Patent ID: 7219580

Claim:
A power tong comprising: (a) a ring gear having a central pipe-receiving region, the ring gear having an inner surface facing such central region; (b) a camming surface formed on the inner surface of the ring gear; (c) twin cage plates rotationally mounted with respect to the ring gear on opposite sides of the ring gear, said cage plates being free to rotate with respect to the ring gear, but being constrained to maintain a center of rotation corresponding to the center of the ring gear; (d) pipe receiving jaw means mounted between said cage plates and positioned to receive pipe to be positioned centrally within the ring gear; (e) at least one jaw assembly supported between the upper and lower cage plates and carrying a jaw positioned to bear, upon advancement towards a pipe-engaging position in the central region of the tong, against pipe to be placed therein, said jaw assembly comprising a circular roller bearing passageway; (f) a cam follower means carried by the jaw assembly and, positioned to contact and advance along the camming surface to effect advancement of the jaw into said pipe-engaging position when the ring gear is rotated with respect to the jaw assembly; wherein the cam follower means comprises a plurality of roller elements that are constrained to circulate in a circulating path along said roller bearing passageway, said circulating path comprising a portion which exposes the roller elements so that they are directed towards the camming surface, and said jaw assembly carrying an alignment guide provided with indexing elements positioned to extend into the roller bearing passageway and maintain the cylindrical roller elements in an orientation that ensures that their longitudinal axes lie perpendicularly to their path of travel.