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

Abstract

The invention relates to a spray boom for an agricultural field sprayer for controlled application of liquid onto a target area, comprising: - a main frame, which is vertically adjustable and can be otherwise rigidly fastened to a frame of the machine; - a central part, which is tiltably fastened to the main frame by a hinge pin; - a first and a second boom arm, each of which is fastened at the side of the central part; - a double-action hydraulic cylinder, which has a cylinder housing and a piston which is movable therein and has a piston rod, wherein a piston chamber and an annular chamber, through which the piston rod passes, are formed in the cylinder housing so as to be separated by the piston; - a further double-acting hydraulic cylinder, provided on the spray boom, which connects the central part to the main frame and via which the tilting of the central part with respect to the main frame can be adjusted; wherein only one of the boom arms is articulatedly fastened to the central part via a pivot pin and the hydraulic cylinder such that said boom arm can be angled and bent about the pivot pin, and the other boom arm is rigidly fastened to the central part; and wherein the pivot pin is arranged asymmetrically at the distance a from the centre of the spray boom, and wherein the distance a is at least 15 cm and at most 60 cm.

Description

[0001] Hydraulic control system for a spray boom on an agricultural field sprayer

[0002] The invention relates to a spray boom for an agricultural field sprayer for the controlled application of liquid on a target area, comprising

[0003] - a main frame which can be adjusted vertically and is otherwise rigidly attached to a vehicle frame of the machine,

[0004] - a central section which is attached to the main frame via a pivot axis,

[0005] - a first and a second linkage arm, each of which is attached to the side of the central part,

[0006] - a double-acting hydraulic cylinder comprising a cylinder housing and a piston with a piston rod movable therein, wherein a piston chamber and an annular chamber, which is penetrated by the piston rod, are formed in the cylinder housing, separated by the piston,

[0007] - another double-acting hydraulic cylinder on the spray boom, which connects the central section to the main frame and allows the inclination of the central section relative to the main frame to be adjusted.

[0008] Field sprayers with spray booms are used for the uniform application of liquid substances, particularly plant protection products, to an agricultural target area. In a field, this could be the soil or the plant itself, for example. To ensure the distribution of the applied substances is as even as possible across the entire width of the spray boom, the distance of the spray boom to the target area must be adjustable. Especially with very wide spray booms, it is important to adapt the inclination and profile of the spray boom to slopes or different plant heights.

[0009] Such spray booms and a control system for adjusting the inclination and profile are described in detail, for example, in DE 202011111069 U. A vertically adjustable main frame is provided on the field sprayer to adjust the general distance of the spray boom from the target area. The spray boom consists of a central section and two lateral boom arms. The inclination of the central section of the spray boom, and thus the entire spray boom, can be adjusted relative to the main frame using hydraulic cylinders. In addition, the arms, each of which is mounted on the central section via a pivot point, can be angled or swiveled up or down using an adjusting cylinder to change the horizontal profile of the spray boom. The adjusting cylinders are controlled by separate levers. The control system is not further described.

[0010] EP 3753407 A1 describes a hydraulic control system for such a spray boom in more detail. The variants shown there have the disadvantage that they require many electronic outputs to control the various valves. For example, the three control valves and three check valves shown require six electronic outputs. This requires a lot of cabling and is prone to failure under harsh operating conditions.

[0011] Another variant is hydraulic control systems for spray booms, for example from EP 3629725 A1. This describes how, without a center section and with only two boom arms, both the inclination and the profile of the spray boom can be adjusted using a control system with two hydraulic cylinders. The disadvantage of this design is that the combination of inclination and profile adjustment requires a complicated wiring of the control valves. This results in a high level of effort for the hydraulic piping. Furthermore, the suspension of the two boom arms is inadequately implemented, as a very large hydraulic accumulator would be necessary to reliably decouple the inclination of the boom arms from vibrations or fluctuations of the vehicle.

[0012] The object of the invention is to develop a simpler spray boom that can be implemented cost-effectively and operated reliably. This object is achieved by a spray boom according to claim 1. Further advantageous features are recited in the dependent claims.

[0013] The design according to the invention is characterized in that only one of the boom arms is articulated to the center section via a pivot axis and the hydraulic cylinder, such that the boom arm can be angled and bent around the pivot axis, and that the other boom arm is rigidly attached to the center section, wherein the pivot axis is arranged asymmetrically at a distance a from the center of the spray boom, and wherein the distance a is at least 20 cm and a maximum of 150 cm, in particular at least 40 cm and a maximum of 100 cm. This significantly simplifies the spray boom and makes it easier to control. The asymmetric arrangement of the pivot axis of the movable boom arm with a distance a in the aforementioned range leaves enough space for connecting the additional hydraulic cylinder to the center section, and prevents excessive asymmetry from being created, which would unnecessarily complicate proper profile adaptation.

[0014] It is particularly advantageous if the hydraulic cylinder is arranged so that the cylinder housing is articulated to the center 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 stationary when the piston is extended. In particular, the pivot axis on the center section is positioned lower than the hydraulic cylinder connection to the center section.

[0015] In a particularly preferred embodiment, a hydraulic control system for angling and unangling the rod arm is provided, which comprises a proportional valve designed as a 4 / 3 proportional directional control valve with only one solenoid coil and which is connected either to the piston chamber or to the annular chamber of the hydraulic cylinder via a working pressure line. Additionally, a hydraulically releasable check valve is provided in the working pressure line, which is connected to the proportional valve via a control line and can be released via this control line. The so-called 4 / 3 proportional directional control valve has four ports and can assume three switching positions. It has two working ports (A, B), one pressure port (P), and one tank return port (T), with one working port (A) connected to the working pressure line and the other working port (B) connected to the control pressure line.This special 4 / 3 proportional directional control valve has only one solenoid coil to switch back and forth between the three switching positions.

[0016] A further advantage of the inventive design is that the control system according to the invention requires only one electronic output for adjusting the profile, namely for the 4 / 3 proportional directional control valve to control the solenoid coil. The check valve requires no additional electronic signals, as it is hydraulically controlled, i.e., unlocked, by the 4 / 3 proportional directional control valve via the control line. This control system can be implemented cost-effectively and with less effort than conventional control systems. Furthermore, it is very robust and reliable.

[0017] The hydraulically pilot-operated check valve is designed to be released when control pressure is applied, allowing the return flow from the corresponding cylinder chamber of the hydraulic cylinder. If no control pressure is applied, it blocks the return flow. This means that the rod arm is held in its current position. If the check valve is released via the control pressure, the rod arm is angled. And if the hydraulic cylinder is supplied with working pressure via the proportional valve, the rod arm is angled.

[0018] The pressure connection of the proportional valve is connected to a pressure supply or pressure source. This can be, for example, a pressure source for constant pressure supply or a load-sensing pump. The tank return connection is connected to a hydraulic tank so that draining hydraulic fluid can flow into the hydraulic tank. A preferred embodiment of the spray boom according to the invention also comprises an additional hydraulic control system, which controls the additional hydraulic cylinder in order to adjust the inclination of the center section. For this purpose, this additional control system has a hydraulic accumulator that branches off from a working pressure line to the additional hydraulic cylinder, wherein the hydraulic accumulator is connected to this working pressure line via a throttle. This provides the center frame with suspension and damping so that vibrations and fluctuations from the vehicle are not transmitted to the spray boom.The control system for the swivel movement of the boom arm can thus be simplified without additional suspension and damping.

[0019] Furthermore, it is advantageous if either the piston chamber or the annular chamber of the hydraulic cylinder—specifically the cylinder chamber not connected to the working line—is connected to a hydraulic tank via a drain line. The drain line contains another hydraulically releasable check valve, which is connected to the proportional valve via a control line. This additional check valve can lock the hydraulic cylinder by trapping the hydraulic fluid in the connected cylinder chamber. This allows the pivoting linkage arm to be held rigidly in its current position, even if the working pressure line is depressurized.

[0020] The invention can be used particularly advantageously when the central section has a horizontal width b of at least 40 cm and a maximum of 300 cm, in particular at least 80 cm and a maximum of 200 cm. This ensures that there is sufficient space for connecting the additional hydraulic cylinder to the central section and that the pivot axis of the boom arm is not arranged too asymmetrically, which could unnecessarily complicate profile adjustment.

[0021] 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 illustrated combination, but also individually combined with one another. The figures show in detail:

[0022] Fig.1 Example of a spray boom according to the invention

[0023] Fig.2 Example of a hydraulic control system of a spray boom according to the invention

[0024] The figures are described in more detail below. Like reference numerals indicate like or similar parts or components.

[0025] Figure 1 shows an inventive embodiment of the spray boom 20 with a hydraulic control system. The main frame 24 is connected to the field sprayer in a vertically height-adjustable manner. This can be a self-propelled field sprayer, a trailer for a tractor, or an attachment on a tractor. The vertical height adjustment allows the distance h to the target surface 40 to be adjusted. The target surface 40 can be, for example, the soil or the plant itself in a field.

[0026] The spray boom 20 comprises the central section 23 and the two boom arms 21, 22. The central section 23 is mounted on the main frame so as to be rotatable about the rotation axis 30. The inclination of the central section 23 and thus of the spray boom 20 relative to the main frame 24 and thus to the vehicle can be adjusted via the additional hydraulic cylinder 9. The additional control system (not shown) for the additional hydraulic cylinder 9 preferably contains a hydraulic accumulator which is connected to the working pressure line via a throttle. This working pressure line leads from a proportional valve to the additional hydraulic cylinder 9 in order to supply it with pressure. The throttle provides damping and the hydraulic accumulator provides suspension. As a result, the central section 23 and thus the spray boom 20 are decoupled from vibrations and fluctuations in the vehicle.

[0027] The boom arm 21 is articulated to the center section 23 via the pivot axis 31 and the double-acting hydraulic cylinder 1. The boom arm 22 is rigidly connected to the center section 23. The articulated arm 21 can be angled or bent by extending and retracting the pistons. This allows the profile of the spray boom 20 to be adjusted to adapt the spray boom 20 as evenly as possible to the contour of the target surface 40. The goal is for the distance h from the target surface to be as even as possible across the entire width of the entire spray boom 20 and to be at least within a specified distance range.

[0028] The hydraulic cylinder 1 is installed in such a way that the cylinder housing is connected to the central part 23 and the piston and the piston rod are connected to the linkage arm 21. Alternatively, the hydraulic cylinder 1 could also be installed the other way around.

[0029] If the entire spray boom 20 is sprung and damped relative to the main frame 24, the control system for the boom arm 21 does not require any further suspension and damping.

[0030] Fig. 2 schematically illustrates the hydraulic control system 10 according to the invention for the linkage arm 21. The double-acting hydraulic cylinder 1 comprises a cylinder housing with two ports and a displaceable piston 18 located therein. In the embodiment shown, the cylinder housing is connected to the central part 23. The piston rod is attached to one side of the piston 18, which, in the embodiment shown, is connected to the linkage arm 21.

[0031] The hydraulic cylinder 1 has two cylinder chambers 11, 12 in the cylinder housing, separated by the piston 18 and each assigned to one of the connections on the cylinder housing. One cylinder chamber is the so-called annular chamber 12, through which the piston rod passes. The other cylinder chamber is the piston chamber 11. The piston chamber has a larger piston pressure area than the annular chamber surrounding the piston rod.

[0032] The control system 10 also includes the proportional valve 3, which is designed as a 4 / 3 proportional directional control valve with a single solenoid coil. It has two working ports A, B, the pressure port P, which is connected to a pressure source, and the tank return port T, which is connected to a hydraulic tank. The proportional valve 3 has only one solenoid coil, so it can be controlled with a single electronic input and switched back and forth between the three switching positions. This eliminates the need for complex wiring.

[0033] The annular space 12 of the hydraulic cylinder 1 is connected to the working port A of the associated proportional valve 3 via the working pressure line 13. If the proportional valve 3 is switched so that the working port A is connected to the pressure source, the annular space 12 is pressurized and the rod arm 21 is angled.

[0034] The check valve 5 prevents the rod arm 21 from unintentionally descending again. The proportional valve 3 is connected to its associated hydraulically releasable check valve 5 via the control pressure line 15a, which is connected to the working port B. If the control pressure line 15a is pressurized, the check valve 5 is released, allowing hydraulic fluid to flow out of the annular space 12. The rod arm 21 is angled.

[0035] In the version shown here, an additional hydraulically releasable check valve 7 is provided, which is arranged in the drain line 17. The drain line 17 connects the piston chamber 11 of the hydraulic cylinder to the hydraulic tank. If the rod arm 21 is angled, the piston 18 of the hydraulic cylinder 1 moves and hydraulic fluid is sucked in from the hydraulic tank via the check valve 7. If the rod arm 21 is to be angled, the check valve 7 is unlocked via the control line 15c so that hydraulic fluid can flow out of the piston chamber 11. The control line 15c is also connected to the proportional valve 3 by being connected to the working port B. When the check valve 7 is blocked, the hydraulic fluid is trapped in the piston chamber 11. This allows the rod arm 21 to be held in position, even if the working pressure line to the hydraulic cylinder is depressurized. List of reference symbols

[0036] I Hydraulic cylinder

[0037] 3 Proportional valve

[0038] 5 Check valve

[0039] 7 additional check valve

[0040] 9 additional hydraulic cylinders

[0041] 10 Control system

[0042] II Piston chamber

[0043] 12 Annular space

[0044] 13 Working pressure line

[0045] 15 a,c control pressure lines

[0046] 17 Drain line

[0047] 18 pistons

[0048] 20 spray booms

[0049] 21 first linkage arm

[0050] 22 second linkage arm

[0051] 23 Middle section

[0052] 24 main frames

[0053] 30 axis of rotation

[0054] 31 Swivel axis

[0055] 40 Target area a Distance to center b Horizontal width h Distance to target area

Claims

Patent claims 1. Spray boom (20) for an agricultural field sprayer for the controlled application of liquid to 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 tiltably attached to the main frame via a pivot axis (30), - a first and a second linkage arm (21, 22), each of which is laterally attached to the central part (23), - a double-acting hydraulic cylinder (1 ) having a cylinder housing and a piston (18) with a piston rod movable therein, wherein a piston chamber (11 ) and an annular chamber (12) penetrated by the piston rod are formed in the cylinder housing, separated by the piston (18), - a further double-acting hydraulic cylinder (9) provided on the spray boom (20), which connects the central part (23) to the main frame (24) and by means of which the inclination of the central part (23) relative to the main frame (24) can be adjusted, characterized in that only one of the boom arms (21) is articulated to the central part (23) via a pivot axis (31) and the hydraulic cylinder (1) in such a way that the boom arm (21) can be angled and bent around the pivot axis (31), and in that the other boom arm (22) is rigidly attached to the central part (23), wherein the pivot axis (31) is arranged asymmetrically at a distance a from the center of the spray boom (20), and wherein the distance a is at least 20 cm and a maximum of 150 cm.

2. Spray boom (20) according to claim 1, characterized in that the hydraulic cylinder (1) is arranged such that the cylinder housing is articulated to the central part (23) and the piston (18) with its piston rod is articulated to the boom arm (21).

3. Spray boom (20) according to one of claims 1 or 2, characterized in that a hydraulic control system (10) for angling and unangling the boom arm (21) is provided, which comprises a proportional valve (3) which is designed as a 4 / 3 proportional directional control valve which has only one solenoid coil and which is connected by means of a working pressure line (13) either to the piston chamber (11) or to the annular chamber (12) of the hydraulic cylinder (1), wherein a hydraulically releasable check valve (5) is provided in the working pressure line (13), which is connected to the proportional valve (5) by means of a control line (15a) and can be unlocked via this control line (15a).

4. Spray boom (20) according to claim 3, characterized in that a further hydraulic control system is provided which controls the further hydraulic cylinder (9) in order to adjust the inclination of the central part (23), and that this further control system comprises a hydraulic accumulator branching off from a working pressure line to the further hydraulic cylinder (9) and connected to this working pressure line via a throttle.

5. Spray boom (20) according to claim 3 or 4, characterized in that either the piston chamber (11) or the annular chamber (12) of the hydraulic cylinder (1), namely the cylinder chamber which is not connected to the working pressure line (13), is connected to a hydraulic tank via a drain line (17), wherein in the drain line (17) there is a further hydraulically unlockable check valve (7) which is connected to the proportional valve (3) via a control line (15c).

6. Spray boom (20) according to one of the preceding claims, characterized in that the central part (23) has a horizontal width b of at least 40 cm and a maximum of 300 cm.

Images