Patent Publication Number: US-7222936-B2

Title: Printhead carrier positioning apparatus and method

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an imaging apparatus, and, more particularly, to a printhead carrier positioning apparatus and method. 
   2. Description of the Related Art 
   A typical ink jet printer forms an image on a print medium by ejecting ink from a plurality of ink jetting nozzles of an ink jet printhead to form a pattern of ink dots on the print medium. The ink jet printhead may be formed integral with a cartridge containing a supply of ink, thus forming a printhead cartridge. Such an ink jet printer typically includes a reciprocating printhead carrier that transports one or more printhead cartridges, that mount the ink jet printheads, across the print medium along a bi-directional scanning path defining a print zone of the printer. A sheet feeding mechanism is used to incrementally advance the print medium sheet in a sheet feed direction, also commonly referred to as a sub-scan direction or vertical direction, through the print zone between scans in the main scan direction. 
   When the ink supply contained in one of the printhead cartridges is depleted, then typically the printhead cartridge is replaced. In order to simplify printhead cartridge replacement, some printers include an opening that provides a user with sufficient space to change-out the printhead cartridge. 
   What is needed in the art is a printhead carrier positioning apparatus and method to aid in the positioning of the printhead carrier at a cartridge exchange opening for convenient printhead cartridge replacement. 
   SUMMARY OF THE INVENTION 
   The present invention provides a printhead carrier positioning apparatus and method to aid in the positioning of the printhead carrier at a cartridge exchange opening for convenient printhead cartridge replacement. 
   The invention, in one form thereof, relates to an imaging apparatus. The imaging apparatus includes a housing having a cartridge exchange opening, and a printhead carrier system contained in the housing. The printhead carrier system has a printhead carrier. A cover is pivotably attached to the housing. The cover has an engagement surface. When the cover is in a closed position the cartridge exchange opening is not exposed. A switch unit has a switch actuator and a switch. The switch actuator is configured for actuating the switch. The engagement surface of the cover is positioned to engage the switch actuator when the cover is in the closed position. The switch actuator is configured with a button that is accessible by a user to facilitate manual manipulation of the switch actuator by a force applied to the button by the user. The printhead carrier is positioned based on an output of the switch. 
   In another form thereof, the present invention relates to a method for positioning a printhead carrier for an imaging apparatus. The method includes activating a printhead carrier drive system of the imaging apparatus to position the printhead carrier at a cartridge exchange opening when a cover of the imaging apparatus is detected to not be in a closed position; activating the printhead carrier drive system to position the printhead carrier at a printhead home position if the cover is not positioned in the closed position within a predetermined amount of time after being opened; and activating the printhead carrier drive system to reposition the printhead carrier at the cartridge exchange opening if, after the predetermined amount of time, the cover is open and a button is pressed by a user. 
   An advantage of the present invention is that it provides for convenient printhead cartridge replacement, even if the printhead cartridge has returned to a home position after the cover has been opened. 
   Another advantage of the present invention is that it reduces the chance of printer damage due to manual positioning of the printhead carrier by a user. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of an imaging apparatus with a cover in a closed position. 
       FIG. 2  is a perspective view of the imaging apparatus of  FIG. 1  with the cover in an open position. 
       FIG. 3  is a diagrammatic representation of the imaging apparatus of  FIGS. 1 and 2 . 
       FIG. 4  is a perspective view of one embodiment of a switch unit of the imaging apparatus of  FIGS. 1–3 . 
       FIG. 5  is a general flowchart of a method for positioning a printhead carrier of the imaging apparatus of  FIGS. 1–3 , in accordance with the present invention. 
   

   Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings, and particularly to  FIGS. 1 and 2 , there is shown an imaging apparatus  10 . Imaging apparatus  10  may be, for example, a conventional ink jet printer, or a multi-function apparatus, such as for example, a standalone unit that has faxing and copying capability, in addition to printing. Accordingly, imaging apparatus  10  may be connected to a host, such as a computer (not shown). 
   Imaging apparatus  10  includes a housing  12 , and a cover  14  mounted to housing  12 . Also mounted to housing  12  is a user interface  16  having control buttons, such as for example, a duplex button  18 , a line feed button  20  and a power ON button  22 . Imaging apparatus  10  also includes a media source  24  and a media exit tray  26 . 
   As shown in  FIGS. 1 and 2 , cover  14  is pivotably attached to housing  12  to facilitate an opening and closing of cover  14  with respect to housing  12  by a pivoting action.  FIG. 1  shows cover  14  a closed position  28 .  FIG. 2  shows cover  14  in an open position  30 . When cover  14  is in open position  30 , there is exposed a cartridge exchange opening  32  formed in housing  12 , and when cover  14  is in closed position  28 , cartridge exchange opening  32  is not exposed. 
   Referring to  FIG. 3 , imaging apparatus  10  further includes a printhead carrier system  34 , a feed roller unit  36 , a mid-frame  38 , a controller  40  and a maintenance station  42 , which are contained in housing  12 . Printhead carrier system  34 , feed roller unit  36 , mid-frame  38 , controller  40  and maintenance station  42  are coupled, e.g., mounted, to an imaging apparatus frame  44 . Housing  12 , as shown in  FIGS. 1 and 2 , may also be attached to imaging apparatus frame  44 . 
   Media source  24  is configured and arranged to supply from a stack of print media a sheet of print media  46  to feed roller unit  36 , which in turn further transports the sheet of print media  46  during a printing operation. 
   Printhead carrier system  34  includes a printhead carrier  48  and a printhead carrier drive system  49 . 
   Printhead carrier  48  carries, for example, one, two, three or more printhead cartridges, such as a monochrome printhead cartridge  50   a  and/or a color printhead cartridge  50   b,  that is mounted thereto. Monochrome printhead cartridge  50   a  includes a monochrome ink reservoir  52   a  provided in fluid communication with a monochrome ink jet printhead  54   a  and formed as an integral unit. Color printhead cartridge  50   b  includes a color ink reservoir  52   b  provided in fluid communication with a color ink jet printhead  54   b  and formed as an integral unit. Alternatively, printhead cartridges  50   a,    50   b  may only include ink reservoirs  52   a,    52   b,  which in turn are coupled to respective remote ink jet printheads  54   a,    54   b  via respective fluid conduits. 
   Printhead carrier  48  is guided by a pair of guide members  56 . Either, or both, of guide members  56  may be, for example, a guide rod, or a guide tab formed integral with imaging apparatus frame  44 . The axes  56   a  of guide members  56  define a bi-directional scanning path  58  of printhead carrier  48 . 
   Printhead carrier  48  is connected to printhead carrier drive system  49 , which includes a carrier transport belt  60  that is driven by a carrier motor  62  via a carrier pulley  64 . In this manner, carrier motor  62  is drivably coupled to printhead carrier  48 , although one skilled in the art will recognize that other drive arrangements could be substituted for the example given, such as for example, a worm gear drive. Carrier motor  62  can be, for example, a direct current motor or a stepper motor. Carrier motor  62  has a rotating motor shaft  66  that is attached to carrier pulley  64 . Carrier motor  62  is coupled, e.g., electrically connected, to controller  40  via a communications link  68 . 
   At a directive of controller  40 , printhead carrier  48  is transported in a controlled manner along bi-directional scanning path  58 , via the rotation of carrier pulley  64  imparted by carrier motor  62 . During printing, controller  40  controls the movement of printhead carrier  48  so as to cause printhead carrier  48  to move in a controlled reciprocating manner, back and forth along guide members  56 . In order to conduct printhead maintenance operations, controller  40  controls the movement of printhead carrier  48  to position printhead carrier in relation to maintenance station  42  and/or cartridge exchange opening  32 . 
   Ink jet printheads  54   a,    54   b  are electrically connected to controller  40  via a communications link  70 . Controller  40  supplies electrical address and control signals to imaging apparatus  10 , and in particular, to the ink jetting actuators of ink jet printheads  54   a,    54   b,  to effect the selective ejection of ink from ink jet printheads  54   a,    54   b.    
   During a printing operation, the reciprocation of printhead carrier  48  transports ink jet printheads  54   a,    54   b  across the sheet of print media  46  along bi-directional scanning path  58 , i.e., a scanning direction, to define a print zone  72  of imaging apparatus  10 . Bi-directional scanning path  58 , also referred to as scanning direction  58 , is parallel with axes  56   a  of guide members  56 , and is also commonly known as the horizontal direction. During each scan of printhead carrier  48  when printing, the sheet of print media  46  is held stationary by feed roller unit  36 . Feed roller unit  36  includes a feed roller  74  and a drive unit  76 . The sheet of print media  46  is transported through print zone  72  by the rotation of feed roller  74  of feed roller unit  36 . A rotation of feed roller  74  is effected by drive unit  76 . Drive unit  76  is electrically connected to controller  40  via a communications link  78 . 
   Maintenance station  42  is provided for performing printhead maintenance. operations on the ink jet nozzles of ink jet printheads  54   a,    54   b.  Such operations may include, for example, a printhead spit maintenance operation, a printhead wiping operation and a printhead capping operation. The printhead capping operation occurs with printhead carrier  48  located in a home position  80 , which is a far-left position along mid-frame  38  with respect to the components arranged as shown in  FIG. 1 . Other services, such as for example, printhead priming and suction, may also be performed if desired by the inclusion of a vacuum device (not shown) of the type well known in the art. 
   Maintenance station  42  includes, for example, a maintenance housing  82  and a movable maintenance sled  84 . Maintenance housing  82  supports movable maintenance sled  84 , which has mounted thereto respective printhead wipers and printhead caps. Maintenance sled  84  is configured for movement in the directions generally depicted by double-headed arrow  86  to predefined elevations, such as for example, a lowered printing elevation, an intermediate wiping elevation and a fully raised capping elevation. Maintenance sled  84  includes a carrier engagement member  88 . 
   With the orientation of components as shown in  FIG. 3 , a leftward movement of printhead carrier  48  causes printhead carrier  48  to engage carrier engagement member  88 , thereby causing maintenance sled  84  to move to the left and upward, as illustrated by arrow  86 , progressing from a lowered, or rest, elevation to an intermediate, or wiping, elevation, and progressing from the wiping elevation to the full raised, or capping, elevation at home position  80 . Maintenance sled  84  is biased to return to the lowered elevation when printhead carrier  48  is moved rightward toward print zone  72 . 
   Referring to  FIG. 3 , imaging apparatus  10  includes a switch unit  89  having a cartridge exchange button  90  (see also  FIG. 2 ), a switch actuator  92  and a switch  94 . As shown in  FIG. 1 , when cover  14  is in closed position  28 , cartridge exchange button  90  is not exposed, and, as shown in  FIG. 2 , when cover  14  is in open position  30 , cartridge exchange button  90  is exposed and is accessible by a user for manual manipulation. 
   Cartridge exchange button  90  is used for both automatic and manual positioning of printhead carrier  48  at cartridge exchange opening  32  in accordance with the present invention. In the embodiment shown, cartridge exchange button  90  is mechanically linked to switch actuator  92 , which in turn is communicatively linked to switch  94 . Cover  14  includes an engagement surface  96 , such as, for example, a protruding tab, positioned to engage cartridge exchange button  90  when cover  14  is moved to closed position  28  ( FIG. 1 ). 
   Switch  94  may be, for example, an electrical micro-switch or an optical switch, the operation of each being well known in the art. Switch  94  is communicatively coupled to controller  40  via a communications link  98 . Controller  40  monitors switch  94  for a change in switch status, i.e., a logic low-to-high transition or a logic high-to-low transition. For example, with cover  14  in closed position  28  depicted in  FIG. 1 , switch  94  may be held in a closed state by engagement of engagement surface  96  of cover  14  with cartridge exchange button  90 . However, as cover  14  is moved from closed position  28  depicted in  FIG. 1  toward the open position  30  depicted in  FIG. 2 , switch  94  may change to an open state by the disengagement of engagement surface  96  of cover  14  with cartridge exchange button  90 , and controller  40  senses the low-to-high transition of this occurrence. Thereafter, when cartridge exchange button  90  is next depressed, either by engagement surface  96  when cover  14  is returned to the closed position  28  or by manual actuation by a user when cover  14  is open, controller  40  senses a high-to-low transition of switch  94 . Then, when cartridge exchange button  90  is next released, controller  40  again senses a low-to-high transition of switch  94 . 
   Those skilled in the art will recognize that whether controller  40  senses a low-to-high transition or a high-to-low transition upon the depressing of cartridge exchange button  90  will depend upon the type of switching mechanism that resides in switch  94 , e.g., a normally closed switching mechanism or a normally open switching mechanism. 
     FIG. 4  shows an exemplary embodiment of a switch unit  89 , wherein switch  94  is in the form of an optical switch, and switch actuator  92  is in the form of a mechanical flag. In this embodiment, switch actuator  92  is pivotably mounted to a switch housing  100  via a pivot pin  102  defining a pivot axis  104 . Switch actuator  92  includes a lever  106  having a first end  108  spaced apart from a second end  110 . Cartridge exchange button  90  is connected to first end  108  and a flag  112  is connected to second end  110 . 
   Referring now to  FIGS. 3 and 4 , lever  106  is biased, such as for example, by gravity or by a spring, such that in the absence of a force F exerted on cartridge exchange button  90 , then flag  112  is positioned to break the optical beam in switch  94 , thereby placing switch  94  in an open condition. Switch  94  thus outputs a logic high signal via communication link  98  to controller  40 . Upon application of force F to cartridge exchange button  90  in the direction indicated by the arrow, then lever  106  pivots about pivot axis  104  and flag  112  is raised, thereby allowing the optical beam to be received by a light detector in switch  94  and placing switch  94  in a closed condition. Switch  94  thus outputs a logic low signal via communication link  98  to controller  40 . 
   In summary, referring to  FIGS. 1 and 2 , cartridge exchange opening  32  and cartridge exchange button  90  are concealed, i.e., not exposed, by cover  14  when cover  14  is in closed position  28 , as in the case of normal printing. When cover  14  is opened, as shown in  FIG. 2 , engagement surface  96  of cover  14  disengages cartridge exchange button  90 , and both cartridge exchange opening  32  and cartridge exchange button  90  are exposed. 
     FIG. 5  is a general flowchart of a method for positioning printhead carrier  48  for imaging apparatus  10 , in accordance with the present invention. 
   At step S 100 , printhead carrier drive system  49  of imaging apparatus  10  is activated, via controller  40 , to position printhead carrier  48  at a cartridge exchange position  114  (see  FIG. 3 ) corresponding to cartridge exchange opening  32  ( FIG. 2 ) when cover  14  of imaging apparatus  10  is detected to not be in closed position  28 , e.g., is in open position  30 . This detection occurs when engagement surface  96  of cover  14  disengages cartridge exchange button  90  of switch actuator  92 . 
   At step S 102 , printhead carrier drive system  49  is activated, via controller  40 , to position printhead carrier  48  at printhead home position  80  if cover  14  is not returned to closed position  28  within a predetermined amount of time after being opened, i.e., cover  14  remains open for too long. This predetermined amount of time may be, for example, in a range of 5 minutes to 50 minutes, or longer if desired, and serves to return printheads  54   a,    54   b  to maintenance station  42  for capping to prevent liquid ink present in or on the nozzles of printheads  54   a,    54   b  from drying and clogging. 
   At step S 104 , if, after the predetermined amount of time, cover  14  was not returned to closed position  28 , and a user applies force F to cartridge exchange button  90 , then printhead carrier drive system  49  is activated, via controller  40 , to reposition printhead carrier  48  at cartridge exchange opening  32 . Accordingly, even if printhead carrier  48  is no longer readily accessible by the time the user is ready to replace one or more of printhead cartridges  54   a,    54   b  after cover  14  was originally opened, by pushing cartridge exchange button  90 , the user may manually reposition printhead carrier  48  at cartridge exchange opening  32  in a manner that is not damaging to printhead carrier system  34 . 
   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.