Patent Document

BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to printers, and, more particularly, to a print medium exit system for a printer.  
           [0003]    2. Description of the Related Art  
           [0004]    Most ink jet printers have a star-wheel exit system in which the star-wheels are directly linked to a feed roll shaft. The feed roll shaft simply keeps turning forward to drive print media out of the printer after printing. A problem is that the star wheels touch the printed surface of the paper and sometimes cause the ink to smear or cause small “star wheel” tracks on the printed image.  
           [0005]    It is also known to control the exiting media in an exit system by requiring motion of a printhead carrier or some other power source. For instance, in a kicker exit system, the kickers emerge from behind a final nip and push/kick the print media out of the printer. The kicker exit system has the advantage that the printed surface of the paper is never touched, so there is no smearing of the ink. Unlike the star-wheel exit system that runs all the time because it is always linked to the feed roll shaft, the kicker exit system requires activation because it only needs to run after a print job. The printhead can be used to activate the kicker system. However, using the printhead has some disadvantages, such as decreasing throughput. This is especially true if the printhead carrier is away from the kicker mechanism because it takes time to bring the printhead over to a desired location for activation. Also, problems may result if the printhead has to go through a maintenance cycle during an exit operation.  
           [0006]    What is needed in the art is a paper exit system that does not touch the printed surface of the paper and that is not activated by a printhead carrier.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a kicker media exit system activated by a mechanical clutch controlled by the presence of media passing through the nip.  
           [0008]    The invention comprises, in one form thereof, a print medium exit system in a printer. A kicker device ejects a sheet of print medium out of the printer. A clutch mechanism prevents actuation of the kicker device when the clutch mechanism is engaged by the sheet of print medium.  
           [0009]    The invention comprises, in another form thereof, a method of ejecting a sheet of print medium from a printer. It is sensed when the sheet of print medium is at a predetermined location along a paper path in the printer. A print medium exit system is activated dependent upon the sensing step.  
           [0010]    An advantage of the present invention is that the exit system does not touch the printed surface of the paper, so no smearing of the ink occurs.  
           [0011]    Another advantage is that the kicker exit system is not activated by a printhead carrier, so throughput is increased and positioning issues are eliminated. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0013]    [0013]FIG. 1 is a fragmentary, perspective view of one embodiment of a printer and an associated print media exit system of the present invention;  
         [0014]    [0014]FIG. 2 is an enlarged perspective view of the exit system of FIG. 1;  
         [0015]    [0015]FIG. 3 is another perspective view of the exit system of FIG. 1;  
         [0016]    [0016]FIG. 4 is yet another perspective view of the exit system of FIG. 1; and  
         [0017]    [0017]FIG. 5 is a side view of the exit system of FIG. 1. 
     
    
       [0018]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one preferred embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    Referring now to the drawings and particularly to FIG. 1, there is shown one embodiment of a printer  10  of the present invention including a print media exit system  12 . Exit system  12  includes a toggle arm  14  having two peripherally attached gears  16 ,  18  (FIG. 2). Toggle arm  14  pivots about an axis  20  of a feed roll shaft  22  with a feed roll gear  24  in the center. Kickers  26  are linked to a pivot shaft  28 .  
         [0020]    At the beginning of a kick cycle, feed roll shaft  22  and toggle arm  14  rotate counterclockwise in the perspective of FIG. 1 to thereby move gear  16  into engagement with a pivot shaft gear  30 . Feed roll gear  24  then rotates counterclockwise, thereby causing a clockwise rotation of gear  16 , which, in turn, causes a counterclockwise rotation of pivot shaft gear  30 . The counterclockwise rotation of pivot shaft gear  30  actuates or advances kickers  26  in direction  32  to push the print medium out of printer  10 . After kickers  26  clear the print medium, feed roll shaft  22  reverses, i.e., feed roll gear  24  rotates clockwise, which causes toggle arm  14  to toggle backward and gear  18  to engage pivot shaft gear  30 . With feed roll gear  24  now rotating clockwise, gear  18  rotates counterclockwise, which, in turn, causes a clockwise rotation of pivot shaft gear  30 . The clockwise rotation of pivot shaft gear  30  causes kickers  26  to move in direction  34 , back to their original positions.  
         [0021]    A clutch flag mechanism  36  (FIGS. 3 and 4) is used as an activation mechanism and includes a clutch flag  38  and a paper-activated flag  40  joined by a connecting bar  42 . Clutch flag  38  is disposed above toggle arm  14 , and paper-activated-flag  40  is disposed in the paper path. Clutch flag mechanism  36  is spring-loaded in the direction indicated by arrow  44 . Clutch flag mechanism  36  is disposed under an automatic sheet feeder and behind a nip  46  (FIG. 5) between a pressure roll arm  48  and a feed roll  50 . Nip  46  is the final nip in the paper path of printer  10 . Clutch flag mechanism  36  pivots about line A and can rotate only about 9 degrees. Without an activation mechanism such as clutch flag mechanism  36 , kickers  26  would operate whenever feed roll shaft  22  turns forward (counterclockwise) because the exit transmission is a simple toggle clutch.  
         [0022]    When the automatic sheet feeder picks a sheet and brings the sheet to nip  46 , feed roll shaft  22  reverses to de-skew. As the picked sheet moves into nip  46 , its forward edge engages paper-activated flag  40  at a predetermined point along the paper path. As the sheet of paper pushes paper-activated flag  40  down, the whole clutch flag mechanism  36  rotates in the counterclockwise direction. Clutch flag  38  is now disposed in the path of a hook  52  on toggle arm  14 . As feed roll shaft  22  changes direction and turns forward (counterclockwise) to bring the sheet into the print zone, toggle arm  14  toggles gear  16  forward toward pivot shaft gear  30 . However, hook  52  on toggle arm  14  mates with clutch flag  38  and prevents toggle arm  14  from rotating further to engage gear  16  with pivot shaft gear  30 . Because of the engagement angle between hook  52  and clutch flag  38 , they cannot come apart unless feed roll shaft  22  reverses (rotates clockwise). Now, with hook  52  mated with clutch flag  38 , printer  10  is able to print without exit system  12  being activated. Clutch flag  38  prevents gear  16  from engaging and rotating pivot shaft gear  30  when paper-activated flag  40  is engaged by the sheet of paper.  
         [0023]    When the print job is finished and the trailing edge of the sheet of paper has advanced past paper-activated flag  40 , a spring-loaded arm sensor  54  detects the presence of the trailing edge of the sheet at another predetermined point along the paper path. More particularly, sensor  54  detects when the trailing edge of the sheet is about to enter nip  46 . This point where sensor  54  detects the trailing edge of the sheet of paper can be approximately adjacent to, or slightly downstream from, the point along the paper path where paper-activated flag  40  is engaged by the sheet of paper. Sensor  54  sends a signal to microcontroller  56  indicating that the trailing edge of the sheet is about to enter nip  46 . When the trailing edge has advanced past nip  46 , printer  10  is ready to eject the printed medium. In response to the signal from sensor  54 , microcontroller  56  activates exit system  12 . That is, microcontroller  56  causes feed roll shaft  22  to reverse, i.e., turn clockwise as indicated by arrow  58 . Spring-loaded clutch flag mechanism  36  is then free to rotate upward, as indicated by arrow  60 , because there is no longer any paper pushing down on paper-activated flag  40 . The angular rotation of feed roll shaft  22  in direction  58  is just enough to release clutch flag  38  from hook  52 , e.g., 90 degrees or less. Then, feed roll  50  turns forward (counterclockwise) so that gear  16  engages and rotates pivot shaft gear  30  such that kickers  26  are activated.  
         [0024]    After kickers  26  kick the paper out of printer  10 , the exit cycle is finished by feed roll shaft  22  rotating in the reverse direction (clockwise) to bring kickers  26  back to their original position. This exit cycle repeats for the next sheet.  
         [0025]    Clutch flag mechanism  36  is print media controlled in the sense that clutch flag  38  locks toggle arm  14  in place only if there is a sheet of paper behind nip  46 . All that is required to activate exit system  12  is a slight reverse motion of feed roll shaft  22  and toggle arm  14 , not an external input such as a movement of a printhead.  
         [0026]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Technology Category: 7