EP0063025A1 - Hydraulischer Steuerkreis für einen Hydraulikzylinder - Google Patents

Hydraulischer Steuerkreis für einen Hydraulikzylinder Download PDF

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Publication number
EP0063025A1
EP0063025A1 EP82301825A EP82301825A EP0063025A1 EP 0063025 A1 EP0063025 A1 EP 0063025A1 EP 82301825 A EP82301825 A EP 82301825A EP 82301825 A EP82301825 A EP 82301825A EP 0063025 A1 EP0063025 A1 EP 0063025A1
Authority
EP
European Patent Office
Prior art keywords
hydraulic
ram
valve
lowering
relief valve
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP82301825A
Other languages
English (en)
French (fr)
Inventor
Phillip Applewhite
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.)
Ruston-Bucyrus Ltd
Original Assignee
Ruston-Bucyrus Ltd
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 Ruston-Bucyrus Ltd filed Critical Ruston-Bucyrus Ltd
Publication of EP0063025A1 publication Critical patent/EP0063025A1/de
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/01—Locking-valves or other detent i.e. load-holding devices
    • F15B13/015—Locking-valves or other detent i.e. load-holding devices using an enclosed pilot flow 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
    • F15B2211/305—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
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40576—Assemblies of multiple valves
    • F15B2211/40584—Assemblies of multiple valves the flow control means arranged in parallel with a check 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
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41527—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a 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
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50518—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means 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
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5153—Pressure control characterised by the connections of the pressure control means in the circuit being connected to an output member and a 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
    • F15B2211/50—Pressure control
    • F15B2211/52—Pressure control characterised by the type of actuation
    • F15B2211/528—Pressure control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/56—Control of an upstream pressure
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/575—Pilot pressure control
    • 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
    • F15B2211/635—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements
    • F15B2211/6355—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements having valve means
    • 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
    • F15B2211/75—Control of speed of the output member
    • 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
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/86—Control during or prevention of abnormal conditions
    • F15B2211/863—Control during or prevention of abnormal conditions the abnormal condition being a hydraulic or pneumatic failure
    • F15B2211/8636—Circuit failure, e.g. valve or hose failure
    • 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
    • F15B2211/80—Other types of control related to particular problems or conditions
    • F15B2211/875—Control measures for coping with failures
    • F15B2211/8752—Emergency operation mode, e.g. fail-safe operation mode

Definitions

  • This invention relates to a hydraulic control circuit for a hydraulic ram (cylinder + piston) controlling raising and lowering of a mechanical member, more particularly but not exclusively for ram cylinder control of the boom of a hydraulic excavator.
  • the over-centre valve is a pilot operated relief valve and is mounted on a ram cylinder.
  • the pilot pressure used to control the valve is obtained from the feed line to the lowering side of the boom cylinders.
  • An object of the present invention is to overcome or substantially reduce the abovementioned disadvantage.
  • the present invention consists in an hydraulic control circuit for a hydraulic ram controlling raising and lowering of a mechanical member, comprising a source of hydraulic pressure, a selector valve for selectively connecting the hydraulic source to opposite sides of the ram whereby actuation of the selector valve operates the ram to raise or lower the mechanical member, a load control valve disposed adjacent to the ram and connected between the raising side of the ram and the selector valve, said load control valve comprising non-return valve means via which hydraulic pressure is applied to the raising side of the ram and hydraulically operated relief valve means for controlling the outlet of hydraulic fluid from said raising side when applying hydraulic fluid pressure to the lowering side and means responsive to a predetermined hydraulic fluid pressure or flow applied to the lowering side for supplying hydraulic fluid pressure to operate the relief valve means at a sufficient pressure to retain the relief valve means open as the lowering speed increases above that determined by the supply of hydraulic fluid pressure to the lowering side.
  • the boom In hydraulic circuits constructed in accordance with the invention for boom ram control, the boom is either locked and prevented from falling after a hose burst or continues the selected movement in a controllable manner depending upon which hose bursts, the maximum speed of lowering of the boom under normal conditions is controlled at a speed faster than would be determined by the flow of oil into the lowering side of the ram cylinder, and boom-drift, i.e. lowering of the boom due to any leakage in the system, is prevented by the load control valve.
  • the circuit shown in Figure 1 is used to control two hydraulic excavator boom rams 1 each comprising a respective cylinder 2 and piston 3. Although two rams 1 have been shown, one larger ram may alternatively be used.
  • the circuit incorporates, for each ram 1, a load control valve 4 with a respective separate ram cylinder relief valve 5 and associated hydraulic lines and connections which are the same in each case. Thus, for simplicity, one ram only will be referred to as if there is only one ram and its associated load control valve 4, relief valve 5 and connecting lines in the hydraulic circuit.
  • the load control valve 4 has good metering characteristics i.e. progressive opening in response to pilot operating pressure, and comprises a non-return valve 6 and a pilot operated relief valve 7.
  • valve pilot pressure used to control the opening of the load control valve 4 i.e. the relief valve 7 is obtained from a boom lowering feed line 8 connected to the lowering side 9 of the ram cylinder 2,via a pilot line 10.
  • a sequence valve 11 is located in the lowering feed line 8 between where the point/valve pilot pressure is taken off through line 10 and the lowering side 9 of the ram cylinder.
  • a main hydraulic pump 12 with reservoir 13 is connected to a selector valve 14 having a directional flow control function which controls the main pump flow through the circuit and which, itself, is controlled remotely via control lines 15 by a servo hand controller 16 with its own pump 17.
  • selector valve 14 When the selector valve 14 is operated to raise the boom, fluid flows along a feed line 18 to the raising side 19 of the ram cylinder via the non-return valve 6 with minimal restriction on flow. Return flow from the cylinder lowering side 9 will also pass with minimal restriction through a non-return valve 20 connected to feed line 8 in parallel with the sequence valve 11.
  • the load control valve 4 and the sequence valve 11 have little effect on the raising of the boom. Should a hose break occur in the feed line 18 to the cylinder raising side 19, the non-return valve 6 ensures that the boom cannot suddenly fall.
  • sequence valve 11 in parallel with the orifice 21 is to limit the maximum level of pressure at the upstream side of the orifice 21 as a protection for the pipe work and load control valve 4. Since the non-return valve 20 is also in parallel there is unimpeded return flow from the cylinder 2 when boom raise is selected.
  • the separate ram cylinder mounted relief valve 5 ensures that transient pressures within the ram cylinder 2 are limited in magnitude, thus giving protection to the structure.
  • the load control valve 4 could provide this feature when used with a selector valve having an open centre spool, (the selector valve 14, has a closed centre spool necessitating the inclusion of the relief valve 5 for operational reasons).
  • Fig. 2 this differs from Fig. 1 in that the sequence valve 11, non-return valve 20 and orifice 21 are replaced by a hydraulic intensifier lla.
  • advantage is taken of the pressure signal from the servo-hand controller 16 for remotely activating the selector valve 14 to cause lowering of the excavator boom by feeding this pressure signal from the appropriate line 15 into the input 24 of the hydraulic intensifier lla.
  • the output signal from the hydraulic intensifier is fed at its output 25 to the pilot line 10 for the relief valve 7 of the load control valve 4.
  • sufficient pilot pressure is obtained to give an acceptable boom lowering speed whilst using a low- pressure energy source.
  • the pilot line 10 from the intensifier lla to the body of the load control valve 4 would normally be a closed line in which entrained air would not be flushed out. This could critically effect the operation of the relief valve 7 since, if sufficient in quantity, the amount of compression required would exceed the available displacement of the intensifier output piston 26.
  • the circuit includes an automatic bleed system operative when boom lowering is not selected, to flush the pilot line 10 from the load control valve body and through the intensifier lla.
  • This bleed system includes a non-return valve 27 and line 28 connected into the pilot port of the relief valve 7 and a non-return valve 29 in the intensifier lla which is unseated when the intensifier is inoperative, such that flow will be induced in the pilot line 10 from the relief valve to the intensifier, thus purging the lines and cavities within the relief valve pilot section and the intensifier.
  • FIG. 3 the circuit of Figure 3 differs from that of Figure 1 in that the sequence valve 11, valve 20 and orifice 21 are omitted and a venting valve 30 is incorporated in a pilot line 31 connected to a port 32 in the relief valve 7 and to the servo-hand controller 16 and one of the lines 15.
  • the load-control valve 4 consists of the relief valve 7 and non-return valve 6 which are independent of each other but which are contained within a common valve body 33.
  • the relief valve 7 has a hollow-cylindrical valve plunger 34 which is slidingly and sealingly mounted within the valve body 33, the annular seals 35 dividing the valve body into four chambers 36, 37, 38 and 39 which are connected respectively through ports 40, 41, 42 and 32 to the raising side 19 of the ram cylinder 2, the raising feed line 18 to the selector valve 14, the pilot line 10 connected to the lowering feed line 8, and the pilot line 31 to the vent valve 30.
  • the left-hand end of the valve plunger 34 is normally biased into a position in which it engages a valve seat 43 on the valve body 33 by means of a compression spring 44 in the valve chamber 39 and acting between the opposite end of the valve body and valve plunger.
  • balancingholes 47 are provided through the plunger 34 to feed this pressure into the spring chamber 39 and thus balance the effects of back pressure on the plunger.
  • the balancing holes 47 must be carefully selected to ensure that the venting valve 30 may be quite small. This valve 30 is set to ensure that only when the servo signal to the selector valve 14 has reached a certain level, predetermined by tests, will the valve 30 open to vent the spring chamber 39 and thus fully open the relief valve 7.
  • the non-return valve 6 comprises a valve plunger 47a which is urged into engagement at one of its ends with a mating seat 48 on the valve body 33 by a spring 49 disposed in a chamber 50. Passages 51, and 52 in the valve body communicate with the port 40 to the raising side of the ram cylinder 2, with the spring chamber 50 and an annular chamber 53 adjacent the valve seat 48 respectively.
  • pump flow through port 41 is connected to raising feed line 18 and the interior of valve plunger 34 causes the valve plunger 47a to be moved to the left as illustrated in Fig. 4 disengaging the latter from its seat and opening the valve 6 against the spring pressure so that flow passes through valve chamber 48 and passage 52 to port 40. Any hose burst in the feed raising line 18 will result in the valve plunger 47a immediately re-engaging the seat 48 and thus closing the non-return valve 6.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
EP82301825A 1981-04-06 1982-04-06 Hydraulischer Steuerkreis für einen Hydraulikzylinder Withdrawn EP0063025A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8110699 1981-04-06
GB8110699 1981-04-06

Publications (1)

Publication Number Publication Date
EP0063025A1 true EP0063025A1 (de) 1982-10-20

Family

ID=10520960

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82301825A Withdrawn EP0063025A1 (de) 1981-04-06 1982-04-06 Hydraulischer Steuerkreis für einen Hydraulikzylinder

Country Status (1)

Country Link
EP (1) EP0063025A1 (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2541735A1 (fr) * 1983-02-25 1984-08-31 Same Spa Circuit hydraulique d'alimentation d'actionneur
US5191826A (en) * 1990-07-05 1993-03-09 Heilmeier & Weinlein Fabrik Fur Oel-Hydraulik Hydraulic control device
US6422804B1 (en) * 2000-02-18 2002-07-23 Deere & Company Inertia load dampening hydraulic system
DE102008053061A1 (de) * 2008-10-24 2010-04-29 Hydac System Gmbh Hydromechanische Abstützeinrichtung
EP2739128B1 (de) 2011-08-05 2016-07-20 Precision Planting LLC Vorrichtungen, systeme und verfahren zur schardrucksteuerung von reiheneinheiten
CN112483500A (zh) * 2020-12-11 2021-03-12 河北新铁虎石油机械有限公司 一种带压作业机升降油缸液压控制系统

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB929481A (en) * 1961-04-03 1963-06-26 New York Air Brake Co Hydraulic mechanism
DE1550452A1 (de) * 1966-06-15 1969-08-21 Martin Presch Gesteuertes Hydraulik-Rueckschlagventil
DE1600970A1 (de) * 1967-02-25 1970-06-18 Berlin Spezialfahrzeugwerk Rohrbruch- und Halteventil mit Ruecklaufdrossel
DE2424973A1 (de) * 1974-05-22 1975-12-04 Montan Hydraulik Gmbh & Co Kg Einrichtung zum steuern von hydroantrieben
US3943825A (en) * 1972-04-17 1976-03-16 Caterpillar Tractor Co. Hydraulic control system for load supporting hydraulic motors

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB929481A (en) * 1961-04-03 1963-06-26 New York Air Brake Co Hydraulic mechanism
DE1550452A1 (de) * 1966-06-15 1969-08-21 Martin Presch Gesteuertes Hydraulik-Rueckschlagventil
DE1600970A1 (de) * 1967-02-25 1970-06-18 Berlin Spezialfahrzeugwerk Rohrbruch- und Halteventil mit Ruecklaufdrossel
US3943825A (en) * 1972-04-17 1976-03-16 Caterpillar Tractor Co. Hydraulic control system for load supporting hydraulic motors
DE2424973A1 (de) * 1974-05-22 1975-12-04 Montan Hydraulik Gmbh & Co Kg Einrichtung zum steuern von hydroantrieben

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2541735A1 (fr) * 1983-02-25 1984-08-31 Same Spa Circuit hydraulique d'alimentation d'actionneur
US5191826A (en) * 1990-07-05 1993-03-09 Heilmeier & Weinlein Fabrik Fur Oel-Hydraulik Hydraulic control device
US6422804B1 (en) * 2000-02-18 2002-07-23 Deere & Company Inertia load dampening hydraulic system
DE102008053061A1 (de) * 2008-10-24 2010-04-29 Hydac System Gmbh Hydromechanische Abstützeinrichtung
EP2739128B1 (de) 2011-08-05 2016-07-20 Precision Planting LLC Vorrichtungen, systeme und verfahren zur schardrucksteuerung von reiheneinheiten
US9955623B2 (en) 2011-08-05 2018-05-01 Precision Planting Llc Apparatus, systems and methods for row unit downforce control
US10238023B2 (en) 2011-08-05 2019-03-26 Precision Planting Llc Apparatus, systems and methods for row unit downforce control
EP3106012B1 (de) 2011-08-05 2019-12-11 Precision Planting LLC Pflanzmaschine mit eine vielzahl an reiheneinheiten, systeme und verfahren zur abtriebssteuerung von reiheneinheiten
US10834863B2 (en) 2011-08-05 2020-11-17 Precision Planting Llc Apparatus, systems and methods for row unit downforce control
EP3106012B2 (de) † 2011-08-05 2023-10-11 Precision Planting LLC Landwirtschaftliche pflanzmaschine mit einer vielzahl an reiheneinheiten und mit einem system zur schardrucksteuerung der reiheneinheiten
CN112483500A (zh) * 2020-12-11 2021-03-12 河北新铁虎石油机械有限公司 一种带压作业机升降油缸液压控制系统

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Inventor name: APPLEWHITE, PHILLIP