A gasket has an annular gasket base extending circumferentially about a gasket axis. A central flange extends inwardly away from the gasket base toward the gasket axis. The central flange has an apex positioned at a first distance from the gasket axis. A first arm is spaced apart from the central flange and extends radially and inwardly away from the gasket base toward the gasket axis. The first arm includes a first sealing portion. The first sealing portion defines a first sealing surface spaced apart from the gasket axis by a second distance which is greater than the first distance. A second arm is spaced apart from the central flange and extends radially and inwardly away from the gasket base toward the gasket axis. The second arm includes a second sealing portion defining a second sealing surface.

A sealing ring provides a fluid seal between a first flange and a second flange. The sealing ring forms a tubular element and includes a tapering wall member defining an interior funnel-shaped through-going opening extending axially and tapering from a proximal end to a distal end. The tapering wall member is made from a resilient material proving an axial deflection of the tapering wall member when exposed to an axial force.

A sealing ring provides a fluid seal between a first flange and a second flange. The sealing ring forms a tubular element and includes a tapering wall member defining an interior funnel-shaped through-going opening extending axially and tapering from a proximal end to a distal end. The tapering wall member is made from a resilient material proving an axial deflection of the tapering wall member when exposed to an axial force.

An arrangement structure for a seal member includes: a first member having a first mating surface and provided with a groove portion; a second member having a second mating surface, and configured to move relatively to the first member; and an annular seal member fitted into the groove portion, providing sealing between the first member and the second member, and serving as a partition between an atmosphere-side space and a pressurized-side space. The seal member includes a plurality of first protruding portions protruding toward the second mating surface and aligned from the atmosphere-side space toward the pressurized-side space. The seal member has such a shape that, in a state of not being fitted into the groove portion, a protrusion height of the first protruding portion increases in stages from the first protruding portion arranged close to the pressurized-side space toward the first protruding portion arranged close to the atmosphere-side space.

An arrangement structure for a seal member includes: a first member having a first mating surface and provided with a groove portion; a second member having a second mating surface, and configured to move relatively to the first member; and an annular seal member fitted into the groove portion, providing sealing between the first member and the second member, and serving as a partition between an atmosphere-side space and a pressurized-side space. The seal member includes a plurality of first protruding portions protruding toward the second mating surface and aligned from the atmosphere-side space toward the pressurized-side space. The seal member has such a shape that, in a state of not being fitted into the groove portion, a protrusion height of the first protruding portion increases in stages from the first protruding portion arranged close to the pressurized-side space toward the first protruding portion arranged close to the atmosphere-side space.

A seal structure between an oil outlet formed in a first case and an oil inlet formed in a second case and having an end face facing an end face of the oil outlet with a clearance between the end faces, the seal structure including an annular first seal disposed in an increased-diameter hole, which is formed on an outlet side or an inlet side of an oil passage in one of the oil outlet and the oil inlet and has a larger diameter than the oil passage, such that the first seal contacts a step surface located at a boundary between the oil passage and the increased-diameter hole; and an annular second seal harder than the first seal and disposed in the increased-diameter hole such that the second seal contacts the first seal and the end face of the other of the oil outlet and the oil inlet.

A seal structure that keeps a needle from sliding with respect to a seal and is easily detachable, and a device having the seal structure. A needle of a valve device is inserted through a seal. A valve device includes a fluid chamber having an outflow hole and au inflow hole, and the needle of which fore end reciprocates in the fluid chamber. The seal includes a main body made of an elastic body having a needle fitting insertion hole formed for the needle to be inserted and fit into. A flange portion is made of an elastic body annularly extending from the main body in a radial direction outward. One end opening diameter (D.sub.3) of the needle fitting insertion hole is smaller than the other end opening diameter (D.sub.2) of the needle fitting insertion hole.

A piston and cylinder assembly structured to reduce breakaway friction (stiction) upon movement of the piston within the cylinder. The assembly includes a cylinder housing, a piston having a piston crown with a top face and one or more peripheral grooves, and an O-ring positioned on the piston in each of the one or more peripheral grooves. The piston crown incorporates one or more passageways extending from a space above the piston to a location within the peripheral groove inside of (behind) the O-ring. An increase in a volume of fluid in the chamber above the piston directs fluid through the passageways into the peripheral groove, thereby pressing the O-ring against the cylinder wall. A double acting piston embodiment uses at least two O-rings positioned within at least two grooves, each with associated fluid flow passageways into the grooves behind the O-rings.

A sealing assembly for use downhole may include a plug having a first end and a second end opposite the first end. The plug may have an expandable sealing member positioned between the first end and the second end of the plug. The expandable sealing member having a run-in-hole diameter and an expanded diameter that is greater than the run-in-hole diameter. A support device may extending at least partially between a first end of the plug and the expandable sealing member. The support device may include a recess. An elastomeric material may be positioned at least partially within the recess of the support device. A cover may be positioned at least partially over the support device for reducing extrusion of the elastomeric material from within the recess of the support device in the expanded diameter.

A sealing assembly for use downhole may include a plug having a first end and a second end opposite the first end. The plug may have an expandable sealing member positioned between the first end and the second end of the plug. The expandable sealing member having a run-in-hole diameter and an expanded diameter that is greater than the run-in-hole diameter. A support device may extending at least partially between a first end of the plug and the expandable sealing member. The support device may include a recess. An elastomeric material may be positioned at least partially within the recess of the support device. A cover may be positioned at least partially over the support device for reducing extrusion of the elastomeric material from within the recess of the support device in the expanded diameter.