Abstract:
A tank for liquid metal processing tilting about an axis and fed by a fixed chute and pouring the liquid metal into a fixed evacuating chute. The tank includes at least a passage hole for supplying, discharging, or emptying the liquid metal arranged in one of its walls and extended by a mobile nozzle integral with the tank. At least the fixed evacuation chute merges with the tilting axis and the nozzle. Further, the fixed chute is assembled together by a linking device articulated in rotation about the tilting axis.

Description:
FIELD OF THE INVENTION 
     The present invention concerns a tilting vessel for treatment of liquid metal, typically for the gas treatment or filtration of liquid aluminium or magnesium or their alloys, and its sealed connection device with fixed troughs used to feed or evacuate said liquid metal from the vessel. 
     DESCRIPTION OF RELATED ART 
     A vessel for the treatment of liquid metal by gases or filtration or simply for its storage, generally has a capacity of no more than 3 tonnes and comprises feed and outlet devices for the liquid metal. Said liquid metal enters and leaves the vessel continuously, however it is necessary to empty the vessel regularly either in full or in part by tilting about a horizontal axis at an angle which typically lies between 30° and 90°. In addition, the vessel may be provided with a special drainage hole positioned in its lower part. 
     The outlet device for the liquid metal comprises a port, or tap out, usually provided at the top of one of the vessel walls, extended by a casting spout to pour the liquid metal into a fixed evacuation trough. The feed device for supplying liquid metal from a fixed trough is generally of the same type. Typically the vessel is a rectangular parallelepiped and the tilting axis is parallel to its greatest length. It is essential that the articulated connection between the spout integral with the vessel and the fixed trough should remain impervious to liquid metal at high temperature, despite the repeated cycles of heating and cooling in the installation. 
     Liquid metal is known to be poured into a fixed trough perpendicular to the axis of horizontal tilting. The latter, usually positioned at the level of the tap out, is then offset outside the vessel and passes through the end common to the spout and trough which are arranged in continuation of one another. 
     When the vessel is tilted, it is seen that the outlet spout of the said vessel and the fixed trough form a variable angle, and that the connection between these two parts must be articulated and sealed. To achieve the seal of this articulation, a metal knuckle joint is known to be placed on the outside around the ends of the spout and fixed trough, and the inner surface of the said knuckle joint is packed with a lining, which may be graphite-based braided rope, to ensure the seal with the outer surfaces of the spout and the trough. Therefore, when the vessel is tilted, its outlet spout rubs against the lining of the knuckle joint, moving in sealed manner. 
     When tilted, the vessel provided with this arrangement requires considerable space, in particular when the tilt angle is 90°, this space requirement being due to the fact that the tilt axis passes through the end of the spout. In addition, metal may freeze in the articulated device, in particular between the metal knuckle joint, the spout and the trough, which complicates and substantially hinders maintenance or dismounting operations. 
     Also, furnaces for melting and storing liquid metal are known, having a large capacity (several dozen tonnes) which tilt about a horizontal axis and pour the liquid metal into a fixed trough positioned in the continuation of said axis, whose angle of tilt generally does not exceed 10 to 20°. In this case, a sealed rotating connection between the casting spout integral with the furnace, also positioned on the tilt axis, and the fixed trough of semi-circular section, consists of fitting and adjusting inside the latter the spout that is integral with the vessel which also has a semi-circular section slightly smaller in diameter, and of causing the two semi-circular parts to slide in rotation relative to one another by means of a seal lining, often in graphite-based, placed between the two. 
     Such device can only be used over small angles of tilt owing to the fact that the lining is pulled as soon as the tilt angle becomes fairly wide. Therefore, this device cannot be applied to treatment vessels, in particular to those which tilt at wide angles. In addition, it is difficult to obtain a good seal owing to the fact that said two parts fitted into one another have different dilation in diametrical direction, that the troughs easily deform after the numerous heat cycles they undergo, and that the clamping force of the lining cannot be adjusted. Moreover, there is a considerable risk of the device becoming blocked on account of the metal which may slide into and freeze inside the interstice between the spout and the trough. 
     The applicant therefore set out to avoid the above disadvantages and to develop a tilting vessel for treatment with reduced tilt volume which is simultaneously provided with an articulated connection device, between the spout integral with the vessel and the fixed trough, which is perfectly sealed while being of simple design and use (adjustment, maintenance, dismounting, cleaning) and without the possibility of said device causing freezing of the liquid metal. 
     SUMMARY OF THE INVENTION 
     The invention is a vessel for treating liquid metal, tilting about an axis, fed by a fixed trough and pouring said liquid metal into a fixed evacuation trough, said vessel comprising at least one passage hole for feeding, evacuating or emptying the liquid metal, arranged in one of its walls and extended by a so-called mobile spout integral with the vessel, characterized in that at least the axis of the fixed evacuation trough merges with the tilt axis. 
     Usually the axis of the feed trough also merges with the tilt axis. It is particularly advantageous to provide this arrangement for vessels which tilt at an angle greater than 30° which may reach 90°. 
     Generally, the vessel is at least approximately a rectangular parallelepiped, its walls possibly being slightly tapered, and the tilt axis is parallel to its greater length, that is to say parallel to the longer walls and perpendicular to the shorter walls. 
     Said tilt axis preferably passes through an upper angle of said shorter walls; in this case, it not only merges with the axes of the fixed troughs and mobile casting or feed spouts, but also with those of the casting or feed holes. But it may very well be located at another point of the vessel or even offset outside the vessel; in this case it again merges with the axes of the fixed troughs and mobile spouts. 
     According to the invention, the ends of the mobile spouts and fixed troughs having a circular section, aligned along the tilt axis, are linked by a connection device articulated in rotation about said axis, impervious to liquid metal, able to rotate at an angle of more than 30° which may reach 90° without losing its seal properties and thereby allowing full or partial emptying of the vessel. 
     Said device articulated in rotation according to the invention comprises: 
     an adapter flange secured to the end of the spout, centred over the tilt axis, comprising a circular seal bearing whose plane is perpendicular to said axis, 
     a connection flange secured to the end of the fixed trough, centred over the tilt axis, comprising a circular seal bearing whose plane is perpendicular to said axis, facing and co-operating with the preceding seal bearing; 
     at least one seal resistant to heat and liquid metal positioned between the two bearings; 
     a clamp device, optionally supported by a fixed part, used to adjust and maintain the clamping of the flanges relative to one another to ensure the sealed connection while allowing said flanges to pivot relative to one another. 
     Preferably two graphite-based seals are provided, one fixed to the bearing of each flange, which rub against one another. 
     The mobile spout and fixed trough being positioned in continuation one after the other so that the bearings of the seals which face one another correspond perfectly, it is advantageous to place centering means on each of the flanges which co-operate together and may form a centering device. 
     Therefore one of the flanges may comprise a cylindrical projection at whose end the seal bearing may be placed; this circular projection, like the flange, is designed so that it slide fits into a corresponding housing positioned on the other flange at the bottom of which the other seal bearing may be placed so that it faces the bearing of the first flange. It is seen that these two parts, by fitting into one another, ensure the centering of the seal bearings. 
     To achieve the liquid metal seal, while maintaining an appropriate friction force to enable the rotation of one flange relative to the other, all that is needed is to tighten the two seals against each other using the clamp device. To prevent the fixed trough from being pulled when the spout rotates, it is advantageous to reinforce its immobilisation in the vicinity of the connection flange, for example by means of reinforcement bars integral with a frame. 
     The clamp device may comprise screw tie rods supported firstly by one of the support parts integral with the frame, either fixed or preferably manoeuvrable, and secondly on the connection flange via elastic parts, for example springs or cambered washers of “belleville” type. Nuts are used to adjust the clamping force by compressing the elastic parts as required. The elastic parts also enable the seal to be maintained during heat cycles by absorbing the dilatations. 
     It can be seen that with this kind of device, in which the dilatations occur in the axis, it is possible to overcome recurrent or endemic deformations due to the heat cycles to which the unit is subjected during stoppage and re-start up of the vessel, and to achieve the desired seal while preventing any undue leakage or freezing of the liquid metal which could hinder vessel operation. Also, to dismount the device for its cleaning or maintenance (for example to change the seals) all that is required is to draw the two flanges away from one another. 
     To facilitate dismounting, it is also possible to extend the connection flange by a portion of fixed trough secured to the actual fixed trough by means of a rigid fixing device (for example using flanges integral with the trough and the portion of trough, bolted together) that is sealed, easy to dismount and accessible, and to lay the entire unit (portion of fixed trough, connection flange, clamp device) on a mobile carriage which also carries the support frame for the clamp device. To dismount, the fixed trough only needs to be uncoupled from the portion of trough and the latter can then be drawn away, with its connection flange, from the mobile spout fitted with its adapter flange after releasing the clamp device. 
     The flanges are generally in steel or refractory cast iron; the inside of the portion of fixed trough may be lined with the same refractory product as the spouts, troughs or vessel for liquid metal. 
     The device of the invention applies to the connection of the liquid metal vessel to its evacuation trough as well as to its feed trough. When it applies to both, the latter are positioned on the same axis, as described above. 
     The invention also concerns vessels for liquid metal comprising one or more articulated connection devices, and the processes which use the vessels or said devices according to the invention. These processes are in particular filtration or gas treatment of liquid metals such as aluminium, magnesium or their alloys. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates the invention and shows a view of a vessel for liquid metal whose tilt axis passes through the upper part of one of its walls. 
     FIG. 2 shows a profile view of a connection articulated in rotation mounted on a vessel for liquid metal of the type shown in FIG.  1 . 
     FIG. 3 shows a profile view of the preferred embodiment of the connection articulated in rotation according to the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows the positioning of a passage hole  5  for casting, emptying or feeding the liquid metal, and of the spout  7  extending it towards a shorter wall  2  of vessel  1 . The passage hole  5  is located in the upper part of said vessel, adjacent to a long wall  25  (cross-section view) perpendicular to the short wall  2 . The tilt axis  6  passes through its centre and is parallel to said long wall  25 . It can be seen that by means of this arrangement and the sealed, articulated connection device according to the invention, it is easily possible to empty the vessel completely by tilting it in the direction of the arrow  24 , the space needed for this operation being reduced to the minimum. 
     In FIG. 2, reference  1  shows a vessel for liquid metal which is parallelepiped, with a short wall  2  that is slightly tapered, coated on the inside with a refractory material  2   a  and a lid  3  also coated on the inside with a refractory material  4 . At the top part of vessel  1  is a passage hole  5  for casting, emptying or feeding the liquid metal. The vessel tilts about the tilt axis  6  passing through said passage hole  5 . The latter is extended by a mobile spout  7  integral with vessel  1 , and pivots with the latter; it is coated on the inside with a refractory material  8 . 
     The adjustable clamping of seals  12 ,  13  may be made by screw tie rods  19  which are supported by a fixed part  20  integral with a frame  21 , by means of a spring  22  whose compression is adjusted by nuts. 
     As shown in FIGS. 2 and 3, the connection devices sealed against liquid metal, articulating in rotation about an axis  6  and enabling titling of vessel  1  of liquid metal, comprises: 
     an adapter flange  10 ,  10   a ,  10   b ,  10   c  secured to the end of spout  7 ,  8 , centred over the tilt axis  6  and comprising a circular seal bearing perpendicular to said axis  6 ; 
     a connection flange  15 ,  15   a ,  15   b  secured to the end of the fixed trough  17 ,  18 , centred over the tilt axis  6  and comprising a circular seal bearing perpendicular to said axis  6 , facing and co-operating with the preceding bearing; 
     at least one seal  12 ,  13  resistant to heat and liquid metal, positioned between the two bearings; 
     a clamp device  19 ,  19   a ,  22 ,  22   a ,  22   b ,  22   c  used to adjust the clamp force of flanges  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b  relative to one another, in order to ensure the seal of the connection while allowing said flanges  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b  to pivot relative to one another. 
     The connection device of the invention advantageously comprises a centering device  11 ,  11   a ,  14 ,  14   a  for flanges  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b  to center the latter relative to one another. This centering device may comprise, on one of flanges  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b , a cylindrical projection  11 ,  11   a  which slide fits into a corresponding housing  14 ,  14   a  positioned on the other flange  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b . According to the variant shown in FIG. 2, one of the seal bearings may be positioned at the end of projection  11 , the other seal bearing being positioned in the bottom part of housing  14  so that the two seal bearings face one another. According to the variant in FIG. 3, the seal bearings are provided at the end of specific projections  15   b ,  10   b  of flanges  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b , said bearings being arranged so that they face one another. 
     According to a first embodiment of the invention, the adjustable clamp device comprises screw tie rods  19  supported firstly by one or more fixed support parts  20 , preferably integral with a frame  21 , and secondly by one of flanges  10 ,  15  via elastic parts or a spring  22 ; nuts are used to adjust the compression and therefore the clamping force. 
     According to a second embodiment of the invention, the adjustable clamp device comprises a projection  22   c  on one of flanges  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b , a ring flange  22   b  and clamp adjusting means  19   a ,  22   a , such as bolts  19   a  and washers of “belleville” type  22   a . This variant further simplifies the opening and dismounting of the connection device. 
     Spout  7  may comprise a counter-flange  9  at its end, on which the adapter flange  10  is fixed in sealed manner comprising a cylindrical projection  11 . According to one variant of the invention, on the seal bearing positioned at the end of said projection  11 , seal  12  is placed which is preferably a graphite-based seal. This seal  12  is applied against the corresponding seal  13  positioned on the seal bearing located in the bottom part of cylindrical housing  14  forming part of connection flange  15  and co-operating with projection  11  to center the device. According to another variant of the invention, flanges  10 ,  10   a ,  10   b ,  10   c ,  15 ,  15   a ,  15   b  may comprise several separate parts which are preferably fixed to one another, for example by means of rotating stop parts  26 ,  27  or fixation means  28 . The rotating stop parts  26 ,  27  may be welded to the corresponding flanges  10   b ,  15   b  and specific housings may be provided in corresponding flanges  10   a ,  15   a.    
     The connection flange  15 ,  15   a ,  15   b  is fixed by means of a counter-flange  16  onto a removable portion of fixed trough  17  positioned in the continuation of the main body of the fixed trough  18 . A device  23  is seen for the sealed coupling of the main body  18  to the removable portion  17  of the fixed trough. 
     It may be advantageous to provide a seal  29  resistant to heat and liquid metal, between the connection flange  15 ,  15   a ,  15   b  and the counter-flange  16 .