| 摘要 |
1279190 Retrievable drill apparatus CHRISTENSEN DIAMOND PRODUCTS CO 2 July 1970 [3 Oct 1969] 32056/70 Heading E1F A drill bit apparatus for passing through a drilling string comprises a sleeve, Fig. 1d, which surrounds an annular cutter 19 and which is integral with three equi-spaced slotted sprung arms 22 and with three equi-spaced V-shaped cams 25. The lower apex of each cam is formed in a portion attached to the outer side of the adjacent arm 22. The apparatus is lowered through a drill string 13 until cams 25 engage with and are supported by complementary cams 27 formed in a mandrel 14 attached to the string. Each arm 22 is thus aligned with one of the grooves 77 in mandrel 14. The subsequent lowering of cutter 19 through sleeve 23 expands arms 22 until, Fig. 2d, arms 22 lie within grooves 77 and cutters 30 lie within slots 15. The apparatus is latched to the drill string, in the lowered position. The cutters 19 and 30 rotate with the drill string to produce a core which is retained in a tube carrying the cutter 19. To raise the core and the drill bit apparatus, cutter 19 is raised until its keys 20, which slide in slots 21, engage and raise sleeve 23. In a modification the pilot bit is replaced by a non-cutting member which serves to expand the cutters, and the cutters are larger such that they are rotated, when being retracted, by additional internal cams on the mandrel. |
