Metering device for metering liquid metals

Abstract

The invention relates to a metering device (10) for metering liquid metals (50), in particular for a diecasting installation (100), comprising a metering tube (1) designed to fluidically connect a holding furnace (101) to a casting chamber (102), and a heating device (2) for heating the metering tube (1), the heating device (2) being designed to keep the metal (50) in the liquid state over the entire length of the metering tube (1) via controlled actuation of the heating device (2).

Description

[0001] Description

[0002] Dosing device for dosing liquid metals

[0003] The present invention relates to a dosing device for dosing liquid metals, in particular for a die-casting system. Furthermore, the invention relates to a die-casting system.

[0004] Die casting systems are well known for producing metal components from liquid metal, such as aluminum. Typically, liquid metal located in a casting chamber is pressed into a mold under high pressure to produce the metal component. Before the liquid metal is fed into the casting chamber, it is usually stored in a holding furnace, which can hold a large amount of liquid metal and is kept liquid, for example, by heating. The liquid melt can flow from the holding furnace into the casting chamber via a dosing device, which often includes a dosing pipe. Due to the distance that often has to be bridged for design reasons, environmental influences on the melt to be dosed, such as temperature changes, which impair the material quality of the components to be cast.

[0005] It is therefore an object of the present invention to provide a dosing device for dosing liquid metals that, while being simple in design, enables an improvement in the material properties of the components to be cast during a casting process. Furthermore, it is an object of the invention to provide a die-casting system suitable for efficiently producing metal components with high material quality.

[0006] The object is achieved by a dosing device according to claim 1 and by a die casting system according to claim 13.

[0007] The metering device according to the invention comprises a metering tube configured for fluidly connecting a holding furnace to a casting chamber, for example, a die casting machine. The metering device also comprises a heating device configured for heating the metering tube. The heating device is configured to keep the metal inside the metering tube in a liquid state along its entire length by controlled heating of the metering tube.

[0008] In other words, a dosing device is provided which has a dosing tube that can be specifically and controllably heated by means of the heating device. The heating device is controlled in such a way that, by heating along the entire longitudinal direction of the dosing tube, a liquid melt of the metal is always provided inside the dosing tube. This means that solidification and, particularly preferably, oxidation of the melt are avoided by the targeted heating of the dosing tube.

[0009] The dosing device is characterized by a simple and cost-effective design, which can be manufactured and enables the casting of metal components using a die casting system with particularly high material quality. In particular, it can be achieved that, for example, a temperature of the liquid metal set in the holding furnace can be maintained particularly precisely and reliably over the entire dosing section within the dosing device such that the metal remains in a liquid state. The optimized properties of the liquid metal dosed by the dosing device subsequently enable improved material quality to be achieved for the components to be cast using the die casting system. In particular, the optimized melt temperatures can prevent casting defects, oxide inclusions, corundum formation, and undershoots of the target values ​​in the finished component.Furthermore, the heat balance of the casting mold can be optimized, which can also reduce wear on the casting mold, for example. Furthermore, the dosing device allows a reduction in temperature losses during the transport of the liquid metal from the holding furnace to the casting chamber. This makes it possible, for example, to reduce the temperature of the liquid metal in the holding furnace when the target temperature in the casting chamber is to be achieved, i.e., severe overheating can be avoided. In addition to saving energy, this also makes it possible to avoid a reduction in material properties caused by overheating of the melt. Particularly preferably, the dosing device further comprises a temperature sensor and a controller. In particular, the temperature sensor is arranged on or in the dosing tube and configured to detect a temperature on or in the dosing tube.The control system is configured to operate the heating device in a controlled manner depending on the temperature detected by the temperature sensor. In other words, temperature control of the heating device can be provided. This allows a specific desired temperature of the melt within the dosing tube to be achieved with particular precision, thereby achieving particularly good material properties for the components to be cast.

[0010] Preferably, the control system is configured to maintain the liquid metal, which can be metered by means of the metering device, at a predetermined target temperature at an outlet of the metering tube through the controlled actuation of the heating device. This means that the temperature of the meterable liquid metal is controlled with regard to an outlet temperature from the metering tube. This enables particularly efficient operation of the metering device and of a die casting system in which it is used, since, for example, precise control of the outlet temperature enables particularly efficient heating by means of the heating device, as well as, for example, in the holding furnace. Furthermore, by maintaining the optimal target temperature, particularly good material properties can be achieved, since corundum formation can be particularly reliably prevented.

[0011] Particularly preferably, the dosing tube is designed to completely shield the liquid metal from the environment, in particular from ambient oxygen. In other words, the dosing tube is designed to completely prevent contact of the liquid metal contained therein with the ambient air along its entire length. This allows for particularly reliable prevention of oxidation of the liquid metal, thereby preventing the formation of corundum in the melt. This allows for the production of components with particularly high material quality.

[0012] More preferably, the metering tube is designed as a completely enclosed tube. This means that, by being completely closed in the circumferential direction, the metering tube shields the melt being conveyed from the environment. This allows contact of the melt with the ambient air to be easily and reliably prevented. This prevents, in particular, oxidation of the liquid metal in the metering device and thus the formation of corundum, thus enabling particularly high material qualities for the components to be cast.

[0013] The heating device is preferably configured to independently heat at least two different sections of the metering tube along a longitudinal direction of the metering tube. In other words, a metering device is provided which has a metering tube that can be heated locally to different degrees. At least two separate sections of the metering tube, which are arranged adjacent to one another in particular along the longitudinal direction of the metering tube, can be heated independently of one another by means of the heating device. As a result, different temperatures of the melt-carrying metering tube can be provided at the at least two sections along the longitudinal direction of the metering tube. Due to the metering tube being individually heatable at the at least two different sections, melt transport by means of the metering device can be carried out in a particularly flexible and precisely tempered manner.This allows a desired melting temperature of the liquid metal to be provided particularly precisely and reliably at the outlet of the dosing tube, for example at the inlet of the casting chamber. The heating device preferably has at least two, preferably three, separate heating elements. In particular, the heating elements can be operated independently of one another. For example, this makes it possible for one of the heating elements to be operated with a constant heating output, with another heating element preferably being operated in a temperature-controlled manner. This provides simple, efficient, and at the same time flexible heating of the dosing tube. The heating elements are preferably designed as separate, individual components. This allows for a modular structure and thus a simple and flexible design of the dosing device.

[0014] The dosing device preferably comprises at least one separate temperature sensor for each section of the dosing tube. The controlled heating for each section is preferably based on a temperature detected by the respective temperature sensor. This allows for particularly precise and reliable temperature control to be provided, ensuring that the liquid metal is always kept at optimal temperatures to ensure high material quality.

[0015] Further preferably, the heating device comprises at least one heating element which extends in the form of, in particular a plurality of, windings around a circumference of the dosing tube. This means that the heating element, which is particularly designed to generate the heat for heating, is wound around the circumference of the dosing tube. This allows the liquid metal melt to be heated evenly around the entire circumference, i.e. from every direction, thereby enabling the melt to be kept in a liquid state in a particularly reliable manner. Preferably, the heating device comprises a heating wire, which is preferably designed as an electrical heating wire. Further preferably, the heating device comprises a refractory material, wherein the heating wire is embedded in the refractory material.This makes it possible to provide a simple, cost-effective, and particularly robust heating device design that is suitable for long-lasting and efficient use in a die-casting system. Preferably, the windings per section are arranged at a predetermined, constant winding spacing from one another. The winding spacing is considered to be, in particular, an axial distance between adjacent windings, i.e., along the longitudinal direction of the metering tube. In other words, the windings are arranged with a uniform winding density. This enables particularly simple manufacture of the metering device and simple provision of uniform heating power. Particularly preferably, multiple heating elements can be provided, each heating element having different winding spacings.This makes it possible, for example, to achieve locally different heating levels of the dosing tube with the same power supply, so that flexible adjustment of the heating can be achieved with a particularly simple design.

[0016] Alternatively, the windings of the heating element are preferably arranged along a flow direction of the liquid metal, i.e., downstream in the longitudinal direction of the metering tube, at a progressively decreasing winding spacing from one another. This means that the windings are arranged increasingly closer to one another along the longitudinal direction. A uniform reduction in the winding spacing can be regarded as progressively decreasing. The winding spacing can preferably decrease linearly, alternatively, preferably exponentially or the like. This can ensure that, in the direction of the outlet of the metering tube, an increasing heat input into the melt occurs per length. This can ensure particularly reliably that the metal is kept in a liquid state during transport within and along the metering tube.

[0017] The dosing tube preferably has an inner tube, within which the liquid metal can preferably be conveyed. The dosing tube further comprises a heating tube surrounding the inner tube. In addition, the dosing tube comprises an outer tube surrounding the heating tube. The dosing tube preferably also has insulation surrounding the outer tube. The heating device is integrated into the heating tube. In other words, the dosing tube is constructed from the inner tube, the heating tube, and the outer tube, which are preferably arranged coaxially to one another. This enables a simple and cost-effective construction of the dosing tube. In addition, the outer tube can, for example, provide protection and thermal insulation for the heating tube.

[0018] The temperature sensor is preferably arranged outside the inner tube and radially adjacent to the inner tube, preferably directly adjacent to it. The temperature sensor can preferably be a thermocouple. More preferably, the temperature sensor is arranged centrally between two adjacent windings of the heating element with respect to the longitudinal direction of the metering tube. This allows for a precise temperature determination in a simple and cost-effective manner. In particular, this allows for particularly reliable and precise determination of the current temperature of the melt inside the inner tube.

[0019] More preferably, the dosing device further comprises a non-return device which permits the liquid metal to flow within the dosing tube exclusively in a predetermined conveying direction. This means that the non-return device prevents the liquid metal from flowing back, in particular toward the holding furnace. This allows the liquid metal to be held within the dosing tube without flowing back, for example, during interruptions in the casting process and / or between filling the casting chamber for several consecutive casting processes. The heating device can additionally maintain the temperature of the correspondingly held liquid metal. In particular, this can provide a faster cycle time, allowing castings to be produced particularly efficiently and cost-effectively.

[0020] The dosing tube and / or the heating device are preferably composed of several parts. A multi-part design of both the dosing tube and the heating device is particularly advantageous, with a common dividing plane preferably being provided for each. This allows for a modular construction of the dosing tube and / or heating device, enabling a flexible design of the dosing device for different applications, for example, in a simple and cost-effective manner.

[0021] Furthermore, the invention leads to a die casting system, in particular for die casting liquid metals, preferably aluminum or magnesium. The die casting system comprises a holding furnace designed to hold liquid metal, preferably in a holding chamber. The holding furnace is preferably configured to heat the liquid metal. The die casting system further comprises a feed device and the described metering device. The feed device is configured to feed liquid metal from the holding furnace into the metering device. Furthermore, the metering device is configured for fluid communication with the casting chamber. The metering tube is preferably arranged so as to rise vertically from the feed device toward the casting chamber.In other words, the casting chamber can be positioned higher vertically than the holding furnace, with the metering tube being arranged so that it rises vertically toward the casting chamber. In particular, the vertical direction corresponds to a direction of gravity. This enables an optimized, compact design of the die casting system. Furthermore, particularly precise filling of the casting chamber is possible, since, for example, dripping of liquid metal can be minimized by the special arrangement of the metering tube.

[0022] More preferably, the die-casting system further comprises a shot device configured to convey liquid metal, which has been metered via the metering device, into the casting chamber, preferably by means of a shot piston. In particular, the metered liquid metal is conveyed into the casting chamber under high pressure by means of the shot piston. For example, the shot piston can be arranged horizontally.

[0023] For example, the die casting system can be a cold chamber die casting system.

[0024] The invention is explained in more detail below using exemplary embodiments. These show:

[0025] Figure 1 is a simplified schematic view of a die casting plant with a dosing device according to a first embodiment of the invention,

[0026] Figure 2 is a simplified schematic sectional view of the dosing device of Figure 1,

[0027] Figure 3 is a simplified schematic detailed view of the dosing device of Figure 1, and

[0028] Figure 4 is a simplified schematic detailed view of a dosing device according to a second embodiment of the invention.

[0029] Preferred embodiments of a dosing device 10 according to the invention are described in more detail below. Reference is made to Figures 1 to 4. Identical or functionally identical components are always provided with the same reference numerals. Figure 1 shows a simplified schematic view of a die casting system 100 with a dosing device 10 according to a preferred embodiment of the invention.

[0030] The die casting system 100 comprises a holding furnace 101 with a receiving chamber 106 in which liquid metal 50 can be received and stored, for example, for later use in die casting. For example, the liquid metal 50 can be poured into the receiving chamber 106 of the holding furnace 101 via a filling opening 105.

[0031] The die casting system 100 comprises a casting chamber 102, a feed device 103 and the dosing device 10 according to the invention.

[0032] By means of the feed device 103, a specific amount of liquid metal 50 can be removed from the receiving chamber 106 of the holding furnace 101 and transported further for use in die casting. For this purpose, the feed device 103 can comprise a pumping device 104, which preferably has a control system.

[0033] The amount of liquid metal 50 metered by means of the feed device 103 is then transported to the casting chamber 102 via the metering device 10.

[0034] For example, the casting chamber 102 may have a shot device and a casting mold, wherein the shot device conveys the metered liquid metal 50 under high pressure into the casting mold in order to produce metal components.

[0035] This is preferably a cold chamber die casting process.

[0036] The dosing device 10 thus serves to connect the holding furnace 101 with the feeding device 103 and the casting chamber 102, i.e. for melt transport.

[0037] The dosing device 10 comprises a dosing tube 1, which forms the fluid connection between the holding furnace 101 and the casting chamber 102. The dosing tube 1 extends, for example at least partially cylindrically, along a longitudinal direction 15 and is designed as a circumferentially completely closed tube, within which the melt conveyed by the feed device 103 can flow along a conveying direction 51. Because the dosing tube 1 is circumferentially completely closed, it is possible to shield the liquid metal from the environment, thereby avoiding or reducing oxidation of the liquid metal. In particular, this prevents contact with the ambient air, thereby preventing oxidation and thus, in particular, corundum formation. This allows components with particularly high material quality to be manufactured.

[0038] The dosing tube 1 is arranged so as to rise from the holding furnace 101 or the feed device 103 along the conveying direction 51 toward the casting chamber 102 with respect to a vertical direction, specifically with respect to a direction of gravity G. This makes it possible, for example, to lower the top of the holding furnace 101, i.e., to arrange it lower, thereby reducing the overall height of the die casting system 100. Furthermore, this results in advantages with regard to filling the melt into the casting chamber 102, since, for example, dripping of melt in the dosing tube 1 can be reduced.

[0039] The dosing tube 1 comprises, for example, at an end facing the feed device 103, a non-return device 5, which prevents the melt from flowing back. This means that the non-return device 5 allows the liquid metal 50 to flow exclusively in the conveying direction 51.

[0040] Furthermore, the dosing tube 1 is segmented and comprises a plurality of sections 17. The sections 17 are separated from one another by parting planes 10a. In particular, the dosing tube 1 is formed from the various sections 17 at the parting planes 10a, i.e., joined together.

[0041] The dosing device 10 further comprises a heating device 2, which is configured to heat the dosing tube 1, as well as several temperature sensors 3 and a controller 4. In detail, the heating device 2 is configured to heat the three different sections 17 independently of one another.

[0042] The heating device 2 comprises a total of three heating elements 21, which are assembled at the parting planes 10a corresponding to the sections 17 of the metering tube 1. Overall, the assembly of the metering device 10, consisting of the metering tube 1 and the heating device 2, can thus be considered to be modularly composed of several parts. For example, the length of the metering device 10 can be easily adjusted by removing or adding parts, thus enabling flexible application options for different die casting systems 100.

[0043] The temperature of the dosing tube 3 can be detected by means of the temperature sensors 3. For example, the temperature of the melt in the dosing tube 1 can be estimated based on this. The controller 4 is configured to actuate the heating device 2 depending on the temperature values ​​detected by the temperature sensors 3. In particular, the controlled actuation of the heating device 2 takes place in such a way that the liquid metal within the dosing tube 1 is kept liquid over its entire length and preferably at a predetermined temperature. It is particularly advantageous if controlled heating with the controller 4 and the heating device 2 takes place in such a way that the liquid metal 50 is kept at a predetermined target temperature at the casting chamber-side outlet 19 of the dosing tube 1.

[0044] The heating device 2 and the special heating of the liquid metal within the dosing tube 1 enable the casting of metal components with particularly high material quality. The ability to heat the three sections 17 of the dosing tube 1 independently of one another allows the melt transport within the dosing device 10 to be particularly flexible and precisely controlled. In particular, this makes it particularly easy and efficient to maintain a temperature of the liquid metal 50 set at the holding furnace 101 with particular precision and reliability over the entire dosing section within the dosing device 10. The optimized melt temperatures thus prevent casting defects, oxide inclusions, and underachieved target values ​​in the finished component.

[0045] Further details of the structure of the dosing tube 1 are described below with reference to Figures 2 and 3, which show simplified schematic detailed views of the dosing tube 1. Figure 2 shows a sectional view in a plane orthogonal to the longitudinal direction 15.

[0046] The dosing tube 1 comprises a plurality of tubular elements which are formed and arranged coaxially with one another and are also coaxial with the longitudinal direction 15. In particular, all of these tubular elements, which are described in more detail below and have the reference numerals 11, 12, 13, and 14 in Figure 2, are each arranged and formed radially directly adjacent to one another. In detail, the dosing tube comprises an inner tube 11, which forms the radially innermost region of the dosing tube 1. This means that the liquid metal 50 is guided in the inner tube 11. The inner tube 11 is preferably formed from ceramic or a ceramic material in order to have a high level of durability. In addition, the inner tube 11 has a smooth inner surface, which is preferably formed as a sintered surface, in order to enable efficient melt transport.

[0047] The inner tube 11 is surrounded by a heating tube 12, with the heating device 2 integrated into the heating tube 12. The heating tube 12 comprises, in detail, a refractory material 22 that is resistant to high temperatures and an electric heating wire 21 embedded in the refractory material 22. By supplying the heating wire 21 with an electric current via the controller 4, the dosing tube 1 can be heated.

[0048] In addition, the dosing tube 1 comprises an outer tube 13 that surrounds the heating tube 12. The outer tube 13 is preferably made of steel or another metallic material and can provide protection and thermal insulation for the heating tube 12.

[0049] Furthermore, the dosing tube 1 can additionally have insulation 14 surrounding the outer tube 13. The insulation 14 can be configured to provide additional thermal insulation to reduce heat loss, for example, via the outer tube 13. This can further increase the efficiency of the die casting system 100.

[0050] The heating elements 21 of the heating device 2 are designed in particular in the form of windings 21a, which extend spirally around the circumference of the dosing tube 1, as shown in Figure 3. With respect to the longitudinal direction 15, adjacent windings 21a are arranged at a predetermined winding spacing 21b from one another.

[0051] In the first embodiment, the first two sections 17 along the longitudinal direction 15 are formed with the same winding pitch 21b, while in the third section 17, where the outlet 19 is located, a smaller winding pitch 21b, which is preferably at least 30% smaller, is provided. As a result, the windings 21a in the third section are closer to one another.

[0052] With the same power supply to all heating elements 21, a larger amount of heat is introduced per length in the third section 17. This means that the melt is heated more intensely in this section 17. This ensures particularly reliable retention of the metal throughout the entire length of the dosing tube 1.

[0053] As can be seen in Figure 3, a separate temperature sensor 3 is provided on each section 17, which is arranged centrally on the respective section 17 along the longitudinal direction 15.

[0054] Figure 4 shows a simplified schematic detailed view of a dosing device 10 according to a second embodiment of the invention. The second embodiment essentially corresponds to the first embodiment, with the difference of an alternative design of the heating device 2. In the second embodiment, the heating device 2 comprises precisely a single heating element 21, which has windings 21a arranged at a winding spacing 21b that progressively decreases along the longitudinal direction 15 toward the outlet 19. This enables a more intense heating of the dosing tube 1 on the outlet side by means of a particularly simple construction with few components.

[0055] List of reference symbols

[0056] Dosing tube Heating device T emperature sensors Control system Check valve Dosing device a Separation planes Inner tube Heating tube Outer tube Insulation Longitudinal direction Sections Outlet Heating elements Liquid metal Conveying direction 0 Die casting system 1 Holding furnace 2 Casting chamber 3 Feeding device 4 Pumping device 5 Filling opening 6 Receiving chamber Gravitational direction

Claims

Patent claims 1. Dosing device for dosing liquid metals (50), in particular for a die casting plant (100), comprising: - a dosing pipe (1) which is arranged for the fluid connection of a holding furnace (101) with a casting chamber (102), and - a heating device (2) for heating the dosing tube (1), - wherein the heating device (2) is arranged to keep the metal (50) inside the dosing tube (1) in a liquid state along the entire length of the dosing tube (1) by a controlled actuation of the dosing tube (1).

2. Dosing device according to claim 1, further comprising a temperature sensor (3) and a controller (4), wherein the controller (4) is configured to actuate the heating device (2) in a controlled manner as a function of a temperature detected by means of the temperature sensor (3).

3. Dosing device according to claim 2, wherein the controller (4) is arranged to keep the liquid metal (50) at an outlet (19) of the dosing tube (1) at a predetermined target temperature by the controlled actuation of the heating device (2).

4. Dosing device according to one of the preceding claims, wherein the dosing tube (1) is designed to completely shield the liquid metal (50) from an environment, in particular from oxygen.

5. Dosing device according to one of the preceding claims, wherein the dosing tube (1) is designed as a circumferentially completely closed tube.

6. Dosing device according to one of the preceding claims, wherein the heating device (2) is configured to heat at least two different sections (17) of the dosing tube (1) along a longitudinal direction (15) of the dosing tube (1) independently of one another, in particular wherein the heating device (2) has at least two, preferably three, separate heating elements (21).

7. Dosing device according to one of claims 2 to 6, comprising at least one separate temperature sensor (3) per section (17).

8. Dosing device according to one of the preceding claims, wherein the heating device (2) comprises at least one heating element (21) which extends in the form of windings (21a) around a circumference of the dosing tube (1).

9. Dosing device according to claim 8, wherein the windings (21a) are arranged at least per section (17) at a predetermined constant winding distance (21b) from one another, or wherein the windings (21a) are arranged along a flow direction of the liquid metal (50) in the dosing tube (1) at a progressively decreasing winding distance (21b) from one another.

10. Dosing device according to one of the preceding claims, wherein the dosing tube (1) comprises an inner tube (11), a heating tube (12) surrounding the inner tube (11), and an outer tube (13) surrounding the heating tube (12), and preferably an insulation (14) surrounding the outer tube (13), and wherein the heating device (2) is integrated into the heating tube (12).

11. Dosing device according to one of claims 2 to 10, wherein the temperature sensor (3) is arranged outside the inner tube (11) and in the radial direction, in particular directly, adjacent to the inner tube (11).

12. Dosing device according to one of the preceding claims, further comprising a non-return device (5) which allows a flow of the liquid metal (50) exclusively in a predetermined conveying direction (51).

13. Die casting plant, comprising: - a holding furnace (101) for holding liquid metal (50) - a casting chamber (102), - a feeding device (103), and - a dosing device (10) according to one of the preceding claims, - wherein the feed device (103) is arranged to feed liquid metal (50) from the holding furnace (101) into the dosing device (10), and - wherein the dosing device (10) is arranged for fluid connection with the casting chamber (101).

14. Die casting system according to claim 13, wherein the metering pipe (1) is arranged so as to rise vertically from the feed device (103) towards the casting chamber (102).

15. Die-casting system according to claim 13 or 14, further comprising a shot device which is designed to convey liquid metal (50) dosed via the dosing device (10) into the casting chamber (102) in particular by means of a shot piston.

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