GB2130503A - Droplet distributor - Google Patents

Abstract

A droplet distributor, for use for example in applying liquid for horticultural or weed-killing and like purposes, has a spreader element 2 with a liquid-flow surface receiving liquid from the outlet 1a of a feed tube and forming it into droplets on fingers 3 contiguous with the liquid-flow surface, each finger extending by its free end beyond the liquid-flow surface, the fingers being of narrow cross-section such that the droplets are supported thereon by surface tension and can run along the finger and pass off the free end of the finger. The spreader element may be carried on a feed tube which is resiliently flexible to facilitate swinging of the distributor in an arcuate oscillation to distribute the droplets laterally over a wider area as the distributor is advanced. <IMAGE>

Description

SPECIFICATION Distribution of droplets This invention relates to the formation of droplets of liquid and their distribution over an area. It is particularly of use in, but is not restricted to, the formation and distribution of droplets of liquid for the purpose of treatment of ground, plants, crops and the like for horticultural, agricultural, pest control and weed-killing and like purposes.

The object of the invention is to provide a device which, without moving parts and thus without need for drive, serves to transform a flow of liquid into a succession of droplets originating at a plurality of spaced filaments, such that a relatively wide or narrow swathe to be treated can be covered by progressing movement of the device.

According to the present invention, a device, for the formation and distribution of droplets of a liquid, comprises means for conducting a flow of liquid to an outlet opening, a spreader element having a liquid-flow surface positioned for reception of liquid discharged from the outlet opening and adapted to form the liquid flow into a relatively thin and broad film, and a plurality of dropletforming fingers contiguous with the liquidflow surface, each finger extending by a free end portion beyond the liquid-flow surface, each finger being spaced laterally from each adjacent finger, each finger having a portion of its length adjacent the liquid-flow surface so as to be contacted by the liquid film flowing thereover, the fingers being of such narrow cross-section as to cause liquid from the film contacting them to be formed on the finger into a droplet which can run along the finger, whilst supported thereon by surface tension, and can pass off the free end of the finger.

In use, progressing of the liquid at least from the outlet opening across the liquid-flow surface, and onto and along the fingers, and off the end of the fingers, may be obtained by gravity, or as a result of centrifugal force due to movement of the device, or as a result of pumping of the liquid to the outlet opening, or by any combination of these means.

In a preferred construction, the spreader element has its liquid-flow surface in the form of a sector of a circle, with the outlet opening disposed adjacent the centre of arc, and the fingers extending substantially radially from the circumference of the liquid-flow surface, each finger preferably extending by a free end portion of the same length beyond the liquid flow surface.

The device may include baffle means on the liquid-flow surface between that zone of it which receives liquid from the outlet opening, and the fingers, and conveniently said baffle means comprise a plurality of ribs upstanding on the liquid-flow surface and disposed in spaced formation along rows which are spaced between the outlet opening and the fingers.

Conveniently, the fingers may be simple rods, wires, bristles of linear or smoothly curved shape secured directly to a surface of the spreader element serving as the liquidflow surface.

In a preferred form, the free end portion of the fingers is downturned with respect to the remainder of the finger.

The spreader element may include one or more upstanding walls to serve to restrict or prevent flow of liquid off an edge or portion of edge not occupied by fingers.

The means for conducting a flow of liquid to the outlet opening may comprise a resiliently flexible portion of feed tube having the spreader element at one end such that the spreader element can be oscillated in an arc by oscillating the other end of the portion of feed tube.

The feed tube may conveniently serve as a support or handle for the spreader element and its fingers, and in a preferred form, the liquid is supplied through an elongated tube serving as a handle by which the user may readily swing the device in a horizontal arcuate reciprocation for distribution of droplets over a wide swathe. To assist in, or to facilitate, lateral swinging motion of the device, the liquid supply means, e.g. an elongated handle, may otherwise be articulated or made flexible, for setting up and maintaining a natural lateral oscillation of the device with the hand.

Change of flow of the liquid from an outlet opening of relatively large bore to a film on the spreader provides the advantage that there are no fine holes which are likely to become blocked by deposits or dirt during use.

The device may be provided with a receptacle for bulk storage of liquid communicating with said feed tube.

In order that the nature of the invention may be readily ascertained, an embodiment of droplet distributor constructed in accordance therewith, and a manner of use, are hereinafter particularly described, by way of nonlimiting example, with reference to the figures of the accompanying drawing, wherein: Figure 1 is a plan view of the distributor; Figure 2 is a side elevation corresponding to Fig. 1; Figure 3 is a perspective view to show a manner of use.

The droplet distributor illustrated comprises a bulk delivery tube 1 secured on a spreader plate 2 on which are mounted a plurality of drop-forming fingers 3. In practical use of the distributor, liquid is supplied from any convenient source through the tube 1 to an outlet 1 a and then contacts the baffle ribs 4 so as to become spread out over the surface of the spreader plate 2. As the spreader plate is held, when in use, in an inclined position, or centrifugal force arises as a result of being swung in an arc, or both, the liquid film passes towards the radially inner end of the drop-forming fingers 3. The liquid encounters one or other of the fingers 3 and then runs along the fingers until beyond the edge of the spreader plate 2. Due to the small crosssection of the fingers 3, the liquid tends to break up into a succession of droplets, the dimensions of the droplets being a function of the cross-section of the fingers. Droplets forming from the fingers, due to inclination and/or centrifugal force, fall or are impelled towards the target area, e.g. a portion of soil, grass or other material to be treated with the liquid. A target area is covered by lateral swinging per arrow "A", coupled with advancing movement per arrow "B".

Referring now in detail to the components of the distributor, the delivery tube 1 may be of any convenient structure and formation, the only essential being that a bulk supply of the liquid is made available at the outlet 1 a.

In a preferred construction, the delivery tube 1 is made up of an inner tube, e.g. of stainless steel, having a fine bore selected to provide suitable flow of the liquid, and an outer covering tube, e.g. a hard plastics reinforcement, for protection of the inner tube and ease of handling.

The spreader plate needs to be oscillated from side to side for effective operation to cover a wider area than will result from simple flow of liquid off the lateral extremes of the distributor. This oscillation can be obtained by hand or mechanically. When obtained by hand, it can be obtained by the lateral swinging of a rigid supply tube 1, or a supply tube having a pivot joint or a resiliently bendable joint along its length, or again in a preferred form by making substantially the whole of the delivery tube of a resiliently bendable nature.

It is particularly convenient, for hand operation, if the nature of the delivery tube is such that the spreader plate end of it can be swung in an oscillatory arc (see Fig. 3) with a suitable natural period oscillation, so that the user's hand only has to supply a small impetus to keep the motion going. A natural swing of about 100 cycles per minute has been found to be useful for a hand held device.

Obviously, it would be possible to provide a motor-driven oscillation of the device, and two or more of them could be operated in tandem.

The spreader plate 2 serves as a means for forming the supplied liquid into a thin but widely spread film which is fed in the general direction of the fingers 3. To avoid loss-of liquid at the edges of the spreader plate, it may have edge portions (not shown) upturned, say by a few millimetres, to form a bounding wall. A similar upturned edge (not shown) to form a bounding wall, could be provided between each adjacent pair of fingers 3.

The device can be used for the distribution in droplets of any treatment liquid having a suitably low viscosity and surface tension.

Some commonly used treatment liquids, e.g.

fertilisers, weedkillers and the like, may normally have too high a surface tension, in which case it may be suitable to add a surface tension reducer to the liquid prior to use.

The bulk supply may be obtained from a container carried by the user, or from a tank or the like connected through a hose. In a convenient form for personai use, the operator has a bottle 5 of the liquid carried at a suitable height above the device, and feed is by gravity down to the distributor at a rate governed by the relative height of the bottle and distributor and the bore of the delivery tube. The rate of feed can readily be changed during use by altering the relative height, and starting and stopping of delivery entails no more than bringing the height of the bottle to, or below, that of the delivery device. In a more complex structure there may be provided means for ensuring a substantially constant rate of flow, irrespective of variations of relative height of the bottle and distributor, and such rate of flow may be adjustable and controllable on-off.

The droplet distributor can be used for very rapid total coverage of an area of ground, e.g.

for weed control or the like. The amplitude of lateral swinging movement determines the width of a swathe to be covered, with the droplets being propelled up to several metres laterally beyond the limit of swing of the device. The rate of forward movement governs the rate of application per unit of area, and in practice the operator can adjust this with experience as progress is made. The longer arcuate swing can be used for coverage of relatively large areas, and a much smaller natural, or hand-controlled, lateral swing can be used for more constricted areas, say narrow borders and the like.

Passage of the liquid from the bulk delivery outlet 1 a over the spreader plate 2 and onto the fingers 3 may be obtained by passage of air over the device, or venturi action, with or without the addition of pumping or gravity flow of the liquid, or inclination of the spreader plate 2. Such use could occur for example in crop-spraying from an aircraft fitted with one or a number of "heads" constituted substantially by that portion of the device which is illustrated in Figs. 1 and 2.

Rapid passage of air over the device, e.g.

aircraft slipstream, in the direction of the arrow "B" could cause the liquid to be sucked from the outlet 1 a, especially if a cowling were added to cause a lowering of local pressure by venturi action. Lateral swinging of the "heads" may not be necessary in an air stream in practice, but could be obtained by mechanical drive, or by addition of a pivoted wind vane adapted to give reversal of movement at the end of each swing.

Claims (10)

1. A device, for the formation and distribution of droplets of a liquid, comprising means for conducting a flow of liquid to an outlet opening, a spreader element having a liquid-flow surface positioned for reception of liquid discharged from the outlet opening and adapted to form the liquid flow into a relatively thin and broad film, and a plurality of droplet-forming fingers contiguous with the liquid-flow surface, each finger extending by a free end portion beyond the liquid-flow surface, each finger being spaced laterally from each adjacent finger, each finger having a portion of its length adjacent the liquid-flow surface so as to be contacted by the liquid film flowing thereover, the fingers being of such narrow cross-section as to cause liquid from the film contacting them to be formed on the finger into a droplet which can run along the finger, whilst supported thereon by surface tension, and can pass off the free end of the finger.

2. A device, as claimed in claim 1, wherein said spreader element hs its liquidflow surface in the form of a sector of a circle, with said outlet opening disposed adjacent the centre of arc, and said fingers extending substantially radially from the circumference of the liquid-flow surface.

3. A device, as claimed in either of claims 1 and 2, wherein each finger extends by a free end portion of the same length beyond the liquid-flow surface.

4. A device, as claimed in any one of claims 1 to 3, including baffle means on the liquid-flow surface between that zone of it which receives liquid from the outlet opening, and the fingers.

5. A device, as claimed in claim 4, wherein said baffle means comprise a plurality of ribs upstanding on the liquid-flow surface and disposed in spaced formation along rows which are spaced between the outlet opening and the fingers.

6. A device, as claimed in any one of the preceding claims, wherein the free end portion of the fingers is downturned with respect to the remainder of the finger.

7. A device, as claimed in any one of the preceding claims, wherein said means for conducting a flow of liquid to the outlet opening comprises a resiliently flexible portion of feed tube having the spreader element at one end such that the spreader element can be oscillated in an arc by oscillating the other end of the portion of feed tube.

8. In combination, a device, as claimed in claim 7, and a receptacle for bulk storage of liquid communicating with said feed tube.

9. A device, for the formation and distribution of droplets of a liquid, substantially as described herein with reference to Figs. 1 and 2 of the accompanying drawing.

10. The combination of droplet forming and distributing device and bulk storage receptacle substantially as described herein with reference to Fig. 3 of the accompanying drawing.