Patent ID: 6990876

Claim:
A power tong apparatus for rotating a pipe, the apparatus comprising: a tong housing defining a central housing aperture; a ring gear, having an outer periphery, and having an inner periphery defining a central ring aperture, the ring gear rotatably mounted in the tong housing such that an inner portion thereof extends into the central housing aperture such that the central ring aperture is inside the central housing aperture; a top cage plate positioned above a top surface of the inner portion of the ring gear and a corresponding bottom cage plate positioned below a bottom surface of the inner portion of the ring gear, the top and bottom cage plates defining a central cage aperture oriented such that the central cage aperture is inside the central ring aperture, the top and bottom cage plates fastened together to form a cage rotatable with respect to the tong housing and the ring gear; at least one jaw pivotally attached to the cage and bearing against the inner periphery of the ring gear and operative to grip the pipe when the ring gear is rotated with respect to the cage; and a drive operative to rotate the ring gear; wherein the ring gear and cage rotate about a substantially vertical rotational axis located substantially in the center of the central cage aperture; and wherein the top and bottom cage plates are fastened together by a fastener extending through a slot in the ring gear located between the inner and outer peripheries of the ring gear, such that the cage plates can rotate with respect to the ring gear through a limited arc, the fastener operative to maintain the cage plates in a fixed vertical relationship relative to each other.