CH626314A5 - Ceramic veneer - Google Patents

Description

The invention relates to a ceramic veneer, which is made from a thin slurry by drying and firing the slip.

Such veneers are manufactured, among other things. in such a way that the slip is applied to an endless circulating belt in as uniform a thickness as possible, dried on this belt and then fired in a kiln. A deficiency of this method is that a large percentage of the veneers produced in this way are unusable because the veneers are uneven and / or bulged at the edges. The object of the invention is the formation of a veneer made from a slip, which remains flat during firing and subsequent cooling.

A veneer according to the invention is characterized in that it consists of at least two different layers made of slip, which either have different shrinkage mass during firing and / or different thermal expansion coefficients in the fired state, and that shrinkage mass and expansion coefficient of the individual layers are determined so that the Veneer is.

In itself, a veneer made from a uniform slip has no reason to shrink unevenly when fired or to expand unevenly when it cools down. However, as has been found, the composition of the wet slip layer does not remain uniform during drying. Slurry consists of fine clay particles and coarser, hard particles, e.g. finely shredded chamotte etc. When drying, the coarser particles settle in the lower part of the slip layer, the fine particles remain on top. The shrinkage mass and the coefficient of expansion along the height of the layer then become uneven, and the veneer deforms when fired and when it cools down.

The uneven distribution of the slip particles that occurs when drying a slip layer cannot be avoided even with the layers of the veneer according to the invention, but the additions to the two different slips can be selected such that the mean values of the shrinkage mass and the coefficient of thermal expansion assume values that deform the Prevent veneers in the oven and on subsequent cooling. Differences in the shrinkage mass can be e.g. achieve otherwise the same composition of two slurries by adding finely ground fireclay to one slip and finely ground, fired chamotte to the other. Further examples are given later in the description.

The invention is described below with reference to the drawing, in which:

1 is a schematic representation, partly in side view, partly in section, of a device for applying slip to an endless carrier and conveyor belt,

Fig. 2 in section the end of the conveyor belt and the front part of a drying oven and

Fig. 3 also in section the rear part of the drying oven, a kiln and a subsequent cooling oven for the fired veneer.

In the drawing, 1 and 2 denote two rollers which are mounted in a frame consisting of two posts 3 and 4 and a bridge 5. A carrier tape 6 is wound around these rollers and is used to receive and transport the slip. With 7, 8, 9 and 10, schematically shown application devices are designated.

The device 7 serves to apply formwork oil to the carrier tape 6, which should prevent the slip from adhering to the tape. With the device 8, a first layer of slip is applied to the tape in such a way that it forms a thin layer 13. A glass fleece 14 is introduced into this layer. The fleece is unwound from a roll 15, the axis 16 of which is mounted in an arm 17 of a frame. The fleece 14 is rotatably supported on a roller 17 on the arm

19 introduced into the slip layer 13 so that it is soaked by the slip. The device 9 is used to introduce a second slip layer 20 onto the fleece so impregnated, and a glass fleece 21 is introduced into the latter again. The fleece 21 comes from a roll 22 and is introduced into the slip via a roller 23.

With 24 an arrangement of radiant heaters is designated, which for drying the slip layers 13 and

20 serve. Finally, if desired, a glaze mixture 25 is applied with the device 10.

From the belt 6, the pre-dried veneer, as shown in FIG. 2, goes into a drying oven, generally designated 27. The furnace forms a channel 28. Transport rollers 29 and heating resistors 30 are arranged in this channel. The channel is closed at the top and bottom and on the sides by refractory walls 31. The rollers 29 are used to transport the pre-dried veneer, the strength of which has now been achieved, which permits further transport on rollers. The veneer is pulled through the drying oven.

The drying oven 27 can form part of a kiln 32, the firing zone of which is formed in FIG. 3 by a channel 33 which is closed on all sides and which is preferably divided by a ceramic plate 34. Under this horizontal plate 34, heating resistors 35 are arranged in individual chambers and 33 in the upper part of the channel designated 36. A cooling furnace 37 connects to the firing zone. It also forms a channel 38 with heating resistors 39, 40. At the beginning of the channel 38, rollers 41, 26 are attached, over which an endless belt 11 is wound.

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626314

Counter rolls belonging to this are no longer shown in FIG. 3. One of the rollers is driven, the belt is used to transport the finished veneer. It is a tape made of a highly temperature-resistant material. A weight-loaded roller 12 is arranged above the roller 41 and ensures that the veneer is carried along by the belt 11.

According to the invention, the two slip layers 13 and 20 differ in their composition. Several suitable layers are given below:

Both layers have different shrink mass. Different shrinkage masses of both layers can also be achieved by partially burning the usual hard-fired chamotte, also known as hard-fired chamotte, Fireclay which is subjected to a fire is replaced, e.g. with the following composition:

10th

1st example

Layer 13

Layer 20

volume

40%

30%

Burnt hard

Chamotte

20%

30%

Feldspar

40%

40%

20th

25th

2nd example:

Layer 13

Layer 20

volume

30%

30%

Burnt hard

Chamotte

15%

30%

Firebrick

15%

-

Feldspar

40%

40%

With the specified composition, the layers 13 and 20 have different shrink masses. If you want different coefficients of thermal expansion at the same time, this can e.g. can be achieved with the following composition:

3rd example:

Layer 13

Layer 20

volume

Chamotte with a high coefficient of thermal expansion Chamotte with a low coefficient of thermal expansion

30% 15%

15% 40%

30%

30% 40%

The influence of the glaze can also be taken into account in the composition of the layers insofar as it contributes to the deformation of the flat slip layers.

The percentages given are approximate values and can be exceeded or fallen below.

3 sheets of drawings

Claims (5)

626 314 1. Ceramic veneer made from a low-viscosity slip by drying and firing the slip, characterized in that it consists of at least two different layers made of slip, which either have different shrinkage mass during firing and / or different thermal expansion coefficients in the fired state, and that the shrinkage mass and expansion coefficient of the individual layers are determined so that the veneer is even. 2. Veneer according to claim 1, characterized in that it is made of a lower layer of 40% clay, 20% hard fire chamotte and 40% feldspar and an upper layer of 30% clay, 30% hard fire chamotte and 40% feldspar. 2nd PATENT CLAIMS 3. veneer according to claim 1, characterized in that it is made of a lower layer of 30% clay, 15% hard fire chamotte, 15% firebrick and 40% feldspar and an upper layer of 30% clay, 30% hard fire chamotte and 40% feldspar . 4. veneer according to claim 1, characterized in that it consists of a lower layer of 30% clay, 15% chamotte with a high coefficient of thermal expansion, 15% firebrick with a high coefficient of thermal expansion and 40% feldspar and an upper layer of 30% clay, 30% chamotte with a low coefficient of thermal expansion and 40% feldspar. 5. veneer according to claim 1, characterized in that a glass fleece is placed either on the uppermost slip layer and / or between two slip layers.