EP0049248B1 - Device for coating parts by powder spraying in an electrostatic field - Google Patents

Abstract

A carriage (2) moving on the ground (1) comprises a support column (3) to which are adjustably fixed heightwise a support (5) integral with a container (6) and spraying guns (8) held by arms (7). The support (5) is connected to a compressed air source by means of a flexible hose (11) and to a high voltage source by means of a collectorcable (13) which is connected to each gun (8) by means of a high voltage cable (14) passing through each hollow arm (7). Each arm (7) is fixed by a mandrel (47) with a longitudinal motion and pivotingly at least about one axis. The gun (8) is supported by the free end of the arm (7) so as to pivot at least about one transverse axis, and is connected to one of a plurality of orifices (32) of the container (6) by means of a flexible hose (44) and an injector (40). The container (6) comprises a stirrer and processing means associated with each orifice (32). The guns (8) which are adjustable independently of each other may be operated and controlled independently by means of injectors (40) so that a variation of the spraying of one gun has no influence on the spraying capacity of other guns.

Description

The invention relates to a coating device for coating workpieces by spraying powder in the electrostatic field, with a processing container arranged near the spraying point and connected to a powder supply, which has removal openings for a plurality of gas-pressure-operated spray guns held in a pivotable manner and processing means assigned to each removal opening.

From DE-A-2 020 055 it is known to arrange an elongated vertical preparation container close to the spray point, which has a number of discharge openings for the powder to be sprayed one above the other in a generatrix, a gas pressure-operated spray gun being adjustably attached to each discharge opening via an articular surface , which is operated by secondary air like an injector. The processing container, which is fitted with a ventilation floor at the bottom, is refilled with a powder storage container during operation. In this way, an exceptionally short conveying path from the preparation container to the spraying point is achieved, which enables correspondingly low flow resistances and a reduction in the powder discharge speed from the gun. In this way, a better electrostatic charge is achieved, which increases the adhesive force of the powder particles on the workpiece. The reduced flow velocity also counteracts the risk of the deposited powder detaching from the workpiece, so that considerably reduced blow-off effects can be achieved.

In the known embodiment described above, however, it is not possible to supply the individual spray guns with a uniform powder, since the powder supply is determined by the storage height and by the loosening effect exerted by the ventilation floor, which results in slightly different conditions for the individual spray guns. To remedy this, with a substantially unchanged design according to DE-A-2 207 466, a special ventilation floor has been attached underneath each spray gun, and the container has thus been divided into individual sub-containers with a limited fill level. However, even supply of the individual spray guns cannot be achieved in this way. In addition, switching off individual guns is practically not possible, since the air introduced through the air floor always looks for its own byways. The pistols therefore always spray when they have long been switched off. Another disadvantage of this known design is the rigid assignment of the powder guns to the processing container. Even the swivel adjustability is limited, so that for many applications, no matter how many guns, the desired spray pattern cannot be achieved.

The invention is based on the type of coating device described at the outset and serves the task of developing this coating device in such a way that the spray guns can be charged with greater reliability and uniformity and can be arranged and aligned more freely, despite the arrangement close to the processing container.

To achieve this object, the processing means are designed according to the invention as stirring elements of a motor-operated mechanical processing device, and the spray guns operated by a compressed gas injector are each connected to their removal opening by means of a short hose and arranged at a distance from the processing container and are to be aligned independently of this, but with the other spray guns and the processing container movably provided as a closed unit.

In this way, with a limited spatial connection to the processing container, the fixed geometrical assignment to the removal openings is avoided and for the arrangement and alignment of the individual pistols, each degree of freedom, which in practice is only somehow significant, i.e. the guns can be set to a workpiece as desired. They can be laterally offset from one another in different ways, have different types of spacing at high altitudes and can be inclined in extremely different ways to one another or to any reference direction. The guns are also completely independent of each other with regard to switching on and off and - if the appropriate control devices are available - can also be controlled with regard to the spray intensity, since the mechanical preparation means that no secondary air passages can arise. Such conceivable secondary flows are also counteracted by the fact that a hose, however short, slows down the flow due to the friction on its wall, which also benefits the desired equalization of the powder flow. Despite the different spatial distances between the spray guns and the processing container, they can be moved with it as a closed structural unit without changing the relative arrangement, the position of the intermediate hoses and the like, so that the uniformity of the powder delivery is retained even when the spraying device is adjusted.

In principle, the spray guns can be carried by the preparation container and then replaced with this container. Expediently, however, the preparation container is easily exchangeably connected by quick coupling means to an equipment carrier which has the electrical fluidic connections for the spray guns and the injectors assigned to them, preferably attached to the removal openings. You then only have to loosen the couplings and hose connections and you can change the treatment tank.

The pistols are preferably attached to the implement carrier so as to be adjustable in length in at least one direction.

According to a proposal of the invention, each spray gun is attached to the free end of a cantilever arm, which is fastened on the back at least length-adjustable in a holder of the device carrier. It is even better if the extension arm is around his own axis and, if possible, another axis can be swiveled so that each gun can be held and adjusted as desired.

Even with these numerous setting options, it is advisable to design the extension arm in a tubular shape; it can then enclose an electrical cable, in particular the high-voltage supply.

The equipment carrier is expediently guided in a height-adjustable manner on a stand, which can be moved in particular horizontally, and connected to it by flexible lines. For example, the equipment carrier can be attached in a vertical guide by means of a servomotor, such as a cylinder unit, with adjustable speed. This actuator can be used for positioning, but also for automatic back and forth movement during the spraying process. In principle, instead of a hydraulic drive, a pneumatic or electrical one can also be provided.

The stand itself can form a storage container for coating powder, which is connected to the processing container by at least one feed line. To control the powder feed to the processing container, two sensors can be attached to the powder level, which also enable the control of fresh air and recovery powder in a certain ratio.

The processing container, which is cylindrical in a known manner and expediently arranged vertically, can rotatably accommodate a stirring shaft which has at least one transversely projecting stirring element in the region of each removal opening, which is preferably moved back and forth. For example, an axially parallel stirring pin can be attached to the end of a radial arm.

The lower end of the agitator shaft can be coupled to an agitator motor attached to the implement carrier by means of a coupling, in particular a claw coupling, which can be brought into and out of engagement by means of axial relative movement. The coupling is effected immediately when the processing container can be suspended in angular slots in the side wall parts of the device carrier.

The cylindrical powder container is expediently provided at its upper end with tangentially entering powder feed connections and a central exhaust pipe. The powder is then introduced in a rotating manner and the transport air is drawn off from a lower point and conveyed up.

Due to the separate arrangement of the spray gun and the injector, this can be designed in a special way; according to the invention, in addition to a conveying gas or conveying air connection, means for feeding and regulating metering gas can be assigned to it.

• Fig. 1 eine teilweise geschnittene Seitenansicht eines erfindungsgemässen Beschichtungsgerätes und
• Fig. 2 eine teilweise nach der Linie 11-11 geschnittene Ansicht von oben in Fig. 1.

The drawing shows an embodiment of the invention, for example. Show it:

• Fig. 1 is a partially sectioned side view of a coating device according to the invention and
• FIG. 2 is a top view partly in section along line 11-11 in FIG. 1.

The coating device shown consists essentially of a carriage 2 which can be moved on the room floor 1 and which holds a device carrier 5 on a towering stand 3 by means of guides 4 which are adjustable in height, on which a processing container 6 is detachably and interchangeably held and three spray guns 8 are held by means of cantilever arms 7.

The upper part of the stand 3 can form a powder container 9, the lower part 10 a high-voltage generator, a compressed air source such as a compressor and possibly further electrical and pneumatic connections and assemblies. The compressed air source is connected by a hose 11 to a connection 12 of the device carrier 5, which may be designed as a quick coupling, and a collecting cable 13 leads from the high-voltage generator to the device carrier, where it is branched into individual high-voltage cables 14, each of which is formed by the tubular boom 7 to one Spray gun 8 are performed.

Deviating from the illustration chosen here, only a control cabinet for the pneumatic and electrical control processes can also be accommodated in the stand 3, possibly also the high-voltage generator. The compressed air is then obtained through a hose connection from the compressed air network, the powder from a stationary or, in turn, mobile large storage container over possibly larger distances, and the hose 11, similar to the collecting cable 13, is designed as an enveloping hose for individual branched compressed air hoses that lead to individual connections of the Guide pistols or injectors. In the latter case, the entire pneumatic control and regulation can also be carried out from the control cabinet.

A double-acting cylinder unit 15 with a cylinder 16 and a piston rod 17, which protrudes from the cylinder on both sides and is screwed with its ends to two connecting blocks 18 of the device carrier 5, is used to adjust the height of the device carrier. The cylinder 16, on the other hand, is fastened to the stand 3 by means of a plate 55 in the guides 4 in an adjustable manner via an intermediate carrier 19. On this plate there are also guide rollers 56 which run from the inside on the walls of the device carrier 5 and thereby form a swivel alignment around the axis of the cylinder unit 15, which represents the actual longitudinal guide.

The cylinder 16 can be fed by two hoses 20 from a control (not shown) in the lower space 10 of the stator by compressed air from the compressed air source there or by a separate, possibly interposed flow medium such as pressurized oil or the like. Instead of a cylinder unit, any other suitable drive motor can be used, such as a rotary compressed air motor with rack or spindle drive or an electric motor, possibly with a cable winch.

The adjustment can be used for the usual height positioning of the carrier 5 up to the upper end position shown with broken lines 54, but also for a constant oscillation between these end positions lungs or certain intermediate positions, for example occupied by limit switches, the instantaneous speed, in turn, being able to change independently as a function of the distance traveled.

The equipment carrier 5 has essentially the shape of a rectangular box, which is opened on opposite sides and whose interior is divided into two pockets 22, 23 by an intermediate wall 21. The two connection blocks 18 for the cylinder unit 15 enclosed by the pocket 22 are attached to the intermediate wall 21. At least one coupling projection 24 of the processing container 6 protrudes in the pocket 23 and is suspended on both sides by an attached screw 25 in angle slots 26 of the side pocket walls. By tightening the screw 25 by means of the lever 27, the processing container 6 can be fixed in a predetermined position on the device carrier 5. The reprocessing container can be removed and attached in a few simple steps, and yet the specified end position is always reached.

Instead of using a lever screw 25, one can also place a lever nut, a wing nut or the like on a possibly continuous threaded bolt. Sometimes it is sufficient to clamp only on one of the two sides or to separate the guide and alignment on the one hand from the clamping devices on the other.

The processing container 6 has the shape of an elongated thin cylinder, which has at its upper end two tangentially opening supply nozzles 28 for fresh powder and for recovered powder. At least one of these feed nozzles is connected to the powder storage container 9 mounted in the stand by a feed line (not shown). This storage container can possibly also be divided into two container spaces for fresh powder and recovered powder, and means can be provided for metering both powders in a predetermined ratio.

Due to the tangential arrangement of the supply nozzle 28, the powder-air mixture is introduced into the processing container 6 in a rotating manner, which on the one hand causes the two types of powder to mix and on the other hand to separate the powder from the gas stream, which collects further inside during a helical downward movement and through one central outlet pipe 29, which is guided down about 15% of the container height, comes out again. For this purpose, lateral inlet openings 30 are provided above the lower end of the outlet pipe 29.

In the lower end of the outlet pipe 29, an agitator shaft 31 sits rotatably and centrally to the processing container in the bearing 35, which has at least one radially projecting stirring arm 33 at the level of each removal opening 32 for the individual spray guns, at the end of which a pin-shaped stirring element 34 is fastened axially parallel. The lower end of the agitator shaft 31 protrudes from the processing container 6 into another bearing 36 and is connected to an agitator motor 38 by means of a claw coupling 37 or another coupling that can only be opened by relative movement in the axial direction. This is connected by a hose 39 to the compressed air source in the stand space 10 and constantly executes a back and forth movement over an optionally adjustable angle of approximately 90 ° to 180 ° according to double arrow 52 in FIG. 2. The two coupling parts are automatically centered when the processing container is suspended in the angled slots 26 and are brought into engagement in the same way as they are released again when the container handles 53 are lifted off.

Instead of having the agitator move back and forth, it can also be rotated continuously, which alone results in an improved loosening effect with some types of powder. A further improvement can be achieved in the case of a rotating agitator, above all, by introducing a further regularly or irregularly movable part, for example a planet-like rotating part, a spring which reacts in an irregular manner or the like.

At each removal opening 32 of the processing container 6, an injector 40 is connected, to which, by means of a short line 41, conveying air and a further short line 42 are metered air from a socket-like quick connector 43 fixedly attached to the device carrier 5. The individual quick couplings 43 are connected to the compressed air connection 12 in a manner not shown in detail. Short line parts can also be fixedly attached to the equipment carrier and easily detachably connected to the injector 40 by quick-release couplings.

The injector is in turn connected to the spray gun 8 by means of a hose 44, which can have a length of approximately 40 to 60 cm. This hose also has to be disconnected if a processing container 6 is to be unhooked when changing colors.

A setting valve 45 for conveying air and a setting valve 46 for metering air are provided on each injector 40. The dosing air is placed as a rotary veil around the suction path of the powder from the removal opening 32 in such a way that the conveying of powder is completely prevented when the dosing air valve 46 is fully open. When the metering air flow is throttled, more powder is continuously brought into the conveying gas flow. With separate hose routing for conveying air and dosing air from a control cabinet, the setting valves 45 and 46 or corresponding adjusting elements can of course also be provided there. Before changing the powder, the metering valve 46 will therefore first be opened completely and then the delivery air valve 45 may be opened further to blow out all powder residues from the flow paths to the spray gun 8. The quick coupling 12 is then released, automatically closing a shut-off valve, and then the flow connections of the injectors 40 to the spray gun 8 and to the quick coupling 43 fixed to the stand can be released, so that the powder container 6 can then be freely suspended. In addition to changing the color, this can also be done for maintenance purposes and to rectify any faults.

Each boom arm 7 is longitudinally displaceable in a clamping chuck 47 is held, which is fixed to the device carrier 5 and can be clamped by a screw lever 48. The cantilever arm 7 can thus be freely moved in the longitudinal direction in the released clamping chuck. It goes without saying that the clamping chuck 47 or another holding means can also be provided such that it can be pivoted about a horizontal axis or about several axes.

Another pivot adjustment is provided on the bracket at the free end of the cantilever arm 7. There, the spray gun 8 can therefore be pivoted and locked almost indefinitely at least about a vertical axis. It is even better to use a spherical surface. The setting angle is only limited when the high-voltage cable 14 is to be passed through the holder 49. This limitation does not apply if the cable is led to the gun outside of this holder. Moreover, in the case of the cylindrical configuration of the cantilever arm 7, it can also be rotated about its axis in the pipe clamp 47 with the spray gun. As a result, all spray guns used can be arranged and adjusted in almost any way to enable optimal coating of a workpiece from different directions.

At the lower end of the processing container 6, an air tray 50 is also installed here, which can possibly be fed through a line 51 and can be put into operation in the case of an unfavorable powder composition, but this is only about a temporary use, which is under the loosen the powder located at the bottom of the dispensing opening, which could otherwise condense. This air floor is not required for the actual spraying operation. In principle, several powder storage containers can be attached to the carriage 2 or on a separate carriage and can only be connected to the feed connector 28 by coupling. Likewise, complete coating devices with powder storage containers as a whole can be replaced if one changes to a different color. Since the air floor 50 is only switched on briefly and generally outside of the gun operation, the preparation here takes place exclusively mechanically, so that no different flow paths can be formed and in fact only the gun whose injector 40 is switched on is operated, with the hose 44 additionally acts as a conveyor brake.

The agitator shown appears to be extraordinarily simple, but can be replaced by other suitable agitating devices, for example with mechanical vibrators, planet-like rotating elements and the like. The invention is not tied to either the cylindrical or the elongated design of the processing container. In principle, it is also possible to use a short drum-shaped container which has uniformly or unevenly distributed removal openings in the same or different axial position on the circumference. The removal openings can be provided in the peripheral wall in the bottom or in the ceiling of such a container. Under certain circumstances, a single stirring element loosens the powder for all gun connections.

Claims (15)

1. Coating device for coating workpieces by spraying-on powder in an electrostatic field, having a processing container (6) which is disposed close to the spraying location and which is connected to a powder supply (28, 9), said container having outlet orifices (32) for a plurality of pivotally adjustable, gas-pressure operated spraying guns (8) and said container having processing means (31, 33, 34) associated with each outlet orifice, characterised in that the processing means are in the form of stirrers (33, 34) or a motor-driven, mechanical processing device (31, 33, 34), and characterised in that each of the spraying guns (8), which are operated by means of a compressed gas injector (40), is connected to its respective outlet orifice (32) by means of a short hose (44) and is spaced from the processing container (6), each spraying gun being adjustable independently of said processing container but being adapted so as to be movable with the other spraying guns (8) and with the processing container (6) as a self-contained structural unit.

2. Coating device according to claim 1, characterised in that the processing container (6) is connected to a device support (5) by a quick coupling means (25, 26) so as to be easily detachable from said device support which is provided with the electrical and hydraulic connections for the spraying guns (8) and with the injectors (40) which are associated with said spraying guns and are preferably mounted atthe outlet orifices.

3. Coating device according to claim 2, characterised in that the spraying guns (8) are mounted on the device support (5) so as to be longitudinally adjustable in at least one direction.

4. Coating device according to claim 3, characterised in that each spraying gun (8) is mounted at the free end of a cantilever arm (7) which is secured in a mounting (47) of the device support (5) at its rear end so as to be at least longitudinally adjustable therein.

5. Coating device according to claim 4, characterised in that the cantilever arm (7) is tubular and encloses an electrical cable, in particular the high-voltage supply line (14).

6. Coating device according to one of claims 2 to 5, characterised in that the device support (5) is vertically adjustably guided on a support column (3), which is displaceable, especially in a horizontal direction, and the device support is connected to said support column by means of flexible lines (11, 13).

7. Coating device according to claim 6, characterised in that the device support (5) is mounted in a vertical guide (15, 56) so as to be adjustable at regu- latable speed by means of a servo motor in the form of a cylinder assembly (15).

8. Coating device according to claim 6, characterised in that the support column (3) forms a storage container (9) for coating powder, which is connected to the processing container (6) by means of at least one supply line.

9. Coating device according to claim 1 or 8, characterised in that, to control the supply of powder to the processing container (6), two sensors are mounted in said processing container and detect the powder level.

10. Coating device according to one of claims 1 to 9, characterised in that the processing container (6) is cylindrical and rotatably accommodates a stirrer shaft (31) which has at least one transversely protruding stirrer (33, 34) in the region of each and every extraction orifice.

11. Coating device according to claim 10, characterised in that an axis-parallel stirring pin (34) is mounted at the end of radial arm (33).

12. Coating device according to claim 10 or 11, characterised in that, by means of its lower end, the stirrer shaft (31) is connectable to a stirrer motor (38), which is mounted on the device support, by means of a coupling (37), more particularly a claw coupling, which is to be brought into engagement and out of engagement by relative axial movement.

13. Coating device according to claim 2 or 12, characterised in that the processing container (6) is insertable in angled slots (26) formed in lateral wall portions of the device support (5).

14. Coating device according to claim 8, 9 or 10, characterised in that the cylindrically-shaped processing container (6) is provided, at its upper end, with tangentially extending powder supply connections (28) and with a centrally mounted exhaust pipe (29).

15. Coating device according to one of claims 1 to 14, characterised in that each injector (40) is provided with means for supplying and regulating dosage gas.

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