EP2974997B1

EP2974997B1 - Electrohydraulic power supply system for a mobile working machine, in particular for an elevating work system having an aerial platform

Info

Publication number: EP2974997B1
Application number: EP14425097.4A
Authority: EP
Inventors: Pierangelo Ballestrero
Original assignee: Individual
Current assignee: Individual
Priority date: 2014-07-17
Filing date: 2014-07-17
Publication date: 2019-05-29
Anticipated expiration: 2034-07-17
Also published as: DK2974997T3; EP2974997A1

Description

Field of application

The present invention relates in its more general aspect to an electrohydraulic power supply system.
More specifically the invention relates to an electrohydraulic power supply system for a mobile working machine of the type comprising at least one electrical motor and an hydraulic pump.
The invention relates particularly, but not exclusively, to an electrohydraulic power supply system suitable to power a mobile working machine in general, and particularly an elevating work system having an aerial platform. The following description is made with reference to this field of application, for convenience of exposition only.

Prior art

As it is well known, mobile working machines are usually equipped with a power supply system, particularly an endothermic motor, generally Diesel, capable to drive at least one pump ensuring the hydraulic power necessary to all machine movements.
Among mobile working machines, elevating work systems, particularly those having an aerial platform, have a particular importance, that is working machines making a working area located at a certain height accessible to operators with their equipment, in safety conditions, avoiding the assembly of scaffolds or the use of trestles. These systems are generally used in the building and plant engineering sector.
In recent years they have been widely spread also in other sectors, such as the removals, building maintenance and cleaning sectors.
Particularly, as shown in Figure 1, an elevating work system of the known type, globally and schematically indicated with 1, comprises an aerial platform 2 and a base 3. The aerial platform 2 is connected to the base 3 by means of an articulated arm 4.
More particularly, the base 3 can be mounted on tracks and be stabilized by means of appropriate feet as shown in Figure 1; alternatively, the base 3 can be trucked as shown in Figure 2, which has the same numeral references as Figure 1 for identical or similar elements of the elevating work system being shown.
The elevating work system 1 comprises the mechanical structure, hydraulic circuits, electrical ones, suitable safety circuits, mounted on board of the aerial platform 2 and of the articulated arm 4, respectively, capable to detect the slant of the aerial platform 2 and of the articulated arm 4, indeed, so as to ensure the stability and slant of the aerial platform 2.
In substance, safety circuits are arranged so as to ensure that the slant of the aerial platform 2 and of the articulated arm 4 is blocked before potentially dangerous situations.
The elevating work system 1 also comprises at least one main mechanical power source, particularly a main motor 5, capable to operate at least one hydraulic pump 6, charged in turn of providing the hydraulic power suitable to raise the aerial platform 2; more commonly, the elevating work system 1 comprises several hydraulic pumps 6 powering several movement actuators of the aerial platform 2.
In general, the main motor 5 is an endothermic motor; it is also possible to use as main motor 5 a single-phase or three-phase direct-current or alternating-current electric motor powered by an external electric line or by a set of internal batteries. However it is known that elevating work systems having an endothermic motor (Diesel or petrol) are generally more powerful than systems driven by electric motors and are therefore able to reach higher working speeds.
Systems having a main endothermic motor are conceived particularly to work outside, even on hard and uneven grounds, and mostly provided with jack arms resting on the ground.
However they are unsuited to internal use, for example in big buildings (such as a shopping center or a church) or in industrial warehouses. They are in fact a source of pollution, also sound pollution.
It is therefore usual to use a further motor or secondary motor, always an electric one, indicated with 8 in Figures 1 and 2.
In general, the elevating work system 1 of the prior art comprises therefore at least two power sources, the main motor 5 and the secondary motor 8, generally of different types and different sizes and powers, for example an endothermic motor and an electric motor, respectively, which coexist within the same system and they can be used by the operator according to working requirements.
Moreover, elevating work systems, particularly having an aerial working platform, are very often equipped with secondary electrohydraulic systems capable to supply electric power to tool devices (lamps, beacons, drills, electric tools,...) generally used on board of the platform itself.
In that case, the elevating work system 1 of the prior art comprises at least one electric power drawing point 7 located on board of the aerial platform 2 and powered by an electric generator coupled to an hydraulic motor, particularly to reach at height voltage values equal to 220V or 380V according to needs.
More particularly, when the elevating work system 1 is in the open air, where there are no environmental and/or sound pollution problems, it is possible to use the main endothermic motor 5 to move the system as a whole, to move the aerial platform 2 and to power the electric power drawing point 7 by means of an alternator, if needed, while when it is in closed rooms where noise and/or exhaust gases represent a problem the secondary electric motor 8 is used to perform all these operations; in that case, it is also possible to use the powering of the secondary electric motor 8 and in case the electric power drawing point 7 (and therefore the tools at height) by means of a domestic or industrial electric line, if any. It should be underlined that it is necessary to use the secondary electric motor 8 also when numerous power supply stop & goes are required, which can be hardly managed by a main endothermic motor 5, especially if a Diesel one.
Double-power elevating work systems of the type being described are therefore much more versatile than systems equipped with a single motor and particularly they allow the possibilities of use to be maximized, making them independent of the working conditions.
Moreover, the elevating work system 1 usually comprises a single-phase or three-phase power generator 9A, coupled to an hydraulic motor 9B powered by an hydraulic pump or pumps 6. The mechanical power of the main motor 5 is thus turned by the hydraulic pump or pumps 6 into hydraulic power, particularly an hydraulic flow used to move the aerial platform 2; a small part of that hydraulic flow outputted by the hydraulic pump or pumps 6 is used to power the hydraulic motor 9B coupled to the power generator 9A.
Such an elevating work system 1 having an aerial platform, equipped with the main endothermic motor 5, with the secondary electric motor 8 and with the power generator 9A, requires a complicated and expensive hydraulic system composed of pipes, connectors, hydraulic pumps and motors allowing all power exchanges between the different system components to be managed. Moreover, it happens very often that the elevating work system is also equipped with at least one inverter (not shown) which is necessary to optimize the working of the secondary electric motor 8.
For obvious mechanical and plant engineering reasons, neither any synergy between the indicated components nor any simplification appears unfortunately to be possible. The secondary electric motor and the power generator are in fact two different components which take up some room, increase the weight of the platform as a whole and are however alternately activated. Particularly, the alternator is necessary only when the primary endothermic motor is working and the secondary electric motor is turned off. On the other hand, when the electric power to power the secondary electric motor is present, the alternator is not needed. These known elevating work systems require therefore numerous electrohydraulic driving components which complicate the assembly of the platform and therefore the related costs.
The European patent application No. EP 2 738 397 discloses a construction machinery comprising an engine driving a main pump which in turn drives two actuators, one responsible for lifting/lowering a boom of the machinery, the other responsible for a swing operation of the machinery structure. An additional motor, connected to an additional hydraulic pump/motor, acts also as a current generator storing electric power in a storage device, for example when the boom is lowered. Such additional electric motor and hydraulic pump thus act as additional energy generating means for the construction machinery, providing additional energy thereto. In particular, when a predetermined amount of electric power is stored in the storage device, the machinery actuators are mainly operated by the additional motor and hydraulic pump and the main pump discharge flow rate is reduced accordingly, thus reducing the fuel consumption of the machinery engine. A system comprising two control valves and a plurality of electro-valves controlled by a controller regulates the fluid passage during the operation of the construction machinery.
The technical problem of the present invention is to provide an electrohydraulic power supply system, particularly for an elevating work system having an aerial platform, having such structural and functional features so as to allow the limitations and drawbacks of the systems realized according to the prior art to be overcome and particularly capable to manage the electric power and the hydraulic power in order to provide the power supply to move a working machine or an aerial platform and to correctly power an electric power drawing point which can be used by the electric devices used at height, within the platform itself, allowing in the meantime the hydraulic system and the mechanical assembly operations to be simplified, thus reducing production costs and the weight of the elevating work system as a whole.

Summary of the invention

The solution idea underlying the present invention is to realize a power supply system which is bidirectional, i.e. suitable to turn the input electric power into mechanical power and therefore into output hydraulic power and on the contrary to turn the input hydraulic power into mechanical power and therefore into output electric power with a minimum number of components using reversible devices.
Based on that solution idea, the technical problem is solved by a power supply system according to the features of claim 1.
According to an aspect of the invention, the power supply system may further comprise a solenoid valve connected to the electronic controller and turned on and off thereby, as well as to the hydraulic pump. According to another aspect of the invention, the solenoid valve may be an electrohydraulic device capable to let an hydraulic fluid flow from an inlet to an outlet in correspondence with an hydraulic power output terminal of the power supply system when the solenoid valve is powered by a control electric current from the electronic controller.
Yet according to another aspect of the invention, the washout valve is arranged to protect the hydraulic pump powered by the electric motor, this washout valve being an hydraulic device capable to let an hydraulic fluid flow from an inlet to an outlet when the pressure of the input hydraulic fluid exceeds a given value that can be adjusted by means of a mechanical regulator, thus determining a maximum pressure of the power supply system as a whole.
According to the invention the system comprises a check valve, inserted between the hydraulic pump and an hydraulic power input terminal, the check valve being an hydraulic device capable to let an hydraulic fluid flow in a single direction and the hydraulic power input terminal being connected to hydraulic circuits powered by a main endothermic motor outside the power supply system.
According to the invention the system comprises an output terminal for external connection with an hydraulic fluid tank.
The electric motor is a three-phase or single-phase asynchronous electric motor, a reversible device suitable to work also as a power generator. Furthermore, the hydraulic pump may be a gear pump, a reversible device capable to work also as an hydraulic motor.
According to the invention, the power supply system comprises at least one flow regulator, inserted between the check valve and the hydraulic power input terminal and also connected to the hydraulic fluid tank and to the washout valve, the flow regulator being an hydraulic device capable to receive in correspondence with an inlet a certain flow rate of the hydraulic fluid not being constant in time and to return in correspondence with an outlet a flow rate of the hydraulic fluid being lower or equal to the flow rate of the input hydraulic fluid and constant in time and adjustable by means of a mechanical regulator.
Furthermore, the power supply system may comprise an integrated pipe system, comprising in turn at least one block wherein a pipe network is integrated connected to a plurality of connecting openings for the different hydraulic elements of the power supply system.
Particularly, this integrated pipe system may also comprise at least one metallic case in contact with the block and suitable to house an electronic circuitry of the power supply system, the flow of the hydraulic fluid flowing in the pipe network realized within the block allowing the electronic circuitry housed in the metallic case to be cooled, that block thus serving as a heat exchanger.
According to this aspect of the invention, the power supply system may comprise at least a first opening corresponding to an hydraulic power input terminal, a second opening corresponding to an hydraulic power output terminal and a third opening corresponding to an output terminal for external connection, these openings surfacing from the block.
Particularly, the integrated pipe system may comprise at least a plurality of connections for a plurality of valves of the power supply system.
Finally, the block may be a metallic block, particularly made out of aluminum.
Conveniently, the power supply system according to the invention may be used to move the mobile working machine in a first working mode and to generate a current suitable to operate electrical tools on board of the mobile working machine in a second working mode.
The problem is also solved by a method for generating a power supply using a power supply system of the above-indicated type and characterized in that it comprises the steps of:

activating the power supply system in a first working mode with a motor-driven pump function to feed an hydraulic fluid to hydraulic actuators, the electronic controller driving the solenoid valve so that it is enabled and powers the electric motor and controlling therefore also the hydraulic pump and the hydraulic power provided on an hydraulic power output terminal; and
activating the power supply system in a second working mode with an alternator function, capable to feed electric power to electric tools, the electronic controller disabling the solenoid valve so as to block any flow of the hydraulic fluid towards an hydraulic power output terminal connected to the solenoid valve, the power supply system being used as a converter of hydraulic power into electric power provided on an electric power output terminal of the electronic controller.

According to another aspect of the invention, the electric motor may be a three-phase asynchronous electric motor and in the second working mode the electronic controller injects a current pulse in the three-phase asynchronous electric motor, particularly in the stator windings in order to magnetize the rotor of the three-phase asynchronous electric motor, that initial magnetization allowing the three-phase asynchronous electric motor to work as a power generator.
The features and advantages of the power supply system according to the invention will be apparent from the following description of an embodiment thereof given by way of non-limiting example with reference to the attached drawings.

Brief description of the drawings

In the drawings:

Figures 1A and 1B schematically show an elevating work system having an aerial platform realized according to the prior art;
Figure 2 schematically shows a power supply system not according to the claimed invention, particularly for an elevating work system having an aerial platform;
Figures 3A and 3B schematically show the power flows within the power supply system of Figure 2 in two different steps of the working thereof;
Figure 4 schematically shows an embodiment of the power supply system according to the invention; and
Figure 5 schematically shows a detail of the power supply system of Figure 2 or of Figure 4.

Detailed description

With reference to those figures, and particularly to Figure 2, a power supply system 10 for a mobile working machine is described, particularly for an elevating work system having an aerial platform, for example of the type described with reference to the prior art and shown in Figures 1A and 1B.
It should be underlined that the figures are only schematic views and they are not drawn to scale, the different components represented therein being depicted in a schematic way, the actual implementation being susceptible to changes according to the desired application.
The power supply system 10 comprises at least one electronic controller 11 connected to an electric motor 12, in turn coupled to an hydraulic pump 13.
Conveniently, the electronic controller 11 is a device suitable to manage and coordinate the working of the electric motor 12 and of a solenoid valve 15, particularly when turning on and off (ON/OFF). Besides to the electric motor 12 and to the solenoid valve 15, the electronic controller 11 is also connected to an electric power input terminal INel and to an electric power output terminal OUTel, intended to power an electric power drawing point, for example on board of an aerial platform.
Furthermore, the solenoid valve 15 is connected to the hydraulic pump 13, protected by a washout valve 14 and powered by the electric motor 12, and it is connected to an hydraulic power output terminal OUTid, intended to power hydraulic movement actuators, for example for an aerial platform.
The power supply system 10 also comprises a check valve 16 inserted between the hydraulic pump 13 and an hydraulic power input terminal INid coming from the hydraulic circuits powered by a main endothermic motor, not shown in the figures and outside the power supply system 10. The check valve 16 is moreover connected to the washout valve 14 and to the solenoid valve 15.
Obviously, when a user of the power supply system 10 injects an hydraulic fluid 18, particularly oil, in the hydraulic power input terminal INid, it will have simultaneously to activate the working of the generator of the electronic controller 11 that, as it will be explained hereafter in the description, will activate the injection of magnetizing current in the electric motor working as an alternator.
Finally, the power supply system 10 has an output terminal for external connection OUText, particularly for the connection to a tank 17 of an hydraulic fluid 18.
In a preferred embodiment, the power supply system 10 according to the invention comprises an hydraulic gear pump 13 and a three-phase asynchronous electric motor 12.
In fact it should be underlined that, advantageously, an hydraulic gear pump 13 is a very strong device, already used in the hydraulic circuits of known elevating work systems having an aerial platform. Moreover, an hydraulic gear pump 13 is a reversible device, therefore capable to be used also as an hydraulic motor.
Furthermore, it should be remembered that a three-phase asynchronous electric motor 12 is known to be one of the electric machines that are most used in automation since it is very economic, simple to control and strong. Advantageously, such a three-phase asynchronous electric motor 12 is also a reversible device, therefore capable to work also as a power generator.
It is obviously possible to use other devices to realize the electric motor 12 and the hydraulic pump 13, provided that they are reversible devices for a correct working of the power supply system 10 according to the invention, as it is clarified hereafter.
The power supply system 10 is in fact an electrohydraulic power supply system of the bidirectional type.
More particularly, in a first working mode, the power supply system 10 works as a motor-driven pump to feed the hydraulic fluid 18 to hydraulic actuators, for example to move a mobile working machine, more particularly to move an elevating work system and the aerial platform thereof.
In that case, the electronic controller 11 drives the solenoid valve 15 so that it is enabled (ON) and powers the electric motor 12; in these working conditions, the electronic controller 11 works therefore as an inverter, particularly a variable-frequency three-phase inverter so as to manage the rotation speed of the electric motor 12, particularly a three-phase asynchronous one; therefore the electronic controller 11 also controls the hydraulic pump 13 and particularly the flow rate of the output hydraulic fluid (for example oil), i.e. the hydraulic power provided on the hydraulic power output terminal OUTid for hydraulic actuators.
For sake of clarity, Figure 3A points out a first path Fid1 related to a flow of the hydraulic fluid 18, for example oil, between the tank 17 and the hydraulic power output terminal OUTid, particularly through the hydraulic pump 13 and the solenoid valve 15.
Conveniently, the check valve 16 prevents that flow of the hydraulic fluid 18, that is generated by the hydraulic pump 13, from coming out from an inlet pipe.
Furthermore, the washout valve 14 safeguards hydraulic circuits, and particularly the hydraulic pump 13, against possible overpressures due to delays in the activation of the solenoid valve 15 and/or possible damages in external circuits connected to the power supply system 10. In substance, the washout valve 14 determines the maximum pressure of the system as a whole.
In that case, the power supply system 10 is used as a converter of the electric power into hydraulic power: the electric motor 12, conveniently driven by the electronic controller 11, drives the rotation of the hydraulic pump 13 which draws the hydraulic fluid 18 from the tank 17 and supplies it to an outlet pipe by means of the solenoid valve 15.
In a second working mode, the power supply system 10 works instead as an alternator, capable to power electric tools, for example tools to be used within an aerial platform. In that case, the electronic controller 11 disables (OFF) the solenoid valve 15, blocking the flow of the hydraulic fluid 18 towards the hydraulic power output terminal OUTid; also the inverter function of the electronic controller 11 is excluded.
Conveniently, each time the power supply system 10 is turned on as an alternator, the electronic controller 11 injects a current pulse in the electric motor 12, particularly in the stator windings in order to magnetize the rotor of the asynchronous electric motor 12. That initial magnetization allows the electric motor 12 to work as a power generator.
In fact, it should be remembered that, although an asynchronous motor is theoretically a reversible machine that can always work also as a generator, in practice, if the motor stays at rest for a lot of time, the rotor thereof can completely loose the residual magnetization and therefore prevent the electric current from being generated and the working as a generator from being triggered.
In that case, after the initial magnetization provided, the so-generated stator current succeeds, in practice, in keeping the rotor of the electric motor 12 magnetized and therefore it allows the power supply system 10 to work correctly.
Therefore, Figure 3B shows a second path Fid2 related to a flow of the hydraulic fluid 18 between the hydraulic power input terminal INid and the tank 17, that powers the hydraulic pump 13, in that case with an hydraulic motor function.
In that case, the power supply system 10 is used as a converter of the hydraulic power into electric power: the flow of the input hydraulic fluid 18 is fed by a pump fitted on the main endothermic motor, the pump not being shown in the figures; that flow of the hydraulic fluid 18 passes therefore through the check valve 16 and, the solenoid valve 15 being disenabled, it powers the hydraulic pump 13 that works as an hydraulic motor, and it activates the rotation of the rotor of the electric motor 12 working as a generator.
In its more general form, the power supply system 10 comprises therefore:

an element 12 having an electric motor function or a power generator function, and
an element 13 having an hydraulic pump function or an hydraulic motor function,

electronic controller

Particularly, it should be underlined that:

the electronic controller 11 is an electronic device capable to control and optimize the bidirectional flow of the electric power - mechanical power - hydraulic power;
the electric motor 12 is a device capable to turn the electric power into mechanical power, provided, for example, on a rotary shaft; and
the hydraulic pump 13 is a device capable to turn the mechanical power received at the input of a rotary shaft into hydraulic power provided in an outlet as a flow of an hydraulic fluid (generally oil) with a given flow rate and a given pressure.

Furthermore, the power supply system 10 comprises:

the washout valve 14, that is an hydraulic device capable to let an hydraulic fluid (generally oil) flow from an inlet to an outlet when the pressure of said input fluid exceeds a given value that can be adjusted by means of a mechanical regulator;
the solenoid valve 15, that is an electrohydraulic device capable to let an hydraulic fluid (generally oil) flow from an inlet to an outlet when it is powered by a control electric current; and
the check valve 16, that is an hydraulic device capable to let an hydraulic fluid (generally oil) flow in a single direction.

Figure 2 also indicates the power flow in case of a conversion of the electric power into hydraulic power (arrows F1 and F2 in full lines) and the power flow during the inverse conversion, wherein an input oil-pressure flow, fed by a pump fitted on the main endothermic motor, powers a current generator (arrows F3 and F4 in dotted lines).
In substance, the power supply system 10 is a bidirectional electrohydraulic system wherein, when some hydraulic power comes in, for example from an hydraulic pump powered by a main endothermic motor, for example a Diesel one, of a working machine, such as an elevating work system, some electric power is generated, for example for an electric power drawing point to power some on-board tools; likewise, when some electric power comes in, some hydraulic power is generated, particularly a flow of the hydraulic fluid, to move the machine.
According to the invention, shown in Figure 4, the power supply system 10 further comprises a flow regulator 19, inserted between the check valve 16 and the hydraulic power input terminal INid; moreover the flow regulator 19 is connected to the tank 17 of the hydraulic fluid 18 and to the washout valve 14.
Such a flow regulator 19 is an hydraulic device capable to receive in correspondence with an inlet a certain flow rate of the hydraulic fluid (generally oil) not being constant in time and to return in correspondence with an outlet a flow rate of the hydraulic fluid being lower or equal to the flow rate of the inlet hydraulic fluid constant in time and adjustable by means of a mechanical regulator.
Conveniently, the power supply system 10 further comprises an integrated pipe system 20, schematically shown in Figure 5.
The integrated pipe system 20 comprises particularly at least one block 21 wherein a pipe network is integrated connected to a plurality of connecting openings for the different hydraulic elements of the power supply system 10, as well as at least one metallic case 22, suitable to house the electronic circuitry of the power supply system 10.
More particularly, at least a first opening 23A corresponding to the hydraulic power input terminal INid, a second opening 23B corresponding to the hydraulic power output terminal OUTid, as well as a third opening 23C corresponding to the output terminal for external connection OUText surface from the block 21.
Moreover, the integrated pipe system 20 comprises at least a first connection 24 for the washout valve 14, a second connection 25 for the solenoid valve 15 and a third connection for the check valve 16.
In practice, the block 21 is a metallic block (generally made out of aluminum) wherein the hydraulic pipelines of the power supply system 10 are obtained.
In that way, the integrated pipe system 20 allows the production of hydraulic circuits to be industrialized, reducing the number of pipes: all hydraulic connections of the power supply system 10 are realized within the block 21, which also provides the connections for the valves and the connecting openings with the tank 17 and with the hydraulic pump 13.
It should be underlined that the flow of the hydraulic fluid 18, particularly an oil-pressure flow, schematically shown in Figures 3A and 3B, flows within the block 21. Conveniently, the integrated pipe system 20 also comprises the metallic case 22, in contact with the block 21, and that can be used also as a heat exchanger capable to cool the possible power circuits of the electronic controller 11 housed in the metallic case 22, indeed.
It is well known that commercial inverters are provided with appropriate heat sinks and cooling fans required for the thermal equilibrium of the power circuits contained therein; advantageously according to the invention, these further elements for heat dissipation can be avoided and, due to the synergy between electric circuits and hydraulic circuits realized by the integrated pipe system 20, it is possible to use an electronic controller 11 without any device for heat dissipation but simply contained in a metallic box that can be fastened on the block 21 with the function of the metallic case 22 so as to exploit the flow of the hydraulic fluid 18 as a coolant.
It should be underlined that an integrated solution of this type allows a thermal equilibrium to be kept for the electronic controller 11 without having to employ bulky and expensive forced ventilation systems, as those used in the prior art.
In conclusion, the power supply system according to the invention allows a bidirectional system to be realized, which is capable to convert the input electric power into mechanical power and therefore into output hydraulic power and on the contrary capable to convert the input hydraulic power into mechanical power and therefore into output electric power.
Conveniently, the power supply system comprises an electronic device managed by a microcontroller, particularly an electronic controller, capable to control an electric motor to turn the electric power into hydraulic power and capable in the meantime to manage the same motor as a generator to activate the inverse conversion.
According to another advantageous aspect of the invention, the power supply system comprises an integrated pipe system capable to manage input and output hydraulic flows, limiting the number of interface ducts with the external world, due to a block wherein appropriate ducts are realized, connected to connections and openings for the system hydraulic elements.
Conveniently, the block of the system of integrated pipes run by the hydraulic fluid realizes a heat dissipation system, for example for electronic power devices comprised in the electronic controller.
Finally, it is underlined that, advantageously according to the invention, the power supply system can be used alternately to move the mobile working machine or to generate a current suitable to operate electric tools on board of that machine, particularly with voltage values equal to 220V or 380V according to needs.
Obviously, in order to meet contingent and specific requirements, a person skilled in the art will be able to make several modifications and changes to the above-described power supply system, all falling within the scope of protection of the invention as defined by the following claims.

Claims

A power supply system (10) for a mobile working machine comprising at least one electric motor (12) and an hydraulic pump (13), said electric motor (12) being a bidirectional element having an electric motor function or a power generator function and said hydraulic pump (13) being a bidirectional element having an hydraulic pump function or an hydraulic motor function, depending on the working conditions of the system as a whole, said bidirectional elements being driven by an electronic controller (11) connected to said electric motor (12) as well as to at least one electric power input terminal (INel) and to an electric power output terminal (OUTel), said electric motor (12) being a three-phase or single-phase asynchronous electric motor, said electronic controller (11) injecting a current pulse in said asynchronous electric motor (12), particularly in the stator windings, in order to magnetize a rotor of said asynchronous electric motor (12), said initial magnetization allowing said asynchronous electric motor (12) to work as a power generator, the system further comprising a check valve (16), inserted between said hydraulic pump (13) and an hydraulic power input terminal (INid), said check valve (16) being an hydraulic device capable to let an hydraulic fluid (18) flow in a single direction and said hydraulic power input terminal (INid) being connected to hydraulic circuits powered by a main endothermic motor outside said power supply system (10) as well as an output terminal for external connection (OUText) with a tank (17) of an hydraulic fluid (18) and being characterized in that it further comprises at least one flow regulator (19), inserted between said check valve (16) and said hydraulic power input terminal (INid) and connected to said tank (17) of said hydraulic fluid (18) and to said washout valve (14), said flow regulator (19) being an hydraulic device capable to receive in correspondence with an inlet a certain flow rate of the hydraulic fluid (18) not being constant in time and to return in correspondence with an outlet a flow rate of the hydraulic fluid being lower or equal to said flow rate of the input hydraulic fluid (18) and constant in time and adjustable by means of a mechanical regulator.
The power supply system (10) according to claim 1, characterized in that it further comprises a solenoid valve (15) connected to said electronic controller (11) and turned on and off thereby (ON/OFF), as well as to said hydraulic pump (13).
The power supply system (10) according to claim 2, characterized in that said solenoid valve (15) is an electro hydraulic device capable to let an hydraulic fluid (18) flow from an inlet to an outlet in correspondence with an hydraulic power output terminal (OUTid) of said power supply system (10) when said solenoid valve (15) is powered by a control electric current by said electronic controller (11).
The power supply system (10) according to claim 2, characterized in that the washout valve (14) is arranged to protect said hydraulic pump (13) and powered by said asynchronous electric motor (12), said washout valve (14) being an hydraulic device capable to let an hydraulic fluid (18) flow from an inlet to an outlet when the pressure of said input hydraulic fluid (18) exceeds a given value that can be adjusted by means of a mechanical regulator, thus determining a maximum pressure of said power supply system (10) as a whole.
The power supply system (10) according to any of the previous claims, characterized in that said hydraulic pump (13) is a gear pump, a reversible device capable to work also as an hydraulic motor.
The power supply system (10) according to any of the previous claims, characterized in that it further comprises an integrated pipe system (20), comprising in turn at least one block (21) wherein a pipe network is integrated connected to a plurality of connecting openings for the different hydraulic elements of said power supply system (10) .
The power supply system (10) according to claim 6, characterized in that said integrated pipe system (20) also comprises at least one metallic case (22) in contact with said block (21) and suitable to house an electronic circuitry of said power supply system (10), a flow of the hydraulic fluid (18), which flows in said pipe network realized within said block (21), allowing said electronic circuitry housed in said metallic case (22) to be cooled, said block (21) thus serving as a heat exchanger.
The power supply system (10) according to claim 6 or 7, characterized in that it comprises at least a first opening (23A) corresponding to an hydraulic power input terminal (INid), a second opening (23B) corresponding to an hydraulic power output terminal (OUTid) and a third opening (23C) corresponding to an output terminal for external connection (OUText), said openings (23A, 23B, 23C) surfacing from said block (21).
The power supply system (10) according to any of claims 6 to 8, characterized in that said integrated pipe system (20) comprises at least a plurality of connections (24, 25, 26) for a plurality of valves (14, 15, 16) of said power supply system (10).
The power supply system (10) according to any of claims 6 to 9, characterized in that said block (21) is a metallic block, particularly made out of aluminum.
A use of a power supply system (10) according to any of the previous claims to move said mobile working machine in a first working mode and to generate a current suitable to operate electric tools on board of said mobile working machine in a second working mode.
A method for generating a power supply using a power supply system (10) according to any of the claims 1-10, characterized in that it comprises the steps of:
- activating said power supply system (10) in a first working mode with a motor-driven pump function to feed an hydraulic fluid (18) to hydraulic actuators, said electronic controller (11) driving said solenoid valve (15) so that it is enabled (ON) and powers said asynchronous electric motor (12) and controlling therefore also said hydraulic pump (13) and the hydraulic power provided on an hydraulic power output terminal (OUTid); and

- activating said power supply system (10) in a second working mode with an alternator function, capable to feed electric power to electric tools, said electronic controller (11) disabling (OFF) said solenoid valve (15) so as to block any flow of the hydraulic fluid (18) towards an hydraulic power output terminal (OUTid) connected to said solenoid valve (15), said power supply system (10) being used as a converter of hydraulic power into electric power provided on an electric power output terminal (OUTel) of said electronic controller (11), said electronic controller (11) injecting a current pulse in said asynchronous electric motor (12), particularly in the stator windings, in order to magnetize a rotor of said asynchronous electric motor (12), said initial magnetization allowing said asynchronous electric motor (12) to work as a power generator..
The method according to claim 12, characterized in that said electronic controller (11) injects said current pulse in said asynchronous electric motor (12) each time said power supply system (10) is turned on as an alternator.