EP2527102A2 - Blade and cutting device and cutting method - Google Patents

Abstract

The knife i.e. idealized helical-shaped knife (1), has a cutting leg (2) whose lower end is provided with a base surface (5) and a cutting surface (3). The cutting surface includes a cutting edge (4) along front edges, where hardness in a front region (7) of the cutting leg is larger than hardness in a rear region (8). An interface (9) separates the front and rear regions, and is aligned parallel to a front cutting leg surface (10) of the cutting leg. The front region of the cutting leg has thickness (D1) less than 200 micrometers and hardness larger than 1000 HV. Independent claims are also included for the following: (1) a cutting device for cutting material (2) a method for cutting a material.

Description

The present invention relates to a knife in the form of a helical line, having a longitudinal axis and a cutting leg having both at a lower end a foot surface and at an upper end a cutting surface, wherein the cutting surface along a front edge having a cutting edge and the cutting edge in a front region has a greater hardness than in a rear region, wherein a separating surface separating the two regions is aligned approximately parallel to a front cutting leg surface of the cutting edge.

The invention further relates to a cutting device for cutting a material, comprising a cylinder body rotatable about a longitudinal axis with an outer lateral surface and at least one knife in the form of a helical line, which has a cutting edge, wherein a foot surface of the knife, facing at a lower, the cylinder body End of the cutting edge is arranged, with the cylinder body, preferably with its lateral surface, is connected and the cutting edge at an upper, facing away from the cylinder body end has a cutting surface, wherein the cutting surface at a set in a set during a cutting operation rotational direction of the cylinder body front edge Having a cutting edge, and a strip element, which comes so in contact with the cutting surface of the blade in a rotation of the cylinder body in such a way that continuously with each point of the cutting surface of the knife with a corresponding point of the strip element comes into contact, wherein the cutting edge in a viewed in the direction of rotation front region has a greater hardness than the point of the strip element and the point of the strip element again has a higher hardness, as viewed in the direction of rotation rear portion of the cutting edge wherein a separating surface separating the two region is aligned approximately parallel to a front cutting edge surface of the cutting edge.

1. a) Ein Zylinderkörper einer Schneideinrichtung mit mindestens einem mit dem Zylinderkörper verbundenen Messer mit einem Schneidenschenkel wird um eine Längsachse rotiert.
2. b) Während einer Rotation des Zylinderkörpers wird das mindestens eine Messer fortlaufend mit jeder Stelle einer Schneidenkante, die an einem in eine während eines Schneidbetriebs eingestellte Rotationsrichtung des Zylinderkörpers betrachteten vorderen Rand einer von dem Zylinderkörper abgewandten Schneidenfläche des Schneidenschenkels angeordnet ist, an einer jeweilig korrespondierenden Stelle mit dem zu schneidenden Material in Eingriff gebracht, wodurch letzteres geschnitten wird.
3. c) Das Leistenelement wird während einer Rotation des Zylinderkörpers mit der Schneidenfläche des Messers sowohl mit einem härteren Bereich als auch mit einem weicheren Bereich in einen derartigen schleifenden Kontakt gebracht, dass fortlaufend jede Stelle der Schneidenfläche mit einer korrespondierenden Stelle des Leistenelements in Kontakt gebracht wird, wobei eine die beiden Bereich trennende Trennfläche in etwa parallel zu einer vorderen Schneidenschenkelfläche des Schneidenschenkels ausgerichtet ist.

Finally, the present invention discloses a method for cutting a material, comprising the following method steps:

1. a) A cylinder body of a cutting device with at least one connected to the cylinder body knife with a cutting edge is rotated about a longitudinal axis.
2. b) During rotation of the cylinder body, the at least one blade is continuously positioned at a respective corresponding location with each point of a cutting edge located at a front edge of a cutting surface of the cutting edge facing away from the cylinder body in a rotational direction of the cylinder body set during a cutting operation engaged with the material to be cut, thereby cutting the latter.
3. c) the strip element is brought into such a sliding contact during a rotation of the cylinder body with the cutting surface of the knife both with a harder area and with a softer area, in such a way that each point of the cutting surface is brought into contact with a corresponding point of the strip element, wherein a separating surface separating the two region is aligned approximately parallel to a front cutting edge surface of the cutting edge.

State of the art

Knives, cutting devices and methods of the type described above are well known. This applies equally to the textile and leather processing industries. Furthermore, knives and cutting devices of the type described above are used for a variety of other cutting applications, such as for cutting paper, rubber, plastic, cork and the like.

A general endeavor in the use of initially described knives or cutting devices is to increase their service life. The longer a cutting device can be continuously in operation, the more economical it can be used. A limiting factor with respect to the life of a cutting device are primarily the mounted on a cylinder body of the cutter knives. by virtue of Wear during a cutting operation, a cutting edge of the knife is rounded and as a result dull. Further, by a continuous abrasion of the knife both by engagement with material to be cut but also by engagement with components of the cutting device - for example, a counter-blade, as it is always present in the field of textile fiber processing - the knife is steadily removed, so that it to substance loses.

With regard to the blades of the cutting device is therefore an interruption of the cutting operation primarily in a significant loss of sharpness of the knife necessary or in the event that the or the knife "have expired", that is, have reached their wear limit. Especially in the last, rarer case, the affected blades must be replaced with new ones. For the former case, however, that the knives have become dull, they must be resharpened to improve a possibly impaired due to blunt knife cutting result and to ensure a consistently high quality cutting. In comparison to a necessary replacement of the knife, this case occurs much more often.

This resharpening is usually achieved by means of grinding devices. It is customary in the prior art to expand the cylinder body of the cutter together with the knives mounted thereon from the cutting device and externally resharpen or sharpen. In addition, grinding devices are known, which are mounted directly in the associated cutting device and can be brought in the course of re-sharpening with the knives in contact while the cutting operation is interrupted. This is done so that the respective cutting device for the re-sharpening process is no longer brought into engagement with material to be cut or folded, but is rotated during rotation of the cylinder body against the grinding device, so that the blades are brought into abrading contact with this. As a result of this sliding contact, the knives are sharpened. However, the grinder comes only quasi selectively, that is, only over a short distance, with the knives in contact. In order to achieve a sharpness effect over the entire length of a knife, it is therefore necessary that the grinding device is moved along the cylinder body and so can reach the entire respective knife to be ground. This process requires - as described - an interruption of the cutting operation and is therefore not desirable, but due to the wear of the knife is absolutely necessary.

Self-sharpening cutting or cutting tools have therefore been known for quite some time in order to considerably extend intervals between re-sharpening. For example, from a technical article in the "wt workshop technology online", Year 97 (2007), No. 6, page 425 et seq., A principle of self-sharpening is known. This provides that a rake face of a respective tool is softer than an open face of the tool, which engages only at a cutting edge with the material to be machined and is subjected to abrasion. As a result, the rake face is continually "washed out" of the material to be machined, while at the knife edge, the harder material of the flank face is substantially retained. This results in the formation of a self-sharpening edge. A model for the aforementioned principle is also found in nature, for example, in regrowing rat teeth, where the dentin is softer and bounded by a hard layer. Experiments of a comparable design of a knife described above in a cutting device described above have remained unsuccessful in practice.

Another strategy for extending the time between re-sharpening is to reduce knife wear. This is achieved nowadays, for example, by applying plating on a face of each knife, viewed in the direction of rotation of the knives, which consists, for example, of a specially hardened steel, whereas the remaining knife consists of unhardened steel. Alternatively, a case hardening or hardening of the complete knife is conceivable. Although these methods bring about a certain degree of success in that the knives are removed less quickly completely, a considerable extension of the period during which the knives are "sharp" is not yet sufficiently achieved. Furthermore, such hitherto applied curing to an increase in manufacturing costs, which reduce a more economical use despite prolonged life again.

task

The invention has for its object to further develop a knife, a cutting device and a method of the type described above in such a way that the blades or the cutting device can be kept in operation over such long intervals without the need for re-sharpening that the cost of an associated cutting device significantly improved.

solution

The object is achieved on the basis of a knife of the type described above in that the front region has a thickness of less than 200 microns and also has a hardness of greater than 1000 HV.

As already described above, deposits or inserts in the front region of the knife or of the cutting edge are already known. To achieve a better longevity of the knife, however, these areas have been carried out relatively thick and have a thickness in the range of a few tenths of a millimeter to a few millimeters. In the case of a knife according to the invention, precisely this thickness is deliberately significantly reduced and limited to the very small extent of 200 μm upwards. In particular, the combination of very small thickness and at the same time very high hardness of at least 1000 HV of the front region has proven to be the key to achieving the desired self-sharpening effect. Optimally, this thickness should be set even lower. By analogy with the above explanation, the front region is to be understood as meaning the region of the knife which, when the knife is mounted on a cylindrical body, is arranged "in front" in a direction of rotation and consequently reaches or passes a fictitious position in an orbit in front of the rear region. The direction of rotation is to be understood as a set during a cutting operation direction of rotation.

The limitation of the thickness of such a front region harder than the rear region, in combination with the greater hardness, leads to a desired self-sharpening effect. This effect results from the fact that upon contact of the knife with a fixed, non-rotating element of the associated cutting device during a Rotation of the cylinder body, the cutting edge of the knife is steadily removed. By increasing the hardness in the front region, wear of this region can be reduced, while the rear region of the cutting surface is removed relatively more in relation to the front region. By an interaction of these two, due to the differences in hardness of the areas with varying speed abrasive effects, a sense of a "sharpening" of the knife is obtained because due to the small thickness of the front region, the knife at its foremost point, the cutting edge, sharp-edged, since the hardness of the material residing there exceeds the hardness of the rest of the material in the rear area and therefore dissipates less quickly.

For this purpose, the front region of the cutting edge should extend from the cutting edge over at least 20%, preferably 50%, of a height of the cutting edge.

In this context, the height of the cutting edge is to be understood as meaning a length of a straight line perpendicular to the cutting edge, which extends from the cutting edge edge of a new, unused knife to an edge of a foot surface of the knife opposite the cutting surface. A certain minimum height for the front area should be provided because the cutting edge will wear away over the time of operation of the knife, despite the greater hardness of the front area. Since the self-sharpening effect without the front area can not be achieved, for example, in a knife with a front hard area that extends only over a height of 5% of the cutting edge, no self-sharpening from a total removal of the knife from 5% of its height more to take place. The minimum heights already mentioned should be adhered to accordingly.

With regard to a concrete embodiment of the front region, it is likewise possible to form it by an insert strip or alternatively by a coating on the basis of the prior art. When using an insert strip, in contrast to the prior art, the particularly small thickness is to be pointed out. Today standard application strips in the form of case hardening or cladding usually have a considerably greater thickness.

Titanium nitride (TiN), carbide, ceramic or diamond coatings are possible, for example, as coatings. Similarly, all other coatings are conceivable, provided that they have a greater hardness than a base material of the knife, which is usually formed of steel. Compared to the attachment of an insert strip, spraying, detonating or sintering of a respective type of coating can be significantly simpler and correspondingly advantageous.

Moreover, when using a coating, it may be advantageous if not only the front region of the cutting edge, but rather the entire knife is coated with a coating.

Instead of a specific application in a more or less small area of the knife, a complete coating can be carried out, if necessary, much more rapidly, since expensive area delineations and the like are dispensed with. Depending on the cost of the particular coating material, a complete coating may therefore be more favorable than a partial coating of the front region. A complete coating also has the advantage that the entire knife is protected against corrosion. Since in conventional applications of such knives moisture in the form of water and oxygen are often present and the knives are usually made of steel, it is not uncommon that by oxidation of the metal, the hardness of the knife is reduced and then it loses its sharpness. By means of a complete, corrosion-free coating, such an effect can be prevented. It is also conceivable to equip the blades by means of a complete coating with a non-stick effect. This can be particularly advantageous depending on the field of use.

Regardless of whether a coating is provided only partially or completely or completely, the coating should have a hardness of greater than 1250 HV, preferably a hardness of greater than 1500 HV, more preferably a hardness greater than 1800 HV.

The base material of the blades is usually made of steel. This may be both uncured steel or hardened steel, the knife may be only partially or fully cured. Hardened steels usually have a hardness in the range of about 600 HV to 900 HV. To an effect of the previously described To be able to achieve a type, as explained, a hardness difference between the front and the rear portion of the cutting edge is necessary. This is always ensured using a 1250 HV hard coating. Which hardness or which coating material should be used concretely may depend in detail strongly on the combination of the materials for the two areas.

With regard to the base material of the blade, that is to say the material of the "rear region", use of an uncured steel may be just as advantageous as the use of a partially or fully hardened steel. The former is cheaper and easier to process, while especially the fully hardened steel is able to withstand abrasive wear very well. In combination with a front coating, an unhardened steel can be well used because the mainly abrasive area of the particular blade is protected by the coating.

Particularly advantageous is such a knife whose front cutting leg surface has a stroke. By means of the "serrated" shape of the cut, a clean separation of the fibers is particularly easy and effectively possible, especially in the field of textile fiber processing.

Also known from the textile processing field is such a knife, which has a Fußschenkel which extends from the lower end of the cutting edge in an approximately perpendicular to the cutting edge direction and forms on a side facing away from the cutting edge leg surface. This shape allows a particularly simple mounting of the knife on a cylinder body and is particularly advantageous in terms of dimensional stability and rigidity.

In addition to an isolated consideration of an inventive embodiment of the knife itself, the object is further achieved in that such a knife with a relative to a rear portion of the cutting edge harder front portion having a thickness of the front region of 200 microns and a hardness of greater than 1000 HV is used in a cutting device of the type described above.

In such a cutting device, there is a sliding contact between the knife and the strip member during each revolution, with each point continuously the cutting surface touches a certain associated point of the strip element. This contact causes abrasion of both the knife and the inguinal member. As a result of this abrasion, the knife is sharpened steadily in accordance with the above-described mode of action. This is possible in addition to the necessary small thickness of the front portion of the cutting edge of the knife of 200 microns mainly because the strip member has a hardness that is less than said front portion, but larger than the rear portion of the cutting edge of the knife. This staggering means that although the front portion of the cutting edge leg is not excessively abraded, the rear portion is very well, so that the already described "sharpening" of the cutting edge of the knife takes place.

Accordingly, such a cutting device is of particular advantage, the strip element is partially or completely coated. By means of such a strip element, the hardness of the same is particularly easy on the hardness of the base material of the knife - ie the rear area - also raised. By a skillful coordination of the various coatings, it is also very easy to choose the hardness of the strip element less than that of the front portion of the cutting edge.

In the context of a partial coating of the strip element, it is particularly advantageous if only one end face of the strip element has a coating and, moreover, if this coating has a thickness of less than 200 μm at the end face. The latter is however also advantageous using a complete coating. The end face also has, corresponding to the cutting edge of the knife, a cutting edge or a grinding edge, which comes into contact with the knife as the first part of the strip element during each rotation of the knife.

Such a trained strip element is continuously resharpened comparable to the knife according to the invention during a cutting operation. This is of particular interest when the strip element is used as a so-called "counter-blade", as is the case, for example, in the field of textile fiber processing. This is done as follows: The knife continuously comes in contact with each point of its cutting edge with a respectively corresponding point of the cutting edge of the strip element. Due to the increased hardness of the front area of the knife, it comes at the edge of the cutting edge Strip element to an increased material removal. Using a hard end face, precisely this removal of material on the cutting edge of the strip element is reduced, so that only in a region of the strip element connected downstream of the end face does a considerable removal take place. Consequently, a sharp edge forms on the end face of the strip element-using a thickness of the coating on the end face of less than 200 μm-which considerably simplifies cutting, for example, of textile fibers or the like.

If, on the other hand, a sharp front edge of the strip element is not of interest, since the strip element, for example, is not used in the context of a cutting process, but is merely intended for the purpose of re-sharpening the rotating blade (for example in the field of leather processing), it can all the more be more advantageous if the coating of the strip element has a thickness of 200 microns to 20 mm. By means of such a coating, a service life of the strip element in function of a grinding element can be particularly increased. In addition, in this context, this should not be applied partially but over the whole area.

Regardless of the type of use of the strip element, be it as a counter-blade or merely as a grinding element, the same - just like the knife - is subject to constant wear. In the course of a cutting operation, therefore, a contact between the knife and the strip element would fail without a corresponding compensation, since all excess material would be removed sometime. To avoid this, a pushing force should always act on the strip element, which causes a wear adjustment of the strip element. In this way, a continuous sliding contact between the strip element and the knife is secured.

Advantageously, the strip element should extend over an entire axial length of the cylinder body. When used as a counter-blade, the advantageousness of such a strip element is trivial, since cutting takes place only in the presence of a counter-blade for corresponding applications. However, an extension over the entire axial length of the cylinder body is also particularly advantageous in the context of using the strip element as a grinding element. In contrast to the prior art, which provides only grinding elements with limited axial length, thus a continuous re-sharpening of the cutting surface or in the course of its continuous resharpening of each point of the cutting edge of the knife done.

For the latter purpose, it may be advantageous if the strip element along an axis parallel to the longitudinal axis of the cylinder body axis is movable. A continuous movement of the strip element prevents a "shrinkage" of the knife, that is, locally "furrows" are ground and consequently a grinding action or cutting action of the strip element is adversely affected.

• e) Fortlaufend wird jede Stelle der Schneidenkante des Messers an einer jeweilig korrespondierenden Stelle des Leistenelements mit einem vorderen härteren Bereich desselben in Kontakt gebracht.

The object of the present invention is further solvable by supplementing a method step to the method described above. This additional process step is as follows:

• e) Continuously, each point of the blade edge of the blade is brought into contact with a front harder portion thereof at a respective corresponding position of the strip member.

According to the above explanations, the object can be solved particularly easily by means of this method step.

It may also be equally advantageous to permanently or only periodically position the strip element during operation of the cutting device so that it comes into sliding contact with the knife. For example, in the field of leather processing, a permanent use of the strip element as a grinding element is usually not necessary and would lead to an unnecessarily increased removal of both the knife and the strip element. In order to maintain the knife or the knife at a desired degree of severity, it is usually sufficient to make a periodic contact with the grinding element.

With regard to the production of both the said front area of the knife and the end face of the strip element, it may be advantageous to use a completely coated knife and / or strip element and the front and the rear area of the cutting edge of the knife or the end face and a remaining free surface of the strip element only at a first start of the knife and / or the strip element by grinding a coating on the cutting surface of the knife or on the free surface of the strip element is ground.

As a result of this grinding, only those regions of the coating which are present on the side surfaces of the cutting edge of the knife, the so-called cutting edge surfaces, or of the strip element, are retained. By definition, these form the front area on the respective knife and the end face on the strip element. The thickness of the coating should assume the maximum value of 200 microns for such a case in order to realize the Selbstschärfeffekt.

Finally, such a method is advantageous in which the strip element is moved along an axis parallel to the longitudinal axis of the cylinder body. A "running in" of the strip element according to the above explanation can thus be prevented.

embodiments

The knife according to the invention as well as the cutting device and the method are explained below with reference to exemplary embodiments which are illustrated in the figures.

Fig. 1:

ein erfindungsgemäßes Messer aus dem Bereich der Lederbearbeitung,

Fig. 2:

ein erfindungsgemäßes Messer aus dem Bereich der Textilverarbeitung,

Fig. 3:

einen Schnitt durch eine erfindungsgemäße Schneideinrichtung mit einem Leistenelement in Form einer Gegenschneide und

Fig. 4:

wie Figur 3, jedoch mit einem Leistenelement in Form eines Schleifelements.

It shows:

Fig. 1:

an inventive knife from the field of leather processing,

Fig. 2:

an inventive knife from the field of textile processing,

3:

a section through a cutting device according to the invention with a strip element in the form of a counter-blade and

4:

as FIG. 3 , but with a strip element in the form of a sanding element.

An in FIG. 1 illustrated first embodiment of a knife according to the invention shows a short section of an idealized helical knife 1, which consists solely of a cutting edge 2. FIG. 1 is to be understood only as a schematic diagram, so that a helical shape is not derivable from the figure. At an upper end of the cutting edge 2 is a cutting surface 3 and at the edge of a cutting edge 4. At a lower end of the cutting edge. 2 is located opposite the cutting surface 3, a foot surface 5. With this foot surface 5, the knife 1, for example, on a in FIG. 1 Cylinder body 6, not shown, can be mounted. Such an assembly can be done for example by means of a so-called caulking the knife 1 in the cylinder body 6 or alternatively via a screw of the knife 1 with a holder, the latter being fixedly connected to the cylinder body 6.

The cutting edge 2 of the knife 1 has a front region 7, which differs from a rear region 8 by its hardness, wherein the front region 7 is harder than the rear region 8. Both regions 7, 8 are separated from each other by means of a separation surface 9 , This separating surface 9 runs approximately parallel to a front cutting edge surface 10 of the knife 1. As a combination of materials for the two regions 7, 8, for example, an uncured steel for the rear region 8 and a TiN coating for the front region 7 would be considered.

Starting from the cutting edge 4, which is a component of the front region 7, the front region extends over approximately 50% of a height H 1 of the cutting edge 2 of the knife 1. The height H 1 can generally be considered a length perpendicular to the edge of the cutting edge 4 oriented path, which extends from the cutting edge 4 to a arranged on an opposite side of the cutting edge 2 on the foot surface 5 edge 11.

Although in FIG. 1 Due to a better depictability shown clearly exaggerated, a thickness D1 of the coating consisting of a front portion 7 of the blade 1 is about 100 microns, with a hardness of the front portion 7 1500 HV. Further, the separation surface 9 may be understood as a three-dimensional object having its own thickness. If a coating is applied, for example, by means of a flame spraying method, a diffusion region can form, which can not be unambiguously assigned to the front region 7, or clearly to the rear region 8. The separating surface 9 extends in such a case over an entire thickness of this diffusion region, so that clearly on one side of the separating surface 9 of the front region 7 and on another side of the separating surface 9 of the rear region 8 is arranged.

Would that be in FIG. 1 The blade 1 shown installed on a cylinder body 6, it would be arranged so that it with the front portion 7 in a rotational direction of the cylinder body 6 is oriented so that upon rotation of the cylinder body 6 in a cutting operation, the front portion 7 of the knife 1 passes an imaginary point along an orbit of the knife 1 in front of the rear portion 8.

Analogously shows FIG. 2 a further embodiment of a knife according to the invention 1 ', which has a stylized L-shape compared to the knife 1. The knife 1 'has, comparable to the knife 1, a cutting edge 2 with a cutting surface 3 and a cutting edge 4. Further, the cutting edge 2 is divided into a front portion 7 and a rear portion 8, wherein the front portion 7 has a thickness D 1 of about 100 microns (in FIG. 2 shown elevated) and also has a hardness of 1500 HV. The separating surface 9 between the front region 7 and the rear region 8 again runs approximately parallel to the front cutting edge surface 10 of the knife 1 '. The foot surface 5 is disposed on a leg of foot 12 which extends from a lower end of the cutting edge 2 in a direction of the rear portion 8 of the cutting edge 2. The front region 7 extends similar to the first embodiment over approximately 50% of a height H2 of the blade 1 '. This is defined as a length of a distance which extends approximately perpendicular to the foot surface 5, extending from a height level of an edge 11 of the foot surface 5 up to another height level of the cutting edge 4. An alignment of the blade 1 'on a cylinder body 6 would take place such that the leg of the foot 12 of the cylinder body 6 is arranged on a side facing away from the cutting blade 2 in a direction of rotation of the cylinder body 6.

In a further embodiment, which is in FIG. 3 is shown, a plurality of blades 1 'mounted on a cylinder body 6. For this purpose, the blades 1 'are connected with their leg 14 with a lateral surface 17 of the cylinder body 6. The cylinder body 6 is mounted along a longitudinal axis 13, around which it can rotate. A rotational direction during a cutting operation is indicated by an arrow 14 in FIG FIG. 3 graphically illustrated. At a lowest point 15 of an orbit of the cutting edges 4 of the blade 1 ', a strip element in the form of a counter-blade 16 is arranged. Such counter-blades 16 are used for example in the field of processing of textile fibers. During the cutting operation, a material to be cut is guided along the counter-blade 16 in such a way that fibers of the material to be cut are in an area above an end face 19 of the counter-blade 16 are located. The end face 19 is a short end face of the counter-blade 16, which is arranged at a front end thereof. In the following, it is due to a rotation of the cylinder body 6 in the direction indicated by arrow 14 direction that the cutting edge 4 of the knife 1 'with a cutting edge 20 of the counter-blade 16 in a sliding contact and the fibers by an interaction of cutting edge 4 and Cutting edge 20 are separated from the material. For this purpose, it is of particular advantage if the cutting surfaces 3 of the blades 1 'run as sharp as possible towards their respective cutting edge 4, so that the cutting edge 4 forms a "sharp" edge, by means of which the fibers to be cut are much easier and cleaner to separate are. The same applies to the cutting edge 20 of the counter-blade 16.

Since the counter-blade 16 with the knife 1 'must be constantly in a sliding contact for a successful cutting operation, it comes during operation to a continuous abrasive wear of both the knife 1' and the counter-blade 16. This manifests itself in particular in that the Cutting edge 4 of the knife 1 'and the cutting edge 20 of the counter-blade 16 are "rounded" and a previously described sharp-edged run from the cutting surfaces 3 toward the cutting edges 4 and from a free surface 18 toward the cutting edge 20 is no longer given. Specifically, an advantageous embodiment of the free surface 18 will later in connection with FIG. 3a separately. As a result of the described "rounding" decreases a quality of a fiber section or any other, cut in this way material. As explained above, for the purpose of avoiding a described rounding of the cutting edges 4 of the blades 1 ', a front region 7 is provided whose thickness D 1 is approximately 100 μm and which has a hardness of 1500 HV. This hardness of the front portion 7, which is formed by a coating, for example, is higher than a hardness of the rear portion 8. This has the consequence that continuously with each contact of each point of the cutting edge 4 of the blade 1 'with a respective corresponding point the cutting edge 20 of the counter-blade 16 is a certain part of the cutting edge 2 of the blade 1 'is ground, with much less material is lost from the respective front portions 7 due to their higher hardness, as of the rear regions 8. This effect describes a kind of "sharpening "The knife 1 'by the cutting surfaces 3 of the cutting edge 2 of the rear portions 8 by a described Abrading towards the front portions 7 containing the cutting edges 4, sharp-edged. However, this succeeds only if the front regions 7 are particularly thin, so that the cutting surfaces 3 of the blades 1 'form a distinct wear-resistant edge on the cutting edges 4.

In a similar manner, a "sharpening" of the cutting edge 20 of the counter-blade 16 can take place. The counter-blade 16 has for this purpose at its end face 19, comparable to the region 7 of the blades 1 ', a hard layer formed, for example, by a coating. As well as the front portion 7 of each blade 1 ', this hard layer of the end face 19 should have a maximum thickness of 200 μm, but a hardness of this layer should be less than that of the front portion 7 of the blades 1'. In this way, a contact of the knife 1 'with the cutting edge 20 of the counter-blade 16 does not lead to excessive wear of the cutting edges 4. At the same time, however, the end face 19 should be made harder according to the above explanation of the Nachschärfeeffekts the knife 1, as the respective rear area 8 of the knife 1 ', so that by means of the counter-blade 16 of the rear portion 8 of a respective blade 1' can be effectively abraded. The free surface 18 of the counter-sheath 16, which is viewed in the direction of rotation of the cylinder body 6 in the cutting operation behind the end face 19, however, has - analogous to the area 8 of the blade 1 '- a lower hardness both as the end face 19 and as the front portion the knife 1 'on. One way of re-sharpening the cutting edge 20 is to move the entire cylinder body 6 according to double arrow 22 in a horizontal direction relative to the counter-blade 16, so that the lowest point 15 of the orbit of the blade 1 'is positioned over the flank 18. By commissioning the cutting device and simultaneously lowering the cylinder body in such a way that the blades 1 'remove material from the relatively soft free surface 18, a circular-arc-shaped recess is formed, which optimally runs exactly to the cutting edge 20. If the process is completed, the counter-blade 16 is sharpened insofar as that the free surface 18 to the edge of the cutting edge 20 towards sharp-edged. Such a ground clearance surface 18 is particularly FIG. 3a clearly visible. This process of re-sharpening the counterknife 16 described above must be repeated periodically as soon as the edge of the cutting edge 20 is rounded off too much despite the hard end face 19 so that a clean cut can no longer take place. In addition to a pure effect on a sharp edge of the cutting edge 20, the grinding of the material from the free surface 18 also has the advantage that at the cutting edge 20 cut material can be better dissipated by it can dodge into the circular arc-shaped recess of the free surface 18.

In addition to a rotation of the cylinder body 6 in the direction indicated by arrow 14 further may be a short-term rotation of the cylinder body 6 in an opposite, indicated by arrow 23 direction for the sole purpose of resharpening advantage. Due to another sequence in which the harder region 7 and the softer region 8 of the knife 1 'pass through the cutting edge 20, it is possible for both the cutting edge 20 and the cutting edge 4 of the blades 1' itself to improve material removal and consequently a short-term sharpness effect come. A reversal of the direction of rotation can likewise be advantageous in the course of an abrading of the free surface 18 on the counter-blade 16 explained above.

A cutting device whose knife 1 'and counter-blade 16 are so formed with a maximum of 200 microns thick and hard front areas 7 or with a maximum 200 microns thick and hard face 19, can achieve significantly longer service life than conventional cutting devices using a described Nachschärfeeffekts conventional knife and counter cutting.

An identical principle of action is also possible without the use of a strip element in the form of a counter-blade 16. For example, in the field of leather processing in the form of folding and fleshing counterblades 16 are not used. In order nevertheless to achieve a continuous Nachschärfeeffekt comes in a last embodiment - which in FIG. 4 is shown - a strip element in the form of a grinding element 21 is used. The knives 1 shown on the cylinder body 6 rotate analogously to that in FIG FIG. 3 illustrated embodiment during the cutting operation in a direction indicated by the arrow 14 direction. At the lowermost point 15 of the orbit of the knife 1, they come into contact with the grinding element 21 at a grinding edge 24. A occurring effect of re-sharpening the knife 1 is finally carried out analogously to the explanation of the embodiment described above from the Figures 3 and 3a , Since the strip element in function of the grinding element 21 does not depend on a sharp grinding edge 24 comparable to the cutting edge 20, because the grinding element is not used for cutting by definition, also grinding in the free surface 18 'is based on figure 3a not necessary, since a sharp-edged run from the free surface 18 'to the grinding edge 24 is not required. Furthermore, a ground clearance surface 18 'is not necessary in terms of improved Schnittgutabfuhr because the grinding element 21 - as explained - is not used for cutting. Instead, a high level of wear resistance of the grinding element 21 is of primary interest, so that it is ready for use over as long a period as possible. Therefore, it should, for example, be completely or partially coated and have a coating thickness which assumes a value of 15 mm in the case shown.

Out FIG. 4 it is clear that the grinding element 21 is arranged such that the cutting edge 24 is positioned directly at the lowest point 15 of the orbit of the knife 1. Alternatively, it is also conceivable that the lowest point 15 is positioned over the free surface 18 " FIG. 4 indicated by the dashed lines shown grinding element 21 ', wherein not the lowest point of the orbit, but to a highest point 25 of the orbit of the knife 1 reference is made. It can be seen that the grinding edge 24 'of the grinding element 21' is arranged so that it is positioned next to the highest point 25 of the orbit of the knife 1. In this way, a contact duration of each individual knife 1 with the grinding element 21 'compared to the grinding element 21 increases and optionally a better Nachschärfewirkung be achieved. Accordingly, the term "open space" for open space 18 "is not to be understood literally, since an area designated as such very well with the knives 1 'is engaged and not" non-contact. "The grinding elements 21, 21' from FIG. 4 can be used both alternatively and simultaneously.

Both grinding elements 21, 21 ', as they are both present, extend over an entire length of the longitudinal axis 13 of the cylinder body 6, so that continuously all points of the sheath edges 4 of the knife 1 each with a corresponding point of the grinding elements 21, 21' in Contact, without this would have to be moved in an axial direction. The grinding elements 21, 21 'are nevertheless arranged axially displaceable, so that small corrections can be made, which prevent them from becoming worn out at the same points and thus due to the respective blades 1 "shrinking". By contrast, an axial displacement of the grinding elements 21, 21 ', the same is worn substantially uniformly over its entire length.

Both in the case of using a counter-blade 16 and a grinding element 21, 21 ', the strip elements are equipped with adjusting springs that maintain a sliding contact between the strip elements and the blades 1, 1' despite wear and track the respective strip elements accordingly.

LIST OF REFERENCE NUMBERS

1, 1 '

knife

2

cut leg

3

cutting surface

4

cutting edge

5

foot surface

6

cylinder body

7

front area

8th

the backstage area

9

interface

10

Cut leg surface

11

edge

12

foot legs

13

longitudinal axis

14

arrow

15

Job

16

against cutting

17

lateral surface

18, 18 ', 18 "

open space

19

face

20

cutting edge

21, 21 '

grinding element

22

double arrow

23

arrow

24

grinding edge

25

Job

D1

thickness

H1

height

H3

height

Claims (15)

Knife (1, 1 ') in the form of a helical line, having a longitudinal axis and a cutting edge (2), both at a lower end of a foot surface (5) and at an upper end of a cutting surface (3), wherein the cutting surface ( 3) along a front edge has a cutting edge (4) and the cutting edge (2) in a front region (7) has a greater hardness than in a rear region (8), wherein the two areas (7, 8) separating surface (9) is aligned approximately parallel to a front cutting edge surface (10) of the cutting edge (2), characterized in that the front region (7) has a thickness (D1) of less than 200 microns and further has a hardness greater than 1000 HV , Knife (1, 1 ') according to claim 1, characterized in that the front region (7) of the cutting edge (2) starting from the cutting edge (4) over at least 20%, preferably 50%, a height (H1, H2) of the cutting edge (2) extends. Knife (1, 1 ') according to claim 1 or 2, characterized in that the front region (7) of the cutting edge (2) is formed by an insert strip or by a coating, wherein preferably the knife (1, 1') completely with a coating is coated. Knife (1, 1 ') according to claim 3, characterized in that the coating has a hardness of greater than 1250 HV, preferably a hardness of greater than 1500 HV, more preferably a hardness greater than 1800 HV. Knife (1, 1 ') according to one of claims 1 to 4, characterized in that the knife (1, 1') consists of an uncured material, in particular of an uncured steel, or of a partially hardened or of a through hardened steel. Cutting device for cutting a material, comprising a cylinder body (6) rotatable about a longitudinal axis (13) with an outer lateral surface (17) and at least one knife (1, 1 ') in the form of a helical line, which forms a cutting edge (2), wherein a foot surface (5) of the blade (1, 1 ') which is arranged on a lower, the cylinder body (6) facing the end of the cutting edge leg (2), with the cylinder body (6), preferably with the Has lateral surface (17), and the cutting edge (2) at an upper, of the cylinder body (6) facing away from a cutting surface (3), wherein the cutting surface (3) at a in a set during a cutting operation direction of rotation of the cylinder body ( 6) has a cutting edge (4) and a strip element which comes into contact with the cutting surface (3) of the blade (1, 1 ') during a rotation of the cylinder body (6) in such a way that each point of the chain is continuously in contact Cutting surface (3) of the knife (1, 1 ') comes into contact with a corresponding point of the strip element, said cutting edge (2) in a viewed in the direction of rotation front portion (7) has a larger H in that the location of the strip element and the location of the strip element again have a greater hardness than a rear area (8) of the cutting edge (2) considered in the direction of rotation, a separating area (9) separating the two areas (7, 8). is aligned approximately parallel to a front cutting edge surface (10) of the cutting edge (2), characterized in that the front region (7) of the cutting edge (2) has a thickness of less than 200 microns and further has a hardness greater than 1000 HV. Cutting device according to claim 6, characterized in that the strip element is coated partially or completely, wherein in partial coating preferably only one end face (19) of the strip element has a coating. Cutting device according to claim 6 or 7, characterized in that the coating has a thickness of less than 200 μm at an end face (19) of the strip element. Cutting device according to claim 6, characterized in that the coating has a thickness of 200 microns to 20 microns. Cutting device according to one of claims 5 to 9, characterized in that the strip element is a counter-blade (16) or a grinding element (21, 21 '). Cutting device according to one of claims 4 to 10, characterized in that a Nachdrückkraft acts on the strip element, which causes a wear adjustment of the strip element. Cutting device according to one of claims 4 to 11, characterized in that the strip element extends over an entire axial length of the cylinder body and / or the strip element along an axis to the longitudinal axis (13) of the cylinder body (6) parallel axis is movable. Method for cutting a material, comprising the following method steps: a) A cylinder body (6) of a cutting device with at least one with the cylinder body (6) connected to knives (1, 1 ') with a cutting edge (2) is rotated about a longitudinal axis (13). b) During a rotation of the cylinder body (6), the at least one blade (1, 1 ') is continuously contiguous with each edge of a cutting edge (4) contiguous with a front edge of a cutting edge in a rotational direction of the cylinder body (6) set during a cutting operation from the cylinder body (6) facing away from cutting surface (3) of the cutting edge (2) is arranged, at a respective corresponding point with the material to be cut into engagement, whereby the latter is cut. c) The strip element is brought into such a sliding contact during a rotation of the cylinder body (6) with the cutting surface (3) of the knife (1, 1 ') both with a harder area (7) and with a softer area (8) in that each point of the cutting surface (3) is continuously brought into contact with a corresponding point of the strip element, a separating surface (9) separating the two regions (7, 8) being approximately parallel to a front cutting edge surface (10) of the cutting edge (2 ),
characterized by the following process step: d) Consecutively, each point of the cutting edge (4) of the knife (1, 1 ') is brought into contact at a respective corresponding point of the strip element with a front harder area thereof. A method according to claim 13, characterized in that the strip element during operation of the cutting device is permanently or only periodically positioned so that it comes into sliding contact with the knife (1, 1 '). A method according to claim 13 or 14, characterized in that when using a fully coated knife (1, 1 ') and / or strip element of the front portion (7) and the rear portion (8) of the cutting surface (3) of the knife (1 , 1 ') or of the strip element during a first start-up of the knife (1, 1') and / or the strip element are formed by a coating on the cutting surface (3) of the knife (1, 1 ') or on the strip element is ground ,

Images