Patent Description:
Ring-type rolling mills are machines with high technological content and are widely used and widespread throughout the world.

The machines in question were originally operated by hydraulic oil cylinders, controlled by valves, which in turn are powered by hydraulic pumps, therefore requiring connection pipes, large volumes of oil and very high environmental and fire risks.

Progress in the sector of hydraulic components has led to the evolution of the cylinder, valve and pump system, incorporating the three devices into a single device, the so-called servo-pump, a compulsory step in the evolution of a system which, like all sectors, evolves with respect for environment and safety. The only problem that remains to be solved is the permanence of the oil propulsion, which is more performing but still controlled by oil.

The mechanical characteristics of the hot rolling mill, supported by a latest generation and precise electro-hydraulic system, allow obtaining rings with minimal tolerances; in some cases, where the process is consolidated, it will be possible to do without calibration, an operation that allows increasing the mechanical precision of the pieces produced.

The main peculiarities and their final state of the above described systems are:.

In order to continue eliminating oil from the hot rolling mills, some of them have changed their propulsion.

Their drive has been completely replaced with an electric type, electric axes that move worm screws and/or gearboxes, completely eliminating hydraulic oil from the rolling mill edge.

This system, highly respectful of the environment and fire risks, however has a limit: the electric drives used are not reversible, therefore the electric-to-mechanical-motion transmission systems receive peaks of force, from the inhomogeneity of the piece to be deformed, which limit their duration, but in any case they brought improvements. Therefore, the following features have also been added to the peculiarities stated above for the electro-hydrostatic pump system:.

The objective of hot rolling mills for rings, made by numerous manufacturers worldwide, is to make the structure of the starting material, precisely the one to be rolled, more tenacious for extreme uses, having the need for the shape to be made, an obligation to choose the final shape, in order to facilitate their use.

The present invention is applied to the family of rolling mills for hot deformation, justifying the choice of using electromagnetic actuators since, given that the transformation must be carried out hot, the temperatures involved are close to <NUM>,<NUM>, and the electro-magnetic actuator completely eliminates the risk of fire, having as a fundamental characteristic the absence of hydraulic oil, as well as leading to a drastic reduction in environmental pollution.

This great discriminant leads rolling mills to have a mandatory shape, which arises from the geometry of the piece to be produced and its working temperature, taking care to have tools in contact with the piece to be produced that have well-defined and protected positions: the same can be done applying for the technical choices of linear and/or angular actuators.

Ring rolling machines are anything but simple machines, precisely for this reason: ring rolling mills are the most complicated iron and steel machines, and this characteristic makes them objects of innovation and test benches for hydraulic technological innovations. All manufacturers of hydraulic components look at the ring rolling mill with the aim of making it simple to use and ecological: this objective is achieved with the use of electro-magnetic actuators.

This solution allows the possibility of drastically eliminating the risk of fire, and intrinsically provides the safety function in the event of fail-safe: in fact, this type of actuator has an internal position measurement system directly connected to the axis to be moved, thus allowing continuous monitoring.

The electromagnetic actuator has a positioning resolution in the micron range, giving the ring mill the numerical control function; furthermore, its torque control offers the possibility, in case of roughness of the blank, to absorb shocks without damaging the mechanics of connection to the tool to be deformed. Last, but not least, a contact is absent between the mobile part and the fixed part of the actuator, with only the necessary energy being used without dispersion: this makes it reliable and repeatable.

To understand how we arrived at this technical solution, below is a summary of the evolution of the ring rolling mill control systems.

The evolution aimed at energy saving, workplace safety and elimination of components that could generate fire is evident from the above.

Documents <CIT>, <CIT>, <CIT>, <CIT> and <CIT> describe rolling mills or gauges according to the prior art. In particular, <CIT> and <CIT> disclose a rolling mill with a single linear actuator which is not an electromagnetic linear actuator and do not disclose a pair of electromagnetic linear actuators which are used on respective linear axes to be moved. In <CIT>, the mandrel is vertically driven by an electric gear motor and toothed rack, whereas said mandrel is horizontally driven by a second electric gear motor and toothed rack combined with a hydraulic system.

Taking into account what has been stated above, the object of the present invention is providing a rolling mill for rings and/or discs with at least one first electromagnetic axis of operational movement and at least one second electromagnetic axis of operational movement controlled by at least one first and one second linear electromagnetic actuators in a precise and position controllable manner.

The above and other objects and advantages of the invention, as will appear from the following description, are achieved with a rolling mill equipped with electromagnetic actuators such as the one claimed in claim <NUM>. Preferred embodiments and non-trivial variants of the present invention form <NUM> the subject matter of the dependent claims.

It is understood that all attached claims form an integral part of this description.

It will be immediately obvious that countless variations and modifications can be made to what is described (for example relating to shape, dimensions, arrangements and parts with equivalent functionality) without departing from the scope of the invention as appears from the attached claims.

The present invention will be better described by some preferred embodiments, provided by way of example and not by way of limitation, with reference to the attached drawings, in which:.

Referring to the Figures, a possible nonlimiting embodiment of the rolling mill to which the present invention is applied is shown.

The invention concerns machines for the hot rolling of ferrous and non-ferrous materials of a circular shape, for example rings and/or discs.

The ring-type rolling mill in question is made up of a cylindrical radial roller (<NUM>) set in rotation by an electric motor, connected to the radial roller (<NUM>) via a speed reducer; the radial roller (<NUM>) determines the rotation speed of the ring (<NUM>) to be rolled.

The external diameter of the radial roller (<NUM>) is determined taking into account the maximum peripheral speed of the ring (<NUM>) to be rolled and the maximum applicable torque.

The ring rolling mill is also made up of one or more conical rollers (<NUM>) called axial conical rollers. The axial conical rollers (<NUM>) are installed opposite each other, when there are more than one: this antagonism serves to determine, by changing the distance of the conical rollers (<NUM>) between them, the height of the ring (<NUM>) to be rolled. The axial conical rollers (<NUM>) are orthogonal to the radial rolling roller (<NUM>), and are effectively connected to a drive shaft which, at the opposite end, is connected to a speed reducer (not shown). The speed reducer, on its secondary shaft, is connected to electric motors which rotate the entire reduction system of the axial conical rollers (<NUM>). The peripheral speed of the axial conical rollers (<NUM>) is determined by tracking the speed of the radial roller (<NUM>), and by the position of the ring (<NUM>) on the axial conical rollers (<NUM>). The combination of the speeds of the radial roller (<NUM>) - axial conical rollers (<NUM>) has the objective of centering the ring (<NUM>) on the rolling table, as well as avoiding the screwing phenomenon, and the ascent of the ring (<NUM>) along the radial roller (<NUM>) during their rolling.

The ring rolling mill is also made up of other centering rollers (<NUM>) which rotate around first linear centering axes (<NUM>) and move radially with respect to the radial roller (<NUM>) and the ring (<NUM>).

The centering rollers (<NUM>) move on a circumferential arc independently of each other: by acting on the ring (<NUM>), they move it, bringing it to the center of the rolling table, facilitating the task of the axial conical rollers (<NUM>). Their position corrects the speeds of the radial roller motors (<NUM>) with respect to the speed of the axial conical rollers (<NUM>); during rolling, the ring (<NUM>) crushed by the radial roller (<NUM>) but at the same time rotated, in an attempt to also be crushed in height by the axial conical rollers (<NUM>), moves from the center of the axes on the rolling table lamination. The centering rollers (<NUM>), being radially supported on the ring (<NUM>) to be rolled, controlled in force, perceive, via torque sensors (not shown), the movement of the ring (<NUM>) in the two directions orthogonal to the ring (<NUM>): their retraction controls the speed of the axial conical rollers (<NUM>), which, by slowing down or accelerating compared to the speed of the radial roller (<NUM>), changes the center of the ring (<NUM>) to be rolled.

The axial conical rollers (<NUM>) have a conical shape in an attempt to keep the peripheral speed of the ring (<NUM>) constant; in fact, the ring (<NUM>) increases its external diameter as it grows, also changing the peripheral speed. The ring (<NUM>) growing under the conical roller (<NUM>) encounters increasingly larger diameters of the axial conical roller (<NUM>), thus compensating for the change in speed of the ring (<NUM>) itself, and perfect synchronism, on a ring (<NUM>) in continuous growth, determines the centering of the ring (<NUM>) without having to resort to the use of centering rollers (<NUM>). Unfortunately, this is very difficult due to the dynamic nature of the process, while a fast lamination could be completed in just a few seconds.

Due to the need to keep the rotation speed of the axes involved synchronized, the conical rollers (<NUM>), when the ring (<NUM>) grows beyond the length of the conical rollers (<NUM>) themselves, must move back, trying to maintain the ideal position of the ring (<NUM>) to be rolled at the center of the taper of the axial conical rollers (<NUM>): this operation is entrusted to the axial carriage (<NUM>).

The axial carriage (<NUM>) sets the axial conical rollers (<NUM>) in motion, moving axially with respect to the ring (<NUM>) via a linear axis; the axial conical rollers (<NUM>) thus change their contact position on the ring (<NUM>) to be rolled via the linear axis connected to the axial carriage (<NUM>). The movement of the axial carriage (<NUM>), changing the position of the ring (<NUM>) on the conical rollers (<NUM>), affects the rotation speed of the ring (<NUM>), while the re-synchronization of the speeds occurs, as previously described, by the centering rollers (<NUM>).

The radial roller (<NUM>), set in rotation by the reducer and the motor, has a mandrel (<NUM>) as an antagonist for the radial deformation of the ring (<NUM>) to be rolled. The mandrel (<NUM>), circular in shape, is set in motion via a second linear axis (<NUM>'); the axial movement of the mandrel (<NUM>) with respect to the rotating radial roller (<NUM>), but still in its position, causes the reduction of the space between the mandrel (<NUM>) and the radial roller (<NUM>) with consequent crushing of the ring section (<NUM>): this deformation causes the diameter of the ring (<NUM>) to grow, and thus, as described above, causes the diameter of the axial conical rollers (<NUM>) to grow, which determine the height of the ring (<NUM>) by moving backwards, controlled by a linear axis with the aim of having the ring (<NUM>) to be deformed always in its center and in the center of the rolling table.

The mandrel (<NUM>), which could be shaped to give the shape to the ring (<NUM>), is driven axially by a linear axis, and this allows the loading of the ring (<NUM>) to be rolled and the positioning to give the shape to the ring (<NUM>); the position of the mandrel (<NUM>) on its axis is also maintained to keep the force on the lower mandrel bearing assembly constant (not shown); furthermore, as described above, the ring (<NUM>), during growth, tries to screw onto the radial roller (<NUM>), causing an axial force on the mandrel (<NUM>) which is held in position with a linear axis, counteracting its movement.

From the above description of the ring rolling mill, it is clear that its movement, similar to a numerical control, must be precise, reliable and repeatable; for this purpose, it is equipped with first and second linear axes (<NUM>, <NUM>') which determine the deformation of the ring (<NUM>) to be deformed, controlling force and position moment by moment.

The object of the present invention is providing a rolling mill for rings and/or discs with at least one first electromagnetic axis (<NUM>) of operational movement and at least one second electromagnetic axis (<NUM>') of operational movement controlled by at least one first and at least one second linear electromagnetic actuators (<NUM>) in a precise and position controllable manner.

In particular, the linear electromagnetic actuators (<NUM>) must control at least the mandrel axis (<NUM>).

The invention allows eliminating the connection by means of pipes for each first or second axis (<NUM>, <NUM>') connected: therefore, the larger the first and/or second axes (<NUM>, <NUM>') controlled by an electromagnetic actuator (<NUM>), the fewer connection pipes there will be to the ring and/or disc rolling mill, the greater the benefits will be, up to the complete elimination of the pipes, with consequent movement of all axes (<NUM>) via electromagnetic actuators (<NUM>), as can be clearly seen in <FIG>.

The application of these electromagnetic actuators (<NUM>) simplifies the structure of the machine, doing without traditional hydraulic or electro-hydraulic systems, even advanced ones.

The invention limits the risks linked to the possibility of fire and environmental pollution, by working the rolling mill with metal parts close to and above <NUM>; furthermore, it brings the rolling mill to a state of modernization in line with the technologies of our time.

The work of compressing the metal is performed by electromagnetic actuators (<NUM>); these directly control the first and/or second axes (<NUM>, <NUM>') limiting errors due to the compressibility of the process fluid and its variation in viscosity with temperature.

The advantages of the electromagnetic actuator (<NUM>) are also achieved in the presence of only one axis (<NUM>) regulated by it.

These advantages multiply when more electromagnetic axes (<NUM>, <NUM>') are used on the ring and/or disc rolling mill.

The electromagnetic actuators (<NUM>) are electrically driven servomotors with position and/or force control, and can also be used directly on the axis (<NUM>, <NUM>') to be moved.

The operating principle of an electromagnetic actuator (<NUM>) is as follows.

The solenoid is the most common of electric actuators. It is a device that converts an electrical signal into a linear movement caused by an electromagnetic field. The solenoid consists of a coil and a core that can move freely or mechanically constrained to the part to be moved.

The advantages of electromagnetic actuators (<NUM>) are:.

The invention therefore allows, thanks to the elimination of mechanical components, to reduce the weight of the actuator (<NUM>) by <NUM>% compared to any actuator known to the state of the art. The ring rolling mill moved by electromagnetic actuators (<NUM>) is therefore overall lighter than any version with the same mechanical characteristics: less weight translates into less waste of energy for moving masses that are not useful for the process.

The electromagnetic actuator (<NUM>), unlike hydraulic or mechanical actuators, has no connection and motion transmission systems that must pass through reducers, screws and/or cylinders; the electromagnetic actuators (<NUM>) are in themselves cylinders powered by the Faraday-Neumann law, and the absence of mechanical connections and transmissions drastically reduces their dimensions. The reduction in size also causes a reduction in weight and therefore overall dimensions of the ring rolling mill, thus favoring the ergonomics of the ring rolling mill itself.

The invention provides reduced weights, absence of mechanical contact, to obtain quality rolled rings (<NUM>) and thus avoid reworking; as known from the state of the art, acceleration is inversely proportional to mass and friction, and the invention allows high accelerations to be applied so as to react quickly to variations in the process.

Due to the absence of mechanical contact and the direct actuation without intermediate drive and/or mechanical connections, the invention is extremely reliable, given that the electronic control of the magnetic actuator allows the control of the variables to the point of being subject of predictive maintenance in a native way, without therefore adding any sophistication to implement it.

The electromagnetic actuator (<NUM>) applied to the ring-type rolling mill drastically reduces maintenance, simply using: native predictive maintenance due to the absence of mechanical contact; electronic maintenance reduced to a minimum, given that the integrated retraction components make it immune or almost maintenance-free. The components that replace the invention are mainly electronic. As known from the state of the art, electronic components are the least subject to maintenance.

Claim 1:
Rolling mill for hot deformations of circular-shaped materials, in particular for rings and/or discs, comprising at least one radial roller (<NUM>), one or more axial conical rollers (<NUM>), a plurality of centering rollers (<NUM>), at least one mandrel (<NUM>) and at least one linear electromagnetic actuator (<NUM>), said mandrel (<NUM>) and said one or more axial conical rollers (<NUM>) being configured to be operatively moved along a first respective linear axis (<NUM>) and along a second respective linear axis (<NUM>') perpendicular to the first linear axis (<NUM>), said plurality of centering rollers (<NUM>) being configured to be operatively moved along said first respective linear axis (<NUM>), said linear electromagnetic actuator being configured to control said at least one mandrel (<NUM>) to carry out its operational movement along said first linear axis (<NUM>), said rolling mill comprising a second linear electromagnetic actuator (<NUM>) configured to control said at least one mandrel (<NUM>) to carry out its operative movement along said second respective linear axis (<NUM>'), wherein the first and second linear electromagnetic actuators (<NUM>) are electrically driven servomotors with position and/or force control, and wherein the first and second electromagnetic actuators (<NUM>) are used directly on the first and/or second respective linear axis (<NUM>, <NUM>') to be moved.