KELLY SPEED BUSHING

摘要

1,235,827. Boring earth, &c. J. L. FOSTER. 20 May, 1970 [22 May, 1969], No. 24398/70. Heading E1F. [Also in Division F2] A bushing 20 driving a kelly 16 co-acts with a rotary table 14 to drive the kelly at a speed different from that of the table. The bushing has a housing 22 with a non-circular part engaged in the kelly drive square 26 of the table. The housing is rotated about a ring gear 28 normally fixed against rotation. First stage planet gears 42 journalled to the housing mesh with the gear 28 and a first sun wheel 54. The wheel 54 carries second stage planet gears 58 meshing with the gear 28 and a second sun wheel 70 rotatable relative to the wheel 54. The wheel 70 has splines 78 engaging a kelly drive bush 82 formed by two parts. During drilling, in which the kelly rotates faster than the table, the ring gear 28 is prevented from rotation by brake blocks 100, 102 on a fixed ring 96 engaging a ring 94 fixed to a depending portion 38 of the gear 28. The ring 96 is supported by a fixed ring 118, rotation of the ring 96 being prevented by a hydraulic piston and cylinder device 122. Excessive torque acting on the kelly causes a rise in pressure in the device which rise reduces or cuts-off a supply 114 of air, to release the blocks from the ring 94 to free the gear 28 and render the drive of the bush inoperative. The housing is filled with oil up to the level of a weep hole 150 which supplies oil to the second stage of the gearing whilst a block 152 (Fig. 4) between the support rings 56, 64 of the gears 58 forces oil up passage 154 to lubricate the first stage. In a modification in which the kelly is driven slower than the table the first sun wheel (206, Fig. 6, not shown) is fixed to the housing (202), the first planet gears (214) are carried by the second sun wheel (222), the second planet gears (226) are carried by a sleeve (234) splined to the kelly drive bush (82). In another modification (Fig. 7, not shown) the anchor ring (300) is fixed to the drilling structure, the housing (304) is splined to the kelly drive bushing (312), the second stage planet gears (314) are journalled to the housing, the second sun wheel (318) carries the first stage planet gears (322) and the first sun wheel (326) has a port co-acting with the kelly drive hole in the table. In further modifications the brake blocks are electro-magnetically operated and the bushing has more than two stages of gearing.