Abstract: A self-locking device for a gear set is configured to permit forward-driving an input in either of first and second rotational directions and for substantially preventing an output from being back-driven in either of the rotational directions. The device includes a gear disposed to rotate with a drive shaft. The device further includes first and second releasable couplings coupled to the gear and, respectively, to first and second ratchets. The first ratchet is disposed to prevent rotation in a first direction and to permit rotation in a second direction. The second ratchet is disposed to prevent rotation in the second direction and permit rotation in the first direction. The device may be useful, for example, in a valve gearbox. A gearbox and a method of fabricating a gearbox are also disclosed.

Abstract: A self-locking device for a gear set is configured to permit forward-driving an input in either of first and second rotational directions and for substantially preventing an output from being back-driven in either of the rotational directions. The device includes a gear disposed to rotate with a drive shaft. The device further includes first and second releasable couplings coupled to the gear and, respectively, to first and second ratchets. The first ratchet is disposed to prevent rotation in a first direction and to permit rotation in a second direction. The second ratchet is disposed to prevent rotation in the second direction and permit rotation in the first direction. The device may be useful, for example, in a valve gearbox. A gearbox and a method of fabricating a gearbox are also disclosed.