GB2150047A - Spray device - Google Patents

Abstract

A spray device for spraying plants has a spinning inverted cone (20). The liquid to be sprayed is introduced at the vertex (28) of the cone, travels up the internal cone wall under the influence of centrifugal force and leaves the top edge (30) of the cone in the form of droplets. In order to control the spray pattern, an area of low pressure (34) is created below the cone, thus drawing the droplets towards the cone axis. This is done by mounting a fan (32) coaxially below the cone so that air is drawn from above the fan to create a low pressure area. <IMAGE>

Description

SPECIFICATION Spray device Field of the invention This invention relates to a spray device, for producing a finely divided spray of liquid, for example for applying liquid agrochemicals over an area planted with a crop.

Background to the invention In order to ensure efficient application of agricultural or horticultural chemicals to crops or other targets, it is desirable first to finely disperse the chemical into fine droplets and then secondly to direct these droplets to the desired target area.

A conventional controlled droplet application technique makes use of an inverted, spinning cone into which the liquid is introduced at the bottom. The liquid travels up the cone wall under the influence of centrifugal force, and leaves the top edge of the cone in the form of finely dispersed droplets.

This technique is very effective in producing the necessary finely dispersed spray. Unfortunately however the droplets are ejected in a horizontal plane and only move downwards towards the ground under the influence of gravity. As a result, an umbrella shaped pattern of droplets, with a hollow centre is formed. Furthermore, since the droplets are not directed after they have left the cone, the umbrella shaped pattern is rather sensitive to distortion produced by windy conditions, which means that the droplets may not actually fall where intended.

Summary of the invention According to the present invention, there is provided a spray device comprising an inverted hollow cone, means for rotating the cone at high speed, and means for introducing liquid to be sprayed into the vertex of the cone, wherein a fan is mounted below the cone and means are provided for rotating the fan at a high speed in order to produce an area of low pressure immediately below the outlet from the periphery of the cone.

The fan and the cone may be fixed to one another, and driven by a common drive means. The cone and the fan may typically be revolving at speeds of between one thousand and eight thousand rpm.

The area of low pressure produced by the rotating fan causes the droplets emitted from the periphery of the cone to be drawn downwards towards this low pressure area. As a result, the droplets are provided with a positive directional influence after leaving the cone which makes them less sensitive to ambient wind and also causes them to travel in an effective direction towards the target area.

An associated advantage is that the down draught produced by operation of the fan, below the fan, tends to blow apart the foliage to which the spray is to be applied, so that the droplets are given access right into the plant.

Brief description of the drawings The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of the action of a known spray device; Figure 2 is a cross section through a spray device in accordance with the invention; and Figure 3 is a schematic diagram showing the spray pattern produced in accordance with the invention.

Description of the embodiments Fig. 1 shows a spray device 10 mounted on a boom 1 2. The spray device 10 has an inverted cone 1 4 which is rotated at high speed to cause liquid introduced from the boom 1 2 into the cone 14 to be emitted from the rotating cone periphery in the form of droplets 1 6. Fig. 1 showns the droplet pattern which is produced where the droplets travel in a trajectory horizontal with respect to the ground until gravitational forces overcome the droplet emittance velocity when they will tend to descend vertically at their terminal velocity.

It has been found that droplets produced in this way are sensitive to ambient wind conditions, and the whole "umbrella" pattern of droplet dispersal can be distorted under windy conditions.

Fig. 2 shows a spray device in accordance with the invention. An inverted cone 20 is mounted below a fixed plate 22. The cone 20 is spun at a high speed, for example at between one thousand and eight thousand rpm. Two inlet pipes 24 and 26 for the liquid to be dispersed are shown in the figure. These inlets lead down into the vertex 28 of the cone. Liquid which enters the cone from these inlets is then driven up the internal cone wall by the centrifugal force resulting from the rotation of the cone. The centrifugal force also serves to ensure that when the liquid reaches the lip 30 of the cone, it is finely dispersed and the hydrodynamic conditions at this point lead to the liquid leaving this lip in the form of fine droplets. The droplets at this stage have a strong horizontal component of velocity.

Below the cone 20, a fan 32 is mounted and is secured to the cone so that the cone and the fan rotate together. The fan is arranged so that it draws air from above and discharges air below itself. This results in the production of an area of low pressure above the fan, which is indicated in the drawing as a shaded area 34. Air from the surroundings is drawn into this low pressure area through the curtain of droplets, and the droplets are influenced by this flow and caused to move in a downward direction.

Fig. 3 shows the influence that the fan 32 has on the droplet pattern. When compared with Fig. 1, Fig. 3 shows a much tighter droplet pattern, with the droplets moving vertically much sooner than they do in the known device. Furthermore, because the droplets are subjected to a positive directing influence after having left the cone, they are much less susceptible to being displaced in windy conditions, and tests have shown that winds as high as 25 mph have not caused any pattern displacement.

Furthermore, as shown in Fig. 3, the down draught produced by the fan 32 opens up the plant below, and allows the spray to be directed right to the heart of the plant.

The fan 32 can be of any convenient form, so long as it acts to move air in a downward direction relative to the cone axis.

Claims (4)

1. A spray device comprising an inverted hollow cone, means for rotating the cone at high speed about its own axis and means for introducing liquid to be sprayed into the vertex of the cone such that the liquid travels up the internal wall of the cone and emerges around the upper periphery of the cone, wherein a fan is mounted below the cone and means are provided for rotating the fan at a high speed in order to produce an area of low pressure immediately below the outlet from the periphery of the cone.

2. A device as claimed in Claim 1, wherein the fan and the cone are fixed to one another, and are driven by a common drive means.

3. A device as claimed in Claim 2, wherein the drive means is arranged to drive the cone and the fan at speeds of between one thousand and eight thousand rpm.

4. A spray device substantially as herein described with reference to Fig. 2 and Fig. 3 of the accompanying drawings.