A power tong system is used to make up and break out threaded pipe connections. Rotary power tongs are connected to an integral backup tong through an extendable hydraulic cylinder and rod. A brake is secured to the rotary tong to selectively hold the pipe stationary relative to the rotary tong. When...http://www.google.fr/patents/US6334376?utm_source=gb-gplus-shareBrevet US6334376 - Mechanical torque amplifier
