Adjustable screw and nut device

Claim 1

A screw and nut device comprising a screw, a pair of nuts having identical screw threads and mounted coaxially on said screw in succession, the confronting ends of said nuts being formed with externally screw threaded portions of the same direction but slightly different pitches, a coupling ring having a pair of internally threaded portions complementary to said externally screw threaded portions of said nuts and rotatable relative thereto to adjust the axial spacing of said nuts relative to one another, means for locking said nuts against mutual rotation including aligned grooves in the outer periphery of said nuts adjacent and outboard of said externally screw threaded portions and locking key means engageable in the aligned grooves of said nuts, a plurality of circumferentially spaced longitudinal grooves in the outer periphery of said coupling ring adapted to be aligned with the grooves of said nut by rotating said coupling ring relative to said nuts, said locking key means consisting of a first key of a configuration to engage in the grooves of said nuts and coupling ring to thereby prevent relative rotation of the nuts and coupling ring and second key means of a configuration to engage in only the aligned grooves of said nuts thereby permitting rotation of the coupling ring relative to said nuts.