| 摘要 |
<p>The tool has a hollow elongated body (10) made up of three sections namely, a leading cylindrical section (12); an intermediate section (14) consisting of a first part (16) and a second part (18); a cylindrical trailing section (20); a wedge (22) arranged between parts (16) and (18); and a hydraulic cylinder (24) housed in the trailing section (20) and having a piston rod (26) connected to the wedge (22). The tool is towed through the main to be burst by a towing device such as a self-advancing mechanism inside the main or by a cable connected to a winch and attached to the clevis (28) at the leading end of the tool. The tool forms an enlarged cavity in the ground by displacement and draws into the cavity a tubular liner (30) which is clamped (32) to the trailing section (20) of the tool. Parts (16) and (18) are formed of walls (44) of part-frustoconical shape and covering each 180 DEG of the circumference of the intermediate section (14) wall (44) of the first part (16) is carried by an inner elongate support (48) having an inner bearing pad (50) slidably engaging pad (52) on the upper side of wedge (22). Parts (16) and (18) carry both longitudinal cutting ribs (68, 70). The first part (16) is moved outwardly by the wedge (22) to burst the main and enlarge the cavity, allowing the tool to be advanced after the retraction of part (16).</p> |
