Patent Description:
The present invention finds its preferred, although not exclusive, application in earth-moving vehicle provided with a boom such as a scraper.

Work vehicles such as scrapers, i.e. vehicles provided with a hydraulic actuated boom, may be provided with so-called energy recovery systems.

Energy recovery systems are configured to reduce the energy consumption during the movement of a boom that is controlled via a hydraulic actuator. Indeed, when the boom is controlled to be lowered, the fluid discharged by hydraulic actuator is stored to be used then the boom is controlled to be lifted.

Such systems foresees the presence of accumulators to allow the storing of the fluid discharged by the actuator and a control block configured to manage the fluid flow between the accumulators, the tank and the actuator as shown in <CIT> and <CIT>.

However, if a vehicle is provided with such energy recovery system it is currently impossible to avoid its use. Accordingly, it is not possible, for instance, making boom cylinders to be discharged as in standard operation.

Therefore, the need is felt to allow the use of the energy recovery system only when needed by the typology of work executed by the work vehicle.

An aim of the present invention is to satisfy the above mentioned needs.

The aforementioned aim is reached by a hydraulic arrangement and a work vehicle as claimed in the appended set of claims.

<FIG> and <FIG> discloses a hydraulic arrangement <NUM> according to the invention for a work vehicle (not shown) comprising a boom assembly provided with an operational element such as a scraper.

Accordingly, the work vehicle may comprise an arm and an operational element that are controlled by respective hydraulic cylinders <NUM>, <NUM> that will be not further described for sake of brevity.

The work vehicle advantageously comprises a pair of boom cylinders <NUM>, <NUM>, namely a right cylinder <NUM> and a left cylinder <NUM> configured, together, to lift or lower the boom according to the vehicle operation.

As shown in the exemplarily drawings, the cylinders <NUM>, <NUM> comprise a housing 4a, 5a housing a sliding piston 4b, 5b in a tight manner thereby dividing the space defined by the housing into a piston chamber <NUM>', <NUM>' and a rod chamber <NUM>", <NUM>". Preferably, cylinders <NUM>, <NUM> are double actuated cylinders i.e. the piston and rod chambers <NUM>', <NUM>', <NUM>", <NUM>" are respectively fluidly connected to a source of fluid in pressure to control the operation of the cylinders <NUM>, <NUM>.

The vehicle comprises an energy recovery system <NUM> comprising a pair of support cylinder <NUM>, <NUM>, i.e. a right support cylinder <NUM> and a left support cylinder <NUM>. The left and right support cylinders <NUM>, <NUM> are mechanically connected to, respectively, right and left cylinders <NUM>, <NUM> as shown in the following.

In detail, left and right support cylinders <NUM>, <NUM> are preferably single acting cylinders therefore comprising a housing 8a, 9a that accommodates a piston 8b, 9b sliding in tight manner so as to divide the housing space into a piston chamber <NUM>', <NUM>' and a rod chamber <NUM>", <NUM>".

Advantageously, the pistons 8b, 9b of left and right support cylinders <NUM>, <NUM> are respectively connected to pistons 4b, 5b of the left and right cylinders <NUM>, <NUM> via a mechanical link <NUM>, schematized by a line in the figures, that may be realized of any typology provided that the movement of one of pistons 8b, 9b is transferred to the other pistons 4b, 5b and vice versa.

The energy recovery system <NUM> further comprises at least an accumulator <NUM>, in the disclosed example three accumulators <NUM>, that are fluidly connectable the left and right support cylinders <NUM>, <NUM> via the hydraulic arrangement <NUM>.

Hydraulic arrangement <NUM> is fluidly interposed between accumulators <NUM> and support cylinders <NUM>, <NUM> in order to manage their operation. In particular, hydraulic arrangement <NUM> comprises a feeding conduit <NUM> that is fluidly connectable between the accumulators <NUM> and left and right support cylinders <NUM>, <NUM>.

Furthermore, hydraulic arrangement <NUM> comprises a balancing conduit <NUM> configured to fluidly connect together support cylinders <NUM>, <NUM>; in particular the balancing conduit <NUM> is fluidly connectable to the feeding conduit <NUM> from one side and, on the opposite side, comprises two branches <NUM>', <NUM>'' both fluidly connected to a respective piston chamber <NUM>', <NUM>' of the cylinders <NUM>, <NUM>.

The hydraulic arrangement <NUM> further comprises a filling module <NUM> configured to manage the filling of accumulators <NUM>, when needed.

Accordingly, the filling module <NUM> comprises pump means <NUM> preferably carried by a torque source <NUM> such as an electric motor. The pump means <NUM> are fluidly connected by a conduit <NUM> to a tank <NUM> and are configured to suck fluid from the tank and push this latter, in pressure, towards the accumulators <NUM>.

The pump means <NUM> are fluidly connected to accumulators via a conduit <NUM>. Preferably, the hydraulic arrangement <NUM> comprises valve means <NUM> configured to regulate the flow passage between the pump means <NUM> and the accumulators <NUM>.

In detail, the pump means may comprise a four ways proportional valve, preferably electro actuated, configured to allow the passage of fluid between a first configuration from pump means <NUM> towards accumulators <NUM> or a second opposite configuration, as better detailed hereinafter.

The actuation is preferably given by a control signal S<NUM> that, in the disclosed embodiment is an electronic signal coming from a control unit.

The hydraulic arrangement <NUM> further preferably comprises a relief valve <NUM> fluidly interposed on a conduit <NUM> that is fluidly connected between tank <NUM> and conduit <NUM>.

Preferably, hydraulic arrangement <NUM> comprises filtering means <NUM> fluidly interposed on conduit <NUM> downstream to relief valve <NUM> and upstream to tank <NUM>.

The hydraulic arrangement <NUM> further preferably comprises a relief valve <NUM> fluidly interposed on a conduit <NUM> that is fluidly connected between conduit <NUM>, downstream to valve means <NUM>, and conduit <NUM> downstream to relief valve <NUM> and, preferably, upstream to filtering means <NUM>.

Between the relief valve <NUM>, accumulators <NUM> and the valve means <NUM> it may be provided a check valve piloted to regulate the pressure or to discharge pressure of accumulator <NUM> portion circuit.

According to the invention, the hydraulic arrangement <NUM> comprises a selection module <NUM> configured to partition the fluid passage between accumulators <NUM>, support cylinders <NUM>, <NUM> and tank <NUM> according to a user's request.

In particular, the selection module <NUM> comprises valve means <NUM> configured to regulate the fluid passage between tank <NUM> and support cylinders <NUM>, <NUM>.

Preferably, valve means <NUM> comprises a three ways proportional valve configured to allow the passage of fluid between a first configuration between accumulators <NUM> and support cylinders <NUM>, <NUM> or a second opposite configuration between support cylinders <NUM>, <NUM> and tank.

The selection module <NUM> further comprises a pair of check valves <NUM>, <NUM> that are fluidly interposed on respective conduits <NUM>, <NUM> that are both fluidly connected to tank <NUM>, from one side and to valve means <NUM> on the opposite, in particular fluidly in parallel one with respect to the other.

In particular the two check valves <NUM>, <NUM> are configured to allow the passage of fluid into two different opposite fluid directions.

Preferably, conduits <NUM>, <NUM> are fluidly joint into a single conduit <NUM> towards valve means <NUM>.

According to the embodiment of <FIG>, the conduits <NUM>, <NUM> are both fluidly connected to tank <NUM> in two different points X<NUM>, X<NUM> thereof. In detail, the conduit <NUM> housing check valve <NUM> that allows the passage of fluid from valve means towards tank <NUM> is fluidly connected to the tank <NUM> in a point X<NUM> placed vertically above with respect the point X<NUM> of connection of conduit <NUM>.

According to the embodiment of <FIG>, the hydraulic arrangement <NUM> comprises a further, buffer, tank <NUM>' that is fluidly connected to only the fluid selection module <NUM> and the conduits <NUM>, <NUM> are singularly fluidly connected to such buffer tank <NUM>' in two different points X<NUM>, X<NUM> thereof. In such configuration the tank <NUM> is fluidly connected only to accumulators <NUM> to manage their pressurization.

In detail, the conduit <NUM> housing check valve <NUM> that allows the passage of fluid from valve means towards tank <NUM>' is fluidly connected to the tank <NUM>' in a point X<NUM> placed vertically above with respect the point X<NUM> of connection of conduit <NUM>.

In both embodiments, advantageously, point X<NUM> is realized on a top wall defining tank <NUM>, <NUM>' and point X<NUM> is realized on a bottom wall defining tank <NUM>, <NUM>'.

The operation of the two above described embodiments according to the invention is the following.

According to a first mode of operation it is provided a signal S<NUM> (e.g. directly by the user via a button/ display) enabling the use of the energy recovery system <NUM>. Accordingly, valve means <NUM> moves to allow the passage of fluid mainly between accumulators <NUM> and support cylinders <NUM>, <NUM>. In this way, as per se known, pressurized fluid into accumulators <NUM> is used for helping lifting cylinders <NUM>, <NUM>, i.e. the lifting force of support cylinders <NUM>, <NUM> is transmitted to cylinders <NUM>, <NUM> via mechanical link <NUM>.

According to a second mode of the provided signal S<NUM> disables the use of the energy recovery system <NUM>. Accordingly, valve means <NUM> moves to allow the passage of fluid mainly between tank <NUM>, <NUM>' and support cylinders <NUM>, <NUM>. In this way, as per se known, cylinders <NUM>, <NUM> are not helped in their work and excess fluid present in support cylinders <NUM>, <NUM> will be discharged, when cylinders <NUM>, <NUM> are lowered.

The operation in the two embodiments is similar. The difference is that in first embodiment the fluid is discharged or sucked by a single tank <NUM> while in the second embodiment fluid may be discharged or sucked by the buffer tank <NUM>'.

In view of the foregoing, the advantages of a hydraulic arrangement and a work vehicle according to the invention are apparent.

Thanks to the selection module <NUM>, it is possible to select the recovery system <NUM> only when needed. Otherwise, the boom is operated only by cylinders <NUM>, <NUM> as in vehicle that are not provided with a recovery system <NUM>.

In this way, the proposed work vehicle is more versatile with respect to existing system that are or provided with a recovery system either not.

Moreover, the provided arrangement of check valves with two different coupling points X<NUM>, X<NUM> optimizes the sucking and the filling of the tank <NUM>.

Furthermore, if the oil volume is too great for a single tank, the system may be used with two different tanks, wherein one is a buffer for the great oil volume.

Furthermore, in case of failure of accumulators <NUM> or of any other system of the recovery system <NUM>, the vehicle may be operated in standard way, i.e. the work vehicle can continue its operation without interruption.

Moreover, the use of a proportional valve <NUM> is particularly advantageous since its control may be designed to decreased pump load when the boom lowers with better efficiency of the system. Accordingly, the work vehicle would decrease its fuel consumption. It is clear that modifications can be made to the described hydraulic arrangement and work vehicle which do not extend beyond the scope of protection defined by the claims.

For example, the proposed valve means and the topology of conduits may be varied.

Claim 1:
Hydraulic arrangement (<NUM>) for a work vehicle provided with a boom configured to be controlled via a pair of cylinders (<NUM>, <NUM>) and an energy recovery system (<NUM>) comprising a pair of support cylinders (<NUM>, <NUM>) configured to cooperate with said pair of cylinders (<NUM>, <NUM>) and at least an accumulator (<NUM>),
said hydraulic arrangement (<NUM>) comprising a feeding conduit (<NUM>) fluidly connecting said accumulator (<NUM>) and said support cylinders (<NUM>, <NUM>) and a selection module (<NUM>) fluidly interposed on said feeding conduit (<NUM>), said selection module (<NUM>) being configured to regulate the fluid passage between said accumulator (<NUM>), said support cylinders (<NUM>, <NUM>) and a tank (<NUM>, <NUM>') of said work vehicle,
wherein said selection module (<NUM>) comprises valves means (<NUM>) fluidly interposed on said feeding conduit (<NUM>) and said tank (<NUM>, <NUM>'), said valve means(<NUM>) comprising an electro-actuated valve,
the hydraulic arrangement is characterized in that said selection module (<NUM>) comprises pair of check valves (<NUM>, <NUM>) fluidly interposed on respective conduits (<NUM>, <NUM>), said conduits (<NUM>, <NUM>) being fluidly in parallel between said tank (<NUM>,<NUM>') and said valve means (<NUM>), said check valves (<NUM>, <NUM>) allowing the passage of fluid each in a direction opposite with respect to the other.