EP0595763B1 - Cutter bar with a high wear resistance and method of making it - Google Patents

Abstract

A cutter bar which is suitable particularly as a counter blade or anvil blade for cutting rotors in granulators, consists of a blade (3) which is inserted into a groove in a highly wear-resistant carrier (2). The blade (3) has, as cutting surface, an ultra-hard layer of sintered material, which preferably consists of polycrystalline diamond or cubic boron nitride. The joint between the blade (3) and the carrier (2) is preferably made by soldering, the contact surfaces which are to be soldered being metallised beforehand, or else is made by means of anchors which engage into a groove (15) in the carrier (2). The flanks of the carrier (2), which extend almost without gaps up to the layer of sintered material, protect the flanks of the blade (3) which have only a moderate wear resistance. The cutting bar can also have a holder (8) to which one or more carriers (2) with sintered material blades (3) are releasably fastened. <IMAGE>

Description

The present invention relates to cutting strips, which are preferably used in cooperation with cutting rotors, inter alia for the production of granules, and to a method for producing such cutting strips.

As a counter tool to cutting rotors, cutting strips are exposed to high abrasive loads. This affects not only the cutting zone itself, but also the surrounding surface of the cutting bar, which means that the cutting edge, which can be made of highly wear-resistant material with moderate effort, is undermined, so to speak. H. their mechanical stability is weakened. If the cutting bar is not checked regularly, parts can break out of the cutting edge and finally the cutting edge can break off. As a result, severe damage to the machine and especially the cutting rotor often occurs.

Knives are known which consist entirely of hard metal or of a support made of steel and a knife made of hard metal soldered thereon. This solder connection is problematic in itself, since hard metal is poorly wetted by the common soldering materials, but the reject rate is still within acceptable limits. However, the relatively soft steel beam is subject to a high degree of abrasion, which limits the life of such cutting strips.

But also the hard metal has not grown satisfactorily over the whole range of the materials processed today in granulate machines. Starting material with mineral inclusions, such as glass fibers, carbon fibers or abrasive fillers lead to a rapid wear and also due to the higher load on the connection to an increased risk of breaking the solder joint. There have therefore been isolated attempts to produce the cutting edge from a harder material. Known materials are the non-metallic hard materials polycrystalline diamond (PCD) and cubic boron nitride (CBN). For the sake of simplicity, these substances are simply referred to below as hard materials in contrast to hard metals. Both materials, PCD and CBN, are commercially available as a layer structure consisting of a carrier, which in the context of the present invention consists of a hard metal and is called a knife carrier, and an associated layer or coating of a hard material. In principle, strips made of this material can be used as knives for cutting strips.

However, the knife carrier is chemically changed when the hard material layer is applied, specifically the carrier is enriched with carbon, and it is also not always possible to select the optimal materials for the carrier for the respective application. The hard-coated knives, such as the hard-metal knives previously, are to be soldered onto another carrier in order to obtain a cutting bar. However, it has been shown that the hard-coated knives can be soldered onto a carrier even more poorly than hard-metal knives. This is primarily attributed to the above-mentioned carbon enrichment in the knife holder.

In addition, the knife carrier material is subject to wear where it comes to the surface of the cutting bar, and all the more because the knife carrier material loses part of its wear resistance during the application of the hard material layer.

As a result, there were unbearably high failure rates of the hard material cutting edges due to poor connection between the measuring carrier and the carrier while simultaneously increasing the abrasive undermining of the cutting edge.

It is therefore an object of the present invention to provide a hard material cutting bar with increased stability and reliability.

Such a cutting bar is specified in claim 1. The further claims include preferred designs, methods for producing the cutting bar according to the invention and types of use.

Accordingly, the cutting bar according to the invention consists of a carrier which preferably consists of a highly wear-resistant hard metal and onto which a knife coated with a hard material is soldered. The contact surface of the knife carrier is shaped in such a way that the carrier closes with the hard material at most with a functionally negligible joint on the surfaces exposed to the material to be processed.

The connection point between the cutting edge support and the knife is preferably made by soldering. For this purpose, the surfaces to be soldered are provided with a solder-friendly metal layer. This is preferably done according to the method described in the applicant's Swiss patent specification CH-649 098, which is hereby incorporated into the description. A metal layer of a few micrometers to a few 100 micrometers is applied and alloyed into the surface of the hard metal at high temperature, which not only creates a solder-friendly surface, but also fills up existing surface irregularities (voids) with the metal. Nickel is particularly suitable for surface treatment for price reasons. Other metals are possible, e.g. B. silver, copper or cobalt.

So far, however, it was assumed that the temperature used in this process would damage the hard material layer. Surprisingly, however, tests have shown that the hard material layer, if at all, is only subject to imperceptible changes when the coating is carried out in an inert environment. High or maximum vacuum and / or protective gases, in particular hydrogen or nitrogen, are used to produce the inert environment. For example, B. also noble gases such as argon or helium. The protective gases are preferably under reduced pressure or normal pressure, but high pressure is also conceivable.

One embodiment of the invention consists of the hard material knife and the carrier, the carrier having the necessary fastening devices in order to be able to fasten the bar, for example in a cutting machine. A preferred embodiment of the invention consists in fastening the carrier on a holder by means of a releasable connection technique. This makes it possible to replace worn or damaged sections of the cutting edge. In addition, the holder can also be made in a less wear-resistant material, which on the other hand, for example, an easier attachment of fasteners such. B. threaded holes allowed. A direct screwing of the knife holder to the holder is problematic since the knife holder is only a few millimeters thick and the insertion of threaded bushings is therefore practically impossible with the required durability.

In another embodiment, an undercut groove, ie a groove that widens towards the bottom, is incorporated into the knife carrier, into which suitable slot nuts can be inserted as anchors. The sliding blocks are connected to the carrier using suitable fastening elements. You can e.g. B. z. B. have holes with an internal thread, whereby they by means of screws which are inserted through the carrier, can be used and fix the hard material knife on the carrier.

Fig. 1

zeigt einen Schnitt durch eine bekannte Ausführung einer Hartstoffschneidleiste,

Fig. 2

zeigt einen Schnitt durch ein Ausführungsbeispiel einer erfindungsgemässen Schneidleiste,

Fig. 3

zeigt einen Schnitt durch eine Schneidleiste mit zusätzlichem Halter,

Fig. 4

zeigt einen Schnitt durch ein anderes Ausführungsbeispiel einer erfindungsgemässen Schneidleiste, und

Fig. 5

zeigt eine Teilvergrösserung von Fig. 4.

The invention is explained in more detail using an exemplary embodiment.

Fig. 1

shows a section through a known embodiment of a hard material cutting bar,

Fig. 2

shows a section through an embodiment of a cutting bar according to the invention,

Fig. 3

shows a section through a cutting bar with additional holder,

Fig. 4

shows a section through another embodiment of a cutting bar according to the invention, and

Fig. 5

shows a partial enlargement of FIG. 4.

The known hard material cutting strip 1 shown in FIG. 1 consists of a carrier 2 onto which the hard material knife 3 is soldered. The hard material knife consists of the knife carrier 4, on which the hard material layer 5 is applied. The hard material 5 is preferably polycrystalline diamond (PCD) or cubic boron nitride (CBN).

The exposed flanks 6 of the knife carrier 4 are exposed to wear in the conventional cutting bar 1 (FIG. 1). After a short time, the hard material layer 5 is undermined, which leads to damage to the cutting edge. 2, this problem can be solved according to the invention in that the knife 3 is inserted into a V-shaped groove in the carrier 2, for which purpose the flanks 6 of the knife carrier 4 are removed in mirror image to the shape of the groove. The resulting bevels preferably extend without borders to the hard material layer 5. After insertion, the sides of the carrier 2 can be ground to the mass of the knife 3. Experiments have shown that the abrasion initially removes something in one area from the cutting edge where the highly wear-resistant carrier 2 already has a larger wall thickness and can thus protect the knife 3 from undermining over a longer period of time. From the same finding, it is also not critical if there is a slight gap between the hard material layer and the lateral upper edges of the V-groove in the carrier 2 as a result of manufacturing tolerances.

The second problem area is the soldered connection 7 between the knife carrier 4 and the carrier 2. According to the above, the knife carrier 4 has an excess of carbon which on the one hand worsens the mechanical properties of the carrier material 4 and on the other hand also reduces the solderability. Even or especially when inserting the knife 3 into a V-groove, an insufficient reliability of the connection between the carrier 2 and the knife 3 was found in practice. Since with the V-groove the forces occurring during cutting are converted to a greater extent into shear stresses, with the V-groove the quality of the connection between carrier 2 and knife 3 is of increased importance.

It has surprisingly been found that the surface of the knife carrier 4 can be metallized at high temperatures and thus made solder-friendly, preferably according to the method as described in CH-649 098. Contrary to the expectation that the hard material layer would be attacked at the temperatures necessary for the metallization and, in the worst case, decomposed, no such effects were surprisingly observed to any appreciable extent if the metallization was carried out in an inert, at least oxygen-free atmosphere or in a vacuum.

The reliable solder connection achieved in this way allows the advantages of the V connection to be exploited. The knife according to the invention achieves a long service life since highly wear-resistant supports 2 can be used, and can be used in high yield. The risk of the knife detaching from the carrier 2 during operation is reduced to an insignificant value by the high quality solder connection. It is also advantageous that the cutting bar according to the invention can have two cutting edges, as a result of which the service life is increased again. With the knife according to the invention, tool life of ½ a per cutting edge is easily achieved, after which the second cutting edge can be used by turning the bar.

In one embodiment of the cutting bar, two fastening elements, such as holes, inserted threaded bushings, etc., are present on the carrier in order to fasten the arrangement at the place of use. In a preferred embodiment according to FIG. 3, the cutting bar 1 is connected to a holder 8 which has the fastening elements mentioned above. Since the holder 8 is no longer exposed to the effects of abrasion to the extent that the cutting bar 1, other suitable materials can also be used in addition to hard metal, such as, for. B. stainless steel, in which the fasteners are easier to attach. 3 shows transverse holes 12 as an example.

The connection between holder 8 and carrier 2 is preferably releasable, for. B. by means of screw elements. A preferred solution is to provide at least one bore in the carrier 2, into which a threaded rod 9 is inserted and permanently attached, e.g. B. is soldered. A corresponding bore 10 is provided in the holder 8, through which the threaded rod 9 projects. On the side of the holder 8 opposite the carrier 2, a nut 11 is screwed onto the threaded rod 9 and tightened. Another version uses a screw instead of the threaded rod, which is screwed into a threaded bushing inserted in the carrier 2.

Exact positioning takes place, analogous to the connection between carrier 2 / hard material knife 3, by making a groove with inclined flanks, ie a V-groove, in the holder 8 and a complementary design of the connecting surface of the carrier 2. Here too, the groove can be made somewhat deeper to compensate for tolerances.

In this embodiment, it is possible to mount several, shorter hard material knives next to one another on the holder 8, each of which can be replaced individually. This subdivision is necessary on the one hand, because the common hard material knives 3 are not available in any lengths, which are often smaller than the required length of the cutting bar 1. As an example, a cutting bar with a length of 350 mm is given, the cutting surface of which consists of seven hard material knives composed of 50 mm length. The possibility of being able to replace the hard material knives separately or by turning the second cutting edge around can be used in view of the considerable cost factor of these parts.

In a further preferred embodiment according to FIGS. 4 and 5, an undercut groove 15 is machined into the carrier 4 in the longitudinal direction of the hard material knife 3. In this groove 15 slot nuts 16 can be used, into which a thread is cut. As FIG. 4 shows, a screw 17 is passed from below through a bore 18 in the carrier 2 and screwed into a slot nut 16, as a result of which the hard material knife 3 is fixed on the carrier 2 in the V-groove. For a secure fit of the hard material knife 3 on the carrier 2, it is particularly advantageous in view of the high forces acting obliquely on the cutting edge of the hard material layer 5 to choose the angle α larger than the angle β (FIG. 5). This reliably prevents the hard material knife from sliding into the gap between the sliding block 16 and the support 2. At least 2 slot nuts are preferably provided for fastening per hard material knife. The bore 18 is preferably designed such that the head of the screw 17 is countersunk in the carrier. By choosing the depth this recess can also be adapted to the length of the screws 17 available.

The groove 15 is preferably produced in the knife carrier 4 by means of erosion. This is simply done in one step with the production of the oblique flanks of the knife carrier 4. In addition, the cutting bar can be attached to an additional holder 8 analogously to the embodiment according to FIG. 3.

Changes are readily apparent within the scope of the invention. It is possible to find any other recessed arrangement for the connecting surfaces instead of the V-groove-like design, e.g. B. in the form of a circular arc section. It should be noted that the wall thickness of the beam reaches a sufficient thickness in the area of the primary abrasion effects. Any other hard material layers can also be used for the knives.

It is also conceivable to provide another type of connection between the knife and the carrier, such as. B. welding. To achieve greater lengths than the available hard material knives have, several hard material knives 3 can be arranged next to one another on a carrier 2, as can several carriers 2 next to one another on the holder 8. Other known positioning means can also be used for positioning the carrier 2 on the holder 8 , such as B. positioning pins.

For fastening the hard material knife using slot nuts as shown in Fig. 4 and 5, other, releasable or non-releasable connection techniques are also conceivable, such as rivets, bolts attached to the slot nuts for screwing, riveting, welding, etc.

Claims (18)

1. Cutter bar (1) having a high wear resistance, comprising at least one cutter support (2) and at least one hard material knife (3) consisting of a knife carrier (4) of hard metal that comprises a non-metallic hard material layer (5) on at least one surface limited by at least one cutting edge, characterised in that that the knife carrier (4) tapers from the hard material layer (5), that this tapor begins at the transition between the hard material layer and the carrier or in a small distance thereof, and that the hard material knife (3) is inserted into an essentially mirror-invertedly shaped groove of the cutter support (2).
2. Cutter bar according to claim 1, characterized in that the hard material layer (5) consists of cubic boron nitride or polycrystalline diamond.
3. Cutter bar according to any one of claims 1 and 2, characterised in that the taper has a conical or rounded sectional shape, the angle between the connecting face of the cutter support with the knife carrier and the sides of the cutter support (2) being greater than 0°.
4. Cutter bar according to any one of claims 1 to 3, characterised in that the taper of the knife carrier (4) is V shaped, the legs of the V including an angle of about 90°.
5. Cutter bar according to any one of claims 1 to 4, characterised in that the hard material knife (3) is inseparably joined to the support (2) in the region of the groove.
6. Cutter bar according to claim 5, characterised in that the hard material knife (3) is soldered to the support (2), and the joining surfaces on the cutter support (2) and the knife carrier (4) comprise a preferably alloyed in-creased metal content.
7. Cutter bar according to any one of claims 1 to 6, characterised in that the support (2) consists of a highly wear resistant hard metal, especially having a Vickers hardness of more than 1,800.
8. Cutter bar according to any one of claims 1 to 4 or 7, characterised in that the knife carrier (4) of the hard material knife (3) has an undercut groove (15) in which at least two tenon blocks (16) per hard material knife (3) are inserted which act as anchors of a fastening means engaging the support (2).
9. Cutter bar according to claim 8, characterised in that said fastening means are bolts (17) that are traversing bores (18) of the support (2) and are screwed into internal screw threads of the tenon blocks (16) corresponding to the bolts (17).
10. Cutter bar according to any one of claims 8 and 9, characterized in that the tenon blocks (16) have pressure surfaces contacting the undercut faces of the groove (15), each pressure surface forming with the groove of the support (2) a slit which tapers to the bottom of the groove in the support (2) and into which extend the side walls of the knife carrier (4).
11. Cutter bar according to any one of claims 1 to 10, characterised in that the support (2) is joined to a holder (8) at the opposite side of the hard material knife (3) by a removable connection.
12. Cutter bar according to claim 11, characterised in that the connecting faces of the removable connection on the support (2) and the holder (8) are V or boat shaped wherein the inclined flanks may also be curved and may especially be circle are sections.
13. Cutter bar according to any one of claims 11 and 12, characterised in that the removable connection is at least one screw connection per hard material knife (1, 2), and that the holder (8) comprises bores through which screw elements can pass.
14. Process for the manufacture of a cutter bar according to any one of claims 1 to 7 and 11 to 13, characterised in that the tapering connection face on the knife carrier (4) and the mirror-inverted connecting face on the cutter support (2) are worked cut, that these connecting faces are provided on their surfaces with a soldering promoting metal layer strongly adhering by alloying to the materials of the support (2) and carrier (4), respectively, and that the knife (3) and the cutter support (2) are inseparably joined to each other by their connecting faces, preferably by soldering.
15. Process according to claim 14, characterized in that the application of the soldering enhancing metal layer is operated in a protective gas atmosphere or under vacuum and at temperatures substantially higher than the soldering temperature, particularly at temperatures higher than 1,000 K.
16. Process for the manufacture of a cutter bar according to any one of claims 1 to 13, characterised in that the support (2) is ground off even with the cutting edge after being connected to the knife (3).
17. Process for the manufacture of a cutter bar according to any one of claims 11 to 13, characterised in that holes are bored into the support (2), threaded rods (9) are inserted and soldered into the holes, the support comprising the hard material knife (3) and the threaded rods (9) is mounted on the holder (8), the threaded rods (9) passing through the bores (10) provided therefor until an opposite second side of the holder (8) and being blocked by a nut (11) at said second side.
18. Use of the cutter bar according to any one of claims 1 to 13 as a counter-knife of a cutting rotor, especially in a granulator.

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