US 2069059 A
Description (OCR text may contain errors)
Jan. 26, 1937. FESSLER 2,069,059
METHOD OF PRODUCING CERAMIC WARE Filed Aug. 23, 1954 CLAY GZRNULES WATEQ MIXING TANK f PUGGING flncmuz' VACUUH EXTEUDEE jn-ucnict Patented Jan. 26, 1937 PATENT OFFICE METHOD OF PRODUCING CERAMIC WARE Albra H. Fessler, Flint, Mich., assignor to General Motors Corporation, Flint, Mich, a corporation of Delaware Application August 23, 1934, Serial No. 741,089
This invention relates to a process for making blanks for ceramic ware, and more specifically to a process for mixing the ingredients of the blanks thoroughly and without segregation of the different sized grains in the mixture, the blanks being used, for example, in the making of insulation for spark plugs.
In the manufacture of blanks for various kinds of ceramic ware, an uneven distribution of the different sized grains of the ingredients in the mix to give a segregation of the larger grains to one spot is very disadvantageous for through the firing and subsequent use of the article uneven surfaces are formed thereon and strains set up within the article which sooner or later cause failure and the part will crack.
In the processes that have been used heretofore, the slip or mixture of the desired ingredients with water, is led to a series of periodic filter presses. These presses are large and cylindrical, the slip being introduced on the axis of the cylinder and feeding radially outward in comparatively thin sheets or disks, this action being caused by separators. It can be seen that as these compartments fill up the rate of flow of the slip will be changed and when they are nearly full the outer surface will be completely covered and the fiow of water from the edges will be slower. Also the particle flow of the ingredients will vary due to their size and specific gravity so that as the last part of the slip enters to fill the particular compartment the water flowing out radially will carry with it the smaller grains toward the edge and leave the larger ones in the center. In this way, each disk or cake taken from the filter press has a central portion that is formed of coarse grains and gives a segregated non-uniform structure to the cake. The cakes are then aged for approximately a week in order to allow the moisture content to become as uniform as possible and then taken to a wedging or kneading table where a kneading action is applied to them for a given period of time to give it uniformity. The resulting mixture is then cut into fairly large chunks and again aged for approximately a week. It is then inserted in long cylinders having a small round opening in one end and the cylinders placed in a press with a piston fitting inside the cylinder to press the mixture up and extrude it through the opening in the other end to form a small cylinder. In this extruding action, the mix fiows first from the center of the mass within the cylinder and then from various points on the outside surface, and
this action also tends to cause a certain nonuniformity of structure and segregation.
It is an object of the present invention to provide a method for accomplishing the mixing uniformly throughout.
It is a further object to provide a continuous filter for the slip in conjunction with an evacuated extrusion machine to overcome the disadvantages of the former method which tend to give non-uniformity and segregation.
For a better understanding of the nature and objects of this invention, reference is made to the following specification wherein are disclosed the embodiments of my invention which are illustrated in the accompanying drawing, in which the figure is a diagrammatic showing of the steps in the preparation of a blank.
The clay or plastic and granules or non-plastics are placed in a mixing tank I with water and the Whole is thoroughly mixed together to form the slip as in the former process. The slip is stored until it is needed, at which time it is led to the filter by any desired means such as a pipe line. The filter has a large pan 2 which surrounds and extends part way up around a large drum 3, into which the slip is led and brought up to a level to contact the lower surface of the drum. This drum has a porous surface and a vacuum is created within it so that the slip is drawn up to the surface, the water passing through and being discharged and the mixture of plastics and non-plastics sticking to the outer surface. Over this surface are led a plurality of parallel strings 4 around which the mixture gathers in contact with the drum surface. These endless strings are led over a heated drum 5 from the filter drum and then over a pair of heated guide rollers 6 and 7 and back to the filter drum. The mixture adheres to the strings and is carried over the large heated drum and part of the moisture content removed, then after the whole passes over the first guide roller it contacts a comb 8 supported so that its teeth project between the adjacent strings and scrape off the partially dry mix.
This substance is then carried by a conveyor belt 9 to the pugging machine H] where it is macerated and again thoroughly mixed under a vacuum, the connection for exhausting the air being shown at II. It is then fed into the extruding end I 2 of the machine still under vacuum and extruded in a long cylindrical shape which is cut off at the desired length to form the blanks.
This methodhas the double advantage of a continuous filter which keeps operating at all times taking from the slip a uniform homogeneous mass with no opportunity for segregation, and also by even extrusion under vaccum all parts work toward the extrusion nozzle at the same time and do away with any segregation here. So two steps in the older process where segregation is formed are overcome to give an even mix and avoid strain in the final product This method hasalso the added advantage that there is no aging necessary since the moisture content is removed evenly and to the same degree throughout. The mixture that is obtained from the slip by the continuous filter may be used in production the same day, where by the old method aging for from one to two weeks was necessary and it was necessary therefore to carry a larger stock on hand.
It will therefore be seen that my invention is capable of a wide scope of use and should not be limited except as by the following claims.
1. In a continuous process for forming blanks for ceramic ware, the successive steps of mixing the necessary ingredients with water,-continuously filtering the mixture, heating and partially drying the filtered substance, further continuously mixing the partially dry result under vacuum and extruding it under vacuum.
2. A continuous process for forming blanks for ceramic ware comprising, mixing the necessary ingredients with water, continuously filtering the slip, applying heat to the result of the filtration, pugging the partially dry mixture under vacuum and extruding the result under vacuum in continuous succession.
3. In a continuous process for forming blanks for ceramic ware, the steps of continuously filtering a slip to extract the moisture therefrom and continuously pugging and extruding the filtered mass under vacuum whereby a uniform structure without segregation is obtained.
4. A continuous process for forming blanks, comprising mixing the ingredients with water, continuously filtering the slip by vacuum to extract the moisture therefrom, continuously applying heat to the filtered mass to further reduce the moisture content, and continuously pugging and extruding the result under vacuum to give a homogeneous uniform structure blank.
5. In a continuous process for forming blanks, the steps of continuously filtering a slip by vacuum to extract moisture therefrom, and continuously pugging and extruding the filtered mass under vacuum to obtain uniform structure in the blank.
ALBRA H. FESSLER.