5 The present invention relates to a method for manufacturing a diamond wire for cutting stone material and the diamond wires thus obtained.

As is known, in order to manufacture a diamond wire, firsdy it is required to produce composite elements, each of which comprises a diamond bead inside which a support bush is inserted and fixed. Thereafter a steel cable with a diameter slighdy smaller than the inner 0 diameter of the bushes is inserted inside a plurality of composite elements.

The cable is then joined at the two ends so as to form a ring suitable for being wound onto the pulleys of the cutting machines.

The composite elements comprising a bead and bush are arranged spaced at regular intervals and finally the whole assembly is coated with a polymer material which covers5 completely the steel cable and partially the bush-and-bead composite elements, with the exception obviously of the bead.

For this purpose injection moulds may be used, wherein the polymer material is injected inside them, which covers the steel cable and penetrates deep into the small gap formed between cable and bushes so as to fix permanently the composite bush-and-bead0 eletnents to the steel cable.

The steel cable consists of a plurality of strands which are woven together and are each formed by various steel wires which are also interwoven.

In order to form the joint between the two ends of the cable and create the abovementioned ring, the so-called splicing technique is used, namely the various ends of the5 strands are interwoven using a very precise and well-established technique.

The steel cable consists usually of seven strands, i.e. one central strand and six outer strands which are wound around the central strand. Each strand in turn consists usually of seven wires so that forty-nine steel wires may be present in a steel cable.

As is known per se to the person skilled in the art, the compositions may differ and0 therefore both the number of strands and the number of wires per strand may vary, for example there may be a total of 61, 90 or 133 wires.

With the splicing operation only the outer strands of the two ends are interwoven, while the two ends of the central strand are simply positioned end-to-end, namely in an adjacent and aligned manner.

5 The six outer strands are interwoven so that their end portions are superimposed along a length of about three metres and the cut end of one strand is placed against the cut end of the other strand and so on so as to form a single unit. It is therefore evident that the diameter of the cable remains more or less constant along the whole of its length.

At the end there are six points in the steel cable where there are two strand ends arranged end-to-end, and the cable is perfectly regular and uniform, except for these interruption points.

In figure 1 it is shown in diagrammatic form an example of a steel cable 13 in which two strand ends 14, 16 arranged end-to-end along the interruption line 18 can be seen.

The splicing operation is a delicate and very important operation which must carried out in the correct manner. However, no matter how correctly this operation is carried out, it always creates a weak part in the diamond wire.

In fact, the six interruption points, where the cut ends of the strands are arranged end-to-end, form a preferential breakage point. Considering the significant stresses involved, and in particular the high tension to which the diamond wire is subject, the fatigue stress following winding around the pulleys and the wear following cutting of the blocks of stone material, it is clear that the strands with time tend to fray at their cut ends, no longer performing their function in a suitable manner.

Not even the polymer coating is able to help limit this problem and much less so solve it.

In the present state of the art some attempts to solve this problem are known, for example by positioning the interruptions in such a way that they are aligned with a composite bush-and-bead element and are therefore covered by the element.

However, this solution has proved to be not very effective since a small amount of play nevertheless remains between bush (which is a rigid element) and steel cable, so that with time a relative movement of bush and steel cable occurs, this giving rise to the risk of fraying of the adjacent ends of the strands. It has also been noted that in some cases the fraying is even increased owing to the friction between the ends and the bush.

For this reason, generally the interruption points are positioned between one composite bush-and-bead element and the next one.

The object of the invention is therefore to solve the drawbacks of the prior art, by attempting to eliminate these critical points in the diamond wire and attempting to increase as far as possible the working life thereof.

The idea which has occurred, therefore, is to provide a method for manufacturing a diamond wire for cutting stone material, comprising the steps of:

- providing a plurality of composite bush-and-bead elements;

- inserting a steel cable inside the plurality of composite bush-and-bead elements; - splicing the two ends of the steel cable; and

- performing plastic-coating;

wherein the method is characterized in that it comprises a step where a reinforcing element is positioned on at least one joining point prior to the plastic-coating step.

Moreover, the idea which has also occurred is that of manufacturing a diamond wire for cutting stone material comprising:

- a steel cable joined together by means of splicing so as to form a ring;

- a plurality of composite bush-and-bead elements arranged on said steel cable;

- at least one reinforcing element positioned on at least one joining point;

wherei the plurality of composite bush-and-bead elements and the at least one reinforcing element are at least partially coated by a polymer.

The characteristic features and advantages of the method and the diamond wire according to the present invention will emerge more clearly from the description, provided hereinbelow, of a number of examples of embodiment provided by way of a non-limiting illustration with reference to the accompanying drawings, in which:

Fig. 1 shows a steel cable with two strands arranged end-to-end;

Fig. 2 shows in diagrammatic form a part of a diamond wire according to the present invention before the plastic-coating step;

Fig. 3 shows in diagrammatic form a diamond wire according to the present invention after the plastic-coating step;

Fig. 4 shows in diagrammatic form a cross-section of a reinforcing element according to the present invention;

Fig. 5 shows in diagrammatic form a perspective view of a reinforcing element according to the present invention;

Fig. 6 shows in diagrammatic form a reinforcing element in position on a steel cable before the plastic-coating step;

Fig. 7 shows in diagrammatic form a possible embodiment of a reinforcing element in position on a steel cable before the plastic-coating step;

Figs. 8 and 9 show two configurations of a possible embodiment of a reinforcing element according to the present invention; and

Fig. 10 shows a possible embodiment of a reinforcing element according to the present invention.

Fig. 3 shows in diagrammatic form a diamond wire for cutting stone material according to the present invention, indicated generally by the reference number 13.

With particular reference to Figure 1, a diamond wire 12 comprises a steel cable 13 composed of a plurality of strands (visible in Figure 1). Each strand is composed of a plurality of steel wires (even though for simpler illustration the plurality of wires for each strand is not shown). As mentioned further above, the number of strands and wires for each steel cable 13 may vary depending on specific requirements.

In accordance with a possible embodiment of the present invention, the steel cable 13 may comprise seven strands, one of which is central and six outer strands which surround the central strand. Advantageously each strand may in turn consist of seven wires.

In accordance with alternative embodiments of the present invention, the number of strands and wires per strand may vary, for example there may be a total of 61, 90 or 133 wires.

In order to close the cable in ring form, the technique of splicing is used, in a manner known per se. By performing splicing, in the manner indicated at the start of the present description, each outer strand will have an interruption, characterized by two strands ends 14, 16 arranged end-to-end, resulting in an interruption point, indicated by the reference number 18 in Figures 1, 2, 3, 6 and 7. In accordance with a preferred embodiment of the present invention, the two ends 14, 16 do not belong to the same strand.

In the embodiment with seven strands (one central strand and six outer strands) there will be six interruption points 18, i.e. one for each outer strand.

The six interruption points are not concentrated in a short section of steel cable, but are distributed along the section of steel cable where the two ends thereof are superimposed during the splicing step. Advantageously, the two ends of the cable may be superimposed over a length of about 3 metres. The six interruption points will be distributed over the whole section.

Advantageously, the interruption points 18 are arranged at regular intervals along the section of steel cable 13 where the two ends 14, 16 thereof are superimposed.

As will be evident to the person skilled in the art, the diameter of the cable is more or less constant over its whole length.

Before performing joining together of the steel cable in ring form by means of splicing, the steel cable is inserted inside the hole of the composite bush-and-bead elements 22 assembled beforehand.

As mentioned above, each composite bush-and-bead element 22 comprises a diamond-lined bead 24 inside which a bush 26 is inserted, said bush having an inner diameter slightly greater than the outer diameter of the cable 13 which will be inserted inside it. The bush 26 is fixed to the diamond-lined bead 24 in a manner known per se.

Since the method of assembling the composite bush-and-bead elements 22 is a method which is per se known to the person skilled in the art, it will not be further described.

According to the invention reinforcing elements 20 are arranged on the interruption points 18 of the strands so as to cover the section of steel cable 12 at the interruption point 18. Figures 2, 3, 4, 5 and 6 show in diagrammatic form a reinforcing element 20.

In accordance with a possible embodiment of the present invention, the reinforcing element may be as long as the interspace between the bushes. Advantageously, the outer diameter of the reinforcing element may be slightly smaller than that of the bush. In accordance with a first embodiment of the present invention, the reinforcing element 20 is positioned on an interruption point 18 before the steel cable 12 is joined to form a ring. The reinforcing elements 20 are therefore positioned in a manner similar to that of the composite bush-and-bead elements 22.

Advantageously, the reinforcing element 20 may have a substantially cylindrical form, with a central hole 26 inside which the steel cable 12 is inserted (see Figs. 4 and 5).

In accordance with possible embodiments of the present invention, the reinforcing element 20 may be a woven or mesh element made using threads of interwoven material, for example metallic material such as steel. Advantageously, the reinforcing element 20 may be a woven element, made using threads of interwoven material such as high-strength polymer material, for example nylon or aramid fibre. The woven element must adhere as closely as possible to the steel cable section adjacent to the interruption point.

Advantageously, the woven or mesh reinforcing element 20 may consist of a heat- shrinkable polymer so that, once positioned, it may be heated to adhere as closely as possible to the steel cable.

In accordance with an alternative embodiment of the present invention, shown in diagrammatic form in Figure 7, the reinforcing element 20 may be a so-called reinforcing "enlacement" 38 formed by a steel wire wound spirally around the steel cable. The cross- section of the steel wire may be circular, but is preferably rectangular. The turns are wound so as to adhere as tightly as possible to the steel cable. Advantageously, the steel wire used for the enlacement may have a diameter of between 0.3 and 0.5 mm, and even more advantageously in the region of 0.4 mm.

In accordance with a further embodiment of the present invention, the reinforcing element may consist of a rigid covering band (not shown), for example a strip of polymer material which is wound around the cable section adjacent to the interruption point and on the interruption point itself.

These solutions, while being effective, envisage however that the cable is inserted inside the woven element or mesh element at the same time as the composite bush-and-bead elements and therefore before performing splicing.

This operation complicates the production process since it is required to fit at the same time the reinforcing elements 20 and the composite bush-and-bead elements 22 in a well-defined sequence and, thereafter, perform the joining step by means of splicing.

This operation is long and laborious.

Moreover, the operator who performs the operation could forget to insert one or more of the reinforcing elements 20.

Therefore the idea which has occurred is that of designing also a reinforcing element 20 which may be positioned on the interruption points 8 after splicing of the steel cable. In accordance with a possible embodiment of the present invention, the reinforcing element may consist of a sleeve 30 which can be opened and closed as shown in diagrammatic form in Figures 8 and 9. The sleeve 30 may be made of metallic material, polymer material or other material. Advantageously, the sleeve 30 is a substantially cylindrical element with a through-hole, on which the steel cable section with the interruption point is positioned. The sleeve may be formed by two parts, preferably two halves 32, 34 which are joined together along a generatrix 36. The joint is such as to allow opening and closing of the sleeve 30. Advantageously, locking in the closed position may be obtained by means of a form-fit or in some other way which, considering the description provided above of the characteristic features of the sleeve, will be obvious to the person skilled in the art. For example by means of an outer covering band, snap-fit, etc.

In this case also the sleeve may consist of heat-shrinkable material in a manner per se well known to the person skilled in the art.

In a further embodiment, shown in diagrammatic form in Figure 10, the reinforcing element, which is made of a material with a sufficient elasticity such as metallic material, polymer material or some other material, may be a cylinder which is slitted and therefore has an opening or aperture along its generatrix which is smaller than the diameter of the steel cable. In this way, by means of elastic deformation of the reinforcing element 20, the opening may be expanded and the steel cable inserted inside, said opening then closing up elastically around the Cable and thus remaining tightly fixed thereto.

The last step consists of plastic-coating of the whole of the steel wire onto which the composite bush-and-bead elements 22 and the reinforcing elements 20 have been fitted.

Plastic-coating, which is normally performed by means of an injection process, has the function of stably fixing the composite bush-and-bead elements 22 and the reinforcing elements 20 to the cable. In figure 3 it is shown an example of a diamond wire to which a plastic-coating layer 40 has been applied. Advantageously, the polymer material may have an outer diameter the same as that of the bush, and the reinforcing elements may be completely embedded in the plastic. Since plastic-coating is a method known per se to the person skilled in art, it will not be further described. Advantageously, the injected plastic may form a small tube with a diameter of 5 mm.

Below a number of numerical values are indicated, merely by way of example, for some of the parameters of the invention:

- rope cable diameter: 3.5 mm

- bush length: 12 mm

- inner diameter of bush: 4.0 mm

- outer diameter of bush: 5.0 mm

- outer diameter of bead: 7.3 mm - length of bead: 7 mm; and

- interspace between the bushes: 15 mm

The advantages of the present invention compared to the prior art are therefore clear. Firsdy it has been found that, during practical application, the diamond wire has a longer working life than the diamond wires of the prior art, where the interruption points 18 do not have a specific protection, and a diamond wire where the composite bush-and-bead elements are positioned on these interruption points.

The elasticity of the reinforcing element according to the present invention when following the movements of the diamond wire, for example when passing around the pulleys onto which the wire is wound, allows to gready increase the working life of the diamond wire.

Moreover, the method may be easily implemented also by unskilled personnel and it may be carried out both before and after the steel cable has been joined together.

The main advantage of the invention consists in the strengthening of the interruption points, namely the points where the cut ends of the strands are arranged end-to-end, such as to reduce to a minimum the risk of premature- breakage of the diamond wire.

The person skilled in the art, in order to satisfy specific requirements, may make modifications to the embodiments described above and/ or replace the parts described with equivalent parts, without thereby departing from the scope of the accompanying claims.

For example, solutions (not shown in the accompanying figures) may be envisaged where the reinforcing element is provided on the bush of the composite bush-and-bead element.

Constructional solutions may be envisaged where not all the interruption points are covered with a reinforcing element. Moreover, other solutions may be envisaged where the interruption points of a steel cable are covered with reinforcing elements which are different from each other.