EP3525946A1

EP3525946A1 - Multi-stand rolling mill for rod-shaped bodies comprising mill stands with four motorized rolls

Info

Publication number: EP3525946A1
Application number: EP17797186.8A
Authority: EP
Inventors: Ettore Cernuschi; Danilo Galletti
Original assignee: Danieli and C Officine Meccaniche SpA
Current assignee: Danieli and C Officine Meccaniche SpA
Priority date: 2016-10-14
Filing date: 2017-10-13
Publication date: 2019-08-21
Anticipated expiration: 2037-10-13
Also published as: IT201600103504A1; EP3525946B1; WO2018069876A1

Abstract

The present invention relates to a rolling mill (1) for tubular bodies comprising rolling mills (10) with four rolls. The rolling mill comprises a structure defining a housing (4) for the mill stands (10) and a plurality of drive shafts (31, 32, 33, 34) for rotating a corresponding roll (11, 12, 13, 14) for each mill stand. Each drive shaft (31, 32, 33, 34) extends in reversible manner from a retracted configuration, in which it is operatively disconnected from said corresponding roll (11, 12, 13, 14), to an extended configuration, in which it is operatively connected to said corresponding roll (11, 12, 13, 14). According to the invention, each drive shaft (31, 32, 33, 34) is actuated independently from the other drive shafts and at least one of said drive shafts, when it is in said retracted configuration, is inclinable between a first reference position and a second reference position, so that said at least one drive shaft is outside the space comprised between the two planes which vertically delimit the housing (4).

Description

MULTI-STAND ROLLING MILL FOR ROD-SHAPED BODIES COMPRISING MILL STANDS WITH FOUR MOTORIZED ROLLS

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DESCRIPTION FIELD OF THE INVENTION

The present invention relates to the field of rolling systems of tubular bodies. More precisely, the invention relates to a multi-stand rolling mill comprising mill stands with four rolls motorized by means of control drive shafts.

PRIOR ART

The use of multi-stand rolling mills with motorized rolls, in which each mill stand is provided with four rolls, is known for rolling rod-shaped bodies, in particular tubes or bars. The use of four-roll mill stands, in which the axes of the two adjacent, or contiguous, rolls are arranged by 90°, allows a more uniform peripheral speed with respect to what can be obtained with three-roll mill stands in which the rotation axes of two adjacent rolls are arranged at 120°. Substantially, the four-roll mill stands allow a greater feed effect, the number of mill stands being equal. At the same time, with respect to a three-roll mill stand, the presence of four rolls advantageously reduces the pinching (crushing) effect of the edges of the rolls of on the rod-shaped body. This translates into a higher end quality of the rolled product.

Patent EP 2391460 to the Applicant relates to such a rolling mill comprising a central body, which defines a space in which a plurality of mill stands is accommodated, each of which having four motorized rolls. Each mill stand has a conformation obtained by rotating a previous or successive mill stand by 180 degrees with respect to the vertical axis. For each mill stand, the rotation axis of two non-contiguous rolls is inclined by 22,5° with respect to a horizontal plane, while the rotation angle of the other two non-contiguous rolls is inclined by 67,5°, again with respect to the same horizontal plane.

The rolling mill described in patent EP 2391460 has various drawbacks, the first of which is related to the complicated configuration of the mechanical system used for rotating the mill stand rolls. For each mill stand, the rolls are motorized by means of retractable drive shafts actuated by external controls. The external controls comprise two motors. Each motor is connected to a split ratio motor with two outputs, a first output controls a first drive shaft which engages/disengages a first half-joint integral with a first roll to be actuated. A second output of the motor comprises a second drive shaft, with axis parallel to the first drive shaft, which actuates, via a transmission, a third drive shaft having an axis orthogonal to the first and to the second drive shaft. Such third drive shaft engages/disengages a second half-joint, which is integral with a second roller to be moved contiguous to the first. The engagement/disengagement of the first drive shaft and the third drive shaft and the third drive shaft in/from the respective half-joint is achieved by means of a corresponding hydraulic thrust device.

The complex configuration of the system of drive shafts described above is one of the main drawbacks of the rolling mill described in EP 2391460. In this regard, the presence of the split ratio motor which actuates the first and the second drive shaft, like the presence of the 90° transmission necessary to transmit the motion of the second and third drive shaft, appear critical. The presence of these transmission assemblies strongly weighs on the overall size of the supporting structure of the rolling mill in both vertical and transversal terms. In this regard, it is worth emphasizing the considerable length of the two drive shafts (first and second) inclined by 22,5° with respect to the horizontal. Such length strongly weighs on the transversal extension of the rolling mill.

In the solution described in EP 2391460, the radial position of the rolls can be adjusted by means of an eccentric adjustment system. In this regard, each roll is provided with bearings mounted inside eccentric bushings, one on the control system (drive shaft side), the other on the opposite side. The two bushings are connected by a bridge which connects them rigidly. An eccentric adjustment device, which controls the eccentric rotation by exploiting a connection tube, which is integral with the control side eccentric bushing, is arranged on the control side of the roll. The adjustment device is integral with the supporting structure of the rolling mill and rotates between a working position, in which it is connected to the tube, and a resting position, in which it is disconnected from the tube itself. The adjustment device comprises a reducer, e.g. formed by a worm screw, which imposes the eccentric rotation. The complexity of the eccentricity adjustment device is another technical limit of the rolling mill described in EP 2391460. In particular, the adjustment device is critical also in terms of reliability. In this regard, it is worth noting that in the concerned solution, the adjustment device is also configured to interact with the structure of the mill stand which supports the rolls to define a retainer for the mill stand itself in the working position. This further function performed by the device contributes to its complexity.

From these considerations, the need arises to improve the rolling mill described above, particularly in terms of transversal and vertical dimensions. Therefore, it is a main task of the present invention to provide a rolling mill for four-roll mill stands which allows solving the drawbacks indicated above. In the scope of this task, it is a first object of the present invention to provide a rolling mill in which the rolls are actuated by means of a less complicated system than the one used in the known solutions. It is another object of the present invention to provide a rolling mill, in which the radial position of the rolls is adjusted by means of less complicated technical solutions than those used in the known solutions. A not last object of the present invention is to provide a rolling mill which is reliable and easy to implement at competitive costs.

SUMMARY

These and other objects, which will be more apparent in light of the description which follows, are achieved by a rolling mill for tubular bodies, comprising:

- a structure defining a housing for at least one mill stand with four rolls, wherein each roll is operatively connectable to a drive shaft, said housing being vertically delimited between a substantially horizontal support plane and a reference plane substantially parallel to said support plane;

- four drive shafts, each of which can rotate a respective roll of said mill stand, wherein each drive shaft can axially extend and retract in reversible manner, passing from a retracted configuration, in which it is operatively disconnected from the respective roll, to an extended configuration, in which it is operatively connected to the respective roll, and vice versa,

characterized in that each drive shaft is actuated independently from the other drive shafts provided to rotate the other rolls of the same mill stand by means of a respective drive motor, installed in a different position from that of the motors which actuate the other drive shafts,

and in that two first of said drive shafts rotate two respective first non-contiguous and reciprocally opposite rolls of the mill stand, and can be inclined angularly between a first reference position and a second reference position, so that they are outside the space comprised between said support plane and said reference plane when they are in the retracted configuration,

and in that two second of said drive shafts rotate two respective second noncontiguous and reciprocally opposite rolls of the mill stand, and wherein, when the second drive shafts are in the retracted configuration, they are outside the space comprised between said support plane and said reference plane.

BRIEF DESCRIPTION OF THE FIGURES

Objects and advantages of the present invention will be apparent from the following detailed description of an embodiment of the same and from the accompanying drawings provided by way of non-limiting example only, in which:

- Figure 1 is a cross section view of a rolling mill according to the invention;

- Figure 2 is a section view of a mill stand of a rolling mill according to the present invention;

- Figures 3 and 4 are views related to a group of components of the rolling mill of Figure 1 in a first and a second operative configuration, respectively;

- Figure 5 is a view of the rolling mill in Figure 1 during a mill stand replacement operation;

- Figures 6, 7 and 7 A are views of a drive shaft of a rolling mill according to the present invention;

- Figures 8 and 9 are views of another drive shaft of a rolling mill according to the present invention;

- Figures 10 and 1 1 are views related to an actuating device of the drive shaft of Figures 8 and 9;

- Figures from 12 to 16 show the drive shaft in Figures 8 and 9 during the rotation from a first reference position to a second reference position;

- Figure 17 is a view related to a possible embodiment of a rolling mill according to the present invention; - Figures 18 and 18A are respectively a side view and a front view of mill stands of a rolling mill according to the present invention;

- Figures 19, 19A are respectively a side view and a front view of a mandrel-holder stand of a rolling mill according to the present invention.

The same reference numbers and letters in the figures refer to the same elements or components.

DETAILED DESCRIPTION

The present invention thus relates to a rolling mill for tubular bodies, generically indicated by reference numeral 1 in the figures. The rolling mill 1 according to the invention comprises a structure 3 defining a housing 4 for one or more rolling mill stands 10 defining a rolling axis 100. Figure 1 is a view of the rolling mill taken along a cross section with respect to the rolling axis 100.

The mill stands 10 of the rolling mill 1 comprise four rolls 1 1 ,12,13,14 and the rotation axis (indicated in Figure 2) of each roll 301 , 302, 303, 304 is arranged at 90° with respect to the rotation axis of the contiguous roll.

Figure 2 shows in detail a mill stand 10, which has a configuration known in itself. In particular, the mill stand 10 comprises a first pair of non-contiguous rolls 1 1 , 13 having a rotation axis which is inclined by an angle CM of 22,5° with respect to the support plane 101 of the mill stand 10, while the rotation angle of the other non- contiguous pair of rolls 12, 14 is inclined by an angle 02 of 67,5° with respect to the support plane 101 itself. Each roll 1 1 , 12, 13, 14 is fitted on a bushing 501 , 502, 503, 504 axially connected (e.g. by means of a toothed engagement system) to a first side sleeve 701 , 702, 703, 704, the end of which can be connected to a corresponding control drive shaft 31 , 32, 33, 34. Each bushing 501 , 502, 503, 504 is further connected to a second side sleeve 601 , 602, 603, 604 on the opposite side with respect to the first sleeve 701 , 702, 703, 704. A longitudinal pin 401 , 402, 403, 404 is inserted in the bushing 501 , 502, 503, 504 and the side sleeves 601 - 701 , 602-702, 603-703, 604-704 to prevent the pulling out of the corresponding "set of elements" (e.g. 701 -501 -601 with reference to the first roll) thus formed. Advantageously, the axial connection between the elements which form the "set of elements" is removable in order to allow an easy extraction of the corresponding roller from the operative cavity of the mill stand in which the roll themselves are arranged. In this regard, the mill stand 10 comprises a monobloc body which supports the rolls 1 1 , 12, 13, 14 and the corresponding set of elements which allows its rotation, as well as the rotation of the system which allows adjusting the position of the rolls themselves with respect to the rolling axis. In particular, the body defines said operative cavity which accommodates the rolls. The pulling out of the set of elements thus allows extracting the rolls through such operative cavity without "opening" the mill stand, i.e. without needing to envisage the mill stand body as divided into two bolted plates. This "removable roller solution is thus particularly advantageous because it facilitates the assembly operations of the mill stand on one hand and the maintenance operations on the other. At the same time, this solution allows reducing the number of mill stands needed to cover a given series of products to be rolled; indeed, spare rolls and not mill stands are kept, with considerable saving in terms of investment.

Furthermore, with the removable roller solution, a standard type lathe may be used to restore the surface of the worn rolls, the use of a special lathe for turning the rolls without removing them from the mill stand being no longer necessary.

The position of the rolls 1 1 ,12,13,14 with respect to the rolling axis 100 can be adjusted by means of an eccentric adjustment system which may be, for example, of the type described in patent application EP2391460 mentioned above. In particular, each roll 1 1 , 12, 13,1 4, together with the corresponding longitudinal pin 401 , 402, 403, 404, is mounted on eccentric bushings 371 , 372 at its sides, one on the control side (drive shaft side) and one on the opposite side, the two bushings 371 , 372 are connected by a rigid bridge 373 which transmits the rotation from one bushing to another. The eccentric bushing 372 of the control side can rotate by means of a control device 60 of the eccentric rotation described below.

Again according to a solution known in itself, the eccentric systems related to two contiguous, or adjacent, rolls are connected by means of conical tooth sectors 79 configured so as to transmit the rotation of an eccentric system, controlled from the outside, to an eccentric bushing driven by an eccentric system of an adjacent roll, in which such driven bushing is connected on the side opposite to the control side. In this manner, for example, in the configuration of the mill stand 10 shown in Figure 2, the rotation of the eccentric system associated with the roll with reference to 14 is transmitted to the eccentric system associated with the roll indicated by reference numeral 1 1 .

The housing 4 in which the mill stands 10 are accommodated is vertically delimited between the substantially horizontal support plane 101 , on which the mill stands 10 rest, and a reference plane 102, which is substantially parallel to the support plane 101 . The distance between the mentioned planes 101 , 102, measured according to the vertical direction, is greater than the height 5 of the mill stands 10 (see Figure 2) measured according to the same direction. In this manner, the mill stands 10 can be introduced in the housing 4 and removed from it according to a transversal displacement direction 105 substantially orthogonal to the rolling direction 100. In this regard, the replacement of the mill stands 10 may be achieved by means of the system and according to the principles described in patent EP 2391460.

For each mill stand 10, each roll 1 1 , 12, 13, 14 is motorized by means of a corresponding drive shaft 31 , 32, 33, 34 connected to an actuating motor 41 , 42,

43, 44. In particular, according to a first aspect of the present invention, each drive shaft 31 , 32, 33, 34 is actuated, by means of a corresponding motor 41 , 42, 43,

44, independently from the drive shafts provided to rotate the other rolls of the same mill stand. The word "independently" here means that the motor which actuates one of said drive shafts 31 , 32, 33, 34 is different, thus installed in a different position, from the motor which actuates another drive shaft. This solution, thus appears entirely different from the one discussed above and described in EP 2391460, in which the four drive shafts are actuated by only two motors.

Each drive shaft 31 , 32, 33, 34 extends in reversible manner, along a direction parallel to the axis of the corresponding roll 1 1 , 12, 13, 14, from a retracted configuration, in which the drive shaft is operatively disconnected from the corresponding roll 1 1 , 12, 13, 14, to an extended configuration, in which the drive shaft is operatively connected to the corresponding roll 1 1 , 12, 13, 14, and more precisely to the end part of the side sleeve 701 , 702, 703, 704 which supports the roll itself. The expression "in reversible manner means that each drive shaft is configured not only to extend, but also to retract from said extended configuration to said retracted configuration. The rolling mill 1 according to the present invention comprises at least one inclinable drive shaft 31 , 33, when it assumes said retracted configuration (i.e. when the drive shaft is disconnected from the corresponding roll), between a first reference position (or aligned position), in which the rotation axis 31 1 , 333 of the drive shaft 31 , 33 is parallel to the rotation axis of the corresponding roll 1 1 , 13, and a second reference position (or rotated position), in which the rotation axis 31 1 , 333 itself is inclined with respect to the axis of the corresponding roll 1 1 , 33. In particular, according to the present invention, the rotated position which can be reached by the inclinable drive shaft 31 , 33 is such that the drive shaft 31 , 33 is outside the space comprised between the support plane 101 and the reference plane 102. In this manner, in the rotated position, said at least one drive shaft 31 ,33 does not hinder the replacement operations of the mill stand 10, i.e. the transversal movement of the mill stand along the transversal direction 105. For the purposes of the present invention, the expression "rotation axis of the drive shaft' means the rotation axis of the portion of the drive shaft which connects/couples to the corresponding side sleeve 701 , 702, 703, 704 which rotates the corresponding roll 1 1 , 12, 13, 14.

In the operative configuration shown in Figures 1 and 3, the drive shafts 31 , 32, 33, 34 are all shown on the extended configuration so that each one is operatively connected to the end part of the corresponding side sleeve 701 , 702, 703, 704. The first drive shaft 31 and the third drive shaft 33 respectively actuate the two non-contiguous rolls 1 1 ,13, the rotation axis of which is inclined by 22,5° with respect to the support plane 101 . The second drive shaft 32 and the fourth drive shaft 34 actuate the other two rolls 12, 14 with axis inclined by 67,5° with respect to the support plane 101 itself.

In the configuration shown in Figure 4, the drive shafts 31 , 32, 33, 34 are operatively released from the corresponding roll 1 1 , 12, 13, 14. In particular, by comparing figures 3 and 4, it is worth noting that the first drive shaft 31 and the third drive shaft 33 are orientable drive shafts according to the definition provided above. More precisely, these two drive shafts 31 , 33 are inclinable between the first reference position, in which the rotation axis 31 1 , 333 of each orientable drive shaft 31 , 33 is parallel to the rotation axis of the corresponding roll 1 1 , 13, and a second reference position, in which the drive shafts 31 , 33 themselves assume a position, which is entirely outside the space comprised between the support plane 101 and the reference plane 102. Specifically, the third drive shaft 33 is completely under the support plane 101 , while the first drive shaft 31 is completely over the reference plane 102.

Again with reference to Figures 3 and 4, the second drive shaft 32 and the fourth drive shaft 34 are not orientable drive shafts, but may be extended or retracted according to a direction parallel to that of the corresponding roll 12, 14. In particular, in the configuration in Figure 4, the two drive shafts 32, 34 (not orientable) are shown in the retracted configuration, in which they are completely outside the space comprised between the support plane 101 and the reference plane 102. In such retracted configuration, the second drive shaft 32 is completely under the support plane 101 , while the fourth drive shaft 34 is completely over the reference plane 102.

As a whole, it is worth noting that in the configuration of Figure 4, all the drive shafts 31 , 32, 33, 34 are outside the space comprised between the support plane 101 and the reference plane 102, space which is useful for displacing the mill stand transversally. In this regard, Figure 5 is a transversal view of the rolling mill in Figure 1 in a configuration corresponding to that of Figure 4. It is worth noting that the mill stand 10 can be displaced transversally (direction 105) to an unloading platform 801 to be replaced by a new mill stand (indicated by reference numeral 10') previously located on a loading platform 802. In particular, the new mill stand 10' is introduced transversally and pushes the mill stand 10 towards the unloading platform 801 , according to the principles described in EP 2391460.

Figures 6 and 7 show a possible embodiment of the second drive shaft 32 (also valid for the fourth drive shaft 34) respectively in the retracted configuration and in the extended configuration. Figure 7A is an axial view of the drive shaft in Figure 7. As shown, the second drive shaft 32 comprises a first portion 32A operatively connected to motor 42, which actuates, i.e. rotates, the drive shaft itself. The second drive shaft 32 also comprises a second portion 32B which is movable with respect to the first portion 32A. Such second portion 32B comprises an end which operatively couples to the side sleeve 702 associated with the second roll 12. The second portion 32B is movable with respect to the first portion 32A by effect of an inner spring 39. The latter acts so as to move the second portion 32B away from the first portion 32A. The two portions 32A, 32B are connected by means of internal toothings. Specifically, the portion 32B is defined by a tube which is axially movable, rotating and inclinable between the toothings to compensate for the eccentric movement which is imposed between the axis of the second portion 32B and that of the first portion 32A by effect of the eccentric control device 60 described below.

To vary the configuration of the second drive shaft 32, the use of thrust means is envisaged. Such means vary the position of the first portion 32A with respect to the second portion 32B. Preferably, the thrust means comprise a hydrodynamic actuator 81 stably fixed to structure 3 of the rolling mill 1 , the rod of which is integral with a slide 720 which is movable with respect to structure 3 and also with respect to the drive shaft 32. Such slide 720 supports the control device mentioned above.

Again with reference to figures 6 and 7, the first portion 32A of the drive shaft 32 does not vary its position during the change of configuration because it remains stably connected to the corresponding motor 42 fixed in turn to structure 3 (see for example Figure 1 ). The slide 720 is moved in axial sense by the actuator 81 and moves independently from the drive shaft 32. This means a condition in which the parts of the drive shaft 32A, 32B rotate, while the slide 720 translates without rotating. The spring 39 shown above pushes the second portion 32B in the coupling configuration of figure 7. In such configuration, the rod of the actuator 81 is extended and keeps the slide 720 in advanced position and more precisely so that the end part 720B of the slide 720 assumes a more advanced position (towards the roll 12) with respect to a collar 32C integral with the second portion 32B of drive shaft 32. The variation of configuration from extended (Figure 7) to retracted (Figure 6) occurs by activating the actuator 81 . Slide 720 is retracted by actuator 81 towards motor 42. During such displacement, the end part 720B of slide 720 intercepts the collar 32C of the second portion 32B, feeding the latter towards motor 42, in opposition to spring 39. Such feeding determines the operative release of the drive shaft 32 of the corresponding roll 12. Figures 8 and 9 show a possible embodiment of the first drive shaft 31 (also valid for the third drive shaft 33) respectively in the retracted configuration and in the extended configuration. Also the first drive shaft 31 comprises a first portion 31 A connected to the corresponding actuating motor 41 and a second portion 31 B, movable with respect to the first portion 31 A, and provided with an end which operatively couples to the first roll 1 1 . The first portion 31 A is connected to the corresponding actuating motor 41 by means of a Cardan joint 48 which defines a rotation axis about which the drive shaft 31 is rotated between the reference positions defined above. From the mechanical point of view, the two portions 31 A, 31 B of the first drive shaft 31 are connected in manner substantially corresponding to that envisaged for the portions 32A, 32B of the second drive shaft 32.

The first drive shaft 31 is rotated by an actuating device which rotates and guides the drive shaft itself between the two positions defined above. Figures from 10 to 16 show a possible embodiment of such device which comprises a lever body 8 hinged to structure 3 so as to rotate about an axis 7. Body 8 comprises a first part 8A, connected to a hydraulic actuator 82, and a second part 8B which configures a "fork' provided with two tines 88B. Such second part 8B develops from a side opposite to the first part 8A with respect to the rotation axis 7 of the lever body 8. The second portion 31 B of the first drive shaft 31 comprises pairs of wheels 36 diametrically opposite (see also figures 8 and 9) and configured to slide inside two guides 85 fixed to structure 3. Such guides 85 develop on substantially opposite vertical planes 185 between which the drive shaft 31 is operatively arranged. Wheels 36 are moved along guides 85 by means of tines 88B which intervene on them following the rotation of the lever body 8 about the mentioned axis 7. In this regard, Figures from 12 to 16 show the steps of the rotation, induced by the actuating device, between the first and the second reference position. In such figures, for description purposes only, the reference plane 102 is inclined by 22,5° with respect to a horizontal reference line 106. In the actual configuration (see figures 1 , 3 and 4) the reference plane 102 is substantially horizontal.

In Figure 12, the first drive shaft 31 is shown in the extended configuration, in which it is operatively connected to the corresponding roll 1 1 . In the condition in Figure 12, wheels 36 integral with the drive shaft 31 are outside guides 85 because the drive shaft 31 must be free to rotate the corresponding roll. In the condition in Figure 13, the first drive shaft 31 is shown in the retracted (releasing) configuration, in which it is free to rotate about the axis configured by the Cardan joint 48. In particular, before releasing the first drive shaft 31 , wheels 36 are aligned with guides 85, preferably by means of a motor encoder which controls the rotation of the first drive shaft 31 to the required condition. In the condition of Figure 13, wheels 36 of the drive shaft 31 are arranged substantially at the inlet of the corresponding guides 85. The rotation of the first drive shaft 31 is determined by the thrust of the hydraulic actuator 82 on the first part 8A of the lever body 8 so as to rotate the second part 8B in a sense such that tines 88B act on wheels 36. More precisely, following such rotation, wheels 36 are pushed by tines 88B along guides 85 which are shaped so as to cause a lifting of the first drive shaft 31 and a concurrent sliding of the second portion 31 B with respect to the first portion 31 A (see in sequence figures 13, 14 and 15). Such sliding occurs towards the rotation axis of the drive shaft 31 configured by the Cardan joint 48. The final position (second reference position) of the drive shaft 31 is established by the reaching of the end of travel in guides 85 (condition in Figure 16). In particular, the drive shaft 31 is held in the second reference position by tines 88B.

It is apparent that the reverse rotation of the drive shaft 31 , from the second to the first reference position, is obtained by means of a rotation of the lever body 8 in the opposite side. Such inverse rotation materializes in a lowering of tines 88B which determines a consequent lowering of the first extension 31 .

For the rotation of the third drive shaft 33, an actuation device equivalent to the new just described above may be used.

According to a preferred embodiment of the invention, the actuation device is configured also to vary the configuration of the first drive shaft 31 from the retracted condition to the extended condition. In this regard, the translation movement of the second part 31 B, at the end of which the first drive shaft 31 is operatively released from the corresponding roll 1 1 , may also be obtained by effect of the rotation of the lever body 8 and thus by the thrust of tines 88B. The latter, by acting on wheels 36, move the second portion 31 B of the drive shaft 31 towards the rotation axis configured by the Cardan joint 48, until the rotation of the drive shaft itself starts according to what has been described above. In other words, the actuating device described above is advantageously configured to vary the configuration of the first drive shaft 31 and to rotate it between the two reference positions. In other words, both operations are advantageously performed with only one device.

With reference again to Figures 1 and 3, according to another aspect of the invention, the second drive shaft 32 and the fourth drive shaft 34 comprise a control device 60 to adjust the eccentric system by means of which the radial position of the rotation axis of the rolls may be varied with respect to the rolling axis 100. For ease of description, reference will be made hereinafter to the second drive shaft 32, but the conditions remain valid also for the fourth drive shaft 34. In general, unlike the solutions known in the prior art, in particular the solution described in patent EP 2391460, the control device 60 is advantageously installed on the slide 720 (indicated above), moved through the actuator 81 , and not on the fixed structure. This solution thus allows simplifying structure 3 and thus eliminating, for example, the tipping control device described in EP 2391460. At the same time, when the second drive shaft takes the coupling configuration, the control device 60 is arranged in the correct operative position to intervene on the eccentric adjustment system. In other words, the control device operatively connects to the eccentric system when the drive shaft 32 reaches the coupling configuration.

With reference to figures 6, 7 and 7A, the control device 60 is in all cases integral with the slide 720, which translates axially by effect of the action of the thrust means 81 described above. The control device 60 comprises a ratio motor 61 which acts on an eccentric sleeve 27 with respect to the hollow shaft 322 of the second part 32B connected to, and rotated by, the first portion 32A of the drive shaft integral with motor 42. When the hollow shaft 322 is coupled to the side sleeve 702 of the corresponding roll 12 (extended configuration), sleeve 27 engages in the eccentric system associated with the second roll 12 so that a rotation of the eccentric sleeve 27 corresponds to a rotation of said eccentric system. The rotation of the eccentric system translates into a variation of the radial position of the roll and thus of the set of elements 602-502-702 which allows the rotation thereof. At the same time, by effect of the connection with sleeve 702, the corresponding radial position of the second portion 32B of the drive shaft 32 is varied. The rotation of the eccentric sleeve 27 is adjusted by the ratio motor 61 which acts on a crown gear externally associated with the same eccentric sleeve 27. By effect of the conical toothed sectors 79 envisaged in the mill stand 10, the rotation of the eccentric system associated with the second roll 12 is also transferred to the eccentric systems associated with the third roll 13.

The control device 60 described above is envisaged also for the first drive shaft 34, as clearly visible in Figures 3 and 4, for example. By effect of the transmission ensured by the conical tooth sectors 79, no control device is associated with the first drive shaft 31 and with the third drive shaft 33.

According to a further aspect of the present invention, shown in Figures 3 and 4, the rolling mill 1 comprises a retaining device 80 to lock the mill stand 10 in the housing 4 in a predetermined position. The latter is defined so that the rolls 1 1 ,12,13,14 assume the correct position with respect to the rolling axis 100. In particular, the retaining device 80 is installed underneath the support plane 101 and comprises a retainer 880 configured to assume at least one locking position and at least one unlocking position. In the unlocking position, the retainer 880 intercepts a housing of the base 10C of the mill stand 10 fixing the position of the latter in the housing 4 of the rolling mill. In the releasing position, the retainer 880 is under or on the level of the support plane 101 , thus allowing the translation of the mill stand 10 in the movement space defined between the two planes 101 , 102. So, advantageously, the retaining device 80 is entirely independent from the adjustment device of the eccentric, contrary to what has been envisaged, for example in the solution described in EP 2391460.

The rolling mill 1 according to the invention may be advantageously used as sizer rolling mill for making tubular bodies. In particular, the sizing is performed by means of a plurality of four-roll mill stands having the peculiarities described above.

Figure 17 is a side view of a rolling mill 1 according to the invention in a preferred embodiment, in which the housing 4 of the rolling mill 1 defines a first rolling section 410 and a second rolling section 420. The latter is defined downstream of the first sector 410 with respect to the feeding sense (indicated with reference 2) of the perforated bodies along the roll 100. In the first section 410, a first plurality of rolling mill stands 10A,10B (hereinafter also indicated with the expression first mill stands 10A,10B) is arranged in succession along the rolling axis 100 starting from an inlet section 4A of the housing 4. In particular, the mill stands 10A, 10B implement rolling on mandrel. In the second section 420, instead, a second plurality of rolling mill stands 15A, 15, 15B (hereinafter also indicated with the expression second mill stands 15A, 15, 15B) is arranged, which implement rolling without an internal tool. Such second mill stands 15A, 15, 15B, perforated bodies are thus arranged immediately downstream of the first mill stands 10A, 10B along the rolling axis 100 with respect to the sense of advancement 2. In other words, the second mill stands 15A, 15, 15B are arranged immediately in succession with the first mill stands 10A, 10B. So, as a whole, the rolling mill 1 appears as a single machine, defined in the scope of the same structure 3, which implements two rolling processes in series: the first on mandrel, the second without an internal tool. In particular, the first mill stands 10A, 10B and the second mill stands 15A, 15, 15B are four-roll mill stands having the features described above. It is worth noting that in Figure 17, the motors which actuate the drive shafts of the rolling mill stands are generically indicated by reference numeral 40.

Again with reference to Figure 17, the rolling mill 1 comprises a first mandrel- holder stand 1 12, arranged between the inlet section 4A of the housing 4 and the first plurality of mill stands 10A, 10B, and a second mandrel-holder stand, 1 13 arranged instead between the first mill stands 10A, 10B of the first section 410 and the second rolling mill stands 15A, 15, 15B of the second section 420. The mandrel-holder stands 1 12, 1 13 support the mandrel 7 when the perforated body is pulled out from the mandrel itself to be rolled without an internal tool in the second section 420.

Figures from 19 to 19A relate to a possible embodiment of a mandrel-holder stand which can be used in the rolling mill 1 according to the invention. Such embodiment is known in itself and will not be described in greater detail.

It is worth noting that from the operative point of view, the first mandrel rolling section 410 and the second section 420 for rolling without an internal tool may replace a REELER machine and a SIZER machine, respectively. In other words, the first section 410 can perform the thickness reeling function, while the second section 420 can perform the sizing of the perforated body. Therefore, the rolling mill 1 according to the invention may be advantageously used instead of these two machines (REELER-SIZER), at the same time allowing eliminating the heating furnace envisaged in traditional systems between the machines themselves. In particular, according to another advantageous aspect, it is worth noting that the first section 410 allows a reeling of the thickness of the "longitudinaf and not of the "helicoidaf type as in the traditional REELER machines. This possibility translates into a reduction of the number of faults with respect to the case of helicoidal reeling, which can be achieved by means of a traditional type REELER machine. As a result, the rolling mill 1 shown in Figure 17 may be advantageously used in a rolling system comprising, as main station or machine, an oblique type thickness- finishing rolling mill, such as for example an EXPANDER rolling mill, an ASSEL, DIESCHER or PLANETARY rolling mill. A possible use is envisaged also in a system in which a HOT WALKING BEAM type rolling mill or a PLUG MILL rolling mill is provided to define the thickness of the perforated bodies. The rolling mill types described above are well known to a person skilled in the art and for this reason are not described in detail. In general, the rolling mill 1 in figure 17 may be advantageously used instead of the REELER and SIZER machines normally envisaged in the rolling system indicated above.

Figures 18 and 18A relate to a possible embodiment of the first mill stand 10A,10B and/or of the second mill stands 15A,15,15B of the rolling mill 1 . As shown, the rolling mill 1 comprises an aligning and locking system of the mill stands in the housing 4. In a preferred embodiment, shown in the figures, the mill stands 10A, 10B, 1 12, 1 13 accommodated in the first section 410 and those accommodated in the second section 420 are provided with at least one pair of floating pins 71 A, 71 located on opposite sides of the mill stand and on a horizontal plane 300 passing through the rolling axis 100. The alignment system comprises at least one first pair of hydraulic cylinders 181 and one second pair of hydraulic cylinders 182 fixed to structure 3 at an outlet section 4B of the housing 4 and of the inlet section 4A of the housing 4, respectively. The cylinders 181 of the first pair act on a corresponding floating pin 71 of the last mill stand 15B of the second section 420, while the cylinders 181 of the second pair act on a floating pin 71 A of the first mill stand housed in the first section 410, i.e. the mandrel-holder stand 1 12. The cylinders 181 of the first pair push the floating pins 71 of the mill stand 15B from the second section 420 so that they are inserted in the corresponding female housings defined in the adjacent mill stand 15 pushing at the same time the floating pins already present in such housings. Such action repeats up to the first mandrel-holder stand 1 12 adjacent to the inlet section 4A of the housing 4. In particular, the pins 71 A of the first mandrel-holder stand 1 12 are inserted in corresponding housings in structure 3. In this manner, all the mill stands are constrained and axially locked. The cylinders 182 are fixed to structure 3 at the inlet section 4A and act on the floating pins 71 A of the mandrel-holder stand 1 12 so as to push them in opposite sense, i.e. towards the outlet section 4B. In this manner, the floating pins 71 , 71 A are released from the housings in which they were previously engaged so as to allow the successive removal of one or more mill stands of the rolling mill 1 .

According to a preferred embodiment, the mill stands 1 12, 1 OA, 10B, 1 13, 15A, 15, 15B of the rolling mill 1 are provided with a further pair of thrust points 73, 73A arranged on opposite sides of the mill stand, at a substantially vertical plane 312 passing through the rolling axis 100. In this configuration, the rolling mill 1 comprises further thrust cylinders 91 fixed to structure 3 as the outlet section 4B of the housing 4. Such further pairs of cylinders 91 act on thrust points 73, 73A arranged on the vertical plane 312 in manner similar to that described above for the cylinders which act on the floating pins arranged on the horizontal plane. The actions exchanged between cylinders 91 and the mill stands 1 12, 10A, 10B, 1 13, 15A, 15, 15B are of compression only.

The present invention thus further relates to a rolling system comprising at least one rolling mill having the peculiarities described above. As mentioned above, the rolling mill 1 may be used as sizer rolling mill or alternatively for rolling on mandrel and a rolling without an internal tool on perforated bodies, the thickness of which was already defined by means of a thickness-finishing rolling mill. The latter may be of the oblique type, e.g. of the EXPANDER, ASSEL, DIESCHER or PLANETARY type. Alternatively, the finishing rolling mill may be of the HOT WALKING BEAM or also of the PLUG MILL type.

The rolling mill according to the invention allows fully fulfilling the predetermined tasks and objects. In particular, the structure of the rolling mill appears simpler and with smaller dimensions than the structures currently envisaged in rolling mills with four-roll mill stands. In particular, the structure is simplified by effect of the independent actuation of the drive shafts combined with the use of the orientable drive shafts. At the same time, the installation position envisaged for the eccentric control device also contributes to simplifying the structure, at least in terms of transversal dimensions.

Claims

1 ) A rolling mill (1 ) for tubular bodies comprising:

- a structure (3) defining a housing (4) for at least one mill stand (10) with four rolls (1 1 , 12, 13, 14), wherein each roll is operatively connectable to a drive shaft (31 , 32, 33, 34), said housing (4) being vertically delimited between a substantially horizontal support plane (101 ) and a reference plane (102) parallel to said support plane (101 );

- four drive shafts (31 , 32, 33, 34), each of which can rotate a respective roll (1 1 , 12, 13, 14) of said mill stand (10), wherein each drive shaft (31 , 32, 33,

34) can axially extend and retract in reversible manner, passing from a retracted configuration, in which it is operatively disconnected from the respective roll (1 1 , 12, 13, 14), to an extended configuration, in which it is operatively connected to the respective roll (1 1 , 12, 13, 14) and vice versa, characterized in that each drive shaft (31 ,32,33,34) is actuated independently from the other drive shafts which can rotate the other rolls of the same mill stand (10) by means of a respective drive motor (41 , 42, 43, 44), installed in a different position from that of the motors which actuate the other drive shafts,

and in that two first (31 , 33) of said drive shafts can rotate two respective noncontiguous and reciprocally opposite first rolls (1 1 , 13) of the mill stand (10), and are angularly inclinable between a first reference position and a second reference position, such that they are outside the space comprised between the support plane (101 ) and said reference plane (102) when they are in the retracted configuration,

and in that two second (32, 34) of said drive shafts can rotate two respective non-contiguous and reciprocally opposite second rolls (12, 14) of the mill stand (10) and wherein, when the second drive shafts (32, 34) are in the retracted configuration, they are outside the space comprised between said support plane (101 ) and said reference plane (102).

2) A rolling mill (1 ) according to claim 1 , wherein the two second drive shafts (31 ,

32) have a telescopic configuration comprising a first portion (31 A, 32A) connected to the related actuating motor (42, 44) and a second portion (31 B, 32B) which slides telescopically with respect to the first portion (32A, 34A).

3) A rolling mill (1 ) according to claim 1 or 2, wherein the two inclinable drive shafts (31 , 33) also have a telescopic configuration, wherein a respective first portion (31 A, 33A) is connected to the respective actuating motor (41 ) and a respective second portion (31 B, 33B) can slide telescopically with respect to the first portion (31 A, 33A), wherein said respective first portion (31 A, 33A) is connected to the respective actuating motor (41 , 43) by means of a Cardan joint (48) which defines a rotation axis about which said inclinable drive shafts (31 , 33) are inclined between the first reference position and the second reference position.

4) A rolling mill (1 ) according to claim 3, wherein the two telescopic drive shafts

(32, 34) comprise thrust means (81 ) to vary the position of said second portion (32B, 34B) with respect to said first portion (32A, 34A) so as to vary the configuration of the two drive shafts (32, 34).

5) A rolling mill (1 ) according to claim 3 or 4, comprising an actuating device for rotating and guiding the two inclinable drive shafts (31 , 33) between the first reference position and the second reference position.

6) A rolling mill (1 ) according to any one of the claims from 1 to 5, wherein the rotation axis of the two first non-contiguous rolls (1 1 , 13) of the mill stand (10) is inclined by a 22,5° angle with respect to said support plane (101 ).

7) A rolling mill (1 ) according to claim 6, wherein the rotation axis of the two second non-contiguous rolls (14) of the mill stand (10) is inclined by a 67,5° angle with respect to said support plane (101 ).

8) A rolling mill (1 ) according to claim 7, wherein said actuating device comprises a lever body (8) hinged to said structure (3) to rotate about an axis (7), said body (8) comprising a first part (8A) connected to an actuator (82), and a second part (8B) provided with two tines (88B), said second part (8B) developing from a side opposite to that of the first part (8A) with respect to the axis (7), said second part (31 B) of said drive shaft (31 ) comprising pairs of diametrically opposite wheels (36) sliding within two opposite guides (85) fixed to said structure (3), said guides (85) developing on opposite vertical planes (185) between which the drive shaft (31 ) is operatively arranged, wherein said tines (88B), after the activation of said actuator (82), act on said wheels (36) moving them along said guides (85) and causing the rotation of said drive shaft (31 ).

9) A rolling mill (1 ) according to any one of claims from 1 to 8, wherein said rolling mill (1 ) comprises:

- an adjustment system for adjusting the radial position of a respective roll (12, 14) with respect to said rolling axis (100), and

- at least one control device (60) which is connected to said adjustment system to control the activation thereof,

wherein said control device (60) is connected to said adjustment system when the drive shaft (32, 34) of said respective roll (1 2, 14) takes said extended configuration.

10) A rolling mill (1 ) according to any one of claims from 1 to 9, wherein said rolling mill (1 ) comprises a retaining device (80) to lock said mill stand (10) in said housing (4) in a predetermined position, wherein said retaining device (80) is installed in a position under said support plane (101 ), said retaining device comprising a retainer (880) configured to take at least one locking position in which said mill stand (1 ) is locked in said predetermined position, and a releasing position in which said mill stand (1 ) may translate in said housing (4).

1 1 ) A rolling mill (1 ) according to any one of claims from 1 to 10, wherein said mill stand (10) comprises a monoblock body which sustains said rolls (1 1 , 12, 13, 14) within an operative cavity, said rolls (1 1 , 12, 13, 14) being removable from said monoblock body through said operative cavity.

12) A rolling mill (1 ) according to any one of claims from 1 to 1 1 , wherein said housing (4) comprises:

- a first section (410) for milling on mandrel, in which a first plurality of rolling mill stands (10A, 10B) is arranged in sequence along said rolling axis (100) from an inlet section (4A) of said housing (4);

- a second section (420) for milling without an internal tool, downstream of said first section (41 ), with respect to the advancement direction of said tubular bodies, said second section (420) comprising a second plurality of rolling mill stands (15A, 15, 15B) arranged in sequence along said rolling mill (100), wherein said rolling mill (1 ) comprises a first mandrel-holder stand (1 12) and a second mandrel-holder stand (1 13) arranged in said first section (410) upstream and downstream of said first plurality of rolling mill stands (10A, 10B), respectively, with respect to said advancement direction of said tubular bodies.

13) A rolling mill (1 ) according to claim 12, comprising a system for aligning and locking said rolling mill stands in said housing (4).

14) A rolling system characterized in that it comprises a rolling mill according to any one of claims from 1 to 13.

15) A rolling system according to claim 14, wherein said system comprises a thickness-finishing rolling mill upstream of said rolling mill according to any one of claims from 1 to 13, wherein said thickness-finishing rolling mill is of the oblique or of the HOT WALKING BEAM or HOT PILGER MILL type.