Field of the invention

The field of the invention is that of rolling production, for example for wires or bars, for example by means of a separation or "slit rolling" process.

Background art

The two-wire slit rolling process is used to increase the output of a plant manufacturing wires and/or bars and, after passing the starting billet in one or more stands or rolling units to reach a substantially rectangular section, it provides for the rolled product to be divided longitudinally into two equal parts by passing through channels made in suitably shaped rolling mills, generating two rolled products which move in parallel and consequently generating two rolling lines. A first important limitation to the development of the two-wire/bar technology is due to the fact that the two wires obtained by the rolling division process are then processed separately, by means of separate machines. For this reason, two-wire slit rolling therefore implies a double cost for machinery, replacement parts thereof and maintenance of what is downstream of the separation. For example, in document JP61238405, the two wires generated by the splitter are spaced apart and dragged by two distinct pinch rolls, which act separately on each of the two wires.

An analogous system is also adopted in the device described by document US6647604 wherein a chasers die uses a plurality of pinch rolls for pulling and guiding metal strands along predetermined paths.

Also the equipment shown in patent US6920772 uses multiple motors for controlling distinct pinch rolls dynamically acting on the wires produced by a rolling plant.

A second limiting aspect difficult to manage is represented by the fact that in plants using two-wire slit rolling usually wires/bars with sections different from each other are produced, therefore the bulk difference existing between the two wires results in a different elongation of the same in the various rolling steps. In fact the rings of the rolling units have a determined gap which is predetermined as a function of the manufacturing batch and then kept constant, and therefore the bulk difference in the two wires, with same pressing in the respective rolling units, generates a different speed for each wire. If this drawback and the consequent use of arrangements to compensate for the asymmetry of behavior between the wires are to be avoided, there is provided the possibility of forming wires with diameters that fall within the tolerances required by the market and therefore are commercially accepted, but that may optionally have non-identical diameters. This, however, is a problem not easy to solve at the level of the pinch rolls, which therefore have to ensure a controllable and even behavior while concurrently managing both wires, also in the case of ring diameters of different sizes because of wear.

This is what happens, for example, in the case of the device described in document JP9155449, wherein the different shape and diameter of the two wires resulting from processing are managed by multiplying the pinch rolls, since there is no other possibility to ensure an even traction and advancing of the same wires. Furthermore, in this specific case, no compensation for the grip and movement of the two parallel wires is provided if the corresponding rings of the pinch roll have different sections due to wear.

An improving solution, illustrated in document DE624692C, provides two opposite pinch rolls, of which the upper pinch roll consists of at least twenty rings. The single rings have the capability of lifting individually or in groups depending on the size and shape of the material they have to drag. This is made possible by a member made of a flexible material which always keeps the rings in abutment with respect to the material to be dragged or with respect to the lower pinch roll. Therefore, such solution allows dragging different elements, also having different shapes. The hub remains always fixed and the rings may only lift parallel to a horizontal reference plane when the material to be dragged gets underneath these. Disadvantageously, the compensation for the shape differences, for example differences in diameter, among the products to be dragged, takes place with a structurally bulky and complex solution both in the manufacturing and maintenance steps, especially in the case of replacement of the innermost rings because of wear.

Summary of the invention Based on the limitations found in the prior art, it is therefore a primary object of the present invention to provide a single pinch roll which allows dragging two parallel wires with a single machine.

Another object of the invention is to make a pinch roll which allows dragging two wires having different diameters.

A further object of the present invention is to make a pinch roll which allows compensating for the difference in diameter between the two wires and the different wear of the rings.

Another object of the invention is to make a pinch roll which allows dragging two parallel wires occupying a very small volume with respect to the prior art, wherein two machines or a single bulky machine are used, and accordingly reducing the related costs.

These objects are achieved by means of a single pinch roll, or a single pinch roll for rolled bars or wires which, in accordance with claim 1 , comprises two ring- holder assemblies and two pairs of rings, each pair of rings being mounted on one of the two ring-holder assemblies, each ring-holder assembly comprising an anchoring shaft and a hub to which the pair of rings is fixed, and wherein at least one of the two ring-holder assemblies comprises a mobile joint elastically connected to the respective hub and adapted to to allow said respective hub to vary its inclination with respect to a horizontal reference plane.

Such objects, in a further aspect of the invention, are achieved by means of a method for dragging wires and bars coming from a rolling process, using the above-mentioned pinch roll, which, in accordance with claim 1 1 , comprises the following steps:

(a) exerting a continuous force on at least one of the two ring-holder assemblies so that a force sufficient to produce a dragging of the wires is applied on the rings by means of the respective hub,

(b) balancing the possible angular displacement of the axis of at least one hub with respect to a horizontal reference plane P by means of a respective mobile joint which allows the inclination of said at least one hub to be varied with respect to said horizontal reference plane.

In the following description, it is understood that using the term wire for reasons of brevity also means the rolled bar product. It is further taken as an example a two- wire slit rolling process, but it should be understood that the invention relates without distinction to any pair of wires, for example coming from different processes, which work in parallel.

By means of the pinch roll of the present invention all the problems of the prior art due to the use of multiple pinch rolls, also different from each other, are avoided, and it is possible to control the advancing of the rolling wires by the even application of the same traction or thrust force when dragging two identical wires with identical wear of the rings, or by the application of different traction or thrust forces in the case of two different wires and/or different wear of the two rings. For example, in the case of two wires having different diameter the rings that drag the wire of greater diameter are subjected to a greater force than the rings that drag the wire of smaller diameter.

This may be made thanks to the use of the mobile joint elastically connected to at least one of the hubs of the rings, which allows dynamically managing both the possible differences of the wires and the sectional differences of the rings. In fact, the joint allows varying the inclination of the hub with respect to a horizontal reference plane and thus adapting to the different configurations of the rings and of the rolling wires always maintaining the force applied to the wires for the dragging thereof at a sufficient level.

The solution allows dragging a maximum of two wires, by means of the friction exerted by the rings, which have the possibility, together with the corresponding hub, to be inclined by angles Ω with respect to a horizontal reference plane P, thanks to the peculiarity of the mobile joint which is an adjustable joint, that is oscillating about a horizontal axis perpendicular to the horizontal rotation axis of the anchoring shaft supporting the respective ring-holder assembly. The wires are each dragged by a pair of rings mutually operating in the vertical direction. The profile of the contact surface of the rings with the respective wire is selected based on the shape of the cross section of the product to be dragged. The contact between the wire and the rings is constantly ensured at three points: two contact points with the rings of the lower assembly and one contact point with the rings of the upper assembly. Furthermore, the dynamic dissipation of force acting on the wires is avoided thanks to the combined use of at least one elastic actuator and abutment surfaces which restrict the movement of the mobile joint within predetermined degrees of freedom.

Although an application of the pinch roll of the invention is that in which the difference of diameter is in the order of 10%, such a solution may also be applied to solutions in which the two wires have diameters that differ from one another by more than 0%, for example up to 25%.

The dependent claims describe preferred embodiments of the invention.

Brief description of the figures

Further features and advantages of the invention will appear more clearly from the detailed description of preferred but non-exclusive embodiments of a pinch roll according to the present invention, shown by way of a non-limiting example with the aid of the accompanying drawing tables, in which:

Fig. 1 schematically shows a detail of a pinch roll according to the present invention;

Fig. 2 schematically shows a sectional view of the pinch roll of the invention dragging two wires having the same diameter,

Fig. 3 schematically shows the possible angular displacement Ω of the axis of the hub in the case of wires having the same diameter (a), wires having different diameter (b) or rings having different sections (c);

Fig. 4 schematically shows a sectional view of the pinch roll of the invention dragging wires having different diameter;

Fig. 5 shows a schematic view of part of a variant of pinch roll according to the invention, dragging wires having the same diameter;

Fig. 6 shows an enlargement of the view of Fig. 5;

Fig. 7 shows an enlargement of the view of Fig. 5 with two wires having different diameter between the rings;

Fig. 8 shows an enlargement of the view of Fig. 5 with two wires having equal diameter, but rings having a different shape due to wear.

Same reference numerals in the various figures designate the same members or components. Detailed description of preferred embodiments of the invention

As schematically shown in Figure 1 and more in detail in Figure 2, the present invention provides a single pinch roll to drag together two rolled bars or wires only, having two pair of rings mounted on a ring-holder assembly, so as to move the two bars close and parallel to each other.

!n the embodiment exemplified in Figure 2, both the two wires 1 and 1 ' must be dragged: this means that between the upper rings 2 and 2' and the lower rings 3 and 3' a certain force has to be continuously exerted on both wires 1 and 1 ', sufficient for their dragging. To this end, the force exerted by a pneumatic cylinder 4 or other suitable actuating means, is transmitted by the upper ring-holder assembly 5 to the upper rings 2 and 2' and optionally also to the lower rings 3 e 3' through the lower ring-holder assembly 7.

Fig. 3 very schematically shows possible situations that occur in the case of wires having equal diameter and rings having equal section (a), wires having different diameter and rings having equal section (b), and rings having different sections and wires having equal diameter (c). Only in cases (b) and (c) there is an angular displacement Ω, Ω', Ω" of the axis of the hub or hubs with respect to a horizontal reference plane P. In this figure the profile of the contact surface of the rings 2, 2', 3, 3' is rectilinear for simplicity of illustration.

If the two wires have the same diameter and the rings of the two dragging lines are identical (Figure 3a), the upper hub 6 remains horizontal and transmits, through the two rings 2 and 2', the force coming from the pneumatic cylinder 4 to the wires 1 and 1 ' in an equal manner, so as to allow the dragging thereof. In this case, therefore, the angular displacement Ω of the hubs 6 and 8 is zero, their longitudinal axis being virtually horizontal.

If the diameters of the two wires 1 and 1 ' are different (Figure 3b) or the rings show signs of wear, and therefore have different thicknesses (Figure 3c), the upper hub 6 initially contacts the wire having greater diameter with the respective upper ring (Figure 3b) or the less worn ring with the respective wire (Figure 3c), and subsequently the force coming from the cylinder 4 causes the upper hub 6 and optionally also the lower hub 8 to become inclined so that also the second wire contacts the respective rings and the force needed for dragging is transmitted to both wires. In this case, the forces transmitted to the two wires are different from each other.

The upper hub 6, and optionally also the lower hub 8, becoming inclined with respect to a horizontal reference plane P (see schemes of Figure 3) is made possible by the mobile joints 9, in particular oscillating joints consisting of a suitable pivoting system, comprised in the ring-holder assemblies 5 and 7, respectively.

In a first embodiment, there is provided that only one of the two hubs, for example the upper hub 6, is elastically connected to a mobile joint 9 and can thus undergo angular displacement. In this variant, if the diameters of the two wires 1 and V a e different, as per Figure 3b, and/or the rings show signs of wear and therefore have different thicknesses, the upper hub 6 will become inclined while the lower hub 8 will remain horizontal.

In a second embodiment, provided especially for considerable variations between the diameters of the two wires and/or between the thicknesses of the rings, both hubs 6, 8 are elastically connected to a respective mobile joint 9 so that both may become inclined, as shown in Figure 3c.

The angular displacement Ω of the hub 6 and optionally also of the hub 8 takes values other than zero, shown in Figure 3b and 3c from Ω and Ω' for hub 6 and from Ω" for hub 8, respectively. Such values of angular displacement will be given by the inclination angle of the longitudinal axis of the hubs 6 and 8 with respect to the horizontal reference plane P. The mobile joint 9 therefore allows tolerating and managing different diameters of the two wires and different signs of wear between the respective rings. As shown in Fig. 1 , the mobile joint 9 consists of an inner annular component 10 rigidly fixed to the shaft 101 and having an outer convex surface and an outer annular component 1 1 on which the hub 6 is fixed and having a surface substantially mating the convex surface of the inner component 10. The outer component 1 can slide with its inner surface on the outer convex surface of the inner component 10 causing a rotation of the same outer component 1 , of the hub 6 and of the rings 2 and 2' along the circumference A described by the convex surface of the inner component 10.

Transmission means 12, for example a toothed coupling, allow transmitting the torque from the shaft 101 to the hub 6, so as to cause the rings 2, 2' to rotate. In a preferred variant said toothed coupling is made by providing first teeth protruding from the central zone of the inner annular component 10 and corresponding second teeth made in a hollow central zone of the outer annular component 1. The outer component 1 1 of the joint 9 may be advantageously provided with an elastic movement attenuator 14 connected to the anchoring shaft 101 ; such actuator 14 counterbalances the rotational movement of the outer component 1 1 on the inner component 10 and, when the wires or bars are not in the grip, returns the outer component 1 1 and therefore the rings 2, 2' to the standard symmetrical central position; in this way, in the absence of the wires, the ring-holder assembly 5 is not free to move and is kept in a central position, ready to accommodate the wires and perform an immediate grip thereon. The elastic movement attenuators 14 may for example consist of springs or an analogous system.

A predetermined clearance 13, provided between the first teeth of the inner component 10 and the shoulders of the hollow central zone of the outer component 1 1 , limits the range of inclination of the hub 6 making the operation of the pinch roll possible also when there is a single wire.

In one alternative variant, it is possible to provide a third ring on the hub, placed centrally with respect to the two above-mentioned rings, which allows dragging a single wire without changing the entire ring-holder assembly.

A joint and an elastic movement attenuator may also be in the lower ring-holder assembly 7 (variant not shown in Figures), analogously with what has just been described.

The configuration of the pinch roll according to the present invention, in the case when the diameter of the wires 1 and V is different, is shown in Figure 4. This figure shows the use of the ring-holder assembly 5 according to the invention in a rolling plant and highlights the asymmetrical positioning of the parts making up the joint 9 and of the rings 2, 2' when a force F is applied to the ring-holder assembly 5 which is transmitted differently on the wires 1 , 1 ' having different diameter. The hub 6, acting on the pair of wires 1 and 1 ', shows an angular displacement which is made possible by the sliding of the outer component 1 1 on the convex surface of the inner component 10. Furthermore, the joint 9, alternatively to the articulation defined by the above- mentioned components 10, 1 , can also be replaced by a different pivoting system which allows the oscillation of the ring-holder assembly with respect to an axis: such systems can for example consist of oscillating bearings or suitably shaped bushings.

The operation of the pinch roll according to the present invention takes place as follows. The two wires or bars 1 , 1 ', coming from the same rolling process or different processes, are gripped between the two respective rings 2, 3 and 2', 3' of the pinch roll and actuating means are actuated, for example a pneumatic cylinder 4, to exert a certain continuous design force F, for example, on the ring-holder assembly 5 which is transmitted to the wires or bars 1 , 1 ' in a manner sufficient to produce a dragging thereof. The force F is transmitted through the hub 6 of the ring-holder assembly 5 to the rings 2, 2' and, in the presence of differences in diameter between the sections of the two wires 1 and 1 ' and/or different wear of the rings, a balancing of the angular displacement Ω of the axis of the hub 6 with respect to the horizontal reference plane P is made thanks to the sliding of the inner surface of the outer component 1 1 on the outer convex surface of the inner component 10 of the joint 9.

As is schematically understood from Figures 3, 6, 7 and 8, the angular displacement Ω, Ω', Ω" of the axis of the hubs 6, 8

(i) is = 0 if the diameters of the wires or bars 1 , 1 ' are reciprocally equal and the sections of the rings 2, 2', 3, 3' are reciprocally identical (Fig. 3 or 6), or for the ring-holder assemblies not provided with the joint 9, 9', while

(ii) is≠ 0 when the diameters of the wires or bars 1 , 1 ¹ are different from one another (Fig. 7) and/or the sections of the rings 2, 2', 3, 3' are not identical to each other (Fig. 8).

With reference to Fig. 5, a schematic view is shown of part of a pinch roll according to the invention, which drags two wires 1 , 1 ' having equal diameter. This schematic view corresponds to the configuration shown in Figures 1 and 2.

One of the two ring-holder assemblies, in this case the lower ring-holder assembly 7, is the one for reference, that is fixed, which determines and ensures the position of the wires to be dragged. To give the position, each wire 1 , 1 ' has two contact points 20, 21 and 20', 21 ' with the respective rings 3, 3' of the lower ring-holder assembly 7. The other ring-holder assembly, in this case the upper ring-holder assembly 5 (as well as in Figures 1 , 2 and 4), has a mobile joint 9 which is an adjustable/oscillating joint allowing the ring-holder assembly 5 to pivot about an axis perpendicular to the sheet of Fig. 5 and passing through the point O belonging to the rotation axis of the anchoring shaft 101 which supports said ring- holder assembly 5. Such upper ring-holder assembly exerts the dragging force on the wires 1 , 1 ' by means of a third contact point 22, 22' of the oscillating rings 2, 2' with the same wires 1 , 1 '.

In the case of a different diameter between the wires or bars 1 , 1 ' to be dragged, the force exerted on the wire having the greater diameter is greater than that exerted on the wire having the smaller diameter. Therefore, in order to grip both wires, it is necessary to apply a great force on the wire having the greater diameter to obtain a force sufficient to also drag the wire having the smaller diameter.

With reference to Fig. 5 the forces that cause the mobile joint 9, and therefore the upper ring-holder assembly 5 to pivot depend on the reaction of contact between the wires and rings along the axes X, X' delimiting the arms "r" and "s" relative to point O.

The value of the force applied to the mobile joint can be reduced increasing the length of the arms "r" and "s". This can be achieved by advantageously providing a V-shaped profile of the rings 2, 2' and designing an appropriate inclination of the sides of the V-shaped profile or contact surfaces of the rings 2, 2', that is the adjustable or oscillating rings, and the wires 1 , 1 ', whereby r>a/2 and s>a/2 are obtained (Fig. 5) unlike a horizontal rectilinear profile of the contact surface of the rings whereby the arm r, s equals a/2.

Advantageously, to obtain greater lever arms, it is necessary to ensure the wire/oscillating ring contact at a single point of the contact surface of the rings 2, 2'. This can be achieved by maintaining the V-shaped profile with the distance between centers "b" of the oscillating rings 2, 2' lower than the distance between centers "a" of the fixed reference rings 3, 3', that is a>b. Therefore, as is already visible in Figures 1 , 2 and 4, there is a different width of the dragging devices comprising the respective hub 6, 8 and the respective rings 2, 2' and 3, 3': for example the distance between centers "a" of the rings 3, 3' is 80 mm while the distance between centers "b" of the rings 2, 2' is 75 mm. This difference in width is made in order to reduce the force F exerted on the upper ring-holder assembly 5: if the width of the two dragging devices were equal, and the diameters of the two wires quite different, in order to obtain the contact between the wire having the smaller diameter and the two respective rings, a significantly great force would have to be applied to the other two rings and to the respective wire having the greater diameter, with the risk of deforming it by plasticization. By the expedient of the different distances between centers between the upper rings 2, 2' and lower rings 3, 3', the contact between the wire 1 ' having the smaller diameter (Fig. 7) and the corresponding upper ring 2' is facilitated and requires a smaller force due to the greater arm applied to the system.

It is further preferred that the angle β defined by the V-shaped profile of the rings 2, 2' is greater than the angle a defined by the V-shaped profile of the rings 3, 3' so as to maintain the wire always in contact with the rings to avoid the inward lateral sliding thereof. In this way, the wire 1 , 1 ' remains closed between three contact surfaces (Figure 6). Substantially, the angle a of the lower rings is slightly narrower, for example of about 8-12°, with respect to the angle β of the upper rings. In order to ensure the constant support of the rings on the material to be dragged, the at least three contact points 20, 21 , 22, 20', 21 ', 22' are needed for each pair of rings 2, 3 or 2', 3' in the vertical direction. In fact, if these angles a and β were equal, when the upper ring-holder assembly 5 is inclined, it would allow the wire having the greater diameter to move inwards and optionally disrupt the contact with the rings. On the contrary, by differentiating the angles as described, such possibility of movement is prevented.

The rotation of the mobile joint or oscillating joint 9 takes place either when the two wires dragged have different diameters (Fig. 7) or when the rings are different, for example due to wear (Fig. 8).

Thanks to the invention described herein, it is therefore possible to obtain a single machine replacing the use of multiple pinch rolls and different pinch rolls inside the same plant, thus allowing to drag two parallel bars at extremely small distances, to drag two bars having different diameters and to compensate for the different wear of the rings thus addressing all the problems found to date.