EP0202140B1 - Durchlauffarbdrucker - Google Patents

Durchlauffarbdrucker Download PDF

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Publication number
EP0202140B1
EP0202140B1 EP19860400773 EP86400773A EP0202140B1 EP 0202140 B1 EP0202140 B1 EP 0202140B1 EP 19860400773 EP19860400773 EP 19860400773 EP 86400773 A EP86400773 A EP 86400773A EP 0202140 B1 EP0202140 B1 EP 0202140B1
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EP
European Patent Office
Prior art keywords
print
media
paper
transport path
station
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EP19860400773
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English (en)
French (fr)
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EP0202140A1 (de
Inventor
Peter Kamas
Douglas Hardy
David Emmett
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Oce Graphics USA Inc
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Benson Inc
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G15/00—Apparatus for electrographic processes using a charge pattern
    • G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
    • G03G15/0142—Structure of complete machines

Definitions

  • This invention relates generally to electrostatic printing, and particularly to electrostatic color printing/plotting using multiple color print stations to produce a full-color image in a single-pass.
  • Electrostatic printing is accomplished by placing electrostatic charges in the form of the image to be printed on an electrographic media, usually paper. The paper is then exposed to a liquid toner to produce a permanent visible image.
  • electrostatic color printing separate images are electrostatically printed on the paper and toner applied, each image typically corresponding to one of four colors: The three colors of yellow, cyan and magenta, and for true black, a fourth color of black.
  • Electrostatic printing paper is drawn between the recording head and styli while individual ones of the styli are selected and impressed with a voltage potential that, together with the back-plane (usually also impressed with a voltage potential) creates a "dot" of charge on the paper.
  • the image for each color may be thought of as comprising lines or "rasters" of these dots which, when toned combine to form the image of that color.
  • the yellow, magenta, cyan, and (if used) black images are separately printed, each registered to be relatively superimposed on one another to form the full-color image.
  • any particular dot location on the paper may have one or more colors printed thereat.
  • Printing the full-color image has been performed by passing the paper through the print station (which usually has a single electrostatic recorder and multiple toner/dryers - one for each separate image) to print the first image, rewinding the paper and passing the paper through again for each subsequent image.
  • the print station which usually has a single electrostatic recorder and multiple toner/dryers - one for each separate image
  • US patent US-A 4 401 024 (FRENTRESS) describes a printing system comprising four print stations positioned along the transport path of the media and a drive system to move the print media along the transport path. To achieve registration control, the position of the print media proximate each station is detected by measuring the distances between previously placed registration marks at each print station and comparing the measured values obtained at the first print station with the measured values obtained at each downstream print station.
  • the present invention provides a printer/plotter apparatus comprising plural print stations arranged along a transport path for single-pass printing of an image on a print media, a drive system to move the print media along the transport path, and means for detecting the position of the print media proximate each print station.
  • the drive system comprises separately controllable entry and exit drive means respectively positioned at input and output locations of each print station for moving the print media; tension monitoring means engageable with the print media for providing a signal indicative of the print media tension as it moves between the entry and exit drive means of each print station; and control means coupled to the entry and exit drive means and to the detecting means and the tension monitoring means for providing drive signals in response to receipt of the signal to maintain media tension within a predetermined range.
  • the drive system further comprises means defining a transport path along which the media travels; means mounted to the transport path for constraining one periphery of the media along a predetermined line of travel of the transport path; said drive means being adapted to impart a first force to the media in the direction of media travel and a second force in a direction generally transverse the direction of media travel and away from the constrained periphery; and means for monitoring the opposing periphery to detect transverse media variations along the transport path.
  • the constrained periphery of the media may be the edge of the media.
  • the media has a plurality of spaced-apart apertures proximate the media edge
  • the constraining means includes a plurality of sprocketed means mounted to the transport path at spaced locations along the line of travel, the sprockets being operable to engage the apertures to constrain said apertures to said line of travel.
  • the printing/plotting procedure can be varied to accommodate data flow from the source (i. e., computer or the like) supplying image data and the complexity of the image being printed by any one print station.
  • the data to be printed could be supplied from a main frame computer, and the data flow may vary.
  • the printing speed can be varied (within limits of the printer itself) to accommodate such data flow variations on a real time basis.
  • the registration system employed by the present invention allows each print station to calculate exactly where any particular point on the paper is located, despite media variations, allowing accurate placement and registration of the separate images printed on the paper. Additionally, constraining one edge of the paper to a specific line of travel, together with applying a small lateral force to the print media, away from the constrained edge, accurately aligns and guides the media along the transport path and through the print stations.
  • each print station with a drive roller that is independently variable, and by monitoring the tension of the media (i.e., paper) within the print station, the tension of the paper across the print head can be accurately controlled.
  • the overall drag imposed by the print station can be kept to a predetermined minimum, thereby allowing a plurality of print stations to be sequentially placed along a transport path for producing single-pass full-color printing/plotting.
  • the printer/plotter 10 includes a pair of side plates 12 and 14, mounted in generally fixed, spaced and parallel relation to one another by appropriate means (not shown).
  • the side plates 12 and 14 generally define, at the upper portion thereof, a transport path 18 along which the media 16 (such as, for example, electrostatic paper) travels from a paper supply roll (not shown), located proximate an entry area 20 of the transport path 18, to a take-up roll 22, located at an exit area 24 of the transport path.
  • the media 16 such as, for example, electrostatic paper
  • a paper supply roll not shown
  • At spaced locations along the transport path 18 are four print stations 30Y, 30M, 30C and 30B, each respectively structured to print an image in the separate colors of yellow, magenta, cyan, and black.
  • a marker station 32 Proximate the entry area 20 of the transport path 18, and mounted to the side plate 14, is a marker station 32, which functions to print registration indicia along one edge of the paper 16 as it enters the transport path 18.
  • the registration indicia comprising a registration line and spaced markers (104 and 102, respectively, Figs. 3 and 3A) are used to track any variations in paper size as the paper moves along the transport path.
  • the print stations 30Y, 30M, 30C and 30B are each equipped to sense any such variations and adjust the print operation to compensate.
  • Each of the print stations 30Y, 30M, 30C and 30B operate independently to electrostatically print their corresponding yellow, magenta, cyan or black images on the paper 16 in registered relation to one another by monitoring the registration indicia.
  • Fig. 1 illustrates the print station 30Y being preceded by an entry drive 36, which functions to pull paper from the paper supply roll (now shown) onto the transport path 18 and through the marker station 32, feeding the paper to the print station 30Y.
  • the print station 30Y includes an exit drive 38 to pull the paper through the print station, and, preceding the exit drive 38 is a back-plane 40, and a tension bar 42.
  • Tension bar 42 is coupled to a detector 44 for determining the depth of the tension bar 42, obtaining thereby an indication of the tension of the paper 16 between the entry and exit drives 36 and 38.
  • the print stations 30Y, 30M, 30C and 30B are identically structured, so that hereinafter only the print station 30Y will be described. It should be understood, therefore, that any description of the print station 30Y will apply equally to the print stations 30M, 30C and 30B - unless otherwise noted.
  • the individual print stations 30Y-30B use an electrostatic print process generally of the type that employs a printer head that extends between the side plates 12 and 14 (and underlies the back-plane bar 40 of Fig. 1) and comprises an elongate array of staggered rows of styli.
  • the print heads, and the electronics to operate the print heads are described in U.S. Patent No. 4,419,679.
  • Fig. 2 illustrates, in greater detail, the marker station 32, the entry drive 36, and the configuration of the print station 30Y.
  • data and command information is supplied from a source of data to the print station 30Y and received by an input controller 48, which functions as an intelligent buffer for the information to be printed.
  • Status information respecting operation of the print station 30Y is generated by a microprocessor 50, and is communicated to the input controller 48 via a command/control data path 52, and made available for transmission to a data source (not shown) by the input controller 48.
  • the data path 52 connects the microprocessor 50 to a memory unit 54, which includes both random access memory (RAM) and read-only memory (ROM).
  • the memory unit 54 contains the necessary programming to operate the microprocessor 50 to effect control over printing operations performed by the print station 30Y.
  • An input/output (I/O) port 56 provides a buffered input/output data path between the print stations 30Y, 30M, 30C and 30B. Status information such as, for example, adjustment of the tension, is transmitted via the I/O port 56 between the various print stations to coordinate paper flow therethrough.
  • a motor controller 58 which, in turn, is connected to micro-stepper motors 60 and 62.
  • the motor controller 58 controls operation of the micro-stepper motors 60 and 62.
  • the motor controller 58 causes the micro-stepper motors 60 and 62 to take the required number of micro-steps (one for each pulse) individually, together at different rates, or together in synchronism.
  • the micro-stepper motor 60 operatively connects to drive roller 66 that, together with a pinch roller 68, form the entry drive 36 (Fig. 1) to grip and pull the paper 16 into the print station 30Y.
  • the drive roller 66 is provided with a knurled surface, and the pinch roller 68 is coated with an elastomeric material, together forming a combination that extends between side plates 12 and 14 (Fig. 1) to grip the paper 16 therebetween to pull the paper into the print station 30Y or hold the paper fixed, as the case may be.
  • micro-stepper motor 62 connects to and powers the exit drive 38, also comprising a knurled drive roller 70 and an elastomeric- coated pinch roller 72.
  • Fig. 3 shows the pinch roller 68 mounted between the side plates 12 and 14 and skewed an angle e relative to the direction of travel (arrow 76) of the paper 16 along the transport path 18.
  • the angle e of skew is approximately 0.072 ° . Since the companion drive roller 66 (which would generally underlie the pinch roller 68, but is not seen in Fig.
  • Fig. 3 also illustrates, the paper 16 is perforated proximate one edge 16a.
  • the print station 30Y is provided with a sprocketed roller 99 (Fig. 2) that is journalled to extend between side plates 12 and 14.
  • the sprockets are located proximate the end journalled to side plate 12 to operatively engage the apertures 92 (Fig. 3) formed in the paper.
  • an identical sprocketed roller 98 (Fig. 2) is located proximate the entry 20 of the transport path 18.
  • the five sprocket rollers (sprocketed roller 98, and the sprocketed rollers 99 in each of the print stations 30Y-30B) cooperatively operate with the apertures 92 to constrain the edge 16a in a line along the transport path 18.
  • This constraint operates with the skewing of the entry and exit drives 36 and 38 to any size variation of the paper 16 to two directions only: One in the direction of travel, and one in a transverse direction. Knowing which way paper size varies allows one to more accurately detect, and compensate for, such variations. The preferred detection and compensation is discussed further hereinafter.
  • the sprocket/paper aperture combination also accurately align and guide the paper along the transport path.
  • the forward and lateral forces imparted to the paper 16 by the drive rollers pull the paper against the sprockets, accurately aligning the paper as it travels through each print station and, in particular, just prior to entering the print head/back-plane 86/40 combination.
  • the microprocessor 50 also communicates via the command/control data path 52 with a write control circuit 80 which, in response to instructions from the microprocessor 50, controls the write operation via print head drivers 82 and back-plane drivers 84.
  • the print head drivers 82 are connected to an electrostatic print head 86.
  • the electrostatic print head 86 is, as indicated above, an elongate array of individual styli (not shown) held by a matrix of epoxy and positioned beneath the back-plane bar 40 (Figs. 1 and 2).
  • the print head drivers 82 and back-plane drivers 84 function to produce, between individual selected ones of the styli (not shown) of the electrostatic print head 86 and the back-plane 40, approximately a 600-volt potential to produce electrostatic charges on the paper 16.
  • a toner station 88 Located downstream of the print head 86 - back-plane 80 combination is a toner station 88. It is here that toner (for print station 30Y - yellow; for print stations 30M, 30C and 30B - magenta, cyan and black, respectively) is applied to the electrostatically charged paper (adhering only to the charged area), dried, and any residual charge neutralized.
  • the toning roller 89 of the print station 88 is driven by the stepper motor 62 to apply the liquid toner to the charged paper.
  • the printing process used by the present invention is known to those skilled in the art, except as to the construction and operation of the electrostatic printing head 86, in which case resort should be had to the above-referenced U.S. Patents 4,419,679 for further information.
  • an optical sensor array 90 Located upstream and proximate the electrostatic print head 86 is an optical sensor array 90, comprising a pair of optical sensors (not shown, but whose locations are indicated in Fig. 3A at 118 and 120 by the dotted circles) that are used to detect and track the registration marks placed on an edge of the paper 16 by the marker station 32 (Figs. 1 and 2).
  • the marker station 32 comprises a small electrostatic registration print station 96 (including toning and drying apparatus) for printing the registration indicia on the paper 16.
  • the registration indicia consisting of registration marks 102 and line 104, is placed proximate the edge 16b - opposite the constrained edge 16a.
  • the registration line and marks 104, 102 are printed on the downward- facing surface of the paper 16.
  • the registration marks 102 define the portion of each line of dots to be printed at each of the print stations 30Y-30B. Between each registration mark 102 - that is from leading edge to leading edge - are 50 raster lines (i.e., lines of dots) across the paper 16, and 800 micro-steps of the micro-stepper motors 60 and 62. The printing of each registration mark 102 is keyed to rotation of the sprocketed roller 98. As the paper 16 travels along the transport path 18, the apertures 92 capture and rotate the sprocketed roller 98. An optical encoder 94 is coupled to the sprocketed roller 98 to produce timing signals indicative of rotation.
  • timing signals are conveyed to the registration print station 96, via the optics control unit 93, to cause a registration mark 102 to be printed on the paper 16.
  • the sprocketed roller 94 sees to it that registration marks are accurately spaced on the paper 16 - independent of paper velocity.
  • the print stations 30Y-30B can rely on the registration marks to determine if any variation in size of the paper, in the direction of travel, has occurred, and act accordingly to compensate for any such variation.
  • the registration line 104 establishes a transverse dimension of the paper 16 as it enters the transport path. Detected variations of the registration line 104 at the print stations 30Y-30B allow the print stations to signal the print process to compensate in a manner discussed further below. It is the function of the optical sensor array 90 to detect these variations, if any. As indicated above, the registration marks 102 so placed on the paper 16 correspond to the start of a print line formed by the print head 86. The markers are read by the optical sensor array 90, and used to accurately position the lines of print data at the print station 30Y and at each print station 30M-30B relative to any preceding print station.
  • micro-stepper motors 60 and 62 are possible (and, correspondingly, separate control of the microstepper motors of print stations 30M, 30C, and 30B, corresponding to micro-stepper motor 62).
  • the micro-stepper motor 60 can be slowed down, relative to the micro-stepper motor 62, to slow down the paper being fed into the print station 30Y.
  • micro-stepper motor 62 operation of the micro-stepper motor 62 is continued or speeded up to cause the exit drive 38 to continue to pull the paper 16 from the print station 30Y but at a faster rate - until the desired paper tension is obtained, at which time both micro-stepper motors 60 and 62 can be synchronously operated.
  • microprocessor 50 places status data on the Internal Status Bus via the I/O port 56 that is communicated to the downstream print stations 30M, 30C, and 30Y. They, in turn, will adjust the speed of their micro-stepper motors 62 to take up the slack.
  • the tension bar 42 performs a variety of addition functions: First, it operates the maintain a paper path of predetermined length between the upstream entry drive 36 and the downstream exit drive 30; second, it operates to straighten the paper as it is fed from the upstream entry drive 36 into the print station 30Y (the skewed rollers tend to cause the paper to buckle or wrinkle somewhat); third, it operates to ensure that the constrained edge 16a properly engages the sprocketed roller 99 to align the paper just before it is pulled across the electrostatic print head 86; and fourth, the vertical position of the bias bar can vary to compensate for disparities between the micro-stepper motors 60 and 62.
  • tension bar 42 While indeed it is tension that the tension bar 42 monitors, it may be more accurate to say that what really is being monitored is the force exerted on the print head 86. If this paper path shortens, it is an indication that the paper is tightening, imposing higher forces on the print head 86 and possibly causing a deterioration in print/plot quality.
  • the vertical position of the tension bar 42 is monitored by a shuttered optical detector 44 to which the tension bar 42 is connected. Two signals are produced by the optical detector 44: A HI signal that indicates when the tension bar 42 has been moved by a shortening of the paper path to its vertically upward extreme; and a LO signal to indicate that an extension of the paper path has released the tension bar 42 to its extreme low position. Absence of both the HI and LO signals indicate the tension bar 42 is in a median range and that the paper path is within an acceptable range.
  • the shuttered optical detector 44 used to monitor the position of the tension bar 42, is illustrated in greater detail in Fig. 4.
  • the ' detector 44 includes a planar shutter 106 mounted in the detector 44 in a vertical orientation.
  • the shutter 106, so mounted, is capable of vertical movement with the tension bar 42 which is biased downward by, for example, a spring 106 that exerts approximately a two-pound force thereon at the end connected to the shutter 106.
  • An equal bias force is applied to the opposite end of the tension bar 42 in order to exert an equal force against the paper 16 along the length of the tension bar.
  • the shutter 106 is apertured at 110 to, depending upon the relative vertical position of the shutter 106 and the aperture 110, allow light communication between one or the other light sources 112a, 112b and their corresponding optical sensors 114a, 114b, respectively.
  • Optical communication between the light source/optical sensors 112a/114a and 112b/114b produces the HI and LO signals, respectively; no communication, no signals.
  • the HI and LO signals therefore, provide indicia of the lengthening or shortening of the paper path, in the form of paper tension, so that the microprocessor 50, via the motor controller 58, can independently control the micro-stepper motors 60 and 62, and with them the drive rollers 66 and 70, to maintain the desired paper path length.
  • This is accomplished in the following manner: Assume, at the outset, that the paper 16 has just been installed in the print station 30Y (as well as the following print stations 30M, 30C and 30B). At the initiation of operation, the paper will have very little tension, indicating that the path of the paper 16 in print station 30Y is too long for proper print operation.
  • the tension bar 42 therefore, will be allowed by the paper 16 to drop to its lower extreme, positioning the aperture 110 of the shutter 106 (Fig. 4) so that optical communication is established between the light source 112b and its corresponding optical sensor 114b.
  • the LO signal becomes active, indicating to the microprocessor 50, via the optics control unit 92 and command/control data path 52, that little or no tension is present on the paper 16 and that the paper path must be shortened. Accordingly, the microprocessor 50 will issue commands (i.e., a micro- step count) to the motor controller 58 to begin operation of the micro-stepper motor 62 while, at the same time, holding the micro-stepper motor 60 fixed.
  • micro-stepper motor 62 The number of micro-steps that a micro-stepper motor must take to move the tension bar from its low limit to its high limit is known; in the preferred embodiment this number is approximately 6,000 micro-steps. Accordingly, the microprocessor program knows that from the point the LO signal terminates there will be approximately 3,000 micro-steps required by the micro-stepper motor 62 to position the tension bar 42 midway its limits.
  • the microprocessor 50 will issue commands (counts) to the motor controller 58 to cause the micro-stepper motor 62 to set through approximately 3,000 micro-steps while holding the micro-stepper motor 60 inactive.
  • the drive roller 70 With the paper held fixed between the drive rollers 66 and pinch roller 68, the drive roller 70 begins pulling the paper 16 to shorten the paper path in the print station 30Y and thereby increase paper tension, moving the tension bar 42 until the micro-stepper motor 62 makes its approximately 3,000 steps.
  • This paper-tightening operation also takes place in the remaining print stations 30M, 30C and 30B so that, when complete, the path of the paper 16 in each print station is the desired length and the paper properly tensioned.
  • the tightening operation is somewhat different - only because the print stations 30M, 30C, and 30B directly control only one micro-stepper motor - the one corresponding the micro-stepper motor 62 of the print stations exit drive 38.
  • Print station 30Y is the only one having direct microprocessor control over two micro-stepper motors; control over what would correspond to the micro-stepper motor 60 for print stations 30M, 30C, and 30B is exercised by the microprocessor immediately preceding the print station.
  • paper tightening in the downstream print station 30M will be identical to that described above, except that the microprocessor 50 of print station 30Y will control its micro-stepper 62 at the exit station 38 to hold the paper 16 fixed while the corresponding microprocessor 50 of print station 30M will control its corresponding micro-stepper motor 62 to shorten the paper path therein.
  • the entry drive 36 for print stations 30M, 30C, and 30B are also the exit drives 38 of print stations 30Y, 30M, and 30C, respectively.
  • This requires communication between the respective microprocessors 50 of the print stations 30Y and 30M so that their efforts are synchronized as described.
  • This communication is made between the microprocessors 50 via the I/O ports 56 (of each print station 30Y and 30M) and the Internal Status Bus.
  • This paper tightening procedure is substantially identical for print stations 30C and 30B, except that it should be evident that all upstream print stations are involved in the paper-tightening operation of any particular downstream print station.
  • the HI and LO signals from the optical detector 44 also allow the microprocessor 50 to readjust tension at any of the print stations 30Y-30B, independent of the others, during print operations. For example, assume that the paper is moving at a constant speed through the print station and that, for whatever reason, the paper path at the print station 30Y (Fig. 2) has decreased. This decrease, or shortening, of the paper path causes the tension bar 42 to be moved upward against the bias spring 108 (Fig. 4). Ultimately, the paper path will shorten, moving tension bar 42 so that the aperture 110 in the shutter 106 of the optical detector 44 is positioned to allow light communication between the light source 112a and the optical sensor 114a.
  • the HI signal is active, and communicated to the microprocessor via the optics control unit 93 and the command/control data path 52.
  • This will cause the microprocessor 50 to issue commands to the motor controller 58 to (1) slow down operation of the micro- stepper motor 62 while (2) continuing operation of the micro-stepper motor 60 at a slightly higher rate.
  • the micro-stepper motor 62 will operate at a slightly lower rate of micro-steps per second than before; the micro-stepper motor 60 will, at the same time, operate at a slightly higher rate of micro-steps than before; and, since the paper 16 is being fed into the print station 30Y at a faster rate than it leaves, the paper path lengthens in a smooth, continuous fashion.
  • the microprocessor 50 keeps a running accumulation of the excess micro-steps taken by the micro-stepper motor 60 relative to the micro-stepper motor 62. When this excess totals approximately 3000, the microprocessor 50 will terminate running the micro- stepper motors 60 and 62, and begin operating them at the same rate, thereby terminating this paper path lengthening procedure.
  • the procedure is somewhat different for downstream print stations 30M, 30C, and 30B.
  • all upstream print stations 30Y, 30M, and 30C must increase their respective paper transport rates while the microprocessor 50 of the print station 30B slows its micro-stepper motor 62.
  • Coordination of this procedure is established between the respective microprocessors 50 of the print stations 30Y-30B by communication of status information (i.e., micro-stepper motor rates) on the Internal Status Bus.
  • the actual size of the paper can change - primarily due to humidity differences to which the paper was subjected when rolled and unrolled. Changes in the direction of travel are measured by detecting the timing marks 102 at each of the print stations 30Y-30B by the optical sensor group 90.
  • the optical sensor group as indicated in Fig. 3A comprises two independent sensors (indicated, in Fig. 3A in dotted line) 118 and 120.
  • the sensor 118 monitors the registration marks 102, providing a signal every 50 raster lines (i.e., lines of printed dots) at the detection of each mark to the microprocessor 50 via the optical control unit 93 and command/control data path 52.
  • the microprocessor 50 then functions to register the write operation with the registration mark. If, due to variations in paper length along the direction of travel, the registration mark has not yet appeared, or alternatively has appeared earlier than the 16 micro-steps allotted between raster lines, the microprocessor 50 coordinates the write operation accordingly, and resets the motor controller 58. In this manner, the lines of (yellow) image printed by the print station 30Y can be registered accurately, relative to the registration marks 102, so that a printed yellow "dot" can be superimposed (either in overlapping or side- by-side relation) with a magenta dot at print station 30M, a cyan dot at print station 30C, a black dot at print station 30B, or any combination thereof, to produce the desired color.
  • the registration is checked by each print station 30Y-30B every 50 raster lines and brought back into exact registration if necessary.
  • any change will be detected by the optical sensor 120 which produces an analog voltage varied by the black strip relative to the white background of the paper that is communicated to the optics control unit 92. There, the analog voltage is converted to digital information via a conventional analog-to-digital converter (not shown) that is conveyed to the microprocessor 50 on the command/control data path 52.
  • Paper can stretch, in the lateral direction, as much as 3-5 dot positions (each "dot" being approximately 1/254 of an inch).
  • the print station 30M for placing the magenta dot must know the X, Y location of that yellow dot. This information is provided both by the registration marks 102 and the registration line 104.
  • Registration marks 102 when counted by the microprocessor 50, determine exactly which line contains the yellow dot of our example, and the signal produced by the optical sensor 120 provides information as to whether that dot position has shifted away from the edge 16a (Fig. 3) of the paper that has been constrained.
  • the microprocessor 50 can act on the dot information applied to the print head drivers 82 accordingly, adding or subtracting dots to superimpose the proper magenta dot printed by the print station 30M over the yellow dot previously printed by the print station 30Y.
  • This latter aspect is achieved, in part, by ensuring that lateral changes in the print media (i.e., paper) are in a single direction, and by using registration marks that determine, relative to the paper, the placement of each print line and each dot in that print line, thereby allowing microprocessor compensation "on the fly” for media variations; and (3) guide and monitor the exact position of the media (e.g., print paper) with sprocketed rollers and apertured media together with transport drive apparatus, including the tension bars 42, to accurately locate the media to the sprockets.
  • These features combine to provide a printer/plotter that generates, in a single pass, a full color image from a number of individual, superimposed, accurately registered monochrome images each printed by separate print stations - independent of velocity.
  • each individual print station 30Y, 30M, 30C and 30B are provided with a separate microprocessor.
  • Other embodiments may incorporate the teachings of the present invention using a single microprocessor to control all four print stations, thereby obviating much of the data communications therebetween via the internal status bus 56. Therefore, the above description should not be taken as limiting the present invention, the scope of which is defined by the appended claims.

Claims (11)

1. Druck/Zeichen-Einrichtung mit mehreren Druckstationen (30Y, 30M, 30C, 30B), die längs einer Transportbahn (18) angeordnet sind zum Durchlauf-Drucken eines Bildes auf ein Druckmedium (16), einem Antriebssystem zum Bewegen des Druckmediums längs der Transportbahn und Mitteln (93) zum Abtasten der Position des Druckmediums in der Nähe jeder Druckstation, dadurch gekennzeichnet, daß das Antriebssystem aufweist:
getrennt steuerbare Eingangs- (36, 60) und Ausgangs- (38, 62) Antriebsmittel, die an den Eingangs- bzw. Ausgangsstellen jeder Druckstation angeordnet sind, um das Druckmedium (16) zu bewegen,
Spannungsüberwachungsmittel (42, 44) die mit dem Druckmedium (16) in Berührung gebracht werden können, um ein Signal zu liefern, das die Spannung des Druckmediums bei der Bewegung zwischen den Eingangs- und Ausgangs-Antriebsmitteln (36, 60, 38, 62) jeder Druckstation angibt, und
Steuermitteln (58), die mit den Eingangs- und Ausgangs-Antriebsmitteln und mit den Abtastmitteln sowie den Spannungsüberwachungsmitteln gekoppelt sind, um Treibersignale zu liefern in Abhängigkeit von dem Empfang des Signals, um die Spannung des Druckmediums innerhalb eines vorgegebenen Bereichs zu halten.
2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Eingangs- (36, 60) und die Ausgangs- (38, 62) Antriebsmittel eine langgestreckte Antriebswalze (66, 70) und eine langgestreckte Klemmwalze (68, 72) aufweisen, die parallel zueinander angeordnet sind und das Druckmedium (16) zwischen sich aufnehmen und erfassen.
3. Einrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Eingangs- und Ausgangs-Antriebsmittel jeweils einen Mikroschrittmotor (60, 62) aufweisen, der in Abhängigkeit von den Steuermitteln betreibbar ist.
4. Einrichtung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, daß die Spannungsüberwachungsmittel ein Element (42) und Mittel (108), die das Element (42) beweglich gegen das Druckmedium (16) spannen, wenn dieses sich durch die Druckstation bewegt, sowie mit dem Element (42) gekoppelte Mittel (106) zum Erzeugen des Signals als Funktion der Lageänderungsbewegung des Elements aufweisen.
5. Einrichtung nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß die mehreren Druckstationen eine erste Druckstation (30Y) und eine Anzahl weiterer Druckstationen (30M, 30C, 30B) umfassen, die so angeordnet sind, daß sie das Druckmedium (16) der Reihe nach aufnehmen, wobei jeweils die Ausgangs-Antriebsmittel (38, 62) der unmittelbar vorangehenden Druckstation die Eingangs-Antriebsmittel (36, 60) für die nachfolgende Druckstation bilden.
6. Einrichtung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß das Antriebssystem aufweist:
Mittel (12, 14) die eine Transportbahn (18) definieren, längs derer sich das Druckmedium bewegt,
Mittel (98, 99), die an der Transportbahn montiert sind um einen Rand des Druckmediums (16) längs einer vorgegebenen Bewegungslinie (76) der Transportbahn zu begrenzen, wobei die Antriebsmittel (36, 60, 38, 62) so ausgelegt sind, daß sie eine erste Kraft (78a) in Bewegungsrichtung des Druckmediums und eine zweite Kraft (78b) in einer Richtung im wesentlichen quer zur Bewegungsrichtung des Druckmediums und von dem begrenzten Rand weg auf das Druckmedium ausüben, und
Mitteln (90) zur Überwachung des gegenüberliegenden Randes um Querabweichungen des Druckmediums längs der Transportbahn zu erfassen.
7. Einrichtung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß die Mittel zum Abtasten der Position des Druckmediums (16) aufweisen:
eine Markierungsstation (32) zum Aufdrucken sequentieller Registermarken (102, 104) auf das Druckmedium, um eine vorherbestimmte Positionsbeziehung zwischen den Registermarken auf dem Druckmedium herzustellen, und
in jeder der Druckstationen: Fühlmittel (90) zum Abtasten der Registermarken und Mittel (50) zum Ausrichten des durch die Druckstation gedruckten Bildes an den Registermarken.
8. Einrichtung nach Anspruch 7, bei der das Druckmedium (16) eine im wesentlichen geradlinige Kante (16b) aufweist, dadurch gekennzeichnet, daß das Antriebssystem Mittel (99) aufweist, die die Kante (16a) des Druckmediums auf eine vorgegebene Bewegungslinie längs der Transportbahn (18) beschränken.
9. Einrichtung nach Anspruch 8, bei der das Druckmedium eine Vielzahl von in Abstand zueinander angeordneten Öffnungen (92) in der Nähe der Kante (16a) aufweist, dadurch gekennzeichnet, daß die Beschränkungsmittel mehrere in Abstand längs der Bewegungslinie an der Transportbahn montierte gezahnte Mittel (99) aufweisen, die so betreibbar sind, daß sie in die Offnungen eingreifen um diese Öffnungen auf der Bewegungslinie zu halten.
10. Einrichtung nach Anspruch 8 oder 9, dadurch gekennzeichnet, daß die Eingangs- (36, 60) und Ausgangs- (38, 62) Antriebsmittel jeweils eine Kraft auf das Druckmedium ausüben, die eine erste Komponente (78a) im wesentlichen in Bewegungsrichtung des Druckmediums längs der Transportbahn und eine zweite Komponente (78b) in einer von der Kante (16a) des Druckmediums weg weisenden Richtung aufweist.
11. Einrichtung nach Anspruch 9, gekennzeichnet durch Mittel (68) zum Vorspannen des Druckmediums in Eingriff mit den gezahnten Mitteln.
EP19860400773 1985-04-12 1986-04-11 Durchlauffarbdrucker Expired - Lifetime EP0202140B1 (de)

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US5043749A (en) * 1989-12-29 1991-08-27 Am International Inc. Printing press and method
US6160564A (en) * 1995-10-30 2000-12-12 Nippon Steel Corporation Color electrostatic recorder with adjustable pressure on a recording medium

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DE2445541C2 (de) * 1974-09-24 1984-02-02 Agfa-Gevaert Ag, 5090 Leverkusen Verfahren und Vorrichtung zur Herstellung von Kopien
US4419679A (en) * 1980-06-03 1983-12-06 Benson, Inc. Guadrascan styli for use in staggered recording head
US4401024A (en) * 1982-04-07 1983-08-30 Milliken Research Corporation Electronic patterning with registration control
CA1214494A (en) * 1982-11-24 1986-11-25 Robert P. St.John Color electrographic recording apparatus

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