Abstract: Airborne wind turbine systems with multiple aerial vehicles connected via multiple tethers to a single ground station are disclosed. A node is coupled to the tethers. The node includes a drive system. At a proximate end of the node, each of the tethers is adjacent to neighboring tethers. And at a distal end of the node, each of the tethers is separated from the neighboring tethers. The airborne wind turbine system includes a control system configured to operate the drive system to translate the node along the tethers.

Abstract: A method for mitigating noise during high wind speed conditions of a wind turbine includes providing a backward twist to the outboard region of the rotor blade having an angle of less than 6°. The method may also include reducing a tip chord taper within at least a portion of the outboard region of the rotor blade. Further, the method may include increasing a local tip chord length of the rotor blade. In addition, the method may include increasing a torsional stiffness of the outboard region of the rotor blade. As such, a combination of one or more of the blade properties described above are configured to reduce noise associated with high wind speed conditions.

Abstract: Wind turbine, including a tower, a nacelle which is rotatable connected to the tower, a yaw motor for rotating the nacelle relatively to the tower, a yaw brake which is configured to fix the nacelle relatively to the tower and which is configured to be brought from an open position into a brake position and vice versa, wherein the yaw brake is pre-tensioned into the brake position, a switch which is electrically connected to the yaw motor and the yaw brake and which is configured to be brought from an open state into a closed state and vice versa, wherein, when the switch is brought from the closed state into the open state a power supply to the yaw brake and the yaw motor is interrupted and the yaw brake goes into the brake position by releasing at least partially the pre-tension.

Abstract: The present disclosure discloses a control system for enhancing a frequency support capability of a wind turbine generator system. The control system includes a wind turbine, a gearbox, an electric generator and a converter. The control system is characterized by further including a supercapacitor energy storage apparatus, which includes a DC-DC converter and a supercapacitor. The converter includes DC buses, and the supercapacitor is electrically connected to the DC buses via the DC-DC converter. The supercapacitor may be orderly charged or discharged according to an operating state of the wind turbine generator system to maintain its operating condition, and has a superior reliability.

Abstract: The present invention relates to control of a wind turbine, and in particular it relates to a distributed control system including a blade controller for each blade of the wind turbine. The electrical connection between each blade controller and the power supply of the blade controller is arranged to be functionally isolated from the electrical connection of each other blade controller and the power supply of the respective blade controllers.

Abstract: A system for controlling a wind turbine generator includes a rotor blade assembly having rotor blades and a pitch actuator to control a pitch of the rotor blades, a gear box coupled to the rotor blade assembly, a power generator coupled to the gear box, and a main controller. The main controller is configured to control the aerodynamic torque applied on the rotor blades based on pitch control commands, and separately configured to control a generator speed of the power generator based on torque control commands. The system further includes a pitch controller configured to receive pitch calculation information from the main controller, calculate the pitch control commands, and return the pitch control commands to the main controller. The system further includes a torque controller configured to receive torque calculation information from the main controller, calculate the torque control commands, and return torque control commands to the main controller.

Abstract: A system and method for preventing voltage collapse of a wind turbine power system includes receiving a power input value and a voltage input value from a point of common coupling of the wind turbine power system. The method also includes determining a limit cycle reference point of the wind turbine power system as a function of the input values. The method further includes comparing the limit cycle reference point to at least one predetermined threshold. If the limit cycle reference point is greater than the at least one predetermined threshold, the method includes determining a delta value for the real and reactive voltage commands of the wind turbine power system. Further, the method includes determining updated real and reactive voltage commands based on the delta value. As such, the method also includes operating the wind turbine power system based on the updated real and reactive voltage commands.

Abstract: The disclosed describes a method of operating a wind turbine yaw assembly comprising a yaw ring and a number of yaw drive units, wherein a yaw drive unit comprises a pinion arranged to engage with the yaw ring, which method comprises the steps of identifying a damaged tooth on the yaw ring; providing damage descriptor parameters to the yaw drive controller; and controlling a yaw drive unit on the basis of the damage descriptor parameters to reduce the force exerted by its pinion on a damaged tooth. The disclosed further describes a wind turbine yaw assembly, a wind turbine, and a computer program product.

Abstract: A method and device for detecting equivalent load of wind turbine are provided. The method includes: detecting environment data of each wind turbine of multiple wind turbines in wind farm in each detection period; and in each detection period, detecting load of one or more calibration wind turbines in the multiple wind turbines, calculating equivalent load of the calibration wind turbines based on detected load, and determining equivalent load of each wind turbine based on detected environment data of each wind turbine with load estimation model, where load estimation model represents relation between environment data and equivalent load of wind turbine, and before load estimation model is applied in each detection period, parameter of load estimation model is calibrated based on the equivalent load calculated in current detection period and the equivalent load of the calibration wind turbines determined with load estimation model in previous detection period.

Abstract: Aspects of the present invention provide an approach for controlling energy generation by an airflow originating from a moving elevator cabin. Wing pressure pads are positioned outside the elevator cabin extending to walls of the elevator shaft for preventing an airflow in the elevator shaft from above the elevator cabin to an area in the shaft below the elevator cabin. The elevator shaft is pressure-tight, and the elevator shaft has, at one end of the elevator shaft, an air conduit in which a first power generator stage having a propeller-driven electrical power generator is positioned. The method further intercepts a floor selection for the cabin and disables the power generators if a floor difference from a current position of the elevator cabin to a target position of the elevator cabin is below a predefined threshold value.

Abstract: A device and method for rotating a rotor of a wind power generator and a wind power generator are provided. The device includes at least two rotating units, and each of the rotating units includes a telescopic cylinder, a mounting base configured to connect a fixed end of the telescopic cylinder to a stand of the wind power generator, and detachably connected to the stand; and a pin arranged at a movable end of the telescopic cylinder, configured to be releasably fixed to the rotor, and configured to drive the rotor to rotate relative to the stand by a stroke movement of the telescopic cylinder.

Abstract: Wind turbine, having a tower and a nacelle mounted rotatably around a center axis of the tower on top of the tower, the tower having at least one tower lift for transportation and/or at least one tower climbing means, in particular a ladder, for climbing between the bottom of the tower and at least one tower platform inside the tower which allows access to an access arrangement for the nacelle, characterized in that the access arrangement includes an access platform suspended below a bed frame of the nacelle and rotatable with the nacelle and an access climbing means, in particular stairs, and/or an access lift leading from the access platform to an interior of the nacelle.

Abstract: Disclosed are a conductive ring assembly, a conductive device and a wind turbine. The conductive ring assembly includes a sun gear, a ring gear and one or more planet gear. The sun gear is located in the ring gear, and the sun gear and the ring gear are coaxially arranged. The one or more planet gear is engaged between the sun gear and the ring gear. The planet gear is conducted with the sun gear and the ring gear at the same time, so that an electrical signal is transmitted between the sun gear and the ring gear by means of the one or more planet gear. The conductive ring assembly uses a planet gear structure for communication data transmission to improve the interference resistance of the conductive ring assembly.

Abstract: A wind turbine includes a main shaft rotatable around a rotation axis. The main shaft includes a first piece axially extending along the rotation axis, at least a second piece axially extending along the rotation axis, the second piece being axially adjacent to the first piece, a plurality of connections for fixing the second piece to the first piece.

Abstract: An airborne device comprising a wind turbine with an axis of rotation, an airborne structure configured to support the wind turbine, a lift system configured to keep the airborne structure in flight, at least one belt for transmitting a rotational movement of the wind turbine to a ground station, said belt being guided by at least one ground-based return pulley, wherein each ground-based return pulley is rigidly secured to a pivoting shaft, is positioned in a guide plane perpendicular to the pivoting shaft and is configured to guide the belt, wherein the axis of rotation of the wind turbine and the guide plane of each ground-based return pulley form an angle of less than 60°.

Abstract: Disclosed is a method of condition monitoring a WTG (Wind Turbine Generator) comprising acts of collecting and storage of at least the following data sets together with their time stamps. Collection of generator power production measurements. Collection of mechanical status measurements. Collection of generator torque measurements. Collection of nacelle direction measurements. Collection of meteorological conditions measurements. The method compromises a further act of synchronizing the data sets. The invention also relates to a system for condition monitoring a WTG. The invention further relates to a system for visually inspecting a WTG.

Abstract: Provided is a wind turbine including a hub and several blades rotatably attached to the hub by means of blade bearings including an inner ring coupled with the respective blade and an outer ring coupled with the hub, or vice versa, and rolling elements provided between the rings, wherein the outer ring or the inner ring has a cross section with a circumferentially varying thickness.

Abstract: A wind turbine nacelle platform structure including a beam assembly with at least two beams arranged to extend from a front region of a nacelle outward beyond the back end of the nacelle and a platform assembly mounted to the underside of the outward extending portion of the beam assembly. The disclosed further describes a wind turbine including a nacelle mounted on top of a tower, and such a nacelle platform structure secured to the nacelle.

Abstract: A self-contained portable solar powered fluid pump dispenser for concrete release agents having a movable supporting base pallet upon which a bulk container of release agent fluid is carried, along with a supporting framework which carries a solar panel, electric pump and rechargeable battery that is energized by the solar panel. An elongated dispensing hose is coiled on a hose reel carried by the supporting framework, such that the dispensing hose and dispensing wand connected thereto may be efficiently stored when not in use. The solar powered pump is fluidly sealed between the bulk container of release agent fluid and the dispensing wand to prevent undesirable contaminants from entering the fluid dispensing system.

Abstract: A motor-less pump includes: (a) a housing having an inlet provided to allow fluid flow into the housing and an outlet provided to allow fluid flow out of the housing; (b) an elastic diaphragm positioned in the housing such that motion in the elastic diaphragm drives the fluid flows at the inlet and the outlet of the housing; and (c) one or more electromechanical polymer (EMP) actuators each being provided on a surface of the elastic diaphragm, wherein the mechanical responses to electrical stimuli applied on the EMP actuators cause the motion in the diaphragm. The EMP actuators may include one or more bimorphs.

Abstract: A gear pump includes at least a first and a second rotatable element, wherein the first rotatable element has a toothing system which interacts with a toothing system of the second rotatable element. The gear pump further includes a housing in which the first and/or the second rotatable element are at least partially arranged, and at least one transmitter, which is arranged on the housing, for exciting acoustic waves in the housing. At least one receiver is arranged on the housing, for receiving the acoustic waves which are excited in the housing. Information about properties of the gear pump and/or of a pumping medium can be determined by evaluating a signal which is generated by the receiver when the acoustic waves are received.

Abstract: A suction cover nut for a reciprocating pump includes a body configured to be at least partially received within an access port of a fluid cylinder of the reciprocating pump. The body extends a length along a central longitudinal axis. The body includes a thread configured to threadably connect the suction cover nut to the fluid cylinder within the access port. The thread extends along the central longitudinal axis of the body. The body includes a recess configured to receive a suction cover of the reciprocating pump therein. The recess is tapered inwardly along the central longitudinal axis of the body.

Abstract: A fluid end assembly includes a fluid end and a plurality of valve assemblies each located within a cavity that has curved internal profiles. The curved internal profiles of the cavities are concaved outward. A plunger is included to provide variations in pressure within the fluid end so as to facilitate movement of the working fluid. A discharge plug is included in communication with the fluid end. The discharge plug may include a curved profile along an inner surface that corresponds with one of the cavities therein. A suction plug is releasably coupled to the fluid end and includes a curved profile along an inner surface. The suction plug also includes a recess for acceptance of a spring retainer. The spring retainer is included to support a suction valve assembly.

Abstract: A downhole pumping apparatus comprising a positive displacement rotary gear pump (RGP), driven by a rotating rod string or a submersible electric motor.

Abstract: A vane pump includes a rotor that is rotationally driven; vanes inserted into the rotor in a freely slidable manner; pump chambers that are defined between the vanes at adjacent positions; suction ports that guide working oil to the pump chambers; suction pressure chamber that is communicated with the suction ports and that stores the working oil; and a suction passage that is connected to the suction pressure chamber and that has an suction opening end that opens at an outer surface of a pump body. In a state in which the vane pump is mounted, the suction pressure chamber is mounted below the suction opening end of the suction passage.

Abstract: A scroll compressor includes a fixed scroll including a fixed mirror-like surface and a fixed wrap that is extended from the fixed mirror-like surface, formed in a hybrid curve, and includes a thick portion thicker than other portions; an orbiting scroll including an orbiting mirror-like surface and an orbiting wrap extended from the orbiting mirror-like surface and formed in a hybrid curve; and a rotating shaft configured to rotate the orbiting scroll, wherein the orbiting scroll revolves relative to the fixed scroll. A center of a curve of a center portion of the fixed wrap is located at a position offset by a predetermined distance in a direction of reducing a thickness of the thick portion of the fixed wrap from a center of the fixed mirror-like surface, and a center of a curve of a center portion of the orbiting wrap is offset to correspond to the fixed wrap.

Abstract: A compression device includes: a compressor including a casing, a rotor that is housed in a rotor chamber inside the casing and compresses gas by rotating, a bearing that is provided inside the casing and supports a rotor shaft so that the rotor is rotatable, and a first shaft-sealing part and a second shaft-sealing part that are provided to line up between the rotor chamber and the bearing in the casing to seal a periphery of the rotor shaft; a first supply line adapted to supply injection oil to the rotor chamber; a second supply line that is provided independent of the first supply line to supply lubrication oil to the bearing; a third supply line adapted to supply sealing gas to the first shaft-sealing part; and a fourth supply line adapted to supply the second shaft-sealing part with sealing oil to be used for sealing.

Abstract: The invention relates to a displacement machine according to the spiral principle, in particular a scroll compressor or scroll expander, with a high-pressure chamber, a low-pressure chamber and an orbiting displacement spiral, which engages in a counter-spiral such that chambers are formed between the displacement spiral and the counter-spiral for receiving a working medium, wherein a counter-pressure chamber is formed between the low-pressure chamber and the displacement spiral. According to the invention a pressure regulating device which is fluidically connected to the counter-pressure chamber sets a pressure difference between the counter-pressure chamber and the low-pressure chamber by means of a set value specified by the computing unit.

Abstract: An oil flooded screw compressor includes a housing with an inlet and an outlet, and a rotor supported within the housing by a bearing. The rotor is rotatable to compress air from the inlet to the outlet when the compressor is in an operating state, and the rotor is rotatable without compressing air when the compressor is in an idle state. The compressor also includes a pump configured to supply oil to the bearing only when the compressor is in the idle state.

Abstract: A subsea assembly comprising an electric subsea machine having an electric motor driving an operator, and a coolant circuit at least partially located in thermal contact with the electric motor, the coolant circuit including a cooling assembly located externally from the subsea machine, the cooling assembly comprising at least a heat transfer element, the subsea machine and the cooling assembly being supported by a common supporting frame; at least a part of the heat transfer element is integrated in the frame.

Abstract: A ceiling fan includes a motor and a heat-dissipating device. The heat-dissipating device includes a plurality of blades and a plurality of end plates. The motor includes a shaft and a hub. The hub includes a plurality of vents and a plurality of first coupling portions. Each blade is coupled with at least one first coupling portion and includes a first end and a second end. Each blade forms a second coupling portion at the first end thereof. The second coupling portion is coupled with the at least one first coupling portion. Each blade includes a first air channel extending in a radial direction. The first air channel includes first and second ends. The first end of the first air channel is relatively adjacent to the vents than the second end is. Each end plate includes at least one third coupling portion coupled with the second end of the blade.

Abstract: A ceiling fan including a motor, an intermediate transition member and a plurality of blades is disclosed. The motor includes a stator, a rotor, and a shaft coupled with the stator. An outer face of the motor includes a plurality of heat dissipating holes. The intermediate transition member is coupled with the motor and includes a body and a plurality of first coupling portions integrally formed with the body. The body includes a central hole at a center thereof The shaft extends through the central hole. The plurality of first coupling portions extends radially away from the shaft. The plurality of blades is coupled with the plurality of first coupling portions of the intermediate transition member.

Abstract: The invention discloses a single-knob air pump. The single-knob air pump comprises a housing which is provided with a first air inlet/outlet and a second air inlet/outlet; an air extracting mechanism is arranged in the housing; fan blades of the air extracting mechanism are arranged in a fan blade chamber provided with an air inlet and an air outlet; an air channel switching mechanism is arranged near the fan blade chamber and is provided with an air inlet and an air outlet; the air channel switching mechanism is operatively connected to a knob mechanism which can control the displacement of the air channel switching mechanism; the second air inlet/outlet is provided with an air valve mechanism capable of closing or opening the second air inlet/outlet; and an ejector rod mechanism capable of closing or opening the second air inlet/outlet through the air valve mechanism under the action of the air channel switching mechanism is arranged between the air valve mechanism and the air channel switching mechanism.

Abstract: A gas seal structure includes: a first member with a first flow path where seal gas flows; a second member that is disposed to face the first member and includes a second flow path where the seal gas flowing from the first flow path flows toward a predetermined seal surface; and a communicating pipe disposed across the first and second flow paths. The communicating pipe includes: a first pipe end and a first seal member that are held within the first flow path, a second pipe end and a second seal member that are held within the second flow path, and a flexible pipe that connects the first pipe end and the second pipe end. A rigidity of the flexible pipe end is lower than a rigidity of each of the first pipe end and the second pipe end.

Abstract: It is an object of the present invention to provide a sealing structure for a casing that can reduce the number of used gaskets and achieve further weight reduction, with the sealing function of the gaskets secured. The object is solved by including: a case 2 having an opened top; a cover 3 attached to the top of the case 2 to form a fluid flow path therein; a center plate 5 interposed between the case 2 and the cover 3 and partitions an inner space into the side of the case 2 and the side of the cover 3; and a gasket 4, which is disposed between the case 2 and the cover 3, and forming the center plate 5 so as to have a size that is within an inner peripheral side relative to a sealing line 41 of the gasket 4 and stacking this center plate on the gasket 4, and attaching the cover 3 to the top of the case 2 with the stacked gasket 4 and center plate 5 sandwiched there between to compress the gasket 4 with the mutual butting surfaces between the case 2 and the cover 3.

Abstract: A compressor system includes a gas compressor with dry gas seals about a driveshaft. The compressor system also includes a fugitive gas system having a gas conduit in fluid communication with a collection cavity in a collector coupled to the gas compressor to receive fugitive gas leaked through a pressurized gas leakage path. The fugitive gas system may be structured for flaring the gas, and includes a pressure control system with an accumulator tank, and a vent line for venting gas pressure and having a backpressure regulator therein. Fugitive combustible gas is conveyed through a flow restriction orifice downstream of the compressor.

Abstract: An apparatus comprises a gas turbine engine having a compressor for increasing a total pressure of a working fluid prior to delivery to a combustor for mixing with fuel. The compressor has a plurality of airfoil members that extend between a first flow surface and a second flow surface. The plurality of airfoil members have a first camber shape at a tip portion that provides a cumulative integral according to the relationship 0.4 < ? 0 1 ? [ ? 0 x ? ? ? ? dx ] ? dx ? 0 1 ? ? ? ? dx ? 0.5 where x is chord location, ? ? = ? i - ? ? i - ? e , ?i is inlet metal angle, ?e is exit metal angle, and ? is a camber angle at a given chord location.

Abstract: A fan wheel has a hub cup and a plurality of blades which are arranged on the hub cup and extend radially outward from an outer wall of the hub cup which is in particular at least substantially cylindrical. Each blade has a leading edge and a trailing edge, wherein for at least one blade, an axial unit depth z*(t) of the blade has an aperiodically wave-like shape. A radiator fan module has a fan wheel of the type described above, and the fan wheel can be used in a motor vehicle.

Abstract: A fan wheel has a hub cup and a plurality of blades extending radially outward from an outer wall of the hub cup, which is in particular at least substantially cylindrical. Each blade has a leading edge and a trailing edge, wherein for at least one blade, the progression of a relative position of the blade's leading edge and/or the progression of a relative position of the blade's trailing edge has an aperiodically wave-like shape. There is also described a radiator fan module with a fan wheel of the type described above, and a motor vehicle with such a radiator fan module.

Abstract: Disclosed is a fan blade for a gas turbine engine, the fan blade having: an airfoil having a leading edge, a trailing edge, a tip, and a frangible strip connected to the blade tip and extending outwardly therefrom, the frangible strip being less resistant to plastic deformation than the fan blade tip.

Abstract: A flow guiding device includes a flow-guiding member and a blade. The flow-guiding member includes a flow-guiding portion, a neck portion and a first coupling portion. The flow-guiding portion is connected to a first end of the neck portion. The first coupling portion is located at a second end of the neck portion. The flow-guiding portion, the neck portion and the first coupling portion are connected in series in a radial direction. The blade includes a second coupling portion at a free end of the blade. The second coupling portion is coupled with the first coupling portion. The flow-guiding portion has a cross-sectional area smaller than or equal to a cross-sectional area of the blade. A cross-sectional area of the neck portion viewed from the radial direction at the first end is smaller than a cross-sectional area of the neck portion viewed from the radial direction at the second end.

Abstract: A compressor includes: an upper half casing having upper half casing parting planes; upper half diaphragms configured to be disposed on an inner circumferential side of the upper half casing and having upper half diaphragm parting planes; and upper half position regulating parts that regulate positions of the upper half casing and the upper half diaphragms. The upper half position regulating parts are fixed to at least one of the upper half casing and one of the upper half diaphragms, and have upper half abutting members at which upper half abutting surfaces, each of which comes into contact with an upper half casing recessed surface of the upper half casing and an upper half diaphragm recessed surface of the upper half diaphragm, are formed.

Abstract: A centrifugal blower assembly comprises a scroll wall and a pair of opposing sidewalls. The scroll wall is positioned between the pair of opposing sidewalls such that the scroll wall and opposing sidewalls together define a blower chamber and a blower outlet. The blower outlet defines a blower outlet area. An adjustable outlet plate is pivotably coupled to the pair of opposing sidewalls such that the adjustable outlet plate is moveable between a first position to define a first blower outlet area and a second position to define a second blower outlet area.

Abstract: A ventilation fan with lamp is used to be installed to a ceiling including an installation opening and comprises a housing, a fan module and a lamp module. The housing includes a first opening and a second opening, and the first opening is aligned with the installation opening. The fan module is disposed in the housing. The lamp module is fixed to the first opening by a plurality of elastic elements passing through the housing and includes a lamp cover, a base and a lens. The lamp cover includes a flange portion and a plurality of contact portions, the flange portion and the contact portions are disposed outside the installation opening of the ceiling. The lamp module is connected to the ceiling via the contact portions to make a gap between the lamp cover and the ceiling, and the gap serves as an air inlet of the ventilation fan.

Abstract: A fan shroud includes a bell mouth portion and a rectangular portion. The bell mouth portion includes a circular wall that defines a discharge port and accommodates a propeller fan. The rectangular portion defines a suction port and includes a close wall close to the circular wall, and a farther wall farther from the circular wall than the close wall is from. The close wall includes a closest portion closest to the circular wall in the close wall, and a pair of connection portions connected to the farther wall. The closest wall is between the pair of connection portions. The fan shroud includes an opening portion extending through the rectangular portion from inside to outside of the rectangular portion. At least one of the pair of connection portions includes the opening portion, and the closest portion does not include the opening portion.

Abstract: A centrifugal fan includes a housing and an impeller. The housing includes a sidewall, and the sidewall includes a tongue portion. The impeller includes a fan hub and a plurality of blades. The fan hub is rotatably disposed in the housing, and the tongue portion has an inner contour line on a reference plane. The blades connect to the fan hub. Each one of the blades has an end surface facing the sidewall. The end surface has an outer contour line on the section of the blade. Any two adjacent blades have different outer contour lines. The outer contour line of at least one first blade of the plurality of blades is parallel to the inner contour line. The outer contour line of at least one second blade of the plurality of blades is not parallel to the inner contour line.

Abstract: The disclosure provides a mount bracket which is configured for a fan. The mount bracket includes a button plate, a frame and a plurality of vibration-absorbing components. The button plate is mounted with a motor mount. The frame surrounds the button plate, and the frame has an inner lateral surface and an outer lateral surface. A plurality of fixing structures protrude from the outer lateral surface of the frame. The inner lateral surface of the frame and an outer lateral surface of the button plate form an annular gap therebetween. The vibration-absorbing components are spaced apart from each other and located in the annular gap, and the vibration-absorbing components are located between and connected to the outer lateral surface of the button plate and the inner lateral surface of the frame.

Abstract: The disclosed apparatus, systems and methods relate to devices, systems and methods for the selective application of down pressure or downforce to a row unit. Each row unit has a dual-action actuator which is in fluidic communication with the hydraulic system for independent control of the supplemental downforce. The pressure line can be directly routed to the lift chamber for a constant supply of up pressure, with down pressure selectively applied to the down chamber for accurate control of the supplemental downforce system.

Abstract: A fluid pressure control device includes a first tank passage connecting first tank ports to each other, a second tank passage connecting second tank ports to each other, a connection passage connecting one end side of the first tank passage and one end side of the second tank passage and a discharge port provided on the other end side of the first tank passage and connected to a tank. A communication spool formed with a communication passage allowing communication between the first tank passage and the second tank passage is housed in at least one of a plurality of spool housing holes.

Abstract: A hydraulically powered rotary actuator is described including: a hydraulic linear actuator which is moveable in both directions between a retracted position and an extended position; a clutch device which is operable between an engaged condition and a disengaged condition; and a rotary output member; wherein the linear actuator is coupled to the rotary output member by way of the clutch.