EP2338358A1 - Cutting device and cutting blade for cutting rod-shaped products of the tobacco processing industry - Google Patents

Abstract

The device has a rotating blade carrier with a cutting knife (2). Side surfaces (7, 8) of the knife are formed adjacent to two cutting edges. One of the side surfaces of the cutting knife includes a coating that improves surface hardness and is made of amorphous bound material. Thickness of the coating is 0.003 mm. The cutting knife is led to the side surfaces of a grinding disk. Speed of the grinding disk is controlled based on speed of the blade carrier. A grinding device is provided with an electric motor, and the grinding disk drives the motor in rotary motion.

Description

Cutting device and cutting knife for cutting rod-shaped products of the tobacco processing industry

The invention relates to a cutting device and a cutting blade for cutting rod-shaped products of the tobacco processing industry having the features of the preamble of claim 1.

Rod shaped products of the tobacco processing industry are e.g. Cigarettes, cigarillos, in which the tobacco is held together securely by a wrapping material such as paper, or filters, which are arranged in the cigarettes or cigarillos. To produce the rod-shaped products modern packaging machines are used, which include, inter alia, a step with a cutting device in which the rod-shaped product is cut from a continuously fed strand.

The cutting device is essentially formed from a rotating knife carrier with one or more cutting knives and a tube with a guide for the strand, wherein the tube forms at the same time an abutment for the running through the strand cutting blade in addition to the leadership of the strand. The cutting blade is due to the high cutting frequency natural wear, which can lead to an unclean cutting edge of the cut surface of the strand. To compensate for the wear, the cutting blades are ground in the finishing machine by means of one or more grinding wheels and pushed by a feed device in the direction of the cutting edge. After a certain Wear, the cutting blades must be replaced, for which the operation of the packaging machine must be interrupted.

A disadvantage of such a regrinding of the cutting blades is that sparks occur during grinding, which should always be reduced to a minimum, since the sparks in extreme cases, parts of the machine itself or the strand can be damaged or even set on fire. Furthermore, it has been found that when regrinding the cutting blade on the cutting edge, a burr can occur, which despite the ground cut edge can lead to an unclean cut surface of the rod-shaped product.

The object of the invention is to provide a cutting device and a cutting blade for cutting rod-shaped products of the tobacco processing industry, in which or with which the formation of sparks is avoided and the rod-shaped product is cut from the strand to form a clean cut surface as possible ,

The object is achieved by a cutting device with the features of claim 1 and a cutting blade with the features of claim 9. Further preferred embodiments of the invention can be found in the subclaims, the figures and the associated description.

The basic idea of the invention can be seen in that at least one of the side surfaces of the cutting blade has a surface hardness-increasing coating. Due to the higher surface hardness of the side surface self-sharpening of the cutting blade is achieved by the side surfaces of the cutting blade during the cutting process different to be worn out. The side surface with the higher surface hardness uses less than the side surface with the lower surface hardness. This effect leads to a cutting edge that practically re-sharpens itself without creating a burr, which could lead to an unclean cut surface of the rod-shaped product. This self-sharpening effect is also known in nature as the so-called "beaver tooth effect". Due to this "self-sharpening" of the cutting blade re-sharpening of the cutting blade can be reduced or even eliminated, so that the sparking associated with the grinding process can at least be reduced.

A further preferred embodiment of the invention can be seen in the fact that the side surfaces have a different surface hardness after the expiry of a running-in phase. In this case, the surface hardness of the side surfaces at the beginning of the break-in phase may be identical and vary differently during the break-in phase, so that the effect of self-sharpening occurs only after the break-in phase. As a result, a cost-effective to produce both sides coated cutting blade can be used.

It is further proposed that the side surface with the surface hardness-increasing coating has a hardness of at least 3000-8000 HV, preferably of 7500 HV. The proposed hardness of the cutting blade, the life of the cutting blade can be increased as such in addition, since the wear of the cutting blade is reduced. Due to the reduced wear of the cutting edge, the number of cuts between the advances of the cutting blade can be increased from 750 to about 5000, so that the cutting device operated much longer with a setting can be, and the duration of the change intervals of the cutting blade can be increased. Overall, this can be additionally saved costs both by the increased use of the cutting blade as well as by the reduced maintenance.

It is further proposed that the coating is a coating of an amorphous bonded carbon. The coating of the amorphous bonded carbon has a very low coefficient of friction, so that the frictional forces acting during the cutting process can be reduced and the cut surface is thereby further improved. Such tetrahedrally crosslinked amorphous bonded carbon coatings are known, for example, as ta-C layers, in particular with a high sp ³ , and have an extremely high hardness with a very low coefficient of friction. Furthermore, the coating is temperature-resistant up to 450 degrees Celsius, so that a high cutting speed can be driven without the coating loses its properties due to the frictional heat. The bonding of the coating is covalent, so that it has a low adhesion tendency to the adjacent metallic components. In addition, the lubricating effect of carbon particles on the coated side surface can be achieved by the proposed coating.

It has been found that, in this case, a layer thickness of 0.001-0.004 mm, preferably 0.003 mm, makes sense, so that the self-sharpness effect is achieved, and the mechanical properties of the cutting blade are not adversely affected.

It is further proposed that at least one grinding wheel is provided, on which the rotating cutting blade is guided past with a side surface, and both side surfaces of the cutting blade have a surface hardness-increasing coating. The one-sided grinding of the cutting blade, the surface hardness of the cutting blade on a side surface is deliberately reduced, so that the "beaver tooth effect" is caused by the grinding. In particular, the side surfaces can thereby be provided with an identical coating, which is favorable from a manufacturing point of view, since an identical coating of the side surfaces is much easier to produce. Furthermore, the material removal of the side surfaces due to the "beaver tooth effect" over the surface is generally not uniform, so that the self-sharpening effect along the cut edge is also uneven and leads to an uneven cutting edge. The one-sided grinding not only brings about the "beaver tooth effect" itself, but also compensates for the effect of uneven material removal across the surface, so that grinding can provide a uniform surface side surface and a uniform cut edge. Since the respective other side surface is provided with the surface hardness-increasing coating, the present in the one-sided grinding process burring of the cutting edge compared to the known in the prior art grinding operations is substantially lower, so that the cutting edge is not deteriorated thereby. Since the required due to the grinding material removal of the cutting blade due to the present invention induced self-sharpening of the cutting edge is much lower than was required in the prior art, the grinding of the cutting blade can also be done with a smaller relative movement to the cutting blade. The relative movement of the grinding wheel to the side surface of the cutting blade is at a rectified Relative rotational movement of the grinding wheel to the rotational movement of the cutting blade defined by the difference in peripheral speeds between the rotating grinding wheel and the rotating cutting blade in the region of the abutting surfaces. Thus, the grinding wheel in this case can rotate at a higher speed than was known in the prior art, or the grinding wheel diameter can be increased at the same speed. However, an enlargement of the grinding wheel diameter is preferable in that the grinding wheel thereby runs on the surface of the cutting blade in a more favorable angular relationship or runs away from the cutting edge and thus prevents or reduces the formation of burrs or fraying of the cutting edge. In the case of a grinding wheel rotating in opposition to the rotational movement of the cutting blade, the surface of the grinding wheel runs against the rotational movement of the cutting blade on its surface, so that in this case the peripheral speed of the grinding wheel should be reduced, which is achieved by reducing the rotational speed or reducing the grinding wheel diameter can. Due to the reduction of the relative movement of the surface of the grinding wheel to the surface of the cutting blade, the sparking during the grinding process can be further reduced. With a corresponding adjustment of the differential speed, the sparking can even be reduced to zero despite the grinding. Surprisingly, it has even been found that the side surface of the cutting blade to be ground can even have a greater surface hardness than the grinding wheel itself, and the inventively induced effect of sharpening the cut edge after the "beaver tooth effect" nevertheless occurs.

It is also proposed that the side surfaces have a different Have surface hardness, and the side surface with the lower surface hardness has a coating with a higher hardness than the base material of the cutting blade. Overall, on the one hand, the "beaver tooth effect" can be brought about by the different surface hardnesses of the side surfaces, and the service life of the cutting blade can generally be increased by the deliberately higher surface hardness of the side surface with the lower surface hardness than the base material.

Further, it has been found from experiments that the side surfaces should enclose an angle of 15-25 degrees, preferably up to 35 degrees and preferably 20 degrees between them, in order for the deliberately induced self-sharpening effect to occur.

It is also proposed that at least one rotating driven grinding wheel is provided, on which the rotating cutting blade is guided past with a side surface and that the rotational speed of the driven grinding wheel is controlled in dependence on the rotational speed of the rotating blade carrier. The proposed control of the speed of the grinding wheel, the material removal and the associated sparking can be further reduced because the difference between the peripheral speeds of the grinding wheel and the cutting blade thereby reduced or can be kept constant regardless of the production speeds when braking and starting the machine.

Furthermore, a cutting blade for a cutting device according to the invention is proposed to solve the problem, which is interchangeable.

Fig.1a und 1b:

Schneidvorrichtung mit zwei Schneidmessern und einer Schleifscheibe;

Fig.2a und 2b:

Schneidvorrichtung mit zwei Schneidmessern und zwei Schleifscheiben;

Fig.3:

Schneidmesser;

Fig.4a und 4b:

Schneidmesser nach dem Stand der Technik in Schnittrichtung A-A der Fig.3 vor und nach der Abnutzung;

Fig.5a,5b, 5c und 5d:

Schneidmesser mit einer einseitigen die Oberflächenhärte erhöhenden Beschichtung in Schnittrichtung A-A der Fig.3;

Fig.6a und 6b:

Schneidmesser mit einer beidseitigen die Oberflächenhärte erhöhenden Beschichtung in Schnittrichtung A-A der Fig.3 vor und nach einer Einlaufphase.

The invention will be explained in more detail with reference to a preferred embodiment. The figures show in detail:

1a and 1b:

Cutting device with two cutting blades and a grinding wheel;

2a and 2b:

Cutting device with two cutting blades and two grinding wheels;

Figure 3:

Cutting blade;

4a and 4b:

Cutting knife according to the prior art in the cutting direction AA of Figure 3 before and after wear;

5a, 5b, 5c and 5d:

Cutting knife with a one-sided surface hardness increasing coating in the cutting direction AA of Figure 3 ;

6a and 6b:

Cutting knife with a surface hardening coating on both sides in the cutting direction AA of the Figure 3 before and after a warm-up phase.

In the 1a and 1b is a cutting device 1 can be seen with a rotatable knife carrier 14, on which two cutting blades 2 and 3 are clamped. Furthermore, a grinding device 15 fixed with respect to the knife carrier 14 is arranged on the cutting device 1 with a grinding wheel 4, the grinding surface of which is aligned at an angle to the axis of rotation of the knife carrier 14. The grinding device 15 comprises an electric motor with which the grinding wheel 4 can be driven to rotate. The cutting blades 2 and 3 are additionally pivotable relative to the blade carrier 14 to produce a vertical to the feed direction of the rod-shaped product section, wherein the pivotal movement of the cutting blades 2 and 3 is initiated via a located in the blade carrier 14 not shown mechanism. In addition, a protective device 6 is provided, by which an unintentional intervention of the operating personnel in the circulation area of the cutting blades 2 and 3 is to be prevented.

In the 2a and 2b the cutting device 1 can be seen in the front view. On the cutting device 1, a second grinding device 16 with a second grinding wheel 5 is arranged diametrically to the first grinding device 15. The grinding devices 15 and 16 are arranged in the same angular relationship as the cutting blades 2 and 3 on the blade carrier 14, so that the cutting blades 2 and 3 are always ground simultaneously. Such cutting devices 1 are used in the packaging machines of the tobacco processing industry, for example, to cut off cigarettes or filters of a predetermined length from a supplied strand. The length of the cut cigarette or the filter is determined by the feed rate of the strand and the rotational speed of the blade carrier 14. Thus, the capacity of the packaging machine, inter alia, depends directly on the rotational speed of the blade carrier 14.

In the Figure 3 is a cutting blade 2 with a cutting edge 9 seen in side view. The cutting blade 2 rotates during the cutting process such that the cutting edge 9 through the strand of the rod-shaped product moves.

In the 4a and 4b is the cutting blade 2 from the FIG. 3 to recognize the prior art before and after the wear. The cutting blade 2 has a thickness B of about 0.2 mm and two at an angle A of 20 degrees to each other side surfaces 7 and 8. The angle A between the side surfaces 7 and 8 of the cutting blade 2 corresponds to the angle between the grinding surfaces of the grinding wheels 4 and 5 and the plane of rotation, which spans the cutting blade 2 when passing on the grinding wheels 4 and 5 with the side surface 7. The side surfaces 7 and 8 terminate in the cutting edge 9, which in the FIG. 4a not worn yet. During the cutting process, the cutting edge 9 wears off and thereby changes its shape in the 9a in the 4b marked form. The wear of the cutting edge 9 is justified by a removal of material on the side surfaces 7 and 8 and represented by the surface 10.

In the 5a, 5b, 5c and 5d a cutting knife 2 further developed according to the invention is to be recognized, which on the side face 7 has a coating 13 with a harder surface, in this case of approximately 7500 HV, than the surface of the side face 8. During the cutting process takes place in the cutting blade 2 in contrast to that in the 4b Uneven material removal on the side surfaces 7 and 8, which is characterized by the surface 11, instead of the resulting wear state. Due to the uneven material removal, the cutting edge 9 has a shape 9b, which is substantially sharper than the shape 9a of the cutting edge 9 in a prior art cutting knife 2 with the same number of cuts. The coating 13 is formed from an amorphous bonded carbon layer with a Layer thickness C of 0.003 mm. Such amorphous bonded carbon layers are characterized by a particularly high hardness of 3000 - 8000 HV. They are therefore very resistant to wear and also have a very low coefficient of friction, whereby the frictional forces acting during the cutting process are reduced, and the sectional area of the rod-shaped tobacco or filter product is further improved. Furthermore, due to the carbon particles in the coating, a lubricating effect takes place at the cut surface, by means of which the friction during the cutting process is further reduced.

In the Fig.5c and 5d however, the same cutting blade 2 can now be seen after passing by one of the grinding wheels 4 or 5. The cutting knife 2 is in passing on the grinding wheels 4 and 5 with the side surface 8, which has the lower surface hardness, at the grinding surfaces of the grinding wheels 4 and 5 comes under material removal in contact. The material removed from the side surface 8 is marked by the surface 12. It was ground only the side surface 8; the side surface 7 with the coating 13 has not been ground and therefore has an unchanged shape. The cutting edge 9 is thereby sharpened even sharper to form 9c. Such unilateral grinding is not disadvantageous here, in contrast to the prior art, since the formation of burrs on the cutting edge 9 is at least substantially reduced by the coating 13 of the side surface 7. Furthermore, the material removal required by the grinding and thus the required relative movement between the grinding wheel surfaces and the side surface 7 can be reduced by the inventively induced effect of self-sharpening. At a relative to the rotational movement of Cutting knife 2 and 3 rectified tapered surface of the grinding wheels 4 and 5, this can be achieved by increasing the speed of the grinding wheels 4 or 5 or alternatively by an enlarged grinding wheel diameter at the same speed of the grinding wheels 4 and 5 with an associated increase in peripheral speed. Due to the reduced relative movement of the grinding wheels 4 and 5 to the side surface 7, the sparking is much lower. This makes it possible to achieve a sharp cutting edge 9 while reducing the sparking.

In the Fig. 6a and 6b is the cutting blade 2 also in the cutting direction AA from the Figure 3 can be seen in which the side surface 8 is also provided with a surface hardness-increasing coating 13a. In the simplest case, the coatings 13 and 13a of the side surfaces 7 and 8 are identical and applied in a manufacturing process, whereby the manufacturing costs can be reduced. After a running-in phase during which the cutting blade 2 has been ground, for example, on the side surface 8, the coating 13a has been ground away completely on the side surface 8 or sanded down to a substantially smaller layer thickness, as described, for example, in US Pat Figure 6b is shown. As a result, the surface hardnesses of the side surfaces 7 and 8 are different after the break-in phase, and it follows during the following cutting operations of the present invention intended "beaver tooth effect" with the independent regrinding of the cutting edge. 9

Further, due to the coating 13, it is possible to select grinding wheels 4 and 5 with a larger diameter at the same speed. The edges of the grinding wheels 4 and 5 can thereby during the grinding movement in a larger Angle accumulate laterally on the side surface 7, whereby the burr formation at the cutting edge 9 and a possible fraying of the cutting edge 9 is reduced.

The rotational speed of the grinding wheels 4 and 5 can preferably be controlled as a function of the rotational speed of the rotating blade carrier 14, so that the cutting blades 4 and 5 come to rest against the grinding wheels at a preferably constant relative speed and the material removal at the cutting blades 4 and 5 thereby regardless of the speed of the blade carrier 14 can be kept constant. This is particularly useful in terms of the greatly varying speed of the blade carrier 14 during braking and starting the machine.

Claims (10)

Cutting device (1) for cutting rod-shaped products of the tobacco-processing industry, with - At least one rotating blade carrier (14) with at least one cutting blade (2,3), with a cut edge (9, 9a, 9b) and two side faces (7, 8) adjoining the cut edge (9, 9a, 9b),
characterized in that - At least one of the side surfaces (7,8) of the cutting blade (2,3) has a surface hardness increasing coating (13). Cutting device (1) according to claim 1, characterized in that - The side surfaces (7,8) have a different surface hardness after the expiry of a running-in phase. Cutting device (1) according to claim 1 or 2, characterized in that - The side surface (7) having the higher surface hardness has a hardness of at least 3000 - 8000 HV, preferably of 7500 HV. Cutting device (1) according to one of the preceding claims, characterized in that - The coating (13,13a) is a coating (13) made of an amorphous bonded carbon. Cutting device (1) according to claim 4, characterized in that - The coating (13) has a layer thickness of 0.001 - 0.004 mm, preferably of 0.003 mm. Cutting device (1) according to one of the preceding claims, characterized in that - At least one grinding wheel (4,5) is provided, on which the rotating cutting blade (2,3) with a side surface (8) is guided past, and - Both side surfaces (7,8) of the cutting blade (2,3) have a surface hardness increasing coating (13). Cutting device (1) according to one of the preceding claims, characterized in that - The side surfaces (7,8) have a different surface hardness, and - The side surface (8) having the lower surface hardness, a coating (13 a) having a higher hardness than the base material of the cutting blade (2,3). Cutting device (1) according to one of the preceding claims, characterized in that - Include the side surfaces (7,8) an angle (A) of 15 to 25 degrees, preferably to 35 degrees, and preferably of 20 degrees between them. Cutting device (1) according to one of the preceding claims, characterized in that - At least one rotating driven grinding wheel (4,5) is provided, on which the rotating cutting blade (2,3) is guided past with a side surface, and - The speed of the driven grinding wheel (4,5) in response to the rotational speed of the rotating blade carrier (14) is controlled. Cutting knife (2,3) for a cutting device (1) with the features of one of claims 1 to 8, characterized in that the cutting blade (2,3) is replaceable.

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