Abstract:
In one embodiment, a device for a printer includes a movable tray for supporting a print media. The tray is movable between an open position in which media may be moved on to the tray and a closed position in which media is blocked from moving on to the tray. The device also includes a rotatable media drive component for moving print media on to the tray and a movable restraint operatively connected to the tray. The restraint is movable between: a first position, corresponding to the open position of the tray, in which the restraint does not restrain the media drive component; and a second position, corresponding to the closed position of the tray, in which the restraint restrains rotation of the media drive component.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of copending U.S. patent application Ser. No. 12/766,308, filed on Apr. 23, 2010, and incorporated herein by reference. 
    
    
     BACKGROUND 
     Some printers use folding media trays to enable a compact product size for shipping and a smaller footprint when not in use. The user must fold out the trays for proper printer operation. For example, the user must clear the media discharge area by folding the output tray out from its closed position. This step may be overlooked by the user on printers where the output tray is positioned separately from the input tray, such as printers with a straight through or “L” shaped media path (e.g., top in, front out). If a print job is attempted with the output tray folded in the closed position, the media will crash into the output tray as it is discharged from the printer, resulting in a media jam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram illustrating one example of an inkjet printer in which embodiments of the present disclosure may be implemented. 
         FIGS. 2 and 3  are perspective views illustrating an inkjet printer with a folding media output tray, according to one embodiment of the disclosure. The output tray is folded in to the closed position in  FIG. 2  and folded out to the open position in  FIG. 3 . 
         FIGS. 4-8  are detail views from  FIGS. 2 and 3  showing one embodiment of a media output roller shaft restraint used for detecting a closed output tray. 
         FIG. 9  is a block diagram illustrating components of the printer shown in  FIGS. 2 and 3  used for detecting when the output tray is in the closed position, according to one embodiment of the disclosure. 
         FIG. 10  is a flow chart illustrating one embodiment of a method for detecting a closed printer output tray. 
     
    
    
     DESCRIPTION 
     Embodiments of the present disclosure were developed in an effort to automatically detect when a printer output tray is in the closed position so that the output tray may be opened before printing, and thus avoid the difficulties of running a print job with the output tray closed. Although embodiments will be described with reference to an inkjet printer, the disclosure is not limited to inkjet printers. The example embodiments described below should not be construed to limit the scope of this disclosure, which is defined in the claims that follow the description. 
     As used in this document: a “controller” means a processor (or processors) and associated memory (or memories) and programming at the printer used to control operative elements of the printer, and may include multiple hardware and programming components and multiple circuit boards; and a “print engine” means a component or group of components used to apply ink or toner or other imaging material to a print media, for example the printhead(s) or ink pen(s) in an inkjet printer and the toner developer and photoconductor in a laser printer. 
     One example of an inkjet printer in which embodiments of the present disclosure may be implemented will be described with reference to  FIG. 1 . A shaft restraint used for automatically detecting a closed output tray will then be described with reference to  FIGS. 2-8 . Other components used to detect a closed output tray are then described with reference to  FIG. 9  and a method for detecting a closed output tray described with reference to  FIG. 10 . 
     Referring first to the block diagram of an inkjet printer  10  in  FIG. 1 , printer  10  includes a print cartridge  12 , a carriage  14 , a print media transport mechanism  16 , an input/output device  18 , and a printer controller  20  connected to each of the operative components of printer  10 . Print cartridge  12  includes one or more ink holding chambers  22  and one or more printheads  24 . A print cartridge is sometimes also referred to as an ink pen or an ink cartridge. Printhead  24  represents generally a small electromechanical part that contains an array of miniature thermal resistors or piezoelectric devices that are energized to eject small droplets of ink out of an associated array of nozzles. A typical thermal inkjet printhead, for example, includes a nozzle plate arrayed with ink ejection nozzles and firing resistors formed on an integrated circuit chip. Each printhead is electrically connected to printer controller  20  through external electrical contacts. In operation, printer controller  20  selectively energizes the firing resistors through the electrical contacts to eject a drop of ink through a nozzle on to media  22 . 
     Print cartridge  12  may include a series of stationary cartridges or printheads that span the width of print media  26 . Alternatively, cartridge  12  may include one or more cartridges that scan back and forth on carriage  14  across the width of media  26 . Other cartridge or printhead configurations are possible. A movable carriage  14  may include a holder for cartridge  12 , a guide along which the holder moves, a drive motor, and a belt and pulley system that moves the holder along the guide. Media transport  16  advances print media  26  lengthwise past cartridge  12  and printhead  24 . For a stationary cartridge  12 , media transport  16  may advance media  26  continuously past printhead  12 . For a scanning cartridge  12 , media transport  16  may advance media  26  incrementally past printhead  24 , stopping as each swath is printed and then advancing media  26  for printing the next swath. Controller  20  may communicate with external devices through input/output device  18 , including receiving print jobs from a computer or other host device. Controller  20  controls the movement of carriage  14  and media transport  16 . By coordinating the relative position of cartridge  12  and printhead  24  with media  26  and the ejection of ink drops, controller  20  produces the desired image on media  26 . 
       FIGS. 2 and 3  are perspective views illustrating one embodiment of an inkjet printer  10  with a folding media output tray  28 . Output tray  28  is folded in to the closed position in  FIG. 2  and folded out to the open position in  FIG. 3 . Referring to  FIGS. 2 and 3 , in addition to output tray  28 , printer  10  includes an external housing  30 , a folding input tray  32 , and a user control panel  34 . A print engine (not shown) and controller (not shown) for printer  10  are housed in housing  30 . A print engine for printer  10  may include, for example, a set of print cartridges  12  and a carriage  14  from  FIG. 1 . A media path  36  extends from input tray  32  to output tray  28 . The most downstream part of media path  36  is visible in  FIG. 3  where media is discharged to output tray  28  at the urging of rollers  38  mounted along a shaft  40 . 
     Also visible in  FIG. 3  is part of an output roller shaft restraint  42  used for detecting when the output tray  28  is in the closed position. Restraint  42  is shown in detail in  FIGS. 4-8 . Referring now to  FIGS. 4-8 , restraint  42  includes an elongated member  44  pinned to output tray  28  at a near end  46  and gear teeth  48  formed at a far end  50  to engage a gear  52  on roller shaft  40 . In the embodiment shown, teeth  48  are formed on a short pivot arm  54  projecting from far end  50 . Far end  50  is connected to and rotates on a stationary pin  56  ( FIGS. 7 and 8 ). Pin  56  is affixed to or integral with housing  30  or another suitable support within printer  10 . 
     When output tray  28  is open, as shown in  FIGS. 4, 5 and 7 , restraint teeth  48  are disengaged from roller shaft gear  52 . When output tray  28  is closed, as shown in  FIGS. 6 and 8 , teeth  48  engage gear  52  to restrain rotation of roller shaft  40 . As best seen by comparing  FIGS. 7 and 8 , closing output tray  28  lifts near end  46  of member  44  so that member far end  50  rotates on pin  56  to pivot restraint teeth  48  into engagement with roller shaft gear  52 . Thus, output tray  28  functions as the actuator for restraint  42  to engage and disengage gear  52 . The near end  46  of member  44  is allowed to pivot on pins  58  in a tray mount  60  as output tray  28  is opened and closed. 
     Referring now to the block diagram of  FIG. 9 , a motor  62  drives roller shaft  40  at the direction of controller  20 . A detector  64  detects the electrical power drawn by motor  62 . When roller shaft  40  is restrained by restraint  42  as described above, motor  62  will draw more power trying to drive shaft  40 . The increased power draw is detected by detector  64  so that controller  20  can alert the user that output tray  28  is closed. Detector  64  may implemented, for example, as part of the servo control firmware (programming) along with circuitry, typically in the motor control ASIC, that measures or senses the power drawn by motor  62 . (And, thus, detector  64  may be considered part of controller  20  even though it is shown as a separate block in  FIG. 9 .) A motor overload limit is set in the servo control firmware to prevent excessive power draw by motor  62 . When the power drawn by motor  62  reaches the overload limit, controller  20  shuts down motor  62  to prevent damage to the printer. This shut-down is commonly referred to as motor stall. The general printer firmware determines whether or not the motor stall was caused by a closed output tray  28  based on information about the stalling event (i.e. a so-called stall signature), knowledge of what printer function was being performed or attempted at the time of the stall, and feedback from the media sensor(s). If the motor stall occurred abruptly (e.g., minimal rotation of shaft  40  and a rapid rise in power draw), there was no media in the media path, and the printer function being attempted required a check to be sure output tray  28  was open, then controller  20  determines that restraint  42  is engaged and output tray  28  is closed. 
     In one example, controller  20  checks during the initial processing of a print job to determine if output tray  28  is closed. Upon receipt of a print job and prior to attempting to feed media from input tray  32 , motor  62  is driven forward to rotate output roller shaft  40 . If, during this forward move, restraint  42  is engaged and motor  62  is therefore unable to rotate shaft  40 , detector  64  will detect that motor  62  is overloaded and controller  20  may determine that output tray  28  is closed—if the printer was initially in an error free, idle state and a pick move has not been initiated, then controller  20  may correctly determine that output tray  28  is closed. A determination that output tray  28  is closed may trigger an alert or message to the user that output tray  28  must be opened prior to continuing the print job. The user may be alerted to the problem through the printer&#39;s control panel  34  ( FIGS. 2 and 3 ) and/or through a message sent to a host device. The check for a closed output tray may be repeated at discreet timing intervals after a print job is initiated until there is no longer a determination that output tray  28  is closed. 
       FIG. 10  is a flow chart illustrating one embodiment of a method for detecting a closed printer output tray. Referring to  FIG. 10 , as indicated at block  100 , a printer motor (e.g., motor  62  in  FIG. 9 ) is overloaded in response to the media output tray being in the closed position (e.g., output tray  28  in  FIG. 2 ). As described above, attempting to rotate output roller shaft  40  with restraint  42  engaged will overload motor  62 . Thus, in this example, attempting to rotate shaft  40  when output tray  28  is in the closed position overloads motor  62  in response to output tray  28  being in the closed position, in which restraint  42  restrains the rotation of shaft  40 . Then, a motor overload is detected at block  102 . At block  104 , when a motor overload is detected, an indication is given at the printer and/or at a device communicating with the printer that the media tray is closed. For example, a visual and/or audio alert is given at the printer and/or a message sent to the host device. 
     The embodiments of a media drive restraint and method for automatically detecting a closed media tray described above provide a simple, low cost solution to the problem of running a print job with a closed output tray. Base part  60  supporting member pins  58  on the near end  46  of member  44  may be molded into a plastic output tray  28 . Similarly, stationary pin  56  supporting the far end  50  of member  44  may be molded into housing  30 . The same gear used to drive roller shaft  40  may be used for gear  52 . Thus, restraint  42  may be implemented with the addition of a single new part, member  44 , and the method implemented with a comparatively simple modification to the printer firmware (i.e., the programming for controller  20 ). 
     As noted at the beginning of this Description, the exemplary embodiments shown in the figures and described above illustrate but do not limit the disclosure. Other forms, details, and embodiments may be made and implemented. Therefore, the foregoing description should not be construed to limit the scope of the disclosure, which is defined in the following claims.