Abstract:
A directional pointing device produces cardinal and intercardinal directional output reliably by providing more stable axes of rotation. In some cases, the rotation is made more stable by guiding the activation of the pad in a generally perpendicular manner. In one embodiment, a directional pointing device comprises a substrate; a plurality of switches disposed on the substrate; and a cap movably coupled with the substrate to activate the switches for directional selection. The cap includes a plurality of activation features each disposed above a corresponding one of the switches to activate the corresponding switches by moving with respect to the substrate. The activation features are arranged in different radial directions with respect to a center position of the cap. Each activation feature has a width oriented generally perpendicular to the radial direction from the center position of the cap to the activation feature and a thickness oriented generally along the radial direction. The width is substantially larger than the thickness.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application is based on and claims the benefit of U.S. Provisional Patent Application No. 60/541,574, filed Feb. 3, 2004. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present application relates generally to directional pads for use in a variety of devices and, more particularly, to directional pads that provide cardinal direction selection (north, south, east, west) and intercardinal direction selection (northeast, northwest, southeast, southwest).  
         [0003]     Directional pads are used in numerous devices such as pointing devices, input devices, and other control devices to provide directional selection. Existing directional pads often produce directional output by pivoting that is unstable, and are unable to provide accurate and reliable directional output based on a user&#39;s selection, especially in the intercardinal directions.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     The present invention relates to a directional pad that produces cardinal and intercardinal directional output reliably by providing more stable axes of rotation. In some cases, the directional selection is made more stable by guiding the activation of the pad in a generally perpendicular manner.  
         [0005]     In accordance with an aspect of the present invention, a directional pointing device comprises a substrate; a plurality of switches disposed on the substrate; and a cap movably coupled with the substrate to activate the switches for directional selection. The cap includes a plurality of activation features each disposed above a corresponding one of the plurality of switches to activate the corresponding switches by moving with respect to the substrate. The activation features are arranged in different radial directions with respect to a center position of the cap. Each activation feature has a width oriented generally perpendicular to the radial direction from the center position of the cap to the activation feature and a thickness oriented generally along the radial direction from the center position of the cap to the activation feature. The width is substantially larger than the thickness.  
         [0006]     In some embodiments, the cap includes four activation features being spaced substantially uniformly apart from each other by about 90° and being spaced from the center position by substantially an equal radial distance. The activation features are disposed generally on a plane. The activation features contact corresponding tops of the corresponding switches to move the switches with respect to the substrate to activate the switches.  
         [0007]     In specific embodiments, a plurality of pistons are each disposed above one of the switches and being constrained to move generally parallel to each other. The activation features each contact a corresponding top of one of the pistons to move the pistons with respect to the substrate. A case frame having a plurality of cylindrical openings in which the pistons are disposed to guide movement of the pistons. The pistons are constrained to move in a direction generally perpendicular to the substrate. An alignment member keeps the activation features of the cap aligned with the corresponding tops of the corresponding pistons. A resilient biasing member is configured to resiliently bias the cap toward a position with the activation features disposed generally on a plane parallel to the substrate. The switches each comprise a conductive contact member having a convex surface for movably contacting the substrate and a resilient membrane connected to the conductive contact member to resiliently bias the conductive contact member away from the substrate. In other embodiments, the conductive contact member has a generally flat surface.  
         [0008]     In accordance with another aspect of the invention, a directional pointing device comprises a substrate; a plurality of switches disposed on the substrate; a plurality of pistons each being disposed above one of the switches and being constrained to move generally parallel to each other with respect to the substrate to activate the switches; and a cap coupled with the plurality of pistons to activate the switches for directional selection. The cap includes a plurality of activation features each coupled with a corresponding one of the plurality of pistons to activate the corresponding switches by moving the pistons with respect to the substrate. The activation features are arranged in different radial directions with respect to a center position of the cap.  
         [0009]     In accordance with another aspect of the present invention, a directional pointing device comprises a substrate; a plurality of switches each having a contact member movable between a contact position to contact the substrate and a noncontact position to be spaced from the substrate; and a cap movable with respect to the substrate to activate the switches for directional selection. The cap includes a plurality of activation features each corresponding to one of the plurality of switches to activate the corresponding switch by moving the switch with respect to the substrate. The activation features are arranged in different radial directions with respect to a center position of the cap. The device further comprises a mechanism coupled with the cap and the switches for moving one or more of the switches between the contact position and the noncontact position in a direction generally perpendicular to the substrate in response to movement of the cap for directional selection. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view with partial cross sections illustrating a directional pad according to one embodiment of the present invention.  
         [0011]      FIG. 2  is an exploded perspective view of the directional pad of  FIG. 1 .  
         [0012]      FIG. 3  is a perspective view of the directional pad of  FIG. 1  illustrating cardinal directional selections.  
         [0013]      FIG. 4  is a perspective view of the directional pad of  FIG. 1  illustrating intercardinal directional selections.  
         [0014]      FIG. 5  is a perspective view of the directional pad of  FIG. 1  illustrating a specific cardinal directional selection.  
         [0015]      FIG. 6  is a perspective view of the directional pad of  FIG. 5  with partial cut-out to illustrate the interior components.  
         [0016]      FIG. 7  is a perspective view of a cap showing in cutaway the activation feature arrangement and location of the directional pad of  FIG. 6 .  
         [0017]      FIG. 8  is another perspective view of the directional pad of  FIG. 6  illustrating the rotational characteristics thereof.  
         [0018]      FIG. 9  is an elevational view of the directional pad of  FIG. 6  illustrating the rotational characteristics thereof.  
         [0019]      FIG. 10  is another elevational view of the directional pad of  FIG. 6  illustrating buckling of the switch membrane according to one embodiment of the invention.  
         [0020]      FIG. 11  is a plot of force versus travel for the buckling of the switch membrane.  
         [0021]      FIG. 12  is a cross-sectional view of a switch according to one embodiment of the invention.  
         [0022]      FIG. 13  is a partial cross-sectional view of a switch in the directional pad of  FIG. 1  illustrating perpendicular activation thereof.  
         [0023]      FIG. 14  is a partial cross-sectional view of a switch in an existing directional pad.  
         [0024]      FIG. 15  is a plot of force versus travel comparing the buckling of the switch in the existing directional pad of  FIG. 14  and the switch in the directional pad of  FIG. 1 .  
         [0025]      FIG. 16  is another partial cross-sectional view of the switch of  FIG. 14 .  
         [0026]      FIG. 17  is a perspective view with partial cut-out of the directional pad of  FIG. 14 .  
         [0027]      FIG. 18  is a perspective view of the directional pad of  FIG. 1  illustrating a specific intercardinal directional selection.  
         [0028]      FIG. 19  is a perspective view of the directional pad of  FIG. 18  with partial cut-out to illustrate the interior components.  
         [0029]      FIG. 20  is another perspective view of the directional pad of  FIG. 18  illustrating the rotational characteristics thereof.  
         [0030]      FIG. 21  is an elevational view of the directional pad of  FIG. 18  illustrating the rotational characteristics thereof.  
         [0031]      FIG. 22  is an exploded perspective view of a directional pad according to another embodiment of the present invention.  
         [0032]      FIG. 23  is a perspective view with partial cut-out of the directional pad of  FIG. 22  illustrating the rotational characteristics thereof.  
         [0033]      FIG. 24  is an elevational view of the directional pad of  FIG. 22  illustrating the rotational characteristics thereof. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     As shown in  FIGS. 1 and 2 , a directional pad (D-pad)  10  includes a cap  12  which has four activation features  14  located generally in a plane and at the four cardinal directions (north, south, east, and west). The activation features  14  are arranged in different radial directions with respect to a center position of the cap  12 , and are spaced from the center position by substantially an equal distance. These four features are in contact with the tops  18  of four piston actuators  19  which provide hard surfaces at the top of the pistons  19 . The pistons  19  are constrained to vertical movement, perpendicular to the keymat  20  by cylinders or cylindrical openings  22  located in a case frame  24 . As seen in  FIG. 2 , the keymat switches  26  are located at the four cardinal directions, and aligned with the four cylinders  22  and four corresponding pistons  19 . The keymat switches  26  each include a silicone cylindrical webbed membrane  28  with a conductive “pill” or member  30  at the center thereof. These conductive pills  30  are aligned to trace contact areas  32  located on a substrate or printed circuit board (PCB)  34 . Each conductive pill  30  is movable between a contact position to contact the PCB  34  and a noncontact position to be spaced from the PCB  34 . The membrane  28  resiliently biases the conductive pill  30  away from the PCB  34 . The D-pad cap  12  is desirably held to the tops of the pistons  19 , for instance, with a resilient member in the form of a spring  40 . The spring  40  preferably generates enough force to hold the cap  12  in contact with the pistons  19 , but not enough to depress the keymat switches  26 . The spring  40  is constrained by a cap alignment member or alignment stopper  42 , which keeps the cap&#39;s four activation features  14  aligned with the four piston tops using four alignment arms  44  that fit into ribbed spaces in the case frame  24 . The activation features  14  of the cap  12  are resiliently biased to lie generally on a plane parallel to the PCB  34 . A screw  48  attaches the cap alignment stopper  42  to the cap  12  with the spring  40  sandwiching the case frame  24  therebetween.  
         [0035]     The D-pad  10  functions by instantly creating an axis of rotation when reacting to the pressure created by the user in selecting a direction. There are commonly eight directions that can be selected, including four cardinal directions (north  51 , south  52 , east  53 , west  54 ) as shown in  FIG. 3  and four intercardinal directions (northeast  55 , northwest  56 , southeast  57 , southwest  58 ).  
         [0036]     The first type of axis creation is cardinal direction selection. When the user wants to select a cardinal direction (e.g., “north”), he or she presses the “north” position on the D-pad cap  12  toward and above the north switch and piston, as illustrated by the arrow  60  in  FIG. 5 .  FIG. 6  shows various parts of the D-pad  10  in a cutaway view to illustrate the internal features. At this time there are three interactions that occur to provide a very stable and “directionally” intuitive feedback to the user ensuring only “north” is selected. First, the leading corners of the east and west activation features  14  create an axis of rotation  64  caused by the resistance to vertical movement of each of these two locations created by the east and west switch membranes  28 . They rotate on the solid platforms created by, and in the plane of, the hard piston tops  18  of the east and west pistons  16 . This causes a resistance to tipping either to the left (east) or to the right (west), thereby limiting accidental selection of a neighboring intercardinal direction (northeast or north west). This reactive axis does not carry the full load or torque of switch activation. What it does is to carry a portion of the load of the switch activation to create a stabilizing effect. Second, as seen in  FIG. 7 , the cap activation features  14  each have a large width “side to side”  70 , and a narrow dimension or thickness  72  in the direction of tipping, further stabilizing the D-pad cap  12  from tilting to the sides. The width  70  is substantially larger than the thickness  72 , and is typically at least about twice, more desirably at least about four times, as large as the thickness  72 . These two features work together to produce an isosceles trapezoid  76  in the direction of D-pad cap rotation  76 , as seen in  FIG. 8 . As shown in the region  78  of  FIG. 9 , the cap  12  floats on top of the pistons  19 . The moment arm is the distance from the leading edge of the activation feature  14  to the axis of rotation  64 , defined here as the radius “r.” The angle that the cap  12  tips through is θ. The third unique feature of this configuration results from the perpendicular action of the piston  19  on the switch  26 . Since the force is applied evenly to the entire top of the switch  26 , the buckling action of the switch membrane  28  is uniform and consistent, as illustrated in  FIG. 10 , and at its highest value  80 , as shown in  FIG. 11 . This buckling point  80  provides the user with the distinctive “click” that produces the tactile feedback indicating that the correct switch was activated. Some D-pads use conductive pills  30  that have a convex surface such as a cone-shaped surface  84  with a small flat tip  86 , as seen in  FIG. 12 . These “analog progressive” switches change their output as a function of the amount of deformation of the conductive pill due to variations of the applied force. On the piston design, this conductive pill is moved perpendicularly to the trace, as illustrated by the arrow  90  in  FIG. 13 , thereby resulting in consistent placement and deformation of the pill point at the center  92  of the trace. In alternative embodiments, the conductive pill  30  has a generally flat surface for contacting the PCB  108 , for example, in a digital switch.  
         [0037]      FIG. 14  shows a currently available D-pad  100 , which generally relies on a central pivot point  102  to provide the directional bias. While this pivot point may come in various forms and at various points relative to the switch top plan of action, it always relies on a tipping movement that results in the switch membrane web  104  of the switch  106  being deformed at an angle. The conductive pill  107  makes an off-center contact with the PCB  108  under a force along a line  109 . This asymmetric application of force causes early buckling on one side that results in a lower buckling force  110  as compared to the buckling point  80  in  FIG. 11 , creating a smaller tactile feedback to the user, as illustrated in  FIG. 15 . A second consequence of this angled depression of the switch  106  is that the contact point of the conductive pill  107  is altered and its alignment to the trace altered. As seen in  FIG. 16 , the resultant contact point  114  is shifted from the center or intended contact point  116  of the conductive pill  107 , and away from the center  118  of the trace on the printed circuit board. In the tipping configuration, the pill point or center of the conductive pill  107  does not touch the board first and the deformation is not equal on all sides of the trace, resulting in erratic progressive output. This also leads to “scuffing” of the trace and pill due to a small component of the applied force acting in the radial direction. A third consequence of the pivot approach to D-pad operation is that the moment arm that exists between the pivot point of contact  120  and the top of the keymat switch  106  creates a triangle  124  with a very small base that is located in a plane perpendicular to the plane of the switch tops, as illustrated in  FIG. 17 . This results in a rather unstable application of force to the top of the switch  106  without any exterior forces available to prevent the activation of another switch to the left or the right of the intended switch.  
         [0038]     The second type of axis creation is intercardinal direction selection. When the user wants to select an intercardinal direction (e.g., “northwest”), the force is applied between the north and west positions on the D-pad Cap  12 , as illustrated by the arrow  130  in  FIG. 18 . Once again, there are three interactions that occur to provide a stable and “directionally” intuitive feedback to the user, thereby promoting the selection of the “northwest” direction. First, the outside, front corners of the east and south activation features  14  create an axis of rotation  132  caused by the resistance to vertical movement of each of these points as generated by the east and south switch membranes. They rotate on the solid platforms created by, and in the plane of, the hard piston tops. This causes a resistance to tipping either to the left (north) or to the right (west), thereby resisting accidental selection of a neighboring cardinal direction. Second, the forward inside corners  134 ,  138  of the cap activation features for north and west are disposed at a large distance from each other, creating a stable platform between these two points relative to the tops of the north and west pistons  19 , further stabilizing the D-pad cap  12  from tilting to the sides. These two features work together to produce an isosceles trapezoid  140  in the direction of D-pad cap rotation, as shown in FIG.  20 . As illustrated in the region  144  of  FIG. 21 , the cap  12  floats on top of the pistons  19 . The moment arm is the distance from the corner of the activation feature  14  to the axis of rotation, defined here as the radius “1.8r.”. This moment arm is longer than the cardinal moment arm resulting in a smaller angle of rotation of about 0.58 θ as compared to the rotation in the cardinal direction of  FIG. 9 . As noted before, this axis of rotation  132  does not carry the full load or torque at this axis. It acts only to provide a stabilizing effect. The third unique feature of this design results from the perpendicular action of the pistons  19  on the switches  26 . Since the force is applied evenly to the entire top of each switch  26 , the buckling action of each switch membrane  28  is uniform, consistent, and at its highest value (see  FIGS. 10 and 11 ). Because two switches are being depressed at one time in the intercardinal direction, the user feels a higher resistance to operation, and since the moment arm is longer, the angle that the D-pad cap  12  tips through is smaller providing yet another form of tactile feed back to the user. Therefore, the buckling point for the intercardinal direction provides the user with a distinctive “click” which is different from the cardinal “click,” thereby providing a different tactile feedback to inform the user that the correct switch is activated.  
         [0039]      FIGS. 22-24  show another D-pad  200  that has a simpler structure and is less costly to manufacture. The cost structure of some products that utilize a D-pad can make the piston activation feature in the D-pad  10  of  FIGS. 1-13  and  18 - 21  too expensive. In these situations, a reduced cost version such as the D-pad  200  shown in  FIGS. 22-24  is possible by removing the pistons and floating the D-pad cap  202  directly over the tops of the keymat switches  204  on the keymat  206 . The keymat  206  is disposed over traces on a PCB  208 . A retaining member  210  is placed over the assembly to hold the components of the D-pad  200  together. The retaining member  210  places an upper constraint of movement on the four tabs  212  of the cap  202 , which maintains alignment of the cap  202 . This D-pad  200  does not produce the vertical displacement in the D-pad  10 , but is able to generate substantial stability in the directional selection. For instance, the activation features  214  are similar to the activation features  14  in the D-pad  10 . As seen in  FIG. 23 , the activation features  214  of the D-pad  200  produce an isosceles trapezoid  218  in the direction of the D-pad cap rotation similar to that shown in  FIG. 8  for the D-pad  10 . As illustrated in  FIG. 24 , the moment arm is the distance from the line of application of the force  222  to the axis of rotation  224 , defined here as the radius “r.” There is a slight nonuniform buckling of the switch membrane  228  of the switch  204 , but the buckling is more uniform than that in existing D-pads. Since there is no pivot point as in existing D-pads, most of the benefits of the floating actuator are available in this embodiment of the D-pad  200 . Operation in the cardinal, and inter-cardinal directions create generally the same active axis and planar tetrahedron as in the piston configuration of the D-pad  10 . Because the switches  204  in the simplified D-pad  200  operate at an angle, there is a decrease of accuracy. Experiments show that the accuracy of the D-pad  10  ( FIGS. 1-13  and  18 - 21 ) is about 95% or higher and the accuracy of the simplified D-pad  200  ( FIGS. 22-24 ) is about 90%, which represent significant improvement over existing D-pads such as the D-pad  100  ( FIGS. 14-17 ) at an accuracy of about 80% or lower.  
         [0040]     It is to be understood that the above description is intended to be illustrative and not restrictive. Many embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.