Abstract:
A printing device for use with a peripheral media-handling device defining a peripheral media path with a first sensor therealong including a print engine coupled with the peripheral media-handling device to accommodate conveyance of media therebetween, the print engine defining an engine media path between an inlet and an outlet thereof, and including a second sensor therealong, and a processor configured to calculate a greatest distance collectively along the media paths that media can travel without reaching one of the sensors, the processor being further configured to command substantially simultaneous flushing of the peripheral media-handling device and the print engine to advance media the calculated greatest distance.

Description:
BACKGROUND 
     Printing systems typically include one or more input trays for holding media (e.g., paper) with feed mechanisms for picking off one sheet of media at a time and feeding it downstream, a print engine that receives the media from the trays and prints a desired image on the media, and post-printing media handlers that sort, collate, staple, bind, stack, punch or otherwise handle the printed media. Each of the feed mechanisms, print engine, and post-printing media handlers may include several sets of rollers or belts for advancing the media along a media path, which may have an effective length equivalent to the length of several sheets of media. The printing system typically will maximize the overall print processing speed by moving several sheets of media along the media path at any given time. The sheets are tracked by sensors distributed along the path, but typically the sensors are not spaced so closely as to allow one sheet to trip a sensor at all points along the path—blind locations exist along the path. 
     When a sheet of media is in a blind location between two sensors, one way for the printing system to determine the location of the sheet is to advance the adjacent rollers, belts, or other drive mechanisms, until the sheet is moved to the next sensor. While printing, this occurs in the ordinary course as the drive mechanisms run substantially constantly to advance the media along the media path without concern about whether the sheet is triggering a sensor at any instant of time, other than to set up the next operation in the printing process. 
     However, under several conditions, the drive mechanisms may be initially turned off, and it may be desirable to detect the presence of media within the media path and to flush it out before continuing with printing. These conditions include: after boot-up of the printing system; after an urgent stop of the printing system, typically caused either by a media jam or a user&#39;s opening a sensed door in the printing system; when a device requires a mechanical initialization, i.e., the resetting of its rollers and other mechanics to a home position; and when a device determines that it has a page within its path that needs to be flushed. 
     The print engine is typically part of a printer which may include a built-in media input tray and which may be coupled to an optional media input device for coordinating media delivery from one or more trays of the media input device to print engine. A given printer may be couplable to several different models of media input device, each model having its own unique, configuration for a media path with one or more sensors and feed mechanisms distributed along the media path. The printer may also have a built-in output tray and be couplable to several different models of media output devices, i.e., collators, binders, etc., each model having its own unique configuration for a media path with one or more sensors and feed mechanisms distributed along the media path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a printing device, coupled to a media input device and a media output device, and showing the media path and the sensors and feed mechanisms distributed thereon, in accordance with an example embodiment of the present invention. 
         FIG. 2  is a flowchart showing a method for a printing device, including a print engine configured to be coupled to a peripheral device, to flush media from a media path within the print engine and the peripheral device, in accordance with an example embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIG. 1 , a printing device, such as a printer  10  may be coupled to one or more peripheral media-handling devices, such as a media input device  12  and a media output device  14 . As used herein, media refers to all types of media that can be handled and printed in a printing system, including without limitation, paper of all type, card stock, vellum, transparencies, photographic stock, etc. Printer  10  may include a print engine  16  with a media inlet  18 , a printhead  20 , and a media outlet  22 , and associated rollers  24   a ,  24   b  or other feed mechanisms. Print engine  16  thus defines a path  26  for media from inlet  18  to outlet  22 . 
     Print engine  16  also includes a plurality of sensors  28   a ,  28   b ,  28   c  distributed along media path  26  for detecting media in the path. Three sensors are shown, but a greater or lesser number may be used. The sensors may be of any type for sensing media, such as mechanical vanes or photoelectric detectors. As can be seen in  FIG. 1 , the sensors may be separated by a distance greater than a length of media, e.g., sensor  28   a  and sensor  28   b  within print engine  16  are located on opposite sides of printhead  20 , which typically is about equal in length to the longest sheet of media that can be printed in the print engine. Thus, a blind spot may exist between sensors  28   a  and  28   b , or between others, where media can be detected only by advancing the associated rollers. 
     It may be seen in  FIG. 1 , represented schematically, that sensor  28   a  is located a distance  30  from media inlet  18  along media path  26 . Similarly, sensors  28   a  and  28   b  are separated from one another by a distance  32 , sensors  28   b  and  28   c  by a distance  34 , and sensor  28   c  and media outlet  22  by a distance  36 . Distances  30 ,  36  from the closest adjacent sensor  28   a ,  28   c  to inlet  28  or the outlet  22 , respectively, are typically defined from an outermost point on the inlet or outlet where it will contact or butt against an outermost point on a media input device or a media output device, respectively, and the reasons for this definition will become apparent from the description below. In general, the values for distances  30 ,  32 ,  34 ,  36 , etc. in print engine  16  will be registered in a PROM accessible by a printer processor  38 , or will be reported to printer processor  38  by print engine  16 , or otherwise made known to processor  38 . 
     The print engine  16  is controlled by printer processor  38  which routes print jobs from a computer, server, or other source, and performs processing. Printer processor  38  typically monitors the status of the print engine sensors, either directly or through the print engine, which typically includes its own embedded processor  39  for controlling the print head and the feed mechanisms. 
     Printer processor  38  may be coupled to an embedded processor  40  within media input device  12  and an embedded processor  42  in media output device  14 . Typically the communications between printer processor  38  and processors  40 ,  42  makes use of the JetLink protocol, and alternatively or additionally may make use of any other suitable protocol. 
     Media input device  12  typically includes one or more media trays, such as high-capacity tray  44  with an associated pick roller  46  and feed rollers  48   a ,  48   b  for routing media along a media path  50  that leads to an outlet  52  that may be coupled to inlet  18  of print engine  16 . A plurality of sensors  54   a ,  54   b ,  54   c ,  54   d ,  54   e  may be distributed along media path  50  for sensing media. Five sensors are shown, but a greater or lesser number may be used. 
     The distances between sensors  54 , e.g., distance  56  between sensors  54   d  and  54   e , and a distance  58  from closest adjacent sensor  54   e  to outlet  52  of media input device  12 , typically are registered in a PROM accessed by the embedded processor  40  in the media input device, and thus may be reported to the printer processor  38 . Such distances in the media input device may vary for different models of media input device, all of which models may nonetheless be compatible with printer  10  by virtue of the reporting of the distances to the printer. These distances may also vary dynamically for a given model as various paths are selected from the one or more media trays to the outlet, or possibly to multiple outlets. All such variations can be reported to the printer for proper coordination of media flushing and other operations. 
     Media output device  14  typically includes one or more post-printing media handling devices, such as binder  60  with associated feed rollers  62  for routing media along a media path  64  that leads from an inlet  66  that may be coupled to outlet  22  of print engine  16 . One or more sensors  68  may be distributed along media path  64  for sensing media. One sensor is shown, but a greater or lesser number may be used. 
     A distance  70  from inlet  66  to closest adjacent sensor  68  of media output device  14 , typically is registered in a PROM accessed by the embedded processor  42  in the media output device, and thus may be reported to the printer processor  38 . Typically, in the case where more than one sensor is distributed along media path  64  in the media output device, the distances between sensors is not of concern to printer processor  38 , because it will typically coordinate flushing only up to the point where media is successfully fed into the media output device. However, in situations where the printer processor coordinates flushing through the media output device, e.g., where a second media output device is coupled in series with a first media output device, then processor  42  will know and report to the printer processor the distances between sensors, in a manner similar to that for the media input device. 
     Distance  70  and other distances in the media output device  14  may vary for different models of media output devices, all of which models may nonetheless be compatible with printer  10  by virtue of the reporting of the various distances and other information to the printer. These distances may also vary dynamically for a given model as various paths are selected from the inlet to one or more post-printing processors. All such variations may be reported to the printer for proper coordination of media flushing and other operations. 
     Thus it will be seen that paths  50 ,  26 , and  64  define a total media path from the media input device  12  through the print engine  16  to the media output device  14 . Printer processor  38  may be programmed to calculate a maximum or greatest distance (D 1 max) along the total media path that media can travel before reaching one of the sensors.
 
 D 1max=the greatest of { D sensor(input); ( S out(input)+ S in(engine));  D sensor(engine); ( S out(engine)+ S in(output);  D sensor(output))}
 
where
         Dsensor(input) is the maximum distance media can advance within the media input device without reaching a sensor,   Sout(input) is the distance in the media input device between a device outlet and a sensor closest to the outlet,   Sin(engine) is the distance in the print engine between an engine inlet and a sensor closest to the engine inlet,   Dsensor(engine) is the maximum distance media can travel within the print engine without reaching a sensor,   Sout(engine) is the distance in the print engine between the engine outlet and the sensor closest to the outlet,   Sin(output) is the distance in the media output device between the device inlet and the sensor closest to the inlet, and   Dsensor (output) is the maximum distance media can travel within the output device without reaching a sensor.       

     In certain cases, described herein, other values for the media output device may be defined and used in the above calculation. 
     The coordinated media flushing may be used in a situation where the media path is in an unknown state in terms of the location of media within the path, for example, on boot-up of the printer, or after an urgent stop due to a jam or an opened door. Another such situation occurs when the media input device or the media output device either requests a mechanical initialization to align its rollers at a home position or the device indicates it has a page to flush. 
     In any of these situations and others it is at least possible that a sheet of media is sitting in the media path, but is in a blind location, not triggering any sensor, and in these situations the feed mechanisms are nominally shut off, so the media remains there at risk of jamming on the next print operation. Thus, the printer may perform in these situations a coordinated flushing of the media path. A method for carrying out the coordinated flushing is shown in the flowchart in  FIG. 2 . 
     When it is determined that a coordinated flush operation is in order, printer processor  38  may send to embedded processor&#39;s  40 ,  42  in the media input and output devices and to print engine  16  a signal indicating a request to flush. The request to flush does not start the feed mechanisms in the devices and engines, but instead gives the opportunity for the devices and engines to respond when they are ready to flush. Printer processor  38  may wait until all of the devices and engine have responded that they are ready to flush, and then issues a coordinated flush command, which commences substantially simultaneously a flush operation in the devices and the engines. That is, the rollers and other feed mechanisms in the devices and engines are turned on in the ordinary flow direction to move any media forward in the media path, typically with the exception of the pick rollers in the media input trays that would feed new media into the path. The desired rollers of all of the devices and the engines begin turning substantially simultaneously so as to prevent media jamming that may occur when rollers at one point in the media path begin turning, but rollers that are directly downstream do not, causing the media pushed by the turning rollers to be crushed and jammed into the non-turning rollers. 
     Typically, printer processor  38  will select a flushing speed, e.g., the highest flushing speed that is supported by all of the media input device, the print engine, and the media output device, or a slower speed, so long as all of the devices and engine can handle it. Printer processor typically learns the speeds supported by the devices and engine from the processors embedded in the devices and engine, which may obtain the values from PROMs coupled to the processors. Printer processor  38  then uses D 1 max as calculated above, and determines a T 1 max, which is equal to D 1 max divided by the flushing speed, and the coordinated flush command continues in effect for at least T 1 max, while printer processor  38  monitors the status of the sensors in the total media path, typically by monitoring a set of media-in-path signals, one signal from each of the media input device, the print engine, and the media output device, typically relayed to printer processor  38  by the embedded processors. 
     In the case where no media happened to be in the media path before the coordinated flushing, e.g., on a boot-up after a clean shutdown, or after a jam wherein the user removed all the media from the media path, then the lack of media will be apparent after T 1 max, because none of the sensors will report media in the path throughout T 1 max. 
     In the alternate case, where at least one sheet of media was in the media path before the coordinated flushing, then sometime before or at the expiration of T 1 max the sheet will be moved into one of the sensors, and a media-in-path signal will be reported to printer processor  38 . Once a media-in-path signal is detected during the coordinated flushing, printer processor  38  typically is no longer concerned with T 1 max, but instead monitors the media-in-path signals to determine when they all are again in a no-media status, while flushing continues. When the media-in-path signals return to no-media status, this is considered to indicate that either all of the media has been flushed, or at least the media has been flushed out of the device or engine where it triggered the media-in-path signal. At this point, printer processor  38  can determine if media is traveling from the media input device to the engine or from the engine to the media output device by continuing the flushing for a time of T 2 max, which is calculated as follows:
 
 D 2max=the greater of { S out(input)+ S in(engine);  S out(engine)+ S in(output)}
 
 T 2max= D 2max/flushing speed.
 
     During T 2 max, printer processor  38  continues to flush and continues to check the media-in-path signals. If the media-in-path signals remain in the no-media status during T 2 max, then the flushing is complete. If any media-in-path signal is detected during T 2 max, then the flushing will need to continue until the media-in-path signals all return to no-media status followed by a successive period of flushing for T 2 max with the media-in-path signals remaining in the no-media status. This testing may need to continue for further cycles, depending, e.g., on whether further media output devices are connected downstream of media output device  14 . It will be understood that while the embodiment described herein includes one media input device, one print engine, and one media output device, the system could be scaled to incorporate additional devices and print engines connected in series or in parallel. 
     During coordinated media flushing, any of the peripheral devices or the print engine may detect a media jam, an open door, or another condition that may require an urgent stop. In such cases, the device or engine may report the condition to printer processor  38 , e.g., in an urgent stop request. The printer processor may in turn issue an urgent stop command to the devices and the engine, or to a subset of these as appropriate to halt flushing where necessary to prevent subsequent jams. The urgent stop command will typically stop the flushing when received. For example, if the print engine reports a jam, the printer processor may issue an urgent stop to the print engine and the media input device, while allowing the media output device to continue flushing media to its output. On restart, after an urgent stop, the printer processor may command a coordinated flushing, as described above. 
     After all media is flushed from the total media path, printer processor  38  may command a mechanical initialization of the print engine, the media input device, and the media output device. As described herein, the printer processor  38  generally controls the operation of the printing system by sending instructions and monitoring the signals from the embedded processor&#39;s in the media input device, the print engine, and the media output device, and typically the program for controlling printer processor will be stored in firmware on a PROM or other storage medium in machine-readable instructions. It will be understood that the control might be partitioned differently amongst the processors, and a processor or other controller other than the printer processor may be responsible for general control. 
     An example embodiment of the coordinated flushing is shown in  FIG. 2 , which may include a calculation, shown at  100 , of the maximum or greatest distance (D 1 max) along the total media path that media can travel before reaching one of the sensors or the greatest distance between any two adjacent sensors along the media path, using the formulas described above. A flushing speed, for use in commanding one or more peripheral devices and the engine to flush, may be determined as shown at  102 . Proceeding with the coordinated flushing, a signal indicating a request to flush may be sent to the one or more devices and to the print engine as shown at  104 . Then, as shown in the loop at  106 , further processing of the coordinated flushing may await the device(s) and the engine returning signals indicating they are ready to flush. 
     When all of the device(s) and the engine are believed ready to execute a flush, a substantially simultaneous start of flushing may be commanded in the device(s) and the engine, as shown at  108 . While the flushing is ongoing, the status of the sensors in the media path are monitored for an indication of media in the path as shown at  110 . If media is indicated in the path, then the flushing and monitoring may continue, as shown at  112  and  114 . If media is not indicated in the path, then, flushing and monitoring may continue until the media would have been advanced the greatest distance (as calculated above), as shown at  116 . Once any media would have been advanced the greatest distance without an indication of media in the path, then a substantially simultaneous end of flushing may be commanded, as shown at  118 . After flushing ends, a mechanical initialization of the device(s) and the print engine may be commanded as shown at  120 . 
     From the description it will be seen that the printer may be used with any of a plurality of models of media input devices and any of a plurality of models of media output devices. Each of the models of media input device will typically contain a plurality of sensors and be capable of reporting a maximum distance between adjacent sensors within the device and of reporting a distance between an outlet of the media input device and the closest sensor within the media input device. Each of the models of media output device will typically contain at least one sensor and be capable of reporting a distance between an inlet of the media output device and the closest sensor within the media output device. 
     While the present disclosure has been made with reference to the foregoing preferred embodiments, those skilled in the art will understand that many variations may be made therein without departing from the spirit and scope defined in the following claims. The disclosure should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements.