TO A DIE-CASTING MACHINE

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Field of the Invention

This invention relates, in general, to the field of the equipment for metallurgical plants and refers, in particular, to a furnace integrating a supply system to feed molten metal, such as an aluminium alloy or the like, to die- casting or high-pressure die-casting machines.

State of the Technique

A system or island for die-casting operations usually comprises at least a die-casting machine, a furnace for supplying molten metal to be used by this machine and an equipment, or a dosing charger, to transfer the molten metal from the furnace to the machine by means of a container.

In particular, the furnace can be:

- a maintenance furnace, or

- a smelting and maintenance furnace.

A maintenance furnace depends on the presence of a general smelting furnace for metal fusion, and use of only one type of aluminium alloy. In this case the metal, in the liquid state and at a high temperature, is transferred from the smelting furnace to the storage furnace by means of appropriate ladles.

A smelting and maintenance furnace also lends itself to the use of different types of aluminium alloy. Therefore, the dimensions of the furnace can be reduced to a great extent compared to the usual smelting furnace, and the molten metal contained in it becomes fully used before a new type of aluminium alloy is used.

In a die-casting island peripheral devices are then necessary and used, usually defined as loaders, for the transport of doses of molten aluminium from the furnace (both maintenance furnace and melting and maintenance furnace) to the container of the device to be fed.

According to the known technique, one of said peripheral devices, or loaders, comprises control means carrying a casting ladle or cup and susceptible to movements such as to immerge the ladle in the metal bath, to turn the ladle to collect a certain dose of molten metal, to straighten and translate the ladle as far as the container of the die-casting machine to be fed and to turn the ladle in order to pour in the molten metal. Furthermore, however, such well known devices were made to operate in a melting pot or in a free surface basin in and ambient atmosphere, a condition that however favours the formation of oxides on the molten metal, spoiling the results of the items to be made.

Furthermore such devices are positioned on the outside of the melting pot or basin containing the molten metal, implying therefore an increase in volume of the arrangement or die-casting island and a thermal dispersion.

The document JP 62 114760 is indicative as regards to state of the technique and discloses, in particular, a device for feeding molten metal to a die-casting machine that is clearly on the outside of pot containing the molten metal.

Maintenance furnaces (of the "Westomat" type ) are also well known and available in which pressurized air is injected under control into a chamber that contains molten metal. In these furnaces the molten metal is directly dosed into the container of the die-casting machine by means of an appropriate siphon and a refractory channel.

The molten metal is transferred into the maintenance furnace by means of a filler cone in order to be able to carry out loading without reducing the pneumatic pressure into the furnace and therefore without interrupting the production. Practically the pneumatic pressure in the chamber of the furnace increases the level of the molten metal in the siphons, provoking in this way a discharge of the molten metal from the dosage channel in the set quantity/doses.

Nevertheless, the "Westomat" technology is applicable exclusively with the maintenance furnaces, therefore usable only by foundries equipped with a general smelting furnace and wherein rarely the type of aluminium alloy in used is changed.

The systems used at present in the delivery of molten metal to the die-casting or high-pressure die-casting machines, including the one described in the above document JP 62 114760, have various drawbacks and disadvantages which can be identified in the:

- loss of temperature in the transport and in the pouring by a loader of the molten metal from the furnace to the die-casting machine;

- pollution of the metal in the furnace and during the transfer; in fact given the high temperature, some metal parts, have the tendency to combine with the iron content in the aluminium alloy, modifying the mechanical characteristics and generating the so-called hard points; - reduction in the efficiency due to the oxidation of the molten metal because of the presence of oxygen which combines with the molten metal on the free surface of the furnace;

- loss of temperature in the transport and in the pouring of the molten metal from the smelting furnace to the maintenance furnace; and furthermore

- reduction in the efficiency deriving from the oxidation of the metal due to the presence of gas burners which are pointed directly towards the skin of the metal in the smelting furnace (e.g. equipment for the Westomat system);

- complexity of the control system of the dosages by means of the PLC;

- difficult repeatability of the dosage quantity of the metal;

- danger due to the presence of a furnace under pressure, containing material at a high temperature (Westomat system).

Object and Summary of the Invention

An object of this invention is to avoid the drawbacks and disadvantages of the known technique by an innovative equipment able to simplify and improve the feed conditions of the molten metal, such as aluminium alloy, to die-casting or high-pressure die-casting machines, starting indifferently from a smelting or maintaining furnace.

This object is reached by a set of furnaces and dosage loader assembly for a plant or die-casting island, where the furnace delimits a collection basin containing molten metal to be transferred by the loader to a container of at least a die-casting or high-pressure die-casting machine, where between said furnace and the container of said machine a delivery channel is positioned with a lead-in above the molten metal in said basin and an outlet towards the container of said machine, and wherein the loader for the transfer of the molten metal from said collection basin to the delivery channel is integrated and confined in said furnace and the delivery channel extends and is enclosed in a thermo-insulation casing that extends from a side of the furnace.

With this arrangement both thermal dispersion to the advantage of a saving of energy and the pollution and oxidation of the molten metal during its transfer from the furnace to the machine to be fed are avoided.

In particular the dosage loader is made up of:

- a collection ladle which is moveable in height between a lowered position for the collection of molten material from said basin and a raised position to the level of the lead-in of said delivery channel, and

- a transfer body which is moveable in height between a raised position above the molten metal contained in said ladle and a lowered position immerged in the molten metal in said ladle so as to cause an overflow of molten metal from the ladle into the delivery channel when the ladle is on a level with the lead-in of said channel.

Preferably and advantageously all the operating elements designed to transfer the molten metal from the collection basin to the container of the machine to be fed are subject to rectilinear movements which are easier to produce and control in a different way than the angular/rotator movements of a ladle or cup as in the case of the known technique.

Furthermore, the inside of the collection basin does not need to be pressurized in that the spilling action of the metal from the collection ladle to the delivery channel is not pneumatic, but basically mechanical, carried out by plunging the transfer body into the molten metal contained by the ladle, it being possible to finely adjust the doses of material to be transferred from time to time to the machine to be fed.

Brief Description of the Drawings

The invention will be described in greater detail in the following specification made in reference to the attached indicative and not limiting drawings, in which:

Fig. 1 shows a schematic view of the equipment in an initial rest position; and

Figs, from 2 to 5 show the equipment in a succession of operating phases of a dosage cycle of molten metal towards a for die-casting or high- pressure die-casting machine.

Detailed Description of the Invention

In said drawings a dosage loader is represented and is indicated globally by the number 11 in association with a smelting furnace 12, in particular for aluminium alloys.

This furnace 12 is made of a refractory material, complete with external metal covering, and delimits a collection basin 13 designed to contain molten metal. The furnace 12 is covered by a cover 14 provided with a nose 15 in which extends a delivery channel /! 6 that has a lead-in 16' on the part of said : furnace 12 and an outlet 16" on the side of the container - not shown - of the die-casting or high-pressure die-casting machine to be fed, also not shown.

In particular the delivery channel 16 is guided and moveable at least longitudinally in an ambient comprised between a collection zone of the molten metal from the furnace and the pouring zone of the molten metal into the container of the machine to be fed. For its longitudinal movements channel 16 is connected to an appropriate electromechanical, pneumatic or hydraulic control system, not represented, but however well known.

The dosage loader 11 is placed in the smelting furnace 12 in line with the basin 13, becoming integrated and enclosed between thermo isolating walls 25 which extend also along the nose 15 inside of which extends the delivery channel 16, so that all the equipment, loader and delivery channel, may be kept at the same temperature as the molten metal.

Said dosage loader 11 comprises 12 a collection ladle 17 in refractory material, to be used to collect the molten metal from the basin 13 and provided on its side with a pouring mouth 18 facing towards the lead-in 16' of the delivery channel 16.

In the represented realisation example, the collection Iadle17 is fixed to vertical bars 19 which extend downwards from a carriage 20 which in turn is guided vertically along guide columns 21 supported above the cover and moveable in height by means of a lifting system 22 connected to it.

Above the collecting ladle and in line with it, the dosage loader 11 also comprises a transfer body 23 in a refractory material, that is to say made of ceramic or the like, the section of which can have any geometric shape, as long as it has a known area. Said body, is similar to a piston and preferably, il . is susceptible to movements in height so as to be able to be immersed in the molten metal contained in the collecting ladle. For this purpose said body 23, or piston, is connected to a lifting device 24 and is moved by this towards and away from the bottom of the collecting ladle, said lifting device 24 being able to be made from, for example, a hydraulic cylinder or from an electromechanical actuator or another appropriate system the strokes of which can be controlled and limited according to needs. It should be understood that the transfer body 23, or piston, does not require any connection with the collection ladle 17, therefore anchoring parts such as compression rings, seals and the like between one and the other are not needed,.

In particular the equipment is managed so that the collection Iadle17 is at first moved from the top downwards towards the bottom of the collection basin, so that it becomes immersed on collecting the molten metal, and then towards the top on feeding the molten metal in the delivery channel 16 to the container of the machine to be fed.

The strokes and the times of the vertical movements both of the collection ladle and the transfer body or piston will be run by appropriate means of control.

At the start of every operating cycle of the equipment, the collection

Iadle17 is positioned above the collection basin 13, the transfer body or piston 23 is lifted in a non operating position above the bottom of the collection ladle, and the delivery channel 16 is moved towards the container of the machine, a position in which the lead-in of said channel is moved away from the collection ladle so as not to interfere with it, as shown in Fig.1. H ■ ^{■ ,} ·

The operating cycle therefore starts with a lowering of both the collection ladle and the transfer body 17, 23 in the collection basin of molten metal -Fig. 2. Consequently the molten metal passes from the collection basin 13 to the ladle 17 which becomes filled up to the level of the pouring mouth After a set period of time, the collection ladle - transfer body group ^' is moved upwards until the pouring mouth 18 reaches the level of the a lead-in 16' of the delivery channel 16 which, however, still remains away from the collection ladle -Fig. 3. During this movement, the excess molten metal in the collection ladle 17 drips into the basin 13 through transfer body pouring mouth 18; then on terminating the rise, where necessary, the transfer body 23, or piston, is made to advance slightly towards the collection Iadle17 until it eventually breaks the film on the surface of the collected molten metal.

After, as soon as the machine is ready to receive the molten metal, the delivery channel 16 is moved towards the collection ladle 17 until it fits its lead-in 16' into the charging mouth 18 -Fig. 4.

At this stage, the transfer casing, or piston 23 is lowered into the contents of the ladle 17 as far as a level corresponding to volume of molten metal to feed to the machine in question. Obviously, with this movement of the transfer casing 23 the molten metal overflows from the ladle towards the delivery channel through the charging mouth -Fig. 5. So, knowing the area of the transversal section of the transfer casing, it is sufficient to check the extent of its immersion in the molten metal stored by the ladle to determine from time to time and then to correctly repeat the dosage of molten metal to feed to the machine for die-casting or high-pressure- die-casting.

The whole above and its modality of utilization have an innovative high value in the specified field of application for which they were conceived besides adding numerous and undoubted advantages such as the following.

The temperature of the molten metal does not vary during each collection and transfer phase in that all its movements take place in a closed ambient inside a furnace and thermo isolated, therefore in the presence of an identical temperature to that of the molten metal.

The composition of the metal used maintains its chemical characteristics because it is only in contact with refractory material during all the working cycle, from the fusion up to the pouring into the container of the machine to be fed.

The efficiency of the furnace increases considerably in that both the thermal dispersion due to the transport of molten metal and the thermal dispersion of the surface of the furnace fails given that the molten metal remains closed in the furnace also during the collection on the part of the ladle.

Furthermore, the quantity of metal which has to be re-melted due to the presence of hard areas drops, increasing in this way the percentage between the quantity of metal used compared with that put in the furnace also due to the absence of oxidation. The dose of material is easily computable and repeatable in that the operation takes place due to the overflow caused by the transfer body or piston immersed in the ladle with the level of the molten metal on a level with the pouring mouth.

The quantity of metal poured out is equal to the variation in volume of the immersion of the piston. ^■ . >· .·. . ......... ....■;::■ ^■ .· -'...; ^· . =,

The operating temperature and consequently the use of energy become considerably less compared to the traditional furnace, in which the temperature varies in fact from 730 to 750°C, whereas the temperature of the necessary metal at the injection phase in the machine is roughly between 670 to 690°C. This difference is due to the free surface of furnace and to the transfer of the molten metal. Therefore, evaluating the transport at a utilization temperature of the molten metal (from 670 to 690°C), the energetic efficiency of the furnaces where the consumption of energy, exceeds 650°C, is exponential, the remarkable saving of energy of the system described above appears evident.

And again, the assembly according to the invention is applicable both for smelting furnaces and maintenance furnaces in that no pneumatic pressure is required inside the tank of the furnace.

The management system becomes simplified due to the adjustment of the dosage which consists only in the calculation of the volume of the transfer body which moves to immerse in the molten metal contained by the collection ladle attained through a control of the travel of said piston.

The assembly according to the invention can undergo variations or changes without however moving away from the protection ambient defined by the claims that follow. For example, the transfer body 23 can be kept stopped at the same height in a high position, both during the movements of the collection ladle between the lowered and raised positions and both when the collection ladle is in the lifted position; in this case simply adjust the upstroke of the collection ladle to adjust the dose of molten metal to be transferred to the delivery channel. , .- v., ,, . . ..