a fixed plate brick mounted on the bottom of a molten metal vessel through a base plate and having at least one pouring port;

a collector nozzle brick disposed in confrontation with the fixed plate brick with its pouring port located concentrically;

a slide plate brick sandwiched between the collector nozzle brick and the fixed plate brick and being in contact therewith so as to slidingly turn on the sliding surfaces of the collector nozzle brick and the fixed plate brick and having at least one pouring port;

a frame on which the slide plate brick is mounted;

an outer race mounted on the outer peripheral side of the fixed plate brick so as to be turned by an extendable unit;

wherein the device controls the pouring amount of the molten metal by adjusting a relatively open position of the pouring port of the slide plate brick and the pouring port of the fixed plate brick by turning the outer race with the extendable unit;

wherein the frame is attached to the outer race through a pivotal hinge so as to be capable of opening and closing movements through the pivotal hinge independently of the turning of the outer race with the extendable unit,

wherein the outer race is turned by a crank mechanism using triangle points consisting of a support pivot for supporting the extendable unit, the center of turn of the outer race, and a pivot engaged with an end of an extendable rod of the extendable unit and disposed on the outer peripheral portion of the outer race, and the stroke of the extendable unit and the position of the support pivot of the extendable unit are selected to provide a completely open position, in which the pouring port of the slide plate brick is aligned with the pouring port of the fixed plate brick, to form an end position, and a completely closed stop position, which is angularly offset from the end position by a predetermined angle, to form a start position, so that a turn stop position corresponds to a rotation angle between the completely open position and the completely closed position to an entire stroke of the extendable unit;

and wherein the position of the support pivot, the distance between the support pivot and the center of rotation, the radius of the turn of the outer race, and the entire stroke of the extendable unit are selected so that a turn angle is set at the start position to generate at least 90% of a maximum value of the ratio of a component force effective for the turn torque to an axial output of the extendable unit.