Three-plate slide valve closure for liquid melt containers

Claim 1

In a three-plate slide valve closure for liquid melt containers such as steel ladles, said closure being of the type including an upper stationary apertured refractory plate adapted to be fixedly positioned beneath an outlet in a liquid melt container, a lower stationary apertured refractory plate adapted to be fixedly positioned at a location spaced from said upper stationary plate, an apertured refractory slide plate mounted between said upper and lower stationary plates for sliding movement between open and closed positions, and said upper stationary plate, said slide plate and said lower stationary plate having extending therethrough first, second and third flow-through openings, respectively, which are aligned when said slide plate is in said open position, the improvement wherein: at least an inlet portion of said third flow-through opening, adjacent said slide plate, has a dimension in the direction of movement of said slide plate at least twice as great as the dimension of an outlet end of said second flow-through opening in said direction, such that said outlet end of said second flow-through opening is constantly in communication with said third flow-through opening during movement of said slide plate between said open and closed positions, and no portion of an upper inlet edge of said third flow-through opening is ever positioned inwardly of any portion of a lower outlet edge of said second flow-through opening at all positions of said slide plate.