US2944100A - Tilting electrode furnace - Google Patents

Description

July 5, 1960 w, so T AL 2,944,100

TILTING ELECTRODE FURNACE Filed Jan. 16, 1958 2 Sheets-Sheet 1 INVENTORS. ZJ/LHELM 50/26 KARL PFl/TZ/VER July 5, 1960 w. sons ET AL TILTING ELECTRODE FURNACE 2 She ets-Sheet 2 Filed Jan. 16, 1958 flaw? WM V 3 7 roe/var United States Patent ce TILTING ELECTRODE FURNACE Wilhelm Sorg and Karl Pfiitzner, Duisberg, Germany,

assignors to Demag-Elektrometallurgie G.m.b.H., Duisberg, Germany, a corporation of Germany Filed Jan. 16, 1958, Ser. No. 709,378

Claims priority, application Germany Jan. 26, 1957 7 Claims. (CI. 13-10) This invention relates generally to electric arc furnaces whose electrodes tilt bodily with the arc furnace body.

When melting scrap metal with conventional arc furnaces, severe vibrations are often set up in the furnace structure as a result of the electrode regulator rapidly moving the electrodes to compensate for changes in arc voltage and current incident to collapse of the stack of metal being melted. The compensating movements of the electrodes in one direction are suddenly arrested and reversed so that severe vibrations are set up in the furnace structure. The effect of the vibrationsmay be cumulative or contrary to the direction in which" the electrodes are driven by the regulator, so that the regulator hunts and further attempts to establish equilibrium of the electrodes in accordance with the desired electrical conditions in the arc.

In some prior art furnace designs attempts were made to overcome the above noted vibrations by mounting the electrode supports directly on the furnace body, thereby increasing rigidity and shortening the arms which support and carry current to the electrodes. This, however, amounted to sacrificing the ability of the electrodes to tilt with the furnace. In other cases, the electrode supports were mounted independently of the furnace so that during operation, the vibratory forces could not be amplified as they were transmitted from the furnace support to the electrode support. I

Other attempts to solve the problem involve mounting the electrode supporting members, the regulating devices, and the electrode swinging members on an extremely heavy platform carrying the furnace body. This design was abandoned intentionally for large furnaces because it did not wholly solve the problem of eliminating vibrations and it raised other problems. Also, in many cases, the components of prior art furnaces were arranged in such manner that the vibratory reactive forces incident to electrode regulation were transmitted to the furnace foundation through long moment arms and cantilever beams which served to amplify the vibrations and thereby aggravated the attempts of the regulating device to establish equilibrium.

.Accordingly, it is a general object of this invention to provide an arc furnace in which the usual vibrations, due to magnetic forces accompanying arcing and those incident to quick regulatory movements of the electrodes, are virtually eliminated.

Another object is to increase electric furnace efiiciency and reduce melting-time by eliminating vibrations that cause the electrode regulators to hunt and respond to false impulses.

Another object is to so arrange the elements of an arc furnace that reactive forces from the electrode supporting and regulating means are transmitted, without traversing vibration amplifying moment arms, to the furnace supports.

Another object is the provision of an arc furnace whose electrodes tilt with the furnace body and wherein Fatented July 5, 1960 certain elements such as the electrode supporting masts,

guide column for the masts, furnace cover support, electrode regulating device and the cover lifting mechanism are all carried on a swingable table that is adapted to transmit reactive forces through a furnace platform as near as possible to the plane of one or more rockers supporting the platform. a

Another object is to arrange the elements mentioned in the last paragraph so that when the furnace cover is,

' Achievement of the foregoing and other more specific objects will be evident from time to time when proceeding through the following specification.

' In general terms, the present invention is characterized by a platform supported on rockers which are spaced from each other along a tilting axis and located near opposite sides of the platform. In certain cases it may be satisfactory to use only the two outside rockers, while in other cases, it may be preferable to use a third or intermediately located rocker. At any rate, theer is mounted on the platform a furnace body which is as close as practical to a swinging table also bearing on the platform. The swinging table is adapted to carry electrode supporting masts and regulating mechanism therefor. The table is further provided with columns in which the masts are guided and which include laterally extending beam portions which carry furnace cover supporting mechanism. The table also carries mechanism for lifting the furnace cover when it is desired to swing the cover and the electrodes from the furnace body.

Since the means for supporting, regulating and swinging the electrodes are all carried in common on a swinging table, the vibratory effects of these elements are cancelled to a substantial degree. Furthermore, the swinging table is adapted to turn on a bearing pivot pin that transmits reactive forces of thrust or tension on a line coincident with the plane of a rocker which is situated directly underneath the axis of the pin. This, of course, obviates amplifying bending forces as they are transmitted from the table to the rockers and the furnace foundation. Where a third or intermediate rocker is used, the reactive forces of the table divide by reason of the table being further supported on rollers at a position radially extreme from the table pivot axis. These rollers are located as near as possible to being directly above the intermediate rocker so as again to transmit reactive forces to the rocker with a minimum, if any, moment arm.

Construction of a furnace, according to the invention, will now be described in greater detail in connection with the following drawings in which:

Fig. 1 is an elevational view of a furnace, embodying the invention, as it appears when observed transversely to the tilting axis; and

Fig. 2 is a top view of the furnace represented in Fig. 1, with parts omitted.

Referring to Fig. 1, it may be seen that the furnace assembly comprises a platform 1 that is supported near opposite sides on rockers 2 and 4, and further supported intermediately, by another similar rocker 3. The rockers 24 are the equivalent of a ring gear segment which is provided with lugs 5, instead of teeth, that engage appropriate holes 6 in a fixed track 7 to effect controlled rocking of platform 1. As viewed in Fig. 1 the rockhydraulic piston, not shown, but adapted to exert a tilt-v ing force on a pair of links 8 which are hinged. to the.

platform. 7

Supported on platform 1 is a refractory lined furnace shell or body, generally designated by the reference numeral 9, of any conventional design. Furnace body. 9 is enclosed by a cover 10, formed in the usual way with a metal ring memberll and an arched refractory roof material.

Projecting through. the cover 10 and into the furnace body are axially adjustable electrodes 12 which are secured by electrode clamps 13 located at the outermost end of an electrode arm. 14. Electrode arm 14 is carried on an electrode supporting column-or mast to which it is engaged by means of a clamp, symbolically represented, and indicated by the reference numeral 21. As depicted in Fig. 1, the electrodes are withdrawn from the furnace body to a position in the cover which would allow swinging of the cover 10 without interference by the body 9. The dash-dot outis seen a table 22 which is largely rectangular but curved in its front portion as indicated by the numeral 22'.

The curve portion carries three table supporting rollers 23 which run on a segment of an arcuate rail 24 whose configuration may be seen best in Fig. 2. Table 22 is hingedly connected to platform 1 by means of a bo'gie pin or heavy shaft 25 connected to the tableby a flange at 26 and suitably journalled in bearings, sug-v gested symbolically at 27 and 2$, which are adapted to accept thrust and tension forces along the axis of the shaft 25. Note that the pivot axis of shaft 25 projects downwardly substantially into the plane of one of the rockers 2. The shaft may project somewhat through platform 1, as illustrated, but it should be readily un-- derstandable how the rocker may be suitably notched in order to accommodate this projection.

Rigidly fixed on table 22 is a vertical box-like column 29 which has a pair of integral box-like beam portions 30 extending outwardly over the furnace cover 10. In Fig. 2 it may be seen that the pair of beams 30 enable four-point suspension of the cover 10 when it is lifted from the furnace body 9 for being swung away with the electrodes 12. The outer ends of beams 30 may be tied together by any suitable girder means like the member 30.

The cover lifting mechanism may take many forms but it is here shown to consist in bell cranks 31 that are connected for simultaneous rotation on their pivots 32 by means of a clevised link 33. The cranks are provided with short cable groove sectors 34 for accommodating cables 35 that extend downwardly to the furnace cover from their point of attachment on the bell crank. clockwise. as viewed in Fig. 1, cover 10 will be lifted and suspended from the beams 30. Lifting force maybe Obviously, when the bell cranks are rocked exerted on cover 10 by means of links 36 and lever ;37

to counterbalancethe table 22. Actually thereare two...

cover lifting cylinders 39 and two setsof associatedslink- 1 Each of theelectrodes 12 is, in the last'analysis, supported on a vertically movable mast 20, one for each phase, that is in turn slidably mounted in sliding ways 45 encompassed by the columns 29. Each mast 20 is provided with a bracket 46 to which is attached a cable 47 for altering the height of the mast and accordingly ad usting the electrodes 12 within the furnace body 9. Actually, there may be a pair of such cables 47 for each mast 20. As shown, each cable runs over a suitable pulley 43 which is supported for rotation on the end of a'clevised piston rod 49 that extends from a 'piston in a hydraulic cylinder 50. When pressure in hydraulic cylinder 50 is varied, the piston rod 49 and, therefore, pulley 48 move vertically so that a lifting force is exerted on the electrode masts 2G by means of the cable. By reason of cable 47 being anchored to the table 22 at one of its ends 51, any movement of the pulley 48 in a vertical direction causes twice the vertical movement of an associated mast 20. Here-again we may observe that the cylinder 50 and cable anchor attachment 51 are located as near as possible to the axis of the pivot pin 25 so that any reactive forces developed by these elements is transmitted with a minimum, if any, moment arm to the plane of rocker 2.

It will be understood that vertical positions of the electrodes 12 are established in accordance withcontrolled variations in the hydraulic fluid within cylinder 50. The fluid variations may be effected by any conventicnal means adapted to deliver fluid to the cylinder. or remove fluid therefrom in response to voltage and current conditions existing across the arc. Because voltage and current responsive hydraulic electrode controls are well known to those practicing the art, they will not be discussed here.

Furnace platform 1 is provided with a suitable opening 53, see Fig. 2, through which the lower ends of eleci trode masts 20 project, the lowermost position of the electrode masts being represented by broken lines in Fig. 1. Opening 53 is irregularly shaped to allow sufficient clearance around masts 20 so that they may swing with table side of the platform as represented by the brokenlines in Fig. 2. Masts 20 are always perpendicular with the table 22 and platform 1. The whole of masts 20 and the electrodes 12 tilt with the platform and the furnace It has been lifted from furnace shell 9.

Because of the position of rockers 2, 3 and ,4, and

the location of the swinging table 22, swinging of the table and the electrode masts 20', and swinging of the electrodes 12, and the beams 30 along with coverltl-v does not shift the center of gravity of the system to outside the platform 1. Hence, the platform and all its associated elements remain stabilized against tipping. ,In fact, the furnace body 9 may be removed from platform 1 without adversely shifting the center of gravity of the system or tending to unbalance the platform.

Location of intermediate rocker 3 form 1. This is true since elimination of vibrations in thefurnace assembly is largely dependent upon transferring most of the reactive forces developed by table 22.

directly to outside rocker 2 through the agency of table pivot pin .25.

In accordance with the invention described aboveitis seen that elimination of vibrations will lead to faster; smeltingby reason of eliminating hunting. action -,in the electrode regulator when it seeks to compensate for .inadvertent vibratory movement of the electrodes .rath er 22 when it is desired to swing the cover 10 away from the furnace body 9 and somewhat to the is influenced to, I some extent by the location of furnace body 9 on plat-.

than respond correctly to voltage and current conditions existing across the arc. It has been further shown how the reactive forces of a furnace structure may be transmitted to the foundation without passing through vibration amplifying moment arms and that thereby the furnace components may be of considerably lighter weight without sacrificing vibration free operation.

It is claimed:

1. An arc furnace assembly comprising platform means, at least two rocker means supporting said platform means at opposite sides for tilting, a furnace body mounted on said platform means between said rocker means and having a removable cover, a swingable table disposed laterally of said furnace body along the general direction of the tilting axis of the platform means and swingable on an axis normal to the platform means and lying in a plane substantially coincident with the plane of one rocker means, column means fixed on said swingable table, cover support means for suspending said cover from said column means for swinging said cover means with said column means away from said furnace body, electrode support means mounted on said column means for adjustable vertical movement, and electrode adjusting means operatively connected with said support means, said adjusting means including drive means mounted on said table approximately in the plane of said one rocker means most remote from the furnace body, to thereby transfer reaction of the table with minimum bending moment or directly to said one rocker means.

2. An arc furnace assembly comprising platform means, at least two rocker means supporting said platform means at opposite sides for tilting, a furnace body mounted on said platform means between said rocker means, a swingable table disposed laterally of said furnace body along the general direction of the tilting axis of the platform means and swingable on an axis normal to the platform means and lying in a plane substantially coincident with the plane of one of said rocker means, column means fixed on said swingable table, electrode support means mounted on said column means for adjustable vertical movement, electrode adjusting means operatively connected with said support means and including drive means comprising a substantially vertical cylinder and a cooperating piston means, said cylinder being anchored to said table laterally more remote from said furnace body than said column means, said adjusting means also including pulley means rotatably carried on said piston means for executingvertical movement therewith, and flexible cable means running over said pulley and having one end attached to said electrode support means and another end anchored to said table in a plane substantially coincident with the plane of said one rocker means, said cylinder being mounted on said table approximately in plane of said one rocker means most remote from the furnace body to thereby transfer reaction of the cable with minimum bending moment more directly to said one rocker means.

3. The invention set forth in claim 1 including fluid operated cylinder means including a piston, linkage means operatively connecting said piston with said cover support means to raise the cover when the table is to be swung, said cylinder means being anchored to saidswingable table in a plane substantially coincident with the plane of said one rocker means. 7

4. An arc furnace assembly comprising platform means, at least two rocker means supporting said platform at its sides and in a region intermediate the sides, a furnace body mounted on said platform means between said first and intermediately located rocker means, a swingable table mounted on said platform means and including a swinging axis more laterally remote from the furnace body than is the intermediate rocker means, roller means supporting said table in a region less laterally rmote from the furnace body, the reactive forces of said roller means lying in a vertical plane substantially coincident with the plane of said intermediately located rocker means when said table is in furnace operating position, column means fixed on said swingable table, electrode support means mounted on said column means for adjustable vertical movement with respect thereto when the furnace is operating, and electrode adjusting means operatively connected with the support means, said adjusting means including drive means mounted on said swingable table, whereby reaction of said table is transferred with a minimum bending moment or directly to said intermediate rocker means.

5. An arc furnace assembly comprising platform means, first and second rocker means supporting said platform means at opposite sides for tilting, a furnace body mounted on said platform means near said first rocker means, a swinging table means whose swinging axis is located substantially over the second rocker directly transferring reactive forces to that rocker and for swinging the table in parallelism with the platform, column means fixed on the table and including a pair of furnace cover supporting beams extending over the furnace body, electrode support masts slidably mounted in said column means for vertical movement and projecting through an opening in said platform between said rocker means, whereby said masts may swing with said table and with said cover supporting beams, and roller means supporting said table means at an end remote from the swinging axis thereof, whereby the reactive forces on the second rocker means do not shift appreciably when furnace body is removed from the platform and the center of gravity of the combination of elements associated with the swinging table.

6. An arc furnace assembly comprising a platform, first, second and third rockers supporting said platform at laterally spaced intervals for tilting, a furnace body mounted on said platform between the first and second rockers, a-swinging table swingable in a plane parallel with the table on a pivot pin means whose axis is substantially directly over said third rocker, roller means supporting said table radially remote from the pivot pin and substantially over the second rocker when said table is not swung, column means fixed to said table, electrode support means slidably mounted in said column means and projecting through an opening in said platform, electrode support regulating means mounted on said table laterally more remote from said furnace body than said I electrode supportmeans, a furnace body cover, and beams extending from said column including means for supporting and raising said cover to allow swinging the same with said table.

v7. In an arc furnace assembly comprising platform means, at least two rocker means supporting said platform means at opposite sides for tilting, a furnace body mounted on said platform means between said rocker means, column means mounted on said platform and disposed laterally of said furnace body in the general direction of the tilting axis of said platform means and toward the one of said rocker means most remote from said furnace body, electrode support means mounted on said column means for adjustable vertical movement, and electrode adjusting means operatively connected with said support means, said adjusting means including drive means mounted on said platform approximately in the plane, of the said one rocker means to thereby transfer the reaction'of said adjusting means directly to said one rocker means with a minimum bending moment.

References Cited in the file of this patent UNITED STATES PATENTS 2,396,663 7 Kuelthau et al. Mar. 19, 194

Images