CN1289294A - Method and device for stepwise printing of a continuous material web - Google Patents

Abstract

In a method for step-printing continuous roll material (4), particularly a fiber web, the method is carried out using one or more nozzles of a printing section (9). According to the invention, the roll material (4) is guided upward through the one or more nozzles under constant tension. During the implementation of this method, no large amount of waste is generated, and substrate loss is reduced at the start of printing. Furthermore, the components of the device are prevented from being contaminated by printing ink. An apparatus for implementing this method is also described.

Description

Method and apparatus for printing continuous webs step by step

The present invention relates to the stepwise printing of continuous webs, especially webs, with one or more nozzles of a printing station.

This method is well known. In existing methods, the substrate to be printed is resin-bonded to an (endless) belt. After the desired design is printed on the substrate with the nozzles of the printing station, the substrate is torn off from the tape. During this process, matrix material, residual ink, etc. remain on the resin. Rinse the resin off the tape so that the tape can be reused. Since the resin contains dyes that are harmful to the environment, the resulting wastewater must be treated as chemical waste. Operating costs increase due to the large volumes of wastewater to be treated.

It is an object of the present invention to provide a method of stepping printing webs, especially webs, which produces no waste water containing resins and dyes, thereby reducing operating costs.

Another object of the present invention is to provide a method in which the parts of the apparatus used to carry out the method are not contaminated by printing ink or the like.

Another object of the invention is to provide a device for carrying out the method of the invention which is particularly easy to maintain.

Another object of the invention is to provide a compact device so that there is little waste when tenting the web to be printed.

The printing method according to the invention is characterized in that the web is guided such that it hangs freely upwards through the one or more nozzles under constant tension. In the method according to the invention, the web is not supported in this position as it is guided upwards through the nozzles of the printing station under constant tension. Web tension depends on the type of material from which the substrate to be printed is made. The web is not supported while printing, otherwise components such as the backing roller can become soiled due to ink droplets penetrating the substrate. In the method of the present invention, the support layer on which the roll material is stuck is not used, so there is no need to wash the support layer after printing, so the advantages are reduced operating costs and no pollution to the environment.

According to a preferred embodiment of the method, the web is guided vertically through nozzles at right angles to the web. In the nozzles used, a large number of ink droplets (approximately 625,000 drops per second) are ejected from the nozzle, pass a charging electrode that charges the ink droplets, and then pass a deflection electrode that deflects the ink droplets in the desired direction. A "squeegee" positioned between the printhead and the web collects ink droplets that are incorrectly charged and thus deviate from the desired deflection direction. If the print head is positioned over a horizontally moving substrate, it is difficult to collect and discharge incorrectly charged ink droplets. Printing from below presents the same problem, with the risk of nozzle clogging. Therefore, in the present invention, the web to be printed is preferably passed vertically through the nozzles at right angles to the web. However, it is also possible to deviate slightly from the vertical direction.

In addition, the distance between the nozzle and the web is preferably kept constant, so that the uneven thickness of the web will not affect the printing quality. The shorter this distance, the higher the vertical clarity when the substrate passes vertically through the horizontal nozzle.

The printing of the present invention is carried out step by step, that is, after each strip of pattern is printed, the web is moved by a suitable conveying device for a small step (for example, about 8 mm), which will be described in detail below.

The invention also relates to an apparatus for incrementally printing continuous webs, in particular webs, comprising a web transport system comprising: an infeed for feeding the web to be printed and an ejection of the printed web material; a printing section, including one or more nozzles used to print the web; and a component that keeps the tension of the web constant, a web passing path for the web to pass through in the device, the web The through path has a free printing section in the direction upwards through the nozzles of the printing station.

Preferred embodiments of the device according to the invention are found in the dependent claims.

Describe the present invention in detail below in conjunction with accompanying drawing, in the accompanying drawing:

Fig. 1 shows the first embodiment of the device of the present invention;

Fig. 2 shows the second embodiment of the device of the present invention;

FIG. 3 shows a third embodiment of the device according to the invention.

FIG. 1 shows an exemplary embodiment of a printing device according to the invention, which is designated 1 in its entirety. The printing unit 1 comprises a web transport system comprising a first feed roller 2 driven by a stepper motor (not shown) and a second feed roller 3 also driven. The rollers 2 and 3 are made, for example, of aluminum whose frictional resistance is sufficiently high to drive the coil 4 in the direction of movement indicated by the arrows. If the frictional resistance is not high enough to cause the substrate to slip on the aluminum roll, the aluminum roll may be provided with a suitable coating, such as rubber. The web 4 is unwound from a base material roll 5 , which is optionally pretreated, and the web unwound from the base roll 5 passes through a straightening roll 6 and stretching roll 7 . The straightening roller generally includes a rotating shaft with helical grooves (threads) extending from the center to both sides. The stretch roll has such grooves only at its ends. There is a pressure roller 8 at the first driven roller 2 . Between the rollers 2 and 3 there is a printing station 9 with horizontal nozzles. The printing section 10 of the web-passing path of the web traveling in the device 1 is vertically upwards, so that the web 4 passes upwardly through the printing section 9 . It should be noted that "coil passing path" refers to the path of the coil from the inlet through the device to the outlet. At both ends of the printing section 10 there are two spacer rollers 11 along which the web 4 is guided in the manner shown so that the distance between the printing head 9 and the substrate 4 remains constant even in this device Printing substrates with different thicknesses or the same substrate with uneven thickness. Due to the use of spacer rollers, the positions of the driven rollers 2 and 3 as well as the printing section 9 can be fixed, and there is no need to change their positions when changing the web. The distance from the top spacer roller 11 to the printing position is selected such that at a given printing and conveying speed (about 12 m per hour when the printing width is 1.7 m), the printed web has Allow enough time to dry. Under the above conveying speed, the distance between the centers of the two spacer rollers is 30 cm, which is sufficient for drying. The roller 3 maintains a constant tension of the web on the printing section 10 with a moment. Pressing roller 12 next to roller 3 ensures that the printed web is further conveyed to, say, a take-up roller 13 and wound up thereon. Another advantage of arranging the rollers 2 and 3 one above the other is that the bottom feed roller 2 is easily accessible when required, eg for maintenance.

In order to feed the coils into the device, a coil passing system is used, comprising a coil pick-up on which one end of the coil is fastened and a guide for the coil pick-up, for example a coil passing through the device along the coil-passing path. guide. As the coil is fed through the unit, the stretching, pressing and spacer rolls are all in a neutral position, while the coil rests against the straightening rolls so that the coil is as straight as possible and reduces material loss. During feed, the rotating shafts of the various parts of the device are free to rotate. After the web has been fed, all components are actuated.

In the device according to the invention, the web passage path is preferably as short as possible in order to reduce substrate loss when the device is operated. The total length of the web passing path of the above-mentioned device can be about 1m, and the distance from the printing section 9 to the pressure roller 12 is about 40cm at this time, that is to say, the substrate loss (the wasted web without printing) is also 40cm. Thus the whole device appears compact.

The detection means for determining whether the web has been fed is preferably located at strategic points such as the beginning and end of the path through which the web passes. The detection device is used to control the device, for example, to start the device for printing when detecting the roll material fed into the device.

In order to intercept and collect ink droplets penetrating the substrate, a collecting container (not shown) is arranged behind the substrate.

FIG. 2 shows a second embodiment of the invention, the same parts as in FIG. 1 are denoted by the original reference numerals plus 20. In FIG. In this embodiment, there are no pressure rollers next to the driven rollers 22 and 23 , but a coil tensioning mechanism 34 between the feed roller 25 and the straightening roller 26 . This coil tensioning mechanism is known and will not be described in detail. Downstream of the second roll 23 there is a further straightening roll 35 and pressing roll 36 .

The printing process is the same for both devices. The web passes through the nozzles of the printing station in the vertical printing section. The web is now unsupported and the tension remains constant as shown in Figures 1 and 2. The ink does not stain the parts of the device and therefore does not generate waste as in the prior art where large volumes of waste water had to be treated because the waste water contained chemicals which had to be treated. Furthermore, the device of the present invention appears to be compact, so matrix loss is reduced. The printing position between the two feeding rollers is convenient for the maintenance of the whole device, etc.

FIG. 3 shows a third embodiment of the device according to the invention, the same parts as in FIG. 1 are denoted by the original reference numerals plus 40 . The continuously unwound web 44 from the driven roll 45 is conveyed to a buffer device 60 . The buffer device 60 comprises a non-driven auxiliary roller 61 , a so-called tensioning roller 62 and a straightening roller 63 provided with threads extending from the center to both ends in order to level the web 44 . The tensioning roller 62 moves downward during printing of the web 44 (ie, when the roller 48 comes to a standstill as described below); and moves upward as the web 44 passes further. After the buffer device 60 , the web 44 passes a non-driven roller 48 and a driven roller 42 and then passes a guide plate 64 in front of the printing head 49 in the printing section 50 . The guide plate 64, which extends over the entire width of the web 44, is rigid and has a smooth surface, for example made of aluminium. After the printing section 50, the printed web passes over a driven roller 43 and a non-driven roller 52, both of which are rubber-coated. The coil is finally wound onto a driven roller 53 .

Figure 3 device compares with Figure 1 device, the function of determining the distance between the web 4 and the printing head 9 of the two rollers 11 is replaced by the roller 43 and the guide plate 64, which tighten the web 44 so that the web is as close as possible to the printing head 49. In terms of cost, the device of Fig. 3 is superior to that of Figs. 1 and 2. In addition to the functions described above, the guide plate 64 is also used to remove grease from the web prior to printing. The guide plate 64 has a certain radian, so that a part of the coil is against the guide plate 64 .

In contrast to web tensioner 34 in FIG. 2 , web 44 in FIG. 3 is held tensioned by a combination of rollers 42 , 48 and 43 , 52 .

Claims (15)

1. A method for step-by-step printing of a continuous web (4; 24; 44), especially a fiber web, with one or more nozzles of a printing section (9; 29; 49); characterized in that the web (4; 24; 44) such that the web hangs freely upward through the one or more nozzles under constant tension. 2. The method as claimed in claim 1, characterized in that the web (4; 24; 44) is guided vertically through the one or more nozzles. 3. Method according to claim 1 or 2, characterized in that the distance between the web (4; 24; 44) and the one or more nozzles remains constant. 4. A printing device (1) for step-by-step printing of continuous webs (4; 24; 44), especially fibrous webs, the device comprising a web delivery system comprising: a feeding of the web to be printed (4; 24; 44) and an outfeed for the printed web; a printing station (9; 29; 49) comprising one or more printed webs (4; 24; 44) and a component (3; 34; 42, 48, 43, 52) for keeping the tension of the coil constant, the device defines a coil passing path for the coil (4; 24; 44) to pass through, and its characteristic In that, the web passage path has a free printing section (10; 50) in the upward direction through the nozzles of the printing station (9; 29; 49). 5. The device as claimed in claim 4, characterized in that the free printing section (10; 50) extends vertically. 6. Device according to claim 4 or 5, characterized in that there are spacers before and after the printing section (10; 50) to keep the distance between the nozzle and the web (4; 44) constant. 7. The device according to claim 6, characterized in that the spacer is a spacer roller (11), a guide plate (64) or a combination thereof. 8. Apparatus according to any one of claims 4-7, characterized in that the feed member comprises a driven feed roller (2; 22; 42). 9. Device according to claim 8, characterized in that the feed roller (2; 22; 42) is driven by a stepper motor. 10. Device according to any one of claims 4-9, characterized in that the discharge member comprises a second driven discharge roller (3) for setting the tension of the coil by torque. 11. Device according to any one of claims 4-9, characterized in that the feed roller (22) is preceded by a web tensioning device (34). 12. The device according to any one of claims 4-9, characterized in that the means for maintaining the constant tension of the web comprises: a first pair of rollers, including a driven roller (42) and a driven roller (42) interacting with each other a free roller (48), these two rollers are located before the printing section (50); and a second pair of rollers, including a driven roller (43) and a free roller (52), which interact (50) after. 13. Apparatus according to any one of claims 4-12, characterized in that one or more stretching rollers (7; 27) and leveling rollers (2; 22; 42) are upstream of the feed roller Rollers (6; 26; 63). 14. Apparatus according to any one of claims 4-13, characterized in that, at a position opposite to one or more nozzles of the printing section (9; 29; 49) there is a device for collecting ink droplets passing through Collection container. 15. Apparatus as claimed in any one of claims 4-14, characterized in that the apparatus is provided with detectors for detecting the presence or absence of a web in the apparatus.

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