Chaplet.

p0001The invention relates to a hub support for positioning of cores in molds, in particular for thin-walled cast parts made from aluminum alloys in sand casting processes.

p0002In the foundry art forms are used, be used in the cores for the production of castings. A distinction is made inside cores that reflect the inner contours of castings, and outer cores of the outer contours, which are provided to fix the cores in the mold core brands and core supports.

p0003The inner cores made of core sand or metal. Because they are surrounded by the cast metal, you must be highly fire-resistant. After the casting, they may shrinkage of the casting does not interfere and should, if they are made of sand, disintegrate easily. The the outer contours of castings reproducing outer cores consist of core sand.

p0004The core brands are extensions in the core than necessary addition that are enclosed on all sides of the molding sand. Is it not possible to work with core brands, core supports are used, the weld in the casting. The core supports most commonly used are to comply with the predetermined wall thicknesses of the castings.

p0005In the casting of castings without using chaplets it may happen that the core is pressure-loaded on one side and thus undergoes a shift in position of the irregular casting speeds the melt. This leads to defective castings with different wall thicknesses. The counteract core supports which are placed in critical areas such as to prevent a shift in position of the core.

p0006A known core support made of metal consists of two perforated support plates with a connecting web arranged therebetween. Since the core supports remain in the casting after the casting, this leads, in particular with thin-walled castings to the fact that the casting experiences a weakening at this point. However, even with thick-walled castings, an inhomogeneous cast wall is generated by the remaining in the casting after the casting core support.

p0007The object of the invention is therefore to provide a core support of the aforementioned type, with the cores safely in a desired position in the mold can be kept and the finished castings have a homogeneous cast wall in the area of ​​core supports.

p0008This object is achieved essentially by the fact that the core support consists of a flame-resistant plastic. The plastic core support keeps the core while in the desired position until it is completely surrounded by the melt and thus experiences a uniform load. However, since the plastic core support gassed during the casting process, is the space that the core support has taken over in a homogeneous cast structure. This also makes the area that has taken over the core support before the casting process, a homogeneous cast wall with absolute tightness.

p0009According to an advantageous embodiment of the invention it is provided that the core support consists of a hard foam, especially foamed polystyrene. Foams have only a small elastic deformability at a relatively high resistance to deformation. Polystyrene has the advantage that almost no residue remains after the gasifying the core support in the form of over other plastics. An invention consisting of an extruded, flame-retardant polystyrene rigid foam core support can be formed in a cylindrical or cubic shape in a particularly simple manner. It reserves even with larger dimensions as long as their position until the core is completely enclosed by the melt.

p0010In development of this invention the core support is cut, sawed or punched out of polystyrene foam plate. Thus, the core support can not only be easily adapted to the required dimensions of the mold, but also very simple, rational and thus inexpensively manufactured.

p0011To fix the known metal core supports these have an additional Ansteckstift which must be taken in the core or the wall of the outer mold. This often results in particular with thin cores to a core breakage or cracking of the outer mold. therefore the Ansteckstifte the metal core supports are often glued or tucked into pre-drilled holes in the core or the outer mold. Advantageously, therefore, the core support of the invention on one side of an adhesive layer. Using this adhesive layer, the core supports can be positioned in a simple manner to cores and core packages. The adhesive layer is kept so thin that the required dimensions of the castings can be complied with.

p0012The invention is characterized in that the adhesive layer consists of a solvent-free hot melt adhesive. The hot melt adhesive has the advantage that it can be applied easily at higher temperatures ensures a stable connection and high temperature has only a slight evolution of gas.

p0013Conveniently, on the adhesive layer, a protective strip, arranged in particular a siliconized paper. Through these strips not only the adhesive layer is protected, but also prevents accidental gluing several chaplets.

p0014Further features, advantages and applications of the invention will become apparent from the following description of an embodiment, which is shown in more detail in the drawing. All of the described and / or illustrated features, alone or in any combination form the subject matter of the invention, irrespective of their summary in the claims or their back-reference.

p0015Show it:<ul><li>FIG. 1 is a hub support according to the invention for positioning an inner core in a mold in a sectional view,</li><li>Fig. 2 shows a section along the line II-II in Fig. 1 and</li><li>Fig. 3 is a perspective view of a core support with an adhesive layer.</li></ul>

p0016In Fig. 1, a mold 1 is shown for the casting of thin-walled Hohlgußteilen. This has two outer core molds 2 and 3, in which an inner core 4 is arranged. The inner core 4 is cantilevered by a formed by the outer core molds 2 and 3 core lock. 5 In the area formed by the inner core 4 and the outer core forms 2 and 3 space 6 a hub support 7 is arranged. The hub support 7 by means of an adhesive layer 8 (Fig. 3) adhered Festge at a predetermined location on the outer core mold 3. The core supports 4 are arranged in a mold in such places, where a shift in position of the core could be due to one-sided pressure load through the melt.

p0017From Fig. 2 it can be seen that the inner core 2 is fixed by means of three supports 7 in the mold core 1 in the illustrated embodiment, the core supports 7 are arranged uniformly on the circumference of the inner core 4.

p0018The hub support 7 illustrated in FIG. 3 enlarged has a cylindrical shape which is stamped out of an extruded polystyrene rigid foam board. On one side, the hub support 7 a hot melt adhesive layer 6, which is applied very thinly. On the adhesive layer 6, a siliconized paper strip 9 is arranged. The hub support 7 may also have any other shape, such as a cube shape.

p0019The plastic core supports showing their particular advantages in the casting of aluminum alloys in sand casting processes, for example during casting and Röhrenguß described by Hohlgußteilen, the inner core 4 is cantilevered by a core lock 5 (Fig. 1).

p0020The setting time of the molten aluminum is short, especially at low wall thicknesses of, for example 4 to 6 mm. The flame-retardant plastic core support now holds the core as long as in the previously fixed position until it is completely surrounded by the melt and thus experiences a uniform load. During the casting process the core support, which the space has been taken the core support, merges into a homogeneous cast structure gassed.