EP0134526A2 - Method and device for feeding sheets exactly in register with a printing machine - Google Patents

Abstract

In a paper transport conveyor from a sheet feeder to a printing machine, the sheets are underlapped for speed reasons and for this purpose, the sheets are held and transported in a defined position using a conveyor table to which a vacuum is applied. In order to optimize the feed register in the printing machine in all states of operation, an additional conveyor device holds the sheets at the front gauges and aligns them. The vacuum at the conveyor table is quantitatively variable and the vacuum is so controlled according to operation as to be applied when sheets are required to be held on the conveyor table but interrupted when its action would obstruct the sheet alignment on the conveyor table.

Description

The invention relates to a method and an apparatus for continuously conveying a stream of flaked sheets from a feeder to a printing press or other sheet-processing machine, in which the sheets are held in a defined position on a conveyor with the aid of suction air.

A method or a device of this type is known from DE-PS 713 529.

With the help of conveying tables pressurized with suction air, sheets can be conveyed to printing machines under scaling. The advantage here is that no devices with holding elements block the top of the conveyor table. As a result, the sheets on the conveyor table are easily accessible even in the event of business interruptions. The risk of accidents is avoided and the adjustment of all elements of the frame is unnecessary.

DE-PS 713 529 describes a sheet conveying device, in particular on sheet feeders for letterpress and similar machines. There, endless belts with suction openings run over suction slots in the conveyor table. By sucking air out of the suction slots, sheets of paper are held on the perforated belts and transported forward. The disadvantage is the small volume of the suction slots and the arrangement of a piston pump. This means that this device cannot be safely transported. In addition, relatively high negative pressures are necessary to achieve a trans-- 2 - to achieve port effect, which in turn leads to increased friction of the belts on the conveyor table.

Disadvantages of the device mentioned are avoided in a device for the automatic loading of moistened veneer sheets into a belt or roller dryer and for unloading and stacking of the emerging dried veneer sheets, as described in DE-OS 2 523 482. Here the perforated conveyor belts are guided around a large-volume suction box. They run on the underside of this suction box parallel to its surface, which is provided with openings there. On the opposite side, the suction box is equipped with a fan as a source of suction air. As a result, a uniformly distributed vacuum is generated over the entire area of the underside of the suction box, and the large volume of the suction box also ensures that the vacuum is stored. The serious disadvantage of this device, however, is that, since it is designed as a single sheet conveyor, it is not possible to deliver flaky paper sheets in a targeted and precisely timed manner. Above all, there is no possibility of specifically promoting the individual sheets in the area of the transfer to the alignment means of the printing press, which are replaced here by the dryer. The sheet is held to the last without having to take into account the position or the exact arrival of the sheet.

However, devices that allow the alignment of the sheet have also become known. A sheet application device is described in DE-PS 836 355. It has additional suction means at the end of the conveyor table working with conveyor belts. These absorbents are called Suction rollers are formed and act from the top on the end of the sheet to be conveyed to the front marks. A disadvantage of this device is that the rollers must be controlled both in terms of their movement and in terms of their suction air supply. It cannot be ensured that the sheet is not conveyed too far and that it is supported by the front marks and bulges up in the middle. Then the next following sheet could be grasped by the suction rolls and conveyed further in an uncontrolled manner. In addition, the entire device must be adjusted precisely to the end of the sheet and blocks access to the sheets lying on the feed table.

Another device of this type is described in DE-PS 1 152 707. This sheet deceleration and alignment device has suction chambers in the form of suction rolls or suction boxes wrapped with perforated conveyor belts, arranged on the left and right of the conveyor table and suitable for slowing and aligning the sheet against the front marks. The speed of the conveyor belts is below the speed of the conveyor belts of the conveyor table. The transport devices are also arranged here after the conveyor table in front of the feed table of the printing press. They are therefore at a large distance from the front marks and their effect is therefore subject to the risk that the sheet will be supported on the front mark and be bulged by the conveying action of the alignment means. The disadvantage of the device described above, that there are again alignment means above the feed table, is avoided here, but the disadvantage of the control effort is also present here. In addition, the working speed of this mooring device slowed down by the reduced transport speed of the additional alignment means.

It is therefore an object of the present invention to ensure the registration register of a printing press, the side mark must be able to pull properly and the sheets must not rebound from the front marks. In particular, both the first and the last sheets of a print job are to be fed to the printing press with a precise fit.

The object is achieved by the features described in the characterizing part of claim 1. With the described method and the associated device, it becomes possible to produce a good fitting behavior in every situation of sheet transport between the feeder and the printing press. The additional drive belt used in front of the front brands in a special embodiment has the effect that the sheet cannot bounce back from the front brands and is also conveyed against the front brands in an inclined position. This results from the effect that the sheet swings around the drive belt like a hinge when it is in one-sided contact with the front marks and in this way aligns itself completely against the front marks. Because the drive belt has at least the same speed as the perforated belts of the conveyor table, and the suction air on this drive belt acts continuously, the same drive force is always applied to the sheets arriving at the front marks, which can align them sufficiently quickly and also to rest there brings. The side alignment is due to the small hold effect on the drive belt, as proposed in one embodiment of the invention, is not hindered. When the last sheet runs over the conveyor table, the suction air source should be switched off. By using the volume of the suction box as a suction air reservoir for the operation of the conveyor table, it is possible to interrupt the suction air flow in time so that the vacuum in the suction box only slowly dissipates and is only compensated for when the conveyor table runs empty. The last sheet can no longer be held on the perforated belts of the conveyor table. This is also desirable insofar as the scaling due to another arch is missing for him, which would cause the perforated tapes to be covered. In this way, the last sheet of the stack or a print job or the last sheet before deliberate printing interruption can still be printed cleanly, without causing difficulties on the contact sheet. The advantages of the conveyor table, which transports sheets with the aid of suction air, are well known in that there is no risk of accidents and operating difficulties caused by a holding frame for rollers and brushes to ensure sheet transport on a conventional feed table with conveyor belts.

The arrangement of the additional drive belt near the front brands avoids the risk of bow compression between the front brands and the drive belt. Due to the small effective area of the drive belt, an exact front and side alignment of the sheets is guaranteed in connection with the side mark, since at the time of influencing they are free at their rear edge. The additional facilities on the conveyor table do not work if a stopper stops the feeder. It is irrelevant if the drive belt continues to run when the front brands are locked, since it also functions in the same way as in normal machine operation. And it is rather favorable that the fan for the conveyor table remains in operation so that the sheets are held in their original scaled-down position on the conveyor table. The system is freely accessible, however, so that double sheets or sheets with wavy or damaged leading edges can be eliminated.

The arrangement according to the invention is particularly simple in that no special control is necessary for the operation of the drive belt. Both the air extraction and the drive of the drive belt can run completely continuously while the machine is operating. The low air requirement means that no additional source of suction air is necessary. Furthermore, the control for switching off the suction air on the conveyor table is not subject to great accuracy requirements, it can also be coupled with the switching off of the stack stroke when the feeder stack has run empty or with the switching off of the feeder. It is only sufficient to switch off the fan when the last sheet arrives on the table and at the same time to close the throttle valve. Due to the sufficient volume capacity of the suction box for negative pressure, the last sheets are still securely held on the conveyor table.

• Fig. 1 eine Seitenansicht des Saugbändertisches und des zusätzlichen Förderbandes vor den Vordermarken, in
• Fig. 2 eine Aufsicht auf den Bereich der Bogenanlage einer Druckmaschine, in
• Fig. 3 A bis D der schematisierte Ablauf des Bogentransports über den Fördertisch bis zu den Vordermarken, und in
• Fig. 4 schematisch die Ausrichtung eines Papierbogens an Vorder- und Seitenmarke.

A device according to the invention is described in more detail below. This includes other advantages and features of the invention clearly. For this purpose, the drawings are shown in detail in

• Fig. 1 is a side view of the suction belt table and the additional conveyor belt in front of the front brands, in
• Fig. 2 is a plan view of the area of the sheet feeder of a printing press, in
• Fig. 3 A to D the schematic flow of sheet transport over the conveyor table to the front brands, and in
• Fig. 4 shows schematically the alignment of a sheet of paper on the front and side mark.

As shown in FIG. 1, the conveyor table 1 for transporting the shingled sheet stream is located between the printing press 2 and the feeder 3. The sheets are separated in the feeder 3 from a stack to a shingled stream of sheets and are in the system of the printing press 2 hand over their printing unit. The sheets run there individually over a contact plate 4. The conveyor table 1 consists of a suction box 5 and a fan 6. Around the suction box 5, several endless perforated belts 7 are arranged. The perforated tapes 7 are driven by shafts 8 and tensioned over tensioning rollers 9. Two rows of suction openings 10 are arranged in the perforated belts 7 and connect the surface of the conveyor table 1 to the suction box 5. The top of the suction box 5 is otherwise next to the perforated bands 7 with covers 11 that can be moved laterally covered from pattern-rolled sheet metal, so that only air can be sucked in through the perforated strips 7. The sheet friction is particularly low on the pattern-rolled sheet. At the bottom of the suction box 5, there is a suction pipe 12 in which a throttle valve 13 is arranged. When the fan 6 is running, an air flow is generated from the surface of the conveyor table 1 through the suction openings 10 and the suction box 5, further through the suction pipe 12, past the throttle valve 13 shown in broken lines, and towards the fan 6. The air flow through the suction box 5 can be controlled by the laterally displaceable cover plates in relation to the sheet format to be processed, in that the covers 11 can be pushed under the outer rows of the suction openings 10 in the perforated bands 7 and can be changed by changing the exhaust air opening on the fan 6 Size can be adjusted.

In Fig. 2 it can be seen that in the area of the contact plate 4 at the level of a side mark 14 and near the front marks 15, both of a known type, an additional conveyor is arranged in the middle between the perforated belts 7. It consists of a drive belt 16 provided with suction openings 20, which runs endlessly around a suction element 17. The drive belt 16 is constantly driven and also tensioned via shafts 18. A suction air connection 19 is provided on the suction element 17, from which air is sucked through the suction openings 20 in the drive belt 16. The drive belt 16 runs at a speed which is at least as great as the speed of the perforated belts 7. The suction air for the suction element 17 is not controlled in time but is applied continuously. This acts on the suction openings 20 in the drive belt 16 always the same holding forces. These holding forces should be set so that the sheet is not held but is only driven slightly forward. In this way, the drive belt 16 will always slip under the sheet abutting the front marks 15. Due to the proximity to the front marks 15, however, the sheet cannot bulge and thus cause investment difficulties. This also ensures that the sheet can be pulled from the side mark 14 against the side stop 21 for side alignment without difficulty. The additional conveying device does not have to be adjusted in any way during operation, but it always remains constant both in its effectiveness and in its position during a print job. The suction effect on the suction element 17 should, however, be adjustable as a function of the paper weight and the negative pressure must be stronger than on the suction box 5, since there is a larger effective area there. For this purpose, the suction air connection 19 on the suction element 17 is simply connected to the suction air source of the printing press 2, which, as can be seen later, also proves to be advantageous and the suction air source mentioned is used very little by a very low air consumption.

• In den Figuren 3a bis 3d ist dargestellt, wie Bogen 22 bis 25 vom Anleger 3 über den Fördertisch 1 bis zu den Vordermarken 15 und in die Druckmaschine 2 transportiert werden.

The operation of the device described using the method according to the invention now proceeds as follows:

• FIGS. 3a to 3d show how sheets 22 to 25 are transported from the feeder 3 via the conveyor table 1 to the front marks 15 and into the printing press 2.

In Fig. 3a, the sheet 22 is just on the front marks 15 on and is held there by the drive belt 16. During this, the sheets 23 and 24 are shingled behind the sheet 22 on the conveyor table and the sheet 25 is pushed from the feeder 3 under the sheet 24.

3b, the first sheet 22 is being drawn off into the printing press 2, the sheet 23 runs from the conveying table 1 onto the contact plate 4, while the sheets 24 and 25 are transported further on the conveying table 1. The sheets 23, 24, 25 are only held on their front, not shingled part by the suction air effect of the conveyor table 1.

In Fig. 3c, the penultimate sheet 24 has just run to the front marks 15 and is held there by the drive belt 16 with the help of the suction of the suction element 17. The drive belt 16 slips continuously under the sheet 24 and transmits a force directed against the front marks 15 to the sheet 24 by friction. At the same time, the sheet 25 has been transported to the end of the conveyor table 1. The scaling under the arch 24 means that the suction table 1 can no longer exert suction on the arch 24. So that the sheet 24 is released for the side drawing.

In Fig. 3d it is shown what the conditions look like for the last incoming sheet. The sheet 25 can be the last sheet of a print job or the last sheet of a paper stack from the feeder 3. If you let the sheet 25 run into the system without precautionary measures, it will now, since it is no longer on its rear side is shingled, still held by the conveyor table 1, because at this point the suction box 5 would still be supplied with negative pressure. In this case, it could no longer be guaranteed that the side mark 14 would also pull the sheet 25 properly. It is therefore provided that the suction air flow is interrupted before the sheet in question arrives when the last sheet 25 to be printed runs onto the conveying table 1. The throttle valve 13 is therefore closed when the sheet 25 has arrived on the conveyor table 1, as shown in Figure 3b. This is done by rotating the cranked axis 31 with the aid of the electromagnet 30 in the intake manifold 12 into the position indicated in FIG. 1. The dashed position of the throttle valve 13 shows the open position. Due to the volume capacity of the suction box 5, the negative pressure in the suction box 5 is only slowly reduced. It is only reduced enough when the conveyor table 1 is released from the sheets 23 and 24, ie when the last sheet 25 has reached the front marks 15 and is held there by the drive belt 16. The vacuum in the suction box 5 is then so low that the small holding forces acting on the underside of the sheet 25 still resting on the conveying table 1 can no longer hinder the side drawing by the side mark 14. This means that the last sheet 25 can also be printed without any registration problems.

The advantages of the arrangement of the additional conveying device for the so-called registration register of the printing press 2 are described below.

Fig. 4 shows the entry of an inclined sheet 26 against the front marks 27, 28. For simplification only two front marks 27, 28 are shown here. The sheet 26 runs against the front mark 27 due to its inclined position. The driving force from the perforated belts 7 is interrupted by the following sheet, not shown, and the drive belt 16 takes over the further conveyance of the sheet 26 with the suction element 17. Because the drive belt 16 is arranged in the middle of the contact plate 4, the sheet 26 rotate around the drive belt 16 or around the active surface of the suction openings 20 in the drive belt 16, supported on the front mark 27, and are conveyed up to the front mark 28. This is possible above all because there is deliberate slippage between the sheet 26 and the drive belt 16, ie the drive belt 16 slips under the sheet 26 or the sheet 26 can move relative to the drive belt 16. Only when the sheet 26 also abuts the second front mark 28 is an exact side alignment guaranteed. However, since the drive belt 16 acts continuously on the sheet 26, this orientation towards the second front mark 28 will also occur during the side pulling process. Due to the high machine speeds, however, the drive belt 16 must run at least at the sheet travel speed of the conveyor table 1 in order to generate the alignment process sufficiently quickly. Due to the action of the side mark 14 and the drive belt 16, the sheet 26 is moved diagonally in the bearing direction 29 against the side stop 21 and the front marks 27, 28. This ensures that the sheet 26 is properly aligned for printing in the printing press 2. This position is shown in dashed lines in Fig. 4.

Further setting options on the device for the Settings for different types of paper are given by adjusting the exhaust air opening of the fan 6 and shifting the covers 11 transversely to the sheet running direction under the perforated bands 7. This makes it possible to set a lower suction effect on lighter papers or only half of the suction openings 10 in on smaller formats to let the perforated bands 7 act. This is also important if heavier papers are printed. Then an adjustment of the suction on the additional conveyor is also necessary. Overall, however, only very few adjustment processes are necessary, which only have to be carried out in the case of extreme paper differences. The device is very flexible and the method ensures that the operation of the entire sheet system is extremely simple and can be done in a short amount of time.

Further advantages of the device are given by the arrangement of the fan 6 in the conveyor table 1 and the uninterrupted effect of the drive belt 16 and the suction element 17. In the event of a pressure interruption in which the system is blocked by blocking the front marks 15 because of any pressure disturbances or also because double sheets have entered the system, the feeder 3 can be uncoupled from the printing press 2. However, the negative pressure in the suction box 5 of the conveyor table 1 remains and holds the sheets on the conveyor table 1 in their original position. If the cause of the print interruption lies in the printing press 2, printing can be continued immediately after rectification, since the sheet lying on the front marks 15 also retains its position without any particulars Measures should be taken.

If the last sheet runs over the conveyor table 1 and the suction air flow is interrupted by the throttle valve 13, it is important that the suction air on the suction element 17 is still present for the function of the drive belt 16. This is possible because the suction element 17 is connected to the air supply of the printing press 2, which in this case is not yet interrupted. On the other hand, however, the suction air is shut off on the suction element 17 when the printing press 2 is switched off, since the air supply is then also switched off. This makes it possible for the front 15 and side marks 14 to be adjusted with the sheet loosely inserted.

Reference symbol list

• 1 conveyor table
• 2 printing press
• 3 feeders
• 4 sheet metal
• 5 suction box
• 6 fans
• 7 perforated tape
• 8 wave
• 9 tension pulley
• 10 suction opening
• 11 cover
• 12 suction pipe
• 13 throttle valve
• 14 side mark
• 15 front mark
• 16 drift belt
• 17 suction element
• 18 wave
• 19 Suction air connection
• 20 suction opening
• 21 side stop
• 22-sheet
• 26
• 27 front mark
• 28 front mark
• 29 Investment direction
• 30 electromagnet
• 31 axis

Claims (10)

1.) Method for continuously conveying a stream of flaked sheets from a feeder to a printing press or other sheet-processing machine, in which the sheets are held in a defined position on a conveyor with the aid of suction air,
characterized,
that the suction air in the conveyor table (1) is matched to the sheet to be conveyed, that the sheet is released when the alignment means (14, 15) for the front and side edges are reached by the suction table (1) and is passed through one or more transverse to the sheet running direction in or additional conveying means (16, 17, 18) arranged near the center of the sheet can be moved further after the conveying table (1) for alignment with the aligning means (14, 15), but remain movable for alignment on their front and side edges. 2.) Method according to claim 1,. characterized,
that for sheets that are no longer shingled, the air extraction at the conveyor table (1) taking into account the volume capacity of the conveyor table (1) is interrupted in good time so that the sheets of paper still under shingled are still safely transported over the conveyor table (1), but the sheets that are not shingled are released by the suction table (1), which is subjected to suction air, for alignment movements transverse to the direction of sheet travel. 3.) Method according to claim 1, characterized in that the throughput of suction air in the conveyor table (1) is influenced by reducing the cross section of the air inlet on the conveyor table (1) or the air outlet on the fan (6). 4.) Method according to claim 1, characterized in that the additional conveying means (16, 17, 18) run at the same or faster speed than the sheet transport speed on the conveying table (1), and in that the holding force on the additional conveying means (16, 17th , 18) is generally less than the tensile force on the elements provided for the lateral alignment. 5.) Method according to claim 1, characterized in that the additional conveying means (16, 17, 18) are operated at constant speed and constant holding action, the conveying means (16, 17, 18) among those on the alignment means (14, 15th ) for the leading edge in the sheet running direction slips through and thereby a driving force on the sheet applies, which is only so large that it can not compress the sheet, but still holds on the alignment means (14, 15). 6.) Device for carrying out a method according to claims 1 to 5 with a conveyor table consisting of a suction box, around these continuous perforated belts which are guided over openings on the top of the suction box, and a fan closing the underside of the suction box,
characterized in that in the area of a contact plate (4) between front marks (15, 27, 28) and the conveyor table (1) an additional conveyor (16, 17, 18) is provided that closable openings are provided on the suction box (5), wherein at least the openings in the suction box (5) facing away from the conveyor table (1) have a closure (13, 30, 31) which is connected to the feeder (3) in such a way that the air extraction is switched off when the feeder is stopped but the printing machine (2) continues to run becomes. 7.) Device according to claim 6, characterized in that the additional conveying means consists of an endless drive belt (16) provided with suction openings (20) which is guided around a suction element (17) and driven by shafts (18), with the suction element (17) a suction air connection (19) is provided, through which air is sucked through the suction openings (20) of the part of the drive belt (16) running in the plane of the contact plate (4). 8.) Device according to claim 6, characterized in that in addition to the perforated strips (7) of the suction box (5) covers (11), which consist of pattern-rolled sheet metal, are loosely placed on the conveyor table (1) and under the perforated strips (7) can be inserted without opening the suction box (5) at other points. 9.) Device according to claim 6, characterized in that the closure for interrupting the air suction as in the intake manifold (12) between the suction box (5) and fan (6) arranged, electromagnetically controlled throttle valve (13) is formed, the throttle valve (13 ) is pivoted about an axis (31) by an electromagnet (30). 10.) Device according to claim 1 and 6, characterized in that the electromagnet (30) for controlling the throttle valve (13) and the drive of the fan (6) with the drive of the feeder (3) are connected in terms of control technology such that in normal Feeder operation of the fan (6) with the throttle valve (13) open, that the fan (6) also runs during pressure interruptions that are machine-related, that the throttle valve (13) is closed and the fan (6) is switched off when the feeder ( 3) if the stack of paper runs empty, if a print job is ended or if there are other non-machine-related printing interruptions.

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