A pressure back-up valve (300) includes a release piston (320) movable between first and second stop positions and a closing body (340) movable to a closing position in which this separates first and second connection pressure chambers (327, 326) when the release piston (320) is in a first stop position. The release piston (320) moves the closing body (340), in the second stop position, into an opening position. The release piston (320) is pressurizable on a first pressure surface (A1) from a first side via a third connection pressure chamber (324) and on a second pressure surface (A2) from a second side via a second connection pressure chamber (326). The closing body (340) is pressurized, in the closing position, from a first side via the second connection pressure chamber (326) on a first pressure surface (A4) and from a second side via the first connection pressure chamber (327) on a second pressure surface (A3) of the closing body (34).

An improved one-piece cage and an improved insert and their assembly create a zero-restriction fluid flow ball check valve. The improved insert for ball and seat valve comprises external screw threads on the base of the insert and have circumferentially spaced ribs extending upwards and converging towards the longitudinal axis of the insert, forming a hemi-spherical ball stop and arched side openings. The inside diameter of the insert bore is substantially equal to the ball valve diameter preventing the ball from rattling when positioned in the improved insert's passageway during the fluid flow. The outside diameter of the ribs is less than the inside diameter of the improved one-piece cage cavity producing a zero-restriction fluid flow ball check valve in comparison to the volumetric fluid flow through the annular seat. The improved cage that receives the improved insert is a one piece in construction and has internal threads that correspond to the external threads on the improved insert. The insert is assembled inside the cage using a screw thread connection and simultaneously forming a fluid seal between the insert and the cage.

An improved one-piece cage and an improved insert and their assembly create a zero-restriction fluid flow ball check valve. The improved insert for ball and seat valve comprises external screw threads on the base of the insert and have circumferentially spaced ribs extending upwards and converging towards the longitudinal axis of the insert, forming a hemi-spherical ball stop and arched side openings. The inside diameter of the insert bore is substantially equal to the ball valve diameter preventing the ball from rattling when positioned in the improved insert's passageway during the fluid flow. The outside diameter of the ribs is less than the inside diameter of the improved one-piece cage cavity producing a zero-restriction fluid flow ball check valve in comparison to the volumetric fluid flow through the annular seat. The improved cage that receives the improved insert is a one piece in construction and has internal threads that correspond to the external threads on the improved insert. The insert is assembled inside the cage using a screw thread connection and simultaneously forming a fluid seal between the insert and the cage.

A pipeline assembly includes a hollow body having a first opening and a second opening. A valve port fluidly coupled to the first opening is provided on the body and a valve port seat is disposed in the valve port. A shutter is urged against the valve port seat by a spring fluidly de-coupling the second opening from the first opening and the valve port. A valve plug includes a check valve. When the valve plug is disposed in the valve port, the valve plug decouples the shutter from the valve port seat to fluidly couple the first opening and the second opening with a fluid flow in only a first direction when the check valve is in an open condition.

A pipeline assembly includes a hollow body having a first opening and a second opening. A valve port fluidly coupled to the first opening is provided on the body and a valve port seat is disposed in the valve port. A shutter is urged against the valve port seat by a spring fluidly de-coupling the second opening from the first opening and the valve port. A valve plug includes a check valve. When the valve plug is disposed in the valve port, the valve plug decouples the shutter from the valve port seat to fluidly couple the first opening and the second opening with a fluid flow in only a first direction when the check valve is in an open condition.

A negative pressure pipeline opening-and-closing device includes a blocking member and a buoyant member. The buoyant member comprises two floats and a connection rod connected to the two floats. The liquid reservoir is provided with a guide therein, and the guide confines the two floats, the blocking member and the liquid outlet port in the same vertical line. A limiting member is arranged between the two floats and is fixed to an inner wall of the liquid reservoir. A maximum distance between the limiting member and a top wall of a lower float of the two floats is smaller than a maximum distance between a top wall of an upper float of the two floats and a top wall of the liquid reservoir. The negative pressure pipeline opening-and-closing device can replace an existing electrically controlled valve. Therefore, the cost is reduced, the maintenance is convenient and service life is prolonged.

A pressure back-up valve (300) includes a release piston (320) movable between first and second stop positions and a closing body (340) movable to a closing position in which this separates first and second connection pressure chambers (327, 326) when the release piston (320) is in a first stop position. The release piston (320) moves the closing body (340), in the second stop position, into an opening position. The release piston (320) is pressurizable on a first pressure surface (A1) from a first side via a third connection pressure chamber (324) and on a second pressure surface (A2) from a second side via a second connection pressure chamber (326). The closing body (340) is pressurized, in the closing position, from a first side via the second connection pressure chamber (326) on a first pressure surface (A4) and from a second side via the first connection pressure chamber (327) on a second pressure surface (A3) of the closing body (34).

To provide a simple-structured check valve unit that allows for retention of a seat relief in an attachment part of a plunger bore, facilitates production without increasing components, and prevents deformation of the plunger. The check valve unit includes the seat relief and a cap member. The plunger has an outlet relief hole in the attachment part for communication between the inside and outside of the plunger. The cap member includes a cap top, an oil flow portion, and a skirt wall. The skirt wall includes a plurality of outwardly raised contact surfaces and a plurality of inwardly raised contact surfaces. The circumscribed circle of the outwardly raised contact surfaces has a larger radius than the inside radius of the attachment part, and the inscribed circle of the inwardly raised contact surfaces has a smaller radius than the outside radius of an engaging part of the seat relief.

A press-fit check valve for a hydraulic tensioner includes a retainer, a seat, a ball, and a spring. The seat of the check valve is press-fit against the wall of the check valve counterbore of the hydraulic tensioner body. In some embodiments, the seat is cup-shaped to provide a predetermined level of press force retention of the press-fit check valve. In some embodiments, the seat includes a plurality of legs separated by leg openings. In some embodiments, a backflow path is provided past the press-fit check valve by a combination of the leg openings and at least one backflow slot through a flange of the retainer. In some embodiments, a lip at the outer end of the check valve counterbore prevents the seat from backing out of the check valve counterbore.

To provide a tensioner that improves, with a simple structure, maintenance operation efficiency, as well as enhances the sealing performance and the degree of freedom of check valve design. Either a plunger or a housing has a valve setting hole for disposing a check valve therein, and a valve movement restricting part that restricts movement of the check valve, disposed in the valve setting hole, toward an oil supply passage. A coil spring includes a small-diameter part and a large-diameter part continuous with the small-diameter part and disposed in contact with the check valve. The coil spring is disposed so as to urge the check valve toward the oil supply passage. The largest diameter of the large-diameter part is set larger than the inner diameter of the valve setting hole.