Patent Publication Number: US-11654480-B2

Title: Sliding closure for a metallurgical vessel, preferably a distributor vessel for a continuous casting facility

Description:
FIELD OF THE INVENTION 
     The invention relates to a slide closure for a metallurgical vessel, preferably a tundish for a strand casting system, with a housing that can be fastened onto the bottom of the vessel, an upper closure plate arranged in a cover of the housing, a lower closure plate and a central closure plate that can be longitudinally displaced between the upper and lower closure plates, and wherein the upper, lower and central closure plates are tensioned against one another with spring arrangements extending between the housing and the cover. 
     BACKGROUND OF THE INVENTION 
     Slide closures of this type are known in advance, for example from document EP 0 891 829. They are characterized in that, with them, the flow restriction or closing of the outlet is caused by the longitudinal movement of the slide plate. They thus serve in particular as a positioning member for controlled casting of the quantity of molten material from the metallurgical vessel. 
     For uninterrupted functioning of the slide closure, the plate tension is set such that it ensures both the free movability of the slide plate and the tightness of the slide closure required to prevent air from being sucked in. However, in operation, plate tension is subjected to additional stresses which result especially due to the thermal extension of the fire-proof plates. There are also stresses due to the likewise fire-proof upper inner shell in the vessel due to its thermal extension or reduction. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object of the invention is to produce a slide closure of the type named at the outset which absorbs, in optimal manner, the operational stresses of the plate tensioning due to the thermal extension of the closure plates and/or the extension or reduction of the upper inner shell. 
     This object is achieved according to the invention by providing a slide closure for a metallurgical vessel having a sleeve, with a housing fastenable to a bottom of the vessel and having a cover and an insertion frame, an upper closure plate in the cover of the housing, a lower closure plate in the insertion frame of the housing, and a central, displaceable closure plate longitudinally displaceable between the upper closure plate and the lower closure plate. The slide closure also includes a first compensation unit for tensioning the upper, lower and displaceable closure plates against one another and which includes a first set of spring arrangements that act on a tensile load between the cover and the housing, and a second compensation unit for pressing the upper, lower and displaceable closure plates against the sleeve and which includes a second set of spring arrangements that press the insertion frame in a direction toward the lower closure plate. 
     An optimal absorption of the fire-proof extensions can be achieved with this first compensation unit with spring arrangements for tightening the closure plates against one another, as well as this second compensation unit with spring arrangements for tightening the closure plates against the upper inner shell with an additional insertion frame, adjustable in the housing, which frame can be pressed against the lower closure plate. 
     By making the two compensation units interact with one another, both overloads due to the thermal extension of the fire-proof plates and also due to the extension or reduction of the fire-proof inner sleeve are minimized. Unlike the slide closure according to EP 0 891 829, such overloads are thus not limited initially by the rigidity of the fire-proof parts and the metallic slide housing. This is advantageous for the operability or the lifespan of the fire-proof parts of the slide closure. 
     The invention provides that the spring arrangement of the first compensation unit is composed of plate springs, the pretension of which can be set preferably using a stroke limiting stop of the fastening screws. The plate tensioning can thus be adapted to a broad range of extension of the fire-proof parts which results for thermal reasons or spreading of the fire-proof closure plate thicknesses conditional on manufacturing. The starting pretension of the springs can also be set, in precise and repeatable manner, with the stroke limiting stop. 
     In so doing, it is expedient if the plate springs transmit the spring stroke via swivel pins, the guides of which are provided with inserts. Wear of these parts is minimized as a result. 
     The invention also provides that the insertion frame of the second compensation unit is fixed on the bottom of the housing by means of fastening screws arranged in pairs on both sides of the outlet, with plate springs inserted between the screw head thereof and the insertion frame, which springs form the spring arrangement of the second compensation unit. In this way, a uniform load of the insertion frame and thus the lower closure plate can be achieved using means which are simple in design. 
     In order to ensure that the lower closure plate abuts tightly against the insertion frame satisfactorily, it is expedient to provide a sealing element comprising the outlet between the insertion frame and the housing, which element is inserted preferably in a groove in the housing and/or in the insertion frame. 
     The slide closure is advantageously provided with a replaceable casting tube which is pressed against the lower closure plate with spring-loaded pressing elements. The pressing elements are expediently arranged such that they are effective independently of the two compensation units of the slide closure. They thus remain operational in all operational phases, both with and without the casting tube. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below using an embodiment example, with reference to the drawings. There are shown in: 
         FIG.  1    is a partial longitudinal section of a slide closure according to the invention, 
         FIG.  2    is a perspective top view of the slide closure according to  FIG.  1    on the top thereof which can be fastened to the vessel, 
         FIG.  3    is a section of a spring arrangement with a tensioning screw, which can be moved away, of the slide closure, 
         FIG.  4    is a partial view of the slide closure with an insertion frame, 
         FIG.  5    is a spring member of the slide closure, represented in section, 
         FIG.  6    is a pictorial schematic of the compensation units in the slide closure according to  FIG.  1    with a section of the closure plates and partially of the inner sleeve or of the casting tube, and 
         FIG.  7    is a perspective top view on a clamping device for clamping a closure plate in a metal frame of the slide closure according to  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The slide closure according to  FIG.  1    can be mounted on the outlet of a metallurgical vessel. The vessel is designed preferably as a tundish of a strand casting system, wherein the slide closure serves to regulate the quantity of molten material supplied to the strand casting ingot mould during the casting process. A casting tube  3  arranged on the bottom of the slide closure makes possible a covered casting of the molten metal into the ingot. However, this slide closure could also be used on a socket, a tap of a converter or the like. 
     The slide closure according to  FIG.  1    and  FIG.  2    comprises a housing  4  with a seal  4 ′ arranged all around its upper end surface, in order that it is sealed in encircling manner on its top, at the vessel. Fixed, fire-proof closure plates  5 ,  6  and a slider plate  8  (also referred to as a movable or displaceable closure plate), which can be moved back and forth therebetween by a drive mechanism  7 , can be inserted in the housing  4 , with the longitudinal movement of which an opening, restricting or closing of the outlet  9  (which is inside of an upper inner sleeve or sleeve  1 ) is brought about. The upper closure plate  5  is arranged in a cover  11  of the housing  4 , rotatably housed about an axis  10 , whereas the lower closure plate  6  is fixed in an insertion frame  25  of the housing  4  and the movable closure plate  8  is fixed in a metal frame  12  coupled to the drive mechanism  7 . The casting tube  3  is pressed against the lower closure plate  6  with spring-loaded rockers  33  (also referred to as pressing elements herein). The housing  4  has supports  13  projecting on the top which abut against the outer steel casing of the tundish  2  when in operation. 
     As illustrated in  FIG.  3   , a spring arrangement  23  has a base  16  guided in the housing  4  with a screw thread  17  and a crossways bolt  18 , about which a swivel pin  20  provided with a screw  19  can be swivelled, wherein the swivel pin  20  is guided into a recess  21  of the cover  11  and is screwed into a nut  22  above the cover  11 . In order to make possible access to the closure plates  5 ,  6  and  8 , the nuts  22  can be loosened and the swivel pins  20  swivelled out of the recesses  21  of the cover  11 . The swivel pins  20  are provided with a stroke limiting stop  20   a  with which the initial pre-stressing of the plate springs  23 ′ acting on tensile load can be set in precise and repeatable manner Inserts  24  in the cover  11  are allocated to the nuts  22  of the fastening screws  15   a - 15   d , which inserts minimize wear as a consequence of the frequent assembly and disassembly of the screw connections during operation. 
     During operation, the nuts  22  are screwed so far onto the swivel pins  20  that the closure plates of the slide closure lying between the insertion frame  25  and the cover  11  are tensioned against one another with the respectively provided contact pressure. This contact pressure is such that, during operation, it ensures the uninterrupted movability of the slider plate  8  when the slide closure is fully impermeable to metal or gas from the outside. 
     During operation, the fire-proof closure plates  5 ,  6 ,  8  experience a dispersive mechanical extension of up to 3 millimetres due to heating or manufacturing tolerances, whereby plate tensioning is subjected to an additional stress. According to the invention, this is compensated by a first compensation unit I, because the plate springs  23 ′ of the spring arrangement  23  more or less yield due to the additional stress. The stress compensation is very uniformly distributed over the closure plates in effective manner due to the paired arrangement of the fastening screws  15   a  to  15   d  on both sides of the outlet  1 . 
     According to  FIG.  4    and  FIG.  5   , an insertion frame  25  with a spring arrangement  30  is arranged on the bottom of the housing  4  for tensioning the closure plates  5 ,  6 ,  8  against the upper inner shell  1  of the outlet. This additional insertion frame  25  is fixed to the housing  4  with fastening screws  26  arranged in pairs on both sides of the outlet. 
     For its part, the spring arrangement  30  consists of plate springs  30 ′ which are inserted between the screw head  28  of the fastening screws  26  and the insertion frame  25  and have the function of pressing the insertion frame  25  against the lower closure plate  6  abutting against same, and thus tensioning the three closure plates  5 ,  6 ,  8  together against the upper inner shell  1  of the outlet. 
     The additional stress caused by an extension or reduction of the inner shell  1  is compensated with this second compensation unit II formed according to the invention, by the plate springs  30 ′ more or less yielding due to this stress. It is advantageous if these plate springs  30 ′ are produced such that they are provided with a steep characteristic curve in respect of its stroke in relation to the spring force, in order to bring about a relatively high change in force with little lift. This is matched to the corresponding characteristic curves of the plate springs  23 ′ of the compensation unit I, in order that an optimal tensioning is always achieved. In so doing it is intended to be avoided that, depending on the position of the movable closure plate  8 , a tipping of the closure plates could take place, wherein this could occur due to an external application of force primarily through the casting tube  3 . 
     Furthermore, to improve the support between the housing  4  and the insertion frame  25 , a last, comprehensive sealing element  31  in a groove  32  is approximately half in the housing  4  and approximately half in the insertion frame  25 . A labyrinth effect is thus achieved which additionally improves the tightness. The groove could also be designed only in the housing or in the insertion frame. 
       FIG.  6    shows, schematically, the arrangement of the two compensation units I and II in the slide closure. The first compensation unit I is formed by spring arrangements  23  between the cover  11  and the housing  4  acting on tensile load for flexibly tensioning the closure plates  5 ,  6 ,  8 , because the second compensation unit II is effective due to the spring arrangements  30  between the insertion frame  25  and the housing  4  acting on pressure for tensioning the closure plates  5 ,  6 ,  8  against the inner shell  1 . 
     These compensation units can be set independently of one another and are also effective independently of one another, with the result that they can carry out their function both individually and also in combination with one another. As a result, they protect the fire-proof parts of the slide closure against overloads which can result from thermal extension and spreading of the fire-proof closure plate thicknesses conditional on manufacturing and/or of the upper inner shell, wherein the inner shell can also be reduced in operation. 
     Also, a choice is made to fix the central slider plate  8  in its metal frame  12  with a clamping device  34  such that the function of the compensation units I and II is not impaired by the arrangement thereof in the housing  4 . 
     The clamping device  34  according to  FIG.  7    is composed of a clamping jaw  38  which can be adjusted against the closure plate  8  in the metal frame  12 , two adjusting elements  35 ,  36  arranged on both sides of the central axis M of the slider plate  8 , as well as a threaded spindle  37  abutting against the adjusting elements. The threaded spindle  37  is rotatably housed transverse to the central axis M in the metal frame  12  and provided with thread sections going in opposite directions. By manually rotating this threaded spindle  37 , the adjusting elements  35 ,  36  are adjusted outwards or inwards, symmetrically to one another, and by corresponding wedge surfaces  35 ′,  36 ′ in the adjusting elements  35 ,  36  or the clamping jaw  38 , the latter is pressed against the closure plate  8 , with the result that a self-locking wedging is created in order that these do not become loose during operation. 
     The invention is displayed sufficiently using the above explained embodiment example. Self-evidently, other variants can also be provided. Other springs, such as helical springs or the like, could thus also be used instead of these plate springs  23 ′,  30 ′.