SPRAY NOZZLE

Abstract: A spray nozzle (1) has a pre-chamber (39) and a mixing region (32). A first inlet (12) defines a first fluid flow path for admittance of a first fluid to the pre-chamber (39). A second inlet (14) defines a second fluid flow path which is crossed by the first fluid flow path for admittance of a second fluid to the pre-chamber (39). A wall (21) is positioned between the pre-chamber (39) and the mixing region (32) and has an aperture (22) therethrough coaxial with the first fluid flow path. Fluid can pass from the mixing region (32) out of the spray nozzle (1) through an outlet (36), the outlet (36) not lying on the first and second fluid flow paths. A first fluid entering through the first inlet (12) mixes with a second fluid entering through the second inlet (14) in the mixing region (32) prior to the mixed first and second fluids passing out through the outlet (36).

Description: flPPAV NOZZLE The present invention relates to a spray nozzle. Various forms of agricultural spray nozzles are known. In each, a liquid such as a fertiliser or pesticide is supplied to the spray nozzle. The spray nozzle breaks up the liquid into droplets on exiting through an outlet provided in the spray nozzle tip. The spray nozzles may produce various different spray patterns, such as a flat spray pattern, a " solid" cone of drops, a " hollow" cone of drops, etc. Various spray nozzles have been produced which attempt to provide a better dispersion of the liquid being sprayed in order to reduce the amount of liquid used per unit area of crop in order both to keep down costs and also to minimise any adverse effect on the environment. In the spray nozzle marketed by the present applicant as " TurboDrop" , a flow of liquid through the spray nozzle passes through a venturi restriction which causes air to be entrained with the liquid flow, the air being drawn in through an air inlet in the side of the spray nozzle assembly. The liquid and entrained air pass into a relatively long mixing chamber. The liquid and air mix and air-filled droplets form when the mixed liquid and air pass out through the spray tip in a selected spray pattern. The air-filled droplets tend to drift much less than droplets produced by conventional spray apparatus and provide excellent coverage of an area. A similar device is disclosed in GB-A-2256817 in which liquid passes into a convergent inlet end of a venturi in the spray nozzle, there being a gas inlet to that convergent inlet end of the venturi. The venturi itself is relatively long and passes to a so-called mixing chamber though it is understood that mixing will take place in the venturi as well as in the mixing chamber itself. In each of these prior art spray nozzles, each of which relies on the venturi effect, the venturi or mixing chamber has to be relatively long in order to ensure that sufficient mixing of the liquid with the entrained air is achieved to allow turbulence to be created thereby to provide air-filled liquid droplets. The venturi/mixing chamber also has to be long in order to prevent liquid passing straight out of the nozzle; in other words, there must be sufficient time for mixing to occur before liquid exits the spray nozzle. This means that these prior art spray nozzles as a whole are long. This causes a problem in the field because such spray nozzles are mounted on booms which are either carried by or towed by a tractor, for example. Such booms are usually folded for storage or during transit between spraying areas . The long prior art spray nozzles are easily knocked off when the booms are folded. Moreover, it is usually recommended to use a liquid supply pressure of typically 7 bar (approximately 700 kPa) for some of the prior art spray nozzles. Such high pressures (compared to a typical value of 3 bar (approximately 300 kPa) for conventional spray nozzles) means that the user has to obtain and use expensive powerful pumps. Such high pressures can also cause damage to the spray components which incorporate the spray nozzle assembly. Moreover, the long mixing chambers/venturi make these prior art spray nozzles difficult to clean especially as, in practice, such spray nozzles will typically be covered in mud having been carried behind a tractor. Another type of prior art spray nozzle is a so-called twin fluid nozzle. A liquid is forced into a mixing and atomising chamber in the spray nozzle and typically strikes a plate provided within the chamber. Pressurised air is forced into the chamber to carry the liquid out of the chamber outlet to a spray nozzle outlet where the liquid atomises and droplets issue as a spray. It should be noted that the air is forced into the chamber in a twin fluid nozzle rather than being drawn in by movement of liquid through the chamber as in a venturi nozzle. Examples of twin fluid nozzles are disclosed in EP-A-0225193 , GB-A-2157591 and US-A-4828182. According to a first aspect of the present invention, there is provided a spray nozzle, the nozzle comprising a pre-chamber and a mixing region, a first inlet defining a first fluid flow path for admittance of a first fluid to the pre-chamber, a second inlet defining a second fluid flow path which is crossed by the first fluid flow path for admittance of a second fluid to the pre-chamber, a wall between the pre-chamber and the mixing region and having an aperture therethrough coaxial with the first fluid flow path, and an outlet from the mixing region through which fluid can pass from the mixing region out of the spray nozzle, the outlet not lying on the first and second fluid flow paths such that in use a first fluid entering through the first inlet mixes with a second fluid entering through the second inlet in the mixing region prior to the mixed first and second fluids passing out through the outlet . The aperture in the wall between the pre-chamber and the mixing region allows fluid to pass from the pre-chamber to the mixing region whilst the wall itself tends to prevent fluid in the mixing region passing back to and out of the second inlet. In the preferred embodiment, the wall defines the pre-chamber positioned upstream of the mixing region and into which the first and second inlets open. In a venturi nozzle where air is drawn in as the second fluid through the second inlet, the size of the aperture in the wall can be adjusted to provide some degree of control over the amount of air which is drawn in through the second inlet. The pre-chamber helps to keep down the overall length of the nozzle by promoting more efficient mixing of the first and second fluids. A first end of the second inlet is preferably open to atmosphere and a second end of the second inlet preferably opens to a position adjacent the first fluid flow path whereby passage of a first fluid through the first inlet causes air to be drawn in through the second inlet . Alternatively, there may be means for connecting the second inlet to a supply of pressurised air. The spray nozzle may have a wall opposite the first inlet and transverse to the first fluid flow path, said wall having an aperture defining the outlet which is offset from the first fluid flow path. The aperture of the wall between the pre-chamber and the mixing region preferably has a cross-sectional area which is greater than the cross-sectional area of the first inle . The first inlet preferably consists of two first inlet apertures. In this embodiment, the wall between the pre- chamber and the mixing region preferably has two apertures therethrough which are respectively coaxial with the two first inlet apertures . The use of two inlet apertures helps to ensure that the pattern of fluid exiting the outlet in use is symmetrical, ensuring more uniform coverage during spraying. The inlet apertures are preferably symmetrically spaced either side of a central longitudinal axis of the spray nozzle. Preferably, the first fluid flow path is at a right angle to the second fluid flow path. The second inlet preferably comprises two second inlet apertures . The outlet may lie on a central longitudinal axis of the spray nozzle. The spray nozzle is preferably in two parts, the first part having the first and second inlets, the second part having the outlet. The use of two parts means that the size of the outlet can be altered easily by using a different outlet part having a different size outlet. The use of two parts also facilitates cleaning of the nozzle. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1A to IE are respectively a view from an inlet end, a first side view, a first longitudinal cross- sectional view, a view from the outlet end of an inlet part, and a second side view of a first example of a spray nozzle according to the present invention; Figures 2A to 2E are respectively a view from an outlet end, a first side view, a longitudinal cross- sectional view, a view from an inlet end, and a second side view of an outlet part of the first example of the spray nozzle; Figures 3A to 3E are respectively a view from an outlet end, a first longitudinal cross-sectional view, a first side view, a second side view, and a second cross- sectional view of the first example of the assembled spray nozzle; Figures 4A and 4B are perspective views of the assembled spray nozzle and the disassembled spray nozzle of the first example respectively; and, Figures 5A and 5B are perspective views of a disassembled spray nozzle and an assembled spray nozzle of a second example of the present invention. In Figures 1A to IE, there are shown various views of an inlet part 10 of a first example of a spray nozzle 1 according to the present invention. In Figures 2A to 2E, there are shown various views of an outlet part 30 of the spray nozzle 1. The assembled inlet and outlet parts 10,30 are shown in Figures 3A to 3E and 4A. The inlet part 10 generally has a circular cross- sectional shape having reduced stepped outer diameters as shown particularly clearly in the side views Figures IB, 1C and IE. Figure 1C is a cross-section on lines I-I of Figure 1A. The base portion 11 of the inlet part 10 has the greatest external diameter and has two apertures or through holes 12 which define first inlets for a first fluid. The through holes or first fluid inlets 12 pass through the base portion 11 in a direction parallel to the central longitudinal axis X-X of the inlet part 10. The first fluid inlets 12 are symmetrically placed either side of the central longitudinal axis X-X of the inlet part 10 and so are positioned at an equal spacing on opposite sides of the central longitudinal axis X-X. The first fluid inlets 12 define flow paths A for the first fluid in a direction parallel to the central longitudinal axis X-X of the inlet part 10. A second or intermediate portion 13 of reduced external diameter is adjacent the base portion 10. Opposite sections of the wall defining the second or intermediate portion 13 are relieved or absent so as to provide opposed second inlets 14 for a second fluid to enter through the second fluid inlets 14 into the hollow centre 16 of the inlet part 10 in a direction B transverse to the first fluid flow paths A. As can be seen from the drawings, the second fluid inlets 14 open onto the first fluid flow paths A and are thus crossed by flow of the first fluid through the first fluid inlets 12. The second fluid inlets 14 are at a position which is rotated through 90° around the longitudinal axis X-X relative to the first fluid inlets 12. In the embodiment shown, the second fluid inlets 14 are open to atmosphere. The intermediate portion 13 of the inlet part 10 leads onto a final portion 15 of reduced external diameter. This final portion 15 defines therein a hollow cylindrical volume 16 which will be discussed further below. The end portion 15 of the inlet part 10 has a first external annular bead 17 and a second external annular bead 18. In this example, the intermediate portion 13 of the inlet part 10 has four locating wedge-shape recesses 19 facing in a direction parallel to the longitudinal axis X-X on the stepped surface 20 which connects the intermediate portion 13 externally to the final portion 15. Within the inlet part 10, at a position just downstream of the second fluid inlets 14 and corresponding to the junction between the intermediate portion 13 and final portion 15 of the inlet part 10, is an intermediate wall 21. This intermediate wall 21 has two circular apertures 22 which are coaxial with and of slightly larger diameter than the first fluid inlets 12. The outlet part 30 of the spray nozzle 1 has a first circular wall 31 which defines a mixing chamber 32 in the form of a cylindrical central volume 32. The circular wall 31 is sized to fit over the narrow portion 15 of the inlet part 10 and has an internal annular recess 33. The outlet part 30 has wedge-shape teeth 34 which correspond to and are received in the wedge-shape recesses 19 of the inlet part 10 to fix the relative orientation of the two parts 10,30 in the assembled spray nozzle 1. As can be seen particularly clearly in Figures 2C, which is a cross-sectional view on II-II of Figure 2A, and in Figure 3B and 3E, which are cross-sectional views on IV-IV and III-III of Figure 3A respectively, the central volume 32 of the outlet part 30 terminates in a wall 35 which is opposite the first fluid inlets 12 in the assembled spray nozzle 1. A through hole 36 which provides an outlet from the central volume 32 is provided centrally of the wall 35. The longitudinal extent of the outlet 36 is defined by a short cylindrical wall 37 running parallel to the central longitudinal axis of the spray nozzle 1. The short wall 37 has a wedge-shape recess 38 which flares outwardly away from the outlet 36 to define a fan spray tip as is well known in the art of spray nozzles. It will be appreciated that the portion of the wall 37 surrounding the outlet 36 can be provided with different shapes in order to provide spray patterns of different shapes, such as cones for example. In use, the spray nozzle 1 is formed by assembling the inlet and outlet parts 10,30 with the wall of the final portion 15 of the inlet part 10 being received in the central volume 32 of the outlet part 30. The second bead 18 snaps into the annular recess 33 and the first bead 17 provides a seal for the junction of the inlet and outlet parts 10,30. The intermediate wall 21 of the inlet part 10 provides a pre-chamber 39 upstream of the mixing chamber 32. The assembled spray nozzle 1 can then be fitted to an agricultural boom by means of a conventional spray cap (not shown) for example. A first fluid, which may be a liquid such as a solution of a pesticide or fertiliser for example, is supplied under pressure to the first fluid inlets 12 so that the first fluid flows in the direction indicated by arrows A. The flow of the first fluid transversely past the laterally disposed second fluid inlets 14 draws air in through the second fluid inlets 14 into the pre-chamber 39 and the air is entrained with the first fluid. On passing through the apertures 22 of the intermediate wall 21 into the mixing chamber 32 provided by the volume 32 defined in the outlet part 30, the first fluid strikes the opposed wall 35 of the inlet part 30. It will be appreciated that because the first fluid inlets 12 are offset relative to the outlet 36, there is very little tendency for the first fluid to pass straight out of the outlet 36. The intermediate wall 21 tends to prevent the fluid in the mixing chamber 32 passing back to and out of the second fluid inlets 14. After striking the wall 35 opposite the first fluid inlets 12, the first fluid having entrained air atomises to produce air- filled droplets on being forced out of the mixing chamber 32 by the action of further incoming first fluid entering the mixing chamber 32 through the first fluid inlets 12 and apertures 22 of the intermediate wall 21. It will be appreciated that this is achieved without requiring a long mixing chamber, in contrast to the prior art spray nozzles of this type. The effective mixing chamber of the present invention is provided by the relatively short volume 32 of the second part 30. A second example of a spray nozzle 1 in accordance with the present invention is shown in Figures 5A and 5B. The second example is similar to the first example described above and those parts which are the same have the same reference numerals and will not be further described. The second example of the spray nozzle 1 differs in the way relative orientation of the two parts 10,30 is achieved. In the second example of the spray nozzle 1, the wedge-shape recesses 19 and wedge-shape teeth 34 of the first example are replaced by a pair of opposed lugs 40 on the second part 30 which project rearwards of the second part to engage with corresponding opposed recesses 41 provided in the stepped surface 20 which connects the intermediate portion 13 externally to the final portion 15 of the first part 10. It has been found that the spray nozzle of the present invention can operate at a pressure of only 3 bar (approximately 300 kPa) which is much less than the 7 bar (approximately 700 kPa) required of some prior art spray nozzles of this type as discussed above. A pressure of 3 bar (approximately 300 kPa) is more typical of the pressures used in conventional spraying equipment and therefore the spray nozzle 1 of the present invention is much more convenient for the user. The spray components which incorporate the spray nozzle 1 are much less likely to suffer damage, for example to seals, due to the supply pressure of the first fluid. It has also been found that the manufacturing tolerances required of the spray nozzle 1 of the present invention are much less stringent than those similar spray nozzles of the prior art. For example, in the " TurboDrop" spray nozzle mentioned above, it is necessary to balance carefully the inlet orifice size compared to the outlet orifice size to within very fine tolerances in order to prevent flooding and liquid outflow through the air inlet. In the present invention, the requirements on manufacturing are much less stringent. The present invention allows the outlet orifice size to be varied relatively freely, which allows much greater freedom in manufacture which in turn enables the ultimate droplet size to be varied simply by providing different outlet parts 30 having different sizes for the outlet 36. Different droplet sizes have different dispersion characteristics and therefore the present invention allows the user to obtain the required dispersion characteristic more easily. In some circumstances, a small droplet size is preferred whereas in other circumstances a larger droplet size is preferred. At present, the reason for the less stringent requirements on manufacturing tolerances is not clear but it is believed to be related to the non-alignment of the inlets and outlets in the spray nozzle 1 of the present invention. Moreover, the size of the apertures 22 of the intermediate wall 21 can be adjusted to provide some degree of control over the amount of air which is drawn in through the second fluid inlets 14. The inlet and outlet parts 10,30 can be made of any suitable materials, including plastics such as acetal . An embodiment of the present invention has been described with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention. For example, more than two first fluid inlets may be provided, there preferably being a corresponding number of apertures in the intermediate wall. More than two second fluid inlets may be provided.

Claims: £ MS 1. A spray nozzle (1), the nozzle (1) comprising a pre- chamber (39) and a mixing region (32) , a first inlet (12) defining a first fluid flow path for admittance of a first fluid to the pre-chamber (39) , a second inlet (14) defining a second fluid flow path which is crossed by the first fluid flow path for admittance of a second fluid to the pre-chamber (39) , a wall (21) between the pre-chamber (39) and the mixing region (32) and having an aperture (22) therethrough coaxial with the first fluid flow path, and an outlet (36) from the mixing region (32) through which fluid can pass from the mixing region out of the spray nozzle (1) , the outlet (36) not lying on the first and second fluid flow paths such that in use a first fluid entering through the first inlet (12) mixes with a second fluid entering through the second inlet (14) in the mixing region (32) prior to the mixed first and second fluids passing out through the outlet (36) . 2. A spray nozzle according to claim 1, wherein a first end of the second inlet (14) is open to atmosphere and a second end of the second inlet (14) opens to a position adjacent the first fluid flow path whereby passage of a first fluid through the first inlet (12) causes air to be drawn in through the second inlet (14) . 3. A spray nozzle according to claim 1, comprising means for connecting the second inlet (14) to a supply of pressurised air. 4. A spray nozzle according to any of claims 1 to 3 , comprising a wall (35) opposite the first inlet (12) and transverse to the first fluid flow path, said wall (35) having an aperture (36) defining the outlet which is offset from the first fluid flow path. 5. A spray nozzle according to any of claims 1 to 4, wherein the aperture (22) of the wall (21) between the pre- chamber (39) and the mixing region (32) has a cross- sectional area which is greater than the cross-sectional area of the first inlet (12) . 6. A spray nozzle according to any of claims 1 to 5, wherein the first inlet comprises two first inlet apertures (12) . 7. A spray nozzle according to claim 6, wherein the wall (21) between the pre-chamber (39) and the mixing region (32) has two apertures (22) therethrough which are respectively coaxial with the two first inlet apertures (12) . 8. A spray nozzle according to claim 6 or claim 7, wherein the first inlet apertures (12) are symmetrically spaced either side of a central longitudinal axis of the spray nozzle (1) . 9. A spray nozzle according to any of claims 1 to 8 , wherein the first fluid flow path is at a right angle to the second fluid flow path. 10. A spray nozzle according to any of claims 1 to 9 , wherein the second inlet comprises two second inlet apertures (14) . 11. A spray nozzle according to any of claims 1 to 10, wherein the outlet (36) lies on a central longitudinal axis of the spray nozzle (1) . 12. A spray nozzle according to any of claims 1 to 11, wherein the spray nozzle (1) is in two parts, the first part (10) having the first and second inlets (12,14), the second part (30) having the outlet (36) .

Inventors: SWAN TREVOR WILLIAM BARTLETT, SWAN, TREVOR, WILLIAM, BARTLETT
Applicants: LURMARK LTD, SWAN TREVOR WILLIAM BARTLETT, LURMARK LIMITED, SWAN, TREVOR, WILLIAM, BARTLETT
Application year: 1998
Main classification: B05B7
IPC codes: B05B7