Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/02—Spray pistols; Apparatus for discharge
  • B05B7/08—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point
  • B05B7/0892—Spray pistols; Apparatus for discharge with separate outlet orifices, e.g. to form parallel jets, i.e. the axis of the jets being parallel, to form intersecting jets, i.e. the axis of the jets converging but not necessarily intersecting at a point the outlet orifices for jets constituted by a liquid or a mixture containing a liquid being disposed on a circle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
  • B05B7/02—Spray pistols; Apparatus for discharge
  • B05B7/04—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge
  • B05B7/0416—Spray pistols; Apparatus for discharge with arrangements for mixing liquids or other fluent materials before discharge with arrangements for mixing one gas and one liquid

Definitions

• This invention relates to a method and apparatus applicable to agricultural and horticultural and other spraying systems.
• the invention is particularly applicable to such spraying systems as disclosed in our prior patents and patent applications relating to boom-type sprayers having droplegs carrying spray nozzles.
• the invention is more widely applicable than to dropleg-type sprayers and is applicable to conventional spray-from-above sprayers likewise, and to lance and other hand-held sprayers for certain applications.
• An additional application of the invention is in harvesting machines such as potato harvesters for spray-treatment of the harvested crop and in related applications such as the spray- treatment of potatoes coming into or coming out of store. Additional applications are likely to arise in which a facility to provide a low dosage rate of treatment material in a spraying operation is advantageous. Further applications include de-icing treatment of aircraft with de-icing fluid and industrial uses including industrial spray-treatment processes. It is entirely possible that the invention may be applicable to the spraying of liquids which have a significantly higher viscosity than water and the like.
• a problem which arises generally in relation to sprayers concerns effective penetration of the crop or other material to be sprayed, by the spray of droplets produced by the sprayer.
• various forms of spray nozzle are utilised in which a spray of droplets is produced solely by virtue of the energy derived from the supply of liquid under pressure.
• droplegs to permit crops to be sprayed from a low location generally below the canopy of leaves in the case of crops such as potatoes has been found to improve very substantially the ability to cover the under surfaces of plants, as compared with conventional spraying arrangements in which the droplets are discharged onto the canopy of leaves from above.
• a further prior proposal known to the Applicants utilises an air supply in association with a liquid supply. However, the liquid supply is directed via a restrictor onto a baffle plate where primary atomisation occurs before the liquid is mixed with the compressed air. The compressed air then forces the thus-produced droplets through a circular passage onto an inner face of a flood jet. There, secondary atomisation takes place, prior to the spray emerging in a flat fan-shaped pattern.
• the system disclosed facilitates pre-atomization of liquids by means of an insert member which includes an elongated impingement element having a transversely extending circular hole which is struck by the pressurised liquid, to break up same.
• a pressurised stream of air is admitted to the device and a side surface area defines an impingement surface which deflects and breaks up the airstream and considerable turbulence for pre-atomizing the liquid stream is created, and as a result of the airstream being injected transversely into the longitudinally flowing liquid stream, there is produced a liquid flow in the downstream direction towards an outlet nozzle, in the form of finely divided pre-atomized particles.
• This preliminarily atomized liquid flow stream is then directed through a discharge orifice and a deflector flange which is transversely oriented to the line of travel of the liquid, directs same through a discharge orifice where the pre-atomized droplets are broken into extremely fine liquid particles which are then deflected into a flat, wide spray pattern in a manner which maximises their exposure to the ambient air.
• a cup-shaped recess is believed to produce pressure waves or acoustic energy which assists in the liquid breakdown.
• the nozzle assembly has particular utility in humidification and evaporative cooling applications.
• the US '937 patent discloses the use of the same nozzle assembly in a manner in which it can be easily removed from the nozzle body to enable the nozzle to be used as an hydraulic nozzle.
• an object of the present invention is to provide a method and apparatus offering improvements in relation to one or more of these matters, or generally.
• a droplet generator comprising an air-and-liquid supply chamber to which both a liquid supply and an air flow supply are connected for supply of air and liquid towards an internal wall or target formed by a closed end of the chamber.
• the droplet generator further comprises structure defining an edge or boundary of an external outlet from the chamber and the liquid supply means is adapted to supply the liquid to the outlet through the chamber via the closed end of the chamber.
• the air flow supply means and the liquid supply means are adapted in relation to the chamber to supply air and liquid towards the closed chamber end for production of the spray of droplets from the chamber outlet by entrainment of the liquid in the air flow.
• the arrangement is capable of producing a suitable or optimum droplet size which is consistent with very low liquid volume requirements while achieving satisfactory or better crop penetration.
• the mode of droplet generation is particularly adapted to enable the droplets to be effectively carried by the air flow in a required direction into the crop, for example from a dropleg.
• the advantage is provided that the flow of air and entrained droplets has the required physical and dynamic characteristics and can be directed in any required direction.
• considerable flexibility exists in designing the direction and width of the spray output. For example, if it is required to generate a relatively wide and fan-shaped output of spray in a given direction then the apparatus is provided with a series of suitably spaced orifices with suitable directions corresponding to the requisite fan-shaped output.
• the embodiments of the present invention enable liquid volume supply to be reduced, at will, to levels very substantially below those required for conventional spray nozzles, provided that the air supply is always sufficient for the required entrainment and droplet formation steps.
• the one or more orifices is or are formed in a chamber or gallery to which the liquid is supplied in the form of an unatomised jet directed at a closed end of the chamber which has an associated outlet through which the liquid and air flows supplied to the chamber proceed. It is not known whether some or all of the droplet formation occurs at the closed wall of the chamber, or later in the flow path of the materials through the chamber. Possibly, a surface layer of liquid is produced in the chamber which proceeds to the outlet opening and is formed into droplets at that region.
• both the air and liquid supply paths to the chamber are generally axially thereof and lengthwise of the chamber towards its opposite closed end, but it may not be necessary for the air supply direction to be exactly axial.
• the location of the one or more outlets relative to the chamber may be but need not be strictly at the outer periphery of the wall or target at which the liquid supply is directed.
• the outlets are somewhat axially (of the chamber) offset from that wall, and the arrangement is such that the outlet(s) is or are located so as to enable a smooth and effective flow of materials from the chamber end wall outwardly thereof.
• the jet or flow of liquid supplied to the chamber is disposed generally symmetrically with respect to two or more orifices formed in the chamber so that each orifice receives a generally equal supply of liquid to its entrainment edge or boundary.
• the surface of the wall or target towards which the jet or flow of liquid is supplied to the air-and- liquid supply chamber may be constructed to promote uniform distribution of liquid to the entrainment edge or boundary of the associated orifice or outlet.
• the surface may have a convex and outwardly broadening form having its apex directed at the source of the jet or flow of liquid, and the form of the convex structure being such as to promote the production of a uniform outward liquid flow to the one or more orifices provided in the chamber.
• a flat surface may alternatively be provided as shown in Fig 7.
• the invention utilises an approach to droplet formation having some technical common ground with carburettor technology.
• the air supply provides power in the spray plume to penetrate the crop.
• Droplet formation may occur, as mentioned above, either at the chamber wall which intercepts the liquid supply and/or in the region of the edge or boundary defining the outlet orifice or orifices of the chamber.
• the plume of spray produced by the apparatus of the invention includes an inner portion, which may for example be of length about 10 to 20 centimeters, and in this portion of the plume the air and entrained liquid is relatively significantly less visible than in the outer portion of the plume where it assumes the characteristic mist or fog-like form. It is not known what effect gives rise to this change in appearance, which is uncharacteristic of conventional spray nozzles.
• An important aspect of the embodiments described below is the relatively low power consumption of the air supply system. Whereas currently available so-called airbag sprayers usually require a power input of the order of 80 kilowatts to the fan, the air supply system of the embodiments described below requires only about 10 to 15 kilowatts for a 12 metre spray boom.
• the orifice or outlet from which the droplets are discharged may be modified in shape with respect to the round profile disclosed below.
• the principal advantages of the described embodiment are the simple construction of the droplet generator and the low tendency for orifice blockage, the highly directional droplet propagation, and the low liquid volumes involved. Moreover, very little lateral dispersal of the droplets occurs away from the main jet thereof, as compared with prior proposals, such as those discussed above, which tend to produce a fogging effect.
• the embodiments substantially reduce the usual sprayer down time which is about 40 per cent of working time which is devoted to refilling the tank. Therefore, approaching 40 per cent more work can be produced.
• a further factor is that the orifices or outlets from which the droplets emerge no longer need to be at the relatively very small sizes required by liquid spray systems.
• orifices of the order of 1 millimetre diameter can be utilised compared with 0.3 millimetres for prior liquid systems. This reduces the occurrence of blockages.
• the embodiments of the invention are extremely tolerant of changes in the pressure of the liquid supply.
• the liquid supply pressure can be reduced to a level which is even below that of the air flow supply pressure.
• the embodiments of the invention do not require a liquid supply in the form of a jet of liquid which must intercept, for example, an end wall of the air-and-liquid supply chamber so as to produce a dynamic effect.
• it appears to be sufficient for the purposes of the invention that merely a sufficient supply of liquid is provided so that the droplet entrainment process can proceed without any shortfall in the supply of liquid therefor.
• test work shows that modification of the form of the closed chamber end wall in the embodiment, against which the jet of liquid is projected, does not significantly affect the performance of the apparatus and this also appears to support the likelihood that the droplet entrainment process does not significantly occur within the chamber as such.
• An important practical aspect of the invention relates to the several inter-related magnitude parameters of the main components of the liquid and air supply system.
• These parameters include the size of the outlet openings or orifices in the air and liquid supply chamber, the air supply pressure, the liquid supply pressure, and the output of the air compressor which supplies air to the system etc.
• the size of the outlet openings in the air and liquid supply chamber these may be in the range of 0.5 to 2.0 millimetres in diameter, or openings of a similar area in non-circular shapes. It is found that sizes of less than 0.5 millimetres lead to a significantly reduced throw or travel of the plume of droplets produced by the apparatus.
• a preferred range of diameters is from 1.3 to 1.8 millimetres and preferably 1.6 to 1.7 millimetres. These latter larger sizes provide the significant advantage of avoiding the frequent nozzle blockages which are a feature of conventional spraying systems. It is found that droplet size is not greatly affected by outlet opening size, but as such size increases, crop penetration increases due to increased velocity of the droplets caused by higher volume throughput as flow resistance reduces.
• air supply pressure in the range of up to 0.6 bar and 0.6 to 1.0 bar (above atmospheric pressure) , and preferably between 0.7 and 0.9 bar, are convenient utilising a compressor capable of supplying an output of approximately 5 to 20 cubic feet of air (measured at such pressure) per spraying head or dropleg, per minute. Usually, an output in the range of 10 to 15 cubic feet per droplet per minute will be suitable.
• droplets which are too small for the purposes envisaged, namely to be propelled towards and to adhere to or coat crop and other surfaces exposed to them.
• droplets preferably in the range of 80 to 120 or up to 150 microns in maximum dimension are found to be suitable for these purposes. Larger droplets are used for spraying crops from above (not using droplegs) to reduce spray drift caused by wind. Droplets significantly below 80 microns are found to be too small to adhere effectively to sprayed surfaces.
• the contrasting approach of the present invention is based upon the use of an internal target or wall within an empty or open chamber to which the air and liquid supplies are delivered.
• a change of direction of the liquid flow is effected accordingly towards an outlet or orifice which is not directly in-line with the liquid flow through the chamber.
• the liquid and air flows through the outlet or orifice produce a spray of air-entrained droplets which, at air pressures which are readily determinable, produce droplet sizes suitable for effective coating of plant and other surfaces.
• the present invention represents somewhat of a reversal of existing technology in the area of air-facilitation of droplet generation for agricultural and horticultural and related applications, which can benefit from the enhanced generation of the droplets of a size which promotes uniform coating of a substrate utilising minimum volumes of a liquid vehicle for the purpose of diluting an active surface treatment medium.
• the technique utilises air as a means for replacing the diluting liquid vehicle.
• the technique is independent to a significant extent of the pressure of the liquid supply. As regards air supply pressure, this is chosen in accordance with the required range of droplet sizes.
• the range and degree of penetration provided by the plume or jet of spray droplets is determined to a large extent by the size of the outlet openings from the air and liquid supply chamber in combination with the corresponding required volume of air flow at the chosen air supply pressure (the latter being in accordance with droplet size requirements) .
• these technical features and advantages are provided by the relatively simple combination of features to be found in the air-and-liquid supply chambers shown in the described embodiments, most notably the provision of a wall or target in the open- centre chamber to which the liquid flow is supplied and which enables, with a change of flow direction, the liquid to reach the requisite number of outlets or orifices in combination with the required air flow through those orifices whereby droplet entrainment occurs in accordance with matters described above.
• the liquid flow to and through the orifice is generally outwardly of the target or wall and indeed of the chamber, though by no means necessarily in a truly radial direction.
• Fig 1 shows an axial section through a jet and tube assembly
• Fig 2 shows a corresponding longitudinal section through a complementary entrainment chamber adapted to be mounted on the jet and tube assembly
• Fig 3 is an end elevation view of the jet and tube assembly as viewed in the direction III in Fig 1;
• Figs 4 , 5 and 6 are taken from the present applicants' corresponding published prior International applications including inter alia PCT/GB92/01356 showing tractor-drawn spraying apparatus of the dropleg kind and to which the present invention is applicable;
• Fig 4 shows a plan view of tractor drawn spraying apparatus incorporating a compressor for supply of air to individual droplegs
• Fig 5 shows, on a larger scale, a corresponding plan view of an individual dropleg passing between two crop rows and with a direction of a plume or spray of droplets indicated;
• Fig 6 shows an end elevation view of a spray boom of the spraying apparatus of Fig 4 showing the boom itself and an associated dropleg;
• Fig 7 shows, on a larger scale, a droplet generation or entrainment chamber representing a second embodiment of same and incorporating angularly inclined outlet openings to produce simultaneous jets or plumes of spray droplets in the indicated inclined directions.
• a liquid and air supply and connection assembly 10 comprises a machined connection and supply jet member 12 which is a friction fit within the end of a tube member 14.
• Tube 14 forms the lower end portion of a dropleg of a dropleg-type sprayer as described in one or more of my prior patents, for example EP 0 600 919 B and EP
• Jet member 12 is a tight friction fit in tube 14 and has a projecting portion 16 formed with an external screw thread 18 to co-operate with a corresponding internal screw thread 20 provided on the internal surface of a collar portion 22 of an entrainment or chamber member 24 - see Fig 2.
• Jet or connection member 12 is formed with a pattern of six axial bores 26 extending lengthwise thereof to deliver air from the pressurised internal volume of dropleg tube 14 to a chamber 28 defined within entrainment or chamber member 24.
• Jet or connection member 12 also serves to provide an unatomised jet or flow of liquid into chamber 28, for the purpose to be described. Accordingly the connection member 12 is also provided with a hose sleeve 30 at its inner end, a lengthwise bore 32 leading therefrom, and a jet or supply member 34 to produce an unatomised jet or supply of spray liquid. Jet 34 has its own axial bore 36 which opens into bore 32 and receives liquid therefrom. The lengthwise bore 36 of jet 34 is simply a uniform- section endwise bore with no provision for the generation of droplets in the manner of a spray nozzle.
• jet or connection member 12 serves to receive spray liquid from a hose which extends lengthwise of the dropleg tube or shank 14 within that tube, and receives also supplies of air pumped lengthwise of that tube in the annular space between the hose and the tube's inner surface.
• the spray liquid is delivered from jet 34 as a thin uniform stream or supply of liquid.
• the air is delivered generally uniformly around the periphery of jet member 12 by virtue of the six streams of air produced by bores 26. These flows of liquid and air are delivered to chamber 28 of the entrainment or liquid and air supply chamber member 24.
• entrainment or chamber member 24 the principal structural features are its internal form and the provision of orifices or outlets 38 leading outwardly from chamber 28 for the delivery of air and spray liquid from chamber 28.
• That chamber, 28, is of cylindrical form, comprising an axial bore 40.
• it is formed with a conical-form end wall 42 with a fairly large cone angle and having an apex 44 at which the jet of liquid from jet 34 is delivered in use.
• the orifices 38 are disposed in two groups of three orifices or outlets, making six in all, these groups of three being spaced within the group and between the groups so as to produce two laterally-and- upwardly directed plumes of spray in use from the dropleg tube 14 upwardly and laterally outwardly into the crop in directions in accordance with the teaching contained in my above-mentioned prior patents.
• Figs 4, 5 and 6 show tractor-drawn spraying apparatus of the kind suitable for incorporation of droplet generation apparatus in accordance with the above-described embodiment of the invention.
• a tractor 50 has mounted on the hitch links thereof boom type spraying apparatus 52 comprising spraying booms 54, 56 having associated droplegs 58, as described in our prior published PCT applications.
• Each dropleg 58 comprises a downwardly-projecting dropleg shank portion 60 (corresponding to shank 14 in Fig 1) which enters between crop rows 62, 64 and carries a droplet generator 66 for crop spraying purposes.
• Each dropleg 58 has its own droplet generator indicated in Fig 5 at 66, and this is provided with air and liquid supplies delivering liquid (to be sprayed) and air supplies from the liquid tank 68 and a compressor 70 shown in Fig 4.
• the droplet generator 66 produces twin spray jets or plumes 72 (see Fig 5) directed generally forwardly and upwardly and laterally with respect to the direction F of forward travel of the tractor and the droplegs, and symmetrically with respect to the crop rows.
• Droplet generator 66 corresponds to the entire apparatus of Figs 1, 2 and 3 described above.
• Such a plume 72 is produced at each side of the dropleg to provide spray treatment of each of the crop rows 62, 64.
• the dropleg 58 shown is constructed as described in our above-mentioned prior PCT applications, whereas in Fig 6 the dropleg 58 is adapted for the purpose of the present invention to receive both the air and the liquid supplies for transmission of these within the dropleg tube lengthwise thereof to the droplet generator 66 at the lower end thereof, the supplies being delivered thereto as described above and as illustrated in Fig 1.
• liquid and air supplies are delivered to the upper end of each dropleg 58 and thus to its jet or connection member 12 as mentioned above and chamber 28 is pressurised by the air while receiving a jet or supply of liquid on the chamber end wall or target 42 at the apex 44 of the conical form of that end wall.
• This jet or supply is believed to produce at least a partial film of liquid on the inner surface of the chamber end wall 42 which flows outwardly towards orifices or outlets 38 and passes, likewise as a film, outwardly and lengthwise of the orifice bores 46 to their end edges 48.
• a degree of droplet formation may occur at the end wall or target 42 of chamber 24.
• the droplet generator 100 of Fig 7 comprises a air and liquid supply chamber 102 to which are provided air 104 and liquid 106 supplies, these being provided in the same relative spacial dispositions as in the previous embodiment, for delivery towards the chamber end wall or target 108, which is planar.
• the chamber outlets 110 are disposed in two groups comprising generally forwardly-directed outlets 112 and generally rearwardly-directed outlets 114, with respect to the direction F of normal forward motion of the sprayer.
• the entrances 116 to the oulets are disposed so that liquid passing to the bores 118 of the outlets from the end wall 108 must change in direction before entrying the bores. Moreover, the entrances 116 are offset from the end wall 108 by a distance d in the axial or liquid flow direction of chamber 102.
• This embodiment of the invention is able to discharge spray droplets simultaneously in the two indicated directions which is of benefit for certain agricultural operations.
• the use of the flow of air to cause movement of the spray of liquid droplets has the effect of replacing the water or similar vehicle conventionally used for spraying purposes, whereby it becomes possible to spray treat agricultural or horticultural or industrial or other objects with a liquid treatment medium without the need for the use of any liquid as a diluent or carrier medium, or at least to reduce the effective volume of such a liquid vehicle by a factor of 10 or more.
• a system in which the viscosity of the liquid to be sprayed is chosen in accordance with the desired size of the droplet to be generated.
• the liquid vehicle for the treatment material may be non-aqueous, for example the liquid vehicle may be an oil-based liquid comprising an aromatic hydrocarbon.
• the liquid vehicle which forms part of the liquid to be sprayed will be chosen in accordance not only with the nature of the active chemical ingredient involved, but also in relation to the surface tension and other characteristics of the liquid to be sprayed, these being chosen in order to achieve a desired degree of adhesion to plant surfaces, or related requirements.
• An example of a related requirement may be the requirement for the sprayed material to be rain- resistant.
• the invention offers the additional advantage of permitting non- aqueous based liquid vehicles to be offered for spraying purposes whereas such a basis for spraying operation has hitherto been considered commercially unacceptable in view of the relatively high cost of the liquid vehicle due to its volumetric requirements as determined by prior art spraying apparatus.
• a further aspect of the present invention relates to the relative importance of providing an ability to inject or otherwise deliver the liquid to be sprayed to the delivery system close to the spraying nozzles on the boom. In this way, the lengths of spraying lines in which relatively concentrated chemicals are transmitted are reduced. This leads to significant advantages in terms of ability to switch from one spraying medium to another at relatively short notice.
• the actual cross sectional shape and dimensions of the air and liquid supply chamber may be varied.
• a non cylindrical chamber may be used and its axial length in the liquid flow direction may be varied, as indicated by comparison of Figs 2 and 7.
• Routine test work by a competent technical person in the field will reveal the applicable limits.
• variations in the dispositions of the outlets relative to the chamber end wall can be accommodated and provided.
• the wall or target towards which the liquid supply flows can itself be modified considerably in terms of its profile being planar, generally convex or generally concave. Indeed, the target may be provided as an internal construction in the chamber providing for suitable liquid flow outwards to the chamber outlets.

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• Catching Or Destruction (AREA)
• Nozzles (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)
• Special Spraying Apparatus (AREA)

Applications Claiming Priority (9)

Publications (2)

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Country Status (10)

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• 1996
  • 1996-09-16 GB GBGB9619260.4A patent/GB9619260D0/en active Pending
  • 1996-10-31 AT AT96935135T patent/ATE221417T1/de not_active IP Right Cessation
  • 1996-10-31 DK DK96935135T patent/DK0855938T3/da active
  • 1996-10-31 EP EP96935135A patent/EP0855938B1/fr not_active Expired - Lifetime
  • 1996-10-31 ES ES96935135T patent/ES2180801T3/es not_active Expired - Lifetime
  • 1996-10-31 AU AU73213/96A patent/AU713843B2/en not_active Ceased
  • 1996-10-31 WO PCT/GB1996/002664 patent/WO1997016257A1/fr active IP Right Grant
  • 1996-10-31 JP JP9517150A patent/JP2000504990A/ja not_active Ceased
  • 1996-10-31 CN CN96197950.XA patent/CN1092545C/zh not_active Expired - Fee Related
  • 1996-10-31 DE DE69622733T patent/DE69622733T2/de not_active Expired - Fee Related

Non-Patent Citations (1)

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