US2993724A - Drop-bottom charging bucket for charging metallurgical furnaces - Google Patents

Description

July 25, 1961 PAKULLA 2,993,724

DROP-BOTTOM CHARGING BUCKET FOR CHARGING METALLURGICAL FURNACES Filed May 31, 1957 4 SheetsSheet 1 fnvemor:

15pm; N1) PHKULLH 15%. MW)? lf MM HT'foRNEYS July 25, 1961 LL 2,993,724

DROP-BOTTOM CHARGING BUCKET F R HARGING METALLURGICAL FURNAC Filed May 31, 1957 4 Sheets-Sheet 2 F|G.5 I I ATTORNEYS;

July 25, 1961 E. PAKULLA 2,993,724

DROP-BOTTOM CHARGING BUCKET FOR CHARGING METALLURGICAL FURNACES Filed May 31, 1957 4 Sheets-Sheet 3 IINVENTOR Zia/WWO P/MZIL L/i July 25, 1961 E. PAKULLA 2,993,724

DROP-BOTTOM CHARGING BUCKE OR CHARGING METALLURGICAL FUR A ES Filed May 51, 1957 4 Sheets-Sheet 4 NTOR [EMU/VD K041.

ATTnRN EYS United States Patent 2,993,724 DROP-BOTTOM CHARGING BUCKET FOR CHARGING IVIETALLURGICAL FUR- NACES Edmund Pakulla, Krefeld, Germany, assignor to Deutsche Edelstahlwerke Aktiengesellschaft, Krefeld, Germany Filed May 31, 1957, Ser. No. 662,901 Claims priority, application Germany June 5, 1956 7 Claims. (Cl. 294-69) The present invention relates to drop-bottom furnace charging buckets by which I mean buckets with a bottom opening closed by segmental shutters adapted to be opened in the furnace for discharge, these buckets to be used for supplying a charge to a metallurgical furnace, e.g., an electric furnace. These buckets are filled outside the furnace with a charge of scrap, pig iron, or the like, after the segmental shutters which form the bottom of the bucket have been secured by a hemp rope, a chain, or a wire cable. After removal of electrodes and cover from the furnace the full bucket is lowered into the furnace. If such a rope is used, the heat in the furnace burns away the rope and the shutters are released, discharging the contents of the bucket onto the furnace hearth, when the bucket is withdrawn. If the shutters have been secured by chain or cable, release is efiected with the help of the auxiliary tackle of the crane or by means of a bar.

These charging buckets have been found in practice to serve their purpose. They permit charges to be introduced quickly and safely, and they can be reloaded whilst the previous charge is being melted down in the furnace. On the other hand, they suffer froma number of serious drawbacks. In principle two methods of operation can be adopted for introducing a charge by means of a bucket of such a kind. The bucket may either be lowered until the segmental shutters rest practically on the floor of the hearth or it can be lowered to leave the shutters at an appropriate height above the floor of thehearth. The advantage of the first-mentioned method is that the contents of the bucket will be gently discharged on to the hearth. On the other hand, the segmental shutters and especially .the eyelet ends are liable to be damaged or even to melt away in the slag sump of the hearth. Moreover, the segments scrape over the hearth when the bucket is being raised and become damaged. .The side walls are also liable to sustain damage especially if the shutters are embodied in chain form. Consequently the second above-mentioned method is adopted and the bucket lowered into the furnace to a depth that will ensure that the ends' of the released shutters will not foul the hearth or come into contact with the slag when the bucket is raised. This avoids damage being done to the shutters or by the shutters to the hearth, but the charge in the bucket which, according to the capacity of the furnace may weigh 20 tons, 30 tons or even 70 tons and more, will then drop from a certain height on to the floor of the hearth. This not only causes damage to the hearth, but it also severely jolts the supporting structure of the furnace such as the bearings, rollers, and the components of the tipping gear, aswell as the furnace foundations. The greater the capacity of the, furnace the greater is the risk that these periodic heavy shocks will give rise to serious damage. Consequently hearths with a sintered shell, known as hard heartbs, cannot be used at all in bucket-charged furnaces becausethey will develop cracks.

It is the object of the present invention to propose a bucket which may have the same capacity as a conventional bucket but which in a simple and economical way will prevent the charge in the bucketfrom falling sud- 2,993,724 Patented July 25, 1961.

are opened. The problem thus posed is resolved by proa viding a bucket with segmental type shutters, in which the segmental shutters are secured to a funnel portion arranged below the body portion defining the peripheral, and usually cylindrical, wall of the bucket. When the segmental shutters in such a bucket are released, only part of the charge in the bucket will fall immediately on to the hearth, a major proportion sliding more slowly down the sloping walls of the funnel-shaped ring. The angle of slope of the ring and its opening at the end where the segments are attached must be adjusted to the size and bulk of the individual components of the scrap. If this is done the charge and the bucket will be released gently onto the hearth without considerable impact and shock.

The funnel portion may be shaped to form an inwardly convex surface. The object of this is to ensure that the contents of the bucket will slide easily through the lower end of the funnel-shaped ring without becoming laterally jammed whereas the remainder of the contents can follow slowly down the sides of the curved convex walls of the ring. I

It has been found especially useful both in manufacture and in subsequent use if the convex curvature of the funnel portion defines the arc of a circle.

In the drawings:

FIGURE 1 is a view in elevation of a conventional charging bucket;

FIGURE 2 is a view in elevation of one embodiment of the charging bucket of this invention in which the 1 funnel portion is in the shape of a truncated cone;

FIGURE 3 is an elevational view, partly broken away of the embodiment shown in FIGURE 2 with a second funnel forming member having a greater angle of slope shown in place and with extended side walls;

FIGURE 4 is a view'in elevation of another embodiment of the charging bucket of this invention in which the funnel portion is shaped to form an inwardly convex surface; a l

FIGURE 5 is an elevational view, partly in section, showing the charging bucket 'of FIGURE 2 with'the' shutter segments open and lowered into charging position in a furnace;

FIGURE 6 is a' bottom plan view showing the shutter segments'of the charging bucket held in the latched position' by'the latching device; I i

FIGURE 7 is an enlarged bottom plan view, partly in section, of a portion of the shutter segments of FIGURE 6 showing the latching devicein' the latched position;

FIGURE 8 is a further enlarged end sectional view of the latching device showing the pin and opposed latches in the latched position;

Referring now tothe drawings, FIGURE 1 illustrates diagrammatically a known bucket of thiskind and of a structure customarilyused; .The bucket consists of a cylindrical portion 1." Conneoted to 'the bottom of this.

, bucket shut. The' segments consist either of thin sheet-".

metal strips or of chains composed of plates which progressively diminish in width and are held togetherby: eyelets.

Three embodiments of a charging bucket constructed according to the invention are illustratively shown in the drawings in'FIGURES 2 to 4. 11

.The funnel-shaped ring 4 is secured to the cylindrical portion 1. The lower edge of this funnel portion carries. the known and conventional shutter segments 2 which;

are closed by securing themin likewise conventional. denly as a whole with a single impact when the shutters v manner at 3. The slope of the wall of the funnel portion 4 may vary between 35 and 75. Preferably, its slope will be roughly between 45 and 60". FIG. 2. shows an angle of slope of about 45. It has also been found to be an advantage if the diameter d of the bottom opening is about half that of the cylindrical portion 1. However, other dimensions may likewise be used and the diameter d might be designed to be of the diameter of the cylindrical bucket.

' A comparison between the buckets shown in FIGS. 1 and 2 will show that the total capacity of a bucket constructed according to the invention is practically the same as that of the known type of bucket. The design of the bucket according to the invention permits the bucket to be lowered deeper into the furnace than the conventional bucket without risk of the shutter segments fouling the hearth because the segments are appreciably shorter. Consequently the cost of the shutter segments will likewise be less. That portion of the charge which falls straight through on to the hearth will be only a fraction of the total contents of the bucket, whereas the remainder will slide down the sloping sides of the funnel portion when the bucket is raised.

By suitably designing the slope of the wall of the funnel portion and the diameter d of its bottom opening the bucket can be adapted to the size and bulk of the components of the scrap. A particularly useful arrangement is to provide interchangeable funnel portions 4 and to provide several funnel portions for use with each individual bucket. This will permit the bucket to be prepared for handling scrap of any size. It will be readily understood that it is also possible to provide several buckets for use with each furnace in the hitherto conventional manner, in which case the several buckets may each have a funnel portion with a slope diiferent from the others.

If the size of the scrap should change, a second funnel forming member 5 indicated in FIG. 3 with the same bottom opening d can be inserted into the bucket from above the bucket being otherwise as shown in FIG. 2. However, in the illustrated example the slope of the walls of this second funnel member 5, shown in place, is about 60. Other angles of slope exceeding 45 may likewise be used. Funnel member 5 will firmly locate itself in the base of the bucket and can be withdrawn by inserting the hooks of the tackle of a crane into holes burnt into its walls. The advantage of this form of construction is that the same bucket can be readily converted to a different angle of slope of its funnel without the need of providing a special additional support of the kind conventionally used for supporting the buckets when they are being charged. In some cases it may be an advantage if the loss in capacity due to the insertion of a funnel member '5 is compensated by suitably extending the upper edgeof the bucket as shown in FIG. 3.

FIG. 4 shows yet another form of construction which afliords special advantages.

The funnel-shaped ring 4 with the segmental shutters 2 and their locking means 3 is secured to the cylindrical portion 1 of the bucket. As shown at 60 the walls of the funnel-shaped ring are inwardly arched to form a convex surface. wall defines the arc of a circle. The center 7 of the circle of curvature is located on the line of intersection between the extended surface 8 and the plane 9 which contains the lower circular edge of the funnel portion 4.

The diameter d ofthe lower edge of funnel portion 4 may be equal to from one-third to two-thirds of the diameter of the cylindrical portion 1 of the bucket, as in the previous examples.

The advantages offered by the previously described embodiments in regard to capacity, lowering the bucket into the furnace, releasing the shutters, and so forth, are also inherent in the present embodiment, but owing .to the convex conformation of the inside wall 60v the slope of the wall progressively increases to point 10 where In the illustrated example the arched it is practically Between points 10 the contents of the bucket can therefore drop straight through the opening, whereas the remainder must slide slowly down the arched sloping walls. This substantially eliminates risk of the charge becoming jammed and at the same time ensures that it will be quickly and smoothly deposited on the floor of the hearth without giving rise to the major shocks caused by heavy charges dropping suddenly as a whole on to the floor.

Charging buckets contrived as proposed by the present invention can even be used for charging furnaces of maximum capacity. Since major impacts on the floor of the hearth will not occur and subject the sub-structure of the hearth to considerable shock, even sintered hearths can be used. Moreover, the life of :the tipping gear will be prolonged. So far as the mechanical handling of a bucket according to the invention .is concerned this does not appreciably differ from that employed in the case of conventional buckets. A bucket as described can also be used with advantage for charging metallurgical furnaces of other descriptions which are not equipped with electrodes.

FIGS. 5 to 8 illustrate a connection of the inwardly tapering shutter segments to the bucket, it being understood that the invention does not concern any improvement in the shutter device per se. The segments are loosely pivoted by eyelets 12. through holes 13 around a ring 14 and their inner ends are provided with eyelets 15 through which a temporary connecting ring formed by the chain 16 is threaded, the said chain 16 being held by a latching device comprising a pin 17 which is retained by opposed latches 17a and 17b attached to the chain 16, the pin being carried by a chain 11 so that when the latter is pulled, the pin is withdrawn, the ends of the chain 16 are released and they slide out of the latching elements as well as out of the eyelets in the several shutters, allowing the latter to drop and discharge the contents of the bucket. FIG. 5 shows the shutter segments open and how the mass of material in the funnel portion tends to slide inwards and restrict the fall of, the material through the funnel opening adjacent which the segments are pivoted and to spread out within the shutters in falling onto the hearth.

What I claim is:

1. A drop-bottom charging bucket for supplying a charge of scrap, pig-iron or the like to a metallurgical furnace comprising a body portion defining a peripheral wall, a funnel portion at what in use of the bucket is the lower endof the body portion, and shutter segments at the exit of the funnel portion adapted to be opened for central falling discharge of the charge, said funnel serving to control the rate of discharge through the said exit when the shutters are open.

2. A bucket according to claim 1, in combination with at least one funnel member adapted to be inserted in the bucket through the top and having a greater base angle of slope than, but not necessarily a dilferent size of exit opening from, the aforesaid funnel portion.

3. A bucket according to claim 1, in which the funnel portion has an inwardly arched convex wall.

4. A bucket according to claim 1 in which the curve of the convex wall is the arc of a circle.

5. A bucket according to claim 4 in which the center of the circle which determines the sectional curvature of the convex wall is located on thev line of intersection between the extended peripheral surface of the cylindrical portion of the bucket and the plane containing the lower edge of the funnel portion.

' 6. A drop-bottom charging bucket for supplying a charge of scrap, pig-iron or the like to a metallurgical furnace, comprising a substantially cylindrical body portion and a ring of inwardly tapering segmental shutters which normally close the bottom of the bucket but can swing open to allow for central falling discharge from the bucket, wherein the body portion has a downward funnel-like extension terminating in an exit opening, said shutters being pivoted in circular formation adjacent the said exit opening, said funnel serving to control the rate of discharge through the said exit when the shutters are open. 5

7. A drop-bottom charging bucket according to claim 6, said tunnel forming a shallow extension of said body portion, the base angle of the slope of the Wall of the funnel portion being between 35 and 60, said opening being at least one-third but not more than two-thirds 10 the diameter of the said cylindrical portion.

References Cited in the file of this patent UNITED STATES PATENTS Hunt July 23, 1895 Provay May 13, 1924 Kiplinger Mar. 3, 1931 Lintz Nov. 19, 1940 McIlwrick et a1. Oct. 23, 1945 Richardson July 1, 1952 Consoldane et al May 11, 19-54- Beckenbach Mar. 5, 1957

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