WO2024246343A1

WO2024246343A1 - Feeder

Info

Publication number: WO2024246343A1
Application number: PCT/EP2024/065117
Authority: WO
Inventors: Alessandro ZANIRATO; Enrico PONZANO
Original assignee: Foseco International Ltd
Current assignee: Foseco International Ltd
Priority date: 2023-06-01
Filing date: 2024-05-31
Publication date: 2024-12-05
Anticipated expiration: 2025-12-01
Also published as: AU2024278744A1

Abstract

A feeder system (1) for use in casting moulds comprises a sleeve (2) and a breaker core (3) One or more retaining elements (21, 31) is/are arranged on the sleeve (2) and/or the breaker core (3) by means of which retaining elements (21, 31) the breaker core (3) supports the sleeve (2). The retaining elements (21, 31) are adapted to interact with the respective other one of the sleeve (2) and the breaker core (3) to which the respective retaining element (21, 31) is not attached in such a way as to make possible displacement of the breaker core (3) inside the sleeve (2). The breaker core (3) is made of insulating material having a scratch hardness higher than a scratch hardness of the sleeve (2). The breaker core (3) is made by core-shooting and the sleeve (2) is made by slurry-forming.

Description

Feeder

The present invention relates to a feeder system for use in metal casting operations utilizing disposable (non-reusable) casting moulds.

In a disposable mould casting process a molten metal is poured into an disposable mould that contains a mould cavity defining a three-dimensional negative image of an intended shape of a casting. After solidification of the metal, the mould is destroyed and the casting is removed.

The disposable mould is often generated in a sand mold production process by embedding a pattern having the intended shape of the casting in moulding material (such as moulding sand or plaster) in a moulding box and by compacting the moulding material. After the moulding material has bonded, the moulding box (which usually consists of segments that may be latched to each other and to end closures) is split into segments (for simple patterns an upper and lower hall) and the pattern is removed. The disposable mould is completed by combining the segments of the moulding box again.

As the density of the melt is lower than the density of the solidified metal, the metal shrinks as it cools down. In order to avoid that this effect distorts the intended shape of the casting, a solution is to provide additional molten metal to the mould cavity as the metal cools down. This is often addressed by integrating feeders into the mould. Each feeder system provides a feeder system cavity which is in communication with the mould cavity. During casting, molten metal enters into the feeder system cavity of the feeder system, and is then flowing into the mould cavity during cooling down and solidification of the metal to compensate for the shrinkage.

For integrating feeder sleeves into the mould, the feeder sleeves are placed on the pattern before the pattern is covered by moulding material. To locate the feeder systems at predetermined locations on the pattern, it is common that the pattern comprises centring pins for the feeder systems. The feeder systems remain embedded in the bonded moulding material of the mould even after removal of the pattern from the mould. As an alternative that is often used with feeder systems having a small resistance against pressure, it is known to embed the feeder systems into cavities in the bonded moulding material after removal of the pattern from the mould. After removing the casting from the mould, residual metal resulting from the feeder system cavity remains attached to the casting. This residual metal has to be removed since it is not part of the intended shape of the casting.

Usually, a feeder system consists of at least two parts:

- a lower part having the shape of a truncated cone that is called breaker core and that is to be located closest to the pattern; and

- an almost cylindrical upper part that is called sleeve.

A major part of the feeder system cavity is provided inside the sleeve, while only a minor part of the feeder cavity is provided inside the breaker core. The breaker core facilitates removal of residual metal after casting, as at least the lowermost part of the breaker core (the part containing an inlet/outlet for the molten metal that is to be located closest to the pattern) is usually tapered towards the mould cavity.

Different types of materials are available for the breaker core and for the sleeve, namely insulating, exothermic-insulating and highly exothermic. Insulating materials extend solidification time, promote directional solidification and improve yield. In exothermic-insulating and highly exothermic materials an exothermic reaction is initiated when molten metal meets the material, heating the metal and extending solidification time still further than insulating materials.

As the feeder systems may impede compaction of the moulding material, feeders have been proposed that are able to perform some relative movement towards the pattern as the moulding material is compressed.

Document US2019/255600A1 describes a feeder system for metal casting comprising a feeder sleeve mounted on a tubular body. The feeder sleeve comprises at least one cut-out that extends into the sidewall from the base to a first depth and the tubular body projects into the cut-out to a second depth, the tubular body having at least one abrading region in contact with a surface of the feeder sleeve within the cut-out. The second depth is equal to or less than the first depth so that upon application of a force in use the abrading region abrades the surface of the feeder sleeve with which it is in contact such that the tubular body is pushed towards the second end.

Document EP3682983A1 describes a kit for assembling a modular feeder sleeve which can be tailored in size and shape according to the desired application. Document EP2792432A1 describes a metallic breaker core having a flange to receive a sleeve. During sand compaction, the height of the breaker core is reduced.

Document US2008/223543A1 describes a feeder comprising a feeder head a tubular body which is guided through an opening of the tubular body and arranged in a mobile manner. The tubular body comprises an abutment capable of taking its bearing on a surface adjacent to the opening in the cavity.

According to an approach described in EP 1 184 104 Bl, the feeder system consists of a sleeve and a breaker core that allow for telescopic movement relative to each other. Retaining means are provided outside the breaker core to allow stacking the sleeve on top of the breaker core without telescopic movement as long as no or little downward pressing force is applied on the feeder system. The retaining means are projections that are supposed to break off under downward pressing force. However, it has been found that the casting quality in the vicinity of the feeder system is still not satisfying. Indeed, the feeders tend to crack during compaction of the moulding material even though they are able to perform telescopic movement.

Thus, it is an object of the present invention to provide a feeder system consisting of a sleeve and a breaker core that allow for telescopic movement relative to each other, wherein the feeder system is less prone to cracking. It is a further obj ect to provide a use of such a feeder system and a method for manufacturing such a feeder system.

This object is solved by the combination of features of the independent claims. Preferred embodiments are defined in dependent claims.

According to embodiments a feeder system comprises a sleeve and a breaker core. The sleeve is made of a first material. The first material is preferably a ceramic material, possibly a refractory material. The first material is preferably exothermic and insulating, or insulating. It may also be exothermic. The feeder system is particularly well suited when casting metals in casting moulds. The first material is preferably a slurry-formed material, also called vacuum-formed material.

According to an embodiment, the sleeve has the shape of a cylindrical can with a closed bottom and a circular opening opposite to the bottom. For ease of manufacturing the inner walls of the cylindrical can are slightly tapered such that the inner diameter at the bottom is smaller than at the opening.

The breaker core provides a spout for receiving and discharging molten metal. The breaker core is tapered towards the spout. The sleeve and the breaker core together define a feeder system cavity for receiving liquid metal through the spout of the breaker core. The breaker core is displaceable inside the sleeve along a longitudinal feeder system axis.

According to an embodiment, the breaker core consists of a tube shaped section and a frustro- conical section. In this embodiment, the outer diameter of the tube-shaped section is slightly smaller than the inner diameter of the sleeve at the opening of the sleeve. To this end, “slightly smaller” means smaller by at least 0.1% and preferably by at least 0.2%, but not smaller by more than 4% and preferably not smaller by more than 2%. Such an adaptation of the outer diameter of the tube-shaped section of the breaker core and the inner diameter of the sleeve at the opening allows a sliding movement of the tube-shaped section of the breaker core inside the sleeve while the risk of leak of molten metal trough the resulting gap is still small.

One or more retaining elements is/are arranged on the sleeve and/or the breaker core by means of which retaining elements the breaker core supports the sleeve. The retaining elements are adapted to interact with the respective other one of the sleeve and the breaker core to which the respective retaining element is not attached in such a way as to make possible displacement of the breaker core inside the sleeve along the longitudinal feeder axis.

To summarize, the feeder generally may have a structure as defined in EP 1 184 104 Bl cited above.

According to the present invention, the breaker core is made of a second material (different from the first material), which is preferably an insulating material, and the scratch hardness of the breaker core is higher, preferably by at least 10 % and more preferably by at least 25% and even more preferably by 30%, than the scratch hardness of the sleeve. In this way, the breaker core scratches the sleeve during the displacement of the breaker core inside the sleeve, resulting in a loss of first material from the sleeve. The second material is preferably a core-shot material. The second material is preferably a ceramic material, possibly a refractory material. As the breaker core is preferably made of insulating material, it is made of a material having a low thermal conductivity and thus a material other than e.g. metal.

It has been found by the inventors that the reason for the unsatisfying casting quality resulting from feeders sleeve of the prior art was triggered by cracks in the breaker core that were resulting from too high stress during compaction of the moulding material and probably even removal or deformation of retaining elements attached to the breaker cores. It has been found that these cracks can be avoided significantly by promoting the scratch of the sleeve by the breaker core and by producing the sleeve by a slurry -formed process and the breaker core by a core-shooting process. Experimental results of the inventors with 40 mouldings show that in case the scratch hardness of the breaker core and the sleeve was about the same (as it is the case with the feeder system of the prior art) and both the breaker core and the sleeve were made by the same process, only 22.5% of the residues resulting from the feeder systems could be removed from the casting during shot blasting for reasons of cracks in the breaker cores. In contrast, if the scratch hardness of the sleeve is lower than the scratch hardness of the breaker core (i.e. if the sleeve is less resistant to abrasion than the breaker core) and if the sleeve is slurry-formed and the breaker core is core-shot, 75% of the residues resulting from the feeder systems could be removed from the casting during shot blasting. It is believed that a sufficient effect is already achieved as soon as the breaker core scratches/ abrades the sleeve (and not the opposite), provided that the sleeve is made from a slurry- formed material and the breaker core is made from a core-shot material. It seems that stress applied to the breaker core is deflected towards the sleeve and transformed in deformation of the sleeve due to the reduced scratch hardness of the sleeve and probably due to the presence of air gaps created in the sleeve by the slurry -forming process. Shot blasting is a process which is conducted to clean the surface of the casting after a solidified casting has been removed out of the mould.

A possible explanation is that having the sleeve softer than the breaker core allows the compression forces to be discharged inside the sleeve while preserving the feed neck, the internal structure of the slurry-formed material of the sleeve allowing for a good absorption of the stress.

In the frame of the present document, the scratch hardness may be measured by the “Electronic Scratch Hardness Tester” manufactured by Simpson-Gerosa. The “Electronic Scratch Hardness Tester” (additionally known as “Electronic Hardness Tester 28111410”) is an instrument for determining scratch hardness of a mold or core. The instrument incorporates a four points cutter that penetrates a finished core or mold surface when rotated. The depth of penetration of the cutter into the specimen determines the hardness of the core or mold. The instrument can be retrieved under the part No. 0042145 from Simpson Technologies Corporation, 751 Shoreline Drive, Aurora, IL, United States of America.

The scratch hardness of the sleeve may be below 75 and preferably below 70 and more preferably below 65 if measured by the “Electronic Scratch Hardness Tester” manufactured by Simpson- Gerosa. The sleeve is comparatively soft.

The scratch hardness of the breaker core may be 75 or higher and preferably above 77 and more preferably above 79 if measured by the “Electronic Scratch Hardness Tester” manufactured by Simpson-Gerosa. Thus, the breaker core is comparatively hard.

A key point in the present invention is that during the relative motion of the sleeve and the breaker core, it is the breaker core that scratches and abrades the sleeve, and not the opposite, resulting in a higher loss of material from the sleeve than from the breaker core. Such effect occurs when the scratch hardness (SHB) of the breaker core is higher than the scratch hardness (SHS) of the sleeve and occurs when the abrasion resistance (ARB) of the breaker core is higher than the abrasion resistance (ARS) of the sleeve. In other words, there is a positive correlation between scratch hardness and abrasion resistance.

In the frame of the present document, the abrasion resistance, is preferably measured according to the ASTM C704/C704M standard, for example in its 2015 version, which is the ASTM C704/C704M - 15 standard. The measurement determines the volume of material in cubic centimeters abraded from a flat surface at a right angle to a nozzle through which 1000 g of size- graded silicon carbide grain is blasted by air at a given air pressure. When assessing that the abrasion resistance of the breaker core is higher than the abrasion resistance of the sleeve, the air pressure, and all other parameters, are the same for the sleeve and for the breaker core. The measurement is preferably done on a sample of 4!4 x 4!4 x 1 inch (11,43 x 11, 43 x 2.54 cm).

The slurry -formed material of the sleeve is a composite material comprising a binder (also called matrix) and a reinforcement material. The reinforcement material is preferably fibers. The first material preferably comprises at least 2 % fibers. Core-shooting process is not suitable for a composite material. Indeed, the core-shooting process involves a step of blowing a fluid mixture into a mould that does not work properly when the fluid mixture comprises a reinforcement material like fibers because the reinforcement material tends to agglomerate and create blocking. The second material preferably comprises less than 1% fibers.

Preferably, the density of the first material is 0.4 g/cm³ to 0.7 g/cm³; and/or the density of the second material is above 0.7 g/cm³ and especially above 0.8 g/cm³.

Embodiments of the present invention involve use of the above feeder system in a sand mold production process comprising embedding the feeder in moulding material before compacting the moulding material and compacting the moulding material together with the embedded feeder(s) to prepare a mould. So far, feeders with sleeves made of comparatively soft material (as the material used for the sleeve according to the present invention) have only been added to the mould after compacting the moulding material and after removing the pattern. It has been found that the combination of a relatively hard and core-shot breaker core with a relatively soft and slurry -formed sleeve allows for compacting the moulding material together with the embedded feeder system without damaging the breaker core or the sleeve more often than it was the case with the feeder systems that are conventionally used for this purpose.

Embodiments of a method of manufacturing the feeder system comprise manufacturing a breaker core by a core-shoot technology using powdery insulating material containing a binder and less than 1 % fibers and/or less than 3 % ash. In the core-shoot technology, a blow head filled with powdery insulating material containing a binder is pressurized with air, leading to the fluidization of the powdery insulating material which results in a “fluid” consisting of a mixture of air and insulating material. This fluid flows from the blow head through shooting nozzles into a mould that is often denoted core box, the mould repelling the air out through venting nozzles. The coreshoot technology achieves a rather uniform density distribution of the material in the mould and a rather high density. This high density allows for a comparatively high scratch hardness of the breaker core. The method of manufacturing the feeder system further comprises manufacturing a sleeve by a slurry moulding technology using exothermic and/or insulating material containing 2 % to 5 % fibers (the fibers preferably having a length of less than 50 mm) and/or 5 % to 25 % ash. This results in a sleeve having a comparatively low density and a comparatively low scratch hardness of the sleeve. Thus, different technologies are applied to manufacture the breaker core and the sleeve of the feeder system in order to achieve the required material properties of the breaker core and the sleeve. In both technologies, solidifying the material may be performed physically e.g. by applying heat and melting part of the binder or chemically by a chemical reaction of the binder. For exothermic material, the heat that is used for solidifying the material needs to be kept below the ignition temperature of the material.

In the following, an embodiment of the invention is described by referring to figures. In the figures, identical elements are denoted by identical reference signs. As all figures relate to the same embodiment, some reference signs have been omitted in some figures to reduce complexity of the figures. Moreover, figure 1 shows a coordinate system that equally applies to figures 2 and 3 as well.

Figure 1 shows a schematic cross-sectional view of a feeder system according to an embodiment in a disassembled state;

Figure 2 shows a schematic cross-sectional view of the feeder system of figure 1 in an assembled state;

Figure 3 shows a schematic cross-sectional view of the feeder system of figure 1 in a compressed state; and

Figure 4 shows a schematic top view of a breaker core used in the feeder system of figure 1.

Figure 1 shows a schematic cross-sectional view of a feeder system 1 according to an embodiment in a disassembled state.

The feeder system 1 comprises a sleeve 2 and a breaker core 3 that are distinct elements. The main purpose of the sleeve 2 is to provide a sufficiently large cavity for molten metal and to avoid rapid cooling down of the molten metal. The main purpose of the breaker core 3 is to supply the molten metal through a spout to the sleeve 2 and vice versa. Furthermore, the breaker core 3 shall promote removal of residual feeder system metal remaining in the feeder system after casting. The breaker core 3 provides a spout 32 for receiving and discharging molten metal. The breaker core 3 is tapered towards the spout 32. The sleeve 2 and the breaker core 3 together define a feeder cavity 10 for receiving liquid metal through the spout 32. The sleeve 2 has been manufactured by a slurry moulding technology, preferably using material containing 25 mass % hollow aluminum silicate cenospheres, 20 mass-% aluminum metal powder, 15 mass % rice husk ash, 10 mass % aluminum oxide, 5 mass % iron oxide, 5 mass % phenol formaldehyde resin, 5 mass % cellulose fibers, 5 mass % iro ore, 5 mass % potassium hexafluoroaluminate and 5 mass % silica sand. Thus, the sleeve 2 is made of one piece of uniform slurry-formed material (the first material). After draining off the liquid and curing of the material scratch hardness has been determined to be 59 by using the “Electronic Scratch Hardness Tester” manufactured by Simpson-Gerosa.

In an embodiment, the first material contains:

• 10 to 40 mass % hollow aluminum silicate cenospheres;

• 15 to 25 mass % aluminum metal powder / aluminum metal granules;

• 2 to 7 mass % iron oxide;

• 5 to 25 mass % ash, and especially rice husk;

• 2 to 10 mass % aluminum oxide;

• 2 to 8 mass % phenol formaldehyde resin;

• 2 to 5 mass % fibers, and especially cellulose fibers;

• 0 to 10 mass % iro ore;

• 0 to 8 mass % sodium hexafluoroaluminate or potassium hexafluoroaluminate;

• 0 to 6 mass % silica sand; and

• 0 to 5 mass % aluminum sulfate.

The breaker core 3 has been manufactured by a core shoot technology from non-exothermic insulating material, preferably mainly consisting of hollow aluminum silicate cenospheres and silica sand that was free of fibers and ash. Thus, the breaker core 3 is made in one piece of uniform material (the second material), the second material being different from the material used for the sleeve 2 (and different from metal). After curing of the material scratch hardness has been determined by the using the “Electronic Scratch Hardness Tester” manufactured by Simpson- Gerosa to be 80. In the present embodiment, both the sleeve 2 and the breaker core 3 mainly have rotational symmetry (rotation symmetry is missing for retaining elements 21 and 31 that will be described later).

In the embodiment, the sleeve 2 is an elongated cylindrical can with a closed bottom 23 and a circular opening 22 opposite to the bottom 23. For ease of manufacturing the inner walls 25 are slightly tapered with an aperture of 3° such that the inner diameter at the bottom 23 is smaller than the inner diameter D22 at the opening 22. The bottom 23 of the sleeve 2 contains a recess 24 for receiving a centering pin (not shown) of a pattern (not shown). The circular opening 23 allows access to an almost tubular recess. The outside surface of the lower end of the sleeve 2 is generally flat and provides a rim surrounding the circular opening 23.

The breaker core 3 comprises a cone section 33 having the shape of a right circular truncated cone and a cylinder section 34 having the shape of a right circular cylinder. The cone section 33 is provided with a circular outlet opening 32 at its end opposite to the cylinder section 34. This circular outlet opening 32 is defining the spout of the feeder system 1. An outer diameter D34 of the cylinder section 34 is set to be smaller by 1 mm than the inner diameter D22 at the opening 22 of the sleeve 2, thus allowing a sliding movement of the cylinder section 34 of the breaker core 3 inside the sleeve 2.

To restrict this sliding movement of the cylinder section 34 of the breaker core 3 inside the sleeve 2, and in order to allow stacking the sleeve 2 on top of the breaker core 3, four retaining elements 21, 31 are equally distributed around a circumference of both the inner wall 25 of the sleeve 2 and the outer wall of the cylinder section 34 of the breaker core 3. In the present embodiments, said retaining elements 21 of the sleeve 2 are arc-shaped projections that extend in a radially inward direction from the inner wall 25 of the sleeve 2 respectively arc-shaped projections that extend in a radially outward direction from the outer wall of the cylinder section 34 of the breaker core 3. At the side surface of the projections at which the sleeve 2 and the breaker core 3 face each other there is a small rim (not shown in the figures) serving as predetermined breaking point. The thickness 39 of the breaker core 3, for example measured inwards from the retaining elements 31, is preferably more than 5%, more preferably more than 10%, even possibly more than 15% than the inner diameter D22 at the opening 22 of the sleeve 2. The retaining elements 31 of the breaker core 3 are shown best in Figure 4, which is a schematic top view of the breaker core 3 (as seen in the minus Y direction of Figure 1).

As can be derived from Figures 2 and 3, a feeder system 1 having the above structure allows the retaining elements 21 of the sleeve 2 and the retaining elements 31 of the breaker core 3 to support the sleeve 2 on top of the breaker core 3 if the cylinder section 34 of the breaker core 3 is partially inserted in the circular opening 22 of sleeve 2. As soon as a downward pressing force extending a predefined amount is applied on the sleeve 2 along the direction of the Y-axis (minus Y direction of Figure 1), the retaining elements 21 and 31 break off and the breaker core 3 is allowed to move further relative to the sleeve 2 inside the sleeve 2 as the sleeve 2 moves down under pressure. Thus, the feeder system 1 performs a telescopic movement.

If the retaining elements 21 are attached to the sleeve 2, atop surface of the breaker core 3 supports the retaining elements 21 and is in direct contact with the retaining elements 21, and the retaining elements 21 are inside the feeder cavity 10. If the retaining elements 31 are attached to the breaker core 3, a bottom surface of the sleeve 2 is supported by the retaining elements 31 and is in direct contact with the retaining elements 31, and the retaining elements 31 are outside the feeder cavity 10.

As the materials for the sleeve 2 and the breaker core 3 are selected such that scratch hardness of the breaker core 3 is higher by approx. 36% than a scratch hardness of the sleeve 2, the risk of cracking the breaker core 3 is low as any stress on the breaker core 3 will be transformed in a deformation of the inner wall 25 of the sleeve 2 and/or a scratching off of material from the inner wall 25 of the sleeve 2.

The loose retaining elements 21 that have been removed from the inner wall 25 of the sleeve 2 can (and should) be removed before casting. It is emphasized that the retaining elements 21 at the inner wall 25 of the sleeve 2 are only optional. For ease of manufacturing it may be preferred to use guiding grooves filled with scratchable material at the inner wall 25 of the sleeve rather than breakable retaining elements. Such guiding grooves should preferably be oriented parallel to a longitudinal axis of the sleeve 2 and distributed evenly around an inner circumferential surface of the sleeve 2. The feeder system 1 of the present embodiment has enough resistance to be placed on a pattern used in a sand mold production process such that the breaker core 3 is located next to the pattern and the sleeve 2 is supported by the breaker core 3 before covering the pattern and the feeder system 1 by moulding material. Thus, the feeder system 1 can be compacted together with the moulding material to prepare a mould. The height of the breaker core 3, remains the same during the displacement of the breaker core 3 inside the sleeve 2. Detached retaining elements may be removed from the feeder 1 after splitting the mould into segments and removing the pattern. Preferably, this is done after adding channels for supplying molten metal to a mould cavity defined by the removed pattern and together with removing residual moulding material generated at the process of adding channels. By combining the segments of the mould again the mould comprising the embedded feeder system 1 is completed.

The invention relates to a feeder system 1 for use when casting metals in casting moulds, the feeder system comprising:

• a sleeve 2 made of a first material, which is a ceramic material and is a slurry-formed material, the sleeve 2 having an abrasion resistance ARS; and

• a breaker core 3 providing a spout 32 for receiving and discharging molten metal, the breaker core 3 being tapered towards the spout 32, the breaker core 3 being made of a second material, the breaker core having an abrasion resistance ARB; wherein the sleeve 2 and the breaker core 3 together define a feeder cavity 10 for receiving liquid metal through the spout 32, wherein the breaker core 3 is displaceable inside the sleeve 2 along a longitudinal feeder system axis 11, wherein one or more retaining elements 21, 31 is/are arranged on the sleeve 2 and/or the breaker core 3 in such a way that the breaker core 3 supports the sleeve 2 by means of the retaining elements 21, 31, wherein the retaining elements 21, 31 are adapted to interact with the respective other one of the sleeve 2 and the breaker core 3 to which the respective retaining element 21, 31 is not attached in such a way as to make possible displacement of the breaker core 3 inside the sleeve 2 along the longitudinal feeder axis 11, wherein the second material is a ceramic material and is a core-shot material; and wherein the abrasion resistance ARB of the breaker core 3 is higher than the abrasion resistance ARS of the sleeve 2, so that the breaker core 3 abrades the sleeve 2 during the displacement of the breaker core 3 inside the sleeve 2, resulting in a loss of material; the loss of material occurring in the material of the sleeve 2.

Claims

1. A feeder system (1) for use when casting metals in casting moulds, the feeder system comprising: a sleeve (2) made of a first material, which is a ceramic material and is a slurry-formed material, the sleeve (2) having a scratch hardness (SHS); and a breaker core (3) providing a spout (32) for receiving and discharging molten metal, the breaker core (3) being tapered towards the spout (32), the breaker core (3) being made of a second material, the breaker core having a scratch hardness (SHB); wherein the sleeve (2) and the breaker core (3) together define a feeder cavity (10) for receiving liquid metal through the spout (32), wherein the breaker core (3) is displaceable inside the sleeve (2) along a longitudinal feeder system axis (11), wherein one or more retaining elements (21, 31) is/are arranged on the sleeve (2) and/or the breaker core (3) in such a way that the breaker core (3) supports the sleeve (2) by means of the retaining elements (21, 31), wherein the retaining elements (21, 31) are adapted to interact with the respective other one of the sleeve (2) and the breaker core (3) to which the respective retaining element (21, 31) is not attached in such a way as to make possible displacement of the breaker core (3) inside the sleeve (2) along the longitudinal feeder axis (11), characterized in that the second material is a ceramic material and is a core-shot material; and the scratch hardness (SHB) of the breaker core (3) is higher than the scratch hardness (SHS) of the sleeve (2), so that the breaker core (3) scratches the sleeve (2) during the displacement of the breaker core (3) inside the sleeve (2), resulting in a loss of material; the loss of material occurring in the material of the sleeve (2).

2. The feeder system (1) of claim 1, wherein the scratch hardness (SHB) of the breaker core (3) is higher by at least 10 % and preferably by at least 25% and more preferably by 30% than the scratch hardness (SHS) of the sleeve (2).

3. The feeder system (1) of claim 1 or 2, wherein the abrasion resistance (ARB) of the breaker core (3) is higher by at least 10%, and preferably by at least 25% and more preferably by 30% than the abrasion resistance (ARS) of the sleeve (2).

4. The feeder system (1) of one of claims 1 to 3, wherein the thickness (39) of the breaker core (3) is preferably more than 5%, more preferably more than 10% than an inner diameter (D22) at the opening (22) of the sleeve (2).

5. The feeder system (1) of one of claims 1 to 4, wherein the density of the second material is higher than the density of the first material and preferably higher by at least 10 % and more preferably at least 15% than the density of the first material.

6. The feeder system (1) of one of claims 1 to 5, wherein, if the retaining elements (21) are attached to the sleeve (2), atop surface of the breaker core (3) supports the retaining elements (21) and is in direct contact with the retaining elements (21), and the retaining elements (21) are inside the feeder cavity (10); and if the retaining elements (31) are attached to the breaker core (3), a bottom surface of the sleeve (2) is supported by the retaining elements (31) and is in direct contact with the retaining elements (31), and the retaining elements (31) are outside the feeder cavity (10).

7. The feeder system (1) of one of claims 1 to 6, wherein the sleeve (2) is manufactured by: o Providing of a hollow mould defining the outer and inner shapes of the sleeve (2), the mould having screens to separate solids from liquid; o Providing a slurry of exothermic and/or insulating material together with liquid, the exothermic and/or insulating material preferably containing at least 2% of fibers; o Filling the mould with the slurry; o Allowing the liquid to drain off the mould through the screens; and o Curing the material chemically and physically; and/or wherein the breaker core (3) is manufactured by: o Providing of a hollow mould defining the outer and inner shapes of the breaker core (2), the mould having air venting nozzles; o Providing a blow head filled with powdery insulating material containing a binder, the material containing less than 1 % of fibers; o Pressurizing the blow head with air to achieve a fluid mixture; o Blowing the fluid mixture into the mould; and o Solidifying the material chemically and/or physically.

8. The feeder system (1) of one of claims 1 to 7, wherein the first material contains 2 % to 5 % fibers, the fibers being preferably cellulose fibers and/or calcium silicate fibers and/or aluminum silicate fibers and/or rockwool fibers; and/or wherein the first material contains 5 % to 25 % ash, the ash containing at least 85 mass-% silicon dioxide, wherein the ash optionally is rice husk ash.

9. The feeder system (1) of one of claims 1 to 8, wherein the second material contains less than 1 % fibers and/or less than 3 % ash; or wherein the second material is free from fibers and/or ash.

10. The feeder system (1) of one of claims 1 to 9, wherein the height of the breaker core (3), remains the same during the displacement of the breaker core (3) inside the sleeve (2).

11. The feeder system (1) of one of claims 1 to 10, wherein the second material contains at least 20 mass% and preferably at least 30 mass% of cenospheres made of silica and/or alumina; and/or wherein the second material contains at least 20 mass% and preferably at least 30 mass% of silica sand.

12. The feeder system (1) of one of claims 1 to 11, wherein interaction of the retaining elements (21, 31) to make possible displacement of the breaker core (3) inside the sleeve (2) along the longitudinal feeder system axis (11) involves separation of the retaining elements (21, 31) from the respective other one of the sleeve (2) and the breaker core (3) to which the respective retaining element (21, 31) is attached; and/or deformation of the respective retaining element (21, 31); and/or deformation of the respective other one of the sleeve (2) and the breaker core (3) to which the respective retaining element (21, 31) is not attached.

13. The feeder system (1) of one of claims 1 to 12, wherein a predetermined breaking point is provided at the retaining elements (21, 31), said predetermined breaking point optionally being a notch.

14. The feeder system (1) of one of claims 1 to 13, wherein the retaining elements (21) are retaining projections of the breaker core (3) that are distributed evenly around an outer circumferential surface of the breaker core (3); and/or wherein the retaining elements (31) are guiding grooves of the sleeve (2) that are oriented parallel to a longitudinal axis of the sleeve (2) and distributed evenly around an inner circumferential surface of the sleeve (2), the guiding grooves being filled with scratchable material.

15. Use of the feeder system (1) of one of claims 1 to 14 in a sand mold production process comprising the steps of:

• Providing a pattern having the intended shape of a casting;

• Placing the feeder system (1) on the pattern such that the breaker core (3) is located next to the pattern and the sleeve (2) is supported by the breaker core (3);

• Covering the pattern and the feeder system (1) by moulding material;

• Compacting the moulding material to prepare a mould;

• Splitting the mould into segments and removing the pattern; and

• Combining the segments of the mould again to complete the mould.

16. Method of manufacturing the feeder system (1) of one of claims 1 to 14, the method comprising the following steps:

- Manufacturing a breaker core (3) by o Providing of a hollow mould defining the outer and inner shapes of the breaker core (2), the mould having air venting nozzles; o Providing a blow head filled with powdery insulating material containing a binder, the material containing preferably less than 1 % fibers and/or less than 3 % ash; o Pressurizing the blow head with air to achieve a fluid mixture; o Blowing the fluid mixture into the mould; and o Solidifying the material chemically and/or physically;

- Manufacturing a sleeve (2) by o Providing of a hollow mould defining the outer and inner shapes of the sleeve (2), the mould having screens to separate solids from liquid; o Providing a slurry of exothermic and/or insulating material together with liquid, the exothermic and/or insulating material preferably containing 2 % to 5 % fibers and/or 5 % to 25 % ash; o Filling the mould with the slurry; o Allowing the liquid to drain off the mould through the screens; and o Curing the material chemically and physically;

- Completing the feeder (1) by placing the sleeve (2) on top of the breaker core (3).