EP2236453A1 - Hydraulic lifting assembly for forklifts - Google Patents

Hydraulic lifting assembly for forklifts Download PDF

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Publication number
EP2236453A1
EP2236453A1 EP10157297A EP10157297A EP2236453A1 EP 2236453 A1 EP2236453 A1 EP 2236453A1 EP 10157297 A EP10157297 A EP 10157297A EP 10157297 A EP10157297 A EP 10157297A EP 2236453 A1 EP2236453 A1 EP 2236453A1
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EP
European Patent Office
Prior art keywords
hydraulic
lifting device
filter
return
control valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP10157297A
Other languages
German (de)
French (fr)
Other versions
EP2236453B1 (en
Inventor
Hans-Peter Essig
Alfred Gröner
Gerd Jarbot
Wolfgang Kugel
Harald Kuhn
Albert Schick
Reinhard Wierling
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Mahle International GmbH
Original Assignee
Mahle International GmbH
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Publication date
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Publication of EP2236453A1 publication Critical patent/EP2236453A1/en
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Publication of EP2236453B1 publication Critical patent/EP2236453B1/en
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Classifications

    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/023—Excess flow valves, e.g. for locking cylinders in case of hose burst
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/04—Special measures taken in connection with the properties of the fluid
    • F15B21/041—Removal or measurement of solid or liquid contamination, e.g. filtering
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/615—Filtering means

Definitions

  • the present invention relates to a hydraulic lifting device, in particular on a vehicle, preferably a forklift.
  • the invention also relates to a forklift with such a hydraulic lifting device.
  • the invention relates to a filter control valve for such a lifting device.
  • Lifting devices of this type in particular when they are arranged on a forklift, comprise a lifting device for lifting trucks, for example in the form of a lifting fork, which is arranged to be adjustable in stroke along a mast.
  • the lifting device comprises at least one hydraulic piston-cylinder unit for driving the lifting device.
  • a hydraulic supply is usually provided, which connects a hydraulic fluid reservoir with a hydraulic pump via a hydraulic pump with a pressure chamber of the piston-cylinder unit.
  • a simple interconnection is preferred in which, for lifting the lifting device, a pressure generated by the hydraulic pump is supplied to the pressure chamber of the piston-cylinder unit. About the relative movement between the piston and cylinder then the lifting device is raised. To lower the lifting device of the pressure chamber is relaxed.
  • the load of the lifting device then drives the relative movement between the piston and cylinder.
  • the hydraulic fluid is expelled from the pressure chamber and passes, for example, bypassing the hydraulic pump in the reservoir.
  • a stroke control valve may be arranged in the hydraulic line, by means of which the hydraulic pump can be activated and deactivated.
  • impurities in the hydraulic fluid which is preferably a hydraulic oil
  • these impurities are, for example, solid particles which, during operation of the piston-cylinder assembly, are abraded into the hydraulic medium.
  • particulate impurities in the production of the piston-cylinder unit can get into the pressure chamber, which are then rinsed out during operation.
  • the present invention is concerned with the problem of providing for a hydraulic lifting device of the type mentioned or for a forklift equipped with an improved embodiment, which is particularly characterized in that the risk of damage to the hydraulic pump or other component of the lifting device is reduced ,
  • the invention is based on the general idea, in a return branch of the hydraulic supply, in which the hydraulic fluid flows when lowering the lifting device from the pressure chamber to arrange a filter control valve, which leads the return flow in dependence of the lubricating oil pressure either by a hydraulic filter or by a hydraulic bypass bypass branch ,
  • the filter control valve performs the return flow through the hydraulic filter when the hydraulic pressure is above a predetermined control pressure, and through the bypass branch when the hydraulic pressure is below the predetermined control pressure. This ensures that the return flow is only passed through the hydraulic filter when a sufficient hydraulic pressure is available, which can easily overcome the flow resistance of the hydraulic filter.
  • the filter control valve is thus also for such Cases a sufficiently rapid lowering of the lifting device allows in which no or no sufficient load is arranged on the lifting device, so that only a relatively low pressure can build up in the hydraulic return.
  • the impurities originating from the piston-cylinder unit are filtered out of the lubricant for a large number of lowering operations, without the operation of the lifting device being impaired. Overall, this can improve the quality of the lubricant, which reduces the risk of damage to the hydraulic pump and / or other components of the lifting device.
  • the predetermined control pressure at which the filter control valve switches be selected so that the lifting device with a predetermined load and at a predetermined speed is passively lowered, when the hydraulic pump is deactivated.
  • the flow resistance of the hydraulic filter is taken into account.
  • the control pressure is set so high that the hydraulic fluid return is passed through the hydraulic filter only if it is ensured that despite the throttling effect of the hydraulic filter, the lifting device with the predetermined load and at the predetermined speed is passively lowered.
  • the return branch comprising the filter control valve and the hydraulic filter and the bypass, spaced from the piston-cylinder unit branches off from the hydraulic line which connects the reservoir via the pump to the pressure chamber. Furthermore, the Return branch from the hydraulic fluid reservoir spaced open into the hydraulic line.
  • the proposed construction has the advantage that the entire hydraulic supply of the lifting device can remain largely unchanged if it is to be modified in the sense of the invention. For example, the hydraulic supply from the pressure chamber to the branch point of the return branch remain unchanged. In addition, the hydraulic supply from the hydraulic reservoir to the discharge point of the return branch remain unchanged.
  • the lifting device according to the invention can be particularly easily realized in a conventional lifting device. This reduces the manufacturing costs. In addition, a relatively simple conversion or retrofitting is possible.
  • FIG. 1 includes a here only partially illustrated forklift 1 a hydraulic lifting device 2 for lifting loads 3.
  • a forklift a hydraulic lifting device 2 for lifting loads 3.
  • any other vehicle can be equipped with such a lifting device 2.
  • the respective vehicle or forklift 1 in addition to the lifting device 2 usually has a chassis and a generally well-known structure, which need not be discussed in detail.
  • the hydraulic lifting device 2 comprises a lifting device 4, with the aid of which the respective load 3 can be raised and lowered.
  • the load 3 is here represented by a frame shown with a broken line.
  • An arrow 5 represents a lifting direction, while an arrow 6 represents a lowering direction.
  • the lifting device 4 can for example be designed as a lifting fork or as a platform.
  • the lifting device 4 comprises a guide, not shown here, for example in the form of a mast on or on which, for example, the lifting fork 4 is mounted vertically adjustable.
  • the lifting device 2 further comprises at least one hydraulic piston-cylinder unit 7.
  • the piston-cylinder unit 7 has a piston 8 which is arranged to be adjustable in stroke in a cylinder 9 and limits a pressure chamber 10 in the cylinder 9.
  • a piston rod 11 is led out of the cylinder 9.
  • a piston 8 with piston rod 11 may also be provided a plunger.
  • the piston-cylinder unit 7 is used to drive the lifting device 4, here for lifting the lifting device 4.
  • this is the cylinder 9 stationary, for example, the respective vehicle 1, arranged while the piston rod 11 is connected to the lifting device 4 , Likewise, a reverse construction is conceivable in which the lifting device 4 is connected to the cylinder 9.
  • the lifting device 2 also has a hydraulic supply 12.
  • This includes at least one hydraulic line 13, a hydraulic fluid reservoir 14 and a hydraulic pump 15.
  • the hydraulic line 13 connects the reservoir 14 with the pressure chamber 10 of the piston-cylinder unit 7 and contains the hydraulic pump 15.
  • the hydraulic supply 12 also has a return branch 16, in a hydraulic filter 17 is arranged.
  • a filter control valve 18 is provided, which is arranged in the return branch 16. In this case, the filter control valve 18 with respect to a return flow upstream of the hydraulic filter 17 to the filter control valve 18 is also a bypass branch 19 is connected, which bypasses the hydraulic filter 17.
  • the filter control valve 18 is designed such that, in the case of a return flow, that is to say in the case of a hydraulic fluid flow, leading from the pressure chamber 10 back to the reservoir 14, depending on the pressure in the hydraulic fluid upstream of the filter control valve 18, the return flow more or less through the hydraulic filter 17 or more or less through the bypass 17, bypassing the hydraulic filter 17 leads. If the hydraulic fluid pressure upstream of the filter control valve 18 above a predetermined control pressure, the filter control valve 18, the return flow more or less completely through the hydraulic filter 17. To block the filter control valve 18 expediently the inflow to the bypass branch 19. However, the input-side pressure of the filter control valve 18 below the predetermined Control pressure, the filter control valve 18, the return flow more or less completely through the bypass branch 19, so that the return flow bypasses the hydraulic filter 17.
  • the leading through the hydraulic filter 17 portion of the return branch 16 may be blocked by the filter control valve 18, but does not have, because the higher flow resistance of the hydraulic filter 17 ensures that the return flow with open bypass branch 19 this preferred.
  • the control pressure at which the filter control valve 18 activates or deactivates the bypass branch 19 is, according to a preferred embodiment, predetermined so that the lifting device 4, when loaded with a predetermined reference load, is passively lowered at a predetermined speed when the hydraulic pump 15 is disabled.
  • the dead weight of the lifting device 4 together with the weight of the predetermined load 3, drives the lifting device 4 in the lowering direction 6.
  • the volume of the pressure chamber 10 is reduced, whereby the hydraulic fluid is expelled.
  • the return flow is generated.
  • the pressure in the hydraulic fluid is determined by the pressure generated in the pressure chamber 10, ie by the weight of the lifting device 4 with the load 3, which is applied via the piston 8 to the hydraulic fluid.
  • Threshold for the switching operation of the filter control valve 18 ensures that the lifting device 4 can always be lowered at a sufficient speed. If the hydraulic fluid pressure when lowering above the control pressure, it is sufficient, despite the flow resistance of the hydraulic filter 17 to generate a sufficient volume flow, which leads to the desired lowering speed. If the pressure in the pressure chamber 10 is too small, the filter control valve 18 leads the return flow through the bypass branch 19, whereby the flow resistance of the hydraulic filter 17 is bypassed, so that even for pressures below the control pressure, a sufficient lowering speed for the lifting device 4 can be realized. This is especially true when the lifting device 4 is unloaded, so that only their own weight for generating a pressure in the return flow is present.
  • the hydraulic fluid can be passed through the hydraulic filter 17 when lowering the lifting device 4, whereby impurities that arise in the piston-cylinder unit 7 and get into the hydraulic fluid can be filtered out of the hydraulic fluid.
  • a stroke control valve 20 is arranged in the preferred embodiment shown here, with the aid of which the hydraulic pump 15 can be activated and deactivated.
  • This stroke control valve 20 is arranged downstream of the pump 15 with respect to a flow, ie with respect to a flow oriented in the pumping direction of the pump 15, which leads from the reservoir 14 to the pressure chamber 10.
  • the stroke control valve 20 has two switch positions 21 and 22. In Fig. 1 In this first switching position 21, the pressure side of the pump 15 is connected to the pressure chamber 10, while a return line 23 is blocked, which is also connected to the stroke control valve 20 and leading to the reservoir 14. In the second switching position 22, the pressure side of Pump 15 locked while the return 23 is connected bypassing the pump 15 with the remaining hydraulic line 13.
  • the pump 15 may have an internal return, which opens at an overpressure and returns to the reservoir 14 or internally shorts the pump 15.
  • the stroke control valve 20 may be configured as a proportional valve in order to divide the pressure or flow rate of the pump 15 variably on the leading to the pressure chamber 10 portion of the hydraulic line 13 and the return 23 can.
  • an auxiliary hydraulic filter 24 can be arranged between the hydraulic pump 15 and the stroke control valve 20. As a result, a protection of the stroke control valve 20 is realized against contamination even at a flow.
  • the return branch 16 is connected to the hydraulic line 13, so that the return branch 16 branches off from the hydraulic line 13 at a distance from the piston-cylinder unit 7.
  • a corresponding branch point is designated by 25. This makes it possible to maintain the conventional connection configuration between hydraulic supply 12 and piston-cylinder unit 7. Only the branch point 25 must be created in the hydraulic line 13. Alternatively, an embodiment is possible in which the return branch 16 can be connected separately to the hydraulic line 13 to the piston-cylinder unit 7.
  • the return branch 16 is connected at a distance from the hydraulic reservoir 14 to the hydraulic line 13.
  • a corresponding connection point is designated here by 26.
  • This connection point 26 is arranged in the preferred example between the branch point 25 and the stroke control valve 20. This makes it possible, in particular, to design the hydraulic supply 12 conventionally from the hydraulic reservoir 14 to the connection point 26 that in the hydraulic line 13, only the connection point 26 must be created. Alternatively, it is basically possible to connect the return branch 16 separately to the hydraulic line 13 to the hydraulic fluid reservoir 14.
  • bypass branch 19 is also connected to the return branch 16 with respect to the return flow downstream of the hydraulic filter 17.
  • a corresponding connection point is designated by 27.
  • only one connection point 26 between return branch 16 and hydraulic line 13 is required to integrate the return branch 16 with filter control valve 18, hydraulic filter 17 and associated bypass branch 19 into the hydraulic supply 12.
  • the hydraulic line 13 has in a section 28 which leads from the connection point 26 to the branch point 25, a non-return valve 29 which opens in a leading from the hydraulic fluid reservoir 14 to the pressure chamber 10 feed direction and locks in a leading from the pressure chamber 10 to the reservoir 14 return direction.
  • a non-return valve 29 which opens in a leading from the hydraulic fluid reservoir 14 to the pressure chamber 10 feed direction and locks in a leading from the pressure chamber 10 to the reservoir 14 return direction.
  • the return branch 16 contains at least one return check valve 30, which is permeable in the return direction and which blocks in the advance direction. This ensures that a flow stream can not flow through the return branch 16, but 16 passes to the pressure chamber 10, bypassing the return branch.
  • such a return check valve 30 is contained both in the bypass branch 19 and in the section of the return branch 16 containing the hydraulic filter 17.
  • a single such return check valve 30 may be sufficient.
  • the filter control valve 18 has a leading to the piston-cylinder unit 7 input 31, leading to the hydraulic filter 17 filter output 32 and a bypass branch 19 leading bypass output 33. Further, the filter control valve 18 in a housing 34, a valve member 35, with the aid of the outputs 32, 33 can be controlled. The valve member 35 is adjustable depending on the prevailing at the input 31 hydraulic fluid pressure in the housing 34. Furthermore, the filter control valve 18 in the illustrated embodiments, a return spring 36, the valve member 35 in one in the Fig. 2 and 4 pretensioned starting position shown. In this starting position the Fig. 2 and 4 the bypass output 33 is communicatively connected to the input 31.
  • the valve member 35 is designed sleeve-shaped or cup-shaped. It is open at an input 31 facing the axial end face and closed at an axial end face facing away from it. Furthermore, it has a radial window 37, which in the starting position according to Fig. 2 is aligned with the bypass outlet 33, whereby it is connected through the valve member 35 through to the input 31.
  • the valve member 35 is secured with an anti-rotation device 38 against changing its rotational position relative to the housing 34.
  • the applied pressure at the input 31 drives the valve member 35 against the restoring force of the return spring 36 at. With sufficient hydraulic pressure at the input 31, the valve member 35 reaches into its in Fig. 3 shown end position.
  • the window 37 is arranged in alignment with the filter output 32, so that then the filter output 32 communicates with the input 31.
  • the return flow can then flow to the hydraulic filter 17. It is clear that depending on the pressure and any intermediate positions are conceivable. It is noteworthy in this embodiment that in the end position of Fig. 3 the bypass opening 19 is locked. It is also worth noting that in this embodiment in the starting position according to Fig. 2 the filter output 32 is blocked.
  • the housing 34 has a cover 39 for ease of assembly, which may be bolted to the housing 34, wherein also an axial seal 40 between the housing 34 and cover 39 for sealing the housing 34 may be provided.
  • valve member 35 is configured as a ball.
  • a ball guide 41 allows adjustment of the valve member 35 in the housing 34.
  • the cover 39 is screwed in this example by means of a thread 42 in the housing 34, so that in principle can be dispensed with additional seals.
  • both outputs 32, 33 communicating with the input 31 are connected.
  • the flow resistance of the hydraulic filter 17 causes a large part of the return flow flows through the bypass outlet 33.
  • a small proportion of the return flow can flow off via the filter outlet 32, which is indicated here by an additional arrow shown with a broken line.
  • the pressure at the input 31 is so great that it presses the valve member 35 against the restoring force of the return spring 36 against a valve seat 43, whereby the valve member 35 blocks the bypass outlet 33.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Transportation (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Structural Engineering (AREA)
  • Analytical Chemistry (AREA)
  • Civil Engineering (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Forklifts And Lifting Vehicles (AREA)

Abstract

The device has a hydraulic piston cylinder aggregate (7) for driving a lifting gear (4), and a hydraulic supply (12) for connecting a hydraulic central reservoir (14) with a hydraulic line (13) by a hydraulic pump (15). A hydraulic filter (17) is arranged in a return branch (16) of the hydraulic supply. A filter control valve (18) is arranged in the return branch, and guides return flow above pre-determined control pressure by the return branch and below pre-determined actuating pressure by a bypass branch (19) surrounding the hydraulic filter.

Description

Die vorliegende Erfindung betrifft eine hydraulische Hebeeinrichtung, insbesondere an einem Fahrzeug, vorzugsweise eines Gabelstaplers. Die Erfindung betrifft außerdem einen Gabelstapler mit einer derartigen hydraulischen Hebeeinrichtung. Außerdem betrifft die Erfindung ein Filtersteuerventil für eine derartige Hebeeinrichtung.The present invention relates to a hydraulic lifting device, in particular on a vehicle, preferably a forklift. The invention also relates to a forklift with such a hydraulic lifting device. Moreover, the invention relates to a filter control valve for such a lifting device.

Hebeeinrichtungen dieser Art, insbesondere wenn sie an einem Gabelstapler angeordnet sind, umfassen eine Hubeinrichtung zum Anheben von Lastern, zum Beispiel in Form einer Hubgabel, die entlang eines Masts hubverstellbar angeordnet ist. Ferner umfasst die Hebeeinrichtung zumindest ein hydraulisches Kolben-Zylinder-Aggregat zum Antreiben der Hubeinrichtung. Ferner ist üblicherweise eine Hydraulikversorgung vorgesehen, die mit einer Hydraulikleitung ein Hydraulikmittelreservoir über eine Hydraulikpumpe mit einem Druckraum des Kolben-Zylinder-Aggregats verbindet. Dabei wird eine einfache Verschaltung bevorzugt, bei der zum Anheben der Hubeinrichtung ein von der Hydraulikpumpe erzeugter Druck dem Druckraum des Kolben-Zylinder-Aggregats zugeführt wird. Über die Relativbewegung zwischen Kolben und Zylinder wird dann die Hubeinrichtung angehoben. Zum Absenken der Hubeinrichtung wird der Druckraum entspannt. Die Last der Hubeinrichtung treibt dann die Relativbewegung zwischen Kolben und Zylinder an. Hierdurch wird das Hydraulikmittel aus dem Druckraum ausgetrieben und gelangt beispielsweise unter Umgehung der Hydraulikpumpe in das Reservoir. Um eine derartige einfache Verschaltung realisieren zu können, kann beispielsweise ein Hubsteuerventil in der Hydraulikleitung angeordnet sein, mit dessen Hilfe die Hydraulikpumpe aktiviert und deaktiviert werden kann.Lifting devices of this type, in particular when they are arranged on a forklift, comprise a lifting device for lifting trucks, for example in the form of a lifting fork, which is arranged to be adjustable in stroke along a mast. Furthermore, the lifting device comprises at least one hydraulic piston-cylinder unit for driving the lifting device. Furthermore, a hydraulic supply is usually provided, which connects a hydraulic fluid reservoir with a hydraulic pump via a hydraulic pump with a pressure chamber of the piston-cylinder unit. In this case, a simple interconnection is preferred in which, for lifting the lifting device, a pressure generated by the hydraulic pump is supplied to the pressure chamber of the piston-cylinder unit. About the relative movement between the piston and cylinder then the lifting device is raised. To lower the lifting device of the pressure chamber is relaxed. The load of the lifting device then drives the relative movement between the piston and cylinder. As a result, the hydraulic fluid is expelled from the pressure chamber and passes, for example, bypassing the hydraulic pump in the reservoir. In order to realize such a simple interconnection, for example, a stroke control valve may be arranged in the hydraulic line, by means of which the hydraulic pump can be activated and deactivated.

Es hat sich gezeigt, dass Verunreinigungen in das Hydraulikmittel, bei dem es sich bevorzugt um ein Hydrauliköl handelt, gelangen können, die zu einer Beschädigung der Hydraulikpumpe und in besonderem Maße des Hubsteuerventils führen können. Diese Verunreinigungen sind z.B. Festkörperpartikel, die im Betrieb des Kolben-Zylinder-Aggregats durch Abrieb in das Hydraulikmittel gelangen. Ebenso können partikelartige Verunreinigungen bei der Herstellung des Kolben-Zylinder-Aggregats in den Druckraum gelangen, die dann im Betrieb ausgespült werden.It has been found that impurities in the hydraulic fluid, which is preferably a hydraulic oil, can pass, leading to damage the hydraulic pump and in particular the stroke control valve can lead. These impurities are, for example, solid particles which, during operation of the piston-cylinder assembly, are abraded into the hydraulic medium. Likewise, particulate impurities in the production of the piston-cylinder unit can get into the pressure chamber, which are then rinsed out during operation.

Die vorliegende Erfindung beschäftigt sich mit dem Problem, für eine hydraulische Hebeeinrichtung der eingangs genannten Art bzw. für einen damit ausgestatteten Gabelstapler eine verbesserte Ausführungsform anzugeben, die sich insbesondere dadurch auszeichnet, dass die Gefahr einer Beschädigung der Hydraulikpumpe oder einer anderen Komponente der Hebeeinrichtung reduziert ist.The present invention is concerned with the problem of providing for a hydraulic lifting device of the type mentioned or for a forklift equipped with an improved embodiment, which is particularly characterized in that the risk of damage to the hydraulic pump or other component of the lifting device is reduced ,

Dieses Problem wird erfindungsgemäß durch die Gegenstände der unabhängigen Ansprüche gelöst. Vorteilhafte Ausführungsformen sind Gegenstand der abhängigen Ansprüche.This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

Die Erfindung beruht auf dem allgemeinen Gedanken, in einem Rücklaufzweig der Hydraulikversorgung, in dem das Hydraulikmittel beim Absenken der Hubeinrichtung aus dem Druckraum abströmt, ein Filtersteuerventil anzuordnen, das die Rücklaufströmung in Abhängigkeit des Schmieröldrucks entweder durch ein Hydraulikfilter oder durch einen das Hydraulikfilter umgehenden Bypasszweig führt. Dabei führt das Filtersteuerventil die Rücklaufströmung durch das Hydraulikfilter, wenn der Hydraulikdruck oberhalb eines vorbestimmten Steuerdrucks liegt, und durch den Bypasszweig, wenn der Hydraulikdruck unterhalb des vorbestimmten Steuerdrucks liegt. Hierdurch wird erreicht, dass die Rücklaufströmung nur dann durch das Hydraulikfilter geführt wird, wenn ein hinreichender Hydraulikdruck zur Verfügung steht, der ohne weiteres den Strömungswiderstand des Hydraulikfilters überwinden kann. Mit Hilfe des Filtersteuerventils wird somit auch für solche Fälle ein hinreichend rasches Absenken der Hubeinrichtung ermöglicht, bei denen keine oder keine ausreichende Last auf der Hubeinrichtung angeordnet ist, so dass sich im Hydraulikrücklauf nur ein vergleichsweise niedriger Druck aufbauen kann.The invention is based on the general idea, in a return branch of the hydraulic supply, in which the hydraulic fluid flows when lowering the lifting device from the pressure chamber to arrange a filter control valve, which leads the return flow in dependence of the lubricating oil pressure either by a hydraulic filter or by a hydraulic bypass bypass branch , In this case, the filter control valve performs the return flow through the hydraulic filter when the hydraulic pressure is above a predetermined control pressure, and through the bypass branch when the hydraulic pressure is below the predetermined control pressure. This ensures that the return flow is only passed through the hydraulic filter when a sufficient hydraulic pressure is available, which can easily overcome the flow resistance of the hydraulic filter. With the help of the filter control valve is thus also for such Cases a sufficiently rapid lowering of the lifting device allows in which no or no sufficient load is arranged on the lifting device, so that only a relatively low pressure can build up in the hydraulic return.

Durch das Hydraulikfilter im Rücklaufzweig werden für eine Vielzahl der Absenkvorgänge die aus dem Kolben-Zylinder-Aggregat stammenden Verunreinigungen aus dem Schmiermittel herausgefiltert, ohne dass es zu einer Beeinträchtigung des Betriebs der Hebeeinrichtung kommt. Insgesamt kann dadurch die Qualität des Schmiermittels verbessert werden, was die Gefahr einer Beschädigung der Hydraulikpumpe und/oder anderer Komponenten der Hebeeinrichtung reduziert.Due to the hydraulic filter in the return branch, the impurities originating from the piston-cylinder unit are filtered out of the lubricant for a large number of lowering operations, without the operation of the lifting device being impaired. Overall, this can improve the quality of the lubricant, which reduces the risk of damage to the hydraulic pump and / or other components of the lifting device.

Entsprechend einer vorteilhaften Ausführungsform kann der vorbestimmte Steuerdruck, bei dem das Filtersteuerventil schaltet, so gewählt sein, dass die Hubeinrichtung mit einer vorbestimmten Last und mit einer vorbestimmten Geschwindigkeit passiv absenkbar ist, wenn die Hydraulikpumpe deaktiviert ist. Durch diese Bauweise wird der Durchströmungswiderstand des Hydraulikfilters berücksichtigt. Mit anderen Worten, der Steuerdruck wird so hoch gewählt, dass der Hydraulikmittelrücklauf nur dann durch das Hydraulikfilter geleitet wird, wenn sichergestellt ist, dass trotz der Drosselwirkung des Hydraulikfilters die Hubeinrichtung mit der vorbestimmten Last und mit der vorbestimmten Geschwindigkeit passiv absenkbar ist. Durch diese Bauweise ergibt sich eine reduzierte Beeinträchtigung der Hebeeinrichtung durch den Strömungswiderstand des Hydraulikfilters auch für solche Konfigurationen, bei denen die Hubeinrichtung passiv abgesenkt wird.According to an advantageous embodiment, the predetermined control pressure at which the filter control valve switches, be selected so that the lifting device with a predetermined load and at a predetermined speed is passively lowered, when the hydraulic pump is deactivated. By this construction, the flow resistance of the hydraulic filter is taken into account. In other words, the control pressure is set so high that the hydraulic fluid return is passed through the hydraulic filter only if it is ensured that despite the throttling effect of the hydraulic filter, the lifting device with the predetermined load and at the predetermined speed is passively lowered. This construction results in a reduced impairment of the lifting device by the flow resistance of the hydraulic filter for such configurations in which the lifting device is lowered passively.

Besonders vorteilhaft ist eine Ausführungsform, bei welcher der Rücklaufzweig, der das Filtersteuerventil und das Hydraulikfilter sowie den Bypass umfasst, vom Kolben-Zylinder-Aggregat beabstandet von der Hydraulikleitung abzweigt, welche das Reservoir über die Pumpe mit dem Druckraum verbindet. Ferner kann der Rücklaufzweig vom Hydraulikmittelreservoir beabstandet in die Hydraulikleitung einmünden. Die vorgeschlagene Bauweise hat den Vorteil, dass die gesamte Hydraulikversorgung der Hebeeinrichtung weitgehend unverändert bleibt kann, wenn sie im Sinne der Erfindung modifiziert werden soll. Beispielsweise kann die Hydraulikversorgung vom Druckraum bis zur Abzweigstelle des Rücklaufzweigs unverändert bleiben. Außerdem kann die Hydraulikversorgung vom Hydraulikreservoir bis zur Einleitstelle des Rücklaufzweigs unverändert bleiben. Lediglich zwischen der Abzweigstelle und der Einleitstelle ist in der Hydraulikleitung ein Rückschlagsperrventil anzuordnen, damit die Rücklaufströmung durch den Rücklaufzweig strömt und nicht durch diesen Teil der Hydraulikleitung. Somit kann die erfindungsgemäße Hebeeinrichtung besonders einfach bei einer konventionellen Hebeeinrichtung realisiert werden. Hierdurch werden die Herstellungskosten reduziert. Außerdem wird eine vergleichsweise einfache Umrüstung oder Nachrüstung ermöglicht.Particularly advantageous is an embodiment in which the return branch, comprising the filter control valve and the hydraulic filter and the bypass, spaced from the piston-cylinder unit branches off from the hydraulic line which connects the reservoir via the pump to the pressure chamber. Furthermore, the Return branch from the hydraulic fluid reservoir spaced open into the hydraulic line. The proposed construction has the advantage that the entire hydraulic supply of the lifting device can remain largely unchanged if it is to be modified in the sense of the invention. For example, the hydraulic supply from the pressure chamber to the branch point of the return branch remain unchanged. In addition, the hydraulic supply from the hydraulic reservoir to the discharge point of the return branch remain unchanged. Only between the branching point and the point of introduction, a non-return valve is to be arranged in the hydraulic line, so that the return flow flows through the return branch and not through this part of the hydraulic line. Thus, the lifting device according to the invention can be particularly easily realized in a conventional lifting device. This reduces the manufacturing costs. In addition, a relatively simple conversion or retrofitting is possible.

Weitere wichtige Merkmale und Vorteile der Erfindung ergeben sich aus den Unteransprüchen, aus den Zeichnungen und aus der zugehörigen Figurenbeschreibung anhand der Zeichnungen.Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings.

Es versteht sich, dass die vorstehend genannten und die nachstehend noch zu erläuternden Merkmale nicht nur in der jeweils angegebenen Kombination, sondern auch in anderen Kombinationen oder in Alleinstellung verwendbar sind, ohne den Rahmen der vorliegenden Erfindung zu verlassen.It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Bevorzugte Ausführungsbeispiele der Erfindung sind in den Zeichnungen dargestellt und werden in der nachfolgenden Beschreibung näher erläutert, wobei sich gleiche Bezugszeichen auf gleiche oder ähnliche oder funktional gleiche Bauteile beziehen.Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

Es zeigen, jeweils schematisch

Fig. 1
eine stark vereinfachte, schaltplanartige Prinzipdarstellung eines Gabelstaplers mit einer Hebeeinrichtung,
Fig. 2
einen vereinfachten Längsschnitt durch ein Filtersteuerventil in einer ersten Schaltstellung,
Fig. 3
eine Ansicht wie in Fig. 2, jedoch bei einer zweiten Schaltstellung,
Fig. 4
eine Ansicht wie in Fig. 2, jedoch bei einer anderen Ausführungsform des Filtersteuerventils,
Fig. 5
eine Ansicht wie in Fig. 3, jedoch bei der Ausführungsform aus Fig. 4.
It show, each schematically
Fig. 1
a greatly simplified, schematics-like schematic diagram of a forklift with a lifting device,
Fig. 2
a simplified longitudinal section through a filter control valve in a first switching position,
Fig. 3
a view like in Fig. 2 but at a second switching position,
Fig. 4
a view like in Fig. 2 but in another embodiment of the filter control valve,
Fig. 5
a view like in Fig. 3 , but in the embodiment of Fig. 4 ,

Entsprechend Fig. 1 umfasst ein hier nur teilweise dargestellter Gabelstapler 1 eine hydraulische Hebeeinrichtung 2 zum Anheben von Lasten 3. Anstelle eines Gabelstaplers 1 kann grundsätzlich auch ein beliebiges anderes Fahrzeug mit einer derartigen Hebeeinrichtung 2 ausgestattet sein. Das jeweilige Fahrzeug bzw. der Gabelstapler 1 besitzt zusätzlich zur Hebeeinrichtung 2 üblicherweise ein Fahrwerk und einen im Übrigen allgemein bekannten Aufbau, auf den im Detail nicht eingegangen werden muss.Corresponding Fig. 1 includes a here only partially illustrated forklift 1 a hydraulic lifting device 2 for lifting loads 3. Instead of a forklift 1, in principle, any other vehicle can be equipped with such a lifting device 2. The respective vehicle or forklift 1 in addition to the lifting device 2 usually has a chassis and a generally well-known structure, which need not be discussed in detail.

Die hydraulische Hebeeinrichtung 2 umfasst eine Hubeinrichtung 4, mit deren Hilfe die jeweilige Last 3 anhebbar und auch absenkbar ist. Die Last 3 ist hier durch einen mit unterbrochener Linie dargestellten Rahmen repräsentiert. Ein Pfeil 5 repräsentiert eine Anheberichtung, während ein Pfeil 6 eine Absenkrichtung repräsentiert. Die Hubeinrichtung 4 kann beispielsweise als Hubgabel ausgestaltet sein oder als Plattform. Insbesondere umfasst die Hubeinrichtung 4 eine hier nicht gezeigte Führung, z.B. in Form eines Masts an der bzw. an dem zum Beispiel die Hubgabel 4 vertikal verstellbar gelagert ist.The hydraulic lifting device 2 comprises a lifting device 4, with the aid of which the respective load 3 can be raised and lowered. The load 3 is here represented by a frame shown with a broken line. An arrow 5 represents a lifting direction, while an arrow 6 represents a lowering direction. The lifting device 4 can for example be designed as a lifting fork or as a platform. In particular, the lifting device 4 comprises a guide, not shown here, for example in the form of a mast on or on which, for example, the lifting fork 4 is mounted vertically adjustable.

Die Hebeeinrichtung 2 umfasst des Weiteren zumindest ein hydraulisches Kolben-Zylinder-Aggregat 7. Im Beispiel ist nur ein einziges solches Kolben-Zylinder-Aggregat 7 dargestellt. Es ist klar, dass auch mehrere, insbesondere parallel arbeitende, Kolben-Zylinder-Aggregate 7 vorhanden sein können. Das Kolben-Zylinder-Aggregat 7 besitzt einen Kolben 8, der in einem Zylinder 9 hubverstellbar angeordnet ist und im Zylinder 9 einen Druckraum 10 begrenzt. Eine Kolbenstange 11 ist aus dem Zylinder 9 herausgeführt. Anstelle eines Kolbens 8 mit Kolbenstange 11 kann auch ein Plunger vorgesehen sein. Das Kolben-Zylinder-Aggregat 7 dient zum Antreiben der Hubeinrichtung 4, und zwar hier zum Anheben der Hubeinrichtung 4. Üblicherweise ist hierzu der Zylinder 9 stationär, zum Beispiel am jeweiligen Fahrzeug 1, angeordnet, während die Kolbenstange 11 mit der Hubeinrichtung 4 verbunden ist. Ebenso ist eine umgekehrte Bauweise denkbar, bei der die Hubeinrichtung 4 mit dem Zylinder 9 verbunden ist.The lifting device 2 further comprises at least one hydraulic piston-cylinder unit 7. In the example, only a single such piston-cylinder unit 7 is shown. It is clear that several, in particular parallel, piston-cylinder units 7 may be present. The piston-cylinder unit 7 has a piston 8 which is arranged to be adjustable in stroke in a cylinder 9 and limits a pressure chamber 10 in the cylinder 9. A piston rod 11 is led out of the cylinder 9. Instead of a piston 8 with piston rod 11 may also be provided a plunger. The piston-cylinder unit 7 is used to drive the lifting device 4, here for lifting the lifting device 4. Usually, this is the cylinder 9 stationary, for example, the respective vehicle 1, arranged while the piston rod 11 is connected to the lifting device 4 , Likewise, a reverse construction is conceivable in which the lifting device 4 is connected to the cylinder 9.

Die Hebeeinrichtung 2 weist außerdem eine Hydraulikversorgung 12 auf. Diese umfasst zumindest eine Hydraulikleitung 13, ein Hydraulikmittelreservoir 14 und eine Hydraulikpumpe 15. Die Hydraulikleitung 13 verbindet das Reservoir 14 mit dem Druckraum 10 des Kolben-Zylinder-Aggregats 7 und enthält die Hydraulikpumpe 15. Die Hydraulikversorgung 12 weist außerdem einen Rücklaufzweig 16 auf, in dem ein Hydraulikfilter 17 angeordnet ist. Außerdem ist ein Filtersteuerventil 18 vorgesehen, das im Rücklaufzweig 16 angeordnet ist. Dabei befindet sich das Filtersteuerventil 18 bezüglich einer Rücklaufströmung stromauf des Hydraulikfilters 17. An das Filtersteuerventil 18 ist außerdem ein Bypasszweig 19 angeschlossen, der das Hydraulikfilter 17 umgeht. Das Filtersteuerventil 18 ist so ausgestaltet, dass es bei einer Rücklaufströmung, also bei einer Hydraulikmittelströmung, die vom Druckraum 10 zurück zum Reservoir 14 führt, in Abhängigkeit des Drucks im Hydraulikmittel stromauf des Filtersteuerventils 18 die Rücklaufströmung mehr oder weniger durch das Hydraulikfilter 17 oder mehr oder weniger durch den Bypass 17 unter Umgehung des Hydraulikfilters 17 führt. Liegt der Hydraulikmitteldruck stromauf des Filtersteuerventils 18 oberhalb eines vorbestimmten Steuerdrucks, führt das Filtersteuerventil 18 die Rücklaufströmung mehr oder weniger vollständig durch das Hydraulikfilter 17. Hierzu sperrt das Filtersteuerventil 18 zweckmäßig die Zuströmung zum Bypasszweig 19. Liegt der eingangsseitige Druck des Filtersteuerventils 18 jedoch unterhalb des vorbestimmten Steuerdrucks, führt das Filtersteuerventil 18 die Rücklaufströmung mehr oder weniger vollständig durch den Bypasszweig 19, so dass die Rücklaufströmung das Hydraulikfilter 17 umgeht. Hierbei kann der durch das Hydraulikfilter 17 führende Abschnitt des Rücklaufzweigs 16 durch das Filtersteuerventil 18 gesperrt sein, muss aber nicht, da der höhere Durchströmungswiderstand des Hydraulikfilters 17 dafür sorgt, dass die Rücklaufströmung bei geöffnetem Bypasszweig 19 diesen bevorzugt.The lifting device 2 also has a hydraulic supply 12. This includes at least one hydraulic line 13, a hydraulic fluid reservoir 14 and a hydraulic pump 15. The hydraulic line 13 connects the reservoir 14 with the pressure chamber 10 of the piston-cylinder unit 7 and contains the hydraulic pump 15. The hydraulic supply 12 also has a return branch 16, in a hydraulic filter 17 is arranged. In addition, a filter control valve 18 is provided, which is arranged in the return branch 16. In this case, the filter control valve 18 with respect to a return flow upstream of the hydraulic filter 17 to the filter control valve 18 is also a bypass branch 19 is connected, which bypasses the hydraulic filter 17. The filter control valve 18 is designed such that, in the case of a return flow, that is to say in the case of a hydraulic fluid flow, leading from the pressure chamber 10 back to the reservoir 14, depending on the pressure in the hydraulic fluid upstream of the filter control valve 18, the return flow more or less through the hydraulic filter 17 or more or less through the bypass 17, bypassing the hydraulic filter 17 leads. If the hydraulic fluid pressure upstream of the filter control valve 18 above a predetermined control pressure, the filter control valve 18, the return flow more or less completely through the hydraulic filter 17. To block the filter control valve 18 expediently the inflow to the bypass branch 19. However, the input-side pressure of the filter control valve 18 below the predetermined Control pressure, the filter control valve 18, the return flow more or less completely through the bypass branch 19, so that the return flow bypasses the hydraulic filter 17. Here, the leading through the hydraulic filter 17 portion of the return branch 16 may be blocked by the filter control valve 18, but does not have, because the higher flow resistance of the hydraulic filter 17 ensures that the return flow with open bypass branch 19 this preferred.

Der Steuerdruck, bei dem das Filtersteuerventil 18 den Bypasszweig 19 aktiviert bzw. deaktiviert, ist entsprechend einer bevorzugten Ausführungsform so vorbestimmt, dass die Hubeinrichtung 4, wenn sie mit einer vorbestimmten Referenzlast belastet ist, mit einer vorbestimmten Geschwindigkeit passiv absenkbar ist, wenn die Hydraulikpumpe 15 deaktiviert ist. Mit anderen Worten, bei deaktivierter Pumpe 15 treibt das Eigengewicht der Hubeinrichtung 4 zusammen mit dem Gewicht der vorbestimmten Last 3 die Hubeinrichtung 4 in der Absenkrichtung 6 an. Hierdurch wird das Volumen des Druckraums 10 verkleinert, wodurch das Hydraulikmittel ausgetrieben wird. Hierdurch wird die Rücklaufströmung erzeugt. Der Druck im Hydraulikmittel wird dabei durch den im Druckraum 10 erzeugten Druck bestimmt, also durch die Gewichtskraft der Hubeinrichtung 4 mit der Last 3, die über den Kolben 8 auf das Hydraulikmittel aufgebracht wird. Durch den gewählten Schwellwert für den Schaltvorgang des Filtersteuerventils 18 wird gewährleistet, dass die Hubeinrichtung 4 stets mit einer hinreichenden Geschwindigkeit abgesenkt werden kann. Liegt der Hydraulikmitteldruck beim Absenken oberhalb des Steuerdrucks, reicht er aus, trotz des Strömungswiderstands des Hydraulikfilters 17 einen hinreichenden Volumenstrom zu erzeugen, was zur gewünschten Absenkgeschwindigkeit führt. Ist der Druck im Druckraum 10 zu klein, führt das Filtersteuerventil 18 die Rücklaufströmung über den Bypasszweig 19, wodurch der Strömungswiderstand des Hydraulikfilters 17 umgangen wird, so dass auch für Drücke unterhalb des Steuerdrucks eine ausreichende Absenkgeschwindigkeit für die Hubeinrichtung 4 realisierbar ist. Dies gilt insbesondere dann, wenn die Hubeinrichtung 4 unbelastet ist, so dass nur ihr Eigengewicht zum Erzeugen eines Drucks in der Rücklaufströmung vorhanden ist.The control pressure at which the filter control valve 18 activates or deactivates the bypass branch 19 is, according to a preferred embodiment, predetermined so that the lifting device 4, when loaded with a predetermined reference load, is passively lowered at a predetermined speed when the hydraulic pump 15 is disabled. In other words, when the pump 15 is deactivated, the dead weight of the lifting device 4, together with the weight of the predetermined load 3, drives the lifting device 4 in the lowering direction 6. As a result, the volume of the pressure chamber 10 is reduced, whereby the hydraulic fluid is expelled. As a result, the return flow is generated. The pressure in the hydraulic fluid is determined by the pressure generated in the pressure chamber 10, ie by the weight of the lifting device 4 with the load 3, which is applied via the piston 8 to the hydraulic fluid. By the chosen Threshold for the switching operation of the filter control valve 18 ensures that the lifting device 4 can always be lowered at a sufficient speed. If the hydraulic fluid pressure when lowering above the control pressure, it is sufficient, despite the flow resistance of the hydraulic filter 17 to generate a sufficient volume flow, which leads to the desired lowering speed. If the pressure in the pressure chamber 10 is too small, the filter control valve 18 leads the return flow through the bypass branch 19, whereby the flow resistance of the hydraulic filter 17 is bypassed, so that even for pressures below the control pressure, a sufficient lowering speed for the lifting device 4 can be realized. This is especially true when the lifting device 4 is unloaded, so that only their own weight for generating a pressure in the return flow is present.

In den meisten Fällen kann somit das Hydraulikmittel beim Absenken der Hubeinrichtung 4 durch das Hydraulikfilter 17 geleitet werden, wodurch Verunreinigungen, die im Kolben-Zylinder-Aggregat 7 entstehen und in das Hydraulikmittel gelangen, aus dem Hydraulikmittel herausgefiltert werden können.In most cases, therefore, the hydraulic fluid can be passed through the hydraulic filter 17 when lowering the lifting device 4, whereby impurities that arise in the piston-cylinder unit 7 and get into the hydraulic fluid can be filtered out of the hydraulic fluid.

In der Hydraulikleitung 13 ist bei der hier gezeigten, bevorzugten Ausführungsform ein Hubsteuerventil 20 angeordnet, mit dessen Hilfe die Hydraulikpumpe 15 aktiviert und deaktiviert werden kann. Dieses Hubsteuerventil 20 ist dabei bezüglich einer Vorlaufströmung, also bezüglich einer in der Pumprichtung der Pumpe 15 orientierten Strömung, die vom Reservoir 14 zum Druckraum 10 führt, stromab der Pumpe 15 angeordnet. Erkennbar besitzt das Hubsteuerventil 20 zwei Schaltstellungen 21 und 22. In Fig. 1 befindet sich das Hubsteuerventil 20 in seiner ersten Schaltstellung 21. In dieser ersten Schaltstellung 21 ist die Druckseite der Pumpe 15 mit dem Druckraum 10 verbunden, während eine Rücklaufleitung 23 gesperrt ist, die ebenfalls an das Hubsteuerventil 20 angeschlossen ist und die zum Reservoir 14 führt. In der zweiten Schaltstellung 22 ist die Druckseite der Pumpe 15 gesperrt, während der Rücklauf 23 unter Umgehung der Pumpe 15 mit der übrigen Hydraulikleitung 13 verbunden ist. Die Pumpe 15 kann einen internen Rücklauf aufweisen, der bei einem Überdruck öffnet und zum Reservoir 14 zurückführt oder die Pumpe 15 intern kurzschließt. Ebenso kann das Hubsteuerventil 20 als Proportionalventil ausgestaltet sein, um den Druck bzw. Förderstrom der Pumpe 15 variabel auf den zum Druckraum 10 führenden Abschnitt der Hydraulikleitung 13 und auf den Rücklauf 23 aufteilen zu können.In the hydraulic line 13, a stroke control valve 20 is arranged in the preferred embodiment shown here, with the aid of which the hydraulic pump 15 can be activated and deactivated. This stroke control valve 20 is arranged downstream of the pump 15 with respect to a flow, ie with respect to a flow oriented in the pumping direction of the pump 15, which leads from the reservoir 14 to the pressure chamber 10. Visible, the stroke control valve 20 has two switch positions 21 and 22. In Fig. 1 In this first switching position 21, the pressure side of the pump 15 is connected to the pressure chamber 10, while a return line 23 is blocked, which is also connected to the stroke control valve 20 and leading to the reservoir 14. In the second switching position 22, the pressure side of Pump 15 locked while the return 23 is connected bypassing the pump 15 with the remaining hydraulic line 13. The pump 15 may have an internal return, which opens at an overpressure and returns to the reservoir 14 or internally shorts the pump 15. Likewise, the stroke control valve 20 may be configured as a proportional valve in order to divide the pressure or flow rate of the pump 15 variably on the leading to the pressure chamber 10 portion of the hydraulic line 13 and the return 23 can.

In der Hydraulikleitung 13 kann bei der hier gezeigten bevorzugten Ausführungsform zwischen der Hydraulikpumpe 15 und dem Hubsteuerventil 20 ein Zusatzhydraulikfilter 24 angeordnet sein. Hierdurch wird auch bei einer Vorlaufströmung ein Schutz des Hubsteuerventils 20 vor Verunreinigungen realisiert.In the hydraulic line 13, in the preferred embodiment shown here, an auxiliary hydraulic filter 24 can be arranged between the hydraulic pump 15 and the stroke control valve 20. As a result, a protection of the stroke control valve 20 is realized against contamination even at a flow.

Im gezeigten Beispiel ist der Rücklaufzweig 16 an die Hydraulikleitung 13 angeschlossen, so dass der Rücklaufzweig 16 beabstandet vom Kolben-Zylinder-Aggregat 7 von der Hydraulikleitung 13 abzweigt. Eine entsprechende Abzweigstelle ist dabei mit 25 bezeichnet. Hierdurch ist es möglich, die konventionelle Anschlusskonfiguration zwischen Hydraulikversorgung 12 und Kolben-Zylinder-Aggregat 7 beizubehalten. Lediglich die Abzweigstelle 25 muss in der Hydraulikleitung 13 geschaffen werden. Alternativ ist auch eine Ausführungsform möglich, bei welcher der Rücklaufzweig 16 separat zur Hydraulikleitung 13 an das Kolben-Zylinder-Aggregat 7 angeschlossen sein kann.In the example shown, the return branch 16 is connected to the hydraulic line 13, so that the return branch 16 branches off from the hydraulic line 13 at a distance from the piston-cylinder unit 7. A corresponding branch point is designated by 25. This makes it possible to maintain the conventional connection configuration between hydraulic supply 12 and piston-cylinder unit 7. Only the branch point 25 must be created in the hydraulic line 13. Alternatively, an embodiment is possible in which the return branch 16 can be connected separately to the hydraulic line 13 to the piston-cylinder unit 7.

Im gezeigten Beispiel ist der Rücklaufzweig 16 beabstandet vom Hydraulikreservoir 14 an die Hydraulikleitung 13 angeschlossen. Eine entsprechende Anschlussstelle ist hier mit 26 bezeichnet. Diese Anschlussstelle 26 ist im bevorzugten Beispiel zwischen der Abzweigstelle 25 und dem Hubsteuerventil 20 angeordnet. Hierdurch ist es insbesondere möglich, die Hydraulikversorgung 12 vom Hydraulikreservoir 14 bis zur Anschlussstelle 26 konventionell auszugestalten, so dass in der Hydraulikleitung 13 lediglich die Anschlussstelle 26 geschaffen werden muss. Alternativ ist es auch hier grundsätzlich möglich, den Rücklaufzweig 16 separat zur Hydraulikleitung 13 an das Hydraulikmittelreservoir 14 anzuschließen.In the example shown, the return branch 16 is connected at a distance from the hydraulic reservoir 14 to the hydraulic line 13. A corresponding connection point is designated here by 26. This connection point 26 is arranged in the preferred example between the branch point 25 and the stroke control valve 20. This makes it possible, in particular, to design the hydraulic supply 12 conventionally from the hydraulic reservoir 14 to the connection point 26 that in the hydraulic line 13, only the connection point 26 must be created. Alternatively, it is basically possible to connect the return branch 16 separately to the hydraulic line 13 to the hydraulic fluid reservoir 14.

Im gezeigten Beispiel ist außerdem der Bypasszweig 19 bezüglich der Rücklaufströmung stromab des Hydraulikfilters 17 an den Rücklaufzweig 16 angeschlossen. Eine entsprechender Anschlussstelle ist mit 27 bezeichnet. Hierdurch ist nur eine Anschlussstelle 26 zwischen Rücklaufzweig 16 und Hydraulikleitung 13 erforderlich, um den Rücklaufzweig 16 mit Filtersteuerventil 18, Hydraulikfilter 17 und zugehörigem Bypasszweig 19 in die Hydraulikversorgung 12 einzugliedern. Alternativ ist es auch möglich, den Bypasszweig 19 separat zum Rücklaufzweig 16 an die Hydraulikleitung 13 oder sogar direkt an das Reservoir 14 anzuschließen.In the example shown, the bypass branch 19 is also connected to the return branch 16 with respect to the return flow downstream of the hydraulic filter 17. A corresponding connection point is designated by 27. As a result, only one connection point 26 between return branch 16 and hydraulic line 13 is required to integrate the return branch 16 with filter control valve 18, hydraulic filter 17 and associated bypass branch 19 into the hydraulic supply 12. Alternatively, it is also possible to connect the bypass branch 19 separately to the return branch 16 to the hydraulic line 13 or even directly to the reservoir 14.

Die Hydraulikleitung 13 weist in einen Abschnitt 28, der von der Anschlussstelle 26 zur Abzweigstelle 25 führt, ein Rückschlagsperrventil 29 auf, das in einer vom Hydraulikmittelreservoir 14 zum Druckraum 10 führenden Vorlaufrichtung öffnet und in einer vom Druckraum 10 zum Reservoir 14 führenden Rücklaufrichtung sperrt. Hierdurch wird erreicht, dass die Rücklaufströmung zwangsläufig durch den Rücklaufzweig 16 strömt. Des Weiteren enthält der Rücklaufzweig 16 zumindest ein Rücklaufsperrventil 30, das in der Rücklaufrichtung durchlässig ist und das in der Vorlaufrichtung sperrt. Hierdurch wird erreicht, dass eine Vorlaufströmung nicht durch den Rücklaufzweig 16 strömen kann, sondern unter Umgehung des Rücklaufzweigs 16 zum Druckraum 10 gelangt. Im gezeigten Beispiel ist sowohl im Bypasszweig 19 als auch in dem das Hydraulikfilter 17 enthaltenden Abschnitt des Rücklaufzweigs 16 jeweils ein solches Rücklaufsperrventil 30 enthalten. Alternativ kann auch zwischen den beiden Anschlussstellen 26 und 27 ein einziges solches Rücklaufsperrventil 30 ausreichend sein.The hydraulic line 13 has in a section 28 which leads from the connection point 26 to the branch point 25, a non-return valve 29 which opens in a leading from the hydraulic fluid reservoir 14 to the pressure chamber 10 feed direction and locks in a leading from the pressure chamber 10 to the reservoir 14 return direction. This ensures that the return flow inevitably flows through the return branch 16. Furthermore, the return branch 16 contains at least one return check valve 30, which is permeable in the return direction and which blocks in the advance direction. This ensures that a flow stream can not flow through the return branch 16, but 16 passes to the pressure chamber 10, bypassing the return branch. In the example shown, such a return check valve 30 is contained both in the bypass branch 19 and in the section of the return branch 16 containing the hydraulic filter 17. Alternatively, between the two connection points 26 and 27, a single such return check valve 30 may be sufficient.

Entsprechend den Fig. 2 bis 4 besitzt das Filtersteuerventil 18 einen zum Kolben-Zylinder-Aggregat 7 führenden Eingang 31, einen zum Hydraulikfilter 17 führenden Filterausgang 32 und einen zum Bypasszweig 19 führenden Bypassausgang 33. Ferner enthält das Filtersteuerventil 18 in einem Gehäuse 34 ein Ventilglied 35, mit dessen Hilfe die Ausgänge 32, 33 gesteuert werden können. Das Ventilglied 35 ist dabei in Abhängigkeit des am Eingang 31 herrschenden Hydraulikmitteldrucks im Gehäuse 34 verstellbar. Des Weiteren weist das Filtersteuerventil 18 bei den gezeigten Ausführungsformen eine Rückstellfeder 36 auf, die das Ventilglied 35 in eine in den Fig. 2 und 4 gezeigte Ausgangsstellung vorspannt. In dieser Ausgangsstellung der Fig. 2 und 4 ist der Bypassausgang 33 mit dem Eingang 31 kommunizierend verbunden.According to the Fig. 2 to 4 the filter control valve 18 has a leading to the piston-cylinder unit 7 input 31, leading to the hydraulic filter 17 filter output 32 and a bypass branch 19 leading bypass output 33. Further, the filter control valve 18 in a housing 34, a valve member 35, with the aid of the outputs 32, 33 can be controlled. The valve member 35 is adjustable depending on the prevailing at the input 31 hydraulic fluid pressure in the housing 34. Furthermore, the filter control valve 18 in the illustrated embodiments, a return spring 36, the valve member 35 in one in the Fig. 2 and 4 pretensioned starting position shown. In this starting position the Fig. 2 and 4 the bypass output 33 is communicatively connected to the input 31.

Bei der in den Fig. 2 und 3 gezeigten Ausführungsform ist das Ventilglied 35 hülsenförmig bzw. topfförmig ausgestaltet. Es ist an einer dem Eingang 31 zugewandten axialen Stirnseite offen und an einer davon abgewandten axialen Stirnseite verschlossen. Ferner besitzt es ein radiales Fenster 37, das in der Ausgangsstellung gemäß Fig. 2 mit dem Bypassausgang 33 fluchtet, wodurch dieser durch das Ventilglied 35 hindurch mit dem Eingang 31 verbunden ist. Das Ventilglied 35 ist mit einer Verdrehsicherung 38 gegen ein Verändern seiner Drehlage relativ zum Gehäuse 34 gesichert. Der am Eingang 31 anliegende Druck treibt das Ventilglied 35 entgegen der Rückstellkraft der Rückstellfeder 36 an. Bei hinreichendem Hydraulikdruck am Eingang 31 gelangt das Ventilglied 35 bis in seine in Fig. 3 gezeigte Endstellung. In dieser Endstellung ist das Fenster 37 fluchtend zum Filterausgang 32 angeordnet, so dass dann der Filterausgang 32 mit dem Eingang 31 kommuniziert. Die Rücklaufströmung kann dann zum Hydraulikfilter 17 strömen. Es ist klar, dass abhängig vom Druck auch beliebige Zwischenstellungen denkbar sind. Bemerkenswert ist bei dieser Ausführungsform, dass in der Endstellung der Fig. 3 die Bypassöffnung 19 gesperrt ist. Ferner ist bemerkenswert, dass bei dieser Ausführungsform in der Ausgangsstellung gemäß Fig. 2 der Filterausgang 32 gesperrt ist.In the in the FIGS. 2 and 3 the embodiment shown, the valve member 35 is designed sleeve-shaped or cup-shaped. It is open at an input 31 facing the axial end face and closed at an axial end face facing away from it. Furthermore, it has a radial window 37, which in the starting position according to Fig. 2 is aligned with the bypass outlet 33, whereby it is connected through the valve member 35 through to the input 31. The valve member 35 is secured with an anti-rotation device 38 against changing its rotational position relative to the housing 34. The applied pressure at the input 31 drives the valve member 35 against the restoring force of the return spring 36 at. With sufficient hydraulic pressure at the input 31, the valve member 35 reaches into its in Fig. 3 shown end position. In this end position, the window 37 is arranged in alignment with the filter output 32, so that then the filter output 32 communicates with the input 31. The return flow can then flow to the hydraulic filter 17. It is clear that depending on the pressure and any intermediate positions are conceivable. It is noteworthy in this embodiment that in the end position of Fig. 3 the bypass opening 19 is locked. It is also worth noting that in this embodiment in the starting position according to Fig. 2 the filter output 32 is blocked.

Das Gehäuse 34 besitzt zur Vereinfachung der Montage einen Deckel 39, der mit dem Gehäuse 34 verschraubt sein kann, wobei außerdem eine Axialdichtung 40 zwischen Gehäuse 34 und Deckel 39 zum dichten Verschließen des Gehäuses 34 vorgesehen sein kann.The housing 34 has a cover 39 for ease of assembly, which may be bolted to the housing 34, wherein also an axial seal 40 between the housing 34 and cover 39 for sealing the housing 34 may be provided.

Bei der in den Fig. 4 und 5 gezeigten Ausführungsform ist das Ventilglied 35 als Kugel ausgestaltet. Eine Kugelführung 41 ermöglicht eine Verstellung des Ventilglieds 35 im Gehäuse 34. Der Deckel 39 ist in diesem Beispiel mittels eines Gewindes 42 in das Gehäuse 34 eingeschraubt, so dass auf zusätzliche Dichtungen grundsätzlich verzichtet werden kann.In the in the 4 and 5 As shown embodiment, the valve member 35 is configured as a ball. A ball guide 41 allows adjustment of the valve member 35 in the housing 34. The cover 39 is screwed in this example by means of a thread 42 in the housing 34, so that in principle can be dispensed with additional seals.

Bei der in Fig. 4 gezeigten Ausgangsstellung sind beide Ausgänge 32, 33 mit dem Eingang 31 kommunizierend verbunden. Der Strömungswiderstand des Hydraulikfilters 17 führt jedoch dazu, dass ein Großteil der Rückflussströmung über den Bypassausgang 33 abströmt. Dennoch kann grundsätzlich auch ein kleiner Anteil der Rücklaufströmung über den Filterausgang 32 abfließen, was hier durch einen mit unterbrochener Linie dargestellten zusätzlichen Pfeil angedeutet ist. Mit zunehmendem Druck im Hydraulikmittel am Eingang 31 kommt es auch hier zu einer Verstellung des Ventilglieds 35 entgegen der Rückstellkraft der Rückstellfeder 36. Bei der in Fig. 5 gezeigten Situation ist der Druck am Eingang 31 so groß, dass er das Ventilglied 35 entgegen der Rückstellkraft der Rückstellfeder 36 gegen einen Ventilsitz 43 andrückt, wodurch das Ventilglied 35 den Bypassausgang 33 versperrt. Die gesamte Rücklaufströmung ist dann vom Eingang 31 zum Filterausgang 32 geführt. Es ist klar, dass auch bei dieser Ausführungsform quasi beliebige Zwischenstellungen denkbar sind, bei denen eine grundsätzlich beliebige Aufteilung des Rücklaufstroms zwischen den beiden Ausgängen 32 und 33 erfolgt. Bevorzugt ist jedoch bei beiden gezeigten Ausführungsformen eine definierte Schaltung des Filtersteuerventils 18, was durch eine entsprechende Auslegung der Rückstellfeder 36 realisierbar ist.At the in Fig. 4 shown starting position, both outputs 32, 33 communicating with the input 31 are connected. However, the flow resistance of the hydraulic filter 17 causes a large part of the return flow flows through the bypass outlet 33. Nevertheless, in principle, a small proportion of the return flow can flow off via the filter outlet 32, which is indicated here by an additional arrow shown with a broken line. With increasing pressure in the hydraulic fluid at the inlet 31, it is also here to an adjustment of the valve member 35 against the restoring force of the return spring 36. In the in Fig. 5 shown situation, the pressure at the input 31 is so great that it presses the valve member 35 against the restoring force of the return spring 36 against a valve seat 43, whereby the valve member 35 blocks the bypass outlet 33. The entire return flow is then guided from the inlet 31 to the filter outlet 32. It is clear that even in this embodiment virtually any intermediate positions are conceivable in which a basically arbitrary distribution of the return flow between the two outputs 32nd and 33 takes place. Preferably, however, in both embodiments shown, a defined circuit of the filter control valve 18, which is realized by a corresponding design of the return spring 36.

Claims (15)

Hydraulische Hebeeinrichtung, insbesondere an einem Fahrzeug, vorzugsweise an einem Gabelstapler (1), - mit einer Hubeinrichtung (4) zum Anheben von Lasten (3), - mit mindestens einem hydraulischen Kolben-Zylinder-Aggregat (7) zum Antreiben der Hubeinrichtung (4), - mit einer Hydraulikversorgung (12), die mit einer Hydraulikleitung (13) ein Hydraulikmittelreservoir (14) über eine Hydraulikpumpe (15) mit einem Druckraum (10) des Kolben-Zylinder-Aggregats (7) verbindet, - mit einem Hydraulikfilter (17), das in einem Rücklaufzweig (16) der Hydraulikversorgung (12) angeordnet ist, - mit einem Filtersteuerventil (18), das im Rücklaufzweig (16) bezüglich einer Rücklaufströmung stromauf des Hydraulikfilters (17) angeordnet ist und das bei einer Rücklaufströmung in Abhängigkeit des Hydraulikmitteldrucks stromauf des Filtersteuerventils (18) die Rücklaufströmung oberhalb eines vorbestimmten Steuerdrucks durch den Rücklaufzweig (16) und unterhalb des vorbestimmten Steuerdrucks durch einen das Hydraulikfilter (17) umgehenden Bypasszweig (19) führt. Hydraulic lifting device, in particular on a vehicle, preferably on a forklift (1), - With a lifting device (4) for lifting loads (3), - With at least one hydraulic piston-cylinder unit (7) for driving the lifting device (4), - With a hydraulic supply (12) which connects with a hydraulic line (13) a hydraulic fluid reservoir (14) via a hydraulic pump (15) with a pressure chamber (10) of the piston-cylinder unit (7), - With a hydraulic filter (17) which is arranged in a return branch (16) of the hydraulic supply (12), - with a filter control valve (18) which is arranged in the return branch (16) with respect to a return flow upstream of the hydraulic filter (17) and which at a return flow in response to the hydraulic medium pressure upstream of the filter control valve (18), the return flow above a predetermined control pressure by the return branch ( 16) and below the predetermined control pressure by a hydraulic filter (17) bypassing bypass branch (19) leads. Hebeeinrichtung nach Anspruch 1,
dadurch gekennzeichnet,
dass der vorbestimmte Steuerdruck so gewählt ist, dass die Hubeinrichtung (4) bei einer vorbestimmten Last (3) mit einer vorbestimmten Geschwindigkeit passiv absenkbar ist, wenn die Hydraulikpumpe (15) deaktiviert ist.Lifting device according to claim 1,
characterized,
that the predetermined control pressure is selected so that the lifting device (4) is passively lowered at a predetermined load (3) at a predetermined speed when the hydraulic pump (15) is deactivated. Hebeeinrichtung nach Anspruch 1 oder 2,
dadurch gekennzeichnet,
dass in der Hydraulikleitung (13) bezüglich einer Vorlaufströmung stromab der Hydraulikpumpe (15) ein Hubsteuerventil (20) zum Aktivieren und Deaktivieren der Hydraulikpumpe (15) angeordnet ist.Lifting device according to claim 1 or 2,
characterized,
that in the hydraulic line (13) of a forward flow downstream of the hydraulic pump (15) is a displacement control valve (20) for activating and deactivating the hydraulic pump (15) is arranged with respect to. Hebeeinrichtung nach Anspruch 3,
dadurch gekennzeichnet,
dass in der Hydraulikleitung (13) zwischen der Hydraulikpumpe (15) und dem Hubsteuerventil (20) ein Zusatzhydraulikfilter (24) angeordnet ist.Lifting device according to claim 3,
characterized,
in that an additional hydraulic filter (24) is arranged in the hydraulic line (13) between the hydraulic pump (15) and the stroke control valve (20). Hebeeinrichtung nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet,
dass der Rücklaufzweig (16) separat zur Hydraulikleitung (13) an das Kolben-Zylinder-Aggregat (7) angeschlossen ist.Lifting device according to one of claims 1 to 4,
characterized,
that the return branch (16) separately from the hydraulic line (13) is connected to the piston-cylinder unit (7). Hebeeinrichtung nach einem der Ansprüche 1 bis 4,
dadurch gekennzeichnet,
dass der Rücklaufzweig (16) vom Kolben-Zylinder-Aggregat (7) beabstandet von der Hydraulikleitung (13) abzweigt.Lifting device according to one of claims 1 to 4,
characterized,
that the return branch (16) branches off from the piston-cylinder unit (7) at a distance from the hydraulic line (13). Hebeeinrichtung nach einem der Ansprüche 1 bis 6,
dadurch gekennzeichnet,
dass der Rücklaufzweig (16) separat zur Hydraulikleitung (13) an das Hydraulikmittelreservoir (14) angeschlossen ist.Lifting device according to one of claims 1 to 6,
characterized,
that the return branch (16) is separately connected to the hydraulic line (13) to the hydraulic fluid reservoir (14). Hebeeinrichtung nach einem der Ansprüche 1 bis 6,
dadurch gekennzeichnet,
dass der Rücklaufzweig (16) vom Hydraulikmittelreservoir (14) beabstandet in die Hydraulikleitung (13) einmündet.Lifting device according to one of claims 1 to 6,
characterized,
that the return branch (16) from the hydraulic fluid reservoir (14) spaced in the hydraulic line (13) opens. Hebeeinrichtung nach den Ansprüchen 3 und 8,
dadurch gekennzeichnet,
dass der Rücklaufzweig (16) bezüglich einer Rücklaufströmung stromauf des Hubsteuerventils (20) in die Hydraulikleitung (13) einmündet, wobei das Hubsteuerventil (20) zum Deaktivieren der Hydraulikmittelpumpe (15) die Hydraulikleitung (13) mit einer die Hydraulikmittelpumpe (15) umgehenden, zum Hydraulikmittelreservoir (14) führenden Rücklaufleitung (23) verbindet.Lifting device according to claims 3 and 8,
characterized,
in that the return branch (16) opens into the hydraulic line (13) upstream of the stroke control valve (20), the stroke control valve (20) for disabling the hydraulic fluid pump (15) bypassing the hydraulic line (13) with a hydraulic fluid pump (15), to the hydraulic fluid reservoir (14) leading return line (23) connects. Hebeeinrichtung nach einem der Ansprüche 1 bis 9,
dadurch gekennzeichnet,
dass der Bypasszweig (19) separat zum Rücklaufzweig (16) an die Hydraulikleitung (13) oder an das Hydraulikmittelreservoir (14) angeschlossen ist oder bezüglich einer Rücklaufströmung stromab des Hydraulikfilters (17) in den Rücklaufzweig (16) einmündet.Lifting device according to one of claims 1 to 9,
characterized,
that the bypass branch (19) separately to the return branch (16) to the hydraulic line (13) or to the hydraulic fluid reservoir (14) a return flow downstream of the hydraulic filter (17) in the return branch (16) is connected or with respect opens. Hebeeinrichtung nach einem der Ansprüche 1 bis 10,
dadurch gekennzeichnet,
dass das Filtersteuerventil (18) einen zum Kolben-Zylinder-Aggregat (7) führenden Eingang (31), einen zum Hydraulikfilter (17) führenden Filterausgang (32), einen zum Bypasszweig (19) führenden Bypassausgang (33) und ein in Abhängigkeit des Hydraulikmitteldrucks am Eingang (31) verstellbares Ventilglied (35) zum Steuern der Ausgänge (32, 33) aufweist.Lifting device according to one of claims 1 to 10,
characterized,
in that the filter control valve (18) has an inlet (31) leading to the piston-cylinder unit (7), a filter outlet (32) leading to the hydraulic filter (17), a bypass outlet (33) leading to the bypass branch (19) and a function of the Hydraulic fluid pressure at the input (31) adjustable valve member (35) for controlling the outputs (32, 33). Hebeeinrichtung nach Anspruch 11,
dadurch gekennzeichnet,
dass das Ventilglied (35) mit einer Rückstellfeder (36) in eine Ausgangsstellung vorgespannt ist, in welcher der Bypassausgang (33) mit dem Eingang (31) kommunizierend verbunden ist.Lifting device according to claim 11,
characterized,
in that the valve member (35) is biased by a return spring (36) into an initial position, in which the bypass outlet (33) is communicatively connected to the inlet (31). Hebeeinrichtung nach Anspruch 12,
dadurch gekennzeichnet,
dass das Ventilglied (35) in der Ausgangsstellung den Filterausgang (32) sperrt.Lifting device according to claim 12,
characterized,
that the valve member (35) in the initial position, blocks the filter output (32). Gabelstapler mit einer hydraulischen Hebeeinrichtung (2) nach einem der Ansprüche 1 bis 13.Forklift with a hydraulic lifting device (2) according to one of claims 1 to 13. Filtersteuerventil einer hydraulischen Hebeeinrichtung (2) nach einem der Ansprüche 1 bis 13.Filter control valve of a hydraulic lifting device (2) according to one of claims 1 to 13.
EP10157297A 2009-04-04 2010-03-23 Hydraulic lifting assembly for forklifts Not-in-force EP2236453B1 (en)

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JP7448406B2 (en) 2020-03-31 2024-03-12 住友重機械工業株式会社 Hydraulic equipment and injection molding machines

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