Patent Publication Number: US-4843614-A

Title: Metallurgical vessel

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates in general to metallurgical furnaces and in particular to a new and useful electric metallurgical furnace having a bottom with a central counter-contact which is engaged by strap elements of current cables on respective opposite sides through bolts which are limited to the straps and biased against them. 
     Electric furnaces, in particular d-c arc furnaces, have a contact system in their bottom which establishes, during the melting process, the necessary electrical contact with the scrap or with the melt. 
     Such a contact system is described e.g. in EP-PS No. 0058817. 
     These bottom electrodes are subject to wear sooner than the hearth lining. As it is relatively labor-intensive to replace individual contact rods, it has become common practice to replace all contact rods jointly at appropriate intervals of time. 
     This changing is done preferably by removing the bottom electrode from the furnace vessel in one piece and replacing it with a new one. In this operation the current cables remain suspended from the furnace vessel bottom. 
     SUMMARY OF THE INVENTION 
     The invention provides a suspension for the current cables which simultaneously also established the reliable contact to the bottom electrode required for current conduction, in a simple manner, and which adapts itself to possbile displacements and inaccuracies of alignment of the counter-contact at the bottom electrode. 
     According to the invention, the current cables are secured to movable straps which are biased into engagement with a furnace counter-contact. The new design of the suspension device is outstanding for the fact that even after replacement of the bottom electrode the contact systems are reusable. 
     Accordingly, it is an object of the invention to provide an approved current contact connection through a counter-contact of a metallurgical furnace which includes current carrying cables which has strap portions which are biased against respective opposite sides of a counter-contact of the furnace by pivot bolts which are supported on the furnace by a tensioning frame. 
     A further object of the invention is to provide a metallurgical furnace which is simple in design, rugged in construction and economical to manufacture. 
     The various features of novelty which characterize the invention are pointed with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects obtained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention is illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS In the drawings: 
     FIG. 1, is a section through an electric furnace vessel having current cable connections in accordance with the invention; 
     FIG. 2, is a section on a larger scale through the cable suspension and the insulated attachment; and 
     FIG. 3, is a view similar to FIG. 1 of the invention in a plane 90° from that of FIG. 2. 
    
    
     GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in particular the invention embodied therein comprises a current connection for a furnace vessel 1 having a refractory lining 2 and a bottom which includes contact rods 5 connected to a support plate 3 which in turn is connected to a base plate 4 and has a central counter-contact 14. In accordance with the invention current carrying cable 7, 7 has ends with straps 8 which have interior strap faces which abut against respective exterior sides of the counter-contact 14. The invention includes tensioning frame 10 including support 11 which carries bolt members 9 which are universally pivotally connected at 12 to exterior faces of the straps 8 and hold the straps against the counter-contact 14 by biasing means in the form of a spring 13. 
     FIG. 1 shows a furnace vessel 1 with a refractory lining 2 in its interior. In the center of the furnace vessel bottom can be seen the bottom electrode, comprising a support plate 3, base plate 4, contact rods 5 and refractory tamping 6. The current cables 7 are attached to the straps 8. By means of carrying bolts 9 the straps are suspended in a tensioning frame 10. 
     The tensioning frame 10 is fastened under insulation to two supports 11, which in turn are anchored on the furnace vessel. 
     FIG. 2 shows the details of the described arrangement. The union between the carrying bolts 9 and the strap 8 is angularly movable; it may be e.g. an articulated bearing. Due to the angular mobility the strap is able to place itself without forcing exactly against the counter-contact 14 of the bottom electrode;. A spring 13 installed in the tensioning frame 10 pushes, by means of a displaceable carrying bolt 9 and articulated bearing 12, the strap 8 against the counter-contact 14. Opening of the contact system as required for changing the bottom electrode is done by retracting the carrying bolts 9 from outside the tensioning frame. Thereby also the straps 8 are pulled back and the contact is opened. 
     In the practical realization of the invention numerous variations are conceivable. Thus, applying of the straps can be brought about by hydraulic or pneumatic elements rather than by springs. The pulling back of the carrying bolts can be done by forcing screws, wedges or hydraulic or pneumatic elements. 
     FIG. 3 shows the apparatus in a sectional view rotated by 90°. It can be seen that the tensioning frame 10 is fastened to the insulators 16 through a sliding connection 15. By means of this sliding connection, the tensioning frame 10 can automatically align itself toward the counter-contact 14 as the straps 8 are being applied. This freedom from undue force of the straps 8 achieved by the sliding connection and the angular mobility of the articulated bearings makes possible for the straps correct application on the counter-contact 14 and a uniform pressure distribution over the entire contact surface. 
     The insulators 16 are applied on supports 11. The supports 11 are attached to the furnace vessel 1. Through this arrangement it is brought about that current flows into the melt exclusively via the straps and the bottom electrode. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principals of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.