EP1896248B1 - Product compaction method and device for implementing same - Google Patents

Abstract

The invention relates to a method of compacting products (2), such as a paste for forming anodes, using a compaction device (1) comprising at least one mould (3) which is intended to receive the products (2) and a vibration generator (5) which can transmit vibrations to the products (2). The inventive method consists in tamping the products (2) contained in the mould (3) by subjecting same to vibrations. According to the invention, the frequency of the vibrations is determined such as to ensure optimum tamping as a function of the energy consumed by the vibration generator (5) during a vibration tamping phase.

Description

The invention relates to a product compaction method and a device for implementing the method.

In the field of compaction devices, such as in particular that of vibrotasseuses, machines are known in particular to form anodic blocks molded by compression and vibratory settlement of the paste which constitutes them.

The dough is poured into a mold resting on a vibrating table. The mold is closed at its upper part by an pressing mass which rests on the dough. The vibrating table rests on the ground via elastic elements. The vertical vibrations are generated by two systems with synchronous rotation unbalanced trees and in phase opposition at a fixed speed throughout the period of vibrotassage. The unbalanced shafts are rotated by an electric motor powered by a frequency converter.

The packing of the dough brings about a variation in the elasticity of the dough and thus a variation in the vibratory behavior of the pressing mass and that of the whole machine.

Apparent density is one of the criteria that defines the quality of an anode. It is known that for a given configuration of the machine and for a given quality of the dough corresponds a rotational speed of the unbalanced shafts which give the best results in terms of apparent density of the produced anodes.

For most machines, the rotational speed of unbalanced shafts is determined intuitively or by a posteriori analysis of the anodes produced according to an experimental design. Given the variations in the quality of the dough, this speed is in practice not optimized.

• une masse oscillante entraînée par un générateur de mouvements comprenant notamment un excitateur à balourds et,
• un premier système de masse comprenant un châssis de moulage, des corps moulés et une plaque de base.

Document is also known DE-4434687 a method for controlling the operation of a compaction device, in particular for making concrete pavers. This process is intended for compaction devices comprising:

• an oscillating mass driven by a motion generator comprising in particular an unbalance exciter and,
• a first ground system comprising a molding frame, moldings and a base plate.

• la masse oscillante vient impacter la face inférieure de la plaque de base et entraîne le premier système de masse à la montée,
• à partir d'une certaine hauteur, il peut être observé un décollement de la plaque de base de la masse oscillante,
• le premier système de masse effectue alors une phase de vol pendant laquelle il est ramené par l'intermédiaire de ressorts en direction de la bande d'impact.

In such a compaction device, it is noted during operation that:

• the oscillating mass impacts the lower face of the base plate and drives the first mass system upwards,
• from a certain height, it can be observed a detachment of the base plate of the oscillating mass,
• the first mass system then performs a flight phase during which it is returned via springs in the direction of the impact band.

The document DE 44 34 687 allows, by the method it describes, the control of the evolution of the own movements of the first mass system with respect to the movements of the oscillating mass, by acting on several parameters in order to adjust the impact phase angle, according to the preamble of claim 1. The implementation of this method requires a compaction device equipped with a displacement sensor for measuring the displacement of the oscillating mass and / or an acceleration sensor at the strip level. impact. Optionally, in order to deal with changing conditions, and in particular a change of product type to another or also to products of the same type manufactured successively in time, it can be expected to measure the energy of unbalance motors .

The document DE 196 11 068 relates to a control member equipping a compaction device for concrete blocks, in particular for storing information relating to or derived from the compaction pulses in order to assess the quality of said compaction.

The present invention aims to remedy these disadvantages by proposing a method of compaction of products by vibrotassage, the frequency of the vibrations transmitted to the products is regulated in such a way as to obtain optimum packing of the products.

Another object of the invention is to propose a device for implementing the method.

Other aims and advantages of the invention will become apparent from the description which follows, which is given for information only, and which is not intended to limit it.

The invention relates to a method of compaction of products, such as in particular a paste for the formation of anode, via a compaction device having at least one mold, intended to receive the products, an urgent form suitable for compressing the products contained in the mold, and a vibration generator capable of transmitting the vibrations to the products, in which process the products contained in the mold are squeezed by subjecting them to vibrations.

According to the invention, the frequency of the vibration generator is adjusted to ensure the best possible transmission of the compaction energy to said products, and in which it is carried out by iteration, and for each said iteration, the energy consumed by the vibration generator for a short time for a fixed vibration frequency, and changes the frequency of the vibration generator, increasing or reducing it, so that the energy consumed by the vibration generator during the moment which follows the change of the frequency of the vibration generator is greater than that measured during the previous moment.

• la figure 1 est une vue schématique d'un dispositif mis en oeuvre dans le procédé de compaction conforme à l'invention,
• la figure 2 est un graphique représentant, pour trois configurations de vibrotasseuses différentes, la densité apparente des produits obtenus en fonction de la vitesse de rotation des arbres à balourds,
• la figure 3 est un diagramme illustrant le fonctionnement par itération d'un procédé de compaction de produits conformes à l'invention selon un mode de réalisation.

The invention will be better understood on reading the following description accompanied by the appended drawings among which:

• the figure 1 is a schematic view of a device used in the compaction process according to the invention,
• the figure 2 is a graph representing, for three different configurations of vibrotasseuses, the apparent density of the products obtained as a function of the speed of rotation of the unbalanced trees,
• the figure 3 is a diagram illustrating the operation by iteration of a method of compaction of products according to the invention according to one embodiment.

The invention relates to a method of compaction of products, in particular vibrotassage, using a vibration system with unbalanced shafts.

The figure 2 illustrates, with three curves, the apparent density of products obtained by a vibrotassage process, as a function of the speed of rotation of the unbalanced shafts of compaction devices.

Each curve corresponds to a different configuration of the compaction device or to a different pasta quality. Whatever the quality of the pulp used or whatever the compaction device used, it can be seen that each curve passes through a maximum, that is to say an optimum apparent density, which corresponds to a speed rotation of unbalanced shafts and therefore at a given vibration frequency.

The invention is based on the assumption that the apparent density, on the same compaction device, from the same quality of dough is all the better that the energy absorbed by the products during the vibrotassage phase is big. Therefore, finding the frequency of vibration that causes the greatest energy consumption during the vibro-massage phase is equivalent to finding the vibration frequency that will give the best apparent density of the products.

The invention therefore firstly relates to a method of compaction of products 2, such as in particular a paste for the formation of anodes, by means of a compaction device 1, based on these characteristics.

The compaction device has at least one mold 3 intended to receive the products 2 and a vibration generator 5 capable of transmitting the vibrations to the products 2.

So we cup 2 products contained in the mold 3 by subjecting them to vibrations.

According to the process according to the invention, the frequency of the vibrations is determined, ensuring an optimum packing according to the energy consumed by the vibration generator 5 during a vibrotassage phase.

By vibrotassage phase is meant a time base shorter than the time necessary to ensure the final compression state of the products.

The method according to the invention makes it possible to constantly search for and adjust the frequency of vibrations to ensure optimum packing of the products throughout the compaction process.

As illustrated in figure 1 a compaction device 1 may be provided, in particular equipped with a pressing form 4, capable of compressing the products 2 contained in the mold 3. The products are then compressed by subjecting them, in addition, to a compression force.

The mold 3 has a bottom wall and a side wall. The vibration generator 5, especially unbalanced, can be in the form of a vibrating table 8. The vibrating table 8 comprises a plurality of unbalanced shafts driven by motor means, including electrical. The vertical vibrations, according to a variant, are generated by two unbalanced shafts, in synchronous rotation and in phase opposition.

The vibrating table 8 rests on the ground via elastic elements 7, in particular inflatable.

According to one embodiment, the frequency of the vibrations ensuring optimum tamping by iteration is determined, and for each iteration, the energy consumed by the vibration generator 5 during a vibrotassage phase and for a fixed vibration frequency is measured.

The vibration generator can be controlled in such a way that the energy consumed during a vibrocompaction phase is maximum.

According to one variant, the energy consumed during a vibrotassage phase, at a given fixed frequency, may correspond to the energy total, especially electrical, consumed by the vibration generator 5 at a given fixed frequency, removed from the energy consumed by the vibration generator 5 at said given fixed frequency, when the compaction device 1 runs empty, that is, ie without product in the mold 3.

The measurements of the energy consumed by the generator 5 when the device is running empty may be performed beforehand, in particular during an initialization phase of the device and for example during the first start-up. The measurements can be stored in a memory of a logic processing unit for controlling the vibration generator 5.

According to the embodiment illustrated in figure 1 , the vibration generator 5 is provided with imbalances driven in rotation by motor means. According to this embodiment, it is then possible to control the speed of rotation of the imbalances 6 so as to ensure optimum packing of the products.

Advantageously, as illustrated in the diagram at figure 3 for each iteration, the energy consumed by the vibration generator 5 for a fixed vibration frequency is measured 40, 70 cyclically, over a measurement period Pn, said measurement period being substantially greater than the period of the vibrations.

• on modifie 60 la fréquence des vibrations d'un incrément, positif ou négatif,
• on mesure 70 l'énergie consommée par le générateur de vibrations sur une période Pn de mesures déterminées,
• on compare 80 l'énergie mesurée Eb sur la période Pn de mesure et l'énergie mesurée Ea sur la période Pn - 1 de mesure précédente, et dans le cas d'une baisse d'énergie mesurée Ea >Eb,
• on inverse 90 le signe de l'incrément.

According to one embodiment, one proceeds by successive iterations and for each iteration:

• the frequency of the vibrations of an increment, positive or negative, is modified 60
• the energy consumed by the vibration generator over a period Pn of determined measurements is measured 70,
• the measured energy Eb is compared with the measurement period Pn and the measured energy Ea with the period P1 of the preceding measurement, and in the case of a measured energy drop Ea> Eb,
• we reverse the sign of the increment.

In the case of an unbalanced device, the frequency of the vibrations by modifying the setpoint of the excitation motor Spv by an increment Iv, in particular of fixed absolute value. The value of the increment Iv can be adjusted experimentally between 1 rpm and 5 rpm.

The measurement period Pn must be significant with respect to the vibration period, in particular the pressing mass and the excitation period. According to one variant, the measurement period Pn is of the order of 0.2 to 0.5 sec.

The increment, in particular frequency or speed Iv, may be variable, determined in correlation with the absolute value of the energy difference Eb - Ea consumed by the vibration generator for two periods Pn -1, Pn of successive measurements.

Advantageously, it is possible to perform the first energy measurement 40 after the establishment of a determined minimum vibration frequency, in particular a minimum rotational speed of the unbalanced shafts. The establishment of a determined minimum vibration frequency can be obtained by means of a time delay 30 allowing in particular the establishment of a minimum engine speed.

Furthermore, the vibration generator 5 can be controlled between a minimum vibration frequency and a maximum vibration frequency, and in particular in the case of an unbalance device between a lower limit speed and an upper limit speed of unbalance rotation.

In the case of an unbalanced vibration generator 5, the latter can be equipped with an electric motor controlled by a frequency converter. According to the method, the energy consumed by the vibration generator 5 is measured by integrating the instantaneous power measurement supplied by the frequency converter.

The invention also relates to a compaction device for implementing the compaction process. The compaction device 1 has at least one mold 3 for receiving products 2 and a vibration generator 5 capable of transmitting the vibrations to the products.

According to the invention, the device has means for measuring the energy consumed by the vibration generator 5 as well as a logic processing unit for controlling the vibration frequency of said vibration generator 5, the logic unit of FIG. treatment comprising means for reading the measured consumed energy.

The compaction device also has an urgent form 4 capable of compressing the products 2 contained in the mold 3.

The vibration generator 5 may be an unbalanced vibration generator 6 equipped with motor means. The logic processing unit then allows the control of the unbalance speed.

Naturally, other embodiments, within the reach of those skilled in the art, could have been envisaged without departing from the scope of the present, as defined by the claims below.

Claims (8)

1. A method of compacting products (2) by means of a compaction device (1), exhibiting at least one mould (3) intended for receiving the products (2), a pressing form (4) which can compress the products (2) contained in the mould (3), and a vibration generator (5) which can transmit the vibrations to the products (2), a method wherein the products (2) contained in the mould (3) are tamped by subjecting them to vibrations, characterised in that the frequency of the vibration generator is adjusted permanently for ensuring the better possible transmission of the compaction energy to said products, and wherein one proceeds by iteration, and for each said iteration, the energy consumed by the vibration generator during a short time is measured for a fixed vibration frequency, and the frequency of the vibration generator is changed, by increasing or decreasing it, so that the energy consumed by the vibration generator during the moment following the change in frequency of the vibration generator is greater than that measured during the previous moment.
2. A method according to claim 1, wherein one measures (40, 70), cyclically, for each iteration, the energy consumed by the vibration generator (5) for a fixed vibration frequency, over a measurement period Pn, said measuring period being substantially greater than the period of the vibrations.
3. A method according to claim 2, wherein one proceeds by successive iterations and for each iteration :

   - one modifies (60) the frequency of the vibrations by one increment, positive or negative.

   - one measures (70) the energy consumed by the vibration generator over a measurement period Pn.

   - one compares (80) the energy measured (Eb) over a measurement period Pn and the energy measured (Ea) over the previous measuring period Pn-1, and in the case of a drop of energy measured (Ea > Eb),

   - one reverses (90) the sign of the increment.
4. A method according to claim 3, wherein the increment is variable, determined in correlation with the absolute value of the difference in energy consumed (Eb - Ea) by the vibration generator for two successive measurement periods (Pn-1, Pn).
5. A method according to one of the claims 1 to 4, wherein the first measurement of energy (40) is conducted after establishing a minimal vibration frequency.
6. A method according to one of the claims 1 to 5, wherein the vibration generator (5) is fitted with unbalances (6) driven into rotation by motorised means, a method wherein the rotational speed of the unbalances (6) is controlled so as to ensure tamping of the products.
7. A method according to claim 6, wherein the vibration generator (5) is fitted with an electrical motor controlled by a frequency variator, and wherein one measures the energy consumed by the vibration generator (5) by integrating the instant power measurement provided by the frequency variator.
8. A use of the compaction method according to any of the claims 1 to 7 for obtaining a paste for forming an anode.

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