ROLLER FOR HOT ROLLING OF WIRE RODS AND THE LIKE, AND WIRE-ROD AND THE LIKE, HOT-ROLLING MACHINE PROVIDED WITH SAID ROLLER

Abstract

A wire-rod and the like, hot-rolling machine wherein the two rollers are fitted on respective frustoconical end portions of as many counter-rotating supporting shafts, via interposition of corresponding centering and coupling bushings having a frustoconical internal profile, each of which is fitted on the end portion of a respective supporting shaft, between the supporting shaft and the corresponding roller, and is structured so as to mesh on the supporting shaft so as to be angularly integral to said supporting shaft, and so as to be inserted/wedged between the supporting shaft and the roller thus to center the roller on the supporting shaft and moreover make the roller angularly integral to the body of the supporting shaft. Each centering and coupling bushing is provided with an annular flange having an eccentric lobe-shaped profile and which cantilevered projects from the outer surface of the bushing, at one of the two mouths of the central through hole of the roller, and is designed to engage a corresponding annular groove with eccentric lobe-shaped profile which is formed on the body of the roller at the mouth of the roller central through hole, and has a shape complementary to that of the annular flange.

Description

TECHNICAL FIELD

The present invention relates to a roller for hot rolling of wire rods and the like and to a wire-rod and the like, hot-rolling machine provided with said roller.

More in detail, the present invention relates to a roller for hot rolling of concrete reinforcing bars and to a machine for hot rolling of concrete reinforcing bars. Use to which the following description will make explicit reference, without this implying any loss of generality.

BACKGROUND ART

As is known, concrete reinforcing bars are obtained by subjecting a steel wire rod with a roughly circular cross section to a hot-rolling process that causes a progressive reduction of the nominal section of the wire rod.

The hot-rolling lines that are used for carrying out this particular metallurgical process are usually formed by a fair number of rolling machines, traditionally called “rolling stands”, which are arranged in succession one after the other along the wire-rod feeding path so that each rolling machine is able to cause a slight reduction of the nominal cross section of the wire rod while the latter advances along the rolling line.

More in detail, each rolling machine is provided with: two opposed and counter-rotating rollers, which are arranged in specular positions on opposite sides of the wire-rod feeding path, parallel and slightly spaced apart to one another so as to delimit in between themselves a slot through which the wire rod to be hot-rolled is forced to pass; and a big electric or hydraulic motor able to drive the two rollers in rotation about their respective longitudinal reference axes at the same speed of rotation.

Obviously, the width of the slot, i.e. the minimum distance between the peripheral surfaces of the rollers, progressively reduces along the wire-rod feeding path so that each pair of rollers is able to deform and draw out the wire rod causing a slight reduction of the nominal section thereof.

In more recent rolling machines, in particular, the two rollers are rigidly fitted on the ends of two counter-rotating supporting shafts that are arranged in specular positions on opposite sides of the wire-rod feeding path, locally substantially perpendicular to the feeding path itself, and are connected to the electric or hydraulic motor via a gear train that enables the motor to drive the two supporting shafts in rotation in mutually opposite directions, with identical angular velocities.

To be able to withstand the mechanical and thermal stresses typical of a hot-rolling process, each roller instead usually consists of a cylindrical-shaped monolithic block of tungsten carbide, which is provided with a large central through hole dimensioned to enable the fitting/insertion of the roller on the end of the corresponding supporting shaft.

Unfortunately, the tungsten carbide that is used for making the rollers is a very hard material resistant to abrasion, but is also extremely brittle, so that the roller cannot be rigidly fitted on the supporting shaft via blocking pins, meshing between toothed sectors, or other systems of interference fit, because use of these fitting systems would cause, during normal operation of the machine, formation of small crackings in the material that rapidly lead to breaking-up of the roller.

For this reason, in stands currently available on the market, fitting of the roller on the end of the supporting shaft is obtained by friction by interposing between the roller and the supporting shaft a centring and coupling bushing having a frustoconical internal profile and which is structured so as to mesh on a toothed rim formed on the body of the supporting shaft and simultaneously be force fitted/driven between the roller and a frustoconical portion of the supporting shaft so as to grip against the inner surface of the roller thus to keep the monolithic block of tungsten carbide angularly integral to the body of the supporting shaft.

Given that any sliding between the roller and the coupling bushing could lead to the break of the roller, in order to prevent any sliding between the roller and the blocking bushing, the centring and coupling bushing is moreover pressed/forced against the roller by a pack of suitably pre-loaded cup springs, which are fitted on the supporting shaft so as to be interposed between the annular rim of the centring bushing that protrudes from the hole of the roller and a big locknut that, in turn, is screwed directly on the end of the supporting shaft, beside the roller.

Obviously, by varying the distance between the bushing and the locknut it is possible to adjust the pre-load of the cup springs, and hence the force applied on the centring and coupling bushing.

Unfortunately, the torque that is normally transmitted by the supporting shaft to the roller has very high values so that the cup springs must exert on the centring and coupling bushing an extremely high axial thrust. Axial thrust that obviously must be countered by the locknut, with all the problems that this entails.

In rolling machines currently available on the market, in fact, the tightening torque that must be applied to the locknut can reach 40.000 kgm, a value that can be reached only by screwing the locknut on the end portion of the supporting shaft with the aid of large hydraulic torque wrenches which, due to their weight and size, must be handled with extreme care. Consequently, the periodic replacement of the rollers of an entire hot-rolling line becomes a particularly long and laborious operation that causes long machine downtimes, and has a significant incidence upon the costs of production of concrete reinforcing bars.

DISCLOSURE OF INVENTION

Aim of the present invention is to drastically reduce the times for roller replacement so as to increase the hour productivity of the hot-rolling line.

In compliance with the above aims, according to the present invention there is provided a wire rods and the like, hot-rolling machine as defined in Claim 1 and preferably, though not necessarily, in any one of the claims depending thereon.

Moreover according to the present invention there is provided a roller for hot rolling of wire rods and the like as defined in Claim 14 and preferably, though not necessarily, in any one of the claims depending thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described with reference to the annexed drawings, which illustrate a non-limiting example of embodiment thereof and in which:

FIG. 1 is a perspective view of a wire-rods and the like, hot-rolling machine realized according to the teachings of the present invention;

FIG. 2 is a cross-sectional view of the top part of the wire-rods and the like, hot-rolling machine shown in FIG. 1, with parts removed for clarity;

FIG. 3 is an exploded perspective view of the top part of the wire-rods and the like, hot-rolling machine shown in FIG. 2, with parts removed for clarity; and

FIG. 4 is a plan view of one of the rollers of the wire-rods and the like, hot-rolling machine shown in FIGS. 1, 2, and 3.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIGS. 1, 2, and 3, number 1 designates as a whole a machine for hot rolling of wire rods and other similar semifinished steel products, which finds particularly advantageous use in the production of steel concrete reinforcing bars.

More in detail, the machine 1 is structured for hot rolling a wire rod 2 or other similar semifinished steel product, that movers through the machine following a locally substantially rectilinear, feeding path p.

The wire-rods and the like, hot-rolling machine 1 basically comprises: an external supporting casing 3 which preferably, though not necessarily, has a substantially parallelepipedal shape, and is located against the wire-rod feeding path p; and two rotating supporting shafts 4, which are fixed/mounted in an axially rotatable manner in the supporting casing 3 and cantilevered protrude from the supporting casing 3 in substantially specular position on opposite sides of the wire-rod feeding path p, while remaining locally parallel and facing to one another and substantially perpendicular to the wire-rod feeding path p, so as to arrange their respective ends portions 4a in substantially specular position on opposite sides of the wire-rod feeding path p.

In other words, the two supporting shafts 4 are placed on opposite sides of the wire-rod feeding path p, with their respective reference longitudinal axes A parallel and facing to one another and locally substantially perpendicular to the wire-rod feeding path p, so that their respective end portions 4a are placed in substantially specular position on opposite sides of the wire-rod feeding path p.

The two supporting shafts 4 are moreover able to rotate about their respective longitudinal reference axes A in mutually opposite directions, substantially with identical angular velocities.

More in detail, the wire-rods and the like, hot-rolling machine 1 is preferably provided with a gear train (not shown), which is housed within the supporting casing 3 and is structured so as to connect the two supporting shafts 4 to a same driving motor (not shown) preferably, though not necessarily, of an electric or hydraulic type, so as to enable said motor to drive in rotation the two supporting shafts 4 simultaneously about their respective longitudinal reference axes A in mutually opposite directions, substantially with identical angular velocities.

With reference to FIGS. 1, 2, and 3, the wire-rods and the like, hot-rolling machine 1 moreover comprises two opposed and counter-rotating rollers 6 having a substantially cylindrical shape and which are provided with a central through hole 6a, and are fitted/mortised each on the end portion 4a of a respective supporting shaft 4 so that each of them is perfectly coaxial with the longitudinal axis A of the corresponding supporting shaft 4.

The two rollers 6 are therefore placed, in specular positions, on opposite sides of the wire-rod feeding path p, locally substantially parallel to and facing one another and with their respective longitudinal axes locally substantially perpendicular to the wire-rod feeding path p, and are moreover dimensioned to delimit, in between themselves and at the wire-rod feeding path p, a slot within which the wire rod 2 to be hot-rolled is forced to pass.

More in detail, each roller 6 consists of a substantially cylindrical-shaped, monolithic block 6 of tungsten carbide which is provided with a substantially cylindrical-shaped, central through hole 6a which has a diameter such to enable the fitting of the monolithic block 6 of tungsten carbide on the end portion 4a of supporting shaft 4.

With reference to FIGS. 2 and 3, in particular, the end portion 4a of each supporting shaft 4 preferably presents a substantially frustoconical profile converging towards the distal end of the same shaft, and the wire-rods and the like, hot-rolling machine 1 also comprises two centring and coupling bushings 7 which preferably present a frustoconical internal profile, and each of which is fitted on the end portion 4a of a respective supporting shaft 4, between the supporting shaft 4 and the corresponding roller 6, and is structured so as to directly mesh on the supporting shaft 4 so as to be angularly integral to the supporting shaft 4, and at same time so as to be inserted/wedged between supporting shaft 4 and roller 6 so as to centre the roller 6 on the supporting shaft 4 and in addition make the roller 6 angularly integral to the body of supporting shaft 4.

In the example shown, in particular, each supporting shaft 4 is preferably provided with a protruding shank 4b that cantilevered extends from the end portion 4a of supporting shaft 4, while remaining perfectly coaxial to the longitudinal axis A of the same shaft, and each centring and coupling bushing 7 is structured so as to mesh on a toothed ring 8 preferably with straight teeth, which is provided on the body of supporting shaft 4 roughly at the base of the projecting shank 4b.

More in detail, in the example shown each centring and coupling bushing 7 has an overall length greater than that of the end portion 4a of supporting shaft 4 so as to cantilevered project from the roller 6 towards the distal end of the supporting shaft 4 so as to surround/cover also at least a part of the projecting shank 4b, and is moreover provided, along the stretch of the central through hole that directly faces the projecting shank 4b, with an internal toothed ring 9 structured so to be able to mesh directly in the toothed ring 8 of supporting shaft 4.

In addition, the frustoconical internal part of the centring and coupling bushing 7 preferably has a coning degree lower than that of the frustoconical-shaped end portion 4a of supporting shaft 4, in such a way that the body of bushing 7 is forced to expand against roller 6 when the centring and coupling bushing 7 is force fitted/driven on the end portion 4a of supporting shaft 4, causing the gripping of bushing 7 against the inner surface of roller 6.

With reference to FIGS. 2, 3, and 4, each centring and coupling bushing 7 is moreover provided with an annular flange 11 with an eccentric lobe-shaped profile, which cantilevered projects from the outer cylindrical surface of the bushing 7 at one of the two mouths of the central through hole 6a of the roller 6 (i.e. at one of the two bases of the roller 6), lies on a reference plane orthogonal to the longitudinal axis of the centring and coupling bushing 7 (and hence also locally orthogonal to the longitudinal axis A of supporting shaft 4), and is designed to engage into a corresponding annular groove 6b which, in turn, is formed on the body of roller 6 at the mouth of the central through hole 6a of the roller (i.e. directly on the base of the roller 6), and has a shape complementary to that of the outer annular flange 11 of bushing 7 so as to make the centring and coupling bushing 7 angularly integral to roller 6.

In other words, with reference to FIGS. 3 and 4, each roller 6 has, on the base directly facing the annular flange 11, an annular groove 6b with eccentric lobe-shaped profile, which is formed in the body of roller 6 at the mouth of the central through hole 6a, and has a shape substantially complementary to that of the outer annular flange 11 of the centring and coupling bushing 7 so as to be engaged by the with lobe-shaped profiled, annular flange 11 of bushing 7.

In the example shown, in particular, the profile of the outer peripheral edge of the annular flange 11 of the centring and coupling bushing 7 is preferably defined by a closed curved line that has a variable radius of curvature r which, for one or more stretches, is eccentric with respect to the longitudinal axis of bushing 7 (i.e. not intersecting it) which, in turn, coincides with the longitudinal axis A of supporting shaft 4.

Preferably, the annular flange 11 of the centring and coupling bushing 7 is moreover shaped/profiled so that its barycentre is located on the longitudinal axis of centring and coupling bushing 7, which in turn coincides with the longitudinal axis A of supporting shaft 4.

Likewise, the annular groove 6b of roller 6 is preferably shaped/profiled so that its barycentre is located on the longitudinal axis of roller 6 which, in turn, coincides with the longitudinal axis A of supporting shaft 4.

With reference to FIG. 4, similarly to the annular flange 11 of bushing 7, in the example shown the profile of the outer peripheral edge of the annular groove 6b formed on the base of roller 6, at the mouth of the central through hole 6a of the same roller, is preferably defined by a closed curved line that has a variable radius of curvature r which, for one or more stretches, is eccentric with respect to the longitudinal axis of roller 6 (i.e. not intersecting it) which, in turn, coincides with the longitudinal axis A of supporting shaft 4.

The profile of the outer peripheral edge of annular groove 6b is furthermore substantially identical to the profile of the outer peripheral edge of the annular flange 11 of centring and coupling bushing 7.

With reference to FIGS. 3 and 4, in the example shown, in particular, the annular flange 11 of the centring and coupling bushing 7 and the annular groove 6b formed on the base of roller 6, have a substantially elliptical shape, with the two foci located, in specular position, on opposite sides respectively of the longitudinal axis of bushing 7 and of the longitudinal axis of roller 6, which in use coincide with the longitudinal axis A of supporting shaft 4.

With reference to FIGS. 1, 2, and 3, the wire-rods and the like, hot-rolling machine 1 finally comprises, for each centring and coupling bushing 7, a respective removable blocking device 12 which is structured to stably withhold the centring and coupling bushing 7 fitted/inserted on the end portion 4a of supporting shaft 4, between supporting shaft 4 and roller 6, with the outer annular flange 11 of bushing 7 inserted/fitted in the annular groove 6b of roller 6.

In the example shown, in particular, each blocking device 12 preferably comprises: a lock nut 13 preferably substantially cup-shaped or bell-shaped, which is screwed directly on a threaded portion of the distal end of supporting shaft 4, or rather of the projecting shank 4b of supporting shaft 4; and a pack of pre-compressed cup springs 14 or other similar elastic members, which are fitted on the distal end of supporting shaft 4, or rather on the projecting shank 4b of supporting shaft 4, so as to be interposed between the body of lock nut 13 and the centring and coupling bushing 7, so as to be able to press and withhold the centring and coupling bushing 7 stably in abutment on roller 6, with the outer annular flange 11 of bushing 7 fitted within the annular groove 6b of roller 6.

More in detail, with reference to FIG. 2, in the example shown the pack of cup springs 14 is preferably fitted on the free end of the centring and coupling bushing 7, in abutment against a projecting annular shoulder 15 present on the outer surface of the bushing 7; whereas the central part of lock nut 13 is structured/shaped so to fit in telescopic manner on the free end of bushing 7, thus to be able to arrive in abutment against the pack of cup springs 14 fitted on the same end of the bushing 7 and then compress the pack of cup springs 14 against the projecting annular shoulder 15 of the centring and coupling bushing 7.

With reference to FIGS. 1, 2, and 3, preferably each blocking device 12 is moreover provided with a substantially cylindrical protective sleeve 16 which is shaped/structured so as to be fitted on supporting shaft 4, with the bottom annular rim 16a of the sleeve in abutment against the base of roller 6 where the annular groove 6b is formed, and with the top annular rim 16b of the sleeve in abutment against the lock nut 13 so as to surround and protect the pack of cup springs 14.

In other words, the protective sleeve 16 is shaped/structured so as to be fitted on the portion of the bushing 7 that cantilevered projects from roller 6 towards the distal end of supporting shaft 4, with the bottom annular rim 16a of the sleeve in abutment on the base of roller 6 where the annular groove 6b is formed, and with the top annular rim 16b of the sleeve in abutment against the lock nut 13.

More in detail, in the example shown, the protective sleeve 16 is preferably shaped/structured so as to bring the bottom annular rim 16a of the sleeve in abutment on the base of roller 6, outside of the annular groove 6b, so as to surround and cover the coupling area between centring and coupling bushing 7 and roller 6.

The top annular rim 16b of sleeve 16 is, instead, preferably shaped so as to be able to couple with the perimetral edge of lock nut 13 substantially for the whole length, so as to cover and protect the pack of cup springs 14 fitted on the free end of centring and coupling bushing 7.

In addition, sleeve 16 is preferably also shaped/structured so as to be able to mesh directly on the portion of bushing 7 that cantilevered projects outside of roller 6, so as to be angularly integral to the centring and coupling bushing 7.

In the example shown, in particular, sleeve 16 is preferably structured so as to be able to mesh on a toothed ring 17 preferably with straight teeth, which is provided on the outer surface of bushing 7, between the outer annular flange 11 of bushing 7 and the annular shoulder 15.

More in detail, in the example shown sleeve 16 has, along a stretch of its central through hole, an internal toothed ring 18 which is structured so as to be able to mesh directly in the toothed ring 17 of centring and coupling bushing 7.

With reference to FIG. 2, preferably the wire-rods and the like, hot-rolling machine 1 finally comprises, along each supporting shaft 4, an annular thrust-bearing element 20 which is fitted on the stretch of supporting shaft 4 immediately adjacent to the end portion 4a of supporting shaft 4, without possibility of further axial displacement along the same supporting shaft 4, so as to abut against the base of roller 6 without the annular groove 6b, and prevent the roller 6 from misalign with respect to the frustoconical end portion 4a of supporting shaft 4.

In other words, the annular thrust-bearing element 20 is fitted on the supporting shaft 4 beside the roller 6 and the centring and coupling bushing 7, on the opposite side with respect to the projecting shank 4b, with no possibility of displacing along the supporting shaft 4 in a direction opposite to the end portion 4a, so as to support and hold the roller 6 in place on the frustoconical end portion 4a of supporting shaft 4.

Operation of the wire-rods and the like, hot-rolling machine 1 is easily inferable from the foregoing description and hence does not require any further explanation.

As regards, instead, the coupling between roller 6 and centring and coupling bushing 7, experimental tests have revealed that the particular shape of the outer annular flange 11 of centring and coupling bushing 7 and of the annular groove 6b present on the base of roller 6, allows to keep the roller 6 angularly integral to the centring and coupling bushing 7, without the mechanical stresses generated between the two components during normal operation of the machine 1 to cause, in the material that forms the roller 6, cracks that might lead to breaking-up of roller 6.

The advantages deriving from the particular structure of the roller 6 and of the centring and coupling bushing 7 are considerable.

The two blocking devices 12, in fact, now simply have to withhold the two centring and coupling bushings 7 in place without any need to exert particularly high axial thrusts, because the blocking of the roller on the centring and coupling bushing 7 is no longer obtained by friction.

Consequently, the tightening torque to be applied on the lock nuts 13 has values that are lower, by at least two orders of magnitude, than those required by current systems for blocking rollers and can be easily reached using normal wrenches.

This possibility renders superfluous the use of hydraulic torque wrenches and enables drastic reduction of the times for replacement of the rollers, thus enormously simplifying the operations of maintenance of the hot-rolling line.

It is finally apparent that changes and variants can be made to the above-described, wire-rods and the like, hot-rolling machine 1 and to the roller 6 described herein, without departing from the scope of the present invention.

For example, in a different, less sophisticated embodiment, the blocking device 12 may comprise: a cup-shaped body structured/shaped so to be fitted directly on the distal end of supporting shaft 4, or rather on the projecting shank 4b of supporting shaft 4, and so as to arrange its perimetrical rim in abutment against the base of roller 6 where the annular groove 6b is provided, outside the same annular groove 6b; and one or more anchoring bolts that engage in pass-through manner the bottom of the cup-shaped body and then are screwed in the body of supporting shaft 4, or rather in the projecting shank 4b of supporting shaft 4, so as to rigidly block the cup-shaped body on the distal end of supporting shaft 4, or rather on the projecting shank 4b of supporting shaft 4.

In another embodiment, moreover, roller 6, instead of being made of tungsten carbide, could also consist in a monolithic block 6 of high-resistance cast iron or special steel, once again substantially cylindrical-shaped and once more provided with a cylindrical-shaped, central through hole 6a with a diameter such as to enable the fitting of the monolithic block of cast iron on the frustoconical end portion 4a of supporting shaft 4.

Claims

1. Wire-rod and the like, hot-rolling machine which is adapted to hot-roll a wire-rod or the like moving forward along a pre-established feeding path, and which comprises: two counter-rotating supporting shafts which are arranged on opposite sides of the wire-rod feeding path, with respective longitudinal axes parallel to and facing each other and locally substantially perpendicular to the wire-rod feeding path, so as to arrange respective end portions in a substantially specular position on opposite sides of the wire-rod feeding path;two rollers which are provided with a central through hole and are each fitted onto a respective supporting shaft, at the end portion of said supporting shaft; andtwo centering and coupling bushings, each of which is fitted on the end portion of a respective supporting shaft, between the supporting shaft and the corresponding roller, and is structured so as to mesh on the supporting shaft to be angularly integral to said supporting shaft, and so as to be inserted/wedged between the supporting shaft and the roller, thus to center the roller on the supporting shaft and also to make the roller angularly integral to the body of the supporting shaft;wherein each centering and coupling bushing is provided with an annular flange having eccentric lobe-shaped profile and which cantilevered projects from the outer surface of the bushing at one of the two mouths of the central through hole of the roller, and wherein each roller has, on the base facing the annular flange of the bushing, a corresponding annular groove which is formed on the body of the roller so as to surround the mouth of the central through hole of the roller, and has an eccentric lobe-shaped profile which is complementary in shape to that of the annular flange of the centering and coupling bushing so as to be engaged by the annular flange of said bushing.

2. Machine according to claim 1, wherein the profile of the outer peripheral edge of the annular flange of the centering and coupling bushing is defined by a closed curved line that has a variable radius of curvature which, for one or more stretches, is eccentric with respect to the longitudinal axis of the bushing.

3. Machine according to claim 1, wherein the profile of the outer peripheral edge of the annular groove of the roller is defined by a closed curved line that has a variable radius of curvature which, for one or more stretches, is eccentric with respect to the longitudinal axis of the roller.

4. Machine according to claim 3, wherein the profile of the outer peripheral edge of the annular groove is substantially identical to the profile of the outer peripheral edge of the annular flange of the centering and coupling bushing.

5. Machine according to claim 1, wherein the end portions of the two supporting shafts have a substantially frustoconical profile, and in that the two centering and coupling bushings present on the inside a frustoconical profile.

6. Machine according to claim 1, wherein the annular flange of the centering and coupling bushing is shaped/profiled so as to have its bary center located on the longitudinal axis of the centering and coupling bushing.

7. Machine according to claim 1, wherein the annular groove of the roller is preferably shaped/profiled so as to have its bary center located on the longitudinal axis of the roller.

8. Machine according to claim 1, wherein the annular flange of the centering and coupling bushing and the annular groove of the roller are substantially elliptical in shape.

9. Machine according to claim 1, further comprising an external supporting casing which is located against the wire-rod feeding path; the two supporting shafts being mounted in an axially rotatable manner on the supporting casing so as to cantilevered project from the supporting casing in substantially specular position, on opposite sides of the wire-rod feeding path, thus to arrange the respective end portions in a substantially specular position on opposite sides of the wire-rod feeding path.

10. Machine according to claim 9, further comprising a gear train which is housed within the supporting casing and is structured so as to connect the two supporting shafts to a same driving motor, so as to allow said motor to drive the two supporting shafts simultaneously in rotation about their respective longitudinal axes in mutually opposite directions, substantially with identical angular velocities.

11. Machine according to claim 1, further comprising, for each centering and coupling bushing, a respective removable blocking device which is structured so as to withhold the centering and coupling bushing stably fitted/inserted on the end portion of the supporting shaft, between the supporting shaft and the roller, with the annular flange of the bushing inserted/fitted in the annular groove of the roller.

12. Machine according to claim 11, wherein the removable blocking device comprises a lock nut which is screwed directly on the distal end of the supporting shaft, and elastic means which are fitted on the distal end of the supporting shaft so as to be interposed between the body of the lock nut and the centering and coupling bushing, thus to press and withhold the centering and coupling bushing stably in abutment against the roller.

13. Machine according to claim 1, wherein each roller consists of a substantially cylindrical-shaped, monolithic block of tungsten carbide which is provided with a central through hole with a diameter such as to allow the fitting of the monolithic block of tungsten carbide on the end portion of the supporting shaft.

14. Roller for hot rolling of wire rods and the like, comprising a substantially cylindrical-shaped, monolithic block of high-resistance material which is provided with a central through hole designed to allow the fitting of the monolithic block of high-resistance material on a supporting shaft; wherein said monolithic block of high-resistance material has, on one of its two bases, an annular groove which is formed on the body of the monolithic block of high-resistance material so as to surround the mouth of the central through hole, and has an eccentric lobe-shaped profile.

15. Roller according to claim 14, wherein the profile of the outer peripheral edge of the annular groove of the monolithic block of high-resistance material is defined by a closed curved line having a variable radius of curvature which, for one or more stretches, is eccentric with respect to the longitudinal axis of the monolithic block of high-resistance material.

16. Roller according to claim 14, wherein the annular groove with eccentric lobe-shaped profile is substantially elliptical in shape.

17. Roller according to claim 16, wherein the two foci of the ellipse are located, in specular position, on opposite sides of the longitudinal axis of the monolithic block of high-resistance material.

18. Roller according to claim 14, wherein the monolithic block of high-resistance material is a substantially cylindrical-shaped, monolithic block of tungsten carbide.