Abstract: Provided is a single degree of freedom vibration isolator/damper system capable of overload protection. The vibration isolator reduces vibration transmitted to or from an isolated spacecraft component that generates micro-vibrations. The system isolates sensitive components and vibration sources from the spacecraft. The system may consist of a 1) first spring element in series with a first damper element; 2) a second spring element in parallel with the first spring element and first damper element; and 3) a support member that serves as the overload protection device.

Abstract: An S-cam brake including a brake chamber to which compressed air is supplied; a slack adjuster rotatably connecting to the brake chamber; an S-cam unit having an S-cam connecting to and rotating around the slack adjuster; and a drum having a lining generating braking force with widening according to rotation of the S-cam is provided, wherein the brake chamber includes an upper housing having an air supply port through which compressed air is introduced; a lower housing coupled to the upper housing to form an internal space; a diaphragm having edges fixed to the upper housing and the lower housing and deformed by compressed air; a piston disposed to contact the diaphragm and move linearly; a piston push rod extending from the piston and having one end connected to the slack adjuster; and a spring having one end supported by the piston and the other end supported by the lower housing, wherein a thickness of the upper housing is greater than a thickness of the lower housing.

Abstract: A coupling e.g. for an actuator, comprises a housing which is preferably in the form of a ring mounted around the end of the outer rod and which can be mounted to a component e.g. a cowl being deployed. Within the housing of the coupling is provided a ring disk. This is sized and arranged within the housing such that there is some clearance between the ring disk and the housing so as to permit some eccentric movement.

Abstract: An actuator for operating a linear valve, such as a gate valve, includes a quick connect coupling between the housing and at least one of a bonnet and a power head assembly. In embodiments, the quick connect coupling includes a plurality of lugs spaced apart around an annular actuator housing surface, and a plurality of lugs spaced apart around an annular surface of another member such as a bonnet or power head, each of the lugs defining a plurality of slots therebetween. The lugs pass through corresponding slots, and then the housing is rotated relative to the other member until at least a portion of the lugs of each component are axially aligned in a locked position. The rotation is less than one full revolution of the rotated component. A latch prevents the component from rotating out of the locked position.

Abstract: A support for supporting a structure on a surface, comprising at least one support element, each support element comprising a piston, a cylinder in which the piston is moveable, and a brake for maintaining the piston in a position that is stable relative to the cylinder, wherein the piston and the cylinder are arranged so that a loading associated with the structure effects an adjustment of the support element, and wherein an increase in hydraulic pressure within the cylinder, effected by the loading associated with the structure, activates the brake.

Abstract: A two piston cylinder providing asymmetrical expansion and retraction capabilities is disclosed having two linked expansion chambers and a single chamber for retraction. The retraction chamber is situated between the two expansion chambers, and the expansion chambers are linked together by a tube passing through the piston that provides hydraulic fluid to both the retraction chamber and one of the expansion chambers.

Abstract: A pneumatic cylinder includes a cylinder housing, a central piston displaceable longitudinally in the cylinder housing, a first trailing piston configured to work with a first trailing stop of the central piston and a first positioning stop on the cylinder housing, and a second trailing piston configured to work with a second trailing stop of the central piston and a second positioning stop on the cylinder housing. The cylinder housing comprises a base body in which the first trailing piston runs, a cylinder cover in which the second trailing piston runs, and an intermediate washer on which the first positioning stop and the second positioning stop are formed.

Abstract: A two piston cylinder providing asymmetrical expansion and retraction capabilities is disclosed having two linked expansion chambers and a single chamber for retraction. The refraction chamber is situated between the two expansion chambers, and the expansion chambers are linked together by a tube passing through the piston that provides hydraulic fluid to both the retraction chamber and one of the expansion chambers.

Abstract: Systems and methods for recovering power fluid used to power a device under water and for pumping the recovered power fluid to a fluid container above a surface of the water, the method in certain aspects including: flowing fluid from a subsurface apparatus to a subsurface recovery system, the fluid initially provided to the subsurface apparatus to power the subsurface apparatus; and the subsurface recovery system including a pump system for selectively pumping recovered power fluid to a fluid container above a surface of the water, the pump system having at least one pump and, in some aspects, a first pump, a second pump, and a valve system; the valve system controlling the first pump and the second pump to allow only one pump of the first pump and the second pump to pump recovered power fluid to the fluid container above the surface of the water; and pumping recovered power fluid to the fluid container with only one pump at a time.

Abstract: A driving device for pivoting a flap with respect to a body includes a cylindrical pressure tube having a closed first end and a second end with a seal, a piston dividing the pressure tube into a first working chamber and a second working chamber, a piston rod extending through the first working chamber and the seal, a gas under pressure in the first and second working chambers, and a sealing and guiding cap fixed to the second end of the pressure tube. An outer tube has a closed first end and an open second end which receives the pressure tube in a telescoping manner, thereby forming a third working chamber between the second end of the pressure tube and the first end of the outer tube, wherein a fluid can be conveyed into and out of the third working chamber.

Abstract: A support for supporting a structure on a surface, comprising at least one support element, each support element comprising a piston, a cylinder in which the piston is moveable, and a brake for maintaining the piston in a position that is stable relative to the cylinder, wherein the piston and the cylinder are arranged so that a loading associated with the structure effects an adjustment of the support element, and wherein an increase in hydraulic pressure within the cylinder, effected by the loading associated with the structure, activates the brake.

Abstract: A hydraulic mechanism includes an outer cylinder having an expansion side working port and a contraction side working port respectively formed on a top of the outer cylinder; an inner cylinder insertedly installed inside the outer cylinder to come in and out toward a bottom of the outer cylinder; an inner rod having two flow paths respectively connected to the expansion side working port and the contraction side working port, one end of which is fixed to an inner top surface of the outer cylinder, and the other end of which passes through a top of the inner cylinder and protrudes to be positioned inside the inner cylinder; and a piston combined with the other end of the inner rod to be positioned inside the inner cylinder and formed with a hole connected to the flow path of the inner rod connected to the expansion side working port.

Abstract: A hydraulic actuator has an armored section having concentric cylinders and an unarmored section having a cylinder with a frangible piston and a frangible upper gland nut. The hydraulic actuator may have leakage vents adapted to prevent leakage between hydraulic systems used to power the cylinders. The hydraulic actuator also may have a gland seal for sealing an end of the cylinder of the unarmored section and a sensing port adapted for allowing detection of fluid leaking due to damage of the gland seal.

Abstract: An extendable sprinkler device comprises a base cylinder having a first end fluidly communicable with a second end via a through passageway. A primary extension assembly is coupled within the through passageway of the base cylinder and is positionable between collapsed and extended positions. The primary extension assembly comprises a primary extension cylinder having a first end fluidly communicable with a second end via a through passageway. A stop is coupled to the first end of the primary extension cylinder. An actuator cylinder is coupled within the primary extension cylinder. The actuator cylinder comprises a first end fluidly communicable with a second end via a through passageway. The second end of the actuator cylinder is coupled with the second end of the primary extension cylinder.

Abstract: An active material actuator assembly is provided having first and second active material components operatively connected to a movable member. Movement of the movable member is modulated, which may be due to activation of the first and second active material components being at least partially temporally distinct or the active material components differing in at least one characteristic affecting movement.

Abstract: An integrated breakaway cylinder for controlling a boom of a self-propelled sprayer and method for constructing a boom assembly is disclosed in the present application. The integrated breakaway cylinder is constructed from a first stage cylinder and a second stage cylinder. The first stage cylinder is configured in a rod and barrel arrangement. The second stage cylinder is also configured in a rod and barrel arrangement, with the barrel of the first stage cylinder serving as the rod of the second stage cylinder. The first stage cylinder operates to extend and retract a boom. The second stage cylinder operates to absorb shock from inertia or the boom impacting an object. The design of various embodiments of the present invention couples the operation of maneuvering a boom with shock absorption into a single integrated cylinder.

Abstract: An axial piston hydraulic device. The device has a housing that uses a servo piston in order to control the displacement of a swashplate within the device. By using a servo member disposed within a cavity of an end cap on the housing the axial piston hydraulic device is able to provide three operating positions depending on the angle of the swashplate.

Abstract: The present invention provides a telescopic hoist comprising a series of telescopically arranged tubular sections wherein the tubular sections are made in nitrided steel.

Abstract: A hydraulically-operated press-driven tool actuation system includes a press-driven hydraulic power device and/or a hydraulically-powered tool actuator. In the tool actuator, at least two pistons are carried by a housing, and at least one return device is carried by the housing laterally inboard of the pistons. In the power device, a pump includes a piston disposed in a pump cylinder for pressurizing hydraulic fluid therein. An accumulator is in fluid communication with the pump cylinder, and includes a piston disposed in an accumulator cylinder that houses hydraulic fluid on one side of the piston. A body supports the pump and accumulator thereon and is in fluid communication between the pump and accumulator cylinders. The body includes a pressure relief valve downstream of the pump cylinder and upstream of the accumulator cylinder, and a check valve downstream of the accumulator cylinder and upstream of the pump cylinder.

Abstract: Linear actuators including coupled elongate members formed of shape memory alloys are provided. Members that lengthen when heated are coupled to members that shorten when heated such that stroke amplification gains are derived from each member. The members may be tubular and may be coaxially arranged for telescopic extension and collapse. Sections of a modular structure such as a space vehicle may be latched and clamped together for assembly or for docking by utilizing linear actuators having shape memory alloys that are actuated thermally.

Abstract: A combined service brake and spring brake cylinder for the braking system of a motor vehicle, in particular for utility vehicles, includes service and spring brake pistons guided inside a casing which is common for the two brake cylinders. The spring brake piston is loaded by at least one storage spring and has an external diameter greater than that of the service brake piston. The spring brake piston is in the form of an annular piston, and at least a part of the rod thereof is constructed in the form of a piston tube, which surrounds the service brake piston and forms an external radial running and sealing surface therefor.

Abstract: A hydraulic actuator for an active of semi-active vehicle suspension system has a cylinder with a piston therein. A piston rod is attached to the piston and extends out of the cylinder. First and second chambers are formed on opposites sides of the piston enabling the piston to be driven in a manner that counteracts vibrations in the vehicle, A third chamber is provided in the cylinder for connection to a load leveling apparatus. A novel structure reduces the overall length of the hydraulic actuator. A displacement sensor is incorporated into the hydraulic actuator to provide an electrical signal that indicated how far the piston rod extends from the cylinder.

Abstract: The invention relates to a telescopic lifting column. The lifting column comprises a plurality of tube bodies which are arranged concentrically inside one another and are axially movable in each case with respect to each other. Furthermore, the lifting column comprises a hydraulic actuator unit which is arranged in the tube bodies so as to be operating in the axial direction. The hydraulic actuator unit comprises a first hydraulic cylinder-piston unit and a second hydraulic cylinder-piston unit connected with the first, the first cylinder-piston unit being connected to a first end of the telescopic lifting column and the second cylinder-piston unit being connected to a second end of the telescopic lifting column. The first cylinder-piston unit is of the type having a first variable operating chamber and a second variable operating chamber.

Abstract: A telescoping hydraulic hoist with tube stages formed from a heat treated aluminum alloy from one of the series 2000, 6000 or 7000 aluminum alloys. These alloys retain good “memory” properties, and under the force of a pressure spike undergoes a momentary elastic deformation which acts as a shock absorber, expanding the tube wall to absorb the peak stresses and resist buckling. The hoist of the invention is thus much lighter than a comparably rated steel hoist, and much more resistant to corrosion.

Abstract: The present invention relates to a power cylinder apparatus for varying actuation forces applied to a workpiece. The present invention provides an enclosure having a piston rod connectable to a workpiece and slidably disposed within an enclosure. The piston rod moves between a retracted position, wherein the piston rod is retracted within the enclosure, and an extended position, wherein the piston rod extends outwardly from the enclosure. A piston is slidably disposed on the piston rod for movement between the retracted position and the extended position. A bushing is provided within the enclosure for slidably supporting the piston rod and positively stopping the piston in the extended position. The piston rod and piston have varying surface areas substantially perpendicular to the direction of movement such that varying actuation forces may be provided to the workpiece through a supply of a constant fluid pressure.

Abstract: The linear path slide (100) with a slide (10) which is arranged with a sliding guide (12) slidingly movable and resistant to torsion in a housing (11) and with a hydraulic driving gear which causes the translation movement of the slide (10) and which has a piston (24) arranged slidingly movable in a cylinder by constituting a hydraulic working space (13), is configured in such a way that the cylinder and the working space (13) are placed in the slide (10), the piston (24) being fixed with respect to the housing (11).

Abstract: An ultrathin cylinder includes a cylinder bore formed in a short columnar cylinder body and having an axial length smaller than its radius, a short cylindrical piston for sliding in the cylinder bore and also functioning as a piston rod, a guide rod positioned at a central portion of the cylinder bore and passing for sliding through an end wall of the piston to extend into a cylindrical portion of the piston, a rod cover fixed to an end portion of the guide rod in the cylindrical portion to slide in the cylindrical portion, a first pressure chamber defined in the cylinder bore by the piston, and a second pressure chamber defined in the cylindrical portion by the rod cover.

Abstract: A high pressure fuel pump having a variable fuel injection rate, including a pump body, a pump cylinder formed in the pump body and a piston reciprocable within the pump cylinder, which defines a pressurization chamber. The pump piston has a reduced diameter portion which provides a primary piston. A piston annulus is slidably mounted thereon and provides a secondary piston. An annular actuation chamber adjoins the secondary piston opposite the pressurization chamber. An actuation passage is provided between a return fuel drain and the actuation chamber, which is selectively open or closed passively by pump piston movement and/or dynamically by operation of an actuation solenoid valve. If the actuation chamber passage is open, then during the pressurization stroke the secondary piston will remain stationary relative to the pump body, but if it is closed then the secondary piston must stroke in unison with the primary piston.

Abstract: A multi-stroke air cylinder providing a precisely directed and controlled stroke in the face of lateral, torsional and tilting loads on a tooling plate. The multi-stroke cylinder utilizes a plurality of mechanically linked pneumatic or hydraulic pistons having different stroke lengths that can be added together in any combination, allowing the user to select any stroke length up to a predetermined, total combined stroke length, in increments equal to the stroke length of the smallest cylinder. The multi-stroke cylinder includes a head assembly having a fluid inlet for introducing fluid to the cylinder at a first pressure. The cylinder also includes a first positioning system having a plurality of pistons capable of moving a piston rod away from the first positioning system, and a second positioning system located between the head assembly and the first positioning system.

Abstract: A hydraulic cylinder includes piston and plunger assemblies fitted together with a retention ring. This design allows finish-machined pistons to be assembled without welding of semi-finished machine components.

Abstract: A load bearing apparatus includes a first container having enclosed ends and at least one expansion segment. The expansion segment includes a first cylinder and a second cylinder of diameter smaller than the first cylinder disposed along a longitudinal axis of the first cylinder. An elastomer seal is connected between the first and second cylinders to form a fluid tight seal between the cylinders. The elastomer seal further permits translation of the first cylinder with respect to the second cylinder in a direction along the longitudinal axis of the first cylinder.

Abstract: A telescoping hydraulic hoist which improves stability and rigidity in the extended position without sacrificing the maximum extension length of the hoist and with fewer machined parts which may be dislodged or damaged in operation. The base member has a recess into which intermediate and inner tube stages recede when the hoist is in a fully collapsed position, and a stop-collar on the gland nut bearings overlaps the exposed end of the next broader tube stage, defining a limit of retraction for each intermediate tube stage, so that a tube stage when fully retracted contacts the exposed end of the next broader tube stage, thus dispensing with the need for stop rings.

Abstract: An apparatus for synchronizing a telescopic ram in a hydraulic elevator in which two or more pistons and a cylinder are simultaneously extended from and retracted into a foot portion mounted at the bottom of an elevator shaft includes a connecting cable which is fixed on one end to the shaft wall and on the other to one of the pistons and the cylinder and is deflected over a roller used for the synchronization. The connecting cable is a sheathed synthetic fiber cable.

Abstract: An analytical database system provides access to all of the data collected by an entity in interactive time. The analytical database system transforms relational database data. The relational database is denormalized and inverted such that the data fields of tables in the relational database are stored in separate files that contain a row number field and a single data field. At least one of the files, that contains repeating data values that are stored in successive rows, is compressed. The files include files with partition values and files with analytical data. Processing of the files is distributed by creating sub-rowsets of the files and by assigning the sub-rowsets to servers. The partial result sets are merged into a complete result set.

Abstract: A manual air pump includes an outer cylinder comprising a chamber therein, a head provided to an end of the outer cylinder, the head including an outlet passage communicated with the chamber for supplying air to an object to be inflated, and an inner cylinder reciprocatingly mounted in the outer cylinder. An outer piston is attached to an end of the inner cylinder to move therewith and includes a passage for communicating a longitudinal bore of the inner cylinder with one of the outlet passage of the head and the chamber of the outer cylinder. A piston rod is reciprocatingly mounted in longitudinal bore of the inner cylinder and an inner piston is attached to an end of the piston rod to move therewith. A handle is secured to the other end of the piston rod to move therewith. The inner cylinder is rotatable relative to the outer cylinder.

Abstract: For a hydraulically actuated device a hydraulic power cylinder with an actuator slidably received for reciprocation within the cylinder and a piston slidably received for reciprocation within a sleeve of the actuator and defining a gas chamber on one side of the piston and a hydraulic fluid chamber on the other side of the piston so that the maximum pressure in the hydraulic fluid chamber is limited as a function of the force of compressed gas in the gas chamber acting on the piston. In this way, the maximum system pressure is a function of and substantially corresponds to the pressure of the compressed gas within the gas chamber and acting on the piston. Desirably, the pressure of the compressed gas in the gas chamber can be readily changed to change the maximum hydraulic fluid pressure.

Abstract: A cylinder and piston unit, which can be utilized to select the gears of and/or to shift a change-speed transmission in the power train of a motor vehicle, has a housing provided with two internal chambers and internal stops and receiving a reciprocable assembly of three pistons including two interconnected pistons each adjacent a different one of the two chambers and a hollow cylindrical piston which surrounds one of the two interconnected pistons. The chambers can receive a pressurized hydraulic or pneumatic fluid jointly or independently of each other to thus effect movements of the interconnected pistons (with and/or relative to the holow piston) against selected stops and to thus select the positions of the interconnected pistons. Such interconnected pistons can be utilized to select the ratio of the change-speed transmission. The chambers can confine springs which assist or oppose the action of fluid upon the surfaces of the interconnected pistons.

Abstract: A roller control unit (2) for a continuously-variable-ratio transmission includes a cylinder (6) having a cylinder wall and an end wall; and a piston (8), within the cylinder (6) and to which the roller assembly (4) is connected for movement therewith, said unit includes an axially extending shroud (10) of variable length extending between the piston (8) and the end wall, thereby to define in combination with the piston (8) and cylinder (6) a chamber (16) for receiving hydraulic fluid, and in which the shroud (10) comprises a telescopic shroud which in a first position of the piston (8) is extended and in a second position of the piston (8) is retracted.

Abstract: A hydraulic lifting-lowering-system for a working table, a couch or lying furniture or another heavy object allows the height level or position to be frequently adjusted or changed. The system includes a predetermined amount of hydraulic fluid, a hydraulic fluid accumulator, the fluid pressure of which on the hydraulic fluid side is adjustable, a single acting hydraulic cylinder with two end caps, a piston pressure chamber and a piston rod which, via a piston rod sealing ring, extends sealingly out through the one end cap of the cylinder. The piston pressure chamber is pressure fluid connected to the hydraulic fluid side of the accumulator. The hydraulic cylinder is of the plunger piston type, and the cylindric tube of the hydraulic cylinder is slideably and telescopically mounted in a cylindrical guiding tube, which surrounds the piston rod in its entire length and is rigidly secured to the one end of the piston rod via a cross plate or similar construction part.

Abstract: The double telescopic prop comprises an outer cylindrical casing tube 1, an inner tube 2 which is displaceable therein and a piston rod 3 which can be extended therefrom. The hydraulic fluid for extending the two prop stages is conveyed through a connection 14 to the piston 5 of the inner tube 2 and is conveyed via a bottom valve to the piston 7 of the piston rod 3. The prop is retracted if hydraulic fluid flows via the connection 17 into the outer annulus 11 between the cylindrical casing tube 1 and the inner tube 2. A size ratio of 8.8:1 at most, which is favourable for the retraction of the prop, exists between the area of the inner tube 2 and the ring area of the annulus 11.

Abstract: The pneumatic actuator comprises at least one double-acting cylinder having a tubular body and two closure heads which define a piston chamber for a reciprocable piston; the body of the cylinder consists of an extruded tubular section provided with at least one longitudinal conduit for the air flow, which extends in a wall between the two end portions of the tubular body. One of the closure heads at an end side of the tubular body is provided with air-flow passage for connecting one end of the piston chamber via said longitudinal conduit to an air inlet/outlet opening close to the other end side of the body. The second closure head of the cylinder is in turn provided with an air inlet/outlet opening connected to the end of the piston chamber which is opposite the previous one. The actuator is made in the form of a single cylinder or of a telescopically extending cylinder having several stages.

Abstract: A seismic vibrator system for imparting compressional and shear wave vibrations into the earth has an earth contacting base with a vertical post. A tubular hub is slidably received on the post in a piston/cylinder relationship. Spaced apart horizontal top and bottom plates are secured to the hub. A mass is slidably supported between the plates. Pistons interconnect the hub and the mass. Hydraulic energy is used to reciprocate the mass vertically on the post and horizontally between the plates.

Abstract: A telescoping hydraulic hoist formed from a non-corrosive material provides bearings and hydraulic seals about the bottom portion of each intermediate moving stage. The bearings and hydraulic seals are thus always maintained within the hoist and are not exposed to dust or particulate matter from outside the hoist. Air flows into and out of the air spaces between adjacent stages through air breathers. The hoist may also include variable length stroke limiters, and a cushion member which partially closes off the hydraulic inlet as the innermost stage is fully retracted to slow the hoist motion in the final stages of retraction.

Abstract: A trim-tilt device 20 for a marine boat motor has a housing 31 forming a large-diameter trim chamber 32, a cylinder 41 inserted into the trim chamber 32 of the housing 31 to form a small-diameter tilt chamber 42, and a piston rod telescopically inserted into the tilt chamber 42 of the cylinder 41. Built into the wall of the cylinder 41 is the passage 46 for interconnecting a first trim chamber 32A and a first tilt chamber 42A.

Abstract: A small diameter cylinder 1a and a large diameter cylinder 1b connected to it are formed in a housing, and a stepped piston 8 comprising a large diameter part 8b and small diameter part 8a is inserted in these cylinders. A first pressure chamber 14a is formed on the small diameter cylinder side and a third pressure chamber 14c is formed on the large diameter cylinder side by the stepped piston 8, and an annular second pressure chamber 14b is formed on the outer circumference of the small diameter part of the stepped piston 8. An intermediate cylinder 10 is formed inside the stepped piston 8, and houses a piston 5 free to slide inside it which forms a fourth pressure chamber 14d. The fourth pressure chamber 14d is permanently connected to the third pressure chamber 14c. A rod 4 connected to the piston 5 passes through the stepped piston 8 in an axial direction. An end stopper 11 limiting the magnum stroke L1 of the piston 5 is provided, and sets the maximum stroke L2 of the stepped piston 8.

Abstract: A fluid-operated cylinder-piston unit has a cylinder forming an inner space, a piston unit movable in the inner space and including a first piston and a second piston movable relative to one another and each having a displacement area at one end and a force applying area at another opposite end. The pistons are arranged so as to form a smaller displacement area associated with one of the pistons and a larger displacement area associated with both of the pistons. A fluid supply to the piston unit is performed so that first only one of the pistons moves and another of the pistons remains stationary during an advance stroke, and during a return stroke fluid has to be applied only to the displacement area of the one piston, while thereafter another of the pistons is moved as well under the action of fluid and both pistons move to apply a larger force due the larger total displacement area and during a return stroke fluid is applied to the larger displacement area.

Abstract: A hydraulic actuator for a hydraulically driven device has a hydraulic cylinder, a first piston slidably received for reciprocation within the cylinder and defining a hydraulic fluid chamber with the cylinder, a second piston slidably received for reciprocation within a cavity in an actuator rod connected to the first piston and defining a gas chamber on one side of the second piston and an accumulator chamber on the other side of the second piston. A passage formed in the first piston communicates the hydraulic chamber with the accumulator chamber and a pressure relief valve selectively permits hydraulic fluid flow through the passage from the hydraulic chamber to the accumulator chamber to limit the maximum pressure of the hydraulic fluid within the hydraulic chamber and the hydraulically driven device. Preferably, during normal operation of the actuator and the hydraulically driven device the pressure of the hydraulic fluid is less than that required to open the pressure relief valve.

Abstract: A hydraulic pressure generator having a body (1) with a first bore (11) therein for receiving a cylinder (21) of a piston assembly (2) to define a pressure chamber (12). The cylinder (21) has a second bore (211) for receiving an auxiliary piston (22) which defines a variable volume compensation chamber (23). The compensation chamber encloses a deformable member (5) which is adapted to exert an elastic force between the auxiliary piston (22) and a closed end (210) of cylinder (21). The compensation chamber (23) communicates with the pressure chamber (12) through a restriction (221) formed in a longitudinal duct (222) of the auxiliary piston (22). A sealing member (4) borne by a portion (222) of the auxiliary piston (22) closes the pressure chamber (12) such that the elastomeric member (5) dampens pressure differences between the pressure chamber (12) and compensation chamber (23).

Abstract: A valve mechanism for self-expanding booms. The mechanism is preferably a mechanical expansion device that folds out the boom so that air flows into the boom to fill the boom. When the boom is folded, the air is pressed out of the boom. A novel feature is an automatic control mechanism that is adapted to permit an inflow of air into the boom when the boom is expanded and to permit an outflow of air when the boom is collapsed, rolled up and stored. The control mechanism is affected by the relative position between the valve mechanism and other parts of the boom when the boom is in the expanded or collapsed position.

Abstract: An apparatus for raising and lowering devices such as an antenna including a multiple-stage cylinder system composed of a plurality of telescopically connected cylinder units each of which comprising an internal cylinder and an external cylinder that are connected at their lower ends so that the internal cylinders of the plurality of cylinder units form a sealed space so as to be filled with pressure oil used for extending and contracting the cylinder system. In addition, a fixture structure is provided on the lowest stage cylinder unit so that the cylinder system is held upright by the fixture structure at two points on the lowest stage cylinder unit in a vertical direction.