EP0615835B1 - Automatic process for determining, monitoring and controlling a forced draining phase prior to the pressing in discontinuous fruit presses. - Google Patents

Abstract

The subject of the present invention is an automatic process for determining, monitoring and controlling a forced draining phase prior to the pressing in discontinuous fruit presses. Automatic process, characterised in that it consists, after filling of the fruit press (1) and before beginning the normal pressing cycle, in continuously measuring the rate of flow of the liquids without applying pressing pressure, in noting the minimum value and maximum value of the said rate, in particular when the vat of the fruit press (1) is rotating, in then comparing these values respectively with predetermined quantities, then, as a function of the results of the said comparisons, in carrying out, if appropriate, a forced draining phase on the materials to be pressed (2), simultaneously verifying the possible presence of a blocking of the orifices (3) for discharge of the liquids, in repeating the above operations until the results of the abovementioned comparisons no longer involve carrying out a forced draining phase and, finally, in beginning the normal pressing cycle. <IMAGE>

Description

The present invention relates to the field of methods and methods for extracting liquids or juices from materials to be pressed and for controlling presses, especially membrane presses and relates to an automatic method for determining, commanding and controlling a forced draining before pressing for discontinuous presses.

Currently, pressing of destemmed harvests or pressing materials containing a lot of free juice generally poses many problems, at the start of the pressing cycle, for users of discontinuous presses (with membranes, trays, ...).

Among the most frequently encountered problems, one can note on the one hand, the spraying of juice, and on the other hand, the blockage of juice, causing risks of clogging of the draining elements, such as the orifices allowing the evacuation of liquids out of the press tank.

These dysfunctions result, for the user, in significant loss of time, in a need for monitoring the press and in difficulties in defining an automatic pressing cycle (cycle variable according to filling conditions).

These problems and malfunctions are due to the presence of large quantities of free juice in the press after it has been filled, the evacuation of these juices being poorly controlled by known automatic pressing methods.

The study of the abovementioned harmful phenomena makes it possible to distinguish two main causes of dysfunction of the presses when the pressed harvest contains a lot of free juice.

Indeed, at the beginning of the pressing cycle, the air located between the mobile pressing member and the harvest is trapped, it does not cannot pass through liquids blocked in the press, nor the mass of materials to be pressed.

In addition, the pressure generated in the press tank by the displacement of the pressing member (membrane, for example) is transmitted, by liquids, on the materials in contact with the orifices ensuring the evacuation of liquids or juices out of the press and thus causes clogging of the latter.

The present invention aims in particular to overcome the aforementioned drawbacks, by preparing the materials to be pressed for a normal pressing cycle, such as, for example, that described in French patent application No. 90 14488 filed on November 16, 1990 in name of the applicant.

To this end, the subject of the present invention is an automatic process for determining, ordering and controlling a forced drainage before pressing for discontinuous presses, characterized in that it consists, after filling the press and before starting the normal pressing cycle, to continuously measure the flow rate of liquids without applying pressing pressure, to note the minimum value and the maximum value of said flow, in particular when the press tank is rotating, then compare these values respectively with predetermined quantities, then, depending on the results of said comparisons, to carry out, if necessary, a forced draining of the materials to be pressed, by simultaneously checking the possible presence of a clogging of the liquid discharge orifices, to repeat the previous operations until the results of the above-mentioned comparisons no longer imply that a forced dripping and finally to begin the normal pressing cycle.

• les figures 1A, 1B, 1C et 1D illustrent, par des vues en coupe d'un pressoir à membrane, les différentes phases d'un égouttage forcé selon l'invention, et,
• la figure 2 représente, sur un même chronogramme, les courbes d'évolution du débit d'écoulement des liquides et de la pression de pressurage appliquée au cours d'un égouttage forcé selon l'invention.

The invention will be better understood from the description below, which relates to a preferred embodiment, given by way of nonlimiting example, and explained with reference to the appended schematic drawings, in which:

• FIGS. 1A, 1B, 1C and 1D illustrate, by sectional views of a membrane press, the different phases of a forced draining according to the invention, and,
• FIG. 2 represents, on the same chronogram, the curves of evolution of the flow rate of the liquids and of the pressing pressure applied during a forced draining according to the invention.

In accordance with the invention, and as shown in FIGS. 1 and 2 of the appended drawings, the automatic method for determining, commanding and checking a forced drainage consists, after filling of the press 1 and before starting the cycle of pressing C normal, to continuously measure the flow D of liquid flow without applying pressing pressure, to note the minimum value Dmin and the maximum value Dmax of said flow D, in particular when the tank of press 1 is rotating, to compare then these values Dmin and Dmax respectively with predetermined quantities K1 x Do and K2 x Do, then, depending on the results of said comparisons, to carry out, if necessary, a forced drainage of the materials to be pressed 2, while simultaneously checking for the possible presence clogging of the liquid discharge orifices 3, repeating the previous operations until the results of the above comparisons do not imply plus carrying out a forced drainage and, finally, starting the normal pressing cycle C.

The latter can be constituted by one of the many pressing cycles known to those skilled in the art, and, advantageously, by that described in the above-mentioned French patent application No. 9014488.

où K1 est une constante dont la valeur est comprise entre 0,5 et 2, où K2 est une constante dont la valeur est comprise entre 0,05 et 0,4 et où Do est une valeur de débit déterminée en fonction de la taille et du taux de remplissage de la cuve du pressoir 1.According to a first characteristic of the invention, forced draining of the materials to be pressed is carried out only when at least one of the following conditions is satisfied: $$\text{Dmax ≥ K1 x Do or Dmin ≥ K2 x Do,}$$

where K1 is a constant whose value is between 0.5 and 2, where K2 is a constant whose value is between 0.05 and 0.4 and where Do is a flow value determined according to the size and the filling rate of the press 1 tank.

It is understood that if neither of the two aforementioned conditions is satisfied, the normal pressing cycle C is immediately started.

For a membrane press, Do can advantageously be determined automatically as indicated in the patent application in the name of the applicant mentioned above.

As regards the constants K1 and K2, the latter may preferably be equal to 1 and 0.15 respectively.

As shown, by way of example relating to a membrane press, in FIGS. 1A, 1B, 1C and 1D of the appended drawings, the forced draining of the materials to be pressed 2 consists in causing, first of all, the evacuation air 4 contained in the tank of the press 1, then in carrying out a controlled pressing at low pressure, followed by a decompression of said tank.

In order to be able to expel the air 4 trapped between the membrane 5, on the one hand, and the materials to be pressed 2 and the free juices or liquids, on the other hand, the press tank 1 is brought into a position allowing the air evacuation 4 through an appropriate opening, for example one of the drains 3 'used to evacuate the liquids during the pressing phase (Figure 1B).

Then, the pressing member, in this case the membrane 5 (Fig. 3), is moved so as to raise the materials to be pressed 2 in the tank in the direction of the aforementioned drain 3 ', until all of the air is expelled from this tank.

Consequently, the air 4 contained in the tank of the press 1 is expelled from said tank by the orifices 3 and at least one drain 3 'provided for the evacuation of liquids, said tank being positioned in such a way that said orifices 3 and said drain 3 'are located in the upper part of the tank and the air 4 is then expelled by the ascent of the materials to be pressed 2 into the tank under the action of the pressing member.

This operation can, in the case of a membrane press 1, be perfectly controlled, by controlling the pressure applied to said membrane 5, which is a function of the diameter of the tank of said press 1.

As soon as the air 4 is completely expelled from the tank of the press 1, the latter is returned to the normal pressing position, corresponding to a maximum capacity for discharging the liquids or juices extracted, and controlled pressing at low pressure is started.

This controlled pressing at low pressure with a view to forced draining consists, after evacuation of the air 4 contained in the tank of the press 1, to apply a first pressing pressure P1 of low value, for a duration T1 determined according to of the flow of the liquids, then to apply, if no clogging of the orifices 3 for discharging the liquids was detected during the pressure level P1, a second pressing pressure P2, of intensity greater than P1 and, then, to carry out a decompression and, optionally, a stirring of the materials to be pressed 2 after completion of the pressure level P2.

The pressures P1 and P2 may, by way of indication, have values between 0.1 and 0.2 bar respectively and between 0.2 and 0.5 bar.

The duration T1 may, for its part, be calculated, during the pressure level P1, by analyzing the decrease in the flow rate of the liquids or juices extracted as described in the aforementioned patent application in the name of the applicant.

According to a characteristic of the invention, the pressure level P2 is maintained for at least a predetermined duration T2 and, if necessary, beyond this latter until the flow rate D of the extracted liquids drops below a setpoint D2, a function of Do.

For a membrane press, the value of the duration T2 may advantageously be between 1 minute and 5 minutes, preferably being of the order of 2 minutes and the set value D2 may be between 2 x C and 5 x C, preferably around 3 x C.

Decompression after forced draining is accompanied by stirring of the materials to be pressed 2, in the form, for example, for a membrane press, of 1 to 5 complete rotations of the tank of press 1, and, preferably, of 2 rotations of this type.

It can also happen that overpressures generated during filling, by means of a pump for example, of the tank of the press 1, lead to clogging of the orifices ensuring, in normal operation, the evacuation of liquids or juices.

lors de la phase précédent l'application de la pression P1.However, in accordance with a characteristic of the invention, the orifices 3 are considered to be clogged when, after application of the first pressure P1 for a period TC during a forced draining, the flow rate D of the extracted liquids is less than Do , while $\text{Dmin ≥ K2 x Do}$

during the phase preceding the application of pressure P1.

When the aforementioned conditions are verified, therefore in the event of a clogging being detected, the method according to the invention may consist in prolonging the application of the pressure P1 for a predetermined TP period, then in clearing the orifices 3 clogged by carrying out vigorous mixing of the materials to be pressed 2 after decompression.

As an indication, the duration TC can be of the order of 10 seconds, the duration TP can be between 1 minute and 5 minutes (preferably 2 minutes) and, the number of rotations of rotation of the tank of press 1, for a membrane press, be between 2 turns and 5 turns (preferably 3 turns).

During this decompression phase, the conditions involving forced draining are again checked.

Thanks to the invention, it is therefore possible to detect the need for forced drainage of the materials to be pressed, before the initiation of a normal pressing cycle C and to automate and control this forced drainage.

In addition, the invention also makes it possible to detect any clogging of the orifices for discharging clogged liquids and to automate the unclogging of the latter.

Thus, the method according to the invention leads, by avoiding the mishaps associated with the presence of large quantities of free juice, an optimization of the yield of the press 1 considered, in particular for materials to be pressed containing a lot of free juice and after filling of the press 1, for example by means of a closable opening 7.

Of course, the invention is not limited to the embodiment described and shown in the accompanying drawings. Modifications remain possible, in particular from the point of view of the constitution of technical equivalents, without thereby departing from the scope of protection of the invention.

Claims (8)

1. Automatic process for determining, controlling and monitoring a forced draining phase prior to pressing in discontinuous presses, characterised in that, after filling the press (1) and prior to beginning the normal pressing cycle (C), it consists in continuously measuring the flow rate (D) of the liquids without applying pressing pressure, recording the minimum value, Dmin, and the maximum value, Dmax, of the said flow rate (D), in particular when the vat of the press (1) is rotating, then comparing these values (Dmin and Dmax) respectively with predetermined quantities (K1 x Do and K2 x Do), then, as a function of the results of the said comparisons, if necessary, effecting forced draining of the material to be pressed (2), simultaneously checking for possible clogging of the outlets (3) for the liquids, repeating the preceding operations until the results of the aforesaid comparisons no longer imply forced draining and, finally, beginning the normal pressing cycle (C).
2. Process according to claim 1, characterised in that it consists in effecting forced draining of the material to be pressed (2) solely when at least one of the following conditions is established: $$\text{Dmax ≥ K1 x Do or Dmin ≥ K2 X Do,}$$

   

   where K1 is a constant with a value of between 0.5 and 2, K2 is a constant with a value of between 0.05 and 0.4 and Do is a flow rate value determined as a function of the dimensions and filling ratio of the vat of the press (1).
3. Process according to either of claims 1 and 2, characterised in that the forced draining of the material to be pressed (2) consists firstly in evacuating the air (4) contained in the vat of the press (1), then effecting controlled pressing at low pressure, followed by decompression of the said vat.
4. Process according to claim 3, characterised in that the air (4) contained in the vat of the press (1) is expelled from the said vat via the outlets (3) and at least one drain (3') provided for the discharge of the liquids, the said vat being positioned in such a manner that the said outlets (3) and the said drain (3') are situated partly above the vat, the air (4) then being expelled by the material to be pressed (2) rising in the vat by the action of the pressing member.
5. Process according to either of claims 3 and 4, characterised in that, after evacuation of the air (4) contained in the vat of the press (1), the controlled pressing at low pressure for forced draining consists in applying a first pressing pressure (P1) of low value for a period of time (T1) determined as a function of the flow of the liquids, then, provided that no clogging of the outlets (3) for the liquids has been detected during the first pressure stage (P1), applying a second pressing pressure (P2) of greater intensity than the first pressure (P1) and then effecting decompression and optionally mixing of the material to be pressed (2) after the second pressure stage (P2).
6. Process according to claim 5, characterised in that the second pressure stage (P2) is maintained for at least a predetermined period of time (T2) and, if necessary, beyond the latter until the flow rate (D) of the liquids extracted falls below a set point, D2, a function of Do.
7. Process according to claims 2 and 5, characterised in that the outlets (3) for the liquids are considered to be clogged when, after the application of the first pressure (P1) for a period of time (TC) during a forced draining phase, the flow rate (D) of the liquids extracted is less than Do, whereas $\text{Dmin ≥ K2 x Do}$

   

   during the phase preceding the application of the first pressure (P1).
8. Process according to any one of claims 1 to 7, characterised in that, after the detection of clogging, it consists in prolonging the application of the first pressure (P1) for a predetermined period of time (TP), then clearing the clogged outlets (3) by effecting thorough mixing of the material to be pressed (2) after decompression.

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