EP4713156A1 - Rolling mill stand with roll distance adjustment system - Google Patents

Abstract

A rolling mill stand (1) for rolling semi-finished iron-and-steel products, in particular for obtaining long products, comprising at least one pair of rolling rolls (2a 2b), each rolling roll (2a, 2b) being mounted on a respective shaft (3a, 3b); wherein each shaft (3a, 3b) is inserted in a respective eccentric bushing (4a, 4b), each adapted to rotate about a respective rotation axis (A, B), so that a rotation of the eccentric bushings (4a, 4b) allows an adjustment of the distance (G1, G2) between the rolling rolls (2a, 2b); characterized in that it comprises at least two distance sensors (51a, 52a, 51b, 52b) for each shaft (3a, 3b) adapted to detect the distance (c1, c2, c3, c4, d1, d2, d3, d4) between each sensor (51a, 52a, 51b, 52b) and the respective shaft (3a, 3b), or between each sensor (51a, 52a, 51b, 52b) and a body which supports the respective shaft (3a, 3b).

Description

ROLLING MILL STAND WITH ROLL DISTANCE ADJUSTMENT SYSTEM

Field of the invention

The present invention relates to the field of rolling for making semi-finished long iron-and-steel products, such as steel bars, wire rods starting from a billet.

In particular, the invention relates to a rolling mill stand provided with a system for adjusting the distance between the rolling rolls, which, in particular, comprises eccentric bushings. The invention further relates to a rolling apparatus and a method for adjusting the distance between the rolling rolls.

Background art

So-called "long" semi-finished iron-and-steel products, e.g., such as bars or wire rods are generally produced by means of a rolling apparatus comprising a plurality of rolling mill stands arranged in sequence.

The term "rolling" in the context of this description means hot rolling of iron-and- steel products, which can be either a roughing or finishing rolling in tolerance.

The size of the iron-and-steel semi-finished product is substantially determined by the distance between the rolling rolls, also called the rolling gap or working gap.

Some rolling stands can be equipped with a system for adjusting the distance between the rolling rolls.

To date, the roll distance adjustment systems do not allow for optimal adjustment and have technological limitations.

In particular, the current control systems do not allow adjustment of the rolling gap under load, i.e. , while rolling.

On the other hand, it would be advantageous to be able to adjust the rolling gap under load, to obtain material in tolerance, reduce waste, and maintain said tolerance by compensating for wear and deferring the need to replace the rolling rolls.

Disadvantageously, with the currently known systems, the effect of adjusting the gap between the rolling rolls of a mill stand can only be noted on the next billet that is rolled, because said adjustment occurs in the inter-billet mode.

Indeed, the adjustment system is not designed to make it possible to verify whether the rolling rolls were actually moved successfully during the rolling of a billet. This is due, in particular, to the fact that the rolling gap is not measured in real-time or is not reliably measured.

Furthermore, the adjustment mechanism is not structurally designed to allow adjustment under load. Indeed, the mechanism has points with low flexural and torsional stiffness and sliding couplings under high friction load.

The low stiffness of the mechanism, added to the lack of feedback on the actual width of the rolling gap, which varies as a function of the progressive wear of the rolling channels, introduces an error which leads to ineffective or incorrect adjustment.

Therefore, the need is felt to overcome the limits of the prior art.

Summary of the invention

It is an object of the present invention to make a rolling mill stand of the type which is provided with eccentric bushings for adjusting the distance between rolling rolls, in particular of the type with cantilevered shafts, which allows the adjustment of the distance between rolling rolls in a better, in particular more reliable, manner than in the prior art.

In particular, it is an object of the present invention to make a rolling mill stand which makes it possible to adjust the distance between the rolling rolls under load, i.e. , while rolling.

More in particular, it is an object of the present invention to make a rolling mill stand which allows the distance between rolling rolls to be verified even under load.

Furthermore, it is an object of the invention to make a rolling mill stand in which the mechanism for adjusting the distance between the rolling rolls is more rigid, in particular, so as to minimize deformation and bending of the structures which could lead to the premature wear of the mill stand and its components.

The present invention achieves at least one of these objects, and other objects which will be apparent in the light of the present description, by means of a rolling mill stand, according to claim 1 , for rolling semi-finished iron-and-steel products, in particular for obtaining long products, in particular steel products, comprising at least one pair of rolling rolls, each rolling roll being mounted on a respective shaft; wherein each shaft is inserted in a respective eccentric bushing, each adapted to rotate about a respective rotation axis, so that a rotation of the eccentric bushings allows an adjustment of the distance between the rolling rolls; the rolling mill stand comprising at least two distance sensors for each shaft adapted to detect the distance between each sensor and the respective shaft or adapted to detect the distance between each sensor and a body supporting the respective shaft.

The invention further relates to a rolling apparatus according to claim 16.

The invention further relates to a method, according to claim 17, for adjusting the distance between the rolling rolls, or rolling gap, of a rolling mill stand, wherein a control circuit or electronic control unit is provided, connected to said sensors, wherein the adjustment of the distance between the rolling rolls is performed as a function of distance values detected by said sensors; in particular, as a function of the position of each shaft determined by triangulating the position of each shaft relative to the rotation axis of the respective eccentric bushing, said triangulation being performed as a function of distance values detected by said distance sensors.

Advantageously, as will also be explained later, two distance sensors are provided for each shaft so that the values detected by said sensors can be used by a control circuit, or electronic control unit, to triangulate the position of the shafts, in particular relative to the rotation axis of the respective eccentric bushing, and to determine the distance between the rolls as a function of triangulating the position of the shafts. Therefore, advantageously, a rolling mill stand according to the invention makes it possible to verify the actual distance between the rolling rolls and thus allows the distance between the rolls to be adjusted more precisely and reliably even under load.

Advantageously, in the rolling mill stand the roll distance adjustment is performed by means of eccentric bushings, whereby the distance adjustment is particularly reliable and is better, e.g., than the adjustment performed by hydraulic cylinders. Indeed, the latter can lead to synchronization errors of the hydraulic cylinders and undesirable asymmetric movement of the rolls.

Therefore, there is a synergistic effect (more precise and reliable rolling gap adjustment, even under load) given by the adjustment by means of eccentric bushings and the use of distance sensors which allow the position of the shafts to be triangulated, and therefore allow the width of the rolling gap to be determined.

Preferably, in all embodiments, the rolling mill stand can have the features of claim 11 or 12. Advantageously, in this manner, the mechanism for adjusting the distance between the rolling rolls is structurally more rigid, and therefore enables particularly precise and reliable adjustment, even under load, of the distance between the rolling rolls without stressing the components.

Therefore, it is possible to have a synergistic effect given by the use of the distance sensors, which make it possible to triangulate the position of the shafts and thus allow the width of the rolling gap to be determined, and by an adjustment mechanism that is structurally more rigid. The synergistic effect is, in particular, the possibility of particularly precise and reliable adjustment of the rolling gap under load.

Preferably, in all embodiments, the sensors are positioned and oriented so that they point orthogonally to the rotation axis of the eccentric bushing in which the respective shaft is inserted.

The rolling mill stand according to the invention is particularly adapted to roll semifinished iron-and-steel products, in particular long semi-finished iron-and-steel products, such as wire rods or bars.

Further features and advantages of the invention will become more apparent in light of the detailed description of exemplary but not exclusive embodiments. The dependent claims describe particular embodiments of the invention.

Brief description of the drawings

The description of the invention refers to the accompanying drawings, which are provided by way of non-limiting example, in which:

Fig. 1 diagrammatically shows a rolling apparatus according to the invention;

Fig. 2 is a perspective view of parts of a rolling mill stand according to the invention, in which only one roll is shown for illustrative purposes;

Fig. 3 is a perspective view of parts of a rolling mill stand, from which, compared with Fig. 2, components were removed for the sake of illustration;

Fig. 4 is a top plan view of parts of a rolling mill stand according to the invention, in a first configuration; Fig. 5 diagrammatically shows a plan view from the top of the parts shown in Fig. 4, in a second configuration;

Fig. 6 shows a perspective view of parts of a rolling mill stand according to the invention;

Fig. 7 is a perspective view of parts of a rolling mill stand, from which, compared with Fig. 6, components were removed for the sake of illustration.

The same elements or components have the same reference numerals.

Description of example embodiments of the invention

Non-limiting examples of embodiments of a rolling mill stand 1 according to the invention are described with reference to the figures.

The rolling mill stand 1 is particularly adapted for rolling semi-finished iron-and- steel products, in particular long semi-finished iron-and-steel products, in particular to perform a roughing operation or a finishing operation. For example, the rolling mill stand 1 is particularly adapted for processing wire rods or bars.

The rolling mill stand 1 according to the invention is adapted for rolling substantially any long iron-and-steel semi-finished product.

The rolling is performed along a rolling axis R.

In all embodiments, the rolling mill stand 1 comprises at least one pair of rolling rolls 2a 2b, each rolling roll 2a, 2b being mounted (either directly or indirectly by means of ring-bearing elements) on a respective shaft 3a, 3b; each shaft 3a, 3b is inserted (either directly or indirectly by means of bushings) into a respective eccentric bushing 4a, 4b, each adapted to rotate about a respective rotation axis A, B, so that a rotation of the eccentric bushings 4a, 4b, in particular performed by means of actuating systems connected either directly or indirectly to the eccentric bushings 4a, 4b, allows an adjustment of the distance G1 , G2 between the rolling rolls 2a, 2b; and advantageously the rolling mill stand 1 comprises at least two distance sensors 51 a, 52a, 51 b, 52b for each shaft 3a, 3b adapted to detect (or measure) the distance c1 , c2, c3, c4, d1 , d2, d3, d4 between each sensor 51 a, 52a, 51 b, 52b and the respective shaft 3a, 3b (particularly preferable option), in particular between each sensor 51 a, 52a, 51 b, 52b and an outer surface 30a, 30b of the respective shaft 3a, 3b; or wherein said at least two distance sensors 51 a, 52a, 51 b, 52b for each respective shaft 3a, 3b are adapted to detect the distance between each sensor 51 a, 52a, 51 b, 52b and a body, in particular tubular, supporting the respective shaft 3a, 3b, said body being preferably the eccentric bushing 4a, 4b or another body that supports the respective shaft 3a, 3b and in particular in which the respective shaft 3a, 3b is inserted.

The aforesaid outer surface 30a, 30b is in particular an outer side surface, which extends about the longitudinal axis X, Y of the respective shaft 3a, 3b. In particular, said outer surface 30a, 30b is cylindrical. Preferably, said outer surface 30a, 30b is the surface defining the largest diameter of shaft 3a, 3b (or of said body), so that the sensors 51 a, 52a, 51 b, 52b are as close as possible to the respective shaft 3a, 3b or said body.

Advantageously, two distance sensors 51 a, 52a, 51 b, 52b are provided for each shaft 3a, 3b so that the values detected by said sensors 51 a, 52a, 51 b, 52b can be used by a control circuit (not shown), or electronic control unit, to triangulate the position of shafts 3a, 3b, in particular relative to the rotation axis A, B of the respective eccentric bushing 4a, 4b, and to determine the distance G1 , G2 between the rolling rolls 2a, 2b as a function of the triangulation of the position of the shafts 3a, 3b.

It was chosen to position the sensors 51 a, 52a, 51 b, 52b so that they can measure the distance c1 , c2, c3, c4, d1 , d2, d3, d4 between the sensors 51 a, 52a, 51 b, 52b and the respective shaft 3a, 3b (or the aforementioned body which supports the respective shaft 3a, 3b) so as to have a more accurate measurement than measuring the distance between the sensors and the rolling rolls (indeed, many types of sensors are more accurate by reading short distances, such as inductive sensors). Furthermore, the rolls are subject to wear and tear. Furthermore, with the positioning of the sensors 51a, 52a, 51 b, 52b according to the invention, they are more distant from the rolling axis R, so they are less exposed to damage risks and less exposed to dirt and cooling fluids.

For each sensor 51 a, 52a, 51 b, 52b, the distance c1 , c2, c3, c4, d1 , d2, d3, d4 with the respective shaft 3a, 3b (or with the aforementioned body) is in particular measured along an axis orthogonal, in particular radial, to the longitudinal axis X, Y of the respective shaft 3a, 3b. The eccentric bushings 4a, 4b are housed in a structure 61 relative to which they are adapted to rotate about their respective rotation axis A, B.

The rotation axes A, B about which the eccentric bushings 4a, 4b are adapted to rotate are shown in Figs. 2 and 3. Each shaft 3a, 3b is inserted into the respective eccentric bushing 4a, 4b so that the longitudinal axis X, Y of each shaft 3a, 3b is distinct and parallel to the rotation axis A, B of the eccentric bushing 4a, 4b into which it is inserted.

When the eccentric bushings 4a, 4b rotate about their respective rotation axis A, B, shafts 3a, 3b can be mutually distanced or approached. Therefore, to adjust the distance G1 , G2 (Fig. 4 and 5) between the rolling rolls 2a, 2b, the rolling rolls 2a, 2b rotate around a respective axis A, B.

For rolling, the rolls 2a, 2b rotate around the longitudinal axis X, Y of the respective shaft 3a, 3b.

Fig. 4 shows an initial configuration of rolling mill stand 1 , in which the distance between rolls 2a, 2b is indicated by reference G1. Fig. 5 shows a second configuration of rolling mill stand 1 , in which the distance between rolls 2a, 2b is shown with reference G2. The distance G1 is greater than the distance G2. For example, the distance G1 can be the maximum distance between the rolls 2a, 2b, and the distance G2 can be the minimum distance between the rolls 2a, 2b.

The distances between each sensor 51 a, 52a, 51 b, 52b and the respective shaft 3a, 3b are diagrammatically shown with a thick line, and are indicated by the references c1 , c2, c3, c4, d1 , d2, d3, d4.

In particular, in the first configuration, the distance between the sensor 51 a and the shaft 3a is indicated by reference c1 ; the distance between the sensor 52a and the shaft 3a is indicated by reference c2; the distance between the sensor 51 b and the shaft 3b is indicated by reference d1 ; and the distance between the sensor 52b and the shaft 3b is indicated by reference d2.

In the second configuration, the distance between sensor 51 a and shaft 3a is indicated by reference c3; the distance between the sensor 52a and the shaft 3a is indicated by reference c4; the distance between the sensor 51 b and the shaft 3b is indicated by reference d3; and the distance between the sensor 52b and the shaft 3b is indicated by reference d4. The sensors 51 a, 52a, 51 b, 52b are constrained, in particular either directly or indirectly by means of additional elements, to said structure 61 , in particular so as to be stably positioned. In particular, in all embodiments, the sensors 51 a, 52a, 51 b, 52b are integral with the structure 61 .

Preferably, said sensors 51a, 52a, 51 b, 52b are constrained to a face 611 of said structure 61 , which is proximal to the rolling rolls 2a, 2b, so, advantageously, they are easily accessible by the operators, e.g., to be able to replace or repair them during the maintenance steps. Said face 611 , in particular, is the face relative to which the shafts 3a, 3b protrude.

In all embodiment, preferably, said at least two sensors 51 a, 52a, 51 b, 52b for each shaft 3a, 3b are positioned between the structure 61 and the rolling rolls 2a, 2b, in particular under the rolling rolls 2a, 2b.

Preferably, said at least two sensors 51 a, 52a, 51 b, 52b for each shaft 3a, 3b are positioned between the respective eccentric bushing 4a, 4b and the respective roll 2a, 2b.

Said at least two sensors 51a, 52a, 51 b, 52b for each shaft 3a, 3b are, in particular, facing the outer side surface 30a, 30b of the respective shaft 3a, 3b or of the respective body which supports the respective shaft.

Preferably, the sensors 51 a, 52a, 51 b, 52b are covered by a flange 62 or plate, which advantageously protects the sensors 51 a, 52a, 51 b, 52b.

The flange 62 is fixed, in particular either directly or by means of additional elements, to said structure 61 . In particular, the flange 62 is provided with two through holes, each through hole being crossed by a respective shaft 3a, 3b. The flange 62 can be disassembled from the structure 61 to make the sensors 51 a, 52a, 51 b, 52b accessible.

The sensors 51a, 52a, 51 b, 52b are preferably inductive sensors, in particular eddy current inductive proximity sensors. The inductive sensors are particularly advantageous because they work even in dirty environments, in particular even in dirty environments with water and/or steam.

Alternatively, other types of distance sensors can be used, such as capacitive, laser, or with touch probes. Preferably, each sensor 51a, 52a, 51 b, 52b is arranged at a distance from the respective shaft 3a, 3b (or from the aforesaid body which supports the respective shaft) of 0.5 to 100 mm, preferably 0.5 to 15 mm.

Preferably, said at least two sensors 51 a, 52a, 51 b, 52b for each shaft 3a, 3b are arranged along a same circumference, however, they could also be placed at different distances from the respective shaft 3a, 3b.

The number of sensors 51 a, 52a, 51 b, 52b for each shaft 3a, 3b can be two or even greater than two. A higher number of sensors make it possible to obtain a more precise triangulation.

The rolling mill stand 1 advantageously comprises a control circuit or electronic control unit, configured to determine the distance G1 , G2 between the rolls 2a, 2b, or rolling gap, as a function of distance values c1 , c2, c3, c4, d1 , d2, d3, d4 detected by said sensors 51 a, 52a, 51 b, 52b.

In particular, the control circuit is preferably configured to determine the distance G1 , G2 between the rolling rolls 2a, 2b by means of a triangulation of the position of each shaft 3a, 3b, in particular relative to the rotation axis A, B of the respective eccentric bushing 4a, 4b, said triangulation being performed as a function of distance values c1 , c2, c3, c4, d1 , d2, d3, d4 detected by said sensors 51a, 52a, 51 b, 52b.

In particular, preferably, the control circuit, or electronic control unit, is configured to be able to adjust the distance G1 , G2 between the rolling rolls 2a, 2b, or rolling gap; said adjustment being in particular made as a function of distance values c1 , c2, c3, c4, d1 , d2, d3, d4 detected by said sensors 51 a, 52a, 51 b, 52b, more particularly as a function of said position of each shaft 3a, 3b determined by means of the aforesaid triangulation.

The triangulation may be performed in various ways. Preferably, to perform the triangulation, the sensors 51 a, 52a, 51 b, 52b are positioned and oriented so that they point orthogonally to the rotation axis A, B of the eccentric bushing 4a, 4b into which the respective shaft 3a, 3b is inserted. The sensors 51 a, 52a, 51 b, 52b are preferably positioned in dedicated housings or fixed cavities.

When, for example, a respective shaft 3a, 3b, or more in particular when the outer surface 30a, 30b of the respective shaft 3a, 3b, intercepts the field of view (or field of action) of sensors 51 a, 52a, 51 b, 52b, they detect the distance values c1 , c2, c3, c4, d1 , d2, d3, d4 between a point of said outer surface 30a, 30b and said sensors 51 a, 52a, 51 b, 52b.

Using the well-known canonical equation of a circumference, according to which a generic point belongs to a respective circumference if, and only if, its distance from a center is equal to the radius, by virtue of the measurement of the position of at least two points and knowing the value of the radius of the shafts 3a, 3b (design value), it is possible to monitor the positioning of the circumference over time and thus the position of the shafts 3a, 3b themselves, as a function of their mutual distance.

As there could be some play (e.g., 0.15 mm) between the shafts 3a, 3b and their respective eccentric bushings 4a, 4b, as well as in the positioning of the sensors 51 a, 52a, 51 b, 52b in their respective housings, periodic realignments can be used to ensure that the readings are correct over time.

Indeed, it is possible to make a calibration, e.g., by zeroing the gap between the rolls 2a, 2b (or taking it to the minimum allowed by the rolling mill stand), measuring the corresponding distances c1 , c2, c3, c4, d1 , d2, d3, d4, and vice versa successively opening the gap to the maximum allowed by the rolling mill stand in order to record all the intermediate distances c1 , c2, c3, c4, d1 , d2, d3, d4.

Optionally, to be additionally sure of the readings, it is then possible to verify the correctness of the intermediate readings by inserting certain mechanical references into the gap between the rolls 2a, 2b in order to check for accidental misalignment over time.

The aforesaid adjustment of the distance G1 , G2 between the rolling rolls 2a, 2b, or rolling gap can advantageously be performed under load, i.e. , while rolling, or in other words can advantageously be an online adjustment.

In all embodiments, each shaft 3a, 3b is preferably cantilevered. In particular, each shaft 3a, 3b is cantilevered relative to said structure 61 , i.e., the shafts 3a, 3b are cantilevered relative to the same structure 61 .

Substantially, the rolling rolls 2a, 2b are cantilevered.

The cantilevered shafts 3a, 3b offer several advantages, comprising the fact that the rolling rolls 2a, 2b are particularly easily accessible. Each shaft 3a, 3b, in particular, is supported on one side only.

In particular, each shaft 3a, 3b protrudes from said structure 61 , more in particular each shaft 3a, 3b has a respective end portion which protrudes from the structure 61.

Each roll 2a, 2b is mounted on an end portion of the respective shaft 3a, 3b. Said end portion is the portion which protrudes from said structure 61 .

The longitudinal axes X, Y of the shafts 3a, 3b are distinct and parallel to each other.

Preferably, the number of rolls in rolling mill stand 1 is equal to two. By way of example only, a rolling train for long products may comprise a number of rolling mill stands 1 greater than or equal to 20. A finishing apparatus or unit may comprise up to 12 rolling mill stands 1 , e.g., it can comprise from 4 to 8 rolling mill stands 1 .

The rolling mill stand 1 is provided with a mechanism for adjusting the distance G1 , G2 between the rolling rolls 2a, 2b. With particular reference to Figures 6 and 7, said mechanism for adjusting the distance preferably comprises a worm screw 71 connected to the eccentric bushings 4a, 4b by means of a respective nut screw 72a, 72b and respective arms 73a, 74a, 73b, 74b hinged to the respective nut screw 72a, 72b and to the respective eccentric bushing 4a, 4b so that a rotation of the worm screw 71 determines a displacement of the nut screws 72a, 72b along the worm screw 71 , causing a rotation of the eccentric bushings 4a, 4b about the respective rotation axis A, B.

The worm screw 71 is, in particular, arranged orthogonally relative to the shafts 3a, 3b or more precisely is arranged orthogonally relative to the longitudinal axes X, Y of the shafts 3a, 3b.

Each eccentric bushing 4a, 4b is constrained to the respective nut screw 72a, 72b preferably by means of two respective arms 73a, 74a, 73b, 74b. Preferably, the pin 75a crosses the arm 73a and the nut screw 72a, constraining them to each other; the pin 76a crosses the arm 74a and nut screw 72a, constraining them to each other; the pin 75b crosses the arm 73b and the nut screw 72b, constraining them to each other; the pin 76b crosses the arm 74b and the nut screw 72b, constraining them to each other. However, the pin 75a and the pin 76a can be made in one piece, i.e., one pin constrains the nut screw 72a and the two arms 73a, 74a to one another; similarly, the pin 75b and the pin 76b can be made in one piece, i.e., one pin constrains the nut screw 72b and the two arms 73b, 74b to one another.

Other pins constrain each eccentric bushing 4a, 4b to their respective arms 73a, 74a, 73b, 74b.

Advantageously, two sliding guides 77, 78 (or grooves) are provided, and the pins 75a, 76a, 75b, 76b, which connect each arm 73a, 74a, 73b, 74b to the respective nut screw 72a, 72b are partially arranged in a respective sliding guide 77, 78 of said two sliding guides 77, 78; therefore, advantageously, the stresses to which the worm screw 71 is subjected are at least partially discharged to the sliding guides 77, 78. Advantageously, both the torsional stresses, which are generated when the worm screw 71 rotates about its longitudinal axis, and the forces that are generated during rolling due to the strain of the material being rolled, which would tend to bend the worm screw 71 , are discharged onto the sliding guides 77, 78.

The pin 75a and the pin 75b, in particular an end thereof, are partially arranged in the sliding guide 77. The pin 76a and the pin 76b, in particular an end thereof, are partially arranged in sliding guide 78. The sliding guide 78 is more outer, i.e. farther from the rolling rolls 2a, 2b, and the sliding guide 77 is more inner.

Preferably, the end of each pin 75a, 76a, 75b, 76b arranged in the respective sliding guide 77, 78 has two flat surfaces, so as to better unload the forces on the respective sliding guide 77, 78.

The sliding guides 77, 78 are parallel to the worm screw 71. The worm screw 71 extends along the two sliding guides 77, 78.

The two sliding guides 77, 78 are constrained to each other, in particular, by means of two bodies 79a, 79b transverse thereto. The worm screw 71 crosses the body 79a and preferably also the body 79b. The end 711 of the worm screw 71 which protrudes from the body 79b is adapted to be connected to actuation means (not shown) adapted to rotate the worm screw 71 about its longitudinal axis. Preferably, the end of the worm screw 71 opposite to the end 711 protrudes from the body 79a and is also adapted to be connected to the actuating means adapted to rotate the worm screw 71 about its longitudinal axis. When the worm screw 71 rotates about its longitudinal axis, the pins 75a, 76a, 75b, 76b translate rigidly with their respective nut screws 72a, 72b, and move along their respective sliding guides 77, 78.

The sliding guides 77, 78 are adapted to guide the sliding of the pins 75a, 76a, 75b, 76b orthogonally relative to the rotation axes A, B of the eccentric bushings 4a, 4b. The two sliding guides 77, 78 and the bodies 79a, 79b are constrained, in particular rigidly, to the structure 61 where eccentric bushings 4a, 4b are housed.

The invention further relates to a method for adjusting the distance G1 , G2 between the rolling rolls 2a, 2b, or rolling gap, of a rolling mill stand 1 , wherein a control circuit (or electronic control unit) is connected to said sensors 51a, 52a, 51 b, 52b, and wherein the adjustment of the distance G1 , G2 between the rolling rolls 2a, 2b is performed as a function of distance values c1 , c2, c3, c4, d1 , d2, d3, d4 detected by said sensors 51a, 52a, 51 b, 52b; in particular as a function of the position of each shaft 3a, 3b determined by triangulating the position of each shaft 3a, 3b, in particular relative to the rotation axis A, B of the respective eccentric bushing 4a, 4b, said triangulation being performed as a function of distance values c1 , c2, c3, c4, d1 , d2, d3, d4 detected by said distance sensors 51 a, 52a, 51 b, 52b. In particular, the control circuit can be connected to a user interface. By means of the user interface, the desired distance between rolling rolls 2a, 2b can be set. The actual distance G1 , G2 between the rolling rolls 2a, 2b before and/or after the distance between the rolling rolls 2a, 2b has been set and can be verified by means of the aforesaid triangulation of the position of the shafts 3a, 3b. In other words, the aforesaid triangulation provides feedback on the actual distance G1 , G2 between the rolling rolls 2a, 2b. Preferably, means are also provided to detect the size of the rolled product, so as to have additional feedback.

The invention further relates to a rolling apparatus 100 comprising at least one rolling mill stand 1. Optionally, the rolling apparatus 100 comprises a plurality of rolling mill stands 1 arranged sequentially with each other along the rolling axis R, i.e. , said rolling apparatus 100 is a rolling train. Preferably, the rolling mill stands 1 are arranged sequentially with each other so that the rotation axes of the rolls of consecutive rolling mill stands with each other are mutually orthogonal.

Preferably, said rolling train is used to carry out a finishing operation.

Claims

1. A rolling mill stand (1 ) for rolling semi-finished iron-and-steel products, in particular for obtaining long products, comprising at least one pair of rolling rolls (2a 2b), each rolling roll (2a, 2b) being mounted on a respective shaft (3a, 3b); wherein each shaft (3a, 3b) is inserted in a respective eccentric bushing (4a, 4b), each adapted to rotate about a respective rotation axis (A, B), so that a rotation of the eccentric bushings (4a, 4b) allows an adjustment of the distance (G1 , G2) between the rolling rolls (2a, 2b); the rolling mill stand (1 ) comprising at least two distance sensors (51 a, 52a, 51 b, 52b) for each shaft (3a, 3b) adapted to detect the distance (c1 , c2, c3, c4, d1 , d2, d3, d4) between each distance sensor (51 a, 52a, 51 b, 52b) and the respective shaft (3a, 3b), or between each distance sensor (51 a, 52a, 51 b, 52b) and a body supporting the respective shaft (3a, 3b).

2. A rolling mill stand (1 ) according to claim 1 , wherein the eccentric bushings (4a, 4b) are housed in a structure (61 ) relative to which they are adapted to rotate.

3. A rolling mill stand (1 ) according to claim 2, wherein said distance sensors (51 a, 52a, 51 b, 52b) are constrained, in particular either directly or by means of further elements, to said structure (61 ); in particular so that said distance sensors (51 a, 52a, 51 b, 52b) are integral with said structure (61 ).

4. A rolling mill stand (1 ) according to any one of the preceding claims, wherein each shaft (3a, 3b) is cantilevered, in particular wherein each shaft (3a, 3b) is cantilevered relative to said structure (61 ); in particular wherein each shaft (3a, 3b) protrudes from said structure (61 ).

5. A rolling mill stand (1 ) according to any one of claims 2 to 4, wherein each rolling roll (2a, 2b) is mounted on an end portion of the respective shaft (3a, 3b), said end portion protruding from said structure (61 ).

6. A rolling mill stand (1 ) according to any of the proceeding claims, wherein the longitudinal axes (X, Y) of the shafts (3a, 3b) are mutually distinct and parallel.

7. A rolling mill stand (1 ) according to any one of claims 2 to 6, wherein said distance sensors (51a, 52a, 51 b, 52b) are covered by a flange (62) or plate constrained, in particular directly or by means of further elements, to said structure (61 ); in particular wherein said flange (62) or plate is provided with two through holes, each through hole being crossed by a respective shaft (3a, 3b).

8. A rolling mill stand (1 ) according to any one of the claims from 2 to 7, wherein said distance sensors (51 a, 52a, 51 b, 52b) are constrained to a face (611 ) of said structure (61 ) which is proximal to the rolls (2a, 2b).

9. A rolling mill stand (1 ) according to any one of the preceding claims, wherein said at least two distance sensors (51 a, 52a, 51 b, 52b) for each shaft (3a, 3b) are arranged along a same circumference; and/or wherein each distance sensor (51 a, 52a, 51 b, 52b) is arranged at a distance of 0.5 to 100 mm, preferably 0.5 to 15 mm from the respective shaft (3a, 3b) or from said body.

10. A rolling mill stand (1 ) according to any one of the preceding claims, comprising a control circuit or electronic control unit, configured to determine the distance (G1 ,G2) between the rolling rolls (2a, 2b), or rolling gap, as a function of distance values (c1 , c2, c3, c4, d1 , d2, d3, d4) detected by said distance sensors (51 a, 52a, 51 b, 52b); preferably wherein said control circuit is configured to determine the distance (G1 , G2) between the rolling rolls (2a, 2b), or rolling gap, by triangulating the position of each shaft (3a, 3b), in particular relative to the rotation axis (A, B) of the respective eccentric bushing (4a, 4b), performed as a function of distance values (c1 , c2, c3, c4, d1 , d2, d3, d4) detected by said distance sensors (51 a, 52a, 51 b, 52b).

11. A rolling mill stand (1 ) according to any one of the preceding claims, provided with a mechanism for adjusting the distance (G1 , G2) between the rolling rolls (2a, 2b) comprising a worm screw (71 ) connected to the eccentric bushings (4a, 4b) by means of a respective nut screw (72a, 72b) and respective arms (73a, 74a, 73b, 74b) hinged to the respective nut screw (72a, 72b) and to the respective eccentric bushing (4a, 4b) so that a rotation of the worm screw (71 ) determines a displacement of the nut screws (72a, 72b) along the worm screw (71 ), causing a rotation of the eccentric bushings (4a, 4b); wherein two sliding guides (77, 78) are provided and wherein the pins (75a, 76a, 75b, 76b) which connect each arm (73a, 74a, 73b, 74b) to the respective nut screw (72a, 72b) are partially arranged in a respective sliding guide (77, 78) of said two sliding guides (77, 78).

12. A rolling mill stand (1 ) according to claim 11 , wherein said sliding guides (77, 78) are fixed to the structure (61 ) in which the eccentric bushings (4a, 4b) are housed and relative to which the eccentric bushings (4a, 4b) are adapted to rotate.

13. A rolling mill stand (1 ) according to any one of the preceding claims, wherein said body has an outer side surface, which extends about the longitudinal axis (X, Y) of the respective shaft (3a, 3b); said outer side surface being in particular cylindrical.

14. A rolling mill stand (1 ) according to any one of the preceding claims, wherein said body is an eccentric bushing (4a, 4b); in particular wherein said at least two distance sensors (51a, 52a, 51 b, 52b) for each shaft (3a, 3b) are adapted to detect the distance (c1 , c2, c3, c4, d1 , d2, d3, d4) between each distance sensor (51 a, 52a, 51 b, 52b) and the eccentric bushing (4a, 4b), which supports the respective shaft (3a, 3b).

15. A rolling mill stand (1 ) according to any one of claims 1 to 12, wherein said at least two distance sensors (51 a, 52a, 51 b, 52b) for each shaft (3a, 3b) are adapted to detect the distance (c1 , c2, c3, c4, d1 , d2, d3, d4) between each distance sensor (51 a, 52a, 51 b, 52b) and the respective shaft (3a, 3b).

16. A rolling mill stand (100) comprising at least one rolling mill stand (1 ) according to any one of the preceding claims; preferably wherein said at least one rolling mill stand (1) is a finishing rolling mill stand.

17. A method for adjusting the distance (G1 , G2) between the rolling rolls (2a, 2b), or rolling gap, of a rolling mill stand (1 ) according to any one of the claims from 1 to 15, wherein a control circuit, or electronic control unit is provided, connected to said distance sensors (51 a, 52a, 51 b, 52b), wherein the adjustment of the distance between the rolling rolls (2a, 2b) is performed as a function of distance values (c1 , c2, c3, c4, d1 , d2, d3, d4) detected by said sensors (51 a, 52a, 51 b, 52b); in particular as a function of the position of each shaft (3a, 3b) determined by triangulating the position of each shaft (3a, 3b), in particular relative to the rotation axis (A, B) of the respective eccentric bushing (4a, 4b), said triangulation being performed as a function of distance values (c1 , c2, c3, c4, d1 , d2, d3, d4) detected by said distance sensors (51 a, 52a, 51 b, 52b).