| 摘要 |
The present invention relates to power tongs used in the oil and gas industry to make up and break apart the joints on drill pipe and other tubular members. The invention provides a selectively releasable braking apparatus for a power tong. The selectively releasable braking apparatus comprises a braking ring operatively connected to a cage plate of the power tong and a braking surface mechanically connected to the cage plate. The apparatus further has a gripping device capable of selectively gripping and holding the braking surface and has a gear train transferring torque from said brake ring to said braking surface. Power tongs also typically have a throat, a ring gear with an opening, and a cage plate with an opening. The present invention further provides an apparatus for aligning the openings in the ring gear and the cage plate with the throat of the power tong and remotely reversing the direction of rotation of the ring gear and cage plate. The apparatus comprises a stop device preventing relative rotation of the ring gear and the cage plate until a preselected torque load is placed on said stop device. The apparatus also has a selectively releasable cage plate brake and a cage plate latch selectively preventing rotation of the cage plate.
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