Bottom plate assembly comprising a bayonet free collector nozzle

Abstract

A gate for metallurgic vessels is provided with a collector nozzle coupled to a bottom plate assembly of the gate. The bottom plate assembly allows a collector nozzle to be coupled to a bottom gate plate without need of a separate bayonet ring. A bayonet ring is integrated to the bottom plate assembly, allowing a collector nozzle to be mounted by a single robot, or by a single operator more easily than existing systems.

Claims

1. A casting assembly comprising: (A) a collector nozzle comprising: (a) an upstream surface and a downstream surface joined to one another by a lateral surface, and comprising a bore extending along a longitudinal axis (Z) from the upstream surface to the downstream surface, (b) N protrusions, wherein N≥2, distributed around a perimeter of the lateral surface, each protrusion comprising an upper surface which is adjacent to the upstream surface of the collector nozzle and a lower surface separated from the upper surface by a height of the protrusion, and having an azimuthal width (W) measured normal to the longitudinal axis (Z), (B) a frame comprising a gate plate receiving unit for receiving a lower gate plate, and (C) a nozzle coupling unit for receiving and rigidly coupling the collector nozzle to the frame, said nozzle coupling unit comprising a nozzle receiving bushing rigidly fixed to the frame, wherein, the nozzle coupling unit further comprises a bayonet ring comprising an upstream edge and a downstream edge separated by a height of the bayonet ring, which is permanently and rotatably mounted in the nozzle receiving bushing such that the bayonet ring can rotate about the longitudinal axis (Z) and wherein the bayonet ring comprises an inner surface provided with N channels extending along the longitudinal axis (Z) from the downstream edge to the upstream edge, wherein the N channels have a downstream width (Wd) at the level of the downstream edge which is larger than the azimuthal width (W) of the protrusions, allowing the translation along the longitudinal axis (Z) of the collector nozzle through the downstream edge of the bayonet ring with the protrusions engaged in corresponding channels until they contact and mate with mating structures of the corresponding protrusion, and wherein the N channels have an upstream width (Wu) at the level of the upstream edge which is larger than the downstream width (Wd), the N channels thus being configured to allow the rotation of the bayonet ring about the longitudinal axis (Z) with respect to the collector nozzle until an edge of the channel contacts the lower surface of the corresponding protrusion, thus locking the collector nozzle in an operating position.

2. The assembly according to claim 1, wherein N comprises a value selected from the group consisting of 3 and 4, and wherein the N protrusions are distributed evenly around the perimeter of the lateral surface.

3. The assembly according to claim 1, wherein the N channels extend from the downstream edge over at least 40% of the height of the bayonet ring with a constant width (Wd) and widen until reaching the width (Wu) at the upstream edge.

4. The assembly according to claim 1, wherein the bayonet ring comprises an outer surface provided with a thread mating a thread provided at an inner surface of the nozzle receiving bushing, the bayonet ring being configured such that rotation of the bayonet ring with respect to the nozzle receiving bushing translates the bayonet ring along the longitudinal axis (Z).

5. The assembly according to claim 1, wherein the nozzle receiving bushing comprises protrusion mating structures configured to receive the protrusions and preventing the collector nozzle from rotating about the longitudinal axis, Z.

6. The assembly according to claim 5, wherein the bayonet ring comprises an outer surface provided with a rotation stop, and wherein the nozzle receiving bushing comprises a corresponding rotation stop provided at an inner surface of the nozzle receiving bushing, which stops rotation of the bayonet ring when the channels of the bayonet ring face the protrusion mating structures of the nozzle receiving bushing.

7. The assembly according to claim 1, wherein the nozzle receiving bushing is formed of an upstream portion rigidly fixed to the frame, and of a downstream portion coupled to the upstream portion and sandwiching the bayonet ring, configured to allow rotation of the bayonet ring with respect to the nozzle receiving bushing, but not extraction of the bayonet ring from the nozzle receiving bushing.

8. The assembly according to claim 1, wherein the downstream edge of the bayonet ring comprises a rotation gripper, configured to allow the insertion of a tool for rotating the bayonet ring about the longitudinal axis (Z).

9. The assembly according to claim 1, wherein the frame is selected from the group consisting of: (a) a mobile carriage in a two-plate gate, and (b) a fixed frame in a three-plate gate.

10. The assembly according to claim 1, which is part of a gate system mounted at a bottom of a metallurgic vessel.

11. A method for mounting a collector nozzle onto a gate system, said method comprising the following steps: (a) providing a bottom plate assembly according to claim 1, (b) engaging the upstream surface of the collector nozzle through the bayonet ring from the downstream edge, with the N protrusions engaged in the corresponding channels, (c) inserting the collector nozzle along the longitudinal axis (Z) through the bayonet ring all the way until the collector nozzle reaches an operating position, and (d) rotating the bayonet ring about the longitudinal axis (Z) with respect to the collector nozzle until the collector nozzle is locked into its operating position and cannot move along the longitudinal axis (Z).

12. The method according to claim 11, wherein the nozzle receiving bushing comprises protrusion mating structures configured to receive the protrusions and preventing the collector nozzle from rotating about the longitudinal axis, Z, the method comprising the step of positioning the channels of the bayonet ring face to face with the corresponding nozzle mating structures of the nozzle receiving bushing, prior to step (c) of inserting the collector nozzle along the longitudinal axis (Z) through the bayonet ring all the way until the collector nozzle reaches its operating position with the protrusions engaged in the nozzle mating structures and thus prevented from rotating with respect to the longitudinal axis (Z).

13. The method according to claim 11, wherein prior to engaging the collector nozzle through the bayonet ring in step (c), a bottom gate plate is positioned into the gate plate receiving unit and is rigidly coupled to the frame, a refractory sealing material is applied onto the upstream surface of the collector nozzle, such that when the collector nozzle reaches its operating position in step (d), the sealing material contacts a downstream surface of the bottom gate plate.

14. The method according to claim 11, wherein at least one of the steps of claim 11 is carried out by a robot.

15. The assembly according to claim 1, wherein Wd is at least 1% larger than W to allow for movement of the protrusions along the N channels.

16. The assembly according to claim 1, wherein Wd is between 5% and 10% larger than W to allow for guidance of the protrusions.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) 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:

(2) FIGS. 1A and 1B are prior art general views of a casting installation for casting metal;

(3) FIGS. 2A-2C show a collector nozzle as defined in the present invention;

(4) FIG. 3 shows an exploded view of the coupling elements of a bottom carriage assembly according to the present invention;

(5) FIG. 4 shows a bottom carriage assembly according to the present invention;

(6) FIGS. 5A-5C illustrate the principle of coupling a collector nozzle to a bottom carriage assembly according to the present invention;

(7) FIGS. 6A and 6B show a bottom plate assembly according to the present invention belonging to a two-plate gate and;

(8) FIGS. 7A and 7B show a bottom plate assembly according to the present invention belonging to a three-plate gate.

DETAILED DESCRIPTION

(9) As discussed supra, FIGS. 1A and 1B show a metallurgic installation comprising a ladle (200L) containing molten metal filled from a furnace, and located above a tundish (200T), which is itself in fluid communication with a mould (300). The transfer of molten metal from the ladle to the tundish and from the tundish to the mould are carried out through corresponding nozzles: a ladle shroud (111) for the former, and a pouring nozzle (101) for the latter. Practically in all cases for ladles and in some cases for tundishes, the flow rate of metal through the corresponding nozzles is controlled by a gate comprising sliding plates (20g, 30g) bringing in and out of alignment bores provided in each plate. In continuation, the description focuses on ladles, but it is clear that the same teaching applies mutatis mutandis to tundishes and to any metallurgic vessels which are provided with a gate.

(10) The ladle shroud (111) protects the molten metal from any contact with air as it is poured out of the ladle (200L) into the tundish (200T). It is coupled to the outlet of the ladle by means of a collector nozzle (10) over which it fits snugly (cf. FIG. 1B). As illustrated in FIGS. 2A-2C, the collector nozzle used in the present invention comprises:

(11) (a) an upstream surface (10u) and a downstream surface (10d) joined to one another by a lateral surface (10L), and comprising a bore (10b) extending along a longitudinal axis, Z, from the upstream surface to the downstream surface,

(12) (b) N protrusions (11), with N≥2, distributed around a perimeter of the lateral surface, each protrusion comprising an upper surface (11u) which is adjacent to the upstream surface of the collector nozzle and a lower surface (11d) separated from the upper surface by a height of the protrusion, and having an azimuthal width, W, measured normal to the longitudinal axis, Z

(13) As illustrated in FIG. 2C, the azimuthal width, W, is herein defined as the largest width of the protrusions (11) measured normal to the longitudinal axis, Z.

(14) The collector nozzle is coupled to the bottom outlet of the ladle with a gate sandwiched between the two. The gate comprises a bottom plate assembly comprising a frame (200 comprising a gate plate receiving unit for receiving a lower gate plate (20g) and provided with a nozzle coupling unit (20) for receiving and rigidly coupling the collector nozzle (10) to the frame. As shown in FIGS. 6A, 6B, 7A, and 7B, the nozzle coupling unit (20) can be fixed to the frame (200 with fixing means (3) well known to a person of ordinary skill in the art, including screws and/or bolts. The nozzle coupling unit comprises a nozzle receiving bushing (21) rigidly fixed to the frame and advantageously comprising protrusion mating structures (21m) for receiving the protrusions and preventing the collector nozzle from rotating about the longitudinal axis, Z. The gist of the present invention is the new design of the nozzle coupling unit combined with the mating protrusions (11) of the collector nozzle which, in combination, allow for an easier coupling and withdrawal of the collector nozzle to and from the gate.

(15) As shown in FIGS. 3 and 4, the nozzle coupling unit comprises a bayonet ring (22) comprising an upstream edge (22u) and a downstream edge (22d) separated by a height of the bayonet ring, which is permanently and rotatably mounted in the nozzle receiving bushing such that the bayonet ring can rotate about the longitudinal axis, Z. The bayonet ring comprises an inner surface provided with N channels extending along the longitudinal axis, Z, from the downstream edge to the upstream edge. The N channels have a downstream width, Wd, at the level of the downstream edge which is substantially equal to, slightly larger than the width, W, of the protrusions, allowing the translation along the longitudinal axis, Z, of the collector nozzle through the downstream edge of the bayonet ring with the protrusions engaged in corresponding channels. In a preferred embodiment, the nozzle receiving bushing is provided with protrusion mating structures (21m). The collector nozzle can thus be translated through the bayonet ring until the protrusions engage the corresponding protrusion mating structures, thus preventing the collector nozzle from rotating about the longitudinal axis, Z. The N channels have an upstream width, Wu, at the level of the upstream edge which is larger than the downstream width, Wd, thus allowing the rotation of the bayonet ring about the collector nozzle until an edge of the channel contacts the lower surface of the corresponding protrusion, thus locking the collector nozzle in an operating position.

(16) The nozzle coupling element of the present invention is substantially advantageous over conventional coupling systems comprising a separate bayonet which must be engaged over the collector nozzle as it is held in place by hand or by a robot, often requiring a second operator or a second robot. It is also advantageous over collecting nozzles provided with an integrated bayonet because (1) such collecting nozzles are very heavy to handle, and (2) collector nozzles, comprising a refractory portion exposed to molten metal flow, must be changed at regular intervals, whilst bayonets, made of metal and not exposed to excessive heat and wear can be re-used several times, thus unnecessarily increasing the cost of a collector nozzle.

(17) Collector Nozzle (10)

(18) An embodiment of collector nozzle suitable for the present invention is illustrated in FIGS. 2A-2C. As traditional collector nozzles, a collector nozzle suitable for the present invention comprises an upstream surface (10u) and a downstream surface (10d) joined to one another by a lateral surface (10L) and comprising a bore (10b) extending along a longitudinal axis, Z, from the upstream surface to the downstream surface. The lateral surface (10L) generally has a circular cross section, concentric with the bore. It may comprise a downstream portion tapering towards the downstream surface (10d), to facilitate the coupling of a ladle shroud thereto, having a tapered bore matching the geometry of the downstream portion.

(19) The collector nozzle (10) comprises N protrusions (11), with N≥2, distributed around a perimeter of the lateral surface, and adjacent to the upstream surface (10u). The number, N, of protrusions is advantageously N=3 or 4. N=3 protrusions ensures a stable setting of the collector nozzle in the nozzle coupling unit and, at the same time, reduces frictions upon rotation of the bayonet. The N protrusions are advantageously distributed evenly around the perimeter of the lateral surface (10L).

(20) The N protrusions (11) serve for securing the collector nozzle to the bottom plate assembly by interaction of the protrusions with the portion of the channels adjacent to the upstream edge of the bayonet, of upstream width, Wu. In embodiments wherein the nozzle receiving bushing comprises protrusion mating structures (21m), the protrusions (11) engaged in said protrusion mating structures prevent the collector nozzle from rotating. This is useful as when the bayonet ring is being rotated, the collector nozzle should not rotate together with the bayonet ring.

(21) The N protrusions (11) have an upper surface (11u) and a lower surface (11d) separated from the upper surface by a height of the protrusion. The height of the protrusions must be sufficient for the protrusions to mechanically resist the forces applied thereto during coupling of the nozzle to the ladle and during a casting operation. For example, the height of the protrusions can be comprised between 10 and 100 mm, or between 20 and 70 mm, or between 30 and 60 mm. Similarly, the azimuthal width, W, measured normal to the longitudinal axis, Z, must be sufficient for ensuring stability of the coupling during casting operation. The azimuthal width, W, depends on the number, N, of protrusions. As illustrated in FIG. 2C, for a collector nozzle having a circular cross-section of radius, R, the azimuthal width, W=α R, wherein α is the azimuthal angle encompassing a protrusion. The azimuthal angle, α, is preferably comprised between 360°/5 N=72°/N and 360°/2 N=180°/N, preferably between 90°/N and 135°/N. For example, for N=3 protrusions, the azimuthal angle can be of the order of α=30 to 50°

(22) The collector nozzle is made of a refractory material for resisting the high temperatures of the molten metal flowing through the bore (10b). The collector nozzle preferably comprises a metal can (10c) cladding a portion of the lateral surface (10L) comprising an upstream edge adjacent to, yet recessed from, the upstream surface (10u). The metal can advantageously lines at least a portion of the protrusions which interacts with the channel edges upon rotation of the bayonet ring. A portion of the downstream portion of the collector nozzle can also be clad by the metal can, to protect the refractory material from wear as a ladle shroud is engaged over the lateral surface thereof. The metal can comprises a downstream edge recessed from the downstream surface of the collector nozzle. The downstream edge can be adjacent to the downstream surface of the collector nozzle, or not. DE102004008382 describes an interchangeable metal can made of cast iron.

(23) Nozzle Coupling Unit (20)

(24) The nozzle coupling unit is used for receiving and rigidly coupling the collector nozzle (10) to the frame. It comprises a nozzle receiving bushing (21) rigidly fixed to the frame and advantageously comprises protrusion mating structures (21m) for receiving the protrusions and preventing the collector nozzle from rotating about the longitudinal axis, Z, when the collector nozzle has reached its operating position along the longitudinal axis, Z. The operating position of the collector nozzle along the longitudinal axis, Z, corresponds to a position wherein the upstream surface (10u) of the collector nozzle can be sealingly coupled to a bottom surface of a bottom plate (20g) of the gate, by means of a sealing material (2), with the bore (10b) of the collector nozzle being in registry with a bore of the bottom plate (20g) (cf. FIGS. 6A, 6B, 7A, and 7B). At this stage, the collector nozzle is positioned in its operating position, but it is not secured yet. The protrusion mating structures (21m) can be in the form of channels as illustrated in FIG. 3, of width mating the azimuthal width of the protrusions (11) and of height lower than the height of the protrusions. Alternatively, the protrusion mating structures (21m) can be formed by protruding members flanking on either side a protrusion when the collector nozzle is in operating position, as shown in FIGS. 5A-5C. As long as the protrusion mating structures (21m) prevent the collector nozzle from rotating about the longitudinal axis, Z, the present invention is not restricted by any particular geometry or design thereof. In case the nozzle receiving bushing is not equipped with protrusion mating structures (21m), care must be taken when rotating the bayonet ring to prevent the collector nozzle from rotating therewith.

(25) The gist of the present invention is to permanently mount a bayonet ring (22) in the nozzle receiving bushing, such that it can rotate about the longitudinal axis. The bayonet ring comprises an upstream edge (22u) and a downstream edge (22d) separated by a height of the bayonet ring. It also comprises an inner surface provided with N channels extending along the longitudinal axis, Z, from the downstream edge to the upstream edge. The N channels have a downstream width, Wd, at the level of the downstream edge which is substantially equal to, slightly larger than the width, W, of the protrusions, allowing the translation along the longitudinal axis, Z, of the collector nozzle through the downstream edge of the bayonet ring with the protrusions engaged in corresponding channels until they contact the corresponding protrusion mating structures (21m). When the protrusions of the collector nozzle are engaged in the portion of channels of downstream width, Wd, the collector nozzle can be translated along the longitudinal axis, Z, but there cannot be any substantial rotation of the bayonet ring with respect to the collector nozzle.

(26) The N channels have an upstream width, Wu, at the level of the upstream edge which is larger than the downstream width, Wd. When the protrusions are in this portion of the channels, the bayonet ring can rotate about the longitudinal axis, Z, with respect to the collector nozzle until an edge of the channel contacts the lower surface of the corresponding protrusion, thus locking the collector nozzle in an operating position.

(27) As shown in FIGS. 3 and 5A, the channels (22c) of the bayonet ring can have a downstream portion of constant downstream width, Wd, followed an upstream portion flaring out progressively from the downstream width, Wd, to the upstream width, Wu, with Wu>Wd. Alternatively, the channels may abruptly pass from the downstream width, Wd, to the upstream width, Wu. A progressive transition from the downstream width, Wd, to the upstream width, Wu, is preferred because the rotation of the bayonet ring also forces the collector nozzle along the longitudinal axis, thus allowing a sealed contact with the bottom plate (20g) of the gate. The downstream portion of the channels (22c) may extend over at least 40% of the height of the bayonet ring. Advantageously the downstream portion extends over not more than 80% of the height of the bayonet ring. The upstream portion must have a height greater than the height of the protrusions of the collector nozzle, else the bayonet ring could never rotate with respect to the collector nozzle.

(28) The channel width can increase at one side only of an axis of the channel forming an L-shaped channels, as shown in FIGS. 3 and 5A-5C, thus allowing rotation of the bayonet ring in one direction only. Alternatively, the channel width can increase symmetrically with respect to the axis of the channel, forming a T-shaped channel and allowing rotation of the ring in both directions. In the latter case, it is important to remember in which direction the bayonet ring has been rotated to secure the collector nozzle, so that it can be rotated in the right direction when retrieving a spent collector nozzle.

(29) In an advantageous embodiment illustrated in FIG. 3, the bayonet ring comprises an outer surface provided with a thread (22t) mating a thread (21t) provided at an inner surface of the nozzle receiving bushing. This way, the rotation of the bayonet ring with respect to the nozzle receiving bushing translates the bayonet ring along the longitudinal axis, Z, and presses the collector nozzle deeper towards the bottom plate (22g). With this embodiment, the channel may abruptly widen from the downstream width, Wd, to the upstream width, and yet still allows pushing the collector nozzle along the longitudinal axis, Z, upon rotation of the bayonet ring.

(30) In another advantageous embodiment, the bayonet ring comprises an outer surface provided with a rotation stop (22b) shown in FIG. 3; and wherein the nozzle receiving bushing comprises a corresponding rotation stop (21b) provided at an inner surface of the nozzle receiving bushing, which stops rotation of the bayonet ring when the channels (22c) of the bayonet ring face the protrusion mating structures (21m) of the nozzle receiving bushing. With this embodiment, the position of a collector nozzle along the longitudinal axis, Z, can be reproduced consistently and very easily, without requiring any measurement or additional tool.

(31) As illustrated in FIG. 3, in order to facilitate rotation of the bayonet ring, it is preferred to provide the downstream edge of the bayonet ring with rotating means (22r), including protrusions or recesses, allowing the insertion of a tool for rotating the bayonet ring about the longitudinal axis, Z. This is very helpful for tightly securing the collector nozzle in place, and even more useful for unfastening the collector nozzle from the bayonet ring after use.

(32) The bayonet ring (22) is part of the nozzle coupling unit and remains in place when coupling a new collector nozzle to the bottom plate assembly. In one embodiment illustrated in 3 and 4, the bayonet ring is sandwiched between an upstream portion (21u) and a downstream portion (21d) of the nozzle receiving bushing. The upstream portion (21u) is rigidly fixed to the frame (200, and the downstream portion (20d) is rigidly fixed to the upstream portion. With this construction, the bayonet ring can rotate about the longitudinal axis but cannot be removed from the nozzle coupling unit without first uncoupling the downstream portion of the bushing from the upstream portion. Alternatively, the nozzle receiving bushing can be monolithic and coupled directly to the frame (200 sandwiching the bayonet ring between the bushing and the frame.

(33) Coupling of the Collector Nozzle to the Bottom Plate Assembly

(34) FIGS. 5A-5C show the various steps for securing a collector nozzle to a nozzle coupling unit, and FIG. 4 shows a transverse cut of a bottom plate assembly according to the present invention, with a collector nozzle secured in its operating position. The nozzle receiving bushing of FIGS. 5A-5C is provided with nozzle mating structures (21m). In such embodiment, as shown in 5A, the bayonet ring must first be rotated until the channels (22c) of the bayonet ring are positioned face to face with the corresponding nozzle mating structures (21m). The upstream surface of the collector nozzle (10) is then engaged through the bayonet ring (22) from the downstream edge (22d), with the N protrusions engaged in the corresponding channels (22c). As shown in FIG. 5B, the collector nozzle is then inserted along the longitudinal axis, Z, through the bayonet ring all the way until the protrusions (11) of the collector nozzle are engaged in the protrusion mating structures (21m). The collector nozzle is thus prevented from rotating with respect to the longitudinal axis, Z, but at this stage, it is not secured and can slide out along the longitudinal axis, Z. Absent protrusion mating structures (21m) the collector nozzle is not prevented from rotating about the longitudinal axis, Z. As shown in FIG. 5C, for securing the collector nozzle, the bayonet ring is rotated with respect to the longitudinal axis, Z, engaging the upstream portion of the channels over the protrusions until they contact an edge of the channels, thus locking the collector nozzle into its operating position, which cannot move along the longitudinal axis, Z, anymore.

(35) To optimize the locking operation, it is preferred that the geometry of the upstream portions of the channels and the portions of the protrusions which contact the channels' edges be complementary, avoiding contact areas generating excessive stress concentration, such as corners and the like. These portions of the protrusions are advantageously lined with a metal can (10c) lest the refractory would break upon rotating the bayonet ring too tightly.

(36) The same operations are carried in reverse to unlock and withdraw a spent collector nozzle. The bayonet ring (22) is first rotated to unlock the collector nozzle. Advantageously this is carried out with a tool gripping the rotation gripping means or rotation gripper (22r) of the bayonet ring. The collector nozzle can then be pulled out along the longitudinal axis, Z, with sufficient force to disrupt the sealing material (2). The bayonet ring remains within the nozzle receiving bushing and a new collector nozzle can be mounted again as described above.

(37) The present invention is highly advantageous in that all the foregoing operations can be carried out easily by a single operator or by a single robot. This is not the case with conventional systems comprising a separate bayonet ring, and collector nozzles provided with an integrated bayonet ring are much heavier to handle.

(38) Two- and Three-Plate Gates

(39) As illustrated in FIGS. 6A, 6B, 7A and 7B, the upstream surface (10u) of a collector nozzle is coupled to a surface of a bottom plate of a gate. A sealing contact between the two refractory surfaces is ensured by a sealing material (2). Prior to engaging the collector nozzle through the bayonet ring as discussed above, a bottom gate plate (20g) is positioned into the gate plate receiving unit of the frame (20f) and is rigidly coupled to the frame. A refractory sealing material (2) is applied onto the upstream surface (10u) of the collector nozzle, such that when the collector nozzle reaches its operating position with the upstream surface thereof contacting a downstream surface of the bottom gate plate, the sealing material is sandwiched between the collector nozzle and the bottom gate plate, forming a sealed contact between the two.

(40) The bottom plate assembly of the present invention is part of a gate system which is fixed to a bottom surface of a ladle (200L) by fixing means (3) well known to a person of ordinary skill in the art, and generally including screws and/or bolts.

(41) In a two-plate gate system as illustrated in FIGS. 6A and 6B, the bottom gate plate (20g) is provided with a bore and is coupled in sliding relationship by translation or rotation) to a top gate plate (30g) provided with a similar bore. The top gate plate (30g) is rigidly coupled to a top frame (30f which is itself rigidly coupled to the bottom of the ladle. The frame (20f) to which the bottom gate plate is rigidly coupled is a carriage which is mobile with respect to the top frame (30f). The movements of the carriage frame (20f) with respect to the top frame (300 are actuated by a pneumatic or hydraulic cylinder (20p) and/or an electric drive and allow sliding the bottom gate plate over the top gate plate (30g) such as to bring the bore of the gate plates in and out of registry, to open or close the gate (cf. FIGS. 6A and 6B).

(42) As can be seen in FIGS. 6A and 6B, because in two-plate gates, the collector nozzle is coupled to a mobile carriage frame (20f), the ladle shroud, which is an elongated tube engaged over the collector nozzle and extending far below the ladle bottom (cf. FIG. 1A), moves with the carriage as the bottom gate plate is being operated to open or close the gate, to control the molten metal flow rate. In some applications, such movements of the ladle shroud are not acceptable. In order to operate a gate without moving the collector nozzle and the ladle shroud coupled thereto, a three-plate gate can be used instead.

(43) A three-gate plate is illustrated in FIGS. 7A and 7B. Contrary to a two-gate plate, in a three gate-plate the bottom gate plate (20g) to which the collector nozzle is coupled is fixed with respect to the top gate plate (30g) and to the ladle outlet. The frame (200 is either rigidly fixed to, or forms a single structure with, the top frame (300. The flow rate of molten metal is controlled by moving a mid-gate plate (25g) sandwiched between the bottom and top gate plates. The mid-gate plate (25g) is provided with a bore similar to the bores of the bottom and top gate plates. By moving the mid-gate plate with respect to the bottom and top gate plates, the bore of the mid-gate plate is brought in or out of registry with respect to the bores of the bottom and top gate plates. This way, the flow rate of molten metal can be controlled without moving the collector nozzle (10) and the ladle shroud (111) coupled thereto.

(44) The description above focused on a collector nozzle coupled to a ladle (200L), for coupling a ladle shroud (111). It is clear that the same applies mutatis mutandis to a collector nozzle coupled to a tundish (200T) for coupling a pouring nozzle (101), or to any metallurgic vessel provided with a nozzle to be coupled thereto.

(45) Various features and characteristics of the invention are described in this specification and illustrated in the drawings to provide an overall understanding of the invention. It is understood that the various features and characteristics described in this specification and illustrated in the drawings can be combined in any operable manner regardless of whether such features and characteristics are expressly described or illustrated in combination in this specification. The Inventor and the Applicant expressly intend such combinations of features and characteristics to be included within the scope of this specification, and further intend the claiming of such combinations of features and characteristics to not add new matter to the application. As such, the claims can be amended to recite, in any combination, any features and characteristics expressly or inherently described in, or otherwise expressly or inherently supported by, this specification. Furthermore, the Applicant reserves the right to amend the claims to affirmatively disclaim features and characteristics that may be present in the prior art, even if those features and characteristics are not expressly described in this specification. Therefore, any such amendments will not add new matter to the specification or claims and will comply with the written description requirement under 35 U.S.C. § 112(a). The invention described in this specification can comprise, consist of, or consist essentially of the various features and characteristics described in this specification.

(46) TABLE-US-00001 Ref. # Feature  1 Molten metal  2 Sealing material  3 Rigid fixation  10 Collector nozzle  10b Collector nozzle bore  10c Can  10d Collector nozzle downstream surface  10L Collector nozzle lateral surface  10u Collector nozzle upstream surface  11 Protrusion  11d Protrusion lower surface  11u Protrusion upper surface  20 Nozzle coupling unit  20f Frame  20g Lower gate plate  20p Hydraulic piston  21 Nozzle receiving bushing  21b Blocking stop of bayonet ring rotation  21d Downstream portion of the nozzle receiving bushing  21m Protrusion mating structure  21t Thread of nozzle receiving bushing  21u Upstream portion of the nozzle receiving bushing  22 Bayonet ring  22b Rotation blocking stop  22c Channel for receiving protrusions  22d Downstream edge of the bayonet ring  22r Rotation gripping means or rotation gripper  22t Thread of bayonet ring  22u Upstream edge of the bayonet ring  25f Carriage supporting mid-gate plate 25 g  25g Mid-gate plate in a 3-plate gate  30f Upper frame  30g Upper gate plate 100 Inner nozzle 101 Pouring nozzle 111 Ladle shroud 200 Metallurgic vessel 200L Ladle 200r Refractory lining of the Metallurgic vessel 200T Tundish 211 Robot W Protrusion width (maximum) Wd Channel width adjacent the downstream edge Wu Channel width adjacent the upstream edge Z Longitudinal axis