| 摘要 |
1,271,339. Boring earth &c. CHRISTENSEN DIAMOND PRODUCTS CO. 10 Nov., 1970 [19 Jan., 1970], No. 53416/70. Heading E1F. A drill comprises cutters 32, 33 which are lowered through a drill string to be expanded into engagement with a drive section 14 for drilling. An assembly comprising a latch 79, a swivel 22 supported by the latch, a core tube 19 hanging from the swivel, a cutter carrier 18 supported by fingers 26 from the core tube, cutters 32 hanging from the carrier, and cutters 33 hanging from the cutters 32 is supported by an overshoot 89 and lowered down through the string to the section, a shoulder 16 in the section being engaged by hooks 49 on the cutters 33 to align the assembly with the section. After the hooks engage the shoulder, the cutters 32 expand the cutters 33 and both sets of cutters are expanded by the core tube into the drilling position shown in Fig. 2a in which threads 15 on the section are engaged by companion threads on the cutters. The assembly is held in the drilling position by blades 82 of the latch engaging in groove 84 in the string. The assembly may be removed by pulling on the overshoot. A ring 29 is not fitted if the core barrel only is to be removed. In a bit cutting a full cross-sectional area, the carrier is solid with the barrel and has a lower face carrying cutting elements. |
