Method for controlling a blister packaging machine

Abstract

The invention concerns a method for controlling a blister packaging machine having a work station which at least operates in cycles and which performs at least one first adjusting motion for a time period TV1 during one work cycle, followed by a treatment state for a time period TB, in which a product and/or material is treated. A second adjusting motion is then performed for a time period TV2. A cycle rate R (=cycles/min) of the packaging machine can be entered through an input means. The time periods TV1, TB and TV2 can each be entered directly or indirectly irrespective of each other via the input means. A processing unit examines whether the entered time periods TV1, TB, TV2 are within predetermined limits and whether their sum is smaller or equal to a maximum cycle time Tmax.

Description

The invention concerns a method for controlling a blister packaging machine having a work station which at least operates in cycles and performs at least one first adjusting motion for a time period T_V1 during one work cycle, assumes a subsequent treatment state for a time period T_B, in which a product and/or material is/are treated, and performs a second adjusting motion for a time period T_V2, wherein a cycle rate R (=cycles/min) of the packaging machine can be entered by an input means.

A blister packaging machine of conventional-structure comprises a forming station, in which a plurality of cup-shaped depressions are formed into a bottom sheet which consists of plastic material or aluminium, into which a product, e.g. a pharmaceutical tablet is inserted in a downstream filling station. After product supply, the bottom sheet is supplied to a sealing station. A cover sheet is fed directly before or within the sealing station and disposed on the bottom sheet. The cover sheet is sealed tightly onto the bottom sheet within the sealing station using heat thereby enclosing the product in the cup-shaped depression.

The forming station is operated in cycles and therefore discontinuously. The sealing station can also be operated in cycles or, alternatively, continuously, wherein conventional compensation means effect transfer between cyclical operation of the forming station and continuous operation of the sealing station.

The efficiency of a blister packaging machine depends mainly on the cycle rate R, i.e. the number of cycles per minute to be effected. The cycle rate R defines the maximum cycle time T_max available for a working cycle in milliseconds with T_max=60,000/R ([ms], i.e. at a cycle rate R of 75 cycles/min, the maximum cycle time T_max=800 ms. A graph of a corresponding working cycle is shown in FIG. 2a in the form of a simplified polygonal path-time-diagram and is briefly explained below.

The cyclically operated forming station must e.g. carry out various motions and treatments or processes within the maximum cycle time T_max. Departing from a basic or zero position at the beginning of the cycle (point 0 in FIG. 2a), in which two forming plates, between which the bottom sheet to be formed extends, are completely separated, a first adjusting motion, i.e. the closing motion of the forming plates is initially carried out. The closing path sv is defined by the technical production requirements and the closing motion is performed over a predetermined time period T_V1 until point 1 (FIG. 2a) is reached, at which time the forming plates are closed and have reached their final position.

The forming plates have now reached their treatment state in which e.g. a pre-heated plastic bottom sheet is cooled for a time period T_B, wherein the cup-shaped depressions are additionally formed in the bottom sheet, in particular through compressed air or forming dies. At point 2 of the cycle curve, cooling or treatment of the bottom sheet is completed and is followed by a second adjusting motion, i.e. the opening motion of the forming plates, which is effected again via path s_V (however, in the opposite direction) over a time period T_V2. At the end of the opening motion, i.e. at point 3 of the cycle curve, the initial position has been reached again.

A very short, negligible opening time caused by computer or software processing or a resting period may follow which will be neglected herein. As soon as the forming plates are opened to a sufficient degree, further transport of the bottom sheet can be initiated and performed. With respect to FIG. 2a, it is assumed that the further transport of the bottom sheet starts when the forming plates have been moved apart by a distance s_V/2, i.e. a time period t_Z1 is available for further transport of the bottom sheet to the end of the cycle, and a time period t_Z2 from the start of the subsequent cycle to the time when the forming plates are half closed again, which produces a total transport time T_Z from the sum of t_Z1 and t_Z2.

In earlier blister packaging machines, the curve shapes were mechanically determined by rotating cam plates whose rotary motion was derived from a central driven main shaft, the so-called king shaft. In modern blister packaging machines, the curves are stored in software and the motor drive of the adjusting motions is effected via servomotors which are controlled by control electronics or corresponding software. The servo drive is particularly advantageous if an additional stroke adjustment or switching off is required during operation. These functions can be realized and changed without additional mechanical effort.

The motion sections of the cycle curve of a blister packaging machine are usually designed to optimally satisfy the process requirements of the customer thereby providing maximum cycle rates. Once set, this cycle curve is taken as a basis for later processing of all products during operation of the blister packaging machine.

In practice, the blister packaging machine often cannot be operated at the maximum possible cycle rate of e.g. 75 cycles per minute, since e.g. the warm bottom sheet is relatively sensitive to tensile forces and the time T_Z available for further transport of the sheet (FIG. 2a) requires such a high sheet acceleration at maximum drawn length that the sheet is deformed. Problems in other stations of the blister packaging machine, e.g. in the filling station, may necessitate reduction of the cycle rate.

If the cycle rate R is reduced to prevent sheet deformation, the maximum cycle time T_max is increased for each cycle. If the cycle rate R is reduced to 50 cycles per minute, the maximum cycle time is T_max=60,000/50=1,200 (ms). In a conventional blister packaging machine, the stored cycle curve is basically maintained, however, all time periods T_V1, T_B and T_V2 are extended by a factor 1,200/800=1.5. This facilitates controlled coordination of all motions which depend on the forming plate motion, e.g. the forming die motion, the distorting motion or the heating plate motion. FIG. 2b shows a corresponding expanded cycle curve which shows that the transport time T_Z for the sheet which results from the sum of the extended time periods t′_Z1 and t′_Z2 is also increased by 50% which provides e.g. more time for sheet transport. However, extension of the working cycle reduces the efficiency of the packaging machine from 75 cycles per minute to 50 cycles per minute, i.e. to 50/75=66.7%.

It is the underlying purpose of the invention to provide a method for controlling a blister packaging machine which permits the machine operator to variably adjust the cycle curve or the motion curve to the production and working conditions of the packaging machine.

This object is achieved in accordance with the invention with a method having the characterizing features of claim 1. The time period T_V1, the time period T_B and the time period T_V2 are each input directly or indirectly, independently of each other via the input means, and a processing unit is provided for examining whether the entered time periods T_V1, T_B and T_V2 are within predetermined limits and whether their sum is smaller or equal to a maximum cycle time T_max.

The invention is based on the fundamental idea of not only compressing or expanding a predetermined curve shape in total but to individually adjust the individual sections of the curve and merely check whether the predetermined boundary conditions are met. In this fashion, each curve section can be individually adjusted to the respective production conditions to obtain a higher cycle rate R and therefore a better efficiency of the packaging machine compared to conventional compression or expansion of the overall cycle curve.

The work station whose cycle curve can be varied, may be a forming station of a blister packaging machine. The forming station has two forming plates which can be adjusted relative to each other and between which a bottom sheet having cup-shaped receptacles is provided. If the bottom sheet is made from plastic material, it is processed in a pre-heated state and cooled in the forming station. The first adjustment motion is then provided through the closing motion of the forming plates, wherein the closing motion is terminated only when the final position of the forming plates has been reached, and the forming plates may already abut in the last motional phase of the closing motion. At the end of the closing motion, the forming plates remain in a treatment state for a time period T_B, in which the bottom sheet is shaped and optionally cooled. The second adjusting motion is the opening motion of the forming plates which return into their initial open position.

Alternatively, the work station may be a sealing station with sealing plates which can be adjusted relative to each other and between which a cover sheet is sealed onto the bottom sheet. In this case, the first adjusting motion is the closing motion of the sealing plates which remain in a treatment state at the end of the closing motion for a time period T_B in which the cover sheet is sealed onto the bottom sheet. The second adjusting motion is the opening motion of the sealing plates.

Time values, in particular in ms, can be entered directly for the independent input of the time periods T_V1, T_B and T_V2. In practice, indirect input of the mentioned time periods has proven to be advantageous by entering a value for a desired speed v_sg of the first adjusting motion or the closing motion and a value for a desired speed v_og of the second adjusting motion or opening motion. These values are preferably input not as absolute values but as relative values. Towards this end, a speed v_s of the first adjusting motion is limited to a maximum speed v_smax and the desired average speed v_sg of the first adjusting motion is input as percentage (≦100%) of the maximum possible speed v_smax from which the processing unit determines the time period T_V1=s_v/v_sg for a predetermined adjustment path s_v.

The speed v₀ of the second adjusting motion is correspondingly limited to a maximum speed v_0max and the desired average speed v_og of the second adjusting motion is input as percentage (≦100%) of the maximum speed v_0max from which the processing unit determines the time period T_V2=s_V/v_og for a predetermined adjustment path.

The duration T_B of the treatment state is preferably directly input as an absolute value in ms via the input means.

The desired cycle rate R (=cycles per minute) is also directly entered via the input means, wherein the processing unit determines the maximum available cycle time T_max=1/R [min]=60,000/R [ms] from the input cycle rate R.

Further details and features of the invention can be extracted from the following description of an embodiment with reference to the enclosed drawing.

FIG. 1 shows a schematic illustration of the essential components of a blister packaging machine;

FIG. 2 a shows a simplified normal cycle curve as path-time-diagram;

FIG. 2 b shows the cycle curve stretched by the factor 1.5 in accordance with FIG. 2a;

FIG. 3 shows the possible selections for the time period T_V1;

FIG. 4 shows the possible selections for the time period T_B;

FIG. 5 shows the possible selections for the time period T_V2;

FIG. 6 shows an inventive modified cycle curve; and

FIG. 7 shows a schematic plan view of an input means.

FIG. 1 schematically shows the essential components of a blister packaging machine 10. A plastic bottom sheet 11 delivered by a supply is initially supplied to a heating station 12 which comprises a lower heating plate 12b and an upper heating plate 12a which can be adjusted relative to the lower heating plate 12b. When the two heating plates 12a and 12b are closed, the bottom sheet received therebetween is heated.

A forming station 13 is directly adjacent to the heating station 12 and comprises a lower forming plate 13a and an upper forming plate 13b which can be adjusted relative thereto. The two forming plates 13a and 13b, which are shown in the open position, can be closed thereby cooling the bottom sheet which is received between the closed forming plates 13a and 13b and at the same time providing it with cup-shaped depressions via a compressed air supply or forming dies. The forming station 13 is followed by a transport device 14 for pulling the bottom sheet 11 in cycles through the individual stations.

The bottom sheet 11 which is provided with the cup-like depressions is supplied to a filing station 17 via deflecting rollers 15 and 16, in which a product, e.g. a pharmaceutical tablet, is inserted into each depression. The bottom sheet 11 extends to a sealing station 20. A cover sheet 18 is disposed onto the bottom sheet 11 directly before the sealing station 20 via a deflecting roller 19. The cover sheet 18 is sealed onto the bottom sheet 11 in the sealing station 20, which comprises a lower sealing plate 20b and an upper sealing plate 20a, by closing the warm sealing plates 20a and 20b and under thermal action on the sheet. The sealing station 20 is followed by a further transport device 21 whose motion is synchronized with the transport device 14 and provides cyclic transport of the sheet compound provided after the sealing station 20.

FIG. 2 a shows the above-explained simplified path-time-diagram of a cycle curve of e.g. the forming station 13. The assumed maximum cycle time T_max is 800 ms which corresponds to a cycle rate R of 75 cycles per minute. The two forming plates 13a and 13b start from an open basic position and are closed within a time period T_V1, thereby moving along the closing path s_V as predetermined by production considerations. As soon as the forming plates 13a, 13b have reached the final position of their closing motion (point 1 of the curve in FIG. 2a), the treatment state starts which extends over a time period T_B. During the treatment state, the bottom sheet is provided with cup-shaped depressions. If the bottom sheet is made from plastic material, it is also cooled. The treatment state is finished at point 2 of the curve and the forming plates 13a and 13b are subsequently opened via path s_V in an opposite direction to the closing motion and over a time period T_V2. The initial position is reached again at the end of the opening motion at point 3 of the curve.

In FIG. 2a it was assumed that the further transport of the sheet with half-opened forming plates 13 and 13b starts or ends to obtain a total transport time T_Z=t_Z1+t_Z2.

If the user notices that this total transport time T_Z is not sufficient, he/she can re-define the cycle curve. The user will initially check whether he/she can reduce the duration T_B of the treatment state thereby maintaining the current cycle rate R. Moreover, the closing speed v_s may optionally be increased which reduces the time period T_V1. Additionally or alternatively, the opening speed v₀ may be increased which reduces the time period T_V2. If one of these changes is possible without violating specifications determined by production needs or machine constraints, the user gains time which he/she can use to increase the total transport time T_Z of the sheet.

If the time periods T_V1, T_B, T_V2 cannot be changed or only to an insufficient degree, the user will reduce the cycle rate R. Towards this end, the user will set a reduced cycle rate R (=cycles per minute) to determine the maximum available cycle time T_max=60,000/R [ms]. It is e.g. assumed that the user reduces the cycle rate R to 60 cycles per minute which corresponds to a modified maximum cycle time T_max=1000 ms.

The user can then set another closing speed of the forming plates 13a and 13b via the input means shown in FIG. 7. A maximum speed v_smax is predetermined for the closing motion which corresponds to a minimum time period T_V1min for a fixed closing path s_V. Moreover, a minimum value is given for the closing speed which corresponds to a maximum time period T_v1max (FIG. 3). The user can select any value within these limits.

The closing motion of the forming plates should preferably be carried out as quickly as possible. If no problems occurred during closing, the user can select the same closing speed as for the originally predetermined cycle curve of FIG. 2a. The closing speed is selected via the input means 30 of FIG. 7 as a percentage of the maximum closing speed v_smax, i.e. in the present embodiment 100%.

The user can also change the opening motion of the forming plates within predetermined limits in accordance with the closing motion. These limits are determined by a predetermined maximum opening speed v_omax which corresponds for a predetermined opening path s_V to a minimum opening time T_V2min and a minimum opening speed v_Omin which corresponds to a maximum opening time T_V2max. Between these two limits, the user can select from a plurality of opening curves as indicated in FIG. 5. The user enters the desired opening speed for the opening motion as a percentage of the maximum opening speed v_omax. It is assumed that the maximum opening speed v_omax is also selected in this case which also corresponds to an input of “100%”.

The user can also set the duration of the treatment state on the input means 30 as an absolute value in ms, i.e. the time period T_B in which the two forming plates are closed and the sheet is shaped (forming station) or sealed (sealing station). In accordance with FIG. 4, he/she can select within predetermined limits, i.e. between a minimum cooling time T_Bmin and a maximum time T_Bmax. The user will select the duration of the treatment state in correspondence with the material-specific characteristics of the bottom sheet such that proper treatment of the bottom sheet, e.g. cooling and shaping in the forming station 13, is reliably ensured. In the embodiment shown, it is assumed that he/she will use the duration of the treatment state from the original cycle curve of FIG. 2a.

Since the user has selected the same motion curve as in the initial situation of FIG. 2a, but has reduced the cycle rate to 60 cycles per minute thereby increasing the cycle time to 1,000 ms, 200 ms are still available within a working cycle when the opening motion is terminated and the forming plates are re-opened. The user can use these 200 ms for transport of the bottom sheet (FIG. 6) and can also use at least part of the time gained to increase the duration of the treatment state TB.

FIG. 6 shows that it is possible through the user-dependent determination of the cycle curve within predetermined limits to increase the time periods for the sheet transport and/or duration of the treatment period without delaying the closing or opening motions of the forming plates.

FIG. 7 shows that the input means 30 is associated with a processing unit 40 which determines the corresponding cycle curves from the input values and in particular examines whether the entered values of the cycle curve are within the predetermined limits and whether the cycle curve in total is smaller or equal to the cycle time T_max. The sum of the time periods T_v1, T_B, T_V2 is also confirmed to be smaller or equal to the cycle time T_max.

Claims

1-9. (canceled)

10. A method for controlling a blister packaging machine, the machine having a work station which operates in cycles and which performs at least one first adjusting motion within a time period TV1, performs a subsequent treatment stage within a time period TB in which a product and/or material is processed, and then executes a second adjusting motion throughout a time period TV2, the method comprising the steps of: a) entering a cycle rate R of the packaging machine using an input means; b) entering the time period TV1 via the input means; c) entering the time period TB via the input means; d) entering the time period TV2 via the input means; e) examining, using a processing means, whether TV1, TB, and TV2 are each within a respective predefined limit; and f) examining whether the sum of TV1+TB+TV2 is less than or equal to a maximum cycle time Tmax.

11. The method of claim 10, wherein the work station is a forming station having forming plates which can be adjusted relative to each other and between which a bottom sheet is provided with cup-like receptacles.

12. The method of claim 11, wherein the first adjusting motion is a closing motion of the forming plates, the bottom sheet being provided with the cup-like depressions in the treatment stage, wherein the second adjusting motion is an opening motion of the forming plates.

13. The method of claim 10, wherein the work station is a sealing station with sealing plates which can be adjusted relative to each other and between which a cover sheet is sealed onto a bottom sheet.

14. The method of claim 13, wherein the first adjusting motion is a closing motion of the sealing plates, and the cover sheet is sealed onto the bottom sheet during the treatment stage, with the second adjusting motion being an opening motion of the sealing plates.

15. The method of claim 10, wherein a speed vS of the first adjusting motion is limited to a maximum speed vsmax and a desired speed vsg of the first adjusting motion is entered as a percentage (≦100%) of the maximum speed vsmax, wherein the processing unit determines the time period Tv1=sv/vsg for a predetermined adjusting path sv.

16. The method of claim 10, wherein a speed v0 of the second adjusting motion is limited to a maximum speed vomax and a desired speed vog of the second adjusting motion is entered as percentage (≦100%) of the maximum speed vomax, wherein the processing unit determines the time period TV2=sv/vog for a predetermined adjusting path sv.

17. The method of claim 10, wherein the time period TB is entered directly via the input means.

18. The method of claim 10, wherein the cycle rate R is entered directly via the input means and the processing unit determines the maximum cycle time, Tmax=1/R (min)=60,000/R [ms], therefrom.