EP0161192B1 - Adjusting method for a cross-rolling mill, and mill using this method - Google Patents

Abstract

The invention relates to a process for controlling a rolling mill having oblique rolls which is used for rolling metal rods or tubes, and to the rolling mill for carrying out the process. The rolling mill according to the invention comprises at least three rolls distributed round the rolling axis, each of the rolls having a profile generated by revolution of decreasing cross-section, the roll axes not intersecting the rolling axis, and each of the rolls exerting on the product a pressure which permits helicoidal rolling to be carried out. The process involves controlling the forward feed while keeping the angle of inclination of each of the axes of revolution of the rolls constant relative to a secant straight line, the so-called control axis, which is a straight line perpendicular to the rolling axis and intersecting said rolling axis and which traverses the zone of contact between the roll and the product to be rolled. The process also relates to a particular method of rolling in which combined variation of the feed angle and the gap between the rolls is effected during rolling.

Description

The invention relates to a method for adjusting a rolling mill with oblique cylinders, of the type used for rolling metal bars or tubes in order to obtain a high reduction ratio in a single pass. The invention also relates to a rolling mill allowing the implementation of this adjustment method.

Such a process applies in particular to the hot rolling of bars or tubes, for example of steel.

Patent FR 1 576 091 describes, on pages 5 and 6 as well as in FIG. 2, a rolling mill with oblique cylinders comprising three working cylinders in the shape of a mushroom. These cylinders are arranged inside a cage formed by a casing 30, to which three cylinder supports 31 are fixed, distributed around the axis of the material to be laminated. The cage rotates around this axis, thanks to a motor whose drive pinion drives a toothed ring 37. The rotation of each cylinder 27 around its axis 36 is obtained by a planetary system comprising a toothed ring 32 fixed on a shaft hollow inside which the material to be laminated moves.

Three satellite systems mesh on this ring gear and each rotate a cylinder such as 27 by means of a pair of angle gears 35. One of these gears is mounted on the axis of the satellite 34, the another on the axis 36 of the rolling cylinder.

The adjustment means of a rolling mill of this type, so as to adjust the advance to the desired value in particular as a function of the laminated diameter is described in the article by E.J.F.E. Breitschneider published in Iron and Steel Engineer (October 1981 pages 51 to 54). It consists (see page 51 left column), to rotate the axis of each rolling cylinder around the axis of the corresponding satellite, so as to obtain the desired degree of inclination which allows the advance. This rotation from one axis around the other is carried out without modifying the angle between these two axes which is imposed by construction, and can be, for example, 60 ° (see page 52 left column). This inclination allowing the advance can, according to the author, vary from 0 to 10 °.

Furthermore, FR 1 576 091 describes a means for adjusting the rolling diameter. This means consists in sliding each working cylinder along its axis 36, by acting on an approach device 38, which makes it possible to vary the outlet section of the material to be laminated.

The adjustment of the rolls of rolling mills of this type, by these two means, has serious drawbacks. Indeed, the adjustment of the advance, which is carried out by rotating the axis of each cylinder around the axis of the corresponding satellite, causes a displacement of the working area of each cylinder in contact with the product.

This transverse displacement is due to the fact that, the more the angle of advance is increased, the more the cylinder deviates from the plane of symmetry which passes through the rolling axis and the axis of the satellite. This results in a first cause of disturbance of the rolling conditions, which, in such a process, are particularly critical and must be able to be adjusted with great precision. The adjustment of the outlet section, obtained by sliding the cylinder along its axis, also has the disadvantage of displacing the rolling zone along the rolling axis. The combination of such an axial displacement with the transverse displacement consecutive to the adjustment of the advance, has the effect of further disrupting the rolling conditions and therefore adversely affecting the quality of the product, in particular with regard to the state of surface and in the case of a tube the regularity of thickness.

French patent 1,475,645 describes another type of oblique rolling mill with three rolls in which a joint adjustment is made of the spacing of the rolls with respect to the rolling axis and the feed angle. For this each cylinder is mounted on two bearings arranged on either side of the cylinder. FIG. 1 of this document shows that this combined adjustment is achieved by rotating a flange around the rolling axis which carries the three bearings located on the same side of the cylinders.

It is thus possible during rolling, in particular at the end of rolling of a tube blank, to simultaneously vary the spacing of the rolls and the feed angle, in order to avoid in particular tearing of blanks and even blockages. . This possibility is particularly important for high cross-section reduction rates.

This adjustment method has the disadvantage of causing a displacement of the working area of each cylinder in contact with the product.

Furthermore, as can be seen in FIGS. 1 to 6 of this same document, the method applies to rolling mills the axis of the rolls of which is only slightly inclined relative to the rolling axis.

Also known is the Russian patent 733 748 which describes a rolling mill with three oblique cylinders fixed in cantilever at the end of their respective shaft of revolution. These trees are themselves mounted in cages. In this rolling mill, it is possible to adjust the spacing of the rolls relative to the rolling axis and to modify the angle of advance by moving the cages relative to an axis perpendicular to the rolling axis. The essential characteristic of SU 733 748 is that the cylinder holder cage can move perpendicular to its axis. This displacement device perpendicular to the axis of the cylinder cage allows, as said in this patent, to widen the range of adjustment of the feed angles, but this results in a modification of the working area of each cylinder in contact with the therefore produces rolling conditions as explained above.

The present invention aims to produce a rolling mill with oblique cylinders of the type mentioned above, making it possible to adjust the advance of the product during rolling virtually independently of the other adjustment parameters. It also relates to the possibility in such a rolling mill to vary within wide limits the diameter of the laminated products obtained, while preserving the optimal rolling conditions in particular by using the same set of rolling rolls.

The invention also aims to produce a rolling mill having a structure as compact and robust as possible as well as a minimum bulk.

The rolling mill according to the invention provides a particularly effective solution to these problems.

The invention relates to a rolling mill with oblique cylinders making it possible to obtain metallic bars or tubes of revolution, comprising at least three cylinders distributed around the rolling axis, each cylinder having a profile of revolution of generally decreasing section, at least in the part ensuring the reduction in outside diameter of the product to be laminated, from the entry side thereof to its exit side and being mounted in cantilever at one end of a shaft of revolution connected by means transmission to a rotary drive means, this shaft of revolution being supported by bearings mounted inside a cylinder holder cage itself mounted in rotation about an adjustment axis which cuts the axis of revolution of the cylinder by forming an angle of 20 to 70 ° with it, crosses the surface of the cylinder in the area of contact with the product being rolled and cuts the rolling axis at right angles, a first means of setting allowing to adjust the spacing of each cylinder relative to the rolling axis by moving the cylinder holder cage along the adjustment axis. The rolling mill is characterized in that the first adjustment means comprises a screw / nut assembly centered on the adjustment axis, one of the two components of which, preferably the screw, is disposed at the periphery of the cylinder holder cage, and integral with it, the other component being mounted free in rotation on a bearing fixed relative to the frame of the rolling mill, a drive means in rotation making it possible to rotate the free component in rotation relative to that which is integral of the cylinder holder cage, around the adjustment axis, by a determined amount to move the cylinder holder cage of the desired length along the adjustment axis.

According to known practices, each rolling cylinder has a calibration zone at the end of the reduction deformation zone.

Advantageously, the adjustment axis crosses the. surface of the cylinder in an area of this cylinder corresponding to the middle of the calibration area.

Preferably the component free in rotation of the screw / nut assembly comprises a toothed ring which can be driven in rotation by a first motor means which actuates a toothed pinion which meshes on this ring. Preferably also the screw of the screw / nut assembly is constituted by a thread, produced at the periphery of the cylinder holder cage, the nut being a nut crown mounted in rotation on a bearing fixedly connected to the rolling mill frame. .

Preferably at each cylinder holder cage, a second adjustment means comprises a rotary drive means which makes it possible to rotate the cylinder holder cage around the adjustment axis, under the action of a second motor means. This makes it possible to orient the cylinder holder cage so as to give the cylinder the desired angle of advance A with respect to the rolling axis. Preferably, a wedging means can make it possible to prevent the rotation of the free component in rotation of the screw / nut assembly, during the drive in rotation of the cylinder-holder cage around the adjustment axis. The action of this wedging means makes it possible, by acting only on the second adjusting means, to combine the advance angle and the spacing of the cylinder with respect to the rolling axis.

The feed angle A is preferably adjusted between 3 ° and 30 °.

One can also provide for securing the two components of the screw / nut assembly when the second adjustment means is acted on, so as to vary only the angle of advance.

Such an arrangement using a screw / nut assembly surrounding the cage makes it possible to produce a very robust and very compact structure with in particular a radial space requirement reduced to a minimum.

For example, the means for driving in rotation of each cylinder-carrying cage is a pivot fixed to the periphery of this cage on which a rod actuated by the second motor means is articulated; it is advantageously a jack. The pivot is advantageously mounted on a revolution ring fixed in rotation on the cylinder holder cage and surrounding the screw / nut assembly.

A means of synchronizing the angular displacements of all of the cylinder carrier cages connects these cages to each other, so as to impose at all times on their cylinders the same angle of advance relative to the rolling axis. This synchronization means can for example be produced with articulated connecting means.

Advantageously, at each cylinder carrier cage, a prestressing means makes it possible to support the cylinder carrier cage on the frame, canceling the existing clearances, in particular at the screw / nut contact and at the level of the bearing against which door the free rotating component of the screw / nut assembly. Advantageously, this prestressing means comprises a traction means, disposed along the adjustment axis, connected on the one hand to the cylinder holder cage and on the other hand to the frame. This traction means applies a force oriented parallel to the cylinder holder cage. the adjustment axis and directed towards the frame. This traction means is advantageously a jack.

Advantageously also, each rolling cylinder is driven by means of a pair of conical toothed pinions, by means of a drive shaft disposed either radially with respect to the rolling axis or perpendicular to the adjustment axis.

Advantageously, the drive shaft is connected to the drive means by a flexible articulation such as a universal joint.

A particularly effective method of implementing the rolling mill thus designed consists in using, during the rolling of a tube blank, the second adjustment means, so as to effect a combined variation of the angle of advance and of the spacing of each cylinder relative to the rolling axis, the movable component of the screw / nut assembly being locked in rotation.

Thanks to the arrangement according to the invention of the adjustment axis, and to the combined variation, it is possible to simultaneously vary the feed angle and the thickness of the tube, which makes it possible to laminate the tube up to at its end, avoiding blockages at the end of rolling, blockages due to excessive triangular deformations which have been observed, contrary to what one might expect on such a rolling mill with three rolls.

In this case, the spacing of the cylinders is increased and the angle of advance is reduced.

It is possible to use screw / nut assemblies whose pitch is adapted so as to adjust the ratio between the variation in angle of advance and the variation in the spacing of the cylinders to the optimal value. The first and second adjustment means can also be synchronized so as to superimpose on the variation in spacing combined with the variation in angle of advance, an independent variation in spacing which can be added or subtracted. of the first, in the direction of rotation of the free rotating component of the screw / nut assembly.

• La figure 1 est une vue en élévation et en coupe d'une cage porte-cylindre d'un laminoir oblique, comportant les moyens de réglage suivant l'invention, équipée d'un arbre moteur monté radialement par rapport à l'axe de laminage.
• La figure 2 est une vue de dessus, du cylindre de laminage de la figure 1 en position de travail sur un tube ou une barre en cours de laminage.
• La figure 3 est une vue selon l'axe de laminage côté sortie, d'un laminoir à trois cylindres équipé des moyens de réglage suivant l'invention.
• La figure 4 est une vue en élévation et en coupe d'une cage porte-cylindre d'un laminoir oblique, comportant les moyens de réglage suivant l'invention, équipée d'un arbre moteur perpendiculaire à l'axe de réglage.
• La figure 5 est une vue de dessus de la figure 4.
• La figure 6 est une vue schématique du côté aval d'un autre mode de réalisation d'un laminoir à cylindres obliques, suivant l'invention, permettant la mise en oeuvre du procédé suivant l'invention, de façon particulièrement avantageuse.
• La figure 7 est une vue en coupe suivant A-A de la figure 6.
• La figure 8 est une vue schématique du côté amont du laminoir de la figure 6.
• La figure 9 est une vue de dessus de la figure 7.
• La figure 10 est une vue partielle en coupe suivant H-H de la figure 9.

The detailed description and the figures below make it possible to better understand, without limitation, the characteristics of the adjustment method according to the invention of a rolling mill with oblique cylinders, and those of the various embodiments of the rolling mill which also part of the invention.

• Figure 1 is an elevational and sectional view of a cylinder holder cage of an oblique rolling mill, comprising the adjusting means according to the invention, equipped with a motor shaft mounted radially with respect to the rolling axis .
• Figure 2 is a top view of the rolling cylinder of Figure 1 in the working position on a tube or bar during rolling.
• FIG. 3 is a view along the rolling axis on the outlet side, of a rolling mill with three cylinders equipped with adjustment means according to the invention.
• Figure 4 is an elevational and sectional view of a cylinder holder cage of an oblique rolling mill, comprising the adjusting means according to the invention, equipped with a motor shaft perpendicular to the adjusting axis.
• Figure 5 is a top view of Figure 4.
• Figure 6 is a schematic view from the downstream side of another embodiment of a rolling mill with oblique cylinders, according to the invention, allowing the implementation of the method according to the invention, in a particularly advantageous manner.
• FIG. 7 is a sectional view along AA of FIG. 6.
• FIG. 8 is a schematic view of the upstream side of the rolling mill of FIG. 6.
• FIG. 9 is a top view of FIG. 7.
• FIG. 10 is a partial sectional view along HH of FIG. 9.

Figure 1 shows schematically in elevation and in section, a rolling cylinder, of an oblique rolling mill with three cylinders equipped with the adjusting device according to the invention.

In this figure, we note the rolling axis X _o X _i , along which a tube or a revolution bar 1 is being rolled.

The oblique cylinder 2 is mounted on an axis of revolution Y _o Y, inside a cage 3 of generally cylindrical shape, in which it rests on bearings 4.

The cage 3 is itself rotatably mounted around an adjustment axis Z ₀ Zi, perpendicular to the axis X ₀ X ₁ , and intersecting it. This adjustment axis Z _o Z ₁ intersects the axis Y _o Y ₁ , and crosses the surface of the cylinder in the zone of contact with the tube 1. The point 5 crossing the surface of the cylinder by the axis Z ₀ Z ₁ , is located in the calibration zone, at the end of the contact zone on the outlet side of the tube, zone in which the work of the cylinder essentially consists in leveling the cylindrical surface of the tube, so as to eliminate the undulations in profile helical resulting from the advance.

In the case of this figure the perpendicular axes X _o X _I and Z _o Z, are in the plane of the figure and the axis of revolution Y _o Y, of the cylinder 2 is inclined relative to this plane which it crosses at its point of intersection with the adjustment axis Z ₀ Z ₁ .

Figure 2 is a top view along the axis of adjustment Z _o Z, of Figure 1. The plane of this figure, perpendicular to Z ₀ Z, contains the axis X _o X ₁ . Only the cylinder 2 and the tube or bar 1 have been shown, the cage 3 being removed. The projection onto the plane of the figure of the axis of revolution Y _o Y, makes with the axis X _o X _I an angle A. This angle A is, by definition, the angle of advance of the cylinder 2 with respect to the rolling axis.

This angle is adjustable by rotation of the cage 3 around the axis Z _o Z ₁ . It can for example be 10 °.

In the case of FIG. 2, the cylinder 2 seen from above rotates in the direction of the arrow (clockwise) to drive the product along the axis XO X1 from right to left.

As shown in FIG. 1, the angle of inclination i of the axis of revolution Y _o Y ₁ relative to the adjustment axis Z _o Z, is approximately 45 °. This angle is fixed and independent of the angle of advance. It can vary according to the characteristics of the rolling mills from around 20 ° to around 70 °.

It is also noted that the axis of revolution Y _o Y ₁ is oriented so as to approach the rolling axis X _o X ₁ , in the direction of the exit zone of the rolled product from the rolling mill. By construction, this axis does not intersect the rolling axis except when the feed angle A is equal to 0, which is never the case in the rolling position. The rolling roll 2 has a profile of revolution whose section decreases towards the exit zone of the product to be laminated. In the calibration zone, the profile of the generator of the cylinder is determined so as to smooth the surface of the bar by attenuating or eliminating the helical undulations which it may present.

According to the invention, the adjustment of the advance angle A is carried out by rotating the cage 3 around the adjustment axis Z _o Z, until it gives the desired angular orientation. In the case of FIG. 1, the feed angle A is adjusted to the desired value, by rotating, by known means and not shown, the cage 3 inside a fixed annular envelope 6, which is itself secured to the fixed structure of the rolling mill, also not shown.

An angular wedging means, not shown, makes it possible to wedge the cage 3 in a determined angular position inside the envelope 6. It can be seen that, thanks to this method of adjusting the advance angle according to the invention, it is possible to vary the feed angle, within very wide limits, without significantly disturbing the rolling conditions. In fact, it can be seen that the rotation of the cage around the axis Z ₀ Z ₁ rotates the cylinder, in its zone of contact with the bar or the tube around the fixed point 5 which is on the adjustment axis. This point 5 is normally located in the calibration zone C of the cylinder. In FIG. 1, the reference mark 7 represents on the cylinder the limit between the calibration zone C and the reduction zone.

Such possibilities are not offered by known adjustment methods, such as that described in the article published in "Iron and Steel Engineer" (October 1981 pages 51 to 54).

It is also possible, according to the invention, to adjust the outlet diameter of the rolled products, without significantly modifying the rolling conditions. This is achieved by sliding the cylinder holder cage 3, inside the fixed envelope 6, along the axis Z _o Z _l . Known means and not described make it possible to achieve this sliding and to axially wedge the cage 3 relative to the casing 6, at any point within the adjustment range. This adjustment by sliding, along the axis Z _o Z ₁ , does not involve displacement of the cylinder along the axis X _o X ₁ and therefore also no displacement of its point 5 of rotation in contact with the product being rolled. This guarantees the possibility of adjusting the feed angle A to the new rolling conditions without significant disturbances. It is indeed necessary to adapt the feed angle to the product outlet diameter, if we want to maintain a good surface condition.

Still in the case of FIG. 1, the rolling cylinder 2 is rotated, whatever the adjustment position, by a pair of toothed bevel gears 8 and 9. The pinion 8 is wedged on the shaft 10 which drives the cylinder around the axis Y _o Y _i . The pinion 9 is wedged on the motor shaft 11 mounted on the axis Z _o Z ₁ which drives it by means of a motor means not shown.

A rolling mill of this type comprises at least three stands, such as that shown in FIG. 1, whose adjustment axes, such as Z _o Z _l , are distributed around a rolling axis, such as X ₀ X ₁ . In the case of a rolling mill with three cylinders, these axes such as Z ₀ Z ₁ are arranged, at 120 ° from one another around the axis X _o X ₁ and are concurrent.

The envelopes 6 occupy, most often, a fixed position in space, which facilitates the driving of the drive shafts 11 by suitable drive means. The rotational speeds of these shafts are preferably synchronized.

Figure 3 is a view along the rolling axis of the outlet side of the rolled product of a rolling mill with three oblique rollers according to the invention. The plane of the figure is perpendicular to the rolling axis, which is marked in X ₂ . We see three rolling rolls 12, 13, 14 whose axes of revolution are Y ₂ , Y ₃ , Y ₄ . These cylinders are mounted in cages 15, 16, 17 of cylindrical shape of revolution which can slide and rotate with a minimum of play inside annular envelopes 18, 19, 20 mounted integral with each other by means of the parts. 55 56 57.

Each of these stands can rotate around one of the three adjustment axes Z ₂ , Z ₃ , Z ₄ perpendicular to the rolling axis and concurrent in X ₂ in the case of the figure. Each of these cages has the same adjustment means according to the invention. These means are shown, schematically, in the case of the cage 15. The latter has on its side wall a lug 21 which is held in an angular position determined by two screw stops 22, 23 which can be move by engaging them more or less inside the threaded housings 24, 25 fixed on the casing 18. By screwing and unscrewing these stops, the lug can be moved transversely relative to the adjustment axis Z ₂ and therefore rotate the cage 15 by a determined angle and wedge it in a very precise angular position. The angle of advance is thus adjusted as described above.

Similarly, the cage 15 can be moved along the axis Z ₂ so as to adjust the exit section of the laminated bar. Simple means of achieving this movement are constituted by adjustable stops.

The figure shows four stops comprising rods 26, 27, 28, 29 parallel to the axis Z ₂ . The rods 27 28 which are pressure screws of adjustable length, are mounted screwed into threaded sleeves 31 32 fixed on a cover 34 perpendicular to Z ₂ and integral with the envelope 18. The rods 26 29 which are return rods hydraulic cylinder rod type are mounted on bodies 30 33 fixed to the cover 34 perpendicular to Z ₂ and integral with the casing 18. At the other end the two rods 26 29 have heads 35 36 housed in an annular groove 37, having retaining edges 39, formed on the upper face 38 of the cage 15. The two screw rods 27 28 are in direct contact by their free ends 40 41 on the face 38 while the rods 26 29 exert a force in the opposite direction.

It is understood that by correctly adjusting the rods 26 27 28 29 it is possible to move the cage 15 axially and wedge it axially at any point on the axis Z ₂ .

As a variant, the axial adjustment device with stops as described may comprise, instead of two pressure screws such as 27 28, a wedging at three or more points instead of two, the return rods such as 26 29 being associated as required. .

Each of the cages 16 17 is adjusted axially, in the same way as the cage 15 by similar means not shown. The three rolling rolls 12, 13 and 14 are thus adjusted with the same angle of advance A with respect to the rolling axis and the same spacing with respect to this axis.

The drive in rotation of each cylinder is made by a pair of bevel gears 42 43 shown in dashes. Motor means, not shown, drive motor shafts, arranged radially along the adjustment axes, such as shaft 44.

A frame 45 maintains the assembly in a fixed position. The products rolled by means of this rolling mill circulate through it, turning on themselves, along the rolling axis.

By way of example, it is possible to laminate with a rolling mill such as that described in FIG. 3 equipped with three rollers whose maximum diameter of the part used during rolling is 800 mm of tubes whose finished outside diameter is between 200 and 400 mm without changing cylinders.

With a cylinder assembly such that the angle i is 60 °, the finished diameter is obtained by adjusting for each desired diameter the feed angle A and the radial position of the cylinders according to their respective adjustment axis Z ₂ , Z ₃ , Z ₄ .

Thus for the dimensions mentioned, the feed angle can vary from A = 17 ° for a finished outside diameter of 219 mm to A = 11 ° for a finished outside diameter of 406 mm.

• 1) Ebauche : diamètre (extérieur) -270 mm, épaisseur - 45 mm
  • tube fini obtenu : diamètre (extérieur) - 219 mm, épaisseur - 8 mm
  • soit un allongement (rapport longueur du tube fini/tube ébauche) de 6.
• 2) Ebauche : diamètre (extérieur) - 460 mm, épaisseur - 50 mm
  • tube fini obtenu : diamètre (extérieur) ― 406 mm, épaisseur - 9,5 mm
  • soit un allongement de 5,4.

The following ranges of lamination, on internal chucks, are used as an example:

• 1) Roughing: diameter (outside) -270 mm, thickness - 45 mm
  • finished tube obtained: diameter (outside) - 219 mm, thickness - 8 mm
  • either an elongation (ratio of finished tube to rough tube) of 6.
• 2) Roughing: diameter (outside) - 460 mm, thickness - 50 mm
  • finished tube obtained: diameter (outside) - 406 mm, thickness - 9.5 mm
  • or an extension of 5.4.

Figures 4 and 5 show an alternative embodiment of the method and the device according to the invention. It is a rolling mill with three oblique cylinders of which only one cylinder is shown. Figure 4 is an elevational view in section passing through the adjustment axis. Figure 5 is a top view along the axis Z _s Z _a of Figure 4. As in the case of the previous figures, the cylinder 46 rotates around an axis of revolution Y ₅ Y ₆ inside a cylindrical cage of revolution 47. This cage can rotate around an adjustment axis Z ₅ Z ₆ , or slide along it inside a fixed annular envelope 48. The axis Z ₅ Z _a is perpendicular and cuts the rolling axis X ₃ X ₄ . It also cuts the axis of revolution Y5 Y6. As shown in FIG. 4, the adjustment axis passes through the wall of the cylinder 46 in its zone of contact with the tube 49, during rolling, in accordance with the invention. The cylinder 46 is driven in rotation by means of a pair of toothed bevel gears 50 51. The pinion 51 is mounted on the motor shaft 52 perpendicular to the adjustment axis Z ₅ Z ₆ , which is driven by an engine not shown.

This shaft 52, as shown in FIGS. 4 and 5, is mounted so as to move as little as possible from the parallelism with respect to the rolling axis X ₃ X ₄ .

For this, the shaft 52 is arranged by construction inside the cage 47 so that, in projection on the plane of Figure 5, it forms, with the projection on this same plane of the axis of revolution Y ₅ Y _s , an angle B whose value is close to the average value which is given to the angle A of the cylinder 46. This arrangement makes it possible to connect the motor shaft 52 to a motor means whose shaft is substantially parallel to the rolling axis. In order, however, to be able to adjust the angle of advance A within the desired adjustment range, one or more articulated connections are provided, such as cardan joints and extensions between the shaft 52 and the shaft of the drive means. Such a connection is shown diagrammatically at 53. It is understood that if the angle B has been well chosen, it suffices to be able to separate the shaft 52 from the axis of the shaft of the drive means by an angle which is not not more than half the maximum feed angle A. The possibility of adjusting A is therefore fully preserved by rotation of the cage 47 around the adjustment axis Z ₅ Z ₆ . The movement of the shaft 52 is allowed by the notch 54 formed in the cage 47 and its envelope 48.

Such an arrangement makes it possible to produce a rolling mill with three cylinders comprising cages which are themselves driven in rotation about the rolling axis X ₃ X ₄ by their envelopes, which in turn are mounted in rotation relative to a fixed frame. By giving the cages an equal and opposite direction of rotation to that of the product being rolled, this can be laminated. product without rotating relative to the rolling mill frame. This facilitates the introduction and extraction of the products being rolled, which is particularly advantageous in the case of products of great lengths. Thanks to such an assembly, it is also possible to drive each cylinder by planetary and satellite gear. It suffices to provide an articulated connection, for example a cardan joint between the planet carrier shaft and the drive shaft of each cylinder, such as the shaft 52.

Figures 6 to 10 show another embodiment of a rolling mill with oblique cylinders according to the invention comprising special means for adjusting the spacing of the rolls relative to the rolling axis, as well as the angle d 'advance of these cylinders with respect to this same axis.

FIG. 6 is a schematic overall view, on the downstream side, of a rolling mill with three oblique cylinders according to the invention, used for the rolling of a tube blank 101. The rolling axis X _s is perpendicular to the plan of the figure. The three cylinders 102, 103, 104 are mounted in cylinder carrier cages 105, 106, 107 themselves connected by base plates 108, 109, 110 to the frame 111 of the rolling mill. This frame is in two parts, articulated with respect to each other around the axis X _s perpendicular to the plane of the figure. The ends 112, 113 of these two parts are held in abutment against one another at 114, thanks to a jack not shown. In the event of excessive forces during rolling, exceeding the clamping force of the jack, the opening of the frame makes it possible to avoid breakage of parts.

Three jacks 115, 116, 117, with hydraulic control not shown, make it possible to vary the angle of advance of the cylinders 102, 103, 104 and also, in a combined manner, the spacing of these cylinders. The bodies of these jacks are articulated on the frame 111 at 118, 119, 120. Their rods 121, 122, 123 are articulated on pivots 124, 125, 126 fixed on rings 127, 128, 129 which are themselves respectively secured to cylinder holder cages 105, 106, 107. In this way the jacks allow the axes, such as Y ₇ , (see FIG. 7) of the cylinders to rotate, around 102, around their adjustment axes such as Z7.

Figure 7 is a sectional view of the cylinder holder cage 105, along a plane passing through the rolling axis X ₅ and the adjusting axis Z ₇ which are, according to the invention concurrent and perpendicular. The axis Y ₇ of the cylinder 102 intersects at (M) the adjustment axis at an angle α of approximately 30 °. This axis Y ₇ is shown in the plane of Figure 7. Its inclination relative to the rolling axis X ₅ is in this condition of about 60 °, the angle of advance then being zero. The cylinder 102 is set in rotation relative to the cylinder-carrying shaft 130, of revolution, by means of the threaded end rod 131 which is screwed into the threaded housing 132 of the cylinder 102. An opening 133 is formed in the frame 111 for screwing or unscrewing the rod 131.

The cylinder-holder shaft 130 is mounted in rotation around Y ₇ by means of bearings 134, 135, 177 bearing on the cylinder-holder cage 105. These bearings are designed, in known manner, to support the rolling forces. The cylinder-holder shaft 130 comprises a conical crown 136, locked in rotation on it, on which meshes a conical pinion 137 mounted on a shaft (138). This arrangement is similar to that shown in Figure 4.

In the case of this figure 7 the axis X ₇ of the shaft 138 is in the plane of the figure. Under the rolling conditions, this axis makes an angle with the plane of the figure which corresponds to the feed angle. In known manner, the shaft 138 is connected to a drive shaft, not shown, by one or more articulated connections, such as cardan shafts, which are also not shown.

The cylinder holder cage 105 comprises an annular zone 139, of axis Z ₇ , provided with a male thread 140. This thread comprises less than three threads and its pitch is calculated so as to achieve a determined relationship between the variation of feed angle and the combined variation of the spacing of the rolls, with respect to the rolling axis X ₅ that is to be obtained. This relationship is mainly a function of the dimensions of the tube blanks, the mechanical characteristics of the metal, under the rolling conditions, and the reduction rates that it is proposed to achieve.

A nut ring 141 is provided with a female thread 142 in engagement with the male thread 140 which constitutes the screw of this screw / nut assembly. The ring 141 is mounted to rotate freely on a bearing 143 which also includes a centering and retaining ring 144 which ensures the centering of the ring 141 relative to the axis Z ₇ and keeps it in abutment against the plate. base 108.

The nut ring 141 comprises a toothed crown 145, on which meshes a toothed pinion 146 mounted on an axis 147 which passes through the frame 111 and is driven in rotation by a first drive means such as a hydraulic motor shown at 176 (see figures 9 and 10). This arrangement is a first means of independent adjustment of the spacing of the cylinder 102 relative to the rolling axis X ₅ . Indeed, for a given angular position of the cylinder holder cage 105 around the adjustment axis, corresponding to a determined feed angle, the rotation of the nut ring 141 in one direction or the other causes a displacement of the cylinder holder cage 105 along the adjustment axis and therefore a variation in the spacing of the cylinder 102 relative to the rolling axis X ₅ . It is possible, in a known manner, to drive the nut ring 141 by the first drive means independently, or in conjunction with the drive of the other two nut rings 149, 150 which move each of the two other cylinder holder cages 106, 107.

The base plate 108 is fixed by known means, such as screws, not shown, to the frame 111. The ring 127, mounted in revolution with respect to the axis Z ₇ is locked in rotation on the cylinder holder cage 105 and surrounds the screw / nut assembly 140,141.

It includes an axis control pivot 124 X ₈ parallel to Z ₇ on which the end of the rod 121 of the jack 115 shown in FIG. 6 is articulated in rotation.

The rotary drive of the ring 127 around the axis Z ₇ allows a combined adjustment of the angle of advance and the spacing of the cylinder 102 relative to the rolling axis X _s the nut ring 141 being set in rotation by known means. Thus, in the case of FIG. 7, a rotation of the ring 127, seen along F1, in a clockwise direction, brings the cylinder 102 closer to the axis X ₅ in the case of a screw nut system having a step to the right and increases the angle of advance, initially equal to zero.

The articulations of the jack rods 121, 122, 123 around the control pivots 124, 125, 126 and those 118, 119, 120 of the jack bodies 115, 116, 117 on the frame 111 are designed to allow, in known manner, the displacement of the pivots 124, 125, 126 parallel to the axis Z ₇ within the limits for adjusting the spacing of the cylinders relative to the axis X ₅ .

The three synchronization pivots 151, 152, 153, diametrically opposite the three control pivots, make it possible to synchronize in a rigorous manner the action of the three cylinders 115, 116, 117. FIG. 8 shows the synchronization means used in the case of the present rolling mill. Two levers bent at 120 ° 154, 155 are each articulated around a pivot 156, 157 fixed on the frame 111 and with an axis parallel to X ₅ . The axis of each of these pivots intersects a bisector of the angle of 120 ° formed by two adjustment lines. The angular movements of these levers 154, 155 are synchronized by a link 158 articulated at 159, 160 at the ends of the arms 161, 162 of these levers. The axes of the articulation points 156, 159, 160, 157 are parallel to the rolling axis X ₅ and form the vertices of a deformable parallelogram. Each of the three synchronization pivots 151, 152, 153 is connected to an arm of one of the two levers 154, 155 by an identical link 163, 164, 165 at the articulation points 166, 167, 168. In order to cancel the clearance between the threads 140 and 142 and thus to support each cylinder holder cage, such as 105, against the frame 111, a prestressing means such as 169 makes it possible to exert traction on each cage along the adjustment axis Z ₇ in the direction of the frame 111. This device comprises a traction rod 170 of axis Z ₇ , screwed onto the top of the cylinder holder cage (105). This rod passes through a jack whose body 171 is integral with the frame 111. An annular piston 172 slides in the body 171 and exerts a thrust on the flange 173, via the annular bearing 174, when a pressurized fluid is introduced in the annular chamber 175 by a pipe not shown. The collar 173 is integral with the rod 170.

Such a rolling mill has the advantage of a very large compactness combined with great robustness and great rigidity. This results from the use of a screw / nut assembly, mounted at the periphery of each cylinder holder cage which minimizes the radial size.

Claims (16)

1. Rolling mill having oblique rolls for obtaining metal rods or tubes generated by revolution, comprising at least three rolls (102, 103, 104) distributed round the rolling axis (X_o, X1, X5), each roll having a profile generated by revolution of generally decreasing cross-section, at least in the portion producing the reduction in the external diameter of the product to be rolled from its entry side to its outlet side and being mounted in overhanging fashion at one end of an axis of revolution (10, 130) connected by a transmission means (10, 8, 9, 11) to a rotary drive means, this axis of revolution being supported by bearings (4, 134) mounted inside a roll-bearing housing (3, 105), which is in turn rotationally mounted about a control axis (Z_O-Z,-Z₇) which intersects the axis of revolution of the roll, forming with it an angle (i, a) of 20 to 70°, traverses the surface of the roll in the region of contact with the product (5) during the rolling operation and intersects at right angles the rolling axis, a first control means for controlling the gap between each roll and the rolling axis by displacing the roll-bearing housing along the control axis, characterised in that this first control means comprises a nut and bolt assembly (140, 141) which is centred on the control axis (Z₇), of which one of the two components, preferably the bolt (140), is arranged at the periphery of the roll-bearing housing (105) and integral therewith, the other component being mounted freely rotatably on a bearing (143) which is fixed relative to the frame (111) of the rolling mill, a rotary driving means (176) permitting the freely rotatable component (141) to be rotated relative to the component which is integral with the roll-bearing housing about the control axis by the amount desired for sliding the roll-bearing housing along the control axis by the desired length.

2. Rolling mill according to Claim 1, characterised in that the freely rotatable component (141) of the nut and bolt assembly comprises a toothed crown (145) which can be rotated by a first driving means (176) which actuates a toothed pinion (146) which meshes with this crown.

3. Rolling mill according to Claim 1 or 2, characterised in that the bolt (140) of the nut and bolt assembly is constituted by a screw thread produced at the periphery of the roll-bearing housing, the nut (141) being a crown nut mounted rotatably on a bearing (143) rigidly connected to the frame of the rolling mill.

4. Rolling mill according to one of Claims 1 to 3, characterised in that it comprises, in the region of each roll-bearing housing, a second control means which comprises a means for rotating (124, 125, 126) the roll-bearing housing about the control axis under the influence of a second driving means (115, 116, 117) permitting the roll-bearing housing to be orientated so as to give the roll the desired feed angle (A) relative to the rolling axis.

5. Rolling mill according to Claim 4, characterised in that the gap for controlling the feed angle (A) is between 3 and 30°.

6. Rolling mill according to Claim 4 or 5, characterised in that a locking means may prevent rotation of the freely rotatable component (141) of the nut and bolt assembly while the roll-bearing housing (105) is being rotated about the control axis (Z7).

7. Rolling mill according to one of Claims 4 to 6, characterised in that the rotary driving means of each roll-bearing housing is a control pivot (124, 125, 126) arranged at the periphery of this roll-bearing housing, on which there is articulated a rod actuated by the second driving means (115, 116,117).

8. Rolling mill according to one of Claims 4 to 7, characterised in that the second driving means is a jack.

9. Rolling mill according to one of Claims 4 to 8, characterised in that it comprises means (151, 152_; 153) for synchronising the angular movements of the roll-bearing housing so as to impose the same feed angle relative to the rolling axis on their rolls at each moment.

10. Rolling mill according to one of Claims 4 to 9, characterised in that it comprises, in the region of each roll-bearing housing, a pretensioning means (169) which exerts a tensile stress on the roll-bearing housing in the direction of the frame.

11. Rolling mill according to one of Claims 1 to 10, characterised in that a pair of conical pinions (136, 137) permits the movement to be transmitted from a driving shaft to the shaft on which each roll of the rolling mill is mounted.

12. Rolling mill according to Claim 11, characterised in that the driving shaft (11) of each roll is mounted radially with respect to the rolling axis (XO-X1).

13. Rolling mill according to Claim 11, characterised in that the driving shaft (138) of each roll is perpendicular to the control axis.

14. Rolling mill according to Claim 13, characterised in that the driving shaft is connected to the driving means by a flexible joint such as a cardan joint (53).

15. Process for rolling a tubular blank, characterised in that a rolling mill according to one of Claims 1 to 14 is used and in that combined control of the feed angle and the gap between the rolls is effected during the rolling of the blank by acting only on the second control means, the moving component of the nut and bolt assembly being rotationally blocked.

16. Process according to Claim 15, characterised in that the combined control is effected in the vicinity of the rear end of the blank so as to increase the gap between the rolls and to reduce the feed angle.

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