DE2551659A1 - SYSTEM FOR ELECTROSTATIC POWDER COATING OF HANGING MOVING PARTS - Google Patents

Description

PATENT LAWYERS Π

DR.-ING. R. DÖRING 'DIPL.-PHYS. DR. J. FRICKE

BRAUNSCHWEIG MUNICH

Dr. Carola Malkmus-Dörnemann 3327 Salzgitter-Bad, Am Lappenspring 3

"System for electrostatic powder coating of hanging moving parts"

The invention relates to a system for electrostatic powder coating from hanging on a conveyor through a coating booth moving parts, especially elongated parts, in which the coating cabin in the conveying direction of the Parts open and with a device for recovery and for feeding in the powder consisting of a suction conveyor fan, Filter with discharge sluice, sieve machine and powder container with discharge sluice and powder feed line connected is.

Systems of the aforementioned type have become known for electrostatic powder coating in which the electrostatic Charging and powder atomization are carried out by means of individual spray guns which are arranged on appropriate holding frames. For the coating of elongated parts that are sagging

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the coating booths being transported are either one Variety of spray guns required to produce their spray jet Have to eject in different directions in order to have a coating on all sides of the hanging through the cabin To obtain parts, or the spray guns are arranged on so-called lifting gears, which may have a electronic control to transfer the spray guns to the various heights and swivel positions. When using Such a lifting gear can be done with a relatively small number of spray guns to also elongate parts in to provide sufficient electrostatic powder coating.

The known arrangements are very complex, since relatively high pressures are necessary for the operation of the spray guns and the spray guns themselves are expensive and sensitive devices. Through the use of lifting gears, the required number of spray guns reduced, but the lifting gear itself is a very expensive device, which high Generates costs and is hardly suitable for installation in narrow spray booths. In addition, when installing such Screw jacks in spray booths these screw jacks are available in the powder-interspersed environment and within a very short time Periods of time cleaned by the powder deposited on the lifting gears and in the interior of the same at short intervals Need to become.

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The object of the present invention is to provide a system of the eirifeitend mentioned type so that with simple means and without a large number of spray guns or movable on lifting gears Or the like. Spray guns held a uniform and safe coating even longer hanging through the booth moving Parts is made possible.

To solve the above problem, the invention is characterized in that at least one powder atomizer in the cabin Electrically conductive, single-ended, closed nozzle tube with insulating sheath kept at high voltage potential and an approximately perpendicular axis and at least one row of nozzles pointing transversely to the conveying direction of the parts is provided, which is directly connected to the outlet the! discharge sluice of the powder container passing and with this connected compressed air line is connected to a conveyor fan is.

It has been shown that the arrangement of the nozzle pipes mentioned Sufficient atomization of the powder takes place in the cabin without the application of high pressure, with the powder is brought to high voltage potential by the high voltage applied to the nozzle tube, while that through the cabin moving parts are kept at ground potential. This is followed by the supply of the powder to be atomized from the nozzle tubes directly by means of the pressure line required between the nozzle pipe and the conveying fan, which is at the discharge lock of the powder container is passed and depending on

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speed of the degree of opening of the discharge lock, the respectively required amount of the powder to be atomized is transferred into the nozzle tube in order to pass it there through the nozzle openings into the
Spray booth. The nozzle tube is a stationary part of the system and therefore does not require any maintenance, which is absolutely necessary for all movable atomizing devices. The nozzles provided in the tube can be designed differently. They can be provided in the form of screw-in nozzle heads, for example, or they can be used alone
consist in that corresponding holes are made in the nozzle tube. It is up to you to equip the nozzle tube with nozzles that point in different directions transversely to the conveying direction of the parts, or to equip the tube with one or, if necessary, two rows of nozzles and
to have all nozzles belonging to a row point in the same direction.

It is useful to have several opposite one another in the cabin or staggered nozzle pipes are provided, so that a powder coating on all sides is guaranteed the suspended parts conveyed through the cabin take place. The individual nozzles of the pipes can be in the above-described Eject their atomizer jets at a different angle across the conveying direction of the parts.

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A particularly simple and uniform coating of the Parts-promoting training is achieved when the parts to be coated are held on the conveyor so that they can rotate about the perpendicular as well as rotating around its hanging axis through the cabinet are. With such a training you can even get by with a nozzle pipe in the cabin, the nozzles evenly in the are arranged facing the same direction transversely to the conveying direction, because as a result of the rotary movement of the parts in the cabin a reliable coating of all surfaces is guaranteed, as all surfaces run vertically as a result of the rotary movement the moving parts are once turned towards the nozzle tube.

A particularly simple construction of the fastening of the parts held in the cabin rotatable about the hanging axis results, if the parts to be coated can be attached to a bracket connected to a rod, which rod is via a pivot bearing is connected to the conveyor and carries a pinion which is in a rack provided above the coating booth or chain engages. As a result, the rotary drive for the suspension of the parts to be coated is in the area outside relocated to the cabin so that this rotary drive and the associated storage are not exposed to the action of the atomized powder are exposed.

To achieve the highest possible concentration of the atomized powder To get inside the cabin, it is convenient when

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the side walls of the cabin have only a small distance, so that the clear cross-section of the Cabin is kept as small as possible in the direction transverse to the conveying movement of the elongated parts. To the distance of this To be able to design the cabin walls independently of the dimensions of the nozzle pipes, it is advantageous if the nozzle pipe or pipes are arranged in laterally projecting niches of the cabin.

The supply of the powder to the nozzle pipes is expedient in that the nozzle tubes are connected at their lower ends to the powder feed line, while their upper ends Ends form the closed part of the tubes. Practice shows that you get good coating results if you works with cylindrical nozzle pipes. In the case of very elongated pipes, i. H. however, it can be useful in the case of very high cabins be, to achieve a uniform air and pressure distribution over the entire length of the pipe and thus to Achieving a uniform discharge of the powder from the nozzles, the tubes are conical in the direction of their closed end to train rejuvenated. The degree of tapering depends on the number of nozzle openings in the pipe per unit of length / and is designed in such a way that the same pressure as possible occurs at all points in the entire nozzle tube.

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In order to take along and distribute the material to be transferred from the discharge lock of the powder container into the compressed air line To ensure powder, it is provided in a preferred embodiment of the invention that the compressed air and powder feed line to the nozzle tube or tubes in the area of their connection to the discharge lock of the powder container one in cross section Has expanded section, in which a flap running obliquely in the conveying direction "directly below the {Outlet opening of the discharge lock | protrudes. Achieved by this one in the area of the powder introduction into the compressed air flow. Reduction of the flow rate of the compressed air and at the same time to a certain extent a turbulence due to the sloping flap. This cross-sectional expansion of the supply line is practically below the discharge lock an ejector effect, which entrains and distributes of the powder on the entire conveying flow.

To vacuum the cabin, there are suction openings with lines and suction fans connected to them in the area of the cabin floor intended. Experience has shown that it is not necessary in areas outside the cabin floor make additional suction, as the powder that does not get onto the parts passed through the booth is in Towards the floor and then using the suction

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direction is fed to a filter, from which it is fed into the powder container can be traced back.

Although the cabin described above is solely due to the suction in the area of the cabin floor with a correspondingly elongated design of the opposing cabin walls does not lead to any dust or powder nuisance outside the cabin interior, it is also possible with regard to a possible Shorter construction of the cabin is expedient if there are devices for training on the sides of the cabin that are open in the conveying direction are arranged by air curtains. Such devices are known in various designs. In general they consist of a source connected to a compressed air source Distribution device which has an outlet gap for the compressed air pointing in the direction of the veil and one The slotted nozzle that collects the air curtain and is connected to a suction device.

The drawing shows an embodiment of the invention in a schematic representation.

Show it:

Fig. 1 is a side view of the inventively designed System;

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Pig. Figure 2 is a plan view of the Pig's cabin. I;

Fig. 3 shows a detail of the system for the suspension of by the booth moved parts to be coated;

4 shows the lower part of the powder container in an enlarged representation 1 with the device for transferring the powder into the supply line;

FIGS. 5 and 6 detail animals in the device shown in FIG for creating an air curtain;

7 and 8 are sectional views through a nozzle tube.

The system shown in FIG. 1 has a high-voltage generator 1 with an associated switch cabinet and also a control cabinet 2 which is equipped with the necessary control buttons 3. In FIG. 1, next to the control cabinet 2, the cabin k is shown, in which a nozzle pipe 5 can be seen in dash-dotted lines, which has nozzle openings 6 arranged at a distance along its length. The nozzle tube 5 is arranged in a niche 7. A high-voltage cable 8 leads from the high-voltage generator 1 to the nozzle tube 5, so that it is connected to high voltage, as will be described in detail below.

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In the upper part of the booth 4, above the nozzle pipe 5, you can see a chain conveyor 9, which extends over the booth *! extends away. _{The elongated parts 11 to be coated 3} to be conveyed through the cabin are arranged on the conveyor 9 via suspension devices Io, the conveying direction being indicated by the arrow 12. In the area of the cabin 4, a toothed rack 13 is provided just below the chain conveyor 9, which cooperates with the hanging devices Io in a manner to be described below.

A suction line 14 opens out in the floor area of the cabin 4, which leads to a conveyor fan 15, from which a pressure line 16 is led to a filter 17, which in turn with Filter elements 18, e.g. B. is equipped with bag or bag filters. Below the dust or powder collecting space 17a of the filter 17, a rotary valve 19 is provided for the discharge of the powder collected there, which is located above a sieve machine 20 is provided. The screening machine 20 stands on 'a powder collecting container 21, whose discharge in turn with a Rotary valve 22 is equipped, which is provided immediately above a cross-sectional widening 23 of a compressed air Mt ung 24 which connects a compressed air blower 25 to the lower open end of the nozzle pipe 5.

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Above the filter 17 is the clean gas discharge line 26 indicated, which leads to the open air.

In the cabin 4 is indicated by the arrows shown there The direction of the air flow is indicated, as has happened in the pressure or suction lines of the system. The one in that Filter 17 and arrows shown in the powder container 21 indicate the movement of the powder, which apart from the respective on the parts to be coated 11 remaining subsets is circulated.

Fig. 1 shows that through the fan 15 and thus connected suction nozzle only in the lower floor area of the Beschxchtungskabxne the suction takes place, which is in the Practice has proven to be completely sufficient. By the amount of powder emerging from the nozzle openings 6, compared to the amount necessary for the coating of the parts 11 worked with a very large excess, so that during loading operation of the system, the space limited by the Beschxchtungskabxne is largely enriched with the atomized powder.

From the top view of Fig. 2 it can be seen that the Beschxchtungskabxne 17 consists essentially of two walls 26 and 27 striking a gap between them, the

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Gap 28 located between these walls is closed at the bottom by the floor of the cabin, while he upwards is in open connection with the surrounding atmosphere. Extends immediately above the gap In its longitudinal direction the conveyor 9 and parallel to it at a small distance the rack 13

The walls 26 and 27 of the coating booth form niches 29 and 30 in the middle area of the booth, in which the Nozzle pipes 5 are arranged.

In Fig. 2, the arrangement is only one in the upper part Nozzle tube 5 shown in the niche 29, while in the opposite niche 30 two parallel to each other Nozzle tubes 5a and 5b are shown. In practice you will only be in the two niches 29 and 30 respectively a nozzle pipe 5, or two nozzle pipes 5a and 5b arrange. The niches 29 and 30 do not have to be arranged opposite one another as in the example shown, but rather can also be offset from one another. Also the nozzle jets emerging from the nozzle tubes 5 or 5a and 5b need not point perpendicular to the conveying direction of the parts 11 to be coated, but they can be a component have against or in the conveying direction, so that the opposing nozzle tubes are not mutually exclusive spray with the powder to be atomized.

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The coating compartment is provided in the embodiment of Fig. 2 with further slots 31 and 32 and 33 and 3 ¹ *, which serve for receiving devices for forming air curtains so that the atomized in the cabin amounts of powder can not escape from the coating booth sideways. In the niches 32 and 3 ¹ J, air supply devices 35, approximately triangular in cross section, are provided, which are shown in the side view in FIG. These air supply devices form triangular tubes which are connected to a fan 37 via a connecting pipe 36. The triangular tubes 35 have in the direction of the opposing niches 31 and 33 open exit gaps 38 extending over the entire height of the hollow profiles, so that an air curtain is created across the entire height of the coating booth, which is directed transversely to the conveying direction of the parts to be coated and which is formed in the opposite Cabin is caught by the suction boxes 39 provided there and discharged via the suction line ho and the fan 41 connected to it. The design of the suction box results from the side view of FIG. 6, which shows that the suction box has a funnel-shaped cross section in this side view. The air discharged via the fan 41 can either be fed to the filter 17 if the pressure is set accordingly, or it can be freed from the powder carried in a separate centrifugal dust separator before the air is released into the open.

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The fans 37 and 4l, which are shown in connection with the niches 33 and 34, can also be used for air supply or suction of the devices in niches 31 and 32 can be used, or separate fans can be used for these niches be provided.

The device for supplying the powder to the coating booth can be seen in an enlarged view from FIG. In this figure, the lower part of the funnel-shaped outlet of the powder collecting container 21 is shown, to which the already described rotary valve 22 is connected at the bottom. The rotary valve 22 is located immediately above the cross-sectional widening 23 of the compressed air line 24 leading from the fan 25 to the nozzle tube or tubes 5. Below the Rotary feeder 22, directly below the outlet opening 42, through which, depending on the control of the rotary feeder A predetermined amount of the powder per unit of time is transferred into the cross-sectional widening 23 of the compressed air line 24 is provided, a flap 43 is provided which is inclined in the direction of flow and onto which the flap from the outlet opening 42 escaping powder arrives before it is distributed over the entire cross-section by the air flow, namely by turbulence is taken. The cross-sectional expansion 23 acts in conjunction with the flap 43 as an ejector through which the evenly Powder feed distributed over the cross section is very much favored.

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At

The design of the nozzle pipes is shown in FIGS. The nozzle tubes consist of a metallic, electrically conductive inner tube 44 which, for. B. made of copper or brass and that of an insulating jacket 45 »z. B. is surrounded by polyamide. The nozzle bores in the metal tube 44 generally have a diameter of only a few mm, while in the insulating jacket 45 a cone-shaped outward widening recess is provided in front of each nozzle opening 46, which determines the spray cone.

A nozzle tube with a Inside diameter of 32 mm and an outside diameter of 34 mm and an insulating jacket made of pdyamide with an inner diameter of 35 mm and an outside diameter of 63 mm in practice proven. The nozzle bores 46 had a diameter d of about 3.6 mm and the opening angle of the conical recesses in the insulating jacket 45 in front of each nozzle opening was about 60 ° with a nozzle spacing a of approx. 50 mm. With such a Training could be worked with an air pressure for the powder feed in the order of 6OO mm ws to good To achieve coating results. The parts 11 to be coated were thereby conveyed through the coating booth rotated through it. In the embodiment of FIG. 8 it is indicated by dashed lines 44a that that the inner diameter of the metallic tube 44 can also be provided tapered conically.

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From the Pig. 3 shows how the suspension Io of the to be coated Parts 11 is made on the conveyor chain to during the transport of the parts 11 to be coated by through the cabin to accomplish the rotary movements of the parts about their longitudinal axis.

In Fig. 3, a rod or bolt 47 can be seen on whose A bracket 48 for hanging the parts 11 to be coated is attached at the lower end. The rod or bolt is in the area its upper end equipped with a chain pinion 49, which is secured against rotation, but against axial displacement on the bolt. The upper end of the bolt 47 is in one designed as a shoulder bearing pivot bearing 50 held, which is in turn attached to a support plate 51 which can be connected to the conveyor chain 9.

In the area of the coating booth 4 arrives during the conveying path the pinion 49 meshes with that in the upper region the coating booth provided rack or chain 13, so that only by the conveying movement of the bolt 47 with the its bracket 48 attached to the part 11 to be coated is set in rotational movements about its longitudinal axis. Has it stood by the chain and crevice division in the hand by appropriate Choice of the pitch of the rack or chain 13 and the pinion 49 the number of revolutions of the to be coated Part 11 to set in the cabin. The intervention and disengagement -

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bring the pinion 49 with the rack or chain 13 takes place by setting the distance β accordingly between the ring gear of the pinion 49 and the rack or Chain 13 automatically.

The entire system is operated centrally from the control cabinet 2. From there it can be attached to the nozzle tube or tubes 5 regulate applied high voltage, and it will also be from there from the discharge devices from the filter or the powder container, ie the rotary feeders 19 and 22 to the respective required values are set and thus the powder feed to the nozzle tubes 5 is regulated.

To remedy any malfunctions in the nozzle pipes 5 or 5a and 5b, or to replace the nozzle pipes Lockable doors 29a and 30a are provided in the niches 29 and 30, respectively. Similarly, you can also work on the niches 31 to 35 such doors or lockable inspection openings can be provided for receiving the devices for generating an air curtain.

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Claims (10)

Claims 1.) System for electrostatic powder coating from hanging Parts moving through a coating cabin on a conveyor, in particular elongated parts, in which the coating cabin is designed to be open in the conveying direction of the parts and is equipped with a device for recovering and feeding in the powder, consisting of a suction conveyor fan, filter with discharge lock, sieve machine and powder container with discharge lock as well Powder feed line is connected, characterized in that as a powder atomizer in the cabin ( ¹ I) at least one electrically conductive nozzle tube (5) closed at one end and kept at high voltage potential with an insulating jacket and an approximately perpendicular axis as well as at least one row from transverse to the conveying direction of the parts ( 11) pointing nozzles (^ 6) is provided, which is connected to a conveying fan (25) ^{via a compressed air line (2 1} I) which passes directly to the outlet of the discharge sluice (cellular wheel 22) of the powder container (21) and is connected to it. 2. Plant according to claim 1, characterized in that the parts to be coated (11) are held on the conveyor (9) so as to be rotatable about the perpendicular and can be moved through the cabin (4) while rotating about their hanging axis. _7om1 / (J ₀₁₈ 3. Plant according to claim 2, characterized in that the parts to be coated (11) on a bracket (48) connected to a rod (47) can be attached, which rod is connected to the conveyor via a pivot bearing (50) (9) is connected and carries a pinion (49) which is in a rack provided above the coating booth (4) or chain (13) engages. 4. Installation according to one of the preceding claims, characterized in that the Booth (4) with several opposing or offset nozzle pipes (5; 5a, 5b) is equipped. 5. Installation according to one of the preceding claims, characterized in that the or the nozzle pipes (5; 5a, 5b) in relation to the conveying direction of the parts (11) laterally projecting niches (29,30) of the cabin (4) are arranged. 6. Plant according to one of the preceding claims, characterized in that the Nozzle tubes (5i5a, 5b) at their lower ends with the powder feed line (Compressed air line 24) are connected. 709841/0018 7. Plant according to one of the preceding claims, characterized in that the Nozzle pipes (5; 5a, 5b) in the direction of their closed end are conically tapered. 8. Plant according to one of the preceding claims, characterized in that the compressed air and powder supply line (24) to the or the Nozzle pipes (5; 5a, 5b) in the area of their connection to the discharge lock (cellular wheel 22) of the powder container (21) has a section (23) with a widened cross section, into which a flap extending obliquely in the conveying direction (43) protrudes directly below the outlet opening (42) of the discharge lock. 9. Plant according to one of the preceding claims, characterized in that for vacuuming the cabin (4) in the area of the cabin floor at least one suction opening with a line (14) and suction fan (15) connected to it are provided. 10. Plant according to one of the preceding claims, characterized in that on the sides of the cabin (4) that are open in the conveying direction are arranged with devices for forming air curtains. 709841/0018