Hydraulic impactor

A hydraulic impactor comprising:

• a cylinder,
• a hydraulic accumulator at one end of said cylinder,
• a differential area piston reciprocable within said cylinder, said piston having a large diameter central portion and reduced-diameter shank portions extending axially from its opposite sides,
• said piston large diameter central portion having a first annular face at one end and a second annular face at the other end with said second annular face being disposed closer to said hydraulic accumulator than is said first annular face,
• a first one of said shank portions being adapted to impart an impact to an anvil element,
• a second of said shank portions being adapted to slide into said hydraulic accumulator to compress a fluid therein,
• a sleeve valve surrounding said piston and reciprocable along the axis of said cylinder,
• means responsive to movement of said piston to a position where it is farthest removed from said accumulator for moving said sleeve valve to a position where it connects a source of liquid under pressure to said first annular face of said large diameter piston portion,
• means responsive to movement of said piston to a position where it is closest to said accumulator for moving said sleeve valve to a position where it connects said first annular face of said large diameter piston portion to a hydraulic reservoir,
• means for causing said liquid under pressure to act on the total area of said first annular face of said large diameter piston portion and said first shank portion during movement of said piston toward said accumulator and
• said second shank portion being reciprocable within a cylindrical bore and having an area less than that of the combined areas of said first annular face of said large diameter piston portion and first shank portion.