GB2099725A - Spraying apparatus - Google Patents

Abstract

Spraying apparatus comprises a rotary atomiser 10 and an axial fan 11 coupled to the atomiser to form a rotatable unit. The rotary atomiser 10 comprises a tubular spindle 12 for receiving a liquid to be sprayed, and a hollow foraminous atomising cylinder 15 rotatable around the spindle, means being provided to permit flow of liquid outwardly from the tubular spindle and through the foraminous atomising cylinder. A number of vanes 24 are mounted within the foraminous cylinder 25 radially outwardly of the tubular spindle 12 and rotatable with the cylinder so as to intercept and effect an initial breaking up of the liquid flow as it passes outwardly from the spindle to the foraminous cylinder. <IMAGE>

Description

SPECIFICATION Spraying apparatus The invention relates to spraying apparatus for distributing liquids and relates particularly to the low volume distribution of chemical aids to growing crops. Apparatus according to the invention is also suitable for low volume spraying of chemicals for many other purposes, such as for control of tsetse flies, mosquitoes, flies and locusts, and other forms of spraying for public health purposes.

Our co-pending British Patent Application No.

7929867 (Published Patent Specification No.

2,057,299A) discloses spraying apparatus comprising a rotary atomiser and an axial fan coupled to the atomiser to form a rotatable unit therewith, the axial fan being situated within a cowl which is shaped aerodynamically to control a blast of air generated by the axial fan when the unit is rotated, whereby, in use, the blast of air passes over the atomiser to disperse the droplets produced thereby. The present invention provides modifications and developments of the apparatus described and claimed in the above-mentioned patent application, and in particular provides an arrangement for improving the dispersion of droplets from the atomiser.

According to the invention there is provided spraying apparatus comprising a rotary atomiser and an axial fan coupled to the atomiser to form a rotatable unit therewith, wherein the rotary atomiser comprises a tubular spindle for receiving a liquid to be sprayed, a hollow foraminous atomising cylinder rotatable around the spindle, means being provided to permit flow of liquid outwardly from the tubular spindle and through the foraminous atomising cylinder, and one or more vanes mounted within the foraminous cylinder radially outwardly of the tubular spindle and rotatable with the cylinder so as to intercept and effect an initial breaking up of the liquid flow as it passes outwardly from the spindle to the foraminous cylinder.

The initial breaking up of the flow of liquid before it reaches the inner surface of the foraminous cylinder improves the dispersion of droplets from the apparatus so that an extremely low volume of liquid may be widely dispersed over a large area.

There may be provided a plurality of elongate vanes spaced around the axis of rotation of the foraminous cylinder and extending parallel thereto. Each said vane may lie in a plane extending substantially radially with respect to the foraminous cylinder. For example, there may be provided three vanes equally spaced around the axis of rotation of the cylinder.

The rotary atomiser may also comprise a perforate diffuser tube disposed concentrically between the tubular spindle and the foraminous cylinder. Preferably the vanes are located adjacent the internal surface of the diffuser tube.

In use, the apparatus may be mounted in a location where the axial fan is rotated by an air blast, and thus rotates the atomiser, the droplets from the atomiser being dispersed by the air blast.

For example, the apparatus may be mounted in the slipstream of a crop-spraying aircraft.

Alternatively, means may be provided for driving the rotatable unit, in which case the axial fan itself produces the blast of air for dispersing the droplets. In this case, the axial fan may be situated within a cowl which is shaped aerodynamically to control the blast of air, as described in the abovementioned British Patent Specification No.

2,057,299A.

The following is a detailed description of embodiments of the invention, reference being made to the accompanying drawings in which: Figure 1 is an axial section through a unit comprising a rotary atomiser and axial fan, Figure 2 is a section through an hydraulically driven spraying unit incorporating the atomiser of Figure 1, Figure 3 is a front view of the unit of Figure 2, and Figure 4 is a scrap section on the line A-A of Figure 3.

Referring to Figure 1 , the spraying apparatus comprises a rotary atomiser 10 and an axial fan 11 coupled together to form a single rotatable unit.

The atomiser comprises a fixed tubular spindle 12 which is supported on a mounting bar 13 and is provided at one end with a union 14 to which is connected a flexibie conduit for supplying the liquid to be sprayed to the interior of the spindle 12. The opposite end of the spindle 1 2 is closed by an end plug 15 and radial holes 1 6 are formed in the walls of the spindle 12 adjacent the end plug so that the liquid under pressure may pass radially outwardly of the spindle.

The hub 17 of the axial fan 11 is rotatably mounted on the spindle 1 2 by means of bearings 1 8. The hub is formed in two parts 19 and 20 which are held together by screws 21. The cylindrical root ends of three fan blades 22 are clamped in circular sockets formed by cooperating shaped parts of the hub portions 19 and 20, the arrangement being such that the pitch angle of the blades may be adjusted by loosening the screws 21 and separating the hub portions 19 and 20.

The blades 22 may then be turned to adjust their pitch whereafter the screws 21 are tightened up again to clamp the blades in their new position.

The fan blades may be formed from plastics material, such as "Delrin".

Although three fan blades are shown, any other suitable number of blades may be employed. For example, five blades may be used.

A diffuser tube 23 projects from one face of the hub portion 20 and encircles the end of the tubular spindle 12. The diffuser tube 23 may be formed from stainless steel and has a perforated surface, the perforations preferably extending over 80% of the surface of the tube, to allow the liquid passing from the spindle 1 2 to pass through the diffuser tube. Equally spaced around the internal surface of the diffuser tube 23 are three iongitudinally extending vanes 24 each vane lying in a generally radial plane. The vanes are secured at one end to an annular disc 24a which encircles the spindle 12, and at the other end to a disc 24b which is bolted to an end cap 27. The vanes 24 serve to intercept and effect initial breaking up of the liquid at it passes outwardly from the spindle 12 and before it passes through the diffuser tube 23.Although three vanes are shown, any other suitable number may be used, and the vanes may also be of other shapes. For example, the vanes may extend spirally as they extend longitudinally of the diffuser tube.

Encircling the diffuser tube 23 and spaced radially outwardly therefrom is a foraminous atomising cylinder 25, which may be formed from metal gauze. One end of the cylinder 25 is attached to a radially projecting flange 26 on the hub portion 20 and the opposite end is secured to the aforementioned end cap 27.

As shown in Figures 2 and 3, the axial fan 11 rotates within the downstream end of a fixed cowl 28. The rotary atomiser 1 0 projects clear of the downstream end of the cowl 28. The cowl may be formed from metal or plastics, such as glass fibre reinforced plastics.

In use the unit comprising the fan 11 and atomiser 10 is rotated and the liquid to be sprayed is delivered under pressure to the interior of the spindle 12. The liquid under pressure passes radially outwardly through the holes 1 6 in the spindle and is intercepted and broken up into droplets by the vanes 24 before passing through the diffuser tube 23. The droplets continue to move radially outwardly and pass through the gauze atomising cylinder 25 where they are further broken up to form extremely fine droplets.

As the droplets pass outwardly through the gauze cylinder 25 they become entrained in the blast of air from the axial fan 11, the blast being controlled and directed by the cowl 28, and the droplets are dispersed as a fine spray over the area towards which the unit is directed. The combination of the particular arrangement of the atomiser and the controlled blast of air causes extremely small volumes of liquid to be dispersed over a very wide area but in a controlled fashion, the dispersion being controlled by the pressure of the liquid and the pitch angle of the axial fan 11.

As best seen in Figure 2, a pulley 42 is coupled to the hub 17 of the axial fan and is driven through a drive belt 31 from a pulley 43. The pulley 43 may be driven from the output shaft of an internal combustion engine or, as shown in Figures 2 and 3, may be coupled to the output shaft of an hydraulic motor 44. The hydraulic motor 44 is driven in known manner by hydraulic fluid under pressure passing along flexible conduits. The hydraulic fluid may be pressurised by a portable power-driven fluid pump.

In a further alternative arrangement, not shown, the rotary atomiser is driven by a pneumatic motor, the motor being provided with air under pressure from any known portable air pump.

The aforementioned mounting bar 1 3 supporting the atomiser unit and the cowl 28 is connected to a support by support stays 45. The ends of the bar 1 3 are connected to the support stays 45 by adjustable clamping screws 46 so that the bar 13, and hence the cowl and atomising unit, may be tilted with respect to the support stays 45 by loosening the clamping screws 46, adjusting the position of the atomiser and cowl and then retightening the clamping screws. This arrangement is possible using an hydraulic or pneumatic motor since the motor can tilt with the atomiser unit due to the flexibility of the conduits supplying the hydraulic fluid or air under pressure to the motor. This tilting arrangement enables the angle of the cowl and atomiser unit to be adjusted with respect to the support as required.

The atomiser unit described with relation to Figure 1 has many applications and may be used in vehicle mounted spraying apparatus or in other large transportable spraying equipment or on aircraft.

In the case where a plurality of atomisers are mounted on a vehicle, for example on a spray bar on a tractor, the hydraulic or pneumatic motors of the atomisers are supplied with hydraulic fluid or air under pressure from a single pump mounted on the vehicle.

The rotatable unit comprising the axial fan 11 and atomiser 10 may also be used in situations where an air blast is separately provided, the cowl being omitted and the axial fan in this case merely acting as a turbine which is acted on by the air blast to rotate the atomiser. The provision of adjustable pitch blades allows them to be adjusted to the optimum pitch angle for such use. For example, the rotatable unit may be mounted on the conventional spray bar of a crop-spraying aircraft so that the axial fan rotates in the slipstream of the aircraft, the slipstream also dispersing the spray of droplets emitted by the rotating atomiser.The rotatable unit may also be used to adapt a conventional air blast orchard sprayer to low-volume spraying by mounting the unit in the air blast from the sprayer so that, again, the axial fan acts as a turbine which rotates the atomiser, the air blast also serving to disperse the droplets from the rotating atomiser.

In the above-described arrangements the rotating dispersion element of the atomiser is in the form of a cylindrical wire gauze. It will be appreciated however that other forms of rotating element may be used. Thus the wire gauze cylinder may be replaced by any other form of foraminous cylinder. For example, the cylinder may be formed from foamed metal which provides a labyrinth path for the liquid as it flows outwardly from the central spindle under centrifugal force.

Rotary atomisers employing such a construction are described in British Patent Specification No.

1,486,427. Alternatively, the atomiser may comprise a plurality of axially spaced rotating discs, the liquid flowing outwardly over the surfaces of the discs and being dispersed as fine droplets from the outer peripheries thereof.

Claims (9)

1. Spraying apparatus comprising a rotary atomiser and an axial fan coupled to the atomiser to form a rotatable unit therewith, wherein the rotary atomiser comprises a tubular spindle for receiving a liquid to be sprayed, a hollow foraminous atomising cylinder rotatable around the spindle, means being provided to permit flow of liquid outwardly from the tubular spindle and through the foraminous atomising cylinder, and one or more vanes mounted within the foraminous cylinder radially outwardly of the tubular spindle and rotatable with the cylinder so as to intercept and effect an initial breaking up of the liquid flow as it passes outwardly from the spindle to the foraminous cylinder.

2. Spraying apparatus according to claim 1, wherein there is provided a plurality of elongate vanes spaced around the axis of rotation of the foraminous cylinder and extending parallel thereto.

3. Spraying apparatus according to claim 2, wherein each said vane lies in a plane extending substantially radially with respect to the foraminous cylinder.

4. Spraying apparatus according to claim 2 or claim 3, wherein there are provided three vanes equally spaced around the axis of rotation of the cylinder.

5. Spraying apparatus according to any of claims 1 to 4, wherein the rotary atomiser includes a perforate diffuser tube disposed concentricaliy between the tubular spindle and the foraminous cylinder.

6. Spraying apparatus according to claim 5, wherein the vanes are located adjacent the internal surface of the diffuser tube.

7. Spraying apparatus according to any of claims 1 to 6, further comprising means for driving the rotatable unit.

8. Spraying apparatus according to claim 7, wherein the axial fan is situated within a cowl which is shaped aerodynamically to control the blast of air produced by the fan.

9. Spraying apparatus according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.