Patent Application
20070170639
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1. Field of the Invention
The present invention relates generally to media handling system such as those found in printers, and more particularly to a media pulse-pick system.
2. Background
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.
The present invention provides a method for a media pick system.
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's de-skew and/or top-of-form move.
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.
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.
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.
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's de-skew and/or top-of-form move.
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's de-skew and/or top-of-form move.
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.
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.
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.
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.
The invention can be implemented to realize one or more of the following advantages:
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;
pulse-pick repeats application of a proper balance of shear and normal forces on micro-porous photo media;
pulse-pick is a low cost solution to pick system stalling because it does not require any hardware change; and
a smaller radius C-shaped feed path may be used, reducing the overall height of the printer.
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:
Like reference numbers and designations in the various drawings indicate like elements.
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.
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.
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.
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.
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).
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.
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.
As shown in
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.
As shown in
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's de-skew and top-of-form move.
As shown in
A generalized flow diagram 300 of the processes is illustrated in
Shown in
In
A process for deskewing the media (block 318) after it has reached the feed roll assembly is illustrated in
As shown in
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.
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.
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.
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.
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.
