GB725175A - Improvements in or relating to drilling arrangements for wells, bore-holes, shot-holes and the like - Google Patents

Abstract

725,175. Boring earth and rock. CARRUTHERS, C. J. D. March 6, 1953, No. 6315/53. Class 85. A rotary impact drill consists of a cylindrical casing 10 provided at its upper edge with cam surfaces 6 and housing a hammer 7 and anvil 11 which are splined to a hollow shaft 8, the shaft being secured at 1 to the rotating drill string. The hammer is provided at its upper end with a collar which is formed to present downwardly facing cam surfaces 5 to engage with cams 6, rotation of the shaft 8 causing cams 5 to ride up over cams 6 against the pressure of a spring 2 and then to drop suddenly so that a blow is delivered on to the anvil 11. The anvil carries a percussion bit 23 at its lower end, a sleeve 22 being loosely keyed at 20 to the bit stem 21 for rotation therewith and carrying rotary cutters 25. Rotation of casing 10 is prevented by three anchor bars 14 which are forced outwardly'to engage the sides of the bore hole by a number of pistons 15 which are projected by the pressure of the drilling fluid pumped down the drill string and shaft 8 to the pit 23 and cutters 25. The tapered lead on the bars 14 allows the drill to advance as boring proceeds. In a modified form (Fig. 4, not shown) the casing 10 is provided with an internal groove of sinusoidal form, the hammer being connected by springs to an intermediate element having outwardly projecting rollers which engage in this groove to give the reciprocatory motion when the drill is rotated.