EP1789741A1

EP1789741A1 - Furnace for hardening a lacquer layer applied to continuous material

Info

Publication number: EP1789741A1
Application number: EP05769975A
Authority: EP
Inventors: Gerald Pascher
Original assignee: "Kaizen" Consulting GmbH
Current assignee: "Kaizen" Consulting GmbH
Priority date: 2004-08-10
Filing date: 2005-08-09
Publication date: 2007-05-30
Also published as: AT414041B; ATA13622004A; WO2006015398A1

Abstract

Disclosed is a furnace (1) for hardening a lacquer layer applied to continuous material, especially wire. At least one draft duct (2) into which an air flow is directed to harden the lacquer layer is provided for the continuous material. Said draft duct (2) comprises at least one air inlet (17) near a furnace outlet (6) which is open towards the environment and via which the continuous material is discharged from the draft duct (2). Used air of a wire-cooling device (7) that is not directly joined to the furnace outlet (6) is introduced into the draft duct (2) via the air inlet (17).

Description

Oven for curing a applied to continuous material

paint layer

The invention relates to a furnace for curing a lacquer layer applied to endless material, in particular wire, wherein at least one passage channel is provided for the endless material into which an air flow for curing the lacquer layer is introduced.

In the case of such furnaces, when the lacquer layer applied to a final material, in particular a wire, is applied, the evaporation of solvent takes place. As a result, the atmosphere inside the furnace consists of a mixture of air, solvent vapors and paint fine dust. In order not to release this contaminated atmosphere to the environment, this mixture of air, solvent vapors and paint fine dust is usually conducted in the circulating air principle via heating coils and catalysts, so that the process atmosphere is purified by sublimation and catalytic reaction. The exhaust gas discharged from the furnace is therefore to be regarded as pure within legally defined pollutant limits.

The problem is, however, the inlet and outlet of the furnace, since contaminated atmosphere can escape from the oven. At the inlet opening of the furnace leakage of the contaminated atmosphere can be reliably prevented by a negative pressure in the furnace is generated so that fresh air is sucked in constantly both at the Ofen¬ inlet and at the Ofenauslauföffnung and thus at least at the kiln inlet an escape of the furnace atmosphere is prevented.

In the region of the kiln outlet, however, this is not completely possible since the continuous material guided through the passage channel of the kiln entrains a small amount of contaminated kiln atmosphere from the kiln by adhesion to its surface. This leads after a certain period of time (usually less than 10 weeks) in the region of the kiln outlet to the formation of deposits of hardened lacquer mixed with solvent condensate, which adversely affect the function of the furnace and consequently make maintenance work necessary. _ o _

In the furnaces described above, in which the contaminated atmosphere is circulated, it is known to provide so-called injectors, in which the circulating air in the region of the furnace outlet is guided through a cross-sectional constriction and thus the velocity of the introduced into the duct Circulating air is increased, whereby a negative pressure is generated at the furnace outlet, which in addition to the negative pressure by the extracted exhaust gas contributes to the intake of fresh air. However, in particular in the case of vertically arranged ovens, the negative pressure which can be achieved hereby is too small to prevent the oven atmosphere entrained by the wire from escaping via the oven outlet.

Furthermore, it is known, for example from DE 31 18 830 A, to provide furnaces for curing a coating layer applied to a wire with a so-called "pressure box", in which a wire cooling device is mounted directly on the furnace and the backpressure in the area However, such combinations of oven and wire cooling device have proved to be disadvantageous because they are very difficult to set, since small changes in the process parameters (production speeds, temperatures, wire diameter, etc.) are very high As a result of the assembly of the furnace with the wire cooling device, such combination devices could not be controlled in terms of process technology and have, therefore, a different adjustment of the furnace / wire cooling device combination Therefore, it is not enforced in practice on the market.

EP 1 070 927 A2 further discloses a different type of device for drying with photoresist or similar coated plates and webs, in which the highest possible uniformity in drying of the coating should be ensured. For this purpose, a continuous dryer is provided with a drying carton, which is divided into three Prheizzessheizzonen and two Zuluftheizzonen. In this case, a removed from a directly adjacent to the drying chamber cooling zone entnom- Mener air flow through a blower in the two Zuluftheizzonen introduced for drying, which is heated for a qualitatively high-quality drying of the derived from the cooling zone air flow before entering the Zuluftheizzonen first over several heating coils.

The aim of the present invention is now to provide a furnace of the initially mentioned kind, which is reliably sealed in the region of the furnace outlet against an escape of the contaminated furnace atmosphere, whereby a simple adaptation to different process parameters should be possible.

In the case of the furnace of the type mentioned at the outset, this is achieved by virtue of the fact that the passage channel has at least one air inlet opening in the vicinity of an oven outlet open to the environment via which the endless material leaves the passage channel, wherein exhaust air does not escape via the air inlet opening is introduced directly to the furnace outlet subsequent wire cooling device in the passage channel. By introducing the exhaust air of a wire cooling device into the through-channel in the vicinity of the kiln outlet, a sufficient back pressure can be built up to prevent the kiln atmosphere entrained with the endless material from exiting the kiln. In this case, the backpressure of the air exhausted from the exhaust air of the wire cooling device can be adjusted dynamically, wherein the process parameters in the furnace and in the wire cooling device can be regulated independently of each other, so that both the furnace and the wire cooling device can be controlled in a simple manner , By introducing the exhaust air of the wire cooling device can thus be reliably prevented leakage of the furnace atmosphere, whereby the environment of the furnace is not contaminated with polluted air and thus the formation of condensates in the oven outlet opening is prevented. Furthermore, the exhaust air supplied to the furnace of the wire cooling device is already preheated to about 60 ⁰ C, whereby the energy balance of the furnace is positively influenced.

In order to easily initiate the branched off from the exhaust duct of Drahtkühlvorrich¬ device air into the duct, it is advantageous if for introducing the exhaust air, the wire cooling device is provided in the passage channel of the furnace a the feed channel and an exhaust duct of the wire cooling device connecting Luftzu¬ guide line.

For an efficient introduction of the exhaust air of the wire cooling device into the passage channel, it is advantageous if the air supply line is connected to a sealing shaft which adjoins the air inlet opening.

To heat the exhaust air of the wire cooling device prior to introduction into the passage channel of the furnace and to introduce at a favorable angle in the passage channel, it is advantageous if the sealing shaft comprises a preheating shaft and a Einblas¬ shaft.

In this case, it is favorable for utilizing the furnace heat loss if the preheating shaft has a return section and a lead-forward section, which run essentially parallel to one another and are connected to one another via a connecting section curved by approximately 180 °. Thus, the preheating shaft can be arranged over a relatively large area adjacent to the passage channel and thus over the waste heat of the furnace heating of Ab¬ air of the wire cooling device of about 60 ° up to about 300 ⁰ C can be achieved. By using the furnace waste heat and reintroduction into the furnace, the energy balance of the furnace is thus positively influenced. In particular, it is favorable for heating the exhaust air of the wire cooling device in the preheating shaft when the preheating shaft extends substantially over the entire length of the furnace.

In order to bring in the exhaust air of the wire cooling device substantially counter to the advance direction of the endless material in the passage channel, it is expedient for the injection shaft to be connected to the preheating shaft via a curved connecting section, preferably by approximately 120 °.

Tests have shown that heating of the exhaust air in the preheating shaft is achieved particularly efficiently when the sealing shaft has a length in cross section of 280 mm to 340 mm, in particular substantially of 320 mm, and a width of 40 mm mm to 80 mm, in particular substantially of 60 mm.

If the furnace is designed in a manner known per se as a circulating air oven and the duct has an air inlet opening, the atmosphere conducted in a circulating air circuit, which is preferably conducted via heating coils and catalysts, can be circulated by sublimation and catalytic reaction be cleaned, also in the passage channel, in particular by means of an injector, introduced, and thus a back pressure in the region of the furnace outlet are generated.

Since the exhaust air branched off from the wire cooling device can be regulated independently of the process parameters in the furnace, it is advantageous if the air inlet opening is arranged closer to the outlet of the furnace than the recirculation air inlet opening, since thus the overpressure the circulating air not yet retained furnace atmosphere on the separately controllable back pressure of the introduced exhaust air of the wire cooling device can be prevented from escaping.

The invention will be explained in more detail with reference to preferred embodiments illustrated in the drawings, to which, however, it is not intended to be restricted. In detail, in the drawing:

1 schematically shows a longitudinal section of a furnace with a Luf¬ teintrittsöffnung for introducing exhaust air of a Drahtkühlvor¬ direction;

FIG. 2 shows in detail a longitudinal section of the outlet end of the furnace according to FIG. 1; FIG.

3 schematically shows a longitudinal section of a furnace with a be¬ adjacent wire cooling device, wherein the exhaust duct of the wire cooler is connected via an air supply line and a sealing shaft with the passage channel of the furnace.

Figure 4 is a perspective view of the outlet end of the furnace, but with a sealing shaft having a comparatively short compared to Figure 3 Vorwärmschacht. and - S -

5 is a perspective view of the seal shaft according to FIG .. 4

FIG. 1 shows a longitudinal section of a furnace 1 with a through-feed channel 2 for passing through the continuous material or wire provided with a lacquer layer, a retort 3 with a burn-in zone 4 being provided for this purpose.

The wire passed through the furnace 1 enters the furnace 1 at a furnace inlet 5 and leaves the furnace 1 at a furnace outlet 6, the wire subsequently being fed to a wire cooling device 7 arranged adjacently (see FIG.

The circulating air introduced into the pass-through duct 2 via a circulating-air air inlet opening 8 is circulated in the furnace 1 with the aid of a blower 9, a heat exchanger 10 and heating devices 11 being provided for heating the air flow. Wei¬ ters is a catalyst 12 for cleaning the circulating air, which is composed of a mixture of air, solvent vapors and fine paint dust provided. The circulating air is in this case introduced via a so-called injector 13 in the passage channel 2, wherein the injector 13 has a tapering to the circulating air inlet opening 8 cross section, so that increases the speed of the circulating air to the circulating air inlet opening 8 and so¬ a negative pressure in the region of the furnace outlet 6 is generated.

This negative pressure increases the negative pressure in the passage channel 2, which is discharged from the furnace 1 via an exhaust gas fan 14, with which circulating air withdrawn via openings 15 on the inside of an injector shaft 16 (see FIG. By means of this negative pressure present in the passage 2, it is ensured that an exit of the furnace atmosphere is prevented in the region of the kiln inlet 5. In order to reliably prevent leakage in the region of the oven outlet 6, the passage channel 2 has an air inlet opening 17 in the vicinity of the oven outlet 6 (cf., in particular, FIG. 2), via which exhaust air from the wire cooling device 7 into the passage channel 2 is introduced and thus an increased back pressure in the region of the furnace outlet 6 is generated, so that reliable discharge of the Konta Rαinierten furnace atmosphere, which adheres to the wire passed through the passage 2, is prevented.

As can be seen in particular from FIG. 3, an exhaust air channel 18 of the wire cooler 7 is connected to the passage channel 2 of the furnace 1 via a connecting line 19 and a sealing shaft 20 adjoining the connecting line 19. In order to control the back pressure introduced by the introduction of the exhaust air of the wire cooling device 7 in the passage channel 2 of the furnace 1 exhaust air, a wire cooling exhaust fan 18 'in the exhaust duct 18 of the wire cooling device 7 is arranged.

As can be seen in particular from FIG. 2, the sealing shaft 20 can have a preheating shaft 21, which is arranged parallel to the through-channel 2 and is divided into a return section 21 'and into a preliminary section 21 ", which extend parallel to one another and over a 180 ° curved Ver¬ connection portion 22 are interconnected. Through the Aus¬ a formation in the furnace 1 installed Vorwärmschachts 21 can thus the furnace heat loss are exploited and introduced into the passage channel 2 via the connecting line 19 Ab¬ air the wire cooling device 7 of about 6O ^0C to about 300 ^0C heated ,

As can be seen in FIGS. 3 to 5, the preheating shaft 21 can be made considerably shorter in comparison with the exemplary embodiments according to FIGS. 1 and 2. Although in comparison with the preheating shaft 21 shown in FIG. 2, a lower heating of the exhaust air of the wire cooling device 7 is achieved, such a short preheating shaft 21 can also subsequently be easily inserted into already existing furnaces 1.

The sealing shaft 20 opens via an injection shaft 23 in the air inlet opening 17 of the passage channel 2, wherein the injection shaft 23 ver¬ over a substantially by about 120 ° curved connecting portion 23 'with the preheating shaft 21 is connected.

The air inlet opening 17 can in this case, as in the in Fig. 4th shown embodiment, either on the underside of the passage channel 2 or even, as can be seen in particular in Fig. 3, be arranged on the upper side of the passage channel 2. All that is essential is that the exhaust air removed from the wire cooling device 7 is introduced into the passage channel 2 in the area of the outlet end 6 of the furnace 1, in order to reliably prevent an exchange of the contaminated furnace atmosphere entrained with the wire.

Claims

claims

1. Furnace (1) for curing an applied to continuous material, in particular wire, lacquer layer, wherein at least one Durchzugs¬ channel (2) is provided for the continuous material, in which an air flow for curing the lacquer layer is initiated, da¬ characterized in that the passage channel (2) has at least one air inlet opening (17) in the vicinity of an oven outlet (6) open towards the surroundings, via which the endless material leaves the passage chamber (2), whereby via the air inlet opening (17) Exhaust air of a not directly to the furnace outlet (6) adjoining wire cooling device (7) in the passage channel (2) is introduced.

2. Oven according to claim 1, characterized in that for introducing the exhaust air of the wire cooling device (7) in the Durch¬ zugskanal (2) of the furnace (1) a passage channel (2) and an exhaust duct (18) of the wire cooling device ( 7) connecting air supply line (19) is provided.

3. Furnace according to claim 2, characterized in that the air supply line (19) with a sealing shaft (20) is connected, which adjoins the air inlet opening (17).

4. Furnace according to claim 3, characterized in that the sealing shaft (20) comprises a preheating shaft (21) and an injection shaft (23).

5. Oven according to claim 4, characterized in that the preheating shaft (21) has a return section (21 ') and Vorführab¬ section (21' ') which extend substantially parallel to each other and over a curved by about 180 ° Verbindungsab¬ cut (22) are interconnected.

6. Furnace according to claim 4 or 5, characterized in that the preheating shaft (21) extends substantially over the entire length of the furnace (1).

7. Oven according to one of claims 4 to 6, characterized net, that the injection shaft (23) via a, preferably by about 120 °, curved connecting portion (23 ¹ ) with the preheating bay (21) is connected.

8. Oven according to one of claims 4 to 7, characterized gekennzeich¬ net, that the sealing shaft (17) in cross section has a length of 280 mm to 340 mm, in particular substantially of 320 mm, and a width of 40 mm to 80 mm, in particular essenli chen of 60 mm.

9. Oven according to one of claims 1 to 8, characterized gekennzeich¬ net, that the furnace (1) is formed in a conventional manner as a convection oven and the passage channel (2) has a recirculation Lufttein¬ outlet opening (8).

10. Oven according to claim 9, characterized in that the Luft¬ inlet opening (17) closer to the oven outlet (6) is arranged as the circulating air-air inlet opening (8).