Coating apparatus – Projection or spray type – Coating moving mass of solid particulate work
Patent
1989-10-25
1992-02-04
Chiesa, Richard L.
Coating apparatus
Projection or spray type
Coating moving mass of solid particulate work
34 57A, 118323, 118DIG5, 427213, B05C 502
Patent
active
050851705
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a fluidized bed apparatus, in particular for granulation of pulverulent substance, comprising therebelow a wind chamber, and top, is rotatably drivable about an upright central axis and comprises at least one opening which is elongated in approximately radial direction and which permits a gas flow from the wind chamber into the treatment space.
DISCUSSION OF PRIOR ART
In a fluidized bed apparatus belonging to this class and known from U.S. Pat. No. 3,849,900, which is provided for drying particles, the rotor consists of a vertical shaft with a flat circular disc. The latter has a somewhat greater diameter than the sieve bottom and has two or more circular-sector-shaped openings. The sieve bottom belongs to a drawer-like box which can be drawn out of the container and in its operating position is sealed with respect to the container by inflatable hose seals. One of said hose seals lies between a lower frame portion of the box surrounding the sieve bottom or tray and a step formed therebelow in the container. Below said step the rotor disc is disposed. In operation of this known fluidized bed apparatus heated dry air is blown through the rotating rotor and through the sieve bottom into the treatment space so that a pulverulent substance contained therein is fluidized and dried in continuously circulating zones of the treatment space. This known apparatus soils very easily because small particles of the substance to be treated, on insertion of the drawer-like box filled with said substance into the apparatus, can drop through the sieve bottom downwardly into the wind chamber before the pressure gradient between the wind chamber and treatment space necessary for the treatment has developed. The apparatus is as a whole difficult to clean and thus does not always meet the strict hygienic requirements made in particular in the pharmaceutical industry.
Another fluidized bed apparatus known from DE 2932803 A1 comprises a rotor having a U-shaped profile in axial cross-section which is partially covered upwardly by a diaphragm provided with air exit openings. The rotor is mounted on a hollow shaft and connected drivably via the latter and to the pressure side of a fan. Extending upwardly within the hollow shaft is a liquid conduit which terminates in a stationary spray nozzle disposed centrally directly above the sieve bottom. The region around the rotor beneath the sieve bottom is constructed as suction chamber and connected to the suction side of the fan. In this apparatus dry air from the hollow shaft is deflected radially outwardly into the U-shaped rotor profile to flow from there upwardly through the sieve bottom into the treatment space and to fluidize the substance contained therein. Through the central nozzle liquid is sprayed into the fluidized substance so that depending on the nature of the latter and the liquid an agglomeration granulate is for example formed or the particles of the already granulate-like substance are provided with a coating. The used air flows once again through the sieve bottom out of the treatment space into the suction chamber. This apparatus can be filled with the substance to be treated particularly easily pneumatically so that in this respect risks of soiling can be avoided. Nevertheless, cleaning problems arise here as well if the hygienic demands are strict.
More favourable from the hygienic point of view is a fluidized bed apparatus known from DE 2551578 A1 in which a treatment space is defined downwardly by a sealing bottom and upwardly by a filter arrangement. Arranged directly above the bottom is a two-vane or multi-vane rotor which is driven by a hollow shaft and is connected to the pressure side of a fan. The individual vanes of the rotor are provided with air exit openings which are rearwardly directed with respect to the direction of rotation. In one embodiment of this known apparatus in the treatment space a liquid nozzle is disposed centrally above the rotor. In another embodiment liquid nozzles are installed into the vanes of the rotor in
REFERENCES:
patent: 3386182 (1968-06-01), Lippert
patent: 3849900 (1974-11-01), Dale et al.
patent: 4724794 (1988-02-01), Itoh
patent: 4740390 (1988-04-01), Kulling
patent: 4834299 (1989-05-01), Kishibata et al.
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