ES2268141T3 - APPARATUS FOR FORMING METALLIC FUNDED PARTS. - Google Patents

Abstract

An apparatus for forming metal castings, particularly with hydraulic connection between the holding furnace and the mold and a method performed by the apparatus, the hydraulic connection comprising: at least one duct (36) for connecting the holding furnace (11), which contains the molten metal ready for molding, to one or more inlets (12) for introducing metal into the cavity (13) of a corresponding mold (14); and a piston pump (15), interposed between portions (20, 21) of the duct (36), for pumping a controlled quantity of metal through the one or more inlets into the cavity, the piston pump being connected to an electronic control unit (16).

Description

Apparatus for forming castings metallic

Technical field

The present invention refers to a apparatus for forming metal castings, particularly with hydraulic connection between the maintenance oven and the mold and to a method to form metal castings performed by the apparatus.

State of the art

As is known, the castings made Metal or light alloys are molded using processes of pouring, such as gravity feed from metal or melted alloy in closed molds, and pressure generation inside the mold by feeding heads, which feed the cast piece, increasing the hydrostatic load on the metal or alloy, and prevents the formation of cavities or porosities inside of the cast during the shrinkage in the passage of solidification.

Another method to form castings pouring metal or alloys is the so-called low cast piece pressure, which substantially consists of placing a mold on a closed oven whose cavity is fed through a tube elevator connected to the oven, within which pressure is applied to the free surface of the metal so that part of said metal is lift through the lifting tube and feed the mold.

However, in practice, the techniques of Known castings are not always adequate to ensure the formation of castings that are free of defects structural, for example internal stresses and microporosities, especially in the case of the formation of castings taking a complex shape, such as wheels of motor vehicles made Light alloy and the like.

In particular, for the technique of parts low pressure melts problems are related, about everything, with the poor feeding of the mold cavity, especially in the case of castings that have a complex geometry, which generates porosities that can be detected by x-rays as a result of turbulent movements of metal and overheating.

After the solidification step, in addition, the oven under the mold is depressurized and due to this operation the column of molten metal inside the lifting tube, initially at the level of the mold, returns to the level of the metal that is present Inside the oven.

During this descent, a fraction of the metal remains attached along the inner wall of the tube elevator, forming metal films and solidified oxides.

This problem gradually increases, since during production the level of the metal inside the oven decreases, the path followed by the aluminum during filling increases, and from according to the exposed surface inside the lifting tube increases, generating a greater amount of metal and oxide films solidified

The films and oxides of course are dragged by the metal into the mold, forming an alloy not uniform and reducing the final quality of the cast provided.

In order to generate the pressure that allows the lifting of the metal through the lifting tube, a gas is injected Inside the oven; said gas is usually air, which generates oxides due to the presence of oxygen.

Also, when the metal inside the oven has been used, the oven must be opened to allow filling, exposing it completely to contact with air.

In addition, the process of castings at low pressure is a substantially discontinuous process, since entails downtime in the production step due to time required to fill the lift tube and to the steps of filling of said oven.

In particular, the problems related to oven are substantially due to detention times for fill it and to the variation of the internal pressure during said fill.

In addition, it is currently difficult to control the amount of metal injected into the mold cavity.

EP-A-0 711 616 shows an apparatus as defined in the preamble of the claim 1.

US-4 408 651 shows a pumping mechanism for an injection molding machine a Pressure.

US-4 595 044 shows an apparatus injection molding for pumping metal melted.

US-A-3 800 986 shows a pumping mechanism as defined in the preamble of claim 1.

The objective of the present invention is solve or substantially reduce type problems known apparatus for forming metal castings.

Within this objective, an object of the invention is to provide an apparatus comprising a connection Hydraulics constantly loaded between the maintenance furnace and the mold and in which the molten metal never contact the air.

Another object is to provide a device that eliminates flows up and down the metal along the tube elevator, eliminating the formation of oxides and metal films solidified

Another object is to provide an apparatus that allows safe control of the level of metal that is present under the mold.

Another object is to provide an apparatus by which is possible to provide a continuous cycle of castings, eliminating stop times to load the connected oven With the lifting tube.

Another object is to provide an apparatus by which molten metal is exposed to air as little as possible, consequently avoiding the formation of oxides.

Another object is to provide an apparatus that allows provide metal castings without pressure limitations operation except those dictated by the technological limitations of the device itself.

Another object is to provide a device that offers high productivity

Another object is to provide an apparatus that allows Better feeding of the mold cavity.

Another object is to provide an apparatus that allows obtain improved mechanical characteristics of the casting solidified

Another object is to provide a device that you do not use the air or gas pressure to move the metal and feed the mold.

This goal and these and other objects that they will be apparent better then they get by means of an apparatus for forming metal castings, such and as defined in claim 1.

The device performs a method to form parts molten metal consisting of:

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        control the level of molten metal, keeping it just below of said one or more entries to introduce the metal into the cavity of said matrix;

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        feed the die cavity with a chosen amount of metal at a controlled pressure, causing the level of said metal to raise

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        continue feeding the mold cavity, keeping the metal under pressure, at the end of the solidification phase;

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        lower the level of molten metal to a chosen height just under those entries;

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        finish the formation of the cast piece;

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        remove the cast from the mold.

Other features and advantages of the invention will be better apparent from the description of a preferred but not exclusive embodiment, illustrated only by a non-limiting example in the accompanying drawings, in the
that:

Figure 1 is a schematic view of a apparatus particularly for forming metal castings according to the invention;

Figure 2 is a view of a first portion of the apparatus of Figure 1;

Figure 3 is a view of a second portion of the apparatus of Figure 1.

With reference to the figures, an apparatus for form metal castings, particularly with connection hydraulic between the maintenance oven and the mold, according to the invention, is generally designated by the reference number 10.

The apparatus 10 comprises a hydraulic connection between a maintenance oven 11, which contains the molten metal ready to form, and a mold 14, which in turn comprises a conduit 36 to connect the maintenance oven 11 to one or more entries 12 to insert the metal into a cavity 13 of the mold 14, said one or more entries 12 being arranged, in this case, under said mold 14, and pumping means 15, which are interposed between portions of said conduit 36, to pump a controlled amount of metal through one or more entries 12 within said cavity 13, said means being connected to and controlled by an electronic control unit 16.

As shown in Figure 3, in this case there is an entry in the form of slot 12, which runs continuously and circumferentially by 360 degrees sexagesimal at the edge bottom of the cavity 13 of a mold 14, for example to form A wheel for motor vehicles.

The inlet 12 is formed by a distribution unit 17, which is arranged under the mold 14 and is connected to the upper end of a tube
elevator 18.

Induction type measurement devices 19 to measure the level of the metal present inside the unit of distribution 17 are arranged adjacent and below the entrance 12, in the distribution unit 17, and are connected and managed by the control unit 16, as described better then.

Advantageously, entries 12 also they can be arranged laterally to the mold 14.

The conduit 36 comprises a first portion 20, which extends from the maintenance oven 11 and is connected to the pumping means 15, from which a second portion 21 protrudes and leads to a reservoir 22.

The lifting tube 18 rises from the tank 22, and the distribution unit 17 is arranged above it.

The apparatus 10 further comprises devices 23 to heat molten metal and temperature sensors 24 to detect the temperature of said metal, which are willing to length of the hydraulic connection and are connected to the unit control 16.

The heating devices 23 are constituted by heating resistors, designated by the same reference number, which are arranged within longitudinally elongated ceramic containers arranged in the pumping means 15, in the first portion 20 and in the second portion 21 of conduit 36, in reservoir 22 and in the unit of distribution 16.

The temperature sensors 24 are on the contrary constituted by thermocouples, designated by it reference number, which are also arranged in the apparatus 10, such as heating devices 23.

The pumping means 15 are constituted by a piston pump 25, upstream and downstream of the which is a first valve 26 and a second valve 27 for control the flow of metal that flows respectively within said first and second portions 20 and 21 of the conduit 36.

The first and second valves 26 and 27 are designated to provide controlled unidirectional flow of metal in the direction from mold 14 to the maintenance oven eleven.

The piston pump 25 comprises a first piston 28, which can slide tightly in a first cylinder  corresponding 29, is fixed to the head of a first rod 30 of a hydraulic activator 31, whose travel is controlled by the control unit 16.

The first and second valves 26 and 27 are completely identical, and each valve comprises a second piston 32 that can slide tightly inside a second cylinder corresponding 33, which is fixed to the head of a second stem 34 of a corresponding pneumatic activator 35.

As shown in Figure 2, the first valve 26 and the second valve 27 are arranged to control respectively the first portion 20 and the second portion 21 of the conduit 36 when activated by the control unit 16.

In particular, the first valve 26 (such as the second valve 27) is disposed between a first part 20a and a second part 20b of the first portion 20 of the conduit 36, said parts being arranged with a longitudinal axis to different heights.

The second piston 32, once lowered, affects the entrance of the second part 20b, whose diameter is smaller than that of the second cylinder 33, and the output of the first part 20a, which is substantially in a horizontal plane and is coaxial to the second piston 32.

As for the operation, when the pump pistons 25 is fully loaded, with the first valve 26 closed and the second valve 27 open, the mold 14 is closed to connect cavity 13 to input 12.

Induction measuring devices 19 they can detect temperatures and detect that the metal level is just below entrance 12.

At this point, the control unit 16 activates the advance of the first cylinder 29 of the piston pump, which allows metal injection into the cavity 13.

The cycle to form the cast, which in This case is a motor vehicle wheel, it starts and consists of the steps of filling, feeding, cooling and solidifying; said cycle is allowed by the injection of a preset amount of material inside cavity 13 following the movement of the pump of pistons 25 activated by control unit 16.

During the solidification step, the pump pistons 25 continues to feed cavity 13, maintaining the metal under pressure.

At the end of the solidification step, the unit control 16 activates the piston pump 25 so that it retract with the first cylinder 29, to lower the metal level with respect to input 12 by a preset value, by example 5-6 millimeters, making it separate from the cast piece.

At the end of the formation of the cast piece, the mold 14 is opened and the cast is removed, while the Aluminum level is always maintained directly below the tickets 12.

The piston pump 25 must now be recharged, and this occurs by removing the first stem 30 when the second valve 27 is closed and the first valve 26 is open, removing metal from the maintenance oven 11.

Once the piston pump 25 has removed a sufficient amount of metal, the cycle can return to start.

Advantageously, a plurality of ducts 36 for corresponding molds can be associated with the oven of maintenance 11 in order to increase the productivity of said apparatus.

Since the apparatus 10 is provided with a plurality of heating devices 23, this ensures that the metal always remain liquid, at a temperature that is controlled by temperature sensors 24.

Deposit 22, in addition, is designated for keep the metal at a chosen temperature, which is also determined by heating devices 23 and is measured by the temperature sensors 24.

The amount of metal contained in the deposit is in fact such as to ensure the dissipation of any higher temperature acquired by the metal on the road from the piston pump 25 to said reservoir 22.

In practice, the purpose of deposit 22 is make the metal or alloy more homogeneous before entering the mold 14.

In practice it has been discovered that this invention has achieved the objective and the intended objects.

A device has in fact been provided that allows use a hydraulic system that is always loaded, a level of the metal that is always present in the lower level of the mold, with a closed hydraulic circuit that prevents exposure of the Metal in the air, preventing the formation of oxides.

The metal injected into the cavity is therefore more homogeneous and allows to obtain a solidified cast piece whose mechanical characteristics are improved with respect to devices known, even using very operating pressures high.

In addition, the times to move the material are reduced downtime to load the oven arranged under the mold have been removed, and there is an increase considerable production, since such production occurs In a continuous cycle.

The present invention is susceptible to numerous modifications and variations, all of which are within the scope of the appended claims.

Technical details can be replaced. by other technically equivalent elements.

The materials, provided they are compatible with contingent use, as well as dimensions, They can be any according to the requirements.

Claims (18)

1. An apparatus for forming castings metal, particularly with hydraulic connection between the oven of maintenance and the mold, comprising:

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to the minus a conduit (36) to connect the maintenance oven (11), containing molten metal ready to be molded, to one or more entries (12) to introduce the metal into the cavity (13) of a corresponding mold (14); Y

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pumping means (15), interposed between portions (20, 21) of said conduit (36), for pumping a controlled amount of metal through said one or more inlets (12) into said cavity (13), said means of pumping (15) being connected to an electronic control unit (16), said pumping means (15) comprising a piston pump (25) and a first and a second valve (26, 27) to control the flow of metal , said valves being arranged respectively upstream and downstream of said piston pump (25), said first and second valves (26, 27) being adapted to prevent the return of the metal in the direction of the mold (14) to the maintenance furnace (eleven); characterized in that said piston pump (25) and said first and second valve (26, 27) are activated by said electronic control unit (16).

2. The apparatus according to claim 1, characterized in that it comprises measuring devices (19) for measuring the metal level, which are arranged near said one or more inputs (12) and are connected to said control unit (16). The apparatus according to one or more of the preceding claims, characterized in that said conduit (36) comprises a first portion (20) extending from the maintenance oven (11) and connected to said pumping means (15), of which at least a second portion (21) extends for connection to the cavity (13) of the mold (14). The apparatus according to claim 1, characterized in that said piston pump (25) comprises a first piston (28), which can be sealed tightly within a corresponding first cylinder (29), the piston being fixed to the head of a first rod (30) of a first activator (31) whose path is controlled by said control unit (16). 5. The apparatus according to claim 4, characterized in that said first activator (31) is hydraulic. 6. The apparatus according to one or more of the preceding claims, characterized in that said first and second valve (26, 27) are each constituted by a second piston (32), which can be sealed tightly within a corresponding second cylinder (33), the piston being fixed to the head of a second rod (34) of a second activator (35) that is controlled by said control unit (16). 7. The apparatus according to claim 6, characterized in that the second activator (35) is pneumatic. The apparatus according to one or more of the preceding claims, characterized in that said hydraulic connection comprises a reservoir (22) that is disposed downstream of said second portion (21) and of which at least one lifting tube (18 ) extends to introduce molten metal into said cavity (13). The apparatus according to one or more of the preceding claims, characterized in that said hydraulic connection comprises a distribution unit (17), which is suitable for forming said one or more inlets (12) for introducing the metal into said cavity (13), said distribution unit (17) being connected to said at least one lifting tube (18), in which said level measuring devices (19) are arranged. The apparatus according to one or more of the preceding claims, characterized in that said one or more entries (12) are arranged under said mold (14). The apparatus according to one or more of claims 1 to 9, characterized in that said one or more entries (12) are arranged laterally to said mold (14). The apparatus according to one or more of claims 1 to 9, characterized in that said one or more entrances (12) are arranged laterally and under said mold (14). 13. The apparatus according to one or more of the preceding claims, characterized in that said level measuring devices (19) are induction devices. 14. The apparatus according to one or more of claims 1 to 12, characterized in that said level measuring devices (19) are induction devices adapted to act as temperature measuring devices. 15. The apparatus according to one or more of the preceding claims, characterized in that said hydraulic connection comprises heating devices (23) for heating said molten metal, said devices being connected to said control unit (16). 16. The apparatus according to claim 15, characterized in that said heating devices (23) are constituted by heating resistors, each arranged inside a ceramic container correspondingly extended longitudinally. 17. The apparatus according to one or more of the preceding claims, characterized in that said hydraulic connection comprises sensors (24) for detecting the temperature of said molten metal, said sensors being connected to said control unit (16). 18. The apparatus according to claim 17, characterized in that said temperature sensors (24) are constituted by thermocouples, each arranged inside correspondingly extended ceramic ceramic containers.