FR2766414A1 - OFFICE MACHINE PRINTER WITH IMPROVED IMAGE FRAMING - Google Patents

Abstract

The printer for an office machine comprises means (1, 6) for introducing and guiding sheets to be printed (10) arranged to cooperate with means (19) for jointly driving a sheet (10) and of an ink ribbon (20) in front of a print head (14), by transfer from the ribbon (20), arranged to receive an electronic image (16) to be printed, and it comprises means (7, 8, 12 ) for detecting the position deviation of the sheet to be printed (10) with respect to a predetermined position, arranged to consequently control means (4, 17) for relative cropping of the sheet (10) and of the image electronic (16).

Description

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  FRAMING OFFICE MACHINE PRINTER

IMPROVED IMAGE

  In a printer, you must be able to control the position of the sheets of paper to be printed, in order to respect the framing

desired for printing.

  If we take the particular example at the origin of the present invention, but which should not limit the scope of the present application, it was a color transfer printer

thermal of an office machine.

  113,1, IIIIlll ll'I In such a printer, three partial printing passes are made, for the three basic colors

  respective, cyan, magenta and yellow, to be printed on a sheet.

  i! Therefore, first of all, as in any printer, initially align the sheet with respect to the print head and it is also necessary to keep the alignment throughout

printing passes.

  The classic way to control the framing is to guide the input sheet as input, to align it correctly, and to

  enter to release it only after printing is complete.

  Stepper motors allow a controlled back and forth of the sheet to successively press it with adhesion on three respective color ranges of a thermal transfer ribbon, by rollers of a rolling mill which drive by

  rubbing the whole scrolling in front of the print head.

  However, the input guidance is imprecise and the initial framing is therefore uncertain. In addition, the framing drifts during the maneuvers. Indeed, the sheet, driven by friction by the rollers, is capable of sliding slightly relative to the tape, II111111 11111111I 1, _ 'r ....--. III

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  possibly skewing if the rollers have any asymmetry, so that its return position is imprecise

  and also unfaithful because this imprecision grows with each pass.

  The solution consisting in spreading and fixing the sheet on a drum with a single direction of rotation, to carry out successively

  the three printing passes is very restrictive in volume.

  The present invention aims to eliminate the positioning uncertainty of the image, obtained by one or more passes

  printing, on a printing medium.

  To this end, the invention relates to a printer for an office machine comprising means for introducing and guiding sheets to be printed, arranged to cooperate with means for jointly driving a sheet and an ink ribbon in front of a print head, by transfer from the ribbon,, It arranged to receive an electronic image to be printed, characterized in that it comprises means for detecting the position deviation of the sheet to be printed relative to a position predetermined, arranged to control accordingly relative cropping means of the sheet and the electronic image. Thus, the concept of the invention can be described as dynamic positioning between the sheet and the image to be printed, which avoids all the uncertainties and technical constraints linked to a permanent holding of the sheet within close position tolerances. The cropping can be mechanical, between the sheet and the printing block, or electronic by translation and / or rotation of

the image to print.

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  For printing in several passes, as for color, you can thus manually or mechanically bring the

  sheet in its starting position, without specific precautions.

  s The invention will be better understood using the description

  following of a preferred embodiment of a color printer according to the invention, with reference to the accompanying drawing, in which: - Figure I is a schematic side section of the printer, - Figure 2 shows schematically in perspective of position sensors of a sheet to be printed and a cropping device thereof, and - Figure 3 shows, also in perspective, a variant

  of the cropping device of FIG. 2.

  The printer shown, of the color type, comprises, in the direction of travel of the sheets 10 to be printed, a slide I with lateral guide edges of sheets 10 of virgin paper with, opposite, a support 2, rotatable around a axis 3, of a pair of rollers or drive rollers 4 of the sheet 10, arranged symmetrically with respect to the longitudinal axis of the sheet 10. The rollers 4 are opposite to a freewheel roller with fixed axis 5 disposed downstream of the slide I and comprising an outer layer of rubber with a high coefficient of friction. There is also provided a motorized central roller or roller 55, opposite the roller 5, for

  the introduction of the sheets 10, by limited friction.

  The set of axes indicated is perpendicular to the plane of the figure, that is to say parallel to the front edge of a printed sheet 10. The various drive motors have not been shown. Two opposite guide slides 6 are arranged downstream of the rollers 4, 5, 55 and ends at two positioning stops in the form of retractable articulated hooks 7, 8, mounted rotatably on an axis 9. Slightly upstream of the stops 7, 8

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  is arranged a position sensor 12 of a lateral edge of the sheet

, behind the cutting plane.

  Downstream of the stops 7, 8, the guide 6 continues through a channel 13 leading to a printing block comprising a printing head 14 controlled by an electronic image memory 16 (three partial three-color images) to which a access to a circuit 17 for cropping the image, belonging to a central unit at

microprocessor 18.

  A counter-supporting motor roller 19, with a layer of rubber with a high coefficient of friction, is arranged opposite

  I ... of the head 14, which is pressed thereon by a return spring 15.

  A tributary channel 23 opens upstream of the head 14 for the passage of an ink ribbon 20, here by thermal transfer, or by sublimation, coming from a supply roller 21 and leading to a

take-up roller 22.

  An exhaust channel 24 for the sheet 10 and the ribbon 20 branches off into a channel 25 for ejecting the printed sheet 10 and in

  channel 26 for accessing the take-up roller 22.

  In FIG. 2 is shown a first variant in which the stops 7 and 8 have been replaced by sensors 37 and 38 of point position of sheet edge 10, shown very schematically, arranged at a distance from each other according to the intended direction of the front edge 101 of the sheet 10, therefore transverse to the direction 11 of advance of the sheet 10. The sensor 12 of the lateral edge 102 of the sheet 10 comprises a row of point cells extending transversely to the direction d advance 11 over a length sufficient to cover the range of position uncertainty of the lateral edge 102. The representation of the

position is only functional.

  All of the printer's sensors and motors are connected to the central unit 18, which manages the cropping and printing operations. s The means for cropping the sheet 10 comprise two motors 31, 32 driving, by respective gears 33, 34, two rollers or rollers 35, 36 for driving the sheet 10, generally referenced 4 in FIG. 1. The rollers 35, 36, which are mutually independent, are here aligned along an axis 30 transverse to the direction of advance 11 of the sheet 10, that is to say perpendicular to the plane of FIG. 1. In general, it rollers may be provided in number and orientations such that the sheet 10 can be translated, in the direction of advance 11 and perpendicular thereto, and that it can also be rotated in its plane. In this example, the cropping, between the sheet 10 and the electronic image, in the transverse direction, parallel to the anterior edge 101, is carried out by a corresponding translation of the electronic image and therefore here without mechanical action on the

sheet 10.

  In the variant of FIG. 3, where the elements homologous to those of FIG. 2 have retained their reference, the motor 32 has been replaced by a motor 42 for advancing the printer sheet

(entrance rolling mill).

  A motor 41 here rotates a screw 47, substantially parallel to the direction 11, cooperating with a nut 49 integral, in an articulated manner, with one end of an axis rod 40 common to the rollers 35 and 36, rod 40 pivoting at the level of the motor 42. The operation of the printer will now be

explained in more detail.

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  A sheet 10 being introduced into the printer on the slide 1, the central roller 55 drives it by slight friction until contact with one of the stops 7, 8, and, like the driving force of the central roller 55 passes between the two stops 7 and 8, it produces a torque from applying the sheet 10 to the other stop 7, 8. The sheet 10 is thus aligned correctly. The support 2 is then in a separated position (solid line) which prohibits contact between the rollers 4 and the sheet 10. In place of the roller 55, it could still have been

  provided an intermediate position, limited support, rollers 4.

  In the case of variants of FIGS. 2 and 3, if the sheet 10 is oriented incorrectly in its plane, the front edge 101 activates only one of the sensors 37, 38 first, so that the central unit 18 deduces therefrom sign of the angle of misalignment of the front edge 101 with respect to the direction transverse to the direction of advance 11. The sheet 10 being rectangular, the angle between the edge

  lateral 102 and direction 11 is also equal to that determined above

  above. It will be appreciated that, in the case of FIG. 1, a single stop (7; 8) could have been provided, with a single mechanical function, associated with, overall, an orientation sensor for the front edge 101 (or side 102) , that is to say determining the relative advance (11) of two points spaced from the front edge 101, as in the case of FIGS. 2 and 3. Likewise, if it is possible to provide for integrating sensors position (37, 38) of the front edge 101 of the sheet 10 in the stops 7, 8, the stop function can however be replaced by a control of the advance of the sheet 10 by the roller 55, so as to stop this advances when the leading edge 101 reaches the area

  of the position sensors 37, 38.

  As explained below, the sheet 10 is redirected, if necessary, and it can only pass the two sensors 37, 38 if it makes them switch simultaneously. Sheet 10 can be viewed

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  like an image whose position is determined in the printer

  to superimpose the image to be printed on it.

  The cropping circuit 17 of the central unit 18 then controls the motor 31 or 32 opposite the activated sensor 37, 38, in order to rotate the sheet 10 in its plane, with possible retraction, until the two sensors 37, 38 simultaneously detect the arrival of the front edge 101, thus correctly aligned. The sensor 12 for the position of a point on the lateral edge 102, then aligned with the direction o10 of advance 11, provides the transverse position of the edge 102 of the sheet 10. The circuit 17 thus deduces the difference between this lateral position measured and a lateral reference position, in memory, and therefore

  determines the crop needed.

  Thus, in the direction of advance 11, the sheet 10 is positioned in the desired, predetermined manner relative to the print head 14 and any framing error is thus excluded. In the transverse direction 101, the framing error or difference between the sheet 10 and the head 14 is measured and the correction occurs by processing (17) of the image (16), that is to say here a translation lateral. The print head 14 is long enough to print the entire width of an image, regardless of the offset

side of sheet 10.

  In the variant of FIG. 3, the rod 40 is pivoted, at the level of the motor 42, by translation of the nut 49 controlled by the screw 47, which, by friction of the rollers 35 and 36 on the sheet 10, makes rotate it in its plane, until it aligns as expected. The sheet feed rolling mill is thus used in differential

translating one of its sides.

  The position of the sheet 10 being thus perfectly determined, the support 2 pivots (dotted line) to strongly pinch the sheet 10 between the rollers 4 and 5 and drive it in front of the print head 14, the stops 7, 8 present in the case of

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  Figure 1 having been retracted by pivoting in their position

retracted (dotted line).

  The counter-support roller 19, rotating, under the control of a stepping motor, at a linear speed slightly higher than that of the rollers 4, 5, begins by gripping the front edge 101 and extends the sheet 10 longitudinally while

  driving the ribbon 20, plated on the sheet 10.

  After a determined engagement (upper margin) of the sheet 10 at the roller 19 (number of motor steps), the unit

  central 18 releases the rollers 4 by pivoting the support 2.

  Printing then takes place and the printed sheet 10 is ejected

  (25), in a tray not shown, then the roller 19 stops.

  In this example of a color printer, the print pass above corresponded to the printing of one of the three colors, cyan, magenta, yellow, of range of ribbon 20. This comprises sequences of three ranges slightly larger than that of the sheets 10 and, during the first pass, the ribbon 20 has been advanced to permanently compare the transverse line of the sheet 10 being printed and a corresponding strip of the range of the color considered. The excess format of

  ranges excludes any problem of framing sheet 10 / zone of ribbon 20.

  For the printing of the two other partial images corresponding to the two colors not yet processed, sheet 10

  ejected is manually reinserted twice into the printer.

  There may also be a guide for reintroducing, automatically by looping, twice the sheet 10, before ejecting it. A mechanism for retracting the partially printed sheet 10 can likewise be provided to bring it back into the area

position sensors.

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  In general, three point sensors are sufficient to determine the position of the sheet according to two non-parallel reference edges, therefore adjacent in the case of a parallelepiped sheet. Two mutually spaced sensors determine the orientation and the position of a transverse 101 or lateral 102 reference edge and the third sensor determines the

  position of the other edge, lateral or transverse.

  The correction for the cropping corresponding to the three lo degrees of freedom mentioned above, two degrees of freedom in translation, a degree of freedom in rotation, can be carried out, in whole or in part, by mechanical means of cropping the sheet 10 relative to the head 14, or of the latter, then movable, relative to the sheet 10, respectively electronic means for moving the electronic image according to these three degrees of freedom, insofar as the printer comprises such a memory 16. Otherwise, only a transverse shift, over the water, is possible

in the printer itself.

IlI 1111 il * il1 1111.

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Claims (5)

  1 - Printer for office machine, comprising means for introducing and guiding (1, 6) sheets to be printed (10) arranged to cooperate with means (19) for jointly driving a sheet (10) and an ink ribbon (20) in front of a print head (14), by transfer from the ribbon (20), arranged to receive an electronic image (16) to be printed, characterized in that it comprises means (37, 38, 12) for detecting the position deviation of the sheet to be printed (10) relative to a predetermined position, arranged to consequently control means (17, 31-36; 47, 49) for cropping relative of the sheet (10) and of the electronic image (16).   1s 2 - Printer according to claim 1, in which the position deviation detection means comprise at least three sensors (37, 38, 12) for point detection of two adjacent edges   reference (101, 102) of the sheet (10).   3 - Printer according to claim 2, wherein two of the sensors (37, 38) are arranged to detect the anterior edge (101) of the sheet (10).   4 - Printer according to claim 3, wherein the two sensors (37, 38) form positioning stops retractable (7, 8).   - Printer according to one of claims 1 to 4, in   which the cropping means (17, 31-36; 47, 49) are arranged to effect a relative movement between the sheet (10) and the head printing (14).   6 - Printer according to claim 5, wherein the cropping means comprise two rollers (35, 36)   differential sheet drive (10).   Mll 1 11 I II liii111 11 111 11111 -Illll,,., I l 2766414   - 7 - Printer according to one of claims 1 to 6, in   which the cropping means (17) are arranged to crop   the electronic image (16) relative to the print head (14).   8 - Printer according to one of claims 1 to 7, in   which means (1, 6) for introducing the sheets (10) are associated with means (19, 25) for ejecting them for color printing in several passes by a polychrome ribbon (20). I :. t lr 1