Patent Description:
Different types of vibrating machines are known, whose difference from one another lies in the structure and in the overall shape for the special use or application they are destined to. Some examples of vibrating machines are: a vibrating feeder to feed a material to a material processing station; a vibrating sieve to sieve granular or powder material; a vibrating extractor for silos or hoppers to facilitate the extraction of granular or powder material from silos or hoppers; vibrating pipe transporters; shaking tables to carry out tests of different types or to compact granular or powder materials; a shakeout device to separate sand from casting; and vibrating gravimetric separators to separate materials that are different from one another exploiting their different specific weight.

The aforesaid examples of vibrating machines all share the fact of comprising a fixed base, which is designed to rest on a ground or floor, a body, for example a tray, a sieve, a wall or a support beam, which is mounted on the base by means of elastic means, for example springs or rubber elements, and a motor-vibrator assembly, which typically comprises a plurality of motor-vibrators fixed to the body in order to generate a predetermined vibratory motion and transmit it to the body. Depending on the special use or application, the generated vibratory motion is, for instance, a straight reciprocating motion or a circular motion or an elliptical motion.

Each motor-vibrator comprises an asynchronous electric motor and an eccentric mass, which is fixed on the shaft of the motor. The motor-vibrator assembly very often comprises mechanical joints, for example universal joints, to connect the shafts of the motors to one another so as to allow the motor-vibrators to be synchronized with one another, namely so as to maintain a certain angular deviation (phase displacement) between the centres of mass of the eccentric masses in order to generate the desired vibratory motion.

The installation, protection, set-up and maintenance of the aforesaid mechanical joints are difficult and, hence, economically burdensome.

There is another type of motor-vibrator assembly, which comprises a plurality of vibrating units and one single electric motor to operate the vibrating units through a transmission shaft. Each one of the vibrating units comprises eccentric masses coupled to one another by means of a large number of oil-bath transmission members according to a modular structure and the vibrating units of a same vibrating machine are often coupled to one another through mechanical joints. Despite the presence of a lubricating oil bath, the large number of moving parts, which, in addition, are subjected to the substantial vibrations intentionally generated by the motor-vibrator assembly, leads to a significant mechanical wear of the transmission members, which, hence, frequently need to be replaced and/or subjected to maintenance.

United States Patent No. <CIT> discloses an unbalanced vibrator for stone forming machine, in particular for compacting concrete components during their manufacture. The vibrator has a vibrating table, unbalance shafts arranged on the vibrating table, and electronic motors allocated to the unbalance shafts in order to drive them, wherein the electronic motors have a device for controlling and regulating of the rotational speed and/or the relative phase position of the unbalance shafts. The electronic motors are designed as servo-motors and are provided with a device having sine-cosine transmitters, which determine the angular position and rotational speed of the unbalance shafts.

United States Patent Application No. <CIT> discloses a vibratory drive system, suitable for a material screening apparatus. The vibratory drive system includes rotatable drive shafts each having a centre of mass offset from its rotational axis. A respective drive mechanism is coupled to each drive shaft and is controlled by a controller. The controller adjusts the relative rotational speed of the drive shafts to adjust the relative angular position of the respective centre of mass of the drive shafts.

United States Patent Application No. <CIT> discloses a method for measuring the moment of inertia of a washing machine drum containing a load. The drum is set in a rotation by means of a permanent magnet synchronous electric motor.

Russian Patent No. <CIT> discloses a method for automatic setting of resonant modes of oscillation of a vibration machine driven by induction motor.

Chinese Patent Application No. <CIT> discloses a vibration displacement sensor for a displacement measuring instrument, which is used for the measurement of mechanical vibration.

The object of the invention is to provide a motor-vibrator assembly for a vibrating machine, which does not suffer from the drawbacks discussed above and, at the same time, can be manufactured in a simple and economic fashion.

According to the present invention, there are provided a motor-vibrator assembly, a vibrating machine and a method to control a vibrating machine according to the appended claims.

The invention will now be described with reference to the accompanying drawings, showing a non-limiting embodiment thereof, wherein:.

In <FIG>, number <NUM> generically indicates, as a whole, a vibrating machine resting on a base <NUM>. The vibrating machine <NUM> comprises a body <NUM>, which can be mounted on the base <NUM> by means of a plurality of known elastic elements <NUM>, and a motor-vibrator assembly <NUM>, which comprises a plurality of motor-vibrators <NUM> fixed to the body <NUM> in order to generate a predetermined vibratory motion and transmit it to the body <NUM>.

In the example shown herein, the vibrating machine <NUM> is a vibrating feeder, in which the body <NUM> comprises a grille bottom <NUM> and two side walls <NUM> parallel to one another, there are four elastic elements <NUM> and the motor-vibrator assembly <NUM> comprises two motor-vibrators <NUM>, each fixed to a respective side wall <NUM>.

According to variants which are not shown herein, the base <NUM> consists of the ground or the floor, namely the elastic elements <NUM> have respective ends that can be fixed to the ground or the floor.

With reference to <FIG>, each motor-vibrator <NUM> comprises an electric motor <NUM> and an eccentric mass <NUM>, which is fixed to the shaft <NUM> of the motor <NUM>, namely is integral to the shaft <NUM>. The shaft <NUM> rotates around a respective axis 11a. In the example shown herein, the motor <NUM> is arranged through a hole (not shown) of the side wall <NUM>, with the axis 11a perpendicular to the side wall <NUM>, and has a casing <NUM> of its own, which is provided with a flange <NUM> fixed to the side wall <NUM>. The eccentric mass <NUM> is divided into two bodies 10a and 10b, which are fixed, namely integral, to the two free ends of the shaft <NUM>. The two free ends of the shaft <NUM> project from the casing <NUM> in the area of two respective opposite longitudinal ends of the motor <NUM>. Each one of the two bodies 10a and 10b has a substantially semi-cylindrical shape relative to the axis 11a. The two motor-vibrators <NUM> are fixed to the respective side walls <NUM> so as to be coaxial to one another, namely the axes 11a of the respective shafts <NUM> coincide in one single axis.

With reference to <FIG>, each motor <NUM> is a synchronous motor, for example a permanent-magnet brushless motor or a reluctance motor, and can be operated by an electronic drive device <NUM> of its own. Each motor-vibrator <NUM> comprises respective position sensing means to sense the angular position and measure the angular velocity of the shaft <NUM>. In the example shown in <FIG>, the position sensing means comprises a position sensor <NUM> in board the motor <NUM> of the respective motor-vibrator <NUM>. The electronic drive device <NUM> is on board the respective motor <NUM> and, in particular, is integrated in the casing <NUM>. Each electronic drive device <NUM> comprises an inverter <NUM>, which is designed to operate the respective synchronous motor <NUM> in a known manner based on commands of an electronic control unit. The position sensor <NUM> comprises an angular encoder consisting of a phonic wheel <NUM> integral to the shaft <NUM> and a sensor element <NUM> fixed to the casing <NUM> and facing the phonic wheel <NUM> in order to read the angular movements thereof in a known manner.

With reference again to <FIG>, the motor-vibrator assembly <NUM> comprises an electronic control unit <NUM>, which is configured to control the electronic drive devices <NUM> of the motors <NUM> based on the angular positions sensed and on the angular velocities measured by means of the position sensors <NUM>, so that the motor-vibrator assembly <NUM> generates a predetermined vibratory motion.

According to a further embodiment of the invention which is not shown herein, the electronic drive devices <NUM> are not integrated on board the respective motors <NUM>. By way of example, the electronic drive devices <NUM> are located on board the electronic control unit <NUM>.

According to a further embodiment of the invention which is not shown herein, each drive device <NUM> comprises a pair of inverters <NUM> to operate a pair of motors <NUM> of two different motor-vibrators <NUM>.

According to a further embodiment of the invention shown in <FIG>, in which the corresponding elements are indicated with the same numbers as in <FIG>, the position sensing means comprise, instead of the position sensors <NUM>, a plurality of electromagnetic flux observatory means, indicated with 15a in <FIG>, each integrated in a respective electronic drive device <NUM> and designed to determine the reciprocal angular position between rotor and stator of the respective motor <NUM> and, hence, the angular position of the respective shaft <NUM>. In other words, according to the embodiment of <FIG>, the motor-vibrator assembly <NUM> comprises electronic drive devices <NUM> of the sensorless type to sense the position and to measure the angular velocity of the respective motors <NUM> in the absence of position sensors <NUM>.

In <FIG>, which shows a portion of the vibrating machine <NUM> according to a side view, namely according to a direction of observation that is parallel to the axes 11a of the motors <NUM>, number <NUM> indicates an axis that is parallel to the axes 11a and goes through the centre of gravity of the body <NUM> subjected to the vibratory motion and number <NUM> indicates an axis that is parallel to the axes 11a and goes through the centre of gravity of the eccentric mass <NUM> of the motor-vibrator <NUM> shown in <FIG>. In other words, in the view of <FIG> the centres of gravity of the body <NUM> and of the eccentric mass <NUM> correspond to the axes <NUM> and <NUM>, respectively, and, therefore, hereinafter they are indicated with the same number. The angular position of the centre of gravity <NUM> relative to a polar coordinate system centred on the axis 11a is defined by a radial direction going through the axis 11a and the centre of gravity <NUM> and is indicated with <NUM> in <FIG>.

The electronic control unit <NUM> is configured to control the electronic drive devices <NUM> of the two motor-vibrators <NUM> so as to cause the rotation of the shafts <NUM> according to respective angular velocity profiles along the turn angle and according to respective rotation directions, keeping the centres of gravity <NUM> of the eccentric masses <NUM> in phase with one another.

The phase of the centre of gravity <NUM> is defined by an initial angular position of the centre of gravity <NUM>, namely the angular position in an initial instant of operation of the motor-vibrator <NUM>. The centres of gravity <NUM> are considered in phase with one another when the deviation between the respective phases is zero.

In particular, the velocity profiles of the two motor-vibrators <NUM> are identical and consist of an angular velocity equal to a constant value VK along the entire turn angle and the two rotation directions coincide with the one indicated with <NUM> in <FIG>. The phases of the two centres of gravity <NUM> are allowed to remain constant (zero phase displacement) thanks to the constant value VK of the rotation velocities and to the coinciding rotation directions.

The electronic control unit <NUM> is advantageously configured to initially position the shafts <NUM> of the motor vibrators <NUM> in such a way that the centres of gravity <NUM> are in phase with one another, before causing the rotation of the shafts <NUM> with the respective angular velocity profiles along the turn angle and with the respective rotation directions.

The configuration of the motor-vibrator assembly <NUM> of <FIG> produces a circular vibratory motion, indicated with <NUM> in <FIG>, namely a motion that can be represented as a circular rotation around a direction that is parallel to the axis of the centre of gravity <NUM>.

According to a further embodiment of the invention shown in <FIG>, the motor-vibrator assembly <NUM> differs from the one described with reference to <FIG> in that it comprises two motor-vibrators <NUM> for each side wall <NUM>, which are fixed to the latter in the way described above and are arranged with the respective axes 11a perpendicular to a direction <NUM>. The two motor-vibrators <NUM> of a side wall <NUM> are coaxial to the corresponding two motor-vibrators <NUM> of the other side wall <NUM>. Furthermore, the electronic control unit <NUM> is configured to control the electronic drive devices <NUM> of the two motor-vibrators <NUM> of each side wall <NUM> with the same angular velocity profile, which is equal to the constant value VK, and with opposite rotation directions. The centres of gravity <NUM> of the eccentric masses <NUM> are kept in phase with one another in the same way described above.

The configuration of the motor-vibrator assembly <NUM> of <FIG> produces a straight reciprocating vibratory motion along a direction <NUM> that is perpendicular to the axis of the centre of gravity <NUM> and to the direction <NUM>.

According to a further embodiment of the invention shown in <FIG>, the motor-vibrator assembly <NUM> differs from the one described with reference to <FIG> in that it comprises three motor-vibrators <NUM> for each side wall <NUM>, which are arranged with the respective axes 11a at the vertexes of a triangle. Said triangle has two top vertexes, which lie in a given direction <NUM>, and the third vertex faces downward relative to the direction <NUM>. In other words, the two motor-vibrators <NUM> at the two top vertexes of the triangle have the respective axes 11a perpendicular to the direction <NUM>.

Furthermore, the electronic control unit <NUM> is configured to control the electronic drive devices <NUM> of the three motor-vibrators <NUM> of each side wall <NUM> in such a way that the rotation direction <NUM> of the shaft <NUM> of the motor-vibrator <NUM> of a top vertex of the triangle is contrary to the rotation direction of the shafts <NUM> of the other two motor-vibrators <NUM> and in such a way that the centres of gravity <NUM> of the two motor-vibrators <NUM> of the two top vertexes of the triangle are maintained in phase with one another, while the centre of gravity <NUM> of the third motor-vibrator <NUM> is out of phase relative to the centres of gravity <NUM> of the other two motor-vibrators <NUM>, according to an angular or phase deviation α. In the example of <FIG>, the angular deviation α is equal to <NUM>°.

The electronic control unit <NUM> is advantageously configured to initially position the shafts <NUM> of the motor-vibrators <NUM> in such a way that the centres of gravity <NUM> of the two motor-vibrators <NUM> at the two top vertexes of the triangle are in phase with one another and the centre of gravity <NUM> of the third motor-vibrator <NUM> is out of phase relative to the first two according to the angular deviation α, before causing the rotation of the shafts <NUM>.

The configuration of the motor-vibrator assembly <NUM> of <FIG> produces a substantially elliptical vibratory motion, indicated with <NUM> in <FIG>, namely a motion that can be represented as a rotation, around a direction that is parallel to the axis of the centre of gravity <NUM>, which substantially has the shape of an ellipse having a main axis transverse to the direction <NUM>.

According to a further embodiment that makes reference to <FIG>, <FIG> and <FIG>, namely an embodiment that entails a motor-vibrator <NUM> for each side wall <NUM>, identical velocity profiles and rotation directions of the shafts <NUM> as well as identical centres of gravity <NUM> for the two motor-vibrators <NUM>, the angular velocity profile of each shaft <NUM> comprises a portion of turn angle β (<FIG>), in which the angular velocity, at first, increases from the constant value VK to a maximum value VM and, then, decreases from the maximum value VM to the constant value VK so as to modify the unbalance of the eccentric masses <NUM> at the portion of turn angle β. The portion of turn angle β is centred in a predetermined angular position γ with respect to a polar coordinate system integral to the body <NUM> of the vibrating machine. In a portion of turn angle θ (<FIG>) that is complementary to the portion of turn angle β, the angular velocity remains equal to the constant value VK. In the example of <FIG>, which shows a representation of the velocity profile described above, the portion of turn angle β is <NUM>° and the angular position γ is <NUM>°.

The configuration of the motor-vibrator assembly <NUM> of <FIG>, <FIG> and <FIG> produces a complex vibratory motion, indicated with <NUM> in <FIG>, which can be represented as a rotation, around a direction that is parallel to the axis of the centre of gravity <NUM>, which substantially has the shape of a cam having a main axis <NUM> oriented according to the angular position γ.

The vibratory motion <NUM> can be configured by changing the maximum value VM of the angular velocity, the width of the portion of turn angle β and the angular position γ. In other words, the configuration of the motor-vibrator assembly <NUM> of <FIG>, <FIG> and <FIG> defines an electronic cam.

According to a further embodiment shown in <FIG>, in which the corresponding elements are indicated with the same numbers as in <FIG>, each motor-vibrator <NUM> comprises, on board, a respective accelerometer <NUM> to sense the vibrations to which the motor-vibrator <NUM> is subjected. In particular, the accelerometer <NUM> is fixed to the casing <NUM> of the motor <NUM>. The accelerometer <NUM> is a three-axis accelerometer.

The electronic control unit <NUM> is configured to process the vibrations sensed by the accelerometer <NUM> so as to determine a vibrational state of the motor-vibrator assembly <NUM> and so as to control the electronic drive devices <NUM> of the motors <NUM> based not only on the angular positions sensed and on the angular velocities measured by means of the position sensors <NUM>, but also on the vibrational state. In particular, the electronic control unit <NUM> is configured to modulate the angular velocity profiles of the shafts <NUM> and/or the angular deviation between the phases of the centres of gravity <NUM> of the respective eccentric masses <NUM> based on the aforesaid vibrational state. Modulation of the angular velocity profile means a modulation of the angular velocity value.

According to further embodiments of the invention which are not shown herein, the vibrating machine <NUM> comprises a plurality of motor-vibrator assemblies <NUM> of the type described above with reference to <FIG>, which are arranged, for example, in the way shown in <FIG> and <FIG>.

According to a further embodiment shown in <FIG>, in which the corresponding elements are indicated with the same numbers as in <FIG>, the motor-vibrator assembly <NUM> comprises the accelerometers <NUM> (<FIG>) and the vibrating machine <NUM> comprises one or more accelerometers <NUM> fixed in suitable points of the body <NUM>, for example at two longitudinal ends of each one of the side walls <NUM> of the body <NUM>, in order to sense the vibrations to which the body <NUM> is subjected. The electronic control unit <NUM> is configured to process the vibrations sensed by the accelerometers <NUM> in combination with the vibrations processed by the accelerometers <NUM> so as to determine the vibrational state of the motor-vibrator assembly <NUM> and so as to control the electronic drive devices <NUM> based on the angular positions sensed and on the angular velocities measured by means of the position sensors <NUM> as well as on the vibrational state.

The body <NUM> of the vibrating machine <NUM> is designed to contain material to be treated by means of the predetermined vibratory motion. In the particular example shown in the figures and, in particular, in <FIG>, the vibrating machine <NUM> is a vibrating feeder, which sieves the material placed on the grille <NUM>. The vibrating machine <NUM> receives the material from an upstream processing process and, in particular, from a further machine, which is not shown in the figures and has a container or a loading plane.

According to a further embodiment shown in <FIG>, in which the corresponding elements are indicated with the same numbers as in <FIG>, the further machine, which supplies the material to the vibrating machine <NUM>, is provided with one or more load cells <NUM> arranged under the container or loading plane in order to sense the load of material in the further machine and, in particular, measure the weight of the material present in the container or loading plane, namely before the material is transferred onto the vibrating machine <NUM>. The electronic control unit <NUM> is configured to control the electronic drive devices <NUM> based on the sensed load.

The embodiments described above with reference to <FIG> provide a method to control the vibrating machine <NUM>, which automatically adjusts to the current and future load of the vibrating machine <NUM>.

In particular, in the embodiments described above with reference to <FIG>, the motor-vibrator assembly <NUM> automatically adjusts to the load of the vibrating machine <NUM>, namely to the actual quantity of material contained in the body <NUM>, in order to quickly reach the predetermined vibratory motion. Indeed, the angular velocity profiles and the angular deviations between the phases of the centres of gravity <NUM> of the eccentric masses <NUM> are predetermined as a function of a supposed load of the vibrating machine <NUM>. If the load of the vibrating machine <NUM> changes relative to the supposed load, the vibrational motion generated by the motor-vibrator assembly <NUM> could not be the desired one.

The embodiment of <FIG> permits a more precise adjustment, as the vibrational state is determined based on a larger number of items of information, namely not only the vibrations sensed on the motors <NUM> of the motor-vibrators <NUM>, but also the vibrations directly sensed on the body <NUM> of the vibrating machine <NUM>.

The embodiment of <FIG> enables a predictive adjustment, thanks to the information provided by the load cells <NUM> used by a processing process upstream of the vibrating machine <NUM>.

The main advantage of the motor-vibrator assembly <NUM> disclosed above lies in the quick set-up, since, unlike known motor-vibrators, it does not require mechanical joints to synchronize the eccentric masses, thanks to the use of synchronous motors provided with position sensors and controlled by an electronic control unit. Furthermore, the use of synchronous brushless motors and the absence of mechanical joints reduce the mechanical parts subjected to friction, and hence wear, to the sole bearings of the motors.

Another advantage lies in the possibility of controlling the velocity profile of the synchronous motor in a precise manner along the turn angle leads to the chance of generating complex vibratory motions even using one single motor-vibrator <NUM>. The use of the accelerometers <NUM> and <NUM> mounted on board the motor-vibrators <NUM> and the body <NUM> of the vibrating machine <NUM> allows the behaviour of the motor-vibrator assembly <NUM> to be modulated as a function of the load of the vibrating machine <NUM>, in order to quickly reach the predetermined vibratory motion.

Claim 1:
Motor-vibrator assembly for a vibrating machine, the motor-vibrator assembly (<NUM>) comprising a plurality of motor-vibrators (<NUM>), each of which comprises an electric motor consisting of a synchronous motor (<NUM>) and at least one eccentric mass (<NUM>) connected on the drive shaft (<NUM>) of the synchronous motor (<NUM>), position sensing means (<NUM>; 15a) to sense the angular position and measure the angular velocity of the drive shafts (<NUM>), electronic drive means (<NUM>) to drive the synchronous motors (<NUM>), and electronic control means (<NUM>), which are configured to control said electronic drive means (<NUM>) based on the angular positions sensed and on the angular velocities measured so that the motor-vibrator assembly (<NUM>) generates a predetermined vibratory motion; the motor-vibrator assembly (<NUM>) being characterized in that the eccentric mass (<NUM>) is fixed to the drive shaft (<NUM>) of the relative synchronous motor (<NUM>) and is divided into two bodies (10a, 10b) which are fixed to two respective free ends of the drive shaft (<NUM>), the two free ends of the drive shaft (<NUM>) projecting from a casing (<NUM>) of the synchronous motor (<NUM>) in the area of two respective opposite longitudinal ends of the synchronous motor (<NUM>).