| 摘要 |
<p>POWERED BACK-UP TONGS, A powered back-up assembly is provided for securing a pipe against rotation. A plurality of heads are supported by a cage plate assembly, and are brought into gripping engagement with the pipe by rotating the cage plate assembly relative to a cam ring fixed to the body of the tong body. The cage plate assembly is rotated by a pair of hydraulic cylinders each connected at one end to a bar pivotably connected to the tong body. A third hydraulic cylinder interconnected between adjacent upper and lower tong bodies may be employed to achieve a reliable scissors tong, whereby the body of the upper tong is rotatable relative to the body of the lower tong.</p> |
