Patent ID: 8025324

Claim:
A device on a spreader comprising: a flipper arm which is supported at a corner of the spreader such that the flipper arm is pivotable between an upraised rest position and a lowered operative position wherein the flipper arm is effective for positioning of the spreader corner relative to a corresponding corner of a container upon connecting the spreader to the container, wherein the flipper arm is carried on a rotatable shaft and driven by a motor; and a power transmission inserted between the motor and the flipper arm, the power transmission being effective for transferring torque from the motor to the flipper arm for pivoting the flipper arm upon energizing the motor, and the power transmission being operative for locking the flipper arm in either one of the upraised rest position or the lowered operative position upon de-energizing the motor; wherein the power transmission between the motor and the flipper arm is a self-locking worm drive having a helical thread worm screw which is driven by the motor and engaging tangentially a gear-wheel carried on the rotatable shaft, and wherein a pitch of threads in the worm screw and the gear-wheel are chosen to permit the gear-wheel to be rotated by the worm screw while preventing the worm screw from being rotated by the gear-wheel.