Abstract: A dual concentric pipe string for bore hole coring having inner and outer concentric pipe sections, the outer pipe sections being secured together by the usual threaded connection, the inner pipe sections being connected through coupling devices containing elastomeric bodies that make a friction fit with the end portions of adjacent inner pipe sections, the inner pipe sections being frictionally secured to longitudinally spaced elastomeric centralizers having circumferentially spaced longitudinal ribs engaging the inner wall of the outer pipe sections to maintain the inner sections coaxial of the outer sections, with some of the centralizers engaging transverse shoulders in the outer sections to secure the inner sections in the outer sections against substantial longitudinal movement with respect thereto.

Abstract: A swivel, particularly useful in core drilling a bore hole, including a rotor rotatable in a stator, the rotor having a passage through which compressed air is forced to an air operated device for producing cores in the bore hole, and also having a return passage through which the cores conveyed by a portion of the compressed air flow into a core receiving chamber in the stator, a pusher or wiper in the chamber being secured to the rotor to rotate therewith and move around the chamber to shift the cores and core particles toward and into a stator outlet.

Abstract: An airhammer and core bit apparatus including a housing and a hammer piston reciprocable in the housing for delivering repeated impact blows to an anvil secured to or forming part of a core bit which produces a core in a bore hole being drilled. A central core receiving tube extends through the housing and hammer piston, through which the core formed by the bit is conducted upwardly and through the hammer piston to the top of the bore hole, part of the compressed air supplied to the airhammer being diverted to the central tube for elevating the core therewithin toward the top of the bore hole.

Abstract: An impact type of anvil core bit includes a body having a central opening through its bottom drilling face, a plurality of spaced cutters, such as sintered tungsten carbide buttons, being secured to the body and extending downwardly from the face to drill against the bottom of the bore hole outwardly of the central opening, the cutters including inner cutters for forming the core in the bottom of the hole, a cutter ring being secured to the body and circumscribing the opening above the bottom of the hole to shape the core for movement into the central opening.