GB2322822A

GB2322822A - Longitudinal web slitting device

Info

Publication number: GB2322822A
Application number: GB9804983A
Authority: GB
Inventors: Klaus Theilacker
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1997-03-07
Filing date: 1998-03-09
Publication date: 1998-09-09
Anticipated expiration: 2018-03-09
Also published as: FR2760402A1; GB9804983D0; DE19709485A1; DE19709485C2; FR2760402B1; GB2322822B; CH692786A5

Abstract

In a cutting device, known as a skip-slitter, for cutting a print web 1 in sections in the longitudinal direction a circular knife 4 has a knife blade 4a which protrudes over half of the outer circumference of the running disc 5. The knife blade 4a cooperates with an annular groove(2 Fig 2) of a grooved roller 3. In order to ensure a clean cut in the cutting line in which it cuts into the printed material web 1 the knife blade 4a is arranged to move longitudinally with respect to the print web 1. The knife disc 5 preferably rotates at the same angular speed as a forme cylinder but has a different, preferably smaller, diameter; this ensures on the one hand the difference in linear speeds and on the other hand the precise registration of the slits with respect to the prints produced by the forme cylinder.

Description

2322822 i_ Longitudinal cutting of printing material is The invention

relates to a process for cutting a printed material web in sections or intermittently in the longitudinal direction by means of a circular cutting knife which has a knife blade which protrudes from the outer contour of the cutting knife over a portion of its circumference in order to cut through the printed material web.

In order to cut a printed material web at intervals, running wheels are used which carry, for example over one half of their circumference, a knife of a circular arc shape. A cutting device of this type is also called a skip-slitter.

A skip-slitter of this type is known from DE 43 19 806 Al. It produces a so-called jumping or intermittent cut in the printed material web. A skipslitter can be used when a printed material web has two different print subjects which are one behind the other in the circumferential direction of the forme cylinder, i.e. if the forme cylinder is equipped with two different plates in the circumferential direction. In this case, for example, the print subject contained on the first plate can be applied to a so-called broadsheet sheet, while the print subject which is transferred to the printed material web by the second printing plate is printed onto two tabloid sheets. In order to obtain these two tabloid sheets, the printed material web has to be cut over half of the circumferential length of the plate cylinder. The cut must end precisely at the point at which the next broadsheet copy starts in the print web.

Known skip-slitters have the same diameter as the forme cylinder and the blanket cylinder and rotate with the same angular velocity. This means that for the is cutting action the knife blade of the circular cutting knife is pushed through the printed material web, causing it to burst. Such a bursting cut results in the tabloid copies having a rough longitudinal edge. Furthermore, it is very difficult to make a knife having the circumference of a double-format forme cylinder, i.e. having a diameter of approximately 300 to 350 mm, while still ensuring the desired level runout. This difficulty is further increased as a result of the fact that the edge of the circular cutting knife has to be hardened.

An object of the invention is to improve the cutting of a printed material web into sections in such a way that the printed material is cut precisely.

With the invention the blade is arranged to move longitudinally relative to the web as it cuts it. This is most simply achieved by giving the cutter disc a different diameter from the forme cylinder that prints the web. The precision of the cut is then ensured by making the knife rotate at the same angular speed as the forme roller. The proportion of one revolution, for the tabloid/broadsheet division one half, over which a cut is made is then just the same as if the knife blade had had the same diameter as the forme cylinder and the blade extended over the same fraction of the circumference.

A particular advantage of the invention consists in that a skip-slitter having a single fixed knife diameter having a fixed suspension geometry is able to cut all variable circumferential dimensions, became the circular arc length of the knife blade of the circular cutting knife is released from the necessity to be the same as the cut length of the sections to be produced in the printed material web.

A particular advantage results if the circular cutting knife has a smaller diameter than the forme cylinder. In this case, less material is required for the manufacture of the circular cutting blade, something which results in it being possible to manufacture the latter in a more cost-favourable way. It is also easier to realise the desired runout in the case of a smaller circular cutting knife.

With reference to an exemplary embodiment, the invention is explained in greater detail in the following with the aid of the drawings, in which:

Figure 1 shows a lateral plan view of the cutting device; and Figure 2 shows the cutting device in crosssection.

A printed material web 1 (Figure 1) runs over a metal plate la of a folder former and at a tangent to a roller 3 which is provided with an annular groove 2 (Figure 2). The groove 2 forms the lower blade to a knife blade 4a, which protrudes over half of the circumference of a running wheel 5 or disc, protrudes through a slit (not shown here) in the metal plate la and cuts through the printed material web 1 in the area of contact with the grooved roller 3 by penetrating into the groove 2. The running wheel 5 and the grooved roller 3 rotate synchronously with each other. The angular position of the knife blade 4a of a circular cutting knife 4 is synchronised with respect to the start and the end of the print subject in the print web 1 to be cut. The running wheel 5 therefore rotates with the same angular velocity as the forme cylinder and the impression cylinder. However, the circumference of the running wheel 5 is different from the circumference of the forme cylinder and of the impression cylinder. As a result of this difference in circumference, a relative velocity is generated between the knife blade 4a and the print web 1. If the diameter of the running wheel 5 is smaller than that of is the forme cylinder, the running wheel 5 rolls more slowly on the surface of the printed material web 1 than the forme cylinder. The knife blade 4a thus has a relative velocity with respect to the printed material web 1. As a result of this relative movement, an exact and precise cut is achieved.

If the diameter of the running wheel 5 is larger than that of the forme cylinder, the knife blade 4a moves faster than the printed material web 1; the same effect occurs. However, in order to simplify the manufacture of the knife blade 4a and in order to be able to manufacture a running wheel 5 which is constructed so as to be as light as possible, the latter preferably has a smaller diameter than the forme cylinder, with the diameter being at least 5% to 10% smaller, the diameter of the running wheel 5 preferably being half that of the forme cylinder. The wheel preferably forms a complete circle, though this is not strictly necessary.

At any rate the proportion of the knife blade 4a at the circumferential contour of the running wheel 5 is retained. The portion of the printed material web 1 that is to be cut and the portion which is not to be cut are usually equally long. In order that the tabloid product is also reliably cut off from start to end, a small incision into the otherwise closed broadsheet product is accepted at the leading and trailing edges. The result of this is that the proportion of the circumference of the wheel 5 that is taken up by the cutting knife blade 4a, which would theoretically amount to 1800, is preferably a little over this, say approximately 1820.

The grooved ring roller 3 is, for example, arranged centrally over the folder former. The skipslitter having the running wheel 5 and the knife blade 4a is arranged below the folder former. The running wheel 5 is mounted by means of a bearing lever 6 in a manner such that it can swivel about a bearing 7. At the same time, a piston rod 10 of a pneumatic cylinder 11 is articulated on the bearing lever 6. The cylinder 11 is mounted so as to be rotatable about a fixed bearing 12. The bearing 12 is arranged in a holder which is in turn fastened to the underside of the metal plate la. As a result of the movement of the piston rod 10 out of an on position A into an off position B, the running wheel 5 can be moved out of the position in which it is engaged, where it slightly penetrates the print web 1 with the knife blade 4a, into a position B in which it is taken off the web 1. When the running wheel 5 is in the on position A, the knife blade 4a cuts the printed material web 1.

The piston rod 10 is constructed so as to be of variable length, so that the depth of penetration of the knife blade 4a into the groove 2 can be altered.

As an alternative, the running wheel 5 can be arranged so as not to be able to swivel but instead to be fixed. With this construction the bearing lever 6 with the bearing 7, the pneumatic cylinder 11, and the control and the air supply can be omitted. In this case, the engaged and disengaged positions are ensured as follows: the engaging corresponds to the knife blade 4a rotating synchronously with respect to the plate cylinder so that it consequently periodically penetrates the printed material web 1 and thus cuts it. The taking-off function is ensured by making the running wheel 5 remain in a predetermined inoperative position. In this position, the knife blade 4a lies under a protective cover 15, with which the running wheel 5 is covered for protection against injuries. The print web 1 is thus opposite the set-back portion of the running wheel 5, so that there is a sufficient distance between the circular cutting blade 4 and the printed material web 1. The angular position of the running wheel 5 can be precisely defined and fixed using an incremental encoder. This incremental encoder is needed anyway in order to synchronise the running wheel 5 with the plate cylinder.

The running wheel 5 is driven by its own motor 16 (Figure 2); it can, however, also be connected via a gearing to the drive of the other rotating parts of the printing machine. It is crucial that the running wheel 5 is synchronised with these parts, i.e. has the same angular velocity, and that the phase angle is fixed with respect to the printed material web. A control loop can also be provided in order to synchronise the running wheel 5 to the speed of rotation of the other components of the printing machine. The same applies for the grooved roller 3. Its diameter is selected to be as small as possible; it preferably has an even smaller diameter than the running wheel 5.

If one or more printed material webs run over a roller 3 provided with a plurality of grooves 2, the running wheel 5 with the knife blade 4a and the cylinder 11 can be arranged so as to be movable in the direction of its axis of rotation, in order to be able to cut the printed material web 1 into sections at various places over its width.

The invention may thus provide a cutting device for cutting a printed material web 1 into sections in the longitudinal direction. A circular knife 4 has a knife blade 4a which extends over half of the circumference of the running wheel 5 and forms the upper blade of the cutting device. The knife blade 4a co-operates with an annular groove 2 of a grooved roller 3. In the cutting line in which it cuts into the printed material web 1, the knife blade 4a has a relative velocity with respect to the printed material web 1. As a result of this relative movement, a precise and clean cut of the printed material web 1 is achieved.

Because the running wheel 5 always has the same angular velocity as the forme cylinder, if the relative velocity with respect to the printed material web 1 changes, the latter can be cut into sections in the longitudinal direction independently of the circumference of the plate cylinder or the knife blade 4.

Instead of arranging the skip-slitter in the region of the metal plate la of the folder former, the skip-slitter can also be arranged above the entrance of the folder former.

Claims

1. A process for cutting a printed material web (1) in sections in the longitudinal direction in a printing machine by means of a circular cutting knife (4), which has a knife blade (4a) which protrudes over a portion of the outer contour of the cutting knife and cuts through the printed material web (1), wherein in the plane formed by the printed material web (1) the knife blade (4a) has a relative velocity with respect to the printed material web (1), while the circular cutting knife (4) has the same angular velocity as the forme cylinder.

2. A cutting device for cutting a printed material web (1) in sections of predetermined length in the longitudinal direction in a printing machine, having a generally circular cutting knife (4), which is arranged on a running wheel (5) and has a knife blade (4a) which protrudes over a portion of the outer contour of the said cutting knife for cutting through the printed material web (1), characterised in that on the line in which the knife blade (4a) cuts through the printed material web (1), the circular arc length of the knife blade (4a) deviates from the said cut length of the sections in the printed material web (1).

3. A cutting device according to claim 2, in which the circular cutting knife (4) has a smaller diameter than the forme cylinder by which the printed material web (1) is to be printed.

4. A cutting device according to claim 3, in which the circular cutting knife (4) has a diameter which is at least 5% smaller than that of the forme cylinder.

5. A cutting device according to claim 4, in which the circular cutting knife (4) has half the diameter of the forme cylinder.

6. A cutting device according to one of claims 2 -g- is to 5, in which the running wheel (5) is arranged so that it can be swivelled away from and towards the printed material web (1).

7. A cutting device according to any of claims 2 to 5, in which the running wheel (5) can be arrested under control by means of an incremental encoder in such a way that the knife blade (4a) of the circular cutting knife (4) does not touch the printed material web (1).

8. A cutting device according to claim 6 or 7, in which the running wheel (5) with the circular cutting knife (4) is arranged underneath the folder former of the printing machine.

9. A cutting device according to claim 6, in which the running wheel (5) can be swivelled towards the printed material web (1) from underneath.

10. A cutting device according to any of claims 2 to 9, in which the circular cutting knife (4) is arranged so that it can be shifted laterally with respect to the printed material web (1).

11. A cutting device according to claim 6, in which the depth of penetration of the knife blade (4a) into an annular groove (2) of a roller (3) acting as a knife support can be altered by a lengthvariable piston rod (10) on which the running wheel (5) is articulated.

12. A cutting device substantially as described herein with reference to the accompanying drawings.

13. A printing machine including a forme roller and an associated cutting device according to any of claims 2 to 12.