Abstract:
A two-axis ball-based cursor control apparatus with tactile feedback is provided, which includes a housing, a spherical ball contained partially within the housing, a plurality of magnetic elements fixed within the spherical ball, and a plurality of magnetic elements fixed within the housing. When the spherical ball is at rest, an attractive magnetic force between some or all of the first magnetic elements and some or all of the second magnetic elements resists motion of the ball. When a sufficient rotational force is applied to the ball, the ball rotates about one or both axes until the applied force no longer exceeds the magnetic force, at which point the magnetic force causes the ball to stop at a new position, providing the user with tactile feedback to indicate that the ball position has changed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates in general to a two-axis ball-based cursor control apparatus, such as a mouse or trackball, and in particular to a cursor control apparatus which provides the user with tactile feedback corresponding to uniform incremental movements of the cursor about both axes of movement.  
           [0003]    2. Background Art  
           [0004]    Two-axis cursor control devices are well-known in the art. These types of devices are common components of personal computer systems used for controlling the movement of a cursor appearing on a video monitor. Cursor control devices are also finding use in handheld devices such as PDA&#39;s and cellular telephones where graphical user interfaces are manipulated by the user. Two well-known forms of such devices include the computer mouse and the trackball. A computer mouse consists of a spherical ball, approximately one-half inch in diameter and freely rotatable about two axes of rotation, mounted within a larger housing which rests on a flat surface, so that a portion of the ball protrudes from the bottom of the housing and comes into contact with the surface. Typically, a pair of rotors are positioned in contact with the ball, one aligned with each axis. Each of these rotors are in turn connected by an axle to a disk with uniformly spaced slots or holes around the outer portion thereof When the mouse is moved along the flat surface, the rotation of the ball is translated to the rotors, and in turn to the associated disks. Light emitters and sensors are positioned spanning each of the disks whereby the beam of light is alternatively passed through the disk to the sensors and then blocked from the sensors as the disk rotates. Each disk typically has two pairs of emitters and sensors associated therewith in order to determine the rate and direction of rotation of the disk. The sensors are connected to an electrical circuit which generates an electrical signal. From the signals generated by each of the two disks positioned perpendicular to one another, the direction and acceleration of the displacement of the ball, and hence of the mouse itself, is determined. This information is then translated into motion of the cursor on the screen of the computer using a predetermined relationship between the magnitude of the mouse displacement in each direction and the distance which the cursor moves in that direction. Thus, the user&#39;s horizontal and vertical movement of the mouse on the flat surface is translated into horizontal and vertical movement of the cursor on the screen.  
           [0005]    A trackball is a similar type of cursor control apparatus in which the user merely rotates the ball itself instead of moving the entire housing. The ball typically protrudes from the top of its housing, where it can be rotated directly by the user by hand. The remainder of the device is typically substantially similar to that described above, with the rotation of the ball translated to a pair of rotors associated with each axis of rotation, and then to a pair of disks, whose motion is then translated into cursor motion by light sensors. Thus, unlike a mouse, a trackball apparatus remains stationary while the user directly rotates the ball itself.  
           [0006]    There are, however, certain disadvantages to these types of cursor control devices. In order to achieve precise targeting of the cursor, the user must possess a certain degree of hand to eye coordination to align the cursor with the desired location. This can be troublesome in certain applications, such as pull-down menus implemented in PC graphical user interface based operating systems. Typically a single mouse click causes a number of further commands or options to appear in row after row. To select a give command or option the user must position the cursor over the text label for the desired option to execute same. Any slight movement of the device by the user will cause the cursor displayed on the screen to move to a different command or option item than that desired. Positioning is accomplished by moving the mouse or trackball, which moves in one continuous motion, until the cursor is in position. The absence of any tactile feedback corresponding to the movement of the cursor makes such precise targeting even more difficult. In addition, some devices have a tendency for the cursor to drift from its desired location because any slight or unintentional force exerted on the control device will cause it to move, and correspondingly displace the cursor from the desired location. In applications where precise targeting and control of the cursor is essential, for instance in computer aided drafting, these drawbacks are particularly unwelcome. Incorporating graphical user interfaces into smaller devices, such as cellular phones, causes potential safety issues. For example, a person using a phone in a car to recall a speed dial number using the graphical interface may cause an accident by trying to align a cursor over the display of names or numbers stored in memory.  
           [0007]    Also known in the prior art are control devices consisting of a rotatable disk or wheel which is rotatable about only one axis in discrete, uniform increments. Examples of such devices include dials for applications such as frame-by-frame movement in a video-disc player or to switch tracks on an audio-disc player. Such devices may provide tactile feedback to the user in the form of a “clicking” or ratcheting effect which occurs when the disk or wheel is rotated. The user knows when such a device has advanced from one position to the next because of the tactile sensation triggered by the dial “snapping” into the next position. Such known devices, however, have the disadvantage of providing such incremental rotation about only one axis, therefore making them ill-suited for applications requiring control of a cursor moving in two dimensions.  
           [0008]    It would therefore be desirable to provide a cursor control device which would allow the user to move the cursor in discrete, uniform increments in two dimensions, in order to more easily achieve precise targeting of the cursor with its intended position on the screen. Further, it would also be desirable to provide for such a device which provides tactile feedback to the user which corresponds to the movement of the cursor on the screen. In addition, it would be desirable to provide for such a device in which the unintentional motion of the cursor due to inadvertent movement of the device is minimized.  
           [0009]    These and other objects of the present invention will become apparent to those of ordinary skill in the art in light of the present specifications, drawings, and claims.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention is directed to a two-axis ball-based cursor control apparatus providing for discrete, uniform displacements in each direction of rotation in order to achieve a precise alignment of cursor and target in electronic displays, and also providing for tactile feedback corresponding to each incremental displacement. The cursor control apparatus comprises a housing, a spherical ball partially within said housing capable of freely rotating about at least two axes, a plurality of first magnetic elements within the spherical ball securely positioned relative to one another, and a plurality of second magnetic elements fixed within the housing. The second magnetic elements are positioned so that, when the spherical ball is at rest, an attractive magnetic force exists between one or more of the first magnetic elements and one or more of the second magnetic elements, in order to maintain the spherical ball at rest until a rotational force greater than the attractive force is applied to it by the user. When such a force is applied, the ball rotates about at least one axis until such time as the applied force no longer exceeds the attractive force, at which time the attractive force causes the spherical ball to come to a stop at a new stationary position. This provides the user with tactile feedback indicating that the position of the spherical ball has changed.  
           [0011]    In one embodiment, each of the first magnetic elements is composed of a magnetically responsive material, such as ferrous metal, and each of the second magnetic elements is composed of a permanent magnet or electromagnet. It is deemed within the scope of the present invention to utilize any material or combination of materials provided that they are attracted to one another by magnetic force. In a second embodiment, each of the first magnetic elements is composed of a permanent magnet and each of the second magnetic elements is composed of a magnetically responsive material, such as a ferrous metal. In a third embodiment, each of the first magnetic elements and each of the second magnetic elements are composed of permanent magnets, with the first and second elements positioned so that when a first magnetic element and a second magnetic element come into close proximity with one another, the ends of each which are nearest to one another are of opposite polarity, thereby attracting one to the other.  
           [0012]    In a preferred embodiment, the cursor control apparatus also comprises a means for measuring the displacement of the spherical ball about each axis of rotation. This may comprise a plurality of rotors adjacent to the spherical ball, and an axle and a rotating disk associated with each rotor. The rotors are positioned so as to transfer the rotational motion of the spherical ball about one axis of rotation to the corresponding rotating disk. This embodiment also comprises at least one electronic sensor associated with each rotating disk for measuring the direction and magnitude of the rotation of the rotating disks and for providing a signal to the associated electronic device, which changes the position of the cursor.  
           [0013]    In another embodiment of the invention, the spherical ball further comprises a stabilizer which provides an additional force to maintain the spherical ball in a stationary position. This stabilizer may comprise an arm extending from said housing and a rotor attached to the arm which is positioned so as to exert a force on the surface of the spherical ball biasing the ball toward the two rotors.  
           [0014]    A further embodiment includes a plurality of pivoting members within the spherical ball, each of which contains one of the first magnetic elements. The pivoting members are allowed to pivot in order to maintain a uniform separation between the first magnetic elements and the second magnetic elements when the spherical ball is stationary.  
           [0015]    In another embodiment, the invention further comprises at least one switch element for allowing the user to select options corresponding to particular cursor locations on an electronic display screen. This at least one switch element may comprise at least one button element which is manipulated directly by pressure applied thereto by the user in order to trigger the switch element. The at least one switch element may also be positioned so as to come into contact with the spherical ball when pressure is applied to the spherical ball by the user, causing the spherical ball to depress the switch element, thereby triggering the switch element.  
           [0016]    In the event that an electromagnet is utilized, the user may be provided with the option of disconnecting the power to the electromagnet such that the present device can operate as a conventional cursor control apparatus providing for continuous movement and reconnecting the power to operate the present apparatus with tactile feedback.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    [0017]FIG. 1 is a perspective view of a cursor control apparatus according to the present invention.  
         [0018]    [0018]FIG. 2 is a top view of the cursor control apparatus shown in FIG. 1.  
         [0019]    [0019]FIG. 3 is a left elevational view of the cursor control apparatus shown in FIG. 1.  
         [0020]    [0020]FIG. 4 is a cross-sectional view of the cursor control apparatus shown in FIG. 1, showing the interior of the spherical ball portion.  
         [0021]    [0021]FIG. 5 is a cross-sectional view of a cursor control apparatus according to another embodiment of the invention, in which the first magnetic elements are fixed in place relative to the spherical ball.  
         [0022]    [0022]FIG. 6 is an exploded perspective view of the cursor control apparatus shown in FIG. 5.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will be described herein one specific embodiment, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated.  
         [0024]    Two-axis ball-based cursor control apparatus with tactile feedback  20  is shown in FIGS.  1 - 4  as including outer housing,  22 , spherical ball  24 , second magnetic elements  26 , rotor  28 , rotor disks  30 , and stabilizer  32 . Cursor control apparatus  20  is intended for use in controlling the movement of a cursor on electronic display screens, including cathode-ray screens, such as those commonly found in computers, and liquid crystal displays of the type commonly used in hand-held electronic devices, such as personal digital assistants (PDAs), cellular telephones, and the like. Cursor control apparatus  20  is designed to provide cursor motion in two directions in discrete, uniform increments, along with tactile feedback to the user corresponding to each increment of motion. The size of the desired increments of motion can vary depending on the type of device in which the apparatus is used. For instance, if cursor control apparatus  20  is used in a hand-held device with a small liquid crystal display, each increment of cursor motion may correspond to one pixel on the display screen. If, on the other hand, cursor control apparatus  20  is used with a conventional computer monitor with dimensions of thousand of pixels in length and width, then each increment of cursor motion may correspond to many pixels.  
         [0025]    Spherical ball  24  is shown as including first magnetic elements  40 , central bushing  42 , universal joints  44 , arms  46 , and screw holes  48 . Spherical ball  24 , shown in cross-section in FIG. 4, is symmetrical about each of the three principal axes. Central bushing  42  is fixed in place at the center of spherical ball  24 . One arm  46  extends in either direction from central bushing  42  along each of the three principal axes, resulting in a total of six arms  46 . Affixed to the end of each arm  46  in the embodiment illustrated is a universal joint  44 , each of which contains a first magnetic element  40 , which is attracted by one of second magnetic elements  26  when in proximity therewith. In an alternative embodiment, the universal joints  44  can be omitted, and first magnetic elements  40  may be fixed in place relative to spherical ball  24 , as described below. Screw holes  48  are provided for joining the component parts of spherical ball  24  together by means of several screws.  
         [0026]    It is contemplated that first magnetic elements  40  and second magnetic elements  26  will be composed of materials which will give rise to an attractive magnetic force between the two of sufficient strength to retard motion of spherical ball  24  when one of first magnetic elements  40  and one of second magnetic elements  26  come into close proximity with one another. For example, each of first magnetic elements  40  may be composed of a magnetically responsive material, such as a ferrous metal and each of second magnetic elements  26  may be composed of a permanent magnet. Alternatively, each of first magnetic elements  40  may be composed of a permanent magnet and each of second magnetic elements  26  may be composed of a magnetically responsive material, such as ferrous metal. Additionally, each of first magnetic elements  40  and second magnetic elements  26  may be composed of a permanent magnet, with the first and second elements positioned so that when a first magnetic element  40  and a second magnetic element  26  come into close proximity with one another, the ends of each which are nearest to one another are of opposite polarity, thereby generating an attractive magnetic force between them.  
         [0027]    Second magnetic elements  26  are fixed within housing  22 , adjacent to the outer surface of spherical ball  24 , such that the distance between second magnetic elements  26  and first magnetic elements  40  is at a minimum when spherical ball  24  is stationary. In this orientation, an attractive force exists between second magnetic elements  26  and first magnetic elements  40  which tends to keep spherical ball  24  at rest. The present embodiment includes five second magnetic elements  26 , three of which are shown in FIG. 4 (the remaining two are located out of the cross-section plane). However, the number of second magnetic elements  26  can vary depending on the space constraints imposed by the size of housing  22  and the desired magnitude of the attractive force between the second magnetic elements  26  and the first magnetic elements  40 . As the number (or strength) of second magnetic elements  26  is increased, the total attractive force increases. As a result, cursor control apparatus  20  becomes more resistant to inadvertent rotation of spherical ball  24 , and the accompanying undesired motion of the cursor, due to the fact that the user must exert more force in order to rotate spherical ball  24  to overcome the attractive force between the second magnetic elements  26  and the first magnetic elements  40 .  
         [0028]    In order to move the cursor, the user rotates spherical ball  24  about one or both of its axes of rotation by exerting a rotational force on the portion of spherical ball  24  extending out of housing  22 . Initially, spherical ball  24  is in a stable position due to the forces of attraction between first magnetic elements  40  and second magnetic elements  26 . When a force is exerted on spherical ball  24  which exceeds the combined forces of attraction at that instant, spherical ball  24  will begin to rotate about one or both of its axes. Spherical ball  24  will then quickly “snap” to the next stable position due to the decrease and subsequent increase in the attractive forces as each first magnetic element  40  approaches the next second magnetic element  26 . This snapping effect will provide the user with tactile feedback which indicates that the cursor has moved another increment in the direction of motion of spherical ball  24 .  
         [0029]    The number of first magnetic elements  40  corresponds to the number of increments of cursor motion for each revolution of spherical ball  24 , and can be varied as desired. The configuration of the present embodiment provides that each increment of cursor motion requires one-quarter revolution of spherical ball  24  by the user. As seen in FIG. 4, the portion of spherical ball protruding from the opening in housing  22  contains about one-third of the circumference of spherical ball  24 . This configuration, therefore, allows the user to rotate spherical ball  24  through one increment of cursor motion, or one-quarter revolution, without removing his/her fingers from the surface of spherical ball  24 . Such a configuration is well-suited for applications in which it is anticipated that the typical number of desired increments of cursor motion at any one time will be small, such as in small liquid crystal displays having relatively few pixels. However, for applications in which the number of desired increments of cursor motion at any one time is significantly larger, a configuration in which spherical ball  24  contains a greater number of first magnetic elements  40  would be optimal, as it would result in more increments of cursor motion for each revolution of spherical ball  24 .  
         [0030]    In the current embodiment, each of second magnetic elements  26  (except for the one on the bottom side of spherical ball  24 ) are offset downward from the axes of rotation of spherical ball  24 . This allows a larger portion of spherical ball  24  to extend out of the opening in housing  22 , providing more surface area for the user to manipulate spherical ball  24 . This configuration, however, requires a means for adjusting the position of first magnetic elements  40  in order to provide for a stable position of spherical ball  24  when at rest. Accordingly, universal joints  44  are used to allow first magnetic elements  40  to rotate about arms  46 . As a result, the distance between each of second magnetic elements  26  and its corresponding first magnetic element  40  when spherical ball  24  is at rest is substantially identical, resulting in a more stable rest position, which minimizes the possibility of inadvertent cursor motion. Without the presence of universal joints  44 , the distances, and hence the attractive forces, between first magnetic elements  40  and second magnetic elements  26  would vary, resulting in a less stable rest position of spherical ball  24 , and increasing the possibility of inadvertent cursor motion.  
         [0031]    Rotor  28  is positioned in contact with spherical ball  24  so that the rotational motion of spherical ball  24  about one axis is transferred to rotor  28 . Cursor control apparatus  20  includes another substantially similar rotor (not shown) which is positioned so as to reflect rotation about the second axis of rotation of spherical ball  24 . This rotation is then transferred to rotor disks  30  by means of axles  31 . The rotational motion of spherical ball  24  about its two axes can then be determined in a conventional manner based on the direction and magnitude of rotation of rotor disks  30 , for example through sensors using beams of light to measure the rotational displacement of rotor disks  30 , as is well known in the art of computer mice.  
         [0032]    In this embodiment of the invention, spherical ball  24  is also held in the stationary position by stabilizer  32 , which takes the form of an arm  34  extending from the top of housing  22  with an attached rotor  36  held against the top of spherical ball  24 , preferably by a spring-loaded mechanism.  
         [0033]    Cursor control apparatus  20  preferably also includes button or switch elements allowing the user to make selections in conjunction with the position of the cursor on the screen. These elements may take any of several forms, including buttons such as those found on the top side of a conventional computer mouse and/or a switch element located beneath spherical ball  24  which is activated by pressing down on spherical ball  24 , thereby depressing the switch element.  
         [0034]    In an alternative embodiment of the invention shown in FIGS. 5 and 6, the universal joints are eliminated, and first magnetic elements  140  are fixed in place relative to spherical ball  124 . In this embodiment, cursor control apparatus  120  is shown in FIG. 6 as including top housing portion  122 , spherical ball  124 , second magnetic elements  126 , and bottom housing portion  128 . Cursor control apparatus  120  also includes a pair of rotors and corresponding rotor disks (not shown) for translating the rotation of spherical ball  124  into cursor motion, in a similar fashion as the previous embodiment.  
         [0035]    Spherical ball  124  is shown in FIG. 6 as including first magnetic elements  140 , top half  142 , inner core  144 , bottom half  146 , and posts  150 . Top half  142  and bottom half  146  are preferably joined together by means of screws, as in the previous embodiment, or by an adhesive. First magnetic elements  140  are held within inner core  144 , as shown in FIG. 5, which serves to hold each of first magnetic elements  140  in place relative to one another. Inner core  144  is in turn held in place by posts  150 , which interact with holes  152  on inner core  144  to prevent inner core  144  from rotating relative to top half  142  and bottom half  146 .  
         [0036]    As shown in FIG. 5, this embodiment of the invention contains a larger number of second magnetic elements  126  than does the previous embodiment. As a result, this configuration provides that each increment of cursor motion requires only one-eighth revolution of spherical ball  124 , which is the amount of rotation required for spherical ball  124  to transition from one stable position to the next. Thus, each full revolution of spherical ball  124  will generate eight increments of cursor motion. This is contrasted with the previous embodiment, in which each increment of cursor motion required one-quarter rotation, thereby generating four increments of motion per revolution.  
         [0037]    Additional second magnetic elements  126  may be added or removed as desired in order to provide for different numbers of increments per revolution of spherical ball  124 . However, several factors exert a practical limit on the number of second magnetic elements  126  which may be added. The first of these is size, as the magnitude of the magnetic force generated by the interaction between first magnetic elements  140  and second magnetic elements  126  depends in part on the size of each. As they are reduced in size, the corresponding reduction in strength of the magnetic force generated will serve to minimize the amount of tactile feedback provided to the user. Also, as second magnetic elements  126  are added, the interval between stable positions of spherical ball  124  is reduced. At a certain point, the interval between each stable position will become so small that the user is not able to discern between movements of one increment and multiple increments.  
         [0038]    The foregoing description and drawings are merely to explain and illustrate the invention, and the invention is not limited thereto except insofar as the independent claims are so limited, as those skilled in the art with the present disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.