| 摘要 |
<p>A valve (10) includes a housing (12) having an inlet (14) and an outlet (16) for the flow of a first fluid therethrough. A cup-shaped cover dome (18) is attached to the housing. The cover dome has a cylindrical bore (24). A valve stem (32) has a plug (36) to regulate the flow of the first fluid through the housing. A piston (26) is connected to the valve stem. The piston is reciprocatably received within the cylindrical bore of the cover dome to define a first chamber (42) disposed between the piston and the housing and a second chamber (44) disposed between the piston and the cover dome. The piston has a sliding circumferential surface (30) received in an inner surface of the cylindrical bore. The sliding circumferential surface is adapted to fuse with the inner surface of the bore at a predetermined fused temperature, so that the piston fuses with respect to the cylinder along the sliding circumferential surface thereby effectively creating a gas-tight permanent closure between the first chamber and the second chamber, thereby preventing the first fluid from escaping from the first chamber into the second chamber.</p> |
