Abstract:
A method and system for a cam-actuated lever capping arm for use in a maintenance station of an ink jet printer, the printer including a bi-directional translatable carriage supporting a print cartridge having a print head with nozzles in a nozzle face for printing ink droplets ejecting from said nozzles onto a recording medium at a printing zone in the printer, the translatable carriage being controlled by drive members under the control of a printer controller, the maintenance station being positioned at one side of the printing zone for translation of a print cartridge thereto on the translatable carriage for capping by the cap carriage, the cap carriage including, a pair of movable caps for sealing the nozzles in the printhead nozzle face, and a cam-actuated lever for moving the cap into a position in which the cap seals against the printhead nozzle face.

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 
     Fluid ejection systems, such as ink jet printers, have at least one fluid ejector head that directs droplets of fluid towards a receiving medium. Within the fluid ejector head, the fluid may be contained in a plurality of channels. Energy pulses are used to expel the droplets of fluid, as required, from orifices at the ends of the channels. 
     In a thermal fluid ejection system, such as 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 fluid in the channels. As a vapor bubble grows in any one of the channels, fluid bulges from the channel orifice until the current pulse has ceased and the bubble begins to collapse. At that stage, the fluid within the channel retracts and separates from the bulging fluid to form a droplet moving in a direction away from the channel and towards the receiving medium. The channel is then re-filled by capillary action, which in turn draws fluid from a supply container. Operation of a thermal ink jet printer is described in, for example, U.S. Pat. 4,849,774, incorporated herein by reference in its entirety. 
     A carriage-type thermal ink jet printer is described in U.S. Pat. No. 4,638,337, incorporated herein by reference in its entirety. 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 receiving medium as the carriage is moved in one direction. The receiving medium is then stepped, perpendicular to the line of carriage movement, by a distance equal to or less than the width of the printed swath. The carriage is then moved in the reverse direction to print another swath of information. 
     The fluid ejecting orifices of a fluid ejector head need to be maintained, for example, by periodically cleaning the orifices when the fluid ejection system is in use, and/or by capping the fluid ejector head when the fluid ejection system is out of use or is idle for extended periods. Capping the fluid ejector head is intended to prevent the fluid in the fluid ejector head from drying out. The cap provides a controlled environment to prevent fluid exposed in the nozzles from drying out. 
     A fluid ejector head may also need to be primed before initial use, to ensure that the fluid ejector head channels are completely filled with the fluid and contain no contaminants or gas bubbles. After significant amounts of ejecting, and at the discretion of the user, an additional but reduced volume prime may be used to clear particles or gas bubbles that can cause defects in the ejected swath of information. 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, each incorporated herein by reference in its entirety. 
     The priming operation, which usually involves either forcing or drawing fluid through the fluid ejector head, can leave drops of fluid on the face of the fluid ejector head. As a result, fluid residue builds up on the fluid ejector head face. This fluid residue can have a deleterious effect on the quality of the ejected swath of information. Material from the receiving medium and other foreign material can also collect on the fluid ejector head face while ejecting fluid. Like the fluid residue, this foreign material can also have deleterious effects on the quality of the ejected swath of information. 
     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 for a maintenance station for a fluid ejector head that carries and actuates one or more caps movably mounted on a cap carriage to cap the fluid ejector head nozzles. 
     In one exemplary embodiment of the maintenance station according to this invention, one or more caps are mounted on a translatable carriage and moves with the carriage. When the fluid ejection system is ejecting fluid, the translatable carriage is located in an ejection zone, where the one or more fluid ejector heads can eject fluid onto a receiving medium. When the fluid ejection system is placed into a non-ejection mode, the translatable carriage can be translated to the maintenance station located outside and to one side of the ejection zone. Once the cartridge is translated to the maintenance station, various maintenance functions can be performed on the one or more fluid ejector heads of the fluid ejection system depending on the rotational position of a cam shaft in the maintenance station. The cam shaft rotates in one direction, such as, for example, counterclockwise, to engage and drive the hardware that in turn operates the individual maintenance functions. 
     Rotating the cam shaft activates various maintenance mechanisms of the maintenance station, including a cap carriage. After the one or more fluid ejector heads arrive at the maintenance station, a vacuum pump is energized, and the cap carriage is elevated to the position where the one or more caps engage the one or more fluid ejector heads. The one or more caps are mounted on the cap carriage in a capping location. The fluid ejector heads are primed when a pinch tube mechanism opens one or more pinch tubes connected to the one or more caps. Opening the pinch tubes releases negative pressure created by the vacuum pump. In response, fluid is drawn from the one or more fluid ejector heads into the one or more caps. 
     The vacuum pump is then deenergized, while the cap carriage remains in position so that the one or more caps cap the one or more fluid ejector heads awaiting the ejection mode of the fluid ejection system. Thus, the one or more fluid ejector heads remain capped at the maintenance station until the fluid ejection system is placed into the ejection mode. 
     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 the maintenance station of FIG. 1 according to this invention; 
     FIG. 3 is a partial perspective view of the cam shaft of FIG. 2; 
     FIG. 4 is a top plan view of one exemplary embodiment of the cam-actuated lever capping arm according to this invention; and 
     FIG. 5 is a partial perspective view of the cam-actuated lever capping arm. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The following detailed description of various exemplary embodiments of the fluid ejection systems according to this invention are directed to one specific type of fluid ejection system, an ink jet printer, for sake of clarity and familiarity. However, it should be appreciated that the principles of this invention, as outlined and/or discussed below, can be equally applied to any known or later developed fluid ejection system, beyond the ink jet printer specifically discussed herein. 
     FIG. 1 shows an ink jet 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 an 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 ink jet 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 receiving medium, such as paper, positioned in the printing zone, to record 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 receiving medium is stationary. At the end of each pass, the recording medium is stepped in the direction of the arrow  26  for the at most distance or the height of one printed swath. U.S. Pat. No. 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 ink jet 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 . 
     In contrast to copending U.S. patent application Ser. No. 09/594,693, incorporated herein by reference in its entirety, the cam shaft  100  rotates in a single direction. In various exemplary embodiments, this single direction is the counterclockwise direction. However, depending on the relative orientations of the various elements of the maintenance station, the cam shaft  100  can rotate only clockwise. Additionally, as described in U.S. patent application Ser. No. 09/594,695, incorporated herein by reference in its entirety, the cam shaft  100  can rotate in both a clockwise and counterclockwise direction, depending upon the activation required by a particular maintenance function and/or timing sequence. 
     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 . In particular, as shown in FIG. 2, and more clearly seen in FIG. 3, the cam shaft  100  includes at least a driving and control portion  110 , and a cam-actuated lever capping arm drive portion  130 . 
     In various exemplary embodiments, as shown in FIGS. 2 and 3, the driving and control portion  110  may, for example, include 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 direction 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, incorporated herein by reference in its entirety. 
     In a first reference 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 , for example, one complete revolution, the optical window  114  formed in the sensor wheel  112  is again 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, with the sensor wheel  112  at the first reference 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, the sensor wheel  112  again advances the window  114  into alignment 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 controller (not shown). In response, the controller 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 controller starts the gear train to drive the main drive gear  116 , and thus the cam shaft  100 , in the counterclockwise direction. The cam shaft  100  continues rotating in the counterclockwise 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 controller again senses the closed circuit condition of the optical relay, the controller again stops the gear train from driving the main drive gear  116 , and thus the cam shaft  100 , in the counterclockwise direction. 
     In particular, in various exemplary embodiments, depending on the rotational position of the camshaft  100 , when the cam shaft  100  rotates in the counterclockwise direction, 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 or from the engaged position to the disengaged position. The cap carriage  300  approaches the one or more printheads  12  at a slight angle from normal (i.e., perpendicular to the nozzle face  23 ), to rollingly engage the one or more printheads  12  with one or more printhead caps  600 . The rolling engagement of the one or more printheads  12  with the one or more printhead caps  600  causes the leading edge portions  610  of the one or more printhead caps  600  to first contact the one or more printheads  12 . As the cam shaft  100  continues to rotate further in the counterclockwise direction, the rolling engagement of the one or more printheads  12  with the one or more printhead caps  600  causes each of the one or more printhead caps  600  to gradually engage the printheads  12  until the trailing edge portions  620  of the one or more printhead caps  600  eventually contact the one or more printheads  12 . 
     By rollingly engaging the one or more printheads  12  with the one or more printhead caps  600 , the impact force is evenly distributed to the one or more printheads  12  through the entire time over which the one or more printhead caps  600  rollingly engages the one or more printheads  12 . That is, rollingly engaging the one or more printheads with the impact force of the one or more printhead caps  600  tends to reduce the impact force against the one or more printheads  12 , by spreading the contact force out over the period between the one or more printheads  12  contacting the leading edge portions  610  of the one or more printhead caps  600  and the trailing edge portions  620  of the one or more printhead caps  600 . Additionally, in various exemplary embodiments, by spreading the contact force out over a period of time, the possibility of de-priming the one or more printheads  12  is reduced. 
     During the rolling engagement between the leading edge portions  610  of the one or more printhead caps  600  and the trailing edge portions  620  of the one or more printhead caps  600 , the air contained in the one or more printhead caps  600  is allowed to escape before the one or more printhead caps  600  are fully engaged over the one or more printheads  12 . By allowing the air to escape, and not forcing air down through the nozzles of the one or more printheads  12 , the de-priming one or more printheads  12  becomes less likely. 
     In various exemplary embodiments, once in the engaged position, one or more printhead caps  600  carried by the cap carriage  300  remain engaged with the one or more printheads  12 , while the cam shaft  100  continues to rotate in the counterclockwise direction. Several exemplary embodiments of the structure and operation of the printhead caps  600  are described in greater detail in copending U.S. patent applications Ser. No. 09/594,682 and 09/594,690 each incorporated herein by reference in its entirety. 
     As outlined above, the cap carriage  300  includes one or more printhead caps  600 . As outlined above, when the cap carriage  300  is moved from the disengaged position to the engaged position by the cam-actuated capping lever arm  200 , the one or more printhead caps  600  engage the nozzle faces  23  of one or more printheads  12 . In particular, each of the printhead caps  600  needs to securely engage the nozzle face  23  of one of the one or more printheads  12  to ensure the negative pressure applied through one or more pinched tubes (not shown) is able to withdraw ink from the ink channels of the corresponding printhead  12 . 
     That is, if the printhead cap  600  does not securely engage the nozzle face  23  of the corresponding printhead  12 , the negative pressure applied through the one or more pinched tube (not shown) merely draws atmospheric into the interior of the printhead cap  600  rather than withdrawing ink from the ink channels of the corresponding printhead  12 . Accordingly, in various exemplary embodiments of the printhead cap  600 , the printhead caps  600  are provided with a compressible gasket  650 . However, even with the compressible gasket  650 , the printhead caps  600  cannot securely engage the printhead nozzle faces  23  if the printhead caps  600  are not substantially parallel to, and biased against, the nozzle faces  23 . 
     Accordingly, as shown in FIGS. 2 and 4, the printhead caps  600  are not mounted on the cap carriage  300  in a fixed position. Rather, as shown in FIG. 2, in various exemplary embodiments, printhead caps  600  are mounted using a cap gimbal structure. The cap carriage portion of the cap gimbal structure includes four support springs  310 ,  320 ,  330  and  340 ; four support tabs  315 ,  325 ,  335  and  345 ; two pivot tabs  350  and  360 ; and two pivot tab receiving slots  370  and  380 . 
     The four support tabs  315 ,  325 ,  335  and  345  fit within and hold in position one end of the four support springs  310 ,  320 ,  330  and  340 , on each of a first cap mounting position  302  and a second cap mounting position  304 , of the cap carriage  300 . The two pivot tabs  350  and  360  are located, respectively, on the leading edge portion  610  and the trailing edge portion  620 , of the one or more printhead caps  600 . The two pivot tab receiving slots  370  and  380  are located, respectively, on the leading wall portion  306  and the trailing wall portion  308 , of a first cap mounting position  302 , and a second cap mounting position  304 , of the cap carriage  300 . The two pivot tabs  350  and  360  slide into the two pivot receiving slots  370  and  380 , to engage and biasedly support against the four support springs  310 ,  320 ,  330  and  340 , the one or more printhead caps  600 . 
     As a result, the printhead cap  600 , using this gimbal structure according to this invention, has at least two degrees of rotational freedom. Accordingly, when that printhead cap  600  is biased against the corresponding nozzle face  23 , the printhead cap  600  will securely engage the nozzle face  23  so that the negative pressure applied through the pinch tube (not shown) is able to withdraw ink from the ink channels of that printhead  12 , rather than merely drawing ambient air from the region surrounding the nozzle face  23  of that printhead  12 . 
     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, in various exemplary embodiments, a pinch tube actuating portion actuates one or more pinch tubes to apply the negative pressure to the one or more printheads cap  600  mounted on the cap carriage  300 . Several exemplary embodiments of the structure and operation of the pinch tubes and pinch mechanism is described in greater detail in copending U.S. patent application Ser. No. 09/594,680, incorporated herein by reference in its entirety. The cam shaft  100  then continues to rotate in the counterclockwise direction until the cam shaft  100  has traveled, for example, approximately 180 degrees from the first reference position. In various exemplary embodiments, the controller, based on the signal from the optical relay generated when the optical window  114  was in the first reference position and on the amount of rotation assumed for the cam shaft  100  since then, stops the cam shaft  100  when the cam shaft  100  is, for example, approximately 180 degrees out of alignment with the optical relay, and maintains the cam shaft  100  in that position for one of the predetermined times. 
     Then, after the predetermined time has elapsed, the controller engages the drive motor of the drive gear train to continue to rotate the cam shaft  100  in the counterclockwise direction. When the cam shaft  100  continues rotating in the counterclockwise direction, the pinch tube actuation portion 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 . 
     As shown in FIGS. 2 and 3, the various elements of the cam shaft drive portion  110 , and the cam-actuated lever capping arm drive portion  130  are mounted on a shaft  102  of the cam shaft  100 . 
     In the exemplary embodiments shown in FIGS. 2-5, the cam-actuated lever capping arm drive portion  130  of the cam shaft interacts with a cam-actuated lever arm  200  to move the cap carriage  300  from either the disengaged position to the engaged position against the one or more printheads  12 , or from the engaged position against the one or more printheads  12  to the disengaged position. The cam-actuated lever capping arm  200  includes a biasing spring  210 , as described in detail below. The biasing spring  210  operates in conjunction with the capping arm drive portion  130  to create a smooth transition of the cap carriage  300  from either the disengaged position to the engaged position against the one or more printheads  12 , or from the engaged position against the one or more printheads  12  to the disengaged position. While the cam-actuated lever capping arm drive portion  130  can include, in various exemplary embodiments, a single drive portion  130 , it should be appreciated that the drive portion  130 , may include, in various other exemplary embodiments, one or more hold down cams  132  and one or more capping cams (not shown) that actuate, drive or bias, in conjunction with actuation and/or driving, one or more engaging portion  220  of the cam-actuated lever capping arm  200 , as described in detail below. 
     FIGS. 4 and 5 show a top plan and a front perspective view, respectively, of the cam-actuated lever capping arm  200 . When the cam shaft  100  is in the first reference position, the cam-actuated lever capping arm  200  is fully “lowered” to place the cap carriage  300  in the disengaged position. 
     As shown in FIGS. 2,  4  and  5 , the cam-actuated lever capping arm  200  includes the biasing spring  210  having two maintenance station lever engaging portions  212  and  214 , a cam engaging portion  220 , a spring support shaft  240  having two end portions  242  and  244 , and a lever arm portion  250 . The spring support shaft  240  rotatably mounts the cam-actuated lever capping arm  200  in the maintenance station  1000 , with the two end portions  242  and  244  supported within the maintenance station  1000 . In various exemplary embodiments, the two end portions  242  and  244  of the mounting portion  240  “snap-fit” into a receiving structure (not shown) in the maintenance station  1000 . In particular, the biasing spring  210  provides a bias force acting opposite the force applied by the cam-actuated lever capping arm drive portion  130  of the cam shaft  100  against the cam engaging portion  220  due to the counterclockwise rotation of the cam shaft  100 . 
     In various exemplary embodiments, the cam engaging portion  220  includes a cam follower  222  having a curvilinear surface  223  and a protruding leading portion  224 . When the cam shaft  100  rotates in the counterclockwise direction, the cam-actuated lever capping arm drive portion  130  interacts with various elements of the cam engaging portion  220 . 
     In various exemplary embodiments, in conjunction with the biasing spring  210 , the cam-actuated lever capping arm  200 , may, for example, include a inverted cam surface as the curvilinear surface  223  of the cam follower  222  and a protruding follower portion  224 . When the cam shaft  100  rotates in the counterclockwise direction, a hold-down cam surface  133  of a hold-down cam  132  engages the cam-actuated lever capping arm drive portion  130  of the inverted cam surface. The cam follower  222  contacting the hold-down cam  132  terminates at the protruding portion  224 . The cam shaft  100 , as it rotates counterclockwise, drives the hold-down cam surface  133  of the hold-down cam  132  against the inverted cam surface  223  of the cam follower  222  until the protruding follower portion  224  contacts a notch portion  134  of the hold-down cam surface  133 . 
     After the hold-down cam  132  contacts the protruding portion  224 , the cam-actuated capping arm is in its fully disengaged position from the one or more printheads  12 . When the cam shaft  100  continues to rotate in the counterclockwise direction, beyond the contact with the notch portion  134  of the hold-down cam surface  133 , the spring  210  and the hold-down cam  132 , working in conjunction with each other, raise the lever arm  200  towards the engaged position so that the at least one cap  600  rollingly engage the at least one printheads  12 . 
     In various exemplary embodiments, many individual systems cooperate to maintain and maximize the useful life of the one or more printheads  12 , and may, for example, take place at a maintenance station. The maintenance station  1000 , may be, for example, at one side of the printer, outside of the printing zone  24 . At the end of a printing operation or upon the printer  10  terminating the printing mode, the carriage  16  is moved to the maintenance station  1000 . With the one or more printhead nozzle faces  23  positioned adjacent to the maintenance station, the controller activates the maintenance station motor to drive the maintenance station gear train (not shown). 
     Thus, once the one or more printhead nozzle faces  23  are capped by the one or more caps  600 , the controller may optionally have the one or more printheads  12  eject a number of ink droplets into the caps  600 . 
     While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.