FLUID PRESSURE TYPE EXPANSION HEAD

PROBLEM TO BE SOLVED: To provide a fluid pressure type expansion head free from malfunction, with the minimum possible equipment cost. SOLUTION: A hydraulic expansion head is provided with a hydraulic cylinder having a head rod coaxially equipped within it, a reciprocating component supported in the hydraulic cylinder so that it can be axially movable to and away from the lower end of the head rod, expandable wings supported by the reciprocating component so that they can swing within the longitudinal plane of the head rod, and also linked with the head rod so that they can expand and shrink as the reciprocating component goes and back, a heavy excavation head fixed to the reciprocating component, a pressure water outlet provided at the hydraulic cylinder to discharge the pressure water supplied out of the cylinder after it pushes the reciprocating component to an end point. Thereby, the hydraulic cylinder can only serve to open the expandable wings, and their closure may be achieved by the dead weight of the excavation head after the pressure water supplied is released. Further, the system is provided with an expandable wing closure retainer to releasably hold the closed wings in such state when they are closed. COPYRIGHT: (C)2006,JPO&NCIPI