EP3892384A1 - Dispensing device - Google Patents

Abstract

A device for generating and dispensing electrostatically charged particles for coating objects has a dispensing head (1) with an inlet opening (3) and a discharge nozzle (4) in fluid communication with the inlet opening (3). A cavity (9) is arranged in the dispensing head (1), into which a channel insert (10) can be inserted, which has a first end (11) and a second end (12), between which a continuous flow channel (13) extends , wherein the flow channel (13) has a multiple change in direction along a running length.

Description

The invention relates to a device for generating and dispensing electrostatically charged particles for coating objects, in particular the head of such a device.

Such devices are known from the prior art and can be used, for example, for powdering or powder coating, in that particles within the device are electrostatically charged and released from the device by means of a gas flow in order to adhere to the object to be coated due to the charge. It is known to actively charge the particles in question using a suitable electrical voltage and to discharge them by means of an air stream. Such a device is manufactured under the type designation RS-Powdertech by Rolf Schlicht GmbH in Reinfeld and sold worldwide. As an alternative to this, devices are also known, for example in the form of spray guns, in which the charging of the particles to be dispensed takes place tribologically in the interior of the spray gun. Here, too, the discharge takes place by means of an air stream.

Temporary contacting of the particles with a suitable material is necessary for the electrostatic charging of particles on the basis of the tribological effect. For this purpose, flow channels are to be provided through which fluid containing particles is conveyed, the particles having to touch the inner wall. To ensure that as many particles as possible in a particle stream are charged, a correspondingly long flow channel is required, which is a spray gun or similar Device can make unwieldy and requires a comparably large volume. In addition, the success of the tribological effect for certain particles can depend on the material on the inner wall of the flow channel, so that several spray guns with different equipment are required when using different particles.

The object of the present invention is therefore to propose an alternative device of the type mentioned at the outset, in which a tribological charge that is as optimal as possible takes place, which, if possible, is also suitable for different particles and which is compact in size.

This object is achieved according to the invention by a device having the features specified in claim 1. Advantageous configurations of the device emerge from the subclaims, the following description and the drawings, the features specified in the subclaims and the description being applicable individually but also in suitable combination.

The device according to the invention for generating and dispensing electrostatically charged particles for coating objects has a head with an inlet opening and an outlet opening, which are in fluid-conducting connection via a flow channel. According to the invention, the flow channel has a multiple change in direction at least along part of its length.

The basic idea of the solution according to the invention is therefore to be able to provide a comparatively long flow channel by changing the direction of the flow channel several times, which is significantly longer than the distance between the inlet and outlet opening of the head, which on the one hand allows a compact design of the head, on the other hand, with a suitable shape, the change of direction ensures that the particles traveling along the flow channel with the fluid flow are in intensive contact with it the surrounding wall and thus the tribological effect of charging the particles occurs with high effectiveness. The multiple change in direction ensures that practically all particles touch the channel wall on their way through the flow channel and thus the desired electrostatic charging of the particles occurs.

It goes without saying that the device according to the invention has means for supplying and transporting the particles in a manner known per se. Typically, but not necessarily, a structure of the device can be designed in such a way that in a stationary part of the device there is a storage container for the particles and a fan arrangement for generating a fluid flow for transporting the particles into the head and also for discharging them from the head Any necessary ancillary units are provided. The connection from the stationary part of the machine to the head is then made via a hose. Alternatively, a discharge container can be provided on the head, similar to a paint spray gun, and the fluid flow can be implemented by a central compressed air supply. This is not important for the present invention, which relates to the design of the head.

The head is an element which can be gripped by a user in order to direct the discharge opening in the manner of a nozzle onto an object to be coated and to discharge particles. The head can also be arranged on a holder in order to experience a constant alignment or on a manipulator (robot arm). The inlet opening can be with a hose or be connected to another line in order to lead a fluid, for example compressed air, with particles contained therein into the inlet opening. The fluid flows through the head and leaves it through the discharge opening. When passing through the flow channel, which is located between the inlet opening and the discharge nozzle when the channel insert is inserted, the particles contained in the fluid hit inner surfaces of the flow channel. With a suitable choice of material on the inner surfaces, the particles are electrostatically charged due to the tribological effect.

According to an advantageous development of the invention, a cavity is arranged in the head, into which a channel insert can be inserted, which has a first end and a second end, between which the flow channel provided with multiple changes of direction extends.

According to the invention, the flow channel is located in the channel insert, which is designed as a separate component. The channel insert is introduced into the cavity of the head, for example inserted, and thereby forces a flow through the flow channel located therein.

The peculiarity of the flow channel lies in the multiple change of direction. While the fluid follows the changes in direction, the particles contained therein come into contact with the inner surfaces of the flow channel due to their inertia in the areas of the changes in direction. Since several changes of direction adjoin one another, preferably in opposite directions, it can be achieved that a predominant and almost complete proportion of the particles come into contact with the inner surfaces. This proportion can be influenced in particular by the strength and the number of changes in direction. The aim is to keep the distance between the inlet opening as short as possible and the discharge nozzle electrostatically charge as high a proportion of particles as possible in this way, so that a particularly good electrostatic charge of the particles results over the shortest possible length of the discharge head.

At least one section of the cavity is designed to be complementary to the channel insert. The channel insert should be able to be positioned in the head largely without play, so that the fluid can be introduced into the flow channel in a targeted manner and can flow in a targeted manner to the discharge opening. Vibrations and lateral flow around the duct insert can thus be avoided. The channel insert is also not necessarily made of the same material as the head itself. The tribological effect can depend on the material pairing between the particles and the inner surfaces of the flow channel. The device according to the invention, in particular the head, accordingly makes it possible to provide channel inserts specially designed for certain particles, which can be inserted into the head as required.

As explained further below, the head can be designed to make the channel insert as easily exchangeable as possible. In addition to the choice of material for the channel insert, the course of the flow channel can also be made dependent on the type and size of the particles. It is important to ensure that the flow cross-section is sufficiently large so that it does not clog or impair the efficiency of the dispensing device.

In an advantageous embodiment, the flow channel has a meandering shape, in particular between the first end of the channel insert and the second end. A meander shape is characterized by successive loops or sections running in opposite directions. For example, the flow channel could be implemented in the form of a serpentine line. The individual loops or sections do not necessarily have to be provided with a continuous curvature. For manufacturing reasons, it could also be advisable to implement rectilinear sections that run at an angle to one another in order to achieve the changes in direction. The meander shape could be realized uniformly and at least partially symmetrically in the channel insert.

The flow channel preferably has a flow cross-section which is offset along the length of the channel several times along a first axis which is transverse to a connecting line between the inlet opening and the discharge opening, in particular between the first end and the second end of the channel insert. The flow channel is particularly preferably offset exclusively along this first axis. The shape of the flow channel therefore does not have to be complex, but can also be produced with simple, cutting means. The offset only along a first axis can nevertheless produce the desired effect of intensive contact between the particles and an inner wall of the flow cross-section.

In an advantageous embodiment, the flow channel is open to a surface section of the channel insert running between the first end and the second end and closed to an opposite surface section of the channel insert. As a result, the flow channel can be produced by dipping a milling cutter into a corresponding side of a workpiece and then moving it on a desired track to achieve the intended shape. It is also irrelevant whether the flow channel remains open on one side of the channel insert, since the channel insert is pushed completely into the cavity of the dispensing head and is preferably fixed there. The channel insert is completely surrounded by the material of the head, so that the open side is closed and the flow channel is only accessible at the two ends.

In a further advantageous embodiment, the inlet opening has an opening cross section which at least covers a receiving cross section of the cavity, so that the channel insert can be introduced into the cavity or removed from the cavity through the inlet opening. The channel insert can therefore be exchanged very easily, which means that the channel insert can be quickly adapted to the type of particles contained in the fluid in order to optimize the tribologically based electrostatic charge. In addition, replacing the channel insert is also resource-saving, because only different channel inserts are required for the delivery of different particles instead of several delivery heads.

According to a particularly advantageous embodiment, the cavity has at least one shoulder on a side facing away from the inlet opening, which shoulder is designed to make surface contact with the channel insert in the inserted state. The channel insert can consequently only be pushed into the cavity up to the shoulder. The shoulder could be designed in an annular manner and only come into contact with an edge surface of the channel insert. By restricting the insertion of the duct insert, it can be completely fixed by an additional securing device in the area of the inlet opening.

It is advantageous if the inlet opening has an internal thread for receiving a connecting flange with an external thread on a screw section. The connecting flange can have a receptacle facing away from the screw section for receiving a hose or the like. As it can be screwed, the connection flange can easily be removed, for example to insert or replace the duct insert. It is conceivable that the connecting flange is designed to be screwable by hand without tools. This could be done through an appropriate Surface structure can be achieved on a peripheral surface, which leads to improved static friction. As an alternative to this, a tool holder is also conceivable, for example in the form of at least one pair of opposing receiving surfaces for a wrench or the like. A connection with a bayonet lock is also conceivable.

The screw section is particularly preferably designed to fix the channel insert by pressing it in the cavity in the screwed-in state. Pressing in can take place with a comparatively low force, which leads to only insignificant tension on the channel insert, but allows sufficient fixation. As a result, the channel insert is fixed in the cavity without additional means and, as already mentioned above, can be exchanged simply by temporarily removing the connecting flange

It is also advantageous if the discharge opening is provided in a discharge nozzle which can be removed. The discharge nozzle can therefore also be exchanged to adapt to the respective application.

In an advantageous embodiment, the head is formed from a plastic, in particular the flow channel is lined with a plastic in order to produce the tribological effect. From a manufacturing point of view, it is advantageous if the head is made entirely of plastic, but it can also consist of different plastics that are manufactured in a multi-component injection molding process, especially if the integration of a channel insert is to be dispensed with. The head can thus be manufactured inexpensively and additional electrical insulation is not necessary for this.

The head is preferably designed to electrostatically charge particles contained in a fluid flowing into the inlet opening by temporary contact on inner surfaces of the flow channel. The material located on the inner surfaces should be suitable for charging the corresponding particles when they come into contact and subsequently detach. It is conceivable to use different materials in the channel insert for different particles. In addition, it is conceivable to manufacture the inner wall of the flow channel in sections from different plastics in order, for example, to be able to remove particles of different materials in one operation. The sections do not necessarily have to adjoin one another in the longitudinal direction of the channel; rather, they can also be arranged next to one another.

• Fig. 1 zeigt eine Seitenansicht eines Kopfes der Vorrichtung,
• Fig. 2 zeigt eine erste Schnittansicht des Kopfes,
• Fig. 3 zeigt eine zweite Schnittansicht des Kopfes,
• Fig. 4 zeigt eine Vorderansicht auf den Kopf der Vorrichtung, und
• Fig. 5 zeigt eine dreidimensionale Ansicht des Kopfes.

The invention is explained in more detail below with reference to an exemplary embodiment shown in the drawing. Show it:

• Fig. 1 shows a side view of a head of the device,
• Fig. 2 shows a first sectional view of the head,
• Fig. 3 shows a second sectional view of the head,
• Fig. 4 shows a front view of the head of the device, and
• Fig. 5 shows a three-dimensional view of the head.

The in Fig. 1 The dispensing head 1, shown in side view, of a device for generating and dispensing electrostatically charged particles is the part of the device with which the charging of the particles and the discharge from the device takes place. It deals is typically a handpiece, which can, however, also be part of a machine or be guided on a robot arm. This head 1 has an essentially cylindrical body 2 with an inlet opening 3 and a discharge opening 5 in a discharge nozzle 4 in fluid connection with the inlet opening 3. The discharge nozzle 4 is designed merely by way of example as a slot nozzle which is beveled in a wedge shape on both sides and has an elongated discharge opening 5. The inlet opening 3 is connected to a connecting flange 6 which carries a hose 7 in order to introduce a fluid containing particles into the inlet opening 3. The connection flange 6 is electrically connected to a grounding cable 8. The grounding ensures that the particles flowing through are brought into a defined initial state in terms of charge technology. This is typically a zero potential, after which the particles are then charged either positively or negatively in the subsequent flow channel. The charge orientation, whether positive or negative, is determined by the choice of material for the surrounding discharge channel.

The body 2 has a cylindrical basic shape and can be held in the hand by a user for coating or powdering an object. As an alternative to this, the dispensing head 1 with its body 2 can also be clamped in a holder suitable for this purpose, for example in order to powder a wire moving past by machine before an insulating layer is applied. The body 2 is largely made entirely of a plastic.

Fig. 2 FIG. 11 shows a sectional view of the dispensing head 1, the sectional plane in FIG Fig. 1 marked by the letter B. Here, a cavity 9 can be seen in the body 2, which extends from the inlet opening 3 in the direction of the discharge nozzle 4. A channel insert 10 is inserted into the cavity 9 and in this state directly adjoins the inlet opening 3. The cavity 9 and the channel insert 10 are designed to be complementary to one another, so that the channel insert 10 can be positioned in the cavity 9 largely without play.

The channel insert 10 has a first end 11 and a second end 12, the first end 11 being positioned at the inlet opening 3. A continuous flow channel 13 extends between the two end faces 11 and 12 and has a multiple change of direction along a length. A particle-entrained gas, which is passed through the hose 7 into the inlet opening 3, gets into the flow channel 13 via the first end 11 and is conveyed to the discharge nozzle 4 while passing through all changes of direction.

In the exemplary embodiment, an edge surface of the second end 12 of the channel insert 10 rests flush on an annular shoulder 14, which is located at a point of the cavity 9 facing away from the inlet opening 3. The shoulder 14 secures the channel insert 10 in an axial direction running towards the discharge nozzle 4. The inlet opening 3 has an internal thread 15 which can be brought into engagement with an external thread 16 of a screw section 23 of the connecting flange 6. The connecting flange 6 has at least one pair of mutually opposite receiving surfaces 24 (see FIG Fig. 5 ), which can be brought into contact with a wrench or the like.

The screw section 23 is dimensioned such that it is in surface contact with the first end 11 of the channel insert 10 when it is screwed into the inlet opening 3 and consequently presses it against the shoulder 14. As a result, the channel insert 10 is fixed axially in both directions. At the same time, the inlet opening 3 is dimensioned such that its opening cross section completely covers the cross section of the channel insert 10 or a receiving cross section of the cavity 9. Through this it is possible to introduce the channel insert 10 through the inlet opening 3 into the dispensing head 2, the screw section 23 simultaneously functioning as a cover for the cavity 9. Since the opening cross section of the inlet opening 3 is larger than the receiving cross section of the cavity 9 in which the channel insert 10 is located, the cavity 9 can be manufactured very easily by machining from the side of the inlet opening 3.

Between the shoulder 14 and the discharge nozzle 4, the cross section of the cavity 9 expands in several stages 17 in order to enable a harmonious and continuous transition to an initial cross section of the discharge nozzle 4. Should it be necessary, longer channel inserts 10 with graduated diameters could also be used, which then extend at least into the first of these steps 17 and are nevertheless fixed by the shoulder 14.

As a result of the multiple change in direction of the flow channel 13, intensive contact of the particles contained in the fluid with an inner wall of the flow channel 13 is brought about. The particles are charged due to the triboelectric effect. It makes sense to use different channel inserts 10 for different types of particles in order to optimize the electrostatic charge in each case. It is advantageous if the material on the inner wall of the flow channel 13 differs from the material of the respective particles, so that the materials have different Fermi potentials. The intensive contact between the particles and the inner wall due to the multiple changes in direction allows the overall length of the channel insert 10 and thus of the dispensing head 2 as a whole to be significantly shortened compared to dispensing devices with straight channels.

For example, the flow channel 13 has a widening 18 at the first end 11, so that the entry of the fluid containing particles from the inlet opening 3 into the flow channel 13 is facilitated. In the exemplary embodiment shown, the change in direction of the flow channel 13 is expressed as a local offset along an axis which is identified here as the Y-axis by way of example. This runs perpendicular to an X axis, which extends as a longitudinal axis in the form of a connecting line between the first end 11 and the second end 12. While the flow channel 13 extends essentially along an axial direction, that is to say along the X-axis, it shifts alternately in a transverse direction, that is to say along the Y-axis. As a result, a meandering, serpentine course of the flow channel 13 is formed, which forces the contact between the particles and the inner wall of the flow channel 13. To simplify production, there is no offset along a Z-axis running transversely to the X-axis and the Y-axis. This is especially good in Fig. 3 can be seen in which a sectional view is shown, the sectional plane of which in Fig. 2 marked with the letter A.

the end Fig. 3 it can be seen that the flow channel 13 is closed to a first surface section 19 of the channel insert 10 and is open to an opposite, second surface section 20. The channel insert 10 can have a cylindrical shape. The two surface sections 19 and 20 could consequently be two opposing areas of a cylindrical jacket surface. The flow channel 13 can consequently be integrated very easily by milling from the second surface section 20. If more complex processes are desired, casting processes or additive manufacturing processes could be considered.

It is conceivable to equip the channel insert 10 with an additional anti-twist device or an alignment aid, so that it is in a desired position Alignment in the head 1 remains. This could be done by a local deviation from a round cross section of the channel insert 10 (not shown), the cavity 9 being designed to be complementary thereto.

The discharge nozzle 4 is designed to be removable, so that the dispensing device 1 as a whole can be adapted very easily to different applications. To fasten the discharge nozzle 4, connecting means 21 are provided, which are arranged radially. They could include screws, for example, which protrude through an annular mounting flange 22 of the discharge nozzle and can be screwed into corresponding threads (not shown) in the discharge head 1 there.

Fig. 4 shows the dispensing head 1 in a front view. The circular shape of the discharge nozzle 4 and the narrow shape of the slot 5 can be seen here in particular.

Finally shows Figure 5 in a three-dimensional representation of the dispensing head 1 as a very compact and easily manageable part of the device.

List of reference symbols

1

Head, dispensing head

2

body

3

Inlet opening

4th

Discharge nozzle

5

Discharge opening

6th

Connecting flange

7th

hose

8th

Grounding cable

9

cavity

10

Channel use

11

first end

12th

second end

13th

Flow channel

14th

unit volume

15th

inner thread

16

External thread

17th

step

18th

Widening

19th

first surface section

20th

second surface section

21

Lanyard

22nd

Mounting flange

23

Screw section

24

Recording area

Claims (15)

Device for generating and dispensing electrostatically charged particles for coating objects, comprising a head (1) with an inlet opening (3) and a discharge opening in fluid communication with the inlet opening (3) via a flow channel (13), characterized in that the Flow channel (13) has a multiple change of direction at least over a section along its length. Device according to claim 1, characterized in that a cavity (9) is arranged in the head (1), into which a channel insert (10) can be inserted, which has a first end (11) and a second end (12) between which the section of the flow channel (13) provided with changes in direction extends. Device according to Claim 1 or 2, characterized in that the flow channel (13) has a meandering shape in the region of its section provided with changes in direction. Device according to one of the preceding claims, characterized in that the flow channel (13) has a flow cross-section which, along the length of the run, is repeated several times along a first axis (Y) which is transverse to a connecting line between the first end (11) and the second end ( 12) runs in the channel insert (10) is offset. Device according to one of the preceding claims, characterized in that the flow channel (13) is open to a surface section (20) of the channel insert (10) running between the first end (11) and the second end (12) and is closed to an opposite surface section (19) of the channel insert (10). Device according to one of the preceding claims, characterized in that the inlet opening (3) has an opening cross section which at least covers a receiving cross section of the cavity (9) so that the channel insert (10) can be introduced into the cavity (9) through the inlet opening (3) or can be removed from the cavity (9). Device according to one of the preceding claims, characterized in that the cavity (9) has at least one shoulder (14) on a side facing away from the inlet opening (3) which is designed to make surface contact with the channel insert (10) in the inserted state enter into. Device according to one of the preceding claims, characterized in that the inlet opening (3) has an internal thread (15) for receiving a connecting flange (6) with an external thread (16) on a screw section (23). Device according to Claim 7 or 8, characterized in that the screw section (23) is designed to fix the channel insert (10) by pressing it into the cavity (9) in the screwed-in state. Device according to one of the preceding claims, characterized in that the discharge opening (5) is provided in a discharge nozzle (4) which can be removed. Device according to one of the preceding claims, characterized in that the head (1) is provided with a plastic at least in its flow channel-forming area. Device according to one of the preceding claims, characterized in that the head (1), in particular the plastic in the flow channel-forming area, is designed to remove particles that are contained in a fluid flowing into the inlet opening (3) by temporary contact on inner surfaces of the Electrostatically charge the flow channel (13). Head (1) for a device according to one of the preceding claims with a flow channel (13) which has a multiple change of direction over a section along its running length. Head according to claim 13, with features of one or more of claims 2 to 12. Channel insert for a head according to claim 13 or 14.

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