EP0405164B1 - Installation and method for making coated flat pieces, in particular flat metal sheets - Google Patents

Abstract

The invention relates to an installation for making powder-coated flat components, in particular flat sheet metal components. In its overall structure, the installation consists of a charging station (1), a pretreatment station (4) with a cleaning and pretreatment zone of a drying station (9), a cooling station (13), a powder-coating station (15), a lock station (17), a drying station (18) for curing the powder coating, a further cooling station (19) and a delivery station (20) for the components treated in this installation. With this installation, flat components, in particular flat sheet metal components for equipment, vehicle bodies or the like, can be provided with a powder coating after being cut to size, before they are then subsequently fed to the further shaping process for ultimate shaping depending on the type of components. Furthermore, it is possible with this installation to apply a layer of powder to the flat sheet metal components in an additional coating stage (21) which follows the powder coating, said layer of powder serving as a lubricant aid for the subsequent shaping process.

Description

The invention relates to a system for the production of powder-coated, flat sheet metal parts with a feed and a delivery station for the sheet metal parts with at least one pretreatment station, a drying station, a powder coating station and a curing station with a transport device through which the sheet metal parts are transported through the treatment stations and wherein the Sheet metal parts are successively exposed to the necessary treatment processes in these treatment stations.

Furthermore, the invention relates to a method for producing powder-coated sheet metal parts for devices, bodies or the like, using a system according to the invention.

In the sheet metal processing industry, especially in the household appliance industry, different manufacturing and coating processes are used for the manufacture of devices and parts. Enamelling fulfills a high quality standard with regard to the surface. Parts that have already been deformed or finished housing parts are treated in a molding and coating process comprising several stages. Disadvantages of the enamelling process are seen in the fact that dimensional deviations due to the high baking temperature can cause problems, that a high and costly pretreatment effort for the enamel application has to be accepted and that a high energy input is required for the enamelling.

Another common coating method is wet painting with a solvent-based paint. When The main disadvantage of this type of coating is that the environmentally harmful aspects caused by the solvents contained in the varnish are increasingly mentioned. Furthermore, a wet-painted surface does not meet high quality requirements.

Furthermore, the process has already started to manufacture from a fully coated coil. Here, however, there is the disadvantage that in some cases there is no edge coating and that the cut edges increase the risk of accidents in handling.

In addition, the principle of electrostatic powder coating for sheet metal and finished parts has found application in the device industry. The advantage of organic powder as a coating material is particularly its economical and environmentally friendly use. Furthermore, it is also possible in a suitable manner to subsequently deform finished coated parts. This enables simple and flexible manufacturing processes.

In the DE magazine "Metallfläche", 1975, Issue 1, page 24, a powder coating system for fully formed sheet metal parts, or for sheet metal parts shaped into housings (refrigerator sheet metal parts) is described, in which the sheets to be coated are suspended vertically by means of a hanging conveyor transported through the facility. This system consists of a loading, degreasing, drying, coating and dispensing station.

The disadvantage of this basic system structure, however, is essentially that completely deformed sheet metal parts - in some cases complete housing bodies - are coated here. This means that the sheet metal parts have to be hooked onto a overhead conveyor system by hand and that these sheet metal parts then have to be passed through all treatment stations in a hanging manner. This becomes clear from the pictures shown in the previous publication. In such a system, the automation of the manufacturing process, in particular when loading and unloading the workpieces to be treated, is made more difficult.

The relatively voluminous, deformed sheet metal parts and the suspension conveyor system required for this also have the consequence that the individual stations of the overall system require a very large amount of space both in terms of the footprint and in terms of space. As a result, it is usually not possible to house the entire system with all of its treatment stations in a single hall. Furthermore, for such systems according to the prior art, more or less "isolated" treatment stages are required, which cannot be arranged "seamlessly" one behind the other without gaps. This ultimately results in a fairly long treatment route for these systems. The scheme of the system shown in Figure 1 of the previous publication makes this clear. The treatment stations indicated there are not located directly one behind the other on a straight path, but rather are shown approximately circular or offset from one another.

In addition, because of the often relatively bulky moldings in the previously known systems, a particularly high outlay had to be carried out in all treatment stations in order to be able to achieve a corresponding surface quality in the pretreatment, drying and also in the coating process. This is inevitably due to the fact that finished and bent workpieces cannot always be reached evenly from all sides and in all corners by the respective surface treatment.

In general in connection with the coating of workpieces reference can also be made to EP-A-0 260 539. It describes a device for spray coating workpieces in general although these are already guided horizontally through the coating station, the primary concern here is to electrostatically apply photoresists and solder lacquers to copper-clad printed circuit boards using a rotary atomizer. Such devices are known from the field of electronics in order to coat plastic boards with electronic components with a photoresist or solder varnish. These boards are usually relatively small, handy workpieces that are not comparable to a sheet metal part for device housings.

In addition, the object according to EP-A-0 260 539 is based on the actual task of collecting the coating substance which does not hit the board during the coating process by means of the paper covering sheet by the clever arrangement of a conveyor belt transporting the sheets and an underlying cover sheet. This is to prevent the excess material passing the workpiece to be coated from reaching the bottom of the spray booth or the parts of the system located in the area of influence of the spray coating. Essentially, the device according to EP-A-0 260 539 is therefore concerned with achieving a functional separation between the conveyor belt and the cover sheet.

Overall, the disadvantage of the systems and methods for powder coating that have become known so far is that top layers are sometimes only of lower quality and that the processing of the powder can be difficult in order to achieve consistently good and uniform coatings. Furthermore, a high level of system-related effort is usually necessary, which usually always requires a conversion to a completely new system. In addition, sometimes bulky parts have to be handled after the deformation, which of course also requires an increased space for the body painting. The known problems with Faraday cages and uneven coating also have to be accepted.

The object of the invention is to create a system of the type mentioned, which is characterized in its entirety by a compact structure and an easy to implement automation and with which you can achieve a high-quality surface finish of the powder coating with economic effort. Furthermore, a method for the production of powder-coated sheet metal parts is said to be applicable, which reduces the outlay in terms of the system and allows the production process to be made efficient and automatable overall.

This object is achieved by a system according to claim 1. A method according to the invention for the production of powder-coated parts results from claim 28. Appropriate developments and refinements of the invention result from the dependent subclaims.

A system constructed according to the invention provides a coating system in which the parts to be treated can automatically pass through the treatment stations required for powder coating in the lying state. The treatment stations in their entirety are effectively coordinated with one another and contain details each treatment station effective devices that allow a quick and fast passage of the part.

The advantages that can be achieved by the invention also lie in particular in the economical and environmentally friendly use of powder coating, it being possible for a coating system to be used in existing production lines with little effort, simple pretreatment and an automated production process.

Several procedural and system improvements in the individual treatment stations result in a coated sheet metal part with a high quality surface finish, effective edge protection and also a uniform layer thickness.

The powder coating station designed according to the invention also has the advantage that, in addition to the actual parts coating, the coating of a covering which serves as a sliding and pulling aid can also be carried out for the later deformation processes. The formation of an intermediate station within the powder coating station provides an advantageous separation between the coating process in the coating station for the actual powder application and that of the sliding aid coating. In addition, the possibility is created via flexible and connectable air line elements and via pluggable connections of the other supply lines that the powder coating stations z. B. in a color change in a simple manner out of the line and are designed to be replaceable.

The special design of the conveyor belt made of electrically conductive material gives the advantage that the sheet metal part to be treated without sliding contacts and the like. in the electrostatic system of powder coating. Safe and permanent earthing can be established here, capacitor charging is avoided in a simple manner.

The special design of the gun arrangement of the powder guns ensures an even and flexibly adjustable coating application.

The skillful design of the roller pairs in the pretreatment station and the nozzle sets in the drying and cooling stations allow easy access for cleaning and maintenance work.

Figur 1

in vereinfachter, perspektivischer Ansicht eine Pulverbeschichtungsanlage mit allen Behandlungstationen von der Aufgabe- bis zur Abgabestation im grundsätzlichen Aufbau,

Figur 2

eine weitere Aufbauform gemäß Figur 1, wobei die einzelnen Behandlungsstationen im Detail weitergebildet sind,

Figur 3

den Teil der Pulverbeschichtungsstation von der Seite im Schnitt, in dem der Pulverauftrag für die Gleithilfe erfolgt,

Figur 4

den Teil der Pulverbeschichtungsanlage gemäß Figur 3 in der Vorderansicht,

Figur 5

die schematische Prinzipskizze der Pistolenanordnung für die Pulverbeschichtungsstation in vereinfachter Form,

Figur 6

in einem Auszug die Ausbildung der Transportwelle für die Gleithilfe-Beschichtungsstation.

Furthermore, numerous advantages result in detail from the following description of the exemplary embodiments of the invention, which are shown schematically in the drawings and are explained in more detail below.
Show it:

Figure 1

in a simplified, perspective view a powder coating system with all treatment stations from the feed to the delivery station in the basic structure,

Figure 2

1 a further design according to FIG. 1, the individual treatment stations being further developed in detail,

Figure 3

the section of the powder coating station from the side in which the powder is applied for the sliding aid,

Figure 4

the part of the powder coating system according to Figure 3 in front view,

Figure 5

the schematic principle sketch of the gun arrangement for the powder coating station in a simplified form,

Figure 6

in an excerpt the formation of the transport shaft for the sliding aid coating station.

In the drawing according to Figure 1, a powder coating system is shown in its entire, basic structure. The feed station is designated by (1). Here the sheet metal parts (2) punched and cut in a press are fed in batches in the form of blanks. In the feed station (1), a destacking and feed device (not shown in detail) is integrated, through which the sheet metal parts (2) to be treated are destacked and placed on the transport device (3) of the system and placed at an appropriate distance. The necessary data is transmitted to the central control device of the system via an object recognition so that the sheet metal part is automatically subjected to the predetermined treatments and can leave the system with a coating. Furthermore, a follow-up distance monitoring ensures that the necessary distances between the parts are observed. Special regulating and control devices ensure precise escape and centering.

The sheet metal part (2) reaches a pretreatment station (4) via the transport device (3) of the system. The pretreatment station (4) contains a cleaning stage (5) which has one or more mechanical removal devices (6) for liquids, grease, oil, dirt or the like adhering to the sheet. Furthermore, one or more chemical washing stages can be provided in the cleaning stage, in which the sheet metal parts (2) can be sprayed with appropriate liquids.

In the embodiment shown, a mechanical removal device (6) is arranged at the beginning of the pretreatment station (4) and consists of several rollers with a special covering made of textile and / or plastic. The sheet metal parts are conveyed between two rollers rotating in opposite directions, two pairs of rollers being arranged one behind the other in the version shown. These so-called textile rollers mechanically remove the residues such as liquid, oil, grease or dirt adhering to the sheet metal parts (2). As a result, a pre-cleaned sheet (2) passes into the next cleaning stage, in which a washing and rinsing process is carried out in one or more stages by means of spray devices directed onto the sheet metal part using appropriate flooding, washing or cleaning liquids. The washing or rinsing liquid used is carried out in a circuit, with appropriate filters or separators being interposed.

Additional coated rollers can be arranged between the individual washing stages in order to remove the detergent or rinsing agent residues adhering to the sheet metal, thereby avoiding carryover of the bath. The rollers can have a rubberized covering of certain hardness. A textile covering or the use of brush rollers would also be conceivable.

The cleaned sheet metal (2) is then treated in a pre-coating or pre-treatment stage (7) in a spray process for the purpose of metal pre-treatment or adhesion promotion. Here, the sheet can be chromated, applied with an organic primer or provided with an amorphous hybrid layer.

This last stage of treatment could, however, be dispensed with if a corresponding starting material is already available pretreated sheet metal is used.

At the end and, if necessary, between the pretreatment stages (7), excess liquid is then removed again as described above via a roller arrangement.

Via the air connection piece (8) any vapors that may be created are extracted and, if necessary, fresh air is supplied.

The sheet metal parts (2) coming from the pretreatment station (4) are then transported to the drying station (9). Here the pretreated sheet metal parts (2) are dried using a contact and convection drying device.

Textile rollers (10) provided with a special covering are arranged at the beginning of the drying station (9). These textile rollers (10) are blown with hot air by means of a blower. Intensive predrying of the sheet metal part (2) is thereby already achieved. The contact drying of the sheet metal parts can, however, also take place via one or more metal rollers or metal plates arranged at the beginning of the drying station (9), which are heated or acted upon by warm air.

The sheet metal part (2) is then dried further by appropriate convection of the warm air in the drying station (9). The necessary air supply is provided via the connection piece (12).

After drying, the sheet metal parts (2) reach the cooling station (13). Here the sheet metal part is cooled down to the necessary sheet metal temperature for the coating process by air and / or contact cooling.

An air supply or air discharge takes place via the connecting piece (14).

The sheet metal parts pretreated in this way are then transported to the actual powder coating station (15). Here the powder coating is carried out with the appropriate guns. In this station there are usually facilities for the powder supply, the powder circuit, for the recovery of the powder passing by the parts and the dosing quantity control for the guns. Furthermore, the powder coating station (15) is provided with filter devices for the exchange of air with the environment.

In an advantageous embodiment, the powder coating station (15) arranged centrally in the overall system also contains the regulating and control device for the automatic process sequence of the entire system in the form of a so-called control center.

The powder coating station (15) is expediently equipped with changing booths (16) in order to be able to replace the booths (16) in the event of a color change. This means that there can be no problems with possible color spreading. The changing cabins (16) are designed to be extendable so that a quick cab change is possible in a simple manner.

At its entrance and exit, the powder coating station (15) can be equipped with a transfer device that takes over or delivers the sheet metal parts (2) to another conveyor system. The conveyor system used in the powder coating system (15) can have appropriate facilities which can bring the sheet metal part (2) into the optimal position for the coating.

The coated sheet metal part (2) passes from the powder coating station (15) into the lock station (17), which could also be referred to as an air conditioning station. With this lock station (17) a temperature and air separation to the subsequent drying station (18) is to be achieved. Furthermore, a transfer device to another conveyor system can be provided, which takes into account the higher temperature in the drying station (18).

In the drying station (18), the sheet metal part coated with powder is subjected to the curing process in several zones by supplying heat. At the beginning, the sheet metal part (2) is brought to a high temperature using a radiation drying device. The radiation drying device preferably consists of medium-wave IR emitters, which bring the radiant heat onto the workpiece using reflectors. After this intensive heating, the sheet metal part subsequently remains in the drying station under the influence of the convection heat maintained in the drying station.

After the powder layer has dried and hardened sufficiently, the sheet metal part is then conveyed to the cooling station (19). Here, the sheet metal part is cooled down to a lower temperature in a manner similar to that in the cooling station (13).

The sheet metal parts (2) are then stacked in packages in the delivery station (20) and can be fed from here for further deformation.

FIG. 2 shows a system provided for the powder coating of flat sheet metal parts (2) in a structure in which individual treatment stations are further developed in detail. It's just missing the feed stations arranged at the beginning of the system and the discharge station arranged at the end for the removal of the finished coated parts.

As can be seen in FIG. 2, the sheet metal parts (2) run horizontally into the pretreatment station (4) of the system by means of the transport device (3). In the so-called cleaning stage (5), the residues such as oil, grease or the like adhering to the sheet metal parts (2) are removed by means of the roller pairs (61, 62) arranged one behind the other and provided with a textile covering. The residues can be collected in a collecting container (27) below the rollers (61, 62), collected and then disposed of.

The sheet metal parts (2), which have been mechanically pre-cleaned in this way, then reach the pretreatment stages (28, 29, 30) of the pretreatment station (4), in which the sheet metal parts (2) use washing devices (31) to improve washing, rinsing or adhesion serving pretreatment process are suspended

The pretreatment stages can consist of a degreasing stage (28), a one- or multi-part rinsing stage (29) and a one- or multi-part rinsing stage (30).

In the example shown, the sheet metal parts (2) are sprayed with an alkaline cleaner in the degreasing stage (28). In the two-stage rinsing stage (29), the parts are rinsed with water, preferably with demineralized water, and in the rinsing stage (30) they are treated with a special rinsing solution which improves the adhesion and improves the corrosion resistance.

At the beginning, at the end and between the above Pre-treatment stages (28, 29, 30) further pairs of rollers (63) are arranged, which preferably have a plastic or rubber coating and through which a separation or completion of the treatment stages is achieved, so that, for. B. Bad carry-over is avoided.

All of the pairs of rollers shown in the system are designed as individual structural units which are partially enclosed by a housing and which are arranged in the system in a removable manner upwards by means of a lifting device, not shown here. This makes possible maintenance or repair easier.

The spray devices (31) of the pretreatment station (4) are designed in the manner of a nozzle set arranged on a plate, it being possible for the individual nozzles to be pivotably mounted in the plate.

The spray devices (31) are connected to the liquid supply via flexible feed lines and are pivotally mounted in the system, so that they can be folded up or down. Between the individual treatment stages in the pretreatment station (4) also in other parts of the system, the partition walls that may be necessary can be designed such that their position can preferably be shifted upwards so that the accessibility of the individual parts is further improved. For maintenance and repair work, a quick interchangeability of the individual parts and better accessibility for repair and cleaning are guaranteed.

At the end of the pre-treatment station (4), after leaving the post-rinse zone (30), the pre-treated sheet metal part is mechanically pre-dried with a pair of textile rollers (64) before it then goes into the actual drying station (9). runs in, at the beginning of which another pair of textile rollers (65) again provides mechanical predrying. The textile rollers (65) can preferably be heated.

Air nozzle devices (32) are arranged in the drying station (9) so that the sheet metal parts (2) are subjected to convection drying with warm air. Here, too, the air nozzles arranged on a support plate are arranged to be pivotable and adjustable.

The sheet metal parts (2) then reach the cooling station (13), where air nozzle devices (33) with supplied cold air also cool the sheet metal parts. The air nozzle devices (32, 33), like the spray devices (31), are arranged in the system so as to be pivotable in order to make maintenance easier.

A centering and straightening device (not shown in more detail) is provided in the cooling station (13), by means of which the sheet metal parts are precisely fixed in position before they are conveyed into the powder coating station (15).

The powder coating station (15) has three stages connected in series, the coating station (25) for the actual surface coating of the parts, the intermediate station (26) and a coating station (21), in which a powder application serving as a sliding aid is carried out. The coating station intended only for the application of the sliding aid can have a simple structure.

In the embodiment shown in Figures 3 and 4, four spray guns (22) are provided under the transport device (3), which are arranged such that the coated sheet metal parts (2) can be provided with a powder application on the back. The transport device should be designed so that the back of the sheet metal parts (2) are freely accessible for the spray jet of the spray guns (22).

Since this powder application only serves as a sliding aid for the subsequent shaping process, a powder layer with a small layer thickness, a powder layer that does not cover the entire surface, or even a powder application in a punctiform or strip-like manner is sufficient. Even a hint of powder can be enough to get the desired sliding effect in the tool. This can be done by one or, as shown, several spray guns that may only be switched on for a short time.

Since no high demands are made on the quality of the powder application, it should also be entirely sufficient if the fine powder that can be removed from the previous coating station is used.

The coating stations (21, 25) are equipped with retractable changing booths so that a quick and automatic change can be made. The coating station (25) is connected to the air circuit of the powder coating system via the fixed intermediate station (26). At the same time, the intermediate station (26) establishes a separation from the sliding aid coating station (21). The intermediate station (26) has flexible air line connections (34) so that a separable and connectable connection can be created to the coating station (25).

Furthermore, all powder-carrying and electrical lines of the coating booths are also pluggable Separation points designed so that the cabins can be changed quickly and easily.

The transport device (35) within the coating station (25) is designed in the manner of a belt conveyor. The conveyor belt on which the sheet metal parts are transported is formed over the entire surface from electrically conductive material and establishes the electrical connection to the sheet metal part and to earth in the coating operation. This special design ensures safe and permanent grounding during powder coating. Slip contacts to the sheet metal part, which are susceptible to faults, are avoided, and undesirable capacitor charging cannot form.

At the end of the transport device (35), a cleaning device (36) for the conveyor belt is provided in the coating station (25), through which the powder residues that form during the application can be removed from the conveyor belt.

The sheet metal parts are coated using a gun set (38) which is arranged in the coating station (25) and consists of a plurality of powder guns.

In order to achieve a uniform coating of the sheet metal part, a special arrangement of the individual powder guns is provided. The principle of the gun arrangement can be seen from the simplified illustration in FIG. The individual powder guns are indicated with (39).

The entire gun set (38) essentially consists of two gun support devices (40, 41). The gun support device (40) located at the beginning of the coating zone is fixed and has an exterior lateral area a powder gun (39). The adjustability of these two pistols is indicated by the dashed lines of further positions of the powder pistols. This allows you to change the distance between these guns to match the width of the sheet to be coated. The guns (39) of the carrying device (40) are aimed at the edge region of the sheet metal part (2) during the coating process.

The gun carrying device (41) has six powder guns (39), three powder guns each being mounted on a carriage (42, 43). These carriages (42, 43) are in turn connected together with a support device (41) which is arranged pivotably about an axis. The distance between the slides (42, 43) can be adjusted.

Likewise, the carriages (42, 43) can be adjusted in the lateral direction transversely to the transport direction. The arrangement is preferably chosen such that, as shown in FIG. 5, the two groups of pistols are offset from one another, as a result of which a good coverage of the spray pattern on the sheet is achieved. During the coating process, the carriages (42, 43) can be brought into an oscillating movement by means of a drive in a laterally reciprocating movement, preferably in one as indicated by the arrow (45).

This design of the gun set (38) in the coating station (25) ensures a uniform coating of the sheet metal parts to be treated. Furthermore, a simple possibility is obtained to adjust the gun arrangement to different shapes and dimensions of the sheet metal parts.

After coating, the sheet metal parts reach the coating station (21) via the intermediate station (26) for the application of sliding aid. The transport device (3) in the coating station (21) for the sliding aid coating contains special transport and support shafts (48) designed according to FIG. 6. Knife edges (49) formed in a special manner ensure that the sheet metal parts to be transported are supported in a small area so that the sheet metal parts can be acted upon as large as possible by the powder guns arranged underneath for the sliding aid coating.

After leaving the powder coating station (15), the coated sheet metal parts pass through the lock station (17) into the drying station (18) and then into the cooling station (19). The cooling station (19) is then followed by a control station (46) in front of the delivery station, in which a check of the coating quality of the sheet metal parts is carried out by means of a suitable sensor scan. Corresponding feedback goes to the central control station (47), from which the coating process can then be corrected or regulated.

In order to simplify maintenance and cleaning work on the system even further, e.g. B. the drying or cooling stations, similar to the changing booths in the powder coating stations, can be designed to be removable from the system. This creates a free space in the line of the system from which you can access the neighboring stations. Or you can move devices from the neighboring stations in the direction of flow out of the system.

In a preferred embodiment, the feed station for the sheet metal parts provided at the beginning of the system be designed as a buffer with several storage locations, the parts located on the pallets being conveyed in cycles and automatically until the individual sheet metal task in the buffer.

At the end of the system, the delivery station can preferably be designed such that it has stack removal stations for the usable sheet metal parts on both sides of the transport device, which can be loaded alternately. At the end of the delivery station, an additional stack removal station can be provided in the transport direction, to which reject parts can be fed.

In the household appliance industry, a manufacturing process using the powder coating system described above can proceed as follows:
A sheet metal coil with lightly oiled and / or pre-treated in the sense of corrosion protection or adhesion promotion is supplied by the steelworks as the starting material. In the equipment factory, the sheet can still be oiled. The sheet metal strip unwound from the sheet coil is cut into corresponding sheet metal parts in a press device. These flat sheet metal blanks are fed in batches to the powder coating system described above, treated in this as described above and then removed in batches from the delivery station. Only then are the fully coated sheet metal blanks formed into finished parts in appropriately designed molds.

Claims (29)

1. Apparatus for producing powder-coated, flat sheet metal parts, including a charging station (1) and a discharging station (20) for the sheet metal parts, at least one preliminary treatment station (4), a drying station (9), a powder-coating station (15) and a hardening station (18), and a conveying device (3), by means of which the sheet metal parts are conveyed through the treatment stations, the sheet metal parts being subjected to the required treatment processes in succession in these treatment stations, characterised in that

   a) the charging station (1) is provided with an unstacking and charging device, by means of which the sheet metal parts (2) to be treated are unstacked and placed so as to lie on the conveying device (3) of the apparatus, and said parts are conveyed in a horizontal position through the treatment stations by means of the conveying device (3),

   b) the preliminary treatment station (4) includes a cleaning stage (5), which has one or more mechanical removal devices (6) for removing liquids, grease, oil, dirt or the like, and one or more washing and/or rinsing stages in which the sheet metal parts are washed and/or rinsed via spraying devices,

   c) the drying station (9) is provided with a contact and/or a convection drying device, by means of which the liquid adhering to the sheet metal part is removed, and the sheet metal part is dried,

   d) a cooling station (13), which is situated downstream of the drying station (9), has a contact and/or convection cooling device, in order to cool the parts down to the coating temperature prior to their entering the coating station (15),

   e) the powder-coating station (15) has one or more changeover compartments (16) and is provided with a controllable spray gun device for the application of powder,

   f) a sluicing station (17) for the separation of heat and air is connected downstream of the powder-coating station (15),

   g) a further drying station (18) for hardening the powder coating is provided with a radiation and a convection drying device,

   h) an additional cooling station (19) has a contact and/or convection cooling device in order to cool the sheet metal parts after hardening, and

   i) a discharging station (20), having a removal and stacking device, is disposed at the end of the apparatus.
2. Apparatus according to claim 1, characterised in that the powder-coating station (15) includes a coating station (25) for coating the sheet metal parts with powder, an intermediate station (26) and a coating station (21) for coating the sheet metal parts with a grinding aid for the subsequent deforming process.
3. Apparatus according to claim 2, characterised in that the intermediate station (26) can communicate with the coating station (25) by means of flexible air conducting elements (34).
4. Apparatus according to claim 3, characterised in that the coating stations (25, 21) are provided with changeover compartments, which are disposed so as to be displaceable from the apparatus, the changeover compartments being able to communicate with the powder-coating system via insertable supply lines.
5. Apparatus according to one of claims 2, 3 and 4, characterised in that the conveying device (35) within the coating station (25) is configured in the form of a belt conveyor, the conveyor belt for receiving the sheet metal parts being formed from electrically conductive material.
6. Apparatus according to claim 5, characterised in that a cleaning device (36) for cleaning the conveyor belt is disposed at the end of the conveying device (35) of the coating station (25), and powder residues are removed from the conveyor belt by means of said cleaning device.
7. Apparatus according to one of claims 1 to 6, characterised in that an assembly of guns (38) for powder-coating is disposed in the powder-coating station (25) and comprises both fixed guns and guns which execute a lateral or oscillatory movement during the coating process.
8. Apparatus according to claim 7, characterised in that the powder guns, which are stationary during the powder-coating operation, are disposed in a gun-supporting device (40) in such a manner that they are orientated towards the outer region of the sheet metal parts.
9. Apparatus according to claim 7, characterised in that the assembly of guns, which is displaceable in a lateral or oscillatory manner during the powder-coating operation, is disposed on a gun supporting device (41), this supporting device (41) being pivotally mounted.
10. Apparatus according to one of claims 7 to 9, characterised in that the guns of the assembly of guns (38) are adjustably disposed on the supporting devices (40, 41), so that the spacings between the guns are variable in respect of one another.
11. Apparatus according to claim 2, characterised in that the conveying device in the coating station (21) has rotatably mounted conveying and supporting shafts (48) for the sheet metal parts, the conveying and supporting shafts (48) being provided with annular cutting edges (49) which are shaped thereon or mountable thereon.
12. Apparatus according to claim 1, characterised in that the preliminary treatment station (4) includes one or more preliminary treatment and/or precoating stages for the preliminary treatment of metal for anti-corrosion and adhesion purposes, and in that one or more mechanical removal devices (6) are provided in the form of rollers, which are coated with a plastics material and/or textile covering, for the removal of the remains from the preliminary treatment agents which adhere to the sheet metal part.
13. Apparatus according to claim 12, characterised in that the preliminary treatment station (4) includes a mechanical cleaning stage (5), a degreasing stage (28), a rinsing stage (29) and a subsequent rinsing stage (30).
14. Apparatus according to claim 13, characterised in that the mechanical cleaning stage (5) comprises two pairs of rollers (61, 62), which are disposed behind each other and are provided with a textile covering, in that a respective pair of rollers (63) is disposed in front of, between and after the treatment stages (28, 29, 30), by means of which rollers the respective treatment stage is isolated, the sheet metal part to be treated being moved through the rollers of the pairs of rollers rotating in opposite directions.
15. Apparatus according to claim 14, characterised in that the pairs of rollers (63) have a plastics material or rubber covering.
16. Apparatus according to claim 2, characterised in that an additional pair of textile rollers (64, 65) is disposed both at the end of the preliminary treatment station (4) and at the beginning of the drying station (9) for the mechanical preliminary drying of the sheet metal parts, the rollers being configured to be selectively heatable.
17. Apparatus according to one of claims 12 to 16, characterised in that the pairs of rollers (61, 62, 63, 64, 65) are configured as structural elements, which are partially surrounded by a housing and are disposed in the apparatus so as to be upwardly removable by means of a lifting device.
18. Apparatus according to one of claims 12 to 17, characterised in that dividing plates, which are upwardly slidably disposed between the structural elements of the pairs of rollers, are provided between the treatment stages (5, 28, 29, 30) in the preliminary treatment station (4).
19. Apparatus according to claim 12, characterised in that the spraying devices (31), which are disposed in the degreasing, rinsing and subsequent rinsing stage (28, 29, 30), are provided with flexible supply lines and are pivotally tiltable upwardly or downwardly, and in that the individual spray nozzles of the spraying devices are adjustably disposed in the nozzle plate.
20. Apparatus according to claim 1, characterised in that a contact drying device is disposed in the drying station (9) and comprises rollers, which are coated with a textile or plastics material covering, the rollers being actuatable with hot air.
21. Apparatus according to claim 20, characterised in that one or more metal rollers or metal plates, which are heated or actuatable with hot air, are disposed in the drying station (9) for contact drying.
22. Apparatus according to one of claims 1 to 21, characterised in that a centring arrangement is disposed in the cooling station (13) and effects a possible positional correction and/or position-fixing of the sheet metal parts prior to the sheet metal parts entering the coating station (15).
23. Apparatus according to one or more of the preceding claims, characterised in that the drying stations (9, 18) and/or cooling stations (13, 19) are disposed so as to removable, and in that the neighbouring treatment stations or devices thereof which are disposed therein are displaceable into the space formed thereby in the conveying direction.
24. Apparatus according to one or more of the preceding claims, characterised in that a monitoring station (46) is provided at the end of the coating apparatus for measuring the coating properties of the sheet metal parts, and in that the data determined via suitable sensors is conducted to the control station (47), whereby a correcting or regulating influence is exerted upon the coating process in the coating stations (21 or 25).
25. Apparatus according to one or more of the preceding claims, characterised in that the charging station for the sheet metal parts is configured as a buffer having a plurality of storage locations, the sheet metal parts, which are situated on the pallets, being conveyed further in a sequential and automatic manner in the buffer until the individual sheet metals are charged.
26. Apparatus according to one or more of the preceding claims, characterised in that the discharging station on both sides of the conveying device includes stack removing locations for the usable sheet metal parts, which locations can be alternately filled, and in that an additional stack removing location is provided at the end of the discharging station in the conveying direction, waste parts being suppliable to said stack removing location.
27. Apparatus according to one or more of the preceding claims, characterised in that the regulating and controlling arrangements, which control the entire process sequence, are accommodated in the powder-coating station (15) in the form of a central control unit.
28. Method of producing powder-coated sheet metal parts for appliances, car bodies or the like, using an apparatus according to one of the preceding claims 1 to 27, characterised

    - in that a more or less pretreated sheet metal coil is used as the starting material,

    - in that the sheet metal strip, wound from the sheet metal coil, is cut to size in a pressing device,

    - in that the flat sheet metal blanks are stackwisely supplied to a powder-coating apparatus, conveyed so as to lie in the powder-coating apparatus, pretreated and coated, and they are stackwisely removed from the powder-coating apparatus,

    - and in that the powder-coated sheet metal parts are subsequently deformed in appropriately configured shaping tools to form finished parts.
29. Method according to claim 28, characterised in that the sheet metal parts in the powder-coating station, on the upwardly orientated side, are provided with the final coating and, on the downwardly orientated side, are provided with a powder application which serves as a grinding aid in the subsequent deforming process.

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