Strip flotation furnace

Abstract

The invention relates to a strip flotation furnace (1) for heating a strip (2), comprising a chamber (3) within which a strip plane (4) is formed for receiving the strip (2), and a plurality of lower gas cushion nozzles (5) arranged below the strip plane (4), which are configured to at least help to hold the strip (2) in the strip plane (4) by ejecting a gas, wherein the lower gas cushion nozzles (5) each have two nozzle openings (7) for discharging from the gas a marginal jet (8), in each case directed onto the strip plane (4), and have a plurality of outlet openings (9) arranged between the nozzle openings (7) for discharging the gas into an intermediate region (10) between the marginal jets (8), wherein the nozzle openings (7) are designed such that the marginal jet (8) thus discharged in each case exits the nozzle opening (7) at an angle of at least 45° to the strip plane (4), wherein at least some of the lower gas cushion nozzles (5) each have a downstream guide plate (11) and / or an upstream guide plate (12).

Description

[0001] Belt floatation furnace

[0002] The invention relates to a strip floatation furnace which can be used in particular for the contactless heat treatment of a strip made of a non-ferrous metal such as copper, aluminum or alloys of these metals.

[0003] It is known to heat a strip, for example made of metal, in a so-called strip floatation furnace. The strip is moved contactlessly on a gas cushion through a chamber, often divided into several zones, and is heat-treated during this process. The strip is often first heated in a heating zone and then cooled in a cooling zone. Due to the gas cushion, the strip floats through the chamber, which explains the term "strip floatation furnace." Strip floatation furnaces typically use a nozzle system with several gas cushion nozzles. Conventional nozzle systems for metal strips are often designed for high load-bearing capacities, and stabilization for thinner strips is only a minor feature and in need of improvement.

[0004] The object of the present invention is to present a strip floatation furnace with which a particularly stable strip run can be achieved, in particular for very thin to medium strip thicknesses.

[0005] This object is achieved by the belt flotation furnace and its use according to the independent claims. Further advantageous embodiments are specified in the dependent claims. The features presented in the claims and in the description can be combined with one another in any technologically expedient manner.

[0006] According to the invention, a strip floatation furnace for heat treating a strip is presented. The strip floatation furnace comprises a chamber within which a strip plane is formed to receive the strip, as well as several lower gas cushion nozzles arranged below the strip plane, which are designed to at least contribute to keeping the strip in the strip plane by discharging a gas. The lower gas cushion nozzles each have two nozzle openings for discharging a respective marginal jet of gas directed toward the strip plane, as well as several outlet openings arranged between the nozzle openings for discharging the gas into an intermediate region between the marginal jets. The nozzle openings are designed such that the marginal jet thus discharged exits the nozzle opening at an angle of at least 45° to the strip plane. At least some of the lower gas cushion nozzles each have a downstream guide plate.which is arranged downstream of the nozzle openings in the direction of travel of the belt and is aligned parallel to the belt plane or is inclined downwards in the direction of travel of the belt and / or has a guide plate arranged upstream of the nozzle openings in the direction of travel of the belt and is aligned parallel to the belt plane or is inclined upwards in the direction of travel of the belt.

[0007] The described strip floatation furnace is designed for heat-treating a strip. The heat treatment preferably involves heating. However, it is also possible to cool the strip within the strip floatation furnace. The strip is preferably made of metal. In particular, the strip can be made of a non-ferrous metal, for example, copper, aluminum, or alloys of these metals. Especially for these materials, the use of a strip floatation furnace such as the one described here is often useful. However, for the basic functionality of the strip floatation furnace described here, the material of which the strip is made is irrelevant. Therefore, the strip floatation furnace described here can be used to heat a strip made of any material.

[0008] The strip preferably has a thickness in the range of 0.02 to 1 mm. Such a strip can be described as thin or medium-thin. The advantages described here are particularly achievable for such sheets. However, there is nothing to prevent the strip flotation furnace from being operated with a thicker or thinner sheet.

[0009] The belt is preferably guided at a floating height in the range of 30 to 60 mm. The floating height is the distance between the belt and the highest point of the lower gas cushion nozzles.

[0010] The strip floatation furnace comprises a chamber within which a strip plane is formed for receiving the strip. The chamber is preferably divided into several zones. For example, the chamber can be divided into a heating zone and a cooling zone. The heating zone is designed to heat the strip. The cooling zone is designed to cool the strip. The cooling zone is preferably located downstream of the heating zone in the direction of travel of the strip. The chamber can also be divided into more than two zones. In general, it is preferred that the chamber have at least one heating zone for heating the strip.

[0011] The strip plane is preferably aligned horizontally. The strip can be heat-treated, i.e. heated or cooled, using the strip floatation furnace by moving the strip through the chamber in the strip plane. The strip plane is therefore the location at which the strip is located during the intended use of the strip floatation furnace. The term strip plane is used herein to refer to the position of the strip in the strip floatation furnace, even though the strip as such is not part of the strip floatation furnace. The strip plane does not have to be evident as such through physical characteristics. The position of the strip plane does not have to be fixed either. In particular, the position of the strip plane can be changed by adjusting the pressure at which the gas cushion nozzles are operated. Furthermore, the strip plane does not have to be designed as a plane in the strictly mathematical sense.In particular, it is possible and even preferred for the belt to be wave-shaped as it moves through the chamber. The wave shape increases the belt's stability.

[0012] The belt can be moved through the chamber. For this purpose, the belt can be driven by a conveyor located outside the furnace. For example, a portion of the belt that is no longer in the chamber can be pulled.

[0013] The strip floatation furnace comprises several lower gas cushion nozzles arranged below the strip plane, which are designed to at least contribute to keeping the strip in the strip plane by emitting a gas. The lower gas cushion nozzles are designed to form a gas cushion beneath the strip. For this purpose, a gas is discharged with the lower gas cushion nozzles, which collects beneath the strip. The gas can be air or nitrogen, for example. The gas cushion can accordingly be an air cushion or a nitrogen cushion. Air has the advantage of being readily available. Nitrogen has the advantage of being inert. In general, it is preferred that the gas be inert. This applies particularly, but not exclusively, if the strip is made of copper or a copper alloy. Aluminum alloys and brass (a copper alloy) are preferably annealed in air.The gas can also be a mixture of nitrogen and hydrogen, for example, with a hydrogen concentration in the range of 2 to 4%. The hydrogen can combust with the oxygen present in the chamber, thus creating a furnace atmosphere with a particularly low oxygen concentration.

[0014] However, the gas used is irrelevant for the basic functioning of the belt flotation furnace.

[0015] The belt flotation furnace preferably has a fan through which the gas is fed to the lower gas cushion nozzles. The gas can, for example, be taken from the chamber and circulated there.

[0016] The belt can generally be held in the belt plane using the lower gas cushion nozzles. However, in addition to the lower gas cushion nozzles, other elements can also contribute to this, for example additional nozzles such as the upper gas cushion nozzles described below. It is therefore not necessary for the lower gas cushion nozzles alone to hold the belt in the belt plane. Consequently, the only provision is that the lower gas cushion nozzles are designed to at least contribute to keeping the belt in the belt plane by emitting a gas. However, it is not necessary for other elements besides the lower gas cushion nozzles to contribute to keeping the belt in the belt plane. The lower gas cushion nozzles can therefore also be designed to keep the belt in the belt plane by emitting a gas.Such a design also falls under the formulation that the lower gas cushion nozzles are designed to at least contribute to keeping the strip in the strip plane by emitting a gas.

[0017] The strip can be heated or cooled in particular by the gas discharged through the lower gas cushion nozzles. The lower gas cushion nozzles are therefore preferably designed to at least contribute to keeping the strip in the strip plane by discharging a gas and to at least contribute to heating or cooling the strip. The heat treatment via the lower gas cushion nozzles is convective. The strip floatation furnace preferably has a heating device for heating the gas discharged through the lower gas cushion nozzles and / or a cooling device for cooling the gas discharged through the lower gas cushion nozzles. However, uncooled gas can also be used for cooling. It is also not mandatory that the gas used for the gas cushion is also used for the heat treatment of the strip.It is also conceivable that the strip could be heated by another means, such as radiant heat, as an alternative to or in addition to the heat treatment via the lower gas cushion nozzles. In particular, the upper gas cushion nozzles described below can also contribute to the heat treatment of the strip or even completely effect it.

[0018] Preferably, the heat treatment is carried out convective to at least 90%. In this case, the lower gas cushion nozzles can contribute to the heat treatment of the strip without completely effecting it. Convective heat treatment has the advantage that the gas that comes into contact with the strip anyway simultaneously enables the heat treatment to be carried out entirely, or at least largely.

[0019] The lower gas cushion nozzles each have two nozzle openings for discharging a respective edge jet of gas directed towards the strip plane, as well as several outlet openings arranged between the nozzle openings for discharging the gas into an intermediate region between the edge jets. The two edge jets define the intermediate region into which more gas is introduced via the outlet openings. In particular, an overpressure region is formed between the two edge jets. This overpressure region in particular can be regarded as the gas cushion described above. This overpressure region helps to keep the strip in the strip plane. The design of gas cushion nozzles with edge jets is known in itself. Such gas cushion nozzles can also be referred to as support nozzles.

[0020] The nozzle openings are preferably each designed as a slot that is aligned transversely to the direction of travel of the strip. The direction of travel of the strip is the direction in which the strip is moved through the strip floatation furnace during normal use. Due to the described design of the nozzle openings as slots, the edge jets can be designed as flat jets. This allows the intermediate region to be separated from its surroundings by continuous edge jets. The outlet openings are preferably round. In a direction transverse to the direction of travel of the strip, several of the outlet openings are preferably arranged next to one another. The outlet openings can also be referred to as nozzles. However, for linguistic reasons, this is omitted here to distinguish them from the terms gas cushion nozzle and nozzle opening.The nozzle openings are designed such that the edge jet discharged thereby exits the nozzle opening at an angle of at least 45°, preferably at least 60°, particularly preferably at least 70° to the strip plane. This information refers to the center of gravity of the respective edge jet. Naturally, an upper limit for this angle is 90°. If the edge jets do not exit the nozzle opening perpendicular to the strip plane, the edge jets are preferably oriented such that the intermediate area between the edge jets increases from the nozzle openings toward the strip plane. The two edge jets are preferably directed away from each other.

[0021] The edge jets should hit the underside of the belt as vertically as possible. This allows the lower gas cushion nozzles to exert a particularly effective upward force on the belt. This force counteracts the belt's weight.

[0022] The strip floatation furnace is preferably designed such that the edge jets are not deflected between the corresponding nozzle opening and the strip plane. This is particularly in contrast to designs in which a jet flows out of an opening, is then guided horizontally over a surface, and finally deflected by a deflection element toward the strip plane. The turbulence resulting from such deflection would counteract the advantages described herein.

[0023] At least some of the lower gas cushion nozzles each have a downstream guide plate and / or an upstream guide plate. A downstream guide plate is a guide plate that is located downstream of the nozzle openings in the direction of travel of the belt. An upstream guide plate is a guide plate that is located upstream of the nozzle openings in the direction of travel of the belt. Preferably, at least half of the lower gas cushion nozzles, or even all of the lower gas cushion nozzles, each have a downstream guide plate and / or an upstream guide plate.

[0024] Whether a baffle is positioned downstream or upstream depends on the direction of strip travel. If the strip floatation furnace can be operated in two different directions, a baffle can be used either as a downstream baffle or as an upstream baffle. The only important factor is that the strip floatation furnace allows a strip travel direction that simultaneously meets the conditions described here. Where the downstream and upstream baffles are discussed below, this naturally only applies to the lower gas cushion nozzles, which are equipped with the respective baffle.

[0025] The downstream guide vanes are aligned parallel to the belt plane or inclined downwards in the direction of travel of the belt. The upstream guide vanes are aligned parallel to the belt plane or inclined upwards in the direction of travel of the belt. The gas discharged with a lower gas cushion nozzle can leave the area between the lower gas cushion nozzle and the belt, particularly in the direction of travel and against the direction of travel. In this case, the gas passes the downstream guide vane in the direction of travel. If the downstream guide vane is inclined downwards in the direction of travel of the belt, the flow cross-section available for the gas increases the further the gas is away from the nozzle openings. This helps the gas flow between the belt and the guide vane and then leave this area with little or no back pressure.This creates a vacuum area that pulls the belt downward. It has been found that downstream guide vanes inclined downwards in the direction of belt travel create the vacuum area in such a way that the belt can be guided particularly stably. However, a similar effect can also be achieved to a lesser extent with a downstream guide vane aligned parallel to the belt plane.

[0026] In this case, the gas passes against the direction of travel of the strip through the upstream guide vane. If the upstream guide vane is inclined upwards in the direction of travel of the strip, the flow cross-section available for the gas increases the further the gas moves away from the nozzle openings. This creates a negative pressure area in a similar way to the downstream guide vane, which pulls the strip downwards. It has been found that with upstream guide vanes inclined upwards in the direction of travel of the strip, the negative pressure area is created in such a way that the strip can be guided particularly stably. To a lesser extent, a similar effect can also be achieved with an upstream guide vane that is aligned parallel to the plane of the strip. The downstream guide vane and the upstream guide vane therefore have the same function.Both serve to create a negative pressure area below the belt, which pulls the belt downwards.

[0027] The lower gas cushion nozzles primarily serve to exert an upward force on the strip, counteracting its weight. Nevertheless, the negative pressure area described above has proven to be useful. The resulting downward force stabilizes the strip's path. Alternating between negative and positive pressure areas allows the strip to be guided through the strip floatation furnace in a wave-like pattern. This allows the same effect to be utilized that gives corrugated sheet metal its additional stability compared to flat sheet metal.

[0028] In particular, it has been found that the combination of the described guide vanes with the described angle between the strip plane and the edge jets stabilizes the strip travel. The combination of these features requires that the gas, after flowing out of the nozzle openings of the lower gas cushion nozzles, must change its direction as an edge jet in order to be able to be discharged via the guide vane. This is in particular in contrast to solutions in which the gas is deliberately discharged tangentially to a guide vane. The latter would be the case, for example, if the edge jets were aligned at a smaller angle to the strip plane and / or if the upstream guide vanes were inclined downwards in the direction of travel, at least in a section adjacent to the remaining lower gas cushion nozzle, or if the downstream guide vanes were inclined upwards in the direction of travel, at least in a section adjacent to the remaining lower gas cushion nozzle.This would not change even if, in such a solution, the upstream guide vanes continued to have a section that slopes upwards in the direction of travel, spaced apart from the remaining lower gas cushion nozzle, or if the downstream guide vanes continued to have a section that slopes downwards in the direction of travel, spaced apart from the remaining lower gas cushion nozzle. Even with such sections, the advantages described herein would not be achieved. Accordingly, such solutions should not fall under the definition of a rising or falling guide vane used herein. The same applies if the guide vanes are aligned parallel to the belt plane.

[0029] The lower gas cushion nozzles preferably have a main plate. This term is chosen for linguistic reasons to distinguish it from the guide plates. The nozzle openings are preferably formed within the main plate or at an edge of the main plate. The outlet openings are preferably formed within the main plate. The main plate is preferably aligned parallel to the strip plane. However, this condition is not required to be strictly adhered to. Therefore, it is also preferred that the main plate be at an angle of less than 20° to the strip plane.

[0030] The downstream guide plate preferably borders the remaining lower gas sender nozzle. The main plate and the downstream guide plate preferably form a continuous guide surface for the gas. However, this continuous guide surface can be interrupted, in particular, by the nozzle openings and the outlet openings. It is preferred that the nozzle opening facing the downstream guide plate is formed in the main plate and the downstream guide plate borders the main plate, or that the nozzle opening facing the downstream guide plate is formed between the main plate and the downstream guide plate, wherein the main plate and the downstream guide plate border this nozzle opening. In this case, this nozzle opening can be considered to be formed at the edge of the main plate and at the edge of the downstream guide plate.

[0031] The upstream guide plate preferably borders the rest of the lower gas cushion nozzle. The main plate and the upstream guide plate preferably form a continuous guide surface for the gas. However, this continuous guide surface can be interrupted, in particular, by the nozzle openings and the outlet openings. It is preferred that the nozzle opening facing the upstream guide plate is formed in the main plate, and the upstream guide plate borders the main plate, or that the nozzle opening facing the upstream guide plate is formed between the main plate and the upstream guide plate, with the main plate and the upstream guide plate bordering this nozzle opening. In this case, this nozzle opening can be considered to be formed at the edge of the main plate and at the edge of the upstream guide plate.

[0032] The downstream and upstream guide vanes each form a continuous guide surface with the main vane. If a lower gas cushion nozzle has both a downstream guide vane and an upstream guide vane, the upstream guide vane, the main vane, and the downstream guide vane preferably form a continuous guide surface for the gas. In any case, the continuous guide surface can contribute to creating the previously described negative pressure area between the guide vane and the strip.

[0033] In a preferred embodiment of the strip floatation furnace, at least in some of the lower gas cushion nozzles, a respective outflow opening for discharging the gas is formed between adjacent lower gas cushion nozzles.

[0034] The gas discharged by the lower gas cushion nozzle can exit the area directly below the belt through the discharge opening. The discharge opening is preferably designed as a gap. The discharge opening preferably extends transversely to the flow direction over the entire extent of the lower gas cushion nozzles. This allows the gas to flow out in the same way at every point transverse to the flow direction.

[0035] The outlet opening separates the adjacent lower gas cushion nozzles from each other. There is no continuous gas guide surface extending beyond the outlet opening.

[0036] The lower gas cushion nozzles are separated from one another, in particular due to the outflow opening. This contrasts the present embodiment in particular with designs in which a large-area nozzle box with a plurality of nozzle openings is arranged beneath the belt. Such a nozzle box could at most be conceptually divided into sections that could be understood as lower gas cushion nozzles. However, such a design should not fall under the term "lower gas cushion nozzles" as used herein. In any case, the outflow openings described in the present embodiment are not implemented in a large-area nozzle box. In a large-area nozzle box, the gas can only escape laterally. The negative pressure regions described above cannot be achieved with this, or not as well as with the outflow openings described here.

[0037] In a further preferred embodiment of the strip flotation furnace, the outflow openings open into a respective outflow chamber, which is at least partially delimited at the top by one of the downstream guide plates and / or by one of the upstream guide plates.

[0038] The design of the outflow chambers emphasizes that the guide vanes can influence the flow not only through their surface facing the belt, but also through their surface facing away from it. The latter is the case insofar as the guide vanes define the outflow chamber.

[0039] The outflow spaces can be formed between two adjacent lower gas cushion nozzles. The outflow spaces can then, for example, be delimited at the top by the downstream guide plate of a first of the lower gas cushion nozzles and the upstream guide plate of a second of the lower gas cushion nozzles, which follows the first lower gas cushion nozzle in the flow direction. The outflow opening can then be formed between the downstream guide plate of the first lower gas cushion nozzle and the upstream guide plate of the second lower gas cushion nozzle. If the first lower gas cushion nozzle does not have a downstream guide plate, the outflow opening can be formed between the first lower gas cushion nozzle and the upstream guide plate of the second lower gas cushion nozzle.If the second lower gas cushion nozzle does not have an upstream guide plate, the outflow opening can be formed between the downstream guide plate of the first lower gas cushion nozzle and the second lower gas cushion nozzle.

[0040] In a further preferred embodiment of the strip floatation furnace, a respective highest point of the downstream guide plates is arranged at a maximum height equal to the nozzle openings of the corresponding lower gas cushion nozzle and / or a respective highest point of the upstream guide plates is arranged at a maximum height equal to the nozzle openings of the corresponding lower gas cushion nozzle. The "and" case is preferred.

[0041] This design increases the available flow cross-section for the outflowing gas, starting from the nozzle openings, the further the gas moves away from the nozzle openings. It has been found that this allows the described negative pressure regions to be formed in a particularly well-controlled manner. This applies particularly to the designs described below.

[0042] The lower gas cushion nozzles preferably have a main plate. The nozzle openings are preferably formed within the main plate or at an edge of the main plate. In both cases, a respective highest point of the downstream guide plates is arranged at most as high as the main plate of the corresponding lower gas cushion nozzle and / or a respective highest point of the upstream guide plates is arranged at most as high as the main plate of the corresponding lower gas cushion nozzle. The "and" case is preferred. The respective highest point of the downstream guide plates is preferably formed at the end of the downstream guide plate facing the remaining lower gas cushion nozzle. The respective highest point of the upstream guide plates is preferably formed at the end of the upstream guide plate facing the remaining lower gas cushion nozzle.

[0043] In a further preferred embodiment of the strip flotation furnace, the downstream guide plates are each designed to create a negative pressure region between the strip and the downstream guide plate, and / or the upstream guide plates are each designed to create a negative pressure region between the strip and the upstream guide plate. The "and" case is preferred.

[0044] In a further preferred embodiment of the strip floatation furnace, the downstream guide plates are each rounded at their end facing away from the remaining lower gas cushion nozzle and / or the upstream guide plates are each rounded at their end facing away from the remaining lower gas cushion nozzle. The "and" case is preferred.

[0045] It has been found that the described rounding of the guide vanes results in the outflowing gas being subjected to particularly few turbulences, which promotes the formation of the negative pressure areas.

[0046] In a further preferred embodiment of the strip floatation furnace, the downstream guide plates each enclose an angle of maximum 30° with the strip plane and / or the upstream guide plates each enclose an angle of maximum 30° with the strip plane.

[0047] Preferably, the downstream guide vanes each enclose an angle of maximum 15° with the belt plane and / or the upstream guide vanes each enclose an angle of maximum 15° with the belt plane.

[0048] It has been found that the comparatively low inclination of the guide vanes makes it particularly effective in creating the desired vacuum zone. This allows the belt to be guided with exceptional stability.

[0049] In a further preferred embodiment of the strip floatation furnace, a respective extension of the downstream guide plates in the direction of travel of the strip corresponds to at least 20% of a distance between the two nozzle openings of the corresponding lower gas cushion nozzle in the direction of travel of the strip and / or a respective extension of the upstream guide plates corresponds to at least 20% of a distance between the two nozzle openings of the corresponding lower gas cushion nozzle in the direction of travel of the strip.

[0050] In a further preferred embodiment of the strip floatation furnace, a respective extension of the downstream guide plates in the direction of travel of the strip is at least 5 cm, preferably at least 10 cm and / or a respective extension of the upstream guide plates in the direction of travel of the strip is at least 5 cm, preferably at least 10 cm.

[0051] The extension of a guide plate in the direction of belt travel is the distance, measured in the direction of belt travel, between the two furthest points on the guide plate in this direction. These points can be spaced apart transversely to the belt travel direction.

[0052] In this embodiment, the desired technical effect of the guide vanes can be achieved to a particularly pronounced extent.

[0053] For example, the respective extension of the downstream guide vanes in the direction of travel of the belt can be between 5 and 50 cm, preferably between 10 and 25 cm, and / or the respective extension of the upstream guide vanes in the direction of travel of the belt can be between 5 and 50 cm, preferably between 10 and 25 cm.

[0054] In a further preferred embodiment, the strip floatation furnace further comprises a plurality of upper gas cushion nozzles arranged above the strip plane, which are designed to contribute to keeping the strip in the strip plane by discharging a gas, wherein the upper gas cushion nozzles each have two nozzle openings for discharging a respective edge jet of the gas directed onto the strip plane and a plurality of outlet openings arranged between the nozzle openings for discharging the gas into an intermediate region between the edge jets.

[0055] In this embodiment, the strip floatation furnace comprises a plurality of upper gas cushion nozzles arranged above the strip plane, which are configured to help keep the strip in the strip plane by discharging a gas. The gas can be the same gas as the gas discharged via the lower gas cushion nozzles. However, the gas can also be a different gas. The upper gas cushion nozzles are thus configured to help keep the strip in the strip plane by discharging the previously described gas or another gas. Where "the gas" is mentioned herein with reference to the upper gas cushion nozzles, this can also be understood as "the gas or the other gas."

[0056] The upper gas cushion nozzles are designed to create a gas cushion above the strip. To do this, a gas is discharged from the upper gas cushion nozzles, which collects above the strip. The gas can be air or nitrogen, for example. The gas cushion can be an air cushion or a nitrogen cushion, accordingly. Air has the advantage of being readily available. Nitrogen has the advantage of being inert. Inert gas is generally preferred. However, the gas used is irrelevant to the operation of the strip floatation furnace.

[0057] The belt flotation furnace preferably has a fan through which the gas is supplied to the upper gas cushion nozzles. This can be the same or a different fan through which the gas is supplied to the lower gas cushion nozzles. The gas can, for example, be taken from the chamber and circulated there. Alternatively or additionally, it is preferred that the belt flotation furnace has a gas source for the gas, which is connected to the fan and / or to the lower gas cushion nozzles and / or to the upper gas cushion nozzles. The same gas source or different gas sources can be used for the lower gas cushion nozzles and the upper gas cushion nozzles.

[0058] The belt can be held in the belt plane using the lower gas cushion nozzles. In this embodiment, the upper gas cushion nozzles also contribute to this alongside the lower gas cushion nozzles. In addition to the lower gas cushion nozzles and the upper gas cushion nozzles, other elements can also contribute, such as additional nozzles. It is therefore not necessary for the upper gas cushion nozzles alone to be able to hold the belt in the belt plane. In principle, an upward force can also be generated on the belt via the upper gas cushion nozzles by generating a negative pressure. However, the weight of the belt is generally borne more by the lower gas cushion nozzles than by the upper gas cushion nozzles. Consequently, the upper gas cushion nozzles are only designed to contribute to keeping the belt in the belt plane by emitting a gas.

[0059] The strip can be heated or cooled in particular by the gas discharged via the upper gas cushion nozzles. The upper gas cushion nozzles are therefore preferably designed to help keep the strip in the strip plane by discharging a gas and at least to help heat or cool the strip. The heat treatment via the upper gas cushion nozzles is convective. The strip floatation furnace preferably has a heating device for heating the gas discharged via the upper gas cushion nozzles. This can be the same or a different heating device that is designed to heat the gas discharged via the lower gas cushion nozzles and / or a cooling device for cooling the gas discharged via the upper gas cushion nozzles. However, uncooled gas can also be used for cooling.It is also not mandatory that the gas used for the gas cushion is also used for the heat treatment of the strip. It is also conceivable that the strip is heated by another means, such as radiant heat, as an alternative or in addition to the heat treatment via the upper gas cushion nozzles. It is also possible for the lower gas cushion nozzles to contribute to the heat treatment of the strip, but not the upper gas cushion nozzles. It is also possible for the upper gas cushion nozzles to contribute to the heat treatment of the strip, but not the lower gas cushion nozzles. Preferably, however, both the lower gas cushion nozzles and the upper gas cushion nozzles contribute to the heat treatment of the strip.

[0060] Preferably, the heat treatment is carried out convective to at least 90%. In this case, the lower gas cushion nozzles and the upper gas cushion nozzles can contribute to the heat treatment of the strip without completely effecting it. Convective heat treatment has the advantage that the gas that comes into contact with the strip anyway simultaneously enables the heat treatment entirely, or at least predominantly.

[0061] The upper gas cushion nozzles each have two nozzle openings for discharging a respective edge jet of gas directed towards the strip plane, as well as several outlet openings arranged between the nozzle openings for discharging the gas into an intermediate region between the edge jets. The two edge jets define the intermediate region into which more gas is introduced via the outlet openings. In particular, an overpressure region is formed between the two edge jets. This overpressure region in particular can be regarded as the gas cushion described above. This overpressure region contributes to holding the strip in the strip plane from above. By combining lower gas cushion nozzles and upper gas cushion nozzles, the strip can be held between the gas cushions generated by these gas cushion nozzles. The design of gas cushion nozzles with edge jets is known in itself.Such gas cushion nozzles can also be called support nozzles.

[0062] The nozzle openings are preferably each designed as a slot that is aligned transversely to the direction of travel of the strip. The direction of travel of the strip is the direction in which the strip is moved through the strip floatation furnace during normal use. Due to the described design of the nozzle openings as slots, the edge jets can be designed as flat jets. This allows the intermediate region to be separated from its surroundings by continuous edge jets. The outlet openings are preferably round. In a direction transverse to the direction of travel of the strip, several of the outlet openings are preferably arranged next to one another. The outlet openings can also be referred to as nozzles. However, for linguistic reasons, this is omitted here to distinguish them from the terms gas cushion nozzle and nozzle opening.

[0063] The nozzle openings are designed such that the edge jet discharged thereby exits the nozzle opening at an angle of at least 45°, preferably at least 60°, particularly preferably at least 70° to the strip plane. This information refers to the center of gravity of the respective edge jet. Naturally, an upper limit for this angle is 90°. If the edge jets do not exit the nozzle opening perpendicular to the strip plane, the edge jets are preferably oriented such that the intermediate area between the edge jets increases from the nozzle openings toward the strip plane. The two edge jets are preferably directed away from each other.

[0064] The edge jets should hit the underside of the belt as vertically as possible. This allows a downward force to be exerted on the belt via the upper gas cushion nozzles. This force, like the belt's weight, is directed downward. However, these two forces are counteracted by an upward force generated by the lower gas cushion nozzles. All of these forces allow the belt to be held stably in the belt plane. This also prevents unwanted bowing of the belt.

[0065] The strip floatation furnace is preferably designed such that the edge jets are not deflected between the corresponding nozzle opening and the strip plane. This is particularly in contrast to designs in which a jet flows out of an opening, is then guided horizontally over a surface, and finally deflected by a deflection element toward the strip plane. The turbulence resulting from such deflection would counteract the advantages described herein.

[0066] In a further preferred embodiment of the strip floatation furnace, it is provided that at least some of the upper gas cushion nozzles each have a downstream guide plate which is arranged downstream of the nozzle openings in the direction of travel of the strip and is aligned parallel to the strip plane or is inclined upwards in the direction of travel of the strip and / or has an upstream guide plate which is arranged upstream of the nozzle openings in the direction of travel of the strip and is aligned parallel to the strip plane or is inclined downwards in the direction of travel of the strip.

[0067] At least some of the upper gas cushion nozzles each have a downstream guide plate and / or an upstream guide plate. A downstream guide plate is a guide plate that is located downstream of the nozzle openings in the direction of travel of the belt. An upstream guide plate is a guide plate that is located upstream of the nozzle openings in the direction of travel of the belt. Preferably, at least half of the upper gas cushion nozzles, or even all of the upper gas cushion nozzles, each have a downstream guide plate and / or an upstream guide plate.

[0068] Whether a baffle is positioned downstream or upstream depends on the direction of strip travel. If the strip flotation furnace can be operated in two different directions, a baffle can be used either as a downstream baffle or as an upstream baffle. The only important factor is that the strip flotation furnace allows for a strip travel direction that simultaneously meets the conditions described here.

[0069] As far as the downstream and upstream guide vanes are discussed below, this naturally only applies to the upper gas cushion nozzles, which have the respective guide vane.

[0070] The downstream guide vanes are aligned parallel to the belt plane or inclined so as to rise in the direction of travel of the belt. The upstream guide vanes are aligned parallel to the belt plane or inclined so as to fall in the direction of travel of the belt. The gas discharged with an upper gas cushion nozzle can leave the area between the upper gas cushion nozzle and the belt, particularly in the direction of travel and against the direction of travel. In this case, in the direction of travel, the gas passes the downstream guide vane. If the downstream guide vane is inclined so as to rise in the direction of travel of the belt, the flow cross-section available for the gas increases the further the gas moves away from the nozzle openings. This helps the gas flow between the belt and the guide vane and then leave this area with little or no back pressure.This creates a vacuum area that pulls the belt upward. It has been found that downstream guide vanes inclined upwards in the direction of belt travel create the vacuum area in such a way that the belt can be guided particularly stably. However, a similar effect can also be achieved to a lesser extent with a downstream guide vane aligned parallel to the belt plane.

[0071] In this case, the gas passes against the direction of travel of the strip through the upstream guide vane. If the upstream guide vane is inclined downwards in the direction of travel of the strip, the flow cross-section available for the gas increases the further the gas moves away from the nozzle openings. This creates a negative pressure area in a similar way to the downstream guide vane, which pulls the strip upwards. It has been found that with downstream guide vanes inclined downwards in the direction of travel of the strip, the negative pressure area is created in such a way that the strip can be guided particularly stably. To a lesser extent, a similar effect can also be achieved with an upstream guide vane that is aligned parallel to the plane of the strip.

[0072] The downstream and upstream guide vanes therefore have the same function. Both serve to create a vacuum area above the belt, which pulls the belt upward.

[0073] The upper gas cushion nozzles primarily serve to exert a downward force on the strip. This is intended to keep the strip stable in the strip plane. Nevertheless, the described negative pressure area has proven to be useful. The resulting upward force further stabilizes the strip path. If negative and positive pressure areas alternate, the strip is guided through the strip floatation furnace in a wave-like pattern. This allows the same effect to be utilized that also gives corrugated sheet metal its additional stability compared to flat sheet metal.

[0074] In particular, it has been found that the combination of the described guide vanes with the described preferred angle between the strip plane and the edge jets stabilizes the strip travel. The combination of these features requires that the gas, after flowing out of the nozzle openings of the upper gas cushion nozzles, must change its direction as an edge jet in order to be able to be discharged via the guide vane. This is in particular in contrast to solutions in which the gas is deliberately discharged tangentially to a guide vane. The latter would be the case, for example, if the edge jets were aligned at a smaller angle to the strip plane and / or if the upstream guide vanes were inclined so as to rise in the direction of travel, at least in a section adjacent to the remaining upper gas cushion nozzle, or if the downstream guide vanes were inclined so as to fall in the direction of travel, at least in a section adjacent to the remaining lower gas cushion nozzle.This would not change even if, in such a solution, the upstream guide vanes continued to have a section that slopes downwards in the direction of travel, spaced apart from the remaining upper gas cushion nozzle, or if the downstream guide vanes continued to have a section that slopes upwards in the direction of travel, spaced apart from the remaining upper gas cushion nozzle. Even despite such sections, the advantages described herein would not be achieved. Accordingly, such solutions should not fall under the definition of a rising or falling guide vane used herein. The same applies if the guide vanes are aligned parallel to the belt plane.

[0075] The upper gas cushion nozzles preferably have a main plate. This term is chosen for linguistic reasons to distinguish it from the guide plates. The nozzle openings are preferably formed within the main plate or at an edge of the main plate. The outlet openings are preferably formed within the main plate. The main plate is preferably aligned parallel to the strip plane. However, this condition is not required to be strictly adhered to. Therefore, it is also preferred that the main plate be at an angle of less than 20° to the strip plane.

[0076] The downstream guide plate preferably borders the rest of the upper gas cushion nozzle. The main plate and the downstream guide plate preferably form a continuous guide surface for the gas. However, this continuous guide surface can be interrupted, in particular, by the nozzle openings and the outlet openings. It is preferred that the nozzle opening facing the downstream guide plate is formed in the main plate and the downstream guide plate borders the main plate, or that the nozzle opening facing the downstream guide plate is formed between the main plate and the downstream guide plate, wherein the main plate and the downstream guide plate border this nozzle opening. In this case, this nozzle opening can be considered to be formed at the edge of the main plate and at the edge of the downstream guide plate.

[0077] The upstream guide plate preferably borders on the rest of the upper gas cushion nozzle. The main plate and the upstream guide plate preferably form a continuous guide surface for the gas. However, this continuous guide surface can be interrupted, in particular, by the nozzle openings and the outlet openings. It is preferred that the nozzle opening facing the upstream guide plate is formed in the main plate and the upstream guide plate borders the main plate, or that the nozzle opening facing the upstream guide plate is formed between the main plate and the upstream guide plate, with the main plate and the upstream guide plate bordering this nozzle opening. In this case, this nozzle opening can be considered to be formed at the edge of the main plate and at the edge of the upstream guide plate. The downstream guide plates and the upstream guide plates therefore each form a continuous guide surface with the main plate.If an upper gas cushion nozzle has both a downstream guide plate and an upstream guide plate, the upstream guide plate, the main plate and the downstream guide plate preferably form a continuous guide surface for the gas.

[0078] In any case, the continuous guide surface can help to create the previously described negative pressure area between the guide plate and the belt.

[0079] In a further preferred embodiment of the strip floatation furnace, at least in some of the upper gas cushion nozzles, a respective outflow opening for discharging the gas is formed between adjacent upper gas cushion nozzles.

[0080] The gas discharged by the upper gas cushion nozzles can exit the area directly above the belt through the discharge opening. The discharge opening is preferably designed as a gap. The discharge opening preferably extends transversely to the flow direction over the entire extent of the upper gas cushion nozzles. This allows the gas to flow out in the same way at every point transverse to the flow direction.

[0081] The adjacent upper gas cushion nozzles are separated from each other by the outlet opening. There is no continuous gas guide surface extending beyond the outlet opening.

[0082] The upper gas cushion nozzles are separated from one another, in particular due to the outflow opening. This contrasts the present embodiment in particular with designs in which a large-area nozzle box with a plurality of nozzle openings is arranged above the belt. Such a nozzle box could at most be conceptually divided into sections that could be understood as upper gas cushion nozzles. However, such a design should not fall under the term “upper gas cushion nozzles” as used herein. In any case, the outflow openings described in the present embodiment are not implemented in a large-area nozzle box. In a large-area nozzle box, the gas can only escape laterally. The negative pressure regions described above cannot be achieved with this, or not as well as with the outflow openings described here.In a further preferred embodiment of the strip flotation furnace, the outflow openings open into a respective outflow chamber, which is at least partially delimited at the top by one of the downstream guide plates and / or by one of the upstream guide plates.

[0083] The design of the discharge chambers emphasizes that the guide vanes can influence the flow not only through their surface facing the belt, but also through their surface facing away from it. The latter is true insofar as the guide vanes define the discharge chamber.

[0084] The outflow spaces can be formed between two adjacent upper gas cushion nozzles. The outflow spaces can then, for example, be delimited at the top by the downstream guide plate of a first of the upper gas cushion nozzles and the upstream guide plate of a second of the upper gas cushion nozzles, which follows the first upper gas cushion nozzle in the flow direction. The outflow opening can then be formed between the downstream guide plate of the first upper gas cushion nozzle and the upstream guide plate of the second upper gas cushion nozzle. If the first upper gas cushion nozzle does not have a downstream guide plate, the outflow opening can be formed between the first upper gas cushion nozzle and the upstream guide plate of the second upper gas cushion nozzle.If the second upper gas cushion nozzle does not have an upstream guide plate, the outflow opening can be formed between the downstream guide plate of the first upper gas cushion nozzle and the second upper gas cushion nozzle.

[0085] In a further preferred embodiment of the strip floatation furnace, a respective lowest point of the downstream guide plates is arranged at least as high as the nozzle openings of the corresponding upper gas cushion nozzle and / or a respective lowest point of the upstream guide plates is arranged at least as high as the nozzle openings of the corresponding upper gas cushion nozzle. The "and" case is preferred.

[0086] This configuration increases the flow cross-section available for the outflowing gas, starting from the nozzle openings, the further the gas moves away from the nozzle openings. It has been found that this allows the described negative pressure regions to be formed in a particularly well-controlled manner. This applies particularly to the configurations described below. The upper gas cushion nozzles preferably have a main plate. The nozzle openings are preferably formed within the main plate or at an edge of the main plate. In both cases, a respective lowest point of the downstream guide plates is arranged at least as high as the main plate of the corresponding upper gas cushion nozzle and / or a respective lowest point of the upstream guide plates is arranged at least as high as the main plate of the corresponding upper gas cushion nozzle. The "and" case is preferred.

[0087] The respective lowest point of the downstream guide vanes is preferably formed at the end of the downstream guide vane facing the remaining upper gas cushion nozzle. The respective lowest point of the upstream guide vanes is preferably formed at the end of the upstream guide vane facing the remaining upper gas cushion nozzle.

[0088] In a further preferred embodiment of the strip flotation furnace, the downstream guide plates are each designed to create a negative pressure region between the strip and the downstream guide plate, and / or the upstream guide plates are each designed to create a negative pressure region between the strip and the upstream guide plate. The "and" case is preferred.

[0089] In a further preferred embodiment of the strip floatation furnace, the downstream guide plates are each rounded at their end facing away from the remaining upper gas cushion nozzle and / or the upstream guide plates are each rounded at their end facing away from the remaining upper gas cushion nozzle. The "and" case is preferred.

[0090] It has been found that the described rounding of the guide vanes results in the outflowing gas being subjected to particularly few turbulences, which promotes the formation of the negative pressure areas.

[0091] In a further preferred embodiment of the strip floatation furnace, the downstream guide plates each form an angle of a maximum of 30° with the strip plane and / or the upstream guide plates each form an angle of a maximum of 30° with the strip plane. Preferably, the downstream guide plates each form an angle of a maximum of 15° with the strip plane and / or the upstream guide plates each form an angle of a maximum of 15° with the strip plane.

[0092] It has been found that the comparatively low inclination of the guide vanes makes it particularly effective in creating the desired vacuum zone. This allows the belt to be guided with exceptional stability.

[0093] In a further preferred embodiment of the strip floatation furnace, a respective extension of the downstream guide plates in the direction of travel of the strip corresponds to at least 20% of a distance between the two nozzle openings of the corresponding upper gas cushion nozzle in the direction of travel of the strip and / or a respective extension of the upstream guide plates corresponds to at least 20% of a distance between the two nozzle openings of the corresponding upper gas cushion nozzle in the direction of travel of the strip.

[0094] In a further preferred embodiment of the strip floatation furnace, a respective extension of the downstream guide plates in the direction of travel of the strip is at least 5 cm, preferably at least 10 cm and / or a respective extension of the upstream guide plates in the direction of travel of the strip is at least 5 cm, preferably at least 10 cm.

[0095] The extension of a guide plate in the direction of belt travel is the distance, measured in the direction of belt travel, between the two furthest points on the guide plate in this direction. These points can be spaced apart transversely to the belt travel direction.

[0096] In this embodiment, the desired technical effect of the guide vanes can be achieved to a particularly pronounced extent.

[0097] For example, the respective extension of the downstream guide vanes in the direction of travel of the belt can be between 5 and 50 cm, preferably between 10 and 25 cm, and / or the respective extension of the upstream guide vanes in the direction of travel of the belt can be between 5 and 50 cm, preferably between 10 and 25 cm.

[0098] In a further preferred embodiment of the strip floatation furnace, the lower gas cushion nozzles and the upper gas cushion nozzles are arranged offset from one another in the direction of travel of the strip. Ideally, the lower gas cushion nozzles and the upper gas cushion nozzles are arranged offset from one another in the direction of travel of the strip such that an overpressure area below the strip is opposite a negative pressure area above the strip, and vice versa. This particularly supports the undulation of the strip.

[0099] It is therefore preferred that the lower gas cushion nozzles and the upper gas cushion nozzles are offset from one another in the direction of travel of the belt by a distance corresponding to an average extension of the lower gas cushion nozzles. However, the advantages described can also be achieved if this condition is not strictly adhered to. It is therefore also preferred that the lower gas cushion nozzles and the upper gas cushion nozzles are offset from one another in the direction of travel of the belt by a distance that deviates from an average extension of the lower gas cushion nozzles by a maximum of 20%, preferably by a maximum of 10%.

[0100] In general, it is also preferred that at least some of the lower gas cushion nozzles have a downstream guide plate and at least some of the upper gas cushion nozzles have an upstream guide plate, or that at least some of the lower gas cushion nozzles have an upstream guide plate and at least some of the upper gas cushion nozzles have a downstream guide plate.

[0101] It is also generally preferred that the lower gas cushion nozzles and the upper gas cushion nozzles are arranged offset from one another in the direction of travel of the belt such that the lower gas cushion nozzles each overlap with one of the upper gas cushion nozzles in the direction of travel of the belt. Particularly preferably, the lower gas cushion nozzles and the upper gas cushion nozzles are arranged offset from one another in the direction of travel of the belt such that at least some of the guide vanes of the lower gas cushion nozzles overlap with an area between the two nozzle openings of one of the upper gas cushion nozzles in the direction of travel of the belt. This configuration enables the desired generation of the negative pressure region to be achieved particularly successfully. This allows the belt to be guided particularly stably.

[0102] As a further aspect of the invention, the use of a strip flotation furnace configured as described is presented for heat treating a strip made of a non-ferrous metal. The described advantages and features of the strip flotation furnace are applicable and transferable to the use, and vice versa. The strip flotation furnace described above is preferably suitable for heating a strip made of a non-ferrous metal.

[0103] The non-ferrous metal can be, in particular, copper, aluminum, or alloys of these metals. The use of the described strip floatation furnace is particularly useful in this context. The heat treatment is preferably heating.

[0104] The strip is preferably heated to a temperature of at least 200°C, in particular at least 400°C. Preferably, the strip is heated to a temperature in the range of 200 to 1000°C, in particular in the range of 400 to 900°C.

[0105] The invention is explained in more detail below with reference to the figures. The figures show particularly preferred embodiments to which the invention is not limited. The figures and the proportions depicted therein are merely schematic. They show:

[0106] Fig. 1 : a cross-sectional view of a first embodiment of a strip flotation furnace according to the invention,

[0107] Fig. 2: a cross-sectional view of a second embodiment of a strip flotation furnace according to the invention,

[0108] Fig. 3: a cross-sectional view of a third embodiment of a strip flotation furnace according to the invention,

[0109] Fig. 4: a perspective view of one of the gas cushion nozzles as used in the

[0110] Belt floatation furnace from Fig. 2 or 3 can be used.

[0111] Fig. 1 shows a strip floatation furnace 1 for heating a strip (not shown here), for example made of a non-ferrous metal. Only those elements of the strip floatation furnace 1 are shown for the following explanation. The remaining components have been omitted for the sake of clarity. The strip floatation furnace 1 comprises a chamber 3, within which a strip plane 4 is formed to receive the strip, as well as several lower gas cushion nozzles 5 arranged below the strip plane 4. The lower gas cushion nozzles 5 are designed to help keep the strip in the strip plane 4 by emitting a gas. The gas can be supplied to the lower gas cushion nozzles 5 via an inlet 20 indicated by an arrow.

[0112] The lower gas cushion nozzles 5 each have two nozzle openings 7 for discharging a respective marginal jet 8 from the gas directed onto the strip plane 4, as well as several outlet openings 9 arranged between the nozzle openings 7 for discharging the gas into an intermediate region 10 between the marginal jets 8. The nozzle openings 7 are designed such that a center of gravity 14 of the marginal jet 8 thus discharged forms an angle of 90° and thus of at least 45° with the strip plane 4. The nozzle openings 7 and the outlet openings 9 are each formed in a main sheet 19 of the lower gas cushion nozzle 5.

[0113] The lower gas cushion nozzles 5 each have a downstream guide plate 11, which is located downstream of the nozzle openings 7 in the belt's travel direction d and is inclined downwards in the belt's travel direction d. The lower gas cushion nozzles 5 also each have an upstream guide plate 12, which is located upstream of the nozzle openings 7 in the belt's travel direction d and is inclined upwards in the belt's travel direction d. The respective highest point of the downstream guide plates 11 and the upstream guide plates 12 is arranged at a maximum height equal to the nozzle openings 7.

[0114] An outlet opening 13 for discharging the gas is formed between the lower gas cushion nozzles 5. The gas discharged through the outlet opening 13 enters an outlet chamber 15. In this chamber, the gas can flow transversely to the flow direction d and thus be discharged.

[0115] The downstream guide plates 11 are each designed to create a vacuum region 16 between the belt and the downstream guide plate 11. The upstream guide plates 12 are each designed to create a vacuum region 16 between the belt and the upstream guide plate 12. A positive pressure region 17 is formed between the main plates 19 of the lower gas cushion nozzles 5 and the belt.

[0116] The downstream guide vanes 11 and the upstream guide vanes 12 are each rounded at their end 18 facing away from the remaining lower gas cushion nozzle 5.

[0117] Fig. 2 shows another embodiment of a strip floatation furnace 1 for heating a strip. In contrast to the embodiment shown in Fig. 1, only guide vanes arranged on one side are provided here. In the specific example, these are downstream guide vanes 11. Otherwise, the description for Fig. 1 applies analogously here.

[0118] Fig. 3 shows a further embodiment of a strip floatation furnace 1 for heating a strip 2, which is also shown here. In contrast to the embodiments according to Figs. 1 and 2, a plurality of upper gas cushion nozzles 6 are provided here, arranged above the strip plane 4. These are designed analogously to the lower gas cushion nozzles 5 shown in Fig. 2. The lower gas cushion nozzles 5 and the upper gas cushion nozzles 6 are offset from one another in the direction of travel d of the strip 2. As a result, the negative pressure regions 16 and the positive pressure regions 17 are opposite one another. This results in the indicated wave shape of the strip 2. Otherwise, the description for Figs. 1 and 2 applies analogously here.

[0119] Fig. 4 shows a gas cushion nozzle 5, 6, such as can be used in the strip floatation furnace 1 from Fig. 2 or 3. Depending on how the gas cushion nozzle 5, 6 is oriented, it can be used as a lower gas cushion nozzle 5 or as an upper gas cushion nozzle 6. Depending on the flow direction d, the guide plate 11, 12 is either a downstream guide plate 11 or an upstream guide plate 12. Otherwise, the description for Figs. 1 to 3 applies analogously here.

[0120] List of reference symbols

[0121] 1 belt floatation furnace

[0122] 2 volumes

[0123] 3 chamber

[0124] 4 Band level

[0125] 5 lower gas cushion nozzle

[0126] 6 upper gas cushion nozzle

[0127] 7 nozzle openings

[0128] 8 marginal ray

[0129] 9 Exit opening

[0130] 10 Intermediate area

[0131] 11 downstream guide plate

[0132] 12 upstream guide plate

[0133] 13 Outlet opening

[0134] 14 Focus

[0135] 15 Outflow chamber

[0136] 16 Negative pressure range

[0137] 17 Overpressure range

[0138] 18 End

[0139] 19 Main sheet

[0140] 20 Inlet d Flow direction

Claims

Claims 1. Strip flotation furnace (1) for heating a strip (2), comprising a chamber (3), within which a belt plane (4) is formed for receiving the belt (2), as well as a plurality of lower gas cushion nozzles (5) arranged below the belt plane (4), which are designed to at least contribute to holding the belt (2) in the belt plane (4) by discharging a gas, wherein the lower gas cushion nozzles (5) each have two nozzle openings (7) for discharging a respective marginal jet (8) from the gas directed towards the belt plane (4), as well as a plurality of outlet openings (9) arranged between the nozzle openings (7) for discharging the gas into an intermediate region (10) between the marginal jets (8), wherein the nozzle openings (7) are designed such that the marginal jet (8) thus discharged exits the nozzle opening (7) at an angle of at least 45° to the belt plane (4), wherein at least some of the lower gas cushion nozzles (5) each have a downstream guide plate (11),which is located downstream of the nozzle openings (7) in the direction of travel (d) of the belt (2) and parallel to the belt plane, (4) or is inclined downwards in the direction of travel (d) of the belt (2), and / or has an upstream guide plate (12) which is arranged upstream of the nozzle openings (7) in the direction of travel (d) of the belt (2) and is aligned parallel to the belt plane (4) or is inclined upwards in the direction of travel (d) of the belt (2).

2. Belt floatation furnace (1) according to claim 1, wherein at least in some of the lower gas cushion nozzles (5) a respective outflow opening (13) for discharging the gas is formed between adjacent ones of the lower gas cushion nozzles (5).

3. Belt floatation furnace (1) according to claim 2, wherein the outflow openings (13) open into a respective outflow chamber (15) which is delimited at the top at least partially by one of the downstream guide plates (11) and / or by one of the upstream guide plates (12).

4. Belt floatation furnace (1) according to one of the preceding claims, wherein a respective highest point of the downstream guide plates (11) is arranged at most as high as the nozzle openings (7) of the corresponding lower gas pole nozzle (5) and / or a respective highest point of the upstream guide plates (12) is arranged at most as high as the nozzle openings (7) of the corresponding lower gas cushion nozzle (5).

5. Belt floatation furnace (1) according to one of the preceding claims, wherein the downstream guide plates (11) are each designed to generate a negative pressure region (16) between the belt (2) and the downstream guide plate (11) and / or the upstream guide plates (12) are each designed to generate a negative pressure region (16) between the belt (2) and the upstream guide plate (12).

6. Belt floatation furnace (1) according to one of the preceding claims, wherein the downstream guide plates (11) are each rounded at their end (18) facing away from the remaining lower gas cushion nozzle (5) and / or the upstream guide plates (12) are each rounded at their end (18) facing away from the remaining lower gas cushion nozzle (5).

7. Belt floatation furnace (1) according to one of the preceding claims, wherein the downstream guide plates (11) each enclose an angle of maximum 30° with the belt plane and / or the upstream guide plates (12) each enclose an angle of maximum 30° with the belt plane.

8. Belt floatation furnace (1) according to one of the preceding claims, wherein in the direction of travel (d) of the belt (2) a respective extension of the downstream guide plates (11) corresponds to at least 20% of a distance between the two nozzle openings (7) of the corresponding lower gas cushion nozzle (5) and / or in the direction of travel (d) of travel of the belt (2) a respective extension of the upstream guide plates (12) corresponds to at least 20% of a distance between the two nozzle openings (7) of the corresponding lower gas cushion nozzle (5).

9. Belt floatation furnace (1) according to one of the preceding claims, wherein in the direction of passage (d) of the belt (2) a respective extension of the downstream guide plates (11) is at least 5 cm and / or in the direction of passage (d) of the belt (2) a respective extension of the upstream guide plates (12) is at least 5 cm.

10. Belt floatation furnace (1) according to one of the preceding claims, further comprising a plurality of upper gas cushion nozzles arranged above the belt plane (4). sen (6) which are designed to help hold the strip (2) in the strip plane (4) by discharging a gas, wherein the upper gas cushion nozzles (6) each have two nozzle openings (7) for discharging a respective edge jet (8) from the gas directed onto the strip plane, and each have a plurality of outlet openings (9) arranged between the nozzle openings (7) for discharging the gas into an intermediate region (11) between the edge jets (8).

11. Belt floatation furnace (1) according to claim 10, wherein at least some of the upper gas cushion nozzles (6) each have a downstream guide plate (11) which is arranged downstream of the nozzle openings (7) in the direction of travel (d) of the belt (2) and is aligned parallel to the belt plane (4) or is inclined so as to rise in the direction of travel (d) of the belt (2) and / or have an upstream guide plate (12) which is arranged upstream of the nozzle openings (7) in the direction of travel (d) of the belt (2) and is aligned parallel to the belt plane (4) or is inclined so as to fall in the direction of travel (d) of the belt (2).

12. Belt floatation furnace (1) according to claim 10 or 11, wherein the lower gas cushion nozzles (5) and the upper gas cushion nozzles (6) are arranged offset from one another in the direction of passage (d) of the belt (2).

13. Use of a strip flotation furnace (1) according to one of the preceding claims for the heat treatment of a strip (2) made of a non-ferrous metal.

Images