Device for inserting a retractable blank shutting off plate in a device for the conveyance and exchange of a pouring tube

Emergency blank plate shutting off device for a conveyance and exchange device of pouring tubes (3) having a movable upper plate tightly pressed against a lower fixed face of a fixed reference refractory plate (5) fixedly mounted at a bottom wall of a bottom pour vessel (1) or of a mobile plate of sliding gate of said bottom pour vessel (1), under the effect of an upward thrust transmitted by guide-rails (6,7) which determine a first rectilinear trajectory along which slides each of the plates (4) of said pouring tubes, actuated by a jack (10), from a loading position to an operating position in the axis of pouring, and from the operating position to a retracting position, wherein a carrier on which is set an emergency blank refractory plate (8) shutting off device moves said blank plate (8) along a second trajectory, which crosses over said first trajectory, from a readiness position (14), off the second trajectory to an alert position (15) on a zone overlapping the two trajectories adjacent to the operating position of a pouring tube (3) in the pouring axis.