Abstract:
A device ( 10 ) for adjusting the locking point of the electrode of a smelting furnace includes a vice ( 120 ) for supporting said electrode and supplying it with power. A structure ( 13 ) is coupled with the vice ( 120 ), supports the electrode and moves the electrode vertically.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention refers to a device for adjusting the locking point of an electrode through an electrode-holding vice of an electric arc smelting furnace. 
     2. Description of the Related Art 
     Smelting furnaces, generally used in the steel sector, make use of the heat released by electric arcs created through graphite electrodes in order to work. 
     These electrodes, which are of substantial size, possibly even having a diameter of 800 mm and a length of over 10 m, are supported by vices that are the end part of long steel and copper arms, through which the current necessary for creating the aforementioned electric arcs passes. Such arms stay outside the furnace. Only the part of electrode situated below the vice enters into the furnace. 
     During operation the electrodes wear down in the bottom part where the arc sparks, and therefore they become gradually shorter. The arc must however always stay in the bottom area of the furnace, in other words where the steel to be poured is located, for which reason the arms go down as low as the cover of the furnace will allow, after which it is necessary to intervene to adjust the relative position between arm and electrode. This normally occurs, after stopping the furnace from operating, through the bridge crane that, in different ways, hooks and holds the electrode while the vice is opened, moved vertically and closed again higher up. 
     This system, which is currently used in almost all steelworks, has some substantial drawbacks. 
     In order to carry out the operation it is necessary to stop the furnace for the entire duration of the operation itself, in other words for 2-5 minutes, which, for a modern steelworks, represents a very long time and therefore a very high cost. 
     The overwhelming majority of steelworks uses the hook of the crane directly to take hold of the electrode. Such a hook, in order to be able to hook onto and unhook from the ring of the nipple located on the top part of the electrode, must be without the obligatory safety device. 
     The crane in a steelworks is an extremely valuable piece of machinery, which should always be available for emergencies. 
     BRIEF SUMMARY OF THE INVENTION 
     The purpose of the present invention is to provide a device that can carry out the adjustment of the positioning of the electrode, with respect to the vice of the furnace, automatically, without the use of the crane and preferably exploiting the idle times that exist when the furnace is open to be able to tap the molten steel. 
     Another purpose is to provide a device, which can also operate at the high temperatures connected with melting of steel. 
     In accordance with the present invention, such purposes and others are accomplished by a device for adjusting the locking point of the electrode of a smelting furnace comprising: a vice for supporting and supplying said electrode with power, characterised in that it comprises a structure coupled with said vice comprising support means for said electrode and means for moving said electrode vertically. 
     Such purposes are also accomplished by a method for adjusting the locking point of an electrode of a smelting furnace through an electrode-holding vice, comprising the steps of coupling support means of said electrode with said vice and means for moving said electrode vertically. 
     Further characteristics of the invention are described in the dependent claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The characteristics and advantages of the present invention shall become clear from the following detailed description of some practical embodiments thereof, illustrated as non-limiting examples in the attached drawings, in which: 
         FIGS. 1 ,  2 ,  3  and  4  show a device for adjusting the locking point of the electrode in accordance with a first embodiment, the first two figures with the device open and with the gripping members in their highest point, and the other two with the device closed and with the gripping members in their lowest point; 
         FIGS. 5 ,  6 ,  7  and  8  show a device for adjusting the locking point of the electrode in accordance with a second embodiment, the first two figures with the device open and with the gripping members in their highest point, and the other two with the device closed and with the gripping members in their lowest point; 
         FIGS. 9 ,  10 ,  11 ,  12 ,  13  and  14  show a device for adjusting the locking point of the electrode in accordance with a third embodiment, the first three figures with the device open and with the gripping members in their highest point, and the other three with the device closed and with the gripping members in their lowest point; 
         FIGS. 15 ,  16 ,  17  and  18  show a device for adjusting the locking point of the electrode in accordance with a fourth embodiment, the first two figures with the device closed, and the other two with the device open; 
         FIGS. 19 ,  20 ,  21  and  22  show a device for adjusting the locking point of the electrode in a fifth embodiment, the first two figures with the device closed and the gripping members in their highest point and the other two with the device open and the gripping members in their lowest point. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the attached figures, a device  10  for adjusting the locking point of the electrode  11  through an arm  12  with relative electrode-holding tongs  120 , or electrode-holding vice, comprises a metallic structure  13  intended to be fixed through screws  14 , suitably electrically insulated, to the electrode-holding arm  12 , in the bottom part or even in the top part. Such a structure  13  is intended to be adjusted along the length of the arm, to define the correct position with respect to the electrode  11 . 
     The structure  13  comprises support means and means for moving the electrode  11  vertically. 
     As indicated above, the structure  13  can be fixed to the arm  12  in the bottom part or in the top part thereof. 
     In the first four embodiments of the device  10  illustrated in  FIGS. 1-18 , the structure  13  is fixed to the bottom part of the arm  12 . In this case, in operating configuration, the support means and the means for moving the electrode  11  vertically are at a lower height than that of the electrode-holding tongs  120 , in other words they are below them. 
     In the fifth embodiment of the device  10 , illustrated in  FIGS. 19-22 , the structure  13  is fixed to the top part of the arm  12 . In this case, in operating configuration, the support means and the means for moving the electrode  11  vertically are at a greater height than that of the electrode-holding tongs  120 , in other words they are above them. This arrangement, as shall become clearer hereafter, offers advantages both in terms of structure and in terms of operation. 
     In accordance with a first embodiment of the present invention, a horizontal plate  20  is connected to the structure  13 . The plate  20  is hinged, on one side, to a suspension pin  21 , having its axis arranged along an axis alongside the electrode  11 , and perpendicular to it. 
     On the other side of the plate  20  two tongs  22  and  23  are coupled, through the respective pivots  24  and  25 . 
     A first hydraulic cylinder  26  is connected between the structure  13  and the plate  20 , on the opposite side to where the plate  20  is hinged. The cylinder  26  provides a vertical movement of an extremity of the plate  20  and thus a vertical movement of the tongs  22  and  23 . 
     A second hydraulic cylinder  27  is connected between the two tongs  22  and  23  on the opposite side to that of the gripping members  28  and  29 . The cylinder  27  provides an opening and closing movement of the tongs  22  and  23  and thus of the gripping members  28  and  29 . 
     The adjustment of the position of the electrode  11  with respect to the arm  12  is carried out automatically or manually with the following sequence. 
     The cylinder  26  closes and positions the gripping members  28  and  29  in their highest point. 
     The cylinder  27  extends and closes the gripping members  28  and  29  of the two tongs  22  and  23  on the electrode  11 . 
     The electrode-holding tongs  120  of the arm  12  open. 
     The cylinder  26  extends and moves the electrode  11  downwards. 
     The electrode-holding tongs  120  of the arm  12  close. 
     The cylinder  27  closes and opens the gripping members  28  and  29 . 
     What has been described above relates to the downward movement of the electrode  11 , for a possible raising of the electrode  11  the sequence is reversed but is analogous. 
     Since the vertical movement is relatively small (for example 100 mm), it is foreseen for it to be possible to programme many successive cycles also automatically. 
     As an alternative to the suspension pin  21  and the hydraulic cylinder  26  it is possible to use four hydraulic cylinders  30 ,  31 ,  32 ,  33 , as better described in the following embodiments. The two structures should be considered equivalent for the vertical movement of the electrode. 
     In accordance with a second embodiment of the present invention, the structure  13  has four hydraulic cylinders  30 ,  31 ,  32 ,  33  connected to it, which are in turn connected to a bar  34  ending with a ring  35  that encircles the electrode  11 . 
     The four hydraulic cylinders  30 ,  31 ,  32 ,  33  allow the vertical movement of the bar  34 . 
     Three jaws  36 ,  37 ,  38  are mounted on the ring  35  that moves only radially, by means of special guides, controlled by a circular crown  39  provided with three oblique grooves  40 ,  41  and  42 . 
     On the bar  34  there is a first gear  43  that engages on the circular crown  39  and on a second gear  44 . The second gear  44  has a lever  45  positioned on it that is controlled by a hydraulic piston  46 . 
     The hydraulic piston  46  actuates the gears  43  and  44 , making the circular crown  39  rotate. When the circular crown  39  rotates, the grooves  40 ,  41  and  42 , engaged on three rollers mounted on the jaws  36 ,  37 ,  38 , force them towards the electrode locking it. 
     The adjustment of the position of the electrode  11  with respect to the arm  12  is carried out substantially like for the previous case. 
     The cylinders  30 ,  31 ,  32 ,  33  close and position the ring  35  in its highest point. 
     The cylinder  46  extends and closes the jaws  36 ,  37 ,  38  on the electrode  11 . 
     The electrode-holding tongs  120  of the arm  12  open. 
     The cylinders  30 ,  31 ,  32 ,  33  extend and the electrode  11  moves downwards. 
     The electrode-holding tongs  120  of the arm  12  close. 
     The cylinder  46  contracts and the jaws  36 ,  37 ,  38  open. 
     In accordance with a third embodiment of the present invention, the structure  13  has four hydraulic cylinders  30 ,  31 ,  32 ,  33  connected to it, which are in turn connected to a bar  34  ending with a ring  35  that encircles the electrode  11 . 
     The four hydraulic cylinders  30 ,  31 ,  32 ,  33  allow the vertical movement of the bar  34 . 
     The ring  35  has six jaws  50 ,  51 ,  52 ,  53 ,  54  and  55  mounted on it that move only radially, by means of special guides, controlled by a metallic cable  56  in a closed loop that closes on the jaws themselves through the effect of the movement of a hydraulic cylinder  57 . The hydraulic cylinder  57  actuates a pulley  58 , which can move along the longitudinal axis of the bar  34 , on which the metallic cable  56  is made to run. 
     In order to lock the electrode  11 , the hydraulic cylinder  57  is closed, which, bringing the pulley  58  closer to it, places the cable  56  under tension, which makes the six jaws  50 ,  51 ,  52 ,  53 ,  54  and  55  run in the special guides that come into contact with the electrode  11 . 
     In order to release the electrode  11  and move the ring  35 , the hydraulic cylinder  57  is opened, and some springs (not shown) take the pulley  58  back into its rest position. 
     In accordance with a fourth embodiment of the present invention, the structure  13  has a structure  60  connected to it on which two tongs  61  and  62  are coupled, through the respective pivots  63  and  64 . A hydraulic cylinder  65  is connected between the two tongs  61  and  62  on the opposite side to that of the gripping members  66  and  67 . 
     The gripping members  66  and  67  consist of two gears, controlled by two hydraulic motors  68  and  69 , which, rotating in synchrony with each other, move the electrode  11  with continuity downwards or upwards. 
     The hydraulic cylinder  65  opens and closes the two tongs  61  and  62  and the two hydraulic motors  68  and  69  raise and lower the electrode  11 . 
     In accordance with a fifth embodiment of the device  10  object of the present invention, the structure  13  is fixed to the arm  12  in the top part thereof so that, in operating configuration, the support means and the means for moving the electrode  11  vertically are at a greater height than that of the electrode-holding tongs  120 , in other words they are above them. 
     The support means and the means for moving the electrode  11  vertically comprise a pair of tongs  70  and  71  each of which is pivoted around a respective pin  72  and  73  and has an end for gripping the electrode  11  provided with respective gripping members  74  and  75 . The ends of the tongs  70  and  71  opposite the gripping end are connected together by a first cylinder  76  that controls its closing and opening, respectively, to hold and release the electrode  11 . 
     The two tongs  70  and  71  are also hinged to the structure  13  around respective pins with horizontal axis  77  so as to be able to oscillate on the vertical plane. 
     The oscillation of the two tongs  70  and  71  around the horizontal axis  77  is controlled by a second cylinder  78 , which has one end  78   a  articulated to the structure  13  and the opposite end  78   b  articulated to a bracket  79  fixedly connected to the two tongs  70  and  71 . The extension and the retraction of the second cylinder  78  control the oscillation of the tongs  70  and  71  around the horizontal axis  77  in the two opposite directions, so as to move the gripping ends of the tongs  70  and  71  vertically downwards or upwards. 
     The adjustment of the position of the electrode  11  with respect to the arm  12  takes place in the following way: 
     When the electrode-holding tongs  120  are still clamped around the electrode  11 , the second cylinder  78  is actuated so as to make the tongs  70  and  71  rotate around the horizontal axis  77  so as to lift their gripping ends, kept in open configuration, vertically upwards. 
     When the gripping ends of the tongs  70  and  71  have been raised to the desired height, the first cylinder  76  is extended so that the two tongs  70  and  71 , oscillating around the respective pins  72  and  73 , are closed to clamp their gripping ends around the electrode  11 . 
     The electrode-holding tongs  120  are released and the electrode  11  is supported by the tongs  70  and  71 . 
     The second cylinder  78  is then actuated so as to make the tongs  70  and  71  rotate around the horizontal axis  77  so as to lower their gripping ends, kept in closed configuration around the electrode  11 , vertically downwards; in this way the electrode  11  is moved vertically downwards by a programmed height. 
     At this point, the electrode-holding tongs  120  are clamped around the electrode  11  and the first cylinder  76  is retracted so that the two tongs  70  and  71 , oscillating around the respective pins  72  and  73 , are opened moving their gripping ends away from the electrode  11 . 
     The electrode-holding tongs  120  support the electrode  11  and feed it with power and the device  10  is ready to repeat the sequence of operations described above. 
     Should it be necessary to raise the electrode  11 , for example to add a portion of graphite, the operations indicated above are carried out in reverse. 
     The arrangement of the tongs  70  and  71  and, more generally, of the support means and of the means for moving vertically to a greater height, in operating conditions, than that of the electrode-holding tongs  120 , has some advantages compared to the opposite arrangement. 
     Indeed, with such an arrangement the tongs  70  and  71  and, more generally, the support means and the means for moving the electrode  11  vertically, are connected to a portion of the electrode itself that, with the furnace in working configuration, does not have current passing through it. Such a portion, therefore, constitutes an open electric circuit and is at the same electrical potential with the power supply provided by the electrode-holding tongs  120 . 
     In this case, therefore, it is not strictly necessary to electrically insulate the device  10  from the arm  12 , since it is not possible for so-called “electric loop” effects to be created that, on the other hand, are created with the opposite arrangement, in other words with the arrangement of the means for supporting the electrode  11  and for moving it vertically beneath the electrode-holding tongs  120 . 
     The arrangement of the tongs  70  and  71  and, more generally, of the means for supporting the electrode  11  and for moving it vertically, at a greater height than that of the electrode-holding tongs  120 , thus results in the bulk and weight of the entire device being kept low. 
     In any case, the device object of the invention allows the electrode to be moved vertically in shorter periods of time compared to what is required by the prior art with consequent gains in terms of productivity. Moreover, the device object of the present invention allows the height of the electrode to be modified without the need to open the furnace, with a consequent energy saving. 
     In practice, the materials used, as well as the sizes, can be whatever according to the requirements and the state of the art. 
     The device thus conceived can undergo numerous modifications and variants, all of which are covered by the scope of protection of the inventive concept; moreover, all of the details can be replaced with technically equivalent elements.