EP0238377A1 - Roll bending control in a rolling mill with axially shiftable rolls - Google Patents

Abstract

The subject of the invention is a rolling mill with axially displaceable cylinders, comprising, a support cage (4), at least two working rolls (1, 1 ') and at least two support rolls (2, 2'), at least one of the working rolls (1) being associated, on the one hand with means (42) for moving said cylinder (1) along its axis (10), and on the other hand for each chock ( 3), two symmetrical assemblies of at least two camber cylinders (6, 66). According to the invention, the offset of the cylinder (1) is continuously measured with respect to a centering position and the pressure exerted by each bending cylinder (6) is adjusted at all times, as a function of the offset measured and of the position at the same instant of the jack (6) considered relative to the median plane P5 of the bearing (12), so that the result of the cambering forces exerted by all the jacks (6, 66) remains directed, at each instant, along the median plane P5 of the bearing (12), the camber cylinders bear on the chocks by means of sliding faces.

Description

The subject of the invention is a method for adjusting the profile of cylinders which can be moved axially in a rolling mill and also covers the rolling mill which has been improved for implementing the method.

In general, a rolling mill comprises, inside a support cage, at least two working rolls resting, along a rolling plane, on at least two supporting rolls. The cylinders are carried at their two ends by means of bearings, in chocks mounted mobile, parallel to the rolling plane, in windows provided on the sides of the support cage. Usually called "quarto" rolling mills comprising two working rolls, each resting on a support cylinder and so-called "sexto" rolling mills in which intermediate rolls are interposed between the support rolls and the working rolls. In both cases, the axes of the cylinders are placed in the rolling plane, generally vertical, but it is also possible to support each working cylinder on a larger number of intermediate and / or support cylinders placed symmetrically on either side. other of the rolling plan.

To control the thickness of the rolled product and in particular to obtain a thickness equal in the direction transverse to the rolling direction, a bending or bending of the working rolls and possibly of the intermediate rolls is carried out by means of bending devices acting on the chocks of the corresponding cylinder. A distinction is made between the positive bending corresponding to a spacing of the chocks on either side of the plane of the product and the negative bending corresponding to an approximation of the chocks.

Generally, the bending device consists, for each chock, of two sets of jacks placed symmetrically on either side of the plane of the lami swimming and each acting, in the desired direction, on a support part integral with the chock. Normally, each support part of the chock rests on two cylinders spaced in the axial direction symmetrically on either side of the median plane of the chock bearings so that the bending force is well distributed over the bearings.

The rolling mill stand is symmetrical with respect to a median plane perpendicular to the rolling plane and which corresponds to that of the rolled product. Normally the cylinders are therefore centered on this plane with respect to which the chocks are arranged symmetrically.

However, it may be advantageous to make a longitudinal displacement and in the opposite direction or not of these rolls in order to satisfy various objectives such as the regularity of the wear of the rolls or the control of the flatness or of the profile of the rolled product. It is understood that the axial displacement of the cylinders presents difficulties when the latter are subjected to a bending force. This is why generally, the two operations are carried out separately, the bending effort being eliminated when an axial movement is carried out. However, it is advantageous, during rolling, to combine the effects of axial displacement and bending of the rolls.

In addition, the torque is generally applied to a single pair of cylinders, for example the working cylinders, and transmitted to the corresponding support cylinders by friction. However, it is necessary that all the cylinders remain driven at the same peripheral speed.

Consequently, even if the axial displacement is carried out when the rolling force does not exist, it is useful to maintain a certain camber to maintain sufficient friction between the rolls.

So that the axial displacement of the cylinders can be carried out without ceasing to exert the bending effort, it has been proposed to associate with each movable cylinder and its chocks a frame consisting of two beams mounted to slide axially on the stand of the rolling mill and on which bear the bending devices which, in this way, move at the same time as the cylinders, their chocks and the frame. This arrangement, however, complicates the production of the rolling mill and requires placing four relatively bulky beams inside the rolling mill stand and near the working rolls, that is to say in a space which is advantageous to clear.

The subject of the invention is a new device which, without substantially modifying the constitution of the rolling mill, makes it possible at the same time to bend and to move axially the working rolls or the intermediate rolls.

In accordance with the invention, the cambering force is exerted by means of fixed jacks bearing, on one side on a support integral with the cage and on the other on a sliding face formed on the corresponding chock parallel to the axial direction of movement, and, to achieve the camber of the displaceable cylinder, the displacement of the latter is measured at all times relative to the centering position of the cylinder on the median plane of the product and is continuously adjusted for each chock, the individual pressure exerted by each cylinder as a function of the measured offset and the position at the same instant of the cylinder considered with respect to the median plane of the bearing so that, in each choke, the result of the cambering forces exerted by the all cylinders remain directed at all times along the median plane of the bearing.

The invention also covers an improved rolling mill for implementing the method in which the camber cylinders of each chock are mounted on a fixed support integral with the cage and bear, in the direction of the cambering force, on a sliding face formed on the chock, parallel to the axial direction of movement; in addition, the rolling mill is associated with a balancing device comprising a means for measuring the offset of the cylinder considered relative to its centering position relative to the median plane of the product and means for individual adjustment, at each instant, of the pressure exerted by each cambering cylinder, as a function of the measured offset and of the position, at the same instant of the cylinder considered with respect to the median plane of the bearing, so that the result of the cambering forces exerted by all the cylinders remains directed, at each instant according to the median plane of the bearing.

In a preferred embodiment, the two chocks of each displaceable cylinder being each associated with two symmetrical sets of camber cylinders, arranged on either side of the rolling plane, the jacks placed respectively, in each of the sets, in the same relative positions relative to the median plane of their respective bearings are connected in parallel to the same branch of a common circuit for supplying pressurized fluid comprising as many branches as there are jacks in each assembly, each branch being provided with a means for individual adjustment of the fluid pressure with maintenance of equal flow rates in all branches.

Advantageously, the means for individually adjusting the pressures in the jacks comprise, on each branch of the supply circuit, a servo-valve controlled by a means of calculating the corrections to be made. at pressures as a function of the offset measured and displayed on the calculation means and of the respective positions in cylinders supplied by the branch considered.

According to a particularly advantageous characteristic of the invention, each chock can be associated with positive and negative bending means each comprising two opposite sets of at least two jacks acting respectively in the direction of spacing of the cylinders for positive bending and in the direction of approximation for negative cambering. These sets of cylinders are formed in hydraulic blocks placed on either side of the rolling plane, in the windows of the cage; each block consists of a solid support piece comprising a projecting central part framed by two longitudinal recesses in which the support ears of the chock engage, these being each provided with a continuous sliding face parallel to the axis and said sliding faces are placed opposite the lateral faces of the central part on which are arranged opposing bores two by two along an axis parallel to the rolling plane and each forming a cylinder body in which slides a piston secured to a rod opening into the corresponding recess to rest on the sliding surface of the chock.

Preferably, the rods of the jacks are capped by bearing pads on the sliding surfaces associated with columns for taking up the axial forces slidingly mounted, parallel to the rod of the jack, in guide bores made in the hydraulic block, elastic washers being advantageously interposed between the support pads and the sliding surfaces.

• La figure 1 représente schématiquement, en pers­pective, le fonctionnement d'un laminoir quarto à cylindres déplaçables.
• La figure 2 est une vue de dessus, partiellement en coupe axiale, d'un cylindre et de ses moyens de déplacement.
• La figure 3 est une vue des empoises des deux cy­lindres de travail et des dispositifs de cambrage, en coupe par un plan perpendiculaire au plan de laminage.
• La figure 4 est une vue de détail d'un vérin de cambrage.
• La figure 5 donne un schéma hydraulique du dispo­sitif d'équilibrage.

The invention will be better understood from the following description of a particular embodiment, given by way of example and shown in the accompanying drawings.

• Figure 1 shows schematically, in perspective, the operation of a quarto rolling mill with movable cylinders.
• Figure 2 is a top view, partially in axial section, of a cylinder and its displacement means.
• FIG. 3 is a view of the chocks of the two working rolls and of the bending devices, in section through a plane perpendicular to the rolling plane.
• Figure 4 is a detail view of a bending cylinder.
• Figure 5 gives a hydraulic diagram of the balancing device.

In Figure 1, there is shown schematically a quarto rolling mill comprising two working rolls 1 and 1ʹ and two support rollers 2 and 2ʹ. The axes of the cylinders are parallel and arranged along a rolling plane P1 passing through the contact generators.

The rolled product 20 passes between the working rolls 1 and 1ʹ and its median plane P2 corresponding to the plane of symmetry of the whole of the rolling mill stand and in particular of the support rolls 2 and 2ʹ. Normally, the cylinders are all aligned and centered on the plane P2. However, for the reasons indicated above, the working rolls 1 and 1ʹ can be moved axially relative to the centering position so that their respective transverse plane of symmetry is offset on one side or the other by relation to the median plane P2. To this end, an axial displacement force F1 is applied to the working rolls 1 and 1ʹ.

On the other hand, according to another known arrangement, bending forces F2 are applied to the ends of the shafts of the working cylinders 1 and 1ʹ, by means of their chocks so as to bend a corresponding cylinder.

Thanks to the arrangements according to the invention, the working rolls 1 and 1ʹ can be subjected at the same time to an axial displacement force F1 and to the bending forces F2.

In Figure 2, there is shown the assembly of a working cylinder, its chocks, and the axial displacement device.

The working cylinder 1 is provided at its ends with centered pins 11, by means of bearings 12 inside chocks 3 forming bearing bodies and mounted slidingly, parallel to the rolling plane P1, in windows 40 provided in the two uprights 4 of the rolling stand.

As shown in FIG. 3, each chock 3 of the working cylinder is provided for this purpose with sliding faces 31 parallel to the rolling plane P1 and which can slide along corresponding faces 51 formed inwards on support pieces 5 fixed in the windows 40 of the stand 4 of the rolling mill. Each support part 5 is common for the two working rolls 1 and 1ʹ and comprises longitudinal recesses 52 placed on either side of a projecting central part 53 and limited towards the outside by lateral parts 54, the guide faces 51 being formed at the end of the central part 53 and of the lateral parts 54. The chocks 3 and 3ʹ of the working rolls 1 and 1ʹ are provided with support parts or "ears" 32, 32ʹ which engage in the corresponding recesses 52, 52ʹ of the support part 5 and are provided with continuous planar faces 33, 34 facing the lateral faces 55, 56, respectively of the central part 53 and of the lateral part 54.

In the example shown, the rolling mill is provided with positive and negative bending means. The positive cambering means consist, for each chock, of two pairs of jacks 6 placed on either side of the median plane P1 in the central parts 53 of the support parts 5, the camber cylinders of the two working cylinders 1 and 1ʹ being opposite in pairs, forming two rows centered in planes P3, P4 parallel to the median plane P2 and axially spaced apart one from the other by a distance a (figure 2). FIG. 3 is a section through the axial plane of a line, for example P3.

In the central part 53 of the support part 5 are therefore provided, for each row of jacks, two opposite bores 57, 57ʹ centered on the axis 60 of the positive bending jacks 6 and 6ʹ and opening respectively on the lateral faces 55, 55ʹ of the central part 53. The two bores 57, 57ʹ are separated by a central partition 58 and constitute the bodies of the two jacks 6 and 6ʹ inside which pistons 61, 61ʹ slide extended by rods 62, 62ʹ which pass through partitions 63, 63ʹ sealingly closing the bores 57, 57ʹ. The two actuator chambers thus formed, inside each bore 57, 57ʹ can be supplied by a hydraulic circuit not shown, the support part 5 thus constituting a real hydraulic block. The rods 62 of the two jacks 6 and 6ʹ bear on the faces 34 of the supports 32 of the chocks 3 by means of pads 64 also shown in Figures 2 and 4. As can be seen in Figure 2, each pad 64 has a diamond shape comprising two points on which are fixed the ends of guide columns 65 slidably mounted, parallel to the axis 60 of the jack in bores made in the central part 53. Furthermore, the shoe 64 rests on the face 34 of the support part 32 of the chock 3 via a pad 66 and an elastic washer 67.

Advantageously, each chock 3, 3ʹ is also associated with negative cambering cylinders 7, 7ʹ placed in bores 59, 59ʹ formed in the lateral parts 54, 54ʹ of the support piece (5) and opening onto the lateral faces 56, 56ʹ. Each bore 59 constitutes the body of the jack 7 inside which slides a piston 71 secured to a rod 72 which passes in leaktight manner through a partition 73 closing the bore 59 inside which the piston 71 therefore limits two chambers of cylinders connected to a hydraulic circuit arranged in the support part 5.

Normally, there is no need to perform negative bending during axial displacements.

The rod 72 of each actuator 7 therefore bears directly on the face 33 of the support 32 placed opposite.

As seen in Figure 2, each chock 3 can slide parallel to the axis 10 of the cylinder along the guide faces 51 of the support piece 5. On the other hand, the two chocks 3 of each cylinder 1 are secured to the latter in the axial direction by means of caps 13 for closing the bearing cages 12, the latter being liable to withstand axial forces, for example tapered bearings. In this way, the two chocks 3 of each cylinder 1 follow the movements of axial displacement of the cylinder. Several devices for axial displacement of the cylinders are already known, which therefore need not be described in detail. It is possible, for example, to use a jack bearing on a lifting beam making it possible to apply the axial displacement force on the two sides of the chock 3.

However, if the displaced cylinder 1 is a driving cylinder, it is also possible, as shown in the figure, to use two displacement cylinders 42 supplied in synchronism, placed symmetrically on either side of the drive means 43 in rotation of the cylinder 1 and bearing on the supports 32 of the corresponding chock 3, each jack 42 being centered in a plane parallel to the rolling plane and passing through the axes of the camber jacks 6 and 7 and supplying it in synchronism .

According to one of the essential characteristics of the invention, the offset of the displaced cylinder 1 is measured relative to the median plane P1 by means of a displacement sensor 44 made up of two parts sliding relative to each other, fixed, for example on the two parts of one of the cylinders 42 and providing an analog signal proportional to the offset of the working cylinder relative to the centering position in the median plane of the product and of sign corresponding to the direction of the offset. This signal is used for balancing the pressures in the cambering cylinders by means of a device 8 shown diagrammatically in FIG. 5.

In this figure, there is shown by way of example a displaceable cylinder 1 and its two cambering devices each consisting of two sets of jacks placed in hydraulic blocks 5a, 5b, 5ʹa, 5ʹb each set comprising two jacks 6a, 66a and 6b, 66b, (6ʹa, 66ʹa, 6ʹb, 66ʹb).

As indicated above, the four jacks are centered in two transverse planes P3 and P4 spaced from each other by a distance a.

The hydraulic blocks 5a, 5b and 5ʹa, 5ʹb of the two chocks are connected by a single supply circuit 80 to a source of pressurized fluid not shown. The circuit 80 is divided into two branches 81 and 82. The branch 81 supplies the jacks 6a, 6b, 6ʹa, 6ʹb in parallel with the two wires P3 and Pʹ3 while the branch 82 supplies the jacks 66a, 66b, 66ʹa, 66ʹb in parallel of the two queues P4 and Pʹ4.

The hydraulic circuit is designed so that all of the cylinders are supplied with the same flow rate to determine equal displacements at the same speed.

Each branch 81, 82 of the supply circuit 8 is provided with a pressure regulator 83 which, depending on the signals received on its input 84 regulates the pressure in the corresponding circuit by maintaining a constant flow there.

The sensor 44 for the axial displacements of the cylinder 1 provides an analog signal proportional to the displacement which is applied to a computing unit 85. From the signals received, the latter develops the pressure setpoints S1 and S2 applied to the inputs 84 of the sensors 83 of the two branches 81 and 82 according to a law programmed in advance to ensure a pressure distribution such that the result of the thrust forces applied by the camber cylinders in the planes P3 and P4 always remains directed at each instant following the median plane of the corresponding bearings. In this way, as shown in FIG. 2, even in the centering position of the cylinders 1 in the median plane P1 of the product, the two rows of cylinders P3 and P4 are not necessarily symmetrical with respect to the median plane P5 of the bearing and this makes it possible to arrange the jacks in the most adequate manner inside the hydraulic blocks 5 whose plane of symmetry does not necessarily coincide with that of the bearing.

During movement, the pads 64 for supporting the cambering cylinders slide along the faces 34 of the chocks, the axial forces being collected by the columns 65 so as not to be transmitted to the rods 62 of the jacks 6.

Thanks to this arrangement, it is therefore possible to carry out the bending of the working cylinder at the same time as its axial displacement without appreciably modifying the size of the bending devices acting on the chocks which remain fixed inside the cage and are simply associated with hydraulic blocks connected to a pressure balancing circuit.

Of course, the invention is not limited to the details of the embodiment which has just been described, variants which can be imagined by employing in particular equivalent means without departing from the protective framework. defined by the claims.

Thus, if we have described, in the example shown, bending devices using at least two cylinders, we could, thanks to the pressure balancing performed according to the invention, also use a larger number of cylinders allowing better distribution of pressures.

Likewise, the various members used for balancing the pressures could be replaced by means fulfilling the same functions, these means being able to be hydraulic, electrical or even mechanical (cam, lever arm, etc.). In general, any technology for measuring displacements, calculating corrections and balancing pressures can be used to obtain the desired result.

Finally, it will be noted that, as can be seen in FIG. 3, the fixed bending devices according to the invention can adapt to different diameters of cylinders and / or adapt to a variation in diameter due to wear in the limit of the stroke of the cylinders.

Claims (9)

1. Rolling mill with axially displaceable rollers comprising, inside a support cage (4), at least two working rolls (1,1ʹ) resting, according to a rolling plane P1, on at least two rolls support (2,2ʹ) and the ends of which are carried, by means of bearings (12), in chocks (3) capable of being displaced, in the support cage, parallel to the rolling plane P1, at least one of the working cylinders (1) being associated, on the one hand with means (42) for moving said cylinder (1) along its axis (10) on either side of a position for centering the working rolls on the median plane P2 of the rolled product (20), and on the other hand means (6) for bending said roll (1) comprising, for each chock (3) two symmetrical assemblies of at least two camber cylinders (6, 66) spaced from one another in the axial direction,
characterized in that the cambering jacks (6) of each chock are mounted on a fixed support integral (5) with the cage and bear, in the direction of the cambering force, on a sliding face (34) formed on the chock (3) parallel to the axial direction of movement and that the rolling mill is associated with a balancing device (8) comprising a means (44) for measuring the offset of the cylinder (1) considered with respect to the centering position and means (83) for individual adjustment, at each instant of the pressure exerted by each camber cylinder (6), as a function of the measured offset and of the position at the same instant of the cylinder (6) considered relative to the plane median P5 of the bearing (12), so that the result of the cambering forces exerted by all of the jacks (6.66) remains directed, at all times, along the median plane P5 of the bearing (12). 2. Rolling mill according to claim 1, characterized in that the two chocks (3) of each cylinder displaceable being each associated with two symmetrical sets of camber cylinders, arranged on either side of the rolling plane P1, the cylinders (6a and 6b) (66a and 66b) placed respectively, in each of the assemblies, in the same positions relative to the median plane P5 of their respective bearings, are connected in parallel to the same branch (81) (82) of a common circuit (80) for supplying pressurized fluid comprising as many branches as cylinders (6 , 66) in each assembly, each branch being provided with means (83) for individual adjustment of the fluid pressure, with maintenance of equal flow rates in all branches. 3. Rolling mill according to claim 2, characterized in that the means for individually adjusting the pressures in the jacks comprise, a servo-valve (83) on each branch (81) of the supply circuit, said servo-valves being controlled by a means (85) of calculation, from a programmed law, of the corrections to be made to the pressures as a function of the offset measured and displayed by the calculation means and of the respective positions of the jacks supplied by the branch in question to ensure correct distribution pressure effort. 4. Rolling mill according to one of the preceding claims, characterized in that each chock (3) is associated with positive (6) and negative (7) bending means each comprising two opposite sets of at least two jacks acting respectively in the direction of spacing of the cylinders for positive cambering and in the direction of approximation for negative bending. 5. Rolling mill according to one of claims 1 and 4, characterized in that the sets of cylinders are formed in hydraulic blocks (5) placed on either side of the rolling plane P1, in the windows (40) of the cage (4) in which the chocks slide (3), that each block consists of a solid support piece (5) com taking a central projecting part (53) framed by two longitudinal recesses (52) in which engage support parts (32) of the chock (3) each provided with a continuous sliding face (34) parallel to the axis, said faces (34) being placed opposite the lateral faces (55) of the central part (53) on which are bores (57, 57ʹ) opposite two by two along an axis ( 60) parallel to the rolling plane P1 and each forming a cylinder body in which slides a piston (61) secured to a rod (62) opening into the corresponding recess (52) to rest on the sliding face ( 34) of chock (3). 6. Rolling mill according to claim 5, characterized in that the rods (62) of the jacks are capped by pads (64) bearing on the sliding faces (34), associated with columns (65) for taking forces , axial sliding mounted, parallel to the rod (62) of the cylinder in guide bores formed in the hydraulic block (53). 7. Rolling mill according to claim 6, characterized in that elastic washers (62, 67) are interposed between the support pads (64) and the sliding surfaces (34). 8. Rolling mill according to claim 5, characterized in that each support part (32) of chock is provided, on the side opposite to the central part (53), with a second sliding face (33) facing a projecting lateral part (54) of the support piece (5) in which are bores (59) with an axis parallel to the rolling plane P1, constituting the cylinders bodies (7) of negative cambering in which slide pistons (71) integral with rods (72) resting on said second sliding face (33) in the direction of tightening of the chocks (3). 9. Method for adjusting the profile of axially displaceable rolls in a rolling mill comprising, at inside a support cage (4) at least two working rolls (1,1ʹ) resting, according to a rolling plane P1, on at least two support rolls (2,2ʹ), and of which the ends are carried, by means of bearings (12), in chocks (3) mounted mobile in the support cage (4), parallel to the rolling plane P1, a process in which one simultaneously performs, on the one hand an axial displacement of at least one working roll (1) relative to a centering position for which the two working rolls (1,1ʹ) are symmetrical with respect to the median plane P2 of the rolled product and on the other hand a bending of the cylinder moved by applying on its ends a bending force, said force being exerted on each chock (3) by two sets of at least two camber cylinders spaced apart axially, characterized by the fact that the bending effort by means of fixed cylinders bearing, on one side on a support (5) integral with the ca ge (4) and on the other on a sliding face (34) formed on the chock (3) corresponding parallel to the axial direction of movement, and that, to achieve the bending of the cylinder during its displacement, we measure at at any time the offset of the movable cylinder with respect to the centering position and the individual pressure exerted by each cylinder (6, 66) is permanently adjusted for each chock (3) as a function of the offset measured and the position at the same instant of the jack in question (6, 66) relative to the median plane P5 of the bearing (12), so that, in each chock (3), the result of the bending forces exerted by all the jacks remains directed at each instant following the median plane P5 of the bearing (12).

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