EP4360773A1

EP4360773A1 - Rolling mill equipped with electromagnetic actuators

Info

Publication number: EP4360773A1
Application number: EP23205989.9A
Authority: EP
Inventors: Nicola Lioce
Original assignee: Hts Srl
Current assignee: Hts Srl
Priority date: 2022-10-31
Filing date: 2023-10-26
Publication date: 2024-05-01

Abstract

A rolling mill for hot deformation of circular-shaped materials is described, comprising at least one radial roller (1), one or more axial conical rollers (2), a plurality of centering rollers (3), a mandrel (4) and a radial electromagnetic actuator (10), the mandrel (4) and the axial conical rollers (2) being configured to be operatively moved along a first linear axis (5) and along a second linear axis (5') perpendicular to the first linear axis (5), the plurality of centering means (3) being configured to be operatively moved along the first linear axis (5), the radial electromagnetic actuator being configured to control the spindle (4) to carry out its operative movement along the its first linear axis (5).

Description

The present invention refers to a rolling mill, in particular a ring- and/or disc-type rolling mill, equipped with electromagnetic actuators.
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:

minimization of the presence of hydraulic oil with increased safety against fires
integrated safety function of the collector for operator protection in case of emergency
reduced noise for the benefit of a user
reduction in consumption thanks to the high efficiency of the servo pump
almost complete absence of pipes
absence of supply tanks for hydraulic pumps
energy consumption halved.

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:

total elimination of hydraulic oil with increased safety against fires
integrated safety function by means of electronic emergency controls
almost total elimination of noise for the benefit of a user
absence of pipes
energy consumption halved.

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 1,200 °C, 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.

I. from oil tank to variable flow pump to movement cylinder piping (one solution for each axis)
II. from oil tank to fixed flow pump to piping to servo valve to motion cylinder (one pump for multiple axes)
III. from oil tank to variable flow pump to servo valve to movement cylinder (variable flow pumps to optimize consumption)
IV. electric movement cylinder (absence of pipes and related problems with mechanical transmissions)
V. electro-hydrostatic actuator (absence or minimal presence of pipes) with residual presence of oil, even if in small quantities
VI. electromagnetic actuator (absence of oil, pipes and mechanical connections for motion).

The evolution aimed at energy saving, workplace safety and elimination of components that could generate fire is evident from the above.
Documents FR-A-568815 , SU-A1-698 710 , DE-A1-38 24 856 , US-A1-2020/261962 and EP-A1-3 300 814 describe rolling mills or gauges according to the prior art.
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 controlled by at least one linear electromagnetic actuator 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 1. Preferred embodiments and non-trivial variants of the present invention form 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:

FIG. 1 shows a schematic view of the main components of a rolling mill to which the present invention applies;
FIG. 2 shows a schematic side view of an electromagnetic actuator; and
FIG. 3 shows a schematic side view of a possible implementation of the rolling mill equipped with electromagnetic actuators according to the present invention.

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 (1) set in rotation by an electric motor, connected to the radial roller (1) via a speed reducer; the radial roller (1) determines the rotation speed of the ring (6) to be rolled.
The external diameter of the radial roller (1) is determined taking into account the maximum peripheral speed of the ring (6) to be rolled and the maximum applicable torque.
The ring rolling mill is also made up of one or more conical rollers (2) called axial conical rollers. The axial conical rollers (2) are installed opposite each other, when there are more than one: this antagonism serves to determine, by changing the distance of the conical rollers (2) between them, the height of the ring (6) to be rolled. The axial conical rollers (2) are orthogonal to the radial rolling roller (1), 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 (2). The peripheral speed of the axial conical rollers (2) is determined by tracking the speed of the radial roller (1), and by the position of the ring (6) on the axial conical rollers (2). The combination of the speeds of the radial roller (1) - axial conical rollers (2) has the objective of centering the ring (6) on the rolling table, as well as avoiding the screwing phenomenon, and the ascent of the ring (6) along the radial roller (1) during their rolling.
The ring rolling mill is also made up of other centering rollers (3) which rotate around first linear centering axes (5) and move radially with respect to the radial roller (1) and the ring (6).
The centering rollers (3) move on a circumferential arc independently of each other: by acting on the ring (6), they move it, bringing it to the center of the rolling table, facilitating the task of the axial conical rollers (2). Their position corrects the speeds of the radial roller motors (1) with respect to the speed of the axial conical rollers (2); during rolling, the ring (6) crushed by the radial roller (1) but at the same time rotated, in an attempt to also be crushed in height by the axial conical rollers (2), moves from the center of the axes on the rolling table lamination. The centering rollers (3), being radially supported on the ring (6) to be rolled, controlled in force, perceive, via torque sensors (not shown), the movement of the ring (6) in the two directions orthogonal to the ring (6): their retraction controls the speed of the axial conical rollers (2), which, by slowing down or accelerating compared to the speed of the radial roller (1), changes the center of the ring (6) to be rolled.
The axial conical rollers (2) have a conical shape in an attempt to keep the peripheral speed of the ring (6) constant; in fact, the ring (6) increases its external diameter as it grows, also changing the peripheral speed. The ring (6) growing under the conical roller (2) encounters increasingly larger diameters of the axial conical roller (2), thus compensating for the change in speed of the ring (6) itself, and perfect synchronism, on a ring (6) in continuous growth, determines the centering of the ring (6) without having to resort to the use of centering rollers (3). 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 (2), when the ring (6) grows beyond the length of the conical rollers (2) themselves, must move back, trying to maintain the ideal position of the ring (6) to be rolled at the center of the taper of the axial conical rollers (6): this operation is entrusted to the axial carriage (9).
The axial carriage (9) sets the axial conical rollers (2) in motion, moving axially with respect to the ring (6) via a linear axis; the axial conical rollers (2) thus change their contact position on the ring (6) to be rolled via the linear axis connected to the axial carriage (9). The movement of the axial carriage (9), changing the position of the ring (6) on the conical rollers (2), affects the rotation speed of the ring (6), while the re-synchronization of the speeds occurs, as previously described, by the centering rollers (3) .
The radial roller (1), set in rotation by the reducer and the motor, has a mandrel (4) as an antagonist for the radial deformation of the ring (6) to be rolled. The spindle (4), circular in shape, is set in motion via a second linear axis (5'); the axial movement of the mandrel (4) with respect to the rotating radial roller (1), but still in its position, causes the reduction of the space between the mandrel (4) and the radial roller (1) with consequent crushing of the ring section (6): this deformation causes the diameter of the ring (6) to grow, and thus, as described above, causes the diameter of the axial conical rollers (2) to grow, which determine the height of the ring (6) by moving backwards, controlled by a linear axis with the aim of having the ring (6) to be deformed always in its center and in the center of the rolling table.
The mandrel (4), which could be shaped to give the shape to the ring (6), is driven axially by a linear axis, and this allows the loading of the ring (6) to be rolled and the positioning to give the shape to the ring (6); the position of the spindle (4) on its axis is also maintained to keep the force on the lower spindle bearing assembly constant (not shown); furthermore, as described above, the ring (6), during growth, tries to screw onto the radial roller (1), causing an axial force on the mandrel (4) 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 can be equipped with first and second linear axes (5, 5') which determine the deformation of the ring (6) 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 (5) of operational movement controlled by at least one linear electromagnetic actuator (10) in a precise and position controllable manner.
In particular, the linear electromagnetic actuator (10) must control at least the spindle axis (4).
The invention allows eliminating the connection by means of pipes for each first or second axis (5, 5') connected: therefore, the larger the first and/or second axes (5, 5') controlled by an electromagnetic actuator (10), 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 (5) via electromagnetic actuators (10), as can be clearly seen in Figure 3.
The application of these electromagnetic actuators (10) 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 1000 °C; 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 (10); these directly control the first and/or second axes (5, 5') limiting errors due to the compressibility of the process fluid and its variation in viscosity with temperature.
The advantages of the electromagnetic actuator (10) are also achieved in the presence of only one axis (5) regulated by it.
These advantages multiply when more electromagnetic axes (5, 5') are used on the ring and/or disc rolling mill.
The electromagnetic actuators (10) are electrically driven servomotors with position and/or force control, and can also be used directly on the axis (5, 5') to be moved.
The operating principle of an electromagnetic actuator (10) 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 (10) are:

(a) absence of brushes and/or mechanical contact, therefore absence of friction, sparks

In environments where electromagnetic actuators are applied, the absence of brushes limits the risk of fire and eliminates mechanical maintenance. The absence of friction drastically increases performance, therefore heat dissipation is very limited, avoiding waste of energy; furthermore, the absence of friction avoids the effects of "stick slip" or gluing: this phenomenon forces actuators with friction, such as half-cylinder ones, to have a minimum movement force threshold, and this threshold often forces the regulation systems to challenging loops to avoid sudden starts beyond the minimum movement threshold. The electromagnetic axis (5, 5') of the present invention, not having friction, reduces the effort on the regulation systems. The above-mentioned peculiarities of the invention improve the degree of safety and consumption of the ring-type rolling mill on which they are installed.

(b) easier cooling since the supply is in the stator and not in the shaft

The moving part of the electromagnetic axis (5, 5'), as described, has no contact with the driving part of the axis (5, 5') itself. Consequently, the driving part remains fixed in the structure: this type of assembly allows the creation of static cooling systems and drastically simplifies the plant engineering of the ring-type rolling mill. The cooling systems of the electromagnetic axes (5, 5') are small in size thanks to the high efficiency of the electromagnetic axis (5, 5') itself. The invention on the ring mill improves maintainability, increasing health at work, eliminating pipes to maintain.

(c) higher starting torques and higher speeds

The starting torques of the electromagnetic actuators (10) are very high due to the total absence of contact and the possibility of delivering the same power in an infinitesimal time; the weight reduction due to the absence of contact drastically reduces the starting torque. The starting torque is precisely the result of the weight to be moved and the mechanical friction. The electromagnetic actuator (10) has reduced weight and zero contact with the driving part. Due to its dynamism, the electromagnetic actuator (10) can reach displacement speeds close to 7 meters per second: such high speeds are impossible to reach with mechanical systems of any type, and these speeds, together with the high starting torque, make the electromagnetic actuator (10) the most performing actuation system currently invented. The ring-type rolling mill, a high-performance machine due to the need to track the growth of the ring (6) to be rolled, takes advantage of the aforementioned peculiarities, improving productivity with a consequent reduction in consumption and increased respect for the environment.

(d) better weight-to-power ratio

Due to the absence of pumps, seals and other mechanical devices, the electromagnetic actuator (10) is the lightest actuator invented. Suffice it to say that the embodiments applied on a ring-type rolling mill always start from an electric motor arriving at a cylinder or a reducer, all useless weight. The electromagnetic actuator (10) has its drive directly connected to electrical energy, exploiting the principle of the Faraday-Neumann law. These laws have been known in the state of the art since 1831.
The invention therefore allows, thanks to the elimination of mechanical components, to reduce the weight of the actuator (10) by 30% compared to any actuator known to the state of the art. The ring rolling mill moved by electromagnetic actuators (10) 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.

(e) very small size

The electromagnetic actuator (10), unlike hydraulic or mechanical actuators, has no connection and motion transmission systems that must pass through reducers, screws and/or cylinders; the electromagnetic actuators (10) 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.

(f) high mechanical accelerations

The invention provides reduced weights, absence of mechanical contact, to obtain quality rolled rings (6) 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.

(g) excellent reliability

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.

(h) minimum maintenance

The electromagnetic actuator (10) 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.

(i) suitability for operation even in hostile environments

One of the objects of the invention is to provide a dangerous and hostile sector with a drive which has the peculiarity of being free from sparks, oil content for fire risk, absence of sliding to avoid wear due to dirt and dust, simplicity of use, absence of pipes to avoid splashes and leaks: the invention accomplishes all this thanks to its mechanical simplicity and its reduced electronic part.

Claims

Rolling mill for hot deformations of circular-shaped materials, in particular for rings and/or discs, comprising at least one radial roller (1), one or more axial conical rollers (2), a plurality of centering rollers (3), at least one mandrel (4) and at least one radial electromagnetic actuator (10), said mandrel (4) and said one or more axial conical rollers (2) being configured to be operatively moved along a first linear axis (5) and along a second linear axis (5') perpendicular to the first linear axis (5), said plurality of centering means (3) being configured to be operatively moved along said first linear axis (5), said radial electromagnetic actuator being configured to control at least said spindle (4) to carry out its operational movement along said first linear axis (5).
Rolling mill according to claim 1, wherein said radial electromagnetic actuator (10) is further configured to control said one or more axial conical rollers (2) and/or said plurality of centering rollers (3) to carry out their operative movement along said their first linear axis (5).
Rolling mill according to claim 1 or 2, wherein said radial electromagnetic actuator (10) is further configured to control said one or more axial conical rollers (2) and/or said mandrel (4) to carry out their operative movement along said their second linear axis (5').
Rolling mill according to claim 1, 2 or 3, wherein the radial electromagnetic actuators (10) are electrically driven servomotors with position and/or force control, and are used directly on the first and/or second linear axis (5, 5') to be moved.