My invention relates to a rotatable atomiser for spraying a liquid, comprising a stationary supporting member with a supply channel for liquid, and an atomiser disk having an inner atomising chamber and one or more discharge channels, the atomiser being secured to a preferably vertical rotatable shaft, a labyrinth seal being provided in combination with a fluid stream.
When such a fast rotating atomiser is utilised the phonomenon of air intrusion may occur notwithstanding the fluid stream. Air intrusion is due to the fact that the atomiser operates as a blower. According to this phenomenon air is sucked in along the shaft and is pumped via the atomiser disk, together with the liquid to be atomised, to a drying chamber. This air mixes with the liquid to be atomised and stimulates, after atomisation, the formation of a voluminous powder with a low dumping weight. The disadvantages of a low dumping weight are:
THE REQUIRED ADDITIONAL PACKING MATERIAL, TRANSPORT MATERIAL, STORAGE SPACE ETC.;
FOAM FORMATION ON DISSOLVING THE PRODUCT;
A LOWER RESISTANCE TO HARMFUL AMBIENT INFLUENCES, SUCH AS OXIDATION, OWING TO A GREATER BOUNDARY SURFACE BETWEEN THE DRY SUBSTANCE AND THE AIR.
Various sealing means have been tried in order to limit this air intrusion, but at high rotational speeds the suction of the air is so strong that the conventional sealing means applied so far do not operate satisfactorily. Besides, it is difficult to seal the atomiser disk mechanically against suction of air from the drying space.