EP0431269B2 - Method and device for monitoring the pressing forces of a pelleting machine - Google Patents

Description

The invention relates to a method for monitoring the maximum pressing forces the one with a rotating die plate interacting Tableting machine. The invention further relates to a tableting machine.

In order to ensure a predetermined quality in the manufacture of tablets during production the pressure forces used for this are continuously measured and with Setpoints compared. Is a measured maximum pressing force value outside of Setpoint limits, the corresponding tablet must be sorted out. Such is done by actuating an ejection device which is arranged behind a press station namely behind the main printing station to which a pre-printing station is assigned. requirement but it is that the maximum press force values of at least the pressure rollers continuously the main printing station can be measured and evaluated. With respect to that high circulation speed of the die plate, the measurement results are evaluated via a computer into which the measured press force values are entered. In addition, however, it is necessary to enter signals into the computer to which the respective position of the associated die hole or the corresponding punch during the circulation of the die plate can be seen in order to make a manufacturing error to assign tablets to a specific pair of stamps for further evaluation of the measurement results.

Monitoring the pressing forces in the manufacture of tablets is not only necessary, to identify errors and sort bad tablets in good time, but Monitoring is also carried out to provide evidence of the quality of the tablets produced to be able to create continuously and thus the proof at a later date to be able to lead that the tablets produced correspond to the required quality, in which was produced under a predetermined pressing force. About the calculator can be used to continuously check and display the measurement results and the Allow size of any errors that occur.

In order to be able to assign the measured maximum pressing forces to the stamps that they caused have, it is known (DE-A 28 24 547) on the die plate as a sensor to arrange a stamp proximity switch with which for each individual press force value Time is specified at which the maximum of the pressing force is present. It is about a proximity switch that triggers a switching pulse, for example, when a metal part traverses an electric field in front of it. On a die plate With 30 die holes, for example, 30 turns per revolution Pulses triggered and put into the computer. This stamp proximity switch is at the known tabletting machine, a second stamp proximity switch as a sensor downstream, whose pulse length depends on the peripheral speed or the speed of the die plate, so that an exact determination of the A stamp can be placed at any time during the circulation of the die plate is.

The application and exploitation of the well-known stamp proximity switches has changed however, it is shown to be imperfect if a tablet machine often has one Die plate with a predefined stamp division, such as 30 stamps should be exchanged for another with a different stamp division such as 24 die holes or another die plate with the same stamp pitch however, a different nature of the die holes for the purpose of Manufacture of larger or smaller tablets. After such interchangeability In practice, the die plates of a tableting machine have a need to different products on one machine with little effort for your To be able to produce changeover there for the production of larger tablets other Die holes and accordingly other stamps are required than for the production of smaller tablets usually results in a smaller number of the die holes distributed over the circumference of the die plates and thus also a different number of stamps. This can be done when using the known stamp proximity switches take into account only with considerable effort, since in the event of a change the stamp division requires a complete changeover of the proximity switches, which generally cannot be carried out by the operating personnel.

EP-A-0 221 091 describes a method for monitoring the maximum pressing forces with a rotating die plate interacting press ram of a tableting machine become known in which an ejection device via a computer control is. The press forces exerted by the press rams are measured and in entered a calculator. When continuously determining the position of the die plate several magnetic sensors are used, with a first sensor at each revolution of the die plate triggers a circulation pulse that is on the at this first sensor connected computer is given. A second with each stamp interacting sensor, which is designed as a proximity switch a continuous series of pulses per revolution, the pulses of which are spaced apart have, which corresponds to the distance between the ram, with a counter a position signal generated which corresponds to the angular position of the ram and at which Calculator determines the position of the die plate, at which the pressing force has a maximum value so that the calculator can determine standard deviations to determine the Determines the quality of the production and supplies the ejection device with an ejection signal, if the press force measured for a press ram is outside setpoint limits lies.

The invention has for its object a method for monitoring the pressing forces the press ram interacting with a rotating die plate to specify a tableting machine, which is replaced by a die plate a different kind is allowed without having to change the electronic device needs to determine the position of the individual ram or die plate is around these values the measured maximum press force values for the purpose to be assigned to a further evaluation.

According to the invention it is provided that the position of the die plate continuously with a Angle pulse generator is determined by emitting pulses, which is connected to a computer with which the pulses are assigned to the entered maximum pressing force values for further evaluation.

An angle pulse generator is a commercially available measuring sensor, which is used either as an inductive pulse generator on a magnet can be formed or works on an optical basis using LEDs and photoelectric cells, the formation can be made such that with an angular pulse generator several independent pulses are to be delivered simultaneously, which is, for example can act three individual pulse generators, which are combined in a housing or a transducer.

The main advantage of the angular pulse generator is the fact that the position is continuous with it to measure a die plate and thus its associated stamp during circulation is independent of which punch pitch or number of die holes the respective die plate has. This is in any case, when the signal generator for the angular pulse generator with the drive of the die plate is connected so that it is not exchanged for another when the die plate is changed needs to be. For this purpose, the invention provides that a coded disk is provided as the signal transmitter, which is preferably arranged on the drive shaft of the die plate, the coding for example can consist of a line marking. It can be used to circulate a die plate For example, trigger 3,600 pulses, so that with a stamp division of 30 or 30 over the scope of the Arranged die plate for the passage of each punch triggered 120 pulses be, taking into account the rotational speed of the die plate through evaluation by allow the computer to be continuously assigned to the independently measured maximum press force values. The rotational speed to be taken into account for this can be continuously with the same angle pulse generator determine if the window or the signal transmitter is provided with a mark by which a separate impulse is caused each time the die plate rotates.

Since the maximum pressing forces to be evaluated are caused by the pressure rollers of the stationary main pressing station it is advisable to use the position of the main pressure rollers as a reference point or as a "zero degree position" to select and then align the angle encoder with the associated signal disk. Becomes which exchanges a die plate for another, the angular pulse encoder does not need to be adjusted to be, since its measurement results depend solely on the position of the fixed main pressure station or are independent of the nature of a die plate.

The invention is explained below using an exemplary embodiment with reference to a drawing.

Figur 1:

die Draufsicht auf eine Matrizenscheibe;

Figur 2:

die Matrizenscheibe mit Winkelimpulsgeber in der Seitenansicht;

Figur 3:

die Matrizenscheibe mit Winkelangaben;

Figur 4:

ein Diagramm vom Preßkraftverlauf und dem Umfangsimpuls;

Figur 5:

Diagramme von Praßkraftverläufen und ausgelösten Impulsen in zeitlicher Zuordnung zueinander;

Figur 6:

eine schematische Darstellung des Rechners mit Ein - und Ausgang und

Figur 7:

ein Blockschaltbild.

The drawing shows:

Figure 1:

the top view of a die plate;

Figure 2:

the die plate with angle pulse generator in side view;

Figure 3:

the die plate with angle information;

Figure 4:

a diagram of the pressure force curve and the circumferential pulse;

Figure 5:

Diagrams of pressure force profiles and triggered impulses in temporal association with one another;

Figure 6:

a schematic representation of the computer with input and output and

Figure 7:

a block diagram.

The die plate 2, which is generally shown only schematically in the drawing, is evenly over at 24 the circumferentially distributed die bores 5 are provided, each of which includes punches 4 that thus have a stamp pitch of α = 15 °. The die plate 2 is part of a high-performance tableting machine, which is designed as a so-called double rotary machine and has two main printing stations 8 and 8 ', which pre-printing stations 7 and 7' are upstream. Relative to the direction of rotation of the die plate counterclockwise according to arrow 6 are located behind the two main printing stations Sorting switches 10 and 10 ', which are to be moved according to the double arrow 11, if one Bad tablet should be excreted. Apart from this mobility of the switches 10 and 10 'are the pre-printing stations 7, 7 'and main printing stations 8 and 8' and sorting switches 10 and 10 'are arranged in a fixed position, while the die plate 2 with the die holes 5 and the punches 4 rotate during operation.

For the production of a single tablet, its powder is first passed through in a die hole 5 Pressure rollers 12 or 12 'pre-pressed in a pre-printing station 7 or 7' and then under maximum pressing force with pressure rollers 13 in a main printing station 8 or 8 'pressed. The pressing forces used for this will be measured continuously using strain gauges at a measuring point 28 (FIG. 7). The measuring point 28 is an amplifier 30 connected downstream, the signals via an analog-digital converter 32 to a Computer 34 transmits, which is designed as a pressure force monitoring device and therefore by electronic Processing compares the received force force signals with setpoint limits. Via this computer 34 (FIG 7), a control device 38 for a sorting switch 10 can be activated in order to have a bad tablet to eliminate them.

In order to assign the stamps triggering them to the measured measuring forces taking into account the continuous change of their position an angle pulse generator 20 is provided for their location, which interacts with a coded disk, which acts as a signal generator, for example with a line marking is provided, by means of which, for example, 3,600 pulses during one revolution of the die plate are triggered so that 150 stamps on each stamp in a passage through a main press station omitted. The signal disk 18 is arranged on the drive shaft 18 of the die plate 2, so that it with however, each revolution of a die plate rotates once, regardless of its special nature the die plate, that is to say is effective regardless of which stamp division for the die plate is provided.

ϕ 0V2, die zweite Hauptdruckstation 8'im Winkel

ϕ 0H2 und die zweite Aussortierweiche 10' im Winkel

ϕ 0A2, während die erste Vordruckstation 7 zu der Nullstellung im Winkel von ϕ 0V1 steht.

Since the pulses given by the pulse generator 20 are to be coordinated in the computer as a representation of the angular position of the die plate 2 with the independently measured pressing force values, it is only logical to orient or adjust or align the pulse generator 20 according to the point at which this maximum Pressing forces are exerted. This is the point at which the pressure rollers 13 of a main printing station 8 are located. If this point is regarded as the reference point or starting position according to FIG. 3, the sorting diverter 10 is at a fixed angle ϕ 0A1, the second pre-printing station 7 'at an angle

ϕ 0V2, the second main printing station 8 'at an angle

ϕ 0H2 and the second sorting switch 10 'at an angle

ϕ 0A2, while the first pre-printing station 7 is at an angle of ϕ 0V1 to the zero position.

If the signal disc is provided with a marking that triggers only one pulse with each revolution, the can be referred to as a circumferential pulse or a circulating pulse 22, it is then expedient for this pulse trigger when the marker passes through the starting position zero, that is, at the time, to which a maximum pressing force is exerted on the main station 8 by a punch. A the corresponding representation can be found in FIG. 4, in the upper diagram of the pressure force curve for the Stamps S1, S2 and S3 are reproduced and below the representation is reproduced for the circumferential pulse 22, the switching edge 23 below the maximum pressing force of the punch S1 corresponding to line 40 lies.

The course of the curves is plotted against time, with the ordinates measuring the force F in one case Specify the voltage U measured in volts (V) in Newtons (N) and in the other case. For such Setting or adjustment, the pressure force of the stamp S1 is measured at the main printing station 8 and the die plate 2 rotated by hand until the maximum pressing force is reached. In this position the signal disc 18 is set such that with the switching edge 23 of the circulation pulse 22 or for this provided mark on the disc 18, a pulse is triggered. Then an assignment is made from triggered pulses to the independently measured pressing forces, as shown in FIG. 5 , although it should be noted that this representation only relates to the conditions, which are present at the main printing station 8 and the pre-printing station 7. In addition to that and leave at the same time emit 20 series of pulses with the same pulse generator, which are assigned to the pressing forces, which the second pre-printing station 7 'and 8' can be determined.

In FIG. 5, curve (1) shows the pressure force curve at the pre-printing station 7 and curve (2) the pressure force curve at the main pressure station 8, in each case over time (t), so that it can be seen that the maximum pressing force of the punch S1 is measured at the main printing station 8 at a later point in time was when at the pre-printing station 7. The maximum of the pressing force of the punch S1 is corresponding to the Curve 2 on the zero line 40, on which the switching edge 23 of the circulation pulse 22 by corresponding Setting the signal disc 18 is. Below this are the pulse chains with curves 4 and 5, which with mit 1 and ϕ 2 are designated and can be assigned to the main printing station 8 and the pre-printing station 7. With these Pulse chains or the curves (4, 5) are those pulses that are generated directly by the pulse generator 20 are entered into a first computer 28 (FIG. 7) in accordance with the representation according to FIG. 6. The computer 26 converts the signals into output signals according to curves 6 and 7 for the pre-pressure - And main printing station, at which the pulses are at a distance from each other, which is the stamp division ϕ corresponds to S1, which is entered for curves 2, 3, 4 and 5.

The pulses corresponding to curves 6 and 7 are parallel to the measured pressing forces in the entered second computer 34 via the analog-digital converter 32, so that a Query of the form as well as the main pressure of individual stamps is made possible and that in double rotary machines also taking into account the second press station and beyond a control the sorting switch 10 and an output of the results in the manner of documents or via a display 36 is possible.

If the above description of one embodiment relates to the use of two Relates computers 26 and 34, the invention is not limited to this. Rather, there is the possibility instead of two computers 26 and 34 to provide additional computers or just a single one.

Claims (6)

1. A method for monitoring maximum pressure forces of punches (4) of a tableting machine which punches co-operate with a rotating die (2),

   wherein an ejection device (10, 10') is to be controlled by a computer (26, 34), wherein said pressure forces exerted by said punches (4) are measured and transmitted into said computer (26, 34),

   wherein for continuously determining the position of said die plate (2), an angular pulse generator (20) is provided, which co-operates with a coded signal transmitter (18) being adjustably coupled with the drive shaft (16) of said die plate (2), and which triggers a separate rotation impulse (22) at each rotation,

   which rotation impulse is transmitted to said computer (26, 34) being connected to said angular pulse generator,

   wherein said coded signal transmitter (18) is adjusted such that said rotation impulse (22) is triggered, when the pressure force of a certain punch (4) reaches maximum value,

   wherein said angular impulse generator (20) produces at least one continuous row of impulses (Fig. 5: ϕ₁, ϕ₂, respectively) at each rotation and transmits it into said computer (26, 34),

   and wherein said computer converts the received impulses into further rows of impulses (Fig. 5: (6), (7), respectively), the impulses of which being spaced at an amount according to the spacing of the punches (4), and coordinates the latter impulses with said transmitted maximum pressure forces such that, for output of evaluations, said computer (26, 34) calculates pressure force standard deviations for determination of quality of the production for each tablet and delivers an ejection signal to the ejection device (10, 10', if said measured pressure force of the punch (4) is out of reference limits.
2. A method according to claim 1, characterized in that separate impulses for two or more punch stations (7, 7', 8, 8') are transmitted to a computer (26, 34) by said angular impulse generator (20).
3. A method according to claim 1, characterized in that said computer (34) controls an elimination switch (10) behind the main pressure station (8,8').
4. A method according to claim 1, characterized in that said angular impulse generator (20) is adjusted such that said rotation impulse (22) is produced in a main punch station (8).
5. A tableting machine having a rotating die plate (2) driven by a drive shaft and having punches (4) being associated to the dies of said die plate (2) comprising

   an ejection device (10, 10') being associated to said die plate (2), and a computer (26, 34) to control the ejection device (10, 10'), and

   a measuring device (28, 30) measuring the pressure forces exerted by said punches (4), the transducer signals of which are transmitted to said computer (26, 34), and

   an angular impulse generator (20) for continuously determining the position of said die plate (2), which angular impulse generator co-operates with a coded signal generator (18) being adjustably coupled with the drive shaft (16) of said die plate (2),

   wherein said angular impulse generator (20) triggers a separate rotation impulse (22) at each rotation of said die plate, which rotation impulse is transmitted to said computer (26, 34) being connected to said angular impulse generator (20),

   wherein said coded signal transmitter 18 is adjustable such that said rotation impulse (22) is triggered, when the pressure force of a certain punch (4) is reaching maximum value,

   wherein said angular impulse generator (20) produces at least one continuous row of impulses (Fig. 5: : ϕ₁, ϕ₂, respectively),

   and wherein said computer converts said received impulses into further rows of impulses (Fig.: (6), (7), respectively), the impulses of which being spaced at a distance according to the distance of said punches (4), and coordinates the latter impulses with said transmitted maximum pressure force values such that for output of evaluations, said computer (26, 34) determines pressure force standard deviations for determination of quality of the production for each tablet and delivers an ejection signal to the ejection device (10, 10'), if said measured pressure force of the punch (4) is out of reference limits.
6. A tableting machine according to claim 5, characterized in that said signal transmitter (18) is formed as a disc provided with a coding.

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