JP3464536B2 - Print unit of web printing machine - Google Patents

Abstract

The printing unit has two interacting nip-forming cylinders (1, 4) which exhibit printing saddles (2, 5) separated by cylinder grooves (3, 6). The paper web (7) passing the nip is transported in pilgrim-step operation in order to print adjoining formats. The two cylinders (1, 4) can be adjusted at an angle, with respect to the position of their printing saddles (2, 5) interacting in the nip, offset with respect to one another by 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 printed image. Consequently, the printed zone is only approximately as large as the printed image, and the printing-free zone available for drawing back the paper web is correspondingly enlarged. <IMAGE>

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print unit of a web printing machine having two cooperating cylinders, and more specifically, both cylinders define a print nip, and a web traveling through the print nip. A printing unit for a sheet having a plurality of print saddles separated by cylinder pits for printing various formats adjacent to each other, wherein the web is a so-called pilgrim-step mode.
od) at varying speeds so that when the web passes through the cylinder pits after each printing operation, successive printed images are effectively aligned (line-up) without gaps to the outer circumference of both cylinders. A printing unit of this type adapted to be relatively retracted and then accelerated again.

[0002]

2. Description of the Related Art This type of print unit is USP
5,062,360. These known printing units are equipped with two cooperating blanket cylinders (blanket cylinders), both cylinders being inked into the printed image so as to obtain recto / verso prints. Or an interglio printing unit comprising a pressing cylinder (impression cylinder) and a plate cylinder (plate cylinder) cooperating with it. The use of a sheet printing unit for printing on a continuous paper web is advantageous because it eliminates the difficult and time consuming production of a plate cylinder and a pressure cylinder or two blanket cylinders with a continuous seamless outer peripheral surface. In this case, a simple cylinder is used instead, which has the print saddles separated from one another and to which the individual print plates or print covers are individually mounted. These plates and print covers can be installed, adjusted and replaced without difficulty. Furthermore, transport of the paper web in the so-called pyriglyme step mode results in adjacent images as a result of non-printing gaps between the images and thus no unprinted strips between successive printed images due to cylinder pits. As a result, images are produced without the loss of paper. For this purpose, specifically USP 5,062,3
As described in 60, the transfer of the paper web is first braked by the control means when the unclamped paper web passes through the mutually aligned cylinder pits of both cylinders after each printing operation, then retracts and finally. And is controlled to be accelerated again to operating speed before being re-clamped between subsequent cooperating print saddles of both cylinders for subsequent printing operations. The distance the paper web is retracted relative to the outer circumference of both cylinders is chosen so that successive printed images are printed with virtually no gaps. Therefore, in order to increase this effect, the pyriglyme step operation is carried out after this pyriglyme step with the paper web at least at approximately the same position with respect to the print nip between the two cylinders, i.e. before the pyriglyme step. Must be controlled to be.

As a result of the proper adoption of the pyriglim step operation, gaps between adjacent images are printed on the same printing machine, even in the case of varying formats of printed images, ie shortened formats. It is possible to print without. The print format is changed by mounting a print plate of the same size as the shorter image, so the print area remains the same and is not shortened.

In known web presses of this type, the two cylinders are in diametrically opposite positions when their print saddles cooperate in the print nip, FIGS.
Are set relative to each other as shown in FIG. In both figures, both cylinders 1, 4 are provided with three print saddles 2, 5 each having an annular length S. Therefore, at the same time the paper web 7 is clamped along the print area between both cylinders, the length D of such a print area being equal to the annular length S of the print saddle, regardless of the annular length B of the print image, i.e. the format. Exactly the same size.

Of course, the time span available for retracting the print-free area between adjacent print areas and the resulting paper web for the cylinder pit length G is always the same.

FIG. 1 shows the start point of each print operation.
FIG. 2 shows the end of each printing operation, that is, the time after both cylinders have been rotated in the direction of the arrow over an angle corresponding to the length D of the printing area. If the largest possible format is to be printed, that is to say the annular length of the printed image is virtually equal to the annular length of the print saddle, after each printing operation the paper web 7 has the free movement of the cylinder pits 3,6. When passing through, depending on the print speed, possible deceleration and acceleration and the time it takes to run the pit, it is almost the same as the web occupied before the pyriglyme step when printing was started again. It must be braked, retracted, and accelerated to occupy a relative position to the print nip.

However, if a relatively small format is printed as shown in FIGS. 1 and 2, the annular length B of the printed image is less than the annular length S of the print saddle, in which case each print operation is Later Paper Web 7
Must be retracted and accelerated again over a relatively large distance. Due to this distance, when the printing is started again, the position of the paper web is added to the print nip backward by the difference between the length of the print area D and the length of the print image B which are opposite in the web running direction, that is, the distance D-B. Guaranteed to be set automatically.

In the example of FIGS. 1 and 2, the print start point A coincides with the image start point, and the print rear end E of the print area is located behind the image end F by the difference distance D-B. . This difference is represented by Z. In this case, therefore, the paper web 7 must occupy the following position relative to the print nip whenever printing is restarted. That is, this position is offset relative to the print nip backwards in the direction of travel by an amount of length Z, provided that the printed image is sequentially obtained on the paper web as shown in FIG. Doing (mismatch)
Must occupy a position.

The fact that the length D of the print area remains constant even when a print image of a relatively small format is produced leads to various disadvantages.

That is, since the paper web must additionally retract by the amount of distance Z after each print operation,
This means that for a relatively small format, i.e. a relatively large Z, it will require a greater degree of deceleration and acceleration compared to the print mode in which the largest print format is produced. At the same time, the following must be considered.

That is, when the paper web is released after the print area, it advances further a short distance from the print speed until it stops at the reduced speed.
This advance distance, which the paper web covers, is a double problem. This is because this distance has to be taken into account again during the acceleration phase after stopping the paper web. Therefore, the paper web must be retracted by twice this distance, and after subsequent acceleration it should again reach with print speed the same point that the web occupied before the pyriglyme step.

If the print saddle length is greater than the print image length, the paper web cannot be slowed down immediately after the end of the print image and will be transported further at print speed before the pyriglyme step can begin. . As mentioned above, this transfer distance needs to be additionally covered in the pyriglyme step.

However, since there is a limit to the deceleration and acceleration of the paper web, it is necessary to reduce the speed of the printing machine (printing speed). This loss of performance effectively doubles. This is because a relatively short print image is created during each rotation, which additionally requires a reduction in speed.

Further, in particular, intaglio print (int
In aglio printing, the paper web is at a very high pressure, which can reach a value of 80 t / m of web width, and the high gloss chrome plating surface of the print plate causes the paper web to be pressed during the next printing operation after retraction. The part Z, which is not printed with ink, is compressed so as to be printed (imprinted) with a quality lower than that of the unpressurized web. 1 and 2 show a web portion Z which is over-pressurized and a portion P which is double-pressurized. The pressurization of the portion Z in FIG. 1 is due to the preceding printing operation.

[0015]

SUMMARY OF THE INVENTION The object of the present invention is to avoid the above mentioned disadvantages and to improve the performance loss and the double pressurization of the paper web during the transition to a relatively small format. To provide a print unit.

[0016]

According to the present invention, various formats adjacent to each other are printed on a web (7) running through the print nip as a print unit for forming a print nip and receiving a sheet supply. A printing unit of a web printing machine comprising two cooperating cylinders (1,4) having a plurality of print saddles (2,5) separated by cylinder pits (3,6). Thus, the web is transported at varying speeds in the so-called pyriglyme step mode, and after each printing operation at the time of passing through the cylinder pits so that the subsequent printed images are effectively aligned without gaps. In such a type of print unit, which retreats relative to the outer circumference of the cylinder (1, 4) and is accelerated again, both Regarding the positions of the cooperating print saddles (2, 5) in the print nip, the binders (1, 4) have a relative angular position with respect to the annular length (S) of the print saddles (2, 5) and the printing. A print area that is set to stagger an amount by an annular distance that is at least approximately equal to the difference in the annular length (B) of the image, thereby clamping the web (7) between the saddles as they pass through the print nip. A printing unit of a web printing machine is provided, characterized in that the length (D) is at least approximately the same as the annular length (B) of the printed image.

[0017]

Since the relative angular positions of both cylinders are set so as to be shifted by the difference between the print saddle length S and the print image length B, the angle setting is adjusted for each print image length at any time, so that the print is performed. After the end of the image, it is always guaranteed that the web will be released from the cylinder clamp by the print pits. As a result, the above-mentioned problems, which have been conventionally problems, are avoided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The two cylinders 1 and 4 shown in FIGS.
For example, a plate cylinder (plate cylinder) 4 and an intaglio (i
This is a pressing cylinder (impression cylinder) 1 of an ntaglio print unit. The direction of rotation of the cylinder is indicated by the curved arrow. Both cylinders each have three print saddles 2, 5 of the same size with an annular length S arranged at equal intervals along the cylinder circumference. The saddles of both cylinders are separated by cylinder pits 3 and 6 having an annular length G, respectively. A print cover is attached to the print saddle 2 of the pressing cylinder 1, and an intaglio print plate is attached to the print saddle 5 of the plate cylinder 4. The printed image on the print plate has an annular length B that is smaller than the length S of each print saddle 5.

In this description example, a print plate (printing plate) is used.
Is mounted so that the rear end E of the print image at the rear when viewed in the rotational direction coincides with the rear end of the print saddle 5, while the start end A of the print image B differs from the start end of the print saddle 5. It corresponds to. As shown, the pressing cylinder 1 has print saddles 2 and 5 belonging to both cylinders cooperating in the print nip that are offset (offset) by cooperating such print saddles clamping paper web 7. It is set to a specific repositioning with respect to the plate cylinder 4 so that the annular length D of the printing area exactly contains only the format to be printed, ie the annular length B of the printed image. Of course, in practice, the print area should be slightly longer than the print image so that the free edge of the print image can be applied to the paper web.

According to FIGS. 3 and 4, the front end of the front print saddle 2 when viewed in the rotational direction of the pressing cylinder 1 is different from the front end of the print saddle 5 by an amount equal to the difference SB. As mentioned above, the size of the offset, or offset, is actually very small.

During the printing operation, as a result of this configuration of both cylinders 1, 4, the clamping area of the paper web is shortened to the annular length B of the format to be printed, resulting in a print-free area of G + (SB). ),
More time can be used to retract (retract) the paper web, ie to decelerate and accelerate.
Moreover, the paper web can be freed and decelerated immediately after the end of the printed image, so that it does not need to be additionally retracted. Therefore, the paper web is necessarily clamped directly only before the beginning A of the printed image and is re-opened immediately after the end E of the image. The advantage is that in the case of constant drive-related deceleration and acceleration movements, the machine speed can be increased by the long print-free area. Therefore, the reduced repeat length in the case of small printed images can be compensated by the great speed. As the length B of the printed image is reduced, the print-free area available for retracting the corresponding larger paper web portion is increased.

A further advantage is that no additional paper web portion is pressed to the outside of the printed image during the printing operation, and thus, as in the double-pressed portion P of the paper web according to FIG. There is no heavy pressing and thus impairing print quality is prevented.

In the example according to FIGS. 3 and 4, the cylinder 1 can be a plate cylinder and the cylinder 4 can be a pressing cylinder. In this case, the starting point A of the print image coincides with the front end of the print saddle of the plate cylinder located in front in the rotational direction, and the plate cylinder is misaligned with the pressing cylinder on the opposite side when viewed in the rotational direction. There is.

In order to take advantage of the above-mentioned beneficial effects of offset of the two cooperating cylinders, does the printed image on the printing plate coincide with the starting point of the respective print saddle at its starting point A? , Or the trailing edge E must match the trailing edge of each print saddle.

The example shown in FIGS. 3 and 4 may be an offset printing unit with two cooperating blanket cylinders. With both blanket cylinders, one-sided offset printing can be performed with one blanket cylinder inking, and recto / verso printing with both blanket cylinder inking. Can be performed in. All the benefits mentioned above apply to this type of offset printing unit.

The length D and the angular position of the print area can be automatically determined. For this purpose, in the example of FIGS. 3 and 4, a release member K is fixed to the outer circumference of the pressing cylinder 1. This attachment is such that the release member has a corresponding fixed initiator.
at the correct start of the print area, that is, when the starting point of the print image passes the line connecting the axes of both cylinders 1 and 4. The location of this pass is shown in FIG. A signal is generated in response to the sensor I, which locks and stores the first counter in a counter controlled by a rotary transmitter in the form of a pulse generator which is fixed to the plate cylinder 5. Similarly, the release member L is fixed to the plate cylinder 5. This attachment is performed when the release member causes the rear end of the print area of the plate cylinder, in other words, the rear end E of the printed image to pass through the line connecting the two axial lines, and the fixed initiator, i.e., the sensor M, is instantaneously moved. To pass through. This passing position is shown in FIG. The signal generated by sensor M is stored as a second count. Both counts are based on the pyriglym step mode (pi
paper web at ligrim step mode)
Serves as a reference value for the control of the pulling roller that moves the. The difference between both counts is actually a measure of the effective print area and the print free area where the web is free. This measure is used to calculate the optimal deceleration and acceleration during the pyriglyme step to ensure gap-free printing of the web, which causes the paper web to be retracted and It will be accelerated. The sensors I and M can be, for example, inductive sensors or optical sensors. In the case of an inductive sensor, the release member K or L is a steel block, for example.

In general, the two types of signals and the time span between the two signals represent measured quantities that respectively determine the angular position and the length of the print area at a predetermined rotation speed of both cylinders 1 and 4.

[0028]

Even when the format length of the print image is shorter than the print saddle length, a print without a blank space (gap) between the formats can be realized as in the case where the both lengths are the same.

[Brief description of drawings]

1 is an illustration showing a printing operation of a known sheet printing unit during the printing of a paper web transported in the pyriglyme process mode.

FIG. 2 is an explanatory diagram showing another time point during the same printing as in FIG.

FIG. 3 is an explanatory diagram showing a print unit according to the present invention and a start time of its operation.

FIG. 4 is an explanatory diagram showing a time point when the operation of FIG. 3 is finished, that is, a time point after two cylinders are rotated by an angle corresponding to the print area D;

[Explanation of sign]

1,4 ... Cylinder 2,5 ... Print saddle 3, 6 ... Print pit 7 ... Web D: Print area length D S ... Print saddle length B: Print image (format) length

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41F 33/06 B41F 13/04

Claims (2)

(57) [Claims] 1. A cylinder pit (3, 6) for printing various formats adjacent to each other on a web (7) running through the print nip, as a print unit forming a print nip and receiving a supply of sheets.
A print unit of a web printing machine comprising two cooperating cylinders (1,4) having a plurality of print saddles (2,5) separated by a web, the web being a so-called pyriglyme step mode. Both cylinders (1, 2) after each printing operation at the time of passing through the cylinder pits, such that the subsequent printed images are effectively aligned without gaps, transported at varying speeds in
In such a type of printing unit, which is retracted relative to the outer circumference of 4) and is accelerated again, both cylinders (1, 4) are related to the position of the cooperating print saddles (2, 5) in the print nip. Depending on the format, the relative angular positions of the print saddles (2, 5) are set to differ from each other by an annular distance that is at least approximately equal to the difference between the annular length (S) of the print saddle (2, 5) and the annular length (B) of the printed image. The length (D) of the print area that clamps the web (7) between the saddles as they pass through the print nip is at least about the same as the annular length (B) of the printed image. A printing unit of a web printing machine characterized by the above. 2. A first release member (K) is fixed to the outer periphery of a cylinder (1) where the start point of the print saddle (2) corresponds to the start point (A) of the print image when viewed in the cylinder rotation direction, and the release is performed. First activated by member (K)
Sensor (I) is installed in the vicinity of the outer circumference of the cylinder (1), and the end of the print saddle is the second end on the outer circumference of another cylinder (4) corresponding to the end (E) of the print image.
The release member (M) is fixed, and the second sensor (M) activated by the release member (L) is installed near the outer circumference of the cylinder (4). L) and both sensors (I, M), the first sensor (I) when the starting point of the print saddle (2) of the first cylinder (1) passes through the connecting line connecting the axes of both cylinders (1, 4). ) Generates a first signal and a second end of the print saddle (5) of the second cylinder (4) cooperating with the print saddle (2) passes through the connecting line.
The sensor (M) is arranged and configured to generate a second signal, the time span between the first and second signals and the two signals being representative of the measured quantity with respect to the angular position and the annular length of the printing area. , The paper web (7) serves to control the movement of the paper web (7) in the pyriglyme step mode as it passes through the print free area.
The printing unit described in.