CH716110A1 - Method for clamping and adjusting a printing substrate in a printing machine. - Google Patents

Abstract

The procedure for clamping and adjusting a printing substrate (3) is carried out by measuring the tension on the side edges of the substrate (3) and displaying the measured values optically or acoustically on signal towers (13) and by moving the substrate (3) until the displayed measured values are balanced .

Description

The invention relates to a method for clamping and adjusting a printing substrate in a printing machine for processing roll material according to the preamble of claim 1. The invention also relates to a device according to the preamble of patent claim 4 for carrying out the method according to claim 1.

Inkjet printing systems print substrates in almost any dimensions which are only limited by the width of the machine. On the one hand, such substrates are printed on flatbed machines, i. the substrates such as plates made of various materials, paper, foils made of various materials, etc. lie on a vacuum table and are held firmly on this during the printing process. In this case, a printing unit is guided back and forth on the one hand and successively from front to back on the other and thus prints essentially the entire surface of the substrate held on the printing table. If, however, substrates have to be printed which are fed to the printing system from a roll, it is difficult to reliably position the substrate, which is fed from the back, for example, from the roll and taken up on a further roll or shaft at the front. In the printing area under the printing unit, the substrate is not or only slightly sucked onto the printing table by a vacuum. However, the substrate fed to the printing area from the roll must be guided exactly at right angles to the direction of movement of the print head in the transport direction in order not to wander laterally from the entrance to the exit area. To achieve this, at the beginning of a print job, the continuously fed substrate is manually adjusted between the input-side deflection rollers and the output-side deflection rollers and then, in the hope that this setting can be maintained, the printed substrate is printed and wound up on the front shaft.

An object of the present invention is to provide a method and a device with which or the continuously fed substrate can be guided in the correct position without lateral displacement during the printing process on the printing machine. Another object of the invention is to create a device with which the method can be carried out and which in particular facilitates the setup at the beginning of a new print job and / or readjustment - if necessary - and which device can maintain the set parameters.

This object is achieved by a method according to the features of claim 1 and a device according to the features of the device according to claim 4. Advantageous embodiments of the method and the device are described in the dependent claims.

By detecting, measuring and equalizing the stresses on the longitudinal edges of the substrate in the area of the two ends of a deflecting shaft arranged on the feed side, it is possible that the drawn-in substrate enters the printing area of the printing machine in an exactly aligned manner. For the comparison of the voltage values at both edge areas of the substrate, optical signals or also acoustic signals can be output, which make it easier for the operator to optimally align the incoming substrate. By displaying the measured values, which do not have to be absolute, the different values can be easily compensated for on the signal pillars due to different heights of the measured values by shifting the substrate sideways by hand until the specified values on the pillars are at the same height. Alternatively, the signal towers can also show different colors if the values are the same on both edges. The same also applies to acoustic information, in that, for example, interrupted tones are reproduced in the case of differently measured values and, as soon as the compensation has taken place, a continuous tone. It is therefore possible in the simplest way to compensate for the tensile forces purely via the optical information and without an exact reproduction of different tensile forces on the substrate. It is also possible to proceed in the same way on the take-off side if the forces acting on the edge areas at the deflection are different there. According to the procedure on the input side, the acting forces can also be compensated on the output side by slight lateral displacement of the substrate, and this can ensure that the substrate is guided exactly from the input to the output of the printing area. The device necessary for this is based solely on the measurement of the forces exerted by the substrate at the deflection points in the area of the two edges of the substrate. Thanks to a display on the signal towers, the employee at the printing press can always see whether something has changed during the printing process and whether a correction may have to be made. The pressure forces are measured in the simplest and, above all, cost-effective way using pressure or displacement sensors. For the optical or acoustic display, a simple signal processing is necessary, which transmits the pressure values to the signal towers. It is not necessary to change the position of the infeed and outfeed rollers, as these rollers are mounted very precisely. Nevertheless, if there are continuous shifts, it is possible to readjust the position of the two rollers. In a particularly advantageous embodiment of the method, the tensile forces on the edge area can also be monitored in the same way on the pull-off side of the printed substrate and conclusions about the unprinted substrate to be run can be displayed and corrected. Pneumatic or electrotechnical means can be used to compensate or correct the tension conditions in the inflowing and outflowing substrate areas if a predetermined tolerance limit is exceeded. Even the smallest voltage differences cause the substrate to shift on the printing table by less than a tenth of a millimeter. These are very quickly visible to the naked eye in printed images. In a particularly advantageous embodiment, the pressure forces on the elastically mounted shaft are absorbed and the shaft is adjusted by mechanical elements to compensate for the pressure forces on the two shaft bearings. To monitor the tension on the incoming substrate, pressure measuring sensors, such as pressure cells, can also be used, which detect pressure changes and / or pressure values and transmit these to suitable actuators for acoustic or optical display or to regulate the pressure forces.

[0006] The invention is explained in more detail using an illustrated exemplary embodiment. Show it: <tb> <SEP> FIG. 1 shows a schematically illustrated printing machine, the printing unit of which has been omitted for the sake of clarity, from a view obliquely from the front, <tb> <SEP> Figure 2 the printing machine in perspective from behind and, <tb> <SEP> Figure 3 shows a vertical section through the printing press.

In Figures 1 and 2 of a printing machine 1, only the printing substrate 3 and the intake side a pair of intake rollers 5, 7 and the withdrawal side a pair of take-off rollers 9, 11 are shown schematically. Between the feed roller 5 and the take-off roller 9, which guide the substrate 3 over a printing table 4, the substrate 3 can be seen stretched over an area. The perforated printing table 4, which is located between the feed roller 5 and the take-off roller 9 under the substrate 3 and can be connected to a vacuum source, is shown. Four signal columns 13 can also be seen, on which different states of the printing machine, e.g. can be read as light strips 14 or rows of light points. At the bottom of the back of the printing machine 1 is a winding roll 15 with an unprinted substrate 3 wound thereon, and on the front side a still empty drivable roll 17 for winding the printed substrate 3 is shown. A first tensioning roller 19 is visible between the two draw-in rollers 5 and 7 or between an upper draw-in roller 5 and the winding roller 15, offset from their axes. A second tensioning roller 21 is arranged analogously on the take-off side. The second tension roller 21 is also rotatably mounted offset to the axes of the two take-off rollers 9, 11, so that the substrate 3 is deflected both on the retraction side and on the extraction side. The two tension rollers 19 and 21 are mounted displaceably in the horizontal guide devices and are held by spring elements 23 and 25 in the direction of the center of the printing press 1. Metallic or pneumatic spring elements 23 can be used as spring elements 23, the forces of which can be adjusted manually or electrically driven. The tensioning rollers 19, 21 function, as it were, as spring-loaded dancer rollers. With pressure sensors or displacement sensors 27, 29, the tension of the substrate 3 in the conveying direction on the input and / or output side of the printing machine 1 can be adjusted at both ends of the tensioning rollers 19, 21, that is, on both sides. The measurement results can be visually displayed directly or indirectly on the signal columns 13 and the displayed values can be compared by the eye. If the measured values are not the same on both sides, there is an indication that the substrate 3 is not fed to the take-off roller 9 evenly tensioned over its entire width, i.e. the longitudinal edges of the substrate 3 do not lie exactly in the predetermined conveying direction. This allows the substrate 3 to migrate to the side. In addition to the display of the measured tension values at the two ends of the tension roller 19 on the signal columns 13, e.g. by means of light strips or points of light of unequal height, there is in an advantageous embodiment the possibility of displaying the different colors of the lights differently as long as the values at the two ends of the tensioning roller 19 do not match. Alternatively, the light columns can flash as long as there is no match between the two values. In a further embodiment of the display, unequal values can be indicated acoustically by a tone that either disappears or begins as soon as a corresponding correction has been made by manually moving the substrate 3 on the way from the feed roller 5 to the take-off roller 3.

A now precisely adjusted substrate 3 can be guided over the take-off roller 9 and over the second tension roller 21 to the lower take-off roller 11 and from there to the winding roller 17 for printed substrate 3 and attached to the latter. Before the start of printing on the substrate 3, the latter can be wound up somewhat on the roller 17 and the tensions at the ends on the second tensioning roller 21 can be checked to see whether it is evenly loaded at both ends by the substrate 3 surrounding it. This load on the second tensioning roller 21 can also be displayed on the signal columns 13, which are located on the trigger side. If the subtraction of the substrate 3 does not take place over the entire width of the substrate 3, a corresponding correction must be made here as well as on the input side. This is done by changing the fastening of the front edge of the substrate 3 on the roller 17 in the same way as on the input side by moving the substrate on the printing table.

In a further embodiment of the device, the first _Spannrolle 19 and, if a second tensioning roller 21 is available, the second tensioning roller 21 at their ends in bearing blocks (bearing blocks not shown), which are each connected to a load cell To detect voltage differences, that is to say forces on the tensioning rollers 19, 21 and to forward the corresponding values to the signal columns 13 via an evaluation unit (not shown). The tensioning pulley 19 or the tensioning pulleys 19 and 21 therefore do not have to be slidably mounted, but it is sufficient if these are attached to the load cells in minimal areas. Such a mounting of the tensioning rollers 19, 21 also makes it possible to manually shift the substrate 3 laterally on the printing table 4 until pressure equalization is achieved at the ends of the tensioning rollers 19, 21. The absolute forces do not play a role here; rather, only the balancing of the forces at the respective ends of the tensioning rollers 19, 21 allow optimal adjustment of the substrate 3 and allow optimal alignment of the substrate 3 on the printing table 4.

Legend of the reference symbols

1 printing machine 3 substrate 4 printing table 5 feed roller 7 feed roller 9 take-off roller 11 take-off roller 13 signal column 15 winding roller 17 winding roller 19 first tensioning roller 21 second tensioning roller 23 spring element 25 spring element 27 pressure sensor

Claims (6)

1. A method for clamping and adjusting a printing substrate (3) on the printing table (4) of a printing machine, in which the substrate (3) from a first winding roll (15) with unprinted substrate (3) over a printing area to a second winding roll (17 ) is guided and wound up for the printed substrate (3), characterized by the following process steps: a1) drawing in the front edge of the substrate (3) from the first winding roller (15) via a fixed feed roller (5) and a first tension roller (19), which is elastically mounted at both ends, b1) transferring the leading edge over the flat printing area over a take-off roller (9) and c1) Aligning the side edges of the substrate (3) in the conveying direction by bringing about equally large common tensile forces at both ends of the first tensioning roller (19) with the help of visual or acoustic signals The conveying direction is shifted until the signals match on both sides. 2. The method according to claim 1, characterized in that a2) the front edge of the substrate (3) is guided around two take-off rollers (9, 11) and a second tensioning roller (21) arranged offset thereto, and b2) aligning the side edges of the substrate (3) before connecting its front edge to the second winding roll (17) with the aid of visual or acoustic signals on the take-off and / or draw-in side. 3. The method according to any one of claims 1 or 2, characterized in that the substrate (3) is sucked between the feed roller (5) and the take-off roller (9) on the printing table (4) with negative pressure. 4. Device for carrying out the method according to one of claims 1 to 3, comprising a printing table (4) with a first deflection element arranged on the intake side, a winding roller (15) for unprinted substrate (3), and on the withdrawal side a second deflection element and a second winding roller ( 17) for winding up the printed substrate (3), characterized in that between the first deflection element and the first winding roller (15) a first tensioning roller (19) for deflecting the substrate (3) is arranged between the printing table (4) and the first winding roller (15) and that the two ends of the tensioning roller (19) with a pressure or displacement sensor (27) are connected and with a signal processing system for the evaluation and display of the measured values. 5. Apparatus according to claim 4, characterized in that a second tension roller (21) for deflecting the printed substrate (3) is arranged on the take-off side between the second deflection element (9) and the second winding shaft (17) and that the two ends of the second tension roller (21) are connected to a pressure or displacement sensor (27) and to a signal processing system for evaluating and displaying the measured values. 6. Device according to one of claims 4 or 5, characterized in that the measured values are displayed on signal pillars (13) on which the measured values can be visually or acoustically displayed and compared with one another.