Apparatus and method for die casting metal objects in a semi-solid state

Abstract

The mold comprises an upper mold half (3) adapted to be joined with a lower mold half (2) to define a mold cavity (4); a furnace (7) arranged below the lower mold half and provided with a supply duct (9) for liquid metal (8) connecting the furnace to the mold cavity (4), the upper mold half (3) having in its cavity a forging piston (5) accommodating therein a flow control plunger (6) freely movable between the upper mold half (3) and the lower mold half (2); and a vacuum channel (10) provided circumferentially around the part to be cast and for allowing the passage of liquid metal. an upper die half (2) having a connecting channel (11) to a vacuum pump connecting the vacuum channel (10) to the outside, the upper die half (2) further having a solenoid valve (21) for controlling the vacuum inside the channel (14) and a solenoid valve (20) for controlling the vacuum in the connecting channel (11) for connection to a vacuum pump.

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for die casting metal objects in a semi-solid state.

[0002] More particularly, the present invention relates to an apparatus and method for providing forged objects at low pressure and in a semi-solid state.

[0003] More specifically, the metal object may be made of brass, bronze, aluminum alloys, magnesium alloys, light alloys and the like. [Background technology]

[0004] In the background art, this method is known as melting and forming metal objects via so-called "low pressure" using an apparatus comprising a lower and upper mold section configured to define a mold cavity for containing a predetermined amount of liquid metal fed through a duct connected to a furnace below.

[0005] According to known techniques, the upper mould comprises a flow control element acting on an opening connected to a liquid metal supply duct, and a compression device punch which defines the upper part of the moulding part of the mould.

[0006] The use of low pressure for the forming process involves that a furnace must be placed below the forming apparatus and pressurized. Pressurizing the furnace, usually with air, cools the metal, necessitating the use of a sealed furnace.

[0007] During the process of filling the mold cavity and pressurizing the furnace, the air in the riser tube and mold cavity must be evacuated from the mold to allow the liquid metal to be delivered.

[0008] In existing systems, pressure is applied to the surface of the metal within the furnace in order to cause the liquid metal to rise from the furnace into the mold cavity. Pressurization of the furnace chamber requires the use of a special type of furnace.

[0009] A solution is also known from WO 2021 / 070044, which makes it possible to avoid using a pressurized oven. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2021 / 070044 Summary of the Invention [Problem to be solved by the invention]

[0011] The above solution envisages a vacuum channel located circumferentially around the part to be cast between the upper and lower mold halves and connected to the mold cavity through a vent channel.

[0012] Additionally, there is a channel for supplying vacuum via a vacuum pump, which is connected to the mold cavity via one or more vent channels.

[0013] A re-rising channel for the metal in the furnace connects the furnace to the mold cavity.

[0014] However, the above solution presents a significant problem in that when the metal rises from the duct, i.e., the re-rise channel, to fill the mold cavity, it inevitably also fills the vent channel, and therefore the previously created vacuum can no longer exist.

[0015] This means that the metal that has risen in the re-rising channel will fall back into the furnace, which is a very undesirable situation. [Means for solving the problem]

[0016] The aim of the present invention is to provide an apparatus and method for die casting metal objects in a semi-solid state, made of brass, bronze, aluminum alloys, magnesium alloys, light alloys and the like, which makes it possible to obtain metal objects without impurities (porosity) despite the use of a pressurized furnace, i.e., eliminating the drawbacks of pressurized furnaces.

[0017] Within this goal, it is an object of the present invention to provide an apparatus and method for die casting metal objects in a semi-solid state that allows the use of existing pressurized furnaces.

[0018] Another object of the present invention is to provide an apparatus and method that is reliable, simple, practical to implement, and low cost.

[0019] This aim, as well as these and other aims that will become more apparent hereinafter, are achieved by an apparatus for die-casting metal objects in a semi-solid state, comprising: a die comprising an upper die half adapted to be joined with a lower die half to define a die cavity; a furnace arranged below the lower die half and provided with a supply duct for liquid metal connecting the furnace to the die cavity, the upper die half provided with a cavity within which a forging piston, containing a flow control plunger therein, is free to move between the upper and lower die halves; and a vacuum channel provided circumferentially around the part to be cast and connected to the die cavity by a vent channel, the casting piston provided with a connection channel for vacuum to generate the vacuum, the upper die half provided with a connection channel for a vacuum pump connecting the vacuum channel to the outside, a solenoid valve for controlling the vacuum inside the channel and a solenoid valve for controlling the vacuum in the connection channel to the vacuum pump.

[0020] Further features and advantages of the present invention will become better apparent from the following description of preferred, but not exclusive, embodiments of the device and method according to the invention, illustrated by way of non-limiting examples in the accompanying drawings, in which: [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a cross-sectional view of the device according to the present invention in a first operating step. [Figure 2] FIG. 3 is a cross-sectional view of the device according to the present invention in a second operating step. [Figure 3] FIG. 4 is a cross-sectional view of the device according to the present invention in a third operating step. [Figure 4] FIG. 4 is a cross-sectional view of the device according to the present invention in a fourth operating step. [Figure 5] FIG. 10 is a cross-sectional view of the device according to the present invention in a fifth operating step. DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring to the figures in which like reference numerals refer to like elements, an apparatus according to the present invention, generally designated by the reference numeral 1, comprises a mold comprising a lower mold half 2 which may be mated with an upper mold half 3 to define a mold portion or mold cavity 4.

[0023] A forging piston 5 may move within a channel defined within the upper die half 3 and houses a flow control plunger 6 therein.

[0024] A furnace 7 is positioned below the lower mold half 2 adapted to contain liquid metal 8. The furnace 7 has a re-ascending channel 9 for the liquid metal to rise towards the mold cavity 4.

[0025] Preferably, a vacuum supply channel 10 is defined between the upper mould half 3 and the lower mould half 2 .

[0026] The vacuum supply channel 10 is connected to a vacuum pump (not shown) via a duct 11 defined in the upper mould half 3 .

[0027] A solenoid valve 20 for controlling the vacuum is arranged in the duct 11 .

[0028] The vacuum supply channel 10 is further connected to the mold cavity 4 through a plurality of vent channels 12 .

[0029] The vent channels 12 are positioned adjacent to and surround the periphery of the surface of the part being cast.

[0030] Preferably, the vent channels 12 are zigzag and in any case are not straight.

[0031] The forged piston 5 housing the flow control plunger 6 has a vacuum generating channel 14 located at its upper end and a vent channel 13 located approximately in the middle which may be closed by the flow control plunger 6 during operation of the flow control plunger 6 inside the forged piston 5.

[0032] An additional solenoid valve 21 for vacuum control is located in the vacuum generating channel 14 of the forged piston 5, where a dedicated vacuum pump may be provided or the vacuum pump may be the same as the one that generates the vacuum in the channel 10.

[0033] Preferably, the upper mould half 3 is equipped with a sensor 15 for the height of the metal in the mould cavity 4 .

[0034] A die casting method according to the present invention using the above described apparatus is described below.

[0035] FIG. 1 illustrates an apparatus according to the invention with the first mold part closed by a furnace 7 containing liquid metal 8 and a vacuum generated both by a vacuum channel 10 (through a vacuum pump attached to a duct 11) and by a vent 13 on the forged piston 5.

[0036] In the process illustrated in FIG. 1, a vacuum is simultaneously created in the vacuum connection channel 14 defined in the forged piston 5 and also in the channel 11 .

[0037] In this process, the solenoid valves 20, 21 are activated to control the vacuum, and the created cavity must be large enough so that the liquid metal 8 cannot rise up to the mold cavity 4 (see Figure 2).

[0038] The pressurization of the chamber of the furnace 7 is controlled so that the liquid metal 8 rises into the mold cavity after a variable time, for example between 1 and 10 seconds, determined as a function of the type of liquid metal 8 present in the furnace 7 and the volume of the mold cavity.

[0039] Next, FIG. 2 shows the step where, as a result of pressurization of the chamber of the furnace 7, liquid metal enters the mold cavity 4 and the liquid metal re-ascent channel 9 and fills the mold cavity 4 in the absence of air in the channel 9.

[0040] In this state, the vent 13 in the forged piston is still open due to the position of the flow control plunger 6 .

[0041] Filling of the mold cavity 4 with liquid metal 8 occurs by pressurizing the chamber of the furnace 7 and raising the forging piston 5 with the "syringe effect".

[0042] The filling process is controlled by a sensor 15 which determines when to stop the flow of liquid metal into the mold cavity 4.

[0043] FIG. 2 next shows the device according to the invention when the syringe effect is complete and the furnace is pressurized.

[0044] 3 shows the descent of the flow control plunger 6 after a set time, thereby closing the liquid metal supply duct 9 and the vent 13. At this point, the pressurization is stopped.

[0045] In this state, the metal 8 present in the feed duct drops to the level of the metal present in the furnace 7 .

[0046] FIG. 4 shows the device according to the invention in a forging process with the metal 8 feed channel 9 closed, the air vent closed and the forging piston 5 lowered to the forging end position.

[0047] During the process, the vacuum is maintained in effect until the end of the forging process, and the air vent / vacuum generating channels are closed with metal 8 rising from the pressurized furnace 7 .

[0048] At this point, the mold may be opened and the cast part can be removed.

[0049] In fact, it has been found that the device and method according to the invention achieve the intended goal and purpose in that it allows the use of a pressurized type furnace without suffering from the drawbacks inherent in the solutions in the known art, while at the same time eliminating the drawbacks of solutions without a pressurized furnace, thus preventing the metal from being allowed to flow back up the re-ascending channel connecting the furnace to the mold cavity after the latter has been filled.

[0050] In the first step, when creating the cavity in the mold for the liquid metal to rise, the air contained in the mold cavity and the re-rise channels is extracted, so the final product is completely porosity-free.

[0051] The method and apparatus thus conceived are susceptible to numerous modifications and variations, all of which are within the scope of the appended claims.

[0052] Moreover, all the details may be substituted by other technically equivalent elements.

[0053] In fact, the materials used, as well as the shape and dimensions depending on the situation, may be anything according to the requirements and the state of the art.

[0054] The disclosures of Italian Patent Application No. 102022000026292, from which this application claims priority, are incorporated herein by reference.

[0055] Where technical features referred to in any claim are accompanied by reference signs and / or symbols, the reference signs and / or symbols are included solely for the purpose of enhancing the comprehension of the claim, and therefore, the reference signs and / or symbols do not have any limiting effect on the interpretation of each element identified as an example by the reference signs and / or symbols.

Claims

1. A mold comprising an upper mold half (3) adapted to be joined to a lower mold half (2) to define a mold cavity (4); a furnace (7) arranged below the lower mold half (2) and provided with a supply duct (9) for liquid metal (8) connecting the furnace to the mold cavity (4), the upper mold half (3) having a cavity within which a forging piston (5) accommodating a flow control plunger (6) can move freely between the upper mold half (3) and the lower mold half (2); a vacuum channel (10) provided circumferentially around the part to be cast and provided with a vent channel (12) ) connected to the die cavity (4) by a forging piston (5) for generating a vacuum, the forging piston (5) comprising a connecting channel (14) for connection to the vacuum, the upper die half (3) comprising the connecting channel (11) for connection to the vacuum pump connecting the vacuum channel (10) to the outside, a solenoid valve (21) for controlling the vacuum inside the channel (14), and a solenoid valve (20) for controlling the vacuum in the connecting channel (11) for connection to the vacuum pump.

2. 2. The device according to claim 1, characterized in that the forged piston (5) comprises an air vent channel (13) adapted to be blocked by the flow control plunger (6) during movement of the flow control plunger (6) within the forged piston (5).

3. 3. Apparatus according to claim 1 or 2, characterized in that the solenoid valves (20, 21) are connected to a single vacuum pump.

4. 3. The device according to claim 1 or 2, characterized in that the solenoid valves (20, 21) are each connected to a vacuum pump.

5. 1. A method for die-casting a metal object in a semi-solid state by means of an apparatus according to one or more of the preceding claims, comprising the steps of: closing the upper mould half (3) onto the lower mould half (2) to define the mould cavity (4); heating the metal (8) contained therein by means of said furnace (7); generating said vacuum in said mold cavity (4), in said vacuum channel and in said channel (14) of said casting piston (5) by actuating said two solenoid valves (20, 21), such that the vacuum is such that the metal contained in said furnace does not rise up to said mold cavity (4); pressurizing the furnace to allow the metal to rise in the feed duct (9) to fill the mould cavity (4) in the absence of air; the vacuum generating step is carried out by returning above the forging piston (5) to generate the vacuum simultaneously in the vacuum channel (14) of the forging piston (5) and in the vacuum channel (10) of the upper die half (3); closing the supply duct (9) using the flow control plunger (6) to prevent pressurization of the furnace; lowering the forging piston (5) to perform the step of forging the cast part contained in the die cavity (4); Opening the molds (2, 3) and removing the cast part.

6. 6. A method for die-casting metal objects in a semi-solid state according to claim 5, characterized in that the step of pressurizing the furnace (7) is controlled after a time that is variable depending on the type of metal contained in the furnace and the volume of the mold cavity (4).

7. 6. The method for die-casting metal objects in a semi-solid state according to claim 5, characterized in that during the steps of the method up to the forging step, the vacuum is active and the vacuum channels (10, 14) and the vent channels are closed by the metal (8) rising from the pressurized furnace (7).

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