DRILLING POWER TONGS Russian patent published in 1995 - IPC

FIELD: well drilling. SUBSTANCE: drilling power tongs include closed pipe catching mechanism in form of concentric inner and outer rings installed for mutual motion, articulated levers and hold-down slips. Tongs have changeable jaws with supporting extensible force rollers. Inner ring is changeable. Articulated levers are bell-cranks with supporting deflecting roller on one arm and changeable jaw is hinged to the other arm. Outer ring has groups of cams rigidly connected to ring inner surface at two different levels. Cams are installed for interaction with respective extensible force and support deflecting rollers. Catching slips are installed on changeable jaws. Changeable jaws have rigidly attached catching slips for reliable catching of pipes of maximum diameter for given tongs. Changeable jaws are provided with floating holders with cylindrical supporting surface for reliable catching of pipes of minimum diameter for given tongs. Floating holders are installed for turning in cylindrical sockets made in changeable jaws, and catching slips are rigidly secured in changeable floating holders. EFFECT: higher efficiency. 3 cl, 7 dwg