GB2324294A

GB2324294A - Sheet guiding apparatus

Info

Publication number: GB2324294A
Application number: GB9811281A
Authority: GB
Inventors: Gunter Stephan
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1995-02-01
Filing date: 1996-02-01
Publication date: 1998-10-21
Anticipated expiration: 2016-02-01
Also published as: GB2324294B; GB9811281D0

Abstract

A sheet guiding apparatus comprises air boxes made up of modules 11,12, the surface of the boxes having air blast nozzles 2,18 for guiding sheets. The nozzles 2,18 are aligned outwards 16 from the sheet transport path towards the edge of the sheets being carried to keep the sheets taught in their lateral dimension. The nozzle distribution may not be uniform, with a high nozzle density in the centre of the sheet transport path and a lower nozzle density at the edges of the sheet transport path.

Description

SHEET GUIDING APPARATUS The invention relates to a sheet guiding apparatus with air supply boxes for the supply of nozzles disposed on guiding surfaces. The apparatus is designed for use in a printing press.

Such a sheet guiding apparatus is known from DE 42 09 067 Al. With regard to said sheet guiding apparatus, no details have been specified with respect to the arrangement in the printing press or with respect to the design for specific regions of the sheet transport path. In this regard, the disclosure contains merely a schematic representation.

The object of the invention is to design a sheet guiding apparatus of the initially mentioned kind such that said sheet guiding apparatus can be adapted in simple manner to the various requirements of the sheet transport path.

According to the present invention, we provide a printing press having a sheet guiding apparatus for guiding sheets in the press, the apparatus comprising a plurality of air box modules disposed in various different regions along a sheet transport path of the press, each module comprising a sheet guiding surface having air blast nozzles disposed and arranged thereon, in dependence upon the position of the module in the sheet transport path and wherein the blast air direction of the nozzles is aligned essentially outwards from the centre of the sheet transport path.

The advantage of the invention is that different modules are available for the various regions and according to various requirements of the sheet-transport path.

Consequently, it is possible in simple manner to construct a sheet transport path that permits a different application of air to the sheets according to the particular requirements.

For example, a first module for blast air operation with a curvature for transfer drums is available, said module being used in the regions of the sheet transport path corresponding to the entry of the sheet into the transfer drums and to the exit of the sheet from the transfer drums of a printing press. A second module for blast air operation is available, said module having the curvature for smaller drums such as the feed drum and the delivery drum.

Said module can, therefore, be employed for all such smaller drums. A first module for sheet guiding regions is provided in regions of the transfer drums that need merely to be subjected to blast air. A second module for sheet guiding regions comprises nozzles aligned diagonally with respect to the sheet transport path for the application of blast air with an increased vertical force component. Said modules may be provided opposite a dryer. In this manner, a defined number of modules is required, each module being usable for different locations in the printing press. It is therefore possible in very economic and simple manner to construct a sheet guiding apparatus that permits an application of air optimally suited to the requirements at the different locations of the printing press.

The guiding surfaces may be made of metal sheets with punched-in nozzles, such as slit nozzles. Such guiding surfaces can be manufactured in simple and cheap manner, and they can also cater for the requirements in terms of the directed application of blast air to the sheet transport path. It is possible to manufacture both modules with straight guiding surfaces and also modules with suitable curved guiding surfaces for sheet guiding on various drums.

The curved guiding surfaces can be manufactured in simple manner in that the pre-punched metal sheets are suitably bent. It is also possible to provide a plate with nozzles made of a thin, flexible material, such as metal sheet, said plate adapting to the curvature of the carrier module when it is mounted thereon.

Various pre-punched metal sheets may be available, namely those for modules with high and those for modules with low area coverage density of nozzles. Guiding surfaces may be provided with uniform or non-uniform distribution of the nozzles. The non-uniform distribution of nozzles may have, for example, a high nozzle density in the centre of a guiding surface and a low nozzle density at the edge. The nozzles of a guiding surface may be aligned at right angles to or diagonally with respect to the sheet transport path, in order to permit the corresponding application of blast air. Lateral tautening of the sheets is obtained because the blast air direction is essentially from the centre of the sheet transport path to the outside edges.

The air boxes may be supplied with air in various manner. For example, it is possible for them to be equipped with axial flow fans, the rotation direction of said axial flow fans being selectable as required, so that the application of suction air instead of blast air is possible.

Such selection makes it possible, in one sided printing mode, to change over to suction air in defined regions. In this manner, it is possible, at the locations of sheet conducting drums positioned before the transfer to an impression cylinder, for such a suction air operating mode to ensure that the sheets are subjected to a frictional force at the guiding surfaces, said frictional force permitting the tautening of the sheets and a good transfer to the impression cylinder. At the infeed regions of sheetconducting drums it is possible for the sheet ends to be held so that, in the event of a printing press stop, there is no dropping down of said sheet ends as a result of which said sheets might fold over, thereby becoming unusable and having to be removed prior to a production run of the printing press.

It is advantageous for the air flow at the various air boxes to be controllable, this making it possible, to set a flotation guiding or making it possible, in such air mode, to set the holding force in order to tauten the sheets.

It is most advantageous to provide various modules, said modules being multiply usable in a printing press.

This results in a particularly economic construction of the sheet guiding apparatus.

Several embodiments of the invention are now described by way of example with reference to the accompanying drawings, in which: FIGURE 1 is a schematic representation of a printing press with a sheet guiding apparatus composed of modules; FIGURE 2 shows an example of the joining together of a plurality of modules; FIGURES 3, 4 & 5 show alternative axial flow fan arrangements on various modules; FIGURE 6 shows a nozzle arrangement on various modules; and FIGURE 7 shows a slit nozzle.

Referring to the drawings, Figure 1 shows a printing press having only two printing units 20. Normally, however, such a printing press has four or more printing units. Each printing unit 20 has an impression cylinder 8, a rubber covered cylinder 9, a plate cylinder 10, as well as inking units (not shown). Between the two printing units 20 a transfer drum 6 ensures the onward transfer of the sheets that are to be printed. If a printing press has a plurality of printing units, transfer drums 6 are always disposed between any two adjacent printing units. Of course, it is also possible, instead of one transfer drum 6, for there to be a plurality of sheet transport drums. In the printing press shown, the sheet transport path 17 is indicated, the arrows 24 showing the sheet transport direction. The sheets are taken from a feeder pile 19 and, by means of a feeder (not shown), are passed on to a feed drum 5, said feed drum 5, with its grippers, transferring the sheet to an impression cylinder 8 for printing. From the impression cylinder 8, the sheet is accepted by grippers of the transfer drum 6 and is fed to a further impression cylinder 8, so that a further printing operation is able to take place. In the printing press shown, the second impression cylinder 8 transfers the sheet to a delivery drum 7 of a delivery 21. The delivery drum 7 is the transfer drum for gripper bars disposed on a delivery chain 22 for transporting the transferred sheet as far as the end of the delivery 21, where the sheets are deposited on a delivery pile 23.

Air boxes 4, each supplied with an axial flow fan 15, and in the form of modules 11, 12, 13, 14 and 26 are provided in regions 3 of the printing press. The module 13 is used four times on said printing press, twice on the feed drum 5 and twice on the delivery drum 7. Used on the feed drum 5 and on the delivery drum 7 are axial flow fans 15 that are capable of operation in both suction and blast air mode. The adjoining module 13 has an axial flow fan 15 that operates merely in blast air mode, because that is sufficient at that point. A further module 11 has a guiding curvature surface 1, corresponding to the transfer drum 6.

The module 11 is equipped with axial flow fans 15 for blast air and suction modes and has been used in the infeed region and in the outlet region of the transfer drum 6. Said module 11 serves in the infeed region to hold the sheet end in the event of the printing press coming to a stop; in the outlet region, it serves to apply a holding force to the sheets, said holding force serving to ensure that said sheets are transferred flat to the impression cylinder 8.

Between the said two modules 11 is a module 12 having a lower nozzle density provided merely for blast air application. Modules 26 for a blast air direction with an increased vertical force component are provided opposite a dryer 27. The blast air application with the increased, vertical force component is achieved by an inclined alignment of nozzles 2, 18 (see Figure 7) with respect to the sheet transport path and serves to apply a counter-force for the hot air blast from the dryer 27.

Figure 2 shows a top view of the guiding surface 1 made up from air box modules 11, 12. The area density of the nozzles 2, in the form of slit nozzles 18, varies. The example corresponds to the module construction that may be provided on the transfer drum 6. The modules 11 are equipped for blast air and suction air modes, there being a high area density of nozzles 2, 18 which guarantee a corresponding holding force in suction air mode. The therebetween lying modules 12 have an area density of nozzles 2, 18 that is higher in the central region and lower at the edges. These guiding zones correspond to the regions in which the application of blast air is sufficient for any operating mode. The depicted slit nozzles 18 are directed outwards to ensure the tautening of the sheets towards the side. This requires the higher nozzle density in the centre of the sheet transport path 17 in order to generate air streams directed towards the side. Towards the outside, however, it is necessary merely for said air streams to be maintained, which can be achieved with a lower nozzle density. The blast air direction is indicated by the arrows 16.

Figure 3 shows how axial flow fans 15 can be associated with the modules 11 and 12 disposed in Figure 2.

It is, however, also possible to provide an arrangement of modules 11 and 12 with axial flow fans 15 as shown in Figure 4.

Figure 5 shows how, in the case of a smaller air demand, it is possible to dispense with a division, with the result that modules 13 and 14 extend across the entire width of the sheet transport path 17. Correspondingly, Figure 6 shows nozzle arrangements that may be provided, by way of example, for said modules 13 and 14.

Figure 7 shows a preferred embodiment of the nozzles 2 which was already indicated in Figure 2. The nozzles are in this case slit nozzles 18, which can be punched in simple manner into the sheet metal of the guiding surfaces 1. This makes it possible in simple manner to obtain a directed blast air direction 16, as is required, for example, for the tautening of the sheets in the aforementioned manner.

Surfaces with such punched in nozzles 18 or, of course, also with other nozzle forms can be used in versatile manner in that they are employed for straight modules 26 or, after bending, are used for curved modules 11, 12, 13. Instead of bending by forming, it is also possible to use a thin, flexible material, e.g. sheet metal, that adapts to the curvature of the carrier module when mounted thereon.

According to the various requirements, it is also possible to provide a corresponding area density of said nozzles 2, 18.

Merely one possibility of a module construction is shown. Of course, a different module construction may be chosen to suit the different requirements in various printing presses. What is essential is that, through the multiple use of modules as well as through the multiple use of punched metal sheets for the guiding surfaces in the construction of said modules, an extremely economic solution is achieved for the construction of sheet guiding apparatus.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

CLAIMS:

1. A printing press having a sheet guiding apparatus for guiding sheets in the press, the apparatus comprising a plurality of air box modules disposed in various different regions along a sheet transport path of the press, each module comprising a sheet guiding surface having air blast nozzles disposed and arranged thereon, in dependence upon the position of the module in the sheet transport path and wherein the blast air direction of the nozzles is aligned essentially outwards from the centre of the sheet transport path.

2. Sheet guiding apparatus according to claim 1, wherein the sheet guiding surfaces are made of metal sheets with punched in nozzles.

3. Sheet guiding apparatus according to claim 1 or 2, wherein the modules have straight sheet guiding surfaces and suitably curved sheet guiding surfaces for sheet guiding on various drums.

4. Sheet guiding apparatus according to claim 3, wherein the curved sheet guiding surfaces are made by bending a plate containing the nozzles.

5. Sheet guiding apparatus according to any one of claims 1-4, wherein at least some of the modules have high and low area coverage density of nozzles.

6. Sheet guiding apparatus according to any one of claims 1-5, wherein at least some of the modules have a nonuniform distribution of the nozzles over the sheet guiding surfaces.

7. Sheet guiding apparatus according to claim 6, wherein -the modules have sheet guiding surfaces having a high nozzle density in the centre and a low nozzle density at the edge.

8. Sheet guiding apparatus according to any one of claims 1-7, wherein at least some of the nozzles have their blast air direction inclined to or aligned diagonally with respect to the sheet transport path.

9. Sheet guiding apparatus according to any one of claims 1-8, wherein the air boxes are equipped with axial flow fans.

10. Sheet guiding apparatus according to claim 11, wherein the rotation direction of the axial flow fans is selectable to change the blast air to a suction mode.

11. Sheet guiding apparatus according to any one of claims 1-10, wherein the air flow is controllable.

12. Sheet guiding apparatus according to any one of claims 1-11, wherein the modules are multiply usable in a printing press.

13. A printing press provided with sheet guiding apparatus as claimed in any one of claims 1-12.