EP3936470B1 - Hydraulic lift drive for a mobile working machine - Google Patents

Hydraulic lift drive for a mobile working machine Download PDF

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Publication number
EP3936470B1
EP3936470B1 EP21181370.4A EP21181370A EP3936470B1 EP 3936470 B1 EP3936470 B1 EP 3936470B1 EP 21181370 A EP21181370 A EP 21181370A EP 3936470 B1 EP3936470 B1 EP 3936470B1
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EP
European Patent Office
Prior art keywords
pressure compensator
pressure
line
control
lifting drive
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EP21181370.4A
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German (de)
French (fr)
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EP3936470A1 (en
Inventor
Markus Schwab
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STILL GmbH
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STILL GmbH
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B66—HOISTING; LIFTING; HAULING
    • B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
    • B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
    • B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
    • B66F9/075—Constructional features or details
    • B66F9/20—Means for actuating or controlling masts, platforms, or forks
    • B66F9/22—Hydraulic devices or systems

Definitions

  • the invention relates to a hydraulic lifting drive of a mobile working machine, in particular an industrial truck, for raising and lowering a load handling device, the lifting drive having a lifting cylinder device and a control valve for controlling the lowering operation of the lifting drive, which is connected to a consumer line leading to the lifting cylinder device and to a consumer line leading to a connected to the tank line that runs from the tank, with an outflow pressure compensator being arranged in the tank line that runs from the control valve to the tank, which pressure compensator is influenced by a spring device and the pressure present in the tank line between the control valve and the outflow pressure compensator in the direction of a flow position and by the pressure in the consumer line Pressure is applied in the direction of a blocking position.
  • a load handling device For handling loads, industrial trucks are provided with a load handling device, which is generally formed by a lifting carriage that can be raised and lowered on the mast and an attachment attached thereto.
  • the attachment can be designed, for example, as a load fork consisting of forks, by means of which a load, for example a pallet, can be driven under.
  • the deflection of the control valve in lowering mode determines the lowering speed of the load-carrying device.
  • a legally prescribed limit value of 0.6 m/s is prescribed for a maximum lowering speed of the load handling device or a load.
  • the control valve is actuated into an open position.
  • the discharge pressure compensator is connected in series with the control valve. When the control valve opens, a sink volume flow begins to flow from the lifting cylinder device to the container via the control valve and the outflow pressure compensator, and the load handling device is lowered.
  • the maximum flow rate for lowering of the load handling device is limited by the adjustment of the discharge pressure compensator.
  • the pressure in the consumer line upstream of the control valve acts on the discharge pressure compensator on one side in the direction of a blocking position, and the spring force of the spring device and the pressure in the tank line between the control valve and the discharge pressure compensator and thus the pressure downstream on the other side in the direction of a flow position the control valve.
  • the sink volume flow increases until a maximum pressure drop of 4 bar, for example, occurs at the control valve, which corresponds to the spring force of the discharge pressure compensator.
  • the discharge pressure compensator goes into the control position and moves in the direction of the blocking position until this pressure drop of 4 bar, for example, is kept constant at the control valve.
  • the object of the present invention is to provide a lifting drive of the type mentioned at the outset, in which higher lowering speeds of the load-carrying means can be achieved in a simple manner at low load pressures.
  • this object is achieved in that a line leading to the container is connected to the container line between the control valve and the discharge pressure compensator another container line is connected, in which a pressure compensator is arranged, which is acted upon by a spring device in the direction of a flow position and by the pressure present in the consumer line in the direction of a blocking position, the spring device of the pressure compensator being set to a limit load pressure of the lifting drive, so that in lowering operation of the lifting drive below the limit load pressure, a lowering volume flow flowing out of the lifting drive flows out via the outlet pressure compensator and the pressure compensator into the container and in lowering operation of the lifting drive above the limit load pressure a lowering volume flow outflowing from the lifting drive flows out exclusively via the outflow pressure compensator into the container.
  • the idea according to the invention is therefore to arrange a pressure compensator parallel to the discharge pressure compensator and to set the pressure compensator to a load limit pressure up to which the pressure compensator is open, so that when the lifting drive is lowering below the load limit pressure, a lowering volume flow flowing out of the lifting drive via the discharge pressure compensator and the pressure compensator can flow into the container.
  • the discharge pressure compensator and the pressure compensator are connected directly after the lowering valve in the tank line or the further tank line.
  • the maximum opening cross section of the control valve can be designed and adjusted to be larger than in the case of generic control valves.
  • the pressure compensator is open up to the limit load pressure, for example a load pressure of approx. 25 bar. Up to this limit load pressure, the sink volume flow flows parallel through the pressure compensator and the discharge pressure compensator via the larger opening cross section of the control valve. In total, at load pressures up to the limit load pressure, a higher volume flow can flow from the lifting cylinder device to the container when lowering, since the dynamic pressure via the control valve, the discharge pressure compensator and the pressure compensator connected in parallel to the discharge pressure compensator is smaller. If the limit load pressure is exceeded when lowering, the load pressure closes the pressure compensator completely.
  • the discharge pressure compensator alone limits the lowering volume flow via the lowering valve.
  • an increased lowering speed of the load-carrying means can thus be achieved in a simple manner at low load pressures.
  • a throttle device in particular an orifice plate, is arranged in the container line between the control valve and the discharge pressure compensator. Since the maximum opening cross section of the control valve can be designed and set larger in the lifting drive according to the invention than in generic control valves, the result is that the same maximum volume flow at 100% lowering speed for lowering via the control valve no longer causes a pressure drop of 4 bar, for example, but causes a reduced pressure drop of, for example, 2 bar.
  • a safety device which, in a safety position, interrupts the pressure applied to the outflow pressure compensator by the pressure present between the control valve and the outflow pressure compensator and reduces the spring prestressing of the spring devices of the outflow pressure compensator and the pressure compensator.
  • the loading of the discharge pressure compensator is interrupted by the pressure present between the control valve and the discharge pressure compensator in the tank line and the spring preloads of the spring devices of the discharge pressure compensator and the pressure compensator are reduced.
  • the discharge pressure compensator and the pressure compensator can thus be actuated into the respective blocking positions even at low load pressures in the consumer line in order to stop the lowering movement of the load handling device.
  • the safety device has a first piston that is operatively connected to the spring device of the outflow pressure compensator and a second piston that is operatively connected to the spring device of the pressure compensator, the first piston and the second piston each having a direction of increasing the spring preload have the control pressure chamber acting on the spring device, a safety valve being provided to control the loading of the control pressure chamber of the first piston and the control pressure chamber of the second piston.
  • the safety valve is connected to the tank line between the control valve and the discharge pressure compensator by means of a connecting line, to the control pressure chamber of the first piston and to the control pressure chamber of the second piston by means of a control line, and to the tank by means of a discharge line.
  • the pressure present in the container line between the control valve and the discharge pressure compensator can thus be used as control pressure, which is present in the control pressure chamber of the first piston and in the control pressure chamber of the second piston, in order to preload the spring devices on the discharge pressure compensator and on to increase the pressure compensator, and by connecting the control line to the container, the control pressure chamber of the first piston and the control pressure chamber of the second piston are relieved in order to reduce the spring preload of the spring devices on the discharge pressure compensator and on the pressure compensator.
  • control line is connected to a control pressure chamber of the discharge pressure compensator that acts in the direction of the flow position.
  • the safety valve can also be used to pressurize the control pressure chamber of the outflow pressure compensator acting in the direction of the flow position with the pressure in the tank line between the control valve and the outflow pressure compensator be controlled and by connecting the control line to the tank line, the pressurization of the control pressure chamber of the discharge pressure compensator acting in the direction of the flow position is interrupted with the pressure in the tank line between the control valve and the discharge pressure compensator and the control pressure chamber of the discharge pressure compensator is relieved to the tank.
  • the safety valve connects the connection line to the control line in an operating position and the safety valve connects the control line to the container in a safety position.
  • the control pressure chamber of the discharge pressure compensator which acts in the direction of the flow position, can be pressurized with the pressure in the tank line between the control valve and the discharge pressure compensator, and the spring preload of the spring devices on the discharge pressure compensator and on the pressure compensator can be increased, and in the safety position, the pressure can be relieved Control pressure chamber of the discharge pressure compensator to the container and a reduction in the spring preloads of the spring devices on the discharge pressure compensator and on the pressure compensator can be achieved.
  • the safety valve is acted upon by a spring in the safety position and by an actuating device, in particular a switching magnet, in the operating position.
  • an actuating device in particular a switching magnet
  • the invention has a number of advantages.
  • the parallel connection of the discharge pressure compensator and the pressure compensator makes it possible to increase the lowering speed of the load handling device with and without partial load, especially in the free lift of a mast, with little additional construction work. As a result, an increase in the handling capacity of the working machine can be achieved.
  • FIG 1 is a schematic structure of a hydraulic lifting drive 1 according to the invention of a mobile working machine, not shown in detail, for example an industrial truck.
  • the elevating drive 1 has a mast 2 on which a lifting device 3 is arranged such that it can be raised and lowered.
  • the load handling device 3 consists of a lifting carriage 4 that can be moved vertically on the mast 2 and to which, for example, a load fork 5 formed by forks is attached as an attachment.
  • the mast 2 consists of a fixed mast 2a and an extension mast 2b which can be raised and lowered on the fixed mast 2a and on which the load handling device 3 can be raised and lowered.
  • the mast 2 of figure 1 has at least two lifting stages.
  • a hydraulic lifting cylinder device 10a is provided for raising and lowering the load handling device 3 relative to the extending mast 2b.
  • the lifting cylinder device 10a forms a first lifting stage (free lift).
  • a flexible traction device 6, for example a lifting chain is provided figure 1 is attached at a first end to the lifting carriage 4, is guided via a deflection roller 7 on the extendable piston rod of the lifting cylinder device 10a and is attached at a second end to the extension mast 2b.
  • a hydraulic lifting cylinder device 10b is used to raise and lower the extension mast 2b relative to the stationary mast 2a.
  • the lifting cylinder device 10b forms a second lifting stage (mast lift).
  • the Lift cylinder device 10a is connected to the lift cylinder device 10b by means of a pressure medium line 11 .
  • the lifting cylinder device 10a, 10b can be actuated by means of a control valve device 12 for raising and lowering the load-carrying means 3.
  • the control valve device 12 has a control valve 13 for controlling the lifting operation of the lifting drive 1 and a control valve 14 for controlling the lowering operation of the lifting drive 1 .
  • the control valve 14 for controlling the lowering operation of the lifting drive 1 is connected to the pressure medium line 20 leading to the lifting cylinder device 11 and to a container line 21 leading to the container 18 .
  • the control valve 14 has a blocking position 14a and a lowering position 14b.
  • the control valve 14 is designed as a proportional valve which throttles in intermediate positions and can be actuated electrically.
  • a discharge pressure compensator 30 is arranged in the tank line 21 leading from the control valve 14 to the tank 18 .
  • the outflow pressure compensator 30 is designed as a proportional valve which throttles in intermediate positions and has a flow position 30a and a blocking position 30b.
  • the discharge pressure compensator 30 is actuated by a spring device 31 and the pressure present in the tank line 21 between the control valve 14 and the discharge pressure compensator 30 and thus the pressure present in the tank line 21 downstream of the control valve 14 in the direction of the flow position 30a.
  • a corresponding control line 32 is routed from the tank line 21 to a control pressure surface of the outflow pressure compensator 30 acting in the direction of the flow position 30a.
  • the spring device 31 is set to a value of 4 bar, for example.
  • the outflow pressure compensator 30 is in the direction of the pressure present in the consumer line 20 and thus the pressure present in the consumer line 20 upstream of the control valve 14 the blocking position 30b actuated.
  • a corresponding control line 34 is routed from the consumer line 20 to a control pressure surface of the discharge pressure compensator 30 acting in the direction of the blocking position 30b.
  • a further tank line 35 leading to tank 18 is connected to tank line 21 between control valve 14 and discharge pressure compensator 30, in which tank line 21 a pressure compensator 40 is arranged.
  • the tank line 35 branches off from the tank line 21 between the control valve 14 and the outflow pressure compensator 30 .
  • the pressure compensator 40 is designed as a proportional valve which throttles in intermediate positions and has a flow position 40a and a blocking position 40b.
  • the pressure compensator 40 is acted upon by a spring device 41 in the direction of the flow position 40a and by the pressure present in the consumer line 20 in the direction of the blocking position 40b.
  • a corresponding control line 42 is routed from the consumer line 20 or the control line 34 to a control pressure surface of the pressure compensator 40 acting in the direction of the blocking position 40b.
  • the spring device 41 of the pressure compensator 40 is set to a limit load pressure of the lifting drive 1, for example to a value of 25 bar.
  • a throttle device 45 for example an orifice plate, is arranged in the tank line 21 between the control valve 14 and the outflow pressure compensator 30 .
  • the maximum opening cross section of the control valve 14 of the lifting drive 1 according to the invention is preferably set larger than a lifting drive of the prior art, which does not have the container line 35 with the pressure compensator 40 .
  • the consequence of this is that the same maximum volume flow at 100% lowering speed for lowering via the control valve 14 is no longer possible generates a pressure drop of 4 bar, for example, but only causes 2 bar, for example.
  • the pressure compensator 40 is open up to the limit load pressure of approximately 25 bar, for example.
  • the lowering volume flow flowing out of the lifting cylinder device 10a, 10b flows via the larger opening cross section from the control valve 14 in parallel through the pressure compensator 40 and through the throttle device 45 and the discharge pressure compensator 30.
  • a sink volume flow flowing out of the lifting drive 1 flows out via the outlet pressure compensator 30 and the pressure compensator 40 into the container 18 .
  • the load pressure present in the control line 42 presses the pressure compensator 40 into the closed position 40b and closes the pressure compensator 40 completely.
  • a lowering volume flow flowing out of the lifting drive 1 can thus flow out into the container 18 exclusively via the discharge pressure compensator 30 .
  • the outlet pressure compensator 30 thus limits above the limit load pressure alone the volume flow via the lowering valve 14 due to the constant pressure drop across the lowering valve 14 and the throttle device 45.
  • the pressure drop across the lowering valve 14 and the throttle device 45 is preferably a total of 4 bar at 100% lowering speed and thus the Value of the spring device 31 of the discharge pressure compensator 30.
  • figure 2 is a further development of figure 1 shown, with the same components being provided with the same reference numbers.
  • FIG 2 is also a safety device 50 provided in a safety position, the loading of the discharge pressure compensator 30 from the in the Container line 21 between the control valve 14 and the discharge pressure compensator 30 interrupts pending pressure and the spring preloads of the spring devices 31, 41 of the discharge pressure compensator 30 and the pressure compensator 40 are reduced.
  • the safety device 50 has a first piston 51 which is operatively connected to the spring device 31 of the outflow pressure compensator 30 and a second piston 52 which is operatively connected to the spring device 41 of the pressure compensator 40 .
  • the first piston 51 and the second piston 52 each have a control pressure chamber 53, 54 which acts in the direction of increasing the spring preload of the spring device 31 or 41, respectively.
  • a safety valve 55 is provided to control the loading of the control pressure chamber 53 of the first piston 51 and the control pressure chamber 54 of the second piston 52 .
  • the safety valve 55 is connected by means of a connecting line 56 to the tank line 21 between the control valve 14 and the outflow pressure compensator 30, in the exemplary embodiment shown to the tank line 21 between the throttle device 45 and the outflow pressure compensator 30.
  • the safety valve 55 is also connected to the control pressure chamber by means of a control line 57 53 of the first piston 51 and to the control pressure chamber 54 of the second piston 52.
  • the safety valve 55 is also connected to the container 18 by means of a drain line 58 .
  • the control line 57 is also connected to the control pressure chamber 59 of the discharge pressure compensator 30, which acts in the direction of the flow position 30a and in which the spring device 31 is arranged.
  • a control pressure chamber 60 opposite the control pressure chamber 53 of the first piston 51 is relieved by means of a line 61 to the container 18 .
  • a control pressure chamber 62 opposite the control pressure chamber 54 of the second piston 52 and the control pressure chamber 63 of the pressure compensator 40 acting in the direction of the flow position 40a, in which the spring device 41 is arranged, is relieved by means of a line 64 to the container 18 .
  • the safety valve 55 has an operating position 55a in which the connecting line 56 is connected to the control line 57 and the drain line 58 is locked.
  • the control pressure chambers 53, 54 of the two pistons 51, 52 are acted upon by the pressure in the tank line 21 between the control valve 14 and the outflow pressure compensator 30, so that the spring devices 31, 41 are prestressed to the desired prestresses.
  • the discharge pressure compensator 30 on the spring side is acted upon by the pressure in the tank line 21 between the control valve 14 and the discharge pressure compensator 30 by means of the control line 57 .
  • the safety valve 55 also has a safety position 55b, in which the control line 57 is connected to the drain line 58 and thus to the container 18 and the connection line 56 is shut off.
  • the safety position 55b the control pressure chambers 53, 54 of the two pistons 51, 52 are thus relieved, so that the spring pretensions of the spring devices 31, 41 are reduced and preferably the spring device 31, 41 is completely relieved.
  • the loading of the discharge pressure compensator 30 is interrupted by the pressure present in the tank line 21 between the control valve 14 and the discharge pressure compensator 30 and the control pressure chamber 59 of the discharge pressure compensator 30 is relieved to the tank 18 .
  • the safety valve 55 is acted upon by a spring 70 into the safety position 55b and by an actuating device 71, in particular a switching magnet, into the operating position 55a.
  • control valve 14 and the safety valve 55 are not energized, so that the control valve 14 is in the blocking position 14a and the safety valve 55 is in the safety position 55b.
  • control valve 14 is driven into the lowering position 14b and the safety valve 55 is energized and thus driven into the operating position 55a.
  • the load pressure is passed after the control valve 14 into the control pressure chambers 53, 54 of the two pistons 51, 52, so that the pistons 51, 52 set the spring devices 31, 41 of the discharge pressure compensator 30 and the pressure compensator 40 to the desired Adjust preloads.
  • the load pressure after Control valve 14 passed into the control pressure chamber 59 of the outflow pressure compensator 30, whereby the flow rate through the outflow pressure compensator 30 can be regulated.
  • the safety valve 55 By actuating the safety valve 55 into the safety position 55b, in the event of a fault, for example a control valve 14 jammed in the lowering position 14b, the lowering movement of the load-carrying means 3 can be stopped.
  • the safety valve 50 relieves the two pistons 51, 52, so that the spring devices 31, 41 of the discharge pressure compensator 30 and the pressure compensator 40 are no longer pretensioned and there is no longer any load pressure on the discharge pressure compensator 30 in the control pressure chamber 39 downstream of the control valve 14.
  • a very small load pressure in the service line 20 and thus upstream of the lowering valve 14 is sufficient to actuate the pressure compensator 40 and the discharge pressure compensator 30 into the blocking position 30b, 40b.
  • a lowering movement of the load handling device 3 can thus be stopped at any time by not energizing the safety valve 55 even when the control valve is jammed in the lowering position 14b.
  • the throttle device 45 can be dispensed with if the pressure compensator 40, which is arranged parallel to the discharge pressure compensator 30, already leads to the desired higher lowering speeds of the load handling device 3 when lowering with load pressures below the limit load pressure, so that the maximum opening cross section of the control valve 14 is not set to be larger Must.

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Description

Die Erfindung betrifft einen hydraulischen Hubantrieb einer mobilen Arbeitsmaschine, insbesondere eines Flurförderzeugs, zum Anheben und Absenken eines Lastaufnahmemittels, wobei der Hubantrieb eine Hubzylindereinrichtung und ein Steuerventil zur Steuerung des Senkenbetriebs des Hubantriebs aufweist, das an eine zu der Hubzylindereinrichtung geführte Verbraucherleitung und an eine zu einem Behälter geführte Behälterleitung angeschlossen ist, wobei in der von dem Steuerventil zu dem Behälter geführten Behälterleitung eine Ablaufdruckwaage angeordnet ist, die von einer Federeinrichtung und dem in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage anstehenden Druck in Richtung einer Durchflussstellung und von dem in der Verbraucherleitung anstehenden Druck in Richtung einer Sperrstellung beaufschlagt ist.The invention relates to a hydraulic lifting drive of a mobile working machine, in particular an industrial truck, for raising and lowering a load handling device, the lifting drive having a lifting cylinder device and a control valve for controlling the lowering operation of the lifting drive, which is connected to a consumer line leading to the lifting cylinder device and to a consumer line leading to a connected to the tank line that runs from the tank, with an outflow pressure compensator being arranged in the tank line that runs from the control valve to the tank, which pressure compensator is influenced by a spring device and the pressure present in the tank line between the control valve and the outflow pressure compensator in the direction of a flow position and by the pressure in the consumer line Pressure is applied in the direction of a blocking position.

Flurförderzeuge sind zur Handhabung von Lasten mit einem Lastaufnahmemittel versehen, das in der Regel von einem am Hubgerüst anhebbaren und absenkbaren Hubschlitten und einem daran befestigten Anbaugerät gebildet ist. Das Anbaugerät kann beispielsweise als eine von Gabelzinken bestehende Lastgabel ausgebildet werden, mittels der eine Last, beispielsweise eine Palette unterfahren werden kann.For handling loads, industrial trucks are provided with a load handling device, which is generally formed by a lifting carriage that can be raised and lowered on the mast and an attachment attached thereto. The attachment can be designed, for example, as a load fork consisting of forks, by means of which a load, for example a pallet, can be driven under.

Bei Flurförderzeugen, bei denen das Lastaufnahmemittel mittels einer hydraulischen Hubzylindereinrichtung anhebbar und absenkbar ist, bestimmt die Auslenkung des Steuerventils im Senkenbetrieb die Senkengeschwindigkeit des Lastaufnahmemittels. Aus Sicherheitsgründen ist ein gesetzlich vorgeschriebener Grenzwert von 0,6 m/s für eine maximale Senkengeschwindigkeit des Lastaufnahmemittels bzw. einer Last vorgeschrieben.In industrial trucks in which the load-carrying device can be raised and lowered by means of a hydraulic lifting cylinder device, the deflection of the control valve in lowering mode determines the lowering speed of the load-carrying device. For safety reasons, a legally prescribed limit value of 0.6 m/s is prescribed for a maximum lowering speed of the load handling device or a load.

Soll bei gattungsgemäßen Hubantrieben eine angehobene Last bzw. ein leeres Lastaufnahmemittel abgesenkt werden, wird das Steuerventil in eine Öffnungsstellung betätigt. Zum Steuerventil ist die Ablaufdruckwaage in Reihe geschaltet. Mit dem Öffnen des Steuerventils beginnt ein Senkenvolumenstrom über das Steuerventil und die Ablaufdruckwaage von der Hubzylindereinrichtung zu dem Behälter zu fließen und das Lastaufnahmemittel wird abgesenkt. Der maximale Volumenstrom zum Senken des Lastaufnahmemittels wird durch das Einregeln der Ablaufdruckwaage begrenzt.If a lifted load or an empty load handling device is to be lowered in the case of lifting drives of this type, the control valve is actuated into an open position. The discharge pressure compensator is connected in series with the control valve. When the control valve opens, a sink volume flow begins to flow from the lifting cylinder device to the container via the control valve and the outflow pressure compensator, and the load handling device is lowered. The maximum flow rate for lowering of the load handling device is limited by the adjustment of the discharge pressure compensator.

Auf die Ablaufdruckwaage wirkt auf der einen Seite in Richtung einer Sperrstellung der Druck in der Verbraucherleitung vor dem Steuerventil und auf der anderen Seite in Richtung einer Durchflussstellung die Federkraft der Federeinrichtung und der Druck in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage und somit der Druck nach dem Steuerventil. Der Senkenvolumenstrom erhöht sich soweit, bis sich am Steuerventil ein maximaler Druckabfall von beispielsweise 4bar einstellt, der der Federkraft der Ablaufdruckwaage entspricht. Die Ablaufdruckwaage geht in Regelposition und fährt soweit in Richtung der Sperrstellung zu, dass dieser Druckabfall von beispielsweise 4bar an dem Steuerventil konstant gehalten wird.The pressure in the consumer line upstream of the control valve acts on the discharge pressure compensator on one side in the direction of a blocking position, and the spring force of the spring device and the pressure in the tank line between the control valve and the discharge pressure compensator and thus the pressure downstream on the other side in the direction of a flow position the control valve. The sink volume flow increases until a maximum pressure drop of 4 bar, for example, occurs at the control valve, which corresponds to the spring force of the discharge pressure compensator. The discharge pressure compensator goes into the control position and moves in the direction of the blocking position until this pressure drop of 4 bar, for example, is kept constant at the control valve.

Bei gattungsgemäßen Hubantrieben stellen sich bei Hubgerüsten mit mehreren Hubstufen, beispielsweise bei einem Hubgerüst mit einem Freihub als erste Hubstufe und einem Masthub als zweite Hubstufe, beim Senken mit geringen Lastdrücken, beispielsweise Lastdrücken unterhalb von ca. 25bar, in der ersten Hubstufe zu geringe maximale Senkengeschwindigkeiten ein, da das Steuerventil für diesen Betriebszustand nicht weit genug öffnet bzw. die Reihenschaltung Steuerventil und Ablaufdruckwaage einen zu großen Widerstand darstellt. Somit ist der geringe Lastdruck zum Senken des Lastaufnahmemittels nicht ausreichend, um auf die geforderte maximale Senkengeschwindigkeit zu kommen.In the case of lifting drives of the generic type, in the case of lifting frames with several lifting stages, for example in the case of a lifting frame with a free lift as the first lifting stage and a mast lift as the second lifting stage, when lowering with low load pressures, for example load pressures below approx. 25 bar, the maximum lowering speeds in the first lifting stage are too low because the control valve does not open far enough for this operating state or the series connection of the control valve and discharge pressure compensator represents too great a resistance. The low load pressure for lowering the load handling attachment is therefore not sufficient to achieve the required maximum lowering speed.

Das Steuerventil müsste bei gattungsgemäßen Hubantrieben für diesen Betriebszustand eines geringen Lastdruckes viel weiter öffnen, damit höhere Senkengeschwindigkeiten realisiert werden können. Dies würde jedoch bedeutet, dass mit höheren Lastdrücken, beispielsweise Lastdrücken oberhalb von 25bar, sich unzulässig hohe Senkengeschwindigkeiten des Lastaufnahmemittels einstellen würden. DE 10 2012 005432 A1 offenbart den Oberbegriff des Anspruchs 1.In the case of generic lifting drives, the control valve would have to open much further for this operating state of a low load pressure, so that higher lowering speeds can be achieved. However, this would mean that with higher load pressures, for example load pressures above 25 bar, impermissibly high lowering speeds of the load handling device would set in. DE 10 2012 005432 A1 discloses the preamble of claim 1.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, einen Hubantrieb der eingangs genannten Gattung zur Verfügung zu stellen, bei dem in einfacher Weise bei geringen Lastdrücken höhere Senkengeschwindigkeiten des Lastaufnahmemittels erzielt werden.The object of the present invention is to provide a lifting drive of the type mentioned at the outset, in which higher lowering speeds of the load-carrying means can be achieved in a simple manner at low load pressures.

Diese Aufgabe wird erfindungsgemäß dadurch gelöst, dass an die Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage eine zu dem Behälter geführte weitere Behälterleitung angeschlossen ist, in der eine Druckwaage angeordnet ist, die von einer Federeinrichtung in Richtung einer Durchflussstellung und von dem in der Verbraucherleitung anstehenden Druck in Richtung einer Sperrstellung beaufschlagt ist, wobei die Federeinrichtung der Druckwaage auf einen Grenzlastdruck des Hubantriebs eingestellt ist, so dass im Senkenbetrieb des Hubantriebs unterhalb des Grenzlastdruckes ein aus dem Hubantrieb abströmender Senkenvolumenstrom über die Ablaufdruckwaage und die Druckwaage in den Behälter abströmt und im Senkenbetrieb des Hubantriebs oberhalb des Grenzlastdruckes ein aus dem Hubantrieb abströmender Senkenvolumenstrom ausschließlich über die Ablaufdruckwaage in den Behälter abströmt.According to the invention, this object is achieved in that a line leading to the container is connected to the container line between the control valve and the discharge pressure compensator another container line is connected, in which a pressure compensator is arranged, which is acted upon by a spring device in the direction of a flow position and by the pressure present in the consumer line in the direction of a blocking position, the spring device of the pressure compensator being set to a limit load pressure of the lifting drive, so that in lowering operation of the lifting drive below the limit load pressure, a lowering volume flow flowing out of the lifting drive flows out via the outlet pressure compensator and the pressure compensator into the container and in lowering operation of the lifting drive above the limit load pressure a lowering volume flow outflowing from the lifting drive flows out exclusively via the outflow pressure compensator into the container.

Der erfindungsgemäße Gedanke besteht somit darin, parallel zur Ablaufdruckwaage eine Druckwaage anzuordnen und die Druckwaage auf einen Grenzlastdruck einzustellen, bis zu dem die Druckwaage geöffnet ist, so dass im Senkenbetrieb des Hubantriebs unterhalb des Grenzlastdruckes ein aus dem Hubantrieb abströmender Senkenvolumenstrom über die Ablaufdruckwaage und die Druckwaage in den Behälter abströmen kann. Die Ablaufdruckwaage und die Druckwaage sind direkt nach dem Senkenventil in die Behälterleitung bzw. die weitere Behälterleitung geschaltet.The idea according to the invention is therefore to arrange a pressure compensator parallel to the discharge pressure compensator and to set the pressure compensator to a load limit pressure up to which the pressure compensator is open, so that when the lifting drive is lowering below the load limit pressure, a lowering volume flow flowing out of the lifting drive via the discharge pressure compensator and the pressure compensator can flow into the container. The discharge pressure compensator and the pressure compensator are connected directly after the lowering valve in the tank line or the further tank line.

Bei dem erfindungsgemäßen Hubantrieb kann der maximale Öffnungsquerschnitt des Steuerventils größer als bei gattungsgemäßen Steuerventilen ausgeführt und eingestellt werden. Die Druckwaage ist bis zu dem Grenzlastdruck, beispielsweise einem Lastdruck von ca. 25bar geöffnet. Bis zu diesem Grenzlastdruck fließt der Senkenvolumenstrom über den größeren Öffnungsquerschnitt des Steuerventils parallel durch die Druckwaage und die Ablaufruckwaage. In Summe kann somit bei Lastdrücken bis zu dem Grenzlastdruck ein höherer Volumenstrom beim Senken von der Hubzylindereinrichtung zum Behälter abströmen, da der Staudruck über das Steuerventil, die Ablaufdruckwaage und die parallel zur Ablaufdruckwaage geschaltete Druckwaage kleiner ist. Wird beim Senken der Grenzlastdruck überschritten, so schließt der Lastdruck die Druckwaage vollständig. Oberhalb des Grenzlastdruckes begrenzt allein die Ablaufdruckwaage den Senkenvolumenstrom über das Senkenventil. Mit der parallel zur Ablaufdruckwaage geschalteten Druckwaage kann somit bei niedrigen Lastdrücken in einfacher Weise eine erhöhte Senkengeschwindigkeit des Lastaufnahmemittels erzielt werden.In the lifting drive according to the invention, the maximum opening cross section of the control valve can be designed and adjusted to be larger than in the case of generic control valves. The pressure compensator is open up to the limit load pressure, for example a load pressure of approx. 25 bar. Up to this limit load pressure, the sink volume flow flows parallel through the pressure compensator and the discharge pressure compensator via the larger opening cross section of the control valve. In total, at load pressures up to the limit load pressure, a higher volume flow can flow from the lifting cylinder device to the container when lowering, since the dynamic pressure via the control valve, the discharge pressure compensator and the pressure compensator connected in parallel to the discharge pressure compensator is smaller. If the limit load pressure is exceeded when lowering, the load pressure closes the pressure compensator completely. Above the limit load pressure, the discharge pressure compensator alone limits the lowering volume flow via the lowering valve. With the pressure compensator connected in parallel to the outflow pressure compensator, an increased lowering speed of the load-carrying means can thus be achieved in a simple manner at low load pressures.

Gemäß einer vorteilhaften Weiterbildung der Erfindung ist in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage eine Drosseleinrichtung, insbesondere eine Blende, angeordnet. Da bei dem erfindungsgemäßen Hubantrieb der maximale Öffnungsquerschnitt des Steuerventils größer als bei gattungsgemäßen Steuerventilen ausgeführt und eingestellt werden kann, ergibt sich als Folge, dass der gleiche maximale Volumenstrom bei 100% Senkengeschwindigkeit zum Senken über das Steuerventil nicht mehr beispielsweise einen Druckabfall von 4bar hervorruft, sondern einen verringerten Druckabfall von beispielsweise 2bar hervorruft. Mit der Drosseleinrichtung wird in einfacher Weise erzielt, dass im Senkenbetrieb oberhalb des Grenzlastdruckes, wobei die Druckwaage geschlossen ist und der Senkenvolumenstrom allein über das Steuerventil und die Ablaufdruckwaage abströmt und die Ablaufdruckwaage allein den Volumenstrom über das Steuerventil begrenzt, sich über das Steuerventil und die Drosseleinrichtung in Summe wieder ein Druckabfall von beispielsweise 4bar bei 100% Senkengeschwindigkeit einstellt, so dass von der Ablaufdruckwaage dieser Druckabfall von beispielsweise 4bar an dem Steuerventil und der Drosseleinrichtung konstant gehalten wird, um mit der Ablaufdruckwaage den maximalen Senkenvolumenstrom und somit die maximale Senkengeschwindigkeit begrenzen zu können.According to an advantageous development of the invention, a throttle device, in particular an orifice plate, is arranged in the container line between the control valve and the discharge pressure compensator. Since the maximum opening cross section of the control valve can be designed and set larger in the lifting drive according to the invention than in generic control valves, the result is that the same maximum volume flow at 100% lowering speed for lowering via the control valve no longer causes a pressure drop of 4 bar, for example, but causes a reduced pressure drop of, for example, 2 bar. With the throttle device it is achieved in a simple manner that in lowering operation above the limit load pressure, with the pressure compensator being closed and the lowering volume flow flowing away solely via the control valve and the discharge pressure compensator and the discharge pressure compensator alone limiting the volume flow via the control valve, via the control valve and the throttling device in total, a pressure drop of, for example, 4 bar at 100% lowering speed is set, so that this pressure drop of, for example, 4 bar at the control valve and the throttle device is kept constant by the outflow pressure compensator in order to be able to limit the maximum lowering volume flow and thus the maximum lowering speed with the outflow pressure compensator.

Gemäß einer vorteilhaften Weiterbildung der Erfindung ist eine Sicherheitseinrichtung vorgesehen, die in einer Sicherheitsstellung die Beaufschlagung der Ablaufdruckwaage von dem zwischen dem Steuerventil und der Ablaufdruckwaage anstehenden Druck unterbricht und die Federvorspannungen der Federeinrichtungen der Ablaufdruckwaage und der Druckwaage reduziert. Mit einer derartigen Sicherheitseinrichtung kann in der Sicherheitsstellung die Senkenbewegung des Lastaufnahmemittels im Fehlerfall des Steuerventils, beispielsweise einem in der Öffnungsstellung klemmenden Steuerventil, in einfacher Weise gestoppt werden. In der Sicherheitsstellung der Sicherheitseinrichtung ist die Beaufschlagung der Ablaufdruckwaage von dem zwischen dem Steuerventil und der Ablaufdruckwaage in der Behälterleitung anstehenden Druck unterbrochen und sind die Federvorspannungen der Federeinrichtungen der Ablaufdruckwaage und der Druckwaage reduziert. Die Ablaufdruckwaage und die Druckwaage können somit bereits bei geringen Lastdrücken in der Verbraucherleitung in die jeweiligen Sperrstellungen betätigt werden, um die Senkenbewegung des Lastaufnahmemittels zu stoppen.According to an advantageous development of the invention, a safety device is provided which, in a safety position, interrupts the pressure applied to the outflow pressure compensator by the pressure present between the control valve and the outflow pressure compensator and reduces the spring prestressing of the spring devices of the outflow pressure compensator and the pressure compensator. With such a safety device, the lowering movement of the load-carrying means can be stopped in a simple manner in the safety position in the event of a fault in the control valve, for example a control valve that is jammed in the open position. In the safety position of the safety device, the loading of the discharge pressure compensator is interrupted by the pressure present between the control valve and the discharge pressure compensator in the tank line and the spring preloads of the spring devices of the discharge pressure compensator and the pressure compensator are reduced. The discharge pressure compensator and the pressure compensator can thus be actuated into the respective blocking positions even at low load pressures in the consumer line in order to stop the lowering movement of the load handling device.

Die Sicherheitseinrichtung weist gemäß einer vorteilhaften Ausgestaltungsform der Erfindung einen mit der Federeinrichtung der Ablaufdruckwaage in Wirkverbindung stehenden ersten Kolben und einen mit der Federeinrichtung der Druckwaage in Wirkverbindung stehenden zweiten Kolben auf, wobei der erste Kolben und der zweite Kolben jeweils einen in Richtung einer Erhöhung der Federvorspannung der Federeinrichtung wirkenden Steuerdruckraum aufweisen, wobei zur Steuerung der Beaufschlagung des Steuerdruckraums des ersten Kolbens und des Steuerdruckraums des zweiten Kolbens ein Sicherheitsventil vorgesehen ist. Mit derartigen Kolben kann in Verbindung mit einem Sicherheitsventil in einfacher Weise durch Beaufschlagen bzw. Entlasten der Steuerdruckräume der beiden Kolben die Federvorspannung der Federeinrichtungen an der Ablaufdruckwaage und an der Druckwaage erhöht bzw. reduziert werden.According to an advantageous embodiment of the invention, the safety device has a first piston that is operatively connected to the spring device of the outflow pressure compensator and a second piston that is operatively connected to the spring device of the pressure compensator, the first piston and the second piston each having a direction of increasing the spring preload have the control pressure chamber acting on the spring device, a safety valve being provided to control the loading of the control pressure chamber of the first piston and the control pressure chamber of the second piston. With such pistons, in conjunction with a safety valve, the spring prestressing of the spring devices on the discharge pressure compensator and on the pressure compensator can be increased or reduced in a simple manner by loading or relieving the control pressure chambers of the two pistons.

Das Sicherheitsventil ist hierzu gemäß einer vorteilhaften Ausgestaltungsform der Erfindung mittels einer Anschlussleitung an die Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage angeschlossen, mittels einer Steuerleitung an den Steuerdruckraum des ersten Kolbens und an den Steuerdruckraum des zweiten Kolbens angeschlossen sowie mittels einer Abflussleitung an den Behälter angeschlossen. Durch Verbinden der Steuerleitung mit der Anschlussleitung kann somit der in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage anstehende Druck als Steuerdruck verwendet werden, der im Steuerdruckraum des ersten Kolbens und im Steuerdruckraum des zweiten Kolbens ansteht, um die Federvorspannung der Federeinrichtungen an der Ablaufdruckwaage und an der Druckwaage zu erhöhen, sowie durch Verbinden der Steuerleitung mit dem Behälter der Steuerdruckraum des ersten Kolbens und der Steuerdruckraum des zweiten Kolbens entlastet werden, um die Federvorspannung der Federeinrichtungen an der Ablaufdruckwaage und an der Druckwaage zu reduzieren.For this purpose, according to an advantageous embodiment of the invention, the safety valve is connected to the tank line between the control valve and the discharge pressure compensator by means of a connecting line, to the control pressure chamber of the first piston and to the control pressure chamber of the second piston by means of a control line, and to the tank by means of a discharge line. By connecting the control line to the connecting line, the pressure present in the container line between the control valve and the discharge pressure compensator can thus be used as control pressure, which is present in the control pressure chamber of the first piston and in the control pressure chamber of the second piston, in order to preload the spring devices on the discharge pressure compensator and on to increase the pressure compensator, and by connecting the control line to the container, the control pressure chamber of the first piston and the control pressure chamber of the second piston are relieved in order to reduce the spring preload of the spring devices on the discharge pressure compensator and on the pressure compensator.

Gemäß einer vorteilhaften Weiterbildung der Erfindung ist die Steuerleitung an einen in Richtung der Durchflussstellung wirkenden Steuerdruckraum der Ablaufdruckwaage angeschlossen. Mit dem Sicherheitsventil kann somit ebenfalls in einfacher Weise durch Verbinden der Steuerleitung mit der Anschlussleitung die Beaufschlagung des in Richtung der Durchflussstellung wirkenden Steuerdruckraums der Ablaufdruckwaage mit dem in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage gesteuert werden und durch Verbinden der Steuerleitung mit der Behälterleitung die Beaufschlagung des in Richtung der Durchflussstellung wirkenden Steuerdruckraums der Ablaufdruckwaage mit dem in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage unterbrochen werden und der Steuerdruckraum der Ablaufdruckwaage zum Behälter entlastet werden.According to an advantageous development of the invention, the control line is connected to a control pressure chamber of the discharge pressure compensator that acts in the direction of the flow position. By connecting the control line to the connection line, the safety valve can also be used to pressurize the control pressure chamber of the outflow pressure compensator acting in the direction of the flow position with the pressure in the tank line between the control valve and the outflow pressure compensator be controlled and by connecting the control line to the tank line, the pressurization of the control pressure chamber of the discharge pressure compensator acting in the direction of the flow position is interrupted with the pressure in the tank line between the control valve and the discharge pressure compensator and the control pressure chamber of the discharge pressure compensator is relieved to the tank.

Gemäß einer vorteilhaften Ausführungsform der Erfindung verbindet das Sicherheitsventil in einer Betriebsstellung die Anschlussleitung mit der Steuerleitung und verbindet das Sicherheitsventil in einer Sicherheitsstellung die Steuerleitung mit dem Behälter. In der Betriebsstellung kann somit eine Beaufschlagung des in Richtung der Durchflussstellung wirkenden Steuerdruckraums der Ablaufdruckwaage mit dem in der Behälterleitung zwischen dem Steuerventil und der Ablaufdruckwaage sowie eine Erhöhung der Federvorspannung der Federeinrichtungen an der Ablaufdruckwaage und an der Druckwaage erzielt werden sowie in der Sicherheitsstellung eine Entlastung des Steuerdruckraums der Ablaufdruckwaage zum Behälter und eine Reduzierung der Federvorspannungen der Federeinrichtungen an der Ablaufdruckwaage und an der Druckwaage erzielt werden.According to an advantageous embodiment of the invention, the safety valve connects the connection line to the control line in an operating position and the safety valve connects the control line to the container in a safety position. In the operating position, the control pressure chamber of the discharge pressure compensator, which acts in the direction of the flow position, can be pressurized with the pressure in the tank line between the control valve and the discharge pressure compensator, and the spring preload of the spring devices on the discharge pressure compensator and on the pressure compensator can be increased, and in the safety position, the pressure can be relieved Control pressure chamber of the discharge pressure compensator to the container and a reduction in the spring preloads of the spring devices on the discharge pressure compensator and on the pressure compensator can be achieved.

Das Sicherheitsventil ist gemäß einer vorteilhaften Ausgestaltungsform der von einer Feder in die Sicherheitsstellung und von einer Betätigungseinrichtung, insbesondere einem Schaltmagnet, in die Betriebsstellung beaufschlagt. Hierdurch wird eine hohe Betriebssicherheit erzielt, da sich im unbestromten Zustand das Sicherheitsventil in der Sicherheitsstellung befindet, in der bereits geringe Lastdrücke in der Verbraucherleitungen die Ablaufdruckwaage und die Druckwaage in die Sperrstellung betätigen.According to an advantageous embodiment, the safety valve is acted upon by a spring in the safety position and by an actuating device, in particular a switching magnet, in the operating position. This achieves a high level of operational safety, since the safety valve is in the safety position in the de-energized state, in which even low load pressures in the consumer lines actuate the discharge pressure compensator and the pressure compensator into the blocking position.

Die Erfindung weist eine Reihe von Vorteilen auf.The invention has a number of advantages.

Die Parallelschaltung der Ablaufdruckwaage und der Druckwaage ermöglicht es mit geringem zusätzlichem Bauaufwand, die Senkengeschwindigkeit des Lastaufnahmemittels ohne und mit Teillast, insbesondere im Freihub eines Hubgerüstes, zu erhöhen. Dadurch ist eine Erhöhung der Umschlagsleistung der Arbeitsmaschine erzielbar.The parallel connection of the discharge pressure compensator and the pressure compensator makes it possible to increase the lowering speed of the load handling device with and without partial load, especially in the free lift of a mast, with little additional construction work. As a result, an increase in the handling capacity of the working machine can be achieved.

Weitere Vorteile und Einzelheiten der Erfindung werden anhand der in den schematischen Figuren dargestellten Ausführungsbeispiele näher erläutert. Hierbei zeigt

Figur 1
den Schaltplan eines erfindungsgemäßen Hubantriebs und
Figur 2
eine Weiterbildung der Figur 1.
Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiments illustrated in the schematic figures. Here shows
figure 1
the circuit diagram of a linear actuator according to the invention and
figure 2
a further development of figure 1 .

In der Figur 1 ist ein schematischer Aufbau eines erfindungsgemäßen hydraulischen Hubantriebs 1 einer nicht näher dargestellten mobilen Arbeitsmaschine, beispielsweise eines Flurförderzeugs, dargestellt.In the figure 1 is a schematic structure of a hydraulic lifting drive 1 according to the invention of a mobile working machine, not shown in detail, for example an industrial truck.

Der Hubantrieb 1 weist ein Hubgerüst 2 auf, an dem ein Lastaufnahmemittel 3 anhebbar und absenkbar angeordnet ist. Das Lastaufnahmemittel 3 besteht im dargestellten Ausführungsbeispiel aus einem am Hubgerüst 2 vertikal bewegbaren Hubschlitten 4, an dem beispielsweise eine von Gabelzinken gebildete Lastgabel 5 als Anbaugerät befestigt ist.The elevating drive 1 has a mast 2 on which a lifting device 3 is arranged such that it can be raised and lowered. In the exemplary embodiment shown, the load handling device 3 consists of a lifting carriage 4 that can be moved vertically on the mast 2 and to which, for example, a load fork 5 formed by forks is attached as an attachment.

Im dargestellten Ausführungsbeispiel besteht das Hubgerüst 2 aus einem Standmast 2a und einem an dem Standmast 2a anhebbar und absenkbar angeordneten Ausfahrmast 2b, an dem das Lastaufnahmemittel 3 anhebbar und absenkbar angeordnet ist.In the exemplary embodiment shown, the mast 2 consists of a fixed mast 2a and an extension mast 2b which can be raised and lowered on the fixed mast 2a and on which the load handling device 3 can be raised and lowered.

Das Hubgerüst 2 der Figur 1 weist mindestens zwei Hubstufen auf. Zum Anheben und Absenken des Lastaufnahmemittels 3 relativ zu dem Ausfahrmast 2b ist eine hydraulische Hubzylindereinrichtung 10a vorgesehen. Die Hubzylindereinrichtung 10a bildet eine erste Hubstufe (Freihub). Zum Anheben und Absenken des Lastaufnahmemittels 3 ist ein flexibles Zugmittel 6, beispielsweise einer Hubkette, vorgesehen, das in der Figur 1 mit einem ersten Ende an dem Hubschlitten 4 befestigt ist, über eine Umlenkrolle 7 an der ausfahrbaren Kolbenstange der Hubzylindereinrichtung 10a geführt ist und mit einem zweiten Ende an dem Ausfahrmast 2b befestigt ist. Eine hydraulische Hubzylindereinrichtung 10b dient zum Anheben und Absenken des Ausfahrmastes 2b relativ zum Standmast 2a. Die Hubzylindereinrichtung 10b bildet eine zweite Hubstufe (Masthub). Die Hubzylindereinrichtung 10a ist mit der Hubzylindereinrichtung 10b mittels einer Druckmittelleitung 11 verbunden.The mast 2 of figure 1 has at least two lifting stages. A hydraulic lifting cylinder device 10a is provided for raising and lowering the load handling device 3 relative to the extending mast 2b. The lifting cylinder device 10a forms a first lifting stage (free lift). To raise and lower the load handling device 3, a flexible traction device 6, for example a lifting chain, is provided figure 1 is attached at a first end to the lifting carriage 4, is guided via a deflection roller 7 on the extendable piston rod of the lifting cylinder device 10a and is attached at a second end to the extension mast 2b. A hydraulic lifting cylinder device 10b is used to raise and lower the extension mast 2b relative to the stationary mast 2a. The lifting cylinder device 10b forms a second lifting stage (mast lift). the Lift cylinder device 10a is connected to the lift cylinder device 10b by means of a pressure medium line 11 .

Die Hubzylindereinrichtung 10a, 10b ist mittels einer Steuerventileinrichtung 12 zum Anheben und Absenken des Lastaufnahmemittels 3 betätigbar. Die Steuerventileinrichtung 12 weist ist im dargestellten Ausführungsbeispiel ein Steuerventil 13 zur Steuerung des Hebenbetriebs des Hubantriebs 1 und ein Steuerventil 14 zur Steuerung des Senkenbetriebs des Hubantriebs 1 auf.The lifting cylinder device 10a, 10b can be actuated by means of a control valve device 12 for raising and lowering the load-carrying means 3. In the exemplary embodiment shown, the control valve device 12 has a control valve 13 for controlling the lifting operation of the lifting drive 1 and a control valve 14 for controlling the lowering operation of the lifting drive 1 .

Das Steuerventil 13 zur Steuerung des Hebenbetriebs des Hubantriebs 1 ist an eine Förderleitung 15 einer Pumpe 16 angeschlossen, die mittels einer Ansaugleitung 17 Druckmittel aus einem Behälter 18 ansaugt, und an eine zu den Hubzylindereinrichtung 11a, 11b geführte Verbraucherleitung 20 angeschlossen. Das Steuerventil 13 weist eine Sperrstellung 13a und eine Hebenstellung 13b auf.The control valve 13 for controlling the lifting operation of the lifting drive 1 is connected to a delivery line 15 of a pump 16, which draws in pressure medium from a container 18 by means of a suction line 17, and is connected to a consumer line 20 leading to the lifting cylinder devices 11a, 11b. The control valve 13 has a blocking position 13a and a lifting position 13b.

Das Steuerventil 14 zur Steuerung des Senkenbetriebs des Hubantriebs 1 ist an die zu der Hubzylindereinrichtung 11 geführte Druckmittelleitung 20 und an eine zu dem Behälter 18 geführte Behälterleitung 21 angeschlossen. Das Steuerventil 14 weist eine Sperrstellung 14a und eine Senkenstellung 14b auf. im dargestellten Ausführungsbeispiel ist das Steuerventil 14 als in Zwischenstellungen drosselndes Proportionalventil ausgebildet, das elektrisch betätigbar ist.The control valve 14 for controlling the lowering operation of the lifting drive 1 is connected to the pressure medium line 20 leading to the lifting cylinder device 11 and to a container line 21 leading to the container 18 . The control valve 14 has a blocking position 14a and a lowering position 14b. In the exemplary embodiment shown, the control valve 14 is designed as a proportional valve which throttles in intermediate positions and can be actuated electrically.

In der von dem Steuerventil 14 zu dem Behälter 18 geführten Behälterleitung 21 ist eine Ablaufdruckwaage 30 angeordnet. Die Ablaufdruckwaage 30 ist als in Zwischenstellungen drosselndes Proportionalventil mit einer Durchflussstellung 30a und einer Sperrstellung 30b ausgebildet. Die Ablaufdruckwaage 30 ist von einer Federeinrichtung 31 und dem in der Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 anstehenden Druck und somit dem in der Behälterleitung 21 stromab des Steuerventils 14 anstehenden Druck in Richtung der Durchflussstellung 30a betätigt. Hierzu ist eine entsprechende Steuerleitung 32 von der Behälterleitung 21 an eine in Richtung der Durchflussstellung 30a wirkende Steuerdruckfläche der Ablaufdruckwaage 30 geführt. Die Federeinrichtung 31 ist auf einen Wert von beispielsweise 4bar eingestellt. Die Ablaufdruckwaage 30 ist von dem in der Verbraucherleitung 20 anstehenden Druck und somit dem in der Verbraucherleitung 20 stromauf des Steuerventils 14 anstehenden Druck in Richtung der Sperrstellung 30b betätigt. Hierzu ist eine entsprechende Steuerleitung 34 von der Verbraucherleitung 20 an eine in Richtung der Sperrstellung 30b wirkende Steuerdruckfläche der Ablaufdruckwaage 30 geführt.A discharge pressure compensator 30 is arranged in the tank line 21 leading from the control valve 14 to the tank 18 . The outflow pressure compensator 30 is designed as a proportional valve which throttles in intermediate positions and has a flow position 30a and a blocking position 30b. The discharge pressure compensator 30 is actuated by a spring device 31 and the pressure present in the tank line 21 between the control valve 14 and the discharge pressure compensator 30 and thus the pressure present in the tank line 21 downstream of the control valve 14 in the direction of the flow position 30a. For this purpose, a corresponding control line 32 is routed from the tank line 21 to a control pressure surface of the outflow pressure compensator 30 acting in the direction of the flow position 30a. The spring device 31 is set to a value of 4 bar, for example. The outflow pressure compensator 30 is in the direction of the pressure present in the consumer line 20 and thus the pressure present in the consumer line 20 upstream of the control valve 14 the blocking position 30b actuated. For this purpose, a corresponding control line 34 is routed from the consumer line 20 to a control pressure surface of the discharge pressure compensator 30 acting in the direction of the blocking position 30b.

Um im Senkenbetrieb bei geringen Lastdrücken eine erhöhte Senkengeschwindigkeit zu erzielen, ist erfindungsgemäß an die Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 eine zu dem Behälter 18 geführte weitere Behälterleitung 35 angeschlossen, in der eine Druckwaage 40 angeordnet ist. Die Behälterleitung 35 zweigt von der Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 ab. Die Druckwaage 40 ist als in Zwischenstellungen drosselndes Proportionalventil mit einer Durchflussstellung 40a und einer Sperrstellung 40b ausgebildet. Die Druckwaage 40 ist von einer Federeinrichtung 41 in Richtung der Durchflussstellung 40a und von dem in der Verbraucherleitung 20 anstehenden Druck in Richtung der Sperrstellung 40b beaufschlagt. Hierzu ist eine entsprechende Steuerleitung 42 von der Verbraucherleitung 20 bzw. der Steuerleitung 34 an eine in Richtung der Sperrstellung 40b wirkende Steuerdruckfläche der Druckwaage 40 geführt.In order to achieve an increased lowering speed in lowering operation at low load pressures, according to the invention, a further tank line 35 leading to tank 18 is connected to tank line 21 between control valve 14 and discharge pressure compensator 30, in which tank line 21 a pressure compensator 40 is arranged. The tank line 35 branches off from the tank line 21 between the control valve 14 and the outflow pressure compensator 30 . The pressure compensator 40 is designed as a proportional valve which throttles in intermediate positions and has a flow position 40a and a blocking position 40b. The pressure compensator 40 is acted upon by a spring device 41 in the direction of the flow position 40a and by the pressure present in the consumer line 20 in the direction of the blocking position 40b. For this purpose, a corresponding control line 42 is routed from the consumer line 20 or the control line 34 to a control pressure surface of the pressure compensator 40 acting in the direction of the blocking position 40b.

Die Federeinrichtung 41 der Druckwaage 40 ist auf einen Grenzlastdruck des Hubantriebs 1 eingestellt, beispielsweise auf einen Wert von 25bar.The spring device 41 of the pressure compensator 40 is set to a limit load pressure of the lifting drive 1, for example to a value of 25 bar.

In der Behälterleitung 21 ist zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 eine Drosseleinrichtung 45, beispielsweise eine Blende, angeordnet.A throttle device 45 , for example an orifice plate, is arranged in the tank line 21 between the control valve 14 and the outflow pressure compensator 30 .

Bei dem erfindungsgemäßen Hubantrieb 1 ist somit parallel zur Ablaufdruckwaage 30 die Druckwaage 40 angeordnet. Die Ablaufdruckwage 30 und die Druckwaage 40 sind jeweils direkt nach dem Steuerventil 14 geschaltet. Zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 ist zusätzlich in der Behälterleitung 21 die Drosseleinrichtung 45 installiert.In the lifting drive 1 according to the invention, the pressure compensator 40 is thus arranged parallel to the outflow pressure compensator 30 . The outflow pressure scale 30 and the pressure scale 40 are each connected directly after the control valve 14 . The throttle device 45 is additionally installed in the tank line 21 between the control valve 14 and the outflow pressure compensator 30 .

Der maximal Öffnungsquerschnitt des Steuerventils 14 des erfindungsgemäßen Hubantriebs 1 ist gegenüber einem Hubantrieb des Standes der Technik, der die Behälterleitung 35 mit der Druckwaage 40 nicht aufweist, bevorzugt größer eingestellt. Dies hat zur Folge, dass der gleiche maximale Volumenstrom bei 100% Senkengeschwindigkeit zum Senken über das Steuerventil 14 nicht mehr beispielsweise einen Druckabfall von 4bar erzeugt, sondern nur noch von beispielswiese 2bar hervorruft.The maximum opening cross section of the control valve 14 of the lifting drive 1 according to the invention is preferably set larger than a lifting drive of the prior art, which does not have the container line 35 with the pressure compensator 40 . The consequence of this is that the same maximum volume flow at 100% lowering speed for lowering via the control valve 14 is no longer possible generates a pressure drop of 4 bar, for example, but only causes 2 bar, for example.

Die Druckwaage 40 ist bis zu dem Grenzlastdruck von ca. beispielsweise 25bar geöffnet. Im Senkenbetrieb zu diesem Grenzlastdruck von beispielsweise 25bar fließt somit der aus der Hubzylindereinrichtung 10a, 10b abströmende Senkenvolumenstrom über den größeren Öffnungsquerschnitt vom Steuerventil 14 parallel durch die Druckwaage 40 und durch die Drosseleinrichtung 45 und die Ablaufdruckwaage 30. Im Senkenbetrieb des Hubantriebs 1 unterhalb des Grenzlastdruckes kann somit ein aus dem Hubantrieb 1 abströmender Senkenvolumenstrom über die Ablaufdruckwaage 30 und die Druckwaage 40 in den Behälter 18 abströmen. In Summe kann bei Lastdrücken kleiner wie der Grenzlastdruck somit ein höherer Volumenstrom beim Senken zum Behälter 18 abströmen, da der Staudruck über das Steuerventil 14 und der parallel geschalteten Druckwaage 40 und Ablaufdruckwaage 30 kleiner ist. Dies ermöglicht bei geringen Lastdrücken unterhalb des Grenzlastdruckes eine erhöhte Senkengeschwindigkeit des Lastaufnahmemittels 3.The pressure compensator 40 is open up to the limit load pressure of approximately 25 bar, for example. In lowering operation at this limiting load pressure of 25 bar, for example, the lowering volume flow flowing out of the lifting cylinder device 10a, 10b flows via the larger opening cross section from the control valve 14 in parallel through the pressure compensator 40 and through the throttle device 45 and the discharge pressure compensator 30. In lowering operation of the lifting drive 1 below the limiting load pressure thus, a sink volume flow flowing out of the lifting drive 1 flows out via the outlet pressure compensator 30 and the pressure compensator 40 into the container 18 . In total, at load pressures lower than the limit load pressure, a higher volume flow can flow out to the container 18 when lowering, since the dynamic pressure via the control valve 14 and the pressure compensator 40 and discharge pressure compensator 30 connected in parallel is smaller. At low load pressures below the limit load pressure, this enables an increased lowering speed of the load handling device 3.

Wird das Lastdruckniveau beim Senken von 25bar und somit der Grenzlastdruck überschritten, beaufschlagt der in der in der Steuerleitung 42 anstehenden Lastdruck die Druckwaage 40 in die Schließstellung 40b und schließt die Druckwaage 40 komplett. Im Senkenbetrieb des Hubantriebs 1 oberhalb des Grenzlastdruckes kann somit ein aus dem Hubantrieb 1 abströmender Senkenvolumenstrom ausschließlich über die Ablaufdruckwaage 30 in den Behälter 18 abströmen. Die Ablaufdruckwaage 30 begrenzt somit oberhalb des Grenzlastdruckes allein den Volumenstrom über das Senkenventil 14 durch den konstanten Druckabfall über das Senkenventil 14 und die Drosseleinrichtung 45. Der Druckabfall über das Senkenventil 14 und die Drosseleinrichtung 45 beträgt bevorzugt in Summe 4bar bei 100% Senkengeschwindigkeit und somit dem Wert der Federeinrichtung 31 der Ablaufdruckwaage 30.If the load pressure level of 25 bar when lowering and thus the limit load pressure is exceeded, the load pressure present in the control line 42 presses the pressure compensator 40 into the closed position 40b and closes the pressure compensator 40 completely. In the lowering operation of the lifting drive 1 above the limit load pressure, a lowering volume flow flowing out of the lifting drive 1 can thus flow out into the container 18 exclusively via the discharge pressure compensator 30 . The outlet pressure compensator 30 thus limits above the limit load pressure alone the volume flow via the lowering valve 14 due to the constant pressure drop across the lowering valve 14 and the throttle device 45. The pressure drop across the lowering valve 14 and the throttle device 45 is preferably a total of 4 bar at 100% lowering speed and thus the Value of the spring device 31 of the discharge pressure compensator 30.

In der Figur 2 ist eine Weiterbildung der Figur 1 dargestellt, wobei gleiche Bauteile mit gleichen Bezugsziffern versehen sind.In the figure 2 is a further development of figure 1 shown, with the same components being provided with the same reference numbers.

In der Figur 2 ist zusätzlich eine Sicherheitseinrichtung 50 vorgesehen, die in einer Sicherheitsstellung die Beaufschlagung der Ablaufdruckwaage 30 von dem in der Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 anstehenden Druck unterbricht und die Federvorspannungen der Federeinrichtungen 31, 41 der Ablaufdruckwaage 30 und der Druckwaage 40 reduziert.In the figure 2 is also a safety device 50 provided in a safety position, the loading of the discharge pressure compensator 30 from the in the Container line 21 between the control valve 14 and the discharge pressure compensator 30 interrupts pending pressure and the spring preloads of the spring devices 31, 41 of the discharge pressure compensator 30 and the pressure compensator 40 are reduced.

Die Sicherheitseinrichtung 50 weist einen mit der Federeinrichtung 31 der Ablaufdruckwaage 30 in Wirkverbindung stehenden ersten Kolben 51 und einen mit der Federeinrichtung 41 der Druckwaage 40 in Wirkverbindung stehenden zweiten Kolben 52 auf. Der erste Kolben 51 und der zweite Kolben 52 weisen jeweils einen in Richtung einer Erhöhung der Federvorspannung der Federeinrichtung 31 bzw. 41 wirkenden Steuerdruckraum 53, 54 auf. Zur Steuerung der Beaufschlagung des Steuerdruckraums 53 des ersten Kolbens 51 und des Steuerdruckraums 54 des zweiten Kolbens 52 ist ein Sicherheitsventil 55 vorgesehen.The safety device 50 has a first piston 51 which is operatively connected to the spring device 31 of the outflow pressure compensator 30 and a second piston 52 which is operatively connected to the spring device 41 of the pressure compensator 40 . The first piston 51 and the second piston 52 each have a control pressure chamber 53, 54 which acts in the direction of increasing the spring preload of the spring device 31 or 41, respectively. A safety valve 55 is provided to control the loading of the control pressure chamber 53 of the first piston 51 and the control pressure chamber 54 of the second piston 52 .

Das Sicherheitsventil 55 ist mittels einer Anschlussleitung 56 an die Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 angeschlossen, im dargestellten Ausführungsbeispiel an die Behälterleitung 21 zwischen der Drosseleinrichtung 45 und die Ablaufdruckwaage 30. Das Sicherheitsventil 55 ist weiterhin mittels einer Steuerleitung 57 an den Steuerdruckraum 53 des ersten Kolbens 51 und an den Steuerdruckraum 54 des zweiten Kolbens 52 angeschlossen. Das Sicherheitsventil 55 ist weiterhin mittels einer Abflussleitung 58 an den Behälter 18 angeschlossen.The safety valve 55 is connected by means of a connecting line 56 to the tank line 21 between the control valve 14 and the outflow pressure compensator 30, in the exemplary embodiment shown to the tank line 21 between the throttle device 45 and the outflow pressure compensator 30. The safety valve 55 is also connected to the control pressure chamber by means of a control line 57 53 of the first piston 51 and to the control pressure chamber 54 of the second piston 52. The safety valve 55 is also connected to the container 18 by means of a drain line 58 .

Die Steuerleitung 57 ist weiterhin an den in Richtung der Durchflussstellung 30a wirkenden Steuerdruckraum 59 der Ablaufdruckwaage 30 angeschlossen, in dem die Federeinrichtung 31 angeordnet ist.The control line 57 is also connected to the control pressure chamber 59 of the discharge pressure compensator 30, which acts in the direction of the flow position 30a and in which the spring device 31 is arranged.

Ein dem Steuerdruckraum 53 des ersten Kolbens 51 gegenüberliegender Steuerdruckraum 60 ist mittels einer Leitung 61 zum Behälter 18 entlastet. Ein dem Steuerdruckraum 54 des zweiten Kolbens 52 gegenüberliegender Steuerdruckraum 62 sowie der in Richtung der Durchflussstellung 40a wirkende Steuerdruckraum 63 der Druckwaage 40, in dem die Federeinrichtung 41 angeordnet ist, ist mittels einer Leitung 64 zum Behälter 18 entlastet.A control pressure chamber 60 opposite the control pressure chamber 53 of the first piston 51 is relieved by means of a line 61 to the container 18 . A control pressure chamber 62 opposite the control pressure chamber 54 of the second piston 52 and the control pressure chamber 63 of the pressure compensator 40 acting in the direction of the flow position 40a, in which the spring device 41 is arranged, is relieved by means of a line 64 to the container 18 .

Das Sicherheitsventil 55 weist eine Betriebsstellung 55a auf, in der die Anschlussleitung 56 mit der Steuerleitung 57 verbunden ist und die Abflussleitung 58 abgesperrt ist. In der Betriebsstellung 55a sind somit die Steuerdruckräume 53, 54 der beiden Kolben 51, 52 von dem Druck in der Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 beaufschlagt, so dass die Federeinrichtungen 31, 41 auf die gewünschten Vorspannungen vorgespannt sind. Weiterhin ist in der Betriebsstellung 55a die Ablaufdruckwaage 30 auf der Federseite mittel der Steuerleitung 57 von dem Druck in der Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 beaufschlagt. Das Sicherheitsventil 55 weist weiterhin eine Sicherheitsstellung 55b auf, in der die Steuerleitung 57 mit der Abflussleitung 58 und somit dem Behälter 18 verbunden ist und die Anschlussleitung 56 abgesperrt ist. In der Sicherheitsstellung 55b sind somit die Steuerdruckräume 53, 54 der beiden Kolben 51, 52 entlastet, so dass die Federvorspannungen der Federeinrichtungen 31, 41 reduziert und bevorzugt die Federeinrichtung 31, 41 vollständig entlastet werden. Zudem wird in der Sicherheitsstellung 55b die Beaufschlagung der Ablaufdruckwaage 30 von dem in der Behälterleitung 21 zwischen dem Steuerventil 14 und der Ablaufdruckwaage 30 anstehenden Druck unterbrochen und der Steuerdruckraum 59 der Ablaufdruckwaage 30 zum Behälter 18 entlastet.The safety valve 55 has an operating position 55a in which the connecting line 56 is connected to the control line 57 and the drain line 58 is locked. In the operating position 55a, the control pressure chambers 53, 54 of the two pistons 51, 52 are acted upon by the pressure in the tank line 21 between the control valve 14 and the outflow pressure compensator 30, so that the spring devices 31, 41 are prestressed to the desired prestresses. Furthermore, in the operating position 55a, the discharge pressure compensator 30 on the spring side is acted upon by the pressure in the tank line 21 between the control valve 14 and the discharge pressure compensator 30 by means of the control line 57 . The safety valve 55 also has a safety position 55b, in which the control line 57 is connected to the drain line 58 and thus to the container 18 and the connection line 56 is shut off. In the safety position 55b, the control pressure chambers 53, 54 of the two pistons 51, 52 are thus relieved, so that the spring pretensions of the spring devices 31, 41 are reduced and preferably the spring device 31, 41 is completely relieved. In addition, in the safety position 55b the loading of the discharge pressure compensator 30 is interrupted by the pressure present in the tank line 21 between the control valve 14 and the discharge pressure compensator 30 and the control pressure chamber 59 of the discharge pressure compensator 30 is relieved to the tank 18 .

Das Sicherheitsventil 55 ist im dargestellten Ausführungsbeispiel von einer Feder 70 in die Sicherheitsstellung 55b und von einer Betätigungseinrichtung 71, insbesondere einem Schaltmagnet, in die Betriebsstellung 55a beaufschlagt.In the exemplary embodiment shown, the safety valve 55 is acted upon by a spring 70 into the safety position 55b and by an actuating device 71, in particular a switching magnet, into the operating position 55a.

Sofern kein Senkenbetrieb des Hubantriebs 1 gewünscht ist, sind das Steuerventil 14 und das Sicherheitsventil 55 nicht bestromt, so dass sich das Steuerventil 14 in der Sperrstellung 14a und das Sicherheitsventil 55 in der Sicherheitsstellung 55b befinden.If no lowering operation of the lifting drive 1 is desired, the control valve 14 and the safety valve 55 are not energized, so that the control valve 14 is in the blocking position 14a and the safety valve 55 is in the safety position 55b.

Sofern ein Senkenbetrieb des Hubantriebs 1 gewünscht ist, wird das Steuerventil 14 in die Senkenstellung 14b angesteuert und das Sicherheitsventil 55 bestromt und somit in die Betriebsstellung 55a angesteuert.If lowering operation of the lifting drive 1 is desired, the control valve 14 is driven into the lowering position 14b and the safety valve 55 is energized and thus driven into the operating position 55a.

In der Betriebsstellung 55a des Sicherheitsventils 55 wird der Lastdruck nach dem Steuerventil 14 in die Steuerdruckräume 53, 54 der beiden Kolben 51, 52 geleitet, so dass die Kolben 51, 52 die Federeinrichtungen 31, 41 der Ablaufdruckwaage 30 und der Druckwaage 40 auf die gewünschten Vorspannungen einstellen. Zusätzlich wird in der Betriebsstellung 55a des Sicherheitsventils 55 der Lastdruck nach dem Steuerventil 14 in den Steuerdruckraum 59 der Ablaufdruckwaage 30 geleitet, wodurch ein Regeln des Volumenstroms durch die Ablaufdruckwaage 30 möglich ist.In the operating position 55a of the safety valve 55, the load pressure is passed after the control valve 14 into the control pressure chambers 53, 54 of the two pistons 51, 52, so that the pistons 51, 52 set the spring devices 31, 41 of the discharge pressure compensator 30 and the pressure compensator 40 to the desired Adjust preloads. In addition, in the operating position 55a of the safety valve 55, the load pressure after Control valve 14 passed into the control pressure chamber 59 of the outflow pressure compensator 30, whereby the flow rate through the outflow pressure compensator 30 can be regulated.

Durch Betätigen des Sicherheitsventils 55 in die Sicherheitsstellung 55b kann bei einem Fehlerfall, beispielswiese einem in der Senkenstellung 14b klemmenden Steuerventil 14 ein Stopp der Senkenbewegung des Lastaufnahmemittels 3 erzielt werden.By actuating the safety valve 55 into the safety position 55b, in the event of a fault, for example a control valve 14 jammed in the lowering position 14b, the lowering movement of the load-carrying means 3 can be stopped.

In der Sicherheitsstellung 55b entlastet das Sicherheitsventil 50 die beiden Kolben 51, 52, so dass die Federeinrichtungen 31, 41 der Ablaufdruckwaage 30 und der Druckwaage 40 nicht mehr vorgespannt und an der Ablaufdruckwaage 30 liegt im Steuerdruckraum 39 kein Lastdruck stromab des Steuerventils 14 mehr an. Somit ist ein sehr kleiner Lastdruck in der Verbracherleitung 20 und somit stromauf des Senkenventils 14 ausreichend, um die Druckwaage 40 und die Ablaufdruckwaage 30 jeweils in die Sperrstellung 30b, 40b zu betätigen. Eine Senkenbewegung des Lastaufnahmemittels 3 kann somit auch bei in der Senkenstellung 14b klemmenden Steuerventil durch nicht bestromen des Sicherheitsventils 55 jederzeit gestoppt werden.In the safety position 55b, the safety valve 50 relieves the two pistons 51, 52, so that the spring devices 31, 41 of the discharge pressure compensator 30 and the pressure compensator 40 are no longer pretensioned and there is no longer any load pressure on the discharge pressure compensator 30 in the control pressure chamber 39 downstream of the control valve 14. Thus, a very small load pressure in the service line 20 and thus upstream of the lowering valve 14 is sufficient to actuate the pressure compensator 40 and the discharge pressure compensator 30 into the blocking position 30b, 40b. A lowering movement of the load handling device 3 can thus be stopped at any time by not energizing the safety valve 55 even when the control valve is jammed in the lowering position 14b.

Die Erfindung ist nicht auf die dargestellten Ausführungsbeispiel beschränkt. Unter Umständen kann auf die Drosseleinrichtung 45 verzichtet werden, wenn die zusätzlich zur Ablaufdruckwaage 30 parallel angeordnete Druckwaage 40 beim Senken mit Lastdrücken unterhalb des Grenzlastdruckes schon zu den gewünschten höheren Senkengeschwindigkeiten des Lastaufnahmemittels 3 führt, so dass der maximale Öffnungsquerschnitt des Steuerventils 14 nicht größer eingestellt werden muss.The invention is not limited to the illustrated embodiment. Under certain circumstances, the throttle device 45 can be dispensed with if the pressure compensator 40, which is arranged parallel to the discharge pressure compensator 30, already leads to the desired higher lowering speeds of the load handling device 3 when lowering with load pressures below the limit load pressure, so that the maximum opening cross section of the control valve 14 is not set to be larger Must.

Claims (8)

  1. Hydraulic lifting drive (1) of a mobile working machine, in particular of an industrial truck, for raising and lowering a load-bearing means (3), wherein the lifting drive (1) has a lifting-cylinder device (10a; 10b) and a control valve (14), which is intended for controlling the lowering operation of the lifting drive (1) and is connected to a consumer line (20), which is led to the lifting-cylinder device (10a, 10b), and to a container line (21), which is led to a container (18), wherein a discharge pressure compensator (30) is arranged in the container line (21), which is led from the control valve (14) to the container (18), the discharge pressure compensator being activated in the direction of a throughflow position (30a) by a spring device (31) and the pressure which is present in the container line (21) between the control valve (14) and the discharge pressure compensator (30) and being activated in the direction of a blocking position (30b) by the pressure which is present in the consumer line (20), characterized in that the container line (21) has connected to it, between the control valve (14) and the discharge pressure compensator (30), a further container line (35), which is led to the container (18) and in which is arranged a pressure compensator (40), which is activated in the direction of a throughflow position (40a) by a spring device (41) and is activated in the direction of a blocking position (40b) by the pressure which is present in the consumer line (20), wherein the spring device (41) of the pressure compensator (40) is set to a limit load pressure of the lifting drive (1), so that, during lowering operation of the lifting drive (1) below the limit load pressure, a lowering volume flow flowing out of the lifting drive (1) flows out into the container (18) via the discharge pressure compensator (30) and the pressure compensator (40) and, during lowering operation of the lifting drive (1) above the limit load pressure, a lowering volume flow flowing out of the lifting drive (1) flows out into the container (18) exclusively via the discharge pressure compensator (30).
  2. Hydraulic lifting drive according to Claim 1, characterized in that a throttle device (45), in particular an orifice, is arranged in the container line (21) between the control valve (14) and the discharge pressure compensator (30).
  3. Hydraulic lifting drive according to Claim 1 or 2, characterized by the provision of a safety device (50), which, in a safety position (55b), interrupts the activation of the discharge pressure compensator (30) by the pressure which is present between the control valve (14) and the discharge pressure compensator (30), and reduces the prestressing of the spring devices (31, 41) of the discharge pressure compensator (30) and of the pressure compensator (40).
  4. Hydraulic lifting drive according to Claim 3, characterized in that the safety device (50) has a first piston (51), which is in operative connection with the spring device (31) of the discharge pressure compensator (30), and a second piston (52), which is in operative connection with the spring device (41) of the pressure compensator (40), wherein the first piston (51) and the second piston (52) each have a control-pressure space (53, 54), which acts in the direction in which the prestressing of the spring device (31, 41) is increased, wherein a safety valve (55) is provided in order to control the loading of the control-pressure space (53) of the first piston (51) and of the control-pressure space (54) of the second piston (52) .
  5. Hydraulic lifting drive according to Claim 4, characterized in that a connection line (56) connects the safety valve (55) to the container line (21) between the control valve (14) and the discharge pressure compensator (30), a control line (57) connects it to the control-pressure space (53) of the first piston (51) and to the control-pressure space (54) of the second piston (52), and an outflow line (58) connects it to the container (18).
  6. Hydraulic lifting drive according to Claim 5, characterized in that the control line (57) is connected to a control-pressure space (59) of the discharge pressure compensator (30), said control-pressure space acting in the direction of the throughflow position (30a).
  7. Hydraulic lifting drive according to Claim 5 or 6, characterized in that, in an operating position (55a), the safety valve (55) connects the connection line (56) to the control line (57) and, in a safety position (55b), it connects the control line (57) to the container (18).
  8. Hydraulic lifting drive according to Claim 7, characterized in that the safety valve (55) is activated into the safety position (55b) by a spring (70) and into the operating position (55a) by an actuating device (71), in particular a switching magnet.
EP21181370.4A 2020-07-09 2021-06-24 Hydraulic lift drive for a mobile working machine Active EP3936470B1 (en)

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DE102012005432A1 (en) * 2012-03-17 2013-09-19 Jungheinrich Aktiengesellschaft Industrial truck for lifting load, has vertical monitoring unit comparing detected pressure values of pressure sensors with each other and generating emergency signal when deviation of pressure values is greater than predetermined value
DE102017107365A1 (en) * 2017-04-06 2018-10-11 Still Gmbh Hydraulic lifting drive of a mobile work machine, especially an industrial truck

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DE102020118139A1 (en) 2022-01-13
EP3936470A1 (en) 2022-01-12

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