CH667222A5 - METHOD FOR CONTROLLING AN AGRI MILL, AND CONTROL DEVICE FOR CARRYING OUT THE METHOD. - Google Patents

Description

DESCRIPTION

The invention relates to a method for controlling an agitator mill containing a grinding media, a grinding container with a product inlet and a product outlet, in which at least one operating parameter is determined and at least one parameter of a controlled system is controlled as a function thereof, and to a control device for carrying it out of the procedure.

Such methods are described for example in DE-A-2 932 783 or 3 038 794. In both cases, several linked control systems are provided. This enabled the performance of agitator mills to be increased to a surprising extent, after experts previously essentially assumed that agitator mills are relatively simple devices on which at most a simple control with a single circuit is sufficient.

The invention is based on the object of further improving such a control method, and this is achieved according to the invention in that the product fineness is determined as the operating parameter, that the determined value for the product fineness is introduced into the rule linkage for the control system, and that depending on the product fineness determined, at least one parameter determining the specific grinding performance is regulated. According to the invention, three steps are therefore carried out in succession or simultaneously, with one of the important

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Most parameters are used for control, and a very special group, namely those which determine the specific grinding performance, are selected for control under the various parameters which determine the conditions of an agitator mill.

This is absolutely no coincidence, but goes back to intensive investigations by the applicant. “Specific grinding performance” is to be understood - in accordance with general usage - as the grinding performance per product unit. In the investigations carried out, it has been found that operating parameters such as the cooling capacity on the rotor and / or stator, the viscosity of the regrind dispersion and the like. have only a minor influence on the end result, although numerous writings have made various suggestions, for example with regard to cooling. Rather, the investigations carried out showed that it is particularly advantageous if the degree of gap in the grinding media in the grinding vessel is regulated, preferably by changing the working volume of the same. Another possibility for controlling the degree of gap could be to change the size of the grinding media, as will be explained later with reference to FIG. 2, but also to fill the grinding chamber with additional grinding media of the same size, which may also be done manually, for example.

The control method defined above can also be applied to existing agitator mills that do not have a device for changing the degree of gaps in the grinding container. In this case it is provided that the speed of at least one drive, e.g. the pump supplying the product and / or the agitator. This solution is preferable to regulating the degree of gaps, because regulating the pump speed means that the throughput must be reduced in the case of insufficient product fineness, so the disadvantage of reducing the throughput must be accepted. On the other hand, the control of the speed of the agitator is usually associated with a higher outlay than the control of the degree of gap in the grinding media, in particular if the latter is carried out by changing the working volume of the grinding container. So if the control of the speed is only to be considered secondly given other possibilities, it must be mentioned that the mentioned speed control leads to very good results, for example in comparison to a cooling capacity control. If, however, the degree of gap in the grinding container can be regulated, it is advantageous if a combination of the regulations mentioned is carried out in such a way that the degree of gap of the grinding elements is sequential and the speed only when the limits of the control range are reached - possibly with an overlapping transition is regulated. In this way, a good optimization can be obtained.

Further details result from the following description of three exemplary embodiments, each of which is shown schematically in FIGS. 1 to 3 of the drawing.

In Fig. 1, an agitator mill 1 is shown, the central part of which has broken away. This agitator mill 1 has a grinding container 2 into which a product dispersed in a liquid can be introduced via a product inlet pipe 3. It should be noted here that the ground material does not necessarily have to be dispersed in a liquid, especially since it is already known to include gases, e.g. inert gases to be provided as a fluid.

After flowing in through the product inlet pipe 3, the ground material passes through an inlet separating device (sieve) 4 into a grinding chamber 5 inside the grinding container 2, which is partly filled with grinding balls 6, which are set in motion by an agitator 7. For this purpose, the agitator 7 has a drive motor 8, which does not necessarily have to be an electric motor, especially since it has already become known to use hydraulic motors (US Pat. No. 3,770,214), the speed of which can be regulated more easily. Finally, the material to be ground enters at the lower end of the grinding container 2 via an outlet separation gap 9 into an outlet channel 10, through which it is then discharged, for example with the aid of a pump 11. In this embodiment, too, if the product flow from top to bottom, i.e. runs from the inlet pipe 3 to the outlet duct 10, it should be pointed out that the invention is in no way restricted to this, and it is generally even preferred if the product flows from the bottom upwards. In addition, the pump 11 can be arranged on the inlet side instead of the outlet side, for example.

The arrangement and construction of the outlet separating device 12 forming the outlet separating gap 10 corresponds to DE-A-3 318 312. Accordingly, the separating device 12 is formed by a rotating disk which delimits the separating gap 9 on the inside and which is mounted in a pressure piston 13, with the aid thereof the working volume of the grinding chamber 5 changed, and thus the degree of gaps, ie the ratio of the volume occupied by the grinding media 6 in the grinding chamber 5 to the volume free of grinding media can be regulated. The piston 13 is adjusted in one direction by supplying pressure medium via a line 14 into a cylinder space 15, in the other direction via a line 16 which opens into a cylinder 17 with an auxiliary piston 18. Both control lines 14, 16 are supplied with pressure medium by a control device 19 which is known per se and which is only shown schematically and which is controlled by electrical signals and thus represents an electro-fluidic converter. The pulley 12 is driven by a drive wheel 20 and belt 21 from a motor, not shown.

The components described so far are known per se, even if from different references. The connection from the outlet duct 10, which also moves with the piston 13, to the pump 11 takes place via a bellows 22 and a line 23. The bellows 22 is arranged within a housing 24, the lower part of which is closed as a container space 26 by a cover 25 is trained. A branch line 27, which can optionally be shut off by a valve (not shown), opens into this container space 26, which is connected to the outlet line system 10, 22, 23 and feeds a (small) part of the product led out of the grinding container 5 to the space 26.

Accordingly, the container space 26 receives part of the product that has already been ground, but it should be mentioned at this point that the branch line 27 can, if desired, also start, for example, from the center of the grinding container 2. Since, as described below, the branch line 27 forms the starting part of a shunt line in this exemplary embodiment, on which a measuring arrangement for determining the product fineness is provided, the removal of the end product for the measurement means, on the other hand, a more precise determination of the product fineness achieved in the operation of the agitator mill 1 In the event of deviations from a desired product fineness, the initial product once subjected to the measurement can no longer be influenced, at least in this passage, even with the fastest readjustment of the mill 1. If, on the other hand, the branch line 27 is connected directly to the grinding container 2 (for example as a shunt line which leads back into the grinding container again), an intermediate product fineness is determined in the course of the grinding process, but regulation that can be used immediately can still be carried out

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prevent bad grinding product or the need for a second passage. In practice, you will have to find a compromise that does not necessarily have to be in the middle, depending on the size of the control time constant, the product and the measurement accuracy that can be achieved at various points.

In the container space, the product supplied via the branch line 27 is mixed with a dilution liquid which is supplied via a line 28. The dilution liquid can, for example, be water, the proportion of the diluent supplied via line 28 generally being relatively high. It may therefore be that the free cross sections of the lines 27, 28 are very different, the branch line 27 has, for example, a throttle cross section.

To mix the liquids supplied from the lines 27, 28, a mixing stirrer 29 may be provided, which either has its own drive or, as in the exemplary embodiment shown, is driven by one of the drives of the agitator mill 1 - here by the drive for the cutting disc 12 . The homogeneous, thin dispersion thus obtained is drawn off by means of a pump 30 via a line 31. Provided within the line 31 is a display chamber 32 with translucent walls which, due to a relatively low pump speed of the pump 30, has the diluted dispersion flowing through it in a relatively smooth and bubble-free manner. The pump 30 finally conveys the dispersion, expediently via a check valve 33, back into the pipeline 23, but it may also be that such a recirculation is not desirable because of a possible excessive dilution and the line 31 behind the pump 30 ins Free or a container or a clarifier opens.

A laser tube 34, preferably a relatively low-energy laser, such as a helium-neon laser, is provided on line 31, on the Brewster plates 35 of which a fully reflecting mirror 36 and a partially transmissive mirror 37 are arranged. These mirrors can be designed, for example, as concave mirrors. The beam 38 of monochromatic, coherent light which is transmitted through the partially transmissive mirror 37 is very thin and strikes the individual particles of the dispersion which are passed by within the display chamber 32. If a relatively large particle enters the laser beam, there is a strong beam deflection on its sides, whereas the beam deflection is smaller for smaller particles. The more or less deflected laser light is thrown via a lens 39 onto a target 40, the center of which is aligned with the axis of the beam 38.

To adapt to different fineness ranges of the material to be ground, either the target 40 has to be replaced or, which is preferred, the objective 39 consists of a basic objective 41 and an afocal attachment 42 with a variable focal length, whereby the magnification achieved by the objective 39 depends on the respective fineness range. can be fitted.

Because of the deflection of the light in all directions,

The target 40 can contain several concentric ring arrangements 43, 43 ', 43 ". Photoelectric converter, as has already been proposed for range finders, but also for optional point light or integral measurement on cameras. The photoelectric converters 43, 43', 43", do not have to be circular themselves, but several such transducers can be arranged along a respective circle, in FIG. 1, these circles being shown raised at different levels from the surface of the target 40, just to clarify the arrangement for will usually be on one level.

However, the expression “target” was deliberately chosen because this converter unit can also be formed by the recording screen of a video camera, which is usually referred to as “target”. In this case either the normal horizontal and vertical deflection is maintained, a downstream arithmetic stage 44 calculating the association with one of the circles 43, 43 ', 43 "from the deflection coordinates (ie practically from the size of the respective deflection signal), or the Distraction is changed from the normal case and takes place in a circular or spiral form. If only three circles 43, 43 ', 43 "are given here by way of example, it should be pointed out that any number is possible. In the case of using the recording screen of a video camera as the target 40 - in the presence of a lens of variable magnification, e.g. if necessary also an interchangeable lens system - the existing lens system of the camera can be used as lens 39.

It follows from the above explanations that with the aid of the measuring device 34 to 43 shown, an absolute determination of the fineness of the regrind particles is possible. Nevertheless, it may be desirable to take a reference measurement. For this purpose, an inclined, semitransparent mirror 45 is provided in the beam path of the laser beam 38, which fades out part of the light. In the beam path of the laser beam 138 thus created there is a further display chamber 132 which is connected to a line 131. A pump 130 is provided in line 131, which pumps a similar dilute dispersion from a container 126. A branch line 127 connected to the inlet pipe 3 and, on the other hand, a branch 128 of the line 28 open into the container 126. Instead of a mechanical mixer, the arrangement here is such that the line 128, together with the line 127 surrounding it in the mouth region, a liquid jet pump 129 forms, which on the one hand exerts a suction effect on the branch line 127, on the other hand also ensures mixing and swirling of the two liquids. If necessary, the nozzle system 129, as known per se for swirl chambers, can be designed to improve swirling.

In any case, the resulting liquid mixture in the container 126 will calm down and be fed via the pump 130 to the sight glass 132, behind which a similar objective 139 and a similar target 140 are arranged. The outputs of the targets 40, 140 are fed to the evaluation stage 144, which emits an output signal to a control stage 46, which can contain a microprocessor, for example. From this control stage 46, in accordance with the prior art cited at the beginning, both the electro-fluid converter 19 and a control circuit 47 for regulating the speed of a motor 48 driving the pump 11 for the regrind, as well as a speed control circuit 49 for the agitator motor 8 regulates which of the latter can contain, for example, the frequency converter stage 50 known from the prior art and a motor control circuit 51. It has already been mentioned that control is simplified if a hydraulic motor is used instead of an electric motor 8. The regulation takes place in the sense that, if the fineness is insufficient, the absolute grinding capacity introduced into the grinding container 2 is either increased or the throughput of the grinding material through the grinding container 2 is reduced by reducing the speed of the motor 48. Since the latter is less desirable, the control stage 46 preferably contains a sequence controller (which can be formed by the program of the microprocessor mentioned), the electro-fluidic converter 19 preferably being controlled first, and in the case of unge5

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sufficient product fineness of the piston 13 is raised. Only when the piston 13 enter the limit of its control range, i.e. towards its uppermost position (as shown), one of the speeds of the motors 8 and / or 48 will be changed. This can take place even before the uppermost position is reached by the piston 13, preferably in such a way that from a certain position of the piston 13 which represents a threshold value, the speed is changed to a certain percentage, which increases with increasing height of the piston 13 then increases (if necessary in stages) until the speed control is fully effective in the uppermost limit position of the piston 13. It is preferred here if the speed of the two motors 8,48 is also controlled sequentially by first increasing the speed of the motor 8 and now in a similar manner a transition to the speed control of the motor 48 takes place, i.e. when a limit value of the control range for the motor 8 is reached, the speed of the motor 48 for the pump 11 is reduced for further regulation. In order to determine the respective position of the piston 13, either the control arrangement 19 can be designed such that the respective amount of fluid that was sent via the lines 14 or 16 is in the form of a signal that is transmitted to the control circuit 46. For example, the connecting line 52 can be designed as a data bus for this purpose, or a separate line (not shown) is provided. Another possibility is to provide a measuring sensor at the lower end of the processed piston rod, which serves as a bearing for the cutting disc 12, or the shaft of the cutting disc 12, similarly as is known on the one hand from the prior art and on the other hand with reference to FIG. 3 will be described later.

The measurement of the product fineness was illustrated above with reference to FIG. 1 and an electro-optical measuring arrangement. However, numerous different methods are possible to determine the fineness of the product directly or indirectly. If one assumes that with coarse particles the gaps that necessarily remain between them - even with the greatest packing density of the individual particles - must remain relatively large, but can be correspondingly smaller with smaller particles, then it is understandable that as the particle size becomes smaller, different physical dimensions Properties of the dispersion of these particles will change. Such physical properties are, for example, the electrical conductance, the value of the resistance for waves passed through, e.g. Ultrasonic waves, or the viscosity. Fig. 2 illustrates a particular embodiment, which i.a. it is remarkable that in this case the product fineness obtained is determined on the basis of a viscosity measurement. In this FIG. 2, parts of the same function have the same reference numerals as in FIG. 1, but parts of a similar function have the same reference numerals with a letter.

Instead of an agitator mill 1 with a vertical shaft 53 (FIG. 1), an agitator mill 1 with a horizontal shaft 53a is provided for an agitator 7a. In contrast to FIG. 1, this agitator 7a is designed without tools 54 (so-called annular gap mill) and has cooling by means of cooling tubes 55a guided helically around the grinding container 2a instead of the cooling jacket 55 shown in FIG. 1, which has an inlet connection 56 and an outlet connection there 57 has. In addition, the rotor 7a also has cooling channels 58.

To change the working volume of the grinding container 2a, however, a piston 13 is not provided, but an actuating piston 18a can be displaced within a cylinder 17a by means of a control 19 constructed essentially in the same way as in FIG. 1. The piston 18a is now connected to the conical rotor 7a, so that the gap between the outer surface of the rotor 7a and the inner surface of the grinding container 2a is narrowed when the rotor 7a is displaced in one direction and expanded in the other direction.

However, this arrangement also belongs to the prior art cited at the beginning, such as a grinding-body circulation line 59 which is routed outside the grinding container 2 and is connected on the one hand to the product inlet 3a and on the other hand to the product outlet 10a of the grinding container 2a. It is also known to arrange additional pumps 1 lb, 1 lc at the inlet 3a or at the outlet 10a in addition to the actual product pump 1a, with more being temporarily supplied via the pump Hb, for example, and via the pump by appropriate control of their two motors 48b, 48c 11c can be dissipated less or vice versa. Such a difference is only possible to a limited extent, especially since this builds up or reduces a pressure within the grinding container 2a, but a compensation results from the fact that the pumps 1 lb, 1 lc are designed as screw pumps, which above all the take solid components inevitably, whereas for the liquid components the promotion is rather non-positive. This has the effect that the difference in the speeds of the motors 48b, 48c mentioned can practically regulate the number of grinding media contained in the grinding container 2a and thus the above-mentioned degree of gap. Another control option for changing the degree of gaps will be described later. However, it is still part of the known prior art that a processor system 146 with a plurality of setpoint inputs 60 is provided. Such setpoint inputs are of course also provided in the arrangement according to FIG. 1, but are not shown there. For example, according to the description of DE-OS 3 038 794, one setpoint input 60 may be provided for specifying a specific position of the piston 18a, the other for setting the speed of the motor 8 and the other inputs for changing the speed of the motors 48b, 48c.

In a departure from the prior art, the pump IIa conveys via a line 61 into a stirred tank 126a, from where the supplied product is fed to the circulation line 59 via a line 62. On the other hand, a similar container 26a is connected to the product outlet 10a in such a way that it is arranged behind a vibrating screen 63 which separates the grinding media 6 from the product and a centrifuge 64 (for separating fragments of the grinding media). Both containers 26a, 126a are initially used to determine the viscosity, from which, however, the fineness of the ground material is deduced on the basis of a corresponding computer program provided in the processor system 146. For this, the prerequisites explained below must be observed.

Both containers 26a, 126a are of completely identical construction, have completely identical agitators 129, both of which can be driven by identical motors 65. The motors are preferably DC motors with permanent magnet and iron-free armature, e.g. brushless motors, the relationship between the resistance to be overcome by the agitators 129 and the current consumption of the motors 65 is expediently linear, although in the case of nonlinearity and known characteristics of the motors, the computer program provided in the processor 146 can provide a corresponding compensation. For this reason, the motors do not necessarily have to be constructed in the manner described.

Since, moreover, the viscosity is a function of the temperature, which of course does not affect the fineness of the product

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has flow, this factor must be switched off, and for this temperature sensors 66 are connected to the container 26a, 126a. Corresponding measuring circuits 67 are provided for measuring the current consumption of the motors 65. The viscosity is calculated in a known manner from this data (cf. PCT publication WO 83/00101), taking into account the speed of the agitators 129, the Nusselt number, the Reynold number, the torque of the agitators 129 and certain conditions, such as a constant, which depends on the structure of the agitator itself and the specific weight of the ground material. As can be seen in FIG. 2, the measuring circuits 67 are connected via two lines on the one hand to the respective motor 65 and on the other hand to the processor system 146, one line being used for measuring the speed, the other for measuring the current consumption (torque).

From the comparison of the viscosities of the supplied and the discharged product with the temperature switched off as an influencing variable (which will normally be higher for the discharged product due to the introduced and converted heat output), a conclusion can be drawn about the product fineness achieved. B. via a further setpoint input 60 a. desired viscosity difference can be entered.

It has already been mentioned above that a number of controlled systems can be influenced via the processor system 146, the control in principle taking place in a manner similar to that described with reference to FIG. 1. This means that the degree of gap is preferably regulated, and this can be done in the embodiment shown in FIG. 2 on the one hand by displacing the piston 18a and on the other hand by influencing the speeds of the motors 48b, 48c, which then influences in the sense of a specific speed difference will. Although it may be the other way round cheaper for some applications or designs, it will generally be preferred if the piston 18a is first controlled via the electro-fluidic converter 19 before the speeds of the motors 48b, 48c will be controlled. It has already been mentioned above that the control of the speeds of the motors 8 and 48 (in this order) is expediently carried out only in the last line.

In the embodiment according to FIG. 2, however, a third possibility is provided in order to change the degree of gap within the grinding container 2a. It is known per se to provide special inlets in agitator mills in order to change the degree of gap (in particular in the case of the enlargement thereof due to the wear of grinding media), i.e. essentially to keep it constant, grinding media can be inserted by hand. In the present embodiment, however, the circulation line 59 can be used for automation and for completely changing the degree of gap during the operation of the agitator mill la. For this purpose, above a provided in the end of the vibrating screen 63, for. B. in cross section rectangular or in longitudinal section converging towards the line 62 (z. B. trapezoidal) pipeline 68 provided several silo-like grinding media container 69, of which again grinding media of a different size, possibly also of a different type (especially different material) . The number of containers 69 provided corresponds to the respective circumstances and can be adapted to these. The outlets of the container 69 which can be closed by automatically operable closures 70 open into a pipe 71 leading to the pipeline 68.

The pipeline 68 can now be moved from the position shown in full lines to a position 68 'shown in broken lines, in which its upper side is aligned with a mixing funnel 72 into which the line 62 also opens. The inside of the pipeline 68, on the other hand, has a washing and separating device 73, which is only indicated schematically. Therefore, if the piping 68 is in the position 68 'shown in broken lines, the grinding media 6 repelled by the vibrating sieve 63 are fed to the washing and separating device 73, in which it is cleaned of any residual coating on product separated from the screen 63 and fed to the container 26a, then sorted by size, for example by means of several screens, and appropriately also automatically returned to the container 69, as is schematically indicated by a line 74. The return can of course also be done by hand or the returned grinding media can be fed to special containers (not shown).

If the pipeline 68 is brought into the position 68 ', which can be done by a corresponding actuator 75 (rotor motor, moving coil magnet or the like), this is done on the basis of a control command from the processor system 146. At the same time, the processor 146 issues a command via at least one from a plurality of output lines 76, whereby a closure 70 of a container (if desired, two containers 69) is opened and a predetermined number of balls of a size determined by the processor 146 into the funnel 71, from there to the top of the inclined one Pipeline 68 and via this into the mixing funnel 72. If it turns out that the product fineness achieved does not meet the requirements, the entire number of grinding media can be exchanged in one cycle through the circulation line 59, the respective closure 70 being kept open for this time (a metering device may be provided at this point) until the quantity of balls determined by the processor 146 has been introduced into the circulation line 59. This amount can be different from the previous one, so that the degree of gap can be regulated both by changing the diameter of the grinding media and by changing the number of grinding media. In addition, there are still the above-mentioned possibilities of control via the piston 18a and with the aid of a speed difference of the motors 48b, 48c determined by the processor system 146. It is also possible, if necessary, to add only individual balls, and for this purpose a separate line (not shown) may be connected to the funnel 71 and connected to the mixing funnel 72, with corresponding shut-off devices or valves being controlled via the processor.

With all of these control options, one should actually manage without additional control of the speed of the motors 8 or 48, but it can be seen that the processor system 146 is also connected to these.

As can be seen from the above explanations, the processor system 146 must have a computer program for determining the fineness of the product on the basis of the measurement data supplied by the measurement arrangements 66, 67. However, if such a computational effort is already being made, a special measuring arrangement can be dispensed with at all, with corresponding space and the costs of expensive measuring devices being avoided by, to a certain extent, using the agitator mill itself as the measuring arrangement, as illustrated in FIG. 3 .

For this purpose it is necessary to know the characteristics of an agitator mill lb exactly and to create a corresponding mathematical model of the operation. Furthermore, all essential operating parameters of an agitator mill 1b controlled in this way, which is essentially similar to the agitator mill 1 of FIG. 1, are recorded, see above

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that the same reference numerals are found in FIG. 3 for most parts as in FIG. 1, possibly with the letter “b”. In addition to the stator cooling jacket 55 with the inlet 56 and the outlet 57, a rotor cooling circuit is also provided, cooling liquid, generally water, being supplied via a coolant inlet 77, passing through the interior of the rotor 7b and, via a pipe 78, a rotary inlet 79 at the upper end of the Mill LB is supplied and in turn leaves via a coolant outlet 80. It can be seen that valves 81, 82 of variable cross-section are provided in both inlets 56, 77 and can be controlled via corresponding actuators 83, 84. A position transmitter 85, which is indicated as a potentiometer, is preferably assigned to each valve 81, 82.

Further measuring arrangements can be in a pressure meter 86 for the pressure of the supplied liquid product, in a temperature meter 87 for the inlet temperature thereof, a temperature meter 88 for the outlet temperature of the product, a tachometer generator 89 for the speed of the motor 48 or the pump 11, in temperature sensors 90 for the input or output temperature of the stator cooling circuit, in temperature sensors 92 for the input or output temperature of the rotor cooling circuit, in a tachometer generator 93 for the speed of the agitator 7b, a measuring arrangement 167 for the current consumption of the motor 8 and one - for example by one Rotary potentiometer formed - transducers 94 exist for the respective position of the piston 13.

The output signals of all these sensors are fed to a two-part computing stage 95. One part of this arithmetic stage 95 may be constructed in the form of an arithmetic stage, referred to as “observer” in control technology, to which the second part is followed by an arithmetic stage, referred to as “parameter identifier” in control engineering. Such arithmetic stages are used to calculate the possibly still missing measured values from existing measured values on the basis of a stored mathematical model. If, therefore, a number of input values n are input into the computing stage 95, at least a number of n + 1 output values result at the output thereof. From Fig. 3 it can be seen that the computing stage 95 has a large number of inputs, which is associated with a corresponding wiring effort. This wiring effort can be reduced by multiplexing or by using a data bus via which the measurement signals are called up sequentially. In principle, it is possible that the computing stage 95 has a correspondingly increased number of output lines, one of these lines 96 carrying an output signal that corresponds to the calculated product fineness. This line 96 could form the input line of a comparator stage 97, to which a setpoint signal from a setpoint generator 98 is supplied at its other input. The electro-fluidic converter 19 could then be controlled via an output line 99, for example, or the control could be carried out analogously to that of FIG. 1.

However, the control is preferably carried out in accordance with the scheme shown in full lines in FIG. 3. If the two-part arithmetic stage 95 is already present, its outputs (only one is shown) can each be connected to a comparator stage 197 which receives the setpoint signal via the setpoint generator (e.g. a memory) 98. In this case, the arrangement can be such that the arithmetic stage 95 - controlled by a clock generator 100 - sequentially outputs the output signals to a single comparator stage 197, the associated values also being sequenced from the setpoint memory 48, likewise via the clock generator 100

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Setpoints can be called up. In this way one can find sufficiency with a single comparator stage 197.

The second part ("parameter identifier") of the computing stage 95 has an output line 101 to which - e.g. via a buffer 102 - a computing stage 103 for adaptive calculation of the respective setpoints to be specified is connected. It goes without saying that by changing the operating conditions after a certain start-up time, then in the course of operation by reducing the viscosity of the product or wearing down the grinding media, a certain adaptation is expedient. The output of the arithmetic stage 103 is then connected to the setpoint generator 98 in order to replace the respectively obsolete setpoints in the memory with the current ones. The calculation is influenced by a memory 104, which contains the data about desired operating processes obtained from an input device 105.

It does not matter whether the output material of the arithmetic stage 95 is fed sequentially to a single comparator stage 197 or whether a comparator stage is provided for each output value (a third possibility is that the stages 95 and 197 and possibly further of the stages shown are parts of a single processor system, for example after Type of system 146 of FIG. 2), each of the differential signals thus obtained is then weighted. This means that it is subjected to a multiplication by a factor assigned in each case. The easiest way to do this is to connect an amplifier 106 of controllable amplification to the output of the or each comparator stage 197. This amplifier 106 receives a signal corresponding to the respective factor via a control line 107, to which a memory 108 is connected for all weighting factors assigned to the respective output signals of the computing stage 95 or the comparator stage 197. If - as shown - the signals from stages 95, 197 are emitted sequentially, then memory 108 is also expediently called up sequentially via clock generator 100.

The weighting factors of the memory 108 can also change during the operation of the agitator mill 1b. Therefore, the memory 1908 is also connected to the output line 101, but this does not necessarily require a separate computing stage (see FIG. 103), as was shown for the memory 98. A cheaper alternative is to provide a table memory 109 which contains all the values - in this case all the weighting factors - and from which, based on the signal supplied via the line 101, the corresponding value is called up and fed to the memory 108, where it contains the previous ones Weighting factor for a specific output signal of the comparator stage 197 replaced. From this function it can already be seen that the memories 98, 104, 108 used are expediently implemented in the form of shift registers.

The differential signals of the comparator stage 197, weighted with the aid of the amplifier stage 106, are fed to a cumulation and control stage 110, in which all the output signals of the arithmetic stage 95, after appropriate processing by the stages 197 and 106, are accumulated and processed into a control signal. According to the exemplary embodiment shown here, there are five output lines, via which the electro-fluidic converter 19 is controlled first, the speed of one of the motors 8, 48 and the valves 81, 82 are controlled in the second line.

It should be pointed out that the control system shown in FIG. 3 with the two-part computing stage 95, the comparator stage 197, the weighting of the output signals with the aid of the amplifier stage 106 and the accumulation and control stage

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Because of the high control accuracy that can be achieved in this way, it is advantageous whether or not a signal corresponding to the fineness of the product is used. On the other hand, it goes without saying from the above explanations that the product fineness signal can be obtained in this way without a high level of metrological effort, which is precisely necessary for measuring such a difficult quantity. Furthermore, it should be pointed out that a ball exchange device, as was shown with the aid of parts 68 to 71 of FIG. 2, can also be advantageously used independently of the measurement of the fineness of the product, particularly where a circulation line 59 is provided, but possibly also with agitator mills a corresponding ball inlet and outlet.

Within the scope of the invention, of course, all of the features explained are interchangeable or

Can be combined with one another, it being possible, for example, to use flow rate meters instead of potentiometers 85 to obtain a parameter over the flow cross-section of valves 81, 82. If the coolant is brought through the lines with the aid of pumps, it is of course also possible to enter their speeds, if necessary their pressures, in the calculation stage 95. On the other hand, to simplify things, you may want to do without entering one or the other measured value. Even though automatic control with the aid of appropriate control loops or (for process control systems better control links) is shown in all of the exemplary embodiments, it goes without saying that the methods explained using the exemplary embodiments could also be carried out by hand.

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Claims (10)

667 222 1. A method for controlling an agitator mill containing a grinding media with a product inlet and a product outlet, in which at least one operating parameter is determined and at least one parameter of a controlled system is controlled as a function thereof, characterized in that the product fineness is determined as the operating parameter that the determined value for the product fineness is introduced into the control link for the controlled system, and that at least one parameter that determines the specific grinding performance is regulated as a function of the ascertained product fineness. 2. The method according to claim 1, characterized in that the degree of gap of the grinding media in the grinding vessel, preferably by changing the working volume thereof, is regulated. 2nd PATENT CLAIMS 3. The method according to claim 1 or 2, characterized in that the speed of at least one drive, e.g. the pump supplying the product and / or the agitator is regulated, and that the speed of the grinding media is preferably sequentially controlled first and only when the limits of the control range have been reached - possibly with an overlapping transition - the speed is regulated. 4. The method according to any one of claims 1 to 3, characterized in that to determine the fineness of the product coming from the grinding container is subjected to a measurement, and that a comparative measurement is optionally carried out on the product fed to the grinding container. 5. The method according to any one of claims 1 to 4, characterized in that the product fineness is determined on the basis of a mathematical model of the operating characteristics, that preferably the target-actual deviations for each determined operating parameter are first determined and then weighted by specifying one of the desired operating modes what the weighted parameter values are accumulated and a regulation is carried out on the basis of the accumulated parameter values, and in particular that at least one additional operating parameter is fed to an adaptive control link for changing at least one target value. 6. Control device for carrying out the method according to one of claims 1 to 5 on an agitator mill, with an agitator which can be driven by a motor and which holds in a, freely movable grinding media receiving grinding container with a product inlet and a product outlet for a material which can be supplied by means of a pump, the material to be ground containing fluid is arranged, at least one control link of a device for determining an operating parameter with an actuator for the purpose of optimizing the operating conditions being provided, characterized in that a) a device (26, 126; 26a, 126a; 95) is provided for determining the product fineness that b) whose output signal can be introduced into the control linkage (46; 146; 110), and that c) at least one device (8, 13, 48; 83, 84) determining the specific grinding capacity is provided as the controlled system. 7. The device according to claim 6, characterized in that - seen in the transport direction of the product - a branch line (27), preferably a shunt line, is provided in an area provided after the product inlet (3), on which a measuring arrangement (32 - 43) is arranged for the product fineness. 8. The device according to claim 6 or 7, characterized in that the device determining the grinding performance of a device changing the grinding media density (13, 17, 18; IIb, 11c, 17a, 18; 68-71), in particular with a piston-cylinder - Unit (13,17,18; 17a, 18a) for changing the grinding chamber volume is formed. 9. Device according to one of claims 6 to 8, characterized in that the device determining the grinding performance of at least one speed control device (47, 50; 146; 110), for. B. for the pump (11; 1 la) and / or the agitator (7; 7a; 7b), and that a sequence link is preferably provided, whereby the control signal only the device changing the grinding media density (13,17,18 ; IIb, 11c, 17a, 18a; 68-71) can be fed and when the limits of their control range are reached, possibly with an overlapping transition, this control signal can be fed to the speed control device (47, 50; 146; 110). 10. The device according to one of claims 6 to 9, characterized in that the outputs of a plurality of sensors (85-94) monitoring the operating parameters of the agitator mill are connected to a computing stage (95) for calculating the fineness of the product and possibly further operating parameters, that preferably the The output signal of this arithmetic stage (95) can be fed to a comparator stage (97, 197), which receives a further input signal from a setpoint generator stage (98), whereupon the output signal of the comparator stage (197) can be fed to an amplifier stage (106) with adjustable gain, the gain for each Parameters compared in the comparator stage (197) separately with the aid of an adjusting device (108) - which can be adjusted in particular to the computing stage (95) for selecting the respective gain factor - which amplified signals can be fed to an ICumulation and control stage (110) to generate an actuating signal , and that expediently to the computing level ( 95) an adaptive control circuit (101-105) is connected, the output of which is connected to the setpoint generator stage (98) for adapting the setpoint values supplied to the comparator stage (197).