WO1981002854A1

WO1981002854A1 - Device for coating parts by gun spraying in an electrostatic field

Info

Publication number: WO1981002854A1
Application number: PCT/EP1981/000027
Authority: WO
Inventors: G Voehringer
Original assignee: Esb Gmbh; G Voehringer
Priority date: 1980-04-10
Filing date: 1981-03-28
Publication date: 1981-10-15
Also published as: EP0049248B1; DE3166777D1; EP0049248A1; DE3013777A1

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

Coating device for coating workpieces by spraying powder in an electrostatic field

The invention relates to a coating device for coating workpieces by spraying powder in an electrostatic field, with a processing container arranged close to the spraying point and connected to a powder supply, which has removal openings for a plurality of spray guns which are held pivotably and preparation means assigned to each removal opening.

From DE-OS 20 20 055 it is known close to the

Spray point to arrange an elongated vertical preparation container, which has a number of discharge openings for the powder to be sprayed, lying one above the other in a generatrix, with a spray gun which is operated by secondary air in the manner of an injector and is adjustable at each extraction opening. 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 danger of Detachment of the deposited powder from the workpiece counteracts the reduced flow rate, so that considerably reduced blow-off effects can be achieved.

In the known design described above, however, no exact control of the individual spray guns is possible, since the powder supply is determined by the storage height and by the Lockerun effect exerted by the ventilation floor, which results in slightly different conditions for the individual spray guns.

To remedy this, one has attached a special ventilation floor underneath each spray gun with otherwise essentially unchanged design according to DE-OS 2 207 466, thereby dividing the container 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 pistols is also practically not possible, since the air introduced through the air floor is always looking for its own side paths. 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 the desired spray pattern cannot be achieved for many applications even with so many guns.

The invention is based on the type of a 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 controlled and adjusted with greater reliability despite the dense arrangement on the preparation tank.

To achieve this object, the Processing means assigned to removal openings are designed to be mechanically independent of the flow, and each spray gun is arranged spatially separated from the assigned removal opening and connected to it by a hose.

In this way, the tight geometrical assignment to the removal openings is avoided with a close spatial connection to the processing container and everyone in the arrangement and alignment of the individual guns

Practice only created somehow significant degree of freedom, i.e. the guns can be set to a workpiece as desired. They can be laterally offset from one another in different ways, have quite different spacing at high altitudes and can be inclined to each other or to any reference direction in extremely different ways. The guns are also completely independent of each other with regard to switching on and off and - if the appropriate control devices are available - also controllable with regard to the spray intensity, since the mechanical preparation means that no secondary air passages can arise. Such conceivable side flows also counteract that a hose, however short, slows down the flow due to the friction on its wall.

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

The pistols are preferably fired in at least one direction adjustable length adjustable on the implement carrier.

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

Even with these numerous adjustment 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, in particular on a horizontally movable stand, and is connected to it by flexible lines. Thus, 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. Instead of a hydraulic drive, a pneumatic or electrical one can in principle also be provided.

The stand can itself form a storage container for coating powder Be, which is connected by at least one feed line to the processing container. 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 pump 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 relative axial 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 injector, this can be designed in a special way; according to the invention, means for supplying and regulating metering gas can be assigned to it in addition to a conveying gas or conveying air connection.

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

1 shows a partially sectioned side view of a coating device according to the invention, and FIG. 2 shows a top view partly in section along the line II-II in FIG. 1.

The coating device shown consists essentially of borrow from a movable on the room floor T carriage 2 which holds a device holder 5 on a towering stand 3 by means of guides 4 adjustable in height, on which, on the one hand, 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. on / The compressed air source is connected by a hose 11 to a possibly designed as a quick connector 12 of the equipment carrier S, and from the high-voltage generator leads a collecting cable 13 to the equipment carrier, where it is branched into individual high-voltage cables 14, each through the tubular boom 7 are guided to a spray gun 8.

Deviating from the illustration chosen here, only a control cabinet for the pneumatic and electrical control processes can also be accommodated in the stator 3, possibly also the high-voltage generator. The compressed air is then drawn through a hose connection from the compressed air supply to the housing, the powder from a stationary or in turn mobile large storage container over possibly larger distances, and the hose 11 is similar to the collecting cable 13 as a sheathed hose for individual branched compressed air hoses that form individual connections of the 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 has ends at two ends, serves to adjust the height of the device carrier end blocks 18 of the equipment carrier 5 is screwed tight. 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 guide rollers 56 are also mounted, 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 any other suitable drive motor, such as a rotary 'compressed air motor with rack or spindle drive or an electric motor, possibly with a cable winch, can be used.

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 or certain intermediate positions, for example with limit switches, the instantaneous speed depending on the covered route can change independently.

The equipment carrier 5 has essentially the shape of a rectangular box which is opened on opposite sides and the interior of which is divided into two pockets 22, 23 by an intermediate wall 21. On the intermediate wall 21, the two connecting blocks 18 for the cylinder unit 15 enclosed by the pocket 22 are attached. At least one coupling projection 24 of the processing container 6 protrudes into 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 equipment 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, 26, it is also possible to place a lever nut, a wing nut or the like on a possibly continuous threaded bolt. Sometimes it is also 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). Possibly. This storage container can 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 a mixing of the two types of powder and on the other hand separates the powder from the gas flow, which collects further inside during a helical downward movement and through one centric outlet pipe 29, which is guided down about 15% of the container height, again got out at the top. 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 preparation tank 6 into a further bearing 36 and is connected to a stirrer motor 38 by a claw coupling 37 or another clutch 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 stator 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 with a rotating agitator, above all, by introducing a further regularly or irregularly movable part, for example a part running like a planet, by introducing a spring or the like which reacts in an irregular manner.

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, metering air is supplied 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 device carrier and connected to the injector 40 in an easily detachable manner by quick 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 detached if a processing container 6 is to be removed during the color change.

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 conveyance of powder is completely prevented when the dosing air valve 46 is fully open. When the metering air flow is throttled, more powder is constantly brought into the conveying gas flow. With separate hose routing for conveying air and dosing air from a control cabinet, the adjustment 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 feed air valve 45 may be opened further to remove all powder residues

Blow out flow paths to spray gun 8. Then the quick coupling 12 is released, automatically closing a shut-off valve, and then the flow connections of the injectors 40 to the spray gun 8 and to the fixed quick coupling 43 can be released, so that the powder container 6 can then be freely suspended. In addition to changing the color, this can also be used for maintenance purposes and to correct any faults become .

Each cantilever arm 7 is held in a longitudinally displaceable manner in a clamping chuck 47 which is fixedly arranged on the equipment carrier 5 and can be braced 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, for example horizontally or about several axes.

Another pivot adjustment is provided on the bracket 49 at the free end of the cantilever arm 7. There, the spray gun 8 can therefore be pivoted and fixed 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 routed 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 a matter of temporary use, which is under the loosen the powder located at the bottom of the dispensing opening, which could otherwise condense otherwise. 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. Complete coating devices with powder storage containers can also be used as

Change the whole thing if you change 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 being used 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. So you can in principle also use a short drum-shaped container that has evenly or unevenly distributed removal openings in the same or under different axis position on the circumference. The removal openings can be provided in the peripheral wall in the floor or in the ceiling of such a container. Under certain circumstances, a single stirring element can be used for the powder. loosen all gun connections.

Claims

Expectations

1. Coating device for coating workpieces by spraying powder in the electrostatic field, with a processing container arranged close to the spraying point and connected to a powder feeder, which has removal openings for several pivotable spray guns and processing means assigned to each removal opening, characterized in that the removal openings (32) assigned preparation means (31, 33, 34) are designed to be mechanically independent of the flow and that each removal opening (32) is spatially separated from the associated spray gun (8) and is connected to it by a hose.

2. Coating device according to claim 1, characterized in that the processing container (6) by quick coupling means (25,26) easily replaceable to a Ge device carrier (5) is connected, the electrical and fluid connections for the spray guns (8) and these preferably assigned injectors (40).

3. Coating device according to claim 2, characterized in that the spray guns (8) in at least one direction are adjustable to different lengths on the device carrier (5).

4. Coating device according to claim 3, characterized in that each spray gun (8) is pivotally adjustable on all sides attached to the free end of a cantilever arm (7) which is at least length-adjustable in the back on a holder (47) of the device carrier (5).

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

6. Coating device according to one of claims 2 to 5, characterized in that the device carrier (5) adjustable in height on an in particular horizontally movable stand (3) and connected to this by flexible lines (11, 13).

7. Coating device according to .Anspruch 6, characterized in that the device carrier (5) in a vertical guide (15,56) by an actuator such as a cylinder unit (15) πit is adjustable adjustable speed.

8. Coating device according to claim 6, characterized in that the stand (3) has a storage container (9). forms for coating powder, which is connected to the preparation container (6) by at least one feed line.

9. Coating device according to claim 1 or 8, characterized in that in order to control the powder supply to the processing container (6) two sensors sensing the powder level are attached in this.

10. Coating device according to one of claims 1 to 9, characterized in that the processing container (6) is cylindrical and rotatably receives an agitator shaft (31) which has at least one transversely projecting agitator (33, 34) in the region of each removal opening.

11. Coating device according to claim 10, characterized in that an axially parallel stirring pin (34) is attached to the end of a radial arm (33).

12. Coating device according to claim 10 or 11, characterized characterized in that the lower end of the agitator shaft (31) can be coupled to an agitator motor (38) attached to the equipment carrier by means of a coupling (37), in particular a claw coupling, which can be brought into and out of engagement by means of axial relative movement.

13. Coating device according to claim 2 or 12, characterized in that the processing container (6) can be suspended in angular slots in the side wall parts of the device carrier (5).

14. Coating device according to claim 8, 9 or 10, characterized in that the cylindrical powder container (6) has at its upper end tangentially a running powder supply connections (28) and a centrally attached exhaust pipe (29).

15. Coating device according to one of claims 1 to

14, characterized in that each injector (8) is assigned means for supplying and regulating dosing gas.