DE29607062U1 - Device for cross cutting a paper web - Google Patents

Description

Device for cross-cutting a paper web.

The invention relates to a device for cross-cutting a paper web according to the preamble of claim

When post-processing printed paper webs, e.g. of computer prints, the paper web should be cut into individual sheets of paper with a pre-print height that can be between 3" and 12". For this purpose, there are automatic cutting machines that, in addition to a cutting tool that serves to cut the paper web crosswise, are also equipped with cutting tools that cut off the perforated edges of the paper web or can also divide it lengthwise. One such automatic cutting machine, which has proven to be extremely useful in practice, is described in the brochure of BDLJE SYSTEC AG, D-B6135 Augsburg, "Automatic cutting machine BÖUiE 310", 3/Sk . This automatic cutting machine processes printed paper webs folded in a zigzag shape. For cross-cutting, it has a cutting tool consisting of a stationary and an up and down moving cutting knife. A first conveyor device, which is designed as a so-called tractor, is arranged in front of this cutting tool. This consists of two endless conveyor belts arranged parallel to each other, which engage with their spikes in perforations on both edges of the paper web. This well-known cutting machine works according to the start-stop principle. While the cutting blades are separated from each other and the passage between them is clear, the tractor advances the paper web by a length corresponding to the height of the conveyor belt. Then the tractor stops.

and the cutting blades of the cutting tool carry out the cutting process. As soon as the passage between the cutting blades is free again, the tractor is started again. Although the cutting performance of these well-known cutting machines is already quite high at around 2700D cuts per hour, with a pressure of 3" (= 7.5 cuts/s), it no longer meets future requirements. Modern data processing systems work with laser printers at such high speeds that the well-known cutting machine would not be able to cut the paper web printed out by the laser printer on line, i.e. after the printer at a speed corresponding to the working speed of the printer. The working speed of the well-known cutting machine cannot be increased significantly. This is due to the system's start-stop principle: before each cut, the paper web must be stopped and after each cut, accelerated from a standstill to full conveying speed within fractions of a second, and this more than 30,000 x per hour. The forces acting on the paper web at even higher cutting performances Acceleration forces are so great that the edge perforations can tear out and, if the paper web is provided with transverse perforations, it will tear at the transverse perforations.

The invention is therefore based on the task of demonstrating a 3D device for cross-cutting a paper web, which significantly increases the cutting performance by more than double compared to the known cutting machine mentioned at the beginning,

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without the risk of tearing or ripping the paper web.

Starting from a device for cross-cutting a paper web, with a stationary cutting tool, which has cooperating cutting blades, and with a first conveyor arranged in front of the cutting tool, by means of which the paper web is fed between two successive cutting processes in a predetermined length, the novelty according to the invention consists in the fact that in the area between the first conveyor, which is continuously driven during operation of the device, and the cutting tool, a clamping device driven synchronously with the latter is arranged.

device is provided by means of which the area of the paper web immediately adjacent to the cutting tool and located in front of it can be clamped for the duration of the cutting process until the passage between the cutting blades is free again, and that in the area between the first conveyor device and the clamping device a free space is provided into which the paper web waste continuously supplied by the first conveyor device during the cutting process can be accommodated.

1G cut in the form of a loop (LJeIIe) that is curved transversely to the theoretically straight feed direction.

The invention is therefore based on the idea of continuously moving the paper web using a first conveyor at a constant speed. However, so that the paper web is not moved further in the immediate area of the cutting tool during the cutting process - a fan movement during the cutting process could lead to diagonal cuts and other problems - the area of the paper web immediately adjacent to the cutting tool and in front of it is held in place by a clamping device for the duration of the cutting process until the passage between the cutting blades is free again. During the cutting process, however, the first conveyor continuously demands more paper web. This further-conveyed paper web section is stored in front of the clamping device in the form of a small loop or wave that extends transversely to the feed direction. During this storage, a certain tension builds up in the loop. Due to this tension, after the clamping device is released, the area of the paper web adjacent to the cutting tool is pulled towards the cutting tool.

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t. This movement can be advantageously supported by a continuously driven second conveyor device, provided between the clamping device and the cutting tool, whose conveyor speed is higher than that of the first conveyor device. However, only small acceleration forces occur here, on the one hand because only the small paper web section stored during the cutting process needs to be accelerated, and on the other hand because the conveyance of this small paper web section is supported by the tension generated in the loop or dent. The loop is deliberately kept only large enough to accommodate the paper section supplied during the cutting process and so that a type of buckling tension is created in the loop, which ensures that the free end of the paper web facing the cutting tool is pushed forward after the clamping device is released. The invention makes it possible to increase the cutting performance to approx. 100,000 cuts per hour at a pre-pressure height of 3", which is more than double the cutting performance of the known cutting machine mentioned at the beginning. The risk of tearing the perforation or tearing the paper web is significantly reduced, since the feed is continuous using the first conveyor and only the small section of paper web stored during the cutting process, aided by the stored tension, needs to be accelerated. Thanks to the high cutting performance, it is possible to carry out cross-cutting online in connection with a laser printer, which brings further advantages.

Advantageous embodiments of the invention are characterized in the subclaims.

The invention is explained in more detail below using several embodiments shown in the drawing. They show:

Figure 1 shows a first embodiment of a device

for cross-cutting a paper web in longitudinal section, Figure 2 is a schematic side view showing

the drive connections,

Figure 3 shows a further embodiment in longitudinal section, Figure k shows a schematic side view of this embodiment showing the drive connections,

Figure 5 shows a partial longitudinal section of a third embodiment,
Figure 6 is a partial plan view in the direction of UI of Figure 5.

The device for cross-cutting a paper web has, according to the embodiment shown in Figures 1 and 2, a cutting tool 1 with a stationary cutting blade 2 and a cutting blade 3 that can be moved up and down. A first conveyor device 4 is provided at a distance in front of the cutting tool 1, which in this embodiment is designed as a so-called tractor. The tractor consists of two conveyor belts 5 arranged parallel to one another, which engage with their spikes 6 in perforations on both longitudinal edges of the paper web 7. The conveyor device k is continuously driven at a circumferential speed U1, which corresponds, for example, to the delivery speed of an upstream conveyor (not shown).

30" laser printer. In the area between the conveyor k and the cutting tool 1, a clamping device ß is provided which is driven synchronously with the latter. This clamping device &thetas; is preferably arranged in the vicinity of the cutting tool 1, ie its distance from the cutting tool 1 is less than its distance from the conveyor h.

Between the clamping device B, which will be described in more detail below, and the cutting tool 1, a continuously driven, second conveyor device 9 is arranged, preferably immediately adjacent to the latter, the conveying speed (= peripheral speed) U2 of which is greater than the conveying speed V1 of the first conveyor device k.

A third conveyor device 10 is expediently provided behind the cutting tool 1, which is also continuously driven at a conveyor speed V2 that corresponds to the conveyor speed V2 of the second conveyor device 9.

The clamping device 8 comprises two clamping jaws 11, which are arranged at a distance from one another in the transverse direction of the paper web 7, and of which only one is shown in the drawing. These clamping jaws 11 interact with a stationary base 12. Each clamping jaw 11 is arranged at one (lower) end of a plunger 13 which is movable transversely to the feed direction A of the paper web 7, the other (upper) end of which carries a roller 14 which interacts with a cam disk 15. The neck disk 15 can be driven synchronously with the cutting tool 1. For this purpose, a common belt drive 16 or the like can be provided according to Figure 2, which is driven by the motor M2. The belt drive 16 drives the cam disk 15 via the wheel 17 and the movable cutting knife 3 via the wheel 18 and the crank 19.

The drive of the belt drive 16 is expediently continuous, but it can also be intermittent. The drive speed η of the belt drive 16 can be adjusted depending on the conveying speed IM of the first conveyor device k so that

a cut is made when the paper web 7 has been moved further by the conveyor device k relative to the cutting tool by a length corresponding to the desired format height (= pre-print height).

The second conveyor device 9 and the third conveyor device 10 each expediently have a continuously drivable conveyor roller 20 or 21 and at least one pressure roller 22, 23 which is axially parallel to the latter and which rests against the conveyor roller or 21 under elastic pre-tension Zk . The elastic pre-tension Zk is preferably adjustable. The two conveyor rollers 20, 21 can be driven, for example, by a third motor M3. This third motor M3 gives the conveyor rollers 20, 21 a conveying speed V2 which is, for example, four times as high as the conveying speed V1 of the first conveyor device it.

Furthermore, it is expedient to provide a bulging device 25 between the first conveyor device k and the clamping device 9, which exerts a force P on the paper web 7, at least temporarily, directed transversely to the feed direction A. If the feed direction A, as is the case in the embodiment shown in Figures 1 and 2, runs essentially horizontally, then the force P should be directed upwards. This has the advantage that the feed of the paper web section 7a stored during the cutting process is also supported by gravity after the clamping device B is released, as will be described in more detail below.

To generate the force P, a guide plate 26 can be provided, which is opposite a

Conveying elements 5 of the first conveyor k and the clamping elements 11, 12 of the clamping device 8 are curved transversely to the feed direction A. In the embodiment shown in Figures 1 and 2, the bulge 26a is upwards. In addition to or instead of this guide plate 26, blow nozzles 27 can also be provided to generate the force P. The air streams emerging upwards from the blow nozzles 27 are expediently controlled so that they only emerge from the blow nozzles 27 when the paper web 7 is clamped by the clamping device B. The expulsion of the paper web section 7a can also take place by means of not shown plungers or the like which can be moved transversely to the feed direction A and which are driven synchronously with the clamping device θ.

The operation of the device described so far is as follows:

2Q During operation of the device, the first conveyor k is continuously driven at a conveyor speed V1 and the second and third conveyors 9 and 10 are continuously driven at a higher conveyor speed V2. The movable cutting blade 3 can also be continuously driven so that a cutting process is carried out alternately or the passage between the cutting blades 2 and 3 is cleared. While the latter is the case, the clamping device 8 is also opened so that the paper web 7 is moved further in direction A by the conveyors k and 9 and, in the case of larger format heights, also by the conveyor 10. As soon as the paper web has been moved further relative to the cutting tool 1 by the set format height, the cam disk 15 presses the plunger 13 downwards so that the paper web is between

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Clamping jaws 11 and stationary base 12 are clamped. The conveyor rollers 20, 21 of the second conveyor device 9 and the third conveyor device 10 continue to rotate. The movable cutting blade 3 goes down and cuts a sheet of paper 7b to the desired format height, which is immediately moved on by the third conveyor device 10. The conveyor rollers 20, 21 have a smooth steel surface and the elastic pre-tension Zh is adjusted so that the conveyor rollers 20, 21 can rotate while the paper web is clamped without damaging it.

Whilst the paper web is held in place by the clamping device 8 for the duration of the cutting process, the first conveyor h continuously feeds paper web. This additional paper web section is stored in the form of a loop 7a which bulges upwards transversely to the theoretically straight feed direction A. The bulging guide plate 25 and/or the blowing nozzles 27 promote the bulging and ensure that the bulging takes place in a predetermined direction, namely upwards. During the bulging, a tension is created in the loop 7a, similar to that in a buckling rod. If the passage between the cutting knives 2, 3 is released again after the cutting process has ended, the clamping device 8 also opens as the area 15a of the cam disk 15 comes into the area of the roll 1^+. As soon as the clamping device B is opened, the second conveyor device 9 conveys the end of the paper web adjacent to the cutting device 1 at a conveying speed MZ that is higher than the conveying speed 1/1 of the first conveyor device k. This

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stored loop 7a is removed. The further bending of the paper web section stored in the form of the loop 7a is also promoted by the tension generated in the loop, which pushes the free end of the paper web in the direction of the cutting tool 1. The loop 7a cannot expand backwards because paper web is constantly being fed forward by the first conveyor device k . In addition to the tension built up in the loop 7a, in the embodiment shown in Figures 1 and 2, gravity can also come into effect, which presses the loop 7a downwards and thereby moves the paper web in the direction of the cutting tool 1. The second conveyor device 9 therefore only ever needs to move the small paper web section 7a stored in the form of the loop, this further movement being promoted by the tension built up during clamping and by gravity.

0 The paper web can also be held in place in other ways, for example by means of clamps that grip the edge of the paper web. The only important thing is that the clamping device is driven synchronously with the cutting tool so that the clamping device 5 holds the paper web during the cutting process.

The embodiment of the device shown in Figures 3 and k works according to the same principle as the previously shown embodiment. 3D Therefore, only the differently designed parts of the device are described. The cutting tool 1' in this case has a stationary cutting blade 2,

which interacts with a rotating cutting knife 3'. Such a rotating cutting knife 3' has the advantage, compared to an up and down moving cutting knife, that the passage between the cutting knives 3' and 2 is immediately released again after the cut has been completed, whereas with an up and down moving knife, this must move upwards again after the cut has been completed. The rotating knife 3' can further increase the cutting performance of the device because the time during which the paper web must be stopped by the clamping device 8 is shortened.

In the device shown in Figures 3 and k, the first conveyor device k has a continuously driven conveyor roller 28 and at least one elastically pressed pressure roller 29. With such a conveyor device k* , the advancement of a paper web can also take place which has no perforations on its longitudinal edges. In this embodiment, the guide plate 26' is also curved downwards relative to the plane EE. This has the advantage that the curvature of the loop 7a formed during the clamping of the paper web is supported by gravity.

In addition to or instead of the guide plate, similar to the previous embodiment, air nozzles 27 can also be provided. Similar to the previous embodiment, in the embodiment shown in Figures 3 and 4,

3G play between the first conveyor device if' and the clamping device 8, a free space 3D is provided in which the paper web section continuously required by the first conveyor device W during the cutting process can bulge out in the form of the loop 7a.

The drive connections are shown in Figure k . A common drive motor M1 is provided to drive the first conveyor device k', the second conveyor device 9 and the third conveyor device 10.

A corresponding gear ratio ensures that the conveying speed V/2 of the second and third conveying devices 9 and 10 is greater than the conveying speed V/1 of the first conveying device t* ' . The clamping device B and the cutting tool 1' are driven by a common belt drive 16 via the motor M2, similar to the previous embodiment.

Since the mode of operation of the embodiment shown in Figures 3 and 4 corresponds to the mode of operation of the previous embodiment, a detailed description of the same is unnecessary. However, since in the embodiment shown in Figures 3 and k gravity counteracts the stretching of the loop 7a after the clamping device B is released, it may be expedient to provide one or more additional blowing nozzles 31 which are activated after the clamping device B is released and exert an upward force on the loop 7a.

An important contribution to increasing cutting performance is the particularly advantageous design of the area in which the loops are formed, as shown in Figures 5 and 6. It was found that at paper feed speeds of around 0.8 m/s (which corresponds to around 3000 cuts per hour at a feed pressure of 3"), unacceptable fluctuations in cutting accuracy occur. In order to achieve sufficient cutting accuracy in the tenth of a millimeter range, e.g. in the range of -0.3 mm, despite high feed speeds and high cutting performance,

To achieve this, it is advisable to apply the measures described below in combination.

The guide plate 26 is curved upwards, whereby the curvature is achieved by a bend 26b of the guide plate. The guide plate 26 is also provided with a large number of openings 36, e.g. circular holes. Through these openings 36, air can quickly enter between the loop and the guide plate during the curvature of the loop, but in particular the air can quickly escape from the space between the loop 7a and the guide plate 26 when the loop is pulled flat again by the second conveyor device 9 after the cutting process has ended.

Here, the paper web 7 comes to rest on the abutment 26b. The friction that occurs at this point ensures that the tension exerted on the paper web by the second conveyor does not spread to the full extent to the first conveyor.

2G can reproduce.

Furthermore, viewed in the paper feed direction A, guide plates 37, 38 are provided in the front and rear areas of the guide plate 26 above it, inclined in opposite directions to one another, which influence the loop formation. These guide plates 37, 38 are installed to support even loop formation. The guide plates 37, 38 ensure that the loop formation always takes place in approximately the same place.

3D and that the loop does not move forwards or backwards in the feed direction A. The loop formation is reproducible, above all, through the guide plates 37, 38. In order to be able to influence the loop formation, it is also expedient that the inclination of each guide plate 37, 38 relative to the guide plate 26 is adjustable.

bar. For this purpose, the guide plates 37, 38 can be pivoted about an axis 39, kD running transversely to the feed direction A and can be locked by a device not shown.

Furthermore, it is expedient if the space above the guide plate 2S and above the guide plates 37, 3B is enclosed by a damping hood 41. The damping hood W\ should be arranged at a greater distance from the loop 7a so that there is still sufficient air space between the loop 7a and the interior of the damping hood. The damping hood acts on the one hand as an air chamber which dampens the vibrations occurring when the loop is formed at high speeds and on the other hand it also serves for sound insulation.

The measures applied together in the embodiment shown in Figures 5 and 6 lead to a stabilization and reproducibility of the loop formation, which, according to experience, is a prerequisite for high cutting accuracy with tolerances in the tenth of a millimeter range at high cutting performances.

Claims (1)

- 16 protection claims 1. Device for cross-cutting a paper web, with a stationary cutting tool, which has cooperating cutting knives, and with a first conveyor device arranged in front of the cutting tool, by means of which the paper web is fed in a predetermined length between two successive cutting processes, characterized in that in the area between the first conveyor device (k, 4 '), which is continuously driven during operation of the device, and the cutting tool (1, 1') a clamping device (S) driven synchronously with the latter is provided, by means of which the area of the paper web (7) immediately adjacent to the cutting tool (1, 1') and lying in front of it can be clamped for the duration of the cutting process until the passage between the cutting knives (2, 3, 3') is free again, and that in the area between the first conveyor device (4, ^ ¹ ) and the clamping device (Θ) a free space (30) is provided, in which the the paper web section continuously fed by the first conveyor device can expand in the form of a loop (UeIIe) (7a) which is curved transversely to the theoretically straight feed direction (A). 2- Device according to claim 1, characterized in that the clamping device (8) is arranged in the vicinity of the cutting tool (1, 1'). 3· Device according to claim 1 or 2, characterized in that a continuously driven, second conveyor device (9) is arranged between the clamping device (B) and the cutting tool (1, 1 ¹ ), the conveyor speed (V2) of which is greater than the conveyor speed (V/1) of the first conveyor device (k, W). - 17 - ^. Device according to claim 3, characterized in that the conveying speed (V2) of the second conveying device (9) is approximately four times as high as the conveying speed (V1) of the first conveying device (if, if'). 5. Device according to one of claims 1 - h, characterized in that behind the cutting tool (1, 1') a third conveyor device (10) is arranged, the conveying speed (V2) of which is greater than the conveying speed (V1) of the first conveyor device (k, k'), S. Device according to claim 3 and 5, characterized in that the conveying speeds (V2) of the second and third conveying devices (9, 10) are equal. 7. Device according to claim 1, characterized in that between the first conveyor device (k, k') and the clamping device (8) a buckling device (25) is provided, which exerts on the paper web (7) at least temporarily a force (P) directed transversely to the feed direction (A). B. Device according to claim 7, characterized in that the feed direction (A) is substantially horizontal and the force (P) is directed upwards. 9. Device according to claim 7, characterized in that the feed direction (A) is essentially horizontal and the force (P) is directed downwards. 1Ü. Device according to one of claims 1 - 9, characterized in that between the first conveyor device (U, W) and the clamping device (8) there is a guide plate (26, 26') which is curved transversely to the feed direction (A) with respect to a plane (EE) tangent to the conveyor elements (5; 28, 29) of the first conveyor device (k, k ^} ) and the clamping elements (11, 12) of the clamping device (8). 11. Device according to one of claims 7 - 9, characterized in that blowing nozzles (27) are provided for generating the transversely directed force (P). 12. Device according to one of claims 7 - 9, characterized in that, in order to generate the transversely directed force (P), plungers or the like are provided which are driven synchronously with the clamping device (8) and can move transversely to the feed direction. 13. Device according to claim 1 or 2, characterized in that the clamping device (8) comprises at least one clamping jaw (11) movable transversely to the feed direction, which cooperates with a stationary base (12). 1A-. Device according to claim 13, characterized in that the clamping jaw (11) is arranged at one end of a plunger (13) that is movable transversely to the feed direction (A), the other end of which is provided with a cam 3D disk (15) which in turn can be driven synchronously with the cutting tool (1, 1 '). 15- Device according to claim 14, characterized in that a common belt drive (16) or the like is provided for the synchronous drive of the cutting disk (15) and the cutting tool (1, ¹¹ ). 16. Device according to claim 3 and 5, characterized in that the second and the third conveyor device (9, 1D) each have a continuously drivable conveyor roller (20, 21) and at least one pressure roller (22, 23) axially parallel thereto, which rests against the associated conveyor roller (20, 21) under elastic prestress (24). . Device according to claim 16, characterized in that the preload (24) is adjustable. 13. Device according to claim 11, characterized in that the guide plate (26) is provided with a plurality of openings (36). 15 19. Device according to claim 11 Ddsr 1&THgr;, characterized in that the guide plate (26) is curved upwards. 20. Device according to claims 11 or 18 and 19, characterized in that in the paper feed direction (A) in the front and rear region of the guide plate (26) above the latter, guide plates (37, 38) are provided which are inclined in opposite directions to one another and influence the loop formation. 21. Device according to claim 20, characterized in that that the inclination of each guide plate (37, 3Θ) relative to the guide plate (26) is adjustable. 30 22. Device according to one of claims 18 - 21, characterized in that the space above the guide plate (26) and the baffles (37, 38) is enclosed by a damping hood (41). 23. Device according to claim 22", characterized in that the damping hood (41) is arranged at a greater distance from the loop (7a).