Patent GB-691400-A (GB)
Title: Power operated slips for a rotary table of a well drilling rig
IPC: E21B19/10
Filed: 1950-11-13
Abstract: 691,400. Rotary tables. NATIONAL SUPPLY CO., and OIL WELL ENGINEERING CO., Ltd. Nov. 13, 1950 [May 16, 1950], No. 27698/50. Class 85 A rotary table for a well drilling rig comprises a plurality of pipe-engaging slips to support the drill string during coupling and uncoupling operations, the slips being receivable with a downwardly converging taper bore, a plurality of upright parallel posts supporting the slips at their upper ends and being allowed to slide longitudinally in the table and rotate therewith, and means for simultaneously raising the posts. The rotary table 13, Fig. 2, driven by the shaft 29 carries a master bushing 12, having a taper slip bowl 11, and three upright posts 15 which are slidable within spaced bearings 16 on the table. To the upper end of each post is attached a quickly removable bracket 18 which carries, through a link 19, the slip 10 which in the " pipe engaging " position is received within the taper bowl 11. The lower ends of the posts 15 are rigid with a lifting ring 20 and the whole raised or lowered by a yoke mechanism 75, Fig. 7, comprising a pair of arms 76, 77 each carrying a roller 82, which runs in the groove 85 of the ring 20, and a rockshaft 78 journalled to the base 22a. The rockshaft 78 is oscillated, and the posts 15 therefore raised and lowered by a fluid cylinder 92, via a crank 86. The cylinder is divided into a front chamber 95 and a rear chamber 96 by a piston 91 and a reduced pressure of fluid, preferably air, is constantly supplied by a pressure regulator 110 to the rear chamber so that the slips are always urged to the raised position. The motion of the piston and therefore of the slips is controlled by a four-way valve 112 at the driller's position. When the foot pedal "D" is actuated, full supply fluid pressure is supplied through the line 114 to the front chamber 95 and the piston 91 is forced down against the reduced pressure in the rear chamber 96, some fluid from which escapes via the exhaust port 105 of the regulator, so that the slips are lowered. When the pedal " U " is actuated, the line 114 is connected to the exhaust port 125 and bled to atmosphere whilst the regulator 110 is again connected to the supply and a reduced pressure applied to the rear chamber so that the piston and slips are raised. Each end of the cylinder is fitted with by-pass ports 97, 98 and a needle valve 99 to prevent impact of the piston on the ends of the cylinder. Each end of the cylinder is also fitted with ports 101, 102 and a spring-loaded valve 100 so that the ports 97, 98 are by-passed when the piston initially moves from the cylinder ends. In another form of fluid pressure control, one chamber is connected to the full supply pressure and the other to atmosphere, so that the slips are raised or lowered, by a sliding piston valve, the motion of which is controlled by fluid pressure from the driller's position. In this form, the slips remain in the position in which they were last set. In operation of the drilling rig, when the pipe sections have been lowered into the hole and coupled and drilling is to commence, the brackets 18 are removed from the posts 15 which are then lowered to their lowest position. The Kelly-drive bushing 66, Fig. 9, is then lowered on to the upper part of the master bushing 12 so that the drive lugs 68 are received in offset recesses 35 in the table 13. The Kelly-drive bushing 66 has driving rollers 67 and may have a pilot sleeve 69 to align the bushing axially with the table 13. U.S.A. Specification 2,422,383 is referred to.