BE1019617A3 - DESILAGE BUCKET. - Google Patents

Abstract

The present invention relates to a silage silage bucket (100) comprising a loading / unloading bucket (200), an operating arm (300) holding at its free end a rotor (340) capable of being driven in rotation by the 'intermediary of at least one hydraulic motor (350), the maneuvering arm (300) being mounted in an articulated manner between a disengaged position and a folding position on the bucket (200), under the effect of a drive by means of at least one hydraulic cylinder (320). According to the invention, the silage removal bucket comprises a valve (410) interposed on a 1st hydraulic connection circuit (422) from a chamber of said cylinder to a control valve (DC), a first nozzle (450) being interposed on said circuit between the valve (410) and said chamber, a second nozzle (452) being interposed on a 2nd hydraulic connection circuit (460) connected as a bypass on the 1st circuit (422), on the one hand, between said chamber of the cylinder and the 1st nozzle (450) and, on the other hand, between the valve (410) and the connection to ....

Description

DESILAGE BUCKET.

The present invention relates to a dewatering bucket of the type comprising a loading / unloading bucket, a maneuvering arm holding at its free end a rotor driven to rotate by means of a hydraulic motor, the operating arm being mounted so articulated between a release position and a crimping position on the bucket, under the effect of a drive via at least one hydraulic cylinder.

In order to distribute feed to animals, it is possible to use, in a known manner, a dewatering bucket which is coupled to a machine such as a tractor in order to extract from a silo a feed feed such as corn, grass silage, and load it into the bucket to then take it and distribute it to the animals.

A dewatering bucket generally comprises a loading bucket, a pivoting arm that can be moved by at least one hydraulic cylinder and at the end of which is disposed a rotor intended to extract material stored in the silo, this rotor being, for this purpose, connected to a hydraulic motor to be rotated.

The operator places the bucket at the foot of the silo after positioning the rotor above the front of the latter, then controls, using a hydraulic distributor, the rotation of the rotor drive, then the descent of the arm using a second distributor. Under the effect of the drive arm down by the hydraulic cylinder, the rotor scrapes the material which is then projected into the bucket.

It is easy to understand that, the more the rotor starts the silo, the more the power necessary for its training increases, so that it is often necessary to slow down the movement of the arm to prevent the hydraulic motor from stalling under the effect of the stuffing of the silo. rotor. The operator must regularly change the speed of descent of the arm by acting on the second distributor.

A known solution to overcome this problem has been to make the control of the movement of the arm dependent on the operation of the rotor. Such a solution is disclosed in patent EP-B1-0 943 232. In this patent is presented a bucket provided with an articulated arm against a hydraulic cylinder and holding at its free end a rotor driven by a motor hydraulic. A single distributor is used to control the operation of the operating cylinder of the arm and the hydraulic motor. A proportional valve is interposed between the cylinder and the hydraulic motor to modulate the cylinder speed according to the supply pressure of the hydraulic motor.

Given the enslavement of the movement of the arm to the supply pressure of the hydraulic motor, it happens that when the pressure in the engine reaches a certain threshold, the movement of the arm is interrupted.

The object of the invention is therefore to provide, in particular, a dewatering bucket of the type which is presented in the introduction, and which can provide a more efficient control of the movement of the arm, in connection with the operation of the hydraulic motor.

For this purpose, there is provided a dewatering bucket comprising a loading / unloading bucket, a maneuvering arm holding at its free end a rotor capable of being rotated by means of at least one hydraulic motor, the arm device being hingedly mounted between a disengagement position and a crimping position on the loading and unloading bucket, under the effect of a drive via at least one hydraulic cylinder, the unloading bucket of the invention being remarkable in that it comprises a valve interposed on a first hydraulic connection circuit of a chamber of said cylinder to a control valve, a first nozzle being interposed on said circuit between the valve and said chamber, a second nozzle being interposed on a second hydraulic connection circuit connected in shunt on the first circuit, on the one hand, between said ch amber cylinder and the first nozzle and, secondly, between the valve and the connection to the control valve, a third hydraulic connecting circuit connecting the other chamber of said cylinder to the control valve, said hydraulic motor being connected between the first circuit and the third circuit, the control of the valve being performed by a fourth hydraulic connection circuit connected to the third circuit, the tilting of the valve in its closed position occurring when the supply pressure of said motor reaches a certain threshold.

In normal operation, that is, when the unloading bucket is connected to the control valve, one of the cylinder chambers and the hydraulic motor are energized. The flow of the other cylinder chamber is reduced by passing through the two nozzles. The operating arm thus moves, at a so-called "working" speed, the rotor which can then normally remove by rotation of the material of a silo. When the supply pressure of this engine reaches a certain threshold, that is to say, when it fails, the flow of the other cylinder chamber flows through only one nozzle. The maneuvering arm then moves the rotor more slowly, at a so-called "reduced" speed, to prevent the engine from stalling. When the engine is less bent, that is to say when its supply pressure rises above a certain threshold, the operating arm moves back to its working speed. The movement of the operating arm is therefore no longer interrupted during rotor work.

According to an additional characteristic of the invention, said hydraulic motor is connected, on the one hand, with the first circuit via a fifth hydraulic connection circuit, on the other hand, with the third circuit via a sixth hydraulic connection circuit, a check valve being interposed on the fifth circuit to prevent the operation of said motor in an operating direction of said cylinder.

In one direction of movement of the arm of the rotor, it is rotated, while in the other direction, it no longer rotates.

According to an additional feature of the invention, a hydraulic pressure reducer is interposed on the third hydraulic connection circuit to limit the supply pressure in a chamber of said cylinder to a threshold value.

Said cylinder is thus fed at a pressure that does not vary when the engine load increases.

According to an additional feature of the invention, a simple balancing hydraulic valve is connected between the first hydraulic connection circuit and the third hydraulic connection circuit.

According to an additional feature of the invention, the unloading bucket incorporates a hydraulic connection unit, comprising two connection ports to the control distributor, two hydraulic motor connection ports, two connection ports to said cylinder.

The different connection orifices being distinctly differentiated, the operation of connecting the hydraulic components of the unloading bucket is facilitated.

According to an additional characteristic of the invention, the valve, the first circuit, the first nozzle, the second nozzle, the second circuit, the third circuit, the fourth circuit, the fifth circuit, the non-return valve, the sixth circuit, the hydraulic pressure reducer, the simple balancing hydraulic valve, are incorporated in the hydraulic block, the various hydraulic connection circuits being constituted by internal passages made in the hydraulic block.

Thanks to this hydraulic block it is possible to greatly simplify the connection of the hydraulic components of the unloading bucket.

According to an additional feature of the invention, at least one nozzle can be removed from the hydraulic block. It can be replaced by another, to calibrate a speed of movement of the arm to a different value or to replace it.

According to an additional feature of the invention, the unloading bucket comprises two hydraulic cylinders connected in parallel.

A hydraulic block intended to be implanted on a dewatering bucket is also claimed. It is necessary to connect the hydraulic block to a control distributor for supplying, on the one hand, at least one hydraulic motor driving a rotation of a rotor, and, secondly, at least one hydraulic cylinder capable of moving an operating arm articulated between two extreme positions, the operating arm holding at its free end said rotor. According to the invention, the hydraulic unit incorporates a valve connected to a first internal passage connecting a connection port to a chamber of said cylinder and a connection port intended to be connected with the control valve, a first nozzle interposed on the first passage. internal, between said valve and the connection port to said chamber of said cylinder, a second nozzle interposed on a second internal passage connected in shunt on the first internal passage, on the one hand, between the connection port to said chamber of said cylinder and the first nozzle and, secondly, between the valve and the branch of the first internal passage connected to the connection port to be connected with the control valve, a third internal passage connected between a connection port to the other chamber of said cylinder and another connection port to the distributor, the hydraulic block incorporan t two connection ports to said hydraulic motor, respectively connected to said branch and the third internal passage, the control of the valve being performed by a fourth internal passage connected to the third internal passage, the tilting of the valve in its closed position intervenant when the pressure measured in the third internal passage reaches a certain threshold.

It is of course necessary to connect the hydraulic block to the control valve of the machine, the hydraulic motor and said hydraulic cylinder to check the latter feature.

According to an additional characteristic of the invention, the valve is provided with a return spring whose setting can be modified by means of a setting means.

The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being made in connection with the attached drawings, among which: FIG. . 1 is a side view of a silage bucket coupled to a machine, the bucket being provided with a maneuver arm holding a rotor and which is placed in the disengaged position according to the invention, FIG. 2 is a side view of a dewatering cup according to the invention, FIG. 3 shows a side view of a silage bucket coupled to a machine, the operating arm holding the rotor being placed in the leading position of a slice of a silo according to the invention, FIG. 4 shows a side view of a silage bucket coupled to a machine, the operating arm holding the rotor being placed in an intermediate nibbling position of a full slice of a silo according to the invention, FIG. 5 shows a side view of a silage bucket coupled to a machine, the operating arm holding the rotor being placed in the crimping position on the bucket according to the invention, FIG. 6 shows a view of a hydraulic diagram of a dewatering bucket according to the invention, FIG. 7 shows a view of a hydraulic diagram showing the output of jack rods at a so-called "working" speed and the rotation of a hydraulic motor of a dewatering bucket according to the invention, FIG. 8 shows a view of a hydraulic diagram showing the output of rods of cylinders at a so-called "reduced" speed and the rotation of a hydraulic motor of a dewatering bucket according to the invention and, FIG. 9 shows a view of a hydraulic diagram showing the retraction of cylinder rods of a silo bucket according to the invention and the stopping of a hydraulic motor.

The unloading bucket 100 shown in FIG. 1 is intended to be coupled to a machine E provided with a lifting means for extracting a feed from a silo S, transporting it and distributing it to animals.

It is composed, in FIG. 2, a bucket 200 for loading and unloading its contents and on which is mounted, in an articulated manner, an operating arm 300 of a rotor 340 for taking material on the front of a silo.

The bucket 200 of loading and unloading comprises a front wall 202, a back wall 204 joined by a bottom wall 206 and two side walls 208 thus defining a container. This container is provided with a filling opening 210 belted between the front wall, the back wall and the side walls. At least one side wall 208 is traversed by an opening that can be closed by an articulated door 209 against an operating means not shown. In an alternative embodiment, not shown, the bucket is devoid of hatch. A fixing device 220, comprising flanges, is fixed on the back wall 204 to allow coupling of the unloading bucket 100 on the machine E.

The operating arm 300 consists of two elements 302 arranged one vis-à-vis the other, joined by at least one cross member 304, each element being fixed at one end, and via a articulation 306, on a side wall 208, near the free edge of the back wall 204.

The operating arm 300 is moved through at least one hydraulic cylinder 320, of the double-acting type, between a disengagement position visible in this FIG. 2 where the arm is disposed approximately in the extension of the back wall 204 and a folding position, visible in FIG. Where the rotor 340 is disposed near the front wall. In this FIG. 2, the jack 320 is mounted above the operating arm 300 to leave the filler opening 210 completely unobstructed during the excursion of the operating arm 300. When the cylinder rod 320 is retracted, the operating arm 300 is placed in its release position while when it is released, the operating arm is placed in its folding position.

In a preferred embodiment, the operating arm 300 is moved by two hydraulic cylinders 320a and 320b to balance the forces in it. The two cylinders are then connected in parallel as shown in FIG. 6.

Between its two extreme positions, the rotor 340 is able to nibble a slice of a silo S in order to transfer the material thus withdrawn inside the bucket 200. Different working positions of the rotor are shown in Figs. 3, 4 and 5.

For this purpose, the rotor 340 is provided, as shown in FIG. 2, a plurality of teeth 342 disposed at the periphery of a cylinder. The rotor 340 is rotatable by means of at least one hydraulic motor 350 placed inside the cylinder. In this FIG. 2, a single hydraulic drive motor is mounted in the cylinder. In an alternative embodiment, not shown, two hydraulic motors, connected in parallel, are mounted respectively in the two ends of the cylinder for, at equal power, reduce by a factor of two hydraulic flow in each engine.

The hydraulic cylinders 320 and the hydraulic motor 350 are supplied with hydraulic fluid via the hydraulic circuit of the machine E.

To impose the operation of these components using a single control valve placed in the cab of the machine, the unloading bucket of the invention incorporates a hydraulic block connection of a particular design and which is connected in the hydraulic circuit of the unloading bucket with reference to FIG. 6.

In this FIG. 6, there are two hydraulic cylinders 320 drive arm of the maneuvering arm, as well as the hydraulic motor 350 rotor drive.

A single control distributor DC placed in the cabin of the machine makes it possible to implement the operation of the unloading bucket by connecting, through the hydraulic block 400, the hydraulic cylinders and motor with the pump P and / or the reservoir RS storage fluid of the hydraulic circuit of the machine E. The DC control valve is preferably of type 4/3, closed center and manually controlled, as shown in this FIG. 6. On some machines, this control valve is of open center type. It is connected to the hydraulic block 400 through two orifices DI and D2, via two pipes C1 and C2. The hydraulic motor 350 is connected to the hydraulic block 400 through two orifices 351 and 352, via two pipes C3 and C4, while the downstream and upstream chambers of the two hydraulic cylinders 320 are connected to the hydraulic block 400 through respectively two orifices 321 and 322, through two channels C5 and C6.

The orifices 321 and DI are connected by a first internal passage 422 to the hydraulic block 400 while the orifices 322 and D2 are connected by a second internal passage 424 thus allowing the DC control distributor to feed, at the option of its control, the rods of the cylinders 320 in both directions of movement. In the intermediate position of the DC control valve, visible in this FIG. 6, any circulation of the fluid is interrupted in the unloading bucket to allow its safe transportation. The orifice 351 is connected to the internal passage 422 via a third internal passage 426, while the orifice 352 is connected. at the second internal passage 424 via a fourth internal passage 428. A first non-return valve 430 is interposed on the third internal passage 426 while passing downstream of the connection orifice 351 towards the hydraulic motor 350 and a second non-return valve 432 is interposed on a fifth internal passage 440 connecting the internal passages 426 and 428, passing between the internal passage 426 and the internal passage 428. Thus, the control distributor DC can supply, of a on the other hand, the cylinders 320 so that their rods move in one direction and, on the other hand, the hydraulic motor 350, as shown respectively by the arrows F1 and F2 on the Fig. 7, while feeding the cylinders 320 so that their rods move in the opposite direction, as shown by the arrows F3 in FIG. 9, the hydraulic motor 350 is no longer powered.

The presence in FIG. 6 of the second non-return valve 432 allows the hydraulic fluid to circulate in a loop in the engine, allowing it to slow down smoothly during its stopping phase.

In Figs. 7, 8 and 9, the flow direction of the hydraulic fluid is symbolized by the arrows I.

In FIG. 6, the hydraulic block 400 incorporates a valve 410, preferably a type 2/2 valve, monostable, normally open (NO), hydraulically controlled and spring return. The orifices of this valve are connected to the circuit of the internal passage 422 while its control is connected with the orifice D2, that is to say also with the second internal passage 424 and the fourth internal passage 428, and this by via a sixth internal passage 442. A first nozzle 450 is interposed on the internal passage 422 between the valve 410 and the connection port 321 to the downstream chambers of the cylinders 320. In operation, when the distributor feeds the upstream chambers 320, the flow rate of the downstream chambers of these cylinders is calibrated through the nozzle 450 so that the speed of descent of the operating arm is limited to a so-called "work" speed so that the rotor 340 can normally extract the material silo during the descent of the maneuvering arm.

In FIG. 3, the operating speed of the operating arm 300 is symbolized by the arrow Vt. Furthermore, the hydraulic motor is mounted so that the rotor 340 can project the material extracted from the silo towards a deflector 308 capable of returning it to the bucket 200. The arrow Rt indicates in this FIG. 3, the direction of rotation of the rotor 340.

Following extensive rotor work to extract the material from the silo, for example when working the silo front over substantially all of its diameter, as shown in FIG. 4, or when the material is strongly packed, the power consumed by the rotor increases and therefore its hydraulic fluid supply pressure also increases.

In FIG. 6, this information is transmitted to the control of the valve 410 through the internal passage 442. The return spring of the control of this valve is calibrated so that it closes the internal passage 422 before the hydraulic motor does not hold . To adapt the unloading bucket to different types of gear, the setting of this spring can be modified by a setting means comprising, for example, a screw and its corresponding nut. We can still replace the spring with another of a different stiffness.

When the valve switches to its closed position, the flow rate of the downstream chambers of the cylinders is interrupted and the operating arm stops.

To avoid this undesired stop of the arm, a second nozzle 452 is interposed in this FIG. 6, on a seventh internal passage 460 taken in parallel with the first internal passage 422 between, on the one hand, the connection orifice 321 and the first nozzle and, on the other hand, between the valve 410 and the branch of the first passage internal 422 connected to the orifice Dl. When the distributor feeds the upstream chambers of the cylinders 320 and rotates the hydraulic motor 350, the flow rate of the downstream chambers of the cylinders is calibrated to a lower level as long as the valve 410 has tilted to its closed position. This situation is presented in FIG. 8 where the arrows F'1 symbolize a reduced speed of the rods of the cylinders 320. A

In use, the operating arm 300 descends at a so-called "reduced" speed enabling the rotor 340 to extract material from the silo even when the etched edge is thick as shown in FIG. 4. In this FIG. 4, the reduced speed of the operating arm 300 is symbolized by the arrow Vr. The movement of the maneuvering arm when descending is no longer interrupted. The speed of this operating arm is thus either a working speed for rapid filling of the bucket, or a reduced speed, when the hydraulic motor barely. The operator no longer has to intervene to control the filling of the bucket.

The reduced flow in the downstream chambers of the cylinders allows the pump to power the hydraulic motor with greater flow, which increases its power when it needs it most.

It will be noted that in the open position of the valve 410, the flow rates of the two nozzles add up to quantify the so-called working speed.

Two other nozzles may be incorporated in the hydraulic block 400. In FIG. 6, a third nozzle 454 can thus be interposed on the internal passage 422 between the valve 410 and the connection to the third internal passage 426, that is to say on the other side of the nozzle 450 to facilitate the decompression of the hydraulic fluid exiting said valve. Another nozzle 456 may be interposed on the sixth internal passage 442 to avoid inflicting a water hammer on the control of the valve 410.

The jets, or at least some of them, are of the dismountable type, that is to say that they can be easily dismantled from the hydraulic block to be replaced by others of different sizes for, in particular, change the two or more speeds of movement of the operating arm or when they are worn.

In FIG. 6, a hydraulic pressure reducer 470 is interposed on the second internal passage 424 to limit to a threshold value the supply pressure in the cylinder chambers. Indeed, the mass of the operating arm could be sufficient to drive it from its release position to its folding position. In addition, the supply pressure of the cylinders remains insensitive to the supply pressure of the hydraulic motor.

In this FIG. 6, a simple balancing hydraulic valve 480 is connected between the first internal passage 422 and the second internal passage 424 to prevent the combined action of the mass of the operating arm and the reaction of the rotor during the extraction of the material the silo can not brutally cause the descent of the maneuvering arm. The detection of a negative pressure in the upstream chambers of the hydraulic cylinders 320 thus makes it possible to interrupt the flow rate of the downstream chambers of the cylinders in order to temporarily brake the movement of the operating arm.

The presence of the hydraulic pressure reducer 470 and the simple hydraulic balancing valve 480 provides a smooth operation of the unloading bucket. In the prior art, the jacks were forced to slow down or stop while their feed pressure increased so that this situation generated jerks in the operation of the unloading bucket.

It should be noted that in order to implement a bucket filling technique from below, the rotor could rotate in the opposite direction to that mentioned in FIG. 3.

In addition, the position of the operating arm and cylinders could be reversed, so that the rods of the jacks pushing the operating arm to take it from its folding position to its release position.

The operation of the unloading bucket 100 of the invention is as follows. The unloading bucket is coupled to a machine E equipped with a lifting arm and connected to the hydraulic circuit of the machine. The bucket is brought facing the cutting edge of a silo after raising the operating arm 300 to its disengaged position. The operator actuates the DC control valve so that the rotor 340 can be rotated and the maneuvering arm 300 initiates a downward movement towards its folding position. The rotor 340 reaches the silo, extracts a slice of the silo and in turn propels the baffle 308 into the cup 200. The rotor 340 moves in its working speed. When the rotor reaches a dense zone of material or when it attacks the silo on a large thickness, the supply pressure of the hydraulic motor 350 rises to exceed a certain threshold, so that the valve 410 switches to its position of closing thus forcing the operating arm, and therefore the rotor, to move at its reduced speed to prevent jamming of the rotor. When the supply pressure lowers again below said threshold, the operating arm then moves to its operating speed.

When the operating arm reaches its crimping position, the operator starts, if necessary, another work cycle of the rotor to complete the filling of the bucket. It then actuates the DC control valve so as to raise the operating arm 300 to its disengaged position. During this maneuver, the hydraulic motor 350 does not work thus allowing a quick rise of the operating arm. When the bucket is filled, the operator drives 1 machine with its bucket loaded to its place of discharge or emptying.

In a first variant embodiment, not shown, of the dewatering bucket, certain components and in particular the nozzles 450, 452, the hydraulic pressure reducer 470, the hydraulic equilibrium valve 480, are not integrated into the construction of the hydraulic block 400 to reduce the manufacturing cost. The hydraulic circuits connecting these components, that is to say the various internal passages, are then replaced by pipes.

In a second alternative embodiment, also not shown, the connection of the various components is achieved without using a hydraulic block, but using pipes, to reduce the cost of purchasing the components of the unloading bucket.

The unloading bucket of the invention operates automatically during the loading phase of its contents. No intervention of the operator is thus required during this phase, except the actuation of the control distributor to initiate it.

It makes it possible to anticipate the setting of the rotor by forcing the maneuvering arm to move in its reduced speed.

While working, the operation of the hydraulic motor and the hydraulic cylinders does not produce jolts.

Claims (10)

A dewatering bucket (100) comprising a loading / unloading bucket (200), an operating arm (300) holding at its free end a rotor (340) rotatable through at least one hydraulic motor (350), the operating arm (300) being hingedly mounted between a release position and a drawdown position on the bucket (200), under the effect of a drive via least one hydraulic cylinder (320), characterized in that it comprises a valve (410) interposed on a first hydraulic connection circuit (422) of a chamber of said cylinder to a control distributor (DC), a first nozzle ( 450) being interposed on said circuit between the valve (410) and said chamber, a second nozzle (452) being interposed on a second hydraulic connection circuit (460) connected in shunt on the first circuit (422), on the one hand between said room of the v rin and the first nozzle (450) and, on the other hand, between the valve (410) and the connection to the control distributor (DC), a third hydraulic connection circuit (424) connecting the other chamber of said cylinder towards the control distributor (DC), said hydraulic motor (350) being connected between the first circuit (422) and the third circuit (424), the control of the valve (410) being performed by a fourth hydraulic connection circuit (442) ) connected to the third circuit (424), the tilting of the valve (410) in its closed position occurring when the supply pressure of said motor reaches a certain threshold. 2. Dewatering bucket according to claim 1, characterized in that said hydraulic motor (350) is connected, on the one hand, with the first circuit (422) via a fifth hydraulic connection circuit (426). on the other hand, with the third circuit (424) via a sixth hydraulic connecting circuit (428), a non-return valve (430) being interposed on the fifth circuit (426) to prohibit operation said engine in a direction of operation of said cylinder. 3. Unilvering bucket according to claim 1 or 2, characterized in that a hydraulic pressure reducer (470) is interposed on the third hydraulic connection circuit (424) to limit the supply pressure to a threshold value in a chamber of said cylinder. 4. Unilvering bucket according to claim 1, 2 or 3, characterized in that a simple balancing hydraulic valve (480) is connected between the first hydraulic connection circuit (422) and the third hydraulic connection circuit (424). ). 5. Unilvering bucket according to any one of the preceding claims, characterized in that it incorporates a hydraulic block (400) for connection comprising two connection ports (D1, D2) to the control distributor, two connection ports ( 351, 352) to the hydraulic motor (350), two connecting ports (321, 322) to said cylinder (320). 6. Dewatering bucket according to claim 5, characterized in that the valve (410), the first circuit (422), the first nozzle (450), the second nozzle (452), the second circuit (460), the third circuit (424), the fourth circuit (442), the fifth circuit (426), the non-return valve (430), the sixth circuit (428), the hydraulic pressure reducer (470), the hydraulic balancing valve simple (480), are incorporated in the hydraulic block (400), the various hydraulic connection circuits being constituted by internal passages made in the hydraulic block. 7. deinking bucket according to claim 5 or 6, characterized in that at least one nozzle (450, 452) can be removed from the hydraulic block (400). 8. deinking bucket according to any one of the preceding claims, characterized in that it comprises two hydraulic cylinders (320a, 320b) connected in parallel. 9. Hydraulic block (400) intended to be installed on a dewatering bucket (100) in order to be connected to a control distributor (DC) for supplying, on the one hand, at least one hydraulic motor (350) of rotational drive of a rotor (340), and, secondly, at least one hydraulic cylinder (320) adapted to move a maneuvering arm (300) articulated between two extreme positions, the maneuvering arm (300) holding at its free end said rotor, characterized in that it incorporates a valve (410) connected to a first internal passage (422) connecting a connection port (321) to a chamber of said cylinder and a connection port (D1) for to be connected with the control distributor (DC), a first nozzle (450) interposed on the first internal passage (422), between said valve (410) and the connection orifice (321), a second nozzle (452) interposed, on a second internal passage (460) connected bypass on the premie internal passage (422), on the one hand, between the connection orifice (321) and the first nozzle (450) and, on the other hand, between the valve (410) and the branch of the first internal passage (422). ) connected to the connection port (D1), a third internal passage (424) connected between a connection port (322) to the other chamber of said cylinder (320) and another connection port (D2) to the distributor (DC), the hydraulic unit incorporating two connection ports (351, 352) towards said hydraulic motor (350), respectively connected to said branch and to the third internal passage (424), the control of the valve (410) being carried out by a fourth internal passage (442) connected to the third internal passage (424), the tilting of the valve (410) in its closed position occurring when the pressure measured in the third internal passage (424) reaches a certain threshold. 10. Hydraulic unit (400) according to claim 9, characterized in that the valve (410) is provided with a return spring whose setting can be modified through an adjusting means.