EP3554712B1 - Printing head for applying a coating material - Google Patents

Description

The invention relates to a print head for applying a coating agent to a component, in particular for applying a lacquer to a motor vehicle body component.

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 print heads do not emit a spray of the paint to be applied, but rather a spatially narrowly delimited jet of paint which is almost completely deposited on the component to be painted, so that almost no overspray occurs.

Numerous nozzles are generally arranged in a nozzle plate of the print head, the individual nozzles being able to be released or closed in each case by a movable valve element. The movable valve element is usually a valve needle with an elastomer insert as a seal. The valve needle with the elastomer insert is here slidable between a closed position and an open position, the elastomer insert sealing the nozzle in the closed position of the valve needle, whereas the elastomer insert is lifted off the nozzle in the open position and thereby releases the fluid flow (mostly ink according to the prior art) through the nozzle.

A disadvantage of this known type of seal between the movable valve element (e.g. valve needle) and the nozzle is first of all the complex manufacturing process in the manufacture of the elastomer insert.

Another disadvantage is that the valve needle can only be miniaturized with the elastomer insert within certain limits, so that a lower limit cannot be exceeded with regard to the nozzle spacings between the adjacent nozzles.

Furthermore, the manufacturing precision in the manufacture of the elastomer insert is limited, so that large fluctuations occur with regard to the required valve lift.

Reference should also be made to the technical background of the invention DE 36 34 747 A1 , DE 10 2014 012 705 A1 , DE 41 38 491 A1 .

Furthermore, the general technical background of the invention also includes DE 10 2009 029 946 A1 , DE 38 04 092 A1 , EP 3 272 669 A1 , EP 2 644 392 A2 and GHASEM G NASR et al .: "Chapter 2. Background on Sprays and Their Production ".

Finally revealed WO 2015/186014 A1 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 another solution for sealing the movable valve element from the nozzle.

This object is achieved by a printhead according to the invention in accordance with the main claim.

First of all, it should be noted that the term “printhead” used in the context of the invention is to be understood generally and is only used to delimit atomizers (for example rotary atomizers, disc atomizers, airless atomizers, air mix atomizers, ultrasonic atomizers), which spray the spraying agent to be applied submit. In contrast to this, the print head according to the invention emits a spatially narrowly limited coating agent jet. Such printheads are known per se from the prior art and for example in DE 10 2013 092 412 A1 , US 9,108,424 B2 and DE 10 2010 019 612 A1 described.

It should also be mentioned that the printing head according to the invention is preferably used to apply a lacquer (e.g. basecoat, clearcoat, water-based lacquer, solvent-based lacquer). However, the print head according to the invention can alternatively also be designed for the application of other coating agents, such as for example the application of sealant, insulating material, adhesive, primer, etc., to name just a few examples.

In accordance with the prior art, the print head according to the invention has a nozzle plate which contains at least one nozzle for dispensing the coating agent. This nozzle preferably emits the abovementioned coating agent jet onto the component to be coated. In principle, however, there is also the possibility that the nozzle is arranged inside the printhead and only passes the coating agent on to the outer outlet nozzle, which then applies the coating agent jet to the component.

In addition, in accordance with the prior art, the print head according to the invention has a plate-shaped valve element which can be displaced by a valve drive in order to control the dispensing of the coating agent through the nozzle.

This valve element is movable relative to the nozzle plate, the valve element closing the nozzle in a closed position, whereas the movable valve element releases the nozzle in an open position.

The movement of the valve element between the closed position and the open position is preferably a purely linear movement (displacement movement), but within the scope of the invention there is in principle also the possibility of other movements of the valve element between the open position and the closed position. A rotary movement, a pivoting movement or a combined rotary and linear movement of the valve element can be mentioned merely by way of example.

Furthermore, according to the invention, the valve element lies in the closed position on the underside of the nozzle plate facing away from the valve drive.

The print head according to the invention can comprise a seal for sealing the nozzle with respect to the movable valve element in the closed position of the valve element.

In the printhead according to the invention, however, this seal is preferably not designed as an elastomer insert on the valve element, since this is associated with the problems described at the outset.

For example, the seal can be arranged on the nozzle plate, ie not on the movable valve element, as is the case with the known elastomer inserts. Alternatively, however, there is also the possibility that the seal according to the invention is attached to the movable valve element, ie not to the nozzle plate. In addition, there is also the possibility of a combination of these two alternatives, a seal being attached both to the movable valve element and to the nozzle plate, in this case the nozzle, the two seals then interacting.

It should also be mentioned that the seal is preferably flat and in the closed position brings about a flat contact between the movable valve element and the seal. For example, flat sealing plates or sealing layers can be applied to the inside of the nozzle plate for this purpose.

According to the invention, the pressure head has a valve drive for moving the movable valve drive. In one exemplary embodiment of this invention, the valve drive comprises a flexible drive membrane, which is mechanically coupled to the movable valve element and can be acted upon by a drive fluid (for example hydraulic fluid, compressed air) in order to deflect the drive membrane and thereby move the valve element.

The valve drive can be designed as a magnetic actuator with a coil and a displaceable armature in the coil, the armature being mechanically coupled to the movable valve element and being displaced between the open position and the closed position depending on the energization of the coil.

It was mentioned briefly at the beginning that the seal can be flat. For example, the seal can have a sealant layer that is vulcanized onto the nozzle plate, vapor-deposited, applied by a layer-forming method or printed on, for example.

Alternatively, there is also the possibility that the seal has a film that can be glued, placed, bonded or laminated onto the nozzle plate, for example.

Regarding the choice of material in the context of the invention, it should be mentioned that the movable element preferably consists at least partially of metal, plastic or silicon.

• Metall auf Metall,
• Kunststoff auf Metall,
• Metall auf Kunststoff,
• Kunststoff auf Silizium,
• Silizium auf Silizium, oder
• Metall auf Silizium.

Furthermore, the print head according to the invention preferably has one of the following material pairs on the nozzle between the side of the valve element and the side of the nozzle:

• Metal on metal,
• Plastic on metal,
• Metal on plastic,
• Plastic on silicon,
• Silicon on silicon, or
• Metal on silicon.

The movable valve element can, for example, consist of metal and can be combined with a valve tappet made of plastic.

In addition, the nozzle can be made of silicon or contain a nozzle insert made of silicon, while the movable valve element is at least partially made of steel or plastic (e.g. PTFE: polytetrafluoroethylene).

When the movable valve element moves from the open position into the closed position, the seal generally also forms a mechanical stop which limits the movement of the valve element into the closed position. The seal has two functions, namely the actual sealing function and the function of a mechanical stop.

In another exemplary embodiment of the invention, however, a separate mechanical stop is provided in order to limit the movement of the valve element into the closed position. This can be advantageous because a defined compression force acts on the seal.

The mechanical stop preferably has a material pairing between the side of the valve element and the side of the nozzle which provides metal on both sides. The seal, however, is preferably elastic and experiences a certain material compression in the closed position, which is defined by the mechanical stop.

According to the invention, the movable valve element is designed as a valve plate, which can be moved by the valve drive, preferably via a tappet, between the open position and the closed position.

The plunger protrudes through the nozzle and, according to the invention, the valve plate lies in the closed position on the underside of the nozzle plate facing away from the valve drive. The valve plate is thus pulled into the nozzle to close the nozzle, whereas the nozzle plate is pressed out of the nozzle to open the nozzle.

It has already been mentioned above that the print head preferably emits a narrowly limited jet of coating agent, in contrast to a spray mist, as is emitted by conventional atomizers (e.g. rotary atomizers).

It should also be mentioned that the printhead can emit a droplet jet, in contrast to a coating agent jet connected in the longitudinal direction of the jet. As an alternative, however, there is also the possibility within the scope of the invention that the printhead emits a coating agent jet which is connected in the longitudinal direction of the jet, in contrast to a droplet jet.

In a special training, it may be advantageous to apply high voltage (30-90 kV) to the entire print head or to individual components of the print head (for example to the nozzle plate 1) in order to take advantage of the additional advantages of electrostatic painting, such as higher application efficiency and / or electrostatic wrapping around edges (the charged paint moves along the electrical Field lines, which also coat surfaces facing away from the applicator near edges).

When using electrostatic charging, a potential separation system must be used in the material supply when processing conductive paints. In this case, too, all components of the applicator must be designed to withstand high voltages.

A particular advantage of the printhead according to the invention is the fact that it works almost without overspray, i.e. the print head preferably has an application efficiency of at least 80%, 90%, 95% or 99%, so that essentially all of the applied coating agent is completely deposited on the component without overspray being produced.

It should also be mentioned that the print head preferably has a large surface coating capacity, so that the print head is also suitable for surface coating in the series coating of motor vehicle body components. Therefore, the print head preferably has a surface coating performance of at least 0.5 m ² / min, 1m ² / min, 2m ² / min or even 3m ² / min.

It should also be mentioned that the invention not only claims protection for the printhead according to the invention described above as a single component. Rather, the invention also claims protection for a complete coating system (for example painting system) for painting components (for example motor vehicle body components), a print head according to the invention being used as the application device.

For example, the print head according to the invention can be guided by a multi-axis painting robot, which preferably has serial kinematics with at least six movable robot axes.

Figur 1

eine schematische Darstellung eines Ausschnitts aus einem nicht erfindungsgemäßen Drucckopf mit einer flächigen Dichtung,

Figur 2

eine Abwandlung von Figur 1 mit einer Formanpassung von Düse und Ventilelement,

Figur 3

eine Abwandlung der Figuren 1 und 2 mit einer flexiblen Membran als Dichtung,

Figur 4

eine weitere nicht erfindungsgemäße Abwandlung mit einer zusätzlichen Antriebsmembran, die hydraulisch angetrieben wird,

Figur 5

eine weitere nicht erfindungsgemäße Abwandlung mit einem Stößel, der verschiebbar ist und eine Ventilplatte in einem Düsenkanal bewegt,

Figur 6

eine erfindungsgemäße Abwandlung von Figur 5, wobei die Ventilplatte auf der Außenseite des Druckkopfs dichtend aufliegen kann,

Figuren 7A und 7B

eine nicht erfindungsgemäße Abwandlung mit einer biegsamen Düsenplatte, die zum Öffnen bzw. Schließen der Düse gebogen werden kann, sowie

Figuren 8A-8C

verschiedene mögliche Konturen der Düse in einem erfindungsgemäßen Druckkopf.

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 illustration of a detail from a pressure head not according to the invention with a flat seal,

Figure 2

a variation of Figure 1 with a shape adjustment of the nozzle and valve element,

Figure 3

a variation of the Figures 1 and 2nd with a flexible membrane as a seal,

Figure 4

a further modification not according to the invention with an additional drive membrane which is driven hydraulically,

Figure 5

a further modification not according to the invention with a plunger which is displaceable and moves a valve plate in a nozzle channel,

Figure 6

a modification of the invention Figure 5 , wherein the valve plate can rest on the outside of the print head,

Figures 7A and 7B

a modification not according to the invention with a flexible nozzle plate which can be bent to open or close the nozzle, and

Figures 8A-8C

different possible contours of the nozzle in a print head according to the invention.

The variant according to FIG. 1 which is not according to the invention is first described below. Thus, this drawing shows a schematic representation of a control valve in a print head for coating application in a painting system for painting motor vehicle body components, the print head being moved by a multi-axis painting robot with serial robot kinematics with at least six robot axes, as is known per se from the prior art is and therefore need not be described in more detail.

The print head has a nozzle plate 1 with a plurality of nozzles 2, only one nozzle 2 being shown here for simplicity.

The paint to be painted is fed from a paint feeder 3 in the print head, the paint feeder 3 being delimited in the drawing below by the nozzle plate 1 and above by a further plate 4.

The upper plate 4 has an opening coaxial with the nozzle 2 in the nozzle plate 1, on which a coil tube 5 is placed coaxially, the coil tube 5 being wound with a coil 6.

In the coil tube 5 there is a coil core 7, which is sealed at the upper end of the coil tube 5 by a seal 8 with respect to the coil tube 5.

In addition, there is an armature 9 in the coil tube 5, which can be displaced in the direction of the double arrow, the movement of the armature 9 being dependent on the energization of the coil 6.

The drawing shows the armature 9 in a lower closed position in order to seal the nozzle 2. For a paint application, however, the coil 6 is energized so that the armature 9 is pulled up in the drawing in order to release the nozzle 2.

In addition, the control valve has a return spring 10 which presses the armature 9 into the closed position shown in the drawing without energizing the coil 6.

At its free end, the armature 9 carries a seal 11 in order to seal the nozzle 2 in the closed position.

The seal 11 on the armature 9 cooperates in the closed position together with a flat seal 12 on the inside of the nozzle plate 1.

In the closed position shown, there is therefore a flat contact contact between the two seals 11, 12 on the armature 9 on the one hand and on the nozzle plate 1 on the other.

The flat seal 12 on the inside of the nozzle plate can consist, for example, of a layer of sealant which is vulcanized onto the inside of the nozzle plate 1, vapor-deposited, applied by a layer-forming method or printed on.

Alternatively, there is the possibility that the seal 12 is a film that is placed on the inside of the nozzle plate 1, glued or laminated on.

Furthermore, there are various possibilities for the material combinations of the seal 11 on the one hand and the seal 12 on the other. For example, metal on metal, plastic on metal, metal on plastic, plastic on silicon, silicon on silicon or metal on silicon can be used as material pairing.

Figure 2 shows a modification of the variant according to Figure 1 , 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 variant is that the nozzle 2 tapers conically in the inlet area in the direction of flow and has lateral nozzle flanks. The seal 12 is therefore applied to the side flanks of the nozzle 2.

In addition, the seal 11 is adapted to this shape of the nozzle and therefore tapers conically towards its free end, so that the seal 11 on the one hand and the nozzle 2 on the other are adapted in shape, which leads to a good sealing effect.

Figure 3 shows a further modification of the variants described above, so that to avoid repetition reference is made to the above description.

A special feature of this variant consists in a flexible sealing membrane 13 instead of the seal 11. The drawing shows the open position in which the armature 9 is raised and the sealing membrane 13 releases the nozzle. To close the nozzle 2, however, the coil 6 is de-energized, so that the armature 9 is pressed downward by the return spring 10 in the drawing until the sealing membrane 13 rests on the internal mouth opening of the nozzle 2 in the nozzle plate 1 and thereby the nozzle 2 closes.

However, the sealing membrane 13 not only has the function of releasing or closing the nozzle 2. Rather, the sealing membrane 13 also effects a seal between the paint supply 3 and the other components of the control valve, such as the armature 9, the coil tube 5 and the coil core 7. This is advantageous because it prevents paint deposits in the control valve and in particular in the coil tube 5 become. This is particularly important when changing colors because the control valve itself does not have to be rinsed because it does not come into contact with the paint at all.

Figure 4 shows a modification of the variant according to Figure 3 , so that reference is made to the above description in order to avoid repetitions.

A special feature of this variant is the constructive design of the valve drive, which is not - as with Figure 3 - works electromagnetically, but hydraulically. For this purpose, the valve drive has a separate drive membrane 14, which can be acted upon by a hydraulic fluid 15 as a drive fluid, around the drive membrane 14 and thus also the sealing membrane 13 with the attached seal 11 in the direction of the double arrow.

It should be mentioned here that the drive membrane 14 and the sealing membrane 13 bring about a double seal between the hydraulic connection 15 and the nozzle 2. This prevents with double certainty that hydraulic fluid can escape through the nozzle 2 in the event of a fault.

Figure 5 shows a modification of the variant according to Figure 1 , so that reference is made to the above description in order to avoid repetitions.

A special feature of this variant is that the return spring 10 has been dispensed with, i.e. the movement of the armature 9 is controlled both in the closed position and in the open position solely by energizing the coil 6.

Another special feature is that the armature 9 is connected via a plunger 16 to a valve plate 17 which can be displaced in the nozzle arrow 18 in the direction of the double arrow. The drawing shows the position of the valve plate 17 in the closed position, in which the valve plate 17 rests on the top of the nozzle channel 18 and thereby seals the nozzle 2.

To open the nozzle 2, the plunger 16 with the valve plate 17, on the other hand, is pressed downward in the drawing and is then no longer in contact with the upper wall of the nozzle channel 18. The paint can then enter the nozzle channel 18 from the paint supply and flow out through the nozzle 2.

Figure 6 shows a modification of the variant according to Figure 5 , so that reference is made to the above description in order to avoid repetitions.

A special feature of this exemplary embodiment is that no nozzle channel 18 is arranged in the nozzle plate 1. Rather, the valve plate 17 lies in the closed position shown in the drawing on the outside of the nozzle plate 1 in a recess sealing.

The Figures 7A and 7B show another concept for opening or closing the nozzle 2. Here shows Figure 7A a closed position while Figure 7B shows an open position in which the nozzle 2 is released.

The nozzle 2 is either sealed or released by a fixed plunger 19. Here, the nozzle plate 1 is either not bent ( Figure 7A ) or so bent ( Figure 7B ) that the nozzle plate 1 is lifted off the fixed plunger 19 in the region of the nozzle 2. It is sufficient here if the nozzle plate 1 executes a bending-related stroke of, for example, 30 pm in the region of the nozzle 2.

The Figures 8A-8C show different possible contours of the nozzle 2, namely a cylindrical contour ( Figure 8A ), a conical contour ( Figure 8B ) and a contour with an elevation 20 on the outlet side of the nozzle 2 ( Figure 8C ).

Reference symbol list:

1

Nozzle plate

2nd

jet

3rd

Paint supply

4th

Upper plate

5

Coil tube

6

Kitchen sink

7

Coil core

8th

Seal between coil core and coil tube

9

anchor

10th

Return spring

11

Seal on the anchor to seal the nozzle

12th

Seal on the nozzle plate to seal the nozzle

13

Sealing membrane

14

Drive membrane

15

Hydraulic connection

16

Pestle

17th

Valve plate

18th

Nozzle channel

19th

Pestle

20

Elevation on the outside of the nozzle

Claims (9)

1. Print head for applying a coating agent to a component, in particular for applying a paint to a motor vehicle body component, having

   a) a nozzle plate (1),

   b) at least one nozzle (2) in the nozzle plate (1) for dispensing the coating agent, and

   c) a valve drive (5, 6, 9)

   d) a valve element (9) movable relative to the nozzle plate (1) for controlling the release of coating agent through the nozzle (2),

   d1) wherein the movable valve element (9) closes the nozzle (2) in a closed position,

   d2) whereas the movable valve element (9) releases the nozzle (2) in an opened position,

   d3) wherein the valve element (17) is plate-shaped and can be displaced by the valve drive (5, 6, 9);

   characterized in that

   e) in the closed position, the valve element (17) rests on the underside of the nozzle plate (1) remote from the valve drive (5, 6, 9).
2. Print head according to claim 1, characterized by a seal (11, 12) for sealing the nozzle (2) relative to the movable valve element (9, 11) in the closed position of the valve element (9, 11), wherein the seal (11, 12) is not formed as an elastomer insert on the valve element (9, 11).
3. Print head according to claim 2, characterized in that

   a) the seal (12) is attached to the nozzle plate (1), and/or

   b) the seal (12) is flat and, in the closed position, produces a flat contact contact between the movable valve element (9, 11) and the seal (12), and/or

   c) the seal (12) makes no relative movement relative to the nozzle (2) when the valve element moves from the closed position to the opened position.
4. Print head according to one of the preceding claims, characterized in that the valve drive (14, 15) has a flexible drive diaphragm (14) which is coupled to the valve element (9) and can be acted upon by a drive fluid, in particular hydraulic fluid or compressed air or the coating agent, in order to deflect the drive diaphragm (14) and thereby move the valve element.
5. Print head according to one of the preceding claims, if dependent on claim 2, characterized in that

   a) the seal (12) has a sealant layer, which is preferably applied to the nozzle plate (1), and

   a1) vulcanised on,

   a2) evaporated,

   a3) applied by a layer-forming process, or

   a4) is imprinted; and/or

   b) the seal (2) has a foil which is applied preferably to the nozzle plate (1)

   b1) on the surface,

   b2) glued on,

   b3) bonded or

   b4) is laminated on, and/or

   c) the movable valve element (9) at least partially consists of

   c1) metal,

   c2) plastic; or

   c3) silicon, and/or

   d) one of the following material pairings is provided on the nozzle (2) between the side of the valve element (9) and the side of the nozzle (2):

   d1) metal on metal,

   d2) plastic on metal,

   d3) metal on plastic,

   d4) plastic on silicon,

   d5) silicon on silicon,

   d6) metal on silicon, and/or

   e) the print head for moving the valve element (9) made of metal has a valve tappet made of a plastics material, and/or

   f) the nozzle (2) consists of silicon or contains a nozzle insert of silicon, while the movable valve element (9) consists at least partially of steel, rubber or plastic, in particular of polytetrafluoroethylene.
6. Print head according to one of the preceding claims, characterised in that

   a) a mechanical stop is provided in order to limit the movement of the valve element (17) into the closed position,

   b) the mechanical stop has a material pairing metal on the side of the valve element (17) and metal on the side of the nozzle (2), and

   c) the seal (11, 12) is elastic and, in the closed position, undergoes a certain material compression defined by the mechanical stop.
7. Print head according to one of the preceding claims, characterized in that

   a) the print head delivers a narrowly confined jet of coating media as opposed to a spray; and/or

   b) the print head emits a droplet jet as opposed to a jet of coating material which is continuous in the longitudinal direction of the jet; or

   c) the print head emits a jet of coating agent which is connected in the longitudinal direction of the jet, in contrast to a droplet jet, and/or

   d) the print head has an application efficiency of at least 80%, 90%, 95% or 99%, so that substantially all of the applied coating agent is completely deposited on the component without overspray; and/or

   e) the print head has an areal coating capacity of at least 0,5 m²/min, 1m²/min, 2m²/min or at least 3m²/min; and/or

   f) the print head has at least one electrically controllable actuator for ejecting drops of the coating agent from the print head, in particular a magnetic actuator or a piezo actuator.
8. Coating installation for coating components, in particular for painting motor vehicle body components, having an application device for applying the coating agent, characterized in that the application device is a print head according to one of the preceding requirements.
9. Coating installation according to claim 8, characterized by a multi-axis painting robot, in particular with a serial kinematics and at least six movable robot axes, wherein the painting robot guides the print head.

Images