Intermittent web feed apparatus

Abstract

A bag machine includes a programmed logic controller intermittently actuating a web feed draw roll motor for controlled web feed during the inoperative period of a cycled seal bar. The controller has separate inputs for the seal bar periods and a web length and establishes a control program of a preferred motion profile, with acceleration and deceleration of the fixed rolls to match the bag length to the available time using the total time available, with acceleration to a maximum and deceleration to reference, with or without a constant speed period. The bag length and time is monitored each machine cycle to calculate the next motion profile and permit changes in the bag length without machine shut-down. A programmed registered mode of control responds to a web mark spacing relative to the seal bar. In the registered mode, a photoscanner detects the mark during a constant speed web feed period prior to the end of the available time and actuates the web feed accordingly. If actual draw roll motion differs from the programmed motion profile, a fault signal may shut-down the machine. Manual control and inputs are provided for setup and for manual machine operations. The controller may vary the length of every other bag slightly to spaced hot seams from each other and permits stacking of the bags. A programmed reverse drive withdraws the web slightly from the seal bar to prevent sticking of the web to the seal bar.