EP1445093A1 - Method and device for controlling a rotary tabletting press - Google Patents

Abstract

Method for controlling a carousel-type tablet producing machine (10), whereby a rotor (12) is set in rotation by a drive motor (24). The rotor has at least a matrix (14), an upper stamp (18) and a lower stamp (16). A press mass that is inserted in the matrix is acted upon by a pressing force. The pressing force is measured and compared with a preset limit value and if the force applied is less than a limit value, the rotation speed of the rotor is reduced to a value below the nominal value. An independent claim is made for a device for controlling a carousel-type tablet producing machine.

Description

The invention relates to a method and a device to control a rotary tablet machine, being a rotor by a prime mover is rotatable, the rotor at least one Die with assigned upper stamps and lower stamps includes and one in the at least one Pressing force filled into the die is determined.

Rotary tableting machines of the generic type Kind are known. It is typical that the rotor by starting the drive machine from standstill is brought up to its nominal speed. About at least the dies with the molding compound become a filling shoe filled and depending on the angular position of the rotor are sub-stamps and Upper punch axially displaced to the matrices. The The lower and upper stamps are on at least one Press station, usually at a pre-press station and a main press station. There will be the upper and lower stamps on stationary Pressure rollers passed essentially tangentially, so that on the inserted in the matrices Press mass a pressing force can be applied.

It is known, for example from EP 0 698 481 B1, adjust and measure the pressing force. in this connection there is an essential connection between measured maximum pressing force and the mass of the in Matrices filled molding compound under the condition same material properties of the molding compound. There is a direct connection between the tablet weight and that for the production of the Tablets necessary pressing force. Depending on The material to be pressed is included with every tablet weight a tablet shape predetermined by the pressing tools and a set tablet height of one assigned specific pressing force. Varies at constant Tablet height, the filling quantity and thus that Tablet weight, results in more direct Dependency a change in pressing force.

Are all in a rotary tablet machine Matrices up to the press station (i.e. up to the Pressure roller) are normally filled with molding compound Pressure rollers and rotor when starting up accelerated to the nominal speed at the same time. This is due to the fact that every stamp by the rotary movement of the rotor under the pressure roller over - touching this - is pulled through and the rotation of the stamp Acceleration of the pressure roller takes place, so that the Acceleration of the pressure roller depends directly on the Rotation speed is the stamp.

This relationship between acceleration of the Rotors and acceleration of the pressure rollers is then disadvantageous if the rotation of the rotor on the Press station (pressure rollers) not arriving matrices or are only partially filled with molding compound. This can for example at the start of the rotary tablet machine after cleaning or when interrupted Replenish over the or the filling shoes with Molding compound should be the case.

Will not be a rotary tablet machine with or only partially filled matrices started, touch the upper or lower stamp in the pressure stations do not or only the pressure rollers partially. By starting the prime mover the rotor with the stamp, however, at its nominal speed accelerated. Now gets a first stamp with the first properly filled die in the Press station, the stamp hits that Pair of stamps corresponding to the one already at nominal speed accelerated rotor to the not yet or only insufficiently accelerated pressure roller. Here comes there is a sudden impact of the stamp the pressure roller, so suddenly a high kinetic Energy from the pressure roller and the affected Stamps must be absorbed. This can cause harm of the pressure rollers and / or the stamp.

The invention is therefore based on the object Method and device of the generic type Way of creating, by means of which such damage is avoided can be.

According to the invention, this object is achieved by a method solved with the features mentioned in claim 1. Because the determined pressing force with a predeterminable limit value is compared and if it falls below the setpoint speed of the rotor reduced to a speed below the nominal speed accelerating is advantageously possible of the rotor and accelerating the pressure rollers towards their nominal speeds in every operating situation synchronize. In particular, this avoids that the rotor in front of the pressure rollers on its Rated speed is accelerated. Thus a abrupt impact of the stamp on the pressure rollers and thus those existing in the prior art Possible damage to pressure rollers and / or stamp avoided.

In a preferred embodiment of the invention, that the rotor speed from its standstill or speed-controlled from its nominal speed becomes. This will avoid the aforementioned Damage in every operating situation of the rotary tablet machine possible.

According to the invention, the object is further achieved by a Device for controlling a rotary tablet machine with the features mentioned in claim 8 solved. Because the rotary tablet machine a control device or the like for control a drive machine of a rotor of the rotary tablet machine, a facility for Determination of a pressing force and means for comparison the determined pressing force with a specifiable Pressing force and at least one means for specifying a target speed of the rotor depending on the Comparison of the determined pressing force with the specifiable one Pressing force is advantageously possible in a simple way a control function in the rotary tablet machine to implement that in Dependency of a degree of filling on matrices of the rotor controls a target speed of the rotor. This will in particular one adapted to the degree of filling of the matrices Starting up of the rotor possible, so that in particular mechanical loads / damage from Pressure rollers and / or press punches can be avoided can.

Further preferred configurations of the invention result from the rest, in the subclaims mentioned features.

Figur 1

eine teilweise schematische Darstellung einer Rundläufer-Tablettiermaschine;

Figur 2

ein Blockschaltbild einer Vorrichtung zur Steuerung der Rundläufer-Tablettiermaschine und

Figur 3

einen Steuerungsablauf.

The invention is explained in more detail in an exemplary embodiment with reference to the accompanying drawings. Show it:

Figure 1

a partially schematic representation of a rotary tablet machine;

Figure 2

a block diagram of a device for controlling the rotary tablet machine and

Figure 3

a control flow.

Rotary tableting machines of the ones mentioned here Are well known, so under the present description on the basic structure and basic functions are not discussed in detail becomes.

Figure 1 shows a schematic partial view the handling of a rotor 12 with a total of 10 designated rotary tablet machine. The rotor 12 has a plurality of spaced apart around its circumference Matrices 14. Each die 14 is a lower stamp 16 and an upper stamp 18 assigned to the via the indicated guide curves 20 or 22 are performed. Rotor 12 and lower punch 16 and upper punch 18 rotate synchronously around the Rotation axis of the rotor 12. The rotor 12 is by a only indicated electric drive machine 24 here rotatable.

In the dies 14 is a filling device, a so-called filler shoe, only indicated here Pressed mass 26 filled. In normal operation the rotary tablet machine 10 becomes the molding compound 26 filled over the entire height of the die 14. The fill level can, for example, by the Height of the lower stamp 16 on a not shown Stripping station can be defined. In the shown An example is an abnormal filling. The molding compound 26 is only part of the height filled into the matrices 14. It is also conceivable that into the matrices 14 - not for the one assumed here normal case - no molding compound 26 filled is. These conditions can occur, for example, when restarting the rotary tablet machine 10 after cleaning, maintenance or the like or after Interruption of the replenishment of the molding compound 26 via enter the filling device.

According to the course of the guide curves 20 and 22, the lower punches 16 and the upper punches 18 dip into the die 14 and compress the molding compound 26 to the desired tablet or the like. For this purpose, the lower punches 16 and the upper punches 18 are guided past at least one pressing station 28, which comprises stationary pressure rollers 30. The pressure rollers 30 are each rotatably supported about an axis of rotation 32. The distance between the pressure rollers 30 is defined and ultimately determines the height of the tablet to be pressed. The pressure rollers 30 are driven in the direction of the arrow 34 - the upper pressure roller 30 counterclockwise, the lower pressure roller 30 clockwise - by passing the lower punches 16 or upper punches 18 in accordance with the direction of movement 36 of the rotor 12. The lower punches 16 or upper punches 18 come in here System contact with the peripheral surface 38 of the pressure rollers 30 and thus set them in rotation, so to speak, by driving. The rotor 12 rotates at a speed n _R , while the pressure rollers 30 rotate at a speed n _D.

As a result of the matrices 14 which are not or only partially filled, the molding compound 26 to be pressed opposes the punches 16 and 18 in the pressing station 28 or in the region immediately preceding the pressing station 28 only with an insufficient counterforce. This leads to the fact that the punches 16 and 18 are accelerated to the nominal speed of the rotor 12 by rotation of the rotor 12, but due to insufficient contact with the pressure rollers 30 these are not accelerated to their nominal speed. If, in this non-normal operating state, a first pair of punches - the punches 16 and 18 - strikes the pressure rollers 30 with a normally filled die 14, there is a significant difference between the instantaneous speeds of the rotor 12 or the pressure rollers 30. During the rotor 12 already n _RNom is accelerated to its rated speed, have the pressure rollers 30, only one well below its rated speed n _dnom lying actual speed n _DIST. As a result, the punches 16, 18 strike the peripheral surfaces 38 of the pressure rollers 30 with great acceleration, so that considerable kinetic energy must be absorbed as a result. This can lead to mechanical damage to both the surfaces 38 of the pressure rollers 30 and the punches 16 and 18, respectively.

To prevent this mechanical stress Provided the following:

The pressure rollers 30 are in a manner known per se provided with sensors 40, by means of which the current pressing force PK is measured. Based on schematic representation in Figure 2, the invention further clarified.

Figure 2 shows that by the electric drive machine 24 drivable rotor 12 and the rotor 12 assigned pressure rollers 30. On the illustration the stamp was made for reasons of clarity waived. The rotary tablet machine 10 is a control unit 42 is assigned that a variety of Control functions can take over. Then only the essential for the invention Structure and function of control unit 42 described.

The control device 42 is connected to the pressing force transducers 40 via a signal line 44 and receives a signal proportional to the _actual pressing force PK _IST pk _IS . The control unit 42 is also connected to the electric drive machine 24 via a signal line 46, via which the electric drive machine 24 receives a control signal n _R receives that corresponds to the target speed of the rotor 12 to be set.

The control unit 42 includes a computing unit 48 which receives the signal pk _IS and a signal provided by a storage means 50 pk _{SHOULD be} supplied such that the desired pressing force PK _SOLL corresponds to the pressure rollers 30.

According to the scheme shown in Figure 3 the following signal processing takes place.

In a step 52, the actual signals delivered by the press force transducers 40 pk _ACTUAL and the desired signal supplied by the storage means 50 pk _SHOULD processed. Here there is a difference between the signal pk _SHOULD and the signal pk _IS determined. This difference signal pk _diff is signaled in a further step 54 pk _border linked. The signal pk _limit is also provided by the storage means 50, for example. The extent to which the signal can be determined can be variably determined, for example pk _limit corresponding pressing force PK _{GRENZ can deviate} from the target pressing force PK _SOLL . This difference between the pressing force limit value and the pressing force target value can be, for example, 10% of the pressing force target value.

If it is now determined in step 54 that the difference between the actual pressing force value and the desired pressing force value is greater than the difference between the desired pressing force value and the pressing force limit value, that is to say that the actual pressing force value falls below the pressing force limit value a signal n _rsoll generated, which corresponds to a target speed n _{R of} the rotor 12. This target speed is less than the nominal speed of the rotor 12 in normal operation. In step 56, the signal corresponding to the target speed n _rsoll with a signal corresponding to the actual speed of the rotor 12 n _installs linked. The speed signal becomes corresponding to a deviation between the actual speed and the target speed of the rotor 12 n _R generated and made available to the drive machine 24. This then accelerates the rotor 12 to the predetermined speed n _R.

From the above explanations, it is clear that the speed of the rotor 12 is controlled as a function of the pressing force. It is hereby achieved that if the pressing force PK is assumed to be lower than the _desired pressing force PK _SHOULD, the rotor 12 does not rotate at its nominal speed. In particular in the case explained that the dies 14 are not or only partially filled with molding compound 26, this means that the rotor 12 rotates at a predeterminable minimum speed n _R. This prevents the lower punch 16 and upper punch 18 of a properly filled die 14 from already hitting the pressure rollers 30 at the nominal speed of the rotor 12 when the lower punch 16 and the upper punch 18 hit for the first time. The mechanical load at this time is thus considerably reduced. If the punches 16 and 18 of a properly filled die 14 hit the pressure rollers 30, this automatically leads to an increase in the pressing force PK, which is measured as the _actual pressing force PK _IST via the pressing force transducer 40. This reduces the difference between the actual pressing force and the target pressing force, so that the speed of the rotor 12 is increased in accordance with the diagram shown in FIGS. 2 and 3 until the rotor 12 reaches its nominal speed.

The solution according to the invention is also suitable for recognizing, when the rotor 12 rotates at the nominal speed, whether the degree of filling of the dies 14 decreases with the molding compound 26. By reducing the degree of filling with molding compound 26, the pressing force PK on the pressure rollers 30 drops due to the direct relationships. In accordance with the sequence shown in FIG. 3, this decrease in the actual pressing force also leads to a reduction in the desired speed n _{R of} the rotor 12. According to different design variants, either a gradual or continuous reduction of the target speed n _R may be provided. Thus, the target speed n _R, for example equal to a predeterminable minimum rotational speed n _Rmin or in intermediate steps of the nominal speed n _RNom to the minimum speed n _Rmin be reduced.

LIST OF REFERENCE NUMBERS

10

Rotary tableting machine

12

rotor

14

die

16

lower punch

18

upper punch

20

guide curve

22

guide curve

24

electric prime mover

26

molding compound

28

pressing station

30

pressure rollers

32

axis of rotation

34

arrow

36

movement direction

38

peripheral surface

40

transducer

42

signal line

44

signal line

46

signal line

48

computer unit

50

storage means

52

step

54

step

56

step

PK

pressing force

PK _SHOULD

Target pressing force

PK _IS

Istpresskraft

PK _LIMIT

Pressing force limit

n _D

Speed of the pressure rollers

n _thin

Rated speed

n _DIST

Actual speed

n _R

Speed of the rotor

n _Rmin

Minimum speed

n _Rnenn

Rated speed

pk _IS

proportional signal

pk _SHOULD

setpoint signal

n _R

control signal

n _Rsoll

signal

n _instep

signal

pk _diff

difference signal

Claims (8)

Method for controlling a rotary tablet machine (10), wherein a rotor (12) can be set in rotation by a drive machine (24), the rotor (12) has at least one die (14) with associated upper punches (18) and lower punches (16) and a pressing force (PK) acting on the pressing mass (26) filled in the at least one die (14) is determined, characterized in that the determined pressing force (PK _IST ) is compared with a predefinable limit value (PK _LIMIT ) and if the _{pressure falls below} the Limit value (PK _LIMIT ) the target speed (n _R ) of the rotor (12) is reduced to a speed below the nominal speed (n _RNENN ). A method according to claim 1, characterized in that the pressing force (PK) is measured. Method according to one of the preceding claims, characterized in that a difference between the limit value (PK _LIMIT ) and a target pressing force (PK _SOLL ) can be set. A method according to claim 3, characterized in that the difference is between 1% and 50%, in particular between 5% and 20%, preferably between 8% and 12%. Method according to one of the preceding claims, characterized in that the target speed (n _R ) of the rotor (12) is compared with an actual speed of the rotor (12); and the rotor (12) is regulated to the target speed (n _R ). Method according to one of the preceding claims, characterized in that the rotor (12) is speed-controlled from standstill. Method according to one of the preceding claims, characterized in that the rotor (12) is speed-controlled from its nominal speed. Device for controlling a rotary tablet machine (10), with a control unit (42) or the like for controlling a drive machine (24) of a rotor (12) of the rotary tablet machine (10), a device (40) for determining a press mass (26) acting pressing force (PK) as well as means for comparing the determined pressing force (PK _IST ) with a predeterminable pressing force (PK _LIMIT ) and at least one means for specifying a target speed (n _R ) of the rotor (12) depending on the comparison of the determined Press force (PK _IST ) with the _{predeterminable press} force (PK _LIMIT ).

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