Abstract: A feeder assembly for an alumina electrolysis cell includes an alumina dose holder (5) defined between inner and outer walls (6, 7, 7') with an inlet port in the outer wall above an outlet port in the inner wall. The inlet and outlet ports (8, 11) are closable and openable by valve means formed by relative movement between the outer wall (7, 7') and a valve seat (10, 12) cooperating with a seating edge of the outer wall (7, 7'). The valve means is moved by drive means (13) including a pneumatically operated piston (14) movable within a cylinder (15) concentric with the shaft (2) of an electrolyte crust-breaking plunger (1). The plunger shaft (2) is axially slidable within an annular sleeve (18) of the piston (14) which is connected to at least one movable component of the valve means.

Abstract: Apparatus for the controlled supply of alumina to an electrolysis tank having an electrolyte crust breaking plunger (2) includes a supply chamber (19) connected to the entry port (16) of a dose holder (10). Alumina leaving an exit port (15) of the dose holder (10) passes via an inclined wall (9) to a delivery chute (21) which directs the alumina to a hole formed in the crust by the plunger. Valve means (14) movable with the plunger (2) controls the opening of the dose holder entry and exit ports (16, 15), closing one port as it opens the other, and allowing alumina to flow through the delivery chute (21) as the plunger (2) is retracted from the crust. The plunger movement required to control the valve means is such that alumina can be fed into the tank substantially continuously without meeting interference from the plunger.