EP2739926B1

EP2739926B1 - Device for loading crucible furnaces

Info

Publication number: EP2739926B1
Application number: EP11808725.3A
Authority: EP
Inventors: Piergianni GANDINI
Original assignee: Gandini SpA
Current assignee: Gandini SpA
Priority date: 2011-11-02
Filing date: 2011-11-18
Publication date: 2016-03-09
Anticipated expiration: 2031-11-18
Also published as: WO2013065076A1; EP2739926A1; ITMI20111978A1

Description

Field of application of the invention

The present invention has application in the foundry field, and more specifically it refers to a device for loading crucible furnaces.

Review of the prior art

Smelting furnaces are furnaces employed in foundries in order to smelt a metal charge. There are various types of smelting furnaces, which differ from each other regarding the structure and the mode with which the heat is transferred to the metal charge. The selection of the furnace to be used first depends on the metal charge. The smelting furnaces usually employed for smelting non-ferrous alloys, like aluminum alloys, copper-based alloys and magnesium-based alloys, are the so-called "crucible" furnaces. In these furnaces, the metal charge is situated in a receptacle (the crucible) placed inside a chamber in which heat is generated via electrical heating elements and/or a natural gas burner. The metal charge is usually constituted by ingots, risers, smelting waste to be resmelted or scraps. The crucible is made of a highly conductive material, such as graphite or silicon carbide, while the chamber where the crucible is placed is insulated, in such a manner optimizing the transfer of heat from the flame to the metal charge.
The loading of crucible furnaces is preceded by an operation called "drying" of the metal charge, which consists of a pre-heating of the same aimed to eliminate possible traces of residual water. This operation is made necessary by the fact that usually, at the time of loading, the crucible contains residual molten charge. If the latter came into contact with traces of water present in the charge to be smelted, this would lead to a violent reaction due to the generation of water vapor and to the immediate expansion thereof: there would be the risk that molten metal spray exits outward from the mouth of the furnace. In order to prevent one such occurrence, it is necessary to pre-heat the metal charge by inserting the same in suitable drying furnaces that are different from the smelting furnaces.
Crucible furnaces are loaded from the top. The crucible has an upper opening and the loading of the furnace occurs by overturning - at the loading mouth of the furnace above said opening - a container (generally a large metal box) in which the charge to be smelted has been previously collected. The overturning of the container is manually carried out by an operator. The latter thus comes to be situated close to the loading mouth of the furnace, and risks being burnt and inhaling fumes. These risks are even greater whenever it is necessary to fill up a crucible that is already partially loaded. The manual loading also requires considerable operator effort, since for safety reasons the loading mouth of the furnace is situated at a height from the ground such that, in case of accidental operator fall, the latter cannot come into contact with the molten metal. Since the loading operation for the crucible furnace is relatively frequent, the strenuous actions are repeated; in the immediate future or over a long period of time, serious damage can be caused to the muscular-skeleton apparatus of the operator.
Another disadvantage of the manual loading consists of the fact that the operator can be injured due to the accidental fall of pieces from the container, or the operator can be cut due to the presence of burrs on non-compliance castings intended to be resmelted. These traumas are even more probable if the operator is obliged to manually insert the pieces to be smelted in the crucible, one at a time, as occurs when the pieces are too heavy or bulky to be collected in the suitable container.
In order to reduce the stresses and the risks for the operator and at the same time accelerate the loading operation, it is possible to employ a mechanically overturnable metal box, open at the top for inserting the metal charge to be smelted. The box is liftable by means of a forklift whose forks are insertable in two tubular elements having one end hinged to the base of the box, allowing the overturning thereof in a nearly instantaneous manner. This does not allow oper-ating in maximum safety conditions since there is the risk that not all the metal charge falls into the crucible. More specifically, part of the charge could bounce against the edge of the furnace loading mouth and be projected beyond the hole itself, with the risk of injuring operators in the immediate vicinity; another part of the charge could remain on the upper wall of the furnace, requiring a subsequent manual intervention to push it into the crucible, with the abovementioned risks for the operator. The pieces that bounce outside the furnace must be reinserted in the container, thus repeating the loading operation, or they must be manually inserted into the crucible. In addition, for the overturning to automatically occur with the release of an immobilization device, it is necessary that the box be filled in a uniform manner - but this is not always possible, especially in the case of smelting waste to be resmelted that is particularly bulky. There is therefore the risk that the operator will be obliged to intervene, by seeking to manually overturn the box or by making it jump slightly with the forklift. Also in these situations, therefore, there is a high risk of injury for the operator.
US 2006/0060133 A discloses means for supplying raw material in additional charging or recharging of solid granular raw material into molten material in the crucible, comprises a raw material supply tube to be filled with said material, a metallic support member which runs through the inside of the tube, connects with the bottom lid, and serves for descending the lid and for ascending the tube and the lid, and a configuration avoiding metallic contamination, whereby the lower-end aperture of the tube is opened for charging said material therein into the crucible in uniform circumferential distribution and in large quantity, thus achieving efficient supply operation to be widely applied for growing silicon single crystals.
JP 11 159972 A discloses an alloy adding device wherein an alloy material is added to a melt melted in an induction furnace or a cold crucible furnace in vacuum or inactive gas atmosphere, a near cylindrical addition bucket and an inverse tapered lid body are provided, and the inverse tapered lid body is vertically moved relative to the addition bucket, while an inverted conical guiding plate fitted to the lower part, in outer periphery, of the addition bucket. A guide having an inclination angle almost equal to the gradient of the inverted conical guiding plate is fitted to the upper part of a crucible, so that the alloy adding device is guided to the center part of melt in the pot with ease. With the inverted conical guiding plate comprising a heat-resistant metal material, heat-resistance characteristics improved further so that the alloy material can be dropped into a high-temperature melt in the pot from a position as near as possible.
CN 201 488 524 U discloses a novel charging structure of a cupola furnace, comprising a furnace body and a furnace cover arranged at a furnace mouth, wherein the furnace cover consists of two parts, and the outer sides of the two parts are hinged at the mouth of the furnace body; the two parts of the furnace cover are respectively and fixedly connected with a balance weight part which extends to the outside of the furnace body; the furnace cover and the balance weight part do opposite direction actions by taking the hinged part of the furnace cover and the furnace body as a rotating fulcrum; when the furnace cover overturns toward the inside of a furnace body cavity to be in an opening state, the balance weight is lifted upward; and when the furnace cover is sealed at the mouth of the furnace body, the balance weight part recovers the normal state. The mouth of the furnace body is provided with a housing which is internally provided with a cone material barrel matched with a material cup; and the conicity of the cone material barrel is same as that of the lower end of the material cup. The novel charging structure leads the whole charging process of the cupola furnace to be carried out in the sealed process, thus greatly improving the surrounding environment and avoiding the overflowing of smoke and dust and harmful gas.
CN 2 861 078 Y discloses a container with a locking device for shipping and storing alloy materials. It consists of main body, fixed cover, active cover, lifting rod, hinge, torsion spring for turning cover, spring lock, guide roller and supports for steel rope, traction steel rope and suspension ring of steel rope. After load alloy materials, presses down the active cover to make the spring lock installed beneath active cover spring out automatically and clip on the edge of steel plate of the container, thus active cover is locked up deadly and can not be opened from outside. After the container is handled onto the supports of unloading opening on the top end of storehouse in factory, the cone-shaped bottom of container is hanged in the air and lets down by driving of alloy materials weight, then the traction steel rope hanged on the lifting rod is driven to make the spring lock exit from the edge of steel plate of the container, only at this time, the torsion spring installed on the pin shaft of hinge of active cover can rise the active cover automatically and the active cover can be opened.
In particular, CN 2 861 078 Y discloses a device suitable for loading a crucible furnace, having a loading mouth above the opening of a crucible. The device contains:

a container openable on the top, in which the metal charge to be melted is stored, said container being delimited by a side wall with overturned frustoconical shape, separatable from a base cone that is projected inside the space delimited by said side wall;
gripping means connected to the container, suitable for allowing the lifting and the emptying of the same, said gripping means including a guide rod connected to the vertex of the base cone;
second gripping means connected to said side wall and that are suitable for providing a seat for the guide rod, allowing the sliding of the side wall in the direction of the guide rod for the emptying of the container;
support means for the container, allowing for the partial insertion of the base cone inside the crucible.

GB 716 885 A discloses a skip having a portion of magnetic material for cooperation with a lifting magnet, and a bucket portion which is either formed of substantially non-magnetic material such as stainless steel, or is insulated from the portion by forming a portion of the stem of such material. The skip illustrated is for charging an iron-melting cupola furnace and its bucket has a conical wall separable from the floor when the wall is supported by the periphery of the charging aperture. In an alternative arrangement the wall is cylindrical and is formed with flanges for resting on the charging opening.

Objects of the invention

The object of the present invention is to indicate a device for loading crucible furnaces whose container in which the metal charge to be melted is stored, has an increased capacity and emptying speed. In other words, the problem to be solved by the present invention is how to increase the capacity and the emptying speed of the above mentioned container.

Summary of the invention

In order to attain such objects, the present invention has as subject a device for loading smelting furnaces, said furnaces having a loading mouth placed above the opening of a crucible, said device including:

a container open on the top, in which the metal charge to be smelted is stored, said container being delimited by a side wall with overturned frustoconical shape, separatable from a base cone that is projected in the space delimited by said side wall;
gripping means connected to the container, suitable for allowing the mechanical lifting and emptying of the same, said gripping means including a guide rod connected to the vertex of the base cone;
second gripping means connected to said side wall and suitable for providing a seat for the guide rod, allowing the sliding of the side wall in the direction of the guide rod for the emptying of the container;

means capable of providing a support on the furnace for the container, said support means of the container including a plurality of legs arranged around said base cone, each leg being constituted by:
- a first segment below said ring of the base cone and welded thereto;
- the first segment being contiguous with a second segment that is upwardly tilted outside the base cone;
- the second segment being contiguous with a third horizontal segment nearly at the same height as the vertex of the base cone;
- the third segment being contiguous with a downwardly-directed terminal segment, of smaller length than the second segment and having, at the end, a foot capable of providing a support on the furnace,
said support means of the container allowing the partial insertion of the base cone in the crucible, as described in claim 1.

Further characteristics of the present invention deemed innovative are described in the dependent claims.
According to one aspect of the invention, the second gripping means comprise a bar whose ends are connected to the edge of the mouth with greater diameter of said side wall with frustoconical shape, the bar being centrally perforated in order to obtain the seat for the guide rod.
According to another aspect of the invention, said gripping means also include two brackets rigidly connected to said bar on both sides of the guide rod and which can be engaged by a forklift:
According to another aspect of the invention, each of two pairs of opposing legs, obtainable from a shearing plate, has a central notch for fitting with the other pair, said first segment of each leg having the same triangular shape as the base cone and being in contact with the mesh that constitutes it.

Advantages of the invention

Given the same base diameter, the frustoconical shape of the side wall confers greater capacity to the container with respect to the cylindrical shape, and the fact that said frustoconical shape is overturned ensures that the weight force of the load to be smelted presses the side wall against the base cone. This contributes to preventing the accidental lifting of the side wall during the movement of the scum loading device.
The emptying of the container occurs more rapidly the higher the side wall is lifted from the base cone. The operator can thus regulate the emptying speed of the container by lifting the side wall as desired.
The fact that the base cone is partially inserted in the crucible facilitates the entrance of the metal charge, preventing the accidental fall in the interspace present between the crucible and the walls of the furnace chamber where the crucible is placed.
The rigid metal mesh that constitutes the base cone and the side wall of the container lightens the device, dampens the noise that is generated during the emptying of the container, and allows drying the metal charge to be smelted without using a drying furnace. Indeed, by positioning the device loaded with pieces to be dried at the mouth of the furnace, as occurs for the loading operation, the heat emanated from the crucible crosses the mesh and reaches the metal charge, drying it.
The presence of the guide rod maintains the two parts of the container joined together, even if allowing the translation of the lateral part with respect to the base; hence, during transport the two parts cannot be separated, which would cause an undesired partial emptying. The guide also confers container emptying uniformity along the circumference of the base cone.

Brief description of the figures

Further objects and advantages of the present invention will be clearer from the following detailed description of an embodiment thereof and from the attached drawings given as a merely non-limiting example, in which:

figures 1A, 1B, 1C are perspective views of the parts composing a device for loading crucible furnaces according to the present invention;
figure 2 is a perspective view of the device obtained from the assembly of the parts visible in the preceding figures;
figure 3 is a perspective view of the loading device of figure 2 set on the ground and filled with risers;
figure 4 is a perspective view of the loading device of figure 3 lifted from the ground by means of a forklift;
figure 5 is a perspective view of the loading device of figure 4 positioned on the mouth of a crucible furnace;
figure 6 is a perspective view of the loading device of figure 5 during the emptying thereof;
figure 7 is a perspective cross section view of the loading device for the crucible furnace of figure 6.

Detailed description of several preferred embodiments of the invention

In the following description, equivalent elements that appear in different figures may be indicated with the same symbols. In the illustration of one figure, it is possible to make reference to elements not expressly indicated in that figure but in preceding or subsequent figures. The scale and the proportions of the various depicted elements do not necessarily correspond to the actual scale and proportions.
Figures 1A, 1B, 1C separately show the components of a loading device for crucible furnaces. With reference to figure 1A ; it is possible to observe a truncated cone obtained from a rigid metal mesh 1 cut with circular rim sector form, folded on itself and then welded along the superimposed lateral edges. The truncated cone 1 is overturned, i.e. with the smaller diameter edge lower down. Two metal rings 2 and 3 are respectively welded to the smaller and greater diameter edges of the truncated cone 1. A horizontal bar 4 has the ends welded to the upper ring 3 in diametric position and a square hole 5 in central position. Two brackets 6 and 7 for the insertion of the forks of a forklift are welded to the bar 4 on opposite sides with respect to the hole 5. Figure 1B shows a cone obtained from a rigid metal mesh 10 cut with circular sector shape, folded on itself and then welded along the superimposed lateral edges. A metal ring 11 is welded to the edge of the cone 10. The diameter of the ring 11 is equal to or at most greater than the diameter of the lower ring 2 of the truncated cone 1. The ring 11 is welded to and rests on four identical legs 12, 13, 14, 15. The legs 12, 13, 14, 15 are of flattened form and are spaced 90° with respect to each other. With reference to the leg 12, it has a first horizontal segment 12a welded to the ring 11 (below the ring) which continues upward and outward into a second segment 12b, which in turn continues into a third horizontal segment 12c, terminating in a fourth segment 12d directed downward and slightly outwardly tilted. The horizontal segment 12c is at about the same height as the vertex of the cone 10. The distal segment 12d is shorter than the oblique segment 12b and is enlarged at the end to form a support foot 12e that comes to be situated at a greater height than the ring 11 of the cone 10. The oblique segment 12b has the same slope as the wall of the truncated cone 1. Figure 1C shows a parallelepiped rod 16 that can slide in the seat 5 of the bar 4. The upper end of the rod 16 is welded to the center of a bar 17 orthogonal to the bar 16. Two brackets 18 and 19 for the insertion of the forks of the forklift are welded to the bar 17 on opposite sides with respect to the rod 16.
Figure 2 shows the loading device 20 for crucible furnaces obtained by assembling together the components visible in the preceding figure. As can be observed in the figure, said loading device 20 is obtained by means of the following constructions steps:

a) setting the legs 12, 13, 14, 15 on the ground at respective first horizontal segments of 12a type, placed below the cone 10, the support feet 12e being raised from the ground;
b) setting the lower ring 2 of the overturned truncated cone 1 on the ring 11 of the cone 10;
c) inserting the rod 16 in its seat 5 in the bar 4 until it reaches the top of the cone 10;
d) cutting the mesh 10 at the top of the relative cone;
e) inserting the rod 16 into the hole thus obtained;
f) overturning the device 20 thus obtained and welding the lower end of the rod 16 to the mesh 10 and to an extension of the legs 12, 13, 14, 15 which is projected towards the interior of the space delimited by the mesh 10 in contact therewith, as will be better illustrated in figure 7.

Upon completion of these steps, one obtains a container for the metal charge to be smelted composed of two meshes 1 and 10, of which the mesh 1 constituting a frustoconical side wall has the possibility to translate with respect to the base constituted by the conical mesh 10 in order to allow the emptying of the container itself.
The rod 16 projects beyond the upper ring 3 with a height corresponding to the length of the upward translation of the frustoconical mesh 1, which determines the desired level of opening of the device 20. It is not recommended to make the frustoconical mesh 1 translate upward beyond twice the height of the base cone 10 since the metal charge, constituted by pieces to be resmelted of variable size, could gain speed such to make the single pieces bounce outside the crucible opening.
The subsequent figures 3 to 7 illustrate the sequence of loading a crucible furnace by means of the device 20.
Figure 3 shows the device 20 of figure 2 filled with risers 25 while the access to the brackets 18 and 19 of the bar 17 remains unobstructed. The metal meshes 1 and 10 are sufficiently close and rigid so as to contain the risers 25 without being deformed.
Figure 4 shows the forklift 26 with the forks 27 and 28 inserted in the brackets 18 and 19 of the bar 17. The forks 27 and 28 are at a height such that the device 20 is lifted from the ground. The lifting of the base cone 10 determines the lifting of the entire device 20 since the ring 11 comes to abut against the lower ring 2 of the frustoconical mesh 1.
Figure 5 shows the device 20 positioned above the loading mouth 29 of a crucible furnace 30. The feet of 12e type of the legs 12, 13, 14 and 15 rest on the upper wall 31 of the furnace 30. After the device 20 has been abutted against the furnace 30, the forks 27 and 28 of the forklift 26 were removed from the brackets 18 and 19 of the bar 17 and subsequently inserted into the brackets 6 and 7 of the bar 4. The loading mouth 29 has a diameter greater than that of the base cone 10. The latter, the legs 12, 13, 14 and 15 and the lower part of the frustoconical mesh 1 at the ring 2 cross the loading mouth 29, partially penetrating into the furnace 30. The device 20 remains in this step until the risers 25 are completely dried.
Figure 6 shows the device 20 of figure 5 in which the frustoconical mesh 1 has been completely lifted by means of the forks 27 and 28, until the brackets 6 and 7 arrive in contact with the bar 17. In such a manner, an opening is created between the base cone 10 and the frustoconical mesh 1 through which the risers 25 fall into the crucible 32 (visible in figure 7). The passage from the step shown in figure 5 to that shown in figure 6 occurs with the gradualness required for emptying the device without the risers overflowing beyond the opening of the crucible 32.
Figure 7 shows, in cross section, the device 20 and the furnace 30 of figure 6. Inside the combustion chamber 34 of the furnace 30, the crucible 32 is placed partially filled with molten metal 33. The crucible 32 rests on the base of the chamber 34 at the center thereof, aligned with the loading mouth 29, the latter having smaller diameter than the diameter of the crucible 32. With reference to the figure, it is possible to note that the base cone 10 and the legs 12, 13, 14 and 15 partially penetrate into the crucible 32. A burner 35 is inserted in a side wall of the furnace 30 in communication with the chamber 34 for the heating of the crucible 32. As can be observed in the figure, the diameter of the base cone 10 is about half the diameter of the crucible 32 opening, leaving sufficient space for the fall of the risers 25. The height of the oblique segment of 12b type is greater than or equal to the sum of: the height of the distal segment of 12d type, the thickness of the upper wall 31 of the furnace 30, the distance between the latter wall and the opening of the crucible 32 and the desired amount of penetration of the base cone 10 inside the crucible 32.
The opposite legs form a single piece obtained via shearing of a plate. The opposite proximal segments of 12a type are in reality two halves of a single triangle whose oblique sides have the same tilt as the base cone 10 resting thereon. Each triangle has a central notch: a first one open on the vertex and a second one open on the base, in a manner so as to allow the fitting between the two pairs of legs. The rod 16 is also welded to the triangular conformation of the legs 12, 13, 14 and 15 inside the cone 10.
In order to remove the open device 20 from the furnace 30, it is necessary to further raise the forks 27 and 28 so as to lift the base cone 10 and the legs 12, 13, 14 and 15 the amount required for extracting them from the mouth 29 of the furnace 30.
On the basis of the description provided for a preferred embodiment, it is clear that several changes can introduced by the man skilled in the art without departing from the scope of the invention, as results from the following claims.

Claims

A device (20) for loading smelting furnaces (30), said furnaces having a loading mouth (29) placed above the opening of a crucible (32), said device (20) including:
- a container (1, 2, 3, 10, 11) open on the top in which the metal charge (25) to be smelted is stored, said container (1, 2, 3, 10, 11) being delimited by a side wall (1, 2, 3) with overturned frustoconical shape, separatable from a base cone (10, 11) that is projected inside the space delimited by said side wall (1);

- gripping means (16, 17, 18, 19) connected to the container (1, 2, 3, 10, 11), suitable for allowing the mechanical lifting and the emptying of the same, said gripping means (16, 17, 18, 19) including a guide rod (16) connected to the vertex of the base cone (10);

- second gripping means (4, 6, 7) connected to said side wall (1, 2, 3) and suitable for providing a seat (5) for said guide rod (16), allowing the sliding of the side wall (1, 2, 3) in the direction of the guide rod (16) for the emptying of the container (1, 2, 3, 10, 11);
characterized in that said side wall (1, 2, 3) is constituted by a rigid metal mesh (1) comprised between two metal rings (2, 3), of which the lower ring (1) acts as an abutment against said base cone (10, 11) during lifting,
said base cone (10, 11) being formed by a rigid metal mesh (10) which constitutes the single side wall thereof, connected at the base to a metal ring (11) which comes to press against said abutment ring (2),
the loading device (20) also including:
- means (12, 13, 14, 15) capable of providing a support on the furnace (30) for the container (1, 2, 3, 10, 11), said support means including a plurality of legs (12, 13, 14, 15) arranged around said base cone (10, 11), each leg (12) being constituted by:
• a first segment (12a) below said ring (11) of the base cone (10, 11) and welded thereto;

• the first segment (12a) being contiguous with a second segment (12b) that is upwardly tilted outside the base cone (10, 11);

• the second segment (12b) being contiguous with a third horizontal segment (12c) nearly at the same height as the vertex of the base cone (10, 11);

• the third segment (12c) being contiguous with a downwardly-directed terminal segment (12d), of smaller length than the second segment (12b) and having, at the end, a foot (12e) capable of providing a support on the furnace (30),
said support means (12, 13, 14, 15) of the container (1, 2, 3, 10, 11) allowing the partial insertion of the base cone (10, 11) inside the crucible (32).
The loading device (20) of claim 1, characterized in that said second gripping means (4, 6, 7) comprise a bar (4) whose ends are connected to the edge (3) of the mouth with greater diameter of said side wall of frustoconical shape (1, 2, 3), said bar (4) being centrally perforated in order to obtain the seat (5) for the guide rod (16).
The loading device (20) of claim 2, characterized in that said gripping means (4, 6, 7, 16, 17, 18, 19) also include two brackets (6, 7; 18, 19) rigidly connected to said bar (4) on the both sides of the guide rod (16) and which can be engaged by a forklift (26).
The loading device (20) of claim 1, characterized in that each of two pairs of opposite legs (12,14; 13, 15), obtainable from a sheet via shearing, has a central notch for fitting with the other pair, said first segment of each leg having the same triangular form of the base cone (10, 11) and being in contact with the mesh (10) that forms it.