Power tong cage plate lock system
An open-throat power tong for making up or breaking apart an oilfield tubular connection, includes a cage plate lock system. The lock system connected to each cage plate extends across the space provided by the open throat in the cage plate when locked in the closed position. This provides support for the cage plates, resisting their tendency for expansion. The cage plates are mounted on the ring gear for rotation about a common center. The support provided to the cage plates for resisting expansion is communicated to the ring gear, thus providing support to the ring gear against expansion.
1. A power tong for rotating a pipe to make up or break up a threaded joint, comprising:
a) a tong body having a center point and a tong body open throat;
b) a ring gear rotatably supported by the tong body and having a ring gear open throat formed therein, the ring gear being positionable about the center point for alignment of the ring gear open throat with the tong body open throat;
c) twin cage plates rotationally mounted with respect to the ring gear on opposite sides of the ring gear, the cage plates each having a cage plate open throat formed therein that is positionable for alignment with the tong body open throat, said cage plates being free to rotate with respect to the ring gear about the center point, but being constrained to maintain a center of rotation substantially corresponding to the center point ; and
d) a cage plate locking means connected to an outer surface of each cage plate adjacent a side of the respective cage plate open throat therein, such cage plate locking means being positionable to extend from one side of the open throat of the cage plate across to the other side of the open throat of the cage plate for restraining the open throat of the cage plate from expansion, thus providing resistance to expansion of the ring gear when the power tong is engaging a pipe.
2. The power tong as claimed in claim 1 , wherein the cage plate locking means comprises two locking arms that are coupled by coupling means to swing in unison across the open throats of the two cage plates.
3. The power tong as claimed in claim 2 , wherein the two locking arms each carry a removable engagement means to secure each locking arm to the outer surface of the respective cage plates when the cage plate locking system is in the closed position.
4. The power tong as claimed in claim 3 , wherein the removable engagement means comprises hooked portions carried by the locking aims at one of their respective ends and the respective cage plates each carry pin means extending from each cage plate for engagement with the corresponding hooked portions of the respective locking arms when the cage plate locking system is in the closed position.
5. The power tong as claimed in claim 4 , comprising actuation means for positioning the locking arms respectively in closed and opened positions.
6. The power tong as claimed in claim 2 wherein the locking arms and coupling means are positioned on the power tong to swing clear of the power tong open throat when the locking arms are in their open position.
7. The power tong as claimed in claim 1 wherein the cage plates are mounted to the ring gear through a friction-minimizing ring and track coupling to enable the cage plate to supply support to the ring gear, thereby absorbing part of the spreading forces that would otherwise be applied to the ring gear.