GB2143757A - Apparatus for removing dross and similar waste material from the surface of molten metals - Google Patents

Abstract

The dross (6) at the surface of molten metal in the molds (1) of a pig casting machine, which molds (1) are circulated by an endless belt conveyor (2), is removed by at least one ladle (20) which is submersible below the surface of the metal. In the submerged state the ladle (20) coacts with a scraper (30) which is also submersible in the molten metal and is displacable towards the ladle (20) by an actuator (31,32) in order to push the dross (6) onto the ladle (20) (see Fig. 5). The ladle (20) can then be swung about a swivel shaft (21) in a substantially vertical plane out from the mold in order to eject the taken-up dross into a container (4) which has a rim (5) acting as a stop for the ladle (20). The ladle (20) and the scraper (30) are conjointly supported at a vertically reciprocable piston of a pneumatic or hydraulic piston-cylinder unit (10,11) which is movable on guides (13) along the direction of a movement of the molds (1), by a piston-cylinder unit (14). <IMAGE>

Description

SPECIFICATION An apparatus for removing dross and similar waste material from the surface of molten metal The present invention relates to a new and improved apparatus for removing dross and similar waste materials from the surface of molten metals of the type comprising drive means drivingly connected to at least one ladle in order to submerse the same beneath a meniscus formed by the molten metal and to remove the dross therefrom.

It is known to produce bars or ingots of metal, for example aluminium ingots, in such a manner that the molten metal is poured into molds. The metal bars or ingots produced in molds are usually designated as pigs. A multiple number of molds runs on an endless conveyor belt through a socalled pig casting machine to obtain a rational production of the bars or ingots.

A substantial problem exists in completely withdrawing in accordance with the operational cycle of the pig machine the dross or like waste mate riais which floats to the surface of the molten metal and consists of a mixture of metal, metal oxides, slag and the like, from the level or meniscus of the molten metal and to remove the withdrawn dross out from the related mold.

In many cases, the dross is still manually withdrawn from the level or meniscus of the liquid metal and the withdrawn dross is removed from the mold into a waste container by the foundry personnel. For this purpose the foundry person pulls a ladle or scoop through the mold and then scoops up the withdrawn dross by performing a turning movement of the ladle or scoop in order to then knock off the dross at the rim of the dross container.

It has already been suggested to simulate exactly these movements by a robot in order to automate this operation which, however, results in comparatively high production costs.

No less expensive and additionally less reliable is another suggestion according to which the dross is first pushed onto a ladle in a mechanical manner and the dross is then, after removal from the mold, again scraped off the ladle by means of a scraper.

Generally the ladles are perforated and thus are rapidly clogged during such operation which requires very frequent cleaning of the ladles.

Therefore, with the foregoing in mind it is a primary object of the present invention to provide a new and improved apparatus for removing dross or like waste materials from the surface of molten metals in a manner which is not afflicted with the aforementiond drawbacks of the prior art constructions.

Another and more specific object of the present invention aims at the provision of a new and improved apparatus for removing dross from the surface of molten metals which, while maintaining the advantageous knockoff or striking of the ladle at the waste container rim, permits a very simple and yet functionally reliable construction of the apparatus.

According to the invention this is achieved by the provision of at least one stripper submersible into the molten metal and coacting with said at least one ladle in the submersed state thereof, by actuating means acting upon said stripper for displacing the same towards the ladle in order to push the dross onto said ladle; and further by drive means drivingly connected to the ladle in order to swing the same about a swivel shaft in a substantially vertical plane to thereby eject the dross taken up by the ladle.

It can be readily seen that these measures permit a relatively simple construction of the apparatus which substantially performs only the necessary linear move ments and one swinging movement for all the sequential steps needed for withdrawing the dross and for lifting and the advantageous knocking-off of the dross from the ladle or the like.

These measures allow a very simple constructional design such that the ladle and the stripper are conjointly supported at a substantially vertically reciprocable piston of a pneumatic or hydraulic piston-cylinder system which permits common vertical movement thereof.

In order to obtain a substantially horizontal relative displacement between the ladle and the stripper in order to withdraw the dross from the mold and push such dross onto the ladle, it is additionally advantageous if the stripper is located at the free end of the piston of a hydraulic or pneumatic piston-cylinder arrangement which, while horizontally extending, is supported at the vertically reciprocable piston and furthermore if the ladle via its swivel shaft is supported at the free end of a bracket which is fixedly connected to the vertically reciprocable piston.

A very simple and functionally reliable construction further results when the drive means for swivelling the ladle comprise a pneumatic or hydraulic system acting upon the swivel or pivot shaft of the ladle via a rack. In this case a receiving or waste container for the withdrawn and removed dross can be supported at a machine frame in the swing region of the ladle. The container has a rim which is constructed as a swing limiting stop or abutment for the ladle which is swung into its dross ejection position.

There is thus generated at the ladle a high impact action and there is consequently realized a reliable and complete knock-off of the dross from the ladle.

It is of advantage for achieving a transient follower movement of the inventive apparatus with respect to the circulating molds if the piston-cylinder system which supports the ladle and the stripper is supported at a slide which can be coupled to guide rods extending substantially parallel to the travel path of the molds of the pig casting machine and which slide rests upon the circulating endless conveyor belt means. For a simplified control of the entire apparatus a further design considers the use of a fluid-operated, for instance a hydraulic or pneumatic piston-cylinder arrangement for transiently resetting the slide arrangement or slide after the dross has been withdrawn and removed from a related one of the molds.

The herein before described very simple, robust and functionally reliable construction of the apparatus according to the invention for removing dross from the surface of molten metals furthermore permits the arrangement of a multiple device in which the slide can support at least two synchronously operating ladle-stripper-systems for simultaneously removing dross from two adjacent ones of the molds.

When the liquid metal in the molds is aluminium or an aluminium alloy, an adhesion between the ladle and the stripper is effectively prevented when the ladle comprises a perforated and smoothed piece of sheet steel or steel plating and the stripper comprises a formed ceramic body.

The invention will be better understood when consideration is given to the following detailed description thereof making reference to the annexed drawings, wherein: Figure 1 is a schematic side view of the apparatus according to the invention for removing dross from the surface of molten metals in a pig casting machine; Figure 2 is a schematic and only partial end view 0of the apparatus shown in Figure 1 serving to illustrate a herein used twin arrangement of such apparatus; and Figure 3 to 10 show different operational phases of the apparatus according to the invention in illustrations corresponding to Figures 1 and 2.

Describing now the drawings, it is to be understood that only enough of the construction of the apparatus for removing dross or similar waste materials has been shown as needed for those skilled in the art to readily understand the underlying principles and concepts of the present development, while simplifying the showing of the drawings. Turning attention now specifically to Figures 1 and 2, there will be firstly recognized a so-called pig casting machine which in the present case is indicated by molds 1 which generally continuously circulate at endless conveyor belt means 2 which is supported at a machine frame 3. In a known manner, which is therefore not particularly illustrated, the circulating molds 1 serve for casting metal bars or ingots which in the present case, for instance, consist of aluminium or aluminium alioys.

In order to remove the dross 6, which floats to the surface of the molten metal in the molds 1, from the molds 1 in accordance with the operational cycle of the circulating molds 1 there is supported at the machine frame 3 an apparatus for withdrawing the dross 6 and which is disclosed in greater detail hereinafter and which transiently travels conjointly with the molds 1 and can be reset back into a desired starting position.

The aforementioned apparatus comprises, for instance, a twin arrangement of ladles or scoops 20, see Figure 2, for simultaneously removing the dross 6 from two adjacent molds 1. it will be selfevident that also triple or multiple arrangements or even merely a single arrangement is conceivable.

Each ladle or scoop 20 can be submersed below the level of the liquid metal in the related mold 1 in a manner still to be described in more detail hereinafter. In the mold 1, the ladle 20 coacts with a related stripper or scraper 30 which also can be immersed into the molten metal in the mold 1. At first the ladle 20 and the stripper 30 are spaced from each other approximately by the full longitudinal dimension of the mold 1. As will be evident from Figure 5, the stripper 30 in the immersed state thereof can be displaced towards the ladle 20 by suitable actuating means 31, 32 to be discussed more fully hereinafter. The dross which covers the level or meniscus of the molten metal is thereby completely withdrawn from the liquid level and pushed onto the ladle 20 which, then, can lift the dross 6 out from the mold 1 by performing an elevational movement, see Figure 6.To achieve the necessary vertical displacement, the ladle 20 and the stripper 30, or the corresponding multiple arrangements thereof, are conjointly supported at drive means comprising a fluid-operated, for instance pneumatic or hydraulic piston-cylinder system 10, 11 with a vertically reciprocable piston 11.

The arrangement is such that the ladle 20 is supported at the free end of a horizontal bracket 25 which is fixedly connected to the vertically reciprocable piston 11 while the stripper 30 is located at the free end of a piston 32 of the actuating means comprising a fluid operated, for instance a hydraulic or pneumatic piston cylinder unit 31, 32 which extends substantially horizontally and is also supported at the essentially vertically reciprocable piston 11. Advantageously, the stripper 30 is releasably connected to the free piston end by means of an appropriate tool holder 33.

To achieve the aforementioned transient joint run or travel of the arrangement described hereinbefore or the resetting thereof after a completed dross removal operation, the piston-cylinder system 10, 11 which supports the ladle 20 and the stripper 30, or multiple arrangements thereof, is supported at a substantially horizontally displaceable slide arrangement or slide 13. This slide arrangement 13 in the present case is supported via ball-bearing bushes 15 or similar means at guide rods or bars 16 which extend parallel to the travel path of the molds 1 of the pig casting machine.

The slide arrangement or slide 13 can be temporarily or transiently coupled by conventional coupling means to the circulating endless conveyor belt means 2 upon which such slide arrangement 13 bears. The slide arrangement 13 is reset each time after suitable decoupling, for example, by resetting means comprising a fluid-operated, for instance a hydraulic or pneumatic piston cylinder arrangement 14. This piston-cylinder arrangement 14 may effect the travel of the slide arrangement 13 in the direction of the conveyor belt means 2 as well as the resetting of such slide arrangement 13.

Conventional displacement transmitters can monitor the instances of coupling and decoupling or, respectively, the final positions of the slide arrangement 13.

It is a further essential feature of the inventive apparatus that the ladle or ladles 20 each can be swung around a swivel or pivot shaft 21 in a sub stantially vertical plane by further drive means in order to throw off the removed dross into a container 4 provided therefor. For this purpose the container 4 for receiving the withdrawn and removed dross is supported at the machine frame 3 in the swing region of the ladles 20 and provided with a protruding rim member 5 which serves as a swing limiting stop or abutment for the swung ladles 20 which can relatively violently impact thereat and thereby completely knock off the dross in an ejection position of the ladles 20.

In order to achieve the swinging rotary movement of the ladle or ladles 20 the further drive means comprise a fluid-operated, for instance a pneumatic or hydraulic system 22 which acts upon the swivel or pivot shaft 21 of the related ladle 20, for example, via a rack 23. The swivel shaft 21 is arranged at the free end of the bracket 25.

Advantageously, all the drive systems.10, 11; 14; 22 and 31, 32 are controlled by common valve control means via fluid feed lines 10', 14', 22' and 31'.

When the melt in the molds 1, as assumed hereinbefore, consists of aluminium or an aluminium alloy, the ladles 20 are preferably made of perforated and smoothed steel sheet or steel plating and the strippers 30 are preferably made of a formed or appropriately shaped ceramic body.

With reference to Figures 3 to 10 there will now be described in more detail the mode of operation of the apparatus as described hereinbefore for removing dross 6 or the like from the surface of the molten metal in the molds 1.

The description starts from an initial position according to Figure 2 in which the ladles 20 and the strippers 30 are precisely placed above two adjacent molds 1 and in which the slide or slide arrangement 13, see Figure 1, moves at the same speed and in the same direction as the circulating molds 1 as indicated by the directional arrows in Figure 4. In order to achieve this, the movement generally starts from a starting position of the slide arrangement 13 and the ladles 20 carried thereby which is displaced towards the left with reference to the position of the ladles 20 as shown in Figure 2, in order to obtain an accelerating path for accelerating the slide arrangement 13 from the rest position to the moving speed of the molds 1 when such slide arrangement 13 and the ladles 20 carried thereby arrive at the position according to Figure 2.

Thereafter the piston-cylinder system 10, 11 lowers the ladles 20 and the strippers 30 as shown in Figures 3 and 4 until they immerse into the liquid metal of the related molds 1. Next the liquid level is scraped by adjusting the piston-cylinder systems 31, 32, and thus, the stripper 30 and the dross 6 are pushed onto the ladles 20 as illustrated in Figure 5.

While maintaining the synchronous run or travel of the slide arrangement 13 conjointly with the molds 1, the ladles 20 and the strippers 30 are again elevated from the region of the molds 1 as shown in Figures 6 and 7 .Thereafter, and as shown in Figures 8 to 9, the swinging or pivoting movement of the ladles 20 is initiated and the removed dross 6 is thrown into the dross waste container 4 and simultaneously therewith the strippers 30 are reset back into their initial or starting position.

Thereafter, and as shown in Figure 10, the slide arrangement 13 is reset into its initial or starting position and the ladles 20 are swung back into their perparatory or ready-position for accomplishing a further dross removing operation at the nextfollowing molds 1.

From the foregoing it will be apparent that there has been realized an apparatus for rationally and optimally removing dross from the circulating molds of a pig casting machine. The apparatus according to the invention is particularly distinguished by its very simple, foundry-adapted and robust design which is pratically free of maintenance and malfunctions.

Claims (16)

1. An apparatus for removing dross and similar waste material from the surface of molten metals, comprising drive means drivingly connected to at least one ladle in order to submerse the same beneath a meniscus formed by the molten metal and to remove the dross therefrom, characterised by at least one stripper submersible into the molten metal and coacting with said at least one ladle in the submersed state thereof, by actuating means acting upon said stripper for displacing the same towards the ladle in order to push the dross onto said ladle, and further by drive means drivingly connected to the ladle in order to swing the same about a swivel shaft in a substantially vertical plane to thereby eject the dross taken up by the ladle.

2. The apparatus as defined in claim 1, wherein the ladle is associated with a mold holding the molten metal and is immersible into said mold.

3. The apparatus as defined in claim 1 or 2, wherein the ladle is associated with a related mold of a pig casting machine containing a multiple number of said molds and endless conveyor belt means for circulating said multiple number of molds.

4. The apparatus as defined in any of claims 1 to 3, wherein the ladle and the stripper are conjointly supported at said drive means.

5. The apparatus as defined in claim 4, wherein said drive means comprise a fluid-operated pistoncylinder system.

6. The apparatus as defined in claim 1, wherein the actuating means extend substantially horizontally, the drive means comprise a fluid-operated piston-cylinder system containing a substantially vertically reciprocable piston, the actuating means are supported at the reciprocable piston and the stripper is connected to said substantially horizontally extending actuating mear;s.

7. The apparatus as defined in claim 6, wherein the horizontally extending actuating means comprise a fluid-operated piston-cylinder unit containing a piston with a free end, the stripper being mounted to said free end of the piston.

8. The apparatus as defined in any of claims 1 to 7, wherein a bracket fixedly connected to said drive means defines a free end and the ladle is supported by the swivel shaft at said free end of said bracket.

9. The apparatus as defined in any of claims 1 to 8, comprising a rack acting upon said swivel shaft, said further drive means for swinging the ladle compri sing a fluid-operated system operating upon said rack.

10. The apparatus as defined in any of claims 1 to 9, further including a receiving container receiving the withdrawn and removed dross and supported at a machine frame, the ladle being swung through a swing region about said swivel shaft into an ejection position and the receiving container including a rim member constructed as a swing limiting stop located in said swing region of the ladle in the ejection position thereof.

11. The apparatus as defined in any of claims 1 to 10, wherein the drive means supporting the ladle and the stripper are supported at a slide arrangement, the pig casting machine containing a multiple number of molds and circulating endless conveyor belt means de fining a travel path of said multiple number of molds, guide rods extending substantially parallel to said travel path of said multiple number of molds and the slide arrangement being engageable with said guide rods and bearing upon the circulating endless conveyor belt means.

12. The apparatus as defined in claim 11, further including resetting means for transiently resetting the slide arrangement after withdrawal and removal of the dross from a related mold of said multiple number of molds.

13. The apparatus as defined in claim 12, wherein said resetting means comprise a fluid-operated piston-cylinder arrangement.

14. The apparatus as defined in claim 13, wherein at least two synchronously operating ladle-and-stripper systems are provided, said slide arrangement supporting these synchronously operating ladle-and-stripper systems in order to simultaneously remove the dross from two adjacent molds of said multiple number of molds.

15. The apparatus as defined in any of claims 1 to 14, wherein the ladle is made of perforated and smoothed steel sheet and the stripper comprises a ceramic body.

16. The apparatus for removing dross from the surface of molten metals substantially as described hereinbefore and as illustrated in the accompanying drawings.