Control method for controlling operating conditions of pressing machine

Abstract

A control method for controlling the operating conditions of a rotary press machine (1) for forming tablets (100) wherein the rotary press machine (1) comprises: a rotary compression turret (2) comprising a die table (3) provided along its circumferential portion with a plurality of dies (4), a plurality of lower punches (6) associated in pairs with respective dies (4), and a corresponding plurality of upper punches (5), said lower ram (6) and said upper ram (5) each have a substantially cylindrical body equipped with abutment ends on which a lower compression roller (12) and an upper compression roller (11) abut, respectively; a supply station (7); a control system (20) for controlling the operating pressure of the lower compression roller (12) and the upper compression roller (11), in which, during a detection phase, the supply of powder (50) into the mold (4) is suppressed so as to have at least one empty mold (4a), the lower ram (6) and / or the upper ram (5) are / is moved towards the at least one empty mould (4a) by means of a respective lower and / or upper compression device, and a resistance pressure value is measured by means of a detection device (14), in an evaluation phase, the pressure resistance value is processed by the control system (20) as a pressure value exerted by the respective lower and / or upper compression means on a corresponding lower punch (6) and / or upper punch (5) moving inside the at least one empty mould (4a), and in an evaluation phase, the pressure resistance value is processed by the control system (20) in order to generate a signal relating to a punch operating state.

Description

[0001] The present invention relates to a control method for controlling the operating conditions of a pressing machine for producing tablets, spheres, pellets, for example, for pharmaceutical, cosmetic, food, chemical use by compressing powder or granules. In particular, the present invention relates to a method for operating a rotary pressing machine in an evaluation step of its operation.

[0002] Rotary pressing machines are known which comprise a compression turret which rotates about a vertical axis and which is formed by a die table or plate provided with a plurality of dies or through-cavities which are angularly distributed and equally spaced along an edge or on a circumferential portion thereof and which are arranged to receive powders or granules dispensed in a suitable feed station.

[0003] The turret also includes a plurality of upper and lower punches that are associated with respective dies and are vertically moved by cams and compression rollers during rotation of the turret.

[0004] The lower punch together with the die forms a corresponding support or housing suitable for receiving the powder at the feeding station. The upper and lower punches compress the powder introduced into the die to prepare tablets, which are then extracted from the die table with the help of the appropriately raised lower punch and transferred to the discharge chute.

[0005] The various steps for preparing the tablets are performed during at least a portion of a revolution of the continuously rotating compression turret.

[0006] During a machine assembly step or a maintenance or specification change step, the operator performs the installation of one or more punches on the machine. In this step, the correct positioning of the one or more punches installed on the turntable is verified by the operator. However, the positive result of this step is strongly influenced by the skills and knowledge of the operator. Errors during the assembly step (for example due to not inserting all the punches into the corresponding turntable housing, or due to incorrect installation of the punches) can lead to problems such as possible dispersion of powder in the machine, malfunctions or even breakage of the machine, resulting in undesired suspension of production necessary to restore correct operation.

[0007] Furthermore, the punch, which is slidingly associated with the die, must slide smoothly within the die in each production cycle without generating excessive friction which would lead to premature wear of the mechanical components involved or to possible breakage within the series of production cycles. Friction not maintained within certain limits also leads to an increase in the temperature of the mechanical parts involved, which may have a negative impact on the powders in contact with them.

[0008] Sensors are provided to detect the compression force of the powder by monitoring the mass of the powder during tablet production.

[0009] The disadvantage of these rotary pressing machines, which use one or more sensors to monitor the compressive forces exerted by the punches on the powder during conversion into tablets, is that there is no information on the operating status of each punch. In fact, when a pressure value outside the permitted range is measured, an error that is not directly attributable to a specific punch is signaled. In addition, these machines do not give any information on the correct on-site assembly of the punches completed before the production step, nor on whether all the punches have been installed.

[0010] It is an object of the present invention to improve known tablet pressing machines, in particular rotary pressing machines having a compression turret provided with dies and punches and provided with means for monitoring the compression force.

[0011] Another object of the invention is to provide a method for detecting the presence or absence of a punch associated with a given die before a production step, ie after an assembly or maintenance step of the tablet press, in order to avoid contamination by dust scattered on the die table.

[0012] A further purpose is to prevent damage to the pressing machine by any ram that is incorrectly mounted on the machine or is of the wrong size.

[0013] A first aspect of the present invention provides a control method for controlling operating conditions of a rotary tablet press according to claim 1 .

[0014] The invention may be better understood and implemented with reference to the accompanying drawings, which illustrate exemplary and non-limiting embodiments, in which:

[0015] - Figure 1 is a schematic diagram of a rotary pressing machine according to the present invention;

[0016] - Figure 2 is during the detection step Figure 1 A schematic diagram of a rotary pressing machine in FIG.

[0017] - Figure 3 is an enlarged view of a compression station of a rotary pressing machine according to various embodiments;

[0018] - Figure 4 Is the one with missing punch like Figure 2 A schematic diagram of a rotary pressing machine is shown;

[0019] refer to Figure 1 , illustrates a rotary pressing machine 1 according to the invention, arranged to produce tablets, spheres, pellets by compressing powders or granules for pharmaceutical, cosmetic, food or chemical use.

[0020] The rotary pressing machine 1 comprises a compression turret 2 which rotates about a vertical rotation axis (not shown) and comprises a die table 3 provided with a plurality of dies 4 along a portion or circumferential edge thereof, a plurality of upper punches 5 and a corresponding plurality of lower punches 6 associated with the respective dies 4. These upper punches 5 and lower punches 6 are movable to compress the powder 50 introduced into the dies 4, thereby preparing tablets 100, spherical tablets or pellets.

[0021] The dies 4 are through-going cavities made in the die table 3 which, in cooperation with the lower punch 6 , form seats or shells into which the powder 50 is fed and subsequently compressed to form the tablets 100 .

[0022] The rotary pressing machine 1 comprises a feed station 7 comprising a filling device for filling the mould and arranged to distribute the powder 50 to be compressed into the mould 4, and at least one compression station 8 or main compression station provided with an upper compression roller 11 and a lower compression roller 12 adapted to actuate an upper punch 5 and a lower punch 6, respectively, inside the respective mould 4 along a compression direction A, to compress the powder 50 distributed into the mould 4 and form a tablet 100. The lower punch 6 and the upper punch 5, respectively, have a substantially cylindrical body with an abutment end on which the lower compression roller 12 and the upper compression roller 11, respectively, abut.

[0023] In the embodiment illustrated in the figures, the compression direction A is substantially vertical, ie parallel to the axis of rotation of the compression turret 2. For simplicity, only the downwardly pointing arrow A is shown in the figures, but it is clear that the powder 50 is also compressed by the lower punch 6.

[0024] The compression station 8 also comprises an actuator 15 connected to the upper compression roller 11 and acting on it so as to keep it in a fixed operating position so that it constrains the upper punch 5 to exert a compression force Fc on the powder 50 in the corresponding die 4. Figure 3 It can be seen that the compression station 8 may also include a further actuator 15, which is connected to the lower compression roller 12 and acts on the lower compression roller to keep the lower compression roller 12 in a fixed operating position so that the lower compression roller 12 constrains the lower punch 6 to exert a further compression force Fc on the powder 50 in the corresponding mold 4. Alternatively, the lower compression roller 12 may be rotatably mounted to the support frame 13 of the rotary pressing machine 1, such as Figure 1 , Figure 2 and Figure 4 shown.

[0025] During operation of the rotary pressing machine 1, under operating conditions in which the upper punch 5, in its movement in the corresponding die 4, opposes the upper compression roller 11 to a resisting pressure less than or equal to the compression force Fc, the actuator 15 holds the upper compression roller 11 in a fixed operating position along the compression direction A. In this way, during the rotation of the compression turret 2, the upper punch 5 is progressively engaged by the upper compression roller 11 and is pushed by it in the die 4 so as to compress the powder 50 against the lower punch 6 below.

[0026] The rotary pressing machine 1 also comprises detection means 14 for measuring the pressure resisting the compression force Fc of the ram when the ram moves in the compression direction A.

[0027] As better explained in the following description, the rotary pressing machine 1 operates according to an operating method having the purpose of monitoring its correct operation. More precisely, the operating method described has the purpose of detecting the presence of all the punches 5, 6 on the compression turret 2 and further verifying their correct assembly / operation.

[0028] During the production of tablets, a step of feeding the powder 50 into the mold 4 is performed by means of said feeding station 7. In this step, the lower punch 6 associated with the respective mold 4 to be filled operates as a bottom wall, thereby creating a temporary cavity into which arrives the powder 50 to be compressed. The amount of powder 50 that occupies the mold 4 depends on the positioning of the lower punch 6 in the mold 4 and on the size of the mold 4.

[0029] It is clear that the term powder 50 also refers to granules and the like.

[0030] There is then provided a step of compressing said powder 50 once it has been fed into the mould 4. Compression of the powder 50 occurs by moving the respective lower punch 6 and upper punch 5 by applying said compression force Fc, wherein this compression force depends on the position of the lower compression roller 12 and the upper compression roller 11 on which said abutting ends of the lower punch 6 and upper punch 5 abut, respectively.

[0031] One aspect of the method according to the invention is provided by a detection step in which the supply of powder 50 by the supply station 7 into the mould 4 is inhibited, i.e. interrupted, such as Figure 2As shown, so that there is no powder 50 inside the mold 4, thereby obtaining at least one empty mold 4a. Then the movement of the lower punch 6 and the upper punch 5 is activated. It is clear that the upper punch 5 and the lower punch 6 that have been moved are the punches associated with one or more empty molds 4a, and the powder 50 has not yet been supplied to the one or more empty molds. When a pair of lower punches 6 and upper punches 5 move toward the empty mold 4a, the resistance pressure value is measured by the detection device 14 as the pressure value applied by the corresponding lower compression device and the upper compression device on the corresponding punch 5, 6 when there is no powder 50 to be compressed inside the corresponding empty mold 4a.

[0032] exist Figure 2 In the specific embodiment depicted in FIG, the lower compression device and the upper compression device correspond to the lower compression roller 12 and the upper compression roller 11, respectively.

[0033] According to a specific embodiment in which the compression device corresponds to a compression roller, in the detection step, the detection device 14 is arranged as a plurality of sensors associated with the lower compression roller 12 and the upper compression roller 11. According to one aspect of the invention, the detection device 14 is connected to the actuator 15. In addition, the detection device 14 may include at least one load cell. According to other embodiments, the detection device 14 may include one or more encoders and / or one or more piezoelectric sensors. In general, the detection device 14 may include one or more sensors of known type, which are suitable for measuring the extrusion force and for converting the measured extrusion force into an associated electrical signal.

[0034] According to another aspect of the present invention, the detection device 14 can be connected to any component that is connected to the lower compression roller 12 and / or the upper compression roller 11, according to a construction that allows measuring the resistance pressure value applied by the corresponding lower compression roller 12 and / or the upper compression roller 11 on the corresponding lower punch 6 and / or the upper punch 5.

[0035] According to a particular embodiment, the compression device may be arranged on the machine 1 as an auxiliary compression device alongside the lower compression roller 12 and the upper compression roller 11 .

[0036] This detection step can be performed under static conditions (i.e. without rotating the compression turntable 2). Alternatively, this detection step can be performed by moving the turntable 2 at a very limited speed relative to the usual speed during the production of tablets (e.g. of the order of about 1% relative to the usual production speed). Furthermore, the speed at which the punches 5, 6 move along the compression direction A is preferably very limited compared to the usual speed during the production of tablets (e.g. of the order of about 1% relative to the usual production speed).

[0037] When the detection step is performed by rotating the compression turntable 2, the rotational movement of the compression turntable 2 causes the lower punch 6 and the upper punch 5 to translate vertically parallel to the compression direction A when these punches abut against the compression device (lower compression roller 12 and / or upper compression roller 11), wherein the resistance pressure value is measured with the aid of the detection device 14.

[0038] When the detection step is carried out under static conditions, the compression device can be moved towards the corresponding punch. More specifically, the compression device is moved towards the corresponding abutment end of the lower punch 6 or the upper punch 5 by means of one or more actuators. The movement applied to the compression device can be along a horizontal axis and therefore parallel to the die table 3, or a vertical axis, perpendicular to the compression direction A. According to another embodiment, during the detection step, both the compression device and the compression turntable 2 can be moved jointly.

[0039] According to the invention, an evaluation step is carried out in which said resistance pressure value is processed by the control system 20 in order to generate a signal related to the ram operating state.

[0040] The control system 20 processes the acquired resistance pressure values ​​by comparing them with suitable predefined thresholds and determines the state of the opposing lower punch 6 and / or upper punch 5 .

[0041] According to another aspect of the invention, the evaluation step comprises a data saving sub-step in which the resistance pressure values ​​acquired during a plurality of detection steps for a specific empty mould 4a are saved in a data storage unit.

[0042] Preferably, in the data saving sub-step, the resistance pressure values ​​obtained during multiple detection steps are aggregated to the corresponding empty mold 4a for which these resistance pressure values ​​are measured, and are aggregated to the data related to the measurement time, thereby generating aggregate data saved in the data storage unit.

[0043] The data storage unit may be included in the control system 20 .

[0044] Alternatively, the data storage unit may be a unit separate from the control system 20. The data storage unit may be configured as a physical memory of a known type and / or may be configured as a cloud system.

[0045] Clearly, by repeating the detection and evaluation steps N times on a particular empty mould 4a, N values ​​of resistance pressure measured over time are obtained. The variation of the resistance pressure in a number of detection steps determines the trend of the resistance pressure over time for a particular empty mould 4a.

[0046] Preferably, in the evaluation step, the resistance pressure value N obtained during the detection step can be compared with one or more resistance pressure values ​​of N-1 resistance pressure values ​​previously obtained and stored in the data storage unit, where N is the total number of resistance pressure measurements performed on the specific empty mold 4a.

[0047] According to a particular embodiment, said signal related to the ram operating state comprises a command to stop the rotary press 1 so that an operator can intervene quickly in the machine.

[0048] The signal generated by the control system 20 may be an alarm signal, such as, for example, Figure 4 The missing plunger alarm in the illustrated case, wherein the resistance pressure value is below a first predefined value. Alternatively, if the resistance pressure value is above a second predefined value, the signal may be a plunger failure alarm. The first predefined value is less than the second predefined value.

[0049] According to further embodiments, the signal generated by the control system 20 may be a warning signal other than the alarm signal.

[0050] According to another aspect of the invention, in the detection step, the trend of the resistance pressure value for a specific empty mold 4a is also evaluated, and when the trend is about to exceed a predefined tolerance window, the control system 20 generates the warning signal so as to intervene before the resistance pressure value exceeds the tolerance window.

[0051] The predefined tolerance window is based on a reference resistive pressure value indicating an optimal resistive pressure value under correct machine operating conditions. The predefined tolerance window has a magnitude of, for example, +-10%, preferably +-5%, more preferably +-2% of the reference resistive pressure value.

[0052] The warning signal is different from the missing ram alarm and different from the ram failure alarm.

[0053] According to a further aspect of the invention, the detection step and the evaluation step are preceded by an assembly step in which one or more lower punches 6 and / or upper punches 5 are associated with the compression turret 2. This assembly step can be performed, for example, during a replacement operation of one or more punches for maintenance operations of the machine 1 or during a size change. In other cases, this assembly step can be performed during the initial assembly of the machine 1, wherein the punches are initially mounted on the compression turret 2. After the assembly of the punches, a detection and evaluation step is performed to verify the correct assembly. In this way, it is possible to detect and evaluate the correct assembly performed by the operator who mounts one or more punches on the machine 1. More precisely, it is possible to detect whether all punches have been mounted on the machine 1 before the production of tablets is carried out, and it is also possible to detect whether all punches associated with the compression turret 2 have been correctly mounted.

Claims

1. A method for controlling the operating conditions of a rotary pressing machine (1) for forming a tablet (100), wherein the rotary pressing machine (1) include: A rotary compression turret (2) comprising a die table (3) provided with a plurality of dies (4) along its circumferential portion, a plurality of lower punches (6) and a corresponding plurality of upper punches (5) associated in pairs with respective dies (4), the lower punches (6) and the upper punches (5) respectively having a substantially cylindrical body with abutting ends on which a lower compression roller (12) and an upper compression roller (11) respectively abut; a supply station (7) comprising a filling device for filling the dies (4), wherein the following steps occur during tablet production: - feeding powder (50) into the mold (4) from the feeding station (7); - compressing the powder (50) supplied to the die (4) by moving the corresponding lower punch (6) and upper punch (5), by contacting the lower compression roller (12) respectively and the upper compression roller (11) to apply a compression force (Fc) on the abutting ends of the lower punch and the upper punch (6, 5) along a vertical compression direction (A) to compress the powder (50) supplied into the at least one die (4) so ​​as to produce a tablet; It is characterized in that it also includes a detection step, in which the supply of the powder (50) into the mold (4) is suppressed so as to have at least one empty mold (4a), the lower punch (6) and / or the upper punch (5) are moved toward the at least one empty mold (4a) by means of the corresponding lower compression device and / or upper compression device, and the resistance pressure value is measured by the detection device (14) as the pressure value applied by the corresponding lower compression device and / or upper compression device to the corresponding lower punch and / or upper punch (6, 5) moving in the at least one empty mold (4a); and an evaluation step, in which the resistance pressure value is processed by the control system (20) to generate a signal related to the punch operation state.

2. A control method according to claim 1, wherein in the evaluation step, in case the resistance pressure value is below a first predefined pressure value, the signal generated by the control system (20) is an indication of a missing punch.

3. A control method according to claim 1 or 2, wherein in the evaluation step, in case the resistance pressure value is above a second predefined pressure value, the signal generated by the control system (20) is an indication of a faulty plunger.

4. The control method according to claim 3 when dependent on 2, wherein the first predefined pressure value is lower than the second predefined pressure value.

5. The control method according to claim 1 or 2, wherein in the detection step, the detection device (14) includes a plurality of sensors associated with the lower compression device and / or the upper compression device. The control method according to claim 5 , wherein the plurality of sensors include at least one load cell.

7. The control method according to any one of the preceding claims, wherein the upper compression device and the lower compression device correspond to the upper compression roller and the lower compression roller (11, 12), respectively.

8. A control method according to any one of the preceding claims, wherein in the detection step, by rotating the compression turntable (2), the lower punch (6) and / or the upper punch (5) are moved toward the at least one empty mold (4a) by the corresponding lower compression device and / or upper compression device.

9. A control method according to any one of the preceding claims, wherein prior to the detection step and the evaluation step, one or more lower punches (6) and / or one or more upper punches (5) are mounted on the compression turret (2).

10. Control method according to any of the preceding claims, wherein in the evaluation step, the signal related to the ram operating state comprises a command to stop the rotary press (1).

11. A control method according to any of the preceding claims, wherein the evaluation step comprises a data saving sub-step, in which the resistance pressure values ​​acquired during a plurality of detection steps for a specific empty matrix (4a) are saved in a data storage unit.

12. A control method according to any one of the preceding claims, wherein in the detection step, the trend of the resistance pressure value for a specific empty mold (4a) is also evaluated, and wherein when the trend is about to exceed a predefined tolerance window, the control system (20) generates a warning signal so as to intervene before the resistance pressure value exceeds the tolerance window.

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