WO2025237713A1

WO2025237713A1 - Gaskets dispenser for nozzle to shroud seal in a metal casting installation

Info

Publication number: WO2025237713A1
Application number: PCT/EP2025/062199
Authority: WO
Inventors: Jean-Luc Renard; Hervé Hubert; Szymon RYNCARZ
Original assignee: Vesuvius Group SA
Current assignee: Vesuvius Group SA
Priority date: 2024-05-15
Filing date: 2025-05-05
Publication date: 2025-11-20
Anticipated expiration: 2026-11-15
Also published as: CN120961903A

Abstract

The invention concerns a gasket dispensing device (10) configured to dispense one gasket unit (1) at a time out of a stack of nested gasket units (1), into an inlet of a shroud (22, 32). The gasket dispensing unit comprises first and second retention systems (11r, 12r) configured to retain the gasket unit (1) at a first position (1.1) and at a second position in the stack, respectively. The retention systems can be moved between a configuration wherein the gasket unit (1) is retained at the first or second position (1.1, 1.2) and a configuration wherein the gasket unit (1) at the first position (1.1) falls into the shroud, and wherein the gasket at the second position (1.2) can fall into the first position (1.1) when vacant. The invention also concerns a metal casting installation comprising the gasket dispensing device (10), and processes using the gasket dispensing device (10).

Description

GASKETS DISPENSER FOR NOZZLE TO SHROUD SEAL IN A METAL CASTING INSTALLATION

TECHNICAL FIELD

[0001] The present invention concerns a gasket unit for sealing a contact between a nozzle and a shroud in a metal casting installation. The present invention also concerns a gasket dispensing device configured to dispense a new gasket unit of the present invention into an inlet of a shroud. The gasket dispensing device of the present invention allows gasket units to be rapidly and reproducibly coupled to the shrouds at an accurate position while protecting operators from close contact with potentially hot shrouds. The dispensing of gasket units can be partially or fully automated.

BACKGROUND OF THE INVENTION

[0002] In metal forming processes, molten metal is transferred from one metallurgic vessel to another, to a mould or to a tool for ingots. For example, as shown in Figure 1 a ladle (20) is filled with molten metal (3) out of a furnace (not shown) and transferred through a nozzle assembly comprising a collector nozzle (21 ) and a ladle shroud (22) into a tundish (30) for casting. The molten metal (3) can then be cast through another nozzle assembly comprising a pouring nozzle (31 ) and a subentry shroud (SES) (32) from the tundish (30) to a mould (not shown) for forming slabs, billets, beams or ingots or directly from a ladle to a tool for ingots. Flow of molten metal out of a metallurgic vessel is driven by gravity through the nozzle systems (21/22, 31/32) located at the bottom of the corresponding vessels. The flow rate can be controlled by a sliding gate (25) generally to control the flow out of a ladle (20) and/or a stopper (7) to control the flow out of a tundish (30).

[0003] The nozzle systems are generally formed by a nozzle (21 , 31 ) allowing molten metal to flow out of the vessel and a shroud (22, 32) in the form of an elongated tube, to protect from contact with air the molten metal flowing out of the vessel (20, 30) into a second vessel (30) or into a mould. To ensure liquid and air tightness of the nozzle system, a gasket (1 g) is generally positioned between the spout of the nozzle (21 , 31 ) and the inlet of the shroud (22, 32). For example, a metal casting installation as illustrated in Figure 1 , comprises a nozzle system (21/22) at the bottom of the ladle (20) formed by a collector nozzle (21 ) and a ladle shroud (22) and two nozzle systems (31/32) at the bottom of the tundish (30) formed by a pouring nozzle (31 ) and a sub-entry shroud (SES) (32). Unless otherwise specified, the term “nozzle” herein refers collectively to collector nozzles (21) positioned at the bottom of a ladle (20) and to pouring nozzles (31 ) positioned at the bottom of a tundish (30). Similarly, unless otherwise specified, the term “shroud” herein refers collectively to ladle shrouds (22) positioned at the bottom of a ladle (20) and to an SES (32) positioned at the bottom of a tundish. [0004] Casting of molten metal (3) out of a ladle (20) into a tundish (30) can last about 30 to 90 min. The empty ladle (20) is then removed and a new ladle (20) filled with molten metal (3) is brought in to replace the empty ladle. The ladle shroud (22) can be re-used with about 6 to 12 new ladles. The ladle shroud (22) must be cleaned before being used with a new ladle. This takes place in a workshop (50) on the same casting floor where the casting installation is located. Cleaning a used shroud comprises showering it with an oxygen lance (51 o) and inspecting the ladle shroud. A new gasket (1 g) is then positioned into the inlet (22I) of the thus cleaned and inspected ladle shroud.

[0005] As the empty ladle is replaced by a new ladle, no more molten metal is poured into the tundish (30), whilst molten metal continues to flow out of the tundish through the corresponding nozzle assemblies (31/32). To prevent the level of molten metal in the tundish to drop below a predefined value, the swap of ladles must be completed as quickly as possible. In general, changing ladles can take about 2 min. By comparison, the showering and inspection of a ladle shroud (22) can take about 40 s. Bringing the shroud to the workshop and back into casting position can take about 20 to 30 s. If the same ladle shroud is to be used again with the new ladle, positioning the new gasket unit (1 ) must be completed in less than 1 min. This operation is often carried out manually by an operator. For safety reasons, steel plants look for systems using robots to complete more and more activities of the workshop including handling of the ladle shroud, showering, inspection and also installation of a new gasket.

[0006] In a tundish, an SES can operate uninterrupted during 6 to 12 h. If the casting operation is not completed in that time, a new SES must replace the used one. As casting into a mould must proceed continuously, the change of shroud must be very quick, and a new SES equipped with a new gasket replaces the used one.

[0007] In the fields of mechanics not concerned with metal casting, dispensing devices for dispensing sealing elements are available. For example, US20230066758 proposes a seals dispensing unit holding a stack of seals, such as cylindrical seals, positioned above a receiving surface of a mechanical element. A seal gripper applicator comprising a pair of gripper elements that move inwardly and outwardly in a coordinated manner is provided. The gripper elements comprise seal contact surfaces engaging above the seal and move the seal downwardly over the mechanical part, e.g., placing the seal into a groove. This dispensing device is not suitable for applying gaskets onto hot shrouds.

[0008] CN1 10253009 describes a gasket dispensing device for automatically positioning a new gasket nested in the inlet of a shroud. A stack of trunco-conical gaskets nested one in the other is positioned above a shroud ready to receive one gasket. Because of their composition, the surfaces of the gaskets are tacky and when nested in one another, they tend to stick to one another. To dispense gaskets one at the time in such conditions, the gasket dispensing device is equipped with a pusher that pushes down the gasket in the first position closest to the shroud. The pusher has a rather complex construction . Furthermore, since tackiness strongly depends on temperature, which can vary from one season to another, from one plant to another, and from the temperature of the shroud positioned below, the force required by the pusher to separate the gasket to be placed into the shroud varies accordingly, which is detrimental to the reproducibility and reliability of the process.

[0009] CN205519629U describes a double-layer sealing gasket for a shroud. The gasket has a trapezoidal cross section, and is a double-layer structure, including a sealing inner side and an antiadhesion outer layer.

[0010] To promote adhesion of the gasket to the collector nozzle when removing a ladle shroud from an empty ladle, RU2296033 describes a gasket comprising an adhesive layer in an inner surface thereof, configured for contacting and adhering to the collector nozzle when in casting position. To allow stacking these gaskets nested in one another for storage and transportation and, at the same time, avoiding them to stick to one another, an inner anti-sticking film is applied to the adhesive layer. Prior to use, the inner anti-sticking film must be removed manually to expose the adhesive layer. Because of the required removal of the inner anti-sticking film prior to use, this gasket cannot be used with a gasket dispensing device.

[0011] In order to simplify maintenance in a continuous flow casting, there is a need for a gasket dispensing device which is simple to use, reproducible in all operating conditions, and quick, allowing placing a new sealing gasket into a shroud in less than 1 min, preferably less than 30 s, regardless of the temperature of the should. The present invention proposes, in order to simplify maintenance in a continuous flow casting, a new gasket that is also particularly suitable for use in a new gasket dispensing device. These and more advantages are described in more details in the following sections.

SUMMARY OF THE INVENTION

[0012] The present invention is defined in the appended independent claims. Preferred embodiments are defined in the dependent claims. In particular, the present invention concerns a gasket unit for sealing a contact between a nozzle and a shroud in a metal casting installation. The gasket unit comprises a gasket, an inner anti-sticking layer, and an outer anti-sticking layer. The gasket, the inner anti-sticking layer, and the outer anti-sticking layer are made of different materials. They are produced separately and then assembled. They can be physically distinguished.

[0013] The gasket is made of a ceramic or polymeric material configured for forming a sealing contact between an outer surface of the nozzle and an inner surface of the shroud. The gasket has a geometry of revolution about a Z-axis, with a central passage defined by an inner surface, extending along the Z- axis and tapering from a large inner diameter (Di) to a small inner diameter (di). The gasket unit is so configured that several of the gasket units can be nested into one another to form a stack of several gasket units nested in one another without sticking to one another at corresponding positions, wherein the stack extends along the Z-axis.

[0014] The inner anti-sticking layer covers an inner surface of the gasket defining the central passage. The inner anti sticking layer degrades, preferably irreversibly, upon exposure to a threshold temperature lower than 500°C, preferably lower than 300°C, more preferably lower than 150°C or more preferably lower than 100°C, thus exposing, at least partially, the inner surface of the gasket. The degradation of the inner anti sticking layer preferably involves a chemical reaction. It may also involve a physical reaction. The degradation of the inner anti sticking layer involves a loss of its adhesive properties.

[0015] The outer anti-sticking layer covers an outer surface of the gasket. The outer anti-sticking layer is different from the inner anti-sticking layer. By contrast with the inner anti-sticking layer, the outer antisticking layer is more resistant to high temperatures and does not degrade upon exposure to a temperature below 700°C, preferably below 750°C, more preferably below 800°C, thus covering the outer surface of the gasket as long as the temperature remains below the foregoing values. In other words, it maintains anti adhesion properties below said temperature. The absence of degradation means that the outer anti-sticking layer keeps some anti adhesion properties in such a way that no adhesion occurs between the gasket and the shroud. In other words, below 700°C, preferably below 750°C, more preferably below 800°C, the gasket does not attach to the shroud because the outer antisticking layer prevents sticking. When the outer anti-sticking layer degrades, its degradation is preferably irreversible.

[0016] In other words, the invention provides gaskets that sticks to the nozzle and not to the shroud when the shroud is removed from the nozzle. In is interesting because it is easier to remove the gasket from the nozzle (for example when the ladle is prepared for another cycle) than from the shroud during showering. In the invention, there is a range of temperature, at least between 500°C and 700°C where: the inner anti sticking layer degrades, so that it exposes the surface it is applied upon, which makes the gasket sticks to the nozzle, the outer anti sticking layer does not degrade, so that it maintains anti adhesion properties, which prevents the gasket from sticking to the shroud.

After exposure to this temperature range, the gasket sticks more to the nozzle than to the shroud.

[0017] In a preferred embodiment, the gasket comprises an adhesive layer between the gasket and the inner anti sticking layer, to promote adhesion of the gasket to the nozzle.

[0018] The present invention also concerns a stack of gasket units comprising several of the gasket units defined supra nested into one another to form a stack of several gasket units without sticking to one another at corresponding positions, wherein the stack extends along a Z-axis. The stack can comprise a dummy gasket unit on a top of the stack, wherein the gasket unit positioned at a top of the stack does not comprise a gasket unit nested therein. [0019] The present invention also concerns a gasket dispensing device for dispensing one by one gasket units as defined supra. The gasket dispensing device comprises,

• a base plate,

• a stacking column, and

• first and second retention systems.

[0020] The gasket dispensing device is suitable for loading a stack of several gasket units nested in one another as defined supra, loaded over the stacking column which extends through the central passages of the nested gasket units forming the stack.

[0021] The base plate is substantially normal to the Z-axis and is provided with a dispensing opening of smallest dimension (d1 1 ) larger than the large inner diameter (Di) (i.e. , d1 1 > D), allowing the free passage of a gasket unit through the dispensing opening along the Z-axis,

[0022] The stacking column extends along the Z-axis and is concentric with the dispensing opening. The stacking column has an outer diameter smaller than the small inner diameter (di) of the gasket.

[0023] The several gasket units forming the stack are nested in one another at corresponding positions (1 .1 -1 .N) wherein

• a first position (1 .1 ) is at a bottom of the stack, directly above the dispensing opening,

• a second position (1 .2) is directly above the first position (1 .1 ) and corresponds to the position of the gasket unit nested in the gasket unit at the first position (1 .1 ) and so on until

• an N^,h position (1 .N) is at a top of the stack, corresponding to the position of the gasket unit nested in the gasket unit at a (N-1 )^,h position (1 .(N-1 )).

[0024] The first retention system is configured for moving between,

• a retention configuration preventing the whole stack from moving along the Z-axis by retaining and preventing the gasket unit located at the first position (1 .1 ) from falling through the dispensing opening and

• a dispensing configuration allowing the same gasket unit located at the first position (1 .1 ) to leave the first position by falling through the dispensing opening and therefore, if not otherwise retained, allowing the whole stack to fall along the Z-axis,

[0025] The second retention system is configured for moving between,

• a holding configuration preventing the whole stack but the gasket unit at the first position (1 .1 ) from moving along the Z-axis by preventing the gasket unit at the second position (1 .2) from moving to the first position (1 .1 ) when the first position is vacant, and • a release configuration allowing the whole stack to fall along the Z-axis when the first position (1 .1 ) is vacant and the first retention system is in the retention configuration, allowing all the gasket units which were at an i^,h position to move down to an (i-1 )^,h position, with i = 2 to N; such that the first position (1 .1 ) is occupied again by the gasket unit which was at the second position (1 .2).

[0026] The gasket dispensing device according to the invention requires a stack of gasket units such that the gasket units do not stick to each other. Otherwise, no gasket unit would fall in the dispensing configuration. The gasket unit according to the invention is thus especially suitable to be used in this gasket dispensing device.

[0027] The present invention also concerns a gasket dispensing device as discussed supra, and comprising a gasket unit loaded over the stacking column at any one of the first to N^,h positions (1 .1 -1 .N).

[0028] The present invention also concerns a metal casting installation, comprising a ladle, a tundish, and a workshop for cleaning a previously used shroud to yield a cleaned shroud ready for further use, and a robot configured to bring the used shroud from a casting position to the workshop and to bring a clean shroud which is the cleaned shroud or is a new clean shroud, from the workshop to the casting position.

[0029] The present invention also concerns a process for automatically positioning a gasket unit at a tube inlet of a shroud comprising the following steps,

(a) providing a shroud configured to be used in a metal casting operation and comprising an elongated tube with a channel extending along the tube from a tube inlet to a tube outlet,

(b) providing a gasket dispensing device as discussed supra,

(c) setting the first retention system in the retention configuration and loading a stack of gasket units over the stacking column such that the gasket unit positioned at the first position (1 .1 ) cannot fall through the dispensing opening,

(d) setting the second retention system in the holding configuration, such that the gasket unit positioned at the second position (1 .2) cannot move into the first position (1 .1 ) even if the first position (1 .1 ) is vacant,

(e) positioning the shroud below the gasket dispensing device with the tube inlet coaxially aligned with the dispensing opening along the Z-axis, and holding the shroud in place,

(f) setting the first retention system into the dispensing configuration, to let the gasket unit positioned at the first position (1 .1 ) to fall through the dispensing opening into position, nested in the tube inlet, whilst the gasket unit positioned at the second position (1.2) is retained by the second retention system which is in the holding configuration,

(g) remove the shroud with the gasket unit nested in the tube inlet,

(h) setting the first retention system back into the retention configuration, with the first position (1.1 ) being vacant,

(i) setting the second retention system into the release configuration to allow the gasket unit positioned at the second position (1 .2) to fall down into the first position (1 .1 ), and concomitantly to allow all the remaining gasket units of the stack to fall down from an i^,h position to an (i-1 )^,h position, with i = 2 to N.

BRIEF DESCRIPTION OF THE FIGURES

[0030] For a fuller understanding of the nature of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings in which:

Figure 1 : shows a typical continuous casting installation showing nozzle assemblies requiring a sealing gasket according to the present invention.

Figures 2a to 2e: show (a) a perspective view and (b) to (e) cross-sections of two embodiments of trunco-conical gasket units according to the present invention, suitable for use to seal the nozzle assembly of a ladle.

Figures 2f to 2h: show (f) a perspective view and (g) and (h) cross-sections of an embodiment of gasket unit according to the present invention having an elliptical (spherical) segment geometry, suitable for use to seal the nozzle assembly of a tundish.

Figures 3a to 3d: show (a) a cross-section and (b) to (d) perspective views of a nozzle assembly for a ladle.

Figures 4a to 4d: show different stages for placing a sealing gasket into a nozzle inlet using a gasket dispensing device according to the present invention.

Figures 5a to 5e: show various views of a first embodiment of the first retention system in both retention and dispensing configurations.

Figures 6a to 6g: show various views of a second embodiment of the first retention system in both retention and dispensing configurations.

Figures 7a to 7e: show various views of a third embodiment of the first retention system in both retention and dispensing configurations.

Figures 7f and 7g: show an example of motorisation of the first retention system illustrated in Figures 7a to 7e.

Figures 8a to 8c: show various steps for dispensing and positioning a new gasket unit into a shroud.

Figures 9a and 9b: show a first embodiment of the second retention system in both holding and release configurations.

Figures 10a and 10b: show a second embodiment of the second retention system in both holding and release configurations.

Figures 11a and 11b: show a third embodiment of the second retention system in both holding and release configurations.

Figures 12a and 12b: show a fourth embodiment of the second retention system in both holding and release configurations.

Figure 13: shows a stack of gasket units, with a dummy gasket equipped with a distance measuring device, and with a weighing scale, both embodiments being suitable for determining the number of gasket units remaining in the stack.

Figure 14: shows an embodiment of automated gasket dispensing device without any gasket unit loaded therein.

Figures 15a to 15d: show various steps of a change of ladles and, at the same time, treatment of the used ladle shroud before using it again with the new ladle, holding a new gasket unit.

DETAILED DESCRIPTION OF THE INVENTION

GASKET UNIT (1)

[0031] As shown in Figures 2b and 2f, the present invention concerns a gasket unit (1 ) for sealing a contact between a nozzle (21 , 31 ) and a shroud (22, 32) in a metal casting installation of the type illustrated in Figures 1 and 15a to 15d. The gasket unit (1 ) comprises a gasket (1 g), an outer anti-sticking layer (1 me), and an inner anti-sticking layer (1 mi). The gasket unit (1 ) is so configured that several of the gasket units (1 ) can be nested into one another to form a stack of several gasket units (1 ) nested in one another without sticking to one another at corresponding positions (1 .1 to 1 .N), wherein the stack extends along a Z-axis.

[0032] The gasket (unit) can have a trunco-conical geometry as shown in Figures 2a to 2e, configured for typically sealing a contact between a collector nozzle (21 ) and a ladle shroud (22) as illustrated in Figures 3a to 3d. Alternatively, the gasket (unit) can have an elliptical (or spherical) segment geometry as illustrated in Figures 2f to 2h, configured for typically sealing a contact between a pouring nozzle (31 ) and a sub-entry shroud (SES) (32). [0033] The gasket (1 g) is made of a ceramic or polymeric material configured to form a sealing contact between an outer surface of the nozzle (21 , 31 ) and an inner surface of the shroud (22, 32). The gasket (1 g) is adapted to withstand a temperature of at least 800°C. As shown in Figures 2a and 2h the gasket (1 g) has a tapered geometry of revolution about the Z-axis, with a central passage. The gasket unit (1 ) formed by the gasket (1 g), the inner and outer anti-sticking layers (1 mi, 1 me) and, optionally, the adhesive layer (1 a), is defined, on the one hand, by the central passage having an inner surface tapering along the Z-axis from a large inner diameter (Di) to a small inner diameter (di) an, on the other hand, by an external surface tapering along the Z-axis from a large outer diameter (De) to a small outer diameter (de). The large outer diameters (De) is simply equal to the sum of the large inner diameter (Di) and a thickness (t1 ) of the gasket unit (1 ) (i.e. , De = Di + t1 ) and, similarly, the small outer diameters (do) is simply equal to the sum of the small inner diameter (di) and the thickness (t1 ) of the gasket unit (1 ) (i.e., de = di + t1 ).

[0034] The large outer diameter (De) can range from 45.0 to 240.0 mm, preferably between 100.0 and 200.0 mm. The small outer diameter (de) can range from 35.0 to 190.0 mm, preferably between 80.0 and 150.0 mm. The thickness (t1 ) can, albeit not necessarily, be uniform over a height of the gasket unit (1 ). The thickness (t1 ) of the gasket unit (1 ) can range from 1 to 10 mm, preferably from 2 to 7 mm. The gasket unit (1 ) can have a height of from 20.0 to 120.0 mm, preferably of 40.0 to 100.0 mm. The gasket (1 g) can be made of a material comprising one or more of an alumina (for example corundum), silica and carbon. Alternatively, the gasket (1 g) can be made of a mix of 3-Pentabecyl Phenol and 5 Pentabecyl Phenol.

[0035] The outer anti-sticking layer (1 me) covers an outer surface of the gasket (1 g). It can have a thickness of 0.2 to 4.0 mm, preferably between 0.5 and 2.0 mm. The outer anti-sticking layer (1 me) can be made of a material comprising at least 90 wt.% carbon, preferably at least 95 wt.% carbon, more preferably the carbon is in the form of graphite. It can be in the form of a film applied to the outer surface of the gasket (1 g) or it can be applied with a brush or other coating techniques. The outer anti sticking layer (1 me) does not degrade upon exposure to a temperature below 700°C, preferably below 750°C, more preferably below 800°C, thus covering the outer surface of the gasket (1 g) as long as the temperature remains below the foregoing values. The outer anti-sticking layer (1 me) is considered to not degrade as long as it maintains its integrity or at least maintains anti-adhesion properties. The outer anti-sticking layer is preferably configured to maintain at least partially its anti-sticking properties during the whole casting operation of the shroud (22, 32).

[0036] The inner anti-sticking layer (1 mi) is different from the outer anti sticking layer (1 me) and covers directly or indirectly (depending on the presence or not of an adhesive layer (1 a)) an inner surface of the gasket (1 g) defining the central passage. The gist of the present invention is that the inner antisticking layer (1 mi) degrades upon exposure to a threshold temperature lower than 500°C, preferably lower than 300°C, more preferably lower than 150°C or more preferably lower than 100°C, thus exposing the surface it is applied upon. After degradation of the inner anti-sticking layer (1 mi), only the sealing gasket (1 s) remains sandwiched between the nozzle and the shroud, thus ensuring a sealing contact between the two. The inner anti-sticking layer (1 mi) is burnt, melted, or pyrolyzed at or above the threshold temperature. The inner anti-sticking layer (1 mi) can be made from an organic, polymeric, or metallic material. For example, the inner anti-sticking layer (1 mi) can be a silicone paper of e.g., 30 to 50 g / m², similar to baking paper. Such silicone paper can have a thickness of 400 to 500 pm. Alternatively, the inner anti-sticking layer (1 mi) can comprise a low surface energy polymer, such as a fluorinated polymer, applied either as a coating onto a paper (like the silicone paper) or applied onto the inner surface of the gasket (1 g) in the form of a solution by brush, sputtering, or the like. The thickness of a thus applied inner anti-sticking layer (1 mi) can be from 10 to 100 pm, preferably of 20 to 70 pm. A metallic inner anti-sticking layer (1 mi) is especially interesting because it can protect the gasket (1 g) from ambient oxygen and thus prevent its auto-ignition when the temperature of the gasket (1 g) suddenly increases when contacting the hot shroud (22, 32). As illustrated in Figures 2c, 2e, and 2h, the sealing gasket (1 s) (i.e., defined as the gasket unit (1 ) without the inner anti-sticking layer (1 mi)) has a thickness (ts) smaller than the thickness of the gasket unit (1 ) (i.e., ts < t1 ).

[0037] The function of the inner anti-sticking layer (1 mi) is to prevent sticking of the inner surface of a first gasket unit (1 ) with the outer anti-sticking layer (1 me) of a second gasket unit (1 ) nested in the first one. This permits an easier dispensing of a gasket unit (1 ) out of a stack than with the gasket dispensing device of CN1 10253009 discussed supra. In particular, with the inner anti-sticking layer (1 mi), no adhesion occurs between two gaskets nested in one another independently of the ambient temperature. As the inner anti-sticking layer (1 mi) degrades, for example pyrolyzes, at a temperature at or above the threshold temperature below 500°C, (preferably below 300°C or below 150°C, and more preferably below 100°C), there is no need to remove the inner anti-sticking layer (1 mi) prior to positioning the gasket unit into the shroud inlet (22i). Indeed, as soon as the gasket unit (1 ) is coupled to the shroud (22, 32) and/or to the nozzle (21 , 31 ), the temperature of the inner anti-sticking layer (1 mi) rapidly rises above the threshold temperature and the inner anti-sticking layer (1 mi) is destroyed, exposing the surface of the gasket (1 g) or of an adhesive layer (1 a) if present, as described below.

[0038] In a preferred embodiment, the gasket (1 g) comprises an adhesive layer (1 a) between the gasket (1 g) and the inner anti sticking layer (1 mi), as shown in Figures 2d, 2e, 2g, and 2h. The adhesive layer (1 g) may be used to ensure that the gasket unit (1 ) sticks to the nozzle (21 , 31 ), at least just after the coupling between the shroud and the nozzle. It is preferably used when the gasket (1 g) is not tacky enough to ensure a good adhesion to the nozzle (21 , 31 ).

[0039] The adhesive layer can be an organic material, such as for example a vinyl acrylic adhesive, or an inorganic mortar, depending on the desired temperature resistance of the adhesive layer (1 a) . The adhesive layer (1 a) can have a thickness of 10 to 100 pm, preferably of 20 to 70 pm.

[0040] The gasket unit (1 ) of the present invention can optimally be dispensed automatically using the gasket dispensing device (10) of the present invention. [0041] Several gasket units (1 ) can be nested into one another to form a stack of several gaskets extending along the Z-axis. The gaskets in the stack are at corresponding positions (1 .1 to 1 .N) along the Z-axis. Thanks to the inner and outer anti-sticking layers (1 mi, 1 me), the gaskets units (1 ) do not stick to one another and a gasket unit at an i^,h position (1 .i) can easily be separated from the gasket units (1 ) at the (i-1 )^,h and (i+1 )^,h positions (1 .(i-1 ), 1 .(i+1 )) directly below and above the i^,h position (1 .i) without adhesion. The terms “below” and “above” are defined along the Z-axis in the direction of gravity.

[0042] In a preferred embodiment, the stack can comprise a dummy gasket unit (1 d) on a top of the stack (initially at the N^,h position (1 .N)). The “top” of the stack is the position in the stack wherein the gasket unit (1 , 1 d) positioned at the top of the stack does not comprise a gasket unit nested therein. The dummy gasket (1 .d) can be heavier than the gasket units (1 ) to apply a force on the stack. It is useful when all but one gasket units (1 ) have been dispensed, to guide and apply a downwards force on the last gasket unit (1 ) in the first position (1 .1 ). As shown in Figure 13, the dummy gasket (1 d) can be equipped with a distance measuring device (1 L) configured to measure a distance to a reference point of the gasket dispensing device (10), to give a direct information on the number of gasket units (1 ) remaining in the stack.

GASKET DISPENSING DEVICE (10)

[0043] The present invention also concerns a gasket dispensing device (10) configured to dispense one by one gasket units (1 ) loaded as a stack on the device. Figure 13 shows a stack of gasket units (1 ) nested in one another. Figure 14 shows the gasket dispensing device (10) without gasket units (1 ), and Figures 4a to 4d, illustrate different configurations of the same gasket dispensing device (10) loaded with a stack of gasket units (1 ). The gasket dispensing device (10) of the present invention is preferably used with the gasket units (1 ) of the present invention as described supra, but it can be used with any gasket unit having a tapered geometry, as long as they do not stick excessively to one another when stacked, nested in one another. Two gasket units nested one above the other do not stick excessively to one another when they can be separated by gravity only (i.e., the gasket unit positioned below along the Z-axis falls by gravity when only the gasket unit positioned above is retained).

[0044] The gasket dispensing device (10) of the present invention comprises a base plate (1 1 ), a stacking column (17), and first and second retention systems (1 1 r, 12r)). In use, the gasket dispensing device (10) is loaded with several gasket units (1 ) forming a stack over the stacking column (17). The stacking column (17) acts as a guide, maintaining all gasket units (1 ) forming the stack in alignment with the Z-axis.

[0045] The base plate (1 1 ) is substantially normal to the Z-axis. It is provided with a dispensing opening (1 1 h) of smallest dimension (d1 1 ) larger than the large outer diameter (De) (i.e., d1 1 > De) of the gasket units (1 ), allowing the free passage of a gasket unit (1 ) through the dispensing opening (1 1 h) along the Z-axis. In continuation, the Z-axis is parallel to gravity, corresponding to a vertical direction. [0046] The stacking column (17) extends along the Z-axis and is concentric with the dispensing opening (1 1 h). The stacking column has an outer diameter (d17) smaller than the small inner diameter (di) of the gasket unit (1 ), preferably the outer diameter of the stacking column is comprised between 90 and 98% of the small inner diameter (di), (i.e., 0.90 di < d17 < 0.98 di) more preferably between 92 and 96% (i.e.0.94 di < d17 < 0.97 di), to guide the gasket units (1 ) along the Z-axis. Depending on the type of first retention system (1 1 r) discussed in continuation, the stacking column can or cannot extend through the dispensing opening (1 1 h). As shown in Figures 5a, 5b, 5e, 6g, 7a, 7b, and 7e, the embodiments where the stacking column (17) extends through the dispensing opening (1 1 h) have the advantage that the gasket unit (1 ) falling from the first position (1 .1 ) through the dispensing opening (1 1 h) is guided and centered by the stacking column (1 ) during part or all of its fall into the inlet (22i) of the shroud (22, 32) aligned with the Z-axis in the opposite side of the base plate (1 1 ). Embodiments wherein the stacking column (17) does not extend through the dispensing opening (1 1 h) can, if required, be equipped with guides (14) to guide the gasket units (1 ) during their falls through the dispensing opening (1 1 h) as shown in Figures 8a to 8c.

[0047] When loaded, the gasket units (1 ), are nested in one another over the stacking column (17), at corresponding positions (1 .1 -1 .N) to form the stack, wherein

• a first position (1 .1 ) is at a bottom of the stack, directly above the dispensing opening (1 1 h),

• a second position (1 .2) is directly above the first position (1 .1 ) along the Z-axis and corresponds to the position of the gasket unit (1 ) nested in the gasket unit (1 ) at the first position (1 .1 ) and so on until

• an N^,h position (1 .N) is at a top of the stack, corresponding to the position of the gasket unit (1 ) nested in the gasket unit (1 ) at a (N-1 )^,h position (1 .(N-1 )),

The terms “above” and “below” are used herein to define a position along the Z-axis relative to gravity.

[0048] The whole stack stands on top of the base plate (1 1 ) in alignment with the dispensing opening (11 h). The stack is prevented from falling or allowed to fall by gravity through the dispensing opening (1 1 h) by controlling the first retention system (1 1 r), which is configured to move between,

• a retention configuration (1 1 rR) preventing the whole stack from moving along the Z-axis by retaining and preventing the gasket unit (1 ) located at the first position (1 .1 ) from falling through the dispensing opening (1 1 h) (cf. Figures 5a, 5b, 6a to 6c, 7a, and 7b), and

• a dispensing configuration (1 1 rD) allowing the same gasket unit (1 ) located at the first position (1 .1 ) to leave the first position by falling through the dispensing opening (1 1 h) and therefore, if not otherwise retained, allowing the whole stack to fall along the Z-axis (cf. Figures 5c, 5d, 6d to 6f, 7c, and 7d), [0049] The second retention system (12r) is configured to only allow the gasket unit (1 ) located at the first position (1 .1 ) to fall through the dispensing opening (1 1 h) when the first retention system (1 1 r) is in the dispensing configuration (1 1 rD). This is achieved by configuring the second retention system (12r) to move between,

• a holding configuration (12rH) preventing the whole stack but the first gasket unit (1 .1 ) from moving along the Z-axis by preventing the gasket unit (1 ) at the second position (1 .2) from moving to the first position (1 .1 ) when the first position is vacant (cf. Figures 9a, 10a, 1 1 a, and 12a), and

• a release configuration (12rR) allowing the whole stack to fall along the Z-axis when the first position (1 .1 ) is vacant and the first retention system (11 r) is in the retention configuration, allowing all the gasket units (1 ) which were at an i^,h position to move down to an (i-1 )^,h position, with i = 2 to N; such that the first position (1 .1 ) is occupied again by the gasket unit (1 ) which was at the second position (1 .2) (cf. Figures 9b, 10b, 1 1 b, and 12b).

FIRST RETENTION SYSTEM (11 r)

[0050] The function of the first retention system (1 1 r) is to retain the gasket unit (1 ) located at the first position (1 .1 ) directly over the dispensing opening (11 h) from falling through the dispensing opening (11 h) of the base plate (1 1 ). There are several solutions to implement this function. A selection of preferred solutions of mechanisms for the first retention system (1 1 r) are presented in continuation.

First retention system (11 r) comprises a sliding plate (l ip)

[0051] In a first embodiment, illustrated in Figures 4a to 4e, 5a to 5e, and 14, the first retention system (11 r) comprises a sliding plate (11 p) configured to slide over a surface of the base plate (1 1 ), in a direction normal to the Z-axis, such that in the retention configuration (11 rR), the dispensing opening (1 1 h) is at least partially covered by the sliding plate (1 1 p), such that the dispensing opening (1 1 h) is either completely obstructed or the portion of the dispensing opening (1 1 h) left uncovered by the sliding plate (1 1 p) is smaller than required to allow a gasket unit (1 ) to fall through. The embodiment wherein the sliding plate (11 p) fully obstructs the dispensing opening (11 h) is illustrated in Figures 4a, 4c, and 4d. The embodiment of partial obstruction is illustrated in Figures 5a and 5b which allows the stacking column (17) to extend through the dispensing opening (11 h) to guide the gasket units (1 ) as they fall one by one through the dispensing opening. The sliding plate can comprise a notch-shaped opening configured to slide around the stacking column (17).

[0052] In the dispensing configuration (1 1 rD), the sliding plate (1 1 p) exposes the dispensing opening’s full span, allowing the gasket unit (1 ) at the first position (1 .1 ) to fall through the dispensing opening (1 1 h). This is illustrated in Figures 4b, 5c, and 5d.

[0053] Sliding the sliding plate (1 1 p) between the retention configuration (11 rR) and the dispensing configuration (11 rD) can be driven manually by an operator. Alternatively, as illustrated in Figures 7f, 7g, and 14, the first retention system (1 1 r) can be motorized, with a first motor (1 1 m) driving the sliding of the sliding plate (1 1 p) between the retention and dispensing configurations (1 1 rR, 1 1 rD). The first motor (1 1 m) can be a hydraulic or pneumatic piston, or an electrical motor. Any motor suitable for sliding the sliding plate (1 1 p) to-and-fro can be used to this effect. The first motor (1 1 m) is preferably controlled by a controller (15) as shown in Figure 14.

[0054] The solution of the sliding plate (1 1 p) to form the first retention system (1 1 r) has the advantage of being particularly robust, fool proof, and comprising little or any moving parts prompt to break. These are important advantages when working in the aggressive environment of a metal casting installation.

First retention system (11 r) comprises trapdoor panels (l it)

[0055] In an alternative embodiment illustrated in Figures 6a to 6g, the first retention system (11 r) comprises trapdoor panels (1 1 t) coupled to the dispensing opening (11 h) and movable between the retention configuration (11 rR) and the dispensing configuration (1 1 rD). As shown in Figures 6a to 6c, in the retention configuration, the trapdoor panels (1 1 t) obturate at least a portion of the dispensing opening (1 1 h), preventing the gasket unit (1 ) located at the first position (1 .1 ) and resting on the trapdoor panels (1 1 t) from falling through the dispensing opening (1 1 h). As illustrated in Figures 6d to 6f, in the dispensing configuration, the trapdoor panels (1 1 t) open to expose the dispensing opening (1 1 h) such that the gasket unit (1 ) located at the first position (1 .1 ) can fall through the dispensing opening (1 1 h) along the Z-axis by gravity.

[0056] As shown in Figures 6a to 6g, the trapdoor panels (1 1 t) can be coupled to the dispensing opening (11 h) by means of hinges (1 1 hi) configured to rotate the trapdoor panels (1 1 t) about corresponding rotation axes. In the retention configuration, the trapdoor panels (1 1 t) close at least a portion of the dispensing opening (1 1 h). In the dispensing configuration, the trapdoor panels (1 11) open by rotation about the corresponding rotation axes, to expose the dispensing opening (11 h). In one embodiment, the rotation axes of the hinges are transverse, preferably normal to the Z-axis. The trapdoor panels (1 1 t) can thus open downwards in the direction of the shroud (22, 32), as shown in Figures 6d to 6g, showing an embodiment with four trapdoor panels (1 1t) hinged to rotate about rotation axes normal to the Z-axis (i.e., comprised within the plane of the base plate (1 1 )). By controlling the opening of the trapdoor panels (1 1t) the falling rate of the gasket unit (1 ) can be controlled (i.e., reduced) and the gasket unit (1 ) can be smoothly guided from the first position (1 .1 ) through the opened dispensing opening (1 1 h) into the inlet (22I) of the shroud (22, 32) (cf. e.g., Figure 6g).

[0057] In an alternative embodiment, the rotation axes of the hinges are parallel to the Z-axes, rotating between the retention and dispensing configurations (1 1 rR, 1 1 rD) like the obturator of a camera. This embodiment does not allow guiding the falling gasket unit to the inlet of the shroud (22, 32). In this case, a gasket centring element (14) as illustrated in Figures 8a to 8c, can be positioned downstream of the dispensing opening (11 h) (downstream being defined relative to the direction of the gasket unit fall). Indeed, with trapdoor panels (1 11), it is difficult to have the stacking column (17) extending through and beyond the dispensing opening to guide the gasket units in their fall. A gasket centring element (14) can be a conical funnel or simply formed by strips distributed around the circumference of the dispensing opening (1 1 h) and converging towards the inlet (22I) of the shroud (22, 32). The strips can be flexible or rigid, but in all cases must be resistant to exposure to high temperatures from a possibly hot shroud (22, 32).

First retention system (11 r) wherein the base plate (11) comprises sliding elements

[0058] In a third embodiment, illustrated in Figures 7a to 7e, the base plate (1 1 ) comprises at least a sliding element and at least a second element which can be static or mobile. The at least one sliding element is configured to slide between the retention and dispensing configurations (1 1 rR, 1 1 rD) and is preferably mounted on rails (1 1 r) extending in a direction normal to the Z-axis.

[0059] In the retention configuration (1 1 rR), the at least one sliding element is close enough to the at least second element of the base plate (1 1 ) defining the dispensing opening (1 1 h) with dimensions small enough to retain the gasket unit (1 ) at the first position (1 .1 ), as shown in Figures 7a and 7b. In the dispensing configuration (1 1 rD) the at least one sliding element slides away from the at least second element, thus increasing the dimensions of the dispensing opening (11 h) until it is large enough to let the gasket unit (1 ) fall from the first position (1 .1 ) through the dispensing opening (1 1 h).

[0060] In a preferred embodiment, the stacking column extends beyond the base plate and the at least one sliding element and the at least second element comprise a recess configured to surround a circumference of the stacking column (17) when in the retention configuration (1 1 rR).

[0061] The sliding of the at least one, preferably two sliding elements can be motorised. As illustrated in Figures 7f and 7g, the at least one or the two elements forming the base plate (1 1 ) can be mounted on a rack-and-pinion mechanism driven by a first motor (1 1 m) which can drive the two elements away from each other to reach the dispensing configuration (1 1 rD) (cf. Figure 7f) and towards one another to reach the retention configuration (11 rR) (cf. Figure 7g).

[0062] When in the dispensing configuration (1 1 rD), the first retention system (1 1 r) allows not only the gasket unit (1 ) at the first position (1 .1 ) but all the gasket units (1 ) of the stack to fall through the dispensing opening (1 1 h) unless otherwise retained. This is the function of the second retention system (12r) discussed in continuation.

SECOND RETENTION SYSTEM (12r)

[0063] As mentioned supra, the function of the second retention system (12r) is to retain the gasket unit (1 ) located at the second position (1 .2) and all gasket units (1 ) located at higher positions (1 .i, i = 3 to N) from falling down through the dispensing opening (1 1 h) together with the gasket unit (1 ) at the first position (1 .1 ) when the first retention system (11 r) is in the dispensing configuration (1 1 rD), leaving the first position (1 .1 ) vacant. There are several solutions to implement this function. A selection of preferred solutions of mechanisms for the second retention system (12r) are presented in continuation.

Second retention mechanism (12r) comprises external clamping elements (12p)

[0064] A first mechanism for the second retention system (12r) illustrated in Figures 4a to 4d, 9a, 9b, 10a, 10b, and 14 comprises first and second clamping elements (12p) movable relative to one another along a direction normal to the Z-axis between the holding configuration (12rH) and the release configuration (12rR) as follows. In the holding configuration, the first and second clamping elements (12p) are separated from one another by a distance lower than the large outer diameter (De) and preferably larger than the small outer diameter (de), such that the gasket (1 ) located at the second position (1 .2) is clamped between the first and second clamping elements (12p) ,and cannot fall down into the first position (1 .1 ) when the first position is vacant. In the release configuration, the first and second clamping elements (12p) are separated from one another by a distance larger than the large outer diameter (De), such that the gasket (1 ) located at the second position (1 .2) is free to fall into the first position (1 .1 ) when the first position is vacant. All gasket units (1 ) at positions (1 .i, i > 2) are allowed to fall down to a lower position (1 .(i-1 )) directly below. It is clear that when the second retention system (12r) is in the release configuration (12rR), the first retention system (11 r) must be in the retention configuration (1 1 rR), lest the whole stack of gasket units (1 ) falls through the dispensing opening (1 1 h). As shown in Figure 14, the second retention system (12r) can be motorised with a second motor (12m), preferably controlled by the controller (15).

[0065] As shown in Figures 9a and 9b the clamping elements (12p) can move between the holding and release configurations (12rH, 12rR) by translation along a direction normal to the Z-axis. As shown in Figures 4a to 4e, the clamping elements (12p) can be mounted on a rails system to thus translate.

[0066] In an alternative embodiment, illustrated in Figures 10a and 10b, the clamping elements (12p) can move between the holding and release configurations (12rH, 12rR) by rotation about one or two rotation axes parallel to the Z-axis. Rotating the clamping elements (12p) about two distinct axes as shown in Figures 10a and 10b has the advantage of being more compact than having a single rotation axis.

Second retention mechanism (12r) comprises inner rotating cams (12c)

[0067] In this embodiment, the stacking column (17) must be a hollow tube defined by a passage extending along the Z-axis. The hollow tube can have one or more windows bringing in fluid communication the passage with an exterior of the stacking column (17), the windows being positioned at the level of a bottom of the second position (1 .2). Alternatively, the passage opens at a lower end of the stacking column (17) which is at the level of the bottom of the second position (1 .2). [0068] The second retention system (12r) comprises one or more rotating cams (12c) located directly below an edge of the small inner diameter (di) of the gasket unit (1 ) located at the second position (1 .2) and configured to rotate about one or more corresponding axes between the holding and release configurations (12rH, 12rR) as follows. In the holding configuration, a portion of the one or more cams extends beyond the edge of small inner diameter (di) of the gasket unit (1 ) located at the second position (1 .2), such that this gasket unit (1 ) rests on top of the one or more rotating cams (12c) and is prevented from falling down into the first position (1 .1 ) when the first position (1 .1 ) is vacant. The rotating cams (12c) rotate either on a plane intersecting the windows or below an edge of the end of the stacking column (17). In the release configuration, the one or more cams do not extend beyond the edge of small inner diameter (di) of the gasket unit (1 ) located at the second position (1 .2), such that this gasket unit is free to fall into the first position (1 .1 ) when the first position is vacant.

[0069] As shown in Figures 1 1 a and 1 1 b, the rotating cams (12c) can be configured to rotate about one or more axes parallel to the Z-axis. Alternatively, the rotating cams (12c) can be configured to rotate about one or more axes normal to the Z-axis, as illustrated in Figures 12a and 12b.

[0070] The rotation of the rotating cams (12c) can easily be motorised with a second motor (12m) as shown in Figures 12a and 12b with pistons (12m).

CONTROL OF THE FIRST AND SECOND RETENTION SYSTEMS (11 r 12r)

[0071] The movements of the first and second retention mechanisms (1 1 r, 12r) between their different configurations can be driven manually by an operator. As shown in Figures 4a to 4e discussed in more detail in continuation, however, the dispensing of one gasket unit (1 ) at a time, out of the stack of gasket units (1 ) requires moving the first and second retention mechanisms (1 1 r, 12r) between their different configurations at specific stages of the operation in a synchronised manner. For this reason, it is preferred to have a controller (15) controlling first and second motors (1 1 m, 12m) configured to move the various components of the first and second retention systems (11 r, 12r) in a coordinated manner. The controller (15) ensures that no mistake can occur. For example, it must be avoided at all costs having the first retention system (1 1 r) in the dispensing configuration (1 1 rD) when at the same time, the second retention system (12r) is at the release configuration (12rR), which would dispense all the gasket units of the stack at a time through the dispensing opening (1 1 h).

[0072] As shown in Figure 14, if the stacking column (17) is hollow, it can be equipped with a viewing system (17v) configured to inspect through the hollow stacking column an inlet and a bore of the shroud (22, 32) positioned in alignment with the dispensing opening (1 1 h) and with the hollow stacking column (17). The viewing system (17v) can be coupled to the controller (15) to display the images from the viewing system. Either an operator or, if trained properly, the controller itself, can thus assess whether the shroud is in conditions to run a next casting session. [0073] The controller can also be configured to determine the number of gasket units (1 ) remaining in the stack. For example, the stack can comprise a dummy gasket (1 d) at the highest position (1 .N) (i.e., with no gasket unit (1 ) nested in the dummy gasket (1 d)). The dummy gasket (1 d) can be equipped with a distance measuring device (1 L) configured to measure a distance along the Z-axis between the dummy gasket (1 d) and a reference point of the gasket dispensing device (10).

[0074] Alternatively, the gasket dispensing device (10) can be equipped with a weighing scale (12w) at the level of the base plate (1 1 ) or of the second retention mechanism (12r), configured to measure the weight of the stack, and thus determine the number of gasket units remaining in the stack.

[0075] Figure 14 shows an embodiment of the gasket dispensing device (10) with no gasket unit loaded therein and Figures 4a to 4e, show the same gasket dispensing device (10) with a stack of gasket units (1 ) loaded over the stacking column (17).

METAL CASTING INSTALLATION

[0076] The present invention also concerns a metal casting installation illustrated in Figures 15a to 15d and comprising a ladle (20), a tundish (30), and a workshop (50) for cleaning a previously used shroud (22u) to yield a cleaned shroud ready for further use. A robot (40) is provided, configured to bring the used shroud (22u) from a casting position to the workshop (50) and to bring a clean shroud (22, 32) which is the cleaned shroud or is a new clean shroud, from the workshop (50) to the casting position.

[0077] The workshop (50) is equipped with all the equipment required to clean and shower a used shroud (22u), including an oxygen lance (51 o) and the like. The workshop (50) is also equipped with the gasket dispensing device (10) of the present invention, as described supra. The robot (40) is configured to drive the used shroud (22u) to a showering station for cleaning with the oxygen lance (51 o) the used shroud to yield a clean shroud (22, 32). Once cleaned, the robot is configured to drive the clean shroud (22, 32) below the dispensing opening (1 1 h) of the gasket dispensing device (10), to hold the clean shroud (22, 32) in place until a gasket unit (1 ) has fallen through the dispensing opening (1 1 h) into position into an inlet (22i) of the shroud (cf. Figure 15c). The robot (40) is further configured to bring and fix the clean shroud (22, 32) holding the gasket unit (1 ) into the casting position by sandwiching the gasket unit (1 ) between the inlet (22i) of the shroud and a tip of a nozzle (21 , 31 ) of a new ladle (20) or of the tundish (30), to seal the contact between shroud and nozzle (cf. Figure 15d).

PROCESS FOR POSITIONING A GASKET UNIT (1) AT AN INLET (22I) OF A SHROUD (22, 32)

[0078] The present invention also concerns a process for automatically positioning a gasket unit (1 ) at a tube inlet (22i) of a shroud (22, 32). The process comprises the following steps. Illustrated in Figures 4a to 4d, (a) providing a shroud (22, 32) as illustrated in Figures 3a to 3d, configured to be used in a metal casting operation and comprising an elongated tube with a channel extending along the tube from a tube inlet (22I) to a tube outlet (22o),

(b) providing a gasket dispensing device (10) of the present invention as described supra,

(c) setting the first retention system (11 r) in the retention configuration (11 rR) and loading a stack of gasket units (1 ) over the stacking column (17) such that the gasket unit (1 ) positioned at the first position (1 .1 ) cannot fall through the dispensing opening (1 1 h), as illustrated in Figure 4a,

(d) setting the second retention system (12r) in the holding configuration (12rH), such that the gasket unit (1 ) positioned at the second position (1 .2) cannot move into the first position (1 .1 ) even if the first position (1 .1 ) is vacant,

(e) positioning the shroud (22, 32) below the gasket dispensing device (10) with the tube inlet (22I) coaxially aligned with the dispensing opening (11 h) along the Z-axis, and holding the shroud in place,

(f) as shown in Figure 4b, setting the first retention system (11 r) into the dispensing configuration (11 rD), to let the gasket unit (1 ) positioned at the first position (1 .1 ) to fall through the dispensing opening (1 1 h) into position, nested in the tube inlet (22I), whilst the gasket unit (1 ) positioned at the second position (1 .2) is retained by the second retention system (12r) which is in the holding configuration (12rH); the proper positioning of the gasket unit (1 ) in the tube inlet (22I) can be controlled using the viewing system (17v).

(g) remove the shroud (22, 32) with the gasket unit (1 ) nested in the tube inlet (22I) as illustrated in Figure 4c,

(h) setting the first retention system (11 r) back into the retention configuration (1 1 rR), with the first position (1 .1 ) being vacant, as shown in Figure 4c,

(i) as shown in Figure 4d, setting the second retention system (12r) into the release configuration (12rR) to allow the gasket unit (1 ) positioned at the second position (1 .2) to fall down into the first position (1 .1 ), and concomitantly to allow all the remaining gasket units (1 ) of the stack to fall down from an i^,h position to an (i-1 )^,h position, with i = 2 to N.

[0079] As discussed supra with reference to Figure 14, the whole process can be automated using a controller (15) controlling first and second motors (1 1 m, 12m) configured to drive the required moves of the first and second retention systems (1 1 r, 12r) between their respective different configurations (1 1 rR, 1 1 rD, 12rH, 12rR). A robot (40) can be used to position the shroud (22, 32) below the gasket dispensing device (10) at step (e).

PROCESS FOR BRINGING A SHROUD INTO SEALED CONTACT WITH A NOZZLE [0080] The present invention also concerns a process for automatically bringing a shroud (22, 32) into a casting position with an inlet of the shroud in sealed contact with a tip of a nozzle (21 , 31 ). The shroud and nozzle can be a ladle shroud (22) coupled to a collector nozzle (21 ) of a ladle (20) as illustrated in Figures 3a to 3d. Alternatively or concomitantly, the shroud and nozzle can be a SES (32) coupled to a pouring nozzle (22) of a tundish (30) as illustrated in Figure 1 . The process comprises the following steps.

• providing a metal casting installation comprising a ladle (20) and a tundish (30), wherein each of the ladle and tundish comprises a nozzle (21 , 31 ) comprising a channel extending from a nozzle inlet (21 i) to a nozzle outlet (21 o) (cf. Figures 1 and 3a to 3d),

• providing a shroud (22, 32) comprising an elongated tube with a channel extending along the tube from a tube inlet (22I) to a tube outlet (22o), wherein the tube inlet (22I) mates a geometry of the nozzle outlet (21 o) (cf. Figures 3a to 3d),

• a robot (40) illustrated in Figure 15d, configured to bring and fix the shroud (22, 32) into a casting position with the nozzle outlet (21 o) in sealed contact with the tube outlet, (22o) sandwiching a gasket unit (1 ) to define a continuous casting channel extending from the nozzle inlet (21 i) to the tube outlet (22o),

[0081] wherein the process comprises the steps of,

• providing a gasket dispensing device (10) loaded with a stack of gasket units (1 ) according to the invention as described supra,

• providing a controller (15) configured to control the robot (40) and to control the first and second retention systems (1 1 r, 12r) , by applying the steps defined in claim 14, and wherein after removing the shroud with the gasket unit (1 ) nested in the tube inlet (22I) in step (g) of claim 14, the controller (15) controls the robot (40) to bring the shroud into the casting position,

• allowing the inner anti-sticking layer (1 mi) to degrade as the temperature of the nozzle (21 , 31 ) reaches the threshold temperature, thus exposing an inner surface of the gasket (1 g) or the adhesive layer (1 a), which contacts the nozzle, such that the sealing gasket (1 s), devoid of the inner anti-sticking layer (1 mi), adheres more to an outer surface of the nozzle (21 , 31 ) than to the shroud inlet (22i).

[0082] Figures 15a to 15d schematically illustrate a cycle of change of a ladle (20) including the process of the present invention. Figures 15a to 15d show a metal casting installation according to the present invention comprising a ladle (20), a tundish (30), and a workshop (50) for cleaning a previously used shroud (22u) to yield a cleaned shroud ready for further use. The installation is also equipped with a robot (40) configured inter alia to bring the used shroud (22u) from a casting position to the workshop (50) and to bring a clean shroud (22, 32) which is the cleaned shroud or is a new clean shroud, from the workshop (50) to the casting position. In Figures 15a to 15d, the shroud is a ladle shroud (22). The workshop (50) is equipped with an oxygen lance (51 o) to shower a used ladle shroud (22u) and yield a cleaned ladle shroud (22), which can be used for a further metal casting operation with a new ladle (20).

[0083] Figure 15a shows the metal casting installation in casting mode, with a ladle (20) full of molten metal (3) pouring molten metal into the tundish (30) through the nozzle assembly formed by the collector nozzle (21 ) and the ladle shroud (22). A sliding gate (25) is in an open configuration allowing molten metal to flow from the ladle (20) into the tundish (30) through the nozzle assembly. Figure 15b shows the metal casting installation when the ladle (20) of Figure 15a has finished pouring molten metal into the tundish (30). The sliding gate (25) is closed to prevent any metal from flowing out of the ladle (20) and the robot (40) removes the used ladle shroud (22u) and brings it to the workshop (50) for showering as shown in Figure 15c. Figure 15c shows that once the used ladle shroud (22u) has been showered with the oxygen lance (51 o) and controlled, the thus cleaned ladle shroud (22) can be brought below the gasket dispensing device (10) of the present invention. Alternatively, a new ladle shroud (22) can be positioned below the gasket dispensing device (10) in case the used ladle shroud (22u) cannot be reused, or in case the showering thereof would take too long.

[0084] A new gasket unit (1 ) is dispensed from the gasket dispensing device (10) and positioned into the inlet (22i) of the ladle shroud (22). In the meantime, the empty ladle (20) is removed from casting position and is replaced by a new ladle (20) full of molten metal (3) as shown in Figure 15c. The new ladle (20) has the sliding gate (25) in closed position, and it comprises a collector nozzle (21 ) but no ladle shroud (22), nor gasket (1 g). The clean ladle shroud (22) comprising the gasket unit (1 ) is brought by the robot (40) from the workshop (50) to the casting position. The robot fixes the ladle shroud (22) with the inner anti-sticking layer (1 mi) in contact with the outlet surface of the collector nozzle (21 ) of the new ladle (20) to form a new nozzle assembly as shown in Figure 15d. The gasket unit (1 ) is sandwiched between the inlet of the ladle shroud (22) and an outer surface of the outlet (31 o) of the collector nozzle (21 ). The inner anti-sticking layer (1 mi) remains in place as long as the temperature thereof is below the threshold temperature. Degradation of the inner anti-sticking layer (1 mi) occurs when the temperature thereof rises above the threshold temperature. This could already happen as the gasket unit is positioned into the inlet (22i) of a shroud (22, 32) which is still hot and above the threshold temperature. Generally, however, the inner anti-sticking layer (1 mi) degrades when the sliding gate (25) is opened, as shown in Figure 15a, and molten metal (3) starts flowing through the nozzle assembly into the tundish, increasing the temperature of the collector nozzle (21 ) until it reaches the threshold temperature of the inner anti-sticking layer (1 mi) which degrades and exposes either an inner surface the gasket (1 g) or the adhesive layer (1 a) coating the inner surface of the gasket (1 g), so that the sealing gasket (1 s) adheres more to the collector nozzle than to the ladle shroud (22).

[0085] The same process can be implemented in a similar manner with a nozzle assembly formed by an SES (32) and a pouring nozzle (31 ) of the tundish (30). Since the time the flow of molten metal (3) out of the tundish must be reduced to a minimum, a new SES is generally coupled to the pouring nozzle (31 ) while the used SES is being showered

[0086] The gasket dispensing device (10) of the present invention can efficiently dispense gasket units (1 ) according to the present invention because the latter comprise the inner anti-sticking layer (1 mi) which degrades at the threshold temperature. This inner anti-sticking layer (1 mi) has the double advantage of (1 ) simplifying and rendering more reproducible the dispensing of the gaskets by the gasket dispensing device (10), since the gasket units (1 ) do not stick to one another when stacked, contrary to the dispensing device of CN1 10253009, and (2) it needs not be removed manually or otherwise, before being dispensed through the dispensing opening (1 1 h) to the inlet (22i) of the shroud

(22, 32), since it degrades when molten melt starts flowing through the nozzle (21 , 31 ) and the temperature rises above the threshold temperature and degrades the inner anti-sticking layer (1 mi).

Claims

1 . A gasket unit (1 ) for sealing a contact between a nozzle (21 , 31 ) and a shroud (22, 32) in a metal casting installation, the gasket unit (1 ) comprising,

• a gasket (1 g) made of a ceramic or polymeric material configured for forming a sealing contact between an outer surface of the nozzle (21 , 31 ) and an inner surface of the shroud (22, 32), the gasket (1 g) having a geometry of revolution about a Z-axis, with a central passage defined by an inner surface, extending along the Z-axis and tapering from a large inner diameter (Di) to a small inner diameter (di), and

• an outer anti-sticking layer (1 me) covering an outer surface of the gasket (1 g),

Characterized in that,

• the gasket unit (1 ) comprises an inner anti-sticking layer (1 mi) covering an inner surface of the gasket (1 g) defining the central passage,

• the gasket unit (1 ) is so configured that several of the gasket units (1 ) can be nested into one another to form a stack of several gasket units (1 ) nested in one another without sticking to one another at corresponding positions (1 .1 to 1 .N), wherein the stack extends along the Z axis,

• the inner anti-sticking layer (1 mi) is different from the outer anti sticking layer (1 me),

• the inner anti sticking layer (1 mi) degrades upon exposure to a threshold temperature lower than 500°C, so that it exposes the surface it is applied upon, and

• the outer anti sticking layer (1 m2) does not degrade upon exposure to a temperature below 700°C, so that it maintains anti adhesion properties below said temperature.

2. Gasket unit (1 ) according to claim 1 , wherein the gasket (1 g) comprises an adhesive layer (1 a) between the gasket (1 g) and the inner anti sticking layer (1 mi).

3. Stack of gasket unit (1 ) comprising several of the gasket units (1 ) of claim 1 or 2 nested into one another to form a stack of several gasket units (1 ) without sticking to one another at corresponding positions (1 .1 to 1 .N), wherein the stack extends along a Z-axis, and preferably comprises a dummy gasket unit (1 d) on a top of the stack, wherein the gasket unit (1 , 1 d) positioned at a top of the stack does not comprise a gasket unit nested therein.

4. Gasket dispensing device (10) for dispensing one by one gasket units (1 ) according to claim 1 or 2, the gasket dispensing device (10) comprising, a base plate (1 1 ) substantially normal to the Z-axis, provided with a dispensing opening (1 1 h) of smallest dimension (d1 1 ) larger than the large inner diameter (Di) (i.e., d1 1 > Di), allowing the free passage of a gasket unit (1 ) through the dispensing opening (1 1 h) along the Z-axis,

• a stacking column (17) extending along the Z-axis and concentric with the dispensing opening (1 1 h), the stacking column having an outer diameter smaller than the small inner diameter (di) of the gasket (1 g), the gasket dispensing device (10) being suitable for loading several gasket units (1 ), nested in one another at corresponding positions (1 .1 -1 .N) to form the stack according to claim 3, wherein o a first position (1 .1 ) is at a bottom of the stack, directly above the dispensing opening (1 1 h), o a second position (1 .2) is directly above the first position (1 .1 ) and corresponds to the position of the gasket unit (1 ) nested in the gasket unit (1 ) at the first position (1 .1 ) and so on until o an N^,h position (1 .N) is at a top of the stack, corresponding to the position of the gasket unit (1 ) nested in the gasket unit (1 ) at a (N-1 )^,h position (1 .(N-1 )), in such a way that the stack is loaded over the stacking column (17) which extends through the central passages of the nested gasket units (1 ) forming the stack,

• a first retention system (1 1 r) configured for moving between, o a retention configuration (1 1 rR) preventing, when the stack is loaded over the stacking column (17), the whole stack from moving along the Z-axis by retaining and preventing the gasket unit (1 ) located at the first position (1 .1 ) from falling through the dispensing opening (1 1 h), and o a dispensing configuration (1 1 rD) allowing, when the stack is loaded over the stacking column (17), the same gasket unit (1 ) located at the first position (1 .1 ) to leave the first position by falling through the dispensing opening (1 1 h) and therefore, if not otherwise retained, allowing the whole stack to fall along the Z-axis,

• a second retention system (12r) configured for moving between, o a holding configuration (12rH) preventing, when the stack is loaded over the stacking column (17), the whole stack but the gasket unit (1 ) at the first position (1 .1 ) from moving along the Z-axis by preventing the gasket unit (1 ) at the second position (1 .2) from moving to the first position (1 .1 ) when the first position is vacant, and o a release configuration (12rR) allowing, when the stack is loaded over the stacking column (17), the whole stack to fall along the Z-axis when the first position (1 .1 ) is vacant and the first retention system (1 1 r) is in the retention configuration, allowing all the gasket units (1 ) which were at an i^,h position to move down to an (i-1 )^,h position, with i = 2 to N; such that the first position (1 .1 ) is occupied again by the gasket unit (1 ) which was at the second position (1 .2).

5. Gasket dispensing device according to claim 4, wherein the first retention system (1 1 r) comprises a sliding plate (1 1 p) configured for sliding along the base plate, normal to the Z-axis, such that,

• In the retention configuration, the sliding plate (1 1 p) covers at least a portion of the dispensing opening (1 1 h), preventing, when the stack is loaded over the stacking column (17), the gasket unit (1 ) located at the first position (1 .1 ) from falling through the dispensing opening (1 1 h), and

• In the dispensing configuration, the sliding plate (11 p) exposes the dispensing opening (1 1 g) such that, when the stack is loaded over the stacking column (17), the gasket unit (1 ) located at the first position (1 .1 ) can fall through the dispensing opening (1 1 h).

6. Gasket dispensing device according to claim 5, wherein the stacking column (17) extends through the dispensing opening (1 1 h) and wherein the sliding plate (1 1 h) comprises an aperture allowing to slide the sliding plate (11 p) into the retention configuration by surrounding the stacking column (17) positioned in the aperture.

7. Gasket dispensing device according to claim 4, wherein the first retention system (1 1 r) comprises trapdoor panels (1 11) coupled to the dispensing opening (1 1 h) and movable, such that

• In the retention configuration, the trapdoor panels (1 1 t) obturate at least a portion of the dispensing opening (1 1 h), preventing, when the stack is loaded over the stacking column (17), the gasket unit (1 ) located at the first position (1 .1 ) from falling through the dispensing opening (11 h), and

• In the dispensing configuration, the trapdoor panels (111) open the dispensing opening (1 1g) such that, when the stack is loaded over the stacking column (17), the gasket unit (1 ) located at the first position (1 .1 ) can fall through the dispensing opening (1 1 h), wherein the trapdoor panels (1 11) are preferably coupled to the dispensing opening (1 1 h) by means of hinges (1 1 hi), such that in the dispensing configuration, when the stack is loaded over the stacking column (17), the trapdoor panels (1 11) are configured for guiding the fall of the gasket unit (1 ) from the first position (1 .1 ) through the opened dispensing opening (1 1 h).

8. Gasket dispensing device according to any one of claims 4 to 7, wherein the second retention system (12r) comprises first and second clamping elements (12p) movable relative to one another along a direction normal to the Z-axis, such that

• In the holding configuration, the first and second clamping elements (12p) are separated from one another by a distance lower than the large inner diameter (Di), such that, when the stack is loaded over the stacking column (17), the gasket (1 ) located at the second position (1 .2) is clamped between the first and second clamping elements (12p) and cannot fall down into the first position (1 .1 ) when the first position is vacant, and

• In the release configuration, the first and second clamping elements (12p) are separated from one another by a distance larger than the large inner diameter (Di), such that, when the stack is loaded over the stacking column (17), the gasket (1 ) located at the second position (1 .2) is free to fall into the first position (1 .1 ) when the first position is vacant.

9. Gasket dispensing device according to any one of claims 4 to 7, wherein the stacking column (17) is a hollow tube and wherein the second retention system (12r) comprises one or more rotating cams (12c) located directly below an edge of the small inner diameter (di) of the gasket unit (1 ) located at the second position (1 .2) when the stack is loaded over the stacking column (17), and configured to rotate about one or more corresponding axes, such that,

• In the holding configuration, when the stack is loaded over the stacking column (17), a portion of the one or more cams extends beyond the edge of small inner diameter (di) of the gasket unit (1 ) located at the second position (1 .2), such that this gasket unit (1 ) rests on top of the one or more rotating cams (12c), and is prevented from falling down into the first position (1 .1 ) when the first position (1 .1 ) is vacant, and

• In the release configuration, the one or more cams do not extend beyond the edge of small inner diameter (di) of the gasket unit (1 ) located at the second position (1 .2) when the stack is loaded over the stacking column (17), such that this gasket unit is free to fall into the first position (1 .1 ) when the first position is vacant.

10. Gasket dispensing device according to any one of claims 4 to 9, comprising,

• a first motor (1 1 m) for driving the first retention system (1 1 r) between the retention and dispensing configurations,

• a second motor (12m) for driving the second retention system (12r) between the holding and release configurations, and a controller (15) configured to control actuation of the first and second motors (1 1 m, 12m).

1 1 . Gasket dispensing device according to any one of claims 4 to 10, wherein the stacking column (17) is hollow and is equipped with a viewing system (17v) configured to inspect through the hollow stacking column an inlet and a bore of the shroud (22, 32) positioned in alignment with the dispensing opening (1 1 h) and the hollow stacking column (17).

12. Gasket dispensing device according to any one of claims 4 to 1 1 , comprising a stack loaded over the stacking column (17) such that gasket units (1 ) are loaded at any one of the first to N^,h positions (1 .1 -1 .N).

13. Metal casting installation, comprising a ladle (20), a tundish (30), and a workshop (50) for cleaning a previously used shroud (22u) to yield a cleaned shroud ready for further use, and a robot (40) configured to bring the used shroud (22u) from a casting position to the workshop (50) and to bring a clean shroud (22, 32) which is the cleaned shroud or is a new clean shroud, from the workshop (50) to the casting position, characterized in that,

• the workshop (50) is equipped with the gasket dispensing device (10) according to claim 12, and in that,

• the robot (40) is configured, o to drive the clean shroud (22, 32) below the dispensing opening (11 h) of the gasket dispensing device (10), o to hold the clean shroud (22, 32) in place until a gasket unit (1 ) has fallen through the dispensing opening (1 1 h) into position into an inlet (22I) of the shroud, and o to bring and fix the clean shroud (22, 32) into the casting position by sandwiching the gasket unit (1 ) between the inlet (22I) of the shroud and a tip of a nozzle (21 , 31 ), to seal the contact between shroud and nozzle.

14. Process for automatically positioning a gasket unit (1 ) at a tube inlet (22I) of a shroud (22, 32) comprising the following steps,

(a) providing a shroud (22, 32) configured to be used in a metal casting operation and comprising an elongated tube with a channel extending along the tube from a tube inlet (22I) to a tube outlet (22o),

(b) providing a gasket dispensing device (10) according to any of claims 4 to 1 1 ,

(c) setting the first retention system (1 1 r) in the retention configuration (1 1 rR) and loading a stack of gasket units (1 ) over the stacking column (17) such that the gasket unit (1 ) positioned at the first position (1 .1 ) cannot fall through the dispensing opening (1 1 h), (d) setting the second retention system (12r) in the holding configuration (12rH), such that the gasket unit (1 ) positioned at the second position (1 .2) cannot move into the first position (1 .1 ) even if the first position (1 .1 ) is vacant,

(e) positioning the shroud (22, 32) below the gasket dispensing device (10) with the tube inlet (22I) coaxially aligned with the dispensing opening (1 1 h) along the Z-axis, and holding the shroud in place,

(f) setting the first retention system (1 1 r) into the dispensing configuration (1 1 rD), to let the gasket unit (1 ) positioned at the first position (1 .1 ) to fall through the dispensing opening (11 h) into position, nested in the tube inlet (22I), whilst the gasket unit (1 ) positioned at the second position (1 .2) is retained by the second retention system (12r) which is in the holding configuration (12rH),

(g) remove the shroud (22, 32) with the gasket unit (1 ) nested in the tube inlet (22I) ,

(h) setting the first retention system (1 1 r) back into the retention configuration (1 1 rR), with the first position (1 .1 ) being vacant,

(i) setting the second retention system (12r) into the release configuration (12rR) to allow the gasket unit (1 ) positioned at the second position (1 .2) to fall down into the first position (1 .1 ), and concomitantly to allow all the remaining gasket units (1 ) of the stack to fall down from an i^,h position to an (i-1 )^,h position, with i = 2 to N.

15. Process for automatically bringing a shroud (22, 32) into a casting position with an inlet of the shroud in sealed contact with a tip of a nozzle (21 , 31 ), comprising the following steps,

• providing a metal casting installation comprising a ladle (20) and a tundish (30), wherein the ladle or the tundish comprises a nozzle (21 , 31 ) comprising a channel extending from a nozzle inlet (21 i) to a nozzle outlet (21 o),

• providing a shroud (22, 32) comprising an elongated tube with a channel extending along the tube from a tube inlet (22I) to a tube outlet (22o), wherein the tube inlet (22I) mates a geometry of the nozzle outlet (21 o),

• a robot (40) configured to bring the shroud (22, 32) into a casting position with the nozzle outlet (21 o) in sealed contact with the tube outlet, sandwiching a gasket unit (1 ) to define a continuous casting channel extending from the nozzle inlet (21 i) to the tube outlet (22o), characterized in that, the process comprises the steps of, providing a gasket dispensing device (10) according to claim 12, • providing a controller (15) configured to control the robot (40) and to control the first and second retention systems (1 1 r, 12r) , by applying the steps defined in claim 14, and wherein after removing the shroud with the gasket unit (1 ) nested in the tube inlet (22I) in step (g) of claim 14, the controller (15) controls the robot (40) to bring the shroud into the casting position, • allowing the inner anti-sticking layer (1 mi) to degrade as the temperature of the nozzle (21 , 31 ) reaches a threshold temperature, thus exposing an inner surface of the gasket (1 g) or the adhesive layer (1 a), which contacts the nozzle, such that the sealing gasket (1 s), devoid of the inner antisticking layer (1 mi), adheres more to an outer surface of the nozzle (21 , 31 ) than to the shroud inlet (22i).