EP3368234B1 - Pin having an expandable casing, and casting model having a pin, and method for casting metals - Google Patents

Description

The invention relates to a forming mandrel for attachment to a casting model which is molded into this during the production of a casting mold used in the casting, having a foot standing on the model surface of the casting model and a receiving area arranged on the foot for receiving a to be formed therein during the production of the casting mold Feeder, the feeder with a feeder opening formed in its bottom surface facing the casting model being plugged onto the forming mandrel before molding. The invention also relates to a casting model having a corresponding molding mandrel and a method for casting metals using a corresponding casting model.

In foundry technology, it is often necessary to arrange additional feeders in the casting molds, the feeder body of which fills with the liquid metal when the cast part is poured and compensates for any volume deficits that occur when the cast part solidifies in order to prevent voids in the cast part. For this purpose, the feeders must be designed in such a way that the liquid metal fed into them solidifies later than the cast part, so that material can be transported to the cast part during the solidification process, which tightly feeds the cast part. For this purpose, the feeders consist of an exothermic and / or insulating material. In the context of known methods for producing casting molds provided with feeders, the feeders are arranged with any geometric shape at the point of the later cast part to be fed on the casting model and are firmly molded in during the creation of the casting mold by compressing an introduced molding material. For fixing the feeder during molding, so-called forming mandrels are known which are attached to the model surface of the respective casting model. Such a forming mandrel with the generic features is for example in a design as a so-called spring mandrel from the DE 10 2010 022 834 B4 known, the technical background for the arrangement of feeders and the use of forming mandrels is also described in this publication. In this respect, the explanations in DE 10 2010 022 834 B4 incorporated by reference into the disclosure of the present application. A forming mandrel with the features of the preamble of claim 1 is also from WO 2005/051568 A1 known.

When using feeders, there is generally the problem that, after casting, solidified casting material remains in the feeder body in the form of what is known as feeder remainder, which has to be removed from the casting after it has been removed from the mold. In order to facilitate this separation, the use of so-called breaker cores is known, which are fixed to the feeder body on the underside of the feeder body facing the casting model, are made of a refractory material and have a passage opening through which the mold cavity formed by the casting model Casting mold rising hot metal flows into the inner cavity of the feeder body or from there back into the mold cavity of the casting mold. The breaker cores, usually produced by shooting in a shooting machine, are disc-shaped, the passage opening being formed by a constriction in the disc-shaped breaker core body in order to create a predetermined breaking point for breaking off the feeder residue from the surface of the casting. Such an arrangement of the feeder with a breaker core is for example from WO 20091103539 A1 known.

If the feeder moves in the direction of the casting model when the feeder is molded in the casting mold due to the mold pressure exerted, the feeder, including a breaker core that may be attached to it, usually does not come to rest on the model surface, but remains in a more or less large one Stand at a distance from it. After the casting model has been removed from the mold with the mandrel, the remaining cavity is filled with the liquid metal during the casting process filled in so that the predetermined breaking point provided by the breaker core is at a corresponding distance from the surface of the cast part. The resulting, more or less large riser remnants must then be removed by extensive cleaning work.

The invention is therefore based on the object of providing a forming mandrel for fixing a feeder during the molding process, by means of which the use of an additional breaker core or other components forming a constriction associated with the feeder opening is dispensed with and yet a smaller feeder neck and an associated simple one Separation of the feeder remainder near the casting surface is made possible.

The solution to this problem results, including advantageous refinements and developments of the invention, from the content of the patent claims, which follow this description.

The basic idea of the invention initially provides a forming mandrel with the features mentioned at the outset, in which on the forming mandrel an elastically expandable, elastically expandable and end-side on the foot of the forming mandrel directly on the model surface, enclosing at least its foot and / or a part of its receiving area for the feeder Adjacent casing is attached in such a way that the casing expanded before the start of molding bridges a gap that still exists between the model surface and the bottom surface of the feeder after the molding of the feeder, so that after the casting model with the mandrel attached to it has been removed from the casting mold, one through the contour the widened envelope formed predetermined breaking point for a feeder remainder remaining after completion of the casting process.

In this respect, the embodiment of the forming mandrel according to the invention has the advantage that, due to the casing which adjoins the model surface at one end and which is expanded during the molding process, it follows After demolding the casting model including the forming mandrel on the surface of the later cast part, a constriction with approximately the diameter of the foot of the forming mandrel is formed as a predetermined breaking point for the later knocking off of the feeder remainder directly on the cast part surface. This means that any cleaning effort that may still be required for removing the remains of the feeder from the cast part is significantly reduced. Since, due to the extent of the envelope from its clamping at the foot of the forming mandrel, at least into the receiving area of the forming mandrel, a distance between the feeder and the model surface that already exists before the action of the molding pressure is bridged, this also occurs in the event of the feeder being displaced due to the Form pressure on the amount of displacement does not further affect. Regardless of the distance at which the bottom surface of the feeder is at the end of the molding process, the remaining distance to the model surface is still bridged by the expanded cover, while at the same time the predetermined breaking point formed by the cover always remains stationary on the model surface. In this respect, the use of a breaker core to form a predetermined breaking point is no longer necessary.

According to one embodiment of the invention it is provided that the space between the envelope and the molding mandrel is connected to a feed line for a medium to be introduced into the space, whereby according to a further embodiment of the invention this feed line is also designed as a discharge line for the medium fed into the space can be. Alternatively, it can be provided that a separate discharge line for the medium introduced into the intermediate space is connected to the intermediate space.

According to one embodiment of the invention, the elastically expandable sheath is designed as a membrane made from a suitable rubber or plastic mixture.

According to one embodiment of the invention it can be provided that the forming mandrel is designed as a rigid mandrel. In this case, the behavior can be such that the riser does not move on the mandrel when it is being molded and the molding pressure is absorbed in the head of the riser. Alternatively, however, a certain displacement of the feeder on the forming mandrel can be permitted, in the context of which the upper end of the forming mandrel, which extends into an inner cavity as the feeder volume of the feeder, penetrates the cover area of the feeder opposite the bottom surface when it is moved on the forming mandrel.

Alternatively, it can be provided that the forming mandrel is designed as a spring mandrel with a receiving area for the feeder that can be displaced against spring force relative to its foot. It can be provided here that the forming mandrel, which is designed as a spring mandrel, is designed with a foot which can be pushed into the casting model, as is the case with the generic DE 10 2010 022 834 B4 is known.

The invention also relates to the use of a shaping mandrel designed according to the invention with a casting model, the shaping mandrel having the correspondingly disclosed elastically expandable envelope attached at the end to the foot of the shaping mandrel. Such a forming mandrel is screwed into a hole made on the model surface of the casting model or otherwise attached to the model surface, so that the expandable casing located on the forming mandrel when molding a feeder then at the beginning of the forming process in the expanded state the existing distance between the casting model and bridged over the bottom surface of the feeder placed on the forming mandrel.

Another object of the invention relates to a casting model for the production of casting molds, in which a molding mandrel designed in accordance with the features described above is used.

Finally, the invention relates to a method for casting metals by means of a casting mold, wherein a casting model is provided with a molding mandrel attached to it and configured in accordance with the features described above. The use of such a forming mandrel, which has an elastically expandable sheath, requires a change in the process sequence which is otherwise usual for a rigid forming mandrel or a so-called spring mandrel. In detail, a feeder is plugged onto the forming mandrel, and the casing located on the forming mandrel is then placed in its expanded state. The casting model, including the feeder fixed to it by being placed on the forming mandrel, is then molded into the casting mold by introducing a molding material, then the casing is returned to its original, unexpanded state, and then the casting model including the forming mandrel is removed from the casting mold. The cavity formed in the casting mold is filled with liquid metal, and after the metal has solidified, the feeder residue remaining on the metal surface of the casting is knocked off at the predetermined breaking point created by the contour of the envelope that was expanded during molding on the model surface.

Fig. 1:

einen auf einer entsprechend angedeuteten Modelloberfläche eines Gießmodells angesetzten Aufformdorn in einer geschnittenen Darstellung bei nicht aufgeweiteter Umhüllung einschließlich eines auf den Aufformdorn aufgesetzten Speisers vor Einbringen des Formstoffes,

Fig. 2:

den Gegenstand der Fig. 1 mit der in einem aufgeweiteten Zustand befindlichen Umhüllung,

Fig. 3:

den Gegenstand der Fig. 2 bei in die Gießform eingefülltem Formstoff vor Einwirken des Formdrucks,

Fig. 4:

den Gegenstand der Fig. 3 nach Einwirken des Formdrucks,

Fig. 5:

den Gegenstand der Fig. 4 bei in den Ausgangszustand gemäß Fig. 1 zurückgeführter Umhüllung vor dem Entformen des Gießmodells einschließlich des Aufformdorns,

Fig. 6:

den nach dem Gießvorgang am Gussteil verbliebenen Speiserrest einschließlich der von der Umhüllung ausgebildeten Sollbruchstelle.

In the drawing, an embodiment of the invention is shown, which is described below. Show it:

Fig. 1:

a molding mandrel attached to a correspondingly indicated model surface of a casting model in a sectional view with the casing not expanded, including a feeder placed on the molding mandrel before the molding material is introduced,

Fig. 2:

the subject of Fig. 1 with the envelope in an expanded state,

Fig. 3:

the subject of Fig. 2 when the molding material is filled into the mold, before the molding pressure is applied,

Fig. 4:

the subject of Fig. 3 after the molding pressure has taken effect,

Fig. 5:

the subject of Fig. 4 when in the initial state according to Fig. 1 returned covering before demolding the casting model including the forming mandrel,

Fig. 6:

the feeder residue left on the cast part after the casting process, including the predetermined breaking point formed by the casing.

In the Fig. 1 a casting model 10 with a model surface 11 on which a forming mandrel 12 is attached is only shown schematically. The shaping mandrel 12 has a foot 13 and a receiving area 14 which is arranged above the foot and ends in a tip 15. A feeder 16 is placed on the forming mandrel 12 and has a circumferential side wall 18, a cover area 19 and a bottom surface 17. In the interior of the feeder 16, an inner cavity 31 is formed as a feeder volume. A feeder opening 20 is also arranged in the bottom surface 17, via which the liquid metal can flow into the inner cavity 31 or flow out again during the casting process.
In the lower area of the forming mandrel 12 an elastically expandable sheath 21 in the form of a membrane made of a suitable rubber or plastic mixture is arranged on this, which is attached with its one end 22 to the foot 13 of the forming mandrel 12 in the immediate vicinity of the model surface 11 and with its the other end 23 is attached to an upper point of the receiving area 14 of the forming mandrel 12 and thereby encloses the corresponding area of the forming mandrel 12. It can be seen that an intermediate space 30 is formed between the casing 21 and the forming mandrel 12.

How out Fig. 2 As can be seen, the casing 21 can be brought into the space 30 by introducing a gaseous or liquid medium via an inlet and outlet line (not shown) into the in Fig. 2 shown expanded state. It can be seen here that the side area of the casing 21 is covered by a Corresponding reinforcement 24 is reinforced to the extent that under the action of the molding pressure the feeder 16 moves relative to the stationary forming mandrel 12 in the direction of the model surface 11 and thereby slides over the outer contour of the casing 21 secured with a reinforcement 24 for this purpose.

As far as based on the in Fig. 2 position shown the molding process begins after introducing a molding material 25 into the casting mold, not shown, this state is over with the filled molding material Fig. 3 evident. It can be seen that even before the start of the molding process, the expanded envelope 21 bridges the distance between the model surface 11 and into the inner cavity 31 of the feeder 16.

In Fig. 4 the position of the feeder 16 on the forming mandrel 12 after the molding pressure has been applied and the end of the molding process is shown, and it can be seen that the bottom surface 17 of the feeder 16 is still at a certain distance from the model surface 11, this distance being expanded by the Sheath 21 is still bridged. It can also be seen that due to the connection of the lower end 22 of the casing 21 to the base 13 of the forming mandrel standing on the model surface, a gusset 27 formed by the molding material 25 has set in in this area.

After the end of the molding, the casing 21 is returned to its original shape according to FIG Fig. 1 returned by the medium introduced, for example, into the space 30 being drained off again. This state is in Fig. 5 shown. Out Fig. 5 it can be seen that the contour 26 of the molding material 25 formed by the expanded envelope during molding is maintained, which also applies to the gusset 27. It is readily apparent that after the casting model 10 including the molding mandrel 12 has been removed from the casting mold, the cavities created thereby are filled with the liquid metal. Thus, the hot metal flows over the from during the casting process Molding mandrel in the path kept free in the molding material into the inner cavity 31 of the feeder 16 and back again.

After completion of the casting process, the metal solidifies, and the metal in the corresponding flow paths or cavities outside of the cast part 29 cast in the mold cavity produced by demolding the casting model 10 forms a feeder residue 28. How out Fig. 6 As can be seen, the feeder remainder 28 has a predetermined breaking point 27 a formed by the gusset 27, which is located directly on the surface of the cast part 29. The feeder remainder 28 can be knocked off at this predetermined breaking point 27a, the amount of cleaning that is then still required for smoothing the surface of the cast part 29 being correspondingly low. For simplicity, in Fig. 6 retain the representation of the feeder, although the feeder largely loses its represented shape during the casting process.

As not shown further, the forming mandrel can alternatively also be used as a so-called spring mandrel according to FIG DE 10 2010 022 834 B4 be formed, whereby there is also a displacement of the feeder 16 in the direction of the model surface 11, but without piercing the cover area of the feeder. Finally, the advantageous function of the shaping mandrel 12 according to the invention is also given when the shaping mandrel 12 is designed as a rigid mandrel and the force caused by the pressure exerted during the molding of the feeder is absorbed in the head of the shaping mandrel 12, so there is no displacement of the feeder 16 comes on the mandrel 12. In this case too, the expanded envelope 21 ensures the formation of a corresponding predetermined breaking point 27a.

Claims (10)

1. Moulding mandrel (12) for application onto a casting model used in the manufacture of a casting mould used for casting metals into this moulded-in casting model (10), comprising an upright foot (13) on the model surface (11) of the casting model (10) and a receiving area (14) arranged on the foot (13) for receiving a riser (16) to be moulded into it during the manufacture of the casting mould, wherein the riser (16) with a riser opening (20) formed in its base surface (17) facing the casting model (10) is inserted onto the moulding mandrel (12) before being moulded in, characterized in that an elastically expandable covering (21) connected to the foot (13) of the moulding mandrel (12) on the end side immediately adjacent to the model surface (11) enclosing at least its foot (13) and/or a zone of its receiving area (14) for the riser (16) is connected onto the moulding mandrel (12) in such a way that the covering (21) expanded prior to beginning the moulding-in process bridges a distance to the model surface (11) still existing after the moulding-in of the riser (16) in such a way that, after de-moulding the casting model (10) from the mould with the moulding mandrel (12) applied to it, a predetermined breaking point (27a) formed by the contour (26) of the expanded covering (21) is formed for a metallic riser residue (28) remaining after completion of the casting process, wherein an intermediate space (30) between the covering (21) and the moulding mandrel (12) is connected to a feed line for a medium to be introduced into the intermediate space (30).
2. Moulding mandrel (12) according to Claim 1, in which the supply line is also designed as a discharge for the medium introduced into the intermediate space (30).
3. Moulding mandrel (12) according to Claim 1, in which the intermediate space (30) is connected to a separate discharge for the medium introduced into the intermediate space (30).
4. Moulding mandrel (12) according to any one of Claims 1 to 3, in which the covering (21) is designed as a membrane made of a suitable rubber or plastic mixture.
5. Moulding mandrel (12) according to any one of Claims 1 to 4, in which the moulding mandrel (12) is designed as a rigid mandrel.
6. Moulding mandrel (12) according to any one of Claims 1 to 4, in which the moulding mandrel (12) is designed as a spring mandrel with a receiving area (14) for the riser (16) that can be shifted against a spring force relative to its foot (13).
7. Moulding mandrel (12) according to any one of Claims 1 to 4, in which the moulding mandrel (12) is designed as a spring mandrel with a foot that can be inserted into the casting model (10) against spring force.
8. Use of a moulding mandrel (12) designed according to any one of Claims 1 to 7 with a casting model (10) for the manufacture of casting moulds used when casting metals, wherein the moulding mandrel (12) is attached to the model surface (11) of the casting model (10).
9. Casting model (10) for the manufacture of casting moulds used when casting metals with a moulding mandrel (12) applied to the model surface (11) of the casting model (10) according to any one of the Claims 1 to 7.
10. Method for casting metals by means of a casting mould, wherein a casting model (10) is provided with a moulding mandrel (12) applied to it according to any one of Claims 1 to 7, in which a riser (16) is set onto the moulding mandrel (12); then, the covering (21) located on the moulding mandrel (12) is expanded; then, the casting model (10) including the attached riser (16) is formed by inserting a moulding material (25) into the mould; the covering is returned to its original, unexpanded state; then, the casting model (10) including the moulding mandrel (12) is removed from the mould; the existing cavity in the mould is filled with the liquid metal; after solidification of the metal, the metallic riser residue (28) remaining on the surface of the cast part (29) is knocked off at the predetermined breaking point (27a) created on the model surface (11) by the contour (26) of the covering (21) expanded during the moulding-in process.

Images