MOBILE SOIL PROCESSING ARRANGEMENT AND SOIL PROCESSING DEVICE WITH AT LEAST ONE SUCH ARRANGEMENT, TRAFFICABLE ALONG A ROW OF CULTURES

Description

[0001] The present invention relates to a soil-working assembly that can be moved along a row of crops, as well as a soil-working device incorporating at least one such assembly.

[0002] It relates in particular to a soil-working unit that can be moved along a row of crops, comprising at least a tool carrier that can be coupled to the chassis of a soil-working machine or a tractor vehicle and has a direction of travel, a non-powered rotary tool, such as a disc, and a system for linking the tool to the carrier.

[0003] Tillage assemblies are known, as illustrated by international application WO 2023 / 187519. Other examples of tillage assemblies are provided in documents EP4023041, EP1125487, FR3121319.

[0004] Row crops, such as fruit trees, vines, shrubs, and others, require hoeing at the base of the plants. The difficulty lies in the fact that the width between two rows of crops can vary. Similarly, the distance between two crops within the same row can vary. Current solutions use sensors to work as close as possible to the plants, which leads to complex systems that do not allow for the simultaneous treatment of two rows of crops within a wide range of widths.

[0005] One aim of the invention is to provide a soil cultivation system whose design allows for working as close as possible to plants arranged in rows, and work that is easily adaptable to different inter-row widths when several systems are mounted on the same frame.

[0006] To this end, the invention relates to a soil cultivation assembly comprising at least one tool carrier support that can be coupled to the chassis of a soil cultivation machine or a tractor vehicle, a non-powered rotary tool, such as a disc, and a system for linking the tool to the support, characterized in that the linking system comprises a first arm coupled to the support pivoting about an axis called the first pivot axis, a second tool carrier arm coupled to the first arm pivoting about an axis called the second pivot axis parallel to the first pivot axis for a displacement of the second arm between a position close to the first arm and a position away from the first arm, in that the rotary tool has an axis of rotation extending substantially parallel, that is to say parallel to within ±15 degrees, to the second pivot axis,in that said assembly includes a device for locking the first arm in an adjustable angular position around the first pivot axis, and in that said assembly includes at least one return element for the second arm in a position away from the first arm, this return element being configured so that, when the second arm is driven from the away position to the position closer to the first arm, it exerts a return force on the second arm to the away position from the first arm. The presence of two arms allows the first arm to preposition the second arm / tool ​​assembly more or less close to the crop to be worked. The presence of a second arm equipped with a return element allows for continuous working as close as possible to the crop without the need for a feeler. Such a soil cultivation system is easy to use and suitable for all types of soil.It does not require high power from the tractor or tillage machine to which the tillage unit is designed to be coupled. Its design allows it to be mounted at the front or rear of the tractor or tillage machine.

[0007] According to one embodiment of the invention, the restoring force of the restoring element is adjustable. This results in the possibility of adapting it to each type of crop.

[0008] According to one embodiment of the invention, the return element is an energy accumulator configured to store energy during the movement of the second arm from its extended position to its close position relative to the first arm, and to release said energy during the movement of the second arm from its close position relative to the first arm to its extended position. This energy accumulator is selected from the group of energy accumulators consisting of springs and hydraulic or hydropneumatic accumulators. The design of such a tillage system is simple.

[0009] According to one embodiment of the invention, the return element is a spring disposed between the support and the second arm.

[0010] According to one embodiment of the invention, the spring is associated with a spring preloading element capable of preloading the spring in an adjustable manner to vary the restoring force of the restoring element formed by said spring.

[0011] According to one embodiment of the invention, the assembly includes a pivoting actuator for controlling the movement of the second arm, located between the support and the second arm. This actuator is configured to control at least the movement of the second arm from a position away from the first arm to a position closer to the first arm. This allows the entire tillage unit to be brought to a more compact position at the end of a row. This design also facilitates the road transport of such a tillage unit.

[0012] According to one embodiment of the invention, the pivoting displacement control actuator of the second arm is a hydraulic or pneumatic cylinder connectable to a source of pressurized fluid, this cylinder comprising a first chamber, configured to, in the state supplied with pressurized fluid, control a displacement of the second arm in the direction of a rapprochement of the first arm and, a second chamber.

[0013] According to one embodiment of the invention, the return element is a hydraulic or hydropneumatic accumulator in fluidic communication with the second chamber of the cylinder constituting the control actuator in pivoting movement of the second arm.

[0014] According to one embodiment of the invention, the accumulator, which is a hydropneumatic accumulator, is composed of two parts separated from each other, one of the parts being filled with a gas under pressure, the other part in fluidic communication with the second chamber of the cylinder, which is a hydraulic cylinder being able to be filled with a hydraulic fluid.

[0015] According to one embodiment of the invention, the soil cultivation unit includes a device, such as a pressure gauge, for measuring the pressure in the second chamber. The presence of this pressure gauge allows for control of the restoring force exerted.

[0016] According to one embodiment of the invention, the device for immobilizing the first arm in an adjustable angular position around the first pivot axis is a cylinder.

[0017] According to one embodiment of the invention, the immobilizing device of the first arm in an adjustable angular position around the first pivot axis being a hydraulic cylinder referred to as the first cylinder, and the actuator controlling the pivoting movement of the second arm being a hydraulic cylinder referred to as the second cylinder, the assembly comprises, for connecting the first and second cylinders to at least one source of pressurized fluid, at least one distributor and fluid circulation lines disposed at least between the distributor and the first and second cylinders, and said assembly comprises a distributor control unit equipped with at least three control elements, one of the control elements being configured to control the fluid supply to the first cylinder,One of the control units is configured to control the fluid supply to the second chamber of the second cylinder, and one of the control units is configured to control the fluid supply to the first chamber of the second cylinder.

[0018] The invention also relates to a soil cultivation device comprising at least one chassis of a tractor vehicle or soil cultivation machine and at least one soil cultivation unit coupling to said chassis, characterized in that the or at least one of the soil cultivation units is of the aforementioned type.

[0019] According to one embodiment of the invention, the number of tillage assemblies being at least equal to 2, the immobilizing element of the first arm in an adjustable angular position around the first pivot axis of each assembly being a hydraulic cylinder referred to as the first cylinder, each tillage assembly comprising a pivoting displacement control actuator of the second arm of each assembly in the form of a hydraulic cylinder referred to as the second cylinder, and each assembly comprising, for the connection of the first and second cylinders of each assembly to at least one source of pressurized fluid, at least one distributor and fluid circulation lines disposed at least between the distributor and the first and second cylinders, the distributor being common to said assemblies and the distributor being associated with a distributor control unit equipped with at least four control elements,One of the control units is configured to control the fluid supply to the first cylinder of one of the assemblies, one of the control units is configured to control the fluid supply to the first cylinder of the other assemblies, one of the control units is configured to control the fluid supply to the second chamber of the second cylinder of each assembly, and one of the control units is configured to control the fluid supply to the first chamber of the second cylinder of each assembly. Brève description des dessins

[0020] The invention will be better understood upon reading the following description of exemplary embodiments, with reference to the attached drawings in which: [ Fig. 1 ] represents a partial perspective view of a soil cultivation device equipped with two soil cultivation assemblies according to the invention, in a position close to the second arm of the first arm; [ Fig. 2 ] represents a partial elevational view of a soil cultivation device equipped with a soil cultivation assembly according to the invention, in a position close to the second arm of the first arm; [ Fig. 3 ] represents a partial top view of a soil-working device equipped with two soil-working assemblies according to the invention, in a position close to the second arm of the first arm; [ Fig. 4 ] represents a top view of a soil cultivation device equipped with two soil cultivation units according to the invention, in a position close to the second arm of the first arm, the hydraulic circuits having been shown; [ Fig. 5 ] represents a partial top view of a tillage device equipped with two tillage assemblies according to the invention during the movement of the tillage device between two rows of crops; [ Fig. 6 ] represents a partial top view of a soil-working device equipped with two soil-working units according to the invention; [ Fig. 7 ] represents a schematic view of an accumulator; [ Fig. 8 ] represents a partially cross-sectional view of the control actuator moving the second arm.

[0021] As mentioned above, the invention relates to a soil-working assembly 1 and a soil-working device that can incorporate one or more soil-working assemblies 1, as illustrated in figures 1 And 2 The tillage unit(s) 1 is thus coupled to a chassis 21 of a tractor vehicle of a tillage machine to form a tillage device. The tillage unit(s) 1 is more specifically designed to move along a row 20 of crops, as illustrated in the figure 5 When the tillage device comprises two tillage units, as illustrated in the figure 5 It is possible to cultivate two parallel rows of crops simultaneously, with the tillage equipment positioned between them. Naturally, when the tillage equipment consists of only one tillage unit, only one row of crops is cultivated. This row could be a row of fruit trees, vines, nursery stock, or other crops.

[0022] When the tillage device comprises several tillage sets 1, these tillage sets 1 are generally identical, so only one tillage set 1 will be described below. This tillage set 1 has a direction of travel represented by an arrow at the figure 5 . Generally, the frame 21 to which the soil working assembly 1 is coupled includes at least one beam extending transversely to the direction of travel of said soil working assembly 1.

[0023] This set 1 of tillage equipment includes at least: a tool holder support 2 attached to the frame 21, a non-powered rotary tool 3 in the form of a disc, and a system 4 for connecting the tool 3 to the tool holder support 2. In the example shown, the tool holder support 2 is a plate fixed to a leading or driven side of the beam forming part of the frame 21.

[0024] The linkage system 4 comprises a first arm 5 coupled to the support 2, pivoting around an axis of the first pivot axis XX'. This first pivot axis XX' extends vertically in the operating configuration of the soil-working assembly 1. This linkage system 4 comprises a second tool-carrying arm 6 coupled to the first arm 5, pivoting around an axis called the second pivot axis YY', parallel to the first pivot axis XX', allowing the second arm 6 to move between a position close to the first arm 5 and a position away from the first arm 5. The second arm 6 carries the tool 3, in this case the disc, which is mounted to rotate around an axis of rotation ZZ' extending substantially parallel, that is, parallel to within ±15° of the second pivot axis YY'. This tool 3 therefore extends partially under the second arm 6 to position itself as close as possible to the base of the crop, as illustrated in the figure 5 .

[0025] This tillage unit 1 includes a locking device 7 for the first arm 5 in an adjustable angular position around the first pivot axis XX'. This allows the position of the first arm 5 to be adapted to the width between two rows, particularly when the tillage device comprises two units 1 as illustrated in figures 3 And 5 For example.

[0026] In the example of figures 1 And 2 The immobilizing element 7 for the first arm 5 in an adjustable angular position around the first pivot axis XX' is a cylinder 71 arranged between the first arm 5 and the tool holder support 2. Alternatively, and as illustrated in the figure 6 This locking device 7 for the first arm 5 in an adjustable angular position can be formed by a connecting rod disposed between the first arm 5 and the tool holder support 2, this connecting rod being of adjustable length. It is also possible to imagine, at the connection point between the first arm 5 and the tool holder support 2, a plurality of holes in the first arm 5 and the tool holder support 2, which can be positioned in pairs to coincide and locked in the selected position by, for example, a pin. The advantage of making the locking device 7 for the first arm 5 in the form of a cylinder 71 is that the position of the first arm 5 can be adjusted remotely by simply actuating the cylinder.

[0027] In the example shown, the cylinder 71 is a hydraulic cylinder connectable to a pressurized fluid source 22, and the soil preparation assembly 1 includes, for connecting the cylinder 71 to said pressurized fluid source 22, a distributor 11 and fluid circulation lines 121, 122 represented by a line and a dot. figure 4 For one of the assemblies, and by a dashed line for the supply of the cylinder 71 of the other assembly 1, these conduits 121 and 122 allow the supply of each chamber of the cylinder 71. Thus, supplying pressurized fluid to one of the chambers of the cylinder 71 generates a pivoting movement of the first arm 5 outwards from the soil treatment assembly 1, while supplying pressurized fluid to the other chamber of the cylinder 71 generates a pivoting movement of the first arm 5 in the opposite direction. The greater the width between crop rows, the greater the tendency to position the first arm 5 in a position inclined outwards from the soil treatment assembly 1. It is clear that, thanks to this arrangement of the first arm 5, a wide range of widths between two crop rows can be covered.

[0028] The tillage assembly 1 includes a return element 9 for the second arm 6 in the extended position relative to the first arm 5. This return element 9 is configured to, when the second arm 6 is moving from the extended position to the close position relative to the first arm 5, exert a return force on the second arm 6 towards the extended position relative to the first arm 5. Ideally, the return force of the return element 9 is adjustable. This return element 9 is an energy accumulator configured to store energy in the form of pressure when the second arm 6 is moving from the extended position relative to the first arm 5 and to release this energy when the second arm 6 is moving from the close position relative to the first arm 5 towards the extended position relative to the first arm. 5.This energy accumulator is chosen from the group of energy accumulators formed by springs 91 and hydraulic or hydropneumatic accumulators 92.

[0029] In a simplified version of the invention, as illustrated in the figure 6 , the return element 9 is a spring 91 arranged between the support 2 and the second arm 6. This spring 91 is associated with a spring 911 preloading element of the spring 91 capable of preloading the spring 91 in an adjustable manner to vary the return force of the return element 9 formed by said spring 91.

[0030] Thus, this spring 91 is equipped at one end with a nut cooperating with a threaded rod to variably pre-compress the spring 91 according to the resistance to the approach of the second arm towards the desired first arm.

[0031] In the example of figures 1 And 4The tillage assembly 1 includes a pivoting actuator 8 for controlling the movement of the second arm 6, located between the tool holder support 2 and the second arm 6. This actuator 8 is configured to control at least the movement of the second arm 6 from a position away from the first arm 5 to a position closer to the first arm 5. The pivoting actuator 8 for controlling the movement of the second arm 6 is a cylinder 81, preferably hydraulic, connectable to a pressurized fluid source 22. This cylinder 81 includes a first chamber 811 configured, when supplied with pressurized fluid, to control the movement of the second arm 6 in the direction of bringing the first arm 5 closer to the first, and a second chamber 812. Details of this cylinder 81 are provided in the figure 8 In this embodiment, the return element 9 is a hydraulic or hydropneumatic accumulator 92 in fluidic communication with the second chamber 812 of the cylinder 81 constituting the actuator 8 for controlling the pivoting movement of the second arm 6. Details of a hydraulic or hydropneumatic accumulator 92 are provided in the figure 7 This accumulator is composed of two separate parts, 921 and 922. One part is filled with a pressurized gas, while the other, in fluidic communication with the second chamber of the cylinder 81, is designed to be filled with a hydraulic fluid. Generally, the pressurized gas is nitrogen. This is why such an accumulator can be called a nitrogen accumulator. The element separating the two parts of the accumulator, shown in 923, is... figure 7 This can take different forms depending on the type of accumulator. Thus, this separator element can be a membrane, a piston, a bladder, or something else. Again, for the operation of the actuator 8 for the pivoting movement control of the second arm 6, when the latter is a hydraulic cylinder 81, the soil-working assembly 1 includes a distributor 11, which may be shared with the distributor of the actuator for the pivoting movement control of the first arm when the latter is a cylinder 71, and fluid circulation lines arranged between the distributor 11 and the pivoting movement control cylinder 81 of the second arm.

[0032] In the example of the figure 4 The conduit 123, represented by crosses, supplies the first chamber 811 of the cylinder 81, while the conduit 124, represented by a solid line, supplies the second chamber 812 of the cylinder 81, which is in fluidic communication with one of the sections of the hydropneumatic or hydraulic accumulator 92 and, consequently, with said section of the hydropneumatic or hydraulic accumulator. The second chamber 812 of the cylinder 81 is in fluidic communication with one of the sections of the hydropneumatic or hydraulic accumulator 92 via a connection that may be closable.

[0033] To control this pre-filling of this second chamber 812 in relation to the accumulator and the resulting restoring force, the soil working assembly 1 includes a device such as a pressure gauge 10, for measuring the pressure in the second chamber 812.

[0034] The advantage of this solution lies in its ease of implementation. The pressure is determined empirically by the user, who can then adjust it according to the desired soil treatment outcome.

[0035] Finally, to complete the soil preparation unit 1, this unit includes a control unit 13 for the distributor 11, equipped with at least three control elements, such as switches, capable of controlling the opening / closing of each pipe. The distributor 11 is a spool valve, and the opening / closing of each pipe depends on the position of the spool.

[0036] In the example of the figure 4 Four control elements are provided, represented by figures 141, 142, 143, and 144, each associated with the line(s) it controls. Thus, control element 141 controls the opening / closing of line 121, i.e., the operation of the control cylinder 71 by pivoting the first arm 5 of one of the soil treatment units 1. Control element 142 controls the opening / closing of line 122, i.e., the operation of the control cylinder 71 by pivoting the first arm 5 of the other soil cultivation unit 1 when the soil cultivation device comprises two soil cultivation units 1.

[0037] The control member 143 controls the opening / closing of the pressurized fluid supply line 123 of the first chamber 811 of the pivoting control actuator 8 of the second arm 6 of one or both of the soil working units when the soil working device includes two soil working units, and the control member 144 controls the opening / closing of the pressurized fluid supply line 124 of the second chamber 812 of the pivoting control actuator 8 of the second arm in fluidic communication with the hydraulic or hydropneumatic accumulator of one or both of the soil working units when the soil working device includes two soil working units 1.

[0038] Of course, one of the control elements can be omitted when the tillage system consists of only one tillage unit. In practice, the tillage system operates as follows. It is assumed that the tillage system is positioned along a row of crops or between two parallel rows of crops, as illustrated in the figure 5 Initially, the user determines the angular position of the first arm 5 using the first arm 5 locking device 7. This position is determined based on the row spacing, i.e., the row spacing. The return force of the return element 9 is then adjusted. In the case of an accumulator, for example, in the offset position of the second arm 6 from the first arm 5, fluid is supplied to the second chamber 812 of the actuator 8 that controls the movement of the second arm 6, and consequently to the fluidic communication portion of the accumulator, until a desired pressure value is reached. When the tillage device moves along the row following the arrow shown in the diagram... figure 5The non-driven disc of each tillage unit 1, or of the tillage unit 1 when the tillage device comprises only one tillage unit 1, encounters, as it advances, a crop in the row which tends, by pressing the disc on the crop, to bring the second arm 6 closer to the first arm 5 against the restoring force exerted by the restoring element 9. At the end of the row, the second arm 6 can be brought closer to the first arm 5 by actuating the pivoting control actuator 8 of the second arm 6 when this actuator 8 is present to facilitate maneuvering at the end of the row before traveling, if necessary, through another alley between two rows.

[0039] Such a soil-working device can work at high travel speeds and can be mounted at the front or rear of the chassis of the tractor vehicle to which it is coupled.

Claims

1. Soil working assembly (1) comprising at least one tool-carrying support (2) couplable to a chassis (21) of a soil working machine or a towing vehicle, a non-motorized rotary tool (3), such as a disc, and a system (4) for connecting the tool (3) to the support (2), the connection system (4) comprises a first arm (5) coupled pivotingly to the support (2) about an axis referred to as the first pivot axis (XX'), a second tool-carrying arm (6) coupled pivotingly to the first arm (5) about an axis referred to as the second pivot axis (YY') parallel to the first pivot axis (XX) for moving the second arm (6) between a position close to the first arm (5) and a position separated from the first arm (5), the rotary tool (3) having a rotation axis (ZZ') extending substantially parallel, i.e. parallel to within plus or minus 15 degrees, to the second pivot axis (YY'), characterized in that said assembly (1) comprises a member (7) for immobilizing the first arm (5) in an adjustable angular position about the first pivot axis (XX'), and in that said assembly (1) comprises at least one biasing element (9) for returning the second arm (6) to a position separated from the first arm (5), this biasing element (9) being configured to exert a biasing force on the second arm (6) towards the position separated from the first arm (5) when the second arm (6) is being moved from the separated position towards the position close to the first arm (5).

2. Soil working assembly (1) according to Claim 1, characterized in that the biasing force of the biasing element (9) is an adjustable force.

3. Soil working assembly (1) according to one of Claims 1 or 2, characterized in that the biasing element (9) is an energy accumulator configured to store energy when the second arm (6) is being moved from the separated position towards the position close to the first arm (5) and to restore said energy to move the second arm (6) from the position close to the first arm towards the position separated from the first arm (5), this energy accumulator being chosen from the group of energy accumulators formed by springs (91) and hydraulic or hydropneumatic accumulators (92).

4. Soil working assembly (1) according to one of Claims 1 to 3, characterized in that the biasing element (9) is a spring (91) arranged between the support (2) and the second arm (6).

5. Soil working assembly (1) according to Claim 4, characterized in that the spring (91) is associated with a prestressing element (911) of the spring (91) for adjustably prestressing the spring (91) to vary the biasing force of the biasing element (9) formed by said spring (91).

6. Soil working assembly (1) according to one of Claims 1 to 5, characterized in that said assembly (1) comprises an actuator (8) for controlling the pivoting movement of the second arm (6) arranged between the support (2) and the second arm (6), this actuator (8) being configured to control at least the movement of the second arm (6) from a position separated from the first arm (5) to a position close to the first arm (5).

7. Soil working assembly (1) according to Claim 6, characterized in that the actuator (8) for controlling the pivoting movement of the second arm (6) is a hydraulic or pneumatic cylinder (81) connectable to a source (22) of pressurized fluid, this cylinder (81) comprising a first chamber (811) configured to control a movement of the second arm (6) towards the first arm (5), when supplied with pressurized fluid, and a second chamber (812).

8. Soil working assembly (1) according to Claim 7, characterized in that the biasing element (9) is a hydraulic or hydropneumatic accumulator (92) in fluidic communication with the second chamber (812) of the cylinder (81) constituting the actuator (8) for controlling the pivoting movement of the second arm (6).

9. Soil working assembly (1) according to Claim 8, characterized in that the accumulator, which is a hydropneumatic accumulator (92), consists of two parts (921, 922) separated from each other, one of the parts being filled with a pressurized gas, the other part being in fluidic communication with the second chamber of the cylinder (81), which is a hydraulic cylinder, and being fillable with a hydraulic fluid.

10. Soil working assembly (1) according to one of Claims 8 or 9, characterized in that the soil working assembly (1) comprises a device, such as a pressure gauge (10), for measuring the pressure in the second chamber (812).

11. Soil working assembly (1) according to one of Claims 1 to 10, characterized in that the member (7) for immobilizing the first arm (5) in an adjustable angular position about the first pivot axis (XX') is a cylinder (71).

12. Soil working assembly (1) according to one of Claims 7 to 10, characterized in that, where the member (7) for immobilizing the first arm (5) in an adjustable angular position about the first pivot axis (XX') is a hydraulic cylinder (71) referred to as the first cylinder (71) and the actuator (8) for controlling the pivoting movement of the second arm (6) is a hydraulic cylinder (81) referred to as the second cylinder (81), the assembly (1) comprises, for connecting the first and second cylinders (71, 81) to at least one source (22) of pressurized fluid, at least one distributor (11) and fluid circulation pipes (121, 122, 123, 124) arranged at least between the distributor (11) and the first and second cylinders (71, 81), and in that said assembly (1) comprises a control unit (13) for the distributor (11) equipped with at least three control members (141, 142, 143, 144), in that one of the control members is configured to control the supply of fluid to the first cylinder (71), in that one of the control members is configured to control the supply of fluid to the second chamber (812) of the second cylinder (81), and in that one of the control members is configured to control the supply of fluid to the first chamber (811) of the second cylinder (81).

13. Soil working device comprising at least one chassis (21) of a towing vehicle or of a soil working machine and at least one soil working assembly (1) connectable to said chassis (21), characterized in that the or at least one of the soil working assemblies (1) is a soil working assembly according to one of Claims 1 to 12.

14. Soil working device according to Claim 13, characterized in that the number of soil working assemblies (1) is at least equal to 2, in that the member (7) for immobilizing the first arm (5) in an adjustable angular position about the first pivot axis (XX') of each assembly (1) is a hydraulic cylinder referred to as the first cylinder (71), in that each soil working assembly (1) comprises an actuator (18) for controlling the pivoting movement of the second arm (6) of each assembly (1) in the form of a hydraulic cylinder referred to as the second cylinder (81) and each assembly (1) comprises, for connecting the first and second cylinders (71, 81) of each assembly (1) to at least one source (22) of pressurized fluid, at least one distributor (11) and fluid circulation pipes (121, 122, 123, 124) arranged at least between the distributor (11) and the first and second cylinders (71, 81), in that the distributor (11) is common to said assemblies (1) and in that the distributor (11) is associated with a control unit (13) for the distributor (11) equipped with at least four control members (141, 142, 143, 144), in that one of the control members is configured to control the supply of fluid to the first cylinder (71) of one of the assemblies (1), in that one of the control members is configured to control the supply of fluid to the first cylinder (71) of the other of the assemblies (1), in that one of the control members is configured to control the supply of fluid to the second chamber (812) of the second cylinder (81) of each assembly (1), and in that one of the control members is configured to control the supply of fluid to the first chamber (811) of the second cylinder (81) of each assembly (1).