US3771422A - Automatic pressure relief and snubbing in hydraulic actuators - Google Patents

Automatic pressure relief and snubbing in hydraulic actuators Download PDF

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Publication number
US3771422A
US3771422A US00188756A US3771422DA US3771422A US 3771422 A US3771422 A US 3771422A US 00188756 A US00188756 A US 00188756A US 3771422D A US3771422D A US 3771422DA US 3771422 A US3771422 A US 3771422A
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pressure
subchambers
line
valve
piston
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US00188756A
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G Kamman
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Houdaille Industries Inc
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Houdaille Industries Inc
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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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/08—Characterised by the construction of the motor unit
    • F15B15/12—Characterised by the construction of the motor unit of the oscillating-vane or curved-cylinder type
    • 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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/22—Other details, e.g. assembly with regulating devices for accelerating or decelerating the stroke
    • F15B15/224—Other details, e.g. assembly with regulating devices for accelerating or decelerating the stroke having a piston which closes off fluid outlets in the cylinder bore by its own movement

Definitions

  • ABSTRACT Rapid start-up acceleration is automatically attained by pressure relief provided for the discharge chamber through a dump valve referenced to the drive chamber of the actuator. Deceleration is accomplished by snubbing hydraulic fluid discharge and by diverting pressure directly from the hydralic feed line. Negative pressure relief or anti-cavitation is provided for in the hydraulic system of the actuator. A novel, efficient snubber valve is carried by the actuator piston to control hydraulic fluid passing through the discharge port of the actuator.
  • Another object of the invention is to attain new and improved start-up acceleration in the operation of hydraulic actuators and more particularly heavy-duty actuators.
  • a further object of the invention is to provide new and improved deceleration method and means in the operation of hydraulic actuators.
  • Still another object of the invention is to provide new and'improved anti-cavitation control for hydraulic actuators.
  • Yet another object of the invention is to provide new and improved snubber valve control means in hydraulic scription of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:
  • FIG. 1 is a schematic illustration of a representative hydraulic actuator and hydraulic operating and control system
  • FIG. 2 is a fragmentary sectional plan view of the actuator and snubber control valve structure
  • FIG. 3 is a fragmentary sectional detail view taken substantially along the line IlIIII of FIG. 2;
  • FIG. 4 is a side elevational view of one of the snubber valve members.
  • a rotary hydraulic actuator 10 comprises an annular housing 11 having opposite end walls 12 (only one being shown) coaxially journalling a wingshaft 13 within an annular working chamber 14 defined within the housing 11. Suitable means (not shown) are provided, as is customary, for securing the housing 11 and the shaft 13 to respective parts of equipment which must be relatively moved by operation of the actuator.
  • Such operation is effected by means of hydraulic fluid such as suitable oil under pressure introduced into the working chamber 14 to cause hydraulic pressure reaction between an abutment 15 carried by the chamber and a piston vane 17 carried by the shaft 13.
  • the abutment 15 is fixedly mounted in the housing and in sliding engagement with the perimeter of the shaft 13 and provides a liquid bar rier across the chamber 14.
  • the piston vane 17 divides the chamber in cooperation with the abutment 15 into respective subchambers, with the result that when hydraulic fluid is introduced under pressure into one subchamber while the opposite subchamber is permitted to drain or discharge, expansion of the pressurized chamber causes relative rotation of the shaft 13 and the housing 11 by driving force of the pressure against the piston vane 17.
  • Hydraulic pressure fluid for driving the actuator 10 is supplied through a hydraulic circuit by a pump 18 controlled and powered in a suitable manner and operative to draw hydraulic fluid through a duct 19 from a tank or sump 20 and force the fluid under pressure into a supply duct 21 under a constant head of pressure of, for example, about 2,000 psi., depending upon service requirements.
  • the supply duct 21 may be blocked by a control valve 22 which may be of the reciprocable manually operated or controlled type having a central non-demand or neutral zone. As thus blocked the hydraulic fluid may by-pass from the duct 21 through a normally closed pressure release valve 23 to return by way of a duct 24 to the intake duct 19 or the sump 20.
  • the control valve 22 When it is desired to operate the-actuator 10 by driving the vane shaft 13 in either the clockwise or counterclockwise direction relative to the housing 11 as shown in FIG. 1, the control valve 22 is shifted to a effect communication between the pressure side of the pump 18 and the actuator subchamber which is to be pressurized and between the low pressure or suction side of the pump and the discharge or low pressure subchamber of the actuator.
  • a symmetrical reversible hydraulic control system is provided wherein each of the working subchambers of the actuator is connectable alternatively with either side of the pump 18 through a similar respective duct 25 communicating with its subchamber through a port 27 in the selected end wall 12 of the actuator housing, such port being located in an instance near but suitably spaced from the abutment 15.
  • the lefthand working subchamber of the actuator as shown in FIG. 1 is pressurized by connecting its duct 25 with the pressure delivery duct 21 while the other communication duct 25 is placed in communication with the low pressure duct 24 communicating with the intake side of the pump 18.
  • the valve 22 is moved towards'the left as shown in FIG. 1, the reverse communication relationship is effected, namely, the right hand working subchamber is pressurized and becomes the drive chamber and the lefthand subchamber becomes the discharge chamber.
  • each such duct is provided with a flow restriction 28 near the valve 22.
  • pressure flows through each of the ducts 25 to its port 27 is controlled by a flow limiting restriction 29 located near the subchamber port.
  • drive chamber pressure Upon adjusting the valve 22 for pressurizing either selected working subchamber of the actuator 10, drive chamber pressure will promptly reach substantially pump pressure, i.e., 2,000 psi., and the actuator wingshaft 13 will begin to turn by reason of the pressure exerted on the piston vane 17.
  • substantially pump pressure i.e., 2,000 psi.
  • back pressure will tend to resist rapid acceleration. Therefore pressure is automatically relieved from the discharge line between the restrictions 28 and 29.
  • means comprising a port 30 adjacent to the abutment and by which pressure is referenced from the drive chamber through a duct 30a to a drive piston 31 by which a dump valve plunger 32 is shifted in opposition to biasing means in the form of a spring 33 to connect a normally blocked bypass duct 34 connecting the duct 25 between the orifices 28 and 29 with a return duct 35 communicating with the suction line 19 and/or the sump 20.
  • a normally blocked bypass duct 34 connecting the duct 25 between the orifices 28 and 29 with a return duct 35 communicating with the suction line 19 and/or the sump 20.
  • the pressure line restrictions 28 and 29 reduce the drive chamber pressure to a lower value, for example to 1,000 psi., and below the bias value of the dump valve spring 33 which is thus closed to disconnect or block the by-pass duct 34 and restore the discharge line 25 to flow through the restriction 28 thereof to pump or sump.
  • the exhausting hydraulic fluid is thereby maintained at a back pressure which nearly approximates the drive pressure to maintain smooth, constant speed in the driving stroke of the operating cycle.
  • This comprises opening the dump valve 32 connected with the pressure line 25 to by-pass and thus relieve sufficient pressure downstream from the orifice 28 to the return line duct 35 to reduce driving pressure in the drive chamber enough to maintain substantially constant running speed.
  • Operation of the pressure line dump valve 32 is the same as already described for the dump valve 32 of the exhaust line, the excess pressure being referenced by way of the port 30 communicating with the exhaust chamber through the associated duct 30a to the drive piston 31 of the dump valve 32 in opposition to its spring bias 33 to open the by-pass line 34.
  • a respective crossover relief valve 38 for each of the working subchambers of the actuator communicates on the pressure responsive or upstream side with the respective referencing duct 30a and on the downstream or discharge side with the return line 35, desirably by way of a branch duct 39.
  • Each of the valves 38 desirably is normally biased as by means of a spring 40 to remain closed until a predetermined pressure is referenced thereto from the exhaust chamber, for example 1800 psi., which pressure is great enough to effect reasonably prompt deceleration of the actuator but low enough to avoid system over-load and damaging stress.
  • make-up hydraulic fluid is supplied to the shut-off pressure chamber from the low pressure or the return line portion of the hydraulic system.
  • a respective anti-cavitation make-up duct 41 communicates with thereturn line duct 35 through the duct 39 with a respective check valve 42 communicating with the associated working subchamber of the actuator through a respective port 43 adjacent to the abutment 15.
  • the check valves 42 prevent outflow through the ports 43 but permit anti-cavitation inflow as required.
  • Anti-cavitation inflow or replenishment to the respective subchamber is implemented by the constant pressure maintained in the return duct line 35 by the restriction 37.
  • New and improved means are provided for snubbing deceleration of the actuator piston at terminus of each driving stroke which, in the actuator and its hydraulic control circuitry as illustrated, is in each opposite direction of travel of the piston vane 17, since the same pump pressure is utilized in each opposite direction and the hydraulic control circuitry in the system is symmetrical as shown.
  • the piston vane 17 has at each side thereofa respective laterally projecting snubber valve plate 44 operative to close off or throttle discharge through the port 27 of the associated working subchamber progressively in the terminal portion of each driving or working stroke, thereby attaining smooth stress-free deceleration and stopping of the actuator.
  • Such pressure is referenced to and operates the dump valve 32 of thepressure line 25, thereby diverting pump pressure to the return line 35 and relieving pressure in the drive chamber of the actuator.
  • each of the valve plates is constructed to provide a slide face 45 arranged to bear against the face of the actuator housing closure 12 through which the port 27 communicates.
  • the face 45 is on a portion of the valve plate which is elongated to project a substantial distance laterally from the associated side of the piston vane 17 and in the direction of movement of the vane into the respective working subchamber.
  • the orifice groove 47 diminishes in depth at a greater angle to a transition point or line 48 from which the throttling orifice groove diminishes at a shallower angle to the terminal end of the groove, both tapering angles being calculated to be complementary for smooth, progressive throttling coordinated with functioning of the pressure line dump valve 32 by reference to the pressure built up in the exhaust chamber as the throttling progresses.
  • the sliding surface 45 At the trailing end of the throttle orifice groove 47, the sliding surface 45 fully covers the port 27 and thus brings the piston vane to a complete halt. Aiding the throttling action of the throttle valve member 45 is the pressure built up in the exhaust chamber as throttling progresses so that at the terminus of throttling the pressure firmly presses the throttle valve face 45 against the face of the closure 12.
  • the valve member 44 is mounted in a manner to enable a limited range of movement toward and away from the face of the closure 12.
  • the side of the vane 17 from which the throttle valve member 44 projects is provided with a mounting recess 49 for the trailing or butt end of the valve member, such recess opening not only from the side of the vane but also from the edge of the vane which opposes the closure 12 in which the port 27 is located.
  • the mounting recess 49 is complementary to and accommodates an integral mounting lug 50 on the butt end portion of the valve member, with the sides of the mounting lug and the sides defining the recess 49 being in close but slidable relation so that movement of the valve member is permitted longitudinally of the recess but the valve member will be held firmly against any significant movement laterally thereof as it is carried into throttling relation to the port 27.
  • means comprising a connecting pin 51 are pro vided which pin is secured at its opposite ends in the vane 17 and extends through a bearing opening 52 in the lug 50 and which bearing lug is sized to retain the valve member against displacement in its longitudinal direction relative to the vane 17.
  • the bearing hole 52 is elongated on an axis normal to the valve face 45, as best seen in FIGS. 3 and 4.
  • the valve member 44 is normally biased toward and into bearing engagement with the closure member 12.
  • means comprising a biasing spring 53 are provided desirably in the form of a coiled torsion or sear spring engaged about the pin 51 within a clearance slot 54 provided therefor in the lug 50.
  • One leg of the spring 53 thrusts against the valve member 44 and the other leg thrusts against the back wall defining the recess 49.
  • Bias provided by the spring 53 need be only sufficient to positively hold the valve member against the confronting face of the closure 12.
  • Such bias should be of only limited thrust value so as to enable quick release of the valve member 44 in response to hydraulic driving pressure through the port 27 closed by the valve, when it is desired to reverse operation of the actuator.
  • a combination according to claim 1 including a return line to said source, and said means for relieving pressure comprising a bypass from said exhaust line to said return line and a normally closed dump valve in said bypass referenced to and driven open by predetermined pressure in said one subchamber greater than normal running pressure.
  • said return line having a restriction therein which is less than the restriction in said exhaust line located downstream from said bypass, whereby to maintain the return line in a filled hydraulic system and enabling bypass pressure relieving dumping from the exhaust line into the return line upon opening of said dump valve.
  • said pressure line including spaced restrictions therein, and said pressure line pressure relief means communicating with said pressure line between said restrictions.
  • a return line to said source said pressure relief means for the pressure line being connected to said return line and including a dump valve normally closed but responsive to excessive pressure in said other chamber to open a passage from the pressure line to said return line.
  • a hydraulic actuator including a housing defining a working chamber divided into subchambers on opposite sides of piston means relatively movable in said chamber;
  • a pressure line for conducting hydraulic pressure fluid from said source to one of said subchambers to drive said piston means
  • overload pressure relief means communicating directly with said pressure line upstream from said one subchamber and referenced for response to pressure buildup in said other subchamber to bypass pressure from the pressure line to said low pressure means;
  • overload pressure relief means comprising a duct leading from said pressure line to said return line and having a normally closed dump valve therein;
  • startup pressure relief means connected to said exhaust line and discharging into said return line and responsiveto pressure in excess of running pressure developed in said one subchamber during startup;
  • said startup pressure relief means comprising a dump valve in a bypass duct from said exhaust line to said return line and normally closed, with a referencing passage leading from said one subchamber to said startup pressure dump valve.
  • a control valve operative to connect or disconnect the pressure and exhaust lines simultaneously relative to said source, crossover pressure relief means connecting said subchambers with said return line, and anti-cavitation means connecting said return line-with said subchambers.
  • a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator;
  • multi-position control valve means operative for selectively and alternatively effecting pressure or exhaust relation between said lines and said source and said low pressure means;
  • respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance;
  • said return line having a restriction therein downstream from said pressure relief means and providing for less restriction than the respective restrictions in said pressure/exhaust lines which are located nearest to said control valve means.
  • valve means being operative to disconnect said pressure/exhaust lines from said source, crossover pressure relief means connecting said subchambers with said return line, and anti-cavitation means leading from said return line to each of the respective subchambers.
  • a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator;
  • multi-position control valve means operative for selectively and alternatively affecting pressure or exhaust relation between said lines and said source and said low pressure means
  • each of said pressure/exhaust lines communicating with its respective subchamber through a port by which pressure fluid is delivered to either respective subchamber to move the piston means into the other of the subchambers from which hydraulic fluid is discharged through the port communicating therewith;
  • snubber valve means carried by the piston means operative to terminate driving stroke of the piston means by closing the discharge port whereby overload pressure in the associated subchamber referenced to the overload relief means of the pressure fluid delivering line bypasses the pressure therefrom to the return line; said ports being in respective surface defining the respective subchamber, and said snubber valve means comprising a valve member slidably engaging the respective surface and having progressively restricting orifice means operative to progressively throttle and close the associated port in the movement of the piston means toward the port; and
  • said throttle valve members being normally biased into snubbing relation to said respective surfaces and being movable away from said port in response to fluid pressure to enable reversal of the piston drive.
  • a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator;
  • multi-position control valve means operative for selectively and alternatively affecting pressure or exhaust relation between said lines and said source and said low pressure means
  • each of said pressure/exhaust lines communicating with its respective subchamber through a port by which pressure fluid is delivered to either respective subchamber to move the piston means into the other of the subchambers from which hydraulic fluid is discharged through the port communicating therewith; snubber valve means carried by the piston means operative to terminate driving stroke of the piston means by closing the discharge port whereby overload pressure in the associated subchamber referenced to the overload relief means of the pressure fluid delivering line bypasses the pressure therefrom to the return line; said actuator being of the rotary type wherein said piston means comprise a vane carried by an oscillating wing shaft with which an abutment in the working chamber cooperates as a barrier to divide the working chamber with said piston vane into said subchambers and said ports are located in an end
  • said snubber valve means comprising respective elongated plate members mounted on and projecting in respectively opposite directions from said piston vane;
  • valve members operatively to the piston vane and enabling limited movement of the valve members toward and away from said 010 sure surfaces
  • each of said valve members having a face slidably engaging with said surfaces and provided with a respective orifice groove diminishing from a leading end to a trailing end for progressively throttling discharge through the associated port as the respective valve member is moved over the port by advance of the piston vane in a driving stroke.
  • a hydraulic actuator including a housing providing a working chamber, piston means movably operative in said chamber in response to hydraulic pressure fluid differential, means for delivering hydraulic pressure fluid to one side of said piston, and means for exhausting hydraulic fluid from the opposite side of said piston including a surface having an exhaust port therein, the improvement comprising:
  • a snubber valve member carried by the piston means and comprising an elongated plate movable therewith on said surface toward said port and having a face slidably engaging said surface;
  • valve member having progressive throttling orifice means comprising a groove in said face of substantially the same width throughout its length and diminishing in depth from a leading end to a trailing end operative as the valve member moves over the port and the groove advances from said leading end in alignment with the port to effect progressive throttling of exhaust flow through the port;
  • said groove having a first portion diminishing in depth from said leading end at a greater angle than a second portion of the groove which diminishes at a shallower angle to said trailing end, for smooth progressive throttling effect in the advance of the groove over the port.
  • said piston includes a wing shaft having a radial vane rotatably movably operative in said chamber relative to an abutment in said chamber, said means for delivering hydraulic pressure fluid delivering the pressure fluid into the chamber between said abutment and one side of said vane and said exhaust port being located between the opposite side of said vane and said abutment, said vane having a mounting recess therein at the side of the vane which faces toward said port, said valve member comprising an elongated plate having lug mounting structure at one end received in said recess and with the remainder of the valve plate projecting from the vane toward said port, and means connecting said mounting lug to said vane within said recess enabling limited relative movement of the valve plate toward and away from said surface but retaining the valve plate against transfers relative movement.
  • said connecting means comprising a pin mounted in said vane across said recess, said mounting lug having a clearance hole therein elongated in the direction of permissible movement of the valve plate toward and away from said surface, said mounting lug having a slot therein across which the pin extends, and a torsion biasing spring engaged about the pin in said slot and having one end thrusting against the valve plate and an opposite end thrusting against the vane in said recess.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
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  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
US00188756A 1971-10-13 1971-10-13 Automatic pressure relief and snubbing in hydraulic actuators Expired - Lifetime US3771422A (en)

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US18875671A 1971-10-13 1971-10-13

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Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4349075A (en) * 1978-10-19 1982-09-14 Atlas Copco Aktiebolag Hydraulically operated impact motor
US4713936A (en) * 1985-11-18 1987-12-22 Deere & Company Motor seal protector valve
US5950519A (en) * 1996-11-26 1999-09-14 Volvo Construction Equipment Korea Co., Ltd. Hydraulic system with secondary exhaust passage
US6038956A (en) * 1998-04-02 2000-03-21 Lane; Norman Dynamic pressure regulator cushion
US20030158010A1 (en) * 2002-02-20 2003-08-21 Winfried Fideler Oil system
US20110120297A1 (en) * 2009-07-22 2011-05-26 Marcus Bitter Hydraulic Circuit
US20130092482A1 (en) * 2010-04-15 2013-04-18 Messier-Bugatti-Dowty Hydraulically regulated electromagnetic actuator, and landing gear fitted with such an actuator for controlling same
US20140034778A1 (en) * 2012-08-02 2014-02-06 Bell Helicopter Textron Inc. Independent blade control system with rotary blade actuator
US8857757B2 (en) 2012-08-02 2014-10-14 Bell Helicopter Textron Inc. Independent blade control system with hydraulic pitch link
US8973864B2 (en) 2012-08-02 2015-03-10 Bell Helicopter Textron Inc. Independent blade control system with hydraulic cyclic control
US9162760B2 (en) 2012-08-02 2015-10-20 Bell Helicopter Textron Inc. Radial fluid device with multi-harmonic output
US9376205B2 (en) 2012-08-02 2016-06-28 Bell Helicopter Textron Inc. Radial fluid device with variable phase and amplitude
CN105723102A (zh) * 2013-06-19 2016-06-29 伍德沃德有限公司 具有液压供应的旋转活塞式致动器
US9709078B2 (en) 2013-02-27 2017-07-18 Woodward, Inc. Rotary piston type actuator with a central actuation assembly
US9816537B2 (en) 2013-02-27 2017-11-14 Woodward, Inc. Rotary piston type actuator with a central actuation assembly
US10030679B2 (en) 2013-02-27 2018-07-24 Woodward, Inc. Rotary piston type actuator
US11199248B2 (en) 2019-04-30 2021-12-14 Woodward, Inc. Compact linear to rotary actuator
US11333175B2 (en) 2020-04-08 2022-05-17 Woodward, Inc. Rotary piston type actuator with a central actuation assembly

Families Citing this family (3)

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Publication number Priority date Publication date Assignee Title
GB2122689B (en) * 1982-06-24 1985-10-09 Dobson Park Ind Rotation limiting system
JPWO2023210455A1 (enExample) * 2022-04-28 2023-11-02
WO2023210457A1 (ja) * 2022-04-28 2023-11-02 パナソニックＩｐマネジメント株式会社 冷凍装置

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US3323422A (en) * 1965-08-02 1967-06-06 Cessna Aircraft Co Cushion stop for hydraulic cylinders
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US3398650A (en) * 1966-02-04 1968-08-27 Moog Inc Apparatus for regulating fluid flow with respect to a hydraulic load
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US3537356A (en) * 1968-01-02 1970-11-03 Dake Corp Hydraulic control systems

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US3191505A (en) * 1961-11-21 1965-06-29 William L Defibaugh Hydraulic control for a slide unit
US3323422A (en) * 1965-08-02 1967-06-06 Cessna Aircraft Co Cushion stop for hydraulic cylinders
US3398650A (en) * 1966-02-04 1968-08-27 Moog Inc Apparatus for regulating fluid flow with respect to a hydraulic load
US3396635A (en) * 1966-11-30 1968-08-13 Cessna Aircraft Co Cushion stop for hydraulic actuators
US3470792A (en) * 1967-08-02 1969-10-07 Cessna Aircraft Co Maximum pressure control apparatus for hydraulic actuators
US3537356A (en) * 1968-01-02 1970-11-03 Dake Corp Hydraulic control systems

Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4349075A (en) * 1978-10-19 1982-09-14 Atlas Copco Aktiebolag Hydraulically operated impact motor
US4713936A (en) * 1985-11-18 1987-12-22 Deere & Company Motor seal protector valve
US5950519A (en) * 1996-11-26 1999-09-14 Volvo Construction Equipment Korea Co., Ltd. Hydraulic system with secondary exhaust passage
US6038956A (en) * 1998-04-02 2000-03-21 Lane; Norman Dynamic pressure regulator cushion
US20030158010A1 (en) * 2002-02-20 2003-08-21 Winfried Fideler Oil system
US6896636B2 (en) * 2002-02-20 2005-05-24 Zf Friedrichshafen Ag Oil system
US20110120297A1 (en) * 2009-07-22 2011-05-26 Marcus Bitter Hydraulic Circuit
US9056672B2 (en) * 2010-04-15 2015-06-16 Messier-Bugatti-Dowty Hydraulically regulated electromagnetic actuator, and landing gear fitted with such an actuator for controlling same
US20130092482A1 (en) * 2010-04-15 2013-04-18 Messier-Bugatti-Dowty Hydraulically regulated electromagnetic actuator, and landing gear fitted with such an actuator for controlling same
US9061760B2 (en) * 2012-08-02 2015-06-23 Bell Helicopter Textron Inc. Independent blade control system with rotary blade actuator
US8973864B2 (en) 2012-08-02 2015-03-10 Bell Helicopter Textron Inc. Independent blade control system with hydraulic cyclic control
US8857757B2 (en) 2012-08-02 2014-10-14 Bell Helicopter Textron Inc. Independent blade control system with hydraulic pitch link
US20140034778A1 (en) * 2012-08-02 2014-02-06 Bell Helicopter Textron Inc. Independent blade control system with rotary blade actuator
US9162760B2 (en) 2012-08-02 2015-10-20 Bell Helicopter Textron Inc. Radial fluid device with multi-harmonic output
US9376205B2 (en) 2012-08-02 2016-06-28 Bell Helicopter Textron Inc. Radial fluid device with variable phase and amplitude
US9709078B2 (en) 2013-02-27 2017-07-18 Woodward, Inc. Rotary piston type actuator with a central actuation assembly
US9816537B2 (en) 2013-02-27 2017-11-14 Woodward, Inc. Rotary piston type actuator with a central actuation assembly
US10030679B2 (en) 2013-02-27 2018-07-24 Woodward, Inc. Rotary piston type actuator
US10767669B2 (en) 2013-02-27 2020-09-08 Woodward, Inc. Rotary piston type actuator with a central actuation assembly
CN105723102A (zh) * 2013-06-19 2016-06-29 伍德沃德有限公司 具有液压供应的旋转活塞式致动器
CN105723102B (zh) * 2013-06-19 2019-03-08 伍德沃德有限公司 具有液压供应的旋转活塞式致动器
US11199248B2 (en) 2019-04-30 2021-12-14 Woodward, Inc. Compact linear to rotary actuator
US11927249B2 (en) 2019-04-30 2024-03-12 Woodward, Inc. Compact linear to rotary actuator
US12270461B2 (en) 2019-04-30 2025-04-08 Woodward, Inc. Compact linear to rotary actuator
US11333175B2 (en) 2020-04-08 2022-05-17 Woodward, Inc. Rotary piston type actuator with a central actuation assembly

Also Published As

Publication number Publication date
JPS4846771A (enExample) 1973-07-03
CA969070A (en) 1975-06-10
GB1363782A (en) 1974-08-14
JPS5644287B2 (enExample) 1981-10-19
GB1363781A (en) 1974-08-14

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