SINGLE OR DOUBLE EFFECT AUXTLTARY EOTJTPMENTS OF A

CONSTRTJCTTON VETTTCLE BACKGROUND OF THE INVENTION

The present invention relates to an hydraulic control circuit for operation of an auxiliary equipment of a construction vehicle, such as a loader, excavator, mini-excavator or the like. In particular the hydraulic circuit controls and powers both a single effect auxiliary equipment, such as a hammer, and a double effect auxiliary equipment, such as a crusher.

A construction vehicle may be provided with a control circuit having a flow summation function for one of its actuators. During flow summation, the flow dedicated to a non-used power line/ power port of control valve is redirected to a preferred actuator in order to increase actuation speed of one effect of the preferred actuator.

For example, in a mini-excavator comprising a boom and an auxiliary attachment for a single effect actuator such as a hammer, when the latter is not used, the flow summation is realized to increase the speed of a boom-up function.

A construction vehicle is often provided with interchangeable auxiliary equipment that may be a single effect hydraulic actuator or a double effect actuator such as a crusher. In particular, a single effect equipment is controlled via a power line connected to a pressure source and a return line directly connected to a tank or to a return line; and a double effect equipment is controlled via a first and a second power line that are selectively connected to a power source and to the sump depending on the controlled effect.

A need is felt to provide an improved hydraulic circuit to control a flow summation function and, at the same time, control a single effect auxiliary equipment and a double effect auxiliary equipment.

SUMMARY OF THE INVENTION

The scope of the present invention is achieved with a hydraulic control circuit according to claim 1.

A construction equipment vehicle may be provided with the control circuit cited above.

Additional features of the invention are comprised in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, the latter will further be disclosed with reference to the accompanying figures in which:

- figure 1 is a scheme of a simplified control circuit according to the present invention, where only components for the understanding of the invention are shown; and

- figure 2 is a scheme of a simplified control circuit according to a second

embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

Figure 1 refers, as a whole, to a control circuit 1 for a construction vehicle, e.g. a mini- excavator, comprising a source of pressurized fluid having preferably a first and a second pump PI, P2 each of which is connected, via respective feed lines FL1, FL2, to a control section of the circuit comprising a first and a second control valve 1, 2. Valves PV branch off from feed lines FL1, FL2 to direct unnecessary fluid to a tank in order to maintain a pre-set maximum pressure limit at the outlet of pumps PI , P2.

According to figure 1 , control valve 1 controls an actuator B via a first and a second power line PLA1, PLA2. Each power line PLA1, PLA2 is associated to a respective effect of the actuator so that, when one power line is connected to the source of pressurized fluid to operate an effect of actuator B, the other power line is connected to tank. Actuator B may be either a single or a double effect actuator. In the example, actuator B is a double effect actuator to control a boom of the construction vehicle.

Control valve 2 controls an auxiliary equipment C, H of the construction vehicle via a power line LI that is associated to one effect of the equipment. Control valve 2 is also connected to first power line PLA1 via an interconnection I in order to provide flow- summation to the effect associated to power line PLA1. According to the embodiment of figure 1, flow- summation is associated to a boom-up function.

Control section of circuit 1 also comprises a power line L2 attached to the auxiliary equipment C, H and a switch valve 3 to intercept interconnection I, power line L2 and a return line preferably connected to a tank.

Control circuit 1 also comprises a piloting section comprising hydraulic commands for commutation of control valves 1, 2 and switch valve 3 when a user, via e.g. a joystick or the like, controls actuator B and equipment C, H from a cockpit or driver's seat of the construction vehicle.

According to the embodiment of figure 1 , piloting section comprises a first and a second control valve pilot line CVPL1, CVPL2 to switch first control valve 1 from a neutral and closed position to respective first and second working position PB 1 , PB2 upon manual commands by the user. In particular, first working position PB 1 is associated to a high speed effect of actuator B such as, according to the embodiment of figure 1 , the effect corresponding to boom-up.

In order to provide flow summation for the high speed effect when equipment C, H is not in use, piloting section also comprises a pilot switch valve 4 having a first input receiving a pressure command from first control valve pilot line CVPL 1 via a T-branch Tl, and a second input receiving a pressure command for equipment C, H. Output of pilot switch valve 4 is such to switch second control valve 2 from a neutral and closed position to a first working position PCH1 to feed interconnection I. Second control valve 2 has a second working PCH2 position to feed a first effect of equipment C, H via first power line LI . Switch to such second working position of second control valve 2 is piloted via a third control valve pilot line CVPL3.

In a neutral position, pilot switch valve 4 is such to enable the switch of second control valve 2 to feed interconnection I when a user pressurizes first control valve pilot line CVPL1 to provide flow summation for the first effect of actuator B. In such a condition, switch valve 3 as well is a neutral position such that interconnection I feeds power line PLA1 of actuator B. Furthermore, pilot switch valve 4 may switch to a further position where flow summation is excluded and first working position PCH1 of second control valve 2 is reached when equipment C is a double effect equipment and the user commands a second effect of equipment C, e.g. a crusher. It is worth noting that the first effect of equipment C, H via power line LI is associated to second working position PCH2 of second control valve 2 via third control valve pilot line CVPL3.

Pilot switch valve 4 switches from neutral position to the further position via a shuttle valve 5 that outputs the higher pressure signal between third control valve pilot line CVPL3 and a user's command for the second effect of equipment C when the latter is a double-effect actuator. In particular, shuttle valve 5 receives the signal from third control valve pilot line CVPL3 via a first pilot line PL1 and the signal for the second effect of equipment C via a second pilot line PL2.

Piloting section also comprises a junction Jl where second pilot line PL2 meets a third pilot line PL3 to switch valve 3. Junction Jl is also connected to second input of pilot switch valve 4 and to the user's command for the second effect of equipment C.

According to a preferred embodiment of the present invention, user's command of equipment's second effect is controlled via a selector valve 6. The latter has a first stable position that pressurizes junction Jl so that both second pilot line PL2 and third pilot line PL3 cause commutation of pilot switch valve 4 and switch valve 3 respectively. This enables the second effect of equipment C.

Selector valve 6 has a second stable position to vent junction Jl . Accordingly, switch valve 3 and pilot switch valve 4 are kept by respective springs in the configuration such to provide flow-summation.

In use, first control valve 1 is switched by the user acting on e.g. a joystick to provide alternate pressure commands on first and second control valve pilot lines CVPL1, CVPL2 to respectively activate actuator B first effect, i.e. high speed effect, and second effect, where available. According to the embodiment of figure 1, high speed effect corresponds to 'boom- up' function.

Upon command signal via first control valve pilot line CVPL1, second control valve 2 is switched to first working position PCH1 via T-junction Tl in order to provide flow- summation to the high speed effect of actuator B, i.e. flow across second control valve 2, i.e. a proportional valve, is directed to power line PLA1 via interconnection I. Flow-summation is possible only when equipment C, H is not actuated by the operator.

Indeed, when operator commands the first effect of equipment C, H via third control valve pilot line CVPL3, second control valve 2 switches to second working position PCH2 that vents interconnection I and feeds power line LI . When first effect of equipment C, H is actuated, power line L2 is vented via switch valve 3. In order to avoid back flow towards second control valve 2 a check valve 7 is provided between power line PL1 and second control valve 2. According to the embodiment of figure 1, check valve 7 is along

interconnection I.

Equipment C, H is detachable from power lines LI, L2 depending on the use of the vehicle. In order to safely provide the correct set of commands for a single effect auxiliary equipment, such as a hammer, and a double effect auxiliary equipment, such a crusher, the user selects the stable position of selector valve 6, which can be a bi-stable lever or button on a dashboard of the vehicle or the joystick.

In particular, the position of selector valve 6 such that junction Jl is vented, inhibits any feed to power line L2 and, thus, the second effect of the equipment. Therefore the user sets selector valve 6 to stably vent junction Jl when a single effect equipment such as a hammer is attached to the construction vehicle.

The user sets selector valve 6 to pressurize junction Jl in order to commute pilot switch valve 4 and switch valve 3 and thus, respectively, associate the command for the second effect of the equipment and the switch to the first working position PCH1 of second control valve 2. Accordingly, interconnection I is closed and flow reaches power line L2 via the further position of switch control valve 3. In particular, junction Jl splits a single command signal for the second effect of equipment C to affect both pilot switch valve 4 and switch valve 3.

Advantages of the control circuit according to the present invention are as follows.

Via switch valve 3 it is possible to add a further degree of flexibility so as to control at the same time flow summation for a first actuator and both a single and a double effect auxiliary equipment.

When control section is piloted by pressure command signals via the piloting section, the provision of shuttle valve 5 provides for the use of a single component, i.e. pilot switch valve 4, to select the correct command signal to enable/disable actuation of the second effect of the auxiliary equipment.

Furthermore, selector valve 6 safely ensures that commands are properly associated to a single effect auxiliary equipment or a double effect auxiliary equipment.

Junction Jl efficiently splits the command signal to reach both pilot switch valve 4 and switch valve 3. The same applies to pilot line PL1 branching from third control valve pilot line CVPL3.

It is possible that changes and variations are made to the control circuit according to the present invention without departing from the scope of protection as defined by the attached claims.

In particular, actuator may be an actuator of a further auxiliary equipment enjoying a flow- summation function. Actuator B and the further auxiliary equipment can be both single or double effect.

It is also possible to provide an existing control circuit having a flow summation with the hydraulic elements to obtain control of an auxiliary equipment either of the single or of the double effect type.

To do so, as a first step, switch valve 3 shall be provided having a first position to intercept interconnection I and to vent power line L2 and a second position to close interconnection I and connect power line L2 to a source of pressurized fluid.

A further step is to provide, within a piloting section, the shuttle valve 5.

An even further step is to provide, within the piloting section, the selector valve 6.

According to a further alternative, shown in figure 2, control circuit 1 comprises solenoid switch valve 3 and solenoid pilot switch valve 4. All the above valves are controlled via an electronic circuit and a first and a second pressure sensors PSl, PS2. In such an embodiment, first control valves 1 is piloted by first and second control valve pilot lines CVPL1, CVPL2 receiving pressure command signals via a manual user interface, e.g. a joystick. The functioning is the same as that of first control valve 1 in figure 1.

Second control valve is piloted by third control valve pilot line CVPL3 and a fourth control valve pilot line CVPL4, such pilot lines being similar to first and second control valve pilot lines CVPL1, CVPL2 and receiving pressure command signals via a manual user interface, e.g. the joystick.

Pressure sensors PSl, PS2 are respectively connected to third and fourth control valve pilot lines CVPL3, CVPL4 in order to detect when the user wants to operate the first or the second effect of equipment C, H.

Electronic control unit is programmed so as to reproduce the same functioning previously discussed in a for piloting section of figure 1. In particular, when the user commands the first effect of equipment C, H via third control valve pilot line CVPL3, second control valve 2 switches to second working position PCH2 that vents interconnection I and feeds power line LI . First pressure sensor PSl detects the pressure command signal and, optionally, electronic control unit checks that switch valve 3 is in the correct position, i.e. that venting power line L2. In the negative, provides for electronic actuation so that venting of power line L2 is obtained.

When the user commands fourth control valve pilot line CVPL4, pressure sensor PS2 detects the pressure signal, consequently, electronic control unit switches solenoid pilot switch valve 4 to exclude flow- summation and solenoid switch valve 3 to feed power line L2.

Optionally, in order to safely switch between a single effect auxiliary equipment or a double effect auxiliary equipment, electronic control unit is connected to a selector 6 on the dashboard or another location reachable by the user on the driver's seat, that outputs a first signal when a single effect auxiliary equipment is used and a second signal when a double effect auxiliary equipment is used. When the electronic control unit receives the first signal, solenoid switch valve 3 is always kept in the position such to vent power line L2 and feed interconnection I regardless that, by mistake, the user inadvertently causes a pressure command on fourth control valve pilot line CVPL4. When electronic selector 6 provides to the electronic control unit the second signal, solenoid switch valve 3 is switched when second pressure sensor PS2 detects a command signal.

Furthermore, figure 2 shows a source of hydraulic fluid under pressure comprising a load sensing pump LSP; such source is alternative to the fixed displacement pump unit PI, P2 of figure 1.

Load sensing pump LSP is controlled by a load sensing piloting line LSL connected to compensators PC 1 , PC2 to ensure that the pressure drop across control valves 1 , 2 is constant over the operating conditions of the control system. Furthermore, control valves 1, 2 have ports to feed compensators PCI, PC2 and to receive flow from the pressure compensators PCI, PC2 before feeding the relative power line.

Furthermore, a first valve PV branches off upstream of fluid lines 1, 2 to direct unnecessary fluid to a tank in order to maintain a pre-set maximum pressure limit at the outlet of load sensing pump LSP. Accordingly, a second valve LSV branches off upstream of both pressure compensators PCI, PC2 to direct unnecessary fluid to a tank in order to maintain a pre-set maximum pressure limit along load sensing piloting line LSL and at the outlet of a load sensing valve of pump LSP.

The hydraulic power source of figure 2 or another load sensing layout may be adapted to power also the circuit of figure 1.

The circuits of figures 1 and 2 are simplified for the purpose of a description focussed on inventive issues. A control circuit embodied in a construction equipment vehicle is more complex and the skilled man is able to introduce the concepts of figures 1 and 2 in a complete power control circuit of a construction vehicle.

Furthermore, depending on the layout and use of the construction vehicle, power actuator B may be a single effect actuator.

First and second control valves 1 , 2 may be combined with pilot switch valve 4 and shuttle valve 5 in a single dedicated valve body to be possibly attached to a valve pack of the construction vehicle for the control of other actuators.