| 摘要 |
<p>A cable-pulling system for moving a cable through a conduit includes a birdie connected to the cable and formed to be located within the conduit, to be movable through the conduit and to create a fluid seal within said conduit. A supply of pressurized fluid is connected to one end of the conduit to create a pressurized region behind the birdie to urge the birdie to move to the opposite end of the conduit. Cable is supplied to permit the movement of the birdie through the conduit; however, the cable is supplied only in response to the existence of the pressurized region, and upon loss of the pressurized region the cable is no longer supplied and movement of the birdie is prevented.</p> |
