IT201900002243A1 - MOTORIZATION AND TRANSMISSION SYSTEM FOR MILL AND MILL GRINDING GROUPS WITH ASYNCHRONOUS MOTORS - Google Patents

Description

TITLE

MOTORIZATION AND TRANSMISSION SYSTEM FOR MILL AND MILL GRINDING GROUPS WITH MOTORS

ASYNCHRONOUS

DESCRIPTION

This patent relates to the sector of cereal rolling mills and in particular it concerns a new motorization and transmission system for grinding units of rolling mills and a new rolling mill with asynchronous motors, for the grinding and processing of cereals, cereal mixtures, granulates and the like. .

Rolling mills for cereals are known, formed by one or more pairs of rollers which grind cereals, cereal mixtures and granulates in general.

The rollers of each pair, which constitute a grinding group, are arranged parallel to each other and at a determined distance, possibly adjustable according to the material to be ground, the product to be obtained and said type / characteristics of the intermediate grinding stages.

In currently known rolling mills, each pair of rollers is rotated by a dedicated asynchronous electric motor, connected to said rollers by means of belt, pulley or other transmission members. Said motor is normally directly connected to a first roller, being for example mounted in axis with said first roller, while a belt transmission system transmits motion synchronously to the second roller next to it, which generally has a lower speed than the first.

Said motor of each pair of rollers is generally mounted on one side of the grinding unit, while on the opposite side the transmission system with belts and pulleys is installed, which allows to maintain the synchronism of speed between the two rollers.

This transmission system also has the task of reducing the rotation speed of the second roller, which is braked in particular stages of the grinding, for example when the rollers are in contact with each other.

The transmission system, on the other hand, has the task of pulling said second roller, keeping it in rotation, when the two rollers are not in contact with each other, for example when the rolling mill is in pause, ready for the next grinding cycle.

The use of such roller transmission systems has some drawbacks.

First of all, the transmission with belts and pulleys is normally very noisy; the various parts of the system are subject to wear and tear and require regular maintenance and furthermore their operation causes considerable energy dissipation.

In addition to this, the situation often occurs whereby, when the second roller is towed, it can happen that, due to excessive strain on the belt, the wheels slip, compromising the correct transmission of the motion. Furthermore, the occurrence of friction between or rollers involves temperature variations on the surface of the rollers themselves, which are difficult to predict and quantify, which negatively affect the quality of the final product obtained.

In the case of rolling mills in which the rollers of a grinding group have different rotation speeds, allowing to obtain a better grinding treatment, there is however the drawback of having to connect the rollers with pulleys and toothed wheels having different pitch diameters, to obtain a transmission ratio other than the unit.

However, this speed ratio is fixed and predetermined by mathematical calculations which define the type and length of the belts and the diameter of the pulleys.

If, on the other hand, the difference in rotation speed between the rollers is to be varied, it will be necessary to interrupt the operation of the machine, and therefore the productivity, to mount a pair of different pulleys.

Rolling mills are known which use one or two permanent magnet motors, mounted axially to the rollers and which allow the speed of each roll to be controlled independently.

Magnetic drive motors, however, have the serious drawback of being very expensive, requiring both ordinary specialized maintenance, since the working environment is very dusty, and extraordinary, raising the overall costs of installation and management of the system significantly and often not sustainable.

To overcome all the aforementioned drawbacks, a new type of motorization and transmission system has been studied and implemented for grinding units in rolling mills and a new rolling mill with asynchronous motors, for the grinding and processing of cereals, cereal mixtures, granulates and the like.

The main aim of the present invention is to optimize the productive, qualitative and energetic performances.

The new motorization and transmission system can also be installed on existing rolling mills with minimal mechanical interventions.

Another purpose of the new rolling mill is to eliminate or reduce the kinematic mechanisms and the transmission members between the rollers, thus reducing the number of all parts that wear out and consequently also the maintenance and control times and costs.

Another object is to be able to vary the speed of each individual roller and also the relative speed between the rollers without requiring any mechanical intervention on the rolling mill. The transmission system is in fact electronically piloted. Another purpose of the new rolling mill is to be able to recover part of the electrical energy generated by the braking of a roller, which can thus be reused for the operation of the rolling mill.

These and other direct and complementary purposes are achieved by the new motorization and transmission system for grinding units of rolling mills and new rolling mill with asynchronous motors, for the grinding and processing of cereals, cereal mixtures, granulates and the like.

The new motorization and transmission system for grinding groups of rolling mills, said rolling groups being generally constituted by a first and a second roller rotatable axially, and arranged parallel to each other, comprises:

- a first three-phase asynchronous motor, adapted to be directly or indirectly connected to a first roller of a grinding unit; preferably said first motor is connected directly to said first roller and preferably in axis thereto; - a second three-phase asynchronous motor, adapted to be directly or indirectly connected to a second roller of a grinding unit; preferably said second motor is connected directly to said second roller and preferably in axis thereto;

- at least one first inverter connected to said first motor.

In said first embodiment, the rolling mill that installs said system is called "partially controlled": said first motor with inverter connected to a first roller of the rolling mill allows the electronic and controlled adjustment of the rotation speed of said roller, which will be the slow roller , ie the one intended to rotate normally at a lower speed than the second roller, or fast roller.

Since said second roller or fast roller, being connected to said second motor without an inverter, it rotates at fixed speed.

In a second embodiment, the system also comprises at least a second inverter, and where each of said first and second motors is connected to one of said inverters.

In said second embodiment, the rolling mill which installs said system is called "totally controlled", where the rotation speed of both said first and second rollers can be electronically and independently adjusted between one roll and another.

In both cases the slower roller, when it rotates in contact with the faster roller due to the interposed material being grinded, will no longer undergo the dragging effect due to the contact with said fast roller but, in order to maintain the speed set with software mode, the inverter will have to cause slow roller braking.

In this way, part of the electrical energy is recovered which will be directed towards the DC BUS of the high speed roller inverter in the case of a fully controlled rolling mill, while it is directed towards the electrical network in the case of the partially controlled rolling mill.

In the case of a "totally controlled" rolling mill, said inverters can be of the conventional type, with BUD DC available at the connection terminals. In the case of a "partially controlled" rolling mill, said first inverter is of the regenerative type and / or is connected to an external regeneration module. Said motorization and transmission system can be usefully installed on newly built rolling mills and also, very effectively, on pre-existing rolling mills of the known type, with a single motor and belt / pulley transmission system, as will be described and claimed below.

The characteristics of the new engine and transmission system will be better clarified by the following description with reference to the drawing table, attached as a non-limiting example.

Figure 1 shows the scheme of the system (1) in the embodiment for obtaining a "totally controlled" rolling mill; Figure 2 shows the scheme of the system (1) of Figure 1 in an alternative configuration; Figure 3 shows the scheme of the system (1 ') in the embodiment for obtaining a "partially controlled" rolling mill.

With reference to the diagram of figure 1, the motorization and transmission system (1) comprises a first three-phase asynchronous motor (M1), able to be directly or indirectly connected to a first roller of a grinding unit, or slow roller, and a second three-phase asynchronous motor (M2), adapted to be directly or indirectly connected to a second roller of a grinding unit, or fast roller, ie intended to have a higher speed than said first roller or slow roller.

Each of said motors (M1, M2) is connected to a relative inverter (V1, V2), which allows to electronically adjust the rotation speed of the corresponding roller.

Said inverters (V1, V2) are connected to each other by BUS DC in parallel.

In this way, the electrical energy recovered by the slow roller which must maintain its set speed can be recovered by being directed towards the inverter (V2) of the fast roller.

All energy is thus reused.

As shown in figure 2 in an alternative embodiment, it is also possible to provide that said inverter (V1) of the slow roller is powered directly by said BUD DC of said inverter (V2) of the fast roller, which in turn is instead powered by the mains electric (R). In this way it is not necessary to directly feed the first motor (M1) of the slow roller. This solution is particularly effective in the case in which the new motorization and transmission system is to be installed on existing rolling mills of the known type, ie equipped with a single motor, connected to the electrical supply network, and a traditional belt / pulley transmission system. For the installation of the new system object of this patent it is in fact sufficient to remove the belt / pulley transmission system, and to install the two motors (M1, M2) with relative inverters (V1, V2) to the respective rollers, connected to each other with BUS DC, and where only one motor, in this case said second motor (M2) is powered directly by the mains (R). With reference to the diagram of figure 3, the motorization and transmission system (1 ') comprises a first three-phase asynchronous motor (M1), adapted to be directly or indirectly connected to a first roller of a grinding unit, or slow roller, and a second three-phase asynchronous motor (M2), adapted to be directly or indirectly connected to a second roller of a grinding unit, or fast roller, ie intended to have a higher speed than said first roller or slow roller.

Said first motor (M1) is connected to a relative inverter (V1), which allows to electronically adjust the rotation speed of the corresponding slow roller. Said fast roller, being motorized by said second motor (M2) without inverter, has a preset fixed speed.

In this way, the electrical energy recovered by the slow roller which must maintain its own set speed can be recovered by being directed towards said network (R).

In this case, said first inverter (V1) is of the regenerative type, comprising a regeneration module (V11), internal and integrated or external, which directs the energy generated into the grid (R).

All energy is thus reused.

The present patent also relates to the rolling mill comprising at least one grinding unit, in turn comprising a first roller, or slow roller, and a second roller, or fast roller, and said motorization and transmission system (1, 1 ') connected to said rollers, where said first motor (M1) with inverter (V1) is connected to said first roller or slow roller, and said second motor (M2) with or without inverter (V2) is connected to said second roller or fast roller.

These are the schematic modalities sufficient for the skilled person to realize the invention, consequently, in concrete application there may be variations without prejudice to the substance of the innovative concept.

Therefore, with reference to the preceding description and to the attached table, the following claims are expressed.

Claims (9)

CLAIMS 1. Motorization and transmission system (1, 1 ') for grinding groups of rolling mills, of the type comprising a first and a second roller rotatable axially, and arranged parallel to each other, characterized in that it comprises: - a first three-phase asynchronous motor (M1), adapted to be directly or indirectly connected to a first roller of a grinding unit; - a second three-phase asynchronous motor (M2), adapted to be directly or indirectly connected to a second roller of a grinding unit; - at least a first inverter (V1) connected to said first motor (M1) for adjusting the rotation speed of said first roller. 2. Motorization and transmission system, as per claim 1, characterized in that it also comprises at least a second inverter (V2) connected to said second motor (M2) for adjusting the rotation speed of said second roller. 3. Motorization and transmission system, as per claim 2, characterized in that it comprises DC BUS for the parallel connection of said first and second inverters (V1, V2). 4. Motorization and transmission system, as per claim 1, characterized by the fact that said first inverter (V1) is of the regenerative type, comprising a regeneration module (V11), internal and integrated or external, which directs to the network (R) the energy recovered during braking of the slow roller. 5. Rolling mill with asynchronous motors, for grinding and processing cereals, cereal mixtures, granulates and the like, comprising at least one grinding unit, in turn comprising at least two axially rotatable rollers, of which a first roller, or slow roller, and a second roller, or fast roller, i.e. intended to rotate with a higher speed than said first roller, and where said first and second rollers are arranged with mutually parallel axes, characterized in that they comprise a motorization and transmission system (1, 1 ') according to one or more of the preceding claims, where said first motor (M1) is connected to said first roller or slow roller, and said second motor (M2) is connected to said second roller or fast roller. 6. Rolling mill, as per claim 5, characterized in that said first motor (V1) is connected to said first inverter (V1), and said second motor (M2) is connected to said second inverter (V2), and where said first and second inverter (V1, V2) are connected to each other by means of BUS DC, and where only said second motor (M2) is powered directly by an electric power supply network (R). 7. Rolling mill, as per the preceding claim, characterized in that it is obtained by installing said motorization and transmission system as per one or more of claims 1 to 4 on a rolling mill of the type comprising a single motor, powered by said network electric (R), directly connected to said second roller and connected by means of a belt / pulley transmission system to said first roller, after removing said motor and belt / pulley transmission system. 8. Rolling mill, according to claims 5 to 7, characterized in that said first and second rollers of the grinding assembly are mutually arranged at an adjustable distance. 9. Rolling mill, as per claims 5 to 8, characterized in that said first motor (M1) is mounted in axis with said first roller and / or said second motor (M2) is mounted in axis with said second roller.