GB351076A - Improvements in reamers or underreamers - Google Patents

Abstract

351,076. Bore-hole apparatus. GRANT, J., 2301, East Vernon Avenue, Los Angeles, U.S.A. Jan. 25, 1930, No. 2684. [Class 85.] In an under-reamer for borehole or well work wherein a mandrel is arranged within a hollow slotted body with cutter carriers arranged in the slots so as to be movable radially by relative movement between the mandrel and the carriers, a sleeve closes the upper ends of the slots when the cutters are at the lower end thereof. As shown, a hollow body 10 is threaded below to a bit 15 and above to an internal mandrel 20 which is extended upwardly for connection to the drill stem ; connected to, or integral with, the mandrel is an extension 21 loosely centred at its lower end by a collar 30. A spring 31 surrounds the extension 21 and acts through a propeller 32 to press upwardly cutter carriers 50 slidably arranged in slots 33 of the body; during upward movement of the cutter carriers, parts 55, 70 of the latter co-operate with tapered parts 43, 41 of the mandrel to expand the carriers into the tilted position shown in Fig. 2. Lateral wings 60 prevent the carriers moving out of the slots and at the lower end the wings may be such as always to remain in contact with adjacent wings and, if desired, with the mandrel, while when the tool is collapsed, the wings may contact throughout their length. The cutter carriers may be provided with integral cutters or they may support roller cutters 51 mounted on spindles 52 held below by pins 76 engaging grooves 75 and provided above with eccentric heads 77 to prevent rotation. The roller cutters may be wholly or partly conical and may have smooth end parts 80, Fig. 15, engaging bearing faces in the carriers. Wear on the upper ends of the carriers may be obviated by means of washers or by U-shaped clips 90 of hard or soft material which co-operate with the lower end of the well casing when the cutters are to be collapsed. The propeller 32 and an upper sleeve 100 prevent admission of mud &c. to the upper part of the body 10. In a modification, the sleeve 100 is replaced by a sleeve outside the body 10 ; such sleeve may be of rubber or of thin metal adapted to be torn or crumpled by upward movement of the cutter carriers. The roller cutters may be mounted eccentrically in the carriers, the latter then having on one side a web 120 to take circumferential strains ; or such a web may be provided on each side. Silt &c. may be removed from the lower part of the body 10 by flushing fluid escaping from the lower end of the mandrel extension 21 and out through ports 35 in the body ; the extension 21 may have apertures 36 to increase the flow of fluid. Specification 259,618, [Class 85, Mining &c.], is referred to.