An agricultural sprayer

Abstract: The invention relates to an agricultural sprayer (1) for spraying a spray in the form of a carrier liquid, e.g. water, mixed with at least one active ingredient and comprising: a container (5) for receiving the carrier liquid, at least one container (10) for receiving an active ingredient, such as a fertilizer, an insect or disease controlling ingredient or a weed killing ingredient, in concentrated form, a mixing chamber (20) for mixing the carrier liquid with active ingredient from the at least one container (10) for providing the spray, connecting lines (11, 14) for feeding the active ingredient to the mixing chamber and connecting lines (6) for feeding the carrier liquid to the mixing chamber, a boom structure (30) having a plurality of nozzles (32) for ejecting the spray from the mixing chamber (20). The invention is characterized in connecting means (17) allowing gas flow communication between said means (18) for generating and discharging a flow of gas under pressure and said at least one container for receiving an active ingredient, said connecting means (17) being located such that a gas flow generated by said means (18) for generating and discharging a flow of gas under pressure sets up a flow of said active ingredient present in said connecting lines (11, 14) for feeding said active ingredient to said mixing chamber (20) in a direction from said mixing chamber (20) toward at least one of said containers (10) for active ingredient.

Description: The present invention relates to an agricultural sprayer of the type defined in the introductory portion of claims 1 and 13, and to a method for using such a sprayer, as stated in claim 14. In this type of sprayer the active ingredient is added continuously to a flow of carrier liquid during the spraying operation. Such agricultural sprayers are generally known, cf. e.g. EP 86 031, and are used as a modern alternative to conventional agricultural sprayers where the active ingredient is mixed with the carrier liquid prior to the sprayer being advanced over the field. The use of this new type of agricultural sprayer often involves, however, a significant loss of expensive active ingredient when the hoses which connect the containers holding the active ingredient with the nozzles, are emptied after the termination of the spraying operation for allowing subsequent spraying of a different active ingredient. This problem is particularly pronounced where the mixing chamber, in which the active ingredient is mixed with the carrier liquid, is arranged at a relatively great distance from the container for the active ingredient. The active ingredient emptied from the hoses is at times merely led to the sewer, leading to severe environmental problems. The object of the invention is to provide simple means whereby the above loss of active ingredient may be prevented, allowing ia. reduction of the costs involved in the spraying operation. As indicated in the characterizing clause of claim 1, this is achieved through the provision of connecting means allowing gas flow communication between the means for generating and discharging a flow of gas under pressure and the container for the active ingredient, said connecting means being located such that discharged gas under pressure sets up a flow of any active ingredient present in the hose connecting the mixing chamber with the container in a direction toward the container. Preferably, the connecting means includes a valve, such as a one-way valve. The use of a suitable valve arranged at the mixing chamber may permit a sealing-off of the mixing chamber when pressurized gas is discharged and active ingredient is led back to the container. The pressurized gas may also be used for simultaneous or subsequent discharge of any liquid present in the mixing chamber through the nozzles. The means for generating and discharging a flow of gas under pressure may preferably be a compressed air container or, alternatively, an air blower, whereby the invention may be implemented to particular advantage in connection with so-called air-assisted agricultural sprayers (see e.g. EP 734 203), where the airflow from the blower may thus be utilized for the mentioned purpose after the termination of the spraying operation. The hoses for feeding active ingredient to the mixing chamber may preferably also be connected with a container for a cleaning or rinsing liquid, such as the container for carrier liquid if the latter is suitable for the purpose, to allow flushing of these hoses after the active ingredient has been passed back to the container for active ingredient. Further, the mixing chamber may advantageously be positioned close to the nozzles on the boom structure, so that a prescribed change of the metered amount of active ingredient per unit of time and thereby of the concentration of active ingredient in the spray, may be registered in the ejected spray immediately after the change has been made. The invention provides quite special advantages in this case, since a degree of freedom is achieved as regards the positioning of the containers for active ingredient, without involving an unnecessary loss of active ingredient after the termination of a spraying operation. It will be appreciated that in this situation the containers for active ingredient may e.g. be positioned at the container for carrier liquid, thereby allowing the operator-operated parts of the agricultural sprayer to be gathered at one place. Preferably, means are provided for equalising the pressure in the container for active ingredient. The provision of such means is, however, no prerequisite for the proper operation of the invention, particularly when collapsible containers for the active ingredient are used. Alternatively, as stated in the characterizing clause of claim 13, the object of the invention may also be achieved by providing means adapted to generate a negative pressure in the container for active ingredient, thereby drawing back active agent present in the hose leading to the mixing chamber. In this case, too, means for providing a pressure equalisation may be provided. It will be appreciated that the invention may find application in connection with agricultural sprayers having one or more containers for different active ingredients, including e.g. where each of these are connected with the same or different mixing chambers by means of hoses, which may thereby be emptied after the termination of a spraying operation. Such an agricultural sprayer may e.g. conceivably be used for spraying during the same operation of an area where e.g. a fungicide is needed in one area, while an insecticide is needed in an adjoining area. The invention will be explained more fully below with reference to the embodiments shown in the drawing, in which fig. 1 shows the agricultural sprayer during a spraying operation, fig. 2 shows the agricultural sprayer during return flow of unused active ingredient in the hoses, fig. 3 shows the agricultural sprayer after return flow of the unused active ingredient during cleaning of the hoses, and fig. 4 shows an alternative embodiment of the invention, during a spraying operation. Fig. 1 shows a section of an agricultural sprayer, more particularly a liquid feeding system, which may be positioned either on an independent propelling unit, an independent trailer coupled to a tractor, or on a frame intended to be mounted on a tractor. The liquid feeding system comprises a container 5 for a carrier liquid, typically water. The container 5 may e.g. have a volume of about 0.5-6 m 3 . A hose connection 6 extends from the container 5 to a mixing chamber 20 in which the carrier liquid is mixed with a highly concentrated active ingredient, such as a fungicide or pesticide. The resultant mixture is fed via a hose connection 22 to a plurality of nozzles 32 arranged on a boom 30. The mixing chamber 20 may alternatively form an integrated part of each nozzle, which thus receives both carrier liquid and active ingredient via separate connecting hoses. As shown, the agricultural sprayer also comprises a container 10 for the mentioned active ingredient. The container 10 is connected with the mixing chamber 20 via a relatively short connecting hose 11, a longer connecting hose 14, a metering pump 12 and shut-off valves 13 and 16 for feeding active ingredient for mixing with the carrier liquid. Instead of using a metering pump 12 the feeding of the active ingredient to the mixing chamber 20 may take place by providing a negative pressure in the mixing chamber 20, e.g. by a venturi effect. Fig. 2 shows a state of the agricultural sprayer after the termination of a spraying operation, where the metering pump 12 and a pump (not shown) carrying carrier liquid to the mixing chamber 20 are stopped. In this state, an amount of active ingredient is left in the connecting hose 14, which hose 14 may have a length of e.g. up to about 1 - 15 metres, according to the structure of the agricultural sprayer. It will be appreciated that even with a modest hose cross-section a considerable amount of active ingredient will be left in the hose 14. To avoid waste of this amount of active ingredient, the agricultural sprayer comprises a compressor or blower 18 which is connected with the container 10 via a hose connection 17, via the valve 16, the hose 14 and via an additional length of hose 15, which extends between the shut-off valve 13 and the container 10. Air under pressure, which is generated by the compressor or blower 18, is used for passing or pressing the active ingredient in the hose 14 back to the container 10, as the valve 16, which may be a three-way valve, is switched so as to block access to the mixing chamber 20, and so as to place the blower 18 in flow communication with the hose 14. The valve 13 is preferably switched so that the hose 11 is isolated from the hose 14. The container 10 may of course be provided with suitable valve arrangements, or may have a venting opening, to provide prescribed pressure equalization. When the active ingredient in the hose 14 has been fed back to the container 10, an outlet valve (not shown) at the container 10 is shut-off. Fig. 3 shows the agricultural sprayer in a cleaning state where the hose 11 is connected with a container 2 for a cleaning liquid via a valve (not shown). The hose 11 may alternatively be connected with the container 5, if this contains water or a similar liquid suitable for cleaning the hoses 11, 14, 22. By simultaneously performing a suitable switching of the valves 13 and 16 it is now possible to carry out cleaning of the hoses 11, 14, 22, which may be flushed by the cleaning liquid e.g. by means of the pump 12. It will be appreciated that solely cleaning of the hoses is performed in this situation, as the liquid from the container 2 does not drive active ingredient out through the nozzles. It may be mentioned that the valve 16 may also be arranged to place the blower 18 in flow communication with the mixing chamber 20 when the active ingredient has been fed back to the container 10, to allow emptying of the liquid present in the hose 22 via the nozzles 32. Fig. 4 shows an alternative embodiment of the invention in which the valve 16 is replaced by a one-way valve 16', which prevents loss of liquid from the hose 14. The one-way valve 16' is arranged in a stub 17 forming a branch of the hose 14. The stub 17 connects to the compressor or blower 18 and the one-way valve 16' is adapted to open when pressurized air leaves the compressor or blower 18 whereby pressurized air enters the hose 14 to drive liquid in the hose 14 towards the container 10. Part of the flow of pressurized air entering the hose 14 may preferably be directed to the mixing chamber 20 to discharge any liquid present therein and in the hose connection 22. A valve (not shown) may suitably be arranged in the hose connection 6 to disconnect the container 5 for the carrier liquid. It is noted that the blower 18 may - in accordance with the invention - also be connected directly to the mixing chamber 20 or at any other location suitable for achieving the overall object of the invention.

Claims: An agricultural sprayer (1) for spraying a spray in the form of a carrier liquid, e.g. water, mixed with at least one active ingredient and comprising: a container (5) for receiving said carrier liquid, at least one container (10) for receiving an active ingredient, such as a fertilizer, an insect or disease controlling ingredient or a weed killing ingredient, in concentrated form, a mixing chamber (20) for mixing said carrier liquid with said active ingredient from said at least one container (10) for providing said spray, connecting lines (11, 14) for feeding said active ingredient to said mixing chamber (20) and connecting lines (6) for feeding said carrier liquid to said mixing chamber (20), a boom structure (30) having at least one nozzle (32) connected with said mixing chamber (20) for ejecting said active ingredient mixed with said carrier liquid, means (18) for generating and discharging a flow of gas under pressure, preferably air, characterized in connecting means (17) allowing gas flow communication between said means (18) for generating and discharging a flow of gas under pressure and said at least one container for receiving an active ingredient, said connecting means (17) being located such that a gas flow generated by said means (18) for generating and discharging a flow of gas under pressure sets up a flow of said active ingredient present in said connecting lines (11, 14) for feeding said active ingredient to said mixing chamber (20) in a direction from said mixing chamber (20) toward at least one of said containers (10) for active ingredient. An agricultural sprayer according to claim 1, characterized in that said connecting means (17) comprises a one-way valve (16'). An agricultural sprayer according to the preceding claim, characterized in that said connecting lines (11, 14) for feeding said active ingredient to said mixing chamber (20) comprise a valve (16) arranged between said connecting means (17) and said mixing chamber (20). An agricultural sprayer according to any of the preceding claims, characterized in that said connecting means (17) is arranged adjacent to said mixing chamber (20) An agricultural sprayer according to any of the preceding claims, characterized in that said means (18) for providing said flow of gas comprise a blower, a compressor or a compressed gas container. An agricultural sprayer according to any of the preceding claims, characterized in that the connecting lines (11, 14) for feeding active ingredient to the mixing chamber (20) comprise a pump (12) for feeding active ingredient to the mixing chamber (20). An agricultural sprayer according to any of the preceding claims, characterized in that the mixing chamber (20) comprises means for providing a negative pressure in the connecting lines (11, 14) for feeding active ingredient to the mixing chamber (20). An agricultural sprayer according to any of the preceding claims, characterized in that the connecting lines (11, 14) for feeding active ingredient are also connected with a container (2) for a cleaning liquid. An agricultural sprayer according to any of the preceding claims, characterized in that the mixing chamber (20) is arranged on the boom structure (30), and that the at least one container (10) for active ingredient is arranged in the vicinity of the container (5) for carrier liquid. An agricultural sprayer according to any of the preceding claims, characterized in that the mixing of active ingredient and carrier liquid takes place immediately before each nozzle (32). An agricultural sprayer according to any of the preceding claims, characterized in that each nozzle (32) is constructively built together with a respective mixing chamber (20). An agricultural sprayer according to any of the preceding claims, characterized in that said at least one container for receiving an active ingredient is provided with venting means. An agricultural sprayer (1) for spraying a spray in the form of a carrier liquid, e.g. water, mixed with an active ingredient and comprising: a container (5) for receiving said carrier liquid, at least one container (10) for receiving an active ingredient, such as a fertilizer, an insect or disease controlling ingredient or a weed killing ingredient, in concentrated form, a mixing chamber (20) for mixing said carrier liquid with active ingredient from said at least one container (10) for providing said spray, connecting lines (11, 14) for feeding said active ingredient to said mixing chamber (20) and connecting lines (6) for feeding said carrier liquid to said mixing chamber (20), a boom structure (30) having at least one nozzle (32) connected with said mixing chamber (20) for ejecting the active ingredient mixed with said carrier liquid, characterized in that said connecting lines (11, 14) for feeding active ingredient to said mixing chamber comprise a valve (16) arranged immediately in front of said mixing chamber (20) and adapted to be set in a first position in which there is flow communication with said mixing chamber (20) and a second position in which there is no flow communication with said mixing chamber (20), and means are arranged to generate a negative pressure in the container (10) for active ingredient for providing a flow of active ingredient in a direction from the mixing chamber (20) toward the container (10) for active ingredient when the valve (16) is set in the second position. A method of operating an agricultural sprayer of the type defined in the introductory part of claims 1 and 13, after the termination of a spraying operation, characterized in that active ingredient in the connecting lines (11, 14) for feeding active ingredient to the mixing chamber (20) is fed back to the container (10) for active ingredient using compressed air.

Inventors: NORMAN THOMAS, SECHER JORGEN BO MORCH, NORMAN, THOMAS, SECHER, JORGEN BO MORCH
Applicants: HARDI INTERNAT A S, HARDI INTERNATIONAL A/S
Application year: 2000
Main classification: A01M7
IPC codes: A01M7