EP3380245B1

EP3380245B1 - Roller mill with direct drive motors

Info

Publication number: EP3380245B1
Application number: EP15820610.2A
Authority: EP
Inventors: Adriano Nalon
Original assignee: Omas Srl
Current assignee: Omas Srl
Priority date: 2015-11-26
Filing date: 2015-11-26
Publication date: 2022-08-17
Anticipated expiration: 2035-11-26
Also published as: EP3380245A1; BR112018010702A2; WO2017089870A1; BR112018010702A8; BR112018010702B1; CN108367295B; CN108367295A

Description

The present invention concerns a roller mill with direct drive motors for grinding and processing cereals, granular materials, cereal mixtures and similar products.
Roller mills are known that are installed in mills and use pairs of cylinders to grind and process various products, like for example cereals, granular materials, cereal mixtures. The cylinders of each pair are arranged so that they are parallel to each other and at a predetermined distance from each other, wherein if necessary said distance can be adjusted depending on the product to be ground, on the final product desired and on the intermediate grinding step. An example of such a roller mill is disclosed in WO 90/14165 .
At present the known cylinders are set rotating by asynchronous electric motors connected through belt and pulley drive units or other mechanical coupling means.
A first cylinder is set rotating by the asynchronous motor, while a belt drive system transmits motion in a synchronous manner to the second cylinder positioned beside the first cylinder and generally rotating at a lower speed compared to the latter.
The main control motor of each pair of cylinders is generally installed on one side of the grinding unit, while the opposite side is provided with a system of pulleys, tightening pulley and timing belt that makes it possible to maintain speed synchronism between the two cylinders. Said second belt, furthermore, has the function of:

reducing the rotation speed and braking the rotation of the second rear cylinder during the grinding step with the cylinders in contact with each other,
driving the second cylinder, and keeping it rotating, when the two cylinders are separated and the machine is at rest, ready for the successive grinding cycle.

The mechanisms and the rotation systems of the two known cylinders pose considerable drawbacks.
The drive units with belts and pulleys are noisy.
The various parts of the drive units are subject to wear and to breakages. The belt drive units produce rubber powder due to wear.
The belt drive units cause energy losses due to the low efficiency of the drive unit.
The various parts of the drive units require periodic and regular checks and maintenance. Both the motor and the various parts of the drive units occupy much space on both sides, thus requiring additional spaces and infrastructures for the installation of the roller mills. The asynchronous motors develop optimal rotation torques only within a determined rotation speed range. At lower speeds, the torque developed by the motors is considerably lower and it is not suitable for the required processing cycles.
It should also be considered that the two cylinders are operated by the same motor, with the same rotation speed or with different rotation speeds.
The roller mills having each pair of cylinders rotating at the same rotation speed do not obtain an optimal treatment of cereals and grain products.
The roller mills having pairs of cylinders in which each cylinder rotates at a different speed obtain a better treatment of cereals and grain products.
In order to obtain different rotation speeds, it is necessary to connect the two cylinders with pulleys or gear wheels having different pitch diameter, thus obtaining a drive ratio different from 1.
If the difference between the rotation speeds of the two cylinders needs to be changed, it is necessary to stop them and install a different pair of pulleys.
The patent document DE 102011001047 concerns a single roller connected to a motor with permanent magnets installed at the end of the roller itself and suited to produce the axial rotation of the roller, and wherein there is no contact between the rotor, which is integral with the roller, and the stator, which is mounted on the roller support in a radial position with respect to the stator. This document does not concern the mills and roller mills for grinding and processing products such a cereals, granular materials, mixtures of cereals etc. but only the drive system that transmits the rotary motion to the roller.
The patent document DE10339733 , analogously to the preceding document, concerns a single roller with a motor with permanent magnets installed axially with respect to the roller, wherein the rotor is integral with the roller, while the stator is mounted on the roller support.
The patent document WO2012159932 concerns a mill for reducing or transforming metal bars into sheets with suitable cross section. The mill comprises a plurality of rolling stands, wherein at least one of said rolling stands in turn comprises a pair of parallel rollers positioned side by side and two synchronous motors, each one suited to rotate one roller.
The speed of the motors of each rolling stand can be varied individually but in a coordinated manner with respect to the speed of the motors of the other rolling stands. Furthermore, the absence of mechanical connections between the two rollers of the same rolling stand allows the rotation speed to be controlled individually.
Further examples of rolling mills directed to different purposes are disclosed in DE 41 10 643 , relating to a roller mill for crushing cement materials, and DE 10 2013 219629 , relating to a processing machine for grinding rocks.
In order to overcome all of the said drawbacks, a new roller mill with direct drive motors has been designed and constructed.
It is one object of the present invention to provide a roller mill with less or no kinematic mechanisms between the motor and the shaft of the driven cylinder.
It is another object of the present invention to provide a roller mill with less parts subject to wear, thus reducing maintenance and control times and costs.
It is another object of the present invention to provide a roller mill with reduced overall dimensions.
It is another object of the present invention to provide a roller mill with less parts to be assembled together and therefore reduced assembly times.
It is another object of the present invention to provide a roller mill in which the rated torque is available for a wide range of rotation speeds.
It is another object of the present invention to provide a roller mill that makes it possible to manage and set different rotation speeds while at the same time maintaining the delivered torque constant.
It is another object of the present invention to provide a roller mill that makes it possible to vary the rotation speed of each cylinder of each pair without modifying or intervening on mechanical parts.
It is another object of the present invention to provide a roller mill that makes it possible to increase the power or torque transferred to the cylinders using the same motor power. It is another object of the present invention to provide a roller mill that makes it possible to recover part of the cylinder rotation energy.
It is another object of the present invention to provide a roller mill that needs reduced maintenance.
It is another object of the present invention to provide a roller mill that makes it possible to control the torque parameters and the number of revolutions of each cylinder, allowing the operators to manage the machine in the best possible manner, adjusting it according to the most varied grinding specifications.
It is another object of the present invention to provide a roller mill that makes it possible to control the operation of each motor.
These and other direct and complementary objects are achieved by the roller mill defined in claim 1.
In practice, the new roller mill with magnetic direct drive motors comprises one or more pairs of cylinders, each cylinder of each pair being provided with a torque motor mounted or built directly on the shaft of the cylinder and on the support of the shaft of the cylinder itself.
The new roller mill comprises one or more pairs of rolling cylinders.
The cylinders of each pair are arranged parallel to each other and at a suitable distance from each other, so that the space included between the two cylinders is optimal for grinding the product introduced therebetween.
Each cylinder comprises a rotation and support shaft held on the frame of the rolling mill through a suitable support.
A torque motor with magnetic drive is mounted or assembled on at least one end of each shaft.
Substantially, the part of the torque motor provided with permanent magnets is fixed to the end of the cylinder shaft, while the corresponding part provided with coils or windings is fixed to the support or supporting flange of the cylinder shaft, wherein said coils or windings generate the rotating magnetic field with variable intensity of the same torque motor.
A control circuit constituted by two separate control units connected with the corresponding coil or winding, and possibly with position sensors suited to locate the position of the cylinder, provides for monitoring and controlling the energy supplied to the coils and consequently the cylinder rotation parameters.
Said control circuit feeds the suitable coils or windings of the support or flange of the cylinder shaft with the suitable current and alternance, in such a way as to transmit the desired speed and rotation torque to the permanent magnets of the shaft and thus to the cylinder. The control circuit supervises the rotation parameters of the two cylinders of each pair, making it possible to set the same speed or different speeds for the two cylinders of each pair.
In this way, said control circuit can set for one cylinder of the rolling pair a lower rotation speed than for the other cylinder coupled with it, and the first cylinder is thus braked, in such a way as to obtain the optimal processing and grinding of the grains introduced between the two cylinders.
As the torque motors operate in a reversible manner, owing to the driving action exerted by the faster cylinder on the lower cylinder, which takes place through the product being ground, it is possible to recover part of the energy supplied by the mains, due exactly to the difference between the rotation speeds of the two cylinders.
The attached table shows an embodiment of the invention, which is described by way of non-limiting example.
Figure 1 shows a pair of cylinders (C, C") of a roller mill, but the considerations made here below should be understood as valid for roller mills having two or more pairs of cylinders (C, C").
Each cylinder (C, C") is arranged with its shaft (A', A") parallel to the shaft (A", A) of the other cylinder (C", C).
The end of the shaft (A, A") of each cylinder (C, C") is housed and rotates in a support or supporting flange (F, F") that is integral with the structure (S) of the roller mill.
A set of identical permanent magnets (M', M") is applied, mounted, connected or in any way joined to the end of each shaft (A, A"), and said magnets are arranged along the circumference in such a way that they are equally distant from one another.
Said permanent magnets (M', M"), housed on the generatrix of the end of the shaft (A', A") of the cylinder (C, C") and arranged longitudinally with respect to the shaft of the cylinder (C, C"), constitute a first part of each torque motor.
A set of coils or windings (B', B") making up the second part of each torque motor is fixed to the structure (S) of the rolling mill by means of a connection flange (FT, H"). Said coils (B', B"), therefore, are installed around the end with permanent magnets (M', M") of the shaft (A^∗, A").
All the coils or windings (B', B") of all the cylinders (C, C") are connected with a control circuit (Z).
Said control circuit (Z) controls and feeds the coils or windings (B', B") of each one of the two cylinders (C, C") independently, by means of the two control units (L', L").
The control unit (L') of the motor of the fast cylinder (C) serves the function of master, while the control unit (L") of the motor of the slow cylinder (C") is set as slave.
In particular, said control circuit (Z) feeds the suitable coils or windings (B', B") with suitable intensity and frequency, or alternates the power supply sequence, in such a way as to transmit the desired torque and rotation speed to the permanent magnets (M', M") and thus to the cylinders (C, C").
The control circuit (Z) supervises the rotation parameters of the two cylinders (C, C"), making it possible to set the same speed or different speeds for said two cylinders (C, C"). For example, said control circuit (Z) can set the same speed for both of the cylinders (C, C"), or it can set the rotation torque of each one of the two cylinders (C, C") at the same or different values, or it can set for one cylinder (C) a lower speed than for the other cylinder (C") coupled with it, so that the first cylinder is thus braked.
Furthermore, said control circuit (Z) can set provide a setting according to which the first cylinder (C) is set rotating at a determined speed while the motor of the second cylinder (C") rotates at a lower speed. In this way, the second cylinder (C") is driven by the motion of the first cylinder (C) and by the material introduced between the cylinders (C, C"). Said second cylinder (C") is braked by its motor and then the corresponding control unit (L"), through the feedback connection (R), makes part of the recovered energy available for the motor of the first cylinder (C), supplying it directly to the control unit (L').
Therefore, with reference to the description provided above and the attached drawing, the following claims are expressed.

Claims

A roller mill for grinding and processing cereals, granular materials, mixtures of cereals and similar products, comprising at least one pair of parallel cylinders (C, C") positioned side by side, characterised in that it comprises:
• permanent magnets (M', M") arranged in proximity to at least one end of the shaft (A', A") of each cylinder (C, C"), wherein said permanent magnets (M', M") are arranged so that they are equally spaced along the circumference of said shaft (A, A");

• coils or windings (B', B") fixed to the structure (S) of the roller mill through flanges (H', H") and arranged radially around the end provided with permanent magnets (M', M") of each shaft (A, A");

• at least one control circuit (Z) that controls the power supply and the change of polarity of the coils or windings (B', B") of the motors of each pair of cylinders (C, C"), and wherein each set of said permanent magnets (M', M") of said shafts (A, A") and each set of said coils or windings (B', B") arranged around said permanent magnets (M', M") respectively constitute the rotor and the stator of the contactless rotation motor of each cylinder (C, C"),
wherein said control circuit (Z) is configured to control the power supply and the change of polarity of the coils or windings (B', B") of each motor independently by means of a respective control unit (L', L") and to provide a setting according to which the speed of the first cylinder (C, C") is higher than that of the second cylinder (C", C), in which said slower cylinder (C", C) is also driven by the motion of said faster cylinder (C, C") and by the material introduced between the cylinders (C, C"), ,
and in that said control circuit (Z) is further configured to provide a setting according to which a given rotation speed and a given torque are transmitted to the first cylinder (C) and no power is transmitted to the second cylinder (C"), the second cylinder (C") is braked by its own motor (C") not powered by said control circuit (Z), wherein the control unit (L") of said second cylinder (C"), through a feedback connection (R), makes part of the recovered energy available for the motor of the first cylinder (C), supplying it directly to the control unit (L') of said first motor.
The roller mill according to claim 1,
wherein said control circuit (Z) is further configured to provide a setting according to which it controls the power supply and the change of polarity of the coils or windings (B', B") of the motors of each pair of cylinders (C, C") transmitting the same rotation speed and the same torque to both cylinders (C, C") of each pair.