Abstract:
A device for generating conditioned electrical signals in response to forces applied to the device. The device includes a shaft attached to a substrate. Several strain sensitive resistors are mounted on the substrate around the shaft for generating an electrical signal representative of a magnitude and direction of force applied to the shaft by a user. Several apertures are in the substrate, each aperture is located between a pair of strain sensitive resistors. The apertures concentrate the stress on the resistors. A signal conditioning device is mounted to the substrate and is electrically connected to the resistors for conditioning the electrical signal. The signal conditioning device receives the electrical signal in an analog form and provides a conditioned signal as an output in a digital form. The device is mounted to a keyboard base. An alternative embodiment is shown using a cavity instead of apertures in the substrate.

Description:
[0001]    The present application is a continuation of U.S. patent application Ser. No. 09/168,022, filed Oct. 7, 1998, and is entitled, “A pointing stick having chip resistors”. 
     
    
     
       BACKGROUND OF THE PREFERRED EMBODIMENT(S)  
         [0002]    1. Field of the Preferred Embodiment(s)  
           [0003]    This invention generally relates to a pointing device for controlling the positioning, movement and operation of an electronic device, for example, a cursor on a display screen. Specifically, the specific embodiment illustrated includes: a shaft, a substrate, resistor based strain gages, a printed circuit board and control electronics mounted on the printed circuit board.  
         CROSS REFERENCE TO RELATED AND COPENDING APPLICATIONS  
         [0004]    The following applications are herein incorporated by reference for supportive and related teachings:  
           [0005]    U.S. patent application Ser. No. 08/717,517, filed Sep. 23, 1996 is a collar mounted pointing stick and has the same assignee as the present invention.  
           [0006]    U.S. patent application Ser. No. 08/756,202, filed Nov. 25, 1996 is a pointing stick with z-axis actuation and has the same assignee as the present invention.  
           [0007]    U.S. patent application Ser. No. 08/938,274, filed Sep. 26, 1997 is a unified bodied z-axis pointing stick and has the same assignee as the present invention.  
           [0008]    U.S. patent application Ser. No. 08/794,703, filed Feb. 4, 1997 is a z-axis pointing stick with ESD protection and has the same assignee as the present invention.  
           [0009]    U.S. patent application identified by docket number CTS-1675 filed May 21, 1997 is a pointing stick having an interposer connecting layer and has the same assignee as the present invention.  
           [0010]    2. Description of the Related Art  
           [0011]    Regarding the example of a pointing device for controlling a cursor, manufacturers of portable laptop computers, recognizing the need for placing the cursor controlling device in a permanent and more convenient location, installed a small stubby, button-like joystick centrally around the keys of the computer keyboard, specifically at the juncture of the “g,” “h” and “b” keys of the standard “QWERTY” keyboard. The joystick, also known as a pointing stick, was sensitive to lateral pressure, the amount and direction of which were sensed and input into the computer to cause movement of the cursor, and the speed and direction of cursor movement corresponded to the amount and direction of pressure on the joystick. That manufacturer may also provide two upwardly extending “mouse” or “click” buttons immediately below the space bar. The joystick is connected by a flexible cable to a computer mother board where it connects to several electronic circuit devices that amplify and condition the signal coming form the joystick. The signal from the joystick is a low level analog signal. Electronic devices on the mother board amplify the low level analog signal and convert it to a digital signal.  
           [0012]    Despite the advantages of each type of prior art cursor control, none have been easily or economically manufactured. In particular, providing the electrical connections between the resistors and the circuitry on the computer mother board has been complicated and expensive. The flexible cable runs for a length along a keyboard before connecting with the motherboard.  
           [0013]    Further, the electrical signal coming from the joystick is a low level analog signal. As the signal travels along the flexible cable it looses some of its amplitude and is skewed due to attenuation of the signal. During travel along the cable, the signal can be corrupted due to coupling from external electromagnetic interference. These problems of routing a low level analog signal along a cable can cause erroneous readings as to the position of the pointing stick. Therefore, there is a current unmet and heretofore long felt need for a pointing stick, which is easily connected and has improved signal integrity.  
         Description of Related Art  
         [0014]    Examples of patents related to the present invention are as follows, and each patent is herein incorporated by reference for the supporting teachings:  
           [0015]    U.S. Pat. No. Re. 35,016, is a three-axis force measurement stylus.  
           [0016]    U.S. Pat. No. 5,489,900, is a strain sensitive columnar transducer for a data entry keyboard contains a column upstanding from the keyboard.  
           [0017]    U.S. Pat. No. 5,473,347, is a computer pointing device for controlling the positioning, movement and operation of a cursor on the display screen of a computer.  
           [0018]    U.S. Pat. No. 5,407,285, is an apparatus for use in a computer keyboard for cursor control is disclosed.  
           [0019]    U.S. Pat. No. 5,521,596, is a sensor device placed either underneath a key cap or a key on a keyboard or between two keys on a keyboard so that cursor movement may be carried out from the keyboard itself.  
           [0020]    U.S. Pat. No. 4,876,524, is an isometric control device or the like of the type having an elastic beam and strain gauges attached to the surface of the beam characterized by at least a first group of three strain gages each having an operative axis thereof inclined with a single predetermined angle with respect to the main axis of the beam, and the strain gauges disposed at a first predetermined level along the beam.  
           [0021]    U.S. Pat. No. 4,680,577, is a multipurpose key switch for controlling cursor movement on a CRT display and for character entry includes a key cap that moves laterally to provide cursor control and that moves vertically for character entry.  
           [0022]    U.S. Pat. No. 5,659,334, is a force sensing pointing device.  
           [0023]    The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicant&#39;s acknowledged duty of candor in disclosing information that may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant&#39;s claimed invention.  
         SUMMARY OF THE PREFERRED EMBODIMENT(S)  
         [0024]    It is a feature of the invention to provide a pointing device for controlling the positioning, movement and operation of an electronic device, for example, a cursor on a display screen. Specifically, there is a shaft, a substrate or printed circuit board having apertures, resistor based strain gages, and control electronics mounted on the printed circuit board. The printed circuit board is mounted to a keyboard base.  
           [0025]    It is a feature of the invention to provide a device for generating conditioned electrical signals in response to forces applied to the device. The device includes a shaft having a first and second end. A substrate has the first end of the shaft attached. Several strain sensitive resistors are mounted on the substrate around the shaft for generating an electrical signal representative of a magnitude and direction of force applied to the shaft by a user. Several apertures are in the substrate, each aperture is located between a pair of strain sensitive resistors. A signal conditioning means is mounted to the substrate, and electrically connected to the resistors for conditioning the electrical signal. The signal conditioning means operates to receive the electrical signal as an input and provides a conditioned signal as an output.  
           [0026]    It is a further feature of the invention to provide a device for generating conditioned electrical signals in response to forces applied thereon, including an actuator, having strain sensitive resistors mounted thereon for generating an electrical signal representative of force applied to the actuator. The resistors each separated by an aperture. A printed circuit board includes the actuator and has signal conditioning means mounted to the printed circuit board and electrically connected to the resistors for receiving the electrical signal, conditioning the electrical signal and outputing the conditioned signal.  
           [0027]    It is a further feature of the invention to provide a device for generating electrical signals in response to forces applied thereon by an operator, the device operable to be connected to an external circuit, including a shaft, having a first and second end. A substrate has the first end of the shaft attached. Several strain sensitive resistors are mounted on the substrate. The resistors are disposed radially around the shaft. The strain sensitive resistors are operable to generate an electrical signal representative of a magnitude and direction of force applied to the shaft by a user. Each resistor is separated by an aperture in the substrate. A mounting bracket contains the printed circuit board and is adapted to mounting to a keyboard base.  
           [0028]    It is a further feature of the invention to provide a cavity disposed on a second substrate surface and the resistors are disposed on a first substrate surface such that each resistor is partially disposed above the cavity.  
           [0029]    It is a further feature of the invention to provide an electronic control device for allowing a user to control the movement or operation of a responsive electronic system including a substrate. A resistor means is mounted to the substrate to generating an analog signal representative of a direction of mechanical force applied thereon by the user. A signal conditioning means is mounted to the substrate, for receiving the analog signal from the resistor means as an input and generate a digital signal as an output. The resistor means includes either a shaft attached to the substrate and several strain sensitive resistors mounted on the substrate, each resistor separated by an aperture, the resistors and the apertures are disposed radially around the shaft or the resistor means includes a cavity disposed on a side of the substrate with a shaft extending through the cavity and attached to the substrate and strain sensitive resistors mounted to another side of the substrate, each resistor being disposed around the shaft and partially over the cavity.  
           [0030]    The invention resides not in any one of these features per se, but rather in the particular combination of all of them herein disclosed and claimed and it is distinguished from the prior art in this combination of all of its structures for the functions specified.  
           [0031]    There has thus been outlined, rather broadly, the more important features of the invention so that the detailed description thereof that follows may be better understood, and so that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the appended claims. Those skilled in the art will appreciate that the preferred embodiment may readily be used as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims are regarded as including such equivalent constructions since they do not depart from the spirit and scope of the present invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    [0032]FIG. 1 is a top view of the preferred embodiment of a pointing stick having chip resistors.  
         [0033]    [0033]FIG. 2 is a side view of FIG. 1.  
         [0034]    [0034]FIG. 3 is a top view of an alternative embodiment of a pointing stick having chip resistors.  
         [0035]    [0035]FIG. 4 is a side view of FIG. 3.  
         [0036]    [0036]FIG. 5 is a cross-sectional view of the pointing stick of FIG. 1 mounted on a keyboard using a mounting bracket.  
         [0037]    [0037]FIG. 6 is a perspective view of a keyboard with the pointing stick.  
         [0038]    [0038]FIG. 7 is a view of a computer system and the pointing stick mounted on a keyboard.  
         [0039]    [0039]FIG. 8 is a side cross-sectional view of a discrete chip resistor of the pointing stick of FIG. 1.  
         [0040]    [0040]FIG. 9 is a top view of an alternative embodiment of a pointing stick having screen printed polymer resistors. 
     
    
       [0041]    It is noted that the drawings of the invention are not to scale. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention, and therefore should not be considered as limiting the scope of the invention. The invention will be described with additional specificity and detail through the accompanying drawings. The description of the invention may contain, for example, such descriptive terms as up, down top, bottom, right or left. These terms are meant to provide a general orientation of the parts of the invention and are not meant to be limiting as to the scope of the invention.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0042]    Referring to both FIGS. 1 and 2, there is a preferred embodiment of a pointing stick with integral control circuitry assembly  10  that can be used to control the movement of a cursor on a computer screen. In particular, pointing stick assembly  10  has a stick or shaft  11  and a substrate or printed circuit board  14 . Stick  11  can be made from ceramic, plastic or metal. Shaft  11  extends through a substrate bore  19 . Shaft  11  is held in bore  19  by crimping, heat staking or by using an epoxy. Printed circuit board  14  has a top side  15  and a bottom side  13 . Several strain gauge chip resistors  16  are located on top side  15 . Resistors  16  could also be located on side  13 . Chip resistors  16  are arrayed in a group of four around shaft  11 . Between each of the resistors  16  is an aperture  17  which extends through printed circuit board  14 . The apertures  17 , cause the stress of flexing printed circuit board  14  by shaft  11 , to be concentrated onto resistors  16 . Electrically conductive circuit lines  18  connect between the resistors and signal conditioning circuit device  20 . Shaft  11 , circuit board  14 , resistors  16  and apertures  17  make up actuator  12 . The resistors  16  are typically connected in a bridge configuration by the circuit lines  18 .  
         [0043]    Printed circuit board or substrate  14  has resistors  16  connected to circuit lines  18  by conventional electronic interconnection techniques such as soldering. Similarly, signal conditioning circuitry  20  is connected to another end of circuit line  18  by another solder joint. Terminals  22  connect with signal processing or conditioning circuit device  20  on printed circuit board  14  via circuit lines  18 . Signal processing device  20  is a conventional pointing stick electronic signal processing device known as Trackpoint and is commercially available from Philips Electronics Semiconductor Division. Several terminals  22  are provided to connect from printed circuit board  14  to an external electrical circuit (not shown) such as a computer motherboard.  
         [0044]    [0044]FIG. 8 shows details of a side cross-sectional view of discrete chip resistor  16  mounted to printed circuit board  14 . The resistor  16  has metallic bond pads  84  on each end. The bond pads  84  are electrically and mechanically connected to circuit lines  18  by solder  81 . During surface mount processing, a glue  83  is used to hold the resistor  16  to the circuit board  14 . The glue  83  also assists in transferring the stress from movement of shaft  11  to the resistors  16 . If desired, an encapsulating cover coat  82  can be placed over the resistor  16  to act as a protective sealant. Various cover coats such as epoxy, or silicones can be used.  
         [0045]    Pointing stick assembly  10  can be assembled as follows: The first step is to screen solder paste  81  onto lines  18  and dispense glue  83  onto board  14  at the location of the resistors. Next, the resistors  16  and device  20  are placed onto printed circuit board  14  using conventional surface mount pick and place techniques. Next, the board  14  is soldered by passing the board through an IR solder reflow oven. Next, an optional cover coat  82  could be applied. The stick  11  is placed into and fastened to board  14 . Finally, assembly  10  is tested.  
         [0046]    Referring to both FIGS. 3 and 4, there is an alternative embodiment of a pointing stick with integral control circuitry assembly  30  that can be used to control the movement of a cursor on a computer screen. In particular, pointing stick assembly  30  has a cylindrical stick or shaft  11  and a planar substrate or printed circuit board  14 . Circuit board  14  has a circular shaped cavity  24  located on bottom side  13 . Stick  11  can be made from ceramic, plastic or metal. Shaft  11  extends through a substrate bore  19 . Shaft  11  has a collar  25  at one end. Shaft  11  is held in bore  19  by crimping, heat staking or by using an epoxy. The printed circuit board  14  has a top side  15  and a bottom side  13 . Several strain gauge chip resistors  16  are located on top side  15 . The chip resistors  16  are arrayed in a group of four around shaft  11 . The chip resistors  16  are strain gage chip resistors. The cavity  24  causes the stress of flexing the printed circuit board  14  by shaft  11  to be concentrated onto resistors  16 . Electrically conductive circuit lines  18  connect between the resistors and signal conditioning circuit device  20 . Shaft  11 , resistors  16  and cavity  24 , make up actuator  32 . The resistor is mounted to the circuit board, the same as in FIGS. 1 and 2.  
         [0047]    Printed circuit board or substrate  14  has resistors  16  connected to circuit lines  18  by conventional electronic interconnection techniques such as soldering. Similarly, signal conditioning circuitry  20  is connected to another end of circuit line  18  by another solder joint. Terminals  22  connect with signal processing or conditioning circuit device  20  on printed circuit board  14  via circuit lines  18 . Signal processing device  20  is a conventional pointing stick electronic signal processing device known as Trackpoint and is commercially available from Philips Electronics Semiconductor Division. Several terminals  22  are provided to connect from printed circuit board  14  to an external electrical circuit (not shown) such as a computer motherboard.  
         [0048]    Pointing stick assembly  30  would be assembled the same as for assembly  10 .  
         [0049]    [0049]FIG. 5 shows a partial cross-sectional view of pointing stick assembly  10  mounted on a keyboard. Keyboard assembly  40  is a representation of a keyboard. Assembly  40  has a keyboard base  41 , keys  42 , and keyboard aperture  43 . Pointing stick  10  is mounted to keyboard  40  with a mounting bracket  45 . Shaft  11  extends through keyboard aperture  43  and between keys  42 . Mounting bracket  45  is attached to keyboard base  41  by conventional fasteners such as rivet  44 . Pointing stick assembly  10  is supported and contained by bracket  45  below the keyboard base  41 .  
         [0050]    [0050]FIG. 6 shows a keyboard base  41  with the shaft  11  extending upwardly between keys  42 . A rubber cap  48  is shown in phantom. The cap  48  may or may not be placed over shaft  11  to improve the ergonomics or feel for the user.  
         [0051]    [0051]FIG. 7 shows a computer system and a keyboard assembly  40  with pointing stick assembly  10 . Pointing stick  10  is located between keys  42 . Keyboard  40  is electrically connected to computer  212  by cable  218 . Computer  206  is electrically connected to monitor  213  by cable  206 . Monitor  213  has a cursor  209  on the screen. Pointing stick assembly  10  allows a user to control the position of cursor  209  on monitor  213 .  
         [0052]    When a user moves shaft  11 , in an X or Y direction, forces exerted on the shaft are translated to substrate  14  and to resistors  16  causing the resistors to change their resistance value. Signal conditioning device  20  supplies a low level voltage through resistors  16 . The change in resistance value is received by signal conditioning device  20  as an analog signal. The signal conditioning device  20  changes the analog signal into a digital signal to be outputted on terminals  22  to another electrical circuit (not shown). When a user moves shaft  11 , in the Z axis direction (along the axis of the length of the shaft), forces exerted on the shaft are translated to substrate  14  and to resistors  16  causing the all the resistors to change their resistance value and to lower the overall resistance of the resistors when they are connected in a bridge configuration.  
         [0053]    It is understood that printed circuit board  14  contains other electronic components necessary for signal conditioning which are mounted using conventional surface mount techniques. The assembly  10  is placed into bracket  45  and shaft  11  is inserted through keyboard base bore  43 . Keyboard assembly  40  is completed by attaching bracket  45  to keyboard base  41  by fasteners  44 .  
         [0054]    [0054]FIG. 9 shows an alternative embodiment of a pointing stick assembly  90  having screen printed polymer resistors. A stick or shaft  11  is shown mounted in a substrate or printed circuit board  14 . The screen printed polymer resistors  91  are applied using conventional screen printing techniques to circuit board  14 . A conductor  92  is connected on each side of resistor  91  and connects to a via connection line  93 . The via connection line  93  is connected to a via  94  which passes through circuit board  14  and electrically connects various layers in the circuit board which contain various wiring geometries. Resistors  91  are arrayed in a group of four around shaft  11 . Between each of the resistors  91  is an aperture  17  which extends through printed circuit board  14 . The apertures  17 , cause the stress of flexing printed circuit board  14  by shaft  11 , to be concentrated onto resistors  91 . The vias  94  electrically connect by a circuit line (not shown) with the vias  95  which connect to circuit line  96  which is connected to signal conditioning circuit device  20 . Electrically conductive circuit lines  18  connect between signal conditioning circuit device  20  and terminal  22 . Again, Signal processing device  20  is a conventional pointing stick electronic signal processing device known as Trackpoint and is commercially available from Philips Electronics Semiconductor Division. Terminals  22  are provided to connect from printed circuit board  14  to an external electrical circuit (not shown) such as a computer motherboard.  
         [0055]    Referring now to FIGS. 5, 6,  7  and  9 , during the operation of keyboard  40 , the motion of actuating the keys may cause undesirable vibrations or forces to be translated from keyboard  40  to device  90  which can result in a drifting cursor  209  on the display screen  213 . These undesirable forces are called Seffernick forces. Seffernick forces are those forces that are applied to a supporting structure, a keyboard for example, that are translated to the pointing stick. For example, typing on a keyboard can generate seffernick forces. In that case, the pointing stick is so sensitive that a user would be activating the pointing stick operation unintentionally. The sensitive electronics on the pointing stick would sense the deformation of the keyboard support surfaces and translate that into deformation of its own support surface and mistakenly generate control signals. Thus, seffernick forces are those forces that are translated from a support structure through the body of the pointing stick and to the electronic components of the pointing stick sufficient to generate unintentional control signals.  
         [0056]    In order to reduce these Seffernick forces, it has been found useful to surround the resistors  91  and shaft  11  with a rigid member or isolator  97  so that the resistor area is somewhat insulated from vibrations. A metal or ceramic ring  97  is shown encircling the resistors  91  and shaft  11 . The vias  94  are required in order to route electrical signals outside the inner circle of ring  97 . The ring  97  could also be used in the embodiments shown in FIGS. 1 and 3 with discrete chip resistors.  
         [0057]    Variations of the Preferred Embodiment(s)  
         [0058]    One of ordinary skill in the art of making pointing sticks or other electronic controls such as remote controls, will realize that there are many different ways of accomplishing the preferred embodiment. For example, although shaft  11  and circuit board  14  were shown as separate pieces, they could be one piece.  
         [0059]    It is further possible to have printed circuitry board  14  be another material such as a ceramic or a flexible film. Even though only one layer of circuit lines  18  are shown, it is possible to have a multilayer circuit board, for a more compact design. It is further possible to have additional signal processing devices  20  mounted on circuit board  14  to add more circuit functions.  
         [0060]    Keyboard  40  is a representation of a keyboard and can be most any multi-layered keyboard design.  
         [0061]    Even though, the specification has shown the pointing stick assembly  10  disposed below keyboard base  41 , with shaft  11  extending upwardly, it is considered equivalent to have pointing stick assembly  10  disposed on the top of the keyboard base  41  and positioned below the keys  42 . Further, assembly  10  could be placed in a cutout region in base  41 .  
         [0062]    The specification has shown the pointing stick assembly  10  mounted to a keyboard base  41 , it is contemplated, however, to mount the pointing stick assembly to other types of bases or structures like remote control devices or joysticks.  
         [0063]    Another variation of the preferred embodiment is to use other types of fasteners to hold the control assembly  10  to the keyboard besides rivet  44  such as glue, pressfitting, a retainer with holding tabs or a separate bracket.  
         [0064]    The circuit lines  18  could be located on the bottom surface  13 . Vias or plated through holes could be used to electrically connect circuit lines  18  to the top surface  15 .  
         [0065]    Shaft  11  has been shown as cylindrical. However, it is contemplated that other shaped shafts could be used such as hexagonal or octagonal or square.  
         [0066]    Even though, the specification has shown the apertures  17  located between resistors  16 . It is contemplated to have the apertures  17  extend under resistors  16  partially or completely to enhance stress concentration. It is contemplated to have the apertures  17  shaped in other shapes than that shown, such as U shaped, or circular or square or rectangular. It is further contemplated that apertures  17  may be omitted.  
         [0067]    Even though the specification has shown the metal ring  97  on the top of substrate  14 , it is considered equivalent to mount ring  97  on the bottom.  
         [0068]    While the invention has been taught with specific reference to these embodiments, someone skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.