GB911168A - Improvements in or relating to impact drilling apparatus incorporating a flushing action - Google Patents

Abstract

911,168. Boring earth. GROSPAS, P. April 19, 1960 [April 18, 1959], No. 13686/60 Class 85. [Also in Group XXV] Impact drilling apparatus comprises a hollow drill string 3 through which flushing liquid flows, a bit 5 slidable on the string, a reciprocable head 6 which latches on to the bit when the latter is at the bottom of the hole, and a stop 8 which releases the head from the bit at the top of the bit's stroke. Fig. 1 shows the stop formed by the casing of the hole, and means 7 for reciprocating the head independent of the string. The head shown in Figs. 4, 7 is fixed to the string so that with the parts positioned as shown, the bit may be lifted by the string, a sleeve 15 biased by a spring 16 holding balls 14 in a groove 20a at the top of the bit, and the balls being engaged by a ring 13 attached to the string. At the top of the bit's stroke a rim 19 on the sleeve is engaged by the stop 8 permitting the balls to move from the groove and the bit to fall (Fig. 7). In modifications, the balls engage slots in the sleeve and the sleeve is inside the upper end of the bit. Fig. 15 shows apparatus having concentric bits 5e, 5i, either or both bits drilling according to the stroke of the string. The bit 5i slides on the string and coacts with a head 6i fixed to the string, the stop 8i being mounted on the head 6e for the bit 5e. The head 6e is slidably mounted on the string, and its sleeve 15e has rods 26 which engage the stop formed by a rim 19 on the sleeve 15i. The apparatus of Fig. 16 is actuated by changes in the pressure of the liquid within the string. The lower end of the string is formed by a bell 27 which encloses a valve seat 28 forming the upper end of a string extension tube 3i. Sliding on the tube 3i is a piston 31 carrying the latching head 6. Slight pressure on the liquid in the string forces a valve 30 on the seat and sinks the piston so that the head is latched to the bit. A reduction in the pressure within the string causes the piston to lift the bit which is released to fall when the rods 36 engage the stop 35 on the tube 3i. The piston continues to rise until it contacts projections 34 to lift the valve so that detritus is swept up the tube and string. In a modification (Fig. 18, not shown), the bell slides upon the string and the bit is lifted by increased air pressure in the string. In a further modification (Fig. 19, not shown), the fall of the bit is assisted by a spring and the cutting part of the bit is formed by scoops which are periodically closed. The flushing liquid flows up the strings, the flow of the liquid may be secured by gas lift, and the bits may be rotated.