FI57737B - KERAMISK EN- ELLER FLERDELIG GJUTFORM FOER TILLVERKNING AV KOMPLICERADE GLASFOEREMAOL - Google Patents

Description

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Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 21 + 35739.9 (71) Rosenthal Aktiengesellschaft, Postfach 1520, 8672 Selh, Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) (72) Claus J. Riedel, Tiroler Glashiitte, German Republiken Tyskland (DE) (7 ^) Oy Borenius & Co Ab (5I +) Ceramic one- or multi-part molds for the manufacture of complex glassware - Keramisk en- eller flerdelig gjutform för tillverkning av komplicerade glasföremäl

The invention relates to a ceramic one-piece or multi-part mold for the production of complex glass objects.

DT-0S 2,249,419 has already proposed ceramic molds made of aluminum titanate or cordierite for the manufacture of glassware. The particular advantage of these molds is that they can be manufactured relatively simply by applying ceramic design methods, and it is possible to obtain simple heel patterns and other structures by casting. However, this method is not possible "in the case of the production of complex glassware or the need for so - called hollow cores for hollow bodies.

To date, no satisfactory mold material and method is known that would meet the structurally difficult requirements of ceramic molds in the glass industry. The object of the invention is therefore to provide a shaped body of ceramic material which, in the case of complex glass objects, is superior to metal molds, in particular in the case of small production series.

The object of the invention is therefore to find a mold material which exceeds the normal operating temperatures of metal molds and, on the other hand, to enable the natural casting of 2 57737 originals even in question from difficult designs.

The object according to the invention is solved in such a way that the core and the outer jacket are essentially a mixture of 2 to 6 parts by volume of chamotte flour, 2 to 6 parts by volume of release agent and 2 parts by volume of hard mold gypsum.

A preferred embodiment of the subject of the invention is further based on the fact that the separating agent contains 50 to 70% by weight of ground quartz, 25 to 45% by weight of mica and 2 to 10% by weight of kaolin.

The molds according to the invention can be manufactured by a method which is particularly suitable for the production of ceramic molds for complex glass objects. The steps of the method are as follows: using a conventional casting method from ceramics with gypsum or other mold materials and assembling the individual mold parts into a complete mold, shaping the resulting cavity to the desired wall thickness of the finished product with wax a casting cavity space into which glass is later drained from the storage tank in the furnace.

In connection with the method of manufacturing the molds according to the invention, beeswax or the like having similar properties can be used as the material to be melted. In addition, for practical implementation, it may be important that the wax model be brushed with a varnish, especially a decal varnish, as is used in the food industry to make decals. The purpose of the varnish is to prevent beeswax from penetrating the porous ceramic mold when firing is carried out at about 250 ° C.

With the mold according to the invention, it is also possible to produce multicolored glass objects by placing different glass in layers in the storage container.

The inventive idea will be explained in detail below on the basis of the accompanying drawings illustrating two exemplary embodiments.

Figure 1 shows a perspective view of a ceramic mold formed from a core and a sheath for a glass-plastic article.

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Figure 2 shows a section of this ceramic mold.

Figure 3 is a sectional view of a head with a grooved core portion.

Figure 4 shows a wax model and its ceramic mold material.

Figure 5 shows a complete ceramic mold after the ceramic material has been stiffened internally and externally.

, Figure 6 shows the finished mold with its melt tanks as placed in the furnace.

Figure 1 shows a two-part mold with an inner core 1, a casting cavity 2 and a two-part outer jacket 3. Furthermore, a latch 5 made of refractory material is important in that it keeps the core in the mold at the necessary distance from the jacket. The series of main work steps of the casting mold manufacturing method according to the invention is as follows: As in most mold shaping methods used in foundries, the necessary mold division is achieved by shaping the original, taking into account the wax used as the working material. The original is varnished, and a mixture of lubricating clay and oil is applied to it as a separating agent, as in the ceramics industry in general. Thereafter, gypsum printing is performed, and the mold is brushed with a transfer varnish for the reasons explained above. After the various mold parts have been assembled into a mold, this is placed on a base plate on which a piece of plasticine has been pre-laid for subsequent draining of the glass 6. The warm wax is then either brushed onto the mold, or the entire model is immersed several times in the wax casting until the desired wall thickness is reached. The ceramic molding compound is prepared by mixing the chamotte flour and the separating agent esnin in water into a thick porridge and then mixing the separately treated gypsum. A chamotte ring 7 fired in the working mold is required as the outer holder. The inner surface of this chamotte ring is also insulated with transfer paint to prevent water from penetrating into this ring from the ceramic mold mass. The cavity between the wax model and the outer chamotte ring is filled with a reconditioned mixture of ceramic material. In this case, it is advantageous to use once used mold material for the outer sheath, which has been ground. The mold must then be dried for about three days, or in a shorter time at 200 to 300 ° C, at the same time the wax is melted off. The cross section of the mold cast for the glass-plastic object is shown in Figure 2.

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The casting temperature of the glass is 850 ... 1000 ° C, in which case the mold is provided with a storage tank 10 made of chamotte arranged above it, which may contain lead glass, marble glass or colored glass laid in layers of different colors. It is clear that no metal molds can be used in such a high temperature range. The storage tank 10 must be dimensioned so that it has a small excess of glass, so that the glass flows downwards from the mold outlet 6. The temperature rise is chosen so that it is heated faster at the beginning, while shorter heating times are achieved at the end of the melting. The heating time is on average 5 to 6 hours to achieve a uniform temperature distribution throughout the ceramic mold. Cooling must also take place relatively slowly to room temperature to avoid stresses in thick glass sections.

The application of the mold according to the invention will be explained below in connection with the casting of a complex object, namely a head, in which case a sub-grooved core 1 is required and other individual measures must be taken. From the working mold or the mother mold, a wax model 11 is made by first brushing the wax flowing in layers to describe the fineness of the profile, after which the additional wax is applied with a spatula or by casting to achieve the durability of the model. The thickness of the layer in this case is 1.5 ... 2 cm. A casting funnel 8 about 5 cm high is further placed on the neck of the head. The inner and outer layers of the wax model 11 are then treated with a transfer varnish 12, as shown in Fig. 3. A grooved core 1 is then made, whereby, for reasons to be explained below, a ceramic mold material having 3 volumes of chamotte flour, 5 volumes of release agent and 2 volumes of hard mold gypsum is fed to the head cavities, and the upside-down end is placed on a foam rubber substrate. At the same time, a refractory latch 5 is also placed in this casting mass so that it holds the hardened ceramic material in place. Once the ceramic casting has hardened, the head is turned upside down and placed on the plate, whereby more mold material is applied to it by means of a brush, in which case a sleeve 9 must be used in the neck part of the head so that the material cannot easily drain away. Figure 4 shows this step. The chamotte ring 7 can then finally be placed on top, in which case its inner surface must also be insulated with transfer varnish 12. The cavity formed between the wax model 11 and the ring 7 is now filled with ceramic mass, in this case containing 4 parts by volume of chamotte flour, 4 parts by volume of separator and 2 parts by volume. The wax can now be removed by melting. In particular, this wax must meet the requirements of 5 57737 for good dimensional stability and low shrinkage. Figure 5 shows a finished casting device which is then placed in an oven-in. The casting is performed as described above. Once the mold has cooled, the ceramic material can be easily removed because it is quite brittle. The object has now solidified to a glassy and homogeneous state, showing all the details of the model. In the case where different colored glass has been used, layered multicolor can also be clearly seen. The glass product now only needs to be cleaned and reworked, e.g. if a two-part jacket has been used, in which case the casting seam must be sanded off. However, this depends on the individual case. In addition, the cast glass article is only slightly translucent and has a number of small air bubbles that do not occur in the usual blown glass. The surface of the glass article has a silky sheen, which is likely to be caused by the ceramic mold material, and which cannot be so easily achieved with other glass molding methods. To get into question the object is still cleaned with dilute hydrochloric acid, and the neck of the head must also be post-ground.

The advantages to be achieved according to the invention are based above all on the fact that such complex glass objects cannot be produced with the aid of the currently available manufacturing methods of glass technology. There is also no need for any highly specialized glassblowers, but continuous production can be achieved with simple auxiliary forces. Thanks to the manufacture of the inner core in particular, weight savings are achieved, which is especially important in the case of large objects.

The amount of scrap can also be reduced due to the fact that there are no longer as many stresses in the glass as when casting full objects.

^ From an artistic point of view, the silky shine of the surface must be especially emphasized, which gives the product an aesthetic appearance.