The present invention relates to a sprayer nozzle and a flow control device which locates in a sprayer nozzle to enable accurate control of the flow rate of a pressurised liquid fertiliser.

The present invention is particularly well suited to use with liquid fertiliser and other liquid agrochemical sprays that require a course spray and will be described with respect thereto.

To improve crop yields, fertiliser may be applied on a regular basis. The fertiliser can either be applied as a solid in the form of granules or prills, or as a liquid aqueous solution or suspension. Each form of fertiliser has respective advantages and disadvantages, and each is in common use. Liquid fertilisers in particular have the advantage of providing accurate placement. Liquid fertiliser is often applied using crop-spraying apparatus.

The rate of application of the fertiliser is chosen to suit the needs of the crop and the condition of the soil in which the crop is being grown. The rate of application can in theory be controlled in three ways - by adjusting the flow rate from the outlet nozzle, adjusting the width of soil covered and by adjusting the speed over the ground of the vehicle applying the fertiliser.

The vehicle's top speed is limited as the vehicles used to apply the fertiliser are often large, and are travelling over uneven ground. However, to minimise costs and time, it is desirable to keep the vehicle speed as high as possible. Further, the width of the sprayer's arms and hence the width of soil covered must be kept to an optimum to ensure adequate coverage and sufficient stability. In practice therefore, the only way of varying the fertiliser application rate over a wide range is to change the size of the metering hole in each outlet. This may even entail changing all the outlet nozzles for different ones that have different flow rate settings. This has to be done manually before application starts.

Further, with the advent of GPS technology, farmers are now able to record crop yield data metre by metre as their crop is harvested. Combined with soil analysis, the fertiliser needed for the next crop can then be determined. This gives rise to a need to vary dynamically the application rate to suit the changing soil requirements. At present the application rate can only be varied from the cab of the vehicle by a small amount by altering the tractor speed and/or the liquid fertiliser feed pressure. If larger changes are required the outlets need to be reset individually. Manually resetting a large number of outlet ports by hand would be impractical, as this would take a long time, with 48 or more ports on one vehicle being normal.

The usable pressure that can be exerted through an outlet nozzle is generally from 1 .25 to 3.5 bar (1 bar being 100 kPa). From Toricelli's law the flow rate is proportional to the square root of the pressure. This gives a flow rate maximum to minimum ratio of 1 .7 to 1 .

The flow rate in litres per second from an orifice is calculated by the equation 1000 ^* agh, where a is the area of the orifice in square metres, g is the gravitational constant 9.81 , and h is the pressure measured in metres of head. The only means of making big changes in flow rate therefore is to change a. As previously mentioned, this is done on the outlet nozzles manually by setting the size of the metering hole. Attempts have been made to produce a nozzle with pressure-dependent metering holes. These prior art methods normally comprise a piston biased by a spring, the piston movement coupled to a valve which opens as the pressure is increased. These prior-art pistons suffer from several drawbacks, for example they are relatively bulky and expensive due to the number of moving parts required. The piston and valve are also liable to seize, as the use of such devices, is only intermittent. Furthermore, the liquid fertiliser only has limited lubrication properties and is corrosive to some metals, making degradation and seizure more likely.

The aim of the invention is to provide a nozzle comprising a flow control device which easily adjusts the flow of a pressurised liquid fertiliser in a linear manner. It is a further aim to accommodate such a flow control device inside each nozzle so that the benefits provided by the present invention can be conferred on existing sprayer apparatus.

Therefore according to the present invention there is provided a liquid fertiliser dispensing nozzle containing a flow control device for adjusting the rate of flow of a pressurised liquid fertiliser being dispensed, the device comprising: - a nozzle main body defining a chamber with spray holes, the main body being adapted for attachment to a supply orifice of a conventional sprayer;

- a metering plug having a part extending into the chamber, the metering plug defining an inlet for receiving liquid under pressure from the supply orifice, one or more aperture through which liquid fertiliser may pass into the chamber, and a flow path from the inlet to the or each aperture; and

- a resilient sheath mounted around that part of the plug extending into the chamber and closing the or each aperture, the sheath being expandable in response to increases in the pressure of the liquid fertiliser to allow the liquid fertiliser to flow out of the or each aperture into the chamber at a rate directly proportional to the pressure of the liquid fertiliser introduced to the inlet, such that an increase in liquid fertiliser pressure increases the effective size of an outlet from the sheath resulting in an increase in flow rate.

The main advantage of the present invention over the prior art nozzles is that the flow rate from the device is dependent on the pressure of liquid entering the device, and that an increase in liquid pressure produces a linear increase in flow rate, something that is not provided by the prior art. Figure 1 shows a graph plotting the flow rate in litres per minute versus pressure measured in bar. The solid line represents flow through a simple hole, and the dotted line represents flow through a nozzle of the present invention. As shown here, liquid does not flow from the device of the present invention until the pressure reaches a certain threshold. Once the threshold is passed, at approximately 1 .25 bar, flow begins and increases linearly with an increase in pressure. Flow through a simple hole on the other hand does not follow such a linear relationship, meaning that it is increasingly complicated to calculate flow rates accurately, and also that the upper limit of the flow rate cannot be reached without submitting the spraying apparatus to unreasonable pressures.

The present invention preferably allows a five-to-one ratio of flow to be controlled by a three-to-one ratio of pressure. Preferably, flow rates of 0.5 to 2.5 litres per minute will be achievable; though of course depending on the use required these rates can be increased or decreased accordingly. At least that part of the metering plug that extends into the chamber, but perhaps all of the plug, may preferably be substantially tubular with at least one closed end. The closed end being preferably the one that extends into the chamber. Preferably, the top end of the plug is open or has an opening and acts as the inlet, and the bottom end of the plug is closed. The or each aperture is preferably disposed in the side wall of the plug where it extends into the chamber. The sheath may at least partially surround the tubular side wall.

The outlet from the sheath is usually defined by the relationship between the sheath and the outer surface of that part of the plug that extends into the chamber. The outlet will usual comprise the gap between the sheath and the plug that forms as the sheath expands.

The liquid enters the chamber from the aperture at a rate dependent on the pressure of the liquid supplied to the inlet because the size of the gap between the surface of the metering plug and the sheath increases in proportion as the sheath expands with an increase in pressure. Therefore, the sheath must be made out of a suitable material that expands a suitable amount under pressure, and retains its elasticity during repeated use. Further, the sheath must be relatively unreactive and if appropriate be able to withstand constant exposure to liquid fertilisers and other volatile chemicals. It has been found that EPDM rubber (ethylene propylene diene Monomer) has all of the suitable properties for use with the present invention. Specifically, it has been found that a tubular sheath with walls about 3.2mm or more preferably about1 .6mm thick with an internal diameter of about 4.8mm, stretched over a part of a metering plug that has a diameter of about 5.8mm or more preferably 6.2mm and having one or more aperture about 2.5mm in diameter provides excellent results.

The nozzle of the present invention will preferably be connected to a sprayer with a pump to supply the liquid fertiliser under pressure to the inlet. The pressure supplied by the pump to the device can be controlled either manually or automatically. A quantity (usually between 20-60 depending on the number of spray orifices) of nozzles according to the present invention may be applied to a spaying rig mounted on a tractor or other vehicle to apply fertiliser to a field. A nozzle can be connected to each supply orifice on the sprayer arms and may potentially be controlled centrally and individually by a computer which calculates the precise amount (and therefore rate of flow) of fertiliser that must be supplied to each area of the field. These amounts and flow rates can be calculated beforehand, and using GPS technology and previous crop yields a complete map of each field may be drawn up with the specific quantities of fertiliser required for each area. The pressure applied to each supply orifice may be changed and hence the rate at which each nozzle spays may also be altered.

Preferably, the metering plug within the nozzle may be easily removed to allow repair or replacement, without replacement of the entire nozzle. The main body may be provided with connection means to allow its releasable connection to the nozzle supply orifice of a conventional sprayer. The nozzle may be adapted to connect to a supply orifice using any means, such as a separate standard boom bayonet fixing. Preferably the main body will incorporate a fixing such as a bayonet so that the present invention provides a complete replacement for existing nozzles.

A seal maybe provided in the main body so that when connected to the supply orifice it locates between orifice and the metering plug. This may serve to hold the metering plug in both in use and when not connected to the supply orifice. The engagement of the orifice on the seal may push it down onto the metering plug to ensure that fluid may flow only through the metering plug, not around it.

According to the present invention there is also provided a sprayer nozzle metering device, for controlling the rate of flow of a pressurised liquid fertiliser through the nozzle, the metering device removably locating in a main body of a nozzle, and comprising:

- a plug having a tubular part extending into a spray chamber defined by the main body of the nozzle,

- an inlet defined on an upper part of the plug that is not extended into the chamber for receiving liquid under pressure,

- an aperture through a side wall of the tubular part

- a liquid fertiliser flow path from the inlet to the aperture; and - a resilient sheath mounted around the tubular part of the plug and closing the aperture, the sheath being expandable in response to increases in the pressure of the liquid fertiliser to allow the liquid fertiliser to flow out of the aperture into the chamber at a rate directly proportional to the pressure of the liquid fertiliser introduced to the inlet, whereby an increase in liquid fertiliser pressure increases the flow rate.

The plug may preferably have a seal that engages with the main body to seal one end of the chamber. The plug may have an annular flange that engages against an equivalent abutment with the main body. Part of the sheath may locate between the flange and abutment to form a seal.

So that the invention may be better understood, but by way of example only, one embodiment thereof will now be described in detail, with reference to the accompanying drawings wherein:

Figure 1 shows a graph plotting the flow rate in litres per minute against pressure measured in bar;

Figures 2 shows a vertical cross section through one embodiment of nozzle of the present invention in a zero flow condition;

Figure 3 shows a similar vertical cross section through the nozzle of the present invention when flow is occurring; and

Figure 4 is a schematic representation of a metering plug removed from the nozzle.

Figure 1 , which has already been described above shows a graph plotting flow rate against pressure. The graph shows the linear relationship between pressure and flow which the present invention provides.

Figures 2 and 3 show a nozzle of the present invention in different flow states, and Figure 3 shows a metering plug that locates within the nozzle. All will be described together.

The nozzle according to the present invention generally comprises a main body 10 in which a metering plug 1 1 is located. An upper portion of the main body 10 comprises an upstanding collar 12 which is adapted to securely connect to a supply orifice 13 of a sprayer (not shown). This may connect by any suitable means such as conventional bayonet type fixings (not shown). Preferably the collar 12 is configured to connect to conventional spraying nozzle fixings.

A lower part of the main body 10 defines a chamber 15 and liquid fertiliser entering the chamber 15 may be ejected through spray holes 16. The nature of the spray pattern formed will depend upon the arrangement and number of spray holes16 as is understood in the art.

The metering plug, which is shown in perspective in Figure 4, comprises a generally tubular section 20 with a closed lower end 21 and a radially extending annular flange 22 defined at the upper end. At the upper end an inlet 24 provides access to the hollow interior 25 of the metering plug 1 1 , and an outlet in the form of an aperture 26 provided in the side wall 20 at the lower end is the opposite end of the flow path defined through the metering plug. A resilient EPDM rubber sheath 28 is located around the tubular section 20. The sheath is also provided with a radially extending sealing flange 29 at the upper end which overlaps the annular flange 22.

The metering plug is removably located within the main body 12. The lower portion extends into the chamber 15 and the annular flange 22 and the sealing flange 29 of the sheath rest upon an annular abutment 30 provided on the inside of the main body 12. This engagement seals the upper end of the chamber 15 and ensures that liquid fertiliser coming from the supply orifice 13 may only enter the chamber through the flow path defined within the metering plug 1 1 . A sealing ring 31 is located above the metering plug and when the nozzle is engaged with a supply orifice 13 the sealing ring 31 helps to form a seal with the orifice. In addition the orifice presses down on the sealing ring 31 which in turn presses down on the metering plug 1 1 to ensure it is correctly seated on the annular abutment 30.

The sheath 28 grips the tube 20 and as shown in Figure 2 blocks the apertures 26 to prevent liquid that has entered the inlet from passing out through the apertures 26. As shown in Figure 3, liquid supplied to the inlet (as represented by arrow 33), which is subject to a pressure in excess of a defined threshold has sufficient force to expand the sheath 28. This allows liquid to pass through the apertures 26 and flow between the sheath 28 and the wall of the tube 20 into the chamber 15 as represented by arrow 34. The radial aperture is shaped to minimise the chance of blockage.

The size of the aperture 26 sets an upper limit for flow rate of liquid through the metering plug. As pressure of liquid entering the inlet increases, once a certain threshold is exceeded the sheath 28 starts to expand. The expansion of the sheath 28 increases the size of a gap through which liquid can flow. When the sheath 28 tightly covers the apertures 26, the gap is closed - i.e. there is zero flow. As pressure increases so does the size of the gap and the rate of flow, up to the maximum rate possible (which is dependent on the area and quantity of apertures 26). There is a linear relationship between the flow rate and the pressure at which the liquid is supplied. Increases in pressure will produce a linear increase in the flow rate, and decreases in pressure produce a decrease in flow until the pressure falls below a minimum threshold after which flow will stop altogether.

In use, the supply orifice 13 receives pressurised liquid fertiliser from a pump, which draws it from a reservoir (neither the pump nor the reservoir are shown). The liquid fertiliser enters that part of the nozzle above the metering plug as well as the filling the flow path itself. If the liquid pressure within the hollow interior 25 exceeds the threshold, then the sheath 28 will stretch and liquid will pass through the apertures 26 and down through a gap between the side wall 20 and the sheath 28. The liquid will then pass into the chamber 15 and out of spray holes 16. Increases in the liquid pressure will cause further expansion of the sheath 28 and lead to a linear increase in the flow of liquid fertiliser to the spray holes 16.

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