A BASIS WEIGHT CONTROL APPARATUS
A basis weight control apparatus (10) is disclosed for controlling the cross-machine direction basis weight of a stream of stock (S) ejected from a headbox (12) onto a forming wire (14). The apparatus includes a plurality of conduits (18-22) with each conduit defining an outlet nozzle (24-28) disposed adjacent to a slice lip (30) of the headbox (12) and spaced relative to each adjacent nozzle in a cross-machine direction (CD). The conduits (18-22) are connected to a source of pressurized air (32). A plurality of control valves (34-38) are arranged with each valve (34-38) cooperating with a corresponding conduit (18-22) for controlling a flow of pressurized air (40) to each nozzle. A control device (42) is connected to the valves (34-38) for controlling the valves such that a flow of air to each of the nozzles (24-28) is permitted for controlling the cross-machine basis weight of the stream of stock (S). The arrangement is such that when the flow of air (40) through one of the nozzles is increased, the basis weight of the stream of stock (S) in the vicinity of the one nozzle is correspondingly reduced so that the basis weight of the stream of stock in a cross-machine direction is selectively controlled.