Abstract: The present invention relates to a mechanism for moving and adjusting the loci of motions of a gripper adapted for seizing the work such as the product of a plastic molder or a sprue runner, etc. It is provided with an actuator, a turnover arm of which one end is connected to the rotary shaft of the actuator, while a gripper is linked to the other end, a noncircular pulley loosely fitted around the rotary shaft of the aforementioned actuator, a circular pulley mounted on the other end of the turnover arm through a shaft rod, a belt spanned between the noncircular pulley and the circular pulley, to be turned therearound, and a spring member which exhibits a maximum elastic rebounding force, when the turnover arm is brought to be realy horizontal.