EP0485901B1 - Method of pressing and device for its application - Google Patents

Abstract

Pressing method for controlling and regulating a press during a juice extraction process, which comprises at least one pressure increase sequence, characterised in that it is based on measuring the flow or the extracted quantity of liquid before, during or after pressing or the partially dried pressed material remaining in the press after pressing and making a comparison with a given value, and using the value, which arises from the difference between the values for the flow or the quantities of liquid extracted and the given values for the flow or the quantities, or the quantity of the possibly partially dried pressed material remaining in the press, in order to begin, continue, interrupt, change or end the method for juice extraction, this method being at least partially programmed. <IMAGE>

Description

The present invention relates to the field of juice extraction from agricultural products and aims to provide a pressing method for controlling a press and an apparatus for performing this method.

Several types of presses are currently known, including membrane presses in particular. The membranes of these presses, which have different shapes, are displaced by the action of a fluid (air, water, etc.), the pressure of which can be regulated. This membrane is arranged in a vat that contains the materials from which liquid is to be obtained.

There are also several pressing processes for controlling the presses.

In general, these known pressing methods comprise several preset pressure levels. At the end of each pressure stage, the pressure is reduced and the materials are mixed. Nevertheless, pressing processes are also known in which several pressure increases can follow one another without intervening mixing. The various parameters of the pressing cycles of these known methods are determined experimentally by the operator of the press, then programmed and completely reproduced by the automatic of the presses.

As a result, each time the type of material to be pressed changes, such as the ripeness and variety of fruit, the user has to re-determine the parameters in order to obtain an appropriate pressing cycle. Since this determination takes a very long time (a pressing cycle generally takes 1 to 4 hours), the user rarely spends the time necessary to determine the corresponding parameters. In addition, the user does not always have the experience or expertise required to optimize the automatic press cycle to be reproduced by the press. In addition, they are programmed parameters and can be changed in the course of a press cycle only by the user, depending on the development and the course of the pressing.

A pressing method for juice from fruits or vegetables known from SU-A-531'765 (M.A. Hussit et al.) Can be controlled by gradually increasing the pressure on the product and stabilizing it at each stage. The pressure is increased if there is no difference between the actual squeezed amount of juice and a setpoint.

From FR-A-2'590'046 (station Oenotechnique de Champagne) a method for automating the function of a grape press is known. This includes a flow meter for the juice outflow from the press tub, the measurement signal of which is fed to an automatic machine. The machine generates a control signal for an electrical control circuit for the pressure inside the tub.

The object of the present invention is therefore to provide a pressing method in which the levels of the working pressure of the press are determined automatically, i.e. without user intervention, as well as the duration of these pressure levels, the possible connection of several pressure levels Execution of pressure reduction phases and the degree of mixing during the pressure reduction phases, that is to say, the entirety of the parameters which determine the course of a pressing cycle and this depends on the development of the pressing. In addition, this process enables a juice of better quality to be obtained and also a better utilization of the pressed material by a type of process which is gentler on the pressed material.

This task is carried out in a pressing process which allows the control and regulation of a press during a juice extraction process and at least a sequence of pressure increases to separate the solid and liquid substances from agricultural products, such as grapes, berries, fruits or vegetables, by means of a pressing device, which can be driven in a container, wherein the juice output or the amount of liquid which is obtained before, during or after the pressing or the material to be pressed which remains partially juiced after the pressing is measured and with an expected value which is before and / or is calculated in the course of the pressing process, compared and the value resulting from the difference in juice output or the amount of liquid obtained or the amount of Pressed material, which may remain partially juiced in the press and gives the value of the expected juice output or quantity, is used to start, continue, interrupt, change or end the juice extraction process, said process being at least partially programmed and wherein the pressing of a batch of pressed material takes place by means of several sequences of pressure increases, which are interspersed with one or more stirring phases of the pressed material and which form a pressing cycle, in that the pressing program for the subsequent sequence of the pressure increase or for the later sequences of the pressure increase occurs is changed.

Another object of the invention is to provide a device for carrying out the automatic pressing process with an automatic machine with a fixed memory, which in particular controls a device for supplying the press with pressurized liquid and a motor for rotating the tub of the press, on the other hand with a pressure sensor, which Press pressure measures and with a flow meter, which is arranged below the emptying opening for the liquids obtained. This device is characterized in that the machine is programmable, comprises a read-write memory and can be controlled by a control panel, which in particular allows the limit duration of a press cycle, as well as the value of at least one factor that determines the course of said cycle, to be determined.

Figur 1

die Kurven der Pressdruckentwicklung und des Durchflusses der abfliessenden, gewonnenen Flüssigkeiten während einer Sequenz von Druckanstiegen zeigt;

Figur 2

die Kurven der Pressdruckentwicklung und des Durchflusses der abfliessenden, gewonnenen Flüssigkeiten während zwei aufeinanderfolgender Sequenzen von Druckanstiegen in einem Presszyklus zeigt;

Figur 3

die Kurven der Pressdruckentwicklung und des Durchflusses der abfliessenden, gewonnenen Flüssigkeiten am Ende eines Presszyklus zeigt; und

Figur 4

ein schematisches Diagramm der Vorrichtung zur Durchführung des automatischen Pressverfahrens gemäss der Erfindung darstellt.

The following description serves to explain the invention in more detail and relates to a preferred embodiment, which is intended as an example and not as a limitation and is explained with reference to the accompanying schematic drawings, of which:

Figure 1

shows the curves of the pressure development and the flow of the discharged liquids obtained during a sequence of pressure increases;

Figure 2

shows the curves of the press pressure development and the flow of the runoff, obtained liquids during two successive sequences of pressure increases in a press cycle;

Figure 3

shows the curves of the pressure development and the flow of the runoff, obtained liquids at the end of a pressing cycle; and

Figure 4

is a schematic diagram of the device for performing the automatic pressing process according to the invention.

According to the invention, the pressing method is based on measuring and comparing the flow rate or the amount of liquid obtained before, during or after the pressing or the partially dried pressed material remaining in the press 1 after the pressing with a given value and the value that results the difference between the values for the flow rate or the amount of liquid obtained and the given values for the flow rate or the amount of liquid obtained, or to use the amount of the remaining, if necessary partially dried, pressed material to start the process for juice extraction , interrupt, change or terminate, this method being at least partially programmed.

In the present description, S _n denotes a sequence of any pressure increase in a pressing operation. This sequence S _{n may be} preceded by a preceding sequence S _n-1 and then possibly followed by a subsequent sequence S _{n + 1} . Likewise, P _n denotes any pressure level of a sequence S _{n of} any pressure increase. The pressure stages P _n-1 and P _{n + 1} are pressure stages which may be lower or higher than pressure stage P _n . In addition, P _n-2 and P _{n + 2} optionally designate the pressure stages which are lower than P _n-1 or higher than P _{n + 1} . Similarly, P₁ denotes the first pressure stage of a sequence S _{n of} any pressure rise, and P₂, P₃, P₄, etc., the corresponding subsequent pressure stages. The values of these pressure levels are always in the range between the lowest and the greatest value of the pressing pressure that can be achieved and maintained by the press 1, the gradation and the total number these sections may vary depending on the application.

According to a first feature of the invention, at least one batch 4 of pressed material is pressed by means of a plurality of pressure increase sequences S _n , which form a pressing cycle C.

According to a feature of the invention, the pressing or the pressure increase sequences S _{n are carried out} during at least one specific pressure stage P _n .

According to another feature of the invention, the pressing program is changed for the following pressure increase sequence S _n or for the later pressure increase sequences S _n .

According to another feature of the invention, the pressing or the pressure increase sequences S _n comprise at least one pressure stage P _n .

According to another feature of the invention, the first pressure stage P 1 of a pressure increase sequence S _{n is} adjustable with respect to its value and / or its duration.

According to another feature of the invention, the flow or the amount of liquid obtained is measured during a pressure stage P _n at a constant pressure.

According to another feature of the invention, the pressing pressure P is changed during a pressure stage P _n on the basis of a flow or a quantity of liquid obtained.

According to another feature of the invention, the pressing pressure P is controlled as a function of the flow or the amount of liquid obtained during a pressure stage P _n .

According to one embodiment of the invention, the pressing process is essentially based on continuously measuring at least one variable during each pressure increase sequence S _n , which depends directly on the amount of liquid currently obtained and is variable during a pressing cycle C, in order to subsequently increase the pressure compare the size measured at certain times and / or its relative fluctuations with the given values and then continue or interrupt the current sequence S _n depending on the result of the previous comparison or the comparisons, possibly repeating the preceding processes until the end of the pressing cycle C and finally to cause the press 1 to be emptied at the end of the press cycle C.

According to a preferred embodiment of the invention and as shown in Figures 1 to 4 of the accompanying drawings, the pressing method is based more precisely on the continuous measurement and increase in the flow of the outflowing liquid obtained during each pressure increase sequence S _n , the subsequent comparison for each pressure level P _n , which is achieved by the pressing pressure P, the value D _{n of} the flow D, which is measured at a time t _n , and / or the relative increase R _{n of} the flow D, which results from the transition of the pressing pressure P from a lower pressure stage P. _n-1 to the pressure level P _n results, with the corresponding predetermined values D ₁ , R, and on the subsequent, either immediate or delayed transition of the pressure P of the pressure level P _n to a higher pressure level P _{n + 1} , or a subsequent, somewhat delayed interruption of the current sequence S _n and the execution of a Pressure reduction of the press 1 followed by mixing of the pressed material, depending on the result of the comparison just carried out and the value of the pressure level P _{n reached} and a possible repetition of the previous processes until the end of the press cycle C.

At the end of the press cycle C, the press 1 can be emptied in an automatic emptying cycle or manually by the user.

According to a feature of the invention, pressing a batch 4 of pressed material after loading the Press 1 only started when the flow D of the outflowing liquid of the press 1 is below a predetermined value D₀, as a result of which free juice can flow off in a first phase. The value D₀ depends on the material to be pressed and the size of the press used. For example, D₀ for grapes and a press 1 with a capacity of 10,000 liters can preferably be set at 7,000 l / h.

At the beginning of each pressing cycle C, it is important that the filling quantity T _r of the tub 2 to determine the press. 1 In the case of a press that is designed with a mobile or deformable pressing member, such as a press 1 with a membrane 3, it is sufficient to determine the volume of hydraulic fluid that is necessary to press the membrane 3 of the press 1 against the batch 4 of material to be pressed to press.

According to one feature of the invention, the determination of the filling quantity T _r is essentially also based on measuring the duration of the pressure fluid supply at the beginning of a press cycle C, which is necessary to achieve the pressure level P _n with the lowest value. In the course of the pressure fluid supply, the membrane 3 or the movable press member of the press 1 is pressed against the batch 4 of the pressed material, the duration of the supply being proportional to the free volume of the tub 2 of the press 1. If the conditions of the liquid supply as well as the capacity of the tub 2 are known, a calculation of the filling quantity T _{r is} possible.

According to a modified implementation of the invention, the determination of the filling quantity T _r is essentially based on the measurement of the weight fluctuation in the same height of the tub 2, which results from the loading of the tub with pressed material. If the volume of the batch 4 is known, it is consequently possible in principle to determine the filling quantity T _r for a tub 2 with a known capacity.

In order to accelerate the pressing process and consequently to increase productivity, the method according to the invention is also based at the beginning of a pressure increase sequence S _{n of} a pressing cycle C on increasing the pressing pressure P per stage and without delay in succession to a pressure stage P _n for which the value D _n of the flow D, measured at the time t _{n, is} higher or equal to a value D 1, which was determined automatically at the beginning of the press cycle C, primarily depending on the measured filling quantity T _r (FIG. 2).

The pressing pressure P is therefore not kept at the pressure stages P _n which result in a flow D with a lower value, but after the result of the comparison between the value D _{n of} the flow D at the time t _n for each pressure stage P _n and the value D₁ immediately increased to pressure levels with higher values. The value D 1 depends, apart from the filling quantity, on the type of material to be pressed and the size of the press 1. Thus, the value D 1 for grapes and for a press 1 with a capacity of 10,000 liters, preferably 400 l / h, 1,100 l / h and 1,700 l / h for filling quantities T _r equal to 10%, 50% and 100%, respectively linear interpolation enables the determination of all values D 1 depending on T _r .

According to a feature of the invention and as shown in FIGS. 1 and 2 of the accompanying drawings, the time t _{n of} the measurement of the value D _{n of} the flow D of the outflowing liquids obtained is calculated from the beginning of the pressure stage P _n and can take, for example, 30 seconds from the beginning of the pressure levels P _n , which are reached by the pressure P, are set.

To further increase the execution speed of the press cycle C, the value of the first pressure stage P 1 of a pressure increase sequence S _{n is} equal to the value of the first pressure stage P _{n of} a previous one Pressure increase sequence S _n-1 , for which the value D _{n of} the flow D, measured at the time t _n , is higher or equal to the value D ₁ (Figure 2).

The various pressure increase sequences S _n are consequently changed depending on the development of the increased pressing during the preceding pressure increase sequences S _n-1 and adapted to new pressing conditions.

As for the first pressure stage P _{n of} a pressure increase sequence S _n , for which the measured value D _{n is} higher than D 1, the pressing pressure P is kept at the pressure stage P _n until the flow D falls below a value D _T , which was previously calculated , then the pressure P is increased to a higher pressure level P _{n + 1} .

   wobei D_M(n) der grösste Wert des während der Druckstufe P_n erhöhten Durchflusses D ist und D_m(n-1) der geringste Wert des Durchflusses D ist, der bei dem Übergang des Pressdrucks P von der Druckstufe P_n-1 auf die Druckstufe P_n zwischen den Werten D_M(n-1), dem grössten Wert des während der Druckstufe P_n-1 erhöhten Durchflusses D, und D_M(n) liegt und dadurch bedingt wird, dass der Druck P für eine bestimmte Dauer auf dem Wert P_n-1 gehalten und nicht erhöht wird. Folglich ist für die Druckstufen P_n, für welche der gemessene Wert D_n höher als D₁ ist, das Auswahlkriterium für einen Übergang des Drucks P auf eine höhere Stufe der Wert R_n, mit Ausnahme der ersten Stufe mit gehaltenem P_n, für die R_n nicht berechnet werden kann, wobei es keinen Wert D_m(n-1) (Figur 1) gibt.According to one feature of the invention, the relative increase R _{n of} the flow D of the outflowing liquids obtained results from the transition of the pressing pressure P from a low pressure level P _n-1 to a pressure level P _n from the following formula: $${\text{R}}_{\text{n}}\text{=}\frac{{\text{D}}_{\text{M}}{\text{(n) - D}}_{\text{m}}\text{(n-1)}}{{\text{D}}_{\text{m}}\text{(n-1)}}$$

where D _M (n) is the largest value of the flow D increased during the pressure stage P _n and D _m (n-1) is the lowest value of the flow D which occurs when the pressing pressure P changes from the pressure stage P _n-1 to the pressure stage P _n lies between the values D _M (n-1), the greatest value of the flow D increased during the pressure stage P _n-1 , and D _M (n) and is caused by the pressure P being present for a certain duration kept at the value P _n-1 and not increased. Consequently, for the pressure stages P _n , for which the measured value D _{n is} higher than D 1, the selection criterion for a transition of the pressure P to a higher stage is the value R _n , with the exception of the first stage with P _{n held} , for which R _n cannot be calculated, there being no value D _m (n-1) (FIG. 1).

According to another feature of the invention, the pressing method is also based on allowing the pressing pressure P to pass from a pressure stage P _n to a higher pressure stage P _{n + 1} if the value of the flow D is higher than D ₁ as soon as that during the pressure stage P _n measured flow D has fallen below a value D _T , which was calculated for the pressure stage P _n , and this if the relative increase R _{n of} the flow D is greater than or equal to the corresponding predetermined value R. In principle, if R _{n is} large and, above all, larger than a given value R, this means that the juice flows easily out of the pressed material and an additional increase in pressure is justified. In contrast, if R _{n is} small and, above all, smaller than a given value R, this means that the liquid is blocked in the mass of the pressed material. A new pressure increase is therefore useless and the pressure reduction phase with subsequent mixing of the pressed material is therefore appropriate. The value R is preferably in the range of 5% for grapes, for example.

   wobei K ein Faktor zwischen 0 und 1 ist, der vor Beginn des Presszyklus C festgelegt wird. Der Wert D_T bestimmt daher die Dauer für das Aufrechterhalten von Druck P auf einer Druckstufe P_n, für die D_n höher als D₁ und R_n höher als R ist, wenn die verhältnismässige Erhöhung R_n messbar ist.The value D _T is preferably determined for each pressure stage P _n using the following formula: $${\text{D}}_{\text{T}}{\text{= K. D}}_{\text{M}}\text{(n)}$$

where K is a factor between 0 and 1, which is determined before the start of the pressing cycle C. The value D _T therefore determines the duration for maintaining pressure P at a pressure level P _n , for which D _{n is} higher than D 1 and R _{n is} higher than R if the relative increase R _{n is} measurable.

The factor K is determined by the user of the press before the start of a press cycle C, depending on the type of the material to be pressed and the speed of execution of the pressing and the desired drying out of the batch 4.

In the course of a press cycle C, a plurality of pressure increase sequences S _n are generally carried out, which are interrupted by phases in which the press 1 is depressurized and the material to be mixed is mixed. As already mentioned above, these pressure reduction and mixing phases are programmed either when the relative increase R _{n of} the flow for a pressure stage P _{n is} less than the given value R, or when the pressure P is the maximum pressure stage P _n that can be reached by the press 1 has reached, and are executed after a delay depending on the change in the flow D during a current pressure stage P _n .

According to a feature of the invention, the method is also based on controlling the pressure reduction of the press as soon as the flow D falls below a fractional value D _{F of} the maximum flow rate D _M that is reached during the corresponding pressure increase sequence S _n , the fractional value D _F of the factor K that was set before the start of the press cycle C. G is the fractional ratio of D _F / D _M. The following table shows an example of the value of the fracture ratio G for various values of the factor K for a press 1 with a capacity of 10,000 liters, which is used for pressing grapes:

   wobei T₁, T₂ oder T₃ Teile der Anzahl der Umdrehungen T sind, die von P_M, K bzw. T_r abhängen. Die folgenden Tabellen zeigen beispielhaft die Veränderungen der Teile T₁, T₂ und T₃ abhängig von P_M, K bzw. T_r und zwar wie oben für Weintrauben und für eine Presse 1 mit einem Fassungsvermögen von 10.000 Litern:

According to another feature of the invention, the mixing process of the pressed material after the pressure reduction of the tub 2 of the press 1 is based on rotating the tub 2 for a number of complete rotations T, the number of rotations T depending on the pressure stage P _M , which was reached before the pressure reduction, and on the other hand from the measured filling quantity T _r and finally from the value K, which was set before the start of the pressing cycle C. The number of rotations T can thus be calculated using the following formula, for example: $$\text{T = T₁ + T₂ + T₃}$$

where T₁, T₂ or T₃ are parts of the number of revolutions T, which depend on P _M , K and T _r . The following tables show examples of the changes in parts T₁, T₂ and T₃ depending on P _M , K and T _r , respectively, as above for grapes and for a press 1 with a capacity of 10,000 liters:

According to a feature of the invention and as shown in Figure 3 of the accompanying drawings, the automatic pressing process also relies on interrupting a pressing cycle C when the maximum value D _{M of} the flow D reached during a pressure increase sequence S _n is less than one is critical value D _c , which was determined at the beginning of the cycle C and mainly depends on the filling quantity T _r and the capacity of the tub 2 of the press 1, or if the duration of the pressing cycle C exceeds a limit value T _L , which is before the start of the Press cycle C was set. In the latter case, it is possible to carry out a further press cycle C with the same batch, the increased values of the last pressure increase sequence S _{n of} the interrupted press cycle C being used, for example, to change the control of the factor K.

Another object of the invention is a device for carrying out the automatic pressing method described above, which is shown in FIG. 4 of the accompanying drawings, the device essentially comprising, on the one hand, a programmable apparatus 5, which primarily comprises a device 6 for supplying hydraulic fluid and a motor 7 controls, which sets the tub 2 of the press 1 in rotation, and on the other hand a pressure transmitter 8, which measures the pressing pressure P, and a flow meter 9, which is arranged below the discharge opening 10 for the liquid obtained and finally a control panel 11, which above all the determination of the limited duration T _{L of} a press cycle C and the value of at least one factor K for the cycle C enables.

According to a feature of the invention, the programmable apparatus 5 comprises a read-only memory 12 which contains the control program for the pressing process, as well as the reference tables which enable the values D₀, D₁, D _F , T and D _{c to be determined} depending on the factor K, which was set before the press cycle C, and the values T _r , D _M (n), D _M and P _M measured at the beginning or during the press cycle C.

According to another feature of the invention, the programmable apparatus 5 further comprises a working memory 13, which allows the immediate treatment and storage of the various increased values for the flow D and the pressure P during a pressure increase sequence S _n and, if appropriate, until the end of a pressure increase sequence S _n Stores values that are necessary to determine the following section or sections in the current pressing cycle C. The latter values can also be written into a magnetic tape storage with autonomous supply, so that the pressing can be resumed after a desired interruption if desired.

The device according to the invention can also include a control panel 14 which enables the user to empty the tub 2 of the press 1 and, if appropriate, also to clean it.

Of course, the invention is not limited to the embodiment described and shown in the accompanying drawings. Modifications are possible, especially with regard to the nature of the individual elements or through the use of appropriate techniques, without departing from the scope of the invention.

Claims (26)

1. Method of pressing which allows for the control of a press during a juice extraction process and includes at least one sequence of pressure increases in order to separate the solid and liquid substances of agricultural products, e.g. grapes, berries, fruits or vegetables, by means of a pressing member which can be driven in a container, the juice yield or the quantity of liquid extracted before, during or after pressing, or the material to be pressed remaining partially dejuiced after pressing in the press (1) being measured and compared with an expected value calculated before and/or in the course of the pressing process, and the value obtained from the difference between the juice yields or the quantities of liquid extracted or the quantity of material to be pressed possibly remaining partially dejuiced in the press (1) and the value of the expected juice yields or quantities being used to begin, continue, interrupt, alter or end the juice extraction process, the said process being at least partially programmed, and a charge (4) of material to be pressed being pressed by means of a plurality of sequences (Sn) of pressure increases which are interspersed with one or more stirring phases of the material to be pressed and form a pressing cycle (C), characterised in that the pressing programme is altered for the next sequence (Sn) of the pressure increase or for the subsequent sequences (Sn) of the pressure increase.
2. Method according to claim 1, characterised in that the pressing or the sequences (Sn) of the pressure increase include at least one pressure stage (Pn).
3. Method according to either of claims 1 and 2, characterised in that the value and/or the duration of the first pressure stage (P1) of a sequence (Sn) of the pressure increase is/are adjustable.
4. Method according to one of claims 1 to 3, characterised in that the juice yield or the quantity of liquid extracted in the course of a pressure stage (Pn) is measured at a constant pressure (P).
5. Method according to one of claims 1 to 4, characterised in that the pressure (P) is altered as a result of the juice yield or quantity of liquid extracted in the course of a pressure stage (Pn).
6. Method according to one of claims 1 to 5, characterised in that the pressure (P) is controlled as a function of the juice yield or quantity of liquid extracted in the course of a pressure stage (Pn).
7. Method according to one of claims 1 to 6, characterised in that it consists in measuring at least one variable which depends directly upon the instantaneously extracted quantity of liquid variable in the course of the pressing cycle (C) substantially continuously in the course of each sequence (Sn) of the pressure increase, then in comparing the said variable measured at specific times and/or its relative variation with expected values, then in continuing or interrupting the current sequence (Sn) as a function of the result of the preceding comparison or comparisons, in possibly repeating the preceding operations to the end of the pressing cycle (C) and finally in optionally emptying the press (1) at the end of the said pressing cycle (C).
8. Method according to claim 7, characterised in that it consists in continuously measuring and recording the juice yield (D) of the outflow of the liquid extracted during each sequence (Sn) of pressure increases, then, for each pressure stage (Pn) reached by the pressure (P), in comparing the value (Dn) of the juice yield (D) measured at a time (tn) and/or the relative increase (Rn) of the said juice yield (D) resulting from the transition of the pressure (P) from a lower pressure stage (P n-1) to the said pressure stage (Pn) with corresponding predetermined values (D1, R), then in allowing the pressure (P) to pass consecutively, either immediately or after a specified time, from the pressure stage (Pn) to a higher pressure stage (P n+1) or, after a specified time, in consecutively interrupting the current sequence (Sn) and in relieving the press (1) from pressure, followed by stirring of the material to be pressed as a function of the result of the preceding comparison and the value of the pressure stage (Pn) reached, and finally in possibly repeating the previous operations until the end of the pressing cycle (C).
9. Method according to one of claims 1 to 8, characterised in that, after filling of the press (1), pressing does not begin until the outflow (D) of the liquid of the said press (1) is situated below a predetermined value (D 0).
10. Method according to one of claims 1 to 9, characterised in that it consists in determining the degree of filling (Tr) of the vat (2) of the press (1) at the beginning of each pressing cycle (C).
11. Method according to claim 10, characterised in that the determination of the degree of filling (Tr) for a press (1) equipped with a movable or deformable pressing member essentially consists in measuring the duration of the pressure fluid supply required to reach the pressure stage (Pn) with the lowest value at the beginning of a pressing cycle (C).
12. Method according to claim 10, characterised in that the said determination of the degree of filling (Tr) mainly consists in measuring the change in weight in the region of the vat (2) of the press (1) resulting from filling the latter with the material to be pressed.
13. Method according to one of claims 1 to 12, characterised in that it consists, at the beginning of a sequence (Sn) of pressure increases of a pressing cycle (C), in increasing the pressure (P) in successive stages and without a time delay to a pressure stage (Pn) for which the value (Dn) of the juice yield (D) measured at the time (tn) is higher than or equal to a value (D1) determined automatically at the beginning of the pressing cycle (C), in particular as a function of the measured degree of filling (Tr).
14. Method according to one of claims 8 to 13, characterised in that the time (tn) of the measurement of the value (Dn) of the juice yield (D) of the liquids extracted is calculated from the beginning of the pressure stage (Pn).
15. Method according to one of claims 1 to 14, characterised in that the value of the first pressure stage (P1) of a sequence (Sn) of pressure increases is equal to the value of the first pressure stage (pn) of a previous sequence (S n-1), for which the value (Dn) of the juice yield (D) measured at the time (tn) was higher than or equal to the value (D1).
16. Method according to one of claims 8 to 15, characterised in that it consists in keeping the pressure (P) at the first pressure stage (Pn) for which the measured value (Dn) is higher than (D1) until the juice yield (D) falls below a previously calculated value (D T) and then in increasing the said pressure (P) to the higher pressure stage (P n+1).
17. Method according to one of claims 8 to 16, characterised in that the relative increase (Rn) of the juice yield (D) of the liquids extracted resulting from the transition of the pressure (P) from a lower pressure stage (P n-1) to the pressure stage (Pn) is given by the formula: $$\text{Rn =}\frac{\text{D M(n) - D m(n-1)}}{\text{D m(n-1)}}$$

    

    where (D M(n)) is the maximum value of the juice yield (D) recorded in the course of the pressure stage (Pn) and (D m(n-1)) is the minimum value of the juice yield (D) recorded at the transition of the pressure (P) from the pressure stage (P n-1) to the pressure stage (Pn) between the measurements of the values (D M(n-1)), i.e. the maximum value of the juice yield (D) recorded in the course of the pressure stage (P n-1) and (D M(n)).
18. Method according to one of claims 8 to 15 and 17, characterised in that it consists, if the value of the juice yield (D) is situated above (D1), in allowing the pressure (P) to pass from a pressure stage (Pn) to a higher pressure stage (P n+1) as soon as the juice yield (D) measured in the course of the pressure stage (Pn) falls below a value (D T) calculated for the said pressure stage (Pn), if the relative increase (Rn) of the juice yield (D) is greater than or equal to the corresponding previously determined value (R).
19. Method according to one of claims 16 and 18, characterised in that the value (D T) is determined by the following formula: $$\text{(D T) = K * (D M(n)),}$$

    

    where K is a factor between 0 and 1 and fixed before the beginning of the pressing cycle (C).
20. Method according to claim 19, characterised in that it consists in relieving the press from pressure as soon as the juice yield (D) falls below a fractional value (D F) of the maximum juice yield (D M) reached during the sequence (Sn) of pressure increases in question, the said fractional value (D F) depending on the factor (K) fixed before the beginning of the pressing cycle (C).
21. Method according to one of claims 8 to 20, characterised in that the process of stirring the material to be pressed once the vat (2) of the press (1) has been relieved from pressure consists in rotating the said vat (2) for a whole number of rotations (T), the said number of rotations (T) being dependent, on the one hand, on the pressure stage (P M) reached before the pressure relief and, on the other hand, on the measured degree of filling (Tr) and finally on the value of K fixed before the beginning of the pressing cycle (C).
22. Method according to one of claims 1 to 21, characterised in that it consists in interrupting a pressing cycle (C) if the maximum value (D M) of the juice yield (D) reached during a sequence (Sn) of pressure increases is lower than a critical value (D C) determined at the beginning of the cycle (C) and dependent in particular on the degree of filling (Tr) and the capacity of the vat (2) of the press (1), or if the duration of the pressing cycle (C) exceeds a limit value (T L) fixed before the beginning of the pressing cycle (C).
23. Method according to one of claims 8 to 22, characterised in that, for grapes, the value of (R) is advantageously approximately 5 %.
24. Device for the application of the method of pressing according to one of claims 1 to 23, comprising an automatic device (5) with a read-only memory which in particular controls a device (6) for supplying the press with pressure fluid and a motor (7) for driving the vat (2) of the press (1) in rotation, and, on the other hand, comprising a pressure sensor (8) which measures the pressure (P) and a flow meter (9) which is arranged below the discharge opening (10) for the liquids extracted, characterised in that the automatic device (5) is programmable, includes a read/write memory and can be controlled via a console (11) which allows in particular for the fixing of the limit duration (T L) of a pressing cycle (C) and the value of at least one factor (K) which determines the course of the said cycle (C).
25. Device according to claim 24, in which the read-only memory (12) of the programmable automatic device (5) contains the control programme for the method of pressing, characterised in that the read-only memory (12) moreover includes the allocation tables which allow for the determination of the values (D 0, D 1, D F, T, D C) as a function of the factor (K) fixed before the pressing cycle (C) and values (Tr, D M(n), D M and P M) measured at the beginning or in the course of the said pressing cycle (C).
26. Device according to one of claims 24 and 25, characterised in that the programmable automatic device (5) moreover includes a read/write memory (13) which allows for processing and temporary storage of the various values of the juice yield (D) and pressure (P) recorded in the course of a sequence (Sn) of pressure increases and for optional storage of the values required to determine the subsequent stage or stages of the current pressing cycle (C) until the end of a sequence (Sn) of pressure increases.

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