Modification unit and coating device for applying a flowable medium to a substrate

Abstract

The invention relates to a coating device for applying a flowable medium, in particular a hot-melt adhesive, to a substrate, having a coating valve (13) which has a closure mechanism which opens a metering opening of the coating valve in an open position, so that flowable medium can flow through the metering opening towards the substrate, wherein the closure mechanism can be moved from a closed position, in which it closes the metering opening, into the open position by means of an electromagnet of the coating valve (13), and having a main control unit (17), in particular an SPS (programmable logic controller), which is connected to the coating valve (13) and which provides an electrical output voltage signal in order to control the voltage supply of the electromagnet, in particular periodically, which moves the closure mechanism into the open position and holds it there. The invention is characterized in that a modification unit (19) is arranged between the main control unit (17) and the coating valve (13), which is configured such that it receives, modifies and continues to pass on the output voltage signal of the main control unit (17) to the electromagnet in modified form.

Description

Technical Field

[0001] This invention relates to an apparatus for coating a flowable medium, particularly a hot melt adhesive, onto a substrate, comprising a coating valve having a closing mechanism that, in an open position, opens a metering opening of the coating valve, allowing the flowable medium to flow toward the substrate through the metering opening. The closing mechanism can be moved from a closed position (closing the metering opening in the closed position) to an open position by an electromagnet of the coating valve. The apparatus also includes a main control unit, particularly an SPS (Programmable Logic Controller or Memory Programmable Controller), connected to the coating valve. This main control unit periodically provides an electrical output voltage signal, specifically for a controlled voltage supply to the electromagnet, which causes the closing mechanism to move to the open position and remain there. Background Technology

[0002] Coating apparatuses with electromagnetically operated coating valves are well-known and used, for example, in the tobacco industry, to apply portions of hot melt adhesive to cigarette packs or similar packaging components to be bonded together, such as folded flaps of packaging blanks. In a simpler main control unit, voltage signals with constant amplitude over a signal duration are periodically transmitted to the electromagnets of the coating valve, causing a constant current consumption in the electromagnets and correspondingly a constant force, which the closing mechanism uses to first move to the open position and then remain there. However, it is known that the so-called holding current required to maintain the closing mechanism already in the open position can be less than the opening current previously required to cause the actual opening movement. Disadvantageously, therefore, in such a (simple) controller, the current consumption of the electromagnets is higher than actually necessary.

[0003] The controller, which is often located in the switch cabinet of the corresponding coating device or in the machine equipped with the coating device, is completely replaced, which is particularly costly in high-speed valves and is usually avoided. Summary of the Invention

[0004] Based on the prior art, the objective of this invention is to further improve the apparatus described at the beginning.

[0005] This task is accomplished by a coating apparatus according to the invention and by a modified unit according to the invention for such a coating apparatus.

[0006] Accordingly, the coating apparatus described at the beginning is characterized by having a modification unit arranged between the main control unit and the coating valve (particularly arranged in an electrically connected series arrangement of the main control unit, the modification unit, and the coating valve), the modification unit being configured to receive, modify, and transmit the output voltage signal of the main control unit to the electromagnet in the modified form.

[0007] According to the present invention, the main control unit is configured such that it generates an output voltage signal with a particularly constant, positive-zero voltage amplitude for each movement of the closing mechanism from the closed position to the open position, the value of which is sufficient to move the closing mechanism from the closed position to the open position by means of an electromagnet. Here, the modification unit can further be configured such that, during a modification time interval—that is, during the entire signal duration of the corresponding output voltage signal or during a portion of the signal duration of the corresponding output voltage signal—it modifies each of these output voltage signals such that the average value of the voltage amplitude of the corresponding output voltage signal relative to the modification time interval is less than the average value of the corresponding output voltage signal when it is not modified. This can be achieved, for example, by appropriately clocking (or clock pulse modulation) the corresponding output voltage signal during the modification time interval.

[0008] This modification unit allows for the cost-effective and low-cost modification of coating apparatuses where the main control unit provides a simple output voltage signal to the electromagnet of the coating valve, without distinguishing between the opening voltage (for opening the coating valve or moving the closing mechanism from the closed to the open position) and the smaller holding voltage (for holding the valve or closing mechanism in the open position). Advantageously, this reduces the current consumption of the corresponding coating valve and thus the overall current consumption of the coating apparatus. Simultaneously, the electromagnet generates less waste heat, which in particular reduces the undesirable effects of this waste heat on the flowable medium, such as its viscosity and the shape and / or amount of the corresponding medium subsequently applied to the substrate.

[0009] In a preferred improvement of this solution, it can be proposed that, in order to transmit the output voltage signal to the modification unit, a wire is connected from the main control unit to the main control unit, and the modification unit is guided to the main control unit; and, in order to transmit the modified output voltage signal to the electromagnet of the coating valve, a wire is guided from the modification unit to the coating valve, and this wire is connected to or is connected to the coating valve. Here, it can be specified that the cable guided to the coating valve is directly connected to the electromagnet or indirectly connected via a corresponding electrical connection wire or connecting cable provided to the coating valve.

[0010] For example, in the case where the main controller is located in a switch cabinet with very little space for other components, the modification unit can be arranged externally away from it without any problems. Therefore, for the general case of subsequent installation of the modification unit, it is only necessary to run new cables from the main controller to the modification unit or the coating valve, or alternatively, to separate the existing cables between the main controller and the coating valve and integrate the modification unit into those cables.

[0011] Accordingly, according to the invention, the modification unit may be arranged away from the main controller, particularly outside the housing of the main controller.

[0012] In this regard, the modification unit can be further configured such that, in the absence of modification by the modification unit, the voltage amplitude of the corresponding output voltage signal has a constant value over the entire signal duration, and by clocking the corresponding output voltage signal during the modification time interval, the effective value of the voltage amplitude during the modification time interval is less than 50% of the aforementioned constant voltage amplitude value of the output voltage signal.

[0013] Furthermore, the modification unit can be configured such that, in the absence of modification by the modification unit, the voltage amplitude of the corresponding output voltage signal has a constant value of 24V over the entire signal duration, and the corresponding output voltage signal is modified during the modification time interval such that the effective value of the voltage amplitude during the modification time interval is less than 12V, preferably less than 10V.

[0014] Regarding the aforementioned clock timing for each output voltage signal, the clock timing can be performed such that a preferred periodic sequence of signal pulses, particularly rectangular ones, with a first voltage amplitude is generated, particularly a preferred periodic sequence of voltage amplitudes corresponding to the voltage amplitudes of the corresponding, yet unmodified, output voltage signals is generated, wherein, applicable to the entire sequence of signal pulses, every two consecutive signal pulses are separated from each other by a signal interval having a second voltage amplitude smaller than the first voltage amplitude, particularly having a voltage amplitude of zero.

[0015] Regarding the corresponding modification time interval, the corresponding output voltage signal is modified during the modification time interval. This modification time interval can be immediately followed by a time interval in which the corresponding output voltage signal is not modified, and in this time interval, the voltage amplitude of the output voltage signal that continues to be transmitted to the electromagnet corresponds to the voltage amplitude of the corresponding unmodified output voltage signal generated by the main controller.

[0016] Here, the corresponding output voltage signal induces an on-start current in the electromagnet during the aforementioned unmodified time interval, thus causing the closing mechanism to move from the closed position to the open position, and in the immediately following modified time interval, it induces a holding current that is relatively small compared to the on-start current.

[0017] Suitably, the modification unit has electronic circuitry for implementing the modification of the output voltage signal, particularly a driver (or exciter).

[0018] Furthermore, the modification unit may have an analysis device, particularly configured as a microcontroller, for analyzing the corresponding output voltage signal and / or a device for identifying the operating status of the coating valve, particularly the electromagnet of the coating valve, or for identifying faults, such as breaks, in the cable leading from the modification unit to the coating valve.

[0019] In addition, the modification unit may have a display for displaying information and / or a transmitting unit for transmitting information, particularly wirelessly, to a remote receiving unit, especially for transmitting information about the operating status of the coating valve or cable malfunctions to the remote receiving unit.

[0020] Furthermore, the modification unit may have a preferred electronic memory in which information can preferably be stored by a microcontroller, and / or information can preferably be read from the memory by a microcontroller, particularly information about the operating status of the coating valve or about faults in the wiring that is directed from the main control unit to the modification unit or from the modification unit to the coating valve, preferably generated or provided by the microcontroller.

[0021] The main control unit can therefore be configured such that it loads an output voltage signal with an additional minimum voltage in order to supply power to the modification unit. Attached Figure Description

[0022] Other features of the invention are derived from the following description of preferred embodiments of the invention and from the accompanying drawings. Hereinafter:

[0023] Figure 1 A perspective view (schematic diagram) of a coating apparatus according to the present invention is shown, comprising an electromagnetically driven coating valve for coating a portion of a liquid medium onto a substrate, a main controller for generating an output voltage signal for the coating valve, and a modification unit for modifying the output voltage signal.

[0024] Figure 2 Show Figure 1 A side view of a portion of the device.

[0025] Figure 3A graph is shown, illustrating the output voltage signal modified using the modification unit, where voltage U is plotted on the vertical axis and time t is plotted on the horizontal axis.

[0026] Figure 4 A graph showing the time-dependent current I curve (vertical axis) is displayed when the coating valve is loaded. Figure 3 When the output voltage signal is in the current, Figure 1 The electromagnet of the coating valve in the coating device appears.

[0027] Figure 5 Show Figure 1 A top view of a portion of the base shown, which has a section composed of Figure 1 The use of Figure 3 The output voltage signal shown indicates the coating valve's coating medium ratio.

[0028] Figure 6 A schematic diagram is shown, which is displayed in Figure 1 The modified unit shown is arranged between the coating valve and the main controller. Detailed Implementation

[0029] exist Figure 1 The coating apparatus 10 shown in this example is used to coat spaced-apart (elongated) portions 11 of a flowable medium (in the present case, a hot melt adhesive) onto a substrate 12, or in the present case, onto a material web 12 (in the present case, a material web made of paper).

[0030] The material profile shown is merely one example of substrate 12, onto which the coating apparatus 10 according to the invention can coat a flowing medium. It should be understood that the invention is not limited to this type of substrate.

[0031] In order to coat the medium portion 11, the coating apparatus 10 includes, in the present case, a coating valve 13, which is known per se, as a core component. This coating valve has a closing mechanism (not shown) in the same known manner, which can be moved from the closed position of the (lower) metering opening 14 of the coating valve 13 to the (upper) open position by means of an electromagnet (not shown).

[0032] In the closed position, such a closing mechanism is typically held in place by a closing mechanism that applies a closing force, such as a spring that applies a restoring force, or by permanent magnets that repel each other and apply a restoring force in this manner.

[0033] The closing mechanism here constitutes the armature of the electromagnet and is correspondingly at least partially made of metal, thereby allowing the closing mechanism to be moved to the open position by the magnetic field generated by the electromagnet.

[0034] The liquid medium, or in the present case, the liquid hot melt adhesive, is supplied to the coating valve 13 from the corresponding medium source 34, in the present case, the melting device, and more precisely, via the medium line 15 or medium hose heated in the present case by a heating device. The wire 16 connected to the current supply unit of the medium source 14 is responsible for supplying current to the heating device of the medium line 15.

[0035] To discharge the various media fractions 11, the electromagnets of the coating valves 13 are appropriately controlled. For this purpose, the coating apparatus 10 includes a main control unit 17, in this case an SPS (Programmable Logic Controller), which periodically generates various time-spaced output voltage signals 18 (see [link to documentation]). Figure 3 ), and provide the output voltage signal to the electromagnet of the coating valve 13.

[0036] Here, these output voltage signals are modified in advance by a modification unit 19, which will be described in detail later. This modification unit is arranged between the coating valve 13 and the main controller 17, and more precisely, it is arranged such that the modification unit receives the output voltage signal from the main control unit 17, modifies it, and finally transmits it in a modified form as the modified output voltage signal 18 to the coating valve 13 or its electromagnet. In other words, the main controller 17, the modification unit 19, and the coating valve 13, or its electromagnet, are electrically connected in series (following each other) or arranged in series for this purpose.

[0037] Here, depending on the type of series circuit, the modification unit 19 is electrically connected to the main control unit 17 via the first wire 20a, and electrically connected to the coating valve 13 or the electromagnet via the second wire 20b.

[0038] In the present case, the main control unit 17 generates periodic (electrical) output voltage signals that are time-spaced apart from each other, the output voltage signals having a constant voltage amplitude or a constant voltage value over the entire signal duration, which in the present case is 24V.

[0039] exist Figure 3 The diagram exemplarily shows two successive output voltage signals 18 that have been modified by the modification unit 19.

[0040] On the one hand, the time interval 21 between the two modified output voltage signals 18 can be observed. This also corresponds to the time interval of the unmodified output voltage signal received by the modification unit 19.

[0041] Modification unit 19 ensures that each output voltage signal received by it is modified within modification time interval 22, which is shorter than the total signal duration of the corresponding received output voltage signal or a portion of the time interval forming the total signal duration. Conversely, during the upstream time interval 25 or for the remainder of the signal duration, the corresponding received output signal is not modified, such that the modified output voltage signal 18 continued to be transmitted by modification unit 19 corresponds there to the received or unmodified output signal.

[0042] Here, the modification in time interval 22 is performed such that a weaker current appears in the electromagnet of the coated valve 13 than in the case without this modification, see [link to relevant documentation]. Figure 4 .

[0043] In the current case, each output voltage signal 18 is clocked for this purpose in the modification time interval 22, such that the modified output voltage signal 18 (only) replaces the time-constant voltage amplitude of the respective received unmodified output voltage signal in the modification time interval 22 and contains a periodic sequence of signal pulses 23 that are rectangular in the current case.

[0044] Here, the corresponding voltage amplitude of each signal pulse 23 is currently the same as the voltage amplitude of the unmodified output voltage signal.

[0045] Furthermore, each pair of consecutive signal pulses 23 is separated from each other by a signal interval 24 or by a short time interval 24 when there is no voltage or when each has a zero voltage amplitude.

[0046] Instead of signal intervals 24 with voltage amplitudes of zero, voltage pulses 23 could theoretically also be separated by voltage pulses with voltage amplitudes of greater than zero, but less than those of the unmodified output voltage signal.

[0047] According to the present invention, corresponding to Figure 3 The modified output voltage signal 18 causes a current I to flow through the electromagnet of the coated valve 13. Figure 4 The curves showing the changes are shown in the figure.

[0048] The signal segment of the modified output voltage signal 18 corresponding to the time interval 25 between the modified and unmodified output voltage signals 18 causes the current I in the electromagnet to rise to its maximum value I. peak .

[0049] This, in turn, results in the (most powerful) magnetic field of the electromagnet, which generates the magnetic force required for the opening movement of the closing mechanism of the coated valve 13, and this magnetic force can be used to overcome the restoring force that holds the closing mechanism in the closed position.

[0050] As a dotted line Figure 4 The diagram shows the time-dependent variation of current curve I and its adjacent curves, as it would appear without modification by output voltage signal 18 or without such modification unit 19. Current I will remain at value I. peak Up, until each signal terminal of the unmodified output voltage signal.

[0051] Conversely, the modification of the corresponding output voltage signal 18 or the current clock timing according to the invention now instead results in a decrease in the current in the modification time interval 22.

[0052] Here, the clock timing is performed in such a way that the average voltage amplitude during the modification time interval is less than the voltage amplitude of the unmodified voltage signal, specifically less than 50%. Here, the effective value of the voltage amplitude is less than 12 volts, preferably less than 10 volts, during the modification time interval 22.

[0053] The output voltage signal 18 is modified in such a way that a holding current I appears in the electromagnet during the modification time interval 22. hold The holding current is sufficient to hold the closing mechanism in the coated valve 13 in its holding position. Here, the electromagnet applies a magnetic force, which is less than and can be less than the opening force required to move the closing mechanism to this open position during the opening movement.

[0054] This reduction in current, in addition to energy-saving effects, also results in the electromagnet heating up less during operation compared to when it operates at a (higher) on-state current for the entire duration of the corresponding signal. Consequently, the undesirable effects of the electromagnet's waste heat on the flowable medium can be significantly reduced.

[0055] exist Figure 5 The dashed lines show how the shape of the corresponding medium portion 11 is adversely adjusted in the case of overheating of the coating valve 13, i.e., it can expand relative to the optimal shape.

[0056] Finally, regarding the structure of the modified unit 19, the modified unit here also has a (protective) housing 26.

[0057] Inside the housing 26, in addition to other components, there is a driver 27, i.e., a suitable electronic circuit, which is used to actually modify the incoming, unmodified output voltage signal.

[0058] In the present case, a microcontroller 28 is also arranged therein, which is capable of analyzing the incoming output voltage signal, see reference numeral 29. It may be specified here that the microcontroller 28 identifies the operating status of the electromagnet of the coating valve 13, in particular the electromagnet of the coating valve 13, or detects faults, such as a break in one of the wires 20a or 20b.

[0059] Here, the modification unit 19 may have a preferred electronic memory (not shown). In this electronic memory, the microcontroller 28 can then store the aforementioned information regarding the operating status of the coating valve 13 or regarding faults in the wires 20a and 20b. This information can then be read or retrieved when needed.

[0060] Modified unit 19 also has, in the present case, a power supply unit 30 specifically for the driver 27 and the microcontroller 28.

[0061] The energy supply unit can be connected to a remote power source, for example, via a separate wire, such as a power source provided by the main controller 17.

[0062] However, it is also conceivable that the main control unit 17 loads each output voltage signal with an additional minimum voltage, which is then converted by the energy supply unit 30 into available energy for modifying the corresponding energy-required components or units of the unit.

[0063] It is further conceivable that the modification unit 19 has a radio module 31, which, in particular, provides the determined operating status or other information via radio to a corresponding (remote) receiver, such as a smartphone 32, after being read from the aforementioned memory. Additionally or alternatively, a display 33 for displaying such information may also be provided.

[0064] List of reference numerals

[0065] 10 Coating Device

[0066] 11 media share

[0067] 12 base

[0068] 13 Coated Valves

[0069] 14 Metering Opening

[0070] 15. Medium Piping

[0071] 16 wire

[0072] 17 Main Control Unit

[0073] 18. Modified output voltage signal

[0074] 19 Modification Units

[0075] 20A wire

[0076] 20b wire

[0077] 21 spacing

[0078] 22 Modification time interval

[0079] 23 signal pulses

[0080] 24 signal intervals

[0081] 25 time interval

[0082] 26 (Protective) Housing

[0083] 27 drives

[0084] 28 microcontrollers

[0085] 29 Analysis

[0086] 30 energy supply units

[0087] 31 radio modules

[0088] 33 smartphones

[0089] 33 display screen

[0090] 34 Media Source

Claims

1. Coating device for applying a flowable medium to a substrate, the coating device having a coating valve (13) with a closing mechanism which opens a metering opening of the coating valve in an open position, so that a flowable medium can flow through the metering opening towards a substrate, wherein, The closing mechanism can be moved from a closed position to an open position by the electromagnet of the coating valve (13). In the closed position, the closing mechanism closes the metering opening. The coating device has a main control unit (17) connected to the coating valve (13). The main control unit provides an electrical output voltage signal for the controlled voltage supply to the electromagnet. The electrical output voltage signal causes the closing mechanism to move to the open position and remain there. A modification unit (19) is arranged between the main control unit (17) and the coating valve (13). The modification unit is configured to receive, modify, and transmit the output voltage signal of the main control unit (17) to the electromagnet in the modified form. The main control unit (17) is configured such that it generates an output voltage signal with a voltage amplitude greater than zero for each movement of the closing mechanism from the closed position to the open position, such that the voltage amplitude is sufficient to move the closing mechanism from the closed position to the open position via the electromagnet. The modification unit (19) is configured such that it modifies each of the output voltage signals during the modification time interval (22), i.e., during the entire signal duration of the corresponding output voltage signal or during a partial time interval of the signal duration of the corresponding output voltage signal, such that the average value of the voltage amplitude of the corresponding output voltage signal related to the modification time interval (22) is less than the average value when the corresponding output voltage signal is not modified.

2. The coating apparatus of claim 1, wherein, In order to transmit the output voltage signal to the modification unit (19), a wire is guided from the main control unit (17) to the modification unit (19), and in order to transmit the modified output voltage signal to the electromagnet, a wire is guided from the modification unit (19) to the coating valve (13).

3. The coating apparatus of claim 1, wherein, The modification unit (19) modifies each of the output voltage signals by clock timing during the modification time interval (22).

4. The coating apparatus of claim 1, wherein, Without modification by the modification unit (19), the voltage amplitude of the corresponding output voltage signal has a constant value over the entire signal duration, and by clocking the corresponding output voltage signal during the modification time interval (22), the effective value of the voltage amplitude during the modification time interval (22) is less than 50% of the constant value of the voltage amplitude of the output voltage signal.

5. The coating apparatus of claim 1, wherein, Without modification by the modification unit (19), the voltage amplitude of the corresponding output voltage signal has a constant value of 24V over the entire signal duration, and the corresponding output voltage signal is modified during the modification time interval (22) such that the effective value of the voltage amplitude in the modification time interval (22) is less than 12V.

6. The coating apparatus of claim 1, wherein, The clock timing of the corresponding output voltage signal is performed to generate a sequence of signal pulses with a first voltage amplitude, wherein, applicable to the entire sequence of signal pulses, every two consecutive signal pulses are separated from each other by a second voltage amplitude that is smaller than the first voltage amplitude.

7. The coating apparatus according to claim 1, characterized in that, The corresponding modification time interval (22) is immediately following a time interval, during which the corresponding output voltage signal is modified, during which the corresponding output voltage signal is not modified, and during which the voltage amplitude of the output voltage signal that is thus transmitted to the electromagnet corresponds to the voltage amplitude of the corresponding unmodified output voltage signal generated by the main control unit.

8. The coating apparatus according to claim 7, characterized in that, The corresponding output voltage signal induces an on-state current in the electromagnet during the unmodified time interval, which causes the closing mechanism to move from the closed position to the open position, and the corresponding output voltage signal induces a holding current in the electromagnet during the immediately following modified time interval (22), which is smaller than the on-state current.

9. The coating apparatus according to claim 1, characterized in that, The modification unit (19) is arranged away from the main control unit (17).

10. The coating apparatus according to claim 1, characterized in that, The modification unit (19) has electronic circuitry for implementing the modification of the output voltage signal.

11. The coating apparatus according to claim 1, characterized in that, The modification unit (19) has an analysis device for analyzing the corresponding output voltage signal and / or a device for identifying the operating status of the coating valve (13) or identifying faults in the cable leading from the modification unit (19) to the coating valve (13).

12. The coating apparatus according to claim 1, characterized in that, The modification unit (19) has a display for displaying information and / or a transmission unit for transmitting information to a remote receiving unit.

13. The coating apparatus according to claim 1, characterized in that, The modification unit (19) has a memory in which information can be stored and / or information can be read from the memory.

14. The coating apparatus according to claim 1, characterized in that, The main control unit (17) is configured such that it loads an output voltage signal with an additional minimum voltage in order to supply energy to the modification unit (19).

15. The coating apparatus according to claim 1, characterized in that, The flowable medium is a hot melt adhesive.

16. The coating apparatus according to claim 1, characterized in that, The main control unit (17) is a programmable logic controller.

17. The coating apparatus according to claim 1, characterized in that, The main control unit periodically provides an electrical output voltage signal.

18. The coating apparatus according to claim 1, characterized in that, The output voltage signal has a constant voltage amplitude that is greater than zero.

19. The coating apparatus according to claim 1, characterized in that, The clock timing of the corresponding output voltage signal is performed to generate a sequence of voltage amplitudes corresponding to the voltage amplitudes of the corresponding, yet unmodified, output voltage signal.

20. The coating apparatus according to claim 9, characterized in that, The modification unit (19) is located outside the housing of the main control unit.

21. The coating apparatus according to claim 12, characterized in that, The transmitting unit transmits information about the operating status of the coating valve (13) or cable malfunctions to the remote receiving unit.

22. The coating apparatus according to claim 13, characterized in that, The information is about the operating status of the coating valve or about a fault in the wiring that is directed from the main control unit (17) to the modification unit (19) or from the modification unit (19) to the coating valve (13).

23. A modification unit for a coating apparatus for applying a flowable medium to a substrate, wherein, The coating apparatus has a coating valve (13) with a closing mechanism that opens the metering opening of the coating valve (13) in the open position, allowing the flowable medium to flow toward the substrate through the metering opening. The closing mechanism can be moved from a closed position to an open position by an electromagnet of the coating valve (13), in which the closing mechanism closes the metering opening. The coating apparatus also has a main control unit (17) connected to the coating valve (13). This main control unit provides an electrical output voltage signal for a controlled voltage supply to the electromagnet, causing the closing mechanism to move to the open position and remain there. The modification unit (19) is configured such that it can be arranged between the main control unit (17) and the coating valve (13) and can receive and modify the main control unit. The modifying unit (19) is configured such that it modifies each output voltage signal generated by the main control unit (17) during a modification time interval (22), i.e., during the entire signal duration of the corresponding output voltage signal or during a partial time interval of the signal duration of the corresponding output voltage signal, such that the average value of the voltage amplitude of the corresponding output voltage signal related to the modification time interval (22) is less than the average value when the corresponding output voltage signal is not modified. The main control unit generates an output voltage signal with a voltage amplitude greater than zero for each movement of the closing mechanism from the closed position to the open position, which is sufficient to move the closing mechanism from the closed position to the open position by the electromagnet.

24. The modification unit according to claim 23, characterized in that, The coating apparatus is the coating apparatus according to any one of claims 1 to 22.

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