Abstract:
A computer input device includes a scrolling apparatus that includes a rotatable scroll wheel and a scroll wheel locking device. The scroll wheel locking device is activated when the document being scrolled reaches its end. When activated, the scroll wheel locking device prevents further rotation of the scroll wheel in the direction that would normally be past the end of the document, but permits rotation of the scroll wheel in the opposite direction towards the other end of the document. The scroll wheel locking device includes lockable wheel rotatable with and spaced from the scroll wheel. The lockable wheel includes angularly spaced pins. A tri-position lever includes locking elements engagable with the teeth to cause unidirectional locking.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a scrolling apparatus for repositioning an image relative to a display screen. More particularly, the invention relates to a scrolling apparatus that utilizes a stopping and locking system to terminate its rotation in a particular direction when the user reaches the end of a document. The invention has application to input devices, such as a mouse, trackball, or keyboard, to scroll an image relative to a display screen.  
         [0003]     2. Description of Background Art  
         [0004]     The viewable contents of a computer file, such as a text document, spreadsheet, digital photograph, Web page, or other image rendered on a conventional display screen, may possess a size exceeding the viewable boundaries of the display screen. To address this issue, an individual may utilize a scrolling apparatus to reposition the image relative to the display screen, thereby permitting the individual to view portions of the computer file not currently rendered. As utilized herein, scrolling describes a translatory movement of the image relative to the display screen and in a particular direction. For example, scrolling down generally describes a movement of the image relative to the display screen so as to produce an effect of moving downward in the image. Similarly, scrolling up, scrolling left, and scrolling right generally describe movement of the image relative to the display screen so as to produce an effect of moving the image upward, left, and right, respectively.  
         [0005]     Scrolling apparatuses have been incorporated into a plurality of peripheral input devices, including computer mice and trackball pointing devices, and keyboards, for example. An example of a computer mouse incorporating a scrolling apparatus is disclosed in U.S. Pat. No. 5,912,661 to Siddiqui, which is hereby incorporated by reference. Elements of the scrolling apparatus include a finger-engageable scroll wheel and a sensor assembly. The scroll wheel is mounted within a housing of the computer mouse, and a portion of the scroll wheel protrudes from an opening in the housing to permit an individual to selectively rotate the scroll wheel. The sensor assembly detects rotation of the scroll wheel and transmits a corresponding signal to a host computer, thereby directing the image to scroll relative to the display screen. By rotating the scroll wheel in a first direction, an image on a display screen may be scrolled upward, for example. Similarly, by rotating the scroll wheel in an opposite second direction, the image may be scrolled downward. Accordingly, a scroll wheel may be operated in a bi-directional manner to vertically scroll the image relative to the display screen.  
         [0006]     Based on the size of the document the user is scrolling within, the user may have to rotate the scroll wheel a large number of revolutions to reach a desired location in the document. Rather than scrolling slowly through the document, users commonly rotate the scroll wheel many times in a rapid manner because a slow controlled rotation can be time consuming. However, under such circumstances, it is common that the user will unintentionally “over-scroll” past the point of the intended location, and scroll to the end of the document, with additional scrolling commands being sent because there is an attempt to over-scroll past the end of the document. This results in the computer system scrolling the image to the end of the document, and then attempting to process extra scrolling commands that are not performed. In addition to wasted finger motion by the user, this results in a loss of efficiency in operating the computer.  
       SUMMARY OF THE INVENTION  
       [0007]     It is an aspect of the invention to provide a mechanism for a scroll wheel that is linked to the document on the computer screen so that when the extremity of the document is reached in any direction (beginning, end, left or right) the scroll wheel of the input device, e.g., mouse, trackball, or keyboard, will “lock” and the wheel can no longer be activated in that direction and can only be reversed from that position.  
         [0008]     In one aspect of the present invention, the invention includes a scroll wheel assembly and a locking system for the scroll wheel assembly. The locking system includes a wheel that is rotatable with the scroll wheel and a locking device that interfaces with the lockable wheel.  
         [0009]     In another aspect, the invention provides an input device for scrolling an image relative to a display screen. The input device includes a scroll wheel that is rotatable in opposing first and second directions. A scroll wheel locking element is movable into a position that prevents the rotation of the scroll wheel in the first direction and permits rotation of the scroll wheel in the second direction.  
         [0010]     In another aspect, the invention provides an input device for scrolling an image relative to a display screen. The input device includes a scroll wheel and a unidirectional scroll wheel locking system.  
         [0011]     According to another aspect, an input device has a scroll wheel and a housing. The scroll wheel extends partially through an aperture in the housing and can be rotated in opposing directions. A controller within the housing is coupled to activate a scroll wheel locking element such that it can prevent the rotation of the scroll wheel in the first direction and permit rotation of the scroll wheel in the second direction.  
         [0012]     In yet another aspect, the invention provides an input device with a scroll wheel for scrolling an image and a scroll wheel locking lever positionable in first, second, and third distinct positions.  
         [0013]     The advantages and features of novelty characterizing the present invention are pointed out with particularity in the appended claims. To gain an improved understanding of the advantages and features of novelty, however, reference may be made to the following descriptive matter and accompanying drawings that describe and illustrate various embodiments and concepts related to the invention.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0014]     The foregoing Summary of the Invention, as well as the following Detailed Description of the Invention, will be better understood when read in conjunction with the accompanying drawings.  
         [0015]      FIG. 1  is a functional block diagram of an illustrative general-purpose digital computing environment in which one or more aspects of the present invention may be implemented.  
         [0016]      FIG. 2  is a perspective view of an input device incorporating a scrolling apparatus in accordance with the present invention, the input device being operatively connected to a host computer and a display device  
         [0017]      FIG. 3  is a schematic side view illustrating an exemplary embodiment of the scroll wheel assembly.  
         [0018]      FIG. 4  is a schematic side view of the locking member of the scroll wheel assembly coupled to an actuator.  
         [0019]      FIGS. 5-7  are schematic side views of the scroll wheel locking assembly with the locking member being in different positions relative to the lockable wheel.  
         [0020]      FIG. 8  is a schematic isometric view of the scroll wheel locking assembly illustrating an alternative arrangement.  
         [0021]      FIG. 9  is a flowchart depicting the operation of scroll wheel according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]     The following discussion and accompanying figures disclose scrolling apparatuses for moving or scrolling an image relative to a display screen. Viewable portions of computer files, which include text documents, spreadsheets, digital photographs, computer-generated drawings, or Web pages, for example, may be rendered as an image on a display screen. The manner in which the image is configured to be rendered on the display screen determines whether all portions of the image are simultaneously rendered within viewable boundaries of the display screen. Accordingly, the image may be configured to possess dimensions fitting entirely within the viewable boundaries of the display screen. The same image, however, may also be configured to possess dimensions exceeding the viewable boundaries of the display screen. In other words, the image may include a rendered portion that is currently viewable on the display screen and a hidden portion that is not simultaneously viewable on the display screen. A scrolling member of the present invention is configured to enable the scrolling of the image relative to the display screen, to thereby revealing the hidden portions of the image, and a locking member is configured to selectively lock the scrolling member under various conditions such as reaching the end of the document.  
         [heading-0023]     Illustrative Operating Environment  
         [0024]     A peripheral device, such as a mouse, trackball, or keyboard, may be operatively connected to a host computer and includes input devices which are configured for freeform cursor control or scrolling for moving an image in multiple axes relative to a display screen. In one aspect, the peripheral device has a rotatable scrolling member. Various aspects of the present invention may at least be described in the general context of apparatus and computer-executable instructions, such as program modules, executed by one or more computers or other devices. Accordingly, it may be helpful to briefly discuss the components and operation of a general purpose computing environment on which various aspects of the present invention may be implemented. Such an illustrative host computer system is illustrated in  FIG. 1 .  
         [0025]     Accordingly,  FIG. 1  illustrates a schematic diagram of an illustrative general-purpose digital computing environment that may be used to implement various aspects of the present invention. In  FIG. 1 , a host computer  100  includes a processing unit  110 , a system memory  120 , and a system bus  130  that couples various system components including the system memory to the processing unit  110 . The system bus  130  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. The system memory  120  includes read only memory (ROM)  140  and random access memory (RAM)  150 .  
         [0026]     A basic input/output system  160  (BIOS), containing the basic routines that help to transfer information between elements within the computer  100 , such as during start-up, is stored in the ROM  140 . The computer  100  also includes a hard disk drive  170  for reading from and writing to a hard disk (not shown), a magnetic disk drive  180  for reading from or writing to a removable magnetic disk  190 , and an optical disk drive  191  for reading from or writing to a removable optical disk  192 , such as a CD ROM or other optical media. The hard disk drive  170 , magnetic disk drive  180 , and optical disk drive  191  are connected to the system bus  130  by a hard disk drive interface  192 , a magnetic disk drive interface  193 , and an optical disk drive interface  194 , respectively. The drives and their associated computer-readable media provide nonvolatile storage of computer readable instructions, data structures, program modules, and other data for the personal computer  100 . It will be appreciated by those skilled in the art that other types of computer readable media that may store data that is accessible by a computer, such as magnetic cassettes, flash memory cards, digital video disks, Bernoulli cartridges, random access memories (RAMs), read only memories (ROMs), and the like, may also be used in the example operating environment.  
         [0027]     A number of program modules may be stored on the hard disk drive  170 , magnetic disk  190 , optical disk  192 , ROM  140 , or RAM  150 , including an operating system  195 , one or more application programs  196 , other program modules  197 , and program data  198 . A user may enter commands and information into the computer  100  through input devices, such as a keyboard  101  and a pointing device such as a mouse  102  and/or a trackball device (not shown). Other input devices (not shown) may include a digitizer  165  and digitizing pen  166 , a microphone, a joystick, a game pad, a satellite dish, a scanner, or the like. These and other input devices often are connected to the processing unit  110  through a serial port interface  106  that is coupled to the system bus  130 , but may be connected by other interfaces, such as a parallel port, game port, or a universal serial bus (USB). Further still, these devices may be coupled directly to the system bus  130  via an appropriate interface (not shown). A monitor  107  or other type of display device with a display screen is also connected to the system bus  130  via an interface, such as a video adapter  108 .  
         [0028]     The computer  100  may operate in a networked environment using logical connections to one or more remote computers, such as a remote computer  109 . The remote computer  109  may be a server, a router, a network PC, a peer device, or other common network node, and may include many or all of the elements described above relative to the computer  100 , although only a memory storage device  111  with related applications programs  196  have been illustrated in  FIG. 1 . The logical connections depicted in  FIG. 1  include a local area network (LAN)  112  and a wide area network (WAN)  113 . Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets, and the Internet.  
         [0029]     When used in a LAN networking environment, the computer  100  is connected to the local network  112  through a network interface or adapter  114 . When used in a WAN networking environment, the personal computer  100  typically includes a modem  115  or other means for establishing a communications link over the wide area network  113 , e.g., to the Internet. The modem  115 , which may be internal or external, is connected to the system bus  130  via the serial port interface  106 . In a networked environment, program modules depicted relative to the personal computer  100 , or portions thereof, may be stored in a remote memory storage device.  
         [0030]     It will be appreciated that the network connections shown are exemplary and other techniques for establishing a communications link between the computers may be used. The existence of any of various well-known protocols such as TCP/IP, Ethernet, FTP, HTTP and the like is presumed, and the system may be operated in a client-server configuration to permit a user to retrieve web pages from a web-based server. Any of various conventional web browsers may be used to display and manipulate data on web pages.  
         [heading-0031]     Overview of the Input Device  
         [0032]      FIG. 2  depicts an embodiment of a host computer  100  operatively connected to a display device such as a monitor  107 , and an input device, which may be a computer mouse  102 . One skilled in the relevant art will recognize that a computer file may be processed by the host computer  100  and a signal may be transmitted to the monitor  107 , thereby directing the monitor  107  to render an image on the monitor  107 . The image includes, in accordance with the discussion above, a schematically-represented rendered portion  201  and a hidden portion (not shown). An individual viewing the image will not, therefore, view all portions of the image simultaneously. To address this issue, the input device  102  incorporates a scrolling apparatus  240  that may be utilized by the individual to scroll the image relative to the display screen  107 . For example, the image may be scrolled in a vertical direction, which corresponds with a y-axis  204 . In further embodiments, or if operated under different conditions, the image may also be scrolled in a horizontal direction, which corresponds with an x-axis  205 , or the image may be scrolled diagonally. Both the y-axis  204  and the x-axis  205  are depicted for reference on the display screen  107 . The individual may, therefore, utilize the scrolling apparatus  240  to scroll the image relative to the display screen  107 , thereby permitting the individual to view currently hidden portions of the image or to move a visible portion to a different location on the display monitor  107 .  
         [0033]     The scrolling apparatus  240  is depicted in the figures as being incorporated into the input device  102 , which, in one embodiment, is a pointing device, particularly a computer mouse. In addition to the mouse-style pointing device, the scrolling apparatus  240  may also be incorporated into other types of input devices, including a trackball pointing device, a touchpad pointing device, and a keyboard  101 , for example. Within the scope of the present invention, however, the scrolling apparatus  240  may also be incorporated into a plurality of other computer-related input devices, such as the bezel of a personal data assistant or handheld computing device, a web pad or other Internet appliance, a gaming controller, or a chassis of a notebook computer, for example. The manner in which the scrolling apparatus  240  may be incorporated into a computer system is not limited, therefore, to the precise example embodied by the input device in the drawings, but may be incorporated into a variety of components to provide the scroll wheel locking functions discussed herein.  
         [0034]     The input device  102  is depicted individually in  FIG. 2  and serves multiple functions, including the functions of the scrolling apparatus  240 . As represented, the input device  102  is a mouse-style pointing device having an outer housing  208  generally shaped to interface with the shape of a hand. A tracking assembly (not depicted) is partially enclosed within the housing  208  for detecting movement of the input device  102  relative to a support surface, as is known in the art. The tracking assembly includes a rollball that engages perpendicular rollers. The rollball protrudes outward from the bottom of the housing  208  and rotates in multiple directions. A first roller senses movement of the mouse (via the movement of the rollball) in a first direction, while a second roller senses movement of the mouse  102  (via the movement of the rollball) in a second direction. An optical tracking system may alternatively be employed, as is known in the art. Upon rotation of the rollball, a signal is transmitted to the host computer  100  through a cord  209 , thereby directing the host computer  100  to move a cursor on the display screen  107 . Alternately, the signal may be transmitted to the host computer  100  through a wireless connection, as is known in the art. On its housing  208 , the input device  102  also includes a primary key  213   a  and a secondary key  213   b  for manipulating objects, such as hypertext links, buttons, or icons, on the display screen  107 , as is known in the art. In general, the cursor may be positioned over an object through use of the tracking assembly, and one of keys  213   a  and  213   b  may be depressed, thereby manipulating the object by transmitting a corresponding signal to the host computer  100 .  
         [0035]     The housing  208  includes an aperture  214  therein for exposing and providing access to a scroll wheel  241  of the scrolling apparatus  240 . The aperture  214  is preferably positioned between keys  213   a  and  213   b . The scrolling apparatus  240  includes the scroll wheel  241  that protrudes upwardly through the aperture  214  and has a generally circular or wheel-shaped structure for engagement by the user. The exterior surface of the scroll wheel  241  may be smooth or grooved. An axle  242  extends through a central portion of the scroll wheel  241  to define an axis of rotation for the scroll wheel  241 . Portions of the axle  242  are rotatably-mounted on a pair of supports  243  and  244  (shown in  FIG. 3 ) thereby permitting the scroll wheel  241  to rotate with the axle  242  in either a forward or backward direction about axis  242   a . As utilized herein, the term “scroll wheel” denotes a rotatable structure configured to enable scrolling of an image on a display screen as it is rotated.  
         [0036]     When operating the mouse  102 , the hand of the individual will generally rest upon an upper surface of the housing  208  such that the fingers extend over keys  213   a  and  213   b  and over the scrolling apparatus  240 . The fingers may then be utilized to operate keys  213   a  and  213   b  and the scrolling apparatus  240 . Within the scope of the present invention, however, the aperture  214  and the scroll wheel  241 , may be located in other portions of the housing  208 . As discussed above, the scrolling apparatus  240  may also be incorporated into other input devices. With regard to the keyboard  101 , trackball, handheld computing device, or notebook computer, for example, an aperture for the scrolling apparatus  240  may be located at any position that provides the individual with convenient access for operating the scroll wheel  241  of the scrolling apparatus  240 .  
         [0037]     The configuration and operation of a rotational sensor assembly will now be discussed. In general, the sensor assembly includes an optical-based arrangement that detects rotational movement of the scroll wheel  241  and transmits a corresponding signal to the host computer  100 , thereby causing the viewable image  201  to move relative to the display screen  107 . More specifically, rotation of the scroll wheel  241  induces a corresponding substantial proportional rotation in an encoder wheel  251 . The encoder wheel  251  and the scroll wheel  241  are preferably mounted to a common axle  242 , and the axle  242  is preferably supported for rotation by upstanding supports  243  and  244 .  
         [0038]     The encoder wheel  251  includes a plurality of blades  252  and openings  253  extending radially outward from a central area of the encoder wheel  251 . Openings  53  are generally located between blades  252  and in peripheral portions of the encoder wheel  251 . A light source  254  and a light sensor  255 , which may be a light emitting diode and a phototransistor, respectively, are positioned on opposite sides of the encoder wheel  251 . As utilized herein, the term “encoder wheel” denotes a rotatable wheel or disk that assists with the detection of rotation, and may include a plurality of openings (or reflective surfaces) that permit the transmission of (or reflect) light or another detectable waveform.  
         [0039]     In a known manner, as the encoder wheel  251  rotates, light from the light source  254  is alternately (1) transmitted through openings  253  and (2) blocked by the material of blades  252 . Pulses of light are transmitted through openings  253  as the encoder wheel  251  rotates enter the light sensor  255 . In response to the pulses of light, the light sensor  255 , or a microprocessor operatively connected to the light sensor  255 , transmits a signal to the host computer  100  that indicates data relating to the angular rotation of the scroll wheel  241 , thereby inducing the image  201  to scroll relative to the display screen  107 . Furthermore, the frequency of the pulses is associated with the rate at which the scroll wheel  241  is being rotated. This can be used to control the speed at which the image  201  scrolls. Alternative arrangements for sensing the rotation of the scroll wheel  241  may be used.  
         [0040]     As can be seen in  FIG. 3 , the scroll wheel assembly  240  also includes a scroll wheel locking assembly  260 . In an exemplary embodiment, the locking assembly  260  is actuable under certain operating conditions prevent the rotation of the scroll wheel in a first direction and permit the rotation of the scroll wheel in the second (opposite) direction. The locking assembly  260  is also actuable under certain operating conditions to permit the rotation of the scroll wheel in the first direction and prevent the rotation of the scroll wheel in the second (opposite) direction. Further, the scroll wheel locking assembly  260  is selectively operable to permit the rotation of the scroll wheel in both rotatable directions under various operating conditions. Thus, for example, when the user scrolls downward to the bottom (end) of a document by rotating the scroll wheel backward (i.e., toward the user), the scroll locking assembly  260  locks the scroll wheel  241  upon reaching the bottom of the document so that the scroll wheel  241  cannot be physically rotated backward any farther and can only be rotated forward. When the user scrolls forward to the top (end) of a document by rotating the scroll wheel forward (i.e., away from the user), the scroll locking assembly  260  locks the scroll wheel  241  upon reaching the top of the document so that the scroll wheel  241  cannot be physically rotated forward any farther and can only be rotated backward. When the portion of the displayed image is in the middle of the document, the scroll locking assembly  260  permits rotation of the scroll wheel  241  in both directions.  
         [0041]     The locking assembly  260  includes a lockable wheel  262  and a locking device  264  that is engagable with the lockable wheel  262 . The lockable wheel  262  is preferably mounted on the axle  242 , and preferably spaced from the scroll wheel  241 , such that the rotation of the scroll wheel  241  in a direction causes the lockable wheel  262  to rotate in that same direction.  
         [0042]      FIG. 4  illustrates the locking device  264  and the system for moving the locking device with the lockable wheel  262  being removed from this figure for clarity. The locking assembly  260  further includes an actuator  266  and an arm  268 . The actuator  266 , which is preferably a solenoid such as a SMT C-frame proportional solenoid, is configured to move the locking device  264  between multiple distinct positions with respect to the lockable wheel  262 . In an exemplary embodiment, the coupling arm  268  has a first end coupled to the actuator  266  and an opposing second end  272  pivotally coupled to the locking device  264 . In one arrangement, the actuator  266  is controlled by a controller  219 , such as a microprocessor, within the input device  102 .  
         [0043]     In an exemplary embodiment, the locking device  264  is movable by the actuator  266  between three predetermined positions: a center or neutral position as shown in  FIG. 5 , a forward locking position (permitting only backward scroll wheel rotation) as shown in  FIG. 6 , and a backward locking position (permitting only forward scroll wheel rotation) as shown in  FIG. 7 . The locking device  264  preferably includes interfacing teeth or steps  280 ,  282 , and  284  that interface with angularly spaced pins  263  located on the lockable wheel  262 . The locking device  264  is disposed tangentially to the lockable wheel  262 . More specifically, the locking device  264  is disposed such that the interfacing teeth  280 ,  282 , and  284  are tangentially disposed from the pins  263 . For reference purposes, the interfacing teeth are referenced as front tooth  280 , middle tooth  282 , and rear tooth  284 . In the depicted arrangement, the locking device  264  is positioned adjacent the top of the lockable wheel  262 . Further, the locking device is preferably, but need not be, configured such that the actuator  266  is behind the scroll wheel  241 .  
         [0044]     When the locking device  264  is in a middle or neutral position as shown in  FIG. 5 , the middle tooth  282  is configured to interface with the pins  263 . The middle tooth  282  includes a pin-interfacing contour that enables the pins  263  from the lockable wheel  262  to ride on the bottom of the middle tooth  282  without being locked as they pass the tooth  282 . In an exemplary embodiment, as shown, the middle tooth  282  includes angled front and rear surfaces  282   a  and  282   c  and a flat center surface  282   b . The angled front and rear surfaces  282   a  and  282   c  are disposed to form an obtuse angle relative to a tangent line of then engaging pin such that the surfaces  282   a - 282   c  permit the then engaging pin to pass. Thus, this configuration permits the pins  263  to contact and pass the middle tooth  282  as the scroll wheel  241  is rotated. When contact is made between the then engaging pin and the applicable angled surface  282   a  or  282   c , the then engaging pin  283  applies an upward force to the locking device  264  via an angled surface  282   a  or  282   c  causing the locking device  264  to pivot about the pivot connection  272  between the arm  268  and the locking device  264 .  
         [0045]     As the scroll wheel  241  is rotated in either direction shown by arrow  301 , the middle tooth  282  alternately gets forced upward (away from the lockable wheel  262 ) by an engaging pin  263  and returns (moves downward) between adjacent pins  263 . This movement of the locking device  264  as indicated by arrow  300 . This arrangement provides a detented feel to the scroll wheel  241 . In an alternate embodiment, not shown, the center surface  282   b  is eliminated. If desired, this detented feel can be eliminated in the center position or a detent system can be provided for elsewhere in the scroll assembly  240 . In such a configuration, the locking device  264  may be guided in such a way that there is no engagement of the pins  263  in the center position and the middle tooth  282  may be eliminated.  
         [0046]     The locking member  264  return process after it is forced upwardly can be caused entirely or in part to gravity. In addition or in lieu of the gravity biasing of the locking device  264 , if desired, one or more springs  275  as shown in  FIG. 4  may be used to provide a slight biasing force to the locking device  264  in the direction of the pins  263 . Since the locking device  264  is movable forward and backward in addition to up and down, a low friction guide plate  276  may be disposed at the bottom of the spring(s)  275  to minimize the friction with the biasing system when the locking device  264  is moved between its positions. Such a biasing arrangement enables a more controlled movement of the locking device  264  as it applies a desired force regardless of the mounting angle of the locking device  264  and the orientation of the input device. Additionally, a frame or guide track, not shown, may be provided to limit or otherwise provide a more controlled movement of the locking device  264 .  
         [0047]     When the lockable device is in a rearward position as shown in  FIGS. 6 , the front tooth  280  is configured to interface with the pins  263 . The front tooth  280  includes a pin-interfacing contour that enables the pins  263  from the lockable wheel  262  to ride on the bottom of the front tooth  280  without being locked when the scroll wheel  241  is rotated backward (i.e., toward the user) as represented by arrow  302 . This typically causes scrolls down in the document. In an exemplary embodiment, as shown, the front tooth  280  includes an angled front surface  280   a  and a flat center surface  280   b . The angled front surface  280   a  is disposed to form an obtuse angle relative to a tangent line of then engaging pin such that the front surface  280   a  permits the then engaging pin to pass.  
         [0048]     This configuration allows the pins  263  to pass the forward tooth  280  as the engagement between the pins  263  and the angled surface  280   a  and the flat surface  280   b  applies an upward force to the locking device  264  causing the locking device  264  to pivot about the pivot connection between the arm  268  and the locking device  264  when the wheel is rotated in the direction of arrow  302 . As the scroll wheel  241  is rotated in the direction of arrow  302 , the front tooth  280  alternately gets forced upward by an engaging pin  263  and returns by gravity and/or a mechanical force into the next gap between adjacent pins  263  as indicated by arrow  300 . This configuration provides a detented feel to the scroll wheel  241 . In an alternate embodiment, not shown, the center surface  280   b  is eliminated.  
         [0049]     In contrast to the front surface  280   a , the rear surface  280   c  of the front tooth  280  is a locking surface. The rear surface  280   c  is disposed to form non-obtuse angle (i.e., either a right angle or an acute angle) relative to a tangent line of then engaging pin such that the rear surface  280   c  prevents the then engaging pin from passing when the scroll wheel  241  is rotated in the direction of arrow  303 . In a preferred arrangement, the rear surface forms an angle in the range between 80 and 90 degrees relative to the tangent line of then engaging pin. This locking feature is due to the fact that then engaging pin substantially applies only a lateral force and fails to apply an upwardly force. Accordingly, the locking member  264  does not move upwardly. Thus, the rear surface  280   c  is disposed relative to pins of the wheel  262  to prevent the lockable wheel  262  (and the scroll wheel  241 ) from rotating when the user attempts to rotate the scroll wheel  241  forwardly away from the user (i.e., in the direction of arrow  303 ).  
         [0050]     The rear tooth  284 , is configured similar to the front tooth  280  in a mirror image arrangement. Thus, when the lockable device is in a forward position as shown in  FIGS. 7 and 8 , the rear tooth  284  is configured to interface with the pins  263 . The rear tooth  284  includes a pin-interfacing contour that enables the pins  263  from the lockable wheel  262  to ride on the bottom of the rear tooth  284  without being locked when the scroll wheel  241  is rotated forward (i.e., away from the user) as represented by arrow  304 . This typically causes scrolls up in the document. In an exemplary embodiment, as shown, the rear tooth  284  includes an angled rear surface  284   a  and a flat center surface  284   b . The angled rear surface  284   c  is disposed to form an obtuse angle relative to a tangent line of then engaging pin such that the rear surface  284   c  permits the then engaging pin to pass.  
         [0051]     This configuration allows the pins  263  to pass the rear tooth  284  as the engagement between the pins  263  and the angled surface  284   a  and the flat surface  284   b  applies an upward force to the locking device  264  causing the locking device  264  to slightly pivot about the pivot connection between the arm  268  and the locking device  264  when the wheel is rotated in the direction of arrow  304 . As the scroll wheel  241  is rotated in the direction of arrow  304 , the rear tooth  284  alternately gets forced upward by an engaging pin  263  and returns by gravity and/or a mechanical force into the next gap between adjacent pins  263  as indicated by arrow  300 . This configuration provides a detented feel to the scroll wheel  241 . In an alternate embodiment, not shown, the center surface  284   b  is eliminated.  
         [0052]     In contrast to the rear surface  284   c , the front surface  284   a  of the rear tooth  284  is a locking surface. The front surface  284   a  is disposed to form non-obtuse angle (i.e., either a right angle or an acute angle) relative to a tangent line of then engaging pin such that the front surface  284   a  prevents the then engaging pin from passing when the scroll wheel  241  is rotated in the direction of arrow  305 . In a preferred arrangement, the front surface  284   a  forms an angle in the range between 80 and 90 degrees relative to the tangent line of then engaging pin. This locking arrangement is due to the fact that then engaging pin substantially applies only a lateral force and fails to apply an upwardly force. Accordingly, the locking member  264  does not move upwardly. Thus, the front surface  284   a  is disposed relative to pins of the wheel  262  to prevent the lockable wheel  262  (and the scroll wheel  241 ) from rotating when the user attempts to rotate the scroll wheel  241  forwardly away from the user (i.e., in the direction of arrow  305 ).  
         [0053]     The lockable wheel  262  with pins  263  and the locking member  264  form a ratchet and pawl device to lock the scroll wheel  241  against movement in certain directions and to permit rotation of the scroll wheel  241  under different conditions. When the locking device  241  is moved to either the rearward or forward positions as shown in  FIGS. 6 and 7 , the lockable wheel  262  will slide over the positioned tooth  280  or  284  when the scroll  241  wheel rotates one way. However, when the scroll wheel  241  rotates the other way, a pin  263  from the lockable wheel  262  catches on the locking surface of the tooth.  
         [0054]      FIG. 8  is similar to  FIG. 3  but illustrates an alternative arrangement of various elements. Specifically, a separate encoder wheel  251  is no longer needed and the lockable wheel  262 ′ includes openings formed by angularly spaced slits in a plate perpendicular to the axis of rotation. The slits are preferably, but need not be, located radially inwardly of the pins  262 . The light source  254  and a light sensor  255  are positioned accordingly such that as the lockable wheel  262 ′ with encoder wheel characteristics rotates, light from the light source  254  is alternately (1) transmitted through the openings and (2) blocked by the material between the openings.  
         [0055]     The computer  100  provides feedback to the input device  102  about the position of the viewable documents relative the display  107 . Based on that feedback, it can provide an instruction to the controller  219  of the input device  102  about when to actuate the lockable member  264  which of the three positions to move it into. One method to control the locking assembly is depicted in  FIG. 9 .  
         [0056]      FIG. 9  illustrates an operational flow chart of the control of wheel locking device  264  according to an exemplary operational method. This method presumes that the document is larger than the display screen and that a scrolling mode is operational. From an initialization point  300 , the actuator  266  moves the lockable member  264  into the middle position at Step  301  as shown in  FIG. 5 . The process then determines whether the viewable document is at one of its ends. This is shown by Step  302  that checks to see whether the viewable document is at the top and by Step  303  that checks to see whether the viewable document is at the bottom. This information exists and is used in various programs, and the results of such are commonly illustrated as a vertically-oriented graphical user image of a scroll bar commonly used by many computer programs. To illustrate the scroll bar, an application may set a scrolling range and calculate the location of an indicator (a “thumb”) that moves within the range. In operation, scrolling movement commands are processed and the graphical user scroll bar interface with the thumb is revised based on the scroll range and the scrolling movements applied. Thus it can be calculated whether the document is at its top or at its bottom and it is that information that can be used at Steps  302  and  303 .  
         [0057]     If at Step  302  and at Step  303  it is determined that the document has not reached either end of the scroll range, the document end checking process continues and the lockable member  264  will remain in its middle position as shown in  FIG. 5 . However, if at Step  302 , the top of the document is reached by the user scrolling upwardly by rotating the scroll wheel  241  away from himself, the computer  100  will instruct the actuator  266  via the controller in the input device to move the locking member to the rearward position as shown in  FIG. 6 . This will stop the rotation of the scroll wheel. With the locking member  264  in this position, the user will not be able to rotate the scroll wheel  241  away from him and scroll upwardly because the scroll wheel  241  will be physically locked. The user will however be able to rotate the scroll wheel  241  in the opposite direction, i.e., toward him, to scroll down in the document.  
         [0058]     At step  305 , it is determined whether the document is still at or adjacent the top (e.g., only a small amount of scrolling has occurred). If the answer to that question is yes, the process continues to check and will not change until the document is no longer adjacent the top. When the document is scrolled down such that it is no longer adjacent to the top, the computer instructs the actuator  266  to move the lockable member  264  into the middle position at Step  301  as shown in  FIG. 5 .  
         [0059]     Whether the document is still “adjacent” an end may be calculated on a unit basis (such as scroll lines) or on the basis of the percentage of the document traveled. Further, the “adjacent” value may be preset into the system or may be made to be modifiable by a user setting. Thus, when the user scrolls downwardly by a small amount and is no longer adjacent to the top of the document, the actuator  266  moves the lockable member  264  into the middle position.  
         [0060]     A similar process occurs at the bottom of the document as shown by Steps  303 ,  306 , and  307 . If at Step  303 , it is determined that the bottom of the document is reached by the user scrolling down by rotating the scroll wheel  241  toward himself, the computer  100  will instruct the actuator  266  via the controller in the input device to move the locking member to the forward position as shown in  FIG. 7 . This will stop the rotation of the scroll wheel. With the locking member  264  in this position, the user will not be able to rotate the scroll wheel  241  toward himself and scroll down because the scroll wheel  241  will be physically locked. The user will however be able to rotate the scroll wheel  241  in the opposite direction, i.e., away from him, to scroll up in the document.  
         [0061]     At step  307 , it is determined whether the document is still at or adjacent the bottom (e.g., only a small amount of scrolling has occurred). If the answer to that question is yes, the process continues to check and will not change until the document is no longer adjacent the bottom. When the document is scrolled up such that it is no longer adjacent to the bottom, the computer instructs the actuator  266  to move the lockable member  264  into the middle position at Step  301  as shown in  FIG. 5 .  
         [0062]     Thus, this process prevents wasted computer processing efforts, and provides touch feedback information to the user as a reminder that the document has reached and/or is at an end, and which end the document is at or near. It further can save the user unnecessary finger movements that can be beneficial especially if the user has a finger injury or other precondition or uses the scrolling wheel on a regular basis. Further, this provides a mechanism for a scroll wheel that is linked to the document on the computer screen so that when the extremity of the document is reached in any direction (beginning, end, left or right) the scroll wheel of the input device, e.g., mouse, trackball, or keyboard, will “lock” and the wheel can no longer be activated in that direction and can only be reversed from that position.  
         [0063]     The specific configurations of the lockable scrolling apparatus described and illustrated herein is intended to provide an example of the many configurations intended to fall within the scope of the present invention. Accordingly, the configuration of the scrolling apparatus may depart from the specific configuration disclosed above.  
         [0064]     The present invention is disclosed above and in the accompanying drawings with reference to a variety of embodiments. The purpose served by the disclosure, however, is to provide an example of the various features and concepts related to the invention, not to limit the scope of the invention. One skilled in the relevant art will recognize that numerous variations and modifications may be made to the embodiments described above without departing from the scope of the present invention, as defined by the appended claims.