Abstract:
A dome assembly for use in a keyboard assembly of an electronic device is provided. The dome assembly includes a deflectable dome shaped element having a concave surface terminating at a periphery and a number of elevating members disposed on the element adjacent the periphery and protruding away from the concave surface. The elevating members serve to space the periphery from a mounting surface. The element is movable between an undeflected position and a deflected position.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The disclosed and claimed concept relates generally to handheld electronic devices and, more particularly, to a key dome assembly for a handheld electronic device, wherein the dome assembly includes micro structures which elevate the dome shaped element from a supporting surface. 
         [0003]    2. Description of the Related Art 
         [0004]    Numerous types of handheld electronic devices are known. Examples of such handheld electronic devices include, for instance, personal data assistants (PDAs), handheld computers, two-way pagers, cellular telephones, and the like. Many handheld electronic devices also feature a wireless communication capability, although many such handheld electronic devices are stand-alone devices that are functional without communication with other devices. 
         [0005]    Such handheld electronic devices are generally intended to be portable, with many of such devices being small enough to fit within, for example, a pocket, a belt holster, a briefcase, or a purse. As the form factor of such devices has shrunk for improved portability, so has the size of components such as keyboards or keypads. The keyboards or keypads include keys that act as switches for input entry when actuated. In furtherance of miniaturization of keyboard assemblies such as keyboards and keypads, one general approach implemented by several different manufacturers has involved the use of an electrical key in the form of a resilient dome shaped element that is electrically conductive and is disposed on a circuit board. 
         [0006]    In simplest form, such a dome assembly is a smooth sector of a hollow sphere. When an actuation force is applied to the apex of the dome assembly, the dome assembly collapses, completing an electrical circuit or at least an open portion of an electrical circuit of the device. The collapsing dome assembly provides a tactile feedback to the user of the handheld electronic device. Such simple sphere segments have been generally effective for their intended purpose; however they have not been without limitation, as the tactile feedback is sometimes not noticeable by the user, particularly in miniaturized keyboard assemblies. 
         [0007]    Accordingly, it is desirable to manufacture a dome assembly which produces a detectable tactile feedback when electrical contact is made. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    A full understanding of the disclosed and claimed concept can be gained from the following Description when read in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a front elevational view of an example handheld electronic device in accordance with the disclosed and claimed concept; 
           [0010]      FIG. 2  is a schematic depiction of the example handheld electronic device of  FIG. 1 ; 
           [0011]      FIG. 3  is a perspective view of the top of an embodiment of a dome assembly disposed on a support structure in accordance with the disclosed and claimed concept; 
           [0012]      FIG. 4  is a perspective view of the embodiment of  FIG. 3  with a section removed along line  4 - 4  to show detail; 
           [0013]      FIG. 5  is the perspective view of  FIG. 4  showing the dome assembly displaced in a second position. 
           [0014]      FIGS. 6-8  are perspective views of alternate embodiments of a dome assembly in accordance with the disclosed and claimed concept; and 
           [0015]      FIG. 9  is a perspective view of the embodiment of  FIG. 8  with a section removed along line  9 - 9  to show detail. 
           [0016]      FIG. 10  is a top view of an embodiment of a dome assembly in accordance with the disclosed and claimed concept. 
           [0017]      FIG. 11  is a perspective view of a portion of a keyboard assembly in accordance with the disclosed and claimed concept. 
       
    
    
       [0018]    Similar reference numerals refer to similar parts throughout the specification. 
       DESCRIPTION 
       [0019]    An improved handheld electronic device  4  in accordance with the disclosed and claimed concept is indicated generally in  FIG. 1  and is depicted schematically in  FIG. 2 . The improved handheld electronic device  4  comprises a housing  6 , and further comprises an input apparatus  8 , an output apparatus  12 , and a processor apparatus  16  disposed on the housing  6 . The input apparatus  8  provides input to the processor apparatus  16 . The processor apparatus  16  provides output signals to the output apparatus  12 . 
         [0020]    The input apparatus  8  comprises a keypad  20  and a track ball  24 . The keypad  20  in the example embodiment depicted herein comprises a plurality of keys  26  that are each actuatable to provide input to the processor apparatus  16 . The track ball  24  is rotatable to provide navigational and other input to the processor apparatus  16 , and additionally is translatable in a direction inwardly toward the handheld electronic device  4  to provide other input, such as selection inputs. The track ball  24  is freely rotatable on the housing  6  and thus is able to provide navigational inputs in the vertical direction, i.e., the up-down direction, in the horizontal direction, i.e., the left-right direction, as well as combinations thereof. The keys  26  and the track ball  24  serve as input members which are actuatable to provide input to the processor apparatus  16 . The example output apparatus  12  comprises a display  32 . 
         [0021]    As shown in  FIG. 1 , many of the keys  26  have a plurality of letters, i.e., linguistic elements, assigned thereto. For instance, one of the keys  26  has assigned thereto the letters “A” and “S”. Another of the keys  26  has assigned thereto the letters “Q” and “w”. The letters of the example keypad  20  are in an arrangement of a reduced QWERTY keyboard. It is to be appreciated that although the example device shown in  FIG. 1  utilizes a reduced keypad  20 , the disclosed and claimed concept may readily be employed in other applications, such as but not limited to, a regular (non-reduced) keypad or other combination of one or more individual keys either integral to an electronic device or part of a separate keyboard assembly external to an electronic device. 
         [0022]    Examples of other input members not expressly depicted herein would include, for instance, a mouse or track wheel for providing navigational inputs, such as could be reflected by movement of a cursor on the display  32 , and other inputs such as selection inputs. Still other example input members would include a touch-sensitive display, a stylus pen for making menu input selections on a touch-sensitive display displaying menu options and/or soft buttons of a graphical user interface (GUI), hard buttons disposed on the housing  6  of the handheld electronic device  4 , and so on. Examples of other output devices would include a touch-sensitive display, an audio speaker, and so on. 
         [0023]    The processor apparatus  16  comprises a processor  36  and a memory  40 . The processor  36  may be, for example and without limitation, a microprocessor (μP) that interfaces with the memory  40 . The memory  40  can be any one or more of a variety of types of internal and/or external storage media such as, without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the like that provide a storage register, i.e., a machine readable medium, for data storage such as in the fashion of an internal storage area of a computer, and can be volatile memory or nonvolatile memory. The memory  40  has stored therein a number of routines  44  that are executable on the processor  36 . As employed herein, the expression “a number of” and variations thereof shall refer broadly to any nonzero quantity, including a quantity of one. One of the routines  44  is a disambiguation routine that is operable to disambiguate ambiguous text input, such as when one of the keys  26  having a plurality of letters assigned thereto is actuated. 
         [0024]    Underlying each of the plurality of keys  26  is a deformable dome assembly  50  such as shown in  FIGS. 3-5 . The dome assembly  50  includes a dome shaped resilient element  52  having a preferably centrally located apex  54  and extending to a periphery  56 . Preferably, resilient element  52  is formed from stainless steel coated with a conductive layer of silver plating after forming. For low end (low cost) devices, there is no post plating process on the metal dome. It is to be appreciated that resilient element  52  may also be formed from other resilient materials, such as, but not limited to, a plastic film coated with a layer of conductive carbon material. 
         [0025]    Referring to  FIGS. 3-5 , the dome assembly  50  further includes a number of elevating members  58  disposed adjacent the periphery  56  which serve to raise the periphery  56  of the resilient element  52  a distance D (see  FIGS. 4 and 5 ) from a mounting surface  60  on which the dome assembly  50  is disposed. In a specific application of the present concept, the distance D which the periphery  56  of the resilient element  52  is raised above the mounting surface  60  is in the range of approximately 0.03 to 0.07 mm. However, such distance D may be of greater or lesser value depending on the application, more specifically the relative size and shape of the resilient element  52 . Although the example shown in  FIGS. 3-5  shows a dome assembly  50  having eight elevating members  58  equally spaced along the periphery, it is to be appreciated that the number and spacing of such elevating members  58  may be varied. 
         [0026]    In an application such as a handheld electronic device  4  such as shown in  FIG. 1 , the mounting surface  60  may be a surface of a printed circuit board or other support formed from, or coupled to a portion of the housing  6  or other similar structure. In other example embodiments, such as, but not limited to, a keyboard or similar device separated from a main housing  6 , mounting surface  60  may be formed from a second housing or other member formed from, or coupled to a portion of the second housing.  FIG. 11  shows a portion of an example keyboard assembly including a number of dome assemblies  50 . 
         [0027]    In the example embodiment shown in  FIGS. 3-5 , elevating members  58  are embossments of dimple-like shape, integrally formed from the resilient element  52 . Formation of such integral elevating members  58  may be carried out by stamping or other equivalent techniques. It is noted that although elevating members  58  shown in the example embodiment of  FIGS. 3-5  are integrally formed with resilient element  52 , such members  58  could also be separately formed and then coupled to resilient element  52 . Additionally, such elevating members  58  could be coupled outside the resilient element  52  adjacent the periphery thereof while still providing the benefits of the present concept. It is to be appreciated that elevating members  58  may be of a variety of shapes including, but not limited to dimple shaped (see  FIGS. 3-7 ), elongated dimple or groove (see  FIGS. 8 and 9 ), cone shaped, cylindrical, or micro solid packs. 
         [0028]    As shown in  FIG. 5 , when one of the keys  26  of keypad  20  is actuated, a force F is applied preferably at or near the apex  54  of dome shaped resilient element  52  causing the dome assembly  50  to collapse from its initial relaxed position as shown in  FIGS. 3-4  to a collapsed position as shown in  FIG. 5 . In an application where the dome assembly  50  is disposed on a printed circuit board, the collapsed resilient element  52 , being constructed from, or coated with a conductive material will electrically engage one or more electrical contacts (not shown) disposed on the underlying printed circuit board to complete a circuit or at least a portion of a circuit. Alternatively, collapse of the resilient member  52  may cause a portion of a circuit to open. In either case, opening/closing of at least a portion of a circuit due to collapse of the resilient element  52  results in an input to the processor  36  of the handheld electronic device  4 . Upon deforming to the collapsed position, resilient element  52  produces a tactile feedback to a user of the handheld electronic device  4  thus providing the user with an indication that an input has been completed. Upon removal of the applied force F, the dome shaped resilient element  52  returns to its initial relaxed position as depicted in  FIGS. 3-4 . 
         [0029]    The addition of elevating members  58  to the resilient element  52  has been found to produce the desirable attribute of enhancing the tactile feedback to a user of the device compared to the use of a resilient element lacking such elevating members  58  in which the periphery  56  is directly disposed on a mounting surface  60 . Such improved tactile feedback can be attributed to a number of characteristics of the present concept. By elevating the periphery  56  of resilient element  52  from the mounting surface  60 , a greater travel distance (not numbered) for a depressed key  26 , and correspondingly for the apex  54  of the dome shaped resilient element  52  is provided when the resilient element  52  is moved from a non-collapsed position ( FIGS. 3-4 ) to a collapsed position ( FIG. 5 ). 
         [0030]    The increase in travel distance of the apex  54  allows for the resilient element  52  to become more collapsed than a resilient element  52  with a periphery  56  disposed directly on a mounting surface  60 . Also, use of the elevating members  58  allows for utilization of a resilient element  52  requiring a smaller footprint than what would be required of a dome element  52  disposed directly on the mounting surface  60  if a specific key depression distance (generally equivalent to the distance traveled by the apex  54  upon collapsing of dome element  52 ) is desired. 
         [0031]    Reduction of such footprint without decreasing the key depression distance makes the present concept readily adaptable to reduced keypad applications commonly found in handheld electronic devices. Additionally, elevation of the periphery  56  above the mounting surface  60  through the use of elevating members  58  provides improved venting of air from beneath the resilient element  52  upon collapse as well as an improved path for air to return when the resilient element  52  returns to the relaxed position. When the air beneath the dome assembly  50  does not have adequate venting for evacuation or return, such as when the periphery  56  is directly disposed on the mounting surface  60 , tactile feedback response is hindered and not as smooth as the case with the elevated periphery  56 . 
         [0032]    Addition of elevating members  58  to the resilient element  52  has also been found to increase the area of the dome assembly  50  to which a force F may be applied to readily collapse the dome. Increase of such area is desirable by lessoning the potential negative effects of off center actuations or slight misalignments of overlying structures which would tend to not fully collapse the dome and thus not properly register an input. 
         [0033]    Use of the elevating members  58  may also provide for reduced constraint of the periphery  56  relative to the underlying mounting surface  60  which in turn reduces the frictional forces acting against dome collapse, thus providing for a more readily collapsible dome. Such reduced constraint may occur by utilizing elevating members  58  that slightly flex outward as the resilient element  52  transitions from the non-collapsed to collapsed position. Such flexure of the elevating members  58  may result in movement of at least a portion of the periphery  56  relative to the mounting surface  60 .  FIG. 10  shows a top view of a dome assembly  50  in which such elevating members  58  that slightly flex are employed. Referring to  FIG. 10 , the solid line shows the position of the periphery  56  when the resilient dome element  52  is in a non-collapsed position, and the phantom line portion shows the flexed position of the periphery  56  when the resilient dome element  52  is collapsed. It is to be appreciated that the movement of the periphery  56  as well as elevating member  58  as shown in  FIG. 10  has been shown for example purposes only as the amount of such potential movement would vary depending on the structure of the particular elevating members  58  and resilient element  52 . 
         [0034]      FIGS. 6 and 7  show additional example embodiments of the present concept which demonstrate potential variations on the number of elevating members  58  utilized and also variations to the shape of the resilient element  52 . In particular,  FIG. 6  shows an embodiment having half as many elevating members  58  as the example embodiment shown in  FIGS. 3-5 .  FIG. 7  shows an embodiment using the same number of elevating members  58  as the embodiment of  FIG. 6  but instead utilizing only a portion of a resilient element  52 ′. 
         [0035]      FIGS. 8 and 9  show a further example embodiment of the present concept in which the elevating members  58  comprise elongated dimples or grooves  58 ′ disposed on a portion of a resilient element  52 ′. Although only two such grooves of approximately equal length are shown in  FIGS. 8-9 , it is to be appreciated that the quantity and size of the grooves as well as the dimensions of dome element  52 ′ can be varied according to the requirements of a specific application and still produce the desirable results of the present concept. 
         [0036]    While specific embodiments of the disclosed and claimed concept have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the disclosed and claimed concept which is to be given the full breadth of the claims appended and any and all equivalents thereof.