Field of the invention

The present invention relates to: a multi-wire machine for cutting blocks of natural or artificial stone, that is to say, a machine which cuts with a plurality of diamond wires, which are put to slide in the known way, on a block of stone for its cutting into slabs, said cutting being simultaneous of all of or part of the block, and comprising a new tensioning device of the wires closed in a ring, which in the cutting of the stone of the block can be subjected to different elongations of the ring. Furthermore, the invention also relates to the specific tensioning device, of the plurality of wires associated with the multi-wire cutting machine, which is single for each wire and collective in maintenance interventions. Prior art

The prior art comprises various types of machines for cutting blocks of stone with multiple diamond wires, where the wires closed in a ring, with an identical or very similar development, are subtended between pulleys and/or drums which provide for the support, the rotation, that is to say, the transmission of the cutting motion of the diamond wire in the block, as well as for the tensioning to the prearranged value, in such a way as to make sufficiently precise planar surfaces of the so cut slabs.

The rotational motion is transmitted to the multitude of wires by a drum with added grooves, advantageously coated or made of rubber or of a non-metallic yielding material, because the diamond wire, having the diamond inserts anchored on the wire and spaced from each other, has a winding in the grooves with the support of the inserts and partially of the wire, in such a way as to realize the transmission of the tangential force and limit wear due to the contact of the diamond inserts with the respective groove.

The tensioning, as said, of each ring occurs, in the prior art, by means of the adjustment of the position of the pulleys or the sendback drum, subdivided for this purpose into single pulleys, spaced from each other by the distance at which the diamond wires must work, to cut slabs of the required thickness. Tensioning devices of the diamond wires are known in which the tensioning pulleys, operating on alternated wires of the sendback or return branches in the ring path, act in a radial way, pushing or pulling, on the single wire in such a way as to tension all the wires. In this case, however, the devices act in at least two different branches or points in the path of the wires.

Other forms of tensioning consist in putting in single tension the wire with the respective wheel of the sendback drum: each wheel being made to slide and pushed from the inside of the hub by a respective hydraulic cylinder, to put in tension the ring of diamond wire placed on it.

In fact, the different yielding and/or stretching of the diamond wire with use and ageing obliges to realize the tensioning for each single wire, in such a way as to realize a similar - if not identical - tension in the different wires which work side by side in the cutting of the slabs from the block of natural stone.

Moreover, the tensioning carried out with the pulleys on the sendback or return branches requires the use of pulleys or wheels not having a large diameter, to avoid very large dimensions of the machine, so as to make the winding of the wire on them penalizing for the life and duration of the wire itself. The diamond wire needs drums, wheels or pulleys having diameters equal to or greater than one meter to have an acceptable average life. In fact, the steel wire supporting the diamond inserts is bent every time it enters bending with a wheel, pulley or drum and with it it makes an - although short - rotational arc.

Finally, in the case of recent realizations the tensioning is subdivided onto two devices, one for the movement of the pulleys for large adjustments, as in case of replacement of one or more rings of diamond wire, and one for the fine adjustment of the tension of the single wire. Examples of this embodiment are described in the prior art documents WO 2009/040841 A1 and also WO 2013/156606 A1 , in which the above-mentioned devices are inserted in each other to exploit the movement of a group or of a single pulley with both devices, of which the device for large movements is always interposed between the structure of the machine and the single tensioning device for the small movements of the single wire closed in a ring. The document WO 2012/143956 A1 is also known, in which the support of the cutting diamond wires for their tensioning is distributed on four supporting points, two on guiding rollers, but present on the upper entry and lower exit branches from the wire tensioning device, and two on single pulleys for each diamond wire, of the tensioning device, supported onto a translating part of it with respect to which in their turn the pulleys, of support and of tensioning of the single wire, are made oscillating independently with respect to the translating part of the tensioning device. In the versions proposed in the document, moreover, the above-mentioned guiding rollers are able to be supported onto the supporting structure of the driving roller and to be movable with it, or onto said translating part of the tensioning device. Finally, in a variant of the support of the single tensioning pulleys of each wire, the same supporting and tensioning pulleys are supported in a cascading way, in which a first oscillating pulley supports a first diamond wire and the adjacent wire is supported by a second oscillating pulley connected not to said translating part, but directly to the oscillating support of said first adjacent pulley; that is to say, to realize a parent oscillating support, with its own pulley on the first wire, and a child oscillating support, oscillating with respect to the first, but to support the adjacent wire, in such a way as to bind the support and tensioning device of one wire to the support and tensioning device of the adjacent wire. By this combination of movable parts one can understand the complexity of the proposed solution, so as to increase the movable means for realizing and controlling the support and tensioning. Said movable means need precise and functional constructions to carry out the purpose of translating or oscillating movement provided in the support and its contribution to the tensioning of the diamond wires of the described multi-wire cutting machine.

Therefore, in the prior art, as described above, devices of support, tensioning and rotation are known, which are very complex, that is to say, they are made up of a large number of parts, having high costs and/or high maintenance costs, which also include the time spent for assembling and disassembling the parts of the devices: both in ordinary maintenance, such as the replacement of the rings of diamond wire, and in extraordinary maintenance, such as the replacement or repair of parts of the device. The replacement of the rolling bearings of the tensioning pulleys or of the non-metallic yielding material for coating the grooves in the wheel or drum for transmitting the cutting motion are the most expensive maintenance operations.

In fact, it is known that the reduction in the number of the contacts of the wire closed in a ring in its path always leads to an improvement in the duration (life) of the diamond wire.

Moreover, the execution and maintenance cost factor influences the choices of customers and users. Considering that these multi-wire cutting machines are intended for almost continuous working, the incidence of maintenance costs, such as labour and spare parts, is preponderant in the purchasing choice, as well as the wear of the supporting surfaces on the rollers or drums and on the sendback and tensioning pulleys.

Furthermore, the realization of a multi-wire machine for cutting blocks of stone, which has low construction costs and low maintenance costs, is a technical problem which cannot be solved easily by the known prior art solutions, therefore, the realization of a multi-wire machine combining both construction economy, maintenance economy and which also allows for the maximum exploitation of the life of the cutting diamond wires is desired and has not been carried out in the art yet.

Said state of the art is susceptible of significant improvements with respect to the possibility of overcoming the above-described drawbacks and realizing a multi-wire machine for cutting blocks of natural or artificial stone with the characteristics of cost-effectiveness intrinsically associated with the machine parts used.

Therefore, the technical problem, which is at the basis of the present invention is to realize a cutting machine with a multitude of diamond wires in which the constitution of the parts of the tensioning device of the wires closed in a ring is characterized by cost-effectiveness, always maintaining maintenance simplicity and cost-effectiveness in the life of the machine, in such a way as to reduce maintenance interventions to short stops of the machine, but at the same time allowing for great adjustments in the development length of the diamond wire closed in a ring, in a simple and fast way.

An additional aim of the present invention is to uniform the constitution of the parts of the tensioning device of the diamond wires, in such a way as to reduce the parts kept in stock for possible maintenance by the final user and directly allow for the replacement of parts without disassembling the adjacent parts of the wire tensioning device.

Finally, a further part of the above-mentioned technical problem concerns the possibility of minimizing the effects of anomalous behaviours of the diamond wires, in such a way as to enable operation also in the presence of deteriorated motion conditions of single wires, which occurs in the presence of vibrations of wires particularly in the upper sub-horizontal return section of the wires from the tensioning device towards the driving drum with a large diameter. Summary of the invention

This technical problem is solved, according to the present invention, by a multi-wire machine for cutting blocks of natural or artificial stone, comprising: rings of diamond wire driven in their cutting motion by a driving drum; a pair of wire-guiding rollers, upstream and downstream of the cutting section, for determining in the cutting section the correct position of the single wire on the block of stone being processed; a tensioning device of the rings of diamond wire with at least one movable support of a single tensioning member for each ring of diamond wire; characterised in that it has the tensioning device subdivided into a first tensioning means for large movements, that is to say, intended to put in tension the rings of diamond wire in assembly-maintenance, and a second tensioning means, single for each wire, for the fine tensioning of each diamond wire closed in a ring; both the first and second tensioning means being made oscillating on respective oscillation pins connected to the supporting structure; the second tensioning means being subdivided into groups in an alternated way, corresponding to the wires they support, even in one group and odd in the other group; finally, said second fine tensioning means are spatially alternated in the groups and those of one group penetrates each other, in the space present between adjacent tensioning means of the other group, and between adjacent diamond wires, in the various tensioning positions which each of the second means assumes in tensioning.

Moreover, in an improved embodiment: the first tensioning means comprises a roller or drum mounted on an oscillating support as an upper sendback roller after the horizontal or sub-horizontal return section in the path of each ring of diamond wire.

Furthermore, in a preferred embodiment: the second tensioning means comprise a multitude of pulleys, which are made oscillating by a respective oscillating support, and which are intended to put in fine tension a respective diamond wire closed in a ring, placed immediately before, in the cutting motion of the diamond wire, of the wire-guiding roller upstream of the block being processed.

Moreover, in an additional embodiment: in the path of each ring of diamond wire the members in contact with the wire being limited to five, that is to say, they include the driving drum, the two wire-guiding rollers and the roller of the first tensioning means and a pulley of the second tensioning means.

Furthermore, in a specific embodiment: each oscillating support has a pin complete with a single pulley, which is applied on it; and wherein the pin of a pulley is made in two halves, complete with labyrinths corresponding to concentric labyrinths present in the hub of the pulley, said hub, too, being made in two halves.

Furthermore, an improved embodiment provides: the application of the pin and of the pulley on the oscillating support comprising a seat with locating elements and threaded holes made on an added intermediate element, which is made replaceable if needed.

Moreover, in a variant of a preferred embodiment: a pin of the single pulley is made with a width a little larger than the thickness of the hub of the single pulley, in such a way as to allow for the penetration each other of the intersecting wire of the other group of wires in tensioning, up to the spatial position reached by the pin of the pulley.

Furthermore, in a variant of first tensioning means for large movements: the sendback drum or roller is made in freely rotating parts of roller on which there are at least two diamond wires in grooves supported on the same freely rotating part of roller.

Moreover, a specific embodiment presents: the sendback roller being made with grooves on added arched sectors with a great radial thickness of the sector; the arched sectors being two or more in the arc of the circle on the sendback roller.

Furthermore, an improved embodiment: the arched sectors are fixed to the external surface of the roller by means of fixing screws with a radial direction in a number not lower than three per each sector.

Moreover, in an embodiment variant: the sendback roller being made with freely rotating parts, each of which is provided with eight housing grooves supporting eight diamond wires closed in a ring.

Finally, in a specific embodiment: the sendback roller being made with added grooves on arched sectors in a number of four sectors per groove.

The features and the advantages of the present invention, in the realization of a multi-wire machine for cutting blocks of natural or artificial stone, provided with a specific tensioning device for tensioning the multitude of wires, are mentioned in the following description of a multi-wire cutting machine with the tensioning device of the wires subject to elongation in the cutting of the block of stone, and are given as a non-exhaustive example, with reference to the enclosed ten drawing tables.

Short description of the drawings

Figure 1 is a schematic overall front view of a multi-wire machine with diamond wires for cutting a block of natural or artificial stone, provided with a tensioning device for tensioning the wires described in the invention, comprising the first tensioning means for large movements and the second fine tensioning means;

Figure 2 is a schematic perspective view limited to it of the tensioning device of the multi-wire machine of Figure 1 , in which one can see the only one fixed roller and the movable means with the path of the multitude of diamond wires highlighted;

Figure 3 is a schematic perspective view limited to the tensioning device of the multi-wire machine of the previous Figures, in which one can see the paths of the diamond wires in support to the single fine tensioning pulleys for each wire, constituting the second tensioning means;

Figure 4 is a schematic enlarged side view of the tensioning pulleys subdivided into two groups and interposed between the diamond wires in the section affected by the tensioning between the upper sub-horizontal return branch and the horizontal cutting section, which occurs between two guiding rollers of the diamond wires known in the art;

Figure 5 is a schematic side view of the tensioning device with the fine tensioning pulleys of each wire of the two groups and interposed between the diamond wires with a short ring development with respect to the average development accepted by the multi-wire machine;

Figure 6 is a schematic side view of the tensioning device with the fine tensioning pulleys of each wire of the two groups and interposed between the diamond wires with a longer ring development than the average development accepted by the multi-wire machine;

Figure 7 is an enlarged schematic representation of a section between the oscillation pins of the single supporting arms of some fine tensioning pulleys of the device, related to both groups, interposed between each other in a generic and intermediate position of the tensioning stroke;

Figure 8 is an enlarged schematic representation of a section of some fine tensioning pulleys of the device, related to one single group, interposed with the diamond wires, tensioned and supported by the other group of pulleys, in an extreme position of the tensioning stroke as one can see in Figure 6;

Figure 9 is a schematic diametrical section limited to a rotational hub of one single fine tensioning pulley of the wires according to the invention in the position of the previous Figure 8;

Figure 10 is a schematic perspective view limited to one side of the two groups of fine tensioning pulleys of the diamond wires closed in a ring, here in the position of the previous Figure 5; Figure 11 is a schematic perspective view limited to the hubs of the fine tensioning pulleys of the diamond wires, here in the replacement position of one of the pulleys, with the removal of the rotational pin of the pulley from the oscillating support;

Figure 12 is a schematic side view of the tensioning device, constituting the first tensioning means, with the upper oscillating roller of the tensioning device of the diamond wires operating on wires in a ring and of the rotational support for the previous and simultaneous tensioning of the multitude of wires;

Figure 13 is a schematic perspective view partially sectioned of the upper roller of the previous tensioning device of the diamond wires in which one can see the internal constitution of the roller;

Figure 14 is a schematic section on a diametrical plane of the upper tensioning roller of the diamond wires in which one can see the internal constitution of the roller subdivided into eight rotating parts of roller with groups of eight grooves, for the support of the diamond wires, in each group of adjacent wires operating on a portion of roller rotating autonomously with respect to the other parts or portions and not constrained to them;

Figure 15 is a schematic perspective section on a diametrical plane of a portion of the upper tensioning roller of the diamond wires; here one can see the internal constitution of the roller with the arched sectors for fixing the group of eight grooves on it, one per each diamond wire by which the rotating portion or part of roller can be affected;

Figure 16 is a schematic perspective view of a portion of the upper tensioning roller of the diamond wires, of a supporting sector of one single groove, of the fixing screws of the arched sector and of the of coating ring of each groove separated from the portion of roller.

Detailed description of a preferred embodiment

In Figures 1 and 2, with the multi-wire cutting machine, 1 indicates the machine as a whole in which the rings of diamond wire 2 are subtended, moved in their cutting motion M by a driving drum 3, comprising a vertically movable supporting structure 4 supporting the members of the machine 1 , to perform the lifting and lowering motions of the wires on the block of stone to be cut, which is not shown here. The wires in their lower path are guided by wire-guiding rollers 5 of the known type in the lower cutting section 7, while in the upper section 8, of the sub-horizontal return path of the rings of diamond wire 2, they are free and supported, at the end opposite to the driving drum 3, by the wire tensioning device 9 according to the invention. The tensioning device 9 is made up on its upper part of an oscillating roller or drum 10 on a pin 1 1 , constituting the first tensioning means, with a horizontal position, which provides for the motion for large movements in the tensioning of all the rings of diamond wire, and under said drum, of single pulleys 12, constituting the second tensioning means, supported in oscillation on horizontal pins 13 and 14, since they are subdivided into two groups 15 and 16, in such a way as to affect the rings of diamond wire 2 subdivided alternated in the two groups in the section between said oscillating drum 10 and the upstream wire-guiding roller 5, in the motion M of the wires, of the lower cutting section 7 of the diamond wires. The oscillation for the tensioning of the oscillating roller 10 is made by the push of hydraulic cylinders 17, while each pulley 12 and oscillating support 18 are pushed by a respective hydraulic cylinder 19.

Figures 3 and 4 show the subdivision into two groups 15 and 16 of the diamond wires to be put in tension, subdivided like the pulleys 12 into odd wires, group 15, and even wires, group 16. In their oscillating motion the oscillating supports 18 and the respective pulleys 12 position themselves in extreme conditions, as one can see in Figures 5 and 6, when the rings of diamond wire 2 are shorter than the average development in the machine, as in Figure 5, that is to say, the pulleys of one group penetrate, interposed, the pulleys of the other group, until coming near the pin 20 of the other pulleys; or, when the rings of diamond wire 2 are longer than the average development in the machine, as one can see in Figure 6, the pulleys of one group are extended until minimizing the penetration each other with the pulleys of the other group; moreover, in this case the penetration each other is maximum between the diamond wires 21 or 22 of one group and the pins 20 of the other group of pulleys 12. Said penetration each other between pulleys and between pins of pulleys and diamond wires can also be seen in Figures 7 and 8. In Figure 9, then, one can see the constitution of a pin 20 of a pulley, in which each pulley 12 is housed in rotation on its oscillating support 18, by means of the pin 20, and provided with a hub in two halves 23 and 24 to tighten the internal edge 27 of the pulleys with screws 28 on the rolling bearing 29, placed for the rotation between the pin 20 and the pulley 12. The oscillating support 18, too, is made in two halves 30 and 31 , which are tightened with screws 32. The pin 20 of each pulley 12, too, is made in two halves 33 and 34 which penetrates each other with the hub in two halves of the pulley including the support for the rotation of said rolling bearing 29 and a labyrinth 35, correspondingly present on both halves and also on the two halves of the hub 23 and 24 of the pulley; the two halves of the pin 20 are tightened in position by the screw 36, which is housed axially to the pin.

In the following Figures 10 and 1 1 one can see the constitution of the connection and tightening of the two halves of the pin 20, when mounted complete with the pulley 12, on the two halves 30 and 31 of the oscillating support 18. The two halves of the pin 20 are put in contact with the oscillating support 18 on the plane 37, as one can also see in Figure 9, of contact of said two halves with the two halves of said oscillating support. The pin 20, complete and mounted on the pulley, is housed in situ on the two respective halves of the oscillating support 18 by the guide of inclined seats 38 present laterally with respect to the support plane 37, by the additional guide of a locating element 39 and tightened with screws 40, two on each half 33, 34 of the pin, and in engagement on threaded holes 41 , made, in a very advantageous way, added with an intermediate element 42 housed and tightened to the support plane 37 on the respective oscillating supporting half 30 or 31 and towards the corresponding half, 33 or 34, of the rotational pin of the pulley.

Moreover, in Figures 12 to 16 one can see a specific and advantageous new constitution of the oscillating tensioning roller 10 in which an oscillating support 43 of the roller supports the roller 10 by means of one single pin 44 on which parts of roller 45 are put in free rotation, each of which is provided with eight grooves 46, that is to say, with the represented eight parts of roller 45 the diamond wires supported in the embodiment shown are 64 in total; obviously the number can change according to the cutting amplitude requirements of the machine, but, considering the presence of eight wires on the part of roller 45, it is disadvantageous, because it is expensive, to reduce the number of wires on the single part of roller, one would increase the number of the parts of roller which are free to rotate, that is to say, the construction-maintenance costs, and it is also disadvantageous to increase the number of wires, which are present on one single part of roller, reducing the number of the parts of roller, because the speed difference, by effect of the different length of each ring of diamond wire 2, decreases very much the compensation effect of the small speed differences between the diamond wires closed in a ring, which are present on the same part of roller. That is to say, the number of eight wires per part of roller 45 is the most advantageous with respect to the obtainable costs and benefits. The rotary support of the hubs 47 of the parts of roller 45 is made in a known way with rolling bearings 48.

The grooves 46 made on the oscillating roller 10 are added, in a specific embodiment, by means of arched sectors 49 of groove with a large thickness 50 in the radial direction; each sector is secured to the external surface 51 , or circumference, of the single part of roller 45 by means of fixing screws 52, placed in a radial direction and on the development arc of the arched sector 45; each groove 46 is, as usual, coated with an abrasion-resistant plastic ring 53, of the known type, closed before assembly or also simply housed with a strip of material inserted in the groove 46 cut to size as it is known in the art.

The operation of the tensioning device 9, according to the invention, occurs as described in the following.

After the laying of the rings of diamond wire 2, in the provided position of the path of each wire, the oscillating drum 10, pushed by the hydraulic cylinders 17, is placed in its extreme extension position, in such a way as to determine the sendback point of the diamond wires between the sub-horizontal return branch 8, of the path of the wires, and the wire-guiding roller 5 placed upstream, on the basis of the cutting motion M, of the section 7 in the path of the wire. The rings of diamond wire, in the sub-vertical section of the path are thus affected by the pulleys 12, which oscillate and are pushed with their respective oscillating support 18, each by one hydraulic cylinder 19. The pulleys are subdivided into two groups 15 and 16, like the diamond wires, in such a way as to minimize the joining spaces of the parts of the oscillating supports 18 and the pulleys with the respective rotational pins, as well as of the penetration each other of the diamond wires between the pulleys on the basis of the oscillating position which each pulley must assume to perform the correct fine tensioning action of its own diamond wire.

The oscillating motion of the pulleys, as previously indicated, occurs between two extreme conditions of Figures 5 and 6: in the presence of rings of diamond wire with a smaller development than the average length provided in the machine, the pulleys penetrates each other as it is shown in the schematic section of Figure 7, in such a way as to approach the external diameter of the pulleys 12 of one group with the position of the rotational hub 20 of the pulleys of the other group; or, in the presence of rings of diamond wire with a larger development than the average length provided in the machine, the pulleys move away, but the subtended diamond wires of the other group, as it is shown in the schematic sections of Figures 8 and 9, penetrates each other so as to position the diamond wire of one group in correspondence of the hub and of the rotational pin 20 of the pulleys of the other group. Such an arrangement allows to keep great the fine tensioning movement of the pulleys on each ring of diamond wire 2, although keeping limited the number of contacts of the wire in its path, keeping limited the development of the ring and keeping practical and economical the realization of the tensioning devices, which, with the described tensioning device 9 with oscillating members, have greater reliability in operation with respect to the sliding members known in the art.

Moreover, a simplified and fast operation, performed by the described tensioning device 9, is carried out during the ordinary maintenance of the diamond wires and extraordinary maintenance of the pulleys 12 since the tensioning members are easily reachable in the low part of the machine not requiring the operator to place himself/herself up in the structure of the machine. Thus, the maintenance intervention on one single pulley 12, either for the coating or for the intervention on the rotational bearing 29 in the pin 20, can take place by simply dismounting the pin itself and the pulley with its hub and bearing, loosening the screws 40 which tighten the two halves 33 and 34 of the pin 20 to the respective oscillating support 18 in two halves 30 and 31 and placing there the new pulley assembly.

In this way the operation of loosening or tightening of the screws 40, allows for the extraction or the assembly of the single pulley 12, complete with its pin 20, bearing and labyrinths, without intervening on the adjacent pulleys and keeping the other diamond wires positioned on them.

Finally, the housing seat of the two halves 33 and 34 of the pin 20 is provided also for frequent assembly and disassembly, being the threaded holes 41 added on the two halves 30 and 31 of the respective oscillating support 18, in a replaceable way with the replacement of the intermediate element 42 in which the threaded holes 41 are made.

The operation of the oscillating tensioning roller 10 occurs by simply positioning, in an extended position, the oscillating support 43 in such a way as to move away as much as possible the roller 10 from the driving drum 3, which precedes it in the path of the diamond wires. The constitution of the roller 10 can also be with one single drum with added grooves of abrasion-resistant soft material of the diamond inserts of the wire, as it is known in the art, different from what is represented and described in the following. In fact, in Figures 12 to 16 the oscillating roller 10 is described and shown in one of its particular constitutions, which has a subdivision of the roller into parts of roller 45 each of which is freely rotating on the rotary supporting pin 44, according to the invention, so on said parts the presence of several supporting grooves of the diamond wires of adjacent rings 2 allows to separate the presence of diamond wires with different speeds which can occur, as it is known in the art for the characteristics of cutting on the block of stone, between the diamond wires during cutting. Being a considerable number (in the Figures there are 64 wires), said wires, if they are present on one single drum, during operation may damage one or more of the grooves of a usual drum which does not allow for sliding between the parts constituting the grooves in the drum. Thus, the solution of limiting to eight the wires which are present in a part of roller allows to moderate the contrasting effects of the greater production- maintenance costs if one adopts a roller made up of single pulleys, one per wire, as compared to a construction solution in which more than eight wires are present on the same part of roller which is free to rotate; that is to say, the more wires concur on the same part of roller, the greater can be the speed difference between the wires, which only on the driving drum 3 have a perfect synchrony, while on all the other contacts, on rollers and pulleys, the difference depends on the behaviour of the wire in cutting and on its start development of length of the ring. Thus, on the single pulleys, like the pulleys 12 of the tensioning device 9, there cannot be damage because the pulley follows the speed of the supported wire, while on the parts of roller 45 the speed of the wires, although slightly different, is compensated for by a sliding of the wires with greater speed, that is to say, which are longer or have been elongated more in cutting with respect to the adjacent wires. Therefore, by limiting to eight the wires supported by one single part of roller 45 of the oscillating roller 10 it is possible to minimize the reciprocal sliding between wires without generating excessive construction and maintenance costs.

Moreover, in the specific constitution of the represented oscillating roller 10 each groove 46, besides being coated with a ring of soft material 53, is constructed on arched sectors 49, in a minimum number of two or more, with the only limit of the greater cost, considering that each arched sector 49 has a side 50 with a large radius with the purpose of moving away the groove 46 from the external surface 51 of the part of roller 45, to prevent damage due to vibrations of diamond wires subtended in the sub-horizontal section 8 of the upper path of the rings of diamond wire 2. When a diamond wire, going through said sub-horizontal section 8, comes into vibration, the latter affects the contact surface of the wire at the end of this section, that is to say, it damages the groove 46 on which it is present in the winding on the oscillating roller 10, the action is hammering and increases at every following turn of the roller, so the damage is obtained in a short time and to take the machine back to normal cutting conditions it is necessary to stop it and replace the involved groove.

In the prior art said replacement concerns the roller and the specific involved groove with the need to dismount the complete roller to replace the damaged groove or grooves. By the solution proposed in the present invention the maintenance intervention in case of damage to a groove 46 can take place in two ways. A first way is to dismount the specific rotating part of roller 45, by extracting it from the oscillation pin 44 and intervening on the groove in the workshop, being able, after the replacement of the rotating part of roller 45, to restart the machine and carry out the maintenance calmly later. A second way of maintenance of the single groove 46, subject to damage, occurs by detachment before the involved arched sector 49: the damage is always concentrated in one single point of the periphery of the groove, so the dismounting intervention of the involved arched sector 49 can also occur with the oscillating roller 10 mounted on the machine, in such a way as to carry out specific and rapid maintenance without intervening on the multitude of diamond wires of the machine and considerably limiting intervention time and the consequent stop of the machine for the replacement of the arched sector. The arrangement of the fixing screws 52 of each sector must be in a minimum number of three screws per sector and with a radial direction to be an impediment to the centrifugation of the arched sector if the damage completely affects a screw head 52.

The advantages, of the multi-wire machine for cutting blocks of stone with the above-described wire tensioning device are many although they can be summarized with a simplification of construction, adopting machine parts which carry out oscillatory movements to put in tension the diamond wires, and a realization of these parts which allow for their safe operation for the purpose of movement required also in the presence of a surrounding environment which is polluted by the water used for cutting, by the stone particles detached in cutting and by the diamond powder for the grinding of the cutting of the diamond inserts, which pollution, as it is known, tends to prevent the movements of the involved machine parts.

Moreover, the simplification of construction with the limitation of the contacts of the ring of diamond wire in its path allows to keep long the working life of the wire even if the pulleys and the rollers which come into contact with the wire have a sufficient diameter, but not comparable to the driving drum 3. Furthermore, the tensioning device 9 with the subdivision into a means, the oscillating roller 10, for the simultaneous tensioning of all the wires but also for the large movements in tensioning, allows to limit the fine tensioning stroke. Fine tensioning is carried out with the groups 15 and 16 of pulleys 12, in such a way as to enable a great oscillation rotation: of the pulleys, subdivided on the even and odd wires of said groups which penetrates each other, but not only, also in a different tensioning position, as described, the wires of one group penetrates each other with the pulleys and oscillating supports 18 of each of them of the other group up to the zone occupied by the pins 20 of the pulleys. Furthermore, the construction and the maintenance interventions of the pulleys 12 can be carried out individually for each pulley 12, without having to intervene on the adjacent pulleys, that is to say, the mounting and dismounting of the single pulley occurs by intervening on the fixing of its rotary supporting pin.

Also in the constitution of the oscillating roller 10, the present invention shows how it is possible to limit construction and maintenance costs without neglecting the problems of wear of the grooves of the sendback roller, which are known in the art, and which are solved by means of the adoption of the roller 10 subdivided into parts 45 free to rotate and on which there are at most eight diamond wires, compensating at most for the small speed differences among said eight wires, rather than with one single roller in which the differences to be compensated for are on 64 wires. Moreover, with the construction solution of the arched sectors 49 juxtaposed to the external diameter 51 of said parts of roller 45, in such a way as to limit damage on the part of roller if said vibrations insist and, by the amplifying effect of the rotation in the operation, occur very rapidly after the activation, the effect of the vibrations from the long sub-horizontal section 8 is minimized, that is to say, the vibrations of some wires which may occur in the operation; maintenance, instead of affecting the whole roller or even only a part free to rotate of it, is carried out directly removing the damaged arched sector 49 and without dismounting the oscillating roller 10 from the machine.

Therefore, summarizing the advantages of the described tensioning device and of the specific constitution of the roller 10, the maintenance time and the replacement-repair interventions of the parts are thus extremely minimized. In conclusion the costs of the machine, in addition to construction, are also minimized for periodic maintenance and for extraordinary maintenance.

Obviously, in the realization of a multi-wire machine for cutting blocks of stone and wire tensioning device, as described above, a person skilled in the art may apply the described characteristics with the variants he/she will consider appropriate but all included in the enclosed claims.

In fact, the sendback oscillating roller or drum, made in the specific constitution in parts free to rotate or with grooves supported by removable arched sectors, can also be used with non-oscillating devices, that is to say, in a fixed position, but provided with specific features of realization in freely rotating parts of the roller, in which a number of wires greater than two are present on the same freely rotating part of roller; moreover, said roller can be provided with arched sectors, at least two per each groove, with a side having a large thickness to compensate for anomalous damage due to the possible vibration of the supported diamond wire. Finally, in a construction variant of the sendback roller or drum (10) the latter is connected in rotation in a fixed position to the supporting structure (4) of the guiding and/or support and driving members of the rings of diamond wire and it is associated with any known tensioning device of the wire rings, obviously, different from what has been described above.

Furthermore, the arrangement of the tensioning members, first and second tensioning means, although less conveniently, can be different from that shown, that is to say, with said means placed in sequence or subdivided in the path of the ring of diamond wire.

Thus, in practice, the materials, the sizes, the execution details can be different from those indicated, but technically equivalent to them, without departing from the protection domain of the following claims.