US3831495A - Remotely controlled electrohydraulic system with fail-safe features - Google Patents

Remotely controlled electrohydraulic system with fail-safe features Download PDF

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Publication number
US3831495A
US3831495A US00387201A US38720173A US3831495A US 3831495 A US3831495 A US 3831495A US 00387201 A US00387201 A US 00387201A US 38720173 A US38720173 A US 38720173A US 3831495 A US3831495 A US 3831495A
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Prior art keywords
electrohydraulic
conductor
source
control
cable
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Expired - Lifetime
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US00387201A
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English (en)
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W Arnold
J Locher
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • 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
    • F15B20/008—Valve 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
    • F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
    • F15B21/08—Servomotor systems incorporating electrically operated control 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
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/0401—Valve members; Fluid interconnections therefor
    • F15B2013/0409—Position sensing or feedback of the valve 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • 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
    • F15B2211/321—Directional control characterised by the type of actuation mechanically
    • F15B2211/324—Directional control characterised by the type of actuation mechanically manually, e.g. by using a lever or pedal
    • 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
    • F15B2211/329—Directional 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
    • F15B2211/80—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
    • F15B2211/8755—Emergency shut-down

Definitions

  • ABSTRACT The system includes a hydraulic user device and a source of hydraulic fluid.
  • a hydraulic arrangement tioned in such path and mounted for movement between a plurality of positions in different ones of which the control member differently affects the flow of fluid from the source to the user device, including a neutral position in which the control member blocks the flow of fluid from the source to the user device.
  • An electrohydraulic moving arrangement is operative when electrically energized for moving the controlmember by applying hydraulic force thereto.
  • a restoring arrangement is bperaii'varar'a fiiyfii'g'ta the control member a restoring force tending to move the control member to said neutral position when the electrohydraulic moving arrangement is electrically unenergized.
  • An electrical control arrangement controls the electrohydraulic moving arrangement and includes a source of electrical power having two terminals, connectors connecting the source of electrical power to the electrohydraulic moving arrangement for furnishing electrical energy to the latter, a remote control arrangement and an electrical control cable having a first cable end connected to the electrohydraulic moving unit and a second cable end connected to the remote control arrangement, the control cable comprising a first conductor having at the first cable end a first end connected to one terminal of the source of electrical power and having a second end at the second cable end, a second.
  • a fail-safe unit prevents electrical energization of the electrohydraulic moving arrangement when a short-circuit develops between the first and second conductors, to prevent the application by the electrohydraulic moving arrangement of hydraulic force to the control member and to thereby cause the control member to be returned to the neutral position by the restoring means.
  • the present invention relates to an electrohydraulic control system having a-distributing piston moved by a differential-piston pilot arrangement provided with a biasing arrangement for biasing the differential-piston of the pilot arrangement to a predeterminedneutral position, with the flow of fluid into and out of the pilot arrangement being controlled by at least two electromagnetically actuated two-port two-position valves controlled remotely from a remote control arrangement provided .with at least two controlswitches and connected to the electrohydraulic pilot arrangement by means of a control cable.
  • electrohydraulic arrangements which must be controlled by the operator at the actual location of the arrangement.
  • electrohydraulic arrangements which can be controlled'at distance, by means of a control cable.
  • uncontrolled operation may cause injury to nearby personnel or cause damage to mechanical components, goods being processed, and the like.
  • a remotely controlled electrohydraulic system in combination, a hydraulic user device; a source of hydraulic fluid; a hydraulic arrange ment connecting said source of fluid to said user device and providing a path for the flow of fluid from said source to said user device, and including a control member positioned in said path and mounted for move: ment between a plurality of positions in different ones of which said control member differently affects the flow of fluid from said source to said user device, and
  • electrohydraulic moving means operative when electricallyenergized for moving said control member by applying hydraulic force thereto; restoring means operative for applying to said control member a restoring force tending to move said member to said neutral position when said electrohydraulic moving means is electrically unenergized; electrical control means for controlling said electrohydraulic moving means, including a source of electrical power having two terminals, connecting means connecting said source of electrical power to said electrohydraulic moving means for furnishing electrical energy to the latter, a remote control arrangement and an electrical control cable having a first cable end connected to said electrohydraulic moving means and a second cable end connected to said remote control arrangement, said control cable comprising first conductor means having at said first cable end a first end connected to one terminal of said source of electrical power and having a second end at said second cable end, second conductor means extending along the length of said cable and having a first end at said first cable end and a second end at said second cable end; and fail-
  • FIG. 1 illustrates a first embodiment of the present invention
  • FIG. 2 illustrates a second embodiment of the invention.
  • FIG. 1 illustrates a first embodiment of the system according to the invention.
  • Reference numeral 1 designates in general an electrohydraulic control arrangement.
  • the arrangement includes a four-port threeposition valve, generally designated with numeral 10.
  • the valve 10 has a valve housing 12 provided with an inlet 13, an outlet flow conduit 14, and two output conduits l5, 16 for connection to a hydraulic user device.
  • the valve housing 12 furthermore defines an internal bore 17 in which a three-land distributor piston 18 is seal-tightly mounted for sliding movement.
  • a pump 24 pumps pressure medium from a fluid reservoir 25 into the valve inlet 13.
  • Two conduits 27, 28 connect respective ones of the two output conduits 15, 16 to respective inlets of a double-acting cylinder-andpiston arrangement 29, 30.
  • the valve 10 is provided with means 31 for manually adjusting the axial position of the three-land distributor piston 18.
  • the valve housing 12 0f valve 10 has a right side wall 32 against which is positioned the left-side wall of the housing 33 of a pilot valve arrangement 11.
  • the housing 33 is provided with an internal cylindrical chamber 34 in which is mounted for sliding movement a differential piston 35.
  • the piston 35 divides the chamber 34 into a first chamber portion 36 located adjacent that axial end face of piston 35 having the smaller effective cross-sectional area, and into a second chamber portion 37 adjacent the axial end face of piston 35 having the larger effective cross-sectional area.
  • a coupling 38 rigidly connects the differential piston 35 with the three-land distributor piston 18, so that the two can move together as a unit.
  • Compression springs 39 and 40 are provided inthe'.
  • chamber portions 36 and 37 serve to bias the differential piston 35 and thereby piston 18 to their illustrated neutral positions.
  • the piston lands block off communication between the inflow chamber 19 and the two user-device outflow chambers 20, 21, and block off communication between the inflow chamber 19 and the two retum-flow outlet chambers 22 and 23.
  • Left-hand chamber 36 communicates via conduits 42, 43 and 50 with the fluid supply inlet 13 of valve 10. Also, left-hand chamber 36 communicates via conduit 42, two-port two-position valves 44 and 47, conduit 48, and conduit 49 with retum-flow outlet 14 of valve 10, which in turn communicates with the fluid reservoir 25 via an outlet conduit 26.
  • the right-hand chamber 37 communicates with fluid inlet 13 of valve 10, via conduit 46, two-port two-position valve 44, conduit 43, and conduit 50. Also, right-hand chamber 37 communicates with the fluid reservoir 25 via two-port twoposition valve 47, conduit 48, conduit 39, outflow conduit l4, and conduit 26.
  • Two-port two-position valves 44 and 47 are electromagnetically actuated two-position valves provided with biasing springs normally biasing them to their respective illustrated positions, in which they permit flow of fluid in the illustrated direction. When their respective electromagnets are energized, they are moved to their non-illustrated positions, in which they completely block the passage of fluid.
  • the electromagnetic valves 44 and 47 are controlled over electrical control conductors 55, via a control switch 56, a voltage supply line 57 and a power supply line 58.
  • the voltage supply line 57 and the two control lines 55 run along the interior of a control cable 2, which connects the electrohydraulic control arrangement 55 with a remote control arrangement 3.
  • the remote control arrangement includes a two-pole switch 56 comprised of two ganged switching members so constructed that when one of them is in the make position the other is in the break position, and vice versa.
  • the powersupply line 58 connected directly to the non-illustrated power source, is connectable to and disconnectable from the voltage supply line 57 by means of two threshold switches 59, 60 here having the form of electromagnetic relays. Diodes 61 and 62 are respectively connected in parallel with the solenoids of relays 59 and 60.
  • One end of the winding of the first relay 59 is connected to the power supply line 58, while the other end of this winding is connected to the collector of an npn transistor 63 having an emitter connected to ground.
  • the base of transistor 63 is connected to ground via a resistor 67, and is connected to a fail-safe switch 69 via a resistor 64, a Zener diode 65, and a fail-safe line 66.
  • the transistor 63 and the resistors 64, 67 together form a semiconductor switch, generally designated by numeral 68.
  • the fail-safe line 66 travels along the length of the control cable 2 to the remote-control arrangement 3 and is there connected to the power supply line 58 via a fail-safe switch 69 and a resistor 70 connected in parallel with switch 69. It will be noted that the power supply cable 58 also travels from the power supply to the remote control arrangement 3, via the length of the control cable 2.
  • the fail-safe conductor 66 may advantageously be an uninsulated, i.e., naked, conductor.
  • the magnetic winding of the second relay 60 is connected between groundand the fail-safe line 66.
  • the distributor piston 18 blocks the flow of fluid from valve inflow chamber 19 into the two inlets of the cylinder-and-piston arrangement 29, 30.
  • the first valve 44 and the second valve 47 establish communication between their respective cylinder chamber portions 36, 37 on the one hand and the outflow conduit 14, on the other hand. Accordingly, there is no substantial build-up of fluid pressure on the two opposite faces of differential piston 35, and the biasing springs 39 and 40 can maintain the differential piston 35 in its illustrated neutral position.
  • valve 47 When double-throw switch 56 is in its illustrated position, the solenoid of the second two-position valve 47 becomes energized, and this valve blocks fluid flow; the first two-position valve 44, however, remains open. Pressure fluid from inflow conduit 13 of valve 10 enter cylinder chamber 36, via conduits 50, 43 and 42, and also enters cylinder chamber 37, via conduits 50 and 43, via valve 44, and via conduits 45 and 46. With ap proximately equal pressures developed in the two cylinder chambers 36, 37, the differential piston 35 moves quickly to its leftmost position, i.e., towards valve 10.
  • the differential piston 35 will move to its rightmost position, i.e., away from valve 10, because pressure fluid will be entering chamber 36 from fluid inlet 13, while pressure fluid can only leave chamber 37 via conduit 46, valve 47, and conduits 48, 49, 14 and 26, to be returned to the fluid reservoir 25.
  • transistor 63 does not conduct, and relay 59 is de-energized, so that its associated switch assumes the illustrated closed position.
  • the switch of energized relay 60 is closed, and the switch of unenergized relay 59 is closed, and accordingly the power supply line 58 is electrically connected to the voltage supply line 57.
  • FIG. 2 depicts a second exemplary embodiment of the invention.
  • the structure shown in FIG. 2 again includes a four-port three-position valve and a pilot valve arrangement 11, as shown in FIG. 1.
  • the differential piston 35 of the pilot valve arrangement is provided with a position transducer 100, 101 which generates an electrical signal indicative of the axial displacement of the piston 35.
  • the two electromagnetically actuated valves 44, 47 in this embodiment, are'connected to the output of power amplifiers 102, the inputs of which are connected to the two outputs of an electronic control stage 103.
  • the electronic control circuitry for the control of valves 44, 47 furthermoreincludes, in this embodiment, a stage 1 04 which generates an analog signal indicative of the se lected axial position for the piston 35.
  • stages 101, 104 and 103 together form a conventional servo positioning system.
  • Transducer 101 may include, for example, a potentiometer connected across a voltage source and having a wiper connected to the linkage rod 100, so that movement of the linkage rod will vary the voltage appearing at the potentiometer tap in a corresponding manner.
  • stage 101 generates for example a volt age indicative of the actual position of the piston 35
  • stage 104 generates a voltage indicative of the desired position for the piston 35.
  • Stage 103 can be a difference amplifier for forming the difference of the two voltages supplied by stage 101 and 104.
  • Such difference amplifier can have its output connected to a first half-wave rectifier having an output connected to one of the two amplifiers 102, and the difference amplifier can have its output further connected to a second half-wave rectifier, of different polarity than the first, having its respective output connected to the other of the two amplifiers 102. Accordingly, if the difference in the voltages at the outputs of stages 101 and 104 is of a first polarity and of sufficient magnitude, then one of valves 44, 47 will become energized. On the other hand, if the just-mentioned voltage difference is of opposite second polarity and of sufficient magnitude, then the-other of valves 44, 47 will become energized.
  • the fail-safe arrangement in the embodiment of FIG. 2 corresponds in many respects to the fail-safe arrangement in the embodiment of FIG. 1.
  • the collector of transistor 63 is connected to the power supply line 58 by way of a resistor 105, instead of via the relay 59 in FIG. 1. Also, the collector of transistor 63 in FIG. 2 is connected, via two diodes 106, with the outputs of valve-control amplifiers 102. Also in this embodiment, there are two voltagesupply lines 57, which are connected not directly to the electrical inputs of valves 44, 47, but rather are connected to the valve-control amplifiers 102 and furnish the biasing voltages for such amplifiers 102.
  • the remote control arrangement 3 is provided with a potentiometer 107.
  • a potentiometer 107 By varying the position of the potentiometer wiper, it is possible to select the desired axial position for the differential piston 35.
  • the two ends and the wiper of potentiometer 107 are connected, via three lines 55, to three corresponding inputs of stage 104, which may for example contain a voltage source across which the end terminals of potentiometer 107 may be connected, with the output of stage 104 being directly connected, for example, to the center input of stage 104.
  • the operation of the arrangement shown in FIG. 2 is evident from the foregoing description.
  • the wiper of potentiometer 107 is adjusted, to select the desired position for piston 35.
  • the control arrangement 103 compares the actual and desired values of the position of piston 105, and energizes one of valves 44, 47, to cause the piston 35 to move to the position selected therefor, in conventional servo fashion.
  • a remotelycontrolled electrohydraulic system in combination, a hydraulic user device; a source of hydraulic fluid; a hydraulic arrangement connecting said source offluid to said user device and providing a path for the flow of fluid from said source to said user device, and including a control member positioned in said path and mounted for movement between a plurality of positions in different ones of which said control member differently affects the flow of fluid from said source to said user device, and including a neutral position in which said control member blocks the flow of fluid from said source to said user device; electrohydraulic moving means operative when electrically energized for moving said control member by applying hydraulic force thereto; restoring means operative for applying to said control member a restoring force tending to move said member to said neutral position when said electrohydraulic moving means is electrically unenergized; electrical control means for controlling said electrohydraulic moving means, including a source of electrical power having two terminals, connecting means connecting said source of electrical power to said electrohydraulic moving means for furnishing electrical energy to the latter, a remote control arrangement and an electrical control
  • said failsafe means comprises voltage-responsive means connected to said first end of said second conductor means and operative for detecting the development of a shortcircuit between said first and second conductor means by detectingthe resulting change in voltage atsaid first end of said second conductor means.
  • said voltage-responsive means comprises a Zener diode circuit including a Zener diode connected to said first end of said second conductor means in such a manner as to break down and become conductive in responsive to a rise of the voltage at said first end of said second conductor means resulting from the development of a short-circuit between said first and second conductor means, and disconnecting means connected to said Zener diode in such a manner as to interrupt the connection between said source of electrical energy and said electrohydraulic means in response to break down of said Zener diode.
  • said failsafe means comprises impedance means connecting together said second ends of said first and second conductor means, so that a predetermined lower voltage will exist at said first end of said second conductor means when said first and second conductor means are not short-circuited to each other, and so that a predetermined higher voltage will exist at said first end of said second conductor means when said first and second conductor means are short-circuited to each other, and wherein the voltage applied to the cathode of said Zener diode when said first and second conductor means are not short-circuited to each other is such as to render said Zener diode conductive, and wherein the voltage applied to the cathode of said Zener diode when said first and second conductor means are shortcircuited to each other is insufficient to render said Zener diode conductive.
  • said failsafe means further includes a fail-safe switch operative for short-circuiting said first and second conductor means to each other, to cause said control member to assume said neutral position.
  • said electrohydraulic moving means comprises a differential cylinder-and-piston unit having inlets and outlets for the flow of hydraulic fluid and a plurality of electrically energized valves for controlling the flow of fluid through such inlets and outlets
  • said connecting means comprises a plurality of valve-control conductors in said cable, one valve-control conductor for each of said electrically energized valves, with each valve-control conductor extending between a respective one of said electrically energized valves and said remote control arrangement
  • said control means includes an additional voltage supply conductor having a first end connected to said one terminal of said source of electrical energy and having a second end at said second cable end
  • said remote control arrangement comprises switch means for connecting said voltage supply conductor to a selected one of said valve-control conductors, to energize a selected one of said electrically energized valves, with any shortcircuiting between said second conductor means and said voltage supply conductor resulting in breakdown of said Zener diode
  • said failsafe means comprises means for preventing electrical energization of said electrohydraulic moving means when a short-circuit develops between said first and second conductor means by shunting energizing current away from said electrohydraulic moving means.
  • said failsafe means further includes means for preventing electrical energization of said electrohydraulic moving means in response to an interruption in the continuity of one of said first and second conductor means.
  • said electrohydraulic moving means comprises electrohydraulic servo positioning means for varying the position of said control member, said servo positioning means comprising electronic circuitry requiring a biasing voltage for operation, and wherein said connecting means comprises means connected to said source of electrical energy for applying a biasing voltage to such electronic circuitry, and wherein said fail-safe means comprises,

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Servomotors (AREA)
  • Magnetically Actuated Valves (AREA)
US00387201A 1972-08-18 1973-08-09 Remotely controlled electrohydraulic system with fail-safe features Expired - Lifetime US3831495A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2240607A DE2240607C3 (de) 1972-08-18 1972-08-18 Elektrohydraulisch« Steuereinrichtung

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US3831495A true US3831495A (en) 1974-08-27

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US (1) US3831495A (sv)
JP (1) JPS4951475A (sv)
AT (1) AT323075B (sv)
CH (1) CH551686A (sv)
DE (1) DE2240607C3 (sv)
FR (1) FR2196441B1 (sv)
GB (1) GB1427835A (sv)
IT (1) IT993003B (sv)
NL (1) NL7311379A (sv)
SE (1) SE399306B (sv)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5119717A (en) * 1989-09-11 1992-06-09 Zexel Corporation Method of controlling solenoid valves for a hydraulic actuator, with a time delay between closing a normally open valve and opening a normally closed valve
WO2001071200A1 (en) * 2000-03-21 2001-09-27 Robert Gardner Improvements to electrical instrument circuits
US20070183901A1 (en) * 2006-02-07 2007-08-09 Chester Mark V Safety override circuit for pneumatic positioner and method of use thereof
WO2017079792A1 (en) * 2015-11-09 2017-05-18 Elite Attachments Australia Pty Ltd A piston and cylinder system

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JPS5167887A (ja) * 1974-12-11 1976-06-11 Shin Meiwa Ind Co Ltd Enkakusosasochi
JPS52160791U (sv) * 1976-05-31 1977-12-06
JPS54111126A (en) * 1978-02-20 1979-08-31 Toa Medical Electronics Fluid control valve
JPS57146901A (en) * 1981-03-04 1982-09-10 Toshiba Mach Co Ltd Pilot operating control valve
DE3110220A1 (de) * 1981-03-17 1982-10-07 Gewerkschaft Eisenhütte Westfalia, 4670 Lünen Hydraulische, insbesondere elektro-hydraulische ausbausteuerung fuer untertaegige gewinnungsbetriebe
GB2200001A (en) * 1987-01-12 1988-07-20 Duraplug Elect Ltd Electric cable assembly with safety device

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US3390387A (en) * 1963-02-21 1968-06-25 Philips Corp Fail-safe monitor alarm circuit
US3407340A (en) * 1966-06-14 1968-10-22 Westinghouse Air Brake Co Fail-safe time delay relay
US3602772A (en) * 1968-12-04 1971-08-31 Wolf Geraete Gmbh Protective circuit for electrically driven lawn mowers and the like
US3613509A (en) * 1968-11-06 1971-10-19 Bosch Gmbh Robert Electrohydraulic remote control arrangement for hydraulic directional valves

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3390387A (en) * 1963-02-21 1968-06-25 Philips Corp Fail-safe monitor alarm circuit
US3407340A (en) * 1966-06-14 1968-10-22 Westinghouse Air Brake Co Fail-safe time delay relay
US3613509A (en) * 1968-11-06 1971-10-19 Bosch Gmbh Robert Electrohydraulic remote control arrangement for hydraulic directional valves
US3602772A (en) * 1968-12-04 1971-08-31 Wolf Geraete Gmbh Protective circuit for electrically driven lawn mowers and the like

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5119717A (en) * 1989-09-11 1992-06-09 Zexel Corporation Method of controlling solenoid valves for a hydraulic actuator, with a time delay between closing a normally open valve and opening a normally closed valve
WO2001071200A1 (en) * 2000-03-21 2001-09-27 Robert Gardner Improvements to electrical instrument circuits
US20030039088A1 (en) * 2000-03-21 2003-02-27 Robert Gardner Electrical instruments circuits
US6930613B2 (en) 2000-03-21 2005-08-16 Robert Gardner Electrical instruments circuits
US20070183901A1 (en) * 2006-02-07 2007-08-09 Chester Mark V Safety override circuit for pneumatic positioner and method of use thereof
WO2007092476A3 (en) * 2006-02-07 2007-12-21 Dresser Inc Safety override circuit for pneumatic positioner and method of use thereof
US7661439B2 (en) 2006-02-07 2010-02-16 Dresser, Inc. Safety override circuit for pneumatic positioner and method of use thereof
US8196595B2 (en) 2006-02-07 2012-06-12 Dresser, Inc. Safety override circuit for pneumatic positioner and method of use thereof
WO2017079792A1 (en) * 2015-11-09 2017-05-18 Elite Attachments Australia Pty Ltd A piston and cylinder system

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Publication number Publication date
NL7311379A (sv) 1974-02-20
CH551686A (de) 1974-07-15
AT323075B (de) 1975-06-25
DE2240607A1 (de) 1974-02-28
GB1427835A (en) 1976-03-10
IT993003B (it) 1975-09-30
DE2240607C3 (de) 1979-04-12
FR2196441A1 (sv) 1974-03-15
FR2196441B1 (sv) 1976-12-03
JPS4951475A (sv) 1974-05-18
SE399306B (sv) 1978-02-06
DE2240607B2 (de) 1978-08-17

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