EP3871805A1 - Device and method for pressure casting metallic material in thixotropic state - Google Patents

Abstract

The invention relates to a device and a method for die casting metallic material in a thixotropic state in a mold (3) which has several sprue openings (4, 5), comprising a heatable distributor (11) with one inlet (14) and several with the Inlet via channels (12, 13) communicating outlets (15, 16), and a plurality of heatable pouring pipes (21, 22) each with an inlet (23, 24) and an outlet (25, 26), each pouring pipe (21, 22) with an end face area (27, 28) lying around its inlet (23, 24) on a surface area (17, 18) of the distributor (11) lying around the associated outlet (15, 16) by means of a linear Relative movement (31 - 33) between this pouring pipe (21, 22) and the distributor (11) can be brought into sealing contact, and with at least one selectively tensionable pulling device (36) engaging with one end (37) of the distributor (11), the other end (38) of which can be anchored to the mold (3).

Description

The present invention relates to an apparatus and a method for die-casting metallic material in a thixotropic state in a mold which has a plurality of gate openings, comprising a heatable manifold with an inlet for the material and a plurality of outlets communicating with the inlet via channels, and a A plurality of heatable pouring pipes, each with an inlet for connection to one of the outlets and an outlet for attachment to one of the sprue openings.

When die-casting metallic material in the thixotropic ("semi-solid" or "solid-liquid") state, also known as metal injection molding, thixoforming, thixocasting or thixomolding, die-cast parts can be produced with improved properties compared to conventional die-casting processes. The materials are brought to the transition temperature between the solid and the liquid phase so that distributed crystallized components are embedded in coherent molten areas ("thixotropic phase"). The additional action of shear forces reduces the size of the crystalline structures of the solid components, the viscosity of the material decreases, which makes it easier to inject it into the die-casting mold and enables precise die-casting.

Devices of the type mentioned at the beginning with a heatable distributor and several heatable pouring pipes are used to feed several molds or a large mold through several sprue openings with a single injection molding machine in order to keep the flow paths in the mold short. The pouring pipes are also referred to as "hot runners", and systems with several pouring pipes as "multiple hot runner systems".

The requirements for multiple hot runner systems for thixoforming differ significantly from "normal" hot runner systems for e.g. plastic injection molding. The process temperature for the thixoforming of e.g. aluminum or magnesium alloys is in the range of 550 - 700 ° C. The pressures required for the injection molding of the thixotropic metal melt are several 100 bar up to over 1000 bar.

At such high temperatures and pressures, many sealing systems fail, such as high-temperature plastic sealing rings and metallic screw connections, that can still be used without problems in plastic injection molding for sealing between the injection molding machine, manifold, pouring pipes and mold. Plastic seals soften and metallic screw connections begin to "creep" at high temperatures, ie they give way, loosen and become leaky. Last but not least, the thermal expansion of the components is significant at high temperature ranges, which increases the material fatigue of all connections and thus leaks. Currently known multiple hot runner systems for thixoforming therefore only have a short service life, which severely limits their practical use.

The aim of the invention is to create a multiple hot runner system for the die casting of metallic materials in a thixotropic state, which enables a long service life.

This goal is achieved in a first aspect with a device of the type mentioned in the introduction, which is characterized according to the invention in that each pouring pipe with an end face area located around its inlet on a surface area of the distributor located around the associated outlet by means of a linear relative movement therebetween The pouring pipe and the distributor can be brought into sealing abutment, with at least one selectively tensionable pulling device engaging the distributor with its one end, the other end of which can be anchored to the mold.

The multiple hot runner system of the invention is based on the novel approach of completely dispensing with fault-prone screw connections between the manifold and pouring pipes and instead providing an optionally tensionable and releasable sealing pressure between the pouring pipes and the manifold. The device can thus be brought in a relaxed state to the operating temperature of 600 ° C (aluminum or magnesium alloys) required for thixoforming, in which the thermal expansion of the pouring pipes and the manifold changes their relative positions, and then the tensioning device is tightened the sealing system is established between the thermally expanded components. The dimensions of the pouring pipes and manifolds components, particularly the orientations the pouring pipe end face areas and the distributor surface areas can already be designed for the hot operating state. When the drawbar is then tensioned while it is hot, all components are perfectly aligned with one another. This enables an optimal sealing system to be achieved between the pouring pipes and the manifold during operation, even with large center-to-center distances between the sprue openings. By dispensing with separate sealing rings and fault-prone metallic screw connections, extraordinary service lives of the device of over 500,000 die-casting processes ("shots") can be achieved.

• Bereitstellen einer Vorrichtung der hier vorgestellten Art;
• Ansetzen der Gießrohre an die Angussöffnungen und Verankern der Zugeinrichtung in entspanntem Zustand an der Form;
• Aufheizen des Verteilers und der Gießrohre auf die für den thixotropen Zustand des Materials erforderliche Temperatur;
• Spannen der Zugeinrichtung, um die Stirnflächenbereiche der Gießrohre an den Oberflächenbereichen des Verteilers in Dichtanlage zu bringen; und
• Ansetzen der Düse einer Spritzgussmaschine an den Einlass des Verteilers und Druckgießen des Materials über den Verteiler und die Gießrohre in die Form.

In this sense, the invention also provides, in a second aspect, a method for die casting metallic material in a thixotropic state in a mold which has several gate openings, with the steps:

• Providing a device of the type presented here;
• Attaching the pouring pipes to the sprue openings and anchoring the pulling device in the relaxed state on the mold;
• Heating the manifold and the pouring tubes to the temperature required for the thixotropic state of the material;
• Tensioning the pulling device in order to bring the end face regions of the pouring pipes into sealing engagement with the surface regions of the manifold; and
• Attach the nozzle of an injection molding machine to the inlet of the manifold and die-cast the material over the manifold and pouring pipes into the mold.

It is particularly advantageous if the pouring pipes diverge from one another as seen from the distributor. As a result, the span of the device can be increased so that larger molds with sprue openings that are further apart can be charged, or conversely, a smaller distributor can be used, which reduces the mass of the device to be heated and cooled, so that the set-up and Downtimes for tool changes or repairs can be shortened. At the same time, due to the inclined position of the pouring pipes in relation to the manifold, self-centering of the manifold is achieved when it is clamped onto the pouring pipes by the pulling device. As a result, any uneven thermal expansion of the pouring pipes can be better absorbed and an even better seal can be achieved in the hot state.

For the self-centering of the manifold with respect to the pouring pipes when tensioning the pulling device, it is particularly favorable if the surface area of each outlet is inclined to a central axis of the manifold and preferably also inclined to the channel leading to this outlet, and / or if the end face area of each pouring pipe is oblique to its longitudinal axis. With each of these measures, the tightness in the hot state can be increased even further. The pulling device in connection with the inclined contact surfaces also ensures that thermal expansion fluctuations during operation, for example when process temperature optimization is necessary, are compensated, as well as minor tolerance deviations from the manufacturing process.

According to a further preferred feature, the longitudinal axis of each pouring tube, when it is connected to the associated outlet, forms an obtuse angle with the channel leading to this outlet. As a result, the flow path of the melt experiences a slight kink at the transition from the distributor to the respective pouring pipe, which makes it easier to tear off the cooled melt if the pouring pipe is to be separated from the distributor in the cold state, for example for repair purposes. When the pouring pipes are separated from the manifold at this bend, the cooled melt is not only subjected to tension but also to shear, which promotes tearing off.

In addition to each outlet, the distributor preferably has an optionally adjustable lateral guide for the inlet-side end of the associated pouring pipe. This allows the pouring pipe inlets to be better aligned with the manifold outlets. In the case of diverging pouring pipes, in particular with inclined end face areas and co-operating inclined manifold surface areas, the lateral guides also form a stop for the sideways movement of the pouring pipes during the self-centering of the manifold on the pouring pipes.

In a first variant of the invention, a separate pulling device can be provided for each pouring pipe in order to tension the distributor against this pouring pipe. In a second, particularly advantageous variant, the aforementioned relative movements are a common pulling device is assigned to all pouring pipes in parallel and all pouring pipes. With a single tensioning or relaxing movement of the common pulling device, the distributor on all casting pipes can be brought to the sealing system or detached from them again.

In a further advantageous embodiment of the invention, the pulling device is a combined pulling / pushing device, which can be actuated to either pull or push. The combined pulling / pushing device can be used to forcefully lift the distributor off the pouring pipes, for example in the cold state, in order to tear off the cooled melt at the interfaces between the distributor outlets and the pouring pipe inlets.

For this purpose, it is particularly advantageous if the pouring pipes can be anchored temporarily to the mold. The pouring pipes can initially be fixed to the mold to make it easier to lift off the distributor, or they can remain anchored to the mold at all if, for example, only the distributor is to be exchanged.

The pulling device can be designed in any manner known in the art, for example as a clamping cam, eccentric, sliding wedge, etc. The pulling device is preferably formed by at least one hydraulic cylinder. With the appropriate hydraulic pressure, for example 5 to 500 bar, and a correspondingly large piston surface, very large clamping forces can be applied, up to several tons. In addition, readjustments can be made at any time by adjusting the hydraulic pressure during operation. It goes without saying that the pulling device also has several on different Hydraulic cylinders acting on points of the distributor can include, for example, at diametrical ends of an elongated distributor or distributed over the circumference of a round or polygonal distributor.

It is particularly favorable if the hydraulic cylinders are double-acting hydraulic cylinders, by means of which a combined pulling / pushing device can be implemented in a simple manner.

According to a further advantageous feature of the invention, one end of the pulling device engages the distributor releasably, preferably via a tongue and groove connection. As a result, the device can be dismantled into its individual parts for repair and maintenance in a particularly simple manner.

The distributor and the pouring pipes are preferably traversed by cooling fluid channels. This allows the device to be cooled down quickly if necessary, e.g. for tool changes or repairs. At least some of the cooling fluid channels can pass through the distributor surface areas and the respective pouring tube end face areas in alignment therewith. The cooling fluid channels in the pouring pipes can thereby be fed from the distributor, so that external cooling fluid feed lines to the pouring pipes are not required.

The pulling device acting between the distributor and the mold is subject to a high temperature gradient. The distributor is at the temperature of the thixotropic melt, for example 600 ° C, while the mold is kept at a temperature of 100-300 ° C, which is cool by comparison. To the pulling device, for example To protect the hydraulic cylinders used for this from the high temperature of the distributor, according to a further preferred feature of the invention, the end of the pulling device engaging the distributor is penetrated by at least one cooling fluid channel with which this end can be cooled.

The apparatus of the invention can form a stand-alone adapter for attaching a conventional injection molding machine to a mold with multiple sprues. The mold only needs to be equipped with an anchor for the end of the pulling device. In an alternative embodiment, the device of the invention can comprise a mold insert which can be connected to the mold or which forms part of the mold itself and has a plurality of sprue openings which form receptacles for the outlets of the pouring pipes. The mold insert can, for example, be part or the entire mold half of a two-part mold.

It is particularly favorable if the longitudinal axis of each pouring tube, when it is attached to the associated sprue opening, forms an obtuse angle with the passage axis of this sprue opening. This also results in a slight kink in the flow path of the molten metal at this point. When demolding the molded part, when the mold is opened and the melt in the pouring tube outlet solidifies to form a plug, this kink between the pouring pipe and the sprue opening reduces the length of the plug. The plug represents scrap that has to be removed before the next printing process must, and a shorter plug means less rejects.

According to a further preferred feature, the mold insert can present an end stop for the distributor during its relative movement with respect to the pouring pipes. This creates safety when the device is used on older injection molding machines, which can sometimes have very high pressure forces which could lead to the destruction of the pouring pipes clamped between the distributor and the mold if they are not caught by such an end stop.

• Fig. 1 die Vorrichtung der Erfindung in gespanntem Zustand zwischen einer Spritzgussmaschine und einer Form im Schnitt;
• Fig. 2 die Vorrichtung von Fig. 1 in entspanntem Zustand mit von den Gießrohren abgehobenem Verteiler im Schnitt;
• Fig. 3 eines der Gießrohre der Vorrichtung von Fig. 1 in einer Seitenansicht; und
• die Fig. 4 und 5 zwei weitere Ausführungsformen der Vorrichtung der Erfindung in einer Perspektivansicht von schrägunten (Fig. 4) bzw. schräg-oben (Fig. 5).

The invention is explained in more detail below with reference to the exemplary embodiments shown in the accompanying drawings. In the drawings show:

• Fig. 1 the device of the invention in the clamped state between an injection molding machine and a mold in section;
• Fig. 2 the device of Fig. 1 in the relaxed state with the manifold lifted from the pouring pipes in section;
• Fig. 3 one of the pouring tubes of the device of Fig. 1 in a side view; and
• the Figures 4 and 5 two further embodiments of the device of the invention in a perspective view obliquely from below ( Fig. 4 ) or diagonally above ( Fig. 5 ).

the Fig. 1 and 2 show a device 1 for die casting of metallic material, for example an aluminum or magnesium alloy. The device 1 is in the form of an adapter or multiple distributor ("multiple hot runner") between the nozzle 2 of an injection molding machine (not shown in more detail) and a mold 3 with a plurality of sprue openings 4, 5 interposed. In the injection molding machine, the metallic material is put into the thixotropic state by the action of temperature and pressure, for example by means of a heated screw unit, and is released as thixotropic metal melt via the nozzle 2 for the die casting process ("shot").

The molten metal from the nozzle 2 is injected by the device 1 via the sprue openings 4, 5 into mold cavities 6, 7 of the mold 3 adjoining these, in order to cast one or more molded articles (not shown) therein. The mold 3 is conventionally in several parts and can be opened, for example by means of two mold halves 8, 9 that can be opened and closed relative to one another, in order to remove the moldings from the mold cavities 6, 7; ejectors used for this in the mold halves 8, 9 are not shown for the sake of simplicity.

The sprue openings 4, 5 can be formed in one mold half 9 or in a mold insert 10 of the mold half 9. The mold 3 or its mold insert 10 with the sprue openings 4, 5 can be separate from the device 1 or a part thereof.

The device 1 has a central distributor 11, for example made of a solid metal block, which is traversed by inner, branching channels 12, 13. The channels 12, 13 connect an inlet 14 on one side of the manifold 11 with two or more outlets 15, 16 on another side of the manifold 11. The outlets 15, 16 are, for example, on a side opposite or adjacent to the inlet 14 of the distributor 11 arranged. In the example shown, the outlets 15, 16 lie on surface areas 17, 18 of the distributor 11 that point obliquely downwards and outwards, while the inlet 14 lies on the upper side 19 of the distributor 11. It goes without saying that the device 1 can be used in any installation position, so that the terms “above” and “below” are only to be understood here relative to one another.

Two or more pouring pipes 21, 22 extend from the distributor 11 and diverge from one another at an angle of divergence α. Each pouring pipe 21, 22 has an inlet 23, 24 and an outlet 25, 26, which are in flow connection with one another via the pipe interior of the pouring pipe 21, 22. The inlet 23, 24 of each pouring tube 21, 22 can each be brought into flow connection with one of the outlets 15, 16 of the distributor 11, and the outlet 25, 26 of each pouring tube 21, 22 each with one of the sprue openings 4, 5 of the mold 3.

The distributor 11 on the one hand and the pouring pipes 21, 22 on the other hand are movable relative to one another, namely between a first, in Fig. 1 position shown, in which the end face areas 27, 28 of the pouring pipes 21, 22 lying around the inlets 23, 24 are each in sealing contact with the surface area 17, 18 of the distributor 11 lying around the associated outlet 15, 16, and a second, in Fig. 2 position shown, in which the end face areas 27, 28 of the pouring pipes 21, 22 are lifted from the surface areas 17, 18 of the distributor 11. For this purpose, for example, each pouring pipe 21, 22 is in a linear movement parallel to its longitudinal axis 29, 30 31, 32 individually relatively movable with respect to the distributor 11, or all the pouring pipes 21, 22 are relatively movable in the same linear direction with respect to the distributor 11 or, conversely, the distributor 11 is relatively movable in a single linear movement 33 with respect to all the pouring pipes 21, 22. This common movement or single linear movement 33 can, for example, be parallel to a central axis 34 of the distributor 11, which axis 34 can in particular also coincide with a central axis 35 of the nozzle 2 of the injection molding machine.

To be in the sealing position ( Fig. 1 ) to press the manifold 11 tightly against the pouring pipes 21, 22, ie to produce the sealing system between the manifold surface areas 17, 18 and the pouring pipe end face areas 27, 28, the device 1 has at least one pulling device 36, which with its one end 37 engages on the manifold 11 and with its other end 38 on the mold 3, more precisely on that mold half 9 or the mold insert 10 which has the sprue openings 4, 5. The pulling device 36 clamps the pouring pipes 21, 22 between the distributor 11 and the mold 3.

For better absorption of the force exerted by the pouring pipes 21, 22 on the mold 3 or the sprue openings 4, 5, the sprue openings 4, 5 can form receptacles 39, 40 specially adapted to the shape of the outlet ends of the pouring pipes 21, 22. As in Fig. 3 As shown, the outlet ends of the pouring tubes 21, 22 are provided with shoulders 41 and bevels 42, and the receptacles 39, 40 of the sprue openings 4, 5 are designed to be complementary to the ends of the pouring pipes 21, 22 in a form-fitting or centering manner and to seal them at the same time.

If the mold half 9 or the mold insert 10 with the sprue openings 4, 5 does not form part of the device 1, ie the device 1 is intended for connection to any "foreign" molds 3, then the mold-side end 38 of the pulling device 36 is accordingly for anchoring formed on such foreign shapes 3. For this purpose, the end 38 can, for example, have bores 43 for screwing to the mold half 9 or the mold insert 10, a bayonet head that can be locked in a corresponding bayonet groove of the mold half 9 or the mold insert 10, or a clasp or clamp which the mold half 9 or the Can take mold insert 10 releasably, or the like. If the mold half 9 or the mold insert 10 are part of the device 1, the end 38 of the pulling device 36 can optionally also be formed in one piece with the mold half 9 or the mold insert 10.

The end 37 of the pulling device 36 can also engage releasably on the distributor 11, for example by means of a screw connection, bayonet coupling, latch connection, dovetail connection or, as shown, a tongue and groove connection with a T-shaped head 37 'which is inserted into a T-groove 37 "of the distributor 11 can be pushed in laterally.

For the pulling device 36, any actuator known in the art can be used, which can establish a pulling force (tensioning force) between the distributor 11 and the mold 3 in order to do so to clamp against each other, for example a clamping cam, eccentric, sliding wedges, a screw clamp or the like. In the example shown, the pulling device 36 has at least one hydraulic cylinder whose piston is connected to one end 37 and whose cylinder part is connected to the other end 38, or vice versa. The hydraulic cylinder can be subjected to a pressure of, for example, 5 to 500 bar.

The pulling device 36 can also be a combined pulling / pushing device, for example with (at least) one double-acting hydraulic cylinder, so that it can also exert a pressure (spreading force) that removes the distributor 11 from the mold 3. In this way, the pouring pipes 21, 22 can not only be loosened from the manifold 11, as is done by releasing the tensioning device 36, but the pouring pipes 21, 22 can also be forcibly detached from the manifold 11 by means of the spreading force ( Fig. 2 ), for example for repair or tool change purposes. Any molten metal that has solidified in the channels 12, 13 of the distributor 11 and the interiors of the pouring pipes 21, 22 can thus be removed by the spreading force of the combined pulling / pushing device 36 in the gaps 44, 45 that open up between the end face areas 27, 28 and the surface areas 17 , 18 are torn off or sheared off in order to be able to completely expand the pouring pipes 21, 22.

The pouring pipes 21, 22 can be temporarily anchored to the mold 3 by means of cross-pins or screws 46 engaging in cross-bores 46 'of the pouring pipes 21, 22 in order to separate the distributor 11 are, for example, on a projection 10 'of the mold insert 10 reaching between the pouring pipes 21, 22.

In the case of a large or elongated distributor 11, a plurality of pulling devices 36 can also be used, distributed over the circumference or the longitudinal extension of the distributor 11.

Instead of one or more common pulling devices 36 for all pouring pipes 21, 22, a separate pulling device 36 could also be used for each pouring pipe 21, 22, in particular in the case of individual linear movements 31, 32 of the pouring pipes 21, 22.

As discussed in the introduction, the device 1 is used as a multiple hot runner system in a hot operation. For this purpose, both the distributor 11 and the pouring pipes 21, 22 can be heated in order to bring them to the thixotropic temperature of the molten metal to be poured. For this purpose, the distributor 11 is equipped with a heating device 47, for example an annular, electrically operated ceramic heating element or other resistance heating band, which surrounds the distributor 11 at a narrow distance and is in turn enclosed by thermal insulation 47 '. The heating element 47 and the thermal insulation 47 ′ can be suspended from a heat-insulating cover hood 48 which is slipped over the distributor 11 and has a central opening 49 in order to allow the spray nozzle 2 access to the inlet 14 of the distributor 11. The covering hood 48 can also rest on peripheral parts of the mold half 9. With the aid of the heating device 47, the distributor 11 can be brought to the process temperature for aluminum or magnesium alloys of, for example, 550-700 ° C.

The pouring pipes 21, 22 are also equipped with their own heating devices 51, 52, for example electrically operated heating sleeves, which are pulled onto the pouring pipes 21, 22 and are thermally insulated from the outside. With the aid of the heating sleeves 51, 52, the pouring tubes 21, 22 are also brought to the thixotropic temperature of the molten metal of, for example, 550 - 700 ° C for aluminum or magnesium alloys.

The mold 3 together with the mold insert 10 and its projection 10 'is tempered to a comparatively low temperature of e.g. 100-300 ° C to solidify the molten metal injected into the mold 3, e.g. by means of temperature control fluid channels (not shown) in the mold 3, which are acted upon with appropriate temperature control fluids such as oil, water or air.

Due to the high temperature of the manifold 11 and the pouring pipes 21, 22 during operation, both the manifold 11 and the pouring pipes 21, 22 experience significant thermal expansion, which, for example, can increase the mutual distance between the outlet ends of the pouring pipes 21, 22 by several millimeters. Since the mutual position of the sprue openings 4, 5 of the mold 3 is predetermined, this could result in considerable thermal stresses in the interior of the device 1, which can lead to leaks between the pouring pipes 21, 22 and the distributor 11 and the mold 3. In order to counteract this, the device 1 is dimensioned and operated as follows using the tensioning and relaxing tensioning device 36.

First, the dimensions of the device 1, in particular the distributor 11 and the pouring pipes 21, 22, are designed for the thixotropic temperature of the metal to be poured, e.g. 600 ° C for a magnesium alloy, by means of a geometric thermal expansion calculation, so that at this temperature the outlets 15, 16 of the manifold 11 are aligned with the inlets 23, 24 of the pouring pipes 21, 22, the surface areas 17, 18 of the manifold 11 are in close contact with the end face areas 27, 28 of the pouring pipes 21, 22, the outlets 25, 26 of the pouring pipes 21, 22 with the sprue openings 4, 5 are aligned and the outlet ends of the pouring pipes 21, 22 sit tightly and positively in the receptacles 39, 40 of the pouring holes 4, 5 without mechanical stresses, in particular bending stresses, of the pouring pipes 21, 22 occurring.

In the cold state of the device 1, when the heating devices 47, 51, 52 are not yet running, this dimensioning results, conversely, due to the cold shrinkage, a misalignment between the distributor outlets 15, 16 and the pouring pipe inlets 23, 24 when the pouring pipe -Exits 25, 26 are aligned with the sprue openings 4, 5 before the start of the injection molding process. For this purpose, the cold pouring pipes 21, 22 are loosely inserted into the receptacles 39, 40 of the mold 3. The distributor 11 is then loosely - in misalignment due to the cold shrinkage - placed on the pouring pipes 21, 22 while the pulling device 36 is still relaxed. Now the distributor 11 and the pouring pipes 21, 22 are heated to the thixotropic temperature of the material to be poured, for example to 600 ° C, while the mold 3 is heated to the comparatively cooler solidification temperature of 200 ° C, for example.

When all temperatures are set for the injection molding process, the initial misalignment between the pour tube end face areas 27, 28 and the manifold surface areas 17, 18 by the thermal expansion is eliminated. The pulling device 36 is now tensioned and thus presses the pouring pipe end face areas 27, 28 tightly against the distributor surface areas 17, 18 and the pouring pipe outlets 25, 26 tightly against the sprue openings 4, 5. The device 1 is now tight and for the Injection molding process ready. For example, the nozzle 2 of an injection molding machine can now be attached to the inlet 14 of the distributor 11 in order to charge the mold 3 with thixotropic molten metal and thus to produce the molded article (s) therein.

The application of the nozzle 2 against the device 1 and thus also against the mold 3 takes place with great force, for example from 1 to 20 tons. To absorb the pressing force of the nozzle 2, the mold 3 is supported in a stationary frame (not shown) on which the injection molding machine can be moved, or, conversely, the injection molding machine is stationary and the mold 3 together with the device 1 moves on the frame.

In order to prevent damage to the device 1 in the event of excessive contact pressure from the injection molding machine, the device 1 can optionally be equipped with a safety device in the form of end stops 53, 54 for the distributor 11. In the example shown, the distributor 11 has extensions 55, 56, with which he can hit the end stops 53, 54. The end stops 53, 54 can for example be supported on the mold 3, the mold half 9, the mold insert 10, its projection 10 'or a frame of these components.

It goes without saying that the end stops 53, 54 should not yet come into effect with the "normal" pulling force of the pulling device 36, because the pulling force of the pulling device 36 is supposed to clamp the distributor 11 onto the pouring pipes 21, 22. Only when the pressure of the nozzle 2 acting on the manifold 11 significantly exceeds the tensile force of the pulling device 36, so that there is a risk that the pouring pipes 21, 22 could bend and be damaged, the end stops 53, 54 come into effect and support the Manifold 11 opposite form 3.

The pulling device 36 lies on its end 37 engaging the manifold 11 at the operating temperature of the manifold 11, for example 600 ° C, while on its end 38 anchored to the mold 3 it is at the operating temperature of the mold 3, for example 200 ° C. In order to protect the pulling device 36 from the harmful effects of such a high temperature gradient and in particular the high temperature at its end 37, the end 37 is equipped with a cooling fluid channel 57 for a cooling fluid such as air, oil or water. The end 37 can be cooled down to the operating temperature of the mold 3 via the cooling fluid channel 57. The anchoring of the end 37 on the distributor 11 can be provided with thermal insulation in order to avoid unintentional cooling of the distributor 11. Also the end stops 53, 54 can be equipped with such cooling fluid channels 57.

For repair and maintenance purposes, eg replacing the pouring pipes 21, 22 or their heating devices 51, 52, or if the mold 3 and / or the device 1 are to be changed, the device 1 should be cooled as quickly as possible in order to convert or Keep repair times as short as possible. For this purpose, the distributor 11 and the pouring pipes 21, 22 can be traversed by further cooling fluid channels 58 in order to be able to force-cool them if necessary. Starting from the distributor 11, the cooling fluid channels 58 can pass through the surface regions 17, 18 and end face regions 27, 28 in an aligned manner, run in the walls of the pouring pipes 21, 22 and back again to the distributor 11 (see FIG Fig. 3 ), so that no separate, external cooling fluid lines to the pouring pipes 21, 22 are required.

As in the Fig. 1 and 2 The surface area 17, 18 of each outlet 15, 16 can be seen inclined to the central axis 34 of the distributor and optionally also inclined to the channel 12, 13 leading to this outlet 15, 16, and the end face areas 27, 28 of each pouring tube 21, 22 also lie obliquely to the longitudinal axis 29, 30 of the respective pouring pipe 21, 22. This inclined position results in an automatic centering of the manifold 11 between the inlet ends of the pouring pipes 21, 22 when the manifold 11 is clamped against the pouring pipes 21, 22, which results in slight deviations in the Can compensate for thermal expansion of the components involved. The more acute the angle β is between the surface or end face areas 17, 18, 27, 28 and the direction of the respective ruler movement 31, 32 or (here) the common linear movement 33, the stronger this self-centering.

In order to limit the lateral movement of the pouring pipes 21, 22 when tensioning the manifold 11 lying thereon at an angle or to center the manifold 11 on the pouring pipes 21, 22, the manifold 11 can have a lateral guide 59 as a kind of side stop next to each outlet 15, 16 exhibit. The guides 59 are, for example, L-brackets which are mounted on the distributor 11 so that they can be adjusted transversely by means of adjusting screws 60.

As in the Fig. 1 and 2 shown, the longitudinal axes 29, 30 of the pouring pipes 21, 22 each form an obtuse angle γ with the distributor channels 12, 13, so that the melt flow undergoes a slight kink on its way from the channels 12, 13 into the pouring pipes 21, 22. The inclinations of the surface areas 17, 18 and end face areas 27, 28 can be selected so that they halve the obtuse angle γ, even if this is not mandatory. The kink in the flow path makes it easier to tear off a melt that has solidified in the channels 12, 13 and the inner spaces of the pouring pipe when the pouring pipes 21, 22 are lifted off the distributor 11 for maintenance purposes or for a tool change ( Fig. 2 ). The solidified melt is not only subjected to tension but also to shear in the gaps 44, 45 that open up, which favors its tearing off.

For the same purpose, the longitudinal axes 29, 30 of the pouring pipes 21, 22 each form an obtuse angle δ with the passage axes 61, 62 of the sprue openings 4, 5. This facilitates the tearing off of the sprue plug which solidifies at the outlet 25, 26 of the respective pouring pipe 21, 22 when the molding is removed from the mold. It also shortens the total length of the plug which extends into the exit 25, 26 and which temporarily closes the exit 25, 26 of the pouring pipe 21, 22 until the next shot. During the next shot, this plug is pushed out of the exit 25, 26 by the hot melt that is pushing in and ejected into a plug catcher in the form 3, where it represents scrap; a smaller or shorter plug therefore also means less waste of material.

Fig. 3 shows one of the pouring pipes 21, 22 in detail. The pouring pipe 21 shown is designed for a divergence angle α / 2 of 20 °. In general, the divergence angle α can be in the range from 10 ° to 185 °, preferably 20 ° to 120 °, particularly preferably 30 ° to 80 °, and in particular symmetrically to the central axis 34 of the distributor 11.

The inlet end of the pouring pipe 21 has a stepped shoulder 63 for the side guide 59 of the distributor 11 to engage. The lateral guide 59 can engage in the shoulder 63 in the manner of a wedge. For this purpose, the side wall of the shoulder 63 in the sealing contact position ( Fig. 1 ) of the pouring pipe 21 extend at an angle ϕ of 1 ° -20 °, for example 10 °, to the central axis 34 of the distributor 11.

The outlet end of the pouring pipe 21 is designed on its outside to be complementary to the respective receptacle 39, 40 of the sprue opening 4, 5. As shown, the end section of the outlet 25, 26 can already contain the kink for deflecting the pouring tube axis 29, 30 to the sprue opening axis 61, 62, if desired.

Fig. 4 shows an embodiment of the device 1 with four symmetrically diverging pouring pipes 21, 21 ', 22, 22' from a round distributor 11 and a common pulling device 36 for all pouring pipes.

Fig. 5 shows a further embodiment of the device 1 with an elongated distributor 11, from which two pouring pipes 21, 22 extend diverging from one another. A common pulling device 36 for both pouring pipes 21, 22 is formed by two double-acting hydraulic cylinders 36 ′, 36 ″ which each engage on the diametrical ends of the distributor 11 and can be anchored on the mold 3.

The device 1 can be equipped with temperature sensors at suitable points, for example on the distributor 11, at the inlets and outlets 23-26 of the pouring pipes 21, 22 and / or at the end stops 53, 54, in order to control the heating devices 47, 51, 52 to regulate and control the injection molding process accordingly. The temperature sensors can also be used to monitor that the pulling device 36 is only tensioned when the distributor 11 and the pouring pipes 21, 22 have reached their correct operating temperatures.

The devices and processes presented here are not only suitable for the thixoforming of aluminum or magnesium alloys in the temperature range of 550 - 700 ° C, but also of other metal alloys, e.g. steel alloys, at temperatures of up to 1500 ° C and more.

The invention is not restricted to the illustrated embodiments, but rather encompasses all variants, modifications and combinations thereof which fall within the scope of the attached claims.

Claims (18)

Device (1) for die-casting metallic material in a thixotropic state in a mold (3) which has a plurality of gate openings (4, 5), comprising
a heatable distributor (11) having an inlet (14) for the material and a plurality of outlets (15, 16) communicating with the inlet via channels (12, 13), and
a plurality of heatable pouring pipes (21, 22) each with an inlet (23, 24) for connection to one of the outlets (15, 16) and an outlet (25, 26) for attachment to one of the sprue openings (4, 5) ),
characterized,
that each pouring pipe (21, 22) with an end face area (27, 28) lying around its inlet (23, 24) on a surface area (17, 18) of the distributor (11) lying around the associated outlet (15, 16) can be brought into sealing contact by means of a linear relative movement (31 - 33) between this pouring pipe (21, 22) and the distributor (11),
with at least one selectively tensionable pulling device (36) engaging the distributor (11) with its one end (37), the other end (38) of which can be anchored to the mold (3). Device according to Claim 1, characterized in that the pouring pipes (21, 22) diverge from one another as seen from the distributor (11). Device according to claim 1 or 2, characterized in that the surface area (17, 18) of each outlet inclined to a central axis (34) of the distributor (11) and preferably also inclined to the channel (12, 13) leading to this outlet (15, 16). Device according to one of Claims 1 to 3, characterized in that the end face region (27, 28) of each pouring pipe (21, 22) lies obliquely to its longitudinal axis (29, 30). Device according to one of claims 1 to 4, characterized in that the longitudinal axis (29, 30) of each pouring tube (21, 22), when it is connected to the associated outlet (15, 16), forms an obtuse angle (γ) with the to this outlet (15, 16) leading channel (12, 13) forms. Device according to one of Claims 1 to 5, characterized in that the distributor (11) has a preferably adjustable lateral guide (59) for the inlet end of the associated pouring pipe (21, 22) next to each outlet (15, 16). Device according to one of Claims 1 to 6, characterized in that the said relative movements (33) are parallel for all pouring pipes (21, 22) and a common pulling device (36) is assigned to all pouring pipes (21, 22). Device according to one of Claims 1 to 7, characterized in that the pulling device (36) is a combined pulling / pushing device which can be actuated either to exert pulling or pushing. Device according to one of claims 1 to 8, characterized in that the pulling device (36) by at least a hydraulic cylinder is formed, preferably at least one double-acting hydraulic cylinder. Device according to one of Claims 1 to 9, characterized in that the pouring pipes (21, 22) can be anchored temporarily to the mold (3). Device according to one of Claims 1 to 10, characterized in that one end (37) of the pulling device (36) releasably engages the distributor (11), preferably via a tongue and groove connection (37 ', 37 "). Device according to one of Claims 1 to 11, characterized in that the distributor (11) and the pouring pipes (21, 22) are traversed by cooling fluid channels (58). Apparatus according to Claim 12, characterized in that at least some of the cooling fluid channels (58) pass through the surface areas (17, 18) and the respective end face areas (27, 28) lying thereon in alignment. Device according to one of Claims 1 to 13, characterized in that the end (37) of the pulling device (36) engaging the distributor (11) is penetrated by at least one cooling fluid channel (57). Device according to one of Claims 1 to 14, further characterized by a mold insert (10) which can be connected to the mold (3) or which forms part of the mold (3) and has several sprue openings (4, 5) which receptacles (39, 40) for the outlets (25, 26) of the pouring pipes (21, 22) form. Apparatus according to claim 15, characterized in that the longitudinal axis (29, 30) of each pouring tube (21, 22) when it is attached to the associated sprue opening (4, 5), forms an obtuse angle (δ) with the passage axis (61, 62) of this sprue opening (4, 5). Device according to Claim 15 or 16, characterized in that the mold insert (10) presents an end stop (53, 54) for the distributor (11) during its relative movement (31-33). Method for die-casting metallic material in a thixotropic state in a mold (3) which has several gate openings (4, 5), with the steps: Providing a device (1) according to one of Claims 1 to 17; Attaching the pouring pipes (21, 22) to the sprue openings (4, 5) and anchoring the pulling device (36) in the relaxed state on the mold (3); Heating the distributor (11) and the pouring tubes (21, 22) to the temperature required for the thixotropic state of the material; Tensioning the pulling device (36) in order to bring the end face regions (27, 28) of the pouring pipes (21, 22) into sealing contact with the surface regions (17, 18) of the distributor (11); and Attaching the nozzle (2) of an injection molding machine to the inlet (14) of the manifold (11) and pressure casting the material via the manifold (11) and the pouring pipes (21, 22) into the mold (3).

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