• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:

    公开号:BE1020507A3
    申请号:E2012/0338
    申请日:2012-05-22
    公开日:2013-11-05
    发明作者:Michel Dubois；Houtte Brice Van
    申请人:Cockerill Maintenance & Ingenierie Sa；
    IPC主号:
    专利说明:

    SYSTEM FOR REDUCING THE CONSUMPTION OF LAUNDRY GAS IN AN AIR BLADE
    Field of the invention
    The present invention relates to a gas smoothing device for controlling the thickness of a film of liquid deposited on a moving web. A typical example is a device for gas smoothing of a liquid metal on large coated sheets, such as those obtained by hot dip coating.
    General context and prior art
    The "air knife" method is a well-known process used to smooth excess fluid entrained by a moving web from a bath. A typical air knife uses a chamber pressure as high as 700 mbar resulting in an output gas velocity close to the sound level. The air discharge opening is usually in the range of 0.5 to 2 mm.
    The air smoothing process generates some waves in the coating because of the high turbulence that occurs when the jet of gas enters the atmosphere. This high turbulence can not be reduced due to the high level of shear forces. However, the amplitude of these waves tends to decrease over time because of the uniformization process that occurs in the state of the liquid, driven by the surface tension of the liquid.
    A countermeasure for limiting the amplitude of these waves to the appearance of the finished product consisting, for example, of a zinc-coated sheet consists of replacing the air as a smoothing medium with nitrogen ( N2) · This process induces a significant reduction in the oxidation of the liquid coating and helps to maintain a high surface tension. Since the surface tension of the liquid metal is kept high, the final surface after solidification is a smoother surface when N 2 is used. This leads to a much better surface appearance after painting. A typical case is that of galvanized sheets used for panels exposed in automobiles.
    In the case of a low line speed, the air can generate defects such as those shown in Figure 1 which are suspected to be due to the oxidation of the metal. Again, N2 smoothing helps to greatly reduce these defects.
    Finally, an air smoothing can induce what is called a "cloudy appearance" as shown in Figure 2 and which is due to differential oxidation of the surface. Here again, N2 smoothing is used to drastically improve this poor surface quality.
    A related problem is that the use of N 2 is expensive since a flow up to 800 Nm 3 / hr per meter nozzle length can be used. The cost becomes particularly high in the case of smoothing of narrow sheets because the gas leaves the nozzle opening along the entire length of the nozzle, whereas smoothing is of course only necessary for the smoothing of the nozzle. 'before the band. All the flow of N2 that is outside the band is indeed lost.
    The solution to reduce these losses and thus reduce operating costs is a flexible closure of the air discharge opening in the region in which the gas has no smoothing effect. To this end, various methods have been proposed such as: a reduction of the nozzle opening by an action on the lips of the nozzle 1 by mechanical means. Figure 3 shows, for example, such a typical opening of this type; the use of a sheet inside the nozzle as shown in FIG. 4, the sheet being indicated by 2 in the figure. The sheet 2 is moved by motors located at the edges of the nozzle (not shown), which means that the sheet is pushed when the opening 4 is to be closed or reduced (see EP 0 249 234 A1, Blow -off device for the continuous two-sided coating of metal strip, Duma Konstructionsbuero).
    The above methods have various drawbacks because of the operating window used in production as well as the specifications of the final coating as described below: the mechanical closure of the opening has side effects on the control of the opening to the front of the strip, which has an impact on the control of the thickness of the final coating. In addition, because of mechanical stresses, the deformation of the lips should be limited to prevent plastic deformation; - the leaf suffers from the strength to which it must resist. As an example, when a chamber pressure of about 600 mbar is used, the force on the surface 2 (FIG. 4) measuring only 5 mm high for example is 120 N on a mask with a length of 400 mm. This designates a friction force of at least 12 N when the latter is moved. Since the sheet is usually thin, it can not be pushed along the nozzle without buckling; at the location at which the gas flow is stopped due to the masking device, the temperature of the nozzle increases because it is not cooled by the gas, while it is still heated by the radiation of the liquid metal. This leads to thermal expansion and deformation of the opening all along the nozzle due to temperature gradients. This deformation can be either elastic, which would not be a too critical situation, plastic, depending on the design of the nozzle, which would have an impact on the uniformity of the weight of the coating in this case.
    Objects of the invention
    The present invention aims to avoid the disadvantages of the prior art.
    More particularly, an object of the invention is to obtain a mobile device that allows a reduction in gas consumption by reducing the flow of gas outside the strip and that can operate in a room environment at differential pressure as high as 1 bar.
    Another object of the invention is to provide a proper closure of the unnecessary nozzle opening section on each side of the web in the case of handling narrow webs.
    The invention also aims to allow the maintenance of a certain cooling of the nozzle openings which limits their thermal deformation.
    Summary of the invention
    The present invention relates to a device for controlling the thickness of a coating made by a film of liquid on a moving web, comprising a nozzle fed with gas under pressure in a chamber of the nozzle, said chamber ending with nozzle providing an elongated opening for discharging the pressurized gas onto the moving web, said elongate opening being provided with automated means for reducing the gas flow of each transverse side of the nozzle outside the web width, characterized in that said automated means for reducing the flow of gas from each of said nozzle sides comprises a movable carriage guiding a retractable cable capable of being deposited respectively on and off the gas discharge opening, within the nozzle chamber.
    According to preferred embodiments, the device of the invention is further limited by a characteristic or an appropriate combination of the following characteristics: each mobile carriage is bidirectional and moved independently by a motorized mechanical device; - on each transverse side of the nozzle, a transition between an outer nozzle section in which the gas flow is reduced and an inner nozzle section in which the gas flow is not reduced, is ensured by means of two moving wheels or pulleys together connected to the movable carriage, located side by side and having their axis perpendicular to the nozzle, so that the cable is successively located against the opening of an outer side of the first pulley, between the two pulleys and away from the opening of an inner side of the second pulley; the mechanical device is a screw; the mechanical device is another cable or similar device; - the cable is permanently live; the cable is made of a material resistant to heat, preferably steel; the diameter of the cable is between 1 and 10 mm, preferably between 2 and 5 mm. Because of the existing roughness of the cable, the closure is not complete and some flow still passes between the nozzle lips, providing some advantageous cooling effect; - The bidirectional carriage with its wheels or pulleys and the motorized mechanical device are located inside the nozzle chamber; the cable is selected and adjusted so that the residual gas flow at the nozzle opening where the cable is applied is less than 20% of the value where the cable is not applied.
    Brief description of the drawings
    Figure 1 shows defects induced by air smoothing at a low line speed.
    Figure 2 shows the phenomenon of cloudy appearance induced by air smoothing and due to a differential oxidation of the surface.
    Figure 3 shows schematically a reduction of the nozzle opening by an action on the lips of the nozzle by mechanical means, according to the prior art.
    Figure 4 shows schematically an inner sheet incorporated inside a nozzle to limit the opening of the nozzle according to the prior art.
    Fig. 5 is a section of a preferred embodiment according to the present invention.
    FIG. 6 is a schematic top view of a nozzle according to a preferred embodiment of the invention, showing an example of positioning a cable, applied against the slot opening at the edges of the nozzle and in a position retracted.
    Figure 7 shows, in cross-sectional view, a typical position of the cable when applied against the slot of the nozzle.
    Figure 8 shows specific measurements of the dynamic pressure at the outlet of the nozzle near the region in which the cable is applied.
    DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS The invention relates to a novel device for reducing the flow of gas from the nozzle outside the bandwidth section. It consists in the use of a cable made either of steel or of another heat-resistant material which is deposited (or placed) and withdrawn alternately from the nozzle opening by a mobile carriage installed inside the nozzle chamber. A carriage is provided on each side of the nozzle and can be moved independently of the carriage on the opposite side by means of a mechanical device such as another cable, a screw or the like. Still according to the invention, the cable is permanently energized.
    The diameter of the cable is generally between 2 and 5 mm. Due to a certain roughness of the cable, the closure is not complete and a certain leakage flow still passes between the lips of the opening, communicating a certain cooling effect to the nozzle.
    FIG. 5 and FIG. 6 show the masking system according to the invention consisting of a cable 9. The system applying the cable 9 to the nozzle lips comprises the carriage 10, a mechanical drive system 8, as well as two wheels or sheaves 6, 7.
    Figure 6 shows an example of the position of the cable 9, applied against the opening 4, at each edge of the nozzle 1 in a retracted position.
    Figure 7 shows a typical sectional position of the cable 9 in place in the nozzle opening 4 when applied.
    The device of the invention has the following advantages compared with the prior art: a possible and easy retraction of the closure system at a pressure of up to 1 bar in the chamber; the existence of a certain residual flow at the location where the opening is closed, which is appropriate for maintaining a certain cooling of the lips; - Adjustments individually controlled on each side by separate drive systems to position the truck.
    Example
    In one embodiment, an embodiment of a device according to the invention has been installed on a gas smoothing nozzle (not shown).
    In this example, the length of the nozzle 1 is about 2.3 m; the opening 4 thereof may be between 1 and 2 mm.
    The cable 9 has a diameter of 5 mm and is applied or retracted by a carriage having two grooved wheels 6, 7, a carriage 10 being present on each side of the nozzle. The truck is moved by a motorized screw. The internal movement of the carriage 10 is limited by a carriage stop 12.
    Tests were carried out with an internal pressure in the chamber of 220 mbar and the dynamic pressure at the outlet was measured by very small pitot tubes (FIG. 8). It can be seen on the right of the graph that the dynamic pressure is greatly reduced at the location where the cable is applied. A detailed analysis of the results showed that the residual flow at the location where the cable is applied is about 15% of what it would be without the device in the case of a 1 mm and 10% opening. in the case of an opening of 2 mm.
    List of reference symbols 1. Nozzle 2. Sheet to close the nozzle opening 3. Band 4. Slit 5. Pressurized nozzle chamber 6. Wheel 7. Wheel 8. Mechanical drive system 9. Cable 10. Trolley 11. Air supply 12. Trolley stop
    权利要求:
    Claims (12)
    [1]
    A device for controlling the thickness of a coating made by a film of liquid on a moving web (3), comprising a nozzle (1) fed with pressurized gas (11) into a chamber (5) of the nozzle said chamber (5) terminating in nozzle lips providing an elongated opening (4) for discharging pressurized gas onto the moving web (3), said elongated opening (4) being provided with automated means for reducing the gas flow from each transverse side of the nozzle (1) outside the bandwidth, characterized in that said automated means for reducing the flow of gas from each of said nozzle sides comprises a movable carriage (10) guiding a retractable cable (9) capable of being deposited respectively on and off the gas discharge opening (4), inside the nozzle chamber (5).
    [2]
    2. Device according to claim 1, characterized in that each movable carriage (10) is bidirectional and moved independently by a motorized mechanical device (8).
    [3]
    3. Device according to claim 1 or 2, characterized in that, on each transverse side of the nozzle, a transition between an outer nozzle section where the gas flow is reduced and an internal nozzle section where the flow of gas is not reduced, is ensured by means of two wheels or sheaves (6, 7) moving together connected to the movable carriage (10), located side by side and having their axis perpendicular to the nozzle, so that the cable (9) is placed successively against the opening (4) on an outer side of the first pulley (6), between the two pulleys (6, 7) and away from the opening (4) of a inner side of the second pulley (7).
    [4]
    4. Device according to claim 2, characterized in that the mechanical device (8) is a screw.
    [5]
    5. Device according to claim 2, characterized in that the mechanical device (8) is another cable.
    [6]
    6. Device according to claim 1, characterized in that the cable (9) is permanently energized.
    [7]
    7. Device according to claim 1, characterized in that the cable (9) is made of a material resistant to heat.
    [8]
    8. Device according to claim 7, characterized in that the cable (9) is made of steel.
    [9]
    9. Device according to claim 1, characterized in that the diameter of the cable (9) is between 1 and 10 mm.
    [10]
    10. Device according to claim 9, characterized in that the diameter of the cable (9) is between 2 and 5 mm.
    [11]
    11. Device according to claim 3, characterized in that the bidirectional carriage (10) with its wheels or pulleys (6, 7) and the motorized mechanical device (8) are located inside the nozzle chamber ( 5).
    [12]
    Device according to claim 1, characterized in that the cable (9) is selected and adjusted so that the residual gas flow at the nozzle opening (4) at the location where the cable is applied is less than 20% of the value at the location where the cable is not applied.
    类似技术:
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
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    KR20060003447A|2004-07-06|2006-01-11|박창식|Apparatus for controling splay width of gas nozzle and air-knife using the same|
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    EP12156291|2012-02-21|
    EP12156291.2A|EP2631012B1|2012-02-21|2012-02-21|System for reducing the wiping gas consumption in an air knife|
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