EP0890807B1 - Process and apparatus for drying work pieces with a surface coating - Google Patents

Description

The invention relates to a method for drying with a fresh surface coating Workpieces, especially sheets, where the workpieces through an enclosed drying zone conveyed while being exposed to hot air be, and being at least a portion of in the range walls in the conveying zone and / or Installation of the drying zone also with hot air is or will be acted upon.

It is known after printing and / or painting of metal sheets, these by means of a run working workpiece conveyor by a Transport drying system. In the drying plant are the holding frames of the run exposed sheets exposed to a hot air flow and transported through the drying zone. At the end of the drying zone a solidified surface coating Sheets of the workpiece conveyor removed and for example automatically on a Stacked. In the known method the danger of sticking to the walls, ceilings or internals of the enclosed drying zone Condensate forms. The mostly viscous Condensate can accumulate sufficiently Crow down or drain, causing the moving freshly coated in this area Sheets dirty and therefore unusable become. Since the pollution is mostly only with some Sheet metal occurs is continuous Production due to the laborious process of sorting out the unusable workpieces are not guaranteed. The pollution problem mentioned occurs especially when using organosols, Phenolic resins or special white paints. Also takes the design of the dryer as well as the setting of his air budget on the pollution problem Influence. High levels of contamination are present the short pre-drying section in a double coating line expected.

The features of the claims are derived from US Pat. No. 1,779,622 1, and 4 according to the preamble. It becomes a process for drying coated Workpiece surfaces in a hot air dryer described, in which hot air in spaces between the workpieces and the side walls the dryer is blown. In addition can be provided that hot air below the workpieces introduced into the interior of the dryer is so that the blown hot air directly on hits the workpieces.

From US 2 817 506 A is also a method for Drying coated surfaces of workpieces known with a hot air dryer, in which Hot air from side walls - at the level of a base plate - introduced into the interior of the dryer and derived at the top of the interior being, the hot air on the way from the bottom to meets the workpieces at the top.

JP 02 133 791 A is a drying system known for granules in the area of the drying zone arranged granulate drain walls with provided with a moisture-absorbing layer are the water droplets adhering to the granulate take up.

The invention has for its object a method for drying with a fresh surface coating provided workpieces create a pollution by falling or dripping condensate avoided is.

According to the invention, this object is achieved by that the walls in the area of an air recirculation making exhaust with hot air be charged. The walls in the Area of the exhaust device by means of the special heated hot air duct according to the invention, so that in the area of air recirculation, the due to lower temperature to condensation tends to remedy the build up of condensate are taken. The return of the Hot air includes both the proportion of hot air required for the workpiece treatment has been used as well the remaining portion of the hot air that is used for the removal of the pollution problem is used.

It is envisaged that the surfaces and / or fixtures in the Inside the drying zone, which is predestined Condensate precipitation points must be considered, by means of the hot air, whereby the Condensation largely avoided, at least however is significantly reduced. This measure represents a peculiarity, because within a Space, namely the enclosed drying zone, in addition to drying the surface coating the hot air now blown in anyway in addition hot air is used to the said Eliminate pollution problems. Areas susceptible to condensation are created by this additional Hot air exposure targeted at a brought higher temperature level, so that condensation does not take place or takes place only very slightly. Because it prevents condensation Hot air is brought into the drying zone this measure becomes the real one Drying process of the surface coating with supports, that is, overall is a high one Efficiency guaranteed because the energy for the Prevention of condensation at the same time as drying energy available for the workpieces stands. The areas exposed to the condensate Hot air preferably forms a hot air curtain or a hot air layer that means it sweeps over the surfaces, making it relative large areas with a relatively small amount of hot air can be treated. The hot air curtain further reduces the entry of fresh, condensate forming, concentrated return air on the walls.

According to a development of the invention, that for heating the walls / internals used hot air from a for the loading of the workpieces Hot air flow is branched off. So there is no additional Hot air preparation to be provided as a Part of the hot air can be used for the drying of the surface coating is available stands. If you look at the flow the one for drying the surface coating hot air used, this forms a primary Air circulation system for heating the workpieces, whereby this is superimposed by a secondary hot air circulation system will prone to heating the condensate Surfaces. Quasi is a kind of bypass system created for the primary air circulation system.

According to a development of the invention, that the hot air obliquely or parallel the condensate susceptible surfaces of the walls / internals is fed. In this way they form optimally hot air curtains and hot air layers. The feed at a pretty acute angle or even in parallel brings the Coanda effect with it that is, a small pulse of hot air is sufficient around this very far along the condensate sensitive area to move.

The invention further relates to a device for Drying with a fresh surface coating provided workpieces, in particular Sheet metal with a hot air drying zone penetrating workpiece conveyor, with at least a portion of in the area of the production zone lying walls and / or internals of Drying zone is subjected to hot air or are, with an air recirculation and with hot air outlet nozzles blowing the workpieces. The invention is characterized by walls in the area an exhaust air device performing the air return outlet nozzles with hot air or outlets. The Hot air is applied in addition to that in the hot air introduced into the hot air drying zone, with which the workpieces are loaded. hereby the risk of contamination of the workpieces due to dripping condensate and also the risk of contamination inside the drying zone and also largely avoided the conveyor.

Since the device for drying the workpieces is preferred - seen on both sides in the workpiece conveying direction Hot air outlet channels in the upper area with hot air nozzles for workpiece loading owns and between the two hot air ducts Exhaust air duct is arranged, the exhaust air openings has, results along the longitudinal median planes the dryer has a zone of increased susceptibility to condensation, the production zone below this zone is therefore the one at risk of pollution Area. The over the longitudinal extent of the Drying outside of the exhaust air duct is therefore above the production zone and therefore represents with regard to draining condensate particularly predestined surface. This outside the exhaust air duct is according to the invention with a Hot air curtain occupied to the desired heating to achieve. The hot air curtain is in the In the course of the mentioned secondary air circulation system from the exhaust air duct recorded, that is, it lies constant air exchange prior to condensation largely or even completely prevented.

According to a development of the invention, that at least one side of the exhaust duct Supply air duct assigned for supplying the supply air is. The exhaust air duct and the supply air duct can meet directly and only with a divider be separated from each other or it is also possible that a distance between the exhaust air duct and the supply air duct consists. This side arrangement of the exhaust duct to the supply air duct results from the above already mentioned construction, in which between the exhaust air duct is arranged in the two supply air ducts is. A particularly simple design results even if the supply air duct Outlet opening / outlet openings assigned is / are from which the walls and / or internals hot air exits. It is therefore only for the formation of the hot air curtain required, the existing supply air duct to be provided with outlet openings. alternative it is also possible to replace the outlet openings Use outlet nozzles.

The outlet openings or outlet nozzles according to a preferred embodiment of the invention assigned at least one air guiding device, which leads the escaping hot air such that large areas that are susceptible to condensate sweeps.

It can be provided that the supply air duct Exceeds bottom of the exhaust duct, that is, it there is an outstanding side wall area of the Supply air duct before, in this side wall area the outlet openings or outlet nozzles arranged for the condensation-preventing hot air could be. This makes it possible to Hot air - without taking additional measures must - roughly parallel to the outside of the exhaust air duct feed, the flow direction of the Hot air roughly horizontal and roughly perpendicular to Direction of movement of the workpieces. The the bottom Exceptional side wall area of the exhaust air duct the supply air duct is also suitable to the air guide there, in particular an air baffle to attach. Hence, between the underside facing the supply air duct of the exhaust duct and the air baffle a gap-shaped themselves at least part of the length of the dryer extending zone into which blowing in the hot air used to combat condensate becomes. This creates an optimal one Flow to form the hot air curtain, a relatively low volume flow is sufficient, the desired pollution-preventing To achieve effect.

In addition, to avoid the Soiling of workpieces due to dripping Condensate should be provided, liquid-binding Use material. Hence the device for drying with a fresh surface coating provided workpieces, in particular Sheet metal, with a workpiece conveyor, which penetrates a hot air drying zone, Liquid binding or absorbent material on that at least prone to condensate Surfaces arranged / applied. As a liquid binding material can be, for example, fleece or felt are used, the materials Take up condensate by storing it prevent dripping. These materials are preferably arranged easily replaceable, in particular designed as disposable parts. With an exchange is the inside of the drying zone inside in a very short time in a clean state. If condensation occurs, this leads to not to drain the condensate as that Liquid binding / liquid storing material this prevents. In an advantageous manner this also means the time interval between two cleaning intervals extended so that the drying device can be used more efficiently.

It can be provided inside the drying zone lying, for the precipitation of Areas and / or fixtures susceptible to condensation easy to replace. Preferably provided that these surfaces and / or internals in Area of the drying zone hooked in and / or snapping into place and / or with quick-release holding means are attached. This makes it possible to especially wall cladding parts, quickly and easy to replace to the dryer operate without significant delay can. Is the drying zone with new wall cladding parts equipped, so the removed Components - during the drying device already works again - clean and, if with the liquid binding or absorbent material equipped with new material, so that at the next cleaning interval are ready for use again. Alternatively to the liquid it is binding or absorbent material also possible, solid, easily attachable wall cladding parts, in particular sheets of sheet metal or Plastic, to be used for cleaning work to be able to carry out as quickly as possible. These wall covering parts are after their very easy cleaning reusable.

The drying zone is preferably equipped easily replaceable liquid binding or absorbent material, preferably fleece or felt, is also an easily executable, yet effective Measure to pollution of workpieces to avoid during a drying process. About that In addition, it is also possible to use existing ones Drying devices in the area of their drying zone with a fleece or felt without great technical Retrofit effort.

It can be provided that in the area of the entrance and / or at least exit of the drying zone a hot sealing air curtain is generated. This measure largely ensures entry of ambient air into the interior of the drying zone prevents, that is, the entry of Cold air largely prevented. Because the entering Cold air promotes condensation the sealing air curtain is a safe measure to avoid condensate represents.

All of the above measures, i.e. the Heating with additional hot air, the use of liquid binding material and training a sealing air curtain at the entrance and / or Exit of the tunnel-like hot air drying zone can be used alone or in any combination to avoid or minimize condensation. In particular can be provided that these measures only in Area of tunnel entry or exit be carried out, for example, in each case a length of three meters because in these areas the formation of condensate is greatest. Further inside the tunnel-like hot air drying zone there are stable high and evenly distributed Temperatures that take such measures makes redundant. In addition to those mentioned It is also possible to take measures at the tunnel entrance and / or the tunnel exit with a suction hood provided to above the tunnel opening respectively of the tunnel exit to create a zone that an immediate onset of the relatively cold Room air of the installation room of the device in prevents the hot air drying zone. Further is it is particularly convenient at the bottom of the tunnel entrance or the tunnel exit Blow hot air up to the mentioned To create sealing air curtain, with existing Hood this helps that the air flow of the Air curtain is stable and defined according to the Circulating air principle can be dissipated.

Figur 1

eine schematische Querschnittsansicht durch den oberen Bereich einer Heißluft-Trocknungszone einer Vorrichtung zum Trocknen von mit frischer Oberflächenbeschichtung versehenen Werkstücken,

Figur 2

eine Draufsicht auf einen Längsseitenabschnitt eines in der Heißluft-Trocknungszone befindlichen Zuluftkanals,

Figur 3

eine der Figur 1 entsprechende Ansicht, wobei jedoch Kondensat anfällige Flächen nicht mit Heißluft beaufschlagt werden, sondern ein Flüssigkeit speicherndes Material aufweisen und

Figur 4

eine Seitenansicht des Eingangs der Heißluft-Trocknungszone, der als Trockner ausgebildeten Vorrichtung, wobei die Eingangsöffnung mit einer Haube überfangen ist und im unteren Bereich der Eingangsöffnung Heißluft-Austrittsdüsen vorgesehen sind, um einen Sperrluftvorhang zu schaffen.

The drawings illustrate the invention on the basis of exemplary embodiments, namely:

Figure 1

2 shows a schematic cross-sectional view through the upper region of a hot air drying zone of a device for drying workpieces provided with a fresh surface coating,

Figure 2

2 shows a plan view of a longitudinal side section of an air supply duct located in the hot air drying zone,

Figure 3

a view corresponding to Figure 1, but condensate-sensitive surfaces are not exposed to hot air, but have a liquid-storing material and

Figure 4

a side view of the entrance of the hot air drying zone, the device designed as a dryer, the inlet opening being covered with a hood and in the lower region of the inlet opening, hot air outlet nozzles are provided in order to create a sealing air curtain.

Figure 1 shows a schematic cross section by a device 1 for drying with a freshly coated workpieces, especially sheets. The device 1, which is designed as a dryer 2, has a housed Hot air drying zone 3 on the side walls 4 and 5 and a ceiling wall 6. in the Corner area between side wall 4 and the ceiling wall 6 or the side wall 5 and the ceiling wall 6 are supply air channels 7 and 8 arranged in Direction of longitudinal extension of the dryer 2. Each supply air duct 7, 8 has a vertical one Side wall 9 or 10, the Sidewalls 9 and 10 spaced parallel to the associated side walls 4 and 5 run. Each supply air duct 7, 8 also has a bottom wall 11, 12, the rows of over arranged the longitudinal extent of the dryer, hot air outlet nozzles spaced apart from one another 13 or 14 is enforced. Between the side walls 9 and 10 is an exhaust air duct 15, the ceiling of part of the ceiling wall 6 and its side walls of sections the side walls 9 and 10 are formed. Parallel a floor wall 16 runs to the ceiling wall 6 of the exhaust duct 15, the down by one Side wall area 17, 18 of the side wall 9 or 10 is towered over, so that each a step to the bottom wall 11 or 12 is trained. In the middle of the bottom wall 16 of the exhaust duct 15 is a suction slot 19 formed of the upward facing edge regions 20 and 21 of the bottom wall 16 limited becomes. The two edge regions 20 and 21 extend a bit into the interior of the exhaust air duct 15 in.

At a distance from the bottom wall 16 are air guiding devices 22 and 23 to the exhaust air duct 15 outstanding side wall area 17 and 18 of the Supply air channels 7 and 8 arranged. The air control devices 22 and 23 are each made of an angle plate 24 or 25 formed, one Leg of the respective angle plate 24, 25 on the associated side wall area 17, 18 attached and the second leg is a free leg forms in the direction of the central plane 26 Bottom wall 16 is inclined, such that the each free end diverges to the bottom wall 16. The side wall areas 17 and 18 are from in rows over the length of the Dryer 2 arranged outlet openings 27 and 28 interspersed these outlet openings 27 and 28 between der.Underside 29 of the bottom wall 16 and the respective inside 30 or 31 of the free leg of the air guide 22 or 23 are located (Figure 2). To that extent Crevice zones 32 and 33 formed from the outlet openings 27 and 28 escaping hot air flows along the bottom 29 of the bottom wall 16 of the exhaust duct 15 lead so that there Hot air curtains are formed.

The figure 1 shows that below of the exhaust duct 15 workpieces 34 are located as Sheets formed with a fresh surface coating are and of holding frames, not shown supported in the longitudinal direction of the Dryer 2 from a workpiece conveyor, not shown be transported. The means below the exhaust air duct 15 Workpieces 34 in a conveyor zone 3 'with a dream-like conveyor through the Drying zone 3 out.

The following functions result: The through the dryer 2 transported workpieces 34 by means of the hot air outlet nozzles 13 and 14 emerging, supplied from the supply air ducts 7 and 8 Blow hot air so that the fresh Surface coating of the workpieces 34 dries. The two, from the hot air outlet nozzles 13 and 14 escaping hot air flows unite in the drying zone and are from there through the suction slot 19 and the exhaust duct 15 discharged and after appropriate treatment - according to the recirculation principle - again introduced into the supply air ducts 7 and 8. This makes it a primary air recirculation system created. Part of the supply air ducts 7 and 8 supplied hot air emerges from the outlet openings 27 and 28 of the side wall regions 17 and 18 and arrives in the respective gap zone 32 or 33, the air guiding devices 22 and 23 make sure that on the bottom 29 of the bottom wall 16 of the exhaust air duct 15 forms a hot air curtain, that is, it takes place heating the underside 29. Die die Hot air forming hot air curtain also becomes discharged through the suction slot 19.

Due to the heating of the bottom 29 of the bottom wall 16 is prevented in this area Condensate that precipitates on the fresh coated workpieces 34 could drip.

Figure 3 shows an arrangement that of the figure 1 corresponds, so that only differences below between the two embodiments of Figures 1 and 3 will be discussed. These differences are that the insides 35 and 36 of the side walls 4 and 5 with liquid binding material 37 are occupied. With this Liquid binding or liquid storing material 37, for example around fleece or felt. Even the bottom 29 of the bottom wall 16 of the exhaust duct 15 is with the material 37 is occupied. This also applies to the inside 38, 39 and 40 of the exhaust duct 15. The Liquid-storing material 37 has the property possible condensate to record, so that its drainage or running down is prevented. In deviation the embodiment of Figure 1 is in the embodiment 3 the bottom wall 16 of the exhaust duct 15 deeper so that the cross section of the exhaust duct 15 is enlarged.

Figure 4 shows a side view of the entrance 41 of the device according to FIG. 1, the Entrance 41 is formed by an entrance opening 42 is. The upper edge 43 of the entrance opening 42 becomes covered by a hood 44, which is an exhaust air duct 45 has. The lower edge 46 of the entrance opening 42 hot air outlet nozzles 47 are assigned in such a way that - according to arrow 48- one from below hot sealing air curtain flowing in the Input opening 42 is formed. Due to the Hood 44 and / or the sealing air curtain is prevented that cool room air from the installation room of the dryer 2 in the entrance area of the Drying zone 3 arrives, causing condensation would be reinforced. This intrusion the cool indoor air is particularly in the range of Lower edge 46 of the entrance opening 42 is critical, whereby however this intrusion due to the arranged there Hot air outlet nozzles 47 largely is prevented.

Otherwise, it is possible to on the inner walls of the Hood 44 to provide liquid-binding material 37. In particular, this material is in the upper area the inside of the hood 44 on the ceiling respectively attached to the side walls.

Claims (17)

1. A method of drying workpieces (34) provided with a fresh surface coating, especially metal sheets, wherein the workpieces (34) are conveyed through a housed drying zone (3) and subjected to hot air and wherein at least a portion of walls and/or fittings of the drying zone (3) lying in the region of the conveying zone (3') is or are also subjected to hot air, characterized in that the walls in the region of an exhaust device (exhaust channel (15)) effecting air recirculation are subjected to hot air.
2. A method according to claim 1, characterized in that the hot air used for heating the walls/fittings is branched off a hot air stream provided for acting on the workpieces (34).
3. A method according to one of the preceding claims, characterized in that the hot air is applied to surfaces of the walls/fittings obliquely or parallel thereto.
4. Apparatus for drying workpieces (34), especially metal sheets, provided with a fresh surface coating, preferably for carrying out the method according to one or more of the preceding claims, with a workpiece conveyor device passing through a housed hot air drying zone (3), wherein at least a portion of the walls and/or fittings lying in the region of the conveying zone (3') is or are subjected to hot air, with air recirculation and with hot air exit nozzles (13, 14) blowing on to the workpieces (34), characterized by exit nozzles or exit openings (27, 28) subjecting walls to hot air in the region of an exhaust device (exhaust channel (15)) effecting the air recirculation.
5. Apparatus according to claim 4, characterized in that the walls form at least a section of the underside (29) of an exhaust channel (15).
6. Apparatus according to one of the preceding claims 4 and 5, characterized in that the exhaust device or exhaust channel (15) lies above the conveying zone (3') of the workpiece conveyor device.
7. Apparatus according to any of the preceding claims 4 to 6, characterized in that the exhaust channel (15) extends in the conveying direction.
8. Apparatus according to any of the preceding claims 4 to 7, characterized in that a fresh air channel (7, 8) for supplying the fresh air is arranged on at least one side of the exhaust channel (15).
9. Apparatus according to claim 8, characterized in that the exit openings (27, 28), from which the hot air acting on the walls and/or fittings emerges, are associated with the fresh air channel (7, 8).
10. Apparatus according to any of the preceding claims 4 to 9, characterized in that air guide devices (22, 23) are associated with the exit opening/openings (27, 28).
11. Apparatus according to any of the preceding claims 8 to 10, characterized in that the fresh air channel (7, 8) projects beyond the underside (29) of the exhaust channel (15) and in that the air exit openings (27, 28) are formed in the projecting sidewall region (17, 18) of the fresh air channel (7, 8).
12. Apparatus according to claim 11, characterized in that the air guide device (22, 23) is fixed on the projecting sidewall region (17, 18).
13. Apparatus according to any of the preceding claims 10 to 12, characterized in that the air guide device (22, 23) is an air guide plate (angled plate (24, 25)).
14. Apparatus according to claim 13, characterized in that the air guide plate (angled plate (24, 25)) runs - as regarded in the airflow direction - parallel or inclined to and spaced from the underside (29) of the exhaust channel (15).
15. Apparatus for drying workpieces (34) provided with a fresh surface coating, especially metal sheets, according to one or more of the preceding claims 4 to 14, with a workpiece conveyor device, which passes through a housed hot air drying zone (3), characterized in that at least surfaces of walls and/or fittings lying in the drying zone (3) which are prone to condensation are provided with a material (37) which binds or stores liquid.
16. Apparatus according to claim 15, characterized in that the material (37) is fleece or felt.
17. Apparatus according to any of the preceding claims 4 to 16, characterized in that at least one hot air barrier curtain (arrow (48)) is created in the region of the input (41) and/or outlet of the drying zone (3).

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