(19)
(11)EP 1 368 995 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
21.06.2006 Bulletin 2006/25

(21)Application number: 02706551.5

(22)Date of filing:  25.02.2002
(51)Int. Cl.: 
H05B 7/12  (2006.01)
(86)International application number:
PCT/CA2002/000241
(87)International publication number:
WO 2002/071811 (12.09.2002 Gazette  2002/37)

(54)

ELECTRODE SEAL FOR ARC FURNACE

ELEKTRODENDICHTUNG FÜR EINEN LICHTBOGENOFEN

GARNITURE D'ETANCHEITE POUR FOUR A ARC


(84)Designated Contracting States:
AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE TR

(30)Priority: 02.03.2001 US 796545

(43)Date of publication of application:
10.12.2003 Bulletin 2003/50

(73)Proprietor: Hatch Ltd.
Mississauga, Ontario L5K 2R7 (CA)

(72)Inventor:
  • McCAFFREY, Felim P.
    Toronto, Ontario M5V 2W7 (CA)

(74)Representative: Gervasi, Gemma 
Notarbartolo & Gervasi GmbH, Bavariaring 21
80336 München
80336 München (DE)


(56)References cited: : 
EP-A- 0 145 219
US-A- 3 709 506
US-A- 4 295 001
US-A- 4 641 320
WO-A-98/53643
US-A- 3 835 233
US-A- 4 457 002
US-A- 5 406 580
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] This invention relates to an electrode seal for an electric furnace having one or more large diameter electrodes extending through an opening in the furnace roof.

    BACKGROUND OF THE INVENTION



    [0002] Electric arc furnaces used for melting metals usually comprise a crucible and one or more generally vertical carbon electrodes supported so as to depend into the crucible. In order to contain fumes, maintain a desired atmosphere within the furnace and control heat loss and noise, it is common practice to provide such furnaces with a lid or roof having apertures through which the electrodes depend.

    [0003] Particularly during the initial stages of melting a charge, current surges through the electrode apply very substantial electromagnetic forces, which can cause significant lateral deflection of the electrodes. Therefore, it is necessary to provide a clearance between the electrode and the aperture in the furnace roof in order to prevent the furnace roof from being damaged by movement of the electrode. However, as such arc furnaces operate at close to atmospheric pressure, and can go into positive pressure, harmful gases such as oxides of nitrogen and carbon-monoxide, are released into the atmosphere through the gap, therefore making it desirable to provide some sort of seal arrangement between the electrode and the furnace roof.

    [0004] The seal must prevent substantial escape of fumes through the gap while permitting vertical and lateral movement of the electrode. The provision of adequate sealing is especially difficult in electric arc furnaces where it is necessary to completely withdraw the electrode from the furnace. Examples of this type of furnace include arc furnaces used to melt scrap steel. Such furnaces have a single electrode which is completely withdrawn from the furnace several times per hour to allow fresh scrap steel to be charged through the hole in the furnace roof. After the scrap material is charged, the electrode is again inserted through the aperture in the furnace roof and bores through the solid scrap material until it reaches a desired depth. During this boring operation, significant noise is generated by arcing between the electrode and the solid scrap material. The noise typically abates as the material is melted.

    [0005] U.S. Patent No. 3, 709,506 (Beerman) discloses an electrode seal having a three-part construction, comprising upper and lower water-cooled annular rings and a frusto-conical packing-retaining hat extending upwardly from the upper seal ring. The seal is partially supported by tie rods extending upwardly away from the furnace roof. The lower ring is stationary and the upper ring is slidable along the upper surface of the lower ring to a limited extent in order to accommodate lateral movement of the electrode.

    [0006] U.S. Patent No. 5,406,580 (McCaffrey) provides an annular seal comprising a number of individually water-cooled segments which are resiliently urged into abutment with the electrode surface. The minimum diameter of the seal is slightly greater than the diameter of the electrode. Separation of the segments during electrode withdrawal/insertion accommodates adherents and joint irregularities on the electrode surface.

    [0007] International Publication No. WO98/53643 (McCaffrey) provides an electrode seal comprising a lower water-cooled ring with a skirt which extends into the roof opening and an upper water-cooled ring having an internal diameter slightly greater than that of the electrode diameter. The upper and lower rings are supported from outside the refractory portion of the roof by separate cantilevering members.

    [0008] U.S. Patent No. 3,835,233 (Prenn) provides a number of ring seals which are attached to a support structure which is supported by a ring beam extending around the outer periphery of the roof. The ring seals, are provided with a packing of refractory material which forms a tight seal with the electrode. Limited lateral movement of the ring seals is provided by complex hinged members connecting the rings to the support structure.

    [0009] Although the prior art contains numerous examples of electrode seals to solve this very problem, none has proved generally acceptable to operators of arc furnaces used for the melting of steel, and particularly where complete withdrawal of the electrode is required. Therefore, many electric arc furnaces continue to be operated without any seal at all.

    SUMMARY OF THE INVENTION



    [0010] The present invention overcomes at least some of the problems of the prior art by providing an electrode seal for electric arc furnaces which is effective to substantially reduce fumes and noise associated with melting of metals in arc furnaces, is of relatively simple and economical construction, can be made sufficiently light to be safely supported on the refractory portion of the furnace roof surrounding the electrodes, is compatible with repeated complete withdrawal of the electrodes from the furnace, and can help extend the life of the electrode and the refractory roof.

    [0011] The electrode seal according to the invention comprises an annular support ring having an internal diameter substantially greater than the diameter of the electrode, and which is secured to the furnace roof by a plurality of mounting feet. The annular support ring has an upper annular sealing surface on which is received an annular sealing ring having an internal diameter which is approximately the same as the diameter of the electrode to form a substantial seal therewith. The sealing ring has a lower annular sealing surface which engages the upper sealing surface of the support ring, while allowing limited sliding movement of the sealing ring along its lower annular sealing surface.

    [0012] Thus, the present invention provides an electrode seal of simple construction in which escape of gas through the aperture in the furnace roof is greatly reduced by a tight-fitting sealing ring, which is laterally movable to account for lateral movement and misalignment of the electrodes.

    [0013] Testing of the electrode seal of the present invention has shown that the electrode seal effectively inhibits escape of gases from the furnace, and also significantly reduces the noise level in the vicinity of the furnace.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0014] The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

    Figure 1 is a perspective view from the top and the side of an electrode seal according to a first preferred embodiment of the invention, shown in isolation;

    Figure 2 is a top plan view of the electrode seal shown in Figure 1;

    Figure 3 is a side elevation view of the electrode seal of Figure 1;

    Figure 4 is a cross-sectional view along line IV-IV of Figure 2;

    Figure 5 is an enlargement of the left-hand portion of the cross-sectional view shown in Figure 4;

    Figure 6 is a partial cross-sectional view along line VI-VI of Figure 2;

    Figure 7 is an isolated, top plan view of the sealing ring portion of the electrode seal of Figure 1;

    Figure 8 is a cross-sectional view along line VIII-VIII of Figure 7;

    Figure 9 is a cross-sectional view along line IX-IX of Figure 7;

    Figure 10 is an isolated, top plan view of the support ring of the electrode seal shown in Figure 1;

    Figure 11 is a cross-sectional view along line XI-XI of Figure 10;

    Figure 12 is an enlargement of the right-hand side of the cross-sectional view of Figure 11; and

    Figure 13 is a cross-sectional view along line XIII-XIII of Figure 10.


    DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS



    [0015] A preferred electrode seal 10 according to the invention will now be described below with reference to the drawings. Electrode seal 10 is described in the context of a DC arc furnace having a single graphite electrode 12 (shown in Figure 4 only), typically having a diameter of 28 inches, and a roof. The roof is preferably of conventional construction, having an outer portion of water-cooled steel (not shown) and an inner refractory portion 14 surrounding the electrode 12. The refractory portion 14 of the roof, sometimes referred to as the "refractory button", is preferably provided with a steel frame (not shown) by which it is supported in an aperture in the water-cooled roof. Although the invention is being described in connection with a DC arc furnace, it will be appreciated by those skilled in the art that the principles of the invention may also be applied to AC arc furnaces.

    [0016] The refractory portion 14 of the furnace roof has an aperture 16 (also shown in Figure 4). The aperture 16 has a diameter of about 32 inches, leaving an annular gap 18 of about 2 inches between electrode 12 and the aperture 16 in the refractory portion 14.

    [0017] The electrode seal 10 comprises an annular support ring 20 defining a first aperture 22 having an internal diameter greater than the external diameter of electrode 12. Preferably, the internal diameter of the annular support ring 20 is substantially the same as the diameter of the aperture 16 in the refractory portion 14 of the roof. In the preferred embodiment shown in the drawings, the internal diameter of support ring 20 is about 32 inches.

    [0018] Support ring 20 further comprises an inner surface 24 which faces radially inwardly and is parallel to the axis of electrode 12, an upper annular sealing surface 26 perpendicular to inner surface 24, a lower annular surface 28 and an outer surface 30 facing radially outwardly.

    [0019] The height of inner surface 24, and the support ring itself, is about 5½ inches and the thickness of the ring, measured perpendicular to the electrode axis is about 7 inches.

    [0020] Extending radially outwardly from the outer surface 30 of support ring 20 are three flanges 50, each of which has a planar lower surface 52 perpendicular to the axis of electrode 12 and a planar upper surface 54 which is also perpendicular to the axis of electrode 12. The flanges are of sufficient strength to support the weight of the electrode seal 10 and to withstand lateral forces exerted on the seal 10 by electrode 12.

    [0021] Electrode seal 10 further comprises an annular sealing ring 32 which is supported on the upper sealing surface 26 of the support ring 20. The sealing ring 32 defines a second aperture 34 having an internal diameter which is approximately the same as the diameter of the electrode 12 and which is less than the diameter of the first aperture 22. In the preferred electrode seal 10, the diameter of the second aperture is preferably about 28⅛ inches, resulting in an annular gap of about 1/16 inch between the sealing ring 32 and the outer surface of electrode 12 to allow for irregularities in the outer surface of electrode 12. Typically, such electrodes are manufactured to a tolerance of about ± 1 mm (about 1/25 of an inch).

    [0022] The annular sealing ring 32 further comprises an inner surface 36 which faces radially inwardly, an upper surface 38, a lower annular sealing surface 40, and an outer surface 42 facing radially outwardly.

    [0023] As shown in Figure 5, the lower annular sealing surface 40 of sealing ring 32 comprises a flat surface which is perpendicular to the axis of electrode 12 and which engages the upper annular sealing surface 26 of the support ring 20 such that the second aperture 34 defined by the sealing ring 32 is in substantially complete registry with the first aperture 22 defined by the support ring 20.

    [0024] As shown in Figures 4 and 8, the inner surface 36 of sealing ring 32 comprises an axially-extending sealing portion 68 proximate the upper surface 38 of sealing ring 32, an outwardly-extending portion 70 generally tapering downwardly and radially outwardly from the axially-extending sealing portion 68 toward the lower annular sealing surface 40 of the sealing ring 32, and a plurality of axially-extending scraper elements 72 spaced from one another along the circumference of the outwardly-extending portion 70 and extending downwardly from the sealing portion 68, each scraper element having a pair of sides extending downwardly toward one another.

    [0025] The sealing portion 68 defines the diameter of the second aperture 34 of electrode seal 10, having a diameter of 28⅛ inches in order to form an effective seal with the surface of electrode 12. The sealing portion 68 preferably has an axial height of about 1½ inches, with a small chamfer preferably being provided between the sealing portion 68 and the upper surface 38 of sealing ring 32 to assist in guiding the electrode 12 into the aperture 34. The chamfer may preferably be about 1/4 inch x 45 degrees.

    [0026] The outwardly-extending portion 70 is preferably angled at about 35 to 40° relative to the lower annular sealing surface 40 of sealing ring 32, and has an axial height of about 2 inches. The outwardly-extending portion 70 gradually increases the inside diameter of the sealing ring 32 such that the diameter of sealing ring 32 proximate its lower surface 40 is approximately the same as that of the support ring 20 which, in the preferred embodiment, is about 32 inches.

    [0027] Preferably, the scraper elements 72 are co-planar with the axially-extending sealing portion 68 and are formed in the shape of triangular wedges, with the sides 74 of each scraper element 72 meeting at a point below the axially-extending sealing portion 68. Preferably, each scraper element 72 has an axial height of 1¾ inches and a maximum width at its upper end of 2 inches. Scraper elements 72 break off solid deposits of slag and steel sticking to the outer surface of electrode 12 as the electrode 12 is lifted out of the furnace.

    [0028] The sealing ring 32 is also provided with three radially outwardly-extending flanges 58 on its outer surface 42. Each flange 58 has an upper surface 60 and a lower surface 62, both of which are perpendicular to the electrode axis. The spacing between adjacent flanges 58 is the same as the spacing between flanges 50 on support ring 20 so that the sealing ring flanges 58 overly the support ring flanges 50 as in Figure 1.

    [0029] As shown in Figure 5, the upper surface 54 of support ring 20 is co-planar with the upper annular sealing surface 26 of support ring 20, and the lower surface 62 of flanges 58 of the sealing ring 32 are axially spaced from the lower annular sealing surface 40 of sealing ring 32, such that the lower surface of each sealing ring flange 58 is spaced from the upper surface 54 of each support ring flange 50. Therefore, the respective flanges 50 and 58 of the support ring 20 and sealing ring 32 do not contact one another during sliding movement of the sealing ring 32.

    [0030] Preferably, the support ring 20 and the sealing ring 32 are each formed from a thermally conductive metal such as copper alloy.

    [0031] The electrode seal 10 further comprises retaining means in the form of three hold-down brackets 44, each of which comprises a pair of spaced, vertically-extending hollow cylindrical posts 46 bridged by a solid bar 48 of rectangular cross-section, bar 48 preferably being welded to post 46. One hold-down bracket is attached to the upper surface 54 of a support ring flange 50, being secured 50 by a pair of bolts 56 extending through the hollow interior of the bracket posts 46.

    [0032] As illustrated in Figure 5, the horizontal bar 48 of hold-down bracket 44 is spaced axially from the upper surface 54 of flange 50, so as to create a gap 64 having an upper edge 66 which is in close proximity, but spaced from, the upper surface 60 of flange 58.

    [0033] In the preferred embodiment shown in the drawings, the gap 64 has an axial height of 1⅜ inches, and the upper edge 66 of gap 64 is spaced from the upper surface 60 of flange 58 by about ⅛ inch, thereby preventing substantial axial separation of the sealing ring 32 and the support ring 20, and thereby maintaining the seal between the two rings.

    [0034] It will be appreciated that the sealing ring flanges 58 extend radially outwardly a sufficient distance such that they are retained in the gaps 64 of brackets 44 regardless of the extent of sliding movement of the sealing ring 32 relative to the support ring 20.

    [0035] Preferably, the hold-down brackets 44 are spaced from the outer surface 42 of sealing ring 32 by a distance such that the sliding movement of the sealing ring 32 along its lower annular sealing surface 40 is limited in all directions to maintain substantially complete registry between the first and second apertures 22 and 34. In other words, lateral movement of the sealing ring 32 is limited such that no part of the second aperture 34 will be permitted to extend radially outwardly of the edges of the first aperture 22. The sliding movement of the sealing ring 32 is limited by engagement of the outer surface 42 of sealing ring 32 with the axially extending posts 46 of hold-down brackets 44. In the preferred embodiment shown in the drawings, the sliding movement of sealing ring 32 is limited to about 2 inches in any direction.

    [0036] As illustrated in the drawings, the support ring 20 and sealing ring 32 are provided with circumferential passages 78 and 80, respectively, for cooling water. These passages 78 and 80 are preferably about 1¾ inches in diameter and extend substantially completely through the entire circumference of the support ring 20 and sealing ring 32.

    [0037] The circular passage 80 of sealing ring 32 is illustrated in Figure 7, extending throughout substantially the entire circumference of sealing ring 32 between inlet port 82 and outlet port 84, both of which are provided in close proximity to one another on a flat connecting surface 86 provided on the outer surface of sealing ring 32.

    [0038] Similarly, as shown in Figure 10, the cooling passage 78 of 20 extends around substantially the entire circumference of support ring 20 between an inlet port 88 and an outlet port 90 provided in close proximity to one another on a flat connecting surface 92 located on the outer surface 30 of support ring 20.

    [0039] As illustrated in Figure 8, the sealing ring 32 is provided with a plurality of water passages 102 on its inner surface 36. As shown in Figure 9, these water passages 102 comprise holes extending through the sealing ring 32 from the inner surface 36 to the interior of the cooling passage 80. Thus, some of the cooling water circulating in the cooling passage 80 is ejected through these water passages 102 onto the outer surface of electrode 12, thereby cooling the electrode 12 and somewhat shielding it from the corrosive atmosphere inside the furnace, thereby extending its life. Preferably, the water passages 102 have a diameter of about 1/8 inch and extend inwardly and downwardly from the cooling passage 80 to the lower outwardly extending portion 70 of the inner surface 36 of sealing ring 32, thereby being spaced from the surface of the electrode 12.

    [0040] As shown in Figures 11 and 13, the support ring 20 is similarly provided with a plurality of spaced water passages 104, comprising holes extending through the support ring from its inner surface 24 to the interior of cooling passage 78. Cooling passages 104 preferably extend horizontally between the cooling passage 78 and the axially extending inner surface 24, and preferably have a diameter of about 1/8 inch.

    [0041] The cooling water is continuously recirculated into and out of the support ring 20 and the sealing ring 32 through hoses which are connected to a source of cooling water. For example, Figure 10 shows a pair of flexible metal hoses 110 connected to threaded counterbores 112 formed in the connecting surface 92 of support ring 20.

    [0042] Still referring to Figure 10, the flexible metal hoses 110 are in electrical contact with electrode 12 through the support ring 20 and are therefore "live". These hoses 110 are connected to a steel header (schematically shown as 114) which is connected to a source of cooling water (schematically shown as 116) through a pair of insulating rubber hoses 118, which are preferably protected from damage inside a pair of mild steel pipes 120 over at least a portion of their length. The steel header 114 is located a sufficient distance from electrode 12 such that there will be no arcing between electrode and header 114, and is provided with a layer of insulation 122 which prevents conduction of electricity through the header 114. Although not shown, it will be appreciated that a similar arrangement is provided for connecting the sealing ring 32 to a source of cooling water.

    [0043] The means for mounting the electrode seal on the roof of a DC arc furnace will now be described below.

    [0044] As illustrated in Figures 1, 2, 4 and 5, the support ring 20 is connected to the refractory portion 14 of the furnace roof by a plurality of mounting feet 124. In the preferred electrode seal 10 shown in the drawings, the support ring 20 is provided with three mounting feet 124, each of which is rigidly secured to the radially outermost end of an extension arm 126, the extension arm 126 being rigidly secured to one of the support ring flanges 50. Extension arms each have a flat upper surface 128 and a flat lower surface 130. The length of the extension arms 126 is such that the mounting feet 124 will be located a sufficient distance from the electrode 12 that arcing will not occur between the electrode 12 and the mounting feet 124. Preferably, the mounting feet 124 are located about 40 inches from the centre of the electrode seal 10 and about 20 inches from the outer surface 30 of support ring 20.

    [0045] Furthermore, the mounting feet 124 are electrically insulated from the support ring 20. This is preferably accomplished by providing a layer 132 of an electrically insulating material over substantially the entire upper surface 128 of each extension arm 126. Thus, when extension arms 126 are secured to the lower surfaces 52 of the support ring flanges 50 by bolts 134 (Figure 5) or the like, there will be no flow of electricity between support ring flanges 50 and extension arms 126 through insulating layer 132. To prevent electrical contact between flanges 50 and extension arms 126 through bolts 134, an insulating sleeve 138 surrounds the shank 140 of each bolt 134, and an insulating washer 142 is provided between the lower surface130 of extension arm and the nut 144 and metal washer 146 connected to the threaded end of shank 140.

    [0046] In the event of failure in the insulating capability of the connection between support ring flange 50 and extension arm 126, each mounting foot 124 is preferably electrically insulated from the extension arm 126 to which it is attached. As shown in Figure 5, each mounting arm 124 comprises a threaded stud 148 extending through an aperture 150 in the radially outer end of the extension arm 126. The stud 148 is secured to the upper and lower surfaces 128 and 130 of mounting arm 126 by nuts 152 and 154, respectively, and metal washers 156 and 158, respectively. The upper washer 156 is insulated from the upper surface 128 of extension arm 126 by the insulating layer 132, and the lower washer 158 is separated from the extension arm 126 by insulating washer 160. In addition, an insulating sleeve 162 is provided inside aperture 150 to prevent electrical contact between stud 148 and extension arm 126.

    [0047] Each mounting foot 124 additionally comprises a metal mounting sleeve 164 at the lower end of threaded stud 148. The mounting sleeve 164 is preferably welded to the steel frame which forms the perimeter of the refractory portion 14, and the studs 148 are secured to the mounting sleeves 164 by pins 166 passing through aligned apertures 168 and 170 in the stud 148 and the mounting sleeve 164, respectively. The electrode seal 10 can be removed from the refractory portion 14 of the furnace roof by removing pins 166 and lifting the seal 10 from the mounting sleeves 164, which remain attached to the refractory portion 14.

    [0048] As shown in the drawings, particularly Figure 4, the mounting feet 124 extend axially below the lower annular surface 28 of support ring 20 by a sufficient distance such that, when the mounting feet 124 are secured to the refractory portion 14 of the furnace roof as described above, an axially extending gap 172 is formed between the lower annular surface 28 of support ring 20 and the refractory portion 14. Thus, substantially the entire weight of the electrode seal is carried by the mounting feet 124.

    [0049] As shown in Figure 4, the lower annular surface 28 of support ring 20 is provided with an annular groove 175 of rectangular cross section extending about the entire circumference of the support ring 20. The annular groove 175 retains a sealing element 176 which is somewhat resilient and is compressed between the support ring 20 and the refractory portion 14, thereby sealing gap 172 against the escape of gases from the furnace. The sealing element 174 is comprised of a temperature resistant material, for example a high temperature fiberglass rope, about 4 cm2, rated to about 538°C.


    Claims

    1. An electrode seal (10) for closing a clearance between an aperture (16) in a roof (14) of an electric arc furnace and an axially extending electrode passing through the aperture (16), the electrode seal comprising:

    (a) an annular support ring (20) defining a first aperture (22) having an internal diameter greater than an external diameter of said electrode (12); said support ring (20) having a radially inwardly facing surface (24), an upper annular sealing surface (26) and a lower annular surface (28);

    (b) an annular sealing ring (32) defining a second aperture (34) having an internal diameter which is less than the diameter of the first aperture (22) and which is greater than the external diameter of the electrode (12), such that an annular gap is formed between the sealing ring and the outer surface of electrode (12), the sealing ring (32) further comprising a radially inwardly facing surface (36), an upper surface (38) and a lower annular sealing surface (40), the lower annular sealing surface (40) of the sealing ring (32) engaging the upper annular sealing surface (26) of the support ring (20) such that the second aperture (34) of the sealing ring is in substantially complete registry with the first aperture (22) of the support ring (20);

    (c) sealing ring retaining means (44) attached to the support ring (20) and positioned radially outwardly of the upper annular sealing surface (26), said retaining means (44) permitting limited sliding movement of the sealing ring (32) along its lower annular sealing surface (40) while maintaining the substantially complete registry between the first (22) and second apertures (34), wherein the sliding movement of the sealing ring (32) is limited by engagement with the retaining means (44) and the sealing ring (32); and

    (d) a plurality of mounting feet (124) attached to the support ring (20) to secure the support ring (20) to the furnace roof (14).


     
    2. The electrode seal (10) according to claim 1,
    characterized in that the radially inwardly facing surface (36) of the sealing ring (32) comprises:

    an axially extending sealing portion (68) proximate the upper surface (38) of the sealing ring (32);

    an outwardly extending portion (70) generally tapering downwardly and radially outwardly from the axially extending sealing portion (68) toward the lower annular sealing surface (40) of the sealing ring (32); and

    a plurality of axially extending scraper elements (72) circumferentially spaced from one another and extending downwardly from the axially extending sealing portion (68), the scraper elements (72) each having a pair of sides (74) extending downwardly toward one another;

    and preferably characterized in that the scraper elements (72) are coplanar with the axially extending sealing portion (68) and are preferably wedge shaped, with the sides (74) of each scraper element (72) preferably meeting at a point below the axially extending sealing portion (68).


     
    3. The electrode seal (10) according to claim 1,
    characterized in that a circumferential passage (80) for cooling water is provided inside the sealing ring (32), and in that the passage (80) for cooling water is in communication with a plurality of spaced apertures (102) extending through the radially inwardly facing surface (36) of the sealing ring (32) or the support ring (20).
     
    4. The electrode seal according to claim 3,
    characterized in that the spaced apertures (102) extend through the radially inwardly facing surface (36) of the sealing ring (32), and in that the radially inwardly facing surface (36) of the sealing ring (32) comprises an axially extending sealing portion (68) proximate the upper surface (38) of the sealing ring (32) and an outwardly extending portion (70) generally tapering downwardly and radially outwardly from the axially extending sealing portion (68) toward the lower annular sealing surface (40) of the sealing ring (32), said plurality of spaced apertures (102) being located on said radially outwardly extending portion (70).
     
    5. The electrode seal (10) according to claim 1,
    characterized in that the sealing ring (32) further comprises at least one radially outwardly extending flange (58) having an upper surface (60) and a lower surface (62), and in that the retaining means (44) has an aperture (64) into which the flange (58) extends, the aperture (64) in the retaining means (44) having an upper edge (66) being located in close proximity to the upper surface (60) of the flange (58) so as to prevent substantial axial separation of the sealing ring (32) and the support ring (30), the flange (58) being of sufficient length so as to be retained in the aperture (64) in the retaining means regardless of the extent of sliding movement of the of the sealing ring (32) relative to the support ring (20); and
    preferably characterized in that the support ring (20) further comprises at least one radially outwardly extending flange (50) having an upper surface (54) and a lower surface (52) and being axially aligned with a flange (58) of the sealing ring (32).
     
    6. The electrode seal (10) according to claim 5,
    characterized in that the sealing ring retaining means (44) are provided on the upper surface (54) of the at least one support ring flange (50); and
    preferably characterized in that the upper surface (54) of the support ring flange (50) is coplanar with the upper annular sealing surface (26) of the support ring (20), and characterized in that the lower surface (62) of the sealing ring flange (58) is axially spaced from the lower annular sealing surface (40) of the sealing ring (32), such that the lower surface (62) of the sealing ring flange (58) is spaced from the upper surface (54) of the support ring flange (50).
     
    7. The electrode seal (10) according to claim 6,
    characterized in that both the sealing ring (32) and the support ring (20) are provided with a plurality of said flanges (58, 50) circumferentially spaced from one another; and
    preferably characterized in that both the sealing ring (32) and the support ring (20) are provided with three of said flanges (58, 50) substantially evenly spaced from one another.
     
    8. The electrode seal (10) according to claim 1,
    characterized in that the mounting feet (124) are electrically insulated from the support ring (20), and are located a sufficient distance from the apertures (34, 22) of the sealing (32) and support rings (20) so as to avoid arcing between the electrode (12) and the mounting feet (124).
     
    9. The electrode seal (10) according to claim 7,
    characterized in that each of the mounting feet (124) is mounted to an extension arm (126) which is secured to one of the support ring flanges (50) and is electrically insulated therefrom.
     
    10. The electrode seal (10) according to claim 1,
    characterized in that the mounting feet (126) extend axially below the lower annular surface (28) of the support ring (20) by a sufficient distance such that, when the mounting feet (124) are secured to the furnace roof (14), an axially extending gap (172) is formed between the lower annular surface (28) of the support ring (20) and the furnace roof (14), and characterized in that the electrode seal (10) further comprises:

    (e) a sealing element (176) secured to the lower annular surface (28) of the support ring (20) to seal the gap (172) between the lower annular surface (28) of the support ring (20) and the furnace roof (14).


     


    Ansprüche

    1. Elektrodendichtung (10) zum Schließen eines Spalts zwischen einer Öffnung (16) im Dach (14) eines Lichtbogenofens und einer sich in axialer Richtung erstreckenden Elektrode (12) welche durch diese Öffnung (16) führt, wobei diese Elektrodendichtung umfasst:

    (a) einen kreisrunden Stützring (20), welcher eine erste Öffnung (22) festlegt, die einen Innendurchmesser aufweist, der größer als der Außendurchmesser der genannten Elektrode (12) ist, wobei der genannte Stützring (20) eine in radialer Richtung nach innen zeigende Fläche (24), eine obere ringförmige Dichtfläche (26) und eine untere ringförmige Fläche (28) aufweist;

    (b) einen kreisrunden Dichtring (32), welcher eine zweite Öffnung (34) festlegt, die dergestalt einen Innendurchmesser aufweist, der kleiner als der Durchmesser der ersten Öffnung (22) und der größer als der Außendurchmesser der Elektrode (12) ist, dass ein ringförmiger Spalt zwischen dem Dichtring und der Außenfläche der Elektrode (12) gebildet wird, wobei der Dichtring (32) ferner eine in radialer Richtung nach innen zeigende Fläche (36), eine obere Fläche (38) und eine untere ringförmige Dichtfläche (40) aufweist, wobei die untere ringförmige Dichtfläche (40) des Dichtringes (32) dergestalt mit der oberen ringförmigen Dichtfläche (26) des Stützringes (20) Kontakt hat, dass die zweite Öffnung (34) des Dichtringes im Wesentlichen völlig mit der ersten Öffnung (22) des Stützringes (20) ausgerichtet ist;

    (c) den Dichtring aufnehmende Mittel (44), welche am Stützring (20) angebracht sind und in radialer Richtung von der oberen ringförmigen Dichtfläche (26) nach außen positioniert sind, wobei die genannten aufnehmenden Mittel (44) eine begrenzte Gleitbewegung des Dichtringes (32) längs seiner unteren ringförmigen Dichtfläche (40) zulassen, während die im Wesentlichen vollständige Ausrichtung zwischen der ersten Öffnung (22) und der zweiten Öffnung (34) aufrecht erhalten bleibt, wobei die Gleitbewegung des Dichtringes (32) durch den Kontakt mit den aufnehmenden Mitteln (44) und dem Dichtring (32) begrenzt wird; und

    (d) eine Anzahl von Montagefüßen (124), die am Stützring (20) angebracht sind, um den Stützring (20) am Ofendach (14) zu befestigen.


     
    2. Elektrodendichtung (10) gemäß Anspruch 1,
    dadurch gekennzeichnet, dass die radial nach innen zeigende Fläche (36) des Dichtringes (32) umfasst:

    - einen sich in axialer Richtung erstreckenden Abdichtbereich (68) nahe der oberen Fläche (38) des Dichtringes (32);

    - einen sich nach außen erstreckenden Bereich (70), der im Allgemeinen von dem sich in axialer Richtung erstreckenden Abdichtbereich (68) in Richtung auf die untere ringförmige Dichtfläche (40) des Dichtringes (32) nach unten und radial nach außen kegelförmig verläuft;

    - eine Anzahl von sich in axialer Richtung erstreckenden Abstreifelementen (72), die sich über den Umfang in einem gewissen Abstand voneinander befinden und sich vom axial erstreckenden Abdichtbereich (68) nach unten erstrecken, wobei jedes dieser Abstreifelemente (72) ein Paar von Seiten (74) aufweist, die sich in Richtung aufeinander nach unten erstrecken;

    - und vorzugsweise dadurch gekennzeichnet, dass die Abstreifelemente (72) mit dem sich in axialer Richtung erstreckenden Abdichtbereich (68) koplanar sind und vorzugsweise keilförmig ausgebildet sind, wobei die Seiten (74) eines jeden Abstreifelementes (72) sich vorzugsweise an einem Punkt unter dem sich in axialer Richtung erstreckenden Abdichtbereich (68) treffen.


     
    3. Elektrodendichtung (10) gemäß Anspruch 1,
    dadurch gekennzeichnet, dass ein umfänglicher Durchgang (80) für Kühlwasser im Innern des Dichtringes (32) vorhanden ist und dass dieser Durchgang (80) für Kühlwasser mit einer Anzahl von auf Abstand befindlichen Öffnungen (102) in Verbindung steht, die sich durch die radial nach innen zeigende Fläche (36) des Dichtringes (32) oder des Stützringes (20) erstrecken.
     
    4. Elektrodendichtung (10) gemäß Anspruch 3,
    dadurch gekennzeichnet, dass die auf Abstand befindlichen Öffnungen (102) sich durch die radial nach innen zeigende Fläche (36) des Dichtringes (32) erstrecken und dass die radial nach innen zeigende Fläche (36) des Dichtringes (32) einen sich in axialer Richtung erstreckenden Abdichtbereich (68) nahe der oberen Fläche (38) des Dichtringes (32) und einen sich nach außen erstreckenden Bereich (70) umfasst, welcher von dem sich in axialer Richtung erstreckenden Abdichtbereich (68) in Richtung auf die untere ringförmige Dichtfläche (40) des Dichtringes (32) nach unten und radial nach außen kegelförmig verläuft, wobei sich auf dem sich radial nach außen erstreckenden Bereich (70) eine Anzahl von auf Abstand befindlichen Öffnungen (102) befindet.
     
    5. Elektrodendichtung (10) gemäß Anspruch 1,
    dadurch gekennzeichnet, dass der Dichtring (32) ferner mindestens einen sich radial nach außen erstreckenden Flansch (58) umfasst, welcher eine obere Fläche (60) und eine untere Fläche (62) aufweist, und dadurch, dass das aufnehmende Mittel (44) eine Öffnung (64) aufweist, in welche hinein sich der Flansch (58) erstreckt, wobei die Öffnung (64) in dem aufnehmenden Mittel (44) einen oberen Rand (66) aufweist, der sich in unmittelbarer Nähe zur oberen Fläche (60) des Flansches (58) befindet, so dass eine wesentliche axiale Trennung von Dichtring (32) und Stützring (30) verhindert wird, wobei der Flansch (58) eine ausreichende Länge aufweist, so dass er in der Öffnung (68) in dem aufnehmenden Mittel gehalten wird ungeachtet des Ausmaßes der Gleitbewegung des Dichtringes (32) in Bezug auf den Stützring (20); und
    vorzugsweise dadurch gekennzeichnet, dass der Stützring (20) ferner mindestens einen sich radial nach außen erstreckenden Flansch (50) umfasst, welcher eine obere Fläche (54) und eine untere Fläche (52) aufweist und in axialer Richtung mit einem Flansch (58) des Dichtringes (32) ausgerichtet ist.
     
    6. Elektrodendichtung (10) gemäß Anspruch 5,
    dadurch gekennzeichnet, dass die den Dichtring aufnehmenden Mittel (44) auf der oberen Fläche (54) des mindestens einen Stützringflansches (50) vorhanden sind; und
    vorzugsweise dadurch gekennzeichnet, dass die obere Fläche (54) des Stützringflansches (50) mit der oberen ringförmigen Dichtfläche (26) des Stützringes (20) koplanar ist, und dadurch gekennzeichnet, dass die untere Fläche (62) des Dichtringflansches (58) sich in axialer Richtung dergestalt in einem gewissen Abstand von der unteren ringförmigen Dichtfläche (40) des Dichtringes (32) befindet, dass die untere Fläche (62) des Dichtringflansches (58) sich in einem gewissen Abstand von der oberen Fläche (54) des Stützringflansches (50) befindet.
     
    7. Elektrodendichtung (10) gemäß Anspruch 6,
    dadurch gekennzeichnet, dass sowohl der Dichtring (32) als auch der Stützring (20) mit einer Anzahl der genannten Flansche (58, 50) ausgestattet sind, die sich über den Umfang verteilt in einem gewissen Abstand voneinander befinden; und
    vorzugsweise dadurch gekennzeichnet, dass sowohl der Dichtring (32) als auch der Stützring (20) mit drei der genannten Flansche (58, 50) ausgestattet ist, die im Wesentlichen den gleichen Abstand voneinander haben.
     
    8. Elektrodendichtung (10) gemäß Anspruch 1,
    dadurch gekennzeichnet, dass die Montagefüße (124) gegen den Stützring (20) elektrisch isoliert sind und sich in einem ausreichenden Abstand von den Öffnungen (34, 22) des Dichtringes (32) und des Stützringes (20) befinden, so dass eine Lichtbogenbildung zwischen der Elektrode (12) und den Montagefüßen (124) verhindert wird.
     
    9. Elektrodendichtung (10) gemäß Anspruch 7,
    dadurch gekennzeichnet, dass jeder der Montagefüße (124) an einen Verlängerungsarm (126) montiert ist, welcher an einem der Stützringflansche (50) befestigt ist, und gegen diese elektrisch isoliert ist.
     
    10. Elektrodendichtung (10) gemäß Anspruch 1,
    dadurch gekennzeichnet, dass die Montagefüße (126) sich in axialer Richtung unter die untere ringförmige Fläche (28) des Stützringes (20) um einen ausreichenden Abstand dergestalt erstrecken, dass, wenn die Montagefüße (124) am Ofendach (14) befestigt werden, ein sich in axialer Richtung erstreckender Spalt (172) zwischen der unteren ringförmigen Fläche (28) des Stützringes (20) und dem Ofendach (14) gebildet wird, und dadurch gekennzeichnet, dass die Elektrodendichtung (10) ferner umfasst:

    (e) ein Dichtelement (176), welches an der unteren ringförmigen Fläche (28) des Stützringes (20) befestigt ist, um den Spalt (172) zwischen der unteren ringförmigen Fläche (28) des Stützringes (20) und dem Ofendach (14) abzudichten.


     


    Revendications

    1. Garniture d'étanchéité pour électrode (10) pour fermer un jeu entre une ouverture (16) dans un toit (14) d'un four à arc électrique et une électrode s'étendant de façon axiale passant à travers l'ouverture (16); la garniture d'étanchéité pour électrode comprenant :

    (a) un anneau de support annulaire (20) définissant une première ouverture (22) ayant un diamètre intérieur supérieur au diamètre extérieur de ladite électrode (12) ; ledit anneau de support (20) ayant une surface (24) orientée vers l'intérieur de façon radiale, une surface (26) d'étanchéité annulaire supérieure et une surface (28) annulaire inférieure ;

    (b) un anneau (28) d'étanchéité annulaire définissant une deuxième ouverture (34) ayant un diamètre intérieur inférieur au diamètre de la première ouverture (22) et supérieur au diamètre extérieur de l'électrode (12), de manière à former un espace annulaire entre l'anneau d'étanchéité et la surface extérieure de l'électrode (12); l'anneau (32) d'étanchéité comprenant, en outre, une surface (36) orientée vers l'intérieur de façon radiale, une surface (38) supérieure et une surface (40) d'étanchéité annulaire inférieure ; la surface (40) d'étanchéité annulaire inférieure de l'anneau (32) d'étanchéité s'engageant dans la surface (26) d'étanchéité annulaire supérieure de l'anneau de support (20) de manière à ce que la deuxième ouverture (34) de l'anneau d'étanchéité se trouve essentiellement en phase complète avec la première ouverture (22) de l'anneau de support (20) ;

    (c) des moyens (44) de retenue de l'anneau d'étanchéité fixé à l'anneau de support (20) et situé de façon radiale vers l'extérieur de la surface (26) d'étanchéité annulaire supérieure ; lesdits moyens de retenue (44) permettant un mouvement de glissement limité de l'anneau d'étanchéité (32) le long de sa surface (40) d'étanchéité annulaire inférieure tout en maintenant essentiellement la mise en phase complète entre la première (22) et la deuxième ouverture (34) ; le mouvement de glissement de l'anneau d'étanchéité (32) étant limité grâce à l'engagement par les moyens de retenue (44) et l'anneau (32) d'étanchéité ; et

    (d) une multitude de pieds de montage (124) fixés à l'anneau de support (20) pour sécuriser l'anneau de support (20) à la voûte (14) du four.


     
    2. La garniture d'étanchéité pour électrode (10) selon la revendication 1, caractérisée en ce que la surface (36) orientée vers l'intérieur de façon radiale de l'anneau d'étanchéité (32) comprend :

    une partie (68) d'étanchéité s'étendant de manière axiale proche de la surface supérieure (38) de l'anneau (32) d'étanchéité ;

    une partie (70) s'étendant vers l'extérieur généralement se réduisant vers le bas et vers l'extérieur de façon radiale à partir de la partie (68) d'étanchéité qui s'étend de manière axiale vers la surface (40) d'étanchéité annulaire inférieure de l'anneau (32) d'étanchéité ; et

    une multitude d'éléments (72) grattoirs s'étendant de façon axiale, espacés l'un de l'autre sur la circonférence et s'étendant vers le bas à partir de la partie (68) d'étanchéité s'étendant de façon axiale ; chaque élément (72) grattoir ayant une paire de côtés (74) s'étendant vers le bas l'un vers l'autre ;

    et tout particulièrement caractérisée en ce que les éléments (72) grattoirs sont coplanaires avec la partie (68) d'étanchéité s'étendant de façon axiale et sont, de préférence, en forme de coin ; les côtés (74) de chaque élément grattoir (72) se rencontrant, de préférence, à un point situé en dessous de la partie (68) d'étanchéité s'étendant de façon axiale.


     
    3. La garniture d'étanchéité pour électrode (10) selon la revendication 1, caractérisée en ce qu'un passage (80) circonférentiel destiné à refroidir l'eau est fourni à l'intérieur de l'anneau d'étanchéité (32), et en ce que le passage (80) destiné à refroidir l'eau communique avec une multitude d'ouvertures (102) espacées les unes des autres, s'étendant à travers la surface (36) orientée vers l'intérieur de façon radiale de l'anneau d'étanchéité (32) ou l'anneau de support (20).
     
    4. La garniture d'étanchéité pour électrode selon la revendication 3, caractérisée en ce que les ouvertures (102) espacées les unes des autres s'étendent à travers la surface (36) orientée vers l'intérieur de façon radiale de l'anneau d'étanchéité (32), et en ce que la surface (36) orientée vers l'intérieur de façon radiale de l'anneau d'étanchéité (32) comprend une partie (68) d'étanchéité s'étendant de façon axiale, proche de la surface (38) supérieure de l'anneau (32) d'étanchéité et une partie (70) s'étendant vers l'extérieur, généralement se réduisant vers le bas et vers l'extérieur de façon radiale à partir de la partie (68) d'étanchéité s'étendant de façon axiale vers la surface (40) d'étanchéité annulaire inférieure de l'anneau d'étanchéité (32) ; ladite pluralité d'ouvertures (102) espacées les unes des autres étant située sur ladite partie (70) s'étendant vers l'extérieur de façon radiale.
     
    5. La garniture d'étanchéité pour électrode (10) selon la revendication 1, caractérisée en ce que l'anneau (32) d'étanchéité comprend, en outre, au moins un flasque (58) s'étendant vers l'extérieur de façon radiale ayant une surface (60) supérieure et une surface (62) inférieure, et en ce que les moyens de retenue (44) ont une ouverture (64) dans laquelle le flasque (58) s'étend ; l'ouverture (64) dans les moyens de retenue (44) ayant un bord (66) supérieur situé tout près de la surface supérieure (60) du flasque (58) de manière à éviter une séparation essentiellement axiale de l'anneau (32) d'étanchéité et l'anneau de support (30) ; le flasque (58) étant d'une longueur suffisante pour être retenu dans l'ouverture (64) dans les moyens de retenue sans tenir compte de l'ampleur du mouvement de glissement de l'anneau (32) d'étanchéité par rapport à l'anneau de support (20) ; et caractérisée, de préférence, en ce que l'anneau (20) de support comprend, en outre, au moins un flasque (50) s'étendant vers l'extérieur de façon radiale qui a une surface (54) supérieure et une surface (32) inférieure et qui est aligné de façon axiale avec un flasque (58) de l'anneau (32) d'étanchéité.
     
    6. La garniture d'étanchéité pour électrode (10) selon la revendication 5, caractérisée en ce que les moyens de retenue (44) de l'anneau d'étanchéité sont prévus sur la surface (54) supérieure d'au moins un flasque (50) d'un anneau de support ; et caractérisée, de préférence, en ce que la surface (54) supérieure du flasque (50) de l'anneau de support est coplanaire avec la surface (26) d'étanchéité annulaire supérieure de l'anneau de support (20), et caractérisée en ce que la surface (62) inférieure du flasque (58) de l'anneau d'étanchéité est espacée de façon axiale de la surface (40) d'étanchéité annulaire inférieure de l'anneau (32) d'étanchéité, de manière à ce que la surface (62) inférieure du flasque (58) de l'anneau d'étanchéité soit espacée de la surface (54) supérieure du flasque (50) de l'anneau de support.
     
    7. La garniture d'étanchéité pour électrode (10) selon la revendication 6, caractérisée en ce que l'anneau d'étanchéité (32) et l'anneau de support (20) sont pourvus d'une multitude desdits flasques (58, 50), espacés les uns des autres sur la circonférence ; et caractérisée, de préférence, en ce que l'anneau (32) d'étanchéité et l'anneau de support (20) sont pourvus avec trois desdits flasques (58, 50), espacés les uns des autres essentiellement de manière régulière.
     
    8. La garniture d'étanchéité pour électrode (10) selon la revendication 1, caractérisée en ce que les pieds de montage (124) sont isolés de manière électrique de l'anneau de support (20), et sont situés à une distance suffisante des ouvertures (34, 22) des anneaux d'étanchéité (32) et de support (20) afin d'éviter la formation d'arc entre l'électrode (12) et les pieds de montage (124).
     
    9. La garniture d'étanchéité pour électrode (10) selon la revendication 7, caractérisée en ce que chacun des pieds de montage (124) est monté sur un bras d'extension (126) qui est sécurisé à un des flasques (50) de l'anneau de support et est isolé contre ledit flasque de façon électrique.
     
    10. La garniture d'étanchéité pour électrode (10) selon la revendication 1, caractérisée en ce que les pieds de montage (126) s'étendent de façon axiale en dessous de la surface (28) annulaire inférieure de l'anneau (20) de support par une distance suffisante, de manière à ce que lors de la sécurisation des pieds de montage (124) sur le toit (14) du four, un espace (172) s'étendant de façon axiale soit formé entre la surface (28) annulaire inférieure de l'anneau de support (20) et le toit (14) du four, et caractérisée en ce que la garniture d'étanchéité pour électrode (10) comprend, en outre :

    (e) un élément d'étanchéité (176) sécurisé sur la surface (28) annulaire inférieure de l'anneau de support (20) pour rendre étanche l'espace (172) entre la surface (28) annulaire inférieure de l'anneau de support (20) et le toit (14) du four.


     




    Drawing