CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from Italian patent application no. 102018000003967 filed on 26/03/2018, the entire disclosure of which is incorporated herein by reference .

TECHNICAL FIELD

The present invention relates to a diamond wire for cutting stone-like material and to the corresponding production method .

BACKGROUND ART

As is known, most of the diamond wires for cutting stone-like material currently available on the market are basically made up of a central multi-strand metal cable; of a series of substantially cylindrical, tubular-shaped diamond beads, which are fitted onto the metal cable at a given and constant distance one from the other; and of an outer tubular sheath made of polymeric material, which completely encases/covers the metal cable interposing itself between the metal cable and the single diamond beads so as to prevent direct contact between the diamond beads and the metal cable and, at same time, block the individual diamond beads firmly on the metal cable .

DISCLOSURE OF INVENTION

Aim of the present invention is to extend the lifetime and thus the productivity of the diamond wires for cutting stone like material currently on the market, without an excessive increase in production costs of the diamond wire.

In compliance with these aims, according to the present invention there is provided a diamond wire for cutting stone- like material as defined in Claim 1 and preferably, though not necessarily, in any one of the claims dependent thereon.

Moreover, according to the present invention there is provided a production method of a diamond wire for cutting stone-like material as defined in Claim 12 and preferably, though not necessarily, in any one of the claims dependent thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting example of embodiment, wherein:

- Figure 1 is a schematic side view of a diamond wire for cutting stone-like material realized according to the teachings of the present invention;

- Figures 2 to 7 schematically depict as many steps of the production method of the diamond wire shown in Figure 1;

Figure 8 is a schematic side view of an alternative embodiment of the diamond wire shown in Figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to Figure 1, number 1 denotes as a whole a diamond wire for cutting stone-like material, that can advantageously be used for cutting marble and granite. In addition, diamond wire 1 can advantageously be also used for cutting walls and/or brick items, reinforced-concrete items and the like.

The diamond wire 1 comprises: a central supporting cable 2 of given length, flexible and preferably made of metal material, which is arranged in a closed loop in known manner and preferably has a multi-strand structure; a series of substantially cylindrical, tubular-shaped abrasive beads 3 that are fitted on the supporting cable 2 spaced one after the other, and are externally made of an abrasive material capable of carving/cutting the stone-like material; and an outer tubular sheath 4 made of polymeric material, which is made by injection moulding directly over the supporting cable 2, and substantially completely encases/covers the supporting cable 2 also interposing itself between the supporting cable 2 and the individual abrasive beads 3, so as to block the abrasive beads 3 in rigid manner on the supporting cable 2.

In other words, the tubular sheath 4 has an outer diameter di greater than the nominal diameter d ₂ of the supporting cable 2, so as to cover and protect the supporting cable 2 substantially for its entire length.

The abrasive beads 3, on the other hand, are fitted onto the supporting cable 2 so as to emerge/protrude outside of tubular sheath 4.

More in detail, the abrasive beads 3 have an inner diameter d3 slightly greater than the nominal diameter d ₂ of supporting cable 2, and are kept locally coaxial and rigidly integral to the supporting cable 2 by the outer sheath 4 that fills up the space/gap between the two components. Preferably, the maximum outer diameter of abrasive beads 3 is moreover greater than the outer diameter di of tubular sheath 4.

Naturally, the outer tubular sheath 4 can also be made by casting moulding directly over the supporting cable 2, i.e. it can be made by moulding directly over the supporting cable 2 via inj ecting/introducing the liquid plastic material into the mould with a pressure equal to the ambient pressure.

With reference to Figure 1, in the example shown, in particular, the supporting cable 2 is preferably made of steel, and is preferably formed by five or more strands suitably helically wound and twisted together.

Moreover, the supporting cable 2 has a nominal diameter d ₂ preferably less than 8 mm (millimetres), and preferably, though not necessarily, ranging between 1 and 5 mm (milli metres) . Preferably, the difference between the nominal diameter d ₂ of supporting cable 2 and the inner diameter d ₃ of abrasive beads 3 moreover ranges between 0,1 and 0,7 mm (millimetres) .

Preferably, the abrasive beads 3 are moreover distributed on supporting cable 2 with a substantially constant pitch p which is preferably also greater than or equal to 2,5 cm (centi metres) .

In other words, the abrasive beads 3 are preferably distributed/spaced in substantially uniform/regular manner substantially along the whole length of supporting cable 2.

Therefore, the abrasive beads 3 delimit/identify, on supporting cable 2, a series of bare longitudinal sections preferably having all substantially the same length.

Naturally, the pitch p of the abrasive beads 3 on supporting cable 2 may also vary along the length of supporting cable 2.

With reference to Figure 1, in addition each abrasive bead 3 preferably comprises: a tubular supporting sleeve 7, preferably substantially cylindrical tubular-shaped, which is preferably made of metal material and is fitted directly onto the tubular sheath 4, locally coaxial to the longitudinal axis of supporting cable 2; and a substantially cylindrical tubular-shaped bushing 8 which is made of an abrasive material and is fitted/fixed in unmovable manner directly on the sleeve 7.

Preferably, the bushing 8 additionally has an axial length less than the axial length of supporting sleeve 7, and is preferably located substantially at centre of the sleeve 7. Preferably, the outer diameter of sleeve 7 is moreover smaller than the outer diameter di of tubular sheath 4, so that sleeve 7 can be locally embedded into tubular sheath 4.

In the example shown, in particular, the axial length of sleeve 7 is preferably less than 1,2 cm (centimetres) . Moreover, the difference between the inner diameter d ₃ of supporting sleeve 7 and the nominal diameter d ₂ of supporting cable 2 preferably ranges between 0,1 and 0,2 mm (millimetres) .

In addition, supporting sleeve 7 is preferably made of steel or bronze, and is preferably also provided with an internal thread adapted to dig/sink into the tubular sheath 4 to increase the grip of abrasive bead 3 on tubular sheath 4.

The bushing 8, on the other hand, is preferably made of an abrasive material comprising diamond grains.

More in detail, the bushing 8 is preferably made of a sintered composite material incorporating synthetic diamond grains, and is fixed in unmovable manner on supporting sleeve 7 preferably by means of brazing.

In other words, the abrasive beads 3 are externally made of sintered diamond.

With reference to Figure 1, the tubular sheath 4, in turn, is longitudinally divided into a succession of tubular segments comprising first and second tubular segments, which alternate one with the other substantially for the entire length of the supporting cable 2, and are made by injection moulding in two distinct/different polymeric materials that differ one from the other by polymer composition and/or density and/or hardness and/or elastic modulus. Preferably, said first and second tubular segments of tubular sheath 4 are moreover consecutive and contiguous to one another.

The first tubular segments, hereinafter denoted with number

10, encase/cover the sections of supporting cable 2 immediately underneath the individual abrasive beads 3, and are adapted to each block the corresponding abrasive bead 3 in rigid manner on supporting cable 2.

The second tubular segments, hereinafter denoted with number

11, instead encase/cover the sections of supporting cable 2 which extend between two consecutive abrasive beads 3.

The tubular segments 10 and 11 of tubular sheath 4 thus have an axial length less than the pitch p of the abrasive beads 3 on supporting cable 2.

Naturally, the tubular segments 10 and 11 of outer tubular sheath 4 may also be made by casting moulding directly over the supporting cable 2, i.e. they can be made by moulding directly over the supporting cable 2 via inj ecting/introducing the liquid plastic material into the mould with a pressure equal to the ambient pressure.

Preferably, at the two axial ends, the tubular segments 10 and 11 additionally have substantially the same outer diameter so as to join to one another seamlessly.

More in detail, at least one/each tubular segment 10 preferably has an axial length fio slightly greater than the axial length of the corresponding abrasive bead 3.

Naturally, the axial length fio of tubular segment 10 could also be substantially equal to that of the corresponding abrasive bead 3. Preferably, at least one/each tubular segment 10 is moreover centred on the abrasive bead 3 immediately above. In other words, the abrasive beads 3 are preferably arranged substantially at the centre of the corresponding first tubular segments 10 of tubular sheath 4.

Preferably at least one/each tubular segment 10 is thus dimensioned so as to include the sleeve 7 of the corresponding abrasive bead 3.

In the example shown, in particular, the axial length fio of tubular segment 10 preferably ranges between 105% and 170% of the axial length of the corresponding abrasive bead 3, or rather of the supporting sleeve 7 of the corresponding abrasive bead 3.

Each tubular segment 11, on the other hand, has an axial length i complementary to the axial length fio of the immediately adjacent tubular segment 10, and thus preferably slightly less than the axial length of the section of supporting cable 2 that extends between the two abrasive beads 3 immediately adjacent to the same tubular segment 11.

More in detail, the/each tubular segment 11 preferably has an axial length i equal to the difference between the pitch p of the abrasive beads 3 on supporting cable 2 and the axial length £io of tubular segment 10.

Preferably, the tubular segments 10 and/or 11 are moreover made of a thermoplastic polymeric material. More in detail, the tubular segments 10 and/or 11 are preferably made of thermoplastic elastomers (TPE) .

In the example shown, in particular, the tubular segments 11 of outer tubular sheath 4 are preferably made of a polyurethane-based polymeric material. More in detail, the tubular segments 11 of outer tubular sheath 4 are preferably made of thermoplastic polyurethane (TPU) or another similar polymeric material.

Instead, the tubular segments 10 of outer tubular sheath 4 are made of a second polymeric material which preferably has an elastic modulus higher than that of the polymeric material with which the tubular segments 11 are made, and optionally also a hardness greater than that of the polymeric material with which the tubular segments 11 are made.

Preferably, the second polymeric material additionally has a density greater than that of the polymeric material with which the tubular segments 11 are made.

More in detail, the tubular segments 10 of outer tubular sheath 4 are preferably made of a polyamide-based (PA) polymeric material, of a polypropylene-based (PP) polymeric material or other similar polymeric material.

In the example shown, in particular, the tubular segments 10 of outer tubular sheath 4 are preferably made of Nylon.

Alternatively, the tubular segments 10 of outer tubular sheath 4 could also be made of polyamide PA66 or of polyamide PA12 or of a blend of polyamide PA66 and polyamide PA12.

In addition, the tubular segments 10 of outer tubular sheath 4 could also be made of polyether-ether-ketone (PEEK) .

Preferably, though not necessarily, the polymeric material which the tubular segments 10 and/or 11 of tubular sheath 4 are made of can be filled with carbon nanoparticles. Preferably the carbon nanoparticles are additionally graphene particles and/or carbon nanotubes. In addition or alternatively to the carbon nanoparticles, the polymeric material which the tubular segments 10 and/or 11 of tubular sheath 4 are made of can be filled with glass fibre, talc (magnesium phyllosilicate ) or similar.

Operation of diamond wire 1 is similar to that of currently known diamond wires and does not require further explanations.

With reference to Figures 2 to 7, the production method of diamond wire 1 basically comprises, in sequence, the steps of:

- distributing the abrasive beads 3 on the supporting cable 2 according to the predetermined spacing/pitch p;

- injection moulding the tubular segments 10 of outer tubular sheath 4 directly over the supporting cable 2 using a first polymeric material, so as to cover the sections of supporting cable 2 located at the abrasive beads 3 and to simultaneously block the individual abrasive beads 3 firmly on supporting cable 2; and then

- injection moulding the tubular segments 11 of outer tubular sheath 4 directly over the supporting cable 2 using a second polymeric material different from the first polymeric material, preferably so as to cover the remaining part of the supporting cable 2.

Therefore, the tubular segments 11 of outer tubular sheath 4 are overmoulded on the tubular segments 10.

Naturally, the tubular segments 10 and 11 of outer tubular sheath 4 can also be made by casting moulding directly over the supporting cable 2.

Preferably, before distributing the abrasive beads 3 on supporting cable 2 according to the predetermined spacing/ pitch p, the production method of diamond wire 1 moreover comprises, in sequence, the steps of: - threading a predetermined number of abrasive beads 3 onto the supporting cable 2; and then

- joining the two ends of supporting cable 2 preferably by suitably twisting the strands which form the supporting cable 2, so as to form a closed loop.

Preferably, before the injection moulding of tubular segments 10 and/or of tubular segments 11, the production method of diamond wire 1 additionally comprises the step of tensioning the portion of supporting cable 2 where the tubular segments 10 and/or 11 of tubular sheath 4 are to be injected moulded.

More in detail, with reference to Figures 2, 3 and 4, injection moulding of the tubular segments 10 of outer tubular sheath 4 preferably comprises, in sequence, the steps of:

- inserting a section of supporting cable 2 of given length and such as to support at least one, and preferably a plurality, of abrasive beads 3 (for example, a segment of 50 cm in length), into a first mould for injection moulding 100 which is provided with a rectilinear through cavity that copies in negative the shape of the section of supporting cable 2, with the addition of the abrasive bead or beads 3 present on supporting cable 2 and of the tubular segment or segments 10 of tubular sheath 4 to be produced on the same section of the supporting cable 2;

- inj ecting/introducing a first polymeric material into the through cavity of mould 100, so that the polymeric material can completely fill the empty space inside the through cavity, forming, on said section of supporting cable 2, the tubular segments 10 of tubular sheath 4; and then

- extracting from the mould 100 said section of supporting cable 2 together with the abrasive bead or beads 3 and with the tubular segment or segments 10 that block the abrasive bead or beads 3 on supporting cable 2. Preferably, before inserting the aforesaid section of supporting cable 2 into the mould for injection moulding 100, the production method of diamond wire 1 additionally comprises the step of tensioning said section of supporting cable 2 so as to straighten and maintain substantially rectilinear the same section of supporting cable 2.

Preferably, the plastic material injected into the mould 100 is moreover a Nylon.

Alternatively, the plastic material injected into the mould 100 could also be a polyamide-based (PA) polymeric material, a polypropylene-based (PP) polymeric material, or a polyether ether ketone (PEEK) .

With reference to Figure 5, 6 and 7, immediately after having extracted from the mould 100 the section of supporting cable 2 with the abrasive bead or beads 3 and the relative tubular segment or segments 10, the production method of diamond wire 1 preferably comprises, in sequence, the steps of:

- inserting the section of supporting cable 2 together with the abrasive bead(s) 3 and with the relative tubular segment or segments 10 into a second mould for injection moulding 200 which is provided with a rectilinear through cavity that copies in negative the shape of the section of supporting cable 2, with the addition of the abrasive bead or beads 3 present on supporting cable 2 and of the whole portion of the tubular sheath 4 to be produced on the same section of supporting cable 2;

- inj ecting/introducing a second polymeric material into the through cavity of mould 200, so that the polymeric material can completely fill the empty space inside the through cavity, forming, on said section of supporting cable 2, the tubular segments 11 of tubular sheath 4; and finally

- extracting the resulting segment of diamond wire 1 from mould 200.

Naturally, the second mould 200 can have some parts in common with the first mould 100.

Preferably, before inserting the aforesaid section of supporting cable 2 into the second mould for injection moulding 200, the production method of diamond wire 1 additionally comprises the step of tensioning said section of supporting cable 2 so as to straighten and maintain substantially rectilinear the same section of the supporting cable 2 .

Preferably, the plastic material injected into mould 200 is moreover a polyurethane-based polymeric material. More in detail, the plastic material injected into the mould 200 is preferably a thermoplastic polyurethane (TPU) or other similar polymeric material.

The diamond wire 1 described above offers numerous advantages.

Experimental tests have shown that the particular structure of the outer tubular sheath 4 allows to block in a more efficient manner the abrasive beads 3 over the supporting cable 2, thereby significantly extending the lifetime and, thus, the productivity of the tool.

Furthermore, the alternation of the two different plastic materials on the outer tubular sheath 4 allows to change locally the flexibility of the diamond wire 1, significantly increasing the tensile strength and the fatigue resistance of the diamond wire 1.

Finally, it is clear that modifications and variants can be made to the production method described above without however departing from the scope of the present invention. For example, each abrasive bead 3 could consist solely of the bushing 8 made of abrasive material.

Moreover, in a less sophisticated and non-shown embodiment, the tubular segments 10 of tubular sheath 4 could be made of a "high modulus polyurethane", i.e. of a thermoplastic poly urethane (TPU) with an elastic modulus greater than 800 N/mm ² and, in any case, greater than that of the thermoplastic polyurethane (TPU) with which the tubular segments 11 of outer tubular sheath 4 are produced. More in detail, in the example shown the "high modulus polyurethane" preferably has an elastic modulus equal to around 1500 MPa.

Finally, with reference to Figure 8, in a more sophisticated embodiment the tubular sheath 4 comprises, in addition to the tubular segments 10 and 11, also third/further tubular segments 12 which are produced via injection moulding (or casting moulding) directly over the supporting cable 2, so as to encase/cover only the central portions of the individual bare longitudinal sections of supporting cable 2, i.e. the sections of supporting cable 2 extending between two consecutive abrasive beads 3, and are therefore immediately adjacent to the tubular segments 11 of tubular sheath 4.

In other words, in this embodiment, the tubular segments 11 of tubular sheath 4 are interposed between the tubular segments 10 of tubular sheath 4 and the tubular segments 12.

The tubular segments 12 of tubular sheath 4 are moreover made of a polymeric material that differs from the polymeric material forming the tubular segments 11 by polymer composi tion and/or density and/or hardness and/or elastic modulus.

More in detail, in the example shown the tubular segments 12 of tubular sheath 4 are preferably made of the same polymeric material that forms the tubular segments 10.

Preferably, though not necessarily, the axial length i of the tubular segments 12 of tubular sheath 4 is moreover substantially equal to the axial length i of the tubular segments 11 immediately adjacent.