EP3624586A1

EP3624586A1 - Agricultural towed sprayer

Info

Publication number: EP3624586A1
Application number: EP18725309.1A
Authority: EP
Inventors: Andrea CERVESATO; Massimo Zubelli; Andrea Bedosti
Original assignee: Matermacc SpA
Current assignee: Matermacc SpA
Priority date: 2017-05-18
Filing date: 2018-05-04
Publication date: 2020-03-25
Also published as: WO2018211347A1; CN108935395A; IT201700054148A1

Abstract

An agricultural sprayer (100) is described, comprising a support frame (105) provided with a pair of sustaining members (110) and adapted to be hooked to an agricultural tractor on which at least one reservoir (115) for a liquid to be sprayed and a pump (125) for pumping the liquid from the reservoir (115) to a plurality of liquid dispensing nozzles are installed, wherein the reservoir (115) is mounted on a first portion (130) of the support frame (105), which is provided with a hooking device (140) for hooking to the agricultural tractor, while the pair of sustaining members (110) is mounted on a second portion (135) of the support frame (105), which is articulated to the first portion (130) by means of an intermediate joint (145) adapted to define at least one articulation axis (A).

Description

AGRICULTURAL TOWED SPRAYER

Field of the invention

The present invention relates in general to an agricultural sprayer adapted to be towed by a tractor for spraying crops with a treatment liquid, such as a herbicide or pesticide. More specifically, the invention relates to a sprayer which is capable of spraying the treatment liquid in fine droplets that are sifted onto the crop to be treated.

Background art

As is known, agricultural towed type sprayers typically comprise a support frame substantially shaped like a carriage or trailer, which generally comprises a rudder provided with an eyelet for coupling with the towing hook of the tractor and a pair of sustaining members, that is, adapted to be in contact with the ground, thereby supporting part of the weight of the sprayer and allowing it to move thereon.

These sustaining members usually consist of a pair of wheels arranged on a single axle but they may be of a different type, for example a pair of tracks or a pair of twin wheels.

On the support frame a reservoir is provided for containing the treatment liquid, one or more spraying bars bearing a plurality of dispensing nozzles, and a hydraulic pump, such as a diaphragm pump, which can be connected to the power socket of the tractor and is adapted to pump the treatment fluid from the reservoir to the dispensing nozzles.

A drawback of these agricultural tow sprayers is that when the tractor reaches the exit of a row and steers to start the next row, the wheels of the support frame may travel over a path with an excessively narrow steering radius, thus treading on a part of the crops that are at the end of the rows.

In order to overcome this drawback, agricultural towed sprayers were proposed in the past, which are provided with steering wheels controlled by an electronic control unit which, based on the steering radius imposed on the tractor, manages the steering angle of the wheels of the sprayer to follow and remain in the track of the tractor wheels.

This solution, while being effective, is however quite complicated and costly from a constructive point of view and, furthermore, does not allow varying the wheel track of the agricultural sprayer, i.e. the distance between the two axle wheels, based on the width of the row.

The rows may in fact have different widths depending on the type of crop, for example about 45 cm for soy cultivation and about 75 cm for corn cultivation, so the possibility of adjusting the distance between the wheels is sometimes essential to allow the agricultural sprayer to advance along the rows without treading on the crops.

In order to allow at least a minimum adjustment of the wheel track, steering wheel sprayers provide only the option of mounting the wheels with the respective rims in a conventional position or with the respective rims tilted. Since the rim profile is generally asymmetrical with respect to the centre line of the wheel, this solution allows for a minimum variation of the wheel track. In this way, however, the variation of the wheel track, in addition to being unable to be a continuous and adjustable variation but only an adjustment between two discrete values, has a significant impact on the steering angles that must be imparted to the steering wheels of the sprayer with respect to the steering angle of the tractor wheels, which must be taken into consideration to avoid undesired misalignments between the sprayer and the tractor during the maneuvering step.

To do this, however, it is necessary to re-program and/or re-parameterize the control unit through a series of quite complicated, slow and little intuitive operations.

Another conventional method used to allow the agricultural sprayer to follow the bends made by the tractor is to separate the support frame into two portions mutually hinged according to a substantially vertical articulation axis, of which a first portion carrying the rudder with the hooking eyelet to be coupled with the tractor and a second portion carrying the axle with the wheels.

In this way, the steering of the agricultural sprayer can be obtained simply by varying the angle of mutual inclination between the first and second portions of the support frame, for example by one or two hydraulic cylinders controlled by an electronic control unit. A drawback of this second solution is however that the reservoir adapted to contain the treatment liquid is mounted onboard the second portion of the support frame, i.e. the one to which the axle with the wheels is connected.

This means that when the second portion of the support frame is inclined with respect to the first portion, the reservoir (generally very heavy as it contains the treatment fluid) undergoes a significant lateral displacement that displaces its centre of gravity from the longitudinal axis of the tractor, and thus considerably increases the tilting moment to which the agricultural sprayer is subjected, making it particularly unstable especially on sloping grounds.

Summary of the invention

In the light of the foregoing, an object of the present invention is to provide an agricultural sprayer which allows overcoming or at least significantly reducing the aforementioned drawbacks of the prior art.

Another object is to achieve the above object with a simple and rational solution and as cost-effective as possible.

These objects are achieved by the features of the invention described in the independent claims. The dependent claims describe preferred and/or particularly advantageous aspects of the invention.

In particular, an embodiment of the present invention provides an agricultural sprayer comprising a support frame provided with a pair of sustaining members (such as wheels, twin wheels, tracks or others) and adapted to be hooked to an agricultural tractor on which at least one reservoir for a liquid to be sprayed and a pump for pumping the liquid from the reservoir to a plurality of liquid dispensing nozzles are provided, wherein said reservoir is mounted on a first portion of the support frame, which is provided with a hooking device for hooking to the agricultural tractor, while the pair of sustaining members is mounted on a second portion of the support frame, which is articulated to the first portion by means of an intermediate joint adapted to define at least one articulation axis.

With this solution, when the agricultural tractor makes a bend, only the sustaining members mounted on the second portion of the support frame vary their orientation, while the treatment fluid reservoir mounted on the first portion of the support frame and thus its centre of gravity, remain substantially aligned with the tractor, greatly reducing the tilting moment applied to the towed agricultural machine, which is therefore much more stable than the prior art.

According to an aspect of the invention, the agricultural sprayer may comprise actuating means for actuating a mutual rotation between the first and second portions of the support frame around the articulation axis defined by the intermediate joint.

In this way, the inclination of the sustaining members of the towed sprayer may be suitably adjusted in a manner corresponding to the steering angle imposed on the tractor, for example by means of an electronic control unit.

For example, the actuating means may comprise at least one linear actuator (e.g. hydraulic jack) whose opposite ends are articulated to the first and second portions of the support frame, respectively, for example according to articulation axes parallel to the articulation axis defined by the intermediate joint. An actuation of this type is in fact particularly simple and allows an effective rotation of the second portion of the support frame with respect to the first one. In this context, it is still preferable that the actuating means comprise at least two linear actuators, which are articulated to the second portion of the support frame so that the shortening of the one corresponds to the elongation of the other and vice versa.

In this way, while a linear actuator pushes the second portion of the support frame to rotate in a certain direction, the other linear actuator can be controlled to pull it in a concurrent direction so that the coordinated action of the two linear actuators increases the rotational moment globally applied to the second portion of the support frame, thereby facilitating and making the rotation more fluid than the first portion, without requiring large actuators.

According to another aspect of the present invention, each sustaining member of the sprayer may be connected to the second portion of the support frame by a respective semi-axle.

With this solution, the sustaining members are mounted on the second portion of the support frame in a substantially independent manner, thereby greatly increasing the adjustment possibilities. In particular, each semi-axle may be extensible and retractable, preferably by means of a telescopic system.

This extensibility of the semi-axles allows modifying and adjusting the distance between the sustaining members, i.e. the sprayer wheel track, in an extremely simple, quick and effective manner.

With the telescopic system, the wheel track adjustment can also be substantially continuous between a minimum value and a maximum value, thus allowing always adopting the most suitable measure based on the width and distance between the rows.

According to another aspect of the invention, each semi-axle may further be articulated to the second portion of the support frame independently of the other semi-axle, according to an articulation axis parallel to the articulation axis defined by the other semi-axle and perpendicular to the articulation axis defined by the intermediate joint of the support frame.

In this way, it is advantageously possible to adjust the height position of each sustaining member independently of the other, for example to allow them to better follow the depressions and the roughness of the ground, thereby increasing the sprayer's stability.

To this end, each semi-axle may be further associated to a respective piston cylinder assembly whose opposite ends are articulated to the semi-axle and to the second portion of the support frame, respectively, for example according to articulation axes parallel to the articulation axis of the semi-axle.

This piston cylinder assembly may be a conventional shock absorber which, optionally combined with a respective spring, implements the suspension of the sustaining member.

In other embodiments, the piston cylinder assembly may, however, be a hydraulic jack which, connected to a suitable hydraulic actuation circuit, allows dampening and damping the vertical displacements of the sustaining member and/or actively varying the height position of the sustaining members, for example in order to vary the inclination of the sprayer with respect to the ground (as a kind of active suspension).

According to a further aspect of the invention, the first portion of the support frame may comprise a box-like structure inside which the pump is housed. In this way, the pump is contained and protected within the box-like portion of the support frame, without creating an encumbrance that could interfere with other sprayer components, such as the treatment fluid reservoir.

Another aspect of the invention further provides that the hooking device for hooking to the agricultural tractor is connected to the box-like structure by means of connecting means that are disconnectable and repositionable, i.e. that can be secured to said box-like structure in two or more positions, preferably corresponding to different heights with respect to the ground.

With this solution it is advantageously possible to secure the first portion of the support frame to tractors having the tow hook at different heights from the ground, while maintaining the pump at the optimum height for coupling with the power socket.

According to another aspect of the present invention, the distance between the articulation axis defined by the intermediate joint and the sustaining members may be smaller than the distance between said articulation axis and the hooking device for hooking to the agricultural tractor.

In this way, the lateral displacement of the sustaining members in the case of steering is in fact rather small, thus further reducing the tilting moment weighing on the sprayer.

Another aspect of the present invention provides that the hydraulic pump may be carried by a support which can be secured in different positions along a direction substantially parallel to the articulation axis of the intermediate joint. With this solution, it is advantageously possible to vary the height of the hydraulic pump from the ground, allowing it to be positioned in the most appropriate position for the connection to the power socket of the tractor by a cardan shaft.

Brief description of the drawings

Further features and advantages of the invention will become apparent from the following description provided by way of non-limiting example with the aid of the figures shown in the accompanying drawings.

Figure 1 is a perspective view of a towed sprayer according to an embodiment of the present invention.

Figure 2 is a lateral view of the sprayer in figure 1 .

Figure 3 is a perspective view of the sprayer in figure 1 , shown in an enlarged scale and without spraying bars, wheels, and some cover casings, so as to make various details of the invention visible.

Figure 4 is a lateral view of the assembly in figure 3.

Figure 5 is a bottom view of the assembly in figure 3.

Figure 6 is a rear view of the assembly in figure 3.

Figure 7 is a front view of the assembly in figure 3.

Figure 8 is section VIII-VIII of figure 6 shown partially and in enlarged scale. Figure 9 is the rear view of figure 6 in which the reservoir is hidden, in order to better illustrate the possible misalignment of the semi-axles.

Figure 10 is the rear view of figure 9, in which the semi-axles are aligned in a neutral position and in a minimum extension configuration.

Figure 1 1 is the rear view of figure 10, in which the semi-axles are in a maximum extension configuration.

Detailed description

In the above figures, reference numeral 100 indicates as a whole an agricultural sprayer of the towed type, i.e. intended to be hooked to an agricultural tractor (not shown) to be towed and advanced on a cultivated field in order to spray the crops with a treatment liquid, such as a herbicide or pesticide.

The sprayer 100 schematically comprises a support frame 105, substantially shaped like a carriage or a trailer, which is adapted to be hooked to the rear of the agricultural tractor and comprises a pair of ground support wheels 1 10 which are arranged opposite each other to define a single axle.

On board the support frame 150 a reservoir 1 15 is mounted adapted to contain the treatment liquid, one or more spraying bars 120, preferably of the foldable type, bearing a plurality of dispensing nozzles (not shown), and a hydraulic pump 125 (see fig. 3), such as a diaphragm pump, which can be connected to the power socket of the agricultural tractor and is adapted to pump the treatment fluid from the reservoir 1 15 to the dispensing nozzles, so that the treatment liquid is sprayed into fine droplets and directed on the crops to be treated. In some embodiments, the sprayer 100 may also comprise a ventilation unit, for example a fan, which is also mounted on the support frame 105 and is designed to generate a high-speed air stream projecting by aeroconvection the droplets of the treatment liquid on the crops.

As shown in fig. 4, the support frame 105 of the sprayer 100 comprises two separate portions, of which a front portion 130 on which reservoir 1 15 is rigidly mounted, and a rear portion 135 on which the wheel hubs 205 carrying the wheels 1 10 are mounted.

The front portion 130 of the support frame 105 comprises a hooking device 140 through which it can be directly hooked to the agricultural tractor.

In the example shown, the hooking device 140 is an eyelet adapted to be tucked in and locked on the tow hook that is present on the back of all agricultural tractors.

The rear portion 135 of the support frame 105 is connected to the front portion 130 by means of an intermediate joint 145, such as a hinge joint, adapted to define a predetermined articulation axis A.

In this way, the rear portion 135 of the support frame 105 and the pair of wheels 1 10 can rotate and vary their inclination with respect to the front portion 130 and to the reservoir 1 15.

Both front 130 and rear 135 portions of the support frame 105 are substantially rigid mechanical structures, i.e. able to rotate one with respect to the other about the articulation axis A substantially without deforming.

The front portion 130 in particular comprises a box-like structure 150, for example made of bent and welded sheets, which delimits an inner volume and extends predominantly along a longitudinal axis B orthogonal to the articulation axis A.

Along this longitudinal axis B, the box-like structure 150 has a rear end at which the intermediate joint 145 is positioned, and a front end at which the hooking device 140 is secured.

In particular, the hooking device 140 is secured to the front end of the box-like structure 150 by means of rigid connection means 155 which can be connected to the box-like structure 150 in multiple different positions, thus allowing the position of the hooking device 140 to be varied along a direction substantially parallel to the articulation axis A.

In the example shown, these connecting means 155 comprise two support arms 160 which are substantially planar in a plane orthogonal to the articulation axis A and protruding cantilevering from the front end of the box-like structure 150, they converge one towards the other so that their free ends are close to each other.

The hooking device 140 is positioned at these free ends of the support arms 160, to which can be coupled by a joint 165 that allows it making at least small oscillations about an articulation axis C orthogonal to the longitudinal axis B and to the articulation axis A.

The opposite ends of the support arms 160 are removably secured to two corresponding connecting plates 170, which define the front end of box-like structure 150 and lie in planes substantially parallel to the articulation axis A.

In this way, the support arms 160, and the hooking device 140 therewith, can be freely removed from the connecting plates 170 and reassembled thereon in many different positions along the direction of the articulation axis A.

In the example shown, the fastening between the support arms 160 and the connecting plates 170 is obtained by bolting but, in other embodiments, the bolts could be replaced by other fastening means, provided they are removable and repositionable.

As shown in figure 3, the two connecting plates 170 are mutually spaced apart and delimit, at the front end of the box-like structure 150, a front opening 175 which makes the inner volume thereof accessible.

In the inner volume of the box-like structure 150, the hydraulic pump 125 is accommodated, which can be coupled to the hydraulic tractor power socket through a cardan shaft 178 that protrudes outside the box-like structure 150 through the front opening 175.

In particular, the hydraulic pump 125 is carried by a movable support, which can be secured to the box-like structure in many different positions, so as to vary the position of the hydraulic pump 125 in a direction substantially parallel to the articulation axis A. With this solution it is advantageously possible to optimize the relative position between the cardan shaft 178 of the hydraulic pump 125 and the hooking device 140 for any mutual assembly condition.

In order to actuate the rotation between the front portion 130 and the rear portion 135 of the support frame 105 about the articulation axis A, the sprayer 100 is provided with dedicated actuating means.

In the example shown, these actuating means comprise a pair of hydraulic jacks 180, preferably double-acting hydraulic jacks, which can be placed co- planar on a plane orthogonal to the articulation axis A.

The opposite ends of each hydraulic jack 180 are articulated to the front portion 130 and to the rear portion 135, respectively, of the support frame 105, according to articulation axes parallel to the articulation axis A, so that a change in the length of the hydraulic jack 180 always corresponds to a mutual rotation of the two portions of the support frame 105.

In particular, the two hydraulic jacks 180 can be positioned on opposite sides with respect to the median plane containing the articulation axis A and the longitudinal axis B of the front portion 130 of the support frame, so that a shortening of a hydraulic jack 180 always corresponds to an elongation of the other hydraulic jack 180 and vice versa.

With this arrangement, the hydraulic jacks 180 can be connected to a hydraulic supply system (not shown), which is configured so that, when a jack 180 is operated to generate a tractive force (i.e. in the shortening direction), the other jack 180 is operated to generate a thrust force (i.e. in the elongation direction), and vice versa by doubling the total force moment applied between the front portion 130 and the rear portion 135 of the support frame 105.

Unlike the front portion 130, the rear portion 135 of the support frame 105 may have a prevailing development in the direction parallel to the articulation axis A and can be implemented, for example, by a base structure 185 which carries the intermediate joint 145 and which can be articulated to the hydraulic jacks 180, and by a pair of studs 190 rising from said base structure 185.

As shown in figure 8, each wheel hub 205 is carried by a respective semi-axle 195A and 195B, which is articulated to the rear portion 135 of the support frame 105 by a respective joint 200, such as a hinge joint, which is adapted to define an articulation axis D perpendicular to the articulation axis A of the support frame 105.

Preferably, the articulation axes E are also mutually coplanar in a plane orthogonal to the articulation axis A (see fig. 8).

The two semi-axles 195A and 195B are in any case two separate and independent entities that, in some embodiments, may not be perfectly symmetric as shown in the figures.

Starting from the respective joints 200, the two semi-axles 195A and 195B project substantially cantilevering from the rear portion 135 of the support frame 105, extending from opposite sides with respect to a median plane containing the articulation axis A and parallel to the articulation axes D.

The free end of each semi-axle 195A and 195B carries the respective wheel hub 205 on which the rim of the respective wheel 1 1 0 is fixed, for example by bolting.

In particular, each wheel hub 205 is rotatably coupled to the respective semi- axle 195A and 195B so as to freely rotate about a predetermined rotation axis E which of course also defines the rotation axis of the respective wheel 1 10. The rotation axis E of each wheel hub 205 is perpendicular to the articulation axis D of the respective semi-axle 195A and 195B and preferably lies coplanar to the rotation axis E of the other wheel hub 205 on a plane orthogonal to the articulation axis F.

In this way, the two semi-axles 195A and 195B can occupy a neutral position (shown in figures 10 and 1 1 ) in which the rotation axes E of the wheel hubs 205, and thus of the wheels 1 10, are substantially coincident with each other and orthogonal to the articulation axis A of the support frame 105, or at most slightly tilted by one or two sexagesimal degrees.

Starting from this neutral position, each semi-axle 195A and 195B can also oscillate, independently of the other semi-axle 195A and 195B, rotating about the respective articulation axis D, as shown in figure 9.

In particular, it is provided that the oscillation of each semi-axle 195A and 195B may be between -10° and +5° sexagesimal degrees with respect to the neutral position.

From a construction point of view, each semi-axle 195A and 195B is designed so as to be extensible and retractable in the direction of the rotation axis E of the respective wheel hub 205, so as to vary the distance between the wheels 1 10, i.e. the wheel track of the sprayer 100.

In order to allow this adjustment, the embodiment shown herein provides that each semi-axle 195A and 195B is telescopic in the direction of the rotation axis E and comprises, for example, a first arm 210 of tubular shape, which is articulated to the rear portion 135 of the support frame 105 through the joint 200, and a second arm 215, which is slidably fitted into the first arm 210 and carries, at the free end thereof, the wheel hub 205 (see fig. 8).

Preferably, the first and second arm 210 and 215 have a prismatic cross section, so as to implement a prismatic coupling that locks them with respect to the mutual rotations.

With this solution, the length of each semi-axle 195A and 195B can be adjusted in a substantially continuous manner, between a minimum value, for example corresponding to the maximum insertion of the second arm 215 in the first arm 210 (see fig. 10), and a maximum value, for example corresponding to the maximum extraction of the second arm 215 with respect to the first arm 210 (see fig. 1 1 ).

In particular, it is provided that the excursion of each semi-axle 195A and 195B between the maximum length configuration and the minimum length configuration is substantially equal to 18 cm, allowing the wheel track of sprayer 100 to be varied from a minimum of 150 cm to a maximum of 186 cm.

After each adjustment of the wheel track, the length of each semi-axle 195A and 195B can be finally secured through special locking means (not shown) that for example allow axially locking the second arm 215 with respect to the first arm 210.

Each semi-axle 195A and 195B is further associated to a respective piston cylinder assembly 220, whose opposite ends are articulated to semi-axle 195A and 195B, such as the first arm 210, and to the rear portion 135 of the support frame 105, such as the stud 190 proximal thereto, respectively, according to articulation axes parallel to the respective articulation axis D.

In this way, each oscillation of semi-axle 195A and 195B about the respective articulation axis D always corresponds to a variation in the length of the piston cylinder assembly 220.

In some embodiments, the piston cylinder assemblies 220 may be conventional shock absorbers which, optionally associated each to a respective spring, substantially implement two independent suspensions for wheels 1 10 of the sprayer 100.

In other embodiments, each piston cylinder assembly 220 may, however, be a hydraulic jack which, connected to a suitable hydraulic actuation circuit, allows actively varying the height position of the respective wheel 1 10, for example in order to vary the inclination of the sprayer 100 with respect to the ground. In the latter case, it is still possible to provide the above hydraulic actuation system with suitable systems, such as hydraulic accumulators, that allow the piston cylinder assemblies 220 to absorb and dampen the vertical displacements of the respective wheel 1 10, acting also as a suspension.

In use, the sprayer 100 is hooked to the tractor through the hooking device 140, specifically by engaging the eyelet in the tow hook of the tractor so that wheels 1 10 are resting on the ground and thus support at least a part of the total weight of sprayer 100, comprising the support frame 105, the reservoir 1 15, the hydraulic pump 125 and the spraying bars 120.

In this position, the articulation axis A defined by the intermediate joint 145 is substantially vertical, i.e. substantially orthogonal to the ground plane, while the rotation axes E of the wheels 1 10 (at least when the semi-axles 195A and 195B are in the neutral position) are substantially horizontal i.e. substantially parallel to the ground plane.

At the same time, the hydraulic pump 125 is connected to the power socket of the agricultural tractor, for example through the cardan shaft 178, so as to pump the treatment liquid from reservoir 1 15 toward the dispensing nozzles that may be installed on the spraying bars 120.

To this end, it is noted that due to the possibility of mounting the hooking device 140 in different positions along the direction of the articulation axis, it is advantageously possible to secure the sprayer 100 to tractors that have the tow hook at different heights above the ground, while ensuring that the hydraulic pump 125 remains at an optimal height to be coupled to the power socket.

This positioning freedom is further increased by the possibility of also varying the mounting position of the hydraulic pump 125, by varying the height thereof from the ground.

While the hydraulic pump 125 is operating, the sprayer 100 can then be towed by the agricultural tractor so as to move on the ground and then sprinkle the treatment liquid on the crops to be treated, which can be for example arranged along parallel rows.

In order not to tread on the crops during the advancement, the wheel track of the sprayer 100, i.e. the distance between the wheels 1 10, can be adjusted in advance by suitably varying the length of the semi-axles 195A and 195B according to the width and the distance between the rows.

Of course during the advancement, the semi-axles 195A and 195B may oscillate independently of each other, allowing the height position of the two wheels 1 10 to be varied so as to follow the roughness of the ground.

These oscillations are damped by the piston cylinder assemblies 220 which, if implemented in the form of hydraulic jacks, also allow the height position of the wheels 1 10 to be actively varied, for example if the sprayer 100 advances on sloping ground.

When the agricultural tractor steers, for example to go back after a row, the rear portion 135 of the support frame 105 of the sprayer 100 can be rotated about the articulation axis, thus varying the orientation of the wheels 1 10 on the ground and thus imparting a steering angle thereto.

This rotation of the rear portion 135 of the support frame 105 is actively actuated by the hydraulic jacks 180, the operation whereof can be controlled by an electronic control unit, which can establish the steering angle of the wheels 1 10 of the sprayer 100 based on the steering angle of the steering wheels of the agricultural tractor, for example so that the wheels 1 10 of the sprayer 100 always remain within the tracks of the tractor wheels. Since the steering angle is defined by a rigid rotation of both wheels 1 10 about the rotation axis A, its value is independent of the distance between the wheels 1 10 themselves, i.e. from the wheel track of the sprayer, so the electronic control unit can be effectively programmed in a single mode for all possible configurations.

It should be noted that when the rear portion 135 of the support frame 105 is rotated to impart a steering angle to the wheels 1 10, the reservoir 1 15 of the treatment liquid and the hydraulic pump 125, being integrally mounted to the front portion 130 of the support frame 105, remain substantially aligned with the tractor, thus greatly reducing the tilting moment applied to the sprayer 100 and thus making it very stable.

The spraying bars 120, being mounted on the rear portion 135 of the support frame 105, move integrally with the wheels 1 10, allowing an optimization of the spraying work, particularly in areas at the end of the rows.

The steering system outlined above allows the wheels 1 10 to remain parallel to the rows longer and, therefore, allows the spraying bars 120 to remain in the correct operating position until almost the end of the field, allowing a uniform treatment of the crops substantially by the entire length of the rows. To further reduce the tilting moment it is also important that the distance between the articulation axis A of the support frame 105 and the rotation axes E of wheels 1 10 is smaller, much smaller in this case (for example, less than one tenth), than the distance between the articulation axis A and the hooking device 140 for hooking to the tractor since in this way, the lateral displacement of the wheels 1 10 in case of steering is very small.

In conclusion, it should be emphasized that, although the above description always refers to a pair of wheels 1 10, in other embodiments, the pair of wheels 1 10 could be replaced by a pair of tracks, a pair of twin wheels or a pair of any other sustaining member adapted to rest on the ground to support at least part of the weight of the agricultural sprayer 100 and allow it to move.

If tracks or similar slidable sustaining members are used, the rotation axis of the track will be intended as an axis perpendicular to the plane where the track or the equivalent sustaining member slides. It should also be noted that while in the above description the relative rotation between the front portion 130 and the rear portion 135 of the support frame 105 is obtained by hydraulic jacks 180, in other embodiments, these hydraulic jacks may be replaced by other linear actuators, such as pneumatic or electric actuators.

Of course, a man skilled in the art may make several technical application changes to the sprayer 100 described above, without thereby departing from the scope of the invention as claimed hereinafter.

Claims

1. An agricultural sprayer (100) comprising a support frame (105) provided with a pair of sustaining members (1 10) and adapted to be hooked to an agricultural tractor, on which at least one reservoir (1 15) for a liquid to be sprayed and a pump (125) for pumping the liquid from the reservoir (1 15) to a plurality of liquid dispensing nozzles are installed, characterized in that the reservoir (1 15) is mounted on a first portion (130) of the support frame (105), which is provided with a hooking device (140) for hooking to the agricultural tractor, while the pair of sustaining members (1 10) is mounted on a second portion (135) of the support frame (105), which is articulated to the first portion (130) by means of an intermediate joint (145) adapted to define at least one articulation axis (A).

2. An agricultural sprayer (100) according to claim 1 , characterized in that it comprises actuating means (180) for actuating a mutual rotation between the first and second portions (130, 135) of the support frame (105) around the articulation axis (A) defined by the intermediate joint (145).

3. An agricultural sprayer (100) according to claim 2, characterized in that said actuating means comprises at least one linear actuator (180) whose opposite ends are articulated to the first and second portions (130, 135), respectively, of the support frame (105).

4. An agricultural sprayer (100) according to claim 3, characterized in that said actuating means comprises at least two of said linear actuators (180), which are articulated to the second portion (135) of the support frame (105) so that the shortening of the one corresponds to the elongation of the other and vice versa.

5. An agricultural sprayer (100) according to any one of the preceding claims, characterized in that each sustaining member (1 10) is connected to the second portion (135) of the support frame (105) by means of a respective semi-axle (195A, 195B).

6. An agricultural sprayer (100) according to claim 5, characterized in that each semi-axle (195A, 195B) is extensible and retractable.

7. An agricultural sprayer (100) according to claim 5 or 6, characterized in that each semi-axle (195A, 195B) is articulated to the second portion (135) of the support frame (105) independently of the other semi-axle (195A, 195B), according to an articulation axis (D) parallel to the articulation axis (D) defined by the other semi-axle (195A, 195B) and perpendicular to the articulation axis (A) defined by the intermediate joint (145) of the support frame (105).

8. An agricultural sprayer (100) according to claim 7, characterized in that each semi-axle (195A, 195B) is associated with a respective piston cylinder assembly (220), the opposite ends whereof are articulated to the semi-axle (195A, 195B) and to the second portion of the support frame (105), respectively.

9. An agricultural sprayer (100) according to any one of the preceding claims, characterized in that the first portion (130) of the support frame (105) comprises a box-like structure (150), inside which the pump (125) is housed.

10. An agricultural sprayer (100) according to claim 9, characterized in that the hooking device (140) for hooking to the agricultural tractor is connected to the box-like structure (150) by means of disconnectable and repositionable connecting means (155).

11. An agricultural sprayer (100) according to any one of the preceding claims, characterized in that the distance between the articulation axis (A) defined by the intermediate joint (145) and the sustaining members (1 10) is smaller than the distance between said articulation axis (A) and the hooking device (140) for hooking to the agricultural tractor.

12. An agricultural sprayer (100) according to any one of the preceding claims, characterized in that the hydraulic pump (125) is carried by a support that can be secured in different positions along a direction substantially parallel to the articulation axis (A) of the intermediate joint (145).