EP3285941B1 - Core box for producing casting cores - Google Patents

Description

The invention relates to a core box for producing casting cores from a molding material that solidifies through the supply of heat, comprising at least two core box parts, which together depict the shape of the casting cores to be produced, and a heating device for heating the core box parts, the heating device having at least one oil line that is in thermal contact stands with at least one of the core box parts and is connected to an oil supply that feeds the oil line with a temperature-controlled oil to heat the core box part.

Core boxes of the type in question here are used in core shooting machines with which casting cores for the production of cast parts are produced. The core boxes delimit a mold cavity with their core box parts, the boundary surfaces of which form the contour of the casting core to be produced. The respective molding material is shot under pressure into the mold cavity of the core box, so that a compact core is created.

A first example of such a core box for producing casting cores from a molding material that solidifies by supplying heat is shown in FIG CN 202 725 947 U shown. The core box comprises at least two core box parts which together map the shape of the casting cores to be produced. It also has a heating device for heating the core box parts, which includes at least one gas line. This is in thermal contact with one core box part and is connected to a gas supply that feeds the gas line for heating the core box part with a temperature-controlled gas. For this purpose, one core box part is divided into a contour plate, which depicts the shape of the casting cores to be produced, and a heating plate coupled to the contour plate, which extends over the contour plate and in which the gas line is provided.

Even with one from the CN 201 768 876 U known core boxes, core box parts, which determine the contour of the cores to be fired, are each seated in a heating plate. The contouring parts are prefabricated independently of the heating plates and then inserted into the heating plates. The heating plates are traversed by heating channels.

Molding materials, for the processing of which a core box according to the invention is particularly suitable, are mixed from a molding sand and an inorganic binder and also optional additives.

For example, in the DE 196 32 293 A1 The production of casting cores described using so-called inorganic warm box core sand binder systems, the cores are in the mold cavity of the core box solidified by dehydration. For this purpose, heat is supplied to the molding material in the core box and the moisture that escapes is drawn off via, as a rule, slot-like openings formed in the core box parts, also called "slot nozzles" in technical terms.

This process can be accelerated by gassing the molding compound injected into the mold cavity with hot air, which is blown into the mold cavity of the core box via injection openings and discharged via the slot-like openings.

In core shooting machines used in practice, the heat is supplied via the core box parts, which are usually made of a sufficiently wear-resistant and highly thermally conductive tool steel, for example steel with the material number 1.2343. For the heat supply, bores are made in the core box parts through which a sufficiently hot oil is passed.

Such drilling of the straight oil lines into the respective core box part is not only complex in terms of production, but also restricts the possibilities of designing and arranging the ventilation slots required in the respective core box part due to the fact that the individual sections of the oil line must necessarily run in a straight line.

Against this background, the task arose of creating an oil-heated core box that can be manufactured with less effort and at the same time allows maximum freedom in design.

To solve this problem, the invention proposes a core box with the features specified in claim 1.

Advantageous embodiments of the invention are specified in the dependent claims and are explained in detail below, like the general inventive concept.

In accordance with the prior art explained at the beginning, a core box according to the invention for producing casting cores from a molding material that is mixed from a molding sand and a binder and optional additives also comprises at least two core box parts, which together represent the shape of the casting cores to be produced, and one Heating device for heating the core box parts. The heating device has at least one oil line that is in thermal contact with at least one of the core box parts and is connected to an oil supply that feeds the oil line with a temperature-controlled oil to heat the core box part.

At least one of the core box parts is subdivided into a contour plate that depicts the shape of the casting cores to be produced and a heating plate in which the oil line is provided, the heating plate being located Extends flat over the contour plate and is coupled to the contour plate.

By dividing the core box part into a contour plate and a heating plate, it is possible to design and design both the contour plate and the heating plate in an optimized manner with regard to their intended use. Compared to conventional oil-heated core boxes, in which the hot oil is passed through oil bores formed in the respective core box part, a core box according to the invention offers unlimited design freedom, particularly with regard to the positioning of slot nozzles on the contour plate. In the case of a core box according to the invention, it is therefore possible without any problems to position any number of slot nozzles in such a way that rapid removal of moisture from the casting cores and, associated with this, an accelerated curing process is guaranteed. In addition, the contour part can easily be dismantled for wear repairs, subjected to a repair, for example by machining or welding, and reassembled. There is no danger that oil-carrying lines will be damaged or that residual oil will ignite during welding work.

The invention thus enables the practical use of an oil heater for the temperature control of a core box with simple means. In contrast to alternative heating devices, such as, for example, electrical heating, a Heating of the contouring plates of a core box according to the invention, based on a heated oil, is characterized by increased process reliability due to a low risk of failure and a long service life. At the same time, core boxes according to the invention are easy to clean by separating contour plates and heating plates. In particular, an ultrasonic bath is suitable for this, which is out of the question, for example, because of the risk of water penetrating in an electrically operated heater.

In principle, it is conceivable to embed the oil line provided in the heating plate as a separately prefabricated line in a suitable carrier material. The heating plate then acts primarily as a holder and protection for the oil line on the contour part. Of course, in this embodiment, the oil line is optimally arranged so that there is direct thermal contact between it and the contour plate.

It is also conceivable to shape the oil line in a heating plate made of an easily machinable, but sufficiently temperature-resistant material. All modern methods are available here that allow lines and cavities to be formed in a sheet of material. Suitable three-dimensional printing processes or the like could be used for this purpose, for example, which allow even complex line courses to be reproduced exactly in a compact plate body after the printing process has been completed.

In the case of a core box according to the invention, the contour plates are of course made of a highly thermally conductive material, in particular a tried and tested tool steel of the type already mentioned above, which is suitable for this purpose. if the heating plate is also made of a thermally highly conductive material. However, since the heating plate is not exposed to high mechanical, extreme or changing thermal loads, inexpensive materials such as a low-alloy steel or a light metal material, in particular an Al material, are sufficient. In particular, the use of light metal materials also has a favorable effect on the weight of a core box according to the invention.

In a core box according to the invention, the oil line is molded into one of the sides of the heating plate in the manner of a channel, which extends parallel to the associated contour plate. From a manufacturing point of view, this proves to be advantageous if the oil line is to be molded into the material of the heating plate and conventionally molding, in particular machining processes are to be used for molding. The oil channel formed into the relevant plate side like a groove is openly accessible when the heating plate is dismantled and can therefore not only be easily molded into the material of the heating plate, but also just as easily cleaned.

If the oil line channel is molded into the side of the heating plate assigned to the contour plate, then it covers when done mounted core box, the contour plate removes the oil line channel on its open side. With a suitable sealing of the joint between the heating plate and the contour plate, there can be direct contact between the warm oil and the contour plate.

It is also conceivable, however, to arrange a separate sealing plate between the heating plate and the contour plate in order to ensure a secure seal in a simple manner. Such a sealing plate is also expediently used when the oil line is molded into a side of the heating plate facing away from the contour plate.

In the event that a sealing plate is arranged between the heating plate and the contour plate, it is expediently made of a material with good thermal conductivity.

A good heat transfer from the heating plate to the contour plate can be ensured by the fact that the contour plate, the heating plate or the sealing plate are made of a material with a thermal conductivity λ of at least 40 W / (m * K), whereby of course at least that plate consists of one should consist of such a highly conductive material that comes into direct contact with the warm oil and the contour plate at the same time. All iron- and light-metal-based alloys have sufficient thermal conductivities for the purposes according to the invention.

Due to its special design features and the advantages achieved thereby, a core box according to the invention is particularly suitable for core production processes that require hot air gas injection. Therefore is an inventive Core box can be used in particular for core production processes in which inorganic binder systems are used.

Fig. 1

einen Kernkasten in einem Längsschnitt;

Fig. 2

eine Konturplatte des Kernkastens gemäß Fig. 1 in Draufsicht;

Fig. 3

eine Heizplatte des Kernkastens gemäß Fig. 1 in Draufsicht;

Fig. 4

ein Kernkastenteil des Kernkastens gemäß Fig. 1 in einer seitlichen Ansicht.

The invention is explained in more detail below with the aid of a drawing showing an exemplary embodiment. Their figures each show schematically:

Fig. 1

a core box in a longitudinal section;

Fig. 2

a contour plate of the core box according to Fig. 1 in plan view;

Fig. 3

a heating plate of the core box according to Fig. 1 in plan view;

Fig. 4

a core box part of the core box according to FIG Fig. 1 in a side view.

The core box 1 includes an upper core box part 2 and a lower core box part 3.

The upper core box part 2 is composed of a contour plate 4, which carries contouring shaped elements 5, 6 on its side assigned to the lower core box part 3, a sealing plate 7 lying on the contour plate 4, a heating plate 8 sitting on the sealing plate 7 and a shot plate 9 supported on it .

The shot plate 9 is coupled to the contour plate 4 via coupling elements in a manner known per se by means of mortise and tenon connections 10, 11 and is aligned in such a way that that the shooting funnels 12 of the shooting plate 9 sit precisely in the assigned shooting openings 13, which are formed in the contour plate 4, the sealing plate 7 and the heating plate 8 in a vertical direction in alignment with one another.

In order to ensure a correctly positioned coupling to the lower core box part 3, pins 14 pointing in the direction of the lower core box part 3 are attached in the edge area of the contour plate 4, which when the upper core box part 2 is lowered into correspondingly shaped depressions that engage in the edge area of the upper core box part 2 associated top of the lower core box part 3 are molded.

The lower core box part 3 comprises a lower part frame 15 which, on its side assigned to the upper core box part 2, carries a contour plate 16 of the lower box part 3. The contour plate 16 carries contour-giving shaped elements 17, 18 on its free side assigned to the upper core box part 2.

When the core box 1 is closed, ie in the stage in which the upper core box 2 is seated on the lower core box 3, the contour plates 4, 16 define a cavity in which several cores, for example the cores for the inlet channel, the outlet channel, the water jacket, the cover and the oil chamber of a cylinder head for an internal combustion engine can be shot at the same time. The shapes of the cores are determined by the shape elements 5,6,17,18, of which in Fig. 2 for the sake of clarity in the Contour plate 4 of the upper core box part 2 only two form elements 5, 6 are shown. Mounting openings 19 provided on the contour plates 4, 16 allow the attachment of the most varied of shaped elements, so that different casting core programs can be produced with the core box 1.

In the upper and lower core box part 2,3 each conventionally designed slot nozzles 20,21 are arranged, which in the upper core box part 2 from its top to the lower core box part 3 associated side of the contour plate 4 and in the lower core box part 3 from its bottom to the upper box part 2 side of the contour plate 16 assigned. In this way, when the core box 1 is closed, gases which are present or are forming in the mold cavity then enclosed by the contour plates 4, 16 can escape via the slot nozzles.

The contour plate 16 is seated via a sealing plate 22 on a heating plate 23 of the lower core box part 3. The package formed from the contour plate 16, sealing plate 22 and heating plate 23 is seated in a receptacle in the lower part frame 15.

An ejector plate 24 is arranged underneath, which carries ejectors 25 pointing in the direction of the contour plate 16. The ejectors 25 reach through through openings formed in the lower contour plate 16. After the casting cores formed in the core box 1 have hardened, the ejector plate 24 is raised with the core box 1 open in the direction of the contour plate 16, so that the ejectors 25 lift the finished casting cores from the mold parts 17, 18. The finished casting cores can then be freely removed from the core box 1.

While the contour plates 4, 16 with the shaped elements 5, 6, 17, 18 carried by them each consist of a high-quality, wear and temperature-resistant tool steel, the heating plates 8, 23 each consist of an aluminum material. Alternatively, they can also consist of a conventional unalloyed structural steel, such as steel with the material number 1.0050.

In the side 26 of the in Fig. 3 shown heating plate 8 of the upper core box 2, an oil line 27 is milled in the form of a channel open to the relevant side. The oil line 27 is routed in a number of turns over the side 26 in such a way that, on the one hand, all of the temperature-critical areas of the contour plate 4 in core shooting operation are covered, but on the other hand, the areas through which the slot nozzles 20, 21 are guided are also bypassed. The inflow 28 and the outflow 29 are connected to an oil supply (not shown here) which circulates oil that has been heated to the required temperature through the oil line 27.

An oil line 30 has been molded into the heating plate 23 in a corresponding manner.

The sealing plates 7, 22 also consist of a highly temperature-conductive material, such as an Al material or a suitable steel, so that the heat carried along by the heated oil flowing through the oil line 27, 30 is transferred to the respective contour plate 4, 16 with almost no loss becomes.

For the production of the already mentioned cores in the core box 1, 24 kg of quartz sand are mixed in a mixer with 2.2% of an inorganic binder and 0.9% of a powder additive added to improve the flow properties. To do this, the sand with the powder additive is first introduced and the liquid binder component is then added while the mixer is running.

After a mixing time of approx. 30 s, the molding material mixture obtained in this way is transferred to a storage bunker of a conventionally constructed core shooter equipped with a core box 1.

The contour plates 4, 16 and the shaped elements 5, 6, 17, 18 carried by them are preheated to a temperature of 130 ° C. by the heating plates 8, 23. Then the molding material mixture is shot into the mold cavity of the closed core box 1 by means of compressed air at 5 bar and remains there for 32 s.

To accelerate the hardening process, hot air with a pressure of 3.5 bar and a temperature of 160 ° C. is passed through the core box 1 for 30 s upon entry into the tool 2 s after the injection.

After the hardening time has ended, the core box 1 is opened and the ejectors 25 are actuated. The fully cured cores can now be removed.

Practical tests carried out in the manner described above have shown that slot nozzles can be introduced at any position in the core box 1 according to the invention in order to optimize the ventilation. The invention thus allows, even when using an oil heater to heat the core box 1, its contour plates 4, 16 and the shaped elements 5, 6, 17, 18 carried by them to be designed just as freely as core boxes are used for the so-called " Cold box method "can be used in which no heating is required, but in which curing takes place through a chemical reaction as a result of gassing with a reaction gas.

The freedom of design opened up by the invention opens up the possibility of introducing additional slot nozzles into the condensation zones of the cores produced in the core box 1, which are determined by the experiments and are critical for the removal of moisture. By optimizing the core box ventilation, the hot air purging time and thus the cycle time could be reduced by 5 s after the first optimization loop.

REFERENCE MARK

1

Core box

2

upper core box part

3

lower core box part

4th

Contour plate of the upper core box part 2

5.6

contour-giving form elements of the upper core box part 2

7th

Upper core box part sealing plate 2

8th

Upper core box heating plate 2

9

Shot plate of the upper core box part 2

10.11

Tenon joints

12

Shot funnel of the shot plate 9

13

Shot openings

14th

Cones

15th

Lower frame of the lower core box part 3

16

Contour plate of the lower core box part 3

17.18

Contouring form elements of the lower core box part 3

19th

Mounting holes

20th

Slot nozzles

21st

Slot nozzles

22nd

Lower core box part sealing plate 3

23

Lower core box part heating plate 3

24

Ejector plate

25th

Ejector

26th

the side of the heating plate 8 associated with the contour plate 4

27

Heating plate oil pipe 8

28

Inflow of the oil line 27

29

Oil line drain 27

30th

Heating plate oil pipe 23

Claims (5)

1. Core box for manufacturing casting cores from a moulding material rigidified by supply of heat, comprising at least two core box parts (2, 3), which together provide the shape of the casting cores to be manufactured and a heating device for heating the core box parts (2, 3), wherein the heating device comprises at least one oil line (27, 30), which is in thermal contact with at least one of the core box parts (2, 3) and is connected to an oil supply which feeds the oil line (27, 30) with a tempered oil for heating the core box parts (2, 3), and wherein at least one of the core box parts (2, 3) is divided into a contour plate (4, 16) providing the shape of the casting core to be manufactured and a heating plate (8, 23) coupled to the contour plate (4, 16) which extends flat over the contour plate (4, 16) and in which the oil line (27, 30) is provided characterised in that the oil line (27, 30) is moulded into the material of the heating plate (8, 23) in the form of a groove which is formed into the side (26) of the heating plate (8, 23)which extends parallel to the associated contour plate (4, 16).
2. Core box according to claim 1, characterised in that the oil line (27, 30) is moulded into the side (26) of the heating plate (8, 23) which is associated with the contour plate (4, 16).
3. Core box according to any one of the preceding claims, characterised in that a sealing plate (7, 22) is located on the side (26) of the heating plate (8, 23) into which the oil channel (27, 30) is moulded.
4. Core box according to claim 3, characterised in that the sealing plate (7, 22) consists of a thermally conductive material.
5. Core box according to any one of the preceding claims, characterised in that the contour plate (4, 16), the heating plate (8, 23) or the sealing plate (7, 22) consist of a material having a conductivity λ of at least 40 W/(m*K).

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