Hydraulic cylinder locking device having indirect electrohydraulic control

Abstract

The invention relates to an electrohydraulically controlled device for locking a cylinder comprising a safety module (5) that comprises: - two inlets (12, 13) intended to be connected to the hydraulic circuit and at least one outlet (8) intended to be connected to an opening in a chamber (10, 11) of the cylinder (1); - a hydraulic passage (16, 17) between a first of these two inlets (12, 13) and the at least one outlet (8), provided so that the chamber (10, 11) can only be filled and emptied through this hydraulic passage (16, 17); and - two mechanical closure devices mounted in series in the hydraulic passage (16, 17) in order to enable the chamber (10, 11) to be locked in a sealed manner, characterised in that it comprises: - a control module (6) connected to the two inlets (12, 13) of the safety module (5); and - a flow selector and a solenoid valve (42), the activation and deactivation of which enables or prevents supply of power to the control module (6).

Description

[0001] Description

[0002] Title of the invention: Device for locking a hydraulic cylinder with indirect electrohydraulic control

[0003] Technical field

[0004] The present invention relates to the technical field of so-called "safety" cylinders. It relates more particularly to a safety and control device for moving and maintaining the position of the rod of a single or double-acting hydraulic cylinder.

[0005] The invention also relates to a single or double-acting hydraulic cylinder equipped with such a safety and control device.

[0006] The invention also relates to a hydraulic circuit containing a set of cylinders equipped with such safety devices and allowing them to be supplied and controlled in a particularly advantageous manner.

[0007] This invention can advantageously be applied to car transporters or other equipment supporting loads by means of single or double-acting hydraulic cylinders. More generally, it can be applied to any device comprising several hydraulic cylinders which it is desired to supply with hydraulic fluid in a centralized manner, while controlling them independently of each other, in a secure manner.

[0008] Prior art

[0009] Single or double-acting hydraulic cylinders are widely used to lift loads and hold them in the air. They are frequently used in the fields of transport, industry, construction and in all areas where it is necessary to carry out lifting, lowering and / or holding movements of a load involving significant forces. This is the case, for example, in car transporters which traditionally have several movable platforms intended to receive the cars to be transported, and whose position and height are adjustable by means of different actuators including hydraulic cylinders, most often double-acting.

[0010] For safety reasons, it is absolutely essential to ensure that the cylinder rod remains in position when its movement is not commanded and especially when it is supporting a load. Indeed, to guarantee the safety of operators and property that may be below, the height of the load must not vary over time without voluntary action on the part of the operator. For this, in the absence of a command, the rod of a hydraulic cylinder must be able to be immobilized in retraction, as in extension, whether it is supporting a load or not. To overcome a possible risk of failure, safety devices associated with these lifting cylinders have been developed in the prior art, consisting of a hydraulic isolation block, examples of which have been described in patents EP 0935715 or EP 3436706.

[0011] This known safety device is an isolation block, through which one of the chambers of the cylinder is supplied, which comprises two shut-off devices of the same type: a primary ball check valve, doubled by a secondary so-called "safety" ball or conical needle check valve, both of which are mechanical shutter check valves. These two successive check valves are arranged in series, each at one of the entrances of an airlock.

[0012] These known devices have several advantages. First, they are safer due to the use of two successive non-return valves arranged in series. In addition, they allow automatic locking without operator intervention and in any position of the cylinder rod.

[0013] However, it is impossible to pressurize the device without causing movement of the cylinder rod (retracting or extending depending on the supply side), because the arrival of oil at one of the device's inlets automatically causes the two non-return valves concerned to open successively.

[0014] Furthermore, when the installation includes several cylinders equipped with such safety devices, it is necessary to install a separate hydraulic distributor for each of the safety devices if it is desired to be able to control the movements of the cylinders independently of each other.

[0015] When the cylinders operate in pairs, as is the case, for example, in the preferred application of a car transporter, it is also necessary to add components to the hydraulic circuit to ensure the synchronism of the movements of the two cylinders, for each of the pairs of cylinders.

[0016] When the installation includes a large number of cylinders (around thirty for example on a conventional car transporter consisting of a tractor and a double-decker trailer), the hydraulic circuit becomes complicated and includes numerous hydraulic components (distributors and flow dividers) which must be provided for each cylinder or pair of cylinders. Thus, if you want to control the cylinders in pairs, it is necessary to use a specific divider for each pair of cylinders, involving dense and complex hydraulic connections.

[0017] Finally, direct electrical control of the hydraulic cylinders is not possible, which does not allow the automation of certain convoy functions.

[0018] Patent application GB 634 293 A is also known, which describes a circuit comprising a mechanical non-return valve and an electro-hydraulic device with two shutters, the closing and opening of which in both directions are electrically controlled. However, the non-return valve and the electro-hydraulic device are not arranged in series, but in parallel. Safety is therefore not optimal and this system does not address the technical problem.

[0019] We also know from document EP 4 077 950, which describes a safety block comprising in series a first level of sealing achieved by a ball sealing valve and an electrically controlled sealing valve, allowing the selection of specific cylinders that we wish to control. On the other hand, it is necessary to use two solenoid valves per cylinder, which involves a significant cost. In addition, when a function is activated, the isolation of unused cylinders is based on only one level of sealing, namely the electrically controlled valve. The risk of untimely control of unselected cylinders is then greater than in the case of double sealing.Furthermore, the electrical coils used to control the safety unit are of considerable size because the opening direction of the valve opposes the supply pressure of a chamber of the cylinder as well as the force of the spring of the ball valve, which requires a significant force to keep the electrically controlled valve open. It should also be noted that the design of electrically controlled valves requires great control of machining tolerances, particularly in terms of coaxial alignment between the valve stem and the axis passing through the center of its seat. The risk of sealing defects is therefore high, which can cause untimely movement of the unstressed cylinders.

[0020] Presentation of the invention

[0021] An aim of the invention is to propose a new locking device with electrohydraulic control to overcome the disadvantages of these previous systems, while retaining their advantages.

[0022] Another object of the invention is to propose hydraulic cylinders equipped with these new locking and control devices and the production of which is technically simple and economical.

[0023] Another object of the invention is to propose scalable hydraulic circuits or systems in which it is possible to add new functions in a simple and reliable manner.

[0024] The aims and objects assigned to the invention are achieved using an electrohydraulically controlled locking device for a hydraulic lifting cylinder comprising a rod, making it possible to hold the rod in position by locking the circulation of the hydraulic fluid, the device comprising a safety module intended to be mounted in a hydraulic circuit which supplies fluid to the cylinder, the safety module comprising:

[0025] - two inputs intended to communicate with the hydraulic circuit and at least one output intended to be connected each to a chamber of the cylinder,

[0026] - at least one hydraulic passage between at least one of these two inlets and a corresponding outlet, provided so that the cylinder chamber can only be filled and emptied through this hydraulic passage,

[0027] - at least one mechanical closure device mounted in the hydraulic passage to allow a sealed locking of the chamber, said closure device being subject to the direct thrust of the fluid entering the hydraulic passage through the first of these two inlets to allow the filling of said chamber and which is also subject to the direct thrust or via the action of a control part, of the fluid then entering through the second of these two inlets to allow the emptying of said chamber, characterized in that it comprises:

[0028] - an electrohydraulic control module for controlling the different operating states corresponding to the extension, retraction, holding in position and non-stressing of the rod, connected to the two inputs of the safety module and to the hydraulic circuit, said control module comprising two sliding control members delimiting between them a control compartment and each associated with a control valve, a first control compartment connected to the hydraulic passage, a second control compartment making it possible to supply high-pressure hydraulic fluid to the safety module and to move the control part in order to empty the chamber, the control valves urged into their open position by the control members making it possible to supply high-pressure fluid to one of the inputs,

[0029] - a solenoid valve whose activation and deactivation allows the control module to be supplied with high-pressure hydraulic fluid or not,

[0030] - a flow selector to connect the pilot compartment to one of the control compartments when the latter is supplied with high-pressure hydraulic fluid.

[0031] According to an exemplary embodiment, the mechanical shut-off device comprises a primary valve and a secondary valve mounted in series, the control part being located close to the primary valve, this control part moving towards the primary valve under the thrust of the hydraulic fluid entering through one of the two inlets and causing the opening of said primary valve. According to an exemplary embodiment, the safety module comprises:

[0032] - an independent sliding rod, arranged longitudinally and inserted between the shutters of the primary and secondary valves but not connected to the latter and capable of sliding towards each of the shutters so as to press with one of its ends against the shutter located opposite,

[0033] - guide members of the bore and guide support type to guide the sliding of the sliding rod,

[0034] - the length of the sliding rod being sufficiently short so as not to be able to be in contact simultaneously with the two shutters resting on respective seats when the two primary and secondary valves are closed, but sufficiently long so that the opening command of the primary valve causes, by the movement of its shutter which pushes the corresponding end of the sliding rod, the sliding of the sliding rod causing the opening of the secondary valve whose shutter is pushed out of its seat by the other end of the sliding rod.

[0035] According to an exemplary embodiment, the control module comprises two control outputs each connected to an input of the safety module and two control inputs connected to the hydraulic circuit, one of which opens onto the first control compartment and the other opens onto the second control compartment, the activation of the solenoid valve and a corresponding active position of the flow selector making it possible to supply fluid under high pressure to the control compartment and one of the control compartments, the other of the compartments of the control compartments being in fluid communication under low pressure with a reservoir, the first and second control compartments being able to be simultaneously in fluid communication under low pressure with the reservoir.

[0036] For example, the control module includes:

[0037] - a bore in which the two control members are arranged, sliding relative to each other in a substantially central zone,

[0038] - a high-pressure fluid supply orifice opening into the bore at the interface of the control members which are in contact or close to each other when not in use,

[0039] - the control compartment corresponding to a space located between the two control members and the volume of which depends on the variable spacing of said control members,

[0040] - the first control compartment being delimited by one end of the bore and by one of the control members, a first control output of which communicates with the first input of the safety module via the control valve,

[0041] - the second control compartment being delimited by the other end of the bore and by the other control member, a second control output of which communicates with the second input of the safety module via a non-return valve,

[0042] - said pilot valves being mounted in opposition and closed when the pilot members are not acted upon by the high-pressure fluid, thus preventing any circulation of fluid through the control module to the safety module, and

[0043] - said pilot valves being opened by the action of the pilot members separated from each other by the filling of the pilot compartment.

[0044] According to an example of implementation, the safety and control modules are each integrated into a drilled block made from a single piece.

[0045] According to an exemplary embodiment, the electrohydraulically controlled locking device is intended for a double-acting hydraulic cylinder comprising a large chamber and a small chamber, the safety module comprising:

[0046] - two inputs intended to be connected to the control module,

[0047] - two outputs intended to be connected, the first to an orifice of the large chamber of the cylinder and the second to an orifice of the small chamber of the cylinder,

[0048] - two hydraulic passages extending for the first between the first of these two inlets and the outlet and for the second hydraulic passage extending between the second of these two inlets and the outlet, said hydraulic passages being provided so that the large chamber and the small chamber can only be filled and emptied through one of these two hydraulic passages, and

[0049] - a primary valve and a secondary valve placed in series in each of these two hydraulic passages so that the large chamber and the small chamber can be sealed tightly by a primary valve and a secondary valve in series.

[0050] According to another exemplary embodiment, the electrohydraulically controlled locking device is intended for a single-acting hydraulic cylinder comprising a large chamber and a small chamber, characterized in that the safety module comprises:

[0051] - two inputs intended to be connected to the control module,

[0052] - an outlet intended to be connected to an orifice of the large chamber of the cylinder,

[0053] - a hydraulic passage extending between the first of these two inlets and the outlet, said hydraulic passage being provided so that the large chamber can only be filled and emptied through the hydraulic passage, and

[0054] - the primary valve and the secondary valve placed in series in the hydraulic passage so that the large chamber can be sealed tightly by the primary and secondary valves.

[0055] The objects assigned to the invention are also achieved using a hydraulic cylinder equipped with an electrohydraulically controlled locking device.

[0056] The objects assigned to the invention are also achieved using a hydraulic circuit comprising several hydraulic cylinders each equipped with an electrohydraulically controlled locking device and comprising a rod and at least one chamber supplied through a hydraulic passage of the safety module, a hydraulic fluid reservoir, a distribution block, a set of pipes connecting the reservoir to the cylinders, via the distribution block, in order to fill and / or empty the chamber(s) of the cylinders, said hydraulic circuit comprising a pumping device making it possible to circulate the hydraulic fluid in the pipes, the distribution block comprising a single proportional hydraulic distributor with three positions including a neutral position interrupting the circulation of the hydraulic fluid to the receivers of the hydraulic circuit,a position putting the pumping device and the reservoir in communication with the control module of at least one cylinder to cause the cylinder rod to extend and a position putting the pumping device and the reservoir in communication with the control module of at least one cylinder to cause the cylinder rod to retract, the control module of each of the electrohydraulic locking and control devices being able to be controlled independently of the other devices.,

[0057] According to an exemplary embodiment of the hydraulic circuit, the cylinders are organized into several pairs of two cylinders operating in a synchronized manner and in that the hydraulic circuit further comprises a single flow divider, which ensures the synchronism of the movements of each pair of cylinders, each pair of cylinders being able to be controlled independently thanks to the corresponding electrohydraulically controlled locking devices.

[0058] The locking and control device according to the invention has the remarkable advantage that it only requires a single proportional distributor to distribute the entire flow of hydraulic fluid.

[0059] In addition, a single flow divider is used to feed two lines crossing an entire convoy and to allow synchronized control of each pair of cylinders.

[0060] The locking and control device also drastically limits the risk of unintentional control of cylinders not requested by the user. It should be noted that only one solenoid valve is required to control a cylinder, which is a very economical solution.

[0061] The invention also makes it possible to design a new hydraulic architecture that minimizes pressure losses. This results in a reduction in fuel or energy consumption and an increase in the autonomy of convoys equipped with such a hydraulic architecture.

[0062] Brief description of the figures

[0063] Other characteristics and advantages of the invention will appear on reading the detailed description which follows, a description made with reference to the appended drawings, in which:

[0064] - Figure 1 is a general perspective view of an example of a double-acting cylinder associated with an electrohydraulically controlled locking device according to the invention,

[0065] - Figure 2 is a longitudinal and vertical sectional view of an exemplary embodiment of the electrohydraulically controlled locking device of the cylinder of Figure 1, in a first operating state corresponding to the extension of the rod of said cylinder,

[0066] - Figure 2a is an enlargement of Figure 2, with a schematic representation of the jack,

[0067] - Figure 2b is a partial enlargement of Figure 2a,

[0068] - Figure 2c is an illustration of the electrohydraulically controlled locking device of Figure 2a, with a representation of the directions of circulation of the hydraulic fluid when the rod is extended,

[0069] - Figure 3 is a hydraulic diagram of the electrohydraulically controlled locking device of the cylinder of Figure 2, in its first operating state,

[0070] - Figure 4 is a longitudinal and vertical sectional view of an exemplary embodiment of the electrohydraulically controlled locking device of a cylinder, in a second operating state corresponding to holding the rod in position without hydraulic pressure in the hydraulic circuit,

[0071] - Figure 5 is a hydraulic diagram of the electrohydraulically controlled locking device of the cylinder of Figure 4 in its second operating state,

[0072] - Figure 6 is a longitudinal and vertical sectional view of an exemplary embodiment of the electrohydraulically controlled locking device of the cylinder of Figure 1, in a third operating state corresponding to the retraction of the rod,

[0073] - Figure 6a is an illustration of the electrohydraulically controlled locking device of the cylinder of Figure 6, with a representation of the directions of circulation of the hydraulic fluid during the retraction of the cylinder rod,

[0074] - Figure 7 is a hydraulic diagram of the electrohydraulically controlled locking device of the cylinder of Figure 6, when the rod is retracted,

[0075] - Figure 7a is a hydraulic diagram of another example of an embodiment of an electrohydraulic control locking device adapted to a single-acting hydraulic cylinder, when the rod is retracted,

[0076] - Figure 8 is a hydraulic diagram of the electrohydraulically controlled locking device of the cylinder of Figure 1, in a fourth operating state corresponding to holding the rod with pressure in the hydraulic circuit, and

[0077] - Figure 9 is a hydraulic diagram of another embodiment of the electrohydraulically controlled locking device of the cylinder of Figure 1.

[0078] Detailed description of the invention

[0079] Structurally and functionally identical elements present in several distinct figures are assigned the same numerical or alphanumeric reference.

[0080] Figure 1 is a general perspective view of an exemplary embodiment of a double-acting cylinder 1, comprising a barrel 2 and a rod 3. The cylinder 1 is equipped with an electrohydraulic control locking device 4 comprising a safety module 5, an electrohydraulic control module 6 and a solenoid flap valve 7.

[0081] In order to avoid any risk of leakage, the safety module 5 is preferably flanged or integrated into the barrel 2 of the jack 1. It can also be attached to the latter, and for example screwed to the barrel 2. Advantageously, the safety module 5 and the control module 6 are each advantageously integrated into a part of a drilled block made in a single piece fixed to the barrel 2.

[0082] The locking and control device 4 is also connected to the barrel 2 via pipes 8 and 9 allowing fluid communication with the chambers of the cylinder 1.

[0083] Figure 2 is a longitudinal and vertical sectional view of an exemplary embodiment of the locking and control device 4 and the jack 1 in a first operating state. In this first operating state, the jack 1 is biased to generate an output of the rod 3 from the barrel 2.

[0084] The rod 3 comprises, in a known manner, at its end located inside the barrel 2, a piston 3a separating the interior space of the barrel 2 and delimiting a large chamber 10 and a small chamber 11. The large chamber 10 and the small chamber 11 communicate respectively with the pipes 8 and 9 via respective orifices 10a and 11a, arranged in the barrel 2.

[0085] The safety module 5 comprises two inlets 12 and 13 intended to be connected to the hydraulic circuit and two outlets 14 and 15 intended to be connected respectively to the ports 10a and 11a of the barrel 2 via the pipes 8 and 9.

[0086] Figure 2a is an enlargement of Figure 2, with a schematic representation of the cylinder 1 and Figure 2b is a partial enlargement of Figure 2a.

[0087] The safety module 5 also comprises and delimits a first hydraulic passage 16 extending between the inlet 12 and the orifice 10a and a second hydraulic passage 17 extending between the inlet 13 and the orifice 11a. These two hydraulic passages 16 and 17 are designed so that the large chamber 10 is filled and emptied only through one 16 of these hydraulic passages 16, 17 and that the small chamber 11 is filled and emptied only through the other 17 of these hydraulic passages 16, 17.

[0088] The safety module 5 comprises at least one mechanical closure device mounted in each of the hydraulic passages 16 and 17 to allow a sealed locking of the respective chamber 10 and 11 by said corresponding closure device.

[0089] Figure 2b is a partial enlargement of Figure 2. Two mechanical shutoff devices are connected in series and advantageously comprise a primary check valve 18 with a primary shutoff valve 18a and a secondary check valve 19 with a secondary shutoff valve 19a. The shutoff valves 18a and 19a are advantageously balls.

[0090] For the sake of simplification, the secondary non-return valve 19 with secondary shutter 19a, located closest to the corresponding chamber of the cylinder 1, will be called in the following “secondary valve 19” and the primary non-return valve 18 with shutter 18a, located on the side of the hydraulic supply circuit, that is to say on the side furthest from the chamber of the cylinder 1, will be called “primary valve 18”.

[0091] Figure 2c is an illustration of the safety module of a locking and control device according to the invention of Figure 2, with a representation of the directions of circulation of the hydraulic fluid when the rod 3 exits the cylinder 1 as indicated by an arrow in Figure 2.

[0092] The primary 18 and secondary 19 valves are open under the direct thrust of the fluid entering the hydraulic passage 16 through the inlet 12 to allow the filling of the large chamber 10. The closure devices 18 and 19, arranged in the hydraulic passage 17, are also open but by means of the action of a control part 20. This situation then results from the action of the hydraulic fluid entering the safety module 5 through the inlet 12 and passing through the hydraulic passage 16, thus generating the movement of the control part 20 which urges the primary 18a and secondary 19a shutters to open in the hydraulic passage 17. This allows the emptying of the large chamber 11 through the hydraulic passage 17, the inlet 13 and the electrohydraulic control module 6.

[0093] The control part 20 is advantageously located near the primary valve 18 and moves towards the primary shutter 18a under the thrust of the hydraulic fluid entering through the inlet 12 and thus pushes to cause the shutter 18a to lift from its seat 18b.

[0094] The safety module 5 also comprises a sliding rod 22, independent, arranged longitudinally and interposed between the shutters 18a and 19a of the primary 18 and secondary 19 valves, but not connected to the latter and capable of sliding towards each of the shutters 18a, 19a so as to press by one of its ends against the primary 18a, secondary 19a shutter located opposite said end.

[0095] Advantageously, guide members are provided, of the guide support type 23 sliding in a bore 23a, to guide the sliding of said sliding rod 22, which is inserted coaxially and fixedly in said guide support 23.

[0096] The length of the sliding rod 22 is sufficiently short so that it cannot be in contact simultaneously with the two shutters 18a and 19a resting on their respective seats 18b, 19b when the two primary 18 and secondary 19 valves are closed. Furthermore, the length of the sliding rod 22 is sufficiently long so that the opening command of the primary valve 18 causes, by the movement of its shutter 18a which pushes the corresponding end of the sliding rod 22, the sliding rod 22 towards the secondary valve 19, thus causing the opening of the secondary valve 19 whose shutter 19a is pushed out of its seat 19b by the other end of the sliding rod 22.In the examples shown, the guide support 23 is substantially cylindrical and has a diameter advantageously chosen to allow guided sliding of the sliding rod 22 - guide support 23 assembly in the bore 23a, which is also provided to house the shutter 18a and a return spring 25a of said shutter 18a. The shutter 19a is advantageously associated with another additional return spring 25b.

[0097] In order to allow the flow of the hydraulic fluid, despite the presence of the sliding rod 22 and its guide support 23 in the bore 23a, one or more longitudinal grooves 24 can advantageously be arranged in the walls of the bore 23a or in the guide support 23. An example of such longitudinal grooves is for example shown in FIG. 2a.

[0098] The sliding rod 22 can thus slide freely from one side to the other of the bore 23a without hindering the flow of the hydraulic fluid, and can thus move in the direction of each shutter 18a and 19a.

[0099] However, by construction, the sliding rod 22 is too short to be able to be in contact simultaneously with the two shutters 18a and 19a when the latter are resting against their respective seats 18b and 19b, in the closed position of the two primary 18 and secondary 19 valves. There is therefore longitudinal play between the rod 22 and the two shutters 18a and 19a resting on their respective seats 18b and 19b.

[0100] According to an exemplary embodiment, the primary valve 18 and the secondary valve 19 are preferably produced without a common mode, that is to say that they are different from each other and that their parts playing a role in sealing are not identical, in order to reinforce safety.

[0101] It will thus be possible, for example, to provide two balls 16 of different diameter and / or of different material for the shutters 18a, 19a. Similarly, the seats 18b, 19b can be made of different materials, for example one in steel and the other in bronze. It is also possible to provide for one to be shaped directly in the body of a part of the safety module 5, while the other is located on an independent, different, added part. The return springs 24 used can also be chosen to be different from each other and advantageously have different stiffnesses.

[0102] The control part 20 is therefore capable of causing the primary valve 18 to open. This control part 20 is preferably located close to the primary valve 18, on the side opposite the secondary valve 20. It is preferably a mechanical part which moves in the direction of the primary valve 18, in order to move the shutter 18a to cause the primary valve 18 to open.

[0103] The control part 20 may advantageously comprise for this purpose a projecting lateral finger 26, which extends in the direction of the primary valve 18 and the free end 27 of which is capable of engaging through the seat 18b of this valve, in order to push the shutter 18a out of its seat 18b.

[0104] As shown, the control part 20 can advantageously be a sliding shuttle serving as a boundary for the two separate hydraulic circuits which independently supply the large chamber 10 and the small chamber 11. The control part 20 thus has opposite lateral faces 28 and 29 thus locally delimiting these two hydraulic circuits.

[0105] A perimeter seal 30 mounted on this shuttle serves to complete the barrier formed by it and guarantee the seal between the two hydraulic circuits, while allowing the longitudinal sliding of the control part 20. This perimeter seal 30 thus makes it possible to guarantee that all of the hydraulic fluid sent ends up in the corresponding chamber of the cylinder 1 and causes the rod 3 of the cylinder 1 to retract or extend by the expected length. This is particularly important in the case where the cylinder 1 is part of a set of several cylinders 1 which must act in a symmetrical and synchronized manner.

[0106] With such an embodiment, the movement of the control part 20 towards the primary valve 18 is caused automatically by the pressure of the hydraulic fluid, as will be explained below, when the operator supplies the cylinder(s) 1 of the hydraulic function to be controlled.

[0107] In the absence of an operator command, the control part 20 is preferably kept away from the primary valve 18 by a return spring 31.

[0108] In the preferred embodiment shown, the closing devices located on either side of the control part 20 are furthermore twinned, that is to say that their operation is linked to one another and is not independent.

[0109] For this, the safety module 5 only comprises a single control part 20, capable of alternately causing the opening of the primary valve 18 of each of the hydraulic passages 16 and 17.

[0110] This single control part 20 is preferably a sliding central shuttle which comprises on each of these lateral faces 28 and 29 a projecting lateral finger 26, extending in the direction of one of the shutters 18a and 19a. Thus, when this control part 20 moves in the direction of one of the primary valves 18, the free end 27 of the projecting lateral finger 26 located opposite, pushes the shutter 18a of the primary valve 18 concerned and thus causes it to open.

[0111] As before, the lateral fingers 26 of the control part 20 are designed by construction to be too short to simultaneously reach the two shutters 18a of the primary valves 18 opposite each other. Longitudinal play is thus guaranteed, and even in the event of incorrect positioning, the control part 20 cannot cause the two primary valves 18 to open simultaneously.

[0112] Advantageously, the control part 20 can be held in a substantially central position by two opposite return springs 31, each of which acts on one of the lateral faces 28, 29 of the single control part 20 to return it to this substantially central position. Similarly, when the single control part 20 is in this central position, its lateral fingers 26 are too short by construction to reach the opposite shutters 18a.

[0113] The electrohydraulic control module 6 is illustrated in particular in Figures 2a, 2c and 3. Figure 3 is a hydraulic diagram of the locking and control device and the double-acting cylinder of Figure 2, in its first operating state corresponding to the output of the rod 3.

[0114] The electrohydraulic control module 6 is connected to the hydraulic circuit via inlet ports opening onto control compartments 39 and 40 and in fluid communication with the two inlets 12 and 13 of the safety module 5. The control module 6 comprises a first control member 35 and a second control member 36, movable in a bore 6a formed in a body forming the drilled block integrating the safety module 5 and the control module 6. The control members 35 and 36 are each associated with a respective control valve 37 and 38, of the non-return valve type.

[0115] The first control member 35 partially delimits in the bore 6a the first control compartment 39 connected to the hydraulic circuit and the second control member 36 partially delimits in the bore 6a, the second control compartment 40 connected to the hydraulic circuit. The first control compartment 39 comprises a control outlet 39a connected to the inlet 12 and consequently to the hydraulic passage 16 of the safety module 5, via the control valve 37. The second control compartment 40 comprises a control outlet 40a connected to the inlet 13 and consequently to the hydraulic passage 17 of the safety module 5, via the control valve 38.

[0116] The first control member 35 and the second control member 36 respectively have a face 35a and a face 36a facing each other, which delimit between them a control compartment 41 of variable volume and connected to the hydraulic circuit.

[0117] The bore 6a further comprises a high-pressure fluid supply orifice opening into the control compartment 41. The control members 35 and 36 are mounted sliding and sealed in the bore 6a and are in contact or close to each other when they are not stressed by the high-pressure fluid. The surface area of ​​the faces 35a and 36a is advantageously larger than the surface area of ​​opposite faces 35b and 36b of said respective control members 35 and 36. This makes it possible to ensure the opening of the control valves 37, 38 when the control compartment 41 and one of the control valves 37, 38 are simultaneously subjected to the high-pressure hydraulic fluid. The force exerted on one of the opposite faces 35b or 36b will therefore always be less than that exerted on the faces 35 and 36.

[0118] The locking and control device also comprises a solenoid valve 42 associated with the control module 6, the activation and deactivation of which makes it possible to supply or not the control module 6 with hydraulic fluid and thus to control the different operating states of said control module 6. The operating states correspond to the extension, the retraction, the holding in position and the non-stressing of the rod 3 of the jack 1.

[0119] Activation of the solenoid valve 42 makes it possible to supply high-pressure hydraulic fluid simultaneously to the control compartment 41 and one of the control compartments 39 and 40, thus authorizing fluid communication between the locking module 5 and the hydraulic circuit via said control compartments 39 and 40.

[0120] The electrohydraulically controlled locking device 4 also comprises a flow selector 43 for connecting the pilot compartment 41 to one of the control compartments 39 or 40 when the latter is supplied with high-pressure hydraulic fluid.

[0121] The activation of the solenoid valve 42, the selection of a position of a proportional distributor 45 and a corresponding active position of the flow selector 43 make it possible to supply fluid under high pressure to the control compartment 41 and one of the control compartments 39 and evacuation 40, the other of the control compartments 39 and 40 being in fluid communication under low pressure with a fluid reservoir 46. In addition, the first and second control compartments 39 and 40 are simultaneously in fluid communication under low pressure with a fluid reservoir 46, when the cylinder 1 is in an operating state corresponding to a holding in position or to a non-solicitation of the rod 3. Depending on the operating state of the cylinder 1, the control compartment 41 has a volume dependent on the spacing of said first and second control members 35 and 36.

[0122] The pilot valves 37 and 38 are mounted in opposition and are closed when the corresponding pilot members 35 and 36 are not moved in response to the filling of the pilot compartment 41 with the high-pressure fluid, thus preventing any circulation of fluid through the control module 6 to the safety module 5. The pilot valves 37 and 38 have respective shutters which are lifted from their seats simultaneously by the pilot members 35 and 36 moved apart from each other by the filling of the pilot compartment 4L.

[0123] Thus, in a first operating state illustrated in Figure 3, the first control compartment 39 is supplied with high-pressure fluid provided by a pump P associated with a motor M through a position of the proportional distributor 45 and a flow divider 47. The control of the solenoid valve 42 induces the filling of the control compartment 41 and consequently the simultaneous opening of the control valves 37 and 38, then making it possible to supply the hydraulic passage 16 of the safety module 5. The filling of the control compartment 41 and consequently the opening of the control valve 38, then simultaneously makes it possible to put the hydraulic passage 17 of the safety module 5 into fluid communication with the reservoir 46 via the second control compartment 40, a return pipe 48 and the proportional distributor 45.The flow selector 43 makes it possible to isolate this low pressure return line 48 from the portion of the hydraulic circuit in which the high pressure fluid circulates. According to an example of operation of the device, the high pressure fluid is at a pressure of approximately 250 bars and the low pressure is at atmospheric pressure.

[0124] For example, the flow divider 47 advantageously comprises two pipes 47a and 47b each communicating with a cylinder 1 thus ensuring the synchronization of a pair of cylinders 1 or a succession of pairs of cylinders 1. These supply pipes 47a and 47b advantageously have a large diameter and extend in a quasi-rectilinear manner along the vehicle so as to convey the hydraulic fluid as close as possible to the hydraulic functions to be supplied. In addition, this advantageous arrangement drastically limits the singular and regular pressure losses in the hydraulic circuit, by limiting the number of obstacles such as elbows or hose and tube connections as well as by reducing the lengths of the latter.Figure 2c illustrates, with arrows, in the operating state shown schematically in Figure 3, the circulation of hydraulic fluid supplying the large chamber 10 via line 8 and the emptying of the small chamber 11 via line 9.

[0125] Figure 4 is a longitudinal and vertical sectional view of an exemplary embodiment of the electrohydraulically controlled locking device 4 and a double-acting cylinder 1 in a second operating state, corresponding to holding the rod 3 in position.

[0126] In this second operating state, neither the pilot compartment 41 nor any of the control compartments 39 and 40 are supplied with a high-pressure fluid. The pilot members 35 and 36 are in quasi-mutual contact, thus closing the pilot valves 37 and 38. The primary 18 and secondary 19 valves in each hydraulic passage 16 and 17 are urged to close by the return springs 24. The hydraulic fluid contained in the large chamber 10 or in the small chamber 11 cannot escape since it also urges the primary 18 and / or secondary 19 valves in the closing direction. The rod 3 is therefore locked.

[0127] Figure 5 is a hydraulic diagram of the electrohydraulically controlled locking device 4 in this second operating state. The latter corresponds to the neutral position of the proportional distributor 45 making it possible to put all the fluid lines in communication with the reservoir 46 and this before having deactivated the solenoid valve 42. This deactivation advantageously takes place in a delayed manner compared to the placing of the proportional distributor 45 in its neutral position. This makes it possible to drain the control compartment 41 before the deactivation of the solenoid valve 42 which would block the emptying of said control compartment 4L. This also makes it possible to decompress all the lines 47a, 47b of the hydraulic circuit as well as the lines supplying the control compartments 39 and 40.

[0128] The first and second control compartments 39 and 40 are then also in low-pressure communication with the reservoir 46. In addition, the control part 20 is not acted upon by the high-pressure fluid and the return springs 3 bring the latter into a central position at a distance from each of the primary valves 18. The flow selector 43 then remains in a neutral position insofar as it is not pushed into an isolation position by a high-pressure fluid. The entire hydraulic circuit is no longer subjected to high pressure from the hydraulic fluid and all the valves close, thus locking the cylinder 1 in position. Figure 6 is a longitudinal and vertical sectional view of an exemplary embodiment of the electrohydraulic control locking device 4 and of a double-acting cylinder 1 in a third operating state, corresponding to the retraction of the rod 3 of said cylinder 1.

[0129] Figure 6a is an illustration of the safety module of a locking and control device according to the invention of Figure 6, with a representation of the directions of circulation of the hydraulic fluid when the rod 3 is retracted. In this operating state, the control compartment 41 is again supplied with the fluid under high pressure causing the movement of the control members 35 and 36 and consequently the opening of the control valves 37 and 38.

[0130] Thus, in this third operating state illustrated in Figure 6 and 6a, the second control compartment 40 is supplied with high pressure fluid supplied through a third position of the proportional distributor 45 and on return through flow divider 47 to reunite the hydraulic fluid.

[0131] The filling of the control compartment 41 and consequently the opening of the control valve 38, then makes it possible to supply the hydraulic passage 17 of the safety module 5 with high-pressure fluid. The filling of the control compartment 41 and consequently the simultaneous opening of the control valves 37 and 38. This then makes it possible to put the hydraulic passage 16 of the safety module 5 into fluid communication with the reservoir 46 via the first control compartment 39, the pipe 47a used as hydraulic return and the proportional distributor 45. The flow selector 43 makes it possible to isolate this low-pressure return pipe 47a from the portion of the hydraulic circuit in which the high-pressure fluid circulates.

[0132] Figure 7 is a hydraulic diagram of the locking and control device of Figure 6 or 6a, in its third operating state corresponding to a retraction phase of the rod 3. Reference may be made, for example, to Figure 6a to better visualize the circulation of the fluid through the safety module 5 to bring the hydraulic fluid into the small chamber 11 and evacuate it from the large chamber 10 to the reservoir 46.

[0133] Figure 7a is a hydraulic diagram of another embodiment of an electrohydraulically controlled locking device 4 according to the invention. The electrohydraulically controlled locking device 4 is adapted to a single-acting hydraulic cylinder 1, illustrated during the retraction of the rod 3. The control module 6 remains unchanged both in its structure and in its operation. On the other hand, the safety module 5 has only one hydraulic passage 16 in which the primary valve 18 and the secondary valve 19 are arranged in series. This hydraulic passage 16 makes it possible to fill and empty the large chamber 10 of the cylinder 1. The small chamber 11 is no longer connected to the safety module 5. The seal provided by the piston 3a in the barrel 2 is no longer necessary for the proper operation of the electrohydraulically controlled locking device 4.

[0134] The safety module 5 comprises a pressurization compartment 17a which replaces the hydraulic passage 17. The pressurization compartment 17a is connected via the inlet 13 to the control output 40a of the control module 6. Thus, when the proportional distributor 45 is in the position in which the supply line is supplied with high-pressure hydraulic fluid and when the solenoid valve 42 is activated, the pilot valve 38 is open and allows the pressurization compartment 17a to be filled with the high-pressure hydraulic fluid.

[0135] The force then exerted on the lateral face 29 of the control part 20 will generate the opening of the primary valves 18 and 19. The opening of the pilot valve 37, concomitant with the opening of the pilot valve 38, then allows the hydraulic passage 16 to be brought to the pressure of the reservoir 46 and the large chamber 10 to empty. This corresponds to the retraction of the rod 3 due to the load supported by the latter.

[0136] Figure 8 is a hydraulic diagram of the electrohydraulically controlled locking device 4 according to the invention in a fourth operating state corresponding to a non-solicitation of the cylinder 1. This state corresponds to the case in which the proportional distributor 45 is placed in its first or in its third position and the solenoid valve 42 is deactivated and not passing. The control compartment 41 is therefore not supplied. The cylinders 1 are thus isolated from the rest of the hydraulic circuit by means of the solenoid valve 42 and by the control valves 37, 38 of the control module 6.

[0137] Figure 9 is a hydraulic diagram of another exemplary embodiment of the electrohydraulically controlled locking device 4 according to the invention. The structural and functional elements identical to the other exemplary embodiments described above will not be described again in the following to avoid any redundancy. In this exemplary embodiment, the safety module 5 and the control module 6 are arranged in a single stage mounted on the cylinder 1. The safety modules 5 and control 6 are for example integrated in a single bore 50 formed in a drilled block. In this exemplary embodiment, the safety module 5 is made in parts located on either side of the control module 6.

[0138] The central part of the bore 50 is occupied by the control module 6. On one side, the first control compartment 39 is connected via a first pipe 51 and via the pilot valve 37 to the hydraulic passage 16. The latter comprises in series the primary valve 18 and the secondary valve 19 through which it is connected to the large chamber 10. On the other side, the second control compartment 40 is connected via a second pipe 52 and via the pilot valve 38 to the hydraulic passage 17. The latter comprises in series the primary valve 18 and the secondary valve 19 through which it is connected to the small chamber 11.

[0139] Between the first control compartment 39 and the hydraulic passage

[0140] 16, the bore 50 integrates a first complementary control system comprising a complementary compartment 53 and a sliding actuating member 54. The movement of the actuating member 54 is caused by the filling of the complementary compartment 53 with the high-pressure fluid. The movement stroke of this actuating member 54 makes it possible to push the primary 18 and secondary 19 valves of the hydraulic passage 16 into the open position.

[0141] Between the second control compartment 40 and the hydraulic passage

[0142] 17, the bore 50 integrates a second complementary control system comprising a complementary compartment 55 and a sliding actuating member 56. The movement of the actuating member 5 is caused by the filling of the complementary compartment 55 with the high-pressure fluid. The movement stroke of this actuating member 56 makes it possible to push the primary 18 and secondary 19 valves of the hydraulic passage 17 into the open position.

[0143] Thus, when the solenoid valve 42 is activated, the high-pressure fluid supplies the pilot compartment 41 and one of the control compartments 39 and 40. The first and third positions of the proportional distributor 45 determine which of the control compartments 39 and 40 will be supplied with the high-pressure fluid. Activation of the solenoid valve 42 also makes it possible to supply the complementary compartments 53 and 55 with high-pressure fluid. Thus, the complementary compartment 53, located for example on the side of the control compartment 39, supplied with high-pressure fluid will not cause the actuating member 54 to slide since the first machined pipe 51 already supplies the hydraulic passage 16 with high-pressure fluid.The primary 18 and secondary 19 valves are then open and the large chamber is supplied. On the other hand, the second control compartment 40, isolated from the high-pressure fluid, is in low-pressure communication with the reservoir 46 and the high-pressure fluid injected into the complementary compartment 55 makes it possible to open the primary 18 and secondary 19 valves via the actuating member 56. The low-pressure fluid can then flow from the small chamber 11 to the reservoir 46 via the hydraulic passage 17 and the second control compartment 40. The rod 3 is then in the exit phase from the barrel 2.

[0144] The embodiment illustrated in Figure 9 also makes it possible to obtain the other operating states, namely the holding in position of the rod 3, the retraction phase of the rod 3 and the non-stressing of the cylinder 1.

[0145] The invention therefore also relates to a hydraulic circuit comprising several hydraulic cylinders 1 each equipped with an electrohydraulically controlled locking device 4 and comprising a rod 3 and two chambers 10 and 11 each supplied through a corresponding hydraulic passage 16 and 17 of the safety module 5. The hydraulic circuit also comprises a reservoir 46 of hydraulic fluid, a distribution block 45, a set of pipes connecting the reservoir 46 to the cylinders 1 via the distribution block 45, in order to fill and / or empty each of the chambers 10 and 11. The hydraulic circuit also comprises a pumping device comprising a pump P associated with a motor M to circulate the hydraulic fluid in the pipes. The distribution block comprises a single three-position proportional hydraulic distributor 45.

[0146] These positions include a neutral position interrupting the circulation of hydraulic fluid to the receivers of the hydraulic circuit or linking the pressure of the circuit to the pressure of the reservoir 46 thus preventing the pressure from increasing in said hydraulic circuit.

[0147] These positions also include a position putting the pumping device P, M and the reservoir 46 into communication with the control module 6 of at least one cylinder 1 to cause the rod 3 of the cylinder 1 to come out.

[0148] These positions also include a position putting the pumping device P, M and the reservoir 46 into communication with the control module 6 of at least one cylinder 1 to cause the rod 3 to retract.

[0149] The control module 6 of each of the electrohydraulic locking and control devices 4 can advantageously be controlled independently of the other devices.

[0150] According to an exemplary embodiment, the cylinders 1 are organized into several pairs of two cylinders 1 operating in a synchronized manner, the hydraulic circuit further comprising a single flow divider 47 which ensures the synchronism of the movements of each pair of cylinders 1. Each pair of cylinders 1 can advantageously be controlled independently thanks to the corresponding electrohydraulic locking and control devices 4. It is obvious that the present description is not limited to the examples explicitly described, but also includes other embodiments. Thus, a technical characteristic described can be replaced respectively by an equivalent technical characteristic, without departing from the scope of the present invention as defined by the claims.

Claims

Claims 1. Electrohydraulically controlled locking device (4) for a hydraulic lifting cylinder (1) comprising a rod (3), making it possible to hold the rod (3) in position by locking the circulation of the hydraulic fluid, the device comprising a safety module (5) intended to be mounted in a hydraulic circuit which supplies fluid to the cylinder (1), the safety module (5) comprising: - two inlets (12, 13) intended to communicate with the hydraulic circuit and at least one outlet (14, 15) each intended to be connected to a chamber (10, 11) of the jack (1), - at least one hydraulic passage (16, 17) between at least one of these two inlets (12, 13) and a corresponding outlet (14, 15), provided so that the chamber (10, 11) of the jack (1) can only be filled and emptied through this hydraulic passage (16, 17), - at least one mechanical closure device mounted in the hydraulic passage (16, 17) to allow a sealed locking of the chamber (10, 11), said closure device being under the direct thrust of the fluid entering the hydraulic passage (16, 17) via the first of these two inlets (12, 13) to allow the filling of said chamber (10, 11) and which is also under the direct thrust or via the action of a control part (20), of the fluid then entering via the second of these two inlets (12, 13) to allow the emptying of said chamber (10, 11), characterized in that it comprises: - an electrohydraulic control module (6) for controlling the different operating states corresponding to the extension, retraction, holding in position and non-stressing of the rod (3), connected to the two inputs (12, 13) of the safety module (5) and to the hydraulic circuit, said control module (6) comprising two sliding control members (35, 36) delimiting between them a control compartment (41) and each associated with a control valve (37, 38), a first control compartment (39) connected to the hydraulic passage (16, 17), a second control compartment (40) for supplying high-pressure hydraulic fluid to the safety module (5) and moving the control part (20) in order to empty the chamber (10, 11), the control valves (37, 38) urged into their open position by the control members (35, 36) for supplying high-pressure fluid one of the entrances (12, 13), - a solenoid valve (42) whose activation and deactivation allows the control module (6) to be supplied or not with high-pressure hydraulic fluid, - a flow selector (43) for connecting the pilot compartment (41) to one of the control compartments (39, 40) when the latter is supplied with hydraulic fluid under high pressure.

2. Device according to claim 1, characterized in that the mechanical closure device comprises a primary valve (18) and a secondary valve (19) mounted in series, the control part (20) being located close to the primary valve (18), this control part (20) moving in the direction of the primary valve (18) under the thrust of the hydraulic fluid entering through one of the two inlets (12, 13) and causing the opening of said primary valve (18).

3. Device according to claim 2, characterized in that the security module (5) comprises: - an independent sliding rod (22), arranged longitudinally and interposed between shutters (18a, 19a) of the primary (18) and secondary (19) valves but not connected to the latter and capable of sliding towards each of the shutters (18a, 19a) so as to press by one of its ends against the shutter (18a or 19a) located opposite, - guide members of the bore type (23a) and guide support (23) for guiding the sliding of the sliding rod (22), - the length of the sliding rod (22) being sufficiently short so as not to be able to be in contact simultaneously with the two shutters (18a, 19a) resting on respective seats (18b, 19b) when the two primary (18) and secondary (19) valves are closed, but sufficiently long so that the opening command of the primary valve (18) causes, by the movement of its shutter (18a) which pushes the corresponding end of the sliding rod (22), the sliding of the sliding rod (22) causing the opening of the secondary valve (19) whose shutter (19a) is pushed out of its seat (19b) by the other end of the sliding rod (22).

4. Device according to any one of claims 1 to 3, characterized in that the control module (6) comprises two control outputs (39a, 40a) each connected to an inlet (12, 13) of the safety module (5) and two control inputs connected to the hydraulic circuit, one of which opens onto the first control compartment (39) and the other opens onto the second control compartment (40), the activation of the solenoid valve (42) and a corresponding active position of the flow selector (43) making it possible to supply fluid under high pressure to the control compartment (41) and one of the control compartments (39, 40), the other of the compartments of the control compartments (39, 40) being in low pressure fluid communication with a reservoir (46), the first and second control compartments (39, 40) being simultaneously able to be in low pressure fluid communication with the reservoir (46).

5. Device according to claim 4, characterized in that the control module (6) comprises: - a bore (6a) in which the two control members (35, 36) are arranged, sliding relative to each other in a substantially central zone, - a high-pressure fluid supply orifice opening into the bore (6a) at the interface of the control members (35, 36) which are in contact or close to each other when they are not under stress, - the control compartment (41) corresponding to a space located between the two control members (35, 36) and the volume of which depends on the variable spacing of said control members (35, 36), - the first control compartment (39) being delimited by one end of the bore (6a) and by one of the control members (35, 36), a first control output (39a) of which communicates with the first input (12) of the safety module (5) via the control valve (37), - the second control compartment (40) being delimited by the other end of the bore (6a) and by the other control member (36), a second control output (40a) of which communicates with the second input (13) of the safety module via a non-return valve, - said pilot valves (37, 38) being mounted in opposition and closed when the pilot members (35, 36) are not acted upon by the high-pressure fluid, thus preventing any circulation of fluid through the control module (6) towards the safety module (5), and - said pilot valves (37, 38) being opened by the action of the pilot members (35, 36) mutually separated by the filling of the pilot compartment (41).

6. Device according to any one of claims 1 to 5, characterized in that the safety (5) and control (6) modules are each integrated into a drilled block made in a single piece.

7. Device according to any one of claims 2 to 6, intended for a double-acting hydraulic cylinder (1) comprising a large chamber (10) and a small chamber (11), characterized in that the safety module (5) comprises: - two inputs (12, 13) intended to be connected to the control module (6), - two outlets (14, 15) intended to be connected for the first (14) to an orifice of the large chamber (10) of the jack (1) and for the second (15) to an orifice of the small chamber (11) of the jack (1), - two hydraulic passages (16, 17) extending for the first (16) between the first (12) of these two inlets (12, 13) and the outlet (14) and for the second hydraulic passage (17) extending between the second (13) of these two inlets (12, 13) and the outlet (15), said hydraulic passages (16, 17) being provided so that the large chamber (10) and the small chamber (11) can only be filled and emptied through one of these two hydraulic passages (16, 17), and - a primary valve (18) and a secondary valve (19) placed in series in each of these two hydraulic passages (16, 17) so that the large chamber (10) and the small chamber (11) can be locked in a sealed manner by a primary valve (18) and a secondary valve (19) in series.

8. Device according to any one of claims 2 to 6, intended for a single-acting hydraulic cylinder (1) comprising a large chamber (10) and a small chamber (11), characterized in that the safety module (5) comprises: - two inputs (12, 13) intended to be connected to the control module (6), - an outlet (14) intended to be connected to an orifice of the large chamber (10) of the jack (1), - a hydraulic passage (16) extending between the first (12) of these two inlets (12, 13) and the outlet (14), said hydraulic passage (16) being provided so that the large chamber (10) can only be filled and emptied through the hydraulic passage (16), and - the primary valve (18) and the secondary valve (19) placed in series in the hydraulic passage (16) so that the large chamber (10) can be locked in a watertight manner by the primary (18) and secondary (19) valves.

9. Hydraulic cylinder (1) characterized in that it is equipped with an electrohydraulically controlled locking device (4) according to any one of claims 1 to 8.

10. Hydraulic circuit comprising several hydraulic cylinders (1) each equipped with an electrohydraulically controlled locking device (4) according to any one of claims 1 to 8 and comprising a rod (3) and at least one chamber (10, 11) supplied through a hydraulic passage (16, 17) of the safety module (5), a reservoir (46) of hydraulic fluid, a distribution block, a set of pipes connecting the reservoir (46) to the cylinders (1), via the distribution block (45), in order to fill and / or empty the chamber(s) (10, 11) cylinders (1), said hydraulic circuit comprising a pumping device (P, M) for circulating the hydraulic fluid in the pipes, the distribution block comprising a single proportional hydraulic distributor (45) with three positions comprising a neutral position interrupting the circulation of the hydraulic fluid to the receivers of the hydraulic circuit, a position putting the pumping device (P, M) and the reservoir (46) in communication with the control module (6) of at least one cylinder (1) to cause the rod (3) of the cylinder (1) to extend and a position putting the pumping device (P, M) and the reservoir (46) in communication with the control module (6) of at least one cylinder (1) to cause the rod (3) of the cylinder (1) to retract, the control module (6) of each of the electrohydraulic locking and control devices (4) being able to be controlled independently of the other devices.

11. Hydraulic circuit according to claim 10, characterized in that the cylinders (1) are organized into several pairs of two cylinders (1) operating in a synchronized manner and in that the hydraulic circuit further comprises a single flow divider (47), which ensures the synchronism of the movements of each pair of cylinders (1), each pair of cylinders (1) being able to be controlled independently thanks to the corresponding electrohydraulically controlled locking devices (4).

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