Pressure ring assembly for contact shoes in an electrode system

Abstract

Provided is a pressure ring assembly for contact shoes in an electrode system of an electric arc furnace provided with at least one electrode column assembly. The electrode column assembly comprises a contact shoe ring formed of a plurality of contact shoe elements, a pressure ring formed of a plurality of pressure blocks, and a heat shield formed of a plurality of heat shield segments. An elongated groove is formed on both substantially vertical side edges of each pressure block, and an elongated lock bar is placed in the grooves of two adjacent pressure blocks to join said pressure blocks with each other. The form of the lock bar essentially matches to the form of the grooves of said two adjacent pressure blocks. Each lock bar is locked in place in the grooves by fastening bolts through holes in the pressure blocks.

Claims

1. A pressure ring assembly for contact shoes in an electrode system of an electric arc furnace provided with at least one electrode column assembly, the lower part of which electrode column assembly comprises a contact shoe ring formed of a plurality of contact shoe elements, a pressure ring formed of a plurality of pressure blocks connected to each other to form an annular ring surrounding the contact shoe ring, the pressure blocks of said pressure ring being provided with hydraulic bellows by which the contact shoe ring is pressed against the steel mantle of the electrode, and a heat shield located above the pressure ring in the axial direction of the electrode column assembly, said heat shield formed of a plurality of heat shield segments connected to each other, wherein an elongated groove is formed on both substantially vertical side edges of each pressure block, so that in two adjacent pressure blocks said grooves are facing and opening towards each other, said grooves being wider at the bottom of the grooves than at the side edges of the pressure blocks, that an elongated lock bar is placed in the grooves of two adjacent pressure blocks to join said pressure blocks with each other, each lock bar being transverse to its longitudinal direction thicker at its both sides than in the middle, so that the form of the lock bar essentially matches to the form of the grooves of said two adjacent pressure blocks, and that each lock bar is locked in place in the grooves by fastening bolts through holes in the pressure blocks, wherein both the lock bars and the grooves are provided with bezels matching each other to form a dove-tail like joint between them, wherein the fastening bolts extend from the outer surface of each pressure block to the lock bar into which said fastening bolts are threaded.

2. The pressure ring assembly as claimed in claim 1, wherein the matching bezels are pressed against each other when the fastening bolts are tightened, so that in the joint formed thereby forces are transmitted through the bezels to the lock bar.

3. The pressure ring assembly as claimed in claim 1, wherein the grooves in the side edges of the pressure blocks extend from the upper end of each pressure block downwards near to the bottom end of the same where said grooves are closed by a shoulder.

4. The pressure ring assembly as claimed in claim 1, wherein the lock bar is made of antimagnetic material.

5. The pressure ring assembly as claimed in claim 4, wherein the material of the lock bar is austenitic steel.

6. The pressure ring assembly as claimed in claim 1, wherein the fastening bolts and the holes made for them in the pressure blocks are covered with caps.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:

(2) FIG. 1 is a schematic elevation side view of an electric arc furnace.

(3) FIG. 2 is schematic elevation side view of a lower electrode column assembly of the electric arc furnace of FIG. 1 in a larger scale.

(4) FIG. 3 is an axonometric view of a part or the lower electrode column assembly.

(5) FIG. 4 is a cross-sectional view of an arrangement for connecting the pressure shoes to each other.

(6) FIG. 5 is a detail from FIG. 4 in a larger scale.

DETAILED DESCRIPTION

(7) FIG. 1 shows a schematic illustration of an electric arc furnace 6. The furnace 6 comprises a plurality of electrode column assemblies 1, but for the sake of simplicity only one of them is shown in FIG. 1.

(8) With reference to FIGS. 1, 2 and 3 an electrode lower column assembly 2 is located in the lower part of the electrode system. The electrode lower column assembly 2 comprises a contact shoe ring 3, a pressure ring 4 and a heat shield 5. The contact shoe ring 3 is configured to be placed in contact with the electrode to conduct electric current to the electrode. The contact shoe ring 3 comprises a plurality of contact shoe elements 31. The contact shoe elements 31 are arranged in an annular form to surround the electrode. The contact shoes 31 are pressed against the steel mantle of the electrode with the aid of a plurality of hydraulic bellows arranged in the pressure ring 4 that surrounds the contact shoe ring 3. The pressure ring 4 comprises a plurality of pressure blocks 41 connected to each other to form an annular ring. Preferably each of the pressure blocks 41 is provided with a hydraulic bellow as mentioned above. A heat shield 5 is located above the pressure ring 4 in the axial direction of the electrode column assembly 1. The heat shield 5 comprises a plurality of heat shield segments 51 connected to each other to form an annular ring surrounding the lower electrode column assembly 2.

(9) As it can best be seen in FIGS. 3 and 4 a groove 46 is made on both side edges 45 of each pressure block 41. The grooves 46 are open upwards and they extend from the upper ends 42 of the pressure blocks 41 near to the bottom ends 43 of the same. So, in each adjacent two pressure blocks 41 the grooves 46 are opening towards each other. An elongated lock bar 61 is placed in said grooves 46 to join the adjacent pressure blocks 41 with each other. In order to ensure the tightness of the fitting between the lock bar 61 and the grooves 46 in the adjacent pressure blocks 41 said grooves 46 do not extend vertically through the pressure blocks 41 from the upper end 42 to the bottom end of the pressure blocks 41 but downwards said grooves 46 are closed with a shoulder 47 near the bottom end 43 of the pressure blocks 41. Holes 48 have been made in the pressure blocks 41, said holes extending from the outer face of the pressure blocks 41 into said grooves 46. Preferably a multiple of such holes 48 are provided for each groove 46. Corresponding holes 54 have been made in the lock bars 61, which holes 51 are provided with threads for fastening bolts 49. So, the lock bars 61 are locked in place in the grooves 46 by the fastening bolts 49 through the holes 48 in the pressure blocks 41.

(10) Now referring especially to FIGS. 4 and 5, both the grooves 46 in the pressure blocks 41 and the lock bars 61 have a specific configuration. In the circumferential direction of the pressure blocks 41 the grooves 46 are wider at the bottom of the grooves than at the side edges 45 of the pressure blocks 41. The lock bars are form in a similar way so that transverse to their longitudinal direction they are thicker at their both sides than in the middle and further so that their form match to the form of the grooves 46 of two adjacent pressure blocks 41. So, the lock bars 61 together with the grooves 46 form a dove-tail like joint. More specifically, both the lock bars 61 and the grooves 46 are provided with matching bezels 52, 53. When tightening the fastening bolts 49 said bezels 52, 53 are pressed to each other, whereby in the joint the forces go through the bezels 52, 53 to the bar, instead of giving transverse strain to the fastening bolts 49. Because of the large area of the bezels 52, 53 surface pressures remain at a low level.

(11) The lock bars 61 are made of antimagnetic material, and one preferable material alternative is austenitic steel. The holes 48 and the fastening bolts 49 therein are from the outer surface of the pressure blocks 41 covered with caps 50 which preferably are made of the same material as the pressure blocks 41, preferably copper.

(12) The contact shoe elements 31 are made of a material having good electrical and thermal conductivity. Further, the mechanical strength of the material must be high. E.g. copper is a material which fulfils these properties. Copper is a massive material which is very well applicable for the contact shoe elements 31. Other materials that could be used for this purpose are e.g. brass and bronze. Also other materials having corresponding properties can be used. Preferably the pressure blocks 41 are made of the same material as the contact shoe elements 31.

(13) It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.