Abstract: A seal assembly for a hydraulic cylinder piston rod of a hydraulic cylinder includes an annular buffer seal and an annular backup ring. A first axial pressure side of the annular buffer ring faces a rod end chamber of the hydraulic cylinder and fits adjacent a first axial side surface of an annular groove defined in a rod end of the hydraulic cylinder through which the piston rod passes, and a second axial seal side opposite from the first axial pressure side includes a radially outer annular seal surface and a radially inner annular seal surface, wherein the radially outer annular seal surface is spaced farther from the first axial pressure side of the annular buffer seal than the radially inner annular seal surface of the buffer seal such that an annular notch is formed around an inner diameter of the annular buffer seal on the second axial seal side of the annular buffer seal.

Abstract: A canned motor, including: a motor housing, a stator fixed to the motor housing, a rotor mounted on the motor housing so as to be rotatable relative to the stator about an axis of rotation, a can fixed to the stator radially between the stator and the rotor, at least one annular seal carrier fixed to the motor housing, radially inside the can, at an axial stator end, and at least one annular seal supported radially and axially on the seal carrier, the at least one annular seal configured to seal off a rotor space, in which the rotor is arranged, from a stator space through which a coolant can flow, wherein the stator space has a main region and an annular region, which extends from the at least one annular seal along the seal carrier and merges into the main region at a distance from the seal.

Abstract: An actuatable sealing mechanism for sealing a fluid channel provided between two co-axially arranged tubular members having a central longitudinal axis. The actuatable sealing mechanism comprises an elastomeric seal, an axially moveable actuating sleeve member (1400; 2400; 3020) and a radially moveable activating member. The activating member is configured to be moveable in a radial direction in use to translate the actuatable sealing mechanism between an unsealed state and a sealed state. When it is in the sealed state, the activating member axially compresses the elastomeric seal sufficiently to expand the elastomeric seal in the said radial direction to seal the fluid channel.

Abstract: A packing assembly providing a seal point configurable at multiple locations. The packing assembly includes a soft bed having at least one energizing ring and at least one seal ring. The assembly includes a spacer ring sealable with the at least one energizing ring. The assembly further includes at 1=least one adapter ring abutting either end of the soft bed to provide two seal locations relative to the spacer ring.

Abstract: A split ring seal has: a first circumferential end and a second circumferential end; an inner diameter surface and an outer diameter surface; a first axial end face and a second axial end face. A circumferentially distributed first plurality of open channels are along the first axial end face. A circumferentially distributed second plurality of open channels are along the second axial end face.

Abstract: A seal assembly for a gas turbine engine having a rotor arranged to rotate about an axis in use. The seal assembly has a static support structure for the gas turbine engine and a casing structure of the engine. Rotation of the engine rotor causes a deflection of the casing structure relative to the static support structure in a first direction. A seal is provided at an interface between the static support structure and the casing structure, and comprising a first seal portion and a second seal portion spaced from one another in the first direction. The first seal portion is provided against a first surface of the casing structure and the second seal portion is provided against a second surface of the casing structure opposing the first surface.

Abstract: A valve seat is provided for use in a rotary valve for use in highly corrosive and abrasive applications. The valve seat includes a seat body adapted to selectively engage a portion of the floating ball element. The valve seat also includes a sealing element disposed in a first groove formed in the seat body and adapted to prevent fluid flow between the seat body and the valve body. The valve seat further includes a first bearing disposed in a second groove formed in the seat body, and a second bearing disposed in a third groove formed in the seat body, wherein the second and third grooves are formed immediately adjacent the first groove such that the first and second bearings are disposed immediately adjacent the sealing element.

Abstract: An isolation tool is described herein. In particular, a double isolation and bleed (DIB) isolation tool for use in line-stopping operations. The isolation tool may include a head unit, at least one groove around a circumference of the head unit, and a circumferential seal element disposed within each of the at least one grooves.

Abstract: The present disclosure relates generally to a sliding seal between two components. The sliding seal includes a first seal section and an uncoupled second seal section which allows the first and second seal sections to move relative to one another during relative movement between the two components. A wave spring and/or a rope seal is disposed between the first and second seal sections biases the first and second seal sections away from one another.

Abstract: A downhole tool body includes an outer surface having at least one O-ring gland. The at least one O-ring gland includes a first contour having a first radius greater than about 0.035? (R0.89 mm) and a second contour having a second radius greater than about 0.035? (R0.89 mm). A backup ring is arranged in the O-ring gland. The backup ring includes a gland contour having a radius that is complimentary to the first radius.

Abstract: A mechanical seal provides bi-directional sealing and comprising a body in hybrid material, being structured in a component of elastomeric material and a component of segmented or non-segmented composite material distributed in a lagged way along said body. The seal is resistant to extrusion failure at high differential pressures, which facilitates its installation in several equipment elements, such as underwater or ground.

Abstract: The present disclosure relates generally to a sliding seal between two components. The sliding seal includes a first seal section and an uncoupled second seal section which allows the first and second seal sections to move relative to one another during relative movement between the two components. A wave spring and/or a rope seal is disposed between the first and second seal sections biases the first and second seal sections away from one another.

Abstract: A sealing device in which diameter expansion of an inserted first back-up ring is suppressed. The sealing device includes a seal ring mounted in a rectangular mounting groove, the first back-up ring, and a second back-up ring. The first back-up ring has an end surface contacting an opposing-sealing-fluid-side side surface of the mounting groove. The second back-up ring has an end surface contacting the seal ring. A contact surface in an inner peripheral end of second back-up ring is perpendicular to the axis to contact an opposing-sealing-fluid-side side surface of the mounting groove. The inner diameter of the first back-up ring is set to be larger than the outer diameter of the contact surface portion of the second back-up ring, and the outer diameter of the first back-up ring is set to be smaller than the inner diameter of a housing.

Abstract: A sealing apparatus and related method for sealing an annular space between concentrically disposed members. In an exemplary embodiment, the method includes providing a sealing ring within the annular space, the sealing ring defining oppositely inclined interior and exterior surfaces each having a generally frusto-conical shape and defining opposing first and second edges, a nose adjoining the respective first edges of the interior and exterior surfaces, and a first convex surface adjoining the respective second edges of the interior and exterior surfaces opposite the nose; and forming a seal against a fluid pressure in the annular space, comprising depressing the first convex surface of the sealing ring so that the interior and exterior surfaces thereof expand radially to exert contact stress on each of the concentrically disposed members.

Abstract: A flow control apparatus for use with a fluid valve includes a plug having a first portion slidably coupled to a second portion. The first and second portions include opposing bleed ports. The second portion contacts a seat of the fluid valve to close the fluid valve. The apparatus further includes a cavity formed in an outer circumferential surface of the plug by the first and second portions. An axial dimension of the cavity decreases when the first portion slides toward the second portion. The decrease radially outwardly displaces a seal disposed in the cavity. The seal has a curved outer surface configured to engage an inner circumferential wall of a cage of the fluid valve in response to the second portion contacting the seat. The apparatus further includes a pin disposed in the opposing bleed ports to align the first and second portions relative to a common longitudinal axis.

Abstract: A seal arrangement includes a first and a second machine element have a sealing gap and are movable in translation relative to one another. A seal element has a sealing lip arranged in a holding groove in the first machine element and which serves to seal off a low-pressure and high-pressure region. A rubber-elastically deformable preloading element in the holding groove serves to preload the seal element. At least one elastically deformable damping member is arranged between a low-pressure side groove flank and the seal element. A free space is formed between the damping member and the sealing surface. The damping member is compressed in the axial direction by the seal element when the high-pressure region is subjected to pressure and can be deformed freely into the free space. The damping member is of a material having a lower elasticity modulus than the seal element.

Abstract: Sealing system of a device for allowing the passage of a medium, in particular in the high pressure range, is provided with a housing that has a bore hole, a component mounted within the housing such as to oscillate and/or rotate and with a pressure chamber formed within the bore hole. A sealing element surrounding the component adjoins this pressure chamber which can be charged with the medium. An additional metal seal is formed here by the housing and a pressure disc surrounding the component. The outer region is thus tightly closed after the sealing element. In this way, the sealing element is completely tightly encapsulated on the outside.

Abstract: Fluid flow control apparatus for use with fluid valves are disclosed. An apparatus includes a plug for a sliding stem fluid valve. The plug has a first portion slidably coupled to a second portion. The apparatus also includes a cavity formed in an outer circumferential surface of the plug by the first portion and the second portion. A dimension of the cavity changes when the first portion slides relative to the second portion to displace a seal disposed in the cavity. The seal sealingly engages a cage of the fluid valve when the second portion contacts a seat of the fluid valve.

Abstract: A pipe sealing gasket is shown which is designed to be received within a raceway provided within a socket end of a female bell plastic pipe end which is assembled with a mating male spigot pipe end to form a plastic pipe joint. The raceway in the female bell plastic pipe end is preformed during manufacture and the gasket is installed thereafter. The gasket has a rubber body portion which is reinforced by a hard corrugated ring-shaped insert. The hard corrugated ring-shaped insert acts to prevent extrusion of the gasket during a variety of pressure conditions as well as preventing displacement during field assembly.

Abstract: A seal for a blind shear ram is configured to extend between a first carrier and a second carrier of the blind shear ram. The seal includes an outer layer configured to contact at least one of the first carrier and the second carrier to seal a wellbore when the blind shear ram is in a closed position. The outer layer has a first stiffness. The seal also includes an inner layer spaced from the outer layer. The inner layer has a second stiffness. The seal further includes an anti-extrusion structure extending between the inner layer and the outer layer. The anti-extrusion structure has a third stiffness greater than the first stiffness and the second stiffness. The outer layer covers the anti-extrusion structure.

Abstract: The present invention concerns a gasket for quick couplers, in particular for the fluid tightness of the first valve of a male coupler. It is characterised in that it must be a composite gasket, having a toroidal shape and circumferentially comprising an O-Ring at its outer surface. The gasket according to the present invention allows a number of advantages to be achieved in terms of the stability and greater reliability of the gasket, which is not subject to extrusion and crushing phenomena during the coupling and decoupling steps of the pressurised coupler.

Abstract: A sealing device has a seal ring, a first backup ring and a second backup ring. The first backup ring is formed into a triangular cross section while having an axially vertical end surface portion, a cylindrical peripheral surface portion, and an inclined surface portion intersecting the end surface portion and the peripheral surface portion. The second backup ring is formed into a triangular cross section while having an axially vertical end surface portion, a cylindrical peripheral surface portion, and an inclined surface portion in correspondence to the inclined surface portion of the first backup ring. A cut portion is provided in a corner portion where the end surface portion and the inclined surface portion in the first backup ring intersect, and a corner portion where the peripheral surface portion and the inclined surface portion in the second backup ring intersect.

Abstract: A sealing element for a shaft coupling is disclosed. The sealing element may include an annular seal body and a plurality of projections circumferentially spaced around the seal body. One or more of the plurality of projections may include at least one of an axial component extending longitudinally in an axial direction from the seal body and/or a radial component extending radially inwards from the seal body towards the center axis. The sealing element is configured to retrofit into existing standard o-ring grooves and provides optimal lubrication, for example in a spline joint, by keeping the spline joint contact area submerged in lubricant and includes heat and debris removal with lubricant flow-through.

Abstract: The invention features a seal assembly for a high pressure liquid system. The seal assembly includes a seal carrier having abuse portion defining a proximal end, a distal end, and a bore. The seal carrier also includes a seal disposed within the bore of the seal carrier. The seal carrier also includes a backup ring disposed within the bore of the seal carrier. The seal carrier also includes a hoop ring disposed substantially between the seal and the backup ring, the hoop ring having a proximal surface and an outer surface.

Abstract: A solenoid actuated valve (10) holds pressure and volume of an accumulator with low leakage and provides low actuation drag during a release stroke for dumping fluid contents of the accumulator at very low current draw. Two elongate valve members (10a, 10b) are assembled to be movable axially relative to one another with a gland or groove (10c) formed in one of the two valve members (10a). An o-ring (12) located within the groove (10c) is in a non-contacting relationship to the other valve member (10b) when in a non-energized state. An energizer ring (14) located within the groove (10c) can reciprocate axially with respect to the o-ring (12). The energizer ring (14) moves axially toward the o-ring (12) in response to fluid pressure against a surface (14a) of the energizer ring (14) opposite from the o-ring (12) to axially compresses the o-ring (12), causing the o-ring (12) to expand radially outwardly into sealing contact with the other valve member (10b).

Abstract: A gas turbine engine includes a compressor assembly that is rotationally coupled to a shaft. The engine includes a radial diffuser assembly coupled to a shroud of the compressor assembly and positioned to receive compressed air from a centrifugal impeller. The radial diffuser assembly includes a first arcuate wall and a second wall, and a near axial diffuser coupled to the radial diffuser assembly and positioned to receive the compressed air from the radial diffuser assembly. The gas turbine includes a gas seal coupled between the second wall and a wall of the near axial diffuser, the gas seal configured to prevent the compressed air from passing through the seal while allowing relative motion between the radial diffuser assembly and the near axial diffuser.

Abstract: A coupling unit is disclosed which includes a sleeve opening that extends in the longitudinal direction and into which at least one medium-conveying plug element can be at least partially inserted, A support sleeve includes at least one circumferential pocket on an inner side that faces a plug element and defines the sleeve opening transverse to the longitudinal direction. A sliding element is arranged in the pocket and movably transferred from a release position into a coupling position during the insertion of the plug element. A sealing element is arranged between the sliding element and the pocket of the support sleeve in the release position and pre-stressed in the direction of the plug element. The sealing element is released by the sliding element in the coupling position in order to close and seal a potential gap formed between the support sleeve and the plug element.

Abstract: A sealing apparatus includes: a case having a hollow portion; a shaft passing through the hollow portion; and a sealing member sealing between the case and the shaft, and including a resin ring and a ring-shaped rubber cap. The rubber cap includes a base portion and a lip portion. The lip portion includes a first lip contacting the resin ring and a second lip configured to contact an inner peripheral surface of the case. If a pressure of a first chamber of the lip portion side is lower than a pressure of a second chamber at the side of the base portion, the second lip is separated from the case to relieve the pressure of the second chamber to the first chamber. The base portion includes a first restricting surface for restricting the base portion from moving, and a second surface for restricting the base portion from moving.

Abstract: A pressure calibration device can include certain features that allow it to be used with a variety of hydraulic and pneumatic systems. A pressure calibration device can be configured to provide pressure or vacuum, and can have a mode selector for selecting to provide pressure or vacuum. A pressure calibration device can have a volume adjuster configured to modify pressures for hydraulic or pneumatic systems. A pressure calibration device can have a pressure release valve and a bleed valve for adjusting pressure values.

Abstract: An apparatus includes a bearing housing, a shaft assembly that extends through the bearing housing along a shaft axis, an annular groove formed on the shaft assembly, and a piston ring assembly that is engaged with the bearing housing and extends into the groove of the shaft assembly. The piston ring assembly includes a first ring portion and a second ring portion. The first ring portion has a first contact face that is oriented at a non-perpendicular with respect to the shaft axis, and the second ring portion has a second contact face that is oriented at a non-perpendicular angle with respect to the shaft axis and is engageable with the first contact face.

Abstract: A plunger seal and a backup ring are provided at a portion of a pump chamber through which a plunger is inserted. A back face of the backup ring is supported on a wall face of a cleaning chamber. The backup ring is a combined backup ring including two resin layers, i.e., a deformable resin layer and a non-deformable resin layer. A face of the backup ring in contact with the plunger seal is made up of a face of the deformable resin layer and an inner peripheral face is made up of a face of the non-deformable resin layer. The deformable resin layer has a higher elastic modulus than the plunger seal and having such an elastic modulus as to be able to absorb deformation of the plunger seal. The non-deformable resin layer has a higher elastic modulus than resin of the deformable resin layer.

Abstract: A shaft sealing device comprising: a first member; a second member provided with a through-hole through which the first member passes; a sealing member configured to seal a gap between the through-hole and the first member; a rotation restricting part restricting relative rotation between the first and second members; and an axial displacement restricting part restricting the axial displacement of the sealing member. The rotation restricting part includes a first contact portion provided on the first member, a second contact portion provided on the sealing member and an inclined surface included on the first contact portion. The axial displacement restricting part includes a stopper surface. When the sealing member rotates in one direction relative to the second member by being dragged by the first member, the sealing member contacts the stopper surface to restrict the axial displacement of the sealing member.

Abstract: A valve includes a stem seal assembly that prevent fluid flow in a first direction and vents in a second direction opposite the first direction. The assembly includes a packing assembly positioned within a valve stem opening of a valve body of the valve to seal a valve stem to the valve body. The packing assembly includes a first seal and a second seal preventing passage of fluid from a body cavity of the valve body to an exterior of the valve body along the valve stem while venting fluid from an exterior of the valve body to the body cavity along the valve stem. The packing assembly isolates the first seal and the second seal so that a load applied to the first seal ring is not transferred to the second seal ring.

Abstract: A spring (1) with fluid (2) including a containment body (3) having an inner chamber (4) in which the fluid (2) is inserted, a compression unit (8) slidably mounted on the containment body (3) and a sealing gasket (11) for the fluid (2) interposed between the containment body (3) and the compression unit (8) for preventing escape of the fluid (2) from the inner chamber (4); the spring (1) includes at least one closed loop (13) surrounding the compression unit (8), connected to the containment body (3) and in contact with the sealing gasket (11) so as to limit the deformation of the latter.

Abstract: Seal ring assemblies for use with rotary valves and methods to manufacture the same are disclosed. A seal ring assembly is described that includes a ring-shaped seal to be fixed within the rotary valve, where the seal enables the sealing engagement of a control member with a flow control aperture. The seal is compressed between a first seal clamp and a second seal clamp by a compressive force maintained by a plurality of fasteners extending through the seal and fixed to the first and second seal clamps.

Abstract: Seal assemblies for use with fluid valves are described. An example valve trim assembly for use with fluid valves includes a cage and a seal assembly to be positioned in at least one of the cage, a cage retainer or a plug. The seal assembly includes a first seal and a first scraper. The first seal is to provide a load to the first scraper to prevent the ingress of contaminate to a dynamic sealing surface to be engaged by the first seal. Additionally, the seal assembly includes a second seal and a second scraper. The second seal is to provide a load to the second scraper. Further, the seal assembly includes a spacer between the first and second seals.

Abstract: A seal arrangement for providing a fluid seal of an annulus between two conforming surfaces such as a stem and a bore. The seal arrangement may include a pair of packing support rings. Preferably, two pairs of the packing support rings are used in order to provide double ended or two sided axial support for the packing. The first and second support rings support a load on the packing during normal or rated temperature use, with preferably an interference fit with the stem to resist extrusion of the packing along the stem. The support rings may be nested together and comprises different materials. For example, one support ring may comprise metal and the other support ring comprise a softer material such as a polymer or elastomer. An example of a packing material is a fire resistant material. The metal support ring may be used to maintain load on the fire resistant packing in the event that the other support ring has been destroyed by fire or other cataclysmic event.

Abstract: A sealing array for positioning in an annular space between tubular members to provide a seal therebetween. The sealing array includes a pair of oppositely disposed backup rings, each defining a primary outer seal member of the sealing array. A pair of rigid cap rings is disposed between the backup rings. Each cap ring has a substantially planar surface and an oppositely disposed surface that engages one of the backup rings to energize the backup rings upon the application of sufficient pressure. The cap rings are sized to form controlled extrusion gaps with both tubular members. An energizing element is disposed between the planar surfaces of the cap rings. The energizing element engages a planar surface of at least one of the cap rings and seals the extrusion gaps associated with the engaged cap ring upon the application of sufficient pressure.

Abstract: A seal assembly for use with valves is described. An example seal assembly includes a first seal and a second seal opposite the first seal. The first and second seals are to sealingly engage a closure member of a valve and a sealing surface opposite the closure member. A spacer ring is disposed between the first and second seals to prevent the first and second seals from contacting each other. Additionally, the spacer ring is sized so that the spacer ring does not contact the closure member or the sealing surface.

Abstract: An elastomeric or polymeric seal assembly (10) includes an annular elastomeric or polymeric sealing element (60), an internal circumferential surface of which sealingly engaging a first component (12), the sealing element abutting a radial annular face of a second component (16) and an external circumferential surface of the sealing element sealingly engaging an internal circumferential surface of a second component, a vent (92) being provided in the internal circumferential surface of the second component adjacent to the radial face, to vent the space between the external circumferential surface of the sealing element and the internal circumferential surface of the second component, an inlet to the vent being defined by an annular groove (88) in the internal circumferential surface of the second component, an annular helically wound element (94) being provided in the annular groove to prevent extrusion of the sealing element into the vent, the helically wound element being formed from a strip of material of

Abstract: The present invention relates to seal ring back-up devices suitable for use on glands in sealing systems. In particular, the present invention relates to seal ring back-up devices that have been designed to fit into essentially all types of glands and close extrusion gaps. Some embodiments of the present invention provide a seal ring back-up device having an annular body having an inner diameter, an outer diameter, and a scarf cut; and where the annular body is configured to fit a gland and engage a seal ring.

Abstract: To prevent breakage of a sealing device having a main sealing body installed within an annular installing groove (31) formed in one member (3) to slidably and concentrically contact with the other member (2) and a backup ring (12) arranged at a non-sealing space side of said main sealing body, a height (h1±?h1) of said backup ring (12) in a facing direction of a bottom surface (31a) of said installing groove (31) to the other member (2) is greater than a facing distance (L±?L) between the bottom surface (31a) and the other member (2), and said backup ring (12) has a cross-sectional shape which is symmetrical in a thickness direction thereof, and has an easily compressible part (12a) which can be compressed to the extent of the difference (x) between said height (h1±?h1) and said facing distance (L±?L).

Abstract: An extrusion resistant ring that is radially expandable and contactable to accommodate the relative movement of two joined bodies relative to each other. The extrusion resistant ring in combination with an elastomeric diaphragm provides a high pressure seal for down-hole oil drilling apparatus.

Abstract: Device, system, and method are described directed to seal assemblies with support to reduce seal extrusion under high to very high pressure changes due to repeated piston reciprocating movement. In some examples, concave features are incorporated on the inner and outer edges of support and backup ring elements to support and hug the preceding element and constrain extrusion, as well as utilizing multiple contact points on certain elements in order to reduce friction against the dynamic surface. The seal assemblies described herein can also incorporate bearing surfaces to reduce damage to seal ID due to off-axis floating rod, such as incorporating one or more multi-point contacts to reduce friction.

Abstract: A high pressure piston for use within a liner sleeve of a reciprocating pump comprises a dual-durometer elastomeric seal having first and second coaxial seal sections and, in certain embodiments, a circumferential bearing ring. Interactions of the seal components, including seal elastomers, result in stress redistribution within the seal which maintains sealing preload, with corresponding improved extrusion resistance and seal durability. When a bearing ring is present, a pump's pressure stroke causes at least a portion of the bearing ring to elastically expand radially to narrow or close the extrusion gap, thus tending to block elastomer extrusion by establishing sliding contact between the bearing ring's external surface and the liner. On the pump's return stroke the slightly wider extrusion gap allows cooling water directed generally toward the proximal flange of the piston hub to better cleanse, as well as cool, the liner wall.

Abstract: A seal assembly is provided for sealing a gap with a high pressure side and a low pressure side between a first component and a second component. The seal assembly can include a primary seal configured to be arranged on the first component and spanning the gap on the high pressure side between the first and second component; and a backup ring configured to be arranged on the first component adjacent the primary seal on the low pressure side. The backup ring includes an inner diameter and a scarf cut slit at an angle that is a function of the inner diameter of the backup ring.

Abstract: A sealing assembly for a shaft includes a sealing component, a first ring, a second ring, and at least one energizer. The first ring is annularly disposed about the shaft, the first ring having at least one first protuberance interfittable with the sealing component. The second ring is annularly disposed about the shaft in facing opposition to the first ring, the second ring having at least one second protuberance interfittable with the sealing component. The at least one energizer energizes the seal component, the at least one energizer being adjacent the at least one first protuberance or the at least one second protuberance.

Abstract: A seal backup ring is provided with undulating surfaces which create circumferential convergence with a relatively rotatable surface. The backup ring is configured so that differential pressure acting across a rotary seal forces portions of the backup ring against the relatively rotatable surface, closing, or substantially closing, the extrusion gap that the rotary seal is exposed to. In response to relative rotation between the backup ring and the mating relatively rotatable surface, the circumferential convergence promotes hydrodynamic lubrication within the dynamic interface that exists between the backup ring and the relatively rotatable surface. The modulus of elasticity of the backup ring is greater than the modulus of elasticity of the rotary seal.

Abstract: A helical backup element includes a tubular body of material and a helical opening in the tubular body.

Abstract: To reduce a shaft insertion load and prevent extrusion of a seal ring to the low pressure side, a sealing device has a seal ring in an installation groove formed on a shaft to have a tapered groove bottom section and a backup ring having a tapered section corresponding to the tapered groove bottom section, a gap is provided between a side wall surface at the low-pressure side of the mounting groove and a side end surface of the backup ring, a peripheral surface of the backup ring at the opposite side of the tapered section has a tapered surface which comes closer to a peripheral surface of a housing at the low-pressure side, and the tapered section is formed to have a two-staged taper.