GB2283560A

GB2283560A - Lifting gear for the cover of a metallurgical vessel.

Info

Publication number: GB2283560A
Application number: GB9420381A
Authority: GB
Inventors: Gerhard Greiner; Gerhard Redl
Original assignee: Voest Alpine Industrienlagenbau GmbH
Current assignee: Primetals Technologies Austria GmbH
Priority date: 1993-11-04
Filing date: 1994-10-10
Publication date: 1995-05-10
Anticipated expiration: 2014-10-10
Also published as: GB2283560B; ITTO940859A1; AT401304B; CA2135045A1; ITTO940859A0; IT1267467B1; GB9420381D0; DE4438710A1; ATA223693A

Description

_r 1 2283560 LIFTING GEAR FOR THE COVER OF A METALLURGICAL VESSEL The

invention relates to lifting gear for a cover which can be placed on and raised from a metallurgical vessel by means of a lifting mechanism, having a supporting pillar which carries the cover when it is raised.

A cover lifting gear of this kind with which the cover can be raised and lowered in a substantially parallel position is known from EP-B-0 203 339. In this a supporting member which can be raised and lowered and which engages directly with the rim of the cover is provided alongside the furnace vessel: in order to operate the supporting member the lifting mechanism is attached to a rotating portal situated beside the furnace vessel.

The supporting member which is used in this design, comprising pillars which can be raised and lowered, involves an expensive structure, especially since the pillars, which are subjected to high bending stresses due to the cover projecting out around them, must be of correspondingly rigid construction and must also be provided with correspondingly generously sized guide means.

A raising and lowering mechanism in the form of pillars by which the cover of a furnace vessel can be raised is known, for example, from DE-C- 26 13 012. The part of the cover supporting pillars which can be raised and lowered is directly connected to the cover by a plurality of supporting tongues rigidly connected to the rim of the cover. In the case of this construction, too, expensive guide means for the part of the pillars which can be raised and lowered has to be provided, since here, too, high bending forces acting directly on the pillars, i.e. on the part which has to be guided vertically, arise because of the extent to which the cover projects.

1 The invention aims to obviate these disadvantages and difficulties, and addresses the problem of providing cover lifting gear in which the cover is supported on a supporting pillar located alongside the metallurgical vessel but in which the vertical guide means for raising and lowering the cover requires little constructional outlay but nevertheless permits the forces which arise to be precisely overcome. In particular it aims to avoid the need for the supporting pillar itself to be capable of being raised and lowered.

This problem is solved, in accordance with the invention, by linking the cover to the supporting pillar by way of at least one link quadrangle, operable by means of the lifting mechanism, of which the fixed link is formed by the supporting pillar and the connecting rod by a part of a cover structure which includes the cover.

Constructions which do without raisable and lowerable supporting pillars for the cover are known, for example, from DE-B-1 216 900, DE-B-1 067 984 and DE-C-750 015. In these known constructions the covers can be raised and lowered by means of lifting mechanisms acting between beams crossing the covers and the covers themselves and made up of hooks or linkage plates movable by means of cams or rods. Although by this means the cover is raised and lowered in the parallel position, it has the disadvantage that lifting it requires a plurality of movable parts and long lever gear and rods; these greatly restrict the space available above the cover, which in the case of electric arc furnaces needs to be kept clear for the electrodes which project through the cover.

According to the invention, to obtain a reduction in turning moment on raising the cover the cover is linked to the supporting pillar by way of two laterally 11 of a r adjacent link quadrangles.

Preferably the two link quadrangles are arranged in parallel planes which are disposed symmetrically to a plane of symmetry which includes the vertical central axis of the furnace vessel.

According to a preferred embodiment the link quadrangles are in intersecting planes which are symmetrical to a plane of symmetry which includes the vertical central axis of the furnace vessel, whereby lateral forces acting on the supporting pillar from the cover, such as may arise on acceleration or braking of the pivoting movement when pivoting the cover by means of the supporting pillar, can be accepted by the supporting pillar. In this embodiment the planes advantageously intersect in the region of the vertical centre axis of the metallurgical vessel.

The link quadrangle can usefully be in the form of a link parallelogram, so that even when the cover is raised it remains parallel to the cover seating of the metallurgical vessel, on which the cover lies in the closed position.

A preferred embodiment is characterised in that the cover construction has a supporting member which forms the connecting rod of the link quadrangle, correct seating of the cover on the metallurgical vessel independently of the guidance through the link quadrangle being ensured by attaching the supporting member to the cover with an amount of play that allows limited relative movement between cover and supporting member.

The lifting mechanism is preferably made up of a single hydraulic cylinder, the point of engagement of the hydraulic cylinder with the supporting member of the cover construction advantageously lying in a plane of symmetry defined by the vertical centre axis of the metallurgical vessel and the vertical centre axis of the supporting pillar.

According to a preferred embodiment the lifting mechanism is made up of two hydraulic cylinders, the points of engagement of the hydraulic cylinders being located, when viewed in plan, closely adjacent to the points of linkage of the rocker arms of the link quadrangle with the supporting member.

The supporting member of the cover construction suitably extends from the rim of the cover to near the centre of the cover.

Preferably the supporting member, when viewed in plan, is substantially triangular in shape, one apex being situated between the centre and the rim of the cover and the other two apices being in the region of the points of linkage of the rocker arms of the link quadrangle: this construction is particularly appropriate when the link quadrangles are disposed in mutually intersecting planes.

A particularly stable construction is characterised in that the supporting member is made up of two substantially parallel supporting arms which are connected at the ends remote from the cover by a crosspiece (yoke), the crosspiece advantageously being resistant to bending but yielding to torsion. This enables the cover to be seated properly on the metallurgical vessel or raised from it even if foreign bodies such as, for example, slag or material being charged into the metallurgical vessel, should lodge between the cover and its seating on the vessel and cause tilting of the cover.

A space-saving arrangement of the four-bar coupling can be achieved by making the supporting arms substantially L-shaped in form in side view, the crosspiece being situated in the corner region of the L-shaped supporting arms.

For lateral stabilisation and to accept lateral 9 1 A acceleration forces such as may occur on pivoting the cover about the supporting pillar, according to a preferred embodiment guide means are provided between the supporting pillar and the cover on which the cover is supported so as to accept lateral forces, the guide means advantageously comprising a guide rail extending longitudinally of the supporting pillar and a countersupport guided on this rail.

Advantageously the supporting pillar can rotate about its vertical centre axis.

The invention is described below in several exemplary embodiments with reference to the drawings, in which Fig. 1 shows a side view of an electric arc furnace and Fig. 2 a plan view of the electric arc furnace, according to a first embodiment. In Figs. 3 & 4 and 5 & 6 respectively, views of further embodiments analogous to those in Figs. 1 and 2 are shown. Fig 7 shows a detail from Fig. 2 in plan.

According to the embodiment shown in Figs. 1 and 2, a supporting pillar 2 is arranged alongside a furnace vessel I of an electric arc furnace, to which a cover structure Of the furnace 1 which includes the cover 3 is linked by way of link quadrangles 4, which are preferably in the form of link parallelograms. The supporting pillar 2, which is mounted so as to be rotatable about its vertical centre axis 5 either on the foundation or, in the case of a tipping electric arc furnace, on a cradle frame 6 of the furnace vessel 1, has an inner part 7 which can be raised and lowered and to which a cantilever arm 9 carrying a graphite electrode 8 projecting centrally into the furnace vessel 1 is attached.

The cover structure includes a supporting member 10 attached to the cover 3 with the provision of play 11, 12 to allow for restricted relative movement between the supporting member 10 and the cover 3. This enables the cover 3 to tilt on being placed on the furnace vessel 1 if foreign bodies such as, for example, slag or material of the furnace charge, should lodge on the cover seating 13 of the furnace vessel 1.

Despite the presence of this foreign body the cover 3 then takes up an optimum, namely inclined, position relative to the furnace vessel 1 independently of the supporting member 10.

The supporting member 10 is made up of two substantially parallel supporting arms 14 which in side view (see Fig. 1) are substantially L-shaped, with their horizontal portions 14' preferably not extending over the electrode 8. The supporting arms 14 are connected in their corner regions 15 by means of a crosspiece (yoke) 16 to form a unit, the crosspiece 16 being resistant to bending but yielding to torsion. This provides for optimum adaptation of the supporting arms 14 to the shape or position of the cover 3, particularly if it comes to lie on the cover seat 13 of the furnace vessel 1 in an inclined position.

Each of the vertically extending portions 14'1 of the supporting arms 14, which are directed parallel to the vertical centre axis 5 of the supporting pillar 2, forms a connecting link or rod of one of the link parallelograms 4 by which these arms are attached to the supporting pillar 2: i.e. each supporting arm 14 is linked to the supporting pillar 2 by its own link parallelogram 4. The link parallelograms 4 are, as can be seen in particular from Fig. 2, arranged in planes parallel to one another.

The bearings 17 of the swing arms 18 of each of the link parallelograms 4, by which the swing arms 18 are linked to the supporting pillar 2, lie substantially in the centre plane through the supporting pillar 2 which is at right angles to the length of the supporting arms 14.

0 I The supporting arms 14 are engaged at their lower ends by respective hydraulic cylinders 19 by means of a linkage 20 closely adjacent to the bearings 21 by which the swing arms 18 are linked to the supporting arms 14. The hydraulic cylinders 19 are counter-supported on brackets 22 located on the jacket of the supporting pillar 2. These hydraulic cylinders 19 thus form the lifting mechanism for raising and lowering the cover 3.

In order to accept the forces of acceleration arising on pivoting of the cover in the raised position by means of the supporting pillar, a guide 23 is provided on the cylindrical surface of the supporting pillar 2 which cooperates with the countersupport 24 situated on the supporting arms 14, i.e. on the crosspiece 16. This guide and countersupport extend vertically, parallel to the vertical centre axis 5 of the supporting pillar 2, i.e. substantially parallel to the direction of lifting. They can comprise rollers or sliding surfaces, etc. According to the embodiment shown, pairs of guide cheeks 23 are arranged spaced apart from one another with a countersupport 24 in the form of a rail attached to the supporting member 10 projecting in between them (see Fig. 7).

According to the embodiment shown in Figs. 3 and 4 a single hydraulic cylinder 19 is provided to raise and lower the cover 3, this being arranged in a plane of symmetry defined by the centre axis 25 of the furnace vessel 1 and the vertical centre axis 5 of the supporting pillar 2. It is supported at one end on a bracket 22 located on the cylindrical surface of the supporting pillar and bears at the other end on the crosspiece 16 connecting the supporting arms 14.

The embodiment shown in Figs. 5 and 6 shows the layout of two link quadrangles 4 which are arranged in two mutually intersecting planes 26, 27. The line of intersection 28 of the planes substantially coincides 1 with the centre axis 25 of the furnace vessel 1, as can be seen from Fig. 6. The supporting member 101 on the cover 3 is - when viewed in plan triangular in shape corresponding to the arrangement of the link quadrangles 4, with one apex region 29 between the centre of the cover and its rim and the two other apex regions 30 on the supporting member 10' in the region of the bearings 21 of the swing arms 18 of the link quadrangles 4. To take account of deviations of the linkage positions from the ideal on raising and lowering of the cover 3 the bearings 21 connecting the rockers with the supporting member 10' and the supporting pillar 2 are formed as articulated bearings.

To raise and lower the supporting member 101 a single hydraulic cylinder can be provided, as shown in Figs. 3 and 4, or else two hydraulic cylinders as shown in Figs. 1 and 2: in Figs. 5 and 6 the hydraulic cylinders have been omitted for the sake of clarity.

The construction in accordance with the invention has the advantage that the relatively heavy cover 3 of the furnace vessel 1 can be raised and lowered by means of a mechanism that is of simple construction and is easy to manufacture, and therefore occasions little expense, particularly since it is not necessary to have a supporting pillar which can be raised and lowered.

The bending forces due to the weight of the cover 3 are transferred to the jacket of the supporting pillar 2 without any adverse effect on the movable parts provided for the raising and lowering operations.

These parts (swing arms 18 and bearings 17, 21) can be of conventional construction. Thus for example standardised bearings can be used and the swing arms can be made from sheet metal. This results in particularly inexpensive construction.

A further advantage of the construction according to the invention is that the central region of the j 4 -g- cover through which the electrode 8 or the plurality of electrodes is or are passed is free from supporting members, thus providing good accessibility.

The invention is not limited to the embodiments illustrated by way of example, but can be modified in various respects. For example it is possible to form the link quadrangle 4 as a link trapezium or some other form of link quadrangle, whereby the cover is no longer raised in the parallel position, but when raised takes up a slightly inclined position which is at an angle to its lowered position. Furthermore a separate supporting member 10 between the cover and the supporting pillar is not absolutely necessary: the supporting member 10 could be made integral with the cover 3. The swing arms 18 could also be linked directly to the cover 3.

The hydraulic cylinder or cylinders 19 which effect the raising and lowering of the cover 3 can also be linked to the swing arms 18, for example to an extension of one swing arm 18. An advantageous arrangement of a hydraulic cylinder is to mount this between the vertical portions 14" of the supporting arms, so that it is well protected by these supporting arm portions 14" as well as by the crosspiece 16, in a similar way to the guide means 23.

A variant which makes for a simple construction of the supporting members 10 or 101 consists in providing, instead of two adjacent link quadrangles, only a total of three swing arms in a spatial arrangement, namely two swing arms which engage with the lower part of the supporting member and one swing arm which is suitably formed as a fork and partly embraces the supporting pillar 2 and which engages as nearly as possible centrally in the upper region of the supporting member 10, 10

Claims

Cover lifting gear for a cover which can be placed on and raised from a metallurgical vessel by means of a lifting mechanism, having a supporting pillar carrying the cover when raised, the cover being linked to the supporting pillar by way of at least one link quadrangle, operable by means of the lifting mechanism, of which the fixed link is formed by the supporting pillar and the connecting link by a part of a cover structure which includes the cover.
2. Cover lifting gear according to claim 1, in which the cover is linked to the supporting pillar by way of two laterally adjacent link quadrangles.
3. Cover lifting gear according to claim 2, in which the two link quadrangles are arranged in parallel planes which are symmetrical to a plane of symmetry containing the vertical centre axis of the vessel.
4. Cover lifting gear according to claim 2, in which the link quadrangles are arranged in mutually intersecting planes which are symmetrical with a plane of symmetry containing the vertical centre axis of the vessel.
5. Cover lifting gear according to claim 4, in which the planes intersect in the region of the vertical centre axis of the metallurgical vessel.
6. Cover lifting gear according to any one of the preceding claims, in which the link quadrangle is in the form of a parallelogram linkage.
7. Cover lifting gear according to any one of the preceding claims, in which the cover construction includes a supporting member which forms the connecting link of the link quadrangle.
8. Cover lifting gear according to claim 7, in which the supporting member is attached to the cover with play allowing a limited amount of relative movement between cover and supporting member.

1 4 1
9. Cover lifting gear according to any one of claims 1 to 6, in which the lifting mechanism comprises a single hydraulic cylinder.
10. Cover lifting gear according to claims 7 and 9 or 8 and 9, in which the point of engagement of the hydraulic cylinder on the supporting member of the cover construction lies in a plane of symmetry defined by the vertical centre axis of the vessel and the vertical centre axis of the supporting pillar.
11. Cover lifting gear according to claim 7 or claim 8, in which the lifting mechanism comprises two hydraulic cylinders, the points of engagement of the hydraulic cylinders on the supporting member, seen in plan, being closely adjacent to the points of linkage of swing arms of the link quadrangles with the supporting member.
12. Cover lifting gear according to any one of claims 7 to 11, in which the supporting member of the cover construction extends from the rim of the cover to near its centre.
13. Cover lifting gear according to claim 12, in which the supporting member, in plan view, is substantially triangular in shape, with one apex being situated between the centre of the cover and its rim and the two other apices being in the region of the points of linkage of the swing arms of the link quadrangle.
14. Cover lifting gear according to claim 12, in which the supporting member comprises two mutually parallel supporting arms which are connected at the end remote from the cover by a crosspiece.
15. Cover lifting gear according to claim 14, in which the crosspiece is resistant to bending but yielding to torsion.
16. Cover lifting gear according to claim 14 or claim 15, in which the supporting arms, viewed from the 0 side, are substantially L-shaped.
17. Cover lifting gear according to claim 16, in which the crosspiece is situated in the corner region of the L-shaped supporting arms.
18. Cover lifting gear according to any one of the preceding claims, in which, between the supporting pillar and the cover, guide means are provided on which the cover is supported, the guide means resiting lateral forces.
19. Cover lifting gear according to claim 18, in which the guide means comprises a guide rail extending longitudinally of the supporting pillar and countersupports guided on this rail.
20. Cover lifting gear according to any one of claims 1 to 18, in which the supporting pillar can be rotated about its vertical centre axis.
21. Cover lifting gear substantially as described herein, with reference to, and as shown in Figures 1, 2 and 7 or Figures 3 and 4 or Figures 5 and 6 of the accompanying drawings.

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