The invention relates to a method for printing a moving substrate web by means of inkjets, in which the substrate web is guided through a printing station in which several inkjet nozzles are fitted, and in which the substrate web is printed.

Such a method is known in various embodiments. In one of the embodiments the moving substrate web is guided in a flat state past a large number of fixed inkjet nozzles which cover the entire or virtually the entire width of the flat substrate web. In another embodiment the substrate web is guided in a flat state past one or more inkjet nozzles moving at least in the transverse direction of the substrate web. These moving inkjet nozzles also cover the entire or virtually the entire width of the substrate web.

However, the known method has disadvantages. In the case of fixed inkjet nozzles a large number of inkjet nozzles are needed to print the full width of the substrate web, which makes the printing apparatus expensive. With a limited number of moving inkjet nozzles, the inkjet nozzles must move quickly and accurately along the substrate web, in order to ensure that the printed images applied during the successive passes of the inkjet nozzles connect seamlessly to each other. Another disadvantage of the known method, in which the substrate web is printed in a flat state, is that the printing station takes up a relatively large amount of space.

The object of the invention is to provide a method in which the above disadvantages are overcome. This object is achieved by a method of the type mentioned at the beginning, which is characterized in that the substrate web, which is supplied in a flat state, in the region of the printing station is bent substantially parallel to its lengthwise direction, so that in the region of the printing station the cross-section of the substrate

web is a curved shape.

When this method is used the printing station can be of a compact design.

Preferred embodiments of the method according to the invention are described in the method subclaims.

The invention also relates to a device for carrying out the method according to the invention, comprising means for moving the substrate web, a printing station with several inkjet nozzles past which the substrate web can be moved, and in which the substrate web can be printed, which device is characterized in that bending means are fitted in the region of the printing station, for bending the substrate web substantially parallel to its lengthwise direction, so that in the region of the printing station the cross-section of the substrate web is a curved shape. Preferred embodiments of the device according to the invention are described in the device subclaims.

The invention will be explained in greater detail in the description which follows with reference to the drawing, in which:

Fig. 1 shows very diagrammatically in perspective a device according to the invention;

Fig. 2 is a cross-section of the substrate web along the line II-II in Fig. 1; Fig. 3 is a cross-section of the substrate web along the line III-III in Fig. 1;

Fig. 4 shows diagrammatically the arrangement of the inkjet nozzles inside the bent-over substrate web;

Fig. 5 shows diagrammatically the arrangement of the inkjet nozzles outside the bent-over substrate web;

Figs. 6a-f show possible other shapes of the cross- sections of the bent-over substrate web in the printing station.

Fig. 1 shows very diagrammatically a device according to the invention for printing a moving substrate web by means of inkjets. The substrate web is indicated by reference number 1. The substrate web 1 is unwound from a stock roll 2, guided through a printing station 3, and wound onto a roll 4 again after printing. In the region of

the printing station 3 the substrate web 1, which comes off the stock roll 2 in a flat state, as illustrated diagrammatically in Fig. 2, is bent substantially parallel to its lengthwise direction, so that in the region of the printing station 3 the cross-section of the substrate web 1 is a curved shape, for example as indicated in Fig. 3. After leaving the printing station 3, the substrate web 1 is returned to the flat state and wound onto the roll 4. In the case of the device shown in Fig. 1 the bending of the substrate web 1 is carried out by means of a plate which is bent substantially to a tube 5. The substrate web 1 in this case glides along the inside of the tube 5.

In the printing station 3 the substrate web 1 gliding along the tube 5 is printed by means of a series of inkjet nozzles 6, which are disposed in a circle, for example inside the tube 5, and are fixed to a holder 7, as indicated diagrammatically in Fig. 4. The substrate web is printed on the inside here. The inkjet nozzles 6 can be in a fixed position, but it is also possible to make the holder 7 with the inkjet nozzles 6 rotate, which makes fewer inkjet nozzles 6 necessary.

As an alternative, it is also possible to set up the inkjet nozzles 6 in a circle on the outside of the tube and to print the substrate web on the outside. This is indicated diagrammatically in Fig. 5. The inkjet nozzles 6 are then fitted on a holder 8 situated outside the tube 5. It is a condition in that case that the tube 5 should consist of two parts between which there is a gap situated in the plane in which the inkjet nozzles 6 are situated.

In this case also, the inkjet nozzles can be set up in a fixed position or can be rotatable about the tube 5, as in the case of the embodiment according to Fig. 4. The shape into which the substrate web 1 is bent in the region of the printing station 3 is not limited to the shape shown in Fig. 3. Other possible shapes are shown in Figs. 6a to 6f. In Figs. 6a to 6d the cross-section of the substrate web 1 in the region of the printing station is

substantially the shape of a circle or an ellipse or a part thereof. In Fig. 6e the substrate web is bent in the shape of a U with relatively sharp bent edges. In the case of the shapes shown in Figs. 6a to 6e the substrate web is bent over in one direction. However, it is also possible to bend the substrate web in two directions and make the cross- section substantially S-shaped at the position of the printing station, as indicated in Fig. 6f.