EP1369598B2 - Electro-hydraulic lifting control device for industrial use vehicles - Google Patents

Description

The invention relates to an electro-hydraulic stroke control device specified in the preamble of claim 1 Art.

At the DE 42 39 321 C known electro-hydraulic stroke control device are present as electrically actuated components only the proportional pressure control valves for the lifting control and the lowering control. The safety requirements are very high especially for industrial trucks, especially forklifts. Dirt in the hydraulic medium, eg chips or the like, can not be avoided with 100% certainty. Such contaminants may cause, for example, the proportional pressure control valve of the lowering control or the lifting control to become stuck and can no longer be adjusted, so that the load borne by the hydraulic cylinder falls or runs uncontrolled. The proportional solenoid generates a force that is then insufficient to overcome the increased resistance to movement in the valve. This means an increased safety risk, which did not exist in earlier, mechanically actuated hydraulic Hubsteuervorrichtungen, since there only the mechanical force had to be increased accordingly to overcome such a resistance.

At the DE 100 10 670 A known electrically controllable lifting module ( Fig. 1 ), the three-way flow regulator in the sink branch downstream with the tank and connected to the suction side of the pump for energy recovery. In the lifting strand, since the speed of the hydraulic cylinder is controlled by the speed of the pump, only one black / white 2/2 solenoid valve is provided. From the lifting strand branches off a drain line with a 2/2-way solenoid valve to the tank, which is electrically connected to the passageway during sinking, if no additional consumer is to be supplied. If the three-way current regulator gets stuck in lowering mode as a result of pollution, the lifting cylinder will stop moving in an uncontrolled manner.

At the DE 41 40 408 A Known stroke control device are provided for raising and lowering control two proportional pressure control valves. If the proportional pressure control valve gets stuck in the lowering mode as a result of pollution, the lifting cylinder moves uncontrolled under load.

Further prior art is contained in EP 0 546 300 A . EP 0 893 607 A . US 5,701,618 A ,

In electrically controlled lift trucks, regardless of whether they are powered by engines or electrically operated, a trend towards increased safety is to provide for the failure of an electrically controlled control or control member at least the lifting cylinder further electrically actuated safety devices, which, u.a. for personal protection, to prevent the load from falling down. Secondary consumers supplied by the same pressure source often operate at a lower pressure than the main lift cylinder. Although these requirements can be fulfilled with electrically actuatable valves placed at different points in the control device, this requires an additional expenditure of valves and actuation magnets or expensive proportional solenoids with complicated wiring.

The invention has for its object to provide an electro-hydraulic stroke control device of this type, the reliability is increased against disturbances due to contamination of the hydraulic medium or developing mechanical damage hydraulic switching elements with minimal effort.

As a side aspect in the context of this task should also be possible without additional effort in the lowering control an additional activatable braking function, or intentional active disconnection of one or both current regulator is desirable, or should adjust the supply pressure for at least one other hydraulic consumer in a simple manner with minimal effort leave as eg for lifting control. The mentioned effort relates mainly to magnets as a valve actuator.

The stated object is achieved with the features of claim 1.

The reliability of the electro-hydraulic Hubsteuervorrichtung is increased because the redundancy switching element then actively engages when at least one other electrically actuated switching element should not work properly. Due to the active engagement of the redundancy switching element, in particular uncontrolled load movements or unintentional lowering of the load are avoided. If, for example, the proportional pressure control valve remains stuck in the lowering control or the lifting control, so that it can no longer be adjusted by its proportional magnet (the lifting hydraulic cylinder would then either move under the load or extend against the load), then the effective redundancy switching element is brought in the open position either the pressure compensator of the two-way flow regulator in the load-holding shut-off position (stopping the sinking Hubhydraulikzylinders) or the pressure compensator of the three-way flow regulator in the open position (deriving the flow to the tank, so that the hydraulic cylinder stops). With proper function of the Proportionaldruckregelventiis the redundancy switching element has no influence in the respective pilot circuit, since it is energized with energization of the respective proportional solenoid and holds its closed position. The redundancy switching element is an easy-to-integrate safety component and requires only minimal effort. For this function, only the magnet of the switching element and hydraulically a simple, small-sized valve for the pilot oil is required for the control electronics.

Thanks to its arrangement, however, the redundancy switching element offers further advantageous possibilities, it being necessary to assume that the electronic control provided in modern industrial trucks contains a microprocessor that offers many possibilities for individual program routines or functions. By adjusting the redundancy switching element in the open position during the lowering control, for example, the lowering movement can be additionally braked individually by the pressure compensator of the two-way flow regulator is brought in another way in the closed position, as by the pressure difference of the proportional pressure control valve. A similar individual braking could also be done in the lift control via the pressure compensator of the three-way current controller. Furthermore, the redundancy switching element can actively activate the two-way current controller or the three-way current controller, ie bring the respective pressure compensator into the closed position or full open position. Finally, the redundancy switching element as a variable pressure limiting valve change the pilot pressure of the pressure compensator of the three-way flow regulator, which adjusts the supply pressure for at least one further hydraulic consumer, which is lower than that of the lifting hydraulic cylinder. It opens up the redundancy switching element in conjunction with the control electronics possibilities for a more universal control of the industrial truck, the inherent performance of the parent electronics is used without additional effort.

The redundancy switching element can, performed by the control electronics and when designed as a proportional pressure control valve, fulfill the function of an electrically adjustable pressure limiting valve, so that the pressure compensator of the three-way flow regulator adjusts a lower supply pressure for further hydraulic consumers. All the aforementioned functions can be achieved with a small valve and a magnet.

Since arranged in the pilot circuit redundancy switching element in a fault, for example, the three-way current regulator in the lowering control in its open position as soon as the proportional solenoid of the three-way current regulator is de-energized, the hydraulic cylinder stroke could yield very slowly over the pilot circuit despite the load-holding function of the pressure compensator , For this reason, it is expedient to form the redundancy switching element as a 4/2-way switching valve with a solenoid as the actuator and shut off the pilot line to Senkzweig at least stacker-tight, while the opening pilot side of the pressure compensator is relieved directly to the tank. This results in a perfect load-holding function of the pressure balance, so that the lifting hydraulic cylinder remains reliably stopped even when stuck proportional-pressure relief valve.

In order to ensure this high safety standard even if the redundancy switching element is to perform the function of reducing the pressure for other consumers, it is expedient to form the redundancy switching element even as a 4/3-way proportional pressure control valve with a proportional solenoid as the actuator and the separate two pilot control lines from Senkzweig and from the closing pilot side of the pressure compensator of the two-way current controller separately. If the 4/3-way proportional pressure control valve de-energized when canceling the lowering control, then it assumes its shutdown, in which relieves the opening pilot side of the pressure compensator of the two-way flow regulator to the tank and the pressure compensator is set to load. This shift position is also assumed when the lift control is canceled. Then the closing pilot side of the pressure compensator of the three-way flow regulator is relieved to the tank, so that the pressure compensator, if supply pressure is present, is set in the closed position. As soon as the current controller is energized for lifting control or lowering control of one of the proportional solenoids, the proportional solenoid of the 4/3-way proportional pressure control valve is also fully energized. The switching position generated thereby sets the pilot line from the Senkzweig to the opening pilot side of the pressure compensator of the two-way flow regulator on passage and interrupts the connection of the pilot line to the closing pilot side of the pressure compensator of the three-way flow regulator to the tank. If, however, another consumer is switched on in the lift control, the proportional solenoid of the 4/3-way proportional pressure control valve is subjected to a desired current reduction in accordance with the desired pressure reduction against the control spring and the pilot pressure, with which a control function for reducing the pilot pressure for the pressure compensator of Three-way current controller is running. All these functions are achieved with a single valve and a single proportional solenoid.

Suitably, the 4/2-way switching valve or the 4/3-way proportional pressure control valve is designed as a slide valve in stapler-tight design. This means that the valve fulfills the requirement valid for the stacker leak criterion.

To get along with the smallest possible and weak and therefore cost-effective solenoids or proportional magnets for the redundancy switching element, it is expedient to provide a pressure-balanced with respect to the tank pressure valve slide in the slide valve. If the redundancy switching element also controls the pressure limit for the other consumers, it is particularly expedient to let the pilot pressure, against which the proportional solenoid operates, act only on a small partial area of the valve slide.

The electro-hydraulic stroke control device is usable with this design both for lift trucks with an internal combustion engine and an electric motor. In electric motor driven lift trucks, the Hubsteuervorrichtung can be used without or with energy recovery (Nutzsenken). For payload operation in which the electric motor is operated as a generator via the pump, it is only necessary to connect the Senkzweig upstream of the pressure compensator of the two-way flow regulator via a Nutzleitung with the suction side of the pump, and to arrange a check valve between the pump and the tank , At high load pressure and without additional connected hydraulic consumers, the full amount (controlled by the pressure compensator of the two-way flow regulator) can be pumped through the pump. If another hydraulic consumer is switched on, then the pressure compensator of the two-way current regulator regulates a current through the pump when it is used, which corresponds to the current demand. The redundancy switching element does not intervene in case of proper function, but only in the case of a fault, and occasionally in the pressure reduction for the other consumers.

The electrically operable components of the stroke control device should be connected to an electronic controller including a microprocessor or logic circuit which executes the different operating routines as needed, as selected, or according to an automated scheme.

Fig. 1

ein Blockschaltbild einer elektrohydraulischen Hubsteuervorrichtung mit einem Redundanz-Schaltglied, das der Senksteuerung zugeordnet ist,

Fig. 2

ein Blockschaltbild einer elektrohydraulischen Hubsteuervorrichtung mit einem Redundanz-Schaltglied, das der Hebesteuerung zugeordnet ist,

Fig. 3

ein Blockschaltbild einer elektrohydraulischen Hubsteuervorrichtung mit weiteren Hydroverbraucher, mit einem Redundanz-Schaltglied, das der Hebesteuerung und der Senksteuerung zugeordnet ist, und bei Zuordnung zur Hebesteuerung zusätzlich als elektrisch verstellbares Druckbegrenzungsventil zur Druckminderung für die weiteren Hydroverbraucher dient, wobei die Hubsteuervorrichtungen in den Fig.1-3 nicht zur Erfindung gehören,

Fig. 4

ein Blockschaltbild einer erfindungsgemäßen Ausführungsvariante, und

Fig. 5

ein Blockschaltbild einer weiteren erfindungsgemäßen Ausführungsvariante.

Reference to the drawings, embodiments of the subject invention will be explained. Show it:

Fig. 1

FIG. 2 is a block diagram of an electro-hydraulic lift control device having a redundancy switch associated with the lowering control. FIG.

Fig. 2

FIG. 2 is a block diagram of an electro-hydraulic lift control device having a redundancy switch associated with the lift control. FIG.

Fig. 3

a block diagram of an electrohydraulic stroke control device with further hydraulic consumer, with a redundancy switching element, which is associated with the lifting control and the lowering control, and additionally serves as an electrically adjustable pressure relief valve for pressure reduction for the other hydraulic consumers when assigned to the lifting control, wherein the Hubsteuervorrichtungen in the Fig.1-3 not belonging to the invention,

Fig. 4

a block diagram of an embodiment variant according to the invention, and

Fig. 5

a block diagram of another embodiment of the invention.

In the electrohydraulic stroke control device S in Fig. 1 a hydraulic cylinder Z for lifting control from a pressure source P (hydraulic pump) is supplied, which is driven for example by electric motor or diesel engine M and, if no other hydraulic consumers are to be supplied, in the lowering control of the hydraulic cylinder Z may be, or ( Fig. 4 ) then to recover energy as an engine is running. The hydraulic pump sucks from a tank T and acts on a lifting strand 1, in which a three-way flow regulator R1 is provided. The three-way flow regulator R1 consists of a proportional pressure control valve 3, with which the lifting speed is adjusted by a proportional solenoid 4, and a pressure compensator 5 between the lifting strand 1 and the tank T. The pressure control valve 3 is acted upon by spring loading in the direction of the shut-off position. Between the hydraulic cylinder Z and the pressure control valve 3, a pilot control line 6 branches off to the closing pilot side (at which a control spring also acts) of the pressure compensator 5. From the lifting strand 1 branches off upstream of the pressure control valve 3, a further pilot line 7 to the opening pilot side of the pressure compensator 5 from.

From the lifting rope 1 branches off between the pressure control valve 3 and the hydraulic cylinder Z a Senkstrang 2 from the tank, in which the lowering control a two-way flow regulator R2 is included. The two-way flow regulator R2 consists of a pressure control valve 8, with which the lowering speed can be adjusted by means of a proportional solenoid 9, and a pressure compensator 10. The pressure control valve 8 is acted upon by spring force in the direction of the shut-off position in which it is able to keep the load pressure leak-free , Between the pressure control valve 8 and the hydraulic cylinder Z branches from the Senkstrang 2 a pilot line 11 to closing pilot pressure side 22 of the pressure compensator 10, while between the pressure compensator 10 and the pressure control valve 8 from the Senkstrang 2 a pilot line 12 to the opening pilot side 19 of the pressure compensator 10 leads. At the opening pilot pressure side also acts a control spring. From the pilot control line 12 branches off a pilot line 12a to the tank T, in the z. B. a pressure relief valve 13 is included.

In addition to the two components (proportional magnets 4, 9) which can be actively actuated electrically, the two-way current controller R2 is assigned an electrically operable redundancy switching element A, which is energized when the proportional magnet 9 is energized. In the embodiment shown, this is a 2/2-way valve 14 of poppet style, i. with leak-free closed position, which can be brought by a black / white magnet 15 against the derived on its opening pilot side 21 from the pilot pressure in the pilot line 12a pressure in the closed position shown. The redundancy switch A is e.g. arranged parallel to the pressure relief valve 13 in the wiring harness.

Function:

Before the lowering control starts, the load pressure is held by the pressure regulating valve 8. Now, the proportional solenoid 9 receives current whose strength corresponds to the desired lowering speed. At the same time, the black / white magnet 15 is energized by a higher-level control, not shown, so that the redundancy switching element A assumes its shut-off position (as shown). The pressure control valve 8 can flow with the energization of the proportional solenoid 9 via a metering orifice pressure medium, the pressure compensator 10 keeps the pressure difference across the orifice and thus the lowering speed constant. The pressure compensator 10 adjusts itself to a position which depends on the pilot control pressures in the pilot control lines 11 and 12 and its control spring (load independence).

If, when canceling the lowering movement due to contamination or mechanical damage, the pressure compensator 10 remain stuck, then by de-energizing the proportional solenoid 9, the pressure control valve 8 can be brought into its closed position, so that the hydraulic cylinder Z stops. The disorder of the pressure compensator 10 is therefore irrelevant. However, should the pressure control valve 8 itself get stuck due to contamination or mechanical damage, and not come in the closed position despite de-energizing the proportional solenoid 9, then the hydraulic cylinder Z would continue to fall under the load, because active with the proportional solenoid 9 is no longer on the pressure control valve 8 can be acted on and the pressure compensator 10 remains open. In this case, the de-energization of the proportional solenoid 9 and the black / white magnet 15 of the redundancy switching element A is de-energized, so that the redundancy switching element A abruptly by the pilot pressure in the pilot line 12a in its open position and the pilot pressure to the tank , The pressure compensator 10 is brought from the pilot pressure in the pilot control line 11 in its closed position and holds the load pressure. The hydraulic cylinder Z comes to a stop. The redundancy switching element A could also be energized and de-energized once or several times in the event of the pressure compensator 10 getting stuck in order to make the pressure balance 10 common again.

In the electrohydraulic stroke control device S in FIG Fig. 2 the redundancy switching element A is assigned to the three-way current regulator R1 for lifting control. That is, the redundancy switching element A is contained in a branched from the pilot line 6 to Schließvorsteuerseite 20 of the pressure compensator 5 pilot line 6a to the tank and provides a way to actively intervene in the event of a fault. For example, should the pressure compensator 5 become stuck due to a malfunction in a middle position, further extension of the hydraulic cylinder Z could be prevented by bringing the pressure control valve 3 into its closed position by means of the proportional magnet 4. However, if the pressure control valve 3 should hang, then the hydraulic cylinder Z would possibly be brought to a halt by switching off the motor M, but then not reliable, if at the same time other hydraulic consumers from the pressure source must be supplied with. In this case, with de-energizing the proportional solenoid 4 also de-energized black / white magnet 15, the 2/2-way valve 14 from the pilot pressure in the pilot line 6, 6a brought quickly into its open position, so that the pilot pressure is abruptly reduced to the tank and the pressure compensator 5 is brought by the prevailing pressure in the lifting strand 1 via the pilot line 7 in the full open position in which the pressure fluid from the lifting strand 1 derived to the tank and the hydraulic cylinder Z is brought to a standstill. The redundancy switching element A could be used in repeated energization and de-excitation to make the hanging pressure compensator 5 common again.

In Fig. 3 is the electrohydraulic stroke control device S combined with additional controls SH, SH 'for further hydraulic consumers of the industrial truck with common supply from the pressure source P is present. The control SH is used, for example, to actuate a further hydraulic consumer Z ', for example a tilting cylinder or a gripper cylinder, which requires a lower supply pressure than the hydraulic cylinder Z. The supply of the further hydraulic consumer Z' via a pressure line 1 ', the upstream of the lifting strand 1 of the pressure control valve 3 of the three-way current regulator R1 branches off. In order to work independently of load in the control SH, the load pressure via a pilot line 6b to the pilot line 6 and then brought to Schließvorsteuerseite 20 of the pressure compensator 5, via a shuttle valve 16, the respective higher control pressure to the closing pilot side 20 of the pressure compensator 5 transmits. The pressure compensator 5 regulates the respectively required pressure.

The redundancy switch A in this embodiment is operatively associated alternately with both the two-way current regulator R2 and the three-way current regulator R1 via a shuttle valve 17 (or, as in FIG 4 and 5 shown via two separate pilot control lines). From the pilot control line 12 of the two-way flow controller R2 branches off a pilot line 12 'to the shuttle valve 17. To the other side of the shuttle valve 17 performs a pilot line 6 ', which branches off from the pilot line 6 of the three-way current regulator R1. The respective higher pilot pressure is transmitted to the pilot line 18, in which optionally the pressure relief valve 13 and the redundancy switching element A are arranged.

The redundancy switch A is in Fig. 3 a 2/2-way proportional pressure control valve 14 ', which is acted upon by the pilot pressure in the pilot line 18 in the opening direction at its Öffnungsvorsteuerseite 21, and can be adjusted by a proportional solenoid 15' in the direction of the closed position shown.

The energization of the proportional magnet 15 'takes place simultaneously with the energization of the proportional magnet 4 in the lifting control, while in the lowering control simultaneously with the energization of the proportional magnet 9. The proportional solenoid 15' can not only set the closed position of the redundancy switching element A, but let Optionally, depending on a weaker energization with sole or additional actuation of the hydraulic cylinder Z 'set intermediate positions to lower the pilot pressure in the pilot line 18 for the pressure compensator 5. Thus, the redundancy switching element fulfills the function of an electrically adjustable pressure relief valve for adjusting the pilot pressure at the closing pilot side 20 of the pressure compensator 5, e.g. in order to set a lower supply pressure for the further hydraulic consumer Z '. The redundancy switch A of this design could also be used for intentionally reducing the pilot pressure level for the lift and / or lower control.

Function:

In the lift control, the shuttle valve 17 is in its left position, so that prevails in the pilot line 18, the pilot pressure from the pilot line 6. If the pressure control valve 3 get stuck, although the proportional solenoid 4 is de-energized, the proportional solenoid 15 'is de-energized, so that the redundancy switching element A via the pilot pressure in the pilot line 18 abruptly assumes its open position and degrades the pilot pressure to the tank. The pressure compensator 5 is abruptly in its open position in which the pressure medium is discharged directly to the tank and the hydraulic cylinder Z stops its extension movement, wherein the load pressure of a check valve downstream of the pressure control valve 3 and the pressure control valve 8 is maintained. Optionally, the proportional solenoid 15 'but then de-energized only after a program routine in which it is determined that the lifting cylinder Z has not stopped properly.

In the lowering control, the shuttle valve 17 assumes the position shown, so that in the pilot line 18, the pressure of the pilot line 12 and 12 'prevails. If the pressure control valve 8 get stuck, then, as explained above, via the going into its open position redundancy switching element A, the pressure compensator 10 is brought into its closed position and held the load pressure of the hydraulic cylinder Z.

In order to set a lower supply pressure upon actuation of the hydraulic consumer Z ', the proportional electronic control unit 15' is supplied with current only to such an extent by the superordinate electronic controller CU, which expediently contains a microprocessor or another logic circuit, that the pressure regulating valve 14 'assumes an intermediate position and regulates one Part of the pressure medium from the pilot pressure line 18 to the tank discharges to reduce the pilot pressure at the closing pilot side 20 of the pressure compensator 5, so that the pressure compensator 20 now controls relatively more pressure fluid to the tank and reduces the supply pressure in the pressure line 1 '.

To ensure that in the open position adjusted redundancy switching element A after canceling the lowering control with stuck proportional pressure control valve 8 is not very slow lowering of the hydraulic cylinder Z, is in the 4 and 5 in each case a redundancy switching element A is provided which shuts off the pilot line 12 to Senkzweig 2 with de-energized solenoid 15 or proportional solenoid 15 'and the opening pilot side 19 of the pressure compensator 10 via a pilot line 12 b relieved directly to the tank.

In Fig. 4 the redundancy switching element A is a 4/2-way switching valve 14 "with a solenoid 15 as an actuator against a spring 26. The redundancy switching element A is not used to set a lower supply pressure for other hydraulic consumers, but to secure the current regulator R1, R2 in the case of a fault and possibly for arbitrary release of the respective pressure balance for other reasons, eg for the purpose of individual braking or other security reasons.

The 4/2-way switching valve 14 "is a spool valve having a spool 27 which is pressure balanced with respect to tank pressure." The switching valve 14 "is between the two pilot lines 12 (from the drawstring 2) and 6a (from the closing pilot side 20) of the pressure compensator 5 and optionally the shuttle valve 16 and the tank T and the pilot control line 12b to the opening pilot side 19 of the pressure compensator 10 are arranged. With de-energized solenoid 15 (this may be a simple black and white solenoid) is the switching position shown in which the pilot lines 12, 12b separated from each other and the pilot lines 6a and 12b are relieved together in a bypass 24 in the valve spool 27 to the tank T. , When energized solenoid 15, a switching position is set in which the pilot line 6a separated from the tank T and the pilot lines 12, 12b are connected to each other.

If the proportional pressure control valve 8 get stuck when canceling the lowering control, then the opening pilot side 19 of the pressure compensator 10 is relieved to the tank in the switching position shown, so that the pressure compensator 10 goes into its closed position and holds the load. The hydraulic cylinder stops. The lift control function is the same as it is Fig. 2 explained.

Dash-dotted lines a Nutzsenkleitung 2 a is shown, which branches off between the proportional pressure control valve 8 and the pressure compensator 10 from the Senkstrang 2 and is connected to the suction side of the pump P. Between the connection of the Nutzsenkleitung 2a and the tank, a check valve V is indicated, which blocks in the direction of the tank to promote the lowering of the pressure fluid through the pump P and to drive this as a motor for the then working as a generator electric motor for energy recovery. The pressure medium then flows via the pressure compensator 20 to the tank, or, if further hydraulic consumers are connected and supplied, on. If a speed-controllable pump P is used, the pressure compensator 10 is set in the case of the connection of additional hydraulic consumers, the amount just required each time by the pump P. The pay reduction option can be easily integrated into any embodiment shown.

In Fig. 5 For example, the redundancy switch A is a 4/3-proportional pressure control valve 14 "having the proportional solenoid 15 'as an actuator of the valve spool 27' against the force of a spring 26 and the pilot pressure in a pilot line 6c branching from the pilot line 6a further interconnection corresponds to in Fig. 4 shown and already explained. The valve spool 27 'is pressure balanced with respect to the tank pressure via the pilot line 25, expediently over the entire surface, while the pilot pressure from the pilot line 6c expediently only a portion of the surface of the valve spool 27 against the proportional magnet 15' applied to a weak and compact or inexpensive proportional magnet 15th 'to be able to use.

For reducing the pilot pressure at the closing pilot side 20 of the pressure compensator 5 in the lift control or in controlling further hydraulic consumers to reduce their supply pressure, e.g. the proportional solenoid 15 'in accordance with the desired pilot pressure in the pilot line 6a energized weaker than in the protection of the respective current regulator to take between end positions with significant coverage regulating intermediate switch positions in which both the pilot lines 12, 12b are connected to each other and the pilot line 6a directly connected to the tank.

Claims (6)

1. An electrohydraulic lifting control device (S) for industrial trucks, in particular, for stacker trucks, comprising a lifting branch (1) provided between a pressure source (P) and a hydraulic cylinder (Z) and including a three-way flow regulator (R1) which is provided with a proportional magnet and a pressure balance (5) and which is adapted to be electrically operated at least for the purpose of lifting control, and further comprising a lowering branch (2) branching off from the lifting branch (1) towards the reservoir (T) and including, for the purpose of lowering control, an electrically operated two-way flow regulator (R2) provided with a proportional magnet and a pressure balance (10) characterized in that a redundancy switching element (A), which is actively, electrically operated by an actuator between closed and open end-positions, is provided between the reservoir (T) and an opening pilot side (19) of the pressure balance (10) of the two-way flow regulator (R2) and a closing pilot side (20) of the pressure balance (5) of the three-way flow regulator (R1), that the redundancy switching element (A) is a four/two-way switching valve (14') which is provided with a black-and-white switching magnet (15), or is a four/three-way proportional pressure regulating control valve (14'''), which is provided with a proportional magnet (15'), which black-and-white switching magnet (15) or proportional magnet (15') respectively is the actuator actuating the redundancy switching element (A) in one switching direction between the closed and opened positions, that from the redundancy switching element (A) and separated from each other, a first pilot line (12) extends to the lowering branch (2), a second pilot line (6a) extends to the closing pilot side (20) of the pressure balance (5) of the three-way flow regulator (R1), a third pilot line extends to the reservoir (T), and a fourth pilot line (12b) extends to the opening pilot side (19) of the pressure balance (10) of the two-way flow regulator (R2), that the redundancy switching element (A) in one end position separates the second and third pilot lines and interconnects the first and fourth pilot lines (12, 12b), and being the other end-position separates the first and fourth pilot lines (12, 12b) and interconnects the second and third pilot lines with the reservoir (T), that the fourth/three-way proportional pressure regulating control valve (14''') as the redundancy switching element (A) is actuated by the proportional magnet (15') into variable intermediate switching positions between the end positions such, that respectively, the first and fourth pilot lines and the second and third pilot lines are connected with each other, for adjusting a target pilot pressure in the second pilot line (6a), that the pressure balance (5) of the three-way flow regulator (R1) additionally is adapted for a load-independent control of at least one additional hydroconsumer (Z') which is supplied from the same pressure source (P), and that the redundancy switching element (A) and the pressure balance (5) of the three-way flow regulator (R) are adapted to adjust a supply pressure for the additional hydroconsumer (Z') which is at least lower than the supply pressure for the lifting control of the hydraulic cylinder (Z).
2. The electrohydraulic lifting control device according to claim 1, characterized in that the four/two-way switching valve (14') or the four/three-way proportional pressure regulating control valve (14''') is a valve slider (27) whose leak-proofness satisfies the requirements for industrial stacker trucks.
3. The electrohydraulic lifting control device according to claim 1, characterized in that the four/two-way switching valve (14') comprises a valve slider (27) which is pressure-compensated at both ends to the reservoir (T) at large pressure receiving areas.
4. The electrohydraulic lifting control device according to claim 1, characterized in that the four/three-way proportional pressure control valve (14''') comprises a valve slider (27) which is pressure-compensated at both ends to the reservoir (T) on full pressure receiving areas, while only a part of the full pressure receiving areas of the valve slider (27) is acted upon counter to the proportional magnet (15') by the pilot pressure in the second pilot line (6a).
5. The electrohydraulic lifting control device according to at least one of claims 1 to 4, characterized in that the pressure source (P) comprises a speed-controlled pump having an electric motor (M) which is adapted to be operated by the pump as a generator for recovering energy during load lowering control, that a check valve (B) blocking in flow direction towards the reservoir (T) is provided between the pump and the reservoir (T), and that a recovering lowering line (2a) branching off from the lowering branch (2) at a point upstream of the pressure balance (10) of the two-way flow regulator (R2) is connected to the pump at a point downstream of the check valve (V).
6. The electrohydraulic lifting control device according to at least one of the preceding claims, characterized in that the electrically actively, operated components (4, 9, 15, 15', M), of the lifting control device (S) are connected to an electronic control unit (CU) comprising a microprocessor or a logic circuit.

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