FR2572024A1 - INK CONTROL DEVICE ON A PRINTING MACHINE FOR RECTO / BACKWARD POLYCHROMY SHEETS - Google Patents

Abstract

INKING CONTROL DEVICE ON A MACHINE FOR PRINTING TWO-SIDED POLYCHROMY SHEETS, INCLUDING AT LEAST ONE SHEET RETURNING DEVICE PLACED BETWEEN TWO PRINTER UNITS. FRONT PRINTING CONTROLS, SUCH AS DENSITOMETRIC DEVICES 19, ARE ARRANGED AFTER THE LAST FRONT PRINTING ZONE, IN THE DIRECTION OF SHEET PASSAGE, NEAR A CYLINDER OF THE MACHINE ON WHICH THE FRONT SHEETS ARE OUTSIDE, AND REVERSE PRINTING CONTROLS 16 ARE LOCATED AFTER THE LAST REVERSE PRINTING AREA. APPLICATION IN PARTICULAR TO THE AUTOMATIC CONTINUOUS CONTROL OF PRINTING MACHINES IN SEVERAL PRINTER UNITS, LIKELY TO PRINT ONLY THE FRONT OF THE SHEETS, OR THIS FRONT AND THE BACK.

Description

The present invention relates to a machine for printing sheets in

  multiple colors on the front as well as front and back, including a number of groups

  printers and at least one switchable return device

  sheet, intended to switch from printing on the front side to double-sided printing and arranged between two

respective printing groups.

  In the most recent evolution of printing in

  In several colors, densitometric devices

  other inking control devices for the various areas across the width of the printed sheet, which

  constantly check the conformity of the inten-

  This is done by comparing the various colors in these areas of the sheet by comparing the print result actually obtained with the predetermined set values. If the density of the inking falls outside the predetermined tolerances with respect to the desired setpoint, an alarm signal is emitted indicating to the printer that one of the inking mechanisms must be set for or more of the zones,

  is caused in closed circuit a readjustment

  automatic feeding of the ink supply

  concerned. In the rest of the description, for a purpose

  simplification, we will only talk about densitometers, but it could be just as well devices of any other

  kind for the control of inking.

  With printing machines, in particular sheet-fed offset machines, comprising several printing units which each comprise an inking mechanism and several cylinders, and in particular with the

  printing machines in several colors, it was neces-

  hitherto, to control the ink density of the printed sheets, to remove one sheet from the completely printed stack, to densitometrically measure the inking density in several places of a printed control strip at the same time and, if there were divergence from the desired inking density, both in the

  transverse direction of the sheet as compared to the various.

  colors, adjust the various inking mechanisms by means of adjusting devices acting on their ink metering devices

  or ink plates. With this way of working, it is necessary to

  permanently control printing, which is slow and slows the work of continuous printing; moreover, it is not possible to avoid large amounts of waste. One known attempt to remedy these drawbacks consists in depositing on at least one cylinder to which the sheet is applied, its at least partially printed face turned towards the outside, a densitometric device intended to measure the density of the ink zones. test of the sheet, the inking mechanism (s) comprising

  each a regulating member which is actuated by a large

  of a regulating device as a function of

  the set value. In this known solution, the arrangement

  densitometric system is adjacent to a measuring cylinder which is arranged between a transfer cylinder of the last

  printer group and the leaf catcher.

  To apply this suggestion, it would be necessary

  each printing group is equipped with a densi-

  tometrically adjacent to an intermediate cylinder immediately following a transfer cylinder of this group. But then it is necessary in practice, in this known solution, each time two additional cylinders to achieve a cylinder on which the printed side of the sheet is

  located outside and close to which the densi-

  tometric can be mounted. In this form, with the machines to print sheets in several colors

  can be switched from printing on the front to printing

  front and back, it is not possible, and in any case not without other arrangement, to control the density of the various colors on both sides of the

  sheet in the case of double-sided printing.

  The invention therefore relates to a printing machine in several colors, which can be switched from printing on the front to printing on both sides, with which the user can, regardless of the mode of printing.

  setting or operation of the machine, check

  the ink density during single-sided printing

  back, by means of a minimum number of densito-

  metrics. It should be noted in this regard that this densitometric control on both sides of the sheet can be performed regardless of the mode of operation of the machine; it should be noted, for example, that with a multi-color printing machine having several sheet transfer devices between the various printing units, sometimes one, sometimes the other of these devices can be turned into a reversing device of sheets, depending on whether the operator of the machine, if it includes for example a total of five printer groups, wants to print a color on the front and four colors on the back, or two colors on the front and three colors on the back, or three colors on the front and two colors on the back, or four colors on the front and

  a color on the back, but also if necessary, five

their on the front.

  In accordance with the invention, densi-

  tometric or other inking control devices, intended to verify the single-sided printing, are arranged, behind the last printing area on the front in the direction of the passage of the sheets, near a cylinder of the machine on which the front of each sheet is on the outside and densitometric devices or other inking control devices, intended to verify the printing on the back, are arranged behind the last

  print area on the back of the machine.

  With this arrangement, each sheet can be checked by densitometric examination as simply as possible on both sides, that is to say both recto and vrrso and this continuously and regardless of the operating mode of the machine with regard to the number of impressions

  on the front and impressions on the back.

  The invention can be implemented various

  ways. For example, it is possible to mount the

  Densitometric controls for printing on the front side near the last impression cylinder following the last

  printing area on the front, so before the device back-

  Leaves neur following. However, it is also possible to mount these densitometric printing devices on the front side near a cylinder, on which the front of the sheets is on the outside, of the sheet-reversing device located after the last zone of single-sided printing Moreover, it is still possible to mount these densitometric devices print control on the front near a cylinder of a device

  leaf transmitter which lies between areas of

  pressure on the back, or a cylinder that is located after the last of these print areas on the back, and on

  where the front of the sheet is on the outside.

  According to another characteristic of the invention, the various densimeters of a densitometric device are conveniently mounted on a single cross member which is removably mounted on the machine and is interchangeable. This has the additional advantage that with machines having several sheet reversing devices (of which of course only one is in use), it suffices to have a single densitometric device, which can be fixed at various points of the machine, always know before the reversing device is in service. In this way, the number

  densitometric devices or devices

  control of the inking is particularly reduced.

  If the areas spread across the width of the sheet, which are to be checked for inking density, are very narrow in order to increase the accuracy, densitometers or other inking control devices may be required those who check the print on the front and those who check the print on the back, can not be mounted side by side on the same cross. In this case, it is proposed, in accordance with the invention, to mount the various zone densitometers on at least two crosspieces which are adjacent to one or more cylinders of the machine on which the front or the back of the sheet

  that it is a question of checking is located respectively outside

  laughing. If these densitometers are mounted for example on two sleepers, they can be distributed over them

  according to the colors they react to

  so that one of these crosspieces carries the densitometers corresponding to the first, third, fifth, etc., areas distributed over the width of the sheet, the other carrying the densitometers which correspond to the

  second, fourth, sixth, etc .... zones.

  The invention will be described in more detail with reference to illustrative and non-limiting examples of implementation, shown in the accompanying diagrammatic drawings, in which FIG. 1 is a side elevation showing the essential elements of a printing machine. in several colors, comprising six printing units and a sheet reversing device;

  FIG. 2 represents a printing machine comprising

  also six printing units, but two sheet reversing devices, each of which can be switched at will from the transfer operation to the overturning operation; and

  Figure 3 shows the assembly of the various densities

  zone tometers or zone-checking devices, on the same cross-piece adjacent to a cylinder of

the machine.

  Print groups are designated in order

  1 to 6 in Figures 1 and 2. As a single example

  these are offset printing groups that are represented; but the invention is applicable to groups

printing of all other kinds.

  The printing machine of Figure 1 has six printer groups 1 to 6; it is therefore a printing machine in six colors. The feeder is designated by 7, the leaf catcher by 8. Each printing group

  comprises a plate cylinder 9, a cylinder

  blanket 10 and a printing cylinder 11; only the cylinders in group 1 carry reference numbers. There is between the printer groups 1 and 2 a sheet transfer device consisting of a small drum 12, a drum 13 twice as large and a second small drum 14.The reference 15 designates the transfer drum 8. Between the printer groups 2 and 3, there is the small normal drum 12 of the sheet transfer device, but there is moreover a device for returning the sheets.

  consisting of a large drum 17 and a small drum 18.

  Unlike the drums of the transfer device pro-

  In fact, these two drums 17 and 18 are represented entirely in black. When the reversing device 17, 18 is set to execute only the transfer of the sheets,

  the machine prints in six colors on the front and only the

  that densitometric device 16 mounted after the last printing unit 6 is necessary, since only one side of the sheets is printed in six colors. If, on the contrary, the reversing device 17, 18 is set for double-sided printing, another densitometer device 19, which is between this reversing device 17, 18, is required.

  and the last previous area of simplex printing, is

  ie the zone of the group 2. The sheet is then printed on the front in two colors by the groups 1 and 2 and on the back in four colors by the groups 3 to 6, the first one

  two-color printing being controlled by the

  Densitometer 19 and the four-color printing on the other side by the densitometer 16.

  FIG. 2 also shows a printer machine

  The machine comprises two sheet-reversing devices 17, 18, one between the printer groups 1 and 2 and another between the printer groups 2 and 3. If these reversing devices 17 , 18 are disabled, the machine prints the front of the sheets in six colors. Yes

  only the device 17, 18, located between the printing groups

  1 and 2 is put into operation, but the one between groups 2 and 3 is not, the machine prints the front of the sheets in one color and their back

  in five colors. If, on the other hand, only the return device

  17, 18 on the left, located between the printer groups 2 and 3, is put into service, the one that precedes it between the groups 1 and 2 are not, the machine prints the front

  leaves in two colors and their backs in four

  their. There is in this machine, in addition to the densi-

  tometric 16 mounted behind the last printer group

  6, two other densitometric devices 19, mounted

  respectively one between the first turner device 17,18, in the direction of the passage of the sheets, and the group

  printer 1, on the one hand, and the other between the second

  17.18 and the printer group 2, on the other hand. One of these two densitometric devices 19, the one that is before the reverser device 17, 18 which is out of order, can naturally be put too

  out of order or even be completely removed from the machine.

  But, one can also, by decreasing correspondingly

  the complication of the machine, use only one

  Densitometric unit 19 which can be removably attached to the machine between the last printing area on the front

  (1 or 2) and the reversing device 17, 18, following.

  FIG. 3 shows a cylinder 20 of any type of printing machine near which the densitometric device 16 or 19 can be arranged transversely over the entire width of this cylinder. This device consists of a cross member 21, which is mounted on the machine, can be disengaged mechanically or electrically and carries densitometers 22, represented by short lines, corresponding to the various zones distributed over the width

of the leaf.

  Instead of the arrangement shown in FIGS. 1 and 2, where the densitometric devices 19 for controlling the printing on the front side are adjacent to the printing cylinder 11 behind the last printing area on the front, they can also, depending on the characteristics of embodiment of the machine, be adjacent to a cylinder of the following reversing device 17,18, on which the front of the sheet

is outside.

  But it is also possible to mount the densitometric device 19 control printing on the front near a cylinder of one of the transfer devices 12, 13, 14 which are respectively between the following areas of impresssion on the back , cylinder on which the front of the sheet is turned outwards. This

  does not interfere with the control of the anchoring density of the

  on the front side, but still offers the advantage of automatically taking into account, when controlling the printing on the front side, the influences that can be exerted on the front side in the printing areas on the back of the document.

machine.

  As already mentioned, the two zone densitometers 22, both those controlling the printing on the front of each sheet, and those controlling the printing on the back of these sheets, can also be mounted on at least two sleepers or even on a much more

  number of sleepers, which are respectively

  one or more cylinders of the machine and on which the impression to be verified, on the front

  or on the back, is outside. This assembly is

  if the zones, arranged in the width and which it is a question of control, are so narrow that all the densitometers intended to control them and all the colored inks printed by the machine can no longer be arranged on

  a single row and therefore on the same cross, because of the encum-

  densitometers in width.

  It goes without saying that it is possible, without departing from the scope of the invention, to make various modifications to the printing machine in several colors represented

and described.

Claims (6)

  1. Machine for printing sheets in several layers   their front side as well as front and back, comprising several printing units and at least one switchable sheet reversing device, located between two of these groups and intended to move the machine from printing on the front to printing on both sides, as well as devices   color control or anchorage, such as   densitometric units, which are intended to check the di-   1 areas spread across the width of the leaves and which, when   there is a divergence from the value of   desired sign for the corresponding zone, either trigger a warning signal or cause in a closed circuit a readjustment of the ink supply of this zone, characterized in that color control devices or inking of the front, which are advantageously densitometric devices (19) are mounted after the last print area on the front, in the direction of the passage of the sheets, adjacent to a cylinder of the machine on which the front of each sheet is facing outwards, and control devices for the inking of   the reverse side, which are advantageously   densitometric heads (16), are placed after the last   back printing area of the machine.   2. Printing machine according to claim 1,   characterized in that the densitometric devices (19) controlling the printing on the front side are adjacent to the last   cylinder (11) of the last printing area   on the front side, ie before the reversing device   leaves (17,18) that follows this area.   3. The printing machine according to claim 1, wherein   characterized in that the densitometric devices (19) for controlling printing on the front side are adjacent to a cylinder, on which the front of the sheets is facing outwards, of the sheet-reversing device (17, 18).   located after the last printing area on the front.   4. Printing machine according to claim 1, characterized   characterized in that the densitometric devices (19) for controlling the printing on the front side are adjacent to either a cylinder of a sheet transfer device (12, 13, 14) which lies between the printing areas at the on the back, either to a cylinder located after the last printing area on the back, the front of the sheets being   outward on these cylinders.   5. Printing machine according to any one of   Claims 1 to 4, characterized in that the various   devices for controlling the inking of an area,   part of an overall control device (16, 19),   the various densitometers (22) of a densitometric device are mounted on the same cross-member (21)   which is removably mounted on the machine and is interchangeable geable.   6. Printing machine according to any one of   Claims 1 to 4, characterized in that the various   zone-checking devices, such as the various densitometers (22) of a densitometric device (16, 19), are mounted on at least two cross-members (21) which are adjacent to at least one cylinder of the machine , on which respectively, either the front or the back side to be checked is outside, these ties   being advantageously removable and interchangeable.