Note: Descriptions are shown in the official language in which they were submitted.
CD, 02876812 2015-01-07
Metering device for tablets and method for metering tablets
The invention relates to a metering device for tablets,
in particular for micro tablets, of the genus specified in
the preamble of Claim 1 as well as to a method for metering
tablets.
Under certain conditions, it is necessary not to
prepack ready compressed tablets individually for example in
blister packs, but to meter them in a certain quantity which
must be precisely adhered to. Said requirement occurs in
particular in the case of so-called micro tablets with a
diameter of less than 3.0 mm. These are provided to be taken
in a measured quantity and are consequently filled, for
example, into two-piece capsules in a suitable quantity as
an individual dose.
In the case of metering tablets which are provided as
bulk goods, a series of requirements should be taken into
consideration. On the one hand, it must be ensured that
precisely the provided number of individual tablets passes
into the target container in order to avoid overdosing or
underdosing. On the other hand, the metering has to be
effected in a manner that protects the material so that no
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tablets are broken. The device and the method must be
insensitive to the barely avoidable presence of fragments
and tablet dust. Basic economic conditions dictate a high
cycle or output rate. Over and above this, the arrangement
provided for the metering can only take up a small
installation space so that it can be incorporated into a
filling system.
Different designs of metering devices for tablets are
known according to the prior art. A rotating drum with a
horizontal rotational axis which is filled by way of a
tablet store is provided in one realization. On the inside
the circumferential wall of the drum comprises tablet
receiving means into which individual tablets are fitted. As
a result of rotating the drum, the tablets, separated into
singles, are conveyed out of the tablet store, ejected in a
corresponding number and supplied to the target container.
As an alternative to this, a rotating disk with an
inclined rotational axis is provided according to the prior
art, corresponding tablet receiving means being installed on
the top surface of the rotating disk. In this connection,
the tablet store is poured onto the rotating disk, as a
result of which the separating out into singles or the
metering operation is performed in an analogous manner to
the drum version.
Various problems arise when such embodiments are used
in practice. Depending on the processing state and in
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particular in the case of a corresponding coating, the
tablets tend to stick to one another, as a result of which
duplicates and triplicates can be realized. These cannot be
entrained by the tablet receiving means, which are adapted
in form and volume to the individual tablets, or can only be
entrained in a limited manner. Consequently, it is difficult
to obtain the precise quantity of tablets for an individual
dose.
It is also problematic that the tablet store, which is
located in the drum or on the disk, is set into movement and
is intermixed as a result of the rotation. The tablets rub
against one another and also against their moved support,
which results in broken tablets, or at least in considerable
development of dust. The tablets can lose their size as per
specification as a result. Tablet fragments and dust can be
removed from the tablet store only at great effort - if at
all. Tablet fragments which pass into the tablet receiving
means do not meet the metering objective on the one hand,
but prevent, on the other hand, tablets as per specification
passing into the corresponding tablet receiving means. All
in all it is difficult to ensure that each tablet receiving
means has received one tablet each and that, as a result,
the desired number of tablets as per specification can be
transferred into the target container.
In the embodiments according to the prior art, it is
certainly possible to monitor the tablet receiving means
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using cameras and image evaluation to the effect that all
the tablet receiving means are filled correctly with one
tablet each. In the event of trouble spots, however,
underdosing has to be accepted, as a result of which the
associated target container has to be eliminated as waste.
The object underlying the invention is to provide a
metering device for tablets, which device meters tablets in
a manner which protects the material, is highly reliable and
has a high pulse rate according to quantity.
Said object is achieved by a metering device with the
features of Claim 1.
In addition, the object underlying the invention is to
provide a method for metering tablets, by means of which
tablets can be metered and filled into target containers
with increased reliability at high cycle rates according to
quantity.
Said object is achieved by a method with the features
of Claim 18.
According to the invention, it is provided that
metering device includes a fixed device part and a metering
element, which rotates in a plane of rotation, having
several tablet receiving means. The plane of rotation lies
at an angle of inclination of no more than 300 with respect
to the weight force direction. The tablet receiving means of
the rotating metering element are open in at least one
lateral direction with reference to the plane of rotation.
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The fixed device part includes a feeder surface for the
tablets which, with reference to the weight force direction,
is arranged in the bottom region of the metering element and
at the side next to the metering element. The feeder surface
borders on the metering element by way of a lead-in edge at
the level of the tablet receiving means. The metering
element can be realized as a rotating conveyor belt, as a
rotating conveyor chain or the like, and is realized in a
preferred manner as a metering wheel which is rotatable
about a rotational axis. The plane of rotation of the
metering element lies in an expedient manner at an angle of
inclination of no more than 15 and in particular is almost
approximately parallel to the weight force direction.
In the associated method according to the invention for
metering tablets, first of all a tablet store with tablets
is provided in a bottom potion of the metering device with
reference to the weight force direction. The metering
element is made to rotate, wherein tablets are supplied from
the tablet store laterally to the tablet receiving means by
means of the feeder surface. The tablet receiving means then
receive in each case at least one, in a preferred manner
precisely one tablet. The geometric development of the
tablet receiving means can be matched in such a manner to
the form and size of the tablets to be metered that, for
example, two or three tablets pass into one tablet receiving
means. In an expedient manner, the geometric development is
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matched in such a manner that precisely one tablet passes
into the tablet receiving means and consequently one tablet
comes to rest in each tablet receiving means. The tablets
are then transported in the tablet receiving means to the
tablet outlet by means of the metering element. In a manner
described in more detail below, the tablets are counted and
are supplied in a counted quantity from the tablet receiving
means through the tablet outlet to a target container.
Different advantages are achieved as a result of the
invention. The weight of the tablet store is carried first
and foremost or even exclusively by the fixed feeder surface
which is associated with the fixed device part. As a result
of this and as a result of the only slight - if at all -
inclination of the plane of rotation of the metering
element, the tablets of the tablet store experience an, at
best, only slight pressing pressure against the rotating
metering element. The rotation of the metering element
induces an only slight inherent movement in the tablet store
with very small frictional forces such that the tablets are
treated in a manner which protects the material. The risk of
fracture and the development of dust are reduced to a
minimum. Tablets which stick together as duplicates or
triplicates can hardly pass into the tablet receiving means
such that they do not occupy them. Rather, the individual
tablet receiving means remain free to receive tablets as per
specification, which increases the effect of separating them
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into singles or the counting or metering reliability.
Unavoidable fragments and dust parts can easily be
discharged in the manner described in more detail below
without impairing the metering operation. All in all, a high
level of operating reliability can be achieved even in the
case of high pulse rates or high rotational speeds.
In a preferred variant of the method, the metering
element rotates continually, the tablet receiving means
continuously receiving tablets from the tablet store. In the
case of a uniform movement with low mass inertia forces, it
is possible to achieve high operating speeds with a high
volume output. In the case of such continuous operation,
different variants of the separating out into singles and
metering according to quantity are possible within the
framework of the invention:
In a first advantageous variant, individual contiguous
rows which are spaced apart from one another are formed from
the continuously received row of tablets. More precisely, as
a result of ejecting tablets in a selective manner from
their tablet receiving means, contiguous rows of tablet
receiving means with tablets are formed in a desired,
counted number, further rows of empty tablet receiving
means, that is without tablets, being formed between the
aforementioned rows. The tablets following one after another
in a contiguous row are supplied as a group through the
tablet outlet into the target container. Whilst the
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following empty row of tablet receiving means without
tablets passes the tablet outlet, the target container is
changed. The cycle of supplying the tablets to the target
container and changing the target container can then start
again.
The ejected tablets can be guided back into the tablet
store so that they are not lost. The number of tablets to be
ejected can be freely chosen in order, for example, to meter
different quantities dependent on the requirement. This can
be carried out, in particular, when, using suitable
monitoring means (sensor, camera, counter), a tablet
receiving means that has remained empty in an unwanted
manner has been detected. Individual tablets can also be
supplied subsequently in conjunction with the selective
ejecting process. As a result it can be ensured that the
correct number of tablets passes into the target container
even in the event of the aforementioned error.
In an advantageous variant of the continuous method,
the tablets received to form a continuous uninterrupted row
are moved continuously to the tablet outlet. At the tablet
outlet, the tablets are ejected from their receiving means
in the desired counted number and are supplied to the target
container by means of the tablet outlet. Subsequent tablets
are guided past the tablet outlet and back to the tablet
store. The target container is changed whilst the tablets
are being returned. The cycle of supplying tablets to the
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target container and changing the target container can then
start again. Here too, high volume output rates can be
achieved with a high level of processing reliability. In
both of the aforementioned cases, without modifying the
device the number of tablets to be removed into the
respective target container can be varied and adapted to the
respective requirements simply by adapting the control
system.
A further advantageous variant of the continuous method
can be realized using a metering element which comprises at
least one continuing and defined row of consecutive tablet
receiving means, which in their number correspond to the
desired, counted number of tablets, and which are followed
by a segment without tablet receiving means. At the tablet
outlet, the tablets are ejected from the continuing, defined
row of tablet receiving means and are supplied to the target
container by means of the tablet outlet. Whilst the
subsequent segment without tablet receiving means passes the
tablet outlet, the target container is changed. The cycle of
supplying the tablets to the target container and changing
the target container can then start again.
In the last-named variant, the metering element is a
format part where the number of tablets of an individual
metering quantity is defined by the number of tablet
receiving means combined in the defined row. An expensive
control system can be omitted. Rather, reception, transport
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and ejection of the tablets is effected in conjunction with
each individual tablet receiving means or with the lack of
such, as a result of which expenditure on the device and
method is kept low whilst the level of process reliability
is high.
As an alternative to this, it can be expedient for the
metering element to rotate in a pulsed manner. In this
connection, no particular measures have to be taken for the
period of the target container change. Rather, the metering
pulse is measured in such a manner that a row of consecutive
tablet receiving means, which correspond in their number to
the desired counted number of tablets, is moved within the
named metering pulse to the tablet outlet where the tablets
are ejected from their respective tablet receiving means and
are supplied to the target container by means of the tablet
outlet. A rest pulse in which the metering element stands
still follows the metering pulse. The target container is
changed during the rest pulse. Following this, the cycle of
the metering pulse and the rest pulse can start again.
Within the framework of the invention different
possibilities are possible for the physical development of
the metering device. For example, it can be expedient to
realize the tablet receiving means as axially parallel bores
in the metering element or in the metering wheel. In a
preferred embodiment, the metering element includes a basic
body and entrainment means which project radially from the
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basic body, wherein the entrainment means lie spaced apart
from one another in the direction of rotation and as a
result in each case define between them a tablet receiving
means. The metering element consequently obtains a
structural shape comparable to a toothed wheel, the teeth of
which form the entrainment means and the tooth spaces of
which form the tablet receiving means. As a result, the
tablet receiving means are not only open at the side for
insertion of the tablets but are also open radially outward.
The opening in the radial direction enables, on the one
hand, optional tablet ejection also in said radial
direction. On the other hand, an advantageous possibility to
separate off tablet fragments, tablet dust or other unwanted
part quantities of the tablet store is created as a result.
With regard to the aforementioned separation, a
separation gap, which, with reference to the weight force
direction, is arranged in the bottom region and radially
outside of the metering element, is advantageously realized
in the fixed device part, wherein the separation gap is
defined at the side by the lead-in edge of the feeder
surface. In an expedient further development, the separation
gap is connected to a suction device. In particular, the
entrainment means, radially outside, in each case comprise a
tapered portion, by way of which they project into the
separation gap when running through the bottom position or
when running through the gap region.
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The lead-in edge of the feeder surface ensures that a
tablet passes into the tablet receiving means between two
entrainment means and at the same time prevents the tablet
from being able to drop down out of the tablet receiving
means through the separation gap. This naturally presupposes
a geometric adaptation of the tablet gap to the tablets to
be metered in such a manner that the width of the separation
gap is smaller than the smallest cross sectional measurement
of the tablets. At the same time, however, the separation
gap is wide enough to enable tablet fragments, tablet dust
or other unwanted part quantities of the tablet store to be
removed through the separation gap out of the tablet
receiving means. This latter can occur as a result of the
acting weight force. The suction device is used
advantageously in a supporting manner, as a result of which
the tablet receiving means and also the separation gap
itself are kept free in a reliable manner. This latter is
also promoted as a result of the portion of the respective
entrainment means which tapers into the separation gap. The
named portion, in this case, also helps to keep tablets
correctly as per specification in the respective tablet
receiving means and at the same time to avoid jamming,
tilting or the like.
The named entrainment means comprise in each case a
front entrainment face, with reference to the direction of
rotation, against which one tablet comes to abut in each
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case. The front entrainment faces can be aligned in a radial
manner. In an advantageous manner, in each case they are at
a positive entrainment angle with reference to the radial
direction, as a result of which they advance or transport
the respective tablets not only in the direction of rotation
but also, at the same time, lift them up from the feed
surface or the lead-in edges. This contributes to avoiding
any jamming or the like.
The feed surface is given central importance for
supplying the tablets laterally from the tablet store into
the respective tablet receiving means. It can be aligned in
a horizontal manner, the lateral feed being provided, for
example, by means of a vibratory movement or other measures
such as suction or blast air or the like. In particular,
however, the feed surface is inclined toward the metering
element at a plane angle of no more than 500 and in
particular of no more than 30 with respect to the
horizontal direction. As a result of the angle of
inclination, the tablets or the tablet store slip
automatically to the side without any additional effort onto
the metering element and also into the laterally open
metering receiving means. The aforementioned defining of the
plane angle ensures that the tablets are only pressed
lightly, brought about by the weight force of the tablets,
against the rotating metering element whilst the weight
force is supported overall at least for the most part by the
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fixed feeder face. The tablets consequently experience only
a slight load with a low level of abrasion and a low risk of
fracture.
In an advantageous embodiment, the metering device
comprises a tablet outlet with a counting device for the
tablets. As a result, reliable counting of the tablets can
be ensured even in the case of high operating speeds. There
is no need to monitor that
tablet receiving means is
properly filled by using image processing which is difficult
to realize at high speeds. As the counting takes places
directly at the tablet outlet, that is to say at the actual
end of the metering operation, it is ensured that the
counted number of tablets also actually pass into the target
container. Insofar as, in this connection, a lesser number
is ascertained, the missing number of tablets can be
supplied additionally by means of the variably actuatable
metering device according to the invention. All in all, it
ensures that each target container contains precisely the
desired number of individual tablets. 100% waste reduction
is possible.
In an expedient embodiment, in the direction of
rotation the metering element comprises a row of tablet
receiving means which, with reference to the plane of
rotation, are open in only one side direction and are closed
in the opposite side direction. A fixed wall part or a wall
part which rotates with the metering element can be used as
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a side closure. On one hand, there is low expenditure on the
device. On the other hand, simple possibilities for tablet
ejection are produced, in particular in the lateral
direction. As an alternative to this, it can be expedient
for the metering element to comprise on the two opposite
sides tablet receiving means which are open toward the
lateral faces of the metering element and which are
separated from one another by means of a central partition
wall. Where the tablets are fed from a tablet store on both
sides, the ejection rate can be increased.
In a preferred embodiment, several metering elements
which are realized as metering wheels are combined to form
one unit which is rotatable about a common rotational axis,
wherein the metering wheels are provide with spokes and run
through a common tablet store. The metering wheels, in this
case, are fed in an advantageous manner from a common tablet
store. Where the fill level is correspondingly sufficient,
the tablets can be moved through between the spokes and
consequently lead to a fill level balancing process.
Consequently, a sufficient tablet store abuts against all
the metering wheels. Using the named realization, as
required, one row or lane of target containers each can be
filled simultaneously by means of each metering wheel
whilst, as an alternative to this or in combination
therewith, it is possible to fill one row or lane of target
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containers with correspondingly increased tablet ejection by
means of several metering wheels.
In an expedient manner, the fixed device part comprises
a fill level sensor which is directed through between the
spokes onto the tablet store, and wherein, in particular,
the spokes are spaced apart from one another at irregular
angular distances. As a result, individual or all the
metering wheels running unintentionally empty is avoided
with only one single fill level sensor. The
irregular
angular distances between the spokes ensure that, in
particular in the case of pulsed operation, the spokes do
not always come to rest in the same position and
consequently cannot cover the fill level sensor.
Exemplary embodiments of the invention are described in
more detail below by way of the drawing, in which:
Figure 1 shows a schematic front view of a first
exemplary embodiment of a metering device according to the
invention with a rotatable metering wheel, at the
circumference of which are situated entrainment means for
tablets, in conjunction with a tablet store;
Figure 2 shows a sectional view of a detail of the
metering wheel according to Figure 1 with one single tablet
receiving means in conjunction with a feeder surface when
receiving one single tablet;
Figure 3 shows a variant of the arrangement according
to Figure 2 with two tablet receiving means located
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laterally opposite one another and associated feeder
surfaces;
Figure 4 shows an enlarged view of a detail of the
arrangement according to Figure 1 in the region of the
tablet receiving means and associated entrainment means;
Figure 5 shows a representation of a cutout of the
arrangement according to Figure 1 with details of a
separation gap arranged in the bottom region;
Figure 6 shows a variant of the arrangement according
to Figure 5 with a segmented separation gap;
Figure 7 shows an enlarged representation of a detail
of a portion of an alternative embodiment of the metering
wheel according to Figures 1 to 6 with tablet receiving
means combined in groups;
Figure 8 shows a longitudinal sectioned representation
of an embodiment of the metering device with several
metering wheels arranged along a common axis of rotation.
Figure 1 shows a schematic front view of a first
exemplary embodiment of a metering device 1 for tablets 2
according to the invention. The tablets 2 in the preferred
exemplary embodiment shown are micro tablets with a diameter
of 3.0 mm or less which are to be metered in each case in a
fixed number and filled into target containers (not shown)
such as two-piece capsules or the like. Larger tablets can
also be metered in place of micro tablets. In each case, the
metering is effected according to quantity by tablets 2
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being separated out into singles from a vibrated tablet
store 19, measured in the predefined quantity and then
supplied to the target container (not shown).
The metering device 1 includes a fixed device part 3
and a metering element which rotates in a plane of rotation
E. The metering element, in the preferred exemplary
embodiment shown, is realized as a metering wheel 5 which is
rotatable about a rotational axis 4. In the representation
according to Figure 1, the plane of rotation E lies in the
drawing plane, whilst the rotational axis 4 is perpendicular
thereto. In the following description, for the purposes of
simplicity, reference is made to the metering wheel 5.
However, the same also applies to other suitable metering
elements within the framework of the invention, for example
in the form of a rotating conveyor belt or a rotating
conveyor chain.
The metering wheel 5 comprises several tablet receiving
means 6 which, in the exemplary embodiment according to
Figure 1, are arranged uniformly and equidistantly along the
wheel circumference. The tablet receiving means 6 can be
bores, blind holes, indentations or the like in at least one
lateral face of the metering wheel 5. In the exemplary
embodiment shown, the tablet receiving means 6 are realized
as gaps between entrainment means 10 which protrude radially
outward from a basic body 9 of the metering wheel 5. As a
result, the tablet receiving means 6 are open radially
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outward. In each case, however, they are open in at least
one lateral direction, that is in a direction parallel to
the rotational axis 4 or perpendicular to the plane of
rotation E, as can also be seen from the representation
according to Figures 2 and 3. Each tablet receiving means 6
is defined by one entrainment means 10 each, at least to the
rear in opposition to the direction of rotation 11, in the
exemplary embodiment shown also to the front in the
direction of rotation 11.
The metering device 1 is shown in its usual operating
position relative to the downwardly acting weight force
direction which is specified by an arrow 27. The fixed
device part 3, that is not rotating with the metering wheel
5, includes a feeder surface 7 for the tablets 2, which is
described in more detail in Figures 2 and 3 and is arranged,
with reference to the weight force direction, in the bottom
region of the metering device 1 and of the metering wheel 5.
From an overall view of Figures 2 and 3 it can also be seen
that the feeder surface 7 is additionally also arranged
laterally next to the metering wheel 5. In the front view
according to Figure 1, the feeder surface 7 is curved in the
form of a circular ring segment following the development of
the tablet receiving means 6 and is arranged in such a
manner in the region of or at the level of the tablet
receiving means 6 that the tablet receiving means 6 are open
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directly above the feeder surface 7 in the lateral or axial
direction.
A large quantity of tablets 2 are supplied as bulk
material by means of a tablet feeder 24, said tablets
forming a tablet store 19 which rests on the feeder surface
7. The metering wheel 5 is provided in the region of its
basic body 9 with spokes 18, between which windows 22 are
realized. The spokes 18 are at irregular angular spacings to
one another. The fixed device part 3 includes a fill level
sensor 20 which is directed between the spokes 18 through
the windows 22 onto the tablet store 19, checks the fill
level and consequently ensures a sufficient fill level of
tablets 2 in the tablet store 19.
Also in the bottom region of the metering device 1, but
in the direction of rotation 11 of the feeder surface 7 and
downstream of the tablet store 19, the metering device 1 is
provided with a tablet outlet 16 as well as, as an option,
with an outlet 25 which is once again downstream and in this
case borders directly on the feeder surface 7. At least in
the upper region of the metering device 1, proceeding from
the feeder surface 7 up to at least the tablet outlet 16, a
cover 26 is provided as part of the fixed device part 3,
said cover covering the circumferential region of the
metering wheel 5 including its tablet receiving means 6 and
its entrainment means 10.
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Figure 2 shows a sectioned view of a detail of the
metering wheel 5 according to Figure 1 in the region of one
single tablet receiving means 6. In the region of the tablet
receiving means 6 the thickness of the metering wheel 5, at
least however the clearance of the metering receiving means
6 is matched in such a manner to the size of the tablets 2
that at least one single tablet 2, in this case precisely
one single tablet fits completely in the tablet receiving
means 6, a second tablet 2, however, is not able to pass
into the tablet receiving means 6 at the same time. From an
overall view with Figure 4 it can also be seen that the
feeder surface 7 borders on the metering wheel 5 by way of a
lead-in edge 8 at the level of the tablet receiving means 6
in such a manner that the tablet 2, proceeding from the
feeder surface 7, is able to pass into the tablet receiving
means 6. In other words, with reference to the radial
direction which is specified by an arrow 31 and proceeds
from the rotational axis 4, the lead-in edge 8 is arranged
relative to the radially inner bottom of the tablet
receiving means 6 such that a sufficiently large lateral
window of the tablet receiving means 6 remains for receiving
the tablet 2.
In an advantageous manner, the tablets 2 are
automatically fed laterally into the tablet receiving means
6 as a result of the weight force acting on the tablets 2.
To this end, the feeder surface 7 - measured in a plane
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perpendicular to the plane of rotation E - is inclined
toward the metering wheel 5 at a plane angle y. The plane
angle y is measured in the section shown according to Figure
2 between the feeder surface 7 and the horizontal direction,
and in this case is no more than 500, in particular no more
than the 30 provided in this case. As a result, on the one
hand a sufficient downwardly acting force is ensured. On the
other hand, the downwardly acting force is not excessively
large with the result that the tablet store 19 which rests
on the feeder surface 7 is not pressed excessively against
the metering wheel 5 and as a consequence is not made to
move excessively.
The feeder surface 7 can be made to vibrate
(horizontally, vertically or in a combination thereof) in a
manner which supports the named downwardly acting force. A
suction air draft or a blast air draft as well as a
combination of the two can also be used in a supporting
manner. In addition, it can be expedient to develop the
surface of the feeder surface 7 in a structured manner. The
surface structuring can be realized such that tablets 2 that
would like to settle into one tablet receiving means at the
same time and in this case mutually obstruct one another,
are influenced such that in a preferred manner one of said
tablets 2 is slipped in. This can be achieved in particular
as a result of a wave profile transversely to the inlet
direction, peaks and troughs extending transversely to the
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plane of rotation E and comprising a wave length which
corresponds to the distance between the tablet receiving
means 6 and the entrainment means 10. As a result, the
tablets 2 are aligned spaced apart from one another by a
distance which corresponds to the distance between the
tablet receiving means 6, as a result of which orderly
merging is promoted.
Corresponding to the representation according to Figure
2, the plane of rotation E lies almost approximately, in
this case precisely parallel to the weight force direction
which is specified by an arrow 27. The rotational axis 4
(Figures 1 and 4) is consequently horizontal thereto.
Consequently, the plane of rotation E and the weight force
direction 27 enclose an angle of inclination a = 0 .
However, a slight inclination of the rotational axis 4 and
consequently of the plane of rotation E can also be
expedient, in this case the angle of inclination a
expediently being no more than 30 and in particular no more
than 15'.
In the exemplary embodiment according to Figures 1 and
2, the metering wheel 5 comprises only or precisely one row
of tablet receiving means 6 in the direction of rotation.
Corresponding to the Cross sectional representation
according to Figure 2, said tablet receiving means, with
reference to the plane of rotation E, are open in only one
lateral direction which is specified by an arrow 28. They
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are closed in the opposite lateral direction, for which
purpose in this case a wall part 30 is provided as a cover.
The wall part 30 can be part of the fixed device part 3. In
the exemplary embodiment shown, it is part of the metering
wheel 5 and is entrained by the same. As an alternative to
this, a realization as is shown in Figure 3 can be
expedient. In this connection, on the two opposite sides the
metering wheel 5 comprises one rotating row of tablet
receiving means 6, 6' each, which are separated from one
another by means of a central partition wall 17. In
this
connection, the tablet receiving means 6, 6' are open in
each case toward the associated lateral face of the metering
wheel 5 in the associated lateral directions specified by
arrows 28, 29. Analogously to the representation according
to Figure 2, in this case feeder surfaces 7, 7' with lead-in
edges 8, 8' border on the two sides.
It can also be seen from the representation according
to Figure 2 that a separation gap 12, which is arranged in
the bottom region and radially outside the metering wheel 5
with reference to the weight force direction 27, is realized
in the fixed device part 3. The separation gap 12 is defined
radially inside, in this case therefore upward, by means of
the lead-in edge 8 of the feeder surface 7. The separation
gap 12 is defined by the wall part 30 in the opposite
lateral direction such that the tablets 2 abut against the
lead-in edge 8 on the one side and against the wall part 30
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on the opposite side. The width of the separation gap 12
shown in cross section here is smaller than the smallest
cross sectional dimension of the tablet 2 such that the
tablet 2 gets caught on the lead-in edge 8 and is not able
to drop down through the separation gap 12 out of the tablet
receiving means 6.
In a representation of a cutout, Figures 5 and 6 each
show variants of the arrangement according to Figures 1 and
2 in a sectioned front view with details for the development
of the separation gap 12 shown in Figures 2 and 3.
Corresponding to the representation according to Figure 5,
the separation gap 12 extends in the direction of rotation
of the metering wheel 5 over an angular region which covers
several tablet receiving means 6. The separation gap 12 is
connected to a schematically indicated suction device 13 so
as to transmit pressure and flow. A suction air flow is
created which, on the one hand, sucks tablets 2 into the
respective tablet receiving means 6 corresponding to the
representation according to Figure 2. On the other hand, it
is clear from looking at Figures 2 and 5 that tablets 2 that
are undersized, tablet fragments, tablet dust or the like
are not able to get caught on the lead-in edge 8 and are
consequently sucked out of the tablet receiving means 6
through the separation gap 12. In the alternative embodiment
according to Figure 6, the separation gap 12 is divided into
different segments, only each next but one segment being
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connected to the suction device 13. During the rotating
movement of the metering wheel 5, each tablet receiving
means 6 is consequently acted upon in an intermittent or
pulsating manner with negative pressure, which can promote
the slipping-in of the tablets 2 and the sucking-up of
unwanted material.
With reference to Figures 2 and 3 again, it can also be
seen that in the preferred exemplary embodiments shown the
entrainment means 10 comprise, radially outside, in each
case a portion 14 which tapers in the direction of the width
or axis and by way of which they project into the separation
gap 12. On the one hand, as a result, clogging of the
separation gap 12 is prevented. On the other hand, the
entrainment means 10 are in full surface contact with the
tablets 2 even where the tablets 2, corresponding to the
representation according to Figure 2, come to rest in part
in the separation gap 12.
Figure 4 shows an enlarged view of a detail of the
arrangement according to Figure 2 corresponding to the
intersection line IV-IV indicated there. The radial
direction which proceeds from the rotational axis 4 is
specified by an arrow 31. It can be seen that the
entrainment means 10 comprise, with reference to the
direction of rotation, a front entrainment face 15 against
which the respective tablets 2 abut as a result of the
rotational movement of the metering wheel 5. In the
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preferred exemplary embodiment shown, the entrainment face
15 lies at a positive entrainment angle with
reference to
the radial direction 31. Corresponding to the representation
according to Figure 4, the entrainment angle p is positive
in such a case in which the entrainment face 15 is inclined
in the direction of rotation 11 proceeding from radially
inside to radially outside. As a result, the feeder surface
7 exerts on the tablet 2 not only a feed force in the
direction of rotation 11, but also in opposition to the
radial direction 31 a lifting force which reduces the
pressing pressure of the tablet 2 onto the lead-in edge 8 or
which even raises the tablet 2 from the lead-in edge 8 in
opposition to the radial direction 31.
Figure 8 shows a longitudinal sectional representation
of an embodiment of the metering device 1 with several
metering wheels 5 which are arranged on a common axis
component 35 along the axis of rotation 4. Each individual
metering wheel 5 has associated therewith at least one
feeder surface 7 each. The individual metering wheels 5 and
feeder surfaces 7 correspond in their design to the
previously described designs. Viewing this together with
Figure 1 it is clear that a tablet store 19 which rests on
the feeder surfaces 7 is able to be distributed through the
windows 22 between the spokes 18 in a uniform manner such
that all the metering wheels 5 are loaded from the same
tablet store 19 at a sufficiently uniform fill level. The
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fill level of the common tablet store 19 can be monitored
through the windows 22 between the spokes 18 by just one
single fill level sensor 20.
With reference to the afore-described Figures, the
method according to the invention for the metering of
tablets in terms of quantities by means of the metering
device 1 according to the invention is realized as follows:
A fairly large volume of tablets 23 is initially poured
in as bulk material through the tablet feed 24, as a result
of which a tablet store 19 is realized resting on the feeder
surface 7 in the bottom portion of the metering device 1.
The metering wheel 5 is then set into motion rotating about
the rotational axis 4 in the direction of rotation 11. In
this connection, tablets 2 are supplied laterally from the
tablet store 19 to the tablet receiving means 6 in the
above-described manner by means of the feeder surface 7. In
this case, the tablet receiving means 2, in dependence on
the geometric adaptation to the form and size of the tablets
2, in each case receive one or several, in this case in a
preferred manner precisely one tablet 2. The tablets 2
received in this manner, lying in the tablet receiving means
6, are transported to the tablet outlet 16 by means of the
metering wheel 5 and there, in a counted number are supplied
from the tablet receiving means 6 through the tablet outlet
16 to the target container (not shown) which has already
been mentioned in the introduction. In the region of the
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feeder surface 7, the tablet receiving means 6 are open at
the side such that they are able to receive the tablets 2.
In the remaining circumferential region, the metering wheel
is covered by means of the cover 26 in such a manner that
the received tablets 2 are not able to fall unintentionally
out of their tablet receiving means 6.
In a first preferred embodiment of the method according
to the invention, the metering element rotates continuously.
In other words, the metering wheel 5 rotates about its
rotational axis 4 at at least approximately uniform angular
speed. Corresponding to the embodiment according to Figure
1, in which the tablet receiving means 6 are distributed
uniformly over the circumference of the metering wheel 5,
the tablet receiving means 6 continuously receive tablets 2
from the tablet store 19. In order to ensure that from this
a certain metering quantity, that is a certain number of
tablets 2 passes into the target container, the tablets have
to be counted and have to pass in the counted quantity from
the tablet receiving means 6 through the tablet outlet 16
into the target container.
In a first variant of the continuous method, the
tablets 2 are selectively ejected for this purpose from
their tablet receiving means 6. This can be effected, for
example, in the upper portion of the metering device 1 which
is shown as having been removed in Figure 1. The ejected
tablets 2 fall back into the tablet store 19. As indicated
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schematically in the left top third of the representation
according to Figure 1, contiguous rows 31 of tablet
receiving means 6 with tablets 2 entrained therein as well
as rows 32 of empty tablet receiving means 6 without tablets
2 are formed alternately as a result of said selective
ejection. Tablet receiving means with tablets 2 are
symbolized here in a schematic manner by means of circles
whilst empty places, that is tablet receiving means without
tablets are symbolized by means of crosses. Each individual
contiguous row 31 includes overall the desired, counted
number of tablets 2 which is supplied to the target
container through the tablet outlet 16. The row 32 following
this in the direction of rotation 11 is matched in its
number of empty tablet receiving means 6 in such a manner to
the rotational speed of the metering wheel 5 that when the
movement of the metering wheel 5 is uninterrupted, a time
window is created in which no tablets 2 are separated off
through the tablet outlet 16. In said time window, that is
whilst the row 32 of empty tablet receiving means 6 passes
the tablet outlet 16, the target container is changed. The
new target container is then filled from the following row
31, the tablet receiving means 6 of which is loaded with
tablets 2. A cycle in which, with the metering wheel 5
rotating continuously, target containers are alternately
filled with a desired, counted number of tablets 2 and then
are exchanged, is produced from the above pattern.
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A camera 23, by means of which the regular loading of
the tablet receiving means 6 with or without tablets 2 can
be checked by way of image-processing monitoring, can be
arranged as an option, on the entry side of the tablet
outlet 16, in this case in the upper portion of the metering
device 1. If a tablet 2 is missing from the provided tablet
receiving means 6, counter measures can be taken, for
example by subsequently delivering one single tablet 2 or by
interrupting the ejection operation from the tablet outlet
16. In particular, however, it is expedient, corresponding
to the representation according to Figure 1, to provide the
tablet outlet 16 with a counting device 21 for tablets 2. In
a preferred manner, a small bore (not shown) branches off
from the tablet receiving means 6 for this purpose, the
counting device 21 being arranged outside said bore. The
sensor of the counting device 21 looks through the named
bore into the tablet outlet 16 and counts the tablets 2
moving through. A small cavity in which a certain over
pressure prevails is realized between the sensor of the
counting device 21 and the bore. As a result, the counting
device 21 or the sensor thereof avoids getting dusty in
spite of a high level of dust developing during the metering
operation. The bore too is always kept free such that
reliable counting is possible. Unlike in the case of optical
image processing, precise counting can be carried out even
at high throughput speeds and high throughput volumes in
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this case with low technical expenditure. In particular,
however, it is ensured that only those tablets 2 which are
actually separated off through the tablet outlet 16 and
which pass into the target container are counted. Faults
caused by tablets 2 not being separated off and jamming in
the tablet receiving means 6 as well as by tablets which
have fallen out beforehand are excluded by said form of
counting operation.
In a second variant of the continuous method according
to the invention, the tablet receiving means 6 which are
continuously loaded with tablets 2 are guided continuously
to the tablet outlet 16. Deviating from the afore-described
method, the tablets are not ejected selectively en route.
Rather, the tablets 2 are not ejected from their tablet
receiving means 6 in the desired, counted number until at
the tablet outlet 16 and they are supplied to the target
container by means of the tablet outlet 16. The ejection
operation is interrupted once the predefined or desired
number is reached. Subsequent tablets 2 which are entrained
in the respective tablet receiving means 6 are guided past
the tablet outlet 16 and back to the tablet store 19. The
target container is changed during said returning of the
tablets 2. Following this, the cycle of supplying tablets to
the target container and changing the target container
starts again.
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A third variant of the continuous method according to
the invention makes use of an embodiment of the metering
wheel 5 which is shown in portions in a frontal view in
figure 7. The metering wheel 5 comprises at least one, in
this case several continuous rows 33 which are defined in
the direction of rotation 11 of consecutive tablet receiving
means 6. The tablet receiving means 6 of one single row 33
correspond in their number to the desired number of tablets
2 to be counted. Each defined row 33 is followed by a
segment 34 in which no tablet receiving means 6 are
realized. The tablet receiving means 6 receive the tablets
2 in the above-described manner. With reference at the same
time to the remaining Figures, the tablets 2 are now ejected
from one single defined row 33 at the tablet outlet 16 and
are supplied to the target container by means of the tablet
outlet 16. With the metering wheel 5 continuing to rotate
continuously, the segment 34 without tablet receiving means
6 then passes the tablet outlet 16 such that no tablets 2
are separated off during this period. The length of the
segment 34 measured in the direction of rotation 11 is
matched to the rotational speed of the metering wheel 5 in
such a manner that a sufficient time window remains to
change the target container. The changeover is therefore
undertaken whilst the segment 34 without tablet receiving
means 6 passes the tablet outlet 16. With the metering wheel
rotating continuously, this is then followed by the next
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defined row 33 with filled tablet receiving means 6 such
that the cycle of supplying tablets to the target container
and changing the target container can start again.
Within the framework of the invention a pulsed method
can be provided as an alternative method. In this
connection, the metering wheel 5 rotates in pulsed manner.
The metering wheel 5 realizes a rotational movement during a
metering pulse. The metering pulse is measured in such a
manner that consecutive tablet receiving means 6, which
correspond in their number to the desired, counted number of
tablets 2, pass the tablet outlet 16 within said metering
pulse. There the tablets are ejected from their respective
tablet receiving means 6 in the named number and are
supplied to the target container by means of the tablet
outlet 16. The metering pulse is followed by a rest pulse in
which the metering wheel 5 stands still. The target
container is changed during the rest pulse. As soon as this
happens, the cycle of metering pulse and rest pulse starts
again.
In all the variants of the method according to the
invention, the fill level in the tablet store 19 can be
monitored in particular using the fill level sensor 20
according to Figure 1, image-processing monitoring by means
of the camera 23 and in particular counting of the tablets 2
actually ejected from the tablet outlet 16 can be monitored
by means of the counting device 21. If, in this connection,
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it is ascertained that not enough tablets 2 have been
ejected, the corresponding missing quantity can be supplied
additionally in a following operation.
It has been pointed out further above that as a result
of the development according to the invention, tablets 2
which stick to one another in the form of duplicates or
triplicates are stopped from passing into the tablet
receiving means 6. As therefore only tablets 2 as per
specification are removed from the tablet store 19, the
concentration of tablets 2 which are not as per
specification is increased over the course of a fairly long
metering operation in the tablet store 19. Consequently, it
can become necessary from time to time to empty the tablet
store 19 from the metering device 1. The outlet 25 shown in
Figure 1 is provided for this purpose. As a result of
rotating the metering wheel 5 in the opposite direction to
the usual direction of rotation 11, the tablet store 19 is
removed through the outlet 25 and can be replaced by fresh
tablets 2 through the tablet feed 24.
Insofar as not described expressly to the contrary, the
different physical embodiments and method variants concur
with one another in their remaining features, references and
options. All the described embodiments are advantageous
examples of the invention, but do not exclude deviating
embodiments within the framework according to the invention.
