Abstract: A rotary sliding closure unit includes stationary and rotary refractory members having respective discharge openings and fixed and rotary mounting devices for supporting the respective refractory members. The rotary member is rotated by the rotary mounting device with respect to the stationary refractory member along respective complementary abutting sliding surfaces thereof. Air is prevented from contacting the abutting sliding surfaces by an annular chamber defined between the fixed and rotary mounting devices and closed by an annular seal positioned therebetween.

Abstract: A holding or smelting furnace for discharging measured quantities of molten metal includes a furnace wall defining a furnace chamber adapted to contain molten metal having an upper free melt level, and at least one melt outlet channel extending from the furnace chamber through the furnace wall at a level below the free melt level. A sliding gate valve is mounted on the furnace wall at the outlet channel and is movable between a closed position blocking the outlet channel and an open position unblocking the outlet channel. Control structure maintains the free melt level at a constant level within the furnace chamber, and thereby maintains the hydrostatic pressure of the molten metal within the furnace chamber at a constant value during discharge of the molten metal. Regulating structure is operable independently of the operation of the control structure and moves the sliding gate valve between the closed and open positions thereof at a predetermined timed cycle.