Hydraulic control system for a spray boom on an agricultural field sprayer

Abstract

Spray boom (20) for an agricultural field sprayer for the controlled application of liquid on a target area (40), comprising - a main frame (24) which can be vertically adjusted and otherwise rigidly attached to a frame of the machine, - a central part (23) which is attached to the main frame, - a first and a second linkage arm (21, 22), each of which is pivotally attached laterally to the middle part (23) via a pivot axis (31, 32), - a first hydraulic cylinder (1) for angling and retracting the first linkage arm (21) about the pivot axis (31) and a second hydraulic cylinder (2) for angling and retracting the second linkage arm (22) about the pivot axis (22), wherein the hydraulic cylinders (1, 2) are designed to be double-acting and each has a cylinder housing and a piston with piston rod movable therein, and wherein a lever linkage (3) is provided on each of the linkage arms (21, 22), which articulately connects the linkage arm (21, 22) to the central part (23) and is designed and connected to the respective hydraulic cylinder (1, 2) such that the hydraulic cylinder (1, 2) retracts the piston rod when the linkage arm (21, 22) is retracted and extends it when the linkage arm (21, 22) is angled.

Description

[0001] The invention relates to a spray boom for an agricultural field sprayer for the controlled application of liquid onto a target area, comprising - a main frame that can be adjusted vertically and is otherwise rigidly attached to a frame of the machine, - a central section that is attached to the main frame, - a first and a second linkage arm, each of which is articulated laterally to the middle section via a pivot axis, - A first hydraulic cylinder for angling and retracting the first boom arm about the pivot axis and a second hydraulic cylinder for angling and retracting the second boom arm about the pivot axis, wherein the hydraulic cylinders are double-acting and each has a cylinder housing and a piston with a piston rod movable therein. The hydraulic cylinders serve to adjust the profile of the spray boom.

[0002] Field sprayers with booms are used for the even application of liquid substances, especially plant protection products, to an agricultural target area. This could be, for example, the soil in a field or the plants themselves. To ensure that the applied substances are distributed as evenly as possible across the entire width of the boom, the distance between the boom and the target area must be adjustable. Particularly with very wide booms, it is important to adjust the boom's angle and profile to accommodate slopes or varying plant heights.

[0003] Such spray booms and a control system for adjusting the tilt and profile are described in principle, for example, in DE 202011111069 U. A vertically adjustable main frame is present on the field sprayer to adjust the overall distance of the spray boom to the target area. The spray boom consists of a central section and two lateral boom arms. The tilt of the central section of the spray boom, and thus the entire spray boom, can be adjusted relative to the main frame by means of hydraulic cylinders. Additionally, the arms, each mounted on a pivot point on the central section, can be angled or tilted—that is, pivoted up or down—by means of an actuating cylinder to change the horizontal profile of the spray boom. The actuating cylinders are controlled by separate levers. The control system is not described further.

[0004] EP 3753407 A1 describes in more detail another such spray boom and a hydraulic control system for it.

[0005] The known designs have the disadvantage that these spray booms are prone to malfunctions under harsh operating conditions and that the hydraulic cylinders have to be large to withstand the forces that occur.

[0006] The purpose of the invention is now to develop a spray boom that can be operated more reliably.

[0007] The problem is solved by a spray boom according to claim 1. Further advantageous features are mentioned in the dependent claims.

[0008] The embodiment according to the invention is characterized in that a lever linkage is provided on each of the two linkage arms, which connects the linkage arm to the central part in a pivotal manner and is designed and connected to the respective hydraulic cylinder in such a way that the hydraulic cylinder retracts the piston rod when the linkage arm is angled and extends it when the linkage arm is angled.

[0009] Angled refers to raising the linkage arm, and angled refers to lowering the linkage arm.

[0010] In the cylinder housing of a double-acting hydraulic cylinder, a piston chamber and an annular chamber are formed, separated by the piston. The annular chamber is penetrated by the piston rod and therefore has a smaller piston contact area than the piston chamber on the other side of the piston, which acts on the entire piston surface. The force applied by the hydraulic cylinder corresponds to the difference in the forces acting on the piston, which result from the pressure in each chamber (piston chamber or annular chamber) multiplied by the corresponding piston contact area. The maximum force can be applied when the pressure on one side of the piston is ambient pressure.

[0011] The design of the hydraulic cylinders used here is based, among other things, on the force required to angle the linkage arm against the force of gravity. By using a lever linkage according to the invention, the force applied to the respective hydraulic cylinder is redirected so that it is subjected to pressure by the downward force of the linkage arm's weight. This offers significant advantages because, during normal operation when the linkage arms are largely angled, the piston chamber of the hydraulic cylinder is subjected to pressure. Since the piston chamber has a larger piston contact area than the annular space, the hydraulic cylinder can be designed to be smaller while still generating the necessary force. Furthermore, this results in advantages with regard to the required hydraulic pressure accumulators. These can be made smaller while maintaining the same spring characteristics for the inclination.The suspension characteristics are necessary to decouple the spray linkage from vibrations and fluctuations of the vehicle.

[0012] Additionally, the piston rod of the hydraulic cylinder is largely retracted when the boom arm is angled and thus in its normal operating position. This provides better protection for the piston rod against contamination, for example from soil or pesticides, during field operations in harsh environmental conditions.

[0013] It is particularly advantageous if the hydraulic cylinders are arranged so that the cylinder housing is articulated to the central section, and the piston, with its piston rod, is articulated to the linkage arm. This ensures that the connections for the working pressure lines on the cylinder housing remain relatively fixed when the piston is extended. Specifically, the pivot axis on the central section is positioned lower than the point where the hydraulic cylinder connects to the central section.

[0014] Alternatively, the hydraulic cylinders could also be installed the other way around, in which case the piston with its piston rod would be connected to the middle part.

[0015] In a particularly preferred embodiment, the respective lever linkage comprises a lever that is rotatable about a pivot point and is pivotally connected at one pivot point to the hydraulic cylinder and at another pivot point to the linkage arm or the central section, the pivot point being located between the two pivot points. This lever enables the force reversal to the hydraulic cylinder to be implemented reliably and simply.

[0016] Furthermore, it is advantageous if the lever is designed such that the distance between one pivot point and the lever's pivot point is smaller than the distance between the other pivot point and the lever's pivot point. With such a lever, a shorter piston stroke can result in a greater pivoting range of the linkage arm when angling or retracting. Due to the specific arrangement with the linkage, the hydraulic cylinder can also generate the necessary greater force required for such a lever.

[0017] In particular, the lever is designed such that the length between one pivot point (33) and the other pivot point (34) is at least 20 cm and at most 80 cm. This allows for sufficient pivot travel while still enabling the lever linkage to be implemented in a sufficiently space-saving manner.

[0018] In another preferred embodiment, the central section is rigidly connected to the main frame. This simplifies the design and the control system. If the central section is not too wide, the adaptation of the spray boom to a slope is not significantly impaired. Particularly preferably, the central section has a horizontal width b of at least 40 cm and a maximum of 300 cm. It is also advantageous if the central section has a horizontal width b that is between 1% and 12% of the total width of the spray boom (20). This ensures reliable adaptation of the profile, especially when the central section is rigidly connected to the main frame.

[0019] The spray boom can also include a hydraulic control system that actuates the hydraulic cylinders to control the angling and retraction of the boom arms. Preferably, the hydraulic control system is designed to provide suspension and / or damping for the pivoting movement of the boom arms by incorporating one or more hydraulic accumulators and / or one or more flow restrictors. In particular, one hydraulic accumulator is provided for each boom arm. The flow restrictor can, for example, be a throttle. This allows the boom arms to be decoupled from fluctuations and vibrations of the vehicle.

[0020] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. These features can be advantageously implemented not only in the combination shown, but also individually combined with one another. The figures show in detail: Fig. 1 Example of a spray boom according to the invention

[0021] The figures are described in more detail below. Identical reference numbers denote identical or analogous parts or components.

[0022] The Fig.Figure 1 schematically shows an embodiment of the spray boom 20 according to the invention. The main frame 24 is vertically height-adjustable and connected to the field sprayer. This can be a self-propelled field sprayer, a trailer for a tractor, or an implement mounted on a tractor. The distance h to the target surface 40 can be adjusted by means of the vertical height adjustment. The target surface 40 can be, for example, the soil or the plant itself in a field.

[0023] The spray boom 20 comprises the central section 23 and the two boom arms 21, 22. In this configuration, the central section 23 is rigidly attached to the main frame 24. The boom arms 21, 22 are articulated to the central section 23 via their respective pivot axes 31, 32 and by means of the double-acting hydraulic cylinders 1, 2 and the lever linkages 3, 4. By extending and retracting the pistons on the hydraulic cylinders 1, 2, the respective articulated arm 21, 22 can be angled. This allows the profile of the spray boom 20 to be adjusted to conform as uniformly as possible to the contour of the target surface 40. The aim is for the distance h to the target surface to be as uniform as possible across the width of the entire spray boom 20 and to lie within at least a specified distance range.

[0024] The rigidly attached central section 23 has a width b, which is preferably between at least 40 cm and at most 300 cm, or preferably between 1% and 12% of the total width of the spray boom (20). This ensures that the profile can be adapted with sufficient flexibility.

[0025] The detailed view shows an enlarged schematic representation of one of the lever linkages 3, 4. The illustrated lever linkage 3 comprises the lever 3a, which is rotatable about the lever pivot point 30. On one side of the lever 3a, it is pivotally connected to the hydraulic cylinder 1 at the first pivot point 33, and on the other side, it is pivotally connected to the linkage arm 21 at the other pivot point 34 via a rod. The lever pivot point 30 is pivotally connected to the central section 23 via a rod. Thus, the lever 3a can redirect the force so that the hydraulic cylinder 1 is subjected to pressure by the weight of the linkage arm 21.

[0026] The other lever linkage 4 is designed analogously.

[0027] The piston and piston rod are retracted when the linkage arms are bent and extended when they are bent. This means that the piston rod is largely protected from contamination during normal operation when the linkage arms 21, 22 are bent. Because the weight of the linkage arm 21, 22 acts as a compressive force on the hydraulic cylinder 1, 2 due to the deflection, the piston chamber is compressed, utilizing the full piston surface as the piston pressure area. This allows the hydraulic cylinder 1, 2 to exert a higher force at the same pressure than if the hydraulic cylinder 1, 2 were under tensile stress and the annular space were compressed.

[0028] In particular, the lever 3a is designed such that the distance between one pivot point 33 and the lever pivot point 30 is smaller than the distance between the other pivot point 34 and the lever pivot point 30. Preferably, the length between one pivot point (33) and the other pivot point (34) is at least 5 cm and at most 40 cm. The other linkage 4 with the lever 4a is designed analogously.

[0029] Alternatively, the hydraulic cylinder 1,2 and the lever linkage 3,4 could also be configured as a mirror image of the illustrated variant. That is, the hydraulic cylinder 1,2 is then arranged between the lever 3a,4a and the linkage arm 21,22. The lever pivot point 30 is also connected to the linkage arm 21,22 via a rod. And the lever 3a,4a is pivotally connected to the central section 23 via a rod. The force is redirected so that the hydraulic cylinder is subjected to pressure when the linkage arm 21,22 is angled.

[0030] The hydraulic control system for actuating the hydraulic cylinders 1, 2 is not explicitly shown. A working pressure line leads from at least one proportional valve to the corresponding hydraulic cylinder 1, 2 to supply it with pressure. Preferably, the control system includes a hydraulic accumulator that is connected to the working pressure line via a flow resistance, for example, a throttle. The flow resistance provides damping, and the hydraulic accumulator provides spring action. This decouples the spray boom 20 from vibrations and fluctuations of the vehicle.

[0031] In the illustrated embodiment, the cylinder housing of the hydraulic cylinders 1, 2 is connected to the central part 23, and the piston rod is connected to the linkage arm 21, 22 via the lever linkage 3, 4. Alternatively, the hydraulic cylinders 1, 2 can also be installed in reverse, i.e., with the piston rod connected to the central part 23 and the cylinder housing connected to the linkage arm 21, 22. Reference symbol list 1 first hydraulic cylinder 2 second hydraulic cylinders 3,4 Lever linkage 3a,4a Lever 20 spray booms 21 first linkage arm 22 second linkage arm 23 Middle section 24 main frames 30 Lever pivot 31,32 Swivel axis 33,34 pivot points 40 Target area h Distance to the target surface QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 202011111069

[0003] EP 3753407 A1

[0004]

Claims

[1] Spray boom (20) for an agricultural field sprayer for the controlled application of liquid on a target area (40), comprising - a main frame (24) which can be vertically adjusted and otherwise rigidly attached to a frame of the machine, - a central part (23) which is attached to the main frame, - a first and a second linkage arm (21, 22), each of which is articulated laterally to the central part (23) via a pivot axis (31, 32), - a first hydraulic cylinder (1) for angling and bending the first linkage arm (21) about the pivot axis (31) and a second hydraulic cylinder (2) for angling and bending the second linkage arm (22) about the pivot axis (22), wherein the hydraulic cylinders (1, 2) are double-acting and each have a cylinder housing and a piston with a piston rod movable therein, characterized by , that on each of the two linkage arms (21, 22) there is a lever linkage (3) which connects the linkage arm (21, 22) to the central part (23) in an articulated manner and is designed and connected to the respective hydraulic cylinder (1, 2) in such a way that the hydraulic cylinder (1, 2) retracts the piston rod when the linkage arm (21, 22) is bent and extends the piston rod when the linkage arm (21, 22) is bent. [2] Spray boom (20) according to claim 1 characterized by that the hydraulic cylinders (1,2) are arranged in such a way that the cylinder housing is connected in an articulated manner to the central part (23) and the piston with its piston rod is connected to the linkage arm (21,22). [3] Spray boom (20) according to one of claims 1 or 2 characterized bythat the respective lever linkage (3) comprises a lever (3a, 4a) which is rotatable about a lever pivot point (30) and which is articulated at one articulation point (33) to the hydraulic cylinder (1, 2) and at another articulation point (34) to the linkage arm (21, 22) or the central part (23), the lever pivot point (30) being located between one articulation point (33) and the other articulation point (34). [4] Spray boom (20) according to claim 3 characterized by that the lever (3a,4a) is designed such that the distance between one articulation point (33) and the lever pivot point (30) is smaller than the distance between the other articulation point (34) and the lever pivot point (30). [5] Spray boom (20) according to claim 3 or 4 characterized by that the lever (3a,4a) has a length between one pivot point (33) and the other pivot point (34) of at least 20 cm and a maximum of 80 cm. [6] Spray boom (20) according to one of the preceding claims characterized bythat the middle part (23) is rigidly connected to the main frame (24). [7] Spray boom (20) according to one of the preceding claims characterized by that the central part (23) has a horizontal width b of at least 40 cm and a maximum of 300 cm. [8] Spray boom (20) according to one of the preceding claims characterized by that the central part (23) has a horizontal width b which is between 1% and 12% of the total width of the spray boom (20). [9] Spray boom (20) according to one of the preceding claims characterized by that a hydraulic control system is present that can control the hydraulic cylinders (1,2). [10] Spray boom (20) according to claim 9 characterized bythat the hydraulic control system is designed to provide suspension and / or damping for the pivoting movement of the linkage arms (21, 22) via the hydraulic cylinders by having one or more hydraulic accumulators and / or one or more flow resistances, in particular one hydraulic accumulator is provided for each linkage arm (21, 22).

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