GB638635A - Screwing and unscrewing tongs particularly for drilling-pipe and drilling-rod joints - Google Patents

Abstract

638,635. Making and breaking screwed joints. EDELBERG, V. April 22, 1947, No. 10774. Convention date, June 28, 1946. [Class 83 (iii)] In screwing and unscrewing tongs for drill rods &c., having two superimposed annular members 5, 6 surrounding the two parts of the joint and connected together by means which drive them in opposite directions, a set of jaws 9 is articulated on each of the annular members, means are provided for tightening the jaws on to the two parts of the joint and for transmitting to the jaws the drive imparted to the annular members, and means are provided for varying the spacing between the annular members according to the height of the thread of the joint. The driving device may be separate from, or carried by, the tongs. In the form shown, the tongs rotate on a plate 1 which is carried from the substructure of the rotary table by means of fluid-pressure pistons 3 which allow for adjustment as to height. The pulley rings 5, 6 are freely rotatable on a median body 4 formed by two hollowed plates 16, 17 joined by springs 24, 25 and rods and sockets 26, 27 which allow separation of the plates 16, 17 according to the height of the thread of the joint. Each ring 5, 6 has pivots 7 for arms 8 ending in spring-centred pivoted jaws 9 which grip the tube 10, the arms 8 being operated by links 19 pivoted at 18 on controlling members 12, 13 carrying circular casings 14, 15 engaging the rings 5, 6 and the plates 16, 17. Slight rotation of the members 12, 13 in opposite directions by means of spring-set handles 21 brings the two sets of jaws 9 into wedging and driving engagement with the two ends of the tube 10. The rings 5, 6 are connected by an endless cable 36 with a turn-buckle for taking up slack, and by an ordinary anchored cable 35, respectively, to upper and lower drums driven by an electric motor, on the same platform as the tongs, through a differential so as to develop the same circumferential pull. When the motor is first started, the cable 35 is stretched and tightens the ring 6 on the tube 10. By progressively stretching the loose part of the cable 36 the ring 5 is rotated in the opposite direction to the ring 6, and the torque on the two rings 5, 6 increases equally until the joint is broken. Rapid unscrewing then follows under reduced torque. In a modified form, the tongs carry three groups of double electric motors, and' separation of the rings 5, 6 is effected by a double circular cam between them.