EP3643467A1 - Use of a blade as machining blade, profiling blade or mincer blade - Google Patents

Abstract

The invention relates to the use of a knife (1) for processing wet wood and / or raw wood. The knife comprises a knife base body (2) and at least one cutting plate (3) with a cutting edge (4), the cutting plate (3) being carried by the knife base body (2). The cutting plate (3) is fastened to the knife base body (2) by means of a hard solder connection (5) with a copper solder (6).

Description

The invention relates to the use of a knife of the type specified in the preamble of claim 1 for processing wet wood and / or raw wood.

In the case of knives for the machining of wood or wood-like materials, there is generally a pronounced interest in reducing or avoiding wear and in maximizing the service life. One tries to achieve this in many areas of application by using inserts made of highly hard materials. Such high-hard cutting inserts are used in particular in the fine machining of dry wood, fiberboard or the like, the cutting inserts then being soldered onto a basic knife body in the usual way. The very hard materials known for this are considered to be very wear-resistant, but also sensitive to impact. In the application mentioned, the tooth feeds are therefore sufficiently low so that the impact loads acting on the individual cutting inserts are low. In such circumstances, very high cutting speeds and long tool lives can be achieved.

Deviating conditions can be found when processing wet or raw wood. For example, in sawmills, the raw wood delivered from forestry is processed in several process steps. In large machinery, lumber is made from the raw wood, with the wood waste being processed into wood chips. Such machine systems are equipped with special knives, equipped with profiling, chip and / or chipper knives, for example. Because of the very high tooth feed rates, such knives are exposed to high impact loads as well as high wear.

From the DE 1 724 727 U a cleaver is known which has a carbide cutting tip to increase wear resistance. The cutting plate is welded onto the chopping knife's body. It is also disadvantageous here that the cutting inserts tend to break due to the high abrupt loads. The experts therefore currently assume that high-hard inserts in chip knives, profiling knives or chipper knives for processing wet wood and / or raw wood are unable to withstand the impact loads that occur and are therefore unsuitable.

The invention has for its object to be able to process wet wood and / or raw wood with increased service life.

This object is achieved by using a knife with the features of claim 1.

The knife according to the invention comprises a basic knife body and at least one cutting plate with a cutting edge. The cutting insert is carried by the knife base body and is fastened to the knife base body by means of a hard solder connection with a copper solder. The knife designed in this way is used according to the invention for processing wet wood and / or raw wood.

The invention is based on the knowledge that, contrary to the technical prejudice of the professional world, a highly hard insert can be exposed to significant operational shock loads if certain conditions are met. It was recognized that it was not the impact load as such, but a resulting bending deformation of the insert with local zones of tensile stress that was responsible for premature failure of the insert. If the knife engages in the workpiece, a cutting force acts on the cutting plate and there in particular on the cutting edge. This cutting force presses the insert against the knife body. The cutting insert experiences a deformation due to the elastic flexibility of its support, which leads to bending stresses in the cutting insert.

In conventional hard solder connections, in which there is an almost full-surface solder connection of the base body and cutting insert, with the silver solder that is usually used, a solder gap with a certain gap thickness is established between the cutting plate and the knife base body within the scope of the known manufacturing processes, the solder gap being filled with the solder material. The comparatively soft solder material creates a resilient bedding of the cutting plate due to its flexibility in conjunction with the gap thickness, which allows the bending deformation of the cutting plate described above. The tensile residual stresses resulting from the bending deformation add up with operational bending stresses and lead to component failure or cutting edge breakage.

In the case of knives with welded cutting inserts, the resilience of the bedding is limited to the resilience of the less soft weld seam, which is why the operational bending stresses are lower. However, it must be taken into account that welded-on cutting plates are not attached to the main body of the knife, but rather like a frame. For example, cutting forces can cause the insert to lift off the center of the knife body and create bending stresses at the weld seams. In addition, welded knives have high, thermally induced internal tensile stresses at the joints of the knife base body and the cutting plate as a result of the welding process. These residual tensile stresses add up with the bending stresses as well as with operational bending stresses and lead to component failure or cutting edge breakage.

The above difficulties are avoided by the use of copper solder according to the invention. Since the braze joint with copper braze has a very low degree of flexibility compared to other braze joints, in particular because of its comparatively small solder gap thickness, the cutting insert is supported by the copper braze against the cutting forces with significantly less flexibility. Due to the stiffer support, the bending stresses in the cutting insert resulting from the particularly sudden application of the cutting force are reduced.

In addition, the differences in joining temperature for hard solder connections with copper solder are significantly smaller than the differences in joining temperature for welded inserts. Due to the comparatively small temperature changes in the joining area, the formation of residual tensile residual stresses is essentially avoided. In addition, locally limited heating occurs during welding, which also leads to internal stresses in the material during the cooling process. Overall, it has been achieved that the special material properties of high-hard materials in cutting inserts are taken into account significantly better: these materials are very wear-resistant and have a very high pressure resistance, but are sensitive to tensile stress. According to the invention it has now been achieved that the bending stresses in the cutting inserts are kept within limits, even with high impact loads, so that work can be carried out with increased tooth feed and a correspondingly increased shock load.

In any case, this has only made it possible to use it for processing wet wood and / or raw wood, in particular the use as a chip knife, profiling knife or chopper knife, which leads to a considerably longer service life than the use of conventional knives. Raw wood is the wood from felled, delimbed and decapitated trees that have not undergone any further processing. Wet wood is damp, not dried wood. In wood processing, wet wood is also called green wood. Have spanish knives, profiling knives and chopper knives common that these are used at high feed speeds and large tooth feeds. The tooth feed is advantageously at least 5 mm, in particular at least 8 mm, preferably at least 10 mm. Compared to drywood processing, there are very high shock loads. However, these can be endured on the basis of the configuration according to the invention, so that overall a pronounced economical use with rapid work progress and nevertheless a long service life has become possible.

The hard solder connection between the at least one cutting plate and the knife base body is advantageously a high-temperature vacuum solder connection. With high-temperature vacuum soldering, the cutting plate is soldered to the knife base with copper solder at a temperature of at least 750 ° C in a furnace. In doing so, a uniform and thorough heat input up to the soldering temperature takes place in the entire knife. The warping of the knife and the thermally induced voltages are very low. In addition, the vacuum serves to prevent oxidation, which means that a separate flux is not required.

It is advantageously provided that the copper solder has a mass fraction of copper of at least 99%. The copper solder is preferably pure copper. Copper solder with a high mass fraction of copper has a particularly good machinability.

The at least one cutting plate is preferably formed from a material from the group of substances comprising uncoated hard metal, coated hard metal, cutting ceramic, super hard cutting materials, natural diamond, PCD, MKD, CVD-D, CBN. As a result, the insert has a high hardness and is particularly resistant to abrasive wear.

The knife advantageously comprises at least one additional cutting plate. The at least one additional cutting insert is also fastened to the basic knife body by means of the braze joint according to the invention with the copper solder. The one from the In a preferred variant, cutting edges of the cutting contour formed are angled. The arrangement of several cutting plates in relation to one another enables the design of a complex cutting edge or a long cutting edge. The geometry of such cutting edges can be designed differently, for example to reduce cutting forces or to design the workpiece surface or the chip geometry in a targeted manner. In an advantageous alternative, the cutting edges of the cutting plates together form a continuous, straight-line cutting contour. When long, in particular rectilinear cutting edges are formed by a plurality of cutting elements, the different expansion coefficients of cutting elements and knife base body are taken into account. By using several and therefore smaller cutting edges, the thermally induced residual stress within the individual cutting edges can be reduced.

The at least one cutting plate and the basic knife body delimit a soldering gap, the width of which is advantageously less than 0.1 mm, preferably less than 0.08 mm. Since the stiffness of the knife body is higher than the stiffness of the copper solder, the smaller the width of the soldering gap, the less the displacement of the insert during the cutting process. As a result, the bending stress is reduced to a minimum, which is accompanied by a corresponding increase in the impact resistance.

Fig. 1

in einer Vorderansicht eine Spanerscheibe mit montierten Messern,

Fig. 2

in einer Schnittdarstellung die Spanerscheibe nach Fig. 1 entlang der mit den Pfeilen II-II in Fig. 1 angegebenen Schnittebene,

Fig. 3

in einer perspektivischen Darstellung ein Spanermesser,

Fig. 4

in einer Vorderansicht das Spanermesser nach Fig. 3,

Fig. 5

in einer Seitenansicht ein Profiliermesser mit Schneidplatte,

Fig. 6

in einer Ansicht von unten das Profiliermesser nach Fig. 5,

Fig. 7

in einer schematischen ausschnittsweisen Darstellung das Messer mit Schneid-platte nach Fig. 5,

Fig. 8

in einer schematischen ausschnittsweisen Darstellung den Lötspalt des Messers nach Fig. 5, und

Fig. 9

in einer perspektivischen Darstellung eine Variante des Messers nach den Fig. 5, 6 mit breiterer und in einzelne Teilstücke aufgeteilter Schneidplatte.

Further features of the invention result from the further claims, the description and the drawing, in which exemplary embodiments of the invention described in detail below are shown. Show it:

Fig. 1

in a front view a Spanersplatte with mounted knives,

Fig. 2

in a sectional view of the chipboard Fig. 1 along the arrows II-II in Fig. 1 specified cutting plane,

Fig. 3

in a perspective view a spanish knife,

Fig. 4

the Span knife in a front view Fig. 3 ,

Fig. 5

in a side view a profiling knife with cutting plate,

Fig. 6

the profiling knife in a view from below Fig. 5 ,

Fig. 7

in a schematic detail representation of the knife with cutting plate after Fig. 5 ,

Fig. 8

the soldering gap of the knife in a schematic partial representation Fig. 5 , and

Fig. 9

a perspective view of a variant of the knife according to the 5, 6 with a wider insert that is divided into individual sections.

In the Fig. 1 A chipping disc 10 is shown, which is used in a profiling chipper system, not shown, for producing plane-parallel surfaces on raw wood and / or wet wood. The woods are conveyed through the profiling machine and processed by two chipping disks 10 arranged opposite one another. The cutting discs 10 are each driven in rotation by a drive unit in the direction of rotation 11 about its axis of rotation 9. When the wood comes into contact with the cutting discs 10, the wood is cut to a defined geometry using so-called profiling knives. At the same time, the residual wood is shredded into wood chips by so-called chip knives so that it can be used as a raw material in the paper industry.

In the Fig. 1 Shaving disk 10 shown has a conical inner side 12 facing the wood, on which a plurality of knives 1 are arranged over the entire circumference of the shaving disk 10. Each knife 1 is fastened to the chipping disk 10 by means of a screw 16. The knives 1 have a rear end 15 and a front end 14 with respect to the direction of rotation 11, a cutting edge 4 being formed on the front end 14 of the knife 1. The cutting disk 10 has a cutting opening 13 for each knife 1. The chip opening 13 is arranged in the direction of rotation 11 of the chip disk 10 directly in front of the knife 1. As a result, the chips that occur when cutting wood at the cutting edge 4 of the knife 1 are discharged through the chip opening 13.

As in Fig. 2 shown, the chipping disk 10 has a conical section 17. Since, in operation, two chipping disks 10 are arranged opposite one another, they form a kind of funnel-shaped passage through which the wood is pushed during processing. When the wood comes into contact with the cutting discs 10, the wood is gradually cut over the funnel-shaped passage of the cutting discs 10 to a minimum width of the passage. In the exemplary embodiment, the knives 1 mounted in the conical section of the chipping disk 10 are designed as chipping knives. The chipboard 10 also has a contact surface 18 on its inside 12, which additionally enables the assembly of a circular saw, not shown.

The chipping disk 10 as well as the profiling chipper system are only examples of the use of a knife according to the invention. In Fig. 3 is a first embodiment of such a knife 1, namely a chip knife 1 for the chip plate 10 according to the Figures 1 and 2 shown. The knife 1, like that in the Figures 5 and 6 Exemplary embodiment shown, on the knife base body 2 two legs 19 and an internal thread 20 ( Fig. 4 ) on. Via the legs 19 and the internal thread 20, the knife 1 can be connected to a corresponding cutting system, in particular to the chipping disk 10 according to FIGS Figures 1 and 2 be positioned and attached. In a alternative embodiment, the knife can also be attached to a cutting system in other ways. For example, instead of the legs 19, a hole or an elongated hole can be formed on the knife 1 for attachment. Furthermore, for example, a clamp fit of the knife for attachment to a cutting system is also possible. The knife 1 comprises a first cutting plate 3 with a cutting edge 4 and an optional additional cutting plate 3 'with an associated cutting edge 4'. The cutting plates 3, 3 'are arranged on the front end 14 of the knife 1 and fastened on the knife base body 2 by means of a hard solder connection 5 using copper solder 6. The cutting plates 3, 3 'contact each other, their cutting edges 4, 4' forming a cutting contour 22. The same applies mutatis mutandis to the formation of the braze joint and the copper solder 6 used as to the exemplary embodiments according to FIGS Figures 5 to 9 Said.

As in Fig. 4 shown, the cutting contour 22 is angled. In the front view of the knife 1, ie in the viewing direction from the front end 14 to the rear end 15 of the knife 1, the cutting edges 4 and 4 'enclose an angle α. In order to be able to also carry the additional cutting plate 3 ', the knife base body 2 has a thickening 23 at the front end 14 on one leg side on which the additional cutting plate 3' is arranged. The additional cutting plate 3 'is held on the thickening of the knife base body 2.

In connection with the Figures 1 to 4 a chipper 10 with associated chipper 1 was described. Profiling lines for processing raw wood and / or wet wood often also have so-called profiling units, which are connected downstream of the cutting discs 10 and which process the longitudinal edges of the surfaces generated by the cutting discs 10. According to the invention, knives 1 designed according to the invention are also used in such profiling units (not shown here), namely in the form of profiling knives. In the Figures 5 and 6 is a second embodiment of an inventive Knife 1 shown, which is designed as such a profiling knife. The knife 1 comprises a knife base body 2 and a cutting plate 3 with a cutting edge 4. The cutting plate 3 is arranged at the front end 14 of the knife 1 with respect to the direction of rotation and is fastened to the knife base body 2 by means of a braze joint 5. An internal thread 20 is formed on the knife base body 2, by means of which the knife 1 is positioned in its longitudinal direction on a corresponding cutting system. To Fig. 6 the knife base body 2 has two legs 19, between which fastening screws pass through in the assembled state and fix the knife 1 in its set position.

In the Figures 7 and 8 is the cutting area of the knife 1 according to the Figures 5 and 6 represented schematically in a longitudinal section. The cutting plate 3 and the knife base body 2 delimit a soldering gap 8 for the braze joint 5. The soldering gap 8 has a width a, which corresponds to the distance between the knife base body 2 and the cutting plate 3. In the exemplary embodiment, the maximum width a of the soldering gap 8 is at most 0.1 mm, preferably at most 0.07 mm. In the soldering gap 8 between the knife base body 2 and the cutting plate 3 there is copper solder 6, which integrally connects the knife base body 2 with the cutting plate 3. The copper solder 6 is in contact with the knife base body 2 and the cutting plate 3 and forms the hard solder connection 5.

In all of the exemplary embodiments shown, the brazed joint 5 is designed as a high-temperature vacuum brazed joint. Accordingly, the soldering process for fastening the cutting plate 3 on the knife base body 2 is carried out with the exclusion of air in a vacuum. The knife 1 is gradually heated in a vacuum oven to a soaking temperature of less than 750 ° C. The temperature is then increased to a soldering temperature of greater than 750 ° C. to melt the copper solder 6. The copper solder 6 is distributed in the soldering gap 8 by capillary action, followed by a diffusion of the copper solder 6 into the surfaces of the Knife base body 2 and the cutting plate 3. After subsequent cooling of the knife 1, the brazed connection is completed.

The mass fraction of copper solder 6 in copper is at least 99%. In an alternative embodiment, however, a copper alloy with a lower copper content, in particular of at least 50%, preferably at least 80%, preferably at least 90%, and corresponding additives can also be useful as solder. The cutting plate 3 consists of a coated or uncoated hard metal. For an even higher wear resistance, the cutting plate 3 can also consist of a cutting ceramic, of super-hard cutting materials or ultra-hard cutting materials. These include, for example, natural diamond, PCD (polycrystalline diamond), MKD (monocrystalline diamond), and CBN (polycrystalline cubic boron nitride) and CVD-D (chemical vapor deposition diamond). The basic knife body 2 consists of steel in the exemplary embodiment. The use of other materials, such as powder metal, may also be appropriate.

With further reference to the Figures 7 and 8 the conditions in operation are clear, which is equally for the embodiment of the Figures 1 to 4 as well as for the embodiment according to the Figures 5 and 6 The following applies: during the cutting process, the cutting plate 3 contacts the workpiece (not shown) in an end-face contact area 21 adjoining the cutting edge 4. In the contact area 21, cutting forces Fc act on the cutting plate 3, which the cutting plate 3 via the intermediate braze joint 5 against the knife base body 2 press and lead to elastic deformations. If the cutting forces Fc are correspondingly high, this can even lead to plastic deformation of the copper solder 6. In any case, a deformation of the base of the cutting plate 3 occurs in particular within the layer of the copper solder 6 by a deformation dimension b, the deformation dimension b representing a percentage of the width a of the soldering gap. The deformation of the base goes with a corresponding deformation of the Cutting plate 3 hand in hand, with corresponding bending deformations with compressive stresses D and tensile stresses Z occurring in the cutting plate 3. The hard insert 3 is particularly sensitive to the tensile stresses Z caused by bending. According to the invention, the bending deformations and thus the tensile stresses Z in the insert 3 have been reduced to a minimum. In particular from the enlarged detailed view Fig. 8 it becomes clear that the smaller the width a of the soldering gap, the smaller the amount of deformation b. It has been shown that a sufficiently small width a of the soldering gap cannot be achieved with ordinary hard solder connections, but in the manner according to the invention with copper solder 6, which consequently leads to a correspondingly low degree of deformation b and correspondingly low tensile stresses Z. The load-bearing capacity of the cutting plate 3 in relation to cutting forces Fc, applied in particular in abrupt or sudden fashion, is correspondingly increased, which enables the use according to the invention for processing wet wood and / or raw wood with correspondingly large tooth feeds and the associated large impact loads. The tooth feed corresponds to the feed of a knife 1 into the workpiece relative to the knife 1 preceding in the direction of rotation. The knives according to the invention are suitable for use with a tooth feed of 5 mm or more. However, it can also be useful to use the knife with a higher tooth feed of 8 mm or more and in particular of at least 10 mm or more.

Fig. 9 shows a perspective view of a variant of the knife 1 according to the 5, 6 with a larger width in comparison. Two U-shaped receptacles for fastening screws are formed in the knife base body 2. In addition to the one insert 3 according to the 5, 6 further cutting plates 3 are provided here, which add up to a total of six pieces, for example. Depending on the application and geometric configuration, however, different total numbers of cutting plates 3 can also be expedient. The cutting tips 3 correspond in their geometric configuration and in their type of attachment of the cutting tip 3 according to the 5 to 8 . They are positioned next to one another without gaps such that their cutting edges 4 complement one another to form a continuous, rectilinear cutting contour 22. Functionally, a single, larger cutting edge is formed, which is composed of smaller individual cutting inserts. The exemplary embodiment is correct in the remaining features and reference numerals Fig. 9 with the previously described embodiments.

What has been described above with regard to the profiling and cutting knives naturally also applies analogously to other knives 1, for example for use as chopper knives or the like wherever high impact loads are to be expected in operation. The chipper knives mentioned are used on chipper machines. Chipper machines of this type are used to shred raw wood, green wood and / or wood waste and mainly produce wood chips for the paper industry.

Claims (10)

Use of a knife (1) for processing wet wood and / or raw wood, the knife comprising a basic knife body (2) and at least one cutting plate (3) with a cutting edge (4), the cutting plate (3) being removed from the basic knife body (2) will be carried,
characterized in that the cutting plate (3) is fastened to the knife base body (2) by means of a hard solder connection (5) with a copper solder (6). Use of a knife according to claim 1
as a chip knife or profiling knife. Use of a knife according to claim 1 or 2,
characterized in that the tooth feed is at least 5 mm. Use of a knife according to one of claims 1 to 3,
characterized in that the braze joint (5) between the at least one cutting plate (3) and the knife base body (2) is a high-temperature vacuum solder joint. Use of a knife according to one of claims 1 to 4,
characterized in that the copper solder (6) has a mass fraction of copper of at least 99%. Use of a knife according to one of claims 1 to 5,
characterized in that the at least one cutting insert (3) consists of the group of uncoated hard metal, coated hard metal, cutting ceramic, super hard cutting materials, natural diamond, PCD, MKD, CVD-D, CBN. Use of a knife according to one of claims 1 to 6,
characterized in that the knife (1) comprises at least one additional cutting plate (3, 3 '), the at least one additional cutting plate (3, 3') by means of the hard solder connection (5) to the copper solder (6) on the knife base body (2 ) is attached. Use of a knife according to claim 7,
characterized in that the cutting edges (4, 4 ') of the cutting plates (3, 3') form an angled cutting contour (22). Use of a knife according to claim 7,
characterized in that the cutting edges (4) of the cutting plates (3) together form a continuous, rectilinear cutting contour (22). Use of a knife according to one of claims 1 to 9,
characterized in that the at least one cutting plate (3) and the knife base body (2) delimit a soldering gap (8) whose width (a) is less than 0.1 mm.

Images