GB1494276A - Drill steel for use with percussive tools - Google Patents

Abstract

1494276 Boring earth &c HYDROACOUSTICS INC 2 June 1975 [10 June 1974] 23836/75 Heading E1F A drill string element for use with an above ground percussive tool (which may also rotate the string) includes a core member for transmitting force pulses generated by the tool, a sheathing surrounding and spaced from the core member and at least one resilient member of elastic material connecting the sheathing to the core. The elastic material and the mass of the sheathing are chosen such that the resonant frequency of the sheathing in the longitudinal direction is different from, and preferably less than, the operating frequency of the percussive tool. The core may be a solid rod or may be hollow. In a first embodiment (Fig. I) the core 24 is hexagonal and is surrounded by a tubular sheathing 22, the space 34 between the core 24 and sheathing 22 being filled with an elastomeric material 35, preferably cast in situ so that it is bonded to both the core 24 and sheathing 22. The core 24 is provided with a threaded pin 28 at each end and adjacent drill string elements are connected by threaded connector members 25. The sheathing 22 and connector 25 are provided with grooves 40, 38 respectively for engagement by a breakout wrench for assembling and disassembling the string. In a second embodiment (Fig. 3) the sheathing 58 is connected to the core 48 by annular rings 62 of resilient material, the ends of the sheathing being swaged inwardly, but spaced from, the core 48. The torque produced by a breakout tool (not shown) is transmitted from the sheathing 58 to the core 48 by lugs 72, 74 on the core which pass through slots 70 or openings 76 in the sheathing 58, the slots 70 and openings 76 being larger than the lugs 72, 74. The connector 78 is also provided with a sleeve 80 mounted on elastic rings 82, breakout torque being transmitted from the sleeve 80 by screws 90 extending into larger holes 86, 88 in the sleeve 80. In a modification (not shown) the lugs 72, 74 are replaced by cross pins extending through the core. In a third embodiment (Fig. 6) the core 114 is provided with flats 116 for engagement by the breakout wrench and the end elastic ring 122 is provided with a flange extending between the end of the sheathing 118 and the top surface of the flats 116. In a fourth embodiment (Fig. 7) the connector 126 and elastic rings 132, 134 are provided with passages 140, 142 to allow drilling fluid to pass along the annulus between the core 128 and sheathing 130.