DESCRIPTION

The present invention relates to a kit for the conversion of a heavy equipment vehicle and a heavy equipment vehicle comprising this conversion kit. In particular, the kit is suitable for converting a conventional heavy equipment vehicle operated by a diesel motor into an electrically operated heavy equipment vehicle.

The following discussion will consider specifically the example of a vehicle for moving materials, or material handler. This example has no limiting intent and the expert will have no difficulty in applying the teachings of the invention to other similar vehicles such as, for example, an excavator. The invention can also be adapted to other heavy equipment vehicles such as, for example, excavators, mobile cranes, forklifts, dumpers, loaders, overhead cranes, trucks, road tractors and the like.

A material handler of a known type is described below with reference to the attached Figure 1. The material handler comprises a main diesel motor that feeds a hydraulic circuit for distributing power to several users. This configuration (usually known as diesel-hydraulic) takes advantage of the great versatility of hydraulic systems and of the high power density they can transmit. In the context of this disclosure, the terms "hydraulic" and "oleodynamic" are considered synonymous.

In a manner known per se, the diesel motor operates one or more hydraulic pumps which pressurize a distribution circuit, which in turn feeds the actuators and ensures the return of the oil to the tank. The management of oil flows to the various actuators is obtained by means of appropriate commands (distributors) manually moved by the levers held by the operator.

The actuators provided on board, which can be linear or rotary, are usually those intended for: the movement of the first arm (or boom), the movement of the second arm (or stick), the rotation of the orange peel grapple, the opening/closing of the orange peel grapple, the rotation of the upper part (or house), the rotation of the wheels for the translation of the entire vehicle, the operation of the steering, the operation of the brakes, the movement of the stabilizers, the adjustment of the cabin, etc.

In other similar heavy equipment vehicles, a different end effector may be provided instead of the orange peel grapple. Among the known devices there are simple ones, which require only one power supply line, and articulated or mobile ones, which instead require two power supply lines intended for two different movements, like the orange peel grapple mentioned above. Some simple end effectors are for example: bucket, ripper, multi-ripper, electromagnet, etc. Some articulated or mobile end effectors are, for example: clamshell bucket, screening bucket, bucket with clamps, shredder bucket, multi-function clamp, demolition hammer, shear, road milling vehicle, shredder, auger, deforestation clamp, grass trimmer, brush cutter, hedge trimmer, circular saw, and the like.

Moreover, for the purpose of moving the entire heavy equipment vehicle, it is possible to provide rubber tyred wheels (as in the examples shown in the attached figures 1 , 4 and 5) or tracks, driven by toothed metal wheels. In one case as in the other, reference will therefore be made to the actuation of wheels, meaning either the rubber tyred wheels or the toothed wheels, depending on the specific case.

The heavy equipment vehicle according to the invention may comprise any combination of the above described features.

Each of these actuators has operating characteristics that require an oil supply within a given design range, a range defined in terms of volume flow rate and of pressure. In other words, each of the actuators will be characterized by different operating regimes in the different operating phases of the material handler. For example, in certain situations, some actuators may have an operating regime characterized by high flow rates and low pressures, while other actuators may have an operating regime characterized by small flow rates and high pressures.

The total power absorbed by the hydraulic circuit is given, instant by instant, by the product of the overall flow rate and the pressure exerted. Since many users are often used simultaneously in common practice, the correct sizing of the main diesel motor must take into account the maximum flow rate and maximum pressure that may be required simultaneously.

As the skilled person may well understand, the fact that the sizing of the main motor is based on the worst case, i.e. maximum power demand, means that in most of the actual operating situations it will result oversized. As is known, the power delivered by the diesel motor can be adjusted within certain terms by varying the fuel supply and the motor revolutions. However, this variability only partially compensates for the excess of installed power. Furthermore, the pressure generated in the hydraulic circuit instant by instant must be adequate to the request of the actuator which at that moment requires the maximum pressure. From this it follows that a pressure reduction is needed for all the other actuators. Pressure reduction is achieved with special throttling pressure regulators within which pressure is reduced, dissipating in fact a portion of the input power. Apart from the limitation of the power supplied by the motor and from the reduction of pressure along the power supply lines of the single actuators, it is also possible that, in some operating situations of the vehicle, the sum of the powers required by all the users is zero or minimum. In such case, it would theoretically be possible to switch off the diesel motor while waiting for a different operating condition that requires power to be supplied again. In practice, the main motor is almost never turned off, except while facing real suspensions of vehicle operation. This is due to the fact that the on and off cycles of the main motor with consequent initialization of the hydraulic circuit require energy and time. Furthermore, the continuous repetition of on and off cycles has great influence on motor wear and therefore on its reliability. In the event wherein there is an excess of hydraulic power generated by the main motor, the pressurized oil is simply discharged through a return circuit which returns it to the tank.

This solution, although widely spread and appreciated, is not without drawbacks.

A first series of drawbacks is directly connected to the use of an internal combustion motor such as the diesel motor. It is known that internal combustion motors are noisy and generate harmful emissions. All this negatively affects user comfort, increasing fatigue, and requires precautions in prolonged use to prevent adverse effects on health. Furthermore, unless providing expensive and complex technical countermeasures, harmful emissions jeopardize the possibility of using the heavy equipment vehicle in closed environments such as industrial sheds, mines or tunnels.

There are also other drawbacks linked to the overall efficiency of the diesel-hydraulic system. The typical thermodynamic productivity of a diesel motor is known, and amounted to about 30%. With regard to the oleodynamic portion of the system, given the high power density, it suffers from a low overall efficiency that can be considered as less than 40% due to the considerations made above about the dissipation of unnecessary overpressures. The complex of the diesel motor and of the hydraulic distribution circuit has therefore an overall efficiency which is indicatively of 12%.

Moreover, as already reported above, it often happens that along a line it is necessary to reduce the supply pressure of an actuator, a reduction which is equivalent to the dissipation of a part of power that is transformed into heat and dispersed. Furthermore, the power supply of the circuit against a minimum or zero power requirement by the actuators is equivalent to the dispersion of all the power made available by the diesel motor and which is not immediately used.

All the phenomena described above, from the operation of the diesel motor to the various voluntary or involuntary dissipations taking place along the hydraulic circuit, involve the generation of large quantities of heat that must be dispersed in the surrounding environment. This implies the need to prepare special cooling fans that operate constantly during vehicle operation. In addition to constituting a further comfort problem, typically when the vehicle operates in hot environments, heat dispersion represents a further dispersion of power, via the operation of the fans.

The increasingly felt need to limit the use of fossil fuels has led some manufacturers to offer heavy equipment vehicles wherein the diesel motor is replaced by an equivalent electric motor. These vehicles therefore maintain the known architecture, with the only difference that the power required to feed the same hydraulic system is generated by an electric motor instead of a diesel motor. In this case, an electro-hydraulic configuration is thus obtained.

This type of vehicle represents only a partial solution to the problems listed above. Certainly, the electrical power supply resolves the problem of harmful emissions and noise, allowing the use of electro-hydraulic vehicles in closed environments in complete safety. However, the problems connected with the oversizing of the main motor, which continues to be necessary, and the low efficiency of the hydraulic system are still completely unresolved.

The low efficiency of these electro-hydraulic vehicles entails the need to supply them with large amounts of electric power. In the current state of the art, similar amounts of energy can be guaranteed for an adequate period of time only by connecting the vehicle to the distribution network. The use of batteries would imply a decisively insufficient autonomy for the usual employment of a heavy equipment vehicle. However, as the skilled person may well understand, the presence of the power cable strongly limits the possibilities of use of this type of vehicle.

Therefore, the object of the present invention is to overcome the drawbacks underlined before with respect to the prior art.

More specifically, it is a task of the present invention to provide a kit for converting or retrofit a heavy equipment vehicle. Another object of the present invention is to provide a kit for the reversible conversion of a heavy equipment vehicle.

Another object of the present invention is to provide a kit that allows to obtain a heavy equipment vehicle with adequate autonomy even without the use of a power cable.

This object and these tasks are achieved by means of a kit according to claim 1 , and by means of a heavy equipment vehicle according to claim 7. In order to better understand the invention and appreciate its advantages, some of its exemplifying and non-limiting embodiments are described below with reference to the accompanying drawings, wherein:

- Figure 1 shows a heavy equipment vehicle suitable to be converted by means of the kit according to the invention;

- Figure 2 shows the diagram of an embodiment of the kit according to the invention;

- Figure 3 shows the diagram of another embodiment of the kit according to the invention;

- Figure 4 shows a perspective view of a heavy equipment vehicle according to the invention, from which the end effector has been removed;

- Figure 5 shows a side view of the heavy equipment vehicle of Figure 4; and

- Figure 6 shows a partial view of the heavy equipment vehicle of Figure 4, along the direction VI of Figure 5.

The invention relates to a kit 10 for the conversion of a heavy equipment vehicle 12 from a diesel-hydraulic configuration to an electro-hydraulic configuration. The kit 10 comprises:

- an electric power supply unit 14;

- a plurality of electric motors 16;

- a control interface unit 18; and

- a control unit 20.

In the kit 10 according to the invention:

- the electric power supply unit 14 is suitable for: - being connected to an external energy source 22,

- receiving energy from the external source 22,

- accumulating a quantity of energy, and

- after being disconnected from the external energy source 22, supplying electric power to at least some of the electric motors 16;

- at least one of said electric motors 16 is mechanically coupled to a hydraulic pump 24;

- at least one of said electric motors 16 is mechanically coupled to a mechanical gear 26;

- at least one of said electric motors 16 is mechanically coupled to a cooling fan 28;

- the control interface unit 18 is suitable to be handled by an operator and to generate electric signals relating to the selective operation of some electric motors 16; and

- the control unit 20 is suitable for selectively operating some electric motors 16 on the base of the electric signals received from the control interface unit 18 and on the base of a pre-loaded logic.

The above described kit 10 is intended for the conversion of a heavy equipment vehicle 12, of a type known per se, from its original diesel- hydraulic configuration to an electro-hydraulic configuration.

In other words, the kit 10 according to the invention is suitable for replacing part of the systems originally provided by the manufacturer on board of the heavy equipment vehicle 12. The systems that are removed from the heavy equipment vehicle 12 are the main diesel motor, the main fuel tank and the related supply system of fuel to the motor, the hydraulic circuit of the joystick control interface unit, some of the hydraulic motors and the cooling fan. Preferably, the kit 10 according to the invention is made in such a manner that the replacement of the original components of the heavy equipment vehicle 12 can be a reversible operation, which does not require structural modifications of the heavy equipment vehicle 12 itself. In this way, if the need arises, the components of the kit 10 according to the invention can be removed from the heavy equipment vehicle 12 and the vehicle itself can be converted back to its original diesel-hydraulic configuration.

The electric power supply unit 14 can comprise a pack of accumulators, or batteries, which can be for example of the Lithium-ion (Li-Ion) type or of the Lead-acid type. Lithium-ion batteries have some advantages in terms of autonomy, number of charging cycles and weight. On the other hand, Lead-acid batteries have the undeniable advantage of requiring a decisively lower initial investment.

In addition or alternatively to the batteries, the electric power supply unit 14 can also comprise a fuel cells assembly and a fuel storage system intended to supply the same cells. In a manner known per se, fuel cells have, with respect to batteries, the great advantage of being able to be supplied almost instantaneously, through the input of a mass of fuel, rather than requiring long periods of connection to the electric power network.

Of course, depending on the type of electric power supply unit 14, the ways in which the latter is connected to the external energy source 22, as well as the type of energy itself, will vary. In the case of batteries, whether Lithium-ion or Lead-acid, the external source of energy 22 will be an electric power distribution network and the connection will be made using appropriate charging cables. On the contrary, in the case of fuel cells, the external energy source 22 will be a reserve of fuel suitable for feeding the cell, such as hydrogen, methanol or the like, and the connection will take place through specific supply ducts.

Regardless of its specific nature, with the connection to the external energy source 22 the electric power supply unit 14 stores an amount of energy which will then be used to power the on-board systems. In particular, the energy will power at least some of the electric motors 16 of the kit 10.

As already stated above, the kit 10 comprises a plurality of electric motors 16. At least one of these electric motors 16 (indicated with Mh in Figure 2) is mechanically coupled to a hydraulic pump 24, forming a motor-pump assembly. This motor-pump assembly is designed to power at least part of the original hydraulic system of the heavy equipment vehicle 12. This portion of the hydraulic system can be maintained as it is, since once the electric motor 16 and the hydraulic pump 24 have been correctly sized, the supply of oil under pressure to the system is absolutely indistinguishable from the one obtained in the original diesel-hydraulic configuration.

Preferably, the kit 10 comprises a plurality of electric motors 16 mechanically coupled to respective hydraulic pumps 24. This allows to section the original hydraulic system in some separate and independent branches and to power each branch with a specific motor-pump assembly. For example, in one embodiment thereof, the kit 10 according to the invention comprises four electric motors 16 (indicated with Mh1 , Mh2, Mh3 and Mh4 in Figure 3) mechanically coupled to respective hydraulic pumps 24. According to this embodiment:

- a first motor-pump assembly (Mh1 ) is intended to power a branch of the original hydraulic circuit comprising the actuators of the first arm 40 (or boom), of a first movement of the end effector 44 (for example the rotation of the orange peel grapple), of the steering and of the stabilizers 46;

- a second motor-pump assembly (Mh2) is intended to power a branch of the original hydraulic circuit comprising the actuators of the second arm 42 (or stick), and of a second movement of the end effector 44 (e.g., the opening/closing of the orange peel grapple);

- a third motor-pump assembly (Mh3) is intended to power a branch of the original hydraulic circuit comprising the actuators of the adjustment of the cabin 48 and of the brakes; and

- a fourth motor-pump assembly (Mh4) is intended to power a hydraulic circuit comprising the motors for moving the heavy equipment vehicle 12. With respect to the fourth motor-pump assembly and to the hydraulic circuit thereof, the following should be noted. The original hydraulic circuit of the heavy equipment vehicle 12 is an open circuit. In this type of circuit, the pump supplies the oil flow rate necessary to feed the actuator in the working direction. The oil is pushed under pressure along a pressure line and, once it has performed its work in the actuator, it is discharged into a return line at atmospheric pressure. In this way the oil returns to the tank and is again available to feed the pressure line. This hydraulic system layout is not very efficient.

In some embodiments of the invention, at least the fourth electric motor 16 mechanically coupled to a hydraulic pump 24 powers a closed hydrostatic hydraulic circuit. In this type of circuit, on the opposite, both the pressure line and the return line are kept under pressure by the pump. This hydraulic system layout is much more efficient than the one described above.

In accordance with an embodiment of the invention, the fourth motor-pump assembly is intended to power the closed hydraulic circuit which drives the wheels 30 to translate the heavy equipment vehicle 12.

At least one of the electric motors 16 (indicated with Mm in Figure 2) is mechanically coupled to a mechanical gear 26, forming a motor- transmission assembly. This motor-transmission assembly is intended to replace an original hydraulic actuator 32 of the heavy equipment vehicle 12. Once the electric motor 16 and the mechanical gear have been correctly sized, the behaviour of the motor-transmission assembly is completely indistinguishable from that of the original hydraulic actuator 32. Preferably, the kit 10 comprises a plurality of electric motors 16 mechanically coupled to respective mechanical gears 26.

For example, in one embodiment thereof, the kit 10 according to the invention comprises two electric motors 16 (indicated with Mm1 and Mm2 in Figure 3) mechanically coupled to respective mechanical gears 26. According to this embodiment, the two motor-transmission assemblies are designed to rotate the upper part with respect to the base 36 (or undercarriage) of the heavy equipment vehicle 12. As already mentioned, there is then at least one electric motor 16 (indicated with Me in Figures 2 and 3) mechanically coupled with a cooling fan 28.

Each of the electric motors 16 forming part of the kit 10 according to the invention allows, once installed on the heavy equipment vehicle 12, to increase the overall efficiency of the system. In fact, unlike the diesel motor, the electric motor 16 can be switched off even during short periods of inactivity and can be controlled to adjust the power generated based on actual instantaneous needs. In this way it is possible to avoid producing excess power which must then be dissipated in the form of heat. The lack of all this amount of heat to be dissipated also makes it possible to significantly reduce the power used to drive the cooling fan 28.

As already mentioned above, the kit 10 according to the invention also comprises the control interface unit 18 suitable for generating electric signals relating to the selective operation of some electric motors 16. Preferably such control interface unit is of the joystick type. Joystick commands of known type are hydraulically operated. In this type of command, by moving the joystick, the operator moves one or more hydraulic distributors that are part of the hydraulic circuit. In other words, the action of the operator on the joystick mechanically determines the displacement of a spool of a distributor which in turn determines the supply of oil under pressure to one pressure line instead of another. This configuration of the joystick control is widespread and appreciated, but it is not without its drawbacks. The hydraulic joystick control requires that all the lines to be controlled must have a more or less important deviation that passes from the cabin 48. This involves a considerable complication in the design of the heavy equipment vehicle 12. Furthermore, the same displacement of the distributor spools requires considerable effort on the joystick and/or a further complication for servo-assisted actuation. Finally, due to the high energy losses typical of hydraulic circuits, the power supply of the hydraulic joystick control itself causes a considerable inefficiency of the system. In fact, the adjustment of the oil supply obtained by means of the conventional spool distributor implies a throttling with consequent dispersion of energy in the form of heat.

The kit 10 according to the invention, on the other hand, comprises an control interface unit 18 having electric operation, advantageously of the joystick type. In this type of commands, the control interface unit 18 simply moves one or more potentiometers, which in turn directly drive the electric motors 16 which, as described above, can be connected to a mechanical gear 26 or to and hydraulic pump 24. In this second case, the motors power the respective branch of the hydraulic circuit, which can preferably comprise an on/off valve, which is also controlled by the same control interface unit 18. In other words, the control of the operation of the electric motor 16 allows, also due to the control unit 20 (whose operation is described in detail later on), to generate instant by instant the exact amount of hydraulic power which is required. In this configuration there is therefore no need to disperse energy by throttling the oil flow and this allows to considerably increase the efficiency of the system. Furthermore, the operator's action on the joystick is mechanically decoupled from the hydraulic system. From this it follows that the driving of the electrical joystick is extremely easy and does not tire the operator. Finally, the connection of the control interface unit 18 occurs by means of electric cables which are much easier to be installed on board the heavy equipment vehicle 12.

In accordance with the kit 10 according to the invention, the control interface unit 18 generates electric signals relating to the selective operation of some electric motors 16, but these electric signals are not transmitted directly to the electric motors 16. On the contrary, the electric signals are sent to the control unit 20, which in turn selectively drives some electric motors 16 on the base of the electric signals received from the control interface unit 18 and on the base of a pre-loaded logic. The pre- loaded logic allows to optimally manage the driving of the electric motors 16, in such a way as to ensure - for example - that no driving comes out of the operating range of the heavy equipment vehicle 12. For example, for each electric motor 16, optimum operating characteristic curves can be predefined. Each motor can be controlled in speed, force or a linear combination of the two (power).

In accordance with some embodiments, the pre-loaded logic in the control unit 20 can also provide different possible operating modes, which can be selected from time to time by the operator based on specific needs.

The intervention of the control unit 20 can also allow to eliminate or limit some peaks of energy demand by the operator. Such peaks, in fact, by approximating or exceeding the maximum availability of instantaneous energy supply by the electric power supply unit 14, can constitute a problem and imply a drastic reduction of the autonomy of the heavy equipment vehicle 12. The control unit 20 can instead recognize the situations wherein these peaks are not really necessary and can therefore distribute over time some drives that the operator had requested simultaneously.

In accordance with another aspect thereof, the invention relates to a heavy equipment vehicle 12. The heavy equipment vehicle 12 according to the invention comprises:

- a base 36 equipped with wheels 30 to support the heavy equipment vehicle 12 and comprising a hydraulic actuator 32 adapted to rotate the wheels 30 for translating the heavy equipment vehicle 12;

- an upper part 34 mounted in swivel manner on the base 36;

- a first arm 40 mounted on the upper part 34, hinged with respect to it and comprising a hydraulic actuator 32 suitable for moving the first arm 40 with respect to the upper part 34;

- a second arm 42 mounted on the first arm 40, hinged with respect to it and comprising a hydraulic actuator 32 adapted to move the second arm 42 with respect to the first arm 40; and

- an end effector 44 mounted on the second arm 42, movable with respect to it and comprising a hydraulic actuator 32 suitable for moving the end effector 44 with respect to the second arm 42.

The vehicle 12 according to the invention further comprises:

- an electric power supply unit 14;

- a plurality of electric motors 16;

- a control interface unit 18; and

- a control unit 20.

wherein

- the electric power supply unit (14) is suitable for:

- being connected to an external energy source 22,

- receiving energy from the external source 22,

- accumulating a quantity of energy, and

- after being disconnected from the external energy source 22, supplying electric power to at least some of the electric motors 16;

- at least one of said electric motors 16 is mechanically coupled to a hydraulic pump 24 connected to at least one of said hydraulic actuators 32;

- at least one of said electric motors 16 is mechanically coupled to a mechanical gear 26 and is suitable for rotating the upper part 34 with respect to the base 36;

- at least one of said electric motors 16 is mechanically coupled to a cooling fan 28;

- the control interface unit 18 is suitable to be handled by an operator and to generate electric signals relating to the selective operation of some electric motors 16; and

- the control unit 20 is suitable for selectively operating some electric motors 16 on the base of the electric signals received from the control interface unit 18 and on the base of a pre-loaded logic.

As the skilled person can well understand, then the heavy equipment vehicle 12 according to the invention derives from a known heavy equipment vehicle 12, marketed in the traditional diesel-hydraulic configuration. In order to obtain the heavy equipment vehicle 12 according to the invention, some components are removed from the known vehicle including the main diesel motor, the main tank and the relative system to supply fuel to the motor. Some hydraulic actuators, the oleodynamic joystick control unit and the cooling fan with the relative hydraulic actuator are also removed. The kit 10 according to the invention described above is then installed on the heavy equipment vehicle 12.

In the light of the above description, it will be clear to the skilled person how the present invention overcomes at least in part the drawbacks highlighted in relation to the prior art.

In particular, it will be clear to the skilled person how the kit 10 and the heavy equipment vehicle 12 according to the invention allow to eliminate many inefficiencies of the heavy equipment vehicles 12 of the known type, for example:

- replacing the diesel motor with some electric motors 16 that are more efficient and that can be activated and deactivated as needed;

- replacing some hydraulic actuators 32 with as many electric motors 16, which are more efficient;

- converting the joystick control interface unit 18 from hydraulic to electric;

- sectioning the hydraulic system in some independent branches in order to optimize the use of the electric motors 16;

- replacing in some sections the original open hydraulic system with a more efficient hydrostatic closed hydraulic system;

- introducing a control unit 20 which optimizes the operation of the electric motors 16 on the base of a pre-loaded logic.

A much greater energy efficiency is thus obtained with respect to the prior art allowing, for the same energy used, to provide on-board a smaller amount of energy than that required by vehicles of the known type. Thanks to this reduction in the energy required, the autonomy of the heavy equipment vehicle 12 can be ensured by an electric power supply unit 14 of the type described above, without the use of a power cable. Moreover, the present invention makes available a kit 10 for the conversion or retrofit of a heavy equipment vehicle 12. If necessary, this conversion can also be reversible.

It is clear that the specific features are described in relation to various embodiments of the invention with exemplifying and non-limiting intent. Obviously, an expert in the art may make further modifications and variations to this invention, in order to meet contingent and specific requirements. For example, the technical features described in connection with an embodiment of the invention may be extrapolated from it and applied to other embodiments of the invention. Such modifications and variations are, however, contained within the scope of the invention, as defined by the following claims.