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WO1998052804A1 - Hydraulic control device, specially for a fork lift - Google Patents

Hydraulic control device, specially for a fork lift Download PDF

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Publication number
WO1998052804A1
WO1998052804A1 PCT/EP1998/001840 EP9801840W WO9852804A1 WO 1998052804 A1 WO1998052804 A1 WO 1998052804A1 EP 9801840 W EP9801840 W EP 9801840W WO 9852804 A1 WO9852804 A1 WO 9852804A1
Authority
WO
WIPO (PCT)
Prior art keywords
pressure
hydraulic
connection
valve
switching position
Prior art date
Application number
PCT/EP1998/001840
Other languages
German (de)
French (fr)
Inventor
Winfried RÜB
Original Assignee
Mannesmann Rexroth Ag
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Mannesmann Rexroth Ag filed Critical Mannesmann Rexroth Ag
Publication of WO1998052804A1 publication Critical patent/WO1998052804A1/en

Links

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
    • B66F9/07509—Braking
    • 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
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • 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
    • F15B20/00—Safety arrangements for fluid actuator systems; Applications of safety devices in fluid actuator systems; Emergency measures for fluid actuator 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20538—Type of pump constant capacity
    • 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
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
    • F15B2211/212—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
    • 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
    • F15B2211/3051—Cross-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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • F15B2211/30515—Load holding 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/30555—Inlet and outlet of the pressure compensating valve being connected to the directional control valve
    • 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
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3105—Neutral or centre positions
    • F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • 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
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6055—Load sensing circuits having valve means between output member and the load sensing circuit using pressure relief 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
    • F15B2211/625—Accumulators
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders

Definitions

  • Hydraulic thruster arrangement especially for a forklift
  • the invention is based on a hydraulic control arrangement which is used in particular for an electric motor-driven forklift and which has the features from the preamble of claim 1.
  • Forklifts are usually equipped with a parking brake, which is designed as a spring-loaded brake and is controlled by the load on the driver's seat.
  • a parking brake which is designed as a spring-loaded brake and is controlled by the load on the driver's seat.
  • the spring-loaded brake is released, so it is not effective.
  • the energy required for this is provided by a pre-tensioned spring.
  • the brake is released with the help of a pressurized hydraulic consumer, usually with the help of a pressurized hydraulic cylinder.
  • Valve means which are usually actuated electromagnetically, are used to supply pressure medium to the hydraulic consumer from a pressure line into which pressure medium is released from a pressure medium source, and to relieve the hydraulic consumer.
  • the invention has for its object to very simply build a hydraulic control arrangement with the features from the preamble of claim 1.
  • valve means comprise a 2/2-way poppet valve which has a first connection which is connected to the pressure line and a second connection which is connected to the hydraulic consumer is in the first switching position from the second can flow through the connection to the first connection of pressure medium and blocks in the second switching position from the second connection to the first connection.
  • the hydraulic consumer In the second switching position, the hydraulic consumer is therefore kept under pressure, so that the spring-loaded brake remains released. So that the brake is applied, the 2/2-way poppet valve is brought into its first switching position, in which pressure fluid can flow from the hydraulic consumer and the preloaded spring can actuate the brake. Namely, according to the invention, the pressure medium flows into the pressure line.
  • the 2/2-way seat valve can be switched to the second switching position by an electromagnet from the first switching position, which it assumes under the action of a spring. This ensures that if the
  • Electromagnet or another component necessary to control the electromagnet the seat valve reaches its open position and the spring-loaded brake can take effect.
  • 2/2-way poppet valves can be freely flowed through in both directions in one of their two switching positions, while in their other switching position their closing element is pressed onto the seat by the pressure in one connection, but flow through the other connection is also not easily possible .
  • the 2/2-way seat valve through which pressure medium can flow in both directions in the first switching position, is switched from the first switching position into the second switching position only after the hydraulic consumer has been pressurized.
  • the seat valve therefore remains in its first switching position to release the brake. Only a certain time after the start of the inflow of pressure medium to the hydraulic consumer, which is sufficient to release the spring brake, is it brought into its second switching position, in which it keeps the hydraulic consumer under pressure.
  • the hydraulic pump can have a constant delivery volume. If no hydraulic consumer that can be supplied with pressure medium is actuated, it conveys pressure medium with low pressure in circulation to a tank. Since the hydraulic consumer assigned to the spring-loaded brake is not like other hydraulic consumers of a forklift e.g. an elevator cylinder, controlled via an arbitrarily actuated directional valve, is provided according to claim 4 that in the
  • a check valve is arranged, which assumes its blocking position for pressurizing the hydraulic consumer, i.e. for releasing the spring brake, so that a pressure can be built up in the pressure line.
  • a hydraulic pump is very often used today, from which pressure medium can be fed to a second hydraulic consumer in a load-sensing-controlled manner.
  • Load-sensing-controlled means that a pressure is built up in the pressure line which is a predetermined pressure difference ⁇ p above the load pressure of the second hydraulic consumer.
  • the hydraulic pump is assigned a load-sensing controller with a control chamber which can be acted upon by the load pressure of the second hydraulic consumer via a load signaling line.
  • a pressure can be applied to the control chamber on the load-sensing controller from the pressure line. This is achieved in a simple manner in that the control chamber of the load-sensing controller is permanently connected to the load-signaling line and a nozzle is present between the latter and the pressure line.
  • shut-off valve which connects the load signal line to a tank line in a first switching position and shuts off to the tank line in a second switching position.
  • This shut-off valve fulfills an emergency stop function.
  • This valve is always brought into its second switching position when no second hydraulic consumer is actuated and only a low pressure corresponding to the amount according to the pressure difference ⁇ p should be present in the pressure line.
  • This check valve can now be used to allow pressure to build up to release the spring brake. To do this, it is briefly brought into its locked position after the driver has sat in his seat.
  • FIG. 1 shows the first embodiment, which is particularly intended for an electric motor-driven forklift
  • Figure 2 shows the second embodiment, in particular for a forklift powered by an internal combustion engine is suitable.
  • Both embodiments include a control block 10 with a pump connection P, a tank connection T, and various consumer connections.
  • a pressure channel 11 begins at the pump connection P and a tank channel 12 of the control block starts at the tank connection T.
  • two load-sensing directional valves 13 and 14 are formed with a closed center, one with the directional valve 13 and one with the directional valve 14
  • Tilt cylinder 22 of a forklift can be controlled.
  • the lift cylinder is a single-acting hydraulic consumer.
  • the directional control valve 13 has only one consumer chamber 15, from which a consumer channel leads via a seat valve 16 which can be actuated electromagnetically to a consumer connection AI of the control block 10.
  • the consumer chamber 15 is shut off both to an inlet chamber 17 connected to the pump channel and to an outlet chamber 18 connected to the tank channel 12.
  • the directional control valve 13 can be brought electrohydraulically into a first working position, in which the consumer chamber 15 is connected to the discharge chamber 18 and the lift cylinders can be retracted in order to lower the lifting slide.
  • the second working position of the directional valve 13 the consumer chamber 15 is connected to the inlet chamber 17.
  • the load pressure of the lift cylinder is tapped at the consumer chamber and placed in a load reporting channel 19 of the control block 10.
  • a speed control part and a direction control part are formed separately from one another on the same control slide.
  • pressure medium coming from the pressure channel 11 flows from the inlet chamber 17 via a measuring orifice 25 into a first intermediate chamber 26, from there over the opening cross section a pressure compensator 27 into a second intermediate chamber 28 and then via the directional part of the directional control valve 14 into a consumer chamber 29 or 30. From there, pressure medium reaches the consumer connection A2 or B2 of the control block 10 via a brake valve 31 or 32.
  • the regulating piston of the pressure compensator 27 is acted upon in the opening direction by the pressure in the intermediate chamber 26, that is to say by the pressure after the measuring orifice 25 and in the closing direction by the pressure in the load-sensing channel 19 and by a weak compression spring 33.
  • the control piston of the pressure compensator 27 is designed in such a way that, when the pressure compensator is completely open, it creates a throttled connection between the intermediate chamber 26 and the load-sensing channel 19. This is the case if the tilt cylinder is operated alone or if the load pressure of the tilt cylinder should be higher than that of the lift cylinder when the lift cylinder and the tilt cylinder are operated simultaneously.
  • a constant pump 40 is used as the pressure medium source, which can be driven by an electric motor 41 in the embodiment according to FIG. 1 and by a diesel engine 42 in the embodiment according to FIG.
  • the pump 40 draws in pressure medium from a tank 43 and discharges it into a pressure line which, for the sake of simplicity, is provided with the same reference number 11 as the pressure channel of the control block 10 and leads to the pump connection P of the control block 10. If no pressure medium is required and the motors 41 and 42 do not stand still, the pump 40 conveys the pressure medium back to the tank 43.
  • a bypass pressure compensator 44 is installed in the control block 10, which is connected with an input to the pressure channel 11 and with an output to the tank channel 12 and whose control piston in the opening direction from the pressure in the pressure channel 11 and in the closing direction from the pressure in Load signaling channel 19 and a compression spring 45 is acted upon, the force of which may be equivalent to a pressure difference of, for example, 5 bar on the control piston.
  • the load signaling channel 19 is open with a 2/2-way valve 46 (FIG. 1) or 47 (FIG. 2) Tank channel 12 connectable or lockable to the tank channel 12. With an open connection between the load signaling channel 19 and the tank channel 12, tank pressure is present on one side of the control piston of the pressure compensator 44.
  • Pressure compensator 44 therefore closes so far that the pressure in the pressure channel 11 is 5 bar above the pressure prevailing in the load reporting channel 19.
  • the directional valve 46 assumes a rest position under the action of a compression spring 48, in which the load-signaling channel 19 is blocked off from the tank channel 12. By actuating an electromagnet 49, it can be brought into its second switching position, in which there is an open connection between the load-signaling channel 19 and the tank channel 12.
  • the directional valve 47 assumes its through position under the action of a compression spring 48 and can be brought into its blocking position by an electromagnet 49.
  • the hydraulic control arrangements shown include a single-acting hydraulic cylinder 55 with which a spring-loaded brake 56, which is only indicated as a rectangular block, can be released.
  • the hydraulic cylinder 55 is connected to the second connection 58 of a 2/2-way seat valve 57, which is seated on the control block 10 and has its first connection 59 on the pressure channel 11.
  • the 2/2-way poppet valve assumes a rest position under the action of a compression spring 60, in which there is an open passage between the two connections 58 and 59 in both directions, so that pressure medium is free from the pressure channel 11 to the hydraulic cylinder 55 or from the hydraulic cylinder 55 flow to the pressure channel 11 can.
  • the directional control valve 57 can be brought into a second switching position by an electromagnet 61, in which the hydraulic cylinder 55 to the pressure channel 11 is shut off without leakage oil.
  • the electromagnet 49 drops off, so that the valve 46 comes into its rest position and a pump pressure which is 5 bar above the load pressure of the cylinder 21 or the cylinder 22 can be built up.
  • valve 47 is actuated in exactly the opposite way. As long as neither of the two directional control valves 13 or 14 is actuated, the directional control valve 47 is in its rest position due to the compression spring 48, in which the pump 40 delivers circulation. If a directional control valve 13 or 14 is activated, the electromagnet 49 is simultaneously energized, so that the load signaling line 19 to the tank channel 12 is shut off.
  • the spring brake 56 should take effect.
  • the electromagnet 61 is therefore disconnected from the voltage source and drops out.
  • the valve 57 reaches its first switching position due to the spring 60.
  • the spring brake 56 When the driver sits down on his seat again, the spring brake 56 must be released. To do this, the hydraulic cylinder 55 must be pressurized. So that a pressure build-up is possible, in the embodiment according to FIG. 1, the pressure channel 11 and the load signaling channel 19 are connected to one another via a nozzle 65. If the driver's seat is loaded, the electromagnet 49 is disconnected from its voltage source in the embodiment according to FIG. 1, so that the valve 46 reaches its first switching position, in which the load signaling channel 19 to the tank channel 12 is shut off.
  • one side of the pressure compensator 44 is acted upon by the pressure in the pressure channel 11, so that a pump pressure can build up which is equivalent to a pressure difference 45 equivalent to the force of the pressure spring 45 above the pressure set on a pressure relief valve 66.
  • the entire quantity of pressure medium conveyed by the hydraulic pump 40 now flows to the hydraulic cylinder 55 via the valve 60, which has not yet been switched.
  • the brake is released.
  • the electromagnet 61 is energized and thereby the valve 57 is brought into its second switching position, in which the hydraulic cylinder 55 is shut off without leakage oil.
  • the electromagnet 49 of the valve 46 is also energized, so that the load signal line 19 is relieved to the tank channel 12 and promotes the hydraulic pump 40 in circulation. Only when one of the
  • the directional control valve 13 and the pressure compensator 27 show that the consumer chamber 15 or the intermediate chamber 26 can be connected to the load-sensing channel 19 via a nozzle 67 or 68.
  • the pressure in the latter does not exactly correspond to the load pressure of one of the consumers 21 or 22.
  • the opening cross section of the nozzle 65 is selected to be significantly smaller than the opening cross section of the nozzles 67 and 68, so that the adulteration of the load pressure is only slight and the pressure drop across the metering orifices in the directional control valves 13 and 14 is only slightly above the pressure difference between the pressure channel 11 and the load signaling line 19 which is predetermined by the pressure spring 45 of the pressure compensator 44.
  • a 2/2-way seat valve 70 is arranged in the pressure channel 11 stro - from the connection of the valve 60 and upstream of the connection of the pressure compensator 44 to the pressure channel, which is held in a through position by a pressure spring 72 and can be brought into a blocking position by driving an electromagnet 71. Electromagnet 71 is excited when the driver sits in the driver's seat. As a result, the valve 70 shuts off the pressure channel 11 from the pressure compensator 44. It is now possible to build up pressure in the section of the pressure channel located upstream of the valve 70 and thus actuate the hydraulic cylinder 55 in order to release the spring-loaded brake 56.
  • the electromagnet 61 is energized, thereby bringing the valve 60 into its second switching position, in which the hydraulic cylinder 55 is shut off without leakage oil and the spring-loaded brake is released.
  • the electromagnet 71 drops off, so that the compression spring 72 brings the valve 70 into its open position.
  • the hydraulic pump 40 now pumps in circulation. If one of the directional control valves 13 or 14 is actuated, the electromagnet 49, the valve 47 switches over.
  • the valve 70 remains in the open position.
  • several valves can also be combined to form a single valve. For example, in a variant of the embodiment according to FIG.
  • the functions of the throttle 65 and the valve 46 can be implemented in a single valve which is designed as a 3/3-way valve with two electromagnets and a connection to the pressure channel 11, a connection to has the tank channel 12 and a connection to the load reporting channel. In a spring-centered middle position, all three connections can be locked against each other.
  • the connection to the load signaling channel is then connected in a first lateral position to the connection to the tank channel and in a second lateral position to the connection to the pressure channel.
  • valves 47 and 70 could be combined to form a single 4/3-way valve with two electromagnets which, in a spring-centered central position, connects two sections of the pressure channel 11 with one another and the load signaling channel and the tank channel with one another. In a first lateral position, the two sections of the pressure channel and in a second lateral position, the load signaling channel and the tank channel are separated from one another, while the other connection is maintained in each case.

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

Abstract

The invention relates to a hydraulic control device, specially for a fork lift, comprising a hydraulic consumer (55) used to bleed a spring-loaded brake (56), valves (46, 47, 57, 65) to supply pressure medium from a pressure line (11) to said consumer (55) and to reduce hydraulic consumer pressure (55), in addition to a hydraulic pump (40) which delivers the pressure medium to the pressure line (11). In order to simplify control of the spring-loaded brake (56), the valves include a 2/2-way seat valve (57) which has a first connection (59) which is connected to the pressure line (11) and a second connection (58) which is connected to the hydraulic consumer (55). In the first switching position, the valve can be cross-flown by a pressure medium from the second connection (58) to the first connection (59) and, in the second switching position, blocks off the connection between the second connection (58) and the first connection (59).

Description

Beschreibungdescription
Hydraulische Stβueranordnunσ. insbesondere für einen GabelstaplerHydraulic thruster arrangement. especially for a forklift
Die Erfindung geht aus von einer hydraulischen Steueranordnung, die insbesondere für einen elektromotorisch angetriebenen Gabelstapler verwendet wird und die die Merkmale aus dem Oberbegriff des Anspruchs 1 aufweist.The invention is based on a hydraulic control arrangement which is used in particular for an electric motor-driven forklift and which has the features from the preamble of claim 1.
Gabelstapler sind üblicherweise mit einer Feststellbremse ausgerüstet, die als Federspeicherbremse ausgebildet ist und von der Belastung des Fahrersitzes gesteuert wird. Wenn der Fahrer auf dem Sitz sitzt, ist die Federspeicherbremse gelüftet, also nicht wirksam. Sobald der Fahrer vom Sitz aufsteht, fällt die Federspeicherbremse ein. Die dazu benötigte Energie wird, wie der Name schon sagt, von einer vorgespannten Feder bereitgestellt. Gelüftet wird die Bremse mithilfe eines druckbeaufschlagten hydraulischen Verbrauchers, üblicherweise mithilfe eines druckbeaufschlagten Hydrozylinders . Zur Zuführung von Druckmittel zum hydraulischen Verbraucher von einer Druckleitung aus, in die Druckmittel von einer Druckmittelquelle abgegeben wird, und zur Entlastung des hydraulischen Verbrauchers dienen Ventilmittel, die üblicherweise elektromagnetisch betä- tigt werden.Forklifts are usually equipped with a parking brake, which is designed as a spring-loaded brake and is controlled by the load on the driver's seat. When the driver is sitting on the seat, the spring-loaded brake is released, so it is not effective. As soon as the driver gets up from the seat, the spring brake is applied. The energy required for this, as the name suggests, is provided by a pre-tensioned spring. The brake is released with the help of a pressurized hydraulic consumer, usually with the help of a pressurized hydraulic cylinder. Valve means, which are usually actuated electromagnetically, are used to supply pressure medium to the hydraulic consumer from a pressure line into which pressure medium is released from a pressure medium source, and to relieve the hydraulic consumer.
Der Erfindung liegt die Aufgabe zugrunde, eine hydraulische Steueranordnung mit den Merkmalen aus dem Oberbegriff des Anspruchs 1 sehr einfach aufzubauen.The invention has for its object to very simply build a hydraulic control arrangement with the features from the preamble of claim 1.
Diese Aufgabe wird bei einer gattungsgemäßen hydraulischen Steueranordnung nach der Erfindung dadurch gelöst, daß die Ventilmittel ein 2/2-Wege-Sitzventil umfassen, das einen ersten Anschluß, der mit der Druckleitung verbunden ist, und einen zweiten Anschluß, der mit dem hydraulischen Verbraucher verbunden ist, besitzt und das in der ersten Schaltstellung vom zwei- ten Anschluß zum ersten Anschluß von Druckmittel durchströmbar ist und in der zweiten Schaltstellung vom zweiten Anschluß zum ersten Anschluß hin sperrt. In der zweiten Schaltstellung wird also der hydraulische Verbraucher unter Druck gehalten, so daß die Federspeicherbremse gelüftet bleibt. Damit die Bremse einfällt, wird das 2/2-Wege-Sitzventil in seine erste Schaltstellung gebracht, in der Druckmittel vom hydraulischen Verbraucher abfließen und die vorgespannte Feder die Bremse betätigen kann. Und zwar fließt nach der Erfindung das Druckmittel in die Druckleitung ab. Dem liegt die Überlegung zugrunde, daß bei den heute üblichen Gabelstaplern in dem Moment, in dem der Fahrersitz entlastet wird, auch der Druck in der Druckleitung zusammenfällt, weil vom Fahrer kein anderer hydraulischer Verbraucher mehr betätigt wird und die Hydropumpe, falls es sich um eine mit konstantem Fördervolumen handelt, mit niedrigem Druck im Umlauf zu einem Tank fördert oder, falls es sich um eine Verstellpumpe handelt, ganz zurückgeschwenkt wird, oder weil der Antrieb der Hydropumpe ausgeschaltet wird, wie dies insbesondere bei einem elektromotorisch angetriebenen Gabelstapler der Fall ist. Somit kann bei einer erfindungsgemäßen hydraulischen Steueranordnung ein einziges zusätzliches Ventil genügen, um die Federspeicherbremse zu steuern.This object is achieved in a generic hydraulic control arrangement according to the invention in that the valve means comprise a 2/2-way poppet valve which has a first connection which is connected to the pressure line and a second connection which is connected to the hydraulic consumer is in the first switching position from the second can flow through the connection to the first connection of pressure medium and blocks in the second switching position from the second connection to the first connection. In the second switching position, the hydraulic consumer is therefore kept under pressure, so that the spring-loaded brake remains released. So that the brake is applied, the 2/2-way poppet valve is brought into its first switching position, in which pressure fluid can flow from the hydraulic consumer and the preloaded spring can actuate the brake. Namely, according to the invention, the pressure medium flows into the pressure line. This is based on the consideration that with today's forklift trucks the moment the driver's seat is relieved, the pressure in the pressure line also collapses because the driver no longer actuates any other hydraulic consumer and the hydraulic pump, if it is a with a constant delivery volume, with low pressure circulating to a tank or, if it is a variable displacement pump, swung back completely, or because the drive of the hydraulic pump is switched off, as is the case in particular with an electric motor-driven forklift. Thus, in a hydraulic control arrangement according to the invention, a single additional valve can be sufficient to control the spring-loaded brake.
Vorteilhafte Ausgestaltungen einer erfindungsgemäßen hydrauli- sehen Steueranordnung kann man den Unteransprüchen entnehmen.Advantageous embodiments of a hydraulic control arrangement according to the invention can be found in the subclaims.
So ist gemäß Anspruch 2 das 2/2-Wege-Sitzventil durch einen Elektromagneten aus der ersten Schaltstellung, die es unter der Wirkung einer Feder einnimmt, in die zweite Schaltstellung um- schaltbar. Dadurch wird erreicht, daß bei einem Ausfall desThus, according to claim 2, the 2/2-way seat valve can be switched to the second switching position by an electromagnet from the first switching position, which it assumes under the action of a spring. This ensures that if the
Elektromagneten oder eines anderen zur Steuerung des Elektromagneten notwendigen Bauteils das Sitzventil in seine Durchgangsstellung gelangt und die Federspeicherbremse wirksam werden kann. 2/2-Wege-Sitzventile sind in einer ihrer beiden Schaltstellungen in beide Richtungen frei durchströmbar, während in ihrer anderen Schaltstellung ihr Schließglied vom Druck in einem Anschluß auf den Sitz gedrückt wird, aber auch ein Durchströmen vom anderen Anschluß her nicht ohne weiteres möglich ist. Deshalb ist gemäß Anspruch 3 vorgesehen, daß das 2/2-Wege- Sitzventil, das in der ersten Schaltstellung in beide Richtungen von Druckmittel durchströmbar ist, von der ersten Schaltstellung in die zweite Schaltstellung erst nach Druckbeauf- schlagung des hydraulischen Verbrauchers umgeschaltet wird. Zum Lüften der Bremse verbleibt das Sitzventil also in seiner ersten Schaltstellung. Erst eine gewisse Zeit nach Beginn des Zuflusses von Druckmittel zum hydraulischen Verbraucher, die zum Lüften der Federspeicherbremse genügt, wird es in seine zweite Schaltstellung gebracht, in der es den hydraulischen Verbraucher unter Druck hält.Electromagnet or another component necessary to control the electromagnet, the seat valve reaches its open position and the spring-loaded brake can take effect. 2/2-way poppet valves can be freely flowed through in both directions in one of their two switching positions, while in their other switching position their closing element is pressed onto the seat by the pressure in one connection, but flow through the other connection is also not easily possible . It is therefore provided according to claim 3 that the 2/2-way seat valve, through which pressure medium can flow in both directions in the first switching position, is switched from the first switching position into the second switching position only after the hydraulic consumer has been pressurized. The seat valve therefore remains in its first switching position to release the brake. Only a certain time after the start of the inflow of pressure medium to the hydraulic consumer, which is sufficient to release the spring brake, is it brought into its second switching position, in which it keeps the hydraulic consumer under pressure.
Wie schon angedeutet, kann die Hydropumpe konstantes Fördervolumen besitzen. Wenn kein von ihr mit Druckmittel versorgbarer hydraulischer Verbraucher betätigt wird, fördert sie Druckmittel mit niedrigem Druck im Umlauf zu einem Tank. Da der der Federspeicherbremse zugeordnete hydraulische Verbraucher nicht wie andere hydraulische Verbraucher eines Gabelstaplers z.B. ein Liftzylinder, über ein willkürlich betätigbares Wegeventil gesteuert wird, ist gemäß Anspruch 4 vorgesehen, daß in derAs already indicated, the hydraulic pump can have a constant delivery volume. If no hydraulic consumer that can be supplied with pressure medium is actuated, it conveys pressure medium with low pressure in circulation to a tank. Since the hydraulic consumer assigned to the spring-loaded brake is not like other hydraulic consumers of a forklift e.g. an elevator cylinder, controlled via an arbitrarily actuated directional valve, is provided according to claim 4 that in the
Druckleitung stromab der Anbindung des 2/2-Wege-Sitzventils ein Sperrventil angeordnet ist, das zur Druckbeaufschlagung des hydraulischen Verbrauchers, also zum Lüften der Federspeicherbremse seine Sperrstellung einnimmt, so daß in der Druckleitung ein Druck aufgebaut werden kann.Pressure line downstream of the connection of the 2/2-way seat valve, a check valve is arranged, which assumes its blocking position for pressurizing the hydraulic consumer, i.e. for releasing the spring brake, so that a pressure can be built up in the pressure line.
Sehr oft wird heute eine Hydropumpe verwendet, .von der einem zweiten hydraulischen Verbraucher Druckmittel load-sensing- geregelt zuführbar ist. Load-sensing-geregelt bedeutet dabei, daß in der Druckleitung ein Druck aufgebaut wird, der um eine vorgegebene Druckdifferenz Δp über dem Lastdruck des zweiten hydraulischen Verbrauchers liegt. Der Hydropumpe ist ein Load- sensing-Regler mit einem Steuerraum zugeordnet, der über eine Lastmeldeleitung mit dem Lastdruck des zweiten hydraulischen Verbrauchers beaufschlagbar ist. Um nun auch dann einen Druck in der Druckleitung aufbauen zu können, wenn kein zweiter hydraulischer Verbraucher betätigt wird, ist gemäß Anspruch 5 der Steuerraum am Load-sensing-Regler von der Druckleitung her mit einem Druck beaufschlagbar. Auf einfache Weise wird dies gemäß Anspruch 6 dadurch erreicht, daß der Steuerraum des Load- sensing-Reglers dauernd mit der Lastmeldeleitung verbunden ist und zwischen dieser und der Druckleitung eine Düse vorhanden ist.A hydraulic pump is very often used today, from which pressure medium can be fed to a second hydraulic consumer in a load-sensing-controlled manner. Load-sensing-controlled means that a pressure is built up in the pressure line which is a predetermined pressure difference Δp above the load pressure of the second hydraulic consumer. The hydraulic pump is assigned a load-sensing controller with a control chamber which can be acted upon by the load pressure of the second hydraulic consumer via a load signaling line. In order to be able to build up a pressure in the pressure line even when no second hydraulic consumer is actuated, a pressure can be applied to the control chamber on the load-sensing controller from the pressure line. This is achieved in a simple manner in that the control chamber of the load-sensing controller is permanently connected to the load-signaling line and a nozzle is present between the latter and the pressure line.
Es ist bekannt, ein Sperrventil vorzusehen, das die Lastmelde- leitung in einer ersten Schaltstellung mit einer Tankleitung verbindet und in einer zweiten Schaltstellung zu der Tankleitung hin absperrt. Mit diesem Sperrventil wird eine Not-AusFunktion erfüllt. Dieses Ventil wird immer dann in seine zweite Schaltstellung gebracht, wenn kein zweiter hydraulischer Ver- braucher betätigt wird und in der Druckleitung nur ein niedriger, dem Betrage nach der Druckdifferenz Δp entsprechender Druck anstehen soll. Dieses Sperrventil kann nun dazu verwendet werden, um einen Druckaufbau zum Lüften der Federspeicherbremse zu ermöglichen. Es wird dazu kurzzeitig in seine Sperrstellung gebracht, nachdem sich der Fahrer auf seinen Sitz gesetzt hat.It is known to provide a shut-off valve which connects the load signal line to a tank line in a first switching position and shuts off to the tank line in a second switching position. This shut-off valve fulfills an emergency stop function. This valve is always brought into its second switching position when no second hydraulic consumer is actuated and only a low pressure corresponding to the amount according to the pressure difference Δp should be present in the pressure line. This check valve can now be used to allow pressure to build up to release the spring brake. To do this, it is briefly brought into its locked position after the driver has sat in his seat.
Zwei Ausführungsbeispiele einer erfindungsgemäßen hydraulischen Steueranordnung sind in den Zeichnungen dargestellt. Anhand dieser Zeichnungen wird die Erfindung nun näher erläutert.Two exemplary embodiments of a hydraulic control arrangement according to the invention are shown in the drawings. The invention will now be explained in more detail with reference to these drawings.
Es zeigenShow it
Figur 1 das erste Ausführungsbeispiel, das insbesondere für einen elektromotorisch angetriebenen Gabelstapler vorgesehen ist, und Figur 2 das zweite Ausführungsbeispiel, das insbesondere für einen von einer Verbrennungskraftmaschine angetriebenen Gabelstapler geeignet ist.1 shows the first embodiment, which is particularly intended for an electric motor-driven forklift, and Figure 2 shows the second embodiment, in particular for a forklift powered by an internal combustion engine is suitable.
Beide Ausführungsbeispiele umfassen einen Steuerblock 10 mit einem Pumpenanschluß P, einem Tankanschluß T, und verschiedenen Verbraucheranschlüssen. Am Pumpenanschluß P beginnt ein Druckkanal 11 und am Tankanschluß T ein Tankkanal 12 des Steuerblocks. Im Steuerblock sind zwei Load-sensing-Wegeventile 13 und 14 mit geschlossener Mitte ausgebildet, wobei mit dem Wege- ventil 13 ein Liftzylinder 21 und mit dem Wegeventil 14 einBoth embodiments include a control block 10 with a pump connection P, a tank connection T, and various consumer connections. A pressure channel 11 begins at the pump connection P and a tank channel 12 of the control block starts at the tank connection T. In the control block, two load-sensing directional valves 13 and 14 are formed with a closed center, one with the directional valve 13 and one with the directional valve 14
Neigezylinder 22 eines Gabelstaplers angesteuert werden können. Der Liftzylinder ist ein einfachwirkender hydraulischer Verbraucher. Demgemäß besitzt das Wegeventil 13 nur eine Verbrau- cherkammer 15 , von der aus ein Verbraucherkanal über ein elek- tromagnetisch betätigbares Sitzventil 16 zu einem Verbraucheranschluß AI des Steuerblocks 10 führt. In der Mittelstellung des Wegeventils 13 ist die Verbraucherkammer 15 sowohl zu einer mit dem Pumpenkanal verbundenen Zulaufkammer 17 als auch zu einer mit dem Tankkanal 12 verbundenen Ablaufkammer 18 hin abge- sperrt. Das Wegeventil 13 kann elektrohydraulisch in eine erste Arbeitsstellung gebracht werden, in der die Verbraucherkammer 15 mit der Ablaufkammer 18 verbunden ist und die Liftzylinder eingefahren werden können, um den Hubschlitten abzusenken. In der zweiten ArbeitsStellung des Wegeventils 13 ist die Verbra - cherkammer 15 mit der Zulaufkammer 17 verbunden. Außerdem wird an der Verbraucherkammer der Lastdruck der Liftzylinder abgegriffen und in einen Lastmeldekanal 19 des Steuerblocks 10 gegeben.Tilt cylinder 22 of a forklift can be controlled. The lift cylinder is a single-acting hydraulic consumer. Accordingly, the directional control valve 13 has only one consumer chamber 15, from which a consumer channel leads via a seat valve 16 which can be actuated electromagnetically to a consumer connection AI of the control block 10. In the middle position of the directional valve 13, the consumer chamber 15 is shut off both to an inlet chamber 17 connected to the pump channel and to an outlet chamber 18 connected to the tank channel 12. The directional control valve 13 can be brought electrohydraulically into a first working position, in which the consumer chamber 15 is connected to the discharge chamber 18 and the lift cylinders can be retracted in order to lower the lifting slide. In the second working position of the directional valve 13, the consumer chamber 15 is connected to the inlet chamber 17. In addition, the load pressure of the lift cylinder is tapped at the consumer chamber and placed in a load reporting channel 19 of the control block 10.
In dem Wegeventil 14 sind ein Geschwindigkeitssteuerteil und ein Richtungssteuerteil voneinander getrennt am selben Steuerschieber ausgebildet. Wenn das Wegeventil 14 aus seiner Mittelstellung in eine seiner beiden seitlichen Arbeitsstellungen gebracht worden ist, strömt vom Druckkanal 11 kommendes Druckmit- tel von der Zulaufkammer 17 über eine Meßblende 25 in eine erste Zwischenkammer 26, von dort über den Öffnungsquerschnitt einer Druckwaage 27 in eine zweite Zwischenkammer 28 und dann über den Richtungsteil des Wegeventils 14 in eine Verbraucherkammer 29 oder 30. Von dort gelangt Druckmittel über ein Bremsventil 31 bzw. 32 zum Verbraucheranschluß A2 oder B2 des Steu- erblocks 10. Der Regelkolben der Druckwaage 27 wird in Öffnungsrichtung vom Druck in der Zwischenkammer 26, also vom Druck nach der Meßblende 25 und in Schließrichtung vom Druck im Lastmeldekanal 19 sowie von einer schwachen Druckfeder 33 beaufschlagt. Der Regelkolben der Druckwaage 27 ist so ausgebil- det, daß er, wenn die Druckwaage ganz offen ist, eine gedrosselte Verbindung zwischen der Zwischenkammer 26 und dem Lastmeldekanal 19 schafft. Dies ist der Fall, wenn der Neigezylinder allein betätigt wird oder wenn bei einer gleichzeitigen Betätigung des Liftzylinders und des Neigezylinders der Lastdruck des Neigezylinders höher als derjenige des Liftzylinders sein sollte.In the directional control valve 14, a speed control part and a direction control part are formed separately from one another on the same control slide. When the directional valve 14 has been moved from its central position into one of its two lateral working positions, pressure medium coming from the pressure channel 11 flows from the inlet chamber 17 via a measuring orifice 25 into a first intermediate chamber 26, from there over the opening cross section a pressure compensator 27 into a second intermediate chamber 28 and then via the directional part of the directional control valve 14 into a consumer chamber 29 or 30. From there, pressure medium reaches the consumer connection A2 or B2 of the control block 10 via a brake valve 31 or 32. The regulating piston of the pressure compensator 27 is acted upon in the opening direction by the pressure in the intermediate chamber 26, that is to say by the pressure after the measuring orifice 25 and in the closing direction by the pressure in the load-sensing channel 19 and by a weak compression spring 33. The control piston of the pressure compensator 27 is designed in such a way that, when the pressure compensator is completely open, it creates a throttled connection between the intermediate chamber 26 and the load-sensing channel 19. This is the case if the tilt cylinder is operated alone or if the load pressure of the tilt cylinder should be higher than that of the lift cylinder when the lift cylinder and the tilt cylinder are operated simultaneously.
Als Druckmittelquelle wird bei beiden Ausführungsbeispielen eine Konstantpumpe 40 verwendet, die bei der Ausführung nach Fi- gur 1 von einem Elektromotor 41 und bei der Ausführung nach Figur 2 von einem Dieselmotor 42 antreibbar ist. Die Pumpe 40 saugt Druckmittel aus einem Tank 43 an und gibt es in eine Druckleitung ab, die der Einfachheit halber mit derselben Bezugszahl 11 wie der Druckkanal des Steuerblocks 10 versehen ist und zum Pumpenanschluß P des Steuerblocks 10 führt. Wenn kein Druckmittel benötigt wird und die Motoren 41 und 42 nicht stillstehen, fördert die Pumpe 40 das Druckmittel im Umlauf zum Tank 43 zurück. Zu diesem Zweck ist in den Steuerblock 10 eine Bypass-Druckwaage 44 eingebaut, die mit einem Eingang an den Druckkanal 11 und mit einem Ausgang an den Tankkanal 12 angeschlossen ist und deren Regelkolben in Öffnungsrichtung von dem Druck im Druckkanal 11 und in Schließrichtung vom Druck im Lastmeldekanal 19 sowie von einer Druckfeder 45 beaufschlagt wird, deren Kraft eine Druckdifferenz von z.B. 5 bar am Regel- kolben äquivalent sein möge. Der Lastmeldekanal 19 ist über ein 2/2-Wegeventil 46 (Figur 1) bzw. 47 (Figur 2) offen mit dem Tankkanal 12 verbindbar oder zum Tankkanal 12 hin absperrbar. Bei offener Verbindung zwischen dem Lastmeldekanal 19 und dem Tankkanal 12 liegt an der einen Seite des Regelkolbens der Druckwaage 44 Tankdruck an. In Schließrichtung des Regelkolbens wirkt deshalb nur die Druckfeder 45, so daß sich im Druckkanal 11 lediglich ein Druck von 5 bar aufbauen kann. Von der Pumpe 40 gefördertes Druckmittel fließt also unter einem Druckabfall von 5 bar über die Druckwaage 44 zum Tank 43 zurück. Sperrt dagegen das Wegeventil 46 bzw. 47, so kann sich im Lastmeldekanal 19 der Lastdruck eines Zylinders 21 bzw. 22 aufbauen. DieIn both exemplary embodiments, a constant pump 40 is used as the pressure medium source, which can be driven by an electric motor 41 in the embodiment according to FIG. 1 and by a diesel engine 42 in the embodiment according to FIG. The pump 40 draws in pressure medium from a tank 43 and discharges it into a pressure line which, for the sake of simplicity, is provided with the same reference number 11 as the pressure channel of the control block 10 and leads to the pump connection P of the control block 10. If no pressure medium is required and the motors 41 and 42 do not stand still, the pump 40 conveys the pressure medium back to the tank 43. For this purpose, a bypass pressure compensator 44 is installed in the control block 10, which is connected with an input to the pressure channel 11 and with an output to the tank channel 12 and whose control piston in the opening direction from the pressure in the pressure channel 11 and in the closing direction from the pressure in Load signaling channel 19 and a compression spring 45 is acted upon, the force of which may be equivalent to a pressure difference of, for example, 5 bar on the control piston. The load signaling channel 19 is open with a 2/2-way valve 46 (FIG. 1) or 47 (FIG. 2) Tank channel 12 connectable or lockable to the tank channel 12. With an open connection between the load signaling channel 19 and the tank channel 12, tank pressure is present on one side of the control piston of the pressure compensator 44. Therefore, only the compression spring 45 acts in the closing direction of the control piston, so that only a pressure of 5 bar can build up in the pressure channel 11. Pressure medium delivered by the pump 40 therefore flows back to the tank 43 via the pressure compensator 44 under a pressure drop of 5 bar. If, on the other hand, the directional control valve 46 or 47 is blocked, the load pressure of a cylinder 21 or 22 can build up in the load signaling channel 19. The
Druckwaage 44 schließt deshalb so weit, daß der Druck im Druckkanal 11 um 5 bar über dem im Lastmeldekanal 19 herrschenden Druck liegt.Pressure compensator 44 therefore closes so far that the pressure in the pressure channel 11 is 5 bar above the pressure prevailing in the load reporting channel 19.
Das Wegeventil 46 nach Figur 1 nimmt unter der Wirkung einer Druckfeder 48 eine Ruhestellung ein, in der der Lastmeldekanal 19 zum Tankkanal 12 hin abgesperrt ist. Durch Ansteuerung eines Elektromagneten 49 kann es in seine zweite Schaltstellung gebracht werden, in der die offene Verbindung zwischen dem Lastmeldekanal 19 und dem Tankkanal 12 besteht. Bei der Ausführung nach Figur 2 nimmt das Wegeventil 47 unter der Wirkung einer Druckfeder 48 seine Durchgangsstellung ein und kann durch einen Elektromagneten 49 in seine Sperrstellung gebracht werden.The directional valve 46 according to FIG. 1 assumes a rest position under the action of a compression spring 48, in which the load-signaling channel 19 is blocked off from the tank channel 12. By actuating an electromagnet 49, it can be brought into its second switching position, in which there is an open connection between the load-signaling channel 19 and the tank channel 12. In the embodiment according to FIG. 2, the directional valve 47 assumes its through position under the action of a compression spring 48 and can be brought into its blocking position by an electromagnet 49.
Zu den gezeigten hydraulischen Steueranordnungen gehört ein einfachwirkender Hydrozylinder 55, mit dem eine nur als rechteckiger Block angedeutete Federspeicherbremse 56 gelüftet werden kann. Der Hydrozylinder 55 ist mit dem zweiten Anschluß 58 eines 2/2-Wege-Sitzventils 57 verbunden, das am Steuerblock 10 sitzt und mit seinem ersten Anschluß 59 am Druckkanal 11 liegt. Das 2/2-Wege-Sitzventil nimmt unter der Wirkung- einer Druckfeder 60 eine Ruhestellung ein, in der zwischen den beiden Anschlüssen 58 und 59 in beiden Richtungen ein offener Durchgang besteht, so daß Druckmittel frei vom Druckkanal 11 zum Hydrozylinder 55 oder vom Hydrozylinder 55 zum Druckkanal 11 strömen kann. Durch einen Elektromagneten 61 kann das Wegeventil 57 in eine zweite Schaltstellung gebracht werden, in der der Hydrozylinder 55 zum Druckkanal 11 hin leckölfrei abgesperrt ist.The hydraulic control arrangements shown include a single-acting hydraulic cylinder 55 with which a spring-loaded brake 56, which is only indicated as a rectangular block, can be released. The hydraulic cylinder 55 is connected to the second connection 58 of a 2/2-way seat valve 57, which is seated on the control block 10 and has its first connection 59 on the pressure channel 11. The 2/2-way poppet valve assumes a rest position under the action of a compression spring 60, in which there is an open passage between the two connections 58 and 59 in both directions, so that pressure medium is free from the pressure channel 11 to the hydraulic cylinder 55 or from the hydraulic cylinder 55 flow to the pressure channel 11 can. The directional control valve 57 can be brought into a second switching position by an electromagnet 61, in which the hydraulic cylinder 55 to the pressure channel 11 is shut off without leakage oil.
Im normalen Betrieb eines Gabelstaplers sitzt der Fahrer auf dem Fahrersitz. Dadurch ist ein elektrischer Schalter betätigt, der eine Erregung des Elektromagneten 61 nach sich zieht, so daß das Ventil 57 seine zweite Schaltstellung einnimmt. Das Druckmittel im Zylinder 55 ist leckölfrei abgesperrt, so daß die Federspeicherbremse gelüftet bleibt. Bei der Ausführung nach Figur 1 ist der Elektromagnet 49 erregt, solange weder das Wegeventil 13 noch das Wegeventil 14 betätigt ist. Die Hydropumpe 40 fördert deshalb mit niedrigem Druck Druckmittel über die Druckwaage 44 zum Tank 43 zurück. Sobald eines der beiden Wegeventile 13 oder 14 angesteuert wird, fällt der Elektromagnet 49 ab, so daß das Ventil 46 in seine Ruhestellung gelangt und ein um 5 bar über dem Lastdruck des Zylinders 21 oder des Zylinders 22 liegender Pumpendruck aufgebaut werden kann.In normal forklift operation, the driver sits in the driver's seat. As a result, an electrical switch is actuated, which causes the electromagnet 61 to be excited, so that the valve 57 assumes its second switching position. The pressure medium in the cylinder 55 is shut off without leakage oil, so that the spring-loaded brake remains released. In the embodiment according to FIG. 1, the electromagnet 49 is excited as long as neither the directional valve 13 nor the directional valve 14 is actuated. The hydraulic pump 40 therefore conveys pressure medium back to the tank 43 at a low pressure via the pressure compensator 44. As soon as one of the two directional control valves 13 or 14 is activated, the electromagnet 49 drops off, so that the valve 46 comes into its rest position and a pump pressure which is 5 bar above the load pressure of the cylinder 21 or the cylinder 22 can be built up.
Bei der Ausführung nach Figur 2 geschieht die Ansteuerung des Ventils 47 genau umgekehrt. Solange keines der beiden Wegeventile 13 oder 14 betätigt ist, befindet sich das Wegeventil 47 aufgrund der Druckfeder 48 in seiner Ruhestellung, in der die Pumpe 40 im Umlauf fördert. Wird ein Wegeventil 13 bzw. 14 an- gesteuert, so wird zugleich der Elektromagnet 49 erregt, so daß die Lastmeldeleitung 19 zum Tankkanal 12 abgesperrt wird.In the embodiment according to FIG. 2, valve 47 is actuated in exactly the opposite way. As long as neither of the two directional control valves 13 or 14 is actuated, the directional control valve 47 is in its rest position due to the compression spring 48, in which the pump 40 delivers circulation. If a directional control valve 13 or 14 is activated, the electromagnet 49 is simultaneously energized, so that the load signaling line 19 to the tank channel 12 is shut off.
Wenn der Fahrer von seinem Sitz aufsteht, soll die Federspeicherbremse 56 wirksam werden. Der Elektromagnet 61 wird deshalb von der Spannungsquelle getrennt und fällt ab. Das Ventil 57 gelangt aufgrund der Feder 60 in seine erste Schaltstellung. Zugleich wird dafür gesorgt, daß dann, wenn kein Wegeventil 13 oder 14 betätigt wird, wenn der Fahrer also tatsächlich das Fahrzeug verlassen hat, das Ventil 46 bzw. 47 in seine Durch- gangsstellung gelangt. Dann steht im Druckkanal 11 entsprechend der Kraft der Feder 45 nur ein niedriger Druck von 5 bar an, so daß Druckmittel aus dem Hydrozylinder 55 über das Ventil 57 in den Druckkanal und über die Druckwaage 44 zum Tank 43 verdrängt werden kann und die Federspeicherbremse 56 wirksam wird.When the driver gets up from his seat, the spring brake 56 should take effect. The electromagnet 61 is therefore disconnected from the voltage source and drops out. The valve 57 reaches its first switching position due to the spring 60. At the same time, it is ensured that, if no directional control valve 13 or 14 is actuated, that is, if the driver has actually left the vehicle, the valve 46 or 47 reaches its open position. Then there is only a low pressure of 5 bar in the pressure channel 11 according to the force of the spring 45, so that pressure medium can be displaced from the hydraulic cylinder 55 via the valve 57 into the pressure channel and via the pressure compensator 44 to the tank 43 and the spring brake 56 becomes effective.
Wenn sich der Fahrer wieder auf seinen Sitz setzt, ist die Federspeicherbremse 56 zu lüften. Dazu ist der Hydrozylinder 55 mit Druck zu beaufschlagen. Damit ein Druckaufbau möglich ist, sind bei der Ausführung nach Figur 1 der Druckkanal 11 und der Lastmeldekanal 19 über eine Düse 65 miteinander verbunden. Wenn der Fahrersitz belastet wird, so wird bei der Ausführung nach Figur 1 der Elektromagnet 49 von seiner Spannungsquelle getrennt, so daß das Ventil 46 in seine erste Schaltstellung gelangt, in der der Lastmeldekanal 19 zum Tankkanal 12 hin abgesperrt ist. Über die Düse 65 wird die eine Seite der Druckwaage 44 mit dem im Druckkanal 11 anstehenden Druck beaufschlagt, so daß sich ein Pumpendruck aufbauen kann, der um eine der Kraft der Druckfeder 45 äquivalente Druckdifferenz über dem an einem Druckbegrenzungsventil 66 eingestellten Druck liegt. Über das noch nicht geschaltete Ventil 60 strömt nun die gesamte von der Hydropumpe 40 geförderte Druckmittelmenge zum Hydrozylinder 55. Nach einer gewissen Zeit, die durch das Hubvolumen und die Drehzahl der Hydropumpe 40 sowie das Aufnahmevolumen des Hydrozylinder 55 bedingt ist, ist die Bremse gelüftet. Nach diesem Zeitraum, den man um ein Sicherheitsintervall verlängern kann, wird der Elektromagnet 61 erregt und dadurch das Ventil 57 in seine zweite Schaltstellung gebracht, in der der Hydrozylinder 55 leckölfrei abgesperrt ist. Zugleich mit dem Elektromagneten 61 wird auch der Elektromagnet 49 des Ventils 46 erregt, so daß die Lastmeldeleitung 19 wieder zum Tankkanal 12 entlastet ist und die Hydropumpe 40 im Umlauf fördert. Erst wenn eines derWhen the driver sits down on his seat again, the spring brake 56 must be released. To do this, the hydraulic cylinder 55 must be pressurized. So that a pressure build-up is possible, in the embodiment according to FIG. 1, the pressure channel 11 and the load signaling channel 19 are connected to one another via a nozzle 65. If the driver's seat is loaded, the electromagnet 49 is disconnected from its voltage source in the embodiment according to FIG. 1, so that the valve 46 reaches its first switching position, in which the load signaling channel 19 to the tank channel 12 is shut off. Via the nozzle 65, one side of the pressure compensator 44 is acted upon by the pressure in the pressure channel 11, so that a pump pressure can build up which is equivalent to a pressure difference 45 equivalent to the force of the pressure spring 45 above the pressure set on a pressure relief valve 66. The entire quantity of pressure medium conveyed by the hydraulic pump 40 now flows to the hydraulic cylinder 55 via the valve 60, which has not yet been switched. After a certain time, which is caused by the stroke volume and the speed of the hydraulic pump 40 and the intake volume of the hydraulic cylinder 55, the brake is released. After this period, which can be extended by a safety interval, the electromagnet 61 is energized and thereby the valve 57 is brought into its second switching position, in which the hydraulic cylinder 55 is shut off without leakage oil. Simultaneously with the electromagnet 61, the electromagnet 49 of the valve 46 is also energized, so that the load signal line 19 is relieved to the tank channel 12 and promotes the hydraulic pump 40 in circulation. Only when one of the
Wegeventile 13 oder 14 betätigt wird, wird der Elektromagnet 49 ausgeschaltet .Directional valves 13 or 14 is actuated, the electromagnet 49 is switched off.
Am Wegeventil 13 sowie an der Druckwaage 27 erkennt man, daß die Verbraucherkammer 15 bzw. die Zwischenkammer 26 über eine Düse 67 bzw. 68 mit dem Lastmeldekanal 19 verbindbar sind. Auf- grund der Düse 65 zwischen dem Druckkanal 11 und dem Lastmeldekanal 19 entspricht der Druck in letzterem nicht genau dem Lastdruck eines der Verbraucher 21 oder 22. Es ist jedoch der Öffnungsquerschnitt der Düse 65 wesentlich kleiner als der Öff- nungsquerschnitt der Düsen 67 und 68 gewählt, so daß die Verfälschung des Lastdrucks nur gering ist und der Druckabfall über die Meßblenden in den Wegeventilen 13 und 14 nur geringfügig über der durch die Druckfeder 45 der Druckwaage 44 vorgegebene Druckdifferenz zwischen dem Druckkanal 11 und der Lastmeldeleitung 19 liegt. Darüber hinaus kann man dieThe directional control valve 13 and the pressure compensator 27 show that the consumer chamber 15 or the intermediate chamber 26 can be connected to the load-sensing channel 19 via a nozzle 67 or 68. On- Because of the nozzle 65 between the pressure channel 11 and the load signaling channel 19, the pressure in the latter does not exactly correspond to the load pressure of one of the consumers 21 or 22. However, the opening cross section of the nozzle 65 is selected to be significantly smaller than the opening cross section of the nozzles 67 and 68, so that the adulteration of the load pressure is only slight and the pressure drop across the metering orifices in the directional control valves 13 and 14 is only slightly above the pressure difference between the pressure channel 11 and the load signaling line 19 which is predetermined by the pressure spring 45 of the pressure compensator 44. In addition, you can
Lastdruckverfälschung auch dadurch berücksichtigen, daß man die Druckfeder 45 etwas schwächer einstellt.Also take account of load pressure falsification by setting the compression spring 45 somewhat weaker.
Bei der Ausführung nach Figur 2 ist in dem Druckkanal 11 stro - ab der Anbindung des Ventils 60 und stromauf der Anbindung der Druckwaage 44 an den Druckkanal ein 2/2-Wege-Sitzventil 70 angeordnet, das von einer Druckfeder 72 in einer Durchgangsstellung gehalten wird und durch Ansteuerung eines Elektromagneten 71 in eine Sperrstellung gebracht werden kann. Der Elektroma- gnet 71 wird erregt, wenn sich der Fahrer auf den Fahrersitz setzt. Dadurch sperrt das Ventil 70 den Druckkanal 11 vor der Druckwaage 44 ab. Es ist nun ein Druckaufbau in dem stromauf des Ventils 70 liegenden Abschnitt des Druckkanals und damit eine Betätigung des Hydrozylinders 55 möglich, um die Feder- speicherbremse 56 zu lüften. Nach einer vorgegebenen Zeit wird der Elektromagnet 61 erregt und dadurch das Ventil 60 in seine zweite Schaltstellung gebracht, in der der Hydrozylinder 55 leckölfrei abgesperrt und die Federspeicherbremse gelüftet ist. Der Elektromagnet 71 dagegen fällt ab, so daß die Druckfeder 72 das Ventil 70 in seine Durchgangsstellung bringt. Die Hydropumpe 40 fördert nun im Umlauf. Wenn eines der Wegeventile 13 oder 14 betätigt wird, schaltet der Elektromagnet 49, das Ventil 47 um. Das Ventil 70 bleibt in Durchgangsstellung. Gemäß Varianten zu den gezeigten Ausführungen können auch mehrere Ventile zu einem einzigen Ventil zusammengefaßt werden. So können z.B. bei einer Variante der Ausführung nach Figur 1 die Funktionen der Drossel 65 und des Ventils 46 in einem einzigen Ventil verwirklicht sein, das als 3/3-Wegeventil mit zwei Elektromagneten ausgebildet ist und einen Anschluß an den Druckkanal 11, einen Anschluß an den Tankkanal 12 und einen Anschluß an den Lastmeldekanal besitzt. In einer federzentrierten Mittelstellung können alle drei Anschlüsse gegeneinander abge- sperrt sein. Der Anschluß an den Lastmeldekanal ist dann in einer ersten seitlichen Stellung mit dem Anschluß an den Tankkanal und in einer zweiten seitlichen Stellung mit dem Anschluß an den Druckkanal verbunden.In the embodiment according to FIG. 2, a 2/2-way seat valve 70 is arranged in the pressure channel 11 stro - from the connection of the valve 60 and upstream of the connection of the pressure compensator 44 to the pressure channel, which is held in a through position by a pressure spring 72 and can be brought into a blocking position by driving an electromagnet 71. Electromagnet 71 is excited when the driver sits in the driver's seat. As a result, the valve 70 shuts off the pressure channel 11 from the pressure compensator 44. It is now possible to build up pressure in the section of the pressure channel located upstream of the valve 70 and thus actuate the hydraulic cylinder 55 in order to release the spring-loaded brake 56. After a predetermined time, the electromagnet 61 is energized, thereby bringing the valve 60 into its second switching position, in which the hydraulic cylinder 55 is shut off without leakage oil and the spring-loaded brake is released. The electromagnet 71, on the other hand, drops off, so that the compression spring 72 brings the valve 70 into its open position. The hydraulic pump 40 now pumps in circulation. If one of the directional control valves 13 or 14 is actuated, the electromagnet 49, the valve 47 switches over. The valve 70 remains in the open position. According to variants of the designs shown, several valves can also be combined to form a single valve. For example, in a variant of the embodiment according to FIG. 1, the functions of the throttle 65 and the valve 46 can be implemented in a single valve which is designed as a 3/3-way valve with two electromagnets and a connection to the pressure channel 11, a connection to has the tank channel 12 and a connection to the load reporting channel. In a spring-centered middle position, all three connections can be locked against each other. The connection to the load signaling channel is then connected in a first lateral position to the connection to the tank channel and in a second lateral position to the connection to the pressure channel.
Bei einer Variante zur Ausführung nach Figur 2 könnten die Ventile 47 und 70 zu einem einzigen 4/3-Wegeventil mit zwei Elektromagneten zusammengefaßt sein, das in einer federzentrierten Mittelstellung zwei Abschnitte des Druckkanals 11 miteinander und den Lastmeldekanal und den Tankkanal miteinander verbindet. In einer ersten seitlichen Stellung sind die beiden Abschnitte des Druckkanals und in einer zweiten seitlichen Stellung sind Lastmeldekanal und Tankkanal voneinander getrennt, während die andere Verbindung jeweils erhalten bleibt. In a variant of the embodiment according to FIG. 2, the valves 47 and 70 could be combined to form a single 4/3-way valve with two electromagnets which, in a spring-centered central position, connects two sections of the pressure channel 11 with one another and the load signaling channel and the tank channel with one another. In a first lateral position, the two sections of the pressure channel and in a second lateral position, the load signaling channel and the tank channel are separated from one another, while the other connection is maintained in each case.

Claims

Patentansprüche claims
1. Hydraulische Steueranordnung, insbesondere für einen Gabelstapler, mit einem zum Lüften einer Federspeicherbremse (56) dienenden hydraulischen Verbraucher (55), mit Ventilmitteln (46, 47, 57, 65) zur Zuführung von Druckmittel zum hydraulischen Verbraucher (55) von einer Druckleitung (11) und zur Entlastung des hydraulischen Verbrauchers (55) von Druck, und mit einer Hydropumpe (40), die Druckmittel in die Drucklei- tung (11) abgibt, dadurch gekennzeichnet, daß die Ventilmittel ein 2/2-Wege-Sitzventil (57) umfassen, das einen ersten Anschluß (59), der mit der Druckleitung (11) verbunden ist, und einem zweiten Anschluß (58), der mit dem hydraulischen Verbraucher (55) verbunden ist, besitzt und das in der ersten Schalt- Stellung vom zweiten Anschluß (58) zum ersten Anschluß (59) von Druckmittel durchströmbar ist und in der zweiten Schaltstellung vom zweiten Anschluß (58) zum ersten Anschluß (59) hin sperrt.1. Hydraulic control arrangement, in particular for a forklift, with a hydraulic consumer (55) serving to release a spring-loaded brake (56), with valve means (46, 47, 57, 65) for supplying pressure medium to the hydraulic consumer (55) from a pressure line (11) and to relieve the hydraulic consumer (55) of pressure, and with a hydraulic pump (40) which delivers pressure medium into the pressure line (11), characterized in that the valve means comprises a 2/2-way seat valve ( 57), which has a first connection (59), which is connected to the pressure line (11), and a second connection (58), which is connected to the hydraulic consumer (55), and that in the first switching position pressure medium can flow through from the second connection (58) to the first connection (59) and blocks in the second switching position from the second connection (58) to the first connection (59).
2. Hydraulische Steueranordnung nach Anspruch 1 , dadurch gekennzeichnet, daß das 2/2-Wege-Sitzventil (57) durch einen2. Hydraulic control arrangement according to claim 1, characterized in that the 2/2-way seat valve (57) by one
Elektromagneten (61) aus der ersten Schaltstellung, die es unter der Wirkung einer Feder (60) einnimmt, in die zweite Schaltstellung umschaltbar ist.Electromagnets (61) can be switched from the first switching position, which it assumes under the action of a spring (60), to the second switching position.
3. Hydraulische Steueranordnung nach Anspruch 1 oder 2 , dadurch gekennzeichnet, daß das 2/2-Wege-Sitzventil (57) in der ersten Schaltstellung vom ersten Anschluß (59) zum zweiten Anschluß (58) von Druckmittel durchströmbar ist und von der ersten Schaltstellung in die zweite Schaltstellung erst nach Druckbeaufschlagung des hydraulischen Verbrauchers (55) umgeschaltet wird.3. Hydraulic control arrangement according to claim 1 or 2, characterized in that the 2/2-way seat valve (57) in the first switching position from the first connection (59) to the second connection (58) can be flowed through by pressure medium and from the first switching position is switched into the second switching position only after the hydraulic consumer (55) has been pressurized.
4. Hydraulische Steueranordnung nach einem vorhergehenden Anspruch, dadurch gekennzeichnet, daß die Hydropumpe (40) kon- stantes Fördervolumen besitzt und Druckmittel mit niedrigem Druck im Umlauf zu einem Tank (43) fördert, wenn kein von ihr mit Druckmittel versorgbarer hydraulischer Verbraucher (55, 21, 22) betätigt wird, und daß in der Druckleitung (11) stromab der Anbindung des 2/2-Wege-Sitzventils (57) ein Sperrventil (70) angeordnet ist, das zur Druckbeaufschlagung des hydraulischen Verbrauchers (55) seine Sperrstellung einnimmt.4. Hydraulic control arrangement according to one of the preceding claims, characterized in that the hydraulic pump (40) has a constant delivery volume and low pressure pressure medium circulates to a tank (43), if none of it hydraulic consumer (55, 21, 22) which can be supplied with pressure medium is actuated, and that in the pressure line (11) downstream of the connection of the 2/2-way seat valve (57) a check valve (70) is arranged which is for pressurizing the hydraulic Consumer (55) assumes its blocking position.
5. Hydraulische Steueranordnung, insbesondere nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, daß von der Hydropumpe (40) einem zweiten hydraulischen Verbraucher (21, 22) Druckmittel load-sensing-geregelt zuführbar ist, daß der Hydropumpe (50) ein Load-sensing-Regler (44) mit einem Steuerraum zugeordnet ist, der über eine Lastmeldeleitung (19) mit dem Lastdruck des zweiten hydraulischen Verbrauchers (21, 22) und zur Druckbeaufschlagung des ersten hydraulischen Verbrauchers (55) von der Druckleitung (11) her mit einem Druck beaufschlagbar ist.5. Hydraulic control arrangement, in particular according to one of claims 1 to 4, characterized in that from the hydraulic pump (40) to a second hydraulic consumer (21, 22) pressure medium can be fed in a load-sensing-controlled manner, that the hydraulic pump (50) has a load -sensing controller (44) is assigned to a control room, which is connected to the load pressure of the second hydraulic consumer (21, 22) via a load signaling line (19) and for pressurizing the first hydraulic consumer (55) from the pressure line (11) a pressure can be applied.
6. Hydraulische Steueranordnung nach Anspruch 5 , dadurch gekennzeichnet, daß der Steuerraum des Load-sensing-Reglers (44) dauernd mit der Lastmeldeleitung (19) und daß die6. Hydraulic control arrangement according to claim 5, characterized in that the control chamber of the load sensing controller (44) continuously with the load signaling line (19) and that
Lastmeldeleitung (19) über eine Düse (65) mit der Druckleitung (11) verbunden ist.Load signaling line (19) is connected to the pressure line (11) via a nozzle (65).
7. Hydraulische Steueranordnung nach Anspruch 6 , dadurch gekennzeichnet, daß ein Sperrventil (46, 47) vorhanden ist, das die Lastmeldeleitung ( 19 ) in einer ersten Schaltstellung mit einer Tankleitung ( 12 ) verbindet und in einer zweiten Schaltstellung zu der Tankleitung (12) hin absperrt. 7. Hydraulic control arrangement according to claim 6, characterized in that a check valve (46, 47) is present, which connects the load signaling line (19) in a first switching position with a tank line (12) and in a second switching position to the tank line (12) shut off.
PCT/EP1998/001840 1997-05-24 1998-03-28 Hydraulic control device, specially for a fork lift WO1998052804A1 (en)

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DE1997121739 DE19721739A1 (en) 1997-05-24 1997-05-24 Hydraulic control arrangement, in particular for a forklift

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CN105439045A (en) * 2015-12-07 2016-03-30 浙江美科斯叉车有限公司 Hydraulic control system for dual brake structure of fork lift truck
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JP2001316096A (en) * 2000-02-28 2001-11-13 Toyota Industries Corp Hydraulic device for industrial vehicle
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CN105439045A (en) * 2015-12-07 2016-03-30 浙江美科斯叉车有限公司 Hydraulic control system for dual brake structure of fork lift truck
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