Abstract:
A media pick method includes receiving an initiation signal, causing a media pick system to complete a series of wait, forward move and reverse move pick actions, and causing the media pick system to complete the last of the series of forward move pick actions in conjunction with a feed roll motor&#39;s de-skew move. Reversing a direction of a pick motor enables a gear train to reset and allow momentum to build before engaging the paper on a second forward pick try. Repeats of pick pulses applies a proper balance of shear and normal forces on media.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     None.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     None.  
       REFERENCE TO SEQUENTIAL LISTING, ETC.  
       [0003]     None.  
       BACKGROUND  
       [0004]     1. Field of the Invention  
         [0005]     The present invention relates generally to media handling system such as those found in printers, and more particularly to a media pulse-pick system.  
         [0006]     2. Background  
         [0007]     Printers include inkjet printers having a tray containing sheets of media and having a mechanism for picking the top or bottom media sheet from the tray and feeding that sheet into the printing region of the printer. Some conventional inkjet printers have a pick system and a separate feed system and include a pick roller and a separate feed roll assembly as well as a media sensor and an end-of-form sensor or flag. The pick roller picks the top media sheet from the media tray and moves it forward along a paper path toward the feed roll assembly. The sheet moves the flag just prior to entering, or as it enters, the nip of the feed roll assembly. Thereafter, the feed roll assembly moves the top edge of the media sheet backward along the paper path out of the grasp of the nip (while the pick roller maintains the trailing edge of the sheet in a fixed position) which buckles the sheet and aligns the top edge squarely to correct for skew. Then, the feed roller rotates forward drawing the leading edge of the sheet in square, and the pick roller releases pressure on the sheet. Other conventional inkjet printers omit the de-skew operation. This operation can occur in printer having a C-shaped media feed path as well as in printers with an L-shaped media feed path. With a C-shaped media feed path, it is known that use of a large radius C-shaped path lessens the possibility of the media stalling. However, this increases the overall height of the printer.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a method for a media pick system.  
         [0009]     In general, in one aspect, the invention features a media pick method including receiving an initiation signal, causing a media pick system to complete a series of wait, forward move and reverse move pick actions, and causing the media pick system to complete the last forward move pick action in conjunction with a feed roll motor&#39;s de-skew and/or top-of-form move.  
         [0010]     In embodiments, the initiation signal is one of a group consisting of a print signal, a tripped End of Form (EOF) sensor signal, a stalled pick system signal, the combination of a tripped End of Form (EOF) sensor signal and a stalled pick system signal and a signal indicating a distance traveled by a pick motor after an EOF sensor is tripped is not sufficient to reach a feed roll.  
         [0011]     In one aspect the method further comprises determining the type of media being picked; and varying, based on the type of media determined, at least one of an amplitude and a duration of at least one of the forward move pick action and reverse move pick action. The amplitude of the forward pick move action can greater than the amplitude of the reverse pick move action, for example the amplitude of the forward pick move action is at least twice the amplitude of the reverse pick move action.  
         [0012]     The series of wait, forward move and reverse move pick actions can include ten cycles of move backwards, wait, move forwards, and wait. A frequency of wait, move forward and move backward pick actions can be tuned for specific types of printers or media type.  
         [0013]     In another aspect, the invention features a printer pulse-pick method including receiving an initiation signal, causing a printer pick system to complete a series of wait and forward move pick actions, and causing the printer pick system to complete a forward move pick action in conjunction with a feed roll motor&#39;s de-skew and/or top-of-form move.  
         [0014]     In another aspect, the invention features a printer pulse-pick method including receiving an initiation signal, causing a printer pick system to complete a series of wait, forward move and reverse move pick actions until receipt of a termination signal, causing the printer pick system to complete a forward pick action in conjunction with a feed roll motor&#39;s de-skew and/or top-of-form move.  
         [0015]     In embodiments, the initiation signal can be a print signal, a stalled pick system signal, a tripped End-of-Form (EOF) sensor signal followed by a stalled pick system signal, and/or a media type signal.  
         [0016]     The series of wait, move forward and move backward pick actions can include at least ten cycles of move backwards, wait, move forwards, and wait. A frequency of wait, move forward and move backward pick actions can be tuned for specific types of printers or media type.  
         [0017]     The termination signal can be a successful pick signal, a signal detecting a change in pick motor voltage and/or a signal indicating a change at an index encoder.  
         [0018]     In embodiments the method further comprises determining the type of media being picked; and varying, based on the type of media determined, at least one of an amplitude and a duration of at least one of the forward move pick action and reverse move pick action.  
         [0019]     The invention can be implemented to realize one or more of the following advantages:  
         [0020]     reversing a direction of a pick motor enables a gear train to reset and allow momentum to build before engaging the paper on a second pick try;  
         [0021]     pulse-pick repeats application of a proper balance of shear and normal forces on micro-porous photo media;  
         [0022]     pulse-pick is a low cost solution to pick system stalling because it does not require any hardware change; and  
         [0023]     a smaller radius C-shaped feed path may be used, reducing the overall height of the printer. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]     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:  
         [0025]      FIG. 1  is a cross-section of an exemplary printer;  
         [0026]      FIG. 2  is a diagram of a pick system;  
         [0027]      FIG. 3  is a flow diagram of a pick-pulse process;  
         [0028]      FIGS. 3A, 3B ,  3 C and  3 D are alternative embodiments of processes illustrated in  FIG. 3 ; and  
         [0029]      FIG. 4  is a timing diagram of the inventive method. 
     
    
       [0030]     Like reference numbers and designations in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0031]     It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings.  
         [0032]     In addition, it should be understood that embodiments of the invention include both hardware and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software-based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.  
         [0033]     Blocks of the flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the flowchart illustrations, and combinations of blocks in the flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions. The inventions may be implemented through an application program running on an operating system of the printer.  
         [0034]     Embodiments of the invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Embodiments of the invention can be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine readable storage device or in a propagated signal, for execution by, or to control the operation of, data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. A computer program can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.  
         [0035]     Method steps of embodiments of the invention can be performed by one or more programmable processors executing a computer program to perform functions of the invention by operating on input data and generating output. Method steps can also be performed by, and apparatus of the invention can be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).  
         [0036]     Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in special purpose logic circuitry.  
         [0037]     The term printer as used herein includes both inkjet and electrophotographic or laser printers and copiers. It also includes devices, such as multifunction machines, that include a printer or print engine.  
         [0038]     As shown in  FIG. 1 , a cross-section of an exemplary printer  10  includes a media tray  12  and an ink cartridge  14  in fluid communication with a printhead  15 . A pick roll  16 , driven by a pick motor not shown, engages a sheet  18  of media in the media tray  12  and pushes the sheet  18  through a “C-shaped” path  20  and into a feed nip  23  defined between two opposed feed rollers  24 ,  25  comprising a feed roll assembly  26 . As the sheet  18  is being conveyed to the feed roll assembly  26 , its leading edge trips an End of Form (EOF) sensor or flag  21  that is shown in the tripped position (dashed line  22  indicates the untripped position). The feed roll assembly  26  which is driven by a motor not shown, then delivers the media sheet  18  in a print zone  27  beneath the printhead  15  and then into a nip  28  defined by a pair of opposed exit rollers  29 ,  30  comprising an exit roll assembly  31 . Exit roller  30  is comprised of one or more star-wheels  32  as is known in the art. Media sensor  33  is positioned in the feed path  20  and is used to determine the type of media being feed. The feed roll assembly  26 , the exit roll assembly  31 , printhead  15 , EOF flag  21 , the pick roll  16  that is part of the pick system  40  (see  FIG. 2 ), and the media sensor  33  are monitored by and under the control of controller  35 . Controller  35  may be comprised of a digital processor, ASICs, memory, both RAM and ROM, firmware and software which act cooperatively to control operation of the printer  10 .  
         [0039]     A common error that can occur with printers using the “C-shaped” path  20  is that some heavy weight media types and micro-porous photo media are difficult to pick without stalling the pick roll  16  before the media  18  arrives at the feed roll assembly  26  because of excessive load. One reason for stalling is that friction significantly increases as the media (e.g., papers heat) travels up the C-shaped paper path  20  due to bending of the media and constrictions in the path  20 . Another reason for stalling is that micro-porous photo media exhibits substantial friction between sheets in the paper tray  12 . Thus, as the micro-porous photo media is picked around the C-shaped paper path  20 , a pick motor driving the pick roll  16  compensates for the increased friction in the C-shaped paper path  20  by pushing harder. Pushing harder increases a normal force exerted by the pick roll  16  onto the paper  18 , making the friction between sheets increase as well. Pick motor compensation continues until the friction between sheets prevents the paper  18  from moving any further and causing a pick motor to stall. In general, with printers having a C-shaped paper path, such as printer  10 , a pick motor stall occurs just after an End of Form (EOF) is detected by an EOF sensor. Typically, media types stall before hitting the EOF sensor because the EOF sensor is usually positioned a significant distance from the feed roll assembly  26 .  
         [0040]     As shown in  FIG. 2 , a pick system  40  includes the pick roll  16  linked via shaft  41  to a pick gear train  42  that is driven by pick motor  44 . Pick system  40  compensates for varying media types that can lead to a pick motor  44  stall by pulsing to successfully pick media  18  and fed it to the feed roll assembly  26  that otherwise would have not made it. The pick system  40  uses a pulse-pick method  100 , that overcomes the problem of the pick motor  44  stalling, before pushing certain heavy media or micro-porous photo media all the way to the feed roll  22 . A pulse-pick motion of rapidly driving the pick roll  16  back and forth has the effect of a jackhammer on heavy media, which is a repeating sequence of building up momentum, reaching peak power, detecting stall, stopping the move, and then slightly unwinding the gear train  42 . This results in a rapid combination of pushes that move the media  18  past high friction areas that no reasonable amount of static torque can achieve. For micro-porous media, during a pick move, there is an optimal range of time while the pick roll  16  engages the media in which the shear force of the pick roll  16  is moving the media  18  and the normal force of the pick roll  16  is not large enough to cause significant friction between sheets. However, as the pick roll  16  continues to move, the normal force increases to the point of causing the friction between sheets to hinder any further media movement. What pulse-pick method  100  does for micro-porous media is to repeat this optimal range of time using several back and forth moves until the media reaches the feed roll assembly  26 .  
         [0041]     Process  100  is initiated, in one example, upon the occurrence of one or more of the following: a print signal; the EOF sensor is tripped; the pick system  40  stalls; or the distance traveled by the pick motor  44  after the EOF sensor is tripped is not sufficient to reach the feed roll assembly  26 . In other examples, specific conditions for launching process  100  can change for different printers. In the present example, if one of these conditions is met, process  100  causes the pick motor  44  to complete a series of wait, move forward and/or move backward actions; this series can be tuned to accommodate a particular printer and/or media type. In one particular example, process  100  causes the pick motor  44  to execute ten cycles of the following sequence: move backwards, wait, move forwards, and wait. The frequency of pulses, pause between pulses, and length of moves can be tuned for specific types of printers or media type. The waits are employed because printer  10  typically includes only a single-channel positioning encoder (no direction feedback), and waiting for 10-20 milliseconds, for example, ensures that the pick motor  44  is finished moving. This allows the single-channel encoder to settle and minimize loss of pick position. The waits are not necessary for a two-channel encoder. After ten cycles of moving back and forth, a final forward move is completed, which is tied with the feed motor&#39;s de-skew and top-of-form move.  
         [0042]     As shown in  FIG. 3 , process  100  includes receiving ( 102 ) an initiation signal. Process  100  causes ( 104 ) the pick motor to complete a series of wait, move forward and move backward actions. Process  100  causes the pick motor to complete a final forward move which is tied with the feed roll motor&#39;s de-skew and top-of-form move.  
         [0043]     A generalized flow diagram  300  of the processes is illustrated in  FIG. 3 . Connections points A, B C, D and E, and their respective identifying numerals  304 ,  308 ,  312 ,  316 , and  320  are provided to show where the alternative processes provided in  FIGS. 3A-3D  may be inserted into the general flow diagram  300 . The process beings at block  302  proceeding through connection point A,  304  to the action of initiating media feeding (block  306 ). Next it is determined if a stall has been detected (block  307 ). The stall detection signal can represent, for example, a print signal, a tripped EOF sensor, a stalled pick system causing a increase in pick motor current above a predetermined limit, and/or notification that a distance traveled by the pick motor after the EOF sensor is tripped is not sufficient to reach the feed roll assembly. If no stall has been detected, the process jumps to connection point D,  316 . If yes, the process continues through connection point B,  308  and the pick pulse signal is used to cycle the pick system  40  a predetermined number of times (block  310 ). We have found that five combinations of a reverse pick pulse signal followed by a forward pick pulse signal can be used. Other combinations may also be used. The process continues through connection point C,  312  and determines if the last of the pick pulse signal cycles is to be performed (block  314 ). If no, the process returns back to execute the next pick pulse cycle (at block  310 ). If yes, the process continues to connection point D,  316  and the media is then deskewed (block  318 ). The process proceeds through connection point E and the pick motor moves the media forward into the feed roll assembly  26  at block  322  and a top of form move can also then be executed by the feed roll assembly. The printing process then continues(block  324 ) ending at block  326 .  
         [0044]     Shown in  FIGS. 3A and 3B  are two alternate embodiments of performing the process between connections points A,  304  and B,  308 . In  FIG. 3A , the pick system is used to pick a sheet  18  of media from the media tray  12  and feed it into the feed path  20  (block  306 - 1 A) and to the print zone and the media type is detected using media sensor  33  (block  306 - 2 A). One use for the detection of the media type is illustrated with respect to the alternative process shown in  FIG. 3C . It is then determined (block  307 - 1 A) if a stall condition has occurred. If a stall is detected the process continues to connection point B,  308 , if not it goes to connection point D,  316 .  
         [0045]     In  FIG. 3B , the pick system is used to pick a sheet  18  of media from the media tray  12  and feed it into the feed path  20  (block  306 - 1 B) and to the print zone. Optionally, the media type can be detected as the media is being fed to the print zone. It is then determined is a stall condition has occurred (block  307 - 1 B). If yes, it is determined if the EOF sensor has tripped (block  307 - 2 B). If the EOF sensor has not been tripped, the user is informed that the media tray is empty (block  307 - 3 B) by displaying a message on the control panel or providing a visual or audible signal. If the EOF sensor is tripped (block  307 - 2 B), the process continues to connection point B,  308 . At block  307 - 1 B if no stall condition was detected, it is determined if the EOF flag has been tripped (block  307 - 4 B). If at block  307 - 1 B, it is determined that the EOF flag has not been tripped, an error message is logged (block  307 - 5 B). If at block  307 - 1 B, it is determined that the EOF flag has been tripped, the process continues to connection point D,  316 .  
         [0046]      FIG. 3C  illustrates one embodiment of cycling the pick motor system in an attempt to move the stalled media beginning at connection point B,  308 . This embodiment assumes that the media type has been detected as previously described. At block  310 - 1 A, a predetermined cycle count and pick pulse signal forward and reverse amplitudes is chosen based on the detected media type. The amplitudes of the forward and reverse pick pulse signals can be the same or different magnitudes. For example, as illustrated in  FIG. 4 , the amplitude of the forward pick pulse signal is about twice that of the reverse pick pulse signal. Also, the amplitudes of each forward or reverse pick pulse signal can be the same or can be varied with respect to the previously applied forward or reverse, pick pulse signal. If media type is not used for selecting the cycle counts and pick pulse forward and reverse signal amplitudes, default values are used. Depending on media type, a reverse pick pulse signal is sent to the pick system (block  310 - 2 A). This is followed by a predetermined wait time T 1  (block  310 - 3 A). Next a forward pick pulse signal is applied (block  310 - 4 A, followed by a predetermined wait time T 2  (block  310 -SA). Again the wait times T 1  and T 2  can be equal or differ in duration. As illustrated in  FIG. 3C , during a media stall condition, the first part of the first cycle involves using a reverse pick system move followed by a forward pick system move. However, this can be reversed or in some instances only a series of forward pick system moves may be used.  
         [0047]     A process for deskewing the media (block  318 ) after it has reached the feed roll assembly is illustrated in  FIG. 3D . There, after going through connection point D,  318  the last pick pulse forward signal is lengthened in duration (block  318 - 1 A) and the reverse feed roll assembly signal is then sent to the feed roll assembly as the same time (block  318 - 2 A). This overlapping of signals results in the media being moved forward by the pick system toward the feed roll assembly while the reverse motion of the feed roll assembly prevents the media from entering the feed roller assembly nip. These actions result in the top edge of the media aligning with the feed roll assembly nip, deskewing the media that may have occurred during the feeding of the media from the media tray.  
         [0048]     As shown in  FIG. 4 , a timing diagram  500  illustrates a pulse-pick example of the pick motor and feed motor reference directions and velocities versus time for pulsing four times. Forward direction  540  of the motor signals are shown above the ordinate axis  545  while reverse direction  550  is shown below. An initial forward pulse pick signal  530  is sent to the pick system  40  to fed a sheet of media into the feed path  20 . As illustrated signal  530  has a velocity magnitude of about 18 inches per second (ips). At point  501  the media has reached the EOF flag  21  tripping it. At point  502  the media has traveled a short distance and has reached a stall point that has been detected and which serves to initiate the inventive method. At point  503 , an illustrate 5 ips reverse pulse pick is applied followed at point  504  by a pick pulse wait state. This is followed at point  505  with an illustrative 8 ips forward pulse pick followed by at point  506  with a pick pulse wait state. The wait states in the forward and reverse directions at points  504  and  506  can be of the same duration or be of differing durations. The sequence of reverse and forward pick pulses is repeated until the last iteration shown at point  507 . At the last iteration the last forward pick pulse is of longer duration than the previous forward pick pulses  505  for use in deskewing the media.  
         [0049]     Occurring from about the time the initial reverse pick pulse signal  503  is applied to the pick system  40 , a reverse feed signal  520  is sent to the feed motor of the feed roll assembly  26 . This reverse feed signal  520  prevents the media from passing through the feed roll assembly  26  in the event that the media reaches the feed roll assembly  26  prior to the completion of the cycling of pick pulse signals. In addition, the overlapping of final forward pick pulse signal  307  with the reverse feed signal  520  shown at point  521  deskews the media prior to entering into the feed nip  23 .  
         [0050]     During pulse-pick, once the cycling of a predetermined number of forward and reverse pick pulses is completed, the controller  35  assumes that the media is in the nip  23  at the feed roll assembly  26 . Printing continues and a top of form feed move is performed by the feed roll assembly  26  on the media at point  508  moving the media into and through the print zone  27  and then into the exit roll assembly  31 . Other implementations of the inventive method and system might pulse until a successful pick is detected by the use of additional sensing such as another flag, detecting a change in motor voltage, and/or a change at the index encoder.  
         [0051]     In a specific example, for particular printer types, certain thick media types can pick better once the pick roll  16  is already engaged with the media, so there is no advantage with making a reverse pick pulse move. Thus, use of reverse pick pulsing can be determined by media type being used.  
         [0052]     In another particular example, when the C-shaped paper path  20  includes two pick rolls, the paper is typically held in place with the secondary pick roll. In this example, the reversing motion of process  100  is substituted by a lower speed forward motion instead of a reverse move. More specifically, the second pick roll tries to move the paper, and if a stall is detected, the second pick roll switches to a low energy profile to keep the paper held in place before giving the pick roll a sudden thrust to move the paper again.  
         [0053]     The foregoing description of several methods and an embodiment of the invention have been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.