Rotary atomizer with asymmetrical teeth

#This invention relates to rotary atomisers, and has particular, though not exclusive, application to crop-spraying equipment.

#Liquid sprays are applied to crops and agricultural land for a variety of reasons but a principal use is for the application of pesticides, which may be herbicides, insecticides or fungicides. For efficient use of these relatively costly materials it is important that the droplets in the spray are of a size suitable for the application (usually between 20-500 microns diameter). Ideally the droplets should be of a completely uniform size, and the nearer this ideal can be approached the better.

#Conventional pressure atomisers are not capable of giving uniform size droplets, so rotary atomisers are preferred, e.g., discs or hollow cones. Liquid is fed to the center of the atomiser and rotation results in migration of the liquid to the periphery and discharge as a spray of droplets. The atomiser may have a serrated perimeter so that the liquid is discharged at a series of points of small dimensions, and it may have radial grooves to feed the liquid to these points. Such a design is based on the observation that the best results in terms of droplet size and uniformity of size, are obtained if the liquid issues as discrete filaments which are broken up into droplets after leaving the atomiser.

#The invention is illustrated with reference to the accompanying drawings in which

#FIG. 1 is a section through a single atomiser,

#FIG. 2 is a section through a stack of atomisers,

#In FIG. 1 a hollow truncated cone has a flat base 1, and a skirt 2 inclined at an angle of 60.degree. to the axis of the cone. On the inside of the skirt are radial grooves 3, there being 180 in all. The top of the skirt is turned over to form a lip 4 at right angles to the central axis of the cone and the inner surface of the cone has a smooth rounded contour 5 where the angle changes. The lip is formed of 180 teeth 6, the shape of which is shown by the detail (FIG. 1(B)) which is a view from direction B in FIG. 1. It will be seen that each tooth 6 has one edge which is radial with respect to the central axis of the cone and one edge which is curved and at an angle to the radius. Each groove 3 is asymmetric, one side being at 90.degree. and the other at 45.degree., and the top of each groove 3 is of the same width and contour as the gap between the teeth to give a smooth feed-way for liquid from each groove to each tooth.

#The flat base 1 has a hollow portion 7, and a hollow central shaft 8 extends upwardly from the base. A bearing (not shown) may be seated in the hollow portion 7, and there may be another bearing (not shown) at the top of shaft 8. The cone is rotatable about the bearings, the drive being either from a belt (not shown) around the shaft 8 or directly from a motor (not shown). The direction of rotation is counterclockwise as shown by the arrow of FIG. 1(B) so that the radial edge of each tooth is the leading edge.

#A stationary pipe 9 is positioned within the cone, this pipe being connected to a reservoir for liquid (not shown). In operation liquid flows by gravity from the reservoir through pipe 9 to form a pool of liquid in the annulus 10 at the base of the cone.