Self-adjusting automatic locking piston for RAM blowout preventers

A hydraulic piston for use in a hydraulic cylinder having an internal annular groove adapted to receive locking segments or dogs for retaining a hydraulic piston at a fixed longitudinal position within said cylinder, said hydraulic piston being characterized by being automatically lockable at a self-adjusting range of forward positions from a rearward groove-engaging locked position, said self-adjusting automatic locking piston comprising;

• a. an outer, hollow main piston of generally cylindrical shape having a rear cylindrical body, a transversely disposed rear circular piston head, a smaller diameter cylindrically-shaped front boss section, and a tapered intermediate annular section joining said rear and front sections, said outer piston including means for fastening thereto a piston rod, a coaxial bore and a plurality of radially disposed apertures through the outer wall surface of said outer piston and communicating with said coaxial bore, and a plurality of circumferentially elongated grooves cut inwards from the outer cylindrical wall surface, one each groove communicating with the rear end of each aperture,
• b. an inner locking piston having a generally cylindrical rear section and a tapered front section longitudinally slidably contained within said coaxial bore of said main outer piston, said inner locking piston having a central coaxial bore adapted to slidably receive said piston rod,
• c. a plurality of driver segments, one each of said driver segments radially slidably located within a separate one of each of said radially disposed apertures through the outer surface of said main outer piston, each of said driver segments having a sloping lower wall surface adapted to slidable engagement by said tapered front surface of said inner locking piston, whereby forward motion of said inner locking piston within said main outer piston forces each of said driver segments to move radially outwards within said aperture, each of said driver segments having a sloping upper rear surface, and
• d. a plurality of locking segments, one each radially slidably positioned in each of said grooves in the outer cylindrical wall surface of said main outer piston, each of said locking segments including a rear portion having an outer surface adapted to engage the inner wall surface of said annular groove in said inner wall surface of said hydraulic cylinder, and each of said locking segments including a narrower front section having a sloping lower front surface adapted to slidable engagement by said sloping upper rear surface of said driver segment, whereby radial outward motion of each of said driver segments forces each of said locking segments radially outwards into locking engagement with said annular cylinder groove.