., as shown in  FIG. 11 ), each one of tuning members  1150  may appear to have any suitable shape (e.g., elliptical, circular, rectangular, and the like). 
       FIG. 4  is a cross-sectional view of low travel dome  100 , taken from line A-A of  FIG. 3 .  FIG. 4  is 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 may merely include key cap  200 , low travel dome  100 , and membrane  500 . As shown in  FIG. 4 , arm portions  132  and  136  of cross-shaped portion  130  may form a contiguous arm portion that may span across domed surface  102 . 
       FIG. 5  is a cross-sectional view, similar to  FIG. 4 , of low travel dome  100 , with low travel dome  100  residing between key cap  200  and membrane  500  in a first state. Key cap  200 , low travel dome  100 , and membrane  500  may, for example, form one of the key switches or switch assemblies of a keyboard. As shown in  FIG. 5 , key cap  200  may include a body portion  201  and a contact portion  210 . Body portion  201  may include a cap surface  202  and an underside  204 , and contact portion  210  may include a contact surface  212 . As shown in  FIG. 5 , key cap  200  may be in its natural position  220  (e.g., prior to cap surface  202  receiving any force (e.g., from a user)). Moreover, each one of low travel dome  100 , and membrane  500  may be in their respective natural positions. 
     In some embodiments, membrane  500  may be a part of a printed circuit board (“PCB”) that may interact with low travel dome  100 . As described above with respect to  FIG. 1 , low travel 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 −Y-direction via an external force). Membrane  500  may include a top layer  510 , a bottom layer  520 , and a spacing  530  between top layer  510  and bottom layer  520 . In some embodiments, membrane  500  may also include a support layer  550  that may include a through-hole  552  (e.g., a plated through-hole). Top and bottom layers  510  and  520  may reside above support layer  550 . In some embodiments, top layer  510  and bottom layer  520  may each have a predefined thickness in the Y-direction, and spacing  530  may have a predefined height. Each one of top, bottom, and support layers  510 ,  520 , and  550  may be composed of any suitable material (e.g., plastic, such as polyethylene terephthalate (“PET”) polymer sheets, etc.). For example, each one of top and bottom layers  510  and  520  may be composed of PET polymer sheets that may each have a predefined thickness. 
     Top layer  510  may couple to or include a corresponding conductive pad (not shown), and bottom layer  520  may couple to or include a corresponding conductive pad (not shown). In some embodiments, each of these conductive pads may be in the form of a conductive gel. The gel-like nature of the conductive pads may provide improved tactile feedback to a user when, for example, the user depresses key cap  200 . The conductive pad associated with top layer  510  may include corresponding conductive traces on an underside of top layer  510 , and the conductive pad associated with bottom layer  520  may include conductive traces on an upper side of bottom layer  520 . These conductive pads and corresponding conductive traces may be composed of any suitable material (e.g., metal, such as silver or copper, conductive gels, nanowire, and so on). 
     As shown in  FIG. 5 , spacing  530  may allow top layer  510  to contact bottom layer  520  when, for example, low travel dome  100  buckles and cross-shaped portion  130  moves in the −Y-direction (e.g., due to an external force being applied to cap surface  202  of key cap  200 ). In particular, spacing  530  may allow the conductive pad associated with top layer  510  physical access to the conductive pad associated with bottom layer  520  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) (not shown), which may generate a code corresponding to key cap  200 . 
     In some embodiments, key cap  200 , low travel dome  100 , and membrane  500  may be included in a surface-mountable package, which may facilitate assembly of, for example, an electronic device or keyboard, and may also provide reliability to the various components. 
     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, low travel dome  100  may include a conductive material. In these embodiments, a separate conductive material may also reside beneath an underside of upper portion  140 . When a keystroke occurs (e.g., when external force A is applied to key cap  200 ), the conductive material of low travel dome  100  may contact the separate conductive material, which may trigger the switch event. 
     As described above, low travel dome  100  may be tuned in any suitable manner such that low travel dome  100  (and thus, key cap  200 ) may operate according to predetermined force-displacement curve characteristics.  FIGS. 6-8  are cross-sectional views, similar to  FIG. 5 , of low travel dome  100 , key cap  200 , and membrane  500  in second, third, and fourth states, respectively.  FIG. 9  shows a predefined force-displacement curve  900  according to which key cap  200  and low travel 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. 5 ) to a maximum displacement position  250  (e.g., as shown in  FIG. 8 ) may vary. As shown in  FIG. 9 , for example, the force required to displace key cap  200  may gradually increase as key cap  200  displaces in the −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 low travel dome  100  to change shape (e.g., the resistance of upper portion  140  to displace in the −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), low travel dome  100  may no longer be able to resist the pressure, and may begin to buckle (e.g., cross-shaped portion  130  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), an underside of upper portion  140  of low travel dome  100  may contact membrane  500  to cause or trigger a switch event or operation. In some embodiments, the underside 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 +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 , low travel dome  100  may also be complete in its buckling. In some embodiments, upper portion  140  may continue to displace in the −Y-direction, but cross-shaped portion  130  of low travel 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, the size or height of contact portion  210  may be defined to determine the maximum displacement position  250  or travel of key cap  200  in the −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. 
     In addition to a cushioning effect provided by the gel-like conductive pads of top and bottom layers  510  and  520  to low travel dome  100  and key cap  200 , in some embodiments, through-hole  552  may also provide a cushioning effect. As shown in  FIG. 8 , for example, when key cap  200  displaces to maximum displacement position  250  and low travel dome  100  completely buckles and presses onto top layer  510 , bottom layer  520  may bend or otherwise interact with support layer  550  such that a portion of bottom layer  520  may enter into a void of through-hole  552 . In this manner, key cap  200  may receive a cushioning effect, which may translate into improved tactile feedback for a user. 
     In some embodiments, key cap  200  may or may not include contact portion  210 . When key cap  200  does not include contact portion  210 , for example, underside  204  of key cap  200  may not be sufficient to press onto upper portion  140  of cross-shaped portion  130 . Thus, in these embodiments, low travel dome  100  may include a force concentrator nub that may contact underside  204  when a force is applied to cap surface  202  in the −Y-direction.  FIG. 12  is a cross-sectional view, similar to  FIG. 4 , of low travel dome  100  including a nub  1200 . As shown in  FIG. 12 , force concentrator nub  1200  may have a block shape having underside  1204  that may contact upper portion  140  of dome  100 , and an upper side  1202  that may contact underside  204  of key cap  200 . In this manner, when key cap  200  displaces in the −Y-direction due to an external force, underside  204  may press onto upper side  1202  and direct the external force onto upper portion  140 . 
       FIG. 13  is an illustrative process  1300  of manufacturing low travel dome  100 . Process  1300  may begin at operation  1302 . 
     At operation  1304 , the process may include providing a dome-shaped surface. For example, operation  1304  may include providing a dome-shaped surface, such as domed surface  102  prior to any tuning members being integrated therewith. 
     At operation  1306 , the process may include selectively removing a plurality of predefined portions of the dome-shaped surface to tune the dome-shaped surface to operate according to a predefined force-displacement curve characteristic. For example, operation  1306  may include forming openings or cutouts  152 ,  154 ,  156 , and  158  at the plurality of predefined portions of the dome-shaped surface, each of the openings having a predefined shape, such as an L-shape or a pie shape. In some embodiments, operation  1306  may include forming a remaining portion of the dome-shaped surface that may appear to be cross-shaped. Moreover, in some embodiments, operation  1306  may include die cutting or stamping of the dome-shaped surface to create cutouts  152 ,  154 ,  156 , and  158 . 
       FIG. 14  illustrates yet another sample dome  1400  that may be employed in certain embodiments. This dome  1400  may be generally square or rectangular. That is, the major sidewalls  1402 ,  1404 ,  1406 ,  1408  may be straight and define all or the majority of an outer edge or surface of the dome  1400 . The dome  1400  may have one or more angled edges  1410 . Here, each of the four corners is angled. The angled corners  1410  may provide clearance for the dome  1400  during assembly of a key and/or keyboard with respect to adjacent domes, holding or retaining mechanisms, and the like. Further, the angled edges may provide additional surface contact with respect to an underlying membrane, thereby providing additional area to secure to the membrane in some embodiments. It should be appreciated that alternative embodiments may omit some or all of the angled edges  1410 . Square and/or partly square bases, such as the one shown in  FIG. 14 , may be employed with any of the foregoing embodiments. Likewise, in some embodiments, a circular base (or base having another shape) may be employed with the arm structure shown in  FIG. 14 . 
     As shown in the embodiment of  FIG. 14 , two beams  1412 ,  1414  may extend between diagonally opposing angled edges  1410  (or corners, if there are no angled edges). Alternative embodiments may include more or fewer beams. Each beam  1412 ,  1416  may be thought of as being formed by multiple arms  1418 ,  1420 ,  1422 ,  1424 . The arms  1418 ,  1420 ,  1422 ,  1424  meet at the top  1428  of the dome  1400 . The shape of the arms may be varied by adjusting the amount of material and the shape of the material removed to form the tuning members  1426 , which are essentially voids or apertures formed in the dome  1400 . The interrelationship of the tuning members  1426  and beams/arms to generate a force-displacement curve has been previously discussed. 
     By employing a dome  1400  having a generally square or rectangular profile, the usable area for the dome under a square keycap may be maximized. Thus, the length of the beams  1412 ,  1416  may be increased when compared to a dome that is circular in profile. This may allow the dome  1400  to operate in accordance with a force-displacement curve that may be difficult to achieve if the beams are constrained to be shorter due to a circular dome shape. For example, the deflection of the beams (in either an upward or downward direction) may occur across a shorter period, once the necessary force threshold is reached. This may provide a crisper feeling, or may provide a more sudden depression or rebound of an associated key. Further, fine-tuning of a force-displacement curve for the dome  1400  may be simplified since the length of the beams  1412 ,  1416  is increased. 
     While there have been described a low travel switch assembly and systems and methods 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: 20140527
Publication Date: 20160809
Grant Date: 20160809
Priority Date: 20130527
Inventors: HENDREN KEITH J.
WILSON, JR. THOMAS W.
BROCK JOHN M.
LEONG CRAIG C.
NIU JAMES J.
OKUMA SATOSHI
WATANABE SHINSUKE
Assignee: APPLE INC
CPC Classifications: [{"code": "H01H13/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/49204", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H2215/004", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/85", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/49204", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2223/042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H65/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H2229/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/85", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H13/48", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H13/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/70", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/48", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y10T29/49204", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H2229/05", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01H13/85", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01H13/14", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01H65/00", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 51033524