Hydraulic impact tool - has plunger with reduced-diameter piston section enclosed by reciprocating valve

摘要

The hydraulic impact tool comprises a bit moving in a bore in a housing, the latter also containing a reciprocating plunger. The plunger has a piston section of smaller diameter than the bore, while an accumulator (71) accelerates the plunger (105) to strike the tool (11) when released. A reciprocating valve (95) around the plunger has a top sealing portion working against the bore and a bottom one against the piston section, dividing the bore into top middle and bottom annular chambers, its internal diameter being grearer than the plunger diameter. A port admits fluid at high pressure to the middle chamber, pressing the bottom of the valve against the piston section. A further port delivers fluid at medium pressure to the bottom chamber thrusting plunger and valve away from the tool.