Note: Descriptions are shown in the official language in which they were submitted.
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Munich 23rd April 2004
Our ref: PM 1295-03W0 MAC/mos
Applicants/proprietors: POLY-CLIP SYSTEM GmbH & Co. KG
Office ref: New application
Poly-clip System GmbH & Co. KG
Westerbachstr. 45, 60489 Frankfurt/Main
Elliptical toothed belt drive
The invention concerns an apparatus for closing a tube-like or bag-
like packaging casing filled with filling material, in particular sausage
meat, comprising means for constricting the packaging casing and forming
a filling material-free plait end portion, closure means for fitting and
closing at least one closure clip around the plait end portion and a drive
for the constricting means and for the closure means.
If for example there is a wish for sausage meat, putty materials or
sealing materials to be packaged in bags or film tubes (which are closed
at one end), then that is effected in known manner by the tube-like or
bag-like packaging casing being filled with filling material by a filling
machine. At the end of the filling operation or shortly before same the
filling machine outputs a synchronization pulse with which the closing
operation by means of the apparatus described in the opening part of this
specification is triggered. That begins with the filled packaging casing
being constricted in a first working step by closure of the means for
constricting the packaging casing, for example two pairs of displacement
shears, in a radial direction with respect to the central axis of the
i
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packaging casing, to form a short plait portion (displacement}. Then, in a
second working step, the two pairs of displacement shears are moved
away from each other in the axial direction, that is to say in the
longitudinal direction of the packaging casing (spreading), whereby filling
material disposed there is displaced so that a filling material-free plait end
portion of the desired length is formed between the two pairs of
displacement shears. Thereupon, in a third working step, a closure clip
which is introduced into the path of a punch - this is part of the closure
means - is fitted onto the packaging casing in the region of the plait end
portion and deformed between the punch and a die - this is also part of
the closure means - in such a way that it is applied around and closes the
plait end portion. With an arrangement of two punches and dies the plait
end portion can be closed by two closure clips arranged in mutually
juxtaposed relationship in the axial direction and possibly severed in the
same working operation between those two closure clips. After the
closure operation in a fourth working step the constricting means and the
closure means are moved back into their starting position and a new
working cycle can begin with the filling operation.
The constricting means and the closure means are driven by a drive
2o for example comprising an electric motor and a transmission means
connected on the output side thereof, in such a way that the movements
thereof are coupled together by drive output shafts of the transmission
means and associated cam disks. The control curves of the cam disks
implement the movements of the constricting means and the closure
means in the desired sequence in respect of time. Accordingly a
revolution of the cam disks results in a working cycle.
DE 196 O1 720 A1 addresses the problem that opening of the
displacement shears, particularly when dealing with sausages of relatively
large diameter, does not last sufficiently long to introduce a sufficient
amount of filling material into the packaging casing. It is therefore
proposed that a non-constant drive speed is provided, for example by a
freely controllable three-phase current servo drive as part of the drive
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arrangement in order to achieve an advantageous shears opening
performance. Accordingly the operating procedures in respect of time are
afforded by superimposition of the non-constant drive speed curve with
the control curves of the cam disks. In accordance with that publication
the rotary speed of the motor is controlled in such a way that the
displacement shears remain open for a long time at a slow drive speed,
which facilitates introduction of the 1=Illing material, and the other
movement phases are accelerated so that the long open times of the
displacement shears are compensated and the duration of a working cycle
1o does not need to be increased in length, even when dealing with sausages
of large diameter.
It is further known from EP 0 935 421 B1 for the rigid coupling
between the movements of the pairs of displacement shears and the clip
levers to be abolished by virtue of the individual working cycles of the
closure procedure, namely, displacement, spreading, fitting and closing
the closure clips, being at least partially controlled independently of each
other. In that way the sequence of movements involved can be adapted
to the respective product. There is in particular the possibility that when
dealing with glutinous-pasty filling material, the spreading operation is
2o caused to take place more slowly but the operations of fitting and closing
the closure clips are caused to take place more quickly, and in that way
the productivity when producing such sausages can be~ increased. In
accordance with that solution, electric motors are actuated by a
programmable control unit as part of the drive in such a way that the
rotary speed is altered in dependence on the respectively desired working
speed for each working step within a cycle.
Apparatuses with such a drive however consume a relatively large
amount of energy, in particular due to the apparatus being periodically
started up and slowed down.
Finally, DE 42 41 231 discloses a wrap transmission arrangement
with a periodically variable transmission ratio, in particular a toothed belt
transmission arrangement, which is used in those cases in which the ratio
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of the angular speeds or the ratio of the torques of the drive input and the
drive output shafts is to be of a variable value. For example the power
requirement of a drive can be evened out by means of such a
transmission arrangement if the driven machine has a high torque
requirement only during a part of the revolution. Another situation of use
involves being able to slow down the speed of a movement for a part of
the revolution in order to be able to perform a working step more
precisely.
The object of the invention is to provide a closure apparatus whose
drive is better adapted to the desired process sequence and at the same
time requires less energy.
In an apparatus of the kind set forth in the opening part of this
specification that object is attained in that the drive has a non-uniformly
transmitting transmission means which converts a uniform drive input
movement into a periodic, non-uniform drive output movement, wherein
the transmission ratio of the transmission means is such that the drive
output speed when fitting the closure means is reduced with respect to
the drive output speed in the constriction and displacement operations.
The invention entails the realization that the torque requirement is
2o very different within a working cycle. More specifically, in the working
steps which require a lower working speed - that is to say a lower rotary
speed of the drive output shaft of the transmission means {drive output
speed) - the torque requirement at that drive output shaft is generally
also increased. For example, when dealing with glutinous-pasty filling
material, the displacement and spreading movements take place slowly,
but at the same time the greatest (linear} force, that is to say the
greatest drive output moment, is required. In a corresponding manner, in
cases in which the operations of fitting and closing the clips take place
more slowly, for example when dealing with filling material of low
viscosity, that process is the one which requires most force and thus drive
output moment. In addition the invention entails the realization that the
torque requirement and the variation, which is inversely proportional
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thereto, in the required working speed recur periodically in each working
cycle, that is to say after each revolution of the cam disk. The use of a
non-uniform transmission ratio means that the drive input speed within a
cycle changes periodically and in inverse proportion to the drive torque.
The delivery cycle of the drive with a periodically non-uniformly
transmitting transmission means is therefore ideally adapted to the take-
off cycle, that is to say the desired process sequence with periodically
recurring working steps involving a non-uniform working speed or non-
uniform torque requirement.
1o As the dimensioning of the drive motor must be designed in
accordance with the torque requirement maximum, the apparatus
according to the invention thus has the advantage that, unlike the
situation in the state of the art, the torque requirement is already reduced
at the drive input side in the region of the peaks, that is to say, during the
slow movement phase. The motor power to be estimated can thus be
reduced in comparison with the known drives with a controlled motor
speed, whereby it is possible to save on cost and energy. A further
advantage of the invention is that the variation in the working speed, at
the transmission side, means that braking and acceleration processes
which are required during a cycle on. the part of the drive motor can be
avoided or at least reduced and therefore the demands on the dynamics
of the motors and the power thereof and thus the power consumption can
also be reduced for that reason.
Advantageous developments of the apparatus according to the
invention are set forth in the appendant claims.
The invention is described in greater detail hereinafter by means of
an embodiment by way of example with reference to the Figures in which:
Figure 1 shows individual working steps of a closure operation of an
embodiment of the apparatus according to the invention in relation to the
drive output speed,
Figure 2 is a diagrammatic view of a first embodiment of a
periodically non-uniformly transmitting transmission means, and
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Figure 3 is a diagrammatic view of a second embodiment of a
periodically non-uniformly transmitting transmission means.
The upper curve 10 in Figure 1 shows a diagrammatic configuration
by way of example of the drive output speed or rotary speed in
dependence on the angle of rotation of the drive output shaft of the
transmission means. The illustrated speed variation covers a full
revolution of the drive output shaft and accordingly is periodically
repeated. In this embodiment the variation in speed arises on the one
hand out of the use according to the invention of a non-uniformly
transmitting transmission means whose transmission effect on the other
hand is superimposed with a drive speed which is regulated in accordance
with a preselected control program.
If for example a toothed belt drive with an elliptical drive gear is
used as the non-uniformly transmitting transmission means, then the
variation in rotary speed of the drive output shaft fluctuates
approximately sinusoidally. As in the illustrated configuration of the curve
10, that fluctuation can be stretched phase-wise and compressed phase-
wise so that over a full revolution the result is an asymmetrical variation
in the drive speed. Compression or stretching of the individual phases can
be adapted for example to the duration of the filling operation or other
demands. In addition the amplitude of the drive output speed can be
compensated at points by an increase and/or reduction in the speed of
rotation of the motor and also increased at another location. In that way
it is possible to achieve even more precise adaptation of the delivery cycle
of the drive to the take-off cycle, with the advantages of the apparatus
according to the invention still being used (at least in phase-wise
manner). For, although additional regulation of the drive speed can
sometimes be required the use of a non-uniform transmission means
provides that the regulating intervention does not have to be so severe
and that an increased torque is available in operating steps involving a
slow working speed.
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The drive output speed is additionally superimposed with the
control curves, shown under the curve 10, in respect of the cam disks, to
afford a desired movement of the means for constricting the packaging
casing and forming a filling material-free plait end portion as well as the
closure means. Curve 12 shows a typical configuration in respect of the
deflection of pairs of displacement shears as the means for constricting
the casing. They move in a radial direction with respect to the axis of a
sausage to be closed, for the purposes of displacing the filling material.
With a rotation of the drive output shaft through 45°, the
displacement
process begins and it ends after a further 80°. It is only thereafter
that
the spreading operation begins, curve 14. In that case, in the course of a
revolution of the drive output shaft through a further 45°, the pairs
of
displacement shears are moved away from each other in the axial
direction with respect to the sausage and thus the sausage meat is
displaced from a region of the casing, which is to be closed, while
constriction of the displacement shears is maintained. A radial movement
of upper and lower clip levers begins approximately simultaneously with
the spreading of the pairs of displacement shears, curves 16 and 18. In
the illustrated embodiment, in that working step the lower clip lever pivots
2o with a die under the filling material-free plait end portion while at the
same time the upper clip lever moves with a punch - the clip levers, the
die and the punch are parts of the closure means - in the opposite
direction from above towards the die. It is only after the spreading
operation is already concluded and a filling material-free plait end portion
is therefore formed between the pairs of displacement shears, that the
lower clip lever with the die reaches the point of maximum approach to
the central axis of the sausage casing. It is at that point that the closure
or clipping operation begins, marking 20. While the lower clip lever still
remains in the point of maximum approach, the upper clip lever with the
punch continues to move towards the center. In that situation the closure
clip is changed in shape until it forms a fixedly fitted closure around the
plait end portion of the tubular casing. In that working step the
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transmission ratio of the toothed belt transmission means is selected to be
short, as the local minimum in the curve IO shows. That provides a
minimum drive output speed at the beginning of the clipping operation
and at the same time the torque at the drive output shaft is increased
during the clip shaping step or clipping operation.
After the conclusion of the clipping operation the upper and lower
clip levers open and release the fitted closure clip. Almost at the same
time the pairs of displacement shears open in a radial direction. In that
case only a low level of torque is required at the drive output shaft.
Consequently, a long transmission ratio can be selected for that working
step. Finally the pairs of displacement shears are retracted in the axial
direction into their original position and a full working cycle is concluded.
The transmission ratios can be altered for example by suitable adaptation
of the eccentricity of the gears and/or the length ratios between the major
axes of the ellipse. The torque maximum or the speed minimum in
respect of the curve 10 can also be brought into coincidence by a phase
displacement with each desired working step, which permits the apparatus
according to the invention to be used to close a packaging casing filled
with widely differing filling material.
The periodically non-uniformly transmitting transmission means as
shown in Figure 2 is a toothed belt transmission means 200 with a first
elliptical gear 202 and a second elliptical gear 204. The, two gears 202,
204 are coupled by way of a toothed belt 208. The first gear 202 is of
more pronounced elliptical shape than the second gear than the second
gear and provides for the non-uniform transmission effect. The ellipse
shape of the second gear serves essentially only for length compensation.
Another example of a periodically non-uniformly transmitting
transmission means is shown in Figure 3. This involves a toothed belt
transmission means 300 with three gears 302, 304 and 306 which are
3o coupled by way of toothed belt 308 and which are mounted eccentrically.
Two of those, 302 and 304, are round and serve for the drive input and
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drive output, while the third 306 is a compensating gear for length
compensation.
The illustrated transmission means respectively convert a uniform
drive input movement, that is to say a constant rotary drive speed, into a
periodically non-uniform drive output movement. In the illustrated
transmission means the drive input and drive output side are not fixed.
The periodicity can be doubled in the case of symmetrical arrangements
like that of Figure 2.
Instead of the toothed belt transmission means 200, 300 it is also
possible in each case to use a chain transmission means involving the
same arrangement. Other arrangements can also be envisaged: for
example a different transmission performance can also be achieved by an
elliptical and at the same time eccentrically mounted gear in combination
with a plurality of gears which are mounted in phase-displaced eccentric
relationship. Instead of a toothed belt transmission means or a chain
transmission means, it is also possible to use a non-uniformly transmitting
gear transmission.
Finally, it is also possible for a plurality of the specified forms of
transmission means to be combined by being connected in succession.
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