METHOD FOR TEST PRESSING PELLETS IN A ROTARY PRESS

Abstract

A method for test pressing pellets in a rotary press, wherein the method comprises the following steps: a punch pair of an upper and lower pressing punch assigned to a receptacle of the die plate is brought into a dosing position in which the upper pressing punch is moved upward out of the receptacle and the lower pressing punch is located partially in the receptacle, such that the lower pressing punch presets a maximum filling height of material to be compressed in the receptacle, material to be compressed is filled into the receptacles, the pressing units of the pressing apparatus are moved toward one another such that an expected web height of a pellet to be manufactured in the test pressing is reached before the punch pair exceeds the place of the smallest distance between the pressing units during a rotation of the rotor, the rotor is put into rotary motion such that the punch pair for compressing into a pellet the material filled into the receptacle comes into contact with the pressing units, wherein the pressing force and/or a parameter characterizing the pressing force is determined, upon reaching a preset pressing force and/or a preset value of the parameter characterizing the pressing force the rotor is arrested and rotated in the opposite direction, such that the punch pair comes out of contact with the pressing units.

Claims

1. A method for test pressing pellets in a rotary press comprising a rotationally driven rotor with upper and lower pressing punches, an upper and lower punch guide for the upper and lower pressing punches and a die plate between the punch guides, wherein in production operation of the rotary press the upper and lower pressing punches interact with receptacles of the die plate, further comprising a filling apparatus into which material to be compressed is filled into the receptacles during production operation of the rotary press, further comprising a pressing apparatus with an upper pressing unit and a lower pressing unit, which interact with the upper and lower pressing punches during production operation such that the pressing units compress material located in the receptacles into pellets, characterized in that the method comprises the following steps: a punch pair of an upper and lower pressing punch assigned to a receptacle of the die plate is brought into a dosing position in which the upper pressing punch is moved upward out of the receptacle and the lower pressing punch is partially located in the receptacle, such that the lower pressing punch presets a maximum fill height of material to be compressed in the receptacle, material to be compressed is filled into the receptacle, the pressing units of the pressing apparatus are moved relative to one another such that an expected web height of a pellet to be manufactured in the test pressing is reached before the punch pair exceeds the place of the smallest distance between pressing units during a rotation of the rotor, the rotor is placed into rotary motion such that the punch pair comes into contact with the pressure units for compressing the material filled in the receptacle into a pellet, wherein the pressing force and/or a parameter characterizing the pressing force is determined, upon reaching a preset pressing force and/or a preset value of the parameter characterizing the pressing force, the rotor is arrested and rotated in the opposite direction, such that the punch pair comes out of contact with the pressing units (36, 38).

2. The method according to claim 1, wherein the parameter characterizing the pressing force can be a rotational position of the rotor, a web height, a pressing force curve and/or a pressing dwell time at a preset pressing force.

3. The method according to claim 1, wherein the pressing force and/or the parameter characterizing the pressing force is taken into account for setting the rotary press for production operation.

4. The method according to claim 1, wherein during the test pressing and/or after the test pressing, further parameters are determined, comprising the pressing force curve, the punch path curve of the upper and/or lower pressing punch, the maximum pressing force, the pressing dwell time at a preset pressing force, and/or the web height of the manufactured pellet.

5. The method according to claim 4, wherein the further parameters for setting the rotary press for production operation are taken into account.

6. The method according to claim 1, wherein only the punch pair assigned to the receptacle of the die plate is installed in the rotor during the test pressing.

7. The method according to claim 1, wherein the filling apparatus is disassembled or deactivated during the test pressing.

8. The method according to claim 1, wherein the material to be compressed in the test pressing is filled manually into the receptacle.

9. The method according to claim 1, wherein in the test pressing the rotor is rotationally driven with at least one third of the rotational speed reached during production operation of the rotary press.

10. The method according to claim 1, wherein multiple test pressings can be carried out, wherein the pressing force curve and/or the punch path curve is varied by a variation of the rotational speed of the rotor.

11. The method according to claim 10, wherein sinusoidal and/or sawtooth-shaped and/or square-shaped pressing force curves and/or punch path curves are set.

12. The method according to claim 1, characterized in that multiple test pressings are carried out, wherein punch pairs with different punch head geometries and/or punch tip geometries are used.

Description

[0031] An exemplary embodiment of the invention is explained below in greater detail with reference to figures. The figures show schematically:

[0032] FIG. 1 schematically shows a rotary press used in the method according to the invention in an unrolled representation of the rotor,

[0033] FIG. 2 an enlargement by sections of parts of the rotary press represented in FIG. 1 for illustrating the method according to the invention.

[0034] The same reference signs refer to the same objects in the figures unless indicated otherwise.

[0035] The rotary press shown in FIG. 1 is a rotary press for manufacturing tablets, as can be used in the present invention, and in which powdered material is compressed into pellets, particularly tablets. The rotor of the rotary press is rotationally driven by a rotary drive and comprises a die plate 10 having multiple receptacles 12. The receptacles 12 can be formed, for example, by bores in the die plate 10. The rotor further comprises multiple upper pressing punches 14 and lower pressing punches 16 which revolve synchronously with the die plate 10. The upper pressing punches 14 are axially guided in an upper punch guide 18 and the lower pressing punches 16 are axially guided in a lower punch guide 20. The axial movement of the upper pressing punches 14 and lower pressing punches 16 in the course of the rotation of the rotor is controlled by upper control cam elements 22 and lower control cam elements 24. A filling apparatus 26 is further provided, which has a filling reservoir 28 and a filling chamber 30 which are connected via a filling pipe 32. In this manner, in the present example, powdered material arrives due to gravity from the filling reservoir 28 via the filling tube 32 in the filling chamber 30 and from there via a filling opening provided on the lower side of the filling chamber 30 into the receptacles 12 of the die plate 10.

[0036] The rotary press further comprises a pressing apparatus 34. In the example represented, the pressing apparatus 34 comprises a pre-pressing apparatus with an upper pressing roller 36 held on an upper holder 35 and a lower pressing roller 38 held on a lower holder 37, as well as a main pressing apparatus with an upper pressing roller 40 held on an upper holder 39 and a lower pressing roller 42 held on a lower holder 41. Furthermore, the rotary press comprises an ejector apparatus 44 and a scraper apparatus 46 having a scraper element which supplies the tablets 48 produced in the rotary press to a discharge apparatus 50 for discharging from the rotary press.

[0037] The scraper apparatus 46 can, for example, comprise a preferably crescent-shaped scraper element which scrapes tablets 48 conveyed by the lower pressing punches 16 onto the upper side of the die plate 10 in the region of the ejector apparatus 44 off of the die plate 10 and supplies them to the discharge apparatus 50.

[0038] The rotary press further comprises a control apparatus 52 for controlling the operation of the rotary press and for carrying out the method according to the invention, as explained in greater detail below.

[0039] FIG. 2 shows a part of the rotary press represented in FIG. 1 for illustrating the method according to the invention. In this context, only an upper control cam element 22 and a lower control cam element 24 are shown, as well as only two punch pairs of the upper and lower pressing punches 14, 16 as well as only the upper pressing roller 36 and the lower pressing roller 38 of the pre-pressing apparatus of the pressing apparatus 34. For carrying out the method, it is possible, for example, for only one punch pair of the upper and lower pressing punches 14, 16 to be mounted in the rotor. FIG. 2 shows two punch pairs for illustrating different method steps of the method.

[0040] The punch pair represented on the left in FIG. 2 of the upper and lower pressing punches 14, 16, is located in the dosing position in which the upper pressing punch 14 is moved upward out of the receptacle 12 of the die plate 10, the receptacle 12 being assigned to the punch pair, in particular by the upper control cam element 22 represented in FIG. 2. The lower pressing punch 16, controlled by the control cam element 24 which is, in particular, a dosing cam element 24, is located partially in the receptacle 12 and thereby defines a maximum fill height of the receptacle 12 for the material filled into the receptacle 12. In this dosing position, the material is filled manually into the receptacle 12 when the rotor is arrested, for example. In this context, the receptacle 12 is filled completely up to its upper edge. If applicable, excess material can be scraped off of the upper side of the die plate 10.

[0041] Then the rotor is put into rotary motion, such that the punch pair moves to the right in FIG. 2 with the rotation of the die plate 10 and comes into contact with the pressing rollers 36 and 38, as is evident for the punch pair represented at the right in FIG. 2. The pressing rollers 36, 38 were previously moved toward one another to an extent, such that an expected web height of a pellet to be manufactured in the test pressing is reached before the punch pair exceeds, in particular reaches, the place of the smallest distance between the pressing rollers 36, 38 during a rotation of the rotor. The invention ensures that in the scope of the test pressing, the upper and lower pressing punches 14, 16 definitely do not exceed, in particular do not reach, the imaginary connection line 54 drawn in FIG. 2 between the axes of rotation of the pressing rollers 36, 38.

[0042] This setting of the pressing rollers 36, 38 ensures that a preset maximum pressing force is reached at the pressing apparatus 34, in particular at the upper and lower pressing rollers 36, 38, before the upper and lower pressing punches 14, 16, during the course of their rotary motion, exceed the region of the smallest distance between the pressing rollers 36, 38. The pressing force and/or a parameter characterizing the pressing force is measured during the contact between the pressing punches 14, 16 and the pressing rollers 36, 38, in particular by means of suitable sensors of the rotary press. Upon reaching a preset pressing force and/or a preset value of the parameter characterizing the pressing force, the rotary motion of the rotor is stopped and the rotor then rotates in the opposite direction, such that the punch pair again comes out of contact with the pressing rollers 36, 38. The manufactured pellet 48 can then be removed from the receptacle 12 of the die plate 10. The ascertained values can be used for setting the rotary press for production operation with the material compressed in the scope of the test pressing.

[0043] As is evident from the explanations in the preceding, with the present rotary press, the test pressing is carried out with the pressing rollers 36, 38 of the pre-pressing apparatus of the pressing apparatus 34. Naturally, the test pressing can be carried out in the same manner with the pressing rollers 40, 42 of the main pressing apparatus of the pressing apparatus 34, either with a rotary press that does not have a pre-pressing apparatus or insofar as the pressing rollers 36, 38 of the pre-pressing apparatus are moved away from one another sufficiently such that the punch pair of the upper and lower pressing punches 14, 16 either does not come into contact with this at all or only to an extent that is not sufficient for reaching the preset pressing force or the value of the parameter characterizing the pressing force.

LIST OF REFERENCE SIGNS

[0044] 10 Die plate

[0045] 12 Receptacle

[0046] 14 Upper pressing punches

[0047] 16 Lower pressing punches

[0048] 18 Upper punch guide

[0049] 20 Lower punch guide

[0050] 22 Upper control cam element

[0051] 24 Lower control cam element

[0052] 26 Filling apparatus

[0053] 28 Filling reservoir

[0054] 30 Filling chamber

[0055] 32 Filling tube

[0056] 34 Pressing apparatus

[0057] 36 Upper pressing roller

[0058] 38 Lower pressing roller

[0059] 40 Upper pressing roller

[0060] 42 Lower pressing roller

[0061] 44 Ejector apparatus

[0062] 46 Scraper apparatus

[0063] 48 Pellet

[0064] 50 Discharge apparatus

[0065] 52 Control apparatus

[0066] 54 Connection line