Anti-lockup drive mechanism for a position controlled linear actuator

Abstract

A linear actuator is provided with an electric motor rotating a drive pinion gear in mesh with an intermediate gearing arrangement which in turn is in mesh with a main drive gear for rotating a drive screw journalled within a main body housing. Rotation of the drive screw causes longitudinal advancement of a drive nut axially advancing an extension rod bearing to move an output load connected to an opposite end of the extension rod. The intermediate gearing arrangement includes a lost motion mechanism allowing the drive pinion to complete approximately one revolution before imparting rotative torque to the drive screw allowing the drive motor to develop an operating torque to prevent lockup of the actuator. The lost motion mechanism includes a pair of arcuate slots formed in a first intermediate gear in contact with the drive pinion and a pair of dowel projections projecting from a second intermediate gear into the slots. The second intermediate gear is connected to the drive screw. Upon actuation of the drive motor, the first intermediate gear rotates through a predetermined angular interval unit the dowel projections move from one extreme position in the associated slot to the opposite extreme position at which time an abrupt force is imparted to the second intermediate gear to rotate the drive screw.