CUTTING OF STONE MATERIAL

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DESCRIPTION

This invention relates to a tensioning device for machines for multiple wire cutting of stone material.

In general, machines for multiple wire cutting of stone material comprise a basic frame and a plurality of cutting devices mounted parallel with each other on the basic frame. Each cutting device comprises: at least a first and a second flywheel which are coplanar, spaced out and rotatably mounted on the basic frame, and a cutting wire wound around at least the flywheels. The first flywheels are usually connected to drive means (which make the wire rotate), whilst the second flywheels are connected to a fine or precision tensioning device for adjusting the tension of the cutting wires. Generally speaking, the tensioning device allows each of the wires to be tensioned independently of the others. One method for independently tensioning each wire is described in patent EP1024314. The device described comprises a plurality of flywheels, each lying in a plane and mounted alongside each other in such a way that the planes in which they lie are parallel with each other. Moreover, each flywheel has an inner housing (central relative to the flywheel considered) delimited, in the plane in which the flywheel lies, by the bearing.

The bearing comprises two concentric rings which slide one inside the other in which the first (with the bigger diameter) is connected to the flywheel considered. In contrast, the second ring (with the smaller diameter) is connected to parallel guides on which a block is slidably mounted. The sliding block is in turn fixed to the (fixed) supporting shaft for the flywheels which runs in the housings inside all of the flywheels. Moreover, inside the housing there is an actuator connected between the sliding block and the second ring of the bearing. Running axially inside the supporting shaft there is a duct for feeding a pressurised liquid to the actuator of each flywheel. The actuators (in practice) can move the second ring (and therefore the flywheel) from a minimum tensioning position to a maximum tensioning position, translating the flywheel axis of rotation perpendicularly to the plane in which the cutting wire lies. Therefore, by keeping the liquid pressurised it is possible to achieve precision tensioning of each cutting wire independently of the others.

A similar solution, for producing a tensioning device, is described in Italian patent TO2005A000669.

However, this known technology has several disadvantages.

A first problem relates to the complex construction of the mechanical parts used to make the device. For example, a duct must be created (for the passage of pressurised liquid) running axially inside the supporting shaft along its entire length. Moreover, radial holes must be made in the shaft in very precise positions at the flywheels which are mounted on it. In addition to said complexity, it also brings an increase in production costs. Specialised machines and technicians are needed for precise production of the holes and the duct.

A second problem relates to maintenance. To work on a flywheel (when necessary) all of the flywheels and all of the actuators from it towards one end of the shaft must be removed, said parts being supported by the shaft and connected to it.

Moreover, since the dimensions of the device vary depending on the machine on which it must be mounted, manufacturers are obliged to draw up specific plans depending on the machine (length of the shaft and therefore of the duct, etc) thus increasing production costs.

In this situation, the technical purpose which forms the basis of this invention is to provide a tensioning device which overcomes the above- mentioned disadvantages.

In particular this invention has for a technical purpose to provide a tensioning device which is first simpler to produce and which simplifies the operations to be carried out for device maintenance.

This invention also has for a technical purpose to provide a tensioning device which is more economical than those of the prior art and which can be mounted on different types of cutting machines.

The technical purpose specified and the aims indicated are substantially achieved by a tensioning device as described in the appended claims. Further features and the advantages of this invention are more apparent in the detailed description below, with reference to a preferred, non- limiting embodiment of a tensioning device, illustrated in the accompanying drawings, in which:

- Figure 1 is a side view of the tensioning device for machines for cutting stone material made in accordance with this invention;

- Figure 2 is an axonometric view of the tensioning device of Figure

1 , in cross-section according to the line II - II (with the exception of the screws which are shown whole);

- Figure 3 is an enlarged detail of the tensioning device of Figure 2;

- Figure 4 is a front view of the tensioning device of Figure 2;

- Figure 5 is a side view, as in Figure 1 , of a module of the tensioning device of Figure 1 with some parts cut away to better illustrate others; - Figure 6 is a cross-section of the tensioning device of Figure 5 according to the line VI - VI;

- Figure 7 is a cross-section of the tensioning device of Figure 5 according to the line VII - VII;

- Figure 8 is a cross-section of the tensioning device of Figure 5 according to the line VIII - VIII;

- Figure 9 is a front view of a machine for multiple wire cutting of stone material on which the tensioning device of the previous figures is mounted.

With reference to the accompanying drawings, the numeral 1 denotes as a whole a tensioning device for machines 70 for multiple wire cutting of stone material 71 in accordance with this invention.

The tensioning device 1 for machines 70 for multiple wire cutting of stone material 71 comprises a plurality of flywheels 2 each lying in its own plane 3 and drawn near one another so that the respective planes 3 in which they lie are parallel with each other. In practice, a cutting wire 72 is wound on each flywheel 2, partly wrapped around the flywheel 2 along a stretch of its outer perimeter 4.

The device 1 also comprises a supporting structure 22 extending between a first end 23 and a second end 24, the ends being mountable on a machine 70 for multiple wire cutting. The flywheels 2 are rotatably mounted on the supporting structure 22 in such a way that each can rotate about its own axis of rotation which is substantially perpendicular to the plane 3 in which the flywheel lies. The tensioning device 1 comprises movement means 73 connected to each flywheel 2 for moving the flywheel 2, relative to the supporting structure 22, between a minimum tensioning position 19 and a maximum tensioning position 20. The movement means 73 connected to a flywheel 2 can preferably translate the axis of rotation (relative to the flywheel 2) between the two positions 19, 20.

According to this invention the supporting structure 22 is formed by a plurality of supporting elements 18 drawn near each other and removably connected to one another, by connecting means 21 , along a main axis 74 extending from the first end 23 to the second end 24 of the supporting structure 22. Each supporting element 18 supports at least one flywheel 2 positioned at the supporting element 18. Advantageously each flywheel 2 is supported by a single supporting element 18.

In the preferred embodiment each supporting element 18 comprises a first surface 25 and a second surface 26 which are opposite each other and substantially parallel with one another. Both of the surfaces 25, 26 are transversal to the main axis 74. Figure 5 shows the second surface 26 of the supporting element 18, whilst Figure 2 shows how the supporting elements 18 are drawn near each other in sequence from the first end 23 of the single structure 22 to the second end 24. Therefore, proceeding from the first end 23 to the second end 24, it can be seen how the second surface 26 of one supporting element 18 is in contact with the first surface 25 of the adjacent supporting element 18 and so on.

The connecting means 21 comprise at least one projection 37 of the first surface 25 of each supporting element 18 and at least one recess 38 of the second surface 26 of each supporting element, shaped to match the projection 37. This projection 37 (of each supporting element 18) is inserted in the recess 38 of the adjacent supporting element 18 with a snap on action so that no play exists between the two elements. Figure 8 shows how the projection 37 extends transversally to the plane 3 in which each flywheel 2 lies, creating a projecting portion 39 of the first surface 25 of each supporting element 18. On the second surface 26 of the supporting element 18 the recess 38 is shaped to match the projection 37, thus creating a concave portion 40 of the second surface 26. Figure 5 shows how the projecting portion 39 and the concave portion 40 are circular. Moreover, in the supporting structure 22 the concave portion 40 of a supporting element 18 is in contact with the projecting portion 39 of the adjacent supporting element 18. Therefore, advantageously, the weight of each supporting element 18 drawn near another is discharged from a projecting portion 39 to a concave portion 40 of the supporting elements 18 and vice versa.

The supporting element 18 also comprises an inner compartment 55 preferably having the shape of a cylinder and extending between two bases 56, 57 respectively bordered by the concave portion 40 and the projecting portion 39. Each supporting element 18 therefore has the projecting portion 39 inserted in the concave portion 40 of the adjacent supporting element 18 and so on for the entire supporting structure 22. Advantageously, all of the compartments 55 of the tensioning device 1 are therefore in communication with each other and can house a system of pipes (not illustrated in the accompanying drawings) for conveying a pressurised liquid along the entire length of the supporting structure 22 (whose use is described below).

These pipes converge outside the tensioning device 1 where a suitable feed system (not illustrated) distributes the pressurised liquid in the pipes. In the preferred embodiment illustrated in Figure 5, the supporting element 18 has a plurality of holes 27, transversal to the lying plane 3, and extending from the second surface 26 towards the first surface 25 of the supporting element 18. These holes 27 are advantageously divided into a plurality of internally threaded first holes 28 (in Figure 5 these are illustrated without a double circle), and a plurality of non-threaded second holes 29 passing from the second surface 26 to the first surface 25 (in Figure 5 these are illustrated with a double circle). For simplicity, the threading is not illustrated in the accompanying drawings. The threaded holes 28 may be through holes (from the second surface 26 to the first surface 25 of the supporting element 18) or they may be dead holes. In the embodiment illustrated in the accompanying drawings the threaded holes 28 are through-holes (as are the non-threaded holes 29).

The supporting elements 18 may in turn advantageously be divided into a first group 30 of supporting elements 18 and a second group 31 of supporting elements 18. Each supporting element 18 belonging to the first group 30 is interposed between two supporting elements 18 belonging to the second group 31 and vice versa in such a way as to form, from the first end 23 to the second end 24 of the supporting structure 22, alternating supporting elements 18 belonging to the first group 30 and the second group 31. The supporting elements 18 of the first group 30 are complementary to those of the second group 31 as regards the holes 27. A non-threaded hole 29 of a supporting element 18 of the first group 30 corresponds to a threaded hole 28 (positioned at the same point) of a supporting element 18 of the second group 31. Otherwise the supporting elements 18 of the first group 30 and of the second group 31 are advantageously identical.

Figure 3 shows how, with the device mounted, each threaded hole 28 of a supporting element 18 of a group 30, 31 continues on from a non- threaded hole 29 of a supporting element 18 of the other group 31 , 30 adjacent to it.

The holes 27 of each supporting element 18 are therefore repeated (in the same positions) in all of the supporting elements 18 of the tensioning device 1 , alternating (from one end 23 to the other end 24 of the supporting structure 22) between a threaded hole 28 (belonging to a supporting element 18 of a group 30, 31) and a non-threaded hole 29 (belonging to a supporting element 18 of the other group 31 , 30).

The holes 27 are part of the connecting means 21 which connect the supporting elements 18 and which also comprise screws 32. These screws 32 are passed through the inside of the non-threaded first holes 29 of a supporting element 18 and screwed in the threaded second holes 28 of the supporting element 18 drawn near it.

Moreover, each of the non-threaded holes 29 preferably comprises a first enlarged part 33, at the second surface 26 of the supporting element 18, for accommodating the head 34 of each screw 32. Figure 6 shows the enlarged part 33 of a non-threaded hole 29 of a supporting element 18. Advantageously, the depth of the enlarged part 33 (measured parallel with the main axis 74 from the second surface 26 of a supporting element 18) is greater than, or equal to, the thickness of the head 34 of each screw 32 so that the head 34 of the screw 32 does not project from the second surface 26 of the supporting element 18 in which it is inserted. In the embodiment illustrated in Figure 3 there are four supporting elements 18 drawn near each other and connected to one another by a plurality of screws 32 (the drawing only shows the two three-dimensional rows at the cross-section plane). For example, Figure 3 shows how the second supporting element 18 (starting the numbering from the first end 23 of the supporting structure 22) is connected to the first supporting element 18 by a first screw 35. This first screw 35 is inserted in a non- threaded hole 29 of the second supporting element 18 (where the screw 32 head 34 is also present) and is screwed into a threaded hole 28 of the first supporting element 18 to fasten the two supporting elements 18 together. The third supporting element 18 is connected to the second by a second screw 36 inserted in a non-threaded hole 29 of the third supporting element 18 and screwed into a threaded hole 28 of the second supporting element 18. Therefore, each threaded hole 28 of a supporting element 18 (for example belonging to the first group 30) is aligned with two non-threaded holes 29 of the two adjacent supporting elements 18 (therefore belonging to the second group 31).

The supporting structure 22 comprises a first closing head 68 connected to the first surface 25 of the supporting element 18 closest to the first end 23, and a second closing head 69 connected to the second surface 26 of the supporting element 18 closest to the second end 24 of the supporting structure 22. The first and second closing heads 68 and 69 respectively form the first end 23 and the second end 24 of the supporting structure 22. Advantageously, each closing head 68, 69 (like the supporting elements 18) comprises a plurality of holes 75 located in the same positions as corresponding holes 27 in the supporting elements and continuing on from them (with the device mounted). In particular, Figure 2 shows how the second closing head 69 has at least one non-threaded hole 76 (only one is illustrated in the drawing) in which a screw 32 is inserted which in turn is screwed into a threaded hole 28 of the supporting element 18 adjacent to the second closing head 69. The same applies for the first closing head 68 which, again in Figure 2, has at least one threaded hole 77 (only one is illustrated in the drawing) in which a screw 32 is screwed, said screw being inserted in a non-threaded hole 29 of the supporting element 18 adjacent to the first head 68.

The supporting structure 22 can be mounted on a machine 70 for cutting stone material 71 at the first end 23 and the second end 24. In particular, in the preferred embodiment, the first end 23 and the second end 24 are mounted on supporting means 78 which can be connected to the cutting machine 70. The drawing shows how there are two sets of supporting means 78, each comprising a seat 79, where the ends 23, 24 of the supporting structure 22 are inserted, and a connecting portion 80 for connection to a machine 70 for cutting stone material 71.

In general, the movement means 73 may have any configuration (for example, those described in patent EP1024314 and in Italian patent applications TO2005A000669 and VI2007A000150). In the embodiment illustrated by way of example, the flywheel 2 comprises an inner housing 5 delimited, in the plane 3 in which the flywheel 2 lies, by a first ring 6 connected to the flywheel 2. The inner housing 5 is advantageously circular (as illustrated in the accompanying drawings) and therefore the first ring 6 is also circular. Each flywheel 2 in turn comprises a second ring 8, with a diameter smaller than the first ring 6, slidably mounted inside the first ring 6 of the flywheel 2 so that the flywheel 2 can rotate relative to the second ring 8 (which is also circular). Therefore, the centres of the circles 9 formed by the two rings 6, 8 coincide. In practice, the first ring 6 and the flywheel 2 rotate about the second ring 8. The second ring 8 has a sliding surface 11 (in contact with the first ring 6) and an inner surface 12 facing towards the inner housing 5.

In the inner housing 5 of each flywheel 2 the movement means 73 are at least partly mounted, comprising at least one guide 13 connected to the second ring 8 and to the supporting element 18 for guiding the translation of the second ring 8 relative to the supporting structure 22, and at least one actuator 44 connected between the second ring 8 and the supporting element 18 for moving the flywheel 2 between the minimum tensioning position 20 and the maximum tensioning position 19.

In the embodiments illustrated the guide 13 is integral with the second ring 8 and is slidably mounted on the supporting element 18 for moving the flywheel 2 between a minimum tensioning position 20 (flywheel 2 in the background in Figure 5), and a maximum tensioning position 19 (flywheel 2 in the foreground in Figure 5).

Therefore, the supporting element 18 is always fixed, whilst the guide 13 with the second ring 8 and with the respective flywheel 2 can translate between a minimum tensioning position 20 and a maximum tensioning position 19. At the same time, the flywheel 2 can rotate about the supporting element 18, sliding on the second ring 8.

The guide 13 is preferably formed by at least two bars 41 extending parallel with each other in the inner housing 5 of each flywheel 2 and which are fastened to the second ring 8, at two first points 16 and two second points 17, at their ends 14, 15. In the preferred embodiment illustrated in Figure 5 there are two bars 41 extending parallel with each other in the housing 5 of each flywheel 2 transversally to the axis of rotation and each fastened to the second ring 8 at the first point 16 (connected to one end 14 of the bar 41) and the second point 17 (connected to the other end 15 of the bar 41). The connection between the bars 41 and the second ring 8 is preferably made using connecting elements 42 illustrated in Figure 5.

The supporting element 18 advantageously has at least two inner guide holes 43 in which the bars 41 are slidably inserted. In this way, each flywheel 2 can slide on the supporting element 18 between the minimum tensioning position 20 and the maximum tensioning position 19. Figure 5 shows the two bars 41 connected to the second ring 8 and mounted on the supporting element 18.

The actuator 44 is connected between the supporting element 18 and the second ring 8 for moving each flywheel 2 between the minimum tensioning position 20 and the maximum tensioning position 19. In the preferred embodiment the actuator 44 comprises a piston 45, and a jacket 46 shaped to match it, the inside of which forms a chamber 47. The piston 45 can move between a first position 48 in which it is mostly located inside the chamber 47, corresponding to the minimum tensioning position 20, and a second position 49 in which it is mostly located outside the chamber 47, corresponding to a maximum tensioning position 19. Figure 8 shows a piston 45 extending between two end parts 50, 51. The first 50 is screwed on a stop element 52 for connecting the piston 45 to the second ring 8, whilst the second 51 is connected to a head 53 which is inserted in the chamber 47 and is in contact, in a sealed fashion, with the inner surface of the actuator 44 jacket 46. In the minimum tensioning position 20 the head 53 of the piston 45 is in contact with an end wall 54 of the actuator 44 chamber 47, whilst in the maximum tensioning position 19 the head 53 of the piston 45 is distanced (according to a maximum distance) from the end wall 54. The stop element 52 is in turn fastened to the second ring 8 by a connecting element 42 connected to the second ring 8.

Each supporting element 18 also comprises a plurality of inner ducts 58 for conveying the pressurised liquid from the compartment 55 towards the actuator 44 chamber 47 for controlling the position of the piston 45 inside the chamber 47. Figure 8 shows how the inner ducts 58 connect the compartment 55 to the actuator 44 chamber 47, in practice conveying the pressurised liquid towards the chamber 47. In this way, by regulating the pressure of the liquid, it is possible to control the actuator 44 and therefore adjust the distance between the piston head 53 and the end wall 54. In the embodiment illustrated in Figure 8 the inner ducts 58 communicate with the supporting element 18 compartment 55 through an opening 81. In the embodiment the inner ducts 58 put the chambers 47 of two actuators 44 (relating to two adjacent flywheels 2) into communication with the same compartment 55 of the supporting element 18 (which in this case supports two flywheels 2) through a single opening 81. Figure 8 also shows a plug 82 used to close all other outlets of the inner ducts 58 towards the outside of the supporting element 18 created during production. It is simpler to make a hole for creating the inner ducts 58 from outside the supporting element 18 and then close it with a plug 82. The tensioning device 1 also comprises at least one casing 67 connected to the supporting structure 22 and running along its entire length, passing inside the housings 5. The inside of the casing 67 forms a free channel 66 for the passage of electric cables or other items. In the preferred embodiment there are two free channels 66 running inside the housings 5 on either side of the actuators 44.

In the preferred embodiment illustrated each supporting element 18 supports two adjacent flywheels 2. This is advantageous for the dimensions of the screws 32 inserted in the holes 27 in the supporting element 18. By increasing the distance between the two surfaces 25, 26 of the supporting element 18 (and therefore its thickness) it is possible to use larger screws 32. In the preferred embodiment illustrated in Figure 3, each supporting element 18 occupies the housings 5 of two flywheels 2 which are drawn near each other. Therefore, the first surface 25 of the supporting element 18 is closest to one of the two flywheels 2, whilst the second surface 26 of the same supporting element 18 is closest to the other flywheel 2.

In the preferred embodiment, the first ring 6 and the second ring 8 of each flywheel 2 together form a bearing 59. Inside the bearing 59, between the two rings 6, 8, there may be rolling balls 60 or other items. The first ring 6 has a hollow 61 (in the plane 3 in which the flywheel 2 lies) along its inner perimeter facing towards the inner housing 5. In turn, the second ring 8 has a hollow 62 (in the plane 3 in which the flywheel 2 lies) along its outer perimeter facing towards the hollow 61 in the first ring 6. When fitted together (one inside the other) the two rings 6, 8 therefore create a circular duct 63 (made between the two hollows 61 , 62) in which balls 60 or the like are inserted, allowing the first ring 6 to slide on the second ring 8.

Each flywheel 2 may preferably comprise wear rings 64 inserted along its outer perimeter 4 and removable. In the preferred embodiment illustrated in Figure 3, the outer part of each flywheel 2 comprises a housing track 65 extending along the entire perimeter of the flywheel 2. A wear ring 64 is inserted in this housing track 65, the wear ring being made of a suitable material for operating in contact with the cutting wire which is impregnated with diamond. This wear ring 64 may advantageously be removed from the flywheel 2 and substituted with a new one if necessary.

The tensioning device 1 is suitable for mounting on a machine 70 for multiple wire cutting of stone material 7 . Figure 9 shows an example of a machine 70 for multiple wire cutting in which the tensioning device 1 according to this invention is mounted. The machine 70 has a supporting frame 83 able to slide on a base structure 84 and a plurality of cutting devices 85 mounted parallel with each other on the supporting frame 83 (only one is illustrated in the drawing). Each of these cutting devices 85 comprises: a first and a second flywheel 86, 87 and at least one return flywheel 89 which are coplanar, spaced out and rotatably mounted on the supporting frame 83, and a cutting wire 72 wound around the flywheels 86, 87, 89. Usually (as shown in Figure 9) the first flywheels 86 are formed by a single drum 90 to which drive means are connected (for making the wire 72 rotate), whilst the second flywheels 87 are connected to a tensioning device 1 for precision tensioning of the cutting wires 72. Rough tensioning means 88 are connected to the return flywheels 89. Tensioning device 1 operation is immediately derived from what is described above. In particular, each flywheel 2 is free to rotate (about the supporting structure 22) following the motion of the cutting wires 72. At the same time, each flywheel 2 can translate its position in space between a minimum tensioning position 20 and a maximum tensioning position 19. The actuator 44 of each central body 7 mounted in the housing 5 of a flywheel 2 causes the second ring 8 to move (and therefore also the first ring 6 and the flywheel 2 connected to it) thus tensioning the cutting wire 72. In particular, pressurised liquid (usually oil) circulates in the pipes passing in the compartments 55 of the supporting elements 18. Through the inner ducts 58 the liquid reaches the chamber 47 of each actuator 44. The piston 45 moves based on the pressure of the liquid. Therefore, by adjusting the pressure of the oil passing through the pipes it is possible to tension the flywheels 2. Mounting of the device 1 derives from what is described above. In particular starting at the first end 23 of the supporting structure 22 and moving towards the second end 24. The first step is to connect a first supporting element 18 (supporting the movement means 73 and the respective flywheels 2) to the first closing head 68 by inserting the screws 32 in the non-threaded holes 29 of the first supporting element 18 and screwing them into the threaded holes 77 of the first closing head 68, thus fastening the two parts together. Then, a second supporting element 18 is connected to the first. In particular, if the first supporting element 18 belongs to the first group 30, the second supporting element 18 belongs to the second group 31 or vice versa. The second supporting element 18 is then drawn near to the first by inserting the projecting portion 39 of the second supporting element 18 in the concave portion 40 of the first supporting element 18 until the first surface 25 of the second supporting element 18 is in contact with the second surface 26 of the first supporting element 18. The screws 32 are then inserted in the non-threaded holes 29 of the second supporting element 18 and screwed into the corresponding threaded holes 28 of the first supporting element 18. This operation is repeated to create the entire device 1 as far as the second end 24 of the supporting structure 22. Finally, the second closing head 69 is connected to the final supporting element 18 (counting from the first end 23 to the second end 24) by passing the screws 32 through the non- threaded holes 76 of the second head 69 and screwing them into the corresponding threaded holes 28 of the final supporting element 18.

This invention brings important advantages.

First, the tensioning device no longer comprises a single shaft, but rather a plurality of identical parts connected to each other. This simplifies the device construction process (the parts are simply connected to one another). Even production costs are lower, since the mechanical machining to be carried out is simpler than that required for the tensioning devices currently in use.

Therefore, the device is also easier to disassemble (since it consists of individual parts which are connected to each other) for any maintenance operations needed.

Second, the device can be mounted on cutting machines with different numbers of wires. By simply changing the number of individual parts used, a device with different dimensions can be created. Consequently, the costs for producing a tensioning device are reduced, since a predetermined number of identical parts can be mass-produced, then the device can be built according to requirements without having to produce specific unique parts.

It should also be noticed that this invention is relatively easy to produce and even the cost linked to implementation of the invention is not very high.

The invention described above may be modified and adapted in several ways without thereby departing from the scope of the inventive concept. All details of the invention may be substituted by other technically equivalent elements and, in practice, all of the materials used, as well as the shapes and dimensions of the various components, may vary according to requirements.