Abstract:
A hardware solution functional including a shaft, an operational range of a full rotation in both directions, translatable force to a plurality of functions, and a translatable sequencing to the plurality of functions by the shaft.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates to maintenance stations for ink jet printing apparatus. 
     2. Description of Related Art 
     Ink jet printers have at least one printhead that directs droplets of ink towards a recording medium. Within the printhead, the ink may be contained in a plurality of channels. Energy pulses are used to expel the droplets of ink, as required, from orifices at the ends of the channels. 
     In a thermal ink jet printer, the energy pulses are usually produced by resistors. Each resistor is located in a respective one of the channels, and is individually addressable by current pulses to heat and vaporize ink in the channels. As a vapor bubble grows in any one of the channels, ink bulges from the channel orifice until the current pulse has ceased and the bubble begins to collapse. At that stage, the ink within the channel retracts and separates from the bulging ink to form a droplet moving in a direction away from the channel and towards the recording medium. The channel is then re-filled by capillary action, which in turn draws ink from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. No. 4,849,774. 
     A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337. That printer has a plurality of printheads, each with its own ink tank cartridge, mounted on a reciprocating carriage. The channel orifices in each printhead are aligned perpendicular to the line of movement of the carriage. A swath of information is printed on the stationary recording medium as the carriage is moved in one direction. The recording medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information. 
     The ink ejecting orifices of an ink jet printer need to be maintained, for example, by periodically cleaning the orifices when the printer is in use, and/or by capping the printhead when the printer is out of use or is idle for extended periods. Capping the printhead is intended to prevent the ink in the printhead from drying out. The cap provides a controlled environment to prevent ink exposed in the nozzles from drying out. 
     A printhead may also need to be primed before initial use, to ensure that the printhead channels are completely filled with the ink and contain no contaminants or air bubbles. After significant amounts of printing, and at the discretion of the user, an additional but reduced volume prime may be needed to clear particles or air bubbles which cause visual print defects. Maintenance and/or priming stations for the printheads of various types of ink jet printers are described in, for example, U.S. Pat. Nos. 4,364,065; 4,855,764; 4,853,717 and 4,746,938, while the removal of gas from the ink reservoir of a printhead during printing is described in U.S. Pat. No. 4,679,059. 
     The priming operation, which usually involves either forcing or drawing ink through the printhead, can leave drops of ink on the face of the printhead. As a result, ink residue builds up on the printhead face. This ink residue can have a deleterious effect on the print quality. Paper fibers and other foreign material can also collect on the printhead face while printing is in progress. Like the ink residue, this foreign material can also have deleterious effects on print quality. 
     The 717 patent discloses moving a printhead across a wiper blade at the end of a printing operation so that dust and other contaminants are scraped off the orifice before the printhead is capped, and capping the printhead nozzle by moving the printer carriage acting on a sled carrying the printhead cap. This eliminates the need for a separate actuating device for the cap. The 938 patent discloses providing an ink jet printer with a washing unit which, at the end of the printing operation, directs water at the face of the printhead to clean the printhead before it is capped. 
     SUMMARY OF THE INVENTION 
     This invention provides a cam-activated lever capping arm, a wiping mechanism and a pinch tube mechanism for a maintenance station for an ink jet printer. 
     In one exemplary embodiment of the maintenance station according to this invention, one or more printheads are mounted on a translatable carriage and moves with the carriage. When the printer is printing, the translatable carriage is located in a printing zone, where the one or more printheads can eject ink onto a recording medium. When the printer is placed into a non-printing mode, the translatable carriage is translated to the maintenance station located outside and to one side of the printing zone. Once the cartridge is translated to the maintenance station, various maintenance functions can be performed on the one or more printheads of the printer depending on the rotational position of a cam shaft in the maintenance station. The cam shaft engages and drives the hardware that in turn operates the individual maintenance functions. 
     Rotating the cam shaft activates various maintenance mechanisms of the maintenance station, including a wiper blade platform and a cap carriage. The wiper platform passes across the printhead nozzle faces when the one or more printheads enter the maintenance station and again just before the one or more printheads leave. A location for collecting ink cleared from the nozzles is placed adjacent to the wiper blades. After the one or more printheads arrive at the maintenance station, a vacuum pump is energized, and the cap carriage is elevated to the position where the one or more printhead caps engage the one or more printheads. The one or more printhead caps are mounted on the cap carriage in a capping location. The printheads are primed when a pinch tube mechanism opens one or more pinch tubes connected to the one or more printhead caps. Opening the pinch tubes releases negative pressure created by the vacuum pump. In response, ink is drawn from the one or more printheads into the one or more printhead caps. 
     Further moving the cam shaft lowers the cap carriage and enables the wiper blades to pass back across the nozzle faces to clean the ink jet printhead nozzles. The vacuum pump is then deenergized, while the cap carriage remains in position so that the one or more printhead caps cap the one or more printheads awaiting the printing mode of the printer. Thus, the one or more printheads remain capped at the maintenance station until the printer is into the printing mode. 
     The predetermined time that the printhead carriage is positioned adjacent to the maintenance station, including the gear and cam-actuated valve closing and the predetermined time that the printhead carriage is located relative to the capping platform, as controlled by the controller, determines pressure profiles and waste ink volumes. The controller enables a spectrum of waste ink volume and pressure profiles. One waste ink volume and pressure profile is appropriate for the initial installation of the cartridge, when the one or more capped printheads are kept a longer time at the capping location, to help ensure that all ink flow paths between the nozzles and supply cartridge are completely primed. A second waste ink volume and pressure profile is appropriate for a manual refresh prime. During such a manual refresh prime, the one or more capped printheads are kept at the capping location a relatively shorter time to prime only the one or more printheads. 
     These and other features and advantages of this invention are described in or are apparent from the detailed description of various exemplary embodiments of the systems and methods according to this invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various exemplary embodiments of this invention will be described in detail with reference to the following figures, wherein like numerals represent like elements, and wherein: 
     FIG. 1 is a schematic front elevation view of an ink jet printer and a maintenance station according to this invention; 
     FIG. 2 is a top perspective view of the interior of a maintenance station of FIG. 1 according to this invention; and 
     FIG. 3 is a partial perspective view of the cam shaft of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     FIG. 1 shows a printer  10 , including one or more printheads  12 , shown in dashed line, fixed to an ink supply cartridge  14 . The ink supply cartridge  14  is removably mounted on a carriage  16 . The carriage  16  is translatable back and forth on one or more guide rails  18  as indicated by the arrow  20 , so that the one or more printheads  12  and the ink supply cartridge  14  move concurrently with the carriage  16 . Each of the one or more printheads  12  contains a plurality of ink channels which terminate in nozzles  22  in a nozzle face  23  (both shown in dashed line). The ink channels carry ink from the ink supply cartridge  14  to the printhead nozzles  22 . 
     When the printer  10  is in a printing mode, the carriage  16  translates or reciprocates back and forth across and parallel to a printing zone  24  (shown in dashed line). Ink droplets are selectively ejected on demand from the printhead nozzles  22  onto a recording medium, such as paper, positioned in the printing zone, to print information on the recording medium one swath or portion at a time. During each pass or translation in one direction of the carriage  16 , the recording medium is stationary. At the end of each pass, the recording medium is stepped in the direction of the arrow  26  for the distance or the height of one printed swath. U.S. Pat. Nos. 4,571,599 and Re. 32,572, each incorporated herein by reference in its entirety, provide a more detailed explanation of the printhead and the printing operation. 
     When the printer  10  is no longer in a printing mode, the carriage  16  travels to a maintenance station  1000  spaced from the printing zone  24 . With the one or more printheads  12  positioned at the maintenance station  1000 , various maintenance functions can be performed on the one or more printheads  12 . 
     FIG. 2 is a top perspective view of the maintenance station  1000 . As shown in FIG. 2, the maintenance station  1000  includes a cam shaft  100 , a cam-actuated lever capping arm  200 , and a cap carriage  300  mounted on a guide shaft  1010 . In particular, as shown in FIG.  2  and more clearly seen in FIG. 3, the cam shaft  100  includes a unitary shaft member  102 , a driving and control portion  110 , a wiper blade drive portion  120 , a cam-actuated lever capping arm drive portion  130  and a pinch tube actuating portion  140 . 
     In various exemplary embodiments, as shown in FIGS. 2 and 3, the driving and control portion  110  includes a sensor wheel  112 , an optical window  114  formed in the sensor wheel  112 , and a main drive gear  116 . In operation, a drive gear train (not shown), comprising a drive motor connected to one or more drive gears, engages the main drive gear  116  to drive the cam shaft  100  in counterclockwise and then clockwise directions to actuate the various maintenance functions enabled by the maintenance station  1000 . This is described in greater detail in copending U.S. patent application Ser. No. 09/594,694 filed herewith and incorporated herein by reference in its entirety. 
     In each of an extreme clockwise position of the cam shaft  100  and the extreme counterclockwise position of the cam shaft  100 , the optical window  114  is aligned with an optical relay (not shown). Thus, after the drive gear train drives the main drive gear  116  to rotate the cam shaft  100  to the extreme clockwise or counterclockwise position, the optical window  114  formed in the sensor wheel  112  is aligned with the optical relay. In various exemplary embodiments, the optical relay includes a photo-emitter positioned on one side of the sensor wheel  112  and a photo-detector positioned on the other side of the sensor wheel  112 . When the optical window  114  is not aligned with the optical relay, the optical relay is in an opened circuit condition. 
     At the start of a maintenance operation, the sensor wheel  112  is in the extreme clockwise position and the optical window  114  is aligned with the optical relay to close the circuit through the optical relay. As a result, when the one or more printheads  12  are aligned with the maintenance station  1000  and the main drive gear  116  is initially driven in the counterclockwise direction, the optical window  114  is no longer aligned with the optical relay and the optical relay is placed into an open circuit condition. Then, when the sensor wheel  112  reaches its extreme counterclockwise position, the window  114  is again aligned with the optical relay. As a result, the optical relay is placed in the closed circuit condition. 
     The open and closed circuit conditions of the optical relay are sensed by a printer controller  40 , as shown in FIG.  1 . In response, the printer controller  40  stops the gear train engaged with the main drive gear  116  from turning the cam shaft  100  for a predetermined time. In particular, this predetermined time depends on the priming mode currently selected for the maintenance station  1000 . 
     Once the predetermined time has elapsed, the printer controller  40  starts the gear train to drive the main drive gear  116 , and thus the cam shaft  100 , in the clockwise direction. The cam shaft  100  continues rotating in the clockwise direction until the optical window  114  in the sensor wheel  112  is again aligned with the optical relay to again put the optical relay in a closed circuit condition. When the printer controller  40  again senses the closed circuit condition of the optical relay, the printer controller  40  again stops the gear train from driving the main drive gear  116 , and thus the cam shaft  100 , in the clockwise direction. 
     As shown in FIGS. 2 and 3, the various elements of the cam shaft drive portion  110 , the wiper blade drive portion  120 , the cam-actuated lever capping arm drive portion  130  and the pinch tube actuation portion  140  are mounted on a shaft  102  of the cam shaft  100 . As shown in FIGS. 2 and 3, in various exemplary embodiments, the wiper blade drive portion  120  includes a forward wiper driving cam  122  that is used to drive the wiper blade platform from the first position to the second position, and a reverse wiper blade driving cam  124  that is used to drive the wiper blade platform from the second position back to the first position. 
     In the exemplary embodiments shown in FIGS. 2 and 3, the cam-actuated lever capping arm drive portion  130  includes a hold-down cam  132  and one or more capping cams  134 . The structure and operation of the cam-actuated lever capping arm drive portion  130  and the cam-actuated lever capping arm  200  are described in greater detail in copending U.S. patent application Ser. No. 09/721,954 filed herewith and incorporated herein by reference in its entirety. 
     In particular, in various exemplary embodiments, when the cam shaft  100  first begins rotating in the counterclockwise direction, the wiper blade portion  120  drives a wiper blade platform (not shown) from a first position to a second position to wipe the nozzle faces  23  of the one or more printheads  12 . Then, when the cam shaft  100  is driven in the clockwise direction, the wiper blade drive portion  120  of the cam shaft  100  lastly drives the wiper blade platform from the second position back to the first position to again wipe the nozzle face  23  of the one or more printheads  12  before the printhead  14  is moved from the maintenance station  1000  to the printer zone  24 . The wiper blade platform, a wiper blade drive mechanism positioned between the cam shaft  100  and the wiper blade platform, and the operation of the wiper blade drive portion  120  is described in greater detail in the incorporated Ser. 09/594,694 application, and in U.S. patent application Ser. No. 09/594,681 filed herewith and incorporated herein by reference in its entirety. 
     In various exemplary embodiments, after the wiper blade drive portion  120  moves the wiper blade platform from the first position to the second position, the cam shaft  100  rotates further in the counterclockwise direction. As a result, the cam-actuated lever capping arm drive portion  130  interacts with a cam-actuated lever arm  200  to move a cap carriage  300  from a disengaged position to an engaged position. In the engaged position, one or more printhead caps  600  carried by the cap carriage  300  engage the one or more printheads  12  as the cam shaft  100  continues to rotate in the counterclockwise direction. Similarly, when the cam shaft  100  continues to rotate in the counterclockwise direction, the cam-actuated lever capping arm drive portion  130  interacts with the cam-actuated lever arm  200  to move the capping carriage  300  from the engaged position to the disengaged position, before the wiper blade drive portion  120  moves the wiper blade platform from the second position back to the first position. This is described in greater detail below. The structure and operation of the printhead caps  600  are described in greater detail in copending U.S. patent applications Ser. Nos. 09/594,682 and 09/594,691, each filed herewith and incorporated herein by reference in its entirety. 
     Likewise, after the cam-actuated lever capping arm drive portion  130  moves the capping station  300  from the disengaged position to the engaged position, the cam shaft  100  rotates further in the counterclockwise direction. As a result, the pinch tube actuating portion  140  actuates one or more pinch tubes  63  to apply a negative pressure to the one or more printheads cap  600  mounted on the cap carriage  300 . The structure and operation of the pinch tubes  63  and the pinch tube mechanism is described in greater detail in copending U.S. patent application Ser. No. 09/594,680 filed herewith and incorporated herein by reference in its entirety. 
     In the exemplary embodiments shown in FIGS. 2 and 3, the cap carriage  300  carries two printhead caps  600 , each having a separate pinch tube  63 . Accordingly, the pinch tube actuation portion  140  includes a first pinch tube actuating cam  142  and a second pinch tube actuation cam  144 . The first pinch tube actuating cam  142  actuates a first pinch mechanism to pinch a first pinch tube  63  connected to the first one of the two printhead caps  600 . Similarly, the second pinch tube actuating cam  144  actuates a second pinch mechanism to pinch a second pinch tube  63  connected to the second one of the two printhead caps  600 . 
     The cam shaft  100  then continues to rotate in the counterclockwise direction until the cam shaft  100  reaches the extreme counterclockwise position. In particular, in various exemplary embodiments, each of at least one of the cam arms of one of the wiper blade drive portion  120 , the cam-actuated lever capping arm drive portion  130  and the pinch tube actuator portion  140  of the cam shaft  100  rigidly contacts a corresponding counterclockwise cam stop formed on one of the wiper blade drive mechanism, the cam-actuated lever capping arm  200  and the punch tube mechanism  140  when the cam shaft  100  reaches the extreme counterclockwise position. This allows the extreme counterclockwise position of the cam shaft  100  to be closely controlled without having to rely on the printer controller  40  precisely stopping the counterclockwise rotation of the cam shaft  100  in response to the signal from the optical relay. In various exemplary embodiments, this counterclockwise cam arm and corresponding cam stop are provided by the hold down cam  132  bearing against the cam-actuated lever capping arm  200 . Similarly, in various exemplary embodiments, each of at least one of the cam arms of the cam shaft  100  rigidly contacts a corresponding clockwise cam stop formed on one of the wiper blade drive mechanism, the cam-actuated lever capping arm  200  and the pinch tube mechanism  140  when the cam shaft  100  reaches the extreme clockwise position. This similarly allows the extreme clockwise position of the cam shaft  100  to be closely controlled without having to rely on the printer shaft  100  in response to the signal from the optical relay. In various exemplary embodiments, the clockwise cam arm and corresponding cam stop are provided by the one or more capping cams  134  and the cam-actuated lever capping arm  200 . The printer controller  40 , based on the signal from the optical relay generated when the optical window  114  is aligned with the optical relay, maintains the cam shaft  100  in the extreme counterclockwise position for one of the predetermined times. 
     Then, after the predetermined time has elapsed, the printer controller  40  engages the drive motor of the drive gear train to rotate the cam shaft  100  in the clockwise direction. When the cam shaft  100  is rotated in the clockwise direction, the pinch tube actuation portion  140  again interacts with the one or more pinch tubes before the cap carriage  300  is moved from the engaged position to the disengaged position by the cam-actuated lever capping arm drive portion  130 , which occurs before the wiper blade drive portion  120  moves the wiper blade platform from the second position to the first position. 
     In various exemplary embodiments, the sensor wheel  112  is positioned relative to the cap carriage  300  and the printhead caps  600  such that the chances any ink from the one or more printheads  12  will negatively affect the operation of the sensor wheel and the optical relay is reduced. In various exemplary embodiments, the sensor wheel  112  is located on an outside of the maintenance station  1000 . While the various mechanisms driven by the cam shaft  100  are located on an interior of the maintenance station  1000 . 
     In various exemplary embodiments, the cam shaft  100  is molded as a single piece. In various exemplary embodiments, the single piece cam shaft  100  molded using any acetyle homopolymer or copolymer with 20% glass fibers and 15% PTFE, i.e., J-80/20/TF/15. 
     In various exemplary embodiments, the wiper blade driving portion  120 , the cam-actuated lever capping arm portion  130  and the pinch tube actuator portion  140  are distributed around the circumference of the cam shaft  100  such that each such portion has a sufficient dwell time that any timing errors do not substantially, or in the limit, do not at all negatively affect the operation of the various mechanisms in, and functions provided by the maintenance station  1000 . 
     While this invention has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.