EP1985726A1 - Cutter tool with a cutting edge reinforced with hard material - Google Patents

Abstract

Cutting tool (1) comprises a base body having a surface provided with a hard material layer in the region of a cutting edge (2).

Description

The present invention relates to a cutting tool, in particular a peeler, in which the surface of the base body is reinforced in the region of the cutting edge with at least one hard material layer. This allows the production of cutting tools with permanent, high sharpness.

Conventional blades are characterized by a compromise between the cutting ability (sharpness) and the cutting edge (durability of the sharpness). The cutting ability is generated by the wedge angle and the radius of curvature of the cutting edge. The smaller these are, the sharper the knife is, however, the cutting edge decreases, ie the initial sharpness of the blade decreases rapidly in conventional materials in use.

However, the blades described in the prior art have significant disadvantages. In the case of steel blades, it is known, for example, that these embodiments each make a compromise between cutting capability and cutting strength. That is, either is given on the geometric design of the blade high cutting ability, but then results in a low cutting edge, or vice versa. A simultaneous achievement of both properties has been difficult. In addition, steel blades have a high susceptibility to corrosion.

Through the use of improved blade steel, e.g. steels produced by the damascene method (folded in several layers) or by using higher quality steel alloys, e.g. For steels with higher carbon content, both the cutting ability and the cutting ability can be improved. However, the degradation of the cutting edge still takes place and regrinding is still necessary from time to time.

Therefore, household knives with ceramic blades have already been developed, which essentially do not have to be reground. However, household knives are subject in use to a relatively large bending load, which is a danger of breakage for the very brittle ceramic blades. The warning not to use ceramic blades as levers is and often has to be ignored by the user, with the effect that parts break out of the blade or break the entire blade. Furthermore, due to the brittleness of the material, the wedge angle must be selected to be larger than in the case of steel, since otherwise the cutting edge breaks out.

For industrial purposes and in the field of medicine, it is already known to construct cutting edges using a diamond material. For example, describes the DE 198 59 905 C2 a cutting tool having a cutting edge formed in a synthetic diamond layer for use as a medical scalpel. To produce the known cutting tool, a support, preferably based on silicon, is first provided by plasma coating with a layer of polycrystalline diamond. Subsequently, the substrate is partially etched away to expose the diamond layer and, at the diamond layer, again by chemical means, a cutting edge is formed by etching. In this way it is possible to produce cutting edges in different shapes and with a smaller radius of use. The blades of scalpels, however, are relatively short, must be very thin, so that clean cuts are achieved and are therefore already handled by the user very carefully, for example, not subjected to bending, which is not necessary for the intended use of a scalpel.

Another method for manufacturing a cutting tool is in EP 577 066 B1 described, but here the cutting edge is formed by laser machining, which allows only larger cutting angle and compared to mechanical or plasma processing leads to relatively large radii of curvature.

The DE 31 08 954 C2 describes a knife for industrial use, in particular a knife for cutting sheet material, such as paper. For this purpose, diamond plates, ie polycrystalline Diamonds, used. Due to the small size of these diamonds and to achieve better interchangeability of damaged parts of the cutting edge, the cutting edge is constructed of a plurality of segments. The diamond plates are attached to a carbide holder. The hard metal holder with the diamond plate is then attached to a carrier, for example screwed. The carrier is then screwed onto a knife holder, wherein the knife holder either only a single carrier or a plurality of carriers are attached. Subsequently, the knife holder is arranged on a support, for example screwed, which specifies the position and the shape of the cutting edge. However, such a construction is by no means suitable for household knives. Also, with diamond plates usual for household knives and required cutting angle of less than 45 ° can not be achieved.

Based on the disadvantages, as known from the prior art, it is an object of the present invention to provide a corrosion-resistant cutting tool with significantly improved cutting ability and simultaneously improved high cutting edge. This object is achieved with the features of the main claim. The dependent claims form advantageous developments.

According to the invention, therefore, a cutting tool is provided with a base body having at least one cutting edge, wherein the surface of the base body is provided at least in regions of the cutting edge with at least one hard material layer. Thus, the invention proposes a cutting tool in which the hard material layer at least partially forms the cutting edge. The hard material layer is positively, positively and materially connected to the base body in connection, whereby an intimate connection between the base body and hard material coating and thus a high overall stability of the cutting tool is achieved. This ensures on the one hand that both high mechanical stresses perpendicular to the cutting edge (as they occur, for example, when cutting hard objects) as well as high mechanical stresses along the cutting edge (for example, when bending the cutting tool along the body, such as when using the cutting tool acts as a lever) ensures excellent structural integrity of the cutting tool. Thus, there is a good bond between the hard material layer and the main body, so that chipping or detachment of the hard material layer is effectively prevented. The hard material layer can be applied, for example, by methods such as CVD, PVD or sputtering techniques.

It has been found that such a cutting tool with a cutting edge made of a hard material formed as described above superior properties in terms of the cutting ability (sharpness) and the cutting edge (durability of the sharpness).

In one advantageous embodiment, the hard material is selected from the group consisting of diamond, diamond-like carbon, carbon, aluminum, zirconium and silicon-based ceramics, such as aluminum oxide, aluminum nitride, zirconium oxide, zirconium nitride, silicon carbide or silicon nitride, boron nitride, refractory metals from the groups VIb, Vb and VI of the Periodic Table and their carbon compounds, such as tantalum, tantalum carbide, tungsten, tungsten carbide, molybdenum, molybdenum carbide, vanadium, titanium nitrides, TiAlN, TiCN, TiB ₂ and hard metals, such as tungsten carbide, TiC, TaC, optionally with cobalt and / or nickel components.

It is also advantageous if the material of the base body is selected from aluminum, copper, titanium, nickel, chromium, niobium, tungsten or their alloys, tungsten carbide, tantalum, tantalum carbide, TiC, molybdenum, molybdenum carbide, ferrous materials, such as steel, hard metals such as tungsten carbide, optionally with cobalt and / or nickel, plastics such as thermoplastics and thermosets, as well as carbon fiber composites or glass fiber composites. In particular, the base body is formed from titanium and its alloys.

A preferred combination is when the base body of titanium or a martensitbildenden steel and the hard material layer of diamond or diamond-like carbon.

Preferably, the base body has a blade-shaped region which forms the cutting edge, and wherein the blade-shaped region is provided at least in regions with the hard material layer.

A further preferred embodiment provides that a broad side surface of the main body is at least partially provided with the hard material layer, while the second broad side surface is uncoated.

Alternatively, however, it is equally possible that Both broad side surfaces of the body are at least partially provided with the hard material layer.

With regard to the layer thickness of the hard material layer, it is advantageous if it has a maximum of 20 μm, preferably a maximum of 10 μm. In particular, in this case, with the exception of carbonaceous layers, layer thicknesses of not more than 5 .mu.m, more preferably at most 1 .mu.m, provided.

It is further preferred if the material of the main body consists of a martensite-forming steel, which undergoes a volume jump (gamma-alpha conversion) of between 0.3% and 2% during the coating in order to reduce the residual stresses.

Further advantages result if at least one adhesion-promoting and / or diffusion-preventing layer is arranged between the base body and the hard material layer. The material of the intermediate layer is preferably selected from the group IVb, Vb and VIb of the Periodic Table of the Elements or their compounds with Ti and / or B and / or N and / or A1, in particular TiB ₂ -TiN.

In a further advantageous variant, the cutting edge of the hard material layer has a rounding radius R _c <20 μm, preferably R _c <5 μm, particularly preferably <1 μm.

Preferably, the surface of the hard material cutting element has a surface roughness R _m <1 μm, preferably <0.5 μm.

The cutting edge itself can be smooth or alternatively jagged, wavy or with a free-form contour be provided.

The cutting tools according to the invention are characterized by a high sharpness. The sharpness of the cutting edge is defined by a force F _max , which can be determined as follows: a nylon thread with a diameter of 0.2 mm is passed over an air gap of 2 d (d = 25 mm), the thread at a Fixed end and held at the other end under a tension of 6 N, the cutting edge is moved at an angle of 90 ° on the thread (vector s _x ) and hits the nylon thread at length 1d at x = 0, the force F _{As a result, x} increases almost linearly with s _x ; the force F _max is then defined by the force at which the thread is severed, the force F _max ≦ 3 N, more preferably F _max ≦ 1 N. In particular, F _max <0.75 N, preferably <0.5 N.

It is also advantageous if the cutting edge has a wedge angle α ₁ of 10 ° to 70 °, preferably 10 ° to 40 °.

When cutting tool of the invention is favorable if it is designed so that the main body has a Wate. In this way, particularly good values can be achieved in terms of sharpness and durability. The cutting edge preferably has two wedge angles, wherein the first wedge angle α _{1 is} from 10 ° to 70 °, in particular from 10 ° to 40 °, and the second wedge angle α _{2 is} from 1 ° to 30 °, in particular from 5 ° to 15 ° ,

It is irrelevant how the main body of the cutting tool is formed. Depending on the application or intended use, however, the main body may have openings and / or depressions for a reduction having the friction surface.

The cutting tool according to the invention has inherently a high sharpness and a high resistance to sharpness. The sharpness can be further increased, for example, by plasma curing. At the same time, the resistance of the sharpness can be increased with this method, since a further hardening of the hard material layer can be achieved.

Advantageously, at least one surface of the cutting tool is optimized for optimizing the friction surface by means of form elements, such as transverse grooves, elevations, etc., or additional coatings such as Teflon, PEK, etc.

The cutting tool according to the invention can be designed in many variants, for example as a household knife, paring knife, chopping knife, table knife, steak knife, dessert knife, fruit knife, cheese knife, planer, hatchet or utility knife.

As a special application, household knives and paring knives are mentioned. The peeler described below, in addition to the inventive design of the blade even further advantages.

For most peelers namely the blade is screwed with two screws in the holder of the peeler. This results in disadvantages, such as assembly costs by screw fastening the blade, poor cleaning options, obstructive screw heads when peeling or the fact that the peeling chip immediately after peeling back on the peel, eg cucumbers or other highly hydrous foods hangs. Thus it is advantageous that when the body is connected to a handle, this integrated or is part of the handle. In particular, when the connection between the base body and gripping force, form-fit or cohesively configured, can eliminate the above-mentioned disadvantages. This can be done for example by ultrasonic welding of the body with the handle. It is further preferred if the connection between the body and the handle is movable. It is also possible that the main body is incorporated by injection into the handle.

Fig. 1

einen Blick auf die Breitseitenfläche 7 eines erfindungsgemäßen Schneidwerkzeugs 1,

Fig. 2

einen Schnitt durch ein erfindungsgemäßes Schneidwerkzeug, das auf beiden Oberflächen des Grundkörpers 3 eine Hartstoffbeschichtung 4 aufweist,

Fig. 3

einen Schnitt durch ein erfindungsgemäßes Schneidwerkzeug, das nur auf einer Oberfläche des Grundkörpers 3 eine Hartstoffbeschichtung 4 aufweist,

Fig. 4a

schematisch verschiedene mögliche Ausbildungen der Schneidgeometrie einer einstufigen Ausführungsform,

Fig. 4b

die Ausführungsformen einer zweistufigen Ausbildung der Schneidkante,

Fig. 5

in der Figurenfolge 4a bis 4b den Ablauf der Bestimmung der Kraft F_max,

Fig. 6

eine erfindungsgemäße Ausgestaltungsform des Schneidwerkzeugs als Schäler, mit einer bezüglich des Griffs drehbar angeordneten Klinge.

The invention is described below by the Figures 1-6 explained in more detail. Show it:

Fig. 1

a view of the broad side surface 7 of a cutting tool 1 according to the invention,

Fig. 2

a section through a cutting tool according to the invention, which has a hard material coating 4 on both surfaces of the main body 3,

Fig. 3

a section through a cutting tool according to the invention, which has a hard material coating 4 only on one surface of the main body 3,

Fig. 4a

schematically different possible designs of the cutting geometry of a single-stage embodiment,

Fig. 4b

the embodiments of a two-stage design of the cutting edge,

Fig. 5

in the sequence 4a to 4b the sequence of determination of the force F _max ,

Fig. 6

an inventive embodiment of the cutting tool as a peeler, with a respect to the handle rotatably mounted blade.

Fig. 1 FIG. 2 illustrates a plan view of a broad side surface 7 of a cutting tool 1 according to the invention, which is designed here in the form of a kitchen knife.

A section along the line II in Fig. 1 by an embodiment of a cutting tool 1 according to the invention is in Fig. 2 shown. In this illustration, the construction of the cutting tool 1 according to the invention can be seen. On the base body 3 made of titanium, a hard material layer 4 made of diamond is applied on both sides, which join at the cutting edge 2. The cutting edge 2 is thus formed solely by the hard material. Likewise, the wedge angle α _{1 is} indicated.

In Fig. 3 is the same cut as in Fig. 2 shown, except that only one surface of the base body 3 is shown with a coating 4 of hard material here.

The material for such a base body 3 can basically be selected from common metallic materials and / or alloys or carbides. Examples include: aluminum, copper, titanium, nickel, chromium, niobium, tungsten or their alloys, tungsten carbide, tantalum, tantalum carbide, molybdenum, molybdenum carbide, iron-containing materials such as steel, hard metals such as tungsten carbide, optionally with cobalt and / or nickel, plastics such as thermoplastics and thermosets, as well as carbon fiber composites or glass fiber composites.

For better clarity are in Fig. 4 illustrated various cutting geometries that can be realized in the cutting tool 1 according to the invention. The Fig. 4a shows the geometric design of various single-stage embodiments, in which case a wedge angle α ₁ of 10 to 70 °, preferably from 20 ° to 50 ° can be realized.

Fig. 4b shows possible embodiments for a two-stage design, in which case a first wedge angle α ₁ of 10 ° to 70 °, preferably from 20 ° to 50 ° and a second wedge angle α2 of 1 ° to 30 °, preferably 5 ° to 50 ° can be realized ,

Fig. 5 The sharpness was thereby defined by a force F _max , which was determined as follows: a nylon thread with a diameter of 0.2 mm is over an air gap of 2 d (d = 25 mm), wherein the thread is firmly fixed at one end and held at the other end under a tensile stress of 6 N. The cutting edge 2 is now moved at an angle 90 ° (both in plan view and in the side view) on the thread (vector S _x ). At x = 0 then the cutting edge 2 hits the thread. As a result, F _{x increases} approximately linearly with S _x . Thus, S _x is always given, F _x is the dependent variable and is measured simultaneously (F _x = f (S _x )). With increasing displacement S _x thus increases the force F _x . In point (F _max ) then the thread is severed. The amount of force F _x goes back up abruptly 0. According to the present invention, the cutting tools 1 have a force F _max of ≦ 1 N.

FIG. 6 an embodiment of the cutting tool 1 according to the invention is shown as a peeler. The blade of the peeler is connected via a movable element 8 with the handle 6, so that a tilting of the blade is made possible. The so-called pendulum blade has in the middle a recess whose edges form the cutting edges 2, 2 '. Also shown is a section (AA) through the peeler.

Claims (27)

Cutting tool (1) with a basic body (3) having at least one cutting edge (2),
characterized,
that the surface of the base body (3) at least in the region of the cutting edge (2) is provided at least partially with at least one hard material layer (4). Cutting tool (1) according to claim 1,
characterized in that the hard material is selected from the group consisting of diamond, diamond-like carbon, carbon, aluminum, zirconium and silicon-based ceramics, such as aluminum oxide, aluminum nitride, zirconium oxide, zirconium nitride, silicon carbide or silicon nitride, boron nitride, refractory metals from groups VIb , Vb and VI of the Periodic Table and their carbon compounds, such as tantalum, tantalum carbide, tungsten, tungsten carbide, molybdenum, molybdenum carbide, vanadium, titanium nitrides, TiAlN, TiCN, TiB ₂ and hard metals such as tungsten carbide, TiC, TaC, optionally with cobalt and / or nickel shares. Cutting tool (1) according to one of the preceding claims,
characterized in that the material of the base body (3) made of titanium and its alloys consists. Cutting tool (1) according to one of the preceding claims,
characterized in that the material of the base body (3) is selected from aluminum, copper, titanium, nickel, chromium, niobium, tungsten or their alloys, tungsten carbide, tantalum, tantalum carbide, TiC, molybdenum, molybdenum carbide, ferrous materials, such as steel, Hard metals, such as tungsten carbide, optionally with cobalt and / or nickel, plastics, such as thermoplastics and thermosets, and carbon fiber composites or glass fiber composites. Cutting tool (1) according to one of the preceding claims,
characterized in that the base body (3) has a blade-shaped region which forms the cutting edge, and that the blade-shaped region is provided at least in regions with the hard material layer. Cutting tool (1) according to one of the preceding claims,
characterized in that a broad side surface (7) of the base body (3) is at least partially provided with the hard material layer (4), while the second broad side surface (7) is uncoated. Cutting tool (1) according to at least one of claims 1 to 5,
characterized in that both broad side surfaces of the base body are at least partially provided with the hard material layer. Cutting tool (1) according to one of the preceding claims,
characterized in that the hard material layer (4) has a layer thickness of not more than 20 μm, in particular not more than 10 μm. Cutting tool (1) according to claim 8,
characterized in that the hard material layer (4), with the exception of carbon-containing layers, has a layer thickness of preferably not more than 5 μm, particularly preferably not more than 1 μm. Cutting tool (1) according to at least one of the preceding claims,
characterized in that the material of the base body (3) consists of a martensitbildenden steel, which undergoes a volume jump (gamma-alpha conversion) between 0.3% and 2% to reduce the residual stresses during the coating. Cutting tool (1) according to one of the preceding claims,
characterized in that between the base body (3) and hard material layer (4) at least one adhesion-promoting and / or diffusion-preventing layer (5) is arranged. Cutting tool (1) according to the preceding claim,
characterized in that the material of the intermediate layer (5) is selected from the group IVb, Vb and VIb of the Periodic Table of the Elements or their compounds with Ti and / or B and / or N and / or A1, in particular TiB ₂ -TiN. Cutting tool (1) according to one of the preceding claims,
characterized in that the cutting edge (2) has a rounding radius R _c <20 microns, preferably R _c <5 microns, more preferably <1 micron. Cutting tool (1) according to at least one of the preceding claims,
characterized in that the cutting edge (2) of the hard material cutting element has a surface roughness R _m <1 μm, preferably <0.5 μm. Cutting tool (1) according to at least one of the preceding claims,
characterized in that the sharpness of the cutting edge (2) is defined by a force F _max determined as follows: a nylon thread with a diameter of 0.2 mm is passed over an air gap of 2 d (d = 25 mm), wherein the thread is firmly fixed at one end and held at the other end under a tension of 6 N, the cutting edge is moved at an angle of 90 ° on the thread (vector s _x ) and hits the Nylon thread at length 1d at x = 0, As a result, the force F _x increases almost linearly with S _x ; the force F _max is then defined by the force at which the thread is severed, the force F _max ≦ 3 N, more preferably F _max ≦ 1 N. Cutting tool (1) according to the preceding claim,
characterized in that F _max <0.75 N, preferably <0.5 N. Cutting tool (1) according to at least one of the preceding claims,
characterized in that the cutting edge (2) has a wedge angle α ₁ of 10 ° to 70 °, preferably 10 ° to 40 °. Cutting tool (1) according to at least one of the preceding claims,
characterized in that the cutting edge (2) has a first wedge angle α ₁ of 10 ° to 70 °, in particular of 10 ° to 40 ° and the second wedge angle α ₂ of 1 ° to 30 °, in particular from 5 ° to 15 ° , Cutting tool (1) according to one of the preceding claims,
characterized in that the main body of the cutting tool (1) has openings and / or depressions for a reduction of the friction surface. Cutting tool (1) according to one of the preceding claims,
characterized in that at least one surface of the cutting tool (1) is optimized with respect to an optimization of the friction surface by form elements such as transverse grooves, elevations, etc. or additional coatings such as Teflon, PEK, etc. Cutting tool (1) according to one of the preceding claims,
characterized in that the cutting edge (2) is serrated, wavy or designed with a free-form contour. Cutting tool (1) according to at least one of the preceding claims,
characterized in that the base body (3) is connected to a handle (6). Cutting tool (1) according to the preceding claim,
characterized in that the base body (3) integrated or part of the handle (6). Cutting tool (1) according to claim 22,
characterized in that the connection between the base body (3) and the handle (6) is non-positive or positive or cohesive, for example by ultrasonic welding. Cutting tool (1) according to claim 22,
characterized in that the connection between Base body (3) and handle (6) is movable. Cutting tool (1) according to claim 22,
characterized in that the base body (3) is injected by injection into the handle (6). Cutting tool (1) according to one of the preceding claims,
characterized in that the cutting tool (1) is a household knife, paring knife, chopping knife, table knife, steak knife, dessert knife, fruit knife, cheese knife, planer, hatchet or utility knife.

Images