REVERSIBLE PNEUMATIC DRIFT Russian patent published in 2001 - IPC

FIELD: construction engineering; trenchless laying of underground service lines. SUBSTANCE: reversible pneumatic drift used for penetrating holed of desired trajectory especially curvilinear ones has body accommodating down-hole drive hammer with drilling in rear part mounted for reciprocal motion, slide valve fastened in rear part of body and built up of pipe connection with duct for feeding compressed air to drilling of down-hole drive hammer and of bush sliding into mentioned drilling and installed on pipe connection for restricted axial movement. Pipe connection and bush of slide valve have three pairs of relatively sliding surfaces of large, small, and medium diameters, respectively. Space between relatively sliding surfaces of large and small diameters continuously communicates with atmosphere; that between relatively sliding surfaces of small and medium diameters periodically communicates with compressed air source through change-over device. Surface area of butt-end of bush on side of down-hole drive hammer bore is smaller than surface area difference of its cross sections of medium and small diameters. EFFECT: improved reliability; enhanced service life and stability; reduced labor consumption and change-over operation time. 3 cl, 8 dwg