EP1010469B1 - Process and system for supplying paint to an electrostatic coating installation - Google Patents

Abstract

Exchangeable containers are movable by a gripping device (26), insulated against earth to the material removal point (1,2), supplied with high voltage from the spraying unit (10), across an insulated stretch (30). The gap is sufficient for ensuring the high voltage insulation of the material removal point (1,2). The containers are movable linearly across the insulated stretch.

Description

The invention relates to a method and a system for ink supply of an electrostatic coating system according to the preamble of the independent claims, which are particularly suitable for the serial coating of vehicle bodies. Such a method and system is known from EP0792695.

In the electrostatic series coating of workpieces of the type considered here with water-based paint and other relatively highly conductive coating material, there is known to be the problem of electrical insulation between high-voltage nebulizers or other spray devices and a grounded material supply system. For plants where the atomizers are supplied from a loop system in which the available materials of different shades continuously circulate, two basically different possibilities are known: Either grounded atomizers with insulated outer electrodes were used to charge the coating material, or instead any intermediate tanks, the alternately for material removal with the high-voltage atomizer and be connected to the grounded supply system for refilling. If coating operation should be possible without switching off the high voltage during refilling, two separate intermediate containers were used (DE 29 00 660, EP 0 455 107 and 0 455 109). For producing the respective connections between the intermediate containers and the spraying device or the earthed supply system, it is known to use, for example, pneumatically displaceable separating couplings (WO 87/05832; US Pat. No. 4,313,475) whose insulating distance is dimensioned according to the electrical flashover width of the applied high voltage.

A paint supply system for an electrostatic coating machine is also known from EP 0 792 695, in which containers which can be filled with the coating material are arranged on a support rotatably mounted in the coating machine and from this support from a filling point to a removal point remote from the filling point and from there are pivotable back to the filling point. The containers are connected via movable color couplings at the sampling point with the sprayer and at the filling with a color changer. During the removal of material during the coating, the containers are thus separated from the external supply lines connected to the color changer, while they are disconnected from the spraying device during filling. During removal of material from the container connected to the sprayer no movements of the rotatable base are possible, which u.a. result in relatively long material change times.

Recently, for important applications, coating systems are also preferred in which the atomizers are supplied from the coating machine externally supplied interchangeable containers.

In one known from US 4,785,760 system of this type, which is, however, used only for painting robots, the interchangeable containers are filled in the spray booth in the range of motion of the robot, connected to paint supply lines taps, from where they get the Lakkierroboter itself as needed , Apart from the fact that the part of the robot, in which the containers are eingsetzt, this can not be under high voltage, resulting in time losses during container change. In addition, the robot must perform consuming controlled movements for container change.

Lower time losses and a comparatively simple control makes it possible to use a system known from EP 0 796 664 and 0 796 665, which also works with interchangeable containers, in which the ink containers are transported from a filling point to a transfer point and from there to a gripper movable by a pneumatic cylinder unit a material removal point are used. After use, the containers are retrieved from the gripper to the transfer point and then transported back to the filling point. The exchangeable containers are advantageously filled with the quantity of paint required for coating a workpiece, for example a vehicle body, or a specific workpiece part.

Based on the last-mentioned known system, the invention has for its object to provide a method and system for supplying ink to an electrostatically-working coating system with sprayable replaceable containers for water-based paint or similar conductive coating material, in which without sacrificing the principal advantages of the known system applied to the spray high voltage when changing the container does not have to be turned off, so that there is the possibility not to interrupt the coating operation when changing the container.

This object is achieved by the methods and systems characterized in the claims.

According to a first aspect of the invention there is the advantage that the desired supply principle with a possibly considerable number of relatively small interchangeable containers (cartridges) with conductive coating material is made possible even with continuous high-voltage spraying device and the material removal point when inserting the container may be at high voltage even though the entire service area for these containers is grounded.

According to another aspect, the invention has the advantage that an endless painting of an unlimited number of containers is made possible, which can be replaced after use without interruption of the coating operation against new containers of the same color type, as long as no color change is required. Also, the color change can be carried out with the least possible loss of time.

Fig. 1

ein schematisches Prinzipbild des hier beschriebenen Systems;

Fig. 2

eine perspektivische Darstellung einer zweckmäßigen Ausführungsform einer Behälterwechseleinrichtung für das System nach Fig. 1; und

Fig. 3

die Einrichtung nach Fig. 2 in einer anderen Betriebsstellung.

On an embodiment shown in the drawing, the invention will be explained in more detail. Show it:

Fig. 1

a schematic diagram of the system described here;

Fig. 2

a perspective view of an expedient embodiment of a container exchange device for the system of FIG. 1; and

Fig. 3

the device of FIG. 2 in another operating position.

The system shown in Fig. 1 is used for color paint supply of a continuous high-voltage spray device 10, which may consist of one or more electrostatic rotary atomizers per se conventional type with upstream metering pump 11, for example. The spraying device 10 is preceded by a distributor valve arrangement 12, to which two lines 14 and 15 serving as color channels are connected or connectable, which can optionally be connected to the spraying device 10 via the distributor valves. Between each of the conduits 14 and 15 and the manifold valve assembly 12 is one in the illustrated example Disconnect 16 and 17 connected, the driven by a pneumatic cylinder and piston unit coupling member is movable over an insulating distance, which is sufficient to isolate the high-voltage spray device 10 to earth. The spraying device 10, the distributor valve assembly 12 and the separating couplings 16, 17 may be located in a movable coating machine part 18, for example in the roof beam of a conventional roofing machine for motor vehicle coating.

The existing in this case of flexible hoses lines 14 and 15 are arranged high voltage insulated against earth and lead at their spraying device 10 remote ends in each one also insulated against earth material removal point 1 and 2 in a generally designated 20 container exchange area, located in a permanently grounded part in or next to the machine or coating plant and may be stationary.

The material change area 20 further includes various grounded supply points 3, 4, 4 'and 4 "for replaceable containers (not shown in Fig. 1) to be inserted into the material removal points 1, 2. After insertion into the supply point 3 via a color change valve arrangement FW in the usual way is connected to ring lines, emptied containers themselves can be filled for reuse in the container exchange area 20. At the supply locations 4 to 4 ", which can serve as buffer locations, externally filled containers are to be provided and / or after use can be removed again from the container exchange region 20. According to a particular advantage of this system, the system can be fitted to the buffer or supply points 4, 4 'and / or 4 "manually with containers, which is useful especially for containers with relatively rarely required special colors can be and the provision of a practically un limited Variety of available shades possible. Also, a rotatable container magazine (not shown) for a plurality of interchangeable container can be provided to one of the supply points 4, 4 'or 4 ".

With few (eg less than 10) additional supply points, especially for less frequently required colors, it can be achieved that a color change without the necessity of being able to rinse a container during the color change is practicable in almost all color wishes occurring in practice (eg in vehicle painting) have to. The same applies to the case that before a color change material of the same color is successively removed from two or more containers.

While the supply points 3 to 4 "are permanently grounded, the material removal points 1 and 2 can be continuously applied to the applied high voltage during continuous coating operation by the spray device 10 via the lines 14, 15 connected to it 2 and 3), which ensure the required high-voltage insulation of the material removal points against the grounded parts of the container exchange region 20.

The container changing device arranged in the region 20 essentially consists of a rotatably mounted grounded rotary table 22 on which two gripper devices 23 and 23 'are mounted. Each gripping device has a drive device 24 or 24 ', for example in the form of a pneumatic piston and cylinder unit for a preferably straight, eg rod-like insulating 25 and 25', at the free end of a gripper 26 and 26 'is arranged. The grippers 26 and 26 'may be made of metal. Arrangement and design of the Isolierarms 25, 25 'are such that the gripper 26, 26' when inserting a container in the material removal points 1, 2 against the earthed parts of the gripping device 23, 23 'connected to the gripper are insulated. The two grippers 26, 26 'are independently movable.

In their reciprocations between their retracted positions shown in Fig. 1 in the vicinity of the grounded parts of the turntable assembly and their end positions on or in the material removal points 1, 2, the grippers 26, 26 'via a likewise for high-voltage insulation of the sprayer 10 moved to high voltage material removal points 1, 2 against earth-sized Isolierstrecke formed between the material removal points and the grounded parts of the gripping means 23, 23 'and the turntable 22. The Isolierstrecke is indicated by the arrow 30 and forms in the illustrated example a concentric to the axis of rotation of the turntable 22 arcuate insulating region in a horizontal plane in the example described in parallel to the directions of movement of the gripper.

Accordingly, the two isolated material removal points 1, 2 are on a concentric to the turntable axis circular arc on which also serve to supply the system with filled containers supply points 3, 4, 4 'and 4'', so that they as well as the material removal points 1, 2 of each of the two grippers 26, 26 'can be reached. The linear directions of movement of the two grippers 26 and 26 'can intersect one another according to FIG. 1 at or in the material removal points 1, 2 and consequently also at or in the supply point 3, 4, 4' and 4 ", to which they respectively depend As a result, it is achieved that in each case one gripper can insert or pick up a container at the relevant point, while at the same rotary table position the other gripper can pick up or insert another container there Container changing devices and their Program control thus correspond to the system described in DE patent application 198 38 805.

Instead, however, it may be more expedient for design reasons, if the directions of movement of the gripper do not intersect on said arc, but are aligned by corresponding small angular movements of the turntable 22 on the positions 1, 2, etc. (Figures 2 and 3).

The replaceable containers may correspond to the metering cylinders described in EP 0 796 664 and 0 796 665, which however may preferably be emptied by pressurizing their inner piston.

Contrary to the representation in FIG. 1, it is assumed that during operation of the system described here, the material removal points 1 and 2 are connected through the separating clutches 16, 17 located in the connection position to the high-voltage spraying device 10, ie continuously via the lines 14 and 15 High voltage. It is also assumed that the spraying device 10 is supplied by its metering pump 11 via the distributor valve arrangement 12 coating material from a container used in the material removal point 1. Thus, while the coating material is sprayed from this container, at the same time, for example, a second container in the supply point 3 can be filled by the color changer connected there. After filling the second container is removed from one of the gripping means 23 or 23 'from the supply point 3, pivoted by turning the turntable 22 in the position shown in the drawing, to reach the second material removal point 2 required position and then by extending the respective gripper 26th or 26 'across the insulating section 30 away in the high-voltage material removal point 2 used. There is the until then at Erdpotential befindiche container automatically raised to the high voltage potential of the spray, with any unwanted sudden potential change can be avoided by appropriate means. Now, the second container can be connected in parallel by opening the associated valve of the distributor valve assembly 12 to the first container, so be connected to the same spraying device 10 for material removal. The spraying operation can thus be continued without interruption. As a rule, the distributor valve arrangement 12 connects the second container to the spraying device only when it has interrupted its connection after emptying the first container. While the spraying device 10 is now supplied from the second container, the first container can be removed from the material removal point 1 by one of the gripping devices 23 or 23 'and either brought to the supply point 3 for filling or instead to one of the buffer supply points 4, 4 'or 4', where it can be removed from the system and replaced with an externally filled container, so that the container coming from the material removal point with high voltage potential can be easily and properly discharged when the gripper is withdrawn into the grounded area of the system to bridge the insulating arm 25, 25 'by a suitably sized resistor connected between the grippers 26, 26' and earth.

After inserting a container in one of the material removal points 1 and 2, the grippers are in the example considered in each case again released from the container remaining in the material removal point and moved back to its retracted initial position.

The separating clutches 16 and 17 are useful here for additional functions not to be described in detail, especially in a color change. For similar reasons, run from the manifold valve assembly 12 via the illustrated additional disconnect couplings isolated rinsing and return hoses 33 and from the material removal points 1 and 2 additional return lines 31 from the movable machine part 18 and from the container exchange area 20 out. The disconnect couplings 16 and 17 could be used in the described continuous spraying operation but possibly also for high-voltage insulation of the sprayer 12 of the grounded material change device, especially if a container exchange device is provided without the function of isolated gripper.

In the embodiment of a container exchange device suitable for the system described in FIG. 2, the two material removal points 1 and 2 are each located in a cylinder housing 41 or 42 made of insulating material. The two cylinder housings 41, 42 stand with their longitudinal axes vertically on a stationary base in or next to the coating machine, that is perpendicular to the horizontally assumed movement plane of the insulating arms of the gripping devices (23 in Fig. 1) shown at 43. In the cylinder housings 41 and 42 all stationary parts of the material removal points 1, 2 are included, which are placed on high voltage. The spacing of these high voltage parts from the metallic grounded parts of the turntable 22 and the gripping means and thus the above-mentioned insulating distance is at least as large as the prescribed and standardized minimum air insulation distance for a given high voltage (380 mm in a typical example).

2 and 3 gripping means 43 and 43 'are provided which have an insulating arm 25 or 25' in the form of a straight elongated body of insulating material, at its one, the material removal points 1, 2 opposite end on the piston as a drive means 24th (Fig. 1) serving pneumatic cylinder unit 44 is attached. At its free other end, the insulating arm 25, 25 'carries an oblong, extending vertically with its longitudinal axis, ie transverse to the plane of movement of the insulating arms extending housing 46 and 46 'of insulating material, which is attached to the end face of the insulating. In this insulating housing 46, for example, the metallic gripper elements are housed with which the gripping device 43 releasably on retaining elements (not shown) on the cylindrical outer side of the interchangeable, can be detected at 48 recognizable paint container. The total length of the insulating body formed from the insulating arm 25 and the attached insulating 46 is dimensioned so that the required for a given high voltage insulation between the metallic gripper elements and earth is ensured.

In Fig. 2 and 3, the supply point 3 is further shown in more detail with their color change valve arrangement FW, in Fig. 2 without color container. The color change valve assembly FW is connected to a connector 50 which includes valve ports to which ports for filling are provided in the bottom of the cylindrical paint containers. Corresponding connection openings (not shown) are located at the bottom of the material removal points 1 and 2 within the cylinder housing 41 and 42 for the removal of material from the containers. Since the ink containers are each placed on these connection openings and to be lifted after filling or material removal again, it is expedient that in the insulating housing 46 gripper elements of a drive unit (not shown) relative to the insulating arm 25 vertically, ie transversely to the plane of movement and to store slidably parallel to the longitudinal axis of the container 48. This lifting movement can be for example about 20 mm. Instead, however, the required lifting movement could also be carried out in a manner known per se by connection elements of the supply point 3 or the removal points 1, 2.

The insulating cylinder housings 41, 42 have in their cylindrical wall each one of the turntable 22 facing opening 52 for insertion of the container 48. The opening 52 is dimensioned so that the container can pass together with the insulating housing 46 of the respective gripping device 43. Normally, the opening 52 is closed by a cylindrical outer wall correspondingly curved shield-like cover 54 made of insulating material, which is pushed away only for inserting and removing a container for releasing the opening 52, so that during the remaining time all high-voltage parts of the container exchange region 20 (FIGS. Fig. 1) are securely enclosed. This has the advantage of reducing the space requirement.

The turntable 22 is preferably made of metal and, like the cylinder units 44 and all other on the side facing away from the cylinder housings 41, 42 side of the insulating arms 25, 25 'continuously grounded conductive parts.

Fig. 2 shows a gripping device 43, for example, when removing a first container from the cylinder housing 41 of a material removal point 1, while the second gripping device 43 'holding another container 48 outside the material removal points for insertion into the same cylinder housing 41. While the first container is removed from the removal point 1 and returned to the grounded turntable 22, it is also connected to earth via the above-mentioned discharge resistor.

In Fig. 3, the changing device is shown in the subsequent position in which the second container 48 has been inserted into the now re-closed cylinder housing 41 and removed from there first container 48 'has been connected by the gripping device 43 in the supply point 3 to the color change valve arrangement is.

Likewise, according to another example, it would be conceivable that starting from Fig. 3 just two containers of the same color in the housing cylinder 41 and 42 are inserted and connected to the spray, while a third container (48 ') with the same or a different color straight at the Supply point 3 is filled. Then, according to FIG. 2, the third container would then be inserted into the housing cylinder 41, while the container (48) previously removed from there waits for the filling or replacement.

Notwithstanding the arrangement shown in Fig. 1, here the two gripping means 43 and 43 'are not mounted on the turntable 22 so that their directions of movement in the material removal points 1 and 2 intersect. To reduce the space they are here rather closely juxtaposed with approximately parallel (or with a small angle to each other inclined) directions of movement of their insulating arms 25, 25 'mounted. Because of this less bulky arrangement, the turntable 22 must make a small angular movement between the removal of a container and the insertion of the provided new container 48 in the same material removal point 1 to bring the new container in the required position for insertion.

Claims (24)

1. Method of supplying paint to an electrostatic coating installation for the series coating of workpieces, in particular vehicle bodies, with a spraying device (10) connected to a high voltage, wherein replaceable containers (48) which can be connected to the spraying device (10) are provided or filled with coating material of selectable colour at a supply station (3, 4) connected to earth potential, whilst they can be decoupled and insulated from the spraying device (10), wherein the containers (48) are moved by a changing device (22, 26) from the supply station (3, 4) to a material removal station (1, 2) remote therefrom, where they are connected to the spraying device (10), and wherein the containers are brought back after use to the other or another supply station (3, 4), characterised in that the replaceable containers (48) are moved by a gripper (26), which is substantially insulated against earth, to the material removal station (1, 2), which in this case is connected by the spraying device (10) to a high voltage, over an insulating section (30) which is sufficient for high-voltage insulation of the material removal station (1, 2) against earth.
2. Method as claimed in Claim 1, characterised in that the containers (48) are moved in a linear manner over the insulating section (30).
3. Method as claimed in Claim 1 or 2, characterised in that during the removal of material from a container (48) inserted into a first removal station (1) another container is moved by the gripper device (23) on the path between an earthed supply station (3, 4) and a second material removal station (2).
4. Method as claimed in Claim 1, characterised in that two containers (48) containing coating material to be sprayed are each provided at a respective material removal station (1, 2) and are each connected by way of a respective electrically conductive connection (14, 15) to the spraying device (10) which is connected to a high voltage.
5. Method as claimed in Claim 4, characterised in that the first container is connected for material removal to the spraying device (10) which is connected to a high voltage, that after the removal of material from the first container the connection between it and the spraying device (10) is shut off for the material, that when the connection between the first container and the spraying device (10) is shut off the second container is connected to the spraying device for removal of material, and that during the removal of material from the second container the first container is transported from the changing device (22, 26) to a refilling or other supply station (3, 4) or is replaced by a third container which is already filled.
6. Method as claimed in any one of the preceding claims, characterised in that that the connection between the material removal stations (1, 2) and the spraying device (10) is made and interrupted by a separating coupling.
7. Method as claimed in any one of the preceding claims, characterised in that the containers are emptied by program-controlled displacement of a piston in the container and at the supply station (3, 4) are connected to a paint change valve arrangement (FW) or are replaced after use by another container which was previously provided.
8. Method as claimed in any one of the preceding claims, characterised in that the direction of movement of the gripper (26) is pivoted to and fro by a rotatable support. (22) about the axis of rotation thereof between the material removal and supply stations (1 to 4).
9. System for supplying paint to an electrostatic coating installation for the series coating of workpieces, in particular vehicle bodies, with a spraying device (10) connected to a high voltage, with a supply station (3, 4) which is connected to earth potential and at which replaceable containers which can be connected to the spraying device (10) can be provided or can be filed with coating material of selectable colour, and with a container change device (22, 26) by which the containers can be moved from the supply station (3, 4) to a material removal station (1, 2) remote therefrom, where they can be connected by way of a line (14, 15) to the spraying device (10), and by which the containers can be brought back after use to the other or another supply station (3, 4), wherein for replacement of the containers a gripper device (23, 43) is provided which is disposed on a support (22) connected to earth potential and has at least one gripper (26) which is movable relative to the support (22) and engages releasably on the respective container, characterised in that the gripper (26) is connected so as to be substantially insulated against high voltage to a part (24) of the gripper device (23, 43) connected to earth potential and can be moved towards and away from the material removal station (1, 2) over an insulating section (30) which is adequate for high-voltage insulation against earth of the material removal station (1, 2) which in this case is connected to a high voltage by the spraying device (10).
10. System as claimed in Claim 9, characterised in that at least two material removal stations (1, 2) are provided which are insulated against earth and which by way of parallel-connected lines (14, 15) and a valve arrangement (12) are connected jointly to the spraying device (10) and can be connected by this latter to a high voltage.
11. System as claimed in Claim 9 or 10, characterised in that the gripper (16) is movable in a linear manner over the insulating section (30) by a drive means (24) which is mounted on a rotatably or pivotably mounted support (22).
12. System as claimed in any one of Claims 9 to 11, characterised in that the gripper (26) is disposed on an insulating arm (25) which is connected to a drive means (24) and which insulates the gripper against earth when the container is inserted into the material removal station (1, 2) which is connected to a high voltage.
13. System as claimed in any one of Claims 9 to 12, characterised in that an earthed supply station (3) connected to a paint change valve arrangement (FW) for filling the replaceable containers at this station (3) and/or one or several earthed supply or container change stations (4) for provision of filled containers and/or for removing used containers are provided.
14. System as claimed in any one of Claims 9 to 13, characterised in that at least two grippers (26, 26') are provided which are movable independently of one another and of which the linear directions of movement intersect one another at the material station(s) (1, 2) and/or at the supply or container change station(s) (4, 4', 4").
15. System as claimed in any one of Claims 9 to 14, characterised in that the gripper or grippers (26, 26') is or are mounted on a rotatably mounted turntable (22) by which the linear directions of movement thereof are pivotable under program control between the material removal stations and the supply or container change stations (3, 4).
16. System as claimed in any one of Claims 9 to 15, characterised in that the or each material removal station (1, 2) is connected to the spraying device (10) by way of a line (14, 15) which is insulated against earth and a separating coupling (16, 17), the separating section of which is adequate for insulating the high voltage against earth.
17. System as claimed in any one of Claims 9 to 16, characterised in that two material removal stations (1, 2) are or can be connected to a distributor valve arrangement (12) which is connected upstream of the spraying devices (10) by way of a line (14, 15) in each case and by which, when two material removal stations (1, 2) are simultaneously connected, the spraying device (10) can be supplied selectively from one container inserted into the first material removal station (1) or another container inserted into the second material removal station (2).
18. System as claimed in Claim 17, characterised in that at lest one additional line (30) is connected to the distributor valve arrangement (12) or can be connected thereto via a high-voltage insulating separating coupling through which the coating material and/or flushing fluid remaining in a paint changer is passed.
19. System as claimed in any one of Claims 9 to 18, characterised in that an additional line (31) through which the coating material and/or flushing material remaining during a paint change is connected to the material removal station (1, 2).
20. System as claimed in any one of Claims 12 to 19, characterised in that the insulating arm (25) is mounted on the piston of a pneumatic cylinder unit (44) and bears on its free end an elongate housing (46) which is made from insulating material and extends with its longitudinal axis transversely with respect to the linear direction of movement of the insulating arm (25) and in which metallic gripper elements are accommodated.
21. System as claimed in Claim 20, characterised in that the gripper elements can be displaced by a drive means relative to the insulating arm (25) transversely with respect to the longitudinal axis thereof and parallel to the longitudinal axis of the generally cylindrical replaceable containers (48).
22. System as claimed in any one of Claims 9 to 21, characterised in that the material removal station (1, 2) is located in a housing cylinder (41, 42) which is made from insulating material and is disposed perpendicular to the plane of movement of the insulating arm (25) and has an opening (52) for the insertion of the container (48).
23. System as claimed in Claim 22, characterised in that the opening (52) of the housing cylinder (41, 42) can be closed by a cover (54).
24. System as claimed in any one of Claims 9 to 23, characterised in that the insulating section (30) is formed by the distance between the elements of the material removal sections (1, 2) connected to a high voltage and the closest edge of the metallic earthed support (22) or the earthed elements (44) located on the support.

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