US Patent 7931455 Injection molding apparatus having magnetic valve pin coupling

An actuated part, such as a valve pin plate or actuator piston, is movable in forward and rearward directions. A coupling part is located rearward of the actuated part and held in position by magnetic attraction between the coupling part and the actuated part. A valve pin is coupled to the coupling part. The valve pin extends in the forward direction for opening and closing a mold gate. When a stopping force applied to the valve pin is greater than a force of the magnetic attraction between the coupling part and the actuated part, the actuated part moves away from the coupling part in the forward direction, thereby reducing the stopping force on the valve pin.