HANDLING MACHINE WITH HYDRAULIC STEERING

Description

FIELD OF INVENTION

[0001] The present invention relates generally to handling machines comprising a hydraulic steering system. EARLIER ART

[0002] As illustrated in the Figure 1 We know of the state of the art of handling machines including hydraulic steering systems which allow the front and rear wheels of the machine to be steered.

[0003] Such a hydraulic steering system includes a steering circuit connected to a front steering cylinder system (VDAV) and a rear steering cylinder system (VDAR). The hydraulic steering system also includes a power steering pump (PDD) and a mechanical control device, such as a steering wheel (VDD). The steering wheel directs the oil to either of the R or L lines connected to the PDD steering pump. A selector switch (S1) allows the operating mode of the steering circuit to be selected. The PDD steering pump has a T port for connection to an oil reservoir and a P port for connection to a supply pump.

[0004] However, known hydraulic steering systems that use mechanical control devices do not offer the possibility of reliably, simply, and safely implementing electrical control of the hydraulic steering circuit to provide assistance or autonomy for maneuvering or driving the material handling machine. US patent 2006 / 089773 describes a work vehicle that includes a chassis, a work system such as linkages and associated hydraulic cylinders, a steering system, a drive system, and a multimode control system including a central controller. In one mode, the central controller operates the work system based on signals received from a control device of the work system. In a second mode, the central controller controls at least the steering system and the drive system based on signals received from the control device of the work system.

[0005] The present invention aims to provide a corresponding handling machine to overcome all or part of the problems described above. SUMMARY OF THE INVENTION

[0006] To this end, the invention relates to a material handling machine comprising: a rolling chassis; a handling system comprising at least one handling element, actuable by a hydraulic cylinder, such as a tilting cylinder for a tool holder of the machine; a steering system comprising: a hydraulic steering circuit including steering cylinders enabling the steering of at least some of the wheels of the machine; a first hydraulic control circuit connected to the steering circuit to supply the steering cylinders, and a manual steering device, such as a steering wheel, connected to the first hydraulic control circuit; a second hydraulic control circuit used for at least the control of the hydraulic cylinder actuating a handling element; characterized in that: the second hydraulic control circuit comprises: a hydraulic distributor, a hydraulic connection circuit connected to the hydraulic steering circuit, and a diverter to which the connection circuit is connected, the hydraulic cylinder for actuating a handling element, and the hydraulic distributor, the diverter being electrically controllable to selectively take: a first state in which the hydraulic distributor of the second hydraulic control circuit is connected to the hydraulic cylinder for actuating said handling element, and a second state in which the hydraulic distributor of the second hydraulic control circuit is connected to the connection circuit which is connected to the steering circuit, to allow the second hydraulic control circuit to control the same steering cylinders as those controllable with the first hydraulic control circuit;a control unit configured to command the diverter to bring it into the second state in which the hydraulic distributor is connected to the connecting circuit which is connected to the steering circuit in order to be able to execute a steering control program of the handling machine, for example to automatically park the handling machine in a given location. ;

[0007] Thus, the handling machine includes an electro-hydraulic control circuit for the steering circuit which is installed in parallel with the classic mechanically controlled hydraulic control circuit.

[0008] This provides the possibility of electrical control of the hydraulic steering, allowing for the implementation of steering assistance or autonomous steering control, while limiting the added components and retaining a mechanical control, such as a steering wheel, to allow for mechanical control of the hydraulic steering circuit.

[0009] The handling machine steering system thus allows for a dual hydraulic steering circuit control system architecture, capable of operating in parallel with each other, independently or in complementarity with each other.

[0010] The steering system may include, in particular: the original approved hydraulic steering system of the material handling machine which allows the hydraulic steering circuit of the machine to be controlled by means of a hydraulic control circuit controlled by a mechanical control, such as a steering wheel, and a hydraulic steering circuit control system, electrically controllable, which may reuse part of a hydraulic distributor of the hydraulic circuit of the machine to allow selective control of a hydraulic cylinder to actuate an element of the material handling system of the machine, and the hydraulic steering circuit of the machine.

[0011] For machine steering control using the second control circuit, the control unit can also operate the hydraulic distributor to provide a specific flow rate on either side of the connecting circuit. The control unit can also operate one or more other components to control machine movement.

[0012] In the case of a modified machine, the original hydraulic steering circuit is retained so that the conformity of the machine is not altered.

[0013] A variation in steering speed can be controlled by a proportional spool of the distributor (for example, an original distributor) of the machine's electro-hydraulic control circuit.

[0014] The machine may also include one or more of the following features taken in any technically permissible combination.

[0015] According to one embodiment of the invention, the steering system is configured so that the first hydraulic control circuit remains controllable by the operator of the handling machine using the manual steering device to act on the steering circuit, in addition to or in correction of the second hydraulic control circuit.

[0016] According to one embodiment of the invention, the first control circuit and the second control circuit are arranged with the steering circuit to act on the same lines of the steering circuit, so that the second control circuit is arranged to act on the direction of the same wheels as those on which the first control circuit is arranged to act, and vice versa.

[0017] In other words, for a given state of the selector when the machine is equipped with a selector, the wheels on which the second control circuit acts, via the steering circuit, are the same as those on which the first control circuit acts.

[0018] According to one embodiment of the invention, the handling machine includes front wheels and rear wheels, the steering circuit being configured to allow steering at least the front wheels.

[0019] According to one embodiment of the invention, the second hydraulic control circuit is connected to lines of the steering circuit which are connected to the first hydraulic control circuit.

[0020] According to one embodiment of the invention, the steering circuit includes a selector for selecting the wheels to be steered.

[0021] According to one embodiment of the invention, the steering circuit includes a selector for selecting the wheels to be steered, and the second hydraulic control circuit is connected to the steering circuit, between the first control circuit and the selector.

[0022] According to one embodiment of the invention, the steering circuit includes a selector configured to be able to selectively assume several states, including: a state in which the steering circuit lines are configured so that only the front wheels are steerable using the hydraulic steering circuit; a state in which the steering circuit lines are configured so that the front and rear wheels are steerable in the same direction using the hydraulic steering circuit; and a state in which the steering circuit lines are configured so that the front and rear wheels are steerable in opposite directions using the hydraulic steering circuit.

[0023] According to one embodiment of the invention, a line of the second hydraulic control circuit is connected to a line of the steering circuit which extends between the selector and the first hydraulic control circuit.

[0024] According to one embodiment of the invention, another line of the second hydraulic control circuit is connected to a line of the steering circuit which extends between a steering cylinder, preferably a steering cylinder of a front wheel, and the first hydraulic control circuit.

[0025] According to one embodiment of the invention, the hydraulic cylinder for actuation of a handling device is a tilting cylinder for a tool holder of the handling machine.

[0026] According to one embodiment of the invention, at least one, preferably each, of the first and second control circuits includes a pressure limiting device.

[0027] According to one embodiment of the invention, at least one, preferably each, of the pressure limiting devices comprises a double balancing valve.

[0028] According to one embodiment of the invention, the pressure limiting device of the first control circuit is located between a distribution pump of the first control circuit and the hydraulic steering circuit.

[0029] According to one embodiment of the invention, the pressure limiting device of the second control circuit is located on the connection circuit.

[0030] To allow the steering circuit to be controlled by two independent control circuits, namely a mechanically actuated control circuit and an electrically actuated control circuit, without these control circuits interfering with each other, each control circuit can be equipped with a pilot-operated pressure limiting device.

[0031] To avoid adding a component as a hydraulic power source for the electro-hydraulic control circuit (the so-called secondary circuit), the electro-hydraulic control circuit can reuse a section of an electro-proportional hydraulic valve already present in the handling machine's hydraulic circuit. This valve was initially used to control an actuating cylinder for a component of the machine's handling system, such as a tool holder tilting cylinder. The diverter valve can be added by connecting, on one side, to a pair of ports of this section of the hydraulic valve and, on the other side, to a hydraulic circuit connecting to the steering circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting and should be read in conjunction with the accompanying drawings, on which: there Figure 1 is a schematic view of a steering system for a material handling machine, based on a known example from the prior art; the Figure 2 is a schematic view of a steering system for a handling machine, according to one embodiment of the invention; the Figure 2A is a schematic view of part of the steering system of the Figure 2 ; there Figure 3 is a schematic view of a pressure limiting device for a steering system of a handling machine, according to an embodiment of the invention; the Figure 3A is a schematic view of the pressure limiting device of the Figure 3 , in an initial state of operation; the Figure 3Bis a schematic view of the pressure limiting device of the Figure 3 , in a second state of operation; the Figure 3C is a schematic view of the pressure limiting device of the Figure 3 , in a third state of operation; the Figure 4 is a schematic view of a handling machine, according to one embodiment of the invention. DETAILED DESCRIPTION

[0033] The concept of the invention is described more fully below with reference to the accompanying drawings, in which embodiments of the concept of the invention are shown. In the drawings, the size and relative sizes of the elements may be exaggerated for clarity. Similar numbers refer to similar elements in all the drawings. However, this concept of the invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are offered so as to make this description complete and to communicate the scope of the concept of the invention to those skilled in the art.

[0034] A reference throughout the specification to "an embodiment" means that a particular feature, structure, or characteristic described in relation to an embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrase "in an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0035] A handling machine is proposed which includes a steering system enabling the steering of at least some of the wheels, preferably at least the front wheels, by means of a manual control, such as a steering wheel, and / or by means of an electric control in addition to the manual control or autonomously.

[0036] The handling machine comprises a rolling chassis that supports a load or personnel handling system, such as a lifting arm equipped at its end with a tool holder and a tool coupled to the tool holder. The handling system includes a system of cylinders that actuates one or more elements of the handling system. For example, the handling system's cylinder system may include a cylinder for actuating the lifting arm and a tilting cylinder for tilting the tool holder relative to the arm. Handling machine

[0037] To the Figure 4An example of a handling machine 1 is shown according to an embodiment to which the steering system presented below is applicable. The handling machine 1 can also be called a handling trolley.

[0038] The handling machine 1 comprises a rolling chassis 2 supported on the ground by means of a front axle 30 comprising two front wheels and a rear axle 40 comprising two rear wheels.

[0039] The handling machine 1 includes a motorized system for moving the machine. The motorized system for moving the machine includes, for example, an electric motor and / or an internal combustion engine, a wheel transmission system, and a steering system for moving and steering the machine.

[0040] The rolling chassis 2 carries a handling system 64. The handling system 64 may include an arm 6, usually called a lifting arm, articulated to the rolling chassis 2 so as to be able to be moved between a so-called lowered position and a raised position, and a handling device 14, 145. Alternatively, the handling system 64 may be carried by a turret mounted pivoting on the chassis.

[0041] The lifting arm 6 is articulated to the chassis 2 in an area closer to the rear axle than to the front axle.

[0042] The handling device 145, 14 is articulated at one end of the lifting arm 6. A system of cylinders includes a cylinder 81 which allows the lifting arm to be moved relative to the frame 2 and a cylinder 82 which allows the handling device 145, 14 to be moved relative to the lifting arm 6.

[0043] The handling machine includes a control unit 10, comprising for example a computer, which allows the operator, via a human-machine interface, which may include a control element 12, such as a joystick, to control the handling machine, and in particular to control the direction of movement (front - back) of the machine and / or the position of the arm 6 and / or the handling device 145,14.

[0044] As detailed below in connection with the Figures 2 And 2A The control unit 10 can also be used to control a control circuit 200 of the steering circuit 3. The handling machine also includes a steering wheel 4 which, as detailed below, allows manual control of another control circuit 100 of the steering circuit 3.

[0045] The lifting arm 6 (or handling arm) is mounted on the chassis 2 and can be oriented around a rotation axis 7. In particular, said rotation axis 7 is horizontal when the rolling chassis 2 is supported on a horizontal surface. The arm 6 protrudes towards the front of the machine.

[0046] In other words, arm 6 is configured to pivot around an axis transverse to the longitudinal axis of the machine (horizontal axis when the machine is supported on a horizontal ground) to be moved between a lowered position and a raised position.

[0047] The lifting arm 6 forms a reference angle A6 with a reference position such as the horizontal (or the machine's ground support plane). At the Figure 4 , the deck 145 is inclined relative to a reference position such as the horizontal at a reference angle A145.

[0048] The arm allows different angles of inclination to be reached relative to the ground support plane of the machine's wheels, and in particular to reach in the high position a maximum angle, for example of a value between 55° and 70°, relative to the ground support plane of the machine's wheels.

[0049] According to one embodiment, the minimum angle that the arm can reach in its lowered position relative to the ground support plane of the machine's wheels is, for example, between -5° and 5°. Advantageously, the arm has an angular deflection of at least 50°. Handling device

[0050] The handling device comprises a tool holder 145, also called an apron, and a handling tool 14 attached to the tool holder in a removable manner. The tool holder can accommodate various types of handling tools. Alternatively, the tool can be integrated into the tool holder (i.e., non-removable).

[0051] The tool holder 145 is mounted articulated relative to the lifting arm 6. The handling device is articulated to the arm 6 by a linkage 15 with an axis parallel to the axis 7 and configured to perform different operations depending on the handling tool coupled to the carriage.

[0052] In the example illustrated in the Figure 4 The handling tool includes forks for handling a load 9, such as a pallet or a bale of straw, but the forks can be replaced by different tools, for example a bucket.

[0053] In the example illustrated in the Figure 4 The arm 6 is of the telescopic type. The arm 6 thus comprises at least two deployable segments using a deployment cylinder, not shown, arranged between the at least two segments. Alternatively, the arm may be a non-telescopic arm.

[0054] As mentioned above, a human-machine interface, which includes the control unit 12, is connected to the control unit 10. This unit can then control the cylinders 81 and 82 via a hydraulic circuit, depending on the operator's input to the control unit 12, such as a joystick. The human-machine interface may also include a screen 13, which allows the operator, for example, to receive feedback on the actions performed.

[0055] To control the hydraulic cylinder system of the handling system, the hydraulic circuit of the handling machine includes a hydraulic pressure source and a hydraulic distributor interposed between the hydraulic pressure source and a control solenoid valve for each hydraulic cylinder. Each control solenoid valve can be controlled by the control unit 10.

[0056] The handling machine also includes a steering system which includes a hydraulic steering circuit shown below. Hydraulic steering system

[0057] The material handling machine's steering system includes a hydraulic steering circuit that comprises hydraulic steering cylinders associated with the machine's wheels and supply lines to these cylinders. The machine steering system described below can be applied to a material handling machine such as the one described with reference to the Figure 4 but also to other handling machines which include a handling system including at least one hydraulic cylinder enabling the operation of an element of the handling system.

[0058] According to one embodiment and as illustrated in the Figure 2, the steering cylinders include a system of cylinders 31, 32 associated with the front wheels (front axle) and supplied by lines L31, L32, and a system of cylinders 33, 34 associated with the rear wheels (rear axle) and supplied by lines L33, L34.

[0059] Each cylinder system associated with the front or rear wheels may comprise two separate cylinders, each comprising a cylinder body and a piston mounted to slide within the cylinder body and having a rod extending from one side of the cylinder body to be coupled to a wheel. Alternatively, each cylinder system may comprise two cylinders, each comprising a common cylinder body and two pistons mounted to slide within the body, each piston having a rod extending from the cylinder body on the opposite side to the other rod.

[0060] A selector switch 300 allows the hydraulic fluid from the steering circuit 3 to be directed to the front steering cylinders only, or to both the front and rear steering cylinders. Specifically, depending on the mode selected on the selector switch, the rear steering cylinders can be operated in the same direction as the front steering cylinders or in the opposite direction.

[0061] The steering circuit 3 also includes a line L300 connected on one side to a track or line of a first hydraulic control circuit 100 and to a track or line of a second hydraulic control circuit 200 shown below, and on the other side to the selector 300. Depending on the position of the selector, the line L300 can be put directly into connection with the line L31 so that only the front wheels can be steered, or with the line L34 so as to steer the rear wheels in the same direction as the front wheels (the line L33 then being put into communication with the line L31), or with the line L33 so as to steer the rear wheels in the opposite direction to the front wheels (the line L34 being put into communication with the line L31). First hydraulic control circuit

[0062] A first hydraulic control circuit 100 is connected to the hydraulic steering circuit 3 in order to be able to supply all or part of the steering cylinder systems.

[0063] The first hydraulic control circuit 100 can be an original hydraulic control circuit of the handling machine, and the machine can be modified to achieve the control circuit 200 shown below.

[0064] The machine steering system includes a steering wheel 4 connected to a PDD steering pump of the first hydraulic control circuit 100 in order to send oil through one of the L, R paths of the first hydraulic control circuit 100 which are connected to the hydraulic steering circuit 3.

[0065] Thus oil can be sent to channel L by turning the steering wheel 4 in one direction, and to the other channel R of the first hydraulic control circuit 100 by turning the steering wheel 4 in the other direction.

[0066] According to one embodiment, track L is connected to line L32 of the front cylinder system, and track R is connected to line L300 which is connected to selector 300 to, depending on the selected mode (state) of the selector, supply via line L300 only the other line L31 of the front cylinder system, or supply either of the lines L33, L34 of the rear cylinder system.

[0067] As detailed below, according to a preferred embodiment, a pressure limiting device 180 is located on the control circuit 100, preferably interposed between the steering pump PDD and the steering circuit 3. Second hydraulic control circuit

[0068] A second hydraulic control circuit 200 is used to selectively control at least one actuating cylinder 5 of a handling system component, such as a tilting cylinder of a machine tool holder, and to control the hydraulic steering circuit 3 as detailed below.

[0069] The hydraulic steering circuit 3 can thus be powered by the first hydraulic control circuit 100 and the second hydraulic control circuit 200. The first hydraulic control circuit 100, which can be operated by the operator using the steering wheel 4, allows, if necessary, for the second hydraulic control circuit 200, which is controlled by a control unit.

[0070] As detailed below, the second hydraulic control circuit 200 can thus be used in addition, as an assistance, to the first hydraulic control circuit 100, or without operation of the first control circuit 100, for example for autonomous control of the hydraulic steering circuit 3.

[0071] The second hydraulic control circuit 200 includes a proportional electrically controlled hydraulic distributor 210.

[0072] As illustrated in Figures 2 And 2A The hydraulic distributor 210 comprises a part (or section) with two lines A1, B1 for supplying: either the actuation cylinder 5; or the steering circuit 3, via the connection circuit 600 shown below.

[0073] The second hydraulic control circuit 200 is electrically controlled proportionally using a solenoid valve to supply the double line A1, B1 with a flow corresponding to the desired function.

[0074] The double line A1, B1 is connected to the diverter 220 so that it can be selectively directed to the double line A3, B3 of the actuation cylinder 5, or to the double line A2, B2 of the connecting circuit connected to the steering circuit 3.

[0075] The hydraulic distributor 210 may include all or part of a hydraulic distributor originally present on the machine and which is used to control the supply of the cylinder 5, such as a tilting cylinder of a tool holder of the machine.

[0076] In the example illustrated in particular at the Figure 2 and to the Figure 2AThe hydraulic distributor 210 includes a distributor inlet plate 211, and several distributor segments 212, 213. Each distributor segment has a double line A0, B0 and respectively A1, B1. The double line A0, B0 can be used to supply another hydraulic actuator.

[0077] In the example of the Figure 2A The LS reference corresponds to a hydraulic load sensing signal, and the Pp reference corresponds to a supply for the distributor's pilot pressure. The T and TO references correspond to a return to the hydraulic reservoir, and the P and P2 references correspond to hydraulic supplies. Deflector

[0078] The second 200 hydraulic control circuit includes an electrically controllable 220 diverter.

[0079] The diverter 220 is connected to the double line A1, B1 of a slice (part) of the hydraulic distributor 210. Advantageously, the slice of the hydraulic distributor 210 chosen to be connected to the diverter provides an oil flow suitable for a steering circuit.

[0080] The 220 diverter features: a first state allowing the two lines A1, B1 to be connected, i.e. a double line, of the hydraulic distributor 210 of the second hydraulic control circuit 200 to a double line A3, B3 of an actuating cylinder 5 of said handling element, to supply the actuating cylinder 5, and a second state, allowing the two lines A1, B1 of the hydraulic distributor 210 of the second hydraulic control circuit 200 to a double line A2, B2 of a connection circuit 600 of the hydraulic distributor 210 to the steering circuit 3, to supply the steering circuit 3 via the connection circuit 600.

[0081] In the second state, the A3, B3 supply lines of the actuating cylinder 5 are no longer connected to the A1, B1 lines so that the actuating cylinder 5 is no longer supplied.

[0082] The diverter 220 thus allows selection of a state in which the double line A1, B1 of the hydraulic distributor 210 is in communication with the double line A3, B3 of an actuating cylinder 5 of said handling element, to supply the actuating cylinder 5, or a state in which the double line A1, B1 of the hydraulic distributor 210 is in communication with the double line A2, B2 to supply the steering circuit 3.

[0083] The control of the diverter valve 220's state, that is, the selection of the connection (or fluidic communication) of the hydraulic distributor 210 with the actuating cylinder 5, or with the steering circuit 3, is achieved electrically. The diverter valve 220 thus includes an electrical control element 221 that can be controlled by a control unit, such as the control unit 10, to switch the diverter valve 220 into the first or second state.

[0084] According to one embodiment, the connecting circuit 600 is connected to the steering circuit 3 between the selector 300 and the first control circuit 100.

[0085] In the example illustrated in the Figure 2 , the 600 connection circuit, which provides the link between lines A1, B1 of the hydraulic distributor 210 and the steering circuit 3, is connected to lines L300, L32 of the front part of the steering circuit 3.

[0086] The connection circuit 600 from the hydraulic distributor 210 to the steering circuit 3 includes a line L62 that connects a channel B2 of the diverter 220 to the line L300 of the steering circuit 3. As explained above, the line L300 is the line that connects a channel R of the control circuit 100 to the selector 300. The connection circuit 600 from the hydraulic distributor 210 to the steering circuit 3 also includes another line L61 that extends from channel A2 of the diverter 220 to the line L32 of the steering circuit 3. As explained above, the line L32 is the line that connects the other channel L of the control circuit 100 to the cylinder 32 of the front wheel cylinder system.

[0087] The diverter valve 220, connected to lines A1 and B1 of section 211 of the hydraulic distributor 210, allows for the selective use of two proportional double lines A2 and B2 and A3 and B3 from a single proportional double line A1 and B1 of a hydraulic distributor. The diverter valve's electrical control is of the on / off type. Steering unit

[0088] The control unit which is used to control the electrical control element 221 of the diverter 220 and the solenoid valve(s) of the hydraulic distributor 210, may be in whole or in part common with the control unit of the handling machine used to control the handling system of the machine.

[0089] The control unit 10 is configured to allow control of the electronic diverter 220 to bring it into the second linkage state of the hydraulic distributor 210 to the connection circuit 600.

[0090] In this second state of the diverter 220, the pilot unit 10 can be configured to execute an automatic steering control program for the handling machine, for example to automatically park the handling machine in a given location.

[0091] The automatic steering control of the handling machine is then carried out by an electrical control of the hydraulic distributor 210 which is connected to the steering circuit 3.

[0092] Such a design of the steering system allows the pilot unit 10 to automatically control the direction of the machine by actuating the on / off electrical control member 221 of the diverter 220 to connect the tracks A1, B1 to the tracks A2, B2, and by piloting the proportional control of the hydraulic distributor 210 to send the desired flow through line A1 or line B1, so as to control the steering circuit 3 via the connecting circuit 600.

[0093] According to one embodiment, the control unit is also configured to allow control of the selector 300. In the example illustrated in the figures, the selector 300 allows the machine to operate in front wheel steering only mode, by isolating the part, called the front part of the steering circuit, located between the selector and the front steering cylinders, which supplies the steering cylinders of the front wheels, from the part, called the rear part of the steering circuit, located between the selector 300 and the rear steering cylinders, which supplies the steering cylinders of the rear wheels.

[0094] As mentioned above, depending on the state in which selector 300 is located, selector 300 also allows the rear steering cylinders to be operated at the same time as the front steering cylinders, in the same direction or in opposite directions.

[0095] Preferably, the first 100 hydraulic control circuit remains controllable by the driver using the steering wheel 4 to act on the steering circuit 3, in addition to or in correction of the second 200 electrically controlled hydraulic control circuit.

[0096] It can be expected that the electrical control element 221 of the deflector will be returned to the first state when a command of the hydraulic cylinder 5 is detected, for example by detection by the control unit of a request by the operator of a control element of the hydraulic cylinder 5.

[0097] Each control unit may, for example, take the form of a processor and a data memory in which computer instructions executable by said processor are stored, or even take the form of a microcontroller.

[0098] In other words, the described functions and steps can be implemented as a computer program or via hardware components (e.g., programmable gate arrays). Specifically, the functions and steps performed by the control unit can be carried out by instruction sets or computer modules implemented in a processor or controller, or by dedicated electronic components or FPGA or ASIC-type components. It is also possible to combine computer and electronic components.

[0099] The control unit is thus an electronic and / or computer unit. When it is specified that said unit is configured to perform a given operation, this means that the unit includes computer instructions and the corresponding means of execution that allow said operation to be carried out and / or that the unit includes corresponding electronic components. Pressure limiting device

[0100] According to one embodiment, at least one, preferably each, of the hydraulic control circuits 100, 200 is equipped with a pressure limiting device (also called a hydraulic coupling device).

[0101] As illustrated in the Figure 2 The first hydraulic control circuit 100 includes a pressure limiting device 180. The connection circuit 600 of the control circuit 200 also includes a pressure limiting device 680.

[0102] The pressure limiting devices 180, 680 prevent a disturbance of the first hydraulic control circuit 100, and of the second electro-hydraulic control circuit 200, relative to each other.

[0103] According to one embodiment, each pressure limiting device comprises a first assembly including a non-return valve 81 and a valve 82 (on the left of the Figure 3), allowing control of fluid flow on a C2, C1 line and a second assembly including a non-return valve 81' and a valve 82' (on the right of the Figure 3 ), allowing control of the fluid flow over a line D2, D1.

[0104] There Figure 3 illustrates such a component and the Figures 3A-3C illustrate operating cases. As the pressure limiting device is symmetrical, half of the operating cases are presented below.

[0105] With a pressure increase at point A of valve 82', i.e., a pilot surface at the inlet of valve 82', the pressure limiting device behaves like a conventional pressure limiter, and valve 82' therefore opens at the corresponding spring setting pressure (for example, 300 bar). In this case, the pressure limiting device functions as a "shock-resistant valve".

[0106] With a pressure increase at point B, i.e., in the pilot zone of valve 82' connected to a port of the other valve 82, a larger pilot area is used, for example, 4 to 8 times larger, than the area used at point A. Therefore, a lower pressure, for example, 4 to 8 times lower than the spring setting, is required to open the spool (e.g., 50 bar). In this case, the component operates as an "externally piloted valve". Example of a motion control on a cylinder

[0107] The case illustrated in the Figure 3AThe system uses an externally piloted valve. Oil sent to line C1 passes through check valve 81 and exits through line C2 to supply a steering cylinder in the steering circuit 3. The steering cylinder discharges a volume of oil onto line D2, the oil initially being blocked by check valve 81' and pressure relief valve 82', which are closed. The pressure then rises along the C1C2 line until valve 82' opens, allowing the cylinder's discharge to flow back to the oil reservoir (i.e., from D2 to D1). Case of an external effect on the pressure limiting device

[0108] The case illustrated in the Figure 3B It uses the anti-shock valve function of both valves. Pressure can be created at C2 or D2 by a driving load (supporting a mass), by an impact on the cylinder, or by a parallel hydraulic supply.

[0109] If the pressures in C2 and D2 are less than the setting pressure of valves 82, 82', there is no flow through the pressure limiting device.

[0110] As illustrated in the Figure 3C As soon as either the pressure at C2 or D2 exceeds the setting value of valve 82 or 82', the corresponding valve 82' opens and releases the necessary volume of oil to bring the pressure back to an acceptable value. This volume is then drawn back in from the other side through the other valve 82 (from C1 to C2) via the check valve.

[0111] The invention is not limited to the embodiments illustrated in the drawings.

[0112] Furthermore, the term "including" does not exclude other elements or steps.

Claims

1. A handling machine including: - a mobile chassis; - a handling system (64) comprising at least one handling member that can be actuated by a hydraulic cylinder (5), such as a cylinder for inclining a tool-holder of the machine; - a steering system comprising: - a hydraulic steering circuit (3) including steering cylinders (31-34) for steering at least some of the wheels of the machine; - a first hydraulic control circuit (100) connected to the steering circuit (3) to be able to feed the steering cylinders (31-34) and a manual steering device (4) such as a steering wheel connected to the first hydraulic control circuit (100); - a second hydraulic control circuit (200) used at least to control the actuator hydraulic cylinder (5) of a handling member; characterized in that: the second hydraulic control circuit (200) includes: - a hydraulic distributor (210); - a hydraulic connection circuit (600) connected to the hydraulic steering circuit (3); and - a diverter (220) to which are connected the connecting circuit (600), the hydraulic cylinder (5) for actuating a handling member, and the hydraulic distributor (210); the diverter (220) being electrically controllable to assume selectively: - a first state in which the hydraulic distributor (210) of the second hydraulic control circuit (200) is connected to the actuator hydraulic cylinder (5) of said handling member; and - a second state in which the hydraulic distributor (210) of the second hydraulic control circuit (200) is connected to the connecting circuit (600) that is connected to the steering circuit (3) to enable the second hydraulic control circuit (200) to control the same steering cylinders as those controllable by the first hydraulic control circuit (100); - a control unit (10) configured to control the diverter (220) to place it in the second state in which the hydraulic distributor (210) is connected to the connecting circuit (600) that is connected to the steering circuit (3) in order to be able to execute a handling machine steering control program, for example for parking the handling machine automatically in a given place.

2. The handling machine as claimed in claim 1 in which the steering system is configured so that the first hydraulic control circuit (100) remains controllable by the driver of the handling machine using the manual steering device (4) to act on the steering circuit (3), complementing or correcting the second hydraulic control circuit (200).

3. The handling machine as claimed in either one of the preceding claims in which the first control circuit (100), the second control circuit (200) and the steering circuit (3) act on the same lines (L32, L300) of the steering circuit (3) so that the second control circuit (200) is adapted to act on the steering of the same wheels as those on which the first control circuit (100) is adapted to act, and vice versa.

4. The handling machine as claimed in any one of the preceding claims including front wheels and rear wheels, the steering circuit (3) being configured to enable steering of at least the front wheels.

5. The handling machine as claimed in any one of the preceding claims in which the second hydraulic control circuit (200) is connected to lines (L32, L300) of the steering circuit (3) that are connected to the first hydraulic control circuit (100).

6. The handling machine as claimed in any one of the preceding claims in which the steering circuit (3) includes a selector (300) for selecting the wheels to be steered.

7. The handling machine as claimed in any one of the preceding claims in which, the steering circuit (3) including a selector (300) for selecting the wheels to be steered, the second hydraulic control circuit (200) is connected to the steering circuit (3) between the first control circuit (100) and the selector (300).

8. The handling machine as claimed in any one of the preceding claims in which the steering circuit (3) includes a selector (300) configured to be able to adopt a plurality of states selectively, said states including: - a state in which the lines of the steering circuit (3) are configured so that only the front wheels are steerable with the aid of the hydraulic steering circuit; - a state in which the lines of the steering circuit (3) are configured so that the front wheels and the rear wheels are steerable in the same sense with the aid of the hydraulic steering circuit; and - a state in which the lines of the steering circuit (3) are configured so that the front wheels and the rear wheels are steerable in opposite senses to one another with the aid of the hydraulic steering circuit.

9. The handling machine as claimed in any one of claims 6 to 8 in which a line (L62) of the second hydraulic control circuit (200) is connected to a line (L300) of the steering circuit (3) that extends between the selector (300) and the first hydraulic control circuit (100).

10. The handling machine as claimed in the preceding claim in which another line (L61) of the second hydraulic control circuit (200) is connected to a line (L32) of the steering circuit (3) that extends between a steering cylinder (300), preferably a front wheel steering cylinder, and the first hydraulic control circuit (100).

11. The handling machine as claimed in any one of the preceding claims in which the hydraulic cylinder (5) for actuating a handling member is a cylinder for inclining a tool-holder of the handling machine.

12. The handling machine as claimed in any one of the preceding claims in which at least one of the first and second control circuits (100, 200) and preferably each of them includes a pressure limiter device (180, 680).

13. The handling machine as claimed in claim 12 in which at least one of the pressure limiter devices (180, 680) and preferably each of them includes a dual balancing valve.

14. The handling machine as claimed in either one of claims 12 or 13 in which the pressure limiter device (180) of the first control circuit (100) is situated between a steering pump (PDD) of the first control circuit (100) and the hydraulic steering circuit (3).

15. The handling machine as claimed in any one of claims 12 to 14 in which the pressure limiter device (680) of the second control circuit (200) is situated in the connecting circuit (600).