Method for producing individual dosages by means of roller dispenser

Abstract

The invention relates to a method for producing individual dispensed quantities of a powdered product by means of a roller dispenser. The roller dispenser comprises a dispensing roller provided with at least one dispensing opening on the circumferential side, and a capacitive measuring device for determining the mass of the dispensing amount. The discharge process is carried out in the discharge position, the dosing opening is loaded with a discharge overpressure and thereby the dosing amount is discharged from the dosing opening, and an associated discharge reference time point is determined. The individual mass of the dispensed quantity of the discharge and the associated measurement reference time point are determined by means of a capacitive measuring device. An actual time span is determined from the difference between the measurement reference time point and the emission reference time point and is compared with at least one theoretical time span. According to a comparison between the actual time span and at least one target time span, the emission overpressure is adapted for a subsequent emission process in such a way that the level of the emission overpressure is increased if the actual time span is too large.

Description

Technical Field

[0001] The invention relates to a method for producing individual doses of a powdered product by means of a roller dispenser. Background Art

[0002] For example, in the pharmaceutical sector, but also in the sector of nutritional supplements, etc., powders are processed which have to be provided in precisely measured portions or doses for the intended delivery form. Target containers, for example in the form of blisters, insert capsules, etc., are filled with such measured doses of the powdered product so that the user can dispose of and take the corresponding unit dose.

[0003] In particular, such powdered products are transferred in individually measured doses to so-called roller dispensers, which are then filled into respectively associated target containers. Such roller dispensers comprise a dispensing roller, which is provided with at least one, usually a plurality of, dispensing openings on the circumference, wherein the dispensing openings are delimited on the inside by means of filter elements and can be acted upon by negative pressure through the filter elements. Under the effect of the negative pressure, the powder is sucked into the dispensing openings, wherein a dose of powder is formed, the volume of which corresponds to the volume of the respective dispensing opening. The dose thus formed is then discharged from the dispensing openings by means of excess pressure and conveyed to the target container.

[0004] It is clear from the above that dispensing by means of a roller dispenser is a volumetric dispensing. However, in general, the aim is to achieve a dispensing in which the measured dispensed quantity has a certain mass within an allowed tolerance range. It is therefore important for volumetric dispensing that there is a relationship between the measured volume and the mass actually obtained that is as reproducible as possible.

[0005] In order to check the actually achieved dosing accuracy, so-called "Advanced Quality Verification" (AMV) systems are increasingly being used, in which capacitive measuring devices are used. The dosing quantity discharged from the dosing opening falls through the capacitive measuring section of the AMV system and generates a capacitive measuring signal there. In the case of correct calibration, this measuring signal provides information about the quality of the dosing quantity and allows random or even 100% control of the dosing process.

[0006] A method is known from EP 3 608 232 A1 in which a continuous quality determination is carried out with the aid of such an AMV system. A trend control of the suction vacuum is carried out by averaging in order to achieve the most uniform possible filling of the dispensing opening.

[0007] However, such a method is not without difficulties. For example, it has been shown that the discharge of the dose does not always take place in the same form. During discharge, the dose in the form of a powder plug does not always come loose in the same shape, which can lead to different falling speeds and also to oscillating movements during the fall. This can therefore lead to a distortion of the measurement results of the AMV system as a whole or even to a disruption of the dosing process. Summary of the invention

[0008] It is therefore an object of the present invention to specify a method by means of which the individual masses produced by a roller dispenser can be discharged and checked in a controlled manner in a simple manner.

[0009] The object is achieved by a method for producing individual doses of a powdered product by means of a roller dispenser, wherein the roller dispenser comprises a product supply, a dispensing roller and a capacitive measuring device for determining the mass of the dosed amount, wherein the dispensing roller is provided with at least one dispensing opening on the circumference, wherein the dispensing opening is delimited on the inside by means of a filter element and can be acted upon with negative pressure through the filter element, and wherein the method comprises the following steps:

[0010] - rotating the dispensing roller to such an extent that at least one dispensing opening is in the filling position;

[0011] in the filling position a filling process takes place in which the dispensing opening is filled with a partial amount of powdered product from the product reservoir, wherein the dispensing opening is acted upon by negative pressure through the filter element and wherein a dispensed amount of powdered product is formed in the dispensing opening;

[0012] - turning the metering roller to such an extent that the metering opening filled with the metering quantity is in the discharge position;

[0013] a discharge process takes place in the discharge position, wherein the metering opening is charged with a discharge overpressure through the filter element and the metering quantity is thereby discharged from the metering opening, and wherein an associated discharge reference time is determined;

[0014] - determining the individual masses of the discharged dosing quantities and the associated measurement-reference points in time by means of a capacitive measuring device;

[0015] - determining the actual time span from the difference between the measurement reference time point and the emission reference time point and comparing it with at least one theoretical time span;

[0016] Based on the comparison of the actual time span with at least one setpoint time span, the discharge overpressure is adapted for the subsequent discharge process in such a way that the level of the discharge overpressure is increased if the actual time span is too long.

[0017] In other words, the comparison of the actual time span with at least one theoretical time span is used to monitor process limits and as a fault response. If the filter element slowly clogs over time, the blowing effect of the fixedly adjusted discharge-overpressure decreases. It becomes difficult for the powder amount to escape from the dosing opening, which leads to an uneven falling movement when the falling speed decreases. In contrast, the tracking of the discharge-overpressure according to the invention is achieved so that the dosing behavior and the falling speed of the discharged dosing amount are kept as constant as possible. By the method according to the invention, a largely constant movement speed of the dosing amount in the measurement field of the capacitive measuring device or the relevant AMV sensor can be achieved, which therefore improves the accuracy during the quality determination. In addition, the comparative measurement according to the invention realizes expanded process monitoring and early reaction to changes present in the process. In addition, a single comparison value can be used as a criterion for process stability by evaluating statistical evaluations such as variance, swing amplitude, etc. Another aspect is that the transferability of process parameters between different roller dosing systems (i.e., for example, from a laboratory machine to a production machine) is simplified.

[0018] When the metered quantity passes through the measuring section of the AMV sensor, a measurement signal with a time profile is generated. From this, a suitable time point (e.g., a start time point or an end time point) can be selected as a measurement-reference time point. Preferably, the peak value or maximum value of the measurement signal and the associated maximum time point are determined from the time profile of the measurement signal, wherein the measurement-reference time point is then set equal to the maximum time point. The maximum time point can be determined accurately with high reproducibility, which is beneficial to the measurement accuracy.

[0019] It may be sufficient to determine a specific time point at which the measurement reference time point should be as the theoretical time point, wherein deviations therefrom then lead to the previously described tracking of the discharge overpressure. However, in a preferred refinement, a tolerance is determined, wherein the pressure tracking is performed only when this tolerance is exceeded. Thus, the upper limit time span and thus the first theoretical time span are formed from the upper tolerance value. If the actual time span then exceeds the upper limit time span, the discharge overpressure is increased. The determination of the tolerance threshold avoids unnecessary interventions in the pressure regulation due to small and production-common pressure fluctuations.

[0020] Previously, it was mainly concerned with an increase in the discharge overpressure due to the actual time span becoming too large. In practice, this is a foreseeable situation when the filter element slowly clogs and the pressure effect is thus reduced. It is therefore possible to dispense with the pressure adaptation in the opposite direction. However, it can be advantageous within the scope of the present invention to apply the method previously described for the pressure increase in a similar manner to the pressure reduction, wherein the discharge overpressure is adapted for the subsequent discharge process based on a comparison of the actual time span with at least one theoretical time span in such a way that the level of the discharge overpressure is reduced in the event that the actual time span is too short. In particular, here, therefore, a second theoretical time span is formed from the lower limit time span. If the actual time span is then below the lower limit time span, a reduction in the discharge overpressure is then carried out.

[0021] In a first advantageous variant, it may be expedient to perform the pressure adaptation incrementally with fixed preset pressure steps. For this purpose, little control effort is required, which helps to simplify the process control. In another alternative variant, the pressure adaptation is performed in a functional manner and in particular proportionally to the deviation between the actual time span and the setpoint time span. With such a functional, in particular proportional, adaptation, very accurate readjustment can be achieved.

[0022] The pressure adaptation can be carried out based on random individual measured values. In an advantageous development, the actual time span is formed from a mean value of a plurality of detected differences between a measurement reference time and a discharge reference time, wherein the mean value is then compared with at least one theoretical time span. The mean value formation compensates for point-like or short-term fluctuations in the measurement results that are not critical for process stability, so that long-term changes that are important, in particular, for process control are taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] An embodiment of the present invention is described in more detail below with reference to the accompanying drawings.

[0024] Figure 1 A schematic cross-sectional view shows a roller dispenser with a product supply, with a dispensing roller and with a capacitive measuring device for determining the quality of individual dispensed quantities when carrying out the method according to the invention.

[0025] Figure 2 The schematic phase diagram shows the punch-through according to Figure 1 The individual dosing quantities at different points in time during the measuring period of the capacitive measuring device, and

[0026] Figure 3 The diagram shows the Figure 1 The signal variation curve of the capacitive measuring device has a Figure 2 different points in time and with a time span between the different points in time for carrying out the method according to the invention. DETAILED DESCRIPTION

[0027] Figure 1 A schematic cross-sectional view shows a roller dispenser 3 for producing individual doses 2 of a powdered product 1 and for conveying such individual doses 2 into a target container 21. Here, the powdered product is a pharmaceutical powder. However, it can also be a nutritional supplement or the like. Here, the target container 21 is a schematically indicated blister, which is also sealed with a covering film after filling. However, insertable capsules or other containers are also considered as target containers 21.

[0028] The roller dispenser 3 comprises a product supply 4, a dispensing roller 5 and a capacitive measuring device 6. The capacitive measuring device 6 is also referred to as an "advanced quality verification system" or AMV system. The powdered product 1 is prepared for measurement in the funnel-shaped product supply 4. A partial amount of the powdered product 1 is removed from the product supply 4 by means of the dispensing roller 5 and a precisely defined volumetric dispensed quantity 2 is thereby formed. The subsequent quality determination of individual, in particular all, dispensed quantities 2 is carried out by means of the capacitive measuring device 6.

[0029] The dispensing roller 5 extends along a longitudinal axis and is substantially cylindrically constructed with respect to the longitudinal axis. On the circumferential side, the dispensing roller has at least one dispensing opening 7. In the preferred embodiment shown, the dispensing roller 5 is provided with a plurality of dispensing openings 7. Although it cannot be seen in the cross-sectional view shown here, three to twelve dispensing openings 7 each form an opening row extending parallel to the axis of rotation 19. Four such opening rows are positioned relative to each other at the same angular interval (i.e., at 90°) around the axis of rotation 19 in the circumferential direction. Here, one (i.e., a total of four) dispensing openings 7 can be seen from the mentioned row openings. However, different numbers of dispensing openings 7 in the axial direction and / or in the circumferential direction may also be suitable.

[0030] The metering roller 5 has a central tensioning core 10 and a roller shell 9 which surrounds the tensioning core 10 at radial intervals. The metering openings 7 are designed as holes with a circular profile that pass through the active roller shell 9 in the radial direction. However, other profile shapes may also be suitable. For example, the shape of the profile may be only partially circular, oval, polygonal, rectangular or square. Radially outward (i.e., on the outer side 22 of the roller shell 9), the metering openings 7 are open. Radially inward (i.e., on the inner side 23 of the roller shell 9), the metering openings 7 are limited by means of a filter element 8, which corresponds in size and shape to the cross section of the respective metering opening 7 and forms its bottom.

[0031] Corresponding to the number of opening rows mentioned above, the tensioning core 10 has a number of receiving grooves extending axially parallel to the rotation axis 19, in which each filter rod 11 is held. An optional seal 13 is arranged between the filter rod 11 and the inner side 23 of the roller shell 9.

[0032] A branched pressure channel 14 is constructed in the filter rod 11, which passes through the filter element 8 and opens into the corresponding dispensing opening 7. The pressure channel 14 includes a main channel 28 and at least one branch 29. In the embodiment, the pressure channel 14 includes twelve branches 29, which correspond to the corresponding number of dispensing openings 7 in the rows parallel to the axes of the dispensing openings. The main channel 28 extends along the longitudinal axis 25 of the pressure channel 14. The longitudinal axis 25 extends parallel to the rotation axis 19 of the dispensing roller 5. The branch 29 of the pressure channel 14 extends radially from the main channel 28 to the dispensing opening 7 with respect to the rotation axis 19.

[0033] The filter element 8 is formed by a web of suitable filter material, which is wound around a tensioning core 10 with filter strips 11. Bonded filter elements 8 can also be used. The filter strips 11 are tensioned radially outwards against the inside of the roller shell 9 via a tensioning cone (not shown) with the filter material in between. The seal 13 here presses the filter material against the inside of the roller material on the one hand, while the seal seals the relevant branch 29 of the pressure channel 14 and also the relevant metering opening 7 around the relevant filter element 8 from the environment on the other hand. This ensures that the pressure balance between the metering opening and the pressure channel 14 is only achieved through the relevant filter element 8, and the metering opening can therefore be loaded with a specific desired pressure via the associated pressure channel 11 through the relevant filter element 8.

[0034] The dispensing roller 5 is supported rotatably around the rotation axis 19 in the direction of the arrow 20 and is provided with an associated rotary drive device, which is not shown here. During operation, the dispensing roller is rotated in a clocked manner, wherein the individual dispensing openings 7 are cyclically located in the upper filling position I in the direction of gravity and the lower discharge position III in the direction of gravity in at least two clocks. Instead of clocked movement, continuous rotation may also be suitable. In the illustrated embodiment, the individual dispensing openings 7 cyclically pass through four different positions in four clocks, starting with the upper filling position I, followed by the first intermediate position II. Then the lower discharge position III and the second intermediate position IV are followed, and then the cycle begins again at the upper filling position I. In the upper filling position I, the corresponding dispensing openings 7 are filled with the powdered product 1 from the product storage device 4 while forming the dispensing quantity 2. In the subsequent first intermediate position II, the filling state control can be optionally performed. In the lower discharge position III, the dispensing quantity 2 is discharged from the dispensing opening 7 and supplied to the target container 21. The now empty dispensing opening 7 moves further into the second intermediate position IV and can optionally be cleaned there, for example by blowing air.

[0035] If necessary, the dispensing opening 7 can be loaded with negative pressure on the inside and through the corresponding filter element 8. For this purpose, at least in the filling position 41, a connection for transmitting negative pressure is established between the pressure channel 14 and the negative pressure source 15. The level of the negative pressure provided by the negative pressure source 15 is adjusted by means of a schematically represented controller 18, which can be achieved by a suitable control device, if necessary, but also by a regulating device. In any case, when the dispensing opening 7 is in the upper filling position 41, the negative pressure adjusted in this way is transmitted to the dispensing opening 7 through the pressure channel 14 and the filter element 8. The negative pressure sucks the powdered product 1 from the product storage device 4 into the dispensing opening 7. The filter element 8 is designed and coordinated with the product 1 in terms of its permeability so that although it is air-permeable and therefore can also transmit pressure, the powdered product 1 is trapped and blocked from passing through. Therefore, a dispensing amount 2 of the powdered product 1 is generated, which completely fills the dispensing opening 7 and its volume corresponds to the volume of the dispensing opening 7. The filling process can also be optionally supported by a stirrer (not shown) in the product reservoir 4. Depending on the level of negative pressure present and the properties of the product 1, a certain degree of compaction of the product 1 in the dispensing opening 7 occurs anyway, so that a certain mass of the dispensing quantity 2 is also produced from the preset volume of the dispensing opening 7.

[0036] The negative pressure applied can still be maintained at the same or reduced level until the discharge position III is reached in order to prevent the dosing amount 2 from falling prematurely from the dosing opening 7. However, the negative pressure loading is terminated at the latest when the lower discharge position III is reached. Instead, the dosing opening 7 is now loaded with overpressure (i.e., with discharge-overpressure p) through the filter element 8 in the discharge position 43. For this purpose, a connection for transmitting overpressure is established between the pressure channel 14 and the overpressure source 16. The level of the overpressure provided by the overpressure source 16 can be adjusted by means of a schematically represented controller 18 as in the case of the above-mentioned negative pressure source. When the dosing opening 7 is in the lower discharge position III, the overpressure thus adjusted is transmitted to the dosing opening 7 through the pressure channel 14 and the filter element 8. The overpressure blows the dosing amount 2 out of the dosing opening 7 as a discharge-overpressure p. In addition, the overpressure can also be used in the subsequent second intermediate position IV for the cleaning process of the emptied dosing opening 7 there.

[0037] Part of the capacitive measuring device 6 for determining the mass of a single dosing amount 2 mentioned above is a capacitive sensor 17, which is also connected to a controller 18. The measurement data of the capacitive sensor 17 are detected and evaluated in the controller 18, which generally leads to the formation of the measuring device 6. However, instead of the capacitive measuring device 6, other suitable measuring devices for determining the individual mass of the dosing amount 2 can also be used. In any case, the dosing amount discharged from the dosing opening 7 in the lower discharge position III, which is marked with 2' here, passes through the sensor, here through the capacitive sensor 17 and falls into the target container 21. From the field change performed in the capacitive sensor 17 here, the mass of the dosing amount 2 that is being passed through is determined according to the AMV system (advanced quality verification system). It is not mandatory for the implementation of the method according to the invention to determine the mass of each single thrown dosing amount 2. Instead, it is sufficient to repeat the single mass determination only after several dosing cycles. However, preferably, the mass determination is performed in 100% of the measured dosing amount 2.

[0038] Figure 2 A schematic phase diagram shows a single metered quantity 2 as it approaches and passes through the measuring path of the capacitive sensor 17. According to the method according to the invention, the time profile of the measurement signal S is recorded as the metered quantity 2 passes through by means of the capacitive measuring device 6 and the capacitive sensor 17 as part of it, which profile is shown in the form of a schematic diagram. Figure 3 In. According to Figure 3 The emission is plotted in the graph at time t a , at this emission-time point in time Figure 1In the discharge position III, the metering quantity 2 is discharged. In the present case, this is the time at which the control unit 18 issues a signal for switching the discharge overpressure p to the metering opening 7 in the discharge position III. Alternatively, it may also be expedient to determine the actual overpressure buildup or the actual time of the discharge via a suitable sensor and to set this as the discharge time t a .

[0039] In addition, from Figure 2 and Figure 3 From the overview of FIG. 1 , it can be seen that the metered quantity 2 is directly in the upper input of the capacitive sensor 17 at the first time t1 and has not yet generated a measurement signal S. The magnitude of the measurement signal S is still approximately zero at the time t1. Subsequently, the metered quantity 2 is in the input section of the measuring section of the capacitive sensor 17 at the second time t2, wherein the profile of the measurement signal S is rising, and is in the output section of the measuring section of the capacitive sensor 17 at the fourth time t4, wherein the profile of the measurement signal S is falling.

[0040] Approximately in the middle, the amount referred to here as the metered amount 2 ′ produces the peak value or maximum value S of the measurement signal S. p , according to its Figure 3 The graph of the relevant maximum value is determined at time t p As the third time point. Now, the emission-time point t is formed a and the maximum time point t p and defines it as the actual time span Δt for the duration until the maximum value Sp is reached.

[0041] According to the method according to the invention, the actual time span Δt is compared with at least one theoretical time span. Such a theoretical time span can be a single fixed predetermined target time span. Figure 3 , use tolerance ranges instead of discrete values. To do this, the emission-time t a The highest limit time point t o The upper limit time span Δt o is defined as the first theoretical time span. In addition, a Until the lower limit time point t u The lower limit time span Δt u Defined as the second theoretical time span.

[0042] Upper limit time span Δt o and the lower limit time span Δt u The tolerance range for the actual time span Δt is limited. If the actual time span Δt is within the tolerance range, that is, if the maximum value time point tp According to Figure 3 The diagram is at the upper limit time point t o and the lower limit time point t u Between, the above combination Figure 1 The described dispensing process remains unaffected.

[0043] However, if the time span comparison mentioned above results in an actual time span Δt exceeding the upper limit time span Δt o , that is, the maximum value time point t p At the upper limit time point t o If the discharge pressure p is too low, the discharge pressure p is increased. If the discharge pressure p is too high, the discharge pressure p is increased. If the discharge pressure p is too high, the discharge pressure p is increased. If the discharge pressure p is increased, the discharge pressure p is increased until the actual time span Δt is within the tolerance range described above.

[0044] In a similar manner, the discharge overpressure p is also adapted in the opposite direction: If the time span comparison results in an actual time span Δt that is lower than the lower limit time span Δt u , that is, the maximum value time point t p At the lower limit time point t u If the discharge pressure p is too high, the discharge excess pressure p is reduced. This means that the discharge excess pressure p is too high. If the discharge excess pressure p is too high, the discharge excess pressure p is reduced. This reduction in discharge excess pressure p occurs until the actual time span Δt is within the tolerance range described above.

[0045] As a result, the invention therefore involves keeping the measured actual time span Δt as constant as possible, but at least within a predefined tolerance range. If the discharge excess pressure p needs to be adapted for this purpose, this adaptation (increase or decrease) can be carried out incrementally with fixed predefined pressure steps. Alternatively, the method according to the invention provides for an adaptation that is proportional to the deviation of the actual time span Δt from the setpoint time value.

[0046] The adaptation can be performed based on a random single-time measurement. In the previously described embodiment, the actual-time span Δt is composed of the measurement-reference time point and the emission-reference time point t a An average value of a plurality of detected differences between the two is formed, wherein the average value is then compared with at least one theoretical time span.

[0047] The comparison result can be displayed to the operator so that he can manually adapt the exhaust excess pressure p. In the present case, the exhaust excess pressure p is automatically adapted by means of a control unit 18 into which the measurement data of the capacitive measuring device 6 are fed, thus forming an automatic control loop.

Claims

1. A method for producing individual doses (2) of a powdered product (1) by means of a roller dispenser (3), wherein: The roller dispenser (3) comprises a product supply (4), a dispensing roller (5) and a capacitive measuring device (6) for determining the mass of the dispensed quantity (2), wherein the dispensing roller (5) is provided with at least one dispensing opening (7) on the circumferential side, wherein the dispensing opening (7) is delimited on the inside by means of a filter element (8) and can be acted upon with negative pressure through the filter element (8), and wherein the method comprises the following steps: - rotating the dispensing roller (5) to such an extent that at least one dispensing opening (7) is in the filling position (I); - a filling process is carried out in the filling position (I), in which the dispensing opening (7) is filled with a partial amount of the powdered product (1) from the product reservoir (4), wherein the dispensing opening (7) is acted upon by negative pressure through the filter element (8), and wherein a dispensed amount (2) of the powdered product (1) is formed in the dispensing opening (7); - rotating the metering roller (5) to such an extent that the metering opening (7) filled with the metering quantity (2) is in the discharge position (III); - in the discharge position (III), a discharge process takes place, wherein the metering opening (7) is acted upon by a discharge excess pressure (p) through the filter element (8), and thereby the metering quantity (2) is discharged from the metering opening (7), and wherein an associated discharge reference time (t a ); - determining the individual masses of the discharged dosing quantities (2) and the associated measurement-reference time points by means of the capacitive measuring device (6); - from the measurement-reference time point and the emission-reference time point (t a ), determining an actual time span (Δt) from the difference between the actual time span and the theoretical time span; - Based on the comparison of the actual time span (Δt) with the at least one theoretical time span, the discharge overpressure (p) is adapted for the subsequent discharge process in such a way that in the actual - In the event of a time span (Δt) that is too long, the level of the discharge overpressure (p) is increased.

2. The method according to claim 1, It is characterized in that The capacitive measuring device (6) records the time profile of the measurement signal (S) when the metering quantity (2) flows through, and determines the maximum value (S) of the measurement signal from the time profile of the measurement signal (S). p ) and the time point of the maximum value (t p ), and the measurement-reference time point is set equal to the maximum value time point (t p ).

3. The method according to claim 1, It is characterized in that The first theoretical time span is given by the upper limit time span (Δt o ) is formed, and if the actual-time span (Δt) exceeds the upper limit time span (Δt o ), then the discharge overpressure (p) is increased.

4. The method according to claim 1, It is characterized in that Depending on the comparison of the actual time span (Δt) with the at least one setpoint time span, the discharge excess pressure (p) is adapted for a subsequent discharge process in such a way that the level of the discharge excess pressure (p) is reduced if the actual time span (Δt) is too short.

5. The method according to claim 4, It is characterized in that The second theoretical time span is given by the lower limit time span (Δt u ) is formed, and if the actual-time span (Δt) is lower than the lower limit time span (Δt u ), then the discharge-overpressure (p) is reduced.

6. The method according to claim 1, It is characterized in that The discharge overpressure (p) is adapted incrementally in fixed predefined pressure steps.

7. The method according to claim 1, It is characterized in that The discharge excess pressure (p) is adapted in proportion to the deviation of the actual time span (Δt) from the setpoint time span.

8. The method according to claim 1, It is characterized in that The actual time span (Δt) is formed from a mean value of a plurality of detected differences between a measurement reference time point and an emission reference time point (ta), and the mean value is compared with the at least one theoretical time span.

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