APPARATUS AND METHOD FOR THE PRODUCTION OF FOODS

Abstract

The invention relates to an apparatus and a method for the production of foods, in particular, a stuffing machine for the production of sausages, with a load circuit that generates a leakage current IA and with a filter, a frequency converter, a motor cable and a motor. The apparatus comprises a leakage current compensator 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.

Claims

1. An apparatus for the production of foods, comprising: a load circuit that generates a leakage current; an EMC filter; a frequency converter; a motor cable; a motor; a leakage current compensator with a device for detecting said leakage current; and 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.

2. The apparatus according to claim 1, wherein said leakage current is substantially eliminated when superimposed with said compensation current.

3. The apparatus according to claim 1, wherein said compensation current is shifted in its phase relative to said leakage current by 180 and has substantially a same amplitude as said leakage current.

4. The apparatus according to claim 1, wherein said device for generating said compensation current comprises an amplifier and a capacitor network via which said compensation current is supplied to individual phases of a multi-phase system.

5. The apparatus according to claim 4, wherein the individual phases of the multi-phase system comprises at least one of three phases of a three-phase system.

6. The apparatus according to claim 4, wherein said leakage current compensator is arranged between a ground fault interrupter and said EMC filter.

7. The apparatus according to claim 4, wherein said leakage current compensator is installed in a device upstream of said apparatus.

8. The apparatus according to claim 7, wherein said apparatus further comprises a plug connected to said leakage current compensator by way of an outlet.

9. The apparatus according to claim 8, wherein a power supply of said leakage current compensator is effected via a power supply of said apparatus.

10. The apparatus according to claim 8, wherein said apparatus further comprises a delay device configured such that said compensation current is superimposed in a time-delayed manner.

11. The apparatus according to claim 10, wherein said compensation current is superimposed in the time-delayed manner only when all phases of said plug have contacted when said apparatus is plugged in, and further wherein said delay device is optionally configured such that said capacitor network is switched on only when all phases of said plug have contacted when said apparatus is plugged in.

12. The apparatus according to claim 1, wherein said leakage current compensator is integrated into said apparatus and is supplied via a separate auxiliary power supply.

13. The apparatus according to claim 12, wherein said apparatus can be unplugged and is movable.

14. The apparatus according to claim 1, wherein said apparatus is at least one apparatus from the following group: a stuffing machine for the production of sausages, a clipper, a spooling unit, a driven suspension unit, a cutter, a separation unit, a grouping unit, a conveyor belt, a charging system, and a packaging machine for food products.

15. A method for the production of foods with an apparatus comprising a load circuit that generates a leakage current, the method comprising: detecting said leakage current during operation of said apparatus; generating, with a leakage current compensator, a compensation current directed opposite to said leakage current; and superimposing said compensation current onto said leakage current, whereby said leakage current is reduced and substantially eliminated.

16. The method according to claim 15, wherein said leakage current compensator comprises an amplifier and a capacitor network, the method further comprising switching on said compensation current via said capacitor network in a time-delayed manner, when said apparatus is plugged in and only when all phases of a plug of said apparatus have contacted when plugged in.

17. The method according to claim 16, wherein a power supply of said leakage current compensator is effected via a power supply of said apparatus, wherein said leakage current compensator is integrated into said apparatus and is supplied via a separate auxiliary power supply.

18. The method according to claim 17, wherein said apparatus is unplugged, moved to another production location, and plugged in again.

19. The method according to claim 17, wherein said leakage current compensator is arranged between a ground fault interrupter and an EMC filter of said apparatus.

20. The method according to claim 19, wherein said apparatus is supplied with voltage via a three-phase mains with three phases, further comprising: detecting a current in the three phases; feeding corresponding signals to an amplifier comprising an evaluation unit; determining, with the evaluation unit, a respective leakage current by subtraction; and generating, with the evaluation unit, a compensation current which is fed via a capacitor network to at least one of the three phases.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0028] FIG. 1 shows a simplified schematic representation of an apparatus according to the invention with a leakage current compensator;

[0029] FIG. 2 shows a simplified schematic representation of an embodiment of an apparatus according to the invention with an external leakage current compensator;

[0030] FIG. 3 shows a simplified schematic representation of an equivalent circuit diagram of a leakage current compensator for the embodiment shown in FIG. 2;

[0031] FIG. 4 shows a simplified schematic representation of a further embodiment of the present invention with an integrated leakage current compensator;

[0032] FIG. 5 shows a simplified schematic representation of an equivalent circuit diagram of a leakage current compensator for the embodiment shown in FIG. 4;

[0033] FIG. 6 shows a simplified schematic representation of a stuffing machine according to the present invention; and

[0034] FIG. 7 shows a further embodiment according to the present invention.

DETAILED DESCRIPTION

[0035] FIG. 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.

[0036] FIG. 1 shows a simplified schematic representation of a load circuit for motor 2. FIG. 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 I.sub.K, which is directed opposite to leakage current I.sub.A. 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 30 mA for currents in the frequency range <100 Hz, of 300 mA for currents with a frequency >1000 Hz.

[0037] Leakage current I.sub.A is the sum of all individual present leakage currents, the sum of I.sub.Filter+I.sub.Frequency-coverter+I.sub.Cabel+I.sub.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 I.sub.K is optionally shifted in its phase by 180 relative to leakage current I.sub.A and has substantially the same amplitude and optionally the same frequency.

[0038] FIG. 2 shows an embodiment according to the present invention with an external leakage current compensator 6 arranged outside of the machine housing. FIG. 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 FIG. 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.

[0039] FIG. 3 shows an equivalent circuit diagram of leakage current compensator 6 for the embodiment shown in FIG. 2. FIG. 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 I.sub.A and a compensation current I.sub.K 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 I.sub.A is present. Compensation current I.sub.K is calculated e.g. such that it is shifted in its phase by 180 relative to leakage current I.sub.A and has substantially the same amplitude as the leakage current. FIG. 3 shows in a simplified representation that amplifier 9 feeds the compensation current to the three phases based on compensation current I.sub.K 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.

[0040] For example, the respective current I.sub.L1, I.sub.L2, I.sub.L3 can there be measured.

[0041] For example, a leakage current and an opposite compensation current, which is then distributed to the three phases L1, L2, L3, are determined by subtraction.

[0042] 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.

[0043] 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.

[0044] The apparatus advantageously comprises a delay device 15. Delay device 15 is configured such that compensation current I.sub.K 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 10 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, 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.

[0045] FIG. 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 FIG. 4, for example, current is branched off downstream of the main switch 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 I.sub.A 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.

[0046] FIG. 7 shows a further embodiment according to the present invention. The embodiment shown in FIG. 7 corresponds to the embodiment shown in FIG. 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.

LIST OF REFERENCE NUMERALS

[0047] 1 apparatus [0048] 2 motor [0049] 3 EMC filter [0050] 4 frequency converter [0051] 5 ground fault interrupter [0052] 6 leakage current compensator [0053] 7 device for measuring leakage current [0054] 8 device for generating a compensation current [0055] 9 amplifier [0056] 10 capacitor network [0057] 11 upstream device [0058] 12 plug [0059] 13 outlet [0060] 14 power supply [0061] 15 delay device [0062] 16 separate power supply