NZ610590A - Spraying apparatus - Google Patents

Abstract

An agricultural spraying apparatus and mixing tank is disclosed. The apparatus has a tank (20) configured to receive a volume of fluid and an opening (11) at an upper part of the tank for introduction of particulates into the volume of fluid. An impeller (21) mounted in a housing (22) within the tank causes a fluid flow through the housing, thereby creating fluid flow within the tank. One wall (38) of the tank may be shaped to receive this flow (36) so to send the flow up and over to create a turbulent water curtain at the opening to the tank. A spray arrangement including one or more spray outlets is fed from the tank. This arrangement allows for efficient mixing of the initial ingredients of the spray and the maintenance of the suspension.

Description

Our Ref: MFD032NZ Patents Form No. 5 S ACT 1953 Complete After Provisional No. 600050 filed 17 May 2012 COMPLETE SPECIFICATION NG APPARATUS We, Metalform (Dannevirke) Limited, a New Zealand company of Easton Road, Dannevirke, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: SPRAYING APPARATUS FIELD OF THE INVENTION The invention relates to a ng apparatus, particularly but not exclusively to an tus for spraying suspended particulate and/or biologically active material in agricultural or horticultural settings. The invention also relates to a spray mixing apparatus, particularly but not exclusively to an tus for mixing particulate spray materials into sion.

BACKGROUND TO THE INVENTION Sprays are widely used in various applications, including horticultural and agricultural applications. Sprays include fertilizers and chemicals for pest or disease control. Liquid sprays may be d directly or diluted with water.

Particulate sprays may be dissolved in water or, for insoluble or partially soluble materials, suspended in water for spraying. Recently various biologically active sprays have been proposed and these are applied in a similar manner.

Sprays are typically applied by a trailer or vehicle-mounted sprayer. ation of fine powders in suspension is ble e it provides faster chemical uptake and reduces undesirable runoff into watenlvays. However, fine powders are difficult to apply. Prior sprayers suffer from poor formation or maintenance of the suspension (i.e. the powder does not mix adequately with water or settles out after mixing but before spraying). If powder settles from the suspension it can solidify into an ely hard substance which is difficult to clean. The settled powder is also wasted. These ulties also lead to undesirable variation in application rates and increased costs.

The Applicant devised certain apparatus and methods as disclosed in its patent application no. PCT/N22011/000086 published as /149365, the contents of which are hereby incorporated by reference herein. In some embodiments that apparatus uses a single pump to cause mixing of particulates into fluid and spraying of the suspended particulates. The Applicant has found that there is room for further improvement, particularly but not exclusively in higher volume spraying machines.

It is an object of the invention to provide an improved spraying system and/or spray mixing apparatus or at least to provide the public with a useful choice.

SUMMARY OF THE INVENTION In a first aspect the invention provides an agricultural or horticultural spraying apparatus including: a tank configured to receive a volume of fluid; an opening at an upper part of the tank for introduction of particulates into the volume of fluid; a spray arrangement including one or more spray outlets; a fluid outlet in the tank, through which fluid may flow to the spray arrangement; and an impeller mounted in a housing within the tank so as to cause, in use, fluid flow through the housing, y creating fluid flow within the tank, wherein the impeller and the opening are arranged such that the fluid flow created by the impeller forms a mixing flow in a region below the opening.

Preferably, in use, the fluid flow within the tank ts particulate from settling out of suspension.

Preferably the fluid flow within the tank es a mixing flow for mixing of particulates into the fluid.

Preferably the er and the opening are arranged such that the fluid flow created by the impeller forms a mixing flow in a region below the opening.

Preferably the mixing flow is a flow downwards and across the opening. ably the mixing flow meets a main fluid body in a region of high turbulence. ably the impeller is positioned near the bottom of the tank.

Preferably the impeller, a first wall of the tank and the opening are arranged such that the impeller causes fluid flow across a lower region of the tank towards the first wall of the tank, upwards near the first wall of the tank and away from the first wall of the tank beneath the opening.

Preferably the first wall of the tank is a curved wall configured to encourage redirection of the fluid flow.

Preferably, in a plane perpendicular to a rotational axis of the impeller, the tank widens from a narrow region in a lower part of the tank in which the propeller is positioned to a wider region above the lower part.

Preferably the impeller is arranged to receive power from a power take-off drive.

Preferably the housing is an elongate g.

Preferably the housing forms an te tunnel within which the impeller is positioned.

Preferably the impeller is positioned at a point along the length of the g.

Preferably the spraying apparatus r includes a pump arranged to supply fluid from the tank to the spray arrangement.

Preferably the spray arrangement is a recirculating spray arrangement Preferably the spray arrangement includes a flow loop leading from the tank and returning to the tank and one or more spray outlets positioned in the flow loop; the pump being arranged to cause flow of fluid from the tank through the flow loop, and the apparatus being configured such that, during spraying, only a portion of fluid passing h the flow loop exits through the spray s, with the remainder of the fluid returning to the tank for recirculation.

Preferably the flow loop includes one or more spray booms, one or more of the spray outlets being positioned in each spray boom.

Preferably the spraying apparatus includes a spray valve positioned ream of the spray s, the spray valve having an open position and at least one restricted flow on, wherein the pressure at the spray s is higher when the spray valve is in the restricted flow position than when it is in the open position. 1O Preferably the spraying apparatus is configured to spray less than 20% of fluid passing h the flow loop. Preferably the spraying apparatus is configured to spray around 3 to 10% of fluid passing through the flow loop.

Preferably the spraying apparatus is configured to supply fluid to the spray arrangement at a rate in the range 500 to 800 litres per minute.

Preferably the spraying apparatus is configured as a trailer for towing behind a vehicle or configured to be mounted on a vehicle.

Preferably the spraying apparatus is configured to operate at a pressure less than 35 pounds per square inch. Preferably the ng apparatus is configured to operate at a pressure less than 30 pounds per square inch. ably the spraying apparatus is configured to operate at a pressure less than 25 pounds per square inch.

Preferably the spraying apparatus is configured to maintain a particulate in suspension in the tank for ng.

Preferably the material to be sprayed is or includes a particulate material and is sprayed in suspension.

Preferably the particulate has an average particle size less than 100 microns.

Preferably the particulate has an average le size less than 50 microns.

Preferably the particulate has an average particle around 5 microns.

Preferably the material to be sprayed is or includes a component that is biologically active.

Preferably the spraying apparatus is an agricultural or horticultural spraying apparatus.

In a second aspect the invention provides a spray mixing apparatus including: a tank configured to e a volume of fluid; an opening at an upper part of the tank for introduction of particulate spray material into the volume of fluid; and an impeller mounted in a housing within the tank so as to cause fluid flow from the tank through the g, thereby creating fluid flow within the tank.

Preferably the apparatus further includes a fluid outlet in the tank, through which fluid may be pumped.

Preferably the fluid flow within the tank provides a mixing flow for mixing of particulates into the fluid.

Preferably the er and the opening are arranged such that the fluid flow created by the impeller forms a mixing flow in a region below the opening.

Preferably the mixing flow is a flow downwards and across the opening.

Preferably the mixing flow meets a main fluid body in a region of high turbulence.

Preferably the impeller is positioned near the bottom of the tank.

Preferably the impeller, a first wall of the tank and the g are arranged such that the er causes fluid flow across a lower region of the tank towards the first wall of the tank, upwards near the first wall of the tank and away from the first wall of the tank beneath the opening.

Preferably the first wall of the tank is a curved wall red to encourage redirection of the fluid flow.

Preferably, in a plane perpendicular to a rotational axis of the impeller, the tank widens from a narrow region in a lower part of the tank in which the propeller is positioned to a wider region above the lower part.

Preferably the impeller is arranged to receive power from a power take-off drive.

Preferably the housing is an elongate housing.

Preferably the housing forms an elongate tunnel within which the er is positioned. ably the impeller is positioned at a point along the length of the housing.

Preferably the apparatus further includes a pump arranged to pump mixed spray al from the tank. ably the apparatus is configured to maintain a particulate in suspension in the tank. ably the particulate spray material has an average particle size less than 100 microns. Preferably the particulate spray material has an average particle size less than 50 microns. Preferably the particulate spray material has an average particle around 5 microns.

The word "fluid" is used in this specification to mean liquids and solutions but also suspensions of ulates in fluids.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example only. with reference to the accompanying drawings, in which: Figure1 is a top perspective view of an apparatus according to one ment; Figure 1A is a bottom perspective view of the apparatus of Figure 1; Figure 2 is a front view of the apparatus of Figure 1; Figure 3 is a simplified cross-section along the line 3-3 in Figure 2; Figure 4 shows a propeller in a housing, as used in the apparatus of Figure Figure 5 is a schematic diagram showing flow paths in an apparatus according to a further embodiment; Figure 6 is a schematic diagram showing flow paths in the apparatus of Figure 1; and Figure 7 further illustrates flow paths in the apparatus of Figure 1.

ED PTION Figure 1 shows a spraying apparatus 1 configured as a trailer unit for towing behind a vehicle. The apparatus 1 includes a towbar 2 for connection to the towing vehicle. The apparatus is supported on a number of wheels 4.

The apparatus 1 es a pump 5, tank 6 and one or more spray booms 7. The pump operates to supply spray fluid from the tank 6 through the spray booms 7 to spray outlets 9.

The pump 5 may be any suitable pump for maintaining the required res and flow rates. In one embodiment the pump 5 may be a hydraulic pump and may be ted to a tractor or truck hydraulic supply. However, other suitable pumps may be used, including petrol-powered pumps, for example.

The tank 6 may be formed of any suitable material, preferably of moulded plastic.

The tank 6 has an g 11 which allows fluids (e.g. water) and spray materials to be added to the tank, and also allows user access to the tank interior.

Alternatively, further openings, for example a hose connector, may be provided for addition of water or other fluids to the tank 6. The opening 11 may be provided with a raised rim 11’.

In a preferred embodiment the spray booms 7 form part of a closed flow loop as discussed in the Applicant’s W02011/149365, the contents of which are hereby incorporated by reference herein. That is, fluid to be sprayed flows from the tank to the spray booms and then back to the tank. Only a part of the fluid circulating in this way is sprayed from the outlets 9 with any one circulation.

In the embodiment shown the spray booms 7 are mounted to fold back along the sides of the tank 6 for ease of transport, as shown in the front view of Figure 2, and to fold out to the operating position of Figure 1. However, in other embodiments the spray boom may be fixed or indeed no spray boom need be provided. For example, a flow path could lead to single spray outlet oned underneath or at the rear of the tank 6.

In the ment shown a crane 12 is mounted near the front of the tank 6.

This allows very large bags of particulate to be lifted for introduction into the tank g 11. While particulates can be stored in small sacks up to around 50kg, they may also be provided in much larger bulk sacks or bags of around 0.5 - 1 tonne in weight. Clearly such large sacks or bags cannot be manually lifted, and must be lifted either by a crane 12, or if the apparatus 1 does not e a crane 12, by a separate machine such as a front-end loader, forklift or the like.

In one embodiment the tank may have a capacity of imately 2 to 20 cubic metres, preferably 2 to 10 cubic , ideally 2 to 5 cubic metres.

Figure 1A is a bottom perspective view of the apparatus of Figure 1. This shows the chassis 13 of the apparatus 1 and the underside of the tank 6. An outlet 14 at a low point of the tank 6 is provided for pumping of spray material from the tank 6 via conduit 45, as will be discussed further below.

Figure 2 is a front view of the spraying apparatus 1. Figure 3 is a section along the line 3-3 shown in Figure 2. Figure 3 is provided to show the tank shape, impeller and housing as described below, and for clarity many other features are omitted from Figure 3.

An impeller 21 is mounted in the tank 6, ably near the bottom of tank 6.

The impeller 21 may be based on any suitable rotor or ler. The impeller 21 is mounted in a housing 22. The housing may form an elongate tunnel within which the er is positioned.

The impeller 21 is mounted on a shaft 23. The shaft 23 is connected via couplings 25, 26, 27 and further shafts 29, 30, 31 to a power take-off (“PTO”) coupling 32 that is configured for connection to the PTO of a farm tractor or other suitable drive . In one embodiment this arrangement therefore provides a rotor driven by the PTO system of a towing vehicle. In other embodiments the tank may be mounted directly on a truck s or truck bed and the impeller may be powered by the truck's PTO system.

The shaft 31, with couplers 27, 32 may be a removable, extendible shaft that can be attached once the apparatus is hitched to a towing e by the tow-bar 2.

Figure 4 is an end view of the housing 22, rotor 21 and shaft 23. The cross- sectional shape of the housing may vary, and may be circular, elliptical or polygonal. In the embodiment shown the housing is nal.

Rotation of the impeller 21 causes fluid to flow in a first end 34 of the housing 22 and out a second end 35 of the housing 22. This highly directional flow causes circulation of fluid within the tank, as indicated by the arrows 36, 37. Flow towards the back of the tank 6 is forced upwards as it meets the back wall 38. At ient impeller power, the fluid will flow upwards in this region beyond the level 39 at which the fluid surface would lie in the absence of any flow. The level 39 is marked by a dashed line 39 in Figure 3. However note that this level 39 will vary, and in particular will fall as material is sprayed from the spraying apparatus 1.

Fluid then flows forwards past the opening 11. As the power provided by the er 21 increases, the flow 36 also becomes increasingly powerful. At sufficient impeller power, the fonlvard flow past the opening 11 forms a descending mixing or curtain flow, with fluid passing from the back of the tank forwards and downwards past the opening 11 before meeting the body of fluid in a highly turbulent manner. This creates a very efficient mixing zone immediately under the opening 11 for the introduction of particulates into the fluid. Particulate introduced into the opening 11 is ed by the n flow and forced downwards into a region of high ence. Fluid then flows forwards in the tank and re—enters the housing 22, as indicated by the arrow 37. in some embodiments the creation of the curtain flow past the opening 11 may be enhanced by suitable shaping of the tank walls. As shown in Figure 3, the rear wall 38 of the tank may be curved to encourage flow as marked by arrow 36.

Further, the upper part 40 of the rear wall may be shaped to encourage flow fonNards and downwards past the opening 11. As shown, the upper part 40 of the rear wall 38 is higher than the g 11 and slopes downwards towards the opening 11.

The formation of the curtain flow may also be assisted by the shape of the tank in a plane perpendicular to the plane shown in Figure 3. As shown in Figure 4 (and see also Figure 2) the propeller is mounted in a lower part of the tank, with side walls 41 extending outwards in a substantially V-shaped configuration. At the top of the V-shaped portion, upper side walls 42 may extend upwards, or may even be angled slightly inwards as shown in Figure 2. The narrow lower part of the tank helps to create a strong linear flow in the lower part of the tank. As the flow moves upwards and then fonNards (as indicated by arrows 36 in Figure 3) the tank widens and the fluid flow therefore also widens, and this helps to form a wide curtain flow moving fonNards past the opening 11.

This mixing mechanism is highly effective. The curtain flow and turbulent mixing region captures the particulate and mixes it effectively. In preferred ments there is no need for a l introduction of particulate. Particulate can be uced in bulk and extremely quickly to the fluid volume.

The ant has found that in a tank of approximately 4 cubic metres, a one tonne bag of ulate fertilizer can be added to the fluid volume simply by lifting the bag over the opening 11 and rapidly emptying the bag into the opening over a period of around 20 to 40 seconds. There is no or only minor splashing or loss of particulate. Furthermore, the particulate is very effectively mixed - particulate does not stay unmixed on the fluid surface to any significant extent.

The dimensions of the tank, er and housing, as well as the required impeller power, will depend on the application and the material being sprayed, as well as on each other. For example, a larger tank may require a larger propeller power. A thicker spray material sion will e a greater propeller power.

In one embodiment the tank may have a volume of around 4 cubic metres. The propeller may have a diameter around 400mm, with the housing extending around 800mm downstream of the propeller. The housing may be sized to provide a clearance of around 5 - 50mm around the propeller. The Applicant has found that such a ng apparatus is capable of quickly and efficiently mixing around 3 tonnes of lime into around one tonne of water, creating a paste that is too thick to be sprayed h conventional spray nozzles. The apparatus is therefore not limited by the mixing capability.

The length of the housing is ably sufficient to create directional flow from the end 35 of the housing. Preferably the downstream end 35 of the housing 22 is positioned sufficiently near to the back wall 38 of the tank 6 to cause the desired flow patterns beneath the opening 11 as discussed above.

Thus mixing of particulate into the fluid volume and constant ation of the fluid within the tank 6 is provided by the single housed rotor 21. In some embodiments the rotor may be used at a higher power for addition and mixing of particulates, and at a relatively lower power once the mixing process is complete.

The lower power may be sufficient to cause circulation of fluid within the tank, thereby preventing ng of ulates out of suspension.

Although the preferred embodiment shown has flow through the housing towards the back wall 38 of the tank 6, in other embodiments the flow may be fonivards or sideways, with the opening appropriately positioned such that the curtain flow is beneath the opening.

Figure 5 is a schematic diagram showing the flow paths provided in one embodiment.

The pump 5, via flow conduit 45, takes fluid or sion from the tank 6 and pumps that fluid into a manifold 46. The manifold has two outlets. In some ments the manifold may be replaced by a T—junction. Adjustable valves may be associated with one or more of the outlets in some embodiments.

A first outlet leads back to the tank 6 via flow conduit 47. This flow path caters for excess fluid that is moved by the pump 5 but cannot pass through the spray arrangement. The pump may ore be a simple fixed rate pump. This flow path also maintains a circulation of fluid through the pump, flow conduit 45 and manifold 46 even when the spray arrangement and its associated flow lines are empty, such as may be the case, for example, when the apparatus is first filled.

However, in some embodiments this flow path 47 (and the manifold 46) may be dispensed with.

A second outlet leads to the spray ement, through flow conduits 48, 49, 50 and spray booms 7, and returns to the tank 6.

A back re valve, or spray control valve, 52 may be provided to control the spray pressure. The function of this valve is described in the Applicant’s /149365. This valve 52 has a first, open position in which fluid or suspension can flow freely through the flow paths 48, 49, 50 and booms 7. In this position pressure does not build up significantly in the booms 7 and this pressure is not sufficient to actuate the spray mechanism shown in Figures 13 and 14 of W0201 1/149365. Therefore, when the spray control valve is open fluid or suspension is not sprayed.

The spray l valve 52 also has a second, restricted flow position. In this position flow through the valve is restricted, and this creates a higher pressure in the flow conduits 48, 49, 50 and booms 7. This higher pressure is sufficient to actuate the spray mechanism, so when the spray control valve is in this restricted flow on, fluid or suspension is sprayed.

The spray control valve may be lled remotely from the e towing the spraying tus, using any suitable mechanical, wired or wireless control system.

Figure 6 is a schematic diagram showing the flow paths provided in a further embodiment. This embodiment is substantially similar to that of Figure 5, except that two spray booms 7 are connected in parallel rather than in series, and this is the arrangement used in the apparatus of Figures 1 to 4. Many of the flow conduits shown in Figure 6 can be seen in Figures 1 and 1A. The flow conduit 48 leads to a junction 54, which connects to two flow lines 55, 56 each leading to a spray boom 7. The spray booms are connected to further flow lines 57, 58 and thence to a further junction 59. Flow conduit 49 leads from the furtherjunction 59 to a spray control valve 52. A further flow conduit 50 leads from the spray control valve back to the tank 6.

Figure 7 shows the flow paths employed in the tus of Figure 1. For clarity the tank and other components of the apparatus have been removed.

The spraying arrangement, i.e. the spray booms, nozzles and pressure ed mechanism may be as described in W02011/149365. In preferred embodiments a recirculating spray arrangement is used, in which spray fluid is pumped through the spray loop with only a portion of that fluid exiting through the spray outlets.

That portion may be less than 2%, but is preferably less than 20%, ideally around 3 to 10% by volume. The Applicant’s recirculating flow path es excellent performance with liquid suspended fertilizers and prevents clogging in the spray loop.

The invention may be d to various ng systems, including systems configured as trailers for towing behind vehicles and vehicle mounted spraying systems.

The system preferably operates to supply fluid to the spray loop at around 500 to 800 litres per minute. Fluid is preferably supplied at a pressure less than 35 pounds per square inch, more preferably less than 25 pounds per square inch.

This low pressure helps to prevent damage to biologically active components of the spray material or fluid. Where particulates are to be sprayed, these will preferably have an average particle size less than 100 microns, preferably less than 50 microns, more preferably around 5 s.

The Applicant’s system provides for improved initial mixing of powders into a fluid using the housed impeller and n flow below the opening, as bed above. This means that insoluble powders move effectively and quickly into suspension and are less likely to float on the fluid surface.

Once a suspension has been formed, the housed rotor or propeller maintains the particulates in sion by maintaining flow within the tank, preferably including flow across the bottom of the tank.

The housed impeller may be driven by a PTO mechanism. rs and other vehicles with PTO drives are capable or providing more than enough power to drive the impeller to perform mixing and agitation.

The recirculating spray loop is arranged to apply only a portion of spray from the spray outlets with each circulation. This also helps to keep the fluid moving, ining the suspension and preventing clogging around the spray outlets.

The Applicant’s apparatus is therefore ely effective for application of all sprays and in particular for application of liquid suspended sprays. The features discussed above allow very thick suspensions to be formed, maintained and sprayed. In fact the housed rotor or ler ism discussed above is capable of mixing particulate into an extremely thick suspension or paste. This means that the thickness of the suspension is limited by the capacity of the spray nozzles etc to handle such thick materials, not by the ability to mix particulate into the suspension. This in turn means that a sprayer of a given size can apply spray to a larger area before refilling.

Any suitable spray materials may be used, including lime, magnesium sulphate, seaweed and other fertilizers, including urea, nium phosphate (DAP) fertilizers, bio-fertilizers (which may include nutrients and/or living bacteria or other organisms). All manner of fine ground insoluble or soluble fertilizers may be used. Liquid, soluble solid and insoluble powders can all be sprayed. Further, the apparatus may be le for hydroseeding applications (i.e. the spraying of suspended seed).

The tus is suited to spraying in ltural and horticultural applications, but may also find application in other areas.

Furthermore, the Applicant’s apparatus may also be used to mix sprays before moving the spray material into a separate ng tus. In this embodiment the spray mixing apparatus is a standalone unit without a spraying ement. The tank, housed impeller and mixing flow may be as described above. However, the pump may be arranged to pump the mixed spray material to a tank in a separate spraying apparatus (such as a truck or aircraft-mounted spraying apparatus).

While the present ion has been illustrated by the description of the embodiments thereof, and while the ments have been described in , it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of the Applicant‘s general inventive concept.

Claims (29)

CLAIMS 1.:

1. An agricultural or horticultural spraying apparatus including: i) a tank configured to e a volume of fluid; ii) an opening at an upper part of the tank for introduction of particulates into the volume of fluid; iii) a spray arrangement including one or more spray outlets; iv) a fluid outlet in the tank, through which fluid may flow to the spray arrangement; and 10 v) an impeller mounted in a housing within the tank so as to cause, in use, fluid flow through the housing, thereby creating fluid flow within the tank, wherein the impeller and the opening are arranged such that the fluid flow created by the impeller forms a mixing flow in a region below the opening.

15 A spraying apparatus as d in claim 1 wherein, in use, the impeller is configured to cause fluid flow within the tank that is sufficient to prevent particulate from settling out of suspension.

A spraying apparatus as claimed in claim 1 or 2 wherein the mixing flow is a 20 flow downwards and across the opening.

A spraying apparatus as claimed in claim any preceding claim wherein the mixing flow meets a main fluid body in a region of high turbulence.

25 A spraying apparatus as claimed in any preceding claim wherein the impeller is oned near the bottom of the tank.

A spraying tus as claimed in claim any preceding claim wherein the impeller, a first wall of the tank and the opening are ed such that the 3O impeller causes fluid flow across a lower region of the tank s the first wall of the tank, upwards near the first wall of the tank and away from the first wall of the tank beneath the opening.

A spraying apparatus as claimed in claim 6 wherein the first wall of the tank is a curved wall configured to encourage redirection of the fluid flow.

A spraying apparatus as claimed in any preceding claim wherein, in a plane perpendicular to a onal axis of the impeller, the tank widens from a narrow region in a lower part of the tank in which the ler is positioned to a wider region above the lower part.

A spraying apparatus as claimed in any preceding claim wherein the er 1O is arranged to receive power from a power take-off drive.

10. A spraying apparatus as claimed in any preceding claim wherein the housing is an elongate housing. 15

11. A spraying apparatus as claimed in claim 10 wherein the housing forms an elongate tunnel within which the impeller is positioned.

12. A spraying tus as claimed in any preceding claim further including a pump arranged to supply fluid from the tank to the spray arrangement.

13. A spraying apparatus as claimed in any preceding claim wherein the spray ement is a recirculating spray arrangement

14. A ng apparatus as claimed in claim 12, wherein the spray arrangement 25 includes a flow loop leading from the tank and returning to the tank and one or more spray outlets positioned in the flow loop; the pump being arranged to cause flow of fluid from the tank through the flow loop, and the apparatus being configured such that, during spraying, only a portion of fluid passing through the flow loop exits through the spray outlets, with the remainder of 3O the fluid ing to the tank for recirculation.

15. A spraying apparatus as claimed in claim 14 wherein the flow loop includes one or more spray booms, one or more of the spray s being positioned in each spray boom.

16. A spraying apparatus as claimed in claim 14 or 15, including a spray valve positioned downstream of the spray outlets, the spray valve having an open position and at least one cted flow position, wherein the pressure at the spray outlets is higher when the spray valve is in the restricted flow position than when it is in the open position.

17. A spraying apparatus as claimed in any one of claims 14 to 16 ured to spray less than 20% of fluid passing through the flow loop.

18. A spraying apparatus as claimed in claim 17 configured to spray 3 to 10% of fluid g through the flow loop.

19. A spraying apparatus as claimed in any preceding claim configured to supply 15 fluid to the spray arrangement at a rate in the range 500 to 800 litres per minute.

20. A spraying apparatus as d in any preceding claim configured as a trailer for towing behind a vehicle or configured to be mounted on a vehicle.

21. A spraying apparatus as claimed in any preceding claim configured to operate at a pressure less than 35 pounds per square inch.

22. A spraying apparatus as claimed in claim 21 configured to operate at a 25 pressure less than 30 pounds per square inch.

23. A spraying apparatus as claimed in claim 22 configured to operate at a pressure less than 25 pounds per square inch. 30

24. A spraying apparatus as d in any preceding claim wherein the material to be sprayed is or includes a particulate al and is sprayed in suspension.

25. A spraying apparatus as claimed in claim 24 n the particulate has an average particle size less than 100 microns.

26. A ng apparatus as claimed in claim 25 wherein the particulate has an average particle size less than 50 microns.

27. A spraying apparatus as claimed in any ing claim wherein the material to be sprayed is or includes a component that is biologically active. 1O

28. An apparatus as claimed in claim 1 ntially as herein described.

29.A spraying apparatus substantially as herein described with reference to