Patent ID: 7237456
Filing Date: 2007-07-03
Classification: E21B

Abstract:
1. A power tong for rotating a tubular to makeup or breakout a threaded connection, comprising: a tong frame having a central opening for receiving the tubular, an upper frame plate, and a lower frame plate; a ring rotatably mounted on the frame about a center of rotation, the ring defining a pair of cam surfaces on an interior surface of the ring, each cam surface having a neutral cam portion, a makeup cam portion and a breakout cam portion, the pair of cam surfaces being spaced on the ring circumferentially approximately 180° apart; a cage plate assembly rotatable within the ring; a plurality of dies supported on the cage plate and adapted to move radially to engage and disengage the tubular in response to movement of the dies along the cam surfaces; an arcuate brake band spaced opposite the lower frame plate with respect to the upper frame plate for frictional engagement with the cage plate assembly; an arcuate plate fixed to the cage plate and extending upward from the cage plate for engagement with the brake band; a fluid powered cylinder for tensioning the brake band to selectively increase frictional forces between the brake band and the cage plate assembly; a drive mechanism for rotating the ring, the cage plate assembly and the dies to rotate the tubular; and the neutral cam portion of each cam surface is spaced radially outward from an imaginary circle intersecting radially inward edges of the throat of the cage plate by a spacing of at least 25% of the imaginary circle diameter.