Background of the invention

[0001] The invention relates to a control device for a hydraulic actuator, in particular for controlling the movement of a movable element of the actuator.

[0002] Specifically, but not exclusively, the invention can be applied to at least one hydraulic actuator of a load lifting apparatus.

[0003] The prior art comprises control systems for controlling the descent of a load which, in general, are provided with a load holding valve that controls the movement and arrest of a dual effect actuator, locks the load substantially in any position, protects the hydraulic circuit from an uncontrolled pressure increase. The load holding valve is a control valve for controlling the pressure that prevents a load on a hydraulic actuator from falling in an uncontrolled manner, for example because of the breakage of a flexible pipe. [0004] In the load holding phase, if the load pressure remains below the calibration pressure, regulated by a spring, the load holding valve is closed and does not allow the load to descend, in practice without oil leaking. The calibration pressure must be greater than the maximum possible load.

[0005] During the load lifting phase, the pump delivers the lifting pressure, through the distributor, so that the oil passes through a check valve and fills the chamber of the pressurized cylinder.

[0006] The function of controlling the descent of the load is performed by the load holding valve by pilot pressure that regulates opening thereof and is added to the pressure induced by the load in the chamber of the cylinder. Opening of the valve is regulated to obtain the required lowering speed.

[0007] Patent publication EP 3228580 A1 shows an embodiment of a device for controlling the descent of a load on a dual effect hydraulic cylinder of a load lifting apparatus.

[0008] Patent publication EP 3312436 A1 shows an embodiment of a protection device for protecting against the breakage of a flexible pipe.

[0009] Patent publication JP 4890147 B2 shows a control device for controlling the descent of the load comprising a retaining valve, a piloting conduit for piloting the retaining valve, a control valve for controlling the pressure of the piloting conduit and a retaining valve arranged for preventing the transmission of pressure from the tube at risk of breakage to the control valve for controlling the pressure. [0010] Patent publication JP 2014206245 A shows a device that reduces the descent speed of the load and that comprises a control valve configured so as to reduce the degree of opening thereof when pressure is reduced in the supply line of the hydraulic actuator. [0011] One of the drawbacks of the prior art is represented by the fact that, in some load lifting apparatuses, it is not possible to have available a pilot signal that is suitable for supplying the pilot pressure that will have to regulate the opening of the control valve of the descent of the load. Think, for example, of the case of an apparatus in which the control lever acts directly on the slider of the distributor.

Summary of the invention

[0012] One object of the invention is to make a device that is able to overcome the aforesaid drawback of the prior art.

[0013] One object of the invention is to provide an alternative solution to the problem of sending a pilot signal to a control valve, in particular to a control valve for controlling the descent of a load in a load lifting apparatus.

[0014] One object of the invention is to provide a control device that can be operationally associated with a hydraulic circuit provided with a distributor for controlling at least one actuator of a load lifting apparatus.

[0015] One advantage is to make available a constructionally simple and cheap device for controlling a hydraulic actuator.

[0016] Other advantages are those of permitting a progressive and gradual control of the load movement, of reducing the dead zone of the operation of a load lifting apparatus, of improving the stability of the control system of the hydraulic actuator, of obtaining an energy saving.

[0017] These objects and advantages and still others are achieved by a control device according to one or more of the claims set out below.

[0018] In one embodiment, a control device comprises a valve body in which a first hole and a second hole are obtained, valve means arranged in the second hole and comprising a movable portion provided with a coupling end arranged in an intermediate zone of the first hole, movable means arranged in the first hole and connected to a cursor of a hydraulic distributor of an operating fluid of a hydraulic actuator, the movable means comprising a coupling portion coupled with the coupling end in such a manner that a displacement of the movable means causes a displacement of the movable portion, thereby a control manoeuvre capable of moving the cursor of the distributor causes a displacement of the movable portion, so that it is possible to send, through the valve means and through the effect of the aforesaid displacement of the movable portion, a pilot signal for regulating the opening of a control valve for controlling the movement of a movable element of the hydraulic actuator.

[0019] The coupling between the aforesaid coupling end of the valve means and the aforesaid coupling portion of the movable means may comprise, in particular, a mechanical coupling, for example a coupling of the profile and tappet type. The coupling end may comprise a tappet end and the coupling portion may comprise a profile portion.

[0020] The control valve for controlling the movement may comprise, in particular, a control valve for controlling the pressure, for example a load holding valve.

[0021] The valve means may comprise, in particular, at least one pressure reducing valve.

Brief description of the drawings

[0022] The invention can be better understood and implemented with reference to the attached drawings that illustrate embodiments thereof by way of non-limiting example, in which:

Figure 1 shows a section of a first embodiment of a control device made according to the invention;

Figures 2 and 3 show in a section a second embodiment of a control device made according to the invention in two different operating configurations;

Figure 4 shows a diagram of a hydraulic circuit of a load lifting apparatus that uses a control device as in the preceding figures;

Figure 5 is an enlarged detail of Figure 4.

Detailed description

[0023] With reference to the aforesaid figures, identical elements of different embodiments have been indicated for the sake of simplicity with the same numbering. [0024] Overall with 1 a control device of a hydraulic actuator has been indicated. The control device 1 may be used, in particular, for controlling at least one hydraulic actuator Cl, C2, C3 of a load lifting apparatus. In particular, the control device 1 may be applied to a hydraulic distributor 2 of a hydraulic circuit for controlling a hydraulic actuator.

[0025] The control device 1 may be used in the ambit of a hydraulic circuit for controlling the descent of a load which may be configured, in particular, for controlling the movement and arrest of a hydraulic actuator Cl, C2, C3 (in the specific embodiments illustrated the actuator is of the dual effect type, although in other embodiments that are not illustrated it is possible to use an actuator of the single effect type) that holds the load and/or locks the load substantially in any position and/or to protect the hydraulic circuit from an uncontrolled pressure increase (for example because of the breakage of a circuit pipe).

[0026] The hydraulic circuit may comprise, in particular, at least one control valve 3 for controlling the movement of a movable element of the hydraulic actuator Cl, C2, C3. This control valve 3 for controlling the movement (or control valve for controlling the descent of a load, or balancing valve) may comprise, in particular, a control valve for controlling the pressure configured for preventing a load on a hydraulic actuator from falling in an uncontrolled manner. This control valve 3 for controlling the movement may comprise, in particular, a load holding valve.

[0027] The control valve 3 for controlling the movement may perform the function of controlling the descent of the load. The control valve 3 for controlling the movement may receive a pilot signal (pressure signal) that regulates the opening thereof.

[0028] The control device 1 is configured for sending to the control valve 3 for controlling the movement the aforesaid pilot signal.

[0029] The control device 1 may comprise, in particular, at least one valve body 4 provided with a plurality of fluid communication ports with the exterior.

[0030] The control device 1 may comprise, in particular, at least one first hole 5 and at least one second hole 6 obtained in the valve body 4. The first hole 5 may be extended, as in these embodiments, between a first opening 7 and a second opening 8 of the valve body 4. The second hole 6 may be extended, as in these embodiments, between an intermediate zone of the first hole 5 and a third opening 9 of the valve body 4.

[0031] The control device 1 may comprise, in particular, valve means 10 arranged inside the second hole 6. The valve means 10 may comprise, in particular, a pressure reducer. The valve means 10 may comprise, in particular, at least one movable portion 11 provided with a tappet end 12 arranged in the intermediate zone of the first hole 5.

[0032] The control device 1 may comprise, in particular, movable means 13 arranged inside the first hole 5.

[0033] The movable means 13 may comprise, as in these embodiments, at least one first end arranged on the side of the first opening 7 and configured for connection with a cursor of a hydraulic distributor 2 of the operating fluid that operates in the hydraulic circuit for controlling the actuator.

[0034] The movable means 13 may comprise, as in these embodiments, a profile portion 14 coupled with the tappet end 12 in such a manner that a displacement of the movable means 13 along an axis of the first hole 5 causes a displacement of the movable portion 11 along an axis of the second hole 6. The coupling between the profile portion 14 and the tappet end 12 is so configured that a control manoeuvre capable of displacing the cursor of the hydraulic distributor 2 can cause a displacement of the movable means 13 and a resulting displacement of the movable portion 11 of the valve means 10.

[0035] The maximum stroke that the cursor of the distributor 2 can travel may be, for example, of the order of a few millimetres, in particular greater than 4, 5 or 6 millimetres and/or less than 10, 12 or 15 millimetres.

[0036] The valve means 10 may comprise, in particular, elastic means 22 configured for maintaining the tappet end 12 in contact with the profile portion 14. The valve means 10 may be configured, as in these embodiments, to control the pressure of the operating fluid of the hydraulic circuit. The valve means 10 may comprise, as said, at least one pressure reducer.

[0037] In particular, the valve means 10 may be connected, as illustrated in the specific embodiment of the circuit of Figure 4, with an auxiliary drain.

[0038] The valve body 4 may comprise, as in these embodiments, at least one third holel5 extending between two pilot ports 16 and communicating with the valve means 10. At least one of the aforesaid pilot ports 16 may be configured, in particular, for the connection with a withdrawal zone of the hydraulic circuit from which it is possible to take a desired pressure signal. The other of the two aforesaid pilot ports 16 may be configured, in particular, for the connection to the control valve 3 for controlling the movement of the movable element of the hydraulic actuator.

[0039] The first opening 7, the second opening 8 and the third opening 9 may be arranged, respectively, on a first side, a second side and a third side of the valve body 4. The second side may be parallel and opposite the first side and may be transverse to the third side. The valve body 4 may be made of one piece. The valve body 4 may be parallelepiped-shaped. The first hole 5 may be rectilinear and orthogonal to the first side and to the second side. The second hole 6 may be rectilinear and orthogonal to the third side.

[0040] The control device 1 may be configured, in particular, so that a pressure signal coming from the withdrawal zone can be sent as a pilot signal for the control valve 3 for controlling the movement, passing through the control device 1 so that the aforesaid pilot signal can be controlled by the valve means 10 (pressure reducer) of the control device 1. [0041] The valve body 4 may comprise, in particular, a fourth hole 17 that may be extended, for example, between two delivery ports 18. The fourth hole 17 may be communicating with the valve means 10. The valve body 4 may comprise, in particular, at least one delivery port 18 that may be configured for connecting to a delivery zone P of the hydraulic circuit connected to at least one pump that supplies the pressure to the operating fluid.

[0042] The delivery pressure (present in the fourth hole 17) may be returned, as in the embodiments disclosed here, to the pilot pressure PIL (present in the third hole 15) through the valve means 10, in particular with regulation of proportional type, depending on the position of the movable portion 11 of the valve means 10. This position, which determines the magnitude of the pilot pressure PIL which will be transmitted to the control valve 3, may be regulated by the coupling between the movable portion 11 and the movable means 13.

[0043] The valve body 4 may comprise, in particular, a fifth hole 19 that may be extended, for example, between two drain ports 20. The fifth hole 19 may be communicating with the valve means 10. The valve body 4 may comprise, in particular, at least one drain port 20 that may be configured for connecting to an unloading zone of the hydraulic circuit connected to at least one drain tank for draining the operating fluid.

[0044] The second hole 6 may comprise at least one inner surface that has a plurality of fluid transit gaps.

[0045] In particular, it is possible to provide at least one gap connected to a pilot line (by the third hole 15), at least one gap connected to a delivery zone P of the hydraulic circuit (by the fourth hole 17) and at least one gap connected to a drain T of the hydraulic circuit (by the fifth hole 19).

[0046] The control device 1 may comprise, in particular, at least one hydraulic distributor 2 configured for distributing the operating fluid to the hydraulic actuator. The hydraulic distributor 2 is connected to the hydraulic actuator and is provided with a movable cursor configured for adjusting the distribution of the operating fluid.

[0047] The cursor of the hydraulic distributor 2 may be connected, as in these embodiments, to the first end of the movable means 13 (for example may be fixed to the movable means 13 by a screw connection) such that an (axial) displacement of the cursor can cause an (axial) displacement of the movable means 13.

[0048] The aforesaid displacement of the movable portion 11 of the valve means 10 causes a variation in the operating configuration of the valve means 10 (pressure reducer) by virtue of which it is possible to send (in particular in a proportional manner, as a function of the position of the movable portion 11) a pilot signal (pilot pressure PIL) to the control valve 3 for controlling the movement of the load (load holding valve), for example to enable the control valve 3 to control the movement of the load, during normal operation, to take on an open position in which it causes a relatively reduced load fall, with consequent energy saving.

[0049] The control device 1 may comprise, in particular, control means of the distributor that may be connected to a second end of the movable means (for example a second end opposite the first end) such that an action of the control means on the hydraulic distributor 2 can cause a displacement of the movable means 13. The control means may comprise, in particular, at least one manual control lever that is directly operational on the cursor of the distributor 2. The movable means 13 may accordingly comprise at least one second end arranged on the side of the second opening 8. The second end may be configured for connection with the control means (in particular manual control means) of the distributor.

[0050] The control device 1 may comprise, in particular, the control valve 3 for controlling the movement of the movable element of the hydraulic actuator.

[0051] The control device 1 may comprise, in particular, a pilot line that connects the control valve 3 for controlling the movement with the valve means 10, in particular with the third hole 15 of the valve body 4 communicating with the valve means 10. The pilot line may be so configured that a pilot signal controlled by the valve means 10 can be sent to the control valve 3.

[0052] The control valve 3 for controlling the movement may comprise, in particular, a load holding valve.

[0053] The control device 1 may comprise, in particular, compensating means (not illustrated) arranged upstream of a delivery zone P of the hydraulic circuit, in particular arranged between the delivery zone P (situated at the inlet of the circuit) and at least one pump (not illustrated) supplying the operating fluid.

[0054] The hydraulic circuit of Figure 2 comprises a delivery zone P, an unloading zone T and a plurality of use zones Al, Bl, A2, B2, A3, B3, A4, and B4.

[0055] In the specific embodiment, the hydraulic circuit 2 comprises a plurality of control devices 1 arranged in a pack alongside one another.

[0056] The first use zone Al, Bl may be configured, for example, for controlling the tilt of an arm of the load lifting apparatus. The second use zone A2, B2 may be configured, for example, for controlling the extension of the arm. The third use zone A3, B3 may be configured, for example, for controlling lifting of the arm. The fourth use zone A2, B2 may can be configured, for example, for controlling auxiliary functions.

[0057] The hydraulic circuit of Figure 4 comprises a distributor 2 for each use zone. The first, the second and the third use zone each comprises a control device 1 comprising valve means 10 with at least one movable portion provided with a coupled end (with coupling of the profile and tappet type) with a portion of the movable means 13 integral with the cursor of the distributor 2 so that a displacement of the cursor of the distributor 2 causes a displacement of the movable portion 11 of the valve means 10. In practice, a control manoeuvre capable of displacing the cursor of the distributor 2 causes a modification of the operating configuration of the valve means 10 (pressure reducer) connected to the control valve 3.

[0058] The hydraulic circuit may comprise, in particular, a control valve for controlling the pressure 23 (for example a maximum pressure valve) arranged for controlling the pressure in the distributor 2. The control valve for controlling the pressure 23 may be configured for a pressure limit value PI (for example PI = 245 bar).

[0059] The hydraulic circuit may comprise, in particular, a one-way valve 24 arranged on the drain line to prevent the fluid returning.

[0060] The hydraulic circuit may comprise, in particular, a control valve for controlling the pressure 21 (for example a reducing valve) arranged for controlling the pressure in the valve means 10. In particular, the control valve for controlling the pressure 21 may be interposed between the delivery zone P and the valve means 10.

[0061] The control valve for controlling the pressure 21 may be configured for a pressure limit value P2 (for example P2 = 40 bar). In particular, the limit value P2 of the valve 21 may be less than the limit value PI of the valve 23.

[0062] The pilot pressure PIL may be controlled, in particular, by the control valve for controlling the pressure 21, which may be interposed between the delivery zone P and the third hole 15 of the valve means 10. [0063] The hydraulic circuit may comprise, in particular, an emergency valve 25 arranged on an emergency line that extends between the delivery zone P and the unloading zone T and is arranged parallel to the distributors 2.

[0064] The control device 1 may comprise, in particular, a control valve for controlling the pressure 26 (for example a maximum pressure valve) connected to the use zone Al. The control valve for controlling the pressure 26 (or shock valve, or anti cavitation valve, or overpressure valve) may be interposed between the use zone Al and the unloading zone T.

[0065] The control valve for controlling the pressure 26 may be configured for a pressure limit value P3 (for example P3 = 280 bar). In particular, the limit value P3 of the valve 26 may be greater than the limit value PI of the valve 23.

[0066] The control device 1 may comprise, in particular, a control valve for controlling the pressure 27 (for example a maximum pressure valve) connected to the use zone Bl. The control valve for controlling the pressure 27 (or shock valve, or anti cavitation valve, or overpressure valve) may be interposed between the use zone Bl and the unloading zone T.

[0067] The control valve for controlling the pressure 27 may be configured for a pressure limit value P4 (for example P4 = 280 bar). In particular, the limit value P4 of the valve 27 may be greater than the limit value PI of the valve 23.

[0068] In use, when the operator or user of the load lifting apparatus performs a manoeuvre by using the control means connected to a hydraulic distributor 2, the movement of the cursor of the distributor 2 causes a displacement of the movable portion 11 of the valve means 10, with the result that the variation of the operating configuration of the valve means 10 automatically causes sending of a pilot signal to the control means (control valve 3) for controlling the movement of the movable element of the actuator. [0069] By virtue of a displacement in one direction or the other of the cursor of the distributor 2, it is possible to provide for a displacement of the movable portion 11 of the valve means 10 occurring in the direction of compressing the elastic means 22 of the valve means 10 or in the direction of extending the elastic means 22.

[0070] In particular, for example if the valve means 10 comprises a pressure reducer, as a function of the displacement in one direction or the other of the cursor of the distributor 2, the control means (control valve 3) for controlling the movement of the movable element of the actuator can receive a pilot signal that increases or decreases the opening thereof, according to how the control system and the operating needs have been set.

[0071] It is noted that in the specific embodiment, the control valve 3 does not receive a pilot signal coming from the drain line of a hydraulic actuator Cl, C2 or C3, but coming from the valve means 10. The pilot signal, which may depend, in particular, on the position of the valve means 10, is thus manageable in a secure and regular manner, obtaining high control stability.

[0072] The movable portion 11 and the movable means 13 may be coupled together by a coupling of the profile and tappet type, as in the illustrated embodiments, or with other types of coupling, for example of the pinion with double rack type, or with connecting rod and double slider, etc.