Abstract: Provided is an actuator including a ball-type thrust amplifier therein that controls a valve in which a high-pressure fluid flows, and having less wear between members and a long lifespan. This actuator for a valve includes a thrust amplification mechanism therein, in which the thrust amplification mechanism includes a disk, a ball presser, a stem, and a plurality of balls that are sandwiched by and in contact with an upper surface of the disk, a tapered surface of the ball presser, and a tapered surface of the stem and disposed to move outward as the stem moves downward, the surfaces of the parts constituting the thrust amplification mechanism are coated with grease containing an additive, and the additive of the grease includes at least chloroalkane.

Abstract: Each of ridges 7 on respective opposite side surfaces of a gasket 4 has a trapezoidal cross sectional shape defined by an outer tapered face 7a providing an outer peripheral surface, an inner tapered face 7b providing an inner peripheral surface and a flat face 7c providing a top end surface. The hardness of the gasket 4, the angle between the tapered faces 7a, 7b of the ridge 7, the height of the ridge 7 and the area of the flat top end face 7c of the ridge are so determined that the value of thrust for tightening up the coupling is between a predetermined minimum value and a predetermined maximum value.

Abstract: Each of ridges 7 on respective opposite side surfaces of a gasket 4 has a trapezoidal cross sectional shape defined by an outer tapered face 7a providing an outer peripheral surface, an inner tapered face 7b providing an inner peripheral surface and a flat face 7c providing a top end surface. The hardness of the gasket 4, the angle between the tapered faces 7a, 7b of the ridge 7, the height of the ridge 7 and the area of the flat top end face 7c of the ridge are so determined that the value of thrust for tightening up the coupling is between a predetermined minimum value and a predetermined maximum value.

Abstract: Each of ridges 7 on respective opposite side surfaces of a gasket 4 has a trapezoidal cross sectional shape defined by an outer tapered face 7a providing an outer peripheral surface, an inner tapered face 7b providing an inner peripheral surface and a flat face 7c providing a top end surface. The hardness of the gasket 4, the angle between the tapered faces 7a, 7b of the ridge 7, the height of the ridge 7 and the area of the flat top end face 7c of the ridge are so determined that the value of thrust for tightening up the coupling is between a predetermined minimum value and a predetermined maximum value.

Abstract: Each of ridges 7 on respective opposite side surfaces of a gasket 4 has a trapezoidal cross sectional shape defined by an outer tapered face 7a providing an outer peripheral surface, an inner tapered face 7b providing an inner peripheral surface and a flat face 7c providing a top end surface.

Abstract: A method for facilitating fabrication of a coupling member includes a first step of boring one of upwardly open, passageways, a communication passageway and an auxiliary passageway in a body block, a second step of inserting a closure member into the auxiliary passageway, a third step of welding the closure member to the inner peripheral body portion defining the auxiliary passageway, and a fourth step of boring the other upwardly open passageway in the body block. The closure member is inserted in the second step so as to be positioned at least party in the portion where the other upwardly open passageway is to be formed.