EP0505461A1

EP0505461A1 - Lip blade and cutting device.

Info

Publication number: EP0505461A1
Application number: EP91901439A
Authority: EP
Inventors: Regis Jean-Marie Remi Munier; Olivier Luc Eloi Berne; Serge Daniel Serpillon
Original assignee: Kodak Pathe SA; Eastman Kodak Co
Current assignee: Kodak Pathe SA; Eastman Kodak Co
Priority date: 1989-12-12
Filing date: 1990-12-06
Publication date: 1992-09-30
Anticipated expiration: 2010-12-06
Also published as: WO1991009711A1; JP3164365B2; DE69009495T2; US5365821A; EP0505461B1; DE69009495D1; FR2655588B1; FR2655588A1; JPH05502824A

Abstract

L'invention concerne un couteau, ainsi qu'un dispositif de coupe pour le découpage de produits en bandes. Le dispositif de coupe comprend au moins un couteau (9) disposé sur un arbre (6) et est tel que ledit couteau (9) est monté directement sur l'arbre (6), ledit couteau étant maintenu en position de coupe au moyen de deux bagues (7) disposées de part et d'autre du couteau (9). Le couteau (9) est tel que, lorsqu'il est monté selon le dispositif suivant la présente invention, il présente une flexibilité appropriée de manière à, lors de son fonctionnement, engendrer une force d'appui sur un contre-couteau dont les variations par rapport à une valeur moyenne n'excèdent pas 10 % en valeur absolue. Application au découpage longitudinal de produits photographiques.The invention relates to a knife and a cutting device for cutting products into strips. The cutting device comprises at least one knife (9) arranged on a shaft (6) and is such that said knife (9) is mounted directly on the shaft (6), said knife being held in the cutting position by means of two rings (7) arranged on either side of the knife (9). The knife (9) is such that, when it is mounted according to the device according to the present invention, it has an appropriate flexibility so as, during its operation, to generate a pressing force on a counter knife, the variations of which compared to an average value do not exceed 10% in absolute value. Application to the longitudinal cutting of photographic products.

Description

The invention relates to a knife as well as a cutting device for the longitudinal cutting of products into strips such as photographic strips. In general, the knives used for this kind of application are mounted on a shaft at a spacing chosen according to the desired cutting width. This knife holder shaft is mounted opposite a second shaft parallel to the first and on which are mounted counter knives against which the knives bear.

Such an arrangement of knives is in common use for the manufacture of photographic films or tapes of soft metal and in particular for the cutting of tapes for recording of magnetic sounds. In use, such tapes are guided on both sides, on their edges, when passing over the heads of a tape recorder, the parallelism faults not to exceed in this case an order of magnitude of a few hundredths of a millimeter.

When cutting products into strips, the knives often wear very quickly and, when the wear becomes too great the knives cut by crushing, which gives strips whose edges are very irregular or curved and whose level of dust is important. The knives must then be replaced and resharpened. It goes without saying that the frequent disassembly and reassembly of the knives greatly reduce the productivity of cutting machines using such knives.

Until now, various cutting devices have been used. Thus, patent FR 2 439 736 describes a cutting device comprising a lower knife holder shaft and an upper knife holder shaft, mutually parallel, both driven and housed in fixed bearings. The lower knives have flat front faces rigidly clamped in the axial direction on the lower knife holder shaft and between which engage the corresponding upper knives, mounted on the upper knife holder shaft. The upper knives are each produced by assembling a hub on which are mounted, a spacer ring centered lengthwise with, on either side thereof, an elastic plane annular knife plated on an inner collar. , these elements being pressed against each other by means of spring disks. According to this patent, the height of the spacer corresponds approximately to the height of the elastic knife. However, when we sharpen such knives, which seems difficult to achieve without removing them from the shaft, we necessarily reduce the height of this knife, which therefore also involves reducing the height of the spacer. This necessarily takes time and constitutes an uneconomic solution, a simpler, but even less economical solution consisting in changing the knives each time a certain degree of wear is reached.

US Patent 3,286,574 describes a cutting device in which the upper knives and the lower knives are flexible discs mounted on two parallel shafts, the upper knives coming from the end of one of their faces pressing on the lower knives. Such a system has drawbacks since, during the sharpening of the discs, the height of these discs is necessarily reduced, just as the flexibility is modified, it is then necessary to then modify the respective positioning of the shafts which does not is not without complicating the device. Added to this are the problems of matching between the upper knives and the lower knives, in particular when the knife shafts contain a large number of discs placed side by side in a step which must be as regular as possible so that all the upper knives come at the same time to press the lower knives. Thus positioning errors of a few microns on each knife will translate at the end of the shaft into an error of up to a few tenths of a millimeter. And since the sharpening of such discs is done by the edge of the disc, it is not possible to correct these errors in a simple way. In addition, such a device does not seem suitable for large bandwidths such as those used for photographic products.

There are also other types of knives commonly used for this kind of application. Among these are the knives which it is common to call "lip knives". These knives, which will be discussed in more detail below, are made up of discs provided with a central hole so that they can be mounted on a cutting shaft with only one degree of freedom, translation, and comprising on the periphery of one of their faces a lip intended to press on a counter knife also mounted on a shaft parallel to the first. The bearing force of the knives on the counter knives is achieved by means of spring devices or other mechanical devices placed on the back of each knife. Such devices, due to mechanical tolerances, pose problems of regularity of the pressing force exerted by the knife on the counter knife, which causes an irregularity in the wear of the lip on the periphery of the knife. This inevitably results in variations in the width of the cut strips. The level of dust obtained on the cutting edges is high, thus adversely affecting the quality of the strips obtained. In addition, such knives are difficult to sharpen directly on the shaft and, in Due to the complex assembly mechanism of these knives, the sharpening operation is very time consuming. Finally, these knives are heavy, which represents a significant drawback for a cutting shaft on which one can mount up to 100 knives and more.

It is therefore one of the objects of the present invention to produce a cutting device whose knives are directly sharpenable on the cutting shaft.

It is another object of the present invention to produce a light knife intended to be mounted on a cutting shaft and the mounting of which on said shaft is simpler than what was previously done.

It is another object of the present invention to produce a knife whose lifespan is greater than that of the knives used in the prior art. It is yet another object of the present invention to provide a cutting device making it possible to obtain a cutting quality higher than that obtained by the devices of the prior art. It is yet another object of the present invention to provide a cutting device suitable for producing strips of large width.

Other objects will appear in the more detailed description which follows. These objects are achieved by means of a cutting device for the longitudinal cutting of products into strips mainly comprising a cutting shaft on which is mounted at least one knife consisting of a disc provided with a central hole and comprising on the periphery from one of its faces a lip intended to press on a counter knife also mounted on a shaft parallel to the first characterized in that said knife is mounted directly on the cutting shaft, said knife being held in the cutting position at by means of two rings arranged on either side of said knife. The invention also relates to a knife consisting of a disc provided with a central hole and comprising on the periphery of one of its faces a lip intended to press on a counter-knife also mounted on a shaft parallel to the first, characterized in that when it is mounted according to the device mentioned above, it has an appropriate flexibility so as, during its operation, to generate a pressing force on said counter knife, the variations of which with respect to an average value n ' not exceed 10% in absolute value.

The more detailed description which follows will be made with reference to the drawings in which:

- Fig. 1 schematically represents a knife as known in the prior art; - Fig. 2 shows a conventional mounting device for the knives shown in FIG. 1; •

- Fig. 3 shows a cutting device according to the present invention;

- Fig. 4 illustrates the results of the dust tests obtained on the one hand with a conventional cutting device and on the other hand the results obtained with the device according to the present invention. Fig. 1 which is now referred to schematically shows a knife as known in the prior art of the lip knife type. The knife shown consists of a disc (1) provided with a central hole (2) so that it can be, according to the prior art, mounted, by means of a ring or mount, on a cutting shaft. It comprises, on the periphery of one of its faces, a lip (3) intended to press on a counter knife also mounted on a shaft arranged parallel to the first shaft. The leading face (4) of the lip, that is to say the face bearing on the counter knife, defines an angle α relative to the vertical, called draft angle, which is between + 0.5 ° and + 5 °. The upper surface of the lip is generally designed so as to achieve an angle of attack (3 between 0 and 45 ° and is optionally followed by a second surface defining an angle γ sometimes called the offset angle which can vary between 10 and 45 °.

In the prior art, these knives (9) are generally, as shown in FIG. 2, mounted on a shaft (6) by means of a ring (7) or frame whose width defines the pitch for mounting the knives. The ring comprises a lower part on which the knife is mounted directly and an upper part blocking said knife in translation when the blade comes out (8), arranged, as shown in FIG. 2, over the entire periphery of the knife, presses on the knife. During operation, the knife holder shaft is moved a certain distance of the order of 0.05 to 0.3 mm in the direction represented by the arrow A. In response to this movement and in proportion to this movement , the leaf spring (8) generates a pressing force of the knife lip on the counter knife. This force is generally between 1 kg and 3 kg. The knife is locked in rotation by means of a spindle (10).

Thus, in the prior art, the thickness of the knife shown in FIG. 1 is approximately 2 millimeters or more, in order to produce a non-deformable blade. The diameter d of the central hole (2) is approximately 95 mm and the total diameter D of the knife is approximately 135 mm, that is to say that the height of what is called "the canvas" or the "soul" of the knife, namely (Dd) / 2, is about 20 mm. The mass of the assembly comprising the stepped ring, the spring blade and the knife is approximately 900 g. According to this same principle, there exists in the technique previous other types of mounting of the same lip knife, which differ from the type previously mentioned by the device for generating the force of support of the knife on the counter knife. Indeed, it is known to use a system in which the support force of the knife is generated by 5 springs distributed equidistantly around the circumference of the knife. According to another known device, the bearing force is generated by a metal rod forming a spring extending in response to the small movement mentioned in the device with leaf spring. Similarly, it is also known to replace this metal tube with an O-ring. For all these devices, the variations in the pressing force on the circumference of the knife are relatively large and lead to poor cutting qualities.

According to the present invention, the knife is of the type described with reference to FIG. 1. However, the dimensions of this knife are different from those known in the prior art. Indeed, the knife according to the present invention is intended to be mounted directly on the knife holder shaft. Under these conditions, the diameter of the central hole is approximately equal to that of the shaft, thus making it possible to have, for the same knife diameter, a canvas height greater than that of the knives previously known and to produce knives whose flexibility is sufficient to generate the necessary support forces on the counter knives (between 1 and 3 kg and preferably between 1 and 2 kg). Similarly, according to the present invention, the thickness of the knives is less than that of conventional knives and is preferably between 0.8 and 1.4 mm.

All the dimensional characteristics of the knife according to the invention are linked together, and the flexibility of the knife actually depends on the force support that we want to obtain, the thickness and diameter of the knife, the thickness of the lip, the height of the knife canvas and also the characteristics of the spacer used between each knife and whose we will talk again in more detail later. Fig. 3 to which reference is now made represents a device for mounting knives according to the present invention. As shown in Fig. 3, the knives (12) are mounted directly on the cutting shaft (11). The knives are separated from each other by a spacer (13) allowing the knives to be kept in the cutting position and also making it possible to maintain the desired distance between them.

We have on the cutting shaft, the number of knives desired, the knives being separated from each other by a spacer whose width depends on the desired cutting width, then, by means of an appropriate clamping device, we all tighten these elements together to block them in rotation. According to a preferred embodiment, it has been found that it is advantageous to use, as shown in FIG. 3, a stepped spacer, the highest part of the spacer being the part facing the knife. Such an arrangement makes it possible to considerably reduce the vibrations generated by the rotation of said knives.

In the cutting position the knives (12) press against the knives (15), themselves mounted on a shaft (14) arranged parallel to the first. The pressing force is generated by the response of the flexible knives to a small movement of the knife-holder shaft in the direction indicated by the arrow B when the knives press on the counter-knives. The mass of the assembly comprising the knife and the spacer does not exceed 200 g.

Such mounting of the knife directly on the cutting shaft makes it possible to obtain a force for pressing the knives on the counter-knives, for a given displacement value, the variations from an average value of between 1 and 2 kg do not exceed 10% in absolute value. It is obvious that such a device can comprise only one knife. In this case, said knife is held in the cutting position by means of two rings arranged on either side of said knife. According to a preferred embodiment, for the reasons mentioned above, at least one of these rings, namely, that located opposite the knife, is stepped.

Such an assembly of the knife makes it possible to carry out the sharpening directly on the cutting shaft. Indeed, we no longer have, as in the prior art, a complex spring assembly which had the disadvantage of storing dust when the sharpening was carried out without dismantling the knives from the shaft or without separating them from their spring mechanism. Such an assembly also makes it possible to reduce the haze of the faces of the knives. According to a particular embodiment, the dimensional characteristics of a knife holder shaft are as follows:

- diameter of the knife holder shaft: 65 mm;

- total diameter of the knives: 138 mm; - height of the knife core: 37.5 mm;

- lip thickness: 4.5 mm;

- thickness of the knife core: 1.2 mm;

- displacement of the knife holder shaft: 0.08 mm;

- bearing force on the counter knives: 1.5 kg; - dimensions of the spacer: d 1 = 80 mm; d2 „= 72 mm.

In reality, the bearing force should not be too great so as not to damage the knives too quickly, and preferably, for knife dimensions and shaft displacement values such as those indicated above, is included between 1 kg and 2 kg. The corresponding thickness of the knife then varies between 0.8 mm and 1.4 mm.

Tests have been carried out in order to measure, for different types of lip knives, the variations in absolute value, relative to an average value, of the support forces F of the knives on the counter knives and this for a given value δ displacement of the knife holder shaft. The average value of the pressing force is of the order of 1.5 kg for a displacement δ = 0.12 mm and of the order of 1 kg for a displacement δ = 0.08 mm.

Type of% var. of F% var. of F knives δ = 0.12 mm δ = 0.08 mm

I 5 knives 16% 13% springs

II Knives with blade 33% 20% spring

III Joint knives 57% 30% O-ring

IV 16% 10.5% metal sausage knives

V Knives according to 10% 6.5% 1 invention

These tests therefore show that, with the knives according to the present invention, variations in the pressing force are obtained not exceeding 10%, which is much lower than the results obtained with conventional knives. Similarly, cutting dust tests have were made using on the one hand conventional lip knives and lip knives according to the invention. The results are represented by the curves in FIG. 4. The measurements were carried out for photographic products comprising a support on which a photographic emulsion is coated. This test consists in measuring, as a function of the operating time of the knives, the dust in different places of the cut. The principle of the measurement is as follows: a strip is cut by means of one or other of the cutting devices; it is passed between two rollers facing each other and covered with a double-sided adhesive; after passing a certain length of strip, the adhesives are recovered and the optical density of the adhesives is measured by reflection or transmission, this density being greater or less depending on the amount of dust recovered by said adhesive. Thus we measured successively the dust from a cut (I), emulsion side and a cut (II), support side, for a cutting edge located in front of the knife then, the dust from a cut (III ), emulsion side and a cut (IV), support side, for a cutting edge located on the back of the knife. The graph (V) represents the average of the results obtained for the four previous measurements. The dashed lines represent the results obtained with conventional knives; the curves in solid lines represent the results obtained with knives according to the invention. The number of hours of operation of the knife is plotted on the abscissa and the dust level of the cut is plotted on the ordinate. The graphs produced show that in all cases, the level of dustiness obtained for the knives according to the invention is lower than that obtained with conventional knives, the difference generally increasing with the knife operating time.

Tests have also shown that, by sharpening the knives carried out directly on the cutting shaft, about half the material is removed from the knives than in the case where this sharpening is carried out when the knives are removed from the shaft. . In addition, the time required for this operation is approximately five times less.

Claims

1 - Cutting device for the longitudinal cutting of products into strips mainly comprising a cutting shaft (11) on which is mounted at least one knife (12) consisting of a disc provided with a central hole and comprising on the periphery of one of its faces a lip intended to press against a knife (15) also mounted on a shaft (14) parallel to the first, characterized in that the knife is mounted directly on the cutting shaft, said knife being maintained in the cutting position by means of two rings arranged on either side of said knife.

2 - Cutting device according to claim 1 characterized in that said ring is a stepped ring, the highest part of the ring being the part facing the knife.

3 - Cutting device according to claim 1 or 2, characterized in that the dimensional characteristics of the knife, as well as those of the ring give said knife an appropriate flexibility so as to, during its operation, generate a pressing force of said knife on the counter knife whose variations from an average value do not exceed 10% in absolute value. - Cutting device according to claim 3, characterized in that the average pressing force of the knife on the counter knife is between approximately 1 kg and 2 kg.

5 - Cutting device according to claim 4, characterized in that the average pressing force of the knife on the counter knife is of the order of 1.5 kg.

6 - Device according to any one of claims

1 to 5, characterized in that there are at least two knives on the cutting shaft, the stepped ring then also serving as a spacer keeping the knives between them at the desired distance. Knife consisting of a disc provided with a central hole and comprising on the periphery of one of its faces a lip intended to press on a counter knife also mounted on a shaft parallel to the first characterized in that, when said knife is mounted according to the device of claim 1, it has an appropriate flexibility so as, during its operation, to generate a pressing force on said counter-knife whose variations compared to an average value do not exceed 10% in ultimate value.