EP0215865B1 - Process for the adjustment of the grinding rollers of a grain mill installation; also, a grain mill installation for carrying out the process - Google Patents

Abstract

In order to adjust spacing of the grinding rollers (2, 2') in the mill frames (1) of a grain mill installation, a sieve system (14) is connected downstream of the mill frames (1) and from which a measurement signal is taken and transmitted to a computer (7). The latter compares it with a stored desired value and in case of it being different, automatically readjusts the grinding roller spacing accordingly by means of a control signal and adjustment gears (4, 5). The measurement signal is only determined by the rejection (17) or fall-through (18) of the sieve system (14) and is only transmitted to the computer by a few selected key grinds. In a grain milling machine for the carrying out of this process, the grits gauzes (14) is equipped with an impulse-weight measurement system (24, 29, 30, 31) for continuous evaluation of the sieving operation.

Description

Technical field

The invention relates to a method for adjusting the grinding roller spacing of roller mills with a downstream screening system in a grain mill system, in which in selected key passages a measurement signal representing an actual value is tapped, fed to a computer, compared there with a stored target value and if the actual value differs from A control signal is generated.

The invention also relates to a grain mill system with a series of roller mills and downstream plan sifters, with controllable drive means for adjusting the roller spacing, with measuring devices for measuring actual values of operating parameters and with a central computer with data memory for monitoring the actual values of selected key passages, for their comparison with corresponding ones , setpoints stored in the data memory and for generating control signals in the event of deviations between actual and setpoints.

Underlying state of the art

To date, there are essentially four proposed solutions for the control or regulation of the grinding roller spacings in a grain mill system. The first and oldest solution is to regulate and control the grinding rollers by the operator (Obermüller) himself. In order to be able to carry out such control "by hand", however, it is absolutely necessary to have complete control over the entire production process. The result of the control is largely dependent on the respective technical skills and experience of the operator, who is usually the supervising miller. Less qualified personnel must be used for the operation, e.g. B. during special times (vacation, night work, etc.), the mill may have a reduced result, for example due to a lower yield of healthy flour or the like.

A second proposal for the control is described in the magazine "Die Mühle und Mischfuttertechnik" from September 3, 1965. The essential part of this known proposal is the use of a test sieve. In production, an absolute classification into the individual grain fractions is not sought, since this would require a too long sieving time and would also result in changes in the product quality. Is z. B. regrind subjected to a sieving process for too long, the sieve diarrhea also contains fine shell parts which would normally float on top of the material in plan sifter operation and would reach the goal. Such finenesses cannot be taken into account in the theoretical treatment of grinding, since they are not least dependent on the manner in which the preceding and subsequent processing machines are operated, and therefore not solely on the grinding itself. In the sense of a complete, absolute regulation of the grinding work, it is therefore logical to subject the material to be ground to a separate, exact laboratory sieve and to make corrections in the event of deviations. Although the proposed test screening is much more precise, it still does not provide a representative picture in practice, since the work of the plan sifter, as already mentioned, represents a combination of screening and screening and requires a certain product layer above the screen mesh.

Another control option is described in EP-A1-13 023. This proposal is based on the assumption that any future-oriented development in the food processing sector should no longer be fundamentally geared towards the displacement of people. Rather, many processes can be carried out directly and more cheaply by humans. Because the ever-growing knowledge of the almost complete interweaving of all processes is increasingly calling for human monitoring and management at grain processing companies. Ultimately, it has been shown that it is not worthwhile to have all the processes that man can monitor with his senses, check and control by hand, carried out by apparatus.

Another known theoretical proposal for controlling a mill (DE-C-2 413 956) is aimed at replacing the operator, in particular the top miller, with computers and control devices. This boils down to incorporating the knowledge and experience of, for example, the upper miller into computer programs and making any routine human intervention superfluous via independent control devices. The known proposal provides that all grinding rollers are adjusted according to a previously worked out scheme for a certain grinding result, namely the ratio of sieve drop to sieve rejection. A corresponding implementation of this proposal in practice has so far not become known.

Disclosure of the invention

Based on the last-mentioned prior art, the invention is based on the object of improving a control method of the type mentioned in such a way that, with greatly reduced effort, an almost fully automatic operation with full functionality and without risk of rocking is made possible, and a mill system for carrying it out propose such a procedure.

According to the invention, this is achieved in a method of the type mentioned at the outset by selecting the repulsion or the diarrhea of the screen systems as actual and target values and using the control signal for specifying new setting values for the roller spacings.

In the case of a grain mill system of the type mentioned at the outset, the object is achieved in that the measuring device is a continuous weight measuring system downstream of the pian classifiers for the continuous detection of sieve rejection or sieve diarrhea, and the control output of the computer is connected to a setpoint memory for specifying new setting values for the drive means is

The measures according to the invention increase the ease of use, while at the same time the actual control of the overall control is left to the miller. This can initially prevent the entire mill run from "vibrating", i.e. that rocking occurs, which is a relatively great danger in many interventions. The really necessary interventions can be reduced to a minimum and carried out by an experienced operator. According to the invention, one or more corrections for the control specification can only be carried out within the framework of an overall overview, since all actual values, including those of the key passages, can be displayed centrally at any time and an intervention can be carried out in a very targeted manner, without any predetermined fixed correction program being executed ought to. If an error actually occurs, the biggest error can be easily eliminated first and then the subsequent errors. In the mill there is a level of knowledge which says that the grinding as such should not be carried out by complicated control devices. To date, it has not yet been possible to mill all effective parameters in theoretically or mathematically ascertainable forms. The practitioner is aware that the same goal can often be achieved in different ways. Often it depends on the special experience of the Obermüller and on his knowledge of plant-specific data. In addition, the grinding is also the result of the use of appropriate machine groups. A significant amount of the grinding work is predetermined by the designer of the machines, the type of operation and maintenance of the machines, as well as by the specifically used machines themselves, the treatment diagram and the special features of the machine, which is why the Obermüller limits the quality of the grinding work are set.

Another complex that has received relatively little attention so far is the question of quantitative grinding work. It has been shown that quantitative grinding work is a very important factor, particularly with regard to automation efforts. For the qualitative assessment, the human being with his senses and the possibility to combine intuitively is superior for a long time, especially in the case of intermediate mill products, automation tendencies through the use of machines. However, this does not apply to the case of quantitative assessment. The operator, such as the miller, cannot be present everywhere in the mill at the same time. The product flow there is partly determined by rigid guidelines, for the most part the individual products find their way into the product flow itself, while people intervene at some important intersections. With the information on selected key passages developed according to the invention, however, the current essential picture of the entire process is available at all times, even after interventions such. B. by the Obermüller. Knowing the conditions at the key passages, together with the overall yield, allows conclusions to be drawn about what is happening on the vast majority of the machines used, which require a lower degree of surveillance. The invention thus represents a happy grip with regard to the use of sensible automation while preserving the possibility of intervention by the top miller. For the first time, the method according to the invention makes use of the surprising finding that when using the measurement results, only a few selected key passages and their processing in one Downstream computers can achieve largely automated control of the grinding roller spacing in a grain mill system without an extraordinarily large number of further measurement results having to be evaluated by correspondingly complicated computer programs, because a deliberate intervention possibility of the upper miller is deliberately planned.

In the grain mill system according to the invention, the measured values determined with the measuring device can be determined from product properties without the occurrence of a disturbance variable, with the accuracy of measured values from the scales. Nevertheless, they offer the advantage of a continuous measuring process, similar to that of a belt scale. The main difference to the belt scale, however, lies in the very simple construction and the correspondingly low manufacturing costs, as is the case with the (however, fault-sensitive) pulse monitors. In fact, the mill system according to the invention has, for the purpose of the invention, a combination of the advantages of the belt scales and the continuous flow meter without their disadvantages occurring. The specification of new setting values for the drive means for setting the roller spacings also serves the purpose mentioned at the outset, namely that the entire mill run does not "start to oscillate".

The invention allows various very advantageous design options:

Der letztgenannten Kombination für die Ableitung des Meßwertes liegt der Gedanke zugrunde, daß mit den Passagen Bi und Ci ein Regelvorgang sichergestellt wird, die Passagen 8₄ und C₄ hingegen nur zur Kontrolle dienen. Es sind hier lediglich besonders bevorzugte Kombinationen für die Ableitung des Meßsignales an besonders wichtigen Meßstellen aufgeführt, die jedoch vom Fachmann je nach spezifischer Mühlenanlage ausgewählt bzw. herangezogen werden können.For the B passages, z. B. the same early detection of the mill input power, with C passages it is advantageous if the input power of each automatically monitored roller mill is recorded simultaneously. With very few product changes, it is entirely sufficient if the measurement signal is determined from the amount of rejection of the first shot (B ₁ passage), preferably at short intervals, during the grinding process. In the case of frequent or very frequent changes in the quality of the raw material or end product, the measurement signal at passages B ₂ and possibly also at further passages (B ₃ ...) is preferably derived equally from the amount of screen rejection or the scrap. However, in addition to the measurement signal derived from the amount of sieve rejection or the meal in the B passages, a further measurement signal derived from the amount of sieve diarrhea or the amount of flour is also particularly preferred in the passages C ₁ , again preferably at short time intervals, derived during the measurement process and fed to the computer. In the case of the grinding passages, however, it also applies, depending on the size and comfort requirements, that corresponding measurement value derivations can be carried out both for the C ₂ passages and any specifically selected grinding passages. The measurement signal is particularly preferably derived from the amount of rejection or diarrhea of the following combinations of passages:

The latter combination for deriving the measured value is based on the idea that passages Bi and Ci ensure a control process, but passages 8 ₄ and C _4, on the other hand, only serve as a control. Only particularly preferred combinations for the derivation of the measuring signal at particularly important measuring points are listed here, which, however, can be selected or used by the person skilled in the art depending on the specific mill system.

In a further preferred embodiment of the method according to the invention, a default setpoint value scheme is stored in the computer for each grain mixture or for each grinding task, in which all the values for the automatic control of the grinding roller spacings, in particular the default setting values corresponding to the grinding gap, as well as those for the minimum and maximum values for the amount of meal or flour obtained, in which the target values of the roller mills are not changed, are specified. In this way, an undesired, too frequent correction of the roller settings can be avoided. Because, at least theoretically, a single grinding gap correction in the first shot roller mill in a larger mill system means that the conditions in all the following twenty to thirty roller mills and plan sifters are also changed. A correction program is therefore preferably assigned to the computer, which automatically carries out correction commands by changing the working setpoints in the order from the largest to the smallest correction. So is z. B. a strong deviation is found in the selection passage C ₁ , this is first corrected, then only z. B. a necessary follow-up correction for passage Bi etc.

It is also very advantageous if the computer contains a basic program that also includes non-automatically recorded parameters (such as grinding pressure, force absorption, effective grinding gap width, etc.), in particular also those of the non-automatically controlled machines (ie non-automatically setting or adjustable roller mills and derived values with regard to sieving work) are recorded and can be called up at any time, so that, based on older values, controls and corresponding manual interventions can be carried out. This solution particularly expresses the benefits of the automatic means for all the necessary controls and manual entries. At the same time, however, this also has the advantage that the miller can reuse the previous values for each shift in a mill. This also makes it possible to ensure relatively constant operational management of the mill system, even with changing personnel. In most cases, it is sufficient if the grinding gap is automatically preset for only a part of all rolling mills and then only for some of these automatically preset rolling mills the screen rejection and / or the screen diarrhea are measured and the measurement signal is derived from this. Thus, the grinding gap is preferably automatically preset only in a part of all rolling mills and then only in some of the automatically presettable rolling mills is the screen rejection and / or screen diarrhea measured or the measurement signal derived therefrom, again: preferably, in less than half of all rolling mills The grinding gap is automatically preset and the sieve diameter or sieve rejection is measured in two to six subsequent plan sifters and a measurement signal is derived from this.

A particularly advantageous development of the method according to the invention is that the measurement signal is derived from instantaneous values of the force components of both the inflow impulse of the product flow and its weight in a weighing vessel, the sieve failure and / or the sieve rejection in continuous operation by recording these instantaneous values over a short period of time determined, a control variable is derived from this and used for the automatic monitoring and, if necessary, control of the roller mills. It is noteworthy that obviously all previous attempts based on the directly operating continuously operating pulse measuring systems have failed. With these continuous weighing systems, due to the impulse of a falling product flow, the amount of product concluded, which leads to relatively good results under ideal conditions. However, if disturbances occur, z. B. to glue the flour to one of the baffle plates, the measurement value falsifies very quickly until it cannot be used. With the method according to the invention, however, this problem can easily be taken into account by simply subtracting two measurements in quick succession in a weighing container from the pulse component and thus any source of interference from atmospheric moisture, product sticking or the like. comes off. However, this pulse measurement requires the goods to flow continuously into the weighing container, so that the measurement can be described as continuous at the same time. If one has the goal of improving the uniformity of the product flow in the mill system, one recognizes the value of intermediate weighing, which is essentially continuous, is often carried out, but takes only a short time. The use of a measured value (as in conventional methods), which itself is a disturbance variable that was precisely the aim of the measurement and control used, is pointless, as the past clearly showed. In an advantageous further development of the method according to the invention, the weight increase in the weighing vessel is therefore recorded without interruption of the product flow per unit of time in order to determine the control variable, the detected value is compared with the total mill output and then communicated to the computer as parameters for the viewing unit. Preferably, weighing is carried out in the weighing vessel according to a predetermined cycle, preferably approximately every 10 to 30 minutes, and it lasts less than 10 seconds, preferably less than 5 seconds.

The grinding rollers are preferably designed to be controllable or regulatable via the computer on the basis of an actual setpoint value comparison for setting or regulating corresponding working parameters that can be set via the grinding rollers (grinding roller speed and / or grinding gap), with, again, preferably, the setting devices or their drive means a central computer can be remotely controlled and a mechanical or electrical coupling is provided between the drive means and the adjusting coupling. This solution is preferably used for grinding passages, ie for smooth rollers. In the case of shot passages or the corrugating rollers, on the other hand, the setting device or its drive means can preferably be remotely controlled via the computer and provided with a pressure or distance or force absorption limiting device to prevent harmful inputs.

Brief description of the drawings

• Figur 1 die schematische Darstellung einer erfindungsgemäßen Vorrichtung für die automatische Überwachung eines Mahlwalzenpaares;
• Figur 2 eine stark vereinfachte, prinzipielle Darstellung des Ablaufs der Überwachung der Mahl- und Sichtarbeit einer gesamten Mühlenanlage;
• Figur 3 eine schematische Darstellung einiger Schrot- und Grießpassagen mit deren Ausgangsprodukten, sowie
• Figur 4 eine schematische Darstellung verschiedener Ausmahl-Passagen.

The invention is explained in more detail below in principle by way of example with reference to the drawing. Show it:

• Figure 1 is a schematic representation of a device according to the invention for the automatic monitoring of a pair of grinding rollers;
• Figure 2 is a greatly simplified, basic illustration of the process of monitoring the grinding and visual work of an entire mill system;
• Figure 3 is a schematic representation of some grist and semolina passages with their starting products, as well
• Figure 4 is a schematic representation of various meal passages.

Detailed description of the drawings

FIG. 1 shows a roller mill 1, of which only half or a pair of grinding rollers 2, 2 'is shown. A special peculiarity of the milling roller mill lies in the fact that, unlike products such as stone or coal, the product is not crushed, but also not only squeezed into it. Rather, an actual pressure-shearing process is used, which is achieved by increasing the rotational speed of one roller, such as roller 2 ', in comparison to the rotational speed of the other roller, such as roller 2. The grinding rollers 2, 2 'may therefore only be engaged if product is present, which can be determined or controlled via a product guiding device 3. A pneumatic piston 4 and a lever 5 and thus the associated roller 2 'are brought into their engaged or disengaged position via a corresponding signal. The grinding gap itself can be preset to a desired dimension using a handwheel 6 or, if necessary, subsequently corrected by the operator. Regardless of this manual setting, however, the grinding gap can also be remotely controlled by a computer 7 with memories 8, 8 ', 8 "for setpoints. The grinding gap can now, for example, as described in EP-B1-0 013 023 certain optimum value found by previous grinding are set automatically in the sense of a rough setting via an adjusting motor 9 and a chain 10 which engages a shaft 11 of the handwheel 6. An analogous value for measuring the grinding gap is carried along with a chain 10 Position indicator 12 determined and reported back to the computer 7 via a control line 13.

In the figure representation according to FIG. 1, a plan sifter 14 is shown schematically at the top right. The product flow is represented as an input power in the roller mill 1 with an arrow 15, the arrow 16 shows the product transfer from the roller mill 1 into the plan sifter 14, the arrow 17 denotes the screen rejection and arrow 18 the screen diarrhea. The plansifter 14 is provided with individual sieve frames 19, 20, 21 and 22, the number of which depends on the product performance and in particular based on the respective product quality.

FIG. 1 shows the detection of the product throughput as a function of the screen rejection (arrow 17) in a control circuit with solid lines. A weighing vessel 23 is mounted separately from the fixed contact elements via elastic sleeves 27, 28; an inlet 25 and an outlet 26 are also provided. The weighing vessel 23 is supported on electronic balance elements 24, which transmit the weight signals to a controller 29 as measurement signals. A converter 30 emits a pneumatic signal to a cylinder 31, which actuates a slide slide 32. The weighing system is described in more detail in EP-A1-140 213, to which reference is made in full. By means of this system, an increase in weight per unit of time is measured, for example during a fraction of a second up to several seconds, and a derived measurement signal for the ratio of weight / unit of time to the computer 7. It is crucial in this new measuring system that the product flow 17 'into the weighing vessel 23 is not interrupted during, before and after the measurement. For weight gain, instantaneous values are measured via the electronic balance elements 24 at intervals, e.g. B. the product quantity A (after a certain delay after closing the slide 32) and the product quantity B in the weighing vessel 23. The difference in level between the product quantities A and B then corresponds exactly to the product quantity, from a corresponding time assigned to the product quantity B up to that the time assigned to the product quantity A has flowed into the container, from which a corresponding signal for the product throughput can thus be derived. All necessary data (such as input power 15, product mixture and specific grinding specifications) are also entered into the computer 7 and kept in the corresponding memories 8, 8 'and 8 ". Another weighing system is described in EP-A1-0 013 023 of the generic type .

The system works as follows:

In the memories 8, 8 'and 8 ", the corresponding memory locations are called up by a central computer 40 (FIG. 2) via a control line 41 and the data are made available to the computer 7 in accordance with the desired grinding work to be carried out. Essential data are the values for the grain mixture and moisture, for the grinding work and for the input power, but in particular the associated value for the roller mill, the grinding gap, the grinding pressure or the electrical current consumption of the drive motor of the roller mill and a current measuring device 34. The grinding roller distance can be derived directly from the measured value of the position indicator 12 or, if the corresponding display 6 'of the handwheel 6 is displayed, the next important value is the acquisition of a corresponding measured value on the plan sifter, in the example of FIG the amount of weight per unit time with respect to the S iebabschlages the z. B. is selected as the preferred key passage in the first shot passage. To simplify the illustration, the measured value of the position indicator 12 (thus a value corresponding to the distance between the grinding rollers) is now referred to as the "roller distance" for the example shown. Furthermore, the amount of product of the first sieve rejection or the instantaneous or averaged output of the second shot or the amount of shot B ₂ obtained per unit of time is measured and compared accordingly. In principle, the absolute value of the roller spacing is no longer of interest for the control to be carried out, since a corresponding numerical value can be determined from previous optimizations, whereas the exact value of the amount of shot B ₂ is very important. If all process parameters have been found to be correct (moistening of the grain, time of rest of the grain, mill input, etc.), experience has shown that the mill does not work fully automatically with constant grinding work and constant grinding quality, since the product (grain) to be ground is "living""It deals with material that is subject to constant influences depending on the place of origin and climatic conditions or depending on its growth phase. The wheat grain breathes, it processes starch, and the protein changes, with various very complex enzymatic and other processes taking place. All of this affects not only the mechanical workability, but also the water absorption behavior and the strength properties of the shell parts and the flour grain. Ultimately, the aim of good grinding is to obtain a high yield of light flour with optimal quality and economically favorable use of the mill system. Although the top miller ultimately has to control the mill himself, control means are indispensable for large plants (only and especially for these) so that a person is actually able to actually run a mill plant as a whole and to keep the necessary overview, which is the main object of the present invention.

To control the grinding work, the values from one or more key passages or the selected sieve diarrhea or sieve rejection as well as one or more important other measured values from the production process are continuously selected and monitored. Is now z. B. the proportion of the rejection of the first shot at 70 to 75% of the mill input, this is an indication for the miller that the processing runs well to the corresponding point. The control can now be set up so that a narrow tolerance band is selected for the sieving value for each individual grinding task and for each individual grinding passage, in within which the grinding process is sufficiently satisfactory, which, for. B. can be displayed via a corresponding indicator lamp. In addition, a second, larger tolerance band is provided, within which a change in the grinding gap is triggered directly by the computer and is maintained after a corresponding time delay if the correction has been successful. However, if a sieve value is measured that is still outside the broader tolerance band, z. B. triggered alarm or, if necessary, the roller mill can be turned off completely.

Since each mill has to meet specific requirements and also has a corresponding special diagram of the process, there are a variety of useful applications. FIG. 2 is used as the basic diagram for this, only individual specimens being shown in principle as processing machines, even if a large number of such machines are used in practical milling work instead of the individual specimen shown.

The central computer 40 has a memory 42 for the target value schemes and can simultaneously be connected to other computer units 43, for example to an accounting computer. Depending on the degree of expansion of the system, the computer can be equipped with a central screen 44 and a central input printer 45. In its full configuration, one or more portable screens with input printers are preferably provided, which are suitable for local interventions, e.g. B. in a roller mill, etc., can be used at the workplace. For the sake of simplicity, only the same reference numerals as in FIG. 1 have been chosen for the first grinding passage B _i , although the corresponding identical elements are located at any other point in the mill, that is to say at B ₂ , B ₃ or Bx and Ci , C ₂ , C ₃ ... Cx can be used. Only part of the passages are fully monitored, in FIG. 2 these are passages Bi and B ₃ and C _i and Cs. Furthermore, another part of the roller mills has an automatic grinding gap control device with a computer, but without a weighing system, in FIG. 2 this is passage B _x , and furthermore, in the case of a large number of the passages, there is neither automatic control of the roller mills nor weighing of the screen rejection or screen diarrhea , in Figure 2 with Div 1 and C _x . As a rule, no mechanical monitoring is carried out for the majority of the passages in the sense of the invention, however, it is conceivable that the current consumption is measured and monitored for all drive motors of the roller mills.

FIGS. 3 and 4 merely represent enlarged representations from FIG. 2, the diagramatic connections being evident. The passages labeled B are the beginning of the grinding, S denotes the semolina cleaning machines and C represents the grinding passages. "Div 1" denotes a diviseur.

Furthermore, it is now essential that in each case the mill input, ie the amount of raw fruit to be processed, is recorded precisely during the entire grinding, for example by means of a weighing system which is denoted by 50 at B _i . Since the grinding passages are fed from different locations, a measurement of the input power is required for the C passages at least for C ₁ A by means 51 (only shown in principle) and for B ₂ , C ₂ by means 52 shown in principle.

Claims (15)

1. Process for setting the distances between milling rollers of roller assemblies (1) with screening system (14) connected downstream in each case, in a grain mill, in which in selected key passages a measurement signal representing an actual value in each case is accessed, fed to a computer (40), and compared there with a stored desired value, and if the actual value deviates from the desired value a control signal (41) is produced, characterized in that the actual and desired values selected are the screen discharge (17) or the screenings (18) of the screening system (14), and the control signal (41) is used to predetermine new settings of the distances between rollers.

2. Process according to Claim 1, characterized in that the measurement signal in the passages Bi or Bi and B2 or B₁, B₂ and B₃ are derived from the quantity of screen discharge or of meal.

3. Process according to Claim 1 or 2, characterized in that the measurement signal in the passages C₁ or C₁ and C₂ or C₁, C₂ and Cs are derived from the quantity of screen discharge or of the meal obtained.

4. Process according to one of Claims 1 to 3, characterized in that stored in the computer for each grain mixture or for each meal input is a preset desired value schedule in which all values for automatic control of the distances between milling rollers, in particular predetermined settings corresponding to the milling clearance, and for the subsequently recorded sifter valid minimum and maximum values for the coarse millings or meal obtained, within which no desired values of the roller assemblies are changed, are predetermined.

5. Process according to Claim 4, characterized in that a correction program which independently carries out correction commands by changing the working desired values in an order going from the largest to the smallest correction is allocated to the computer.

6. Process according to one of Claims 1 to 5, characterized in that the computer contains a basic program which also records parameters not automatically recorded (such as milling pressure, power consumption, effective milling clearance etc.), in particular those of non-automatically controlled machines (non-automatically settable or controllable roller assemblies and derived values as regards screening work) and can be called up at any time, so that checks and appropriate manual interventions can be undertaken based on older values.

7. Process according to claims 1 to 6, characterized in that the milling clearance is automatically preset in only a part of all roller assemblies and the screen discharge and/or screenings are measured subsequently in only a part of the automatically presettable roller assemblies.

8. Process according to Claim 7, characterized in that the milling clearance is automatically preset in fewer than half of all roller assemblies and the screenings or screen discharge are measured in two to six sifters downstream.

9. Process according to one of Claims 1 to 8, characterized in that the measurement signal is derived from current values of the power parts of both the inflow impulse of the product flow and its weight in a weighing vessel, the screenings and/or the screen discharge are established in continuous operation by ascertaining these current values over a short period of time, and from this a control parameter is derived and is used for the automatic monitoring and, if necessary, control of the roller assemblies.

10. Process according to Claim 9, characterized in that to ascertain the control parameter the weight increase in the weighing vessel is ascertained without interrupting the product flow per unit time, and the ascertained value is compared with the overall mill output and is then entered in the computer as a parameter for the sifting unit.

11. Process according to Claim 9 or 10, characterized in that weighing according to a predetermined cycle takes place in the weighing vessel and takes less than 10_'sec., preferably less than 5 sec.

12. Grain milling unit with:

a) a sequence of roller assemblies (1) and sifters (14) connected downstream;

b) controllable drive means (4, 5, 9) for setting the distances between rollers;

c) measuring devices (23, 24) for actual value measurement of operating parameters; and

d) a central computer (40) with data storage unit (42) for monitoring the actual values of selected key passages, for their comparison with corresponding desired values stored in the data storage unit (42), and for the production of control signals (41) in the event of deviations between actual and desired values; characterized in that

e) the measuring device (23, 24) is a continuous weight measuring system connected downstream of the sifters (14) for continuous recording of the screen discharge (17) or of the screenings (17); and

f) the control output (41) of the computer (40) is connected to a desired value storage unit (8) for feeding of new settings to the drive means (4, 5, 9).

13. Grain milling unit according to Claim 12, characterized in that the milling rollers can be controlled or regulated by means of the computer on the basis of an actual value/desired value comparison for setting or controlling relevant working parameters which are settable by means of the milling rollers (milling roller speed and/or milling clearance).

14. Grain milling unit according to claim 12 or 13, characterized in that the setting devices or their drive means are remotely controllable by means of a central computer and a mechanical or electrical coupling is provided between drive means and setting device.

15. Grain milling unit according to claim 12 or 13, characterized in that the setting devices or their drive means are remotely controllable by means of the computer and are provided with a pressure or distance or power consumption limiting device to prevent damaging control operations.

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