METHOD TO PRODUCE A DIAMOND WIRE FOR USE IN CUTTING STONE MATERIALS, AND DIAMOND WIRE PRODUCED WITH SAID METHOD

Abstract: A method for the manufacturing of diamond wires for the use in cutting stone materials, of the type comprising at least a phase of diamond electrolytic deposit on a metal support acting as a cathode. This metal support, according to the invention, is formed by a spring (2) with close coils, said spring having alternatively electrically insulated sectors (2B) and electrically conductive sectors (2A). The diamond electrolytic deposit is directly formed on the sectors (2A), each one of them constituting a diamond pin. A diamond wire is furthermore described, in which, according to a first embodiment, a spring bearing diamond pin is inserted on a steel wire support and, according to another embodiment, the diamond pins formed on the spring are removed from said spring and directly inserted on the steel wire support.

Description: "METHOD TO PRODUCE A DIAMOND WIRE FOR USE IN CUTTING STONE MATERIALS, AND DIAMOND WIRE PRODUCED WITH SAID METHOD" ***g*** The present invention refers to a method for the production of a diamond wire and of a diamond wire obtained by means of said method, to be used in cutting stone materials It is known, in the extraction technique and/or stone materials working, such as marble for instance, the use of the so called "diamond wires " . A diamond v/ire is made of a supporting steel wire, with high resistance and good flexibility, normally with a diameter of about 5 mm, onto which so called "diamond p ns" are inserted and blocked m a suitable way. Diamond pins are very small iron rolls having diamond grains or chips fixed on their external surface; the technique used to fix the diamond chips on the pins is normally the so called "electrolytic deposit of diamond" , which consists of forming on the pin surface an attack layer of electrolytic nichel, applying on said layer diamond chips and fixing said chips through electrolytic deposit of a further layer or nichel coating on the pm support, said coating incorporating the diamond chips The pins have a diameter of about 10 to 11 mm and are kept reciprocally spaced on the steel wire by the interposition of spring or plastic spacers Diamond wires having the above mentioned sizes are properly used in extraction quarries, but are definitely less indicated if used in sawing plants for transforming the blocks in flat or shaped plates or to work thin or thick plates with fretwork machines. The diamond w re dimension, that is the diameter of the pins, is very important in such types of works: as it can be guessed, the smaller is the diameter of the pins the better is in orαεr to produce reduced quantities of scraps, to cut as sharp as possible, and to absorb the minimum power possible A distinction between the most common diamond wires can be made: - 1) diamond wires of the diameter of 10-11 mm with traditional mounting on a steel wire having a diameter of 5 mm, with spring spacers between the diamons p ns, and with the possibility of an easy lmkinα between various wire sections through special junctions, for example as the ones described in the Italian utility model MI94U 000778 m the name of the same Applicant, opened to public on May 1996, they can be covered in rubber or plastic and their use is mainly for quarries, - 2) diamond wires as the previous ones, with the difference that they are shaped in a long ring of about 20 metres and the j unctior is preferably obtained by splicing the steel wire strands, they are normally coateα lr. rubber or plastic and are used in stationary machines to square blocks, 3) diamond wires like the previous ones but of smaller dimensions (diameter of the pins 8-9 mm, diameter of the steel wire 4 mm., closed in rings normally of a length not exceeding about 15 m.) ; they are normally used in shaping machines; - 4) diamond wires similar to the previous ones, but with «»ven smaller dimensions (diameter of the pins 6-7 mm and diameter of the steel wire 3 mr equally ring shaped, and of a length not exceeding 4m ) , they are normally used for fretwork machines It is convenient that the diamond wires described at points 2) , 3) and 4) are coated with rubber or plastic, so as to assure a longer ]ιfe to the ciamond wire structure and a greater safety Furthermore it would be preferable that, in such cases, there are not unctions, which always represent a critical point, but that the r ng shaped structure - produced with the method of progressive splicing of the various strands composing the steel wire - is completed before its coating with rubber or plastic Furtnermore, it is common that diamond pins used to produce plastic coated wires are bored and threaded in order to guarantee that they are axially clocked after having applied a rubber or plastic coating On the other hand it would be better that the types of wires described in particular at points 3) and 4) are coated with rubber or plastic, so that to allow the cutting of abrasive materials, such as sandstones for example; that they are ring shaped through progressive splicing; and that the pins dimensions are as little as possible. The attempts in order to reduce the diameter of the diamond pins and consequently also the diameter of the supporting steel wires, up to now have not given the desired results, mainly for manufacturing reasons. It is moreover opportune to add, to this purpose, that all diamond wires are used after having been ring shaped. The closing of a wire in a ring can be made in two ways: by an easily separable junction or by progressive splicing. The junction method - which can be used either in wires with traditional mounting with springs or spacers, or in wires with plastic or rubber mounting - require nevertheless that the difference between the diameter of the pin and the diameter of the steel wire is large enough to include the junction; therefore the junction will be usually applicable in diamond wires of greater diameter. The progressive splicing method, on the contrary, can be used only in diamond wires coated with rubber or plastic, where the closed ring of diamond wire do not need to be reopened in order to carry out the cutting. It is therefore clear that, as the dimensional constraint of the junction does not exist, the diameter of the diamond pins can be reduced considerably, for the same dimensions of the steel wire. Nevertheless there is a limitation also in this case, due to the type of the manufacturing method presently used. In fact the diamond pins are produced from a steel bar by working on automatic lathe both the profile or external dimensions and the threaded axial bore. As already said, the threaded bore is necessary in order to ensure the blocking of the diamond pins on the supporting steel wire through the rubber coating injected onto the wire after the mounting of the diamond pins. As the aim is that to produce very thin diamond wires, it is clear that it has to be reduced at the minimum both the steel wire diameter and, consequently, the external diameter of the steel support pin, which will become a diamond pin after the electrolytic deposit of diamond There is a limit of workability with the automatic lathe m relation to the dimensions of the external diameter of the steel pm and the internal bore and thread, owing to which it is not possible to descend under certain values, and, in the second place, there is also a great difficulty in the preparation and realization of the diamond electrolytic deposit on very small pins A first object of the present invention is therefore to propose a method to realize, in a more economically and simply way, a diamond wire with a diameter considerably smaller than the ones of the existing wires at present on the market A further object cf the present invention is to propose an l moroved diamond wire, with a considerably reduced diameter, obtained bv said method. These objects can be reached through the characteristics mentioned in claims 1) and 22) or 24) The present invention is now described in further detail, making reference to some preferred embodiments thereof, illustrated m the accompanying drawings, m which: fig. 1 illustrates, partially m section, an initial phase of the diamond wire production method, using a spring with close coils as metal support for tne production of diamond pins according to the presen t invention; fig. 2 illustrates a second phase, wherein the spring support is divided in different sectors; fig. 3 illustrates a third phase, wherein a layer of electrolytic deposit is formed on the spring support, fig. 4 illustrates a fourth phase wherein the formation of the electrolytic deposit produce the fixing of the diamond chips onto the spring support, fig 5 illustrates the end phase of the electrolytic deposit formation incorporating the diamond chips, fig. 6 illustrates a phase wherein the insulating protection is removed from the insulated sectors of the spring support; fig illustrates a phase wherein the spring support is sub j ected to a traction beyond the elasticity limit of the spring itself, and fig. 8 illustrates a phase wherein two spring support sections obtained according to the present invention, are joined together. As illustrated m the drawings and according to the mam characteristic of the method of the present invention, a steel spring 2 with close coils is used as a support for the diamond electrolytic deposit . Before proceeding to the electrolytic deposit of the diamond layer, the surface of tne spring 2 is divided into several side-by-side sectors alternately electroconductors and insulated In order to form the insulated sectors it is necessary to proceed very simply, and according to an aspect of the present invention, to apply insulating bands at regular intervals onto the spring support: by way of example some strips 3 of very plastic insulating tape may be used, which perfectly adhere to the spring support surface. Some electroconductive sections 2A are thus defined, where the diamond electrolytic deposit will be formed, alternately to sections 2B covered by strips 3 (fig. 2) and therefore inert from the point of view of the phenomenon of electrolytic deposit The same result could be achieved by applying little elastic rings to the spring support, placed at regular intervals. The spring support 2 - possibly mounted onto a little rod 1 forming a temporary supporting electric conductor - is immersed in a bath of nichel salts, and electrically linked to a device for electrolytic deposit (not shown) so as to act as a cathod Then a first phase of cathod reduction starts, with deposit of a nichel base layer on the surface sectors 2A (see fig. 3) This base layer adheres to the spring 2 retaining firmly close the coils wherein sucn adhesion occurs. The spring 2 is then immersed m another nichel bath containing also the diamond chips. A second nichel layer is then formed on the base layer, which incorporates the diamond chips leaning on the base layer, so as to form a true diamond pin 5 (fig. 4) . In order to finish the formation of the diamond p n 5, the spring 2 is immersed again m the electrolytic bath containing nichel salts, and a further superficial nichel layer is formed onto the diamond pins 5, which completes the incorporation of the diamond chips (fig. 5) fixing them tightly to the spring support. Only by way of example, tests were made with a supporting steel wire having a diameter of 1,5 mm onto which a spring 2 had been inserted, said spring having, at close coils, an external diameter of 2 mrr Advantageously , the spring 2 was formed by a steel wire having a section of 0 2 mm of diameter wounα in spirals with close coils naving an external diameter of 2 mm and an internal diameter of 1,6 mm, where a steel supporting wire can be passed through, which, as already said, has a diameter of 1,5 mm. For carrying out the electrolytic method of the invention short section of said support spring 2 are used, for example sections having a length of about 50 cm. A first nichel layer is applied on spaced sectors of the external surface of each section, by electrolytic deposit, said layer having a thickness of 0,1 mm., this first layer forms a support base for a further diamond layer of 0,3 - 0,4 mm, using a fairly large granulometry of αiamonα powαer Therefore altogether a layer of 0,4 - 0,5 mm is formed, to reacn a final diameter of said diamond wire of 2,8 - 3 , 0 mm Using smaller granulometry it might be possible to have even more reαuced final diameters. As illustrated in fig 6, at the end of the electrolytic deposit of diamond, the insulating strips 3 are removed, so that the corresponding inert sectors leave some coils uncovered, obtaining in this way spacers 6 between the single diamond pins 5. The next seep of the method (fig 7) is to subject said spring 2 to a traction beyond its elastic limit In this way, the spring 2 is permanently strained in correspondence to the sections 2B, thus rorming open coils and increasing considerably its initial length, for example up to 120-150 cm. starting from sections of 50 cm. The coils in the sections 2B, being no longer close, constitute then, as already said, classic spacers 6 of the damping type. The spring sections 2 so formed are then inserted on the supporting steel wire, furthermore the end parts of each of said spring section 2, after being mounted on the steel wire, can be jointed at the end parts of contiguous spring sections by simply screwing, as shown m fig. 8, in order to obtain a continuous diamond wire of any desired length The whole diamond wire is then slightly axially compressed, so that the spaced spring coils may produce the forseen damping action Then, firs t of all, the splicing of tne steel strand is performed, in this compressed condition of the diamond wire, the splicing blocking the spring sections and the diamonc pins m the diamond wire; at the end also the coating with rubber or plastic is made. In this way a continuous ring of diamond wire s obtained, said ring having the desired length and an extremely reduced transversal section. According to an alternative, very interesting embodiment, it is possible to further reduce the transversal section of the diamond wire: to this purpose a spring 2 is used, having a diameter smaller than requested in relation to the diameter of the steel wire l on which diamonds pins are to be mounted. This smaller spring 2 is used only as temporary support in the phase of formation of the diamond pins through electrolytic deposit, therefore giving up to insert it onto the supporting wire The method remains identical to the one already described, apart from the fact that, once removed the strips 3 of insulating tape, the diamond pins 5 are removed from the same spring 2 unscrewing them from this latter; it is possible to remove said p ns 5 from the spring 2, by an unscrewing action, if the surface of the spring 2, before applying the nickel layer, had been treated with a product inhibiting tne adesion, for exemple with silicon resin. Alternatively, and more simply, it is possibile to subject the spring 2 to traction until total deformation, that is up to reduce it to an extended wire , on which the single diamond pins remain freely inserted. These diamond pins, as they were formed onto the coils of the spring 2, have an internal threaded bore; so when, in a next phase (not shown in the drawings) said pins 5 are inserted on the steel wire l , interposing a spacer of a known type between one and the other, and the coating with rubber or plastic is performed, the rubber penetrates into the thread and achieves a safe blockage of the pins 5 directly on the wire 1. In th s way it is possible to obtain a diamond wire even thinner m respect to tne previous one, overcoming all the inconveniences of the prior art In tests performed with the diamond wire according t o this alternative emoodiment it was possible to use a smaller spring, having an outer diameter of 1,8 mm., the diamond pins had thus an inner diameter of about 1,6 mm and an outer diameter of 2,6 to 2,8 mm. The diamond wire according to the present invention has many advantages, among which a considerable reduction of the power requested for driving the wire, at the same cutting speed, with remarkable saving of energy and plant costs. It is also possible to obtain a cutting speed much greater than the one at present obtainable with the diamond wires of the prior art Furthermore, the dimensions of the diamond wire, much smaller than the wires of the prior art, allows a very reduced production of scraps. A thin diamond wire according to the invenetion is particularly suitable to be used for fretworks, wnere there is the necessity to obtain very small bend radiuses.

Claims: CLAIMS 1) Method to produce diamond wire for use in cutting stone mate ¬ rials, of the type comprising at least a step of diamond electrolytic de ¬ posit on a metal support acting as a cathod , characterized in that, said metal support consists of a spring (2) with close coils, which alternately comprises electrically conductive sectors (2A) and electrically insu ¬ lated sectors (3) . 2) Method as in claim 1), wherein said diamond electrolytic deposit is formed by depositing a first metal layer on the close coils of the spring (2), acting as a support base for a further layer incorporating the diamond chips 3) Method as n claim 2) , wherein said first metal layer has a thickness of at least 0,1 mm. 4) Method as in claim 2) or 3), wherein said diamond layer has a thickness from 0,2 to 0,4 mm. 5) Method as in any one of the previous claims, wherein said electrically insulated sectors are obtained by applying, at regular intervals, a superficial electric insulation (3) on cylindrical sectors of the spring (2) . 6) Method as in claim 5), wherein said insulated cylindrical sectors are obtained by applying, at regular intervals, ring-shaped strips of insulating tape (3) . 7) Method as in claim 5), wherein said insulated cylindrical sectors are obtained by applying, at regular intervals, elastic rings. 8) Method as in any one of the previous claims, wherein, at the end of the method of electrolytic deposit, the insulation (3) is removed from said electrically insulated sectors of the spring (2), leaving the electrolytic diamond deposit untouched m the non-insulated sectors where it forms a diamond pin (5) 9) Method as in any one of the previous claims, wherein, at the end of the method of electrolytic deposit, the spring is stretched beyond its limit of elasticity so as to create, in correspondence of the insulated sectors on which said deposit has not been formed, damping spacing elements (6) between the single diamond pins (5) formed on the non insulated sectors. 10) Method as in any one of the previous claims, wherein the dia ¬ mond electrolytic deposit is formed onto lengths of the spring (2), apt to be inserted in sequence onto a supporting steel wire (l) . 11) Method as m claim 10) , wherein said spring lengths are about 50 cm long 12) Method as in claims 9) and 11) , wherein, after stretching of the spring, said lengths are about 120 to 150 cm long 13) Method as in claims 7) , 8) or 11) , wnerem said spring lengths are joined together by screwing their respective ends one into the other. 14) Method as m any one of the previous claims, wherein said spring (2) has the following dimensions: diameter of the spring wire section 0,2 mm, outside diameter of the spring coils 2 mm, inside diameter of the spring coils 1,6 mm. 15) Method as in claims 10) and 14) , wherein said supporting steel wire (1) has a diameter of about 1,5 mm. 16) Method as in any one of claims l) to 8), wherein said spring (2) is used only as a temporary support, in the step of diamond electrolytic deposit, and wherein the diamond pins (5) are removed from said spring (2) at the end of the method of electrolytic deposit, said pins being then inserted and blocked directly onto a supporting steel wire (1) . 17) Method as in claim 16) , wherein said diamond pins (5) are removed by unscrewing them fron said spring (2) . IB) Method as in claim 15) or 16), wherein said diamond pins (5) are removed by totally deforming the spring and reducing it into a sub- stantially outstretched steel wire. 19) Method as in any one of claims 16) to 18) , wherein said diamond pins (5) are mounted on the supporting steel wire, mutually parted by spacing elements consisting of steel springs and/or of elements of elastomeric material. 20) Method as in any one of claims 16) to 19), wherein said soring (2) has the following dimensions: diameter of the spring wire section 0,2 mm; outside diameter of the spring coils 1,8 mm; inside diameter of the spring coils 1,4 mm. 21) Method as in claim 20) , wherein said supporting steel wire has a diameter of 1,5 mm. 22) Diamond wire, of the type comprising diamond pins (5) obtained by diamond electrolytic deposit onto a metal support and fixed at regular intervals onto a supporting steel wire (1) , characterized in that said support consists of a substantially continuous spring (2), and in tha t said diamond pms (5) are directly formed by electrolytic deposit onto mutually spaced close coil sectors of said spring (2) . 23) Diamond wire as in claim 22), wherein the coils of said spring (2) free of diamond electrolytic deposit and interposed between said mutually spaced coil sectors are apt to form, in their outstretched condition, damping spacing elements (6) between the single diamond pins (5) . 24) Diamond wire, of the type comprising diamond pins (5) obtained by diamond electrolytic deposit onto a metal support and fixed at regular intervals onto a supporting steel wire (1), characterized in that said support consists of a first layer of electrolytic deposit, forming the base for the diamond pins, and in that said diamond pins (5) are directly inserted and blocked onto the supporting steel wire (l) . 25) Diamond wire as in claim 24), wherein the diamond pins (5) are mutually parted by spacing elements consisting of steel springs and/or of elements of elastomeric material.

Inventors: BERNIERI PAOLO, BERNIERI, PAOLO
Applicants: BERNIERI PAOLO, DIAMOND PAUBER SRL, BERNIERI, PAOLO, DIAMOND PAUBER S.R.L.
Application year: 1997
Main classification: C25D7
IPC codes: B23D61, C25D5, C25D7, C25D15