Abstract:
A system and method for enabling an entire touchpad surface to mechanically move if sufficient force is used to press on the touchpad to perform a mouse click function, such as a right click or a left click, when the touchpad is mechanically buttonless, such as a forcepad, in order to provide haptic feedback on a touchpad that otherwise has none.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field Of the Invention 
         [0002]    This invention relates generally to touch sensors. Specifically, the invention pertains to a system and method for enabling an entire touchpad surface to mechanically move if sufficient force is used to press on the touchpad to perform a mouse click function, such as a right click or a left click. 
         [0003]    Description of Related Art 
         [0004]    There are several designs for capacitance sensitive touch sensors which may take advantage of a system and method for providing mechanical movement of a touchpad that is buttonless. It is useful to examine the underlying technology of the touch sensors to better understand how any capacitance sensitive touchpad can take advantage of the present invention. 
         [0005]    The CIRQUE® Corporation touchpad is a mutual capacitance-sensing device and an example is illustrated as a block diagram in  FIG. 1 . In this touchpad  10 , a grid of X ( 12 ) and Y ( 14 ) electrodes and a sense electrode  16  is used to define the touch-sensitive area  18  of the touchpad. Typically, the touchpad  10  is a rectangular grid of approximately 16 by 12 electrodes, or 8 by 6 electrodes when there are space constraints. Interlaced with these X ( 12 ) and Y ( 14 ) (or row and column) electrodes is a single sense electrode  16 . All position measurements are made through the sense electrode  16 . 
         [0006]    The CIRQUE® Corporation touchpad  10  measures an imbalance in electrical charge on the sense line  16 . When no pointing object is on or in proximity to the touchpad  10 , the touchpad circuitry  20  is in a balanced state, and there is no charge imbalance on the sense line  16 . When a pointing object creates imbalance because of capacitive coupling when the object approaches or touches a touch surface (the sensing area  18  of the touchpad  10 ), a change in capacitance occurs on the electrodes  12 ,  14 . What is measured is the change in capacitance, but not the absolute capacitance value on the electrodes  12 ,  14 . The touchpad  10  determines the change in capacitance by measuring the amount of charge that must be injected onto the sense line  16  to reestablish or regain balance of charge on the sense line. 
         [0007]    The system above is utilized to determine the position of a finger on or in proximity to a touchpad  10  as follows. This example describes row electrodes  12 , and is repeated in the same manner for the column electrodes  14 . The values obtained from the row and column electrode measurements determine an intersection which is the centroid of the pointing object on or in proximity to the touchpad  10 . 
         [0008]    In the first step, a first set of row electrodes  12  are driven with a first signal from P, N generator  22 , and a different but adjacent second set of row electrodes are driven with a second signal from the P, N generator. The touchpad circuitry  20  obtains a value from the sense line  16  using a mutual capacitance measuring device  26  that indicates which row electrode is closest to the pointing object. However, the touchpad circuitry  20  under the control of some microcontroller  28  cannot yet determine on which side of the row electrode the pointing object is located, nor can the touchpad circuitry  20  determine just how far the pointing object is located away from the electrode. Thus, the system shifts by one electrode the group of electrodes  12  to be driven. In other words, the electrode on one side of the group is added, while the electrode on the opposite side of the group is no longer driven. The new group is then driven by the P, N generator  22  and a second measurement of the sense line  16  is taken. 
         [0009]    From these two measurements, it is possible to determine on which side of the row electrode the pointing object is located, and how far away. Using an equation that compares the magnitude of the two signals measured then performs pointing object position determination. 
         [0010]    The sensitivity or resolution of the CIRQUE® Corporation touchpad is much higher than the 16 by 12 grid of row and column electrodes implies. The resolution is typically on the order of 960 counts per inch, or greater. The exact resolution is determined by the sensitivity of the components, the spacing between the electrodes  12 ,  14  on the same rows and columns, and other factors that are not material to the present invention. The process above is repeated for the Y or column electrodes  14  using a P, N generator  24   
         [0011]    Although the CIRQUE® touchpad described above uses a grid of X and Y electrodes  12 ,  14  and a separate and single sense electrode  16 , the sense electrode can actually be the X or Y electrodes  12 ,  14  by using multiplexing. 
         [0012]    It should be understood that use of the term “touch sensor” throughout this document may be used interchangeably with “forcepad”, “buttonless touchpad”, “proximity sensor”, “touch and proximity sensor”, “touch panel”, “touchpad” and “touch screen”. 
         [0013]    Buttonless touchpads and forcepads may be touch sensors that may not provide a user friendly haptic sensation of a mechanical “click” when pressed. While the touch sensors are still able to provide the functionality of the mouse click, they nevertheless may fail to provide tactile feedback that may not be necessary, but which may be desirable to users. 
         [0014]    Furthermore, many touch sensors do not allow the user to perform a mechanical click, right or left, at a top portion of the touchpad. This is an inherent design issue due to the mechanical button(s) being mounted at the bottom area of the underside of the touch sensor surface because the touch sensor is hinged near the upper area of the touchpad. It may be that these types of designs allow about 80% of the touch sensor to be used for “clicking” because a mechanical click on the upper 20% of the pad is either not possible or requires excessive force. 
         [0015]    There may be some touch sensors that do not allow any mechanical movement, but instead create an “artificial” click-type response using a motor when the user presses anywhere on the touch sensor, such as in a forcepad. There may also be other forcepad designs that create an audible “click” sound as the user presses on a touch sensor which senses mechanical pressure. However, these touch sensor also lack mechanical movement of the touch sensor itself. 
       BRIEF SUMMARY OF THE INVENTION 
       [0016]    In a first embodiment, the present invention is a system and method for enabling an entire touchpad surface to mechanically move if sufficient force is used to press on the touchpad to perform a mouse click function, such as a right click or a left click, when the touchpad is mechanically buttonless, such as a forcepad, in order to provide haptic feedback on a touch sensor that otherwise has none. 
         [0017]    These and other objects, features, advantages and alternative aspects of the present invention will become apparent to those skilled in the art from a consideration of the following detailed description taken in combination with the accompanying drawings. 
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       [0018]      FIG. 1  is a block diagram of operation of a touchpad that is found in the prior art, and which is adaptable for use in the present invention. 
         [0019]      FIG. 2  is a picture of a top view of a substrate and touch sensor disposed thereon, the substrate having four flex arms on each corner of the touch sensor. 
         [0020]      FIG. 3  is a perspective view of the bottom of a substrate showing a mechanical switch disposed in the center of the substrate to provide a mechanical switch when the touch sensor is pressed. 
         [0021]      FIG. 4  is a view from an edge of the touch sensor showing that the substrate is only supported by the housing at a distal end of each of the four flex arms. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Reference will now be made to the drawings in which the various elements of the present invention will be given numerical designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood that the following description is only exemplary of the principles of the present invention, and should not be viewed as narrowing the claims which follow. 
         [0023]      FIG. 2  is a picture of a first embodiment of the touch sensor  30 . The touch sensor  30  has several features that should be explained. The touch sensor  30  may be disposed on a substrate that is formed as a continuous piece of material. A first feature of the touch sensor  30  may be the four flex arms  32  that may suspend the touch sensor within a housing, not shown. The substrate of the touch sensor  30  may be manufactured from a single sheet of flexible material as shown in this first embodiment. For example, the substrate may be comprised of printed circuit board (PCB). The PCB may be sufficiently flexible to enable the four flex arms  32  to provide the desired mechanical action of the touch sensor  30 . 
         [0024]    In this first embodiment, the four flex arms  32  are shown with a hole  34  at the distal end of each flex arm. The hole  34  may be used to position and hold the touch sensor  30  in place within a housing. For example, the hole  34  may be positioned over a projection on the housing on which the hole may be positioned. Applying a force to any portion of the sensor portion  36  of the touch sensor  30 , may result in the flexing of the four flex arms  32  where the flex arms are attached to the four corners of the touch sensor. 
         [0025]    Alternatively, the four flex arms  32  may be mechanically attached to the touch sensor  30  instead of being an integral part of the structure of the touch sensor, and may still provide the flexibility needed for the touch sensor to be mechanically manipulated by a force applied to the touch sensor. 
         [0026]    The length of each of the four flex arms  32  may be the same or they may vary. The four flex arms  32  may vary in width and length. The four flex arms may or may not have the hole  34  for positioning. 
         [0027]    In this first embodiment, the touch sensor  30  may include four small tabs  38 . While the four flex arms  32  may be disposed on the short sides  40  of the touch sensor  30 , the tabs  38  may be disposed on the long sides  42  of the touch sensor. The tabs  38  may function to prevent undesired movement of the touch sensor  30 . For example, the four tabs  38  may be pivot points that may prevent the touch sensor  30  from lifting out of the housing and to instead assist the touch sensor in moving downward into a depression in the housing when a force is applied to the top surface  44  of the touch sensor. 
         [0028]    For example, when pressing on a far left side of the touch sensor  30 , the far right side of the touch sensor may try to lift out of the housing. However, if the tabs  38  are actually underneath an edge of the housing, then the housing itself may prevent the touch sensor  30  from lifting out of the housing. 
         [0029]    The specific location of the four tabs  38  along the long side  42  may be changed in order to obtain a different depth of movement of the touch sensor  30  when a force is applied to the surface. Accordingly, the position of the four tabs  38  along the long side  42  may be changed in order to achieve different movement characteristics of the touch sensor  30  when a force is applied. 
         [0030]      FIG. 3  is a partial perspective view of a bottom surface  46  of the touch sensor  30 . In this first embodiment, the bottom surface  46  shows a switch  48  disposed in approximately a center of the touch sensor  30 . The switch  48  may provide a mechanical click function. The mechanical click function may be a haptic movement, a clicking sound, or both. 
         [0031]      FIG. 4  is a view of the touch sensor  30  and a supporting structure  50  from a side or edge. The touch sensor  30  is shown as supported by the posts  52  of the supporting structure  50  on the flex arms  32 . The flex arms  32  may be the only part of the touch sensor  30  to be in contact with the supporting structure  50 . When a force is applied to the top surface  44  of the touch sensor  30 , the touch sensor may travel downward, while supported by the four flex arms  32 , until the switch  48  on the bottom surface  46  of the touch sensor makes contact with the bottom of a depression in the housing. 
         [0032]    One aspect of the first embodiment is that a force may be applied at any location on the top surface  44  of the touch sensor  30  and still cause the entire touch sensor to move in the direction that the force is applied. However, the touch sensor  30  may be tilted so that some areas of the touch sensor moves further than other portions of the touch sensor. Nevertheless, all of the top surface  44  of the touch sensor  30  may move down into the housing as the force is applied. Movement continues until the force is removed or until the center switch  48  makes contact with the housing, preventing further movement of the touch sensor  30 . 
         [0033]    It is an aspect of the touch sensor  30  that the material used for the touch sensor will be flexible enough so that the touch sensor may return to an unflexed or rest position when the force is not being applied. 
         [0034]    One advantage of the first embodiment and the use of four flex arms  32  may be that the stress on the touch sensor  30  at the joint  54  (see  FIG. 1 ) between the touch sensor and the four flex arms may be more evenly distributed across the joints of the touch sensor. Thus, it may be easier to cause the mechanical movement of the touch sensor  30 . 
         [0035]    While it is desirable to have the joints  54  flex on the touch sensor  30 , it may be undesirable to have the top surface  44  of the touch sensor to flex when a force is applied to perform a click function. One advantage of the first embodiment is that a material used to prevent flexing of the surface of the touch sensor  30  may not have to be as rigid if only using only two flex arms  32  because the touch sensor may now move more easily with four flex arms. Alternatively, a thickness of the material used to prevent flexing of the touch sensor  30  may not have to be as thick and thereby increasing sensitivity of the touch sensor. 
         [0036]    Another aspect of the first embodiment is that a haptics motor may be used to provide additional movement of the touch sensor  30 . The additional movement of the touch sensor  30  may be a function of the amount of force or pressure that is applied to the touch sensor. The haptics motor may therefore provide an additional degree of movement of the touch sensor  30 . The haptics motor may be located at any location adjacent to or directly on the touch sensor  30  as needed. 
         [0037]    Another aspect of the first embodiment may be a mechanical spring bias feature. The spring bias feature may be used to apply a force to the bottom surface  46  of the touch sensor  30  and hold it away from the housing. The touch sensor  30  may be held within the housing by the four tabs  38 . 
         [0038]    It is noted that a spring mounting platform may be provided having a ramped surface and an opposing feature that bends the spring to form a preloaded condition. The touch sensor  30  may be pushed against an inside bezel surface of the housing when the touch sensor  30  is at a rest position when no downward force on the top surface  44  is being applied. 
         [0039]    Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function.