Percussion-rotary drilling tool

摘要

PCT No. PCT/SU88/00285 Sec. 371 Date Jan. 23, 1990 Sec. 102(e) Date Jan. 23, 1990 PCT Filed Dec. 28, 1988 PCT Pub. No. WO89/11580 PCT Pub. Date Nov. 30, 1989.The proposed tool comprises a body (1) designed to interact with a percussion-rotary device and a casing (2) shaped as a sleeve. The casing (2) accommodates rock-crushing elements (5, 6) arranged in a manner allowing axial displacement thereof and in the form of concentric rows relative to a working end of the casing (2), the rock-crushing elements having shanks (7, 8) which interact with the body (1). Each rock-crushing element (6) in a peripheral row comprises a spring biased pin mechanism (16) for fixing the rock-crushing element (6) in the casing (2). The casing includes a threaded joint (9) for its axial displacement relative to the body (1). The length of axial displacement of the casing (2) relative to the body (1) is at least equal to the length (H) of the wearable portion of the rock-crushing elements (5, 6).