| 摘要 |
<p>A bolt tensioner (1) comprising a body (2) having a central screw-threaded bore (5) for threaded engagement with a bolt projecting from a load bearing surface, and including at least one piston (4) in the body which is located within a cylinder for displacement in a direction parallel to the longitudinal axis of the central bore (5) and operate a to exert a thrust force on the load bearing surface; further comprising: a tensioner body (2) having an upper end and a lower end and a central bore defining an outer wall of a cylinder (3); a piston (4) located within the bore (3) defined by the body (2) and having a central co-axial bore (5) suitable for receiving a threaded stud and further in which the outer face of the piston is stepped such that the piston and the wall of the cylinder define a first chamber (7) and a second chamber (8); a first passage (10) extending from a first inlet port (11) to the first chamber (7) for introducing fluid to the first chamber (7); a second passage (12) extending from a second inlet port (13) to the second chamber (8) for introducing fluid to the second chamber (8); and in which the first (7) and second (8) chambers are so arranged that pressurising the first chamber (7) acts to move the piston (4) towards the upper end of the body (2) as the volume of the first chamber expand (7) and pressurising the second chamber (8) acts to move the piston towards the lower end of the body (2) as the volume of the second chamber (8) increases. Accordingly, the piston can be extended by means of hydraulic fluid to define a hydraulic bolt tensioner but use a pneumatic fluid supply to retract the piston.</p> |
