| 摘要 |
1. A differential hydraulic jack, in particular for the control of high-voltage electric circuit-breakers, of the type in which the jack piston (4) is unprovided with any packing ring forming a seal with the internal surface of the jack cylinder (2), characterized in that the wall (32) of the cylinder (2) is pierced by a plurality of through-bores (34) extending in spaced relation over a distance corresponding to the range of travel of the piston (4) ; a displacement detector (36) is housed within each through-bore (34) aforesaid with its sensitive detection element (38) directed toward the interior of the cylinder (2) in order to be influenced by the passage of the piston (4) opposite to the corresponding through-bore (34) ; sealing means (42-42') are provided between each detector and the cylinder wall (32) in order to ensure integrity of leak-tightness of the cylinder at the high pressure with prevails within said cylinder ; and the output leads (44) of the detectors are connected to an equipment (46) unit for checking the position of the piston (4) within the cylinder (2). |
