Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Producing or treating inorganic material – not as pigments,...
Patent
1998-01-16
2000-05-16
Dye, Rena L.
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Producing or treating inorganic material, not as pigments,...
264433, 264434, 264437, 264474, 264639, 264678, 425113, 425174, B28B 500, B28B 1700, C04B 3564
Patent
active
060633239
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
THIS INVENTION relates to a process of and an installation for use in making an extruded sintered ceramic artifact.
2. Brief Summary of the Invention
According to the invention there is provided a process for making an extruded sintered ceramic product, which process includes the steps of: ceramic composition or a moist precursor thereof; a frequency of 0.3.times.10.sup.9 -1.times.10.sup.10 Hz to cause the profile to become progressively drier in the direction in which it is extruded; and a dried profile, least partially dried by the microwave radiation.
Supporting the profile will comprise applying a supporting force to the profile to prevent it from sagging or deforming unacceptably under gravity, the supporting force being applied to the profile at a position or positions where the profile has been dried sufficiently by the microwave radiation to receive such force without said unacceptable sagging or deforming. The supporting force is preferably applied to the profile at a position or positions removed or spaced from the microwave radiation.
The extruding may be in a downward direction, preferably in a vertically downward direction. The supporting in this case will thus be at a position below that where the extrusion takes place, and also below the position at which the profile is dried by the microwave radiation, to obtain a substantially straight dried extrusion.
Instead, the extrusion may be in an upward direction and the supporting may be at a position above the extrusion position. The supporting may be accompanied by displacing of the profile such as to cause a desired deformation of the profile, as it dries, eg so that the dried profile is curved along its length and/or has a differently shaped cross-section from that of the moist profile.
In each case the process of the invention may include the optional step of sintering the dried profile; and the process may be carried out continuously or batchwise.
As the extruding takes place, supporting the profile may be by frictionally engaging it by means of support means. In other words, when the extrusion is vertically downwardly, supporting the profile may be by frictionally engaging it, eg by means of support means in the form of one or more pairs of profiled rollers, whose rotation is synchronized with the extrusion, or by gripping it with releasable support means such as two or more pneumatic travelling chucks, conveniently arranged in pairs, which are moved synchronously with the rate of extrusion of the profile, said rotation or movement taking into account dimensional changes in the profile caused by the microwave radiation. Gripping the profile may be at a plurality of positions spaced along its length by a plurality of said releasable support means, each of which successively engages the profile at a high level, then descends synchronously with the profile, then releases the profile at a low level and then re-engages the profile at said high level. Preferably, gripping of the profile takes place at a position or positions where the profile has been dried. The profile may have a leading end which is extruded into contact with a support, the leading end resting on the support and the support descending synchronously with the profile.
The extrusion is preferably continuous. More particularly, the extrusion may be continuous, the drying taking place continuously while the profile is extruded, and the profile being supported continuously while it is extruded.
In a particular embodiment of the process of the present invention, the profile may be subjected to a progressively reducing microwave power input along its length during extrusion thereof, the rate of power reduction also preferably reducing progressively. While the rate of microwave power input, and the rate of reduction thereof, may reduce continuously, they preferably reduce stepwise. For example, the profile may, immediately after being extruded, be subjected to a relatively high microwave power input for a relatively short period, by
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Fuls Paul F
Joubert Andre K
Kapp Diederik
Dye Rena L.
Implico B.V.
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