Abstract:
An apparatus for accurately aligning a replacement electrode with a working electrode. The replacement electrode is suspended from a trolley movable in two directions in a rectilinear pattern. The trolley is moved initially in a first direction into general transverse alignment with the working electrode position, then displaced in a second direction against a fixed stop to overlie the desired electrode position. The trolley is adjusted finally in the first direction during its travel toward the fixed stop by contacting a mast on the trolley with a fixed guide adjacent the stop.

Description:
TECHNICAL FIELD 
     In the operation of arc furnaces, melters or smelters utilizing consumable electrodes, the electrodes generally are made of pre-baked carbon and are manufactured in discrete lengths which are spliced together by internal threads or by threaded nipples inserted into threaded recesses formed in the axial extremities of the cylindrical electrodes. As a working electrode is consumed, the next successive new replenishment or replacement electrode is threaded to the working electrode in axial alignment therewith. Preferably, the electrodes are oriented so that the lower, presently installed, working electrode has a threaded, internal recess at its upper end, and the replenishment electrode is provided at its lower end with male threads adapted to matingly engage the threads of the lower electrode recess. 
     To perform the replacement function, the replacement electrode is suspended from an overhead support and is simultaneously lowered and rotated relative to the fixed working electrode until the two electrodes are firmly threaded together. It is necessary that the two electrode sections be precisely aligned axially so that accurate threading can be carried out. 
     Where the furnace has a plurality of vertical electrodes which are spaced laterally and transversely from one another, e.g., in a triangular configuration when viewed in plan, the prior art offers no solution to the problem of accurately aligning a replacement electrode with a selected working electrode. The prior art has proposed various forms of swinging arms or vertical support posts from which the electrode lowering and rotating mechanism is supported. Where the furnace has a plurality of vertical electrodes, the prior art swinging arm or vertical post arrangement requires a plurality of replicated structures which are both expensive and space-consuming. 
     The prior art has also proposed various travelling crane arrangements, but these prior art constructions, as suggested in U.S. Pat. No. 4,185,158, require massive support structures and require extremely accurate manual positioning to carry out the replacement function. Even where the use of a trolley has been proposed in the prior art, as in German Pat. No. 489,475, the same precise manual location of the electrode and its installation means is required. 
     Consequently, there is a need in the art for a single positioning and aligning mechanism capable of servicing a plurality of spaced electrode locations and capable of locating a replacement electrode in precise axial alignment with a selected one of several working electrodes. 
     DISCLOSURE OF INVENTION 
     The present invention now provides a new and novel electrode aligning apparatus and method for use in electric arc furnaces, melters and smelters provided with vertical electrodes spaced laterally and transversely. 
     Generally, the present invention proposes the utilization of a trolley which is movable in two directions in a rectilinear pattern above the location of the electrodes. A replacement electrode is carried by a supporting and rotating mechanism depending from the trolley and vertically alignable by means of the trolley with the vertical axis of the working electrodes. 
     The trolley frame is supported for movement in a first longitudinal direction on a pair of fixed, parallel guide elements until the trolley is generally transversely aligned with the desired working electrode location. The trolley is then displaced relative to the trolley frame in a transverse direction toward the desired working electrode. As the trolley is moved into position, it contacts a fixed guide which is aligned with the desired working electrode location. The trolley-guide contact adjusts the trolley frame longitudinally into precise alignment with the desired working electrode. Finally, the trolley contacts a fixed stop to halt the transverse trolley movement with the replacement electrode in precise vertical axial alignment with the working electrode. 
     By utilizing individual guides for the separate working electrode locations and providing each guide with a specifically located stop, it is possible to translate the rectilinear movement of the trolley frame and trolley, respectively, into a precise location individual to the selected working electrode position no matter what the geometric arrangement of the electrodes may be and no matter how many working electrodes need be serviced by the single trolley mechanism. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a side elevation view of an arc furnace provided with a plurality of vertical working electrodes and a replacement electrode is illustrated as it is installed by the electrode aligning apparatus of the present invention; 
     FIG. 2 is a plan view of the apparatus illustrated in FIG. 1; 
     FIG. 3 is a schematic plan view similar to FIG. 2 and better illustrating the guiding and locating mechanism of the apparatus; and 
     FIG. 4 is an enlarged side elevational view of the trolley, the guide mechanism, and the stop of the illustrated apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As best shown in FIGS. 1 and 2 of the drawings, the electrode replacement mechanism of the present invention is intended to be utilized with an electric arc melter 10 having a plurality of vertical, consumable electrodes 11 which require periodic replacement. 
     Preferably, the electrodes 11 are of compressed carbon and are provided with threaded terminal ends, so that the threaded lower end of a replacement electrode can be threaded onto the threaded upper end of an installed electrode. The structure of the electrodes, the manner in which they are supported, and the specific manner in which the threaded electrodes are replenished or replaced is specifically set out in co-pending applications, filed on even date herewith and assigned to the assignee of the present invention. In FIG. 1, a typical electrode support and movement assembly is indicated by reference numeral 12. Each of the installed electrodes 11 is generally referred to as a &#34;working electrode.&#34; 
     According to the present invention, a rectilinear support frame 14 is provided in surrounding and overlying relation to the furnace 10. More specifically, the rectilinear frame 14 includes vertical corner support posts 15 joined by longitudinal guide rails 16 and transverse support elements 17. As shown, the elements 15, 16 and 17 are all relatively massive I-beams and are secured together by suitable means to form the frame 14. A support platform 18 located medially of one of the transverse members 17 supports a drive motor 19 which drives a transverse shaft 20 through an angle drive 21, drive chain 22 and a sprocket 23 supported on suitable bearings mounted on a transverse beam 24. The drive shaft 20 is suitably journalled in bearings 25 mounted on the longitudinal frame guide members 16 and sprockets 26 are mounted adjacent the remote ends of the shaft 20 to drive chains 27 trained thereabout. A support beam 28 adjacent the remote end of the guide beams 16 supports suitably journalled sprockets 29 about which the chains 27 are trained. 
     A trolley frame indicated generally at 30 is secured to the ends of each of the chain 27, as at 31. As the chains 27 are driven by the motor 19, the angle drive 21, the chain 22, the sprocket 23 and the shaft 20 bearing the sprockets 26, the trolley frame 30 is advanced longitudinally along the longitudinal guide beams 16. The trolley frame 30 includes a pair of transverse I-beams 33 having their ends joined by rectangular frames 34. One of the rectangular frames 34 supports rollers 35 interposed between and engaging the flanges of the one support beam 16, and the other frame 34 carries cylindrical rollers 36 which engage the upper surface of the other guide beam 16. Thus, the chains 27 move the trolley frame 30 longitudinally along the guide beams 16, the trolley frame being supported on the beams 16 by the rollers 35, 36. 
     Mounted on the trolley frame 30 and spanning the transverse beams 33 is a fixed platform 39 upon which is mounted a drive motor 40 and an angle drive unit 41 having its drive chain rotating a drive shaft 43 upon which is mounted a sprocket 44. A trolley drive chain 45 laps the sprocket 44 and a second sprocket 46 supported by bearings 47 mounted on a second fixed platform 48 spanning the beams 33. 
     A trolley indicated generally at 50 is mounted on the I-beams 33 for movement therealong. This trolley 50 comprises a central platform 54 overlying the guide elements 33 and having lateral extensions 51 carrying supporting rollers 52 interposed between and engaging the vertically spaced flanges of the I-beams 33 which serve to guide the trolley 50 for transverse movement. 
     The platform 51 serves to carry the supporting and rotating means, indicated generally at 55, for a replacement electrode. This supporting and rotating means 55 is specifically disclosed and claimed in co-pending application Ser. No. 342,672, filed on even date herewith, and forms no part of the present invention. However, it will be noted that the structure 55 carries a replacement electrode 56 located well beneath and depending from the platform 51 for attachment to one of the working electrodes 11. 
     The trolley 50 is connected to the chain 45, so that the trolley is moved along the length of the guide elements 33 as the motor 40 is actuated, the direction of movement of the trolley 50 being transverse to the direction of movement of the trolley frame 30. Thus, the motor 19 and the motor 40, in combination, drive the trolley 50 in two rectilinear directions relative to the furnace 10. 
     More specifically, the trolley platform 54 carries an upstanding mast indicated generally at 60 and including a vertical arm 61 fixed to the platform to project upwardly therefrom and a downwardly inclined brace arm 62 connecting the upper end of the arm 61 to the platform 51, as best seen in FIG. 4. The upper end of the arm 61 carries a shock absorber 66 terminating in a contact pad 67 projecting beyond the shock absorber 66. The post 63 is surmounted by a pair of transversely spaced rollers 70 for a purpose to be hereafter more fully described. 
     The ends of the chain 55 are attached to the brace arm 62 as at 68. 
     Mounted on one of the guide rails 16 is a pair of upstanding posts 80 joined by a top member 81 parallel to the guide rail 16, a shown in FIG. 1. Secured to the undersurface of the top member 81 is a plurality of &#34;T&#34;-shaped guide elements 82, each such guide element 82 having a depending, planar, vertical guide surface 83. The guide surfaces of the elements 82 are spaced along the length of the guide beams 16 at the spacing of the three electrodes 11, but in offset relation thereto. Each guide element 82 terminates at its remote, cantilevered end in a pair of angularly related, divergent depending guide pads 85 which are spaced apart a sufficient distance to receive therebetween the rollers 70 located on the mast 63. The guide pads 85 are inclined inwardly toward the central guide surfaces 83 of the elements 82 and serve to deflect the rollers 70 centrally toward the depending guide surfaces 83 of the elements 82. 
     Positioned along the length of each of the guide surfaces 83 of the elements 82 is a fixed stop 86. These stops 86 are positioned to abut the shock absorber pad 67 when the trolley 50 is displaced sufficiently to precisely axially align the electrode rotating and supporting means 55 and the replacement electrode 56 carried thereby with the chosen one of the working electrodes 11. 
     In operation, the furnace 10 is provided with a plurality of working electrodes, e.g., three electrodes 11 arranged in a triangular pattern in the illustrated embodiment. These electrodes are each connected to a source of electrical current through the holding and adjusting mechanisms 12 which are individual to the electrodes, and the electrodes are progressively consumed at individual consumption rates dependent upon the furnace operating conditions. 
     When a replacement electrode is required, the replacement electrode 56 is engaged by the electrode supporting and rotating means 55 from a supply source (not shown) preferably located generally beneath the support structure 14 at the left side thereof as illustrated in FIGS. 1 and 2. The motor 19 is then actuated to move the trolley frame 30 longitudinally along the parallel support rails 16 in the direction indicated by the arrow 90 of FIG. 3. Assuming that the electrode 11 located at the right extremity of the electrode pattern shown requires replenishment, the frame 30 moves along the rails 16 until the limit switch LS-3 is actuated by the abutment 87 carried by the trolley frame, as best shown in FIG. 3. The limit switches LS-1, LS-2 and LS-3 have been deleted from FIGS. 1 and 2 for clarity, but their relative positions are shown in FIG. 3. It will be noted that an individual limit switch is provided for each electrode. 
     When the switch LS-3 is actuated, for example, the motor 19 is de-activated, and the frame 30 is halted in general transverse alignment with the desired furnace electrode, i.e., the replacement electrode 56 is in general transverse alignment with the furtherest right working electrode 11. Next, the trolley motor 40 is actuated to move the trolley 50 transversely toward the desired working electrode in the direction of the arrow 91 of FIG. 3. As the trolley advances, the rollers 70 on the mast 60 are centered by the deflector plates 85 of the guide element 82 for the specific electrode. The guide plates 85 defelct the rollers to pass therebetween, so that the rollers engage the opposite vertical guide surfaces 83 of the guide elements 82. Any necessary shifting of the trolley longitudinally of the guide rails 16 is accommodated by the slack in the chains 27, and the mast 60 is sufficiently rigid to cause such shifting movement of the trolley as may be necessary to insure passage of the rollers between the deflector plates. 
     The trolley continues to move transversely, such movement being guided by the guide surfaces 83, until the contact pad 67 of the shock absorber 66 contacts the fixed stop 86 carried by the guide surfaces 83. The abutment of the pad 67 with the stop 86 halts any further transverse movement of the trolley and precisely positions the replacement electrode in axial alignment with the working electrode, since the longitudinal position of the trolley on the guide rails 16 is determined by the roller-guide surface contact and the transverse position of the trolley on the trolley frame rails 33 is determined by the pad-stop contact. 
     After the replacement electrode installation is complete and the replacement electrode is released from the supporting means 55, the transverse movement of the trolley is reversed to remove the abutment pad 66 from the stop 86, the trolley frame 30 then is retracted longitudinally along the guide rails 16, and the mechanism is ready for the next operation.