US3095002A - Dry type hydraulic servo valve - Google Patents

Dry type hydraulic servo valve Download PDF

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Publication number
US3095002A
US3095002A US118373A US11837361A US3095002A US 3095002 A US3095002 A US 3095002A US 118373 A US118373 A US 118373A US 11837361 A US11837361 A US 11837361A US 3095002 A US3095002 A US 3095002A
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United States
Prior art keywords
nozzles
spool
valve
armature
tube
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
US118373A
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English (en)
Inventor
Donald V Healy
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.)
Bendix Corp
Original Assignee
Bendix Corp
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Publication date
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Priority to US118373A priority Critical patent/US3095002A/en
Priority to DEB67721A priority patent/DE1228112B/de
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Publication of US3095002A publication Critical patent/US3095002A/en
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Expired - Lifetime legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K31/00—Actuating devices; Operating means; Releasing devices
    • F16K31/02—Actuating devices; Operating means; Releasing devices electric; magnetic
    • F16K31/06—Actuating devices; Operating means; Releasing devices electric; magnetic using a magnet, e.g. diaphragm valves, cutting off by means of a liquid
    • F16K31/0682—Actuating devices; Operating means; Releasing devices electric; magnetic using a magnet, e.g. diaphragm valves, cutting off by means of a liquid with an articulated or pivot armature
    • 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
    • F15B13/042—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure
    • F15B13/043—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves
    • F15B13/0438—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor operated by fluid pressure with electrically-controlled pilot valves the pilot valves being of the nozzle-flapper type
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/2278—Pressure modulating relays or followers
    • Y10T137/2409—With counter-balancing pressure feedback to the modulating device
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/86493—Multi-way valve unit
    • Y10T137/86574—Supply and exhaust
    • Y10T137/86582—Pilot-actuated
    • Y10T137/86614—Electric

Definitions

  • This invention relates to hydraulic servo valves and, more particularly, to dry" type valves employing a hydraulic housing containing all of the fluid-conducting passages and chambers and an external motive assembly including a coil and armature sealed from the hydraulc housing but operatvely connected to control the flow of fluid through the valve in response to electrical signals applied to the coil.
  • lt is a general object of this invention to provide a selfclearing dry coil type servo valve.
  • Another object is to provide a self-cleariug servo valve in which the self-clearing operation takes place with minimum movement of the armature or disturbance of its normal dynamic equilibrium condition.
  • Another object is to provide a servo valve having improved stability when subject to acceleration force.
  • One further object is to provide a simple, effective, feedback connection from the valve spool to the baffie plate.
  • Still another object is to provide a servo valve including internal feedback from the valve spool and, additionally, provision for external feedback or external overriding controls.
  • the baffle plate is mounted on a central shaft which extends out of the housing through a torque tube. The outermost end of the torque tube and shaft are sealed together and secured to the armature of the driving motor. Operatively associated with the armature .are a pair of coils and a magnetic structure.
  • the nozzles within the fluid housing are connected to a common fluid pressure supply and to a branch circuit to the ends of the Operating sleeve contained in the spool or piston.
  • the shaft carrying the baffle bar extends below the bathe plate in reduced section, the end of which is coupled to the spool of the Operating cylinder to provide mechanical feedback between the spool and the baflie plate and thereby provide a restoring force opposing that of the input signal.
  • the support structure for the armature and baffle plate extend out of the motor space to allow for external feedback or overriding control of the electrical input.
  • One feature of this invention resides in a dry coil servo valve in which a composite structure made up of a torque tube and a rigid shaft mount a dual-arm baffle plate for rotational and translational movement.
  • Another feature resides in mounting the armature and baflle plate oflset from their axis of rotation at a right angle with respect to the direction of travel of the valve spool so that acceleration forces tending to move the spool also afect the baffle plate and armature in a manner which compensates the acceleration forces on the spool.
  • Still another feature involves a second torsion spring for the baffle plate for introducing feedback from the valve spool.
  • One further feature resides in the extension of the baffle support through the motor housing to provide a point for external torque input to the system.
  • FIG. 1 is a Vertical sectional View through the motor of a servo valve incorporating this invention
  • FIG. 2 is a vertical section through the entire servo valve of FIG. 1 taken in the plane at right angles with respect to the plane of the section of FIG. I;
  • FIG. 3 is a horizontal section through the nozzle 'block portion of the valve or" FlG. l;
  • FIG. 4 is an isometric projection of the valve of FIG. l;
  • FIG. 5 is a longitudinal section -to the valve sleeve and spool along lines 5-5 of FIG. 1;
  • FIG. 6 is a fragmentary sectional View of another embodiment of the invention.
  • the servo valve incorporating .this invention consists basically of a hydraulic housing 10 closed by a nozzle ⁇ block 11 to which is secured the motor assembly 12, the last within a cap 13.
  • Motor assembly 12 comprises a pair of bar magnets 14 and 15 mounted :to introduce flux into 'a pair of ferromagnetic frame mern- :bers 16, one of which is shown in the drawing.
  • the rame members 16 include arms 20 ter-minatin-g in faces '21 and 22 opposite the ends of an armature 23 mounted for rotation on 'a supporting arm 24, as best seen in FIG. 2.
  • the armature 23 passes through central openings 27 in a pair of coils 25 and 26. Coils '25 and 26 are held in place within the encl-osure made by the frame member 16 by a pair of spring clips 30, one of which appears in FIG. 1.
  • the armature 23 is lightly held midway -between the :opposing faces 21 and 22 of the magnetic frame members 16, for movement from the mid position under the control of changes in flux in the magnetic system resulting from passage of current through the coils 25 and 26, as well as from the reaction -or feedback forces from the hydraulic spool as hereinafter described.
  • FIGS. 2 and 3 The interaction between the motor assembly 12 and the hydraulic assembly within housing 10 -is more clearly seen in FIGS. 2 and 3.
  • the arm 24 supporting armature 23 in .the opening 27 of coil 25 is carried itself by an upstandng tubular support, hereinafter designated the torque tube 31, including enlarged collar portion 32 sealed in an opening 33 in the nozzle block 11 of the hydraulic assembly.
  • the upper or free end of torque tube *31 is closed by a central shaft member 34 sealed therein as 'by brazing.
  • the seal between the shaft 34 and tube 31 must be adequate to resist at least the drain or return hydraulic pressure and prevent the ingress of hydraulic fluid from the housing 10 into the motor space of the valve.
  • the tube 31 is preferably of a spring material, such as beryllium Copper, having a thin wall in the order of 0.006" to allow the rotational movement of the armature 23 about the aXis of the tube 31 by twisting of the tube 31.
  • the ⁇ rotation of armature '23 is transmitted through shaft 34 into the housing 10.
  • the shaft 34- carries a bafile plate 40, best seen in FIG. 3, including a pair of end bathe portions 41 and 42 directly opposite the orifices in nozzles 43 and 44 respectively.
  • a nominal spacing between the bafile portion of plate 40 and the respective nozzles is in the order of 0.001", and movement from the nominal position varies under maximum signal conditions from 0 .to 0.001" in either direction.
  • the lower end of shaft 34 includes a reduced diameter portion 50 constituting a torsion spring extending into and secured at its lower end to a rigi d hollow shaft 51 tor transmitting torque from a feedback arm 53 to the baflle plate 40.
  • the shaft 51 is journaled in a hearing 52 secured to the nozzle block 11 and has at its upper or tree end an arm 53 secured thereto and extendin g to one side and terminating in a depending finger 54 which rests in annular slot 55 in the spool or pisten 56 of the valve.
  • the .arm 53, hollow shaft 5-1 and torsion spring 50 provide a mechanical feedback between the spool 56 and the baffle plate 40.
  • the hydraulic Components of the valve in addition to the spool 56 include: a filter 60 at the main inlet port 61, a main return or drain port 62, and several communicating passages in the housing 10 and illustrated in schematic form in FIG. 4.
  • the motor elements are all outside of the housing 10 and are sealed therefrorn by the torque tube 31.
  • the eleotrical input to the motor is through a pair of leads 65 which enter a side opening in the housing 10 and pass through a fiange portion 70 of the housing 10, through the nozzle block 11 and into the motor cavity without entering the hydraulic housing proper.
  • the operation of the servo valve is best understood from the simplified isometric showing of FIG. 4.
  • the purpose of the valve is to apply a controlled flow in and out of 'two cylinder ports 70 and 71, which flow is a linear function of the magnitude of the current passing through a pair ot terminals 74.
  • the :output ports 70 and 71 are normally connected to opposite ends of a doubleacting piston 72 within an actuator cylinder 73. Movement of the piston '73 is accomplished upon longitudnal movement of the valve spool 56 from the intermediate ne-utral position toward one end whereby one of the cylinder ports 70 or 71 is connected to the pressure source, and the other cylinder port is connected to the drain port 62.
  • controlled movement of the valve spool 56 is accomplished by applying hydraulic pressure to a pair of pressure ports 90 and 91 from a fluid source by means of a pump 81 and a main pressure line'82.
  • the fluid is introduced through line 82 into an inlet chamber 83 containing a filter 84.
  • the main hydraulic fluid path bypasses the filter 84 flowing through .the enlarged central section of chamber 83 and a pair 'of passages '85 and 86 to the annular pressure ports 90 and 91 of the valve sleeve or cylinder 92.
  • the pressure ports 90 and 91 are closed :by respective lands 93 and 94 When the spool 56 is in its position.
  • the ends of the filter chamber 83 are sealed from the inlet port 82 by the filter 84 'so that hydraulic fluid reaching the end portions passes through the filter 8-4, and contaminants, in particular, particles of suflicient size -to plug restrictors 95 and '96 or interfere with :the operation of the difierential nozzle mechanism hereinafter described, are retained.
  • the ends of filter chamber 83 communicate through the flow restrictors 95 and 96 and passages 100 and 101 with the pair of nozzles 43- and 44 respectively positioned in substantially parallel relationship and each including an outlet orifice 45 or 46 directed toward opposite ends of the ⁇ baflle plate 40.
  • the passage 100 includes a branch passage 106 communicating with one end of the valve sleeve 92.
  • a branch passage 110 from the passage 10 1 communicates with the opposite end of sleeve 92.
  • the bafile plate 40 is precisely located at equal distances from the orifices 45 and 46. Since both orifices are fed by a common supply pressure, and the pressure drops in the restrictors 95 and 96 are equal, the pressure applied to branch lines 106 and 110 is the same, and opposite ends of the valve spool 56 The spool 56 therefore :remains in its centered position. Fluid emerging from the orifices 45 and 46 strik-ing the bathe plate 40 falls into the chamber 63, shown in FIG. 2, down to the drain port 62 and returns to the fiuid supply 80.
  • the bafe plate 40 also rotates in a clockwise direction, moving the battle 42 in close proximity to orifice 46 while the baffie 41 moves away from orifice 45.
  • the pressure in the line 101 increases because of the bathe restriction at the orifice 46, while the pressure in line 100 falls off because of the opening up of orifice 45.
  • the pressure changes in the lines 100 and 101 are communicated through lines 106 and 110 to the ends of the cylinder 92, causing movement of the spool 6 toward the lower right in FIG. 4. This condition is ⁇ illustr ated as well in FIG. 5.
  • An equil-ibrium condition in the moving elements of the valve is thereby established.
  • the pressure port 90 is uncovered as land 93 moves off the inner edge of port 90.
  • the pressure port 90 then communicates with the cylinder port 71 while the cylinder port '70 is connected to the drain port 62.
  • the pressure differential on the opposite ends of the piston 72 results in its movement to the left.
  • the velocity of the -piston 72 depends upon the rate of flow, which is determined by the extent of movement of the spool 56 from its neutral position.
  • Spool 56 moves responsive to pressure differentials on its ends produced by displacement of the 'bafe plate 40 from center position.
  • the position of bafile plate 40 in turn is determined by the summation of armature and feedback torques.
  • Armature torque is a function of command signals applied to terminals 74.
  • Acceleraton Force Stab'l'y Inproved stability under acceleration conditions is achieved employing this invention. It is apparent that when the valve structure ⁇ as shown in FIG. 4 is subjected to acceleration forces, those forces will act upon the spool 56 as well as the valve body and may tend to move the spool 56 with respect to its cylinder or sleeve. Any force Components acting transverse to the axis ot the sleeve 92 are inefiective to change the position of the spool 56. However, forces acting along the -line of the sleeve or valve cylinder 92 axis will tend to move the spool, resulting in unwanted and uncontrolled movement of the operating piston "12.
  • both the armature 23 and the baflle bar 40 are mounted eccentrically on the shaft 34. Both have centers of gravity, marked C. G. in FIG. 4, displaced from the axis of rotation. Displacement is toward the spool 56.
  • the servo valve of FIGS. l through 5 is designed for a single electrical input through the terminal 74 and has internal feedback from the valve spool. In certain applications, it is desirable to have provision for external feedback, for example, from the operated piston 72 itself or from related apparatus. Additionally, it is sometimes desirable to have provision for -an overriding manual control for the valve in case of malfunction of the valve or other parts of the system. In the past, complicated mechanisrns have been required to provide either of these additional inputs to servo valves. However, employing the embodiment of FIG. 6, which is a modification of the same basic structure of FIGS.
  • the sumrn-ation of one or more inputs from manual, mech-anical, hydraulic or electrical sources is possible. This is achieved by the presence of an upper extension of the shaft 34 passing out through a hearing and Secured ⁇ to an input torque arm 131.
  • the upper extension of shaft 34 includes a reduced section 134 constituting -a torsion spring.
  • the torque arm 131 may be quite short, because only -a small torque input to the upper end of sh-aft 34 is necessary in order to produce significant movement of the armature 23 and the hafe plate 40, unshown inthe drawing.
  • 'Dhe arm 131 may be connected ⁇ as a manual override control or as an ⁇ a-dditional torque input to the valve.
  • a lower torsion spring portion 151 of shaft 34 extends through a hearing 152 out of the housing 10.
  • a torque -arm 153 may be suit- -ably attached to the extension to provide ⁇ an additional torque input to the system.
  • the lower input through the spring section 151 is particularly adapted tor the introduction of feedback from the Operating cylinder or other parts of the hy draulic system, since it extends out of the hydraulic side of the valve. Where torque over 153 is 7 connected to the controlled mechanisms to provide feedback, the feedback path 'from spool 56 may be unnecessary or undesirable and may be eliminated.
  • a servo valve comprising:
  • a flow-control system within said housin-g including -a pair of substantially parallel directed nozzles and an elongated baffle having spaced portions positioned to vary the flow of fluid from respective nozzles;
  • said sealing means comprising a nonrigid tube with one end sealed to said hydraulic housing 'and a shaft sealing the free end of said tube and extending through said tube;
  • said shaft coupled to a point midway between the spaced portions to transmit torque from said motor means to said bafi'ie to vary the relative spacing of said -baffle spaced portions with respect to said nozzles simultaneously in opposite sense;
  • said tube and shaft supporting said baflle for simultaneous translation movement in the same sense toward ⁇ and away from said nozzles in response to fluid pressure ohanges thereat.
  • a servo valve comprising:
  • baffles positioned for restricting the flow of hydraulic fluid from said nozzles
  • a motor including -an armature 'for controlling the flow of fluid through said valve;
  • said positioning means comprising a torque tube mounting said armature and baflle' for rotatonal motion under the influence of said coil by twisting of said torque tube;
  • An electrohydraulic servo valve comprising:
  • a coil external to s-aid housing including terminals for applying an electrical signal thereto to energize said coil
  • a torque tube sealing said housing from said coil and :mounting said armature for rotational motion upon the enengizing of said coil;
  • bafl le being resiliently mounted by said torque tube to move bodily toward or away from said nozzlcs responsive to fluid pressure changes thereat;
  • torsion spring means coupled ⁇ between said shaft and said spool constituting a mechanical feedback connection between said spool and said baflle.
  • An electrohydraulic servo valve employing mecbanical feedback comprising:
  • an elongated baffle including portions for restricting the flow from said nozzles and to vary the pressure of hydraulic fluid at said nozzles;

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Servomotors (AREA)
  • Multiple-Way Valves (AREA)
US118373A 1961-06-20 1961-06-20 Dry type hydraulic servo valve Expired - Lifetime US3095002A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US118373A US3095002A (en) 1961-06-20 1961-06-20 Dry type hydraulic servo valve
DEB67721A DE1228112B (de) 1961-06-20 1962-06-19 Elektrohydraulischer Steuerschieber

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US118373A US3095002A (en) 1961-06-20 1961-06-20 Dry type hydraulic servo valve

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3262463A (en) * 1962-09-04 1966-07-26 Itt Pneumatic transmitter with improved control mechanism
US3490339A (en) * 1967-05-01 1970-01-20 Bell Aerospace Corp Torsional mechanical input signal apparatus
US3524473A (en) * 1968-01-11 1970-08-18 Moog Inc Flow control valve having constant outlet orifice area
DE1576118B1 (de) * 1964-04-06 1970-09-24 Kawasaki Heavy Ind Ltd Hydraulischer Drehservomechanismus
US3756262A (en) * 1971-04-09 1973-09-04 Sperry Rand Corp Power transmission
US3771541A (en) * 1971-04-30 1973-11-13 Bendix Corp High gain electrohydraulic servo valve
US3814131A (en) * 1972-11-07 1974-06-04 Tokyo Precision Instr Co Ltd Servo valve
US20130087223A1 (en) * 2011-10-10 2013-04-11 In-Lhc Method of detecting failure of a servo-valve, and a servo-valve applying the method
US20130180606A1 (en) * 2011-05-05 2013-07-18 Hangzhou Xzb Tech Co., Ltd. Floating action type servo-valve
US20130221253A1 (en) * 2012-02-14 2013-08-29 Liebherr-Aerospace Lindenberg Gmbh Servo valve
US20200025219A1 (en) * 2018-07-20 2020-01-23 Hamilton Sundstrand Corporation Servo valve

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2947627C2 (de) * 1979-11-27 1984-05-24 Shoketsu Kinzoku Kogyo K.K., Tokyo Druck- und explosionssichere Stellvorrichtung

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2823689A (en) * 1954-06-18 1958-02-18 Donald V Healy Electro-hydraulic servo valve
US2835265A (en) * 1955-11-16 1958-05-20 Bendix Aviat Corp Transfer valve
US2933106A (en) * 1957-04-01 1960-04-19 Weston Hydraulics Ltd Electro-hydraulic valve
US2942581A (en) * 1958-03-12 1960-06-28 Fisher Governor Co Hydraulic operator
US3054416A (en) * 1960-03-02 1962-09-18 Rech Etudes Prod Primary stage of two-stage hydraulic distributor

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2934765A (en) * 1953-09-21 1960-04-26 Ex Cell O Corp Flow control servo valve
US2771062A (en) * 1954-09-09 1956-11-20 Sanders Associates Inc Two-stage differential servo valve
US2827067A (en) * 1956-03-08 1958-03-18 Bendix Aviat Corp Damped electrohydraulic servo valve
US2964018A (en) * 1957-12-27 1960-12-13 Bendix Corp Electro-hydraulic servo valve
FR1266116A (fr) * 1959-08-31 1961-07-07 Borg Warner Servo-distributeur électro-hydraulique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2823689A (en) * 1954-06-18 1958-02-18 Donald V Healy Electro-hydraulic servo valve
US2835265A (en) * 1955-11-16 1958-05-20 Bendix Aviat Corp Transfer valve
US2933106A (en) * 1957-04-01 1960-04-19 Weston Hydraulics Ltd Electro-hydraulic valve
US2942581A (en) * 1958-03-12 1960-06-28 Fisher Governor Co Hydraulic operator
US3054416A (en) * 1960-03-02 1962-09-18 Rech Etudes Prod Primary stage of two-stage hydraulic distributor

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3262463A (en) * 1962-09-04 1966-07-26 Itt Pneumatic transmitter with improved control mechanism
DE1576118B1 (de) * 1964-04-06 1970-09-24 Kawasaki Heavy Ind Ltd Hydraulischer Drehservomechanismus
US3490339A (en) * 1967-05-01 1970-01-20 Bell Aerospace Corp Torsional mechanical input signal apparatus
US3524473A (en) * 1968-01-11 1970-08-18 Moog Inc Flow control valve having constant outlet orifice area
US3756262A (en) * 1971-04-09 1973-09-04 Sperry Rand Corp Power transmission
US3771541A (en) * 1971-04-30 1973-11-13 Bendix Corp High gain electrohydraulic servo valve
US3814131A (en) * 1972-11-07 1974-06-04 Tokyo Precision Instr Co Ltd Servo valve
US20130180606A1 (en) * 2011-05-05 2013-07-18 Hangzhou Xzb Tech Co., Ltd. Floating action type servo-valve
US9115729B2 (en) * 2011-05-05 2015-08-25 Hangzhou Xzb Tech Co., Ltd Floating action type servo-valve
US20130087223A1 (en) * 2011-10-10 2013-04-11 In-Lhc Method of detecting failure of a servo-valve, and a servo-valve applying the method
US9897116B2 (en) * 2011-10-10 2018-02-20 In-Lhc Method of detecting failure of a servo-valve, and a servo-valve applying the method
US20130221253A1 (en) * 2012-02-14 2013-08-29 Liebherr-Aerospace Lindenberg Gmbh Servo valve
US9702478B2 (en) * 2012-02-14 2017-07-11 Liebherr-Aerospace Lindenberg Gmbh Servo valve
US20200025219A1 (en) * 2018-07-20 2020-01-23 Hamilton Sundstrand Corporation Servo valve

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Publication number Publication date
DE1228112B (de) 1966-11-03

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