EP3535064B1 - Printing head and corresponding operational method - Google Patents

Description

The invention relates to a print head for applying a coating agent to a component, in particular for painting a motor vehicle body component with a paint. The invention further comprises an operating method for such a printhead.

Rotary atomizers are usually used as the application device for the serial painting of motor vehicle body components, but these have the disadvantage of a limited application efficiency, i.e. only a part of the applied paint is deposited on the components to be coated, while the rest of the applied paint has to be disposed of as a so-called overspray.

A newer development line, on the other hand, provides what are known as printheads as application devices, for example DE 10 2013 002 412 A1 , US 9,108,424 B2 and DE 10 2010 019 612 A1 are known. In contrast to the known rotary atomizers, such printheads do not emit a spray of the lacquer to be applied, but rather a spatially narrowly delimited lacquer jet which is almost completely deposited on the component to be lacquered, so that almost no overspray occurs.

Such print heads have control valves for controlling the release of the coating agent, wherein Figure 1 shows a schematic representation of such a control valve which is arranged in a printhead.

There is a nozzle opening 2 in a nozzle plate 1, which is either released or blocked by the control valve. In addition to the nozzle opening 2, there are further nozzle openings in the nozzle plate 1, each of which is controlled by a separate control valve, these further nozzle openings not being shown for the sake of simplicity.

Furthermore, the printhead contains a base plate 3 which delimits a coating agent supply 4, i.e. the paint to be painted is supplied via the coating agent feed 4 and can then exit through the nozzle opening 2 when the control valve is open.

A coil tube 5 is arranged on the upper side of the base plate 3 and is wound on the outside with a coil 6.

In the coil tube 5 there is a magnetic coil core 7, which is arranged in a stationary manner and is sealed off from the coil tube 5 by a seal 8.

In addition, there is a magnetic armature 9 in the coil tube 5, which can also be referred to as a valve needle and, depending on the current supply to the coil 6, can be displaced in the direction of the double arrow in order to either release or close the nozzle opening 2.

The armature 9 carries a seal 10 at its lower end in order to seal the nozzle opening 2 in the closed position shown, so that no paint can escape from the nozzle opening 2.

In addition, the control valve has a return spring 11, which the armature 9 and thus also the seal 10 in the drawing presses down into the closed position shown.

To open the control valve, the coil 6 is thus energized in such a way that the armature 9 with the seal 10 in the drawing is actively pulled upward, specifically against the spring force of the return spring 11.

To close the control valve, on the other hand, the coil 6 is de-energized, so that the return spring 11 can press the armature 9 and thus also the seal 10 in the drawing downward into the closed position shown.

A disadvantage of this known control valve is the fact that the interior of the control valve and in particular an interior 12 of the coil tube 5 is exposed to the paint.

For one, paint residues in the interior 12 of the coil tube 5 can therefore impair the functionality of the control valve. For example, paint deposits in the control valve can impair the freedom of movement of the armature 9.

On the other hand, the paint residues in the interior 12 of the coil tube 5 also prevent a color change, since the control valve cannot be flushed during operation. In the known print heads with such control valves, there is also the possibility of applying a different colored lacquer.

One way to do this is to remove, disassemble, clean and reassemble the control valve, but this takes a period of 1-2 hours and therefore prevents a color change during operation.

Another possibility for a color change is to flush the print head with an extremely high amount of detergent of several liters and over a longer period of several minutes, which also prevents a color change during operation due to the required amount of detergent and the required flushing time.

Finally, there is also the possibility of replacing the control valve or the complete printhead, but this is also not possible during operation and therefore prevents a color change.

The known print heads described above therefore do not allow color changes during operation.

Reference should also be made to the technical background of the invention DE 696 22 407 T2 and DE 36 34 747 A1 .

Reference should also be made to the technical background of the invention WO 2015/071270 A1 , US 5,659,347 A , EP 2 002 898 A1 and WO 2015/186014 A1 .

Finally revealed EP 2 133 154 A2 a printhead according to the preamble of claim 1. However, this known printhead is not yet completely satisfactory.

The invention is therefore based on the object of providing a correspondingly improved printhead and specifying a corresponding operating method.

This object is achieved by the print head according to the invention and the operating method according to the invention according to the independent claims.

The invention encompasses the general technical teaching of technically designing the print head in such a way that a color change is made possible in the coating operation. This is achieved in that the print head can be rinsed with a washing-up liquid in the event of a color change, in order to rinse residues of coating agent out of the print head.

In accordance with the prior art, the print head according to the invention has a coating agent feed in order to feed the coating agent to be applied to the print head. In addition, the print head according to the invention preferably also has a separate detergent supply in order to supply a detergent. It should be mentioned here that the coating agent feed is preferably separate from the flushing agent feed, so that the print head for feeding the coating agent on the one hand and for feeding the washing agent on the other hand preferably has separate inlets.

If there are only a few colors, one color tube (coating agent supply) per color could be connected to the applicator (print head) (integrated color changer technology). Then there is a flushing agent connection and a pulsed air connection in or on the applicator. These are then used for rinsing. In addition, the print head according to the invention also has a return in order to return coating agents and / or dishwashing agents, to be precise either in a ring line or in a disposal. The printhead according to the invention thus has, in addition to the separate connections for supplying the coating agent and the detergent, also a separate connection to return the coating agent or detergent.

The return flow into the return is preferably controlled by a controllable return valve, which can be designed as a return valve operated by the medium or as a proportional valve. Such valve types are known per se from the prior art and therefore do not have to be described in more detail.

According to the invention, the print head has a plurality of nozzles in order to dispense the coating agent. A control valve is assigned to the individual nozzles in order to control the dispensing of the coating agent through the respective nozzle. The above-mentioned flushing agent supply then preferably has branch lines which lead to the individual control valves, so that all of the control valves of the printhead can be flushed with the flushing agent at the same time.

The individual branch lines of the detergent supply are preferably designed such that the detergent supplied is uniformly distributed over the branch lines to the control valves, so that the individual control valves are flushed with essentially the same amount of detergent.

According to the invention, the print head has a plurality of nozzles for dispensing the coating agent and in each case an associated control valve for controlling the dispensing of coating agent through the nozzles, as has already been briefly explained above. As in the known construction described at the beginning, each control valve can have an electrical coil, which can be wound on a coil tube. It was already explained at the beginning of the prior art that coating agent residues can be deposited in this coil tube, which on the one hand impair the functionality of the control valve and on the other hand prevent the ability to change colors. In the print head according to the invention, the flushing agent feed line therefore preferably opens into the coil tube in order to flush the inside of the coil tube.

It should be mentioned here that the coil tube - as in the conventional control valve described at the beginning - is preferred has a circular inner cross section and contains a coil core. It can be advantageous here if the coil core has a profile cross section which does not completely fill the inner cross section of the coil tube in order to leave space between the coil tube and the coil core for the detergent so that the detergent can flow through in the axial direction. For example, for this purpose the coil core can have a star-shaped profile cross section with radially protruding ribs extending in the axial direction, so that the washing-up liquid can flow in the axial direction between the ribs of the coil core.

Alternatively, there is the possibility that the coil core has a flushing groove in its lateral surface, which can run, for example, axially, in the circumferential direction or in a spiral. Furthermore, axially extending rinsing channels can also be arranged in the coil core.

Another example provides that the profile cross section of the coil core is lattice-shaped and through which the detergent can flow.

It should also be mentioned that the coil core is preferably sealed with a seal with respect to the coil tube, in particular with a compressive strength of more than 2 bar, 4 bar or 6 bar.

It has already been briefly mentioned above that the print head has several control valves, all of which can be flushed. The individual control valves generally each have a coil tube, the detergent supply then opening into all coil tubes in order to be able to flush all the coil tubes.

It should also be mentioned that, as in the known control valve described at the beginning, each control valve generally has a displaceable armature which is displaced as a function of the current supply to the coil and which, depending on its position, closes or releases the nozzle. This armature preferably runs coaxially in the coil tube over part of its length and preferably has an axially permeable profile cross section, so that detergent can flow between the armature and the inner wall of the coil tube. For this purpose, the armature preferably has a non-circular profile cross section, which does not completely fill the circular inner cross section of the coil tube and therefore allows an axial flow of detergent. For example, the profile cross section of the anchor can be star-shaped or cross-shaped.

In a variant of the invention, the flushing agent feed opens into the coil tube in the axial direction between the armature and the coil core.

In another variant of the invention, however, the flushing agent feed opens into the coil tube in the axial direction in the region of the coil core, in particular at the end of the nozzle tube facing away from the movable armature.

In another variant of the invention, the movable armature is arranged in a detergent-permeable guide cage, in particular in a slotted cylinder. This has the advantage that the movable armature can be flushed during a flushing process, as a result of which coating agent deposits on the armature are avoided.

In another variant of the invention, the displaceable anchor has a central guide bore, a guide pin projecting into the guide bore. This creates a linear guide that can also be rinsed.

In another exemplary embodiment of the invention, a flexible membrane is provided which separates the control valve from the coating agent supply, so that the control valve is protected by the membrane from contact with a coating agent. Here, the control valve itself does not have to be rinsed at all, since the control valve itself does not come into contact with the respective coating agent at all. Rather, only the smooth surface of the membrane on the coating agent side should be rinsed, which is, however, very simple and efficient, since the smooth membrane surface hardly forms starting points for paint deposits.

The print head according to the invention preferably enables a quick color change within a color change time of less than 1h, 20min, 10min, 30s, 10s or even less than 5s.

Here, the lowest possible color change losses are also sought, which are preferably less than 5l, 2l, 200ml, 20ml, 10ml, 5ml or even less than 2ml in the print head according to the invention.

This also advantageously leads to a very low consumption of detergent when changing colors, the detergent consumption preferably being less than 10l, 5l, 2l, 200ml, 100ml, 50ml, 20ml or even less than 10ml.

Furthermore, there is also the possibility within the scope of the invention that the print head has a plurality of separate detergent feeds in order to supply different detergents, which can be adapted, for example, to the respective coating agent.

In addition, it should be mentioned that the print head with its media-carrying parts is preferably constructed in such a way that the media-carrying parts are free of dead spaces and / or free of undercuts in order to improve flushability.

To improve the flushability, there is also the possibility that the print head is provided with a cleaning-promoting coating on its surfaces which come into contact with the coating agent, such a coating also being known as an "easy-to-clean coating".

In addition, it should be noted that the invention not only claims protection for the print head according to the invention described above as a single component or as a replacement part. Rather, the invention also claims protection for a complete coating device with such a print head.

In addition, the coating device according to the invention preferably also includes a color changer, such as a linear color changer, a rotary color changer, a color changer integrated in the print head, or an A / B color changer. These types of color changers are known per se from the prior art and therefore need not be described further.

Finally, the invention also includes a corresponding operating method for such a printhead, the individual process steps already result from the above description and therefore do not have to be described in more detail.

However, it should be mentioned that the detergent can be a universal detergent that is suitable for both water-based paint and solvent-based paint. In addition, the detergent a VOC-free (VOC: v olatile o rganic c ompounds) can be detergent.

During the rinsing process, the printhead can also be rinsed together with the rinsing agent or alternately with pulsed air.

There is also the possibility that an aerosol is supplied to the printhead for rinsing.

Furthermore, there is the possibility within the scope of the invention that different flushing agents are fed to the print head one after the other.

In a variant of the operating method according to the invention, a solvent-based lacquer is first supplied and applied. The print head is then rinsed with a solvent-based rinsing agent in order to rinse out residues of the solvent-based varnish. A separating agent, for example alcohol, can then optionally be added. In the next step, a water-based paint is then applied and applied. Finally, the print head is then rinsed with a water-based washing-up liquid in order to rinse out residues of the water-based painting.

The above description explains a change from a solvent-based paint to a water-based paint. Of course, the reverse is also a change from a water-based paint possible on a solvent-based lacquer, which requires a correspondingly changed sequence of the process steps described above.

After a color change, the print head is preferably pressed on with the new coating agent, i.e. filled. A defined amount of lacquer is preferably also applied through the nozzle of the printhead.

When the print head according to the invention is in operation, there is also the possibility that all the fluids (coating agent and detergent) dispensed during a rinsing process are collected for disposal.

Furthermore, there is also the possibility that when changing the color, the outer surface of the nozzle head is also rinsed in order to remove residues of coating agent adhering there.

Regarding the rinsing process, it should also be mentioned that the rinsing agent can be discharged one after the other or alternately into the return line or through the nozzle. In addition, there is also the option of rinsing with a mixture of detergent and pulsed air.

Figur 1

eine schematische Darstellung eines herkömmlichen Steuerventils in einem Druckkopf zur Lackapplikation,

Figur 2

eine schematische Darstellung des Steuerventils mit einer Spülmittelzuführung,

Figur 3

eine Abwandlung von Figur 2, bei der das Spülmittel über die Beschichtungsmittelzuführung zugeführt wird,

Figur 4

eine weitere Abwandlung mit einem spülbaren Führungskäfig für den Anker,

Figur 5

eine weitere Abwandlung mit einem spülbaren Führungsstößel,

Figur 6

eine weitere Abwandlung mit einer Spülmittelzuführung am oberen Ende des Spulenrohrs,

Figur 7

eine Abwandlung mit einer flexiblen Membran zur Trennung des Steuerventils von den medienführenden Kanälen,

Figur 8

eine schematische Darstellung eines erfindungsgemäßen Druckkopfs mit einem vorgeschalteten Farbwechsler und einer Rückführung, sowie

Figur 9

eine schematische Darstellung zur Versorgung von mehreren Steuerventilen mit Spülmittel und Beschichtungsmittel.

Other advantageous developments of the invention are characterized in the subclaims or are explained in more detail below together with the description of the preferred exemplary embodiments of the invention with reference to the figures. Show it:

Figure 1

1 shows a schematic representation of a conventional control valve in a print head for coating application,

Figure 2

1 shows a schematic illustration of the control valve with a detergent supply,

Figure 3

a variation of Figure 2 , in which the detergent is supplied via the coating agent feed,

Figure 4

a further modification with a flushable guide cage for the anchor,

Figure 5

a further modification with a flushable guide plunger,

Figure 6

a further modification with a detergent supply at the upper end of the coil tube,

Figure 7

a modification with a flexible membrane for separating the control valve from the media-carrying channels,

Figure 8

a schematic representation of a printhead according to the invention with an upstream color changer and a feedback, and

Figure 9

a schematic representation of the supply of several control valves with detergent and coating agent.

The following is a schematic representation of a control valve according to the invention in Figure 2 described, wherein the control valve is arranged in a printhead. This exemplary embodiment of a control valve according to the invention partially corresponds to the conventional control valve described at the outset and shown in FIG to avoid repetition, reference is made to the above description, the same reference numerals being used for corresponding details.

A special feature of this exemplary embodiment is that the control valve has a flushing agent feed 13, which opens into the interior 12 of the coil tube 5. Flushing agent can thus be supplied via this flushing agent supply 13 in order to flush the control valve with a flushing agent in the event of a color change. This enables a color change during operation to be carried out within a short time.

In addition, the control valve in this exemplary embodiment has a special design of the seal 8 between the coil core 7 and the coil tube 5, the seal 8 permitting a pressure resistance of more than 2 bar.

Figure 3 shows a schematic representation of a further exemplary embodiment of a control valve according to the invention in a printhead, this exemplary embodiment partially matching the exemplary embodiment described above, so that in order to avoid repetition reference is made to the above description, the same reference numerals being used for corresponding details.

A special feature of this exemplary embodiment is that detergent can flow freely around the displaceable armature 9, so that the detergent can also rinse the interior 12 of the coil tube 5. For this purpose, the armature 9 has a cross-shaped profile cross section with axially extending ribs, so that the flushing agent can flow between the ribs of the armature 9 in the axial direction into the interior 12 of the coil tube 5. So the detergent is not - as with Figure 2 - fed via the detergent supply 13, but via the coating agent supply 4, which is therefore used alternately for the supply of coating agent and for the supply of detergent. The coil core 7 is sealed from the interior 12 by the seal 8.

Figure 4 shows a further embodiment, which also largely corresponds to the embodiment described above, so that to avoid repetition reference is made to the above description, the same reference numerals being used for corresponding details.

A special feature of this exemplary embodiment is that the displaceable anchor 9 is arranged in a flushable guide cage 14, which consists of a slotted cylinder, so that the interior of the guide cage 14 can be flushed. The seal 8 seals the interior of the coil tube 5 against the media-carrying area.

Figure 5 shows yet another embodiment, so that again to avoid repetition reference is made to the above description, the same reference numerals being used for corresponding details.

Here, the armature 9 has a guide bore 15 in the center, into which a guide pin 16 engages, the fit from the guide bore 15 and the guide pin 16 also being accessible for detergent.

In addition, the seal 8 seals the annular gap between the coil tube 5 and the coil core 7.

The embodiment according to Figure 6 again partially agrees with the embodiment according to Figure 2 match so that to avoid repetition, reference is made to the above description, the same reference numerals being used for corresponding details.

A special feature of this exemplary embodiment is that the detergent supply 13 does not open into the interior 12 of the coil tube between the coil core 7 and the armature 9. Rather, the detergent supply 13 opens into the coil tube at the upper end of the coil tube 5.

It is important here that the coil core 7 does not completely fill the free inner cross section of the coil tube 5, so that the detergent can flow downward from the detergent supply 13 located above into the interior 12.

Figure 7 shows a further modification of a flushable control valve, which provides a flexible membrane 17 for this purpose, which separates the control valve from the media-carrying parts in the coating agent supply 4. Here, the control valve itself does not have to be rinsed with detergent, since the control valve itself does not come into contact with the respective paint. Rather, only the membrane 17 on its coating agent side is touched by the respective lacquer, so that only this side of the membrane 17 has to be rinsed, which is easily possible by adding detergent via the coating agent supply.

Figure 8 shows a highly simplified schematic representation of a coating device according to the invention with a coating agent feed 18, a color changer 19, a print head 20 according to the invention, a return valve 21 and a return 22.

The color changer 19 can supply the printhead 20 with differently colored coating agents, the printhead 20 optionally being rinsed with detergent via a detergent feed, not shown, or via the coating agent feed 18.

Residues of coating agent and detergent that occur during a rinsing process can then be discharged into the return line 22.

Finally shows Figure 9 a schematic representation of a print head according to the invention with a plurality of control valves 23.1, 23.4, which are supplied with coating agent via a common coating agent supply 24 with a plurality of branch lines 25.

In addition, the coating device also has a common detergent supply 26, which is connected via a branch line 27 to the individual control valves 23.1-23.4, so that all the control valves 23.1-23.4 of the printhead can be flushed with detergent.

Reference symbol list:

1

Nozzle plate

2nd

Nozzle opening

3rd

Base plate

4th

Coating agent feed

5

Coil tube

6

Kitchen sink

7

Coil core

8th

Seal between coil core and coil tube

9

Armature (valve needle)

10th

Seal for sealing the nozzle opening

11

Return spring

12th

Interior of the coil tube

13

Detergent supply

14

Flushable guide cage for the anchor

15

Guide hole in the anchor

16

Guide pin

17th

membrane

19th

Color changer

18th

Coating agent feed

20

Printhead

21

Return valve

22

return

23.1-23.4

Control valves

24th

Coating agent feed

25th

Branch lines of the coating center feed

26

Detergent supply

27

Branch lines of the detergent supply

Claims (15)

1. Printhead for applying a coating agent to a component, in particular for painting a motor vehicle body component with a paint, with

   a) several nozzles (2) for dispensing said coating agent,

   b) several control valves (23.1-23.4) which are associated with the individual nozzles (2) and control the release of coating agent through the individual nozzles (2),

   c) a coating agent supply (4; 24) for supplying the coating agent to be applied and/or for supplying a rinsing agent, wherein the printhead enables a colour change during coating operation and can be rinsed with the rinsing agent during a colour change in order to rinse our coating agent residues from the printhead,
   characterized by

   d) a return system (22) with a separate return connection for recirculating the coating agent and/or the rinsing agent.
2. Printhead according to claim 1, characterized by a separate rinsing agent supply (13; 26) for supplying the rinsing agent.
3. Printhead according to claim 1 or 2, characterized by a return valve (21) for controlling the return flow into the return system, in particular

   a) as a self-actuated return valve or

   b) b) as proportional valve.
4. Printhead according to claim 2 or 3,
   characterized in that

   a) the rinsing agent supply (26) has branch lines (27) to the individual control valves (23.1-23.4),

   b) the branch lines of the rinsing agent supply (13; 26) are designed such that the supplied rinsing agent is evenly distributed among the branch lines to the control valves so that the control valves are rinsed with substantially the same amount of rinsing agent.
5. Printhead according to one of claims 2 to 4, if dependent on claim 2, characterized in that

   a) each control valve (23.1-23.4) has an electric coil (6),

   b) each control valve (23.1-23.4) has a coil tube (5) on which the coil (6) is wound externally,

   c) the rinsing agent supply (13; 26) opens into the coil tube (5) and directs the rinsing agent into the interior of the coil tube (5), and

   d) the coil tube (5) preferably has a circular internal cross-section.
6. Printhead according to claim 5, characterized in that

   a) the coil core (7) has a profile cross-section which does not completely fill the internal cross-section of the coil tube (5) in order to leave space for the rinsing agent between the coil tube (5) and the coil core (7), and/or

   b) the profile cross-section of the coil core (7) is star-shaped, and/or

   c) the profile cross-section of the coil core (7) has in its circumferential surface at least one rinsing groove which preferably runs

   c1) axially,

   c2) in circumferential direction or

   c3) spirally; and/or

   d) the profile cross-section of the coil core (7) has an axially extending rinsing channel, and/or

   e) the profile cross-section of the coil core (7) is grid-shaped.
7. Printhead according to one of claims 5 or 6, characterized in that the coil core (7) is sealed with respect to the coil tube (5) by means of a seal (8), in particular with a pressure resistance of more than 2 bar, 4 bar or 6 bar.
8. Printhead according to claim 5,
   characterized in that

   a) the printhead comprises a plurality of coil tubes (5), and

   b) branch lines branch off from the rinsing agent supply (13; 26) into all coil tubes (5), and/or

   c) the coil tubes (5) can be rinsed together; and/or

   d) the coil tubes (5) can be separately rinsed individually.
9. Printhead according to any of claims 5 to 8,
   characterized in that

   a) each one control valve (23.1-23.4) has a displaceable armature (9) which is displaced as a function of the current supplied to the coil and closes or releases the nozzle as a function of its position,

   b) the armature (9) extends coaxially in the coil tube (5) over part of its length,

   c) the armature (9) has an axially permeable profile cross-section in order to be able to pass rinsing agent through between the armature (9) and the inner wall of the coil tube (5),

   d) the anchor (9) preferably has a non-circular profile cross-section, in particular a star-shaped or cross-shaped profile cross-section, in order to leave space for the coating agent.
10. Printhead according to claim 8 or 9,
    characterized in that

    a) the rinsing agent supply (13; 26) opens into the coil tube (5) in axial direction between the armature (9) and the coil core (7)in order to supply the rinsing agent, or

    b) the rinsing agent supply (13; 26) opens into the coil tube (5) in axial direction in the region of the coil core (7), in particular at the end of the coil tube (5) remote from the armature (9).
11. Printhead according to any of claims 5 to 9,
    characterized in that

    a) each control valve (23.1-23.4) has a displaceable armature (9) which is displaced as a function of the current applied to the coil (6) and closes or releases the nozzle (2) as a function of its position, and the armature (9) is arranged in a guide cage (14) which is permeable to rinsing agent, in particular in a slotted cylinder, or

    b) the displaceable armature (9) has a central guide hole (15), and a stationary guide pin (16) projects into the guide hole (15) of the movable armature (9), and the guide hole (15) can be rinsed in the displaceable anchor core (9).
12. Coating device for coating components, in particular for painting motor vehicle body components with a paint, characterized by a printhead according to one of the preceding claims for applying the coating agent to the component.
13. Coating device according to claim 12, characterized by a colour changer which is arranged upstream of the printhead and is connected on the output side to the printhead in order to feed the printhead selectively with coating agents of different colours, in particular in a construction as

    a) linear colour changer,

    b) rotary colour changers,

    c) integrated colour changer inside the printhead, or

    d) A/B colour changer.
14. Operating method for a printhead according to any of Claims 1 to 11, characterized by the following step:

    a) Supplying the coating agent to be applied through the coating agent supply (4; 24),

    b) rinsing the printhead with a rinsing agent,

    c) recirculating the coating agent and/or the rinsing agent through the separate return connection..
15. Operating method according to claim 14, characterized by the following steps:

    a) supplying a solvent-based paint and applying the solvent-based paint,

    b) rinse the printhead with a solvent-based rinsing agent,

    c) optional supply of a release agent when changing from the solvent-based paint to a water-based paint,

    d) supply of a water-based paint and application of the water-based paint; and

    e) rinse the printhead with a water-based rinsing agent.

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