Abstract:
A surface-mount pointing device controls the movement of an object on a display screen. The device has a base and a shaft. The shaft is mounted to the base. Several sensors are mounted on the base and around the shaft for sensing the amount of strain in the base that is created in response to a force applied on the shaft by a user. Conductors are mounted on the base and electrically connected to the sensors. Electrical leads are electrically and mechanically connected to the conductors. The electrical leads are shaped for mounting on the surface of a circuit board. The electrical leads each have a bifurcated inner terminal end that is electrically connected to the conductors. The bifurcated inner terminal end fits over and grips an edge of the base. An outer terminal end extends outwardly of the base and is shaped for mounting on the surface of a circuit board.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The following applications are herein incorporated by reference for supportive and related teachings: 
     U.S. patent application Ser. No. 09/258,513, filed Mar. 30, 1999 is an integrated surface mount pointing device and has the same assignee as the present invention. 
     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. 
     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. 
     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. 
     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. 
     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. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a pointing device for controlling the positioning, movement and operation of a cursor on a display screen associated with a computer and, more particularly, to an integrated pointing device that is mountable to a printed circuit board. 
     2. Description of the Related Art 
     Various devices are well known for controlling cursor movement over a display screen associated with a computer. Depending on the type of computer program in operation, the position of the cursor on a display screen may indicate a choice of computer commands on a menu associated with the computer program displayed on the display screen menu. One such device is a “mouse” which has a ball mounted to its underside for contacting a horizontal surface and rolling therealong when manipulated by a computer operator. The X- and Y-axis components of movement are sensed and transmitted through a connecting cable to a serial input port of the computer. This signal to the computer is varied by the amount and direction of mouse ball movement, and causes a corresponding movement of the cursor on the display screen. Typically a pair of “mouse” or “click” buttons are located on the top of the mouse at the forward end thereof. The buttons permit a computer operator to enter a selection or other command to the computer (the command typically being shown by the position of the cursor on the displayed menu) upon pressing one or the other or both buttons, depending upon the software associated with the mouse. Such a device, which is separate from the computer console and keyboard, requires a connection to a computer port and a flat, horizontal supporting surface for proper operation. Furthermore, the computer operator must completely remove one hand from the computer keyboard in order to move the mouse and thus the cursor on the display screen and then reposition the hand again over the keys of the keyboard to resume data entry. 
     Another cursor controlling and signaling mechanism is a “joystick” which, like the mouse, is completely separated from the computer console and keyboard. The joystick is typically an elongated, upright stick that extends upwardly from a base connected to the computer console by means of an electrical cable. The joystick is operated by tilting the upright stick in various directions to cause the cursor or other display element to move on the display screen in a direction and usually at a speed corresponding to the direction and pressure exerted on the stick by the computer operator. The operation of a joystick, however, frequently requires that both hands be moved from the computer keyboard, with one hand holding the base and the other hand manipulating the joystick. A “click” button is usually located on the joystick. Although a mouse or joystick can be used with a portable “laptop” or “notebook” sized computer, such devices are cumbersome, since they must be carried separately and connected to the computer before use. Moreover, such devices are not suitable for operation during travel. 
     A “trackball” is still another type of known cursor controlling device. This device, which in essence is an inverted mouse, includes a rotatable ball mounted within a housing. The ball is rotated by a finger, thumb or palm of the computer operator, and the X- and Y-components of movement are sensed and input into the computer with corresponding movement of the cursor across the display screen. “Mouse” or “click” buttons are usually located on the trackball housing, although with some models a selection signal is input by pressing the “enter” key on the standard keyboard. This type of pointing device has been somewhat useful with portable computers because it can be temporarily affixed to one side of the computer case for manipulation by one hand of the computer operator. However, although trackball devices can be removably mounted to the computer case, they still required attachment before use and removal after use and repositioning of the computer operator&#39;s hand during use. It is also noted that some trackball&#39;s are built into the computer keyboard. Nonetheless, these trackball&#39;s required a separate set of “click” buttons for selection of items on the display monitor. 
     Manufacturers of portable laptop computers, recognizing the need for placing the cursor controlling device in a permanent and more convenient location, have more recently installed a small, stubby button-like joystick at a central position on the computer keyboard, such as at the juncture of the “g,” “h” and “b” keys of the standard “QWERTY” keyboard. The button-like joystick, also known as a pointing stick, is sensitive to lateral pressure, the amount and direction of which are sensed and input into the computer to cause movement of the cursor, with the speed and direction of cursor movement corresponding to the amount and direction of pressure on the pointing stick. In order to select items on the display screen, upwardly extending “mouse” or “click” buttons must be provided somewhere on the computer, typically at a location remote from the pointing stick. This, as with the previously described cursor control devices, is disadvantageous since the hand and fingers of the computer operator must be repositioned in order to actuate the buttons and then be moved again to the proper keyboard position for typing. 
     Another disadvantage associated with a keyboard-mounted pointing stick is that a communication cable must extend from the pointing stick to a circuit board that provides a power source, amplifiers, and calibration electronics for the pointing stick. The circuit board is spaced from the pointing stick and care must be exercised when installing the cable therebetween. Moreover, the materials that make up the cable, its process of forming and method of attachment to the pointing stick contribute to increased overall cost of the pointing stick. 
     Examples of patents related to the present invention are as follows, wherein each patent is herein incorporated by reference for related and supporting teachings: 
     U.S. Pat. No. Re. 35,016 discloses a three-axis force measurement stylus. 
     U.S. Pat. No. 5,754,167 discloses a coordinate input device for a computer keyboard, wherein signals from the input device are transmitted to a separate control section by way of a flexible cable. 
     U.S. Pat. No. 5,754,166 discloses a coordinate input device for a computer keyboard. The input device has a pointing stick with heat-shrinkable tubing installed therearound for affixing strain sensors on the side surfaces of the pointing stick. 
     U.S. Pat. No. 5,712,660 discloses a cursor control stick for mounting in a computer keyboard. The control stick has a slidable plunger for generating Z-axis signals for selection of an item on a computer screen. 
     U.S. Pat. No. 5,659,334 discloses a pointing stick with a concave lower surface that rides on a force-sensing resistor network for sensing direction of pointing stick tilt. 
     U.S. Pat. No. 5,489,900 discloses a force sensitive transducer for use in a computer keyboard. 
     U.S. Pat. No. 5,325,081 discloses a supported strain gauge and joy stick assembly and method of making. 
     U.S. Pat. No. 5,263,375 discloses a contact detector using resistance elements and its application. 
     U.S. Pat. No. 4,905,523 discloses a force detector and moment detector using resistance elements. 
     U.S. Pat. No. 4,876,524 discloses 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. 
     The foregoing patents reflect the state of the art of which the applicant is aware and are tendered with the view toward discharging applicants&#39; acknowledged duty of candor in disclosing information that may be pertinent in the examination of this application. It is expressly stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicants&#39; claimed invention. 
     SUMMARY OF THE INVENTION 
     It is a feature of the present invention to provide a pointing stick for controlling cursor movement on a display screen of a computer system. 
     It is a further feature of the present invention is to provide a pointing stick device for controlling cursor movement on a display screen of a computer system that is mountable to a surface of a circuit board. 
     Another feature of the present invention is to provide a surface-mount pointing device for controlling the movement of an object on a display screen. The device includes a base and a shaft having a first end and a second end. The first end is mounted to the base. Several sensors are mounted on the base and around the shaft for sensing the amount of strain in the base that is created in response to an applied force on the shaft in at least a first direction. Several conductors are mounted on the base and electrically connected to the sensors. Several electrical leads are electrically connected to the conductors. The electrical leads are shaped for mounting on the surface of a circuit board. The electrical leads each have a bifurcated inner terminal end that is electrically connected to the conductors. The bifurcated inner terminal end fitting over and gripping an edge of the base. An outer terminal end extends outwardly of the base and is shaped for mounting on the surface of a circuit board. 
     There has thus been outlined 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 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 of basis for designing 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 
     FIG. 1 is an isometric view of a surface-mount pointing device according to the preferred embodiment of the invention; 
     FIG. 2 is an isometric view of the surface-mount pointing device of FIG. 1 mounted in a keyboard; 
     FIG. 3 is a top view of FIG. 1; 
     FIG. 4 is a top view of FIG. 1 with the top half of the molded cover and the solder removed; 
     FIG. 5 is a cross sectional view of FIG. 1 along section line  5 — 5 ; 
     FIG. 6 is an electrical schematic of a bridge circuit using the surface mount pointing device of FIG.  1 . 
    
    
     It is noted that the drawings of the invention may not necessarily be 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. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference now to the drawings, and to FIGS. 1 and 3 in particular, a surface-mount pointing device  10  that can be used to control the movement of a cursor on a computer screen (not shown) is illustrated. In particular, the pointing device  10  comprises an upright pointing stick or shaft  12  that has a first end  12 A, second end  12 B and sides  20 . Outer terminal ends  16  fit into an overmolded cover  18 . Cover  18  supports the stick  12  and the outer terminal ends  16 . Cover  18  has a top surface  17 , a bottom surface  19  and side surfaces  36 . 
     As shown in FIG. 2, the pointing device  10  is surface-mounted on a printed circuit board  21  using well-known techniques. Terminal ends  16  are mounted on a surface mount pad  92  which in turn is connected to circuit lines  82 . The circuit board  21  is in turn installed in a typing keyboard having a plurality of keys, such as keys  22 ,  24  and  26  (shown in phantom line) representative of letters, numerals, and/or symbols. Preferably, the keyboard is of the standard “QWERTY” type and the circuit board is mounted in the keyboard at a location such that the pointing stick  12  is positioned at the juncture between the “G” key  22 , the “H” key  24 , and the “B” key  26 . Although this is the preferred location for the stick  12 , it is to be understood that the pointing device  10  can be mounted at other locations, either on or off the keyboard. A resilient cap  28  (shown in phantom line), which may be formed of rubber-like material, is positioned over the top of stick  12  to increase the ease of operating the stick. The cap is sized to receive a single finger of an operator for controlling cursor movement on a computer screen in response to pressure exerted against the cap (and consequently the stick  12 ) in a desired cursor direction. 
     Referring again to FIGS. 1 and 2, the pointing stick  12  may be is preferably constructed of electrically insulative material, such as a ceramic or plastic. In the embodiment illustrated, the stick  12  is substantially square in cross section, although it could be round. Stick  12  is attached to base  50  by an epoxy. 
     With additional reference to FIGS. 4 and 5, the outer terminal ends  16  are formed on an electrical lead  60 . Each lead  60  has an outer terminal ends  16  and a bifurcated inner terminal end  61 . Each of the bifurcated inner terminal ends  61  has a pair of upper ends  62  and a lower end  64 . Upper and lower ends  62  and  64  fit over and firmly grip base  50 . Preferably, eight leads  60  are arranged on opposite sides  36 . If desired, leads  60  could be arranged on all four sides  36  of the body  18  such that four outer terminals  16  project outwardly and downwardly from each side. Arrangement of the leads  60  in this fashion offers several advantages. Since only the outer terminals  16  are in contact with the printed circuit board (PCB), the number of outer terminals  16  is related to the holding strength of the device  10  on the PCB. A larger number of outer terminals permits increased holding strength than if fewer terminals are used. Consequently, greater resistance to separation of the pointing device  10  from the PCB is realized, especially during operation of the pointing stick  12  where forces may be generated in the X, Y and Z axes, or any combination thereof The symmetrical orientation of the outer terminals  16  contributes to symmetrical loading along these axes when the pointing stick  12  is operated and facilitates alignment of the pointing device  10  with the printed circuit board during the mounting operation. The leads may initially be pre-formed in their proper orientation as part of a lead frame (not shown) for facilitating automatic assembly of the pointing device  10 . Although four outer terminals  16  are shown on two sides  36  of the body  18 , more or less outer terminals may be formed. Leads  60  would be formed from conventional electrical lead materials such as phosphor-bronze that is nickel plated and then solder plated. 
     The outer terminals  16  of the leads  60  are shown in FIG. 5 with a gull-wing shape, but may be formed into any shape so as to be attachable to a printed circuit board, including, but not limited to J-lead, thru-hole and butt terminal shapes. 
     A substrate or base  50  has an upper surface  52  and a lower surface  54  and side surfaces  53 . Upper and lower ends  62  and  64  fit over and firmly grip base  50 . Four strain sensitive resistors R 1 , R 2 , R 3 , and R 4  are arranged surrounding stick  12  on surface  52  of base  50 . Resistors R 1 -R 4  function as a force sensor. Electrically connected to each end of resistors R 1 -R 4  are conductor lines  56 . Each conductor  56  line terminates in a conductor pad  57  near side surface  53 . Conductor lines  56  and pads  57  are located on surface  52  of base  50 . Conductor pads  57  are also located on lower surface  52  of base  50 . On the lower surface, conductor lines  56  are absent. Base  50  is preferably constructed of conventional alumina ceramic. 
     Resistors R 1 -R 4  are formed of a material that exhibits a change in electrical properties, such as resistance, in response to the amount of strain applied thereto. Preferably, a conventional resistive thick film material is screened onto the base  50  using conventional thick film screening techniques. Alternatively, a resistive thin film material can be sputtered onto base  50 . The conductor lines  56  and pads  57  are similarly formed of conventional thick film materials using conventional thick film screening techniques. The strain sensitive resistors R 1 -R 4  may be laser trimmed if desired to increase accuracy. 
     Upper and lower ends  62  and  64  of bifurcated inner end  61  fit over and firmly grip base  50 . Ends  62  slides over and contacts with conductor pad  57 . End  64  contacts lower surface  54 . Solder joints  58  electrically connect conductor pads  57  to upper end  62  and lower end  64 . 
     Cover  18  is formed from an overmolded thermoplastic or thermo-set epoxy. During manufacturing the base  50 , leads  60  and stick  12  would be inserted into a mold and liquid plastic injected into the mold, then cooled to form cover  18 . 
     Referring now to FIG. 6, an electrical schematic  100  of a bridge circuit incorporating the resistors R 1 -R 4  is shown. Specifically, this circuit is an example of how the pointing stick  10  can be arranged to interface with the electronics (not shown) on the circuit board  21 . The resistors on opposite sides of the stick  12  are configured in two half bridge circuits, resistors R 1  (Y+) and R 2  (Y−) form a first half bridge, while resistors R 3  (X+) and R 4  (X−) form the second half bridge. A fixed resistor  102  is connected between the supply voltage  104  of the system and a node  106 . The X OUT output  108 , Y OUT output  110 , and Z OUT output  112  are amplified by three differential amplifiers  114 ,  116 , and  118 , respectively. Each amplifier has a variable reference voltage input. These reference voltages are calibrated to set the output to zero along each axis when no force is applied to the stick  12 . The X and Y axis outputs  116  and  118  are developed when an X or Y directional force is applied to the stick  12 . For example, when a force is applied in the X direction, the X− and X+ strain sensitive resistors R 3 , R 4  change resistance in opposite directions and cause an output change. The same is true for the Y-axis. A Z-axis output is developed when a Z-axis force is applied to the top of the stick  12 . Force in the Z-axis causes all strain gauge resistors R 1 -R 4  to change in a negative direction. This change lowers the total impedance of the two half bridges. The lower bridge impedance causes a voltage change in the Z OUT output  112  since the series resistor  102  is fixed. 
     Remarks About the Preferred Embodiments 
     One of ordinary skill in the arts of strain gages and ceramic materials, and more particularly the art of designing pointing sticks, will realize many advantages from using the preferred embodiment. In particular, strain gages are devices that sense the amount and direction of applied pressure placed upon the pointing stick. The sensed pressure creates electrical output signals used to direct the cursor on a display device. 
     A skilled artisan would realize that the pointing device  10  is now capable of performing selection and dragging of icons on a monitor in addition to double clicking for selection of an item. In this operation, the user would hold down the pointing stick  12  while exerting additional force in the X-Y plane for controlling the direction of the icon being dragged. All of these functions are now capable of being performed with a single finger while the remaining fingers are located on the keyboard. 
     A skilled artisan would realize that the pressure fitting of lead  60  over base  50  and then soldering allows for a simple manufacturing technique that is repeatable and able to hold close registration tolerances during assembly. 
     The above-described embodiments can be constructed with the same dimensions and lead pitches as standard commercially available IC packages and has all of the advantages associated with surface mount printed circuit board assembly. The compact size would allow for its use in a wide variety of applications, while the minimal parts and ease of assembly of the above-described embodiments also renders the device relatively inexpensive to produce. 
     VARIATIONS OF THE PREFERRED EMBODIMENTS 
     One of ordinary skill in the art of making pointing devices will realize that there are many different ways of accomplishing the preferred embodiment. For example, although the electrical leads  60  were shown on two sides of the device, leads on  4  sides could be used. Further, electrical leads  60  were shown as having a bifurcated end  61 , if desired the bifurcated end  61  could be omitted and soldered to conductor pad  57 . Also, leads  60  could be wire bonded to condutor pads  57 . 
     Although base  50  was shown to be made of ceramic, it is contemplated to make base  50  from a printed circuit board material such as FR 4  and to use polymer strain gage resistors or discrete strain gage chip resistors. 
     It is to be understood that the X, Y, and Z axes, as well as the terms upper, lower, etc., and their respective derivatives as used herein are intended to describe relative, rather than absolute directions and/or positions. 
     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.