Abstract:
An electronic mouse with an integral ball cage. The ball cage in one embodiment has integrally formed extensions having openings for enclosed shaft encoders and a pressure roller. The shaft encoders are preferably made of a single piece of plastic. The ball cage is preferably formed as part of the lower housing of the mouse.

Description:
This is a Continuation of application Ser. No. 08/183,897, filed Jan. 21, 1994, now U.S. Pat. No. 5,670,990, which is a continuation of application Ser. No. 08/050,723, filed Apr. 19, 1993 (abandoned), which is a continuation of application Ser. No. 07/768,813, filed Sep. 27, 1991, which is a continuation-in-part of application Ser. No. 07/672,093, filed Mar. 19, 1991. 
    
    
     FIELD OF THE INVENTION 
     This application relates to pointing devices such as electronic mice or trackballs, and particularly relates to the ball cage therein and its components. 
     BACKGROUND OF THE INVENTION 
     Electronic mice are well known for their advantages as pointing devices. Basically, an electronic mouse converts the linear movement of the mouse over a surface into digital signals to control the cursor of the computer. One common type of electronic mouse uses an optomechanical interface, whereby the movement of a ball drives at least two shaft encoders. The shaft encoders in turn drive an encoding wheel located between a photosource and a photodetector. The movement of the encoding wheel causes pulses of light to reach the photodetector, which creates a pulse train indicative of movement of the mouse. 
     To provide accurate correlation between the movement of the mouse and movement of the cursor, the ball in an optomechanical mouse must be supported within fairly close tolerances. In substantial part, these close tolerances are necessary to maintain the ball in constant contact with the shaft encoders. In most such mice, a ball cage is provided to maintain the ball in proper position, and the shaft encoders are integrated into the ball cage. In the past, the ball cage has been a complicated assembly comprising in excess of twenty parts, including multiple parts for the shaft encoders and related mechanical elements, a pressure roller to maintain the ball in contact with the shaft encoders, and the ball cage itself. Also, a traction spring with hooks, which is comparatively difficult to assemble, has been required by many prior designs. 
     Such complicated assemblies increase manufacturing costs and reduce reliability. In addition, prior art designs typically do not lend themselves to use in automatic assembly. There has therefore been a need for a simple ball cage configuration which provides at least equal accuracy while reducing complexity and part count and permitting automatic assembly. 
     SUMMARY OF THE INVENTION 
     The present invention substantially overcomes the limitations of the prior art by providing an integral ball cage having only six parts which is capable of automated assembly. In particular, the shaft encoders are formed integrally, as is the pressure roller, and the integrated shaft encoder and pressure roller simply clip into the remainder of the ball cage. Likewise, the optical elements have been simplified to eliminate the need for a mask by building the mask function into the geometry of the photosensor, thereby also reducing part count. Finally, the pressure roller and its shaft are formed integrally, making assembly much simpler. Additionally, the design has been modified to permit use of an inexpensive, simple, and more easily assembled compression coil spring. 
     Two embodiments, each an improvement over the prior art, are disclosed. In the first embodiment, the ball cage is mounted on the printed circuit board which supports the logic and the optical elements. In a second embodiment, the ball cage can be integrated into the bottom housing rather than being mounted on the printed circuit board, further simplifying assembly and improving reliability, and also allowing the PCB to be reduced in size. 
     In either embodiment, the resulting ball cage is, by comparison with the prior art, much simpler to manufacture and assemble, thereby improving both yield and reliability. Importantly, the new ball cage is adapted well to automated assembly techniques. 
     It is one object of the present invention to provide an improved optomechanical mouse in which the ball cage and remaining elements are capable of automatic assembly. 
     It is another object of the present invention to provide an optomechanical mouse having a highly integrated ball cage. 
     It is a further object of the present invention to provide a ball cage having a minimal number of moving parts. 
     It is a still further object of the present invention to provide an optomechanical mouse having a highly integrated ball cage and optical elements which can be assembled by machine. 
    
    
     These and other objects of the invention will be better understood from the following Detailed Description of the Invention, taken together with the appending drawings. 
     FIGURES 
     FIG. 1 shows an exploded view of a mouse having a ball cage and optical components according to the present invention. 
     FIG.  2   a  shows a top plan view of a ball cage according to the present invention. 
     FIG.  2   b  shows a top left perspective view of the ball cage of FIG.  2   a.    
     FIG.  2   c  shows a left side elevational view of the ball cage of FIG.  2   a.    
     FIG.  2   d  shows a front elevational view of the ball cage of FIG.  2   a.    
     FIG. 3 shows a cross-sectional side view of the ball cage of FIG.  2   a  taken along the lines A—A. 
     FIG. 4 shows a cross-sectional plan view of the ball cage of FIG.  2   d  taken along the lines B—B. 
     FIG. 5 shows, a sectional view of the ball cage of FIG.  2   a  taken along section lines C—C. 
     FIG.  6   a  is a side elevational view of a shaft encoder for use in the ball cage of FIG.  2   a.    
     FIG.  6   b  is an end view of the shaft encoder of FIG.  6   a.    
     FIG.  6   c  is a cross sectional view of the shaft encoder of FIG.  6   a  taken along lines E—E. 
     FIG.  6   d  is a cross sectional view of the shaft encoder of FIG.  6   a  taken along the lines F—F. 
     FIG. 7 is an exploded perspective view of a second embodiment of the invention. 
     FIG. 8A is a broken top plan of the lower housing, showing the ball cage and optomechanical elements of second embodiment. 
     FIG. 8B is a bottom view of the ball cage of the second embodiment. 
     FIG. 9A is a cross-sectional side view of the ball cage of the second embodiment, taken along section lines X—X in FIG.  8 A. 
     FIG. 9B is a detailed view of the circled portion labeled “Z” in FIG.  8 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIG. 1, an optomechanical mouse constructed according to one embodiment of the present invention, indicated generally at  10 , is shown in exploded view. For simplicity, only a ball cage for an electronic mouse will be shown, although the present invention could be implemented in a trackball without major modification. The mouse  10  includes an upper housing  20 , a printed circuit board  30  to which a ball cage  40  is mounted, a lower housing  50 , a ball  60 , and a belly door  70  which connects into the lower housing for retaining the ball within the ball cage  40 . Alternatively, and as is described in greater detail hereinafter, the ball cage  40  could be mounted to another component, and for example could be formed integrally with the lower housing  50 . 
     The printed circuit board  30  shown in FIG. 1 includes circuitry for converting the analog movement of the ball  60  into digital signals. Depending on whether the mouse is a serial device or a bus board device, the printed circuit board may include either a microprocessor (for the serial configuration) or a simpler logic set (the bus version). The logic on the printed circuit board  30  for the serial version is typically equivalent to that included in a Logitech N-9 serial mouse, while the logic for the bus version is equivalent to that included in a Logitech N-9 bus mouse. Alternatively, the logic may be processor based, such as in Logitech&#39;s S2 mouse or Combi mouse. The particular type of logic found on the PCB  30  will depend on the port to which the mouse will be connected. 
     Referring next to FIGS.  2   a-d , the ball cage of the present invention can be better appreciated. Although the ball cage is integrally formed, for purposes of illumination the ball cage will be described as a plurality of separate parts. The ball cage  40  can be seen to include a central ball enclosing section  110  having extensions  120  and  130  extending laterally therefrom. The extension  120  and  130  are positioned orthogonally to one another and provide support for integrated shaft encoders  140  and  150 , which are better described in FIG.  6 . The ball  60  resides within the central section  110 . 
     The extensions  120  and  130  may be further appreciated by taking FIG. 4 in conjunction with FIG.  2   a . FIG. 4 shows in cross-section the arrangement by which a shaft encoder  140  is mounted into the ball cage extension  120 . A similar arrangement is used for the shaft encoder  150  mounted in ball cage extension  130 . The extensions  120  and  130  may each be seen to include an upper shroud  125  and to be formed to include spindle supports for receiving the shaft encoders. 
     The central ball enclosing section  110  further supports an integrally formed pressure roller housing  160 , also seen in cross-sectional view in FIGS. 3 and 5. A pressure roller fork  170 , formed independently from the housing  110 , is suspended from an upper portion of the pressure roller housing  160 , and in turn supports a pressure roller  180 . The pressure roller  180  includes a pair of spindles  190  which extend into holes or slots  200  in the fork  170 , best seen in the sectional view of FIG.  5 . It can be seen that the spindles  190  eliminate the need for a shaft through the pressure roller, and thus substantially simplify assembly of the pressure roller in the pressure roller fork. The pressure roller fork  170 , and in turn the pressure roller itself, is urged into engagement with the ball  60  by means of a spring  210  which extends between an inside portion of the housing  160  and an outside portion of the fork  170 . It will be appreciated that the spring  210  operates in compression, which simplifies assembly. The pressure roller thereby maintains the ball  60  in contact with the shaft encoders  140  and  150  to ensure a high level of accuracy in translating movement of the ball  60  into movement of the cursor on the video screen of the associated computer system. 
     Turning to FIG.  6   a-d , the shaft encoders  140  and  150  can be better appreciated. Each shaft encoder includes an integrally formed slotted disk  220 , a shaft portion  230  and a pair of spindles  240  which extend into appropriate receiving holes in the extensions  120  and  130 . The shaft portion  230  includes a disk support portion  250 , a lightweight strengthening portion  260  and a cylindrical portion  270 . The portion  260  may be seen from FIG.  6   c  to have a “+” shaped cross-section in some embodiments to maintain constant wall thickness and prevent deformation, but in at least some embodiments a cylindrical cross section is preferable. The number of slits in the disk  220  can be adjusted according to the desired resolution of the mouse in dots per inch. The arrangement shown is FIG.  6   b  is appropriate for 400 dpi resolution. From FIG.  6   d , the shaft encoder  140  can be seen to be integrally formed, typically of Minlon 11C1 40 BKB 86 polymer, while the ball cage  40  is typically made from DELRIN 500 CL or other suitably stable polymer having a low frictional coefficient. 
     A key advantage of the present invention is its simplified assembly. The integrated shaft encoders  140  and  150  simply clip into the remainder of the ball cage  40 . The pressure roller  180  simply clips into the pressure roller fork  170 , and the spring  210  is maintained in compression. As a result, these elements are well adapted to conventional automated assembly techniques, unlike the prior art. 
     Shown in FIGS. 7,  8 A-B and  9 A-B is an alternative to the the embodiment of FIGS.  1 - 6 . In particular, the embodiment of FIGS.  7 - 9 A-B further integrates the ball cage into the lower housing, as shown in the exploded perspective view of FIG.  7 . It will be appreciated that the housing of this embodiment can vary significantly from the housing of the first embodiment discussed above without altering any aspect of the present invention. 
     In the arrangement of FIGS.  7 - 9 A-B, the shaft encoders are mounted directly onto the lower housing, and the optical elements are mounted on a printed circuit board containing the other conventional logic. To properly position the PCB over the shaft encoders, the PCB is mounted in an inverted position, and the optical elements fit into retainers on the lower housing. Such an arrangement permits simplified assembly, and again is optimized for automated assembly techniques. 
     In particular, and still referring to FIG. 7, a mouse according to the present invention is indicated at  700 , and includes an upper housing  710 , a printed circuit board  720 , a switch plate  730 , a connecting cable  740  extending between the PCB  720  and the plate  730 , a lower housing  750 , a ball  760  and a belly door  770 . During normal operation, the belly door  770  is interlocked with the lower housing  750  to properly position the ball  760  into a ball cage  772  on the housing  750 . 
     For convenience, the PCB  720  is shown in inverted view, with the component side up, whereas in normal operation the PCB  720  is mounted with the component side down as depicted by the phantom lines  773  in FIG.  7 . The PCB  720  includes first and second pairs of optical emitters and receivers  774 A-B, typically LEDs and phototransistors. When positioned on the lower housing  750 , locating pins  776  in the lower housing  750  are inserted through holes  778  on the PCB  720 . This positioning also places the optical emitters and receivers  774 A-B into enclosure pairs  780 A-B, such that each emitter and receiver  774  inserts into an enclosure  780 . 
     The PCB  720  is locked into position on the locating pins  776  by means of the upper housing  710  which includes positioning pins (not shown) on its underside and is locked into position relative to the lower housing by means of retaining clips  790 , which mate with corresponding parts on the underside of the upper housing  710 . The output of the mouse is provided through a cable connection  808 , to which may be connected a conventional multiwire cable. 
     Referring to FIGS.  8 A-B and  9 A-B, integrally formed shaft encoders  794  and  796  each insert into retainer pairs  798 A-B and  800 A-B, adjacent the ball cage  772 . The ball cage  772  includes openings therethrough, best seen in FIG. 9A, to permit the pressure roller portions  804  of the shaft encoders  794  and  796  to contact the ball  760 . In addition, the ball cage  772  includes an opening  840  (FIG. 8A) for the pressure wheel assembly  806 , constructed the same as the pressure wheel assembly in the first embodiment described hereinabove, to contact the ball  760 . The back end of the compression coil spring of the pressure wheel assembly  806  seats around a pin  842 , and the fork of the pressure wheel assembly  806  is clipped into retainers  844 . The switch plate  730  (FIG. 7) is located on spacers  820  and clips into position by means of retaining clips  822 . The switch plate  730  includes one or more switches  824  for performing control or data functions as dictated by the software. 
     Referring particularly to FIG. 8B, the belly door clip  828  is retained in place on a flange  850 , and openings  852  and  854  are provided through the bottom of the lower housing to ensure clearance for the shaft encoders  794  and  796 . The position of the pin  842  can also be seen relative to the remainder of the ball cage  772 . 
     One feature of the embodiment shown in FIGS.  7 - 9 A-B is that it permits extremely small balls to be used. For example, in the embodiment shown, the roller ball  760  can be on the order of 15 mm, and weigh on the order of 9 grams, using a steel core with a rubber coating. This provides substantially the same weight as the ball in the first embodiment discussed above, but with a substantially reduced diameter. 
     Referring particularly to FIG. 9B, which shows in detail the enclosure pair  780 B as indicated by the circle labeled “Z” in FIG. 8A, the relative locations of the enclosure pair  780 B and the opening  852  for the shaft encoder  796  can be better appreciated. It can be seen from the Figure that one side of the enclosure pair, preferably for the receiver, need not be fully enclosed. 
     Having fully described a preferred embodiment of the present invention together with alternatives, it will be apparent to those of ordinary skill in the art that numerous alternatives and equivalents exist which do not depart from the invention set forth above. It is therefore to be understood that the invention is not to be limited by the foregoing description, but only by the appended claims.