EP0670203B1 - Method and device for cutting paper sheets assembled in a ream - Google Patents

Abstract

The invention relates to the polygraphic industry. The essence of the invention consists in that the penetration of the knife (1) into a ream (2) of paper sheets and the separation of the ream (2) is effected simultaneously with relative movement of the knife (1) and the ream (2). The knife is shaped as a plate (4) with teeth (5) provided with cutting edges (6) and has the form of a non-isosceles triangle. The longer side (7) of the plate (4) is inclined at an acute angle in the direction of movement of the knife (1) in relation to the ream (2), the teeth (5) are located on that side (7) and have two sides (8 and 9) of different lengths, the cutting edges (6) of the teeth (5) being located on their longer sides (8). Most sucessfully the invention may be used for cutting of inner books. The invention may also be used for cutting of non-metallic sheet material.

Description

Technical field

The invention belongs to the graphics industry. It relates to a method for cutting assembled printed sheets and to a device for carrying it out.

Conventional procedure

Graphic engineering, which produces automated production lines that also include the processing of book blocks, is currently in a development stage in which cutting the book blocks is the bottleneck; both in terms of improving the quality of the cutting of the book blocks and in terms of increasing the performance of the entire production line.

At present, a conventional cutting method is mostly used for cutting a paper stack, in which the knife penetrates into the paper stack and divides it in the direction transverse to the plane of the sheet, the knife and the paper stack being moved relative to one another.

For the implementation of this known method for cutting pieces of paper, a device with a knife in the form of a circular saw blade with teeth is used which has cutting edges and which is rotatably mounted on a substructure and is provided with a drive for the relative movement between the knife and the paper stack.

The disadvantage of this method for cutting paper stacks is the low cut quality on the end faces of the paper stacks, since the teeth of the knife inevitably leave visible traces on the surface of the end face of the processed paper stack when it penetrates into the paper stack and when it is divided. The cutting depth of each tooth is limited by its size, which in turn limits the speed of the relative movement of the paper stack to the knife and accordingly the performance of the device. The desire to increase the performance of the device requires increasing the speed of rotation of the knife; this in turn leads to an increase in the noise level due to violent vibrations of the paper sheets in the stack, since the knife moves across the paper sheets. But mostly this device is the most important source of noise among all devices that are used, for example, in the processing of book blocks.

A method according to the preamble of claim 1 or a device according to the preamble of claim 4 is known from SU-A-1355487.

The present invention has for its object to provide a cutting method for collated sheets and a device for its implementation, such that when the knife penetrates into the sheet stack and when it is divided there are no cutting marks on the surfaces of the end faces of the trimmed sheet stack and an increase in relative speed of the sheet stack to the knife is possible and that vibrations of the sheet of the sheet pile during cutting are excluded. The aim of this is to increase the quality of the end faces of the stack of sheets to be processed and the performance, and to reduce the noise during the cutting process.

This object is achieved according to the invention by a method according to claim 1 or a device according to claim 4.

The penetration of the knife into the paper stack and its division with a relative movement of the knife and the printing sheet stack in a direction parallel to the sheets prevents visible traces of the cutting edges of the knife on the processing end faces of the printing sheet stack. This is because of such a relative movement Always cut a certain number of sheets from the beginning to the end between the knife and the stack of printed sheets without touching other sheets.

The quality of the trimmed end faces of the stack of printed sheets is further improved by the fact that each point of the cutting edges of the knife moves parallel to the sheet as it enters the stack of printed sheets and is divided, and thus leaves no visible traces of the cutting tool.

The efficiency of cutting the stack of printed sheets increases because the speed of the knife penetrating and dividing the stack of sheets does not depend on the depth of the cut, which depends on the size of the tooth, and not on the rotational speed of the knife, which increases the noise level increased, limited. In addition, the noise level is reduced since there are no vibrations of the printed sheets, which accompany the conventional cutting of the sheets in the stack, with the knife movement oriented transversely to the printed sheets.

The knife preferably penetrates into the stack of printed sheets in its upper and lower side region.

The quality of the trimmed sheet stack increases due to an improvement in the cut quality of the sole, which consists of a few last sheets, which receive better grip when the knife penetrates from the top and bottom sheets, do not bend and therefore improve the cutting condition of the sole.

The knife can be penetrated into the stack of printed sheets one after the other, first from the top sheet of the paper stack and then from the bottom sheet.

This reduces the cutting quality, since the condition of the knife penetrating into the stack of printed sheets and its division is compensated for all sheets; all bows have a firm hold when divided.

According to the invention, the plate of the device according to the invention has the shape of an isosceles triangle, the longer side being at an acute angle to the relative direction of movement of the knife and the stack of printed sheets. The teeth are on the longer side of the plate and are made with two sides of different lengths. The cutting edges are on the longer sides.

Such a design of the device increases the quality and the performance and ensures a reduction in the noise level.

The design of the plate of the knife in the form of an isosceles triangle, the longer side of which is at an acute angle to the direction of movement of the knife and the stack of printed sheets, results in a reduction in the cutting force; therefore the relative speed of the knife and the stack of printed sheets can be increased. In this case, each tooth of the knife cuts from the beginning to the end a part of the stack of sheets, which consists of a few sheets, which prevents traces of the knife on the trimmed surface of the sheet stack - a reliable and trouble-free way of cutting.

The quality of the trimmed surface of the stack of printed sheets increases because every point of the cutting edge of the knife, including the tips of the teeth, moves parallel to the sheets when entering and dividing them into the stack and does not cross with the sheets and therefore also leaves no visible traces.

The noise level is significantly reduced, since the proposed construction of the knife ensures a uniform penetration of the knife into the stack of printed sheets, that is to say cuts the stack of printed sheets in such a way that each tooth has a certain part of the stack from the beginning to the end, which consists of a few Arch exists, cuts, but there is no violent oscillation of the arches that accompany the traditional cutting method.

This device preferably also has an additional knife, similar to the main knife, which is mounted on the substructure and is located in the plane of the main knife. The teeth of this additional knife would be aligned symmetrically to the teeth of the main knife and shifted from one another.

This additional knife ensures better cutting quality by making it easier to cut the sole (if there are only a few sheets left to cut, the strength of the stack of printed sheets is reduced, which makes cutting the sole more difficult).

You can run this additional knife together with the main knife.

In such a case, the need for an adjustment of the additional knife in the plane of the main knife and other adjustments when mounting the additional knife become obsolete.

Furthermore, the teeth can also be designed individually and mounted on a plate with the possibility of changing their position for the alignment of the cutting edges of the teeth in one plane.

In such a case, the operating conditions of the device improve by reducing the amount of work involved in sharpening the knife, since sharpening is made much easier.

The knife is preferably designed such that the tips of the cutting edges of the teeth on a section whose length is 1/3 to 1/4 of the total length of the longer side of the knife adjoins the shorter side of the knife, on a line with less Angle to the relative direction of movement of the knife and the paper stack than the angle of the remaining section of the longer side of the knife.

In this case, the cutting quality increases due to an improvement in the cutting conditions for the lower sheets, since the cutting force is reduced by a smaller angle of the line of the tooth tips of the knife to the direction of movement of the knife and the paper stack.

In this case, the knife can be designed as two connected plates, the connecting line of which passes between the sections of the longer side of the knife plate.

Such a design facilitates the production and sharpening of the knife.

Furthermore, the device could be designed with two brackets, which are mounted on the base. The knife with the possibility of suspension is mounted on a holder and resiliently against the second holder by means of a spring. It is expedient here that this device is equipped with a stop for limiting the suspension angle, which is attached to the substructure.

In such a case, the life of the knife is increased by reducing the regrinding. Since the cutting force increases when the tooth tips become blunt, pressure is created and the knife is twisted or the blunt cutting edges are twisted off into the non-working zone. Sharper zones of the cutting edge now act as tips of the cutting edges. This brings about a restoration of the operability of the device.

It can be recommended to install a means for regulating the pressure force of the spring in the form of a screw, which is attached to the holder against which the knife springs.

Such a means ensures a nominal angle of the knife to the direction of the relative movement of a stack of paper and the knife, and thus ensures nominal conditions of the cutting force which changes when processing paper stacks of different heights and types of paper.

It is recommended to mount two parallel plates on both sides of the base in the plane of the knife, which ensure the direction of movement of the knife during springing in one plane, but do not prevent the movement of the paper stack.

Brief description of the drawings

Fig. 1

eine schematische Darstellung des erfindungsgemässen Verfahrens zum Schneiden zusammengetragener Papierbogen;

Fig. 2

das Verfahren zum Schneiden zusammengetragener Papierbogen durch Eindringen des Messers von Seiten der obersten und untersten Bogen;

Fig. 3

eine Gesamtansicht der erfindungsgemässen Vorrichtung zum Schneiden zusammengetragener Papierbogen, wobei sich der Papierstapel bewegt und das Messer still steht;

Fig. 4

Schnitt IV-IV in Fig. 3;

Fig. 5

die Geometrie des erfindungsgemässen Messers zum Schneiden zusammengetragener Papierbogen in vergrössertem Massstab;

Fig. 6

Schnitt VI-VI in Fig. 5;

Fig. 7

eine Gesamtansicht der Vorrichtung zum Schneiden zusammengetragener Papierbogen während des Eindringens des Messers in den Papierstapel von Seiten der obersten und untersten Bogen;

Fig. 8

Schnitt VII-VII in Fig. 7;

Fig. 9

eine Variante der Vorrichtung zum Schneiden zusammengetragener Papierbogen mit einem Zusatzmesser, welches gemeinsam mit dem Hauptmesser ausgeführt wurde;

Fig. 10

Schnitt X-X in Fig. 9;

Fig. 11

die Geometrie des erfindungsgemässen Zusatzmessers, welches gemeinsam mit dem Hauptmesser ausgeführt ist;

Fig. 12

Schnitt XII-XII in Fig. 11;

Fig. 13

eine Variante der Vorrichtung für das Schneiden zusammengetragener Papierbogen im Falle montierbarer Zähne des Messers;

Fig. 14

Schnitt XIV-XIV in Fig. 13;

Fig. 15

die Geometrie des erfindungsgemässen Messers mit montierbaren Zähnen in vergrössertem Massstab;

Fig. 16

Schnitt XVI-XVI in Fig. 15;

Fig. 17

eine Variante der erfindungsgemässen Vorrichtung zum Schneiden zusammengetragener Papierbogen mit einem Messer, mit verschiedenen Neigungswinkeln der Abschnitte der Linie der Zahnspitzen zur relativen Bewegungsrichtung des Messers und des Papierstapels;

Fig. 18

Schnitt XVII-XVII in Fig. 17;

Fig. 19

ein erfindungsgemässes Messer ausgeführt aus zwei verbundenen Platten in vergrössertem Massstab;

Fig. 20

Schnitt XX-XX in Fig. 19;

Fig. 21

eine Variante der erfindungsgemässen Vorrichtung zum Schneiden von Papier mit einem federnden Messer;

Fig. 22

Schnitt XXII-XXII in Fig. 21.

The present invention is described in more detail below using a specific exemplary embodiment with references to the accompanying drawings. Show it:

Fig. 1

is a schematic representation of the inventive method for cutting collated paper sheets;

Fig. 2

the method of cutting collated sheets of paper by penetrating the knife from the top and bottom sheets;

Fig. 3

an overall view of the inventive device for cutting collated sheets of paper, with the stack of paper moving and the knife stationary;

Fig. 4

Section IV-IV in Fig. 3;

Fig. 5

the geometry of the knife according to the invention for cutting collated paper sheets on an enlarged scale;

Fig. 6

Section VI-VI in Fig. 5;

Fig. 7

an overall view of the device for cutting collated paper sheets during the penetration of the knife into the paper stack from the top and bottom sheets;

Fig. 8

Section VII-VII in Fig. 7;

Fig. 9

a variant of the device for cutting collated paper sheets with an additional knife, which was carried out together with the main knife;

Fig. 10

Section XX in Fig. 9;

Fig. 11

the geometry of the additional knife according to the invention, which is designed together with the main knife;

Fig. 12

Section XII-XII in Fig. 11;

Fig. 13

a variant of the device for cutting collated paper sheets in the case of mountable teeth of the knife;

Fig. 14

Section XIV-XIV in Fig. 13;

Fig. 15

the geometry of the knife according to the invention with mountable teeth on an enlarged scale;

Fig. 16

Section XVI-XVI in Fig. 15;

Fig. 17

a variant of the inventive device for cutting collated paper sheets with a knife, with different inclination angles of the sections of the line of the tooth tips to the relative direction of movement of the knife and the paper stack;

Fig. 18

Section XVII-XVII in Fig. 17;

Fig. 19

a knife according to the invention made of two connected plates on an enlarged scale;

Fig. 20

Section XX-XX in Fig. 19;

Fig. 21

a variant of the inventive device for cutting paper with a resilient knife;

Fig. 22

Section XXII-XXII in Fig. 21.

Best implementation variant of the invention

The cutting method to be patented for collated sheets of paper provides for the knife 1 (FIG. 1) to penetrate into the paper stack 2 and cut it up. A movement (arrow A) of the knife 1 or a movement (arrow B) of the paper stack 2 or of the knife 1 and the paper stack 2 relative to one another is realized.

According to the invention, the penetration of the knife 1 into the paper stack 2 and the division of the paper stack 2 in the directions of the two arrows A and B is carried out parallel to the sheets of the paper stack.

The penetration of the knife 1 in the direction of the arrows A and B, as can be seen in FIG. 2, into the paper stack 2 is carried out simultaneously by the upper sheets of the paper stack 2 and the lower sheets of the paper stack 2.

This allows the quality of the surface of the cut part of the paper stack to be increased by improved cutting conditions of the sole.

The penetration of the knife 1 into the paper stack 2 can be carried out as follows: first from the side of the upper sheets of the paper stack 2, then from the side of the lower sheets of the paper stack 2.

The proposed cutting method for paper stacks is carried out by means of a device consisting of a base 3 (FIG. 3) on which the knife 1 (FIG. 4) in the form of a plate 4 with teeth 5, which have cutting edges 6 (FIG. 5) carried out. The plate 4 has the shape of an isosceles triangle, where the longest of the sides 7 is at an acute angle (FIG. 3) to the relative direction of movement of the knife 1 and the paper stack 2. The teeth 5 are located on this longest side 7 of the plate 4 (FIG. 5) and are designed with two sides 8 and 9 of different lengths, the cutting edges 6 (FIGS. 5 and 6) being on the longer side 8 of the teeth 5 are located and have a radius R.

Furthermore, the device is equipped with guide elements 10 (FIGS. 3 and 4) mounted on the substructure 3, a carriage 11 placed on the guide elements for receiving the paper stack 2, equipped with pliers 12 for clamping the paper stack 2, and a drive 13 for the relative movement of the Knife 1 and the paper stack 2, which, as can be seen in FIG. 3, is connected to the carriage 11 for its possibility of transportation.

The drive 13 can be connected to the knife 1 or to the carriage 11, on which the paper stack 2 is located and the knife 1, with the possibility of the movement of the knife 1 or the movement of the carriage 1 with the paper stack 2 to one another.

Because the cutting edges of the teeth move parallel to the paper sheets and leave no visible traces, such a device guarantees and allows a better quality of the trimmed surfaces of the paper stack, an increase in the productivity of the cutting and a reduction in the noise level.

Another embodiment variant of the device for cutting a paper stack has a further knife 14 (FIGS. 7, 8) similar to the main knife 1, which is mounted on the substructure and is located in one plane with the main knife 1. The teeth 15 (FIG. 7) of the additional knife 14 are arranged symmetrically to the teeth 5 of the main knife 1 and are displaced from one another. This improves the quality of the trimmed surface of the paper stack by making it easier to cut the sole of the paper stack.

9 and 10, a device with the additional knife 14 is shown, which is carried out together with the main knife 1 in one. 11 and 12, the additional knife 14 is shown on an enlarged scale, which is designed in one with the main knife 1. Such a design reduces the number of parts and in this case no additional fastening or additional regulation of the additional knife is required.

13 and 14 show a further embodiment variant of the device for cutting a paper stack. The knife 1 (Fig. 13) is designed with teeth 5 (Fig. 14) which are detachable and with the possibility of a change of position mounted on the plate 4 in order to cut the cutting edges (Fig. 15) of the teeth (Fig. 16) in one plane bring. This improves the operation of the device by reducing the work involved in grinding the knife, since all cutting edges are aligned like a cutting edge during the grinding process and the tips of the cutting edges of each tooth are reworked.

The device for cutting a stack of paper, which is shown in FIGS. 17 and 18, consists of the knife 1, where the tips 16 (FIG. 17) of the cutting edges 6 of the teeth 5 lie on the section 17, which has a length of approximately Has 1/3 to 1/4 of the total length of the longest sides 7 of the knife 1 and adjoins the shortest side 18 of the knife 1 (FIG. 18), on a line which has a smaller angle β to the relative direction of movement of the knife 1 and of the paper stack 2 has, as the angle γ of the remaining section 19 of the longest side 7 of the knife 1. The cutting quality is improved by the better cutting conditions of the lower sides of the paper stack.

19 and 20, the device for cutting a stack of paper is shown, which has a knife 1 made of two connected plates 20, 21. The plates are mounted on the knife holder 22, the connecting line 23 (FIG. 19) crossing the sections 17 and 19 of the longest side 7 of the knife 1. In this case, the manufacture and grinding of the knife 1 is simplified.

The device for cutting a stack of paper, which is shown in FIG. 21, has two holders 24 and 25, which are mounted on the substructure 3 (FIG. 22). On the holder 24 (FIG. 21), the knife 1 is mounted such that it can vibrate and is resiliently supported against the other holder 25 by means of the spring 26. The device also has a stop 27 mounted on the substructure 3 for limiting the suspension angle of the knife 1.

In this case, the life of the knife is increased by reducing the regrinding of the cutting edges of the teeth. As the cutting pressure of the cutting edges of the knife teeth oriented towards the cutting surface becomes blunt, the spring compresses and the knife rotates in the direction of the paper stack or the blunt cutting edges of the knife teeth are turned away into a non-working zone, with sharper zones of the Cutting edges become tips, which restores the working ability of the device; this increases the life and productivity.

The spring 25 has a means for regulating the spring pressure, which is designed in the form of a screw 28 (FIG. 22) and is mounted on the holder 25, against which the knife 1 springs.

This gives the possibility to regulate the spring pressure and therefore also the position of the knife depending on the cutting force, which changes when cutting different types of paper and many other factors.

On the base 3 (FIG. 21), two parallel plates 29 (FIG. 22) are mounted on both sides of the plane of the knife 1, which ensure the direction of movement of the knife 1 with its springs.

In this case, the stability of the knife increases when cutting a stack of paper.

Cutting sheets gathered into a stack, e.g. Paper is carried out as follows.

With a relative movement of the paper stack 2 (FIGS. 3 and 4) and the knife 1, for example when the carriage 11 is moving with the paper stack 2 clamped in the pliers 12 along the guide elements 10 connected to the base in the direction of the knife mounted on the base 1 with teeth 5, which have cutting edges 6, the knife 1 penetrates parallel to the paper sheet into the paper stack 2 and divides it, each tooth 5 of the knife 1 from the beginning to the end cuts a part of the stack consisting of a specific number of sheets.

The device with additional knife works as follows.

With a relative movement of the paper stack 2, the main and the additional knife 1 and 14, which teeth, corresponding to 5 and 15, have, e.g. When the carriage 11 moves with the paper stack 2 clamped in the pliers 12 along the guide elements 10 connected to the substructure in the direction of the main and additional knives 1 and 14 mounted on the substructure 3, the main knife 1 penetrates into the paper stack 2 parallel to the paper sheets from the side of the upper sheet and cuts the paper stack, the additional knife 14 penetrating parallel to the paper sheet from the side of the lower sheet into the paper stack 2, making an incision in the paper stack 2 from the side of the lower sheet and thus cutting the sole of the paper stack simplified.

The device with an additional knife, which is designed in one with the main knife, works as follows.

With a relative movement of the paper stack 2 (Fig. 9, 10) and the knife 1, which has teeth 5, e.g. when the carriage 11 moves with the paper stack 3 clamped in the pliers 12 along the guide elements 10 connected to the base 3 in the direction of the knives 1 and 14 mounted on the base 3, the knives 1 and 14 penetrate parallel to the paper sheets of the paper stack 3 from sides of the upper and lower sheets in the paper stack 2 and divide the paper stack.

The device for cutting a stack of paper with a knife with removable teeth works as follows.

In the case of a relative movement of the paper stack 2 (FIGS. 13 and 14) and the knife 1 with removable individual teeth, for example when the carriage 11 is moving with the one clamped in the pliers 12 Paper push 2 along the guide elements 10 connected to the base 3 in the direction of the knife 1 mounted on the base 3 with removable teeth, the knife 1 penetrates into the paper stack 2 parallel to the paper sheets and divides the stack.

The knife 1 represents a plate 4 with removable teeth 5 (FIGS. 15 and 16) which are mounted on the plate 4 in order to change their position and thus align the cutting edges 6 of the teeth 5 in one plane. This allows the cutting edges 6 of the teeth 5 to be aligned like a cutting edge during grinding and the radius R of the cutting edge 6 of each tooth 5 to be reworked.

The device for cutting a paper stack with different angles β, γ of the sections 17 and 19 of the side 7 of the knife 1 functions as follows.

With a relative movement of the paper stack 2 (Figs. 17 and 18) and the toothed knife 1, e.g. when the carriage 11 moves with the paper stack 2 clamped in the pliers 12 along the guide elements 10 connected to the base 3 in the direction of the knife 1 mounted on the base 3, the knife 1 penetrates into the paper stack 2 parallel to the paper sheets. Each tooth 5 of the knife 1 on the section z (FIG. 19) cuts from the beginning to the end of the stack with the height h, each tooth of the second part of the knife - on the section z1 - a part of the stack 2 with a lower height h1. The knife 1 can be in the form of a plate 4 or two connected plates 20 and 21, which are mounted on the knife holder 22 and whose connecting line 23 passes through the two sections of the longest side 7 of the knife 1 (FIGS. 19 and 20) be.

The device for cutting a stack of paper with the knife, which swings on one holder and springs against the other holder, functions as follows.

With a relative movement of the paper stack 2 (FIGS. 21 and 22) and the knife 1 with teeth 5, for example, when the carriage 11 is moving with the paper stack 2 clamped in the pliers 12 along the guide elements 10 connected to the substructure in the direction of the substructure 3 by means of a knife 1 mounted by means of a holder 24, the knife 1 penetrates parallel to the paper sheets into the paper stack 2 and divides the paper stack 2.

When the tips of the cutting edges 6 of the teeth 5 of the knife 1 rounded off with the radius R on the cutting surface become blunt, the cutting pressure increases, this leads to the compression of the spring 26, which is located on the spring pressure regulating screw 28, which holds the holder 25 and the projection 30 of the knife 1 connects, for a rotation of the knife 1 in the direction of the paper stack 2 and for a turning away of the blunted cutting edges 6 of the teeth 5 of the knife 1 into a non-working zone, other sharper sections becoming tips of the cutting edges 6. Two parallel plates 29 limit the movement of the knife 1 in the plane where there is no cutting, and the stop 27 fixes the new position of the knife 1.

The proposed cutting method for paper sheets, which are brought together to form a stack and the device for carrying them out to improve the quality of the paper stack to be processed, allow the paper stack to be cut in motion, for example, book blocks at a speed of 0.5-1 m / Sec and faster, this significantly increases the productivity of the cutting machine, simplifies it considerably, reduces the noise level when performing the technological operation of cutting in motion using a knife with teeth.

The device for carrying out the proposed cutting processes for paper stacks is suitable for installing them in automatic lines for processing book blocks and in book production lines. This gives a leap in the development of cutting equipment and raises the bookbindery to a qualitatively new level.

The variants of the device for carrying out the proposed cutting method described above do not limit the scope of the invention, since the new cutting method of paper stacks opens up a wide field of application and there are development possibilities for a wide variety of equipment for cutting sheets from non-metallic material.

Application in industry

The most successful would be to use the present invention for cutting sheets of paper gathered in book block.

However, the invention can also be used for cutting sheets of non-metallic material.

Claims (12)

1. Method for cutting a stack (2) of collated printed sheets of paper or non-metallic material held more or less perpendicular to the supporting surface of a support and along a cutting line, wherein a knife (1), by means of a relative movement of the knife (1) and the stack (2) executed parallel to the supporting surface, penetrates the stack (1) and divides it, characterised in that the cutting of the stack (2) is effected by a plurality of teeth (5) on the knife (1), each of said teeth (5) featuring a cutting edge (6), and the cutting edges (6) forming an acute angle (α) with the supporting surface and being situated in a plane extending substantially perpendicular to the supporting surface and parallel to the direction of the relative movement.
2. Method according to claim 1, characterised in that the knife (1) penetrates the stack (2) in the upper lateral region of the latter.
3. Method according to claim 1, characterised in that the knife (1) penetrates the stack (2) in the upper and lower lateral region of the latter.
4. Device for carrying out the method according to claims 1 to 3, comprising a support having a supporting surface for holding the stack more or less perpendicular to the supporting surface and along the cutting line, and a knife (1) in the form of a plate (4) assembled onto a substructure (3), and also comprising a drive (13) for a relative movement of the knife (1) and the support holding the stack (2) of printed sheets, characterised in that the plate (4) is in the shape of a triangle with unequal sides and is situated in a plane extending substantially perpendicular to the supporting surface and parallel to the direction of the relative movement, the longest side (7) being situated at an acute angle to the direction of movement, parallel to the supporting surface, of the knife (1) and of the stack (2) of printed sheets, that on this longest side (7) of the plate (4) are arranged the teeth (5), which are constructed with two faces (8, 9) of different lengths, and that the cutting edges of the teeth are situated on the longer of the faces (8), with the longer of the faces in each case being situated at an acute angle (α) to the direction of the relative movement.
5. Device according to claim 4, characterised in that in addition it features an auxiliary knife (14) similar to the main knife (1), assembled on the substructure (3) and situated in the plane of the main knife (1), the teeth of the auxiliary knife (14) being aligned symmetrically to the teeth (5) of the main knife (1) and offset relative to one another.
6. Device according to claim 4, characterised in that the auxiliary knife (14) is constructed as a single entity with the main knife (1).
7. Device according to claim 4, characterised in that the teeth (5) are individually constructed and are assembled on the plate (4) with the option of altering their position in order to align the cutting edges (6) of the teeth (5) in one plane.
8. Device according to claim 4, characterised in that one section (17), the length of which accounts for approx. 1/3 to approx. 1/4 of the overall length (7) of the knife (1), is contiguous with the shorter face (18) of the knife (1), that the tips (16) of the cutting edges (6) of the teeth (5) of this section (17) are situated on a line with a smaller angle (β) to the direction of relative movement of the knife (1) and the stack of paper (2) than the angle (γ) of the remaining section (19) of the longer face (7) of the knife (1).
9. Device according to claim 8, characterised in that the knife (1) is manufactured from two joined plates (20 and 21), the line of the join (23) running between the sections (17 and 19) of the longer face (7) of the knife (1).
10. Device according to claim 4, characterised in that it incorporates two mounts (24 and 25) assembled on the substructure (3), the knife (1) being assembled on one with a means of resilience and cushioned by means of a spring (26) with respect to the second mount (25), and being fitted with a stop (27) to delimit the angle of resilience of the knife (1).
11. Device according to claim 10, characterised in that the spring (26) features a spring pressure regulating means in the form of a screw (28) which is assembled on the mount (25), relative to which the knife (1) is resilient.
12. Device according to claim 10, characterised in that assembled on the substructure (3), on both sides in the plane of the knife (1), are two parallel plates (29) which guarantee the direction in which the knife (1) with its resilience moves.

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