GB2156242A - Spraying apparatus - Google Patents

Abstract

A hormone spraying apparatus 10 (Figure 1) comprises a spray applicator (35) operative to provide drops in excess of 1 mm diameter with an average drop-distribution density over the area sprayed of between 1 drop to every 10 sq cm and 1 drop to every 100 sq cm. The apparatus which is mounted on a tractor, has spray nozzles 44 supplied from vertically adjustable heater units 52, 53. <IMAGE>

Description

SPECIFICATION Spraying apparatus The present invention relates to spraying apparatus.

Hormone sprays which will ensure either fruit set or fruit abcission have already been developed, especially for Victoria Plum and Conference Pear, and these offerthe prospect of stabilising yields and quality at a high level of production.

However, at conventional dosage rates e.g. 11 p.p.m for Conference Pear, these sprays generally produce variable results principally because variations in natural fruit setting potential make it unlikely that any particular concentration can be chosen which in any given instance will always set or remove the desired proportion of fruits.

To avoid this last difficulty, the dosage rates can be increased e.g. to above 20 p.p.m for Conference Pear so that at least some minimum proportion of fruits will be set or removed. However these higher concentrations produce their own undesirable side effects, For example, the fruit size of the surviving fruits will be reduced and there will also be a significant reduction in the fruit tonnage produced in the year following treatment.

Moreover, even with these relatively high concentrations, it has been found difficult to control the amount of thinning actually taking place.

It is also common practice where flowers have been subjected to frost, to spray them with a setting agent in an attempt to overcome frost damage but once again in some years fruit size and next year's tonnage suffer even though, in this case, the setting spray is usually applied at the conventional dosage.

The principal resaons for this are the difficulty after frost of estimating the degree of damage that has occured and also the problem of getting round the orchard in time to provide effective treatment for all the trees even if the damage has been correctly assessed.

Pre-frost spraying with conventional sprayers is ruled out because of the risk of overset if a frost does not in fact occur.

Application of high spraying concentrations of guaranteed effectiveness to only a proportion of the flowers or fruits appears to be a more promising approach and an object of the present invention is to provide an apparatus for achieving this. If successful, the present invention could, for example, lead to the use of more potent chemicals than those hitherto applied to all fruitletsto cause a variable proportion to be shed.

According to the present invention, a spraying apparatus comprises a spray applicator operative to provide drops in excess of 1 mm diameter with an average drop-distribution density over the area sprayed of between 1 drop to every 10 sq cm and 1 drop to every 100 sq cm.

Conveniently, the drop size will be about 4 mm diameter. This compares with a typical value of 0.3 mm say with conventional spraying apparatus.

Conveniently, the average drop-distribution density over the area sprayed will be about 1 drop to every 30 sq cm. This compares with a typical value of 1 drop to every 0.5 sq cm with conventional spraying apparatus.

Conveniently, the flow-rate of spray material through the apparatus is about 45 ml per minute per spray nozzle. The volume delivered per tree compares with about three to five times the value applied by conventional spraying apparatus and for this reason the concentration of the spray-material is typically about five to ten times that used with conventional spraying apparatus.

Conveniently, the apparatus includes an autospeed control system operative to ensure that the apparatus delivers substantially the prescribed dosage irrespective of ground speed (typically about 3 m per hour).

Conveniently, to provide the spray distribution, the apparatus will include a plurality of spray nozzles spaced apart so as to have a centre-to-centre separation of about 25 mm between adjacent nozzles.

It should be noted that the invention is not restricted to the situation where the apparatus is adapted to discharge the spray material downwards but should also be interpreted as extending to such an apparatus when it discharges the spray material upwards, sidewards or with a sideways andlor upwards component e.g. as may be required when spraying spindle bushes.

It is a further advantage of apparatus in accordance with the present invention that it can be used to pre-spray the crop for frost protection in which case no harm will result if, in the event, no frost occurs.

Conveniently, the droplets of spray material may be formed discretely by means of a single drop metering device or continuously using a low hydraulic pressure to eject them from the nozzles.

According to a preferred feature, in order to limit the hydraulic pressure, a "dribble bar" type of spray applicator is used in which the spray bar consists of a hollow tube along which the nozzles are positioned.

Conveniently, in this latter case, the spray or bar is carried over the top of the tree canopy during spraying so that a gravity pressurised system with a hydraulic head limited to less than 1 m may be used to supply the spray applicator.

Conveniently, the nozzles each have a diverging cone exit so that, by using the correct combination of hydraulic head and diverging cone dimensions, the desired drop size and distribution pattern may be achieved.

The hydraulic pressure head controls the flow rate through the nozzles and also may affect the drop size and according to a preferred feature of the invention, the pressure head is set by means of an overflow chamber which may be raised and lowered either manually or automatically in relationship to the forward speed of the vehicle on which the applicator is mounted.

Preferably, because of the low pressure head used, the applicator is mounted so that it is subject to the minimum of vibration and is also held substantially horizontal.

Conveniently, this horizontal disposition is achieved in preferred embodiments of the invention by suspending an entire system of tank, tower frame and spray bar on a single pivot carried on a frame attached to the three-point linkage of a tractor. The system acts therefore as a high inertia pendulum which effectively dampens out any oscillations likely to affect the formation of the droplets. Provided the pendulum is correctly balanced, the spray bar will remain horizontal under the influence of gravity.

As an alternative to spray nozzles, the spray applicator may instead comprise a pocketed cylinder operative to discharge drops of the spraymaterial when the cylinder is rotated away from a first pocket-filling orientation in which the pockets, our a proportion of the pockets, are upwardly facing.

Conveniently, the apparatus includes spray control means for producing or optionally producing a pulsed flow to distribute the spray. A pulsed spray could be advantageous, for example, when the apparatus includes a vertical spray bar for treating spindle type trees. The pulsing could, for example, be achieved by solenoid valves switching on and off at a suitable rate.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying somewhat simplified drawings in which: Figure 1 is a perspective view showing most of the principal integers of a spraying apparatus according to the present invention; Figures 2 and 3 are perspective views showing, on enlarged scales, details of two parts of the same apparatus; Figure 4 shows, also on an enlarged scale, one of the spray nozzles used in the apparatus; and Figure 5 is a partially schematic perspective view illustrating the various flow paths for the spray material during operation of the apparatus.

Thus referring first to Figures 1 and 2 of the drawings, a spraying apparatus 10 in accordance with the present invention comprises an A-frame 12 for attachment to a tractor three-point linkage 14.

At its upper end, the A-frame 12 carries a stepped bar 16 providing pivotal supportforthe bushes 18, 19 of a free-swinging framework 21. Compression springs (not shown) acting between a top-plate of the A-frame and the bush-connecting cross-member 27 of the swinging framework ensure that longitudinal movement between the two frames is permitted, but controlled, to help isolate longitudinal vibrations.

Theframeword 21 serves two purposes. Firstly, to support the spray tank 29 and the control box 31, and secondly to support the tower frame 33 for a jib construction 35 to which the spray applicator 37 is attached. Clamps (not shown) are provided for clamping the tower frame 33 to A4rame 12 when the apparatus is not in use.

As will be seen from Figure 2, the tower frame 33 is essentially a triangular-plan frame bolted to the cross-member 27 of framework 21 and to two corner posts 39, 40. Reference numeral 41 in Figure 2 indicates a counterweight secured to the framework 21 to counter-balance the jib 35 when in the operative position of Figure 1.

The cross-member 27 of the framework also carries an upstanding spigot 42 which is engaged by a central boss 43 of the tower frame 33. Thus once the clamps referred to above have been secured to stop the tower frame tipping, the frame 33 can be unbolted from the framework 21, reorientated about the spigot 42 so as to bring it more closely into alignment with the direction of tractor travel, and then rebolted to the framework 21 with what was previously the leading leg of the tower frame now attached to one or other of the corner posts 39,40.

This facilitates transport of the spraying apparatus from one site to another.

Turning now to the spray applicator 35, this comprises a line of spray nozzle 44 spaced along the jib structure 35 on 25 mm centres. The nozzles are divided up into two sets each supplied from an associated reservoir 46,47 on actuation of a solenoid valve 49, 50.

The reservoirs 46,47 are continually topped up from adjustable header units 52, 53. By way of example, header unit 53 is shown on an enlarged scale in Figure 3 from which it will be seen that the unit comprises a closed container 55 vented to atmosphere and fitted with inlet and outlet tubes 57, 58.

Because container 55 is vented to atmosphere, the header unit provides a gravity feed to its associated reservoir but the hydraulic pressure in tube 57 can be varied by raising or lowering the container 55 using the pulley system 60. This can be done manually or, as in the illustrated embodiment, by means of an electric drive unit 62 driving the top pulley of the system. Reference numerals 64, 65 indicate a guide system for the container.

The reservoirs 46,47 are themselves fed from the tank 29 via feed lines 67,68 which include filters 70, 71. This feed is under the control of a distribution box 73 provided with control lever 74 and pressure gauge 75. According to the position of lever 74, liquid from the tank 29 is fed to a selected one or both of the reservoirs 46,47 or, instead, it can be recirculated back to tank 29 via a feedback loop 77.

The prime mover for the system is provided by a tractor-operated pump 79 which removes liquid from the bottom of the tank 29 to feed it into the distribution box 73 via inlet 81. Reference numeral 83 indicates the filler cap for the tank.

As will already be clear from the introductory portion of the present Application, the successful formation of the required drop size and spray distribution depends to a large extent on the design of the spray nozzles in the applicator and one such nozzle 44 is shown in section in the scrap view of Figure 4 which is drawn to twice life size.

Thus referring to this Figure, the more important features of the nozzle 44 are the length and width of the inlet bore (respectively 3 mm and 0.8 mm), the overall length of the nozzle including the inlet bore (25 mm), the diameter of the outlet port of the nozzle (7.5 mm), and the divergence angle of that part of the nozzle bore downstream of the inlet bore (17 included angie). With these dimensions, the nozzle spacing (centre-to-centre) was chosen at 25 mm.

The feed tube 87 has an internal diameter of 16.5 mm and a wall thickness of 1.75 mm to house the upper neck portion of the nozzles 44.

Clearly these dimensions are given by way of example only although it should also be made clear that, as stated above, the successful operation of the spraying apparatus depends to a very large extent on the nozzle design and nozzles of the wrong internal dimensions or shapes will fail to produce the required drop size and spray distribution.

Investigations into what is and what is not acceptable in this respect are still going on but as far as can be ascertained at present, the following ranges would be acceptable, the currently preferred values being given in brackets.

Diameter of nozzle inlet bore: 0.6 to 1 mm (0.8mm) Length of nozzle inlet bore: 2.5 to 3.5 mm (3 mm) Overall length of nozzle: 20 to 30 mm (25 mm) Outlet port diameter: 6 to 9 mm (7.5 mm) Divergence angle of nozzle bore: 12"to 200 (170) It is emphasised, however, that these ranges are only present estimates and further research may show that alterations in the quoted ranges are desirable. Broadly speaking, the inlet diameter of the nozzle controls the flow rate in conjunction with the pressure head used, while the outlet diameter of the nozzle affects the drop size in conjunction with the divergence angle.

In operation of the apparatus described above, the control lever 74 is put in the "recirculation" position and the pump 79 is started to circulate the liquid in tank 29 and thereby stir it up. If necessary, of course, fresh liquid will first have to be added to the tank following removal of the filler cap 83.

The tractor is now driven to position the apparatus in the desired location and as the tractor begins to move forward the control lever 24 is moved to one or other of its "spray" positions, depending on circumstances, and the applicator 37 will commence to spray. As the applicator moves over the canopies of the fruit trees or bushes under treatment, the nozzles 44 will operate to provide a spray discharge in which, with the dimensions given, drops of about 4 mm diameter will, on average, be applied to the tree or bush canopies at an average drop distribution density of about 1 drop for every 30 sq cm of area swept out by the applicator.

As explained in the introductory portion of the application, a spray distribution having these characteristics will have the advantage over conventional spray patterns of providing a more predictable and more accurate crop treatment and it will also allow for unharmful pre-frost protection of the fruit.

Clearly, although a single jib arrangement has been described and shown in the drawings, the invention also includes a double-jib design in which the jibs project on opposite sides of the apparatus in a mirror image of one another. It wiil also be appreciated that both in this iatter case and in variations of the illustrated embodiment, it is not absolutely necessary to divide the nozzles up into sets or to divide the nozzles on any one jib into sets (if two jibs are present) each with its own reservoir and header unit. Generally speaking, however, it is thought desirable, not to have more than 60 nozzles under the control of any one reservoir and header unit. Thus in the illustrated embodiment where the nozzles are arranged on 25 mm centres along a 300 cm jib, each reservoir and header unit is associated with 56 nozzles.

As well as its use for spraying fruit blossom to promote fruit setting and/or abcission, apparatus according to the present invention can also be used in a variety of related applications, for example the apparatus might be of use in the application to the tops of trees of growth retardants. In apples and pears most of the unwanted shoot growth, for which chemical control is sought, emerges from the tops of the trees as vertical shoots. Selective chemical defoliation might be of great benefit for a number of tree crops e.g. Citrus and those tree crops grown in tropical regions where defoliation is practised to substitute for winter chilling. In these cases, the optimum dimensions of the nozzles and their spacing may vary somewhat from the optimum values associated with fruit blossom spraying but, in all cases, it is expected that satisfactory results can only be achieved with nozzles of this general diverging cone design.

Claims (18)

1. A spraying apparatus comprising a spray applicator operative to provide drops in excess of 1 mm diameter with an average drop-distribution density over the area sprayed of between 1 drop to every 10 sq cm and 1 drop to every 100 sq cm.

2. An apparatus as claimed in Claim 1 adapted to produce a drop size of about 4 mm diameter.

3. An apparatus as claimed in Claim 1 or Claim 2 adapted to produce an average drop-distribution density over the area sprayed of about 1 drop to every 30 sq cm.

4. An apparatus as claimed in any preceding claim adapted to operate with a flow-rate of spray material through the apparatus of about 45 ml per minute per spray nozzle.

5. An apparatus as claimed in any preceding claim including an autospeed control system opertive to ensure that the apparatus delivers substantially the prescribed dosage irrespective of ground speed.

6. An apparatus as claimed in any preceding claim including a plurality of spray nozzles spaced apart so as to have a centre-to-centre separation of about 25 mm between adjacent nozzles.

7. An apparatus as claimed in any preceding claim in which the apparatus is adapted to discharge the spray material upwards, sidewards or with a sideways and/or upwards component.

8. An apparatus as claimed in any preceding claim in which the droplets of spray material are formed discretely by means of a single drop metering device.

9. An apparatus as claimed in any preceding claim in which the droplets of spray material are formed continuously using a low hydraulic pressure to eject them from the nozzles.

10. An apparatus as claimed in any preceding claim in which a "dribble bar" type of spray applicator is used in which the spray bar consists of a hollow tube along which the nozzles are positioned.

11. An apparatus as claimed in Claim 10 in which a gravity pressurised system with a hydraulic head limited to less than 1 m is used to supply the spray applicator.

12. An apparatus as claimed in any preceding claim in which the nozzles each have a diverging cone exit so that by using the correct combination of hydraulic head and diverging cone dimensions, the desired drop size and distribution pattern may be achieved.

13. An apparatus as claimed in any preceding claim in which the hydraulic pressure head may be set by means of an overflow chamber which may be raised and lowered either manually, or automatically, in relationship to the forward speed of the vehicle on which the applicator is mounted.

14. An apparatus as claimed in any preceding claim in which the applicator is mounted so that it is subject to the minimum of vibration and is also held substantially horizontal.

15. An apparatus as claimed in Claim 14 and including a spray tank, tower frame and spray bar on a single pivot carried on a frame which is adapted for attachment to the three-point linkage of a tractor.

16. An apparatus as claimed in any preceding claim in which as an alternative to spray nozzles, the spray applicator instead comprises a pocketed cylinder operative to discharge drops of the spraymaterial when the cylinder is rotated away from a first pocket-filling orientation in which the pockets, or a proportion of the pocket, are upwardly facing.

17. An apparatus as claimed in any preceding claim including spray control means for producing or optionally producing a pulsed flow to distribute the spray.

18. A spraying apparatus substantially as hereinbefore described with reference to, and/or as illustrated in, Figures 1 to 5 of the accompanying drawings.