EP0345640B1 - Self-levelling device for shovel loaders - Google Patents

Self-levelling device for shovel loaders Download PDF

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Publication number
EP0345640B1
EP0345640B1 EP89109918A EP89109918A EP0345640B1 EP 0345640 B1 EP0345640 B1 EP 0345640B1 EP 89109918 A EP89109918 A EP 89109918A EP 89109918 A EP89109918 A EP 89109918A EP 0345640 B1 EP0345640 B1 EP 0345640B1
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EP
European Patent Office
Prior art keywords
valve
pressure
bucket
jib
driving element
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.)
Expired - Lifetime
Application number
EP89109918A
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German (de)
French (fr)
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EP0345640A1 (en
Inventor
Bruce Kevin Fryk
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Deere and Co
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Deere and Co
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Publication date
Application filed by Deere and Co filed Critical Deere and Co
Publication of EP0345640A1 publication Critical patent/EP0345640A1/en
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Publication of EP0345640B1 publication Critical patent/EP0345640B1/en
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Expired - Lifetime legal-status Critical Current

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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F3/00—Dredgers; Soil-shifting machines
    • E02F3/04—Dredgers; Soil-shifting machines mechanically-driven
    • E02F3/28—Dredgers; Soil-shifting machines mechanically-driven with digging tools mounted on a dipper- or bucket-arm, i.e. there is either one arm or a pair of arms, e.g. dippers, buckets
    • E02F3/36—Component parts
    • E02F3/42—Drives for dippers, buckets, dipper-arms or bucket-arms
    • E02F3/43—Control of dipper or bucket position; Control of sequence of drive operations
    • E02F3/431—Control of dipper or bucket position; Control of sequence of drive operations for bucket-arms, front-end loaders, dumpers or the like
    • E02F3/432—Control of dipper or bucket position; Control of sequence of drive operations for bucket-arms, front-end loaders, dumpers or the like for keeping the bucket in a predetermined position or attitude
    • E02F3/433—Control of dipper or bucket position; Control of sequence of drive operations for bucket-arms, front-end loaders, dumpers or the like for keeping the bucket in a predetermined position or attitude horizontal, e.g. self-levelling

Definitions

  • the invention relates to a hydraulic control for adjusting the level of a bucket that is tiltably arranged on a pivotable boom, according to the preamble of claim 1.
  • Loader and vehicle handling devices such as industrial and agricultural loaders, often include leveling devices that control the bucket orientation as the bucket carrying boom is raised or lowered.
  • liquid can be supplied from the boom cylinder to the bucket cylinder (GB-A-1599283, DE-B-1122443, US-A-3987920).
  • liquid is supplied to the bucket cylinder from the pump or other sources.
  • the pump capacity must be increased unless higher cycle times are to be accepted.
  • the object is achieved according to the invention by specifying a hydraulic control circuit in accordance with the characterizing features of patent claim 1.
  • the control circuit controls the flow of liquid to the boom and bucket of a load handling device.
  • the hydraulic circuit contains a separate manually operated directional control valve for extending and retracting the boom and bucket cylinder.
  • the flow of liquid returning from the boom cylinder can be passed through a shuttle valve to the inlet opening of a blade alignment valve. Liquid that comes directly from the hydraulic pump can also be directed to this inlet opening.
  • Valves that react to pressure and are located in the supply line of the boom cylinder and between the pump and the inlet opening of the bucket alignment valve ensure an automatic and optional supply of the inlet opening of the bucket alignment valve with backflow from the boom cylinder, flow from the pump or flow from both, if necessary varying degrees.
  • the bucket alignment valve is actuated by solenoids which receive control signals from an electronic position feedback control unit.
  • Latter is connected to sensors for detecting the position of the boom and the bucket.
  • the blade alignment device 10 comprises a blade 12 which is pivotally attached to one end of a boom 14.
  • the boom 14 is attached at its other end to a frame part 16 of a vehicle or loader, not shown.
  • the boom 14 can be pivoted by a boom cylinder 18, and the bucket 12 can be pivoted by a bucket cylinder 20.
  • the bucket cylinder 20 is connected to the boom 14 and the bucket 12 by connecting members 11 and 13.
  • a hydraulic circuit 22 controls the fluid flow to and from the cylinders 18 and 20.
  • An electronic control circuit 28 receives a position signal from a boom position sensor 30 and a bucket position signal from a bucket position sensor 32.
  • the usual rotary potentiometers can serve as sensors 30 and 32.
  • the control unit 28 generates valve control signals which are applied to the input of an electrically actuable blade alignment valve 90 of the hydraulic circuit.
  • the control unit 28 can contain a conventional electronic analog control circuit for position feedback. This function can also be carried out by a digital control device which contains a suitable programmable computer.
  • the hydraulic circuit 22 contains a pump 40 and a sump or reservoir 42.
  • the pump 40 can supply the priority circuit, not shown, of the vehicle with pressurized liquid. It also supplies pressurized fluid via a priority valve 48 to a manually operable spring-centered 4-way, 4-position boom control valve 44 and to a manually-operated spring-centered 4-way, 3-position bucket control valve 46.
  • Valve 44 includes a pump opening, a reservoir opening, a first load opening, via line 52, pressure actuatable valve 54, and line 56 is connected to the head end of the boom cylinder 18, and a second load opening which is connected to the rod end of the cylinder 18 via the line 62, the pressure-actuated valve 64 and the line 66.
  • a shuttle valve 70 includes a bore 71, a first opening 72 which connects the bore 71 to the line 56, a second opening 74 which connects the bore 71 to the line 66, and a third opening 76 which connects the bore 71 to the Line 78 connects.
  • a valve member 80 with spherical ends is movably disposed in the bore 71 to close the openings 72, 74 at which the higher pressure is present and the opening 72, 74 at which the lower pressure is present with the opening 76 connect.
  • the valve 70 also includes a piston 82, one side of which is pressurized by the line 62 and the other side of which is pressurized by the reservoir. High pressure in the line 62 moves the piston 82 and moves the valve part 80 according to FIG. 2 upwards.
  • the bucket control valve 46 includes a pump port, a reservoir port, a first load port that communicates with the top end of the bucket cylinder 20 via line 86, and a second load port that communicates with the rod end of the bucket cylinder 20 via line 88.
  • the hydraulic circuit 22 also contains a 4-way, 3-position vane alignment valve 90 which can be actuated by the solenoid coils 91 and 93.
  • the blade alignment valve 90 contains a reservoir opening which is connected to the reservoir 42 via the line 92 and the filter 94 and to the line 66 via the line 96 and the check valve 98.
  • the bucket alignment valve 90 further includes an inlet or pump opening which can receive liquid from the pump 40 via the priority valve 48, the line 100, the pressure-actuable valve 102, the line 104 and the check valve 106.
  • the inlet or pump port also receives fluid from line 78 via check valve 108 and line 110.
  • Valve 90 also includes a first load port, which is connected via line 114 to the top of bucket cylinder 20 and line 86, and one second load opening, which is connected via line 116 to the rod end of the bucket cylinder 20 and the line 88.
  • the load pressure sensing lines 118, 120 and 122 communicate the pressure of the first load opening of the valve 90 (or via an inner load sensing passage of the second load opening of the valve 90) to the pressure actuable valve 54, 64 and 102, respectively.
  • Another load sensing line 121 may be used if this system is to be used in a hydraulic system that includes pumps or pressure and flow compensation control valves.
  • the pressure actuatable valve 54 is usually held in the closed position by the spring 124 and the pressure in the line 118. It is opened via the control lines 53 and 57 by pressure in the lines 52 and 56.
  • the pressure actuatable valve 64 is usually kept closed by the spring 126 and the pressure in the line 120. It is opened when there is pressure in the lines 62 and 66, which is communicated by the control lines 140 and 142, respectively.
  • the pressure actuatable valve 102 is kept open by the spring 128 and the pressure in the line 122. Pressure in line 130 closes valve 102 against the combined forces that result from spring 128 and the pressure in line 122 and counteract the pressure in line 130.
  • Lowering of the bucket 12 due to leakage can be accomplished by adding a controlled check valve 123 can be reduced in line 114.
  • the control line 125 supplies pump pressure to open the valve 123 when the bucket cylinder 20 is to be lowered.
  • the position sensors 30 and 32, the electronic control circuit 28 and the bucket alignment valve 90 cooperate to maintain the original alignment of the bucket 12 with respect to the frame 16.
  • valve 90 moves into its blade retraction position (a shift to the left according to FIG. 2) and the load pressure in the line 116 is available via the pressure sensing line 118, 120 and 122 the Valves 54, 64 and 102 in connection.
  • This load pressure tends to close valves 54 and 64 and open valve 102.
  • liquid is available at the rod end of the cylinder 20, namely from the pump 40 via the valve 48, the line 100, the valve 102 and the line 104 and / or from the rod end of the cylinder 18 via the line 66, the valve 70 Line 78, valve 108 and line 110.
  • valve 102 closes at a lower pressure differential than valve 64, so valve 102 closes and blocks flow from pump 40 when there is sufficient backflow from cylinder 18 and there is sufficient pressure in line 66 to achieve the desired retraction of cylinder 20 via valve 90. For some reason, if little or no oil flows back from the rod end of the cylinder 18, the valve 64 is closed and the valve 102 remains open to deliver liquid from the pump 40 to the valve 90.
  • the control valve 44 is preferably designed such that, when the slide is moved in the direction of retraction of the boom cylinder 18, the line 52 is connected to the reservoir 42 before the line 62 is applied to the pump pressure. Gravity tends to lower the boom 14 and pressurize the head end of the boom cylinder 18. This pressure causes the valve 54 to open through the lines 56 and 57, as a result of which a backflow through the line 52 and the valve 44 is possible and the boom 14 can lower. At the same time, the expanding rod end of the cylinder 18 receives fluid from the reservoir 42 through line 66, check valve 98, lines 96 and 92, and filter 94.
  • Sensors 30 and 32, electronic control circuit 28, and bucket alignment valve 90 cooperate to extend cylinder 20 and maintain the required position of bucket 12 with respect to frame 16 when boom 14 is lowered.
  • the valve 90 is moved into its bucket cylinder extended position (according to FIG. 2 there is a shift to the right).
  • the fluid pressure in line 114 corresponding to the bucket load is sensed and applied to valves 54, 64 and 102.
  • the piston 82 in valve 70 is pressurized via valve 44, line 62 and control line 140.
  • the valve 70 shifts when the pressure in the line 62 is approximately one third of the pressure in the head end of the cylinder 18 is in a position in which the opening 74 is closed and the opening 72 communicates with the opening 76 so that a backflow from the head end of the cylinder 18 through the line 78, the valve 108, the lines 110 and 104 and the check valve 106 can take place to the valve 90. This backflow then becomes the main source for extending the bucket cylinder 20.
  • valve 90 If the supply of liquid in line 100 exceeds the value required to hold the bucket 12 in place via valve 90, the pressure in line 62 causes valve 64 to open, causing the excess liquid to Rod end of the boom cylinder 18 can flow. If the pressure in the rod end of the boom cylinder 18 and in the control line 130 increases over the sum of the forces resulting from the spring 128 and the pressure in the line 122, the valve 102 closes and drives the entire flow from the pump 40 the rod end of the cylinder 18, causing the cycle time to decrease takes. The excess flow volume in line 56 generated by the required bucket cylinder expansion flows through valve 54, line 52 and valve 44 to collecting container 42.
  • the present invention can be applied to a boom-and-vane cylinder assembly as disclosed in U.S. Patent No. 4,408,518 by exchanging connections to solenoids 91 and 93 such that the boom and bucket-cylinder extend and retract together .
  • the blade position sensor can be arranged in a better protected location, for example between the blade cylinder housing and a connecting member 11. This assumes that the electronic control circuit is modified to derive the boom-bucket relationship from the relationship between the cylinder 20 and the link 11.

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  • Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Physics & Mathematics (AREA)
  • Operation Control Of Excavators (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Servomotors (AREA)
  • Supplying Of Containers To The Packaging Station (AREA)
  • Forklifts And Lifting Vehicles (AREA)

Description

Die Erfindung betrifft eine hydraulische Steuerung zur Niveaueinstellung einer an einem verschwenkbaren Ausleger verkippbar angeordneten Schaufel gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a hydraulic control for adjusting the level of a bucket that is tiltably arranged on a pivotable boom, according to the preamble of claim 1.

Einrichtungen zur Handhabung von Ladern und Fahrzeugen, beispielsweise industrielle und landwirtschaftliche Lader, enhalten häufig Nivelliereinrichtungen, welche die Ausrichtung der Schaufel beim Anheben oder Absenken des die Schaufel tragenden Auslegers steuern. Bei einigen hydraulischen Schaufelausrichtsystemen kann Flüssigkeit aus dem Auslegerzylinder dem Schaufelzylinder zugeführt werden (GB-A-1599283, DE-B-1122443, US-A-3987920). In anderen Ausrichtsystemen wird Flüssigkeit von der Pumpe oder anderen Quellen dem Schaufelzylinder zugeführt. Bei Systemen, die die Ausflußmenge der Pumpe zur Schaufelausrichtung verwenden, indem der Pumpenausfluß von dem Auslegerzylinder zu dem Schaufelzylinder abgeleitet wird, muß die Pumpenkapazität erhöht werden, wenn nicht höhere Zykluszeiten in Kauf genommen werden sollen. Systeme, die sich lediglich auf Flüssigkeit aus dem Auslegerzylinder stützen, können ungenau arbeiten, da zeitweise keine Rückströmung von dem Auslegerzylinder vorhanden ist oder da sich die Rückströmung aufgrund von Änderungen des Lastdruckes oder der Arbeitstaktzahl ändert. Systeme, die die Strömung für die Ausrichtung der Schaufel von einem Nebenzylinder herleiten, machen eine sehr sorgfältige Anpassuung des Nebenzylinderhubvolumens an die Geometrie und das Hubvolumen des Schaufelzylinders in dem Ausleger-Schaufel-System erforderlich.Loader and vehicle handling devices, such as industrial and agricultural loaders, often include leveling devices that control the bucket orientation as the bucket carrying boom is raised or lowered. In some hydraulic bucket alignment systems, liquid can be supplied from the boom cylinder to the bucket cylinder (GB-A-1599283, DE-B-1122443, US-A-3987920). In other alignment systems, liquid is supplied to the bucket cylinder from the pump or other sources. In systems that use the bucket alignment pump flow rate by diverting the pump flow from the boom cylinder to the bucket cylinder, the pump capacity must be increased unless higher cycle times are to be accepted. Systems that rely solely on fluid from the boom cylinder can operate imprecisely because there is at times no back flow from the Boom cylinder is present or because the backflow changes due to changes in the load pressure or the number of working cycles. Systems that derive the flow for the alignment of the bucket from a secondary cylinder require a very careful adjustment of the secondary cylinder stroke volume to the geometry and the stroke volume of the bucket cylinder in the boom-bucket system.

Die mit der Erfindung zu lösende Aufgabe wird darin gesehen, eine hydraulische Steuereinrichtung der eingangs genannten Art anzugeben, durch die die genannten Nachteile vermieden werden.The object to be achieved with the invention is seen in specifying a hydraulic control device of the type mentioned at the outset by which the disadvantages mentioned are avoided.

Die Aufgabe wird erfindungsgemäß durch die Angabe eines hydraulischen Steuerkreises gemäß den kennzeichnenden Merkmalen des Patentanspruches 1 gelöst. Der Steuerkreis steuert den Flüssigkeitsstrom zu dem Ausleger und der Schaufel einer Vorrichtung zur Handhabung von Lasten. Der Hydraulikkreis enthält ein separates manuell betätigbares Richtungssteuerventil zum Ausfahren und Zurückfahren des Ausleger- und Schaufelzylinders. Durch ein Wechselventil kann der von dem Auslegerzylinder zurückkommende Flüssigkeitsstrom an die Eintrittsöffnung eines Schaufelausrichtventils geleitet werden. Zu dieser Eintrittsöffnung kann auch Flüssigkeit geleitet werden, die direkt von der Hydraulikpumpe kommt. Auf Druck reagierende Ventile, die in der Versorgungsleitung des Auslegerzylinders und zwischen der Pumpe und der Eintrittsöffnung des Schaufelausrichtventiles liegen, sorgen für eine automatische und wahlweise Versorgung der Eintrittsöffnung des Schaufelausrichtventiles mit Rückströmung von dem Auslegerzylinder, Strömung von der Pumpe oder Strömung von beiden, gegebenenfalls in unterschiedlichem Ausmaß. Das Schaufelausrichtventil wird durch Magnetspulen betätigt, welche Steuersignale von einer elektronischen Lagerückkopplungssteuereinheit erhalten. Letztere steht mit Sensoren zur Erfassung der Lage des Auslegers und der Schaufel in Verbindung.The object is achieved according to the invention by specifying a hydraulic control circuit in accordance with the characterizing features of patent claim 1. The control circuit controls the flow of liquid to the boom and bucket of a load handling device. The hydraulic circuit contains a separate manually operated directional control valve for extending and retracting the boom and bucket cylinder. The flow of liquid returning from the boom cylinder can be passed through a shuttle valve to the inlet opening of a blade alignment valve. Liquid that comes directly from the hydraulic pump can also be directed to this inlet opening. Valves that react to pressure and are located in the supply line of the boom cylinder and between the pump and the inlet opening of the bucket alignment valve ensure an automatic and optional supply of the inlet opening of the bucket alignment valve with backflow from the boom cylinder, flow from the pump or flow from both, if necessary varying degrees. The bucket alignment valve is actuated by solenoids which receive control signals from an electronic position feedback control unit. Latter is connected to sensors for detecting the position of the boom and the bucket.

Steht eine Rückströmung vom antreibenden Element des Auslegers an, so wird diese automatisch zur Ausrichtung der Schaufel ausgenutzt. Andernfalls wird der von der Pumpe zur Verfügung gestellte Flüssigkeitsstrom automatisch für die Ausrichtung der Schaufel herangezogen, wenn die von dem antreibenden Element des Auslegers ausgehende Rückströmmenge oder der Rückströmdruck hierfür nicht ausreicht. Ferner kann automatisch eine Kombination aus Rückströmung und Pumpendruck zur Ausrichtung der Schaufel ausgenutzt werden.If there is a backflow from the driving element of the boom, this is automatically used to align the bucket. Otherwise, the liquid flow provided by the pump is automatically used for the alignment of the bucket if the backflow quantity or the backflow pressure emanating from the driving element of the boom is not sufficient for this. Furthermore, a combination of backflow and pump pressure can be automatically used to align the blade.

Dies ermöglicht kurze Zykluszeiten bei genauer Ausrichtung der Schaufel. Besondere Aufwendungen für die Anpassung von Hubvolumen sind nicht erforderlich.This enables short cycle times with precise blade alignment. Special expenses for the adjustment of the stroke volume are not necessary.

Weitere vorteilhafte Weiterbildungen und Ausgestaltungen der Erfindung gehen aus den Unteransprüchen hervor.Further advantageous developments and refinements of the invention emerge from the subclaims.

Anhand der Zeichnung, die ein Ausführungsbeispiel der Erfindung zeigt, sollen die Erfindung sowie weitere Ausgestaltungen und Weiterbildungen der Erfindung näher beschrieben und erläutert werden.The invention and further refinements and developments of the invention are to be described and explained in more detail with reference to the drawing, which shows an exemplary embodiment of the invention.

Es zeigt:

  • Fig. 1 ein einfaches schematisches Diagramm eines Schaufelausrichtsystems mit einem erfindungsgemäßen Hydraulikkreis und
  • Fig. 2 das Diagramm eines erfindungsgemäßen Hydraulikkreises.
It shows:
  • Fig. 1 is a simple schematic diagram of a blade alignment system with a hydraulic circuit according to the invention and
  • Fig. 2 shows the diagram of a hydraulic circuit according to the invention.

Die Schaufelausrichteinrichtung 10 umfaßt eine Schaufel 12, welche verschwenkbar an einem Ende eines Auslegers 14 befestigt ist. Der Ausleger 14 ist mit seinem anderen Ende an einem Rahmenteil 16 eines nicht näher dargestellten Fahrzeuges oder Laders befestigt. Der Ausleger 14 läßt sich durch einen Auslegerzylinder 18, und die Schaufel 12 läßt sich durch einen Schaufelzylinder 20 verschwenken. Der Schaufelzylinder 20 ist mit dem Ausleger 14 und der Schaufel 12 durch Verbindungsglieder 11 und 13 verbunden. Ein Hydraulikkreis 22 steuert den Flüssigkeitsstrom zu und von den Zylindern 18 und 20. Ein elektronischer Steuerkreis 28 empfängt ein Lagesignal von einem Auslegerlagesensor 30 und ein Schaufellagesignal von einem Schaufellagesensor 32. Als Sensoren 30 und 32 können übliche Drehpotentiometer dienen. Die Steuereinheit 28 erzeugt Ventilsteuersignale, welche an den Eingang eines elektrisch betätigbaren Schaufelausrichtventils 90 des hydraulischen Kreises angelegt werden. Die Steuereinheit 28 kann einen üblichen elektronischen analogen Steuerkreis zur Lagerückkopplung enthalten. Diese Funktion kann auch durch eine digitale Steuereinrichtung ausgeführt werden, die einen geeigneten programmierbaren Computer enthält.The blade alignment device 10 comprises a blade 12 which is pivotally attached to one end of a boom 14. The boom 14 is attached at its other end to a frame part 16 of a vehicle or loader, not shown. The boom 14 can be pivoted by a boom cylinder 18, and the bucket 12 can be pivoted by a bucket cylinder 20. The bucket cylinder 20 is connected to the boom 14 and the bucket 12 by connecting members 11 and 13. A hydraulic circuit 22 controls the fluid flow to and from the cylinders 18 and 20. An electronic control circuit 28 receives a position signal from a boom position sensor 30 and a bucket position signal from a bucket position sensor 32. The usual rotary potentiometers can serve as sensors 30 and 32. The control unit 28 generates valve control signals which are applied to the input of an electrically actuable blade alignment valve 90 of the hydraulic circuit. The control unit 28 can contain a conventional electronic analog control circuit for position feedback. This function can also be carried out by a digital control device which contains a suitable programmable computer.

Gemäß Fig. 2 enthält der Hydraulikkreis 22 eine Pumpe 40 und einen Sumpf oder Vorratsbehälter 42. Die Pumpe 40 kann den nicht dargestellten Prioritätskreis des Fahrzeuges mit unter Druck stehender Flüssigkeit versorgen. Ferner liefert sie über ein Prioritätsventil 48 unter Druck stehende Flüssigkeit an ein manuell betätigbares federzentriertes 4-Wege, 4-Positionen Auslegersteuerventil 44 und an ein manuell betätigbares federzentriertes 4-Wege, 3-Positionen Schaufelsteuerventil 46.2, the hydraulic circuit 22 contains a pump 40 and a sump or reservoir 42. The pump 40 can supply the priority circuit, not shown, of the vehicle with pressurized liquid. It also supplies pressurized fluid via a priority valve 48 to a manually operable spring-centered 4-way, 4-position boom control valve 44 and to a manually-operated spring-centered 4-way, 3-position bucket control valve 46.

Das Ventil 44 enthält eine Pumpenöffnung, eine Vorratsbehälteröffnung, eine erste Lastöffnung, die über die Leitung 52, das druckbetätigbare Ventil 54 und die Leitung 56 mit dem Kopfende des Auslegerzylinders 18 verbunden ist, und eine zweite Lastöffnung, die über die Leitung 62, das druckbetätigbare Ventil 64 und die Leitung 66 mit dem Stangenende des Zylinders 18 verbunden ist.Valve 44 includes a pump opening, a reservoir opening, a first load opening, via line 52, pressure actuatable valve 54, and line 56 is connected to the head end of the boom cylinder 18, and a second load opening which is connected to the rod end of the cylinder 18 via the line 62, the pressure-actuated valve 64 and the line 66.

Ein Wechselventil 70 enthält eine Bohrung 71, eine erste Öffnung 72, welche die Bohrung 71 mit der Leitung 56 verbindet, eine zweite Öffnung 74, welche die Bohrung 71 mit der Leitung 66 verbindet, und eine dritte Öffnung 76, welche die Bohrung 71 mit der Leitung 78 verbindet. Ein Ventilteil 80 mit kugelförmigen Enden ist bewegbar in der Bohrung 71 angeordnet, um jeweils die Öffnung 72, 74, an der der höhere Druck ansteht, zu verschließen und die Öffnung 72, 74, an der der niedriegere Druck ansteht, mit der Öffnung 76 zu verbinden. Das Ventil 70 enthält ferner einen Kolben 82, dessen eine Seite mit dem Druck der Leitung 62 und dessen andere Seite mit dem Druck des Vorratsbehälters beaufschlagt ist. Hoher Druck in der Leitung 62 bewegt den Kolben 82 und verschiebt das Ventilteil 80 gemäß Fig. 2 nach oben.A shuttle valve 70 includes a bore 71, a first opening 72 which connects the bore 71 to the line 56, a second opening 74 which connects the bore 71 to the line 66, and a third opening 76 which connects the bore 71 to the Line 78 connects. A valve member 80 with spherical ends is movably disposed in the bore 71 to close the openings 72, 74 at which the higher pressure is present and the opening 72, 74 at which the lower pressure is present with the opening 76 connect. The valve 70 also includes a piston 82, one side of which is pressurized by the line 62 and the other side of which is pressurized by the reservoir. High pressure in the line 62 moves the piston 82 and moves the valve part 80 according to FIG. 2 upwards.

Das Schaufelsteuerventil 46 enthält eine Pumpenöffnung, eine Vorratsbehälteröffnung, eine erste Lastöffnung, welche über die Leitung 86 mit dem Kopfende des Schaufelzylinders 20 in Verbindung steht, und eine zweite Lastöffnung, welche über die Leitung 88 mit dem Stangenende des Schaufelzylinders 20 in Verbindung steht.The bucket control valve 46 includes a pump port, a reservoir port, a first load port that communicates with the top end of the bucket cylinder 20 via line 86, and a second load port that communicates with the rod end of the bucket cylinder 20 via line 88.

Der Hydraulikkreis 22 enthält ferner ein 4-Wege, 3-Positionen Schaufelausrichtventil 90, welches durch die Magnetspulen 91 und 93 betätigbar ist. Das Schaufelausrichtventil 90 enthält eine Vorratsbehälteröffnung, welche über die Leitung 92 und den Filter 94 mit dem Vorratsbehälter 42 und über die Leitung 96 und das Rückschlagventil 98 mit der Leitung 66 verbunden ist. Das Schaufelausrichtventil 90 enthält ferner eine Eingangs- oder Pumpenöffnung, welche über das Prioritätsventil 48, die Leitung 100, das druckbetätigbare Ventil 102, die Leitung 104 und das Rückschlagventil 106 Flüssigkeit von der Pumpe 40 erhalten kann. Die Eingangs- oder Pumpenöffnung erhält ferner über das Rückschlagventil 108 und die Leitung 110 Flüssigkeit aus der Leitung 78. Das Ventil 90 enthält ferner eine erste Lastöffnung, welche über die Leitung 114 mit dem Kopfende des Schaufelzylinders 20 und der Leitung 86 verbunden ist, und eine zweite Lastöffnung, welche über die Leitung 116 mit dem Stangenende des Schaufelzylinders 20 und der Leitung 88 verbunden ist. Die Lastdruckfühlleitungen 118, 120 und 122 teilen den Druck der ersten Lastöffnung des Ventils 90 (oder über eine innere Lastfühlpassage der zweiten Lastöffnung des Ventils 90) dem druckbetätigbaren Ventil 54, 64 bzw. 102 mit. Eine weitere Lastfühlleitung 121 kann verwendet werden, wenn dieses System in einem Hydrauliksystem verwendet werden soll, welches Pumpen oder Druck- und Durchflußkompensationssteuerventile enthält.The hydraulic circuit 22 also contains a 4-way, 3-position vane alignment valve 90 which can be actuated by the solenoid coils 91 and 93. The blade alignment valve 90 contains a reservoir opening which is connected to the reservoir 42 via the line 92 and the filter 94 and to the line 66 via the line 96 and the check valve 98. The bucket alignment valve 90 further includes an inlet or pump opening which can receive liquid from the pump 40 via the priority valve 48, the line 100, the pressure-actuable valve 102, the line 104 and the check valve 106. The inlet or pump port also receives fluid from line 78 via check valve 108 and line 110. Valve 90 also includes a first load port, which is connected via line 114 to the top of bucket cylinder 20 and line 86, and one second load opening, which is connected via line 116 to the rod end of the bucket cylinder 20 and the line 88. The load pressure sensing lines 118, 120 and 122 communicate the pressure of the first load opening of the valve 90 (or via an inner load sensing passage of the second load opening of the valve 90) to the pressure actuable valve 54, 64 and 102, respectively. Another load sensing line 121 may be used if this system is to be used in a hydraulic system that includes pumps or pressure and flow compensation control valves.

Das druckbetätigbare Ventil 54 wird durch die Feder 124 und den Druck in der Leitung 118 gewöhnlich in geschlossener Stellung gehalten. Es wird über die Steuerleitungen 53 und 57 durch Druck in den Leitungen 52 und 56 geöffnet. Das druckbetätigbare Ventil 64 wird durch die Feder 126 und den Druck in der Leitung 120 gewöhnlich geschlossen gehalten. Es wird bei anstehendem Druck in den Leitungen 62 und 66, der durch die Steuerleitungen 140 bzw 142 mitgeteilt wird, geöffnet. Das druckbetätigbare Ventil 102 wird durch die Feder 128 und den Druck in der Leitung 122 offen gehalten. Druck in der Leitung 130 schließt das Ventil 102 gegen die vereinigten Kräfte, die von der Feder 128 und dem Druck in der Leitung 122 herrühren und dem Druck in der Leitung 130 entgegenwirken.The pressure actuatable valve 54 is usually held in the closed position by the spring 124 and the pressure in the line 118. It is opened via the control lines 53 and 57 by pressure in the lines 52 and 56. The pressure actuatable valve 64 is usually kept closed by the spring 126 and the pressure in the line 120. It is opened when there is pressure in the lines 62 and 66, which is communicated by the control lines 140 and 142, respectively. The pressure actuatable valve 102 is kept open by the spring 128 and the pressure in the line 122. Pressure in line 130 closes valve 102 against the combined forces that result from spring 128 and the pressure in line 122 and counteract the pressure in line 130.

Eine Absenkung der Schaufel 12 aufgrund einer Leckage kann durch Hinzufügung eines gesteuerten Rückschlagventils 123 in der Leitung 114 reduziert werden. Die Steuerleitung 125 liefert Pumpendruck, um das Ventil 123 zu öffnen, wenn der Schaufelzylinder 20 abgesenkt werden soll.Lowering of the bucket 12 due to leakage can be accomplished by adding a controlled check valve 123 can be reduced in line 114. The control line 125 supplies pump pressure to open the valve 123 when the bucket cylinder 20 is to be lowered.

Im folgenden wird die Betriebsweise des Hydraulikkreises beschrieben:The operation of the hydraulic circuit is described below:

Wird das Steuerventil 44 verschoben, um den Zylinder 18 auszufahren, so überwindet der Druck in der Leitung 52 die Kraft der Feder 124 und öffnet das Ventil 54, so daß Hydraulikflüssigkeit zum Kopfende des Zylinders 18 fließen kann. Zur gleichen Zeit bewegt sich das Wechselventil 70 in die dargestellte Lage, so daß die Flüssigkeit von dem Stangenende des Zylinders 18 über die Leitung 66, die Öffnungen 74 und 76, die Leitung 78, das Rückschlagventil 108, die Leitungen 110 und 104 und das Rückschlagventil 106 zur Pumpenöffnung des Schaufelausrichtventils 90 fließen kann. Flüssigkeit von dem Stangenende des Zylinders 18 kann auch über die Leitung 66, das Ventil 64, die Leitung 62 und das Ventil 44 zum Vorratsbehälter 42 zurückfließen, wenn der Druck in der Leitung 66 groß genug ist, um die Kraft der Feder 126 zu überwinden und das Ventil 64 zu öffnen.When the control valve 44 is displaced to extend the cylinder 18, the pressure in the line 52 overcomes the force of the spring 124 and opens the valve 54 so that hydraulic fluid can flow to the head end of the cylinder 18. At the same time, shuttle valve 70 moves to the position shown so that the liquid from the rod end of cylinder 18 via line 66, ports 74 and 76, line 78, check valve 108, lines 110 and 104, and check valve 106 can flow to the pump opening of the blade alignment valve 90. Liquid from the rod end of cylinder 18 may also flow back through line 66, valve 64, line 62 and valve 44 to reservoir 42 if the pressure in line 66 is high enough to overcome the force of spring 126 and to open the valve 64.

Wird der Zylinder 18 ausgefahren (oder eingefahren), um den Ausleger 14 zu verschwenken, so wirken die Lagesensoren 30 und 32, der elektronische Steuerkreis 28 und das Schaufelausrichtventil 90 zusammen, um die ursprüngliche Ausrichtung der Schaufel 12 in Bezug auf den Rahmen 16 beizubehalten.When the cylinder 18 is extended (or retracted) to pivot the boom 14, the position sensors 30 and 32, the electronic control circuit 28 and the bucket alignment valve 90 cooperate to maintain the original alignment of the bucket 12 with respect to the frame 16.

Wird beispielsweise der Zylinder 18 ausgefahren, um den Ausleger 14 anzuheben, so bewegt sich das Ventil 90 in seine Schaufelrückzugslage (gemäß Fig. 2 erfolgt eine Verschiebung nach links) und der Lastdruck in der Leitung 116 steht über die Druckfühlleitung 118, 120 und 122 mit den Ventilen 54, 64 und 102 in Verbindung. Dieser Lastdruck tendiert dazu, die Ventile 54 und 64 zu schließen und das Ventil 102 zu öffnen. Damit steht Flüssigkeit am Stangenende des Zylinders 20 bereit und zwar von der Pumpe 40 über das Ventil 48, die Leitung 100, das Ventil 102 und die Leitung 104 und/oder von dem Stangenende des Zylinders 18 über die Leitung 66, das Ventil 70, die Leitung 78, das Ventil 108 und die Leitung 110.If, for example, the cylinder 18 is extended in order to raise the boom 14, the valve 90 moves into its blade retraction position (a shift to the left according to FIG. 2) and the load pressure in the line 116 is available via the pressure sensing line 118, 120 and 122 the Valves 54, 64 and 102 in connection. This load pressure tends to close valves 54 and 64 and open valve 102. Thus, liquid is available at the rod end of the cylinder 20, namely from the pump 40 via the valve 48, the line 100, the valve 102 and the line 104 and / or from the rod end of the cylinder 18 via the line 66, the valve 70 Line 78, valve 108 and line 110.

Die Federn 128 und 126 sind so ausgewählt, daß das Ventil 102 bei einer tieferen Druckdifferenz schließt, als das Ventil 64, so daß das Ventil 102 immer dann geschlossen wird und eine Strömung von der Pumpe 40 abblockt, wenn ausreichend Rückströmung von dem Zylinder 18 und genügend Druck in der Leitung 66 vorhanden sind, um den gewünschten Rückzug des Zylinders 20 über das Ventil 90 zu erreichen. Strömt aus irgend einem Grund nur wenig oder kein Öl von dem Stangenende des Zylinders 18 zurück, so wird das Ventil 64 geschlossen und das Ventil 102 bleibt offen, um Flüssigkeit von der Pumpe 40 zu dem Ventil 90 zu liefern.Springs 128 and 126 are selected so that valve 102 closes at a lower pressure differential than valve 64, so valve 102 closes and blocks flow from pump 40 when there is sufficient backflow from cylinder 18 and there is sufficient pressure in line 66 to achieve the desired retraction of cylinder 20 via valve 90. For some reason, if little or no oil flows back from the rod end of the cylinder 18, the valve 64 is closed and the valve 102 remains open to deliver liquid from the pump 40 to the valve 90.

Das Steuerventil 44 ist vorzugsweise so ausgelegt, daß bei einer Verschiebung des Schiebers in Richtung Rückzug des Auslegerzylinders 18 die Leitung 52 mit dem Vorratsbehälter 42 verbunden wird, bevor die Leitung 62 an den Pumpendruck angelegt wird. Die Gravitation ist bestrebt, den Ausleger 14 abzusenken und das Kopfende des Auslegerzylinders 18 unter Druck zu setzen. Dieser Druck bewirkt durch die Leitungen 56 und 57 ein Öffnen des Ventils 54, wodurch eine Rückströmung durch die Leitung 52 und das Ventil 44 möglich ist und sich der Ausleger 14 absenken kann. Zur gleichen Zeit erhält das sich ausdehnende Stangenende des Zylinders 18 über die Leitung 66, das Rückschlagventil 98, die Leitungen 96 und 92 und den Filter 94 Flüssigkeit aus dem Vorratsbehälter 42.The control valve 44 is preferably designed such that, when the slide is moved in the direction of retraction of the boom cylinder 18, the line 52 is connected to the reservoir 42 before the line 62 is applied to the pump pressure. Gravity tends to lower the boom 14 and pressurize the head end of the boom cylinder 18. This pressure causes the valve 54 to open through the lines 56 and 57, as a result of which a backflow through the line 52 and the valve 44 is possible and the boom 14 can lower. At the same time, the expanding rod end of the cylinder 18 receives fluid from the reservoir 42 through line 66, check valve 98, lines 96 and 92, and filter 94.

Die Sensoren 30 und 32, der elektronische Steuerkreis 28 und das Schaufelausrichtventil 90 wirken zusammen, um den Zylinder 20 auszufahren und die erforderliche Lage der Schaufel 12 hinsichtlich des Rahmens 16 aufrechtzuerhalten, wenn der Ausleger 14 abgesenkt wird. Beispielsweise wird während einer Auslegerabsenkung das Ventil 90 in seine Schaufelzylinderausfahrposition (gemäß Fig. 2 erfolgt eine Verschiebung nach rechts) bewegt. Der der Schaufellast entsprechende Flüssigkeitsdruck in der Leitung 114 wird erfaßt und an die Ventile 54, 64 und 102 angelegt. Zur gleichen Zeit wird über das Ventil 44, die Leitung 62 und die Steuerleitung 140 der Kolben 82 in dem Ventil 70 mit Druck beaufschlagt. Da die wirksame Fläche des Kolbens 82 wenigstens dreimal größer ist als die Fläche der Kugel, durch die die Öffnung 72 verschlossen wird, verschiebt sich das Ventil 70 dann, wenn der Druck in der Leitung 62 etwa ein Drittel des Druckes in dem Kopfende des Zylinders 18 beträgt, in eine Position, in der die Öffnung 74 verschlossen ist und die Öffnung 72 mit der Öffnung 76 in Verbindung steht, so daß eine Rückströmung von dem Kopfende des Zylinders 18 durch die Leitung 78, das Ventil 108, die Leitungen 110 und 104 und das Rückschlagventil 106 zu dem Ventil 90 erfolgen kann. Diese Rückströmung wird dann die Hauptquelle für das Ausfahren des Schaufelzylinders 20.Sensors 30 and 32, electronic control circuit 28, and bucket alignment valve 90 cooperate to extend cylinder 20 and maintain the required position of bucket 12 with respect to frame 16 when boom 14 is lowered. For example, during a boom lowering, the valve 90 is moved into its bucket cylinder extended position (according to FIG. 2 there is a shift to the right). The fluid pressure in line 114 corresponding to the bucket load is sensed and applied to valves 54, 64 and 102. At the same time, the piston 82 in valve 70 is pressurized via valve 44, line 62 and control line 140. Since the effective area of the piston 82 is at least three times greater than the area of the ball through which the opening 72 is closed, the valve 70 shifts when the pressure in the line 62 is approximately one third of the pressure in the head end of the cylinder 18 is in a position in which the opening 74 is closed and the opening 72 communicates with the opening 76 so that a backflow from the head end of the cylinder 18 through the line 78, the valve 108, the lines 110 and 104 and the check valve 106 can take place to the valve 90. This backflow then becomes the main source for extending the bucket cylinder 20.

Übersteigt die Flüssigkeitszufuhr in der Leitung 100 den Wert, der erforderlich ist, um die Schaufel 12 über das Ventil 90 in ihrer Lage zu halten, so führt der Druck in der Leitung 62 dazu, daß sich das Ventil 64 öffnet, so daß der Flüssigkeitsüberschuß zum Stangenende des Auslegerzylinders 18 fließen kann. Wächst der Druck im Stangenende des Auslegerzylinders 18 und in der Steuerleitung 130 über die Summe der Kräfte , die von der Feder 128 und dem Druck in der Leitung 122 herrühren, an, so schließt das Ventil 102 und treibt den gesammten Fluß von der Pumpe 40 in das Stangenende des Zylinders 18, wodurch die Taktdauer ab nimmt. Der durch die erforderliche Schaufelzylinderausdehnung erzeugte Überschuß an Durchflußmenge in der Leitung 56 fließt über das Ventil 54, die Leitung 52 und das Ventil 44 zum Sammelbehälter 42 ab.If the supply of liquid in line 100 exceeds the value required to hold the bucket 12 in place via valve 90, the pressure in line 62 causes valve 64 to open, causing the excess liquid to Rod end of the boom cylinder 18 can flow. If the pressure in the rod end of the boom cylinder 18 and in the control line 130 increases over the sum of the forces resulting from the spring 128 and the pressure in the line 122, the valve 102 closes and drives the entire flow from the pump 40 the rod end of the cylinder 18, causing the cycle time to decrease takes. The excess flow volume in line 56 generated by the required bucket cylinder expansion flows through valve 54, line 52 and valve 44 to collecting container 42.

Auch wenn die Erfindung hier lediglich an Hand eines Ausführungsbeispieles beschrieben wurde, versteht es sich, daß für den Fachmann viele Alternativen, Modifikationen und Variationen ersichtlich sind, die von dem Erfindungsgedanken Gebrauch machen und unter das Patent fallen. Beispielsweise kann die vorliegende Erfindung auf eine Ausleger-Schaufel-Zylinderanordnung angewendet werden, wie sie aus der US-PS 4,408,518 hervorgeht, indem die Verbindungen zu den Magnetspulen 91 und 93 derart ausgetauscht werden, daß der Ausleger- und der Schaufelzylinder gemeinsam aus- und einfahren. Ferner kann der Schaufellagensensor an einem besser geschützten Ort, beispielsweise zwischen dem Schaufelzylindergehäuse und einem Verbindungsglied 11 angeordnet sein. Dies setzt voraus, daß der elektronische Steuerkreis so modifiziert ist, daß er die Ausleger-Schaufel-Beziehung aus der Beziehung zwischen dem Zylinder 20 und dem Verbindungsglied 11 ableitet.Even if the invention has only been described here with the aid of an exemplary embodiment, it is understood that many alternatives, modifications and variations are obvious to the person skilled in the art which make use of the inventive idea and are covered by the patent. For example, the present invention can be applied to a boom-and-vane cylinder assembly as disclosed in U.S. Patent No. 4,408,518 by exchanging connections to solenoids 91 and 93 such that the boom and bucket-cylinder extend and retract together . Furthermore, the blade position sensor can be arranged in a better protected location, for example between the blade cylinder housing and a connecting member 11. This assumes that the electronic control circuit is modified to derive the boom-bucket relationship from the relationship between the cylinder 20 and the link 11.

Claims (12)

1. Hydraulic control device for level adjustment of a bucket (12) pivotally arranged on a pivoting jib (14), wherein at least one hydraulic driving element (18, 20) is provided in each case for pivoting the jib (14) and tilting the bucket (12), with a pump (40), a reservoir (42), a control valve (44) for controlling the fluid coupling between the pump (40), the reservoir (42) and the driving element (18) of the jib (14), and with a bucket level regulating valve (90) which has a valve inlet port connectable to the driving element (18) of the jib (14) as well as load ports connectable to the driving element (20) of the bucket (12), and which so controls a fluid connection between the valve inlet port and the load ports that a desired attitude of the bucket (12) is maintained when the jib (14) is pivoted, characterized in that, the control valve (44) being by-passed, the valve inlet port is connected to the pump (40) and a reservoir port of the bucket level regulating valve (90) is connected to the reservoir (42), and in that fluid feed means (70) are provided, through which the valve inlet port can automatically be selectively connected to the driving element (18) of the jib (14), to the pump (40) or to both the driving element (18) of the jib and the pump (40).
2. Control device according to claim 1, characterized in that the driving elements include at least one jib cylinder (18) and at least one bucket cylinder (20).
3. Control device according to claim 1 or 2, characterized in that the bucket valve means are designed for selective fluid supply both during extension and retraction of the driving element (18) of the jib (14).
4. Control device according to any of claims 1 to 3, characterized in that pressure-sensitive valve means (102) are provided which increase the coupling between pump (40) and driving element (20) of the bucket (12) in dependence on the load pressure acting on the driving element (20) of the bucket (12).
5. Control device according to any of claims 2 to 4, characterized in that the driving element (18) of the jib (14) is in communication through a return line (62, 66) with the control valve (44), in that a branch line (78) in communication a valve inlet port of a bucket level regulating valve (90) is in communication with the return line (62, 66) via valve means (70), in that a first pressure-sensitive valve (64) is arranged in the return line (62, 66) between the control valve (44) and the valve means (70), in that a second pressure-sensitive valve (102) is arranged in a supply line (100), which connects the pump (40) directly to the valve inlet port of the bucket level regulating valve (90), and in that load pressure sensor means are provided, through which the pressure present on the valve inlet port of the bucket level regulating valve (90) is so applied to the first and second pressure-sensitive valves (64, 102) that the first pressure-sensitive valve (64) closes and the second pressure-sensitive valve (102) opens in dependence on an increase in the pressure sensed by the load pressure sensor means.
6. Control device according to claim 5, characterized in that the return line (66) is connected to a rod end of the driving element (18) driving the jib (14), in that a third pressure-sensitive valve (54) is arranged in a line (52, 56) connecting the control valve (44) to a head end of the driving element (18) driving the jib (14), and in that the third pressure-sensitive valve (54) closes in dependence on an increase in the pressure sensed by the load pressure sensor means.
7. Control device according to claim 5 or 6, characterized by a first pressure-sensitive valve (64) with two ports which are connected to separate section of the return line (62, 66), a movable valve part for controlling the through-flow opening between the two ports, a spring element (126) which biases the valve part into its closed position, at least one first release device (140, 142), which is subjected to the pressure in the return line (62, 66) and which urges the valve part into its open position, and a second release device (120) which is subjected to the pressure of the load pressure sensor means and urges the valve part into its closed position with increasing pressure.
8. Control device according to any of claims 5 to 7, characterized by a second pressure-sensitive valve (102) with two ports, which are connected to separate sections of the supply line (100, 104), a movable valve part for controlling the through-flow opening between the two ports, a spring element (128) which biases the valve part into its open position, a first actuating device (130), which is subjected to the pressure in the return line (66) and which urges the valve part agains the spring bias into its closed position, and a second actuating device (122) which is subjected to the pressure of the load pressure sensor means and acts against the first actuating device (130) with increasing pressure.
9. Control device according to claim 8, characterized in that the first actuating device of the second pressure-sensitive valve (102) is subjected to the pressure which reigns in the return line (66) between the driving element (18) driving the jib (14) and the first pressure-sensitive valve (64).
10. Control device according to any of claims 2 to 9, characterized in that a selector valve (70) is provided as the fluid feed means, whose housing comprises a first inlet port (74) which is connected to the rod end of the driving element (18) driving the jib (14), a second inlet port (72) which is connected to the head end of the driving element (18) driving the jib (14), and an outlet port (76) which is connected to a branch line (78) connected to the valve inlet port of the bucket level regulating valve (90), the selector valve (70) including a selector valve part (80) movable in the housing and through which the inlet port with the lower pressure is connectable to the outlet port (76) and the other inlet port can be blocket off from the outlet port (76).
11. Control device according to claim 10, characterized in that the selector valve (70) includes a pressure-sensitive part (82) which is in engagement with the selector valve part (80) and is so subject to the pressure in the return line (62) that, with increasing pressure, the selector valve (70) assumes a position in which the first inlet port (74) is closed and the second inlet port (72) is connected to the outlet port (76).
12. Control device according to claim 11, characterized in that the selector valve part (80) includes a first pressure-responsive surface which is subjected to the pressure in the return line (66) in the section between the driving element (18) and the first pressure-sensitive valve (64), and a second pressure-responsive surface which is subjected to the pressure of the supply line (56), and in that the pressure-sensitive part (82) has a third pressure-responsive surface which is subjected to the pressure of the return line (62) in the section between the control valve (44) and the first pressure-sensitive valve (64), the third surface being larger than the first surface.
EP89109918A 1988-06-06 1989-06-01 Self-levelling device for shovel loaders Expired - Lifetime EP0345640B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/202,286 US4923362A (en) 1988-06-06 1988-06-06 Bucket leveling system with dual fluid supply
US202286 1988-06-06

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EP0345640A1 EP0345640A1 (en) 1989-12-13
EP0345640B1 true EP0345640B1 (en) 1992-04-29

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EP (1) EP0345640B1 (en)
AU (1) AU608712B2 (en)
CA (1) CA1308073C (en)
DE (1) DE58901263D1 (en)
HU (1) HU205323B (en)
NO (1) NO169503C (en)
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Also Published As

Publication number Publication date
NO892217D0 (en) 1989-06-01
AU3601189A (en) 1989-12-07
ZA894274B (en) 1991-02-27
US4923362A (en) 1990-05-08
NO169503C (en) 1992-07-01
CA1308073C (en) 1992-09-29
HU205323B (en) 1992-04-28
HUT51569A (en) 1990-05-28
EP0345640A1 (en) 1989-12-13
DE58901263D1 (en) 1992-06-04
NO169503B (en) 1992-03-23
AU608712B2 (en) 1991-04-11
NO892217L (en) 1989-12-07

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