Stack top control method and apparatus

摘要

A stack top control method and apparatus includes sensing the vertical position of a top of signatures being stacked on a stacking platform at two spaced apart locations. Two belt assemblies tangentially contact at least a portion of opposed sides of the stack being formed adjacent the top locations being sensed. Each belt assembly is driven by a variable drive motor and applies a tangential, frictional drive force to the opposed sides of the stack being formed toward the stacking platform. A control circuit monitors the vertical position of the two spaced apart locations and controls the speed of each drive motor of the belt assemblies responsive to the sensed vertical position of the top of the signatures being formed into the stack. The top of the stack is thereby substantially leveled.