Transfer system for liquid metals

Description

BACKGROUND OF THE INVENTION

Field of the Invention

[0001] The invention relates to a transfer system for liquid metals such as aluminum, zinc and magnesium. The invention also refers to a method of transferring liquid metals using the transfer system.

Description of the Related Art

[0002] The use of canals in the transfer of liquid metals from the furnace to the casting machine is widely known and used. In the past, these canals were made of refracting concrete but the use of such material generated a great loss of temperature in the liquid metal during its transfer. Due to the enormous amount of materials available nowadays, there are at least two conditions that must comply when choosing the correct material in the process of making the canals. The first condition that a chosen material chosen must comply is that the loss of temperature of the liquid metal when transferred from the furnace to the casting machine must be minimum. The second condition that a chosen material must meet is the resistance to chemical attack deriving from the molten metal transferred.

[0003] Most of the processes that in the past where made inside the furnace were converted into continuum process incorporating specific equipments for filtering and removing contaminating gases for the metal. Due to this modification, the length of the canals transporting the melted metal had to be lengthened, increasing therefore the loss of temperature during the transfer of liquid metal. In order to reduce such loss of temperature, the common solution was to increase the temperature of the liquid metal at the furnace, rendering a reduced loss of temperature of the liquid metal during its transfer. However, this obvious solution made the liquid metal to oxidize at a faster rate, rendering it to a more chemical aggressive material hence reducing the life of the canals. It is also important to mention that the increase of temperature in the liquid metal generated the incorporation of several contaminants such as hydrogen which solubility increased with the rise of the temperature.

[0004] At the late 70's, ceramic fibers were incorporated into the world of technological material. By using ceramic fibers in the construction of canals, the results of durability were surprisingly increased. However, the use of such canals was only useful in short casting process usually lasting between 4 to 5 hours. After that period the canals had to be replaced. As the use of aluminum was increased over time, the industry developed new equipments known as continuous casting machines, where the duration of the casting process can last up to several days.

[0005] The problem encountered, when using the canals made of ceramic fiber in the continuous casting process, was that after every casting period the canals had to be replaced, therefore generating an increase in the final cost of the product. A partial solution to such problem was to develop canals using materials with increased resistance to the chemical attack but the problem encountered then was that using such materials also increased the loss of temperature in the liquid metal. Therefore, the canals included improved thermal insulation in order to obtain a satisfactory result. However, at the beginning of the continuum casting process the use of gas burners had to be applied in such process. Gas burners are widely known and use in the casting process, but it is also widely known that the expose of a material to a constant and powerful flame stream reduced the life term of such material producing cracks and clefts. Alternatively, in the near zones of the burners it could be found a temperature difference within several hundreds of degrees which generates tensions and micro cracks shortening the life term of the canal. In order to avoid the use of gas burners to maintain the temperature with in the canal, the use of electrical heaters were implemented reducing the deterioration of the canal.

[0006] Due to the constant deterioration of the canals and the casting equipment where the liquid metal passes through, the maintenance schedule to follow in order to continue with the normal casting procedure requires several stopping times, which is inadmissible in continuous casting process. By using conventional canals, the average temperature of the liquid metal is sometimes greater than 100°C which is more that the normal temperature needed for casting. This represents a loss of 5° to 10°C by meter in the length of the canal. This loss of temperature can also generate the reduction or even the loss of the casting process. In the event that the casting process includes several hours, the interruption of a casting process due to parametrical miscalculations in the process can generate an important economic damage.

[0007] As stated before, transferring canals are made of ceramic fibers and the same are placed in a metal cradle which is used to support the canal and abut the canal with an adjacent one by means of a bridle in order to conform a full canal for transferring the liquid metal. Another important factor to consider is the great difference between the thermal expansion coefficient of the canal and the metal cradle, which generates metal leaks in the junction between abutting canals increasing the leakage during several casting processes.

[0008] Another important factor to consider is the level of the liquid metal during the transfer between the furnace and the casting machine. When the liquid metal gets in contact with the mould a thin layer of solid is formed which contains the remaining of the liquid metal. This is a dynamic process where the solid layer generated is removed at constant speed and the new liquid metal arrives at the mould. The quality of the obtained piece depends mostly on the stability of the solid/liquid interaction and its contact with the mould in the process of solidification. The variation in the metal level at the feeding system of the moulds modifies the liquid pressure and disarrays the contact between the thin solid layer and the mould. The final result becomes a noticeable reduction in the length of the casting process

SUMMARY OF THE INVENTION

[0009] The present invention relates to a transfer system for liquid metal from a furnace to a casting machine wherein the system lengthens the life term of the transfer canal while used on several casting process.

[0010] The present invention also relates to

[0011] a method for controlling the liquid metal transfer between a furnace and a casting machine allowing to automatically maintaining the liquid metal level during said liquid metal transfer.

[0012] The above-discussed and other features and advantages of the present invention will be appreciated and understood by those of ordinary skill in the art from the following detailed discussion and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Referring now to the drawings, wherein like elements are numbered alike in the several FIGURES:

FIG. 1 a schematic view of the system in accordance with the present invention;

FIG. 2 is a front elevation view, partly in cross-section, of a canal in accordance with the present invention;

FIG. 3 is a schematic drawing of the use of the method of the present invention with the system of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Referring initially to FIG. 1 the transfer system of the present invention comprises a central operation panel 2 which controls and commands a PLC (Programmable Logic Controller) 3. As stated on FIG. 1, the PLC controls the performance of a hydraulic central 4 which commands the movement of a balanced valve 5. This balanced valve actuates on a hydraulic cylinder 6 controlling the tilt of a casting furnace 7.

[0015] A laser sensor 8 detects the liquid metal level in the conduit 9 when the liquid metal is poured from the furnace 7 towards the casting machine 22 (FIG. 3). The data acquired by the laser sensor 8 is sent to the PLC 3 to adjust the furnace's tilting. The sensor 8 must be configured to detect the presence of liquid metal at a pre settled level bearing that the level 0 is the base of the canal. Said level can be settled according to the specific configuration of the casting process. The laser sensor 8 should be placed near the outlet of the furnace 7 but said sensor 8 can be used in any available position where it can be determined the level of the liquid metal in the conduit 9.

[0016] Making reference to FIG. 3, the conduit 9 is build based on a plurality of adjacent canals 10 abutted each other by means of nuts and bolts. Between every abutment a compressible gasket I made of ceramic fiber is placed in order to reduce the leakage of the liquid metal once is transferred from the furnace 7 towards the casting machine 22. Any skilled in the art could notice that the use of bolts and nuts as a mean for abutting several canals 10 in order to make the conduit 10 is just an example and that any means for joining two or more canals such as welding, riveting, clinching and so, can be used without leaving the scope of the present invention. However, it is preferable to use any means to adjoin two or more canals that will allow performing a fast replacement of the damaged canals and thus maintaining the modular condition of the conduit 9.

[0017] The canal 10 showed in FIG. 2 comprises a first U shape profile 12 in which a second U shape profile 14 is placed, being separated both profiles by an insulate layer 13. The profile 14 defines a path for the liquid metal to be transferred from the furnace 7 to the casting machine 22. In the present embodiment, the first profile 12 is made of a steel alloy while the second profile 14 is made of a refracting ceramic material. Moreover, the insulated layer 13 can be made of any insulate material such as fiber glass, ceramic fiber, microporous insulation panels, asbestos, refracting mud or the combination thereof. A lid 15 is placed on top of first and second profiles protecting the edges of such profiles from breakage when cleaning the conduit 10 once the casting process is over.

[0018] As seen on FIG. 2, a cover 17 is attached with a hinge 18 to the first profile 12. The cover is actuated by pneumatic or hydraulic means (not shown) controlled by said PLC 3. Said cover includes heat generating means 16 attached to the internal portion of the cover by an insulate layer 19. The insulate layer 19 can be made of the same material as the insulated layer 13. Said heat generating means 16 are defined by electric resistance heating elements 20 enclosed in metal tubes that emit heat in the form of infrared rays. Even though the number of electrical resistance heating elements 20 illustrated in FIG. 2 are only two, the number of such heating elements 20 can be as many as needed depending on the particular casting process. On the other hand, even if it is possible to replace said heating elements 20 with gas burners, the use of such gas burners can compromise the safety of the whole casting line. However, the use of heating elements 20 as means for generating heat in the canals 9 cannot be considered as limiting the scope of the invention, since it will be obvious to any skilled in the art replacing the heating elements 20 by any other heating source available. As seen on FIG 3, the transfer system of the present invention comprises at least two heat sensors 23. Said sensors 23 are placed preferably one near the outlet of the furnace 7 and the other near the inlet of the casting machine 22. This sensor deployment allows the system to strictly control any differential of temperature along the total transfer of the liquid metal over the conduit 10. It can be appreciated that the use of more than two heat sensors is included within the bound of the scope of the invention, since it will be obvious to any skilled in the art to notice that the greater the number of heat sensors the better the result in maintaining the temperature level would be. On the other hand, the heat sensors 23 can be any sensor commercially available such as laser beam sensor, thermocouple or a combination of both.

[0019] From the safety point of view, the transfer system includes a complex electrical wiring (not shown) including current and voltage detectors that controls any variation such as in the heating elements 20 or heat sensors 23, allowing the operator of the casting line to control the temperature process. As it is shown in FIG. 2, canals 9 are placed over a double T beam 21. Such beam 21 is used as a strong and firm support platform for the total length of the conduit 10.

[0020] For a better comprehension of the present invention, an explanation of the use and functionality of the whole system will be explained in detail using all the figures mentioned before. As every casting process, the same begins at the furnace 7. The metal in liquid form is placed inside said furnace 7 kept at a melting point until it is ready to be poured in the conduit 10. For the present embodiment, the casting process will be explained using aluminum as the metal to be transferred. The aluminum in liquid form is kept in the furnace at approximately 720 °C. Once the furnace 7 is tilted the pouring of the liquid metal in the conduit 10 occurs. This pouring method is based on a gravity pouring and the tilting degree is graduated and maintained by the hydraulic cylinder 6. Once the furnace 7 is tilted and the pouring begins, the laser sensor 8 controls the level of the metal poured and acquires data about the minimum and maximum levels and sends them to the PLC unit 3. The PLC unit then verifies that said data sent by the sensor 8 is within the parameters already configured in the PLC unit. In the event that the data sent by the sensor 8 is either over or below the parameters configured, the PLC unit sends the instructions to the hydraulic central 4 to command, by means of the balanced valve 5, the corresponding hydraulic cylinder 6 to either increase or decrease the tilt degree of the furnace 7. Once the data sent by the sensor 8 is within the parameters configured in the PLC unit, the tilting of the furnace 7 stops.

[0021] Once the liquid metal starts flowing through the conduit 10 in order to reach the casting machine, the breach in the temperature from the furnace's outlet and from the casting machine's inlet is increased proportionally to the length of the conduit 10. Therefore, sensors 23 gather the temperature in both places and each one sends the information to the PLC unit. The PLC unit compares the data received with the parameters previously configured. In the event that the temperature drops a few degrees, the PLC unit sends the instructions to a hydraulic center (not shown) which commands the closing of the covers 17 in order to reduce the loss of temperature. If the temperature keeps dropping the sensors 23 detect such drop and send the information to the PLC unit. Afterwards, the PLC unit processes the information and controls the ignition of the heating elements 20 in order to rise and maintain the heat of the liquid metal within the temperature parameters. In order to keep the temperature as homogenous as possible in the total length of the conduit 10, the PLC unit can individually control the ignition of the heat elements 20 in each canal 9, thus keeping a stricter control on the temperature range.

[0022] Once the casting procedure is finished, which as stated before it could last several days, the maintenance routine commences. This routine comprises the complete checking and control of each and every canal 9. In the event that one or more canals 9 show any sign of major attrition such canal can be easily replaced by a new one thanks to the modular construction concept that the conduit 10 has. On the other hand, if one or more canals 9 shows any small sign of ware, such as cracks in the ceramic fiber surface in the second profile, the same can be replaced in situ. This is possible since each canal has an easy construction configuration which allows the replacement of any part involved in the construction of the canal 9. As experience shows, the second profile is the part which suffers greater deterioration between several casting processes. Fixing in situ or replacing such second profile reduces the costs of maintenance of the casting process.

[0023] Finally, it is important to mention that even though the length of the canals 9 was not mentioned, the same can vary depending on the casting line to be used and also said canals can be formed in different shapes, not only straight line canals, but also Y shaped canal, curves or any desirable form needed to evade any obstacle in the process of building a casting line.

Claims

1. A method for controlling the transfer of liquid metal from a furnace to a casting machine wherein comprises the steps of:

a) tilting the furnace to a degree until the liquid metal is poured into a conduit;

b) obtaining the level information in said conduit by means of a level sensor (8);

c) sending the data obtained by said level sensor to a programmable logic controller (3);

d) controlling the tilt degree of the furnace by comparing the data sent by the level sensor and the data already pre programmed;

e) controlling the temperature of the liquid metal near inlet and near outlet of the conduit and sending the temperature data to the PLC (3);

f) activating a hinged covers (17) in case the differential temperature is below a level pre settled in the programmable logic controller;

g) igniting heat generator means (16) in the event that the temperature is still below the pre settled level even after the hinged cover was activated;

h) regulating the temperature by activating individually said hinged covers and said heat generator means.

2. The method according to claim 1 wherein comprise the additional steps of:

a) increasing the tilt degree of the furnace in the event that said level detector detects a decrease in the level of the liquid metal in the conduit.

b) decreasing the tilt degree of the furnace in the event that said level detector detects an increase in the level of the liquid metal in the conduit.

3. The method according to claim 1 wherein the activation of said hinged cover is strictly related to data supplied by the heat sensor to the programmable logic controller.

4. A system for performing the method of claim 1 comprising:

- a PLC (3) controlled by a central operation panel (2);

- a hydraulic central system (4) operatively connected to a balanced valve (5) acting on a hydraulic cylinder (6) on command of the PLC (3) for tilting the furnace to a degree so that the liquid metal is poured into a conduit (10);

- a laser level sensor (8) for detecting the level of the liquid metal running through the conduit, said' level sensor (8) being connected to said PLC (3) for sending the level information in said conduit;

- said PLC (3) being able to verify that said level information is within parameters already configured in the PLC (3) and being able to send instructions to the hydraulic central system (4) for commanding said hydraulic cylinder (6) for adjusting the tilt degree of the furnace (7);

- at least two heat sensors (23) for determining the differential temperature of the liquid metal along the conduit (10) and sending the temperature data to the PLC (3);

- a cover (17) actuated by pneumatic or hydraulic means controlled by said PLC (3) for being closed in case the detected differential temperature is below a level pre settled in the PLC (3);

- said cover (17) including heat generating means (16) attached to the internal portion of the cover by an insulate layer (19);

- said PLC (3) being able to process the temperature data for igniting the heat generator means (16) in order to rise and maintain the heat of the liquid metal within preset parameters.

5. The system according to claim 4 wherein said a conduit (9) comprises at least a canal (10) containing a first profile (12) and a second profile (14) within said first profile (12).

6. The system according to claims 4 and 5 wherein a plurality of said canals (10) is abutted each other by attaching means such as nuts and bolts, welding, bridle, defining a modular conduit.

7. The system according to claim 4 wherein said at least one level sensor (8) is placed in the vicinity of the furnace's outlet.

8. The system according to claim 5 wherein the first profile (12) and the second profile (14) of the canal (10) are U shaped, said two profile (12, 14) being separated by an insulate layer (13), said second u shaped profile (14) defining a path fro the liquid metal to be transferred from the furnace (7) to the casting machine, said cover (17) being attached with a hinge (18) to the first U shaped profile (12).

9. The system according to claim 8 wherein said first U shaped profile (12) is attached to a double T beam.

10. The system according to claim 8 wherein the insulate layer (13) is made of fiber glass, ceramic fiber, microporous insulation panels, asbestos, refracting mud or the combination thereof.

11. The system according to claim 8 wherein said first U shaped profile (12) is made of a steel alloy.

12. The system according to claim 8 wherein said second U shaped profile (14) is made of any of fiber glass, ceramic fiber, microporous insulation panels, asbestos, refracting mud or the combination thereof.

13. The system according to claim 4 wherein said heating generator means (16) are electric resistance heating elements (20) enclosed in metal tubes that emit heat in the form of infrared rays.

14. The system according to claim 8 wherein a lid (15) is placed on top of first and second profiles (12, 14) protecting the edges of such profiles from breakage.

15. The system according to claim 8 wherein said hinged cover (17) attached to said first U shaped profile (12) is actuated by hydraulic means.

16. The system according to claim 8 wherein the canal (10) comprises said heat sensors (23) placed on either ends of the canal.

17. The system according to claim 16 wherein said heat sensors (23) are one of a laser beam sensors, a thermocouples or a combination of both.

Ansprüche

1. Übergabe-System für Flüssigmetalle aus einem Ofen in eine Gießmaschine, umfassend die Schritte:

a) Kippen des Ofens um einen Winkel, das ausreichend ist, das Flüssigmetall in eine Leitung einzugießen,

b) Einholen von Daten über den Flüssigkeitsfüllstand in der genannten Leitung mittels eines Füllstandsensors (8),

c) Zuführen der durch den genannten Füllstandsensor erhaltenen Daten einer PLC-Steuerung (3),

d) Überprüfen des Kippengrads des Ofens durch Vergleich der von dem genannten Füllstandsensor gesendeten Daten mit den vorprogrammierten Daten,

e) Ermitteln der Temperatur des Flüssigmetalls nahe am Leitungseinlass und -auslass sowie Zuführen der Temperaturdaten der PLC-Steuerung (3),

f) Antrieb einer eingehängten Kappe (17), falls die Differentialtemperatur unterhalb eines in der PLC-Steuerung vorbestimmten Pegels liegt,

g) Einschalten eines Wärmeerzeugers (16), falls die Temperatur noch unterhalb des vorbestimmten Pegels liegt, nachdem die eingehängte Kappe angetrieben worden ist,

h) Einstellen der Temperatur durch individuellen Antrieb der genannten eingehängten Kappe sowie des genannten Wärmeerzeugers.

2. System nach Anspruch 1, umfassend die zusätzlichen Schritte:

a) Erhöhung des Kippwinkels des Ofens, falls der genannte Füllstands-Sensor eine Füllstandsenkung des Flüssigmetalls in der Leitung ermittelt,

b) Herabsetzung des Kippwinkels des Ofens, falls der genannte Füllstands-Sensor einen Füllstandanstieg des Flüssigmetalls in der Leitung ermittelt.

3. System nach Anspruch 1, wobei die Ansteuerung der genannten eingehängte Kappe eng von Daten abhängt, die vom Wärmefühler der PLC-Steuerung zugeführt werden.

4. Anlage zur Durchführung des Systems nach Anspruch 1, umfassend:

- eine durch eine Zentralbedienplatte (2) gesteuerte PLC-Steuerung (3),

- ein zentrales hydraulisches System (4), das mit einem Entlastungsventil (5) operativ verbunden ist, welches vom PLC (3) gesteuert auf einen Hydraulikzylinder (6) derart zum Kippen des Ofens wirkt, dass das Flüssigmetall um einen Winkel dermaßen kippt, dass das Flüssigmetall in eine Leitung (10) eingegossen wird,

- einen Laserfüllstandsensor (8) zum Ermitteln des Füllstandes des durch die Leitung fließenden Flüssigmetalls, wobei der genannte Füllstandsensor (8) mit der genannten PLC-Steuerung (3) zum Zuführen der Füllstanddaten betreffend die genannte Leitung verbunden ist,

- wobei die genannte PLC-Steuerung (3) feststellen kann, ob die genannten Füllstanddaten innerhalb von in der PLC-Steuerung (3) vorbestimmten Parametern liegt, und sie ist ferner imstande, dem hydraulischen System (4) Befehle zum Steuern des genannten Hydraulikzylinders (6) zu senden, um den Kippwinkel des Ofens (7) einzustellen,

- wenigstens zwei Wärmefühler (23), um die Differentialtemperatur des Flüssigmetalls entlang der Leitung (10) festzustellen und die Temperaturdaten der PLC-Steuerung (3) zuzuführen,

- eine Kappe (17), die von pneumatischen bzw. hydraulischen durch die genannte PLC-Steuerung (3) gesteuerten Mitteln angetrieben wird, welche geschlossen wird, falls die ermittelte Differentialtemperatur unterhalb eines in der PLC-Steuerung (3) vorbestimmten Wertes liegt,

- wobei die genannte Kappe (17) Wärmeerzeuger (16) umfasst, die mit der inneren Seite der Kappe über eine Isolierschicht (19) verbunden ist,

- wobei die genannte PLC-Steuerung (3) zum Bearbeiten der Temperaturdaten ausgelegt ist, um die Wärmeerzeuger (16) derart einzuschalten, dass die Wärme des Flüssigmetalls erhöht und innerhalb von vorbestimmten Parametern gehalten wird.

5. Anlage nach Anspruch 4, wobei die genannte Leitung (9) wenigstens einen Kanal (10) umfasst, der ein erstes Profil (12) und ein zweites Profil (14) innerhalb des genannten ersten Profils (12) enthält.

6. Anlage nach Anspruch 4 und 5, wobei mehrere unter den genannten Kanälen (10) aneinander über Befestigungsmittel wie Muttern, Bolzen, Schweißen, Sperren befestigt sind, sodass eine Modulleitung gebildet wird.

7. Anlage nach Anspruch 4, wobei der genannte wenigstens eine Füllstandsensor (8) in der Nähe des Ofenauslasses angeordnet ist.

8. Anlage nach Anspruch 5, wobei das erste Profil (12) und das zweite Profil (14) des Kanals (10) U-förmig sind, wobei die genannten zwei Profile (12, 14) durch eine Isolierschicht (13) voneinander getrennt sind, wobei das genannte zweite U-förmige Profil (14) einen Weg zur Übergabe des Flüssigmetalls vom Ofen (7) der Gießmaschine bildet, und wobei die genannte Kappe (17) mit dem ersten U-förmigen Profil (12) über ein Gelenk (18) verbunden ist.

9. Anlage nach Anspruch 8, wobei das genannte U-förmige Profil (12) an einem Doppel-T-Träger befestigt ist.

10. Anlage nach Anspruch 8, wobei die Isolierschicht (13) aus Glasfasern, Keramik fasern, mikroporösen Isolierpaneelen, Asbest, feuerfestem Schlamm, oder deren Kombination besteht.

11. Anlage nach Anspruch 8, wobei das genannte erste U-förmige Profil (12) aus einem Stahllegierung besteht.

12. Anlage nach Anspruch 8, wobei das genannte zweite U-förmige Profil (14) aus irgend einem unter Glasfasern, Keramik fasern, mikroporösen Isolierpaneelen, Asbest, feuerfestem Schlamm, oder deren Kombination besteht.

13. Anlage nach Anspruch 4, wobei die genannten Wärmeerzeuger (16) in Metallrohren enthaltene Elektrowiderstandheizelemente (20) sind, die Wärme in Form von Infrarotstrahlen abgeben.

14. Anlage nach Anspruch 8, wobei ein Deckel (15) auf der Oberseite der ersten bzw. der zweiten Profile (12, 14) angeordnet ist, der die Ränder der genannten Profile schützt.

15. Anlage nach Anspruch 8, wobei die genannte am genannten ersten U-förmigen Profil (12) befestigte eingehängte Kappe (17) durch Hydraulikmittel angetrieben wird.

16. Anlage nach Anspruch 8, wobei der Kanal (10) an dessen beiden Enden die genannten Wärmefühler (23) enthält.

17. Anlage nach Anspruch 16, wobei die genannten Wärmefühler (23) eine unter einem Laserbündelsensor, einem Thermopaar, oder einer Kombination derselben sind.

Revendications

1. Méthode pour contrôler le transfert d'un métal liquide depuis un fourneau jusqu'à une machine de moulage, cette méthode comprenant les étapes de:

a) incliner le fourneau à un certain degré jusqu'à quand le métal liquide est versé dans un conduit;

b) obtenir les informations concernant le niveau dans ledit conduit par l'intermédiaire d'un détecteur de niveau (8);

c) envoyer les données obtenues par ledit détecteur de niveau à un contrôleur logique programmable (PLC) (3);

d) contrôler le degré d'inclinaison du fourneau en comparant les données envoyées par le détecteur de niveau et les données déjà programmées à l'avance;

e) contrôler la température du métal liquide à proximité de l'entrée et de la sortie du conduit et envoyer les données relatives à la température au PLC (3) ;

f) activer une couverture à charnière (17) si la différence de température est au-dessous d'un niveau préétabli dans le contrôleur logique programmable;

g) allumer des moyens générateurs de chaleur (16) dans le cas où la température est encore au-dessous du niveau préétabli même après avoir activé la couverture à charnière;

h) régler la température en activant individuellement lesdites couvertures à charnière et lesdits moyens générateurs de chaleur.

2. Méthode selon la revendication 1, laquelle comprend les étapes supplémentaires de:

a) augmenter le degré d'inclinaison du fourneau dans le cas où ledit détecteur de niveau détecte une diminution du niveau du métal liquide dans le conduit;

b) réduire le degré d'inclinaison du fourneau dans le cas où ledit détecteur de niveau détecte une augmentation du niveau du métal liquide dans le conduit.

3. Méthode selon la revendication 1, dans laquelle l'activation de ladite couverture à charnière est étroitement liée aux données fournies par le détecteur de chaleur au contrôleur logique programmable.

4. Système pour la mise en oeuvre de la méthode de la revendication 1, comprenant:

- un PLC (3) contrôlé par un panneau central de fonctionnement (2);

- un système hydraulique central (4) relié de manière opérante à une soupape équilibrée (5) agissant sur un cylindre hydraulique (6) sur commande du PLC (3) pour incliner le fourneau à un tel degré que le métal liquide est versé dans le conduit (10);

- un détecteur de niveau laser (8) pour détecter le niveau du métal liquide s'écoulant à travers le conduit, ledit détecteur de niveau (8) étant relié audit PLC (3) pour envoyer les informations sur le niveau dans ledit conduit;

- ledit PLC (3) étant en mesure de vérifier si lesdites informations sur le niveaux sont dans les paramètres déjà configurés dans le PLC (3) et étant en mesure d'envoyer des instructions au système hydraulique central (4) pour commander ledit cylindre hydraulique (6) pour le réglage du degré d'oscillation du fourneau (7);

- au moins deux détecteurs de chaleur (23) pour déterminer la différence de température du métal liquide le long du conduit (10) et envoyer les données sur la température au PLC (3);

- une couverture (17) actionnée par des moyens pneumatiques ou hydrauliques contrôlés par ledit PLC (3) pour qu'elle soit fermée dans le cas où la différence de température détectée est au-dessous d'un niveau préétabli dans le PLC (3);

- ladite couverture (17) comprenant des moyens générateurs de chaleur (16) attachés à la portion intérieure de la couverture par une couche d'isolement (19) ;

- ledit PLC (3) étant en mesure de traiter les données relatives à la température pour allumer les moyens générateurs de chaleur (16) dans le but d'élever et maintenir la chaleur du métal liquide dans les paramètres préétablis.

5. Système selon la revendication 4, dans lequel ledit conduit (9) comprend au moins un canal (10) contenant un premier profil (12) et un deuxième profil (14) à l'intérieur dudit premier profil (12).

6. Système selon les revendications 4 et 5, dans lequel une pluralité desdits canaux (10) aboutent les uns contre les autres par des moyens d'attache tels que écrous et boulons, soudage, joints anglais, définissant un conduit modulaire.

7. Système selon la revendication 4, dans lequel ledit au moins un détecteur de niveau (8) est mis à proximité de la sortie du fourneau.

8. Système selon la revendication 5, dans lequel le premier profil (12) et le deuxième profil (14) du canal (10) sont en forme de "U", lesdits deux profils (12, 14) étant séparés par une couche d'isolement (13), ledit deuxième profil en "U" (14) définissant un parcours pour le métal liquide à transférer du fourneau (7) à la machine de moulage, ladite couverture (17) étant attachée par une charnière (18) au premier profil (12) en forme de "U".

9. Système selon la revendication 8, dans lequel ledit premier profil (12) en forme de "U" est attaché à une poutrelle à double "T".

10. Système selon la revendication 8, dans lequel la couche d'isolement (13) est réalisée en fibre de verre, fibre céramique, panneaux microporeux d'isolement, amiante, boue réfractaire ou une combinaison de ceux-ci.

11. Système selon la revendication 8, dans lequel le premier profil en forme de "U" (12) est réalisé en un alliage d'acier.

12. Système selon la revendication 8, dans lequel ledit deuxième profil en forme de "U" (14) est réalisé en une quelconque parmi fibre de verre, fibre céramique, panneaux microporeux d'isolement, amiante, boue réfractaire ou une combinaison de ceux-ci.

13. Système selon la revendication 4, dans lequel lesdits moyens générateurs de chaleur (16) sont des éléments de chauffage (20) comportant des résistances électriques (20) renfermées dans des tubes métalliques émettant de la chaleur sous forme de rayons infrarouges.

14. Système selon la revendication 8, dans lequel un couvercle (15) est mis au sommet des premier et deuxième profils (12, 14) pour protéger les bords desdits profils contre la rupture.

15. Système selon la revendication 8, dans lequel ladite couverture à charnière (17) attachée audit premier profil (12) en forme de "U" est actionnée par des moyens hydrauliques.

16. Système selon la revendication 8, dans lequel le canal (10) comprend lesdits détecteurs de chaleur (23) mis aux deux extrémités du canal.

17. Système selon la revendication 16, dans lequel lesdits détecteurs de chaleur (23) sont un détecteur choisi parmi des détecteurs laser, un thermocouple ou une combinaison des deux.

Drawing