Note: Descriptions are shown in the official language in which they were submitted.
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Method for Controlling a Blister Packaging Machine
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 Tvz during
one work cycle, assumes a subsequent treatment state for a time period
Tg, in which a product and/or material is/are treated, and performs a
second adjusting motion for a time period Tv2, 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
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R defines the maximum cycle time Tmax available for a working cycle in
milliseconds with Tmax = 60,000/R ([ms], i.e. at a cycle rate R of 75
cycles/min, the maximum cycle time TmaX = 800ms. 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 TmaX.
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 s~ is defined by the technical production requirements
and the closing motion is performed over a predetermined time period T~1
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 TB, 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 sv (however, in the
opposite direction) over a time period T~2. 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.
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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~/2, i.e. a time period tZi is available for further transport of
the
bottom sheet to the end of the cycle, and a time period tzz from the start
of the subsequent cycle to the time when the forming plates are half
closed again, which produces a total transport time TZ from the sum of tZi
and tZZ.
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 ail 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 rel~tlV~ly gei~i~ltlv~ ~~ ~~tl~il~ ~~p~~~ bpd the ~Im~ Tz
available for further transport of the sheet (Fig, 2a) requires such a high
sheet acceleration at maximum drawn length that the sheet is deformed.
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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 TmaX is increased for each cycle. If the cycle rate R is reduced to
50 cycles per minute, the maximum cycle time is Tmax = 60,000/50=1,200
(ms). In a conventional blister packaging machine, the stored cycle curve
is basically maintained, however, all time periods Tvl, TB and Tvz 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 TZ 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~1, the
time period T,~ and the time period Tv2 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 Tvl, TB and Tv2
are within predetermined limits and whether their sum is smaller or equal
to a maximum cycle time T~,ax.
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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 TB, 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 seating 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 TB in
which the cover sheet is sealed onto the bottom sheet. The second
adjusting motion is the opening motion of the sealing plates.
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Time values, in particular in ms, can be entered directly for the
independent input of the time periods Tvl, Tg and T~Z. In practice, indirect
input of the mentioned time periods has proven to be advantageous by
entering a value for a desired speed vs9 of the first adjusting motion or the
closing motion and a value for a desired speed vo9 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 vs of the
first adjusting motion is limited to a maximum speed vsmaX and the desired
average speed vs9 of the first adjusting motion is input as percentage
(x100%) of the maximum possible speed vsmaX from which the processing
unit determines the time period T~1=s~/vs9 for a predetermined
adjustment path s~.
The speed vo of the second adjusting motion is correspondingly limited to
a maximum speed vp,rax and the desired average speed vo9 of the second
adjusting motion is input as percentage (<100%) of the maximum speed
VOmax from which the processing unit determines the time period
Tv2=sv/vo9 for a predetermined adjustrnent path.
The duration TB 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 TmaX=1/R [min] = fi0,000/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.
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Fig. 1 shows a schematic illustration of the essential components of a
blister packaging machine;
Fig. 2a shows a simplified normal cycle curve as path-time-diagram;
Fig. 2b 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~1;
Fig. 4 shows the possible selections for the time period TB;
Fig. 5 shows the possible selections for the time period T"2;
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 1i 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
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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 li 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 seating 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 cycl is transport of
the sheet compound provided after the sealing sfiation 20.
Fig. 2a shows the above-explained simplified path-time-diagram of a cycle
curve of e.g. the forming station 13. The assumed maximum_cycle time
Tmax is 800ms 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"1, thereby moving along the closing path
s~ 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 TB. 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~ in an opposite direction to the closing motion and over a time
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period T~2. 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 Tz = tzl + tzZ.
If the user notices that this total transport time Tz is not sufficient,
he/she
can re-define the cycle curve. The user will initially check whether he/she
can reduce the duration TB of the treatment state thereby maintaining the
current cycle rate R. Moreover, the closing speed vs may optionally be
increased which reduces the time period T~1. Additionally or alternatively,
the opening speed vo may be increased which reduces the time period Tv2.
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 Tz of the
sheet.
If the time periods T~~, Te, T~Z 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 Tmax= 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 Tmax = 1,OOOms.
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 vsmax is
predetermined for the closing motion which corresponds to a minimum
time period T~im,n for a fixed closing path sv. Moreover, a minimum value
is given for the closing speed which corresponds to a maximum time
period T"lmax (Fig. 3). The user can select any value within these limits.
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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 tt~e 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 Vsmax~ 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 Vomax which
corresponds for a predetermined opening path s~ to a minimum opening
time Tv2m~n and a minimum opening speed vpmin which corresponds to a
maximum opening time Tvzmax. 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 Vomax~ It is assumed that the maximum
opening speed v°max 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 TB 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 TBm;n
and a maximum time TBmax. 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
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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,OOOms, 200ms 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 200ms 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 Ta.
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 Tmax. The sum of the time periods T~1,
TB, T~2 is also confirmed to be smaller or equal to the cycle time TmaX.
