Coating processes – Particles – flakes – or granules coated or encapsulated – Applying superposed diverse coatings or coating a coated base
Patent
1994-12-05
1997-03-11
Edwards, Laura
Coating processes
Particles, flakes, or granules coated or encapsulated
Applying superposed diverse coatings or coating a coated base
427236, 118313, 118317, B05D 100
Patent
active
056099088
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for coating a substrate with a fluid, which in particular may be a dispersion or a suspension of a coating substance in a vaporizable carrier fluid, by means of a system of nozzles provided with at least one two-substance nozzle for the intermittent discharge of the fluid and the discharge of a gas.
Apparatuses of this kind are utilized, by way of illustration in so-called ink-jet printers, in particular, in "large character printing".
Moreover, such apparatuses can be employed in microdosaging and, in particular, for adding an active substance to a carrier, by way of illustration a tablet.
Another important use of such apparatuses is coating a pressing chamber with a lubricant: by way of illustration in the manufacture of tablets in human and/or veterinary medicine, of catalysts and various foodstuffs it is necessary to coat the top die, respectively the male mould, and the bottom die, respectively the female mould, with a lubricant in order to facilitate the pressing process as well as the ejection of the tablet following termination thereof.
DE-OS 27 17 438 proposes spraying the lubricant onto the pressing tools. Further details concerning the process described therein can be found in the article "Pre.beta.kammerbeschichtung, ein Beltrag zur Optimierung der Tablettenherstellung" (Pressing Chamber Coating, an Aid in Optimizing Tablet Production), published in Pharm. Ind. 50, 7, 839-845 (1988) or DE 39 02 293 A1.
The first figure of this article depicts a pressing chamber coating apparatus on which the generic part of hereto is based. In this apparatus a system of nozzles is employed that is provided with a two-substance nozzle from which the lubricant mixed with air emerges intermittently. For this purpose, the lubrication medium and the air are fed in doses alternately one after the other into the antechamber of the nozzle.
Although this state-of-the-art apparatus permits drastic reduction of the lubricant needed per pressed piece to amounts ranging from 0.01 to 0.01 mg per pressed piece, an element of the present invention is understanding that this state-of-the-art apparatus, too, still has a substantial drawback which prevents further reduction of the amount of lubricant used per pressed piece:
In this apparatus, application of the lubricant occurs essentially on the bottom surface of the male mould and the female mould, respectively the bottom die; an element of the present invention is, however, comprehending that the lubricant is particularly needed along the peripheral edge of the tablet, i.e. of the female mould, and at those sites where only relatively little lubricant is applied in the state-of-the-art apparatus. Thus, in this apparatus more lubricant is applied to the bottom surfaces than is necessary if the amount of lubricant is optimumly dosed along the peripheral wall of the pressing chamber (i.e., female mould).
SUMMARY OF THE INVENTION
The object of the present invention is to improve an apparatus for coating a substrate with a lubricant by means of a system of nozzles having at least one two-substance nozzle for the intermittent discharge of fluid and the discharge of a gas in such a manner that it is possible, i.a., to obtain ring-shaped layers of coating on the substrate, so that, by way of illustration, with the use of the invented apparatus for coating a pressing chamber the lubricant is primarily applied to the peripheral wall of the pressing chamber (mainly female mould).
An inventive step is that the two-substance nozzle has an inside nozzle and a ring chamber which coaxially encompasses it. Into the lateral surface of this ring chamber leads at least one gas inlet nozzle whose longitudinal axis does not intersect the longitudinal axis of the inside nozzle. The ring chamber has an outlet opening which encompasses the outlet opening of the inside nozzle, with a device being provided with which fluid can be supplied intermittently to the inside nozzle as well as another device with which the gas can be c
REFERENCES:
patent: 3857363 (1974-12-01), Ferlito
patent: 4043295 (1977-08-01), Speck et al.
patent: 4374871 (1983-02-01), Steinbis
patent: 4388343 (1983-06-01), Voss et al.
patent: 4758142 (1988-07-01), Voss et al.
Pharm. Ind. 50, 7,839-845 (1988) Prebkammerbeschichtung, ein Beitrag zur Optimierug der Tablettenherstellung, Gruber et al.
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