A gas venting device for vacuum assisted high pressure die casting

Abstract

The invention refers to a venting device (20) for vacuum die casting. The device comprises: an input port (15) meant to be fluidly connected to a die casting mould cavity, an output port (10) meant to be fluidly connected to a vacuum source, a gas evacuation channel (19) fluidly communicating the input port (15) with the output port (10), a cooling channel (18) fluidly communicating the input port (15) with the output port (10), a valve member (17) arranged to open and close the passage between the input port (15) and the gas evacuation channel (19). Preferably, at least a section of the cooling channel (18) has a wavy configuration. The venting device (1) optimizes the efficiency of the mould venting by means of the two channels (18, 19) to discharge the gases from the mould cavity (2).

Description

OBJECT OF THE INVENTION

[0001] The present invention relates in general to vacuum assisted high pressure die casting, HPDC, manufacturing process and related systems.

[0002] More specifically, the invention refers to a device for venting gases from a mould cavity of a die casting system.

[0003] An object of the invention is to improve quality of articles obtained by the vacuum assisted high pressure die casting, by efficiently evacuating gases from a mould cavity.STATE OF THE ART

[0004] As a near-net shape manufacturing process, high pressure die casting (HPDC) is very attractive in producing thin-wall components with high dimensional accuracy, high production efficiency and considerable economic benefits for automotive and other industries.

[0005] However, conventional HPDC castings usually contain randomly distributed gas porosities mainly due to the entrapment of gas under the high-speed shot. The use of vacuum for extracting the air from the mould is one of the proven solutions to prevent the undesired entrapment of gas in the casting component. For that purpose, the mould needs an element, typically named chill vent or suction valve, with the aim communicating the vacuum with the cavity of the mould allowing discharge the gases outside the mould without spouting the molten metal.

[0006] The moulds used in vacuum assisted high pressure die casting usually include a chill vent to communicate the cavity with the vacuum system The gas exhaust passage in a chill vent is generally shaped in a zigzag-manner to ensure that, after the gas has been exhausted outside the chill vent, the molten metal is chilled in the passage before it is flashed outside the die mould.

[0007] In order to prevent flashing of molten metal with an improved reliability, it was considered necessary for the zigzag-shaped gas exhaust passage to have a narrow gap and adopt a relatively steep angle of the zigzag-shape. However, a narrow gap causes the sectional area of the gas exhaust passage to be decreased, while a steep angle causes the gas exhaust resistance to be increased. In any case, the gas exhaust efficiency is lowered, and it becomes difficult to prevent formation of gas hole defects in the product.

[0008] An alternative to the chill vent for vacuum assisted high pressure die casting, the mould might use a suction valve which, as an advantage to the chill vent, provides a higher venting passage area. In the suction valves, the air and gas, removed by the vacuum system, enter the valve together with a flow of metal until a stopper in the valve close the passage by an actuator. There are two kind of suction valves, mechanical or hydraulic / pneumatic valves, depending on the actuator type.

[0009] The mechanical valves operate the stopper by the molten metal itself. At the valve entry the molten metal encounters a piston before reaching the stopper. The pressure of the metal moves the piston which command the closure of the actuator connected to the stopper by means of an idle lever. The advantage of the mechanical valves resides in the operating time since they are open until the end of the die cavity filling. However, have demonstrated problems of reliability, particularly with regard to die casting of metals with high heat conductivity, because the passages made in the valve are not always suitable for an effective slowing and cooling of the molten metal, or for preventing this metal from invading the housing of the stopper and, thereby, rapidly reducing the valve efficiency.

[0010] The hydraulic / pneumatic valves use an actuator connected to the stopper and operated by a hydraulic or pneumatic fluid through an electrovalve which is controlled by means of time or plunger stroke. To guarantee that the molten metal does not invade the exit of the valve, the actuator is normally closed before the plunger begins the filling of the mould cavity, and from that moment until the end of the cavity filling the remaining gases are not discharged since the suction valve is closed and, thereby, reducing the efficiency of the valve.

[0011] Therefore, the provision of a valve capable of efficiently evacuating gases from a mould cavity, remains a challenge in this technical field.DESCRIPTION OF THE INVENTION

[0012] The invention is defined in the attached independent claims, and satisfactorily solves the above-described drawbacks of the prior art, by the provision of a venting device for a vacuum assisted die casting process or high pressure die casting (HPDC) process, to evacuate in the most efficient way a given volume of gases from a mould cavity thus avoiding air porosity and other defects as laminations and blisters in the HPDC castings.

[0013] The venting device of the invention optimizes the efficiency of the mould venting by the provision of two channels to discharge gases from a mould cavity, namely a gas evacuation channel configured as a low resistant flow channel to discharge gases at a high flow rate, before molten metal reaches the gas evacuation channel, and a cooling channel configured to cool down molten metal to solidify the same within the cooling channel. Preferably, the cooling channel is configured as a long and narrow gap where the molten metal cools down and gases are discharged to the outside during the whole molten metal injection process.

[0014] More specifically, an aspect of the invention refers to a venting device for vacuum assisted (high pressure) die casting, wherein the device comprises: an input port meant to be fluidly connected to a die casting mould cavity, an output port meant to be fluidly connected to a vacuum source, a gas evacuation channel fluidly communicating the input port with the output port, a cooling channel fluidly communicating the input port with the output port, and a valve member arranged to open and close the passage between the input port and the gas evacuation channel.

[0015] With the above described configuration of the venting device, gases are evacuated from the mould cavity during the entire molten metal injection process, first through the gas evacuation channel and the cooling channel, before molten metal reaches the mould cavity or a gate area right before the mould cavity , when the venting device is operatively coupled to a die casting mould, and as soon as the molten metal reaches the mould cavity or a gate area, only through the cooling channel wherein molten metal is cooled down and solidified before reaching the output port.

[0016] Preferably, at least a section of the cooling channel has a wavy (sinuous or serrated or zig zag) configuration in order to provide a large heat dissipation surface, for increasing heat transfer from the molten metal to the cooling channel.

[0017] In a preferred embodiment of the invention, at least a section of the gas evacuation channel has a cross-sectional area greater than the a cross-sectional area of a section of the cooling channel.

[0018] Preferably, a major part of the gas evacuation channel and a major part of the cooling channel, have constant cross-sectional area. The gas evacuation channel may be formed as a straight conduit, and the cooling channel with a wavy configuration generally extends parallel to the gas evacuation channel.

[0019] In some embodiments, the venting device is formed by a first body and a second body, wherein the first and second bodies can be coupled and uncoupled together. The gas evacuating channel is formed internally in the first body or in the second body, whereas the cooling channel is formed by the two bodies when they are operatively coupled together. The cooling channel defining a long and narrow gap.

[0020] In a preferred embodiment, the first body is stationary, and the second body is movable relative to the first body. The gas evacuation channel is formed in the stationary first body.

[0021] The venting device can incorporate an actuator to operate the valve member.

[0022] In a preferred embodiment the venting device comprises a filter, suitable to stop the flow of molten metal, installed between the cooling channel and the output port.

[0023] Another aspect of the invention refers to a vacuum assisted die casting system, comprising: a mould cavity, molten metal injection means adapted to inject molten metal into the mould cavity at a predetermined pressure, the venting device previously described, and a vacuum source fluidly coupled to the mould cavity through the venting device.

[0024] Preferably, the venting device and the molten metal injection means are fluidly coupled at opposite end zones of the mould cavity.

[0025] Additionally, the system can comprise control means adapted to operate the actuator of the venting device in a coordinated manner with the molten metal injection means, such that the valve member is closed before the molten metal flow reaches the mould cavity or a gate area right before the mould cavity, in order to prevent molten metal to flow through the gas evacuation channel, so that molten metal flowing out of the mould cavity, would flow through the cooling channel. The actuator opens the valve member at the beginning of the injection cycle i.e when the injection means start the injection of molten metal.

[0026] Another aspect of the invention refers to a die casting method, which comprises: evacuating gases from a mould cavity through a gas evacuation channel and through a cooling channel, closing the entry to the gas evacuation channel before the molten metal reaches the mould cavity or a gate area located right before the mould cavity, and continue evacuating gases from the mould cavity through the cooling channel while molten metal fills the mould cavity, and allowing molten metal to flow out of the mould cavity through the cooling channel, and cooling down molten metal in the cooling channel.

[0027] The method can comprise opening the valve member at the beginning of the injection cycle i.e when the injection means start the injection of molten metal.

[0028] Preferably, gases are evacuated by vacuum generation.

[0029] The method can be implemented as a cold or hot chamber high pressure die casting process.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To complete the description and in order to provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be carried out. The drawings comprise the following figures: Figure 1.- shows two schematic representations of a cross-sectional view of a preferred embodiment of venting device according to the invention, wherein Figure 1A shows the valve actuator in an open position, and Figure 1B shows the valve actuator in a closed position. Figure 2.- shows a front view of the venting device. Figure 3.- shows a schematic representation of a vacuum assisted high pressure die casting system, including the venting device of the invention. PREFERRED EMBODIMENTS OF THE INVENTION

[0031] Figures 1A, 1B and 2 show a preferred embodiment of a venting device (1) according to the invention for vacuum assisted high pressure die casting. The venting device (1) is formed by a first body (11) and a second body (12) which can be coupled and uncoupled. In this embodiment, the first body (11) is stationary, and the second body (12) is movable relative to the first body (11).

[0032] The venting device (1) comprises an input port (15) and an output port (10), and a gas evacuation channel (19) fluidly communicating the input port (15) with the output port (10), and a cooling channel (18) also fluidly communicating the input port (15) with the output port (10). The gas evacuating channel (19) is formed internally in the first body (11), and a cooling channel (18) is formed by the two bodies (11, 12) when they are operatively coupled together. For example, a surface of one of the bodies has a grooves or depression and a surface of the other body has complementary reliefs to the depressions, such that, when the two surfaces are brought together, the cooling channel (18) is formed.

[0033] In this embodiment, the cooling channel and the gas evacuation channel (18, 19) have constant cross-sectional area. The gas evacuation channel (19) is a straight conduit, which allows to discharge gases at a high rate from a mould cavity as it is configured as a low resistant flow conduit without strangulations, that is, with low loss load.

[0034] The cooling channel (18) generally extends parallel to the gas evacuation channel. The cooling channel (18) is narrower and longer than the gas evacuation channel (19). The cooling channel (18) is a sinuous path shaped in a zigzag or waveform manner with a thickness between 0.5mm and 1.5mm to ensure that, the gases can be extracted outside the mould cavity and the speed of the molten metal reduced, the heat exchange surface increased and the temperature of the molten metal lowered up to be solidified in the cooling device before reaching the end of the sinuous path. The cooling channel (18) is connected to the output port (10) at the top of the device (1) where the sinuous path ends. Thus, the gases can be discharged from the mould cavity during the whole molten metal injection process especially when the gas evacuation channel (19) is closed whereas the metal is solidified inside the cooling channel (18).

[0035] A first transversal channel (13) fluidly communicates the cooling channel (18) and the gas evacuation channel (19) with the output port (10). A filter (21) suitable to stop the flow of molten metal, is installed in the first transversal channel (13), to prevent molten metal coming through the cooling channel from reaching the output port (10).

[0036] A second transversal channel (14) fluidly communicates the input port (15) with the cooling channel (18) and with the gas evacuation channel (19).

[0037] A valve member (17) is arranged in the second transversal channel (14) to open and close the passage between the input port (15) and the gas evacuation channel (19). A hydraulic or pneumatic actuator (16) is provided to operate the valve member (17), although in other suitable types of actuators may be also used.

[0038] The cooling channel (18) permanently communicates the input port (15) with the output port (10).

[0039] Figure 2 shows a front view of the first body (11) alone to illustrate the output port (10), the input port (15), and the serrated-shaped surface of the first body (11) to form the zig-zag configuration when coupled with the second body (12).

[0040] Figure 3 shows a hight pressure die casting system (20) comprising: a mould formed by a stationary part (4) and a movable part (3), and a mould cavity (2) formed by the stationary and the movable parts (3, 4) when they are coupled together. The system (20) further comprises a vacuum source (9) connected to the venting device (1) according to the invention, to the mould cavity (2), in a way that the input port (15) of the venting device (1) is fluidly connected to the mould cavity (2), and the output port (10) is fluidly connected to a vacuum source (9).

[0041] The first body (11) is attached to the stationary part (4) of the mould, and the second body (12) is attached to the movable part (3), so that the second body (12) and the movable part (3) jointly move together.

[0042] The die-casting system (20) further comprises molten metal injection means including a shot sleeve (7) and a piston (5) which moves and presses a mass of molten metal (6) into the mould cavity (2) as a result of its linear displacement through a shot sleeve (7). As it can be noted in Figure 3, the venting device (1) and the shot sleeve (7) are fluidly coupled at opposite end zones of the mould cavity (2).

[0043] Molten metal is fed before the beginning of the injection process, through a filing opening (8) into the shot sleeve (7). The casting is obtained by solidification of molten metal alloy in the mould cavity (2).

[0044] The system (20) includes control means (not shown) adapted to operate the actuator (16) of the venting device (1) in a coordinated manner with the molten metal injection means, such that the valve member (17) is closed ( Figure 1B) before molten metal flow reaches the mould cavity or a gate area (22) located right before the mould cavity (2), in order to prevent molten metal to flow through the gas evacuation channel (19), so that molten metal flowing out of the mould cavity, would flow through the cooling channel (18).

[0045] The venting device (1) optimizes the efficiency of the mould venting by means of the two channels (18, 19) to discharge the gases from the mould cavity (2).

[0046] The system of the invention is specially adapted to mould articles from Al, Mg, or Zn alloys.

Examples

Embodiment Construction

[0031]Figures 1A, 1B and 2 show a preferred embodiment of a venting device (1) according to the invention for vacuum assisted high pressure die casting. The venting device (1) is formed by a first body (11) and a second body (12) which can be coupled and uncoupled. In this embodiment, the first body (11) is stationary, and the second body (12) is movable relative to the first body (11).

[0032]The venting device (1) comprises an input port (15) and an output port (10), and a gas evacuation channel (19) fluidly communicating the input port (15) with the output port (10), and a cooling channel (18) also fluidly communicating the input port (15) with the output port (10). The gas evacuating channel (19) is formed internally in the first body (11), and a cooling channel (18) is formed by the two bodies (11, 12) when they are operatively coupled together. For example, a surface of one of the bodies has a grooves or depression and a surface of the other body has complementary reliefs to the...

OBJECT OF THE INVENTION

[0001] The present invention relates in general to vacuum assisted high pressure die casting, HPDC, manufacturing process and related systems.

[0002] More specifically, the invention refers to a device for venting gases from a mould cavity of a die casting system.

[0003] An object of the invention is to improve quality of articles obtained by the vacuum assisted high pressure die casting, by efficiently evacuating gases from a mould cavity.STATE OF THE ART

[0004] As a near-net shape manufacturing process, high pressure die casting (HPDC) is very attractive in producing thin-wall components with high dimensional accuracy, high production efficiency and considerable economic benefits for automotive and other industries.

[0005] However, conventional HPDC castings usually contain randomly distributed gas porosities mainly due to the entrapment of gas under the high-speed shot. The use of vacuum for extracting the air from the mould is one of the proven solutions to prevent the undesired entrapment of gas in the casting component. For that purpose, the mould needs an element, typically named chill vent or suction valve, with the aim communicating the vacuum with the cavity of the mould allowing discharge the gases outside the mould without spouting the molten metal.

[0006] The moulds used in vacuum assisted high pressure die casting usually include a chill vent to communicate the cavity with the vacuum system The gas exhaust passage in a chill vent is generally shaped in a zigzag-manner to ensure that, after the gas has been exhausted outside the chill vent, the molten metal is chilled in the passage before it is flashed outside the die mould.

[0007] In order to prevent flashing of molten metal with an improved reliability, it was considered necessary for the zigzag-shaped gas exhaust passage to have a narrow gap and adopt a relatively steep angle of the zigzag-shape. However, a narrow gap causes the sectional area of the gas exhaust passage to be decreased, while a steep angle causes the gas exhaust resistance to be increased. In any case, the gas exhaust efficiency is lowered, and it becomes difficult to prevent formation of gas hole defects in the product.

[0008] An alternative to the chill vent for vacuum assisted high pressure die casting, the mould might use a suction valve which, as an advantage to the chill vent, provides a higher venting passage area. In the suction valves, the air and gas, removed by the vacuum system, enter the valve together with a flow of metal until a stopper in the valve close the passage by an actuator. There are two kind of suction valves, mechanical or hydraulic / pneumatic valves, depending on the actuator type.

[0009] The mechanical valves operate the stopper by the molten metal itself. At the valve entry the molten metal encounters a piston before reaching the stopper. The pressure of the metal moves the piston which command the closure of the actuator connected to the stopper by means of an idle lever. The advantage of the mechanical valves resides in the operating time since they are open until the end of the die cavity filling. However, have demonstrated problems of reliability, particularly with regard to die casting of metals with high heat conductivity, because the passages made in the valve are not always suitable for an effective slowing and cooling of the molten metal, or for preventing this metal from invading the housing of the stopper and, thereby, rapidly reducing the valve efficiency.

[0010] The hydraulic / pneumatic valves use an actuator connected to the stopper and operated by a hydraulic or pneumatic fluid through an electrovalve which is controlled by means of time or plunger stroke. To guarantee that the molten metal does not invade the exit of the valve, the actuator is normally closed before the plunger begins the filling of the mould cavity, and from that moment until the end of the cavity filling the remaining gases are not discharged since the suction valve is closed and, thereby, reducing the efficiency of the valve.

[0011] Therefore, the provision of a valve capable of efficiently evacuating gases from a mould cavity, remains a challenge in this technical field.DESCRIPTION OF THE INVENTION

[0012] The invention is defined in the attached independent claims, and satisfactorily solves the above-described drawbacks of the prior art, by the provision of a venting device for a vacuum assisted die casting process or high pressure die casting (HPDC) process, to evacuate in the most efficient way a given volume of gases from a mould cavity thus avoiding air porosity and other defects as laminations and blisters in the HPDC castings.

[0013] The venting device of the invention optimizes the efficiency of the mould venting by the provision of two channels to discharge gases from a mould cavity, namely a gas evacuation channel configured as a low resistant flow channel to discharge gases at a high flow rate, before molten metal reaches the gas evacuation channel, and a cooling channel configured to cool down molten metal to solidify the same within the cooling channel. Preferably, the cooling channel is configured as a long and narrow gap where the molten metal cools down and gases are discharged to the outside during the whole molten metal injection process.

[0014] More specifically, an aspect of the invention refers to a venting device for vacuum assisted (high pressure) die casting, wherein the device comprises: an input port meant to be fluidly connected to a die casting mould cavity, an output port meant to be fluidly connected to a vacuum source, a gas evacuation channel fluidly communicating the input port with the output port, a cooling channel fluidly communicating the input port with the output port, and a valve member arranged to open and close the passage between the input port and the gas evacuation channel.

[0015] With the above described configuration of the venting device, gases are evacuated from the mould cavity during the entire molten metal injection process, first through the gas evacuation channel and the cooling channel, before molten metal reaches the mould cavity or a gate area right before the mould cavity , when the venting device is operatively coupled to a die casting mould, and as soon as the molten metal reaches the mould cavity or a gate area, only through the cooling channel wherein molten metal is cooled down and solidified before reaching the output port.

[0016] Preferably, at least a section of the cooling channel has a wavy (sinuous or serrated or zig zag) configuration in order to provide a large heat dissipation surface, for increasing heat transfer from the molten metal to the cooling channel.

[0017] In a preferred embodiment of the invention, at least a section of the gas evacuation channel has a cross-sectional area greater than the a cross-sectional area of a section of the cooling channel.

[0018] Preferably, a major part of the gas evacuation channel and a major part of the cooling channel, have constant cross-sectional area. The gas evacuation channel may be formed as a straight conduit, and the cooling channel with a wavy configuration generally extends parallel to the gas evacuation channel.

[0019] In some embodiments, the venting device is formed by a first body and a second body, wherein the first and second bodies can be coupled and uncoupled together. The gas evacuating channel is formed internally in the first body or in the second body, whereas the cooling channel is formed by the two bodies when they are operatively coupled together. The cooling channel defining a long and narrow gap.

[0020] In a preferred embodiment, the first body is stationary, and the second body is movable relative to the first body. The gas evacuation channel is formed in the stationary first body.

[0021] The venting device can incorporate an actuator to operate the valve member.

[0022] In a preferred embodiment the venting device comprises a filter, suitable to stop the flow of molten metal, installed between the cooling channel and the output port.

[0023] Another aspect of the invention refers to a vacuum assisted die casting system, comprising: a mould cavity, molten metal injection means adapted to inject molten metal into the mould cavity at a predetermined pressure, the venting device previously described, and a vacuum source fluidly coupled to the mould cavity through the venting device.

[0024] Preferably, the venting device and the molten metal injection means are fluidly coupled at opposite end zones of the mould cavity.

[0025] Additionally, the system can comprise control means adapted to operate the actuator of the venting device in a coordinated manner with the molten metal injection means, such that the valve member is closed before the molten metal flow reaches the mould cavity or a gate area right before the mould cavity, in order to prevent molten metal to flow through the gas evacuation channel, so that molten metal flowing out of the mould cavity, would flow through the cooling channel. The actuator opens the valve member at the beginning of the injection cycle i.e when the injection means start the injection of molten metal.

[0026] Another aspect of the invention refers to a die casting method, which comprises: evacuating gases from a mould cavity through a gas evacuation channel and through a cooling channel, closing the entry to the gas evacuation channel before the molten metal reaches the mould cavity or a gate area located right before the mould cavity, and continue evacuating gases from the mould cavity through the cooling channel while molten metal fills the mould cavity, and allowing molten metal to flow out of the mould cavity through the cooling channel, and cooling down molten metal in the cooling channel.

[0027] The method can comprise opening the valve member at the beginning of the injection cycle i.e when the injection means start the injection of molten metal.

[0028] Preferably, gases are evacuated by vacuum generation.

[0029] The method can be implemented as a cold or hot chamber high pressure die casting process.BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To complete the description and in order to provide a better understanding of the invention, a set of drawings is provided. These drawings form an integral part of the description and illustrate embodiments of the invention, which should not be interpreted as restricting the scope of the invention, but just as examples of how the invention can be carried out. The drawings comprise the following figures: Figure 1.- shows two schematic representations of a cross-sectional view of a preferred embodiment of venting device according to the invention, wherein Figure 1A shows the valve actuator in an open position, and Figure 1B shows the valve actuator in a closed position. Figure 2.- shows a front view of the venting device. Figure 3.- shows a schematic representation of a vacuum assisted high pressure die casting system, including the venting device of the invention. PREFERRED EMBODIMENTS OF THE INVENTION

[0031] Figures 1A, 1B and 2 show a preferred embodiment of a venting device (1) according to the invention for vacuum assisted high pressure die casting. The venting device (1) is formed by a first body (11) and a second body (12) which can be coupled and uncoupled. In this embodiment, the first body (11) is stationary, and the second body (12) is movable relative to the first body (11).

[0032] The venting device (1) comprises an input port (15) and an output port (10), and a gas evacuation channel (19) fluidly communicating the input port (15) with the output port (10), and a cooling channel (18) also fluidly communicating the input port (15) with the output port (10). The gas evacuating channel (19) is formed internally in the first body (11), and a cooling channel (18) is formed by the two bodies (11, 12) when they are operatively coupled together. For example, a surface of one of the bodies has a grooves or depression and a surface of the other body has complementary reliefs to the depressions, such that, when the two surfaces are brought together, the cooling channel (18) is formed.

[0033] In this embodiment, the cooling channel and the gas evacuation channel (18, 19) have constant cross-sectional area. The gas evacuation channel (19) is a straight conduit, which allows to discharge gases at a high rate from a mould cavity as it is configured as a low resistant flow conduit without strangulations, that is, with low loss load.

[0034] The cooling channel (18) generally extends parallel to the gas evacuation channel. The cooling channel (18) is narrower and longer than the gas evacuation channel (19). The cooling channel (18) is a sinuous path shaped in a zigzag or waveform manner with a thickness between 0.5mm and 1.5mm to ensure that, the gases can be extracted outside the mould cavity and the speed of the molten metal reduced, the heat exchange surface increased and the temperature of the molten metal lowered up to be solidified in the cooling device before reaching the end of the sinuous path. The cooling channel (18) is connected to the output port (10) at the top of the device (1) where the sinuous path ends. Thus, the gases can be discharged from the mould cavity during the whole molten metal injection process especially when the gas evacuation channel (19) is closed whereas the metal is solidified inside the cooling channel (18).

[0035] A first transversal channel (13) fluidly communicates the cooling channel (18) and the gas evacuation channel (19) with the output port (10). A filter (21) suitable to stop the flow of molten metal, is installed in the first transversal channel (13), to prevent molten metal coming through the cooling channel from reaching the output port (10).

[0036] A second transversal channel (14) fluidly communicates the input port (15) with the cooling channel (18) and with the gas evacuation channel (19).

[0037] A valve member (17) is arranged in the second transversal channel (14) to open and close the passage between the input port (15) and the gas evacuation channel (19). A hydraulic or pneumatic actuator (16) is provided to operate the valve member (17), although in other suitable types of actuators may be also used.

[0038] The cooling channel (18) permanently communicates the input port (15) with the output port (10).

[0039] Figure 2 shows a front view of the first body (11) alone to illustrate the output port (10), the input port (15), and the serrated-shaped surface of the first body (11) to form the zig-zag configuration when coupled with the second body (12).

[0040] Figure 3 shows a hight pressure die casting system (20) comprising: a mould formed by a stationary part (4) and a movable part (3), and a mould cavity (2) formed by the stationary and the movable parts (3, 4) when they are coupled together. The system (20) further comprises a vacuum source (9) connected to the venting device (1) according to the invention, to the mould cavity (2), in a way that the input port (15) of the venting device (1) is fluidly connected to the mould cavity (2), and the output port (10) is fluidly connected to a vacuum source (9).

[0041] The first body (11) is attached to the stationary part (4) of the mould, and the second body (12) is attached to the movable part (3), so that the second body (12) and the movable part (3) jointly move together.

[0042] The die-casting system (20) further comprises molten metal injection means including a shot sleeve (7) and a piston (5) which moves and presses a mass of molten metal (6) into the mould cavity (2) as a result of its linear displacement through a shot sleeve (7). As it can be noted in Figure 3, the venting device (1) and the shot sleeve (7) are fluidly coupled at opposite end zones of the mould cavity (2).

[0043] Molten metal is fed before the beginning of the injection process, through a filing opening (8) into the shot sleeve (7). The casting is obtained by solidification of molten metal alloy in the mould cavity (2).

[0044] The system (20) includes control means (not shown) adapted to operate the actuator (16) of the venting device (1) in a coordinated manner with the molten metal injection means, such that the valve member (17) is closed ( Figure 1B) before molten metal flow reaches the mould cavity or a gate area (22) located right before the mould cavity (2), in order to prevent molten metal to flow through the gas evacuation channel (19), so that molten metal flowing out of the mould cavity, would flow through the cooling channel (18).

[0045] The venting device (1) optimizes the efficiency of the mould venting by means of the two channels (18, 19) to discharge the gases from the mould cavity (2).

[0046] The system of the invention is specially adapted to mould articles from Al, Mg, or Zn alloys.

Examples

Embodiment Construction

[0031]Figures 1A, 1B and 2 show a preferred embodiment of a venting device (1) according to the invention for vacuum assisted high pressure die casting. The venting device (1) is formed by a first body (11) and a second body (12) which can be coupled and uncoupled. In this embodiment, the first body (11) is stationary, and the second body (12) is movable relative to the first body (11).

[0032]The venting device (1) comprises an input port (15) and an output port (10), and a gas evacuation channel (19) fluidly communicating the input port (15) with the output port (10), and a cooling channel (18) also fluidly communicating the input port (15) with the output port (10). The gas evacuating channel (19) is formed internally in the first body (11), and a cooling channel (18) is formed by the two bodies (11, 12) when they are operatively coupled together. For example, a surface of one of the bodies has a grooves or depression and a surface of the other body has complementary reliefs to the...

Claims

1. A venting device (1) for vacuum assisted die casting, the device comprising: an input port (15) meant to be fluidly connected to a die casting mould cavity, an output port (10) meant to be fluidly connected to a vacuum source, a gas evacuation channel (19) fluidly communicating the input port (15) with the output port (10), a cooling channel (18) fluidly communicating the input port (15) with the output port (10), a valve member (17) arranged to open and close the passage between the input port (15) and the gas evacuation channel (19).

2. A venting device according to claim 1, wherein at least a section of the cooling channel (18) has a wavy configuration.

3. A venting device according to claim 1 or 2, wherein at least a section of the gas evacuation channel (19) has a cross-sectional area greater than a cross-sectional area of a section of the cooling channel (18).

4. A venting device according to any of the preceding claims, wherein a major part of the gas evacuation channel (19) and a major part of the cooling channel (18), have constant cross-sectional area.

5. A venting device according to claim 4, wherein the gas evacuation channel (19) is a straight conduit, and wherein the cooling channel (18) has a wavy configuration and generally extends parallel to the gas evacuation channel (19).

6. A venting device according to any of the preceding claims, comprising a first body (11) and a second body (12), wherein the first and second bodies (11, 12) can be coupled and uncoupled together, and wherein the gas evacuating channel (19) is formed internally in the first body (11) or in the second body (12), and the cooling channel (18) is formed by the two bodies (11, 12) when they are operatively coupled together, defining a long and narrow gap.

7. A venting device according to claim 6, wherein the first body (11) is stationary, and the second body (12) is movable relative to the first body (11).

8. A venting device according to any of the preceding claims, further comprising an actuator (16) to operate the valve member (17).

9. A venting device according to any of the preceding claims, further comprising a filter (21), suitable to stop the flow of molten metal, installed between the cooling channel (18) and the output port (10).

10. A vacuum assisted die casting system (20), comprising: a mould cavity (2), molten metal injection means adapted to inject molten metal into the mould cavity (2) at a predetermined pressure, the venting device (1) defined in any of the preceding claims, and a vacuum source (9) fluidly coupled to the mould cavity (2) through the venting device (1).

11. A system according to claim 10, wherein the venting device (1) and the molten metal injection means are fluidly coupled at opposite end zones of the mould cavity (2).

12. A system according to claim 10 or 11, further comprising control means adapted to operate the actuator (16) of the venting device in a coordinated manner with the molten metal injection means, such that the valve member (17) is closed before the molten metal reaches the mould cavity (2) or a gate area (22) located right before the mould cavity (2).

13. A system according to any of the claims 10 to 12, suitable to mould articles from Al, Mg, or Zn alloys.

14. A die casting method, comprising: evacuating gases from a mould cavity (2) through a gas evacuation channel (19) and through a cooling channel (18), closing the entry to the gas evacuation channel (19) before the molten metal reaches the mould cavity (2) or a gate area (22) located right before the mould cavity (2), and continue evacuating gases from the mould cavity (2) through the cooling channel (18) while molten metal fills the mould cavity (2), and allowing molten metal to flow out of the mould cavity through the cooling channel (18), and cooling down molten metal in the cooling channel (18).

15. Method according to claim 14, wherein gases are evacuated by vacuum generation.

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