EP1910024B1 - Device for machining a strip or plate-shaped metal workpiece - Google Patents

Abstract

A laser cutting process on a metal workpiece leaves a layer of oxide that is subsequently removed by an emery cloth belt presented at a transverse angle to or in line with the advancing work piece. The emery cloth is applied as a sandwich block with parallel emery cloth panels separated by pads.

Description

The invention relates to a device for processing a strip-shaped or plate-shaped metallic workpiece, with at least one circulating conveyor provided with processing elements, wherein the conveyor at least approximately linearly passes the processing elements obliquely or transversely to the feed direction of the workpiece in the region of the workpiece to be machined.

The invention also relates to a processing unit for a device for processing a strip-shaped or plate-shaped metal workpiece.

A generic device is from the DE 103 20 295 A1 known.

When laser cutting metallic. Workpieces forms an oxide layer or an oxide skin at the cut edges and at the cut surfaces. A disadvantage of the oxide layer is that a paint or zinc coating applied to it bounces off relatively quickly. For this reason, the metallic workpieces are ground off before painting and galvanizing.

Furthermore, it is generally necessary for the edges, in particular the cut edges, to be deburred or rounded. Furthermore, it may be advantageous to finely grind the surfaces of the strip or plate-shaped metal workpiece.

A particularly advantageous method for removing the oxide layer and for deburring the (cut) edges and the cut surfaces is from the DE 103 20 295 A1 known. In this case, a provided with at least one processing element circulating conveyor is provided, wherein the conveyor at least approximately linearly passes the at least one processing element in the region of the workpiece to be machined.

Since the processing element does not remain rigidly on a position due to the arrangement on a revolving conveyor, but is guided past the entire length which is present for the passage of the workpiece, a uniform wear of the at least one processing element is ensured. The workpiece can be carried out in a simple manner obliquely, preferably transversely to the direction of rotation of the processing element or pulled through, so that the workpiece is processed evenly by the processing element.

Due to the linear course of the processing element in the region of the workpiece to be machined, it is ensured that the processing element penetrates into all recesses or holes of the workpiece and thus removes the oxide layer at all cut surfaces and cut edges. The obliquely or transversely to the feed direction of the workpiece on the workpiece along drawn workpiece penetrates, similar to a brush, which is pulled along on a piece of metal, in each recess.

Advantageously, both the surfaces, ie the main surfaces of the strip-shaped or plate-shaped metal workpiece are processed with the generic device, as well as the cut surfaces and cut edges descaled. The device also deburrs the edges and cut surfaces and can be used for fine grinding.

For further prior art is on the DE 197 39 895 C2 directed.

The present invention has for its object to further develop the generic device, in particular to achieve a particularly cost-effective and uniform machining of band-shaped or plate-shaped metal workpieces, the device should be easy to assemble and maintain.

It is an object of the present invention to provide a machining unit for a device for machining a band-shaped or plate-shaped metal workpiece, wherein the machining element or the machining unit permit a uniform and rapid machining of the band-shaped or plate-shaped metal workpieces and can be easily changed should.

According to the invention this object is achieved with respect to the device to be created by claim 1.

With regard to an advantageous processing unit, this object is achieved by claim 17.

From claim 19 results in a preferred V-belt with a plurality of processing units according to claim 17.

The fact that the processing elements are designed according to claim 1 as abrasive papers and support elements are arranged between the abrasive papers, results in an advantageous Possible use of the device according to the invention. On the one hand, the abrasive paper can be used to remove the oxide layer from the cut surfaces and cut edges; on the other hand, the edges can be deburred and rounded. Even a fine grinding of the band or plate-shaped metal workpiece is possible by the sandpaper. The sanding papers can be used in different grain sizes, for example a 60 or 120 grit. The formation of the processing elements as sandpaper is inexpensive possible. On the one hand, the abrasive papers on the one hand obtain a desired stability due to the support elements, on the other hand it is avoided that the sanding papers rub against each other, ie the sandpaper in the direction of rotation rubs the back of the front sandpaper. The support elements are designed as supporting fleeces, since an embodiment of a nonwoven material has proven to be particularly suitable.

According to the invention, a plurality of abrasive papers are combined as a processing unit, wherein in each case a support fleece is arranged between the abrasive papers.

In a particularly advantageous embodiment, provision is made for a support felt to be arranged behind the last abrasive paper.

As the inventor has found, the arrangement of a supporting felt in the circumferential direction behind the last sandpaper is particularly suitable since felt is on the one hand more durable than nonwoven and on the other hand can absorb a higher bending load.

It is particularly advantageous if the backing fleece has abrasive properties, in particular finely abrasive properties, and thus also contributes to the machining of the workpiece in addition to the support function.

According to the invention it can be provided that the abrasive papers and the support elements have approximately the same height and the same width.

Preferably, the abrasive papers, the backup nonwoven webs and the backing felt may be encased in a support member of the processing unit. It can be provided that the abrasive papers, the backing fleeces and the backing felt are inserted into the carrier element or a mold and then cast together. The processing unit thus formed can be screwed by a screw in a simple manner with a belt of the conveyor, for example. It is advantageous if the processing unit has on its underside or the support element of the processing unit on its underside a threaded opening or is provided with a threaded bushing. It may also be advantageous if the belt of the conveyor has correspondingly adapted through holes, whereby on the one hand the position of the processing units is determined and on the other hand a simple screwing is possible.

A stable, in particular rotationally secure attachment of the processing units on the belt can be supported by the fact that a guide strip is applied to the belt. It can be provided that the processing unit has a groove for receiving the guide strip on its underside facing the belt. A twisting of the processing unit On the V-belt is thus avoided in a simple manner, whereby a uniform and process-optimized processing results. The flanks of the groove may optionally be slightly bevelled (for example by 2 to 8 °, preferably 5 °), so that the groove tapers slightly in the direction of the groove bottom.

The abrasive papers may preferably have a width of 50 mm. These values have proven to be particularly suitable in experiments to be able to work effectively on strip or plate-shaped metal workpieces. It is advantageous if the sandpaper has longitudinal slots which extend from the end facing the workpiece to be machined and extend at least over part of the height of the abrasive papers in the direction of the support member. Alternatively, the abrasive papers can also be designed in each case as a single grinding lamellae. However, a preferred, in particular process-reliable and cost-effective embodiment results from the fact that abrasive papers having a plurality of longitudinal slots are used.

A preferred processing unit for a device for processing a strip-shaped or plate-shaped metal workpiece results from claim 17.

A preferred V-belt results from claim 19. It can be provided that the V-belt is circumferentially provided with successively arranged processing units, wherein the processing units are preferably bolted to the V-belt. The processing units are in this case constructed of a plurality of abrasive papers, wherein between each two abrasive papers each a support web is formed.

In the direction of rotation, a support felt can be arranged behind the last sandpaper.

In experiments, it has been found to be particularly suitable when the belt is designed as a triple V-belt. The protrusions of the processing elements allow it to be supported on all three belts. The forces are thus distributed evenly and kept the loads correspondingly low.

Advantageous embodiments of the invention will become apparent from the other dependent claims. The following is based on the FIGS. 1 and 5-9 an embodiment of the invention shown in principle.

The FIGS. 2 to 4 do not represent an embodiment of the invention.

Fig. 1

eine Seitenansicht der erfindungsgemäßen Vorrichtung mit vier umlaufenden Fördereinrichtungen;

Fig. 2

ein Riemen der Vorrichtung, auf dem mit Borsten versehe- ne Bearbeitungselemente angeordnet sind;

Fig. 3

eine Seitenansicht auf mehrere Bearbeitungselemente, die gemäß Fig. 2 mit dem Riemen verschraubt sind, wobei aus Übersichtlichkeitsgründen nur das in Bewegungsrichtung hinten liegende Bearbeitungselement mit Borsten versehen ist;

Fig. 4

eine Darstellung mehrerer Bearbeitungselemente gemäß Pfeilrichtung IV der Fig. 3;

Fig. 5

ein Riemen der erfindungsgemäßen Vorrichtung; auf dem prinzipmäßig dargestellt eine Bearbeitungseinheit ange- ordnet ist, welche eine Mehrzahl an Bearbeitungselemen- ten aufweist, die als Schleifpapiere ausgebildet und zwischen denen Stützelemente angeordnet sind;

Fig. 6

eine perspektivische Darstellung einer Bearbeitungsein- heit, welche mehrere Schleifpapiere aufweist, zwischen denen jeweils ein Stützvlies und in Umlaufrichtung hin- ter dem letzten Schleifpapier ein Stützfilz angeordnet ist;

Fig. 7

eine Seitenansicht der Bearbeitungseinheit gemäß Fig. 6;

Fig. 8

eine vergrößerte Einzeldarstellung gemäß VIII der Fig. 7; und

Fig. 9

eine Draufsicht auf eine Bearbeitungseinheit gemäß Pfeilrichtung IX der Fig. 7.

It shows:

Fig. 1

a side view of the device according to the invention with four rotating conveyors;

Fig. 2

a belt of the device, are arranged on the bristle-th processing elements;

Fig. 3

a side view of several processing elements, according to Fig. 2 are bolted to the belt, for reasons of clarity, only in the direction of movement downstream processing element is provided with bristles;

Fig. 4

a representation of several processing elements according to arrow IV of the Fig. 3 ;

Fig. 5

a belt of the device according to the invention; on the principle represented a processing unit is arranged, which has a plurality of processing elements, which are formed as abrasive papers and between which support elements are arranged;

Fig. 6

a perspective view of a processing unit, which has a plurality of abrasive papers, between each of which a support web and in the direction of rotation behind the last sandpaper a support felt is arranged;

Fig. 7

a side view of the processing unit according to Fig. 6 ;

Fig. 8

an enlarged detail according to VIII of Fig. 7 ; and

Fig. 9

a plan view of a processing unit according to arrow IX of the Fig. 7 ,

Fig. 1 shows a device for processing a band- or plate-shaped metal workpiece 1. The inventive device is particularly suitable for removing the oxide layer of cut surfaces and / or cutting edges of the workpiece 1 and for deburring the edges. In this case, both circumferential cut surfaces and cut edges of the workpiece 1 as well as cut surfaces and cut edges of recesses, holes or the like in the workpiece 1 can be bled and deburred.

Fig. 1 shows a particularly preferred embodiment of the device according to the invention with four conveyors 2. In principle, a device can be used, the only has a conveyor 2. The conveyors 2 are with the following with reference to the FIGS. 2 to 9 in detail described processing elements 3 and 4 processing units provided. The conveyors 2 guide the processing elements 3 or the processing units 4 at least approximately linearly in the area of the workpiece 1 to be processed. The workpiece 1 to be machined is carried out or pulled through between the conveyors 2 transversely to the direction of rotation of the conveyors 2. For placing the workpiece 1 while a sheet metal insert 5 are provided. For the output of the workpiece 1, a storage table 6 is provided. In the embodiment according to Fig. 1 Feed rollers 7 are provided, which ensures a uniform and reliable transport of the workpiece 1 transverse to the directions of rotation of the conveyor 2.

By the in Fig. 1 illustrated solution according to the invention with four conveyors 2, it is possible to work the workpiece 1 in one go completely. Re-insertion of the workpiece 1 is not necessary.

In an unspecified manner, an adjusting device can be provided, by means of which the depth of engagement of the processing elements 3 and the processing units 4 can be varied. This is particularly advantageous for correcting the wear of the processing elements 3 and optionally for increasing the pressure.

The conveyors 2 are arranged slightly offset from one another in the direction of passage of the workpiece 1. Thus, on the one hand, it is ensured that the respective processing elements 3 or processing units 4 of the conveyor 2 do not interfere with each other, on the other hand, there is still one ensures uniform and balanced pressure of the processing elements 3 and the processing units 4, which compensates each other, so that the workpiece 1 is not prone to tilting.

At the in Fig. 1 The device according to the invention shown is a variant in which the conveyors 2 are arranged lying, so that the processing elements 3 and the processing units 4 in the region of the workpiece 1 are substantially horizontal.

Alternatively, the solution according to the invention may be provided in a manner not shown with standing arranged conveyors 2.

At the in Fig. 1 illustrated embodiment of the device according to the invention with four conveyors 2, it is advantageous if each of the two main surfaces of the workpiece 1 is processed by two counter-rotating conveyor 2 each.

The processing elements 3 and the processing units 4 are arranged on a belt 8, which is part of the respective conveyor 2 and rotates in the manner described transversely to the feed direction of the workpiece 1.

With respect to further advantageous embodiments and the technical operation of the in Fig. 1 illustrated solution according to the invention is applied to the DE 103 20 295 A1 directed.

Fig. 2 shows such a belt 8 in one embodiment as a V-belt. The V-belt is designed as a triple V-belt 8. On the V-belt 8 is a plurality of Machining elements 3 arranged in series, wherein in Fig. 2 for reasons of clarity, only a part of the processing elements 3 is shown. In principle, it is provided that the processing elements 3 in a row completely rotate around the belt 8, thus forming a closed chain. The processing elements 3 are provided with bristles 9. The bristles 9 are formed in a known manner from metal. In a simple representation, the bristles 9 may be straight. However, it is advantageous to form the bristles 9 with a corrugated or twisted course, so that the bristles 9 resemble a scrubby brush or a tuft.

The bristles 9 can be shot in bundles in the processing elements 3. The processing elements 3 can be made of plastic, for example, and have corresponding receiving bores.

For advantageous fastening of the bristles 9, the bristles 9 may be provided with not shown barbs.

The bristles 9 may be inclined up to 45 °, preferably by 15 °, in the direction of rotation of the belt 8. That the tips of the bristles 9 are in the direction of rotation in front of the correspondingly opposite end of the bristles 9, which is connected to the processing elements 3. As has been found in experiments, penetrate the inclined by 15 ° bristles 9 penetrate particularly advantageous in recesses of the workpiece 1, resulting in a particularly advantageous removal of the oxide layer of cut surfaces and cut edges of the workpiece 1 results and a rounding of the edges is possible.

In a manner not shown, the processing elements 3 may also have support bristles which the inclined bristles Stabilize 9 and thus improve their penetration into recesses of the workpiece 1. The support bristles can be made shorter and have a correspondingly high bending force. A vertical or rectangular arrangement of the support bristles to the surface of the processing elements 3 has been found to be advantageous.

The bristles 9 may be advantageously formed as roped bristles.

In an alternative embodiment, also not shown, it can also be provided that the bristles 9 are covered by a jacket in a stabilizing or supporting manner. The sheath can serve as an alternative to the support bristles. The sheath may preferably extend from the lower end of the bristles 9 to approximately the middle of the bristles 9.

According to the FIGS. 2, 3 and 4 For reasons of clarity, only one processing element 3 with bristles 9 is shown. In principle, it is provided that each processing element 3 carries bristles 9.

The processing elements 3 have at one end a groove 10 and at the other end a spring 11, by means of which the processing elements 3 are connectable to each other. A rotation of the processing elements 3 is prevented by the tongue and groove connection in a simple and advantageous manner.

As further from the FIGS. 2, 3 and 4 results, the processing elements 3 viewed in the circumferential direction lateral projections 12. The projections 12 make it possible for the processing elements 3 to be supported on a larger surface of the V-belt 8. In one embodiment of the V-belt 8 as a triple V-belt is achieved in that support the machining elements 3 on all three belts. In the exemplary embodiment, it is provided that the processing elements 3 have two projections 12 on each side. The projections 12 are preferably formed integrally with the processing element 3. The processing elements 3 are screwed in the exemplary embodiment by means of a fastening screw 13 with the V-belt 8. For this purpose, 8 holes 14 are introduced or can be introduced in the V-belt. The processing elements 3 have at their the V-belt 8 facing the underside an opening, not shown, which serves for screwing with the fastening screws 13.

As is clear from the FIGS. 2, 3 and 4 results, it is provided in the embodiment that a processing element 3 has an elongated spring 11a. The spring 11a or the nose of this processing elements 3 serves to compensate for possible belt tolerances and can be correspondingly reduced or removed. In experiments it has been found that an extension of the spring 11a by 1 to 3 mm is sufficient to serve as tolerance compensation. In experiments it has further been found that a processing element 3 with an extended spring 11a per V-belt 8 is sufficient.

A rotational speed of the processing elements 3 with the bristles 9 of preferably 14 to 16 m / s, is particularly advantageous. This speed ensures, on the one hand, a rapid processing of the workpieces 1 and, on the other hand, has proved to be suitable with regard to the reliability of the machining and the loading of the components involved.

Since the bristles 9 are subject to a corresponding wear during operation of the device and thus replaced must be provided, either to replace the processing elements 3 of the V-belt 8 and unscrew new processing elements 3 or raise a completely new V-belt 8 with processing elements 3.

As an alternative to the V-belt 8, a toothed belt, a flat belt (eg with knobs), a chain, a belt or the like may be provided. The in the FIGS. 2 to 5 shown V-belt 8 may be formed of rubber, plastic, synthetic rubber or preferably made of neoprene.

As a V-belt 8, a commercially available V-belt or force band is preferably used.

Fig. 5 shows one to the FIGS. 2 to 4 alternative embodiment of the V-belt 8 and the processing elements 3. The in Fig. 1 In principle, the device according to the invention can readily with both the embodiment according to Fig. 2 as well as with the embodiment according to Fig. 5 operate.

How out Fig. 5 it can be seen, the processing elements 3 are formed in this embodiment as abrasive papers, wherein between the abrasive papers 3 support members 15 are arranged. The support elements 15 arranged between the abrasive papers 3 are designed in the exemplary embodiment as support webs 15 or as nonwoven webs.

According to Fig. 5 are several abrasive papers 3 summarized as processing unit 4. Such a processing unit 4 is in detail in the FIGS. 6 to 9 shown. The processing unit 4 is constructed in such a way that between each two abrasive papers 3 a supporting fleece 15 and in the circumferential direction behind the last sandpaper 3 a supporting felt 16 is arranged. The Sandpaper 3, the backing webs 15 and the backing felt 16 are connected to a support member 17 of the processing unit 4 by pouring. The carrier element 17 is for this purpose preferably made of cast resin. However, a plastic training is also possible. As an alternative to pouring, the abrasive papers 3, the backing fleece 15 and the support felt 16 can also be glued or stapled.

The processing unit 4 can be bolted to the V-belt 8, glued, potted, punched or welded. In the exemplary embodiment, it is provided that the processing unit 4 is screwed to the V-belt 8. For this purpose, a bore 14 can be introduced or introduced in the V-belt 8, through which a fastening screw 13 can be inserted. The carrier element 17 of the processing unit 4 has analogously on its underside a threaded bush 18 or an internal thread. In order to produce a rotationally fixed connection between the V-belt 8 and the processing unit 4, it is further provided that on the V-belt 8, a guide rail 19 is adhered. The guide bar can also be welded or vulcanised. The carrier element 17 of the processing unit 4 in this case has on its side facing the belt 8 a groove 20 for receiving the guide rail 19.

The in Fig. 5 shown V-belt 8 can otherwise analogous to the belt 8 of the Fig. 2 be educated.

As is clear from the FIGS. 5 to 9 shows, the abrasive papers 3, the backing webs 15 and the backing felt 16 in about the same height and the same width. It can be provided that the sandpaper 3 preferably has a width of 25 to 75 mm and a height of 30 to 90 mm. In the exemplary embodiment, it is preferably provided that the abrasive papers 3 have a width of 50 mm and a height of 60 mm. The processing units 4 are formed from a plurality of abrasive papers 3, wherein each processing unit may have, for example, five to twenty abrasive papers 3. In the exemplary embodiment, it is provided that each processing unit 4 has twelve abrasive papers.

The length of a processing unit 4 may be e.g. 30 to 90 mm. In the embodiment, a length of 66 mm is provided.

The support web 15 may for example have a thickness of 2 to 10 mm, preferably 5 mm. The thickness of the backing felt 16 may be e.g. 1 to 8 mm, preferably 3 mm.

In a manner not shown can be provided that the abrasive papers 3, starting from their work to be machined workpiece 1 end facing longitudinal slots which extend at least over part of the height of the abrasive papers 3 in the direction of the support member 17.

The abrasive papers 3, the backing webs 15 and the backing felt 16 are formed close to each other.

The rotational speed of the processing units 4 with the abrasive papers 3 of 7 to 8 m / s is particularly advantageous for the processing result.

The combination of several abrasive papers 3 to a processing unit 4 has been found to be particularly suitable.

The combination of several abrasive papers 3 to a processing unit 4 makes it possible inter alia that the processing elements 3 can be changed quickly and easily attached. Due to the occurring wear this is of particular importance. In case of wear of the processing elements 3, the V-belt 8 can either be provided with new processing elements 3 or the entire device can be equipped with a new V-belt 8, to which the processing elements 3 and the processing units 4 are already applied.

Claims (21)

1. A device for machining a strip- or plate-shaped metal workpiece (1), having at least one revolving conveyor device (2) provided with machining elements (3), wherein the conveyor device (2) directs the machining elements (3) at least approximately linearly in the region of the workpiece (1) to be machined, such that they are at an angle or transverse to the feed direction of the workpiece (1),
   characterised in that
   the machining elements (3) are constructed as abrasive papers, and supporting elements (15, 16) are arranged between the abrasive papers (3), wherein a plurality of abrasive papers (3) are combined to form a machining unit (4), and wherein the supporting elements (15) arranged between two abrasive papers (3) of a machining unit (4) are constructed as supporting fleeces (15) and the abrasive papers (3) and the supporting fleeces (15) of a machining unit (4) are constructed such that they abut tightly against one another.
2. A device according to Claim 1,
   characterised in that
   the supporting fleeces (15) are constructed as abrasive fleeces.
3. A device according to Claim 1 or 2,
   characterised in that
   the supporting element (16) which is arranged behind the last abrasive paper (3) of a machining unit, as seen in the direction of revolution of the conveyor device (2), is constructed as a supporting felt.
4. A device according to one of Claims 1 to 3,
   characterised in that
   the abrasive papers (3), the supporting fleeces (15) and the supporting felt (16) are connected to a carrier element (17) of the machining unit (4).
5. A device according to Claim 4,
   characterised in that
   the abrasive papers (3), the supporting fleeces (15) and the supporting felt (16) are cast into the carrier element (17).
6. A device according to one of Claims 1 to 5,
   characterised in that
   the abrasive papers (3), the supporting fleeces (15) and the supporting felt (16) have approximately the same height and the same width.
7. A device according to Claim 6,
   characterised in that
   the abrasive paper (3) has a width of preferably 50 mm and a height of 30 to 90 mm, preferably 60 mm.
8. A device according to one of Claims 1 to 7,
   characterised in that
   the machining unit (4) has 5 to 20, preferably 12, abrasive papers (3).
9. A device according to one of Claims 1 to 8,
   characterised in that
   the length of a machining- unit (4) is 30 to 90 mm, preferably 66 mm.
10. A device according to one of Claims 1 to 9,
    characterised in that
    the abrasive papers (3), starting from their end facing the workpiece (1) to be machined, have longitudinal slots which extend at least over part of the height of the abrasive papers (3) in the direction of the carrier element (17).
11. A device according to one of Claims 1 to 10,
    characterised in that
    the conveyor device (2) is provided with a V-belt (8) or a toothed belt or a flat belt.
12. A device according to one of Claims 1 to 10,
    characterised in that
    the conveyor device (2) is provided with a triple V-belt (8).
13. A device according to Claim 11 or 12,
    characterised in that
    the machining elements (3) are joined to the V-belt (8) by screwing, adhesion, casting, punching or welding.
14. A device according to Claim 11, 12 or 13,
    characterised in that
    a guide strip (19) is mounted on the V-belt (8).
15. A device according to Claim 14,
    characterised in that
    the carrier element (17) of the machining unit (4) has, on its underside facing the V-belt (8), a groove (20) for receiving the guide strip (19).
16. A device according to one of Claims 4 to 15,
    characterised in that
    the carrier element (17) is provided with a threaded bush (18) on its underside.
17. A machining unit (4) for a device for machining a strip- or plate-shaped metal workpiece, which has at least one revolving conveyor device (2), which may be equipped with the machining units (4), wherein the conveyor device (2) directs the machining units (4) at least approximately linearly in the region of the workpiece (1) to be machined,
    characterised in that
    the machining unit (4) has a plurality of abrasive papers (3), wherein a supporting fleece (15) is constructed in each case between two abrasive papers (3) and the abrasive papers (3) and the supporting fleeces (15) of a machining unit (4) are constructed such that they abut tightly against one another.
18. A machining unit according to Claim 17,
    characterised in that
    the supporting element (16) which is arranged behind the last abrasive paper (3) of a machining unit, as seen in the direction of revolution of the conveyor device (2), is constructed as a supporting felt (16).
19. A V-belt having a plurality of machining units according to one of Claims 17 and 18.
20. A V-belt according to Claim 19,
    characterised in that
    the machining units (4) are screwed to the V-belt (8).
21. A V-belt according to Claim 19 or 20,
    characterised in that
    the V-belt (8) is provided with a guide strip (19) and the machining units (4) have, on their underside, a groove (20) for receiving the guide strip (19).

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