Field of the art

The present invention regards a hydraulic apparatus, more in particular, a hydraulic ap paratus capable of recovering at least one part of the hydraulic energy normally dissi pated in the apparatus.

Prior art

Hydraulic apparatus designated to supply a pressurised operator fluid, typically oil, in a hydraulic device, which is suitable to use the energy of the operator fluid to move the mechanical members or perform other functions.

These hydraulic apparatus are for example present in lifting machines, in which the lift ing and lowering of the load, for example an aerial platform, is often obtained by means of a hydraulic jack which receives pressurised oil from a pump.

In order to adjust the speed with which the load is lifted, in this type of application it is normal to interpose between the delivery mouth of the pump and the inlet of the hydrau lic jack an adjustable restrictor valve, which allows to adjust, depending on the demand, the flow rate of the pressurised oil which reaches the hydraulic jack.

However, the amount of oil that does not reach the hydraulic jack is generally diverted and once again discharged into the tank, basically dissipating all the energy initially used by the pump to increase the pressure thereof.

The energy efficiency of this type of hydraulic circuits is further deteriorated by the fact that a considerable part of the energy dissipated by the restrictor valve is transformed into heat, causing a progressive increase of the oil temperature up to values that are ex tremely high at times.

Thus, cooling the oil often requires using sophisticated cooling systems which, besides complicating the hydraulic apparatus, normally comprise fans suitable to create forced air flows, with ensuing further dissipation of energy.

Description of the invention

In light of the above, an object of the present invention is to overcome or at least miti gate the aforementioned drawbacks of the prior art through a solution that is simple, ra tional and relatively inexpensive.

These and other objects are attained by the characteristics of the invention, which are outlined in the independent claim 1. The dependent claims outline preferred and/or par- ticularly advantageous aspects of the invention.

In particular, an embodiment of the present invention provides a hydraulic apparatus comprising:

- a hydraulic device,

- a pump suitable to pump an operator liquid towards the hydraulic device,

- an adjustable restrictor valve,

- a first hydraulic line suitable to connect a delivery mouth of the pump with an inlet of the restrictor valve,

- a second hydraulic line suitable to connect an outlet of the restrictor valve with the hydraulic device, and

- a hydraulic turbine,

wherein the hydraulic turbine comprises:

- an impeller,

- a plurality of blades fixed to the impeller, and

- at least one nozzle suitable to receive the operator liquid from the first hydraulic line and dispense it pressurised against the blades of the impeller.

Thanks to this solution, when the restrictor valve is actuated, for example so as to adjust the flow rate of the liquid operator which is supplied to the hydraulic device, the residual flow rate of the operator liquid coming from the pump, instead of being discharged di rectly as it occurs in the prior art, is advantageously used for driving the impeller of the turbine in rotation, without completely dissipating the hydraulic energy thereof but at least partly transforming it into mechanical energy which can be effectively utilised for other purposes, hence considerably increasing the overall energy efficiency of the appa ratus.

For example, the impeller of the turbine may be kinematically connected with an electric generator suitable to transform the mechanical energy of the impeller into electrical en ergy.

In this manner, the energy recovered from the hydraulic circuit can be advantageously used for power-supplying any electric device.

For example, should the pump be actuated by an electric motor, the electrical energy produced by the generator can be used for power-supplying the aforementioned electric motor. The electrical energy produced by the generator can also be easily stored, for example in electric accumulators, so as to be used at a later time with respect to the time of gen eration.

According to another aspect of the invention, the impeller of the turbine can be kinemat ically connected with the pump, to provide at least one part of the mechanical energy required for the operation thereof thereto.

For example, a mechanical transmission system can be provided for connecting the im peller of the turbine with a rotary actuation member of the pump, for example with the rotor of a rotary pump or with the drive shaft (e.g. a crankshaft or cam shaft) of a piston pump or a gear pump, so that the torque generated by the turbine is directly used to drive the pump.

In some embodiments, the impeller of the turbine can be kinematically connected with a fan suitable to cool the operator liquid.

Thanks to this solution, the energy recovered using the turbine can be advantageously used for reducing the temperature of the operator liquid circulating in the hydraulic ap paratus, making the cooling systems designated for this purpose superfluous or less dissipating in any case.

According to a preferred aspect of the invention, the hydraulic turbine can be a Pelton turbine.

As a matter of fact, this type of turbine has the advantage guaranteeing satisfactory per formance for quite extensive intervals of the pressure and the flow rate of the operator liquid which is dispensed by the nozzle, thus making it particularly suitable for this type of application.

According to another aspect of the invention, the nozzle may comprise:

- an outer casing defining an internal volume,

- an operative inlet obtained in the outer casing and suitable to place the internal volume in communication with the first hydraulic line,

- an outlet obtained in the outer casing and suitable to dispense the operator liquid contained in the internal volume towards the blades of the turbine,

- a shutter body received in the internal volume and moveable between a position for closing and a position for opening the outlet, and

- control means suitable to maintain the shutter body in a closing position and dis- place it to an opening position when a pressure difference astride the restrictor valve, or between the first hydraulic line and the second hydraulic line, exceeds a pre-set threshold value.

Thanks to this solution, as long as the restrictor valve is fully open, the pressure drop astride the restrictor valve is minimum and the entire operator liquid can flow towards the hydraulic device.

On the other hand, when the restrictor valve is split, for example to reduce the flow rate of the operator liquid supplied to the hydraulic device, the pressure difference astride the restrictor valve increases and the nozzle of the turbine can open, thus allowing the hydraulic liquid that does not reach the hydraulic device to be emitted in form of a jet that impacts the blades of the impeller, thus driving the latter in rotation.

Generally speaking, the control means may comprise any electric, mechanical or hy draulic system or a combination thereof, that allows carrying out the aforementioned function.

Preferably, the control means comprise at least one spring suitable to push the shutter body towards the closing position.

Thanks to this solution, it is effectively possible to maintain the shutter body at a closing position in an extremely simple manner.

Starting from this condition, a preferred aspect of the invention provides for that the dis placement of the shutter body towards the opening position can be carried out in a completely hydraulic fashion.

For example, the control means can further comprise:

- a drive inlet obtained in the outer casing of the nozzle and in communication with the second hydraulic line, and

- a plunger suitable to subdivide the internal volume of the outer casing of the noz zle into two separate chambers, including a first chamber in communication with the operative inlet and with the outlet, and a second chamber in communication with the drive inlet,

wherein the shutter body is received inside the first chamber and it is integrally fixed to the plunger.

Thanks to this solution, the plunger is subjected, on the one side, to the pressure of the first hydraulic line and, on the other side, to the pressure of the second hydraulic line. Thus, when the difference between these two pressures is minimum (restrictor valve open), the action of the spring is effectively capable of maintaining the shutter body in a closing position. Vice versa, when the pressure drop increases (restrictor valve split), the pressure of the operator liquid in the first chamber is capable of automatically dis placing the plunger, displacing the shutter body to the opening position.

However, it cannot be ruled out that, in other embodiments, the displacement of the shutter body towards the opening position can occur electromechanically, for example by means of an electric actuator (e.g. solenoid) suitable to displace the shutter body in opposition with the spring.

This electric actuator can for example be controlled by an electrical control unit, which can be connected to sensor means suitable to detect the pressure drop astride the re strictor valve and it is configured to actuate the electric actuator when the measured pressure drop exceeds a pre-set threshold value.

According to another aspect of the invention, the apparatus may comprise a tank, which is in hydraulic communication with a suctioning mouth of the pump and it is suitable to receive the operator liquid dispensed by the nozzle against the blades of the turbine. Thanks to this solution, the operator liquid which is used for actuating the turbine is ef fectively recovered and re-utilised in the hydraulic apparatus, in an extremely efficient and rational closed circuit operation.

A further aspect of the invention provides for that the hydraulic device can be a hydrau lic jack, for example a double-acting or single-acting hydraulic jack.

In particular, this hydraulic jack may belong to a lifting machine, for displacing - in verti cal direction - a mechanical member suitable to receive and sustain a load to be lifted, for example an aerial platform designated to lift goods and/or people.

As a matter of fact, in this type of application there very often arises the need to adjust the flow rate of the operator fluid supplied to the hydraulic jack, and thus there is a strong need to increase the energy efficiency of the hydraulic apparatus designated for this purpose.

However, it cannot be ruled out that, in other embodiments, the hydraulic device can be any other device that requires to be supplied by the pressurised operator fluid so as to be able to operate, such as a hydraulic motor, by way of non-limiting example. Brief description of the drawings

Further characteristics and advantages of the invention will be apparent from reading the following description - provided by way of non-limiting example - with reference to the figures illustrated in the attached drawings.

Figure 1 is a diagram of the hydraulic apparatus according to an embodiment of the present invention.

Figure 2 is an enlarged detail of figure 1 , in which the turbine is shown as a cross- section for a better illustration of the characteristics thereof.

Figures 3 to 5 show a detail of the nozzle illustrated in figure 2, in three different operat ing positions.

Detailed description

The attached figures show a hydraulic apparatus 100 designated for the actuation of a hydraulic device 105.

The hydraulic device 105 can be any device that requires to be supplied with a pressur ised operator fluid, typically oil, so as to be able to operate.

In particular, the hydraulic device 105 can be any device suitable to transform the ener gy of the operator liquid into mechanical energy, for example to cause the displacement of a mechanical member of the hydraulic device 105.

In the illustrated example, the hydraulic device 105 is a hydraulic jack which generally comprises a cylinder 1 10 and a plunger 1 15 suitable to slide inside the cylinder 1 10.

The plunger 1 15 may comprise a stem 120 which projects outside the cylinder 110 and which can be connected to any mechanical member that requires to be actuated in dis placement, exploiting the overall extension and retraction of the hydraulic jack due to the sliding of the plunger 1 15 with respect to the cylinder 1 10.

For example, the hydraulic jack can be used in a lifting machine, to vertically displace a mechanical member suitable to carry a load to be lifted, for example a luffing boom or an aerial platform for lifting people and/or goods.

In order to allow the extension and retraction of the hydraulic jack, the plunger 1 15 can subdivide the internal volume of the cylinder 1 10 into two separate chambers, including a first chamber 125 and a second chamber 130.

In this manner, by supplying the pressurised operator liquid in the first chamber 125 and by placing the second chamber 130 in communication with a discharge tank 135, it is possible to cause the extension of the hydraulic jack, whose retraction can be obtained by placing, vice versa, the first chamber 125 in communication with the discharge tank 135 and by supplying the pressurised operator liquid in the second chamber 130.

Though the illustrated hydraulic jack is a so-called double-acting hydraulic jack, it can not be ruled out that, in other embodiments, the hydraulic jack can be a simple-acting hydraulic jack, in which the pressurised operator liquid is supplied in only one of the two chambers (for example the first chamber 125) so as to cause the displacement of the plunger 1 15 in only one direction (for example in the extension direction).

In this second case, the return of the plunger 1 15 in the opposite direction (for example in the retraction direction) could be obtained, after having placed the aforementioned chamber in communication with the discharge tank 135, due to an elastic force, for ex ample by means of a spring contained in the other of the chamber of the cylinder 1 10 (for example in the second chamber 130), and/or due to an external force, for example due to the weight of a load which acts on the plunger 1 15.

Other embodiments could provide for that the hydraulic device 105 is not a hydraulic jack but it can for example be a hydraulic motor or another device.

In order to supply the operator liquid to the hydraulic device 105, the hydraulic appa ratus 100 may comprise a hydraulic pump 140.

The hydraulic pump 140 can be of any type, for example a rotary pump or a piston pump or a gear pump.

In any case, the hydraulic pump 140 generally comprises an intake mouth 145, a deliv ery mouth 150 and mechanical pumping members (e.g. an impeller or a reciprocating pump) which, actuated by the rotation of an input shaft 155, are suitable to pump the operator liquid from the intake mouth 145 to the delivery mouth 150.

The input shaft 155 may be driven in rotation by a motor 160, for example an internal combustion engine, more preferably, by an electric motor.

The intake mouth 145 of the hydraulic pump 140 is placed in hydraulic connection with a tank 165 for the storage of the operator liquid, which can coincide, or at least be in hydraulic connection, with the discharge tank 135.

The delivery mouth 150 is instead placed in hydraulic connection with the hydraulic de vice 105 to be supplied.

A restrictor valve 170, which can be actuated so as to adjust (vary) the through-flow section offered to the operator liquid which traverses it, so as to adjust (vary) the flow rate of the operator liquid that reaches the hydraulic device 105, can be interposed be tween the delivery mouth 150 and the hydraulic device 105.

Should the hydraulic device 105 be a hydraulic jack, the adjustment of the operator fluid flow rate for example allows to adjust the sliding speed of the plunger 1 15.

The restrictor valve 170 generally comprises an inlet 175, an outlet 180 and at least one splitting member (not illustrated in that per se common), which can be actuated in vari ous positions, which correspond to various dimensions of the section for the through- flow of the operator liquid which flows from the inlet 175 towards the outlet 180.

The actuation of the splitting member can be manual or automatic, for example it can be obtained by means of an electric actuator connected to a control device.

The inlet 175 of the restrictor valve 170 is connected to the delivery mouth 150 of the hydraulic pump 140 through a first hydraulic line 185, while the outlet 180 of the restric tor valve 170 is connected to the hydraulic device 105 through a second hydraulic line 190.

The expression hydraulic line is generally used to indicate a duct or a set of ducts suita ble to hydraulically connect two devices of the hydraulic apparatus 100, so that the op erator fluid can flow from one to the other.

A hydraulic line may comprise the ducts only, so that the operator liquid is always forced to flow between the two devices, or it can be provided with intermediate hydraulic com ponents, for example valves or other accessories, which can be possibly suitable to shut-off the hydraulic connection between the two devices, for example by fully or partly diverting the operator liquid, as long as there is at least one operative configuration of these components that allows the aforementioned hydraulic connection.

In light of the above, the first hydraulic line 185 may comprise a maximum pressure valve 192 suitable to divert - in the storage tank 165 - the operator fluid coming from the hydraulic pump 140, before it reaches the restrictor valve 170, when the pressure inside the first hydraulic line 185 exceeds a pre-set maximum threshold value.

The maximum pressure valve 192 may for example comprise an inlet 195 connected to the first hydraulic line 185, at an intermediate point between the delivery mouth 150 of the hydraulic line 140 and the inlet 175 of the restrictor valve 170, an outlet 200 con nected with the storage tank 165, and valve members (not illustrated in that per se common), which are moveable between a closing configuration, in which they close the hydraulic connection between the inlet 195 and the outlet 200, and an opening configu ration, in which they open said connection instead.

For example, the valve members can be maintained in closing position by a spring and they can be displaced to opening position by the pressure of the operator liquid in the first hydraulic line 185, which can act thereon in the direction opposite to the action of the spring.

In this manner, when the pressure of the operator liquid in the first hydraulic line 185 exceeds the maximum value set by the load of the spring, the valve members are au tomatically displaced to the opening position.

As regards the second hydraulic line 190, it may for example comprise a four-way hy draulic distributor 205, including a first way 210 hydraulically connected with the outlet 180 of the restrictor valve 170, a second way 215 hydraulically connected with the dis charge tank 135, a third way 220 hydraulically connected with the first chamber 125 of the hydraulic jack and a fourth way 225 hydraulically connected with the second cham ber 130 of the hydraulic jack.

The hydraulic distributor 205 may also comprise valve members that can be controlled in three operative configurations.

In a first operative configuration (obtained by ideally translating the hydraulic distributor of figure 1 to the right), the valve members can be suitable to place the first way 210 in communication with the third way 220 and the second way 215 with the fourth way 225, so as to discharge the second chamber 130 and supply the operator liquid in the first chamber 125 of the hydraulic jack, thus causing the extension thereof.

In a second operative configuration (shown in figure 1 ), the valve members can be suit able to place all ways in communication with each other, so that the first way 210, the third way 220 and the fourth way 225 are all in communication with the second way 215 and thus with the discharge tank 135.

In a third operative configuration (obtained by ideally translating the hydraulic distributor of figure 1 to the left), the valve members can be suitable to place the first way 210 in communication with the fourth way 225 and the second way 215 with the third way 220, so as to discharge the first chamber 125 and supply the operator liquid in the second chamber 130 of the hydraulic jack, causing the retraction thereof. The displacement of the valve members between these three operative configurations may be manual or automatic, for example by means of an electric actuator possibly connected to a control device.

A safety valve 230, which is suitable to limit the speed at which the plunger 1 15 is dis placed in the retraction direction, can be provided along the hydraulic duct which con nects the third way 220 of the hydraulic distributor 205 to the first chamber 125 of the hydraulic jack.

This safety valve 230 is particularly useful when the hydraulic jack is used, in the exten sion direction, to lift a load and, in the retraction direction, to lower said load.

As a mater fact, in this case the weight of the load would simultaneously tend to retract the hydraulic jack, thus the descent speed could increase uncontrollably and inde pendently with respect to the flow rate of the operator liquid supplied in the second chamber 130.

The presence of the safety valve 230 (per se known and conventional) prevents this happening.

The hydraulic apparatus 100 further comprises a hydraulic turbine 250, which is suitable to recover at least one part of the energy of the operator liquid which would be dissipat ed by the restrictor valve 170.

As illustrated in figure 2, the hydraulic turbine 250 generally comprises an impeller 255 suitable to rotate about itself around a pre-set rotation axis, a plurality of blades 260 fixed on the impeller 255, and at least one nozzle 265 suitable to receive the operator liquid from the first hydraulic line 185 and dispense it pressurised against the blades 260 of the impeller 255, so as to drive the latter in rotation.

In particular, the blades 260 can be distributed along the outer perimeter of the impeller 255, in a circumferential or radial-like manner with respect to the rotation axis of the same, and the nozzle 265 can be oriented so as to generate an operator liquid jet which, in order to impact the blades 260, is dispensed in a substantially tangential direc tion with respect to the outer perimeter of the impeller 255.

For example, the turbine 250 can be a Pelton turbine, whose distinctive feature lies in achieving good performance for a wide spectrum of pressure values and flow rate of the operator liquid which is projected against the blades 260 of the impeller 255.

The nozzle 265 can be fixed to a guard 270, which is suitable to contain the impeller 255 and it is provided with a discharge duct 275 which can be hydraulically connected with the storage tank 165 (see figure 1 ), to allow the outflow of the operator liquid after the same has been projected against the blades 260 of the impeller 255.

With particular reference to figure 3, the nozzle 265 of the turbine 250 can comprise an outer casing 280, for example shaped like a cylindrical cartridge, which delimits an in ternal volume.

An operative inlet 285, which communicates with the internal volume and is hydraulical ly connected with the first hydraulic line 185, for example with a section of the first hy draulic line 185 comprised between the delivery mouth 150 of the hydraulic pump 140 and the inlet 175 of the restrictor valve 170, preferably between the latter and the inlet 195 of the maximum pressure valve 192, if present, can be provided on the outer casing 280, for example at the lateral wall thereof.

Furthermore, the outer casing 280 is provided, for example at an axial end thereof, with an outlet 290, which is also in communication with the internal volume and it is desig nated to allow the outflow of the operator liquid coming from the operative inlet 285, dis pensing it in form of a jet which is directed towards the blades 260 of the impeller 255. Inside the outer casing 280, the nozzle 265 further comprises a shutter body 295, which is moveable, for example sliding in the direction parallel and/or coincident with the axis of the outer casing 280, between a position for closing and a position for opening the outlet 290.

In particular, when the shutter body 295 is in a closing position (see fig. 5), it fully oc cludes the outlet 290, preventing the operator liquid from flowing out.

On the contrary, when the shutter body 295 is in an opening position (see fig. 3), the outlet 290 is vacant and open, thus allowing to convey the operator liquid jet towards the external.

Between these two extreme positions, the shutter body 295 occupies partial opening positions, as illustrated in figure 4.

The displacement of the shutter body 295 between a closing position and opening posi tion can be controlled based on the pressure drop astride the restrictor valve 170, or based on the difference between the pressure of the operator liquid in the first hydraulic line 185, for example at the inlet 175, and the pressure of the operator liquid in the sec ond hydraulic line 190, preferably upstream of the hydraulic distributor 205 (if present), for example at the outlet 180 of the restrictor valve 170.

More specifically, the shutter body 295 of the nozzle 265 can be associated to control means suitable to maintain it in closing position, until the pressure drop astride the re strictor valve 170 is lower than a pre-set threshold value, and displace it from one open ing position to another, when said pressure drop exceeds said threshold value.

Strictly by way of example, the threshold value may for example be comprised between 5 and 15 bars, for example about equal to 10 bars.

The control means of the shutter body 295 can be of any type, for example electrical- mechanical, electrical-hydraulic or hydraulic-mechanical.

In the embodiment illustrated in the figures, the control means comprise a spring 300 suitable to constantly push the shutter body 295 towards the closing position and an ac tuation system suitable to overcome the force of the spring 300, causing the displace ment of the shutter body 295 towards the opening position, when the pressure drop astride the restrictor valve 170 exceeds the threshold value.

This actuation system may comprise a plunger 305, which is received in the outer cas ing 280 of the nozzle 265, where it can slide for example in the direction parallel and/or coincident with the longitudinal axis of the outer casing 280.

This plunger 30 is suitable to subdivide the internal volume of the outer casing 280 into two distinct and separate chambers, possibly by interposing suitable sealing elements, including a first chamber 310 and a second chamber 315.

Both the operative inlet 285 and the outlet 290 of the operator liquid terminate in the first chamber 310.

Terminating in the second chamber 315 is a driving inlet 320, which is in hydraulic con nection with the second hydraulic line 190, preferably with a section of the second hy draulic line arranged upstream of the hydraulic distributor 205 (if present), for example at the outlet 180 of the restrictor valve 170.

The driving inlet 320 can be very small do as to smoothen the opening and the closing of the nozzle 265.

The shutter body 295 is received in the first chamber 310 and it is rigidly fixed to the plunger 305, for example by means of a rigid connection rod.

The shutter body 295, the plunger 305 and the possible rigid connection rod can be made of a single body. The spring 300 is contained in the second chamber 315 or in a position such to push the plunger 305 in the direction of reducing the volume of the first chamber 310 and, thus, so as to press the shutter body 295 against the outlet 290 of the nozzle 265.

Thanks to this solution, as long as the pressure difference between the first and the second chamber 310 and 315, which corresponds to the pressure drop astride the re strictor valve 170, is insufficient to overcome the force of the spring 300, the shutter body 295 remains in closing position.

On the contrary, when the aforementioned pressure difference generates - on the plunger 305 - a force exceeding that of the spring 300, the shutter body 295 is automat ically displaced to the opening position.

This allows to obtain an automatic actuation of the nozzle 265, strictly in a hydraulic- mechanical manner, in which the threshold value of the pressure drop which causes the opening of the shutter body 295 is determined by the load (possibly adjustable) exerted by the spring 300.

However, it cannot be ruled out that, in other embodiments, the displacement of the plunger 305 can be obtained by means of an electric actuator, for example by means of a solenoid actuator suitable to be electrically supplied to selectively generate an elec tromotive force suitable to overcome the force of the spring 300.

Such solenoid actuator could be controlled by an electronic control unit connected to one or more sensors suitable to detect a pressure drop astride the restrictor valve 170, and configured so as to supply the solenoid actuator only when such pressure drop ex ceeds the pre-set threshold value.

In any case, the operation of the hydraulic apparatus 100 can be summarised in detail as follows.

When the hydraulic pump 140 is running, the operator liquid is drawn from the storage tank 165 and delivered pressurised to the hydraulic device 105, flowing through the re strictor valve 170.

If the restrictor valve 170 is fully open, the pressure drop astride it is zero, or at least minimum, and thus insufficient to open the nozzle 265.

Thus, entirety of the operator liquid pumped by the hydraulic pump 140 flows towards the hydraulic device 105.

When the restrictor valve 170 is split, for example so as to reduce the flow rate of the operator fluid that is supplied to the hydraulic device 105, the pressure drop astride the restrictor valve 170 increases up to causing the automatic opening of the nozzle 265.

In this manner, the portion of the operator liquid that does not reach the hydraulic device is dispensed by the nozzle 265 in form of a high-pressure jet which impacts the blades 260 of the turbine 250, thus driving the impeller 255 in rotation and thus transforming the hydraulic energy of the operator liquid into mechanical energy.

This recovered mechanical energy can be used for several different purposes.

For example, in the embodiment illustrated in the figures, the impeller 255 of the turbine 250 can be kinematically connected with the hydraulic pump 140, so as to provide a part of the mechanical energy required for the operation thereof thereto.

In particular, by means of a suitable mechanical transmission system 350, the impeller 255 can be kinematically connected with the input shaft 155 of the hydraulic pump 140, so as to be able to transfer the mechanical torque directly from one to the other.

This kinematic connection may be configured so as to act on the input shaft 155 in se ries on the motor 160, so that both the motor 160 and the turbine 250 can contribute (preferably simultaneously) to the action of the hydraulic pump 140.

Preferably, the mechanical transmission system 350 may comprise at least one free wheel suitable to transfer torque from the rotor 255 of the turbine 250 to the input shaft 155 of the hydraulic pump 140 but being idle in the opposite direction.

In this manner, the torque generated by the motor 160 cannot be transferred to the im peller 255 but to the hydraulic pump 140 only.

In other embodiments, the impeller 255 of the turbine 250 could be kinematically con nected, for example by means of a suitable mechanical transmission system, with an electric generator (not shown) suitable to transform the mechanical energy of the rotor 255 into electrical energy.

The electrical energy thus produced could be immediately used for supplying any elec tric device connected with the generator, for example but not exclusively the motor 160 (if electric) which actuates the hydraulic pump 140.

Additionally, or alternatively, the electrical energy produced by the generator could be stored, for example in special electric accumulators (batteries) connected with the gen erator, so as to be used subsequently for these or for other purposes.

In further embodiments, the impeller 255 of the turbine 250 could be kinematically con- nected with at least one fan suitable to cool the operator liquid, for example the operator liquid contained in the storage tank 165.

Basically, the rotation of the impeller 255 could be transferred to the aforementioned fan, which would thus be capable of generating a forced airflow which, touching the out er surfaces of the storage tank 165, or of any other device in which the operator liquid flows through (for example any duct or possible suitable heat exchanger provided in the hydraulic apparatus 100), would allow to effectively dissipate the heat accumulated by the operator liquid.

In conclusion, it should be observed that, though in the illustrated example the restrictor valve 170 and the hydraulic distributor 205 are separate, in some embodiments, the re strictor valve 170 could be directly integrated in the hydraulic distributor 205.

In other words, the hydraulic distributor 205 could be configured so that it can, by means of the controlled displacement thereof, split the flow rate of the operator liquid di rected towards the hydraulic distributor 105, also serving as a restrictor valve.

Obviously, in this case the pressure drop that controls the shutter body 295 would be the one stride the hydraulic distributor 205 (the expression astride being used to indi cate before and after the distributor 205).

Obviously, the hydraulic apparatus 100 described above, may be subjected - by a man skilled in the art - to numerous technical/application modifications, without departing from the scope of protection of the invention as claimed below.