CA2117665C - Printing unit for a web-fed printing machine - Google Patents
Printing unit for a web-fed printing machine Download PDFInfo
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- CA2117665C CA2117665C CA002117665A CA2117665A CA2117665C CA 2117665 C CA2117665 C CA 2117665C CA 002117665 A CA002117665 A CA 002117665A CA 2117665 A CA2117665 A CA 2117665A CA 2117665 C CA2117665 C CA 2117665C
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- saddle
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41F—PRINTING MACHINES OR PRESSES
- B41F13/00—Common details of rotary presses or machines
- B41F13/02—Conveying or guiding webs through presses or machines
- B41F13/04—Conveying or guiding webs through presses or machines intermittently
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Inking, Control Or Cleaning Of Printing Machines (AREA)
- Rotary Presses (AREA)
- Auxiliary Devices For And Details Of Packaging Control (AREA)
- Handling Of Continuous Sheets Of Paper (AREA)
- Unwinding Webs (AREA)
Abstract
The printing unit has two cooperating cylinders (1, 4) which form the printing nip and which have printing saddles (2, 5) separated by cylinder pits (3, 6). The paper web (7) passing through the printing nip is transported in the pilgrim-step mode, in order to print formats adjoining one another. The two cylinders (1, 4) are angularly adjustable relative to one another, in respect of the position of their printing saddles (2, 5) cooperating in the printing nip, in a manner offset by the amount of a circumferential distance which is approximately equal to the difference between the circumferential length (S) of a printing saddle and the circumferential length (B) of a printing image. The printing zone is therefore only approximately as large as the printing image, and the print-free zone available for retracting the paper web is correspondingly enlarged.
Description
C~,Z i i 7665 DE LA RUE GIORI S.A. LAUSANNE/SWITZERLAND
Printino unit for a web-fed printing machine Field of the invention The invention relates to a printing unit for a web-fed printing machine with two cooperating cylinders which form the printing nip and which, as in a sheet-fed printing unit, have a plurality of printing saddles separated by cylinder pits, for printing a web running through the printing nip with variable formats adjoining one another, the web being transported at a variable speed in the so-called pilgrim-step mode and, after each printing operation, when it passes a cylinder pit, being retracted and accelerated again relative to the circum-ference of the two cylinders in such a way that successive printing images are lined up virtually without a gap.
Prior art Printing unite of this type are described in US Patent 5,062,360. These known printing unite are either offset printing units with two cooperating blanket cylinders, which are both inked with printing images and which serve for producing a recto/verso print, or intaglio printing units with a plate cylinder which cooperates with an impression cylinder. The use of sheet-fed printing units for printing a continuous paper web has the advantage that there is no need for the difficult and time-consuming production of plate and impression or blanket cylinders with a continuous seamless CA2ii7665 circumferential surface; use is made, instead, of the cylinders which are simpler to produce and have printing saddles separated from one another and on which the individual printing plates or printing coverings can be individually mounted, adjusted and exchanged without great difficulty. Moreover, the transport of the paper web in the so-called pilgrim-step mode affords the possibility that images adjoining one another can always be produced without a loss of paper as a result of unprinted gaps between the images, hence that no unprinted stripe occur between successive printing images on account of the cylinder pits. For this purpose, as described particularly in US Patent 5,062,360, the transport of the paper web is controlled by means of a control system in such a way that, after each printing operation, the no longer clamped paper web, when it passes the mutually aligned cylinder pits of the two cylinders, is first braked, then moved backward and finally accelerated again to the operating speed, before it is clamped once more between the following cooperating printing saddles of the two cylinders for the subsequent printing operation. The distance over which the paper web is retracted relative to the circumference of the two cylinders is selected so that successive printing images are printed virtually without a gap. To this effect, therefore, the pilgrim-step movement must be controlled in such a way that, after the pilgrim step, the paper web assumes at least approximately the same position relative to the printing nip between the two cylinders, that is to say within the machine, as before the pilgrim step.
As a result of an appropriate adaptation of the pilgrim-step movement, it is possible, with one and the same printing machine, even in the case of varied formats of the printed image, that ie to say in the case of shorter formats, to print images adjoining one another without a gap. The printing format is changed by mounting a printing plate of the same size with a shorter printing image, the printing zone thus remaining the same and not being shortened.
Printino unit for a web-fed printing machine Field of the invention The invention relates to a printing unit for a web-fed printing machine with two cooperating cylinders which form the printing nip and which, as in a sheet-fed printing unit, have a plurality of printing saddles separated by cylinder pits, for printing a web running through the printing nip with variable formats adjoining one another, the web being transported at a variable speed in the so-called pilgrim-step mode and, after each printing operation, when it passes a cylinder pit, being retracted and accelerated again relative to the circum-ference of the two cylinders in such a way that successive printing images are lined up virtually without a gap.
Prior art Printing unite of this type are described in US Patent 5,062,360. These known printing unite are either offset printing units with two cooperating blanket cylinders, which are both inked with printing images and which serve for producing a recto/verso print, or intaglio printing units with a plate cylinder which cooperates with an impression cylinder. The use of sheet-fed printing units for printing a continuous paper web has the advantage that there is no need for the difficult and time-consuming production of plate and impression or blanket cylinders with a continuous seamless CA2ii7665 circumferential surface; use is made, instead, of the cylinders which are simpler to produce and have printing saddles separated from one another and on which the individual printing plates or printing coverings can be individually mounted, adjusted and exchanged without great difficulty. Moreover, the transport of the paper web in the so-called pilgrim-step mode affords the possibility that images adjoining one another can always be produced without a loss of paper as a result of unprinted gaps between the images, hence that no unprinted stripe occur between successive printing images on account of the cylinder pits. For this purpose, as described particularly in US Patent 5,062,360, the transport of the paper web is controlled by means of a control system in such a way that, after each printing operation, the no longer clamped paper web, when it passes the mutually aligned cylinder pits of the two cylinders, is first braked, then moved backward and finally accelerated again to the operating speed, before it is clamped once more between the following cooperating printing saddles of the two cylinders for the subsequent printing operation. The distance over which the paper web is retracted relative to the circumference of the two cylinders is selected so that successive printing images are printed virtually without a gap. To this effect, therefore, the pilgrim-step movement must be controlled in such a way that, after the pilgrim step, the paper web assumes at least approximately the same position relative to the printing nip between the two cylinders, that is to say within the machine, as before the pilgrim step.
As a result of an appropriate adaptation of the pilgrim-step movement, it is possible, with one and the same printing machine, even in the case of varied formats of the printed image, that ie to say in the case of shorter formats, to print images adjoining one another without a gap. The printing format is changed by mounting a printing plate of the same size with a shorter printing image, the printing zone thus remaining the same and not being shortened.
CA2ii7665 In the hitherto known web-fed printing machines of this type, the two cylinders are always set relative to one another in such a way that the printing saddles, when they cooperate in the printing nip, are located exactly opposite one another, as shown in Figures 1 and 2 for the two cylinders 1 and 4 which each have three printing saddles 2 and 5 with the circumferential length S. At the same time, therefore, the length D of the printing zone, along which the paper web 7 is clamped between the two cylinders, is always exactly as large as the circumferential length S of a printing saddle, specifically irrespective of the circumferential length B of the printing image, that is to say of the format.
The print-free zone between two printing zones according to the length G of a cylinder pit and consequently the timespan available for retracting the paper web are therefore, of course, also always the same.
Figure 1 shows the commencement of a printing operation and Figure 2 the end of this printing operation, that is to say after the cylinders have rotated in the direction of the arrows through an angle corresponding to the length D of the printing zone. If the maximum possible format is being printed, that is to say if the circumferential length of the printing image is virtually equal to the circumferential length of a printing saddle, then, after each printing operation, the paper web 7, when it passes the cylinder pits 3, 6 in a freely movable manner, must be braked, retracted and accelerated again in such a way that, depending on the printing speed, the obtainable deceleration and acceleration and the time taken to run through the pit, when printing commences again it assumes approximately the same position relative to the printing nip as that which it had assumed before the pilgrim step.
However, if smaller formats are to be printed, in which, as illustrated in Figures 1 and 2, the circumferential length B of a printing image is smaller than the circumferential length S of a printing saddle, then, after each printing operation, the paper web 7 must CA2ii7665 be retracted and accelerated again over a greater distance which ensures that, when printing commences again, the position of the paper web is additionally set back relative to the printing nip, opposite to the running direction, by the amount of the difference between the length of the printing zone D and the length of the printing image B, that is to say by the amount of the distance D-B.
In an example according to Figures 1 and 2, the print start A coincides with the image start, while the print end E of the.printing zone is located behind the image end F by the amount of said differential distance D-B, this difference being designated by Z. In this case, therefore, whenever printing commences again, the paper web 7 must assume a position relative to the printing nip which is offset rearward opposite to the running direction by the amount of the length Z, if printing images succeeding one another virtually without a gap are to be obtained on the paper web, as indicated in Figure 1.
The fact that the length D of the printing zone always remains ,constant, even when printing-3mages of smaller format are produced, has various disadvantages:
Since, after each printing operation, the paper web must additionally be retracted by the amount of a distance Z, this signifies, for smaller formats, that ie to say for larger Z, a considerably greater deceleration and acceleration of the paper web in comparison with the printing mode in which the maximum printing format is produced. At the same time, the following has to be taken into account:
When the paper web is released after the printing zone, it first moves a little way further according to the magnitude of the printing speed and of the obtainable deceleration, until it stops. This distance which the paper web has thereby covered is doubly critical, since it has to be taken into account once again during acceleration after the standstill of the paper web. The paper web therefore has to be retracted by double this distance, so that, after subsequent acceleration,- it arrives again with the printing speed at the same point which it occupied before the pilgrim step.
If the printing-saddle length is larger than the printing-image length, the paper web cannot be decelerated immediately after the end of the .printing image, but is transported further at the printing speed, .
before the pilgrim step can commence. As mentioned, this distance must be covered additionally in the pilgrim step.
However, since limits are placed on the deceleration and acceleration of the paper web, a reduction in the speed of the machine is necessary. This loss of capacity thus has a twofold effect, since, during each revolution, a shorter printing image is produced and, in addition, the speed must be reduced Furthermore, particularly in intaglio printing, the paper web is compacted by the very high pressure, which can amount to 80 t per meter of web width, and by the high-gloss chromium-plated surface of the printing plate,- in such a way that after retraction, during the subsequent printing operation, the pressed, bu-t not ink-printed portion Z of the paper web is printed With poorer quality than the non-pressed web. Figures 1 and 2 illustrate the excessively pressed web portion Z and the double-pressed portion P. The pressing of the portion Z
in Figure 1 originates from the preceding printing operation.
Objects of the present invention are avoidance of the disadvantages explained above, and to provide a printing unit in which no losses of capacity during the transition to a smaller format and also no double pressings of the paper web occur.
The invention provides a printing unit, for a web-fed printing machine with first and second cooperating cylinders which form a printing nip and which have a plurality of printing saddles separated by non-printing grooves, for printing a web running through the printing nip with variable formats adjoining one another, the web being transported at variable speed in a so-called pilgrim-step mode and after each printing operation, when it passes a groove, being retracted and accelerated again relative to the circumference of the two cylinders in such a way that successive printing images are lined-up virtually without a gap. The two cylinders are set angularly relative to one another, in respect of the positions of their printing saddles co-operating in the printing nip, depending on a format, in a manner offset by an amount of a circumferential distance which is at least approximately equal to a difference between a circumferential length of a printing saddle and a circumferential length of a printing image; so that a length of the impression zone, along which the two printing saddles clamp the web between them when they pass the printing nip, is only approximately as large as the circumferential length of a printing image. As on cylinders of a sheet-printing machine, the cylinders comprise cylinder pits forming said grooves. A first release member. is fastened on the circumference of the first cylinder on which the beginning of a printing saddle, with respect to a direction of rotation of the cylinder, corresponds to a beginning of a printing image, and a first sensor activatable by this release member is installed in proximity to the circumference of this cylinder. A
second release member is fastened on the circumference of the second cylinder, on which the end of a printing saddle corresponds to an end of the printing image, and a second sensor activatable by this release member is installed in proximity to the circumference of this cylinder. The release members and the sensors are so arranged and designed that the first sensor generates a Sa first signal at the moment at which the beginning of a printing saddle passes a connecting line between the axes of the two cylinders, and the second sensor generates a second signal at the moment at which the end of the printing saddle cooperating with said printing saddle and belonging to the second cylinder passes the connecting line. The signals and a time span between the two signals represent measured values for the angular position and the circumferential length of the printing zone, and are used for controlling movement of the paper web in the pilgrim-step mode during passage of an impression-free zone.
The invention is explained in more detail by Sb CA2ii7665 means of an exemplary embodiment with reference to the drawings.
As already mentioned, Figures 1 and 2 illustrate the printing operation of a known sheet-fed printing unit during the printing of a paper web which is transported in the pilgrim-step mode, and Figures 3 and 4 illustrate a printing unit according to the invention and its operation, Figure 3 showing the commencement of a printing operation and Figure 4 the end of this printing operation, that is to say after the two cylinders have rotated through an angle corresponding to the printing zones D.
Description of the preferred embodiment The two cylinders 1 and 4 illustrated in Figures 3 and 4 are, for example, the plate cylinder 4 and the impression cylinder 1 of an intaglio printing unit. The direction of rotation of the cylinders is indicated by curved arrows. The two cylinders have three printing saddles 2 and 5 of equal size and .with the circumferential length S which are arranged equally distantly along their circumference and -which are separated from one another by cylinder pits 3 and 6 with the circumferential length G. Printing coverings are mounted on the printing saddles 2 of 'the impression cylinder 1 and intaglio printing plates are mounted on the printing saddles 5 of the plate cylinder 4. The printing image on the printing plates has a circumferential length B which is smaller than the length S of the respective printing saddle 5.
In the example under consideration, the printing plates are mounted in such a way that the end E of the printing image coincides with that end of the printing saddle 5 at the rear in the direction of rotation, while the start A of the printing image B is offset corres-pondingly relative to the start of the printing saddle 5.
As illustrated, the impression cylinder 1 ie set angularly relative to the plate cylinder 4 so that the printing saddles 2 and 5 cooperating in the printing nip CA2ii7665 and belonging to the two cylinders are offset relative to one another in such a way that the circumferential length D of the printing zone, in which the cooperating printing saddles clamp the paper web 7, exactly includes only the format to be printed, that is to say the circumferential length B of the printing image. In practice, of course, the printing zone must be slightly longer than the printing image so as to allow for the free edges of the printing images applied to the paper web.
According to Figures 3 and 4, that end of the printing saddle 2 of the impression cylinder 1 at the front in the direction of rotation is offset relative to the front end of the printing saddle 5 by the amount of a portion which is equal to the difference S - B. As mentioned, in practice, the size of this offset is very slightly smaller.
Since, during the printing operation, as a result of this arrangement of these two cylinders 1 and 4, the clamping region of the web is shortened essentially to the circumferential length B of the format to be printed and consequently the print-free zone is enlarged to the length G + (S - B), more time is available for-retracting the paper web, that is to say for deceleration and acceleration. Moreover, the paper web does not need to be additionally retracted, since it is freed immediately after the end of the printing image and can be decel-erated. It is therefore essential that the paper web be clamped only directly in front of the start A of the printing image and be freed again immediately after the end E of the printing image. The advantage of this is that, in the case of constant deceleration and accel-eration moments which are drive-related, the machine speed can be increased by means of the lengthened print-free zone. The shorter repeat length in the case of a small printing image can therefore be compensated by a higher speed. The smaller the length B of the printing image, the larger the print-free zone which is available for retracting the correspondingly large paper-web portion.
CA2ii7665 A further advantage is that, during a printing operation, no additional paper-web portion is pressed outside the printing image and therefore double pressing according to the doubly pressed portion P of the paper web according to Figure 2 is absent, thereby preventing the quality from being impaired.
In the example according to Figures 3 and 4, the cylinder 1 could also be the plate cyclinder and the cylinder 4 the impression cylinder. In this case, the start A of the printing image coincides with that end of the printing saddle of the plate cylinder at the front in the direction of rotation, and it is this plate cylinder which is offset opposite to the direction of rotation in relation to the impression cylinder.
In order to utilize fully the above-described advantageous effects of an offset of the two cooperating cylinders, therefore, the printing image on a printing plate must either with its start A coincide with the start of the respective printing saddle or else with its end E coincide with the end of the respective printing saddle.
The embodiment illustrated in Figures 3 and 4 can also be an offset printing unit with two cooperating blanket cylinders, by means of which either a one-sided offset print can be produced With an inking of only one blanket cylinder or a recto/verso print can be produced with an inking of both blanket cylinders. All the advantages mentioned above also apply to an offset printing unit of this type.
The length D and the angular position of the printing zone can be determined automatically. For this purpose, in the example according to Figures 3 and 4, a release member R is fastened to the circumference of the impression cylinder 1 in such a way that it moves past a fixedly installed initiator or sensor I, responding to this member, exactly when the start of the printing zone, that is to say the start A of the printing image, passes the connecting line between the axes of the two cylinders 1 and 4; this position is shown in Figure 3. The response CA~ii7~~~
of the sensor I results in the generation of a signal which, in a counter controlled by a rotary transmitter, fastened to the plate cylinder 5, in the form of a pulse generator, fixes a count and stores this. A release member L is likewise fastened to the plate cylinder 5 in such a way that it passes a fixedly installed initiator or sensor M exactly at the moment when the end of the printing zone of the plate cylinder, that is to say the end E of the printing image, passes said connecting line;
this position is shown in Figure 4. The signal generated by the sensor M causes the storage of a second count.
Said two counts serve as reference values for the control of the drawing rollers which move the paper web 7 in the pilgrim-step mode. The difference between the two counts ie a measure of the printing zone actually effective and the print-free zone, in which the paper web is free. This measure is used to calculate the optimum deceleration and acceleration during the pilgrim step, by means of which the paper web is retracted and accelerated again, in order to guarantee a gap-free printing of the web. The sensors I and M can, for example, be inductive or optical sensors, in the case of ari inductive sensor, the release member FC or L being, for example, a steel block.
In general, therefore, the two signals and the time span between the two signals represent measured quantities which, at a given rotational speed of the cylinders 1 and 4, determine respectively the angular position and the length of the printing zone.
_ g _
The print-free zone between two printing zones according to the length G of a cylinder pit and consequently the timespan available for retracting the paper web are therefore, of course, also always the same.
Figure 1 shows the commencement of a printing operation and Figure 2 the end of this printing operation, that is to say after the cylinders have rotated in the direction of the arrows through an angle corresponding to the length D of the printing zone. If the maximum possible format is being printed, that is to say if the circumferential length of the printing image is virtually equal to the circumferential length of a printing saddle, then, after each printing operation, the paper web 7, when it passes the cylinder pits 3, 6 in a freely movable manner, must be braked, retracted and accelerated again in such a way that, depending on the printing speed, the obtainable deceleration and acceleration and the time taken to run through the pit, when printing commences again it assumes approximately the same position relative to the printing nip as that which it had assumed before the pilgrim step.
However, if smaller formats are to be printed, in which, as illustrated in Figures 1 and 2, the circumferential length B of a printing image is smaller than the circumferential length S of a printing saddle, then, after each printing operation, the paper web 7 must CA2ii7665 be retracted and accelerated again over a greater distance which ensures that, when printing commences again, the position of the paper web is additionally set back relative to the printing nip, opposite to the running direction, by the amount of the difference between the length of the printing zone D and the length of the printing image B, that is to say by the amount of the distance D-B.
In an example according to Figures 1 and 2, the print start A coincides with the image start, while the print end E of the.printing zone is located behind the image end F by the amount of said differential distance D-B, this difference being designated by Z. In this case, therefore, whenever printing commences again, the paper web 7 must assume a position relative to the printing nip which is offset rearward opposite to the running direction by the amount of the length Z, if printing images succeeding one another virtually without a gap are to be obtained on the paper web, as indicated in Figure 1.
The fact that the length D of the printing zone always remains ,constant, even when printing-3mages of smaller format are produced, has various disadvantages:
Since, after each printing operation, the paper web must additionally be retracted by the amount of a distance Z, this signifies, for smaller formats, that ie to say for larger Z, a considerably greater deceleration and acceleration of the paper web in comparison with the printing mode in which the maximum printing format is produced. At the same time, the following has to be taken into account:
When the paper web is released after the printing zone, it first moves a little way further according to the magnitude of the printing speed and of the obtainable deceleration, until it stops. This distance which the paper web has thereby covered is doubly critical, since it has to be taken into account once again during acceleration after the standstill of the paper web. The paper web therefore has to be retracted by double this distance, so that, after subsequent acceleration,- it arrives again with the printing speed at the same point which it occupied before the pilgrim step.
If the printing-saddle length is larger than the printing-image length, the paper web cannot be decelerated immediately after the end of the .printing image, but is transported further at the printing speed, .
before the pilgrim step can commence. As mentioned, this distance must be covered additionally in the pilgrim step.
However, since limits are placed on the deceleration and acceleration of the paper web, a reduction in the speed of the machine is necessary. This loss of capacity thus has a twofold effect, since, during each revolution, a shorter printing image is produced and, in addition, the speed must be reduced Furthermore, particularly in intaglio printing, the paper web is compacted by the very high pressure, which can amount to 80 t per meter of web width, and by the high-gloss chromium-plated surface of the printing plate,- in such a way that after retraction, during the subsequent printing operation, the pressed, bu-t not ink-printed portion Z of the paper web is printed With poorer quality than the non-pressed web. Figures 1 and 2 illustrate the excessively pressed web portion Z and the double-pressed portion P. The pressing of the portion Z
in Figure 1 originates from the preceding printing operation.
Objects of the present invention are avoidance of the disadvantages explained above, and to provide a printing unit in which no losses of capacity during the transition to a smaller format and also no double pressings of the paper web occur.
The invention provides a printing unit, for a web-fed printing machine with first and second cooperating cylinders which form a printing nip and which have a plurality of printing saddles separated by non-printing grooves, for printing a web running through the printing nip with variable formats adjoining one another, the web being transported at variable speed in a so-called pilgrim-step mode and after each printing operation, when it passes a groove, being retracted and accelerated again relative to the circumference of the two cylinders in such a way that successive printing images are lined-up virtually without a gap. The two cylinders are set angularly relative to one another, in respect of the positions of their printing saddles co-operating in the printing nip, depending on a format, in a manner offset by an amount of a circumferential distance which is at least approximately equal to a difference between a circumferential length of a printing saddle and a circumferential length of a printing image; so that a length of the impression zone, along which the two printing saddles clamp the web between them when they pass the printing nip, is only approximately as large as the circumferential length of a printing image. As on cylinders of a sheet-printing machine, the cylinders comprise cylinder pits forming said grooves. A first release member. is fastened on the circumference of the first cylinder on which the beginning of a printing saddle, with respect to a direction of rotation of the cylinder, corresponds to a beginning of a printing image, and a first sensor activatable by this release member is installed in proximity to the circumference of this cylinder. A
second release member is fastened on the circumference of the second cylinder, on which the end of a printing saddle corresponds to an end of the printing image, and a second sensor activatable by this release member is installed in proximity to the circumference of this cylinder. The release members and the sensors are so arranged and designed that the first sensor generates a Sa first signal at the moment at which the beginning of a printing saddle passes a connecting line between the axes of the two cylinders, and the second sensor generates a second signal at the moment at which the end of the printing saddle cooperating with said printing saddle and belonging to the second cylinder passes the connecting line. The signals and a time span between the two signals represent measured values for the angular position and the circumferential length of the printing zone, and are used for controlling movement of the paper web in the pilgrim-step mode during passage of an impression-free zone.
The invention is explained in more detail by Sb CA2ii7665 means of an exemplary embodiment with reference to the drawings.
As already mentioned, Figures 1 and 2 illustrate the printing operation of a known sheet-fed printing unit during the printing of a paper web which is transported in the pilgrim-step mode, and Figures 3 and 4 illustrate a printing unit according to the invention and its operation, Figure 3 showing the commencement of a printing operation and Figure 4 the end of this printing operation, that is to say after the two cylinders have rotated through an angle corresponding to the printing zones D.
Description of the preferred embodiment The two cylinders 1 and 4 illustrated in Figures 3 and 4 are, for example, the plate cylinder 4 and the impression cylinder 1 of an intaglio printing unit. The direction of rotation of the cylinders is indicated by curved arrows. The two cylinders have three printing saddles 2 and 5 of equal size and .with the circumferential length S which are arranged equally distantly along their circumference and -which are separated from one another by cylinder pits 3 and 6 with the circumferential length G. Printing coverings are mounted on the printing saddles 2 of 'the impression cylinder 1 and intaglio printing plates are mounted on the printing saddles 5 of the plate cylinder 4. The printing image on the printing plates has a circumferential length B which is smaller than the length S of the respective printing saddle 5.
In the example under consideration, the printing plates are mounted in such a way that the end E of the printing image coincides with that end of the printing saddle 5 at the rear in the direction of rotation, while the start A of the printing image B is offset corres-pondingly relative to the start of the printing saddle 5.
As illustrated, the impression cylinder 1 ie set angularly relative to the plate cylinder 4 so that the printing saddles 2 and 5 cooperating in the printing nip CA2ii7665 and belonging to the two cylinders are offset relative to one another in such a way that the circumferential length D of the printing zone, in which the cooperating printing saddles clamp the paper web 7, exactly includes only the format to be printed, that is to say the circumferential length B of the printing image. In practice, of course, the printing zone must be slightly longer than the printing image so as to allow for the free edges of the printing images applied to the paper web.
According to Figures 3 and 4, that end of the printing saddle 2 of the impression cylinder 1 at the front in the direction of rotation is offset relative to the front end of the printing saddle 5 by the amount of a portion which is equal to the difference S - B. As mentioned, in practice, the size of this offset is very slightly smaller.
Since, during the printing operation, as a result of this arrangement of these two cylinders 1 and 4, the clamping region of the web is shortened essentially to the circumferential length B of the format to be printed and consequently the print-free zone is enlarged to the length G + (S - B), more time is available for-retracting the paper web, that is to say for deceleration and acceleration. Moreover, the paper web does not need to be additionally retracted, since it is freed immediately after the end of the printing image and can be decel-erated. It is therefore essential that the paper web be clamped only directly in front of the start A of the printing image and be freed again immediately after the end E of the printing image. The advantage of this is that, in the case of constant deceleration and accel-eration moments which are drive-related, the machine speed can be increased by means of the lengthened print-free zone. The shorter repeat length in the case of a small printing image can therefore be compensated by a higher speed. The smaller the length B of the printing image, the larger the print-free zone which is available for retracting the correspondingly large paper-web portion.
CA2ii7665 A further advantage is that, during a printing operation, no additional paper-web portion is pressed outside the printing image and therefore double pressing according to the doubly pressed portion P of the paper web according to Figure 2 is absent, thereby preventing the quality from being impaired.
In the example according to Figures 3 and 4, the cylinder 1 could also be the plate cyclinder and the cylinder 4 the impression cylinder. In this case, the start A of the printing image coincides with that end of the printing saddle of the plate cylinder at the front in the direction of rotation, and it is this plate cylinder which is offset opposite to the direction of rotation in relation to the impression cylinder.
In order to utilize fully the above-described advantageous effects of an offset of the two cooperating cylinders, therefore, the printing image on a printing plate must either with its start A coincide with the start of the respective printing saddle or else with its end E coincide with the end of the respective printing saddle.
The embodiment illustrated in Figures 3 and 4 can also be an offset printing unit with two cooperating blanket cylinders, by means of which either a one-sided offset print can be produced With an inking of only one blanket cylinder or a recto/verso print can be produced with an inking of both blanket cylinders. All the advantages mentioned above also apply to an offset printing unit of this type.
The length D and the angular position of the printing zone can be determined automatically. For this purpose, in the example according to Figures 3 and 4, a release member R is fastened to the circumference of the impression cylinder 1 in such a way that it moves past a fixedly installed initiator or sensor I, responding to this member, exactly when the start of the printing zone, that is to say the start A of the printing image, passes the connecting line between the axes of the two cylinders 1 and 4; this position is shown in Figure 3. The response CA~ii7~~~
of the sensor I results in the generation of a signal which, in a counter controlled by a rotary transmitter, fastened to the plate cylinder 5, in the form of a pulse generator, fixes a count and stores this. A release member L is likewise fastened to the plate cylinder 5 in such a way that it passes a fixedly installed initiator or sensor M exactly at the moment when the end of the printing zone of the plate cylinder, that is to say the end E of the printing image, passes said connecting line;
this position is shown in Figure 4. The signal generated by the sensor M causes the storage of a second count.
Said two counts serve as reference values for the control of the drawing rollers which move the paper web 7 in the pilgrim-step mode. The difference between the two counts ie a measure of the printing zone actually effective and the print-free zone, in which the paper web is free. This measure is used to calculate the optimum deceleration and acceleration during the pilgrim step, by means of which the paper web is retracted and accelerated again, in order to guarantee a gap-free printing of the web. The sensors I and M can, for example, be inductive or optical sensors, in the case of ari inductive sensor, the release member FC or L being, for example, a steel block.
In general, therefore, the two signals and the time span between the two signals represent measured quantities which, at a given rotational speed of the cylinders 1 and 4, determine respectively the angular position and the length of the printing zone.
_ g _
Claims
1. A printing unit, for a web-fed printing machine with first and second cooperating cylinders which form a printing nip and which have a plurality of printing saddles separated by non-printing grooves, for printing a web running through the printing nip with variable formats adjoining one another, the web being transported at variable speed in a so-called pilgrim-step mode and after each printing operation, when it passes a groove, being retracted and accelerated again relative to the circumference of said cylinders in such a way that successive printing images are lined-up virtually without a gap;
in which unit said two cylinders are set angularly relative to one another, in respect of the positions of their printing saddles co-operating in the printing nip, depending on a format, in a manner offset by an amount of a circumferential distance which is at least approximately equal to a difference between a circumferential length of a printing saddle and a circumferential length of a printing image, so that a length of the impression zone, along which the two printing saddles clamp the web between them when they pass the printing nip, is only approximately as large as the circumferential length of a printing image;
wherein, as on cylinders of a sheet-printing machine, said cylinders comprise cylinder pits forming said grooves;
a first release member is fastened on the circumference of the first cylinder on which the beginning of a printing saddle, with respect to a direction of rotation of the cylinder, corresponds to a beginning of a printing image, and a first sensor activatable by this release member is installed in proximity to the circumference of this cylinder; and a second release member is fastened on the circumference of the second cylinder, on which the end of a printing saddle corresponds to an end of the printing image, and a second sensor activatable by this release member is installed in proximity to the circumference of this cylinder;
and wherein said release members and said sensors are so designed and arranged that the first sensor generates a first signal at the moment at which the beginning of a printing saddle of the first cylinder passes a connecting line between the axes of the first and second cylinders and the second sensor generates a second signal at the moment at which the end of the printing saddle cooperating with said printing saddle and belonging to the second cylinder passes said connecting line, and said signals and a time span between the two signals represent measured values for the angular position and the circumferential length of the printing zone and are used for controlling movement of the paper web in the pilgrim-step mode during passage of an impression-free zone.
in which unit said two cylinders are set angularly relative to one another, in respect of the positions of their printing saddles co-operating in the printing nip, depending on a format, in a manner offset by an amount of a circumferential distance which is at least approximately equal to a difference between a circumferential length of a printing saddle and a circumferential length of a printing image, so that a length of the impression zone, along which the two printing saddles clamp the web between them when they pass the printing nip, is only approximately as large as the circumferential length of a printing image;
wherein, as on cylinders of a sheet-printing machine, said cylinders comprise cylinder pits forming said grooves;
a first release member is fastened on the circumference of the first cylinder on which the beginning of a printing saddle, with respect to a direction of rotation of the cylinder, corresponds to a beginning of a printing image, and a first sensor activatable by this release member is installed in proximity to the circumference of this cylinder; and a second release member is fastened on the circumference of the second cylinder, on which the end of a printing saddle corresponds to an end of the printing image, and a second sensor activatable by this release member is installed in proximity to the circumference of this cylinder;
and wherein said release members and said sensors are so designed and arranged that the first sensor generates a first signal at the moment at which the beginning of a printing saddle of the first cylinder passes a connecting line between the axes of the first and second cylinders and the second sensor generates a second signal at the moment at which the end of the printing saddle cooperating with said printing saddle and belonging to the second cylinder passes said connecting line, and said signals and a time span between the two signals represent measured values for the angular position and the circumferential length of the printing zone and are used for controlling movement of the paper web in the pilgrim-step mode during passage of an impression-free zone.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH2804/93-1 | 1993-09-17 | ||
| CH280493 | 1993-09-17 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2117665A1 CA2117665A1 (en) | 1995-03-18 |
| CA2117665C true CA2117665C (en) | 2006-01-10 |
Family
ID=4241967
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002117665A Expired - Fee Related CA2117665C (en) | 1993-09-17 | 1994-09-08 | Printing unit for a web-fed printing machine |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0649740B1 (en) |
| JP (1) | JP3464536B2 (en) |
| KR (1) | KR100336921B1 (en) |
| CN (1) | CN1051281C (en) |
| AT (1) | ATE168071T1 (en) |
| AU (1) | AU7290994A (en) |
| CA (1) | CA2117665C (en) |
| DE (1) | DE59406405D1 (en) |
| RU (1) | RU2114741C1 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2328501B (en) * | 1996-04-12 | 1999-12-08 | Mark Baker | Ventilation fans |
| JPH10116050A (en) * | 1996-10-14 | 1998-05-06 | Sony Corp | Contour correction circuit and rgb monitor |
| JP4740314B2 (en) * | 2005-03-30 | 2011-08-03 | ゴス インターナショナル アメリカス インコーポレイテッド | Web offset printing machine with pivoted tacker |
| EP2722179A1 (en) * | 2012-10-18 | 2014-04-23 | KBA-NotaSys SA | Intaglio printing press and method of monitoring operation of the same |
| CN105015156B (en) * | 2015-07-22 | 2018-06-26 | 河北海贺胜利印刷机械集团有限公司 | Intermittent forward direction leapfrog printing machine and its control method and leapfrog draft gear |
| DE102016207398B3 (en) * | 2015-09-09 | 2016-08-18 | Koenig & Bauer Ag | Machine arrangement for the sequential processing of a plurality of arcuate substrates each having a front side and a rear side |
| RU2624717C1 (en) * | 2016-03-11 | 2017-07-05 | Закрытое акционерное общество "Санкт-Петербургская Образцовая Типография" | Method of tool cliche producing |
| CN107297947B (en) * | 2017-06-26 | 2022-08-09 | 浙江炜冈科技股份有限公司 | Novel intermittent offset press |
| CN108002013B (en) * | 2017-12-22 | 2024-05-24 | 宜宾丝丽雅股份有限公司 | Viscose filament yarn feeding device |
| CN108327387B (en) * | 2018-03-22 | 2024-04-26 | 东莞市鸿程机械有限公司 | Drum-type meshbelt polychrome lithography apparatus |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3645203A (en) * | 1969-10-02 | 1972-02-29 | Fred M Slavic | Press for web printing having intermittent paper-feeding means |
| FR2309337A1 (en) * | 1975-04-29 | 1976-11-26 | Seailles Tison Atel Const Meca | Feed control for variable paper sizes - provides adjustment through differential without stopping printing machine using stepping motors |
| US4137624A (en) * | 1977-10-31 | 1979-02-06 | Amp Incorporated | Apparatus for inserting wires into terminals in a connector |
| FR2454369A1 (en) * | 1979-04-18 | 1980-11-14 | Codimag | METHOD AND DEVICE FOR CONTROLLING THE SCROLLING OF A TABLECLOTH IN A PRINTING MACHINE |
| EP0084939A1 (en) * | 1982-01-20 | 1983-08-03 | Rofrep Limited | Method and means for printing with a variable repeat length |
| GB2190042B (en) * | 1986-05-01 | 1990-11-21 | Rofrep Ltd | Printing of successive images onto an elongate web. |
-
1994
- 1994-09-08 DE DE59406405T patent/DE59406405D1/en not_active Expired - Fee Related
- 1994-09-08 EP EP94810519A patent/EP0649740B1/en not_active Expired - Lifetime
- 1994-09-08 AT AT94810519T patent/ATE168071T1/en not_active IP Right Cessation
- 1994-09-08 CA CA002117665A patent/CA2117665C/en not_active Expired - Fee Related
- 1994-09-12 AU AU72909/94A patent/AU7290994A/en not_active Abandoned
- 1994-09-15 CN CN94116304A patent/CN1051281C/en not_active Expired - Fee Related
- 1994-09-16 KR KR1019940023576A patent/KR100336921B1/en not_active IP Right Cessation
- 1994-09-16 RU RU94033483A patent/RU2114741C1/en not_active IP Right Cessation
- 1994-09-16 JP JP22175894A patent/JP3464536B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0649740B1 (en) | 1998-07-08 |
| CA2117665A1 (en) | 1995-03-18 |
| JPH07148913A (en) | 1995-06-13 |
| RU2114741C1 (en) | 1998-07-10 |
| CN1116986A (en) | 1996-02-21 |
| RU94033483A (en) | 1996-06-27 |
| ATE168071T1 (en) | 1998-07-15 |
| DE59406405D1 (en) | 1998-08-13 |
| CN1051281C (en) | 2000-04-12 |
| KR950008126A (en) | 1995-04-17 |
| JP3464536B2 (en) | 2003-11-10 |
| AU7290994A (en) | 1995-03-30 |
| KR100336921B1 (en) | 2002-11-27 |
| EP0649740A1 (en) | 1995-04-26 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |