Circular rolling mill and rolling method using such a rolling mill

This application is a U.S. non-provisional application claiming the benefit of French Patent Application No. 24 03173 filed on Mar. 28, 2024, the contents of which are incorporated herein by reference in their entirety.

This invention relates to a circular rolling mill equipped, among other things, with a shaping roller and a shaping mandrel making it possible, within a radial stand, to shape the radial outer and inner faces respectively of a workpiece to be rolled.

In the field of rolling, WO2009/125102A1 discloses a rolling mill which includes a radial stand and an axial stand. The radial stand itself includes a roller for shaping an outer radial face of a workpiece to be rolled and a mandrel for shaping an inner radial face of that workpiece. The axial stand includes an auxiliary chassis and lower and upper tapered rollers for shaping the lower and upper radial faces of the workpiece to be rolled. The movement of the mandrel relative to the roller for shaping the radial outer face of the workpiece to be rolled is controlled by a drive assembly located opposite the mandrel relative to this shaping roll. The axial stand is located opposite these drive means, i.e., on the same side as the mandrel with respect to the shaping roller. This makes this rolling mill relatively bulky.

Furthermore, to improve production rates, a circular rolling mill is known to be equipped with two axial stands, each associated with one of the two mandrels of the radial stand and arranged on either side of the roll for shaping the outer radial face of the workpieces to be rolled. This type of rolling mill with two opposing axial stands is sometimes referred to as a “MIRA”. Although this type of rolling mill increases production rates, it has the disadvantage that the diameter of the rolled workpieces is limited by the horizontal length of the tapered rollers in each of the axial stands. As the rolling process progresses, the diameter of the rolled workpiece increases to the point where it can reach the edge of the tapered rollers opposite the adjacent mandrel. If the diameter of the workpiece being rolled increases further, it escapes the tapered rollers of the axial stand. The workpiece can no longer be rolled, which can lead to defects or even the scrapping of the workpiece in question.

These disadvantages are specifically addressed by the invention, which proposes a new circular rolling mill that is compact and capable of rolling relatively large-diameter workpieces.

To that end, the invention relates to a circular rolling mill for shaping annular workpieces, including a main chassis, a radial stand, and at least one axial stand, the radial stand including a roller for shaping an outer radial face of a workpiece to be rolled and a mandrel for shaping an inner radial face of the workpiece to be rolled, the axial stand including an auxiliary chassis and upper and lower tapered rollers for shaping lower and upper radial faces of the workpiece to be rolled, the mandrel being supported by an upper mandrel holder and selectively engaged in a lower mandrel holder, each of the mandrel holders being integral, in translation along a longitudinal axis of the main chassis, with at least one drive bar parallel to the longitudinal axis of the main chassis.

In accordance with the invention, the movement of the mandrel holders parallel to the longitudinal axis of the main chassis is controlled by a movement system located on the same side of the shaping roller as the mandrel. The auxiliary chassis is slidably mounted, parallel to the longitudinal axis of the main chassis, on the drive bars of the mandrel holders, which pass all the way through it. The circular rolling mill further includes a mechanism for translating the auxiliary chassis relative to the drive bars, parallel to the longitudinal axis of the main chassis.

Thanks to the invention, the position of the mandrel, and therefore the intensity of the force it exerts on the radial inner face of the workpiece to be rolled, may be controlled by means of the drive bars integral with the mandrel holders. On the other hand, the tapered rollers, which are carried by the auxiliary chassis of the axial stand, may be moved in translation, in a direction radial to the axis of rotation of the roll for shaping the outer face of the workpiece to be rolled, independently of the mandrel, while it exerts a shaping force on the radial inner face of that workpiece. This makes it possible to adjust the longitudinal position of the tapered rollers in the axial stand according to the actual diameter of the workpiece being rolled.

According to advantageous but not mandatory aspects of the invention, such a circular roller may incorporate one or more of the following features, taken in any combination that is technically feasible:

According to another aspect, the invention relates to a method for rolling an annular workpiece by means of a rolling mill as above, including:

By operating the mechanism for moving the auxiliary chassis, the method of the invention makes it possible to take into account the increase in diameter of the annular workpiece being rolled.

A circular rolling millshown inincludes a main chassiswhich extends along a longitudinal axis X.

Main chassissupports a radial standand an axial stand.

Rolling millis used to shape a workpieceto be rolled, with an outer radial face, an inner radial face, an upper axial face, and a lower axial face.

Radial standincludes a first rollerfor shaping radial outer faceof workpieceto be rolled, which is mounted so that it can rotate about a vertical axis Z, defined by a support and drive assemblyincluding in particular an electric motor. Electric motoris covered by a hood. When activated, electric motorrotates the shaping roller about axis Z.

A is an outer peripheral surface of shaping rollerwhich comes into contact with outer radial faceof workpiecebeing rolled.

Radial standfurther includes a mandrelwhich forms a second roller for shaping radial inner faceof workpiece to be rolled.

Mandrelis supported by a first mandrel holder, or upper mandrel holder, which is mounted at the end of two drive barsand. Mandrel holderis also referred to as a “cradle”. Upper mandrel holdercarries a mechanismfor lowering/raising mandrelalong a longitudinal axis A, which is vertical when mandrelis installed in rolling mill. The lowering/raising mechanism is controlled by two electric motorsandmounted on mandrel holder, from which mandrelextends downwards.

Rolling millfurther includes a second mandrel holder, or lower mandrel holder, which defines a housingfor receiving the lower end of mandrel. Mandrelis selectively engaged in housing, i.e., in lower mandrel holder, during the rolling phases, and released from this housing when loading a workpiece to be rolled or when unloading a rolled workpiece. Lower mandrel holderis mounted at the end of two drive barsand. Mandrel holdermay also be referred to as a “cradle”. Lower mandrel holderis fitted with castors, only one of which can be seen inwith reference. The other castor is arranged symmetrically to the visible one, in relation to main chassis. Mandrel holderrests, via its castorsand equivalent, on two tracksat the top of main chassis. Castorsand equivalent facilitate movement of lower mandrel holderalong longitudinal axis X.

Drive bars,,andextend parallel to longitudinal axis Xof main chassisand are superimposed in pairs, drive barbeing arranged above drive bar, while drive baris arranged above drive bar. Drive barsandare at the same horizontal level, as are drive barsand.

Pis a median longitudinal plane of rolling mill, which is vertical, located midway between the sides of main chassisand includes longitudinal axis X. Drive barsandare arranged on either side of median longitudinal plane P, preferably symmetrically, while drive barsandare also arranged on either side of this plane P, preferably symmetrically.

Upper and lower mandrel holdersandhold mandrelin a flat configuration against inner radial faceof workpieceto be rolled while it is being rolled.

Each of drive bars,,andis moveable, parallel to the longitudinal axis X, by means of a movement systemwhich includes an enclosure, two electric motorsandand two angular gearboxesand, each driven by one of electric motorsand. Each angular gearboxordrives two pinionsarranged on either side of mean longitudinal plane P, each meshing with a rackprovided on one of drive bars,,and.

Actuating electric motortherefore enables drive barsand, and therefore upper mandrel holder, to be moved parallel to longitudinal axis X. Furthermore, actuating electric motorenables drive barsand, and therefore lower mandrel holder, to be moved parallel to axis X. Motorsandare synchronized so that the movements of mandrel holdersandare also synchronized. Movement systemtherefore controls movement of mandrel holdersandparallel to longitudinal axis X.

When loading workpieceto be rolled onto rolling mill, or unloading same from the rolling mill after it has been rolled, mandrel holdersandmay be desynchronized to facilitate loading and unloading.

Movement systemis arranged along longitudinal axis Xon the same side of shaping rolleras mandrel. In, mandrel, mandrel holdersandand drive systemare all positioned to the right of shaping rollerand its axis of rotation Z. Rolling millis therefore compact.

When workpieceto be rolled is in place in rolling mill, as shown ininsert E), this part is subjected to radial compressive forces Fand F, exerted respectively by shaping rollerand by mandrel, on its inner and outer radial facesand. The intensity of these radial compressive forces depends on the intensity of a thrust force exerted on mandrel holdersandby electric motorsand, through drive bars,,and, in the direction of shaping roller.

The movement of mandrel holdersandby movement systemconstitutes a primary movement within rolling mill, which makes it possible to exert radial compressive forces Fand F.

Axial standincludes an auxiliary chassismounted on main chassis, and movable, relative to this chassis, along longitudinal axis X.

Axial standincludes a lower tapered rollersupported by auxiliary chassisand rotated by an electric motor. Axial standfurther includes an upper tapered rollerrotated by an electric motor. Aand Aare axes of symmetry and rotation of tapered rollersandrespectively. These axes are inclined both horizontally and vertically. They converge as they approach mandreland axis A.

Sand Sare effective surfaces of tapered rollersandrespectively. Active surfaces Sand Srefer to the surfaces of tapered rollersandwhich enable axial compressive forces Fand Fto be exerted. Larger diameter edges of active surfaces Sand SareA andA, respectively. Active surfaces Sand Sare superimposed, i.e., vertically aligned, as are their edgesA andB.

Distance dis the maximum distance, measured parallel to axis X, between longitudinal axis Aof mandreland rear edgeA of active surface S. Advantageously, distance dis measured at a horizontal portion of active surface S. Distance dhas a minimum value in the configurations of inserts A) and B) inand C) in.

When the workpieceto be rolled is in place in rolling mill, it is subjected to axial compressive forces Fand Fexerted respectively by upper tapered rollerand by lower tapered rolleron axial facesandof workpiecebeing rolled.

Chassisis inserted along longitudinal axis Xbetween mandrel holdersandon the one hand and movement systemon the other hand. In other words, movement systemis mounted on main chassison the side of auxiliary chassisopposite mandrel holdersand.

To achieve this, chassisis fitted with four sleeves, each of which defines a cylindrical volume Vwhose cross-section corresponds to that of drive bars,,and.

In the example, drive bars,,andare circular in cross-section and volumes Vare also circular in cross-section, with a diameter slightly greater than that of the drive bars.

Alternatively, drive bars,,andmay have cross-sections other than circular, for example polygonal, in which case the geometry of volumes Vis adapted accordingly.

Volumes Vpass all the way through auxiliary chassisand allow drive bars,,andto be guided in translation along the entire length of sleeves, through auxiliary chassis. In other words, auxiliary chassisis slidably mounted on drive bars,,andand guided in longitudinal translation, parallel to axis X, by the cooperation of sleevesand the drive bars.

In addition, sleevesallow forces, in particular weight or axial reaction forces, to be taken up by workpiecebeing rolled, which limits the effect of the overhang of drive bars,,andwith respect to movement system. This is particularly noticeable at upper drive barsand, which support upper mandrel holderand its accessories, including mandreland lowering/raising mechanism. This is less noticeable on lower drive barsand, as the lower mandrel holder rests on tracksvia castorsand equivalent.

In addition, a mechanismis provided to move auxiliary chassis, and therefore axial stand, along longitudinal axis X, relative to the drive bars, i.e., relative to radial stand, in particular relative to lower drive barsand.

More specifically, movement mechanismincludes a framefitted with two sleeves, the interior volume Vof which forms a housing that may accommodate some of drive barsand. The volumes or housings Vgo all the way through frame. Frameis immobilized along drive barsand, for example by screws, pins, or keys (not shown).

Frameis elongated and extends transversely to longitudinal axis X, between drive barsand. It forms a beam resting on these two bars.

Advantageously, as may be seen in particular in, frameconsists of two sheet metal plates joined together and defining between them a volume for receiving accessories for movement mechanism.

Framesupports an electric motorwhich drives a belt, which partially surrounds pulleys, each integral with a worm screw. Beltand pulleysare mounted in frame, in the volume defined between the metal sheets of this frame, and protected by a cover.

Each worm screwis engaged in a casingfitted with ball bearings, not shown, designed to circulate in the threads of the worm screw in question.

In this way, a ball-and-socket joint is formed between elementsand.

As a result, rotating a worm screwabout its longitudinal axis has the effect of moving casing, in which it is engaged, parallel to longitudinal axis X, relative to frame, which is fixed relative to drive bars,,and, as explained above.

The two housingsare integral with auxiliary chassis, so that movement of these housings along the two worm screwshas the effect of simultaneously moving auxiliary chassisrelative to frame.

Beltand the pulleyssynchronize movement of worm screwsaround their respective longitudinal axes A, thus synchronizing movement of housingsand moving auxiliary chassisparallel to longitudinal axis X, without any risk of it jamming relative to main chassis.

To this end, auxiliary chassisis fitted with castors, two of which are shown inwith reference. Other castors are arranged symmetrically to those visible, in relation to plane P. Castorsand equivalent enable auxiliary chassisto move with minimum friction on tracks. Stabilizing castorsengaged against the sides of main chassisensure the stability of auxiliary chassisand prevent it from tilting as it moves along the longitudinal axis Xand during rolling.