GB2118866A - Sprayers - Google Patents

Abstract

A sprayer, particularly for use in agricultural crop-spraying, has a rotary atomiser comprising a rotary frusto- conical part (20), a slotted cylindrical liquid distribution member (22) fixed centrally in the part (20), and a liquid distributor (23), also of frusto-conical form but inverted relative to the part (20), the distributor being fixed to said slotted liquid distribution member and surrounding and substantially enclosing it. The rotary part (20) is arranged to rotate in bearings (11) in a bearing housing (10) in a fixed part of the sprayer and a stationary liquid feed tube (15) supplies liquid to the member (22). The interior surface of the distributor (23) is smooth whilst the interior surface of the rotary part (20) is grooved. In use, the rotary part (20) is driven by the rotation of a turbine (19). A blower as the forward movement of a spray boom drives the turbine. The turbine blades may be of variable pitch. <IMAGE>

Description

SPECIFICATION Sprayers This invention relates to sprayers having rotary atomisers and has particular, though not exclusive application to agricultural 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 and ideally the droplets should be of uniform size.

The significance of control of droplet size is that, if they are too large they will not provide even coverage over foliage or other surfaces to be sprayed and they will also fall to the ground too quickly. Also excessive quantity of liquid tends to be expended. On the other hand if the droplet size is too small, the droplets will be too easily carried on the wind and again even distribution on the surface to be sprayed is impaired. There is therefore an optimum range whereby even distribution and minimum liquid material consumption is obtained this being usually in the range 20-500 microns in diameter.

Conventional pressure atomiser sprayers are not capable of giving small, uniform size droplets, so rotary atomisers having discs or hollow cones are preferred. Liquid is fed to the centre of the atomiser disc or cone and rotation results in migration of the liquid to the periphery from which it is discharged as a seriesfof droplets. The atomiser disc or cone advantageously has a serrated perimeter so that the liquid is discharged from a series of points of small dimensions and there may be 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, are obtained if the liquid issues from the points as discrete filaments which are broken up into droplets after leaving the atomiser.

In order to obtain even spray distribution from a rotary atomiser it is necessary to supply liquid to the rotary part disc or cone in such a manner that the distribution around the periphery, from which the liquid leaves the atomiser, is as uniform as possible. One arrangement is to provide a hollow shaft through which the liquid is discharged through a radial opening onto the adjacent rotating surface of the rotary part, but this can lead to uneven supply to the inner portion of the rotary part and therefore similarly uneven distribution at the periphery.

It is therefore the object of this invention to provide a sprayer of the kind having a rotary atomiser in which the supply of liquid to the surface of a rotary part of the atomiser is performed in a particularly efficient manner, enabling even spray distribution to be obtained, and uniformity of droplet size to be achieved.

According to the present invention there is provided a sprayer having a rotary atomiser including a circular periphery rotary part, to a surface of which liquid to be sprayed is supplied at a circular region disposed inwardly of the periphery of the part and the means for supplying liquid to the rotary part comprises an apertured rotary member, to the interior of which liquid is supplied, in use, and a rotary distributor surrounding the said apertured rotary member, having a circular surface of divergent form onto which liquid is deposited from the apertured rotary member, and the apertured rotary member having an outer peripheral edge disposed adjacent to and radially inwardly of the circular surface of the rotary distributor.

Preferably the rotary part has a frusto-conical surface which is provided with grooves leading towards the peripheral edge.

The arrangement in use is such that liquid is fed to the interior of the apertured rotary member and is discharged therethrough onto the surrounding rotary distributor surface and flows outwardly on this surface, in the form of an even film due to the centrifugal force, to be distributed evenly into the grooves on the circular region of the rotary part and then flows along the grooves towards the peripheral edge, at which it is discharged in droplet form.

The invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a sprayer with rotary atomiser constructed in accordance with the invention; and Figure 2 is a cross-sectional view of a similar sprayer with an alternative connector.

With reference to Figure 1, there is shown a sprayer having fixed and rotatable parts. The fixed parts include a bearing housing and mounting assembly and these in use are mounted on an appropriate structure such as a boom and there is a supply of liquid to be sprayed which may reach the sprayer through flexible piping. The sprayer is suitable for use singly or in multiples for agricultural crop spraying and has been designed to provide distribution of liquid in droplet form wherein the droplet size is as uniform as possible.

The rotary atomiser part is preferably rotated at very high speed for example of the order of 20,000 rpm and this enables the liquid to be discharged in droplet size of the order of 35 to 40 microns. The direction of spray is normally either horizontal or upwardly for example for spraying trees but in some circumstances downward spray is required and the sprayer illustrated is intended for use in any orientation.

Figure 1 shows the sprayer having stationary parts including a bearing housing 10 of cup-shape in which is a pair of contacting bearings 11, each having respective inner and outer races. These bearings are held in place by a member 12 secured by screws 13. The member 12 includes a tubular spigot portion which engages inside the bearing housing 10 and locates against the outer race of one of the bearings 11. In this way the bearings are located axially. The bearings are a press fit in the housing 10 so as to prevent outer race rotation.

The member 12 has a series of holes 14 which open into the interior of the bearing housing. In use, a negative pressure is created at the upper open end of an inner tube 1 5 and this causes air to flow through the holes 14, to assist the prevention of liquid flowing back down the shaft to the ball bearing as well as permitting drainage of excess liquid, as will later be described.

The member 12 has a cylindrical extension which has a small central bore containing the inner tube 1 5. At its end remote from the bearing housing 10 this extension is threaded to receive an adaptor 1 6 for connection to a flexible pipe (not shown) through a conventional fir tree type connection.

The adaptor 1 6 encloses the end of the inner tube 1 5 and this is sealed in the extension of the member 12 by means of an O-ring 17 which is trapped between the end of the adaptor 16 and a shoulder in the extension of the member 12. In trapping the O-ring, it is firmly pressed against the inner tube and thus acts in the manner of an olive.

Surrounding the cylindrical extension of the member 12 is a vibration damping rubber mounting spool 18 whereby the whole assembly can be mounted on the boom or other structure.

The rotary atomiser portion of the sprayer includes a turbine 19 with three blades, although other numbers of blades can be used. This is mounted on a rotary part 20 which is of frustoconical form with a spigot extending from its narrower end. The spigot, which is hollow, is threaded at its end and receives a nut 21 and a lock washer 21 a, whereby the spigot is secured in the inner race of the bearings 11. The internal bore of the spigot of the rotary part 20 is of a size larger than the inner tube 1 5 of the stationary part of the sprayer so that there is a clearance around the tube which extends right through that spigot. The spigot extends into the interior of the cup-shape formed by the frusto-conical part and the inner tube extends a short distance beyond this.

Tightly frictionally or otherwise engaged over this portion of the spigot of the part 20 is an apertured rotary member 22, which thus rotates with the rotary part 20. This is in the form of a small closed ended cylindrical component with radial slots in its wall. The slots may however be replaced by a series of equally spaced slots, holes or other shaped apertures.

The slots extend from the closed end of the component to terminate substantially at the end of the spigot of part 20, as shown in Figure 1.

Surrounding and substantially enclosing the apertured rotary member 22 is a rotary distributor 23. This is in the form of a frusto-conical cup which is inverted with respect to the larger frustoconical cup formed by the rotary part 20. To retain the rotary distributor 23 with its closed narrower end resting on the top of the apertured rotary member 22, a nut 24 is engaged on a threaded portion (not shown) formed integrally on the end of the apertured rotary member 22. Thus the distributor 23 rotates with the member 22 and thus also with the rotary part 20.

The interior surface of the rotary distributor 23 is smooth to allow the formation of a liquid film of even thickness due to centrifugal force but is outwardly divergent and terminates in a circular relatively fine peripheral edge 25, which is disposed close to, but spaced from the interior surface of the rotary part 20.

The interior surface of the rotary part 20 is, like that of the distributor, outwardly divergent, but is of course of opposite slope. This internal surface is grooved (although not shown in the drawing) and the grooves extend substantially in radial planes as described in U.K. Published Patent Specification No. 2026904A. The grooves terminate at the peripheral edge 26 of the rotary part 20 in a series of points. The grooves are aligned with the respective points and there are, in a typical example, 360 grooves and corresponding teeth. The tooth form may however be asymmetrical as shown and described in the specification of U.K. Patent No. 2004204B.

Except for the inner tube 15 and the bearing and screws, the parts may conveniently be made from plastics materials.

In use, liquid is supplied under pressure through the adaptor 16 and into the inner tube 15. From the end of the stationary inner tube, the liquid is ejected by centrifugal force from the interior of the apertured rotary member 22 and is expelled through the slots to be deposited on the interior frusto-conical surface of the rotary distributor 23 at or near the smaller diameter portion thereof.

The liquid flows over this smooth interior surface under the action of centrifugal force and leaves the peripheral edge 25 of the rotary distributor, to be distributed on to the internal frusto-conical surface of the rotary part 20. This occurs onto a circular region of the rotary part surface, at which the grooves start and which is radially outwardly of the peripheral edge 25 of the rotary distributor 23.

The liquid now flows along the respective grooves towards the peripheral edge of the rotary part 20 and leaves from the respective points 26 as a series of droplets. The grooves form respective reservoirs for the liquid in that the radial outward flow of the liquid is restricted by the forces acting on it which are centrifugal and rotational. This arrangement ensures even distribution of the liquid around the rotary part 20 so that spray discharge is evenly distributed.

The use of the rotary distributor 23 provides a particularly efficient manner of distributing the liquid onto the surface of the rotary part 20 and it is possible to provide adequate coverage of crop with minimum liquid usage.

Since the droplets leaving the rotary atomiser have little inertia shortly after leaving the points at the peripheral edge 26, it is therefore convenient to mount the atomiser in the outlet of a blower device such as found on a conventional airblast sprayer used in orchards and vineyards or in an aeroplane boom, where the airstream is created by forward travel.

The blades of the turbine 1 9 are profiled to enable them in a stream of air from a blower or existing by virtue of the forward movement of the boom, to rotate the rotary part of the sprayer and it is possible to provide variable pitch blades whereby the speed can be regulated.

The holes 14 in the member 12 of the stationary part of the sprayer provide for inflow of air which can enter the interior of the apertured rotary member 22, as a result of the negative pressure as already described at the open end of the tube 1 5.

When the device is at rest liquid can sometimes flow between the inner tube 1 5 and the spigot formed integrally with the rotary part 20 and in order to protect the bearings 11 such liquid can escape through the holes 14. Thus if the sprayer is in the position shown in the drawings with the rotary part 20 uppermost any such liquid will flow straight out through the holes 14. If on the other hand, the sprayer is in the opposite position with the rotary part 20 downwards there will be no tendency for the liquid to flow into the bearing housing 10. Similarly the sideways orientation liquid will be allowed to flow out through the holes 14.

By holding the outer race of the bearings 11 stationary and rotating the inner race the tendency for dirt to collect in the outer race is minimised.

In the version shown in Figure 2 most of the parts are the same as those in the Figure 1 construction except that the mounting arrangement differs. The m'ounting spool 1 8 is omitted and in piace of the adaptor 1 6 there is an alternative adaptor 27 with an end flange which engages with a union nut 28. Other mounting arrangements can be adopted as required. In addition, only one bearing 11 is shown.

In this example the inner tube 1 5 has at its end a small disc 29 which prevents liquid flowing through the clearance between the inner tube 15 and the spigot of the rotary part 20 and may also assist in the even discharge of the liquid from the apertured rotary member 22 which surrounds it.

Claims (12)

1. A sprayer having a rotary atomiser including a circular periphery rotary part, to a surface of which liquid to be sprayed is supplied at a circular region disposed inwardly of the periphery of the part and the means for supplying liquid to the rotary part comprises an apertured rotary member, to the interior of which liquid is supplied, in use, and a rotary distributor surrounding the said apertured rotary member, having a circular surface of divergent form onto which liquid is deposited from the apertured rotary member, and the apertured rotary member having an outer peripheral edge disposed adjacent to and radially inwardly of the annular surface of the rotary distributor.

2. A sprayer as claimed in claim 1, wherein said rotary distributor is in the form of a frusto-conicai cup having a base at one end and defining at its other, open end a circular peripheral edge, the interior surface of the distributor being smooth and diverging away from said base towards said open end.

3. A sprayer as claimed in claim 2, wherein said distributor is secured to said apertured rotary member so that it rotates therewith.

4. A sprayer as claimed in claim 3, wherein said apertured rotary member is substantially enclosed by said distributor, with the base of the distributor being secured to an outer end of the apertured rotary member, the inner end of the rotary member being engaged with said rotary part for rotation therewith.

5. A sprayer as claimed in claim 4, wherein said rotary member has an open interior portion which communicates with apertures in the outer surface of said rotary member, and a liquid supply tube terminates within said interior portion to supply liquid thereto, in use, rotation of said rotary member causing liquid to be ejected from said interior portion and through said apertures onto the smooth interior surface of the distributor.

6. A sprayer as claimed in claim 5, wherein said rotary part is in the form of a frusto-conical cup having a base with an upstanding spigot, with which said rotary member is engaged.

7. A sprayer as claimed in claim 6, wherein the frusto-conical interior surface of the rotary part widens in the opposite direction from the frustoconical interior surface of the distributor and said peripheral edge of the distributor is disposed in juxtaposition to said circular region of the rotary part, which region is disposed adjacent said base of the rotary part.

8. A sprayer as claimed in claim 6 or claim 7, wherein said rotary member is of hollow cylindrical form having a multiplicity of equispaced radial slots in its cylindrical surface, each slot extending from said outer end of the rotary member to a position substantially at the end of the spigot of the rotary part.

9. A sprayer as claimed in any one of claims 6 to 8, wherein a hollow spigot depends from said base of the rotary part and is secured to the inner race of at least one bearing comprising a rotatable inner face and a relatively fixed outer race, the or each bearing being disposed in a bearing housing of a relatively fixed part of the sprayer.

10. A sprayer as claimed in claim 9, wherein said liquid supply tube extends through said depending hollow spigot with a clearance therearound, said depending hollow spigot terminates in said bearing housing and at least one aperture is provided in a wall of the bearing housing to allow any liquid flowing into said bearing housing by way of said clearance, in use, to escape therefrom.

11. A sprayer as claimed in any one of the preceding claims, wherein a multiplicity of grooves are provided in the interior surface of the rotary part, the grooves extending from said circular region to the open end of said rotary part.

12. A sprayer substantially as hereinbefore described with reference to, and as shown in, Figure 1 or Figure 2, of the accompanying drawings.