| 摘要 |
<p>The principal piston rapidly closes the press without displacing large volumes of oil by maintaining passages in the piston open. When during closure a higher resistance is encountered the passages are closed and hydraulic pressure acts over the full area of the cylinder. The valve attached to the principal piston is held open during the rapid closure of the press by means of a calibrated spring. When resistance is encountered at complete closure compression of the spring closes the valve and the total hydraulic pressure acts on the piston. The jack may be supplied with fluid under a permanent calculated pressure. Opt. the fluid may be gaseous, in which case it is stored in a reservoir on opening the press. The press permits a great reduction in the volume of oil displaced during closure and a consequent economy in pipework and pump capacity.</p> |
