Variable torque valve actuator

An actuator for moving a threaded valve stem along a longitudinal axis to selectively open or close a valve positioned at a distal end of the valve stem, the actuator comprising:

• a housing;
• a carrier rotatably mounted within the housing for rotation of the carrier about the longitudinal axis, the carrier having
• a stem engagement portion having a bore formed therein, the bore being threaded to engage and receive the threaded valve stem therethrough,
• a first collar engagement portion, and
• a gear engagement portion;
• a gear arrangement comprising a central gear rotatably mounted within the housing for rotation about the longitudinal axis and having a second collar engagement portion, the gear arrangement engaging the gear engagement portion of the carrier for transmitting a rotational force from the central gear to the carrier;
• a cylindrical operator rotatable mounted to the housing for rotation about the longitudinal axis, the operator having a plurality of longitudinally oriented splines on at least a portion of a circumferential surface thereof, the operator being configured for receiving a rotational input force from a drive mechanism;
• and
• an annular collar slidably disposed around the operator, the collar having a cylindrical body with proximal and distal ends, a through bore having a bore surface configured to engage the splines so that the collar must rotate with the operator but can slide longitudinally along the operator between at least a first longitudinal position and a second longitudinal position, and a rotation transmission portion configured for engaging the second collar engagement portion to allow transmission of a rotational force to the central gear when the collar is in its first longitudinal position and for engaging the first collar engagement portion to allow transmission of a rotational force to the carrier when the collar is in its second longitudinal position.