Method and apparatus for controlling the weight per unit length of a

Abstract

Stringent specifications for an extrudate are maintained by accurate control of tread weight per unit length without regard for dimensional changes of the extrudate. This is achieved simply by adjusting the speed of a single variable-speed conveyor, whether the running-weigh-scale ('RWS') conveyor, or, the take-away conveyor, without adjusting the extruder screw, or operation of the extruder, and without measuring any dimension (width or gauge) of the extrudate; therefore, with no regard either to the cross-sectional area, or surface area, or volume of the tread. The accuracy of control depends chiefly on how accurately one can measure the weight/unit length, and how precisely the speed of the single variable-speed conveyor can be controlled. Exceptional on-spec control in the continuous extrusion of a tread stock is achieved because it was recognized that dimensional changes of the tread stock, independent of its change in weight/unit length, do not adversely effect the specifications of the extruded tread. This process and the particular configuration of the equipment in the tread line is particularly adapted to make the necessary comparison of RWS and target values which results in the production of extrudates with a weight tolerance of less than .+-.5%, and preferably less than .+-.2%.