AIR IMPACT DEVICE Russian patent published in 2000 - IPC

FIELD: construction; making holes in earth at trenchless laying of underground service lines. SUBSTANCE: air impact device has housing accommodating striker with through longitudinal channel and ring bores made over its length, striker being installed for axial displacement in housing. Device has also stepped branch pipe whose larger and smaller steps are arranged in ring bores of striker and central hole accommodating a bridge dividing the channel into two parts and ports in its side wall at both sides of bridge, nut with ports to discharge compressed air, flexible bushing locate between nut and branch pipe for fastening the latter, and hose for delivery of compressed air secured in rear part of stepped branch pipe. According to invention, nut is provided with groove and additional ports found in front part of groove. EFFECT: improved reliability of device owing to prevention of overlapping of ports in nut and bushing which provides required discharge of compressed air into atmosphere. 4 cl, 3 dwg