Note: Descriptions are shown in the official language in which they were submitted.
1
Apparatus and method for the production of foods
The invention relates to an apparatus and a method for the production of foods
from pasty or
liquid masses, in particular a stuffing machine for sausage production.
Machines and equipment in food production, in particular stuffing machines,
such as vacuum
stuffing machines, spooling lines, clippers, etc., often use switch-mode power
supplies and
electronically commutated drives. In order to satisfy the legal requirements
for
electromagnetic compatibility (EMC), filter measures against electrical faults
are necessary.
These EMC filters cause leakage currents that can trigger ground fault
interrupters (GPIs) - in
particular where they serve operator protection. This makes operation at
outlets with a
ground fault interrupter for operator protection impossible. With a ground
fault interrupter
having higher tripping thresholds, however, the machines and buildings are
only protected
against fire. The machines and systems are therefore often either fixedly
connected to the
mains, equipped with an isolating transformer, or operated at special outlets
without ground
fault interrupters. Another option is to lead the leakage currents - possibly -
to the neutral
conductor. Operator protection is achieved by way of the grounding conductor
(PE).
However, the aforementioned measures have significant drawbacks.
In particular in food production, compact and mobile machines are needed that
can be
employed in a flexible manner. This includes e.g., that the machines can
easily be moved out
of production areas to another location for cleaning purposes. Attachments,
such as a
spooling line, clippers, a suspension device, etc., are often used in a
flexible manner in
particular in filling lines, so that the individual machines must be movable
for the production.
This is not possible with fixedly connected machines.
Machines with a built-in isolating transformer become larger and heavier,
which also
hampers mobility - just like isolating transformers which are mounted in
external housings
and can be connected upstream of the machine. In the isolating
transformations, the leakage
currents and therefore also the insulation fault current remain on the
secondary side of the
transformer. The detection of whether a compensation current flows, however,
can only be
measured and detected by the ground fault interrupter on the primary side of
the transformer.
Therefore, no protection is ensured by the ground fault interrupter.
Especially in wet rooms,
however, this protection is highly desired. The placement and marking of
special outlets
which are not protected with ground fault interrupters also increase the
complexity and
reduces the flexibility and safety.
Date Recue/Date Received 2020-06-12
2
If the filter currents are to be dissipated via the neutral conductor, special
filters and inverters
are required. The leakage currents of the cable shields continue to dissipate
through the
grounding conductor because the shields can be connected to the neutral
conductor. A
separate neutral conductor is not present in all types of mains, so this
solution cannot be
employed worldwide. Furthermore, with more comprehensive EMC filtering (larger
and
oversized filters), the high-frequency leakage currents can be reduced. For
example, more
efficient EMC input filters can be used in combination with additional output
filters, but at
higher costs. Another drawback of this measure against leakage currents is the
space
problem that arises especially when retrofitting larger and additional
filters.
The use of ground fault interrupters with a high tripping threshold is also
conceivable, but
involves considerable risks since the higher leakage currents cause shifts in
the potential and
the permissible contact voltage of at most of 50 VAC can be exceeded. In
addition, damage
to the individual components of the system is possible.
Starting from there, the present invention is based on the object of providing
an improved
apparatus and an improved method for food production which can be employed in
a flexible
manner and at the same time can be operated safely.
According to the invention, this object is satisfied with the features as
described herein.
The apparatus for the production of foods is, in particular, a stuffing
machine for the
production of sausages with a load circuit that generates a leakage current.
The apparatus
comprises a motor to drive, for example, the conveyor of a stuffing machine.
In order to
satisfy the legal requirements for electromagnetic compatibility, filter
measures against
electrical faults are required. The apparatus also comprises, in particular, a
frequency
converter. Due to this at least one filter and a cable to the motor, leakage
currents can arise
that could trigger a ground fault interrupter. For this reason, a leakage
current compensator is
provided according to the present invention with a device for detecting a
leakage current and
a device for generating a compensation current that is directed opposite to
the leakage
current and is superimposed with the leakage current, such that the leakage
current is
reduced, is in particular substantially eliminated. The leakage current is
there at least
reduced to the extent that it is below the threshold for triggering a GFI
ground fault
interrupter. The leakage current is preferably completely eliminated.
This entails the advantage that the currents cancel each other and the ground
fault
interrupter is no longer tripped due to increased leakage currents. Only
insulation faults or
dangerous body currents can be detected and lead to tripping. E.g. a frequency
range of 100
Hz to 300 kHz should be covered. The frequency range 50-60 Hz may not be
compensated
so that operator protection
Date Recue/Date Received 2020-06-12
3
remains in effect. The invention has the advantage that full operator
protection is ensured and the
apparatus can nevertheless be moved since it does not have to be fixedly
installed and no large
and heavy isolating transformer needs to be integrated. This also entails,
inter alia, better hygiene
due to simplified cleaning of the machine and great flexibility with regard to
the assembly of the
individual machines of a stuffing line. The leakage current compensator is
inexpensive and can
also be easily retrofitted into existing machines. In comparison to isolating
transformer, high
energy efficiency arises. With the present invention, a wide voltage range can
be covered such
that the apparatus can be used worldwide. Insulation faults or device faults
are detected 100%
with upstream ground fault interrupters. With the present invention, currents
up to 1 A can be
compensated.
The compensation current can be shifted in its phase relative to the leakage
current by 180 and
have substantially the same amplitude. The leakage current can then be
completely
compensated. Since it is sufficient to have the leakage current be below the
threshold for
triggering the ground fault interrupter, the leakage current can be e.g. at
approx. 40% of the
switching threshold of the ground fault interrupter. It is essential that the
leakage current is e.g.
lower than the trigger threshold.
The device for generating a compensation current advantageously comprises an
amplifier and a
capacitor network (as filter capacitors) via which the compensation current
can be supplied to
individual phases of a multi-phase system, in particular to at least one of
the three phases,
preferably all three phases of a three-phase system. For example, the current
can be detected in
all three phases and the leakage current of each phase can be determined by
calculating the
difference, and a respective compensation current is conducted to the
corresponding phases in
terms of symmetrical load distribution.
Advantageously, the compensation current generated by the amplifier is
distributed to the three
phases in such a manner that the leakage current is overall compensated or
sufficiently reduced.
The leakage current compensator is preferably located between a ground fault
interrupter (GFI)
and the EMC filter, i.e. the EMC input filter. The leakage currents generated
by the filter can then
be compensated, but also other leakage currents generated in the load circuit
by parasitic
coupling, in particular due to long motor leads and/or a frequency converter.
According to one preferred embodiment, the leakage current compensator is
installed in a device
upstream of the apparatus. The apparatus comprises in particular a plug which
is connectable to
the leakage current compensator by way of an outlet, in particular an
industrial outlet. The
apparatus therefore then comprises this device which in turn can be connected
via an outlet, in
particular an industrial outlet, to the mains by way of a plug, in particular
an industrial plug. This
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entails the advantage that the apparatuses can be flexibly plugged in at
various locations and a
respective device can be easily retrofitted. A respective upstream device
could then also be used =
for various apparatuses. But it is also possible that the apparatus is fixedly
connected to the
upstream device by use of a cable, and then connectable to an outlet, in
particular an industrial
outlet, using a plug.
Power supply for the leakage current compensator, in particular the amplifier,
can be effected
with the power supply of the apparatus, i.e. via the mains voltage. For
example, if the leakage
current compensator is installed in the upstream device, there may be a
problem that the ground
fault interrupter trips when this device is plugged into the industrial
outlet. This is for the reason
that the phases do not contact exactly at the same time during the plug-in
action and asymmetric
charging currents then arise through the Y-capacitors which can trigger the
upstream GFI. In
order to prevent this, the apparatus comprises a delay device which is
configured in such a
manner that the compensation current is superimposed with a time delay, i.e.
in particular only
when all the phases of the plug have contacted when the apparatus is connected
to the mains.
This means that the capacitor network is switched on preferably only when all
phases of the plug
have contacted when the apparatus is plugged in. The delay circuit can there
be formed, for
example, as a switching relay, a semiconductor relay, a time relay or as a
software solution, or
be implemented in the form of a mechanical solution in that the power supply
for the compensation
device is effected by way of plug contacts in a plug which, when plugged
together, are located
farther back than the contacts for the power supply of the apparatus, so that
the contacts of the
compensation device only contact after the power contacts have already
contacted.
It is also possible that the leakage current compensator is integrated in the
apparatus and is
supplied by a separate auxiliary power supply, so that the leakage current
compensator is already
supplied before a leakage current is generated in the load circuit when the
apparatus is switched
on. It is advantageous and space-saving to have the leakage current
compensator be integrated
into the machine. No extra space outside the machine is then required if the
leakage current
compensator is integrated into the machine, it would be possible that the
ground fault interrupter
(GFI) triggers unintentionally if leakage currents already arise once the
apparatus is switched on,
but the compensator is not yet operational. To prevent this, the leakage
current compensator is
supplied with the separate auxiliary voltage that is applied before the load
circuit generates the
leakage current. The system can then compensate the current before the ground
fault interrupter
triggers. In this solution, it is no longer harmful if the phases of the load
circuits are switched on
in a non-symmetric manner. Therefore, no expensive protection with contacts
contacting
simultaneously is required.
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As already described above, the present invention enables the apparatus to be
disconnected
and therefore be movable. If the apparatus comprises the external device with
the leakage
current compensator, this device has a mains plug.
The apparatus is advantageously an apparatus of at least a group: stuffing
machine, clipper,
spooling unit, driven suspension unit, cutter, separation unit, grouping unit,
conveyor belt,
charging system, packaging machine for food products, etc.
In the method according to the invention for the production of foods, in
particular with an
apparatus as described herein, a leakage current generating the load circuit
[sic] is detected
during operation of the apparatus and a compensation current directed opposite
to the
leakage current is generated using a leakage current compensator. The
compensation
current is superimposed onto the leakage current, whereby the leakage current
is reduced, in
particular substantially eliminated.
The leakage current compensator comprises an amplifier and a capacitor
network. When the
apparatus is plugged in, the compensation current is advantageously switched
on via the
capacitor network with a time delay only when all the phases of a plug of the
apparatus have
been contacted during the plug-in action, i.e., are connected to the mains.
It is also possible that the power supply of the leakage current compensator
is effected via
the power supply of the apparatus or that the leakage current compensator is
integrated into
the apparatus and supplied by a separate auxiliary power supply such that the
compensation
current is already applied before a leakage current is generated in the load
circuit. The
system can then compensate the current before the ground fault interrupter
triggers.
According to the present invention, the apparatus can therefore now be
unplugged, i.e. be
disconnected from the mains by way of a mains plug, be moved to another
production
location, and finally plugged in again. This enables increased flexibility
while maintaining
safety.
The leakage current compensator is advantageously located between a ground
fault
interrupter and an EMC filter. When the leakage current compensator is located
upstream of
the EMC input filter, all the leakage currents of the load circuit can be
compensated.
It is particularly advantageous if the apparatus is supplied with power via
three-phase mains
and the current is detected in the three phases and the leakage current is
determined by
subtraction, corresponding signals are fed to an amplifier, comprising an
evaluation unit, for
generating a compensation current which is fed via a capacitor network to at
least one,
preferably all three phases, whereby the leakage current is substantially
eliminated.
Date Recue/Date Received 2020-06-12
5a
In one aspect the present invention resides in an apparatus for the production
of foods with a
load circuit that generates a leakage current and with an EMC filter, a
frequency converter, a
motor cable and a motor, wherein the apparatus further comprises: a leakage
current
compensator with a device for detecting said leakage current and with a device
for
generating a compensation current that is directed opposite to said leakage
current and is
superimposed with said leakage current, such that said leakage current is
reduced wherein
either: said leakage current compensator is installed in a device upstream of
said apparatus,
a power supply of said leakage current compensator is effected via a power
supply of said
apparatus, and said apparatus comprises a delay device which is configured
such that said
compensation current is superimposed in a time-delayed manner,
Or
said leakage current compensator is integrated into said apparatus and is
supplied via a
separate auxiliary power supply, and said apparatus can be unplugged.
In one aspect the present invention resides in a method for the production of
foods, wherein
a leakage current is detected during operation of an apparatus and a
compensation current
directed opposite to said leakage current is generated using a leakage current
compensator
and superimposed onto said leakage current, whereby said leakage current is
reduced
wherein either: said leakage current compensator is installed in a device
upstream of said
apparatus, a power supply of said leakage current compensator is effected via
a power
supply of said apparatus, and said apparatus comprises a delay device which is
configured
such that said compensation current is superimposed in a time-delayed manner,
or
said leakage current compensator is integrated into said apparatus and is
supplied via a
separate auxiliary power supply, and said apparatus can be unplugged.
Date Recue/Date Received 2020-06-12
6
Fig.. 1 shows a simplified schematic representation of an apparatus according
to the invention
with a leakage current compensator;
Fig. 2 shows a simplified schematic representation of an embodiment of an
apparatus according
to the invention with an external leakage current compensator;
Fig. 3 shows a simplified schematic representation of an equivalent circuit
diagram of a leakage
current compensator for the embodiment shown in Figure 2;
Fig. 4 shows a simplified schematic representation of a further embodiment of
the present
invention with an integrated leakage current compensator:
Fig. 5 shows a simplified schematic representation of an equivalent circuit
diagram of a leakage
current compensator for the embodiment shown in Figure 4;
Fig. 6 shows a simplified schematic representation of a stuffing machine
according to the present
invention:
Fig. 7 shows a further embodiment according to the present invention.
Figure 6 shows a simplified schematic representation of an apparatus 1 for the
production of
foods, presently in the form of a stuffing machine 1. Stuffing machine 1
comprises a hopper 20
into which the pasty substance, e.g. sausage meat, is filled and passes
downwardly into a
conveying mechanism, no shown, for example, into a rotary vane pump, via which
it is ejected
into a stuffing tube 21, for example, into a sausage casing, not shown. The
apparatus can also
comprise, for example, a lifting device 22 which raises a sausage meat
carriage 23 upwardly by
way of a lifting arm 24 and empties it into hopper 20. The stuffing machine
can comprise a motor
2, as shall be explained below, which drives, for example, the conveying
mechanism. The stuffing
machine can further comprise a separate motor for lifting device 22.
Figure 1 shows a simplified schematic representation of a load circuit for
motor 2. Figure 1 shows
a simplified schematic representation of a drive system, for example, for a
rotary vane pump,
which substantially comprises an EMC input filter 3, a frequency converter 4,
a motor cable 5 and
a motor 2. The EMC filter as well as frequency converter 4 and the long motor
cable and motor 2
can produce leakage currents that would trigger a ground fault interrupter 5.
According to the
present invention, a leakage current compensator 6 is provided upstream of EMC
filter 3 and
generates a compensation current IK, which is directed opposite to leakage
current IA. The leakage
current can thus be compensated, i.e. be eliminated, at least be reduced so
that it is below the
threshold for triggering GFI ground fault interrupter 5, for example, below
the tripping threshold of
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30 mA for currents in the frequency range < 100 Hz, of 300 mA for currents
with a frequency >
1000 Hz.
Leakage current IA is the sum of all individual present leakage currents, the
sum of 'Filter + 'Frequency-
coverter ICabel 'Motor. According to the present invention, a frequency range
between 100 Hz and
300 kHz is to be covered. The frequency range of 50 to 60 Hz may not be
compensated so that
operator protection remains in effect. In practice, compensation currents up
to 1 A are required.
Compensation current IK is preferably shifted in its phase by 180 relative to
leakage current IA
and has substantially the same amplitude and preferably the same frequency.
Figure 2 shows an embodiment according to the present invention with an
external leakage
current compensator 6 arranged outside of the machine housing. Figure 2 shows
a power supply
14, for example, three-phase mains, as well as an industrial outlet 18 via
which an apparatus with
a mains plug 19 can be plugged on. In this embodiment, leakage current
compensator 6 is
installed in an upstream device 11 which comprises a further industrial outlet
13 into which an
industrial plug 12 of apparatus 1 can in turn be plugged. Industrial plug 12
is connected via a
corresponding line to main switch 25 of the apparatus. A motor protection
switch 26 can be
provided thereafter, and a main contactor 27 without "symmetrical contacts",
i.e. without snap-
action contacts. Thereafter, a mains line choke 28 can be provided, followed
by an EMC filter 3
and a frequency converter from which motor 2 can be supplied. After main
switch 25, a line can
branch off to a transformer protection switch 38 which is connected to a
control transformer 29
and supplies a control unit 30. Control unit 30 is connected to the main
contactor in order to switch
on the main contactor. As shown in Figure 2, leakage current compensator 6 is
supplied with
power in the same load circuit as the motor by way of power supply 14 i.e. the
mains voltage. The
leakage current compensator is therefore located upstream of main switch 25.
Figure 3 shows an equivalent circuit diagram of leakage current compensator 6
for the
embodiment shown in Figure 2. Figure 3 shows three-phase mains. Leakage
current
compensator 6 comprises a device for measuring a leakage current 7 as well as
a device for
generating a compensation current 8. The device for generating a compensation
current 8
comprises an amplifier 9 which is connected to the device for measuring the
leakage current 7
and comprises an evaluation unit which can determine a leakage current IA and
a compensation
current IK on the basis of the values measured. The device for detecting a
leakage current 7 can
comprise, for example, a measuring caliper. The currents of the three phases
can be detected,
and the leakage current from the respective differences. This means that, if
the sum of the
currents in the three phases L1, L2, L3 is not 0, a leakage current IA is
present. Compensation
current IK is calculated e.g. such that it is shifted in its phase by 180
relative to leakage current
IA and has substantially the same amplitude as the leakage current. Figure 3
shows in a simplified
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8
representation that amplifier 9 feeds the compensation current to the three
phases based on
compensation current IK determined such that the sum of the currents of the
individual phases
L1, L2, L3 is e.g. again 0 and the leakage current is thus compensated, is at
least located below
a triggering threshold of the GFI switch.
For example, the respective current ILi, 1L2, lu can there be measured.
E.g. a leakage current and an opposite compensation current, which is then
distributed to the
three phases L1, L2, L3, are determined by subtraction.
However, it is also possible to determine a separate leakage current for each
phase by measuring
the currents in each individual phase and to then determine corresponding
compensation currents
for the individual phases and to supply them accordingly to each phase.
In this embodiment, the leakage current compensator is supplied with power
from power supply
14 via two of the phases of the three-phase system, as already explained.
The apparatus advantageously comprises a delay device 15. Delay device 15 is
configured such
that compensation current IK is superimposed with a time delay, in particular
only when all phases
of plug 19 have contacted when the apparatus is plugged in. This means that
capacitor network
is switched on only when all phases of the plug have contacted when the
apparatus is plugged
in. It can thus be prevented that the GFI can already trigger when apparatus 1
is plugged in. This
problem arises from the fact that phases L1, L2, L3 do not contact at exactly
the same time and
asymmetric charging currents then arise through the Y-capacitors of capacitor
network 10 which
can trigger the upstream GFI. This can be prevented by delay circuit 15. Delay
circuit 15 can be
implemented, for example, as a time relay, a semiconductor relay, a time relay
[sic], or as a
software solution. Furthermore, there is also the possibility of a mechanical
delay device 15, such
that leakage current compensator 6 is supplied with power in a time delayed
manner, for example,
in that plug 19 is configured such that the contacts supplying leakage current
compensator 6 with
power are located further back so they only contact after the power contacts
have already
contacted. This can be realized, for example, by shorter pins.
Figure 4 shows a further embodiment according to the present invention.
Leakage current
compensator 6 is there installed directly into the apparatus i.e. is
integrated. As can be seen,
leakage current compensator 6 is located between industrial plug 12 and EMC
mains filter 3. In
order to here as well prevent that the GFI ground fault interrupter triggers
unintentionally, leakage
current compensator 6 is supplied with a separate auxiliary voltage 16 and not
via mains voltage
14 like in the first embodiment. Different separate auxiliary power supplies
16 can there be used.
In the embodiment shown in Figure 4 e.g. current is branched off downstream of
the main switch
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9
to a circuit breaker for transformers and supplied to leakage current
compensator 6. This avoids
the problem that the GFI triggers unintentionally when leakage currents
already arise once the
machine is switched on but the compensator is not yet ready for operation. To
prevent this, the
compensator is supplied the separate auxiliary voltage that is applied before
the load circuits
generate the leakage current. The system can then compensate leakage current
IA before the
GFI ground fault interrupter triggers. In this solution, it is no longer
harmful if the phases of the
load circuits are switched on in a non-symmetric manner. Therefore, no
expensive protection with
contacts contacting simultaneously is required.
Figure 7 shows a further embodiment according to the present invention. The
embodiment shown
in Figure 7 corresponds to the embodiment shown in Figure 4. In this
embodiment, multiple
motors are present in the apparatus. This means that a further motor for
another functional unit,
for example for a lifting device and/or a spooling device are provided in a
stuffing machine, in
addition to a motor for the rotary vane pump. According to a first
alternative, for example, a further
frequency converter for further motor 2 can be provided downstream of the EMC
mains filter
and/or downstream of the mains line choke and a further frequency converter
can be provided for
a further motor. These load circuits can therefore be protected as well, i.e.
several motors by only
one leakage current compensator 6.
CA 3033980 2019-02-14
=
. .
' List of reference numerals
1 apparatus
2 motor
3 EMC filter
4 frequency converter
5 ground fault interrupter
6 leakage current compensator
7 device for measuring leakage current
8 device for generating a compensation current
9 amplifier
10 capacitor network
11 upstream device
12 plug
13 outlet
14 power supply
delay device
16 separate power supply
CA 3033980 2019-02-14
