EP1444063B1 - Method and mould shooter for producing mould parts, such as casting cores, for casting moulds used to cast metal melts - Google Patents

Abstract

The invention relates to a method for the manufacture of mould parts, in particular of casting cores, for casting moulds for the casting of molten metal heats, wherein, in a shoot-moulding machine (1), with the aid of filling elements, such as shooting nozzles (8) and a shooting hood (6), material mould (F) containing an inorganic binding agent is filled into a cavity (12) of a mould tool (10) which determines the shape of the mould part (K) which is to be manufactured, wherein, heat is supplied to the mould material (F) filled into the mould tool (10), over a hardening period, in order for the mould material (F) to solidify due to the extraction of moisture, and wherein, during the hardening period, at least the filling elements (6,8) of the shoot-moulding machine (1), which contains mould material (F), and which are in a stand-by position during this hardening period, and are heated concomitantly by the radiant heat emitted by the mould tool (10), are kept at a moisture content level which prevents the solidifying of the mould material (F). In this way, mould parts for casting moulds can be manufactured reliably and with reduced defect incidence from a mould material containing an inorganic binding agent.

Description

The invention relates to a method and a molding shooting machine for producing molded parts, such as casting cores, for casting molds for casting molten metal.

In the conventional production of casting cores intended for the casting of light metal melts, a molding material which is usually bound to synthetic resin is filled into the cavity of a molding tool which determines the final shape of the casting core molding to be produced. The mold has a sufficient for a uniform filling of the cavity number of weft openings, via which the filling is done with molding material. In each of these weft openings for filling of the mold in each case a "weft nozzle" is introduced, via which then the molding material is injected. The firing nozzles are usually carried together by a height-adjustable "shooting head plate", which ensures a retraction and extension of the core box in the firing position.

The supply of the guns takes place in the known devices usually via a so-called "shooting hood", which covers the shooting head plate on its side facing away from the mold side and with molding material is filled. To inject the molding sand of the molding material contained in the shooting hood abruptly with a gas, usually air, uniformly pressurized via a shooting cylinder, so that it is driven via the firing nozzles in the mold.

In order to produce the required final strength of the molded part to be produced, on the one hand it is possible, by adding suitable means, to cause a chemical reaction catalytically in the molding material. In this so-called "cold-box process" a cured as a result of the chemical reaction molding is obtained. However, this can no longer be recycled in the cycle used for the molding of materials.

Alternatively, the curing can be initiated by the use of suitable binders by supplying heat. To carry out this so-called "hot-box process" known form-shooting machines are equipped for producing mold cores with heaters for heating the mold. The curing of the molding material is effected in this case by the heat supply in the mold.

Since the use of organic binders can lead to workplace and environmental pollution, it is endeavored to replace the previously used for the production of foundry cores, organic binder-containing molding materials by such molding materials, which are bound by inorganic binders, such as water glass-based binder. A method which uses such composites allows for the production of core moldings, is from the EP 0 917 499 B1 known.

According to this known method, first, a molding material is prepared by mixing an inorganic refractory molding sand with a water glass based inorganic binder. This molding material is then filled in a tempered, exposed to a vacuum mold during filling. The temperature / residence time of the molding material after closing the mold is adjusted so that forms a dimensionally stable and viable edge shell on the core molding. If the core molding has reached this state, the mold is opened and the core molding is removed. Immediately thereafter, the core molding is subjected to complete drying under the action of microwaves. The molding material formed by the mixture filled in the mold is thus removed by physical means moisture. As a result, through this dehumidifying process still in the mold a solidification of the core molding is achieved, which allows at least its handling in the further processing steps.

In practice, in carrying out the known method in conventional, equipped with a device for heating the mold various defects. These manifest themselves, for example, in an undesired premature curing of the molding materials in the components of the form-shooting machine, that of the mold radiated heat to be detected. These components are, in particular, the weft nozzles and the weft hood which, even when waiting, are heated to a critical temperature for the start of curing of the molding material due to dehydration. The premature curing of the molding material leads, for example, in the firing hood to encrustation on the molding surface, so that the molding material can no longer properly bring into the mold. Incomplete fillings of the mold and blockages of the guns are the result. Even in the guns self-curing molding material leads to clogging of the nozzle, so that a uniform, proper filling is no longer guaranteed.

In addition to the above-described prior art are from the FR 2 687 942 A a method and an apparatus for producing cores from a molding material, which is mixed from a molding sand and a curable, synthetic resin. This molding material is filled from a firing pot via filling nozzles into a core box which depicts the core to be produced. After filling the core box, the filling device is moved to a standstill position. In order to prevent clogging of the nozzles, the nozzles are immersed in a foam provided in a special box, which is impregnated with a silicone-based emulsion. In this way, a bonding of the molding material in the nozzle itself can indeed be prevented. At the same time, however, the danger remains that it comes to the curing of molding material in the gunner. The resulting mold lumps can also clog the guns.

The object of the invention is to provide a method and a device with which moldings for casting molds can be produced reliably and with reduced susceptibility to failure from a molding material containing an inorganic binder.

Based on the above-described prior art, this object is achieved with regard to the method according to the invention by the teaching of independent method claim 1.

On the other hand, the object mentioned above with respect to a device is achieved according to the invention by the teaching of the independent device claim.

Preferably, the mold is additionally reciprocable between a filling and a removal station.

Particularly suitable are a method according to the invention and a shape shooting machine according to the invention for the production of casting cores for the casting of light metal melts, which represent in practice by far the largest part of the casting moldings produced in devices of the type in question.

According to the invention, during curing of the molding material filled in the heated mold, those components which are heated by the heat radiated by the mold to a temperature at which the unwanted premature and, as a result, disturbing curing of the molding material could be used, are deliberately kept moist. In this way, the in or on these components due to the heating otherwise entering Dehydration counteracted from the molding material and thus prevents the solidification of molding material in the critical components of the shooting machine. The components which are particularly affected by the heating are typically the shooting nozzles or the shooting hood required for supplying the shooting nozzles with the shooting plate or other molding material-carrying supply channels connected to them.

By these components are specifically moistened during the residence time required for the curing of the molding in the mold, for example, both a crust formation in the weft hood and the bonding of the weft nozzles is prevented by solidifying molding material. In this way, inorganic, water-based binder-containing molding materials can be safely used to moldings for the foundry. The resulting moldings are characterized by good strength and can be returned to their use in the cycle of materials used for the molding of parts.

The moistening of the heat released by the heat emitted by the mold and consequently endangered with respect to the solidification of molding material components according to the invention is characterized in that at least one of the filling is at least temporarily exposed to a humid atmosphere during the curing time. This embodiment of the invention is particularly suitable for avoiding the hardening of molding material in the firing hood, if in the hood targeted a humid atmosphere is maintained. The moisture content of preferably by air As a carrier gas atmosphere formed can be easily adapted to the particular circumstances. Thus, for example, it is conceivable to adjust the humidity of the atmosphere surrounding the waiting nozzles in order to form condensate at the gun nozzles and, as a result, the solidification of mold material contained in the gun nozzles or adhering to them is reliably avoided.

In addition to a moistening by maintaining an atmosphere of certain moisture, it may be advantageous to at least temporarily cool at least one of the co-heated filling elements during the curing time. Also by such targeted cooling can be brought about the formation of condensate. This embodiment of the invention is therefore particularly suitable for protecting the shot nozzles from clogging by solidified molding material. Additionally or alternatively, the firing air itself can be moistened to prevent drying or curing of the molding material from the outset.

Another embodiment of the invention, which is particularly easy to implement and nevertheless effective, is characterized in that at least one of the co-heated filling elements is brought into contact with a moisture carrier at least temporarily during the curing time. This moisture carrier may be an absorbent material impregnated with liquid, in particular water, such as a sponge or a cloth. Practical experiments have shown that, when such a moisture carrier is docked to the waiting in the weft nozzles, the solidification of mold material contained in the nozzles can be safely avoided.

By the cavity of the mold in the course of curing at least temporarily by a hot gas, preferably heated air, flows, which is supplied dry and withdrawn loaded with moisture, the course of curing of the molding contained in the mold can be specifically improved. In this case, after the mold has been filled with molding material, a hot, dry gas stream is passed through the mold during the time required for the molding to harden in addition to the heat introduced via the tool itself. That way on the one hand, the gases produced in the course of curing removed from the mold. On the other hand, additional heat is introduced into the molded part. In this case, this heat does not penetrate slowly over the peripheral shell of the molded part in its interior, but is actively transported by the gas flow in the interior of the core of the molding.

As a result, a fast and uniform core hardening is achieved. The influence of strongly fluctuating thickness gradients of the core is thus minimized. Moldings obtained in compliance with this variant of the procedure according to the invention therefore have a particularly high, homogeneously distributed strength even when they are removed from the mold. At the same time can be achieved in this way, for example, in the production of casting cores cycle times that are not higher than the times required for the production of corresponding cores from organic binders, in particular synthetic resins containing molding materials.

Fig. 1

eine Formschießmaschine zum Herstellen von Gießkernen in einer ersten Betriebsstellung;

Fig. 2

die in Fig. 1 dargestellte Formschießmaschine in einer zweiten Betriebsstellung.

Further advantageous embodiments of the invention are specified in the dependent claims and will be explained in connection with the embodiment described below with reference to a drawing. It show schematically in a partially sectioned representation:

Fig. 1

a form-shooting machine for producing casting cores in a first operating position;

Fig. 2

in the Fig. 1 Shaping machine shown in a second operating position.

The form-casting machine 1 for producing casting cores K according to the "hot-box method" has a mixer 3. In the mixer 3, a molding material F is mixed from an inorganic refractory molding sand and a water glass-based binder.

This molding material F is placed in a hopper 4 arranged below the mixer 3, from which it is passed into a shooting cylinder 5 positioned below the filling hopper 4. The shooting cylinder 5 shoots the filler F in a connected to him, starting from the shooting cylinder 5 in its width and depth widening down shooting hood 6, which is closed at its bottom by a shooting head plate 7. In the weft head plate 7, a plurality of receptacles, not shown further formed, in each of which a shot nozzle 8 is seated.

The weft nozzles 8 extending in the direction of the upper box 9 of a forming tool 10 are arranged corresponding to the weft holes 11 formed in the upper box 9. The weft holes 11 open into a cavity 12 which is formed by corresponding, molded into the upper box 9 and the lower box 13 of the mold 10 recesses. Other elements not shown here may be part of the molding machine 1.

Through the cavity 12, the shape of the casting core K to be generated is determined in the lower box 13 vent openings 14 are formed, on the escape of the filled mold material F escapes during filling of the cavity 12. If necessary corresponding, not shown vents introduced into the upper box. By means of a heater 15, the upper box 9 and the lower box 13 of the mold 10 can be controlled heated.

Not shown adjusting means are provided to drive the core box with the shot holes 11 to the firing nozzles 8 in a firing position in which they sit in the shot holes 11 of the mold 10. With the firing nozzles 8, the firing head plate 7, the firing cap 6, the firing cylinder 5 and the funnel 4 firmly connected to them are brought together ( Fig. 1 ).

After the injection of the molding material F into the mold 10, the molding machine 1 is moved into the waiting position, in which the tips of the nozzles 9 are arranged at a distance above the mold 10 ( Fig. 2 ). This waiting position keep the shot nozzles 8 until the molding material F contained in the cavity 12 of the molding tool 10 has hardened to the casting core K due to the dehumidification that occurs as a result of the heating of the molding material F in the molding tool 10. If no air flow L is passed through the forming tool 10 through overpressure or underpressure to improve the hardening process, then the gases produced in the course of hardening escape automatically via the shot holes 11 and the vent openings 14 out of the molding tool 10.

To the firing hood 6 a humidifying device 16 is connected, can be passed through the humid air into the interior of the firing hood 6. In addition, one is Sponge 17 is mounted on a plate 18 which can be driven with the weft nozzles 8 in the waiting under the firing nozzles 8 and raised so that the sponge 17 presses against the firing nozzles 8 and at least completely surrounds their lower, the nozzle opening portion. In addition, the nozzles 8 are each associated with a nozzle 19 via which moist air supplied by the moistening device 16 when the firing nozzles 8 are in the waiting position is blown onto the firing nozzles 8.

The moisture content of the introduced in the waiting position in the firing hood 6 and blown against the firing nozzles 8 moist air is adjusted so that there is no dehydration of the molding material. In this way, it is reliably prevented that the molding sand F still contained in the firing hood 6 and the firing nozzles 8 solidifies as a result of the heating and the dehydration, which causes the respective components due to the radiant heat W emitted by the hot mold 10 during both Filling process ( Fig. 1 ) as well as in the longer waiting position ( Fig. 2 ) are exposed.

By the pressed in the waiting position against the weft nozzles 8 sponge 17 is additionally specifically ensured that there is no clogging of the nozzle openings of the weft nozzles 8 due to adhesive molding material F. In addition, the formation of condensation in the region of the weft nozzles 8 can be assisted by the fact that the weft nozzles 8 are cooled in the waiting position with the aid of a cooling device not shown here. This cooling also effectively prevents the Temperature in the interior of the guns 8 increases to a critical for the solidification of the molding material F level. By moistening the outside of the weft nozzles 8 it is ensured that it does not come to the caking of solidified molding sand F on the weft nozzles 8.

In order to achieve an improved course of the curing of the casting core K in the mold 10, a device 20 is provided which has an air supply connection 21 and suction connection 22. During the hardening time required for the hardening of the casting core K, the air supply connection 21 of the device 20 with the shot holes 11 and the suction connection 22 of the device 20 with ventilation openings 14 of the molding tool 10 are coupled (FIG. Fig. 2 ). In this case, a hot, dry air stream L is continuously fed into the mold 10 via the air supply connection 21. This air stream L flows through the casting core K contained in the mold 10, which is hardened, and is drawn off via the vent openings 14 of the molding tool 10. In this way, the core interior is heated evenly, so that the moisture contained in the core K escapes faster overall.

At the same time, the air stream L extracted via the suction connection 22 transports the gases produced during the heating of the casting core K in a targeted and rapid manner out of the mold 10. The more homogeneous heat distribution in the casting core K achieved by the air flow L thus results in a shortened curing time with simultaneously improved strength of the casting core K.

REFERENCE NUMBERS

1

Shaping machine for producing casting cores

3

mixer

4

hopper

5

shooting cylinder

6

shot hood

7

Shooting head plate

8th

picking nozzle

9

top box

10

mold

11

shot holes

12

cavity

13

lower box

14

vents

15

heater

16

humidifying

17

sponge

18

plate

19

jet

20

Device for generating and extracting the airflow L

21

Air supply port

22

suction connection

D

Thickness of the casting core K

F

molding

K

casting core

L

dry airflow

W

radiant heat

Claims (18)

1. A method for the manufacture of mould parts, in particular of casting cores, for casting moulds for the casting of molten metal,

   - wherein in a shoot-moulding machine a with the aid of filling elements, such as shooting nozzles (8) and shooting hood (6) mould material (F) containing an inorganic binding agent is filled (1), , into a cavity (12) of a mould tool (10) which determines the shape of the mould part (K) which is to be manufactured,

   - wherein heat is supplied to the mould material (F) filled into the mould tool (10) over a hardening period, in order for the mould material (F) to solidify due to the extraction of moisture, and

   - wherein, during the hardening period, at least the filling elements (6,8) of the shoot-moulding machine which contains mould material, and which are in a stand-by position during this hardening period, and are heated concomitantly by the radiant heat (W) emitted by the mould tool (10), are kept at a moisture content level which prevents the solidifying of the mould material (F), wherein at least one of the filling elements (6,8) heated concomitantly is subjected during the hardening period at least temporarily to a moist atmosphere.
2. The method according to Claim 1, characterised in that the atmosphere is formed by moist air.
3. The method according to Claim 1 or 2, characterised in that the atmosphere contains a sufficient quantity of moisture to form condensation at the filling elements (6,8) heated concomitantly by the heat from the mould tool (10).
4. The method according to one of Claims 1 to 3, characterised in that the filling elements heated concomitantly are the shooting hood (6) and/or the shooting cylinder (5), into the interior of which the moist atmosphere is introduced.
5. The method according to one of the proceeding claims, characterised in that, during the hardening period, at least temporary, at least one of the filling elements (6,8) heated concomitantly is cooled.
6. The method according to Claim 5, characterised in that the filling element heated concomitantly is cooled to a temperature at which moisture condenses on it or in it.
7. The method according to one of the proceeding claims, characterised in that, during the hardening period, at least temporary, at least one of the filling elements (6,8) heated concomitantly is brought into contact with a moisture carrier (17).
8. The method according to Claim 7, characterised in that the moisture carrier (17) is an absorbent material soaked with a liquid, in particular water.
9. The method according to one of Claims 5 to 8, characterised in that the filling element heated concomitantly is at least one shooting nozzle (8).
10. The method according to one of the proceeding claims, characterised in that in the course of the hardening time the cavity (12) of the mould tool (10) is flowed through at least temporary by a hot gas (L), which is delivered dry and extracted loaded with moisture.
11. The method according to Claim 10, characterised in that the gas (L) is delivered via the shooting opening (11) of the mould tool (10), provided for the introduction of the at least one shooting nozzle (8) and is led away via the venting openings (14) of the mould tool (14) .
12. The method according to one of Claims 10 or 11, characterised in that the gas is air (L).
13. A shoot-moulding machine for the manufacture of mould parts, in particular of casting cores (K) for casting moulds for the casting of molten metal heats

    - with a mould tool (10) having a cavity (12) which determines the shape of the mould part (K) which is to be manufactured,

    - with a heating device (15) for heating the mould tool (10),

    - with filling elements (6,8) for the introduction of mould material (F) into the mould tool (10), wherein the mould tool (10) can be moved relative to the filling elements (6,8) and/or the filling elements (6,8) can be moved relative to the mould tool (10) out of a filling position in which they are arranged closely adjacent to one another for the filling of the mould tool (10), into a stand-by position in which they are positioned distant from one another, and

    - with a moistening device (16,17), which, with the filling elements (6,8) located in the stand-by position, keeps those filling elements (6,8) moist which contain mould sand (F) and lie in the radiation range of the heat (W) emitted by the mould tool, wherein the moistening device (16) is connected to a gas supply, which delivers a moist gas to the moistening device (16).
14. The shoot-moulding machine according to Claim 13, characterised in that the moistening device comprises a moisture carrier (17) which, with the filling elements (6,8) in the stand-by position, is in contact with at least one of these filling elements (8).
15. The shoot-moulding machine according to Claim 14, characterised in that the moisture carrier (17) is formed by an absorbent material soaked with a liquid, in particular water.
16. The shoot-moulding machine according to one of Claims 13 to 15, characterised in that at least one of the filling elements (8) is equipped with a cooling device, which, with the filling element (6,8) in the stand-by position, cools this filling element (8).
17. The shoot-moulding machine according to one of Claims 13 to 16, characterised in that a dry gas supply is provided, which can be coupled to the mould tool (10), which, with the filling elements (6,8) in the stand-by position, conducts a dry gas (L) through the mould material (F) present in the cavity of the mould tool (10) .
18. Use of a shoot-moulding machine (1) designed in accordance with one of Claims 13 to 17, for the performance of the method according to one of Claims 1 to 12.

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